1889 files changed, 47480 insertions, 18120 deletions
diff --git a/.codeclimate.yml b/.codeclimate.yml
index 17fcaa4360..7d4ec1c54f 100644
--- a/.codeclimate.yml
+++ b/.codeclimate.yml
@@ -1,6 +1,29 @@
+checks:
+  argument-count:
+    enabled: false
+  complex-logic:
+    enabled: false
+  file-lines:
+    enabled: false
+  method-complexity:
+    enabled: false
+  method-count:
+    enabled: false
+  method-lines:
+    enabled: false
+  nested-control-flow:
+    enabled: false
+  return-statements:
+    enabled: false
+  similar-code:
+    enabled: false
+  identical-code:
+    enabled: false
+
 engines:
   rubocop:
     enabled: true
+    channel: rubocop-0-54
 
 ratings:
   paths:
diff --git a/.github/issue_template.md b/.github/issue_template.md
index 2d071d4a71..2ff6a271db 100644
--- a/.github/issue_template.md
+++ b/.github/issue_template.md
@@ -1,7 +1,7 @@
 ### Steps to reproduce
 
 (Guidelines for creating a bug report are [available
-here](http://guides.rubyonrails.org/contributing_to_ruby_on_rails.html#creating-a-bug-report))
+here](http://edgeguides.rubyonrails.org/contributing_to_ruby_on_rails.html#creating-a-bug-report))
 
 ### Expected behavior
 Tell us what should happen
diff --git a/.github/pull_request_template.md b/.github/pull_request_template.md
index 214d63740c..a36687ec99 100644
--- a/.github/pull_request_template.md
+++ b/.github/pull_request_template.md
@@ -16,6 +16,6 @@ CHANGELOG files by reviewers, please add the CHANGELOG entry at the top of the f
 
 Finally, if your pull request affects documentation or any non-code
 changes, guidelines for those changes are [available
-here](http://guides.rubyonrails.org/contributing_to_ruby_on_rails.html#contributing-to-the-rails-documentation)
+here](http://edgeguides.rubyonrails.org/contributing_to_ruby_on_rails.html#contributing-to-the-rails-documentation)
 
 Thanks for contributing to Rails!
diff --git a/.gitignore b/.gitignore
index 32939b7bfd..ab9ca8a6ac 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,24 +1,16 @@
-# Don't put *.swp, *.bak, etc here; those belong in a global ~/.gitignore.
+# Don't put *.swp, *.bak, etc here; those belong in a global .gitignore.
 # Check out https://help.github.com/articles/ignoring-files for how to set that up.
 
 .Gemfile
-.ruby-version
 .byebug_history
-debug.log
-pkg
+.ruby-version
+/*/doc/
+/*/test/tmp/
 /.bundle
-/dist
-/doc/rdoc
-/*/doc
-/*/test/tmp
-/activerecord/sqlnet.log
-/activemodel/test/fixtures/fixture_database.sqlite3
-/activesupport/test/fixtures/isolation_test
-/railties/test/500.html
-/railties/test/fixtures/tmp
-/railties/test/initializer/root/log
-/railties/doc
-/railties/tmp
-/guides/output
+/dist/
+/doc/
+/guides/output/
+debug.log
 node_modules/
-/actionview/log
+package-lock.json
+pkg/
diff --git a/.rubocop.yml b/.rubocop.yml
index f3ed8bc841..7327f1e631 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,5 +1,7 @@
+require: './ci/custom_cops/lib/custom_cops'
+
 AllCops:
-  TargetRubyVersion: 2.2
+  TargetRubyVersion: 2.4
   # RuboCop has a bunch of cops enabled by default. This setting tells RuboCop
   # to ignore them, so only the ones explicitly set in this file are enabled.
   DisabledByDefault: true
@@ -7,6 +9,17 @@ AllCops:
     - '**/templates/**/*'
     - '**/vendor/**/*'
     - 'actionpack/lib/action_dispatch/journey/parser.rb'
+    - 'railties/test/fixtures/tmp/**/*'
+
+# Prefer assert_not_x over refute_x
+CustomCops/RefuteNot:
+  Include:
+    - '**/test/**/*'
+
+# Prefer assert_not over assert !
+CustomCops/AssertNot:
+  Include:
+    - '**/test/**/*'
 
 # Prefer &&/|| over and/or.
 Style/AndOr:
@@ -26,6 +39,16 @@ Layout/CaseIndentation:
 Layout/CommentIndentation:
   Enabled: true
 
+Layout/ElseAlignment:
+  Enabled: true
+
+# Align `end` with the matching keyword or starting expression except for
+# assignments, where it should be aligned with the LHS.
+Layout/EndAlignment:
+  Enabled: true
+  EnforcedStyleAlignWith: variable
+  AutoCorrect: true
+
 Layout/EmptyLineAfterMagicComment:
   Enabled: true
 
@@ -58,6 +81,9 @@ Layout/IndentationConsistency:
 Layout/IndentationWidth:
   Enabled: true
 
+Layout/LeadingCommentSpace:
+  Enabled: true
+
 Layout/SpaceAfterColon:
   Enabled: true
 
@@ -73,9 +99,15 @@ Layout/SpaceAroundKeyword:
 Layout/SpaceAroundOperators:
   Enabled: true
 
+Layout/SpaceBeforeComma:
+    Enabled: true
+
 Layout/SpaceBeforeFirstArg:
     Enabled: true
 
+Style/DefWithParentheses:
+  Enabled: true
+
 # Defining a method with parameters needs parentheses.
 Style/MethodDefParentheses:
   Enabled: true
@@ -126,12 +158,21 @@ Layout/TrailingWhitespace:
 Style/UnneededPercentQ:
   Enabled: true
 
-# Align `end` with the matching keyword or starting expression except for
-# assignments, where it should be aligned with the LHS.
-Lint/EndAlignment:
-  Enabled: true
-  EnforcedStyleAlignWith: variable
-
 # Use my_method(my_arg) not my_method( my_arg ) or my_method my_arg.
 Lint/RequireParentheses:
   Enabled: true
+
+Lint/StringConversionInInterpolation:
+  Enabled: true
+
+Style/RedundantReturn:
+  Enabled: true
+  AllowMultipleReturnValues: true
+
+Style/Semicolon:
+  Enabled: true
+  AllowAsExpressionSeparator: true
+
+# Prefer Foo.method over Foo::method
+Style/ColonMethodCall:
+  Enabled: true
diff --git a/.travis.yml b/.travis.yml
index 6c7380f050..0fdea1367c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,8 +2,8 @@ language: ruby
 sudo: false
 
 cache:
-  bundler: true
   directories:
+    - vendor/bundle
     - /tmp/cache/unicode_conformance
     - /tmp/beanstalkd-1.10
     - node_modules
@@ -11,29 +11,38 @@ cache:
 
 services:
   - memcached
+  - redis-server
 
 addons:
-  postgresql: "9.4"
+  postgresql: "9.6"
+  chrome: stable
+  apt:
+    sources:
+      - sourceline: "ppa:mc3man/trusty-media"
+      - sourceline: "ppa:ubuntuhandbook1/apps"
+    packages:
+      - ffmpeg
+      - mupdf
+      - mupdf-tools
+      - poppler-utils
 
 bundler_args: --without test --jobs 3 --retry 3
 before_install:
   - "rm ${BUNDLE_GEMFILE}.lock"
-  - "gem update --system"
-  - "gem update bundler"
+  - "travis_retry gem update --system"
+  - "travis_retry gem install bundler"
   - "[ -f /tmp/beanstalkd-1.10/Makefile ] || (curl -L https://github.com/kr/beanstalkd/archive/v1.10.tar.gz | tar xz -C /tmp)"
   - "pushd /tmp/beanstalkd-1.10 && make && (./beanstalkd &); popd"
-  - "[[ -z $encrypted_8a915ebdd931_key && -z $encrypted_8a915ebdd931_iv ]] || openssl aes-256-cbc -K $encrypted_8a915ebdd931_key -iv $encrypted_8a915ebdd931_iv -in activestorage/test/service/configurations.yml.enc -out activestorage/test/service/configurations.yml -d"
+  - "[[ -z $encrypted_0fb9444d0374_key && -z $encrypted_0fb9444d0374_iv ]] || openssl aes-256-cbc -K $encrypted_0fb9444d0374_key -iv $encrypted_0fb9444d0374_iv -in activestorage/test/service/configurations.yml.enc -out activestorage/test/service/configurations.yml -d"
   - "[[ $GEM != 'av:ujs' ]] || nvm install node"
   - "[[ $GEM != 'av:ujs' ]] || node --version"
   - "[[ $GEM != 'av:ujs' ]] || (cd actionview && npm install)"
-  - "[[ $GEM != 'av:ujs' ]] || [[ $(phantomjs --version) > '2' ]] || npm install -g phantomjs-prebuilt"
 
 before_script:
   # Set Sauce Labs username and access key. Obfuscated, purposefully not encrypted.
   # Decodes to e.g. `export VARIABLE=VALUE`
   - $(base64 --decode <<< "ZXhwb3J0IFNBVUNFX0FDQ0VTU19LRVk9YTAzNTM0M2YtZTkyMi00MGIzLWFhM2MtMDZiM2VhNjM1YzQ4")
   - $(base64 --decode <<< "ZXhwb3J0IFNBVUNFX1VTRVJOQU1FPXJ1YnlvbnJhaWxz")
-  - redis-server --bind 127.0.0.1 --port 6379 --requirepass 'password' --daemonize yes
 
 script: 'ci/travis.rb'
 
@@ -52,59 +61,56 @@ env:
     - "GEM=ac:integration"
 
 rvm:
-  - 2.2.7
-  - 2.3.4
-  - 2.4.1
+  - 2.4.4
+  - 2.5.1
   - ruby-head
 
 matrix:
   include:
-    - rvm: 2.4.1
+    - rvm: 2.5.1
       env: "GEM=av:ujs"
-    - rvm: 2.2.7
+    - rvm: 2.4.4
       env: "GEM=aj:integration"
       services:
         - memcached
+        - redis-server
         - rabbitmq
-    - rvm: 2.3.4
-      env: "GEM=aj:integration"
-      services:
-        - memcached
-        - rabbitmq
-    - rvm: 2.4.1
+    - rvm: 2.5.1
       env: "GEM=aj:integration"
       services:
         - memcached
+        - redis-server
         - rabbitmq
     - rvm: ruby-head
       env: "GEM=aj:integration"
       services:
         - memcached
+        - redis-server
         - rabbitmq
-    - rvm: 2.3.4
+    - rvm: 2.5.1
       env:
         - "GEM=ar:mysql2 MYSQL=mariadb"
       addons:
-        mariadb: 10.0
-    - rvm: 2.3.4
+        mariadb: 10.2
+    - rvm: 2.5.1
       env:
         - "GEM=ar:sqlite3_mem"
-    - rvm: 2.3.4
+    - rvm: 2.5.1
       env:
         - "GEM=ar:postgresql POSTGRES=9.2"
       addons:
         postgresql: "9.2"
-    - rvm: jruby-9.1.12.0
+    - rvm: jruby-head
       jdk: oraclejdk8
       env:
         - "GEM=ap"
-    - rvm: jruby-9.1.12.0
+    - rvm: jruby-head
       jdk: oraclejdk8
       env:
         - "GEM=am,amo,aj"
   allow_failures:
     - rvm: ruby-head
-    - rvm: jruby-9.1.12.0
+    - rvm: jruby-head
     - env: "GEM=ac:integration"
   fast_finish: true
 
diff --git a/Brewfile b/Brewfile
new file mode 100644
index 0000000000..4ac325e80a
--- /dev/null
+++ b/Brewfile
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+tap "homebrew/core"
+tap "homebrew/bundle"
+tap "homebrew/services"
+tap "caskroom/cask"
+brew "ffmpeg"
+brew "memcached"
+brew "mysql"
+brew "postgresql"
+brew "redis"
+brew "yarn"
+cask "xquartz"
+brew "mupdf"
+brew "poppler"
diff --git a/CODE_OF_CONDUCT.md b/CODE_OF_CONDUCT.md
index 078d5f1219..ecd56b87d6 100644
--- a/CODE_OF_CONDUCT.md
+++ b/CODE_OF_CONDUCT.md
@@ -8,5 +8,5 @@ http://rubyonrails.org/conduct/
 
 For a history of updates, see the page history here:
 
-https://github.com/rails/rails.github.com/commits/master/conduct/index.html
+https://github.com/rails/homepage/commits/master/conduct.html
 
diff --git a/Gemfile b/Gemfile
index 412cc627b9..f0c489f642 100644
--- a/Gemfile
+++ b/Gemfile
@@ -6,21 +6,16 @@ git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
 gemspec
 
-gem "arel", github: "rails/arel"
-
 # We need a newish Rake since Active Job sets its test tasks' descriptions.
 gem "rake", ">= 11.1"
 
-# This needs to be with require false to ensure correct loading order, as it has to
-# be loaded after loading the test library.
-gem "mocha", "~> 0.14", require: false
+gem "mocha"
 
-gem "capybara", "~> 2.13"
+gem "capybara", ">= 2.15"
 
 gem "rack-cache", "~> 1.2"
-gem "jquery-rails"
 gem "coffee-rails"
-gem "sass-rails", github: "rails/sass-rails", branch: "5-0-stable"
+gem "sass-rails"
 gem "turbolinks", "~> 5"
 
 # require: false so bcrypt is loaded only when has_secure_password is used.
@@ -37,22 +32,21 @@ gem "json", ">= 2.0.0"
 
 gem "rubocop", ">= 0.47", require: false
 
+# https://github.com/guard/rb-inotify/pull/79
 gem "rb-inotify", github: "matthewd/rb-inotify", branch: "close-handling", require: false
 
 group :doc do
-  gem "sdoc", github: "robin850/sdoc", branch: "upgrade"
+  gem "sdoc", "~> 1.0"
   gem "redcarpet", "~> 3.2.3", platforms: :ruby
   gem "w3c_validators"
   gem "kindlerb", "~> 1.2.0"
 end
 
 # Active Support.
-gem "dalli", ">= 2.2.1"
+gem "dalli"
 gem "listen", ">= 3.0.5", "< 3.2", require: false
 gem "libxml-ruby", platforms: :ruby
-
-# Action View. For testing Erubis handler deprecation.
-gem "erubis", "~> 2.7.0", require: false
+gem "connection_pool", require: false
 
 # for railties app_generator_test
 gem "bootsnap", ">= 1.1.0", require: false
@@ -64,13 +58,10 @@ group :job do
   gem "sidekiq", require: false
   gem "sucker_punch", require: false
   gem "delayed_job", require: false
-  gem "queue_classic", github: "QueueClassic/queue_classic", branch: "master", require: false, platforms: :ruby
+  gem "queue_classic", github: "rafaelfranca/queue_classic", branch: "update-pg", require: false, platforms: :ruby
   gem "sneakers", require: false
   gem "que", require: false
   gem "backburner", require: false
-  #TODO: add qu after it support Rails 5.1
-  # gem 'qu-rails', github: "bkeepers/qu", branch: "master", require: false
-  gem "qu-redis", require: false
   gem "delayed_job_active_record", require: false
   gem "sequel", require: false
 end
@@ -79,9 +70,10 @@ end
 group :cable do
   gem "puma", require: false
 
-  gem "em-hiredis", require: false
   gem "hiredis", require: false
-  gem "redis", require: false
+  gem "redis", "~> 4.0", require: false
+
+  gem "redis-namespace"
 
   gem "websocket-client-simple", github: "matthewd/websocket-client-simple", branch: "close-race", require: false
 
@@ -90,12 +82,19 @@ group :cable do
   gem "sprockets-export", require: false
 end
 
+# Active Storage
 group :storage do
-  gem "aws-sdk", "~> 2", require: false
-  gem "google-cloud-storage", "~> 1.3", require: false
+  gem "aws-sdk-s3", require: false
+  gem "google-cloud-storage", "~> 1.11", require: false
   gem "azure-storage", require: false
 
-  gem "mini_magick"
+  gem "image_processing", "~> 1.2"
+  gem "ffi", "<= 1.9.21"
+end
+
+group :ujs do
+  gem "qunit-selenium"
+  gem "chromedriver-helper"
 end
 
 # Add your own local bundler stuff.
@@ -108,13 +107,15 @@ group :test do
   platforms :mri do
     gem "stackprof"
     gem "byebug"
+    # FIXME: Remove this when thor 0.21 is release
+    gem "thor", git: "https://github.com/erikhuda/thor.git", ref: "006832ea32480618791f89bb7d9e67b22fc814b9"
   end
 
   gem "benchmark-ips"
 end
 
 platforms :ruby, :mswin, :mswin64, :mingw, :x64_mingw do
-  gem "nokogiri", ">= 1.6.8"
+  gem "nokogiri", ">= 1.8.1"
 
   # Needed for compiling the ActionDispatch::Journey parser.
   gem "racc", ">=1.4.6", require: false
@@ -124,7 +125,7 @@ platforms :ruby, :mswin, :mswin64, :mingw, :x64_mingw do
 
   group :db do
     gem "pg", ">= 0.18.0"
-    gem "mysql2", ">= 0.4.4"
+    gem "mysql2", ">= 0.4.10"
   end
 end
 
@@ -147,7 +148,7 @@ end
 platforms :rbx do
   # The rubysl-yaml gem doesn't ship with Psych by default as it needs
   # libyaml that isn't always available.
-  gem "psych", "~> 2.0"
+  gem "psych", "~> 3.0"
 end
 
 # Gems that are necessary for Active Record tests with Oracle.
diff --git a/Gemfile.lock b/Gemfile.lock
index b9003f9de5..4a0fba9024 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,10 +1,9 @@
 GIT
-  remote: https://github.com/QueueClassic/queue_classic.git
-  revision: cde82d17ded2799ed726dd7b0df6ce1fd4c1b7da
-  branch: master
+  remote: https://github.com/erikhuda/thor.git
+  revision: 006832ea32480618791f89bb7d9e67b22fc814b9
+  ref: 006832ea32480618791f89bb7d9e67b22fc814b9
   specs:
-    queue_classic (3.2.0.RC1)
-      pg (>= 0.17, < 0.20)
+    thor (0.20.0)
 
 GIT
   remote: https://github.com/matthewd/rb-inotify.git
@@ -24,108 +23,108 @@ GIT
       websocket
 
 GIT
-  remote: https://github.com/rails/arel.git
-  revision: 42510bf71472e2e35d9becb546edd05562672344
-  specs:
-    arel (9.0.0.alpha)
-
-GIT
-  remote: https://github.com/rails/sass-rails.git
-  revision: bb5c1d34e8acad2e2960cc785184ffe17d7b3bca
-  branch: 5-0-stable
+  remote: https://github.com/rafaelfranca/queue_classic.git
+  revision: dee64b361355d56700ad7aa3b151bf653a617526
+  branch: update-pg
   specs:
-    sass-rails (5.0.6)
-      railties (>= 4.0.0, < 6)
-      sass (~> 3.1)
-      sprockets (>= 2.8, < 4.0)
-      sprockets-rails (>= 2.0, < 4.0)
-      tilt (>= 1.1, < 3)
-
-GIT
-  remote: https://github.com/robin850/sdoc.git
-  revision: 0e340352f3ab2f196c8a8743f83c2ee286e4f71c
-  branch: upgrade
-  specs:
-    sdoc (1.0.0.rc2)
-      rdoc (~> 5.0)
+    queue_classic (3.2.0.RC1)
+      pg (>= 0.17, < 2.0)
 
 PATH
   remote: .
   specs:
-    actioncable (5.2.0.alpha)
-      actionpack (= 5.2.0.alpha)
+    actioncable (6.0.0.alpha)
+      actionpack (= 6.0.0.alpha)
       nio4r (~> 2.0)
-      websocket-driver (~> 0.6.1)
-    actionmailer (5.2.0.alpha)
-      actionpack (= 5.2.0.alpha)
-      actionview (= 5.2.0.alpha)
-      activejob (= 5.2.0.alpha)
+      websocket-driver (>= 0.6.1)
+    actionmailer (6.0.0.alpha)
+      actionpack (= 6.0.0.alpha)
+      actionview (= 6.0.0.alpha)
+      activejob (= 6.0.0.alpha)
       mail (~> 2.5, >= 2.5.4)
       rails-dom-testing (~> 2.0)
-    actionpack (5.2.0.alpha)
-      actionview (= 5.2.0.alpha)
-      activesupport (= 5.2.0.alpha)
+    actionpack (6.0.0.alpha)
+      actionview (= 6.0.0.alpha)
+      activesupport (= 6.0.0.alpha)
       rack (~> 2.0)
       rack-test (>= 0.6.3)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.0.2)
-    actionview (5.2.0.alpha)
-      activesupport (= 5.2.0.alpha)
+    actionview (6.0.0.alpha)
+      activesupport (= 6.0.0.alpha)
       builder (~> 3.1)
       erubi (~> 1.4)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.0.3)
-    activejob (5.2.0.alpha)
-      activesupport (= 5.2.0.alpha)
+    activejob (6.0.0.alpha)
+      activesupport (= 6.0.0.alpha)
       globalid (>= 0.3.6)
-    activemodel (5.2.0.alpha)
-      activesupport (= 5.2.0.alpha)
-    activerecord (5.2.0.alpha)
-      activemodel (= 5.2.0.alpha)
-      activesupport (= 5.2.0.alpha)
-      arel (= 9.0.0.alpha)
-    activestorage (5.2.0.alpha)
-      actionpack (= 5.2.0.alpha)
-      activerecord (= 5.2.0.alpha)
-    activesupport (5.2.0.alpha)
+    activemodel (6.0.0.alpha)
+      activesupport (= 6.0.0.alpha)
+    activerecord (6.0.0.alpha)
+      activemodel (= 6.0.0.alpha)
+      activesupport (= 6.0.0.alpha)
+    activestorage (6.0.0.alpha)
+      actionpack (= 6.0.0.alpha)
+      activerecord (= 6.0.0.alpha)
+      marcel (~> 0.3.1)
+    activesupport (6.0.0.alpha)
       concurrent-ruby (~> 1.0, >= 1.0.2)
-      i18n (~> 0.7)
+      i18n (>= 0.7, < 2)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
-    rails (5.2.0.alpha)
-      actioncable (= 5.2.0.alpha)
-      actionmailer (= 5.2.0.alpha)
-      actionpack (= 5.2.0.alpha)
-      actionview (= 5.2.0.alpha)
-      activejob (= 5.2.0.alpha)
-      activemodel (= 5.2.0.alpha)
-      activerecord (= 5.2.0.alpha)
-      activestorage (= 5.2.0.alpha)
-      activesupport (= 5.2.0.alpha)
+    rails (6.0.0.alpha)
+      actioncable (= 6.0.0.alpha)
+      actionmailer (= 6.0.0.alpha)
+      actionpack (= 6.0.0.alpha)
+      actionview (= 6.0.0.alpha)
+      activejob (= 6.0.0.alpha)
+      activemodel (= 6.0.0.alpha)
+      activerecord (= 6.0.0.alpha)
+      activestorage (= 6.0.0.alpha)
+      activesupport (= 6.0.0.alpha)
       bundler (>= 1.3.0)
-      railties (= 5.2.0.alpha)
+      railties (= 6.0.0.alpha)
       sprockets-rails (>= 2.0.0)
-    railties (5.2.0.alpha)
-      actionpack (= 5.2.0.alpha)
-      activesupport (= 5.2.0.alpha)
+    railties (6.0.0.alpha)
+      actionpack (= 6.0.0.alpha)
+      activesupport (= 6.0.0.alpha)
       method_source
       rake (>= 0.8.7)
-      thor (>= 0.18.1, < 2.0)
+      thor (>= 0.19.0, < 2.0)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    addressable (2.5.1)
-      public_suffix (~> 2.0, >= 2.0.2)
+    activerecord-jdbc-adapter (1.3.24)
+      activerecord (>= 2.2, < 5.0)
+    activerecord-jdbcmysql-adapter (1.3.24)
+      activerecord-jdbc-adapter (~> 1.3.24)
+      jdbc-mysql (>= 5.1.22)
+    activerecord-jdbcpostgresql-adapter (1.3.24)
+      activerecord-jdbc-adapter (~> 1.3.24)
+      jdbc-postgres (~> 9.1, <= 9.4.1206)
+    activerecord-jdbcsqlite3-adapter (1.3.24)
+      activerecord-jdbc-adapter (~> 1.3.24)
+      jdbc-sqlite3 (>= 3.7.2, < 3.9)
+    addressable (2.5.2)
+      public_suffix (>= 2.0.2, < 4.0)
     amq-protocol (2.2.0)
-    ast (2.3.0)
-    aws-sdk (2.10.27)
-      aws-sdk-resources (= 2.10.27)
-    aws-sdk-core (2.10.27)
+    archive-zip (0.7.0)
+      io-like (~> 0.3.0)
+    ast (2.4.0)
+    aws-partitions (1.20.0)
+    aws-sdk-core (3.3.0)
+      aws-partitions (~> 1.0)
       aws-sigv4 (~> 1.0)
       jmespath (~> 1.0)
-    aws-sdk-resources (2.10.27)
-      aws-sdk-core (= 2.10.27)
+    aws-sdk-kms (1.1.0)
+      aws-sdk-core (~> 3)
+      aws-sigv4 (~> 1.0)
+    aws-sdk-s3 (1.2.0)
+      aws-sdk-core (~> 3)
+      aws-sdk-kms (~> 1)
+      aws-sigv4 (~> 1.0)
     aws-sigv4 (1.0.1)
     azure-core (0.1.11)
       faraday (~> 0.9)
@@ -140,6 +139,7 @@ GEM
       concurrent-ruby (~> 1.0.1)
       dante (> 0.1.5)
     bcrypt (3.1.11)
+    bcrypt (3.1.11-java)
     bcrypt (3.1.11-x64-mingw32)
     bcrypt (3.1.11-x86-mingw32)
     beaneater (1.0.0)
@@ -161,21 +161,26 @@ GEM
       childprocess
       faraday
       selenium-webdriver
-    bootsnap (1.1.2)
+    bootsnap (1.2.1)
+      msgpack (~> 1.0)
+    bootsnap (1.2.1-java)
       msgpack (~> 1.0)
     builder (3.2.3)
     bunny (2.6.6)
       amq-protocol (>= 2.1.0)
     byebug (9.0.6)
-    capybara (2.15.1)
+    capybara (3.0.1)
       addressable
       mini_mime (>= 0.1.3)
-      nokogiri (>= 1.3.3)
-      rack (>= 1.0.0)
-      rack-test (>= 0.5.4)
-      xpath (~> 2.0)
+      nokogiri (~> 1.8)
+      rack (>= 1.6.0)
+      rack-test (>= 0.6.3)
+      xpath (~> 3.0)
     childprocess (0.7.1)
       ffi (~> 1.0, >= 1.0.11)
+    chromedriver-helper (1.1.0)
+      archive-zip (~> 0.7.0)
+      nokogiri (~> 1.6)
     coffee-rails (4.2.2)
       coffee-script (>= 2.2.0)
       railties (>= 4.0.0)
@@ -184,39 +189,35 @@ GEM
       execjs
     coffee-script-source (1.12.2)
     concurrent-ruby (1.0.5)
+    concurrent-ruby (1.0.5-java)
     connection_pool (2.2.1)
     cookiejar (0.3.3)
+    crass (1.0.3)
     curses (1.0.2)
     daemons (1.2.4)
-    dalli (2.7.6)
+    dalli (2.7.8)
     dante (0.2.0)
-    declarative (0.0.9)
+    declarative (0.0.10)
     declarative-option (0.1.0)
-    delayed_job (4.1.3)
+    delayed_job (4.1.4)
       activesupport (>= 3.0, < 5.2)
     delayed_job_active_record (4.1.2)
       activerecord (>= 3.0, < 5.2)
       delayed_job (>= 3.0, < 5)
     digest-crc (0.4.1)
-    em-hiredis (0.3.1)
-      eventmachine (~> 1.0)
-      hiredis (~> 0.6.0)
     em-http-request (1.1.5)
       addressable (>= 2.3.4)
       cookiejar (!= 0.3.1)
       em-socksify (>= 0.3)
       eventmachine (>= 1.0.3)
       http_parser.rb (>= 0.6.0)
-    em-socksify (0.3.1)
+    em-socksify (0.3.2)
       eventmachine (>= 1.0.0.beta.4)
-    erubi (1.6.1)
-    erubis (2.7.0)
-    et-orbi (1.0.5)
+    erubi (1.7.0)
+    et-orbi (1.0.8)
       tzinfo
     event_emitter (0.2.6)
     eventmachine (1.2.5)
-    eventmachine (1.2.5-x64-mingw32)
-    eventmachine (1.2.5-x86-mingw32)
     execjs (2.7.0)
     faraday (0.13.1)
       multipart-post (>= 1.2, < 3)
@@ -233,46 +234,53 @@ GEM
     faye-websocket (0.10.7)
       eventmachine (>= 0.12.0)
       websocket-driver (>= 0.5.1)
-    ffi (1.9.18)
-    ffi (1.9.18-x64-mingw32)
-    ffi (1.9.18-x86-mingw32)
-    globalid (0.4.0)
+    ffi (1.9.21)
+    ffi (1.9.21-java)
+    ffi (1.9.21-x64-mingw32)
+    ffi (1.9.21-x86-mingw32)
+    globalid (0.4.1)
       activesupport (>= 4.2.0)
-    google-api-client (0.13.1)
+    google-api-client (0.19.8)
       addressable (~> 2.5, >= 2.5.1)
-      googleauth (~> 0.5)
+      googleauth (>= 0.5, < 0.7.0)
       httpclient (>= 2.8.1, < 3.0)
       mime-types (~> 3.0)
       representable (~> 3.0)
       retriable (>= 2.0, < 4.0)
-    google-cloud-core (1.0.0)
+    google-cloud-core (1.2.0)
       google-cloud-env (~> 1.0)
-      googleauth (~> 0.5.1)
     google-cloud-env (1.0.1)
       faraday (~> 0.11)
-    google-cloud-storage (1.4.0)
+    google-cloud-storage (1.11.0)
       digest-crc (~> 0.4)
-      google-api-client (~> 0.13.0)
-      google-cloud-core (~> 1.0)
-    googleauth (0.5.3)
+      google-api-client (~> 0.19.0)
+      google-cloud-core (~> 1.2)
+      googleauth (~> 0.6.2)
+    googleauth (0.6.2)
       faraday (~> 0.12)
-      jwt (~> 1.4)
+      jwt (>= 1.4, < 3.0)
       logging (~> 2.0)
       memoist (~> 0.12)
       multi_json (~> 1.11)
       os (~> 0.9)
       signet (~> 0.7)
     hiredis (0.6.1)
+    hiredis (0.6.1-java)
     http_parser.rb (0.6.0)
     httpclient (2.8.3)
-    i18n (0.8.6)
+    i18n (1.0.0)
+      concurrent-ruby (~> 1.0)
+    image_processing (1.2.0)
+      mini_magick (~> 4.0)
+      ruby-vips (>= 2.0.10, < 3)
+    io-like (0.3.0)
+    jdbc-mysql (5.1.44)
+    jdbc-postgres (9.4.1206)
+    jdbc-sqlite3 (3.8.11.2)
     jmespath (1.3.1)
-    jquery-rails (4.3.1)
-      rails-dom-testing (>= 1, < 3)
-      railties (>= 4.2.0)
-      thor (>= 0.14, < 2.0)
     json (2.1.0)
-    jwt (1.5.6)
+    json (2.1.0-java)
+    jwt (2.1.0)
     kindlerb (1.2.0)
       mustache
       nokogiri
@@ -285,86 +293,90 @@ GEM
     logging (2.2.2)
       little-plugger (~> 1.1)
       multi_json (~> 1.10)
-    loofah (2.0.3)
+    loofah (2.2.1)
+      crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
-    mail (2.6.6)
-      mime-types (>= 1.16, < 4)
+    mail (2.7.0)
+      mini_mime (>= 0.1.1)
+    marcel (0.3.1)
+      mimemagic (~> 0.3.2)
     memoist (0.16.0)
     metaclass (0.0.4)
-    method_source (0.8.2)
+    method_source (0.9.0)
     mime-types (3.1)
       mime-types-data (~> 3.2015)
     mime-types-data (3.2016.0521)
+    mimemagic (0.3.2)
     mini_magick (4.8.0)
-    mini_mime (0.1.4)
-    mini_portile2 (2.2.0)
-    minitest (5.10.3)
+    mini_mime (1.0.0)
+    mini_portile2 (2.3.0)
+    minitest (5.11.3)
     minitest-bisect (1.4.0)
       minitest-server (~> 1.0)
       path_expander (~> 1.0)
-    minitest-server (1.0.4)
+    minitest-server (1.0.5)
       minitest (~> 5.0)
-    mocha (0.14.0)
+    mocha (1.5.0)
       metaclass (~> 0.0.1)
     mono_logger (1.1.0)
-    msgpack (1.1.0)
-    msgpack (1.1.0-x64-mingw32)
-    msgpack (1.1.0-x86-mingw32)
-    multi_json (1.12.1)
+    msgpack (1.2.4)
+    msgpack (1.2.4-java)
+    msgpack (1.2.4-x64-mingw32)
+    msgpack (1.2.4-x86-mingw32)
+    multi_json (1.12.2)
     multipart-post (2.0.0)
     mustache (1.0.5)
-    mustermann (1.0.0)
-    mysql2 (0.4.9)
-    mysql2 (0.4.9-x64-mingw32)
-    mysql2 (0.4.9-x86-mingw32)
-    nio4r (2.1.0)
-    nokogiri (1.8.0)
-      mini_portile2 (~> 2.2.0)
-    nokogiri (1.8.0-x64-mingw32)
-      mini_portile2 (~> 2.2.0)
-    nokogiri (1.8.0-x86-mingw32)
-      mini_portile2 (~> 2.2.0)
+    mustermann (1.0.2)
+    mysql2 (0.5.0)
+    mysql2 (0.5.0-x64-mingw32)
+    mysql2 (0.5.0-x86-mingw32)
+    nio4r (2.2.0)
+    nio4r (2.2.0-java)
+    nokogiri (1.8.2)
+      mini_portile2 (~> 2.3.0)
+    nokogiri (1.8.2-java)
+    nokogiri (1.8.2-x64-mingw32)
+      mini_portile2 (~> 2.3.0)
+    nokogiri (1.8.2-x86-mingw32)
+      mini_portile2 (~> 2.3.0)
     os (0.9.6)
-    parallel (1.12.0)
-    parser (2.4.0.0)
-      ast (~> 2.2)
+    parallel (1.12.1)
+    parser (2.5.1.0)
+      ast (~> 2.4.0)
     path_expander (1.0.2)
-    pg (0.19.0)
-    pg (0.19.0-x64-mingw32)
-    pg (0.19.0-x86-mingw32)
+    pg (1.0.0)
+    pg (1.0.0-x64-mingw32)
+    pg (1.0.0-x86-mingw32)
     powerpack (0.1.1)
-    psych (2.2.4)
-    public_suffix (2.0.5)
+    psych (3.0.2)
+    public_suffix (3.0.2)
     puma (3.9.1)
-    qu (0.2.0)
-      multi_json
-    qu-redis (0.2.0)
-      qu (= 0.2.0)
-      redis-namespace
-      simple_uuid
+    puma (3.9.1-java)
     que (0.14.0)
+    qunit-selenium (0.0.4)
+      selenium-webdriver
+      thor
     racc (1.4.14)
-    rack (2.0.3)
+    rack (2.0.4)
     rack-cache (1.7.0)
       rack (>= 0.4)
-    rack-protection (2.0.0)
+    rack-protection (2.0.1)
       rack
-    rack-test (0.7.0)
+    rack-test (1.0.0)
       rack (>= 1.0, < 3)
     rails-dom-testing (2.0.3)
       activesupport (>= 4.2.0)
       nokogiri (>= 1.6)
     rails-html-sanitizer (1.0.3)
       loofah (~> 2.0)
-    rainbow (2.2.2)
-      rake
-    rake (12.0.0)
+    rainbow (3.0.0)
+    rake (12.3.0)
     rb-fsevent (0.10.2)
-    rdoc (5.1.0)
+    rdoc (6.0.1)
     redcarpet (3.2.3)
-    redis (3.3.3)
-    redis-namespace (1.5.3)
-      redis (~> 3.0, >= 3.0.4)
+    redis (4.0.1)
+    redis-namespace (1.6.0)
+      redis (>= 3.0.4)
     representable (3.0.4)
       declarative (< 0.1.0)
       declarative-option (< 0.2.0)
@@ -375,51 +387,60 @@ GEM
       redis-namespace (~> 1.3)
       sinatra (>= 0.9.2)
       vegas (~> 0.1.2)
-    resque-scheduler (4.3.0)
+    resque-scheduler (4.3.1)
       mono_logger (~> 1.0)
-      redis (~> 3.3)
+      redis (>= 3.3, < 5)
       resque (~> 1.26)
       rufus-scheduler (~> 3.2)
     retriable (3.1.1)
-    rubocop (0.49.1)
+    rubocop (0.54.0)
       parallel (~> 1.10)
-      parser (>= 2.3.3.1, < 3.0)
+      parser (>= 2.5)
       powerpack (~> 0.1)
-      rainbow (>= 1.99.1, < 3.0)
+      rainbow (>= 2.2.2, < 4.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (~> 1.0, >= 1.0.1)
-    ruby-progressbar (1.8.1)
+    ruby-progressbar (1.9.0)
+    ruby-vips (2.0.10)
+      ffi (~> 1.9)
     ruby_dep (1.5.0)
     rubyzip (1.2.1)
     rufus-scheduler (3.4.2)
       et-orbi (~> 1.0)
-    sass (3.5.1)
+    sass (3.5.3)
       sass-listen (~> 4.0.0)
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
+    sass-rails (5.0.7)
+      railties (>= 4.0.0, < 6)
+      sass (~> 3.1)
+      sprockets (>= 2.8, < 4.0)
+      sprockets-rails (>= 2.0, < 4.0)
+      tilt (>= 1.1, < 3)
+    sdoc (1.0.0)
+      rdoc (>= 5.0)
     selenium-webdriver (3.5.1)
       childprocess (~> 0.5)
       rubyzip (~> 1.0)
     sequel (4.49.0)
     serverengine (1.5.11)
       sigdump (~> 0.2.2)
-    sidekiq (5.0.4)
+    sidekiq (5.0.5)
       concurrent-ruby (~> 1.0)
       connection_pool (~> 2.2, >= 2.2.0)
       rack-protection (>= 1.5.0)
-      redis (~> 3.3, >= 3.3.3)
+      redis (>= 3.3.4, < 5)
     sigdump (0.2.4)
-    signet (0.7.3)
+    signet (0.8.1)
       addressable (~> 2.3)
       faraday (~> 0.9)
-      jwt (~> 1.5)
+      jwt (>= 1.5, < 3.0)
       multi_json (~> 1.10)
-    simple_uuid (0.4.0)
-    sinatra (2.0.0)
+    sinatra (2.0.1)
       mustermann (~> 1.0)
       rack (~> 2.0)
-      rack-protection (= 2.0.0)
+      rack-protection (= 2.0.1)
       tilt (~> 2.0)
     sneakers (2.5.0)
       bunny (~> 2.6.4)
@@ -444,13 +465,13 @@ GEM
       daemons (~> 1.0, >= 1.0.9)
       eventmachine (~> 1.0, >= 1.0.4)
       rack (>= 1, < 3)
-    thor (0.20.0)
     thread (0.1.7)
     thread_safe (0.3.6)
+    thread_safe (0.3.6-java)
     tilt (2.0.8)
-    turbolinks (5.0.1)
-      turbolinks-source (~> 5)
-    turbolinks-source (5.0.3)
+    turbolinks (5.1.1)
+      turbolinks-source (~> 5.1)
+    turbolinks-source (5.1.0)
     tzinfo (1.2.3)
       thread_safe (~> 0.1)
     tzinfo-data (1.2017.2)
@@ -458,7 +479,7 @@ GEM
     uber (0.1.0)
     uglifier (3.2.0)
       execjs (>= 0.3.0, < 3)
-    unicode-display_width (1.3.0)
+    unicode-display_width (1.3.2)
     useragent (0.16.8)
     vegas (0.1.11)
       rack (>= 1.0.0)
@@ -469,11 +490,14 @@ GEM
     websocket (1.2.4)
     websocket-driver (0.6.5)
       websocket-extensions (>= 0.1.0)
+    websocket-driver (0.6.5-java)
+      websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.2)
-    xpath (2.1.0)
-      nokogiri (~> 1.3)
+    xpath (3.0.0)
+      nokogiri (~> 1.8)
 
 PLATFORMS
+  java
   ruby
   x64-mingw32
   x86-mingw32
@@ -482,8 +506,7 @@ DEPENDENCIES
   activerecord-jdbcmysql-adapter (>= 1.3.0)
   activerecord-jdbcpostgresql-adapter (>= 1.3.0)
   activerecord-jdbcsqlite3-adapter (>= 1.3.0)
-  arel!
-  aws-sdk (~> 2)
+  aws-sdk-s3
   azure-storage
   backburner
   bcrypt (~> 3.1.11)
@@ -492,43 +515,44 @@ DEPENDENCIES
   blade-sauce_labs_plugin
   bootsnap (>= 1.1.0)
   byebug
-  capybara (~> 2.13)
+  capybara (>= 2.15)
+  chromedriver-helper
   coffee-rails
-  dalli (>= 2.2.1)
+  connection_pool
+  dalli
   delayed_job
   delayed_job_active_record
-  em-hiredis
-  erubis (~> 2.7.0)
-  google-cloud-storage (~> 1.3)
+  ffi (<= 1.9.21)
+  google-cloud-storage (~> 1.11)
   hiredis
-  jquery-rails
+  image_processing (~> 1.2)
   json (>= 2.0.0)
   kindlerb (~> 1.2.0)
   libxml-ruby
   listen (>= 3.0.5, < 3.2)
-  mini_magick
   minitest-bisect
-  mocha (~> 0.14)
-  mysql2 (>= 0.4.4)
-  nokogiri (>= 1.6.8)
+  mocha
+  mysql2 (>= 0.4.10)
+  nokogiri (>= 1.8.1)
   pg (>= 0.18.0)
-  psych (~> 2.0)
+  psych (~> 3.0)
   puma
-  qu-redis
   que
   queue_classic!
+  qunit-selenium
   racc (>= 1.4.6)
   rack-cache (~> 1.2)
   rails!
   rake (>= 11.1)
   rb-inotify!
   redcarpet (~> 3.2.3)
-  redis
+  redis (~> 4.0)
+  redis-namespace
   resque
   resque-scheduler
   rubocop (>= 0.47)
-  sass-rails!
-  sdoc!
+  sass-rails
+  sdoc (~> 1.0)
   sequel
   sidekiq
   sneakers
@@ -536,6 +560,7 @@ DEPENDENCIES
   sqlite3 (~> 1.3.6)
   stackprof
   sucker_punch
+  thor!
   turbolinks (~> 5)
   tzinfo-data
   uglifier (>= 1.3.0)
@@ -544,4 +569,4 @@ DEPENDENCIES
   websocket-client-simple!
 
 BUNDLED WITH
-   1.15.4
+   1.16.1
diff --git a/MIT-LICENSE b/MIT-LICENSE
index 6b3cead1a7..8f769c0767 100644
--- a/MIT-LICENSE
+++ b/MIT-LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2005-2017 David Heinemeier Hansson
+Copyright (c) 2005-2018 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/RAILS_VERSION b/RAILS_VERSION
index d5ebf861d3..747766c587 100644
--- a/RAILS_VERSION
+++ b/RAILS_VERSION
@@ -1 +1 @@
-5.2.0.alpha
+6.0.0.alpha
diff --git a/README.md b/README.md
index 030dd405cb..c7ecaf15cf 100644
--- a/README.md
+++ b/README.md
@@ -1,48 +1,55 @@
 # Welcome to Rails
 
+## What's Rails
+
 Rails is a web-application framework that includes everything needed to
 create database-backed web applications according to the
 [Model-View-Controller (MVC)](http://en.wikipedia.org/wiki/Model-view-controller)
 pattern.
 
 Understanding the MVC pattern is key to understanding Rails. MVC divides your
-application into three layers, each with a specific responsibility.
+application into three layers: Model, View, and Controller, each with a specific responsibility.
+
+## Model layer
 
-The _Model layer_ represents your domain model (such as Account, Product,
-Person, Post, etc.) and encapsulates the business logic that is specific to
+The _**Model layer**_ represents the domain model (such as Account, Product,
+Person, Post, etc.) and encapsulates the business logic specific to
 your application. In Rails, database-backed model classes are derived from
-`ActiveRecord::Base`. Active Record allows you to present the data from
+`ActiveRecord::Base`. [Active Record](activerecord/README.rdoc) allows you to present the data from
 database rows as objects and embellish these data objects with business logic
-methods. You can read more about Active Record in its [README](activerecord/README.rdoc).
+methods.
 Although most Rails models are backed by a database, models can also be ordinary
 Ruby classes, or Ruby classes that implement a set of interfaces as provided by
-the Active Model module. You can read more about Active Model in its [README](activemodel/README.rdoc).
+the [Active Model](activemodel/README.rdoc) module.
+
+## Controller layer
 
-The _Controller layer_ is responsible for handling incoming HTTP requests and
+The _**Controller layer**_ is responsible for handling incoming HTTP requests and
 providing a suitable response. Usually this means returning HTML, but Rails controllers
 can also generate XML, JSON, PDFs, mobile-specific views, and more. Controllers load and
 manipulate models, and render view templates in order to generate the appropriate HTTP response.
 In Rails, incoming requests are routed by Action Dispatch to an appropriate controller, and
 controller classes are derived from `ActionController::Base`. Action Dispatch and Action Controller
-are bundled together in Action Pack. You can read more about Action Pack in its
-[README](actionpack/README.rdoc).
+are bundled together in [Action Pack](actionpack/README.rdoc).
 
-The _View layer_ is composed of "templates" that are responsible for providing
+## View layer
+
+The _**View layer**_ is composed of "templates" that are responsible for providing
 appropriate representations of your application's resources. Templates can
 come in a variety of formats, but most view templates are HTML with embedded
 Ruby code (ERB files). Views are typically rendered to generate a controller response,
-or to generate the body of an email. In Rails, View generation is handled by Action View.
-You can read more about Action View in its [README](actionview/README.rdoc).
+or to generate the body of an email. In Rails, View generation is handled by [Action View](actionview/README.rdoc).
+
+## Frameworks and libraries
 
-Active Record, Active Model, Action Pack, and Action View can each be used independently outside Rails.
-In addition to that, Rails also comes with Action Mailer ([README](actionmailer/README.rdoc)), a library
-to generate and send emails; Active Job ([README](activejob/README.md)), a
+[Active Record](activerecord/README.rdoc), [Active Model](activemodel/README.rdoc), [Action Pack](actionpack/README.rdoc), and [Action View](actionview/README.rdoc) can each be used independently outside Rails.
+In addition to that, Rails also comes with [Action Mailer](actionmailer/README.rdoc), a library
+to generate and send emails; [Active Job](activejob/README.md), a
 framework for declaring jobs and making them run on a variety of queueing
-backends; Action Cable ([README](actioncable/README.md)), a framework to
-integrate WebSockets with a Rails application;
-Active Storage ([README](activestorage/README.md)), a library to attach cloud
+backends; [Action Cable](actioncable/README.md), a framework to
+integrate WebSockets with a Rails application; [Active Storage](activestorage/README.md), a library to attach cloud
 and local files to Rails applications;
-and Active Support ([README](activesupport/README.rdoc)), a collection
+and [Active Support](activesupport/README.rdoc), a collection
 of utility classes and standard library extensions that are useful for Rails,
 and may also be used independently outside Rails.
 
@@ -65,7 +72,7 @@ and may also be used independently outside Rails.
 
    Run with `--help` or `-h` for options.
 
-4. Using a browser, go to `http://localhost:3000` and you'll see:
+4. Go to `http://localhost:3000` and you'll see:
 "Yay! You’re on Rails!"
 
 5. Follow the guidelines to start developing your application. You may find
diff --git a/RELEASING_RAILS.md b/RELEASING_RAILS.md
index 3ff28c29f5..287dd4fa12 100644
--- a/RELEASING_RAILS.md
+++ b/RELEASING_RAILS.md
@@ -14,14 +14,14 @@ Today is mostly coordination tasks. Here are the things you must do today:
 Do not release with a Red CI. You can find the CI status here:
 
 ```
-http://travis-ci.org/rails/rails
+https://travis-ci.org/rails/rails
 ```
 
 ### Is Sam Ruby happy? If not, make him happy.
 
 Sam Ruby keeps a [test suite](https://github.com/rubys/awdwr) that makes
 sure the code samples in his book
-([Agile Web Development with Rails](https://pragprog.com/titles/rails5/agile-web-development-with-rails-5th-edition))
+([Agile Web Development with Rails](https://pragprog.com/book/rails51/agile-web-development-with-rails-51))
 all work. These are valuable system tests
 for Rails. You can check the status of these tests here:
 
@@ -141,7 +141,7 @@ lists where you should announce:
 Use Markdown format for your announcement. Remember to ask people to report
 issues with the release candidate to the rails-core mailing list.
 
-NOTE: For patch releases there's a `rake announce` task to generate the release
+NOTE: For patch releases, there's a `rake announce` task to generate the release
 post. It supports multiple patch releases too:
 
 ```
@@ -157,7 +157,7 @@ break existing applications.
 If you used Markdown format for your email, you can just paste it into the
 blog.
 
-* http://weblog.rubyonrails.org
+* https://weblog.rubyonrails.org
 
 ### Post the announcement to the Rails Twitter account.
 
diff --git a/actioncable/.gitignore b/actioncable/.gitignore
index 0a04b29786..f514e58c16 100644
--- a/actioncable/.gitignore
+++ b/actioncable/.gitignore
@@ -1,2 +1,2 @@
-/lib/assets/compiled
-/tmp
+/lib/assets/compiled/
+/tmp/
diff --git a/actioncable/CHANGELOG.md b/actioncable/CHANGELOG.md
index 560ee89846..959943016f 100644
--- a/actioncable/CHANGELOG.md
+++ b/actioncable/CHANGELOG.md
@@ -1,26 +1,6 @@
-*   Hash long stream identifiers when using PostgreSQL adapter.
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
-    PostgreSQL has a limit on identifiers length (63 chars, [docs](https://www.postgresql.org/docs/current/static/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS)).
-    Provided fix minifies identifiers longer than 63 chars by hashing them with SHA1.
+    *Jeremy Daer*
 
-    Fixes #28751.
 
-    *Vladimir Dementyev*
-
-*   Action Cable's `redis` adapter allows for other common redis-rb options (`host`, `port`, `db`, `password`) in cable.yml.
-
-    Previously, it accepts only a [redis:// url](https://www.iana.org/assignments/uri-schemes/prov/redis) as an option.
-    While we can add all of these options to the `url` itself, it is not explicitly documented. This alternative setup
-    is shown as the first example in the [Redis rubygem](https://github.com/redis/redis-rb#getting-started), which
-    makes this set of options as sensible as using just the `url`.
-
-    *Marc Rendl Ignacio*
-
-*   Action Cable socket errors are now logged to the console
-
-    Previously any socket errors were ignored and this made it hard to diagnose socket issues (e.g. as discussed in #28362).
-
-    *Edward Poot*
-
-
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/actioncable/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/actioncable/CHANGELOG.md) for previous changes.
diff --git a/actioncable/MIT-LICENSE b/actioncable/MIT-LICENSE
index 1a0e653b69..a42759f024 100644
--- a/actioncable/MIT-LICENSE
+++ b/actioncable/MIT-LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2015-2017 Basecamp, LLC
+Copyright (c) 2015-2018 Basecamp, LLC
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/actioncable/README.md b/actioncable/README.md
index a060e8938e..a05ef1dd20 100644
--- a/actioncable/README.md
+++ b/actioncable/README.md
@@ -446,7 +446,7 @@ The WebSocket server doesn't have access to the session, but it has access to th
 
 ## Dependencies
 
-Action Cable provides a subscription adapter interface to process its pubsub internals. By default, asynchronous, inline, PostgreSQL, evented Redis, and non-evented Redis adapters are included. The default adapter in new Rails applications is the asynchronous (`async`) adapter. To create your own adapter, you can look at `ActionCable::SubscriptionAdapter::Base` for all methods that must be implemented, and any of the adapters included within Action Cable as example implementations.
+Action Cable provides a subscription adapter interface to process its pubsub internals. By default, asynchronous, inline, PostgreSQL, and Redis adapters are included. The default adapter in new Rails applications is the asynchronous (`async`) adapter. To create your own adapter, you can look at `ActionCable::SubscriptionAdapter::Base` for all methods that must be implemented, and any of the adapters included within Action Cable as example implementations.
 
 The Ruby side of things is built on top of [websocket-driver](https://github.com/faye/websocket-driver-ruby), [nio4r](https://github.com/celluloid/nio4r), and [concurrent-ruby](https://github.com/ruby-concurrency/concurrent-ruby).
 
@@ -454,9 +454,9 @@ The Ruby side of things is built on top of [websocket-driver](https://github.com
 ## Deployment
 
 Action Cable is powered by a combination of WebSockets and threads. All of the
-connection management is handled internally by utilizing Ruby’s native thread
+connection management is handled internally by utilizing Ruby's native thread
 support, which means you can use all your regular Rails models with no problems
-as long as you haven’t committed any thread-safety sins.
+as long as you haven't committed any thread-safety sins.
 
 The Action Cable server does _not_ need to be a multi-threaded application server.
 This is because Action Cable uses the [Rack socket hijacking API](http://www.rubydoc.info/github/rack/rack/file/SPEC#Hijacking)
@@ -558,7 +558,7 @@ API documentation is at:
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/actioncable/actioncable.gemspec b/actioncable/actioncable.gemspec
index b5b98f1a6b..d946d0797f 100644
--- a/actioncable/actioncable.gemspec
+++ b/actioncable/actioncable.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "WebSocket framework for Rails."
   s.description = "Structure many real-time application concerns into channels over a single WebSocket connection."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
@@ -28,5 +28,5 @@ Gem::Specification.new do |s|
   s.add_dependency "actionpack", version
 
   s.add_dependency "nio4r",            "~> 2.0"
-  s.add_dependency "websocket-driver", "~> 0.6.1"
+  s.add_dependency "websocket-driver", ">= 0.6.1"
 end
diff --git a/actioncable/lib/action_cable.rb b/actioncable/lib/action_cable.rb
index bd828b2d0f..e7456e3c1b 100644
--- a/actioncable/lib/action_cable.rb
+++ b/actioncable/lib/action_cable.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 #--
-# Copyright (c) 2015-2017 Basecamp, LLC
+# Copyright (c) 2015-2018 Basecamp, LLC
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the
@@ -25,7 +25,7 @@
 
 require "active_support"
 require "active_support/rails"
-require_relative "action_cable/version"
+require "action_cable/version"
 
 module ActionCable
   extend ActiveSupport::Autoload
diff --git a/actioncable/lib/action_cable/channel/broadcasting.rb b/actioncable/lib/action_cable/channel/broadcasting.rb
index acc791817b..9a96720f4a 100644
--- a/actioncable/lib/action_cable/channel/broadcasting.rb
+++ b/actioncable/lib/action_cable/channel/broadcasting.rb
@@ -9,7 +9,7 @@ module ActionCable
 
       delegate :broadcasting_for, to: :class
 
-      class_methods do
+      module ClassMethods
         # Broadcast a hash to a unique broadcasting for this <tt>model</tt> in this channel.
         def broadcast_to(model, message)
           ActionCable.server.broadcast(broadcasting_for([ channel_name, model ]), message)
diff --git a/actioncable/lib/action_cable/channel/callbacks.rb b/actioncable/lib/action_cable/channel/callbacks.rb
index 4223c0d996..e4cb19b26a 100644
--- a/actioncable/lib/action_cable/channel/callbacks.rb
+++ b/actioncable/lib/action_cable/channel/callbacks.rb
@@ -13,7 +13,7 @@ module ActionCable
         define_callbacks :unsubscribe
       end
 
-      class_methods do
+      module ClassMethods
         def before_subscribe(*methods, &block)
           set_callback(:subscribe, :before, *methods, &block)
         end
diff --git a/actioncable/lib/action_cable/channel/naming.rb b/actioncable/lib/action_cable/channel/naming.rb
index 03a5dcd3a0..9c324a2a53 100644
--- a/actioncable/lib/action_cable/channel/naming.rb
+++ b/actioncable/lib/action_cable/channel/naming.rb
@@ -5,7 +5,7 @@ module ActionCable
     module Naming
       extend ActiveSupport::Concern
 
-      class_methods do
+      module ClassMethods
         # Returns the name of the channel, underscored, without the <tt>Channel</tt> ending.
         # If the channel is in a namespace, then the namespaces are represented by single
         # colon separators in the channel name.
diff --git a/actioncable/lib/action_cable/connection/base.rb b/actioncable/lib/action_cable/connection/base.rb
index 84053db9fd..11a1f1a5e8 100644
--- a/actioncable/lib/action_cable/connection/base.rb
+++ b/actioncable/lib/action_cable/connection/base.rb
@@ -136,13 +136,10 @@ module ActionCable
         send_async :handle_close
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
+      private
         attr_reader :websocket
         attr_reader :message_buffer
 
-      private
         # The request that initiated the WebSocket connection is available here. This gives access to the environment, cookies, etc.
         def request # :doc:
           @request ||= begin
diff --git a/actioncable/lib/action_cable/connection/client_socket.rb b/actioncable/lib/action_cable/connection/client_socket.rb
index ba33c8b982..4b1964c4ae 100644
--- a/actioncable/lib/action_cable/connection/client_socket.rb
+++ b/actioncable/lib/action_cable/connection/client_socket.rb
@@ -21,7 +21,7 @@ module ActionCable
         return true if env["HTTP_X_FORWARDED_PROTO"] == "https"
         return true if env["rack.url_scheme"] == "https"
 
-        return false
+        false
       end
 
       CONNECTING = 0
@@ -83,7 +83,7 @@ module ActionCable
         when Numeric then @driver.text(message.to_s)
         when String  then @driver.text(message)
         when Array   then @driver.binary(message)
-          else false
+        else false
         end
       end
 
diff --git a/actioncable/lib/action_cable/connection/identification.rb b/actioncable/lib/action_cable/connection/identification.rb
index 4b5f9ca115..cc544685dd 100644
--- a/actioncable/lib/action_cable/connection/identification.rb
+++ b/actioncable/lib/action_cable/connection/identification.rb
@@ -11,7 +11,7 @@ module ActionCable
         class_attribute :identifiers, default: Set.new
       end
 
-      class_methods do
+      module ClassMethods
         # Mark a key as being a connection identifier index that can then be used to find the specific connection again later.
         # Common identifiers are current_user and current_account, but could be anything, really.
         #
diff --git a/actioncable/lib/action_cable/connection/message_buffer.rb b/actioncable/lib/action_cable/connection/message_buffer.rb
index f151a47072..965841b67e 100644
--- a/actioncable/lib/action_cable/connection/message_buffer.rb
+++ b/actioncable/lib/action_cable/connection/message_buffer.rb
@@ -30,13 +30,10 @@ module ActionCable
         receive_buffered_messages
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
+      private
         attr_reader :connection
         attr_reader :buffered_messages
 
-      private
         def valid?(message)
           message.is_a?(String)
         end
diff --git a/actioncable/lib/action_cable/connection/subscriptions.rb b/actioncable/lib/action_cable/connection/subscriptions.rb
index faafd6d0a6..1ad8d05107 100644
--- a/actioncable/lib/action_cable/connection/subscriptions.rb
+++ b/actioncable/lib/action_cable/connection/subscriptions.rb
@@ -43,7 +43,7 @@ module ActionCable
 
       def remove(data)
         logger.info "Unsubscribing from channel: #{data['identifier']}"
-        remove_subscription subscriptions[data["identifier"]]
+        remove_subscription find(data)
       end
 
       def remove_subscription(subscription)
@@ -63,12 +63,8 @@ module ActionCable
         subscriptions.each { |id, channel| remove_subscription(channel) }
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-        attr_reader :connection, :subscriptions
-
       private
+        attr_reader :connection, :subscriptions
         delegate :logger, to: :connection
 
         def find(data)
diff --git a/actioncable/lib/action_cable/connection/web_socket.rb b/actioncable/lib/action_cable/connection/web_socket.rb
index 81233ace34..31f29fdd2f 100644
--- a/actioncable/lib/action_cable/connection/web_socket.rb
+++ b/actioncable/lib/action_cable/connection/web_socket.rb
@@ -34,9 +34,7 @@ module ActionCable
         websocket.rack_response
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
+      private
         attr_reader :websocket
     end
   end
diff --git a/actioncable/lib/action_cable/engine.rb b/actioncable/lib/action_cable/engine.rb
index c961f47342..53cbb597cd 100644
--- a/actioncable/lib/action_cable/engine.rb
+++ b/actioncable/lib/action_cable/engine.rb
@@ -2,7 +2,7 @@
 
 require "rails"
 require "action_cable"
-require_relative "helpers/action_cable_helper"
+require "action_cable/helpers/action_cable_helper"
 require "active_support/core_ext/hash/indifferent_access"
 
 module ActionCable
diff --git a/actioncable/lib/action_cable/gem_version.rb b/actioncable/lib/action_cable/gem_version.rb
index af8277d06e..cd1d9bccef 100644
--- a/actioncable/lib/action_cable/gem_version.rb
+++ b/actioncable/lib/action_cable/gem_version.rb
@@ -7,8 +7,8 @@ module ActionCable
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
     PRE   = "alpha"
 
diff --git a/actioncable/lib/action_cable/remote_connections.rb b/actioncable/lib/action_cable/remote_connections.rb
index a07a517092..283400d9e7 100644
--- a/actioncable/lib/action_cable/remote_connections.rb
+++ b/actioncable/lib/action_cable/remote_connections.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/module/redefine_method"
+
 module ActionCable
   # If you need to disconnect a given connection, you can go through the
   # RemoteConnections. You can find the connections you're looking for by
diff --git a/actioncable/lib/action_cable/server/base.rb b/actioncable/lib/action_cable/server/base.rb
index 6c6f6c2936..1ee03f6dfc 100644
--- a/actioncable/lib/action_cable/server/base.rb
+++ b/actioncable/lib/action_cable/server/base.rb
@@ -30,7 +30,7 @@ module ActionCable
         config.connection_class.call.new(self, env).process
       end
 
-      # Disconnect all the connections identified by `identifiers` on this server or any others via RemoteConnections.
+      # Disconnect all the connections identified by +identifiers+ on this server or any others via RemoteConnections.
       def disconnect(identifiers)
         remote_connections.where(identifiers).disconnect
       end
diff --git a/actioncable/lib/action_cable/server/configuration.rb b/actioncable/lib/action_cable/server/configuration.rb
index 82fed81a18..26209537df 100644
--- a/actioncable/lib/action_cable/server/configuration.rb
+++ b/actioncable/lib/action_cable/server/configuration.rb
@@ -25,13 +25,26 @@ module ActionCable
       # Also makes sure proper dependencies are required.
       def pubsub_adapter
         adapter = (cable.fetch("adapter") { "redis" })
+
+        # Require the adapter itself and give useful feedback about
+        #   1. Missing adapter gems and
+        #   2. Adapter gems' missing dependencies.
         path_to_adapter = "action_cable/subscription_adapter/#{adapter}"
         begin
           require path_to_adapter
-        rescue Gem::LoadError => e
-          raise Gem::LoadError, "Specified '#{adapter}' for Action Cable pubsub adapter, but the gem is not loaded. Add `gem '#{e.name}'` to your Gemfile (and ensure its version is at the minimum required by Action Cable)."
         rescue LoadError => e
-          raise LoadError, "Could not load '#{path_to_adapter}'. Make sure that the adapter in config/cable.yml is valid. If you use an adapter other than 'postgresql' or 'redis' add the necessary adapter gem to the Gemfile.", e.backtrace
+          # We couldn't require the adapter itself. Raise an exception that
+          # points out config typos and missing gems.
+          if e.path == path_to_adapter
+            # We can assume that a non-builtin adapter was specified, so it's
+            # either misspelled or missing from Gemfile.
+            raise e.class, "Could not load the '#{adapter}' Action Cable pubsub adapter. Ensure that the adapter is spelled correctly in config/cable.yml and that you've added the necessary adapter gem to your Gemfile.", e.backtrace
+
+          # Bubbled up from the adapter require. Prefix the exception message
+          # with some guidance about how to address it and reraise.
+          else
+            raise e.class, "Error loading the '#{adapter}' Action Cable pubsub adapter. Missing a gem it depends on? #{e.message}", e.backtrace
+          end
         end
 
         adapter = adapter.camelize
diff --git a/actioncable/lib/action_cable/subscription_adapter/async.rb b/actioncable/lib/action_cable/subscription_adapter/async.rb
index 96c18c4a2f..c9930299c7 100644
--- a/actioncable/lib/action_cable/subscription_adapter/async.rb
+++ b/actioncable/lib/action_cable/subscription_adapter/async.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "inline"
+require "action_cable/subscription_adapter/inline"
 
 module ActionCable
   module SubscriptionAdapter
diff --git a/actioncable/lib/action_cable/subscription_adapter/evented_redis.rb b/actioncable/lib/action_cable/subscription_adapter/evented_redis.rb
deleted file mode 100644
index 07774810ce..0000000000
--- a/actioncable/lib/action_cable/subscription_adapter/evented_redis.rb
+++ /dev/null
@@ -1,89 +0,0 @@
-# frozen_string_literal: true
-
-require "thread"
-
-gem "em-hiredis", "~> 0.3.0"
-gem "redis", "~> 3.0"
-require "em-hiredis"
-require "redis"
-
-EventMachine.epoll  if EventMachine.epoll?
-EventMachine.kqueue if EventMachine.kqueue?
-
-module ActionCable
-  module SubscriptionAdapter
-    class EventedRedis < Base # :nodoc:
-      prepend ChannelPrefix
-
-      @@mutex = Mutex.new
-
-      # Overwrite this factory method for EventMachine Redis connections if you want to use a different Redis connection library than EM::Hiredis.
-      # This is needed, for example, when using Makara proxies for distributed Redis.
-      cattr_accessor :em_redis_connector, default: ->(config) { EM::Hiredis.connect(config[:url]) }
-
-      # Overwrite this factory method for Redis connections if you want to use a different Redis connection library than Redis.
-      # This is needed, for example, when using Makara proxies for distributed Redis.
-      cattr_accessor :redis_connector, default: ->(config) { ::Redis.new(url: config[:url]) }
-
-      def initialize(*)
-        ActiveSupport::Deprecation.warn(<<-MSG.squish)
-          The "evented_redis" subscription adapter is deprecated and
-          will be removed in Rails 5.2. Please use the "redis" adapter
-          instead.
-        MSG
-
-        super
-        @redis_connection_for_broadcasts = @redis_connection_for_subscriptions = nil
-      end
-
-      def broadcast(channel, payload)
-        redis_connection_for_broadcasts.publish(channel, payload)
-      end
-
-      def subscribe(channel, message_callback, success_callback = nil)
-        redis_connection_for_subscriptions.pubsub.subscribe(channel, &message_callback).tap do |result|
-          result.callback { |reply| success_callback.call } if success_callback
-        end
-      end
-
-      def unsubscribe(channel, message_callback)
-        redis_connection_for_subscriptions.pubsub.unsubscribe_proc(channel, message_callback)
-      end
-
-      def shutdown
-        redis_connection_for_subscriptions.pubsub.close_connection
-        @redis_connection_for_subscriptions = nil
-      end
-
-      private
-        def redis_connection_for_subscriptions
-          ensure_reactor_running
-          @redis_connection_for_subscriptions || @server.mutex.synchronize do
-            @redis_connection_for_subscriptions ||= self.class.em_redis_connector.call(@server.config.cable).tap do |redis|
-              redis.on(:reconnect_failed) do
-                @logger.error "[ActionCable] Redis reconnect failed."
-              end
-
-              redis.on(:failed) do
-                @logger.error "[ActionCable] Redis connection has failed."
-              end
-            end
-          end
-        end
-
-        def redis_connection_for_broadcasts
-          @redis_connection_for_broadcasts || @server.mutex.synchronize do
-            @redis_connection_for_broadcasts ||= self.class.redis_connector.call(@server.config.cable)
-          end
-        end
-
-        def ensure_reactor_running
-          return if EventMachine.reactor_running? && EventMachine.reactor_thread
-          @@mutex.synchronize do
-            Thread.new { EventMachine.run } unless EventMachine.reactor_running?
-            Thread.pass until EventMachine.reactor_running? && EventMachine.reactor_thread
-          end
-        end
-    end
-  end
-end
diff --git a/actioncable/lib/action_cable/subscription_adapter/postgresql.rb b/actioncable/lib/action_cable/subscription_adapter/postgresql.rb
index a9c0949950..e384ea4afb 100644
--- a/actioncable/lib/action_cable/subscription_adapter/postgresql.rb
+++ b/actioncable/lib/action_cable/subscription_adapter/postgresql.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-gem "pg", "~> 0.18"
+gem "pg", ">= 0.18", "< 2.0"
 require "pg"
 require "thread"
 require "digest/sha1"
diff --git a/actioncable/lib/action_cable/subscription_adapter/redis.rb b/actioncable/lib/action_cable/subscription_adapter/redis.rb
index facea944ff..c28951608f 100644
--- a/actioncable/lib/action_cable/subscription_adapter/redis.rb
+++ b/actioncable/lib/action_cable/subscription_adapter/redis.rb
@@ -2,7 +2,7 @@
 
 require "thread"
 
-gem "redis", "~> 3.0"
+gem "redis", ">= 3", "< 5"
 require "redis"
 
 module ActionCable
@@ -76,7 +76,7 @@ module ActionCable
 
           def listen(conn)
             conn.without_reconnect do
-              original_client = conn.client
+              original_client = conn.respond_to?(:_client) ? conn._client : conn.client
 
               conn.subscribe("_action_cable_internal") do |on|
                 on.subscribe do |chan, count|
diff --git a/actioncable/lib/rails/generators/channel/channel_generator.rb b/actioncable/lib/rails/generators/channel/channel_generator.rb
index c3528370c6..427eef1f55 100644
--- a/actioncable/lib/rails/generators/channel/channel_generator.rb
+++ b/actioncable/lib/rails/generators/channel/channel_generator.rb
@@ -27,7 +27,7 @@ module Rails
 
       private
         def file_name
-          @_file_name ||= super.gsub(/_channel/i, "")
+          @_file_name ||= super.sub(/_channel\z/i, "")
         end
 
         # FIXME: Change these files to symlinks once RubyGems 2.5.0 is required.
diff --git a/actioncable/lib/rails/generators/channel/templates/application_cable/channel.rb b/actioncable/lib/rails/generators/channel/templates/application_cable/channel.rb.tt
index d672697283..d672697283 100644
--- a/actioncable/lib/rails/generators/channel/templates/application_cable/channel.rb
+++ b/actioncable/lib/rails/generators/channel/templates/application_cable/channel.rb.tt
diff --git a/actioncable/lib/rails/generators/channel/templates/application_cable/connection.rb b/actioncable/lib/rails/generators/channel/templates/application_cable/connection.rb.tt
index 0ff5442f47..0ff5442f47 100644
--- a/actioncable/lib/rails/generators/channel/templates/application_cable/connection.rb
+++ b/actioncable/lib/rails/generators/channel/templates/application_cable/connection.rb.tt
diff --git a/actioncable/lib/rails/generators/channel/templates/assets/cable.js b/actioncable/lib/rails/generators/channel/templates/assets/cable.js.tt
index 739aa5f022..739aa5f022 100644
--- a/actioncable/lib/rails/generators/channel/templates/assets/cable.js
+++ b/actioncable/lib/rails/generators/channel/templates/assets/cable.js.tt
diff --git a/actioncable/lib/rails/generators/channel/templates/assets/channel.coffee b/actioncable/lib/rails/generators/channel/templates/assets/channel.coffee.tt
index 5467811aba..5467811aba 100644
--- a/actioncable/lib/rails/generators/channel/templates/assets/channel.coffee
+++ b/actioncable/lib/rails/generators/channel/templates/assets/channel.coffee.tt
diff --git a/actioncable/lib/rails/generators/channel/templates/assets/channel.js b/actioncable/lib/rails/generators/channel/templates/assets/channel.js.tt
index ab0e68b11a..ab0e68b11a 100644
--- a/actioncable/lib/rails/generators/channel/templates/assets/channel.js
+++ b/actioncable/lib/rails/generators/channel/templates/assets/channel.js.tt
diff --git a/actioncable/lib/rails/generators/channel/templates/channel.rb b/actioncable/lib/rails/generators/channel/templates/channel.rb.tt
index 4bcfb2be4d..4bcfb2be4d 100644
--- a/actioncable/lib/rails/generators/channel/templates/channel.rb
+++ b/actioncable/lib/rails/generators/channel/templates/channel.rb.tt
diff --git a/actioncable/package.json b/actioncable/package.json
index acec1e2e9c..d9df46043d 100644
--- a/actioncable/package.json
+++ b/actioncable/package.json
@@ -1,6 +1,6 @@
 {
   "name": "actioncable",
-  "version": "5.2.0-alpha",
+  "version": "6.0.0-alpha",
   "description": "WebSocket framework for Ruby on Rails.",
   "main": "lib/assets/compiled/action_cable.js",
   "files": [
diff --git a/actioncable/test/channel/base_test.rb b/actioncable/test/channel/base_test.rb
index 866bd7c21b..3b8eb63975 100644
--- a/actioncable/test/channel/base_test.rb
+++ b/actioncable/test/channel/base_test.rb
@@ -97,12 +97,12 @@ class ActionCable::Channel::BaseTest < ActiveSupport::TestCase
     @channel.subscribe_to_channel
 
     assert @channel.room
-    assert @channel.subscribed?
+    assert_predicate @channel, :subscribed?
 
     @channel.unsubscribe_from_channel
 
-    assert ! @channel.room
-    assert ! @channel.subscribed?
+    assert_not @channel.room
+    assert_not_predicate @channel, :subscribed?
   end
 
   test "connection identifiers" do
diff --git a/actioncable/test/channel/stream_test.rb b/actioncable/test/channel/stream_test.rb
index eca06fe365..5c1f308f53 100644
--- a/actioncable/test/channel/stream_test.rb
+++ b/actioncable/test/channel/stream_test.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "test_helper"
+require "active_support/testing/method_call_assertions"
 require "stubs/test_connection"
 require "stubs/room"
 
@@ -53,13 +54,13 @@ module ActionCable::StreamTests
     test "streaming start and stop" do
       run_in_eventmachine do
         connection = TestConnection.new
-        connection.expects(:pubsub).returns mock().tap { |m| m.expects(:subscribe).with("test_room_1", kind_of(Proc), kind_of(Proc)).returns stub_everything(:pubsub) }
+        connection.pubsub.expects(:subscribe).with("test_room_1", kind_of(Proc), kind_of(Proc))
         channel = ChatChannel.new connection, "{id: 1}", id: 1
         channel.subscribe_to_channel
 
         wait_for_async
 
-        connection.expects(:pubsub).returns mock().tap { |m| m.expects(:unsubscribe) }
+        connection.pubsub.expects(:unsubscribe)
         channel.unsubscribe_from_channel
       end
     end
@@ -67,13 +68,14 @@ module ActionCable::StreamTests
     test "stream from non-string channel" do
       run_in_eventmachine do
         connection = TestConnection.new
-        connection.expects(:pubsub).returns mock().tap { |m| m.expects(:subscribe).with("channel", kind_of(Proc), kind_of(Proc)).returns stub_everything(:pubsub) }
+        connection.pubsub.expects(:subscribe).with("channel", kind_of(Proc), kind_of(Proc))
+
         channel = SymbolChannel.new connection, ""
         channel.subscribe_to_channel
 
         wait_for_async
 
-        connection.expects(:pubsub).returns mock().tap { |m| m.expects(:unsubscribe) }
+        connection.pubsub.expects(:unsubscribe)
         channel.unsubscribe_from_channel
       end
     end
@@ -81,7 +83,7 @@ module ActionCable::StreamTests
     test "stream_for" do
       run_in_eventmachine do
         connection = TestConnection.new
-        connection.expects(:pubsub).returns mock().tap { |m| m.expects(:subscribe).with("action_cable:stream_tests:chat:Room#1-Campfire", kind_of(Proc), kind_of(Proc)).returns stub_everything(:pubsub) }
+        connection.pubsub.expects(:subscribe).with("action_cable:stream_tests:chat:Room#1-Campfire", kind_of(Proc), kind_of(Proc))
 
         channel = ChatChannel.new connection, ""
         channel.subscribe_to_channel
@@ -143,6 +145,8 @@ module ActionCable::StreamTests
   end
 
   class StreamFromTest < ActionCable::TestCase
+    include ActiveSupport::Testing::MethodCallAssertions
+
     setup do
       @server = TestServer.new(subscription_adapter: ActionCable::SubscriptionAdapter::Async)
       @server.config.allowed_request_origins = %w( http://rubyonrails.com )
@@ -153,10 +157,11 @@ module ActionCable::StreamTests
         connection = open_connection
         subscribe_to connection, identifiers: { id: 1 }
 
-        connection.websocket.expects(:transmit)
-        @server.broadcast "test_room_1", { foo: "bar" }, { coder: DummyEncoder }
-        wait_for_async
-        wait_for_executor connection.server.worker_pool.executor
+        assert_called(connection.websocket, :transmit) do
+          @server.broadcast "test_room_1", { foo: "bar" }, { coder: DummyEncoder }
+          wait_for_async
+          wait_for_executor connection.server.worker_pool.executor
+        end
       end
     end
 
@@ -167,7 +172,7 @@ module ActionCable::StreamTests
 
         @server.broadcast "channel", {}
         wait_for_async
-        refute Thread.current[:ran_callback], "User callback was not run through the worker pool"
+        assert_not Thread.current[:ran_callback], "User callback was not run through the worker pool"
       end
     end
 
@@ -175,10 +180,10 @@ module ActionCable::StreamTests
       run_in_eventmachine do
         connection = open_connection
         expected = { "identifier" => { "channel" => MultiChatChannel.name }.to_json, "type" => "confirm_subscription" }
-        connection.websocket.expects(:transmit).with(expected.to_json)
-        receive(connection, command: "subscribe", channel: MultiChatChannel.name, identifiers: {})
-
-        wait_for_async
+        assert_called(connection.websocket, :transmit, [expected.to_json]) do
+          receive(connection, command: "subscribe", channel: MultiChatChannel.name, identifiers: {})
+          wait_for_async
+        end
       end
     end
 
@@ -192,15 +197,15 @@ module ActionCable::StreamTests
 
         Connection.new(@server, env).tap do |connection|
           connection.process
-          assert connection.websocket.possible?
+          assert_predicate connection.websocket, :possible?
 
           wait_for_async
-          assert connection.websocket.alive?
+          assert_predicate connection.websocket, :alive?
         end
       end
 
       def receive(connection, command:, identifiers:, channel: "ActionCable::StreamTests::ChatChannel")
-        identifier = JSON.generate(channel: channel, **identifiers)
+        identifier = JSON.generate(identifiers.merge(channel: channel))
         connection.dispatch_websocket_message JSON.generate(command: command, identifier: identifier)
         wait_for_async
       end
diff --git a/actioncable/test/client_test.rb b/actioncable/test/client_test.rb
index 56b3ef143b..92fe59c803 100644
--- a/actioncable/test/client_test.rb
+++ b/actioncable/test/client_test.rb
@@ -7,6 +7,7 @@ require "websocket-client-simple"
 require "json"
 
 require "active_support/hash_with_indifferent_access"
+require "active_support/testing/method_call_assertions"
 
 ####
 # 😷 Warning suppression 😷
@@ -27,6 +28,8 @@ WebSocket::Frame::Data.prepend Module.new {
 ####
 
 class ClientTest < ActionCable::TestCase
+  include ActiveSupport::Testing::MethodCallAssertions
+
   WAIT_WHEN_EXPECTING_EVENT = 2
   WAIT_WHEN_NOT_EXPECTING_EVENT = 0.5
 
@@ -289,9 +292,10 @@ class ClientTest < ActionCable::TestCase
       subscriptions = app.connections.first.subscriptions.send(:subscriptions)
       assert_not_equal 0, subscriptions.size, "Missing EchoChannel subscription"
       channel = subscriptions.first[1]
-      channel.expects(:unsubscribed)
-      c.close
-      sleep 0.1 # Data takes a moment to process
+      assert_called(channel, :unsubscribed) do
+        c.close
+        sleep 0.1 # Data takes a moment to process
+      end
 
       # All data is removed: No more connection or subscription information!
       assert_equal(0, app.connections.count)
@@ -307,7 +311,7 @@ class ClientTest < ActionCable::TestCase
 
       ActionCable.server.restart
       c.wait_for_close
-      assert c.closed?
+      assert_predicate c, :closed?
     end
   end
 end
diff --git a/actioncable/test/connection/authorization_test.rb b/actioncable/test/connection/authorization_test.rb
index 7d039336b8..be41d510ff 100644
--- a/actioncable/test/connection/authorization_test.rb
+++ b/actioncable/test/connection/authorization_test.rb
@@ -1,9 +1,12 @@
 # frozen_string_literal: true
 
 require "test_helper"
+require "active_support/testing/method_call_assertions"
 require "stubs/test_server"
 
 class ActionCable::Connection::AuthorizationTest < ActionCable::TestCase
+  include ActiveSupport::Testing::MethodCallAssertions
+
   class Connection < ActionCable::Connection::Base
     attr_reader :websocket
 
@@ -25,9 +28,9 @@ class ActionCable::Connection::AuthorizationTest < ActionCable::TestCase
         "HTTP_HOST" => "localhost", "HTTP_ORIGIN" => "http://rubyonrails.com"
 
       connection = Connection.new(server, env)
-      connection.websocket.expects(:close)
-
-      connection.process
+      assert_called(connection.websocket, :close) do
+        connection.process
+      end
     end
   end
 end
diff --git a/actioncable/test/connection/base_test.rb b/actioncable/test/connection/base_test.rb
index 99488e38c8..9e480ab60d 100644
--- a/actioncable/test/connection/base_test.rb
+++ b/actioncable/test/connection/base_test.rb
@@ -3,8 +3,11 @@
 require "test_helper"
 require "stubs/test_server"
 require "active_support/core_ext/object/json"
+require "active_support/testing/method_call_assertions"
 
 class ActionCable::Connection::BaseTest < ActionCable::TestCase
+  include ActiveSupport::Testing::MethodCallAssertions
+
   class Connection < ActionCable::Connection::Base
     attr_reader :websocket, :subscriptions, :message_buffer, :connected
 
@@ -39,10 +42,10 @@ class ActionCable::Connection::BaseTest < ActionCable::TestCase
       connection = open_connection
       connection.process
 
-      assert connection.websocket.possible?
+      assert_predicate connection.websocket, :possible?
 
       wait_for_async
-      assert connection.websocket.alive?
+      assert_predicate connection.websocket, :alive?
     end
   end
 
@@ -59,11 +62,12 @@ class ActionCable::Connection::BaseTest < ActionCable::TestCase
     run_in_eventmachine do
       connection = open_connection
 
-      connection.websocket.expects(:transmit).with({ type: "welcome" }.to_json)
-      connection.message_buffer.expects(:process!)
-
-      connection.process
-      wait_for_async
+      assert_called_with(connection.websocket, :transmit, [{ type: "welcome" }.to_json]) do
+        assert_called(connection.message_buffer, :process!) do
+          connection.process
+          wait_for_async
+        end
+      end
 
       assert_equal [ connection ], @server.connections
       assert connection.connected
@@ -76,14 +80,14 @@ class ActionCable::Connection::BaseTest < ActionCable::TestCase
       connection.process
 
       # Setup the connection
-      connection.server.stubs(:timer).returns(true)
       connection.send :handle_open
       assert connection.connected
 
-      connection.subscriptions.expects(:unsubscribe_from_all)
-      connection.send :handle_close
+      assert_called(connection.subscriptions, :unsubscribe_from_all) do
+        connection.send :handle_close
+      end
 
-      assert ! connection.connected
+      assert_not connection.connected
       assert_equal [], @server.connections
     end
   end
@@ -95,7 +99,7 @@ class ActionCable::Connection::BaseTest < ActionCable::TestCase
 
       statistics = connection.statistics
 
-      assert statistics[:identifier].blank?
+      assert_predicate statistics[:identifier], :blank?
       assert_kind_of Time, statistics[:started_at]
       assert_equal [], statistics[:subscriptions]
     end
@@ -106,8 +110,9 @@ class ActionCable::Connection::BaseTest < ActionCable::TestCase
       connection = open_connection
       connection.process
 
-      connection.websocket.expects(:close)
-      connection.close
+      assert_called(connection.websocket, :close) do
+        connection.close
+      end
     end
   end
 
diff --git a/actioncable/test/connection/client_socket_test.rb b/actioncable/test/connection/client_socket_test.rb
index 2051216010..da72501c8e 100644
--- a/actioncable/test/connection/client_socket_test.rb
+++ b/actioncable/test/connection/client_socket_test.rb
@@ -2,8 +2,11 @@
 
 require "test_helper"
 require "stubs/test_server"
+require "active_support/testing/method_call_assertions"
 
 class ActionCable::Connection::ClientSocketTest < ActionCable::TestCase
+  include ActiveSupport::Testing::MethodCallAssertions
+
   class Connection < ActionCable::Connection::Base
     attr_reader :connected, :websocket, :errors
 
@@ -41,9 +44,10 @@ class ActionCable::Connection::ClientSocketTest < ActionCable::TestCase
       # Internal hax = :(
       client = connection.websocket.send(:websocket)
       client.instance_variable_get("@stream").expects(:write).raises("foo")
-      client.expects(:client_gone).never
 
-      client.write("boo")
+      assert_not_called(client, :client_gone) do
+        client.write("boo")
+      end
       assert_equal %w[ foo ], connection.errors
     end
   end
@@ -67,9 +71,9 @@ class ActionCable::Connection::ClientSocketTest < ActionCable::TestCase
       env = Rack::MockRequest.env_for "/test",
         "HTTP_CONNECTION" => "upgrade", "HTTP_UPGRADE" => "websocket",
         "HTTP_HOST" => "localhost", "HTTP_ORIGIN" => "http://rubyonrails.com"
-      io = \
+      io, client_io = \
         begin
-          Socket.pair(Socket::AF_UNIX, Socket::SOCK_STREAM, 0).first
+          Socket.pair(Socket::AF_UNIX, Socket::SOCK_STREAM, 0)
         rescue
           StringIO.new
         end
@@ -77,6 +81,14 @@ class ActionCable::Connection::ClientSocketTest < ActionCable::TestCase
 
       Connection.new(@server, env).tap do |connection|
         connection.process
+        if client_io
+          # Make sure server returns handshake response
+          Timeout.timeout(1) do
+            loop do
+              break if client_io.readline == "\r\n"
+            end
+          end
+        end
         connection.send :handle_open
         assert connection.connected
       end
diff --git a/actioncable/test/connection/identifier_test.rb b/actioncable/test/connection/identifier_test.rb
index 6b6c8cd31a..204197c2a7 100644
--- a/actioncable/test/connection/identifier_test.rb
+++ b/actioncable/test/connection/identifier_test.rb
@@ -1,10 +1,13 @@
 # frozen_string_literal: true
 
 require "test_helper"
+require "active_support/testing/method_call_assertions"
 require "stubs/test_server"
 require "stubs/user"
 
 class ActionCable::Connection::IdentifierTest < ActionCable::TestCase
+  include ActiveSupport::Testing::MethodCallAssertions
+
   class Connection < ActionCable::Connection::Base
     identified_by :current_user
     attr_reader :websocket
@@ -18,52 +21,49 @@ class ActionCable::Connection::IdentifierTest < ActionCable::TestCase
 
   test "connection identifier" do
     run_in_eventmachine do
-      open_connection_with_stubbed_pubsub
+      open_connection
       assert_equal "User#lifo", @connection.connection_identifier
     end
   end
 
   test "should subscribe to internal channel on open and unsubscribe on close" do
     run_in_eventmachine do
-      pubsub = mock("pubsub_adapter")
-      pubsub.expects(:subscribe).with("action_cable/User#lifo", kind_of(Proc))
-      pubsub.expects(:unsubscribe).with("action_cable/User#lifo", kind_of(Proc))
-
       server = TestServer.new
-      server.stubs(:pubsub).returns(pubsub)
 
-      open_connection server: server
+      server.pubsub.expects(:subscribe)
+        .with("action_cable/User#lifo", kind_of(Proc))
+      server.pubsub.expects(:unsubscribe)
+        .with("action_cable/User#lifo", kind_of(Proc))
+
+      open_connection(server)
       close_connection
     end
   end
 
   test "processing disconnect message" do
     run_in_eventmachine do
-      open_connection_with_stubbed_pubsub
+      open_connection
 
-      @connection.websocket.expects(:close)
-      @connection.process_internal_message "type" => "disconnect"
+      assert_called(@connection.websocket, :close) do
+        @connection.process_internal_message "type" => "disconnect"
+      end
     end
   end
 
   test "processing invalid message" do
     run_in_eventmachine do
-      open_connection_with_stubbed_pubsub
+      open_connection
 
-      @connection.websocket.expects(:close).never
-      @connection.process_internal_message "type" => "unknown"
+      assert_not_called(@connection.websocket, :close) do
+        @connection.process_internal_message "type" => "unknown"
+      end
     end
   end
 
   private
-    def open_connection_with_stubbed_pubsub
-      server = TestServer.new
-      server.stubs(:adapter).returns(stub_everything("adapter"))
-
-      open_connection server: server
-    end
+    def open_connection(server = nil)
+      server ||= TestServer.new
 
-    def open_connection(server:)
       env = Rack::MockRequest.env_for "/test", "HTTP_HOST" => "localhost", "HTTP_CONNECTION" => "upgrade", "HTTP_UPGRADE" => "websocket"
       @connection = Connection.new(server, env)
 
diff --git a/actioncable/test/connection/multiple_identifiers_test.rb b/actioncable/test/connection/multiple_identifiers_test.rb
index 7f90cb3876..51716410b2 100644
--- a/actioncable/test/connection/multiple_identifiers_test.rb
+++ b/actioncable/test/connection/multiple_identifiers_test.rb
@@ -16,20 +16,15 @@ class ActionCable::Connection::MultipleIdentifiersTest < ActionCable::TestCase
 
   test "multiple connection identifiers" do
     run_in_eventmachine do
-      open_connection_with_stubbed_pubsub
+      open_connection
+
       assert_equal "Room#my-room:User#lifo", @connection.connection_identifier
     end
   end
 
   private
-    def open_connection_with_stubbed_pubsub
+    def open_connection
       server = TestServer.new
-      server.stubs(:pubsub).returns(stub_everything("pubsub"))
-
-      open_connection server: server
-    end
-
-    def open_connection(server:)
       env = Rack::MockRequest.env_for "/test", "HTTP_HOST" => "localhost", "HTTP_CONNECTION" => "upgrade", "HTTP_UPGRADE" => "websocket"
       @connection = Connection.new(server, env)
 
diff --git a/actioncable/test/connection/stream_test.rb b/actioncable/test/connection/stream_test.rb
index b0419b0994..1e1466af31 100644
--- a/actioncable/test/connection/stream_test.rb
+++ b/actioncable/test/connection/stream_test.rb
@@ -1,9 +1,12 @@
 # frozen_string_literal: true
 
 require "test_helper"
+require "active_support/testing/method_call_assertions"
 require "stubs/test_server"
 
 class ActionCable::Connection::StreamTest < ActionCable::TestCase
+  include ActiveSupport::Testing::MethodCallAssertions
+
   class Connection < ActionCable::Connection::Base
     attr_reader :connected, :websocket, :errors
 
@@ -42,9 +45,10 @@ class ActionCable::Connection::StreamTest < ActionCable::TestCase
         # Internal hax = :(
         client = connection.websocket.send(:websocket)
         client.instance_variable_get("@stream").instance_variable_get("@rack_hijack_io").expects(:write).raises(closed_exception, "foo")
-        client.expects(:client_gone)
 
-        client.write("boo")
+        assert_called(client, :client_gone) do
+          client.write("boo")
+        end
         assert_equal [], connection.errors
       end
     end
diff --git a/actioncable/test/connection/string_identifier_test.rb b/actioncable/test/connection/string_identifier_test.rb
index 4cb58e7fd0..f7019b926a 100644
--- a/actioncable/test/connection/string_identifier_test.rb
+++ b/actioncable/test/connection/string_identifier_test.rb
@@ -18,22 +18,17 @@ class ActionCable::Connection::StringIdentifierTest < ActionCable::TestCase
 
   test "connection identifier" do
     run_in_eventmachine do
-      open_connection_with_stubbed_pubsub
+      open_connection
+
       assert_equal "random-string", @connection.connection_identifier
     end
   end
 
   private
-    def open_connection_with_stubbed_pubsub
-      @server = TestServer.new
-      @server.stubs(:pubsub).returns(stub_everything("pubsub"))
-
-      open_connection
-    end
-
     def open_connection
+      server = TestServer.new
       env = Rack::MockRequest.env_for "/test", "HTTP_HOST" => "localhost", "HTTP_CONNECTION" => "upgrade", "HTTP_UPGRADE" => "websocket"
-      @connection = Connection.new(@server, env)
+      @connection = Connection.new(server, env)
 
       @connection.process
       @connection.send :on_open
diff --git a/actioncable/test/connection/subscriptions_test.rb b/actioncable/test/connection/subscriptions_test.rb
index 149a40604a..7bc8c4241c 100644
--- a/actioncable/test/connection/subscriptions_test.rb
+++ b/actioncable/test/connection/subscriptions_test.rb
@@ -1,8 +1,11 @@
 # frozen_string_literal: true
 
 require "test_helper"
+require "active_support/testing/method_call_assertions"
 
 class ActionCable::Connection::SubscriptionsTest < ActionCable::TestCase
+  include ActiveSupport::Testing::MethodCallAssertions
+
   class Connection < ActionCable::Connection::Base
     attr_reader :websocket
 
@@ -45,7 +48,7 @@ class ActionCable::Connection::SubscriptionsTest < ActionCable::TestCase
       setup_connection
 
       @subscriptions.execute_command "command" => "subscribe"
-      assert @subscriptions.identifiers.empty?
+      assert_empty @subscriptions.identifiers
     end
   end
 
@@ -55,10 +58,12 @@ class ActionCable::Connection::SubscriptionsTest < ActionCable::TestCase
       subscribe_to_chat_channel
 
       channel = subscribe_to_chat_channel
-      channel.expects(:unsubscribe_from_channel)
 
-      @subscriptions.execute_command "command" => "unsubscribe", "identifier" => @chat_identifier
-      assert @subscriptions.identifiers.empty?
+      assert_called(channel, :unsubscribe_from_channel) do
+        @subscriptions.execute_command "command" => "unsubscribe", "identifier" => @chat_identifier
+      end
+
+      assert_empty @subscriptions.identifiers
     end
   end
 
@@ -67,7 +72,7 @@ class ActionCable::Connection::SubscriptionsTest < ActionCable::TestCase
       setup_connection
 
       @subscriptions.execute_command "command" => "unsubscribe"
-      assert @subscriptions.identifiers.empty?
+      assert_empty @subscriptions.identifiers
     end
   end
 
@@ -92,10 +97,11 @@ class ActionCable::Connection::SubscriptionsTest < ActionCable::TestCase
       channel2_id = ActiveSupport::JSON.encode(id: 2, channel: "ActionCable::Connection::SubscriptionsTest::ChatChannel")
       channel2 = subscribe_to_chat_channel(channel2_id)
 
-      channel1.expects(:unsubscribe_from_channel)
-      channel2.expects(:unsubscribe_from_channel)
-
-      @subscriptions.unsubscribe_from_all
+      assert_called(channel1, :unsubscribe_from_channel) do
+        assert_called(channel2, :unsubscribe_from_channel) do
+          @subscriptions.unsubscribe_from_all
+        end
+      end
     end
   end
 
diff --git a/actioncable/test/server/base_test.rb b/actioncable/test/server/base_test.rb
index 1312e45f49..3b5931f0a4 100644
--- a/actioncable/test/server/base_test.rb
+++ b/actioncable/test/server/base_test.rb
@@ -3,8 +3,11 @@
 require "test_helper"
 require "stubs/test_server"
 require "active_support/core_ext/hash/indifferent_access"
+require "active_support/testing/method_call_assertions"
 
 class BaseTest < ActiveSupport::TestCase
+  include ActiveSupport::Testing::MethodCallAssertions
+
   def setup
     @server = ActionCable::Server::Base.new
     @server.config.cable = { adapter: "async" }.with_indifferent_access
@@ -19,17 +22,20 @@ class BaseTest < ActiveSupport::TestCase
     conn = FakeConnection.new
     @server.add_connection(conn)
 
-    conn.expects(:close)
-    @server.restart
+    assert_called(conn, :close) do
+      @server.restart
+    end
   end
 
   test "#restart shuts down worker pool" do
-    @server.worker_pool.expects(:halt)
-    @server.restart
+    assert_called(@server.worker_pool, :halt) do
+      @server.restart
+    end
   end
 
   test "#restart shuts down pub/sub adapter" do
-    @server.pubsub.expects(:shutdown)
-    @server.restart
+    assert_called(@server.pubsub, :shutdown) do
+      @server.restart
+    end
   end
 end
diff --git a/actioncable/test/subscription_adapter/common.rb b/actioncable/test/subscription_adapter/common.rb
index c533a9f3eb..b3e9ae9d5c 100644
--- a/actioncable/test/subscription_adapter/common.rb
+++ b/actioncable/test/subscription_adapter/common.rb
@@ -32,7 +32,7 @@ module CommonSubscriptionAdapterTest
     subscribed = Concurrent::Event.new
     adapter.subscribe(channel, callback, Proc.new { subscribed.set })
     subscribed.wait(WAIT_WHEN_EXPECTING_EVENT)
-    assert subscribed.set?
+    assert_predicate subscribed, :set?
 
     yield queue
 
diff --git a/actioncable/test/subscription_adapter/evented_redis_test.rb b/actioncable/test/subscription_adapter/evented_redis_test.rb
deleted file mode 100644
index e3e0a0c72a..0000000000
--- a/actioncable/test/subscription_adapter/evented_redis_test.rb
+++ /dev/null
@@ -1,61 +0,0 @@
-# frozen_string_literal: true
-
-require "test_helper"
-require_relative "common"
-require_relative "channel_prefix"
-
-class EventedRedisAdapterTest < ActionCable::TestCase
-  include CommonSubscriptionAdapterTest
-  include ChannelPrefixTest
-
-  def setup
-    assert_deprecated do
-      super
-    end
-
-    # em-hiredis is warning-rich
-    @previous_verbose, $VERBOSE = $VERBOSE, nil
-  end
-
-  def teardown
-    super
-
-    # Ensure EM is shut down before we re-enable warnings
-    EventMachine.reactor_thread.tap do |thread|
-      EventMachine.stop
-      thread.join
-    end
-
-    $VERBOSE = @previous_verbose
-  end
-
-  def test_slow_eventmachine
-    require "eventmachine"
-    require "thread"
-
-    lock = Mutex.new
-
-    EventMachine.singleton_class.class_eval do
-      alias_method :delayed_initialize_event_machine, :initialize_event_machine
-      define_method(:initialize_event_machine) do
-        lock.synchronize do
-          sleep 0.5
-          delayed_initialize_event_machine
-        end
-      end
-    end
-
-    test_basic_broadcast
-  ensure
-    lock.synchronize do
-      EventMachine.singleton_class.class_eval do
-        alias_method :initialize_event_machine, :delayed_initialize_event_machine
-        remove_method :delayed_initialize_event_machine
-      end
-    end
-  end
-
-  def cable_config
-    { adapter: "evented_redis", url: "redis://:password@127.0.0.1:6379/12" }
-  end
-end
diff --git a/actioncable/test/subscription_adapter/redis_test.rb b/actioncable/test/subscription_adapter/redis_test.rb
index 69120d5753..63823d6ef0 100644
--- a/actioncable/test/subscription_adapter/redis_test.rb
+++ b/actioncable/test/subscription_adapter/redis_test.rb
@@ -4,12 +4,15 @@ require "test_helper"
 require_relative "common"
 require_relative "channel_prefix"
 
+require "active_support/testing/method_call_assertions"
+require "action_cable/subscription_adapter/redis"
+
 class RedisAdapterTest < ActionCable::TestCase
   include CommonSubscriptionAdapterTest
   include ChannelPrefixTest
 
   def cable_config
-    { adapter: "redis", driver: "ruby", url: "redis://:password@127.0.0.1:6379/12" }
+    { adapter: "redis", driver: "ruby" }
   end
 end
 
@@ -23,6 +26,22 @@ class RedisAdapterTest::AlternateConfiguration < RedisAdapterTest
   def cable_config
     alt_cable_config = super.dup
     alt_cable_config.delete(:url)
-    alt_cable_config.merge(host: "127.0.0.1", port: 6379, db: 12, password: "password")
+    alt_cable_config.merge(host: "127.0.0.1", port: 6379, db: 12)
+  end
+end
+
+class RedisAdapterTest::Connector < ActiveSupport::TestCase
+  include ActiveSupport::Testing::MethodCallAssertions
+
+  test "slices url, host, port, db, and password from config" do
+    config = { url: 1, host: 2, port: 3, db: 4, password: 5 }
+
+    assert_called_with ::Redis, :new, [ config ] do
+      connect config.merge(other: "unrelated", stuff: "here")
+    end
+  end
+
+  def connect(config)
+    ActionCable::SubscriptionAdapter::Redis.redis_connector.call(config)
   end
 end
diff --git a/actioncable/test/test_helper.rb b/actioncable/test/test_helper.rb
index 2a4611fb37..2f186b7193 100644
--- a/actioncable/test/test_helper.rb
+++ b/actioncable/test/test_helper.rb
@@ -4,7 +4,7 @@ require "action_cable"
 require "active_support/testing/autorun"
 
 require "puma"
-require "mocha/setup"
+require "mocha/minitest"
 require "rack/mock"
 
 begin
diff --git a/actionmailer/CHANGELOG.md b/actionmailer/CHANGELOG.md
index 9993a11c9d..6d91d4fbd6 100644
--- a/actionmailer/CHANGELOG.md
+++ b/actionmailer/CHANGELOG.md
@@ -1,12 +1,14 @@
-*   Allow Action Mailer classes to configure their delivery job.
+*   Ensure mail gem is eager autoloaded when eager load is true to prevent thread deadlocks.
 
-        class MyMailer < ApplicationMailer
-          self.delivery_job = MyCustomDeliveryJob
+    *Samuel Cochran*
 
-          ...
-        end
+*   Perform email jobs in `assert_emails`.
 
-    *Matthew Mongeau*
+    *Gannon McGibbon*
 
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/actionmailer/CHANGELOG.md) for previous changes.
+    *Jeremy Daer*
+
+
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/actionmailer/CHANGELOG.md) for previous changes.
diff --git a/actionmailer/MIT-LICENSE b/actionmailer/MIT-LICENSE
index ac810e86d0..1cb3add0fc 100644
--- a/actionmailer/MIT-LICENSE
+++ b/actionmailer/MIT-LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2004-2017 David Heinemeier Hansson
+Copyright (c) 2004-2018 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/actionmailer/README.rdoc b/actionmailer/README.rdoc
index 9993d3777d..14dfb82234 100644
--- a/actionmailer/README.rdoc
+++ b/actionmailer/README.rdoc
@@ -148,7 +148,7 @@ The latest version of Action Mailer can be installed with RubyGems:
 
   $ gem install actionmailer
 
-Source code can be downloaded as part of the Rails project on GitHub
+Source code can be downloaded as part of the Rails project on GitHub:
 
 * https://github.com/rails/rails/tree/master/actionmailer
 
@@ -166,7 +166,7 @@ API documentation is at
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/actionmailer/actionmailer.gemspec b/actionmailer/actionmailer.gemspec
index b8a2e80bd3..f2fb160bdd 100644
--- a/actionmailer/actionmailer.gemspec
+++ b/actionmailer/actionmailer.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Email composition, delivery, and receiving framework (part of Rails)."
   s.description = "Email on Rails. Compose, deliver, receive, and test emails using the familiar controller/view pattern. First-class support for multipart email and attachments."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
diff --git a/actionmailer/lib/action_mailer.rb b/actionmailer/lib/action_mailer.rb
index a170eb7917..69eae65d60 100644
--- a/actionmailer/lib/action_mailer.rb
+++ b/actionmailer/lib/action_mailer.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 #--
-# Copyright (c) 2004-2017 David Heinemeier Hansson
+# Copyright (c) 2004-2018 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the
@@ -24,7 +24,7 @@
 #++
 
 require "abstract_controller"
-require_relative "action_mailer/version"
+require "action_mailer/version"
 
 # Common Active Support usage in Action Mailer
 require "active_support"
@@ -52,6 +52,13 @@ module ActionMailer
   autoload :TestHelper
   autoload :MessageDelivery
   autoload :DeliveryJob
+
+  def self.eager_load!
+    super
+
+    require "mail"
+    Mail.eager_autoload!
+  end
 end
 
 autoload :Mime, "action_dispatch/http/mime_type"
diff --git a/actionmailer/lib/action_mailer/base.rb b/actionmailer/lib/action_mailer/base.rb
index a54eb52dcb..3af95081ee 100644
--- a/actionmailer/lib/action_mailer/base.rb
+++ b/actionmailer/lib/action_mailer/base.rb
@@ -1,13 +1,13 @@
 # frozen_string_literal: true
 
 require "mail"
-require_relative "collector"
+require "action_mailer/collector"
 require "active_support/core_ext/string/inflections"
 require "active_support/core_ext/hash/except"
 require "active_support/core_ext/module/anonymous"
 
-require_relative "log_subscriber"
-require_relative "rescuable"
+require "action_mailer/log_subscriber"
+require "action_mailer/rescuable"
 
 module ActionMailer
   # Action Mailer allows you to send email from your application using a mailer model and views.
@@ -59,7 +59,7 @@ module ActionMailer
   # The hash passed to the mail method allows you to specify any header that a <tt>Mail::Message</tt>
   # will accept (any valid email header including optional fields).
   #
-  # The mail method, if not passed a block, will inspect your views and send all the views with
+  # The +mail+ method, if not passed a block, will inspect your views and send all the views with
   # the same name as the method, so the above action would send the +welcome.text.erb+ view
   # file as well as the +welcome.html.erb+ view file in a +multipart/alternative+ email.
   #
@@ -138,7 +138,7 @@ module ActionMailer
   # You can also define a <tt>default_url_options</tt> method on individual mailers to override these
   # default settings per-mailer.
   #
-  # By default when <tt>config.force_ssl</tt> is true, URLs generated for hosts will use the HTTPS protocol.
+  # By default when <tt>config.force_ssl</tt> is +true+, URLs generated for hosts will use the HTTPS protocol.
   #
   # = Sending mail
   #
@@ -316,7 +316,7 @@ module ActionMailer
   #
   # = Callbacks
   #
-  # You can specify callbacks using before_action and after_action for configuring your messages.
+  # You can specify callbacks using <tt>before_action</tt> and <tt>after_action</tt> for configuring your messages.
   # This may be useful, for example, when you want to add default inline attachments for all
   # messages sent out by a certain mailer class:
   #
@@ -889,7 +889,7 @@ module ActionMailer
         default_values = self.class.default.map do |key, value|
           [
             key,
-            value.is_a?(Proc) ? instance_exec(&value) : value
+            compute_default(value)
           ]
         end.to_h
 
@@ -898,6 +898,16 @@ module ActionMailer
         headers_with_defaults
       end
 
+      def compute_default(value)
+        return value unless value.is_a?(Proc)
+
+        if value.arity == 1
+          instance_exec(self, &value)
+        else
+          instance_exec(&value)
+        end
+      end
+
       def assign_headers_to_message(message, headers)
         assignable = headers.except(:parts_order, :content_type, :body, :template_name,
                                     :template_path, :delivery_method, :delivery_method_options)
diff --git a/actionmailer/lib/action_mailer/gem_version.rb b/actionmailer/lib/action_mailer/gem_version.rb
index 063d4580d8..72eb5d61e8 100644
--- a/actionmailer/lib/action_mailer/gem_version.rb
+++ b/actionmailer/lib/action_mailer/gem_version.rb
@@ -7,8 +7,8 @@ module ActionMailer
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
     PRE   = "alpha"
 
diff --git a/actionmailer/lib/action_mailer/inline_preview_interceptor.rb b/actionmailer/lib/action_mailer/inline_preview_interceptor.rb
index 4bef4a58d3..8a12f805cc 100644
--- a/actionmailer/lib/action_mailer/inline_preview_interceptor.rb
+++ b/actionmailer/lib/action_mailer/inline_preview_interceptor.rb
@@ -4,7 +4,7 @@ require "base64"
 
 module ActionMailer
   # Implements a mailer preview interceptor that converts image tag src attributes
-  # that use inline cid: style urls to data: style urls so that they are visible
+  # that use inline cid: style URLs to data: style URLs so that they are visible
   # when previewing an HTML email in a web browser.
   #
   # This interceptor is enabled by default. To disable it, delete it from the
diff --git a/actionmailer/lib/action_mailer/message_delivery.rb b/actionmailer/lib/action_mailer/message_delivery.rb
index fe7265834f..2377aeb9a5 100644
--- a/actionmailer/lib/action_mailer/message_delivery.rb
+++ b/actionmailer/lib/action_mailer/message_delivery.rb
@@ -4,7 +4,7 @@ require "delegate"
 
 module ActionMailer
   # The <tt>ActionMailer::MessageDelivery</tt> class is used by
-  # <tt>ActionMailer::Base</tt> when creating a new mailer.
+  # ActionMailer::Base when creating a new mailer.
   # <tt>MessageDelivery</tt> is a wrapper (+Delegator+ subclass) around a lazy
   # created <tt>Mail::Message</tt>. You can get direct access to the
   # <tt>Mail::Message</tt>, deliver the email or schedule the email to be sent
@@ -53,6 +53,12 @@ module ActionMailer
     #   Notifier.welcome(User.first).deliver_later!(wait: 1.hour)
     #   Notifier.welcome(User.first).deliver_later!(wait_until: 10.hours.from_now)
     #
+    # Options:
+    #
+    # * <tt>:wait</tt> - Enqueue the email to be delivered with a delay
+    # * <tt>:wait_until</tt> - Enqueue the email to be delivered at (after) a specific date / time
+    # * <tt>:queue</tt> - Enqueue the email on the specified queue
+    #
     # By default, the email will be enqueued using <tt>ActionMailer::DeliveryJob</tt>. Each
     # <tt>ActionMailer::Base</tt> class can specify the job to use by setting the class variable
     # +delivery_job+.
@@ -60,12 +66,6 @@ module ActionMailer
     #   class AccountRegistrationMailer < ApplicationMailer
     #     self.delivery_job = RegistrationDeliveryJob
     #   end
-    #
-    # Options:
-    #
-    # * <tt>:wait</tt> - Enqueue the email to be delivered with a delay
-    # * <tt>:wait_until</tt> - Enqueue the email to be delivered at (after) a specific date / time
-    # * <tt>:queue</tt> - Enqueue the email on the specified queue
     def deliver_later!(options = {})
       enqueue_delivery :deliver_now!, options
     end
@@ -77,6 +77,12 @@ module ActionMailer
     #   Notifier.welcome(User.first).deliver_later(wait: 1.hour)
     #   Notifier.welcome(User.first).deliver_later(wait_until: 10.hours.from_now)
     #
+    # Options:
+    #
+    # * <tt>:wait</tt> - Enqueue the email to be delivered with a delay.
+    # * <tt>:wait_until</tt> - Enqueue the email to be delivered at (after) a specific date / time.
+    # * <tt>:queue</tt> - Enqueue the email on the specified queue.
+    #
     # By default, the email will be enqueued using <tt>ActionMailer::DeliveryJob</tt>. Each
     # <tt>ActionMailer::Base</tt> class can specify the job to use by setting the class variable
     # +delivery_job+.
@@ -84,12 +90,6 @@ module ActionMailer
     #   class AccountRegistrationMailer < ApplicationMailer
     #     self.delivery_job = RegistrationDeliveryJob
     #   end
-    #
-    # Options:
-    #
-    # * <tt>:wait</tt> - Enqueue the email to be delivered with a delay.
-    # * <tt>:wait_until</tt> - Enqueue the email to be delivered at (after) a specific date / time.
-    # * <tt>:queue</tt> - Enqueue the email on the specified queue.
     def deliver_later(options = {})
       enqueue_delivery :deliver_now, options
     end
diff --git a/actionmailer/lib/action_mailer/preview.rb b/actionmailer/lib/action_mailer/preview.rb
index 4a8d3659ec..0aea84fd2b 100644
--- a/actionmailer/lib/action_mailer/preview.rb
+++ b/actionmailer/lib/action_mailer/preview.rb
@@ -17,7 +17,7 @@ module ActionMailer
       #
       #     config.action_mailer.show_previews = true
       #
-      # Defaults to true for development environment
+      # Defaults to +true+ for development environment
       #
       mattr_accessor :show_previews, instance_writer: false
 
@@ -33,7 +33,7 @@ module ActionMailer
 
       # Register an Interceptor which will be called before mail is previewed.
       # Either a class or a string can be passed in as the Interceptor. If a
-      # string is passed in it will be <tt>constantize</tt>d.
+      # string is passed in it will be constantized.
       def register_preview_interceptor(interceptor)
         preview_interceptor = \
           case interceptor
@@ -81,12 +81,12 @@ module ActionMailer
         public_instance_methods(false).map(&:to_s).sort
       end
 
-      # Returns true if the email exists.
+      # Returns +true+ if the email exists.
       def email_exists?(email)
         emails.include?(email)
       end
 
-      # Returns true if the preview exists.
+      # Returns +true+ if the preview exists.
       def exists?(preview)
         all.any? { |p| p.preview_name == preview }
       end
@@ -104,7 +104,7 @@ module ActionMailer
       private
         def load_previews
           if preview_path
-            Dir["#{preview_path}/**/*_preview.rb"].each { |file| require_dependency file }
+            Dir["#{preview_path}/**/*_preview.rb"].sort.each { |file| require_dependency file }
           end
         end
 
diff --git a/actionmailer/lib/action_mailer/rescuable.rb b/actionmailer/lib/action_mailer/rescuable.rb
index 28950eb834..5b567eb500 100644
--- a/actionmailer/lib/action_mailer/rescuable.rb
+++ b/actionmailer/lib/action_mailer/rescuable.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 module ActionMailer #:nodoc:
-  # Provides `rescue_from` for mailers. Wraps mailer action processing,
+  # Provides +rescue_from+ for mailers. Wraps mailer action processing,
   # mail job processing, and mail delivery.
   module Rescuable
     extend ActiveSupport::Concern
diff --git a/actionmailer/lib/action_mailer/test_helper.rb b/actionmailer/lib/action_mailer/test_helper.rb
index ac8b944743..6906472660 100644
--- a/actionmailer/lib/action_mailer/test_helper.rb
+++ b/actionmailer/lib/action_mailer/test_helper.rb
@@ -28,13 +28,13 @@ module ActionMailer
     #
     #     assert_emails 2 do
     #       ContactMailer.welcome.deliver_now
-    #       ContactMailer.welcome.deliver_now
+    #       ContactMailer.welcome.deliver_later
     #     end
     #   end
-    def assert_emails(number)
+    def assert_emails(number, &block)
       if block_given?
         original_count = ActionMailer::Base.deliveries.size
-        yield
+        perform_enqueued_jobs(only: [ActionMailer::DeliveryJob, ActionMailer::Parameterized::DeliveryJob], &block)
         new_count = ActionMailer::Base.deliveries.size
         assert_equal number, new_count - original_count, "#{number} emails expected, but #{new_count - original_count} were sent"
       else
@@ -93,6 +93,48 @@ module ActionMailer
       assert_enqueued_jobs number, only: [ ActionMailer::DeliveryJob, ActionMailer::Parameterized::DeliveryJob ], &block
     end
 
+    # Asserts that a specific email has been enqueued, optionally
+    # matching arguments.
+    #
+    #   def test_email
+    #     ContactMailer.welcome.deliver_later
+    #     assert_enqueued_email_with ContactMailer, :welcome
+    #   end
+    #
+    #   def test_email_with_arguments
+    #     ContactMailer.welcome("Hello", "Goodbye").deliver_later
+    #     assert_enqueued_email_with ContactMailer, :welcome, args: ["Hello", "Goodbye"]
+    #   end
+    #
+    # If a block is passed, that block should cause the specified email
+    # to be enqueued.
+    #
+    #   def test_email_in_block
+    #     assert_enqueued_email_with ContactMailer, :welcome do
+    #       ContactMailer.welcome.deliver_later
+    #     end
+    #   end
+    #
+    # If +args+ is provided as a Hash, a parameterized email is matched.
+    #
+    #   def test_parameterized_email
+    #     assert_enqueued_email_with ContactMailer, :welcome,
+    #       args: {email: 'user@example.com'} do
+    #       ContactMailer.with(email: 'user@example.com').welcome.deliver_later
+    #     end
+    #   end
+    def assert_enqueued_email_with(mailer, method, args: nil, queue: "mailers", &block)
+      if args.is_a? Hash
+        job = ActionMailer::Parameterized::DeliveryJob
+        args = [mailer.to_s, method.to_s, "deliver_now", args]
+      else
+        job = ActionMailer::DeliveryJob
+        args = [mailer.to_s, method.to_s, "deliver_now", *args]
+      end
+
+      assert_enqueued_with(job: job, args: args, queue: queue, &block)
+    end
+
     # Asserts that no emails are enqueued for later delivery.
     #
     #   def test_no_emails
diff --git a/actionmailer/lib/rails/generators/mailer/mailer_generator.rb b/actionmailer/lib/rails/generators/mailer/mailer_generator.rb
index 97eac30db1..c37a74c762 100644
--- a/actionmailer/lib/rails/generators/mailer/mailer_generator.rb
+++ b/actionmailer/lib/rails/generators/mailer/mailer_generator.rb
@@ -23,7 +23,7 @@ module Rails
 
       private
         def file_name # :doc:
-          @_file_name ||= super.gsub(/_mailer/i, "")
+          @_file_name ||= super.sub(/_mailer\z/i, "")
         end
 
         def application_mailer_file_name
diff --git a/actionmailer/lib/rails/generators/mailer/templates/application_mailer.rb b/actionmailer/lib/rails/generators/mailer/templates/application_mailer.rb.tt
index 00fb9bd48f..00fb9bd48f 100644
--- a/actionmailer/lib/rails/generators/mailer/templates/application_mailer.rb
+++ b/actionmailer/lib/rails/generators/mailer/templates/application_mailer.rb.tt
diff --git a/actionmailer/lib/rails/generators/mailer/templates/mailer.rb b/actionmailer/lib/rails/generators/mailer/templates/mailer.rb.tt
index 348d314758..348d314758 100644
--- a/actionmailer/lib/rails/generators/mailer/templates/mailer.rb
+++ b/actionmailer/lib/rails/generators/mailer/templates/mailer.rb.tt
diff --git a/actionmailer/test/base_test.rb b/actionmailer/test/base_test.rb
index 0da969c349..4124aa00bd 100644
--- a/actionmailer/test/base_test.rb
+++ b/actionmailer/test/base_test.rb
@@ -322,22 +322,21 @@ class BaseTest < ActiveSupport::TestCase
 
   test "implicit multipart with attachments creates nested parts" do
     email = BaseMailer.implicit_multipart(attachments: true)
-    assert_equal("application/pdf", email.parts[0].mime_type)
-    assert_equal("multipart/alternative", email.parts[1].mime_type)
-    assert_equal("text/plain", email.parts[1].parts[0].mime_type)
-    assert_equal("TEXT Implicit Multipart", email.parts[1].parts[0].body.encoded)
-    assert_equal("text/html", email.parts[1].parts[1].mime_type)
-    assert_equal("HTML Implicit Multipart", email.parts[1].parts[1].body.encoded)
+    assert_equal(%w[ application/pdf multipart/alternative ], email.parts.map(&:mime_type).sort)
+    multipart = email.parts.detect { |p| p.mime_type == "multipart/alternative" }
+    assert_equal("text/plain", multipart.parts[0].mime_type)
+    assert_equal("TEXT Implicit Multipart", multipart.parts[0].body.encoded)
+    assert_equal("text/html", multipart.parts[1].mime_type)
+    assert_equal("HTML Implicit Multipart", multipart.parts[1].body.encoded)
   end
 
   test "implicit multipart with attachments and sort order" do
     order = ["text/html", "text/plain"]
     with_default BaseMailer, parts_order: order do
       email = BaseMailer.implicit_multipart(attachments: true)
-      assert_equal("application/pdf", email.parts[0].mime_type)
-      assert_equal("multipart/alternative", email.parts[1].mime_type)
-      assert_equal("text/plain", email.parts[1].parts[1].mime_type)
-      assert_equal("text/html", email.parts[1].parts[0].mime_type)
+      assert_equal(%w[ application/pdf multipart/alternative ], email.parts.map(&:mime_type).sort)
+      multipart = email.parts.detect { |p| p.mime_type == "multipart/alternative" }
+      assert_equal(%w[ text/html text/plain ], multipart.parts.map(&:mime_type).sort)
     end
   end
 
@@ -427,12 +426,12 @@ class BaseTest < ActiveSupport::TestCase
 
   test "explicit multipart with attachments creates nested parts" do
     email = BaseMailer.explicit_multipart(attachments: true)
-    assert_equal("application/pdf", email.parts[0].mime_type)
-    assert_equal("multipart/alternative", email.parts[1].mime_type)
-    assert_equal("text/plain", email.parts[1].parts[0].mime_type)
-    assert_equal("TEXT Explicit Multipart", email.parts[1].parts[0].body.encoded)
-    assert_equal("text/html", email.parts[1].parts[1].mime_type)
-    assert_equal("HTML Explicit Multipart", email.parts[1].parts[1].body.encoded)
+    assert_equal(%w[ application/pdf multipart/alternative ], email.parts.map(&:mime_type).sort)
+    multipart = email.parts.detect { |p| p.mime_type == "multipart/alternative" }
+    assert_equal("text/plain", multipart.parts[0].mime_type)
+    assert_equal("TEXT Explicit Multipart", multipart.parts[0].body.encoded)
+    assert_equal("text/html", multipart.parts[1].mime_type)
+    assert_equal("HTML Explicit Multipart", multipart.parts[1].body.encoded)
   end
 
   test "explicit multipart with templates" do
@@ -507,8 +506,8 @@ class BaseTest < ActiveSupport::TestCase
   test "should respond to action methods" do
     assert_respond_to BaseMailer, :welcome
     assert_respond_to BaseMailer, :implicit_multipart
-    assert !BaseMailer.respond_to?(:mail)
-    assert !BaseMailer.respond_to?(:headers)
+    assert_not_respond_to BaseMailer, :mail
+    assert_not_respond_to BaseMailer, :headers
   end
 
   test "calling just the action should return the generated mail object" do
@@ -726,6 +725,15 @@ class BaseTest < ActiveSupport::TestCase
     assert(ProcMailer.welcome["x-has-to-proc"].to_s == "symbol")
   end
 
+  test "proc default values can have arity of 1 where arg is a mailer instance" do
+    assert_equal(ProcMailer.welcome["X-Lambda-Arity-1-arg"].to_s, "complex_value")
+    assert_equal(ProcMailer.welcome["X-Lambda-Arity-1-self"].to_s, "complex_value")
+  end
+
+  test "proc default values with fixed arity of 0 can be called" do
+    assert_equal("0", ProcMailer.welcome["X-Lambda-Arity-0"].to_s)
+  end
+
   test "we can call other defined methods on the class as needed" do
     mail = ProcMailer.welcome
     assert_equal("Thanks for signing up this afternoon", mail.subject)
diff --git a/actionmailer/test/caching_test.rb b/actionmailer/test/caching_test.rb
index e11e8d4676..22f310f39f 100644
--- a/actionmailer/test/caching_test.rb
+++ b/actionmailer/test/caching_test.rb
@@ -40,14 +40,14 @@ class FragmentCachingTest < BaseCachingTest
   def test_fragment_exist_with_caching_enabled
     @store.write("views/name", "value")
     assert @mailer.fragment_exist?("name")
-    assert !@mailer.fragment_exist?("other_name")
+    assert_not @mailer.fragment_exist?("other_name")
   end
 
   def test_fragment_exist_with_caching_disabled
     @mailer.perform_caching = false
     @store.write("views/name", "value")
-    assert !@mailer.fragment_exist?("name")
-    assert !@mailer.fragment_exist?("other_name")
+    assert_not @mailer.fragment_exist?("name")
+    assert_not @mailer.fragment_exist?("other_name")
   end
 
   def test_write_fragment_with_caching_enabled
@@ -90,7 +90,7 @@ class FragmentCachingTest < BaseCachingTest
     buffer = "generated till now -> ".html_safe
     buffer << view_context.send(:fragment_for, "expensive") { fragment_computed = true }
 
-    assert !fragment_computed
+    assert_not fragment_computed
     assert_equal "generated till now -> fragment content", buffer
   end
 
@@ -105,7 +105,7 @@ class FragmentCachingTest < BaseCachingTest
 
     html_safe = @mailer.read_fragment("name")
     assert_equal content, html_safe
-    assert html_safe.html_safe?
+    assert_predicate html_safe, :html_safe?
   end
 end
 
@@ -198,7 +198,7 @@ end
 class CacheHelperOutputBufferTest < BaseCachingTest
   class MockController
     def read_fragment(name, options)
-      return false
+      false
     end
 
     def write_fragment(name, fragment, options)
@@ -214,9 +214,9 @@ class CacheHelperOutputBufferTest < BaseCachingTest
     output_buffer = ActionView::OutputBuffer.new
     controller = MockController.new
     cache_helper = Class.new do
-      def self.controller; end;
-      def self.output_buffer; end;
-      def self.output_buffer=; end;
+      def self.controller; end
+      def self.output_buffer; end
+      def self.output_buffer=; end
     end
     cache_helper.extend(ActionView::Helpers::CacheHelper)
 
@@ -235,9 +235,9 @@ class CacheHelperOutputBufferTest < BaseCachingTest
     output_buffer = ActiveSupport::SafeBuffer.new
     controller = MockController.new
     cache_helper = Class.new do
-      def self.controller; end;
-      def self.output_buffer; end;
-      def self.output_buffer=; end;
+      def self.controller; end
+      def self.output_buffer; end
+      def self.output_buffer=; end
     end
     cache_helper.extend(ActionView::Helpers::CacheHelper)
 
@@ -262,7 +262,7 @@ class ViewCacheDependencyTest < BaseCachingTest
   end
 
   def test_view_cache_dependencies_are_empty_by_default
-    assert NoDependenciesMailer.new.view_cache_dependencies.empty?
+    assert_empty NoDependenciesMailer.new.view_cache_dependencies
   end
 
   def test_view_cache_dependencies_are_listed_in_declaration_order
diff --git a/actionmailer/test/mailers/proc_mailer.rb b/actionmailer/test/mailers/proc_mailer.rb
index b7cf53eb4a..76e730bb79 100644
--- a/actionmailer/test/mailers/proc_mailer.rb
+++ b/actionmailer/test/mailers/proc_mailer.rb
@@ -4,12 +4,19 @@ class ProcMailer < ActionMailer::Base
   default to: "system@test.lindsaar.net",
           "X-Proc-Method" => Proc.new { Time.now.to_i.to_s },
           subject: Proc.new { give_a_greeting },
-          "x-has-to-proc" => :symbol
+          "x-has-to-proc" => :symbol,
+          "X-Lambda-Arity-0" => ->() { "0" },
+          "X-Lambda-Arity-1-arg" => ->(arg) { arg.computed_value },
+          "X-Lambda-Arity-1-self" => ->(_) { self.computed_value }
 
   def welcome
     mail
   end
 
+  def computed_value
+    "complex_value"
+  end
+
   private
 
     def give_a_greeting
diff --git a/actionmailer/test/message_delivery_test.rb b/actionmailer/test/message_delivery_test.rb
index 03e8d4fb66..f8dcb3f4ba 100644
--- a/actionmailer/test/message_delivery_test.rb
+++ b/actionmailer/test/message_delivery_test.rb
@@ -39,7 +39,7 @@ class MessageDeliveryTest < ActiveSupport::TestCase
   end
 
   test "its message should be a Mail::Message" do
-    assert_equal Mail::Message , @mail.message.class
+    assert_equal Mail::Message, @mail.message.class
   end
 
   test "should respond to .deliver_later" do
diff --git a/actionmailer/test/test_helper_test.rb b/actionmailer/test/test_helper_test.rb
index abf50cf4da..8fdc687a8b 100644
--- a/actionmailer/test/test_helper_test.rb
+++ b/actionmailer/test/test_helper_test.rb
@@ -10,6 +10,18 @@ class TestHelperMailer < ActionMailer::Base
       to: "test@example.com",
       from: "tester@example.com"
   end
+
+  def test_args(recipient, name)
+    mail body: render(inline: "Hello, #{name}"),
+      to: recipient,
+      from: "tester@example.com"
+  end
+
+  def test_parameter_args
+    mail body: render(inline: "All is #{params[:all]}"),
+      to: "test@example.com",
+      from: "tester@example.com"
+  end
 end
 
 class TestHelperMailerTest < ActionMailer::TestCase
@@ -42,7 +54,7 @@ class TestHelperMailerTest < ActionMailer::TestCase
   end
 
   def test_encode
-    assert_equal "=?UTF-8?Q?This_is_=E3=81=82_string?=", encode("This is あ string")
+    assert_equal "This is あ string", Mail::Encodings.q_value_decode(encode("This is あ string"))
   end
 
   def test_read_fixture
@@ -57,6 +69,16 @@ class TestHelperMailerTest < ActionMailer::TestCase
     end
   end
 
+  def test_assert_emails_with_enqueued_emails
+    assert_nothing_raised do
+      assert_emails 1 do
+        silence_stream($stdout) do
+          TestHelperMailer.test.deliver_later
+        end
+      end
+    end
+  end
+
   def test_repeated_assert_emails_calls
     assert_nothing_raised do
       assert_emails 1 do
@@ -93,6 +115,18 @@ class TestHelperMailerTest < ActionMailer::TestCase
     end
   end
 
+  def test_assert_no_emails_with_enqueued_emails
+    error = assert_raise ActiveSupport::TestCase::Assertion do
+      assert_no_emails do
+        silence_stream($stdout) do
+          TestHelperMailer.test.deliver_later
+        end
+      end
+    end
+
+    assert_match(/0 .* but 1/, error.message)
+  end
+
   def test_assert_emails_too_few_sent
     error = assert_raise ActiveSupport::TestCase::Assertion do
       assert_emails 2 do
@@ -207,6 +241,36 @@ class TestHelperMailerTest < ActionMailer::TestCase
 
     assert_match(/0 .* but 1/, error.message)
   end
+
+  def test_assert_enqueued_email_with
+    assert_nothing_raised do
+      assert_enqueued_email_with TestHelperMailer, :test do
+        silence_stream($stdout) do
+          TestHelperMailer.test.deliver_later
+        end
+      end
+    end
+  end
+
+  def test_assert_enqueued_email_with_args
+    assert_nothing_raised do
+      assert_enqueued_email_with TestHelperMailer, :test_args, args: ["some_email", "some_name"] do
+        silence_stream($stdout) do
+          TestHelperMailer.test_args("some_email", "some_name").deliver_later
+        end
+      end
+    end
+  end
+
+  def test_assert_enqueued_email_with_parameterized_args
+    assert_nothing_raised do
+      assert_enqueued_email_with TestHelperMailer, :test_parameter_args, args: { all: "good" } do
+        silence_stream($stdout) do
+          TestHelperMailer.with(all: "good").test_parameter_args.deliver_later
+        end
+      end
+    end
+  end
 end
 
 class AnotherTestHelperMailerTest < ActionMailer::TestCase
diff --git a/actionmailer/test/url_test.rb b/actionmailer/test/url_test.rb
index 82035689ad..3c940bc969 100644
--- a/actionmailer/test/url_test.rb
+++ b/actionmailer/test/url_test.rb
@@ -105,7 +105,7 @@ class ActionMailerUrlTest < ActionMailer::TestCase
     assert_url_for "/dummy_model", DummyModel
 
     # array
-    assert_url_for "/dummy_model" , [DummyModel]
+    assert_url_for "/dummy_model", [DummyModel]
   end
 
   def test_signed_up_with_url
diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index 938b24a6b9..a13d9e1078 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,69 +1,44 @@
-*   Deprecate `ActionDispatch::TestResponse` response aliases
+*   Introduce a new error page to when the implict render page is accessed in the browser.
 
-    `#success?`, `#missing?` & `#error?` are not supported by the actual
-    `ActionDispatch::Response` object and can produce false-positives. Instead,
-    use the response helpers provided by `Rack::Response`.
+    Now instead of showing an error page that with exception and backtraces we now show only
+    one informative page.
 
-    *Trevor Wistaff*
+    *Vinicius Stock*
 
-*   Protect from forgery by default
+*   Introduce ActionDispatch::DebugExceptions.register_interceptor
 
-    Rather than protecting from forgery in the generated `ApplicationController`,
-    add it to `ActionController::Base` depending on
-    `config.action_controller.default_protect_from_forgery`. This configuration
-    defaults to false to support older versions which have removed it from their
-    `ApplicationController`, but is set to true for Rails 5.2.
+    Exception aware plugin authors can use the newly introduced
+    `.register_interceptor` method to get the processed exception, instead of
+    monkey patching DebugExceptions.
 
-    *Lisa Ugray*
+        ActionDispatch::DebugExceptions.register_interceptor do |request, exception|
+          HypoteticalPlugin.capture_exception(request, exception)
+        end
 
-*   Fallback `ActionController::Parameters#to_s` to `Hash#to_s`.
+    *Genadi Samokovarov*
 
-    *Kir Shatrov*
+*   Output only one Content-Security-Policy nonce header value per request.
 
-*   `driven_by` now registers poltergeist and capybara-webkit
+    Fixes #32597.
 
-    If poltergeist or capybara-webkit are set as drivers is set for System Tests,
-    `driven_by` will register the driver and set additional options passed via
-    the `:options` parameter.
+    *Andrey Novikov*, *Andrew White*
 
-    Refer to the respective driver's documentation to see what options can be passed.
+*   Move default headers configuration into their own module that can be included in controllers.
 
-    *Mario Chavez*
+    *Kevin Deisz*
 
-*   AEAD encrypted cookies and sessions with GCM
+*   Add method `dig` to `session`.
 
-    Encrypted cookies now use AES-GCM which couples authentication and
-    encryption in one faster step and produces shorter ciphertexts. Cookies
-    encrypted using AES in CBC HMAC mode will be seamlessly upgraded when
-    this new mode is enabled via the
-    `action_dispatch.use_authenticated_cookie_encryption` configuration value.
+    *claudiob*, *Takumi Shotoku*
 
-    *Michael J Coyne*
+*   Controller level `force_ssl` has been deprecated in favor of
+    `config.force_ssl`.
 
-*   Change the cache key format for fragments to make it easier to debug key churn. The new format is:
+    *Derek Prior*
 
-        views/template/action.html.erb:7a1156131a6928cb0026877f8b749ac9/projects/123
-              ^template path           ^template tree digest            ^class   ^id
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
-    *DHH*
+    *Jeremy Daer*
 
-*   Add support for recyclable cache keys with fragment caching. This uses the new versioned entries in the
-    `ActiveSupport::Cache` stores and relies on the fact that Active Record has split `#cache_key` and `#cache_version`
-    to support it.
 
-    *DHH*
-
-*   Add `action_controller_api` and `action_controller_base` load hooks to be called in `ActiveSupport.on_load`
-
-    `ActionController::Base` and `ActionController::API` have differing implementations. This means that
-    the one umbrella hook `action_controller` is not able to address certain situations where a method
-    may not exist in a certain implementation.
-
-    This is fixed by adding two new hooks so you can target `ActionController::Base` vs `ActionController::API`
-
-    Fixes #27013.
-
-    *Julian Nadeau*
-
-
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/actionpack/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/actionpack/CHANGELOG.md) for previous changes.
diff --git a/actionpack/MIT-LICENSE b/actionpack/MIT-LICENSE
index ac810e86d0..1cb3add0fc 100644
--- a/actionpack/MIT-LICENSE
+++ b/actionpack/MIT-LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2004-2017 David Heinemeier Hansson
+Copyright (c) 2004-2018 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/actionpack/README.rdoc b/actionpack/README.rdoc
index 93b2a0932a..f56230ffa0 100644
--- a/actionpack/README.rdoc
+++ b/actionpack/README.rdoc
@@ -30,7 +30,7 @@ The latest version of Action Pack can be installed with RubyGems:
 
   $ gem install actionpack
 
-Source code can be downloaded as part of the Rails project on GitHub
+Source code can be downloaded as part of the Rails project on GitHub:
 
 * https://github.com/rails/rails/tree/master/actionpack
 
@@ -44,11 +44,11 @@ Action Pack is released under the MIT license:
 
 == Support
 
-API documentation is at
+API documentation is at:
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/actionpack/Rakefile b/actionpack/Rakefile
index 4dd7c59ce8..e99eb1723a 100644
--- a/actionpack/Rakefile
+++ b/actionpack/Rakefile
@@ -28,7 +28,7 @@ namespace :test do
 end
 
 task :lines do
-  load File.expand_path("..", __dir__) + "/tools/line_statistics"
+  load File.expand_path("../tools/line_statistics", __dir__)
   files = FileList["lib/**/*.rb"]
   CodeTools::LineStatistics.new(files).print_loc
 end
diff --git a/actionpack/actionpack.gemspec b/actionpack/actionpack.gemspec
index 33d42e69d8..1dc8abf746 100644
--- a/actionpack/actionpack.gemspec
+++ b/actionpack/actionpack.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Web-flow and rendering framework putting the VC in MVC (part of Rails)."
   s.description = "Web apps on Rails. Simple, battle-tested conventions for building and testing MVC web applications. Works with any Rack-compatible server."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
diff --git a/actionpack/lib/abstract_controller/base.rb b/actionpack/lib/abstract_controller/base.rb
index 3761054bb7..a312af6715 100644
--- a/actionpack/lib/abstract_controller/base.rb
+++ b/actionpack/lib/abstract_controller/base.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "error"
+require "abstract_controller/error"
 require "active_support/configurable"
 require "active_support/descendants_tracker"
 require "active_support/core_ext/module/anonymous"
@@ -180,8 +180,6 @@ module AbstractController
       #
       # ==== Parameters
       # * <tt>name</tt> - The name of an action to be tested
-      #
-      # :api: private
       def action_method?(name)
         self.class.action_methods.include?(name)
       end
diff --git a/actionpack/lib/abstract_controller/callbacks.rb b/actionpack/lib/abstract_controller/callbacks.rb
index 715d043b4e..42bab411d2 100644
--- a/actionpack/lib/abstract_controller/callbacks.rb
+++ b/actionpack/lib/abstract_controller/callbacks.rb
@@ -35,8 +35,8 @@ module AbstractController
                        skip_after_callbacks_if_terminated: true
     end
 
-    # Override AbstractController::Base's process_action to run the
-    # process_action callbacks around the normal behavior.
+    # Override <tt>AbstractController::Base#process_action</tt> to run the
+    # <tt>process_action</tt> callbacks around the normal behavior.
     def process_action(*args)
       run_callbacks(:process_action) do
         super
@@ -103,6 +103,10 @@ module AbstractController
       # :call-seq: before_action(names, block)
       #
       # Append a callback before actions. See _insert_callbacks for parameter details.
+      #
+      # If the callback renders or redirects, the action will not run. If there
+      # are additional callbacks scheduled to run after that callback, they are
+      # also cancelled.
 
       ##
       # :method: prepend_before_action
@@ -110,6 +114,10 @@ module AbstractController
       # :call-seq: prepend_before_action(names, block)
       #
       # Prepend a callback before actions. See _insert_callbacks for parameter details.
+      #
+      # If the callback renders or redirects, the action will not run. If there
+      # are additional callbacks scheduled to run after that callback, they are
+      # also cancelled.
 
       ##
       # :method: skip_before_action
@@ -124,6 +132,10 @@ module AbstractController
       # :call-seq: append_before_action(names, block)
       #
       # Append a callback before actions. See _insert_callbacks for parameter details.
+      #
+      # If the callback renders or redirects, the action will not run. If there
+      # are additional callbacks scheduled to run after that callback, they are
+      # also cancelled.
 
       ##
       # :method: after_action
diff --git a/actionpack/lib/abstract_controller/rendering.rb b/actionpack/lib/abstract_controller/rendering.rb
index 41898c4c2e..8ba2b25552 100644
--- a/actionpack/lib/abstract_controller/rendering.rb
+++ b/actionpack/lib/abstract_controller/rendering.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "error"
+require "abstract_controller/error"
 require "action_view"
 require "action_view/view_paths"
 require "set"
@@ -20,7 +20,6 @@ module AbstractController
 
     # Normalizes arguments, options and then delegates render_to_body and
     # sticks the result in <tt>self.response_body</tt>.
-    # :api: public
     def render(*args, &block)
       options = _normalize_render(*args, &block)
       rendered_body = render_to_body(options)
@@ -42,19 +41,16 @@ module AbstractController
     # (as ActionController extends it to be anything that
     # responds to the method each), this method needs to be
     # overridden in order to still return a string.
-    # :api: plugin
     def render_to_string(*args, &block)
       options = _normalize_render(*args, &block)
       render_to_body(options)
     end
 
     # Performs the actual template rendering.
-    # :api: public
     def render_to_body(options = {})
     end
 
-    # Returns Content-Type of rendered content
-    # :api: public
+    # Returns Content-Type of rendered content.
     def rendered_format
       Mime[:text]
     end
@@ -65,7 +61,6 @@ module AbstractController
 
     # This method should return a hash with assigns.
     # You can overwrite this configuration per controller.
-    # :api: public
     def view_assigns
       protected_vars = _protected_ivars
       variables      = instance_variables
@@ -76,11 +71,11 @@ module AbstractController
       }
     end
 
+  private
     # Normalize args by converting <tt>render "foo"</tt> to
     # <tt>render :action => "foo"</tt> and <tt>render "foo/bar"</tt> to
     # <tt>render :file => "foo/bar"</tt>.
-    # :api: plugin
-    def _normalize_args(action = nil, options = {})
+    def _normalize_args(action = nil, options = {}) # :doc:
       if action.respond_to?(:permitted?)
         if action.permitted?
           action
@@ -95,20 +90,17 @@ module AbstractController
     end
 
     # Normalize options.
-    # :api: plugin
-    def _normalize_options(options)
+    def _normalize_options(options) # :doc:
       options
     end
 
     # Process extra options.
-    # :api: plugin
-    def _process_options(options)
+    def _process_options(options) # :doc:
       options
     end
 
     # Process the rendered format.
-    # :api: private
-    def _process_format(format)
+    def _process_format(format) # :nodoc:
     end
 
     def _process_variant(options)
@@ -121,8 +113,7 @@ module AbstractController
     end
 
     # Normalize args and options.
-    # :api: private
-    def _normalize_render(*args, &block)
+    def _normalize_render(*args, &block) # :nodoc:
       options = _normalize_args(*args, &block)
       _process_variant(options)
       _normalize_options(options)
diff --git a/actionpack/lib/action_controller.rb b/actionpack/lib/action_controller.rb
index e893507baa..29d61c3ceb 100644
--- a/actionpack/lib/action_controller.rb
+++ b/actionpack/lib/action_controller.rb
@@ -3,8 +3,8 @@
 require "active_support/rails"
 require "abstract_controller"
 require "action_dispatch"
-require_relative "action_controller/metal/live"
-require_relative "action_controller/metal/strong_parameters"
+require "action_controller/metal/live"
+require "action_controller/metal/strong_parameters"
 
 module ActionController
   extend ActiveSupport::Autoload
@@ -22,8 +22,10 @@ module ActionController
 
   autoload_under "metal" do
     autoload :ConditionalGet
+    autoload :ContentSecurityPolicy
     autoload :Cookies
     autoload :DataStreaming
+    autoload :DefaultHeaders
     autoload :EtagWithTemplateDigest
     autoload :EtagWithFlash
     autoload :Flash
diff --git a/actionpack/lib/action_controller/api.rb b/actionpack/lib/action_controller/api.rb
index ba9af4767e..93ffff1bd6 100644
--- a/actionpack/lib/action_controller/api.rb
+++ b/actionpack/lib/action_controller/api.rb
@@ -2,7 +2,7 @@
 
 require "action_view"
 require "action_controller"
-require_relative "log_subscriber"
+require "action_controller/log_subscriber"
 
 module ActionController
   # API Controller is a lightweight version of <tt>ActionController::Base</tt>,
@@ -122,6 +122,7 @@ module ActionController
 
       ForceSSL,
       DataStreaming,
+      DefaultHeaders,
 
       # Before callbacks should also be executed as early as possible, so
       # also include them at the bottom.
diff --git a/actionpack/lib/action_controller/base.rb b/actionpack/lib/action_controller/base.rb
index bbc48e6eb7..2e565d5d44 100644
--- a/actionpack/lib/action_controller/base.rb
+++ b/actionpack/lib/action_controller/base.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
 require "action_view"
-require_relative "log_subscriber"
-require_relative "metal/params_wrapper"
+require "action_controller/log_subscriber"
+require "action_controller/metal/params_wrapper"
 
 module ActionController
   # Action Controllers are the core of a web request in \Rails. They are made up of one or more actions that are executed
@@ -78,7 +78,7 @@ module ActionController
   #
   # You can retrieve it again through the same hash:
   #
-  #   Hello #{session[:person]}
+  #   "Hello #{session[:person]}"
   #
   # For removing objects from the session, you can either assign a single key to +nil+:
   #
@@ -225,12 +225,14 @@ module ActionController
       Flash,
       FormBuilder,
       RequestForgeryProtection,
+      ContentSecurityPolicy,
       ForceSSL,
       Streaming,
       DataStreaming,
       HttpAuthentication::Basic::ControllerMethods,
       HttpAuthentication::Digest::ControllerMethods,
       HttpAuthentication::Token::ControllerMethods,
+      DefaultHeaders,
 
       # Before callbacks should also be executed as early as possible, so
       # also include them at the bottom.
@@ -263,12 +265,6 @@ module ActionController
       PROTECTED_IVARS
     end
 
-    def self.make_response!(request)
-      ActionDispatch::Response.create.tap do |res|
-        res.request = request
-      end
-    end
-
     ActiveSupport.run_load_hooks(:action_controller_base, self)
     ActiveSupport.run_load_hooks(:action_controller, self)
   end
diff --git a/actionpack/lib/action_controller/metal.rb b/actionpack/lib/action_controller/metal.rb
index 457884ea08..f875aa5e6b 100644
--- a/actionpack/lib/action_controller/metal.rb
+++ b/actionpack/lib/action_controller/metal.rb
@@ -230,18 +230,16 @@ module ActionController
 
     # Returns a Rack endpoint for the given action name.
     def self.action(name)
+      app = lambda { |env|
+        req = ActionDispatch::Request.new(env)
+        res = make_response! req
+        new.dispatch(name, req, res)
+      }
+
       if middleware_stack.any?
-        middleware_stack.build(name) do |env|
-          req = ActionDispatch::Request.new(env)
-          res = make_response! req
-          new.dispatch(name, req, res)
-        end
+        middleware_stack.build(name, app)
       else
-        lambda { |env|
-          req = ActionDispatch::Request.new(env)
-          res = make_response! req
-          new.dispatch(name, req, res)
-        }
+        app
       end
     end
 
diff --git a/actionpack/lib/action_controller/metal/content_security_policy.rb b/actionpack/lib/action_controller/metal/content_security_policy.rb
new file mode 100644
index 0000000000..b8fab4ebe3
--- /dev/null
+++ b/actionpack/lib/action_controller/metal/content_security_policy.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+module ActionController #:nodoc:
+  module ContentSecurityPolicy
+    # TODO: Documentation
+    extend ActiveSupport::Concern
+
+    include AbstractController::Helpers
+    include AbstractController::Callbacks
+
+    included do
+      helper_method :content_security_policy?
+      helper_method :content_security_policy_nonce
+    end
+
+    module ClassMethods
+      def content_security_policy(enabled = true, **options, &block)
+        before_action(options) do
+          if block_given?
+            policy = current_content_security_policy
+            yield policy
+            request.content_security_policy = policy
+          end
+
+          unless enabled
+            request.content_security_policy = nil
+          end
+        end
+      end
+
+      def content_security_policy_report_only(report_only = true, **options)
+        before_action(options) do
+          request.content_security_policy_report_only = report_only
+        end
+      end
+    end
+
+    private
+
+      def content_security_policy?
+        request.content_security_policy
+      end
+
+      def content_security_policy_nonce
+        request.content_security_policy_nonce
+      end
+
+      def current_content_security_policy
+        request.content_security_policy.try(:clone) || ActionDispatch::ContentSecurityPolicy.new
+      end
+  end
+end
diff --git a/actionpack/lib/action_controller/metal/data_streaming.rb b/actionpack/lib/action_controller/metal/data_streaming.rb
index 882f6f3d0a..5a82ccf668 100644
--- a/actionpack/lib/action_controller/metal/data_streaming.rb
+++ b/actionpack/lib/action_controller/metal/data_streaming.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "exceptions"
+require "action_controller/metal/exceptions"
 
 module ActionController #:nodoc:
   # Methods for sending arbitrary data and for streaming files to the browser,
diff --git a/actionpack/lib/action_controller/metal/default_headers.rb b/actionpack/lib/action_controller/metal/default_headers.rb
new file mode 100644
index 0000000000..eef0602fcd
--- /dev/null
+++ b/actionpack/lib/action_controller/metal/default_headers.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module ActionController
+  # Allows configuring default headers that will be automatically merged into
+  # each response.
+  module DefaultHeaders
+    extend ActiveSupport::Concern
+
+    module ClassMethods
+      def make_response!(request)
+        ActionDispatch::Response.create.tap do |res|
+          res.request = request
+        end
+      end
+    end
+  end
+end
diff --git a/actionpack/lib/action_controller/metal/exceptions.rb b/actionpack/lib/action_controller/metal/exceptions.rb
index f808295720..ce9eb209fe 100644
--- a/actionpack/lib/action_controller/metal/exceptions.rb
+++ b/actionpack/lib/action_controller/metal/exceptions.rb
@@ -22,7 +22,7 @@ module ActionController
     end
   end
 
-  class ActionController::UrlGenerationError < ActionControllerError #:nodoc:
+  class UrlGenerationError < ActionControllerError #:nodoc:
   end
 
   class MethodNotAllowed < ActionControllerError #:nodoc:
@@ -34,9 +34,6 @@ module ActionController
   class NotImplemented < MethodNotAllowed #:nodoc:
   end
 
-  class UnknownController < ActionControllerError #:nodoc:
-  end
-
   class MissingFile < ActionControllerError #:nodoc:
   end
 
@@ -53,4 +50,7 @@ module ActionController
 
   class UnknownFormat < ActionControllerError #:nodoc:
   end
+
+  class MissingExactTemplate < UnknownFormat #:nodoc:
+  end
 end
diff --git a/actionpack/lib/action_controller/metal/force_ssl.rb b/actionpack/lib/action_controller/metal/force_ssl.rb
index 0ba1f9f783..8d53a30e93 100644
--- a/actionpack/lib/action_controller/metal/force_ssl.rb
+++ b/actionpack/lib/action_controller/metal/force_ssl.rb
@@ -4,18 +4,10 @@ require "active_support/core_ext/hash/except"
 require "active_support/core_ext/hash/slice"
 
 module ActionController
-  # This module provides a method which will redirect the browser to use the secured HTTPS
-  # protocol. This will ensure that users' sensitive information will be
-  # transferred safely over the internet. You _should_ always force the browser
-  # to use HTTPS when you're transferring sensitive information such as
-  # user authentication, account information, or credit card information.
-  #
-  # Note that if you are really concerned about your application security,
-  # you might consider using +config.force_ssl+ in your config file instead.
-  # That will ensure all the data is transferred via HTTPS, and will
-  # prevent the user from getting their session hijacked when accessing the
-  # site over unsecured HTTP protocol.
-  module ForceSSL
+  # This module is deprecated in favor of +config.force_ssl+ in your environment
+  # config file. This will ensure all communication to non-whitelisted endpoints
+  # served by your application occurs over HTTPS.
+  module ForceSSL # :nodoc:
     extend ActiveSupport::Concern
     include AbstractController::Callbacks
 
@@ -23,45 +15,17 @@ module ActionController
     URL_OPTIONS = [:protocol, :host, :domain, :subdomain, :port, :path]
     REDIRECT_OPTIONS = [:status, :flash, :alert, :notice]
 
-    module ClassMethods
-      # Force the request to this particular controller or specified actions to be
-      # through the HTTPS protocol.
-      #
-      # If you need to disable this for any reason (e.g. development) then you can use
-      # an +:if+ or +:unless+ condition.
-      #
-      #     class AccountsController < ApplicationController
-      #       force_ssl if: :ssl_configured?
-      #
-      #       def ssl_configured?
-      #         !Rails.env.development?
-      #       end
-      #     end
-      #
-      # ==== URL Options
-      # You can pass any of the following options to affect the redirect url
-      # * <tt>host</tt>       - Redirect to a different host name
-      # * <tt>subdomain</tt>  - Redirect to a different subdomain
-      # * <tt>domain</tt>     - Redirect to a different domain
-      # * <tt>port</tt>       - Redirect to a non-standard port
-      # * <tt>path</tt>       - Redirect to a different path
-      #
-      # ==== Redirect Options
-      # You can pass any of the following options to affect the redirect status and response
-      # * <tt>status</tt>     - Redirect with a custom status (default is 301 Moved Permanently)
-      # * <tt>flash</tt>      - Set a flash message when redirecting
-      # * <tt>alert</tt>      - Set an alert message when redirecting
-      # * <tt>notice</tt>     - Set a notice message when redirecting
-      #
-      # ==== Action Options
-      # You can pass any of the following options to affect the before_action callback
-      # * <tt>only</tt>       - The callback should be run only for this action
-      # * <tt>except</tt>     - The callback should be run for all actions except this action
-      # * <tt>if</tt>         - A symbol naming an instance method or a proc; the
-      #   callback will be called only when it returns a true value.
-      # * <tt>unless</tt>     - A symbol naming an instance method or a proc; the
-      #   callback will be called only when it returns a false value.
+    module ClassMethods # :nodoc:
       def force_ssl(options = {})
+        ActiveSupport::Deprecation.warn(<<-MESSAGE.squish)
+          Controller-level `force_ssl` is deprecated and will be removed from
+          Rails 6.1. Please enable `config.force_ssl` in your environment
+          configuration to enable the ActionDispatch::SSL middleware to more
+          fully enforce that your application communicate over HTTPS. If needed,
+          you can use `config.ssl_options` to exempt matching endpoints from
+          being redirected to HTTPS.
+        MESSAGE
+
         action_options = options.slice(*ACTION_OPTIONS)
         redirect_options = options.except(*ACTION_OPTIONS)
         before_action(action_options) do
@@ -70,11 +34,6 @@ module ActionController
       end
     end
 
-    # Redirect the existing request to use the HTTPS protocol.
-    #
-    # ==== Parameters
-    # * <tt>host_or_options</tt> - Either a host name or any of the url and
-    #   redirect options available to the <tt>force_ssl</tt> method.
     def force_ssl_redirect(host_or_options = nil)
       unless request.ssl?
         options = {
diff --git a/actionpack/lib/action_controller/metal/http_authentication.rb b/actionpack/lib/action_controller/metal/http_authentication.rb
index 08d9b094f3..01676f3237 100644
--- a/actionpack/lib/action_controller/metal/http_authentication.rb
+++ b/actionpack/lib/action_controller/metal/http_authentication.rb
@@ -72,10 +72,10 @@ module ActionController
             before_action(options.except(:name, :password, :realm)) do
               authenticate_or_request_with_http_basic(options[:realm] || "Application") do |name, password|
                 # This comparison uses & so that it doesn't short circuit and
-                # uses `variable_size_secure_compare` so that length information
+                # uses `secure_compare` so that length information
                 # isn't leaked.
-                ActiveSupport::SecurityUtils.variable_size_secure_compare(name, options[:name]) &
-                  ActiveSupport::SecurityUtils.variable_size_secure_compare(password, options[:password])
+                ActiveSupport::SecurityUtils.secure_compare(name, options[:name]) &
+                  ActiveSupport::SecurityUtils.secure_compare(password, options[:password])
               end
             end
           end
@@ -248,7 +248,7 @@ module ActionController
       def decode_credentials(header)
         ActiveSupport::HashWithIndifferentAccess[header.to_s.gsub(/^Digest\s+/, "").split(",").map do |pair|
           key, value = pair.split("=", 2)
-          [key.strip, value.to_s.gsub(/^"|"$/, "").delete('\'')]
+          [key.strip, value.to_s.gsub(/^"|"$/, "").delete("'")]
         end]
       end
 
@@ -350,10 +350,7 @@ module ActionController
     #         authenticate_or_request_with_http_token do |token, options|
     #           # Compare the tokens in a time-constant manner, to mitigate
     #           # timing attacks.
-    #           ActiveSupport::SecurityUtils.secure_compare(
-    #             ::Digest::SHA256.hexdigest(token),
-    #             ::Digest::SHA256.hexdigest(TOKEN)
-    #           )
+    #           ActiveSupport::SecurityUtils.secure_compare(token, TOKEN)
     #         end
     #       end
     #   end
diff --git a/actionpack/lib/action_controller/metal/implicit_render.rb b/actionpack/lib/action_controller/metal/implicit_render.rb
index ac0c127cdc..d3bb58f48b 100644
--- a/actionpack/lib/action_controller/metal/implicit_render.rb
+++ b/actionpack/lib/action_controller/metal/implicit_render.rb
@@ -41,18 +41,8 @@ module ActionController
 
         raise ActionController::UnknownFormat, message
       elsif interactive_browser_request?
-        message = "#{self.class.name}\##{action_name} is missing a template " \
-          "for this request format and variant.\n\n" \
-          "request.formats: #{request.formats.map(&:to_s).inspect}\n" \
-          "request.variant: #{request.variant.inspect}\n\n" \
-          "NOTE! For XHR/Ajax or API requests, this action would normally " \
-          "respond with 204 No Content: an empty white screen. Since you're " \
-          "loading it in a web browser, we assume that you expected to " \
-          "actually render a template, not nothing, so we're showing an " \
-          "error to be extra-clear. If you expect 204 No Content, carry on. " \
-          "That's what you'll get from an XHR or API request. Give it a shot."
-
-        raise ActionController::UnknownFormat, message
+        message = "#{self.class.name}\##{action_name} is missing a template for request formats: #{request.formats.map(&:to_s).join(',')}"
+        raise ActionController::MissingExactTemplate, message
       else
         logger.info "No template found for #{self.class.name}\##{action_name}, rendering head :no_content" if logger
         super
diff --git a/actionpack/lib/action_controller/metal/instrumentation.rb b/actionpack/lib/action_controller/metal/instrumentation.rb
index 476f0843b2..be9449629f 100644
--- a/actionpack/lib/action_controller/metal/instrumentation.rb
+++ b/actionpack/lib/action_controller/metal/instrumentation.rb
@@ -83,16 +83,13 @@ module ActionController
     #   def cleanup_view_runtime
     #     super - time_taken_in_something_expensive
     #   end
-    #
-    # :api: plugin
-    def cleanup_view_runtime
+    def cleanup_view_runtime # :doc:
       yield
     end
 
     # Every time after an action is processed, this method is invoked
     # with the payload, so you can add more information.
-    # :api: plugin
-    def append_info_to_payload(payload)
+    def append_info_to_payload(payload) # :doc:
       payload[:view_runtime] = view_runtime
     end
 
@@ -100,7 +97,6 @@ module ActionController
       # A hook which allows other frameworks to log what happened during
       # controller process action. This method should return an array
       # with the messages to be added.
-      # :api: plugin
       def log_process_action(payload) #:nodoc:
         messages, view_runtime = [], payload[:view_runtime]
         messages << ("Views: %.1fms" % view_runtime.to_f) if view_runtime
diff --git a/actionpack/lib/action_controller/metal/params_wrapper.rb b/actionpack/lib/action_controller/metal/params_wrapper.rb
index f4f2381286..a678377d4f 100644
--- a/actionpack/lib/action_controller/metal/params_wrapper.rb
+++ b/actionpack/lib/action_controller/metal/params_wrapper.rb
@@ -112,6 +112,14 @@ module ActionController
               else
                 self.include = m.attribute_names
               end
+
+              if m.respond_to?(:nested_attributes_options) && m.nested_attributes_options.keys.any?
+                self.include += m.nested_attributes_options.keys.map do |key|
+                  key.to_s.concat("_attributes")
+                end
+              end
+
+              self.include
             end
           end
         end
diff --git a/actionpack/lib/action_controller/metal/redirecting.rb b/actionpack/lib/action_controller/metal/redirecting.rb
index 5cd8568d8d..4c2b5120eb 100644
--- a/actionpack/lib/action_controller/metal/redirecting.rb
+++ b/actionpack/lib/action_controller/metal/redirecting.rb
@@ -68,7 +68,7 @@ module ActionController
     # if possible, otherwise redirects to the provided default fallback
     # location.
     #
-    # The referrer information is pulled from the HTTP `Referer` (sic) header on
+    # The referrer information is pulled from the HTTP +Referer+ (sic) header on
     # the request. This is an optional header and its presence on the request is
     # subject to browser security settings and user preferences. If the request
     # is missing this header, the <tt>fallback_location</tt> will be used.
@@ -79,15 +79,18 @@ module ActionController
     #   redirect_back fallback_location: "/images/screenshot.jpg"
     #   redirect_back fallback_location: posts_url
     #   redirect_back fallback_location: proc { edit_post_url(@post) }
+    #   redirect_back fallback_location: '/', allow_other_host: false
     #
-    # All options that can be passed to <tt>redirect_to</tt> are accepted as
+    # ==== Options
+    # * <tt>:fallback_location</tt> - The default fallback location that will be used on missing +Referer+ header.
+    # * <tt>:allow_other_host</tt> - Allow or disallow redirection to the host that is different to the current host, defaults to true.
+    #
+    # All other options that can be passed to <tt>redirect_to</tt> are accepted as
     # options and the behavior is identical.
-    def redirect_back(fallback_location:, **args)
-      if referer = request.headers["Referer"]
-        redirect_to referer, **args
-      else
-        redirect_to fallback_location, **args
-      end
+    def redirect_back(fallback_location:, allow_other_host: true, **args)
+      referer = request.headers["Referer"]
+      redirect_to_referer = referer && (allow_other_host || _url_host_allowed?(referer))
+      redirect_to redirect_to_referer ? referer : fallback_location, **args
     end
 
     def _compute_redirect_to_location(request, options) #:nodoc:
@@ -120,5 +123,11 @@ module ActionController
           302
         end
       end
+
+      def _url_host_allowed?(url)
+        URI(url.to_s).host == request.host
+      rescue ArgumentError, URI::Error
+        false
+      end
   end
 end
diff --git a/actionpack/lib/action_controller/metal/renderers.rb b/actionpack/lib/action_controller/metal/renderers.rb
index 26752571f8..b81d3ef539 100644
--- a/actionpack/lib/action_controller/metal/renderers.rb
+++ b/actionpack/lib/action_controller/metal/renderers.rb
@@ -85,7 +85,7 @@ module ActionController
     def self.remove(key)
       RENDERERS.delete(key.to_sym)
       method_name = _render_with_renderer_method_name(key)
-      remove_method(method_name) if method_defined?(method_name)
+      remove_possible_method(method_name)
     end
 
     def self._render_with_renderer_method_name(key)
diff --git a/actionpack/lib/action_controller/metal/rendering.rb b/actionpack/lib/action_controller/metal/rendering.rb
index d32eabf9ba..6d181e6456 100644
--- a/actionpack/lib/action_controller/metal/rendering.rb
+++ b/actionpack/lib/action_controller/metal/rendering.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/string/filters"
-
 module ActionController
   module Rendering
     extend ActiveSupport::Concern
@@ -42,7 +40,7 @@ module ActionController
     def render_to_string(*)
       result = super
       if result.respond_to?(:each)
-        string = ""
+        string = "".dup
         result.each { |r| string << r }
         string
       else
diff --git a/actionpack/lib/action_controller/metal/request_forgery_protection.rb b/actionpack/lib/action_controller/metal/request_forgery_protection.rb
index d397c62461..953f3c47ed 100644
--- a/actionpack/lib/action_controller/metal/request_forgery_protection.rb
+++ b/actionpack/lib/action_controller/metal/request_forgery_protection.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "rack/session/abstract/id"
-require_relative "exceptions"
+require "action_controller/metal/exceptions"
 require "active_support/security_utils"
 
 module ActionController #:nodoc:
@@ -22,7 +22,7 @@ module ActionController #:nodoc:
   # Since HTML and JavaScript requests are typically made from the browser, we
   # need to ensure to verify request authenticity for the web browser. We can
   # use session-oriented authentication for these types of requests, by using
-  # the `protect_from_forgery` method in our controllers.
+  # the <tt>protect_from_forgery</tt> method in our controllers.
   #
   # GET requests are not protected since they don't have side effects like writing
   # to the database and don't leak sensitive information. JavaScript requests are
@@ -216,7 +216,7 @@ module ActionController #:nodoc:
       # The actual before_action that is used to verify the CSRF token.
       # Don't override this directly. Provide your own forgery protection
       # strategy instead. If you override, you'll disable same-origin
-      # `<script>` verification.
+      # <tt><script></tt> verification.
       #
       # Lean on the protect_from_forgery declaration to mark which actions are
       # due for same-origin request verification. If protect_from_forgery is
@@ -248,8 +248,9 @@ module ActionController #:nodoc:
         "If you know what you're doing, go ahead and disable forgery " \
         "protection on this action to permit cross-origin JavaScript embedding."
       private_constant :CROSS_ORIGIN_JAVASCRIPT_WARNING
+      # :startdoc:
 
-      # If `verify_authenticity_token` was run (indicating that we have
+      # If +verify_authenticity_token+ was run (indicating that we have
       # forgery protection enabled for this request) then also verify that
       # we aren't serving an unauthorized cross-origin response.
       def verify_same_origin_request # :doc:
@@ -266,7 +267,7 @@ module ActionController #:nodoc:
         @marked_for_same_origin_verification = request.get?
       end
 
-      # If the `verify_authenticity_token` before_action ran, verify that
+      # If the +verify_authenticity_token+ before_action ran, verify that
       # JavaScript responses are only served to same-origin GET requests.
       def marked_for_same_origin_verification? # :doc:
         @marked_for_same_origin_verification ||= false
@@ -368,7 +369,7 @@ module ActionController #:nodoc:
       end
 
       def compare_with_real_token(token, session) # :doc:
-        ActiveSupport::SecurityUtils.secure_compare(token, real_csrf_token(session))
+        ActiveSupport::SecurityUtils.fixed_length_secure_compare(token, real_csrf_token(session))
       end
 
       def valid_per_form_csrf_token?(token, session) # :doc:
@@ -379,7 +380,7 @@ module ActionController #:nodoc:
             request.request_method
           )
 
-          ActiveSupport::SecurityUtils.secure_compare(token, correct_token)
+          ActiveSupport::SecurityUtils.fixed_length_secure_compare(token, correct_token)
         else
           false
         end
@@ -399,9 +400,14 @@ module ActionController #:nodoc:
       end
 
       def xor_byte_strings(s1, s2) # :doc:
-        s2_bytes = s2.bytes
-        s1.each_byte.with_index { |c1, i| s2_bytes[i] ^= c1 }
-        s2_bytes.pack("C*")
+        s2 = s2.dup
+        size = s1.bytesize
+        i = 0
+        while i < size
+          s2.setbyte(i, s1.getbyte(i) ^ s2.getbyte(i))
+          i += 1
+        end
+        s2
       end
 
       # The form's authenticity parameter. Override to provide your own.
@@ -414,11 +420,21 @@ module ActionController #:nodoc:
         allow_forgery_protection
       end
 
+      NULL_ORIGIN_MESSAGE = <<~MSG
+        The browser returned a 'null' origin for a request with origin-based forgery protection turned on. This usually
+        means you have the 'no-referrer' Referrer-Policy header enabled, or that the request came from a site that
+        refused to give its origin. This makes it impossible for Rails to verify the source of the requests. Likely the
+        best solution is to change your referrer policy to something less strict like same-origin or strict-same-origin.
+        If you cannot change the referrer policy, you can disable origin checking with the
+        Rails.application.config.action_controller.forgery_protection_origin_check setting.
+      MSG
+
       # Checks if the request originated from the same origin by looking at the
       # Origin header.
       def valid_request_origin? # :doc:
         if forgery_protection_origin_check
           # We accept blank origin headers because some user agents don't send it.
+          raise InvalidAuthenticityToken, NULL_ORIGIN_MESSAGE if request.origin == "null"
           request.origin.nil? || request.origin == request.base_url
         else
           true
diff --git a/actionpack/lib/action_controller/metal/rescue.rb b/actionpack/lib/action_controller/metal/rescue.rb
index 843c99f57b..44f7fb7a07 100644
--- a/actionpack/lib/action_controller/metal/rescue.rb
+++ b/actionpack/lib/action_controller/metal/rescue.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 module ActionController #:nodoc:
-  # This module is responsible for providing `rescue_from` helpers
+  # This module is responsible for providing +rescue_from+ helpers
   # to controllers and configuring when detailed exceptions must be
   # shown.
   module Rescue
@@ -10,8 +10,8 @@ module ActionController #:nodoc:
 
     # Override this method if you want to customize when detailed
     # exceptions must be shown. This method is only called when
-    # consider_all_requests_local is false. By default, it returns
-    # false, but someone may set it to `request.local?` so local
+    # +consider_all_requests_local+ is +false+. By default, it returns
+    # +false+, but someone may set it to <tt>request.local?</tt> so local
     # requests in production still show the detailed exception pages.
     def show_detailed_exceptions?
       false
diff --git a/actionpack/lib/action_controller/metal/streaming.rb b/actionpack/lib/action_controller/metal/streaming.rb
index 0b1598bf1b..8dc01a5eb9 100644
--- a/actionpack/lib/action_controller/metal/streaming.rb
+++ b/actionpack/lib/action_controller/metal/streaming.rb
@@ -183,7 +183,7 @@ module ActionController #:nodoc:
   #   unicorn_rails --config-file unicorn.config.rb
   #
   # You may also want to configure other parameters like <tt>:tcp_nodelay</tt>.
-  # Please check its documentation for more information: http://unicorn.bogomips.org/Unicorn/Configurator.html#method-i-listen
+  # Please check its documentation for more information: https://bogomips.org/unicorn/Unicorn/Configurator.html#method-i-listen
   #
   # If you are using Unicorn with NGINX, you may need to tweak NGINX.
   # Streaming should work out of the box on Rainbows.
diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index ef7c4c4c16..46c0e80194 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/hash/indifferent_access"
-require "active_support/core_ext/hash/transform_values"
 require "active_support/core_ext/array/wrap"
 require "active_support/core_ext/string/filters"
 require "active_support/core_ext/object/to_query"
@@ -335,7 +334,7 @@ module ActionController
     # the same way as <tt>Hash#each_pair</tt>.
     def each_pair(&block)
       @parameters.each_pair do |key, value|
-        yield key, convert_hashes_to_parameters(key, value)
+        yield [key, convert_hashes_to_parameters(key, value)]
       end
     end
     alias_method :each, :each_pair
@@ -375,7 +374,7 @@ module ActionController
     #   Person.new(params) # => #<Person id: nil, name: "Francesco">
     def permit!
       each_pair do |key, value|
-        Array.wrap(value).each do |v|
+        Array.wrap(value).flatten.each do |v|
           v.permit! if v.respond_to? :permit!
         end
       end
@@ -561,12 +560,14 @@ module ActionController
     # Returns a parameter for the given +key+. If the +key+
     # can't be found, there are several options: With no other arguments,
     # it will raise an <tt>ActionController::ParameterMissing</tt> error;
-    # if more arguments are given, then that will be returned; if a block
+    # if a second argument is given, then that is returned (converted to an
+    # instance of ActionController::Parameters if possible); if a block
     # is given, then that will be run and its result returned.
     #
     #   params = ActionController::Parameters.new(person: { name: "Francesco" })
     #   params.fetch(:person)               # => <ActionController::Parameters {"name"=>"Francesco"} permitted: false>
     #   params.fetch(:none)                 # => ActionController::ParameterMissing: param is missing or the value is empty: none
+    #   params.fetch(:none, {})             # => <ActionController::Parameters {} permitted: false>
     #   params.fetch(:none, "Francesco")    # => "Francesco"
     #   params.fetch(:none) { "Francesco" } # => "Francesco"
     def fetch(key, *args)
@@ -581,19 +582,18 @@ module ActionController
       )
     end
 
-    if Hash.method_defined?(:dig)
-      # Extracts the nested parameter from the given +keys+ by calling +dig+
-      # at each step. Returns +nil+ if any intermediate step is +nil+.
-      #
-      #   params = ActionController::Parameters.new(foo: { bar: { baz: 1 } })
-      #   params.dig(:foo, :bar, :baz) # => 1
-      #   params.dig(:foo, :zot, :xyz) # => nil
-      #
-      #   params2 = ActionController::Parameters.new(foo: [10, 11, 12])
-      #   params2.dig(:foo, 1) # => 11
-      def dig(*keys)
-        convert_value_to_parameters(@parameters.dig(*keys))
-      end
+    # Extracts the nested parameter from the given +keys+ by calling +dig+
+    # at each step. Returns +nil+ if any intermediate step is +nil+.
+    #
+    #   params = ActionController::Parameters.new(foo: { bar: { baz: 1 } })
+    #   params.dig(:foo, :bar, :baz) # => 1
+    #   params.dig(:foo, :zot, :xyz) # => nil
+    #
+    #   params2 = ActionController::Parameters.new(foo: [10, 11, 12])
+    #   params2.dig(:foo, 1) # => 11
+    def dig(*keys)
+      convert_hashes_to_parameters(keys.first, @parameters[keys.first])
+      @parameters.dig(*keys)
     end
 
     # Returns a new <tt>ActionController::Parameters</tt> instance that
diff --git a/actionpack/lib/action_controller/metal/testing.rb b/actionpack/lib/action_controller/metal/testing.rb
index b07f1f3d8c..6e8a95040f 100644
--- a/actionpack/lib/action_controller/metal/testing.rb
+++ b/actionpack/lib/action_controller/metal/testing.rb
@@ -12,11 +12,5 @@ module ActionController
         self.params = nil
       end
     end
-
-    module ClassMethods
-      def before_filters
-        _process_action_callbacks.find_all { |x| x.kind == :before }.map(&:name)
-      end
-    end
   end
 end
diff --git a/actionpack/lib/action_controller/railtie.rb b/actionpack/lib/action_controller/railtie.rb
index 769be39004..7d42f5d931 100644
--- a/actionpack/lib/action_controller/railtie.rb
+++ b/actionpack/lib/action_controller/railtie.rb
@@ -4,7 +4,7 @@ require "rails"
 require "action_controller"
 require "action_dispatch/railtie"
 require "abstract_controller/railties/routes_helpers"
-require_relative "railties/helpers"
+require "action_controller/railties/helpers"
 require "action_view/railtie"
 
 module ActionController
diff --git a/actionpack/lib/action_controller/test_case.rb b/actionpack/lib/action_controller/test_case.rb
index 50a96bce98..5d784ceb31 100644
--- a/actionpack/lib/action_controller/test_case.rb
+++ b/actionpack/lib/action_controller/test_case.rb
@@ -4,9 +4,10 @@ require "rack/session/abstract/id"
 require "active_support/core_ext/hash/conversions"
 require "active_support/core_ext/object/to_query"
 require "active_support/core_ext/module/anonymous"
+require "active_support/core_ext/module/redefine_method"
 require "active_support/core_ext/hash/keys"
 require "active_support/testing/constant_lookup"
-require_relative "template_assertions"
+require "action_controller/template_assertions"
 require "rails-dom-testing"
 
 module ActionController
@@ -19,7 +20,7 @@ module ActionController
     # the database on the main thread, so they could open a txn, then the
     # controller thread will open a new connection and try to access data
     # that's only visible to the main thread's txn. This is the problem in #23483.
-    remove_method :new_controller_thread
+    silence_redefinition_of_method :new_controller_thread
     def new_controller_thread # :nodoc:
       yield
     end
@@ -255,7 +256,7 @@ module ActionController
   #
   #   def test_create
   #     json = {book: { title: "Love Hina" }}.to_json
-  #     post :create, json
+  #     post :create, body: json
   #   end
   #
   # == Special instance variables
@@ -459,10 +460,6 @@ module ActionController
       def process(action, method: "GET", params: {}, session: nil, body: nil, flash: {}, format: nil, xhr: false, as: nil)
         check_required_ivars
 
-        if body
-          @request.set_header "RAW_POST_DATA", body
-        end
-
         http_method = method.to_s.upcase
 
         @html_document = nil
@@ -477,6 +474,10 @@ module ActionController
         @response.request = @request
         @controller.recycle!
 
+        if body
+          @request.set_header "RAW_POST_DATA", body
+        end
+
         @request.set_header "REQUEST_METHOD", http_method
 
         if as
@@ -603,6 +604,8 @@ module ActionController
           env.delete "action_dispatch.request.query_parameters"
           env.delete "action_dispatch.request.request_parameters"
           env["rack.input"] = StringIO.new
+          env.delete "CONTENT_LENGTH"
+          env.delete "RAW_POST_DATA"
           env
         end
 
diff --git a/actionpack/lib/action_dispatch.rb b/actionpack/lib/action_dispatch.rb
index 34937f3229..0822cdc0a6 100644
--- a/actionpack/lib/action_dispatch.rb
+++ b/actionpack/lib/action_dispatch.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 #--
-# Copyright (c) 2004-2017 David Heinemeier Hansson
+# Copyright (c) 2004-2018 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the
@@ -42,6 +42,7 @@ module ActionDispatch
 
   eager_autoload do
     autoload_under "http" do
+      autoload :ContentSecurityPolicy
       autoload :Request
       autoload :Response
     end
diff --git a/actionpack/lib/action_dispatch/http/cache.rb b/actionpack/lib/action_dispatch/http/cache.rb
index 2cc609406a..a8febc32b3 100644
--- a/actionpack/lib/action_dispatch/http/cache.rb
+++ b/actionpack/lib/action_dispatch/http/cache.rb
@@ -97,7 +97,7 @@ module ActionDispatch
         # support strong ETags and will ignore weak ETags entirely.
         #
         # Weak ETags are what we almost always need, so they're the default.
-        # Check out `#strong_etag=` to provide a strong ETag validator.
+        # Check out #strong_etag= to provide a strong ETag validator.
         def etag=(weak_validators)
           self.weak_etag = weak_validators
         end
@@ -133,7 +133,7 @@ module ActionDispatch
         end
 
         def generate_strong_etag(validators)
-          %("#{Digest::MD5.hexdigest(ActiveSupport::Cache.expand_cache_key(validators))}")
+          %("#{ActiveSupport::Digest.hexdigest(ActiveSupport::Cache.expand_cache_key(validators))}")
         end
 
         def cache_control_segments
@@ -166,19 +166,23 @@ module ActionDispatch
           @cache_control = cache_control_headers
         end
 
-        def handle_conditional_get!
-          if etag? || last_modified? || !@cache_control.empty?
-            set_conditional_cache_control!(@cache_control)
-          end
-        end
-
         DEFAULT_CACHE_CONTROL = "max-age=0, private, must-revalidate".freeze
         NO_CACHE              = "no-cache".freeze
         PUBLIC                = "public".freeze
         PRIVATE               = "private".freeze
         MUST_REVALIDATE       = "must-revalidate".freeze
 
-        def set_conditional_cache_control!(cache_control)
+        def handle_conditional_get!
+          # Normally default cache control setting is handled by ETag
+          # middleware. But, if an etag is already set, the middleware
+          # defaults to `no-cache` unless a default `Cache-Control` value is
+          # previously set. So, set a default one here.
+          if (etag? || last_modified?) && !self._cache_control
+            self._cache_control = DEFAULT_CACHE_CONTROL
+          end
+        end
+
+        def merge_and_normalize_cache_control!(cache_control)
           control = {}
           cc_headers = cache_control_headers
           if extras = cc_headers.delete(:extras)
@@ -191,7 +195,7 @@ module ActionDispatch
           control.merge! cache_control
 
           if control.empty?
-            self._cache_control = DEFAULT_CACHE_CONTROL
+            # Let middleware handle default behavior
           elsif control[:no_cache]
             self._cache_control = NO_CACHE
             if control[:extras]
diff --git a/actionpack/lib/action_dispatch/http/content_security_policy.rb b/actionpack/lib/action_dispatch/http/content_security_policy.rb
new file mode 100644
index 0000000000..35041fd072
--- /dev/null
+++ b/actionpack/lib/action_dispatch/http/content_security_policy.rb
@@ -0,0 +1,271 @@
+# frozen_string_literal: true
+
+require "active_support/core_ext/object/deep_dup"
+
+module ActionDispatch #:nodoc:
+  class ContentSecurityPolicy
+    class Middleware
+      CONTENT_TYPE = "Content-Type".freeze
+      POLICY = "Content-Security-Policy".freeze
+      POLICY_REPORT_ONLY = "Content-Security-Policy-Report-Only".freeze
+
+      def initialize(app)
+        @app = app
+      end
+
+      def call(env)
+        request = ActionDispatch::Request.new env
+        _, headers, _ = response = @app.call(env)
+
+        return response unless html_response?(headers)
+        return response if policy_present?(headers)
+
+        if policy = request.content_security_policy
+          nonce = request.content_security_policy_nonce
+          headers[header_name(request)] = policy.build(request.controller_instance, nonce)
+        end
+
+        response
+      end
+
+      private
+
+        def html_response?(headers)
+          if content_type = headers[CONTENT_TYPE]
+            content_type =~ /html/
+          end
+        end
+
+        def header_name(request)
+          if request.content_security_policy_report_only
+            POLICY_REPORT_ONLY
+          else
+            POLICY
+          end
+        end
+
+        def policy_present?(headers)
+          headers[POLICY] || headers[POLICY_REPORT_ONLY]
+        end
+    end
+
+    module Request
+      POLICY = "action_dispatch.content_security_policy".freeze
+      POLICY_REPORT_ONLY = "action_dispatch.content_security_policy_report_only".freeze
+      NONCE_GENERATOR = "action_dispatch.content_security_policy_nonce_generator".freeze
+      NONCE = "action_dispatch.content_security_policy_nonce".freeze
+
+      def content_security_policy
+        get_header(POLICY)
+      end
+
+      def content_security_policy=(policy)
+        set_header(POLICY, policy)
+      end
+
+      def content_security_policy_report_only
+        get_header(POLICY_REPORT_ONLY)
+      end
+
+      def content_security_policy_report_only=(value)
+        set_header(POLICY_REPORT_ONLY, value)
+      end
+
+      def content_security_policy_nonce_generator
+        get_header(NONCE_GENERATOR)
+      end
+
+      def content_security_policy_nonce_generator=(generator)
+        set_header(NONCE_GENERATOR, generator)
+      end
+
+      def content_security_policy_nonce
+        if content_security_policy_nonce_generator
+          if nonce = get_header(NONCE)
+            nonce
+          else
+            set_header(NONCE, generate_content_security_policy_nonce)
+          end
+        end
+      end
+
+      private
+
+        def generate_content_security_policy_nonce
+          content_security_policy_nonce_generator.call(self)
+        end
+    end
+
+    MAPPINGS = {
+      self:           "'self'",
+      unsafe_eval:    "'unsafe-eval'",
+      unsafe_inline:  "'unsafe-inline'",
+      none:           "'none'",
+      http:           "http:",
+      https:          "https:",
+      data:           "data:",
+      mediastream:    "mediastream:",
+      blob:           "blob:",
+      filesystem:     "filesystem:",
+      report_sample:  "'report-sample'",
+      strict_dynamic: "'strict-dynamic'",
+      ws:             "ws:",
+      wss:            "wss:"
+    }.freeze
+
+    DIRECTIVES = {
+      base_uri:        "base-uri",
+      child_src:       "child-src",
+      connect_src:     "connect-src",
+      default_src:     "default-src",
+      font_src:        "font-src",
+      form_action:     "form-action",
+      frame_ancestors: "frame-ancestors",
+      frame_src:       "frame-src",
+      img_src:         "img-src",
+      manifest_src:    "manifest-src",
+      media_src:       "media-src",
+      object_src:      "object-src",
+      prefetch_src:    "prefetch-src",
+      script_src:      "script-src",
+      style_src:       "style-src",
+      worker_src:      "worker-src"
+    }.freeze
+
+    NONCE_DIRECTIVES = %w[script-src].freeze
+
+    private_constant :MAPPINGS, :DIRECTIVES, :NONCE_DIRECTIVES
+
+    attr_reader :directives
+
+    def initialize
+      @directives = {}
+      yield self if block_given?
+    end
+
+    def initialize_copy(other)
+      @directives = other.directives.deep_dup
+    end
+
+    DIRECTIVES.each do |name, directive|
+      define_method(name) do |*sources|
+        if sources.first
+          @directives[directive] = apply_mappings(sources)
+        else
+          @directives.delete(directive)
+        end
+      end
+    end
+
+    def block_all_mixed_content(enabled = true)
+      if enabled
+        @directives["block-all-mixed-content"] = true
+      else
+        @directives.delete("block-all-mixed-content")
+      end
+    end
+
+    def plugin_types(*types)
+      if types.first
+        @directives["plugin-types"] = types
+      else
+        @directives.delete("plugin-types")
+      end
+    end
+
+    def report_uri(uri)
+      @directives["report-uri"] = [uri]
+    end
+
+    def require_sri_for(*types)
+      if types.first
+        @directives["require-sri-for"] = types
+      else
+        @directives.delete("require-sri-for")
+      end
+    end
+
+    def sandbox(*values)
+      if values.empty?
+        @directives["sandbox"] = true
+      elsif values.first
+        @directives["sandbox"] = values
+      else
+        @directives.delete("sandbox")
+      end
+    end
+
+    def upgrade_insecure_requests(enabled = true)
+      if enabled
+        @directives["upgrade-insecure-requests"] = true
+      else
+        @directives.delete("upgrade-insecure-requests")
+      end
+    end
+
+    def build(context = nil, nonce = nil)
+      build_directives(context, nonce).compact.join("; ")
+    end
+
+    private
+      def apply_mappings(sources)
+        sources.map do |source|
+          case source
+          when Symbol
+            apply_mapping(source)
+          when String, Proc
+            source
+          else
+            raise ArgumentError, "Invalid content security policy source: #{source.inspect}"
+          end
+        end
+      end
+
+      def apply_mapping(source)
+        MAPPINGS.fetch(source) do
+          raise ArgumentError, "Unknown content security policy source mapping: #{source.inspect}"
+        end
+      end
+
+      def build_directives(context, nonce)
+        @directives.map do |directive, sources|
+          if sources.is_a?(Array)
+            if nonce && nonce_directive?(directive)
+              "#{directive} #{build_directive(sources, context).join(' ')} 'nonce-#{nonce}'"
+            else
+              "#{directive} #{build_directive(sources, context).join(' ')}"
+            end
+          elsif sources
+            directive
+          else
+            nil
+          end
+        end
+      end
+
+      def build_directive(sources, context)
+        sources.map { |source| resolve_source(source, context) }
+      end
+
+      def resolve_source(source, context)
+        case source
+        when String
+          source
+        when Symbol
+          source.to_s
+        when Proc
+          if context.nil?
+            raise RuntimeError, "Missing context for the dynamic content security policy source: #{source.inspect}"
+          else
+            context.instance_exec(&source)
+          end
+        else
+          raise RuntimeError, "Unexpected content security policy source: #{source.inspect}"
+        end
+      end
+
+      def nonce_directive?(directive)
+        NONCE_DIRECTIVES.include?(directive)
+      end
+  end
+end
diff --git a/actionpack/lib/action_dispatch/http/filter_parameters.rb b/actionpack/lib/action_dispatch/http/filter_parameters.rb
index b7141cc1b9..ec012ad02d 100644
--- a/actionpack/lib/action_dispatch/http/filter_parameters.rb
+++ b/actionpack/lib/action_dispatch/http/filter_parameters.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "parameter_filter"
+require "action_dispatch/http/parameter_filter"
 
 module ActionDispatch
   module Http
@@ -9,8 +9,8 @@ module ActionDispatch
     # sub-hashes of the params hash to filter. Filtering only certain sub-keys
     # from a hash is possible by using the dot notation: 'credit_card.number'.
     # If a block is given, each key and value of the params hash and all
-    # sub-hashes is passed to it, the value or key can be replaced using
-    # String#replace or similar method.
+    # sub-hashes are passed to it, where the value or the key can be replaced using
+    # String#replace or similar methods.
     #
     #   env["action_dispatch.parameter_filter"] = [:password]
     #   => replaces the value to all keys matching /password/i with "[FILTERED]"
@@ -48,7 +48,7 @@ module ActionDispatch
         @filtered_env ||= env_filter.filter(@env)
       end
 
-      # Reconstructed a path with all sensitive GET parameters replaced.
+      # Reconstructs a path with all sensitive GET parameters replaced.
       def filtered_path
         @filtered_path ||= query_string.empty? ? path : "#{path}?#{filtered_query_string}"
       end
diff --git a/actionpack/lib/action_dispatch/http/mime_negotiation.rb b/actionpack/lib/action_dispatch/http/mime_negotiation.rb
index 0ca18d98a1..d7435fa8df 100644
--- a/actionpack/lib/action_dispatch/http/mime_negotiation.rb
+++ b/actionpack/lib/action_dispatch/http/mime_negotiation.rb
@@ -12,9 +12,6 @@ module ActionDispatch
       end
 
       # The MIME type of the HTTP request, such as Mime[:xml].
-      #
-      # For backward compatibility, the post \format is extracted from the
-      # X-Post-Data-Format HTTP header if present.
       def content_mime_type
         fetch_header("action_dispatch.request.content_type") do |k|
           v = if get_header("CONTENT_TYPE") =~ /^([^,\;]*)/
diff --git a/actionpack/lib/action_dispatch/http/mime_type.rb b/actionpack/lib/action_dispatch/http/mime_type.rb
index d797e90e52..295539281f 100644
--- a/actionpack/lib/action_dispatch/http/mime_type.rb
+++ b/actionpack/lib/action_dispatch/http/mime_type.rb
@@ -279,8 +279,6 @@ module Mime
 
     def all?; false; end
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
     protected
 
       attr_reader :string, :synonyms
@@ -339,4 +337,4 @@ module Mime
   end
 end
 
-require_relative "mime_types"
+require "action_dispatch/http/mime_types"
diff --git a/actionpack/lib/action_dispatch/http/mime_types.rb b/actionpack/lib/action_dispatch/http/mime_types.rb
index f8e6fca36d..342e6de312 100644
--- a/actionpack/lib/action_dispatch/http/mime_types.rb
+++ b/actionpack/lib/action_dispatch/http/mime_types.rb
@@ -10,6 +10,7 @@ Mime::Type.register "text/css", :css
 Mime::Type.register "text/calendar", :ics
 Mime::Type.register "text/csv", :csv
 Mime::Type.register "text/vcard", :vcf
+Mime::Type.register "text/vtt", :vtt, %w(vtt)
 
 Mime::Type.register "image/png", :png, [], %w(png)
 Mime::Type.register "image/jpeg", :jpeg, [], %w(jpg jpeg jpe pjpeg)
@@ -20,6 +21,18 @@ Mime::Type.register "image/svg+xml", :svg
 
 Mime::Type.register "video/mpeg", :mpeg, [], %w(mpg mpeg mpe)
 
+Mime::Type.register "audio/mpeg", :mp3, [], %w(mp1 mp2 mp3)
+Mime::Type.register "audio/ogg", :ogg, [], %w(oga ogg spx opus)
+Mime::Type.register "audio/aac", :m4a, %w( audio/mp4 ), %w(m4a mpg4 aac)
+
+Mime::Type.register "video/webm", :webm, [], %w(webm)
+Mime::Type.register "video/mp4", :mp4, [], %w(mp4 m4v)
+
+Mime::Type.register "font/otf", :otf, [], %w(otf)
+Mime::Type.register "font/ttf", :ttf, [], %w(ttf)
+Mime::Type.register "font/woff", :woff, [], %w(woff)
+Mime::Type.register "font/woff2", :woff2, [], %w(woff2)
+
 Mime::Type.register "application/xml", :xml, %w( text/xml application/x-xml )
 Mime::Type.register "application/rss+xml", :rss
 Mime::Type.register "application/atom+xml", :atom
diff --git a/actionpack/lib/action_dispatch/http/parameters.rb b/actionpack/lib/action_dispatch/http/parameters.rb
index ae875eb830..8d7431fd6b 100644
--- a/actionpack/lib/action_dispatch/http/parameters.rb
+++ b/actionpack/lib/action_dispatch/http/parameters.rb
@@ -123,9 +123,4 @@ module ActionDispatch
         end
     end
   end
-
-  module ParamsParser
-    include ActiveSupport::Deprecation::DeprecatedConstantAccessor
-    deprecate_constant "ParseError", "ActionDispatch::Http::Parameters::ParseError"
-  end
 end
diff --git a/actionpack/lib/action_dispatch/http/request.rb b/actionpack/lib/action_dispatch/http/request.rb
index dee7be184a..3838b84a7a 100644
--- a/actionpack/lib/action_dispatch/http/request.rb
+++ b/actionpack/lib/action_dispatch/http/request.rb
@@ -3,15 +3,15 @@
 require "stringio"
 
 require "active_support/inflector"
-require_relative "headers"
+require "action_dispatch/http/headers"
 require "action_controller/metal/exceptions"
 require "rack/request"
-require_relative "cache"
-require_relative "mime_negotiation"
-require_relative "parameters"
-require_relative "filter_parameters"
-require_relative "upload"
-require_relative "url"
+require "action_dispatch/http/cache"
+require "action_dispatch/http/mime_negotiation"
+require "action_dispatch/http/parameters"
+require "action_dispatch/http/filter_parameters"
+require "action_dispatch/http/upload"
+require "action_dispatch/http/url"
 require "active_support/core_ext/array/conversions"
 
 module ActionDispatch
@@ -22,6 +22,7 @@ module ActionDispatch
     include ActionDispatch::Http::Parameters
     include ActionDispatch::Http::FilterParameters
     include ActionDispatch::Http::URL
+    include ActionDispatch::ContentSecurityPolicy::Request
     include Rack::Request::Env
 
     autoload :Session, "action_dispatch/request/session"
@@ -199,6 +200,23 @@ module ActionDispatch
       @headers ||= Http::Headers.new(self)
     end
 
+    # Early Hints is an HTTP/2 status code that indicates hints to help a client start
+    # making preparations for processing the final response.
+    #
+    # If the env contains +rack.early_hints+ then the server accepts HTTP2 push for Link headers.
+    #
+    # The +send_early_hints+ method accepts a hash of links as follows:
+    #
+    #   send_early_hints("Link" => "</style.css>; rel=preload; as=style\n</script.js>; rel=preload")
+    #
+    # If you are using +javascript_include_tag+ or +stylesheet_link_tag+ the
+    # Early Hints headers are included by default if supported.
+    def send_early_hints(links)
+      return unless env["rack.early_hints"]
+
+      env["rack.early_hints"].call(links)
+    end
+
     # Returns a +String+ with the last requested path including their params.
     #
     #    # get '/foo'
diff --git a/actionpack/lib/action_dispatch/http/response.rb b/actionpack/lib/action_dispatch/http/response.rb
index b314dbecfe..7e50cb6d23 100644
--- a/actionpack/lib/action_dispatch/http/response.rb
+++ b/actionpack/lib/action_dispatch/http/response.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/module/attribute_accessors"
-require_relative "filter_redirect"
-require_relative "cache"
+require "action_dispatch/http/filter_redirect"
+require "action_dispatch/http/cache"
 require "monitor"
 
 module ActionDispatch # :nodoc:
@@ -433,6 +433,7 @@ module ActionDispatch # :nodoc:
     def before_committed
       return if committed?
       assign_default_content_type_and_charset!
+      merge_and_normalize_cache_control!(@cache_control)
       handle_conditional_get!
       handle_no_content!
     end
diff --git a/actionpack/lib/action_dispatch/http/url.rb b/actionpack/lib/action_dispatch/http/url.rb
index f0344fd927..35ba44005a 100644
--- a/actionpack/lib/action_dispatch/http/url.rb
+++ b/actionpack/lib/action_dispatch/http/url.rb
@@ -274,7 +274,7 @@ module ActionDispatch
       def standard_port
         case protocol
         when "https://" then 443
-          else 80
+        else 80
         end
       end
 
diff --git a/actionpack/lib/action_dispatch/journey.rb b/actionpack/lib/action_dispatch/journey.rb
index 903063d00f..2852efa6ae 100644
--- a/actionpack/lib/action_dispatch/journey.rb
+++ b/actionpack/lib/action_dispatch/journey.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "journey/router"
-require_relative "journey/gtg/builder"
-require_relative "journey/gtg/simulator"
-require_relative "journey/nfa/builder"
-require_relative "journey/nfa/simulator"
+require "action_dispatch/journey/router"
+require "action_dispatch/journey/gtg/builder"
+require "action_dispatch/journey/gtg/simulator"
+require "action_dispatch/journey/nfa/builder"
+require "action_dispatch/journey/nfa/simulator"
diff --git a/actionpack/lib/action_dispatch/journey/gtg/builder.rb b/actionpack/lib/action_dispatch/journey/gtg/builder.rb
index 7e3d957baa..44c31053cb 100644
--- a/actionpack/lib/action_dispatch/journey/gtg/builder.rb
+++ b/actionpack/lib/action_dispatch/journey/gtg/builder.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "transition_table"
+require "action_dispatch/journey/gtg/transition_table"
 
 module ActionDispatch
   module Journey # :nodoc:
diff --git a/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb b/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb
index 6ed478f816..ea647e051a 100644
--- a/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb
+++ b/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../nfa/dot"
+require "action_dispatch/journey/nfa/dot"
 
 module ActionDispatch
   module Journey # :nodoc:
diff --git a/actionpack/lib/action_dispatch/journey/nfa/builder.rb b/actionpack/lib/action_dispatch/journey/nfa/builder.rb
index 3135c05ffa..d22302e101 100644
--- a/actionpack/lib/action_dispatch/journey/nfa/builder.rb
+++ b/actionpack/lib/action_dispatch/journey/nfa/builder.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "transition_table"
-require_relative "../gtg/transition_table"
+require "action_dispatch/journey/nfa/transition_table"
+require "action_dispatch/journey/gtg/transition_table"
 
 module ActionDispatch
   module Journey # :nodoc:
diff --git a/actionpack/lib/action_dispatch/journey/nfa/dot.rb b/actionpack/lib/action_dispatch/journey/nfa/dot.rb
index bdb78d8d48..56e9e3c83d 100644
--- a/actionpack/lib/action_dispatch/journey/nfa/dot.rb
+++ b/actionpack/lib/action_dispatch/journey/nfa/dot.rb
@@ -9,16 +9,16 @@ module ActionDispatch
             "  #{from} -> #{to} [label=\"#{sym || 'ε'}\"];"
           }
 
-          #memo_nodes = memos.values.flatten.map { |n|
-          #  label = n
-          #  if Journey::Route === n
-          #    label = "#{n.verb.source} #{n.path.spec}"
-          #  end
-          #  "  #{n.object_id} [label=\"#{label}\", shape=box];"
-          #}
-          #memo_edges = memos.flat_map { |k, memos|
-          #  (memos || []).map { |v| "  #{k} -> #{v.object_id};" }
-          #}.uniq
+          # memo_nodes = memos.values.flatten.map { |n|
+          #   label = n
+          #   if Journey::Route === n
+          #     label = "#{n.verb.source} #{n.path.spec}"
+          #   end
+          #   "  #{n.object_id} [label=\"#{label}\", shape=box];"
+          # }
+          # memo_edges = memos.flat_map { |k, memos|
+          #   (memos || []).map { |v| "  #{k} -> #{v.object_id};" }
+          # }.uniq
 
           <<-eodot
 digraph nfa {
diff --git a/actionpack/lib/action_dispatch/journey/nfa/simulator.rb b/actionpack/lib/action_dispatch/journey/nfa/simulator.rb
index 8efe48d91c..002f6feb97 100644
--- a/actionpack/lib/action_dispatch/journey/nfa/simulator.rb
+++ b/actionpack/lib/action_dispatch/journey/nfa/simulator.rb
@@ -25,8 +25,6 @@ module ActionDispatch
           state = tt.eclosure(0)
           until input.eos?
             sym   = input.scan(%r([/.?]|[^/.?]+))
-
-            # FIXME: tt.eclosure is not needed for the GTG
             state = tt.eclosure(tt.move(state, sym))
           end
 
diff --git a/actionpack/lib/action_dispatch/journey/nfa/transition_table.rb b/actionpack/lib/action_dispatch/journey/nfa/transition_table.rb
index bfd929357b..fe55861507 100644
--- a/actionpack/lib/action_dispatch/journey/nfa/transition_table.rb
+++ b/actionpack/lib/action_dispatch/journey/nfa/transition_table.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "dot"
+require "action_dispatch/journey/nfa/dot"
 
 module ActionDispatch
   module Journey # :nodoc:
diff --git a/actionpack/lib/action_dispatch/journey/nodes/node.rb b/actionpack/lib/action_dispatch/journey/nodes/node.rb
index 0a84f28c1a..32f632800c 100644
--- a/actionpack/lib/action_dispatch/journey/nodes/node.rb
+++ b/actionpack/lib/action_dispatch/journey/nodes/node.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../visitors"
+require "action_dispatch/journey/visitors"
 
 module ActionDispatch
   module Journey # :nodoc:
@@ -32,7 +32,7 @@ module ActionDispatch
         end
 
         def name
-          left.tr "*:".freeze, "".freeze
+          -left.tr("*:", "")
         end
 
         def type
@@ -82,7 +82,7 @@ module ActionDispatch
         def initialize(left)
           super
           @regexp = DEFAULT_EXP
-          @name = left.tr "*:".freeze, "".freeze
+          @name = -left.tr("*:", "")
         end
 
         def default_regexp?
diff --git a/actionpack/lib/action_dispatch/journey/parser.rb b/actionpack/lib/action_dispatch/journey/parser.rb
index 6ddfe96098..e002755bcf 100644
--- a/actionpack/lib/action_dispatch/journey/parser.rb
+++ b/actionpack/lib/action_dispatch/journey/parser.rb
@@ -8,7 +8,7 @@ require 'racc/parser.rb'
 
 # :stopdoc:
 
-require_relative "parser_extras"
+require "action_dispatch/journey/parser_extras"
 module ActionDispatch
   module Journey
     class Parser < Racc::Parser
diff --git a/actionpack/lib/action_dispatch/journey/parser.y b/actionpack/lib/action_dispatch/journey/parser.y
index 850c84ea1a..f9b1a7a958 100644
--- a/actionpack/lib/action_dispatch/journey/parser.y
+++ b/actionpack/lib/action_dispatch/journey/parser.y
@@ -47,4 +47,4 @@ end
 ---- header
 # :stopdoc:
 
-require_relative "parser_extras"
+require "action_dispatch/journey/parser_extras"
diff --git a/actionpack/lib/action_dispatch/journey/parser_extras.rb b/actionpack/lib/action_dispatch/journey/parser_extras.rb
index dfbc6c4529..18ec6c9b9b 100644
--- a/actionpack/lib/action_dispatch/journey/parser_extras.rb
+++ b/actionpack/lib/action_dispatch/journey/parser_extras.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "scanner"
-require_relative "nodes/node"
+require "action_dispatch/journey/scanner"
+require "action_dispatch/journey/nodes/node"
 
 module ActionDispatch
   # :stopdoc:
diff --git a/actionpack/lib/action_dispatch/journey/path/pattern.rb b/actionpack/lib/action_dispatch/journey/path/pattern.rb
index 2d85a89a56..537f479ee5 100644
--- a/actionpack/lib/action_dispatch/journey/path/pattern.rb
+++ b/actionpack/lib/action_dispatch/journey/path/pattern.rb
@@ -90,7 +90,7 @@ module ActionDispatch
             return @separator_re unless @matchers.key?(node)
 
             re = @matchers[node]
-            "(#{re})"
+            "(#{Regexp.union(re)})"
           end
 
           def visit_GROUP(node)
@@ -183,7 +183,7 @@ module ActionDispatch
               node = node.to_sym
 
               if @requirements.key?(node)
-                re = /#{@requirements[node]}|/
+                re = /#{Regexp.union(@requirements[node])}|/
                 @offsets.push((re.match("").length - 1) + @offsets.last)
               else
                 @offsets << @offsets.last
diff --git a/actionpack/lib/action_dispatch/journey/router.rb b/actionpack/lib/action_dispatch/journey/router.rb
index 9987a9bfa1..30af3ff930 100644
--- a/actionpack/lib/action_dispatch/journey/router.rb
+++ b/actionpack/lib/action_dispatch/journey/router.rb
@@ -1,16 +1,16 @@
 # frozen_string_literal: true
 
-require_relative "router/utils"
-require_relative "routes"
-require_relative "formatter"
+require "action_dispatch/journey/router/utils"
+require "action_dispatch/journey/routes"
+require "action_dispatch/journey/formatter"
 
 before = $-w
 $-w = false
-require_relative "parser"
+require "action_dispatch/journey/parser"
 $-w = before
 
-require_relative "route"
-require_relative "path/pattern"
+require "action_dispatch/journey/route"
+require "action_dispatch/journey/path/pattern"
 
 module ActionDispatch
   module Journey # :nodoc:
@@ -61,7 +61,7 @@ module ActionDispatch
           return [status, headers, body]
         end
 
-        return [404, { "X-Cascade" => "pass" }, ["Not Found"]]
+        [404, { "X-Cascade" => "pass" }, ["Not Found"]]
       end
 
       def recognize(rails_req)
diff --git a/actionpack/lib/action_dispatch/journey/scanner.rb b/actionpack/lib/action_dispatch/journey/scanner.rb
index 4ae77903fa..2a075862e9 100644
--- a/actionpack/lib/action_dispatch/journey/scanner.rb
+++ b/actionpack/lib/action_dispatch/journey/scanner.rb
@@ -34,6 +34,13 @@ module ActionDispatch
 
       private
 
+        # takes advantage of String @- deduping capabilities in Ruby 2.5 upwards
+        # see: https://bugs.ruby-lang.org/issues/13077
+        def dedup_scan(regex)
+          r = @ss.scan(regex)
+          r ? -r : nil
+        end
+
         def scan
           case
             # /
@@ -47,15 +54,15 @@ module ActionDispatch
             [:OR, "|"]
           when @ss.skip(/\./)
             [:DOT, "."]
-          when text = @ss.scan(/:\w+/)
+          when text = dedup_scan(/:\w+/)
             [:SYMBOL, text]
-          when text = @ss.scan(/\*\w+/)
+          when text = dedup_scan(/\*\w+/)
             [:STAR, text]
           when text = @ss.scan(/(?:[\w%\-~!$&'*+,;=@]|\\[:()])+/)
             text.tr! "\\", ""
-            [:LITERAL, text]
+            [:LITERAL, -text]
             # any char
-          when text = @ss.scan(/./)
+          when text = dedup_scan(/./)
             [:LITERAL, text]
           end
         end
diff --git a/actionpack/lib/action_dispatch/middleware/cookies.rb b/actionpack/lib/action_dispatch/middleware/cookies.rb
index c0913715ac..c45d947904 100644
--- a/actionpack/lib/action_dispatch/middleware/cookies.rb
+++ b/actionpack/lib/action_dispatch/middleware/cookies.rb
@@ -49,6 +49,18 @@ module ActionDispatch
       get_header Cookies::AUTHENTICATED_ENCRYPTED_COOKIE_SALT
     end
 
+    def use_authenticated_cookie_encryption
+      get_header Cookies::USE_AUTHENTICATED_COOKIE_ENCRYPTION
+    end
+
+    def encrypted_cookie_cipher
+      get_header Cookies::ENCRYPTED_COOKIE_CIPHER
+    end
+
+    def signed_cookie_digest
+      get_header Cookies::SIGNED_COOKIE_DIGEST
+    end
+
     def secret_token
       get_header Cookies::SECRET_TOKEN
     end
@@ -64,6 +76,11 @@ module ActionDispatch
     def cookies_digest
       get_header Cookies::COOKIES_DIGEST
     end
+
+    def cookies_rotations
+      get_header Cookies::COOKIES_ROTATIONS
+    end
+
     # :startdoc:
   end
 
@@ -83,16 +100,17 @@ module ActionDispatch
   #   cookies[:lat_lon] = JSON.generate([47.68, -122.37])
   #
   #   # Sets a cookie that expires in 1 hour.
-  #   cookies[:login] = { value: "XJ-122", expires: 1.hour.from_now }
+  #   cookies[:login] = { value: "XJ-122", expires: 1.hour }
+  #
+  #   # Sets a cookie that expires at a specific time.
+  #   cookies[:login] = { value: "XJ-122", expires: Time.utc(2020, 10, 15, 5) }
   #
   #   # Sets a signed cookie, which prevents users from tampering with its value.
-  #   # The cookie is signed by your app's `secrets.secret_key_base` value.
   #   # It can be read using the signed method `cookies.signed[:name]`
   #   cookies.signed[:user_id] = current_user.id
   #
   #   # Sets an encrypted cookie value before sending it to the client which
   #   # prevent users from reading and tampering with its value.
-  #   # The cookie is signed by your app's `secrets.secret_key_base` value.
   #   # It can be read using the encrypted method `cookies.encrypted[:name]`
   #   cookies.encrypted[:discount] = 45
   #
@@ -100,7 +118,7 @@ module ActionDispatch
   #   cookies.permanent[:login] = "XJ-122"
   #
   #   # You can also chain these methods:
-  #   cookies.permanent.signed[:login] = "XJ-122"
+  #   cookies.signed.permanent[:login] = "XJ-122"
   #
   # Examples of reading:
   #
@@ -118,7 +136,7 @@ module ActionDispatch
   #
   #  cookies[:name] = {
   #    value: 'a yummy cookie',
-  #    expires: 1.year.from_now,
+  #    expires: 1.year,
   #    domain: 'domain.com'
   #  }
   #
@@ -143,8 +161,8 @@ module ActionDispatch
   #
   # * <tt>:tld_length</tt> - When using <tt>:domain => :all</tt>, this option can be used to explicitly
   #   set the TLD length when using a short (<= 3 character) domain that is being interpreted as part of a TLD.
-  #   For example, to share cookies between user1.lvh.me and user2.lvh.me, set <tt>:tld_length</tt> to 1.
-  # * <tt>:expires</tt> - The time at which this cookie expires, as a \Time object.
+  #   For example, to share cookies between user1.lvh.me and user2.lvh.me, set <tt>:tld_length</tt> to 2.
+  # * <tt>:expires</tt> - The time at which this cookie expires, as a \Time or ActiveSupport::Duration object.
   # * <tt>:secure</tt> - Whether this cookie is only transmitted to HTTPS servers.
   #   Default is +false+.
   # * <tt>:httponly</tt> - Whether this cookie is accessible via scripting or
@@ -156,10 +174,14 @@ module ActionDispatch
     ENCRYPTED_COOKIE_SALT = "action_dispatch.encrypted_cookie_salt".freeze
     ENCRYPTED_SIGNED_COOKIE_SALT = "action_dispatch.encrypted_signed_cookie_salt".freeze
     AUTHENTICATED_ENCRYPTED_COOKIE_SALT = "action_dispatch.authenticated_encrypted_cookie_salt".freeze
+    USE_AUTHENTICATED_COOKIE_ENCRYPTION = "action_dispatch.use_authenticated_cookie_encryption".freeze
+    ENCRYPTED_COOKIE_CIPHER = "action_dispatch.encrypted_cookie_cipher".freeze
+    SIGNED_COOKIE_DIGEST = "action_dispatch.signed_cookie_digest".freeze
     SECRET_TOKEN = "action_dispatch.secret_token".freeze
     SECRET_KEY_BASE = "action_dispatch.secret_key_base".freeze
     COOKIES_SERIALIZER = "action_dispatch.cookies_serializer".freeze
     COOKIES_DIGEST = "action_dispatch.cookies_digest".freeze
+    COOKIES_ROTATIONS = "action_dispatch.cookies_rotations".freeze
 
     # Cookies can typically store 4096 bytes.
     MAX_COOKIE_SIZE = 4096
@@ -188,10 +210,10 @@ module ActionDispatch
       # the cookie again. This is useful for creating cookies with values that the user is not supposed to change. If a signed
       # cookie was tampered with by the user (or a 3rd party), +nil+ will be returned.
       #
-      # If +secrets.secret_key_base+ and +secrets.secret_token+ (deprecated) are both set,
+      # If +secret_key_base+ and +secrets.secret_token+ (deprecated) are both set,
       # legacy cookies signed with the old key generator will be transparently upgraded.
       #
-      # This jar requires that you set a suitable secret for the verification on your app's +secrets.secret_key_base+.
+      # This jar requires that you set a suitable secret for the verification on your app's +secret_key_base+.
       #
       # Example:
       #
@@ -200,40 +222,28 @@ module ActionDispatch
       #
       #   cookies.signed[:discount] # => 45
       def signed
-        @signed ||=
-          if upgrade_legacy_signed_cookies?
-            UpgradeLegacySignedCookieJar.new(self)
-          else
-            SignedCookieJar.new(self)
-          end
+        @signed ||= SignedKeyRotatingCookieJar.new(self)
       end
 
       # Returns a jar that'll automatically encrypt cookie values before sending them to the client and will decrypt them for read.
       # If the cookie was tampered with by the user (or a 3rd party), +nil+ will be returned.
       #
-      # If +secrets.secret_key_base+ and +secrets.secret_token+ (deprecated) are both set,
+      # If +secret_key_base+ and +secrets.secret_token+ (deprecated) are both set,
       # legacy cookies signed with the old key generator will be transparently upgraded.
       #
       # If +config.action_dispatch.encrypted_cookie_salt+ and +config.action_dispatch.encrypted_signed_cookie_salt+
       # are both set, legacy cookies encrypted with HMAC AES-256-CBC will be transparently upgraded.
       #
-      # This jar requires that you set a suitable secret for the verification on your app's +secrets.secret_key_base+.
+      # This jar requires that you set a suitable secret for the verification on your app's +secret_key_base+.
       #
       # Example:
       #
       #   cookies.encrypted[:discount] = 45
-      #   # => Set-Cookie: discount=ZS9ZZ1R4cG1pcUJ1bm80anhQang3dz09LS1mbDZDSU5scGdOT3ltQ2dTdlhSdWpRPT0%3D--ab54663c9f4e3bc340c790d6d2b71e92f5b60315; path=/
+      #   # => Set-Cookie: discount=DIQ7fw==--K3n//8vvnSbGq9dA--7Xh91HfLpwzbj1czhBiwOg==; path=/
       #
       #   cookies.encrypted[:discount] # => 45
       def encrypted
-        @encrypted ||=
-          if upgrade_legacy_signed_cookies?
-            UpgradeLegacyEncryptedCookieJar.new(self)
-          elsif upgrade_legacy_hmac_aes_cbc_cookies?
-            UpgradeLegacyHmacAesCbcCookieJar.new(self)
-          else
-            EncryptedCookieJar.new(self)
-          end
+        @encrypted ||= EncryptedKeyRotatingCookieJar.new(self)
       end
 
       # Returns the +signed+ or +encrypted+ jar, preferring +encrypted+ if +secret_key_base+ is set.
@@ -254,34 +264,18 @@ module ActionDispatch
         end
 
         def upgrade_legacy_hmac_aes_cbc_cookies?
-          request.secret_key_base.present?                       &&
-            request.authenticated_encrypted_cookie_salt.present? &&
-            request.encrypted_signed_cookie_salt.present?        &&
-            request.encrypted_cookie_salt.present?
+          request.secret_key_base.present? &&
+            request.encrypted_signed_cookie_salt.present? &&
+            request.encrypted_cookie_salt.present? &&
+            request.use_authenticated_cookie_encryption
         end
-    end
-
-    # Passing the ActiveSupport::MessageEncryptor::NullSerializer downstream
-    # to the Message{Encryptor,Verifier} allows us to handle the
-    # (de)serialization step within the cookie jar, which gives us the
-    # opportunity to detect and migrate legacy cookies.
-    module VerifyAndUpgradeLegacySignedMessage # :nodoc:
-      def initialize(*args)
-        super
-        @legacy_verifier = ActiveSupport::MessageVerifier.new(request.secret_token, serializer: ActiveSupport::MessageEncryptor::NullSerializer)
-      end
 
-      def verify_and_upgrade_legacy_signed_message(name, signed_message)
-        deserialize(name, @legacy_verifier.verify(signed_message)).tap do |value|
-          self[name] = { value: value }
+        def encrypted_cookie_cipher
+          request.encrypted_cookie_cipher || "aes-256-gcm"
         end
-      rescue ActiveSupport::MessageVerifier::InvalidSignature
-        nil
-      end
 
-      private
-        def parse(name, signed_message)
-          super || verify_and_upgrade_legacy_signed_message(name, signed_message)
+        def signed_cookie_digest
+          request.signed_cookie_digest || "SHA1"
         end
     end
 
@@ -344,6 +338,9 @@ module ActionDispatch
       end
       alias :has_key? :key?
 
+      # Returns the cookies as Hash.
+      alias :to_hash :to_h
+
       def update(other_hash)
         @cookies.update other_hash.stringify_keys
         self
@@ -523,6 +520,7 @@ module ActionDispatch
 
     module SerializedCookieJars # :nodoc:
       MARSHAL_SIGNATURE = "\x04\x08".freeze
+      SERIALIZER = ActiveSupport::MessageEncryptor::NullSerializer
 
       protected
         def needs_migration?(value)
@@ -533,12 +531,16 @@ module ActionDispatch
           serializer.dump(value)
         end
 
-        def deserialize(name, value)
+        def deserialize(name)
+          rotate = false
+          value  = yield -> { rotate = true }
+
           if value
-            if needs_migration?(value)
-              Marshal.load(value).tap do |v|
-                self[name] = { value: v }
-              end
+            case
+            when needs_migration?(value)
+              self[name] = Marshal.load(value)
+            when rotate
+              self[name] = serializer.load(value)
             else
               serializer.load(value)
             end
@@ -560,24 +562,31 @@ module ActionDispatch
         def digest
           request.cookies_digest || "SHA1"
         end
-
-        def key_generator
-          request.key_generator
-        end
     end
 
-    class SignedCookieJar < AbstractCookieJar # :nodoc:
+    class SignedKeyRotatingCookieJar < AbstractCookieJar # :nodoc:
       include SerializedCookieJars
 
       def initialize(parent_jar)
         super
-        secret = key_generator.generate_key(request.signed_cookie_salt)
-        @verifier = ActiveSupport::MessageVerifier.new(secret, digest: digest, serializer: ActiveSupport::MessageEncryptor::NullSerializer)
+
+        secret = request.key_generator.generate_key(request.signed_cookie_salt)
+        @verifier = ActiveSupport::MessageVerifier.new(secret, digest: signed_cookie_digest, serializer: SERIALIZER)
+
+        request.cookies_rotations.signed.each do |*secrets, **options|
+          @verifier.rotate(*secrets, serializer: SERIALIZER, **options)
+        end
+
+        if upgrade_legacy_signed_cookies?
+          @verifier.rotate request.secret_token, serializer: SERIALIZER
+        end
       end
 
       private
         def parse(name, signed_message)
-          deserialize name, @verifier.verified(signed_message)
+          deserialize(name) do |rotate|
+            @verifier.verified(signed_message, on_rotation: rotate)
+          end
         end
 
         def commit(options)
@@ -587,37 +596,47 @@ module ActionDispatch
         end
     end
 
-    # UpgradeLegacySignedCookieJar is used instead of SignedCookieJar if
-    # secrets.secret_token and secrets.secret_key_base are both set. It reads
-    # legacy cookies signed with the old dummy key generator and signs and
-    # re-saves them using the new key generator to provide a smooth upgrade path.
-    class UpgradeLegacySignedCookieJar < SignedCookieJar #:nodoc:
-      include VerifyAndUpgradeLegacySignedMessage
-    end
-
-    class EncryptedCookieJar < AbstractCookieJar # :nodoc:
+    class EncryptedKeyRotatingCookieJar < AbstractCookieJar # :nodoc:
       include SerializedCookieJars
 
       def initialize(parent_jar)
         super
 
-        if ActiveSupport::LegacyKeyGenerator === key_generator
-          raise "You didn't set secrets.secret_key_base, which is required for this cookie jar. " \
-            "Read the upgrade documentation to learn more about this new config option."
+        if request.use_authenticated_cookie_encryption
+          key_len = ActiveSupport::MessageEncryptor.key_len(encrypted_cookie_cipher)
+          secret = request.key_generator.generate_key(request.authenticated_encrypted_cookie_salt, key_len)
+          @encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: encrypted_cookie_cipher, serializer: SERIALIZER)
+        else
+          key_len = ActiveSupport::MessageEncryptor.key_len("aes-256-cbc")
+          secret = request.key_generator.generate_key(request.encrypted_cookie_salt, key_len)
+          sign_secret = request.key_generator.generate_key(request.encrypted_signed_cookie_salt)
+          @encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, cipher: "aes-256-cbc", serializer: SERIALIZER)
+        end
+
+        request.cookies_rotations.encrypted.each do |*secrets, **options|
+          @encryptor.rotate(*secrets, serializer: SERIALIZER, **options)
         end
 
-        cipher = "aes-256-gcm"
-        key_len = ActiveSupport::MessageEncryptor.key_len(cipher)
-        secret = key_generator.generate_key(request.authenticated_encrypted_cookie_salt || "")[0, key_len]
+        if upgrade_legacy_hmac_aes_cbc_cookies?
+          legacy_cipher = "aes-256-cbc"
+          secret = request.key_generator.generate_key(request.encrypted_cookie_salt, ActiveSupport::MessageEncryptor.key_len(legacy_cipher))
+          sign_secret = request.key_generator.generate_key(request.encrypted_signed_cookie_salt)
+
+          @encryptor.rotate(secret, sign_secret, cipher: legacy_cipher, digest: digest, serializer: SERIALIZER)
+        end
 
-        @encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: ActiveSupport::MessageEncryptor::NullSerializer)
+        if upgrade_legacy_signed_cookies?
+          @legacy_verifier = ActiveSupport::MessageVerifier.new(request.secret_token, digest: digest, serializer: SERIALIZER)
+        end
       end
 
       private
         def parse(name, encrypted_message)
-          deserialize name, @encryptor.decrypt_and_verify(encrypted_message)
-        rescue ActiveSupport::MessageVerifier::InvalidSignature, ActiveSupport::MessageEncryptor::InvalidMessage
-          nil
+          deserialize(name) do |rotate|
+            @encryptor.decrypt_and_verify(encrypted_message, on_rotation: rotate)
+          end
+        rescue ActiveSupport::MessageEncryptor::InvalidMessage, ActiveSupport::MessageVerifier::InvalidSignature
+          parse_legacy_signed_message(name, encrypted_message)
         end
 
         def commit(options)
@@ -625,39 +644,15 @@ module ActionDispatch
 
           raise CookieOverflow if options[:value].bytesize > MAX_COOKIE_SIZE
         end
-    end
 
-    # UpgradeLegacyEncryptedCookieJar is used by ActionDispatch::Session::CookieStore
-    # instead of EncryptedCookieJar if secrets.secret_token and secrets.secret_key_base
-    # are both set. It reads legacy cookies signed with the old dummy key generator and
-    # encrypts and re-saves them using the new key generator to provide a smooth upgrade path.
-    class UpgradeLegacyEncryptedCookieJar < EncryptedCookieJar #:nodoc:
-      include VerifyAndUpgradeLegacySignedMessage
-    end
+        def parse_legacy_signed_message(name, legacy_signed_message)
+          if defined?(@legacy_verifier)
+            deserialize(name) do |rotate|
+              rotate.call
 
-    # UpgradeLegacyHmacAesCbcCookieJar is used by ActionDispatch::Session::CookieStore
-    # to upgrade cookies encrypted with AES-256-CBC with HMAC to AES-256-GCM
-    class UpgradeLegacyHmacAesCbcCookieJar < EncryptedCookieJar
-      def initialize(parent_jar)
-        super
-
-        secret = key_generator.generate_key(request.encrypted_cookie_salt || "")[0, ActiveSupport::MessageEncryptor.key_len]
-        sign_secret = key_generator.generate_key(request.encrypted_signed_cookie_salt || "")
-
-        @legacy_encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, cipher: "aes-256-cbc", digest: digest, serializer: ActiveSupport::MessageEncryptor::NullSerializer)
-      end
-
-      def decrypt_and_verify_legacy_encrypted_message(name, signed_message)
-        deserialize(name, @legacy_encryptor.decrypt_and_verify(signed_message)).tap do |value|
-          self[name] = { value: value }
-        end
-      rescue ActiveSupport::MessageVerifier::InvalidSignature, ActiveSupport::MessageEncryptor::InvalidMessage
-        nil
-      end
-
-      private
-        def parse(name, signed_message)
-          super || decrypt_and_verify_legacy_encrypted_message(name, signed_message)
+              @legacy_verifier.verified(legacy_signed_message)
+            end
+          end
         end
     end
 
diff --git a/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb b/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
index 3006cd97ce..33edad8bd9 100644
--- a/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
+++ b/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../http/request"
-require_relative "exception_wrapper"
-require_relative "../routing/inspector"
+require "action_dispatch/http/request"
+require "action_dispatch/middleware/exception_wrapper"
+require "action_dispatch/routing/inspector"
 require "action_view"
 require "action_view/base"
 
@@ -50,10 +50,18 @@ module ActionDispatch
       end
     end
 
-    def initialize(app, routes_app = nil, response_format = :default)
+    cattr_reader :interceptors, instance_accessor: false, default: []
+
+    def self.register_interceptor(object = nil, &block)
+      interceptor = object || block
+      interceptors << interceptor
+    end
+
+    def initialize(app, routes_app = nil, response_format = :default, interceptors = self.class.interceptors)
       @app             = app
       @routes_app      = routes_app
       @response_format = response_format
+      @interceptors    = interceptors
     end
 
     def call(env)
@@ -67,12 +75,26 @@ module ActionDispatch
 
       response
     rescue Exception => exception
+      invoke_interceptors(request, exception)
       raise exception unless request.show_exceptions?
       render_exception(request, exception)
     end
 
     private
 
+      def invoke_interceptors(request, exception)
+        backtrace_cleaner = request.get_header("action_dispatch.backtrace_cleaner")
+        wrapper = ExceptionWrapper.new(backtrace_cleaner, exception)
+
+        @interceptors.each do |interceptor|
+          begin
+            interceptor.call(request, exception)
+          rescue Exception
+            log_error(request, wrapper)
+          end
+        end
+      end
+
       def render_exception(request, exception)
         backtrace_cleaner = request.get_header("action_dispatch.backtrace_cleaner")
         wrapper = ExceptionWrapper.new(backtrace_cleaner, exception)
diff --git a/actionpack/lib/action_dispatch/middleware/debug_locks.rb b/actionpack/lib/action_dispatch/middleware/debug_locks.rb
index c61a941010..03760438f7 100644
--- a/actionpack/lib/action_dispatch/middleware/debug_locks.rb
+++ b/actionpack/lib/action_dispatch/middleware/debug_locks.rb
@@ -43,7 +43,7 @@ module ActionDispatch
 
     private
       def render_details(req)
-        threads = ActiveSupport::Dependencies.interlock.raw_state do |threads|
+        threads = ActiveSupport::Dependencies.interlock.raw_state do |raw_threads|
           # The Interlock itself comes to a complete halt as long as this block
           # is executing. That gives us a more consistent picture of everything,
           # but creates a pretty strong Observer Effect.
@@ -53,29 +53,29 @@ module ActionDispatch
           # strictly diagnostic tool (to be used when something has gone wrong),
           # and not for any sort of general monitoring.
 
-          threads.each.with_index do |(thread, info), idx|
+          raw_threads.each.with_index do |(thread, info), idx|
             info[:index] = idx
             info[:backtrace] = thread.backtrace
           end
 
-          threads
+          raw_threads
         end
 
         str = threads.map do |thread, info|
           if info[:exclusive]
-            lock_state = "Exclusive"
+            lock_state = "Exclusive".dup
           elsif info[:sharing] > 0
-            lock_state = "Sharing"
+            lock_state = "Sharing".dup
             lock_state << " x#{info[:sharing]}" if info[:sharing] > 1
           else
-            lock_state = "No lock"
+            lock_state = "No lock".dup
           end
 
           if info[:waiting]
             lock_state << " (yielded share)"
           end
 
-          msg = "Thread #{info[:index]} [0x#{thread.__id__.to_s(16)} #{thread.status || 'dead'}]  #{lock_state}\n"
+          msg = "Thread #{info[:index]} [0x#{thread.__id__.to_s(16)} #{thread.status || 'dead'}]  #{lock_state}\n".dup
 
           if info[:sleeper]
             msg << "  Waiting in #{info[:sleeper]}"
diff --git a/actionpack/lib/action_dispatch/middleware/exception_wrapper.rb b/actionpack/lib/action_dispatch/middleware/exception_wrapper.rb
index 4f69abfa6f..f05c69137b 100644
--- a/actionpack/lib/action_dispatch/middleware/exception_wrapper.rb
+++ b/actionpack/lib/action_dispatch/middleware/exception_wrapper.rb
@@ -12,6 +12,7 @@ module ActionDispatch
       "ActionController::UnknownHttpMethod"          => :method_not_allowed,
       "ActionController::NotImplemented"             => :not_implemented,
       "ActionController::UnknownFormat"              => :not_acceptable,
+      "ActionController::MissingExactTemplate"       => :not_acceptable,
       "ActionController::InvalidAuthenticityToken"   => :unprocessable_entity,
       "ActionController::InvalidCrossOriginRequest"  => :unprocessable_entity,
       "ActionDispatch::Http::Parameters::ParseError" => :bad_request,
@@ -22,10 +23,12 @@ module ActionDispatch
     )
 
     cattr_accessor :rescue_templates, default: Hash.new("diagnostics").merge!(
-      "ActionView::MissingTemplate"         => "missing_template",
-      "ActionController::RoutingError"      => "routing_error",
-      "AbstractController::ActionNotFound"  => "unknown_action",
-      "ActionView::Template::Error"         => "template_error"
+      "ActionView::MissingTemplate"            => "missing_template",
+      "ActionController::RoutingError"         => "routing_error",
+      "AbstractController::ActionNotFound"     => "unknown_action",
+      "ActiveRecord::StatementInvalid"         => "invalid_statement",
+      "ActionView::Template::Error"            => "template_error",
+      "ActionController::MissingExactTemplate" => "missing_exact_template",
     )
 
     attr_reader :backtrace_cleaner, :exception, :line_number, :file
diff --git a/actionpack/lib/action_dispatch/middleware/flash.rb b/actionpack/lib/action_dispatch/middleware/flash.rb
index 3e11846778..fd05eec172 100644
--- a/actionpack/lib/action_dispatch/middleware/flash.rb
+++ b/actionpack/lib/action_dispatch/middleware/flash.rb
@@ -73,7 +73,7 @@ module ActionDispatch
         end
       end
 
-      def reset_session # :nodoc
+      def reset_session # :nodoc:
         super
         self.flash = nil
       end
diff --git a/actionpack/lib/action_dispatch/middleware/public_exceptions.rb b/actionpack/lib/action_dispatch/middleware/public_exceptions.rb
index 02be97b4cc..3feb3a19f3 100644
--- a/actionpack/lib/action_dispatch/middleware/public_exceptions.rb
+++ b/actionpack/lib/action_dispatch/middleware/public_exceptions.rb
@@ -2,12 +2,12 @@
 
 module ActionDispatch
   # When called, this middleware renders an error page. By default if an HTML
-  # response is expected it will render static error pages from the `/public`
+  # response is expected it will render static error pages from the <tt>/public</tt>
   # directory. For example when this middleware receives a 500 response it will
-  # render the template found in `/public/500.html`.
+  # render the template found in <tt>/public/500.html</tt>.
   # If an internationalized locale is set, this middleware will attempt to render
-  # the template in `/public/500.<locale>.html`. If an internationalized template
-  # is not found it will fall back on `/public/500.html`.
+  # the template in <tt>/public/500.<locale>.html</tt>. If an internationalized template
+  # is not found it will fall back on <tt>/public/500.html</tt>.
   #
   # When a request with a content type other than HTML is made, this middleware
   # will attempt to convert error information into the appropriate response type.
diff --git a/actionpack/lib/action_dispatch/middleware/request_id.rb b/actionpack/lib/action_dispatch/middleware/request_id.rb
index 805d3f2148..da2871b551 100644
--- a/actionpack/lib/action_dispatch/middleware/request_id.rb
+++ b/actionpack/lib/action_dispatch/middleware/request_id.rb
@@ -30,7 +30,7 @@ module ActionDispatch
     private
       def make_request_id(request_id)
         if request_id.presence
-          request_id.gsub(/[^\w\-]/, "".freeze).first(255)
+          request_id.gsub(/[^\w\-@]/, "".freeze).first(255)
         else
           internal_request_id
         end
diff --git a/actionpack/lib/action_dispatch/middleware/session/abstract_store.rb b/actionpack/lib/action_dispatch/middleware/session/abstract_store.rb
index e054fefc9b..5b0be96223 100644
--- a/actionpack/lib/action_dispatch/middleware/session/abstract_store.rb
+++ b/actionpack/lib/action_dispatch/middleware/session/abstract_store.rb
@@ -3,8 +3,8 @@
 require "rack/utils"
 require "rack/request"
 require "rack/session/abstract/id"
-require_relative "../cookies"
-require_relative "../../request/session"
+require "action_dispatch/middleware/cookies"
+require "action_dispatch/request/session"
 
 module ActionDispatch
   module Session
diff --git a/actionpack/lib/action_dispatch/middleware/session/cache_store.rb b/actionpack/lib/action_dispatch/middleware/session/cache_store.rb
index c84bc8bfad..a6d965a644 100644
--- a/actionpack/lib/action_dispatch/middleware/session/cache_store.rb
+++ b/actionpack/lib/action_dispatch/middleware/session/cache_store.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "abstract_store"
+require "action_dispatch/middleware/session/abstract_store"
 
 module ActionDispatch
   module Session
diff --git a/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb b/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb
index 65e93984e3..4ea96196d3 100644
--- a/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb
+++ b/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/hash/keys"
-require_relative "abstract_store"
+require "action_dispatch/middleware/session/abstract_store"
 require "rack/session/cookie"
 
 module ActionDispatch
@@ -21,39 +21,25 @@ module ActionDispatch
     # knowing your app's secret key, but can easily read their +user_id+. This
     # was the default for Rails 3 apps.
     #
-    # If you have secret_key_base set, your cookies will be encrypted. This
+    # Your cookies will be encrypted using your apps secret_key_base. This
     # goes a step further than signed cookies in that encrypted cookies cannot
     # be altered or read by users. This is the default starting in Rails 4.
     #
-    # If you have both secret_token and secret_key_base set, your cookies will
-    # be encrypted, and signed cookies generated by Rails 3 will be
-    # transparently read and encrypted to provide a smooth upgrade path.
-    #
-    # Configure your session store in config/initializers/session_store.rb:
+    # Configure your session store in <tt>config/initializers/session_store.rb</tt>:
     #
     #   Rails.application.config.session_store :cookie_store, key: '_your_app_session'
     #
-    # Configure your secret key in config/secrets.yml:
-    #
-    #   development:
-    #     secret_key_base: 'secret key'
-    #
-    # To generate a secret key for an existing application, run `rails secret`.
+    # By default, your secret key base is derived from your application name in
+    # the test and development environments. In all other environments, it is stored
+    # encrypted in the <tt>config/credentials.yml.enc</tt> file.
     #
-    # If you are upgrading an existing Rails 3 app, you should leave your
-    # existing secret_token in place and simply add the new secret_key_base.
-    # Note that you should wait to set secret_key_base until you have 100% of
-    # your userbase on Rails 4 and are reasonably sure you will not need to
-    # rollback to Rails 3. This is because cookies signed based on the new
-    # secret_key_base in Rails 4 are not backwards compatible with Rails 3.
-    # You are free to leave your existing secret_token in place, not set the
-    # new secret_key_base, and ignore the deprecation warnings until you are
-    # reasonably sure that your upgrade is otherwise complete. Additionally,
-    # you should take care to make sure you are not relying on the ability to
-    # decode signed cookies generated by your app in external applications or
-    # JavaScript before upgrading.
+    # If your application was not updated to Rails 5.2 defaults, the secret_key_base
+    # will be found in the old <tt>config/secrets.yml</tt> file.
     #
-    # Note that changing the secret key will invalidate all existing sessions!
+    # Note that changing your secret_key_base will invalidate all existing session.
+    # Additionally, you should take care to make sure you are not relying on the
+    # ability to decode signed cookies generated by your app in external
+    # applications or JavaScript before changing it.
     #
     # Because CookieStore extends Rack::Session::Abstract::Persisted, many of the
     # options described there can be used to customize the session cookie that
diff --git a/actionpack/lib/action_dispatch/middleware/session/mem_cache_store.rb b/actionpack/lib/action_dispatch/middleware/session/mem_cache_store.rb
index f0aec39c9c..914df3a2b1 100644
--- a/actionpack/lib/action_dispatch/middleware/session/mem_cache_store.rb
+++ b/actionpack/lib/action_dispatch/middleware/session/mem_cache_store.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "abstract_store"
+require "action_dispatch/middleware/session/abstract_store"
 begin
   require "rack/session/dalli"
 rescue LoadError => e
diff --git a/actionpack/lib/action_dispatch/middleware/show_exceptions.rb b/actionpack/lib/action_dispatch/middleware/show_exceptions.rb
index d2e739d27f..3c88afd4d3 100644
--- a/actionpack/lib/action_dispatch/middleware/show_exceptions.rb
+++ b/actionpack/lib/action_dispatch/middleware/show_exceptions.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../http/request"
-require_relative "exception_wrapper"
+require "action_dispatch/http/request"
+require "action_dispatch/middleware/exception_wrapper"
 
 module ActionDispatch
   # This middleware rescues any exception returned by the application
diff --git a/actionpack/lib/action_dispatch/middleware/ssl.rb b/actionpack/lib/action_dispatch/middleware/ssl.rb
index 45290b6ac3..240269d1c7 100644
--- a/actionpack/lib/action_dispatch/middleware/ssl.rb
+++ b/actionpack/lib/action_dispatch/middleware/ssl.rb
@@ -1,50 +1,56 @@
 # frozen_string_literal: true
 
 module ActionDispatch
-  # This middleware is added to the stack when `config.force_ssl = true`, and is passed
-  # the options set in `config.ssl_options`. It does three jobs to enforce secure HTTP
+  # This middleware is added to the stack when <tt>config.force_ssl = true</tt>, and is passed
+  # the options set in +config.ssl_options+. It does three jobs to enforce secure HTTP
   # requests:
   #
-  #   1. TLS redirect: Permanently redirects http:// requests to https://
-  #      with the same URL host, path, etc. Enabled by default. Set `config.ssl_options`
-  #      to modify the destination URL
-  #      (e.g. `redirect: { host: "secure.widgets.com", port: 8080 }`), or set
-  #      `redirect: false` to disable this feature.
+  # 1. <b>TLS redirect</b>: Permanently redirects +http://+ requests to +https://+
+  #    with the same URL host, path, etc. Enabled by default. Set +config.ssl_options+
+  #    to modify the destination URL
+  #    (e.g. <tt>redirect: { host: "secure.widgets.com", port: 8080 }</tt>), or set
+  #    <tt>redirect: false</tt> to disable this feature.
   #
-  #   2. Secure cookies: Sets the `secure` flag on cookies to tell browsers they
-  #      mustn't be sent along with http:// requests. Enabled by default. Set
-  #      `config.ssl_options` with `secure_cookies: false` to disable this feature.
+  #    Requests can opt-out of redirection with +exclude+:
   #
-  #   3. HTTP Strict Transport Security (HSTS): Tells the browser to remember
-  #      this site as TLS-only and automatically redirect non-TLS requests.
-  #      Enabled by default. Configure `config.ssl_options` with `hsts: false` to disable.
+  #      config.ssl_options = { redirect: { exclude: -> request { request.path =~ /healthcheck/ } } }
   #
-  # Set `config.ssl_options` with `hsts: { … }` to configure HSTS:
-  #   * `expires`: How long, in seconds, these settings will stick. The minimum
-  #     required to qualify for browser preload lists is `18.weeks`. Defaults to
-  #     `180.days` (recommended).
-  #   * `subdomains`: Set to `true` to tell the browser to apply these settings
-  #     to all subdomains. This protects your cookies from interception by a
-  #     vulnerable site on a subdomain. Defaults to `true`.
-  #   * `preload`: Advertise that this site may be included in browsers'
-  #     preloaded HSTS lists. HSTS protects your site on every visit *except the
-  #     first visit* since it hasn't seen your HSTS header yet. To close this
-  #     gap, browser vendors include a baked-in list of HSTS-enabled sites.
-  #     Go to https://hstspreload.appspot.com to submit your site for inclusion.
-  #     Defaults to `false`.
+  #    Cookies will not be flagged as secure for excluded requests.
   #
-  # To turn off HSTS, omitting the header is not enough. Browsers will remember the
-  # original HSTS directive until it expires. Instead, use the header to tell browsers to
-  # expire HSTS immediately. Setting `hsts: false` is a shortcut for
-  # `hsts: { expires: 0 }`.
+  # 2. <b>Secure cookies</b>: Sets the +secure+ flag on cookies to tell browsers they
+  #    must not be sent along with +http://+ requests. Enabled by default. Set
+  #    +config.ssl_options+ with <tt>secure_cookies: false</tt> to disable this feature.
   #
-  # Requests can opt-out of redirection with `exclude`:
+  # 3. <b>HTTP Strict Transport Security (HSTS)</b>: Tells the browser to remember
+  #    this site as TLS-only and automatically redirect non-TLS requests.
+  #    Enabled by default. Configure +config.ssl_options+ with <tt>hsts: false</tt> to disable.
   #
-  #    config.ssl_options = { redirect: { exclude: -> request { request.path =~ /healthcheck/ } } }
+  #    Set +config.ssl_options+ with <tt>hsts: { ... }</tt> to configure HSTS:
+  #
+  #    * +expires+: How long, in seconds, these settings will stick. The minimum
+  #      required to qualify for browser preload lists is 1 year. Defaults to
+  #      1 year (recommended).
+  #
+  #    * +subdomains+: Set to +true+ to tell the browser to apply these settings
+  #      to all subdomains. This protects your cookies from interception by a
+  #      vulnerable site on a subdomain. Defaults to +true+.
+  #
+  #    * +preload+: Advertise that this site may be included in browsers'
+  #      preloaded HSTS lists. HSTS protects your site on every visit <i>except the
+  #      first visit</i> since it hasn't seen your HSTS header yet. To close this
+  #      gap, browser vendors include a baked-in list of HSTS-enabled sites.
+  #      Go to https://hstspreload.org to submit your site for inclusion.
+  #      Defaults to +false+.
+  #
+  #    To turn off HSTS, omitting the header is not enough. Browsers will remember the
+  #    original HSTS directive until it expires. Instead, use the header to tell browsers to
+  #    expire HSTS immediately. Setting <tt>hsts: false</tt> is a shortcut for
+  #    <tt>hsts: { expires: 0 }</tt>.
   class SSL
-    # Default to 180 days, the low end for https://www.ssllabs.com/ssltest/
-    # and greater than the 18-week requirement for browser preload lists.
-    HSTS_EXPIRES_IN = 15552000
+    # :stopdoc:
+
+    # Default to 1 year, the minimum for browser preload lists.
+    HSTS_EXPIRES_IN = 31536000
 
     def self.default_hsts_options
       { expires: HSTS_EXPIRES_IN, subdomains: true, preload: false }
@@ -67,7 +73,7 @@ module ActionDispatch
       if request.ssl?
         @app.call(env).tap do |status, headers, body|
           set_hsts_header! headers
-          flag_cookies_as_secure! headers if @secure_cookies
+          flag_cookies_as_secure! headers if @secure_cookies && !@exclude.call(request)
         end
       else
         return redirect_to_https request unless @exclude.call(request)
diff --git a/actionpack/lib/action_dispatch/middleware/static.rb b/actionpack/lib/action_dispatch/middleware/static.rb
index 23492e14eb..8130bfe2e7 100644
--- a/actionpack/lib/action_dispatch/middleware/static.rb
+++ b/actionpack/lib/action_dispatch/middleware/static.rb
@@ -16,7 +16,7 @@ module ActionDispatch
   # does not exist, a 404 "File not Found" response will be returned.
   class FileHandler
     def initialize(root, index: "index", headers: {})
-      @root          = root.chomp("/")
+      @root          = root.chomp("/").b
       @file_server   = ::Rack::File.new(@root, headers)
       @index         = index
     end
@@ -35,7 +35,7 @@ module ActionDispatch
       paths = [path, "#{path}#{ext}", "#{path}/#{@index}#{ext}"]
 
       if match = paths.detect { |p|
-        path = File.join(@root, p.dup.force_encoding(Encoding::UTF_8))
+        path = File.join(@root, p.b)
         begin
           File.file?(path) && File.readable?(path)
         rescue SystemCallError
@@ -43,7 +43,7 @@ module ActionDispatch
         end
 
       }
-        return ::Rack::Utils.escape_path(match)
+        return ::Rack::Utils.escape_path(match).b
       end
     end
 
@@ -69,7 +69,7 @@ module ActionDispatch
 
       headers["Vary"] = "Accept-Encoding" if gzip_path
 
-      return [status, headers, body]
+      [status, headers, body]
     ensure
       request.path_info = path
     end
diff --git a/actionpack/lib/action_dispatch/middleware/templates/rescues/invalid_statement.html.erb b/actionpack/lib/action_dispatch/middleware/templates/rescues/invalid_statement.html.erb
new file mode 100644
index 0000000000..e1b129ccc5
--- /dev/null
+++ b/actionpack/lib/action_dispatch/middleware/templates/rescues/invalid_statement.html.erb
@@ -0,0 +1,21 @@
+<header>
+  <h1>
+    <%= @exception.class.to_s %>
+    <% if @request.parameters['controller'] %>
+      in <%= @request.parameters['controller'].camelize %>Controller<% if @request.parameters['action'] %>#<%= @request.parameters['action'] %><% end %>
+    <% end %>
+  </h1>
+</header>
+
+<div id="container">
+  <h2>
+    <%= h @exception.message %>
+    <% if @exception.message.match? %r{#{ActiveStorage::Blob.table_name}|#{ActiveStorage::Attachment.table_name}} %>
+      <br />To resolve this issue run: bin/rails active_storage:install
+    <% end %>
+  </h2>
+
+  <%= render template: "rescues/_source" %>
+  <%= render template: "rescues/_trace" %>
+  <%= render template: "rescues/_request_and_response" %>
+</div>
diff --git a/actionpack/lib/action_dispatch/middleware/templates/rescues/invalid_statement.text.erb b/actionpack/lib/action_dispatch/middleware/templates/rescues/invalid_statement.text.erb
new file mode 100644
index 0000000000..033518cf8a
--- /dev/null
+++ b/actionpack/lib/action_dispatch/middleware/templates/rescues/invalid_statement.text.erb
@@ -0,0 +1,13 @@
+<%= @exception.class.to_s %><%
+  if @request.parameters['controller']
+%> in <%= @request.parameters['controller'].camelize %>Controller<% if @request.parameters['action'] %>#<%= @request.parameters['action'] %><% end %>
+<% end %>
+
+<%= @exception.message %>
+<% if @exception.message.match? %r{#{ActiveStorage::Blob.table_name}|#{ActiveStorage::Attachment.table_name}} %>
+To resolve this issue run: bin/rails active_storage:install
+<% end %>
+
+<%= render template: "rescues/_source" %>
+<%= render template: "rescues/_trace" %>
+<%= render template: "rescues/_request_and_response" %>
diff --git a/actionpack/lib/action_dispatch/middleware/templates/rescues/layout.erb b/actionpack/lib/action_dispatch/middleware/templates/rescues/layout.erb
index e0509f56f4..39ea25bdfc 100644
--- a/actionpack/lib/action_dispatch/middleware/templates/rescues/layout.erb
+++ b/actionpack/lib/action_dispatch/middleware/templates/rescues/layout.erb
@@ -106,6 +106,7 @@
 
     .line {
       padding-left: 10px;
+      white-space: pre;
     }
 
     .line:hover {
diff --git a/actionpack/lib/action_dispatch/middleware/templates/rescues/missing_exact_template.html.erb b/actionpack/lib/action_dispatch/middleware/templates/rescues/missing_exact_template.html.erb
new file mode 100644
index 0000000000..76ab1691b5
--- /dev/null
+++ b/actionpack/lib/action_dispatch/middleware/templates/rescues/missing_exact_template.html.erb
@@ -0,0 +1,19 @@
+<header>
+  <h1>No template for interactive request</h1>
+</header>
+
+<div id="container">
+  <h2><%= h @exception.message %></h2>
+
+  <p class="summary">
+    <strong>NOTE!</strong><br>
+    Unless told otherwise, Rails expects an action to render a template with the same name,<br>
+    contained in a folder named after its controller.
+
+    If this controller is an API responding with 204 (No Content), <br>
+    which does not require a template,
+    then this error will occur when trying to access it via browser,<br>
+    since we expect an HTML template
+    to be rendered for such requests. If that's the case, carry on.
+  </p>
+</div>
diff --git a/actionpack/lib/action_dispatch/middleware/templates/rescues/missing_exact_template.text.erb b/actionpack/lib/action_dispatch/middleware/templates/rescues/missing_exact_template.text.erb
new file mode 100644
index 0000000000..fcdbe6069d
--- /dev/null
+++ b/actionpack/lib/action_dispatch/middleware/templates/rescues/missing_exact_template.text.erb
@@ -0,0 +1,3 @@
+Missing exact template
+
+<%= @exception.message %>
diff --git a/actionpack/lib/action_dispatch/railtie.rb b/actionpack/lib/action_dispatch/railtie.rb
index 4743a7ce61..eb6fbca6ba 100644
--- a/actionpack/lib/action_dispatch/railtie.rb
+++ b/actionpack/lib/action_dispatch/railtie.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "action_dispatch"
+require "active_support/messages/rotation_configuration"
 
 module ActionDispatch
   class Railtie < Rails::Railtie # :nodoc:
@@ -18,15 +19,21 @@ module ActionDispatch
     config.action_dispatch.signed_cookie_salt = "signed cookie"
     config.action_dispatch.encrypted_cookie_salt = "encrypted cookie"
     config.action_dispatch.encrypted_signed_cookie_salt = "signed encrypted cookie"
+    config.action_dispatch.authenticated_encrypted_cookie_salt = "authenticated encrypted cookie"
     config.action_dispatch.use_authenticated_cookie_encryption = false
     config.action_dispatch.perform_deep_munge = true
 
     config.action_dispatch.default_headers = {
       "X-Frame-Options" => "SAMEORIGIN",
       "X-XSS-Protection" => "1; mode=block",
-      "X-Content-Type-Options" => "nosniff"
+      "X-Content-Type-Options" => "nosniff",
+      "X-Download-Options" => "noopen",
+      "X-Permitted-Cross-Domain-Policies" => "none",
+      "Referrer-Policy" => "strict-origin-when-cross-origin"
     }
 
+    config.action_dispatch.cookies_rotations = ActiveSupport::Messages::RotationConfiguration.new
+
     config.eager_load_namespaces << ActionDispatch
 
     initializer "action_dispatch.configure" do |app|
@@ -39,8 +46,6 @@ module ActionDispatch
       ActionDispatch::ExceptionWrapper.rescue_responses.merge!(config.action_dispatch.rescue_responses)
       ActionDispatch::ExceptionWrapper.rescue_templates.merge!(config.action_dispatch.rescue_templates)
 
-      config.action_dispatch.authenticated_encrypted_cookie_salt = "authenticated encrypted cookie" if config.action_dispatch.use_authenticated_cookie_encryption
-
       config.action_dispatch.always_write_cookie = Rails.env.development? if config.action_dispatch.always_write_cookie.nil?
       ActionDispatch::Cookies::CookieJar.always_write_cookie = config.action_dispatch.always_write_cookie
 
diff --git a/actionpack/lib/action_dispatch/request/session.rb b/actionpack/lib/action_dispatch/request/session.rb
index d86d0b10c2..bc5e0670e0 100644
--- a/actionpack/lib/action_dispatch/request/session.rb
+++ b/actionpack/lib/action_dispatch/request/session.rb
@@ -93,6 +93,14 @@ module ActionDispatch
         @delegate[key.to_s]
       end
 
+      # Returns the nested value specified by the sequence of keys, returning
+      # +nil+ if any intermediate step is +nil+.
+      def dig(*keys)
+        load_for_read!
+        keys = keys.map.with_index { |key, i| i.zero? ? key.to_s : key }
+        @delegate.dig(*keys)
+      end
+
       # Returns true if the session has the given key or false.
       def has_key?(key)
         load_for_read!
@@ -130,6 +138,7 @@ module ActionDispatch
         load_for_read!
         @delegate.dup.delete_if { |_, v| v.nil? }
       end
+      alias :to_h :to_hash
 
       # Updates the session with given Hash.
       #
diff --git a/actionpack/lib/action_dispatch/routing.rb b/actionpack/lib/action_dispatch/routing.rb
index 72f7407c6e..5cde677051 100644
--- a/actionpack/lib/action_dispatch/routing.rb
+++ b/actionpack/lib/action_dispatch/routing.rb
@@ -243,8 +243,9 @@ module ActionDispatch
   #
   #   rails routes
   #
-  # Target specific controllers by prefixing the command with <tt>-c</tt> option.
-  #
+  # Target a specific controller with <tt>-c</tt>, or grep routes
+  # using <tt>-g</tt>. Useful in conjunction with <tt>--expanded</tt>
+  # which displays routes vertically.
   module Routing
     extend ActiveSupport::Autoload
 
diff --git a/actionpack/lib/action_dispatch/routing/endpoint.rb b/actionpack/lib/action_dispatch/routing/endpoint.rb
index e911b6537b..28bb20d688 100644
--- a/actionpack/lib/action_dispatch/routing/endpoint.rb
+++ b/actionpack/lib/action_dispatch/routing/endpoint.rb
@@ -5,8 +5,13 @@ module ActionDispatch
     class Endpoint # :nodoc:
       def dispatcher?;   false; end
       def redirect?;     false; end
-      def matches?(req); true;  end
-      def app;           self;  end
+      def matches?(req);  true; end
+      def app;            self; end
+      def rack_app;        app; end
+
+      def engine?
+        rack_app.is_a?(Class) && rack_app < Rails::Engine
+      end
     end
   end
 end
diff --git a/actionpack/lib/action_dispatch/routing/inspector.rb b/actionpack/lib/action_dispatch/routing/inspector.rb
index b2868b7427..bae50f6a43 100644
--- a/actionpack/lib/action_dispatch/routing/inspector.rb
+++ b/actionpack/lib/action_dispatch/routing/inspector.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "delegate"
-require "active_support/core_ext/string/strip"
+require "io/console/size"
 
 module ActionDispatch
   module Routing
@@ -15,7 +15,7 @@ module ActionDispatch
       end
 
       def rack_app
-        app.app
+        app.rack_app
       end
 
       def path
@@ -47,7 +47,7 @@ module ActionDispatch
       end
 
       def engine?
-        rack_app.respond_to?(:routes)
+        app.engine?
       end
     end
 
@@ -61,11 +61,11 @@ module ActionDispatch
         @routes = routes
       end
 
-      def format(formatter, filter = nil)
+      def format(formatter, filter = {})
         routes_to_display = filter_routes(normalize_filter(filter))
         routes = collect_routes(routes_to_display)
         if routes.none?
-          formatter.no_routes(collect_routes(@routes))
+          formatter.no_routes(collect_routes(@routes), filter)
           return formatter.result
         end
 
@@ -81,12 +81,12 @@ module ActionDispatch
       end
 
       private
-
         def normalize_filter(filter)
-          if filter.is_a?(Hash) && filter[:controller]
+          if filter[:controller]
             { controller: /#{filter[:controller].downcase.sub(/_?controller\z/, '').sub('::', '/')}/ }
-          elsif filter
-            { controller: /#{filter}/, action: /#{filter}/, verb: /#{filter}/, name: /#{filter}/, path: /#{filter}/ }
+          elsif filter[:grep]
+            { controller: /#{filter[:grep]}/, action: /#{filter[:grep]}/,
+              verb: /#{filter[:grep]}/, name: /#{filter[:grep]}/, path: /#{filter[:grep]}/ }
           end
         end
 
@@ -126,62 +126,111 @@ module ActionDispatch
         end
     end
 
-    class ConsoleFormatter
-      def initialize
-        @buffer = []
-      end
+    module ConsoleFormatter
+      class Base
+        def initialize
+          @buffer = []
+        end
 
-      def result
-        @buffer.join("\n")
-      end
+        def result
+          @buffer.join("\n")
+        end
 
-      def section_title(title)
-        @buffer << "\n#{title}:"
-      end
+        def section_title(title)
+        end
 
-      def section(routes)
-        @buffer << draw_section(routes)
-      end
+        def section(routes)
+        end
 
-      def header(routes)
-        @buffer << draw_header(routes)
-      end
+        def header(routes)
+        end
 
-      def no_routes(routes)
-        @buffer <<
-        if routes.none?
-          <<-MESSAGE.strip_heredoc
-          You don't have any routes defined!
+        def no_routes(routes, filter)
+          @buffer <<
+            if routes.none?
+              <<~MESSAGE
+                You don't have any routes defined!
+
+                Please add some routes in config/routes.rb.
+              MESSAGE
+            elsif filter.key?(:controller)
+              "No routes were found for this controller."
+            elsif filter.key?(:grep)
+              "No routes were found for this grep pattern."
+            end
 
-          Please add some routes in config/routes.rb.
-          MESSAGE
-        else
-          "No routes were found for this controller"
+          @buffer << "For more information about routes, see the Rails guide: http://guides.rubyonrails.org/routing.html."
         end
-        @buffer << "For more information about routes, see the Rails guide: http://guides.rubyonrails.org/routing.html."
       end
 
-      private
-        def draw_section(routes)
-          header_lengths = ["Prefix", "Verb", "URI Pattern"].map(&:length)
-          name_width, verb_width, path_width = widths(routes).zip(header_lengths).map(&:max)
+      class Sheet < Base
+        def section_title(title)
+          @buffer << "\n#{title}:"
+        end
 
-          routes.map do |r|
-            "#{r[:name].rjust(name_width)} #{r[:verb].ljust(verb_width)} #{r[:path].ljust(path_width)} #{r[:reqs]}"
-          end
+        def section(routes)
+          @buffer << draw_section(routes)
+        end
+
+        def header(routes)
+          @buffer << draw_header(routes)
         end
 
-        def draw_header(routes)
-          name_width, verb_width, path_width = widths(routes)
+        private
+
+          def draw_section(routes)
+            header_lengths = ["Prefix", "Verb", "URI Pattern"].map(&:length)
+            name_width, verb_width, path_width = widths(routes).zip(header_lengths).map(&:max)
+
+            routes.map do |r|
+              "#{r[:name].rjust(name_width)} #{r[:verb].ljust(verb_width)} #{r[:path].ljust(path_width)} #{r[:reqs]}"
+            end
+          end
+
+          def draw_header(routes)
+            name_width, verb_width, path_width = widths(routes)
+
+            "#{"Prefix".rjust(name_width)} #{"Verb".ljust(verb_width)} #{"URI Pattern".ljust(path_width)} Controller#Action"
+          end
+
+          def widths(routes)
+            [routes.map { |r| r[:name].length }.max || 0,
+             routes.map { |r| r[:verb].length }.max || 0,
+             routes.map { |r| r[:path].length }.max || 0]
+          end
+      end
 
-          "#{"Prefix".rjust(name_width)} #{"Verb".ljust(verb_width)} #{"URI Pattern".ljust(path_width)} Controller#Action"
+      class Expanded < Base
+        def section_title(title)
+          @buffer << "\n#{"[ #{title} ]"}"
         end
 
-        def widths(routes)
-          [routes.map { |r| r[:name].length }.max || 0,
-           routes.map { |r| r[:verb].length }.max || 0,
-           routes.map { |r| r[:path].length }.max || 0]
+        def section(routes)
+          @buffer << draw_expanded_section(routes)
         end
+
+        private
+
+          def draw_expanded_section(routes)
+            routes.map.each_with_index do |r, i|
+              <<~MESSAGE.chomp
+                #{route_header(index: i + 1)}
+                Prefix            | #{r[:name]}
+                Verb              | #{r[:verb]}
+                URI               | #{r[:path]}
+                Controller#Action | #{r[:reqs]}
+              MESSAGE
+            end
+          end
+
+          def route_header(index:)
+            console_width = IO.console_size.second
+            header_prefix = "--[ Route #{index} ]"
+            dash_remainder = [console_width - header_prefix.size, 0].max
+
+            "#{header_prefix}#{'-' * dash_remainder}"
+          end
+      end
     end
 
     class HtmlTableFormatter
@@ -203,7 +252,7 @@ module ActionDispatch
       end
 
       def no_routes(*)
-        @buffer << <<-MESSAGE.strip_heredoc
+        @buffer << <<~MESSAGE
           <p>You don't have any routes defined!</p>
           <ul>
             <li>Please add some routes in <tt>config/routes.rb</tt>.</li>
@@ -212,7 +261,7 @@ module ActionDispatch
               <a href="http://guides.rubyonrails.org/routing.html">Rails Routing from the Outside In</a>.
             </li>
           </ul>
-          MESSAGE
+        MESSAGE
       end
 
       def result
diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index 57a5bc681e..d9dd24935b 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -4,8 +4,8 @@ require "active_support/core_ext/hash/slice"
 require "active_support/core_ext/enumerable"
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/regexp"
-require_relative "redirection"
-require_relative "endpoint"
+require "action_dispatch/routing/redirection"
+require "action_dispatch/routing/endpoint"
 
 module ActionDispatch
   module Routing
@@ -473,7 +473,17 @@ module ActionDispatch
         #   <tt>params[<:param>]</tt>.
         #   In your router:
         #
-        #      resources :user, param: :name
+        #      resources :users, param: :name
+        #
+        #   The +users+ resource here will have the following routes generated for it:
+        #
+        #      GET       /users(.:format)
+        #      POST      /users(.:format)
+        #      GET       /users/new(.:format)
+        #      GET       /users/:name/edit(.:format)
+        #      GET       /users/:name(.:format)
+        #      PATCH/PUT /users/:name(.:format)
+        #      DELETE    /users/:name(.:format)
         #
         #   You can override <tt>ActiveRecord::Base#to_param</tt> of a related
         #   model to construct a URL:
@@ -484,8 +494,8 @@ module ActionDispatch
         #        end
         #      end
         #
-        #   user = User.find_by(name: 'Phusion')
-        #   user_path(user)  # => "/users/Phusion"
+        #      user = User.find_by(name: 'Phusion')
+        #      user_path(user)  # => "/users/Phusion"
         #
         # [:path]
         #   The path prefix for the routes.
@@ -601,7 +611,7 @@ module ActionDispatch
           end
 
           raise ArgumentError, "A rack application must be specified" unless app.respond_to?(:call)
-          raise ArgumentError, <<-MSG.strip_heredoc unless path
+          raise ArgumentError, <<~MSG unless path
             Must be called with mount point
 
               mount SomeRackApp, at: "some_route"
@@ -654,6 +664,7 @@ module ActionDispatch
           def define_generate_prefix(app, name)
             _route = @set.named_routes.get name
             _routes = @set
+            _url_helpers = @set.url_helpers
 
             script_namer = ->(options) do
               prefix_options = options.slice(*_route.segment_keys)
@@ -665,7 +676,7 @@ module ActionDispatch
 
               # We must actually delete prefix segment keys to avoid passing them to next url_for.
               _route.segment_keys.each { |k| options.delete(k) }
-              _routes.url_helpers.send("#{name}_path", prefix_options)
+              _url_helpers.send("#{name}_path", prefix_options)
             end
 
             app.routes.define_mounted_helper(name, script_namer)
@@ -1265,7 +1276,7 @@ module ActionDispatch
         #   POST      /profile
         #
         # === Options
-        # Takes same options as +resources+.
+        # Takes same options as resources[rdoc-ref:#resources]
         def resource(*resources, &block)
           options = resources.extract_options!.dup
 
@@ -1330,7 +1341,7 @@ module ActionDispatch
         #   DELETE    /photos/:photo_id/comments/:id
         #
         # === Options
-        # Takes same options as <tt>Base#match</tt> as well as:
+        # Takes same options as match[rdoc-ref:Base#match] as well as:
         #
         # [:path_names]
         #   Allows you to change the segment component of the +edit+ and +new+ actions.
@@ -1563,7 +1574,7 @@ module ActionDispatch
         # Matches a URL pattern to one or more routes.
         # For more information, see match[rdoc-ref:Base#match].
         #
-        #   match 'path' => 'controller#action', via: patch
+        #   match 'path' => 'controller#action', via: :patch
         #   match 'path', to: 'controller#action', via: :post
         #   match 'path', 'otherpath', on: :member, via: :get
         def match(path, *rest, &block)
@@ -2036,7 +2047,7 @@ module ActionDispatch
       end
 
       module CustomUrls
-        # Define custom url helpers that will be added to the application's
+        # Define custom URL helpers that will be added to the application's
         # routes. This allows you to override and/or replace the default behavior
         # of routing helpers, e.g:
         #
@@ -2056,11 +2067,11 @@ module ActionDispatch
         # arguments for +url_for+ which will actually build the URL string. This can
         # be one of the following:
         #
-        #   * A string, which is treated as a generated URL
-        #   * A hash, e.g. { controller: "pages", action: "index" }
-        #   * An array, which is passed to `polymorphic_url`
-        #   * An Active Model instance
-        #   * An Active Model class
+        # * A string, which is treated as a generated URL
+        # * A hash, e.g. <tt>{ controller: "pages", action: "index" }</tt>
+        # * An array, which is passed to +polymorphic_url+
+        # * An Active Model instance
+        # * An Active Model class
         #
         # NOTE: Other URL helpers can be called in the block but be careful not to invoke
         # your custom URL helper again otherwise it will result in a stack overflow error.
@@ -2072,9 +2083,9 @@ module ActionDispatch
         #     [ :products, options.merge(params.permit(:page, :size).to_h.symbolize_keys) ]
         #   end
         #
-        # In this instance the +params+ object comes from the context in which the the
+        # In this instance the +params+ object comes from the context in which the
         # block is executed, e.g. generating a URL inside a controller action or a view.
-        # If the block is executed where there isn't a params object such as this:
+        # If the block is executed where there isn't a +params+ object such as this:
         #
         #   Rails.application.routes.url_helpers.browse_path
         #
diff --git a/actionpack/lib/action_dispatch/routing/polymorphic_routes.rb b/actionpack/lib/action_dispatch/routing/polymorphic_routes.rb
index 6da869c0c2..e17ccaf986 100644
--- a/actionpack/lib/action_dispatch/routing/polymorphic_routes.rb
+++ b/actionpack/lib/action_dispatch/routing/polymorphic_routes.rb
@@ -120,8 +120,7 @@ module ActionDispatch
                                                opts
       end
 
-      # Returns the path component of a URL for the given record. It uses
-      # <tt>polymorphic_url</tt> with <tt>routing_type: :path</tt>.
+      # Returns the path component of a URL for the given record.
       def polymorphic_path(record_or_hash_or_array, options = {})
         if Hash === record_or_hash_or_array
           options = record_or_hash_or_array.merge(options)
diff --git a/actionpack/lib/action_dispatch/routing/redirection.rb b/actionpack/lib/action_dispatch/routing/redirection.rb
index a04f06de1b..143a4b3d62 100644
--- a/actionpack/lib/action_dispatch/routing/redirection.rb
+++ b/actionpack/lib/action_dispatch/routing/redirection.rb
@@ -1,11 +1,11 @@
 # frozen_string_literal: true
 
-require_relative "../http/request"
+require "action_dispatch/http/request"
 require "active_support/core_ext/uri"
 require "active_support/core_ext/array/extract_options"
 require "rack/utils"
 require "action_controller/metal/exceptions"
-require_relative "endpoint"
+require "action_dispatch/routing/endpoint"
 
 module ActionDispatch
   module Routing
@@ -142,7 +142,7 @@ module ActionDispatch
       #   get "/stories" => redirect("/posts")
       #
       # This will redirect the user, while ignoring certain parts of the request, including query string, etc.
-      # `/stories`, `/stories?foo=bar`, etc all redirect to `/posts`.
+      # <tt>/stories</tt>, <tt>/stories?foo=bar</tt>, etc all redirect to <tt>/posts</tt>.
       #
       # You can also use interpolation in the supplied redirect argument:
       #
@@ -175,8 +175,8 @@ module ActionDispatch
       #   get '/stories', to: redirect(path: '/posts')
       #
       # This will redirect the user, while changing only the specified parts of the request,
-      # for example the `path` option in the last example.
-      # `/stories`, `/stories?foo=bar`, redirect to `/posts` and `/posts?foo=bar` respectively.
+      # for example the +path+ option in the last example.
+      # <tt>/stories</tt>, <tt>/stories?foo=bar</tt>, redirect to <tt>/posts</tt> and <tt>/posts?foo=bar</tt> respectively.
       #
       # Finally, an object which responds to call can be supplied to redirect, allowing you to reuse
       # common redirect routes. The call method must accept two arguments, params and request, and return
diff --git a/actionpack/lib/action_dispatch/routing/route_set.rb b/actionpack/lib/action_dispatch/routing/route_set.rb
index 357eaec572..1134279a7f 100644
--- a/actionpack/lib/action_dispatch/routing/route_set.rb
+++ b/actionpack/lib/action_dispatch/routing/route_set.rb
@@ -1,13 +1,13 @@
 # frozen_string_literal: true
 
-require_relative "../journey"
+require "action_dispatch/journey"
 require "active_support/core_ext/object/to_query"
-require "active_support/core_ext/hash/slice"
+require "active_support/core_ext/module/redefine_method"
 require "active_support/core_ext/module/remove_method"
 require "active_support/core_ext/array/extract_options"
 require "action_controller/metal/exceptions"
-require_relative "../http/request"
-require_relative "endpoint"
+require "action_dispatch/http/request"
+require "action_dispatch/routing/endpoint"
 
 module ActionDispatch
   module Routing
@@ -35,7 +35,7 @@ module ActionDispatch
           if @raise_on_name_error
             raise
           else
-            return [404, { "X-Cascade" => "pass" }, []]
+            [404, { "X-Cascade" => "pass" }, []]
           end
         end
 
@@ -153,13 +153,13 @@ module ActionDispatch
           url_name = :"#{name}_url"
 
           @path_helpers_module.module_eval do
-            define_method(path_name) do |*args|
+            redefine_method(path_name) do |*args|
               helper.call(self, args, true)
             end
           end
 
           @url_helpers_module.module_eval do
-            define_method(url_name) do |*args|
+            redefine_method(url_name) do |*args|
               helper.call(self, args, false)
             end
           end
@@ -198,6 +198,16 @@ module ActionDispatch
               if args.size == arg_size && !inner_options && optimize_routes_generation?(t)
                 options = t.url_options.merge @options
                 options[:path] = optimized_helper(args)
+
+                original_script_name = options.delete(:original_script_name)
+                script_name = t._routes.find_script_name(options)
+
+                if original_script_name
+                  script_name = original_script_name + script_name
+                end
+
+                options[:script_name] = script_name
+
                 url_strategy.call options
               else
                 super
@@ -546,7 +556,7 @@ module ActionDispatch
 
           # plus a singleton class method called _routes ...
           included do
-            singleton_class.send(:redefine_method, :_routes) { routes }
+            redefine_singleton_method(:_routes) { routes }
           end
 
           # And an instance method _routes. Note that
@@ -583,14 +593,14 @@ module ActionDispatch
         if route.segment_keys.include?(:controller)
           ActiveSupport::Deprecation.warn(<<-MSG.squish)
             Using a dynamic :controller segment in a route is deprecated and
-            will be removed in Rails 5.2.
+            will be removed in Rails 6.0.
           MSG
         end
 
         if route.segment_keys.include?(:action)
           ActiveSupport::Deprecation.warn(<<-MSG.squish)
             Using a dynamic :action segment in a route is deprecated and
-            will be removed in Rails 5.2.
+            will be removed in Rails 6.0.
           MSG
         end
 
@@ -841,6 +851,10 @@ module ActionDispatch
         end
 
         req = make_request(env)
+        recognize_path_with_request(req, path, extras)
+      end
+
+      def recognize_path_with_request(req, path, extras, raise_on_missing: true)
         @router.recognize(req) do |route, params|
           params.merge!(extras)
           params.each do |key, value|
@@ -859,10 +873,15 @@ module ActionDispatch
             end
 
             return req.path_parameters
+          elsif app.matches?(req) && app.engine?
+            path_parameters = app.rack_app.routes.recognize_path_with_request(req, path, extras, raise_on_missing: false)
+            return path_parameters if path_parameters
           end
         end
 
-        raise ActionController::RoutingError, "No route matches #{path.inspect}"
+        if raise_on_missing
+          raise ActionController::RoutingError, "No route matches #{path.inspect}"
+        end
       end
     end
     # :startdoc:
diff --git a/actionpack/lib/action_dispatch/routing/url_for.rb b/actionpack/lib/action_dispatch/routing/url_for.rb
index 6f3db258ab..1a31c7dbb8 100644
--- a/actionpack/lib/action_dispatch/routing/url_for.rb
+++ b/actionpack/lib/action_dispatch/routing/url_for.rb
@@ -109,7 +109,7 @@ module ActionDispatch
       end
 
       # Hook overridden in controller to add request information
-      # with `default_url_options`. Application logic should not
+      # with +default_url_options+. Application logic should not
       # go into url_options.
       def url_options
         default_url_options
@@ -155,7 +155,7 @@ module ActionDispatch
       # Missing routes keys may be filled in from the current request's parameters
       # (e.g. +:controller+, +:action+, +:id+ and any other parameters that are
       # placed in the path). Given that the current action has been reached
-      # through `GET /users/1`:
+      # through <tt>GET /users/1</tt>:
       #
       #   url_for(only_path: true)                        # => '/users/1'
       #   url_for(only_path: true, action: 'edit')        # => '/users/1/edit'
@@ -191,7 +191,25 @@ module ActionDispatch
         end
       end
 
-      def route_for(name, *args) # :nodoc:
+      # Allows calling direct or regular named route.
+      #
+      #   resources :buckets
+      #
+      #   direct :recordable do |recording|
+      #     route_for(:bucket, recording.bucket)
+      #   end
+      #
+      #   direct :threadable do |threadable|
+      #     route_for(:recordable, threadable.parent)
+      #   end
+      #
+      # This maintains the context of the original caller on
+      # whether to return a path or full URL, e.g:
+      #
+      #   threadable_path(threadable)  # => "/buckets/1"
+      #   threadable_url(threadable)   # => "http://example.com/buckets/1"
+      #
+      def route_for(name, *args)
         public_send(:"#{name}_url", *args)
       end
 
diff --git a/actionpack/lib/action_dispatch/system_test_case.rb b/actionpack/lib/action_dispatch/system_test_case.rb
index ae4aeac59d..c74c0ccced 100644
--- a/actionpack/lib/action_dispatch/system_test_case.rb
+++ b/actionpack/lib/action_dispatch/system_test_case.rb
@@ -1,13 +1,16 @@
 # frozen_string_literal: true
 
+gem "capybara", ">= 2.15"
+
 require "capybara/dsl"
 require "capybara/minitest"
 require "action_controller"
-require_relative "system_testing/driver"
-require_relative "system_testing/server"
-require_relative "system_testing/test_helpers/screenshot_helper"
-require_relative "system_testing/test_helpers/setup_and_teardown"
-require_relative "system_testing/test_helpers/undef_methods"
+require "action_dispatch/system_testing/driver"
+require "action_dispatch/system_testing/browser"
+require "action_dispatch/system_testing/server"
+require "action_dispatch/system_testing/test_helpers/screenshot_helper"
+require "action_dispatch/system_testing/test_helpers/setup_and_teardown"
+require "action_dispatch/system_testing/test_helpers/undef_methods"
 
 module ActionDispatch
   # = System Testing
@@ -67,6 +70,9 @@ module ActionDispatch
   # size of the browser screen. These two options are not applicable for
   # headless drivers and will be silently ignored if passed.
   #
+  # Headless browsers such as headless Chrome and headless Firefox are also supported.
+  # You can use these browsers by setting the +:using+ argument to +:headless_chrome+ or +:headless_firefox+.
+  #
   # To use a headless driver, like Poltergeist, update your Gemfile to use
   # Poltergeist instead of Selenium and then declare the driver name in the
   # +application_system_test_case.rb+ file. In this case, you would leave out
@@ -119,14 +125,22 @@ module ActionDispatch
     #
     #   driven_by :poltergeist
     #
+    #   driven_by :selenium, screen_size: [800, 800]
+    #
+    #   driven_by :selenium, using: :chrome
+    #
+    #   driven_by :selenium, using: :headless_chrome
+    #
     #   driven_by :selenium, using: :firefox
     #
-    #   driven_by :selenium, screen_size: [800, 800]
+    #   driven_by :selenium, using: :headless_firefox
     def self.driven_by(driver, using: :chrome, screen_size: [1400, 1400], options: {})
       self.driver = SystemTesting::Driver.new(driver, using: using, screen_size: screen_size, options: options)
     end
 
     driven_by :selenium
+
+    ActiveSupport.run_load_hooks(:action_dispatch_system_test_case, self)
   end
 
   SystemTestCase.start_application
diff --git a/actionpack/lib/action_dispatch/system_testing/browser.rb b/actionpack/lib/action_dispatch/system_testing/browser.rb
new file mode 100644
index 0000000000..1b0bce6b9e
--- /dev/null
+++ b/actionpack/lib/action_dispatch/system_testing/browser.rb
@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+module ActionDispatch
+  module SystemTesting
+    class Browser # :nodoc:
+      attr_reader :name
+
+      def initialize(name)
+        @name = name
+      end
+
+      def type
+        case name
+        when :headless_chrome
+          :chrome
+        when :headless_firefox
+          :firefox
+        else
+          name
+        end
+      end
+
+      def options
+        case name
+        when :headless_chrome
+          headless_chrome_browser_options
+        when :headless_firefox
+          headless_firefox_browser_options
+        end
+      end
+
+      private
+        def headless_chrome_browser_options
+          options = Selenium::WebDriver::Chrome::Options.new
+          options.args << "--headless"
+          options.args << "--disable-gpu" if Gem.win_platform?
+
+          options
+        end
+
+        def headless_firefox_browser_options
+          options = Selenium::WebDriver::Firefox::Options.new
+          options.args << "-headless"
+
+          options
+        end
+    end
+  end
+end
diff --git a/actionpack/lib/action_dispatch/system_testing/driver.rb b/actionpack/lib/action_dispatch/system_testing/driver.rb
index 4279336f2f..5252ff6746 100644
--- a/actionpack/lib/action_dispatch/system_testing/driver.rb
+++ b/actionpack/lib/action_dispatch/system_testing/driver.rb
@@ -5,7 +5,7 @@ module ActionDispatch
     class Driver # :nodoc:
       def initialize(name, **options)
         @name = name
-        @browser = options[:using]
+        @browser = Browser.new(options[:using])
         @screen_size = options[:screen_size]
         @options = options[:options]
       end
@@ -31,8 +31,12 @@ module ActionDispatch
           end
         end
 
+        def browser_options
+          @options.merge(options: @browser.options).compact
+        end
+
         def register_selenium(app)
-          Capybara::Selenium::Driver.new(app, { browser: @browser }.merge(@options)).tap do |driver|
+          Capybara::Selenium::Driver.new(app, { browser: @browser.type }.merge(browser_options)).tap do |driver|
             driver.browser.manage.window.size = Selenium::WebDriver::Dimension.new(*@screen_size)
           end
         end
@@ -43,7 +47,7 @@ module ActionDispatch
 
         def register_webkit(app)
           Capybara::Webkit::Driver.new(app, Capybara::Webkit::Configuration.to_hash.merge(@options)).tap do |driver|
-            driver.resize_window(*@screen_size)
+            driver.resize_window_to(driver.current_window_handle, *@screen_size)
           end
         end
 
diff --git a/actionpack/lib/action_dispatch/system_testing/server.rb b/actionpack/lib/action_dispatch/system_testing/server.rb
index 76bada8df1..4fc1f33767 100644
--- a/actionpack/lib/action_dispatch/system_testing/server.rb
+++ b/actionpack/lib/action_dispatch/system_testing/server.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "rack/handler/puma"
-
 module ActionDispatch
   module SystemTesting
     class Server # :nodoc:
@@ -12,29 +10,17 @@ module ActionDispatch
       self.silence_puma = false
 
       def run
-        register
         setup
       end
 
       private
-        def register
-          Capybara.register_server :rails_puma do |app, port, host|
-            Rack::Handler::Puma.run(
-              app,
-              Port: port,
-              Threads: "0:1",
-              Silent: self.class.silence_puma
-            )
-          end
-        end
-
         def setup
           set_server
           set_port
         end
 
         def set_server
-          Capybara.server = :rails_puma
+          Capybara.server = :puma, { Silent: self.class.silence_puma } if Capybara.server == Capybara.servers[:default]
         end
 
         def set_port
diff --git a/actionpack/lib/action_dispatch/system_testing/test_helpers/screenshot_helper.rb b/actionpack/lib/action_dispatch/system_testing/test_helpers/screenshot_helper.rb
index a0203d26ae..d2685e0452 100644
--- a/actionpack/lib/action_dispatch/system_testing/test_helpers/screenshot_helper.rb
+++ b/actionpack/lib/action_dispatch/system_testing/test_helpers/screenshot_helper.rb
@@ -15,12 +15,11 @@ module ActionDispatch
         #
         # You can set the +RAILS_SYSTEM_TESTING_SCREENSHOT+ environment variable to
         # control the output. Possible values are:
-        # * [+inline+ (default)]    display the screenshot in the terminal using the
+        # * [+simple+ (default)]    Only displays the screenshot path.
+        #                           This is the default value.
+        # * [+inline+]              Display the screenshot in the terminal using the
         #                           iTerm image protocol (https://iterm2.com/documentation-images.html).
-        # * [+simple+]              only display the screenshot path.
-        #                           This is the default value if the +CI+ environment variables
-        #                           is defined.
-        # * [+artifact+]            display the screenshot in the terminal, using the terminal
+        # * [+artifact+]            Display the screenshot in the terminal, using the terminal
         #                           artifact format (https://buildkite.github.io/terminal/inline-images/).
         def take_screenshot
           save_image
@@ -44,35 +43,36 @@ module ActionDispatch
           end
 
           def image_path
-            "tmp/screenshots/#{image_name}.png"
+            @image_path ||= absolute_image_path.to_s
+          end
+
+          def absolute_image_path
+            Rails.root.join("tmp/screenshots/#{image_name}.png")
           end
 
           def save_image
-            page.save_screenshot(Rails.root.join(image_path))
+            page.save_screenshot(absolute_image_path)
           end
 
           def output_type
             # Environment variables have priority
             output_type = ENV["RAILS_SYSTEM_TESTING_SCREENSHOT"] || ENV["CAPYBARA_INLINE_SCREENSHOT"]
 
-            # If running in a CI environment, default to simple
-            output_type ||= "simple" if ENV["CI"]
-
-            # Default
-            output_type ||= "inline"
+            # Default to outputting a path to the screenshot
+            output_type ||= "simple"
 
             output_type
           end
 
           def display_image
-            message = "[Screenshot]: #{image_path}\n"
+            message = "[Screenshot]: #{image_path}\n".dup
 
             case output_type
             when "artifact"
-              message << "\e]1338;url=artifact://#{image_path}\a\n"
+              message << "\e]1338;url=artifact://#{absolute_image_path}\a\n"
             when "inline"
-              name = inline_base64(File.basename(image_path))
-              image = inline_base64(File.read(image_path))
+              name = inline_base64(File.basename(absolute_image_path))
+              image = inline_base64(File.read(absolute_image_path))
               message << "\e]1337;File=name=#{name};height=400px;inline=1:#{image}\a\n"
             end
 
@@ -80,7 +80,7 @@ module ActionDispatch
           end
 
           def inline_base64(path)
-            Base64.encode64(path).gsub("\n", "")
+            Base64.strict_encode64(path)
           end
 
           def failed?
diff --git a/actionpack/lib/action_dispatch/system_testing/test_helpers/setup_and_teardown.rb b/actionpack/lib/action_dispatch/system_testing/test_helpers/setup_and_teardown.rb
index ffa85f4e14..e47d5020f4 100644
--- a/actionpack/lib/action_dispatch/system_testing/test_helpers/setup_and_teardown.rb
+++ b/actionpack/lib/action_dispatch/system_testing/test_helpers/setup_and_teardown.rb
@@ -19,6 +19,7 @@ module ActionDispatch
         def after_teardown
           take_failed_screenshot
           Capybara.reset_sessions!
+        ensure
           super
         end
       end
diff --git a/actionpack/lib/action_dispatch/system_testing/test_helpers/undef_methods.rb b/actionpack/lib/action_dispatch/system_testing/test_helpers/undef_methods.rb
index ef680cafed..d64be3b3d9 100644
--- a/actionpack/lib/action_dispatch/system_testing/test_helpers/undef_methods.rb
+++ b/actionpack/lib/action_dispatch/system_testing/test_helpers/undef_methods.rb
@@ -14,7 +14,7 @@ module ActionDispatch
 
           def method_missing(method, *args, &block)
             if METHODS.include?(method)
-              raise NoMethodError
+              raise NoMethodError, "System tests cannot make direct requests via ##{method}; use #visit and #click_on instead. See http://www.rubydoc.info/github/teamcapybara/capybara/master#The_DSL for more information."
             else
               super
             end
diff --git a/actionpack/lib/action_dispatch/testing/integration.rb b/actionpack/lib/action_dispatch/testing/integration.rb
index ae1f368e8b..f0398dc7b1 100644
--- a/actionpack/lib/action_dispatch/testing/integration.rb
+++ b/actionpack/lib/action_dispatch/testing/integration.rb
@@ -7,43 +7,43 @@ require "active_support/core_ext/object/try"
 require "rack/test"
 require "minitest"
 
-require_relative "request_encoder"
+require "action_dispatch/testing/request_encoder"
 
 module ActionDispatch
   module Integration #:nodoc:
     module RequestHelpers
-      # Performs a GET request with the given parameters. See +#process+ for more
-      # details.
+      # Performs a GET request with the given parameters. See ActionDispatch::Integration::Session#process
+      # for more details.
       def get(path, **args)
         process(:get, path, **args)
       end
 
-      # Performs a POST request with the given parameters. See +#process+ for more
-      # details.
+      # Performs a POST request with the given parameters. See ActionDispatch::Integration::Session#process
+      # for more details.
       def post(path, **args)
         process(:post, path, **args)
       end
 
-      # Performs a PATCH request with the given parameters. See +#process+ for more
-      # details.
+      # Performs a PATCH request with the given parameters. See ActionDispatch::Integration::Session#process
+      # for more details.
       def patch(path, **args)
         process(:patch, path, **args)
       end
 
-      # Performs a PUT request with the given parameters. See +#process+ for more
-      # details.
+      # Performs a PUT request with the given parameters. See ActionDispatch::Integration::Session#process
+      # for more details.
       def put(path, **args)
         process(:put, path, **args)
       end
 
-      # Performs a DELETE request with the given parameters. See +#process+ for
-      # more details.
+      # Performs a DELETE request with the given parameters. See ActionDispatch::Integration::Session#process
+      # for more details.
       def delete(path, **args)
         process(:delete, path, **args)
       end
 
-      # Performs a HEAD request with the given parameters. See +#process+ for more
-      # details.
+      # Performs a HEAD request with the given parameters. See ActionDispatch::Integration::Session#process
+      # for more details.
       def head(path, *args)
         process(:head, path, *args)
       end
@@ -189,6 +189,12 @@ module ActionDispatch
       #   merged into the Rack env hash.
       # - +env+: Additional env to pass, as a Hash. The headers will be
       #   merged into the Rack env hash.
+      # - +xhr+: Set to `true` if you want to make and Ajax request.
+      #   Adds request headers characteristic of XMLHttpRequest e.g. HTTP_X_REQUESTED_WITH.
+      #   The headers will be merged into the Rack env hash.
+      # - +as+: Used for encoding the request with different content type.
+      #   Supports `:json` by default and will set the approriate request headers.
+      #   The headers will be merged into the Rack env hash.
       #
       # This method is rarely used directly. Use +#get+, +#post+, or other standard
       # HTTP methods in integration tests. +#process+ is only required when using a
diff --git a/actionpack/lib/action_dispatch/testing/test_process.rb b/actionpack/lib/action_dispatch/testing/test_process.rb
index 3b63706aaa..8ac50c730d 100644
--- a/actionpack/lib/action_dispatch/testing/test_process.rb
+++ b/actionpack/lib/action_dispatch/testing/test_process.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../middleware/cookies"
-require_relative "../middleware/flash"
+require "action_dispatch/middleware/cookies"
+require "action_dispatch/middleware/flash"
 
 module ActionDispatch
   module TestProcess
diff --git a/actionpack/lib/action_dispatch/testing/test_request.rb b/actionpack/lib/action_dispatch/testing/test_request.rb
index 0a4dec1364..6c5b7af50e 100644
--- a/actionpack/lib/action_dispatch/testing/test_request.rb
+++ b/actionpack/lib/action_dispatch/testing/test_request.rb
@@ -11,7 +11,7 @@ module ActionDispatch
       "HTTP_USER_AGENT"          => "Rails Testing",
     )
 
-    # Create a new test request with default `env` values.
+    # Create a new test request with default +env+ values.
     def self.create(env = {})
       env = Rails.application.env_config.merge(env) if defined?(Rails.application) && Rails.application
       env["rack.request.cookie_hash"] ||= {}.with_indifferent_access
diff --git a/actionpack/lib/action_dispatch/testing/test_response.rb b/actionpack/lib/action_dispatch/testing/test_response.rb
index b23ea7479c..1e6b21f235 100644
--- a/actionpack/lib/action_dispatch/testing/test_response.rb
+++ b/actionpack/lib/action_dispatch/testing/test_response.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "request_encoder"
+require "action_dispatch/testing/request_encoder"
 
 module ActionDispatch
   # Integration test methods such as ActionDispatch::Integration::Session#get
diff --git a/actionpack/lib/action_pack.rb b/actionpack/lib/action_pack.rb
index fe2fc7c474..3f69109633 100644
--- a/actionpack/lib/action_pack.rb
+++ b/actionpack/lib/action_pack.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 #--
-# Copyright (c) 2004-2017 David Heinemeier Hansson
+# Copyright (c) 2004-2018 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the
@@ -23,4 +23,4 @@
 # WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #++
 
-require_relative "action_pack/version"
+require "action_pack/version"
diff --git a/actionpack/lib/action_pack/gem_version.rb b/actionpack/lib/action_pack/gem_version.rb
index 28bc153f4d..37969fcb57 100644
--- a/actionpack/lib/action_pack/gem_version.rb
+++ b/actionpack/lib/action_pack/gem_version.rb
@@ -7,8 +7,8 @@ module ActionPack
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
     PRE   = "alpha"
 
diff --git a/actionpack/test/abstract/callbacks_test.rb b/actionpack/test/abstract/callbacks_test.rb
index fdc09bd951..4512ea27b3 100644
--- a/actionpack/test/abstract/callbacks_test.rb
+++ b/actionpack/test/abstract/callbacks_test.rb
@@ -154,7 +154,7 @@ module AbstractController
 
       test "when :except is specified, an after action is not triggered on that action" do
         @controller.process(:index)
-        assert !@controller.instance_variable_defined?("@authenticated")
+        assert_not @controller.instance_variable_defined?("@authenticated")
       end
     end
 
@@ -198,7 +198,7 @@ module AbstractController
 
       test "when :except is specified with an array, an after action is not triggered on that action" do
         @controller.process(:index)
-        assert !@controller.instance_variable_defined?("@authenticated")
+        assert_not @controller.instance_variable_defined?("@authenticated")
       end
     end
 
diff --git a/actionpack/test/abstract_unit.rb b/actionpack/test/abstract_unit.rb
index caa56018f8..f4787ed27a 100644
--- a/actionpack/test/abstract_unit.rb
+++ b/actionpack/test/abstract_unit.rb
@@ -44,7 +44,7 @@ module Rails
       @_env ||= ActiveSupport::StringInquirer.new(ENV["RAILS_ENV"] || ENV["RACK_ENV"] || "test")
     end
 
-    def root; end;
+    def root; end
   end
 end
 
@@ -380,10 +380,8 @@ class ForkingExecutor
   def initialize(size)
     @size  = size
     @queue = Server.new
-    file   = File.join Dir.tmpdir, Dir::Tmpname.make_tmpname("rails-tests", "fd")
-    @url   = "drbunix://#{file}"
     @pool  = nil
-    DRb.start_service @url, @queue
+    @url = DRb.start_service("drbunix:", @queue).uri
   end
 
   def <<(work); @queue << work; end
@@ -449,3 +447,11 @@ end
 class DrivenBySeleniumWithChrome < ActionDispatch::SystemTestCase
   driven_by :selenium, using: :chrome
 end
+
+class DrivenBySeleniumWithHeadlessChrome < ActionDispatch::SystemTestCase
+  driven_by :selenium, using: :headless_chrome
+end
+
+class DrivenBySeleniumWithHeadlessFirefox < ActionDispatch::SystemTestCase
+  driven_by :selenium, using: :headless_firefox
+end
diff --git a/actionpack/test/controller/action_pack_assertions_test.rb b/actionpack/test/controller/action_pack_assertions_test.rb
index f9a037e3cc..763df3a776 100644
--- a/actionpack/test/controller/action_pack_assertions_test.rb
+++ b/actionpack/test/controller/action_pack_assertions_test.rb
@@ -290,29 +290,29 @@ class ActionPackAssertionsControllerTest < ActionController::TestCase
 
   def test_template_objects_exist
     process :assign_this
-    assert !@controller.instance_variable_defined?(:"@hi")
+    assert_not @controller.instance_variable_defined?(:"@hi")
     assert @controller.instance_variable_get(:"@howdy")
   end
 
   def test_template_objects_missing
     process :nothing
-    assert !@controller.instance_variable_defined?(:@howdy)
+    assert_not @controller.instance_variable_defined?(:@howdy)
   end
 
   def test_empty_flash
     process :flash_me_naked
-    assert flash.empty?
+    assert_empty flash
   end
 
   def test_flash_exist
     process :flash_me
-    assert flash.any?
-    assert flash["hello"].present?
+    assert_predicate flash, :any?
+    assert_predicate flash["hello"], :present?
   end
 
   def test_flash_does_not_exist
     process :nothing
-    assert flash.empty?
+    assert_empty flash
   end
 
   def test_session_exist
@@ -322,7 +322,7 @@ class ActionPackAssertionsControllerTest < ActionController::TestCase
 
   def session_does_not_exist
     process :nothing
-    assert session.empty?
+    assert_empty session
   end
 
   def test_redirection_location
@@ -343,46 +343,46 @@ class ActionPackAssertionsControllerTest < ActionController::TestCase
 
   def test_server_error_response_code
     process :response500
-    assert @response.server_error?
+    assert_predicate @response, :server_error?
 
     process :response599
-    assert @response.server_error?
+    assert_predicate @response, :server_error?
 
     process :response404
-    assert !@response.server_error?
+    assert_not_predicate @response, :server_error?
   end
 
   def test_missing_response_code
     process :response404
-    assert @response.not_found?
+    assert_predicate @response, :not_found?
   end
 
   def test_client_error_response_code
     process :response404
-    assert @response.client_error?
+    assert_predicate @response, :client_error?
   end
 
   def test_redirect_url_match
     process :redirect_external
-    assert @response.redirect?
+    assert_predicate @response, :redirect?
     assert_match(/rubyonrails/, @response.redirect_url)
-    assert !/perloffrails/.match(@response.redirect_url)
+    assert_no_match(/perloffrails/, @response.redirect_url)
   end
 
   def test_redirection
     process :redirect_internal
-    assert @response.redirect?
+    assert_predicate @response, :redirect?
 
     process :redirect_external
-    assert @response.redirect?
+    assert_predicate @response, :redirect?
 
     process :nothing
-    assert !@response.redirect?
+    assert_not_predicate @response, :redirect?
   end
 
   def test_successful_response_code
     process :nothing
-    assert @response.successful?
+    assert_predicate @response, :successful?
   end
 
   def test_response_object
diff --git a/actionpack/test/controller/api/conditional_get_test.rb b/actionpack/test/controller/api/conditional_get_test.rb
index fd1997f26c..e366ce9532 100644
--- a/actionpack/test/controller/api/conditional_get_test.rb
+++ b/actionpack/test/controller/api/conditional_get_test.rb
@@ -53,7 +53,7 @@ class ConditionalGetApiTest < ActionController::TestCase
     @request.if_modified_since = @last_modified
     get :one
     assert_equal 304, @response.status.to_i
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal @last_modified, @response.headers["Last-Modified"]
   end
 end
diff --git a/actionpack/test/controller/api/force_ssl_test.rb b/actionpack/test/controller/api/force_ssl_test.rb
index 07459c3753..8191578eb0 100644
--- a/actionpack/test/controller/api/force_ssl_test.rb
+++ b/actionpack/test/controller/api/force_ssl_test.rb
@@ -3,7 +3,9 @@
 require "abstract_unit"
 
 class ForceSSLApiController < ActionController::API
-  force_ssl
+  ActiveSupport::Deprecation.silence do
+    force_ssl
+  end
 
   def one; end
   def two
diff --git a/actionpack/test/controller/base_test.rb b/actionpack/test/controller/base_test.rb
index 9ac82c0d65..a672ede1a9 100644
--- a/actionpack/test/controller/base_test.rb
+++ b/actionpack/test/controller/base_test.rb
@@ -107,9 +107,9 @@ class ControllerInstanceTests < ActiveSupport::TestCase
   end
 
   def test_performed?
-    assert !@empty.performed?
+    assert_not_predicate @empty, :performed?
     @empty.response_body = ["sweet"]
-    assert @empty.performed?
+    assert_predicate @empty, :performed?
   end
 
   def test_action_methods
diff --git a/actionpack/test/controller/caching_test.rb b/actionpack/test/controller/caching_test.rb
index e0300539c9..6fe036dd15 100644
--- a/actionpack/test/controller/caching_test.rb
+++ b/actionpack/test/controller/caching_test.rb
@@ -94,14 +94,14 @@ class FragmentCachingTest < ActionController::TestCase
   def test_fragment_exist_with_caching_enabled
     @store.write("views/name", "value")
     assert @controller.fragment_exist?("name")
-    assert !@controller.fragment_exist?("other_name")
+    assert_not @controller.fragment_exist?("other_name")
   end
 
   def test_fragment_exist_with_caching_disabled
     @controller.perform_caching = false
     @store.write("views/name", "value")
-    assert !@controller.fragment_exist?("name")
-    assert !@controller.fragment_exist?("other_name")
+    assert_not @controller.fragment_exist?("name")
+    assert_not @controller.fragment_exist?("other_name")
   end
 
   def test_write_fragment_with_caching_enabled
@@ -144,7 +144,7 @@ class FragmentCachingTest < ActionController::TestCase
     buffer = "generated till now -> ".html_safe
     buffer << view_context.send(:fragment_for, "expensive") { fragment_computed = true }
 
-    assert !fragment_computed
+    assert_not fragment_computed
     assert_equal "generated till now -> fragment content", buffer
   end
 
@@ -159,7 +159,7 @@ class FragmentCachingTest < ActionController::TestCase
 
     html_safe = @controller.read_fragment("name")
     assert_equal content, html_safe
-    assert html_safe.html_safe?
+    assert_predicate html_safe, :html_safe?
   end
 end
 
@@ -173,6 +173,9 @@ class FunctionalCachingController < CachingController
     end
   end
 
+  def xml_fragment_cached_with_html_partial
+  end
+
   def formatted_fragment_cached
     respond_to do |format|
       format.html
@@ -308,6 +311,11 @@ CACHED
       @store.read("views/functional_caching/formatted_fragment_cached_with_variant:#{template_digest("functional_caching/formatted_fragment_cached_with_variant")}/fragment")
   end
 
+  def test_fragment_caching_with_html_partials_in_xml
+    get :xml_fragment_cached_with_html_partial, format: "*/*"
+    assert_response :success
+  end
+
   private
     def template_digest(name)
       ActionView::Digestor.digest(name: name, finder: @controller.lookup_context)
@@ -317,7 +325,7 @@ end
 class CacheHelperOutputBufferTest < ActionController::TestCase
   class MockController
     def read_fragment(name, options)
-      return false
+      false
     end
 
     def write_fragment(name, fragment, options)
@@ -333,9 +341,9 @@ class CacheHelperOutputBufferTest < ActionController::TestCase
     output_buffer = ActionView::OutputBuffer.new
     controller = MockController.new
     cache_helper = Class.new do
-      def self.controller; end;
-      def self.output_buffer; end;
-      def self.output_buffer=; end;
+      def self.controller; end
+      def self.output_buffer; end
+      def self.output_buffer=; end
     end
     cache_helper.extend(ActionView::Helpers::CacheHelper)
 
@@ -354,9 +362,9 @@ class CacheHelperOutputBufferTest < ActionController::TestCase
     output_buffer = ActiveSupport::SafeBuffer.new
     controller = MockController.new
     cache_helper = Class.new do
-      def self.controller; end;
-      def self.output_buffer; end;
-      def self.output_buffer=; end;
+      def self.controller; end
+      def self.output_buffer; end
+      def self.output_buffer=; end
     end
     cache_helper.extend(ActionView::Helpers::CacheHelper)
 
@@ -382,7 +390,7 @@ class ViewCacheDependencyTest < ActionController::TestCase
   end
 
   def test_view_cache_dependencies_are_empty_by_default
-    assert NoDependenciesController.new.view_cache_dependencies.empty?
+    assert_empty NoDependenciesController.new.view_cache_dependencies
   end
 
   def test_view_cache_dependencies_are_listed_in_declaration_order
diff --git a/actionpack/test/controller/filters_test.rb b/actionpack/test/controller/filters_test.rb
index 9f0a9dec7a..425a6e25cc 100644
--- a/actionpack/test/controller/filters_test.rb
+++ b/actionpack/test/controller/filters_test.rb
@@ -787,7 +787,7 @@ class FilterTest < ActionController::TestCase
     assert_equal %w( ensure_login find_user ), @controller.instance_variable_get(:@ran_filter)
 
     test_process(ConditionalSkippingController, "login")
-    assert !@controller.instance_variable_defined?("@ran_after_action")
+    assert_not @controller.instance_variable_defined?("@ran_after_action")
     test_process(ConditionalSkippingController, "change_password")
     assert_equal %w( clean_up ), @controller.instance_variable_get("@ran_after_action")
   end
@@ -819,7 +819,7 @@ class FilterTest < ActionController::TestCase
       response = test_process(RescuedController)
     end
 
-    assert response.successful?
+    assert_predicate response, :successful?
     assert_equal("I rescued this: #<FilterTest::ErrorToRescue: Something made the bad noise.>", response.body)
   end
 
diff --git a/actionpack/test/controller/flash_hash_test.rb b/actionpack/test/controller/flash_hash_test.rb
index f31a4d9329..e3ec5bb7fc 100644
--- a/actionpack/test/controller/flash_hash_test.rb
+++ b/actionpack/test/controller/flash_hash_test.rb
@@ -44,7 +44,7 @@ module ActionDispatch
       @hash["foo"] = "bar"
       @hash.delete "foo"
 
-      assert !@hash.key?("foo")
+      assert_not @hash.key?("foo")
       assert_nil @hash["foo"]
     end
 
@@ -53,7 +53,7 @@ module ActionDispatch
       assert_equal({ "foo" => "bar" }, @hash.to_hash)
 
       @hash.to_hash["zomg"] = "aaron"
-      assert !@hash.key?("zomg")
+      assert_not @hash.key?("zomg")
       assert_equal({ "foo" => "bar" }, @hash.to_hash)
     end
 
@@ -92,11 +92,11 @@ module ActionDispatch
     end
 
     def test_empty?
-      assert @hash.empty?
+      assert_empty @hash
       @hash["zomg"] = "bears"
-      assert !@hash.empty?
+      assert_not_empty @hash
       @hash.clear
-      assert @hash.empty?
+      assert_empty @hash
     end
 
     def test_each
diff --git a/actionpack/test/controller/flash_test.rb b/actionpack/test/controller/flash_test.rb
index d92ae0b817..34bc2c0caa 100644
--- a/actionpack/test/controller/flash_test.rb
+++ b/actionpack/test/controller/flash_test.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "abstract_unit"
-require "active_support/key_generator"
+require "active_support/messages/rotation_configuration"
 
 class FlashTest < ActionController::TestCase
   class TestController < ActionController::Base
@@ -243,6 +243,7 @@ end
 class FlashIntegrationTest < ActionDispatch::IntegrationTest
   SessionKey = "_myapp_session"
   Generator  = ActiveSupport::LegacyKeyGenerator.new("b3c631c314c0bbca50c1b2843150fe33")
+  Rotations  = ActiveSupport::Messages::RotationConfiguration.new
 
   class TestController < ActionController::Base
     add_flash_types :bar
@@ -348,6 +349,7 @@ class FlashIntegrationTest < ActionDispatch::IntegrationTest
       args[0] ||= {}
       args[0][:env] ||= {}
       args[0][:env]["action_dispatch.key_generator"] ||= Generator
+      args[0][:env]["action_dispatch.cookies_rotations"] = Rotations
       super(path, *args)
     end
 
diff --git a/actionpack/test/controller/force_ssl_test.rb b/actionpack/test/controller/force_ssl_test.rb
index 84ac1fda3c..7f59f6acaf 100644
--- a/actionpack/test/controller/force_ssl_test.rb
+++ b/actionpack/test/controller/force_ssl_test.rb
@@ -13,19 +13,23 @@ class ForceSSLController < ActionController::Base
 end
 
 class ForceSSLControllerLevel < ForceSSLController
-  force_ssl
+  ActiveSupport::Deprecation.silence do
+    force_ssl
+  end
 end
 
 class ForceSSLCustomOptions < ForceSSLController
-  force_ssl host: "secure.example.com", only: :redirect_host
-  force_ssl port: 8443, only: :redirect_port
-  force_ssl subdomain: "secure", only: :redirect_subdomain
-  force_ssl domain: "secure.com", only: :redirect_domain
-  force_ssl path: "/foo", only: :redirect_path
-  force_ssl status: :found, only: :redirect_status
-  force_ssl flash: { message: "Foo, Bar!" }, only: :redirect_flash
-  force_ssl alert: "Foo, Bar!", only: :redirect_alert
-  force_ssl notice: "Foo, Bar!", only: :redirect_notice
+  ActiveSupport::Deprecation.silence do
+    force_ssl host: "secure.example.com", only: :redirect_host
+    force_ssl port: 8443, only: :redirect_port
+    force_ssl subdomain: "secure", only: :redirect_subdomain
+    force_ssl domain: "secure.com", only: :redirect_domain
+    force_ssl path: "/foo", only: :redirect_path
+    force_ssl status: :found, only: :redirect_status
+    force_ssl flash: { message: "Foo, Bar!" }, only: :redirect_flash
+    force_ssl alert: "Foo, Bar!", only: :redirect_alert
+    force_ssl notice: "Foo, Bar!", only: :redirect_notice
+  end
 
   def force_ssl_action
     render plain: action_name
@@ -55,15 +59,21 @@ class ForceSSLCustomOptions < ForceSSLController
 end
 
 class ForceSSLOnlyAction < ForceSSLController
-  force_ssl only: :cheeseburger
+  ActiveSupport::Deprecation.silence do
+    force_ssl only: :cheeseburger
+  end
 end
 
 class ForceSSLExceptAction < ForceSSLController
-  force_ssl except: :banana
+  ActiveSupport::Deprecation.silence do
+    force_ssl except: :banana
+  end
 end
 
 class ForceSSLIfCondition < ForceSSLController
-  force_ssl if: :use_force_ssl?
+  ActiveSupport::Deprecation.silence do
+    force_ssl if: :use_force_ssl?
+  end
 
   def use_force_ssl?
     action_name == "cheeseburger"
@@ -71,7 +81,9 @@ class ForceSSLIfCondition < ForceSSLController
 end
 
 class ForceSSLFlash < ForceSSLController
-  force_ssl except: [:banana, :set_flash, :use_flash]
+  ActiveSupport::Deprecation.silence do
+    force_ssl except: [:banana, :set_flash, :use_flash]
+  end
 
   def set_flash
     flash["that"] = "hello"
diff --git a/actionpack/test/controller/http_digest_authentication_test.rb b/actionpack/test/controller/http_digest_authentication_test.rb
index 76ff784926..3f211cd60d 100644
--- a/actionpack/test/controller/http_digest_authentication_test.rb
+++ b/actionpack/test/controller/http_digest_authentication_test.rb
@@ -9,7 +9,7 @@ class HttpDigestAuthenticationTest < ActionController::TestCase
     before_action :authenticate_with_request, only: :display
 
     USERS = { "lifo" => "world", "pretty" => "please",
-              "dhh" => ::Digest::MD5::hexdigest(["dhh", "SuperSecret", "secret"].join(":")) }
+              "dhh" => ::Digest::MD5.hexdigest(["dhh", "SuperSecret", "secret"].join(":")) }
 
     def index
       render plain: "Hello Secret"
@@ -181,9 +181,10 @@ class HttpDigestAuthenticationTest < ActionController::TestCase
   end
 
   test "authentication request with password stored as ha1 digest hash" do
-    @request.env["HTTP_AUTHORIZATION"] = encode_credentials(username: "dhh",
-                                           password: ::Digest::MD5::hexdigest(["dhh", "SuperSecret", "secret"].join(":")),
-                                           password_is_ha1: true)
+    @request.env["HTTP_AUTHORIZATION"] = encode_credentials(
+      username: "dhh",
+      password: ::Digest::MD5.hexdigest(["dhh", "SuperSecret", "secret"].join(":")),
+      password_is_ha1: true)
     get :display
 
     assert_response :success
@@ -201,7 +202,7 @@ class HttpDigestAuthenticationTest < ActionController::TestCase
 
   test "validate_digest_response should fail with nil returning password_procedure" do
     @request.env["HTTP_AUTHORIZATION"] = encode_credentials(username: nil, password: nil)
-    assert !ActionController::HttpAuthentication::Digest.validate_digest_response(@request, "SuperSecret") { nil }
+    assert_not ActionController::HttpAuthentication::Digest.validate_digest_response(@request, "SuperSecret") { nil }
   end
 
   test "authentication request with request-uri ending in '/'" do
diff --git a/actionpack/test/controller/integration_test.rb b/actionpack/test/controller/integration_test.rb
index fd1c5e693f..9cdf04b886 100644
--- a/actionpack/test/controller/integration_test.rb
+++ b/actionpack/test/controller/integration_test.rb
@@ -14,11 +14,11 @@ class SessionTest < ActiveSupport::TestCase
   end
 
   def test_https_bang_works_and_sets_truth_by_default
-    assert !@session.https?
+    assert_not_predicate @session, :https?
     @session.https!
-    assert @session.https?
+    assert_predicate @session, :https?
     @session.https! false
-    assert !@session.https?
+    assert_not_predicate @session, :https?
   end
 
   def test_host!
@@ -135,7 +135,7 @@ class IntegrationTestTest < ActiveSupport::TestCase
     session1 = @test.open_session { |sess| }
     session2 = @test.open_session # implicit session
 
-    assert !session1.equal?(session2)
+    assert_not session1.equal?(session2)
   end
 
   # RSpec mixes Matchers (which has a #method_missing) into
@@ -345,7 +345,7 @@ class IntegrationProcessTest < ActionDispatch::IntegrationTest
       follow_redirect!
 
       assert_response :ok
-      refute_same previous_html_document, html_document
+      assert_not_same previous_html_document, html_document
     end
   end
 
@@ -375,7 +375,7 @@ class IntegrationProcessTest < ActionDispatch::IntegrationTest
     a = open_session
     b = open_session
 
-    refute_same(a.integration_session, b.integration_session)
+    assert_not_same(a.integration_session, b.integration_session)
   end
 
   def test_get_with_query_string
@@ -412,11 +412,11 @@ class IntegrationProcessTest < ActionDispatch::IntegrationTest
 
       get "/get_with_params", params: { foo: "bar" }
 
-      assert request.env["rack.input"].string.empty?
+      assert_empty request.env["rack.input"].string
       assert_equal "foo=bar", request.env["QUERY_STRING"]
       assert_equal "foo=bar", request.query_string
       assert_equal "bar", request.parameters["foo"]
-      assert request.parameters["leaks"].nil?
+      assert_predicate request.parameters["leaks"], :nil?
     end
   end
 
diff --git a/actionpack/test/controller/live_stream_test.rb b/actionpack/test/controller/live_stream_test.rb
index 8cfb43a6bc..431fe90b23 100644
--- a/actionpack/test/controller/live_stream_test.rb
+++ b/actionpack/test/controller/live_stream_test.rb
@@ -464,7 +464,7 @@ module ActionController
     end
 
     def test_stale_with_etag
-      @request.if_none_match = %(W/"#{Digest::MD5.hexdigest('123')}")
+      @request.if_none_match = %(W/"#{ActiveSupport::Digest.hexdigest('123')}")
       get :with_stale
       assert_equal 304, response.status.to_i
     end
diff --git a/actionpack/test/controller/log_subscriber_test.rb b/actionpack/test/controller/log_subscriber_test.rb
index f0f106c8ba..be455642de 100644
--- a/actionpack/test/controller/log_subscriber_test.rb
+++ b/actionpack/test/controller/log_subscriber_test.rb
@@ -98,7 +98,7 @@ class ACLogSubscriberTest < ActionController::TestCase
 
     @old_logger = ActionController::Base.logger
 
-    @cache_path = File.join Dir.tmpdir, Dir::Tmpname.make_tmpname("tmp", "cache")
+    @cache_path = Dir.mktmpdir(%w[tmp cache])
     @controller.cache_store = :file_store, @cache_path
     ActionController::LogSubscriber.attach_to :action_controller
   end
diff --git a/actionpack/test/controller/metal_test.rb b/actionpack/test/controller/metal_test.rb
index c235c9df86..248ef36b7c 100644
--- a/actionpack/test/controller/metal_test.rb
+++ b/actionpack/test/controller/metal_test.rb
@@ -9,7 +9,7 @@ class MetalControllerInstanceTests < ActiveSupport::TestCase
     end
   end
 
-  def test_response_has_default_headers
+  def test_response_does_not_have_default_headers
     original_default_headers = ActionDispatch::Response.default_headers
 
     ActionDispatch::Response.default_headers = {
@@ -23,9 +23,9 @@ class MetalControllerInstanceTests < ActiveSupport::TestCase
       "rack.input" => -> {}
     )[1]
 
-    refute response_headers.key?("X-Frame-Options")
-    refute response_headers.key?("X-Content-Type-Options")
-    refute response_headers.key?("X-XSS-Protection")
+    assert_not response_headers.key?("X-Frame-Options")
+    assert_not response_headers.key?("X-Content-Type-Options")
+    assert_not response_headers.key?("X-XSS-Protection")
   ensure
     ActionDispatch::Response.default_headers = original_default_headers
   end
diff --git a/actionpack/test/controller/mime/respond_to_test.rb b/actionpack/test/controller/mime/respond_to_test.rb
index f9ffd5f54c..771eccb29b 100644
--- a/actionpack/test/controller/mime/respond_to_test.rb
+++ b/actionpack/test/controller/mime/respond_to_test.rb
@@ -658,13 +658,13 @@ class RespondToControllerTest < ActionController::TestCase
   end
 
   def test_variant_without_implicit_rendering_from_browser
-    assert_raises(ActionController::UnknownFormat) do
+    assert_raises(ActionController::MissingExactTemplate) do
       get :variant_without_implicit_template_rendering, params: { v: :does_not_matter }
     end
   end
 
   def test_variant_variant_not_set_and_without_implicit_rendering_from_browser
-    assert_raises(ActionController::UnknownFormat) do
+    assert_raises(ActionController::MissingExactTemplate) do
       get :variant_without_implicit_template_rendering
     end
   end
diff --git a/actionpack/test/controller/new_base/base_test.rb b/actionpack/test/controller/new_base/base_test.rb
index d9f200b2a7..280134f8d2 100644
--- a/actionpack/test/controller/new_base/base_test.rb
+++ b/actionpack/test/controller/new_base/base_test.rb
@@ -47,7 +47,6 @@ module Dispatching
   end
 
   class BaseTest < Rack::TestCase
-    # :api: plugin
     test "simple dispatching" do
       get "/dispatching/simple/index"
 
@@ -56,14 +55,12 @@ module Dispatching
       assert_content_type "text/plain; charset=utf-8"
     end
 
-    # :api: plugin
     test "directly modifying response body" do
       get "/dispatching/simple/modify_response_body"
 
       assert_body "success"
     end
 
-    # :api: plugin
     test "directly modifying response body twice" do
       get "/dispatching/simple/modify_response_body_twice"
 
diff --git a/actionpack/test/controller/output_escaping_test.rb b/actionpack/test/controller/output_escaping_test.rb
index e33a99068f..d683bc73e6 100644
--- a/actionpack/test/controller/output_escaping_test.rb
+++ b/actionpack/test/controller/output_escaping_test.rb
@@ -4,7 +4,7 @@ require "abstract_unit"
 
 class OutputEscapingTest < ActiveSupport::TestCase
   test "escape_html shouldn't die when passed nil" do
-    assert ERB::Util.h(nil).blank?
+    assert_predicate ERB::Util.h(nil), :blank?
   end
 
   test "escapeHTML should escape strings" do
diff --git a/actionpack/test/controller/parameters/accessors_test.rb b/actionpack/test/controller/parameters/accessors_test.rb
index 43cabae7d2..674b2c6266 100644
--- a/actionpack/test/controller/parameters/accessors_test.rb
+++ b/actionpack/test/controller/parameters/accessors_test.rb
@@ -2,7 +2,6 @@
 
 require "abstract_unit"
 require "action_controller/metal/strong_parameters"
-require "active_support/core_ext/hash/transform_values"
 
 class ParametersAccessorsTest < ActiveSupport::TestCase
   setup do
@@ -22,13 +21,13 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
 
   test "[] retains permitted status" do
     @params.permit!
-    assert @params[:person].permitted?
-    assert @params[:person][:name].permitted?
+    assert_predicate @params[:person], :permitted?
+    assert_predicate @params[:person][:name], :permitted?
   end
 
   test "[] retains unpermitted status" do
-    assert_not @params[:person].permitted?
-    assert_not @params[:person][:name].permitted?
+    assert_not_predicate @params[:person], :permitted?
+    assert_not_predicate @params[:person][:name], :permitted?
   end
 
   test "as_json returns the JSON representation of the parameters hash" do
@@ -51,6 +50,14 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
     @params.each { |key, value| assert_not(value.permitted?) if key == "person" }
   end
 
+  test "each returns key,value array for block with arity 1" do
+    @params.each do |arg|
+      assert_kind_of Array, arg
+      assert_equal "person", arg[0]
+      assert_kind_of ActionController::Parameters, arg[1]
+    end
+  end
+
   test "each_pair carries permitted status" do
     @params.permit!
     @params.each_pair { |key, value| assert(value.permitted?) if key == "person" }
@@ -60,35 +67,43 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
     @params.each_pair { |key, value| assert_not(value.permitted?) if key == "person" }
   end
 
+  test "each_pair returns key,value array for block with arity 1" do
+    @params.each_pair do |arg|
+      assert_kind_of Array, arg
+      assert_equal "person", arg[0]
+      assert_kind_of ActionController::Parameters, arg[1]
+    end
+  end
+
   test "empty? returns true when params contains no key/value pairs" do
     params = ActionController::Parameters.new
-    assert params.empty?
+    assert_empty params
   end
 
   test "empty? returns false when any params are present" do
-    refute @params.empty?
+    assert_not_empty @params
   end
 
   test "except retains permitted status" do
     @params.permit!
-    assert @params.except(:person).permitted?
-    assert @params[:person].except(:name).permitted?
+    assert_predicate @params.except(:person), :permitted?
+    assert_predicate @params[:person].except(:name), :permitted?
   end
 
   test "except retains unpermitted status" do
-    assert_not @params.except(:person).permitted?
-    assert_not @params[:person].except(:name).permitted?
+    assert_not_predicate @params.except(:person), :permitted?
+    assert_not_predicate @params[:person].except(:name), :permitted?
   end
 
   test "fetch retains permitted status" do
     @params.permit!
-    assert @params.fetch(:person).permitted?
-    assert @params[:person].fetch(:name).permitted?
+    assert_predicate @params.fetch(:person), :permitted?
+    assert_predicate @params[:person].fetch(:name), :permitted?
   end
 
   test "fetch retains unpermitted status" do
-    assert_not @params.fetch(:person).permitted?
-    assert_not @params[:person].fetch(:name).permitted?
+    assert_not_predicate @params.fetch(:person), :permitted?
+    assert_not_predicate @params[:person].fetch(:name), :permitted?
   end
 
   test "has_key? returns true if the given key is present in the params" do
@@ -96,7 +111,7 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
   end
 
   test "has_key? returns false if the given key is not present in the params" do
-    refute @params.has_key?(:address)
+    assert_not @params.has_key?(:address)
   end
 
   test "has_value? returns true if the given value is present in the params" do
@@ -106,7 +121,7 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
 
   test "has_value? returns false if the given value is not present in the params" do
     params = ActionController::Parameters.new(city: "Chicago", state: "Illinois")
-    refute params.has_value?("New York")
+    assert_not params.has_value?("New York")
   end
 
   test "include? returns true if the given key is present in the params" do
@@ -114,7 +129,7 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
   end
 
   test "include? returns false if the given key is not present in the params" do
-    refute @params.include?(:address)
+    assert_not @params.include?(:address)
   end
 
   test "key? returns true if the given key is present in the params" do
@@ -122,7 +137,7 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
   end
 
   test "key? returns false if the given key is not present in the params" do
-    refute @params.key?(:address)
+    assert_not @params.key?(:address)
   end
 
   test "keys returns an array of the keys of the params" do
@@ -131,48 +146,48 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
   end
 
   test "reject retains permitted status" do
-    assert_not @params.reject { |k| k == "person" }.permitted?
+    assert_not_predicate @params.reject { |k| k == "person" }, :permitted?
   end
 
   test "reject retains unpermitted status" do
     @params.permit!
-    assert @params.reject { |k| k == "person" }.permitted?
+    assert_predicate @params.reject { |k| k == "person" }, :permitted?
   end
 
   test "select retains permitted status" do
     @params.permit!
-    assert @params.select { |k| k == "person" }.permitted?
+    assert_predicate @params.select { |k| k == "person" }, :permitted?
   end
 
   test "select retains unpermitted status" do
-    assert_not @params.select { |k| k == "person" }.permitted?
+    assert_not_predicate @params.select { |k| k == "person" }, :permitted?
   end
 
   test "slice retains permitted status" do
     @params.permit!
-    assert @params.slice(:person).permitted?
+    assert_predicate @params.slice(:person), :permitted?
   end
 
   test "slice retains unpermitted status" do
-    assert_not @params.slice(:person).permitted?
+    assert_not_predicate @params.slice(:person), :permitted?
   end
 
   test "transform_keys retains permitted status" do
     @params.permit!
-    assert @params.transform_keys { |k| k }.permitted?
+    assert_predicate @params.transform_keys { |k| k }, :permitted?
   end
 
   test "transform_keys retains unpermitted status" do
-    assert_not @params.transform_keys { |k| k }.permitted?
+    assert_not_predicate @params.transform_keys { |k| k }, :permitted?
   end
 
   test "transform_values retains permitted status" do
     @params.permit!
-    assert @params.transform_values { |v| v }.permitted?
+    assert_predicate @params.transform_values { |v| v }, :permitted?
   end
 
   test "transform_values retains unpermitted status" do
-    assert_not @params.transform_values { |v| v }.permitted?
+    assert_not_predicate @params.transform_values { |v| v }, :permitted?
   end
 
   test "value? returns true if the given value is present in the params" do
@@ -182,7 +197,7 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
 
   test "value? returns false if the given value is not present in the params" do
     params = ActionController::Parameters.new(city: "Chicago", state: "Illinois")
-    refute params.value?("New York")
+    assert_not params.value?("New York")
   end
 
   test "values returns an array of the values of the params" do
@@ -192,13 +207,13 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
 
   test "values_at retains permitted status" do
     @params.permit!
-    assert @params.values_at(:person).first.permitted?
-    assert @params[:person].values_at(:name).first.permitted?
+    assert_predicate @params.values_at(:person).first, :permitted?
+    assert_predicate @params[:person].values_at(:name).first, :permitted?
   end
 
   test "values_at retains unpermitted status" do
-    assert_not @params.values_at(:person).first.permitted?
-    assert_not @params[:person].values_at(:name).first.permitted?
+    assert_not_predicate @params.values_at(:person).first, :permitted?
+    assert_not_predicate @params[:person].values_at(:name).first, :permitted?
   end
 
   test "is equal to Parameters instance with same params" do
@@ -257,23 +272,24 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
     assert_match(/permitted: true/, @params.inspect)
   end
 
-  if Hash.method_defined?(:dig)
-    test "#dig delegates the dig method to its values" do
-      assert_equal "David", @params.dig(:person, :name, :first)
-      assert_equal "Chicago", @params.dig(:person, :addresses, 0, :city)
-    end
+  test "#dig delegates the dig method to its values" do
+    assert_equal "David", @params.dig(:person, :name, :first)
+    assert_equal "Chicago", @params.dig(:person, :addresses, 0, :city)
+  end
 
-    test "#dig converts hashes to parameters" do
-      assert_kind_of ActionController::Parameters, @params.dig(:person)
-      assert_kind_of ActionController::Parameters, @params.dig(:person, :addresses, 0)
-      assert @params.dig(:person, :addresses).all? do |value|
-        value.is_a?(ActionController::Parameters)
-      end
-    end
-  else
-    test "ActionController::Parameters does not respond to #dig on Ruby 2.2" do
-      assert_not ActionController::Parameters.method_defined?(:dig)
-      assert_not @params.respond_to?(:dig)
+  test "#dig converts hashes to parameters" do
+    assert_kind_of ActionController::Parameters, @params.dig(:person)
+    assert_kind_of ActionController::Parameters, @params.dig(:person, :addresses, 0)
+    assert @params.dig(:person, :addresses).all? do |value|
+      value.is_a?(ActionController::Parameters)
     end
   end
+
+  test "mutating #dig return value mutates underlying parameters" do
+    @params.dig(:person, :name)[:first] = "Bill"
+    assert_equal "Bill", @params.dig(:person, :name, :first)
+
+    @params.dig(:person, :addresses)[0] = { city: "Boston", state: "Massachusetts" }
+    assert_equal "Boston", @params.dig(:person, :addresses, 0, :city)
+  end
 end
diff --git a/actionpack/test/controller/parameters/always_permitted_parameters_test.rb b/actionpack/test/controller/parameters/always_permitted_parameters_test.rb
index 1e8b71d789..fe0e5e368d 100644
--- a/actionpack/test/controller/parameters/always_permitted_parameters_test.rb
+++ b/actionpack/test/controller/parameters/always_permitted_parameters_test.rb
@@ -25,6 +25,6 @@ class AlwaysPermittedParametersTest < ActiveSupport::TestCase
       book: { pages: 65 },
       format: "json")
     permitted = params.permit book: [:pages]
-    assert permitted.permitted?
+    assert_predicate permitted, :permitted?
   end
 end
diff --git a/actionpack/test/controller/parameters/dup_test.rb b/actionpack/test/controller/parameters/dup_test.rb
index f5833aff46..5403fc6d93 100644
--- a/actionpack/test/controller/parameters/dup_test.rb
+++ b/actionpack/test/controller/parameters/dup_test.rb
@@ -23,7 +23,7 @@ class ParametersDupTest < ActiveSupport::TestCase
   test "a duplicate maintains the original's permitted status" do
     @params.permit!
     dupped_params = @params.dup
-    assert dupped_params.permitted?
+    assert_predicate dupped_params, :permitted?
   end
 
   test "a duplicate maintains the original's parameters" do
@@ -57,11 +57,11 @@ class ParametersDupTest < ActiveSupport::TestCase
     dupped_params = @params.deep_dup
     dupped_params.permit!
 
-    assert_not @params.permitted?
+    assert_not_predicate @params, :permitted?
   end
 
   test "deep_dup @permitted is being copied" do
     @params.permit!
-    assert @params.deep_dup.permitted?
+    assert_predicate @params.deep_dup, :permitted?
   end
 end
diff --git a/actionpack/test/controller/parameters/multi_parameter_attributes_test.rb b/actionpack/test/controller/parameters/multi_parameter_attributes_test.rb
index dcf848a620..c890839727 100644
--- a/actionpack/test/controller/parameters/multi_parameter_attributes_test.rb
+++ b/actionpack/test/controller/parameters/multi_parameter_attributes_test.rb
@@ -21,7 +21,7 @@ class MultiParameterAttributesTest < ActiveSupport::TestCase
 
     permitted = params.permit book: [ :shipped_at, :price ]
 
-    assert permitted.permitted?
+    assert_predicate permitted, :permitted?
 
     assert_equal "2012", permitted[:book]["shipped_at(1i)"]
     assert_equal "3", permitted[:book]["shipped_at(2i)"]
diff --git a/actionpack/test/controller/parameters/mutators_test.rb b/actionpack/test/controller/parameters/mutators_test.rb
index 49dede03c2..312b1e5b27 100644
--- a/actionpack/test/controller/parameters/mutators_test.rb
+++ b/actionpack/test/controller/parameters/mutators_test.rb
@@ -2,7 +2,6 @@
 
 require "abstract_unit"
 require "action_controller/metal/strong_parameters"
-require "active_support/core_ext/hash/transform_values"
 
 class ParametersMutatorsTest < ActiveSupport::TestCase
   setup do
@@ -20,11 +19,11 @@ class ParametersMutatorsTest < ActiveSupport::TestCase
 
   test "delete retains permitted status" do
     @params.permit!
-    assert @params.delete(:person).permitted?
+    assert_predicate @params.delete(:person), :permitted?
   end
 
   test "delete retains unpermitted status" do
-    assert_not @params.delete(:person).permitted?
+    assert_not_predicate @params.delete(:person), :permitted?
   end
 
   test "delete returns the value when the key is present" do
@@ -50,73 +49,73 @@ class ParametersMutatorsTest < ActiveSupport::TestCase
 
   test "delete_if retains permitted status" do
     @params.permit!
-    assert @params.delete_if { |k| k == "person" }.permitted?
+    assert_predicate @params.delete_if { |k| k == "person" }, :permitted?
   end
 
   test "delete_if retains unpermitted status" do
-    assert_not @params.delete_if { |k| k == "person" }.permitted?
+    assert_not_predicate @params.delete_if { |k| k == "person" }, :permitted?
   end
 
   test "extract! retains permitted status" do
     @params.permit!
-    assert @params.extract!(:person).permitted?
+    assert_predicate @params.extract!(:person), :permitted?
   end
 
   test "extract! retains unpermitted status" do
-    assert_not @params.extract!(:person).permitted?
+    assert_not_predicate @params.extract!(:person), :permitted?
   end
 
   test "keep_if retains permitted status" do
     @params.permit!
-    assert @params.keep_if { |k, v| k == "person" }.permitted?
+    assert_predicate @params.keep_if { |k, v| k == "person" }, :permitted?
   end
 
   test "keep_if retains unpermitted status" do
-    assert_not @params.keep_if { |k, v| k == "person" }.permitted?
+    assert_not_predicate @params.keep_if { |k, v| k == "person" }, :permitted?
   end
 
   test "reject! retains permitted status" do
     @params.permit!
-    assert @params.reject! { |k| k == "person" }.permitted?
+    assert_predicate @params.reject! { |k| k == "person" }, :permitted?
   end
 
   test "reject! retains unpermitted status" do
-    assert_not @params.reject! { |k| k == "person" }.permitted?
+    assert_not_predicate @params.reject! { |k| k == "person" }, :permitted?
   end
 
   test "select! retains permitted status" do
     @params.permit!
-    assert @params.select! { |k| k != "person" }.permitted?
+    assert_predicate @params.select! { |k| k != "person" }, :permitted?
   end
 
   test "select! retains unpermitted status" do
-    assert_not @params.select! { |k| k != "person" }.permitted?
+    assert_not_predicate @params.select! { |k| k != "person" }, :permitted?
   end
 
   test "slice! retains permitted status" do
     @params.permit!
-    assert @params.slice!(:person).permitted?
+    assert_predicate @params.slice!(:person), :permitted?
   end
 
   test "slice! retains unpermitted status" do
-    assert_not @params.slice!(:person).permitted?
+    assert_not_predicate @params.slice!(:person), :permitted?
   end
 
   test "transform_keys! retains permitted status" do
     @params.permit!
-    assert @params.transform_keys! { |k| k }.permitted?
+    assert_predicate @params.transform_keys! { |k| k }, :permitted?
   end
 
   test "transform_keys! retains unpermitted status" do
-    assert_not @params.transform_keys! { |k| k }.permitted?
+    assert_not_predicate @params.transform_keys! { |k| k }, :permitted?
   end
 
   test "transform_values! retains permitted status" do
     @params.permit!
-    assert @params.transform_values! { |v| v }.permitted?
+    assert_predicate @params.transform_values! { |v| v }, :permitted?
   end
 
   test "transform_values! retains unpermitted status" do
-    assert_not @params.transform_values! { |v| v }.permitted?
+    assert_not_predicate @params.transform_values! { |v| v }, :permitted?
   end
 end
diff --git a/actionpack/test/controller/parameters/nested_parameters_permit_test.rb b/actionpack/test/controller/parameters/nested_parameters_permit_test.rb
index c9fcc483ee..1403e224c0 100644
--- a/actionpack/test/controller/parameters/nested_parameters_permit_test.rb
+++ b/actionpack/test/controller/parameters/nested_parameters_permit_test.rb
@@ -5,7 +5,7 @@ require "action_controller/metal/strong_parameters"
 
 class NestedParametersPermitTest < ActiveSupport::TestCase
   def assert_filtered_out(params, key)
-    assert !params.has_key?(key), "key #{key.inspect} has not been filtered out"
+    assert_not params.has_key?(key), "key #{key.inspect} has not been filtered out"
   end
 
   test "permitted nested parameters" do
@@ -32,7 +32,7 @@ class NestedParametersPermitTest < ActiveSupport::TestCase
 
     permitted = params.permit book: [ :title, { authors: [ :name ] }, { details: :pages }, :id ]
 
-    assert permitted.permitted?
+    assert_predicate permitted, :permitted?
     assert_equal "Romeo and Juliet", permitted[:book][:title]
     assert_equal "William Shakespeare", permitted[:book][:authors][0][:name]
     assert_equal "Christopher Marlowe", permitted[:book][:authors][1][:name]
diff --git a/actionpack/test/controller/parameters/parameters_permit_test.rb b/actionpack/test/controller/parameters/parameters_permit_test.rb
index ebdaca0162..d2fa0aa16e 100644
--- a/actionpack/test/controller/parameters/parameters_permit_test.rb
+++ b/actionpack/test/controller/parameters/parameters_permit_test.rb
@@ -6,7 +6,7 @@ require "action_controller/metal/strong_parameters"
 
 class ParametersPermitTest < ActiveSupport::TestCase
   def assert_filtered_out(params, key)
-    assert !params.has_key?(key), "key #{key.inspect} has not been filtered out"
+    assert_not params.has_key?(key), "key #{key.inspect} has not been filtered out"
   end
 
   setup do
@@ -53,13 +53,13 @@ class ParametersPermitTest < ActiveSupport::TestCase
   test "if nothing is permitted, the hash becomes empty" do
     params = ActionController::Parameters.new(id: "1234")
     permitted = params.permit
-    assert permitted.permitted?
-    assert permitted.empty?
+    assert_predicate permitted, :permitted?
+    assert_empty permitted
   end
 
   test "key: permitted scalar values" do
     values  = ["a", :a, nil]
-    values += [0, 1.0, 2**128, BigDecimal.new(1)]
+    values += [0, 1.0, 2**128, BigDecimal(1)]
     values += [true, false]
     values += [Date.today, Time.now, DateTime.now]
     values += [STDOUT, StringIO.new, ActionDispatch::Http::UploadedFile.new(tempfile: __FILE__),
@@ -136,7 +136,7 @@ class ParametersPermitTest < ActiveSupport::TestCase
   test "key: it is not assigned if not present in params" do
     params = ActionController::Parameters.new(name: "Joe")
     permitted = params.permit(:id)
-    assert !permitted.has_key?(:id)
+    assert_not permitted.has_key?(:id)
   end
 
   test "key to empty array: empty arrays pass" do
@@ -227,7 +227,7 @@ class ParametersPermitTest < ActiveSupport::TestCase
   test "hashes in array values get wrapped" do
     params = ActionController::Parameters.new(foo: [{}, {}])
     params[:foo].each do |hash|
-      assert !hash.permitted?
+      assert_not_predicate hash, :permitted?
     end
   end
 
@@ -250,7 +250,7 @@ class ParametersPermitTest < ActiveSupport::TestCase
 
     permitted = params.permit(users: [:id])
     permitted[:users] << { injected: 1 }
-    assert_not permitted[:users].last.permitted?
+    assert_not_predicate permitted[:users].last, :permitted?
   end
 
   test "fetch doesnt raise ParameterMissing exception if there is a default" do
@@ -272,12 +272,12 @@ class ParametersPermitTest < ActiveSupport::TestCase
   end
 
   test "not permitted is sticky beyond merges" do
-    assert !@params.merge(a: "b").permitted?
+    assert_not_predicate @params.merge(a: "b"), :permitted?
   end
 
   test "permitted is sticky beyond merges" do
     @params.permit!
-    assert @params.merge(a: "b").permitted?
+    assert_predicate @params.merge(a: "b"), :permitted?
   end
 
   test "merge with parameters" do
@@ -288,12 +288,12 @@ class ParametersPermitTest < ActiveSupport::TestCase
   end
 
   test "not permitted is sticky beyond merge!" do
-    assert_not @params.merge!(a: "b").permitted?
+    assert_not_predicate @params.merge!(a: "b"), :permitted?
   end
 
   test "permitted is sticky beyond merge!" do
     @params.permit!
-    assert @params.merge!(a: "b").permitted?
+    assert_predicate @params.merge!(a: "b"), :permitted?
   end
 
   test "merge! with parameters" do
@@ -309,7 +309,7 @@ class ParametersPermitTest < ActiveSupport::TestCase
     merged_params = @params.reverse_merge(default_params)
 
     assert_equal "1234", merged_params[:id]
-    refute_predicate merged_params[:person], :empty?
+    assert_not_predicate merged_params[:person], :empty?
   end
 
   test "#with_defaults is an alias of reverse_merge" do
@@ -317,11 +317,11 @@ class ParametersPermitTest < ActiveSupport::TestCase
     merged_params = @params.with_defaults(default_params)
 
     assert_equal "1234", merged_params[:id]
-    refute_predicate merged_params[:person], :empty?
+    assert_not_predicate merged_params[:person], :empty?
   end
 
   test "not permitted is sticky beyond reverse_merge" do
-    refute_predicate @params.reverse_merge(a: "b"), :permitted?
+    assert_not_predicate @params.reverse_merge(a: "b"), :permitted?
   end
 
   test "permitted is sticky beyond reverse_merge" do
@@ -334,7 +334,7 @@ class ParametersPermitTest < ActiveSupport::TestCase
     @params.reverse_merge!(default_params)
 
     assert_equal "1234", @params[:id]
-    refute_predicate @params[:person], :empty?
+    assert_not_predicate @params[:person], :empty?
   end
 
   test "#with_defaults! is an alias of reverse_merge!" do
@@ -342,7 +342,7 @@ class ParametersPermitTest < ActiveSupport::TestCase
     @params.with_defaults!(default_params)
 
     assert_equal "1234", @params[:id]
-    refute_predicate @params[:person], :empty?
+    assert_not_predicate @params[:person], :empty?
   end
 
   test "modifying the parameters" do
@@ -353,12 +353,15 @@ class ParametersPermitTest < ActiveSupport::TestCase
     assert_equal "Jonas", @params[:person][:family][:brother]
   end
 
-  test "permit is recursive" do
+  test "permit! is recursive" do
+    @params[:nested_array] = [[{ x: 2, y: 3 }, { x: 21, y: 42 }]]
     @params.permit!
-    assert @params.permitted?
-    assert @params[:person].permitted?
-    assert @params[:person][:name].permitted?
-    assert @params[:person][:addresses][0].permitted?
+    assert_predicate @params, :permitted?
+    assert_predicate @params[:person], :permitted?
+    assert_predicate @params[:person][:name], :permitted?
+    assert_predicate @params[:person][:addresses][0], :permitted?
+    assert_predicate @params[:nested_array][0][0], :permitted?
+    assert_predicate @params[:nested_array][0][1], :permitted?
   end
 
   test "permitted takes a default value when Parameters.permit_all_parameters is set" do
@@ -368,8 +371,8 @@ class ParametersPermitTest < ActiveSupport::TestCase
         age: "32", name: { first: "David", last: "Heinemeier Hansson" }
       })
 
-      assert params.slice(:person).permitted?
-      assert params[:person][:name].permitted?
+      assert_predicate params.slice(:person), :permitted?
+      assert_predicate params[:person][:name], :permitted?
     ensure
       ActionController::Parameters.permit_all_parameters = false
     end
@@ -500,9 +503,9 @@ class ParametersPermitTest < ActiveSupport::TestCase
     params = ActionController::Parameters.new(foo: "bar")
 
     assert params.permit(:foo).has_key?(:foo)
-    refute params.permit(foo: []).has_key?(:foo)
-    refute params.permit(foo: [:bar]).has_key?(:foo)
-    refute params.permit(foo: :bar).has_key?(:foo)
+    assert_not params.permit(foo: []).has_key?(:foo)
+    assert_not params.permit(foo: [:bar]).has_key?(:foo)
+    assert_not params.permit(foo: :bar).has_key?(:foo)
   end
 
   test "#permitted? is false by default" do
diff --git a/actionpack/test/controller/parameters/serialization_test.rb b/actionpack/test/controller/parameters/serialization_test.rb
index 823f01d82a..7708c8e4fe 100644
--- a/actionpack/test/controller/parameters/serialization_test.rb
+++ b/actionpack/test/controller/parameters/serialization_test.rb
@@ -2,7 +2,6 @@
 
 require "abstract_unit"
 require "action_controller/metal/strong_parameters"
-require "active_support/core_ext/string/strip"
 
 class ParametersSerializationTest < ActiveSupport::TestCase
   setup do
@@ -27,21 +26,21 @@ class ParametersSerializationTest < ActiveSupport::TestCase
     roundtripped = YAML.load(YAML.dump(params))
 
     assert_equal params, roundtripped
-    assert_not roundtripped.permitted?
+    assert_not_predicate roundtripped, :permitted?
   end
 
   test "yaml backwardscompatible with psych 2.0.8 format" do
-    params = YAML.load <<-end_of_yaml.strip_heredoc
+    params = YAML.load <<~end_of_yaml
       --- !ruby/hash:ActionController::Parameters
       key: :value
     end_of_yaml
 
     assert_equal :value, params[:key]
-    assert_not params.permitted?
+    assert_not_predicate params, :permitted?
   end
 
   test "yaml backwardscompatible with psych 2.0.9+ format" do
-    params = YAML.load(<<-end_of_yaml.strip_heredoc)
+    params = YAML.load(<<~end_of_yaml)
       --- !ruby/hash-with-ivars:ActionController::Parameters
       elements:
         key: :value
@@ -50,6 +49,6 @@ class ParametersSerializationTest < ActiveSupport::TestCase
     end_of_yaml
 
     assert_equal :value, params[:key]
-    assert_not params.permitted?
+    assert_not_predicate params, :permitted?
   end
 end
diff --git a/actionpack/test/controller/params_wrapper_test.rb b/actionpack/test/controller/params_wrapper_test.rb
index df68ef25a3..c4c74e8f2b 100644
--- a/actionpack/test/controller/params_wrapper_test.rb
+++ b/actionpack/test/controller/params_wrapper_test.rb
@@ -255,6 +255,20 @@ class ParamsWrapperTest < ActionController::TestCase
       assert_equal "", @response.body
     end
   end
+
+  def test_derived_wrapped_keys_from_nested_attributes
+    def User.nested_attributes_options
+      { person: {} }
+    end
+
+    assert_called(User, :attribute_names, times: 2, returns: ["username"]) do
+      with_default_wrapper_options do
+        @request.env["CONTENT_TYPE"] = "application/json"
+        post :parse, params: { "username" => "sikachu", "person_attributes" => { "title" => "Developer" } }
+        assert_parameters("username" => "sikachu", "person_attributes" => { "title" => "Developer" }, "user" => { "username" => "sikachu", "person_attributes" => { "title" => "Developer" } })
+      end
+    end
+  end
 end
 
 class NamespacedParamsWrapperTest < ActionController::TestCase
@@ -262,7 +276,7 @@ class NamespacedParamsWrapperTest < ActionController::TestCase
 
   module Admin
     module Users
-      class UsersController < ActionController::Base;
+      class UsersController < ActionController::Base
         class << self
           attr_accessor :last_parameters
         end
diff --git a/actionpack/test/controller/redirect_test.rb b/actionpack/test/controller/redirect_test.rb
index e447b66486..2959dc3e4d 100644
--- a/actionpack/test/controller/redirect_test.rb
+++ b/actionpack/test/controller/redirect_test.rb
@@ -62,6 +62,10 @@ class RedirectController < ActionController::Base
     redirect_back(fallback_location: "/things/stuff", status: 307)
   end
 
+  def safe_redirect_back_with_status
+    redirect_back(fallback_location: "/things/stuff", status: 307, allow_other_host: false)
+  end
+
   def host_redirect
     redirect_to action: "other_host", only_path: false, host: "other.test.host"
   end
@@ -259,6 +263,23 @@ class RedirectTest < ActionController::TestCase
     assert_equal "http://test.host/things/stuff", redirect_to_url
   end
 
+  def test_safe_redirect_back_from_other_host
+    @request.env["HTTP_REFERER"] = "http://another.host/coming/from"
+    get :safe_redirect_back_with_status
+
+    assert_response 307
+    assert_equal "http://test.host/things/stuff", redirect_to_url
+  end
+
+  def test_safe_redirect_back_from_the_same_host
+    referer = "http://test.host/coming/from"
+    @request.env["HTTP_REFERER"] = referer
+    get :safe_redirect_back_with_status
+
+    assert_response 307
+    assert_equal referer, redirect_to_url
+  end
+
   def test_redirect_to_record
     with_routing do |set|
       set.draw do
diff --git a/actionpack/test/controller/render_test.rb b/actionpack/test/controller/render_test.rb
index 3619afc513..24c5761e41 100644
--- a/actionpack/test/controller/render_test.rb
+++ b/actionpack/test/controller/render_test.rb
@@ -162,6 +162,17 @@ class TestController < ActionController::Base
     render action: "hello_world"
   end
 
+  def conditional_hello_with_expires_and_confliciting_cache_control_headers
+    response.headers["Cache-Control"] = "no-cache, must-revalidate"
+    expires_now
+    render action: "hello_world"
+  end
+
+  def conditional_hello_without_expires_and_confliciting_cache_control_headers
+    response.headers["Cache-Control"] = "no-cache, must-revalidate"
+    render action: "hello_world"
+  end
+
   def conditional_hello_with_bangs
     render action: "hello_world"
   end
@@ -368,6 +379,16 @@ class ExpiresInRenderTest < ActionController::TestCase
     assert_match(/no-transform/, @response.headers["Cache-Control"])
   end
 
+  def test_expires_now_with_conflicting_cache_control_headers
+    get :conditional_hello_with_expires_and_confliciting_cache_control_headers
+    assert_equal "no-cache", @response.headers["Cache-Control"]
+  end
+
+  def test_no_expires_now_with_conflicting_cache_control_headers
+    get :conditional_hello_without_expires_and_confliciting_cache_control_headers
+    assert_equal "no-cache", @response.headers["Cache-Control"]
+  end
+
   def test_date_header_when_expires_in
     time = Time.mktime(2011, 10, 30)
     Time.stub :now, time do
@@ -394,7 +415,7 @@ class LastModifiedRenderTest < ActionController::TestCase
     @request.if_modified_since = @last_modified
     get :conditional_hello
     assert_equal 304, @response.status.to_i
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal @last_modified, @response.headers["Last-Modified"]
   end
 
@@ -409,7 +430,7 @@ class LastModifiedRenderTest < ActionController::TestCase
     @request.if_modified_since = "Thu, 16 Jul 2008 00:00:00 GMT"
     get :conditional_hello
     assert_equal 200, @response.status.to_i
-    assert @response.body.present?
+    assert_predicate @response.body, :present?
     assert_equal @last_modified, @response.headers["Last-Modified"]
   end
 
@@ -422,7 +443,7 @@ class LastModifiedRenderTest < ActionController::TestCase
     @request.if_modified_since = @last_modified
     get :conditional_hello_with_record
     assert_equal 304, @response.status.to_i
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_not_nil @response.etag
     assert_equal @last_modified, @response.headers["Last-Modified"]
   end
@@ -438,7 +459,7 @@ class LastModifiedRenderTest < ActionController::TestCase
     @request.if_modified_since = "Thu, 16 Jul 2008 00:00:00 GMT"
     get :conditional_hello_with_record
     assert_equal 200, @response.status.to_i
-    assert @response.body.present?
+    assert_predicate @response.body, :present?
     assert_equal @last_modified, @response.headers["Last-Modified"]
   end
 
@@ -451,7 +472,7 @@ class LastModifiedRenderTest < ActionController::TestCase
     @request.if_modified_since = @last_modified
     get :conditional_hello_with_collection_of_records
     assert_equal 304, @response.status.to_i
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal @last_modified, @response.headers["Last-Modified"]
   end
 
@@ -466,7 +487,7 @@ class LastModifiedRenderTest < ActionController::TestCase
     @request.if_modified_since = "Thu, 16 Jul 2008 00:00:00 GMT"
     get :conditional_hello_with_collection_of_records
     assert_equal 200, @response.status.to_i
-    assert @response.body.present?
+    assert_predicate @response.body, :present?
     assert_equal @last_modified, @response.headers["Last-Modified"]
   end
 
@@ -571,7 +592,7 @@ class EtagRenderTest < ActionController::TestCase
     end
 
     def strong_etag(record)
-      %("#{Digest::MD5.hexdigest(ActiveSupport::Cache.expand_cache_key(record))}")
+      %("#{ActiveSupport::Digest.hexdigest(ActiveSupport::Cache.expand_cache_key(record))}")
     end
 end
 
@@ -606,6 +627,18 @@ class MetalRenderTest < ActionController::TestCase
   end
 end
 
+class ActionControllerRenderTest < ActionController::TestCase
+  class MinimalController < ActionController::Metal
+    include AbstractController::Rendering
+    include ActionController::Rendering
+  end
+
+  def test_direct_render_to_string_with_body
+    mc = MinimalController.new
+    assert_equal "Hello world!", mc.render_to_string(body: ["Hello world!"])
+  end
+end
+
 class ActionControllerBaseRenderTest < ActionController::TestCase
   def test_direct_render_to_string
     ac = ActionController::Base.new()
@@ -617,7 +650,7 @@ class ImplicitRenderTest < ActionController::TestCase
   tests ImplicitRenderTestController
 
   def test_implicit_no_content_response_as_browser
-    assert_raises(ActionController::UnknownFormat) do
+    assert_raises(ActionController::MissingExactTemplate) do
       get :empty_action
     end
   end
@@ -649,27 +682,27 @@ class HeadRenderTest < ActionController::TestCase
 
   def test_head_created
     post :head_created
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_response :created
   end
 
   def test_head_created_with_application_json_content_type
     post :head_created_with_application_json_content_type
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal "application/json", @response.header["Content-Type"]
     assert_response :created
   end
 
   def test_head_ok_with_image_png_content_type
     post :head_ok_with_image_png_content_type
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal "image/png", @response.header["Content-Type"]
     assert_response :ok
   end
 
   def test_head_with_location_header
     get :head_with_location_header
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal "/foo", @response.headers["Location"]
     assert_response :ok
   end
@@ -685,7 +718,7 @@ class HeadRenderTest < ActionController::TestCase
       end
 
       get :head_with_location_object
-      assert @response.body.blank?
+      assert_predicate @response.body, :blank?
       assert_equal "http://www.nextangle.com/customers/1", @response.headers["Location"]
       assert_response :ok
     end
@@ -693,14 +726,14 @@ class HeadRenderTest < ActionController::TestCase
 
   def test_head_with_custom_header
     get :head_with_custom_header
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal "something", @response.headers["X-Custom-Header"]
     assert_response :ok
   end
 
   def test_head_with_www_authenticate_header
     get :head_with_www_authenticate_header
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal "something", @response.headers["WWW-Authenticate"]
     assert_response :ok
   end
@@ -779,7 +812,7 @@ class HttpCacheForeverTest < ActionController::TestCase
     assert_response :ok
     assert_equal "max-age=#{100.years}, public", @response.headers["Cache-Control"]
     assert_not_nil @response.etag
-    assert @response.weak_etag?
+    assert_predicate @response, :weak_etag?
   end
 
   def test_cache_with_private
@@ -787,7 +820,7 @@ class HttpCacheForeverTest < ActionController::TestCase
     assert_response :ok
     assert_equal "max-age=#{100.years}, private", @response.headers["Cache-Control"]
     assert_not_nil @response.etag
-    assert @response.weak_etag?
+    assert_predicate @response, :weak_etag?
   end
 
   def test_cache_response_code_with_if_modified_since
diff --git a/actionpack/test/controller/request_forgery_protection_test.rb b/actionpack/test/controller/request_forgery_protection_test.rb
index 12ae95d602..7a02c27c99 100644
--- a/actionpack/test/controller/request_forgery_protection_test.rb
+++ b/actionpack/test/controller/request_forgery_protection_test.rb
@@ -2,6 +2,7 @@
 
 require "abstract_unit"
 require "active_support/log_subscriber/test_helper"
+require "active_support/messages/rotation_configuration"
 
 # common controller actions
 module RequestForgeryProtectionActions
@@ -445,6 +446,19 @@ module RequestForgeryProtectionTests
     end
   end
 
+  def test_should_raise_for_post_with_null_origin
+    forgery_protection_origin_check do
+      session[:_csrf_token] = @token
+      @controller.stub :form_authenticity_token, @token do
+        exception = assert_raises(ActionController::InvalidAuthenticityToken) do
+          @request.set_header "HTTP_ORIGIN", "null"
+          post :index, params: { custom_authenticity_token: @token }
+        end
+        assert_match "The browser returned a 'null' origin for a request", exception.message
+      end
+    end
+  end
+
   def test_should_block_post_with_origin_checking_and_wrong_origin
     old_logger = ActionController::Base.logger
     logger = ActiveSupport::LogSubscriber::TestHelper::MockLogger.new
@@ -630,13 +644,14 @@ end
 
 class RequestForgeryProtectionControllerUsingNullSessionTest < ActionController::TestCase
   class NullSessionDummyKeyGenerator
-    def generate_key(secret)
+    def generate_key(secret, length = nil)
       "03312270731a2ed0d11ed091c2338a06"
     end
   end
 
   def setup
     @request.env[ActionDispatch::Cookies::GENERATOR_KEY] = NullSessionDummyKeyGenerator.new
+    @request.env[ActionDispatch::Cookies::COOKIES_ROTATIONS] = ActiveSupport::Messages::RotationConfiguration.new
   end
 
   test "should allow to set signed cookies" do
@@ -731,7 +746,7 @@ class FreeCookieControllerTest < ActionController::TestCase
   test "should not emit a csrf-token meta tag" do
     SecureRandom.stub :base64, @token do
       get :meta
-      assert @response.body.blank?
+      assert_predicate @response.body, :blank?
     end
   end
 end
diff --git a/actionpack/test/controller/rescue_test.rb b/actionpack/test/controller/rescue_test.rb
index 07f8c9dd8a..4ed79073e5 100644
--- a/actionpack/test/controller/rescue_test.rb
+++ b/actionpack/test/controller/rescue_test.rb
@@ -33,7 +33,7 @@ class RescueController < ActionController::Base
   class ResourceUnavailableToRescueAsString < StandardError
   end
 
-  # We use a fully-qualified name in some strings, and a relative constant
+  # We use a fully qualified name in some strings, and a relative constant
   # name in some other to test correct handling of both cases.
 
   rescue_from NotAuthorized, with: :deny_access
diff --git a/actionpack/test/controller/resources_test.rb b/actionpack/test/controller/resources_test.rb
index 3d98237003..30bea64c55 100644
--- a/actionpack/test/controller/resources_test.rb
+++ b/actionpack/test/controller/resources_test.rb
@@ -307,7 +307,7 @@ class ResourcesTest < ActionController::TestCase
         set.draw do
           resources :messages do
             member do
-              match :mark  , via: method
+              match :mark, via: method
               match :unmark, via: method
             end
           end
diff --git a/actionpack/test/controller/routing_test.rb b/actionpack/test/controller/routing_test.rb
index f09051b306..9d0a8b4f00 100644
--- a/actionpack/test/controller/routing_test.rb
+++ b/actionpack/test/controller/routing_test.rb
@@ -23,7 +23,7 @@ class UriReservedCharactersRoutingTest < ActiveSupport::TestCase
     end
 
     safe, unsafe = %w(: @ & = + $ , ;), %w(^ ? # [ ])
-    hex = unsafe.map { |char| "%" + char.unpack("H2").first.upcase }
+    hex = unsafe.map { |char| "%" + char.unpack1("H2").upcase }
 
     @segment = "#{safe.join}#{unsafe.join}".freeze
     @escaped = "#{safe.join}#{hex.join}".freeze
@@ -213,7 +213,7 @@ class LegacyRouteSetTests < ActiveSupport::TestCase
     assert_equal expected, ActiveSupport::JSON.decode(get(u))
   end
 
-  def test_regexp_precidence
+  def test_regexp_precedence
     rs.draw do
       get "/whois/:domain", constraints: {
         domain: /\w+\.[\w\.]+/ },
@@ -676,7 +676,7 @@ class LegacyRouteSetTests < ActiveSupport::TestCase
 
     token = "\321\202\320\265\320\272\321\201\321\202".dup # 'text' in Russian
     token.force_encoding(Encoding::BINARY)
-    escaped_token = CGI::escape(token)
+    escaped_token = CGI.escape(token)
 
     assert_equal "/page/" + escaped_token, url_for(rs, controller: "content", action: "show_page", id: token)
     assert_equal({ controller: "content", action: "show_page", id: token }, rs.recognize_path("/page/#{escaped_token}"))
@@ -1288,14 +1288,14 @@ class RouteSetTest < ActiveSupport::TestCase
   end
 
   def test_routing_traversal_does_not_load_extra_classes
-    assert !Object.const_defined?("Profiler__"), "Profiler should not be loaded"
+    assert_not Object.const_defined?("Profiler__"), "Profiler should not be loaded"
     set.draw do
       get "/profile" => "profile#index"
     end
 
     request_path_params("/profile") rescue nil
 
-    assert !Object.const_defined?("Profiler__"), "Profiler should not be loaded"
+    assert_not Object.const_defined?("Profiler__"), "Profiler should not be loaded"
   end
 
   def test_recognize_with_conditions_and_format
@@ -1687,7 +1687,7 @@ class RouteSetTest < ActiveSupport::TestCase
   def test_routes_with_symbols
     set.draw do
       get "unnamed", controller: :pages, action: :show, name: :as_symbol
-      get "named"  , controller: :pages, action: :show, name: :as_symbol, as: :named
+      get "named", controller: :pages, action: :show, name: :as_symbol, as: :named
     end
     assert_equal({ controller: "pages", action: "show", name: :as_symbol }, set.recognize_path("/unnamed"))
     assert_equal({ controller: "pages", action: "show", name: :as_symbol }, set.recognize_path("/named"))
@@ -1893,7 +1893,7 @@ class RouteSetTest < ActiveSupport::TestCase
     assert_equal({ controller: "blog",  action: "show_date", year: "2006", month: "07", day: "28" }, controller.request.path_parameters)
     assert_equal("/blog/2006/07/25", controller.url_for(day: 25, only_path: true))
     assert_equal("/blog/2005",       controller.url_for(year: 2005, only_path: true))
-    assert_equal("/blog/show/123",   controller.url_for(action: "show" , id: 123, only_path: true))
+    assert_equal("/blog/show/123",   controller.url_for(action: "show", id: 123, only_path: true))
     assert_equal("/blog/2006",       controller.url_for(year: 2006, only_path: true))
     assert_equal("/blog/2006",       controller.url_for(year: 2006, month: nil, only_path: true))
   end
diff --git a/actionpack/test/controller/runner_test.rb b/actionpack/test/controller/runner_test.rb
index a96c9c519b..1709ab5f6d 100644
--- a/actionpack/test/controller/runner_test.rb
+++ b/actionpack/test/controller/runner_test.rb
@@ -17,8 +17,8 @@ module ActionDispatch
 
     def test_respond_to?
       runner = MyRunner.new(Class.new { def x; end }.new)
-      assert runner.respond_to?(:hi)
-      assert runner.respond_to?(:x)
+      assert_respond_to runner, :hi
+      assert_respond_to runner, :x
     end
   end
 end
diff --git a/actionpack/test/controller/send_file_test.rb b/actionpack/test/controller/send_file_test.rb
index fd2399e433..7b1a52b277 100644
--- a/actionpack/test/controller/send_file_test.rb
+++ b/actionpack/test/controller/send_file_test.rb
@@ -178,7 +178,7 @@ class SendFileTest < ActionController::TestCase
       "image.jpg" => "image/jpeg",
       "image.tif" => "image/tiff",
       "image.gif" => "image/gif",
-      "movie.mpg" => "video/mpeg",
+      "movie.mp4" => "video/mp4",
       "file.zip" => "application/zip",
       "file.unk" => "application/octet-stream",
       "zip" => "application/octet-stream"
diff --git a/actionpack/test/controller/test_case_test.rb b/actionpack/test/controller/test_case_test.rb
index 46369ebbb0..734da3de9c 100644
--- a/actionpack/test/controller/test_case_test.rb
+++ b/actionpack/test/controller/test_case_test.rb
@@ -6,7 +6,7 @@ require "active_support/json/decoding"
 require "rails/engine"
 
 class TestCaseTest < ActionController::TestCase
-  def self.fixture_path; end;
+  def self.fixture_path; end
 
   class TestController < ActionController::Base
     def no_op
@@ -670,7 +670,7 @@ XML
     assert_equal "bar", @request.params[:foo]
 
     post :no_op
-    assert @request.params[:foo].blank?
+    assert_predicate @request.params[:foo], :blank?
   end
 
   def test_filtered_parameters_reset_between_requests
@@ -681,6 +681,22 @@ XML
     assert_equal "baz", @request.filtered_parameters[:foo]
   end
 
+  def test_raw_post_reset_between_post_requests
+    post :no_op, params: { foo: "bar" }
+    assert_equal "foo=bar", @request.raw_post
+
+    post :no_op, params: { foo: "baz" }
+    assert_equal "foo=baz", @request.raw_post
+  end
+
+  def test_content_length_reset_after_post_request
+    post :no_op, params: { foo: "bar" }
+    assert_not_equal 0, @request.content_length
+
+    get :no_op
+    assert_equal 0, @request.content_length
+  end
+
   def test_path_is_kept_after_the_request
     get :test_params, params: { id: "foo" }
     assert_equal "/test_case_test/test/test_params/foo", @request.path
@@ -740,6 +756,14 @@ XML
     assert_equal "application/json", @response.body
   end
 
+  def test_request_format_kwarg_doesnt_mutate_params
+    params = { foo: "bar" }.freeze
+
+    assert_nothing_raised do
+      get :test_format, format: "json", params: params
+    end
+  end
+
   def test_should_have_knowledge_of_client_side_cookie_state_even_if_they_are_not_set
     cookies["foo"] = "bar"
     get :no_op
@@ -838,7 +862,7 @@ XML
 
   def test_fixture_file_upload_should_be_able_access_to_tempfile
     file = fixture_file_upload(FILES_DIR + "/ruby_on_rails.jpg", "image/jpg")
-    assert file.respond_to?(:tempfile), "expected tempfile should respond on fixture file object, got nothing"
+    assert_respond_to file, :tempfile
   end
 
   def test_fixture_file_upload
diff --git a/actionpack/test/controller/url_for_integration_test.rb b/actionpack/test/controller/url_for_integration_test.rb
index a7c7356921..a1521da702 100644
--- a/actionpack/test/controller/url_for_integration_test.rb
+++ b/actionpack/test/controller/url_for_integration_test.rb
@@ -35,7 +35,6 @@ module ActionPack
         as: "blog"
 
       resources :people
-      #match 'legacy/people' => "people#index", :legacy => "true"
 
       get "symbols", controller: :symbols, action: :show, name: :as_symbol
       get "id_default(/:id)" => "foo#id_default", :id => 1
diff --git a/actionpack/test/controller/url_for_test.rb b/actionpack/test/controller/url_for_test.rb
index cf11227897..e381abee36 100644
--- a/actionpack/test/controller/url_for_test.rb
+++ b/actionpack/test/controller/url_for_test.rb
@@ -288,7 +288,7 @@ module AbstractController
           kls = Class.new { include set.url_helpers }
 
           controller = kls.new
-          assert controller.respond_to?(:home_url)
+          assert_respond_to controller, :home_url
           assert_equal "http://www.basecamphq.com/home/sweet/home/again",
             controller.send(:home_url, host: "www.basecamphq.com", user: "again")
 
diff --git a/actionpack/test/controller/url_rewriter_test.rb b/actionpack/test/controller/url_rewriter_test.rb
index 0f79c83b6d..ca83b850d5 100644
--- a/actionpack/test/controller/url_rewriter_test.rb
+++ b/actionpack/test/controller/url_rewriter_test.rb
@@ -19,7 +19,7 @@ class UrlRewriterTests < ActionController::TestCase
 
   def setup
     @params = {}
-    @rewriter = Rewriter.new(@request) #.new(@request, @params)
+    @rewriter = Rewriter.new(@request)
     @routes = ActionDispatch::Routing::RouteSet.new.tap do |r|
       r.draw do
         ActiveSupport::Deprecation.silence do
diff --git a/actionpack/test/dispatch/content_security_policy_test.rb b/actionpack/test/dispatch/content_security_policy_test.rb
new file mode 100644
index 0000000000..4f9a4ff2bd
--- /dev/null
+++ b/actionpack/test/dispatch/content_security_policy_test.rb
@@ -0,0 +1,525 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+
+class ContentSecurityPolicyTest < ActiveSupport::TestCase
+  def setup
+    @policy = ActionDispatch::ContentSecurityPolicy.new
+  end
+
+  def test_build
+    assert_equal "", @policy.build
+
+    @policy.script_src :self
+    assert_equal "script-src 'self'", @policy.build
+  end
+
+  def test_dup
+    @policy.img_src :self
+    @policy.block_all_mixed_content
+    @policy.upgrade_insecure_requests
+    @policy.sandbox
+    copied = @policy.dup
+    assert_equal copied.build, @policy.build
+  end
+
+  def test_mappings
+    @policy.script_src :data
+    assert_equal "script-src data:", @policy.build
+
+    @policy.script_src :mediastream
+    assert_equal "script-src mediastream:", @policy.build
+
+    @policy.script_src :blob
+    assert_equal "script-src blob:", @policy.build
+
+    @policy.script_src :filesystem
+    assert_equal "script-src filesystem:", @policy.build
+
+    @policy.script_src :self
+    assert_equal "script-src 'self'", @policy.build
+
+    @policy.script_src :unsafe_inline
+    assert_equal "script-src 'unsafe-inline'", @policy.build
+
+    @policy.script_src :unsafe_eval
+    assert_equal "script-src 'unsafe-eval'", @policy.build
+
+    @policy.script_src :none
+    assert_equal "script-src 'none'", @policy.build
+
+    @policy.script_src :strict_dynamic
+    assert_equal "script-src 'strict-dynamic'", @policy.build
+
+    @policy.script_src :ws
+    assert_equal "script-src ws:", @policy.build
+
+    @policy.script_src :wss
+    assert_equal "script-src wss:", @policy.build
+
+    @policy.script_src :none, :report_sample
+    assert_equal "script-src 'none' 'report-sample'", @policy.build
+  end
+
+  def test_fetch_directives
+    @policy.child_src :self
+    assert_match %r{child-src 'self'}, @policy.build
+
+    @policy.child_src false
+    assert_no_match %r{child-src}, @policy.build
+
+    @policy.connect_src :self
+    assert_match %r{connect-src 'self'}, @policy.build
+
+    @policy.connect_src false
+    assert_no_match %r{connect-src}, @policy.build
+
+    @policy.default_src :self
+    assert_match %r{default-src 'self'}, @policy.build
+
+    @policy.default_src false
+    assert_no_match %r{default-src}, @policy.build
+
+    @policy.font_src :self
+    assert_match %r{font-src 'self'}, @policy.build
+
+    @policy.font_src false
+    assert_no_match %r{font-src}, @policy.build
+
+    @policy.frame_src :self
+    assert_match %r{frame-src 'self'}, @policy.build
+
+    @policy.frame_src false
+    assert_no_match %r{frame-src}, @policy.build
+
+    @policy.img_src :self
+    assert_match %r{img-src 'self'}, @policy.build
+
+    @policy.img_src false
+    assert_no_match %r{img-src}, @policy.build
+
+    @policy.manifest_src :self
+    assert_match %r{manifest-src 'self'}, @policy.build
+
+    @policy.manifest_src false
+    assert_no_match %r{manifest-src}, @policy.build
+
+    @policy.media_src :self
+    assert_match %r{media-src 'self'}, @policy.build
+
+    @policy.media_src false
+    assert_no_match %r{media-src}, @policy.build
+
+    @policy.object_src :self
+    assert_match %r{object-src 'self'}, @policy.build
+
+    @policy.object_src false
+    assert_no_match %r{object-src}, @policy.build
+
+    @policy.prefetch_src :self
+    assert_match %r{prefetch-src 'self'}, @policy.build
+
+    @policy.prefetch_src false
+    assert_no_match %r{prefetch-src}, @policy.build
+
+    @policy.script_src :self
+    assert_match %r{script-src 'self'}, @policy.build
+
+    @policy.script_src false
+    assert_no_match %r{script-src}, @policy.build
+
+    @policy.style_src :self
+    assert_match %r{style-src 'self'}, @policy.build
+
+    @policy.style_src false
+    assert_no_match %r{style-src}, @policy.build
+
+    @policy.worker_src :self
+    assert_match %r{worker-src 'self'}, @policy.build
+
+    @policy.worker_src false
+    assert_no_match %r{worker-src}, @policy.build
+  end
+
+  def test_document_directives
+    @policy.base_uri "https://example.com"
+    assert_match %r{base-uri https://example\.com}, @policy.build
+
+    @policy.plugin_types "application/x-shockwave-flash"
+    assert_match %r{plugin-types application/x-shockwave-flash}, @policy.build
+
+    @policy.sandbox
+    assert_match %r{sandbox}, @policy.build
+
+    @policy.sandbox "allow-scripts", "allow-modals"
+    assert_match %r{sandbox allow-scripts allow-modals}, @policy.build
+
+    @policy.sandbox false
+    assert_no_match %r{sandbox}, @policy.build
+  end
+
+  def test_navigation_directives
+    @policy.form_action :self
+    assert_match %r{form-action 'self'}, @policy.build
+
+    @policy.frame_ancestors :self
+    assert_match %r{frame-ancestors 'self'}, @policy.build
+  end
+
+  def test_reporting_directives
+    @policy.report_uri "/violations"
+    assert_match %r{report-uri /violations}, @policy.build
+  end
+
+  def test_other_directives
+    @policy.block_all_mixed_content
+    assert_match %r{block-all-mixed-content}, @policy.build
+
+    @policy.block_all_mixed_content false
+    assert_no_match %r{block-all-mixed-content}, @policy.build
+
+    @policy.require_sri_for :script, :style
+    assert_match %r{require-sri-for script style}, @policy.build
+
+    @policy.require_sri_for "script", "style"
+    assert_match %r{require-sri-for script style}, @policy.build
+
+    @policy.require_sri_for
+    assert_no_match %r{require-sri-for}, @policy.build
+
+    @policy.upgrade_insecure_requests
+    assert_match %r{upgrade-insecure-requests}, @policy.build
+
+    @policy.upgrade_insecure_requests false
+    assert_no_match %r{upgrade-insecure-requests}, @policy.build
+  end
+
+  def test_multiple_sources
+    @policy.script_src :self, :https
+    assert_equal "script-src 'self' https:", @policy.build
+  end
+
+  def test_multiple_directives
+    @policy.script_src :self, :https
+    @policy.style_src :self, :https
+    assert_equal "script-src 'self' https:; style-src 'self' https:", @policy.build
+  end
+
+  def test_dynamic_directives
+    request = ActionDispatch::Request.new("HTTP_HOST" => "www.example.com")
+    controller = Struct.new(:request).new(request)
+
+    @policy.script_src -> { request.host }
+    assert_equal "script-src www.example.com", @policy.build(controller)
+  end
+
+  def test_mixed_static_and_dynamic_directives
+    @policy.script_src :self, -> { "foo.com" }, "bar.com"
+    request = ActionDispatch::Request.new({})
+    controller = Struct.new(:request).new(request)
+    assert_equal "script-src 'self' foo.com bar.com", @policy.build(controller)
+  end
+
+  def test_invalid_directive_source
+    exception = assert_raises(ArgumentError) do
+      @policy.script_src [:self]
+    end
+
+    assert_equal "Invalid content security policy source: [:self]", exception.message
+  end
+
+  def test_missing_context_for_dynamic_source
+    @policy.script_src -> { request.host }
+
+    exception = assert_raises(RuntimeError) do
+      @policy.build
+    end
+
+    assert_match %r{\AMissing context for the dynamic content security policy source:}, exception.message
+  end
+
+  def test_raises_runtime_error_when_unexpected_source
+    @policy.plugin_types [:flash]
+
+    exception = assert_raises(RuntimeError) do
+      @policy.build
+    end
+
+    assert_match %r{\AUnexpected content security policy source:}, exception.message
+  end
+end
+
+class DefaultContentSecurityPolicyIntegrationTest < ActionDispatch::IntegrationTest
+  class PolicyController < ActionController::Base
+    def index
+      head :ok
+    end
+  end
+
+  ROUTES = ActionDispatch::Routing::RouteSet.new
+  ROUTES.draw do
+    scope module: "default_content_security_policy_integration_test" do
+      get "/", to: "policy#index"
+    end
+  end
+
+  POLICY = ActionDispatch::ContentSecurityPolicy.new do |p|
+    p.default_src :self
+    p.script_src  :https
+  end
+
+  class PolicyConfigMiddleware
+    def initialize(app)
+      @app = app
+    end
+
+    def call(env)
+      env["action_dispatch.content_security_policy"] = POLICY
+      env["action_dispatch.content_security_policy_nonce_generator"] = proc { "iyhD0Yc0W+c=" }
+      env["action_dispatch.content_security_policy_report_only"] = false
+      env["action_dispatch.show_exceptions"] = false
+
+      @app.call(env)
+    end
+  end
+
+  APP = build_app(ROUTES) do |middleware|
+    middleware.use PolicyConfigMiddleware
+    middleware.use ActionDispatch::ContentSecurityPolicy::Middleware
+  end
+
+  def app
+    APP
+  end
+
+  def test_adds_nonce_to_script_src_content_security_policy_only_once
+    get "/"
+    get "/"
+    assert_policy "default-src 'self'; script-src https: 'nonce-iyhD0Yc0W+c='"
+  end
+
+  private
+
+    def assert_policy(expected, report_only: false)
+      assert_response :success
+
+      if report_only
+        expected_header = "Content-Security-Policy-Report-Only"
+        unexpected_header = "Content-Security-Policy"
+      else
+        expected_header = "Content-Security-Policy"
+        unexpected_header = "Content-Security-Policy-Report-Only"
+      end
+
+      assert_nil response.headers[unexpected_header]
+      assert_equal expected, response.headers[expected_header]
+    end
+end
+
+class ContentSecurityPolicyIntegrationTest < ActionDispatch::IntegrationTest
+  class PolicyController < ActionController::Base
+    content_security_policy only: :inline do |p|
+      p.default_src "https://example.com"
+    end
+
+    content_security_policy only: :conditional, if: :condition? do |p|
+      p.default_src "https://true.example.com"
+    end
+
+    content_security_policy only: :conditional, unless: :condition? do |p|
+      p.default_src "https://false.example.com"
+    end
+
+    content_security_policy only: :report_only do |p|
+      p.report_uri "/violations"
+    end
+
+    content_security_policy only: :script_src do |p|
+      p.default_src false
+      p.script_src :self
+    end
+
+    content_security_policy(false, only: :no_policy)
+
+    content_security_policy_report_only only: :report_only
+
+    def index
+      head :ok
+    end
+
+    def inline
+      head :ok
+    end
+
+    def conditional
+      head :ok
+    end
+
+    def report_only
+      head :ok
+    end
+
+    def script_src
+      head :ok
+    end
+
+    def no_policy
+      head :ok
+    end
+
+    private
+      def condition?
+        params[:condition] == "true"
+      end
+  end
+
+  ROUTES = ActionDispatch::Routing::RouteSet.new
+  ROUTES.draw do
+    scope module: "content_security_policy_integration_test" do
+      get "/", to: "policy#index"
+      get "/inline", to: "policy#inline"
+      get "/conditional", to: "policy#conditional"
+      get "/report-only", to: "policy#report_only"
+      get "/script-src", to: "policy#script_src"
+      get "/no-policy", to: "policy#no_policy"
+    end
+  end
+
+  POLICY = ActionDispatch::ContentSecurityPolicy.new do |p|
+    p.default_src :self
+  end
+
+  class PolicyConfigMiddleware
+    def initialize(app)
+      @app = app
+    end
+
+    def call(env)
+      env["action_dispatch.content_security_policy"] = POLICY
+      env["action_dispatch.content_security_policy_nonce_generator"] = proc { "iyhD0Yc0W+c=" }
+      env["action_dispatch.content_security_policy_report_only"] = false
+      env["action_dispatch.show_exceptions"] = false
+
+      @app.call(env)
+    end
+  end
+
+  APP = build_app(ROUTES) do |middleware|
+    middleware.use PolicyConfigMiddleware
+    middleware.use ActionDispatch::ContentSecurityPolicy::Middleware
+  end
+
+  def app
+    APP
+  end
+
+  def test_generates_content_security_policy_header
+    get "/"
+    assert_policy "default-src 'self'"
+  end
+
+  def test_generates_inline_content_security_policy
+    get "/inline"
+    assert_policy "default-src https://example.com"
+  end
+
+  def test_generates_conditional_content_security_policy
+    get "/conditional", params: { condition: "true" }
+    assert_policy "default-src https://true.example.com"
+
+    get "/conditional", params: { condition: "false" }
+    assert_policy "default-src https://false.example.com"
+  end
+
+  def test_generates_report_only_content_security_policy
+    get "/report-only"
+    assert_policy "default-src 'self'; report-uri /violations", report_only: true
+  end
+
+  def test_adds_nonce_to_script_src_content_security_policy
+    get "/script-src"
+    assert_policy "script-src 'self' 'nonce-iyhD0Yc0W+c='"
+  end
+
+  def test_generates_no_content_security_policy
+    get "/no-policy"
+
+    assert_nil response.headers["Content-Security-Policy"]
+    assert_nil response.headers["Content-Security-Policy-Report-Only"]
+  end
+
+  private
+
+    def assert_policy(expected, report_only: false)
+      assert_response :success
+
+      if report_only
+        expected_header = "Content-Security-Policy-Report-Only"
+        unexpected_header = "Content-Security-Policy"
+      else
+        expected_header = "Content-Security-Policy"
+        unexpected_header = "Content-Security-Policy-Report-Only"
+      end
+
+      assert_nil response.headers[unexpected_header]
+      assert_equal expected, response.headers[expected_header]
+    end
+end
+
+class DisabledContentSecurityPolicyIntegrationTest < ActionDispatch::IntegrationTest
+  class PolicyController < ActionController::Base
+    content_security_policy only: :inline do |p|
+      p.default_src "https://example.com"
+    end
+
+    def index
+      head :ok
+    end
+
+    def inline
+      head :ok
+    end
+  end
+
+  ROUTES = ActionDispatch::Routing::RouteSet.new
+  ROUTES.draw do
+    scope module: "disabled_content_security_policy_integration_test" do
+      get "/", to: "policy#index"
+      get "/inline", to: "policy#inline"
+    end
+  end
+
+  class PolicyConfigMiddleware
+    def initialize(app)
+      @app = app
+    end
+
+    def call(env)
+      env["action_dispatch.content_security_policy"] = nil
+      env["action_dispatch.content_security_policy_nonce_generator"] = nil
+      env["action_dispatch.content_security_policy_report_only"] = false
+      env["action_dispatch.show_exceptions"] = false
+
+      @app.call(env)
+    end
+  end
+
+  APP = build_app(ROUTES) do |middleware|
+    middleware.use PolicyConfigMiddleware
+    middleware.use ActionDispatch::ContentSecurityPolicy::Middleware
+  end
+
+  def app
+    APP
+  end
+
+  def test_generates_no_content_security_policy_by_default
+    get "/"
+    assert_nil response.headers["Content-Security-Policy"]
+  end
+
+  def test_generates_content_security_policy_header_when_globally_disabled
+    get "/inline"
+    assert_equal "default-src https://example.com", response.headers["Content-Security-Policy"]
+  end
+end
diff --git a/actionpack/test/dispatch/cookies_test.rb b/actionpack/test/dispatch/cookies_test.rb
index cb225c0f62..aba778fad6 100644
--- a/actionpack/test/dispatch/cookies_test.rb
+++ b/actionpack/test/dispatch/cookies_test.rb
@@ -3,7 +3,7 @@
 require "abstract_unit"
 require "openssl"
 require "active_support/key_generator"
-require "active_support/message_verifier"
+require "active_support/messages/rotation_configuration"
 
 class CookieJarTest < ActiveSupport::TestCase
   attr_reader :request
@@ -36,6 +36,12 @@ class CookieJarTest < ActiveSupport::TestCase
     assert_equal "bar", request.cookie_jar.fetch(:foo)
   end
 
+  def test_to_hash
+    request.cookie_jar["foo"] = "bar"
+    assert_equal({ "foo" => "bar" }, request.cookie_jar.to_hash)
+    assert_equal({ "foo" => "bar" }, request.cookie_jar.to_h)
+  end
+
   def test_fetch_type_error
     assert_raises(KeyError) do
       request.cookie_jar.fetch(:omglolwut)
@@ -59,8 +65,8 @@ class CookieJarTest < ActiveSupport::TestCase
   end
 
   def test_key_methods
-    assert !request.cookie_jar.key?(:foo)
-    assert !request.cookie_jar.has_key?("foo")
+    assert_not request.cookie_jar.key?(:foo)
+    assert_not request.cookie_jar.has_key?("foo")
 
     request.cookie_jar[:foo] = :bar
     assert request.cookie_jar.key?(:foo)
@@ -287,15 +293,25 @@ class CookiesTest < ActionController::TestCase
 
   tests TestController
 
-  SALT = "b3c631c314c0bbca50c1b2843150fe33"
+  SECRET_KEY_BASE = "b3c631c314c0bbca50c1b2843150fe33"
+  SIGNED_COOKIE_SALT = "signed cookie"
+  ENCRYPTED_COOKIE_SALT = "encrypted cookie"
+  ENCRYPTED_SIGNED_COOKIE_SALT = "sigend encrypted cookie"
+  AUTHENTICATED_ENCRYPTED_COOKIE_SALT = "authenticated encrypted cookie"
 
   def setup
     super
 
-    @request.env["action_dispatch.key_generator"] = ActiveSupport::KeyGenerator.new(SALT, iterations: 2)
+    @request.env["action_dispatch.key_generator"] = ActiveSupport::KeyGenerator.new(SECRET_KEY_BASE, iterations: 2)
+    @request.env["action_dispatch.cookies_rotations"] = ActiveSupport::Messages::RotationConfiguration.new
 
-    @request.env["action_dispatch.signed_cookie_salt"] =
-      @request.env["action_dispatch.authenticated_encrypted_cookie_salt"] = SALT
+    @request.env["action_dispatch.secret_key_base"] = SECRET_KEY_BASE
+    @request.env["action_dispatch.use_authenticated_cookie_encryption"] = true
+
+    @request.env["action_dispatch.signed_cookie_salt"] = SIGNED_COOKIE_SALT
+    @request.env["action_dispatch.encrypted_cookie_salt"] = ENCRYPTED_COOKIE_SALT
+    @request.env["action_dispatch.encrypted_signed_cookie_salt"] = ENCRYPTED_SIGNED_COOKIE_SALT
+    @request.env["action_dispatch.authenticated_encrypted_cookie_salt"] = AUTHENTICATED_ENCRYPTED_COOKIE_SALT
 
     @request.host = "www.nextangle.com"
   end
@@ -309,7 +325,7 @@ class CookiesTest < ActionController::TestCase
   def test_setting_the_same_value_to_cookie
     request.cookies[:user_name] = "david"
     get :authenticate
-    assert_predicate response.cookies, :empty?
+    assert_empty response.cookies
   end
 
   def test_setting_the_same_value_to_permanent_cookie
@@ -391,7 +407,7 @@ class CookiesTest < ActionController::TestCase
   def test_delete_unexisting_cookie
     request.cookies.clear
     get :delete_cookie
-    assert_predicate @response.cookies, :empty?
+    assert_empty @response.cookies
   end
 
   def test_deleted_cookie_predicate
@@ -430,28 +446,72 @@ class CookiesTest < ActionController::TestCase
     assert_equal 45, cookies.signed[:user_id]
 
     key_generator = @request.env["action_dispatch.key_generator"]
-    signed_cookie_salt = @request.env["action_dispatch.signed_cookie_salt"]
-    secret = key_generator.generate_key(signed_cookie_salt)
+    secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
 
     verifier = ActiveSupport::MessageVerifier.new(secret, serializer: Marshal, digest: "SHA1")
     assert_equal verifier.generate(45), cookies[:user_id]
   end
 
   def test_signed_cookie_using_custom_digest
-    @request.env["action_dispatch.cookies_digest"] = "SHA256"
+    @request.env["action_dispatch.signed_cookie_digest"] = "SHA256"
+
     get :set_signed_cookie
     cookies = @controller.send :cookies
     assert_not_equal 45, cookies[:user_id]
     assert_equal 45, cookies.signed[:user_id]
 
     key_generator = @request.env["action_dispatch.key_generator"]
-    signed_cookie_salt = @request.env["action_dispatch.signed_cookie_salt"]
-    secret = key_generator.generate_key(signed_cookie_salt)
+    secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
 
     verifier = ActiveSupport::MessageVerifier.new(secret, serializer: Marshal, digest: "SHA256")
     assert_equal verifier.generate(45), cookies[:user_id]
   end
 
+  def test_signed_cookie_rotating_secret_and_digest
+    secret = "b3c631c314c0bbca50c1b2843150fe33"
+
+    @request.env["action_dispatch.signed_cookie_digest"] = "SHA256"
+    @request.env["action_dispatch.cookies_rotations"].rotate :signed, secret, digest: "SHA1"
+
+    old_message = ActiveSupport::MessageVerifier.new(secret, digest: "SHA1", serializer: Marshal).generate(45)
+    @request.headers["Cookie"] = "user_id=#{old_message}"
+
+    get :get_signed_cookie
+    assert_equal 45, @controller.send(:cookies).signed[:user_id]
+
+    key_generator = @request.env["action_dispatch.key_generator"]
+    secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
+    verifier = ActiveSupport::MessageVerifier.new(secret, digest: "SHA256", serializer: Marshal)
+    assert_equal 45, verifier.verify(@response.cookies["user_id"])
+  end
+
+  def test_signed_cookie_with_legacy_secret_scheme
+    @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
+
+    old_message = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33", digest: "SHA1", serializer: Marshal).generate(45)
+
+    @request.headers["Cookie"] = "user_id=#{old_message}"
+    get :get_signed_cookie
+    assert_equal 45, @controller.send(:cookies).signed[:user_id]
+
+    key_generator = @request.env["action_dispatch.key_generator"]
+    secret = key_generator.generate_key("signed cookie")
+    verifier = ActiveSupport::MessageVerifier.new(secret, digest: "SHA1", serializer: Marshal)
+    assert_equal 45, verifier.verify(@response.cookies["user_id"])
+  end
+
+  def test_tampered_with_signed_cookie
+    key_generator = @request.env["action_dispatch.key_generator"]
+    secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
+
+    verifier = ActiveSupport::MessageVerifier.new(secret, serializer: Marshal, digest: "SHA1")
+    message = verifier.generate(45)
+
+    @request.headers["Cookie"] = "user_id=#{Marshal.dump 45}--#{message.split("--").last}"
+    get :get_signed_cookie
+    assert_nil @controller.send(:cookies).signed[:user_id]
+  end
+
   def test_signed_cookie_using_default_serializer
     get :set_signed_cookie
     cookies = @controller.send :cookies
@@ -494,8 +554,7 @@ class CookiesTest < ActionController::TestCase
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
 
     key_generator = @request.env["action_dispatch.key_generator"]
-    signed_cookie_salt = @request.env["action_dispatch.signed_cookie_salt"]
-    secret = key_generator.generate_key(signed_cookie_salt)
+    secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
 
     marshal_value = ActiveSupport::MessageVerifier.new(secret, serializer: Marshal).generate(45)
     @request.headers["Cookie"] = "user_id=#{marshal_value}"
@@ -514,8 +573,8 @@ class CookiesTest < ActionController::TestCase
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
 
     key_generator = @request.env["action_dispatch.key_generator"]
-    signed_cookie_salt = @request.env["action_dispatch.signed_cookie_salt"]
-    secret = key_generator.generate_key(signed_cookie_salt)
+    secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
+
     json_value = ActiveSupport::MessageVerifier.new(secret, serializer: JSON).generate(45)
     @request.headers["Cookie"] = "user_id=#{json_value}"
 
@@ -578,11 +637,10 @@ class CookiesTest < ActionController::TestCase
   def test_encrypted_cookie_using_hybrid_serializer_can_migrate_marshal_dumped_value_to_json
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
 
-    cipher = "aes-256-gcm"
-    salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len(cipher)]
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: Marshal)
+    key_generator = @request.env["action_dispatch.key_generator"]
+    secret = key_generator.generate_key(@request.env["action_dispatch.authenticated_encrypted_cookie_salt"], 32)
 
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: Marshal)
     marshal_value = encryptor.encrypt_and_sign("bar")
     @request.headers["Cookie"] = "foo=#{::Rack::Utils.escape marshal_value}"
 
@@ -592,7 +650,7 @@ class CookiesTest < ActionController::TestCase
     assert_not_equal "bar", cookies[:foo]
     assert_equal "bar", cookies.encrypted[:foo]
 
-    json_encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: JSON)
+    json_encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: JSON)
     assert_not_nil @response.cookies["foo"]
     assert_equal "bar", json_encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
@@ -600,11 +658,10 @@ class CookiesTest < ActionController::TestCase
   def test_encrypted_cookie_using_hybrid_serializer_can_read_from_json_dumped_value
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
 
-    cipher = "aes-256-gcm"
-    salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len(cipher)]
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: JSON)
+    key_generator = @request.env["action_dispatch.key_generator"]
+    secret = key_generator.generate_key(@request.env["action_dispatch.authenticated_encrypted_cookie_salt"], 32)
 
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: JSON)
     json_value = encryptor.encrypt_and_sign("bar")
     @request.headers["Cookie"] = "foo=#{::Rack::Utils.escape json_value}"
 
@@ -691,65 +748,8 @@ class CookiesTest < ActionController::TestCase
     }
   end
 
-  def test_signed_uses_signed_cookie_jar_if_only_secret_token_is_set
-    @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = nil
-    get :set_signed_cookie
-    assert_kind_of ActionDispatch::Cookies::SignedCookieJar, cookies.signed
-  end
-
-  def test_signed_uses_signed_cookie_jar_if_only_secret_key_base_is_set
-    @request.env["action_dispatch.secret_token"] = nil
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-    get :set_signed_cookie
-    assert_kind_of ActionDispatch::Cookies::SignedCookieJar, cookies.signed
-  end
-
-  def test_signed_uses_upgrade_legacy_signed_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
-    @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-    get :set_signed_cookie
-    assert_kind_of ActionDispatch::Cookies::UpgradeLegacySignedCookieJar, cookies.signed
-  end
-
-  def test_signed_or_encrypted_uses_signed_cookie_jar_if_only_secret_token_is_set
-    @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = nil
-    get :get_encrypted_cookie
-    assert_kind_of ActionDispatch::Cookies::SignedCookieJar, cookies.signed_or_encrypted
-  end
-
-  def test_signed_or_encrypted_uses_encrypted_cookie_jar_if_only_secret_key_base_is_set
-    @request.env["action_dispatch.secret_token"] = nil
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-    get :get_encrypted_cookie
-    assert_kind_of ActionDispatch::Cookies::EncryptedCookieJar, cookies.signed_or_encrypted
-  end
-
-  def test_signed_or_encrypted_uses_upgrade_legacy_encrypted_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
-    @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-    get :get_encrypted_cookie
-    assert_kind_of ActionDispatch::Cookies::UpgradeLegacyEncryptedCookieJar, cookies.signed_or_encrypted
-  end
-
-  def test_encrypted_uses_encrypted_cookie_jar_if_only_secret_key_base_is_set
-    @request.env["action_dispatch.secret_token"] = nil
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-    get :get_encrypted_cookie
-    assert_kind_of ActionDispatch::Cookies::EncryptedCookieJar, cookies.encrypted
-  end
-
-  def test_encrypted_uses_upgrade_legacy_encrypted_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
-    @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-    get :get_encrypted_cookie
-    assert_kind_of ActionDispatch::Cookies::UpgradeLegacyEncryptedCookieJar, cookies.encrypted
-  end
-
   def test_legacy_signed_cookie_is_read_and_transparently_upgraded_by_signed_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     legacy_value = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33").generate(45)
 
@@ -766,9 +766,6 @@ class CookiesTest < ActionController::TestCase
 
   def test_legacy_signed_cookie_is_read_and_transparently_encrypted_by_encrypted_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-    @request.env["action_dispatch.encrypted_cookie_salt"] = "4433796b79d99a7735553e316522acee"
-    @request.env["action_dispatch.encrypted_signed_cookie_salt"] = "00646eb40062e1b1deff205a27cd30f9"
 
     legacy_value = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33").generate("bar")
 
@@ -777,17 +774,14 @@ class CookiesTest < ActionController::TestCase
 
     assert_equal "bar", @controller.send(:cookies).encrypted[:foo]
 
-    cipher = "aes-256-gcm"
-    salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len(cipher)]
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: Marshal)
+    secret = @request.env["action_dispatch.key_generator"].generate_key(@request.env["action_dispatch.authenticated_encrypted_cookie_salt"], 32)
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: Marshal)
     assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_legacy_json_signed_cookie_is_read_and_transparently_upgraded_by_signed_json_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.cookies_serializer"] = :json
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     legacy_value = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33", serializer: JSON).generate(45)
 
@@ -805,7 +799,6 @@ class CookiesTest < ActionController::TestCase
   def test_legacy_json_signed_cookie_is_read_and_transparently_encrypted_by_encrypted_json_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.cookies_serializer"] = :json
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     legacy_value = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33", serializer: JSON).generate("bar")
 
@@ -824,7 +817,6 @@ class CookiesTest < ActionController::TestCase
   def test_legacy_json_signed_cookie_is_read_and_transparently_upgraded_by_signed_json_hybrid_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     legacy_value = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33", serializer: JSON).generate(45)
 
@@ -842,7 +834,6 @@ class CookiesTest < ActionController::TestCase
   def test_legacy_json_signed_cookie_is_read_and_transparently_encrypted_by_encrypted_hybrid_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     legacy_value = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33", serializer: JSON).generate("bar")
 
@@ -851,17 +842,15 @@ class CookiesTest < ActionController::TestCase
 
     assert_equal "bar", @controller.send(:cookies).encrypted[:foo]
 
-    cipher = "aes-256-gcm"
     salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len(cipher)]
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: JSON)
+    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len("aes-256-gcm")]
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: JSON)
     assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_legacy_marshal_signed_cookie_is_read_and_transparently_upgraded_by_signed_json_hybrid_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     legacy_value = ActiveSupport::MessageVerifier.new("b3c631c314c0bbca50c1b2843150fe33").generate(45)
 
@@ -878,6 +867,8 @@ class CookiesTest < ActionController::TestCase
 
   def test_legacy_marshal_signed_cookie_is_read_and_transparently_encrypted_by_encrypted_hybrid_cookie_jar_if_both_secret_token_and_secret_key_base_are_set
     @request.env["action_dispatch.cookies_serializer"] = :hybrid
+
+    @request.env["action_dispatch.use_authenticated_cookie_encryption"] = true
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
     @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
@@ -888,16 +879,14 @@ class CookiesTest < ActionController::TestCase
 
     assert_equal "bar", @controller.send(:cookies).encrypted[:foo]
 
-    cipher = "aes-256-gcm"
     salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len(cipher)]
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: JSON)
+    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len("aes-256-gcm")]
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: JSON)
     assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_legacy_signed_cookie_is_treated_as_nil_by_signed_cookie_jar_if_tampered
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     @request.headers["Cookie"] = "user_id=45"
     get :get_signed_cookie
@@ -908,7 +897,6 @@ class CookiesTest < ActionController::TestCase
 
   def test_legacy_signed_cookie_is_treated_as_nil_by_encrypted_cookie_jar_if_tampered
     @request.env["action_dispatch.secret_token"] = "b3c631c314c0bbca50c1b2843150fe33"
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
 
     @request.headers["Cookie"] = "foo=baz"
     get :get_encrypted_cookie
@@ -917,18 +905,50 @@ class CookiesTest < ActionController::TestCase
     assert_nil @response.cookies["foo"]
   end
 
-  def test_legacy_hmac_aes_cbc_encrypted_marshal_cookie_is_upgraded_to_authenticated_encrypted_cookie
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
+  def test_use_authenticated_cookie_encryption_uses_legacy_hmac_aes_cbc_encryption_when_not_enabled
+    @request.env["action_dispatch.use_authenticated_cookie_encryption"] = nil
+
+    key_generator = @request.env["action_dispatch.key_generator"]
+    encrypted_cookie_salt = @request.env["action_dispatch.encrypted_cookie_salt"]
+    encrypted_signed_cookie_salt = @request.env["action_dispatch.encrypted_signed_cookie_salt"]
+    secret = key_generator.generate_key(encrypted_cookie_salt, ActiveSupport::MessageEncryptor.key_len("aes-256-cbc"))
+    sign_secret = key_generator.generate_key(encrypted_signed_cookie_salt)
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, cipher: "aes-256-cbc", digest: "SHA1", serializer: Marshal)
+
+    get :set_encrypted_cookie
+
+    cookies = @controller.send :cookies
+    assert_not_equal "bar", cookies[:foo]
+    assert_equal "bar", cookies.encrypted[:foo]
+    assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
+  end
 
-    @request.env["action_dispatch.encrypted_cookie_salt"] =
-      @request.env["action_dispatch.encrypted_signed_cookie_salt"] = SALT
+  def test_rotating_signed_cookies_digest
+    @request.env["action_dispatch.signed_cookie_digest"] = "SHA256"
+    @request.env["action_dispatch.cookies_rotations"].rotate :signed, digest: "SHA1"
+
+    key_generator = @request.env["action_dispatch.key_generator"]
+
+    old_secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
+    old_value = ActiveSupport::MessageVerifier.new(old_secret).generate(45)
+
+    @request.headers["Cookie"] = "user_id=#{old_value}"
+    get :get_signed_cookie
+
+    assert_equal 45, @controller.send(:cookies).signed[:user_id]
+
+    secret = key_generator.generate_key(@request.env["action_dispatch.signed_cookie_salt"])
+    verifier = ActiveSupport::MessageVerifier.new(secret, digest: "SHA256")
+    assert_equal 45, verifier.verify(@response.cookies["user_id"])
+  end
 
+  def test_legacy_hmac_aes_cbc_encrypted_marshal_cookie_is_upgraded_to_authenticated_encrypted_cookie
     key_generator = @request.env["action_dispatch.key_generator"]
     encrypted_cookie_salt = @request.env["action_dispatch.encrypted_cookie_salt"]
     encrypted_signed_cookie_salt = @request.env["action_dispatch.encrypted_signed_cookie_salt"]
-    secret = key_generator.generate_key(encrypted_cookie_salt)
+    secret = key_generator.generate_key(encrypted_cookie_salt, ActiveSupport::MessageEncryptor.key_len("aes-256-cbc"))
     sign_secret = key_generator.generate_key(encrypted_signed_cookie_salt)
-    marshal_value = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len], sign_secret, serializer: Marshal).encrypt_and_sign("bar")
+    marshal_value = ActiveSupport::MessageEncryptor.new(secret, sign_secret, cipher: "aes-256-cbc", serializer: Marshal).encrypt_and_sign("bar")
 
     @request.headers["Cookie"] = "foo=#{marshal_value}"
 
@@ -938,27 +958,22 @@ class CookiesTest < ActionController::TestCase
     assert_not_equal "bar", cookies[:foo]
     assert_equal "bar", cookies.encrypted[:foo]
 
-    aead_cipher = "aes-256-gcm"
     aead_salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    aead_secret = key_generator.generate_key(aead_salt)[0, ActiveSupport::MessageEncryptor.key_len(aead_cipher)]
-    aead_encryptor = ActiveSupport::MessageEncryptor.new(aead_secret, cipher: aead_cipher, serializer: Marshal)
+    aead_secret = key_generator.generate_key(aead_salt, ActiveSupport::MessageEncryptor.key_len("aes-256-gcm"))
+    aead_encryptor = ActiveSupport::MessageEncryptor.new(aead_secret, cipher: "aes-256-gcm", serializer: Marshal)
 
     assert_equal "bar", aead_encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_legacy_hmac_aes_cbc_encrypted_json_cookie_is_upgraded_to_authenticated_encrypted_cookie
     @request.env["action_dispatch.cookies_serializer"] = :json
-    @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-
-    @request.env["action_dispatch.encrypted_cookie_salt"] =
-      @request.env["action_dispatch.encrypted_signed_cookie_salt"] = SALT
 
     key_generator = @request.env["action_dispatch.key_generator"]
     encrypted_cookie_salt = @request.env["action_dispatch.encrypted_cookie_salt"]
     encrypted_signed_cookie_salt = @request.env["action_dispatch.encrypted_signed_cookie_salt"]
-    secret = key_generator.generate_key(encrypted_cookie_salt)
+    secret = key_generator.generate_key(encrypted_cookie_salt, ActiveSupport::MessageEncryptor.key_len("aes-256-cbc"))
     sign_secret = key_generator.generate_key(encrypted_signed_cookie_salt)
-    marshal_value = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len], sign_secret, serializer: JSON).encrypt_and_sign("bar")
+    marshal_value = ActiveSupport::MessageEncryptor.new(secret, sign_secret, cipher: "aes-256-cbc", serializer: JSON).encrypt_and_sign("bar")
 
     @request.headers["Cookie"] = "foo=#{marshal_value}"
 
@@ -968,19 +983,17 @@ class CookiesTest < ActionController::TestCase
     assert_not_equal "bar", cookies[:foo]
     assert_equal "bar", cookies.encrypted[:foo]
 
-    aead_cipher = "aes-256-gcm"
     aead_salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    aead_secret = key_generator.generate_key(aead_salt)[0, ActiveSupport::MessageEncryptor.key_len(aead_cipher)]
-    aead_encryptor = ActiveSupport::MessageEncryptor.new(aead_secret, cipher: aead_cipher, serializer: JSON)
+    aead_secret = key_generator.generate_key(aead_salt)[0, ActiveSupport::MessageEncryptor.key_len("aes-256-gcm")]
+    aead_encryptor = ActiveSupport::MessageEncryptor.new(aead_secret, cipher: "aes-256-gcm", serializer: JSON)
 
     assert_equal "bar", aead_encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
   def test_legacy_hmac_aes_cbc_encrypted_cookie_using_64_byte_key_is_upgraded_to_authenticated_encrypted_cookie
     @request.env["action_dispatch.secret_key_base"] = "c3b95688f35581fad38df788add315ff"
-
-    @request.env["action_dispatch.encrypted_cookie_salt"] =
-      @request.env["action_dispatch.encrypted_signed_cookie_salt"] = SALT
+    @request.env["action_dispatch.encrypted_cookie_salt"] = "b3c631c314c0bbca50c1b2843150fe33"
+    @request.env["action_dispatch.encrypted_signed_cookie_salt"] = "b3c631c314c0bbca50c1b2843150fe33"
 
     # Cookie generated with 64 bytes secret
     message = ["566d4e75536d686e633246564e6b493062557079626c566d51574d30515430394c53315665564a694e4563786555744f57537454576b396a5a31566a626e52525054303d2d2d34663234333330623130623261306163363562316266323335396164666364613564643134623131"].pack("H*")
@@ -991,15 +1004,35 @@ class CookiesTest < ActionController::TestCase
     cookies = @controller.send :cookies
     assert_not_equal "bar", cookies[:foo]
     assert_equal "bar", cookies.encrypted[:foo]
-    cipher = "aes-256-gcm"
 
     salt = @request.env["action_dispatch.authenticated_encrypted_cookie_salt"]
-    secret = @request.env["action_dispatch.key_generator"].generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len(cipher)]
-    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: Marshal)
+    secret = @request.env["action_dispatch.key_generator"].generate_key(salt, ActiveSupport::MessageEncryptor.key_len("aes-256-gcm"))
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: Marshal)
 
     assert_equal "bar", encryptor.decrypt_and_verify(@response.cookies["foo"])
   end
 
+  def test_encrypted_cookie_rotating_secret
+    secret = "b3c631c314c0bbca50c1b2843150fe33"
+
+    @request.env["action_dispatch.encrypted_cookie_cipher"] = "aes-256-gcm"
+    @request.env["action_dispatch.cookies_rotations"].rotate :encrypted, secret
+
+    key_len = ActiveSupport::MessageEncryptor.key_len("aes-256-gcm")
+
+    old_message = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: Marshal).encrypt_and_sign(45)
+
+    @request.headers["Cookie"] = "foo=#{::Rack::Utils.escape old_message}"
+
+    get :get_encrypted_cookie
+    assert_equal 45, @controller.send(:cookies).encrypted[:foo]
+
+    key_generator = @request.env["action_dispatch.key_generator"]
+    secret = key_generator.generate_key(@request.env["action_dispatch.authenticated_encrypted_cookie_salt"], key_len)
+    encryptor = ActiveSupport::MessageEncryptor.new(secret, cipher: "aes-256-gcm", serializer: Marshal)
+    assert_equal 45, encryptor.decrypt_and_verify(@response.cookies["foo"])
+  end
+
   def test_cookie_with_all_domain_option
     get :set_cookie_with_domain
     assert_response :success
diff --git a/actionpack/test/dispatch/debug_exceptions_test.rb b/actionpack/test/dispatch/debug_exceptions_test.rb
index 60acba0616..045567ff83 100644
--- a/actionpack/test/dispatch/debug_exceptions_test.rb
+++ b/actionpack/test/dispatch/debug_exceptions_test.rb
@@ -3,6 +3,8 @@
 require "abstract_unit"
 
 class DebugExceptionsTest < ActionDispatch::IntegrationTest
+  InterceptedErrorInstance = StandardError.new
+
   class Boomer
     attr_accessor :closed
 
@@ -36,6 +38,8 @@ class DebugExceptionsTest < ActionDispatch::IntegrationTest
         raise RuntimeError
       when %r{/method_not_allowed}
         raise ActionController::MethodNotAllowed
+      when %r{/intercepted_error}
+        raise InterceptedErrorInstance
       when %r{/unknown_http_method}
         raise ActionController::UnknownHttpMethod
       when %r{/not_implemented}
@@ -76,9 +80,13 @@ class DebugExceptionsTest < ActionDispatch::IntegrationTest
     end
   end
 
+  Interceptor = proc { |request, exception| request.set_header("int", exception) }
+  BadInterceptor = proc { |request, exception| raise "bad" }
   RoutesApp = Struct.new(:routes).new(SharedTestRoutes)
   ProductionApp  = ActionDispatch::DebugExceptions.new(Boomer.new(false), RoutesApp)
   DevelopmentApp = ActionDispatch::DebugExceptions.new(Boomer.new(true), RoutesApp)
+  InterceptedApp = ActionDispatch::DebugExceptions.new(Boomer.new(true), RoutesApp, :default, [Interceptor])
+  BadInterceptedApp = ActionDispatch::DebugExceptions.new(Boomer.new(true), RoutesApp, :default, [BadInterceptor])
 
   test "skip diagnosis if not showing detailed exceptions" do
     @app = ProductionApp
@@ -499,4 +507,20 @@ class DebugExceptionsTest < ActionDispatch::IntegrationTest
       end
     end
   end
+
+  test "invoke interceptors before rendering" do
+    @app = InterceptedApp
+    get "/intercepted_error", headers: { "action_dispatch.show_exceptions" => true }
+
+    assert_equal InterceptedErrorInstance, request.get_header("int")
+  end
+
+  test "bad interceptors doesn't debug exceptions" do
+    @app = BadInterceptedApp
+
+    get "/puke", headers: { "action_dispatch.show_exceptions" => true }
+
+    assert_response 500
+    assert_match(/puke/, body)
+  end
 end
diff --git a/actionpack/test/dispatch/debug_locks_test.rb b/actionpack/test/dispatch/debug_locks_test.rb
new file mode 100644
index 0000000000..d69614bd79
--- /dev/null
+++ b/actionpack/test/dispatch/debug_locks_test.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+
+class DebugLocksTest < ActionDispatch::IntegrationTest
+  setup do
+    build_app
+  end
+
+  def test_render_threads_status
+    thread_ready = Concurrent::CountDownLatch.new
+    test_terminated = Concurrent::CountDownLatch.new
+
+    thread = Thread.new do
+      ActiveSupport::Dependencies.interlock.running do
+        thread_ready.count_down
+        test_terminated.wait
+      end
+    end
+
+    thread_ready.wait
+
+    get "/rails/locks"
+
+    test_terminated.count_down
+
+    assert_match(/Thread.*?Sharing/, @response.body)
+  ensure
+    thread.join
+  end
+
+  private
+    def build_app
+      @app = self.class.build_app do |middleware|
+        middleware.use ActionDispatch::DebugLocks
+      end
+    end
+end
diff --git a/actionpack/test/dispatch/executor_test.rb b/actionpack/test/dispatch/executor_test.rb
index 8eb6450385..5b8be39b6d 100644
--- a/actionpack/test/dispatch/executor_test.rb
+++ b/actionpack/test/dispatch/executor_test.rb
@@ -81,7 +81,7 @@ class ExecutorTest < ActiveSupport::TestCase
 
     running = false
     body.close
-    assert !running
+    assert_not running
   end
 
   def test_complete_callbacks_are_called_on_close
@@ -89,7 +89,7 @@ class ExecutorTest < ActiveSupport::TestCase
     executor.to_complete { completed = true }
 
     body = call_and_return_body
-    assert !completed
+    assert_not completed
 
     body.close
     assert completed
@@ -116,7 +116,7 @@ class ExecutorTest < ActiveSupport::TestCase
 
     call_and_return_body.close
     assert result
-    assert !defined?(@in_shared_context) # it's not in the test itself
+    assert_not defined?(@in_shared_context) # it's not in the test itself
   end
 
   private
diff --git a/actionpack/test/dispatch/live_response_test.rb b/actionpack/test/dispatch/live_response_test.rb
index 2901148a9e..a9a56f205f 100644
--- a/actionpack/test/dispatch/live_response_test.rb
+++ b/actionpack/test/dispatch/live_response_test.rb
@@ -73,7 +73,7 @@ module ActionController
         }
 
         latch.wait
-        assert @response.headers.frozen?
+        assert_predicate @response.headers, :frozen?
         e = assert_raises(ActionDispatch::IllegalStateError) do
           @response.headers["Content-Length"] = "zomg"
         end
diff --git a/actionpack/test/dispatch/mime_type_test.rb b/actionpack/test/dispatch/mime_type_test.rb
index 90e95e972d..fa264417e1 100644
--- a/actionpack/test/dispatch/mime_type_test.rb
+++ b/actionpack/test/dispatch/mime_type_test.rb
@@ -30,21 +30,21 @@ class MimeTypeTest < ActiveSupport::TestCase
 
   test "parse text with trailing star at the beginning" do
     accept = "text/*, text/html, application/json, multipart/form-data"
-    expect = [Mime[:html], Mime[:text], Mime[:js], Mime[:css], Mime[:ics], Mime[:csv], Mime[:vcf], Mime[:xml], Mime[:yaml], Mime[:json], Mime[:multipart_form]]
+    expect = [Mime[:html], Mime[:text], Mime[:js], Mime[:css], Mime[:ics], Mime[:csv], Mime[:vcf], Mime[:vtt], Mime[:xml], Mime[:yaml], Mime[:json], Mime[:multipart_form]]
     parsed = Mime::Type.parse(accept)
-    assert_equal expect, parsed
+    assert_equal expect.map(&:to_s), parsed.map(&:to_s)
   end
 
   test "parse text with trailing star in the end" do
     accept = "text/html, application/json, multipart/form-data, text/*"
-    expect = [Mime[:html], Mime[:json], Mime[:multipart_form], Mime[:text], Mime[:js], Mime[:css], Mime[:ics], Mime[:csv], Mime[:vcf], Mime[:xml], Mime[:yaml]]
+    expect = [Mime[:html], Mime[:json], Mime[:multipart_form], Mime[:text], Mime[:js], Mime[:css], Mime[:ics], Mime[:csv], Mime[:vcf], Mime[:vtt], Mime[:xml], Mime[:yaml]]
     parsed = Mime::Type.parse(accept)
-    assert_equal expect, parsed
+    assert_equal expect.map(&:to_s), parsed.map(&:to_s)
   end
 
   test "parse text with trailing star" do
     accept = "text/*"
-    expect = [Mime[:html], Mime[:text], Mime[:js], Mime[:css], Mime[:ics], Mime[:csv], Mime[:vcf], Mime[:xml], Mime[:yaml], Mime[:json]]
+    expect = [Mime[:html], Mime[:text], Mime[:js], Mime[:css], Mime[:ics], Mime[:csv], Mime[:vcf], Mime[:vtt], Mime[:xml], Mime[:yaml], Mime[:json]]
     parsed = Mime::Type.parse(accept)
     assert_equal expect.map(&:to_s).sort!, parsed.map(&:to_s).sort!
   end
@@ -159,7 +159,7 @@ class MimeTypeTest < ActiveSupport::TestCase
 
     types.each do |type|
       mime = Mime[type]
-      assert mime.respond_to?("#{type}?"), "#{mime.inspect} does not respond to #{type}?"
+      assert_respond_to mime, "#{type}?"
       assert_equal type, mime.symbol, "#{mime.inspect} is not #{type}?"
       invalid_types = types - [type]
       invalid_types.delete(:html)
@@ -180,8 +180,8 @@ class MimeTypeTest < ActiveSupport::TestCase
     assert Mime[:js] =~ "text/javascript"
     assert Mime[:js] =~ "application/javascript"
     assert Mime[:js] !~ "text/html"
-    assert !(Mime[:js] !~ "text/javascript")
-    assert !(Mime[:js] !~ "application/javascript")
+    assert_not (Mime[:js] !~ "text/javascript")
+    assert_not (Mime[:js] !~ "application/javascript")
     assert Mime[:html] =~ "application/xhtml+xml"
   end
 end
diff --git a/actionpack/test/dispatch/reloader_test.rb b/actionpack/test/dispatch/reloader_test.rb
index e529229fae..edc4cd62a3 100644
--- a/actionpack/test/dispatch/reloader_test.rb
+++ b/actionpack/test/dispatch/reloader_test.rb
@@ -115,7 +115,7 @@ class ReloaderTest < ActiveSupport::TestCase
     reloader.to_complete { completed = true }
 
     body = call_and_return_body
-    assert !completed
+    assert_not completed
 
     body.close
     assert completed
@@ -129,7 +129,7 @@ class ReloaderTest < ActiveSupport::TestCase
     prepared = false
 
     body.close
-    assert !prepared
+    assert_not prepared
   end
 
   def test_complete_callbacks_are_called_on_exceptions
diff --git a/actionpack/test/dispatch/request/session_test.rb b/actionpack/test/dispatch/request/session_test.rb
index 7b6ce31f29..74da2fe7d3 100644
--- a/actionpack/test/dispatch/request/session_test.rb
+++ b/actionpack/test/dispatch/request/session_test.rb
@@ -22,6 +22,7 @@ module ActionDispatch
         s["foo"] = "bar"
         assert_equal "bar", s["foo"]
         assert_equal({ "foo" => "bar" }, s.to_hash)
+        assert_equal({ "foo" => "bar" }, s.to_h)
       end
 
       def test_create_merges_old
@@ -117,6 +118,18 @@ module ActionDispatch
         end
       end
 
+      def test_dig
+        session = Session.create(store, req, {})
+        session["one"] = { "two" => "3" }
+
+        assert_equal "3", session.dig("one", "two")
+        assert_equal "3", session.dig(:one, "two")
+
+        assert_nil session.dig("three", "two")
+        assert_nil session.dig("one", "three")
+        assert_nil session.dig("one", :two)
+      end
+
       private
         def store
           Class.new {
diff --git a/actionpack/test/dispatch/request_id_test.rb b/actionpack/test/dispatch/request_id_test.rb
index aa3175c986..9df4712dab 100644
--- a/actionpack/test/dispatch/request_id_test.rb
+++ b/actionpack/test/dispatch/request_id_test.rb
@@ -11,6 +11,11 @@ class RequestIdTest < ActiveSupport::TestCase
     assert_equal "X-Hacked-HeaderStuff", stub_request("HTTP_X_REQUEST_ID" => "; X-Hacked-Header: Stuff").request_id
   end
 
+  test "accept Apache mod_unique_id format" do
+    mod_unique_id = "abcxyz@ABCXYZ-0123456789"
+    assert_equal mod_unique_id, stub_request("HTTP_X_REQUEST_ID" => mod_unique_id).request_id
+  end
+
   test "ensure that 255 char limit on the request id is being enforced" do
     assert_equal "X" * 255, stub_request("HTTP_X_REQUEST_ID" => "X" * 500).request_id
   end
diff --git a/actionpack/test/dispatch/request_test.rb b/actionpack/test/dispatch/request_test.rb
index 68c6d26364..84a2d1f69e 100644
--- a/actionpack/test/dispatch/request_test.rb
+++ b/actionpack/test/dispatch/request_test.rb
@@ -329,20 +329,20 @@ class RequestPort < BaseRequestTest
 
   test "standard_port?" do
     request = stub_request
-    assert !request.ssl?
-    assert request.standard_port?
+    assert_not_predicate request, :ssl?
+    assert_predicate request, :standard_port?
 
     request = stub_request "HTTPS" => "on"
-    assert request.ssl?
-    assert request.standard_port?
+    assert_predicate request, :ssl?
+    assert_predicate request, :standard_port?
 
     request = stub_request "HTTP_HOST" => "www.example.org:8080"
-    assert !request.ssl?
-    assert !request.standard_port?
+    assert_not_predicate request, :ssl?
+    assert_not_predicate request, :standard_port?
 
     request = stub_request "HTTP_HOST" => "www.example.org:8443", "HTTPS" => "on"
-    assert request.ssl?
-    assert !request.standard_port?
+    assert_predicate request, :ssl?
+    assert_not_predicate request, :standard_port?
   end
 
   test "optional port" do
@@ -571,7 +571,7 @@ end
 class LocalhostTest < BaseRequestTest
   test "IPs that match localhost" do
     request = stub_request("REMOTE_IP" => "127.1.1.1", "REMOTE_ADDR" => "127.1.1.1")
-    assert request.local?
+    assert_predicate request, :local?
   end
 end
 
@@ -643,37 +643,37 @@ class RequestProtocol < BaseRequestTest
   test "xml http request" do
     request = stub_request
 
-    assert !request.xml_http_request?
-    assert !request.xhr?
+    assert_not_predicate request, :xml_http_request?
+    assert_not_predicate request, :xhr?
 
     request = stub_request "HTTP_X_REQUESTED_WITH" => "DefinitelyNotAjax1.0"
-    assert !request.xml_http_request?
-    assert !request.xhr?
+    assert_not_predicate request, :xml_http_request?
+    assert_not_predicate request, :xhr?
 
     request = stub_request "HTTP_X_REQUESTED_WITH" => "XMLHttpRequest"
-    assert request.xml_http_request?
-    assert request.xhr?
+    assert_predicate request, :xml_http_request?
+    assert_predicate request, :xhr?
   end
 
   test "reports ssl" do
-    assert !stub_request.ssl?
-    assert stub_request("HTTPS" => "on").ssl?
+    assert_not_predicate stub_request, :ssl?
+    assert_predicate stub_request("HTTPS" => "on"), :ssl?
   end
 
   test "reports ssl when proxied via lighttpd" do
-    assert stub_request("HTTP_X_FORWARDED_PROTO" => "https").ssl?
+    assert_predicate stub_request("HTTP_X_FORWARDED_PROTO" => "https"), :ssl?
   end
 
   test "scheme returns https when proxied" do
     request = stub_request "rack.url_scheme" => "http"
-    assert !request.ssl?
+    assert_not_predicate request, :ssl?
     assert_equal "http", request.scheme
 
     request = stub_request(
       "rack.url_scheme" => "http",
       "HTTP_X_FORWARDED_PROTO" => "https"
     )
-    assert request.ssl?
+    assert_predicate request, :ssl?
     assert_equal "https", request.scheme
   end
 end
@@ -700,7 +700,7 @@ class RequestMethod < BaseRequestTest
 
     assert_equal "GET", request.request_method
     assert_equal "GET", request.env["REQUEST_METHOD"]
-    assert request.get?
+    assert_predicate request, :get?
   end
 
   test "invalid http method raises exception" do
@@ -748,7 +748,7 @@ class RequestMethod < BaseRequestTest
 
     assert_equal "POST", request.method
     assert_equal "PATCH",  request.request_method
-    assert request.patch?
+    assert_predicate request, :patch?
   end
 
   test "post masquerading as put" do
@@ -758,12 +758,12 @@ class RequestMethod < BaseRequestTest
     )
     assert_equal "POST", request.method
     assert_equal "PUT",  request.request_method
-    assert request.put?
+    assert_predicate request, :put?
   end
 
   test "post uneffected by local inflections" do
     existing_acronyms = ActiveSupport::Inflector.inflections.acronyms.dup
-    existing_acronym_regex = ActiveSupport::Inflector.inflections.acronym_regex.dup
+    assert_deprecated { ActiveSupport::Inflector.inflections.acronym_regex.dup }
     begin
       ActiveSupport::Inflector.inflections do |inflect|
         inflect.acronym "POS"
@@ -772,12 +772,12 @@ class RequestMethod < BaseRequestTest
       request = stub_request "REQUEST_METHOD" => "POST"
       assert_equal :post, ActionDispatch::Request::HTTP_METHOD_LOOKUP["POST"]
       assert_equal :post, request.method_symbol
-      assert request.post?
+      assert_predicate request, :post?
     ensure
       # Reset original acronym set
       ActiveSupport::Inflector.inflections do |inflect|
         inflect.send(:instance_variable_set, "@acronyms", existing_acronyms)
-        inflect.send(:instance_variable_set, "@acronym_regex", existing_acronym_regex)
+        inflect.send(:define_acronym_regex_patterns)
       end
     end
   end
@@ -785,50 +785,44 @@ end
 
 class RequestFormat < BaseRequestTest
   test "xml format" do
-    request = stub_request
-    assert_called(request, :parameters, times: 2, returns: { format: :xml }) do
-      assert_equal Mime[:xml], request.format
-    end
+    request = stub_request "QUERY_STRING" => "format=xml"
+
+    assert_equal Mime[:xml], request.format
   end
 
   test "xhtml format" do
-    request = stub_request
-    assert_called(request, :parameters, times: 2, returns: { format: :xhtml }) do
-      assert_equal Mime[:html], request.format
-    end
+    request = stub_request "QUERY_STRING" => "format=xhtml"
+
+    assert_equal Mime[:html], request.format
   end
 
   test "txt format" do
-    request = stub_request
-    assert_called(request, :parameters, times: 2, returns: { format: :txt }) do
-      assert_equal Mime[:text], request.format
-    end
+    request = stub_request "QUERY_STRING" => "format=txt"
+
+    assert_equal Mime[:text], request.format
   end
 
   test "XMLHttpRequest" do
     request = stub_request(
       "HTTP_X_REQUESTED_WITH" => "XMLHttpRequest",
-      "HTTP_ACCEPT" => [Mime[:js], Mime[:html], Mime[:xml], "text/xml", "*/*"].join(",")
+      "HTTP_ACCEPT" => [Mime[:js], Mime[:html], Mime[:xml], "text/xml", "*/*"].join(","),
+      "QUERY_STRING" => ""
     )
 
-    assert_called(request, :parameters, times: 1, returns: {}) do
-      assert request.xhr?
-      assert_equal Mime[:js], request.format
-    end
+    assert_predicate request, :xhr?
+    assert_equal Mime[:js], request.format
   end
 
   test "can override format with parameter negative" do
-    request = stub_request
-    assert_called(request, :parameters, times: 2, returns: { format: :txt }) do
-      assert !request.format.xml?
-    end
+    request = stub_request("QUERY_STRING" => "format=txt")
+
+    assert_not_predicate request.format, :xml?
   end
 
   test "can override format with parameter positive" do
-    request = stub_request
-    assert_called(request, :parameters, times: 2, returns: { format: :xml }) do
-      assert request.format.xml?
-    end
+    request = stub_request("QUERY_STRING" => "format=xml")
+
+    assert_predicate request.format, :xml?
   end
 
   test "formats text/html with accept header" do
@@ -853,40 +847,37 @@ class RequestFormat < BaseRequestTest
   end
 
   test "formats format:text with accept header" do
-    request = stub_request
-    assert_called(request, :parameters, times: 2, returns: { format: :txt }) do
-      assert_equal [Mime[:text]], request.formats
-    end
+    request = stub_request("QUERY_STRING" => "format=txt")
+
+    assert_equal [Mime[:text]], request.formats
   end
 
   test "formats format:unknown with accept header" do
-    request = stub_request
-    assert_called(request, :parameters, times: 2, returns: { format: :unknown }) do
-      assert_instance_of Mime::NullType, request.format
-    end
+    request = stub_request("QUERY_STRING" => "format=unknown")
+
+    assert_instance_of Mime::NullType, request.format
   end
 
   test "format is not nil with unknown format" do
-    request = stub_request
-    assert_called(request, :parameters, times: 2, returns: { format: :hello }) do
-      assert request.format.nil?
-      assert_not request.format.html?
-      assert_not request.format.xml?
-      assert_not request.format.json?
-    end
+    request = stub_request("QUERY_STRING" => "format=hello")
+
+    assert_nil request.format
+    assert_not_predicate request.format, :html?
+    assert_not_predicate request.format, :xml?
+    assert_not_predicate request.format, :json?
   end
 
   test "format does not throw exceptions when malformed parameters" do
     request = stub_request("QUERY_STRING" => "x[y]=1&x[y][][w]=2")
     assert request.formats
-    assert request.format.html?
+    assert_predicate request.format, :html?
   end
 
   test "formats with xhr request" do
-    request = stub_request "HTTP_X_REQUESTED_WITH" => "XMLHttpRequest"
-    assert_called(request, :parameters, times: 1, returns: {}) do
-      assert_equal [Mime[:js]], request.formats
-    end
+    request = stub_request "HTTP_X_REQUESTED_WITH" => "XMLHttpRequest",
+                           "QUERY_STRING" => ""
+
+    assert_equal [Mime[:js]], request.formats
   end
 
   test "ignore_accept_header" do
@@ -894,62 +885,58 @@ class RequestFormat < BaseRequestTest
     ActionDispatch::Request.ignore_accept_header = true
 
     begin
-      request = stub_request "HTTP_ACCEPT" => "application/xml"
-      assert_called(request, :parameters, times: 1, returns: {}) do
-        assert_equal [ Mime[:html] ], request.formats
-      end
+      request = stub_request "HTTP_ACCEPT" => "application/xml",
+                             "QUERY_STRING" => ""
 
-      request = stub_request "HTTP_ACCEPT" => "koz-asked/something-crazy"
-      assert_called(request, :parameters, times: 1, returns: {}) do
-        assert_equal [ Mime[:html] ], request.formats
-      end
+      assert_equal [ Mime[:html] ], request.formats
 
-      request = stub_request "HTTP_ACCEPT" => "*/*;q=0.1"
-      assert_called(request, :parameters, times: 1, returns: {}) do
-        assert_equal [ Mime[:html] ], request.formats
-      end
+      request = stub_request "HTTP_ACCEPT" => "koz-asked/something-crazy",
+                             "QUERY_STRING" => ""
 
-      request = stub_request "HTTP_ACCEPT" => "application/jxw"
-      assert_called(request, :parameters, times: 1, returns: {}) do
-        assert_equal [ Mime[:html] ], request.formats
-      end
+      assert_equal [ Mime[:html] ], request.formats
+
+      request = stub_request "HTTP_ACCEPT" => "*/*;q=0.1",
+                             "QUERY_STRING" => ""
+
+      assert_equal [ Mime[:html] ], request.formats
+
+      request = stub_request "HTTP_ACCEPT" => "application/jxw",
+                             "QUERY_STRING" => ""
+
+      assert_equal [ Mime[:html] ], request.formats
 
       request = stub_request "HTTP_ACCEPT" => "application/xml",
-                             "HTTP_X_REQUESTED_WITH" => "XMLHttpRequest"
+                             "HTTP_X_REQUESTED_WITH" => "XMLHttpRequest",
+                             "QUERY_STRING" => ""
 
-      assert_called(request, :parameters, times: 1, returns: {}) do
-        assert_equal [ Mime[:js] ], request.formats
-      end
+      assert_equal [ Mime[:js] ], request.formats
 
       request = stub_request "HTTP_ACCEPT" => "application/xml",
-                             "HTTP_X_REQUESTED_WITH" => "XMLHttpRequest"
-      assert_called(request, :parameters, times: 2, returns: { format: :json }) do
-        assert_equal [ Mime[:json] ], request.formats
-      end
+                             "HTTP_X_REQUESTED_WITH" => "XMLHttpRequest",
+                             "QUERY_STRING" => "format=json"
+
+      assert_equal [ Mime[:json] ], request.formats
     ensure
       ActionDispatch::Request.ignore_accept_header = old_ignore_accept_header
     end
   end
 
   test "format taken from the path extension" do
-    request = stub_request "PATH_INFO" => "/foo.xml"
-    assert_called(request, :parameters, times: 1, returns: {}) do
-      assert_equal [Mime[:xml]], request.formats
-    end
+    request = stub_request "PATH_INFO" => "/foo.xml", "QUERY_STRING" => ""
 
-    request = stub_request "PATH_INFO" => "/foo.123"
-    assert_called(request, :parameters, times: 1, returns: {}) do
-      assert_equal [Mime[:html]], request.formats
-    end
+    assert_equal [Mime[:xml]], request.formats
+
+    request = stub_request "PATH_INFO" => "/foo.123", "QUERY_STRING" => ""
+
+    assert_equal [Mime[:html]], request.formats
   end
 
   test "formats from accept headers have higher precedence than path extension" do
     request = stub_request "HTTP_ACCEPT" => "application/json",
-                           "PATH_INFO" => "/foo.xml"
+                           "PATH_INFO" => "/foo.xml",
+                           "QUERY_STRING" => ""
 
-    assert_called(request, :parameters, times: 1, returns: {}) do
-      assert_equal [Mime[:json]], request.formats
-    end
+    assert_equal [Mime[:json]], request.formats
   end
 end
 
@@ -997,15 +984,14 @@ end
 
 class RequestParameters < BaseRequestTest
   test "parameters" do
-    request = stub_request
+    request = stub_request "CONTENT_TYPE" => "application/json",
+                           "CONTENT_LENGTH" => 9,
+                           "RAW_POST_DATA" => '{"foo":1}',
+                           "QUERY_STRING" => "bar=2"
 
-    assert_called(request, :request_parameters, times: 2, returns: { "foo" => 1 }) do
-      assert_called(request, :query_parameters, times: 2, returns: { "bar" => 2 }) do
-        assert_equal({ "foo" => 1, "bar" => 2 }, request.parameters)
-        assert_equal({ "foo" => 1 }, request.request_parameters)
-        assert_equal({ "bar" => 2 }, request.query_parameters)
-      end
-    end
+    assert_equal({ "foo" => 1, "bar" => "2" }, request.parameters)
+    assert_equal({ "foo" => 1 }, request.request_parameters)
+    assert_equal({ "bar" => "2" }, request.query_parameters)
   end
 
   test "parameters not accessible after rack parse error" do
@@ -1248,8 +1234,8 @@ class RequestVariant < BaseRequestTest
   test "setting variant to a symbol" do
     @request.variant = :phone
 
-    assert @request.variant.phone?
-    assert_not @request.variant.tablet?
+    assert_predicate @request.variant, :phone?
+    assert_not_predicate @request.variant, :tablet?
     assert @request.variant.any?(:phone, :tablet)
     assert_not @request.variant.any?(:tablet, :desktop)
   end
@@ -1257,9 +1243,9 @@ class RequestVariant < BaseRequestTest
   test "setting variant to an array of symbols" do
     @request.variant = [:phone, :tablet]
 
-    assert @request.variant.phone?
-    assert @request.variant.tablet?
-    assert_not @request.variant.desktop?
+    assert_predicate @request.variant, :phone?
+    assert_predicate @request.variant, :tablet?
+    assert_not_predicate @request.variant, :desktop?
     assert @request.variant.any?(:tablet, :desktop)
     assert_not @request.variant.any?(:desktop, :watch)
   end
@@ -1267,8 +1253,8 @@ class RequestVariant < BaseRequestTest
   test "clearing variant" do
     @request.variant = nil
 
-    assert @request.variant.empty?
-    assert_not @request.variant.phone?
+    assert_empty @request.variant
+    assert_not_predicate @request.variant, :phone?
     assert_not @request.variant.any?(:phone, :tablet)
   end
 
@@ -1287,13 +1273,13 @@ end
 
 class RequestFormData < BaseRequestTest
   test "media_type is from the FORM_DATA_MEDIA_TYPES array" do
-    assert stub_request("CONTENT_TYPE" => "application/x-www-form-urlencoded").form_data?
-    assert stub_request("CONTENT_TYPE" => "multipart/form-data").form_data?
+    assert_predicate stub_request("CONTENT_TYPE" => "application/x-www-form-urlencoded"), :form_data?
+    assert_predicate stub_request("CONTENT_TYPE" => "multipart/form-data"), :form_data?
   end
 
   test "media_type is not from the FORM_DATA_MEDIA_TYPES array" do
-    assert !stub_request("CONTENT_TYPE" => "application/xml").form_data?
-    assert !stub_request("CONTENT_TYPE" => "multipart/related").form_data?
+    assert_not_predicate stub_request("CONTENT_TYPE" => "application/xml"), :form_data?
+    assert_not_predicate stub_request("CONTENT_TYPE" => "multipart/related"), :form_data?
   end
 
   test "no Content-Type header is provided and the request_method is POST" do
@@ -1301,6 +1287,21 @@ class RequestFormData < BaseRequestTest
 
     assert_equal "", request.media_type
     assert_equal "POST", request.request_method
-    assert !request.form_data?
+    assert_not_predicate request, :form_data?
+  end
+end
+
+class EarlyHintsRequestTest < BaseRequestTest
+  def setup
+    super
+    @env["rack.early_hints"] = lambda { |links| links }
+    @request = stub_request
+  end
+
+  test "when early hints is set in the env link headers are sent" do
+    early_hints = @request.send_early_hints("Link" => "</style.css>; rel=preload; as=style\n</script.js>; rel=preload")
+    expected_hints = { "Link" => "</style.css>; rel=preload; as=style\n</script.js>; rel=preload" }
+
+    assert_equal expected_hints, early_hints
   end
 end
diff --git a/actionpack/test/dispatch/response_test.rb b/actionpack/test/dispatch/response_test.rb
index a14083c6a2..0f37d074af 100644
--- a/actionpack/test/dispatch/response_test.rb
+++ b/actionpack/test/dispatch/response_test.rb
@@ -15,13 +15,13 @@ class ResponseTest < ActiveSupport::TestCase
       @response.await_commit
     }
     @response.commit!
-    assert @response.committed?
+    assert_predicate @response, :committed?
     assert t.join(0.5)
   end
 
   def test_stream_close
     @response.stream.close
-    assert @response.stream.closed?
+    assert_predicate @response.stream, :closed?
   end
 
   def test_stream_write
@@ -158,7 +158,7 @@ class ResponseTest < ActiveSupport::TestCase
       @response.status = c.to_s
       @response.set_header "Content-Length", "0"
       _, headers, _ = @response.to_a
-      assert !headers.has_key?("Content-Length"), "#{c} must not have a Content-Length header field"
+      assert_not headers.has_key?("Content-Length"), "#{c} must not have a Content-Length header field"
     end
   end
 
@@ -177,7 +177,7 @@ class ResponseTest < ActiveSupport::TestCase
       @response = ActionDispatch::Response.new
       @response.status = c.to_s
       _, headers, _ = @response.to_a
-      assert !headers.has_key?("Content-Type"), "#{c} should not have Content-Type header"
+      assert_not headers.has_key?("Content-Type"), "#{c} should not have Content-Type header"
     end
 
     [200, 302, 404, 500].each do |c|
@@ -191,7 +191,7 @@ class ResponseTest < ActiveSupport::TestCase
   test "does not include Status header" do
     @response.status = "200 OK"
     _, headers, _ = @response.to_a
-    assert !headers.has_key?("Status")
+    assert_not headers.has_key?("Status")
   end
 
   test "response code" do
@@ -257,9 +257,9 @@ class ResponseTest < ActiveSupport::TestCase
     }
     resp.to_a
 
-    assert resp.etag?
-    assert resp.weak_etag?
-    assert_not resp.strong_etag?
+    assert_predicate resp, :etag?
+    assert_predicate resp, :weak_etag?
+    assert_not_predicate resp, :strong_etag?
     assert_equal('W/"202cb962ac59075b964b07152d234b70"', resp.etag)
     assert_equal({ public: true }, resp.cache_control)
 
@@ -275,9 +275,9 @@ class ResponseTest < ActiveSupport::TestCase
     }
     resp.to_a
 
-    assert resp.etag?
-    assert_not resp.weak_etag?
-    assert resp.strong_etag?
+    assert_predicate resp, :etag?
+    assert_not_predicate resp, :weak_etag?
+    assert_predicate resp, :strong_etag?
     assert_equal('"202cb962ac59075b964b07152d234b70"', resp.etag)
   end
 
@@ -311,13 +311,16 @@ class ResponseTest < ActiveSupport::TestCase
     end
   end
 
-  test "read x_frame_options, x_content_type_options and x_xss_protection" do
+  test "read x_frame_options, x_content_type_options, x_xss_protection, x_download_options and x_permitted_cross_domain_policies, referrer_policy" do
     original_default_headers = ActionDispatch::Response.default_headers
     begin
       ActionDispatch::Response.default_headers = {
         "X-Frame-Options" => "DENY",
         "X-Content-Type-Options" => "nosniff",
-        "X-XSS-Protection" => "1;"
+        "X-XSS-Protection" => "1;",
+        "X-Download-Options" => "noopen",
+        "X-Permitted-Cross-Domain-Policies" => "none",
+        "Referrer-Policy" => "strict-origin-when-cross-origin"
       }
       resp = ActionDispatch::Response.create.tap { |response|
         response.body = "Hello"
@@ -327,6 +330,9 @@ class ResponseTest < ActiveSupport::TestCase
       assert_equal("DENY", resp.headers["X-Frame-Options"])
       assert_equal("nosniff", resp.headers["X-Content-Type-Options"])
       assert_equal("1;", resp.headers["X-XSS-Protection"])
+      assert_equal("noopen", resp.headers["X-Download-Options"])
+      assert_equal("none", resp.headers["X-Permitted-Cross-Domain-Policies"])
+      assert_equal("strict-origin-when-cross-origin", resp.headers["Referrer-Policy"])
     ensure
       ActionDispatch::Response.default_headers = original_default_headers
     end
@@ -350,7 +356,7 @@ class ResponseTest < ActiveSupport::TestCase
   end
 
   test "respond_to? accepts include_private" do
-    assert_not @response.respond_to?(:method_missing)
+    assert_not_respond_to @response, :method_missing
     assert @response.respond_to?(:method_missing, true)
   end
 
@@ -378,10 +384,10 @@ class ResponseTest < ActiveSupport::TestCase
     app = lambda { |env| @response.to_a }
     env = Rack::MockRequest.env_for("/")
 
-    status, headers, body = app.call(env)
+    _status, headers, _body = app.call(env)
     assert_nil headers["Content-Length"]
 
-    status, headers, body = Rack::ContentLength.new(app).call(env)
+    _status, headers, _body = Rack::ContentLength.new(app).call(env)
     assert_equal "5", headers["Content-Length"]
   end
 end
diff --git a/actionpack/test/dispatch/routing/inspector_test.rb b/actionpack/test/dispatch/routing/inspector_test.rb
index 438a918567..9150d5010b 100644
--- a/actionpack/test/dispatch/routing/inspector_test.rb
+++ b/actionpack/test/dispatch/routing/inspector_test.rb
@@ -3,6 +3,7 @@
 require "abstract_unit"
 require "rails/engine"
 require "action_dispatch/routing/inspector"
+require "io/console/size"
 
 class MountedRackApp
   def self.call(env)
@@ -15,16 +16,10 @@ end
 module ActionDispatch
   module Routing
     class RoutesInspectorTest < ActiveSupport::TestCase
-      def setup
+      setup do
         @set = ActionDispatch::Routing::RouteSet.new
       end
 
-      def draw(options = nil, &block)
-        @set.draw(&block)
-        inspector = ActionDispatch::Routing::RoutesInspector.new(@set.routes)
-        inspector.format(ActionDispatch::Routing::ConsoleFormatter.new, options).split("\n")
-      end
-
       def test_displaying_routes_for_engines
         engine = Class.new(Rails::Engine) do
           def self.inspect
@@ -305,7 +300,7 @@ module ActionDispatch
       end
 
       def test_routes_can_be_filtered
-        output = draw("posts") do
+        output = draw(grep: "posts") do
           resources :articles
           resources :posts
         end
@@ -321,8 +316,76 @@ module ActionDispatch
                       "          DELETE /posts/:id(.:format)      posts#destroy"], output
       end
 
+      def test_routes_when_expanded
+        previous_console_winsize = IO.console.winsize
+        IO.console.winsize = [0, 23]
+
+        engine = Class.new(Rails::Engine) do
+          def self.inspect
+            "Blog::Engine"
+          end
+        end
+        engine.routes.draw do
+          get "/cart", to: "cart#show"
+        end
+
+        output = draw(formatter: ActionDispatch::Routing::ConsoleFormatter::Expanded.new) do
+          get "/custom/assets", to: "custom_assets#show"
+          get "/custom/furnitures", to: "custom_furnitures#show"
+          mount engine => "/blog", :as => "blog"
+        end
+
+        assert_equal ["--[ Route 1 ]----------",
+                      "Prefix            | custom_assets",
+                      "Verb              | GET",
+                      "URI               | /custom/assets(.:format)",
+                      "Controller#Action | custom_assets#show",
+                      "--[ Route 2 ]----------",
+                      "Prefix            | custom_furnitures",
+                      "Verb              | GET",
+                      "URI               | /custom/furnitures(.:format)",
+                      "Controller#Action | custom_furnitures#show",
+                      "--[ Route 3 ]----------",
+                      "Prefix            | blog",
+                      "Verb              | ",
+                      "URI               | /blog",
+                      "Controller#Action | Blog::Engine",
+                      "",
+                      "[ Routes for Blog::Engine ]",
+                      "--[ Route 1 ]----------",
+                      "Prefix            | cart",
+                      "Verb              | GET",
+                      "URI               | /cart(.:format)",
+                      "Controller#Action | cart#show"], output
+      ensure
+        IO.console.winsize = previous_console_winsize
+      end
+
+      def test_no_routes_matched_filter_when_expanded
+        output = draw(grep: "rails/dummy", formatter: ActionDispatch::Routing::ConsoleFormatter::Expanded.new) do
+          get "photos/:id" => "photos#show", :id => /[A-Z]\d{5}/
+        end
+
+        assert_equal [
+          "No routes were found for this grep pattern.",
+          "For more information about routes, see the Rails guide: http://guides.rubyonrails.org/routing.html."
+        ], output
+      end
+
+      def test_not_routes_when_expanded
+        output = draw(grep: "rails/dummy", formatter: ActionDispatch::Routing::ConsoleFormatter::Expanded.new) {}
+
+        assert_equal [
+          "You don't have any routes defined!",
+          "",
+          "Please add some routes in config/routes.rb.",
+          "",
+          "For more information about routes, see the Rails guide: http://guides.rubyonrails.org/routing.html."
+        ], output
+      end
+
       def test_routes_can_be_filtered_with_namespaced_controllers
-        output = draw("admin/posts") do
+        output = draw(grep: "admin/posts") do
           resources :articles
           namespace :admin do
             resources :posts
@@ -370,24 +433,24 @@ module ActionDispatch
         end
 
         assert_equal [
-          "No routes were found for this controller",
+          "No routes were found for this controller.",
           "For more information about routes, see the Rails guide: http://guides.rubyonrails.org/routing.html."
         ], output
       end
 
       def test_no_routes_matched_filter
-        output = draw("rails/dummy") do
+        output = draw(grep: "rails/dummy") do
           get "photos/:id" => "photos#show", :id => /[A-Z]\d{5}/
         end
 
         assert_equal [
-          "No routes were found for this controller",
+          "No routes were found for this grep pattern.",
           "For more information about routes, see the Rails guide: http://guides.rubyonrails.org/routing.html."
         ], output
       end
 
       def test_no_routes_were_defined
-        output = draw("Rails::DummyController") {}
+        output = draw(grep: "Rails::DummyController") {}
 
         assert_equal [
           "You don't have any routes defined!",
@@ -420,6 +483,13 @@ module ActionDispatch
           "custom_assets GET  /custom/assets(.:format) custom_assets#show",
         ], output
       end
+
+      private
+        def draw(formatter: ActionDispatch::Routing::ConsoleFormatter::Sheet.new, **options, &block)
+          @set.draw(&block)
+          inspector = ActionDispatch::Routing::RoutesInspector.new(@set.routes)
+          inspector.format(formatter, options).split("\n")
+        end
     end
   end
 end
diff --git a/actionpack/test/dispatch/routing_assertions_test.rb b/actionpack/test/dispatch/routing_assertions_test.rb
index e492a56653..009b6d9bc3 100644
--- a/actionpack/test/dispatch/routing_assertions_test.rb
+++ b/actionpack/test/dispatch/routing_assertions_test.rb
@@ -1,14 +1,40 @@
 # frozen_string_literal: true
 
 require "abstract_unit"
+require "rails/engine"
 require "controller/fake_controllers"
 
 class SecureArticlesController < ArticlesController; end
 class BlockArticlesController < ArticlesController; end
 class QueryArticlesController < ArticlesController; end
 
+class SecureBooksController < BooksController; end
+class BlockBooksController < BooksController; end
+class QueryBooksController < BooksController; end
+
 class RoutingAssertionsTest < ActionController::TestCase
   def setup
+    engine = Class.new(Rails::Engine) do
+      def self.name
+        "blog_engine"
+      end
+    end
+    engine.routes.draw do
+      resources :books
+
+      scope "secure", constraints: { protocol: "https://" } do
+        resources :books, controller: "secure_books"
+      end
+
+      scope "block", constraints: lambda { |r| r.ssl? } do
+        resources :books, controller: "block_books"
+      end
+
+      scope "query", constraints: lambda { |r| r.params[:use_query] == "true" } do
+        resources :books, controller: "query_books"
+      end
+    end
+
     @routes = ActionDispatch::Routing::RouteSet.new
     @routes.draw do
       resources :articles
@@ -24,6 +50,10 @@ class RoutingAssertionsTest < ActionController::TestCase
       scope "query", constraints: lambda { |r| r.params[:use_query] == "true" } do
         resources :articles, controller: "query_articles"
       end
+
+      mount engine => "/shelf"
+
+      get "/shelf/foo", controller: "query_articles", action: "index"
     end
   end
 
@@ -83,6 +113,53 @@ class RoutingAssertionsTest < ActionController::TestCase
     assert_match err.message, "This is a really bad msg"
   end
 
+  def test_assert_recognizes_with_engine
+    assert_recognizes({ controller: "books", action: "index" }, "/shelf/books")
+    assert_recognizes({ controller: "books", action: "show", id: "1" }, "/shelf/books/1")
+  end
+
+  def test_assert_recognizes_with_engine_and_extras
+    assert_recognizes({ controller: "books", action: "index", page: "1" }, "/shelf/books", page: "1")
+  end
+
+  def test_assert_recognizes_with_engine_and_method
+    assert_recognizes({ controller: "books", action: "create" }, { path: "/shelf/books", method: :post })
+    assert_recognizes({ controller: "books", action: "update", id: "1" }, { path: "/shelf/books/1", method: :put })
+  end
+
+  def test_assert_recognizes_with_engine_and_hash_constraint
+    assert_raise(Assertion) do
+      assert_recognizes({ controller: "secure_books", action: "index" }, "http://test.host/shelf/secure/books")
+    end
+    assert_recognizes({ controller: "secure_books", action: "index", protocol: "https://" }, "https://test.host/shelf/secure/books")
+  end
+
+  def test_assert_recognizes_with_engine_and_block_constraint
+    assert_raise(Assertion) do
+      assert_recognizes({ controller: "block_books", action: "index" }, "http://test.host/shelf/block/books")
+    end
+    assert_recognizes({ controller: "block_books", action: "index" }, "https://test.host/shelf/block/books")
+  end
+
+  def test_assert_recognizes_with_engine_and_query_constraint
+    assert_raise(Assertion) do
+      assert_recognizes({ controller: "query_books", action: "index", use_query: "false" }, "/shelf/query/books", use_query: "false")
+    end
+    assert_recognizes({ controller: "query_books", action: "index", use_query: "true" }, "/shelf/query/books", use_query: "true")
+  end
+
+  def test_assert_recognizes_raises_message_with_engine
+    err = assert_raise(Assertion) do
+      assert_recognizes({ controller: "secure_books", action: "index" }, "http://test.host/shelf/secure/books", {}, "This is a really bad msg")
+    end
+
+    assert_match err.message, "This is a really bad msg"
+  end
+
+  def test_assert_recognizes_continue_to_recoginize_after_it_tried_engines
+    assert_recognizes({ controller: "query_articles", action: "index" }, "/shelf/foo")
+  end
+
   def test_assert_routing
     assert_routing("/articles", controller: "articles", action: "index")
   end
diff --git a/actionpack/test/dispatch/routing_test.rb b/actionpack/test/dispatch/routing_test.rb
index 446b65a9b9..5efbe5b553 100644
--- a/actionpack/test/dispatch/routing_test.rb
+++ b/actionpack/test/dispatch/routing_test.rb
@@ -3,6 +3,7 @@
 require "erb"
 require "abstract_unit"
 require "controller/fake_controllers"
+require "active_support/messages/rotation_configuration"
 
 class TestRoutingMapper < ActionDispatch::IntegrationTest
   SprocketsApp = lambda { |env|
@@ -3152,7 +3153,7 @@ class TestRoutingMapper < ActionDispatch::IntegrationTest
       after = has_named_route?(:hello)
     end
 
-    assert !before, "expected to not have named route :hello before route definition"
+    assert_not before, "expected to not have named route :hello before route definition"
     assert after, "expected to have named route :hello after route definition"
   end
 
@@ -3165,7 +3166,7 @@ class TestRoutingMapper < ActionDispatch::IntegrationTest
       end
     end
 
-    assert !respond_to?(:routes_no_collision_path)
+    assert_not respond_to?(:routes_no_collision_path)
   end
 
   def test_controller_name_with_leading_slash_raise_error
@@ -3312,7 +3313,7 @@ class TestRoutingMapper < ActionDispatch::IntegrationTest
     end
 
     get "/search"
-    assert !@request.params[:action].frozen?
+    assert_not_predicate @request.params[:action], :frozen?
   end
 
   def test_multiple_positional_args_with_the_same_name
@@ -4224,7 +4225,7 @@ class TestGlobRoutingMapper < ActionDispatch::IntegrationTest
     end
   end
 
-  #include Routes.url_helpers
+  # include Routes.url_helpers
   APP = build_app Routes
   def app; APP end
 
@@ -4266,7 +4267,7 @@ class TestOptimizedNamedRoutes < ActionDispatch::IntegrationTest
   def app; APP end
 
   test "enabled when not mounted and default_url_options is empty" do
-    assert Routes.url_helpers.optimize_routes_generation?
+    assert_predicate Routes.url_helpers, :optimize_routes_generation?
   end
 
   test "named route called as singleton method" do
@@ -4499,7 +4500,7 @@ class TestPortConstraints < ActionDispatch::IntegrationTest
 
       get "/integer", to: ok, constraints: { port: 8080  }
       get "/string",  to: ok, constraints: { port: "8080" }
-      get "/array",   to: ok, constraints: { port: [8080] }
+      get "/array/:idx",   to: ok, constraints: { port: [8080], idx: %w[first last] }
       get "/regexp",  to: ok, constraints: { port: /8080/ }
     end
   end
@@ -4528,7 +4529,10 @@ class TestPortConstraints < ActionDispatch::IntegrationTest
     get "http://www.example.com/array"
     assert_response :not_found
 
-    get "http://www.example.com:8080/array"
+    get "http://www.example.com:8080/array/middle"
+    assert_response :not_found
+
+    get "http://www.example.com:8080/array/first"
     assert_response :success
   end
 
@@ -4947,6 +4951,7 @@ end
 class FlashRedirectTest < ActionDispatch::IntegrationTest
   SessionKey = "_myapp_session"
   Generator  = ActiveSupport::LegacyKeyGenerator.new("b3c631c314c0bbca50c1b2843150fe33")
+  Rotations  = ActiveSupport::Messages::RotationConfiguration.new
 
   class KeyGeneratorMiddleware
     def initialize(app)
@@ -4955,6 +4960,8 @@ class FlashRedirectTest < ActionDispatch::IntegrationTest
 
     def call(env)
       env["action_dispatch.key_generator"] ||= Generator
+      env["action_dispatch.cookies_rotations"] ||= Rotations
+
       @app.call(env)
     end
   end
@@ -5053,3 +5060,40 @@ class TestRecognizePath < ActionDispatch::IntegrationTest
       Routes.recognize_path(*args)
     end
 end
+
+class TestRelativeUrlRootGeneration < ActionDispatch::IntegrationTest
+  config = ActionDispatch::Routing::RouteSet::Config.new("/blog", false)
+
+  stub_controllers(config) do |routes|
+    Routes = routes
+
+    routes.draw do
+      get "/", to: "posts#index", as: :posts
+      get "/:id", to: "posts#show", as: :post
+    end
+  end
+
+  include Routes.url_helpers
+
+  APP = build_app Routes
+
+  def app
+    APP
+  end
+
+  def test_url_helpers
+    assert_equal "/blog/", posts_path({})
+    assert_equal "/blog/", Routes.url_helpers.posts_path({})
+
+    assert_equal "/blog/1", post_path(id: "1")
+    assert_equal "/blog/1", Routes.url_helpers.post_path(id: "1")
+  end
+
+  def test_optimized_url_helpers
+    assert_equal "/blog/", posts_path
+    assert_equal "/blog/", Routes.url_helpers.posts_path
+
+    assert_equal "/blog/1", post_path("1")
+    assert_equal "/blog/1", Routes.url_helpers.post_path("1")
+  end
+end
diff --git a/actionpack/test/dispatch/session/cookie_store_test.rb b/actionpack/test/dispatch/session/cookie_store_test.rb
index 6517cf4c99..e34426a471 100644
--- a/actionpack/test/dispatch/session/cookie_store_test.rb
+++ b/actionpack/test/dispatch/session/cookie_store_test.rb
@@ -3,14 +3,19 @@
 require "abstract_unit"
 require "stringio"
 require "active_support/key_generator"
+require "active_support/messages/rotation_configuration"
 
 class CookieStoreTest < ActionDispatch::IntegrationTest
   SessionKey = "_myapp_session"
   SessionSecret = "b3c631c314c0bbca50c1b2843150fe33"
-  Generator = ActiveSupport::LegacyKeyGenerator.new(SessionSecret)
+  SessionSalt   = "authenticated encrypted cookie"
 
-  Verifier = ActiveSupport::MessageVerifier.new(SessionSecret, digest: "SHA1")
-  SignedBar = Verifier.generate(foo: "bar", session_id: SecureRandom.hex(16))
+  Generator = ActiveSupport::KeyGenerator.new(SessionSecret, iterations: 1000)
+  Rotations = ActiveSupport::Messages::RotationConfiguration.new
+
+  Encryptor = ActiveSupport::MessageEncryptor.new(
+    Generator.generate_key(SessionSalt, 32), cipher: "aes-256-gcm", serializer: Marshal
+  )
 
   class TestController < ActionController::Base
     def no_session_access
@@ -23,12 +28,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
 
     def set_session_value
       session[:foo] = "bar"
-      render plain: Rack::Utils.escape(Verifier.generate(session.to_hash))
-    end
-
-    def set_session_value_expires_in_five_hours
-      session[:foo] = "bar"
-      render plain: Rack::Utils.escape(Verifier.generate(session.to_hash, expires_in: 5.hours))
+      render body: nil
     end
 
     def get_session_value
@@ -70,19 +70,35 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
     end
   end
 
+  def parse_cookie_from_header
+    cookie_matches = headers["Set-Cookie"].match(/#{SessionKey}=([^;]+)/)
+    cookie_matches && cookie_matches[1]
+  end
+
+  def assert_session_cookie(cookie_string, contents)
+    assert_includes headers["Set-Cookie"], cookie_string
+
+    session_value = parse_cookie_from_header
+    session_data = Encryptor.decrypt_and_verify(Rack::Utils.unescape(session_value)) rescue nil
+
+    assert_not_nil session_data, "session failed to decrypt"
+    assert_equal session_data.slice(*contents.keys), contents
+  end
+
   def test_setting_session_value
     with_test_route_set do
       get "/set_session_value"
+
       assert_response :success
-      assert_equal "_myapp_session=#{response.body}; path=/; HttpOnly",
-        headers["Set-Cookie"]
+      assert_session_cookie "path=/; HttpOnly", "foo" => "bar"
     end
   end
 
   def test_getting_session_value
     with_test_route_set do
-      cookies[SessionKey] = SignedBar
+      get "/set_session_value"
       get "/get_session_value"
+
       assert_response :success
       assert_equal 'foo: "bar"', response.body
     end
@@ -90,8 +106,9 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
 
   def test_getting_session_id
     with_test_route_set do
-      cookies[SessionKey] = SignedBar
+      get "/set_session_value"
       get "/persistent_session_id"
+
       assert_response :success
       assert_equal 32, response.body.size
       session_id = response.body
@@ -104,8 +121,12 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
 
   def test_disregards_tampered_sessions
     with_test_route_set do
-      cookies[SessionKey] = "BAh7BjoIZm9vIghiYXI%3D--123456780"
+      encryptor = ActiveSupport::MessageEncryptor.new("A" * 32, cipher: "aes-256-gcm", serializer: Marshal)
+
+      cookies[SessionKey] = encryptor.encrypt_and_sign("foo" => "bar", "session_id" => "abc")
+
       get "/get_session_value"
+
       assert_response :success
       assert_equal "foo: nil", response.body
     end
@@ -133,19 +154,19 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
   def test_does_set_secure_cookies_over_https
     with_test_route_set(secure: true) do
       get "/set_session_value", headers: { "HTTPS" => "on" }
+
       assert_response :success
-      assert_equal "_myapp_session=#{response.body}; path=/; secure; HttpOnly",
-        headers["Set-Cookie"]
+      assert_session_cookie "path=/; secure; HttpOnly", "foo" => "bar"
     end
   end
 
   # {:foo=>#<SessionAutoloadTest::Foo bar:"baz">, :session_id=>"ce8b0752a6ab7c7af3cdb8a80e6b9e46"}
-  SignedSerializedCookie = "BAh7BzoIZm9vbzodU2Vzc2lvbkF1dG9sb2FkVGVzdDo6Rm9vBjoJQGJhciIIYmF6Og9zZXNzaW9uX2lkIiVjZThiMDc1MmE2YWI3YzdhZjNjZGI4YTgwZTZiOWU0Ng==--2bf3af1ae8bd4e52b9ac2099258ace0c380e601c"
+  EncryptedSerializedCookie = "9RZ2Fij0qLveUwM4s+CCjGqhpjyUC8jiBIf/AiBr9M3TB8xh2vQZtvSOMfN3uf6oYbbpIDHAcOFIEl69FcW1ozQYeSrCLonYCazoh34ZdYskIQfGwCiSYleVXG1OD9Z4jFqeVArw4Ewm0paOOPLbN1rc6A==--I359v/KWdZ1ok0ey--JFFhuPOY7WUo6tB/eP05Aw=="
 
   def test_deserializes_unloaded_classes_on_get_id
     with_test_route_set do
       with_autoload_path "session_autoload_test" do
-        cookies[SessionKey] = SignedSerializedCookie
+        cookies[SessionKey] = EncryptedSerializedCookie
         get "/get_session_id"
         assert_response :success
         assert_equal "id: ce8b0752a6ab7c7af3cdb8a80e6b9e46", response.body, "should auto-load unloaded class"
@@ -156,7 +177,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
   def test_deserializes_unloaded_classes_on_get_value
     with_test_route_set do
       with_autoload_path "session_autoload_test" do
-        cookies[SessionKey] = SignedSerializedCookie
+        cookies[SessionKey] = EncryptedSerializedCookie
         get "/get_session_value"
         assert_response :success
         assert_equal 'foo: #<SessionAutoloadTest::Foo bar:"baz">', response.body, "should auto-load unloaded class"
@@ -195,8 +216,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
       get "/set_session_value"
       assert_response :success
       session_payload = response.body
-      assert_equal "_myapp_session=#{response.body}; path=/; HttpOnly",
-        headers["Set-Cookie"]
+      assert_session_cookie "path=/; HttpOnly", "foo" => "bar"
 
       get "/call_reset_session"
       assert_response :success
@@ -214,8 +234,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
     with_test_route_set do
       get "/set_session_value"
       assert_response :success
-      assert_equal "_myapp_session=#{response.body}; path=/; HttpOnly",
-        headers["Set-Cookie"]
+      assert_session_cookie "path=/; HttpOnly", "foo" => "bar"
 
       get "/get_class_after_reset_session"
       assert_response :success
@@ -237,8 +256,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
     with_test_route_set do
       get "/set_session_value"
       assert_response :success
-      assert_equal "_myapp_session=#{response.body}; path=/; HttpOnly",
-        headers["Set-Cookie"]
+      assert_session_cookie "path=/; HttpOnly", "foo" => "bar"
 
       get "/call_session_clear"
       assert_response :success
@@ -251,7 +269,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
 
   def test_persistent_session_id
     with_test_route_set do
-      cookies[SessionKey] = SignedBar
+      get "/set_session_value"
       get "/persistent_session_id"
       assert_response :success
       assert_equal 32, response.body.size
@@ -266,8 +284,7 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
 
   def test_setting_session_id_to_nil_is_respected
     with_test_route_set do
-      cookies[SessionKey] = SignedBar
-
+      get "/set_session_value"
       get "/get_session_id"
       sid = response.body
       assert_equal 36, sid.size
@@ -281,31 +298,53 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
     with_test_route_set(expire_after: 5.hours) do
       # First request accesses the session
       time = Time.local(2008, 4, 24)
-      cookie_body = nil
 
       Time.stub :now, time do
         expected_expiry = (time + 5.hours).gmtime.strftime("%a, %d %b %Y %H:%M:%S -0000")
 
-        cookies[SessionKey] = SignedBar
+        get "/set_session_value"
 
-        get "/set_session_value_expires_in_five_hours"
         assert_response :success
-
-        cookie_body = response.body
-        assert_equal "_myapp_session=#{cookie_body}; path=/; expires=#{expected_expiry}; HttpOnly",
-          headers["Set-Cookie"]
+        assert_session_cookie "path=/; expires=#{expected_expiry}; HttpOnly", "foo" => "bar"
       end
 
       # Second request does not access the session
-      time = Time.local(2008, 4, 25)
+      time = time + 3.hours
       Time.stub :now, time do
         expected_expiry = (time + 5.hours).gmtime.strftime("%a, %d %b %Y %H:%M:%S -0000")
 
         get "/no_session_access"
+
         assert_response :success
+        assert_session_cookie "path=/; expires=#{expected_expiry}; HttpOnly", "foo" => "bar"
+      end
+    end
+  end
+
+  def test_session_store_with_expire_after_does_not_accept_expired_session
+    with_test_route_set(expire_after: 5.hours) do
+      # First request accesses the session
+      time = Time.local(2017, 11, 12)
+
+      Time.stub :now, time do
+        expected_expiry = (time + 5.hours).gmtime.strftime("%a, %d %b %Y %H:%M:%S -0000")
+
+        get "/set_session_value"
+        get "/get_session_value"
 
-        assert_equal "_myapp_session=#{cookies[SessionKey]}; path=/; expires=#{expected_expiry}; HttpOnly",
-          headers["Set-Cookie"]
+        assert_response :success
+        assert_equal 'foo: "bar"', response.body
+        assert_session_cookie "path=/; expires=#{expected_expiry}; HttpOnly", "foo" => "bar"
+      end
+
+      # Second request is beyond the expiry time and the session is invalidated
+      time += 5.hours + 1.minute
+
+      Time.stub :now, time do
+        get "/get_session_value"
+
+        assert_response :success
+        assert_equal "foo: nil", response.body
       end
     end
   end
@@ -345,7 +384,15 @@ class CookieStoreTest < ActionDispatch::IntegrationTest
     def get(path, *args)
       args[0] ||= {}
       args[0][:headers] ||= {}
-      args[0][:headers]["action_dispatch.key_generator"] ||= Generator
+      args[0][:headers].tap do |config|
+        config["action_dispatch.secret_key_base"] = SessionSecret
+        config["action_dispatch.authenticated_encrypted_cookie_salt"] = SessionSalt
+        config["action_dispatch.use_authenticated_cookie_encryption"] = true
+
+        config["action_dispatch.key_generator"] ||= Generator
+        config["action_dispatch.cookies_rotations"] ||= Rotations
+      end
+
       super(path, *args)
     end
 
diff --git a/actionpack/test/dispatch/ssl_test.rb b/actionpack/test/dispatch/ssl_test.rb
index 8ac9502af9..baf46e7c7e 100644
--- a/actionpack/test/dispatch/ssl_test.rb
+++ b/actionpack/test/dispatch/ssl_test.rb
@@ -98,8 +98,8 @@ class RedirectSSLTest < SSLTest
 end
 
 class StrictTransportSecurityTest < SSLTest
-  EXPECTED = "max-age=15552000"
-  EXPECTED_WITH_SUBDOMAINS = "max-age=15552000; includeSubDomains"
+  EXPECTED = "max-age=31536000"
+  EXPECTED_WITH_SUBDOMAINS = "max-age=31536000; includeSubDomains"
 
   def assert_hsts(expected, url: "https://example.org", hsts: { subdomains: true }, headers: {})
     self.app = build_app ssl_options: { hsts: hsts }, headers: headers
@@ -208,6 +208,14 @@ class SecureCookiesTest < SSLTest
     assert_cookies(*DEFAULT.split("\n"))
   end
 
+  def test_cookies_as_not_secure_with_exclude
+    excluding = { exclude: -> request { request.domain =~ /example/ } }
+    get headers: { "Set-Cookie" => DEFAULT }, ssl_options: { redirect: excluding }
+
+    assert_cookies(*DEFAULT.split("\n"))
+    assert_response :ok
+  end
+
   def test_no_cookies
     get
     assert_nil response.headers["Set-Cookie"]
diff --git a/actionpack/test/dispatch/static_test.rb b/actionpack/test/dispatch/static_test.rb
index 0bdff68692..6b69cd9999 100644
--- a/actionpack/test/dispatch/static_test.rb
+++ b/actionpack/test/dispatch/static_test.rb
@@ -71,7 +71,16 @@ module StaticTests
   end
 
   def test_served_static_file_with_non_english_filename
-    assert_html "means hello in Japanese\n", get("/foo/#{Rack::Utils.escape("こんにちは.html")}")
+    assert_html "means hello in Japanese\n", get("/foo/%E3%81%93%E3%82%93%E3%81%AB%E3%81%A1%E3%81%AF.html")
+  end
+
+  def test_served_gzipped_static_file_with_non_english_filename
+    response = get("/foo/%E3%81%95%E3%82%88%E3%81%86%E3%81%AA%E3%82%89.html", "HTTP_ACCEPT_ENCODING" => "gzip")
+
+    assert_gzip  "/foo/さようなら.html", response
+    assert_equal "text/html",          response.headers["Content-Type"]
+    assert_equal "Accept-Encoding",    response.headers["Vary"]
+    assert_equal "gzip",               response.headers["Content-Encoding"]
   end
 
   def test_serves_static_file_with_exclamation_mark_in_filename
diff --git a/actionpack/test/dispatch/system_testing/driver_test.rb b/actionpack/test/dispatch/system_testing/driver_test.rb
index e6f9353b22..a824ee0c84 100644
--- a/actionpack/test/dispatch/system_testing/driver_test.rb
+++ b/actionpack/test/dispatch/system_testing/driver_test.rb
@@ -12,7 +12,24 @@ class DriverTest < ActiveSupport::TestCase
   test "initializing the driver with a browser" do
     driver = ActionDispatch::SystemTesting::Driver.new(:selenium, using: :chrome, screen_size: [1400, 1400], options: { url: "http://example.com/wd/hub" })
     assert_equal :selenium, driver.instance_variable_get(:@name)
-    assert_equal :chrome, driver.instance_variable_get(:@browser)
+    assert_equal :chrome, driver.instance_variable_get(:@browser).name
+    assert_nil driver.instance_variable_get(:@browser).options
+    assert_equal [1400, 1400], driver.instance_variable_get(:@screen_size)
+    assert_equal ({ url: "http://example.com/wd/hub" }), driver.instance_variable_get(:@options)
+  end
+
+  test "initializing the driver with a headless chrome" do
+    driver = ActionDispatch::SystemTesting::Driver.new(:selenium, using: :headless_chrome, screen_size: [1400, 1400], options: { url: "http://example.com/wd/hub" })
+    assert_equal :selenium, driver.instance_variable_get(:@name)
+    assert_equal :headless_chrome, driver.instance_variable_get(:@browser).name
+    assert_equal [1400, 1400], driver.instance_variable_get(:@screen_size)
+    assert_equal ({ url: "http://example.com/wd/hub" }), driver.instance_variable_get(:@options)
+  end
+
+  test "initializing the driver with a headless firefox" do
+    driver = ActionDispatch::SystemTesting::Driver.new(:selenium, using: :headless_firefox, screen_size: [1400, 1400], options: { url: "http://example.com/wd/hub" })
+    assert_equal :selenium, driver.instance_variable_get(:@name)
+    assert_equal :headless_firefox, driver.instance_variable_get(:@browser).name
     assert_equal [1400, 1400], driver.instance_variable_get(:@screen_size)
     assert_equal ({ url: "http://example.com/wd/hub" }), driver.instance_variable_get(:@options)
   end
diff --git a/actionpack/test/dispatch/system_testing/screenshot_helper_test.rb b/actionpack/test/dispatch/system_testing/screenshot_helper_test.rb
index c8711f22d8..de79c05657 100644
--- a/actionpack/test/dispatch/system_testing/screenshot_helper_test.rb
+++ b/actionpack/test/dispatch/system_testing/screenshot_helper_test.rb
@@ -8,26 +8,64 @@ class ScreenshotHelperTest < ActiveSupport::TestCase
   test "image path is saved in tmp directory" do
     new_test = DrivenBySeleniumWithChrome.new("x")
 
-    assert_equal "tmp/screenshots/x.png", new_test.send(:image_path)
+    Rails.stub :root, Pathname.getwd do
+      assert_equal Rails.root.join("tmp/screenshots/x.png").to_s, new_test.send(:image_path)
+    end
   end
 
   test "image path includes failures text if test did not pass" do
     new_test = DrivenBySeleniumWithChrome.new("x")
 
-    new_test.stub :passed?, false do
-      assert_equal "tmp/screenshots/failures_x.png", new_test.send(:image_path)
+    Rails.stub :root, Pathname.getwd do
+      new_test.stub :passed?, false do
+        assert_equal Rails.root.join("tmp/screenshots/failures_x.png").to_s, new_test.send(:image_path)
+      end
     end
   end
 
   test "image path does not include failures text if test skipped" do
     new_test = DrivenBySeleniumWithChrome.new("x")
 
-    new_test.stub :passed?, false do
-      new_test.stub :skipped?, true do
-        assert_equal "tmp/screenshots/x.png", new_test.send(:image_path)
+    Rails.stub :root, Pathname.getwd do
+      new_test.stub :passed?, false do
+        new_test.stub :skipped?, true do
+          assert_equal Rails.root.join("tmp/screenshots/x.png").to_s, new_test.send(:image_path)
+        end
       end
     end
   end
+
+  test "defaults to simple output for the screenshot" do
+    new_test = DrivenBySeleniumWithChrome.new("x")
+    assert_equal "simple", new_test.send(:output_type)
+  end
+
+  test "display_image return artifact format when specify RAILS_SYSTEM_TESTING_SCREENSHOT environment" do
+    begin
+      original_output_type = ENV["RAILS_SYSTEM_TESTING_SCREENSHOT"]
+      ENV["RAILS_SYSTEM_TESTING_SCREENSHOT"] = "artifact"
+
+      new_test = DrivenBySeleniumWithChrome.new("x")
+
+      assert_equal "artifact", new_test.send(:output_type)
+
+      Rails.stub :root, Pathname.getwd do
+        new_test.stub :passed?, false do
+          assert_match %r|url=artifact://.+?tmp/screenshots/failures_x\.png|, new_test.send(:display_image)
+        end
+      end
+    ensure
+      ENV["RAILS_SYSTEM_TESTING_SCREENSHOT"] = original_output_type
+    end
+  end
+
+  test "image path returns the absolute path from root" do
+    new_test = DrivenBySeleniumWithChrome.new("x")
+
+    Rails.stub :root, Pathname.getwd.join("..") do
+      assert_equal Rails.root.join("tmp/screenshots/x.png").to_s, new_test.send(:image_path)
+    end
+  end
 end
 
 class RackTestScreenshotsTest < DrivenByRackTest
diff --git a/actionpack/test/dispatch/system_testing/server_test.rb b/actionpack/test/dispatch/system_testing/server_test.rb
index ed65d93e49..740e90a4da 100644
--- a/actionpack/test/dispatch/system_testing/server_test.rb
+++ b/actionpack/test/dispatch/system_testing/server_test.rb
@@ -6,14 +6,27 @@ require "action_dispatch/system_testing/server"
 
 class ServerTest < ActiveSupport::TestCase
   setup do
+    @old_capybara_server = Capybara.server
+  end
+
+  test "port is always included" do
+    ActionDispatch::SystemTesting::Server.new.run
+    assert Capybara.always_include_port, "expected Capybara.always_include_port to be true"
+  end
+
+  test "server is changed from `default` to `puma`" do
+    Capybara.server = :default
     ActionDispatch::SystemTesting::Server.new.run
+    assert_not_equal Capybara.server, Capybara.servers[:default]
   end
 
-  test "initializing the server port" do
-    assert_includes Capybara.servers, :rails_puma
+  test "server is not changed to `puma` when is different than default" do
+    Capybara.server = :webrick
+    ActionDispatch::SystemTesting::Server.new.run
+    assert_equal Capybara.server, Capybara.servers[:webrick]
   end
 
-  test "port is always included" do
-    assert Capybara.always_include_port, "expected Capybara.always_include_port to be true"
+  teardown do
+    Capybara.server = @old_capybara_server
   end
 end
diff --git a/actionpack/test/dispatch/system_testing/system_test_case_test.rb b/actionpack/test/dispatch/system_testing/system_test_case_test.rb
index b60ec559ae..b078a5abc5 100644
--- a/actionpack/test/dispatch/system_testing/system_test_case_test.rb
+++ b/actionpack/test/dispatch/system_testing/system_test_case_test.rb
@@ -22,6 +22,18 @@ class SetDriverToSeleniumTest < DrivenBySeleniumWithChrome
   end
 end
 
+class SetDriverToSeleniumHeadlessChromeTest < DrivenBySeleniumWithHeadlessChrome
+  test "uses selenium headless chrome" do
+    assert_equal :selenium, Capybara.current_driver
+  end
+end
+
+class SetDriverToSeleniumHeadlessFirefoxTest < DrivenBySeleniumWithHeadlessFirefox
+  test "uses selenium headless firefox" do
+    assert_equal :selenium, Capybara.current_driver
+  end
+end
+
 class SetHostTest < DrivenByRackTest
   test "sets default host" do
     assert_equal "http://127.0.0.1", Capybara.app_host
@@ -36,32 +48,37 @@ end
 
 class UndefMethodsTest < DrivenBySeleniumWithChrome
   test "get" do
-    assert_raise NoMethodError do
+    exception = assert_raise NoMethodError do
       get "http://example.com"
     end
+    assert_equal "System tests cannot make direct requests via #get; use #visit and #click_on instead. See http://www.rubydoc.info/github/teamcapybara/capybara/master#The_DSL for more information.", exception.message
   end
 
   test "post" do
-    assert_raise NoMethodError do
+    exception = assert_raise NoMethodError do
       post "http://example.com"
     end
+    assert_equal "System tests cannot make direct requests via #post; use #visit and #click_on instead. See http://www.rubydoc.info/github/teamcapybara/capybara/master#The_DSL for more information.", exception.message
   end
 
   test "put" do
-    assert_raise NoMethodError do
+    exception = assert_raise NoMethodError do
       put "http://example.com"
     end
+    assert_equal "System tests cannot make direct requests via #put; use #visit and #click_on instead. See http://www.rubydoc.info/github/teamcapybara/capybara/master#The_DSL for more information.", exception.message
   end
 
   test "patch" do
-    assert_raise NoMethodError do
+    exception = assert_raise NoMethodError do
       patch "http://example.com"
     end
+    assert_equal "System tests cannot make direct requests via #patch; use #visit and #click_on instead. See http://www.rubydoc.info/github/teamcapybara/capybara/master#The_DSL for more information.", exception.message
   end
 
   test "delete" do
-    assert_raise NoMethodError do
+    exception = assert_raise NoMethodError do
       delete "http://example.com"
     end
+    assert_equal "System tests cannot make direct requests via #delete; use #visit and #click_on instead. See http://www.rubydoc.info/github/teamcapybara/capybara/master#The_DSL for more information.", exception.message
   end
 end
diff --git a/actionpack/test/dispatch/uploaded_file_test.rb b/actionpack/test/dispatch/uploaded_file_test.rb
index 4673d7cc11..5a584b12e5 100644
--- a/actionpack/test/dispatch/uploaded_file_test.rb
+++ b/actionpack/test/dispatch/uploaded_file_test.rb
@@ -18,7 +18,7 @@ module ActionDispatch
     def test_filename_is_different_object
       file_str = "foo"
       uf = Http::UploadedFile.new(filename: file_str, tempfile: Object.new)
-      assert_not_equal file_str.object_id , uf.original_filename.object_id
+      assert_not_equal file_str.object_id, uf.original_filename.object_id
     end
 
     def test_filename_should_be_in_utf_8
@@ -100,14 +100,14 @@ module ActionDispatch
     def test_delegate_eof_to_tempfile
       tf = Class.new { def eof?; true end; }
       uf = Http::UploadedFile.new(tempfile: tf.new)
-      assert uf.eof?
+      assert_predicate uf, :eof?
     end
 
     def test_respond_to?
       tf = Class.new { def read; yield end }
       uf = Http::UploadedFile.new(tempfile: tf.new)
-      assert uf.respond_to?(:headers), "responds to headers"
-      assert uf.respond_to?(:read), "responds to read"
+      assert_respond_to uf, :headers
+      assert_respond_to uf, :read
     end
   end
 end
diff --git a/actionpack/test/fixtures/functional_caching/_formatted_partial.html.erb b/actionpack/test/fixtures/functional_caching/_formatted_partial.html.erb
new file mode 100644
index 0000000000..aad73c0d6b
--- /dev/null
+++ b/actionpack/test/fixtures/functional_caching/_formatted_partial.html.erb
@@ -0,0 +1 @@
+<p>Hello!</p>
diff --git a/actionpack/test/fixtures/functional_caching/xml_fragment_cached_with_html_partial.xml.builder b/actionpack/test/fixtures/functional_caching/xml_fragment_cached_with_html_partial.xml.builder
new file mode 100644
index 0000000000..2bdda3af18
--- /dev/null
+++ b/actionpack/test/fixtures/functional_caching/xml_fragment_cached_with_html_partial.xml.builder
@@ -0,0 +1,5 @@
+cache do
+  xml.title "Hello!"
+end
+
+xml.body cdata_section(render("formatted_partial"))
diff --git a/actionpack/test/fixtures/public/foo/さようなら.html b/actionpack/test/fixtures/public/foo/さようなら.html
new file mode 100644
index 0000000000..627bb2469f
--- /dev/null
+++ b/actionpack/test/fixtures/public/foo/さようなら.html
@@ -0,0 +1 @@
+means goodbye in Japanese
diff --git a/actionpack/test/fixtures/public/foo/さようなら.html.gz b/actionpack/test/fixtures/public/foo/さようなら.html.gz
new file mode 100644
index 0000000000..4f484cfe86
--- /dev/null
+++ b/actionpack/test/fixtures/public/foo/さようなら.html.gz
diff --git a/actionpack/test/fixtures/公共/foo/さようなら.html b/actionpack/test/fixtures/公共/foo/さようなら.html
new file mode 100644
index 0000000000..627bb2469f
--- /dev/null
+++ b/actionpack/test/fixtures/公共/foo/さようなら.html
@@ -0,0 +1 @@
+means goodbye in Japanese
diff --git a/actionpack/test/fixtures/公共/foo/さようなら.html.gz b/actionpack/test/fixtures/公共/foo/さようなら.html.gz
new file mode 100644
index 0000000000..4f484cfe86
--- /dev/null
+++ b/actionpack/test/fixtures/公共/foo/さようなら.html.gz
diff --git a/actionpack/test/journey/nodes/symbol_test.rb b/actionpack/test/journey/nodes/symbol_test.rb
index 1e687acef2..b0622ac71a 100644
--- a/actionpack/test/journey/nodes/symbol_test.rb
+++ b/actionpack/test/journey/nodes/symbol_test.rb
@@ -8,10 +8,10 @@ module ActionDispatch
       class TestSymbol < ActiveSupport::TestCase
         def test_default_regexp?
           sym = Symbol.new "foo"
-          assert sym.default_regexp?
+          assert_predicate sym, :default_regexp?
 
           sym.regexp = nil
-          assert_not sym.default_regexp?
+          assert_not_predicate sym, :default_regexp?
         end
       end
     end
diff --git a/actionpack/test/journey/route/definition/scanner_test.rb b/actionpack/test/journey/route/definition/scanner_test.rb
index 070886c7df..bcbe4388c3 100644
--- a/actionpack/test/journey/route/definition/scanner_test.rb
+++ b/actionpack/test/journey/route/definition/scanner_test.rb
@@ -10,61 +10,64 @@ module ActionDispatch
           @scanner = Scanner.new
         end
 
-        # /page/:id(/:action)(.:format)
-        def test_tokens
-          [
-            ["/",       [[:SLASH, "/"]]],
-            ["*omg",    [[:STAR, "*omg"]]],
-            ["/page",   [[:SLASH, "/"], [:LITERAL, "page"]]],
-            ["/page!",  [[:SLASH, "/"], [:LITERAL, "page!"]]],
-            ["/page$",  [[:SLASH, "/"], [:LITERAL, "page$"]]],
-            ["/page&",  [[:SLASH, "/"], [:LITERAL, "page&"]]],
-            ["/page'",  [[:SLASH, "/"], [:LITERAL, "page'"]]],
-            ["/page*",  [[:SLASH, "/"], [:LITERAL, "page*"]]],
-            ["/page+",  [[:SLASH, "/"], [:LITERAL, "page+"]]],
-            ["/page,",  [[:SLASH, "/"], [:LITERAL, "page,"]]],
-            ["/page;",  [[:SLASH, "/"], [:LITERAL, "page;"]]],
-            ["/page=",  [[:SLASH, "/"], [:LITERAL, "page="]]],
-            ["/page@",  [[:SLASH, "/"], [:LITERAL, "page@"]]],
-            ['/page\:', [[:SLASH, "/"], [:LITERAL, "page:"]]],
-            ['/page\(', [[:SLASH, "/"], [:LITERAL, "page("]]],
-            ['/page\)', [[:SLASH, "/"], [:LITERAL, "page)"]]],
-            ["/~page",  [[:SLASH, "/"], [:LITERAL, "~page"]]],
-            ["/pa-ge",  [[:SLASH, "/"], [:LITERAL, "pa-ge"]]],
-            ["/:page",  [[:SLASH, "/"], [:SYMBOL, ":page"]]],
-            ["/(:page)", [
+        CASES = [
+          ["/",       [[:SLASH, "/"]]],
+          ["*omg",    [[:STAR, "*omg"]]],
+          ["/page",   [[:SLASH, "/"], [:LITERAL, "page"]]],
+          ["/page!",  [[:SLASH, "/"], [:LITERAL, "page!"]]],
+          ["/page$",  [[:SLASH, "/"], [:LITERAL, "page$"]]],
+          ["/page&",  [[:SLASH, "/"], [:LITERAL, "page&"]]],
+          ["/page'",  [[:SLASH, "/"], [:LITERAL, "page'"]]],
+          ["/page*",  [[:SLASH, "/"], [:LITERAL, "page*"]]],
+          ["/page+",  [[:SLASH, "/"], [:LITERAL, "page+"]]],
+          ["/page,",  [[:SLASH, "/"], [:LITERAL, "page,"]]],
+          ["/page;",  [[:SLASH, "/"], [:LITERAL, "page;"]]],
+          ["/page=",  [[:SLASH, "/"], [:LITERAL, "page="]]],
+          ["/page@",  [[:SLASH, "/"], [:LITERAL, "page@"]]],
+          ['/page\:', [[:SLASH, "/"], [:LITERAL, "page:"]]],
+          ['/page\(', [[:SLASH, "/"], [:LITERAL, "page("]]],
+          ['/page\)', [[:SLASH, "/"], [:LITERAL, "page)"]]],
+          ["/~page",  [[:SLASH, "/"], [:LITERAL, "~page"]]],
+          ["/pa-ge",  [[:SLASH, "/"], [:LITERAL, "pa-ge"]]],
+          ["/:page",  [[:SLASH, "/"], [:SYMBOL, ":page"]]],
+          ["/(:page)", [
+                        [:SLASH, "/"],
+                        [:LPAREN, "("],
+                        [:SYMBOL, ":page"],
+                        [:RPAREN, ")"],
+                      ]],
+          ["(/:action)", [
+                          [:LPAREN, "("],
                           [:SLASH, "/"],
+                          [:SYMBOL, ":action"],
+                          [:RPAREN, ")"],
+                         ]],
+          ["(())", [[:LPAREN, "("],
+                   [:LPAREN, "("], [:RPAREN, ")"], [:RPAREN, ")"]]],
+          ["(.:format)", [
                           [:LPAREN, "("],
-                          [:SYMBOL, ":page"],
+                          [:DOT, "."],
+                          [:SYMBOL, ":format"],
                           [:RPAREN, ")"],
                         ]],
-            ["(/:action)", [
-                            [:LPAREN, "("],
-                            [:SLASH, "/"],
-                            [:SYMBOL, ":action"],
-                            [:RPAREN, ")"],
-                           ]],
-            ["(())", [[:LPAREN, "("],
-                     [:LPAREN, "("], [:RPAREN, ")"], [:RPAREN, ")"]]],
-            ["(.:format)", [
-                            [:LPAREN, "("],
-                            [:DOT, "."],
-                            [:SYMBOL, ":format"],
-                            [:RPAREN, ")"],
-                          ]],
-          ].each do |str, expected|
-            @scanner.scan_setup str
-            assert_tokens expected, @scanner
+        ]
+
+        CASES.each do |pattern, expected_tokens|
+          test "Scanning `#{pattern}`" do
+            @scanner.scan_setup pattern
+            assert_tokens expected_tokens, @scanner, pattern
           end
         end
 
-        def assert_tokens(tokens, scanner)
-          toks = []
-          while tok = scanner.next_token
-            toks << tok
+        private
+
+          def assert_tokens(expected_tokens, scanner, pattern)
+            actual_tokens = []
+            while token = scanner.next_token
+              actual_tokens << token
+            end
+            assert_equal expected_tokens, actual_tokens, "Wrong tokens for `#{pattern}`"
           end
-          assert_equal tokens, toks
-        end
       end
     end
   end
diff --git a/actionpack/test/journey/router_test.rb b/actionpack/test/journey/router_test.rb
index 29cc74471d..183f421bcf 100644
--- a/actionpack/test/journey/router_test.rb
+++ b/actionpack/test/journey/router_test.rb
@@ -30,7 +30,7 @@ module ActionDispatch
       def test_unicode
         get "/ほげ", to: "foo#bar"
 
-        #match the escaped version of /ほげ
+        # match the escaped version of /ほげ
         env = rails_env "PATH_INFO" => "/%E3%81%BB%E3%81%92"
         called = false
         router.recognize(env) do |r, params|
diff --git a/actionpack/test/journey/routes_test.rb b/actionpack/test/journey/routes_test.rb
index 81ce07526f..d5c81a8421 100644
--- a/actionpack/test/journey/routes_test.rb
+++ b/actionpack/test/journey/routes_test.rb
@@ -17,11 +17,11 @@ module ActionDispatch
 
       def test_clear
         mapper.get "/foo(/:id)", to: "foo#bar", as: "aaron"
-        assert_not_predicate routes, :empty?
+        assert_not_empty routes
         assert_equal 1, routes.length
 
         routes.clear
-        assert routes.empty?
+        assert_empty routes
         assert_equal 0, routes.length
       end
 
@@ -43,7 +43,7 @@ module ActionDispatch
         mapper.get "/foo(/:id)", to: "foo#bar", as: "aaron"
 
         assert_equal 1, @routes.anchored_routes.length
-        assert_predicate @routes.custom_routes, :empty?
+        assert_empty @routes.custom_routes
 
         mapper.get "/hello/:who", to: "foo#bar", as: "bar", who: /\d/
 
diff --git a/actionview/.gitignore b/actionview/.gitignore
index 0a04b29786..246aabbb7f 100644
--- a/actionview/.gitignore
+++ b/actionview/.gitignore
@@ -1,2 +1,5 @@
-/lib/assets/compiled
-/tmp
+/lib/assets/compiled/
+/log/
+/test/fixtures/public/absolute/
+/test/ujs/log/
+/tmp/
diff --git a/actionview/CHANGELOG.md b/actionview/CHANGELOG.md
index b22686d1d8..2c1ca12043 100644
--- a/actionview/CHANGELOG.md
+++ b/actionview/CHANGELOG.md
@@ -1,35 +1,71 @@
-*   Remove default `alt` text generation.
+*   Fix JavaScript views rendering does not work with Firefox when using
+    Content Security Policy.
 
-    Fixes #30096
+    Fixes #32577.
 
-    *Cameron Cundiff*
+    *Yuji Yaginuma*
 
-*   Add `srcset` option to `image_tag` helper.
+*   Add the `nonce: true` option for `javascript_include_tag` helper to
+    support automatic nonce generation for Content Security Policy.
+    Works the same way as `javascript_tag nonce: true` does.
 
-    *Roberto Miranda*
+    *Yaroslav Markin*
 
-*   Fix issues with scopes and engine on `current_page?` method.
+*   Remove `ActionView::Helpers::RecordTagHelper`.
 
-    Fixes #29401.
+    *Yoshiyuki Hirano*
 
-    *Nikita Savrov*
+*   Disable `ActionView::Template` finalizers in test environment.
 
-*   Generate field ids in `collection_check_boxes` and `collection_radio_buttons`.
+    Template finalization can be expensive in large view test suites.
+    Add a configuration option,
+    `action_view.finalize_compiled_template_methods`, and turn it off in
+    the test environment.
 
-    This makes sure that the labels are linked up with the fields.
+    *Simon Coffey*
 
-    Fixes #29014.
+*   Extract the `confirm` call in its own, overridable method in `rails_ujs`.
+    Example :
+        Rails.confirm = function(message, element) {
+          return (my_bootstrap_modal_confirm(message));
+        }
 
-    *Yuji Yaginuma*
+    *Mathieu Mahé*
+
+*   Enable select tag helper to mark `prompt` option as `selected` and/or `disabled` for `required`
+    field. Example:
+
+        select :post,
+               :category,
+               ["lifestyle", "programming", "spiritual"],
+               { selected: "", disabled: "", prompt: "Choose one" },
+               { required: true }
+
+    Placeholder option would be selected and disabled. The HTML produced:
+
+        <select required="required" name="post[category]" id="post_category">
+        <option disabled="disabled" selected="selected" value="">Choose one</option>
+        <option value="lifestyle">lifestyle</option>
+        <option value="programming">programming</option>
+        <option value="spiritual">spiritual</option></select>
+
+    *Sergey Prikhodko*
+
+*   Don't enforce UTF-8 by default.
+
+    With the disabling of TLS 1.0 by most major websites, continuing to run
+    IE8 or lower becomes increasingly difficult so default to not enforcing
+    UTF-8 encoding as it's not relevant to other browsers.
+
+    *Andrew White*
 
-*   Add `:json` type to `auto_discovery_link_tag` to support [JSON Feeds](https://jsonfeed.org/version/1)
+*   Change translation key of `submit_tag` from `module_name_class_name` to `module_name/class_name`.
 
-    *Mike Gunderloy*
+    *Rui Onodera*
 
-*   Update `distance_of_time_in_words` helper to display better error messages
-    for bad input.
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
-    *Jay Hayes*
+    *Jeremy Daer*
 
 
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/actionview/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/actionview/CHANGELOG.md) for previous changes.
diff --git a/actionview/MIT-LICENSE b/actionview/MIT-LICENSE
index ac810e86d0..1cb3add0fc 100644
--- a/actionview/MIT-LICENSE
+++ b/actionview/MIT-LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2004-2017 David Heinemeier Hansson
+Copyright (c) 2004-2018 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/actionview/README.rdoc b/actionview/README.rdoc
index d5029599b7..03a0723564 100644
--- a/actionview/README.rdoc
+++ b/actionview/README.rdoc
@@ -11,7 +11,7 @@ The latest version of Action View can be installed with RubyGems:
 
   $ gem install actionview
 
-Source code can be downloaded as part of the Rails project on GitHub
+Source code can be downloaded as part of the Rails project on GitHub:
 
 * https://github.com/rails/rails/tree/master/actionview
 
@@ -29,7 +29,7 @@ API documentation is at
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/actionview/RUNNING_UJS_TESTS.rdoc b/actionview/RUNNING_UJS_TESTS.rdoc
index a575624a06..e30c2aee55 100644
--- a/actionview/RUNNING_UJS_TESTS.rdoc
+++ b/actionview/RUNNING_UJS_TESTS.rdoc
@@ -1,7 +1,8 @@
 == Running UJS tests
 
-Ensure that you can build the project and run tests.
-Run rake ujs:server first, and then run the web tests by
-visiting http://localhost:4567 in your browser.
+Ensure that you can build the project by running:
+   rake ujs:server
 
-rake ujs:server
+Then run the web tests by visiting the following URL in your browser:
+
+   http://localhost:4567
diff --git a/actionview/RUNNING_UNIT_TESTS.rdoc b/actionview/RUNNING_UNIT_TESTS.rdoc
index 6c4e5e983a..4442dbdb9e 100644
--- a/actionview/RUNNING_UNIT_TESTS.rdoc
+++ b/actionview/RUNNING_UNIT_TESTS.rdoc
@@ -2,13 +2,13 @@
 
 The easiest way to run the unit tests is through Rake. The default task runs
 the entire test suite for all classes. For more information, checkout the
-full array of rake tasks with "rake -T"
+full array of rake tasks with <tt>rake -T</tt>
 
-Rake can be found at http://docs.seattlerb.org/rake/.
+Rake can be found at https://ruby.github.io/rake/.
 
 == Running by hand
 
-To run a single test suite
+Run a single test suite:
 
    rake test TEST=path/to/test.rb
 
@@ -18,10 +18,9 @@ which can be further narrowed down to one test:
 
 == Dependency on Active Record and database setup
 
-Test cases in the test/activerecord/ directory depend on having
-activerecord and sqlite3 installed. If Active Record is not in
-actionview/../activerecord directory, or the sqlite3 rubygem is not installed,
-these tests are skipped.
-
+Test cases in the +test/activerecord/+ directory depend on having
+activerecord+ and +sqlite3+ installed. If Active Record is not in
+actionview/../activerecord+ directory, or the +sqlite3+ Ruby gem is not installed,
+  these tests are skipped.
 Other tests are runnable from a fresh copy of actionview without any configuration.
 
diff --git a/actionview/Rakefile b/actionview/Rakefile
index 20dfa4e114..bdfd96c141 100644
--- a/actionview/Rakefile
+++ b/actionview/Rakefile
@@ -29,10 +29,11 @@ namespace :test do
     t.ruby_opts = ["--dev"] if defined?(JRUBY_VERSION)
   end
 
+  desc "Run tests for rails-ujs"
   task :ujs do
     begin
       Dir.mkdir("log")
-      pid = spawn("bundle exec rackup test/ujs/config.ru -p 4567 -s puma > log/test.log 2>&1")
+      pid = spawn("bundle exec rackup test/ujs/config.ru -p 4567 -s puma > log/test.log 2>&1", pgroup: true)
 
       start_time = Time.now
 
@@ -45,10 +46,10 @@ namespace :test do
         end
       end
 
-      system("npm run lint && phantomjs ../ci/phantomjs.js http://localhost:4567/")
-      status = $?.to_i
+      system("npm run lint && bundle exec ruby ../ci/qunit-selenium-runner.rb http://localhost:4567/")
+      status = $?.exitstatus
     ensure
-      Process.kill("KILL", pid) if pid
+      Process.kill("KILL", -pid) if pid
       FileUtils.rm_rf("log")
     end
 
@@ -56,7 +57,7 @@ namespace :test do
   end
 
   namespace :integration do
-    desc "ActiveRecord Integration Tests"
+    # Active Record Integration Tests
     Rake::TestTask.new(:active_record) do |t|
       t.libs << "test"
       t.test_files = Dir.glob("test/activerecord/*_test.rb")
@@ -65,7 +66,7 @@ namespace :test do
       t.ruby_opts = ["--dev"] if defined?(JRUBY_VERSION)
     end
 
-    desc "ActionPack Integration Tests"
+    # Action Pack Integration Tests
     Rake::TestTask.new(:action_pack) do |t|
       t.libs << "test"
       t.test_files = Dir.glob("test/actionpack/**/*_test.rb")
@@ -130,7 +131,7 @@ namespace :assets do
 end
 
 task :lines do
-  load File.join(File.expand_path("..", __dir__), "/tools/line_statistics")
+  load File.expand_path("../tools/line_statistics", __dir__)
   files = FileList["lib/**/*.rb"]
   CodeTools::LineStatistics.new(files).print_loc
 end
diff --git a/actionview/actionview.gemspec b/actionview/actionview.gemspec
index b99137fcf6..49ee1a292b 100644
--- a/actionview/actionview.gemspec
+++ b/actionview/actionview.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Rendering framework putting the V in MVC (part of Rails)."
   s.description = "Simple, battle-tested conventions and helpers for building web pages."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
diff --git a/actionview/app/assets/javascripts/MIT-LICENSE b/actionview/app/assets/javascripts/MIT-LICENSE
index befcbdc7b7..28e1b12496 100644
--- a/actionview/app/assets/javascripts/MIT-LICENSE
+++ b/actionview/app/assets/javascripts/MIT-LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2007-2017 Rails Core team
+Copyright (c) 2007-2018 Rails Core team
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/actionview/app/assets/javascripts/README.md b/actionview/app/assets/javascripts/README.md
index f321b9f720..b74fa1afad 100644
--- a/actionview/app/assets/javascripts/README.md
+++ b/actionview/app/assets/javascripts/README.md
@@ -1,5 +1,4 @@
-Ruby on Rails unobtrusive scripting adapter.
-========================================
+# Ruby on Rails unobtrusive scripting adapter
 
 This unobtrusive scripting support file is developed for the Ruby on Rails framework, but is not strictly tied to any specific backend. You can drop this into any application to:
 
@@ -8,53 +7,51 @@ This unobtrusive scripting support file is developed for the Ruby on Rails frame
 - make forms or hyperlinks submit data asynchronously with Ajax;
 - have submit buttons become automatically disabled on form submit to prevent double-clicking.
 
-These features are achieved by adding certain ["data" attributes][data] to your HTML markup. In Rails, they are added by the framework's template helpers.
+These features are achieved by adding certain [`data` attributes][data] to your HTML markup. In Rails, they are added by the framework's template helpers.
 
-Requirements
-------------
+## Optional prerequisites
 
-- HTML5 doctype (optional).
+Note that the `data` attributes this library adds are a feature of HTML5. If you're not targeting HTML5, these attributes may make your HTML to fail [validation][validator]. However, this shouldn't create any issues for web browsers or other user agents.
 
-If you don't use HTML5, adding "data" attributes to your HTML4 or XHTML pages might make them fail [W3C markup validation][validator]. However, this shouldn't create any issues for web browsers or other user agents.
+## Installation
 
-Installation using npm
-------------
+### NPM
 
-Run `npm install rails-ujs --save` to install the rails-ujs package.
+    npm install rails-ujs --save
+    
+### Yarn
+    
+    yarn add rails-ujs
 
-Installation using Yarn
-------------
+Ensure that `.yarnclean` does not include `assets` if you use [yarn autoclean](https://yarnpkg.com/lang/en/docs/cli/autoclean/).
 
-Run `yarn add rails-ujs` to install the rails-ujs package.
+## Usage
 
-Usage
-------------
+### Asset pipeline
 
-Require `rails-ujs` in your application.js manifest.
+In a conventional Rails application that uses the asset pipeline, require `rails-ujs` in your `application.js` manifest:
 
 ```javascript
 //= require rails-ujs
 ```
 
-Usage with yarn
-------------
+### ES2015+
 
-When using with the Webpacker gem or your preferred JavaScript bundler, just
-add the following to your main JS file and compile.
+If you're using the Webpacker gem or some other JavaScript bundler, add the following to your main JS file:
 
 ```javascript
 import Rails from 'rails-ujs';
 Rails.start()
 ```
 
-How to run tests
-------------
+## How to run tests
 
 Run `bundle exec rake ujs:server` first, and then run the web tests by visiting http://localhost:4567 in your browser.
 
 ## License
+
 rails-ujs is released under the [MIT License](MIT-LICENSE).
 
-[data]: http://www.w3.org/TR/html5/dom.html#embedding-custom-non-visible-data-with-the-data-*-attributes "Embedding custom non-visible data with the data-* attributes"
+[data]: https://www.w3.org/TR/html5/dom.html#embedding-custom-non-visible-data-with-the-data-attributes "Embedding custom non-visible data with the data-* attributes"
 [validator]: http://validator.w3.org/
 [csrf]: http://api.rubyonrails.org/classes/ActionController/RequestForgeryProtection.html
diff --git a/actionview/app/assets/javascripts/rails-ujs/features/confirm.coffee b/actionview/app/assets/javascripts/rails-ujs/features/confirm.coffee
index 72b5aaa218..0738ffcdc9 100644
--- a/actionview/app/assets/javascripts/rails-ujs/features/confirm.coffee
+++ b/actionview/app/assets/javascripts/rails-ujs/features/confirm.coffee
@@ -5,6 +5,10 @@
 Rails.handleConfirm = (e) ->
   stopEverything(e) unless allowAction(this)
 
+# Default confirm dialog, may be overridden with custom confirm dialog in Rails.confirm
+Rails.confirm = (message, element) ->
+  confirm(message)
+
 # For 'data-confirm' attribute:
 # - Fires `confirm` event
 # - Shows the confirmation dialog
@@ -20,7 +24,7 @@ allowAction = (element) ->
 
   answer = false
   if fire(element, 'confirm')
-    try answer = confirm(message)
+    try answer = Rails.confirm(message, element)
     callback = fire(element, 'confirm:complete', [answer])
 
   answer and callback
diff --git a/actionview/app/assets/javascripts/rails-ujs/features/remote.coffee b/actionview/app/assets/javascripts/rails-ujs/features/remote.coffee
index 852587042c..b3448dabac 100644
--- a/actionview/app/assets/javascripts/rails-ujs/features/remote.coffee
+++ b/actionview/app/assets/javascripts/rails-ujs/features/remote.coffee
@@ -62,7 +62,7 @@ Rails.handleRemote = (e) ->
         fire(element, 'ajax:send', [xhr])
       else
         fire(element, 'ajax:stopped')
-        xhr.abort()
+        return false
     success: (args...) -> fire(element, 'ajax:success', args)
     error: (args...) -> fire(element, 'ajax:error', args)
     complete: (args...) -> fire(element, 'ajax:complete', args)
diff --git a/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee b/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee
index a653d3af3d..019bda635a 100644
--- a/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee
+++ b/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee
@@ -1,7 +1,8 @@
+#= require ./csp
 #= require ./csrf
 #= require ./event
 
-{ CSRFProtection, fire } = Rails
+{ cspNonce, CSRFProtection, fire } = Rails
 
 AcceptHeaders =
   '*': '*/*'
@@ -20,13 +21,12 @@ Rails.ajax = (options) ->
     else
       options.error?(response, xhr.statusText, xhr)
     options.complete?(xhr, xhr.statusText)
-  # Call beforeSend hook
-  options.beforeSend?(xhr, options)
-  # Send the request
+
+  if options.beforeSend? && !options.beforeSend(xhr, options)
+    return false
+
   if xhr.readyState is XMLHttpRequest.OPENED
     xhr.send(options.data)
-  else
-    fire(document, 'ajaxStop') # to be compatible with jQuery.ajax
 
 prepareOptions = (options) ->
   options.url = options.url or location.href
@@ -66,9 +66,10 @@ processResponse = (response, type) ->
       try response = JSON.parse(response)
     else if type.match(/\b(?:java|ecma)script\b/)
       script = document.createElement('script')
+      script.setAttribute('nonce', cspNonce())
       script.text = response
       document.head.appendChild(script).parentNode.removeChild(script)
-    else if type.match(/\b(xml|html|svg)\b/)
+    else if type.match(/\bxml\b/)
       parser = new DOMParser()
       type = type.replace(/;.+/, '') # remove something like ';charset=utf-8'
       try response = parser.parseFromString(response, type)
diff --git a/actionview/app/assets/javascripts/rails-ujs/utils/csp.coffee b/actionview/app/assets/javascripts/rails-ujs/utils/csp.coffee
new file mode 100644
index 0000000000..8d2d6ce447
--- /dev/null
+++ b/actionview/app/assets/javascripts/rails-ujs/utils/csp.coffee
@@ -0,0 +1,4 @@
+# Content-Security-Policy nonce for inline scripts
+cspNonce = Rails.cspNonce = ->
+  meta = document.querySelector('meta[name=csp-nonce]')
+  meta and meta.content
diff --git a/actionview/app/assets/javascripts/rails-ujs/utils/dom.coffee b/actionview/app/assets/javascripts/rails-ujs/utils/dom.coffee
index 6bef618147..3d3c5bb330 100644
--- a/actionview/app/assets/javascripts/rails-ujs/utils/dom.coffee
+++ b/actionview/app/assets/javascripts/rails-ujs/utils/dom.coffee
@@ -5,6 +5,13 @@ m = Element.prototype.matches or
     Element.prototype.oMatchesSelector or
     Element.prototype.webkitMatchesSelector
 
+# Checks if the given native dom element matches the selector
+# element::
+#   native DOM element
+# selector::
+#   css selector string or
+#   a javascript object with `selector` and `exclude` properties
+#   Examples: "form", { selector: "form", exclude: "form[data-remote='true']"}
 Rails.matches = (element, selector) ->
   if selector.exclude?
     m.call(element, selector.selector) and not m.call(element, selector.exclude)
diff --git a/actionview/app/assets/javascripts/rails-ujs/utils/event.coffee b/actionview/app/assets/javascripts/rails-ujs/utils/event.coffee
index 8d3ff007ea..a7eee52060 100644
--- a/actionview/app/assets/javascripts/rails-ujs/utils/event.coffee
+++ b/actionview/app/assets/javascripts/rails-ujs/utils/event.coffee
@@ -11,9 +11,26 @@ if typeof CustomEvent isnt 'function'
     evt = document.createEvent('CustomEvent')
     evt.initCustomEvent(event, params.bubbles, params.cancelable, params.detail)
     evt
+
   CustomEvent.prototype = window.Event.prototype
 
+  # Fix setting `defaultPrevented` when `preventDefault()` is called
+  # http://stackoverflow.com/questions/23349191/event-preventdefault-is-not-working-in-ie-11-for-custom-events
+  { preventDefault } = CustomEvent.prototype
+  CustomEvent.prototype.preventDefault = ->
+    result = preventDefault.call(this)
+    if @cancelable and not @defaultPrevented
+      Object.defineProperty(this, 'defaultPrevented', get: -> true)
+    result
+
 # Triggers a custom event on an element and returns false if the event result is false
+# obj::
+#   a native DOM element
+# name::
+#   string that corrspends to the event you want to trigger
+#   e.g. 'click', 'submit'
+# data::
+#   data you want to pass when you dispatch an event
 fire = Rails.fire = (obj, name, data) ->
   event = new CustomEvent(
     name,
@@ -31,6 +48,17 @@ Rails.stopEverything = (e) ->
   e.stopPropagation()
   e.stopImmediatePropagation()
 
+# Delegates events
+# to a specified parent `element`, which fires event `handler`
+# for the specified `selector` when an event of `eventType` is triggered
+# element::
+#   parent element that will listen for events e.g. document
+# selector::
+#   css selector; or an object that has `selector` and `exclude` properties (see: Rails.matches)
+# eventType::
+#   string representing the event e.g. 'submit', 'click'
+# handler::
+#   the event handler to be called
 Rails.delegate = (element, selector, eventType, handler) ->
   element.addEventListener eventType, (e) ->
     target = e.target
diff --git a/actionview/app/assets/javascripts/rails-ujs/utils/form.coffee b/actionview/app/assets/javascripts/rails-ujs/utils/form.coffee
index 5fa337b518..736cab08db 100644
--- a/actionview/app/assets/javascripts/rails-ujs/utils/form.coffee
+++ b/actionview/app/assets/javascripts/rails-ujs/utils/form.coffee
@@ -10,7 +10,7 @@ Rails.serializeElement = (element, additionalParam) ->
   params = []
 
   inputs.forEach (input) ->
-    return unless input.name
+    return if !input.name || input.disabled
     if matches(input, 'select')
       toArray(input.options).forEach (option) ->
         params.push(name: input.name, value: option.value) if option.selected
diff --git a/actionview/lib/action_view.rb b/actionview/lib/action_view.rb
index 3c8a8488a5..c1eeda75f5 100644
--- a/actionview/lib/action_view.rb
+++ b/actionview/lib/action_view.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 #--
-# Copyright (c) 2004-2017 David Heinemeier Hansson
+# Copyright (c) 2004-2018 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the
@@ -25,7 +25,7 @@
 
 require "active_support"
 require "active_support/rails"
-require_relative "action_view/version"
+require "action_view/version"
 
 module ActionView
   extend ActiveSupport::Autoload
@@ -76,7 +76,6 @@ module ActionView
       autoload :MissingTemplate
       autoload :ActionViewError
       autoload :EncodingError
-      autoload :MissingRequestError
       autoload :TemplateError
       autoload :WrongEncodingError
     end
diff --git a/actionview/lib/action_view/base.rb b/actionview/lib/action_view/base.rb
index 637c8e7708..d41fe2a608 100644
--- a/actionview/lib/action_view/base.rb
+++ b/actionview/lib/action_view/base.rb
@@ -3,11 +3,11 @@
 require "active_support/core_ext/module/attr_internal"
 require "active_support/core_ext/module/attribute_accessors"
 require "active_support/ordered_options"
-require_relative "log_subscriber"
-require_relative "helpers"
-require_relative "context"
-require_relative "template"
-require_relative "lookup_context"
+require "action_view/log_subscriber"
+require "action_view/helpers"
+require "action_view/context"
+require "action_view/template"
+require "action_view/lookup_context"
 
 module ActionView #:nodoc:
   # = Action View Base
diff --git a/actionview/lib/action_view/context.rb b/actionview/lib/action_view/context.rb
index e1b02fbde4..3c605c3ee3 100644
--- a/actionview/lib/action_view/context.rb
+++ b/actionview/lib/action_view/context.rb
@@ -10,16 +10,16 @@ module ActionView
   # Action View contexts are supplied to Action Controller to render a template.
   # The default Action View context is ActionView::Base.
   #
-  # In order to work with ActionController, a Context must just include this module.
-  # The initialization of the variables used by the context (@output_buffer, @view_flow,
-  # and @virtual_path) is responsibility of the object that includes this module
-  # (although you can call _prepare_context defined below).
+  # In order to work with Action Controller, a Context must just include this
+  # module. The initialization of the variables used by the context
+  # (@output_buffer, @view_flow, and @virtual_path) is responsibility of the
+  # object that includes this module (although you can call _prepare_context
+  # defined below).
   module Context
     include CompiledTemplates
     attr_accessor :output_buffer, :view_flow
 
     # Prepares the context by setting the appropriate instance variables.
-    # :api: plugin
     def _prepare_context
       @view_flow     = OutputFlow.new
       @output_buffer = nil
@@ -29,7 +29,6 @@ module ActionView
     # Encapsulates the interaction with the view flow so it
     # returns the correct buffer on +yield+. This is usually
     # overwritten by helpers to add more behavior.
-    # :api: plugin
     def _layout_for(name = nil)
       name ||= :layout
       view_flow.get(name).html_safe
diff --git a/actionview/lib/action_view/dependency_tracker.rb b/actionview/lib/action_view/dependency_tracker.rb
index 02bd0545c2..182f6e2eef 100644
--- a/actionview/lib/action_view/dependency_tracker.rb
+++ b/actionview/lib/action_view/dependency_tracker.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "concurrent/map"
-require_relative "path_set"
+require "action_view/path_set"
 
 module ActionView
   class DependencyTracker # :nodoc:
diff --git a/actionview/lib/action_view/digestor.rb b/actionview/lib/action_view/digestor.rb
index e404ebb6b6..39cdecb9e4 100644
--- a/actionview/lib/action_view/digestor.rb
+++ b/actionview/lib/action_view/digestor.rb
@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-require "concurrent/map"
-require_relative "dependency_tracker"
-require "monitor"
+require "action_view/dependency_tracker"
 
 module ActionView
   class Digestor
@@ -46,10 +44,7 @@ module ActionView
       def tree(name, finder, partial = false, seen = {})
         logical_name = name.gsub(%r|/_|, "/")
 
-        options = {}
-        options[:formats] = [finder.rendered_format] if finder.rendered_format
-
-        if template = finder.disable_cache { finder.find_all(logical_name, [], partial, [], options).first }
+        if template = find_template(finder, logical_name, [], partial, [])
           finder.rendered_format ||= template.formats.first
 
           if node = seen[template.identifier] # handle cycles in the tree
@@ -71,6 +66,15 @@ module ActionView
           seen[name] ||= Missing.new(name, logical_name, nil)
         end
       end
+
+      private
+        def find_template(finder, name, prefixes, partial, keys)
+          finder.disable_cache do
+            format = finder.rendered_format
+            result = finder.find_all(name, prefixes, partial, keys, formats: [format]).first if format
+            result || finder.find_all(name, prefixes, partial, keys).first
+          end
+        end
     end
 
     class Node
@@ -89,7 +93,7 @@ module ActionView
       end
 
       def digest(finder, stack = [])
-        Digest::MD5.hexdigest("#{template.source}-#{dependency_digest(finder, stack)}")
+        ActiveSupport::Digest.hexdigest("#{template.source}-#{dependency_digest(finder, stack)}")
       end
 
       def dependency_digest(finder, stack)
diff --git a/actionview/lib/action_view/gem_version.rb b/actionview/lib/action_view/gem_version.rb
index ed92490be7..77ae444a58 100644
--- a/actionview/lib/action_view/gem_version.rb
+++ b/actionview/lib/action_view/gem_version.rb
@@ -7,8 +7,8 @@ module ActionView
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
     PRE   = "alpha"
 
diff --git a/actionview/lib/action_view/helpers.rb b/actionview/lib/action_view/helpers.rb
index 46f20c4277..0d77f74171 100644
--- a/actionview/lib/action_view/helpers.rb
+++ b/actionview/lib/action_view/helpers.rb
@@ -13,6 +13,7 @@ module ActionView #:nodoc:
     autoload :CacheHelper
     autoload :CaptureHelper
     autoload :ControllerHelper
+    autoload :CspHelper
     autoload :CsrfHelper
     autoload :DateHelper
     autoload :DebugHelper
@@ -22,7 +23,6 @@ module ActionView #:nodoc:
     autoload :JavaScriptHelper, "action_view/helpers/javascript_helper"
     autoload :NumberHelper
     autoload :OutputSafetyHelper
-    autoload :RecordTagHelper
     autoload :RenderingHelper
     autoload :SanitizeHelper
     autoload :TagHelper
@@ -46,6 +46,7 @@ module ActionView #:nodoc:
     include CacheHelper
     include CaptureHelper
     include ControllerHelper
+    include CspHelper
     include CsrfHelper
     include DateHelper
     include DebugHelper
@@ -55,7 +56,6 @@ module ActionView #:nodoc:
     include JavaScriptHelper
     include NumberHelper
     include OutputSafetyHelper
-    include RecordTagHelper
     include RenderingHelper
     include SanitizeHelper
     include TagHelper
diff --git a/actionview/lib/action_view/helpers/active_model_helper.rb b/actionview/lib/action_view/helpers/active_model_helper.rb
index 46b514012c..e41a95d2ce 100644
--- a/actionview/lib/action_view/helpers/active_model_helper.rb
+++ b/actionview/lib/action_view/helpers/active_model_helper.rb
@@ -5,7 +5,7 @@ require "active_support/core_ext/enumerable"
 
 module ActionView
   # = Active Model Helpers
-  module Helpers
+  module Helpers #:nodoc:
     module ActiveModelHelper
     end
 
@@ -17,8 +17,8 @@ module ActionView
         end
       end
 
-      def content_tag(*)
-        error_wrapping(super)
+      def content_tag(type, options, *)
+        select_markup_helper?(type) ? super : error_wrapping(super)
       end
 
       def tag(type, options, *)
@@ -43,6 +43,10 @@ module ActionView
           object.respond_to?(:errors) && object.errors.respond_to?(:[]) && error_message.present?
         end
 
+        def select_markup_helper?(type)
+          ["optgroup", "option"].include?(type)
+        end
+
         def tag_generate_errors?(options)
           options["type"] != "hidden"
         end
diff --git a/actionview/lib/action_view/helpers/asset_tag_helper.rb b/actionview/lib/action_view/helpers/asset_tag_helper.rb
index bc2713d13e..14bd8ffa84 100644
--- a/actionview/lib/action_view/helpers/asset_tag_helper.rb
+++ b/actionview/lib/action_view/helpers/asset_tag_helper.rb
@@ -2,8 +2,10 @@
 
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/hash/keys"
-require_relative "asset_url_helper"
-require_relative "tag_helper"
+require "active_support/core_ext/object/inclusion"
+require "active_support/core_ext/object/try"
+require "action_view/helpers/asset_url_helper"
+require "action_view/helpers/tag_helper"
 
 module ActionView
   # = Action View Asset Tag Helpers
@@ -37,19 +39,24 @@ module ActionView
       # When the Asset Pipeline is enabled, you can pass the name of your manifest as
       # source, and include other JavaScript or CoffeeScript files inside the manifest.
       #
+      # If the server supports Early Hints header links for these assets will be
+      # automatically pushed.
+      #
       # ==== Options
       #
       # When the last parameter is a hash you can add HTML attributes using that
       # parameter. The following options are supported:
       #
-      # * <tt>:extname</tt>  - Append an extension to the generated url unless the extension
-      #   already exists. This only applies for relative urls.
-      # * <tt>:protocol</tt>  - Sets the protocol of the generated url, this option only
-      #   applies when a relative url and +host+ options are provided.
-      # * <tt>:host</tt>  - When a relative url is provided the host is added to the
+      # * <tt>:extname</tt>  - Append an extension to the generated URL unless the extension
+      #   already exists. This only applies for relative URLs.
+      # * <tt>:protocol</tt>  - Sets the protocol of the generated URL. This option only
+      #   applies when a relative URL and +host+ options are provided.
+      # * <tt>:host</tt>  - When a relative URL is provided the host is added to the
       #   that path.
       # * <tt>:skip_pipeline</tt>  - This option is used to bypass the asset pipeline
       #   when it is set to true.
+      # * <tt>:nonce<tt>  - When set to true, adds an automatic nonce value if
+      #   you have Content Security Policy enabled.
       #
       # ==== Examples
       #
@@ -74,15 +81,29 @@ module ActionView
       #
       #   javascript_include_tag "http://www.example.com/xmlhr.js"
       #   # => <script src="http://www.example.com/xmlhr.js"></script>
+      #
+      #   javascript_include_tag "http://www.example.com/xmlhr.js", nonce: true
+      #   # => <script src="http://www.example.com/xmlhr.js" nonce="..."></script>
       def javascript_include_tag(*sources)
         options = sources.extract_options!.stringify_keys
         path_options = options.extract!("protocol", "extname", "host", "skip_pipeline").symbolize_keys
-        sources.uniq.map { |source|
+        early_hints_links = []
+
+        sources_tags = sources.uniq.map { |source|
+          href = path_to_javascript(source, path_options)
+          early_hints_links << "<#{href}>; rel=preload; as=script"
           tag_options = {
-            "src" => path_to_javascript(source, path_options)
+            "src" => href
           }.merge!(options)
+          if tag_options["nonce"] == true
+            tag_options["nonce"] = content_security_policy_nonce
+          end
           content_tag("script".freeze, "", tag_options)
         }.join("\n").html_safe
+
+        request.send_early_hints("Link" => early_hints_links.join("\n")) if respond_to?(:request) && request
+
+        sources_tags
       end
 
       # Returns a stylesheet link tag for the sources specified as arguments. If
@@ -92,6 +113,9 @@ module ActionView
       # to "screen", so you must explicitly set it to "all" for the stylesheet(s) to
       # apply to all media types.
       #
+      # If the server supports Early Hints header links for these assets will be
+      # automatically pushed.
+      #
       #   stylesheet_link_tag "style"
       #   # => <link href="/assets/style.css" media="screen" rel="stylesheet" />
       #
@@ -113,14 +137,22 @@ module ActionView
       def stylesheet_link_tag(*sources)
         options = sources.extract_options!.stringify_keys
         path_options = options.extract!("protocol", "host", "skip_pipeline").symbolize_keys
-        sources.uniq.map { |source|
+        early_hints_links = []
+
+        sources_tags = sources.uniq.map { |source|
+          href = path_to_stylesheet(source, path_options)
+          early_hints_links << "<#{href}>; rel=preload; as=style"
           tag_options = {
             "rel" => "stylesheet",
             "media" => "screen",
-            "href" => path_to_stylesheet(source, path_options)
+            "href" => href
           }.merge!(options)
           tag(:link, tag_options)
         }.join("\n").html_safe
+
+        request.send_early_hints("Link" => early_hints_links.join("\n")) if respond_to?(:request) && request
+
+        sources_tags
       end
 
       # Returns a link tag that browsers and feed readers can use to auto-detect
@@ -199,8 +231,69 @@ module ActionView
         }.merge!(options.symbolize_keys))
       end
 
+      # Returns a link tag that browsers can use to preload the +source+.
+      # The +source+ can be the path of a resource managed by asset pipeline,
+      # a full path, or an URI.
+      #
+      # ==== Options
+      #
+      # * <tt>:type</tt>  - Override the auto-generated mime type, defaults to the mime type for +source+ extension.
+      # * <tt>:as</tt>  - Override the auto-generated value for as attribute, calculated using +source+ extension and mime type.
+      # * <tt>:crossorigin</tt>  - Specify the crossorigin attribute, required to load cross-origin resources.
+      # * <tt>:nopush</tt>  - Specify if the use of server push is not desired for the resource. Defaults to +false+.
+      #
+      # ==== Examples
+      #
+      #   preload_link_tag("custom_theme.css")
+      #   # => <link rel="preload" href="/assets/custom_theme.css" as="style" type="text/css" />
+      #
+      #   preload_link_tag("/videos/video.webm")
+      #   # => <link rel="preload" href="/videos/video.mp4" as="video" type="video/webm" />
+      #
+      #   preload_link_tag(post_path(format: :json), as: "fetch")
+      #   # => <link rel="preload" href="/posts.json" as="fetch" type="application/json" />
+      #
+      #   preload_link_tag("worker.js", as: "worker")
+      #   # => <link rel="preload" href="/assets/worker.js" as="worker" type="text/javascript" />
+      #
+      #   preload_link_tag("//example.com/font.woff2")
+      #   # => <link rel="preload" href="//example.com/font.woff2" as="font" type="font/woff2" crossorigin="anonymous"/>
+      #
+      #   preload_link_tag("//example.com/font.woff2", crossorigin: "use-credentials")
+      #   # => <link rel="preload" href="//example.com/font.woff2" as="font" type="font/woff2" crossorigin="use-credentials" />
+      #
+      #   preload_link_tag("/media/audio.ogg", nopush: true)
+      #   # => <link rel="preload" href="/media/audio.ogg" as="audio" type="audio/ogg" />
+      #
+      def preload_link_tag(source, options = {})
+        href = asset_path(source, skip_pipeline: options.delete(:skip_pipeline))
+        extname = File.extname(source).downcase.delete(".")
+        mime_type = options.delete(:type) || Template::Types[extname].try(:to_s)
+        as_type = options.delete(:as) || resolve_link_as(extname, mime_type)
+        crossorigin = options.delete(:crossorigin)
+        crossorigin = "anonymous" if crossorigin == true || (crossorigin.blank? && as_type == "font")
+        nopush = options.delete(:nopush) || false
+
+        link_tag = tag.link({
+          rel: "preload",
+          href: href,
+          as: as_type,
+          type: mime_type,
+          crossorigin: crossorigin
+        }.merge!(options.symbolize_keys))
+
+        early_hints_link = "<#{href}>; rel=preload; as=#{as_type}"
+        early_hints_link += "; type=#{mime_type}" if mime_type
+        early_hints_link += "; crossorigin=#{crossorigin}" if crossorigin
+        early_hints_link += "; nopush" if nopush
+
+        request.send_early_hints("Link" => early_hints_link) if respond_to?(:request) && request
+
+        link_tag
+      end
+
       # Returns an HTML image tag for the +source+. The +source+ can be a full
-      # path, a file or an Active Storage attachment.
+      # path, a file, or an Active Storage attachment.
       #
       # ==== Options
       #
@@ -240,9 +333,9 @@ module ActionView
       #
       #   image_tag(user.avatar)
       #   # => <img src="/rails/active_storage/blobs/.../tiger.jpg" />
-      #   image_tag(user.avatar.variant(resize: "100x100"))
+      #   image_tag(user.avatar.variant(resize_to_fit: [100, 100]))
       #   # => <img src="/rails/active_storage/variants/.../tiger.jpg" />
-      #   image_tag(user.avatar.variant(resize: "100x100"), size: '100')
+      #   image_tag(user.avatar.variant(resize_to_fit: [100, 100]), size: '100')
       #   # => <img width="100" height="100" src="/rails/active_storage/variants/.../tiger.jpg" />
       def image_tag(source, options = {})
         options = options.symbolize_keys
@@ -288,12 +381,13 @@ module ActionView
       # Returns an HTML video tag for the +sources+. If +sources+ is a string,
       # a single video tag will be returned. If +sources+ is an array, a video
       # tag with nested source tags for each source will be returned. The
-      # +sources+ can be full paths or files that exists in your public videos
+      # +sources+ can be full paths or files that exist in your public videos
       # directory.
       #
       # ==== Options
-      # You can add HTML attributes using the +options+. The +options+ supports
-      # two additional keys for convenience and conformance:
+      #
+      # When the last parameter is a hash you can add HTML attributes using that
+      # parameter. The following options are supported:
       #
       # * <tt>:poster</tt> - Set an image (like a screenshot) to be shown
       #   before the video loads. The path is calculated like the +src+ of +image_tag+.
@@ -310,7 +404,7 @@ module ActionView
       #   video_tag("trailer.ogg")
       #   # => <video src="/videos/trailer.ogg"></video>
       #   video_tag("trailer.ogg", controls: true, preload: 'none')
-      #   # => <video preload="none" controls="controls" src="/videos/trailer.ogg" ></video>
+      #   # => <video preload="none" controls="controls" src="/videos/trailer.ogg"></video>
       #   video_tag("trailer.m4v", size: "16x10", poster: "screenshot.png")
       #   # => <video src="/videos/trailer.m4v" width="16" height="10" poster="/assets/screenshot.png"></video>
       #   video_tag("trailer.m4v", size: "16x10", poster: "screenshot.png", poster_skip_pipeline: true)
@@ -337,9 +431,14 @@ module ActionView
         end
       end
 
-      # Returns an HTML audio tag for the +source+.
-      # The +source+ can be full path or file that exists in
-      # your public audios directory.
+      # Returns an HTML audio tag for the +sources+. If +sources+ is a string,
+      # a single audio tag will be returned. If +sources+ is an array, an audio
+      # tag with nested source tags for each source will be returned. The
+      # +sources+ can be full paths or files that exist in your public audios
+      # directory.
+      #
+      # When the last parameter is a hash you can add HTML attributes using that
+      # parameter.
       #
       #   audio_tag("sound")
       #   # => <audio src="/audios/sound"></audio>
@@ -395,6 +494,18 @@ module ActionView
             raise ArgumentError, "Cannot pass a :size option with a :height or :width option"
           end
         end
+
+        def resolve_link_as(extname, mime_type)
+          if extname == "js"
+            "script"
+          elsif extname == "css"
+            "style"
+          elsif extname == "vtt"
+            "track"
+          elsif (type = mime_type.to_s.split("/")[0]) && type.in?(%w(audio video font))
+            type
+          end
+        end
     end
   end
 end
diff --git a/actionview/lib/action_view/helpers/asset_url_helper.rb b/actionview/lib/action_view/helpers/asset_url_helper.rb
index 5ba2370efe..8cbe107e41 100644
--- a/actionview/lib/action_view/helpers/asset_url_helper.rb
+++ b/actionview/lib/action_view/helpers/asset_url_helper.rb
@@ -4,9 +4,9 @@ require "zlib"
 
 module ActionView
   # = Action View Asset URL Helpers
-  module Helpers
+  module Helpers #:nodoc:
     # This module provides methods for generating asset paths and
-    # urls.
+    # URLs.
     #
     #   image_path("rails.png")
     #   # => "/assets/rails.png"
@@ -57,8 +57,8 @@ module ActionView
     # You can read more about setting up your DNS CNAME records from your ISP.
     #
     # Note: This is purely a browser performance optimization and is not meant
-    # for server load balancing. See http://www.die.net/musings/page_load_time/
-    # for background and http://www.browserscope.org/?category=network for
+    # for server load balancing. See https://www.die.net/musings/page_load_time/
+    # for background and https://www.browserscope.org/?category=network for
     # connection limit data.
     #
     # Alternatively, you can exert more control over the asset host by setting
@@ -97,7 +97,7 @@ module ActionView
     # still sending assets for plain HTTP requests from asset hosts. If you don't
     # have SSL certificates for each of the asset hosts this technique allows you
     # to avoid warnings in the client about mixed media.
-    # Note that the request parameter might not be supplied, e.g. when the assets
+    # Note that the +request+ parameter might not be supplied, e.g. when the assets
     # are precompiled via a Rake task. Make sure to use a +Proc+ instead of a lambda,
     # since a +Proc+ allows missing parameters and sets them to +nil+.
     #
@@ -149,13 +149,13 @@ module ActionView
       # Below lists scenarios that apply to +asset_path+ whether or not you're
       # using the asset pipeline.
       #
-      # - All fully qualified urls are returned immediately. This bypasses the
+      # - All fully qualified URLs are returned immediately. This bypasses the
       #   asset pipeline and all other behavior described.
       #
       #     asset_path("http://www.example.com/js/xmlhr.js") # => "http://www.example.com/js/xmlhr.js"
       #
       # - All assets that begin with a forward slash are assumed to be full
-      #   urls and will not be expanded. This will bypass the asset pipeline.
+      #   URLs and will not be expanded. This will bypass the asset pipeline.
       #
       #     asset_path("/foo.png") # => "/foo.png"
       #
@@ -324,7 +324,7 @@ module ActionView
       # Since +javascript_url+ is based on +asset_url+ method you can set :host options. If :host
       # options is set, it overwrites global +config.action_controller.asset_host+ setting.
       #
-      #   javascript_url "js/xmlhr.js", host: "http://stage.example.com" # => http://stage.example.com/assets/dir/xmlhr.js
+      #   javascript_url "js/xmlhr.js", host: "http://stage.example.com" # => http://stage.example.com/assets/js/xmlhr.js
       #
       def javascript_url(source, options = {})
         url_to_asset(source, { type: :javascript }.merge!(options))
@@ -351,7 +351,7 @@ module ActionView
       # Since +stylesheet_url+ is based on +asset_url+ method you can set :host options. If :host
       # options is set, it overwrites global +config.action_controller.asset_host+ setting.
       #
-      #   stylesheet_url "css/style.css", host: "http://stage.example.com" # => http://stage.example.com/css/style.css
+      #   stylesheet_url "css/style.css", host: "http://stage.example.com" # => http://stage.example.com/assets/css/style.css
       #
       def stylesheet_url(source, options = {})
         url_to_asset(source, { type: :stylesheet }.merge!(options))
@@ -381,7 +381,7 @@ module ActionView
       # Since +image_url+ is based on +asset_url+ method you can set :host options. If :host
       # options is set, it overwrites global +config.action_controller.asset_host+ setting.
       #
-      #   image_url "edit.png", host: "http://stage.example.com" # => http://stage.example.com/edit.png
+      #   image_url "edit.png", host: "http://stage.example.com" # => http://stage.example.com/assets/edit.png
       #
       def image_url(source, options = {})
         url_to_asset(source, { type: :image }.merge!(options))
@@ -407,7 +407,7 @@ module ActionView
       # Since +video_url+ is based on +asset_url+ method you can set :host options. If :host
       # options is set, it overwrites global +config.action_controller.asset_host+ setting.
       #
-      #   video_url "hd.avi", host: "http://stage.example.com" # => http://stage.example.com/hd.avi
+      #   video_url "hd.avi", host: "http://stage.example.com" # => http://stage.example.com/videos/hd.avi
       #
       def video_url(source, options = {})
         url_to_asset(source, { type: :video }.merge!(options))
@@ -433,7 +433,7 @@ module ActionView
       # Since +audio_url+ is based on +asset_url+ method you can set :host options. If :host
       # options is set, it overwrites global +config.action_controller.asset_host+ setting.
       #
-      #   audio_url "horse.wav", host: "http://stage.example.com" # => http://stage.example.com/horse.wav
+      #   audio_url "horse.wav", host: "http://stage.example.com" # => http://stage.example.com/audios/horse.wav
       #
       def audio_url(source, options = {})
         url_to_asset(source, { type: :audio }.merge!(options))
@@ -458,7 +458,7 @@ module ActionView
       # Since +font_url+ is based on +asset_url+ method you can set :host options. If :host
       # options is set, it overwrites global +config.action_controller.asset_host+ setting.
       #
-      #   font_url "font.ttf", host: "http://stage.example.com" # => http://stage.example.com/font.ttf
+      #   font_url "font.ttf", host: "http://stage.example.com" # => http://stage.example.com/fonts/font.ttf
       #
       def font_url(source, options = {})
         url_to_asset(source, { type: :font }.merge!(options))
diff --git a/actionview/lib/action_view/helpers/atom_feed_helper.rb b/actionview/lib/action_view/helpers/atom_feed_helper.rb
index 34245b5df5..e6b9878271 100644
--- a/actionview/lib/action_view/helpers/atom_feed_helper.rb
+++ b/actionview/lib/action_view/helpers/atom_feed_helper.rb
@@ -4,7 +4,7 @@ require "set"
 
 module ActionView
   # = Action View Atom Feed Helpers
-  module Helpers
+  module Helpers #:nodoc:
     module AtomFeedHelper
       # Adds easy defaults to writing Atom feeds with the Builder template engine (this does not work on ERB or any other
       # template languages).
diff --git a/actionview/lib/action_view/helpers/cache_helper.rb b/actionview/lib/action_view/helpers/cache_helper.rb
index cd213ad6a2..15d187a9ec 100644
--- a/actionview/lib/action_view/helpers/cache_helper.rb
+++ b/actionview/lib/action_view/helpers/cache_helper.rb
@@ -2,7 +2,7 @@
 
 module ActionView
   # = Action View Cache Helper
-  module Helpers
+  module Helpers #:nodoc:
     module CacheHelper
       # This helper exposes a method for caching fragments of a view
       # rather than an entire action or page. This technique is useful
@@ -111,9 +111,9 @@ module ActionView
       #   <%= render_categorizable_events @person.events %>
       #
       # This marks every template in the directory as a dependency. To find those
-      # templates, the wildcard path must be absolutely defined from app/views or paths
+      # templates, the wildcard path must be absolutely defined from <tt>app/views</tt> or paths
       # otherwise added with +prepend_view_path+ or +append_view_path+.
-      # This way the wildcard for `app/views/recordings/events` would be `recordings/events/*` etc.
+      # This way the wildcard for <tt>app/views/recordings/events</tt> would be <tt>recordings/events/*</tt> etc.
       #
       # The pattern used to match explicit dependencies is <tt>/# Template Dependency: (\S+)/</tt>,
       # so it's important that you type it out just so.
@@ -133,14 +133,14 @@ module ActionView
       #
       # === Collection Caching
       #
-      # When rendering a collection of objects that each use the same partial, a `cached`
+      # When rendering a collection of objects that each use the same partial, a <tt>:cached</tt>
       # option can be passed.
       #
       # For collections rendered such:
       #
       #   <%= render partial: 'projects/project', collection: @projects, cached: true %>
       #
-      # The `cached: true` will make Action View's rendering read several templates
+      # The <tt>cached: true</tt> will make Action View's rendering read several templates
       # from cache at once instead of one call per template.
       #
       # Templates in the collection not already cached are written to cache.
@@ -201,7 +201,7 @@ module ActionView
       end
 
       # This helper returns the name of a cache key for a given fragment cache
-      # call. By supplying +skip_digest:+ true to cache, the digestion of cache
+      # call. By supplying <tt>skip_digest: true</tt> to cache, the digestion of cache
       # fragments can be manually bypassed. This is useful when cache fragments
       # cannot be manually expired unless you know the exact key which is the
       # case when using memcached.
diff --git a/actionview/lib/action_view/helpers/capture_helper.rb b/actionview/lib/action_view/helpers/capture_helper.rb
index 690ce6a0ee..92f7ddb70d 100644
--- a/actionview/lib/action_view/helpers/capture_helper.rb
+++ b/actionview/lib/action_view/helpers/capture_helper.rb
@@ -4,12 +4,12 @@ require "active_support/core_ext/string/output_safety"
 
 module ActionView
   # = Action View Capture Helper
-  module Helpers
+  module Helpers #:nodoc:
     # CaptureHelper exposes methods to let you extract generated markup which
     # can be used in other parts of a template or layout file.
     #
     # It provides a method to capture blocks into variables through capture and
-    # a way to capture a block of markup for use in a layout through content_for.
+    # a way to capture a block of markup for use in a layout through {content_for}[rdoc-ref:ActionView::Helpers::CaptureHelper#content_for].
     module CaptureHelper
       # The capture method extracts part of a template as a String object.
       # You can then use this object anywhere in your templates, layout, or helpers.
@@ -44,7 +44,7 @@ module ActionView
         end
       end
 
-      # Calling content_for stores a block of markup in an identifier for later use.
+      # Calling <tt>content_for</tt> stores a block of markup in an identifier for later use.
       # In order to access this stored content in other templates, helper modules
       # or the layout, you would pass the identifier as an argument to <tt>content_for</tt>.
       #
@@ -110,7 +110,7 @@ module ActionView
       # That will place +script+ tags for your default set of JavaScript files on the page;
       # this technique is useful if you'll only be using these scripts in a few views.
       #
-      # Note that content_for concatenates (default) the blocks it is given for a particular
+      # Note that <tt>content_for</tt> concatenates (default) the blocks it is given for a particular
       # identifier in order. For example:
       #
       #   <% content_for :navigation do %>
@@ -127,7 +127,7 @@ module ActionView
       #
       #   <ul><%= content_for :navigation %></ul>
       #
-      # If the flush parameter is true content_for replaces the blocks it is given. For example:
+      # If the flush parameter is +true+ <tt>content_for</tt> replaces the blocks it is given. For example:
       #
       #   <% content_for :navigation do %>
       #     <li><%= link_to 'Home', action: 'index' %></li>
@@ -147,7 +147,7 @@ module ActionView
       #
       #   <% content_for :script, javascript_include_tag(:defaults) %>
       #
-      # WARNING: content_for is ignored in caches. So you shouldn't use it for elements that will be fragment cached.
+      # WARNING: <tt>content_for</tt> is ignored in caches. So you shouldn't use it for elements that will be fragment cached.
       def content_for(name, content = nil, options = {}, &block)
         if content || block_given?
           if block_given?
@@ -174,7 +174,7 @@ module ActionView
         result unless content
       end
 
-      # content_for? checks whether any content has been captured yet using `content_for`.
+      # <tt>content_for?</tt> checks whether any content has been captured yet using <tt>content_for</tt>.
       # Useful to render parts of your layout differently based on what is in your views.
       #
       #   <%# This is the layout %>
diff --git a/actionview/lib/action_view/helpers/controller_helper.rb b/actionview/lib/action_view/helpers/controller_helper.rb
index 00d8b9665d..79cf86c7d1 100644
--- a/actionview/lib/action_view/helpers/controller_helper.rb
+++ b/actionview/lib/action_view/helpers/controller_helper.rb
@@ -3,7 +3,7 @@
 require "active_support/core_ext/module/attr_internal"
 
 module ActionView
-  module Helpers
+  module Helpers #:nodoc:
     # This module keeps all methods and behavior in ActionView
     # that simply delegates to the controller.
     module ControllerHelper #:nodoc:
diff --git a/actionview/lib/action_view/helpers/csp_helper.rb b/actionview/lib/action_view/helpers/csp_helper.rb
new file mode 100644
index 0000000000..e2e065c218
--- /dev/null
+++ b/actionview/lib/action_view/helpers/csp_helper.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module ActionView
+  # = Action View CSP Helper
+  module Helpers #:nodoc:
+    module CspHelper
+      # Returns a meta tag "csp-nonce" with the per-session nonce value
+      # for allowing inline <script> tags.
+      #
+      #   <head>
+      #     <%= csp_meta_tag %>
+      #   </head>
+      #
+      # This is used by the Rails UJS helper to create dynamically
+      # loaded inline <script> elements.
+      #
+      def csp_meta_tag
+        if content_security_policy?
+          tag("meta", name: "csp-nonce", content: content_security_policy_nonce)
+        end
+      end
+    end
+  end
+end
diff --git a/actionview/lib/action_view/helpers/csrf_helper.rb b/actionview/lib/action_view/helpers/csrf_helper.rb
index d1b83f87d3..69c59844a6 100644
--- a/actionview/lib/action_view/helpers/csrf_helper.rb
+++ b/actionview/lib/action_view/helpers/csrf_helper.rb
@@ -2,7 +2,7 @@
 
 module ActionView
   # = Action View CSRF Helper
-  module Helpers
+  module Helpers #:nodoc:
     module CsrfHelper
       # Returns meta tags "csrf-param" and "csrf-token" with the name of the cross-site
       # request forgery protection parameter and token, respectively.
diff --git a/actionview/lib/action_view/helpers/date_helper.rb b/actionview/lib/action_view/helpers/date_helper.rb
index 339d582f76..620e1e9f21 100644
--- a/actionview/lib/action_view/helpers/date_helper.rb
+++ b/actionview/lib/action_view/helpers/date_helper.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "date"
-require_relative "tag_helper"
+require "action_view/helpers/tag_helper"
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/date/conversions"
 require "active_support/core_ext/hash/slice"
@@ -9,7 +9,7 @@ require "active_support/core_ext/object/acts_like"
 require "active_support/core_ext/object/with_options"
 
 module ActionView
-  module Helpers
+  module Helpers #:nodoc:
     # = Action View Date Helpers
     #
     # The Date Helper primarily creates select/option tags for different kinds of dates and times or date and time
@@ -116,7 +116,7 @@ module ActionView
             when 10..19 then locale.t :less_than_x_seconds, count: 20
             when 20..39 then locale.t :half_a_minute
             when 40..59 then locale.t :less_than_x_minutes, count: 1
-              else             locale.t :x_minutes,           count: 1
+            else             locale.t :x_minutes,           count: 1
             end
 
           when 2...45           then locale.t :x_minutes,      count: distance_in_minutes
@@ -131,7 +131,7 @@ module ActionView
           when 43200...86400    then locale.t :about_x_months, count: (distance_in_minutes.to_f / 43200.0).round
             # 60 days up to 365 days
           when 86400...525600   then locale.t :x_months,       count: (distance_in_minutes.to_f / 43200.0).round
-            else
+          else
             from_year = from_time.year
             from_year += 1 if from_time.month >= 3
             to_year = to_time.year
@@ -302,15 +302,15 @@ module ActionView
       #   time_select("article", "start_time", include_seconds: true)
       #
       #   # You can set the <tt>:minute_step</tt> to 15 which will give you: 00, 15, 30, and 45.
-      #   time_select 'game', 'game_time', {minute_step: 15}
+      #   time_select 'game', 'game_time', { minute_step: 15 }
       #
       #   # Creates a time select tag with a custom prompt. Use <tt>prompt: true</tt> for generic prompts.
-      #   time_select("article", "written_on", prompt: {hour: 'Choose hour', minute: 'Choose minute', second: 'Choose seconds'})
-      #   time_select("article", "written_on", prompt: {hour: true}) # generic prompt for hours
+      #   time_select("article", "written_on", prompt: { hour: 'Choose hour', minute: 'Choose minute', second: 'Choose seconds' })
+      #   time_select("article", "written_on", prompt: { hour: true }) # generic prompt for hours
       #   time_select("article", "written_on", prompt: true) # generic prompts for all
       #
       #   # You can set :ampm option to true which will show the hours as: 12 PM, 01 AM .. 11 PM.
-      #   time_select 'game', 'game_time', {ampm: true}
+      #   time_select 'game', 'game_time', { ampm: true }
       #
       # The selects are prepared for multi-parameter assignment to an Active Record object.
       #
@@ -346,8 +346,8 @@ module ActionView
       #   datetime_select("article", "written_on", discard_type: true)
       #
       #   # Generates a datetime select with a custom prompt. Use <tt>prompt: true</tt> for generic prompts.
-      #   datetime_select("article", "written_on", prompt: {day: 'Choose day', month: 'Choose month', year: 'Choose year'})
-      #   datetime_select("article", "written_on", prompt: {hour: true}) # generic prompt for hours
+      #   datetime_select("article", "written_on", prompt: { day: 'Choose day', month: 'Choose month', year: 'Choose year' })
+      #   datetime_select("article", "written_on", prompt: { hour: true }) # generic prompt for hours
       #   datetime_select("article", "written_on", prompt: true) # generic prompts for all
       #
       # The selects are prepared for multi-parameter assignment to an Active Record object.
@@ -397,8 +397,8 @@ module ActionView
       #   select_datetime(my_date_time, prefix: 'payday')
       #
       #   # Generates a datetime select with a custom prompt. Use <tt>prompt: true</tt> for generic prompts.
-      #   select_datetime(my_date_time, prompt: {day: 'Choose day', month: 'Choose month', year: 'Choose year'})
-      #   select_datetime(my_date_time, prompt: {hour: true}) # generic prompt for hours
+      #   select_datetime(my_date_time, prompt: { day: 'Choose day', month: 'Choose month', year: 'Choose year' })
+      #   select_datetime(my_date_time, prompt: { hour: true }) # generic prompt for hours
       #   select_datetime(my_date_time, prompt: true) # generic prompts for all
       def select_datetime(datetime = Time.current, options = {}, html_options = {})
         DateTimeSelector.new(datetime, options, html_options).select_datetime
@@ -436,8 +436,8 @@ module ActionView
       #   select_date(my_date, prefix: 'payday')
       #
       #   # Generates a date select with a custom prompt. Use <tt>prompt: true</tt> for generic prompts.
-      #   select_date(my_date, prompt: {day: 'Choose day', month: 'Choose month', year: 'Choose year'})
-      #   select_date(my_date, prompt: {hour: true}) # generic prompt for hours
+      #   select_date(my_date, prompt: { day: 'Choose day', month: 'Choose month', year: 'Choose year' })
+      #   select_date(my_date, prompt: { hour: true }) # generic prompt for hours
       #   select_date(my_date, prompt: true) # generic prompts for all
       def select_date(date = Date.current, options = {}, html_options = {})
         DateTimeSelector.new(date, options, html_options).select_date
@@ -476,8 +476,8 @@ module ActionView
       #   select_time(my_time, start_hour: 2, end_hour: 14)
       #
       #   # Generates a time select with a custom prompt. Use <tt>:prompt</tt> to true for generic prompts.
-      #   select_time(my_time, prompt: {day: 'Choose day', month: 'Choose month', year: 'Choose year'})
-      #   select_time(my_time, prompt: {hour: true}) # generic prompt for hours
+      #   select_time(my_time, prompt: { day: 'Choose day', month: 'Choose month', year: 'Choose year' })
+      #   select_time(my_time, prompt: { hour: true }) # generic prompt for hours
       #   select_time(my_time, prompt: true) # generic prompts for all
       def select_time(datetime = Time.current, options = {}, html_options = {})
         DateTimeSelector.new(datetime, options, html_options).select_time
@@ -681,9 +681,8 @@ module ActionView
         options  = args.extract_options!
         format   = options.delete(:format) || :long
         content  = args.first || I18n.l(date_or_time, format: format)
-        datetime = date_or_time.acts_like?(:time) ? date_or_time.xmlschema : date_or_time.iso8601
 
-        content_tag("time".freeze, content, options.reverse_merge(datetime: datetime), &block)
+        content_tag("time".freeze, content, options.reverse_merge(datetime: date_or_time.iso8601), &block)
       end
 
       private
diff --git a/actionview/lib/action_view/helpers/debug_helper.rb b/actionview/lib/action_view/helpers/debug_helper.rb
index 232d688077..88ceba414b 100644
--- a/actionview/lib/action_view/helpers/debug_helper.rb
+++ b/actionview/lib/action_view/helpers/debug_helper.rb
@@ -4,7 +4,7 @@ module ActionView
   # = Action View Debug Helper
   #
   # Provides a set of methods for making it easier to debug Rails objects.
-  module Helpers
+  module Helpers #:nodoc:
     module DebugHelper
       include TagHelper
 
@@ -24,7 +24,7 @@ module ActionView
       #     created_at:
       #   </pre>
       def debug(object)
-        Marshal::dump(object)
+        Marshal.dump(object)
         object = ERB::Util.html_escape(object.to_yaml)
         content_tag(:pre, object, class: "debug_dump")
       rescue # errors from Marshal or YAML
diff --git a/actionview/lib/action_view/helpers/form_helper.rb b/actionview/lib/action_view/helpers/form_helper.rb
index bcda066837..2d5c5684c1 100644
--- a/actionview/lib/action_view/helpers/form_helper.rb
+++ b/actionview/lib/action_view/helpers/form_helper.rb
@@ -1,12 +1,12 @@
 # frozen_string_literal: true
 
 require "cgi"
-require_relative "date_helper"
-require_relative "tag_helper"
-require_relative "form_tag_helper"
-require_relative "active_model_helper"
-require_relative "../model_naming"
-require_relative "../record_identifier"
+require "action_view/helpers/date_helper"
+require "action_view/helpers/tag_helper"
+require "action_view/helpers/form_tag_helper"
+require "action_view/helpers/active_model_helper"
+require "action_view/model_naming"
+require "action_view/record_identifier"
 require "active_support/core_ext/module/attribute_accessors"
 require "active_support/core_ext/hash/slice"
 require "active_support/core_ext/string/output_safety"
@@ -14,12 +14,12 @@ require "active_support/core_ext/string/inflections"
 
 module ActionView
   # = Action View Form Helpers
-  module Helpers
+  module Helpers #:nodoc:
     # Form helpers are designed to make working with resources much easier
     # compared to using vanilla HTML.
     #
     # Typically, a form designed to create or update a resource reflects the
-    # identity of the resource in several ways: (i) the url that the form is
+    # identity of the resource in several ways: (i) the URL that the form is
     # sent to (the form element's +action+ attribute) should result in a request
     # being routed to the appropriate controller action (with the appropriate <tt>:id</tt>
     # parameter in the case of an existing resource), (ii) input fields should
@@ -166,7 +166,7 @@ module ActionView
       #   So for example you may use a named route directly. When the model is
       #   represented by a string or symbol, as in the example above, if the
       #   <tt>:url</tt> option is not specified, by default the form will be
-      #   sent back to the current url (We will describe below an alternative
+      #   sent back to the current URL (We will describe below an alternative
       #   resource-oriented usage of +form_for+ in which the URL does not need
       #   to be specified explicitly).
       # * <tt>:namespace</tt> - A namespace for your form to ensure uniqueness of
@@ -478,6 +478,8 @@ module ActionView
 
       mattr_accessor :form_with_generates_remote_forms, default: true
 
+      mattr_accessor :form_with_generates_ids, default: false
+
       # Creates a form tag based on mixing URLs, scopes, or models.
       #
       #   # Using just a URL:
@@ -606,10 +608,10 @@ module ActionView
       #   This is helpful when fragment-caching the form. Remote forms
       #   get the authenticity token from the <tt>meta</tt> tag, so embedding is
       #   unnecessary unless you support browsers without JavaScript.
-      # * <tt>:local</tt> - By default form submits are remote and unobstrusive XHRs.
+      # * <tt>:local</tt> - By default form submits are remote and unobtrusive XHRs.
       #   Disable remote submits with <tt>local: true</tt>.
-      # * <tt>:skip_enforcing_utf8</tt> - By default a hidden field named +utf8+
-      #   is output to enforce UTF-8 submits. Set to true to skip the field.
+      # * <tt>:skip_enforcing_utf8</tt> - If set to true, a hidden input with name
+      #   utf8 is not output.
       # * <tt>:builder</tt> - Override the object used to build the form.
       # * <tt>:id</tt> - Optional HTML id attribute.
       # * <tt>:class</tt> - Optional HTML class attribute.
@@ -640,16 +642,6 @@ module ActionView
       #
       # Where <tt>@document = Document.find(params[:id])</tt>.
       #
-      # When using labels +form_with+ requires setting the id on the field being
-      # labelled:
-      #
-      #   <%= form_with(model: @post) do |form| %>
-      #     <%= form.label :title %>
-      #     <%= form.text_field :title, id: :post_title %>
-      #   <% end %>
-      #
-      # See +label+ for more on how the +for+ attribute is derived.
-      #
       # === Mixing with other form helpers
       #
       # While +form_with+ uses a FormBuilder object it's possible to mix and
@@ -746,7 +738,7 @@ module ActionView
       #   end
       def form_with(model: nil, scope: nil, url: nil, format: nil, **options)
         options[:allow_method_names_outside_object] = true
-        options[:skip_default_ids] = true
+        options[:skip_default_ids] = !form_with_generates_ids
 
         if model
           url ||= polymorphic_path(model, format: format)
@@ -1022,14 +1014,13 @@ module ActionView
       #   <%= fields :comment do |fields| %>
       #     <%= fields.text_field :body %>
       #   <% end %>
-      #   # => <input type="text" name="comment[body]>
+      #   # => <input type="text" name="comment[body]">
       #
       #   # Using a model infers the scope and assigns field values:
-      #   <%= fields model: Comment.new(body: "full bodied") do |fields| %<
+      #   <%= fields model: Comment.new(body: "full bodied") do |fields| %>
       #     <%= fields.text_field :body %>
       #   <% end %>
-      #   # =>
-      #   <input type="text" name="comment[body] value="full bodied">
+      #   # => <input type="text" name="comment[body]" value="full bodied">
       #
       #   # Using +fields+ with +form_with+:
       #   <%= form_with model: @post do |form| %>
@@ -1044,16 +1035,6 @@ module ActionView
       # or model is yielded, so any generated field names are prefixed with
       # either the passed scope or the scope inferred from the <tt>:model</tt>.
       #
-      # When using labels +fields+ requires setting the id on the field being
-      # labelled:
-      #
-      #   <%= fields :comment do |fields| %>
-      #     <%= fields.label :body %>
-      #     <%= fields.text_field :body, id: :comment_body %>
-      #   <% end %>
-      #
-      # See +label+ for more on how the +for+ attribute is derived.
-      #
       # === Mixing with other form helpers
       #
       # While +form_with+ uses a FormBuilder object it's possible to mix and
@@ -1072,7 +1053,7 @@ module ActionView
       # FormOptionsHelper#collection_select and DateHelper#datetime_select.
       def fields(scope = nil, model: nil, **options, &block)
         options[:allow_method_names_outside_object] = true
-        options[:skip_default_ids] = true
+        options[:skip_default_ids] = !form_with_generates_ids
 
         if model
           scope ||= model_name_from_record_or_class(model).param_key
@@ -1538,10 +1519,10 @@ module ActionView
 
       private
         def html_options_for_form_with(url_for_options = nil, model = nil, html: {}, local: !form_with_generates_remote_forms,
-          skip_enforcing_utf8: false, **options)
+          skip_enforcing_utf8: nil, **options)
           html_options = options.slice(:id, :class, :multipart, :method, :data).merge(html)
           html_options[:method] ||= :patch if model.respond_to?(:persisted?) && model.persisted?
-          html_options[:enforce_utf8] = !skip_enforcing_utf8
+          html_options[:enforce_utf8] = !skip_enforcing_utf8 unless skip_enforcing_utf8.nil?
 
           html_options[:enctype] = "multipart/form-data" if html_options.delete(:multipart)
 
@@ -1985,11 +1966,11 @@ module ActionView
       # See the docs for the <tt>ActionView::FormHelper.fields</tt> helper method.
       def fields(scope = nil, model: nil, **options, &block)
         options[:allow_method_names_outside_object] = true
-        options[:skip_default_ids] = true
+        options[:skip_default_ids] = !FormHelper.form_with_generates_ids
 
         convert_to_legacy_options(options)
 
-        fields_for(scope || model, model, **options, &block)
+        fields_for(scope || model, model, options, &block)
       end
 
       # Returns a label tag tailored for labelling an input field for a specified attribute (identified by +method+) on an object
@@ -2265,7 +2246,7 @@ module ActionView
         @template.button_tag(value, options, &block)
       end
 
-      def emitted_hidden_id?
+      def emitted_hidden_id? # :nodoc:
         @emitted_hidden_id ||= nil
       end
 
@@ -2285,7 +2266,12 @@ module ActionView
           end
 
           defaults = []
-          defaults << :"helpers.submit.#{object_name}.#{key}"
+          # Object is a model and it is not overwritten by as and scope option.
+          if object.respond_to?(:model_name) && object_name.to_s == model.downcase
+            defaults << :"helpers.submit.#{object.model_name.i18n_key}.#{key}"
+          else
+            defaults << :"helpers.submit.#{object_name}.#{key}"
+          end
           defaults << :"helpers.submit.#{key}"
           defaults << "#{key.to_s.humanize} #{model}"
 
diff --git a/actionview/lib/action_view/helpers/form_options_helper.rb b/actionview/lib/action_view/helpers/form_options_helper.rb
index 0f1a452652..d02f641867 100644
--- a/actionview/lib/action_view/helpers/form_options_helper.rb
+++ b/actionview/lib/action_view/helpers/form_options_helper.rb
@@ -2,21 +2,21 @@
 
 require "cgi"
 require "erb"
-require_relative "form_helper"
+require "action_view/helpers/form_helper"
 require "active_support/core_ext/string/output_safety"
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/array/wrap"
 
 module ActionView
   # = Action View Form Option Helpers
-  module Helpers
+  module Helpers #:nodoc:
     # Provides a number of methods for turning different kinds of containers into a set of option tags.
     #
     # The <tt>collection_select</tt>, <tt>select</tt> and <tt>time_zone_select</tt> methods take an <tt>options</tt> parameter, a hash:
     #
     # * <tt>:include_blank</tt> - set to true or a prompt string if the first option element of the select element is a blank. Useful if there is not a default value required for the select element.
     #
-    #     select("post", "category", Post::CATEGORIES, {include_blank: true})
+    #     select("post", "category", Post::CATEGORIES, { include_blank: true })
     #
     #   could become:
     #
@@ -30,7 +30,7 @@ module ActionView
     #
     #   Example with <tt>@post.person_id => 2</tt>:
     #
-    #     select("post", "person_id", Person.all.collect {|p| [ p.name, p.id ] }, {include_blank: 'None'})
+    #     select("post", "person_id", Person.all.collect { |p| [ p.name, p.id ] }, { include_blank: 'None' })
     #
     #   could become:
     #
@@ -43,7 +43,7 @@ module ActionView
     #
     # * <tt>:prompt</tt> - set to true or a prompt string. When the select element doesn't have a value yet, this prepends an option with a generic prompt -- "Please select" -- or the given prompt string.
     #
-    #     select("post", "person_id", Person.all.collect {|p| [ p.name, p.id ] }, {prompt: 'Select Person'})
+    #     select("post", "person_id", Person.all.collect { |p| [ p.name, p.id ] }, { prompt: 'Select Person' })
     #
     #   could become:
     #
@@ -69,7 +69,7 @@ module ActionView
     #
     # * <tt>:disabled</tt> - can be a single value or an array of values that will be disabled options in the final output.
     #
-    #     select("post", "category", Post::CATEGORIES, {disabled: 'restricted'})
+    #     select("post", "category", Post::CATEGORIES, { disabled: 'restricted' })
     #
     #   could become:
     #
@@ -82,7 +82,7 @@ module ActionView
     #
     #   When used with the <tt>collection_select</tt> helper, <tt>:disabled</tt> can also be a Proc that identifies those options that should be disabled.
     #
-    #     collection_select(:post, :category_id, Category.all, :id, :name, {disabled: -> (category) { category.archived? }})
+    #     collection_select(:post, :category_id, Category.all, :id, :name, { disabled: -> (category) { category.archived? } })
     #
     #   If the categories "2008 stuff" and "Christmas" return true when the method <tt>archived?</tt> is called, this would return:
     #     <select name="post[category_id]" id="post_category_id">
@@ -107,7 +107,7 @@ module ActionView
       #
       # For example:
       #
-      #   select("post", "person_id", Person.all.collect {|p| [ p.name, p.id ] }, { include_blank: true })
+      #   select("post", "person_id", Person.all.collect { |p| [ p.name, p.id ] }, { include_blank: true })
       #
       # would become:
       #
@@ -214,9 +214,13 @@ module ActionView
       # * +method+ - The attribute of +object+ corresponding to the select tag
       # * +collection+ - An array of objects representing the <tt><optgroup></tt> tags.
       # * +group_method+ - The name of a method which, when called on a member of +collection+, returns an
-      #   array of child objects representing the <tt><option></tt> tags.
+      #   array of child objects representing the <tt><option></tt> tags. It can also be any object that responds
+      #   to +call+, such as a +proc+, that will be called for each member of the +collection+ to retrieve the
+      #   value.
       # * +group_label_method+ - The name of a method which, when called on a member of +collection+, returns a
-      #   string to be used as the +label+ attribute for its <tt><optgroup></tt> tag.
+      #   string to be used as the +label+ attribute for its <tt><optgroup></tt> tag. It can also be any object
+      #   that responds to +call+, such as a +proc+, that will be called for each member of the +collection+ to
+      #   retrieve the label.
       # * +option_key_method+ - The name of a method which, when called on a child object of a member of
       #   +collection+, returns a value to be used as the +value+ attribute for its <tt><option></tt> tag.
       # * +option_value_method+ - The name of a method which, when called on a child object of a member of
@@ -279,17 +283,17 @@ module ActionView
       # Finally, this method supports a <tt>:default</tt> option, which selects
       # a default ActiveSupport::TimeZone if the object's time zone is +nil+.
       #
-      #   time_zone_select( "user", "time_zone", nil, include_blank: true)
+      #   time_zone_select("user", "time_zone", nil, include_blank: true)
       #
-      #   time_zone_select( "user", "time_zone", nil, default: "Pacific Time (US & Canada)" )
+      #   time_zone_select("user", "time_zone", nil, default: "Pacific Time (US & Canada)")
       #
-      #   time_zone_select( "user", 'time_zone', ActiveSupport::TimeZone.us_zones, default: "Pacific Time (US & Canada)")
+      #   time_zone_select("user", 'time_zone', ActiveSupport::TimeZone.us_zones, default: "Pacific Time (US & Canada)")
       #
-      #   time_zone_select( "user", 'time_zone', [ ActiveSupport::TimeZone['Alaska'], ActiveSupport::TimeZone['Hawaii'] ])
+      #   time_zone_select("user", 'time_zone', [ ActiveSupport::TimeZone['Alaska'], ActiveSupport::TimeZone['Hawaii'] ])
       #
-      #   time_zone_select( "user", 'time_zone', /Australia/)
+      #   time_zone_select("user", 'time_zone', /Australia/)
       #
-      #   time_zone_select( "user", "time_zone", ActiveSupport::TimeZone.all.sort, model: ActiveSupport::TimeZone)
+      #   time_zone_select("user", "time_zone", ActiveSupport::TimeZone.all.sort, model: ActiveSupport::TimeZone)
       def time_zone_select(object, method, priority_zones = nil, options = {}, html_options = {})
         Tags::TimeZoneSelect.new(object, method, self, priority_zones, options, html_options).render
       end
@@ -319,12 +323,12 @@ module ActionView
       #
       # You can optionally provide HTML attributes as the last element of the array.
       #
-      #   options_for_select([ "Denmark", ["USA", {class: 'bold'}], "Sweden" ], ["USA", "Sweden"])
+      #   options_for_select([ "Denmark", ["USA", { class: 'bold' }], "Sweden" ], ["USA", "Sweden"])
       #   # => <option value="Denmark">Denmark</option>
       #   # => <option value="USA" class="bold" selected="selected">USA</option>
       #   # => <option value="Sweden" selected="selected">Sweden</option>
       #
-      #   options_for_select([["Dollar", "$", {class: "bold"}], ["Kroner", "DKK", {onclick: "alert('HI');"}]])
+      #   options_for_select([["Dollar", "$", { class: "bold" }], ["Kroner", "DKK", { onclick: "alert('HI');" }]])
       #   # => <option value="$" class="bold">Dollar</option>
       #   # => <option value="DKK" onclick="alert('HI');">Kroner</option>
       #
@@ -457,9 +461,9 @@ module ActionView
       def option_groups_from_collection_for_select(collection, group_method, group_label_method, option_key_method, option_value_method, selected_key = nil)
         collection.map do |group|
           option_tags = options_from_collection_for_select(
-            group.send(group_method), option_key_method, option_value_method, selected_key)
+            value_for_collection(group, group_method), option_key_method, option_value_method, selected_key)
 
-          content_tag("optgroup".freeze, option_tags, label: group.send(group_label_method))
+          content_tag("optgroup".freeze, option_tags, label: value_for_collection(group, group_label_method))
         end.join.html_safe
       end
 
diff --git a/actionview/lib/action_view/helpers/form_tag_helper.rb b/actionview/lib/action_view/helpers/form_tag_helper.rb
index 14cbed24b0..ba09738beb 100644
--- a/actionview/lib/action_view/helpers/form_tag_helper.rb
+++ b/actionview/lib/action_view/helpers/form_tag_helper.rb
@@ -1,13 +1,13 @@
 # frozen_string_literal: true
 
 require "cgi"
-require_relative "tag_helper"
+require "action_view/helpers/tag_helper"
 require "active_support/core_ext/string/output_safety"
 require "active_support/core_ext/module/attribute_accessors"
 
 module ActionView
   # = Action View Form Tag Helpers
-  module Helpers
+  module Helpers #:nodoc:
     # Provides a number of methods for creating form tags that don't rely on an Active Record object assigned to the template like
     # FormHelper does. Instead, you provide the names and values manually.
     #
@@ -22,6 +22,8 @@ module ActionView
       mattr_accessor :embed_authenticity_token_in_remote_forms
       self.embed_authenticity_token_in_remote_forms = nil
 
+      mattr_accessor :default_enforce_utf8, default: true
+
       # Starts a form tag that points the action to a url configured with <tt>url_for_options</tt> just like
       # ActionController::Base#url_for. The method for the form defaults to POST.
       #
@@ -115,7 +117,7 @@ module ActionView
       #   #    <option>Write</option></select>
       #
       #   select_tag "people", options_from_collection_for_select(@people, "id", "name"), include_blank: true
-      #   # => <select id="people" name="people"><option value=""></option><option value="1">David</option></select>
+      #   # => <select id="people" name="people"><option value="" label=" "></option><option value="1">David</option></select>
       #
       #   select_tag "people", options_from_collection_for_select(@people, "id", "name"), include_blank: "All"
       #   # => <select id="people" name="people"><option value="">All</option><option value="1">David</option></select>
@@ -387,14 +389,14 @@ module ActionView
       # * Any other key creates standard HTML options for the tag.
       #
       # ==== Examples
-      #   radio_button_tag 'gender', 'male'
-      #   # => <input id="gender_male" name="gender" type="radio" value="male" />
+      #   radio_button_tag 'favorite_color', 'maroon'
+      #   # => <input id="favorite_color_maroon" name="favorite_color" type="radio" value="maroon" />
       #
       #   radio_button_tag 'receive_updates', 'no', true
       #   # => <input checked="checked" id="receive_updates_no" name="receive_updates" type="radio" value="no" />
       #
       #   radio_button_tag 'time_slot', "3:00 p.m.", false, disabled: true
-      #   # => <input disabled="disabled" id="time_slot_300_pm" name="time_slot" type="radio" value="3:00 p.m." />
+      #   # => <input disabled="disabled" id="time_slot_3:00_p.m." name="time_slot" type="radio" value="3:00 p.m." />
       #
       #   radio_button_tag 'color', "green", true, class: "color_input"
       #   # => <input checked="checked" class="color_input" id="color_green" name="color" type="radio" value="green" />
@@ -456,7 +458,7 @@ module ActionView
       # submit tag but it isn't supported in legacy browsers. However,
       # the button tag does allow for richer labels such as images and emphasis,
       # so this helper will also accept a block. By default, it will create
-      # a button tag with type `submit`, if type is not given.
+      # a button tag with type <tt>submit</tt>, if type is not given.
       #
       # ==== Options
       # * <tt>:data</tt> - This option can be used to add custom data attributes.
@@ -549,7 +551,8 @@ module ActionView
       #   # => <input src="/assets/save.png" data-confirm="Are you sure?" type="image" />
       def image_submit_tag(source, options = {})
         options = options.stringify_keys
-        tag :input, { "type" => "image", "src" => path_to_image(source) }.update(options)
+        src = path_to_image(source, skip_pipeline: options.delete("skip_pipeline"))
+        tag :input, { "type" => "image", "src" => src }.update(options)
       end
 
       # Creates a field set for grouping HTML form elements.
@@ -866,7 +869,7 @@ module ActionView
               })
             end
 
-          if html_options.delete("enforce_utf8") { true }
+          if html_options.delete("enforce_utf8") { default_enforce_utf8 }
             utf8_enforcer_tag + method_tag
           else
             method_tag
diff --git a/actionview/lib/action_view/helpers/javascript_helper.rb b/actionview/lib/action_view/helpers/javascript_helper.rb
index cce7c1dcfd..830088bea3 100644
--- a/actionview/lib/action_view/helpers/javascript_helper.rb
+++ b/actionview/lib/action_view/helpers/javascript_helper.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-require_relative "tag_helper"
+require "action_view/helpers/tag_helper"
 
 module ActionView
-  module Helpers
+  module Helpers #:nodoc:
     module JavaScriptHelper
       JS_ESCAPE_MAP = {
         '\\'    => '\\\\',
@@ -63,6 +63,13 @@ module ActionView
       #   <%= javascript_tag defer: 'defer' do -%>
       #     alert('All is good')
       #   <% end -%>
+      #
+      # If you have a content security policy enabled then you can add an automatic
+      # nonce value by passing <tt>nonce: true</tt> as part of +html_options+. Example:
+      #
+      #   <%= javascript_tag nonce: true do -%>
+      #     alert('All is good')
+      #   <% end -%>
       def javascript_tag(content_or_options_with_block = nil, html_options = {}, &block)
         content =
           if block_given?
@@ -72,6 +79,10 @@ module ActionView
             content_or_options_with_block
           end
 
+        if html_options[:nonce] == true
+          html_options[:nonce] = content_security_policy_nonce
+        end
+
         content_tag("script".freeze, javascript_cdata_section(content), html_options)
       end
 
diff --git a/actionview/lib/action_view/helpers/record_tag_helper.rb b/actionview/lib/action_view/helpers/record_tag_helper.rb
deleted file mode 100644
index 4303de4209..0000000000
--- a/actionview/lib/action_view/helpers/record_tag_helper.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-# frozen_string_literal: true
-
-module ActionView
-  module Helpers
-    module RecordTagHelper
-      def div_for(*) # :nodoc:
-        raise NoMethodError, "The `div_for` method has been removed from " \
-          "Rails. To continue using it, add the `record_tag_helper` gem to " \
-          "your Gemfile:\n" \
-          "  gem 'record_tag_helper', '~> 1.0'\n" \
-          "Consult the Rails upgrade guide for details."
-      end
-
-      def content_tag_for(*) # :nodoc:
-        raise NoMethodError, "The `content_tag_for` method has been removed from " \
-          "Rails. To continue using it, add the `record_tag_helper` gem to " \
-          "your Gemfile:\n" \
-          "  gem 'record_tag_helper', '~> 1.0'\n" \
-          "Consult the Rails upgrade guide for details."
-      end
-    end
-  end
-end
diff --git a/actionview/lib/action_view/helpers/rendering_helper.rb b/actionview/lib/action_view/helpers/rendering_helper.rb
index 2702fa28b2..1e12aa2736 100644
--- a/actionview/lib/action_view/helpers/rendering_helper.rb
+++ b/actionview/lib/action_view/helpers/rendering_helper.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 module ActionView
-  module Helpers
+  module Helpers #:nodoc:
     # = Action View Rendering
     #
     # Implements methods that allow rendering from a view context.
@@ -13,7 +13,6 @@ module ActionView
       # * <tt>:partial</tt> - See <tt>ActionView::PartialRenderer</tt>.
       # * <tt>:file</tt> - Renders an explicit template file (this used to be the old default), add :locals to pass in those.
       # * <tt>:inline</tt> - Renders an inline template similar to how it's done in the controller.
-      # * <tt>:text</tt> - Renders the text passed in out.
       # * <tt>:plain</tt> - Renders the text passed in out. Setting the content
       #   type as <tt>text/plain</tt>.
       # * <tt>:html</tt> - Renders the HTML safe string passed in out, otherwise
diff --git a/actionview/lib/action_view/helpers/sanitize_helper.rb b/actionview/lib/action_view/helpers/sanitize_helper.rb
index 713b2fbb45..275a2dffb4 100644
--- a/actionview/lib/action_view/helpers/sanitize_helper.rb
+++ b/actionview/lib/action_view/helpers/sanitize_helper.rb
@@ -5,7 +5,7 @@ require "rails-html-sanitizer"
 
 module ActionView
   # = Action View Sanitize Helpers
-  module Helpers
+  module Helpers #:nodoc:
     # The SanitizeHelper module provides a set of methods for scrubbing text of undesired HTML elements.
     # These helper methods extend Action View making them callable within your template files.
     module SanitizeHelper
diff --git a/actionview/lib/action_view/helpers/tag_helper.rb b/actionview/lib/action_view/helpers/tag_helper.rb
index a64d7e396e..d12989ea64 100644
--- a/actionview/lib/action_view/helpers/tag_helper.rb
+++ b/actionview/lib/action_view/helpers/tag_helper.rb
@@ -88,9 +88,10 @@ module ActionView
           if value.is_a?(Array)
             value = escape ? safe_join(value, " ".freeze) : value.join(" ".freeze)
           else
-            value = escape ? ERB::Util.unwrapped_html_escape(value) : value.to_s
+            value = escape ? ERB::Util.unwrapped_html_escape(value) : value.to_s.dup
           end
-          %(#{key}="#{value.gsub('"'.freeze, '&quot;'.freeze)}")
+          value.gsub!('"'.freeze, "&quot;".freeze)
+          %(#{key}="#{value}")
         end
 
         private
@@ -166,7 +167,7 @@ module ActionView
       # This may come in handy when using jQuery's HTML5-aware <tt>.data()</tt>
       # from 1.4.3.
       #
-      #   tag.div data: { city_state: %w( Chigaco IL ) }
+      #   tag.div data: { city_state: %w( Chicago IL ) }
       #   # => <div data-city-state="[&quot;Chicago&quot;,&quot;IL&quot;]"></div>
       #
       # The generated attributes are escaped by default. This can be disabled using
@@ -227,10 +228,10 @@ module ActionView
       #   tag("img", src: "open & shut.png")
       #   # => <img src="open &amp; shut.png" />
       #
-      #   tag("img", {src: "open &amp; shut.png"}, false, false)
+      #   tag("img", { src: "open &amp; shut.png" }, false, false)
       #   # => <img src="open &amp; shut.png" />
       #
-      #   tag("div", data: {name: 'Stephen', city_state: %w(Chicago IL)})
+      #   tag("div", data: { name: 'Stephen', city_state: %w(Chicago IL) })
       #   # => <div data-name="Stephen" data-city-state="[&quot;Chicago&quot;,&quot;IL&quot;]" />
       def tag(name = nil, options = nil, open = false, escape = true)
         if name.nil?
diff --git a/actionview/lib/action_view/helpers/tags.rb b/actionview/lib/action_view/helpers/tags.rb
index 2552ebba4e..566668b958 100644
--- a/actionview/lib/action_view/helpers/tags.rb
+++ b/actionview/lib/action_view/helpers/tags.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 module ActionView
-  module Helpers
+  module Helpers #:nodoc:
     module Tags #:nodoc:
       extend ActiveSupport::Autoload
 
diff --git a/actionview/lib/action_view/helpers/tags/base.rb b/actionview/lib/action_view/helpers/tags/base.rb
index 922d4c5390..eef527d36f 100644
--- a/actionview/lib/action_view/helpers/tags/base.rb
+++ b/actionview/lib/action_view/helpers/tags/base.rb
@@ -35,7 +35,7 @@ module ActionView
 
         private
 
-          def value(object)
+          def value
             if @allow_method_names_outside_object
               object.public_send @method_name if object && object.respond_to?(@method_name)
             else
@@ -43,19 +43,19 @@ module ActionView
             end
           end
 
-          def value_before_type_cast(object)
+          def value_before_type_cast
             unless object.nil?
               method_before_type_cast = @method_name + "_before_type_cast"
 
-              if value_came_from_user?(object) && object.respond_to?(method_before_type_cast)
+              if value_came_from_user? && object.respond_to?(method_before_type_cast)
                 object.public_send(method_before_type_cast)
               else
-                value(object)
+                value
               end
             end
           end
 
-          def value_came_from_user?(object)
+          def value_came_from_user?
             method_name = "#{@method_name}_came_from_user?"
             !object.respond_to?(method_name) || object.public_send(method_name)
           end
@@ -97,7 +97,7 @@ module ActionView
             index = name_and_id_index(options)
             options["name"] = options.fetch("name") { tag_name(options["multiple"], index) }
 
-            unless skip_default_ids?
+            if generate_ids?
               options["id"] = options.fetch("id") { tag_id(index) }
               if namespace = options.delete("namespace")
                 options["id"] = options["id"] ? "#{namespace}_#{options['id']}" : namespace
@@ -109,11 +109,11 @@ module ActionView
             # a little duplication to construct less strings
             case
             when @object_name.empty?
-              "#{sanitized_method_name}#{"[]" if multiple}"
+              "#{sanitized_method_name}#{multiple ? "[]" : ""}"
             when index
-              "#{@object_name}[#{index}][#{sanitized_method_name}]#{"[]" if multiple}"
+              "#{@object_name}[#{index}][#{sanitized_method_name}]#{multiple ? "[]" : ""}"
             else
-              "#{@object_name}[#{sanitized_method_name}]#{"[]" if multiple}"
+              "#{@object_name}[#{sanitized_method_name}]#{multiple ? "[]" : ""}"
             end
           end
 
@@ -150,7 +150,7 @@ module ActionView
               options[:include_blank] ||= true unless options[:prompt]
             end
 
-            value = options.fetch(:selected) { value(object) }
+            value = options.fetch(:selected) { value() }
             select = content_tag("select", add_options(option_tags, options, value), html_options)
 
             if html_options["multiple"] && options.fetch(:include_hidden, true)
@@ -170,7 +170,11 @@ module ActionView
               option_tags = tag_builder.content_tag_string("option", options[:include_blank].kind_of?(String) ? options[:include_blank] : nil, value: "") + "\n" + option_tags
             end
             if value.blank? && options[:prompt]
-              option_tags = tag_builder.content_tag_string("option", prompt_text(options[:prompt]), value: "") + "\n" + option_tags
+              tag_options = { value: "" }.tap do |prompt_opts|
+                prompt_opts[:disabled] = true if options[:disabled] == ""
+                prompt_opts[:selected] = true if options[:selected] == ""
+              end
+              option_tags = tag_builder.content_tag_string("option", prompt_text(options[:prompt]), tag_options) + "\n" + option_tags
             end
             option_tags
           end
@@ -183,8 +187,8 @@ module ActionView
             end
           end
 
-          def skip_default_ids?
-            @skip_default_ids
+          def generate_ids?
+            !@skip_default_ids
           end
       end
     end
diff --git a/actionview/lib/action_view/helpers/tags/check_box.rb b/actionview/lib/action_view/helpers/tags/check_box.rb
index c7d8cd0e97..4327e07cae 100644
--- a/actionview/lib/action_view/helpers/tags/check_box.rb
+++ b/actionview/lib/action_view/helpers/tags/check_box.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "checkable"
+require "action_view/helpers/tags/checkable"
 
 module ActionView
   module Helpers
@@ -18,7 +18,7 @@ module ActionView
           options = @options.stringify_keys
           options["type"]     = "checkbox"
           options["value"]    = @checked_value
-          options["checked"] = "checked" if input_checked?(object, options)
+          options["checked"] = "checked" if input_checked?(options)
 
           if options["multiple"]
             add_default_name_and_id_for_value(@checked_value, options)
diff --git a/actionview/lib/action_view/helpers/tags/checkable.rb b/actionview/lib/action_view/helpers/tags/checkable.rb
index f2f4a655a3..776fefe778 100644
--- a/actionview/lib/action_view/helpers/tags/checkable.rb
+++ b/actionview/lib/action_view/helpers/tags/checkable.rb
@@ -4,12 +4,12 @@ module ActionView
   module Helpers
     module Tags # :nodoc:
       module Checkable # :nodoc:
-        def input_checked?(object, options)
+        def input_checked?(options)
           if options.has_key?("checked")
             checked = options.delete "checked"
             checked == true || checked == "checked"
           else
-            checked?(value(object))
+            checked?(value)
           end
         end
       end
diff --git a/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb b/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
index 91c1135d20..455442178e 100644
--- a/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
+++ b/actionview/lib/action_view/helpers/tags/collection_check_boxes.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "collection_helpers"
+require "action_view/helpers/tags/collection_helpers"
 
 module ActionView
   module Helpers
diff --git a/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb b/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb
index 0b0482f74e..16d37134e5 100644
--- a/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb
+++ b/actionview/lib/action_view/helpers/tags/collection_radio_buttons.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "collection_helpers"
+require "action_view/helpers/tags/collection_helpers"
 
 module ActionView
   module Helpers
diff --git a/actionview/lib/action_view/helpers/tags/collection_select.rb b/actionview/lib/action_view/helpers/tags/collection_select.rb
index ef1d4c8d1e..6a3af1b256 100644
--- a/actionview/lib/action_view/helpers/tags/collection_select.rb
+++ b/actionview/lib/action_view/helpers/tags/collection_select.rb
@@ -15,7 +15,7 @@ module ActionView
 
         def render
           option_tags_options = {
-            selected: @options.fetch(:selected) { value(@object) },
+            selected: @options.fetch(:selected) { value },
             disabled: @options[:disabled]
           }
 
diff --git a/actionview/lib/action_view/helpers/tags/color_field.rb b/actionview/lib/action_view/helpers/tags/color_field.rb
index 8e698ef922..c5f0bb6bbb 100644
--- a/actionview/lib/action_view/helpers/tags/color_field.rb
+++ b/actionview/lib/action_view/helpers/tags/color_field.rb
@@ -6,7 +6,7 @@ module ActionView
       class ColorField < TextField # :nodoc:
         def render
           options = @options.stringify_keys
-          options["value"] ||= validate_color_string(value(object))
+          options["value"] ||= validate_color_string(value)
           @options = options
           super
         end
diff --git a/actionview/lib/action_view/helpers/tags/date_select.rb b/actionview/lib/action_view/helpers/tags/date_select.rb
index 13c0515974..fe4e3914d7 100644
--- a/actionview/lib/action_view/helpers/tags/date_select.rb
+++ b/actionview/lib/action_view/helpers/tags/date_select.rb
@@ -29,7 +29,7 @@ module ActionView
           end
 
           def datetime_selector(options, html_options)
-            datetime = options.fetch(:selected) { value(object) || default_datetime(options) }
+            datetime = options.fetch(:selected) { value || default_datetime(options) }
             @auto_index ||= nil
 
             options = options.dup
diff --git a/actionview/lib/action_view/helpers/tags/datetime_field.rb b/actionview/lib/action_view/helpers/tags/datetime_field.rb
index 0556566130..5d9b639b1b 100644
--- a/actionview/lib/action_view/helpers/tags/datetime_field.rb
+++ b/actionview/lib/action_view/helpers/tags/datetime_field.rb
@@ -6,7 +6,7 @@ module ActionView
       class DatetimeField < TextField # :nodoc:
         def render
           options = @options.stringify_keys
-          options["value"] ||= format_date(value(object))
+          options["value"] ||= format_date(value)
           options["min"] = format_date(datetime_value(options["min"]))
           options["max"] = format_date(datetime_value(options["max"]))
           @options = options
diff --git a/actionview/lib/action_view/helpers/tags/grouped_collection_select.rb b/actionview/lib/action_view/helpers/tags/grouped_collection_select.rb
index 971db8e85d..f24cb4beea 100644
--- a/actionview/lib/action_view/helpers/tags/grouped_collection_select.rb
+++ b/actionview/lib/action_view/helpers/tags/grouped_collection_select.rb
@@ -17,7 +17,7 @@ module ActionView
 
         def render
           option_tags_options = {
-            selected: @options.fetch(:selected) { value(@object) },
+            selected: @options.fetch(:selected) { value },
             disabled: @options[:disabled]
           }
 
diff --git a/actionview/lib/action_view/helpers/tags/label.rb b/actionview/lib/action_view/helpers/tags/label.rb
index 56b48bbd62..02bd099784 100644
--- a/actionview/lib/action_view/helpers/tags/label.rb
+++ b/actionview/lib/action_view/helpers/tags/label.rb
@@ -75,10 +75,6 @@ module ActionView
           def render_component(builder)
             builder.translation
           end
-
-          def skip_default_ids?
-            false # The id is used as the `for` attribute.
-          end
       end
     end
   end
diff --git a/actionview/lib/action_view/helpers/tags/radio_button.rb b/actionview/lib/action_view/helpers/tags/radio_button.rb
index 9e4f1c9e4b..621db2b1b5 100644
--- a/actionview/lib/action_view/helpers/tags/radio_button.rb
+++ b/actionview/lib/action_view/helpers/tags/radio_button.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "checkable"
+require "action_view/helpers/tags/checkable"
 
 module ActionView
   module Helpers
@@ -17,7 +17,7 @@ module ActionView
           options = @options.stringify_keys
           options["type"]     = "radio"
           options["value"]    = @tag_value
-          options["checked"] = "checked" if input_checked?(object, options)
+          options["checked"] = "checked" if input_checked?(options)
           add_default_name_and_id_for_value(@tag_value, options)
           tag("input", options)
         end
diff --git a/actionview/lib/action_view/helpers/tags/select.rb b/actionview/lib/action_view/helpers/tags/select.rb
index 0de4139101..345484ba92 100644
--- a/actionview/lib/action_view/helpers/tags/select.rb
+++ b/actionview/lib/action_view/helpers/tags/select.rb
@@ -15,7 +15,7 @@ module ActionView
 
         def render
           option_tags_options = {
-            selected: @options.fetch(:selected) { value(@object) },
+            selected: @options.fetch(:selected) { value },
             disabled: @options[:disabled]
           }
 
diff --git a/actionview/lib/action_view/helpers/tags/text_area.rb b/actionview/lib/action_view/helpers/tags/text_area.rb
index d8460a4be4..4519082ff6 100644
--- a/actionview/lib/action_view/helpers/tags/text_area.rb
+++ b/actionview/lib/action_view/helpers/tags/text_area.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "placeholderable"
+require "action_view/helpers/tags/placeholderable"
 
 module ActionView
   module Helpers
@@ -16,7 +16,7 @@ module ActionView
             options["cols"], options["rows"] = size.split("x") if size.respond_to?(:split)
           end
 
-          content_tag("textarea", options.delete("value") { value_before_type_cast(object) }, options)
+          content_tag("textarea", options.delete("value") { value_before_type_cast }, options)
         end
       end
     end
diff --git a/actionview/lib/action_view/helpers/tags/text_field.rb b/actionview/lib/action_view/helpers/tags/text_field.rb
index e4c5a49069..d92967e212 100644
--- a/actionview/lib/action_view/helpers/tags/text_field.rb
+++ b/actionview/lib/action_view/helpers/tags/text_field.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "placeholderable"
+require "action_view/helpers/tags/placeholderable"
 
 module ActionView
   module Helpers
@@ -12,7 +12,7 @@ module ActionView
           options = @options.stringify_keys
           options["size"] = options["maxlength"] unless options.key?("size")
           options["type"] ||= field_type
-          options["value"] = options.fetch("value") { value_before_type_cast(object) } unless field_type == "file"
+          options["value"] = options.fetch("value") { value_before_type_cast } unless field_type == "file"
           add_default_name_and_id(options)
           tag("input", options)
         end
diff --git a/actionview/lib/action_view/helpers/tags/time_zone_select.rb b/actionview/lib/action_view/helpers/tags/time_zone_select.rb
index 3b6bcacce0..1d06096096 100644
--- a/actionview/lib/action_view/helpers/tags/time_zone_select.rb
+++ b/actionview/lib/action_view/helpers/tags/time_zone_select.rb
@@ -13,7 +13,7 @@ module ActionView
 
         def render
           select_content_tag(
-            time_zone_options_for_select(value(@object) || @options[:default], @priority_zones, @options[:model] || ActiveSupport::TimeZone), @options, @html_options
+            time_zone_options_for_select(value || @options[:default], @priority_zones, @options[:model] || ActiveSupport::TimeZone), @options, @html_options
           )
         end
       end
diff --git a/actionview/lib/action_view/helpers/tags/translator.rb b/actionview/lib/action_view/helpers/tags/translator.rb
index fcf96d2c9c..e81ca3aef0 100644
--- a/actionview/lib/action_view/helpers/tags/translator.rb
+++ b/actionview/lib/action_view/helpers/tags/translator.rb
@@ -16,13 +16,8 @@ module ActionView
           translated_attribute || human_attribute_name
         end
 
-        # TODO Change this to private once we've dropped Ruby 2.2 support.
-        # Workaround for Ruby 2.2 "private attribute?" warning.
-        protected
-
-          attr_reader :object_name, :method_and_value, :scope, :model
-
         private
+          attr_reader :object_name, :method_and_value, :scope, :model
 
           def i18n_default
             if model
diff --git a/actionview/lib/action_view/helpers/text_helper.rb b/actionview/lib/action_view/helpers/text_helper.rb
index 3044a2c0ef..34138de00e 100644
--- a/actionview/lib/action_view/helpers/text_helper.rb
+++ b/actionview/lib/action_view/helpers/text_helper.rb
@@ -13,9 +13,9 @@ module ActionView
     #
     # ==== Sanitization
     #
-    # Most text helpers by default sanitize the given content, but do not escape it.
-    # This means HTML tags will appear in the page but all malicious code will be removed.
-    # Let's look at some examples using the +simple_format+ method:
+    # Most text helpers that generate HTML output sanitize the given input by default,
+    # but do not escape it. This means HTML tags will appear in the page but all malicious
+    # code will be removed. Let's look at some examples using the +simple_format+ method:
     #
     #   simple_format('<a href="http://example.com/">Example</a>')
     #   # => "<p><a href=\"http://example.com/\">Example</a></p>"
@@ -128,7 +128,7 @@ module ActionView
       #   # => You searched for: <a href="search?q=rails">rails</a>
       #
       #   highlight('<a href="javascript:alert(\'no!\')">ruby</a> on rails', 'rails', sanitize: false)
-      #   # => "<a>ruby</a> on <mark>rails</mark>"
+      #   # => <a href="javascript:alert('no!')">ruby</a> on <mark>rails</mark>
       def highlight(text, phrases, options = {})
         text = sanitize(text) if options.fetch(:sanitize, true)
 
@@ -422,7 +422,7 @@ module ActionView
         def to_s
           value = @values[@index].to_s
           @index = next_index
-          return value
+          value
         end
 
         private
@@ -446,7 +446,7 @@ module ActionView
         # uses an instance variable of ActionView::Base.
         def get_cycle(name)
           @_cycles = Hash.new unless defined?(@_cycles)
-          return @_cycles[name]
+          @_cycles[name]
         end
 
         def set_cycle(name, cycle_object)
diff --git a/actionview/lib/action_view/helpers/translation_helper.rb b/actionview/lib/action_view/helpers/translation_helper.rb
index 75c1161de1..d3cdab0d2f 100644
--- a/actionview/lib/action_view/helpers/translation_helper.rb
+++ b/actionview/lib/action_view/helpers/translation_helper.rb
@@ -1,12 +1,12 @@
 # frozen_string_literal: true
 
-require_relative "tag_helper"
+require "action_view/helpers/tag_helper"
 require "active_support/core_ext/string/access"
 require "i18n/exceptions"
 
 module ActionView
   # = Action View Translation Helpers
-  module Helpers
+  module Helpers #:nodoc:
     module TranslationHelper
       extend ActiveSupport::Concern
 
@@ -59,11 +59,9 @@ module ActionView
       # they can provide HTML values for.
       def translate(key, options = {})
         options = options.dup
-        has_default = options.has_key?(:default)
-        remaining_defaults = Array(options.delete(:default)).compact
-
-        if has_default && !remaining_defaults.first.kind_of?(Symbol)
-          options[:default] = remaining_defaults
+        if options.has_key?(:default)
+          remaining_defaults = Array(options.delete(:default)).compact
+          options[:default] = remaining_defaults unless remaining_defaults.first.kind_of?(Symbol)
         end
 
         # If the user has explicitly decided to NOT raise errors, pass that option to I18n.
@@ -122,9 +120,12 @@ module ActionView
 
       private
         def scope_key_by_partial(key)
-          if key.to_s.first == "."
+          stringified_key = key.to_s
+          if stringified_key.first == "."
             if @virtual_path
-              @virtual_path.gsub(%r{/_?}, ".") + key.to_s
+              @_scope_key_by_partial_cache ||= {}
+              @_scope_key_by_partial_cache[@virtual_path] ||= @virtual_path.gsub(%r{/_?}, ".")
+              "#{@_scope_key_by_partial_cache[@virtual_path]}#{stringified_key}"
             else
               raise "Cannot use t(#{key.inspect}) shortcut because path is not available"
             end
diff --git a/actionview/lib/action_view/helpers/url_helper.rb b/actionview/lib/action_view/helpers/url_helper.rb
index 2d5aac6dc7..cae62f2312 100644
--- a/actionview/lib/action_view/helpers/url_helper.rb
+++ b/actionview/lib/action_view/helpers/url_helper.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "javascript_helper"
+require "action_view/helpers/javascript_helper"
 require "active_support/core_ext/array/access"
 require "active_support/core_ext/hash/keys"
 require "active_support/core_ext/string/output_safety"
@@ -139,6 +139,11 @@ module ActionView
       #   link_to "Profiles", controller: "profiles"
       #   # => <a href="/profiles">Profiles</a>
       #
+      # When name is +nil+ the href is presented instead
+      #
+      #   link_to nil, "http://example.com"
+      #   # => <a href="http://www.example.com">http://www.example.com</a>
+      #
       # You can use a block as well if your link target is hard to fit into the name parameter. ERB example:
       #
       #   <%= link_to(@profile) do %>
@@ -589,10 +594,27 @@ module ActionView
         end
 
         def add_method_to_attributes!(html_options, method)
-          if method && method.to_s.downcase != "get".freeze && html_options["rel".freeze] !~ /nofollow/
-            html_options["rel".freeze] = "#{html_options["rel".freeze]} nofollow".lstrip
+          if method_not_get_method?(method) && html_options["rel"] !~ /nofollow/
+            if html_options["rel"].blank?
+              html_options["rel"] = "nofollow"
+            else
+              html_options["rel"] = "#{html_options["rel"]} nofollow"
+            end
           end
-          html_options["data-method".freeze] = method
+          html_options["data-method"] = method
+        end
+
+        STRINGIFIED_COMMON_METHODS = {
+          get:    "get",
+          delete: "delete",
+          patch:  "patch",
+          post:   "post",
+          put:    "put",
+        }.freeze
+
+        def method_not_get_method?(method)
+          return false unless method
+          (STRINGIFIED_COMMON_METHODS[method] || method.to_s.downcase) != "get"
         end
 
         def token_tag(token = nil, form_options: {})
@@ -614,7 +636,7 @@ module ActionView
         #   to_form_params(name: 'David', nationality: 'Danish')
         #   # => [{name: :name, value: 'David'}, {name: 'nationality', value: 'Danish'}]
         #
-        #   to_form_params(country: {name: 'Denmark'})
+        #   to_form_params(country: { name: 'Denmark' })
         #   # => [{name: 'country[name]', value: 'Denmark'}]
         #
         #   to_form_params(countries: ['Denmark', 'Sweden']})
diff --git a/actionview/lib/action_view/layouts.rb b/actionview/lib/action_view/layouts.rb
index d074654b49..3e6d352c15 100644
--- a/actionview/lib/action_view/layouts.rb
+++ b/actionview/lib/action_view/layouts.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "rendering"
-require "active_support/core_ext/module/remove_method"
+require "action_view/rendering"
+require "active_support/core_ext/module/redefine_method"
 
 module ActionView
   # Layouts reverse the common pattern of including shared headers and footers in many templates to isolate changes in
@@ -279,7 +279,7 @@ module ActionView
       # If a layout is not explicitly mentioned then look for a layout with the controller's name.
       # if nothing is found then try same procedure to find super class's layout.
       def _write_layout_method # :nodoc:
-        remove_possible_method(:_layout)
+        silence_redefinition_of_method(:_layout)
 
         prefixes = /\blayouts/.match?(_implied_layout_name) ? [] : ["layouts"]
         default_behavior = "lookup_context.find_all('#{_implied_layout_name}', #{prefixes.inspect}, false, [], { formats: formats }).first || super"
diff --git a/actionview/lib/action_view/lookup_context.rb b/actionview/lib/action_view/lookup_context.rb
index acc0f57f1d..0e56eca35c 100644
--- a/actionview/lib/action_view/lookup_context.rb
+++ b/actionview/lib/action_view/lookup_context.rb
@@ -3,7 +3,7 @@
 require "concurrent/map"
 require "active_support/core_ext/module/remove_method"
 require "active_support/core_ext/module/attribute_accessors"
-require_relative "template/resolver"
+require "action_view/template/resolver"
 
 module ActionView
   # = Action View Lookup Context
diff --git a/actionview/lib/action_view/railtie.rb b/actionview/lib/action_view/railtie.rb
index b22347c55c..12d06bf376 100644
--- a/actionview/lib/action_view/railtie.rb
+++ b/actionview/lib/action_view/railtie.rb
@@ -9,6 +9,8 @@ module ActionView
     config.action_view = ActiveSupport::OrderedOptions.new
     config.action_view.embed_authenticity_token_in_remote_forms = nil
     config.action_view.debug_missing_translation = true
+    config.action_view.default_enforce_utf8 = nil
+    config.action_view.finalize_compiled_template_methods = true
 
     config.eager_load_namespaces << ActionView
 
@@ -22,12 +24,35 @@ module ActionView
     initializer "action_view.form_with_generates_remote_forms" do |app|
       ActiveSupport.on_load(:action_view) do
         form_with_generates_remote_forms = app.config.action_view.delete(:form_with_generates_remote_forms)
-        unless form_with_generates_remote_forms.nil?
-          ActionView::Helpers::FormHelper.form_with_generates_remote_forms = form_with_generates_remote_forms
+        ActionView::Helpers::FormHelper.form_with_generates_remote_forms = form_with_generates_remote_forms
+      end
+    end
+
+    initializer "action_view.form_with_generates_ids" do |app|
+      ActiveSupport.on_load(:action_view) do
+        form_with_generates_ids = app.config.action_view.delete(:form_with_generates_ids)
+        unless form_with_generates_ids.nil?
+          ActionView::Helpers::FormHelper.form_with_generates_ids = form_with_generates_ids
         end
       end
     end
 
+    initializer "action_view.default_enforce_utf8" do |app|
+      ActiveSupport.on_load(:action_view) do
+        default_enforce_utf8 = app.config.action_view.delete(:default_enforce_utf8)
+        unless default_enforce_utf8.nil?
+          ActionView::Helpers::FormTagHelper.default_enforce_utf8 = default_enforce_utf8
+        end
+      end
+    end
+
+    initializer "action_view.finalize_compiled_template_methods" do |app|
+      ActiveSupport.on_load(:action_view) do
+        ActionView::Template.finalize_compiled_template_methods =
+          app.config.action_view.delete(:finalize_compiled_template_methods)
+      end
+    end
+
     initializer "action_view.logger" do
       ActiveSupport.on_load(:action_view) { self.logger ||= Rails.logger }
     end
diff --git a/actionview/lib/action_view/record_identifier.rb b/actionview/lib/action_view/record_identifier.rb
index b34a793c89..1310a1ce0a 100644
--- a/actionview/lib/action_view/record_identifier.rb
+++ b/actionview/lib/action_view/record_identifier.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/module"
-require_relative "model_naming"
+require "action_view/model_naming"
 
 module ActionView
   # RecordIdentifier encapsulates methods used by various ActionView helpers
diff --git a/actionview/lib/action_view/renderer/partial_renderer.rb b/actionview/lib/action_view/renderer/partial_renderer.rb
index f2edcb750c..d7f97c3b50 100644
--- a/actionview/lib/action_view/renderer/partial_renderer.rb
+++ b/actionview/lib/action_view/renderer/partial_renderer.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "concurrent/map"
-require_relative "partial_renderer/collection_caching"
+require "action_view/renderer/partial_renderer/collection_caching"
 
 module ActionView
   class PartialIteration
@@ -52,12 +52,12 @@ module ActionView
   #     <%= render partial: "ad", locals: { ad: ad } %>
   #   <% end %>
   #
-  # This would first render "advertiser/_account.html.erb" with @buyer passed in as the local variable +account+, then
-  # render "advertiser/_ad.html.erb" and pass the local variable +ad+ to the template for display.
+  # This would first render <tt>advertiser/_account.html.erb</tt> with <tt>@buyer</tt> passed in as the local variable +account+, then
+  # render <tt>advertiser/_ad.html.erb</tt> and pass the local variable +ad+ to the template for display.
   #
   # == The :as and :object options
   #
-  # By default <tt>ActionView::PartialRenderer</tt> doesn't have any local variables.
+  # By default ActionView::PartialRenderer doesn't have any local variables.
   # The <tt>:object</tt> option can be used to pass an object to the partial. For instance:
   #
   #   <%= render partial: "account", object: @buyer %>
@@ -85,7 +85,7 @@ module ActionView
   #
   #   <%= render partial: "ad", collection: @advertisements %>
   #
-  # This will render "advertiser/_ad.html.erb" and pass the local variable +ad+ to the template for display. An
+  # This will render <tt>advertiser/_ad.html.erb</tt> and pass the local variable +ad+ to the template for display. An
   # iteration object will automatically be made available to the template with a name of the form
   # +partial_name_iteration+. The iteration object has knowledge about which index the current object has in
   # the collection and the total size of the collection. The iteration object also has two convenience methods,
@@ -100,7 +100,7 @@ module ActionView
   #
   #   <%= render partial: "ad", collection: @advertisements, spacer_template: "ad_divider" %>
   #
-  # If the given <tt>:collection</tt> is +nil+ or empty, <tt>render</tt> will return nil. This will allow you
+  # If the given <tt>:collection</tt> is +nil+ or empty, <tt>render</tt> will return +nil+. This will allow you
   # to specify a text which will be displayed instead by using this form:
   #
   #   <%= render(partial: "ad", collection: @advertisements) || "There's no ad to be displayed" %>
@@ -114,18 +114,18 @@ module ActionView
   #
   #   <%= render partial: "advertisement/ad", locals: { ad: @advertisement } %>
   #
-  # This will render the partial "advertisement/_ad.html.erb" regardless of which controller this is being called from.
+  # This will render the partial <tt>advertisement/_ad.html.erb</tt> regardless of which controller this is being called from.
   #
-  # == \Rendering objects that respond to `to_partial_path`
+  # == \Rendering objects that respond to +to_partial_path+
   #
   # Instead of explicitly naming the location of a partial, you can also let PartialRenderer do the work
-  # and pick the proper path by checking `to_partial_path` method.
+  # and pick the proper path by checking +to_partial_path+ method.
   #
   #  # @account.to_partial_path returns 'accounts/account', so it can be used to replace:
   #  # <%= render partial: "accounts/account", locals: { account: @account} %>
   #  <%= render partial: @account %>
   #
-  #  # @posts is an array of Post instances, so every post record returns 'posts/post' on `to_partial_path`,
+  #  # @posts is an array of Post instances, so every post record returns 'posts/post' on +to_partial_path+,
   #  # that's why we can replace:
   #  # <%= render partial: "posts/post", collection: @posts %>
   #  <%= render partial: @posts %>
@@ -145,7 +145,7 @@ module ActionView
   #  # <%= render partial: "accounts/account", locals: { account: @account} %>
   #  <%= render @account %>
   #
-  #  # @posts is an array of Post instances, so every post record returns 'posts/post' on `to_partial_path`,
+  #  # @posts is an array of Post instances, so every post record returns 'posts/post' on +to_partial_path+,
   #  # that's why we can replace:
   #  # <%= render partial: "posts/post", collection: @posts %>
   #  <%= render @posts %>
@@ -363,7 +363,7 @@ module ActionView
         @options = options
         @block   = block
 
-        @locals  = options[:locals] || {}
+        @locals  = options[:locals] ? options[:locals].symbolize_keys : {}
         @details = extract_details(options)
 
         prepend_formats(options[:formats])
diff --git a/actionview/lib/action_view/renderer/streaming_template_renderer.rb b/actionview/lib/action_view/renderer/streaming_template_renderer.rb
index ca49eb1144..276a28ce07 100644
--- a/actionview/lib/action_view/renderer/streaming_template_renderer.rb
+++ b/actionview/lib/action_view/renderer/streaming_template_renderer.rb
@@ -65,7 +65,9 @@ module ActionView
         yielder = lambda { |*name| view._layout_for(*name) }
 
         instrument(:template, identifier: template.identifier, layout: layout.try(:virtual_path)) do
+          outer_config = I18n.config
           fiber = Fiber.new do
+            I18n.config = outer_config
             if layout
               layout.render(view, locals, output, &yielder)
             else
diff --git a/actionview/lib/action_view/rendering.rb b/actionview/lib/action_view/rendering.rb
index 2648f9153f..4e5fdfbb2d 100644
--- a/actionview/lib/action_view/rendering.rb
+++ b/actionview/lib/action_view/rendering.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "view_paths"
+require "action_view/view_paths"
 
 module ActionView
   # This is a class to fix I18n global state. Whenever you provide I18n.locale during a request,
@@ -75,8 +75,7 @@ module ActionView
     end
 
     # Returns an object that is able to render templates.
-    # :api: private
-    def view_renderer
+    def view_renderer # :nodoc:
       @_view_renderer ||= ActionView::Renderer.new(lookup_context)
     end
 
@@ -92,7 +91,6 @@ module ActionView
     private
 
       # Find and render a template based on the options given.
-      # :api: private
       def _render_template(options)
         variant = options.delete(:variant)
         assigns = options.delete(:assigns)
@@ -114,7 +112,6 @@ module ActionView
 
       # Normalize args by converting render "foo" to render :action => "foo" and
       # render "foo/bar" to render :template => "foo/bar".
-      # :api: private
       def _normalize_args(action = nil, options = {})
         options = super(action, options)
         case action
@@ -137,7 +134,6 @@ module ActionView
       end
 
       # Normalize options.
-      # :api: private
       def _normalize_options(options)
         options = super(options)
         if options[:partial] == true
diff --git a/actionview/lib/action_view/template.rb b/actionview/lib/action_view/template.rb
index e53c8356af..ee1cd61f12 100644
--- a/actionview/lib/action_view/template.rb
+++ b/actionview/lib/action_view/template.rb
@@ -9,6 +9,8 @@ module ActionView
   class Template
     extend ActiveSupport::Autoload
 
+    mattr_accessor :finalize_compiled_template_methods, default: true
+
     # === Encodings in ActionView::Template
     #
     # ActionView::Template is one of a few sources of potential
@@ -307,7 +309,9 @@ module ActionView
         end
 
         mod.module_eval(source, identifier, 0)
-        ObjectSpace.define_finalizer(self, Finalizer[method_name, mod])
+        if finalize_compiled_template_methods
+          ObjectSpace.define_finalizer(self, Finalizer[method_name, mod])
+        end
       end
 
       def handle_render_error(view, e)
@@ -330,8 +334,8 @@ module ActionView
         locals = @locals - Module::RUBY_RESERVED_KEYWORDS
         locals = locals.grep(/\A@?(?![A-Z0-9])(?:[[:alnum:]_]|[^\0-\177])+\z/)
 
-        # Double assign to suppress the dreaded 'assigned but unused variable' warning
-        locals.each_with_object("".dup) { |key, code| code << "#{key} = #{key} = local_assigns[:#{key}];" }
+        # Assign for the same variable is to suppress unused variable warning
+        locals.each_with_object("".dup) { |key, code| code << "#{key} = local_assigns[:#{key}]; #{key} = #{key};" }
       end
 
       def method_name
diff --git a/actionview/lib/action_view/template/error.rb b/actionview/lib/action_view/template/error.rb
index 2b0b25817b..4e3c02e05e 100644
--- a/actionview/lib/action_view/template/error.rb
+++ b/actionview/lib/action_view/template/error.rb
@@ -10,9 +10,6 @@ module ActionView
   class EncodingError < StandardError #:nodoc:
   end
 
-  class MissingRequestError < StandardError #:nodoc:
-  end
-
   class WrongEncodingError < EncodingError #:nodoc:
     def initialize(string, encoding)
       @string, @encoding = string, encoding
diff --git a/actionview/lib/action_view/template/handlers.rb b/actionview/lib/action_view/template/handlers.rb
index b3df0aa606..7ec76dcc3f 100644
--- a/actionview/lib/action_view/template/handlers.rb
+++ b/actionview/lib/action_view/template/handlers.rb
@@ -2,7 +2,7 @@
 
 module ActionView #:nodoc:
   # = Action View Template Handlers
-  class Template
+  class Template #:nodoc:
     module Handlers #:nodoc:
       autoload :Raw, "action_view/template/handlers/raw"
       autoload :ERB, "action_view/template/handlers/erb"
diff --git a/actionview/lib/action_view/template/handlers/erb.rb b/actionview/lib/action_view/template/handlers/erb.rb
index c41de62e52..b7b749f9da 100644
--- a/actionview/lib/action_view/template/handlers/erb.rb
+++ b/actionview/lib/action_view/template/handlers/erb.rb
@@ -3,11 +3,8 @@
 module ActionView
   class Template
     module Handlers
-      autoload :Erubis, "action_view/template/handlers/erb/deprecated_erubis"
-
       class ERB
         autoload :Erubi, "action_view/template/handlers/erb/erubi"
-        autoload :Erubis, "action_view/template/handlers/erb/erubis"
 
         # Specify trim mode for the ERB compiler. Defaults to '-'.
         # See ERB documentation for suitable values.
diff --git a/actionview/lib/action_view/template/handlers/erb/deprecated_erubis.rb b/actionview/lib/action_view/template/handlers/erb/deprecated_erubis.rb
deleted file mode 100644
index 00c7d7cc7d..0000000000
--- a/actionview/lib/action_view/template/handlers/erb/deprecated_erubis.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-# frozen_string_literal: true
-
-::ActiveSupport::Deprecation.warn("ActionView::Template::Handlers::Erubis is deprecated and will be removed from Rails 5.2. Switch to ActionView::Template::Handlers::ERB::Erubi instead.")
-
-module ActionView
-  class Template
-    module Handlers
-      Erubis = ERB::Erubis
-    end
-  end
-end
diff --git a/actionview/lib/action_view/template/handlers/erb/erubis.rb b/actionview/lib/action_view/template/handlers/erb/erubis.rb
deleted file mode 100644
index dc3bf1ff27..0000000000
--- a/actionview/lib/action_view/template/handlers/erb/erubis.rb
+++ /dev/null
@@ -1,83 +0,0 @@
-# frozen_string_literal: true
-
-gem "erubis"
-require "erubis"
-
-module ActionView
-  class Template
-    module Handlers
-      class ERB
-        class Erubis < ::Erubis::Eruby
-          # :nodoc: all
-          def add_preamble(src)
-            @newline_pending = 0
-            src << "@output_buffer = output_buffer || ActionView::OutputBuffer.new;"
-          end
-
-          def add_text(src, text)
-            return if text.empty?
-
-            if text == "\n"
-              @newline_pending += 1
-            else
-              src << "@output_buffer.safe_append='"
-              src << "\n" * @newline_pending if @newline_pending > 0
-              src << escape_text(text)
-              src << "'.freeze;"
-
-              @newline_pending = 0
-            end
-          end
-
-          # Erubis toggles <%= and <%== behavior when escaping is enabled.
-          # We override to always treat <%== as escaped.
-          def add_expr(src, code, indicator)
-            case indicator
-            when "=="
-              add_expr_escaped(src, code)
-            else
-              super
-            end
-          end
-
-          BLOCK_EXPR = /\s*((\s+|\))do|\{)(\s*\|[^|]*\|)?\s*\Z/
-
-          def add_expr_literal(src, code)
-            flush_newline_if_pending(src)
-            if BLOCK_EXPR.match?(code)
-              src << "@output_buffer.append= " << code
-            else
-              src << "@output_buffer.append=(" << code << ");"
-            end
-          end
-
-          def add_expr_escaped(src, code)
-            flush_newline_if_pending(src)
-            if BLOCK_EXPR.match?(code)
-              src << "@output_buffer.safe_expr_append= " << code
-            else
-              src << "@output_buffer.safe_expr_append=(" << code << ");"
-            end
-          end
-
-          def add_stmt(src, code)
-            flush_newline_if_pending(src)
-            super
-          end
-
-          def add_postamble(src)
-            flush_newline_if_pending(src)
-            src << "@output_buffer.to_s"
-          end
-
-          def flush_newline_if_pending(src)
-            if @newline_pending > 0
-              src << "@output_buffer.safe_append='#{"\n" * @newline_pending}'.freeze;"
-              @newline_pending = 0
-            end
-          end
-        end
-      end
-    end
-  end
-end
diff --git a/actionview/lib/action_view/template/html.rb b/actionview/lib/action_view/template/html.rb
index 540597efa1..a262c6d9ad 100644
--- a/actionview/lib/action_view/template/html.rb
+++ b/actionview/lib/action_view/template/html.rb
@@ -2,7 +2,7 @@
 
 module ActionView #:nodoc:
   # = Action View HTML Template
-  class Template
+  class Template #:nodoc:
     class HTML #:nodoc:
       attr_accessor :type
 
diff --git a/actionview/lib/action_view/template/resolver.rb b/actionview/lib/action_view/template/resolver.rb
index 708dee3164..5a86f10973 100644
--- a/actionview/lib/action_view/template/resolver.rb
+++ b/actionview/lib/action_view/template/resolver.rb
@@ -3,7 +3,7 @@
 require "pathname"
 require "active_support/core_ext/class"
 require "active_support/core_ext/module/attribute_accessors"
-require_relative "../template"
+require "action_view/template"
 require "thread"
 require "concurrent/map"
 
@@ -310,13 +310,13 @@ module ActionView
   # ==== Examples
   #
   # Default pattern, loads views the same way as previous versions of rails, eg. when you're
-  # looking for `users/new` it will produce query glob: `users/new{.{en},}{.{html,js},}{.{erb,haml},}`
+  # looking for <tt>users/new</tt> it will produce query glob: <tt>users/new{.{en},}{.{html,js},}{.{erb,haml},}</tt>
   #
   #   FileSystemResolver.new("/path/to/views", ":prefix/:action{.:locale,}{.:formats,}{+:variants,}{.:handlers,}")
   #
   # This one allows you to keep files with different formats in separate subdirectories,
-  # eg. `users/new.html` will be loaded from `users/html/new.erb` or `users/new.html.erb`,
-  # `users/new.js` from `users/js/new.erb` or `users/new.js.erb`, etc.
+  # eg. <tt>users/new.html</tt> will be loaded from <tt>users/html/new.erb</tt> or <tt>users/new.html.erb</tt>,
+  # <tt>users/new.js</tt> from <tt>users/js/new.erb</tt> or <tt>users/new.js.erb</tt>, etc.
   #
   #   FileSystemResolver.new("/path/to/views", ":prefix/{:formats/,}:action{.:locale,}{.:formats,}{+:variants,}{.:handlers,}")
   #
diff --git a/actionview/lib/action_view/template/text.rb b/actionview/lib/action_view/template/text.rb
index f070005881..f8d6c2811f 100644
--- a/actionview/lib/action_view/template/text.rb
+++ b/actionview/lib/action_view/template/text.rb
@@ -2,7 +2,7 @@
 
 module ActionView #:nodoc:
   # = Action View Text Template
-  class Template
+  class Template #:nodoc:
     class Text #:nodoc:
       attr_accessor :type
 
diff --git a/actionview/lib/action_view/template/types.rb b/actionview/lib/action_view/template/types.rb
index f0f37c9722..67b7a62de6 100644
--- a/actionview/lib/action_view/template/types.rb
+++ b/actionview/lib/action_view/template/types.rb
@@ -3,7 +3,7 @@
 require "active_support/core_ext/module/attribute_accessors"
 
 module ActionView
-  class Template
+  class Template #:nodoc:
     class Types
       class Type
         SET = Struct.new(:symbols).new([ :html, :text, :js, :css, :xml, :json ])
diff --git a/actionview/lib/action_view/test_case.rb b/actionview/lib/action_view/test_case.rb
index 6913c31a20..e1cbae5845 100644
--- a/actionview/lib/action_view/test_case.rb
+++ b/actionview/lib/action_view/test_case.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/module/remove_method"
+require "active_support/core_ext/module/redefine_method"
 require "action_controller"
 require "action_controller/test_case"
 require "action_view"
@@ -171,7 +171,7 @@ module ActionView
 
       def say_no_to_protect_against_forgery!
         _helpers.module_eval do
-          remove_possible_method :protect_against_forgery?
+          silence_redefinition_of_method :protect_against_forgery?
           def protect_against_forgery?
             false
           end
@@ -270,7 +270,7 @@ module ActionView
         begin
           routes = @controller.respond_to?(:_routes) && @controller._routes
         rescue
-          # Dont call routes, if there is an error on _routes call
+          # Don't call routes, if there is an error on _routes call
         end
 
         if routes &&
@@ -286,7 +286,7 @@ module ActionView
         begin
           routes = @controller.respond_to?(:_routes) && @controller._routes
         rescue
-          # Dont call routes, if there is an error on _routes call
+          # Don't call routes, if there is an error on _routes call
         end
 
         routes &&
diff --git a/actionview/lib/action_view/testing/resolvers.rb b/actionview/lib/action_view/testing/resolvers.rb
index 92fdb24a5e..68186c3bf8 100644
--- a/actionview/lib/action_view/testing/resolvers.rb
+++ b/actionview/lib/action_view/testing/resolvers.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../template/resolver"
+require "action_view/template/resolver"
 
 module ActionView #:nodoc:
   # Use FixtureResolver in your tests to simulate the presence of files on the
diff --git a/actionview/package.json b/actionview/package.json
index 4cbf0207e5..624eb5de93 100644
--- a/actionview/package.json
+++ b/actionview/package.json
@@ -1,6 +1,6 @@
 {
   "name": "rails-ujs",
-  "version": "5.2.0-alpha",
+  "version": "6.0.0-alpha",
   "description": "Ruby on Rails unobtrusive scripting adapter",
   "main": "lib/assets/compiled/rails-ujs.js",
   "files": [
diff --git a/actionview/test/abstract_unit.rb b/actionview/test/abstract_unit.rb
index c98270bd12..f20a66c2d2 100644
--- a/actionview/test/abstract_unit.rb
+++ b/actionview/test/abstract_unit.rb
@@ -26,14 +26,6 @@ require "active_record"
 
 require "pp" # require 'pp' early to prevent hidden_methods from not picking up the pretty-print methods until too late
 
-module Rails
-  class << self
-    def env
-      @_env ||= ActiveSupport::StringInquirer.new(ENV["RAILS_ENV"] || ENV["RACK_ENV"] || "test")
-    end
-  end
-end
-
 ActiveSupport::Dependencies.hook!
 
 Thread.abort_on_exception = true
@@ -110,12 +102,6 @@ module ActionDispatch
   end
 end
 
-module ActiveSupport
-  class TestCase
-    include ActionDispatch::DrawOnce
-  end
-end
-
 class RoutedRackApp
   attr_reader :routes
 
@@ -162,29 +148,6 @@ class ActionDispatch::IntegrationTest < ActiveSupport::TestCase
 
   self.app = build_app
 
-  # Stub Rails dispatcher so it does not get controller references and
-  # simply return the controller#action as Rack::Body.
-  class StubDispatcher < ::ActionDispatch::Routing::RouteSet::Dispatcher
-    private
-      def controller_reference(controller_param)
-        controller_param
-      end
-
-      def dispatch(controller, action, env)
-        [200, { "Content-Type" => "text/html" }, ["#{controller}##{action}"]]
-      end
-  end
-
-  def self.stub_controllers
-    old_dispatcher = ActionDispatch::Routing::RouteSet::Dispatcher
-    ActionDispatch::Routing::RouteSet.module_eval { remove_const :Dispatcher }
-    ActionDispatch::Routing::RouteSet.module_eval { const_set :Dispatcher, StubDispatcher }
-    yield ActionDispatch::Routing::RouteSet.new
-  ensure
-    ActionDispatch::Routing::RouteSet.module_eval { remove_const :Dispatcher }
-    ActionDispatch::Routing::RouteSet.module_eval { const_set :Dispatcher, old_dispatcher }
-  end
-
   def with_routing(&block)
     temporary_routes = ActionDispatch::Routing::RouteSet.new
     old_app, self.class.app = self.class.app, self.class.build_app(temporary_routes)
@@ -196,21 +159,6 @@ class ActionDispatch::IntegrationTest < ActiveSupport::TestCase
     self.class.app = old_app
     silence_warnings { Object.const_set(:SharedTestRoutes, old_routes) }
   end
-
-  def with_autoload_path(path)
-    path = File.join(File.expand_path("fixtures", __dir__), path)
-    if ActiveSupport::Dependencies.autoload_paths.include?(path)
-      yield
-    else
-      begin
-        ActiveSupport::Dependencies.autoload_paths << path
-        yield
-      ensure
-        ActiveSupport::Dependencies.autoload_paths.reject! { |p| p == path }
-        ActiveSupport::Dependencies.clear
-      end
-    end
-  end
 end
 
 ActionView::RoutingUrlFor.include(ActionDispatch::Routing::UrlFor)
@@ -274,6 +222,7 @@ module ActionDispatch
 end
 
 class ActiveSupport::TestCase
+  include ActionDispatch::DrawOnce
   include ActiveSupport::Testing::MethodCallAssertions
 
   # Skips the current run on Rubinius using Minitest::Assertions#skip
diff --git a/actionview/test/actionpack/abstract/abstract_controller_test.rb b/actionview/test/actionpack/abstract/abstract_controller_test.rb
index 468a6376c7..4d4e2b8ef2 100644
--- a/actionview/test/actionpack/abstract/abstract_controller_test.rb
+++ b/actionview/test/actionpack/abstract/abstract_controller_test.rb
@@ -236,7 +236,7 @@ module AbstractController
       end
     end
 
-    class RespondToActionController < AbstractController::Base;
+    class RespondToActionController < AbstractController::Base
       def index() self.response_body = "success" end
 
       def fail()  self.response_body = "fail"    end
diff --git a/actionview/test/actionpack/controller/render_test.rb b/actionview/test/actionpack/controller/render_test.rb
index 9df2a73448..3e6b55a87e 100644
--- a/actionview/test/actionpack/controller/render_test.rb
+++ b/actionview/test/actionpack/controller/render_test.rb
@@ -4,12 +4,8 @@ require "abstract_unit"
 require "active_model"
 require "controller/fake_models"
 
-class ApplicationController < ActionController::Base
-  self.view_paths = File.join(FIXTURE_LOAD_PATH, "actionpack")
-end
-
 module Quiz
-  #Models
+  # Models
   Question = Struct.new(:name, :id) do
     extend ActiveModel::Naming
     include ActiveModel::Conversion
@@ -20,7 +16,7 @@ module Quiz
   end
 
   # Controller
-  class QuestionsController < ApplicationController
+  class QuestionsController < ActionController::Base
     def new
       render partial: Quiz::Question.new("Namespaced Partial")
     end
@@ -28,7 +24,7 @@ module Quiz
 end
 
 module Fun
-  class GamesController < ApplicationController
+  class GamesController < ActionController::Base
     def hello_world; end
 
     def nested_partial_with_form_builder
@@ -37,7 +33,7 @@ module Fun
   end
 end
 
-class TestController < ApplicationController
+class TestController < ActionController::Base
   protect_from_forgery
 
   before_action :set_variable_for_layout
@@ -489,6 +485,10 @@ class TestController < ApplicationController
     render partial: "customer", locals: { customer: Customer.new("david") }
   end
 
+  def partial_with_string_locals
+    render partial: "customer", locals: { "customer" => Customer.new("david") }
+  end
+
   def partial_with_form_builder
     render partial: ActionView::Helpers::FormBuilder.new(:post, nil, view_context, {})
   end
@@ -640,10 +640,15 @@ class RenderTest < ActionController::TestCase
     ActionView::Base.logger = ActiveSupport::Logger.new(nil)
 
     @request.host = "www.nextangle.com"
+
+    @old_view_paths = ActionController::Base.view_paths
+    ActionController::Base.view_paths = File.join(FIXTURE_LOAD_PATH, "actionpack")
   end
 
   def teardown
     ActionView::Base.logger = nil
+
+    ActionController::Base.view_paths = @old_view_paths
   end
 
   # :ported:
@@ -1169,6 +1174,11 @@ class RenderTest < ActionController::TestCase
     assert_equal "Hello: david", @response.body
   end
 
+  def test_partial_with_string_locals
+    get :partial_with_string_locals
+    assert_equal "Hello: david", @response.body
+  end
+
   def test_partial_with_form_builder
     get :partial_with_form_builder
     assert_equal "<label for=\"post_title\">Title</label>\n", @response.body
diff --git a/actionview/test/active_record_unit.rb b/actionview/test/active_record_unit.rb
index b39ecd8813..7f48b515a0 100644
--- a/actionview/test/active_record_unit.rb
+++ b/actionview/test/active_record_unit.rb
@@ -38,7 +38,7 @@ class ActiveRecordTestConnector
       end
     rescue Exception => e  # errors from ActiveRecord setup
       $stderr.puts "\nSkipping ActiveRecord assertion tests: #{e}"
-      #$stderr.puts "  #{e.backtrace.join("\n  ")}\n"
+      # $stderr.puts "  #{e.backtrace.join("\n  ")}\n"
       self.able_to_connect = false
     end
 
diff --git a/actionview/test/activerecord/multifetch_cache_test.rb b/actionview/test/activerecord/multifetch_cache_test.rb
new file mode 100644
index 0000000000..12be069e69
--- /dev/null
+++ b/actionview/test/activerecord/multifetch_cache_test.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+require "active_record_unit"
+require "active_record/railties/collection_cache_association_loading"
+
+ActionView::PartialRenderer.prepend(ActiveRecord::Railties::CollectionCacheAssociationLoading)
+
+class MultifetchCacheTest < ActiveRecordTestCase
+  fixtures :topics, :replies
+
+  def setup
+    view_paths = ActionController::Base.view_paths
+
+    @view = Class.new(ActionView::Base) do
+      def view_cache_dependencies
+        []
+      end
+
+      def combined_fragment_cache_key(key)
+        [ :views, key ]
+      end
+    end.new(view_paths, {})
+  end
+
+  def test_only_preloading_for_records_that_miss_the_cache
+    @view.render partial: "test/partial", collection: [topics(:rails)], cached: true
+
+    @topics = Topic.preload(:replies)
+
+    @view.render partial: "test/partial", collection: @topics, cached: true
+
+    assert_not @topics.detect { |topic| topic.id == topics(:rails).id }.replies.loaded?
+    assert     @topics.detect { |topic| topic.id != topics(:rails).id }.replies.loaded?
+  end
+end
diff --git a/actionview/test/activerecord/render_partial_with_record_identification_test.rb b/actionview/test/activerecord/render_partial_with_record_identification_test.rb
index 367d2c3174..3a698fa42e 100644
--- a/actionview/test/activerecord/render_partial_with_record_identification_test.rb
+++ b/actionview/test/activerecord/render_partial_with_record_identification_test.rb
@@ -17,21 +17,11 @@ class RenderPartialWithRecordIdentificationController < ActionController::Base
     render partial: Reply.base
   end
 
-  def render_with_has_many_through_association
-    @developer = Developer.first
-    render partial: @developer.topics
-  end
-
   def render_with_has_one_association
     @company = Company.find(1)
     render partial: @company.mascot
   end
 
-  def render_with_belongs_to_association
-    @reply = Reply.find(1)
-    render partial: @reply.topic
-  end
-
   def render_with_record
     @developer = Developer.first
     render partial: @developer
diff --git a/actionview/test/fixtures/digestor/comments/show.js.erb b/actionview/test/fixtures/digestor/comments/show.js.erb
new file mode 100644
index 0000000000..38b37dfa2b
--- /dev/null
+++ b/actionview/test/fixtures/digestor/comments/show.js.erb
@@ -0,0 +1 @@
+alert("<%=j render("comments/comment") %>")
diff --git a/actionview/test/fixtures/layouts/streaming_with_locale.erb b/actionview/test/fixtures/layouts/streaming_with_locale.erb
new file mode 100644
index 0000000000..e1fdad2073
--- /dev/null
+++ b/actionview/test/fixtures/layouts/streaming_with_locale.erb
@@ -0,0 +1,2 @@
+layout.locale: <%= I18n.locale %>
+<%= yield %>
diff --git a/actionview/test/fixtures/public/.gitignore b/actionview/test/fixtures/public/.gitignore
deleted file mode 100644
index 312e635ee6..0000000000
--- a/actionview/test/fixtures/public/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-absolute/*
diff --git a/actionview/test/fixtures/test/streaming_with_locale.erb b/actionview/test/fixtures/test/streaming_with_locale.erb
new file mode 100644
index 0000000000..b0f2b2f7e9
--- /dev/null
+++ b/actionview/test/fixtures/test/streaming_with_locale.erb
@@ -0,0 +1 @@
+view.locale: <%= I18n.locale %>
diff --git a/actionview/test/template/active_model_helper_test.rb b/actionview/test/template/active_model_helper_test.rb
index a929d8dc3d..36afed6dd6 100644
--- a/actionview/test/template/active_model_helper_test.rb
+++ b/actionview/test/template/active_model_helper_test.rb
@@ -6,7 +6,7 @@ class ActiveModelHelperTest < ActionView::TestCase
   tests ActionView::Helpers::ActiveModelHelper
 
   silence_warnings do
-    Post = Struct.new(:author_name, :body, :updated_at) do
+    Post = Struct.new(:author_name, :body, :category, :published, :updated_at) do
       include ActiveModel::Conversion
       include ActiveModel::Validations
 
@@ -22,10 +22,14 @@ class ActiveModelHelperTest < ActionView::TestCase
     @post = Post.new
     @post.errors[:author_name] << "can't be empty"
     @post.errors[:body] << "foo"
+    @post.errors[:category] << "must exist"
+    @post.errors[:published] << "must be accepted"
     @post.errors[:updated_at] << "bar"
 
     @post.author_name = ""
     @post.body        = "Back to the hill and over it again!"
+    @post.category    = "rails"
+    @post.published   = false
     @post.updated_at  = Date.new(2004, 6, 15)
   end
 
@@ -56,6 +60,25 @@ class ActiveModelHelperTest < ActionView::TestCase
     assert_dom_equal(expected_dom, select("post", "author_name", [:a, :b], prompt: "Choose one..."))
   end
 
+  def test_select_grouped_options_with_errors
+    grouped_options = [
+      ["A", [["A1"], ["A2"]]],
+      ["B", [["B1"], ["B2"]]],
+    ]
+
+    assert_dom_equal(
+      %(<div class="field_with_errors"><select name="post[category]" id="post_category"><optgroup label="A"><option value="A1">A1</option>\n<option value="A2">A2</option></optgroup><optgroup label="B"><option value="B1">B1</option>\n<option value="B2">B2</option></optgroup></select></div>),
+      select("post", "category", grouped_options)
+    )
+  end
+
+  def test_collection_select_with_errors
+    assert_dom_equal(
+      %(<div class="field_with_errors"><select name="post[author_name]" id="post_author_name"><option value="a">a</option>\n<option value="b">b</option></select></div>),
+      collection_select("post", "author_name", [:a, :b], :to_s, :to_s)
+    )
+  end
+
   def test_date_select_with_errors
     assert_dom_equal(
       %(<div class="field_with_errors"><select id="post_updated_at_1i" name="post[updated_at(1i)]">\n<option selected="selected" value="2004">2004</option>\n<option value="2005">2005</option>\n</select>\n<input id="post_updated_at_2i" name="post[updated_at(2i)]" type="hidden" value="6" />\n<input id="post_updated_at_3i" name="post[updated_at(3i)]" type="hidden" value="1" />\n</div>),
@@ -77,6 +100,55 @@ class ActiveModelHelperTest < ActionView::TestCase
     )
   end
 
+  def test_label_with_errors
+    assert_dom_equal(
+      %(<div class="field_with_errors"><label for="post_body">Body</label></div>),
+      label("post", "body")
+    )
+  end
+
+  def test_check_box_with_errors
+    assert_dom_equal(
+      %(<input name="post[published]" type="hidden" value="0" /><div class="field_with_errors"><input type="checkbox" value="1" name="post[published]" id="post_published" /></div>),
+      check_box("post", "published")
+    )
+  end
+
+  def test_check_boxes_with_errors
+    assert_dom_equal(
+      %(<input name="post[published]" type="hidden" value="0" /><div class="field_with_errors"><input type="checkbox" value="1" name="post[published]" id="post_published" /></div><input name="post[published]" type="hidden" value="0" /><div class="field_with_errors"><input type="checkbox" value="1" name="post[published]" id="post_published" /></div>),
+      check_box("post", "published") + check_box("post", "published")
+    )
+  end
+
+  def test_radio_button_with_errors
+    assert_dom_equal(
+      %(<div class="field_with_errors"><input type="radio" value="rails" checked="checked" name="post[category]" id="post_category_rails" /></div>),
+      radio_button("post", "category", "rails")
+    )
+  end
+
+  def test_radio_buttons_with_errors
+    assert_dom_equal(
+      %(<div class="field_with_errors"><input type="radio" value="rails" checked="checked" name="post[category]" id="post_category_rails" /></div><div class="field_with_errors"><input type="radio" value="java" name="post[category]" id="post_category_java" /></div>),
+      radio_button("post", "category", "rails") + radio_button("post", "category", "java")
+    )
+  end
+
+  def test_collection_check_boxes_with_errors
+    assert_dom_equal(
+      %(<input type="hidden" name="post[category][]" value="" /><div class="field_with_errors"><input type="checkbox" value="ruby" name="post[category][]" id="post_category_ruby" /></div><label for="post_category_ruby">ruby</label><div class="field_with_errors"><input type="checkbox" value="java" name="post[category][]" id="post_category_java" /></div><label for="post_category_java">java</label>),
+      collection_check_boxes("post", "category", [:ruby, :java], :to_s, :to_s)
+    )
+  end
+
+  def test_collection_radio_buttons_with_errors
+    assert_dom_equal(
+      %(<input type="hidden" name="post[category]" value="" /><div class="field_with_errors"><input type="radio" value="ruby" name="post[category]" id="post_category_ruby" /></div><label for="post_category_ruby">ruby</label><div class="field_with_errors"><input type="radio" value="java" name="post[category]" id="post_category_java" /></div><label for="post_category_java">java</label>),
+      collection_radio_buttons("post", "category", [:ruby, :java], :to_s, :to_s)
+    )
+  end
+
   def test_hidden_field_does_not_render_errors
     assert_dom_equal(
       %(<input id="post_author_name" name="post[author_name]" type="hidden" value="" />),
diff --git a/actionview/test/template/asset_tag_helper_test.rb b/actionview/test/template/asset_tag_helper_test.rb
index 6645839f0e..e68f03d1f4 100644
--- a/actionview/test/template/asset_tag_helper_test.rb
+++ b/actionview/test/template/asset_tag_helper_test.rb
@@ -19,6 +19,7 @@ class AssetTagHelperTest < ActionView::TestCase
       def ssl?() false end
       def host_with_port() "localhost" end
       def base_url() "http://www.example.com" end
+      def send_early_hints(links) end
     end.new
 
     @controller.request = @request
@@ -28,6 +29,10 @@ class AssetTagHelperTest < ActionView::TestCase
     "http://www.example.com"
   end
 
+  def content_security_policy_nonce
+    "iyhD0Yc0W+c="
+  end
+
   AssetPathToTag = {
     %(asset_path(""))             => %(),
     %(asset_path("   "))          => %(),
@@ -213,6 +218,17 @@ class AssetTagHelperTest < ActionView::TestCase
     %(favicon_link_tag 'mb-icon.png', :rel => 'apple-touch-icon', :type => 'image/png') => %(<link href="/images/mb-icon.png" rel="apple-touch-icon" type="image/png" />)
   }
 
+  PreloadLinkToTag = {
+    %(preload_link_tag '/styles/custom_theme.css') => %(<link rel="preload" href="/styles/custom_theme.css" as="style" type="text/css" />),
+    %(preload_link_tag '/videos/video.webm') => %(<link rel="preload" href="/videos/video.webm" as="video" type="video/webm" />),
+    %(preload_link_tag '/posts.json', as: 'fetch') => %(<link rel="preload" href="/posts.json" as="fetch" type="application/json" />),
+    %(preload_link_tag '/users', as: 'fetch', type: 'application/json') => %(<link rel="preload" href="/users" as="fetch" type="application/json" />),
+    %(preload_link_tag '//example.com/map?callback=initMap', as: 'fetch', type: 'application/javascript') => %(<link rel="preload" href="//example.com/map?callback=initMap" as="fetch" type="application/javascript" />),
+    %(preload_link_tag '//example.com/font.woff2') => %(<link rel="preload" href="//example.com/font.woff2" as="font" type="font/woff2" crossorigin="anonymous"/>),
+    %(preload_link_tag '//example.com/font.woff2', crossorigin: 'use-credentials') => %(<link rel="preload" href="//example.com/font.woff2" as="font" type="font/woff2" crossorigin="use-credentials" />),
+    %(preload_link_tag '/media/audio.ogg', nopush: true) => %(<link rel="preload" href="/media/audio.ogg" as="audio" type="audio/ogg" />)
+  }
+
   VideoPathToTag = {
     %(video_path("xml"))          => %(/videos/xml),
     %(video_path("xml.ogg"))      => %(/videos/xml.ogg),
@@ -305,6 +321,24 @@ class AssetTagHelperTest < ActionView::TestCase
     %(font_path("font.ttf?123")) => %(/fonts/font.ttf?123)
   }
 
+  FontUrlToTag = {
+    %(font_url("font.eot")) => %(http://www.example.com/fonts/font.eot),
+    %(font_url("font.eot#iefix")) => %(http://www.example.com/fonts/font.eot#iefix),
+    %(font_url("font.woff")) => %(http://www.example.com/fonts/font.woff),
+    %(font_url("font.ttf")) => %(http://www.example.com/fonts/font.ttf),
+    %(font_url("font.ttf?123")) => %(http://www.example.com/fonts/font.ttf?123),
+    %(font_url("font.ttf", host: "http://assets.example.com")) => %(http://assets.example.com/fonts/font.ttf)
+  }
+
+  UrlToFontToTag = {
+    %(url_to_font("font.eot")) => %(http://www.example.com/fonts/font.eot),
+    %(url_to_font("font.eot#iefix")) => %(http://www.example.com/fonts/font.eot#iefix),
+    %(url_to_font("font.woff")) => %(http://www.example.com/fonts/font.woff),
+    %(url_to_font("font.ttf")) => %(http://www.example.com/fonts/font.ttf),
+    %(url_to_font("font.ttf?123")) => %(http://www.example.com/fonts/font.ttf?123),
+    %(url_to_font("font.ttf", host: "http://assets.example.com")) => %(http://assets.example.com/fonts/font.ttf)
+  }
+
   def test_autodiscovery_link_tag_with_unknown_type_but_not_pass_type_option_key
     assert_raise(ArgumentError) do
       auto_discovery_link_tag(:xml)
@@ -377,7 +411,7 @@ class AssetTagHelperTest < ActionView::TestCase
   end
 
   def test_javascript_include_tag_is_html_safe
-    assert javascript_include_tag("prototype").html_safe?
+    assert_predicate javascript_include_tag("prototype"), :html_safe?
   end
 
   def test_javascript_include_tag_relative_protocol
@@ -391,6 +425,10 @@ class AssetTagHelperTest < ActionView::TestCase
     assert_dom_equal %(<script src="//assets.example.com/javascripts/prototype.js"></script>), javascript_include_tag("prototype")
   end
 
+  def test_javascript_include_tag_nonce
+    assert_dom_equal %(<script src="/javascripts/bank.js" nonce="iyhD0Yc0W+c="></script>), javascript_include_tag("bank", nonce: true)
+  end
+
   def test_stylesheet_path
     StylePathToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
   end
@@ -421,9 +459,17 @@ class AssetTagHelperTest < ActionView::TestCase
     }
   end
 
+  def test_stylesheet_link_tag_without_request
+    @request = nil
+    assert_dom_equal(
+      %(<link rel="stylesheet" media="screen" href="/stylesheets/foo.css" />),
+      stylesheet_link_tag("foo.css")
+    )
+  end
+
   def test_stylesheet_link_tag_is_html_safe
-    assert stylesheet_link_tag("dir/file").html_safe?
-    assert stylesheet_link_tag("dir/other/file", "dir/file2").html_safe?
+    assert_predicate stylesheet_link_tag("dir/file"), :html_safe?
+    assert_predicate stylesheet_link_tag("dir/other/file", "dir/file2"), :html_safe?
   end
 
   def test_stylesheet_link_tag_escapes_options
@@ -445,6 +491,11 @@ class AssetTagHelperTest < ActionView::TestCase
     assert_dom_equal %(<link href="//assets.example.com/stylesheets/wellington.css" media="screen" rel="stylesheet" />), stylesheet_link_tag("wellington")
   end
 
+  def test_javascript_include_tag_without_request
+    @request = nil
+    assert_dom_equal %(<script src="/javascripts/foo.js"></script>), javascript_include_tag("foo.js")
+  end
+
   def test_image_path
     ImagePathToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
   end
@@ -503,6 +554,10 @@ class AssetTagHelperTest < ActionView::TestCase
     FaviconLinkToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
   end
 
+  def test_preload_link_tag
+    PreloadLinkToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
+  end
+
   def test_video_path
     VideoPathToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
   end
@@ -547,6 +602,14 @@ class AssetTagHelperTest < ActionView::TestCase
     FontPathToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
   end
 
+  def test_font_url
+    FontUrlToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
+  end
+
+  def test_url_to_font_alias_for_font_url
+    UrlToFontToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
+  end
+
   def test_video_audio_tag_does_not_modify_options
     options = { autoplay: true }
     video_tag("video", options)
@@ -627,7 +690,9 @@ class AssetTagHelperNonVhostTest < ActionView::TestCase
     @controller = BasicController.new
     @controller.config.relative_url_root = "/collaboration/hieraki"
 
-    @request = Struct.new(:protocol, :base_url).new("gopher://", "gopher://www.example.com")
+    @request = Struct.new(:protocol, :base_url) do
+      def send_early_hints(links); end
+    end.new("gopher://", "gopher://www.example.com")
     @controller.request = @request
   end
 
@@ -749,6 +814,23 @@ class AssetTagHelperNonVhostTest < ActionView::TestCase
   end
 end
 
+class AssetTagHelperWithoutRequestTest < ActionView::TestCase
+  tests ActionView::Helpers::AssetTagHelper
+
+  undef :request
+
+  def test_stylesheet_link_tag_without_request
+    assert_dom_equal(
+      %(<link rel="stylesheet" media="screen" href="/stylesheets/foo.css" />),
+      stylesheet_link_tag("foo.css")
+    )
+  end
+
+  def test_javascript_include_tag_without_request
+    assert_dom_equal %(<script src="/javascripts/foo.js"></script>), javascript_include_tag("foo.js")
+  end
+end
+
 class AssetUrlHelperControllerTest < ActionView::TestCase
   tests ActionView::Helpers::AssetUrlHelper
 
diff --git a/actionview/test/template/atom_feed_helper_test.rb b/actionview/test/template/atom_feed_helper_test.rb
index 1be20dcaae..8e683cb48a 100644
--- a/actionview/test/template/atom_feed_helper_test.rb
+++ b/actionview/test/template/atom_feed_helper_test.rb
@@ -257,7 +257,7 @@ class AtomFeedTest < ActionController::TestCase
       get :index, params: { id: "provide_builder" }
       # because we pass in the non-default builder, the content generated by the
       # helper should go 'nowhere'.  Leaving the response body blank.
-      assert @response.body.blank?
+      assert_predicate @response.body, :blank?
     end
   end
 
diff --git a/actionview/test/template/capture_helper_test.rb b/actionview/test/template/capture_helper_test.rb
index 8a1c00fd00..131e49327e 100644
--- a/actionview/test/template/capture_helper_test.rb
+++ b/actionview/test/template/capture_helper_test.rb
@@ -49,21 +49,21 @@ class CaptureHelperTest < ActionView::TestCase
   end
 
   def test_content_for_with_multiple_calls
-    assert ! content_for?(:title)
+    assert_not content_for?(:title)
     content_for :title, "foo"
     content_for :title, "bar"
     assert_equal "foobar", content_for(:title)
   end
 
   def test_content_for_with_multiple_calls_and_flush
-    assert ! content_for?(:title)
+    assert_not content_for?(:title)
     content_for :title, "foo"
     content_for :title, "bar", flush: true
     assert_equal "bar", content_for(:title)
   end
 
   def test_content_for_with_block
-    assert ! content_for?(:title)
+    assert_not content_for?(:title)
     content_for :title do
       output_buffer << "foo"
       output_buffer << "bar"
@@ -73,7 +73,7 @@ class CaptureHelperTest < ActionView::TestCase
   end
 
   def test_content_for_with_block_and_multiple_calls_with_flush
-    assert ! content_for?(:title)
+    assert_not content_for?(:title)
     content_for :title do
       "foo"
     end
@@ -84,7 +84,7 @@ class CaptureHelperTest < ActionView::TestCase
   end
 
   def test_content_for_with_block_and_multiple_calls_with_flush_nil_content
-    assert ! content_for?(:title)
+    assert_not content_for?(:title)
     content_for :title do
       "foo"
     end
@@ -95,7 +95,7 @@ class CaptureHelperTest < ActionView::TestCase
   end
 
   def test_content_for_with_block_and_multiple_calls_without_flush
-    assert ! content_for?(:title)
+    assert_not content_for?(:title)
     content_for :title do
       "foo"
     end
@@ -106,7 +106,7 @@ class CaptureHelperTest < ActionView::TestCase
   end
 
   def test_content_for_with_whitespace_block
-    assert ! content_for?(:title)
+    assert_not content_for?(:title)
     content_for :title, "foo"
     content_for :title do
       output_buffer << "  \n  "
@@ -117,7 +117,7 @@ class CaptureHelperTest < ActionView::TestCase
   end
 
   def test_content_for_with_whitespace_block_and_flush
-    assert ! content_for?(:title)
+    assert_not content_for?(:title)
     content_for :title, "foo"
     content_for :title, flush: true do
       output_buffer << "  \n  "
@@ -128,7 +128,7 @@ class CaptureHelperTest < ActionView::TestCase
   end
 
   def test_content_for_returns_nil_when_writing
-    assert ! content_for?(:title)
+    assert_not content_for?(:title)
     assert_nil content_for(:title, "foo")
     assert_nil content_for(:title) { output_buffer << "bar"; nil }
     assert_nil content_for(:title) { output_buffer << "  \n  "; nil }
@@ -144,27 +144,27 @@ class CaptureHelperTest < ActionView::TestCase
   end
 
   def test_content_for_question_mark
-    assert ! content_for?(:title)
+    assert_not content_for?(:title)
     content_for :title, "title"
     assert content_for?(:title)
-    assert ! content_for?(:something_else)
+    assert_not content_for?(:something_else)
   end
 
   def test_content_for_should_be_html_safe_after_flush_empty
-    assert ! content_for?(:title)
+    assert_not content_for?(:title)
     content_for :title do
       content_tag(:p, "title")
     end
-    assert content_for(:title).html_safe?
+    assert_predicate content_for(:title), :html_safe?
     content_for :title, "", flush: true
     content_for(:title) do
       content_tag(:p, "title")
     end
-    assert content_for(:title).html_safe?
+    assert_predicate content_for(:title), :html_safe?
   end
 
   def test_provide
-    assert !content_for?(:title)
+    assert_not content_for?(:title)
     provide :title, "hi"
     assert content_for?(:title)
     assert_equal "hi", content_for(:title)
diff --git a/actionview/test/template/date_helper_test.rb b/actionview/test/template/date_helper_test.rb
index 5a5550438b..4b4939d705 100644
--- a/actionview/test/template/date_helper_test.rb
+++ b/actionview/test/template/date_helper_test.rb
@@ -141,18 +141,16 @@ class DateHelperTest < ActionView::TestCase
   end
 
   def test_distance_in_words_doesnt_use_the_quotient_operator
-    rubinius_skip "Date is written in Ruby and relies on Fixnum#/"
-    jruby_skip "Date is written in Ruby and relies on Fixnum#/"
+    rubinius_skip "Date is written in Ruby and relies on Integer#/"
+    jruby_skip "Date is written in Ruby and relies on Integer#/"
 
-    klass = RUBY_VERSION > "2.4" ? Integer : Fixnum
-
-    # Make sure that we avoid {Integer,Fixnum}#/ (redefined by mathn)
-    klass.send :private, :/
+    # Make sure that we avoid Integer#/ (redefined by mathn)
+    Integer.send :private, :/
 
     from = Time.utc(2004, 6, 6, 21, 45, 0)
     assert_distance_of_time_in_words(from)
   ensure
-    klass.send :public, :/
+    Integer.send :public, :/
   end
 
   def test_time_ago_in_words_passes_include_seconds
@@ -687,7 +685,7 @@ class DateHelperTest < ActionView::TestCase
     expected << %(<option value=""></option>\n<option value="00">00</option>\n<option value="15">15</option>\n<option value="30">30</option>\n<option value="45">45</option>\n)
     expected << "</select>\n"
 
-    assert_dom_equal expected, select_minute(Time.mktime(2003, 8, 16, 8, 4, 18), include_blank: true , minute_step: 15)
+    assert_dom_equal expected, select_minute(Time.mktime(2003, 8, 16, 8, 4, 18), include_blank: true, minute_step: 15)
   end
 
   def test_select_minute_nil_with_blank
@@ -703,7 +701,7 @@ class DateHelperTest < ActionView::TestCase
     expected << %(<option value=""></option>\n<option value="00">00</option>\n<option value="15">15</option>\n<option value="30">30</option>\n<option value="45">45</option>\n)
     expected << "</select>\n"
 
-    assert_dom_equal expected, select_minute(nil, include_blank: true , minute_step: 15)
+    assert_dom_equal expected, select_minute(nil, include_blank: true, minute_step: 15)
   end
 
   def test_select_minute_with_hidden
@@ -3593,25 +3591,25 @@ class DateHelperTest < ActionView::TestCase
   end
 
   def test_select_html_safety
-    assert select_day(16).html_safe?
-    assert select_month(8).html_safe?
-    assert select_year(Time.mktime(2003, 8, 16, 8, 4, 18)).html_safe?
-    assert select_minute(Time.mktime(2003, 8, 16, 8, 4, 18)).html_safe?
-    assert select_second(Time.mktime(2003, 8, 16, 8, 4, 18)).html_safe?
+    assert_predicate select_day(16), :html_safe?
+    assert_predicate select_month(8), :html_safe?
+    assert_predicate select_year(Time.mktime(2003, 8, 16, 8, 4, 18)), :html_safe?
+    assert_predicate select_minute(Time.mktime(2003, 8, 16, 8, 4, 18)), :html_safe?
+    assert_predicate select_second(Time.mktime(2003, 8, 16, 8, 4, 18)), :html_safe?
 
-    assert select_minute(8, use_hidden: true).html_safe?
-    assert select_month(8, prompt: "Choose month").html_safe?
+    assert_predicate select_minute(8, use_hidden: true), :html_safe?
+    assert_predicate select_month(8, prompt: "Choose month"), :html_safe?
 
-    assert select_time(Time.mktime(2003, 8, 16, 8, 4, 18), {}, { class: "selector" }).html_safe?
-    assert select_date(Time.mktime(2003, 8, 16), date_separator: " / ", start_year: 2003, end_year: 2005, prefix: "date[first]").html_safe?
+    assert_predicate select_time(Time.mktime(2003, 8, 16, 8, 4, 18), {}, { class: "selector" }), :html_safe?
+    assert_predicate select_date(Time.mktime(2003, 8, 16), date_separator: " / ", start_year: 2003, end_year: 2005, prefix: "date[first]"), :html_safe?
   end
 
   def test_object_select_html_safety
     @post = Post.new
     @post.written_on = Date.new(2004, 6, 15)
 
-    assert date_select("post", "written_on", default: Time.local(2006, 9, 19, 15, 16, 35), include_blank: true).html_safe?
-    assert time_select("post", "written_on", ignore_date: true).html_safe?
+    assert_predicate date_select("post", "written_on", default: Time.local(2006, 9, 19, 15, 16, 35), include_blank: true), :html_safe?
+    assert_predicate time_select("post", "written_on", ignore_date: true), :html_safe?
   end
 
   def test_time_tag_with_date
diff --git a/actionview/test/template/digestor_test.rb b/actionview/test/template/digestor_test.rb
index 928b1ac7dd..ddaa7febb3 100644
--- a/actionview/test/template/digestor_test.rb
+++ b/actionview/test/template/digestor_test.rb
@@ -4,17 +4,6 @@ require "abstract_unit"
 require "fileutils"
 require "action_view/dependency_tracker"
 
-class FixtureTemplate
-  attr_reader :source, :handler
-
-  def initialize(template_path)
-    @source = File.read(template_path)
-    @handler = ActionView::Template.handler_for_extension(:erb)
-  rescue Errno::ENOENT
-    raise ActionView::MissingTemplate.new([], "", [], true, [])
-  end
-end
-
 class FixtureFinder < ActionView::LookupContext
   FIXTURES_DIR = File.expand_path("../fixtures/digestor", __dir__)
 
@@ -171,6 +160,18 @@ class TemplateDigestorTest < ActionView::TestCase
     assert_equal [:html], tree_template_formats("messages/show").uniq
   end
 
+  def test_template_dependencies_with_fallback_from_js_to_html_format
+    finder.rendered_format = :js
+    assert_equal ["comments/comment"], dependencies("comments/show")
+  end
+
+  def test_template_digest_with_fallback_from_js_to_html_format
+    finder.rendered_format = :js
+    assert_digest_difference("comments/show") do
+      change_template("comments/_comment")
+    end
+  end
+
   def test_recursion_in_renders
     assert digest("level/recursion") # assert recursion is possible
     assert_not_nil digest("level/recursion") # assert digest is stored
diff --git a/actionview/test/template/erb/deprecated_erubis_implementation_test.rb b/actionview/test/template/erb/deprecated_erubis_implementation_test.rb
deleted file mode 100644
index ea088e7cfc..0000000000
--- a/actionview/test/template/erb/deprecated_erubis_implementation_test.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-# frozen_string_literal: true
-
-require "abstract_unit"
-
-module ERBTest
-  class DeprecatedErubisImplementationTest < ActionView::TestCase
-    test "Erubis implementation is deprecated" do
-      assert_deprecated "ActionView::Template::Handlers::Erubis is deprecated and will be removed from Rails 5.2. Switch to ActionView::Template::Handlers::ERB::Erubi instead." do
-        assert_equal "ActionView::Template::Handlers::ERB::Erubis", ActionView::Template::Handlers::Erubis.to_s
-
-        assert_nothing_raised { Class.new(ActionView::Template::Handlers::Erubis) }
-      end
-    end
-  end
-end
diff --git a/actionview/test/template/erb_util_test.rb b/actionview/test/template/erb_util_test.rb
index 8b804105f4..bd702dbe94 100644
--- a/actionview/test/template/erb_util_test.rb
+++ b/actionview/test/template/erb_util_test.rb
@@ -70,24 +70,24 @@ class ErbUtilTest < ActiveSupport::TestCase
 
   def test_json_escape_returns_unsafe_strings_when_passed_unsafe_strings
     value = json_escape("asdf")
-    assert !value.html_safe?
+    assert_not_predicate value, :html_safe?
   end
 
   def test_json_escape_returns_safe_strings_when_passed_safe_strings
     value = json_escape("asdf".html_safe)
-    assert value.html_safe?
+    assert_predicate value, :html_safe?
   end
 
   def test_html_escape_is_html_safe
     escaped = h("<p>")
     assert_equal "&lt;p&gt;", escaped
-    assert escaped.html_safe?
+    assert_predicate escaped, :html_safe?
   end
 
   def test_html_escape_passes_html_escape_unmodified
     escaped = h("<p>".html_safe)
     assert_equal "<p>", escaped
-    assert escaped.html_safe?
+    assert_predicate escaped, :html_safe?
   end
 
   def test_rest_in_ascii
@@ -104,11 +104,11 @@ class ErbUtilTest < ActiveSupport::TestCase
 
   def test_html_escape_once_returns_unsafe_strings_when_passed_unsafe_strings
     value = html_escape_once("1 < 2 &amp; 3")
-    assert !value.html_safe?
+    assert_not_predicate value, :html_safe?
   end
 
   def test_html_escape_once_returns_safe_strings_when_passed_safe_strings
     value = html_escape_once("1 < 2 &amp; 3".html_safe)
-    assert value.html_safe?
+    assert_predicate value, :html_safe?
   end
 end
diff --git a/actionview/test/template/form_helper/form_with_test.rb b/actionview/test/template/form_helper/form_with_test.rb
index c7d49070ce..6b65d740eb 100644
--- a/actionview/test/template/form_helper/form_with_test.rb
+++ b/actionview/test/template/form_helper/form_with_test.rb
@@ -5,6 +5,25 @@ require "controller/fake_models"
 
 class FormWithTest < ActionView::TestCase
   include RenderERBUtils
+
+  setup do
+    @old_value = ActionView::Helpers::FormHelper.form_with_generates_ids
+    ActionView::Helpers::FormHelper.form_with_generates_ids = true
+  end
+
+  teardown do
+    ActionView::Helpers::FormHelper.form_with_generates_ids = @old_value
+  end
+
+  private
+    def with_default_enforce_utf8(value)
+      old_value = ActionView::Helpers::FormTagHelper.default_enforce_utf8
+      ActionView::Helpers::FormTagHelper.default_enforce_utf8 = value
+
+      yield
+    ensure
+      ActionView::Helpers::FormTagHelper.default_enforce_utf8 = old_value
+    end
 end
 
 class FormWithActsLikeFormTagTest < FormWithTest
@@ -99,7 +118,25 @@ class FormWithActsLikeFormTagTest < FormWithTest
     actual = form_with(skip_enforcing_utf8: true)
     expected = whole_form("http://www.example.com", skip_enforcing_utf8: true)
     assert_dom_equal expected, actual
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
+  end
+
+  def test_form_with_default_enforce_utf8_false
+    with_default_enforce_utf8 false do
+      actual = form_with
+      expected = whole_form("http://www.example.com", skip_enforcing_utf8: true)
+      assert_dom_equal expected, actual
+      assert_predicate actual, :html_safe?
+    end
+  end
+
+  def test_form_with_default_enforce_utf8_true
+    with_default_enforce_utf8 true do
+      actual = form_with
+      expected = whole_form("http://www.example.com", skip_enforcing_utf8: false)
+      assert_dom_equal expected, actual
+      assert_predicate actual, :html_safe?
+    end
   end
 
   def test_form_with_with_block_in_erb
@@ -181,6 +218,9 @@ class FormWithActsLikeFormForTest < FormWithTest
           submit: "Save changes",
           another_post: {
             update: "Update your %{model}"
+          },
+          "blog/post": {
+            update: "Update your %{model}"
           }
         }
       }
@@ -218,7 +258,7 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     @post = Post.new
     @comment = Comment.new
-    def @post.errors()
+    def @post.errors
       Class.new {
         def [](field); field == "author_name" ? ["can't be empty"] : [] end
         def empty?() false end
@@ -314,17 +354,45 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts/123", "create-post", method: "patch") do
       "<label for='post_title'>The Title</label>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[secret]' type='hidden' value='0' />" \
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />" \
+      "<select name='post[category]' id='post_category'><option value='animal'>animal</option>\n<option value='economy'>economy</option>\n<option value='sports'>sports</option></select>" \
+      "<input name='commit' data-disable-with='Create post' type='submit' value='Create post' />" \
+      "<button name='button' type='submit'>Create post</button>" \
+      "<button name='button' type='submit'><span>Create post</span></button>"
+    end
+
+    assert_dom_equal expected, output_buffer
+  end
+
+  def test_form_with_not_outputting_ids
+    old_value = ActionView::Helpers::FormHelper.form_with_generates_ids
+    ActionView::Helpers::FormHelper.form_with_generates_ids = false
+
+    form_with(model: @post, id: "create-post") do |f|
+      concat f.label(:title) { "The Title" }
+      concat f.text_field(:title)
+      concat f.text_area(:body)
+      concat f.check_box(:secret)
+      concat f.select(:category, %w( animal economy sports ))
+      concat f.submit("Create post")
+    end
+
+    expected = whole_form("/posts/123", "create-post", method: "patch") do
+      "<label>The Title</label>" \
       "<input name='post[title]' type='text' value='Hello World' />" \
       "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
       "<input name='post[secret]' checked='checked' type='checkbox' value='1' />" \
       "<select name='post[category]'><option value='animal'>animal</option>\n<option value='economy'>economy</option>\n<option value='sports'>sports</option></select>" \
-      "<input name='commit' data-disable-with='Create post' type='submit' value='Create post' />" \
-      "<button name='button' type='submit'>Create post</button>" \
-      "<button name='button' type='submit'><span>Create post</span></button>"
+      "<input name='commit' data-disable-with='Create post' type='submit' value='Create post' />"
     end
 
     assert_dom_equal expected, output_buffer
+  ensure
+    ActionView::Helpers::FormHelper.form_with_generates_ids = old_value
   end
 
   def test_form_with_only_url_on_create
@@ -335,7 +403,7 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts") do
       '<label for="title">Label me</label>' \
-      '<input type="text" name="title">'
+      '<input type="text" name="title" id="title">'
     end
 
     assert_dom_equal expected, output_buffer
@@ -349,7 +417,7 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts/123") do
       '<label for="title">Label me</label>' \
-      '<input type="text" name="title">'
+      '<input type="text" name="title" id="title">'
     end
 
     assert_dom_equal expected, output_buffer
@@ -361,7 +429,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123") do
-      '<input type="text" name="no_model_to_back_this_badboy">'
+      '<input type="text" name="no_model_to_back_this_badboy" id="no_model_to_back_this_badboy" >'
     end
 
     assert_dom_equal expected, output_buffer
@@ -373,7 +441,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: :patch) do
-      '<input type="text" name="post[this_dont_exist_on_post]">'
+      '<input type="text" name="post[this_dont_exist_on_post]" id="post_this_dont_exist_on_post" >'
     end
 
     assert_dom_equal expected, output_buffer
@@ -391,8 +459,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end.new
 
     form_with(model: obj, scope: "other_name", url: "/", id: "edit-other-name") do |f|
-      assert_dom_equal '<input type="hidden" name="other_name[private_property]">', f.hidden_field(:private_property)
-      assert_dom_equal '<input type="hidden" name="other_name[protected_property]">', f.hidden_field(:protected_property)
+      assert_dom_equal '<input type="hidden" name="other_name[private_property]" id="other_name_private_property">', f.hidden_field(:private_property)
+      assert_dom_equal '<input type="hidden" name="other_name[protected_property]"  id="other_name_protected_property">', f.hidden_field(:protected_property)
     end
   end
 
@@ -459,7 +527,7 @@ class FormWithActsLikeFormForTest < FormWithTest
       "<label for='post_active_false'>" \
       "<input checked='checked' name='post[active]' type='radio' value='false' id='post_active_false' />" \
       "false</label>" \
-      "<input name='post[id]' type='hidden' value='1' />"
+      "<input name='post[id]' type='hidden' value='1' id='post_id' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -557,7 +625,7 @@ class FormWithActsLikeFormForTest < FormWithTest
       "<label for='post_tag_ids_3'>" \
       "<input checked='checked' name='post[tag_ids][]' type='checkbox' value='3' id='post_tag_ids_3' />" \
       "Tag 3</label>" \
-      "<input name='post[id]' type='hidden' value='1' />"
+      "<input name='post[id]' type='hidden' value='1' id='post_id' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -587,7 +655,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", "create-post", method: "patch", multipart: true) do
-      "<input name='post[file]' type='file' />"
+      "<input name='post[file]' type='file' id='post_file' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -601,7 +669,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch", multipart: true) do
-      "<input name='post[comment][file]' type='file' />"
+      "<input name='post[comment][file]' type='file' id='post_comment_file'/>"
     end
 
     assert_dom_equal expected, output_buffer
@@ -640,7 +708,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/44", method: "patch") do
-      "<input name='post[title]' type='text' value='And his name will be forty and four.' />" \
+      "<input name='post[title]' type='text' value='And his name will be forty and four.' id='post_title' />" \
       "<input name='commit' data-disable-with='Edit post' type='submit' value='Edit post' />"
     end
 
@@ -658,10 +726,10 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts/123", "create-post", method: "patch") do
       "<label for='other_name_title' class='post_title'>Title</label>" \
-      "<input name='other_name[title]' value='Hello World' type='text' />" \
-      "<textarea name='other_name[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='other_name[title]' value='Hello World' type='text' id='other_name_title' />" \
+      "<textarea name='other_name[body]' id='other_name_body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='other_name[secret]' value='0' type='hidden' />" \
-      "<input name='other_name[secret]' checked='checked' value='1' type='checkbox' />" \
+      "<input name='other_name[secret]' checked='checked' value='1' type='checkbox' id='other_name_secret' />" \
       "<input name='commit' value='Create post' data-disable-with='Create post' type='submit' />"
     end
 
@@ -676,10 +744,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/", "create-post", method: "delete") do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret'/>"
     end
 
     assert_dom_equal expected, output_buffer
@@ -693,10 +761,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/", "create-post", method: "delete") do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body' >\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -710,7 +778,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/search", "search-post", method: "get") do
-      "<input name='post[title]' type='search' />"
+      "<input name='post[title]' type='search' id='post_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -724,10 +792,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/", "create-post", method: "patch") do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body' >\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -744,10 +812,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/", "create-post", method: "patch", local: true) do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -761,7 +829,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/", skip_enforcing_utf8: true) do
-      "<input name='post[title]' type='text' value='Hello World' />"
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -773,12 +841,40 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/", skip_enforcing_utf8: false) do
-      "<input name='post[title]' type='text' value='Hello World' />"
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />"
     end
 
     assert_dom_equal expected, output_buffer
   end
 
+  def test_form_with_default_enforce_utf8_true
+    with_default_enforce_utf8 true do
+      form_with(scope: :post) do |f|
+        concat f.text_field(:title)
+      end
+
+      expected = whole_form("/", skip_enforcing_utf8: false) do
+        "<input name='post[title]' type='text' value='Hello World' id='post_title' />"
+      end
+
+      assert_dom_equal expected, output_buffer
+    end
+  end
+
+  def test_form_with_default_enforce_utf8_false
+    with_default_enforce_utf8 false do
+      form_with(scope: :post) do |f|
+        concat f.text_field(:title)
+      end
+
+      expected = whole_form("/", skip_enforcing_utf8: true) do
+        "<input name='post[title]' type='text' value='Hello World' id='post_title' />"
+      end
+
+      assert_dom_equal expected, output_buffer
+    end
+  end
+
   def test_form_with_without_object
     form_with(scope: :post, id: "create-post") do |f|
       concat f.text_field(:title)
@@ -787,10 +883,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/", "create-post") do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body' >\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -806,10 +902,10 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts/123", method: "patch") do
       "<label for='post_123_title'>Title</label>" \
-      "<input name='post[123][title]' type='text' value='Hello World' />" \
-      "<textarea name='post[123][body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[123][title]' type='text' value='Hello World' id='post_123_title' />" \
+      "<textarea name='post[123][body]' id='post_123_body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[123][secret]' type='hidden' value='0' />" \
-      "<input name='post[123][secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[123][secret]' checked='checked' type='checkbox' value='1' id='post_123_secret' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -823,10 +919,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[][title]' type='text' value='Hello World' />" \
-      "<textarea name='post[][body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[][title]' type='text' value='Hello World' id='post__title' />" \
+      "<textarea name='post[][body]' id='post__body' >\nBack to the hill and over it again!</textarea>" \
       "<input name='post[][secret]' type='hidden' value='0' />" \
-      "<input name='post[][secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[][secret]' checked='checked' type='checkbox' value='1' id='post__secret' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -841,7 +937,7 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts/123", method: "patch") do
       "<div class='field_with_errors'><label for='post_author_name' class='label'>Author name</label></div>" \
-      "<div class='field_with_errors'><input name='post[author_name]' type='text' value='' /></div>" \
+      "<div class='field_with_errors'><input name='post[author_name]' type='text' value='' id='post_author_name' /></div>" \
       "<input name='commit' data-disable-with='Create post' type='submit' value='Create post' />"
     end
 
@@ -859,7 +955,7 @@ class FormWithActsLikeFormForTest < FormWithTest
 
     expected = whole_form("/posts/123", method: "patch") do
       "<div class='field_with_errors'><label for='post_author_name' class='label'>Author name</label></div>" \
-      "<div class='field_with_errors'><input name='post[author_name]' type='text' value='' /></div>" \
+      "<div class='field_with_errors'><input name='post[author_name]' type='text' value='' id='post_author_name' /></div>" \
       "<input name='commit' data-disable-with='Create post' type='submit' value='Create post' />"
     end
 
@@ -925,7 +1021,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
   end
 
-  def test_submit_with_object_and_nested_lookup
+  def test_submit_with_object_which_is_overwritten_by_scope_option
     with_locale :submit do
       form_with(model: @post, scope: :another_post) do |f|
         concat f.submit
@@ -939,6 +1035,21 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
   end
 
+  def test_submit_with_object_which_is_namespaced
+    blog_post = Blog::Post.new("And his name will be forty and four.", 44)
+    with_locale :submit do
+      form_with(model: blog_post) do |f|
+        concat f.submit
+      end
+
+      expected = whole_form("/posts/44", method: "patch") do
+        "<input name='commit' data-disable-with='Update your Post' type='submit' value='Update your Post' />"
+      end
+
+      assert_dom_equal expected, output_buffer
+    end
+  end
+
   def test_fields_with_attributes_not_on_model
     form_with(model: @post) do |f|
       concat f.fields(:comment) { |c|
@@ -947,7 +1058,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: :patch) do
-      '<input type="text" name="post[comment][dont_exist_on_model]">'
+      '<input type="text" name="post[comment][dont_exist_on_model]" id="post_comment_dont_exist_on_model" >'
     end
 
     assert_dom_equal expected, output_buffer
@@ -967,7 +1078,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form do
-      '<input name="posts[post][0][comment][1][dont_exist_on_model]" type="text">'
+      '<input name="posts[post][0][comment][1][dont_exist_on_model]" type="text" id="posts_post_0_comment_1_dont_exist_on_model" >'
     end
 
     assert_dom_equal expected, output_buffer
@@ -982,7 +1093,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[comment][body]' type='text' value='Hello World' />"
+      "<input name='post[comment][body]' type='text' value='Hello World' id='post_comment_body' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1002,7 +1113,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form do
-      "<input name='posts[post][0][comment][1][name]' type='text' value='comment #1' />"
+      "<input name='posts[post][0][comment][1][name]' type='text' value='comment #1' id='posts_post_0_comment_1_name' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1017,8 +1128,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[123][title]' type='text' value='Hello World' />" \
-      "<input name='post[123][comment][][name]' type='text' value='new comment' />"
+      "<input name='post[123][title]' type='text' value='Hello World' id='post_123_title' />" \
+      "<input name='post[123][comment][][name]' type='text' value='new comment' id='post_123_comment__name' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1033,8 +1144,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[1][title]' type='text' value='Hello World' />" \
-      "<input name='post[1][comment][1][name]' type='text' value='new comment' />"
+      "<input name='post[1][title]' type='text' value='Hello World' id='post_1_title' />" \
+      "<input name='post[1][comment][1][name]' type='text' value='new comment' id='post_1_comment_1_name' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1048,7 +1159,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[1][comment][title]' type='text' value='Hello World' />"
+      "<input name='post[1][comment][title]' type='text' value='Hello World' id='post_1_comment_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1062,7 +1173,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[1][comment][5][title]' type='text' value='Hello World' />"
+      "<input name='post[1][comment][5][title]' type='text' value='Hello World' id='post_1_comment_5_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1076,7 +1187,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[123][comment][title]' type='text' value='Hello World' />"
+      "<input name='post[123][comment][title]' type='text' value='Hello World' id='post_123_comment_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1090,7 +1201,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[comment][5][title]' type='radio' value='hello' />"
+      "<input name='post[comment][5][title]' type='radio' value='hello' id='post_comment_5_title_hello' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1104,7 +1215,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[123][comment][123][title]' type='text' value='Hello World' />"
+      "<input name='post[123][comment][123][title]' type='text' value='Hello World' id='post_123_comment_123_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1124,9 +1235,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[123][comment][5][title]' type='text' value='Hello World' />"
+      "<input name='post[123][comment][5][title]' type='text' value='Hello World' id='post_123_comment_5_title' />"
     end + whole_form("/posts/123", method: "patch") do
-      "<input name='post[1][comment][123][title]' type='text' value='Hello World' />"
+      "<input name='post[1][comment][123][title]' type='text' value='Hello World' id='post_1_comment_123_title' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1143,8 +1254,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-        '<input name="post[author_attributes][name]" type="text" value="new author" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+        '<input name="post[author_attributes][name]" type="text" value="new author" id="post_author_attributes_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1170,9 +1281,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />' \
-      '<input name="post[author_attributes][id]" type="hidden" value="321" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />' \
+      '<input name="post[author_attributes][id]" type="hidden" value="321" id="post_author_attributes_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1189,9 +1300,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />' \
-      '<input name="post[author_attributes][id]" type="hidden" value="321" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />' \
+      '<input name="post[author_attributes][id]" type="hidden" value="321" id="post_author_attributes_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1208,8 +1319,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1226,8 +1337,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1244,9 +1355,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />' \
-      '<input name="post[author_attributes][id]" type="hidden" value="321" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />' \
+      '<input name="post[author_attributes][id]" type="hidden" value="321" id="post_author_attributes_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1264,9 +1375,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][id]" type="hidden" value="321" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][id]" type="hidden" value="321" id="post_author_attributes_id" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1285,11 +1396,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />' \
-      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" id="post_comments_attributes_0_id" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />' \
+      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" id="post_comments_attributes_1_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1312,11 +1423,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />' \
-      '<input name="post[author_attributes][id]" type="hidden" value="321" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />' \
+      '<input name="post[author_attributes][id]" type="hidden" value="321" id="post_author_attributes_id" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1339,10 +1450,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1365,11 +1476,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[author_attributes][name]" type="text" value="author #321" />' \
-      '<input name="post[author_attributes][id]" type="hidden" value="321" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[author_attributes][name]" type="text" value="author #321" id="post_author_attributes_name" />' \
+      '<input name="post[author_attributes][id]" type="hidden" value="321" id="post_author_attributes_id" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1388,11 +1499,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />' \
-      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" id="post_comments_attributes_0_id" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />' \
+      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" id="post_comments_attributes_1_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1412,11 +1523,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" id="post_comments_attributes_0_id" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" id="post_comments_attributes_1_id" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1435,9 +1546,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="new comment" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="new comment" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="new comment" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="new comment" id="post_comments_attributes_1_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1456,10 +1567,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #321" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="321" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="new comment" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #321" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="321" id="post_comments_attributes_0_id"/>' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="new comment" id="post_comments_attributes_1_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1474,7 +1585,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1491,11 +1602,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />' \
-      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" id="post_comments_attributes_0_id" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />' \
+      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" id="post_comments_attributes_1_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1512,11 +1623,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />' \
-      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" id="post_comments_attributes_0_id" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />' \
+      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" id="post_comments_attributes_1_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1547,11 +1658,11 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" />' \
-      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #1" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="1" id="post_comments_attributes_0_id" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="comment #2" id="post_comments_attributes_1_name" />' \
+      '<input name="post[comments_attributes][1][id]" type="hidden" value="2" id="post_comments_attributes_1_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1570,10 +1681,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[title]" type="text" value="Hello World" />' \
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #321" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="321" />' \
-      '<input name="post[comments_attributes][1][name]" type="text" value="new comment" />'
+      '<input name="post[title]" type="text" value="Hello World" id="post_title" />' \
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #321" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="321" id="post_comments_attributes_0_id" />' \
+      '<input name="post[comments_attributes][1][name]" type="text" value="new comment" id="post_comments_attributes_1_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1590,8 +1701,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[comments_attributes][abc][name]" type="text" value="comment #321" />' \
-      '<input name="post[comments_attributes][abc][id]" type="hidden" value="321" />'
+      '<input name="post[comments_attributes][abc][name]" type="text" value="comment #321" id="post_comments_attributes_abc_name" />' \
+      '<input name="post[comments_attributes][abc][id]" type="hidden" value="321" id="post_comments_attributes_abc_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1607,8 +1718,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[comments_attributes][abc][name]" type="text" value="comment #321" />' \
-      '<input name="post[comments_attributes][abc][id]" type="hidden" value="321" />'
+      '<input name="post[comments_attributes][abc][name]" type="text" value="comment #321" id="post_comments_attributes_abc_name" />' \
+      '<input name="post[comments_attributes][abc][id]" type="hidden" value="321" id="post_comments_attributes_abc_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1630,8 +1741,8 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[comments_attributes][abc][name]" type="text" value="comment #321" />' \
-      '<input name="post[comments_attributes][abc][id]" type="hidden" value="321" />'
+      '<input name="post[comments_attributes][abc][name]" type="text" value="comment #321" id="post_comments_attributes_abc_name" />' \
+      '<input name="post[comments_attributes][abc][id]" type="hidden" value="321" id="post_comments_attributes_abc_id" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1716,18 +1827,18 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[comments_attributes][0][name]" type="text" value="comment #321" />' \
-      '<input name="post[comments_attributes][0][relevances_attributes][0][value]" type="text" value="commentrelevance #314" />' \
-      '<input name="post[comments_attributes][0][relevances_attributes][0][id]" type="hidden" value="314" />' \
-      '<input name="post[comments_attributes][0][id]" type="hidden" value="321" />' \
-      '<input name="post[tags_attributes][0][value]" type="text" value="tag #123" />' \
-      '<input name="post[tags_attributes][0][relevances_attributes][0][value]" type="text" value="tagrelevance #3141" />' \
-      '<input name="post[tags_attributes][0][relevances_attributes][0][id]" type="hidden" value="3141" />' \
-      '<input name="post[tags_attributes][0][id]" type="hidden" value="123" />' \
-      '<input name="post[tags_attributes][1][value]" type="text" value="tag #456" />' \
-      '<input name="post[tags_attributes][1][relevances_attributes][0][value]" type="text" value="tagrelevance #31415" />' \
-      '<input name="post[tags_attributes][1][relevances_attributes][0][id]" type="hidden" value="31415" />' \
-      '<input name="post[tags_attributes][1][id]" type="hidden" value="456" />'
+      '<input name="post[comments_attributes][0][name]" type="text" value="comment #321" id="post_comments_attributes_0_name" />' \
+      '<input name="post[comments_attributes][0][relevances_attributes][0][value]" type="text" value="commentrelevance #314" id="post_comments_attributes_0_relevances_attributes_0_value" />' \
+      '<input name="post[comments_attributes][0][relevances_attributes][0][id]" type="hidden" value="314" id="post_comments_attributes_0_relevances_attributes_0_id"/>' \
+      '<input name="post[comments_attributes][0][id]" type="hidden" value="321" id="post_comments_attributes_0_id"/>' \
+      '<input name="post[tags_attributes][0][value]" type="text" value="tag #123" id="post_tags_attributes_0_value"/>' \
+      '<input name="post[tags_attributes][0][relevances_attributes][0][value]" type="text" value="tagrelevance #3141" id="post_tags_attributes_0_relevances_attributes_0_value"/>' \
+      '<input name="post[tags_attributes][0][relevances_attributes][0][id]" type="hidden" value="3141" id="post_tags_attributes_0_relevances_attributes_0_id"/>' \
+      '<input name="post[tags_attributes][0][id]" type="hidden" value="123" id="post_tags_attributes_0_id"/>' \
+      '<input name="post[tags_attributes][1][value]" type="text" value="tag #456" id="post_tags_attributes_1_value"/>' \
+      '<input name="post[tags_attributes][1][relevances_attributes][0][value]" type="text" value="tagrelevance #31415" id="post_tags_attributes_1_relevances_attributes_0_value"/>' \
+      '<input name="post[tags_attributes][1][relevances_attributes][0][id]" type="hidden" value="31415" id="post_tags_attributes_1_relevances_attributes_0_id"/>' \
+      '<input name="post[tags_attributes][1][id]" type="hidden" value="456" id="post_tags_attributes_1_id"/>'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1743,7 +1854,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      '<input name="post[author_attributes][name]" type="text" value="hash backed author" />'
+      '<input name="post[author_attributes][name]" type="text" value="hash backed author" id="post_author_attributes_name" />'
     end
 
     assert_dom_equal expected, output_buffer
@@ -1757,10 +1868,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected =
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />"
 
     assert_dom_equal expected, output_buffer
   end
@@ -1773,10 +1884,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected =
-      "<input name='post[123][title]' type='text' value='Hello World' />" \
-      "<textarea name='post[123][body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[123][title]' type='text' value='Hello World' id='post_123_title' />" \
+      "<textarea name='post[123][body]' id='post_123_body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[123][secret]' type='hidden' value='0' />" \
-      "<input name='post[123][secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[123][secret]' checked='checked' type='checkbox' value='1' id='post_123_secret' />"
 
     assert_dom_equal expected, output_buffer
   end
@@ -1789,10 +1900,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected =
-      "<input name='post[][title]' type='text' value='Hello World' />" \
-      "<textarea name='post[][body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[][title]' type='text' value='Hello World' id='post__title' />" \
+      "<textarea name='post[][body]' id='post__body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[][secret]' type='hidden' value='0' />" \
-      "<input name='post[][secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[][secret]' checked='checked' type='checkbox' value='1' id='post__secret' />"
 
     assert_dom_equal expected, output_buffer
   end
@@ -1805,10 +1916,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected =
-      "<input name='post[abc][title]' type='text' value='Hello World' />" \
-      "<textarea name='post[abc][body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[abc][title]' type='text' value='Hello World' id='post_abc_title' />" \
+      "<textarea name='post[abc][body]' id='post_abc_body'>\nBack to the hill and over it again!</textarea>" \
       "<input name='post[abc][secret]' type='hidden' value='0' />" \
-      "<input name='post[abc][secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[abc][secret]' checked='checked' type='checkbox' value='1' id='post_abc_secret' />"
 
     assert_dom_equal expected, output_buffer
   end
@@ -1821,10 +1932,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected =
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body' >\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />"
 
     assert_dom_equal expected, output_buffer
   end
@@ -1837,10 +1948,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected =
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body' >\nBack to the hill and over it again!</textarea>" \
       "<input name='post[secret]' type='hidden' value='0' />" \
-      "<input name='post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' />"
 
     assert_dom_equal expected, output_buffer
   end
@@ -1852,7 +1963,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     assert_dom_equal "<label for=\"author_post_title\">Title</label>" \
-    "<input name='author[post][title]' type='text' value='Hello World' />",
+    "<input name='author[post][title]' type='text' value='Hello World' id='author_post_title' id='author_post_1_title' />",
       output_buffer
   end
 
@@ -1863,7 +1974,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     assert_dom_equal "<label for=\"author_post_1_title\">Title</label>" \
-      "<input name='author[post][1][title]' type='text' value='Hello World' />",
+      "<input name='author[post][1][title]' type='text' value='Hello World' id='author_post_1_title' />",
       output_buffer
   end
 
@@ -1882,10 +1993,10 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", "create-post", method: "patch") do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body' >\nBack to the hill and over it again!</textarea>" \
       "<input name='parent_post[secret]' type='hidden' value='0' />" \
-      "<input name='parent_post[secret]' checked='checked' type='checkbox' value='1' />"
+      "<input name='parent_post[secret]' checked='checked' type='checkbox' value='1' id='parent_post_secret' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1902,9 +2013,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", "create-post", method: "patch") do
-      "<input name='post[title]' type='text' value='Hello World' />" \
-      "<textarea name='post[body]'>\nBack to the hill and over it again!</textarea>" \
-      "<input name='post[comment][name]' type='text' value='new comment' />"
+      "<input name='post[title]' type='text' value='Hello World' id='post_title' />" \
+      "<textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[comment][name]' type='text' value='new comment' id='post_comment_name' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1918,7 +2029,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<input name='post[category][name]' type='text' />"
+      "<input name='post[category][name]' type='text' id='post_category_name' />"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1942,9 +2053,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' /><br/>" \
-      "<label for='body'>Body:</label> <textarea name='post[body]'>\nBack to the hill and over it again!</textarea><br/>" \
-      "<label for='secret'>Secret:</label> <input name='post[secret]' type='hidden' value='0' /><input name='post[secret]' checked='checked' type='checkbox' value='1' /><br/>"
+      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' id='post_title'/><br/>" \
+      "<label for='body'>Body:</label> <textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea><br/>" \
+      "<label for='secret'>Secret:</label> <input name='post[secret]' type='hidden' value='0' /><input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' /><br/>"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1961,9 +2072,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' /><br/>" \
-      "<label for='body'>Body:</label> <textarea name='post[body]'>\nBack to the hill and over it again!</textarea><br/>" \
-      "<label for='secret'>Secret:</label> <input name='post[secret]' type='hidden' value='0' /><input name='post[secret]' checked='checked' type='checkbox' value='1' /><br/>"
+      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' id='post_title' /><br/>" \
+      "<label for='body'>Body:</label> <textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea><br/>" \
+      "<label for='secret'>Secret:</label> <input name='post[secret]' type='hidden' value='0' /><input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' /><br/>"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1980,7 +2091,7 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected = whole_form("/posts/123", method: "patch") do
-      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' /><br/>"
+      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' id='post_title' /><br/>"
     end
 
     assert_dom_equal expected, output_buffer
@@ -1995,7 +2106,7 @@ class FormWithActsLikeFormForTest < FormWithTest
       concat f.text_field(:title)
     end
 
-    expected = "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' /><br/>"
+    expected = "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' id='post_title' /><br/>"
 
     assert_dom_equal expected, output_buffer
   end
@@ -2007,7 +2118,7 @@ class FormWithActsLikeFormForTest < FormWithTest
       concat f.text_field(:title)
     end
 
-    expected = "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' /><br/>"
+    expected = "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' id='post_title' /><br/>"
 
     assert_dom_equal expected, output_buffer
   end
@@ -2020,9 +2131,9 @@ class FormWithActsLikeFormForTest < FormWithTest
     end
 
     expected =
-      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' /><br/>" \
-      "<label for='body'>Body:</label> <textarea name='post[body]'>\nBack to the hill and over it again!</textarea><br/>" \
-      "<label for='secret'>Secret:</label> <input name='post[secret]' type='hidden' value='0' /><input name='post[secret]' checked='checked' type='checkbox' value='1' /><br/>"
+      "<label for='title'>Title:</label> <input name='post[title]' type='text' value='Hello World' id='post_title'/><br/>" \
+      "<label for='body'>Body:</label> <textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea><br/>" \
+      "<label for='secret'>Secret:</label> <input name='post[secret]' type='hidden' value='0' /><input name='post[secret]' checked='checked' type='checkbox' value='1' id='post_secret' /><br/>"
 
     assert_dom_equal expected, output_buffer
   end
@@ -2236,4 +2347,13 @@ class FormWithActsLikeFormForTest < FormWithTest
     ensure
       I18n.locale = old_locale
     end
+
+    def with_default_enforce_utf8(value)
+      old_value = ActionView::Helpers::FormTagHelper.default_enforce_utf8
+      ActionView::Helpers::FormTagHelper.default_enforce_utf8 = value
+
+      yield
+    ensure
+      ActionView::Helpers::FormTagHelper.default_enforce_utf8 = old_value
+    end
 end
diff --git a/actionview/test/template/form_helper_test.rb b/actionview/test/template/form_helper_test.rb
index ac64096908..5244204e42 100644
--- a/actionview/test/template/form_helper_test.rb
+++ b/actionview/test/template/form_helper_test.rb
@@ -68,6 +68,9 @@ class FormHelperTest < ActionView::TestCase
           submit: "Save changes",
           another_post: {
             update: "Update your %{model}"
+          },
+          "blog/post": {
+            update: "Update your %{model}"
           }
         }
       }
@@ -105,7 +108,7 @@ class FormHelperTest < ActionView::TestCase
 
     @post = Post.new
     @comment = Comment.new
-    def @post.errors()
+    def @post.errors
       Class.new {
         def [](field); field == "author_name" ? ["can't be empty"] : [] end
         def empty?() false end
@@ -612,7 +615,7 @@ class FormHelperTest < ActionView::TestCase
   end
 
   def test_check_box_is_html_safe
-    assert check_box("post", "secret").html_safe?
+    assert_predicate check_box("post", "secret"), :html_safe?
   end
 
   def test_check_box_checked_if_object_value_is_same_that_check_value
@@ -747,19 +750,19 @@ class FormHelperTest < ActionView::TestCase
   end
 
   def test_check_box_with_explicit_checked_and_unchecked_values_when_object_value_is_big_decimal
-    @post.secret = BigDecimal.new(0)
+    @post.secret = BigDecimal(0)
     assert_dom_equal(
       '<input name="post[secret]" type="hidden" value="1" /><input checked="checked" id="post_secret" name="post[secret]" type="checkbox" value="0" />',
       check_box("post", "secret", {}, 0, 1)
     )
 
-    @post.secret = BigDecimal.new(1)
+    @post.secret = BigDecimal(1)
     assert_dom_equal(
       '<input name="post[secret]" type="hidden" value="1" /><input id="post_secret" name="post[secret]" type="checkbox" value="0" />',
       check_box("post", "secret", {}, 0, 1)
     )
 
-    @post.secret = BigDecimal.new(2.2, 1)
+    @post.secret = BigDecimal(2.2, 1)
     assert_dom_equal(
       '<input name="post[secret]" type="hidden" value="1" /><input id="post_secret" name="post[secret]" type="checkbox" value="0" />',
       check_box("post", "secret", {}, 0, 1)
@@ -775,7 +778,7 @@ class FormHelperTest < ActionView::TestCase
   end
 
   def test_check_box_with_nil_unchecked_value_is_html_safe
-    assert check_box("post", "secret", {}, "on", nil).html_safe?
+    assert_predicate check_box("post", "secret", {}, "on", nil), :html_safe?
   end
 
   def test_check_box_with_multiple_behavior
@@ -1560,6 +1563,38 @@ class FormHelperTest < ActionView::TestCase
     assert_dom_equal expected, output_buffer
   end
 
+  def test_form_for_is_not_affected_by_form_with_generates_ids
+    old_value = ActionView::Helpers::FormHelper.form_with_generates_ids
+    ActionView::Helpers::FormHelper.form_with_generates_ids = false
+
+    form_for(@post, html: { id: "create-post" }) do |f|
+      concat f.label(:title) { "The Title" }
+      concat f.text_field(:title)
+      concat f.text_area(:body)
+      concat f.check_box(:secret)
+      concat f.submit("Create post")
+      concat f.button("Create post")
+      concat f.button {
+        concat content_tag(:span, "Create post")
+      }
+    end
+
+    expected = whole_form("/posts/123", "create-post", "edit_post", method: "patch") do
+      "<label for='post_title'>The Title</label>" \
+      "<input name='post[title]' type='text' id='post_title' value='Hello World' />" \
+      "<textarea name='post[body]' id='post_body'>\nBack to the hill and over it again!</textarea>" \
+      "<input name='post[secret]' type='hidden' value='0' />" \
+      "<input name='post[secret]' checked='checked' type='checkbox' id='post_secret' value='1' />" \
+      "<input name='commit' data-disable-with='Create post' type='submit' value='Create post' />" \
+      "<button name='button' type='submit'>Create post</button>" \
+      "<button name='button' type='submit'><span>Create post</span></button>"
+    end
+
+    assert_dom_equal expected, output_buffer
+  ensure
+    ActionView::Helpers::FormHelper.form_with_generates_ids = old_value
+  end
+
   def test_form_for_with_collection_radio_buttons
     post = Post.new
     def post.active; false; end
@@ -1960,6 +1995,34 @@ class FormHelperTest < ActionView::TestCase
     assert_dom_equal expected, output_buffer
   end
 
+  def test_form_for_default_enforce_utf8_false
+    with_default_enforce_utf8 false do
+      form_for(:post) do |f|
+        concat f.text_field(:title)
+      end
+
+      expected = whole_form("/", nil, nil, enforce_utf8: false) do
+        "<input name='post[title]' type='text' id='post_title' value='Hello World' />"
+      end
+
+      assert_dom_equal expected, output_buffer
+    end
+  end
+
+  def test_form_for_default_enforce_utf8_true
+    with_default_enforce_utf8 true do
+      form_for(:post) do |f|
+        concat f.text_field(:title)
+      end
+
+      expected = whole_form("/", nil, nil, enforce_utf8: true) do
+        "<input name='post[title]' type='text' id='post_title' value='Hello World' />"
+      end
+
+      assert_dom_equal expected, output_buffer
+    end
+  end
+
   def test_form_for_with_remote_in_html
     form_for(@post, url: "/", html: { remote: true, id: "create-post", method: :patch }) do |f|
       concat f.text_field(:title)
@@ -2239,7 +2302,7 @@ class FormHelperTest < ActionView::TestCase
     end
   end
 
-  def test_submit_with_object_and_nested_lookup
+  def test_submit_with_object_which_is_overwritten_by_as_option
     with_locale :submit do
       form_for(@post, as: :another_post) do |f|
         concat f.submit
@@ -2253,6 +2316,21 @@ class FormHelperTest < ActionView::TestCase
     end
   end
 
+  def test_submit_with_object_which_is_namespaced
+    blog_post = Blog::Post.new("And his name will be forty and four.", 44)
+    with_locale :submit do
+      form_for(blog_post) do |f|
+        concat f.submit
+      end
+
+      expected = whole_form("/posts/44", "edit_post_44", "edit_post", method: "patch") do
+        "<input name='commit' data-disable-with='Update your Post' type='submit' value='Update your Post' />"
+      end
+
+      assert_dom_equal expected, output_buffer
+    end
+  end
+
   def test_nested_fields_for
     @comment.body = "Hello World"
     form_for(@post) do |f|
@@ -3519,4 +3597,13 @@ class FormHelperTest < ActionView::TestCase
     ensure
       I18n.locale = old_locale
     end
+
+    def with_default_enforce_utf8(value)
+      old_value = ActionView::Helpers::FormTagHelper.default_enforce_utf8
+      ActionView::Helpers::FormTagHelper.default_enforce_utf8 = value
+
+      yield
+    ensure
+      ActionView::Helpers::FormTagHelper.default_enforce_utf8 = old_value
+    end
 end
diff --git a/actionview/test/template/form_options_helper_test.rb b/actionview/test/template/form_options_helper_test.rb
index a66db2f3dc..8f796bdb83 100644
--- a/actionview/test/template/form_options_helper_test.rb
+++ b/actionview/test/template/form_options_helper_test.rb
@@ -337,8 +337,24 @@ class FormOptionsHelperTest < ActionView::TestCase
     )
   end
 
+  def test_option_groups_from_collection_for_select_with_callable_group_method
+    group_proc = Proc.new { |c| c.countries }
+    assert_dom_equal(
+      "<optgroup label=\"&lt;Africa&gt;\"><option value=\"&lt;sa&gt;\">&lt;South Africa&gt;</option>\n<option value=\"so\">Somalia</option></optgroup><optgroup label=\"Europe\"><option value=\"dk\" selected=\"selected\">Denmark</option>\n<option value=\"ie\">Ireland</option></optgroup>",
+      option_groups_from_collection_for_select(dummy_continents, group_proc, "continent_name", "country_id", "country_name", "dk")
+    )
+  end
+
+  def test_option_groups_from_collection_for_select_with_callable_group_label_method
+    label_proc = Proc.new { |c| c.continent_name }
+    assert_dom_equal(
+      "<optgroup label=\"&lt;Africa&gt;\"><option value=\"&lt;sa&gt;\">&lt;South Africa&gt;</option>\n<option value=\"so\">Somalia</option></optgroup><optgroup label=\"Europe\"><option value=\"dk\" selected=\"selected\">Denmark</option>\n<option value=\"ie\">Ireland</option></optgroup>",
+      option_groups_from_collection_for_select(dummy_continents, "countries", label_proc, "country_id", "country_name", "dk")
+    )
+  end
+
   def test_option_groups_from_collection_for_select_returns_html_safe_string
-    assert option_groups_from_collection_for_select(dummy_continents, "countries", "continent_name", "country_id", "country_name", "dk").html_safe?
+    assert_predicate option_groups_from_collection_for_select(dummy_continents, "countries", "continent_name", "country_id", "country_name", "dk"), :html_safe?
   end
 
   def test_grouped_options_for_select_with_array
@@ -367,7 +383,7 @@ class FormOptionsHelperTest < ActionView::TestCase
     assert_dom_equal(
       "<optgroup label=\"----------\"><option value=\"US\">US</option>\n<option value=\"Canada\">Canada</option></optgroup><optgroup label=\"----------\"><option value=\"GB\">GB</option>\n<option value=\"Germany\">Germany</option></optgroup>",
 
-      grouped_options_for_select([["US", "Canada"] , ["GB", "Germany"]], nil, divider: "----------")
+      grouped_options_for_select([["US", "Canada"], ["GB", "Germany"]], nil, divider: "----------")
     )
   end
 
@@ -386,7 +402,7 @@ class FormOptionsHelperTest < ActionView::TestCase
   end
 
   def test_grouped_options_for_select_returns_html_safe_string
-    assert grouped_options_for_select([["Hats", ["Baseball Cap", "Cowboy Hat"]]]).html_safe?
+    assert_predicate grouped_options_for_select([["Hats", ["Baseball Cap", "Cowboy Hat"]]]), :html_safe?
   end
 
   def test_grouped_options_for_select_with_prompt_returns_html_escaped_string
@@ -476,7 +492,7 @@ class FormOptionsHelperTest < ActionView::TestCase
   end
 
   def test_time_zone_options_returns_html_safe_string
-    assert time_zone_options_for_select.html_safe?
+    assert_predicate time_zone_options_for_select, :html_safe?
   end
 
   def test_select
@@ -495,6 +511,16 @@ class FormOptionsHelperTest < ActionView::TestCase
     )
   end
 
+  def test_required_select_with_default_and_selected_placeholder
+    assert_dom_equal(
+      ['<select required="required" name="post[category]" id="post_category"><option disabled="disabled" selected="selected" value="">Choose one</option>',
+      '<option value="lifestyle">lifestyle</option>',
+      '<option value="programming">programming</option>',
+      '<option value="spiritual">spiritual</option></select>'].join("\n"),
+      select(:post, :category, ["lifestyle", "programming", "spiritual"], { selected: "", disabled: "", prompt: "Choose one" }, { required: true })
+    )
+  end
+
   def test_select_with_grouped_collection_as_nested_array
     @post = Post.new
 
@@ -1251,6 +1277,25 @@ class FormOptionsHelperTest < ActionView::TestCase
                  html
   end
 
+  def test_time_zone_select_with_priority_zones_and_errors
+    @firm = Firm.new("D")
+    @firm.extend ActiveModel::Validations
+    @firm.errors[:time_zone] << "invalid"
+    zones = [ ActiveSupport::TimeZone.new("A"), ActiveSupport::TimeZone.new("D") ]
+    html = time_zone_select("firm", "time_zone", zones)
+    assert_dom_equal "<div class=\"field_with_errors\">" \
+                 "<select id=\"firm_time_zone\" name=\"firm[time_zone]\">" \
+                 "<option value=\"A\">A</option>\n" \
+                 "<option value=\"D\" selected=\"selected\">D</option>" \
+                 "<option value=\"\" disabled=\"disabled\">-------------</option>\n" \
+                 "<option value=\"B\">B</option>\n" \
+                 "<option value=\"C\">C</option>\n" \
+                 "<option value=\"E\">E</option>" \
+                 "</select>" \
+                 "</div>",
+                 html
+  end
+
   def test_time_zone_select_with_default_time_zone_and_nil_value
     @firm = Firm.new()
     @firm.time_zone = nil
diff --git a/actionview/test/template/form_tag_helper_test.rb b/actionview/test/template/form_tag_helper_test.rb
index 5e328ebf53..a3500a7eb3 100644
--- a/actionview/test/template/form_tag_helper_test.rb
+++ b/actionview/test/template/form_tag_helper_test.rb
@@ -142,14 +142,32 @@ class FormTagHelperTest < ActionView::TestCase
     actual = form_tag({}, { enforce_utf8: true })
     expected = whole_form("http://www.example.com", enforce_utf8: true)
     assert_dom_equal expected, actual
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
   end
 
   def test_form_tag_enforce_utf8_false
     actual = form_tag({}, { enforce_utf8: false })
     expected = whole_form("http://www.example.com", enforce_utf8: false)
     assert_dom_equal expected, actual
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
+  end
+
+  def test_form_tag_default_enforce_utf8_false
+    with_default_enforce_utf8 false do
+      actual = form_tag({})
+      expected = whole_form("http://www.example.com", enforce_utf8: false)
+      assert_dom_equal expected, actual
+      assert_predicate actual, :html_safe?
+    end
+  end
+
+  def test_form_tag_default_enforce_utf8_true
+    with_default_enforce_utf8 true do
+      actual = form_tag({})
+      expected = whole_form("http://www.example.com", enforce_utf8: true)
+      assert_dom_equal expected, actual
+      assert_predicate actual, :html_safe?
+    end
   end
 
   def test_form_tag_with_block_in_erb
@@ -782,4 +800,13 @@ class FormTagHelperTest < ActionView::TestCase
     def root_elem(rendered_content)
       Nokogiri::HTML::DocumentFragment.parse(rendered_content).children.first # extract from nodeset
     end
+
+    def with_default_enforce_utf8(value)
+      old_value = ActionView::Helpers::FormTagHelper.default_enforce_utf8
+      ActionView::Helpers::FormTagHelper.default_enforce_utf8 = value
+
+      yield
+    ensure
+      ActionView::Helpers::FormTagHelper.default_enforce_utf8 = old_value
+    end
 end
diff --git a/actionview/test/template/javascript_helper_test.rb b/actionview/test/template/javascript_helper_test.rb
index 4478c9f4ab..a72bc6c2fe 100644
--- a/actionview/test/template/javascript_helper_test.rb
+++ b/actionview/test/template/javascript_helper_test.rb
@@ -6,11 +6,15 @@ class JavaScriptHelperTest < ActionView::TestCase
   tests ActionView::Helpers::JavaScriptHelper
 
   attr_accessor :output_buffer
+  attr_reader :request
 
   setup do
     @old_escape_html_entities_in_json = ActiveSupport.escape_html_entities_in_json
     ActiveSupport.escape_html_entities_in_json = true
     @template = self
+    @request = Class.new do
+      def send_early_hints(links) end
+    end.new
   end
 
   def teardown
diff --git a/actionview/test/template/log_subscriber_test.rb b/actionview/test/template/log_subscriber_test.rb
index a4d89ba0d1..7f4fd25573 100644
--- a/actionview/test/template/log_subscriber_test.rb
+++ b/actionview/test/template/log_subscriber_test.rb
@@ -30,7 +30,7 @@ class AVLogSubscriberTest < ActiveSupport::TestCase
     ActiveSupport::LogSubscriber.log_subscribers.clear
 
     # We need to undef `root`, RenderTestCases don't want this to be defined
-    Rails.instance_eval { undef :root } if @defined_root
+    Rails.instance_eval { undef :root } if defined?(@defined_root)
   end
 
   def set_logger(logger)
diff --git a/actionview/test/template/lookup_context_test.rb b/actionview/test/template/lookup_context_test.rb
index 402ee9b6ae..38469cbe3d 100644
--- a/actionview/test/template/lookup_context_test.rb
+++ b/actionview/test/template/lookup_context_test.rb
@@ -35,7 +35,7 @@ class LookupContextTest < ActiveSupport::TestCase
 
   test "allows me to freeze and retrieve frozen formats" do
     @lookup_context.formats.freeze
-    assert @lookup_context.formats.frozen?
+    assert_predicate @lookup_context.formats, :frozen?
   end
 
   test "provides getters and setters for variants" do
@@ -195,7 +195,7 @@ class LookupContextTest < ActiveSupport::TestCase
 
     assert @lookup_context.cache
     template = @lookup_context.disable_cache do
-      assert !@lookup_context.cache
+      assert_not @lookup_context.cache
       @lookup_context.find("foo", %w(test), true)
     end
     assert @lookup_context.cache
diff --git a/actionview/test/template/number_helper_test.rb b/actionview/test/template/number_helper_test.rb
index 2b671a6685..357ae1326a 100644
--- a/actionview/test/template/number_helper_test.rb
+++ b/actionview/test/template/number_helper_test.rb
@@ -79,7 +79,7 @@ class NumberHelperTest < ActionView::TestCase
     assert_equal "1.23 &lt;b&gt;km3&lt;/b&gt;", number_to_human(1_234_567_000_000, units: volume)
     assert_equal "1.23 &lt;b&gt;Pl&lt;/b&gt;", number_to_human(1_234_567_000_000_000, units: volume)
 
-    #Including fractionals
+    # Including fractionals
     distance = { mili: "<b>mm</b>", centi: "<b>cm</b>", deci: "<b>dm</b>", unit: "<b>m</b>",
                  ten: "<b>dam</b>", hundred: "<b>hm</b>", thousand: "<b>km</b>",
                  micro: "<b>um</b>", nano: "<b>nm</b>", pico: "<b>pm</b>", femto: "<b>fm</b>" }
@@ -126,43 +126,43 @@ class NumberHelperTest < ActionView::TestCase
   end
 
   def test_number_helpers_outputs_are_html_safe
-    assert number_to_human(1).html_safe?
-    assert !number_to_human("<script></script>").html_safe?
-    assert number_to_human("asdf".html_safe).html_safe?
-    assert number_to_human("1".html_safe).html_safe?
-
-    assert number_to_human_size(1).html_safe?
-    assert number_to_human_size(1000000).html_safe?
-    assert !number_to_human_size("<script></script>").html_safe?
-    assert number_to_human_size("asdf".html_safe).html_safe?
-    assert number_to_human_size("1".html_safe).html_safe?
-
-    assert number_with_precision(1, strip_insignificant_zeros: false).html_safe?
-    assert number_with_precision(1, strip_insignificant_zeros: true).html_safe?
-    assert !number_with_precision("<script></script>").html_safe?
-    assert number_with_precision("asdf".html_safe).html_safe?
-    assert number_with_precision("1".html_safe).html_safe?
-
-    assert number_to_currency(1).html_safe?
-    assert !number_to_currency("<script></script>").html_safe?
-    assert number_to_currency("asdf".html_safe).html_safe?
-    assert number_to_currency("1".html_safe).html_safe?
-
-    assert number_to_percentage(1).html_safe?
-    assert !number_to_percentage("<script></script>").html_safe?
-    assert number_to_percentage("asdf".html_safe).html_safe?
-    assert number_to_percentage("1".html_safe).html_safe?
-
-    assert number_to_phone(1).html_safe?
+    assert_predicate number_to_human(1), :html_safe?
+    assert_not_predicate number_to_human("<script></script>"), :html_safe?
+    assert_predicate number_to_human("asdf".html_safe), :html_safe?
+    assert_predicate number_to_human("1".html_safe), :html_safe?
+
+    assert_predicate number_to_human_size(1), :html_safe?
+    assert_predicate number_to_human_size(1000000), :html_safe?
+    assert_not_predicate number_to_human_size("<script></script>"), :html_safe?
+    assert_predicate number_to_human_size("asdf".html_safe), :html_safe?
+    assert_predicate number_to_human_size("1".html_safe), :html_safe?
+
+    assert_predicate number_with_precision(1, strip_insignificant_zeros: false), :html_safe?
+    assert_predicate number_with_precision(1, strip_insignificant_zeros: true), :html_safe?
+    assert_not_predicate number_with_precision("<script></script>"), :html_safe?
+    assert_predicate number_with_precision("asdf".html_safe), :html_safe?
+    assert_predicate number_with_precision("1".html_safe), :html_safe?
+
+    assert_predicate number_to_currency(1), :html_safe?
+    assert_not_predicate number_to_currency("<script></script>"), :html_safe?
+    assert_predicate number_to_currency("asdf".html_safe), :html_safe?
+    assert_predicate number_to_currency("1".html_safe), :html_safe?
+
+    assert_predicate number_to_percentage(1), :html_safe?
+    assert_not_predicate number_to_percentage("<script></script>"), :html_safe?
+    assert_predicate number_to_percentage("asdf".html_safe), :html_safe?
+    assert_predicate number_to_percentage("1".html_safe), :html_safe?
+
+    assert_predicate number_to_phone(1), :html_safe?
     assert_equal "&lt;script&gt;&lt;/script&gt;", number_to_phone("<script></script>")
-    assert number_to_phone("<script></script>").html_safe?
-    assert number_to_phone("asdf".html_safe).html_safe?
-    assert number_to_phone("1".html_safe).html_safe?
-
-    assert number_with_delimiter(1).html_safe?
-    assert !number_with_delimiter("<script></script>").html_safe?
-    assert number_with_delimiter("asdf".html_safe).html_safe?
-    assert number_with_delimiter("1".html_safe).html_safe?
+    assert_predicate number_to_phone("<script></script>"), :html_safe?
+    assert_predicate number_to_phone("asdf".html_safe), :html_safe?
+    assert_predicate number_to_phone("1".html_safe), :html_safe?
+
+    assert_predicate number_with_delimiter(1), :html_safe?
+    assert_not_predicate number_with_delimiter("<script></script>"), :html_safe?
+    assert_predicate number_with_delimiter("asdf".html_safe), :html_safe?
+    assert_predicate number_with_delimiter("1".html_safe), :html_safe?
   end
 
   def test_number_helpers_should_raise_error_if_invalid_when_specified
diff --git a/actionview/test/template/output_safety_helper_test.rb b/actionview/test/template/output_safety_helper_test.rb
index b5e9a77105..faeeded1c8 100644
--- a/actionview/test/template/output_safety_helper_test.rb
+++ b/actionview/test/template/output_safety_helper_test.rb
@@ -12,7 +12,7 @@ class OutputSafetyHelperTest < ActionView::TestCase
   test "raw returns the safe string" do
     result = raw(@string)
     assert_equal @string, result
-    assert result.html_safe?
+    assert_predicate result, :html_safe?
   end
 
   test "raw handles nil values correctly" do
@@ -53,11 +53,11 @@ class OutputSafetyHelperTest < ActionView::TestCase
 
   test "to_sentence should escape non-html_safe values" do
     actual = to_sentence(%w(< > & ' "))
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
     assert_equal("&lt;, &gt;, &amp;, &#39;, and &quot;", actual)
 
     actual = to_sentence(%w(<script>))
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
     assert_equal("&lt;script&gt;", actual)
   end
 
@@ -80,19 +80,19 @@ class OutputSafetyHelperTest < ActionView::TestCase
     url = "https://example.com"
     expected = %(<a href="#{url}">#{url}</a> and <p>&lt;marquee&gt;shady stuff&lt;/marquee&gt;<br /></p>)
     actual = to_sentence([link_to(url, url), ptag])
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
     assert_equal(expected, actual)
   end
 
   test "to_sentence handles blank strings" do
     actual = to_sentence(["", "two", "three"])
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
     assert_equal ", two, and three", actual
   end
 
   test "to_sentence handles nil values" do
     actual = to_sentence([nil, "two", "three"])
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
     assert_equal ", two, and three", actual
   end
 
diff --git a/actionview/test/template/partial_iteration_test.rb b/actionview/test/template/partial_iteration_test.rb
index 06bbdabac0..1c3c566667 100644
--- a/actionview/test/template/partial_iteration_test.rb
+++ b/actionview/test/template/partial_iteration_test.rb
@@ -18,7 +18,7 @@ class PartialIterationTest < ActiveSupport::TestCase
   def test_first_is_false_unless_current_is_at_the_first_index
     iteration = ActionView::PartialIteration.new 3
     iteration.iterate!
-    assert !iteration.first?, "not first when current is 1"
+    assert_not iteration.first?, "not first when current is 1"
   end
 
   def test_last_is_true_when_current_is_at_the_last_index
@@ -30,6 +30,6 @@ class PartialIterationTest < ActiveSupport::TestCase
 
   def test_last_is_false_unless_current_is_at_the_last_index
     iteration = ActionView::PartialIteration.new 3
-    assert !iteration.last?, "not last when current is 0"
+    assert_not iteration.last?, "not last when current is 0"
   end
 end
diff --git a/actionview/test/template/record_tag_helper_test.rb b/actionview/test/template/record_tag_helper_test.rb
deleted file mode 100644
index 7bbbfccdd0..0000000000
--- a/actionview/test/template/record_tag_helper_test.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-# frozen_string_literal: true
-
-require "abstract_unit"
-
-class RecordTagPost
-  extend ActiveModel::Naming
-
-  attr_accessor :id, :body
-
-  def initialize
-    @id   = 45
-    @body = "What a wonderful world!"
-
-    yield self if block_given?
-  end
-end
-
-class RecordTagHelperTest < ActionView::TestCase
-  tests ActionView::Helpers::RecordTagHelper
-
-  def setup
-    super
-    @post = RecordTagPost.new
-  end
-
-  def test_content_tag_for
-    assert_raises(NoMethodError) { content_tag_for(:li, @post) }
-  end
-
-  def test_div_for
-    assert_raises(NoMethodError) { div_for(@post, class: "special") }
-  end
-end
diff --git a/actionview/test/template/sanitize_helper_test.rb b/actionview/test/template/sanitize_helper_test.rb
index c7714cf205..181f09ab65 100644
--- a/actionview/test/template/sanitize_helper_test.rb
+++ b/actionview/test/template/sanitize_helper_test.rb
@@ -21,8 +21,8 @@ class SanitizeHelperTest < ActionView::TestCase
 
   def test_should_sanitize_illegal_style_properties
     raw      = %(display:block; position:absolute; left:0; top:0; width:100%; height:100%; z-index:1; background-color:black; background-image:url(http://www.ragingplatypus.com/i/cam-full.jpg); background-x:center; background-y:center; background-repeat:repeat;)
-    expected = %(display: block; width: 100%; height: 100%; background-color: black; background-x: center; background-y: center;)
-    assert_equal expected, sanitize_css(raw)
+    expected = %r(\Adisplay:\s?block;\s?width:\s?100%;\s?height:\s?100%;\s?background-color:\s?black;\s?background-x:\s?center;\s?background-y:\s?center;\z)
+    assert_match expected, sanitize_css(raw)
   end
 
   def test_strip_tags
@@ -38,6 +38,6 @@ class SanitizeHelperTest < ActionView::TestCase
   end
 
   def test_sanitize_is_marked_safe
-    assert sanitize("<html><script></script></html>").html_safe?
+    assert_predicate sanitize("<html><script></script></html>"), :html_safe?
   end
 end
diff --git a/actionview/test/template/streaming_render_test.rb b/actionview/test/template/streaming_render_test.rb
index 23edf7b538..ef000300cc 100644
--- a/actionview/test/template/streaming_render_test.rb
+++ b/actionview/test/template/streaming_render_test.rb
@@ -5,7 +5,7 @@ require "abstract_unit"
 class TestController < ActionController::Base
 end
 
-class FiberedTest < ActiveSupport::TestCase
+class SetupFiberedBase < ActiveSupport::TestCase
   def setup
     view_paths = ActionController::Base.view_paths
     @assigns = { secret: "in the sauce", name: nil }
@@ -25,7 +25,9 @@ class FiberedTest < ActiveSupport::TestCase
     end
     string
   end
+end
 
+class FiberedTest < SetupFiberedBase
   def test_streaming_works
     content = []
     body = render_body(template: "test/hello_world", layout: "layouts/yield")
@@ -111,3 +113,20 @@ class FiberedTest < ActiveSupport::TestCase
       buffered_render(template: "test/streaming", layout: "layouts/streaming_with_capture")
   end
 end
+
+class FiberedWithLocaleTest < SetupFiberedBase
+  def setup
+    @old_locale = I18n.locale
+    I18n.locale = "da"
+    super
+  end
+
+  def teardown
+    I18n.locale = @old_locale
+  end
+
+  def test_render_with_streaming_and_locale
+    assert_equal "layout.locale: da\nview.locale: da\n\n",
+      buffered_render(template: "test/streaming_with_locale", layout: "layouts/streaming_with_locale")
+  end
+end
diff --git a/actionview/test/template/tag_helper_test.rb b/actionview/test/template/tag_helper_test.rb
index 8c57803796..9a6226fd04 100644
--- a/actionview/test/template/tag_helper_test.rb
+++ b/actionview/test/template/tag_helper_test.rb
@@ -81,7 +81,7 @@ class TagHelperTest < ActionView::TestCase
 
   def test_content_tag
     assert_equal "<a href=\"create\">Create</a>", content_tag("a", "Create", "href" => "create")
-    assert content_tag("a", "Create", "href" => "create").html_safe?
+    assert_predicate content_tag("a", "Create", "href" => "create"), :html_safe?
     assert_equal content_tag("a", "Create", "href" => "create"),
                  content_tag("a", "Create", href: "create")
     assert_equal "<p>&lt;script&gt;evil_js&lt;/script&gt;</p>",
@@ -92,7 +92,7 @@ class TagHelperTest < ActionView::TestCase
 
   def test_tag_builder_with_content
     assert_equal "<div id=\"post_1\">Content</div>", tag.div("Content", id: "post_1")
-    assert tag.div("Content", id: "post_1").html_safe?
+    assert_predicate tag.div("Content", id: "post_1"), :html_safe?
     assert_equal tag.div("Content", id: "post_1"),
                  tag.div("Content", "id": "post_1")
     assert_equal "<p>&lt;script&gt;evil_js&lt;/script&gt;</p>",
@@ -307,8 +307,8 @@ class TagHelperTest < ActionView::TestCase
 
   def test_tag_builder_disable_escaping
     assert_equal '<a href="&amp;"></a>', tag.a(href: "&amp;", escape_attributes: false)
-    assert_equal '<a href="&amp;">cnt</a>', tag.a(href: "&amp;" , escape_attributes: false) { "cnt" }
-    assert_equal '<br data-hidden="&amp;">', tag.br("data-hidden": "&amp;" , escape_attributes: false)
+    assert_equal '<a href="&amp;">cnt</a>', tag.a(href: "&amp;", escape_attributes: false) { "cnt" }
+    assert_equal '<br data-hidden="&amp;">', tag.br("data-hidden": "&amp;", escape_attributes: false)
     assert_equal '<a href="&amp;">content</a>', tag.a("content", href: "&amp;", escape_attributes: false)
     assert_equal '<a href="&amp;">content</a>', tag.a(href: "&amp;", escape_attributes: false) { "content" }
   end
@@ -316,18 +316,18 @@ class TagHelperTest < ActionView::TestCase
   def test_data_attributes
     ["data", :data].each { |data|
       assert_dom_equal '<a data-a-float="3.14" data-a-big-decimal="-123.456" data-a-number="1" data-array="[1,2,3]" data-hash="{&quot;key&quot;:&quot;value&quot;}" data-string-with-quotes="double&quot;quote&quot;party&quot;" data-string="hello" data-symbol="foo" />',
-        tag("a", data => { a_float: 3.14, a_big_decimal: BigDecimal.new("-123.456"), a_number: 1, string: "hello", symbol: :foo, array: [1, 2, 3], hash: { key: "value" }, string_with_quotes: 'double"quote"party"' })
+        tag("a", data => { a_float: 3.14, a_big_decimal: BigDecimal("-123.456"), a_number: 1, string: "hello", symbol: :foo, array: [1, 2, 3], hash: { key: "value" }, string_with_quotes: 'double"quote"party"' })
       assert_dom_equal '<a data-a-float="3.14" data-a-big-decimal="-123.456" data-a-number="1" data-array="[1,2,3]" data-hash="{&quot;key&quot;:&quot;value&quot;}" data-string-with-quotes="double&quot;quote&quot;party&quot;" data-string="hello" data-symbol="foo" />',
-        tag.a(data: { a_float: 3.14, a_big_decimal: BigDecimal.new("-123.456"), a_number: 1, string: "hello", symbol: :foo, array: [1, 2, 3], hash: { key: "value" }, string_with_quotes: 'double"quote"party"' })
+        tag.a(data: { a_float: 3.14, a_big_decimal: BigDecimal("-123.456"), a_number: 1, string: "hello", symbol: :foo, array: [1, 2, 3], hash: { key: "value" }, string_with_quotes: 'double"quote"party"' })
     }
   end
 
   def test_aria_attributes
     ["aria", :aria].each { |aria|
       assert_dom_equal '<a aria-a-float="3.14" aria-a-big-decimal="-123.456" aria-a-number="1" aria-array="[1,2,3]" aria-hash="{&quot;key&quot;:&quot;value&quot;}" aria-string-with-quotes="double&quot;quote&quot;party&quot;" aria-string="hello" aria-symbol="foo" />',
-        tag("a", aria => { a_float: 3.14, a_big_decimal: BigDecimal.new("-123.456"), a_number: 1, string: "hello", symbol: :foo, array: [1, 2, 3], hash: { key: "value" }, string_with_quotes: 'double"quote"party"' })
+        tag("a", aria => { a_float: 3.14, a_big_decimal: BigDecimal("-123.456"), a_number: 1, string: "hello", symbol: :foo, array: [1, 2, 3], hash: { key: "value" }, string_with_quotes: 'double"quote"party"' })
       assert_dom_equal '<a aria-a-float="3.14" aria-a-big-decimal="-123.456" aria-a-number="1" aria-array="[1,2,3]" aria-hash="{&quot;key&quot;:&quot;value&quot;}" aria-string-with-quotes="double&quot;quote&quot;party&quot;" aria-string="hello" aria-symbol="foo" />',
-        tag.a(aria: { a_float: 3.14, a_big_decimal: BigDecimal.new("-123.456"), a_number: 1, string: "hello", symbol: :foo, array: [1, 2, 3], hash: { key: "value" }, string_with_quotes: 'double"quote"party"' })
+        tag.a(aria: { a_float: 3.14, a_big_decimal: BigDecimal("-123.456"), a_number: 1, string: "hello", symbol: :foo, array: [1, 2, 3], hash: { key: "value" }, string_with_quotes: 'double"quote"party"' })
     }
   end
 
diff --git a/actionview/test/template/test_case_test.rb b/actionview/test/template/test_case_test.rb
index 05e5f21ce4..d98fd4f9a2 100644
--- a/actionview/test/template/test_case_test.rb
+++ b/actionview/test/template/test_case_test.rb
@@ -192,7 +192,7 @@ module ActionView
     helper HelperThatInvokesProtectAgainstForgery
 
     test "protect_from_forgery? in any helpers returns false" do
-      assert !view.help_me
+      assert_not view.help_me
     end
   end
 
diff --git a/actionview/test/template/text_helper_test.rb b/actionview/test/template/text_helper_test.rb
index f247de066f..45edfe18be 100644
--- a/actionview/test/template/text_helper_test.rb
+++ b/actionview/test/template/text_helper_test.rb
@@ -19,12 +19,12 @@ class TextHelperTest < ActionView::TestCase
   end
 
   def test_simple_format_should_be_html_safe
-    assert simple_format("<b> test with html tags </b>").html_safe?
+    assert_predicate simple_format("<b> test with html tags </b>"), :html_safe?
   end
 
   def test_simple_format_included_in_isolation
     helper_klass = Class.new { include ActionView::Helpers::TextHelper }
-    assert helper_klass.new.simple_format("<b> test with html tags </b>").html_safe?
+    assert_predicate helper_klass.new.simple_format("<b> test with html tags </b>"), :html_safe?
   end
 
   def test_simple_format
@@ -123,7 +123,7 @@ class TextHelperTest < ActionView::TestCase
   end
 
   def test_truncate_should_be_html_safe
-    assert truncate("Hello World!", length: 12).html_safe?
+    assert_predicate truncate("Hello World!", length: 12), :html_safe?
   end
 
   def test_truncate_should_escape_the_input
@@ -136,12 +136,12 @@ class TextHelperTest < ActionView::TestCase
 
   def test_truncate_with_escape_false_should_be_html_safe
     truncated = truncate("Hello <script>code!</script>World!!", length: 12, escape: false)
-    assert truncated.html_safe?
+    assert_predicate truncated, :html_safe?
   end
 
   def test_truncate_with_block_should_be_html_safe
     truncated = truncate("Here's a long test and I need a continue to read link", length: 27) { link_to "Continue", "#" }
-    assert truncated.html_safe?
+    assert_predicate truncated, :html_safe?
   end
 
   def test_truncate_with_block_should_escape_the_input
@@ -156,7 +156,7 @@ class TextHelperTest < ActionView::TestCase
 
   def test_truncate_with_block_with_escape_false_should_be_html_safe
     truncated = truncate("<script>code!</script>Here's a long test and I need a continue to read link", length: 27, escape: false) { link_to "Continue", "#" }
-    assert truncated.html_safe?
+    assert_predicate truncated, :html_safe?
   end
 
   def test_truncate_with_block_should_escape_the_block
@@ -165,7 +165,7 @@ class TextHelperTest < ActionView::TestCase
   end
 
   def test_highlight_should_be_html_safe
-    assert highlight("This is a beautiful morning", "beautiful").html_safe?
+    assert_predicate highlight("This is a beautiful morning", "beautiful"), :html_safe?
   end
 
   def test_highlight
@@ -297,7 +297,7 @@ class TextHelperTest < ActionView::TestCase
   end
 
   def test_excerpt_should_not_be_html_safe
-    assert !excerpt("This is a beautiful! morning", "beautiful", radius: 5).html_safe?
+    assert_not_predicate excerpt("This is a beautiful! morning", "beautiful", radius: 5), :html_safe?
   end
 
   def test_excerpt_in_borderline_cases
diff --git a/actionview/test/template/translation_helper_test.rb b/actionview/test/template/translation_helper_test.rb
index 8956a584ff..f40595bf4d 100644
--- a/actionview/test/template/translation_helper_test.rb
+++ b/actionview/test/template/translation_helper_test.rb
@@ -75,7 +75,7 @@ class TranslationHelperTest < ActiveSupport::TestCase
   def test_returns_missing_translation_message_with_unescaped_interpolation
     expected = '<span class="translation_missing" title="translation missing: en.translations.missing, name: Kir, year: 2015, vulnerable: &amp;quot; onclick=&amp;quot;alert()&amp;quot;">Missing</span>'
     assert_equal expected, translate(:"translations.missing", name: "Kir", year: "2015", vulnerable: %{" onclick="alert()"})
-    assert translate(:"translations.missing").html_safe?
+    assert_predicate translate(:"translations.missing"), :html_safe?
   end
 
   def test_returns_missing_translation_message_does_filters_out_i18n_options
@@ -145,11 +145,11 @@ class TranslationHelperTest < ActiveSupport::TestCase
   end
 
   def test_translate_marks_translations_named_html_as_safe_html
-    assert translate(:'translations.html').html_safe?
+    assert_predicate translate(:'translations.html'), :html_safe?
   end
 
   def test_translate_marks_translations_with_a_html_suffix_as_safe_html
-    assert translate(:'translations.hello_html').html_safe?
+    assert_predicate translate(:'translations.hello_html'), :html_safe?
   end
 
   def test_translate_escapes_interpolations_in_translations_with_a_html_suffix
diff --git a/actionview/test/template/url_helper_test.rb b/actionview/test/template/url_helper_test.rb
index 0cd0386cac..08cb5dfea7 100644
--- a/actionview/test/template/url_helper_test.rb
+++ b/actionview/test/template/url_helper_test.rb
@@ -508,16 +508,16 @@ class UrlHelperTest < ActiveSupport::TestCase
   def test_current_page_considering_params
     @request = request_for_url("/?order=desc&page=1")
 
-    assert !current_page?(url_hash, check_parameters: true)
-    assert !current_page?(url_hash.merge(check_parameters: true))
-    assert !current_page?(ActionController::Parameters.new(url_hash.merge(check_parameters: true)).permit!)
-    assert !current_page?("http://www.example.com/", check_parameters: true)
+    assert_not current_page?(url_hash, check_parameters: true)
+    assert_not current_page?(url_hash.merge(check_parameters: true))
+    assert_not current_page?(ActionController::Parameters.new(url_hash.merge(check_parameters: true)).permit!)
+    assert_not current_page?("http://www.example.com/", check_parameters: true)
   end
 
   def test_current_page_considering_params_when_options_does_not_respond_to_to_hash
     @request = request_for_url("/?order=desc&page=1")
 
-    assert !current_page?(:back, check_parameters: false)
+    assert_not current_page?(:back, check_parameters: false)
   end
 
   def test_current_page_with_params_that_match
@@ -562,7 +562,7 @@ class UrlHelperTest < ActiveSupport::TestCase
   def test_current_page_with_not_get_verb
     @request = request_for_url("/events", method: :post)
 
-    assert !current_page?("/events")
+    assert_not current_page?("/events")
   end
 
   def test_link_unless_current
@@ -663,7 +663,7 @@ class UrlHelperTest < ActiveSupport::TestCase
   end
 
   def test_mail_to_returns_html_safe_string
-    assert mail_to("david@loudthinking.com").html_safe?
+    assert_predicate mail_to("david@loudthinking.com"), :html_safe?
   end
 
   def test_mail_to_with_block
diff --git a/actionview/test/tmp/.gitkeep b/actionview/test/tmp/.gitkeep
deleted file mode 100644
index e69de29bb2..0000000000
--- a/actionview/test/tmp/.gitkeep
+++ /dev/null
diff --git a/actionview/test/ujs/.gitignore b/actionview/test/ujs/.gitignore
deleted file mode 100644
index 31dbbff57c..0000000000
--- a/actionview/test/ujs/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-/log
diff --git a/actionview/test/ujs/public/test/call-ajax.js b/actionview/test/ujs/public/test/call-ajax.js
new file mode 100644
index 0000000000..4d0bfb0806
--- /dev/null
+++ b/actionview/test/ujs/public/test/call-ajax.js
@@ -0,0 +1,26 @@
+(function() {
+
+module('call-ajax', {
+  setup: function() {
+    $('#qunit-fixture')
+      .append($('<a />', { href: '#' }))
+  }
+})
+
+asyncTest('call ajax without "ajax:beforeSend"', 1, function() {
+  var link = $('#qunit-fixture a')
+  link.bindNative('click', function() {
+    Rails.ajax({
+      type: 'get',
+      url: '/',
+      success: function() {
+        ok(true, 'calling request in ajax:success')
+      }
+    })
+  })
+
+  link.triggerNative('click')
+  setTimeout(function() { start() }, 50)
+})
+
+})()
diff --git a/actionview/test/ujs/public/test/call-remote-callbacks.js b/actionview/test/ujs/public/test/call-remote-callbacks.js
index 707e21541d..9c0c8cfb4b 100644
--- a/actionview/test/ujs/public/test/call-remote-callbacks.js
+++ b/actionview/test/ujs/public/test/call-remote-callbacks.js
@@ -12,34 +12,20 @@ module('call-remote-callbacks', {
     $(document).undelegate('form[data-remote]', 'ajax:send')
     $(document).undelegate('form[data-remote]', 'ajax:complete')
     $(document).undelegate('form[data-remote]', 'ajax:success')
-    $(document).unbind('ajaxStop')
     $(document).unbind('iframe:loading')
   }
 })
 
-function start_after_submit(form) {
-  form.bindNative('ajax:complete', function() {
-    ok(true, 'ajax:complete')
-    start()
-  })
-}
-
 function submit(fn) {
   var form = $('form')
-  start_after_submit(form)
 
   if (fn) fn(form)
   form.triggerNative('submit')
-}
 
-function submit_with_button(submit_button) {
-  var form = $('form')
-  start_after_submit(form)
-
-  submit_button.triggerNative('click')
+  setTimeout(function() { start() }, 13)
 }
 
-asyncTest('modifying form fields with "ajax:before" sends modified data in request', 4, function() {
+asyncTest('modifying form fields with "ajax:before" sends modified data in request', 3, function() {
   $('form[data-remote]')
     .append($('<input type="text" name="user_name" value="john">'))
     .append($('<input type="text" name="removed_user_name" value="john">'))
@@ -61,7 +47,7 @@ asyncTest('modifying form fields with "ajax:before" sends modified data in reque
   })
 })
 
-asyncTest('modifying data("type") with "ajax:before" requests new dataType in request', 2, function() {
+asyncTest('modifying data("type") with "ajax:before" requests new dataType in request', 1, function() {
   $('form[data-remote]').data('type', 'html')
     .bindNative('ajax:before', function() {
       this.setAttribute('data-type', 'xml')
@@ -74,7 +60,7 @@ asyncTest('modifying data("type") with "ajax:before" requests new dataType in re
   })
 })
 
-asyncTest('setting data("with-credentials",true) with "ajax:before" uses new setting in request', 2, function() {
+asyncTest('setting data("with-credentials",true) with "ajax:before" uses new setting in request', 1, function() {
   $('form[data-remote]').data('with-credentials', false)
     .bindNative('ajax:before', function() {
       this.setAttribute('data-with-credentials', true)
@@ -89,21 +75,18 @@ asyncTest('setting data("with-credentials",true) with "ajax:before" uses new set
 
 asyncTest('stopping the "ajax:beforeSend" event aborts the request', 1, function() {
   submit(function(form) {
-    form.bindNative('ajax:beforeSend', function() {
+    form.bindNative('ajax:beforeSend', function(e) {
       ok(true, 'aborting request in ajax:beforeSend')
-      return false
+      e.preventDefault()
     })
     form.unbind('ajax:send').bindNative('ajax:send', function() {
       ok(false, 'ajax:send should not run')
     })
-    form.unbind('ajax:complete').bindNative('ajax:complete', function() {
-      ok(false, 'ajax:complete should not run')
-    })
-    form.bindNative('ajax:error', function(e, xhr, status, error) {
+    form.bindNative('ajax:error', function(e, response, status, xhr) {
       ok(false, 'ajax:error should not run')
     })
-    $(document).bindNative('ajaxStop', function() {
-      start()
+    form.bindNative('ajax:complete', function() {
+      ok(false, 'ajax:complete should not run')
     })
   })
 })
@@ -165,8 +148,8 @@ function skipIt() {
           .bind('iframe:loading', function() {
             ok(false, 'form should not get submitted')
           })
-          .bindNative('ajax:aborted:file', function() {
-            return false
+          .bindNative('ajax:aborted:file', function(e) {
+            e.preventDefault()
           })
           .triggerNative('submit')
 
@@ -179,25 +162,22 @@ function skipIt() {
 }
 
 asyncTest('"ajax:beforeSend" can be observed and stopped with event delegation', 1, function() {
-  $(document).delegate('form[data-remote]', 'ajax:beforeSend', function() {
+  $(document).delegate('form[data-remote]', 'ajax:beforeSend', function(e) {
     ok(true, 'ajax:beforeSend observed with event delegation')
-    return false
+    e.preventDefault()
   })
 
   submit(function(form) {
     form.unbind('ajax:send').bindNative('ajax:send', function() {
       ok(false, 'ajax:send should not run')
     })
-    form.unbind('ajax:complete').bindNative('ajax:complete', function() {
+    form.bindNative('ajax:complete', function() {
       ok(false, 'ajax:complete should not run')
     })
-    $(document).bindNative('ajaxStop', function() {
-      start()
-    })
   })
 })
 
-asyncTest('"ajax:beforeSend", "ajax:send", "ajax:success" and "ajax:complete" are triggered', 9, function() {
+asyncTest('"ajax:beforeSend", "ajax:send", "ajax:success" and "ajax:complete" are triggered', 8, function() {
   submit(function(form) {
     form.bindNative('ajax:beforeSend', function(e, xhr, settings) {
       ok(xhr.setRequestHeader, 'first argument to "ajax:beforeSend" should be an XHR object')
@@ -218,25 +198,25 @@ asyncTest('"ajax:beforeSend", "ajax:send", "ajax:success" and "ajax:complete" ar
   })
 })
 
-if(window.phantom !== undefined) {
-  asyncTest('"ajax:beforeSend", "ajax:send", "ajax:error" and "ajax:complete" are triggered on error', 7, function() {
-    submit(function(form) {
-      form.attr('action', '/error')
-      form.bindNative('ajax:beforeSend', function(arg) { ok(true, 'ajax:beforeSend') })
-      form.bindNative('ajax:send', function(arg) { ok(true, 'ajax:send') })
-      form.bindNative('ajax:error', function(e, xhr, status, error) {
-        ok(xhr.getResponseHeader, 'first argument to "ajax:error" should be an XHR object')
-        equal(status, 'error', 'second argument to ajax:error should be a status string')
-        // Firefox 8 returns "Forbidden " with trailing space
-        equal($.trim(error), 'Forbidden', 'third argument to ajax:error should be an HTTP status response')
-        // Opera returns "0" for HTTP code
-        equal(xhr.status, window.opera ? 0 : 403, 'status code should be 403')
-      })
+asyncTest('"ajax:beforeSend", "ajax:send", "ajax:error" and "ajax:complete" are triggered on error', 8, function() {
+  submit(function(form) {
+    form.attr('action', '/error')
+    form.bindNative('ajax:beforeSend', function(arg) { ok(true, 'ajax:beforeSend') })
+    form.bindNative('ajax:send', function(arg) { ok(true, 'ajax:send') })
+    form.bindNative('ajax:error', function(e, response, status, xhr) {
+      equal(response, '', 'first argument to ajax:error should be an HTTP status response')
+      equal(status, 'Forbidden', 'second argument to ajax:error should be a status string')
+      ok(xhr.getResponseHeader, 'third argument to "ajax:error" should be an XHR object')
+      // Opera returns "0" for HTTP code
+      equal(xhr.status, window.opera ? 0 : 403, 'status code should be 403')
+    })
+    form.bindNative('ajax:complete', function(e, xhr, status) {
+      ok(xhr.getResponseHeader, 'first argument to "ajax:complete" should be an XHR object')
+      equal(status, 'Forbidden', 'second argument to ajax:complete should be a status string')
     })
   })
-}
+})
 
-// IF THIS TEST IS FAILING, TRY INCREASING THE TIMEOUT AT THE BOTTOM TO > 100
 asyncTest('binding to ajax callbacks via .delegate() triggers handlers properly', 4, function() {
   $(document)
     .delegate('form[data-remote]', 'ajax:beforeSend', function() {
@@ -245,29 +225,15 @@ asyncTest('binding to ajax callbacks via .delegate() triggers handlers properly'
     .delegate('form[data-remote]', 'ajax:send', function() {
       ok(true, 'ajax:send handler is triggered')
     })
-    .delegate('form[data-remote]', 'ajax:complete', function() {
-      ok(true, 'ajax:complete handler is triggered')
-    })
     .delegate('form[data-remote]', 'ajax:success', function() {
       ok(true, 'ajax:success handler is triggered')
     })
-  $('form[data-remote]').triggerNative('submit')
-
-  setTimeout(function() {
-    start()
-  }, 63)
-})
-
-asyncTest('binding to ajax:send event to call jquery methods on ajax object', 2, function() {
-  $('form[data-remote]')
-    .bindNative('ajax:send', function(e, xhr) {
-      ok(true, 'event should fire')
-      equal(typeof(xhr.abort), 'function', 'event should pass jqXHR object')
-      xhr.abort()
+    .delegate('form[data-remote]', 'ajax:complete', function() {
+      ok(true, 'ajax:complete handler is triggered')
     })
-    .triggerNative('submit')
+  $('form[data-remote]').triggerNative('submit')
 
-  setTimeout(function() { start() }, 35)
+  setTimeout(function() { start() }, 13)
 })
 
 })()
diff --git a/actionview/test/ujs/public/test/call-remote.js b/actionview/test/ujs/public/test/call-remote.js
index 5932195363..778dc1b09a 100644
--- a/actionview/test/ujs/public/test/call-remote.js
+++ b/actionview/test/ujs/public/test/call-remote.js
@@ -128,6 +128,17 @@ asyncTest('execution of JS code does not modify current DOM', 1, function() {
   })
 })
 
+asyncTest('HTML content should be plain-text', 1, function() {
+  buildForm({ method: 'post', 'data-type': 'html' })
+
+  $('form').append('<input type="text" name="content_type" value="text/html">')
+  $('form').append('<input type="text" name="content" value="<p>hello</p>">')
+
+  submit(function(e, data, status, xhr) {
+    ok(data === '<p>hello</p>', 'returned data should be a plain-text string')
+  })
+})
+
 asyncTest('XML document should be parsed', 1, function() {
   buildForm({ method: 'post', 'data-type': 'html' })
 
@@ -199,7 +210,7 @@ asyncTest('allow empty form "action"', 1, function() {
   buildForm({ action: '' })
 
   $('#qunit-fixture').find('form')
-    .bindNative('ajax:beforeSend', function(e, xhr, settings) {
+    .bindNative('ajax:beforeSend', function(evt, xhr, settings) {
       // Get current location (the same way jQuery does)
       try {
         currentLocation = location.href
@@ -218,7 +229,7 @@ asyncTest('allow empty form "action"', 1, function() {
 
       // Prevent the request from actually getting sent to the current page and
       // causing an error.
-      return false
+      evt.preventDefault()
     })
     .triggerNative('submit')
 
@@ -246,7 +257,7 @@ asyncTest('intelligently guesses crossDomain behavior when target URL has a diff
       equal(settings.crossDomain, true, 'crossDomain should be set to true')
 
       // prevent request from actually getting sent off-domain
-      return false
+      evt.preventDefault()
     })
     .triggerNative('submit')
 
@@ -265,7 +276,7 @@ asyncTest('intelligently guesses crossDomain behavior when target URL consists o
       equal(settings.crossDomain, false, 'crossDomain should be set to false')
 
       // prevent request from actually getting sent off-domain
-      return false
+      evt.preventDefault()
     })
     .triggerNative('submit')
 
diff --git a/actionview/test/ujs/public/test/data-confirm.js b/actionview/test/ujs/public/test/data-confirm.js
index d1ea82ea7e..1bd57b69ad 100644
--- a/actionview/test/ujs/public/test/data-confirm.js
+++ b/actionview/test/ujs/public/test/data-confirm.js
@@ -173,9 +173,9 @@ asyncTest('binding to confirm event of a link and returning false', 1, function(
   }
 
   $('a[data-confirm]')
-    .bindNative('confirm', function() {
+    .bindNative('confirm', function(e) {
       App.assertCallbackInvoked('confirm')
-      return false
+      e.preventDefault()
     })
     .bindNative('confirm:complete', function() {
       App.assertCallbackNotInvoked('confirm:complete')
@@ -194,9 +194,9 @@ asyncTest('binding to confirm event of a button and returning false', 1, functio
   }
 
   $('button[data-confirm]')
-    .bindNative('confirm', function() {
+    .bindNative('confirm', function(e) {
       App.assertCallbackInvoked('confirm')
-      return false
+      e.preventDefault()
     })
     .bindNative('confirm:complete', function() {
       App.assertCallbackNotInvoked('confirm:complete')
@@ -216,9 +216,9 @@ asyncTest('binding to confirm:complete event of a link and returning false', 2,
   }
 
   $('a[data-confirm]')
-    .bindNative('confirm:complete', function() {
+    .bindNative('confirm:complete', function(e) {
       App.assertCallbackInvoked('confirm:complete')
-      return false
+      e.preventDefault()
     })
     .bindNative('ajax:beforeSend', function() {
       App.assertCallbackNotInvoked('ajax:beforeSend')
@@ -238,9 +238,9 @@ asyncTest('binding to confirm:complete event of a button and returning false', 2
   }
 
   $('button[data-confirm]')
-    .bindNative('confirm:complete', function() {
+    .bindNative('confirm:complete', function(e) {
       App.assertCallbackInvoked('confirm:complete')
-      return false
+      e.preventDefault()
     })
     .bindNative('ajax:beforeSend', function() {
       App.assertCallbackNotInvoked('ajax:beforeSend')
@@ -314,3 +314,29 @@ asyncTest('clicking on the children of a disabled button should not trigger a co
     start()
   }, 50)
 })
+
+asyncTest('clicking on a link with data-confirm attribute with custom confirm handler. Confirm yes.', 7, function() {
+  var message, element
+  // redefine confirm function so we can make sure it's not called
+  window.confirm = function(msg) {
+    ok(false, 'confirm dialog should not be called')
+  }
+  // custom auto-confirm:
+  Rails.confirm = function(msg, elem) { message = msg; element = elem; return true }
+
+  $('a[data-confirm]')
+    .bindNative('confirm:complete', function(e, data) {
+      App.assertCallbackInvoked('confirm:complete')
+      ok(data == true, 'confirm:complete passes in confirm answer (true)')
+    })
+    .bindNative('ajax:success', function(e, data, status, xhr) {
+      App.assertCallbackInvoked('ajax:success')
+      App.assertRequestPath(data, '/echo')
+      App.assertGetRequest(data)
+
+      equal(message, 'Are you absolutely sure?')
+      equal(element, $('a[data-confirm]').get(0))
+      start()
+    })
+    .triggerNative('click')
+})
diff --git a/actionview/test/ujs/public/test/data-disable-with.js b/actionview/test/ujs/public/test/data-disable-with.js
index b29cbbc867..645ad494c3 100644
--- a/actionview/test/ujs/public/test/data-disable-with.js
+++ b/actionview/test/ujs/public/test/data-disable-with.js
@@ -132,7 +132,8 @@ test('form input[type=submit][data-disable-with] re-enables when `pageshow` even
 })
 
 asyncTest('form[data-remote] input[type=submit][data-disable-with] is replaced in ajax callback', 2, function() {
-  var form = $('form:not([data-remote])').attr('data-remote', 'true'), origFormContents = form.html()
+  var form = $('#qunit-fixture form:not([data-remote])').attr('data-remote', 'true'),
+      origFormContents = form.html()
 
   form.bindNative('ajax:success', function() {
     form.html(origFormContents)
@@ -146,7 +147,8 @@ asyncTest('form[data-remote] input[type=submit][data-disable-with] is replaced i
 })
 
 asyncTest('form[data-remote] input[data-disable-with] is replaced with disabled field in ajax callback', 2, function() {
-  var form = $('form:not([data-remote])').attr('data-remote', 'true'), input = form.find('input[type=submit]'),
+  var form = $('#qunit-fixture form:not([data-remote])').attr('data-remote', 'true'),
+      input = form.find('input[type=submit]'),
       newDisabledInput = input.clone().attr('disabled', 'disabled')
 
   form.bindNative('ajax:success', function() {
@@ -238,9 +240,9 @@ asyncTest('a[data-remote][data-disable-with] re-enables when `ajax:before` event
   App.checkEnabledState(link, 'Click me')
 
   link
-    .bindNative('ajax:before', function() {
+    .bindNative('ajax:before', function(e) {
       App.checkDisabledState(link, 'clicking...')
-      return false
+      e.preventDefault()
     })
     .triggerNative('click')
 
@@ -256,9 +258,9 @@ asyncTest('a[data-remote][data-disable-with] re-enables when `ajax:beforeSend` e
   App.checkEnabledState(link, 'Click me')
 
   link
-    .bindNative('ajax:beforeSend', function() {
+    .bindNative('ajax:beforeSend', function(e) {
       App.checkDisabledState(link, 'clicking...')
-      return false
+      e.preventDefault()
     })
     .triggerNative('click')
 
@@ -293,8 +295,9 @@ asyncTest('form[data-remote] input|button|textarea[data-disable-with] does not d
       submit = $('<input type="submit" data-disable-with="submitting ..." name="submit2" value="Submit" />').appendTo(form)
 
   form
-    .bindNative('ajax:beforeSend', function() {
-      return false
+    .bindNative('ajax:beforeSend', function(e) {
+      e.preventDefault()
+      e.stopPropagation()
     })
     .triggerNative('submit')
 
@@ -343,9 +346,9 @@ asyncTest('button[data-remote][data-disable-with] re-enables when `ajax:before`
   App.checkEnabledState(button, 'Click me')
 
   button
-    .bindNative('ajax:before', function() {
+    .bindNative('ajax:before', function(e) {
       App.checkDisabledState(button, 'clicking...')
-      return false
+      e.preventDefault()
     })
     .triggerNative('click')
 
@@ -361,9 +364,9 @@ asyncTest('button[data-remote][data-disable-with] re-enables when `ajax:beforeSe
   App.checkEnabledState(button, 'Click me')
 
   button
-    .bindNative('ajax:beforeSend', function() {
+    .bindNative('ajax:beforeSend', function(e) {
       App.checkDisabledState(button, 'clicking...')
-      return false
+      e.preventDefault()
     })
     .triggerNative('click')
 
diff --git a/actionview/test/ujs/public/test/data-disable.js b/actionview/test/ujs/public/test/data-disable.js
index ccc38cf9ae..e9919764b6 100644
--- a/actionview/test/ujs/public/test/data-disable.js
+++ b/actionview/test/ujs/public/test/data-disable.js
@@ -91,7 +91,7 @@ asyncTest('form input[type=submit][data-disable] disables', 6, function() {
 })
 
 asyncTest('form[data-remote] input[type=submit][data-disable] is replaced in ajax callback', 2, function() {
-  var form = $('form:not([data-remote])').attr('data-remote', 'true'), origFormContents = form.html()
+  var form = $('#qunit-fixture form:not([data-remote])').attr('data-remote', 'true'), origFormContents = form.html()
 
   form.bindNative('ajax:success', function() {
     form.html(origFormContents)
@@ -105,7 +105,7 @@ asyncTest('form[data-remote] input[type=submit][data-disable] is replaced in aja
 })
 
 asyncTest('form[data-remote] input[data-disable] is replaced with disabled field in ajax callback', 2, function() {
-  var form = $('form:not([data-remote])').attr('data-remote', 'true'), input = form.find('input[type=submit]'),
+  var form = $('#qunit-fixture form:not([data-remote])').attr('data-remote', 'true'), input = form.find('input[type=submit]'),
       newDisabledInput = input.clone().attr('disabled', 'disabled')
 
   form.bindNative('ajax:success', function() {
@@ -168,9 +168,9 @@ asyncTest('a[data-remote][data-disable] re-enables when `ajax:before` event is c
   App.checkEnabledState(link, 'Click me')
 
   link
-    .bindNative('ajax:before', function() {
+    .bindNative('ajax:before', function(e) {
       App.checkDisabledState(link, 'Click me')
-      return false
+      e.preventDefault()
     })
     .triggerNative('click')
 
@@ -186,9 +186,9 @@ asyncTest('a[data-remote][data-disable] re-enables when `ajax:beforeSend` event
   App.checkEnabledState(link, 'Click me')
 
   link
-    .bindNative('ajax:beforeSend', function() {
+    .bindNative('ajax:beforeSend', function(e) {
       App.checkDisabledState(link, 'Click me')
-      return false
+      e.preventDefault()
     })
     .triggerNative('click')
 
@@ -223,8 +223,9 @@ asyncTest('form[data-remote] input|button|textarea[data-disable] does not disabl
       submit = $('<input type="submit" data-disable="submitting ..." name="submit2" value="Submit" />').appendTo(form)
 
   form
-    .bindNative('ajax:beforeSend', function() {
-      return false
+    .bindNative('ajax:beforeSend', function(e) {
+      e.preventDefault()
+      e.stopPropagation()
     })
     .triggerNative('submit')
 
@@ -273,9 +274,9 @@ asyncTest('button[data-remote][data-disable] re-enables when `ajax:before` event
   App.checkEnabledState(button, 'Click me')
 
   button
-    .bindNative('ajax:before', function() {
+    .bindNative('ajax:before', function(e) {
       App.checkDisabledState(button, 'Click me')
-      return false
+      e.preventDefault()
     })
     .triggerNative('click')
 
@@ -291,9 +292,9 @@ asyncTest('button[data-remote][data-disable] re-enables when `ajax:beforeSend` e
   App.checkEnabledState(button, 'Click me')
 
   button
-    .bindNative('ajax:beforeSend', function() {
+    .bindNative('ajax:beforeSend', function(e) {
       App.checkDisabledState(button, 'Click me')
-      return false
+      e.preventDefault()
     })
     .triggerNative('click')
 
diff --git a/actionview/test/ujs/public/test/data-remote.js b/actionview/test/ujs/public/test/data-remote.js
index 9bbefc18f2..3503c2cff3 100644
--- a/actionview/test/ujs/public/test/data-remote.js
+++ b/actionview/test/ujs/public/test/data-remote.js
@@ -191,9 +191,10 @@ asyncTest('submitting form with data-remote attribute should include inputs in a
     .triggerNative('submit')
 })
 
-asyncTest('submitting form with data-remote attribute submits input with matching [form] attribute', 5, function() {
+asyncTest('submitting form with data-remote attribute submits input with matching [form] attribute', 6, function() {
   $('#qunit-fixture')
     .append($('<input type="text" name="user_data" value="value1" form="my-remote-form">'))
+    .append($('<input type="text" name="user_email" value="from@example.com" disabled="disabled" form="my-remote-form">'))
 
   $('form[data-remote]')
     .bindNative('ajax:success', function(e, data, status, xhr) {
@@ -201,6 +202,7 @@ asyncTest('submitting form with data-remote attribute submits input with matchin
       App.assertRequestPath(data, '/echo')
       equal(data.params.user_name, 'john', 'ajax arguments should have key user_name with right value')
       equal(data.params.user_data, 'value1', 'ajax arguments should have key user_data with right value')
+      equal(data.params.user_email, undefined, 'ajax arguments should not have disabled field')
       App.assertPostRequest(data)
     })
     .bindNative('ajax:complete', function() { start() })
@@ -270,9 +272,10 @@ asyncTest('returning false in form\'s submit bindings in non-submit-bubbling bro
 
   form
     .append($('<input type="submit" />'))
-    .bindNative('submit', function() {
+    .bindNative('submit', function(e) {
       ok(true, 'binding handler is called')
-      return false
+      e.preventDefault()
+      e.stopPropagation()
     })
     .bindNative('ajax:beforeSend', function() {
       ok(false, 'form should not be submitted')
@@ -294,8 +297,8 @@ asyncTest('clicking on a link with falsy "data-remote" attribute does not fire a
     .bindNative('ajax:beforeSend', function() {
       ok(false, 'ajax should not be triggered')
     })
-    .bindNative('click', function() {
-      return false
+    .bindNative('click', function(e) {
+      e.preventDefault()
     })
     .triggerNative('click')
 
@@ -312,8 +315,8 @@ asyncTest('ctrl-clicking on a link with falsy "data-remote" attribute does not f
     .bindNative('ajax:beforeSend', function() {
       ok(false, 'ajax should not be triggered')
     })
-    .bindNative('click', function() {
-      return false
+    .bindNative('click', function(e) {
+      e.preventDefault()
     })
     .triggerNative('click', { metaKey: true })
 
@@ -331,8 +334,8 @@ asyncTest('clicking on a button with falsy "data-remote" attribute', 0, function
     .bindNative('ajax:beforeSend', function() {
       ok(false, 'ajax should not be triggered')
     })
-    .bindNative('click', function() {
-      return false
+    .bindNative('click', function(e) {
+      e.preventDefault()
     })
     .triggerNative('click')
 
@@ -345,8 +348,8 @@ asyncTest('submitting a form with falsy "data-remote" attribute', 0, function()
     .bindNative('ajax:beforeSend', function() {
       ok(false, 'ajax should not be triggered')
     })
-    .bindNative('submit', function() {
-      return false
+    .bindNative('submit', function(e) {
+      e.preventDefault()
     })
     .triggerNative('submit')
 
@@ -427,7 +430,7 @@ asyncTest('changing a select option without "data-url" attribute still fires aja
       ajaxLocation = settings.url.replace(settings.data, '').replace(/&$/, '').replace(/\?$/, '')
       equal(ajaxLocation, currentLocation, 'URL should be current page by default')
 
-      return false
+      e.preventDefault()
     })
     .val('optionValue2')
     .triggerNative('change')
diff --git a/actionview/test/ujs/public/test/override.js b/actionview/test/ujs/public/test/override.js
index 299c7018cc..d73276ee4f 100644
--- a/actionview/test/ujs/public/test/override.js
+++ b/actionview/test/ujs/public/test/override.js
@@ -25,7 +25,7 @@ asyncTest('the getter for an element\'s href is overridable', 1, function() {
   $('#qunit-fixture a')
     .bindNative('ajax:beforeSend', function(e, xhr, options) {
       equal('/data/href', options.url)
-      return false
+      e.preventDefault()
     })
     .triggerNative('click')
   start()
@@ -35,7 +35,7 @@ asyncTest('the getter for an element\'s href works normally if not overridden',
   $('#qunit-fixture a')
     .bindNative('ajax:beforeSend', function(e, xhr, options) {
       equal(location.protocol + '//' + location.host + '/real/href', options.url)
-      return false
+      e.preventDefault()
     })
     .triggerNative('click')
   start()
diff --git a/actionview/test/ujs/public/test/settings.js b/actionview/test/ujs/public/test/settings.js
index 299c71bb00..b1ce3b8c64 100644
--- a/actionview/test/ujs/public/test/settings.js
+++ b/actionview/test/ujs/public/test/settings.js
@@ -103,14 +103,16 @@ $.fn.extend({
   bindNative: function(event, handler) {
     if (!handler) return this
 
-    this.bind(event, function(e) {
+    var el = this[0]
+    el.addEventListener(event, function(e) {
       var args = []
-      if (e.originalEvent.detail) {
-        args = e.originalEvent.detail.slice()
+      if (e.detail) {
+        args = e.detail.slice()
       }
       args.unshift(e)
-      return handler.apply(this, args)
-    })
+      return handler.apply(el, args)
+    }, false)
+
     return this
   }
 })
diff --git a/actionview/test/ujs/server.rb b/actionview/test/ujs/server.rb
index 7d1bab4b2a..48e9bcb65f 100644
--- a/actionview/test/ujs/server.rb
+++ b/actionview/test/ujs/server.rb
@@ -23,18 +23,30 @@ module UJS
     config.public_file_server.enabled = true
     config.logger = Logger.new(STDOUT)
     config.log_level = :error
+
+    config.content_security_policy do |policy|
+      policy.default_src :self, :https
+      policy.font_src    :self, :https, :data
+      policy.img_src     :self, :https, :data
+      policy.object_src  :none
+      policy.script_src  :self, :https
+      policy.style_src   :self, :https
+    end
+
+    config.content_security_policy_nonce_generator = ->(req) { SecureRandom.base64(16) }
   end
 end
 
 module TestsHelper
   def test_to(*names)
-    names = ["/vendor/qunit.js", "settings"] + names
-    names.map { |name| script_tag name }.join("\n").html_safe
-  end
+    names = names.map { |name| "/test/#{name}.js" }
+    names = %w[/vendor/qunit.js /test/settings.js] + names
 
-  def script_tag(src)
-    src = "/test/#{src}.js" unless src.index("/")
-    %(<script src="#{src}" type="text/javascript"></script>).html_safe
+    capture do
+      names.each do |name|
+        concat(javascript_include_tag(name))
+      end
+    end
   end
 end
 
@@ -56,7 +68,7 @@ class TestsController < ActionController::Base
     elsif params[:iframe]
       payload = JSON.generate(data).gsub("<", "&lt;").gsub(">", "&gt;")
       html = <<-HTML
-        <script>
+        <script nonce="#{request.content_security_policy_nonce}">
           if (window.top && window.top !== window)
             window.top.jQuery.event.trigger('iframe:loaded', #{payload})
         </script>
diff --git a/actionview/test/ujs/views/layouts/application.html.erb b/actionview/test/ujs/views/layouts/application.html.erb
index c787e77b84..8f6f6fc17f 100644
--- a/actionview/test/ujs/views/layouts/application.html.erb
+++ b/actionview/test/ujs/views/layouts/application.html.erb
@@ -2,9 +2,10 @@
 <html id="html">
   <head>
     <title><%= @title %></title>
+    <%= csp_meta_tag %>
     <link href="/vendor/qunit.css" media="screen" rel="stylesheet" type="text/css" media="screen, projection" />
     <script src="/vendor/jquery-2.2.0.js" type="text/javascript"></script>
-    <script>
+    <%= javascript_tag nonce: true do %>
       // This is for test in override.js.
       // Must go before rails-ujs.
       document.addEventListener('rails:attachBindings', function() {
@@ -15,8 +16,8 @@
           e.preventDefault();
         });
       });
-    </script>
-    <%= script_tag "/rails-ujs.js" %>
+    <% end %>
+    <%= javascript_include_tag "/rails-ujs.js" %>
   </head>
 
   <body id="body">
diff --git a/actionview/test/ujs/views/tests/index.html.erb b/actionview/test/ujs/views/tests/index.html.erb
index 8de6cd0695..6b16535216 100644
--- a/actionview/test/ujs/views/tests/index.html.erb
+++ b/actionview/test/ujs/views/tests/index.html.erb
@@ -1,6 +1,6 @@
 <% @title = "rails-ujs test" %>
 
-<%= test_to 'data-confirm', 'data-remote', 'data-disable', 'data-disable-with', 'call-remote', 'call-remote-callbacks', 'data-method', 'override', 'csrf-refresh', 'csrf-token' %>
+<%= test_to 'data-confirm', 'data-remote', 'data-disable', 'data-disable-with', 'call-remote', 'call-remote-callbacks', 'data-method', 'override', 'csrf-refresh', 'csrf-token', 'call-ajax' %>
 
 <h1 id="qunit-header"><%= @title %></h1>
 <h2 id="qunit-banner"></h2>
diff --git a/activejob/CHANGELOG.md b/activejob/CHANGELOG.md
index 77dfdefc05..dcb9d27f45 100644
--- a/activejob/CHANGELOG.md
+++ b/activejob/CHANGELOG.md
@@ -1,8 +1,32 @@
-*   Change logging instrumentation to log errors when a job raises an exception.
+*   Pass the error instance as the second parameter of block executed by `discard_on`.
 
-    Fixes #26848.
+    Fixes #32853.
 
-    *Steven Bull*
+    *Yuji Yaginuma*
 
+*   Remove support for Qu gem.
 
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/activejob/CHANGELOG.md) for previous changes.
+    Reasons are that the Qu gem wasn't compatible since Rails 5.1,
+    gem development was stopped in 2014 and maintainers have
+    confirmed its demise. See issue #32273
+
+    *Alberto Almagro*
+
+*   Add support for timezones to Active Job.
+
+    Record what was the current timezone in effect when the job was
+    enqueued and then restore when the job is executed in same way
+    that the current locale is recorded and restored.
+
+    *Andrew White*
+
+*   Rails 6 requires Ruby 2.4.1 or newer.
+
+    *Jeremy Daer*
+
+*   Add support to define custom argument serializers.
+
+    *Evgenii Pecherkin*, *Rafael Mendonça França*
+
+
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/activejob/CHANGELOG.md) for previous changes.
diff --git a/activejob/MIT-LICENSE b/activejob/MIT-LICENSE
index daa726b9f0..274211f710 100644
--- a/activejob/MIT-LICENSE
+++ b/activejob/MIT-LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2014-2017 David Heinemeier Hansson
+Copyright (c) 2014-2018 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/activejob/README.md b/activejob/README.md
index 8a9a23929b..d49fcfe3c2 100644
--- a/activejob/README.md
+++ b/activejob/README.md
@@ -88,6 +88,12 @@ Active Job has built-in adapters for multiple queueing backends (Sidekiq,
 Resque, Delayed Job and others). To get an up-to-date list of the adapters
 see the API Documentation for [ActiveJob::QueueAdapters](http://api.rubyonrails.org/classes/ActiveJob/QueueAdapters.html).
 
+**Please note:** We are not accepting pull requests for new adapters. We
+encourage library authors to provide an ActiveJob adapter as part of
+their gem, or as a stand-alone gem. For discussion about this see the
+following PRs: [23311](https://github.com/rails/rails/issues/23311#issuecomment-176275718),
+[21406](https://github.com/rails/rails/pull/21406#issuecomment-138813484), and [#32285](https://github.com/rails/rails/pull/32285).
+
 ## Auxiliary gems
 
 * [activejob-stats](https://github.com/seuros/activejob-stats)
@@ -100,7 +106,7 @@ The latest version of Active Job can be installed with RubyGems:
   $ gem install activejob
 ```
 
-Source code can be downloaded as part of the Rails project on GitHub
+Source code can be downloaded as part of the Rails project on GitHub:
 
 * https://github.com/rails/rails/tree/master/activejob
 
@@ -117,7 +123,7 @@ API documentation is at:
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/activejob/Rakefile b/activejob/Rakefile
index 6f13ef449d..0f88b22e8d 100644
--- a/activejob/Rakefile
+++ b/activejob/Rakefile
@@ -2,7 +2,6 @@
 
 require "rake/testtask"
 
-#TODO: add qu back to the list after it support Rails 5.1
 ACTIVEJOB_ADAPTERS = %w(async inline delayed_job que queue_classic resque sidekiq sneakers sucker_punch backburner test)
 ACTIVEJOB_ADAPTERS.delete("queue_classic") if defined?(JRUBY_VERSION)
 
@@ -39,7 +38,7 @@ namespace :test do
       t.libs << "test"
       t.test_files = FileList["test/cases/**/*_test.rb"]
       t.verbose = true
-      t.warning = false
+      t.warning = true
       t.ruby_opts = ["--dev"] if defined?(JRUBY_VERSION)
     end
 
@@ -57,7 +56,7 @@ namespace :test do
         t.libs << "test"
         t.test_files = FileList["test/integration/**/*_test.rb"]
         t.verbose = true
-        t.warning = false
+        t.warning = true
         t.ruby_opts = ["--dev"] if defined?(JRUBY_VERSION)
       end
     end
diff --git a/activejob/activejob.gemspec b/activejob/activejob.gemspec
index 71e32f695b..be6292f737 100644
--- a/activejob/activejob.gemspec
+++ b/activejob/activejob.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Job framework with pluggable queues."
   s.description = "Declare job classes that can be run by a variety of queueing backends."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
diff --git a/activejob/lib/active_job.rb b/activejob/lib/active_job.rb
index 56dab66544..01fab4d918 100644
--- a/activejob/lib/active_job.rb
+++ b/activejob/lib/active_job.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 #--
-# Copyright (c) 2014-2017 David Heinemeier Hansson
+# Copyright (c) 2014-2018 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the
@@ -25,7 +25,7 @@
 
 require "active_support"
 require "active_support/rails"
-require_relative "active_job/version"
+require "active_job/version"
 require "global_id"
 
 module ActiveJob
@@ -33,6 +33,7 @@ module ActiveJob
 
   autoload :Base
   autoload :QueueAdapters
+  autoload :Serializers
   autoload :ConfiguredJob
   autoload :TestCase
   autoload :TestHelper
diff --git a/activejob/lib/active_job/arguments.rb b/activejob/lib/active_job/arguments.rb
index de11e7fcb1..86bb0c5540 100644
--- a/activejob/lib/active_job/arguments.rb
+++ b/activejob/lib/active_job/arguments.rb
@@ -14,8 +14,8 @@ module ActiveJob
   end
 
   # Raised when an unsupported argument type is set as a job argument. We
-  # currently support NilClass, Integer, Fixnum, Float, String, TrueClass, FalseClass,
-  # Bignum, BigDecimal, and objects that can be represented as GlobalIDs (ex: Active Record).
+  # currently support NilClass, Integer, Float, String, TrueClass, FalseClass,
+  # BigDecimal, and objects that can be represented as GlobalIDs (ex: Active Record).
   # Raised if you set the key for a Hash something else than a string or
   # a symbol. Also raised when trying to serialize an object which can't be
   # identified with a Global ID - such as an unpersisted Active Record model.
@@ -25,7 +25,6 @@ module ActiveJob
     extend self
     # :nodoc:
     TYPE_WHITELIST = [ NilClass, String, Integer, Float, BigDecimal, TrueClass, FalseClass ]
-    TYPE_WHITELIST.push(Fixnum, Bignum) unless 1.class == Integer
 
     # Serializes a set of arguments. Whitelisted types are returned
     # as-is. Arrays/Hashes are serialized element by element.
@@ -44,13 +43,24 @@ module ActiveJob
     end
 
     private
+
       # :nodoc:
       GLOBALID_KEY = "_aj_globalid".freeze
       # :nodoc:
       SYMBOL_KEYS_KEY = "_aj_symbol_keys".freeze
       # :nodoc:
       WITH_INDIFFERENT_ACCESS_KEY = "_aj_hash_with_indifferent_access".freeze
-      private_constant :GLOBALID_KEY, :SYMBOL_KEYS_KEY, :WITH_INDIFFERENT_ACCESS_KEY
+      # :nodoc:
+      OBJECT_SERIALIZER_KEY = "_aj_serialized"
+
+      # :nodoc:
+      RESERVED_KEYS = [
+        GLOBALID_KEY, GLOBALID_KEY.to_sym,
+        SYMBOL_KEYS_KEY, SYMBOL_KEYS_KEY.to_sym,
+        OBJECT_SERIALIZER_KEY, OBJECT_SERIALIZER_KEY.to_sym,
+        WITH_INDIFFERENT_ACCESS_KEY, WITH_INDIFFERENT_ACCESS_KEY.to_sym,
+      ]
+      private_constant :RESERVED_KEYS
 
       def serialize_argument(argument)
         case argument
@@ -70,7 +80,7 @@ module ActiveJob
           result[SYMBOL_KEYS_KEY] = symbol_keys
           result
         else
-          raise SerializationError.new("Unsupported argument type: #{argument.class.name}")
+          Serializers.serialize(argument)
         end
       end
 
@@ -85,6 +95,8 @@ module ActiveJob
         when Hash
           if serialized_global_id?(argument)
             deserialize_global_id argument
+          elsif custom_serialized?(argument)
+            Serializers.deserialize(argument)
           else
             deserialize_hash(argument)
           end
@@ -101,6 +113,10 @@ module ActiveJob
         GlobalID::Locator.locate hash[GLOBALID_KEY]
       end
 
+      def custom_serialized?(hash)
+        hash.key?(OBJECT_SERIALIZER_KEY)
+      end
+
       def serialize_hash(argument)
         argument.each_with_object({}) do |(key, value), hash|
           hash[serialize_hash_key(key)] = serialize_argument(value)
@@ -117,14 +133,6 @@ module ActiveJob
         result
       end
 
-      # :nodoc:
-      RESERVED_KEYS = [
-        GLOBALID_KEY, GLOBALID_KEY.to_sym,
-        SYMBOL_KEYS_KEY, SYMBOL_KEYS_KEY.to_sym,
-        WITH_INDIFFERENT_ACCESS_KEY, WITH_INDIFFERENT_ACCESS_KEY.to_sym,
-      ]
-      private_constant :RESERVED_KEYS
-
       def serialize_hash_key(key)
         case key
         when *RESERVED_KEYS
diff --git a/activejob/lib/active_job/base.rb b/activejob/lib/active_job/base.rb
index 6af41260db..2b2a59e969 100644
--- a/activejob/lib/active_job/base.rb
+++ b/activejob/lib/active_job/base.rb
@@ -1,15 +1,16 @@
 # frozen_string_literal: true
 
-require_relative "core"
-require_relative "queue_adapter"
-require_relative "queue_name"
-require_relative "queue_priority"
-require_relative "enqueuing"
-require_relative "execution"
-require_relative "callbacks"
-require_relative "exceptions"
-require_relative "logging"
-require_relative "translation"
+require "active_job/core"
+require "active_job/queue_adapter"
+require "active_job/queue_name"
+require "active_job/queue_priority"
+require "active_job/enqueuing"
+require "active_job/execution"
+require "active_job/callbacks"
+require "active_job/exceptions"
+require "active_job/logging"
+require "active_job/timezones"
+require "active_job/translation"
 
 module ActiveJob #:nodoc:
   # = Active Job
@@ -59,6 +60,7 @@ module ActiveJob #:nodoc:
   # * SerializationError - Error class for serialization errors.
   class Base
     include Core
+    include Serializers
     include QueueAdapter
     include QueueName
     include QueuePriority
@@ -67,6 +69,7 @@ module ActiveJob #:nodoc:
     include Callbacks
     include Exceptions
     include Logging
+    include Timezones
     include Translation
 
     ActiveSupport.run_load_hooks(:active_job, self)
diff --git a/activejob/lib/active_job/core.rb b/activejob/lib/active_job/core.rb
index c4e12fc518..61d402cfca 100644
--- a/activejob/lib/active_job/core.rb
+++ b/activejob/lib/active_job/core.rb
@@ -31,6 +31,9 @@ module ActiveJob
 
       # I18n.locale to be used during the job.
       attr_accessor :locale
+
+      # Timezone to be used during the job.
+      attr_accessor :timezone
     end
 
     # These methods will be included into any Active Job object, adding
@@ -85,9 +88,10 @@ module ActiveJob
         "provider_job_id" => provider_job_id,
         "queue_name" => queue_name,
         "priority"   => priority,
-        "arguments"  => serialize_arguments(arguments),
+        "arguments"  => serialize_arguments_if_needed(arguments),
         "executions" => executions,
-        "locale"     => I18n.locale.to_s
+        "locale"     => I18n.locale.to_s,
+        "timezone"   => Time.zone.try(:name)
       }
     end
 
@@ -97,17 +101,23 @@ module ActiveJob
     # ==== Examples
     #
     #    class DeliverWebhookJob < ActiveJob::Base
+    #      attr_writer :attempt_number
+    #
+    #      def attempt_number
+    #        @attempt_number ||= 0
+    #      end
+    #
     #      def serialize
-    #        super.merge('attempt_number' => (@attempt_number || 0) + 1)
+    #        super.merge('attempt_number' => attempt_number + 1)
     #      end
     #
     #      def deserialize(job_data)
     #        super
-    #        @attempt_number = job_data['attempt_number']
+    #        self.attempt_number = job_data['attempt_number']
     #      end
     #
-    #      rescue_from(TimeoutError) do |exception|
-    #        raise exception if @attempt_number > 5
+    #      rescue_from(Timeout::Error) do |exception|
+    #        raise exception if attempt_number > 5
     #        retry_job(wait: 10)
     #      end
     #    end
@@ -119,22 +129,35 @@ module ActiveJob
       self.serialized_arguments = job_data["arguments"]
       self.executions           = job_data["executions"]
       self.locale               = job_data["locale"] || I18n.locale.to_s
+      self.timezone             = job_data["timezone"] || Time.zone.try(:name)
     end
 
     private
+      def serialize_arguments_if_needed(arguments)
+        if arguments_serialized?
+          @serialized_arguments
+        else
+          serialize_arguments(arguments)
+        end
+      end
+
       def deserialize_arguments_if_needed
-        if defined?(@serialized_arguments) && @serialized_arguments.present?
+        if arguments_serialized?
           @arguments = deserialize_arguments(@serialized_arguments)
           @serialized_arguments = nil
         end
       end
 
-      def serialize_arguments(serialized_args)
-        Arguments.serialize(serialized_args)
+      def serialize_arguments(arguments)
+        Arguments.serialize(arguments)
       end
 
       def deserialize_arguments(serialized_args)
         Arguments.deserialize(serialized_args)
       end
+
+      def arguments_serialized?
+        defined?(@serialized_arguments) && @serialized_arguments
+      end
   end
 end
diff --git a/activejob/lib/active_job/enqueuing.rb b/activejob/lib/active_job/enqueuing.rb
index ad32d3065b..53cb98fc71 100644
--- a/activejob/lib/active_job/enqueuing.rb
+++ b/activejob/lib/active_job/enqueuing.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "arguments"
+require "active_job/arguments"
 
 module ActiveJob
   # Provides behavior for enqueuing jobs.
@@ -10,7 +10,7 @@ module ActiveJob
     # Includes the +perform_later+ method for job initialization.
     module ClassMethods
       # Push a job onto the queue. The arguments must be legal JSON types
-      # (string, int, float, nil, true, false, hash or array) or
+      # (+string+, +int+, +float+, +nil+, +true+, +false+, +hash+ or +array+) or
       # GlobalID::Identification instances. Arbitrary Ruby objects
       # are not supported.
       #
diff --git a/activejob/lib/active_job/exceptions.rb b/activejob/lib/active_job/exceptions.rb
index dfc74deb1a..31bbb18d7f 100644
--- a/activejob/lib/active_job/exceptions.rb
+++ b/activejob/lib/active_job/exceptions.rb
@@ -49,7 +49,7 @@ module ActiveJob
             retry_job wait: determine_delay(wait), queue: queue, priority: priority
           else
             if block_given?
-              yield self, exception
+              yield self, error
             else
               logger.error "Stopped retrying #{self.class} due to a #{exception}, which reoccurred on #{executions} attempts. The original exception was #{error.cause.inspect}."
               raise error
@@ -61,18 +61,28 @@ module ActiveJob
       # Discard the job with no attempts to retry, if the exception is raised. This is useful when the subject of the job,
       # like an Active Record, is no longer available, and the job is thus no longer relevant.
       #
+      # You can also pass a block that'll be invoked. This block is yielded with the job instance as the first and the error instance as the second parameter.
+      #
       # ==== Example
       #
       #  class SearchIndexingJob < ActiveJob::Base
       #    discard_on ActiveJob::DeserializationError
+      #    discard_on(CustomAppException) do |job, exception|
+      #      ExceptionNotifier.caught(exception)
+      #    end
       #
       #    def perform(record)
       #      # Will raise ActiveJob::DeserializationError if the record can't be deserialized
+      #      # Might raise CustomAppException for something domain specific
       #    end
       #  end
       def discard_on(exception)
         rescue_from exception do |error|
-          logger.error "Discarded #{self.class} due to a #{exception}. The original exception was #{error.cause.inspect}."
+          if block_given?
+            yield self, error
+          else
+            logger.error "Discarded #{self.class} due to a #{exception}. The original exception was #{error.cause.inspect}."
+          end
         end
       end
     end
diff --git a/activejob/lib/active_job/execution.rb b/activejob/lib/active_job/execution.rb
index 85e050b489..d75be376ec 100644
--- a/activejob/lib/active_job/execution.rb
+++ b/activejob/lib/active_job/execution.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/rescuable"
-require_relative "arguments"
+require "active_job/arguments"
 
 module ActiveJob
   module Execution
diff --git a/activejob/lib/active_job/gem_version.rb b/activejob/lib/active_job/gem_version.rb
index 7ee61780e1..770f70dc5e 100644
--- a/activejob/lib/active_job/gem_version.rb
+++ b/activejob/lib/active_job/gem_version.rb
@@ -7,8 +7,8 @@ module ActiveJob
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
     PRE   = "alpha"
 
diff --git a/activejob/lib/active_job/logging.rb b/activejob/lib/active_job/logging.rb
index f53b7eaee5..3312857ac7 100644
--- a/activejob/lib/active_job/logging.rb
+++ b/activejob/lib/active_job/logging.rb
@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/hash/transform_values"
 require "active_support/core_ext/string/filters"
 require "active_support/tagged_logging"
 require "active_support/logger"
@@ -12,13 +11,13 @@ module ActiveJob
     included do
       cattr_accessor :logger, default: ActiveSupport::TaggedLogging.new(ActiveSupport::Logger.new(STDOUT))
 
-      around_enqueue do |_, block, _|
+      around_enqueue do |_, block|
         tag_logger do
           block.call
         end
       end
 
-      around_perform do |job, block, _|
+      around_perform do |job, block|
         tag_logger(job.class.name, job.job_id) do
           payload = { adapter: job.class.queue_adapter, job: job }
           ActiveSupport::Notifications.instrument("perform_start.active_job", payload.dup)
diff --git a/activejob/lib/active_job/queue_adapter.rb b/activejob/lib/active_job/queue_adapter.rb
index dd05800baf..006a683b85 100644
--- a/activejob/lib/active_job/queue_adapter.rb
+++ b/activejob/lib/active_job/queue_adapter.rb
@@ -29,28 +29,22 @@ module ActiveJob
       # Specify the backend queue provider. The default queue adapter
       # is the +:async+ queue. See QueueAdapters for more
       # information.
-      def queue_adapter=(name_or_adapter_or_class)
-        interpret_adapter(name_or_adapter_or_class)
-      end
-
-      private
-
-        def interpret_adapter(name_or_adapter_or_class)
-          case name_or_adapter_or_class
-          when Symbol, String
-            assign_adapter(name_or_adapter_or_class.to_s,
-                           ActiveJob::QueueAdapters.lookup(name_or_adapter_or_class).new)
+      def queue_adapter=(name_or_adapter)
+        case name_or_adapter
+        when Symbol, String
+          queue_adapter = ActiveJob::QueueAdapters.lookup(name_or_adapter).new
+          assign_adapter(name_or_adapter.to_s, queue_adapter)
+        else
+          if queue_adapter?(name_or_adapter)
+            adapter_name = "#{name_or_adapter.class.name.demodulize.remove('Adapter').underscore}"
+            assign_adapter(adapter_name, name_or_adapter)
           else
-            if queue_adapter?(name_or_adapter_or_class)
-              adapter_name = "#{name_or_adapter_or_class.class.name.demodulize.remove('Adapter').underscore}"
-              assign_adapter(adapter_name,
-                             name_or_adapter_or_class)
-            else
-              raise ArgumentError
-            end
+            raise ArgumentError
           end
         end
+      end
 
+      private
         def assign_adapter(adapter_name, queue_adapter)
           self._queue_adapter_name = adapter_name
           self._queue_adapter = queue_adapter
diff --git a/activejob/lib/active_job/queue_adapters.rb b/activejob/lib/active_job/queue_adapters.rb
index c1a1d3c510..7854467cc1 100644
--- a/activejob/lib/active_job/queue_adapters.rb
+++ b/activejob/lib/active_job/queue_adapters.rb
@@ -7,7 +7,6 @@ module ActiveJob
   #
   # * {Backburner}[https://github.com/nesquena/backburner]
   # * {Delayed Job}[https://github.com/collectiveidea/delayed_job]
-  # * {Qu}[https://github.com/bkeepers/qu]
   # * {Que}[https://github.com/chanks/que]
   # * {queue_classic}[https://github.com/QueueClassic/queue_classic]
   # * {Resque}[https://github.com/resque/resque]
@@ -16,6 +15,7 @@ module ActiveJob
   # * {Sucker Punch}[https://github.com/brandonhilkert/sucker_punch]
   # * {Active Job Async Job}[http://api.rubyonrails.org/classes/ActiveJob/QueueAdapters/AsyncAdapter.html]
   # * {Active Job Inline}[http://api.rubyonrails.org/classes/ActiveJob/QueueAdapters/InlineAdapter.html]
+  # * Please Note: We are not accepting pull requests for new adapters. See the README for more details.
   #
   # === Backends Features
   #
@@ -23,7 +23,6 @@ module ActiveJob
   #   |-------------------|-------|--------|------------|------------|---------|---------|
   #   | Backburner        | Yes   | Yes    | Yes        | Yes        | Job     | Global  |
   #   | Delayed Job       | Yes   | Yes    | Yes        | Job        | Global  | Global  |
-  #   | Qu                | Yes   | Yes    | No         | No         | No      | Global  |
   #   | Que               | Yes   | Yes    | Yes        | Job        | No      | Job     |
   #   | queue_classic     | Yes   | Yes    | Yes*       | No         | No      | No      |
   #   | Resque            | Yes   | Yes    | Yes (Gem)  | Queue      | Global  | Yes     |
@@ -114,7 +113,6 @@ module ActiveJob
     autoload :InlineAdapter
     autoload :BackburnerAdapter
     autoload :DelayedJobAdapter
-    autoload :QuAdapter
     autoload :QueAdapter
     autoload :QueueClassicAdapter
     autoload :ResqueAdapter
diff --git a/activejob/lib/active_job/queue_adapters/delayed_job_adapter.rb b/activejob/lib/active_job/queue_adapters/delayed_job_adapter.rb
index 1978179948..8eeef32b99 100644
--- a/activejob/lib/active_job/queue_adapters/delayed_job_adapter.rb
+++ b/activejob/lib/active_job/queue_adapters/delayed_job_adapter.rb
@@ -34,6 +34,10 @@ module ActiveJob
           @job_data = job_data
         end
 
+        def display_name
+          "#{job_data['job_class']} [#{job_data['job_id']}] from DelayedJob(#{job_data['queue_name']}) with arguments: #{job_data['arguments']}"
+        end
+
         def perform
           Base.execute(job_data)
         end
diff --git a/activejob/lib/active_job/queue_adapters/qu_adapter.rb b/activejob/lib/active_job/queue_adapters/qu_adapter.rb
deleted file mode 100644
index bd7003e177..0000000000
--- a/activejob/lib/active_job/queue_adapters/qu_adapter.rb
+++ /dev/null
@@ -1,46 +0,0 @@
-# frozen_string_literal: true
-
-require "qu"
-
-module ActiveJob
-  module QueueAdapters
-    # == Qu adapter for Active Job
-    #
-    # Qu is a Ruby library for queuing and processing background jobs. It is
-    # heavily inspired by delayed_job and Resque. Qu was created to overcome
-    # some shortcomings in the existing queuing libraries.
-    # The advantages of Qu are: Multiple backends (redis, mongo), jobs are
-    # requeued when worker is killed, resque-like API.
-    #
-    # Read more about Qu {here}[https://github.com/bkeepers/qu].
-    #
-    # To use Qu set the queue_adapter config to +:qu+.
-    #
-    #   Rails.application.config.active_job.queue_adapter = :qu
-    class QuAdapter
-      def enqueue(job, *args) #:nodoc:
-        qu_job = Qu::Payload.new(klass: JobWrapper, args: [job.serialize]).tap do |payload|
-          payload.instance_variable_set(:@queue, job.queue_name)
-        end.push
-
-        # qu_job can be nil depending on the configured backend
-        job.provider_job_id = qu_job.id unless qu_job.nil?
-        qu_job
-      end
-
-      def enqueue_at(job, timestamp, *args) #:nodoc:
-        raise NotImplementedError, "This queueing backend does not support scheduling jobs. To see what features are supported go to http://api.rubyonrails.org/classes/ActiveJob/QueueAdapters.html"
-      end
-
-      class JobWrapper < Qu::Job #:nodoc:
-        def initialize(job_data)
-          @job_data = job_data
-        end
-
-        def perform
-          Base.execute @job_data
-        end
-      end
-    end
-  end
-end
diff --git a/activejob/lib/active_job/queue_adapters/sidekiq_adapter.rb b/activejob/lib/active_job/queue_adapters/sidekiq_adapter.rb
index 5a1135854b..f726e6ad93 100644
--- a/activejob/lib/active_job/queue_adapters/sidekiq_adapter.rb
+++ b/activejob/lib/active_job/queue_adapters/sidekiq_adapter.rb
@@ -18,7 +18,7 @@ module ActiveJob
     #   Rails.application.config.active_job.queue_adapter = :sidekiq
     class SidekiqAdapter
       def enqueue(job) #:nodoc:
-        #Sidekiq::Client does not support symbols as keys
+        # Sidekiq::Client does not support symbols as keys
         job.provider_job_id = Sidekiq::Client.push \
           "class"   => JobWrapper,
           "wrapped" => job.class.to_s,
diff --git a/activejob/lib/active_job/railtie.rb b/activejob/lib/active_job/railtie.rb
index 7b0742a6d2..d0294854d3 100644
--- a/activejob/lib/active_job/railtie.rb
+++ b/activejob/lib/active_job/railtie.rb
@@ -7,17 +7,28 @@ module ActiveJob
   # = Active Job Railtie
   class Railtie < Rails::Railtie # :nodoc:
     config.active_job = ActiveSupport::OrderedOptions.new
+    config.active_job.custom_serializers = []
 
     initializer "active_job.logger" do
       ActiveSupport.on_load(:active_job) { self.logger = ::Rails.logger }
     end
 
+    initializer "active_job.custom_serializers" do |app|
+      config.after_initialize do
+        custom_serializers = app.config.active_job.delete(:custom_serializers)
+        ActiveJob::Serializers.add_serializers custom_serializers
+      end
+    end
+
     initializer "active_job.set_configs" do |app|
       options = app.config.active_job
       options.queue_adapter ||= :async
 
       ActiveSupport.on_load(:active_job) do
-        options.each { |k, v| send("#{k}=", v) }
+        options.each do  |k, v|
+          k = "#{k}="
+          send(k, v) if respond_to? k
+        end
       end
     end
 
diff --git a/activejob/lib/active_job/serializers.rb b/activejob/lib/active_job/serializers.rb
new file mode 100644
index 0000000000..df66e66659
--- /dev/null
+++ b/activejob/lib/active_job/serializers.rb
@@ -0,0 +1,64 @@
+# frozen_string_literal: true
+
+require "set"
+
+module ActiveJob
+  # The <tt>ActiveJob::Serializers</tt> module is used to store a list of known serializers
+  # and to add new ones. It also has helpers to serialize/deserialize objects.
+  module Serializers # :nodoc:
+    extend ActiveSupport::Autoload
+    extend ActiveSupport::Concern
+
+    autoload :ObjectSerializer
+    autoload :SymbolSerializer
+    autoload :DurationSerializer
+    autoload :DateTimeSerializer
+    autoload :DateSerializer
+    autoload :TimeWithZoneSerializer
+    autoload :TimeSerializer
+
+    mattr_accessor :_additional_serializers
+    self._additional_serializers = Set.new
+
+    class << self
+      # Returns serialized representative of the passed object.
+      # Will look up through all known serializers.
+      # Raises <tt>ActiveJob::SerializationError</tt> if it can't find a proper serializer.
+      def serialize(argument)
+        serializer = serializers.detect { |s| s.serialize?(argument) }
+        raise SerializationError.new("Unsupported argument type: #{argument.class.name}") unless serializer
+        serializer.serialize(argument)
+      end
+
+      # Returns deserialized object.
+      # Will look up through all known serializers.
+      # If no serializer found will raise <tt>ArgumentError</tt>.
+      def deserialize(argument)
+        serializer_name = argument[Arguments::OBJECT_SERIALIZER_KEY]
+        raise ArgumentError, "Serializer name is not present in the argument: #{argument.inspect}" unless serializer_name
+
+        serializer = serializer_name.safe_constantize
+        raise ArgumentError, "Serializer #{serializer_name} is not known" unless serializer
+
+        serializer.deserialize(argument)
+      end
+
+      # Returns list of known serializers.
+      def serializers
+        self._additional_serializers
+      end
+
+      # Adds new serializers to a list of known serializers.
+      def add_serializers(*new_serializers)
+        self._additional_serializers += new_serializers.flatten
+      end
+    end
+
+    add_serializers SymbolSerializer,
+      DurationSerializer,
+      DateTimeSerializer,
+      DateSerializer,
+      TimeWithZoneSerializer,
+      TimeSerializer
+  end
+end
diff --git a/activejob/lib/active_job/serializers/date_serializer.rb b/activejob/lib/active_job/serializers/date_serializer.rb
new file mode 100644
index 0000000000..e995d30faa
--- /dev/null
+++ b/activejob/lib/active_job/serializers/date_serializer.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Serializers
+    class DateSerializer < ObjectSerializer # :nodoc:
+      def serialize(date)
+        super("value" => date.iso8601)
+      end
+
+      def deserialize(hash)
+        Date.iso8601(hash["value"])
+      end
+
+      private
+
+        def klass
+          Date
+        end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/serializers/date_time_serializer.rb b/activejob/lib/active_job/serializers/date_time_serializer.rb
new file mode 100644
index 0000000000..fe780a1978
--- /dev/null
+++ b/activejob/lib/active_job/serializers/date_time_serializer.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Serializers
+    class DateTimeSerializer < ObjectSerializer # :nodoc:
+      def serialize(time)
+        super("value" => time.iso8601)
+      end
+
+      def deserialize(hash)
+        DateTime.iso8601(hash["value"])
+      end
+
+      private
+
+        def klass
+          DateTime
+        end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/serializers/duration_serializer.rb b/activejob/lib/active_job/serializers/duration_serializer.rb
new file mode 100644
index 0000000000..715fe27a5c
--- /dev/null
+++ b/activejob/lib/active_job/serializers/duration_serializer.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Serializers
+    class DurationSerializer < ObjectSerializer # :nodoc:
+      def serialize(duration)
+        super("value" => duration.value, "parts" => Arguments.serialize(duration.parts))
+      end
+
+      def deserialize(hash)
+        value = hash["value"]
+        parts = Arguments.deserialize(hash["parts"])
+
+        klass.new(value, parts)
+      end
+
+      private
+
+        def klass
+          ActiveSupport::Duration
+        end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/serializers/object_serializer.rb b/activejob/lib/active_job/serializers/object_serializer.rb
new file mode 100644
index 0000000000..6d280969be
--- /dev/null
+++ b/activejob/lib/active_job/serializers/object_serializer.rb
@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Serializers
+    # Base class for serializing and deserializing custom objects.
+    #
+    # Example:
+    #
+    #   class MoneySerializer < ActiveJob::Serializers::ObjectSerializer
+    #     def serialize(money)
+    #       super("amount" => money.amount, "currency" => money.currency)
+    #     end
+    #
+    #     def deserialize(hash)
+    #       Money.new(hash["amount"], hash["currency"])
+    #     end
+    #
+    #     private
+    #
+    #       def klass
+    #         Money
+    #       end
+    #   end
+    class ObjectSerializer
+      include Singleton
+
+      class << self
+        delegate :serialize?, :serialize, :deserialize, to: :instance
+      end
+
+      # Determines if an argument should be serialized by a serializer.
+      def serialize?(argument)
+        argument.is_a?(klass)
+      end
+
+      # Serializes an argument to a JSON primitive type.
+      def serialize(hash)
+        { Arguments::OBJECT_SERIALIZER_KEY => self.class.name }.merge!(hash)
+      end
+
+      # Deserializes an argument from a JSON primitive type.
+      def deserialize(_argument)
+        raise NotImplementedError
+      end
+
+      private
+
+        # The class of the object that will be serialized.
+        def klass # :doc:
+          raise NotImplementedError
+        end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/serializers/symbol_serializer.rb b/activejob/lib/active_job/serializers/symbol_serializer.rb
new file mode 100644
index 0000000000..7e1f9553a2
--- /dev/null
+++ b/activejob/lib/active_job/serializers/symbol_serializer.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Serializers
+    class SymbolSerializer < ObjectSerializer # :nodoc:
+      def serialize(argument)
+        super("value" => argument.to_s)
+      end
+
+      def deserialize(argument)
+        argument["value"].to_sym
+      end
+
+      private
+
+        def klass
+          Symbol
+        end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/serializers/time_serializer.rb b/activejob/lib/active_job/serializers/time_serializer.rb
new file mode 100644
index 0000000000..fe20772f35
--- /dev/null
+++ b/activejob/lib/active_job/serializers/time_serializer.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Serializers
+    class TimeSerializer < ObjectSerializer # :nodoc:
+      def serialize(time)
+        super("value" => time.iso8601)
+      end
+
+      def deserialize(hash)
+        Time.iso8601(hash["value"])
+      end
+
+      private
+
+        def klass
+          Time
+        end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/serializers/time_with_zone_serializer.rb b/activejob/lib/active_job/serializers/time_with_zone_serializer.rb
new file mode 100644
index 0000000000..43017fc75b
--- /dev/null
+++ b/activejob/lib/active_job/serializers/time_with_zone_serializer.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Serializers
+    class TimeWithZoneSerializer < ObjectSerializer # :nodoc:
+      def serialize(time)
+        super("value" => time.iso8601)
+      end
+
+      def deserialize(hash)
+        Time.iso8601(hash["value"]).in_time_zone
+      end
+
+      private
+
+        def klass
+          ActiveSupport::TimeWithZone
+        end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/timezones.rb b/activejob/lib/active_job/timezones.rb
new file mode 100644
index 0000000000..ac018eb752
--- /dev/null
+++ b/activejob/lib/active_job/timezones.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Timezones #:nodoc:
+    extend ActiveSupport::Concern
+
+    included do
+      around_perform do |job, block|
+        Time.use_zone(job.timezone, &block)
+      end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/translation.rb b/activejob/lib/active_job/translation.rb
index fb45c80d67..0fd9b9fc06 100644
--- a/activejob/lib/active_job/translation.rb
+++ b/activejob/lib/active_job/translation.rb
@@ -5,7 +5,7 @@ module ActiveJob
     extend ActiveSupport::Concern
 
     included do
-      around_perform do |job, block, _|
+      around_perform do |job, block|
         I18n.with_locale(job.locale, &block)
       end
     end
diff --git a/activejob/lib/rails/generators/job/job_generator.rb b/activejob/lib/rails/generators/job/job_generator.rb
index 69b4fe7d26..03346a7f12 100644
--- a/activejob/lib/rails/generators/job/job_generator.rb
+++ b/activejob/lib/rails/generators/job/job_generator.rb
@@ -28,6 +28,10 @@ module Rails # :nodoc:
       end
 
       private
+        def file_name
+          @_file_name ||= super.sub(/_job\z/i, "")
+        end
+
         def application_job_file_name
           @application_job_file_name ||= if mountable_engine?
             "app/jobs/#{namespaced_path}/application_job.rb"
diff --git a/activejob/lib/rails/generators/job/templates/application_job.rb b/activejob/lib/rails/generators/job/templates/application_job.rb.tt
index f93745a31a..f93745a31a 100644
--- a/activejob/lib/rails/generators/job/templates/application_job.rb
+++ b/activejob/lib/rails/generators/job/templates/application_job.rb.tt
diff --git a/activejob/lib/rails/generators/job/templates/job.rb b/activejob/lib/rails/generators/job/templates/job.rb.tt
index 4ad2914a45..4ad2914a45 100644
--- a/activejob/lib/rails/generators/job/templates/job.rb
+++ b/activejob/lib/rails/generators/job/templates/job.rb.tt
diff --git a/activejob/test/adapters/qu.rb b/activejob/test/adapters/qu.rb
deleted file mode 100644
index 5b471fa347..0000000000
--- a/activejob/test/adapters/qu.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-# frozen_string_literal: true
-
-require "qu-immediate"
-
-ActiveJob::Base.queue_adapter = :qu
diff --git a/activejob/test/cases/argument_serialization_test.rb b/activejob/test/cases/argument_serialization_test.rb
index 13e6fcb727..e5f1f087fe 100644
--- a/activejob/test/cases/argument_serialization_test.rb
+++ b/activejob/test/cases/argument_serialization_test.rb
@@ -12,7 +12,10 @@ class ArgumentSerializationTest < ActiveSupport::TestCase
   end
 
   [ nil, 1, 1.0, 1_000_000_000_000_000_000_000,
-    "a", true, false, BigDecimal.new(5),
+    "a", true, false, BigDecimal(5),
+    :a, 1.day, Date.new(2001, 2, 3), Time.new(2002, 10, 31, 2, 2, 2, "+02:00"),
+    DateTime.new(2001, 2, 3, 4, 5, 6, "+03:00"),
+    ActiveSupport::TimeWithZone.new(Time.utc(1999, 12, 31, 23, 59, 59), ActiveSupport::TimeZone["UTC"]),
     [ 1, "a" ],
     { "a" => 1 }
   ].each do |arg|
@@ -21,7 +24,7 @@ class ArgumentSerializationTest < ActiveSupport::TestCase
     end
   end
 
-  [ :a, Object.new, self, Person.find("5").to_gid ].each do |arg|
+  [ Object.new, self, Person.find("5").to_gid ].each do |arg|
     test "does not serialize #{arg.class}" do
       assert_raises ActiveJob::SerializationError do
         ActiveJob::Arguments.serialize [ arg ]
@@ -46,6 +49,49 @@ class ArgumentSerializationTest < ActiveSupport::TestCase
     assert_arguments_roundtrip([a: 1, "b" => 2])
   end
 
+  test "serialize a hash" do
+    symbol_key = { a: 1 }
+    string_key = { "a" => 1 }
+    indifferent_access = { a: 1 }.with_indifferent_access
+
+    assert_equal(
+      { "a" => 1, "_aj_symbol_keys" => ["a"] },
+      ActiveJob::Arguments.serialize([symbol_key]).first
+    )
+    assert_equal(
+      { "a" => 1, "_aj_symbol_keys" => [] },
+      ActiveJob::Arguments.serialize([string_key]).first
+    )
+    assert_equal(
+      { "a" => 1, "_aj_hash_with_indifferent_access" => true },
+      ActiveJob::Arguments.serialize([indifferent_access]).first
+    )
+  end
+
+  test "deserialize a hash" do
+    symbol_key = { "a" => 1, "_aj_symbol_keys" => ["a"] }
+    string_key = { "a" => 1, "_aj_symbol_keys" => [] }
+    another_string_key = { "a" => 1 }
+    indifferent_access = { "a" => 1, "_aj_hash_with_indifferent_access" => true }
+
+    assert_equal(
+      { a: 1 },
+      ActiveJob::Arguments.deserialize([symbol_key]).first
+    )
+    assert_equal(
+      { "a" => 1 },
+      ActiveJob::Arguments.deserialize([string_key]).first
+    )
+    assert_equal(
+      { "a" => 1 },
+      ActiveJob::Arguments.deserialize([another_string_key]).first
+    )
+    assert_equal(
+      { "a" => 1 },
+      ActiveJob::Arguments.deserialize([indifferent_access]).first
+    )
+  end
+
   test "should maintain hash with indifferent access" do
     symbol_key = { a: 1 }
     string_key = { "a" => 1 }
@@ -56,6 +102,14 @@ class ArgumentSerializationTest < ActiveSupport::TestCase
     assert_instance_of ActiveSupport::HashWithIndifferentAccess, perform_round_trip([indifferent_access]).first
   end
 
+  test "should maintain time with zone" do
+    Time.use_zone "Alaska" do
+      time_with_zone = Time.new(2002, 10, 31, 2, 2, 2).in_time_zone
+      assert_instance_of ActiveSupport::TimeWithZone, perform_round_trip([time_with_zone]).first
+      assert_arguments_unchanged time_with_zone
+    end
+  end
+
   test "should disallow non-string/symbol hash keys" do
     assert_raises ActiveJob::SerializationError do
       ActiveJob::Arguments.serialize [ { 1 => 2 } ]
diff --git a/activejob/test/cases/exceptions_test.rb b/activejob/test/cases/exceptions_test.rb
index 7a3c372143..15938e3fc7 100644
--- a/activejob/test/cases/exceptions_test.rb
+++ b/activejob/test/cases/exceptions_test.rb
@@ -58,10 +58,17 @@ class ExceptionsTest < ActiveJob::TestCase
     end
   end
 
+  test "custom handling of discarded job" do
+    perform_enqueued_jobs do
+      RetryJob.perform_later "CustomDiscardableError", 2
+      assert_equal "Dealt with a job that was discarded in a custom way. Message: CustomDiscardableError", JobBuffer.last_value
+    end
+  end
+
   test "custom handling of job that exceeds retry attempts" do
     perform_enqueued_jobs do
       RetryJob.perform_later "CustomCatchError", 6
-      assert_equal "Dealt with a job that failed to retry in a custom way after 6 attempts", JobBuffer.last_value
+      assert_equal "Dealt with a job that failed to retry in a custom way after 6 attempts. Message: CustomCatchError", JobBuffer.last_value
     end
   end
 
diff --git a/activejob/test/cases/job_serialization_test.rb b/activejob/test/cases/job_serialization_test.rb
index 440051c427..86f3651564 100644
--- a/activejob/test/cases/job_serialization_test.rb
+++ b/activejob/test/cases/job_serialization_test.rb
@@ -23,16 +23,16 @@ class JobSerializationTest < ActiveSupport::TestCase
 
   test "serialize and deserialize are symmetric" do
     # Round trip a job in memory only
-    h1 = HelloJob.new
-    h1.deserialize(h1.serialize)
+    h1 = HelloJob.new("Rafael")
+    h2 = HelloJob.deserialize(h1.serialize)
+    assert_equal h1.serialize, h2.serialize
 
     # Now verify it's identical to a JSON round trip.
     # We don't want any non-native JSON elements in the job hash,
     # like symbols.
-    payload = JSON.dump(h1.serialize)
-    h2 = HelloJob.new
-    h2.deserialize(JSON.load(payload))
-    assert_equal h1.serialize, h2.serialize
+    payload = JSON.dump(h2.serialize)
+    h3 = HelloJob.deserialize(JSON.load(payload))
+    assert_equal h2.serialize, h3.serialize
   end
 
   test "deserialize sets locale" do
@@ -54,4 +54,11 @@ class JobSerializationTest < ActiveSupport::TestCase
     job.provider_job_id = "some value set by adapter"
     assert_equal job.provider_job_id, job.serialize["provider_job_id"]
   end
+
+  test "serialize stores the current timezone" do
+    Time.use_zone "Hawaii" do
+      job = HelloJob.new
+      assert_equal "Hawaii", job.serialize["timezone"]
+    end
+  end
 end
diff --git a/activejob/test/cases/serializers_test.rb b/activejob/test/cases/serializers_test.rb
new file mode 100644
index 0000000000..bee0c061bd
--- /dev/null
+++ b/activejob/test/cases/serializers_test.rb
@@ -0,0 +1,98 @@
+# frozen_string_literal: true
+
+require "helper"
+require "active_job/serializers"
+
+class SerializersTest < ActiveSupport::TestCase
+  class DummyValueObject
+    attr_accessor :value
+
+    def initialize(value)
+      @value = value
+    end
+
+    def ==(other)
+      self.value == other.value
+    end
+  end
+
+  class DummySerializer < ActiveJob::Serializers::ObjectSerializer
+    def serialize(object)
+      super({ "value" => object.value })
+    end
+
+    def deserialize(hash)
+      DummyValueObject.new(hash["value"])
+    end
+
+    private
+
+      def klass
+        DummyValueObject
+      end
+  end
+
+  setup do
+    @value_object = DummyValueObject.new 123
+    @original_serializers = ActiveJob::Serializers.serializers
+  end
+
+  teardown do
+    ActiveJob::Serializers._additional_serializers = @original_serializers
+  end
+
+  test "can't serialize unknown object" do
+    assert_raises ActiveJob::SerializationError do
+      ActiveJob::Serializers.serialize @value_object
+    end
+  end
+
+  test "will serialize objects with serializers registered" do
+    ActiveJob::Serializers.add_serializers DummySerializer
+
+    assert_equal(
+      { "_aj_serialized" => "SerializersTest::DummySerializer", "value" => 123 },
+      ActiveJob::Serializers.serialize(@value_object)
+    )
+  end
+
+  test "won't deserialize unknown hash" do
+    hash = { "_dummy_serializer" => 123, "_aj_symbol_keys" => [] }
+    error = assert_raises(ArgumentError) do
+      ActiveJob::Serializers.deserialize(hash)
+    end
+    assert_equal(
+      'Serializer name is not present in the argument: {"_dummy_serializer"=>123, "_aj_symbol_keys"=>[]}',
+      error.message
+    )
+  end
+
+  test "won't deserialize unknown serializer" do
+    hash = { "_aj_serialized" => "DoNotExist", "value" => 123 }
+    error = assert_raises(ArgumentError) do
+      ActiveJob::Serializers.deserialize(hash)
+    end
+    assert_equal(
+      "Serializer DoNotExist is not known",
+      error.message
+    )
+  end
+
+  test "will deserialize know serialized objects" do
+    ActiveJob::Serializers.add_serializers DummySerializer
+    hash = { "_aj_serialized" => "SerializersTest::DummySerializer", "value" => 123 }
+    assert_equal DummyValueObject.new(123), ActiveJob::Serializers.deserialize(hash)
+  end
+
+  test "adds new serializer" do
+    ActiveJob::Serializers.add_serializers DummySerializer
+    assert ActiveJob::Serializers.serializers.include?(DummySerializer)
+  end
+
+  test "can't add serializer with the same key twice" do
+    ActiveJob::Serializers.add_serializers DummySerializer
+    assert_no_difference(-> { ActiveJob::Serializers.serializers.size }) do
+      ActiveJob::Serializers.add_serializers DummySerializer
+    end
+  end
+end
diff --git a/activejob/test/cases/timezones_test.rb b/activejob/test/cases/timezones_test.rb
new file mode 100644
index 0000000000..e2095b020d
--- /dev/null
+++ b/activejob/test/cases/timezones_test.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+require "helper"
+require "jobs/timezone_dependent_job"
+
+class TimezonesTest < ActiveSupport::TestCase
+  setup do
+    JobBuffer.clear
+  end
+
+  test "it performs the job in the given timezone" do
+    job = TimezoneDependentJob.new("2018-01-01T00:00:00Z")
+    job.timezone = "London"
+    job.perform_now
+
+    assert_equal "Happy New Year!", JobBuffer.last_value
+
+    job = TimezoneDependentJob.new("2018-01-01T00:00:00Z")
+    job.timezone = "Eastern Time (US & Canada)"
+    job.perform_now
+
+    assert_equal "Just 5 hours to go", JobBuffer.last_value
+  end
+end
diff --git a/activejob/test/integration/queuing_test.rb b/activejob/test/integration/queuing_test.rb
index 0d8aa336a6..32afb5ca62 100644
--- a/activejob/test/integration/queuing_test.rb
+++ b/activejob/test/integration/queuing_test.rb
@@ -45,6 +45,13 @@ class QueuingTest < ActiveSupport::TestCase
     end
   end
 
+  test "should supply a wrapped class name to DelayedJob" do
+    skip unless adapter_is?(:delayed_job)
+    ::HelloJob.perform_later
+    job = Delayed::Job.first
+    assert_match(/HelloJob \[[0-9a-f-]+\] from DelayedJob\(default\) with arguments: \[\]/, job.name)
+  end
+
   test "resque JobWrapper should have instance variable queue" do
     skip unless adapter_is?(:resque)
     job = ::HelloJob.set(wait: 5.seconds).perform_later
@@ -75,7 +82,7 @@ class QueuingTest < ActiveSupport::TestCase
   end
 
   test "should supply a provider_job_id when available for immediate jobs" do
-    skip unless adapter_is?(:async, :delayed_job, :sidekiq, :qu, :que, :queue_classic)
+    skip unless adapter_is?(:async, :delayed_job, :sidekiq, :que, :queue_classic)
     test_job = TestJob.perform_later @id
     assert test_job.provider_job_id, "Provider job id should be set by provider"
   end
@@ -103,6 +110,22 @@ class QueuingTest < ActiveSupport::TestCase
     end
   end
 
+  test "current timezone is kept while running perform_later" do
+    skip if adapter_is?(:inline)
+
+    begin
+      current_zone = Time.zone
+      Time.zone = "Hawaii"
+
+      TestJob.perform_later @id
+      wait_for_jobs_to_finish_for(5.seconds)
+      assert job_executed
+      assert_equal "Hawaii", job_executed_in_timezone
+    ensure
+      Time.zone = current_zone
+    end
+  end
+
   test "should run job with higher priority first" do
     skip unless adapter_is?(:delayed_job, :que)
 
diff --git a/activejob/test/jobs/retry_job.rb b/activejob/test/jobs/retry_job.rb
index a12d09779b..a12c65015b 100644
--- a/activejob/test/jobs/retry_job.rb
+++ b/activejob/test/jobs/retry_job.rb
@@ -10,6 +10,7 @@ class ExponentialWaitTenAttemptsError < StandardError; end
 class CustomWaitTenAttemptsError < StandardError; end
 class CustomCatchError < StandardError; end
 class DiscardableError < StandardError; end
+class CustomDiscardableError < StandardError; end
 
 class RetryJob < ActiveJob::Base
   retry_on DefaultsError
@@ -17,8 +18,9 @@ class RetryJob < ActiveJob::Base
   retry_on ShortWaitTenAttemptsError, wait: 1.second, attempts: 10
   retry_on ExponentialWaitTenAttemptsError, wait: :exponentially_longer, attempts: 10
   retry_on CustomWaitTenAttemptsError, wait: ->(executions) { executions * 2 }, attempts: 10
-  retry_on(CustomCatchError) { |job, exception| JobBuffer.add("Dealt with a job that failed to retry in a custom way after #{job.arguments.second} attempts") }
+  retry_on(CustomCatchError) { |job, error| JobBuffer.add("Dealt with a job that failed to retry in a custom way after #{job.arguments.second} attempts. Message: #{error.message}") }
   discard_on DiscardableError
+  discard_on(CustomDiscardableError) { |job, error| JobBuffer.add("Dealt with a job that was discarded in a custom way. Message: #{error.message}") }
 
   def perform(raising, attempts)
     if executions < attempts
diff --git a/activejob/test/jobs/timezone_dependent_job.rb b/activejob/test/jobs/timezone_dependent_job.rb
new file mode 100644
index 0000000000..41f473d533
--- /dev/null
+++ b/activejob/test/jobs/timezone_dependent_job.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require_relative "../support/job_buffer"
+
+class TimezoneDependentJob < ActiveJob::Base
+  def perform(now)
+    now = now.in_time_zone
+    new_year = localtime(2018, 1, 1)
+
+    if now >= new_year
+      JobBuffer.add("Happy New Year!")
+    else
+      JobBuffer.add("Just #{(new_year - now).div(3600)} hours to go")
+    end
+  end
+
+  private
+
+    def localtime(*args)
+      Time.zone ? Time.zone.local(*args) : Time.utc(*args)
+    end
+end
diff --git a/activejob/test/support/delayed_job/delayed/backend/test.rb b/activejob/test/support/delayed_job/delayed/backend/test.rb
index 4721c1cc17..1691896b7c 100644
--- a/activejob/test/support/delayed_job/delayed/backend/test.rb
+++ b/activejob/test/support/delayed_job/delayed/backend/test.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-#copied from https://github.com/collectiveidea/delayed_job/blob/master/spec/delayed/backend/test.rb
+# copied from https://github.com/collectiveidea/delayed_job/blob/master/spec/delayed/backend/test.rb
 require "ostruct"
 
 # An in-memory backend suitable only for testing. Tries to behave as if it were an ORM.
@@ -77,7 +77,7 @@ module Delayed
             self.locked_by = worker
           end
 
-          return true
+          true
         end
 
         def self.db_time_now
diff --git a/activejob/test/support/integration/adapters/qu.rb b/activejob/test/support/integration/adapters/qu.rb
deleted file mode 100644
index 67db03e279..0000000000
--- a/activejob/test/support/integration/adapters/qu.rb
+++ /dev/null
@@ -1,40 +0,0 @@
-# frozen_string_literal: true
-
-module QuJobsManager
-  def setup
-    require "qu-rails"
-    require "qu-redis"
-    ActiveJob::Base.queue_adapter = :qu
-    ENV["REDISTOGO_URL"] = "redis://127.0.0.1:6379/12"
-    backend = Qu::Backend::Redis.new
-    backend.namespace = "active_jobs_int_test"
-    Qu.backend  = backend
-    Qu.logger   = Rails.logger
-    Qu.interval = 0.5
-    unless can_run?
-      puts "Cannot run integration tests for qu. To be able to run integration tests for qu you need to install and start redis.\n"
-      exit
-    end
-  end
-
-  def clear_jobs
-    Qu.clear "integration_tests"
-  end
-
-  def start_workers
-    @thread = Thread.new { Qu::Worker.new("integration_tests").start }
-  end
-
-  def stop_workers
-    @thread.kill
-  end
-
-  def can_run?
-    begin
-      Qu.backend.connection.client.connect
-    rescue
-      return false
-    end
-    true
-  end
-end
diff --git a/activejob/test/support/integration/adapters/resque.rb b/activejob/test/support/integration/adapters/resque.rb
index 484b476567..2ed8302277 100644
--- a/activejob/test/support/integration/adapters/resque.rb
+++ b/activejob/test/support/integration/adapters/resque.rb
@@ -3,11 +3,12 @@
 module ResqueJobsManager
   def setup
     ActiveJob::Base.queue_adapter = :resque
-    Resque.redis = Redis::Namespace.new "active_jobs_int_test", redis: Redis.connect(url: "redis://:password@127.0.0.1:6379/12", thread_safe: true)
+    Resque.redis = Redis::Namespace.new "active_jobs_int_test", redis: Redis.new(url: "redis://127.0.0.1:6379/12", thread_safe: true)
     Resque.logger = Rails.logger
     unless can_run?
       puts "Cannot run integration tests for resque. To be able to run integration tests for resque you need to install and start redis.\n"
-      exit
+      status = ENV["CI"] ? false : true
+      exit status
     end
   end
 
@@ -41,11 +42,8 @@ module ResqueJobsManager
   end
 
   def can_run?
-    begin
-      Resque.redis.client.connect
-    rescue
-      return false
-    end
-    true
+    Resque.redis.ping == "PONG"
+  rescue
+    false
   end
 end
diff --git a/activejob/test/support/integration/adapters/sidekiq.rb b/activejob/test/support/integration/adapters/sidekiq.rb
index ceb7fb61f2..c79de12eaf 100644
--- a/activejob/test/support/integration/adapters/sidekiq.rb
+++ b/activejob/test/support/integration/adapters/sidekiq.rb
@@ -5,20 +5,13 @@ require "sidekiq/api"
 require "sidekiq/testing"
 Sidekiq::Testing.disable!
 
-Sidekiq.configure_server do |config|
-  config.redis = { url: "redis://:password@127.0.0.1:6379/12" }
-end
-
-Sidekiq.configure_client do |config|
-  config.redis = { url: "redis://:password@127.0.0.1:6379/12" }
-end
-
 module SidekiqJobsManager
   def setup
     ActiveJob::Base.queue_adapter = :sidekiq
     unless can_run?
       puts "Cannot run integration tests for sidekiq. To be able to run integration tests for sidekiq you need to install and start redis.\n"
-      exit
+      status = ENV["CI"] ? false : true
+      exit status
     end
   end
 
@@ -58,6 +51,7 @@ module SidekiqJobsManager
         self_write.puts("TERM")
       end
 
+      require "sidekiq/cli"
       require "sidekiq/launcher"
       sidekiq = Sidekiq::Launcher.new(queues: ["integration_tests"],
                                        environment: "test",
diff --git a/activejob/test/support/integration/dummy_app_template.rb b/activejob/test/support/integration/dummy_app_template.rb
index ac382bd1b7..b56dd3e591 100644
--- a/activejob/test/support/integration/dummy_app_template.rb
+++ b/activejob/test/support/integration/dummy_app_template.rb
@@ -4,8 +4,6 @@ if ENV["AJ_ADAPTER"] == "delayed_job"
   generate "delayed_job:active_record", "--quiet"
 end
 
-rails_command("db:migrate")
-
 initializer "activejob.rb", <<-CODE
 require "#{File.expand_path("jobs_manager.rb",  __dir__)}"
 JobsManager.current_manager.setup
@@ -23,6 +21,7 @@ class TestJob < ActiveJob::Base
     File.open(Rails.root.join("tmp/\#{x}.new"), "wb+") do |f|
       f.write Marshal.dump({
         "locale" => I18n.locale.to_s || "en",
+        "timezone" => Time.zone.try(:name) || "UTC",
         "executed_at" => Time.now.to_r
       })
     end
diff --git a/activejob/test/support/integration/helper.rb b/activejob/test/support/integration/helper.rb
index a058da141f..a02d874e2e 100644
--- a/activejob/test/support/integration/helper.rb
+++ b/activejob/test/support/integration/helper.rb
@@ -18,6 +18,7 @@ Rails::Generators::AppGenerator.start args
 require "#{dummy_app_path}/config/environment.rb"
 
 ActiveRecord::Migrator.migrations_paths = [ Rails.root.join("db/migrate").to_s ]
+ActiveRecord::Tasks::DatabaseTasks.migrate
 require "rails/test_help"
 
 Rails.backtrace_cleaner.remove_silencers!
diff --git a/activejob/test/support/integration/test_case_helpers.rb b/activejob/test/support/integration/test_case_helpers.rb
index f02a32a38e..3d9b265b66 100644
--- a/activejob/test/support/integration/test_case_helpers.rb
+++ b/activejob/test/support/integration/test_case_helpers.rb
@@ -62,4 +62,8 @@ module TestCaseHelpers
     def job_executed_in_locale(id = @id)
       job_data(id)["locale"]
     end
+
+    def job_executed_in_timezone(id = @id)
+      job_data(id)["timezone"]
+    end
 end
diff --git a/activemodel/CHANGELOG.md b/activemodel/CHANGELOG.md
index 048c43f2c4..6b557a7cb1 100644
--- a/activemodel/CHANGELOG.md
+++ b/activemodel/CHANGELOG.md
@@ -1,41 +1,6 @@
-*   Add method `#merge!` for `ActiveModel::Errors`.
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
-    *Jahfer Husain*
+    *Jeremy Daer*
 
-*   Fix regression in numericality validator when comparing Decimal and Float input
-    values with more scale than the schema.
 
-    *Bradley Priest*
-
-*   Fix methods `#keys`, `#values` in `ActiveModel::Errors`.
-
-    Change `#keys` to only return the keys that don't have empty messages.
-
-    Change `#values` to only return the not empty values.
-
-    Example:
-
-        # Before
-        person = Person.new
-        person.errors.keys     # => []
-        person.errors.values   # => []
-        person.errors.messages # => {}
-        person.errors[:name]   # => []
-        person.errors.messages # => {:name => []}
-        person.errors.keys     # => [:name]
-        person.errors.values   # => [[]]
-
-        # After
-        person = Person.new
-        person.errors.keys     # => []
-        person.errors.values   # => []
-        person.errors.messages # => {}
-        person.errors[:name]   # => []
-        person.errors.messages # => {:name => []}
-        person.errors.keys     # => []
-        person.errors.values   # => []
-
-    *bogdanvlviv*
-
-
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/activemodel/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/activemodel/CHANGELOG.md) for previous changes.
diff --git a/activemodel/MIT-LICENSE b/activemodel/MIT-LICENSE
index ac810e86d0..1cb3add0fc 100644
--- a/activemodel/MIT-LICENSE
+++ b/activemodel/MIT-LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2004-2017 David Heinemeier Hansson
+Copyright (c) 2004-2018 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/activemodel/README.rdoc b/activemodel/README.rdoc
index 772df0f8f6..1aaf4813ea 100644
--- a/activemodel/README.rdoc
+++ b/activemodel/README.rdoc
@@ -251,11 +251,11 @@ Active Model is released under the MIT license:
 
 == Support
 
-API documentation is at
+API documentation is at:
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/activemodel/activemodel.gemspec b/activemodel/activemodel.gemspec
index a070a2898c..7be466dc4c 100644
--- a/activemodel/activemodel.gemspec
+++ b/activemodel/activemodel.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "A toolkit for building modeling frameworks (part of Rails)."
   s.description = "A toolkit for building modeling frameworks like Active Record. Rich support for attributes, callbacks, validations, serialization, internationalization, and testing."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
diff --git a/activemodel/lib/active_model.rb b/activemodel/lib/active_model.rb
index dfd9be34a9..bc10d6b4b9 100644
--- a/activemodel/lib/active_model.rb
+++ b/activemodel/lib/active_model.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 #--
-# Copyright (c) 2004-2017 David Heinemeier Hansson
+# Copyright (c) 2004-2018 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the
@@ -25,11 +25,13 @@
 
 require "active_support"
 require "active_support/rails"
-require_relative "active_model/version"
+require "active_model/version"
 
 module ActiveModel
   extend ActiveSupport::Autoload
 
+  autoload :Attribute
+  autoload :Attributes
   autoload :AttributeAssignment
   autoload :AttributeMethods
   autoload :BlockValidator, "active_model/validator"
@@ -45,6 +47,7 @@ module ActiveModel
   autoload :SecurePassword
   autoload :Serialization
   autoload :Translation
+  autoload :Type
   autoload :Validations
   autoload :Validator
 
diff --git a/activerecord/lib/active_record/attribute.rb b/activemodel/lib/active_model/attribute.rb
index fc474edc15..3f19cda07b 100644
--- a/activerecord/lib/active_record/attribute.rb
+++ b/activemodel/lib/active_model/attribute.rb
@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
-module ActiveRecord
+require "active_support/core_ext/object/duplicable"
+
+module ActiveModel
   class Attribute # :nodoc:
     class << self
       def from_database(name, value, type)
@@ -130,13 +132,7 @@ module ActiveRecord
       coder["value"] = value if defined?(@value)
     end
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
     protected
-
-      attr_reader :original_attribute
-      alias_method :assigned?, :original_attribute
-
       def original_value_for_database
         if assigned?
           original_attribute.original_value_for_database
@@ -146,6 +142,9 @@ module ActiveRecord
       end
 
     private
+      attr_reader :original_attribute
+      alias :assigned? :original_attribute
+
       def initialize_dup(other)
         if defined?(@value) && @value.duplicable?
           @value = @value.dup
@@ -233,10 +232,15 @@ module ActiveRecord
           false
         end
 
+        def forgetting_assignment
+          dup
+        end
+
         def with_type(type)
           self.class.new(name, type)
         end
       end
+
       private_constant :FromDatabase, :FromUser, :Null, :Uninitialized, :WithCastValue
   end
 end
diff --git a/activerecord/lib/active_record/attribute/user_provided_default.rb b/activemodel/lib/active_model/attribute/user_provided_default.rb
index 690a931615..9dc16e882d 100644
--- a/activerecord/lib/active_record/attribute/user_provided_default.rb
+++ b/activemodel/lib/active_model/attribute/user_provided_default.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../attribute"
+require "active_model/attribute"
 
-module ActiveRecord
+module ActiveModel
   class Attribute # :nodoc:
     class UserProvidedDefault < FromUser # :nodoc:
       def initialize(name, value, type, database_default)
@@ -22,10 +22,29 @@ module ActiveRecord
         self.class.new(name, user_provided_value, type, original_attribute)
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
+      def marshal_dump
+        result = [
+          name,
+          value_before_type_cast,
+          type,
+          original_attribute,
+        ]
+        result << value if defined?(@value)
+        result
+      end
+
+      def marshal_load(values)
+        name, user_provided_value, type, original_attribute, value = values
+        @name = name
+        @user_provided_value = user_provided_value
+        @type = type
+        @original_attribute = original_attribute
+        if values.length == 5
+          @value = value
+        end
+      end
 
+      private
         attr_reader :user_provided_value
     end
   end
diff --git a/activemodel/lib/active_model/attribute_assignment.rb b/activemodel/lib/active_model/attribute_assignment.rb
index aa931119ff..217bf1ac01 100644
--- a/activemodel/lib/active_model/attribute_assignment.rb
+++ b/activemodel/lib/active_model/attribute_assignment.rb
@@ -35,6 +35,8 @@ module ActiveModel
       _assign_attributes(sanitize_for_mass_assignment(attributes))
     end
 
+    alias attributes= assign_attributes
+
     private
 
       def _assign_attributes(attributes)
diff --git a/activerecord/lib/active_record/attribute_mutation_tracker.rb b/activemodel/lib/active_model/attribute_mutation_tracker.rb
index 94bf641a5d..6abf37bd44 100644
--- a/activerecord/lib/active_record/attribute_mutation_tracker.rb
+++ b/activemodel/lib/active_model/attribute_mutation_tracker.rb
@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
-module ActiveRecord
+require "active_support/core_ext/hash/indifferent_access"
+
+module ActiveModel
   class AttributeMutationTracker # :nodoc:
     OPTION_NOT_GIVEN = Object.new
 
@@ -9,6 +11,10 @@ module ActiveRecord
       @forced_changes = Set.new
     end
 
+    def changed_attribute_names
+      attr_names.select { |attr_name| changed?(attr_name) }
+    end
+
     def changed_values
       attr_names.each_with_object({}.with_indifferent_access) do |attr_name, result|
         if changed?(attr_name)
@@ -21,7 +27,7 @@ module ActiveRecord
       attr_names.each_with_object({}.with_indifferent_access) do |attr_name, result|
         change = change_to_attribute(attr_name)
         if change
-          result[attr_name] = change
+          result.merge!(attr_name => change)
         end
       end
     end
@@ -63,13 +69,8 @@ module ActiveRecord
       forced_changes << attr_name.to_s
     end
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
-    protected
-
-      attr_reader :attributes, :forced_changes
-
     private
+      attr_reader :attributes, :forced_changes
 
       def attr_names
         attributes.keys
@@ -79,6 +80,10 @@ module ActiveRecord
   class NullMutationTracker # :nodoc:
     include Singleton
 
+    def changed_attribute_names(*)
+      []
+    end
+
     def changed_values(*)
       {}
     end
@@ -107,5 +112,8 @@ module ActiveRecord
 
     def original_value(*)
     end
+
+    def force_change(*)
+    end
   end
 end
diff --git a/activerecord/lib/active_record/attribute_set.rb b/activemodel/lib/active_model/attribute_set.rb
index 492067e2b3..a890ee3932 100644
--- a/activerecord/lib/active_record/attribute_set.rb
+++ b/activemodel/lib/active_model/attribute_set.rb
@@ -1,11 +1,12 @@
 # frozen_string_literal: true
 
-require_relative "attribute_set/builder"
-require_relative "attribute_set/yaml_encoder"
+require "active_support/core_ext/object/deep_dup"
+require "active_model/attribute_set/builder"
+require "active_model/attribute_set/yaml_encoder"
 
-module ActiveRecord
+module ActiveModel
   class AttributeSet # :nodoc:
-    delegate :each_value, :fetch, to: :attributes
+    delegate :each_value, :fetch, :except, to: :attributes
 
     def initialize(attributes)
       @attributes = attributes
diff --git a/activerecord/lib/active_record/attribute_set/builder.rb b/activemodel/lib/active_model/attribute_set/builder.rb
index e3a9c7fdb3..2b1c2206ec 100644
--- a/activerecord/lib/active_record/attribute_set/builder.rb
+++ b/activemodel/lib/active_model/attribute_set/builder.rb
@@ -1,39 +1,34 @@
 # frozen_string_literal: true
 
-require_relative "../attribute"
+require "active_model/attribute"
 
-module ActiveRecord
+module ActiveModel
   class AttributeSet # :nodoc:
     class Builder # :nodoc:
-      attr_reader :types, :always_initialized, :default
+      attr_reader :types, :default_attributes
 
-      def initialize(types, always_initialized = nil, &default)
+      def initialize(types, default_attributes = {})
         @types = types
-        @always_initialized = always_initialized
-        @default = default
+        @default_attributes = default_attributes
       end
 
       def build_from_database(values = {}, additional_types = {})
-        if always_initialized && !values.key?(always_initialized)
-          values[always_initialized] = nil
-        end
-
-        attributes = LazyAttributeHash.new(types, values, additional_types, &default)
+        attributes = LazyAttributeHash.new(types, values, additional_types, default_attributes)
         AttributeSet.new(attributes)
       end
     end
   end
 
   class LazyAttributeHash # :nodoc:
-    delegate :transform_values, :each_key, :each_value, :fetch, to: :materialize
+    delegate :transform_values, :each_key, :each_value, :fetch, :except, to: :materialize
 
-    def initialize(types, values, additional_types, &default)
+    def initialize(types, values, additional_types, default_attributes, delegate_hash = {})
       @types = types
       @values = values
       @additional_types = additional_types
       @materialized = false
-      @delegate_hash = {}
-      @default = default || proc {}
+      @delegate_hash = delegate_hash
+      @default_attributes = default_attributes
     end
 
     def key?(key)
@@ -81,23 +76,20 @@ module ActiveRecord
     end
 
     def marshal_dump
-      materialize
+      [@types, @values, @additional_types, @default_attributes, @delegate_hash]
     end
 
-    def marshal_load(delegate_hash)
-      @delegate_hash = delegate_hash
-      @types = {}
-      @values = {}
-      @additional_types = {}
-      @materialized = true
+    def marshal_load(values)
+      if values.is_a?(Hash)
+        empty_hash = {}.freeze
+        initialize(empty_hash, empty_hash, empty_hash, empty_hash, values)
+        @materialized = true
+      else
+        initialize(*values)
+      end
     end
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
     protected
-
-      attr_reader :types, :values, :additional_types, :delegate_hash, :default
-
       def materialize
         unless @materialized
           values.each_key { |key| self[key] }
@@ -110,6 +102,7 @@ module ActiveRecord
       end
 
     private
+      attr_reader :types, :values, :additional_types, :delegate_hash, :default_attributes
 
       def assign_default_value(name)
         type = additional_types.fetch(name, types[name])
@@ -119,7 +112,12 @@ module ActiveRecord
         if value_present
           delegate_hash[name] = Attribute.from_database(name, value, type)
         elsif types.key?(name)
-          delegate_hash[name] = default.call(name) || Attribute.uninitialized(name, type)
+          attr = default_attributes[name]
+          if attr
+            delegate_hash[name] = attr.dup
+          else
+            delegate_hash[name] = Attribute.uninitialized(name, type)
+          end
         end
       end
   end
diff --git a/activerecord/lib/active_record/attribute_set/yaml_encoder.rb b/activemodel/lib/active_model/attribute_set/yaml_encoder.rb
index 9254ce16ab..ea1efc160e 100644
--- a/activerecord/lib/active_record/attribute_set/yaml_encoder.rb
+++ b/activemodel/lib/active_model/attribute_set/yaml_encoder.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-module ActiveRecord
+module ActiveModel
   class AttributeSet
     # Attempts to do more intelligent YAML dumping of an
-    # ActiveRecord::AttributeSet to reduce the size of the resulting string
+    # ActiveModel::AttributeSet to reduce the size of the resulting string
     class YAMLEncoder # :nodoc:
       def initialize(default_types)
         @default_types = default_types
@@ -33,10 +33,7 @@ module ActiveRecord
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
+      private
         attr_reader :default_types
     end
   end
diff --git a/activemodel/lib/active_model/attributes.rb b/activemodel/lib/active_model/attributes.rb
new file mode 100644
index 0000000000..7d44f7f2a3
--- /dev/null
+++ b/activemodel/lib/active_model/attributes.rb
@@ -0,0 +1,111 @@
+# frozen_string_literal: true
+
+require "active_model/attribute_set"
+require "active_model/attribute/user_provided_default"
+
+module ActiveModel
+  module Attributes #:nodoc:
+    extend ActiveSupport::Concern
+    include ActiveModel::AttributeMethods
+
+    included do
+      attribute_method_suffix "="
+      class_attribute :attribute_types, :_default_attributes, instance_accessor: false
+      self.attribute_types = Hash.new(Type.default_value)
+      self._default_attributes = AttributeSet.new({})
+    end
+
+    module ClassMethods
+      def attribute(name, type = Type::Value.new, **options)
+        name = name.to_s
+        if type.is_a?(Symbol)
+          type = ActiveModel::Type.lookup(type, **options.except(:default))
+        end
+        self.attribute_types = attribute_types.merge(name => type)
+        define_default_attribute(name, options.fetch(:default, NO_DEFAULT_PROVIDED), type)
+        define_attribute_method(name)
+      end
+
+      private
+
+        def define_method_attribute=(name)
+          safe_name = name.unpack1("h*".freeze)
+          ActiveModel::AttributeMethods::AttrNames.set_name_cache safe_name, name
+
+          generated_attribute_methods.module_eval <<-STR, __FILE__, __LINE__ + 1
+            def __temp__#{safe_name}=(value)
+              name = ::ActiveModel::AttributeMethods::AttrNames::ATTR_#{safe_name}
+              write_attribute(name, value)
+            end
+            alias_method #{(name + '=').inspect}, :__temp__#{safe_name}=
+            undef_method :__temp__#{safe_name}=
+          STR
+        end
+
+        NO_DEFAULT_PROVIDED = Object.new # :nodoc:
+        private_constant :NO_DEFAULT_PROVIDED
+
+        def define_default_attribute(name, value, type)
+          self._default_attributes = _default_attributes.deep_dup
+          if value == NO_DEFAULT_PROVIDED
+            default_attribute = _default_attributes[name].with_type(type)
+          else
+            default_attribute = Attribute::UserProvidedDefault.new(
+              name,
+              value,
+              type,
+              _default_attributes.fetch(name.to_s) { nil },
+            )
+          end
+          _default_attributes[name] = default_attribute
+        end
+    end
+
+    def initialize(*)
+      @attributes = self.class._default_attributes.deep_dup
+      super
+    end
+
+    def attributes
+      @attributes.to_hash
+    end
+
+    private
+
+      def write_attribute(attr_name, value)
+        name = if self.class.attribute_alias?(attr_name)
+          self.class.attribute_alias(attr_name).to_s
+        else
+          attr_name.to_s
+        end
+
+        @attributes.write_from_user(name, value)
+        value
+      end
+
+      def attribute(attr_name)
+        name = if self.class.attribute_alias?(attr_name)
+          self.class.attribute_alias(attr_name).to_s
+        else
+          attr_name.to_s
+        end
+        @attributes.fetch_value(name)
+      end
+
+      # Handle *= for method_missing.
+      def attribute=(attribute_name, value)
+        write_attribute(attribute_name, value)
+      end
+  end
+
+  module AttributeMethods #:nodoc:
+    AttrNames = Module.new {
+      def self.set_name_cache(name, value)
+        const_name = "ATTR_#{name}"
+        unless const_defined? const_name
+          const_set const_name, value.dup.freeze
+        end
+      end
+    }
+  end
+end
diff --git a/activemodel/lib/active_model/callbacks.rb b/activemodel/lib/active_model/callbacks.rb
index 5768eec7f5..8fa9680cb1 100644
--- a/activemodel/lib/active_model/callbacks.rb
+++ b/activemodel/lib/active_model/callbacks.rb
@@ -103,8 +103,8 @@ module ActiveModel
     #     end
     #   end
     #
-    # NOTE: +method_name+ passed to `define_model_callbacks` must not end with
-    # `!`, `?` or `=`.
+    # NOTE: +method_name+ passed to define_model_callbacks must not end with
+    # <tt>!</tt>, <tt>?</tt> or <tt>=</tt>.
     def define_model_callbacks(*callbacks)
       options = callbacks.extract_options!
       options = {
diff --git a/activemodel/lib/active_model/dirty.rb b/activemodel/lib/active_model/dirty.rb
index 943db0ab52..eaf8dfb223 100644
--- a/activemodel/lib/active_model/dirty.rb
+++ b/activemodel/lib/active_model/dirty.rb
@@ -2,6 +2,7 @@
 
 require "active_support/hash_with_indifferent_access"
 require "active_support/core_ext/object/duplicable"
+require "active_model/attribute_mutation_tracker"
 
 module ActiveModel
   # == Active \Model \Dirty
@@ -130,6 +131,26 @@ module ActiveModel
       attribute_method_affix prefix: "restore_", suffix: "!"
     end
 
+    def initialize_dup(other) # :nodoc:
+      super
+      if self.class.respond_to?(:_default_attributes)
+        @attributes = self.class._default_attributes.map do |attr|
+          attr.with_value_from_user(@attributes.fetch_value(attr.name))
+        end
+      end
+      @mutations_from_database = nil
+    end
+
+    def changes_applied # :nodoc:
+      unless defined?(@attributes)
+        @previously_changed = changes
+      end
+      @mutations_before_last_save = mutations_from_database
+      @attributes_changed_by_setter = ActiveSupport::HashWithIndifferentAccess.new
+      forget_attribute_assignments
+      @mutations_from_database = nil
+    end
+
     # Returns +true+ if any of the attributes have unsaved changes, +false+ otherwise.
     #
     #   person.changed? # => false
@@ -148,6 +169,60 @@ module ActiveModel
       changed_attributes.keys
     end
 
+    # Handles <tt>*_changed?</tt> for +method_missing+.
+    def attribute_changed?(attr, from: OPTION_NOT_GIVEN, to: OPTION_NOT_GIVEN) # :nodoc:
+      !!changes_include?(attr) &&
+        (to == OPTION_NOT_GIVEN || to == _read_attribute(attr)) &&
+        (from == OPTION_NOT_GIVEN || from == changed_attributes[attr])
+    end
+
+    # Handles <tt>*_was</tt> for +method_missing+.
+    def attribute_was(attr) # :nodoc:
+      attribute_changed?(attr) ? changed_attributes[attr] : _read_attribute(attr)
+    end
+
+    # Handles <tt>*_previously_changed?</tt> for +method_missing+.
+    def attribute_previously_changed?(attr) #:nodoc:
+      previous_changes_include?(attr)
+    end
+
+    # Restore all previous data of the provided attributes.
+    def restore_attributes(attributes = changed)
+      attributes.each { |attr| restore_attribute! attr }
+    end
+
+    # Clears all dirty data: current changes and previous changes.
+    def clear_changes_information
+      @previously_changed = ActiveSupport::HashWithIndifferentAccess.new
+      @mutations_before_last_save = nil
+      @attributes_changed_by_setter = ActiveSupport::HashWithIndifferentAccess.new
+      forget_attribute_assignments
+      @mutations_from_database = nil
+    end
+
+    def clear_attribute_changes(attr_names)
+      attributes_changed_by_setter.except!(*attr_names)
+      attr_names.each do |attr_name|
+        clear_attribute_change(attr_name)
+      end
+    end
+
+    # Returns a hash of the attributes with unsaved changes indicating their original
+    # values like <tt>attr => original value</tt>.
+    #
+    #   person.name # => "bob"
+    #   person.name = 'robert'
+    #   person.changed_attributes # => {"name" => "bob"}
+    def changed_attributes
+      # This should only be set by methods which will call changed_attributes
+      # multiple times when it is known that the computed value cannot change.
+      if defined?(@cached_changed_attributes)
+        @cached_changed_attributes
+      else
+        attributes_changed_by_setter.reverse_merge(mutations_from_database.changed_values).freeze
+      end
+    end
+
     # Returns a hash of changed attributes indicating their original
     # and new values like <tt>attr => [original value, new value]</tt>.
     #
@@ -155,7 +230,9 @@ module ActiveModel
     #   person.name = 'bob'
     #   person.changes # => { "name" => ["bill", "bob"] }
     def changes
-      ActiveSupport::HashWithIndifferentAccess[changed.map { |attr| [attr, attribute_change(attr)] }]
+      cache_changed_attributes do
+        ActiveSupport::HashWithIndifferentAccess[changed.map { |attr| [attr, attribute_change(attr)] }]
+      end
     end
 
     # Returns a hash of attributes that were changed before the model was saved.
@@ -166,45 +243,51 @@ module ActiveModel
     #   person.previous_changes # => {"name" => ["bob", "robert"]}
     def previous_changes
       @previously_changed ||= ActiveSupport::HashWithIndifferentAccess.new
+      @previously_changed.merge(mutations_before_last_save.changes)
     end
 
-    # Returns a hash of the attributes with unsaved changes indicating their original
-    # values like <tt>attr => original value</tt>.
-    #
-    #   person.name # => "bob"
-    #   person.name = 'robert'
-    #   person.changed_attributes # => {"name" => "bob"}
-    def changed_attributes
-      @changed_attributes ||= ActiveSupport::HashWithIndifferentAccess.new
+    def attribute_changed_in_place?(attr_name) # :nodoc:
+      mutations_from_database.changed_in_place?(attr_name)
     end
 
-    # Handles <tt>*_changed?</tt> for +method_missing+.
-    def attribute_changed?(attr, from: OPTION_NOT_GIVEN, to: OPTION_NOT_GIVEN) # :nodoc:
-      !!changes_include?(attr) &&
-        (to == OPTION_NOT_GIVEN || to == _read_attribute(attr)) &&
-        (from == OPTION_NOT_GIVEN || from == changed_attributes[attr])
-    end
+    private
+      def clear_attribute_change(attr_name)
+        mutations_from_database.forget_change(attr_name)
+      end
 
-    # Handles <tt>*_was</tt> for +method_missing+.
-    def attribute_was(attr) # :nodoc:
-      attribute_changed?(attr) ? changed_attributes[attr] : _read_attribute(attr)
-    end
+      def mutations_from_database
+        unless defined?(@mutations_from_database)
+          @mutations_from_database = nil
+        end
+        @mutations_from_database ||= if defined?(@attributes)
+          ActiveModel::AttributeMutationTracker.new(@attributes)
+        else
+          NullMutationTracker.instance
+        end
+      end
 
-    # Handles <tt>*_previously_changed?</tt> for +method_missing+.
-    def attribute_previously_changed?(attr) #:nodoc:
-      previous_changes_include?(attr)
-    end
+      def forget_attribute_assignments
+        @attributes = @attributes.map(&:forgetting_assignment) if defined?(@attributes)
+      end
 
-    # Restore all previous data of the provided attributes.
-    def restore_attributes(attributes = changed)
-      attributes.each { |attr| restore_attribute! attr }
-    end
+      def mutations_before_last_save
+        @mutations_before_last_save ||= ActiveModel::NullMutationTracker.instance
+      end
 
-    private
+      def cache_changed_attributes
+        @cached_changed_attributes = changed_attributes
+        yield
+      ensure
+        clear_changed_attributes_cache
+      end
+
+      def clear_changed_attributes_cache
+        remove_instance_variable(:@cached_changed_attributes) if defined?(@cached_changed_attributes)
+      end
 
       # Returns +true+ if attr_name is changed, +false+ otherwise.
       def changes_include?(attr_name)
-        attributes_changed_by_setter.include?(attr_name)
+        attributes_changed_by_setter.include?(attr_name) || mutations_from_database.changed?(attr_name)
       end
       alias attribute_changed_by_setter? changes_include?
 
@@ -214,18 +297,6 @@ module ActiveModel
         previous_changes.include?(attr_name)
       end
 
-      # Removes current changes and makes them accessible through +previous_changes+.
-      def changes_applied # :doc:
-        @previously_changed = changes
-        @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
-      end
-
-      # Clears all dirty data: current changes and previous changes.
-      def clear_changes_information # :doc:
-        @previously_changed = ActiveSupport::HashWithIndifferentAccess.new
-        @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
-      end
-
       # Handles <tt>*_change</tt> for +method_missing+.
       def attribute_change(attr)
         [changed_attributes[attr], _read_attribute(attr)] if attribute_changed?(attr)
@@ -238,15 +309,16 @@ module ActiveModel
 
       # Handles <tt>*_will_change!</tt> for +method_missing+.
       def attribute_will_change!(attr)
-        return if attribute_changed?(attr)
+        unless attribute_changed?(attr)
+          begin
+            value = _read_attribute(attr)
+            value = value.duplicable? ? value.clone : value
+          rescue TypeError, NoMethodError
+          end
 
-        begin
-          value = _read_attribute(attr)
-          value = value.duplicable? ? value.clone : value
-        rescue TypeError, NoMethodError
+          set_attribute_was(attr, value)
         end
-
-        set_attribute_was(attr, value)
+        mutations_from_database.force_change(attr)
       end
 
       # Handles <tt>restore_*!</tt> for +method_missing+.
@@ -257,18 +329,13 @@ module ActiveModel
         end
       end
 
-      # This is necessary because `changed_attributes` might be overridden in
-      # other implementations (e.g. in `ActiveRecord`)
-      alias_method :attributes_changed_by_setter, :changed_attributes # :nodoc:
+      def attributes_changed_by_setter
+        @attributes_changed_by_setter ||= ActiveSupport::HashWithIndifferentAccess.new
+      end
 
       # Force an attribute to have a particular "before" value
       def set_attribute_was(attr, old_value)
         attributes_changed_by_setter[attr] = old_value
       end
-
-      # Remove changes information for the provided attributes.
-      def clear_attribute_changes(attributes) # :doc:
-        attributes_changed_by_setter.except!(*attributes)
-      end
   end
 end
diff --git a/activemodel/lib/active_model/errors.rb b/activemodel/lib/active_model/errors.rb
index 971bdd08b1..275e3f1313 100644
--- a/activemodel/lib/active_model/errors.rb
+++ b/activemodel/lib/active_model/errors.rb
@@ -322,9 +322,13 @@ module ActiveModel
     #  person.errors.added? :name, :too_long                                # => false
     #  person.errors.added? :name, "is too long"                            # => false
     def added?(attribute, message = :invalid, options = {})
-      message = message.call if message.respond_to?(:call)
-      message = normalize_message(attribute, message, options)
-      self[attribute].include? message
+      if message.is_a? Symbol
+        self.details[attribute].map { |e| e[:error] }.include? message
+      else
+        message = message.call if message.respond_to?(:call)
+        message = normalize_message(attribute, message, options)
+        self[attribute].include? message
+      end
     end
 
     # Returns all the full error messages in an array.
diff --git a/activemodel/lib/active_model/gem_version.rb b/activemodel/lib/active_model/gem_version.rb
index 39269c159c..cef5441e4a 100644
--- a/activemodel/lib/active_model/gem_version.rb
+++ b/activemodel/lib/active_model/gem_version.rb
@@ -7,8 +7,8 @@ module ActiveModel
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
     PRE   = "alpha"
 
diff --git a/activemodel/lib/active_model/lint.rb b/activemodel/lib/active_model/lint.rb
index 34d9ac6c96..b7ceabb59a 100644
--- a/activemodel/lib/active_model/lint.rb
+++ b/activemodel/lib/active_model/lint.rb
@@ -29,7 +29,7 @@ module ActiveModel
       # <tt>to_key</tt> returns an Enumerable of all (primary) key attributes
       # of the model, and is used to a generate unique DOM id for the object.
       def test_to_key
-        assert model.respond_to?(:to_key), "The model should respond to to_key"
+        assert_respond_to model, :to_key
         def model.persisted?() false end
         assert model.to_key.nil?, "to_key should return nil when `persisted?` returns false"
       end
@@ -44,7 +44,7 @@ module ActiveModel
       # tests for this behavior in lint because it doesn't make sense to force
       # any of the possible implementation strategies on the implementer.
       def test_to_param
-        assert model.respond_to?(:to_param), "The model should respond to to_param"
+        assert_respond_to model, :to_param
         def model.to_key() [1] end
         def model.persisted?() false end
         assert model.to_param.nil?, "to_param should return nil when `persisted?` returns false"
@@ -56,7 +56,7 @@ module ActiveModel
       # <tt>to_partial_path</tt> is used for looking up partials. For example,
       # a BlogPost model might return "blog_posts/blog_post".
       def test_to_partial_path
-        assert model.respond_to?(:to_partial_path), "The model should respond to to_partial_path"
+        assert_respond_to model, :to_partial_path
         assert_kind_of String, model.to_partial_path
       end
 
@@ -68,7 +68,7 @@ module ActiveModel
       # will route to the create action. If it is persisted, a form for the
       # object will route to the update action.
       def test_persisted?
-        assert model.respond_to?(:persisted?), "The model should respond to persisted?"
+        assert_respond_to model, :persisted?
         assert_boolean model.persisted?, "persisted?"
       end
 
@@ -79,14 +79,14 @@ module ActiveModel
       #
       # Check ActiveModel::Naming for more information.
       def test_model_naming
-        assert model.class.respond_to?(:model_name), "The model class should respond to model_name"
+        assert_respond_to model.class, :model_name
         model_name = model.class.model_name
-        assert model_name.respond_to?(:to_str)
-        assert model_name.human.respond_to?(:to_str)
-        assert model_name.singular.respond_to?(:to_str)
-        assert model_name.plural.respond_to?(:to_str)
+        assert_respond_to model_name, :to_str
+        assert_respond_to model_name.human, :to_str
+        assert_respond_to model_name.singular, :to_str
+        assert_respond_to model_name.plural, :to_str
 
-        assert model.respond_to?(:model_name), "The model instance should respond to model_name"
+        assert_respond_to model, :model_name
         assert_equal model.model_name, model.class.model_name
       end
 
@@ -100,13 +100,13 @@ module ActiveModel
       # If localization is used, the strings should be localized for the current
       # locale. If no error is present, the method should return an empty array.
       def test_errors_aref
-        assert model.respond_to?(:errors), "The model should respond to errors"
+        assert_respond_to model, :errors
         assert model.errors[:hello].is_a?(Array), "errors#[] should return an Array"
       end
 
       private
         def model
-          assert @model.respond_to?(:to_model), "The object should respond to to_model"
+          assert_respond_to @model, :to_model
           @model.to_model
         end
 
diff --git a/activemodel/lib/active_model/naming.rb b/activemodel/lib/active_model/naming.rb
index a09659ad77..dfccd03cd8 100644
--- a/activemodel/lib/active_model/naming.rb
+++ b/activemodel/lib/active_model/naming.rb
@@ -2,7 +2,7 @@
 
 require "active_support/core_ext/hash/except"
 require "active_support/core_ext/module/introspection"
-require "active_support/core_ext/module/remove_method"
+require "active_support/core_ext/module/redefine_method"
 
 module ActiveModel
   class Name
@@ -218,7 +218,7 @@ module ActiveModel
   # provided method below, or rolling your own is required.
   module Naming
     def self.extended(base) #:nodoc:
-      base.remove_possible_method :model_name
+      base.silence_redefinition_of_method :model_name
       base.delegate :model_name, to: :class
     end
 
diff --git a/activemodel/lib/active_model/serialization.rb b/activemodel/lib/active_model/serialization.rb
index 47cb81bee5..c4b7b32291 100644
--- a/activemodel/lib/active_model/serialization.rb
+++ b/activemodel/lib/active_model/serialization.rb
@@ -179,7 +179,7 @@ module ActiveModel
         return unless includes = options[:include]
 
         unless includes.is_a?(Hash)
-          includes = Hash[Array(includes).map { |n| n.is_a?(Hash) ? n.to_a.first : [n, {}] }]
+          includes = Hash[Array(includes).flat_map { |n| n.is_a?(Hash) ? n.to_a : [[n, {}]] }]
         end
 
         includes.each do |association, opts|
diff --git a/activemodel/lib/active_model/type.rb b/activemodel/lib/active_model/type.rb
index cb603b3d25..1d7a26fff5 100644
--- a/activemodel/lib/active_model/type.rb
+++ b/activemodel/lib/active_model/type.rb
@@ -1,21 +1,21 @@
 # frozen_string_literal: true
 
-require_relative "type/helpers"
-require_relative "type/value"
-
-require_relative "type/big_integer"
-require_relative "type/binary"
-require_relative "type/boolean"
-require_relative "type/date"
-require_relative "type/date_time"
-require_relative "type/decimal"
-require_relative "type/float"
-require_relative "type/immutable_string"
-require_relative "type/integer"
-require_relative "type/string"
-require_relative "type/time"
-
-require_relative "type/registry"
+require "active_model/type/helpers"
+require "active_model/type/value"
+
+require "active_model/type/big_integer"
+require "active_model/type/binary"
+require "active_model/type/boolean"
+require "active_model/type/date"
+require "active_model/type/date_time"
+require "active_model/type/decimal"
+require "active_model/type/float"
+require "active_model/type/immutable_string"
+require "active_model/type/integer"
+require "active_model/type/string"
+require "active_model/type/time"
+
+require "active_model/type/registry"
 
 module ActiveModel
   module Type
@@ -24,7 +24,7 @@ module ActiveModel
     class << self
       attr_accessor :registry # :nodoc:
 
-      # Add a new type to the registry, allowing it to be get through ActiveModel::Type#lookup
+      # Add a new type to the registry, allowing it to be gotten through ActiveModel::Type#lookup
       def register(type_name, klass = nil, **options, &block)
         registry.register(type_name, klass, **options, &block)
       end
@@ -32,6 +32,10 @@ module ActiveModel
       def lookup(*args, **kwargs) # :nodoc:
         registry.lookup(*args, **kwargs)
       end
+
+      def default_value # :nodoc:
+        @default_value ||= Value.new
+      end
     end
 
     register(:big_integer, Type::BigInteger)
diff --git a/activemodel/lib/active_model/type/big_integer.rb b/activemodel/lib/active_model/type/big_integer.rb
index d080fcc0f2..89e43bcc5f 100644
--- a/activemodel/lib/active_model/type/big_integer.rb
+++ b/activemodel/lib/active_model/type/big_integer.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "integer"
+require "active_model/type/integer"
 
 module ActiveModel
   module Type
diff --git a/activemodel/lib/active_model/type/binary.rb b/activemodel/lib/active_model/type/binary.rb
index dc2eca18be..76203c5a88 100644
--- a/activemodel/lib/active_model/type/binary.rb
+++ b/activemodel/lib/active_model/type/binary.rb
@@ -40,7 +40,7 @@ module ActiveModel
         alias_method :to_str, :to_s
 
         def hex
-          @value.unpack("H*")[0]
+          @value.unpack1("H*")
         end
 
         def ==(other)
diff --git a/activemodel/lib/active_model/type/date.rb b/activemodel/lib/active_model/type/date.rb
index 8cecc16d0f..8ec5deedc4 100644
--- a/activemodel/lib/active_model/type/date.rb
+++ b/activemodel/lib/active_model/type/date.rb
@@ -42,7 +42,7 @@ module ActiveModel
         end
 
         def new_date(year, mon, mday)
-          if year && year != 0
+          unless year.nil? || (year == 0 && mon == 0 && mday == 0)
             ::Date.new(year, mon, mday) rescue nil
           end
         end
diff --git a/activemodel/lib/active_model/type/helpers.rb b/activemodel/lib/active_model/type/helpers.rb
index a4e1427b64..403f0a9e6b 100644
--- a/activemodel/lib/active_model/type/helpers.rb
+++ b/activemodel/lib/active_model/type/helpers.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "helpers/accepts_multiparameter_time"
-require_relative "helpers/numeric"
-require_relative "helpers/mutable"
-require_relative "helpers/time_value"
+require "active_model/type/helpers/accepts_multiparameter_time"
+require "active_model/type/helpers/numeric"
+require "active_model/type/helpers/mutable"
+require "active_model/type/helpers/time_value"
diff --git a/activemodel/lib/active_model/type/helpers/time_value.rb b/activemodel/lib/active_model/type/helpers/time_value.rb
index 250c4021c6..cb6aa67a9d 100644
--- a/activemodel/lib/active_model/type/helpers/time_value.rb
+++ b/activemodel/lib/active_model/type/helpers/time_value.rb
@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/string/zones"
 require "active_support/core_ext/time/zones"
 
 module ActiveModel
diff --git a/activemodel/lib/active_model/type/integer.rb b/activemodel/lib/active_model/type/integer.rb
index fe396998a3..da74aaa3c5 100644
--- a/activemodel/lib/active_model/type/integer.rb
+++ b/activemodel/lib/active_model/type/integer.rb
@@ -31,13 +31,8 @@ module ActiveModel
         result
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-        attr_reader :range
-
       private
+        attr_reader :range
 
         def cast_value(value)
           case value
diff --git a/activemodel/lib/active_model/type/registry.rb b/activemodel/lib/active_model/type/registry.rb
index 7272d7b0c5..a19dc0f011 100644
--- a/activemodel/lib/active_model/type/registry.rb
+++ b/activemodel/lib/active_model/type/registry.rb
@@ -23,13 +23,8 @@ module ActiveModel
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-        attr_reader :registrations
-
       private
+        attr_reader :registrations
 
         def registration_klass
           Registration
@@ -59,10 +54,7 @@ module ActiveModel
         type_name == name
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
+      private
         attr_reader :name, :block
     end
   end
diff --git a/activemodel/lib/active_model/type/string.rb b/activemodel/lib/active_model/type/string.rb
index 6ba2c2a3d2..36f13945b1 100644
--- a/activemodel/lib/active_model/type/string.rb
+++ b/activemodel/lib/active_model/type/string.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "immutable_string"
+require "active_model/type/immutable_string"
 
 module ActiveModel
   module Type
diff --git a/activemodel/lib/active_model/type/time.rb b/activemodel/lib/active_model/type/time.rb
index ad7ba0351a..b3056b1333 100644
--- a/activemodel/lib/active_model/type/time.rb
+++ b/activemodel/lib/active_model/type/time.rb
@@ -18,6 +18,8 @@ module ActiveModel
         case value
         when ::String
           value = "2000-01-01 #{value}"
+          time_hash = ::Date._parse(value)
+          return if time_hash[:hour].nil?
         when ::Time
           value = value.change(year: 2000, day: 1, month: 1)
         end
@@ -28,14 +30,10 @@ module ActiveModel
       private
 
         def cast_value(value)
-          return value unless value.is_a?(::String)
+          return apply_seconds_precision(value) unless value.is_a?(::String)
           return if value.empty?
 
-          if value.start_with?("2000-01-01")
-            dummy_time_value = value
-          else
-            dummy_time_value = "2000-01-01 #{value}"
-          end
+          dummy_time_value = value.sub(/\A(\d\d\d\d-\d\d-\d\d |)/, "2000-01-01 ")
 
           fast_string_to_time(dummy_time_value) || begin
             time_hash = ::Date._parse(dummy_time_value)
diff --git a/activemodel/lib/active_model/validations.rb b/activemodel/lib/active_model/validations.rb
index cdf11d190f..7f14d102dd 100644
--- a/activemodel/lib/active_model/validations.rb
+++ b/activemodel/lib/active_model/validations.rb
@@ -164,14 +164,14 @@ module ActiveModel
 
         if options.key?(:on)
           options = options.dup
+          options[:on] = Array(options[:on])
           options[:if] = Array(options[:if])
           options[:if].unshift ->(o) {
-            !(Array(options[:on]) & Array(o.validation_context)).empty?
+            !(options[:on] & Array(o.validation_context)).empty?
           }
         end
 
-        args << options
-        set_callback(:validate, *args, &block)
+        set_callback(:validate, *args, options, &block)
       end
 
       # List all validators that are being used to validate the model using
diff --git a/activemodel/lib/active_model/validations/acceptance.rb b/activemodel/lib/active_model/validations/acceptance.rb
index f35e4dec7f..ea3a6b52ab 100644
--- a/activemodel/lib/active_model/validations/acceptance.rb
+++ b/activemodel/lib/active_model/validations/acceptance.rb
@@ -58,13 +58,8 @@ module ActiveModel
             klass.send(:attr_writer, *attr_writers)
           end
 
-          # TODO Change this to private once we've dropped Ruby 2.2 support.
-          # Workaround for Ruby 2.2 "private attribute?" warning.
-          protected
-
-            attr_reader :attributes
-
           private
+            attr_reader :attributes
 
             def convert_to_reader_name(method_name)
               method_name.to_s.chomp("=")
diff --git a/activemodel/lib/active_model/validations/callbacks.rb b/activemodel/lib/active_model/validations/callbacks.rb
index 4d0ab2a2fe..887d31ae2a 100644
--- a/activemodel/lib/active_model/validations/callbacks.rb
+++ b/activemodel/lib/active_model/validations/callbacks.rb
@@ -54,15 +54,18 @@ module ActiveModel
         #   person.valid? # => true
         #   person.name   # => "bob"
         def before_validation(*args, &block)
-          options = args.last
-          if options.is_a?(Hash) && options[:on]
-            options[:if] = Array(options[:if])
+          options = args.extract_options!
+
+          if options.key?(:on)
+            options = options.dup
             options[:on] = Array(options[:on])
+            options[:if] = Array(options[:if])
             options[:if].unshift ->(o) {
-              options[:on].include? o.validation_context
+              !(options[:on] & Array(o.validation_context)).empty?
             }
           end
-          set_callback(:validation, :before, *args, &block)
+
+          set_callback(:validation, :before, *args, options, &block)
         end
 
         # Defines a callback that will get called right after validation.
@@ -93,15 +96,18 @@ module ActiveModel
         #   person.status # => true
         def after_validation(*args, &block)
           options = args.extract_options!
+          options = options.dup
           options[:prepend] = true
-          options[:if] = Array(options[:if])
-          if options[:on]
+
+          if options.key?(:on)
             options[:on] = Array(options[:on])
+            options[:if] = Array(options[:if])
             options[:if].unshift ->(o) {
-              options[:on].include? o.validation_context
+              !(options[:on] & Array(o.validation_context)).empty?
             }
           end
-          set_callback(:validation, :after, *(args << options), &block)
+
+          set_callback(:validation, :after, *args, options, &block)
         end
       end
 
diff --git a/activemodel/lib/active_model/validations/clusivity.rb b/activemodel/lib/active_model/validations/clusivity.rb
index 0b9b5ce6a1..bafb8e2106 100644
--- a/activemodel/lib/active_model/validations/clusivity.rb
+++ b/activemodel/lib/active_model/validations/clusivity.rb
@@ -32,7 +32,7 @@ module ActiveModel
         @delimiter ||= options[:in] || options[:within]
       end
 
-      # In Ruby 2.2 <tt>Range#include?</tt> on non-number-or-time-ish ranges checks all
+      # After Ruby 2.2, <tt>Range#include?</tt> on non-number-or-time-ish ranges checks all
       # possible values in the range for equality, which is slower but more accurate.
       # <tt>Range#cover?</tt> uses the previous logic of comparing a value with the range
       # endpoints, which is fast but is only accurate on Numeric, Time, Date,
diff --git a/activemodel/lib/active_model/validations/confirmation.rb b/activemodel/lib/active_model/validations/confirmation.rb
index 0abec56b68..1b5d5b09ab 100644
--- a/activemodel/lib/active_model/validations/confirmation.rb
+++ b/activemodel/lib/active_model/validations/confirmation.rb
@@ -9,7 +9,7 @@ module ActiveModel
       end
 
       def validate_each(record, attribute, value)
-        if (confirmed = record.send("#{attribute}_confirmation"))
+        unless (confirmed = record.send("#{attribute}_confirmation")).nil?
           unless confirmation_value_equal?(record, attribute, value, confirmed)
             human_attribute_name = record.class.human_attribute_name(attribute)
             record.errors.add(:"#{attribute}_confirmation", :confirmation, options.except(:case_sensitive).merge!(attribute: human_attribute_name))
diff --git a/activemodel/lib/active_model/validations/exclusion.rb b/activemodel/lib/active_model/validations/exclusion.rb
index a6cbfcc813..3be7ab6ba8 100644
--- a/activemodel/lib/active_model/validations/exclusion.rb
+++ b/activemodel/lib/active_model/validations/exclusion.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "clusivity"
+require "active_model/validations/clusivity"
 
 module ActiveModel
   module Validations
diff --git a/activemodel/lib/active_model/validations/inclusion.rb b/activemodel/lib/active_model/validations/inclusion.rb
index 00e27b528a..9c12dc14c5 100644
--- a/activemodel/lib/active_model/validations/inclusion.rb
+++ b/activemodel/lib/active_model/validations/inclusion.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "clusivity"
+require "active_model/validations/clusivity"
 
 module ActiveModel
   module Validations
@@ -19,7 +19,7 @@ module ActiveModel
       # particular enumerable object.
       #
       #   class Person < ActiveRecord::Base
-      #     validates_inclusion_of :gender, in: %w( m f )
+      #     validates_inclusion_of :role, in: %w( admin contributor )
       #     validates_inclusion_of :age, in: 0..99
       #     validates_inclusion_of :format, in: %w( jpg gif png ), message: "extension %{value} is not included in the list"
       #     validates_inclusion_of :states, in: ->(person) { STATES[person.country] }
diff --git a/activemodel/lib/active_model/validations/length.rb b/activemodel/lib/active_model/validations/length.rb
index d1a4197286..d6c80b2c5d 100644
--- a/activemodel/lib/active_model/validations/length.rb
+++ b/activemodel/lib/active_model/validations/length.rb
@@ -31,8 +31,8 @@ module ActiveModel
         keys.each do |key|
           value = options[key]
 
-          unless (value.is_a?(Integer) && value >= 0) || value == Float::INFINITY
-            raise ArgumentError, ":#{key} must be a nonnegative Integer or Infinity"
+          unless (value.is_a?(Integer) && value >= 0) || value == Float::INFINITY || value.is_a?(Symbol) || value.is_a?(Proc)
+            raise ArgumentError, ":#{key} must be a nonnegative Integer, Infinity, Symbol, or Proc"
           end
         end
       end
@@ -45,6 +45,12 @@ module ActiveModel
           next unless check_value = options[key]
 
           if !value.nil? || skip_nil_check?(key)
+            case check_value
+            when Proc
+              check_value = check_value.call(record)
+            when Symbol
+              check_value = record.send(check_value)
+            end
             next if value_length.send(validity_check, check_value)
           end
 
diff --git a/activemodel/lib/active_model/validations/validates.rb b/activemodel/lib/active_model/validations/validates.rb
index 43d9f82d9f..88cca318ef 100644
--- a/activemodel/lib/active_model/validations/validates.rb
+++ b/activemodel/lib/active_model/validations/validates.rb
@@ -63,7 +63,7 @@ module ActiveModel
       # and strings in shortcut form.
       #
       #   validates :email, format: /@/
-      #   validates :gender, inclusion: %w(male female)
+      #   validates :role, inclusion: %(admin contributor)
       #   validates :password, length: 6..20
       #
       # When using shortcut form, ranges and arrays are passed to your
@@ -154,7 +154,7 @@ module ActiveModel
       # When creating custom validators, it might be useful to be able to specify
       # additional default keys. This can be done by overwriting this method.
       def _validates_default_keys
-        [:if, :unless, :on, :allow_blank, :allow_nil , :strict]
+        [:if, :unless, :on, :allow_blank, :allow_nil, :strict]
       end
 
       def _parse_validates_options(options)
diff --git a/activemodel/test/cases/attribute_assignment_test.rb b/activemodel/test/cases/attribute_assignment_test.rb
index 5ecf0a69c4..b06291f1b4 100644
--- a/activemodel/test/cases/attribute_assignment_test.rb
+++ b/activemodel/test/cases/attribute_assignment_test.rb
@@ -18,10 +18,7 @@ class AttributeAssignmentTest < ActiveModel::TestCase
       raise ErrorFromAttributeWriter
     end
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
-    protected
-
+    private
       attr_writer :metadata
   end
 
@@ -71,6 +68,14 @@ class AttributeAssignmentTest < ActiveModel::TestCase
     assert_equal "world", model.description
   end
 
+  test "simple assignment alias" do
+    model = Model.new
+
+    model.attributes = { name: "hello", description: "world" }
+    assert_equal "hello", model.name
+    assert_equal "world", model.description
+  end
+
   test "assign non-existing attribute" do
     model = Model.new
     error = assert_raises(ActiveModel::UnknownAttributeError) do
diff --git a/activemodel/test/cases/attribute_methods_test.rb b/activemodel/test/cases/attribute_methods_test.rb
index d2837ec894..0cfc6f4b6b 100644
--- a/activemodel/test/cases/attribute_methods_test.rb
+++ b/activemodel/test/cases/attribute_methods_test.rb
@@ -220,7 +220,7 @@ class AttributeMethodsTest < ActiveModel::TestCase
     ModelWithAttributes.define_attribute_methods(:foo)
     ModelWithAttributes.undefine_attribute_methods
 
-    assert !ModelWithAttributes.new.respond_to?(:foo)
+    assert_not_respond_to ModelWithAttributes.new, :foo
     assert_raises(NoMethodError) { ModelWithAttributes.new.foo }
   end
 
@@ -255,7 +255,7 @@ class AttributeMethodsTest < ActiveModel::TestCase
     m = ModelWithAttributes2.new
     m.attributes = { "private_method" => "<3", "protected_method" => "O_o" }
 
-    assert !m.respond_to?(:private_method)
+    assert_not_respond_to m, :private_method
     assert m.respond_to?(:private_method, true)
 
     c = ClassWithProtected.new
diff --git a/activerecord/test/cases/attribute_set_test.rb b/activemodel/test/cases/attribute_set_test.rb
index 8be77ed88f..b868dba743 100644
--- a/activerecord/test/cases/attribute_set_test.rb
+++ b/activemodel/test/cases/attribute_set_test.rb
@@ -1,9 +1,10 @@
 # frozen_string_literal: true
 
 require "cases/helper"
+require "active_model/attribute_set"
 
-module ActiveRecord
-  class AttributeSetTest < ActiveRecord::TestCase
+module ActiveModel
+  class AttributeSetTest < ActiveModel::TestCase
     test "building a new set from raw attributes" do
       builder = AttributeSet::Builder.new(foo: Type::Integer.new, bar: Type::Float.new)
       attributes = builder.build_from_database(foo: "1.1", bar: "2.2")
@@ -73,8 +74,8 @@ module ActiveRecord
 
       clone.freeze
 
-      assert clone.frozen?
-      assert_not attributes.frozen?
+      assert_predicate clone, :frozen?
+      assert_not_predicate attributes, :frozen?
     end
 
     test "to_hash returns a hash of the type cast values" do
@@ -104,8 +105,8 @@ module ActiveRecord
 
     test "known columns are built with uninitialized attributes" do
       attributes = attributes_with_uninitialized_key
-      assert attributes[:foo].initialized?
-      assert_not attributes[:bar].initialized?
+      assert_predicate attributes[:foo], :initialized?
+      assert_not_predicate attributes[:bar], :initialized?
     end
 
     test "uninitialized attributes are not included in the attributes hash" do
@@ -162,12 +163,13 @@ module ActiveRecord
     end
 
     test "the primary_key is always initialized" do
-      builder = AttributeSet::Builder.new({ foo: Type::Integer.new }, :foo)
+      defaults = { foo: Attribute.from_user(:foo, nil, nil) }
+      builder = AttributeSet::Builder.new({ foo: Type::Integer.new }, defaults)
       attributes = builder.build_from_database
 
       assert attributes.key?(:foo)
       assert_equal [:foo], attributes.keys
-      assert attributes[:foo].initialized?
+      assert_predicate attributes[:foo], :initialized?
     end
 
     class MyType
@@ -207,11 +209,6 @@ module ActiveRecord
       assert_equal "value from user", attributes.fetch_value(:foo)
     end
 
-    def attributes_with_uninitialized_key
-      builder = AttributeSet::Builder.new(foo: Type::Integer.new, bar: Type::Float.new)
-      builder.build_from_database(foo: "1.1")
-    end
-
     test "freezing doesn't prevent the set from materializing" do
       builder = AttributeSet::Builder.new(foo: Type::String.new)
       attributes = builder.build_from_database(foo: "1")
@@ -220,6 +217,22 @@ module ActiveRecord
       assert_equal({ foo: "1" }, attributes.to_hash)
     end
 
+    test "marshaling dump/load legacy materialized attribute hash" do
+      builder = AttributeSet::Builder.new(foo: Type::String.new)
+      attributes = builder.build_from_database(foo: "1")
+
+      attributes.instance_variable_get(:@attributes).instance_eval do
+        class << self
+          def marshal_dump
+            materialize
+          end
+        end
+      end
+
+      attributes = Marshal.load(Marshal.dump(attributes))
+      assert_equal({ foo: "1" }, attributes.to_hash)
+    end
+
     test "#accessed_attributes returns only attributes which have been read" do
       builder = AttributeSet::Builder.new(foo: Type::Value.new, bar: Type::Value.new)
       attributes = builder.build_from_database(foo: "1", bar: "2")
@@ -251,5 +264,11 @@ module ActiveRecord
       assert_equal attributes, attributes2
       assert_not_equal attributes2, attributes3
     end
+
+    private
+      def attributes_with_uninitialized_key
+        builder = AttributeSet::Builder.new(foo: Type::Integer.new, bar: Type::Float.new)
+        builder.build_from_database(foo: "1.1")
+      end
   end
 end
diff --git a/activerecord/test/cases/attribute_test.rb b/activemodel/test/cases/attribute_test.rb
index 1731e7926e..ea2b0efd11 100644
--- a/activerecord/test/cases/attribute_test.rb
+++ b/activemodel/test/cases/attribute_test.rb
@@ -2,8 +2,8 @@
 
 require "cases/helper"
 
-module ActiveRecord
-  class AttributeTest < ActiveRecord::TestCase
+module ActiveModel
+  class AttributeTest < ActiveModel::TestCase
     setup do
       @type = Minitest::Mock.new
     end
@@ -175,33 +175,33 @@ module ActiveRecord
 
     test "an attribute has not been read by default" do
       attribute = Attribute.from_database(:foo, 1, Type::Value.new)
-      assert_not attribute.has_been_read?
+      assert_not_predicate attribute, :has_been_read?
     end
 
     test "an attribute has been read when its value is calculated" do
       attribute = Attribute.from_database(:foo, 1, Type::Value.new)
       attribute.value
-      assert attribute.has_been_read?
+      assert_predicate attribute, :has_been_read?
     end
 
     test "an attribute is not changed if it hasn't been assigned or mutated" do
       attribute = Attribute.from_database(:foo, 1, Type::Value.new)
 
-      refute attribute.changed?
+      assert_not_predicate attribute, :changed?
     end
 
     test "an attribute is changed if it's been assigned a new value" do
       attribute = Attribute.from_database(:foo, 1, Type::Value.new)
       changed = attribute.with_value_from_user(2)
 
-      assert changed.changed?
+      assert_predicate changed, :changed?
     end
 
     test "an attribute is not changed if it's assigned the same value" do
       attribute = Attribute.from_database(:foo, 1, Type::Value.new)
       unchanged = attribute.with_value_from_user(1)
 
-      refute unchanged.changed?
+      assert_not_predicate unchanged, :changed?
     end
 
     test "an attribute can not be mutated if it has not been read,
@@ -209,15 +209,15 @@ module ActiveRecord
       type_which_raises_from_all_methods = Object.new
       attribute = Attribute.from_database(:foo, "bar", type_which_raises_from_all_methods)
 
-      assert_not attribute.changed_in_place?
+      assert_not_predicate attribute, :changed_in_place?
     end
 
     test "an attribute is changed if it has been mutated" do
       attribute = Attribute.from_database(:foo, "bar", Type::String.new)
       attribute.value << "!"
 
-      assert attribute.changed_in_place?
-      assert attribute.changed?
+      assert_predicate attribute, :changed_in_place?
+      assert_predicate attribute, :changed?
     end
 
     test "an attribute can forget its changes" do
@@ -226,7 +226,7 @@ module ActiveRecord
       forgotten = changed.forgetting_assignment
 
       assert changed.changed? # sanity check
-      refute forgotten.changed?
+      assert_not_predicate forgotten, :changed?
     end
 
     test "with_value_from_user validates the value" do
diff --git a/activemodel/test/cases/attributes_dirty_test.rb b/activemodel/test/cases/attributes_dirty_test.rb
new file mode 100644
index 0000000000..f9693a23cd
--- /dev/null
+++ b/activemodel/test/cases/attributes_dirty_test.rb
@@ -0,0 +1,205 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+
+class AttributesDirtyTest < ActiveModel::TestCase
+  class DirtyModel
+    include ActiveModel::Model
+    include ActiveModel::Attributes
+    include ActiveModel::Dirty
+    attribute :name, :string
+    attribute :color, :string
+    attribute :size, :integer
+
+    def save
+      changes_applied
+    end
+
+    def reload
+      clear_changes_information
+    end
+  end
+
+  setup do
+    @model = DirtyModel.new
+  end
+
+  test "setting attribute will result in change" do
+    assert_not_predicate @model, :changed?
+    assert_not_predicate @model, :name_changed?
+    @model.name = "Ringo"
+    assert_predicate @model, :changed?
+    assert_predicate @model, :name_changed?
+  end
+
+  test "list of changed attribute keys" do
+    assert_equal [], @model.changed
+    @model.name = "Paul"
+    assert_equal ["name"], @model.changed
+  end
+
+  test "changes to attribute values" do
+    assert_not @model.changes["name"]
+    @model.name = "John"
+    assert_equal [nil, "John"], @model.changes["name"]
+  end
+
+  test "checking if an attribute has changed to a particular value" do
+    @model.name = "Ringo"
+    assert @model.name_changed?(from: nil, to: "Ringo")
+    assert_not @model.name_changed?(from: "Pete", to: "Ringo")
+    assert @model.name_changed?(to: "Ringo")
+    assert_not @model.name_changed?(to: "Pete")
+    assert @model.name_changed?(from: nil)
+    assert_not @model.name_changed?(from: "Pete")
+  end
+
+  test "changes accessible through both strings and symbols" do
+    @model.name = "David"
+    assert_not_nil @model.changes[:name]
+    assert_not_nil @model.changes["name"]
+  end
+
+  test "be consistent with symbols arguments after the changes are applied" do
+    @model.name = "David"
+    assert @model.attribute_changed?(:name)
+    @model.save
+    @model.name = "Rafael"
+    assert @model.attribute_changed?(:name)
+  end
+
+  test "attribute mutation" do
+    @model.name = "Yam"
+    @model.save
+    assert_not_predicate @model, :name_changed?
+    @model.name.replace("Hadad")
+    assert_predicate @model, :name_changed?
+  end
+
+  test "resetting attribute" do
+    @model.name = "Bob"
+    @model.restore_name!
+    assert_nil @model.name
+    assert_not_predicate @model, :name_changed?
+  end
+
+  test "setting color to same value should not result in change being recorded" do
+    @model.color = "red"
+    assert_predicate @model, :color_changed?
+    @model.save
+    assert_not_predicate @model, :color_changed?
+    assert_not_predicate @model, :changed?
+    @model.color = "red"
+    assert_not_predicate @model, :color_changed?
+    assert_not_predicate @model, :changed?
+  end
+
+  test "saving should reset model's changed status" do
+    @model.name = "Alf"
+    assert_predicate @model, :changed?
+    @model.save
+    assert_not_predicate @model, :changed?
+    assert_not_predicate @model, :name_changed?
+  end
+
+  test "saving should preserve previous changes" do
+    @model.name = "Jericho Cane"
+    @model.save
+    assert_equal [nil, "Jericho Cane"], @model.previous_changes["name"]
+  end
+
+  test "setting new attributes should not affect previous changes" do
+    @model.name = "Jericho Cane"
+    @model.save
+    @model.name = "DudeFella ManGuy"
+    assert_equal [nil, "Jericho Cane"], @model.name_previous_change
+  end
+
+  test "saving should preserve model's previous changed status" do
+    @model.name = "Jericho Cane"
+    @model.save
+    assert_predicate @model, :name_previously_changed?
+  end
+
+  test "previous value is preserved when changed after save" do
+    assert_equal({}, @model.changed_attributes)
+    @model.name = "Paul"
+    assert_equal({ "name" => nil }, @model.changed_attributes)
+
+    @model.save
+
+    @model.name = "John"
+    assert_equal({ "name" => "Paul" }, @model.changed_attributes)
+  end
+
+  test "changing the same attribute multiple times retains the correct original value" do
+    @model.name = "Otto"
+    @model.save
+    @model.name = "DudeFella ManGuy"
+    @model.name = "Mr. Manfredgensonton"
+    assert_equal ["Otto", "Mr. Manfredgensonton"], @model.name_change
+    assert_equal @model.name_was, "Otto"
+  end
+
+  test "using attribute_will_change! with a symbol" do
+    @model.size = 1
+    assert_predicate @model, :size_changed?
+  end
+
+  test "reload should reset all changes" do
+    @model.name = "Dmitry"
+    @model.name_changed?
+    @model.save
+    @model.name = "Bob"
+
+    assert_equal [nil, "Dmitry"], @model.previous_changes["name"]
+    assert_equal "Dmitry", @model.changed_attributes["name"]
+
+    @model.reload
+
+    assert_equal ActiveSupport::HashWithIndifferentAccess.new, @model.previous_changes
+    assert_equal ActiveSupport::HashWithIndifferentAccess.new, @model.changed_attributes
+  end
+
+  test "restore_attributes should restore all previous data" do
+    @model.name = "Dmitry"
+    @model.color = "Red"
+    @model.save
+    @model.name = "Bob"
+    @model.color = "White"
+
+    @model.restore_attributes
+
+    assert_not_predicate @model, :changed?
+    assert_equal "Dmitry", @model.name
+    assert_equal "Red", @model.color
+  end
+
+  test "restore_attributes can restore only some attributes" do
+    @model.name = "Dmitry"
+    @model.color = "Red"
+    @model.save
+    @model.name = "Bob"
+    @model.color = "White"
+
+    @model.restore_attributes(["name"])
+
+    assert_predicate @model, :changed?
+    assert_equal "Dmitry", @model.name
+    assert_equal "White", @model.color
+  end
+
+  test "changing the attribute reports a change only when the cast value changes" do
+    @model.size = "2.3"
+    @model.save
+    @model.size = "2.1"
+
+    assert_equal false, @model.changed?
+
+    @model.size = "5.1"
+
+    assert_equal true, @model.changed?
+    assert_equal true, @model.size_changed?
+    assert_equal({ "size" => [2, 5] }, @model.changes)
+  end
+end
diff --git a/activemodel/test/cases/attributes_test.rb b/activemodel/test/cases/attributes_test.rb
new file mode 100644
index 0000000000..5483fb101d
--- /dev/null
+++ b/activemodel/test/cases/attributes_test.rb
@@ -0,0 +1,97 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+
+module ActiveModel
+  class AttributesTest < ActiveModel::TestCase
+    class ModelForAttributesTest
+      include ActiveModel::Model
+      include ActiveModel::Attributes
+
+      attribute :integer_field, :integer
+      attribute :string_field, :string
+      attribute :decimal_field, :decimal
+      attribute :string_with_default, :string, default: "default string"
+      attribute :date_field, :date, default: -> { Date.new(2016, 1, 1) }
+      attribute :boolean_field, :boolean
+    end
+
+    class ChildModelForAttributesTest < ModelForAttributesTest
+    end
+
+    class GrandchildModelForAttributesTest < ChildModelForAttributesTest
+      attribute :integer_field, :string
+    end
+
+    test "properties assignment" do
+      data = ModelForAttributesTest.new(
+        integer_field: "2.3",
+        string_field: "Rails FTW",
+        decimal_field: "12.3",
+        boolean_field: "0"
+      )
+
+      assert_equal 2, data.integer_field
+      assert_equal "Rails FTW", data.string_field
+      assert_equal BigDecimal("12.3"), data.decimal_field
+      assert_equal "default string", data.string_with_default
+      assert_equal Date.new(2016, 1, 1), data.date_field
+      assert_equal false, data.boolean_field
+
+      data.integer_field = 10
+      data.string_with_default = nil
+      data.boolean_field = "1"
+
+      assert_equal 10, data.integer_field
+      assert_nil data.string_with_default
+      assert_equal true, data.boolean_field
+    end
+
+    test "reading attributes" do
+      data = ModelForAttributesTest.new(
+        integer_field: 1.1,
+        string_field: 1.1,
+        decimal_field: 1.1,
+        boolean_field: 1.1
+      )
+
+      expected_attributes = {
+        integer_field: 1,
+        string_field: "1.1",
+        decimal_field: BigDecimal("1.1"),
+        string_with_default: "default string",
+        date_field: Date.new(2016, 1, 1),
+        boolean_field: true
+      }.stringify_keys
+
+      assert_equal expected_attributes, data.attributes
+    end
+
+    test "nonexistent attribute" do
+      assert_raise ActiveModel::UnknownAttributeError do
+        ModelForAttributesTest.new(nonexistent: "nonexistent")
+      end
+    end
+
+    test "children inherit attributes" do
+      data = ChildModelForAttributesTest.new(integer_field: "4.4")
+
+      assert_equal 4, data.integer_field
+    end
+
+    test "children can override parents" do
+      data = GrandchildModelForAttributesTest.new(integer_field: "4.4")
+
+      assert_equal "4.4", data.integer_field
+    end
+
+    test "attributes with proc defaults can be marshalled" do
+      data = ModelForAttributesTest.new
+      attributes = data.instance_variable_get(:@attributes)
+      round_tripped = Marshal.load(Marshal.dump(data))
+      new_attributes = round_tripped.instance_variable_get(:@attributes)
+
+      assert_equal attributes, new_attributes
+    end
+  end
+end
diff --git a/activemodel/test/cases/callbacks_test.rb b/activemodel/test/cases/callbacks_test.rb
index a5d29d0f22..1ec12d8222 100644
--- a/activemodel/test/cases/callbacks_test.rb
+++ b/activemodel/test/cases/callbacks_test.rb
@@ -85,21 +85,21 @@ class CallbacksTest < ActiveModel::TestCase
   end
 
   test "only selects which types of callbacks should be created" do
-    assert !ModelCallbacks.respond_to?(:before_initialize)
-    assert !ModelCallbacks.respond_to?(:around_initialize)
+    assert_not_respond_to ModelCallbacks, :before_initialize
+    assert_not_respond_to ModelCallbacks, :around_initialize
     assert_respond_to ModelCallbacks, :after_initialize
   end
 
   test "only selects which types of callbacks should be created from an array list" do
     assert_respond_to ModelCallbacks, :before_multiple
     assert_respond_to ModelCallbacks, :around_multiple
-    assert !ModelCallbacks.respond_to?(:after_multiple)
+    assert_not_respond_to ModelCallbacks, :after_multiple
   end
 
   test "no callbacks should be created" do
-    assert !ModelCallbacks.respond_to?(:before_empty)
-    assert !ModelCallbacks.respond_to?(:around_empty)
-    assert !ModelCallbacks.respond_to?(:after_empty)
+    assert_not_respond_to ModelCallbacks, :before_empty
+    assert_not_respond_to ModelCallbacks, :around_empty
+    assert_not_respond_to ModelCallbacks, :after_empty
   end
 
   class Violin
diff --git a/activemodel/test/cases/dirty_test.rb b/activemodel/test/cases/dirty_test.rb
index 2cd9e185e6..b120e68027 100644
--- a/activemodel/test/cases/dirty_test.rb
+++ b/activemodel/test/cases/dirty_test.rb
@@ -5,12 +5,13 @@ require "cases/helper"
 class DirtyTest < ActiveModel::TestCase
   class DirtyModel
     include ActiveModel::Dirty
-    define_attribute_methods :name, :color, :size
+    define_attribute_methods :name, :color, :size, :status
 
     def initialize
       @name = nil
       @color = nil
       @size = nil
+      @status = "initialized"
     end
 
     def name
@@ -40,6 +41,15 @@ class DirtyTest < ActiveModel::TestCase
       @size = val
     end
 
+    def status
+      @status
+    end
+
+    def status=(val)
+      status_will_change! unless val == @status
+      @status = val
+    end
+
     def save
       changes_applied
     end
@@ -54,11 +64,11 @@ class DirtyTest < ActiveModel::TestCase
   end
 
   test "setting attribute will result in change" do
-    assert !@model.changed?
-    assert !@model.name_changed?
+    assert_not_predicate @model, :changed?
+    assert_not_predicate @model, :name_changed?
     @model.name = "Ringo"
-    assert @model.changed?
-    assert @model.name_changed?
+    assert_predicate @model, :changed?
+    assert_predicate @model, :name_changed?
   end
 
   test "list of changed attribute keys" do
@@ -68,7 +78,7 @@ class DirtyTest < ActiveModel::TestCase
   end
 
   test "changes to attribute values" do
-    assert !@model.changes["name"]
+    assert_not @model.changes["name"]
     @model.name = "John"
     assert_equal [nil, "John"], @model.changes["name"]
   end
@@ -99,82 +109,93 @@ class DirtyTest < ActiveModel::TestCase
 
   test "attribute mutation" do
     @model.instance_variable_set("@name", "Yam".dup)
-    assert !@model.name_changed?
+    assert_not_predicate @model, :name_changed?
     @model.name.replace("Hadad")
-    assert !@model.name_changed?
+    assert_not_predicate @model, :name_changed?
     @model.name_will_change!
     @model.name.replace("Baal")
-    assert @model.name_changed?
+    assert_predicate @model, :name_changed?
   end
 
   test "resetting attribute" do
     @model.name = "Bob"
     @model.restore_name!
     assert_nil @model.name
-    assert !@model.name_changed?
+    assert_not_predicate @model, :name_changed?
   end
 
   test "setting color to same value should not result in change being recorded" do
     @model.color = "red"
-    assert @model.color_changed?
+    assert_predicate @model, :color_changed?
     @model.save
-    assert !@model.color_changed?
-    assert !@model.changed?
+    assert_not_predicate @model, :color_changed?
+    assert_not_predicate @model, :changed?
     @model.color = "red"
-    assert !@model.color_changed?
-    assert !@model.changed?
+    assert_not_predicate @model, :color_changed?
+    assert_not_predicate @model, :changed?
   end
 
   test "saving should reset model's changed status" do
     @model.name = "Alf"
-    assert @model.changed?
+    assert_predicate @model, :changed?
     @model.save
-    assert !@model.changed?
-    assert !@model.name_changed?
+    assert_not_predicate @model, :changed?
+    assert_not_predicate @model, :name_changed?
   end
 
   test "saving should preserve previous changes" do
     @model.name = "Jericho Cane"
+    @model.status = "waiting"
     @model.save
     assert_equal [nil, "Jericho Cane"], @model.previous_changes["name"]
+    assert_equal ["initialized", "waiting"], @model.previous_changes["status"]
   end
 
   test "setting new attributes should not affect previous changes" do
     @model.name = "Jericho Cane"
+    @model.status = "waiting"
     @model.save
     @model.name = "DudeFella ManGuy"
+    @model.status = "finished"
     assert_equal [nil, "Jericho Cane"], @model.name_previous_change
+    assert_equal ["initialized", "waiting"], @model.previous_changes["status"]
   end
 
   test "saving should preserve model's previous changed status" do
     @model.name = "Jericho Cane"
     @model.save
-    assert @model.name_previously_changed?
+    assert_predicate @model, :name_previously_changed?
   end
 
   test "previous value is preserved when changed after save" do
     assert_equal({}, @model.changed_attributes)
     @model.name = "Paul"
-    assert_equal({ "name" => nil }, @model.changed_attributes)
+    @model.status = "waiting"
+    assert_equal({ "name" => nil, "status" => "initialized" }, @model.changed_attributes)
 
     @model.save
 
     @model.name = "John"
-    assert_equal({ "name" => "Paul" }, @model.changed_attributes)
+    @model.status = "finished"
+    assert_equal({ "name" => "Paul", "status" => "waiting" }, @model.changed_attributes)
   end
 
   test "changing the same attribute multiple times retains the correct original value" do
     @model.name = "Otto"
+    @model.status = "waiting"
     @model.save
     @model.name = "DudeFella ManGuy"
     @model.name = "Mr. Manfredgensonton"
+    @model.status = "processing"
+    @model.status = "finished"
     assert_equal ["Otto", "Mr. Manfredgensonton"], @model.name_change
+    assert_equal ["waiting", "finished"], @model.status_change
     assert_equal @model.name_was, "Otto"
   end
 
   test "using attribute_will_change! with a symbol" do
     @model.size = 1
-    assert @model.size_changed?
+    assert_predicate @model, :size_changed?
   end
 
   test "reload should reset all changes" do
@@ -201,7 +222,7 @@ class DirtyTest < ActiveModel::TestCase
 
     @model.restore_attributes
 
-    assert_not @model.changed?
+    assert_not_predicate @model, :changed?
     assert_equal "Dmitry", @model.name
     assert_equal "Red", @model.color
   end
@@ -215,8 +236,12 @@ class DirtyTest < ActiveModel::TestCase
 
     @model.restore_attributes(["name"])
 
-    assert @model.changed?
+    assert_predicate @model, :changed?
     assert_equal "Dmitry", @model.name
     assert_equal "White", @model.color
   end
+
+  test "model can be dup-ed without Attributes" do
+    assert @model.dup
+  end
 end
diff --git a/activemodel/test/cases/errors_test.rb b/activemodel/test/cases/errors_test.rb
index ab18af0de1..6ff3be1308 100644
--- a/activemodel/test/cases/errors_test.rb
+++ b/activemodel/test/cases/errors_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_support/core_ext/string/strip"
 require "yaml"
 
 class ErrorsTest < ActiveModel::TestCase
@@ -83,7 +82,7 @@ class ErrorsTest < ActiveModel::TestCase
 
     assert_equal 1, person.errors.count
     person.errors.clear
-    assert person.errors.empty?
+    assert_empty person.errors
   end
 
   test "error access is indifferent" do
@@ -128,8 +127,8 @@ class ErrorsTest < ActiveModel::TestCase
   test "detecting whether there are errors with empty?, blank?, include?" do
     person = Person.new
     person.errors[:foo]
-    assert person.errors.empty?
-    assert person.errors.blank?
+    assert_empty person.errors
+    assert_predicate person.errors, :blank?
     assert_not_includes person.errors, :foo
   end
 
@@ -208,19 +207,26 @@ class ErrorsTest < ActiveModel::TestCase
 
   test "added? returns false when no errors are present" do
     person = Person.new
-    assert !person.errors.added?(:name)
+    assert_not person.errors.added?(:name)
   end
 
   test "added? returns false when checking a nonexisting error and other errors are present for the given attribute" do
     person = Person.new
     person.errors.add(:name, "is invalid")
-    assert !person.errors.added?(:name, "cannot be blank")
+    assert_not person.errors.added?(:name, "cannot be blank")
   end
 
   test "added? returns false when checking for an error, but not providing message arguments" do
     person = Person.new
     person.errors.add(:name, "cannot be blank")
-    assert !person.errors.added?(:name)
+    assert_not person.errors.added?(:name)
+  end
+
+  test "added? returns false when checking for an error by symbol and a different error with same message is present" do
+    I18n.backend.store_translations("en", errors: { attributes: { name: { wrong: "is wrong", used: "is wrong" } } })
+    person = Person.new
+    person.errors.add(:name, :wrong)
+    assert_not person.errors.added?(:name, :used)
   end
 
   test "size calculates the number of error messages" do
@@ -313,7 +319,7 @@ class ErrorsTest < ActiveModel::TestCase
 
   test "generate_message works without i18n_scope" do
     person = Person.new
-    assert !Person.respond_to?(:i18n_scope)
+    assert_not_respond_to Person, :i18n_scope
     assert_nothing_raised {
       person.errors.generate_message(:name, :blank)
     }
@@ -364,7 +370,7 @@ class ErrorsTest < ActiveModel::TestCase
 
     assert_equal 1, person.errors.details.count
     person.errors.clear
-    assert person.errors.details.empty?
+    assert_empty person.errors.details
   end
 
   test "copy errors" do
@@ -399,7 +405,7 @@ class ErrorsTest < ActiveModel::TestCase
   end
 
   test "errors are backward compatible with the Rails 4.2 format" do
-    yaml = <<-CODE.strip_heredoc
+    yaml = <<~CODE
     --- !ruby/object:ActiveModel::Errors
     base: &1 !ruby/object:ErrorsTest::Person
       errors: !ruby/object:ActiveModel::Errors
diff --git a/activemodel/test/cases/naming_test.rb b/activemodel/test/cases/naming_test.rb
index 009f1f47af..4693da434c 100644
--- a/activemodel/test/cases/naming_test.rb
+++ b/activemodel/test/cases/naming_test.rb
@@ -248,7 +248,7 @@ class NamingHelpersTest < ActiveModel::TestCase
 
   def test_uncountable
     assert uncountable?(@uncountable), "Expected 'sheep' to be uncountable"
-    assert !uncountable?(@klass), "Expected 'contact' to be countable"
+    assert_not uncountable?(@klass), "Expected 'contact' to be countable"
   end
 
   def test_uncountable_route_key
diff --git a/activemodel/test/cases/secure_password_test.rb b/activemodel/test/cases/secure_password_test.rb
index d19e81a119..c347aa9b24 100644
--- a/activemodel/test/cases/secure_password_test.rb
+++ b/activemodel/test/cases/secure_password_test.rb
@@ -49,14 +49,14 @@ class SecurePasswordTest < ActiveModel::TestCase
 
   test "create a new user with validation and a blank password" do
     @user.password = ""
-    assert !@user.valid?(:create), "user should be invalid"
+    assert_not @user.valid?(:create), "user should be invalid"
     assert_equal 1, @user.errors.count
     assert_equal ["can't be blank"], @user.errors[:password]
   end
 
   test "create a new user with validation and a nil password" do
     @user.password = nil
-    assert !@user.valid?(:create), "user should be invalid"
+    assert_not @user.valid?(:create), "user should be invalid"
     assert_equal 1, @user.errors.count
     assert_equal ["can't be blank"], @user.errors[:password]
   end
@@ -64,7 +64,7 @@ class SecurePasswordTest < ActiveModel::TestCase
   test "create a new user with validation and password length greater than 72" do
     @user.password = "a" * 73
     @user.password_confirmation = "a" * 73
-    assert !@user.valid?(:create), "user should be invalid"
+    assert_not @user.valid?(:create), "user should be invalid"
     assert_equal 1, @user.errors.count
     assert_equal ["is too long (maximum is 72 characters)"], @user.errors[:password]
   end
@@ -72,7 +72,7 @@ class SecurePasswordTest < ActiveModel::TestCase
   test "create a new user with validation and a blank password confirmation" do
     @user.password = "password"
     @user.password_confirmation = ""
-    assert !@user.valid?(:create), "user should be invalid"
+    assert_not @user.valid?(:create), "user should be invalid"
     assert_equal 1, @user.errors.count
     assert_equal ["doesn't match Password"], @user.errors[:password_confirmation]
   end
@@ -86,7 +86,7 @@ class SecurePasswordTest < ActiveModel::TestCase
   test "create a new user with validation and an incorrect password confirmation" do
     @user.password = "password"
     @user.password_confirmation = "something else"
-    assert !@user.valid?(:create), "user should be invalid"
+    assert_not @user.valid?(:create), "user should be invalid"
     assert_equal 1, @user.errors.count
     assert_equal ["doesn't match Password"], @user.errors[:password_confirmation]
   end
@@ -125,7 +125,7 @@ class SecurePasswordTest < ActiveModel::TestCase
 
   test "updating an existing user with validation and a nil password" do
     @existing_user.password = nil
-    assert !@existing_user.valid?(:update), "user should be invalid"
+    assert_not @existing_user.valid?(:update), "user should be invalid"
     assert_equal 1, @existing_user.errors.count
     assert_equal ["can't be blank"], @existing_user.errors[:password]
   end
@@ -133,7 +133,7 @@ class SecurePasswordTest < ActiveModel::TestCase
   test "updating an existing user with validation and password length greater than 72" do
     @existing_user.password = "a" * 73
     @existing_user.password_confirmation = "a" * 73
-    assert !@existing_user.valid?(:update), "user should be invalid"
+    assert_not @existing_user.valid?(:update), "user should be invalid"
     assert_equal 1, @existing_user.errors.count
     assert_equal ["is too long (maximum is 72 characters)"], @existing_user.errors[:password]
   end
@@ -141,7 +141,7 @@ class SecurePasswordTest < ActiveModel::TestCase
   test "updating an existing user with validation and a blank password confirmation" do
     @existing_user.password = "password"
     @existing_user.password_confirmation = ""
-    assert !@existing_user.valid?(:update), "user should be invalid"
+    assert_not @existing_user.valid?(:update), "user should be invalid"
     assert_equal 1, @existing_user.errors.count
     assert_equal ["doesn't match Password"], @existing_user.errors[:password_confirmation]
   end
@@ -155,21 +155,21 @@ class SecurePasswordTest < ActiveModel::TestCase
   test "updating an existing user with validation and an incorrect password confirmation" do
     @existing_user.password = "password"
     @existing_user.password_confirmation = "something else"
-    assert !@existing_user.valid?(:update), "user should be invalid"
+    assert_not @existing_user.valid?(:update), "user should be invalid"
     assert_equal 1, @existing_user.errors.count
     assert_equal ["doesn't match Password"], @existing_user.errors[:password_confirmation]
   end
 
   test "updating an existing user with validation and a blank password digest" do
     @existing_user.password_digest = ""
-    assert !@existing_user.valid?(:update), "user should be invalid"
+    assert_not @existing_user.valid?(:update), "user should be invalid"
     assert_equal 1, @existing_user.errors.count
     assert_equal ["can't be blank"], @existing_user.errors[:password]
   end
 
   test "updating an existing user with validation and a nil password digest" do
     @existing_user.password_digest = nil
-    assert !@existing_user.valid?(:update), "user should be invalid"
+    assert_not @existing_user.valid?(:update), "user should be invalid"
     assert_equal 1, @existing_user.errors.count
     assert_equal ["can't be blank"], @existing_user.errors[:password]
   end
@@ -187,7 +187,7 @@ class SecurePasswordTest < ActiveModel::TestCase
   test "authenticate" do
     @user.password = "secret"
 
-    assert !@user.authenticate("wrong")
+    assert_not @user.authenticate("wrong")
     assert @user.authenticate("secret")
   end
 
diff --git a/activemodel/test/cases/serialization_test.rb b/activemodel/test/cases/serialization_test.rb
index 9002982e7f..6826d2bbd1 100644
--- a/activemodel/test/cases/serialization_test.rb
+++ b/activemodel/test/cases/serialization_test.rb
@@ -174,4 +174,11 @@ class SerializationTest < ActiveModel::TestCase
                            { "name" => "Sue", "email" => "sue@example.com", "gender" => "female" }] }
     assert_equal expected, @user.serializable_hash(include: [{ address: { only: "street" } }, :friends])
   end
+
+  def test_all_includes_with_options
+    expected = { "email" => "david@example.com", "gender" => "male", "name" => "David",
+                "address" => { "street" => "123 Lane" },
+                "friends" => [{ "name" => "Joe" }, { "name" => "Sue" }] }
+    assert_equal expected, @user.serializable_hash(include: [address: { only: "street" }, friends: { only: "name" }])
+  end
 end
diff --git a/activemodel/test/cases/type/big_integer_test.rb b/activemodel/test/cases/type/big_integer_test.rb
index 3d29235d52..0fa0200df4 100644
--- a/activemodel/test/cases/type/big_integer_test.rb
+++ b/activemodel/test/cases/type/big_integer_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/binary_test.rb b/activemodel/test/cases/type/binary_test.rb
index ef4f125a3b..3221a73e49 100644
--- a/activemodel/test/cases/type/binary_test.rb
+++ b/activemodel/test/cases/type/binary_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/boolean_test.rb b/activemodel/test/cases/type/boolean_test.rb
index 97b165ab48..2de0f53640 100644
--- a/activemodel/test/cases/type/boolean_test.rb
+++ b/activemodel/test/cases/type/boolean_test.rb
@@ -1,15 +1,14 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
     class BooleanTest < ActiveModel::TestCase
       def test_type_cast_boolean
         type = Type::Boolean.new
-        assert type.cast("").nil?
-        assert type.cast(nil).nil?
+        assert_predicate type.cast(""), :nil?
+        assert_predicate type.cast(nil), :nil?
 
         assert type.cast(true)
         assert type.cast(1)
diff --git a/activemodel/test/cases/type/date_test.rb b/activemodel/test/cases/type/date_test.rb
index 15c40a37b7..e8cf178612 100644
--- a/activemodel/test/cases/type/date_test.rb
+++ b/activemodel/test/cases/type/date_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/date_time_test.rb b/activemodel/test/cases/type/date_time_test.rb
index 598ccf485e..60f62becc2 100644
--- a/activemodel/test/cases/type/date_time_test.rb
+++ b/activemodel/test/cases/type/date_time_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/decimal_test.rb b/activemodel/test/cases/type/decimal_test.rb
index a0acdc2736..c0cf6ce590 100644
--- a/activemodel/test/cases/type/decimal_test.rb
+++ b/activemodel/test/cases/type/decimal_test.rb
@@ -1,29 +1,28 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
     class DecimalTest < ActiveModel::TestCase
       def test_type_cast_decimal
         type = Decimal.new
-        assert_equal BigDecimal.new("0"), type.cast(BigDecimal.new("0"))
-        assert_equal BigDecimal.new("123"), type.cast(123.0)
-        assert_equal BigDecimal.new("1"), type.cast(:"1")
+        assert_equal BigDecimal("0"), type.cast(BigDecimal("0"))
+        assert_equal BigDecimal("123"), type.cast(123.0)
+        assert_equal BigDecimal("1"), type.cast(:"1")
       end
 
       def test_type_cast_decimal_from_invalid_string
         type = Decimal.new
         assert_nil type.cast("")
-        assert_equal BigDecimal.new("1"), type.cast("1ignore")
-        assert_equal BigDecimal.new("0"), type.cast("bad1")
-        assert_equal BigDecimal.new("0"), type.cast("bad")
+        assert_equal BigDecimal("1"), type.cast("1ignore")
+        assert_equal BigDecimal("0"), type.cast("bad1")
+        assert_equal BigDecimal("0"), type.cast("bad")
       end
 
       def test_type_cast_decimal_from_float_with_large_precision
         type = Decimal.new(precision: ::Float::DIG + 2)
-        assert_equal BigDecimal.new("123.0"), type.cast(123.0)
+        assert_equal BigDecimal("123.0"), type.cast(123.0)
       end
 
       def test_type_cast_from_float_with_unspecified_precision
@@ -49,7 +48,7 @@ module ActiveModel
       def test_type_cast_decimal_from_object_responding_to_d
         value = Object.new
         def value.to_d
-          BigDecimal.new("1")
+          BigDecimal("1")
         end
         type = Decimal.new
         assert_equal BigDecimal("1"), type.cast(value)
diff --git a/activemodel/test/cases/type/float_test.rb b/activemodel/test/cases/type/float_test.rb
index 46e8b34dfe..28318e06f8 100644
--- a/activemodel/test/cases/type/float_test.rb
+++ b/activemodel/test/cases/type/float_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/immutable_string_test.rb b/activemodel/test/cases/type/immutable_string_test.rb
index 72f5779dfb..751f753ddb 100644
--- a/activemodel/test/cases/type/immutable_string_test.rb
+++ b/activemodel/test/cases/type/immutable_string_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/integer_test.rb b/activemodel/test/cases/type/integer_test.rb
index d2e635b447..8c5d18c9b3 100644
--- a/activemodel/test/cases/type/integer_test.rb
+++ b/activemodel/test/cases/type/integer_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 require "active_support/core_ext/numeric/time"
 
 module ActiveModel
diff --git a/activemodel/test/cases/type/registry_test.rb b/activemodel/test/cases/type/registry_test.rb
index f34104286c..0633ea2538 100644
--- a/activemodel/test/cases/type/registry_test.rb
+++ b/activemodel/test/cases/type/registry_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/string_test.rb b/activemodel/test/cases/type/string_test.rb
index d39389718b..825c8bb246 100644
--- a/activemodel/test/cases/type/string_test.rb
+++ b/activemodel/test/cases/type/string_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/type/time_test.rb b/activemodel/test/cases/type/time_test.rb
index 0bea95768d..3fbae1a169 100644
--- a/activemodel/test/cases/type/time_test.rb
+++ b/activemodel/test/cases/type/time_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
@@ -18,6 +17,21 @@ module ActiveModel
         assert_equal ::Time.utc(2000,  1,  1, 16, 45, 54), type.cast("2015-06-13T19:45:54+03:00")
         assert_equal ::Time.utc(1999, 12, 31, 21,  7,  8), type.cast("06:07:08+09:00")
       end
+
+      def test_user_input_in_time_zone
+        ::Time.use_zone("Pacific Time (US & Canada)") do
+          type = Type::Time.new
+          assert_nil type.user_input_in_time_zone(nil)
+          assert_nil type.user_input_in_time_zone("")
+          assert_nil type.user_input_in_time_zone("ABC")
+
+          offset = ::Time.zone.formatted_offset
+          time_string = "2015-02-09T19:45:54#{offset}"
+
+          assert_equal 19, type.user_input_in_time_zone(time_string).hour
+          assert_equal offset, type.user_input_in_time_zone(time_string).formatted_offset
+        end
+      end
     end
   end
 end
diff --git a/activemodel/test/cases/type/value_test.rb b/activemodel/test/cases/type/value_test.rb
index 671343b0c8..55b5d9d584 100644
--- a/activemodel/test/cases/type/value_test.rb
+++ b/activemodel/test/cases/type/value_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_model/type"
 
 module ActiveModel
   module Type
diff --git a/activemodel/test/cases/validations/absence_validation_test.rb b/activemodel/test/cases/validations/absence_validation_test.rb
index 801577474a..8bc4f4723a 100644
--- a/activemodel/test/cases/validations/absence_validation_test.rb
+++ b/activemodel/test/cases/validations/absence_validation_test.rb
@@ -17,16 +17,16 @@ class AbsenceValidationTest < ActiveModel::TestCase
     t = Topic.new
     t.title = "foo"
     t.content = "bar"
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["must be blank"], t.errors[:title]
     assert_equal ["must be blank"], t.errors[:content]
     t.title = ""
     t.content = "something"
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["must be blank"], t.errors[:content]
     assert_equal [], t.errors[:title]
     t.content = ""
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_absence_of_with_array_arguments
@@ -34,7 +34,7 @@ class AbsenceValidationTest < ActiveModel::TestCase
     t = Topic.new
     t.title = "foo"
     t.content = "bar"
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["must be blank"], t.errors[:title]
     assert_equal ["must be blank"], t.errors[:content]
   end
@@ -43,7 +43,7 @@ class AbsenceValidationTest < ActiveModel::TestCase
     Person.validates_absence_of :karma, message: "This string contains 'single' and \"double\" quotes"
     p = Person.new
     p.karma = "good"
-    assert p.invalid?
+    assert_predicate p, :invalid?
     assert_equal "This string contains 'single' and \"double\" quotes", p.errors[:karma].last
   end
 
@@ -51,19 +51,19 @@ class AbsenceValidationTest < ActiveModel::TestCase
     Person.validates_absence_of :karma
     p = Person.new
     p.karma = "good"
-    assert p.invalid?
+    assert_predicate p, :invalid?
     assert_equal ["must be blank"], p.errors[:karma]
     p.karma = nil
-    assert p.valid?
+    assert_predicate p, :valid?
   end
 
   def test_validates_absence_of_for_ruby_class_with_custom_reader
     CustomReader.validates_absence_of :karma
     p = CustomReader.new
     p[:karma] = "excellent"
-    assert p.invalid?
+    assert_predicate p, :invalid?
     assert_equal ["must be blank"], p.errors[:karma]
     p[:karma] = ""
-    assert p.valid?
+    assert_predicate p, :valid?
   end
 end
diff --git a/activemodel/test/cases/validations/acceptance_validation_test.rb b/activemodel/test/cases/validations/acceptance_validation_test.rb
index c5f54b1868..7662f996ae 100644
--- a/activemodel/test/cases/validations/acceptance_validation_test.rb
+++ b/activemodel/test/cases/validations/acceptance_validation_test.rb
@@ -15,54 +15,54 @@ class AcceptanceValidationTest < ActiveModel::TestCase
     Topic.validates_acceptance_of(:terms_of_service)
 
     t = Topic.new("title" => "We should not be confirmed")
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_terms_of_service_agreement
     Topic.validates_acceptance_of(:terms_of_service)
 
     t = Topic.new("title" => "We should be confirmed", "terms_of_service" => "")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["must be accepted"], t.errors[:terms_of_service]
 
     t.terms_of_service = "1"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_eula
     Topic.validates_acceptance_of(:eula, message: "must be abided")
 
     t = Topic.new("title" => "We should be confirmed", "eula" => "")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["must be abided"], t.errors[:eula]
 
     t.eula = "1"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_terms_of_service_agreement_with_accept_value
     Topic.validates_acceptance_of(:terms_of_service, accept: "I agree.")
 
     t = Topic.new("title" => "We should be confirmed", "terms_of_service" => "")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["must be accepted"], t.errors[:terms_of_service]
 
     t.terms_of_service = "I agree."
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_terms_of_service_agreement_with_multiple_accept_values
     Topic.validates_acceptance_of(:terms_of_service, accept: [1, "I concur."])
 
     t = Topic.new("title" => "We should be confirmed", "terms_of_service" => "")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["must be accepted"], t.errors[:terms_of_service]
 
     t.terms_of_service = 1
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.terms_of_service = "I concur."
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_acceptance_of_for_ruby_class
@@ -71,11 +71,11 @@ class AcceptanceValidationTest < ActiveModel::TestCase
     p = Person.new
     p.karma = ""
 
-    assert p.invalid?
+    assert_predicate p, :invalid?
     assert_equal ["must be accepted"], p.errors[:karma]
 
     p.karma = "1"
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
@@ -83,6 +83,6 @@ class AcceptanceValidationTest < ActiveModel::TestCase
   def test_validates_acceptance_of_true
     Topic.validates_acceptance_of(:terms_of_service)
 
-    assert Topic.new(terms_of_service: true).valid?
+    assert_predicate Topic.new(terms_of_service: true), :valid?
   end
 end
diff --git a/activemodel/test/cases/validations/callbacks_test.rb b/activemodel/test/cases/validations/callbacks_test.rb
index d3a9a17a05..ff3cf61746 100644
--- a/activemodel/test/cases/validations/callbacks_test.rb
+++ b/activemodel/test/cases/validations/callbacks_test.rb
@@ -59,6 +59,18 @@ class DogValidatorWithOnCondition < Dog
   def set_after_validation_marker;  history << "after_validation_marker" ; end
 end
 
+class DogValidatorWithOnMultipleCondition < Dog
+  before_validation :set_before_validation_marker_on_context_a, on: :context_a
+  before_validation :set_before_validation_marker_on_context_b, on: :context_b
+  after_validation :set_after_validation_marker_on_context_a, on: :context_a
+  after_validation :set_after_validation_marker_on_context_b, on: :context_b
+
+  def set_before_validation_marker_on_context_a; history << "before_validation_marker on context_a"; end
+  def set_before_validation_marker_on_context_b; history << "before_validation_marker on context_b"; end
+  def set_after_validation_marker_on_context_a;  history << "after_validation_marker on context_a" ; end
+  def set_after_validation_marker_on_context_b;  history << "after_validation_marker on context_b" ; end
+end
+
 class DogValidatorWithIfCondition < Dog
   before_validation :set_before_validation_marker1, if: -> { true }
   before_validation :set_before_validation_marker2, if: -> { false }
@@ -98,6 +110,37 @@ class CallbacksWithMethodNamesShouldBeCalled < ActiveModel::TestCase
     assert_equal [], d.history
   end
 
+  def test_on_multiple_condition_is_respected_for_validation_with_matching_context
+    d = DogValidatorWithOnMultipleCondition.new
+    d.valid?(:context_a)
+    assert_equal ["before_validation_marker on context_a", "after_validation_marker on context_a"], d.history
+
+    d = DogValidatorWithOnMultipleCondition.new
+    d.valid?(:context_b)
+    assert_equal ["before_validation_marker on context_b", "after_validation_marker on context_b"], d.history
+
+    d = DogValidatorWithOnMultipleCondition.new
+    d.valid?([:context_a, :context_b])
+    assert_equal([
+      "before_validation_marker on context_a",
+      "before_validation_marker on context_b",
+      "after_validation_marker on context_a",
+      "after_validation_marker on context_b"
+    ], d.history)
+  end
+
+  def test_on_multiple_condition_is_respected_for_validation_without_matching_context
+    d = DogValidatorWithOnMultipleCondition.new
+    d.valid?(:save)
+    assert_equal [], d.history
+  end
+
+  def test_on_multiple_condition_is_respected_for_validation_without_context
+    d = DogValidatorWithOnMultipleCondition.new
+    d.valid?
+    assert_equal [], d.history
+  end
+
   def test_before_validation_and_after_validation_callbacks_should_be_called
     d = DogWithMethodCallbacks.new
     d.valid?
diff --git a/activemodel/test/cases/validations/conditional_validation_test.rb b/activemodel/test/cases/validations/conditional_validation_test.rb
index 68dade556c..1704db9a48 100644
--- a/activemodel/test/cases/validations/conditional_validation_test.rb
+++ b/activemodel/test/cases/validations/conditional_validation_test.rb
@@ -13,75 +13,63 @@ class ConditionalValidationTest < ActiveModel::TestCase
     # When the method returns true
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: :condition_is_true)
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
-  def test_unless_validation_using_method_true
-    # When the method returns true
-    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: :condition_is_true)
+  def test_if_validation_using_array_of_true_methods
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: [:condition_is_true, :condition_is_true])
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.valid?
-    assert_empty t.errors[:title]
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
+    assert_equal ["hoo 5"], t.errors["title"]
   end
 
-  def test_if_validation_using_method_false
-    # When the method returns false
-    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: :condition_is_true_but_its_not)
+  def test_unless_validation_using_array_of_false_methods
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: [:condition_is_false, :condition_is_false])
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.valid?
-    assert_empty t.errors[:title]
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
+    assert_equal ["hoo 5"], t.errors["title"]
   end
 
-  def test_unless_validation_using_method_false
-    # When the method returns false
-    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: :condition_is_true_but_its_not)
+  def test_unless_validation_using_method_true
+    # When the method returns true
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: :condition_is_true)
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
-    assert_equal ["hoo 5"], t.errors["title"]
+    assert_predicate t, :valid?
+    assert_empty t.errors[:title]
   end
 
-  def test_if_validation_using_string_true
-    # When the evaluated string returns true
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: "a = 1; a == 1")
-    end
+  def test_if_validation_using_array_of_true_and_false_methods
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: [:condition_is_true, :condition_is_false])
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
-    assert_equal ["hoo 5"], t.errors["title"]
+    assert_predicate t, :valid?
+    assert_empty t.errors[:title]
   end
 
-  def test_unless_validation_using_string_true
-    # When the evaluated string returns true
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: "a = 1; a == 1")
-    end
+  def test_unless_validation_using_array_of_true_and_felse_methods
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: [:condition_is_true, :condition_is_false])
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
     assert_empty t.errors[:title]
   end
 
-  def test_if_validation_using_string_false
-    # When the evaluated string returns false
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: "false")
-    end
+  def test_if_validation_using_method_false
+    # When the method returns false
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: :condition_is_false)
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
     assert_empty t.errors[:title]
   end
 
-  def test_unless_validation_using_string_false
-    # When the evaluated string returns false
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: "false")
-    end
+  def test_unless_validation_using_method_false
+    # When the method returns false
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: :condition_is_false)
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
@@ -90,8 +78,8 @@ class ConditionalValidationTest < ActiveModel::TestCase
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}",
       if: Proc.new { |r| r.content.size > 4 })
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
@@ -100,7 +88,7 @@ class ConditionalValidationTest < ActiveModel::TestCase
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}",
       unless: Proc.new { |r| r.content.size > 4 })
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
     assert_empty t.errors[:title]
   end
 
@@ -109,7 +97,7 @@ class ConditionalValidationTest < ActiveModel::TestCase
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}",
       if: Proc.new { |r| r.title != "uhohuhoh" })
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
     assert_empty t.errors[:title]
   end
 
@@ -118,32 +106,23 @@ class ConditionalValidationTest < ActiveModel::TestCase
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}",
       unless: Proc.new { |r| r.title != "uhohuhoh" })
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
-  # previous implementation of validates_presence_of eval'd the
-  # string with the wrong binding, this regression test is to
-  # ensure that it works correctly
-  def test_validation_with_if_as_string
-    Topic.validates_presence_of(:title)
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_presence_of(:author_name, if: "title.to_s.match('important')")
-    end
-
-    t = Topic.new
-    assert t.invalid?, "A topic without a title should not be valid"
-    assert_empty t.errors[:author_name], "A topic without an 'important' title should not require an author"
-
-    t.title = "Just a title"
-    assert t.valid?, "A topic with a basic title should be valid"
-
-    t.title = "A very important title"
-    assert t.invalid?, "A topic with an important title, but without an author, should not be valid"
-    assert t.errors[:author_name].any?, "A topic with an 'important' title should require an author"
+  def test_validation_using_conbining_if_true_and_unless_true_conditions
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: :condition_is_true, unless: :condition_is_true)
+    t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
+    assert_predicate t, :valid?
+    assert_empty t.errors[:title]
+  end
 
-    t.author_name = "Hubert J. Farnsworth"
-    assert t.valid?, "A topic with an important title and author should be valid"
+  def test_validation_using_conbining_if_true_and_unless_false_conditions
+    Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: :condition_is_true, unless: :condition_is_false)
+    t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
+    assert_equal ["hoo 5"], t.errors["title"]
   end
 end
diff --git a/activemodel/test/cases/validations/confirmation_validation_test.rb b/activemodel/test/cases/validations/confirmation_validation_test.rb
index e84415a868..8603a8ac5c 100644
--- a/activemodel/test/cases/validations/confirmation_validation_test.rb
+++ b/activemodel/test/cases/validations/confirmation_validation_test.rb
@@ -14,27 +14,40 @@ class ConfirmationValidationTest < ActiveModel::TestCase
     Topic.validates_confirmation_of(:title)
 
     t = Topic.new(author_name: "Plutarch")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title_confirmation = "Parallel Lives"
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title_confirmation = nil
     t.title = "Parallel Lives"
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title_confirmation = "Parallel Lives"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_title_confirmation
     Topic.validates_confirmation_of(:title)
 
     t = Topic.new("title" => "We should be confirmed", "title_confirmation" => "")
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title_confirmation = "We should be confirmed"
-    assert t.valid?
+    assert_predicate t, :valid?
+  end
+
+  def test_validates_confirmation_of_with_boolean_attribute
+    Topic.validates_confirmation_of(:approved)
+
+    t = Topic.new(approved: true, approved_confirmation: nil)
+    assert_predicate t, :valid?
+
+    t.approved_confirmation = false
+    assert_predicate t, :invalid?
+
+    t.approved_confirmation = true
+    assert_predicate t, :valid?
   end
 
   def test_validates_confirmation_of_for_ruby_class
@@ -42,12 +55,12 @@ class ConfirmationValidationTest < ActiveModel::TestCase
 
     p = Person.new
     p.karma_confirmation = "None"
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["doesn't match Karma"], p.errors[:karma_confirmation]
 
     p.karma = "None"
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
@@ -64,7 +77,7 @@ class ConfirmationValidationTest < ActiveModel::TestCase
       Topic.validates_confirmation_of(:title)
 
       t = Topic.new("title" => "We should be confirmed", "title_confirmation" => "")
-      assert t.invalid?
+      assert_predicate t, :invalid?
       assert_equal ["doesn't match Test Title"], t.errors[:title_confirmation]
     ensure
       I18n.load_path.replace @old_load_path
@@ -109,13 +122,13 @@ class ConfirmationValidationTest < ActiveModel::TestCase
     Topic.validates_confirmation_of(:title, case_sensitive: true)
 
     t = Topic.new(title: "title", title_confirmation: "Title")
-    assert t.invalid?
+    assert_predicate t, :invalid?
   end
 
   def test_title_confirmation_with_case_sensitive_option_false
     Topic.validates_confirmation_of(:title, case_sensitive: false)
 
     t = Topic.new(title: "title", title_confirmation: "Title")
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 end
diff --git a/activemodel/test/cases/validations/exclusion_validation_test.rb b/activemodel/test/cases/validations/exclusion_validation_test.rb
index 68d611e904..50bd47065c 100644
--- a/activemodel/test/cases/validations/exclusion_validation_test.rb
+++ b/activemodel/test/cases/validations/exclusion_validation_test.rb
@@ -14,8 +14,8 @@ class ExclusionValidationTest < ActiveModel::TestCase
   def test_validates_exclusion_of
     Topic.validates_exclusion_of(:title, in: %w( abe monkey ))
 
-    assert Topic.new("title" => "something", "content" => "abc").valid?
-    assert Topic.new("title" => "monkey", "content" => "abc").invalid?
+    assert_predicate Topic.new("title" => "something", "content" => "abc"), :valid?
+    assert_predicate Topic.new("title" => "monkey", "content" => "abc"), :invalid?
   end
 
   def test_validates_exclusion_of_with_formatted_message
@@ -24,8 +24,8 @@ class ExclusionValidationTest < ActiveModel::TestCase
     assert Topic.new("title" => "something", "content" => "abc")
 
     t = Topic.new("title" => "monkey")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["option monkey is restricted"], t.errors[:title]
   end
 
@@ -35,8 +35,8 @@ class ExclusionValidationTest < ActiveModel::TestCase
     assert Topic.new("title" => "something", "content" => "abc")
 
     t = Topic.new("title" => "monkey")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
   end
 
   def test_validates_exclusion_of_for_ruby_class
@@ -44,12 +44,12 @@ class ExclusionValidationTest < ActiveModel::TestCase
 
     p = Person.new
     p.karma = "abe"
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["is reserved"], p.errors[:karma]
 
     p.karma = "Lifo"
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
@@ -60,26 +60,26 @@ class ExclusionValidationTest < ActiveModel::TestCase
     t = Topic.new
     t.title = "elephant"
     t.author_name = "sikachu"
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title = "wasabi"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_exclusion_of_with_range
     Topic.validates_exclusion_of :content, in: ("a".."g")
 
-    assert Topic.new(content: "g").invalid?
-    assert Topic.new(content: "h").valid?
+    assert_predicate Topic.new(content: "g"), :invalid?
+    assert_predicate Topic.new(content: "h"), :valid?
   end
 
   def test_validates_exclusion_of_with_time_range
     Topic.validates_exclusion_of :created_at, in: 6.days.ago..2.days.ago
 
-    assert Topic.new(created_at: 5.days.ago).invalid?
-    assert Topic.new(created_at: 3.days.ago).invalid?
-    assert Topic.new(created_at: 7.days.ago).valid?
-    assert Topic.new(created_at: 1.day.ago).valid?
+    assert_predicate Topic.new(created_at: 5.days.ago), :invalid?
+    assert_predicate Topic.new(created_at: 3.days.ago), :invalid?
+    assert_predicate Topic.new(created_at: 7.days.ago), :valid?
+    assert_predicate Topic.new(created_at: 1.day.ago), :valid?
   end
 
   def test_validates_inclusion_of_with_symbol
@@ -92,7 +92,7 @@ class ExclusionValidationTest < ActiveModel::TestCase
       %w(abe)
     end
 
-    assert p.invalid?
+    assert_predicate p, :invalid?
     assert_equal ["is reserved"], p.errors[:karma]
 
     p = Person.new
@@ -102,7 +102,7 @@ class ExclusionValidationTest < ActiveModel::TestCase
       %w()
     end
 
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
diff --git a/activemodel/test/cases/validations/format_validation_test.rb b/activemodel/test/cases/validations/format_validation_test.rb
index 3ddda2154a..2a7088b3e8 100644
--- a/activemodel/test/cases/validations/format_validation_test.rb
+++ b/activemodel/test/cases/validations/format_validation_test.rb
@@ -5,7 +5,7 @@ require "cases/helper"
 require "models/topic"
 require "models/person"
 
-class PresenceValidationTest < ActiveModel::TestCase
+class FormatValidationTest < ActiveModel::TestCase
   def teardown
     Topic.clear_validators!
   end
@@ -16,22 +16,22 @@ class PresenceValidationTest < ActiveModel::TestCase
     t = Topic.new("title" => "i'm incorrect", "content" => "Validation macros rule!")
     assert t.invalid?, "Shouldn't be valid"
     assert_equal ["is bad data"], t.errors[:title]
-    assert t.errors[:content].empty?
+    assert_empty t.errors[:content]
 
     t.title = "Validation macros rule!"
 
-    assert t.valid?
-    assert t.errors[:title].empty?
+    assert_predicate t, :valid?
+    assert_empty t.errors[:title]
 
     assert_raise(ArgumentError) { Topic.validates_format_of(:title, :content) }
   end
 
   def test_validate_format_with_allow_blank
     Topic.validates_format_of(:title, with: /\AValidation\smacros \w+!\z/, allow_blank: true)
-    assert Topic.new("title" => "Shouldn't be valid").invalid?
-    assert Topic.new("title" => "").valid?
-    assert Topic.new("title" => nil).valid?
-    assert Topic.new("title" => "Validation macros rule!").valid?
+    assert_predicate Topic.new("title" => "Shouldn't be valid"), :invalid?
+    assert_predicate Topic.new("title" => ""), :valid?
+    assert_predicate Topic.new("title" => nil), :valid?
+    assert_predicate Topic.new("title" => "Validation macros rule!"), :valid?
   end
 
   # testing ticket #3142
@@ -42,7 +42,7 @@ class PresenceValidationTest < ActiveModel::TestCase
     assert t.invalid?, "Shouldn't be valid"
 
     assert_equal ["is bad data"], t.errors[:title]
-    assert t.errors[:content].empty?
+    assert_empty t.errors[:content]
 
     t.title = "-11"
     assert t.invalid?, "Shouldn't be valid"
@@ -58,14 +58,14 @@ class PresenceValidationTest < ActiveModel::TestCase
 
     t.title = "1"
 
-    assert t.valid?
-    assert t.errors[:title].empty?
+    assert_predicate t, :valid?
+    assert_empty t.errors[:title]
   end
 
   def test_validate_format_with_formatted_message
     Topic.validates_format_of(:title, with: /\AValid Title\z/, message: "can't be %{value}")
     t = Topic.new(title: "Invalid title")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["can't be Invalid title"], t.errors[:title]
   end
 
@@ -114,10 +114,10 @@ class PresenceValidationTest < ActiveModel::TestCase
     t = Topic.new
     t.title = "digit"
     t.content = "Pixies"
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.content = "1234"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_format_of_without_lambda
@@ -126,10 +126,10 @@ class PresenceValidationTest < ActiveModel::TestCase
     t = Topic.new
     t.title = "characters"
     t.content = "1234"
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.content = "Pixies"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_format_of_for_ruby_class
@@ -137,12 +137,12 @@ class PresenceValidationTest < ActiveModel::TestCase
 
     p = Person.new
     p.karma = "Pixies"
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["is invalid"], p.errors[:karma]
 
     p.karma = "1234"
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
diff --git a/activemodel/test/cases/validations/inclusion_validation_test.rb b/activemodel/test/cases/validations/inclusion_validation_test.rb
index 94df0649a9..daad76759f 100644
--- a/activemodel/test/cases/validations/inclusion_validation_test.rb
+++ b/activemodel/test/cases/validations/inclusion_validation_test.rb
@@ -13,61 +13,61 @@ class InclusionValidationTest < ActiveModel::TestCase
 
   def test_validates_inclusion_of_range
     Topic.validates_inclusion_of(:title, in: "aaa".."bbb")
-    assert Topic.new("title" => "bbc", "content" => "abc").invalid?
-    assert Topic.new("title" => "aa", "content" => "abc").invalid?
-    assert Topic.new("title" => "aaab", "content" => "abc").invalid?
-    assert Topic.new("title" => "aaa", "content" => "abc").valid?
-    assert Topic.new("title" => "abc", "content" => "abc").valid?
-    assert Topic.new("title" => "bbb", "content" => "abc").valid?
+    assert_predicate Topic.new("title" => "bbc", "content" => "abc"), :invalid?
+    assert_predicate Topic.new("title" => "aa", "content" => "abc"), :invalid?
+    assert_predicate Topic.new("title" => "aaab", "content" => "abc"), :invalid?
+    assert_predicate Topic.new("title" => "aaa", "content" => "abc"), :valid?
+    assert_predicate Topic.new("title" => "abc", "content" => "abc"), :valid?
+    assert_predicate Topic.new("title" => "bbb", "content" => "abc"), :valid?
   end
 
   def test_validates_inclusion_of_time_range
     range_begin = 1.year.ago
     range_end = Time.now
     Topic.validates_inclusion_of(:created_at, in: range_begin..range_end)
-    assert Topic.new(title: "aaa", created_at: 2.years.ago).invalid?
-    assert Topic.new(title: "aaa", created_at: 3.months.ago).valid?
-    assert Topic.new(title: "aaa", created_at: 37.weeks.from_now).invalid?
-    assert Topic.new(title: "aaa", created_at: range_begin).valid?
-    assert Topic.new(title: "aaa", created_at: range_end).valid?
+    assert_predicate Topic.new(title: "aaa", created_at: 2.years.ago), :invalid?
+    assert_predicate Topic.new(title: "aaa", created_at: 3.months.ago), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: 37.weeks.from_now), :invalid?
+    assert_predicate Topic.new(title: "aaa", created_at: range_begin), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: range_end), :valid?
   end
 
   def test_validates_inclusion_of_date_range
     range_begin = 1.year.until(Date.today)
     range_end = Date.today
     Topic.validates_inclusion_of(:created_at, in: range_begin..range_end)
-    assert Topic.new(title: "aaa", created_at: 2.years.until(Date.today)).invalid?
-    assert Topic.new(title: "aaa", created_at: 3.months.until(Date.today)).valid?
-    assert Topic.new(title: "aaa", created_at: 37.weeks.since(Date.today)).invalid?
-    assert Topic.new(title: "aaa", created_at: 1.year.until(Date.today)).valid?
-    assert Topic.new(title: "aaa", created_at: Date.today).valid?
-    assert Topic.new(title: "aaa", created_at: range_begin).valid?
-    assert Topic.new(title: "aaa", created_at: range_end).valid?
+    assert_predicate Topic.new(title: "aaa", created_at: 2.years.until(Date.today)), :invalid?
+    assert_predicate Topic.new(title: "aaa", created_at: 3.months.until(Date.today)), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: 37.weeks.since(Date.today)), :invalid?
+    assert_predicate Topic.new(title: "aaa", created_at: 1.year.until(Date.today)), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: Date.today), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: range_begin), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: range_end), :valid?
   end
 
   def test_validates_inclusion_of_date_time_range
     range_begin = 1.year.until(DateTime.current)
     range_end = DateTime.current
     Topic.validates_inclusion_of(:created_at, in: range_begin..range_end)
-    assert Topic.new(title: "aaa", created_at: 2.years.until(DateTime.current)).invalid?
-    assert Topic.new(title: "aaa", created_at: 3.months.until(DateTime.current)).valid?
-    assert Topic.new(title: "aaa", created_at: 37.weeks.since(DateTime.current)).invalid?
-    assert Topic.new(title: "aaa", created_at: range_begin).valid?
-    assert Topic.new(title: "aaa", created_at: range_end).valid?
+    assert_predicate Topic.new(title: "aaa", created_at: 2.years.until(DateTime.current)), :invalid?
+    assert_predicate Topic.new(title: "aaa", created_at: 3.months.until(DateTime.current)), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: 37.weeks.since(DateTime.current)), :invalid?
+    assert_predicate Topic.new(title: "aaa", created_at: range_begin), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: range_end), :valid?
   end
 
   def test_validates_inclusion_of
     Topic.validates_inclusion_of(:title, in: %w( a b c d e f g ))
 
-    assert Topic.new("title" => "a!", "content" => "abc").invalid?
-    assert Topic.new("title" => "a b", "content" => "abc").invalid?
-    assert Topic.new("title" => nil, "content" => "def").invalid?
+    assert_predicate Topic.new("title" => "a!", "content" => "abc"), :invalid?
+    assert_predicate Topic.new("title" => "a b", "content" => "abc"), :invalid?
+    assert_predicate Topic.new("title" => nil, "content" => "def"), :invalid?
 
     t = Topic.new("title" => "a", "content" => "I know you are but what am I?")
-    assert t.valid?
+    assert_predicate t, :valid?
     t.title = "uhoh"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is not included in the list"], t.errors[:title]
 
     assert_raise(ArgumentError) { Topic.validates_inclusion_of(:title, in: nil) }
@@ -81,30 +81,30 @@ class InclusionValidationTest < ActiveModel::TestCase
   def test_validates_inclusion_of_with_allow_nil
     Topic.validates_inclusion_of(:title, in: %w( a b c d e f g ), allow_nil: true)
 
-    assert Topic.new("title" => "a!", "content" => "abc").invalid?
-    assert Topic.new("title" => "",   "content" => "abc").invalid?
-    assert Topic.new("title" => nil,  "content" => "abc").valid?
+    assert_predicate Topic.new("title" => "a!", "content" => "abc"), :invalid?
+    assert_predicate Topic.new("title" => "",   "content" => "abc"), :invalid?
+    assert_predicate Topic.new("title" => nil,  "content" => "abc"), :valid?
   end
 
   def test_validates_inclusion_of_with_formatted_message
     Topic.validates_inclusion_of(:title, in: %w( a b c d e f g ), message: "option %{value} is not in the list")
 
-    assert Topic.new("title" => "a", "content" => "abc").valid?
+    assert_predicate Topic.new("title" => "a", "content" => "abc"), :valid?
 
     t = Topic.new("title" => "uhoh", "content" => "abc")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["option uhoh is not in the list"], t.errors[:title]
   end
 
   def test_validates_inclusion_of_with_within_option
     Topic.validates_inclusion_of(:title, within: %w( a b c d e f g ))
 
-    assert Topic.new("title" => "a", "content" => "abc").valid?
+    assert_predicate Topic.new("title" => "a", "content" => "abc"), :valid?
 
     t = Topic.new("title" => "uhoh", "content" => "abc")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
   end
 
   def test_validates_inclusion_of_for_ruby_class
@@ -112,12 +112,12 @@ class InclusionValidationTest < ActiveModel::TestCase
 
     p = Person.new
     p.karma = "Lifo"
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["is not included in the list"], p.errors[:karma]
 
     p.karma = "monkey"
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
@@ -128,10 +128,10 @@ class InclusionValidationTest < ActiveModel::TestCase
     t = Topic.new
     t.title = "wasabi"
     t.author_name = "sikachu"
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title = "elephant"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_inclusion_of_with_symbol
@@ -144,7 +144,7 @@ class InclusionValidationTest < ActiveModel::TestCase
       %w()
     end
 
-    assert p.invalid?
+    assert_predicate p, :invalid?
     assert_equal ["is not included in the list"], p.errors[:karma]
 
     p = Person.new
@@ -154,7 +154,7 @@ class InclusionValidationTest < ActiveModel::TestCase
       %w(Lifo)
     end
 
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
diff --git a/activemodel/test/cases/validations/length_validation_test.rb b/activemodel/test/cases/validations/length_validation_test.rb
index a0d8e058f5..774a2cde74 100644
--- a/activemodel/test/cases/validations/length_validation_test.rb
+++ b/activemodel/test/cases/validations/length_validation_test.rb
@@ -13,153 +13,153 @@ class LengthValidationTest < ActiveModel::TestCase
   def test_validates_length_of_with_allow_nil
     Topic.validates_length_of(:title, is: 5, allow_nil: true)
 
-    assert Topic.new("title" => "ab").invalid?
-    assert Topic.new("title" => "").invalid?
-    assert Topic.new("title" => nil).valid?
-    assert Topic.new("title" => "abcde").valid?
+    assert_predicate Topic.new("title" => "ab"), :invalid?
+    assert_predicate Topic.new("title" => ""), :invalid?
+    assert_predicate Topic.new("title" => nil), :valid?
+    assert_predicate Topic.new("title" => "abcde"), :valid?
   end
 
   def test_validates_length_of_with_allow_blank
     Topic.validates_length_of(:title, is: 5, allow_blank: true)
 
-    assert Topic.new("title" => "ab").invalid?
-    assert Topic.new("title" => "").valid?
-    assert Topic.new("title" => nil).valid?
-    assert Topic.new("title" => "abcde").valid?
+    assert_predicate Topic.new("title" => "ab"), :invalid?
+    assert_predicate Topic.new("title" => ""), :valid?
+    assert_predicate Topic.new("title" => nil), :valid?
+    assert_predicate Topic.new("title" => "abcde"), :valid?
   end
 
   def test_validates_length_of_using_minimum
     Topic.validates_length_of :title, minimum: 5
 
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "not"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is too short (minimum is 5 characters)"], t.errors[:title]
 
     t.title = ""
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is too short (minimum is 5 characters)"], t.errors[:title]
 
     t.title = nil
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is too short (minimum is 5 characters)"], t.errors["title"]
   end
 
   def test_validates_length_of_using_maximum_should_allow_nil
     Topic.validates_length_of :title, maximum: 10
     t = Topic.new
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_optionally_validates_length_of_using_minimum
     Topic.validates_length_of :title, minimum: 5, allow_nil: true
 
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = nil
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_maximum
     Topic.validates_length_of :title, maximum: 5
 
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "notvalid"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is too long (maximum is 5 characters)"], t.errors[:title]
 
     t.title = ""
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_optionally_validates_length_of_using_maximum
     Topic.validates_length_of :title, maximum: 5, allow_nil: true
 
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = nil
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_within
     Topic.validates_length_of(:title, :content, within: 3..5)
 
     t = Topic.new("title" => "a!", "content" => "I'm ooooooooh so very long")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["is too short (minimum is 3 characters)"], t.errors[:title]
     assert_equal ["is too long (maximum is 5 characters)"], t.errors[:content]
 
     t.title = nil
     t.content = nil
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["is too short (minimum is 3 characters)"], t.errors[:title]
     assert_equal ["is too short (minimum is 3 characters)"], t.errors[:content]
 
     t.title = "abe"
     t.content = "mad"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_within_with_exclusive_range
     Topic.validates_length_of(:title, within: 4...10)
 
     t = Topic.new("title" => "9 chars!!")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "Now I'm 10"
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["is too long (maximum is 9 characters)"], t.errors[:title]
 
     t.title = "Four"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_optionally_validates_length_of_using_within
     Topic.validates_length_of :title, :content, within: 3..5, allow_nil: true
 
     t = Topic.new("title" => "abc", "content" => "abcd")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = nil
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_is
     Topic.validates_length_of :title, is: 5
 
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "notvalid"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is the wrong length (should be 5 characters)"], t.errors[:title]
 
     t.title = ""
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title = nil
-    assert t.invalid?
+    assert_predicate t, :invalid?
   end
 
   def test_optionally_validates_length_of_using_is
     Topic.validates_length_of :title, is: 5, allow_nil: true
 
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = nil
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_bignum
@@ -187,45 +187,45 @@ class LengthValidationTest < ActiveModel::TestCase
   def test_validates_length_of_custom_errors_for_minimum_with_message
     Topic.validates_length_of(:title, minimum: 5, message: "boo %{count}")
     t = Topic.new("title" => "uhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["boo 5"], t.errors[:title]
   end
 
   def test_validates_length_of_custom_errors_for_minimum_with_too_short
     Topic.validates_length_of(:title, minimum: 5, too_short: "hoo %{count}")
     t = Topic.new("title" => "uhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors[:title]
   end
 
   def test_validates_length_of_custom_errors_for_maximum_with_message
     Topic.validates_length_of(:title, maximum: 5, message: "boo %{count}")
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["boo 5"], t.errors[:title]
   end
 
   def test_validates_length_of_custom_errors_for_in
     Topic.validates_length_of(:title, in: 10..20, message: "hoo %{count}")
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 10"], t.errors["title"]
 
     t = Topic.new("title" => "uhohuhohuhohuhohuhohuhohuhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 20"], t.errors["title"]
   end
 
   def test_validates_length_of_custom_errors_for_maximum_with_too_long
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}")
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
@@ -233,29 +233,29 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of :title, minimum: 3, maximum: 5, too_short: "too short", too_long: "too long"
 
     t = Topic.new(title: "a")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["too short"], t.errors["title"]
 
     t = Topic.new(title: "aaaaaa")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["too long"], t.errors["title"]
   end
 
   def test_validates_length_of_custom_errors_for_is_with_message
     Topic.validates_length_of(:title, is: 5, message: "boo %{count}")
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["boo 5"], t.errors["title"]
   end
 
   def test_validates_length_of_custom_errors_for_is_with_wrong_length
     Topic.validates_length_of(:title, is: 5, wrong_length: "hoo %{count}")
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
@@ -263,11 +263,11 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of :title, minimum: 5
 
     t = Topic.new("title" => "一二三四五", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "一二三四"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is too short (minimum is 5 characters)"], t.errors["title"]
   end
 
@@ -275,11 +275,11 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of :title, maximum: 5
 
     t = Topic.new("title" => "一二三四五", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "一二34五六"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is too long (maximum is 5 characters)"], t.errors["title"]
   end
 
@@ -287,12 +287,12 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of(:title, :content, within: 3..5)
 
     t = Topic.new("title" => "一二", "content" => "12三四五六七")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["is too short (minimum is 3 characters)"], t.errors[:title]
     assert_equal ["is too long (maximum is 5 characters)"], t.errors[:content]
     t.title = "一二三"
     t.content = "12三"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_optionally_validates_length_of_using_within_utf8
@@ -312,11 +312,11 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of :title, is: 5
 
     t = Topic.new("title" => "一二345", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "一二345六"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is the wrong length (should be 5 characters)"], t.errors["title"]
   end
 
@@ -324,11 +324,11 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of(:approved, is: 4)
 
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever", approved: 1)
-    assert t.invalid?
-    assert t.errors[:approved].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:approved], :any?
 
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever", approved: 1234)
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_for_ruby_class
@@ -336,12 +336,12 @@ class LengthValidationTest < ActiveModel::TestCase
 
     p = Person.new
     p.karma = "Pix"
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["is too short (minimum is 5 characters)"], p.errors[:karma]
 
     p.karma = "The Smiths"
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
@@ -350,64 +350,95 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of(:title, within: 5..Float::INFINITY)
 
     t = Topic.new("title" => "1234")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
 
     t.title = "12345"
-    assert t.valid?
+    assert_predicate t, :valid?
 
     Topic.validates_length_of(:author_name, maximum: Float::INFINITY)
 
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.author_name = "A very long author name that should still be valid." * 100
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_maximum_should_not_allow_nil_when_nil_not_allowed
     Topic.validates_length_of :title, maximum: 10, allow_nil: false
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
   end
 
   def test_validates_length_of_using_maximum_should_not_allow_nil_and_empty_string_when_blank_not_allowed
     Topic.validates_length_of :title, maximum: 10, allow_blank: false
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title = ""
-    assert t.invalid?
+    assert_predicate t, :invalid?
   end
 
   def test_validates_length_of_using_both_minimum_and_maximum_should_not_allow_nil
     Topic.validates_length_of :title, minimum: 5, maximum: 10
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
   end
 
   def test_validates_length_of_using_minimum_0_should_not_allow_nil
     Topic.validates_length_of :title, minimum: 0
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title = ""
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_is_0_should_not_allow_nil
     Topic.validates_length_of :title, is: 0
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title = ""
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_with_diff_in_option
     Topic.validates_length_of(:title, is: 5)
     Topic.validates_length_of(:title, is: 5, if: Proc.new { false })
 
-    assert Topic.new("title" => "david").valid?
-    assert Topic.new("title" => "david2").invalid?
+    assert_predicate Topic.new("title" => "david"), :valid?
+    assert_predicate Topic.new("title" => "david2"), :invalid?
+  end
+
+  def test_validates_length_of_using_proc_as_maximum
+    Topic.validates_length_of :title, maximum: ->(model) { 5 }
+
+    t = Topic.new("title" => "valid", "content" => "whatever")
+    assert_predicate t, :valid?
+
+    t.title = "notvalid"
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
+    assert_equal ["is too long (maximum is 5 characters)"], t.errors[:title]
+
+    t.title = ""
+    assert_predicate t, :valid?
+  end
+
+  def test_validates_length_of_using_proc_as_maximum_with_model_method
+    Topic.send(:define_method, :max_title_length, lambda { 5 })
+    Topic.validates_length_of :title, maximum: Proc.new(&:max_title_length)
+
+    t = Topic.new("title" => "valid", "content" => "whatever")
+    assert_predicate t, :valid?
+
+    t.title = "notvalid"
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
+    assert_equal ["is too long (maximum is 5 characters)"], t.errors[:title]
+
+    t.title = ""
+    assert_predicate t, :valid?
   end
 end
diff --git a/activemodel/test/cases/validations/numericality_validation_test.rb b/activemodel/test/cases/validations/numericality_validation_test.rb
index 001815e28f..01b78ae72e 100644
--- a/activemodel/test/cases/validations/numericality_validation_test.rb
+++ b/activemodel/test/cases/validations/numericality_validation_test.rb
@@ -20,7 +20,7 @@ class NumericalityValidationTest < ActiveModel::TestCase
   INTEGER_STRINGS = %w(0 +0 -0 10 +10 -10 0090 -090)
   FLOATS = [0.0, 10.0, 10.5, -10.5, -0.0001] + FLOAT_STRINGS
   INTEGERS = [0, 10, -10] + INTEGER_STRINGS
-  BIGDECIMAL = BIGDECIMAL_STRINGS.collect! { |bd| BigDecimal.new(bd) }
+  BIGDECIMAL = BIGDECIMAL_STRINGS.collect! { |bd| BigDecimal(bd) }
   JUNK = ["not a number", "42 not a number", "0xdeadbeef", "0xinvalidhex", "0Xdeadbeef", "00-1", "--3", "+-3", "+3-1", "-+019.0", "12.12.13.12", "123\nnot a number"]
   INFINITY = [1.0 / 0.0]
 
@@ -59,7 +59,7 @@ class NumericalityValidationTest < ActiveModel::TestCase
   end
 
   def test_validates_numericality_of_with_integer_only_and_symbol_as_value
-    Topic.validates_numericality_of :approved, only_integer: :condition_is_true_but_its_not
+    Topic.validates_numericality_of :approved, only_integer: :condition_is_false
 
     invalid!(NIL + BLANK + JUNK)
     valid!(FLOATS + INTEGERS + BIGDECIMAL + INFINITY)
@@ -81,10 +81,10 @@ class NumericalityValidationTest < ActiveModel::TestCase
   end
 
   def test_validates_numericality_with_greater_than_using_differing_numeric_types
-    Topic.validates_numericality_of :approved, greater_than: BigDecimal.new("97.18")
+    Topic.validates_numericality_of :approved, greater_than: BigDecimal("97.18")
 
-    invalid!([-97.18, BigDecimal.new("97.18"), BigDecimal("-97.18")], "must be greater than 97.18")
-    valid!([97.19, 98, BigDecimal.new("98"), BigDecimal.new("97.19")])
+    invalid!([-97.18, BigDecimal("97.18"), BigDecimal("-97.18")], "must be greater than 97.18")
+    valid!([97.19, 98, BigDecimal("98"), BigDecimal("97.19")])
   end
 
   def test_validates_numericality_with_greater_than_using_string_value
@@ -102,10 +102,10 @@ class NumericalityValidationTest < ActiveModel::TestCase
   end
 
   def test_validates_numericality_with_greater_than_or_equal_using_differing_numeric_types
-    Topic.validates_numericality_of :approved, greater_than_or_equal_to: BigDecimal.new("97.18")
+    Topic.validates_numericality_of :approved, greater_than_or_equal_to: BigDecimal("97.18")
 
-    invalid!([-97.18, 97.17, 97, BigDecimal.new("97.17"), BigDecimal.new("-97.18")], "must be greater than or equal to 97.18")
-    valid!([97.18, 98, BigDecimal.new("97.19")])
+    invalid!([-97.18, 97.17, 97, BigDecimal("97.17"), BigDecimal("-97.18")], "must be greater than or equal to 97.18")
+    valid!([97.18, 98, BigDecimal("97.19")])
   end
 
   def test_validates_numericality_with_greater_than_or_equal_using_string_value
@@ -123,10 +123,10 @@ class NumericalityValidationTest < ActiveModel::TestCase
   end
 
   def test_validates_numericality_with_equal_to_using_differing_numeric_types
-    Topic.validates_numericality_of :approved, equal_to: BigDecimal.new("97.18")
+    Topic.validates_numericality_of :approved, equal_to: BigDecimal("97.18")
 
     invalid!([-97.18], "must be equal to 97.18")
-    valid!([BigDecimal.new("97.18")])
+    valid!([BigDecimal("97.18")])
   end
 
   def test_validates_numericality_with_equal_to_using_string_value
@@ -144,10 +144,10 @@ class NumericalityValidationTest < ActiveModel::TestCase
   end
 
   def test_validates_numericality_with_less_than_using_differing_numeric_types
-    Topic.validates_numericality_of :approved, less_than: BigDecimal.new("97.18")
+    Topic.validates_numericality_of :approved, less_than: BigDecimal("97.18")
 
-    invalid!([97.18, BigDecimal.new("97.18")], "must be less than 97.18")
-    valid!([-97.0, 97.0, -97, 97, BigDecimal.new("-97"), BigDecimal.new("97")])
+    invalid!([97.18, BigDecimal("97.18")], "must be less than 97.18")
+    valid!([-97.0, 97.0, -97, 97, BigDecimal("-97"), BigDecimal("97")])
   end
 
   def test_validates_numericality_with_less_than_using_string_value
@@ -165,10 +165,10 @@ class NumericalityValidationTest < ActiveModel::TestCase
   end
 
   def test_validates_numericality_with_less_than_or_equal_to_using_differing_numeric_types
-    Topic.validates_numericality_of :approved, less_than_or_equal_to: BigDecimal.new("97.18")
+    Topic.validates_numericality_of :approved, less_than_or_equal_to: BigDecimal("97.18")
 
     invalid!([97.19, 98], "must be less than or equal to 97.18")
-    valid!([-97.18, BigDecimal.new("-97.18"), BigDecimal.new("97.18")])
+    valid!([-97.18, BigDecimal("-97.18"), BigDecimal("97.18")])
   end
 
   def test_validates_numericality_with_less_than_or_equal_using_string_value
@@ -237,13 +237,13 @@ class NumericalityValidationTest < ActiveModel::TestCase
     Topic.validates_numericality_of :approved, less_than: 4, message: "smaller than %{count}"
     topic = Topic.new("title" => "numeric test", "approved" => 10)
 
-    assert !topic.valid?
+    assert_not_predicate topic, :valid?
     assert_equal ["smaller than 4"], topic.errors[:approved]
 
     Topic.validates_numericality_of :approved, greater_than: 4, message: "greater than %{count}"
     topic = Topic.new("title" => "numeric test", "approved" => 1)
 
-    assert !topic.valid?
+    assert_not_predicate topic, :valid?
     assert_equal ["greater than 4"], topic.errors[:approved]
   end
 
@@ -252,12 +252,12 @@ class NumericalityValidationTest < ActiveModel::TestCase
 
     p = Person.new
     p.karma = "Pix"
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["is not a number"], p.errors[:karma]
 
     p.karma = "1234"
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
@@ -268,7 +268,7 @@ class NumericalityValidationTest < ActiveModel::TestCase
     topic = Topic.new
     topic.approved = (base + 1).to_s
 
-    assert topic.invalid?
+    assert_predicate topic, :invalid?
   end
 
   def test_validates_numericality_with_invalid_args
diff --git a/activemodel/test/cases/validations/presence_validation_test.rb b/activemodel/test/cases/validations/presence_validation_test.rb
index 22c2f0af87..c3eca41070 100644
--- a/activemodel/test/cases/validations/presence_validation_test.rb
+++ b/activemodel/test/cases/validations/presence_validation_test.rb
@@ -17,25 +17,25 @@ class PresenceValidationTest < ActiveModel::TestCase
     Topic.validates_presence_of(:title, :content)
 
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["can't be blank"], t.errors[:title]
     assert_equal ["can't be blank"], t.errors[:content]
 
     t.title = "something"
     t.content = "   "
 
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["can't be blank"], t.errors[:content]
 
     t.content = "like stuff"
 
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_accepts_array_arguments
     Topic.validates_presence_of %w(title content)
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["can't be blank"], t.errors[:title]
     assert_equal ["can't be blank"], t.errors[:content]
   end
@@ -43,7 +43,7 @@ class PresenceValidationTest < ActiveModel::TestCase
   def test_validates_acceptance_of_with_custom_error_using_quotes
     Person.validates_presence_of :karma, message: "This string contains 'single' and \"double\" quotes"
     p = Person.new
-    assert p.invalid?
+    assert_predicate p, :invalid?
     assert_equal "This string contains 'single' and \"double\" quotes", p.errors[:karma].last
   end
 
@@ -51,24 +51,24 @@ class PresenceValidationTest < ActiveModel::TestCase
     Person.validates_presence_of :karma
 
     p = Person.new
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["can't be blank"], p.errors[:karma]
 
     p.karma = "Cold"
-    assert p.valid?
+    assert_predicate p, :valid?
   end
 
   def test_validates_presence_of_for_ruby_class_with_custom_reader
     CustomReader.validates_presence_of :karma
 
     p = CustomReader.new
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["can't be blank"], p.errors[:karma]
 
     p[:karma] = "Cold"
-    assert p.valid?
+    assert_predicate p, :valid?
   end
 
   def test_validates_presence_of_with_allow_nil_option
@@ -78,7 +78,7 @@ class PresenceValidationTest < ActiveModel::TestCase
     assert t.valid?, t.errors.full_messages
 
     t.title = ""
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["can't be blank"], t.errors[:title]
 
     t.title = "  "
diff --git a/activemodel/test/cases/validations/validates_test.rb b/activemodel/test/cases/validations/validates_test.rb
index 77cb8ebdc1..ae5a875c24 100644
--- a/activemodel/test/cases/validations/validates_test.rb
+++ b/activemodel/test/cases/validations/validates_test.rb
@@ -19,7 +19,7 @@ class ValidatesTest < ActiveModel::TestCase
   def test_validates_with_messages_empty
     Person.validates :title, presence: { message: "" }
     person = Person.new
-    assert !person.valid?, "person should not be valid."
+    assert_not person.valid?, "person should not be valid."
   end
 
   def test_validates_with_built_in_validation
@@ -37,7 +37,7 @@ class ValidatesTest < ActiveModel::TestCase
 
     person = Person.new
     person.title = 123
-    assert person.valid?
+    assert_predicate person, :valid?
   end
 
   def test_validates_with_built_in_validation_and_options
@@ -62,56 +62,62 @@ class ValidatesTest < ActiveModel::TestCase
   end
 
   def test_validates_with_if_as_local_conditions
-    Person.validates :karma, presence: true, email: { unless: :condition_is_true }
+    Person.validates :karma, presence: true, email: { if: :condition_is_false }
     person = Person.new
     person.valid?
     assert_equal ["can't be blank"], person.errors[:karma]
   end
 
   def test_validates_with_if_as_shared_conditions
-    Person.validates :karma, presence: true, email: true, if: :condition_is_true
+    Person.validates :karma, presence: true, email: true, if: :condition_is_false
+    person = Person.new
+    assert_predicate person, :valid?
+  end
+
+  def test_validates_with_unless_as_local_conditions
+    Person.validates :karma, presence: true, email: { unless: :condition_is_true }
     person = Person.new
     person.valid?
-    assert_equal ["can't be blank", "is not an email"], person.errors[:karma].sort
+    assert_equal ["can't be blank"], person.errors[:karma]
   end
 
   def test_validates_with_unless_shared_conditions
     Person.validates :karma, presence: true, email: true, unless: :condition_is_true
     person = Person.new
-    assert person.valid?
+    assert_predicate person, :valid?
   end
 
   def test_validates_with_allow_nil_shared_conditions
     Person.validates :karma, length: { minimum: 20 }, email: true, allow_nil: true
     person = Person.new
-    assert person.valid?
+    assert_predicate person, :valid?
   end
 
   def test_validates_with_regexp
     Person.validates :karma, format: /positive|negative/
     person = Person.new
-    assert person.invalid?
+    assert_predicate person, :invalid?
     assert_equal ["is invalid"], person.errors[:karma]
     person.karma = "positive"
-    assert person.valid?
+    assert_predicate person, :valid?
   end
 
   def test_validates_with_array
     Person.validates :gender, inclusion: %w(m f)
     person = Person.new
-    assert person.invalid?
+    assert_predicate person, :invalid?
     assert_equal ["is not included in the list"], person.errors[:gender]
     person.gender = "m"
-    assert person.valid?
+    assert_predicate person, :valid?
   end
 
   def test_validates_with_range
     Person.validates :karma, length: 6..20
     person = Person.new
-    assert person.invalid?
+    assert_predicate person, :invalid?
     assert_equal ["is too short (minimum is 6 characters)"], person.errors[:karma]
     person.karma = "something"
-    assert person.valid?
+    assert_predicate person, :valid?
   end
 
   def test_validates_with_validator_class_and_options
@@ -153,7 +159,7 @@ class ValidatesTest < ActiveModel::TestCase
     topic = Topic.new
     topic.title = "What's happening"
     topic.title_confirmation = "Not this"
-    assert !topic.valid?
+    assert_not_predicate topic, :valid?
     assert_equal ["Y U NO CONFIRM"], topic.errors[:title_confirmation]
   end
 end
diff --git a/activemodel/test/cases/validations/with_validation_test.rb b/activemodel/test/cases/validations/with_validation_test.rb
index fbe20dc000..8239792c79 100644
--- a/activemodel/test/cases/validations/with_validation_test.rb
+++ b/activemodel/test/cases/validations/with_validation_test.rb
@@ -65,71 +65,35 @@ class ValidatesWithTest < ActiveModel::TestCase
   test "with multiple classes" do
     Topic.validates_with(ValidatorThatAddsErrors, OtherValidatorThatAddsErrors)
     topic = Topic.new
-    assert topic.invalid?
+    assert_predicate topic, :invalid?
     assert_includes topic.errors[:base], ERROR_MESSAGE
     assert_includes topic.errors[:base], OTHER_ERROR_MESSAGE
   end
 
-  test "with if statements that return false" do
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_with(ValidatorThatAddsErrors, if: "1 == 2")
-    end
-    topic = Topic.new
-    assert topic.valid?
-  end
-
-  test "with if statements that return true" do
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_with(ValidatorThatAddsErrors, if: "1 == 1")
-    end
-    topic = Topic.new
-    assert topic.invalid?
-    assert_includes topic.errors[:base], ERROR_MESSAGE
-  end
-
-  test "with unless statements that return true" do
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_with(ValidatorThatAddsErrors, unless: "1 == 1")
-    end
-    topic = Topic.new
-    assert topic.valid?
-  end
-
-  test "with unless statements that returns false" do
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_with(ValidatorThatAddsErrors, unless: "1 == 2")
-    end
-    topic = Topic.new
-    assert topic.invalid?
-    assert_includes topic.errors[:base], ERROR_MESSAGE
-  end
-
   test "passes all configuration options to the validator class" do
     topic = Topic.new
     validator = Minitest::Mock.new
-    validator.expect(:new, validator, [{ foo: :bar, if: "1 == 1", class: Topic }])
+    validator.expect(:new, validator, [{ foo: :bar, if: :condition_is_true, class: Topic }])
     validator.expect(:validate, nil, [topic])
     validator.expect(:is_a?, false, [Symbol])
     validator.expect(:is_a?, false, [String])
 
-    ActiveSupport::Deprecation.silence do
-      Topic.validates_with(validator, if: "1 == 1", foo: :bar)
-    end
-    assert topic.valid?
+    Topic.validates_with(validator, if: :condition_is_true, foo: :bar)
+    assert_predicate topic, :valid?
     validator.verify
   end
 
   test "validates_with with options" do
     Topic.validates_with(ValidatorThatValidatesOptions, field: :first_name)
     topic = Topic.new
-    assert topic.invalid?
+    assert_predicate topic, :invalid?
     assert_includes topic.errors[:base], ERROR_MESSAGE
   end
 
   test "validates_with each validator" do
     Topic.validates_with(ValidatorPerEachAttribute, attributes: [:title, :content])
     topic = Topic.new title: "Title", content: "Content"
-    assert topic.invalid?
+    assert_predicate topic, :invalid?
     assert_equal ["Value is Title"], topic.errors[:title]
     assert_equal ["Value is Content"], topic.errors[:content]
   end
@@ -149,28 +113,28 @@ class ValidatesWithTest < ActiveModel::TestCase
   test "each validator skip nil values if :allow_nil is set to true" do
     Topic.validates_with(ValidatorPerEachAttribute, attributes: [:title, :content], allow_nil: true)
     topic = Topic.new content: ""
-    assert topic.invalid?
-    assert topic.errors[:title].empty?
+    assert_predicate topic, :invalid?
+    assert_empty topic.errors[:title]
     assert_equal ["Value is "], topic.errors[:content]
   end
 
   test "each validator skip blank values if :allow_blank is set to true" do
     Topic.validates_with(ValidatorPerEachAttribute, attributes: [:title, :content], allow_blank: true)
     topic = Topic.new content: ""
-    assert topic.valid?
-    assert topic.errors[:title].empty?
-    assert topic.errors[:content].empty?
+    assert_predicate topic, :valid?
+    assert_empty topic.errors[:title]
+    assert_empty topic.errors[:content]
   end
 
   test "validates_with can validate with an instance method" do
     Topic.validates :title, with: :my_validation
 
     topic = Topic.new title: "foo"
-    assert topic.valid?
-    assert topic.errors[:title].empty?
+    assert_predicate topic, :valid?
+    assert_empty topic.errors[:title]
 
     topic = Topic.new
-    assert !topic.valid?
+    assert_not_predicate topic, :valid?
     assert_equal ["is missing"], topic.errors[:title]
   end
 
@@ -178,8 +142,8 @@ class ValidatesWithTest < ActiveModel::TestCase
     Topic.validates :title, :content, with: :my_validation_with_arg
 
     topic = Topic.new title: "foo"
-    assert !topic.valid?
-    assert topic.errors[:title].empty?
+    assert_not_predicate topic, :valid?
+    assert_empty topic.errors[:title]
     assert_equal ["is missing"], topic.errors[:content]
   end
 end
diff --git a/activemodel/test/cases/validations_test.rb b/activemodel/test/cases/validations_test.rb
index ab8c41bbd0..7776233db5 100644
--- a/activemodel/test/cases/validations_test.rb
+++ b/activemodel/test/cases/validations_test.rb
@@ -30,7 +30,7 @@ class ValidationsTest < ActiveModel::TestCase
   def test_single_attr_validation_and_error_msg
     r = Reply.new
     r.title = "There's no content!"
-    assert r.invalid?
+    assert_predicate r, :invalid?
     assert r.errors[:content].any?, "A reply without content should mark that attribute as invalid"
     assert_equal ["is Empty"], r.errors["content"], "A reply without content should contain an error"
     assert_equal 1, r.errors.count
@@ -38,7 +38,7 @@ class ValidationsTest < ActiveModel::TestCase
 
   def test_double_attr_validation_and_error_msg
     r = Reply.new
-    assert r.invalid?
+    assert_predicate r, :invalid?
 
     assert r.errors[:title].any?, "A reply without title should mark that attribute as invalid"
     assert_equal ["is Empty"], r.errors["title"], "A reply without title should contain an error"
@@ -111,8 +111,8 @@ class ValidationsTest < ActiveModel::TestCase
 
   def test_errors_empty_after_errors_on_check
     t = Topic.new
-    assert t.errors[:id].empty?
-    assert t.errors.empty?
+    assert_empty t.errors[:id]
+    assert_empty t.errors
   end
 
   def test_validates_each
@@ -122,7 +122,7 @@ class ValidationsTest < ActiveModel::TestCase
       hits += 1
     end
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal 4, hits
     assert_equal %w(gotcha gotcha), t.errors[:title]
     assert_equal %w(gotcha gotcha), t.errors[:content]
@@ -135,7 +135,7 @@ class ValidationsTest < ActiveModel::TestCase
       hits += 1
     end
     t = CustomReader.new("title" => "valid", "content" => "whatever")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal 4, hits
     assert_equal %w(gotcha gotcha), t.errors[:title]
     assert_equal %w(gotcha gotcha), t.errors[:content]
@@ -146,16 +146,16 @@ class ValidationsTest < ActiveModel::TestCase
   def test_validate_block
     Topic.validate { errors.add("title", "will never be valid") }
     t = Topic.new("title" => "Title", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["will never be valid"], t.errors["title"]
   end
 
   def test_validate_block_with_params
     Topic.validate { |topic| topic.errors.add("title", "will never be valid") }
     t = Topic.new("title" => "Title", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["will never be valid"], t.errors["title"]
   end
 
@@ -214,7 +214,7 @@ class ValidationsTest < ActiveModel::TestCase
   def test_errors_conversions
     Topic.validates_presence_of %w(title content)
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     xml = t.errors.to_xml
     assert_match %r{<errors>}, xml
@@ -232,14 +232,14 @@ class ValidationsTest < ActiveModel::TestCase
     Topic.validates_length_of :title, minimum: 2
 
     t = Topic.new("title" => "")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal "can't be blank", t.errors["title"].first
     Topic.validates_presence_of :title, :author_name
     Topic.validate { errors.add("author_email_address", "will never be valid") }
     Topic.validates_length_of :title, :content, minimum: 2
 
     t = Topic.new title: ""
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     assert_equal :title, key = t.errors.keys[0]
     assert_equal "can't be blank", t.errors[key][0]
@@ -258,8 +258,8 @@ class ValidationsTest < ActiveModel::TestCase
     t = Topic.new(title: "")
 
     # If block should not fire
-    assert t.valid?
-    assert t.author_name.nil?
+    assert_predicate t, :valid?
+    assert_predicate t.author_name, :nil?
 
     # If block should fire
     assert t.invalid?(:update)
@@ -270,18 +270,18 @@ class ValidationsTest < ActiveModel::TestCase
     Topic.validates_presence_of :title
 
     t = Topic.new
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
 
     t.title = "Things are going to change"
-    assert !t.invalid?
+    assert_not_predicate t, :invalid?
   end
 
   def test_validation_with_message_as_proc
     Topic.validates_presence_of(:title, message: proc { "no blanks here".upcase })
 
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["NO BLANKS HERE"], t.errors[:title]
   end
 
@@ -331,13 +331,13 @@ class ValidationsTest < ActiveModel::TestCase
     Topic.validates :content, length: { minimum: 10 }
 
     topic = Topic.new
-    assert topic.invalid?
+    assert_predicate topic, :invalid?
     assert_equal 3, topic.errors.size
 
     topic.title = "Some Title"
     topic.author_name = "Some Author"
     topic.content = "Some Content Whose Length is more than 10."
-    assert topic.valid?
+    assert_predicate topic, :valid?
   end
 
   def test_validate
@@ -381,7 +381,7 @@ class ValidationsTest < ActiveModel::TestCase
 
   def test_strict_validation_not_fails
     Topic.validates :title, strict: true, presence: true
-    assert Topic.new(title: "hello").valid?
+    assert_predicate Topic.new(title: "hello"), :valid?
   end
 
   def test_strict_validation_particular_validator
@@ -414,7 +414,7 @@ class ValidationsTest < ActiveModel::TestCase
 
   def test_validates_with_false_hash_value
     Topic.validates :title, presence: false
-    assert Topic.new.valid?
+    assert_predicate Topic.new, :valid?
   end
 
   def test_strict_validation_error_message
@@ -439,19 +439,19 @@ class ValidationsTest < ActiveModel::TestCase
 
     duped = topic.dup
     duped.title = nil
-    assert duped.invalid?
+    assert_predicate duped, :invalid?
 
     topic.title = nil
     duped.title = "Mathematics"
-    assert topic.invalid?
-    assert duped.valid?
+    assert_predicate topic, :invalid?
+    assert_predicate duped, :valid?
   end
 
   def test_validation_with_message_as_proc_that_takes_a_record_as_a_parameter
     Topic.validates_presence_of(:title, message: proc { |record| "You have failed me for the last time, #{record.author_name}." })
 
     t = Topic.new(author_name: "Admiral")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["You have failed me for the last time, Admiral."], t.errors[:title]
   end
 
@@ -459,7 +459,7 @@ class ValidationsTest < ActiveModel::TestCase
     Topic.validates_presence_of(:title, message: proc { |record, data| "#{data[:attribute]} is missing. You have failed me for the last time, #{record.author_name}." })
 
     t = Topic.new(author_name: "Admiral")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["Title is missing. You have failed me for the last time, Admiral."], t.errors[:title]
   end
 end
diff --git a/activemodel/test/models/person.rb b/activemodel/test/models/person.rb
index b61fdf76b1..8dd8ceadad 100644
--- a/activemodel/test/models/person.rb
+++ b/activemodel/test/models/person.rb
@@ -9,6 +9,10 @@ class Person
   def condition_is_true
     true
   end
+
+  def condition_is_false
+    false
+  end
 end
 
 class Person::Gender
diff --git a/activemodel/test/models/topic.rb b/activemodel/test/models/topic.rb
index 2f4e92c3b2..b0af00ee45 100644
--- a/activemodel/test/models/topic.rb
+++ b/activemodel/test/models/topic.rb
@@ -23,7 +23,7 @@ class Topic
     true
   end
 
-  def condition_is_true_but_its_not
+  def condition_is_false
     false
   end
 
diff --git a/activerecord/.gitignore b/activerecord/.gitignore
new file mode 100644
index 0000000000..884ee009eb
--- /dev/null
+++ b/activerecord/.gitignore
@@ -0,0 +1,3 @@
+/sqlnet.log
+/test/config.yml
+/test/fixtures/*.sqlite*
diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 1a1a3a8092..dda7d19915 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,237 +1,48 @@
-*   Remove deprecated `#migration_keys`.
+*   Fix logic on disabling commit callbacks so they are not called unexpectedly when errors occur.
 
-    *Ryuta Kamizono*
+    *Brian Durand*
 
-*   Automatically guess the inverse associations for STI.
+*   Ensure `Associations::CollectionAssociation#size` and `Associations::CollectionAssociation#empty?`
+    use loaded association ids if present.
 
-    *Yuichiro Kaneko*
+    *Graham Turner*
 
-*   Ensure `sum` honors `distinct` on `has_many :through` associations
+*   Add support to preload associations of polymorphic associations when not all the records have the requested associations.
 
-    Fixes #16791.
+    *Dana Sherson*
 
-    *Aaron Wortham*
+*   Add `touch_all` method to `ActiveRecord::Relation`.
 
-*   Add `binary` fixture helper method.
+    Example:
 
-    *Atsushi Yoshida*
+        Person.where(name: "David").touch_all(time: Time.new(2020, 5, 16, 0, 0, 0))
 
-*   When using `Relation#or`, extract the common conditions and put them before the OR condition.
+    *fatkodima*, *duggiefresh*
 
-    *Maxime Handfield Lapointe*
+*   Add `ActiveRecord::Base.base_class?` predicate.
 
-*   `Relation#or` now accepts two relations who have different values for
-    `references` only, as `references` can be implicitly called by `where`.
+    *Bogdan Gusiev*
 
-    Fixes #29411.
+*   Add custom prefix option to ActiveRecord::Store.store_accessor.
 
-    *Sean Griffin*
+    *Tan Huynh*
 
-*   `ApplicationRecord` is no longer generated when generating models. If you
-    need to generate it, it can be created with `rails g application_record`.
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
-    *Lisa Ugray*
+    *Jeremy Daer*
 
-*   Fix `COUNT(DISTINCT ...)` with `ORDER BY` and `LIMIT` to keep the existing select list.
+*   Deprecate `update_attributes`/`!` in favor of `update`/`!`.
 
-    *Ryuta Kamizono*
+    *Eddie Lebow*
 
-*   When a `has_one` association is destroyed by `dependent: destroy`,
-    `destroyed_by_association` will now be set to the reflection, matching the
-    behaviour of `has_many` associations.
-
-    *Lisa Ugray*
-
-*   Fix `unscoped(where: [columns])` removing the wrong bind values
-
-    When the `where` is called on a relation after a `or`, unscoping the column of that later `where` removed
-    bind values used by the `or` instead. (possibly other cases too)
-
-    ```
-    Post.where(id: 1).or(Post.where(id: 2)).where(foo: 3).unscope(where: :foo).to_sql
-    # Currently:
-    #     SELECT "posts".* FROM "posts" WHERE ("posts"."id" = 2 OR "posts"."id" = 3)
-    # With fix:
-    #     SELECT "posts".* FROM "posts" WHERE ("posts"."id" = 1 OR "posts"."id" = 2)
-    ```
-
-    *Maxime Handfield Lapointe*
-
-*   Values constructed using multi-parameter assignment will now use the
-    post-type-cast value for rendering in single-field form inputs.
-
-    *Sean Griffin*
-
-*   `Relation#joins` is no longer affected by the target model's
-    `current_scope`, with the exception of `unscoped`.
-
-    Fixes #29338.
-
-    *Sean Griffin*
-
-*   Change sqlite3 boolean serialization to use 1 and 0
-
-    SQLite natively recognizes 1 and 0 as true and false, but does not natively
-    recognize 't' and 'f' as was previously serialized.
-
-    This change in serialization requires a migration of stored boolean data
-    for SQLite databases, so it's implemented behind a configuration flag
-    whose default false value is deprecated.
-
-    *Lisa Ugray*
-
-*   Skip query caching when working with batches of records (`find_each`, `find_in_batches`,
-    `in_batches`).
-
-    Previously, records would be fetched in batches, but all records would be retained in memory
-    until the end of the request or job.
-
-    *Eugene Kenny*
-
-*   Prevent errors raised by `sql.active_record` notification subscribers from being converted into
-    `ActiveRecord::StatementInvalid` exceptions.
-
-    *Dennis Taylor*
-
-*   Fix eager loading/preloading association with scope including joins.
-
-    Fixes #28324.
-
-    *Ryuta Kamizono*
-
-*   Fix transactions to apply state to child transactions
-
-    Previously, if you had a nested transaction and the outer transaction was rolledback, the record from the
-    inner transaction would still be marked as persisted.
-
-    This change fixes that by applying the state of the parent transaction to the child transaction when the
-    parent transaction is rolledback. This will correctly mark records from the inner transaction as not persisted.
-
-    *Eileen M. Uchitelle*, *Aaron Patterson*
-
-*   Deprecate `set_state` method in `TransactionState`
-
-    Deprecated the `set_state` method in favor of setting the state via specific methods. If you need to mark the
-    state of the transaction you can now use `rollback!`, `commit!` or `nullify!` instead of
-    `set_state(:rolledback)`, `set_state(:committed)`, or `set_state(nil)`.
-
-    *Eileen M. Uchitelle*, *Aaron Patterson*
-
-*   Deprecate delegating to `arel` in `Relation`.
-
-    *Ryuta Kamizono*
-
-*   Fix eager loading to respect `store_full_sti_class` setting.
-
-    *Ryuta Kamizono*
-
-*   Query cache was unavailable when entering the `ActiveRecord::Base.cache` block
-    without being connected.
-
-    *Tsukasa Oishi*
-
-*   Previously, when building records using a `has_many :through` association,
-    if the child records were deleted before the parent was saved, they would
-    still be persisted. Now, if child records are deleted before the parent is saved
-    on a `has_many :through` association, the child records will not be persisted.
-
-    *Tobias Kraze*
-
-*   Merging two relations representing nested joins no longer transforms the joins of
-    the merged relation into LEFT OUTER JOIN. Example to clarify:
-
-    ```
-    Author.joins(:posts).merge(Post.joins(:comments))
-    # Before the change:
-    #=> SELECT ... FROM authors INNER JOIN posts ON ... LEFT OUTER JOIN comments ON...
-
-    # After the change:
-    #=> SELECT ... FROM authors INNER JOIN posts ON ... INNER JOIN comments ON...
-    ```
-
-    TODO: Add to the Rails 5.2 upgrade guide
-
-    *Maxime Handfield Lapointe*
-
-*   `ActiveRecord::Persistence#touch` does not work well when optimistic locking enabled and
-    `locking_column`, without default value, is null in the database.
-
-    *bogdanvlviv*
-
-*   Fix destroying existing object does not work well when optimistic locking enabled and
-    `locking_column` is null in the database.
-
-    *bogdanvlviv*
-
-*   Use bulk INSERT to insert fixtures for better performance.
-
-    *Kir Shatrov*
-
-*   Prevent creation of bind param if casted value is nil.
-
-    *Ryuta Kamizono*
-
-*   Deprecate passing arguments and block at the same time to `count` and `sum` in `ActiveRecord::Calculations`.
-
-    *Ryuta Kamizono*
-
-*   Loading model schema from database is now thread-safe.
-
-    Fixes #28589.
-
-    *Vikrant Chaudhary*, *David Abdemoulaie*
-
-*   Add `ActiveRecord::Base#cache_version` to support recyclable cache keys via the new versioned entries
-    in `ActiveSupport::Cache`. This also means that `ActiveRecord::Base#cache_key` will now return a stable key
-    that does not include a timestamp any more.
-
-    NOTE: This feature is turned off by default, and `#cache_key` will still return cache keys with timestamps
-    until you set `ActiveRecord::Base.cache_versioning = true`. That's the setting for all new apps on Rails 5.2+
+*   Add ActiveRecord::Base.create_or_find_by/! to deal with the SELECT/INSERT race condition in
+    ActiveRecord::Base.find_or_create_by/! by leaning on unique constraints in the database.
 
     *DHH*
 
-*   Respect `SchemaDumper.ignore_tables` in rake tasks for databases structure dump
+*   Add `Relation#pick` as short-hand for single-value plucks.
 
-    *Rusty Geldmacher*, *Guillermo Iguaran*
-
-*   Add type caster to `RuntimeReflection#alias_name`
-
-    Fixes #28959.
-
-    *Jon Moss*
-
-*   Deprecate `supports_statement_cache?`.
-
-    *Ryuta Kamizono*
-
-*   Quote database name in `db:create` grant statement (when database user does not have access to create the database).
-
-    *Rune Philosof*
-
-*   Raise error `UnknownMigrationVersionError` on the movement of migrations
-    when the current migration does not exist.
-
-    *bogdanvlviv*
-
-*   Fix `bin/rails db:forward` first migration.
-
-    *bogdanvlviv*
-
-*   Support Descending Indexes for MySQL.
-
-    MySQL 8.0.1 and higher supports descending indexes: `DESC` in an index definition is no longer ignored.
-    See https://dev.mysql.com/doc/refman/8.0/en/descending-indexes.html.
-
-    *Ryuta Kamizono*
-
-*   Fix inconsistency with changed attributes when overriding AR attribute reader.
-
-    *bogdanvlviv*
-
-*   When calling the dynamic fixture accessor method with no arguments, it now returns all fixtures of this type.
-    Previously this method always returned an empty array.
-
-    *Kevin McPhillips*
+    *DHH*
 
 
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/activerecord/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/activerecord/CHANGELOG.md) for previous changes.
diff --git a/activerecord/MIT-LICENSE b/activerecord/MIT-LICENSE
index f9e4444f07..04ba107c48 100644
--- a/activerecord/MIT-LICENSE
+++ b/activerecord/MIT-LICENSE
@@ -1,4 +1,6 @@
-Copyright (c) 2004-2017 David Heinemeier Hansson
+Copyright (c) 2004-2018 David Heinemeier Hansson
+
+Arel originally copyright (c) 2007-2016 Nick Kallen, Bryan Helmkamp, Emilio Tagua, Aaron Patterson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/activerecord/README.rdoc b/activerecord/README.rdoc
index ae53ecd177..19650b82ae 100644
--- a/activerecord/README.rdoc
+++ b/activerecord/README.rdoc
@@ -26,7 +26,7 @@ The Product class is automatically mapped to the table named "products",
 which might look like this:
 
    CREATE TABLE products (
-     id int NOT NULL auto_increment,
+     id bigint NOT NULL auto_increment,
      name varchar(255),
      PRIMARY KEY  (id)
    );
@@ -208,7 +208,7 @@ API documentation is at:
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/activerecord/Rakefile b/activerecord/Rakefile
index 57c82bf469..170c95b827 100644
--- a/activerecord/Rakefile
+++ b/activerecord/Rakefile
@@ -41,9 +41,11 @@ namespace :test do
   end
 end
 
-desc "Build MySQL and PostgreSQL test databases"
 namespace :db do
+  desc "Build MySQL and PostgreSQL test databases"
   task create: ["db:mysql:build", "db:postgresql:build"]
+
+  desc "Drop MySQL and PostgreSQL test databases"
   task drop: ["db:mysql:drop", "db:postgresql:drop"]
 end
 
@@ -68,7 +70,7 @@ end
         (Dir["test/cases/**/*_test.rb"].reject {
           |x| x.include?("/adapters/")
         } + Dir["test/cases/adapters/#{adapter_short}/**/*_test.rb"]).all? do |file|
-          sh(Gem.ruby, "-w" , "-Itest", file)
+          sh(Gem.ruby, "-w", "-Itest", file)
         end || raise("Failures")
       end
     end
diff --git a/activerecord/activerecord.gemspec b/activerecord/activerecord.gemspec
index 7ad06fe840..a857d00c05 100644
--- a/activerecord/activerecord.gemspec
+++ b/activerecord/activerecord.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Object-relational mapper framework (part of Rails)."
   s.description = "Databases on Rails. Build a persistent domain model by mapping database tables to Ruby classes. Strong conventions for associations, validations, aggregations, migrations, and testing come baked-in."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
@@ -30,6 +30,4 @@ Gem::Specification.new do |s|
 
   s.add_dependency "activesupport", version
   s.add_dependency "activemodel",   version
-
-  s.add_dependency "arel", "9.0.0.alpha"
 end
diff --git a/activerecord/bin/test b/activerecord/bin/test
index 83c192531e..9ecf27ce67 100755
--- a/activerecord/bin/test
+++ b/activerecord/bin/test
@@ -1,6 +1,12 @@
 #!/usr/bin/env ruby
 # frozen_string_literal: true
 
+adapter_index = ARGV.index("--adapter") || ARGV.index("-a")
+if adapter_index
+  ARGV.delete_at(adapter_index)
+  ENV["ARCONN"] = ARGV.delete_at(adapter_index).strip
+end
+
 COMPONENT_ROOT = File.expand_path("..", __dir__)
 require_relative "../../tools/test"
 
@@ -17,4 +23,5 @@ module Minitest
   end
 end
 
+Minitest.load_plugins
 Minitest.extensions.unshift "active_record"
diff --git a/activerecord/examples/.gitignore b/activerecord/examples/.gitignore
deleted file mode 100644
index 0dfc1cb7fb..0000000000
--- a/activerecord/examples/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-performance.sql
diff --git a/activerecord/lib/active_record.rb b/activerecord/lib/active_record.rb
index 0c19fed9e1..d198466dbf 100644
--- a/activerecord/lib/active_record.rb
+++ b/activerecord/lib/active_record.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 #--
-# Copyright (c) 2004-2017 David Heinemeier Hansson
+# Copyright (c) 2004-2018 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the
@@ -27,19 +27,20 @@ require "active_support"
 require "active_support/rails"
 require "active_model"
 require "arel"
+require "yaml"
 
-require_relative "active_record/version"
-require_relative "active_record/attribute_set"
+require "active_record/version"
+require "active_model/attribute_set"
 
 module ActiveRecord
   extend ActiveSupport::Autoload
 
-  autoload :Attribute
   autoload :Base
   autoload :Callbacks
   autoload :Core
   autoload :ConnectionHandling
   autoload :CounterCache
+  autoload :DatabaseConfigurations
   autoload :DynamicMatchers
   autoload :Enum
   autoload :InternalMetadata
@@ -104,6 +105,7 @@ module ActiveRecord
 
     autoload :Result
     autoload :TableMetadata
+    autoload :Type
   end
 
   module Coders
@@ -162,6 +164,7 @@ module ActiveRecord
       "active_record/tasks/postgresql_database_tasks"
   end
 
+  autoload :TestDatabases, "active_record/test_databases"
   autoload :TestFixtures, "active_record/fixtures"
 
   def self.eager_load!
@@ -181,3 +184,7 @@ end
 ActiveSupport.on_load(:i18n) do
   I18n.load_path << File.expand_path("active_record/locale/en.yml", __dir__)
 end
+
+YAML.load_tags["!ruby/object:ActiveRecord::AttributeSet"] = "ActiveModel::AttributeSet"
+YAML.load_tags["!ruby/object:ActiveRecord::Attribute::FromDatabase"] = "ActiveModel::Attribute::FromDatabase"
+YAML.load_tags["!ruby/object:ActiveRecord::LazyAttributeHash"] = "ActiveModel::LazyAttributeHash"
diff --git a/activerecord/lib/active_record/aggregations.rb b/activerecord/lib/active_record/aggregations.rb
index e5e89734d2..27a641f05b 100644
--- a/activerecord/lib/active_record/aggregations.rb
+++ b/activerecord/lib/active_record/aggregations.rb
@@ -35,7 +35,7 @@ module ActiveRecord
       # the database).
       #
       #   class Customer < ActiveRecord::Base
-      #     composed_of :balance, class_name: "Money", mapping: %w(amount currency)
+      #     composed_of :balance, class_name: "Money", mapping: %w(balance amount)
       #     composed_of :address, mapping: [ %w(address_street street), %w(address_city city) ]
       #   end
       #
@@ -177,9 +177,9 @@ module ActiveRecord
       #
       # Once a #composed_of relationship is specified for a model, records can be loaded from the database
       # by specifying an instance of the value object in the conditions hash. The following example
-      # finds all customers with +balance_amount+ equal to 20 and +balance_currency+ equal to "USD":
+      # finds all customers with +address_street+ equal to "May Street" and +address_city+ equal to "Chicago":
       #
-      #   Customer.where(balance: Money.new(20, "USD"))
+      #   Customer.where(address: Address.new("May Street", "Chicago"))
       #
       module ClassMethods
         # Adds reader and writer methods for manipulating a value object:
@@ -212,8 +212,7 @@ module ActiveRecord
         #
         # Option examples:
         #   composed_of :temperature, mapping: %w(reading celsius)
-        #   composed_of :balance, class_name: "Money", mapping: %w(balance amount),
-        #                         converter: Proc.new { |balance| balance.to_money }
+        #   composed_of :balance, class_name: "Money", mapping: %w(balance amount)
         #   composed_of :address, mapping: [ %w(address_street street), %w(address_city city) ]
         #   composed_of :gps_location
         #   composed_of :gps_location, allow_nil: true
diff --git a/activerecord/lib/active_record/association_relation.rb b/activerecord/lib/active_record/association_relation.rb
index 2b0b2864bc..403667fb70 100644
--- a/activerecord/lib/active_record/association_relation.rb
+++ b/activerecord/lib/active_record/association_relation.rb
@@ -2,8 +2,8 @@
 
 module ActiveRecord
   class AssociationRelation < Relation
-    def initialize(klass, table, predicate_builder, association)
-      super(klass, table, predicate_builder)
+    def initialize(klass, association)
+      super(klass)
       @association = association
     end
 
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index a61c0336db..3b581d6fe8 100644
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -3,7 +3,7 @@
 require "active_support/core_ext/enumerable"
 require "active_support/core_ext/string/conversions"
 require "active_support/core_ext/module/remove_method"
-require_relative "errors"
+require "active_record/errors"
 
 module ActiveRecord
   class AssociationNotFoundError < ConfigurationError #:nodoc:
@@ -140,26 +140,6 @@ module ActiveRecord
   class HasOneThroughCantAssociateThroughHasOneOrManyReflection < ThroughCantAssociateThroughHasOneOrManyReflection #:nodoc:
   end
 
-  class HasManyThroughCantAssociateNewRecords < ActiveRecordError #:nodoc:
-    def initialize(owner = nil, reflection = nil)
-      if owner && reflection
-        super("Cannot associate new records through '#{owner.class.name}##{reflection.name}' on '#{reflection.source_reflection.class_name rescue nil}##{reflection.source_reflection.name rescue nil}'. Both records must have an id in order to create the has_many :through record associating them.")
-      else
-        super("Cannot associate new records.")
-      end
-    end
-  end
-
-  class HasManyThroughCantDissociateNewRecords < ActiveRecordError #:nodoc:
-    def initialize(owner = nil, reflection = nil)
-      if owner && reflection
-        super("Cannot dissociate new records through '#{owner.class.name}##{reflection.name}' on '#{reflection.source_reflection.class_name rescue nil}##{reflection.source_reflection.name rescue nil}'. Both records must have an id in order to delete the has_many :through record associating them.")
-      else
-        super("Cannot dissociate new records.")
-      end
-    end
-  end
-
   class ThroughNestedAssociationsAreReadonly < ActiveRecordError #:nodoc:
     def initialize(owner = nil, reflection = nil)
       if owner && reflection
@@ -189,16 +169,6 @@ module ActiveRecord
     end
   end
 
-  class ReadOnlyAssociation < ActiveRecordError #:nodoc:
-    def initialize(reflection = nil)
-      if reflection
-        super("Cannot add to a has_many :through association. Try adding to #{reflection.through_reflection.name.inspect}.")
-      else
-        super("Read-only reflection error.")
-      end
-    end
-  end
-
   # This error is raised when trying to destroy a parent instance in N:1 or 1:1 associations
   # (has_many, has_one) when there is at least 1 child associated instance.
   # ex: if @project.tasks.size > 0, DeleteRestrictionError will be raised when trying to destroy @project
@@ -271,7 +241,7 @@ module ActiveRecord
       association
     end
 
-    def association_cached?(name) # :nodoc
+    def association_cached?(name) # :nodoc:
       @association_cache.key?(name)
     end
 
@@ -322,13 +292,13 @@ module ActiveRecord
       #
       # The project class now has the following methods (and more) to ease the traversal and
       # manipulation of its relationships:
-      # * <tt>Project#portfolio, Project#portfolio=(portfolio), Project#portfolio.nil?</tt>
-      # * <tt>Project#project_manager, Project#project_manager=(project_manager), Project#project_manager.nil?,</tt>
-      # * <tt>Project#milestones.empty?, Project#milestones.size, Project#milestones, Project#milestones<<(milestone),</tt>
-      #   <tt>Project#milestones.delete(milestone), Project#milestones.destroy(milestone), Project#milestones.find(milestone_id),</tt>
-      #   <tt>Project#milestones.build, Project#milestones.create</tt>
-      # * <tt>Project#categories.empty?, Project#categories.size, Project#categories, Project#categories<<(category1),</tt>
-      #   <tt>Project#categories.delete(category1), Project#categories.destroy(category1)</tt>
+      # * <tt>Project#portfolio</tt>, <tt>Project#portfolio=(portfolio)</tt>, <tt>Project#reload_portfolio</tt>
+      # * <tt>Project#project_manager</tt>, <tt>Project#project_manager=(project_manager)</tt>, <tt>Project#reload_project_manager</tt>
+      # * <tt>Project#milestones.empty?</tt>, <tt>Project#milestones.size</tt>, <tt>Project#milestones</tt>, <tt>Project#milestones<<(milestone)</tt>,
+      #   <tt>Project#milestones.delete(milestone)</tt>, <tt>Project#milestones.destroy(milestone)</tt>, <tt>Project#milestones.find(milestone_id)</tt>,
+      #   <tt>Project#milestones.build</tt>, <tt>Project#milestones.create</tt>
+      # * <tt>Project#categories.empty?</tt>, <tt>Project#categories.size</tt>, <tt>Project#categories</tt>, <tt>Project#categories<<(category1)</tt>,
+      #   <tt>Project#categories.delete(category1)</tt>, <tt>Project#categories.destroy(category1)</tt>
       #
       # === A word of warning
       #
@@ -483,14 +453,14 @@ module ActiveRecord
       # The tables for these classes could look something like:
       #
       #   CREATE TABLE users (
-      #     id int NOT NULL auto_increment,
-      #     account_id int default NULL,
+      #     id bigint NOT NULL auto_increment,
+      #     account_id bigint default NULL,
       #     name varchar default NULL,
       #     PRIMARY KEY  (id)
       #   )
       #
       #   CREATE TABLE accounts (
-      #     id int NOT NULL auto_increment,
+      #     id bigint NOT NULL auto_increment,
       #     name varchar default NULL,
       #     PRIMARY KEY  (id)
       #   )
@@ -557,9 +527,8 @@ module ActiveRecord
       #     has_many :birthday_events, ->(user) { where(starts_on: user.birthday) }, class_name: 'Event'
       #   end
       #
-      # Note: Joining, eager loading and preloading of these associations is not fully possible.
+      # Note: Joining, eager loading and preloading of these associations is not possible.
       # These operations happen before instance creation and the scope will be called with a +nil+ argument.
-      # This can lead to unexpected behavior and is deprecated.
       #
       # == Association callbacks
       #
@@ -850,7 +819,7 @@ module ActiveRecord
       #   project.milestones             # fetches milestones from the database
       #   project.milestones.size        # uses the milestone cache
       #   project.milestones.empty?      # uses the milestone cache
-      #   project.milestones(true).size  # fetches milestones from the database
+      #   project.milestones.reload.size # fetches milestones from the database
       #   project.milestones             # uses the milestone cache
       #
       # == Eager loading of associations
@@ -1092,12 +1061,6 @@ module ActiveRecord
       #      belongs_to :dungeon, inverse_of: :evil_wizard
       #    end
       #
-      # There are limitations to <tt>:inverse_of</tt> support:
-      #
-      # * does not work with <tt>:through</tt> associations.
-      # * does not work with <tt>:polymorphic</tt> associations.
-      # * inverse associations for #belongs_to associations #has_many are ignored.
-      #
       # For more information, see the documentation for the +:inverse_of+ option.
       #
       # == Deleting from associations
@@ -1310,6 +1273,9 @@ module ActiveRecord
         #   Specify the foreign key used for the association. By default this is guessed to be the name
         #   of this class in lower-case and "_id" suffixed. So a Person class that makes a #has_many
         #   association will use "person_id" as the default <tt>:foreign_key</tt>.
+        #
+        #   If you are going to modify the association (rather than just read from it), then it is
+        #   a good idea to set the <tt>:inverse_of</tt> option.
         # [:foreign_type]
         #   Specify the column used to store the associated object's type, if this is a polymorphic
         #   association. By default this is guessed to be the name of the polymorphic association
@@ -1383,8 +1349,7 @@ module ActiveRecord
         #   <tt>:autosave</tt> to <tt>true</tt>.
         # [:inverse_of]
         #   Specifies the name of the #belongs_to association on the associated object
-        #   that is the inverse of this #has_many association. Does not work in combination
-        #   with <tt>:through</tt> or <tt>:as</tt> options.
+        #   that is the inverse of this #has_many association.
         #   See ActiveRecord::Associations::ClassMethods's overview on Bi-directional associations for more detail.
         # [:extend]
         #   Specifies a module or array of modules that will be extended into the association object returned.
@@ -1400,7 +1365,7 @@ module ActiveRecord
         #   has_many :tags, as: :taggable
         #   has_many :reports, -> { readonly }
         #   has_many :subscribers, through: :subscriptions, source: :user
-        def has_many(name, scope = nil, options = {}, &extension)
+        def has_many(name, scope = nil, **options, &extension)
           reflection = Builder::HasMany.build(self, name, scope, options, &extension)
           Reflection.add_reflection self, name, reflection
         end
@@ -1480,6 +1445,9 @@ module ActiveRecord
         #   Specify the foreign key used for the association. By default this is guessed to be the name
         #   of this class in lower-case and "_id" suffixed. So a Person class that makes a #has_one association
         #   will use "person_id" as the default <tt>:foreign_key</tt>.
+        #
+        #   If you are going to modify the association (rather than just read from it), then it is
+        #   a good idea to set the <tt>:inverse_of</tt> option.
         # [:foreign_type]
         #   Specify the column used to store the associated object's type, if this is a polymorphic
         #   association. By default this is guessed to be the name of the polymorphic association
@@ -1495,6 +1463,9 @@ module ActiveRecord
         #   <tt>:primary_key</tt>, and <tt>:foreign_key</tt> are ignored, as the association uses the
         #   source reflection. You can only use a <tt>:through</tt> query through a #has_one
         #   or #belongs_to association on the join model.
+        #
+        #   If you are going to modify the association (rather than just read from it), then it is
+        #   a good idea to set the <tt>:inverse_of</tt> option.
         # [:source]
         #   Specifies the source association name used by #has_one <tt>:through</tt> queries.
         #   Only use it if the name cannot be inferred from the association.
@@ -1515,8 +1486,7 @@ module ActiveRecord
         #   <tt>:autosave</tt> to <tt>true</tt>.
         # [:inverse_of]
         #   Specifies the name of the #belongs_to association on the associated object
-        #   that is the inverse of this #has_one association. Does not work in combination
-        #   with <tt>:through</tt> or <tt>:as</tt> options.
+        #   that is the inverse of this #has_one association.
         #   See ActiveRecord::Associations::ClassMethods's overview on Bi-directional associations for more detail.
         # [:required]
         #   When set to +true+, the association will also have its presence validated.
@@ -1534,7 +1504,7 @@ module ActiveRecord
         #   has_one :club, through: :membership
         #   has_one :primary_address, -> { where(primary: true) }, through: :addressables, source: :addressable
         #   has_one :credit_card, required: true
-        def has_one(name, scope = nil, options = {})
+        def has_one(name, scope = nil, **options)
           reflection = Builder::HasOne.build(self, name, scope, options)
           Reflection.add_reflection self, name, reflection
         end
@@ -1601,6 +1571,9 @@ module ActiveRecord
         #   association will use "person_id" as the default <tt>:foreign_key</tt>. Similarly,
         #   <tt>belongs_to :favorite_person, class_name: "Person"</tt> will use a foreign key
         #   of "favorite_person_id".
+        #
+        #   If you are going to modify the association (rather than just read from it), then it is
+        #   a good idea to set the <tt>:inverse_of</tt> option.
         # [:foreign_type]
         #   Specify the column used to store the associated object's type, if this is a polymorphic
         #   association. By default this is guessed to be the name of the association with a "_type"
@@ -1650,8 +1623,7 @@ module ActiveRecord
         #   +after_commit+ and +after_rollback+ callbacks are executed.
         # [:inverse_of]
         #   Specifies the name of the #has_one or #has_many association on the associated
-        #   object that is the inverse of this #belongs_to association. Does not work in
-        #   combination with the <tt>:polymorphic</tt> options.
+        #   object that is the inverse of this #belongs_to association.
         #   See ActiveRecord::Associations::ClassMethods's overview on Bi-directional associations for more detail.
         # [:optional]
         #   When set to +true+, the association will not have its presence validated.
@@ -1678,7 +1650,7 @@ module ActiveRecord
         #   belongs_to :company, touch: :employees_last_updated_at
         #   belongs_to :user, optional: true
         #   belongs_to :account, default: -> { company.account }
-        def belongs_to(name, scope = nil, options = {})
+        def belongs_to(name, scope = nil, **options)
           reflection = Builder::BelongsTo.build(self, name, scope, options)
           Reflection.add_reflection self, name, reflection
         end
@@ -1820,6 +1792,9 @@ module ActiveRecord
         #   of this class in lower-case and "_id" suffixed. So a Person class that makes
         #   a #has_and_belongs_to_many association to Project will use "person_id" as the
         #   default <tt>:foreign_key</tt>.
+        #
+        #   If you are going to modify the association (rather than just read from it), then it is
+        #   a good idea to set the <tt>:inverse_of</tt> option.
         # [:association_foreign_key]
         #   Specify the foreign key used for the association on the receiving side of the association.
         #   By default this is guessed to be the name of the associated class in lower-case and "_id" suffixed.
@@ -1848,7 +1823,7 @@ module ActiveRecord
 
           builder = Builder::HasAndBelongsToMany.new name, self, options
 
-          join_model = ActiveSupport::Deprecation.silence { builder.through_model }
+          join_model = builder.through_model
 
           const_set join_model.name, join_model
           private_constant join_model.name
@@ -1877,7 +1852,7 @@ module ActiveRecord
             hm_options[k] = options[k] if options.key? k
           end
 
-          ActiveSupport::Deprecation.silence { has_many name, scope, hm_options, &extension }
+          has_many name, scope, hm_options, &extension
           _reflections[name.to_s].parent_reflection = habtm_reflection
         end
       end
diff --git a/activerecord/lib/active_record/associations/alias_tracker.rb b/activerecord/lib/active_record/associations/alias_tracker.rb
index 096f016976..4f3893588e 100644
--- a/activerecord/lib/active_record/associations/alias_tracker.rb
+++ b/activerecord/lib/active_record/associations/alias_tracker.rb
@@ -6,46 +6,36 @@ module ActiveRecord
   module Associations
     # Keeps track of table aliases for ActiveRecord::Associations::JoinDependency
     class AliasTracker # :nodoc:
-      def self.create(connection, initial_table)
-        aliases = Hash.new(0)
-        aliases[initial_table] = 1
-        new(connection, aliases)
-      end
-
-      def self.create_with_joins(connection, initial_table, joins)
+      def self.create(connection, initial_table, joins)
         if joins.empty?
-          create(connection, initial_table)
+          aliases = Hash.new(0)
         else
           aliases = Hash.new { |h, k|
             h[k] = initial_count_for(connection, k, joins)
           }
-          aliases[initial_table] = 1
-          new(connection, aliases)
         end
+        aliases[initial_table] = 1
+        new(connection, aliases)
       end
 
       def self.initial_count_for(connection, name, table_joins)
-        # quoted_name should be downcased as some database adapters (Oracle) return quoted name in uppercase
-        quoted_name = connection.quote_table_name(name).downcase
+        quoted_name = nil
 
         counts = table_joins.map do |join|
           if join.is_a?(Arel::Nodes::StringJoin)
+            # quoted_name should be case ignored as some database adapters (Oracle) return quoted name in uppercase
+            quoted_name ||= connection.quote_table_name(name)
+
             # Table names + table aliases
-            join.left.downcase.scan(
-              /join(?:\s+\w+)?\s+(\S+\s+)?#{quoted_name}\son/
+            join.left.scan(
+              /JOIN(?:\s+\w+)?\s+(?:\S+\s+)?(?:#{quoted_name}|#{name})\sON/i
             ).size
-          elsif join.respond_to? :left
-            join.left.table_name == name ? 1 : 0
+          elsif join.is_a?(Arel::Nodes::Join)
+            join.left.name == name ? 1 : 0
+          elsif join.is_a?(Hash)
+            join.fetch(name, 0)
           else
-            # this branch is reached by two tests:
-            #
-            # activerecord/test/cases/associations/cascaded_eager_loading_test.rb:37
-            #   with :posts
-            #
-            # activerecord/test/cases/associations/eager_test.rb:1133
-            #   with :comments
-            #
-            0
+            raise ArgumentError, "joins list should be initialized by list of Arel::Nodes::Join"
           end
         end
 
@@ -79,10 +69,7 @@ module ActiveRecord
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-        attr_reader :aliases
+      attr_reader :aliases
 
       private
 
diff --git a/activerecord/lib/active_record/associations/association.rb b/activerecord/lib/active_record/associations/association.rb
index 268b022ab8..ca8c7794e0 100644
--- a/activerecord/lib/active_record/associations/association.rb
+++ b/activerecord/lib/active_record/associations/association.rb
@@ -124,14 +124,14 @@ module ActiveRecord
       # Can be overridden (i.e. in ThroughAssociation) to merge in other scopes (i.e. the
       # through association's scope)
       def target_scope
-        AssociationRelation.create(klass, klass.arel_table, klass.predicate_builder, self).merge!(klass.all)
+        AssociationRelation.create(klass, self).merge!(klass.all)
       end
 
       def extensions
         extensions = klass.default_extensions | reflection.extensions
 
-        if scope = reflection.scope
-          extensions |= klass.unscoped.instance_exec(owner, &scope).extensions
+        if reflection.scope
+          extensions |= reflection.scope_for(klass.unscoped, owner).extensions
         end
 
         extensions
@@ -156,9 +156,9 @@ module ActiveRecord
         reset
       end
 
-      # We can't dump @reflection since it contains the scope proc
+      # We can't dump @reflection and @through_reflection since it contains the scope proc
       def marshal_dump
-        ivars = (instance_variables - [:@reflection]).map { |name| [name, instance_variable_get(name)] }
+        ivars = (instance_variables - [:@reflection, :@through_reflection]).map { |name| [name, instance_variable_get(name)] }
         [@reflection.name, ivars]
       end
 
@@ -201,8 +201,8 @@ module ActiveRecord
           if (reflection.has_one? || reflection.collection?) && !options[:through]
             attributes[reflection.foreign_key] = owner[reflection.active_record_primary_key]
 
-            if reflection.options[:as]
-              attributes[reflection.type] = owner.class.base_class.name
+            if reflection.type
+              attributes[reflection.type] = owner.class.polymorphic_name
             end
           end
 
diff --git a/activerecord/lib/active_record/associations/association_scope.rb b/activerecord/lib/active_record/associations/association_scope.rb
index 3d79e540b8..0a90a6104a 100644
--- a/activerecord/lib/active_record/associations/association_scope.rb
+++ b/activerecord/lib/active_record/associations/association_scope.rb
@@ -23,15 +23,10 @@ module ActiveRecord
         reflection = association.reflection
         scope = klass.unscoped
         owner = association.owner
-        alias_tracker = AliasTracker.create(klass.connection, klass.table_name)
-        chain_head, chain_tail = get_chain(reflection, association, alias_tracker)
+        chain = get_chain(reflection, association, scope.alias_tracker)
 
         scope.extending! reflection.extensions
-        add_constraints(scope, owner, reflection, chain_head, chain_tail)
-      end
-
-      def join_type
-        Arel::Nodes::InnerJoin
+        add_constraints(scope, owner, chain)
       end
 
       def self.get_bind_values(owner, chain)
@@ -40,38 +35,35 @@ module ActiveRecord
 
         binds << last_reflection.join_id_for(owner)
         if last_reflection.type
-          binds << owner.class.base_class.name
+          binds << owner.class.polymorphic_name
         end
 
         chain.each_cons(2).each do |reflection, next_reflection|
           if reflection.type
-            binds << next_reflection.klass.base_class.name
+            binds << next_reflection.klass.polymorphic_name
           end
         end
         binds
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
+      private
         attr_reader :value_transformation
 
-      private
         def join(table, constraint)
-          table.create_join(table, table.create_on(constraint), join_type)
+          table.create_join(table, table.create_on(constraint))
         end
 
-        def last_chain_scope(scope, table, reflection, owner)
+        def last_chain_scope(scope, reflection, owner)
           join_keys = reflection.join_keys
           key = join_keys.key
           foreign_key = join_keys.foreign_key
 
+          table = reflection.aliased_table
           value = transform_value(owner[foreign_key])
           scope = apply_scope(scope, table, key, value)
 
           if reflection.type
-            polymorphic_type = transform_value(owner.class.base_class.name)
+            polymorphic_type = transform_value(owner.class.polymorphic_name)
             scope = apply_scope(scope, table, reflection.type, polymorphic_type)
           end
 
@@ -82,15 +74,17 @@ module ActiveRecord
           value_transformation.call(value)
         end
 
-        def next_chain_scope(scope, table, reflection, foreign_table, next_reflection)
+        def next_chain_scope(scope, reflection, next_reflection)
           join_keys = reflection.join_keys
           key = join_keys.key
           foreign_key = join_keys.foreign_key
 
+          table = reflection.aliased_table
+          foreign_table = next_reflection.aliased_table
           constraint = table[key].eq(foreign_table[foreign_key])
 
           if reflection.type
-            value = transform_value(next_reflection.klass.base_class.name)
+            value = transform_value(next_reflection.klass.polymorphic_name)
             scope = apply_scope(scope, table, reflection.type, value)
           end
 
@@ -98,12 +92,11 @@ module ActiveRecord
         end
 
         class ReflectionProxy < SimpleDelegator # :nodoc:
-          attr_accessor :next
-          attr_reader :alias_name
+          attr_reader :aliased_table
 
-          def initialize(reflection, alias_name)
+          def initialize(reflection, aliased_table)
             super(reflection)
-            @alias_name = alias_name
+            @aliased_table = aliased_table
           end
 
           def all_includes; nil; end
@@ -111,43 +104,34 @@ module ActiveRecord
 
         def get_chain(reflection, association, tracker)
           name = reflection.name
-          runtime_reflection = Reflection::RuntimeReflection.new(reflection, association)
-          previous_reflection = runtime_reflection
+          chain = [Reflection::RuntimeReflection.new(reflection, association)]
           reflection.chain.drop(1).each do |refl|
-            alias_name = tracker.aliased_table_for(
+            aliased_table = tracker.aliased_table_for(
               refl.table_name,
               refl.alias_candidate(name),
               refl.klass.type_caster
             )
-            proxy = ReflectionProxy.new(refl, alias_name)
-            previous_reflection.next = proxy
-            previous_reflection = proxy
+            chain << ReflectionProxy.new(refl, aliased_table)
           end
-          [runtime_reflection, previous_reflection]
+          chain
         end
 
-        def add_constraints(scope, owner, refl, chain_head, chain_tail)
-          owner_reflection = chain_tail
-          table = owner_reflection.alias_name
-          scope = last_chain_scope(scope, table, owner_reflection, owner)
+        def add_constraints(scope, owner, chain)
+          scope = last_chain_scope(scope, chain.last, owner)
 
-          reflection = chain_head
-          while reflection
-            table = reflection.alias_name
-            next_reflection = reflection.next
-
-            unless reflection == chain_tail
-              foreign_table = next_reflection.alias_name
-              scope = next_chain_scope(scope, table, reflection, foreign_table, next_reflection)
-            end
+          chain.each_cons(2) do |reflection, next_reflection|
+            scope = next_chain_scope(scope, reflection, next_reflection)
+          end
 
+          chain_head = chain.first
+          chain.reverse_each do |reflection|
             # Exclude the scope of the association itself, because that
             # was already merged in the #scope method.
             reflection.constraints.each do |scope_chain_item|
-              item = eval_scope(reflection, table, scope_chain_item, owner)
+              item = eval_scope(reflection, scope_chain_item, owner)
 
-              if scope_chain_item == refl.scope
-                scope.merge! item.except(:where, :includes)
+              if scope_chain_item == chain_head.scope
+                scope.merge! item.except(:where, :includes, :unscope, :order)
               end
 
               reflection.all_includes do
@@ -156,10 +140,8 @@ module ActiveRecord
 
               scope.unscope!(*item.unscope_values)
               scope.where_clause += item.where_clause
-              scope.order_values |= item.order_values
+              scope.order_values = item.order_values | scope.order_values
             end
-
-            reflection = next_reflection
           end
 
           scope
@@ -173,8 +155,9 @@ module ActiveRecord
           end
         end
 
-        def eval_scope(reflection, table, scope, owner)
-          reflection.build_scope(table).instance_exec(owner, &scope)
+        def eval_scope(reflection, scope, owner)
+          relation = reflection.build_scope(reflection.aliased_table)
+          relation.instance_exec(owner, &scope) || relation
         end
     end
   end
diff --git a/activerecord/lib/active_record/associations/belongs_to_association.rb b/activerecord/lib/active_record/associations/belongs_to_association.rb
index 7a9f5f7937..c8716741b0 100644
--- a/activerecord/lib/active_record/associations/belongs_to_association.rb
+++ b/activerecord/lib/active_record/associations/belongs_to_association.rb
@@ -1,26 +1,24 @@
 # frozen_string_literal: true
 
 module ActiveRecord
-  # = Active Record Belongs To Association
   module Associations
+    # = Active Record Belongs To Association
     class BelongsToAssociation < SingularAssociation #:nodoc:
       def handle_dependency
-        target.send(options[:dependent]) if load_target
-      end
+        return unless load_target
 
-      def replace(record)
-        if record
-          raise_on_type_mismatch!(record)
-          update_counters_on_replace(record)
-          replace_keys(record)
-          set_inverse_instance(record)
-          @updated = true
+        case options[:dependent]
+        when :destroy
+          target.destroy
+          raise ActiveRecord::Rollback unless target.destroyed?
         else
-          decrement_counters
-          remove_keys
+          target.send(options[:dependent])
         end
+      end
 
-        self.target = record
+      def target=(record)
+        replace_keys(record)
+        super
       end
 
       def default(&block)
@@ -45,13 +43,25 @@ module ActiveRecord
       end
 
       private
+        def replace(record)
+          if record
+            raise_on_type_mismatch!(record)
+            update_counters_on_replace(record)
+            set_inverse_instance(record)
+            @updated = true
+          else
+            decrement_counters
+          end
+
+          self.target = record
+        end
 
         def update_counters(by)
           if require_counter_update? && foreign_key_present?
             if target && !stale_target?
-              target.increment!(reflection.counter_cache_column, by)
+              target.increment!(reflection.counter_cache_column, by, touch: reflection.options[:touch])
             else
-              klass.update_counters(target_id, reflection.counter_cache_column => by)
+              klass.update_counters(target_id, reflection.counter_cache_column => by, touch: reflection.options[:touch])
             end
           end
         end
@@ -78,11 +88,8 @@ module ActiveRecord
         end
 
         def replace_keys(record)
-          owner[reflection.foreign_key] = record._read_attribute(reflection.association_primary_key(record.class))
-        end
-
-        def remove_keys
-          owner[reflection.foreign_key] = nil
+          owner[reflection.foreign_key] = record ?
+            record._read_attribute(reflection.association_primary_key(record.class)) : nil
         end
 
         def foreign_key_present?
diff --git a/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb b/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
index 13b4a084ea..75b4c4481a 100644
--- a/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
+++ b/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
 module ActiveRecord
-  # = Active Record Belongs To Polymorphic Association
   module Associations
+    # = Active Record Belongs To Polymorphic Association
     class BelongsToPolymorphicAssociation < BelongsToAssociation #:nodoc:
       def klass
         type = owner[reflection.foreign_type]
@@ -13,12 +13,7 @@ module ActiveRecord
 
         def replace_keys(record)
           super
-          owner[reflection.foreign_type] = record.class.base_class.name
-        end
-
-        def remove_keys
-          super
-          owner[reflection.foreign_type] = nil
+          owner[reflection.foreign_type] = record ? record.class.polymorphic_name : nil
         end
 
         def different_target?(record)
diff --git a/activerecord/lib/active_record/associations/builder/association.rb b/activerecord/lib/active_record/associations/builder/association.rb
index 496b16b58f..7c69cd65ee 100644
--- a/activerecord/lib/active_record/associations/builder/association.rb
+++ b/activerecord/lib/active_record/associations/builder/association.rb
@@ -38,11 +38,6 @@ module ActiveRecord::Associations::Builder # :nodoc:
     def self.create_reflection(model, name, scope, options, extension = nil)
       raise ArgumentError, "association names must be a Symbol" unless name.kind_of?(Symbol)
 
-      if scope.is_a?(Hash)
-        options = scope
-        scope   = nil
-      end
-
       validate_options(options)
 
       scope = build_scope(scope, extension)
@@ -109,8 +104,8 @@ module ActiveRecord::Associations::Builder # :nodoc:
 
     def self.define_readers(mixin, name)
       mixin.class_eval <<-CODE, __FILE__, __LINE__ + 1
-        def #{name}(*args)
-          association(:#{name}).reader(*args)
+        def #{name}
+          association(:#{name}).reader
         end
       CODE
     end
diff --git a/activerecord/lib/active_record/associations/builder/belongs_to.rb b/activerecord/lib/active_record/associations/builder/belongs_to.rb
index 9904ee4bed..c161454c1a 100644
--- a/activerecord/lib/active_record/associations/builder/belongs_to.rb
+++ b/activerecord/lib/active_record/associations/builder/belongs_to.rb
@@ -114,9 +114,13 @@ module ActiveRecord::Associations::Builder # :nodoc:
         BelongsTo.touch_record(record, record.send(changes_method), foreign_key, n, touch, belongs_to_touch_method)
       }}
 
-      model.after_save    callback.(:saved_changes), if: :saved_changes?
-      model.after_touch   callback.(:changes_to_save)
-      model.after_destroy callback.(:changes_to_save)
+      unless reflection.counter_cache_column
+        model.after_create callback.(:saved_changes), if: :saved_changes?
+        model.after_destroy callback.(:changes_to_save)
+      end
+
+      model.after_update callback.(:saved_changes), if: :saved_changes?
+      model.after_touch callback.(:changes_to_save)
     end
 
     def self.add_default_callbacks(model, reflection)
diff --git a/activerecord/lib/active_record/associations/builder/collection_association.rb b/activerecord/lib/active_record/associations/builder/collection_association.rb
index 753fde5146..35a72c3850 100644
--- a/activerecord/lib/active_record/associations/builder/collection_association.rb
+++ b/activerecord/lib/active_record/associations/builder/collection_association.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../associations"
+require "active_record/associations"
 
 module ActiveRecord::Associations::Builder # :nodoc:
   class CollectionAssociation < Association #:nodoc:
diff --git a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
index 12fcfbcd45..1981da11a2 100644
--- a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
+++ b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
@@ -47,7 +47,7 @@ module ActiveRecord::Associations::Builder # :nodoc:
       habtm = JoinTableResolver.build lhs_model, association_name, options
 
       join_model = Class.new(ActiveRecord::Base) {
-        class << self;
+        class << self
           attr_accessor :left_model
           attr_accessor :name
           attr_accessor :table_name_resolver
diff --git a/activerecord/lib/active_record/associations/collection_association.rb b/activerecord/lib/active_record/associations/collection_association.rb
index ceedf150e3..d61d105544 100644
--- a/activerecord/lib/active_record/associations/collection_association.rb
+++ b/activerecord/lib/active_record/associations/collection_association.rb
@@ -45,6 +45,8 @@ module ActiveRecord
       def ids_reader
         if loaded?
           target.pluck(reflection.association_primary_key)
+        elsif !target.empty?
+          load_target.pluck(reflection.association_primary_key)
         else
           @association_ids ||= scope.pluck(reflection.association_primary_key)
         end
@@ -52,11 +54,11 @@ module ActiveRecord
 
       # Implements the ids writer method, e.g. foo.item_ids= for Foo.has_many :items
       def ids_writer(ids)
-        pk_type = reflection.association_primary_key_type
+        primary_key = reflection.association_primary_key
+        pk_type = klass.type_for_attribute(primary_key)
         ids = Array(ids).reject(&:blank?)
         ids.map! { |i| pk_type.cast(i) }
 
-        primary_key = reflection.association_primary_key
         records = klass.where(primary_key => ids).index_by do |r|
           r.public_send(primary_key)
         end.values_at(*ids).compact
@@ -79,7 +81,13 @@ module ActiveRecord
       def find(*args)
         if options[:inverse_of] && loaded?
           args_flatten = args.flatten
-          raise RecordNotFound, "Couldn't find #{scope.klass.name} without an ID" if args_flatten.blank?
+          model = scope.klass
+
+          if args_flatten.blank?
+            error_message = "Couldn't find #{model.name} without an ID"
+            raise RecordNotFound.new(error_message, model.name, model.primary_key, args)
+          end
+
           result = find_by_scan(*args)
 
           result_size = Array(result).size
@@ -181,8 +189,6 @@ module ActiveRecord
       # are actually removed from the database, that depends precisely on
       # +delete_records+. They are in any case removed from the collection.
       def delete(*records)
-        return if records.empty?
-        records = find(records) if records.any? { |record| record.kind_of?(Integer) || record.kind_of?(String) }
         delete_or_destroy(records, options[:dependent])
       end
 
@@ -192,8 +198,6 @@ module ActiveRecord
       # Note that this method removes records from the database ignoring the
       # +:dependent+ option.
       def destroy(*records)
-        return if records.empty?
-        records = find(records) if records.any? { |record| record.kind_of?(Integer) || record.kind_of?(String) }
         delete_or_destroy(records, :destroy)
       end
 
@@ -210,9 +214,11 @@ module ActiveRecord
       def size
         if !find_target? || loaded?
           target.size
+        elsif @association_ids
+          @association_ids.size
         elsif !association_scope.group_values.empty?
           load_target.size
-        elsif !association_scope.distinct_value && target.is_a?(Array)
+        elsif !association_scope.distinct_value && !target.empty?
           unsaved_records = target.select(&:new_record?)
           unsaved_records.size + count_records
         else
@@ -229,10 +235,10 @@ module ActiveRecord
       # loaded and you are going to fetch the records anyway it is better to
       # check <tt>collection.length.zero?</tt>.
       def empty?
-        if loaded?
+        if loaded? || @association_ids
           size.zero?
         else
-          @target.blank? && !scope.exists?
+          target.empty? && !scope.exists?
         end
       end
 
@@ -376,6 +382,8 @@ module ActiveRecord
         end
 
         def delete_or_destroy(records, method)
+          return if records.empty?
+          records = find(records) if records.any? { |record| record.kind_of?(Integer) || record.kind_of?(String) }
           records = records.flatten
           records.each { |record| raise_on_type_mismatch!(record) }
           existing_records = records.reject(&:new_record?)
diff --git a/activerecord/lib/active_record/associations/collection_proxy.rb b/activerecord/lib/active_record/associations/collection_proxy.rb
index 412e89255d..9a30198b95 100644
--- a/activerecord/lib/active_record/associations/collection_proxy.rb
+++ b/activerecord/lib/active_record/associations/collection_proxy.rb
@@ -32,7 +32,7 @@ module ActiveRecord
     class CollectionProxy < Relation
       def initialize(klass, association) #:nodoc:
         @association = association
-        super klass, klass.arel_table, klass.predicate_builder
+        super klass
 
         extensions = association.extensions
         extend(*extensions) if extensions.any?
@@ -988,6 +988,12 @@ module ActiveRecord
         load_target == other
       end
 
+      ##
+      # :method: to_ary
+      #
+      # :call-seq:
+      #   to_ary()
+      #
       # Returns a new array of objects from the collection. If the collection
       # hasn't been loaded, it fetches the records from the database.
       #
@@ -1021,10 +1027,6 @@ module ActiveRecord
       #   #       #<Pet id: 5, name: "Brain", person_id: 1>,
       #   #       #<Pet id: 6, name: "Boss",  person_id: 1>
       #   #    ]
-      def to_ary
-        load_target.dup
-      end
-      alias_method :to_a, :to_ary
 
       def records # :nodoc:
         load_target
@@ -1072,7 +1074,6 @@ module ActiveRecord
       end
 
       # Reloads the collection from the database. Returns +self+.
-      # Equivalent to <tt>collection(true)</tt>.
       #
       #   class Person < ActiveRecord::Base
       #     has_many :pets
@@ -1086,9 +1087,6 @@ module ActiveRecord
       #
       #   person.pets.reload # fetches pets from the database
       #   # => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]
-      #
-      #   person.pets(true)  # fetches pets from the database
-      #   # => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]
       def reload
         proxy_association.reload
         reset_scope
diff --git a/activerecord/lib/active_record/associations/has_many_association.rb b/activerecord/lib/active_record/associations/has_many_association.rb
index 88fe33eef2..cf85a87fa7 100644
--- a/activerecord/lib/active_record/associations/has_many_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_association.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
 module ActiveRecord
-  # = Active Record Has Many Association
   module Associations
+    # = Active Record Has Many Association
     # This is the proxy that handles a has many association.
     #
     # If the association has a <tt>:through</tt> option further specialization
@@ -63,7 +63,7 @@ module ActiveRecord
           count = if reflection.has_cached_counter?
             owner._read_attribute(reflection.counter_cache_column).to_i
           else
-            scope.count
+            scope.count(:all)
           end
 
           # If there's nothing in the database and @target has no new records
diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index 89ce00f98e..59929b8c4e 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -1,16 +1,14 @@
 # frozen_string_literal: true
 
 module ActiveRecord
-  # = Active Record Has Many Through Association
   module Associations
+    # = Active Record Has Many Through Association
     class HasManyThroughAssociation < HasManyAssociation #:nodoc:
       include ThroughAssociation
 
       def initialize(owner, reflection)
         super
-
-        @through_records     = {}
-        @through_association = nil
+        @through_records = {}
       end
 
       def concat(*records)
@@ -50,11 +48,6 @@ module ActiveRecord
       end
 
       private
-
-        def through_association
-          @through_association ||= owner.association(through_reflection.name)
-        end
-
         # The through record (built with build_record) is temporarily cached
         # so that it may be reused if insert_record is subsequently called.
         #
@@ -140,21 +133,15 @@ module ActiveRecord
 
           scope = through_association.scope
           scope.where! construct_join_attributes(*records)
+          scope = scope.where(through_scope_attributes)
 
           case method
           when :destroy
             if scope.klass.primary_key
-              count = scope.destroy_all.length
+              count = scope.destroy_all.count(&:destroyed?)
             else
               scope.each(&:_run_destroy_callbacks)
-
-              arel = scope.arel
-
-              stmt = Arel::DeleteManager.new
-              stmt.from scope.klass.arel_table
-              stmt.wheres = arel.constraints
-
-              count = scope.klass.connection.delete(stmt, "SQL")
+              count = scope.delete_all
             end
           when :nullify
             count = scope.update_all(source_reflection.foreign_key => nil)
diff --git a/activerecord/lib/active_record/associations/has_one_association.rb b/activerecord/lib/active_record/associations/has_one_association.rb
index 9a88c1af70..d211884135 100644
--- a/activerecord/lib/active_record/associations/has_one_association.rb
+++ b/activerecord/lib/active_record/associations/has_one_association.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
 module ActiveRecord
-  # = Active Record Has One Association
   module Associations
+    # = Active Record Has One Association
     class HasOneAssociation < SingularAssociation #:nodoc:
       include ForeignAssociation
 
@@ -23,35 +23,6 @@ module ActiveRecord
         end
       end
 
-      def replace(record, save = true)
-        raise_on_type_mismatch!(record) if record
-        load_target
-
-        return target unless target || record
-
-        assigning_another_record = target != record
-        if assigning_another_record || record.has_changes_to_save?
-          save &&= owner.persisted?
-
-          transaction_if(save) do
-            remove_target!(options[:dependent]) if target && !target.destroyed? && assigning_another_record
-
-            if record
-              set_owner_attributes(record)
-              set_inverse_instance(record)
-
-              if save && !record.save
-                nullify_owner_attributes(record)
-                set_owner_attributes(target) if target
-                raise RecordNotSaved, "Failed to save the new associated #{reflection.name}."
-              end
-            end
-          end
-        end
-
-        self.target = record
-      end
-
       def delete(method = options[:dependent])
         if load_target
           case method
@@ -60,6 +31,7 @@ module ActiveRecord
           when :destroy
             target.destroyed_by_association = reflection
             target.destroy
+            throw(:abort) unless target.destroyed?
           when :nullify
             target.update_columns(reflection.foreign_key => nil) if target.persisted?
           end
@@ -67,6 +39,33 @@ module ActiveRecord
       end
 
       private
+        def replace(record, save = true)
+          raise_on_type_mismatch!(record) if record
+
+          return target unless load_target || record
+
+          assigning_another_record = target != record
+          if assigning_another_record || record.has_changes_to_save?
+            save &&= owner.persisted?
+
+            transaction_if(save) do
+              remove_target!(options[:dependent]) if target && !target.destroyed? && assigning_another_record
+
+              if record
+                set_owner_attributes(record)
+                set_inverse_instance(record)
+
+                if save && !record.save
+                  nullify_owner_attributes(record)
+                  set_owner_attributes(target) if target
+                  raise RecordNotSaved, "Failed to save the new associated #{reflection.name}."
+                end
+              end
+            end
+          end
+
+          self.target = record
+        end
 
         # The reason that the save param for replace is false, if for create (not just build),
         # is because the setting of the foreign keys is actually handled by the scoping when
@@ -106,6 +105,14 @@ module ActiveRecord
             yield
           end
         end
+
+        def _create_record(attributes, raise_error = false)
+          unless owner.persisted?
+            raise ActiveRecord::RecordNotSaved, "You cannot call create unless the parent is saved"
+          end
+
+          super
+        end
     end
   end
 end
diff --git a/activerecord/lib/active_record/associations/has_one_through_association.rb b/activerecord/lib/active_record/associations/has_one_through_association.rb
index eb54977aa0..10978b2d93 100644
--- a/activerecord/lib/active_record/associations/has_one_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_one_through_association.rb
@@ -1,22 +1,21 @@
 # frozen_string_literal: true
 
 module ActiveRecord
-  # = Active Record Has One Through Association
   module Associations
+    # = Active Record Has One Through Association
     class HasOneThroughAssociation < HasOneAssociation #:nodoc:
       include ThroughAssociation
 
-      def replace(record)
-        create_through_record(record)
-        self.target = record
-      end
-
       private
+        def replace(record, save = true)
+          create_through_record(record, save)
+          self.target = record
+        end
 
-        def create_through_record(record)
+        def create_through_record(record, save)
           ensure_not_nested
 
-          through_proxy  = owner.association(through_reflection.name)
+          through_proxy  = through_association
           through_record = through_proxy.load_target
 
           if through_record && !record
@@ -29,8 +28,12 @@ module ActiveRecord
             end
 
             if through_record
-              through_record.update(attributes)
-            elsif owner.new_record?
+              if through_record.new_record?
+                through_record.assign_attributes(attributes)
+              else
+                through_record.update(attributes)
+              end
+            elsif owner.new_record? || !save
               through_proxy.build(attributes)
             else
               through_proxy.create(attributes)
diff --git a/activerecord/lib/active_record/associations/join_dependency.rb b/activerecord/lib/active_record/associations/join_dependency.rb
index ac37c3c015..f88e383fe0 100644
--- a/activerecord/lib/active_record/associations/join_dependency.rb
+++ b/activerecord/lib/active_record/associations/join_dependency.rb
@@ -43,8 +43,6 @@ module ActiveRecord
         Column = Struct.new(:name, :alias)
       end
 
-      attr_reader :alias_tracker, :base_klass, :join_root
-
       def self.make_tree(associations)
         hash = {}
         walk_tree associations, hash
@@ -69,30 +67,8 @@ module ActiveRecord
         end
       end
 
-      # base is the base class on which operation is taking place.
-      # associations is the list of associations which are joined using hash, symbol or array.
-      # joins is the list of all string join commands and arel nodes.
-      #
-      #  Example :
-      #
-      #  class Physician < ActiveRecord::Base
-      #    has_many :appointments
-      #    has_many :patients, through: :appointments
-      #  end
-      #
-      #  If I execute `@physician.patients.to_a` then
-      #    base # => Physician
-      #    associations # => []
-      #    joins # =>  [#<Arel::Nodes::InnerJoin: ...]
-      #
-      #  However if I execute `Physician.joins(:appointments).to_a` then
-      #    base # => Physician
-      #    associations # => [:appointments]
-      #    joins # =>  []
-      #
-      def initialize(base, table, associations, joins, eager_loading: true)
-        @alias_tracker = AliasTracker.create_with_joins(base.connection, base.table_name, joins)
-        @eager_loading = eager_loading
+      def initialize(base, table, associations, alias_tracker)
+        @alias_tracker = alias_tracker
         tree = self.class.make_tree associations
         @join_root = JoinBase.new(base, table, build(tree, base))
         @join_root.children.each { |child| construct_tables! @join_root, child }
@@ -158,6 +134,9 @@ module ActiveRecord
         parents.values
       end
 
+      protected
+        attr_reader :alias_tracker, :base_klass, :join_root
+
       private
 
         def make_constraints(parent, child, tables, join_type)
@@ -220,12 +199,11 @@ module ActiveRecord
             reflection.check_eager_loadable!
 
             if reflection.polymorphic?
-              next unless @eager_loading
               raise EagerLoadPolymorphicError.new(reflection)
             end
 
-            JoinAssociation.new reflection, build(right, reflection.klass)
-          end.compact
+            JoinAssociation.new(reflection, build(right, reflection.klass), alias_tracker)
+          end
         end
 
         def construct(ar_parent, parent, row, rs, seen, model_cache, aliases)
@@ -256,7 +234,8 @@ module ActiveRecord
             else
               model = construct_model(ar_parent, node, row, model_cache, id, aliases)
 
-              if node.reflection.scope_for(node.base_klass).readonly_value
+              if node.reflection.scope &&
+                  node.reflection.scope_for(node.base_klass.unscoped).readonly_value
                 model.readonly!
               end
 
diff --git a/activerecord/lib/active_record/associations/join_dependency/join_association.rb b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
index a526468bf6..c36386ec7e 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_association.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "join_part"
+require "active_record/associations/join_dependency/join_part"
 
 module ActiveRecord
   module Associations
@@ -11,11 +11,12 @@ module ActiveRecord
 
         attr_accessor :tables
 
-        def initialize(reflection, children)
+        def initialize(reflection, children, alias_tracker)
           super(reflection.klass, children)
 
-          @reflection      = reflection
-          @tables          = nil
+          @alias_tracker = alias_tracker
+          @reflection    = reflection
+          @tables        = nil
         end
 
         def match?(other)
@@ -38,11 +39,12 @@ module ActiveRecord
             joins << table.create_join(table, table.create_on(constraint), join_type)
 
             join_scope = reflection.join_scope(table, foreign_klass)
+            arel = join_scope.arel(alias_tracker.aliases)
 
-            if join_scope.arel.constraints.any?
-              joins.concat join_scope.arel.join_sources
+            if arel.constraints.any?
+              joins.concat arel.join_sources
               right = joins.last.right
-              right.expr = right.expr.and(join_scope.arel.constraints)
+              right.expr = right.expr.and(arel.constraints)
             end
 
             # The current table in this iteration becomes the foreign table in the next
@@ -55,6 +57,9 @@ module ActiveRecord
         def table
           tables.first
         end
+
+        private
+          attr_reader :alias_tracker
       end
     end
   end
diff --git a/activerecord/lib/active_record/associations/join_dependency/join_base.rb b/activerecord/lib/active_record/associations/join_dependency/join_base.rb
index 8a8fa8993b..988b4e8fa2 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_base.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_base.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "join_part"
+require "active_record/associations/join_dependency/join_part"
 
 module ActiveRecord
   module Associations
diff --git a/activerecord/lib/active_record/associations/preloader.rb b/activerecord/lib/active_record/associations/preloader.rb
index 62caf02a2c..5c2ac5b374 100644
--- a/activerecord/lib/active_record/associations/preloader.rb
+++ b/activerecord/lib/active_record/associations/preloader.rb
@@ -44,16 +44,8 @@ module ActiveRecord
       extend ActiveSupport::Autoload
 
       eager_autoload do
-        autoload :Association,           "active_record/associations/preloader/association"
-        autoload :SingularAssociation,   "active_record/associations/preloader/singular_association"
-        autoload :CollectionAssociation, "active_record/associations/preloader/collection_association"
-        autoload :ThroughAssociation,    "active_record/associations/preloader/through_association"
-
-        autoload :HasMany,             "active_record/associations/preloader/has_many"
-        autoload :HasManyThrough,      "active_record/associations/preloader/has_many_through"
-        autoload :HasOne,              "active_record/associations/preloader/has_one"
-        autoload :HasOneThrough,       "active_record/associations/preloader/has_one_through"
-        autoload :BelongsTo,           "active_record/associations/preloader/belongs_to"
+        autoload :Association,        "active_record/associations/preloader/association"
+        autoload :ThroughAssociation, "active_record/associations/preloader/through_association"
       end
 
       # Eager loads the named associations for the given Active Record record(s).
@@ -91,13 +83,13 @@ module ActiveRecord
       #   { author: :avatar }
       #   [ :books, { author: :avatar } ]
       def preload(records, associations, preload_scope = nil)
-        records       = Array.wrap(records).compact.uniq
-        associations  = Array.wrap(associations)
+        records = Array.wrap(records).compact
 
         if records.empty?
           []
         else
-          associations.flat_map { |association|
+          records.uniq!
+          Array.wrap(associations).flat_map { |association|
             preloaders_on association, records, preload_scope
           }
         end
@@ -106,26 +98,30 @@ module ActiveRecord
       private
 
         # Loads all the given data into +records+ for the +association+.
-        def preloaders_on(association, records, scope)
+        def preloaders_on(association, records, scope, polymorphic_parent = false)
           case association
           when Hash
-            preloaders_for_hash(association, records, scope)
+            preloaders_for_hash(association, records, scope, polymorphic_parent)
           when Symbol
-            preloaders_for_one(association, records, scope)
+            preloaders_for_one(association, records, scope, polymorphic_parent)
           when String
-            preloaders_for_one(association.to_sym, records, scope)
+            preloaders_for_one(association.to_sym, records, scope, polymorphic_parent)
           else
             raise ArgumentError, "#{association.inspect} was not recognized for preload"
           end
         end
 
-        def preloaders_for_hash(association, records, scope)
+        def preloaders_for_hash(association, records, scope, polymorphic_parent)
           association.flat_map { |parent, child|
-            loaders = preloaders_for_one parent, records, scope
+            loaders = preloaders_for_one parent, records, scope, polymorphic_parent
 
             recs = loaders.flat_map(&:preloaded_records).uniq
+
+            reflection = records.first.class._reflect_on_association(parent)
+            polymorphic_parent = reflection && reflection.options[:polymorphic]
+
             loaders.concat Array.wrap(child).flat_map { |assoc|
-              preloaders_on assoc, recs, scope
+              preloaders_on assoc, recs, scope, polymorphic_parent
             }
             loaders
           }
@@ -143,8 +139,8 @@ module ActiveRecord
         # Additionally, polymorphic belongs_to associations can have multiple associated
         # classes, depending on the polymorphic_type field. So we group by the classes as
         # well.
-        def preloaders_for_one(association, records, scope)
-          grouped_records(association, records).flat_map do |reflection, klasses|
+        def preloaders_for_one(association, records, scope, polymorphic_parent)
+          grouped_records(association, records, polymorphic_parent).flat_map do |reflection, klasses|
             klasses.map do |rhs_klass, rs|
               loader = preloader_for(reflection, rs).new(rhs_klass, rs, reflection, scope)
               loader.run self
@@ -153,10 +149,11 @@ module ActiveRecord
           end
         end
 
-        def grouped_records(association, records)
+        def grouped_records(association, records, polymorphic_parent)
           h = {}
           records.each do |record|
             next unless record
+            next if polymorphic_parent && !record.class._reflect_on_association(association)
             assoc = record.association(association)
             next unless assoc.klass
             klasses = h[assoc.reflection] ||= {}
@@ -166,8 +163,6 @@ module ActiveRecord
         end
 
         class AlreadyLoaded # :nodoc:
-          attr_reader :owners, :reflection
-
           def initialize(klass, owners, reflection, preload_scope)
             @owners = owners
             @reflection = reflection
@@ -178,11 +173,13 @@ module ActiveRecord
           def preloaded_records
             owners.flat_map { |owner| owner.association(reflection.name).target }
           end
+
+          private
+            attr_reader :owners, :reflection
         end
 
         # Returns a class containing the logic needed to load preload the data
-        # and attach it to a relation. For example +Preloader::Association+ or
-        # +Preloader::HasManyThrough+. The class returned implements a `run` method
+        # and attach it to a relation. The class returned implements a `run` method
         # that accepts a preloader.
         def preloader_for(reflection, owners)
           if owners.first.association(reflection.name).loaded?
@@ -190,13 +187,10 @@ module ActiveRecord
           end
           reflection.check_preloadable!
 
-          case reflection.macro
-          when :has_many
-            reflection.options[:through] ? HasManyThrough : HasMany
-          when :has_one
-            reflection.options[:through] ? HasOneThrough : HasOne
-          when :belongs_to
-            BelongsTo
+          if reflection.options[:through]
+            ThroughAssociation
+          else
+            Association
           end
         end
     end
diff --git a/activerecord/lib/active_record/associations/preloader/association.rb b/activerecord/lib/active_record/associations/preloader/association.rb
index 4915a37f06..d6f7359055 100644
--- a/activerecord/lib/active_record/associations/preloader/association.rb
+++ b/activerecord/lib/active_record/associations/preloader/association.rb
@@ -4,7 +4,6 @@ module ActiveRecord
   module Associations
     class Preloader
       class Association #:nodoc:
-        attr_reader :owners, :reflection, :preload_scope, :model, :klass
         attr_reader :preloaded_records
 
         def initialize(klass, owners, reflection, preload_scope)
@@ -17,62 +16,60 @@ module ActiveRecord
         end
 
         def run(preloader)
-          preload(preloader)
-        end
-
-        def preload(preloader)
-          raise NotImplementedError
-        end
-
-        # The name of the key on the associated records
-        def association_key_name
-          raise NotImplementedError
-        end
+          records = load_records do |record|
+            owner = owners_by_key[convert_key(record[association_key_name])]
+            association = owner.association(reflection.name)
+            association.set_inverse_instance(record)
+          end
 
-        # The name of the key on the model which declares the association
-        def owner_key_name
-          raise NotImplementedError
+          owners.each do |owner|
+            associate_records_to_owner(owner, records[convert_key(owner[owner_key_name])] || [])
+          end
         end
 
         private
-          def options
-            reflection.options
+          attr_reader :owners, :reflection, :preload_scope, :model, :klass
+
+          # The name of the key on the associated records
+          def association_key_name
+            reflection.join_primary_key(klass)
           end
 
-          def associated_records_by_owner(preloader)
-            records = load_records do |record|
-              owner = owners_by_key[convert_key(record[association_key_name])]
-              association = owner.association(reflection.name)
-              association.set_inverse_instance(record)
-            end
+          # The name of the key on the model which declares the association
+          def owner_key_name
+            reflection.join_foreign_key
+          end
 
-            owners.each_with_object({}) do |owner, result|
-              result[owner] = records[convert_key(owner[owner_key_name])] || []
+          def associate_records_to_owner(owner, records)
+            association = owner.association(reflection.name)
+            association.loaded!
+            if reflection.collection?
+              association.target.concat(records)
+            else
+              association.target = records.first unless records.empty?
             end
           end
 
           def owner_keys
-            unless defined?(@owner_keys)
-              @owner_keys = owners.map do |owner|
-                owner[owner_key_name]
-              end
-              @owner_keys.uniq!
-              @owner_keys.compact!
-            end
-            @owner_keys
+            @owner_keys ||= owners_by_key.keys
           end
 
           def owners_by_key
             unless defined?(@owners_by_key)
               @owners_by_key = owners.each_with_object({}) do |owner, h|
-                h[convert_key(owner[owner_key_name])] = owner
+                key = convert_key(owner[owner_key_name])
+                h[key] = owner if key
               end
             end
             @owners_by_key
           end
 
           def key_conversion_required?
-            @key_conversion_required ||= association_key_type != owner_key_type
+            unless defined?(@key_conversion_required)
+              @key_conversion_required = (association_key_type != owner_key_type)
+            end
+
+            @key_conversion_required
           end
 
           def convert_key(key)
@@ -84,11 +81,11 @@ module ActiveRecord
           end
 
           def association_key_type
-            @klass.type_for_attribute(association_key_name.to_s).type
+            @klass.type_for_attribute(association_key_name).type
           end
 
           def owner_key_type
-            @model.type_for_attribute(owner_key_name.to_s).type
+            @model.type_for_attribute(owner_key_name).type
           end
 
           def load_records(&block)
@@ -113,17 +110,17 @@ module ActiveRecord
           end
 
           def reflection_scope
-            @reflection_scope ||= reflection.scope_for(klass)
+            @reflection_scope ||= reflection.scope ? reflection.scope_for(klass.unscoped) : klass.unscoped
           end
 
           def build_scope
             scope = klass.scope_for_association
 
             if reflection.type
-              scope.where!(reflection.type => model.base_class.sti_name)
+              scope.where!(reflection.type => model.polymorphic_name)
             end
 
-            scope.merge!(reflection_scope)
+            scope.merge!(reflection_scope) if reflection.scope
             scope.merge!(preload_scope) if preload_scope
             scope
           end
diff --git a/activerecord/lib/active_record/associations/preloader/belongs_to.rb b/activerecord/lib/active_record/associations/preloader/belongs_to.rb
deleted file mode 100644
index ae9695f26a..0000000000
--- a/activerecord/lib/active_record/associations/preloader/belongs_to.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-# frozen_string_literal: true
-
-module ActiveRecord
-  module Associations
-    class Preloader
-      class BelongsTo < SingularAssociation #:nodoc:
-        def association_key_name
-          options[:primary_key] || klass && klass.primary_key
-        end
-
-        def owner_key_name
-          reflection.foreign_key
-        end
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/associations/preloader/collection_association.rb b/activerecord/lib/active_record/associations/preloader/collection_association.rb
deleted file mode 100644
index fb920a642c..0000000000
--- a/activerecord/lib/active_record/associations/preloader/collection_association.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-# frozen_string_literal: true
-
-module ActiveRecord
-  module Associations
-    class Preloader
-      class CollectionAssociation < Association #:nodoc:
-        private
-
-          def preload(preloader)
-            associated_records_by_owner(preloader).each do |owner, records|
-              association = owner.association(reflection.name)
-              association.loaded!
-              association.target.concat(records)
-            end
-          end
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/associations/preloader/has_many.rb b/activerecord/lib/active_record/associations/preloader/has_many.rb
deleted file mode 100644
index 29a1ce099d..0000000000
--- a/activerecord/lib/active_record/associations/preloader/has_many.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-# frozen_string_literal: true
-
-module ActiveRecord
-  module Associations
-    class Preloader
-      class HasMany < CollectionAssociation #:nodoc:
-        def association_key_name
-          reflection.foreign_key
-        end
-
-        def owner_key_name
-          reflection.active_record_primary_key
-        end
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/associations/preloader/has_many_through.rb b/activerecord/lib/active_record/associations/preloader/has_many_through.rb
deleted file mode 100644
index 0639fdca44..0000000000
--- a/activerecord/lib/active_record/associations/preloader/has_many_through.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-# frozen_string_literal: true
-
-module ActiveRecord
-  module Associations
-    class Preloader
-      class HasManyThrough < CollectionAssociation #:nodoc:
-        include ThroughAssociation
-
-        def associated_records_by_owner(preloader)
-          records_by_owner = super
-
-          if reflection_scope.distinct_value
-            records_by_owner.each_value(&:uniq!)
-          end
-
-          records_by_owner
-        end
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/associations/preloader/has_one.rb b/activerecord/lib/active_record/associations/preloader/has_one.rb
deleted file mode 100644
index d87abf630f..0000000000
--- a/activerecord/lib/active_record/associations/preloader/has_one.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-# frozen_string_literal: true
-
-module ActiveRecord
-  module Associations
-    class Preloader
-      class HasOne < SingularAssociation #:nodoc:
-        def association_key_name
-          reflection.foreign_key
-        end
-
-        def owner_key_name
-          reflection.active_record_primary_key
-        end
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/associations/preloader/has_one_through.rb b/activerecord/lib/active_record/associations/preloader/has_one_through.rb
deleted file mode 100644
index 17734d0257..0000000000
--- a/activerecord/lib/active_record/associations/preloader/has_one_through.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-# frozen_string_literal: true
-
-module ActiveRecord
-  module Associations
-    class Preloader
-      class HasOneThrough < SingularAssociation #:nodoc:
-        include ThroughAssociation
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/associations/preloader/singular_association.rb b/activerecord/lib/active_record/associations/preloader/singular_association.rb
deleted file mode 100644
index 266b5f6b1c..0000000000
--- a/activerecord/lib/active_record/associations/preloader/singular_association.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-# frozen_string_literal: true
-
-module ActiveRecord
-  module Associations
-    class Preloader
-      class SingularAssociation < Association #:nodoc:
-        private
-
-          def preload(preloader)
-            associated_records_by_owner(preloader).each do |owner, associated_records|
-              record = associated_records.first
-
-              association = owner.association(reflection.name)
-              association.target = record
-            end
-          end
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/associations/preloader/through_association.rb b/activerecord/lib/active_record/associations/preloader/through_association.rb
index de4b847a41..a6b7ab80a2 100644
--- a/activerecord/lib/active_record/associations/preloader/through_association.rb
+++ b/activerecord/lib/active_record/associations/preloader/through_association.rb
@@ -3,107 +3,103 @@
 module ActiveRecord
   module Associations
     class Preloader
-      module ThroughAssociation #:nodoc:
-        def through_reflection
-          reflection.through_reflection
-        end
-
-        def source_reflection
-          reflection.source_reflection
-        end
-
-        def associated_records_by_owner(preloader)
-          through_scope = through_scope()
-
-          preloader.preload(owners,
-                            through_reflection.name,
-                            through_scope)
-
-          through_records = owners.map do |owner|
-            center = owner.association(through_reflection.name).target
-            [owner, Array(center)]
-          end
-
-          reset_association(owners, through_reflection.name, through_scope)
-
-          middle_records = through_records.flat_map(&:last)
-
-          preloaders = preloader.preload(middle_records,
-                                         source_reflection.name,
-                                         reflection_scope)
-
+      class ThroughAssociation < Association # :nodoc:
+        def run(preloader)
+          already_loaded     = owners.first.association(through_reflection.name).loaded?
+          through_scope      = through_scope()
+          reflection_scope   = target_reflection_scope
+          through_preloaders = preloader.preload(owners, through_reflection.name, through_scope)
+          middle_records     = through_preloaders.flat_map(&:preloaded_records)
+          preloaders         = preloader.preload(middle_records, source_reflection.name, reflection_scope)
           @preloaded_records = preloaders.flat_map(&:preloaded_records)
 
-          middle_to_pl = preloaders.each_with_object({}) do |pl, h|
-            pl.owners.each { |middle|
-              h[middle] = pl
-            }
-          end
-
-          through_records.each_with_object({}) do |(lhs, center), records_by_owner|
-            pl_to_middle = center.group_by { |record| middle_to_pl[record] }
-
-            records_by_owner[lhs] = pl_to_middle.flat_map do |pl, middles|
-              rhs_records = middles.flat_map { |r|
-                r.association(source_reflection.name).target
-              }.compact
-
-              # Respect the order on `reflection_scope` if it exists, else use the natural order.
-              if reflection_scope.values[:order].present?
-                @id_map ||= id_to_index_map @preloaded_records
-                rhs_records.sort_by { |rhs| @id_map[rhs] }
-              else
-                rhs_records
+          owners.each do |owner|
+            through_records = Array(owner.association(through_reflection.name).target)
+            if already_loaded
+              if source_type = reflection.options[:source_type]
+                through_records = through_records.select do |record|
+                  record[reflection.foreign_type] == source_type
+                end
               end
+            else
+              owner.association(through_reflection.name).reset if through_scope
+            end
+            result = through_records.flat_map do |record|
+              association = record.association(source_reflection.name)
+              target = association.target
+              association.reset if preload_scope
+              target
             end
+            result.compact!
+            if reflection_scope
+              result.sort_by! { |rhs| preload_index[rhs] } if reflection_scope.order_values.any?
+              result.uniq! if reflection_scope.distinct_value
+            end
+            associate_records_to_owner(owner, result)
           end
         end
 
         private
-
-          def id_to_index_map(ids)
-            id_map = {}
-            ids.each_with_index { |id, index| id_map[id] = index }
-            id_map
+          def through_reflection
+            reflection.through_reflection
           end
 
-          def reset_association(owners, association_name, through_scope)
-            should_reset = (through_scope != through_reflection.klass.unscoped) ||
-               (options[:source_type] && through_reflection.collection?)
+          def source_reflection
+            reflection.source_reflection
+          end
 
-            # Don't cache the association - we would only be caching a subset
-            if should_reset
-              owners.each { |owner|
-                owner.association(association_name).reset
-              }
+          def preload_index
+            @preload_index ||= @preloaded_records.each_with_object({}).with_index do |(id, result), index|
+              result[id] = index
             end
           end
 
           def through_scope
             scope = through_reflection.klass.unscoped
-            values = reflection_scope.values
+            options = reflection.options
 
             if options[:source_type]
               scope.where! reflection.foreign_type => options[:source_type]
-            else
-              unless reflection_scope.where_clause.empty?
-                scope.includes_values = Array(values[:includes] || options[:source])
-                scope.where_clause = reflection_scope.where_clause
-                if joins = values[:joins]
-                  scope.joins!(source_reflection.name => joins)
-                end
-                if left_outer_joins = values[:left_outer_joins]
-                  scope.left_outer_joins!(source_reflection.name => left_outer_joins)
-                end
+            elsif !reflection_scope.where_clause.empty?
+              scope.where_clause = reflection_scope.where_clause
+              values = reflection_scope.values
+
+              if includes = values[:includes]
+                scope.includes!(source_reflection.name => includes)
+              else
+                scope.includes!(source_reflection.name)
+              end
+
+              if values[:references] && !values[:references].empty?
+                scope.references!(values[:references])
+              else
+                scope.references!(source_reflection.table_name)
+              end
+
+              if joins = values[:joins]
+                scope.joins!(source_reflection.name => joins)
+              end
+
+              if left_outer_joins = values[:left_outer_joins]
+                scope.left_outer_joins!(source_reflection.name => left_outer_joins)
               end
 
-              scope.references! values[:references]
               if scope.eager_loading? && order_values = values[:order]
                 scope = scope.order(order_values)
               end
             end
 
-            scope
+            scope unless scope.empty_scope?
+          end
+
+          def target_reflection_scope
+            if preload_scope
+              reflection_scope.merge(preload_scope)
+            elsif reflection.scope
+              reflection_scope
+            else
+              nil
+            end
           end
       end
     end
diff --git a/activerecord/lib/active_record/associations/singular_association.rb b/activerecord/lib/active_record/associations/singular_association.rb
index 441bd715e4..ead89bfe6c 100644
--- a/activerecord/lib/active_record/associations/singular_association.rb
+++ b/activerecord/lib/active_record/associations/singular_association.rb
@@ -63,10 +63,6 @@ module ActiveRecord
         end
 
         def _create_record(attributes, raise_error = false)
-          unless owner.persisted?
-            raise ActiveRecord::RecordNotSaved, "You cannot call create unless the parent is saved"
-          end
-
           record = build_record(attributes)
           yield(record) if block_given?
           saved = record.save
diff --git a/activerecord/lib/active_record/associations/through_association.rb b/activerecord/lib/active_record/associations/through_association.rb
index cba565448f..5afb0bc068 100644
--- a/activerecord/lib/active_record/associations/through_association.rb
+++ b/activerecord/lib/active_record/associations/through_association.rb
@@ -1,12 +1,27 @@
 # frozen_string_literal: true
 
 module ActiveRecord
-  # = Active Record Through Association
   module Associations
+    # = Active Record Through Association
     module ThroughAssociation #:nodoc:
-      delegate :source_reflection, :through_reflection, to: :reflection
+      delegate :source_reflection, to: :reflection
 
       private
+        def through_reflection
+          @through_reflection ||= begin
+            refl = reflection.through_reflection
+
+            while refl.through_reflection?
+              refl = refl.through_reflection
+            end
+
+            refl
+          end
+        end
+
+        def through_association
+          @through_association ||= owner.association(through_reflection.name)
+        end
 
         # We merge in these scopes for two reasons:
         #
@@ -38,24 +53,22 @@ module ActiveRecord
         def construct_join_attributes(*records)
           ensure_mutable
 
-          if source_reflection.association_primary_key(reflection.klass) == reflection.klass.primary_key
+          association_primary_key = source_reflection.association_primary_key(reflection.klass)
+
+          if association_primary_key == reflection.klass.primary_key && !options[:source_type]
             join_attributes = { source_reflection.name => records }
           else
             join_attributes = {
-              source_reflection.foreign_key =>
-                records.map { |record|
-                  record.send(source_reflection.association_primary_key(reflection.klass))
-                }
+              source_reflection.foreign_key => records.map(&association_primary_key.to_sym)
             }
           end
 
           if options[:source_type]
-            join_attributes[source_reflection.foreign_type] =
-              records.map { |record| record.class.base_class.name }
+            join_attributes[source_reflection.foreign_type] = [ options[:source_type] ]
           end
 
           if records.count == 1
-            Hash[join_attributes.map { |k, v| [k, v.first] }]
+            join_attributes.transform_values!(&:first)
           else
             join_attributes
           end
diff --git a/activerecord/lib/active_record/attribute_assignment.rb b/activerecord/lib/active_record/attribute_assignment.rb
index 8b0d9aab01..b6f0e18764 100644
--- a/activerecord/lib/active_record/attribute_assignment.rb
+++ b/activerecord/lib/active_record/attribute_assignment.rb
@@ -4,14 +4,8 @@ require "active_model/forbidden_attributes_protection"
 
 module ActiveRecord
   module AttributeAssignment
-    extend ActiveSupport::Concern
     include ActiveModel::AttributeAssignment
 
-    # Alias for ActiveModel::AttributeAssignment#assign_attributes. See ActiveModel::AttributeAssignment.
-    def attributes=(attributes)
-      assign_attributes(attributes)
-    end
-
     private
 
       def _assign_attributes(attributes)
diff --git a/activerecord/lib/active_record/attribute_methods.rb b/activerecord/lib/active_record/attribute_methods.rb
index e4ca6c8408..83b5a5e698 100644
--- a/activerecord/lib/active_record/attribute_methods.rb
+++ b/activerecord/lib/active_record/attribute_methods.rb
@@ -33,7 +33,9 @@ module ActiveRecord
 
     BLACKLISTED_CLASS_METHODS = %w(private public protected allocate new name parent superclass)
 
-    class GeneratedAttributeMethods < Module; end # :nodoc:
+    class GeneratedAttributeMethods < Module #:nodoc:
+      include Mutex_m
+    end
 
     module ClassMethods
       def inherited(child_class) #:nodoc:
@@ -42,7 +44,7 @@ module ActiveRecord
       end
 
       def initialize_generated_modules # :nodoc:
-        @generated_attribute_methods = GeneratedAttributeMethods.new { extend Mutex_m }
+        @generated_attribute_methods = GeneratedAttributeMethods.new
         @attribute_methods_generated = false
         include @generated_attribute_methods
 
@@ -57,7 +59,7 @@ module ActiveRecord
         # attribute methods.
         generated_attribute_methods.synchronize do
           return false if @attribute_methods_generated
-          superclass.define_attribute_methods unless self == base_class
+          superclass.define_attribute_methods unless base_class?
           super(attribute_names)
           @attribute_methods_generated = true
         end
@@ -165,6 +167,57 @@ module ActiveRecord
         end
       end
 
+      # Regexp whitelist. Matches the following:
+      #   "#{table_name}.#{column_name}"
+      #   "#{column_name}"
+      COLUMN_NAME_WHITELIST = /\A(?:\w+\.)?\w+\z/i
+
+      # Regexp whitelist. Matches the following:
+      #   "#{table_name}.#{column_name}"
+      #   "#{table_name}.#{column_name} #{direction}"
+      #   "#{table_name}.#{column_name} #{direction} NULLS FIRST"
+      #   "#{table_name}.#{column_name} NULLS LAST"
+      #   "#{column_name}"
+      #   "#{column_name} #{direction}"
+      #   "#{column_name} #{direction} NULLS FIRST"
+      #   "#{column_name} NULLS LAST"
+      COLUMN_NAME_ORDER_WHITELIST = /
+        \A
+        (?:\w+\.)?
+        \w+
+        (?:\s+asc|\s+desc)?
+        (?:\s+nulls\s+(?:first|last))?
+        \z
+      /ix
+
+      def enforce_raw_sql_whitelist(args, whitelist: COLUMN_NAME_WHITELIST) # :nodoc:
+        unexpected = args.reject do |arg|
+          arg.kind_of?(Arel::Node) ||
+            arg.is_a?(Arel::Nodes::SqlLiteral) ||
+            arg.is_a?(Arel::Attributes::Attribute) ||
+            arg.to_s.split(/\s*,\s*/).all? { |part| whitelist.match?(part) }
+        end
+
+        return if unexpected.none?
+
+        if allow_unsafe_raw_sql == :deprecated
+          ActiveSupport::Deprecation.warn(
+            "Dangerous query method (method whose arguments are used as raw " \
+            "SQL) called with non-attribute argument(s): " \
+            "#{unexpected.map(&:inspect).join(", ")}. Non-attribute " \
+            "arguments will be disallowed in Rails 6.0. This method should " \
+            "not be called with user-provided values, such as request " \
+            "parameters or model attributes. Known-safe values can be passed " \
+            "by wrapping them in Arel.sql()."
+          )
+        else
+          raise(ActiveRecord::UnknownAttributeReference,
+            "Query method called with non-attribute argument(s): " +
+            unexpected.map(&:inspect).join(", ")
+          )
+        end
+      end
+
       # Returns true if the given attribute exists, otherwise false.
       #
       #   class Person < ActiveRecord::Base
@@ -234,7 +287,7 @@ module ActiveRecord
         return has_attribute?(name)
       end
 
-      return true
+      true
     end
 
     # Returns +true+ if the given attribute is in the attributes hash, otherwise +false+.
@@ -390,33 +443,24 @@ module ActiveRecord
       @attributes.accessed
     end
 
-    protected
-
-      def attribute_method?(attr_name) # :nodoc:
+    private
+      def attribute_method?(attr_name)
         # We check defined? because Syck calls respond_to? before actually calling initialize.
         defined?(@attributes) && @attributes.key?(attr_name)
       end
 
-    private
-
-      def arel_attributes_with_values_for_create(attribute_names)
-        arel_attributes_with_values(attributes_for_create(attribute_names))
+      def attributes_with_values_for_create(attribute_names)
+        attributes_with_values(attributes_for_create(attribute_names))
       end
 
-      def arel_attributes_with_values_for_update(attribute_names)
-        arel_attributes_with_values(attributes_for_update(attribute_names))
+      def attributes_with_values_for_update(attribute_names)
+        attributes_with_values(attributes_for_update(attribute_names))
       end
 
-      # Returns a Hash of the Arel::Attributes and attribute values that have been
-      # typecasted for use in an Arel insert/update method.
-      def arel_attributes_with_values(attribute_names)
-        attrs = {}
-        arel_table = self.class.arel_table
-
-        attribute_names.each do |name|
-          attrs[arel_table[name]] = typecasted_attribute_value(name)
+      def attributes_with_values(attribute_names)
+        attribute_names.each_with_object({}) do |name, attrs|
+          attrs[name] = _read_attribute(name)
         end
-        attrs
       end
 
       # Filters the primary keys and readonly attributes from the attribute names.
@@ -441,9 +485,5 @@ module ActiveRecord
       def pk_attribute?(name)
         name == self.class.primary_key
       end
-
-      def typecasted_attribute_value(name)
-        _read_attribute(name)
-      end
   end
 end
diff --git a/activerecord/lib/active_record/attribute_methods/dirty.rb b/activerecord/lib/active_record/attribute_methods/dirty.rb
index c622df132e..233ee29fac 100644
--- a/activerecord/lib/active_record/attribute_methods/dirty.rb
+++ b/activerecord/lib/active_record/attribute_methods/dirty.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/module/attribute_accessors"
-require_relative "../attribute_mutation_tracker"
 
 module ActiveRecord
   module AttributeMethods
@@ -33,71 +32,19 @@ module ActiveRecord
       # <tt>reload</tt> the record and clears changed attributes.
       def reload(*)
         super.tap do
+          @previously_changed = ActiveSupport::HashWithIndifferentAccess.new
           @mutations_before_last_save = nil
-          clear_mutation_trackers
-          @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
-        end
-      end
-
-      def initialize_dup(other) # :nodoc:
-        super
-        @attributes = self.class._default_attributes.map do |attr|
-          attr.with_value_from_user(@attributes.fetch_value(attr.name))
-        end
-        clear_mutation_trackers
-      end
-
-      def changes_applied # :nodoc:
-        @mutations_before_last_save = mutation_tracker
-        @mutations_from_database = AttributeMutationTracker.new(@attributes)
-        @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
-        forget_attribute_assignments
-        clear_mutation_trackers
-      end
-
-      def clear_changes_information # :nodoc:
-        @mutations_before_last_save = nil
-        @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
-        forget_attribute_assignments
-        clear_mutation_trackers
-      end
-
-      def clear_attribute_changes(attr_names) # :nodoc:
-        super
-        attr_names.each do |attr_name|
-          clear_attribute_change(attr_name)
-        end
-      end
-
-      def changed_attributes # :nodoc:
-        # This should only be set by methods which will call changed_attributes
-        # multiple times when it is known that the computed value cannot change.
-        if defined?(@cached_changed_attributes)
-          @cached_changed_attributes
-        else
-          super.reverse_merge(mutation_tracker.changed_values).freeze
-        end
-      end
-
-      def changes # :nodoc:
-        cache_changed_attributes do
-          super
+          @attributes_changed_by_setter = ActiveSupport::HashWithIndifferentAccess.new
+          @mutations_from_database = nil
         end
       end
 
-      def previous_changes # :nodoc:
-        mutations_before_last_save.changes
-      end
-
-      def attribute_changed_in_place?(attr_name) # :nodoc:
-        mutation_tracker.changed_in_place?(attr_name)
-      end
-
-      # Did this attribute change when we last saved? This method can be invoked
-      # as `saved_change_to_name?` instead of `saved_change_to_attribute?("name")`.
-      # Behaves similarly to +attribute_changed?+. This method is useful in
-      # after callbacks to determine if the call to save changed a certain
-      # attribute.
+      # Did this attribute change when we last saved?
+      #
+      # This method is useful in after callbacks to determine if an attribute
+      # was changed during the save that triggered the callbacks to run. It can
+      # be invoked as +saved_change_to_name?+ instead of
+      # <tt>saved_change_to_attribute?("name")</tt>.
       #
       # ==== Options
       #
@@ -114,24 +61,25 @@ module ActiveRecord
       # attribute was changed, the result will be an array containing the
       # original value and the saved value.
       #
-      # Behaves similarly to +attribute_change+. This method is useful in after
-      # callbacks, to see the change in an attribute that just occurred
-      #
-      # This method can be invoked as `saved_change_to_name` in instead of
-      # `saved_change_to_attribute("name")`
+      # This method is useful in after callbacks, to see the change in an
+      # attribute during the save that triggered the callbacks to run. It can be
+      # invoked as +saved_change_to_name+ instead of
+      # <tt>saved_change_to_attribute("name")</tt>.
       def saved_change_to_attribute(attr_name)
         mutations_before_last_save.change_to_attribute(attr_name)
       end
 
       # Returns the original value of an attribute before the last save.
-      # Behaves similarly to +attribute_was+. This method is useful in after
-      # callbacks to get the original value of an attribute before the save that
-      # just occurred
+      #
+      # This method is useful in after callbacks to get the original value of an
+      # attribute before the save that triggered the callbacks to run. It can be
+      # invoked as +name_before_last_save+ instead of
+      # <tt>attribute_before_last_save("name")</tt>.
       def attribute_before_last_save(attr_name)
         mutations_before_last_save.original_value(attr_name)
       end
 
-      # Did the last call to `save` have any changes to change?
+      # Did the last call to +save+ have any changes to change?
       def saved_changes?
         mutations_before_last_save.any_changes?
       end
@@ -141,39 +89,75 @@ module ActiveRecord
         mutations_before_last_save.changes
       end
 
-      # Alias for `attribute_changed?`
+      # Will this attribute change the next time we save?
+      #
+      # This method is useful in validations and before callbacks to determine
+      # if the next call to +save+ will change a particular attribute. It can be
+      # invoked as +will_save_change_to_name?+ instead of
+      # <tt>will_save_change_to_attribute("name")</tt>.
+      #
+      # ==== Options
+      #
+      # +from+ When passed, this method will return false unless the original
+      # value is equal to the given option
+      #
+      # +to+ When passed, this method will return false unless the value will be
+      # changed to the given value
       def will_save_change_to_attribute?(attr_name, **options)
         mutations_from_database.changed?(attr_name, **options)
       end
 
-      # Alias for `attribute_change`
+      # Returns the change to an attribute that will be persisted during the
+      # next save.
+      #
+      # This method is useful in validations and before callbacks, to see the
+      # change to an attribute that will occur when the record is saved. It can
+      # be invoked as +name_change_to_be_saved+ instead of
+      # <tt>attribute_change_to_be_saved("name")</tt>.
+      #
+      # If the attribute will change, the result will be an array containing the
+      # original value and the new value about to be saved.
       def attribute_change_to_be_saved(attr_name)
         mutations_from_database.change_to_attribute(attr_name)
       end
 
-      # Alias for `attribute_was`
+      # Returns the value of an attribute in the database, as opposed to the
+      # in-memory value that will be persisted the next time the record is
+      # saved.
+      #
+      # This method is useful in validations and before callbacks, to see the
+      # original value of an attribute prior to any changes about to be
+      # saved. It can be invoked as +name_in_database+ instead of
+      # <tt>attribute_in_database("name")</tt>.
       def attribute_in_database(attr_name)
         mutations_from_database.original_value(attr_name)
       end
 
-      # Alias for `changed?`
+      # Will the next call to +save+ have any changes to persist?
       def has_changes_to_save?
         mutations_from_database.any_changes?
       end
 
-      # Alias for `changes`
+      # Returns a hash containing all the changes that will be persisted during
+      # the next save.
       def changes_to_save
         mutations_from_database.changes
       end
 
-      # Alias for `changed`
+      # Returns an array of the names of any attributes that will change when
+      # the record is next saved.
       def changed_attribute_names_to_save
-        changes_to_save.keys
+        mutations_from_database.changed_attribute_names
       end
 
-      # Alias for `changed_attributes`
+      # Returns a hash of the attributes that will change when the record is
+      # next saved.
+      #
+      # The hash keys are the attribute names, and the hash values are the
+      # original attribute values in the database (as opposed to the in-memory
+      # values about to be saved).
       def attributes_in_database
-        changes_to_save.transform_values(&:first)
+        mutations_from_database.changed_values
       end
 
       private
@@ -183,34 +167,6 @@ module ActiveRecord
           result
         end
 
-        def mutation_tracker
-          unless defined?(@mutation_tracker)
-            @mutation_tracker = nil
-          end
-          @mutation_tracker ||= AttributeMutationTracker.new(@attributes)
-        end
-
-        def mutations_from_database
-          unless defined?(@mutations_from_database)
-            @mutations_from_database = nil
-          end
-          @mutations_from_database ||= mutation_tracker
-        end
-
-        def changes_include?(attr_name)
-          super || mutation_tracker.changed?(attr_name)
-        end
-
-        def clear_attribute_change(attr_name)
-          mutation_tracker.forget_change(attr_name)
-          mutations_from_database.forget_change(attr_name)
-        end
-
-        def attribute_will_change!(attr_name)
-          super
-          mutations_from_database.force_change(attr_name)
-        end
-
         def _update_record(*)
           partial_writes? ? super(keys_for_partial_write) : super
         end
@@ -222,30 +178,6 @@ module ActiveRecord
         def keys_for_partial_write
           changed_attribute_names_to_save & self.class.column_names
         end
-
-        def forget_attribute_assignments
-          @attributes = @attributes.map(&:forgetting_assignment)
-        end
-
-        def clear_mutation_trackers
-          @mutation_tracker = nil
-          @mutations_from_database = nil
-        end
-
-        def mutations_before_last_save
-          @mutations_before_last_save ||= NullMutationTracker.instance
-        end
-
-        def cache_changed_attributes
-          @cached_changed_attributes = changed_attributes
-          yield
-        ensure
-          clear_changed_attributes_cache
-        end
-
-        def clear_changed_attributes_cache
-          remove_instance_variable(:@cached_changed_attributes) if defined?(@cached_changed_attributes)
-        end
     end
   end
 end
diff --git a/activerecord/lib/active_record/attribute_methods/primary_key.rb b/activerecord/lib/active_record/attribute_methods/primary_key.rb
index 63c059e291..9b267bb7c0 100644
--- a/activerecord/lib/active_record/attribute_methods/primary_key.rb
+++ b/activerecord/lib/active_record/attribute_methods/primary_key.rb
@@ -17,13 +17,15 @@ module ActiveRecord
       # Returns the primary key value.
       def id
         sync_with_transaction_state
-        _read_attribute(self.class.primary_key) if self.class.primary_key
+        primary_key = self.class.primary_key
+        _read_attribute(primary_key) if primary_key
       end
 
       # Sets the primary key value.
       def id=(value)
         sync_with_transaction_state
-        _write_attribute(self.class.primary_key, value) if self.class.primary_key
+        primary_key = self.class.primary_key
+        _write_attribute(primary_key, value) if primary_key
       end
 
       # Queries the primary key value.
@@ -81,7 +83,7 @@ module ActiveRecord
           end
 
           def reset_primary_key #:nodoc:
-            if self == base_class
+            if base_class?
               self.primary_key = get_primary_key(base_class.name)
             else
               self.primary_key = base_class.primary_key
@@ -129,7 +131,7 @@ module ActiveRecord
             def suppress_composite_primary_key(pk)
               return pk unless pk.is_a?(Array)
 
-              warn <<-WARNING.strip_heredoc
+              warn <<~WARNING
                 WARNING: Active Record does not support composite primary key.
 
                 #{table_name} has composite primary key. Composite primary key is ignored.
diff --git a/activerecord/lib/active_record/attribute_methods/read.rb b/activerecord/lib/active_record/attribute_methods/read.rb
index 615b2fa701..0f7bcba564 100644
--- a/activerecord/lib/active_record/attribute_methods/read.rb
+++ b/activerecord/lib/active_record/attribute_methods/read.rb
@@ -5,7 +5,7 @@ module ActiveRecord
     module Read
       extend ActiveSupport::Concern
 
-      module ClassMethods
+      module ClassMethods # :nodoc:
         private
 
           # We want to generate the methods via module_eval rather than
@@ -27,7 +27,7 @@ module ActiveRecord
           # Making it frozen means that it doesn't get duped when used to
           # key the @attributes in read_attribute.
           def define_method_attribute(name)
-            safe_name = name.unpack("h*".freeze).first
+            safe_name = name.unpack1("h*".freeze)
             temp_method = "__temp__#{safe_name}"
 
             ActiveRecord::AttributeMethods::AttrNames.set_name_cache safe_name, name
@@ -58,8 +58,9 @@ module ActiveRecord
           attr_name.to_s
         end
 
-        name = self.class.primary_key if name == "id".freeze && self.class.primary_key
-        sync_with_transaction_state if name == self.class.primary_key
+        primary_key = self.class.primary_key
+        name = primary_key if name == "id".freeze && primary_key
+        sync_with_transaction_state if name == primary_key
         _read_attribute(name, &block)
       end
 
@@ -68,7 +69,7 @@ module ActiveRecord
       if defined?(JRUBY_VERSION)
         # This form is significantly faster on JRuby, and this is one of our biggest hotspots.
         # https://github.com/jruby/jruby/pull/2562
-        def _read_attribute(attr_name, &block) # :nodoc
+        def _read_attribute(attr_name, &block) # :nodoc:
           @attributes.fetch_value(attr_name.to_s, &block)
         end
       else
diff --git a/activerecord/lib/active_record/attribute_methods/serialization.rb b/activerecord/lib/active_record/attribute_methods/serialization.rb
index ebc2baed34..6e0e90f39c 100644
--- a/activerecord/lib/active_record/attribute_methods/serialization.rb
+++ b/activerecord/lib/active_record/attribute_methods/serialization.rb
@@ -7,7 +7,7 @@ module ActiveRecord
 
       class ColumnNotSerializableError < StandardError
         def initialize(name, type)
-          super <<-EOS.strip_heredoc
+          super <<~EOS
             Column `#{name}` of type #{type.class} does not support `serialize` feature.
             Usually it means that you are trying to use `serialize`
             on a column that already implements serialization natively.
diff --git a/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb b/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
index f12a9f915c..d2b7817b45 100644
--- a/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
+++ b/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
@@ -62,7 +62,7 @@ module ActiveRecord
         class_attribute :time_zone_aware_types, instance_writer: false, default: [ :datetime, :time ]
       end
 
-      module ClassMethods
+      module ClassMethods # :nodoc:
         private
 
           def inherited(subclass)
diff --git a/activerecord/lib/active_record/attribute_methods/write.rb b/activerecord/lib/active_record/attribute_methods/write.rb
index 62c5ce059b..c7521422bb 100644
--- a/activerecord/lib/active_record/attribute_methods/write.rb
+++ b/activerecord/lib/active_record/attribute_methods/write.rb
@@ -9,11 +9,11 @@ module ActiveRecord
         attribute_method_suffix "="
       end
 
-      module ClassMethods
+      module ClassMethods # :nodoc:
         private
 
           def define_method_attribute=(name)
-            safe_name = name.unpack("h*".freeze).first
+            safe_name = name.unpack1("h*".freeze)
             ActiveRecord::AttributeMethods::AttrNames.set_name_cache safe_name, name
             sync_with_transaction_state = "sync_with_transaction_state" if name == primary_key
 
@@ -39,8 +39,9 @@ module ActiveRecord
           attr_name.to_s
         end
 
-        name = self.class.primary_key if name == "id".freeze && self.class.primary_key
-        sync_with_transaction_state if name == self.class.primary_key
+        primary_key = self.class.primary_key
+        name = primary_key if name == "id".freeze && primary_key
+        sync_with_transaction_state if name == primary_key
         _write_attribute(name, value)
       end
 
diff --git a/activerecord/lib/active_record/attributes.rb b/activerecord/lib/active_record/attributes.rb
index afb559db71..35150889d9 100644
--- a/activerecord/lib/active_record/attributes.rb
+++ b/activerecord/lib/active_record/attributes.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "attribute/user_provided_default"
+require "active_model/attribute/user_provided_default"
 
 module ActiveRecord
   # See ActiveRecord::Attributes::ClassMethods for documentation
@@ -57,7 +57,7 @@ module ActiveRecord
       #   store_listing = StoreListing.new(price_in_cents: '10.1')
       #
       #   # before
-      #   store_listing.price_in_cents # => BigDecimal.new(10.1)
+      #   store_listing.price_in_cents # => BigDecimal(10.1)
       #
       #   class StoreListing < ActiveRecord::Base
       #     attribute :price_in_cents, :integer
@@ -250,14 +250,14 @@ module ActiveRecord
           if value == NO_DEFAULT_PROVIDED
             default_attribute = _default_attributes[name].with_type(type)
           elsif from_user
-            default_attribute = Attribute::UserProvidedDefault.new(
+            default_attribute = ActiveModel::Attribute::UserProvidedDefault.new(
               name,
               value,
               type,
               _default_attributes.fetch(name.to_s) { nil },
             )
           else
-            default_attribute = Attribute.from_database(name, value, type)
+            default_attribute = ActiveModel::Attribute.from_database(name, value, type)
           end
           _default_attributes[name] = default_attribute
         end
diff --git a/activerecord/lib/active_record/autosave_association.rb b/activerecord/lib/active_record/autosave_association.rb
index 6974cf74f6..9575cc24c8 100644
--- a/activerecord/lib/active_record/autosave_association.rb
+++ b/activerecord/lib/active_record/autosave_association.rb
@@ -400,8 +400,11 @@ module ActiveRecord
               if autosave != false && (@new_record_before_save || record.new_record?)
                 if autosave
                   saved = association.insert_record(record, false)
-                else
-                  association.insert_record(record) unless reflection.nested?
+                elsif !reflection.nested?
+                  association_saved = association.insert_record(record)
+                  if reflection.validate?
+                    saved = association_saved
+                  end
                 end
               elsif autosave
                 saved = record.save(validate: false)
@@ -436,6 +439,9 @@ module ActiveRecord
             if (autosave && record.changed_for_autosave?) || new_record? || record_changed?(reflection, record, key)
               unless reflection.through_reflection
                 record[reflection.foreign_key] = key
+                if inverse_reflection = reflection.inverse_of
+                  record.association(inverse_reflection.name).loaded!
+                end
               end
 
               saved = record.save(validate: !autosave)
diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 541ff51fbe..7ab9160265 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -9,20 +9,19 @@ require "active_support/core_ext/module/attribute_accessors"
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/hash/deep_merge"
 require "active_support/core_ext/hash/slice"
-require "active_support/core_ext/hash/transform_values"
 require "active_support/core_ext/string/behavior"
 require "active_support/core_ext/kernel/singleton_class"
 require "active_support/core_ext/module/introspection"
 require "active_support/core_ext/object/duplicable"
 require "active_support/core_ext/class/subclasses"
-require_relative "attribute_decorators"
-require_relative "define_callbacks"
-require_relative "errors"
-require_relative "log_subscriber"
-require_relative "explain_subscriber"
-require_relative "relation/delegation"
-require_relative "attributes"
-require_relative "type_caster"
+require "active_record/attribute_decorators"
+require "active_record/define_callbacks"
+require "active_record/errors"
+require "active_record/log_subscriber"
+require "active_record/explain_subscriber"
+require "active_record/relation/delegation"
+require "active_record/attributes"
+require "active_record/type_caster"
 
 module ActiveRecord #:nodoc:
   # = Active Record
@@ -291,6 +290,7 @@ module ActiveRecord #:nodoc:
     extend CollectionCacheKey
 
     include Core
+    include DatabaseConfigurations
     include Persistence
     include ReadonlyAttributes
     include ModelSchema
diff --git a/activerecord/lib/active_record/callbacks.rb b/activerecord/lib/active_record/callbacks.rb
index a2439e6ec7..fd6819d08f 100644
--- a/activerecord/lib/active_record/callbacks.rb
+++ b/activerecord/lib/active_record/callbacks.rb
@@ -75,21 +75,7 @@ module ActiveRecord
   #   end
   #
   # Now, when <tt>Topic#destroy</tt> is run only +destroy_author+ is called. When <tt>Reply#destroy</tt> is
-  # run, both +destroy_author+ and +destroy_readers+ are called. Contrast this to the following situation
-  # where the +before_destroy+ method is overridden:
-  #
-  #   class Topic < ActiveRecord::Base
-  #     def before_destroy() destroy_author end
-  #   end
-  #
-  #   class Reply < Topic
-  #     def before_destroy() destroy_readers end
-  #   end
-  #
-  # In that case, <tt>Reply#destroy</tt> would only run +destroy_readers+ and _not_ +destroy_author+.
-  # So, use the callback macros when you want to ensure that a certain callback is called for the entire
-  # hierarchy, and use the regular overwritable methods when you want to leave it up to each descendant
-  # to decide whether they want to call +super+ and trigger the inherited callbacks.
+  # run, both +destroy_author+ and +destroy_readers+ are called.
   #
   # *IMPORTANT:* In order for inheritance to work for the callback queues, you must specify the
   # callbacks before specifying the associations. Otherwise, you might trigger the loading of a
@@ -98,9 +84,9 @@ module ActiveRecord
   # == Types of callbacks
   #
   # There are four types of callbacks accepted by the callback macros: Method references (symbol), callback objects,
-  # inline methods (using a proc), and inline eval methods (using a string). Method references and callback objects
+  # inline methods (using a proc). Method references and callback objects
   # are the recommended approaches, inline methods using a proc are sometimes appropriate (such as for
-  # creating mix-ins), and inline eval methods are deprecated.
+  # creating mix-ins).
   #
   # The method reference callbacks work by specifying a protected or private method available in the object, like this:
   #
@@ -232,7 +218,7 @@ module ActiveRecord
   #
   # For example:
   #
-  #   class Topic
+  #   class Topic < ActiveRecord::Base
   #     has_many :children
   #
   #     after_save :log_children
@@ -240,7 +226,7 @@ module ActiveRecord
   #
   #     private
   #
-  #     def log_chidren
+  #     def log_children
   #       # Child processing
   #     end
   #
@@ -257,7 +243,7 @@ module ActiveRecord
   #
   # For example:
   #
-  #   class Topic
+  #   class Topic < ActiveRecord::Base
   #     has_many :children
   #
   #     after_commit :log_children
@@ -265,7 +251,7 @@ module ActiveRecord
   #
   #     private
   #
-  #     def log_chidren
+  #     def log_children
   #       # Child processing
   #     end
   #
diff --git a/activerecord/lib/active_record/collection_cache_key.rb b/activerecord/lib/active_record/collection_cache_key.rb
index b1937a3c68..dfba78614e 100644
--- a/activerecord/lib/active_record/collection_cache_key.rb
+++ b/activerecord/lib/active_record/collection_cache_key.rb
@@ -3,22 +3,24 @@
 module ActiveRecord
   module CollectionCacheKey
     def collection_cache_key(collection = all, timestamp_column = :updated_at) # :nodoc:
-      query_signature = Digest::MD5.hexdigest(collection.to_sql)
+      query_signature = ActiveSupport::Digest.hexdigest(collection.to_sql)
       key = "#{collection.model_name.cache_key}/query-#{query_signature}"
 
-      if collection.loaded?
-        size = collection.size
+      if collection.loaded? || collection.distinct_value
+        size = collection.records.size
         if size > 0
           timestamp = collection.max_by(&timestamp_column)._read_attribute(timestamp_column)
         end
       else
-        column_type = type_for_attribute(timestamp_column.to_s)
-        column = "#{connection.quote_table_name(collection.table_name)}.#{connection.quote_column_name(timestamp_column)}"
+        if collection.eager_loading?
+          collection = collection.send(:apply_join_dependency)
+        end
+        column_type = type_for_attribute(timestamp_column)
+        column = connection.column_name_from_arel_node(collection.arel_attribute(timestamp_column))
         select_values = "COUNT(*) AS #{connection.quote_column_name("size")}, MAX(%s) AS timestamp"
 
         if collection.has_limit_or_offset?
-          query = collection.spawn
-          query.select_values = [column]
+          query = collection.select(column)
           subquery_alias = "subquery_for_cache_key"
           subquery_column = "#{subquery_alias}.#{timestamp_column}"
           subquery = query.arel.as(subquery_alias)
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
index 0759f4d2b3..c730584902 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -63,15 +63,13 @@ module ActiveRecord
     # There are several connection-pooling-related options that you can add to
     # your database connection configuration:
     #
-    # * +pool+: number indicating size of connection pool (default 5)
-    # * +checkout_timeout+: number of seconds to block and wait for a connection
-    #   before giving up and raising a timeout error (default 5 seconds).
-    # * +reaping_frequency+: frequency in seconds to periodically run the
-    #   Reaper, which attempts to find and recover connections from dead
-    #   threads, which can occur if a programmer forgets to close a
-    #   connection at the end of a thread or a thread dies unexpectedly.
-    #   Regardless of this setting, the Reaper will be invoked before every
-    #   blocking wait. (Default +nil+, which means don't schedule the Reaper).
+    # * +pool+: maximum number of connections the pool may manage (default 5).
+    # * +idle_timeout+: number of seconds that a connection will be kept
+    #   unused in the pool before it is automatically disconnected (default
+    #   300 seconds). Set this to zero to keep connections forever.
+    # * +checkout_timeout+: number of seconds to wait for a connection to
+    #   become available before giving up and raising a timeout error (default
+    #   5 seconds).
     #
     #--
     # Synchronization policy:
@@ -82,11 +80,8 @@ module ActiveRecord
     # * private methods that require being called in a +synchronize+ blocks
     #   are now explicitly documented
     class ConnectionPool
-      # Threadsafe, fair, FIFO queue.  Meant to be used by ConnectionPool
-      # with which it shares a Monitor.  But could be a generic Queue.
-      #
-      # The Queue in stdlib's 'thread' could replace this class except
-      # stdlib's doesn't support waiting with a timeout.
+      # Threadsafe, fair, LIFO queue.  Meant to be used by ConnectionPool
+      # with which it shares a Monitor.
       class Queue
         def initialize(lock = Monitor.new)
           @lock = lock
@@ -175,7 +170,7 @@ module ActiveRecord
 
           # Removes and returns the head of the queue if possible, or +nil+.
           def remove
-            @queue.shift
+            @queue.pop
           end
 
           # Remove and return the head the queue if the number of
@@ -283,12 +278,12 @@ module ActiveRecord
           end
       end
 
-      # Every +frequency+ seconds, the reaper will call +reap+ on +pool+.
-      # A reaper instantiated with a +nil+ frequency will never reap the
-      # connection pool.
+      # Every +frequency+ seconds, the reaper will call +reap+ and +flush+ on
+      # +pool+. A reaper instantiated with a zero frequency will never reap
+      # the connection pool.
       #
-      # Configure the frequency by setting "reaping_frequency" in your
-      # database yaml file.
+      # Configure the frequency by setting +reaping_frequency+ in your database
+      # yaml file (default 60 seconds).
       class Reaper
         attr_reader :pool, :frequency
 
@@ -298,11 +293,12 @@ module ActiveRecord
         end
 
         def run
-          return unless frequency
+          return unless frequency && frequency > 0
           Thread.new(frequency, pool) { |t, p|
             loop do
               sleep t
               p.reap
+              p.flush
             end
           }
         end
@@ -326,6 +322,10 @@ module ActiveRecord
         @spec = spec
 
         @checkout_timeout = (spec.config[:checkout_timeout] && spec.config[:checkout_timeout].to_f) || 5
+        if @idle_timeout = spec.config.fetch(:idle_timeout, 300)
+          @idle_timeout = @idle_timeout.to_f
+          @idle_timeout = nil if @idle_timeout <= 0
+        end
 
         # default max pool size to 5
         @size = (spec.config[:pool] && spec.config[:pool].to_i) || 5
@@ -356,7 +356,10 @@ module ActiveRecord
 
         @lock_thread = false
 
-        @reaper = Reaper.new(self, spec.config[:reaping_frequency] && spec.config[:reaping_frequency].to_f)
+        # +reaping_frequency+ is configurable mostly for historical reasons, but it could
+        # also be useful if someone wants a very low +idle_timeout+.
+        reaping_frequency = spec.config.fetch(:reaping_frequency, 60)
+        @reaper = Reaper.new(self, reaping_frequency && reaping_frequency.to_f)
         @reaper.run
       end
 
@@ -450,6 +453,21 @@ module ActiveRecord
         disconnect(false)
       end
 
+      # Discards all connections in the pool (even if they're currently
+      # leased!), along with the pool itself. Any further interaction with the
+      # pool (except #spec and #schema_cache) is undefined.
+      #
+      # See AbstractAdapter#discard!
+      def discard! # :nodoc:
+        synchronize do
+          return if @connections.nil? # already discarded
+          @connections.each do |conn|
+            conn.discard!
+          end
+          @connections = @available = @thread_cached_conns = nil
+        end
+      end
+
       # Clears the cache which maps classes and re-connects connections that
       # require reloading.
       #
@@ -575,6 +593,35 @@ module ActiveRecord
         end
       end
 
+      # Disconnect all connections that have been idle for at least
+      # +minimum_idle+ seconds. Connections currently checked out, or that were
+      # checked in less than +minimum_idle+ seconds ago, are unaffected.
+      def flush(minimum_idle = @idle_timeout)
+        return if minimum_idle.nil?
+
+        idle_connections = synchronize do
+          @connections.select do |conn|
+            !conn.in_use? && conn.seconds_idle >= minimum_idle
+          end.each do |conn|
+            conn.lease
+
+            @available.delete conn
+            @connections.delete conn
+          end
+        end
+
+        idle_connections.each do |conn|
+          conn.disconnect!
+        end
+      end
+
+      # Disconnect all currently idle connections. Connections currently checked
+      # out are unaffected.
+      def flush!
+        reap
+        flush(-1)
+      end
+
       def num_waiting_in_queue # :nodoc:
         @available.num_waiting
       end
@@ -866,11 +913,31 @@ module ActiveRecord
     # about the model. The model needs to pass a specification name to the handler,
     # in order to look up the correct connection pool.
     class ConnectionHandler
+      def self.unowned_pool_finalizer(pid_map) # :nodoc:
+        lambda do |_|
+          discard_unowned_pools(pid_map)
+        end
+      end
+
+      def self.discard_unowned_pools(pid_map) # :nodoc:
+        pid_map.each do |pid, pools|
+          pools.values.compact.each(&:discard!) unless pid == Process.pid
+        end
+      end
+
       def initialize
         # These caches are keyed by spec.name (ConnectionSpecification#name).
         @owner_to_pool = Concurrent::Map.new(initial_capacity: 2) do |h, k|
+          # Discard the parent's connection pools immediately; we have no need
+          # of them
+          ConnectionHandler.discard_unowned_pools(h)
+
           h[k] = Concurrent::Map.new(initial_capacity: 2)
         end
+
+        # Backup finalizer: if the forked child never needed a pool, the above
+        # early discard has not occurred
+        ObjectSpace.define_finalizer self, ConnectionHandler.unowned_pool_finalizer(@owner_to_pool)
       end
 
       def connection_pool_list
@@ -924,6 +991,13 @@ module ActiveRecord
         connection_pool_list.each(&:disconnect!)
       end
 
+      # Disconnects all currently idle connections.
+      #
+      # See ConnectionPool#flush! for details.
+      def flush_idle_connections!
+        connection_pool_list.each(&:flush!)
+      end
+
       # Locate the connection of the nearest super class. This can be an
       # active or defined connection: if it is the latter, it will be
       # opened and set as the active connection for the class it was defined
@@ -931,9 +1005,7 @@ module ActiveRecord
       def retrieve_connection(spec_name) #:nodoc:
         pool = retrieve_connection_pool(spec_name)
         raise ConnectionNotEstablished, "No connection pool with '#{spec_name}' found." unless pool
-        conn = pool.connection
-        raise ConnectionNotEstablished, "No connection for '#{spec_name}' in connection pool" unless conn
-        conn
+        pool.connection
       end
 
       # Returns true if a connection that's accessible to this class has
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
index 36048bee03..41553cfa83 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
@@ -356,38 +356,36 @@ module ActiveRecord
       # Inserts a set of fixtures into the table. Overridden in adapters that require
       # something beyond a simple insert (eg. Oracle).
       def insert_fixtures(fixtures, table_name)
+        ActiveSupport::Deprecation.warn(<<-MSG.squish)
+          `insert_fixtures` is deprecated and will be removed in the next version of Rails.
+          Consider using `insert_fixtures_set` for performance improvement.
+        MSG
         return if fixtures.empty?
 
-        columns = schema_cache.columns_hash(table_name)
+        execute(build_fixture_sql(fixtures, table_name), "Fixtures Insert")
+      end
 
-        values = fixtures.map do |fixture|
-          fixture = fixture.stringify_keys
+      def insert_fixtures_set(fixture_set, tables_to_delete = [])
+        fixture_inserts = fixture_set.map do |table_name, fixtures|
+          next if fixtures.empty?
 
-          unknown_columns = fixture.keys - columns.keys
-          if unknown_columns.any?
-            raise Fixture::FixtureError, %(table "#{table_name}" has no columns named #{unknown_columns.map(&:inspect).join(', ')}.)
-          end
+          build_fixture_sql(fixtures, table_name)
+        end.compact
 
-          columns.map do |name, column|
-            if fixture.key?(name)
-              type = lookup_cast_type_from_column(column)
-              bind = Relation::QueryAttribute.new(name, fixture[name], type)
-              with_yaml_fallback(bind.value_for_database)
-            else
-              Arel.sql("DEFAULT")
+        table_deletes = tables_to_delete.map { |table| "DELETE FROM #{quote_table_name table}".dup }
+        total_sql = Array.wrap(combine_multi_statements(table_deletes + fixture_inserts))
+
+        disable_referential_integrity do
+          transaction(requires_new: true) do
+            total_sql.each do |sql|
+              execute sql, "Fixtures Load"
+              yield if block_given?
             end
           end
         end
-
-        table = Arel::Table.new(table_name)
-        manager = Arel::InsertManager.new
-        manager.into(table)
-        columns.each_key { |column| manager.columns << table[column] }
-        manager.values = manager.create_values_list(values)
-        execute manager.to_sql, "Fixtures Insert"
       end
 
-      def empty_insert_statement_value
+      def empty_insert_statement_value(primary_key = nil)
         "DEFAULT VALUES"
       end
 
@@ -416,6 +414,44 @@ module ActiveRecord
       alias join_to_delete join_to_update
 
       private
+        def default_insert_value(column)
+          Arel.sql("DEFAULT")
+        end
+
+        def build_fixture_sql(fixtures, table_name)
+          columns = schema_cache.columns_hash(table_name)
+
+          values = fixtures.map do |fixture|
+            fixture = fixture.stringify_keys
+
+            unknown_columns = fixture.keys - columns.keys
+            if unknown_columns.any?
+              raise Fixture::FixtureError, %(table "#{table_name}" has no columns named #{unknown_columns.map(&:inspect).join(', ')}.)
+            end
+
+            columns.map do |name, column|
+              if fixture.key?(name)
+                type = lookup_cast_type_from_column(column)
+                bind = Relation::QueryAttribute.new(name, fixture[name], type)
+                with_yaml_fallback(bind.value_for_database)
+              else
+                default_insert_value(column)
+              end
+            end
+          end
+
+          table = Arel::Table.new(table_name)
+          manager = Arel::InsertManager.new
+          manager.into(table)
+          columns.each_key { |column| manager.columns << table[column] }
+          manager.values = manager.create_values_list(values)
+
+          manager.to_sql
+        end
+
+        def combine_multi_statements(total_sql)
+          total_sql.join(";\n")
+        end
 
         # Returns a subquery for the given key using the join information.
         def subquery_for(key, select)
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
index 9ad04c3216..aec5fa6ba1 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
@@ -11,19 +11,6 @@ module ActiveRecord
       def quote(value)
         value = id_value_for_database(value) if value.is_a?(Base)
 
-        if value.respond_to?(:quoted_id)
-          at = value.method(:quoted_id).source_location
-          at &&= " at %s:%d" % at
-
-          owner = value.method(:quoted_id).owner.to_s
-          klass = value.class.to_s
-          klass += "(#{owner})" unless owner == klass
-
-          ActiveSupport::Deprecation.warn \
-            "Defining #quoted_id is deprecated and will be ignored in Rails 5.2. (defined on #{klass}#{at})"
-          return value.quoted_id
-        end
-
         if value.respond_to?(:value_for_database)
           value = value.value_for_database
         end
@@ -37,10 +24,6 @@ module ActiveRecord
       def type_cast(value, column = nil)
         value = id_value_for_database(value) if value.is_a?(Base)
 
-        if value.respond_to?(:quoted_id) && value.respond_to?(:id)
-          return value.id
-        end
-
         if column
           value = type_cast_from_column(column, value)
         end
@@ -147,7 +130,7 @@ module ActiveRecord
       end
 
       def quoted_time(value) # :nodoc:
-        quoted_date(value).sub(/\A2000-01-01 /, "")
+        quoted_date(value).sub(/\A\d\d\d\d-\d\d-\d\d /, "")
       end
 
       def quoted_binary(value) # :nodoc:
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
index 8bf3879a4c..529c9d8ca6 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/string/strip"
-
 module ActiveRecord
   module ConnectionAdapters
     class AbstractAdapter
@@ -17,9 +15,8 @@ module ActiveRecord
         end
 
         delegate :quote_column_name, :quote_table_name, :quote_default_expression, :type_to_sql,
-          :options_include_default?, :supports_indexes_in_create?, :supports_foreign_keys_in_create?, :foreign_key_options, to: :@conn
-        private :quote_column_name, :quote_table_name, :quote_default_expression, :type_to_sql,
-          :options_include_default?, :supports_indexes_in_create?, :supports_foreign_keys_in_create?, :foreign_key_options
+          :options_include_default?, :supports_indexes_in_create?, :supports_foreign_keys_in_create?, :foreign_key_options,
+          to: :@conn, private: true
 
         private
 
@@ -62,11 +59,11 @@ module ActiveRecord
           end
 
           def visit_PrimaryKeyDefinition(o)
-            "PRIMARY KEY (#{o.name.join(', ')})"
+            "PRIMARY KEY (#{o.name.map { |name| quote_column_name(name) }.join(', ')})"
           end
 
           def visit_ForeignKeyDefinition(o)
-            sql = <<-SQL.strip_heredoc
+            sql = +<<~SQL
               CONSTRAINT #{quote_column_name(o.name)}
               FOREIGN KEY (#{quote_column_name(o.column)})
                 REFERENCES #{quote_table_name(o.to_table)} (#{quote_column_name(o.primary_key)})
@@ -95,6 +92,7 @@ module ActiveRecord
             if options_sql = options[:options]
               create_sql << " #{options_sql}"
             end
+            create_sql
           end
 
           def column_options(o)
@@ -132,7 +130,7 @@ module ActiveRecord
             when :cascade  then "ON #{action} CASCADE"
             when :restrict then "ON #{action} RESTRICT"
             else
-              raise ArgumentError, <<-MSG.strip_heredoc
+              raise ArgumentError, <<~MSG
                 '#{dependency}' is not supported for :on_update or :on_delete.
                 Supported values are: :nullify, :cascade, :restrict
               MSG
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
index 3b2c51ef94..5f090d16cd 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
@@ -6,7 +6,7 @@ module ActiveRecord
     # this type are typically created and returned by methods in database
     # adapters. e.g. ActiveRecord::ConnectionAdapters::MySQL::SchemaStatements#indexes
     class IndexDefinition # :nodoc:
-      attr_reader :table, :name, :unique, :columns, :lengths, :orders, :where, :type, :using, :comment
+      attr_reader :table, :name, :unique, :columns, :lengths, :orders, :opclasses, :where, :type, :using, :comment
 
       def initialize(
         table, name,
@@ -14,6 +14,7 @@ module ActiveRecord
         columns = [],
         lengths: {},
         orders: {},
+        opclasses: {},
         where: nil,
         type: nil,
         using: nil,
@@ -23,13 +24,23 @@ module ActiveRecord
         @name = name
         @unique = unique
         @columns = columns
-        @lengths = lengths
-        @orders = orders
+        @lengths = concise_options(lengths)
+        @orders = concise_options(orders)
+        @opclasses = concise_options(opclasses)
         @where = where
         @type = type
         @using = using
         @comment = comment
       end
+
+      private
+        def concise_options(options)
+          if columns.size == options.size && options.values.uniq.size == 1
+            options.values.first
+          else
+            options
+          end
+        end
     end
 
     # Abstract representation of a column definition. Instances of this type
@@ -85,6 +96,15 @@ module ActiveRecord
         options[:primary_key] != default_primary_key
       end
 
+      def validate?
+        options.fetch(:validate, true)
+      end
+      alias validated? validate?
+
+      def export_name_on_schema_dump?
+        name !~ ActiveRecord::SchemaDumper.fk_ignore_pattern
+      end
+
       def defined_for?(to_table_ord = nil, to_table: nil, **options)
         if to_table_ord
           self.to_table == to_table_ord.to_s
@@ -135,20 +155,15 @@ module ActiveRecord
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-        attr_reader :name, :polymorphic, :index, :foreign_key, :type, :options
-
       private
+        attr_reader :name, :polymorphic, :index, :foreign_key, :type, :options
 
         def as_options(value)
           value.is_a?(Hash) ? value : {}
         end
 
         def polymorphic_options
-          as_options(polymorphic).merge(null: options[:null])
+          as_options(polymorphic).merge(options.slice(:null, :first, :after))
         end
 
         def index_options
@@ -204,6 +219,7 @@ module ActiveRecord
         :decimal,
         :float,
         :integer,
+        :json,
         :string,
         :text,
         :time,
@@ -396,6 +412,9 @@ module ActiveRecord
       alias :belongs_to :references
 
       def new_column_definition(name, type, **options) # :nodoc:
+        if integer_like_primary_key?(type, options)
+          type = integer_like_primary_key_type(type, options)
+        end
         type = aliased_types(type.to_s, type)
         options[:primary_key] ||= type == :primary_key
         options[:null] = false if options[:primary_key]
@@ -410,6 +429,14 @@ module ActiveRecord
         def aliased_types(name, fallback)
           "timestamp" == name ? :datetime : fallback
         end
+
+        def integer_like_primary_key?(type, options)
+          options[:primary_key] && [:integer, :bigint].include?(type) && !options.key?(:default)
+        end
+
+        def integer_like_primary_key_type(type, options)
+          type
+        end
     end
 
     class AlterTable # :nodoc:
@@ -470,6 +497,9 @@ module ActiveRecord
     #     t.date
     #     t.binary
     #     t.boolean
+    #     t.foreign_key
+    #     t.json
+    #     t.virtual
     #     t.remove
     #     t.remove_references
     #     t.remove_belongs_to
@@ -634,19 +664,19 @@ module ActiveRecord
 
       # Adds a foreign key.
       #
-      # t.foreign_key(:authors)
+      #  t.foreign_key(:authors)
       #
       # See {connection.add_foreign_key}[rdoc-ref:SchemaStatements#add_foreign_key]
-      def foreign_key(*args) # :nodoc:
+      def foreign_key(*args)
         @base.add_foreign_key(name, *args)
       end
 
       # Checks to see if a foreign key exists.
       #
-      # t.foreign_key(:authors) unless t.foreign_key_exists?(:authors)
+      #  t.foreign_key(:authors) unless t.foreign_key_exists?(:authors)
       #
       # See {connection.foreign_key_exists?}[rdoc-ref:SchemaStatements#foreign_key_exists?]
-      def foreign_key_exists?(*args) # :nodoc:
+      def foreign_key_exists?(*args)
         @base.foreign_key_exists?(name, *args)
       end
     end
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb
index 1926603474..622e00fffb 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/hash/compact"
-
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
     class SchemaDumper < SchemaDumper # :nodoc:
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
index f36c1f111a..199674f531 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../../migration/join_table"
+require "active_record/migration/join_table"
 require "active_support/core_ext/string/access"
-require "digest"
+require "digest/sha2"
 
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
@@ -79,7 +79,7 @@ module ActiveRecord
       end
 
       # Returns an array of indexes for the given table.
-      def indexes(table_name, name = nil)
+      def indexes(table_name)
         raise NotImplementedError, "#indexes is not implemented"
       end
 
@@ -216,7 +216,7 @@ module ActiveRecord
       # generates:
       #
       #   CREATE TABLE suppliers (
-      #     id int auto_increment PRIMARY KEY
+      #     id bigint auto_increment PRIMARY KEY
       #   ) ENGINE=InnoDB DEFAULT CHARSET=utf8
       #
       # ====== Rename the primary key column
@@ -228,7 +228,7 @@ module ActiveRecord
       # generates:
       #
       #   CREATE TABLE objects (
-      #     guid int auto_increment PRIMARY KEY,
+      #     guid bigint auto_increment PRIMARY KEY,
       #     name varchar(80)
       #   )
       #
@@ -255,8 +255,8 @@ module ActiveRecord
       # generates:
       #
       #   CREATE TABLE order (
-      #       product_id integer NOT NULL,
-      #       client_id integer NOT NULL
+      #       product_id bigint NOT NULL,
+      #       client_id bigint NOT NULL
       #   );
       #
       #   ALTER TABLE ONLY "orders"
@@ -265,15 +265,15 @@ module ActiveRecord
       # ====== Do not add a primary key column
       #
       #   create_table(:categories_suppliers, id: false) do |t|
-      #     t.column :category_id, :integer
-      #     t.column :supplier_id, :integer
+      #     t.column :category_id, :bigint
+      #     t.column :supplier_id, :bigint
       #   end
       #
       # generates:
       #
       #   CREATE TABLE categories_suppliers (
-      #     category_id int,
-      #     supplier_id int
+      #     category_id bigint,
+      #     supplier_id bigint
       #   )
       #
       # ====== Create a temporary table based on a query
@@ -305,7 +305,7 @@ module ActiveRecord
         yield td if block_given?
 
         if options[:force]
-          drop_table(table_name, **options, if_exists: true)
+          drop_table(table_name, options.merge(if_exists: true))
         end
 
         result = execute schema_creation.accept td
@@ -361,8 +361,8 @@ module ActiveRecord
       # generates:
       #
       #   CREATE TABLE assemblies_parts (
-      #     assembly_id int NOT NULL,
-      #     part_id int NOT NULL,
+      #     assembly_id bigint NOT NULL,
+      #     part_id bigint NOT NULL,
       #   ) ENGINE=InnoDB DEFAULT CHARSET=utf8
       #
       def create_join_table(table_1, table_2, column_options: {}, **options)
@@ -406,6 +406,8 @@ module ActiveRecord
       #
       #   Defaults to false.
       #
+      #   Only supported on the MySQL and PostgreSQL adapter, ignored elsewhere.
+      #
       # ====== Add a column
       #
       #   change_table(:suppliers) do |t|
@@ -430,7 +432,7 @@ module ActiveRecord
       #     t.references :company
       #   end
       #
-      # Creates a <tt>company_id(integer)</tt> column.
+      # Creates a <tt>company_id(bigint)</tt> column.
       #
       # ====== Add a polymorphic foreign key column
       #
@@ -438,7 +440,7 @@ module ActiveRecord
       #    t.belongs_to :company, polymorphic: true
       #  end
       #
-      # Creates <tt>company_type(varchar)</tt> and <tt>company_id(integer)</tt> columns.
+      # Creates <tt>company_type(varchar)</tt> and <tt>company_id(bigint)</tt> columns.
       #
       # ====== Remove a column
       #
@@ -520,6 +522,8 @@ module ActiveRecord
       #   Specifies the precision for the <tt>:decimal</tt> and <tt>:numeric</tt> columns.
       # * <tt>:scale</tt> -
       #   Specifies the scale for the <tt>:decimal</tt> and <tt>:numeric</tt> columns.
+      # * <tt>:comment</tt> -
+      #   Specifies the comment for the column. This option is ignored by some backends.
       #
       # Note: The precision is the total number of significant digits,
       # and the scale is the number of digits that can be stored following
@@ -596,7 +600,7 @@ module ActiveRecord
       # to provide these in a migration's +change+ method so it can be reverted.
       # In that case, +type+ and +options+ will be used by #add_column.
       def remove_column(table_name, column_name, type = nil, options = {})
-        execute "ALTER TABLE #{quote_table_name(table_name)} DROP #{quote_column_name(column_name)}"
+        execute "ALTER TABLE #{quote_table_name(table_name)} #{remove_column_for_alter(table_name, column_name, type, options)}"
       end
 
       # Changes the column's definition according to the new options.
@@ -711,7 +715,7 @@ module ActiveRecord
       #
       #   CREATE INDEX by_branch_desc_party ON accounts(branch_id DESC, party_id ASC, surname)
       #
-      # Note: MySQL doesn't yet support index order (it accepts the syntax but ignores it).
+      # Note: MySQL only supports index order from 8.0.1 onwards (earlier versions accepted the syntax but ignored it).
       #
       # ====== Creating a partial index
       #
@@ -734,6 +738,28 @@ module ActiveRecord
       #
       # Note: only supported by PostgreSQL and MySQL
       #
+      # ====== Creating an index with a specific operator class
+      #
+      #   add_index(:developers, :name, using: 'gist', opclass: :gist_trgm_ops)
+      #
+      # generates:
+      #
+      #   CREATE INDEX developers_on_name ON developers USING gist (name gist_trgm_ops) -- PostgreSQL
+      #
+      #   add_index(:developers, [:name, :city], using: 'gist', opclass: { city: :gist_trgm_ops })
+      #
+      # generates:
+      #
+      #   CREATE INDEX developers_on_name_and_city ON developers USING gist (name, city gist_trgm_ops) -- PostgreSQL
+      #
+      #   add_index(:developers, [:name, :city], using: 'gist', opclass: :gist_trgm_ops)
+      #
+      # generates:
+      #
+      #   CREATE INDEX developers_on_name_and_city ON developers USING gist (name gist_trgm_ops, city gist_trgm_ops) -- PostgreSQL
+      #
+      # Note: only supported by PostgreSQL
+      #
       # ====== Creating an index with a specific type
       #
       #   add_index(:developers, :name, type: :fulltext)
@@ -802,24 +828,19 @@ module ActiveRecord
       end
 
       # Verifies the existence of an index with a given name.
-      def index_name_exists?(table_name, index_name, default = nil)
-        unless default.nil?
-          ActiveSupport::Deprecation.warn(<<-MSG.squish)
-            Passing default to #index_name_exists? is deprecated without replacement.
-          MSG
-        end
+      def index_name_exists?(table_name, index_name)
         index_name = index_name.to_s
         indexes(table_name).detect { |i| i.name == index_name }
       end
 
-      # Adds a reference. The reference column is an integer by default,
+      # Adds a reference. The reference column is a bigint by default,
       # the <tt>:type</tt> option can be used to specify a different type.
       # Optionally adds a +_type+ column, if <tt>:polymorphic</tt> option is provided.
       # #add_reference and #add_belongs_to are acceptable.
       #
       # The +options+ hash can include the following keys:
       # [<tt>:type</tt>]
-      #   The reference column type. Defaults to +:integer+.
+      #   The reference column type. Defaults to +:bigint+.
       # [<tt>:index</tt>]
       #   Add an appropriate index. Defaults to true.
       #   See #add_index for usage of this option.
@@ -830,7 +851,7 @@ module ActiveRecord
       # [<tt>:null</tt>]
       #   Whether the column allows nulls. Defaults to true.
       #
-      # ====== Create a user_id integer column
+      # ====== Create a user_id bigint column
       #
       #   add_reference(:products, :user)
       #
@@ -887,7 +908,7 @@ module ActiveRecord
             foreign_key_options = { to_table: reference_name }
           end
           foreign_key_options[:column] ||= "#{ref_name}_id"
-          remove_foreign_key(table_name, **foreign_key_options)
+          remove_foreign_key(table_name, foreign_key_options)
         end
 
         remove_column(table_name, "#{ref_name}_id")
@@ -943,6 +964,8 @@ module ActiveRecord
       #   Action that happens <tt>ON DELETE</tt>. Valid values are +:nullify+, +:cascade+ and +:restrict+
       # [<tt>:on_update</tt>]
       #   Action that happens <tt>ON UPDATE</tt>. Valid values are +:nullify+, +:cascade+ and +:restrict+
+      # [<tt>:validate</tt>]
+      #   (Postgres only) Specify whether or not the constraint should be validated. Defaults to +true+.
       def add_foreign_key(from_table, to_table, options = {})
         return unless supports_foreign_keys?
 
@@ -1016,16 +1039,6 @@ module ActiveRecord
         insert_versions_sql(versions) if versions.any?
       end
 
-      def initialize_schema_migrations_table # :nodoc:
-        ActiveRecord::SchemaMigration.create_table
-      end
-      deprecate :initialize_schema_migrations_table
-
-      def initialize_internal_metadata_table # :nodoc:
-        ActiveRecord::InternalMetadata.create_table
-      end
-      deprecate :initialize_internal_metadata_table
-
       def internal_string_options_for_primary_key # :nodoc:
         { primary_key: true }
       end
@@ -1036,8 +1049,8 @@ module ActiveRecord
         sm_table = quote_table_name(ActiveRecord::SchemaMigration.table_name)
 
         migrated = ActiveRecord::SchemaMigration.all_versions.map(&:to_i)
-        versions = ActiveRecord::Migrator.migration_files(migrations_paths).map do |file|
-          ActiveRecord::Migrator.parse_migration_filename(file).first.to_i
+        versions = migration_context.migration_files.map do |file|
+          migration_context.parse_migration_filename(file).first.to_i
         end
 
         unless migrated.include?(version)
@@ -1049,13 +1062,7 @@ module ActiveRecord
           if (duplicate = inserting.detect { |v| inserting.count(v) > 1 })
             raise "Duplicate migration #{duplicate}. Please renumber your migrations to resolve the conflict."
           end
-          if supports_multi_insert?
-            execute insert_versions_sql(inserting)
-          else
-            inserting.each do |v|
-              execute insert_versions_sql(v)
-            end
-          end
+          execute insert_versions_sql(inserting)
         end
       end
 
@@ -1131,7 +1138,7 @@ module ActiveRecord
       def add_index_options(table_name, column_name, comment: nil, **options) # :nodoc:
         column_names = index_column_names(column_name)
 
-        options.assert_valid_keys(:unique, :order, :name, :where, :length, :internal, :using, :algorithm, :type)
+        options.assert_valid_keys(:unique, :order, :name, :where, :length, :internal, :using, :algorithm, :type, :opclass)
 
         index_type = options[:type].to_s if options.key?(:type)
         index_type ||= options[:unique] ? "UNIQUE" : ""
@@ -1170,7 +1177,7 @@ module ActiveRecord
       end
 
       # Changes the comment for a column or removes it if +nil+.
-      def change_column_comment(table_name, column_name, comment) #:nodoc:
+      def change_column_comment(table_name, column_name, comment)
         raise NotImplementedError, "#{self.class} does not support changing column comments"
       end
 
@@ -1184,20 +1191,22 @@ module ActiveRecord
         end
 
         def add_index_sort_order(quoted_columns, **options)
-          if order = options[:order]
-            case order
-            when Hash
-              order = order.symbolize_keys
-              quoted_columns.each { |name, column| column << " #{order[name].upcase}" if order[name].present? }
-            when String
-              quoted_columns.each { |name, column| column << " #{order.upcase}" if order.present? }
-            end
+          orders = options_for_index_columns(options[:order])
+          quoted_columns.each do |name, column|
+            column << " #{orders[name].upcase}" if orders[name].present?
           end
+        end
 
-          quoted_columns
+        def options_for_index_columns(options)
+          if options.is_a?(Hash)
+            options.symbolize_keys
+          else
+            Hash.new { |hash, column| hash[column] = options }
+          end
         end
 
-        # Overridden by the MySQL adapter for supporting index lengths
+        # Overridden by the MySQL adapter for supporting index lengths and by
+        # the PostgreSQL adapter for supporting operator classes.
         def add_options_for_index_columns(quoted_columns, **options)
           if supports_index_sort_order?
             quoted_columns = add_index_sort_order(quoted_columns, options)
@@ -1351,6 +1360,20 @@ module ActiveRecord
           options.is_a?(Hash) && options.key?(:name) && options.except(:name, :algorithm).empty?
         end
 
+        def add_column_for_alter(table_name, column_name, type, options = {})
+          td = create_table_definition(table_name)
+          cd = td.new_column_definition(column_name, type, options)
+          schema_creation.accept(AddColumnDefinition.new(cd))
+        end
+
+        def remove_column_for_alter(table_name, column_name, type = nil, options = {})
+          "DROP COLUMN #{quote_column_name(column_name)}"
+        end
+
+        def remove_columns_for_alter(table_name, *column_names)
+          column_names.map { |column_name| remove_column_for_alter(table_name, column_name) }
+        end
+
         def insert_versions_sql(versions)
           sm_table = quote_table_name(ActiveRecord::SchemaMigration.table_name)
 
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
index 147e16e9fa..b59df2fff7 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
@@ -17,11 +17,19 @@ module ActiveRecord
       end
 
       def committed?
-        @state == :committed
+        @state == :committed || @state == :fully_committed
+      end
+
+      def fully_committed?
+        @state == :fully_committed
       end
 
       def rolledback?
-        @state == :rolledback
+        @state == :rolledback || @state == :fully_rolledback
+      end
+
+      def fully_rolledback?
+        @state == :fully_rolledback
       end
 
       def fully_completed?
@@ -55,10 +63,19 @@ module ActiveRecord
         @state = :rolledback
       end
 
+      def full_rollback!
+        @children.each { |c| c.rollback! }
+        @state = :fully_rolledback
+      end
+
       def commit!
         @state = :committed
       end
 
+      def full_commit!
+        @state = :fully_committed
+      end
+
       def nullify!
         @state = nil
       end
@@ -75,7 +92,6 @@ module ActiveRecord
 
     class Transaction #:nodoc:
       attr_reader :connection, :state, :records, :savepoint_name
-      attr_writer :joinable
 
       def initialize(connection, options, run_commit_callbacks: false)
         @connection = connection
@@ -89,10 +105,6 @@ module ActiveRecord
         records << record
       end
 
-      def rollback
-        @state.rollback!
-      end
-
       def rollback_records
         ite = records.uniq
         while record = ite.shift
@@ -104,10 +116,6 @@ module ActiveRecord
         end
       end
 
-      def commit
-        @state.commit!
-      end
-
       def before_commit_records
         records.uniq.each(&:before_committed!) if @run_commit_callbacks
       end
@@ -146,12 +154,12 @@ module ActiveRecord
 
       def rollback
         connection.rollback_to_savepoint(savepoint_name)
-        super
+        @state.rollback!
       end
 
       def commit
         connection.release_savepoint(savepoint_name)
-        super
+        @state.commit!
       end
 
       def full_rollback?; false; end
@@ -169,12 +177,12 @@ module ActiveRecord
 
       def rollback
         connection.rollback_db_transaction
-        super
+        @state.full_rollback!
       end
 
       def commit
         connection.commit_db_transaction
-        super
+        @state.full_commit!
       end
     end
 
@@ -240,7 +248,7 @@ module ActiveRecord
                 rollback_transaction if transaction
               else
                 begin
-                  commit_transaction
+                  commit_transaction if transaction
                 rescue Exception
                   rollback_transaction(transaction) unless transaction.state.completed?
                   raise
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 47881e3305..8bdf1712b1 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -1,11 +1,11 @@
 # frozen_string_literal: true
 
-require_relative "../type"
-require_relative "determine_if_preparable_visitor"
-require_relative "schema_cache"
-require_relative "sql_type_metadata"
-require_relative "abstract/schema_dumper"
-require_relative "abstract/schema_creation"
+require "active_record/connection_adapters/determine_if_preparable_visitor"
+require "active_record/connection_adapters/schema_cache"
+require "active_record/connection_adapters/sql_type_metadata"
+require "active_record/connection_adapters/abstract/schema_dumper"
+require "active_record/connection_adapters/abstract/schema_creation"
+require "active_support/concurrency/load_interlock_aware_monitor"
 require "arel/collectors/bind"
 require "arel/collectors/composite"
 require "arel/collectors/sql_string"
@@ -105,10 +105,11 @@ module ActiveRecord
         @logger              = logger
         @config              = config
         @pool                = nil
+        @idle_since          = Concurrent.monotonic_time
         @schema_cache        = SchemaCache.new self
         @quoted_column_names, @quoted_table_names = {}, {}
         @visitor = arel_visitor
-        @lock = Monitor.new
+        @lock = ActiveSupport::Concurrency::LoadInterlockAwareMonitor.new
 
         if self.class.type_cast_config_to_boolean(config.fetch(:prepared_statements) { true })
           @prepared_statements = true
@@ -118,6 +119,14 @@ module ActiveRecord
         end
       end
 
+      def migrations_paths # :nodoc:
+        @config[:migrations_paths] || Migrator.migrations_paths
+      end
+
+      def migration_context # :nodoc:
+        MigrationContext.new(migrations_paths)
+      end
+
       class Version
         include Comparable
 
@@ -128,6 +137,10 @@ module ActiveRecord
         def <=>(version_string)
           @version <=> version_string.split(".").map(&:to_i)
         end
+
+        def to_s
+          @version.join(".")
+        end
       end
 
       def valid_type?(type) # :nodoc:
@@ -164,6 +177,7 @@ module ActiveRecord
               "Current thread: #{Thread.current}."
           end
 
+          @idle_since = Concurrent.monotonic_time
           @owner = nil
         else
           raise ActiveRecordError, "Cannot expire connection, it is not currently leased."
@@ -183,6 +197,12 @@ module ActiveRecord
         end
       end
 
+      # Seconds since this connection was returned to the pool
+      def seconds_idle # :nodoc:
+        return 0 if in_use?
+        Concurrent.monotonic_time - @idle_since
+      end
+
       def unprepared_statement
         old_prepared_statements, @prepared_statements = @prepared_statements, false
         yield
@@ -196,16 +216,6 @@ module ActiveRecord
         self.class::ADAPTER_NAME
       end
 
-      def supports_migrations? # :nodoc:
-        true
-      end
-      deprecate :supports_migrations?
-
-      def supports_primary_key? # :nodoc:
-        true
-      end
-      deprecate :supports_primary_key?
-
       # Does this adapter support DDL rollbacks in transactions? That is, would
       # CREATE TABLE or ALTER TABLE get rolled back by a transaction?
       def supports_ddl_transactions?
@@ -274,6 +284,11 @@ module ActiveRecord
         false
       end
 
+      # Does this adapter support creating invalid constraints?
+      def supports_validate_constraints?
+        false
+      end
+
       # Does this adapter support creating foreign key constraints
       # in the same statement as creating the table?
       def supports_foreign_keys_in_create?
@@ -309,12 +324,18 @@ module ActiveRecord
       def supports_multi_insert?
         true
       end
+      deprecate :supports_multi_insert?
 
       # Does this adapter support virtual columns?
       def supports_virtual_columns?
         false
       end
 
+      # Does this adapter support foreign/external tables?
+      def supports_foreign_tables?
+        false
+      end
+
       # This is meant to be implemented by the adapters that support extensions
       def disable_extension(name)
       end
@@ -377,6 +398,19 @@ module ActiveRecord
         reset_transaction
       end
 
+      # Immediately forget this connection ever existed. Unlike disconnect!,
+      # this will not communicate with the server.
+      #
+      # After calling this method, the behavior of all other methods becomes
+      # undefined. This is called internally just before a forked process gets
+      # rid of a connection that belonged to its parent.
+      def discard!
+        # This should be overridden by concrete adapters.
+        #
+        # Prevent @connection's finalizer from touching the socket, or
+        # otherwise communicating with its server, when it is collected.
+      end
+
       # Reset the state of this connection, directing the DBMS to clear
       # transactions and other connection-related server-side state. Usually a
       # database-dependent operation.
@@ -402,10 +436,7 @@ module ActiveRecord
       # Checks whether the connection to the database is still active (i.e. not stale).
       # This is done under the hood by calling #active?. If the connection
       # is no longer active, then this method will reconnect to the database.
-      def verify!(*ignored)
-        if ignored.size > 0
-          ActiveSupport::Deprecation.warn("Passing arguments to #verify method of the connection has no effect and has been deprecated. Please remove all arguments from the #verify method call.")
-        end
+      def verify!
         reconnect! unless active?
       end
 
@@ -442,7 +473,11 @@ module ActiveRecord
       end
 
       def column_name_for_operation(operation, node) # :nodoc:
-        visitor.accept(node, collector).value
+        column_name_from_arel_node(node)
+      end
+
+      def column_name_from_arel_node(node) # :nodoc:
+        visitor.accept(node, Arel::Collectors::SQLString.new).value
       end
 
       def default_index_type?(index) # :nodoc:
@@ -474,6 +509,8 @@ module ActiveRecord
           m.alias_type %r(number)i,    "decimal"
           m.alias_type %r(double)i,    "float"
 
+          m.register_type %r(^json)i, Type::Json.new
+
           m.register_type(%r(decimal)i) do |sql_type|
             scale = extract_scale(sql_type)
             precision = extract_precision(sql_type)
@@ -518,12 +555,7 @@ module ActiveRecord
         end
 
         def extract_limit(sql_type)
-          case sql_type
-          when /^bigint/i
-            8
-          when /\((.*)\)/
-            $1.to_i
-          end
+          $1.to_i if sql_type =~ /\((.*)\)/
         end
 
         def translate_exception_class(e, sql)
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index 3683522a0c..07acb5425e 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -1,17 +1,15 @@
 # frozen_string_literal: true
 
-require_relative "abstract_adapter"
-require_relative "statement_pool"
-require_relative "mysql/column"
-require_relative "mysql/explain_pretty_printer"
-require_relative "mysql/quoting"
-require_relative "mysql/schema_creation"
-require_relative "mysql/schema_definitions"
-require_relative "mysql/schema_dumper"
-require_relative "mysql/schema_statements"
-require_relative "mysql/type_metadata"
-
-require "active_support/core_ext/string/strip"
+require "active_record/connection_adapters/abstract_adapter"
+require "active_record/connection_adapters/statement_pool"
+require "active_record/connection_adapters/mysql/column"
+require "active_record/connection_adapters/mysql/explain_pretty_printer"
+require "active_record/connection_adapters/mysql/quoting"
+require "active_record/connection_adapters/mysql/schema_creation"
+require "active_record/connection_adapters/mysql/schema_definitions"
+require "active_record/connection_adapters/mysql/schema_dumper"
+require "active_record/connection_adapters/mysql/schema_statements"
+require "active_record/connection_adapters/mysql/type_metadata"
 
 module ActiveRecord
   module ConnectionAdapters
@@ -33,7 +31,7 @@ module ActiveRecord
         string:      { name: "varchar", limit: 255 },
         text:        { name: "text", limit: 65535 },
         integer:     { name: "int", limit: 4 },
-        float:       { name: "float" },
+        float:       { name: "float", limit: 24 },
         decimal:     { name: "decimal" },
         datetime:    { name: "datetime" },
         timestamp:   { name: "timestamp" },
@@ -44,9 +42,9 @@ module ActiveRecord
         json:        { name: "json" },
       }
 
-      class StatementPool < ConnectionAdapters::StatementPool
+      class StatementPool < ConnectionAdapters::StatementPool # :nodoc:
         private def dealloc(stmt)
-          stmt[:stmt].close
+          stmt.close
         end
       end
 
@@ -117,11 +115,11 @@ module ActiveRecord
       end
 
       def get_advisory_lock(lock_name, timeout = 0) # :nodoc:
-        query_value("SELECT GET_LOCK(#{quote(lock_name)}, #{timeout})") == 1
+        query_value("SELECT GET_LOCK(#{quote(lock_name.to_s)}, #{timeout})") == 1
       end
 
       def release_advisory_lock(lock_name) # :nodoc:
-        query_value("SELECT RELEASE_LOCK(#{quote(lock_name)})") == 1
+        query_value("SELECT RELEASE_LOCK(#{quote(lock_name.to_s)})") == 1
       end
 
       def native_database_types
@@ -225,7 +223,7 @@ module ActiveRecord
         end
       end
 
-      def empty_insert_statement_value
+      def empty_insert_statement_value(primary_key = nil)
         "VALUES ()"
       end
 
@@ -249,7 +247,7 @@ module ActiveRecord
       #   create_database 'matt_development', charset: :big5
       def create_database(name, options = {})
         if options[:collation]
-          execute "CREATE DATABASE #{quote_table_name(name)} DEFAULT CHARACTER SET #{quote_table_name(options[:charset] || 'utf8')} COLLATE #{quote_table_name(options[:collation])}"
+          execute "CREATE DATABASE #{quote_table_name(name)} DEFAULT COLLATE #{quote_table_name(options[:collation])}"
         else
           execute "CREATE DATABASE #{quote_table_name(name)} DEFAULT CHARACTER SET #{quote_table_name(options[:charset] || 'utf8')}"
         end
@@ -284,7 +282,7 @@ module ActiveRecord
       def table_comment(table_name) # :nodoc:
         scope = quoted_scope(table_name)
 
-        query_value(<<-SQL.strip_heredoc, "SCHEMA")
+        query_value(<<~SQL, "SCHEMA").presence
           SELECT table_comment
           FROM information_schema.tables
           WHERE table_schema = #{scope[:schema]}
@@ -292,14 +290,10 @@ module ActiveRecord
         SQL
       end
 
-      def create_table(table_name, **options) #:nodoc:
-        super(table_name, options: "ENGINE=InnoDB", **options)
-      end
-
       def bulk_change_table(table_name, operations) #:nodoc:
         sqls = operations.flat_map do |command, args|
           table, arguments = args.shift, args
-          method = :"#{command}_sql"
+          method = :"#{command}_for_alter"
 
           if respond_to?(method, true)
             send(method, table, *arguments)
@@ -311,6 +305,11 @@ module ActiveRecord
         execute("ALTER TABLE #{quote_table_name(table_name)} #{sqls}")
       end
 
+      def change_table_comment(table_name, comment) #:nodoc:
+        comment = "" if comment.nil?
+        execute("ALTER TABLE #{quote_table_name(table_name)} COMMENT #{quote(comment)}")
+      end
+
       # Renames a table.
       #
       # Example:
@@ -351,26 +350,27 @@ module ActiveRecord
 
       def change_column_default(table_name, column_name, default_or_changes) #:nodoc:
         default = extract_new_default_value(default_or_changes)
-        column = column_for(table_name, column_name)
-        change_column table_name, column_name, column.sql_type, default: default
+        change_column table_name, column_name, nil, default: default
       end
 
       def change_column_null(table_name, column_name, null, default = nil) #:nodoc:
-        column = column_for(table_name, column_name)
-
         unless null || default.nil?
           execute("UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote(default)} WHERE #{quote_column_name(column_name)} IS NULL")
         end
 
-        change_column table_name, column_name, column.sql_type, null: null
+        change_column table_name, column_name, nil, null: null
+      end
+
+      def change_column_comment(table_name, column_name, comment) #:nodoc:
+        change_column table_name, column_name, nil, comment: comment
       end
 
       def change_column(table_name, column_name, type, options = {}) #:nodoc:
-        execute("ALTER TABLE #{quote_table_name(table_name)} #{change_column_sql(table_name, column_name, type, options)}")
+        execute("ALTER TABLE #{quote_table_name(table_name)} #{change_column_for_alter(table_name, column_name, type, options)}")
       end
 
       def rename_column(table_name, column_name, new_column_name) #:nodoc:
-        execute("ALTER TABLE #{quote_table_name(table_name)} #{rename_column_sql(table_name, column_name, new_column_name)}")
+        execute("ALTER TABLE #{quote_table_name(table_name)} #{rename_column_for_alter(table_name, column_name, new_column_name)}")
         rename_column_indexes(table_name, column_name, new_column_name)
       end
 
@@ -390,19 +390,20 @@ module ActiveRecord
 
         scope = quoted_scope(table_name)
 
-        fk_info = exec_query(<<-SQL.strip_heredoc, "SCHEMA")
+        fk_info = exec_query(<<~SQL, "SCHEMA")
           SELECT fk.referenced_table_name AS 'to_table',
                  fk.referenced_column_name AS 'primary_key',
                  fk.column_name AS 'column',
                  fk.constraint_name AS 'name',
                  rc.update_rule AS 'on_update',
                  rc.delete_rule AS 'on_delete'
-          FROM information_schema.key_column_usage fk
-          JOIN information_schema.referential_constraints rc
+          FROM information_schema.referential_constraints rc
+          JOIN information_schema.key_column_usage fk
           USING (constraint_schema, constraint_name)
           WHERE fk.referenced_column_name IS NOT NULL
             AND fk.table_schema = #{scope[:schema]}
             AND fk.table_name = #{scope[:name]}
+            AND rc.constraint_schema = #{scope[:schema]}
             AND rc.table_name = #{scope[:name]}
         SQL
 
@@ -477,7 +478,7 @@ module ActiveRecord
 
         scope = quoted_scope(table_name)
 
-        query_values(<<-SQL.strip_heredoc, "SCHEMA")
+        query_values(<<~SQL, "SCHEMA")
           SELECT column_name
           FROM information_schema.key_column_usage
           WHERE constraint_name = 'PRIMARY'
@@ -512,7 +513,7 @@ module ActiveRecord
           s.gsub(/\s+(?:ASC|DESC)\b/i, "")
         }.reject(&:blank?).map.with_index { |column, i| "#{column} AS alias_#{i}" }
 
-        [super, *order_columns].join(", ")
+        (order_columns << super).join(", ")
       end
 
       def strict_mode?
@@ -523,23 +524,49 @@ module ActiveRecord
         index.using == :btree || super
       end
 
-      def insert_fixtures(*)
-        without_sql_mode("NO_AUTO_VALUE_ON_ZERO") { super }
+      def insert_fixtures_set(fixture_set, tables_to_delete = [])
+        with_multi_statements do
+          super { discard_remaining_results }
+        end
       end
 
       private
+        def combine_multi_statements(total_sql)
+          total_sql.each_with_object([]) do |sql, total_sql_chunks|
+            previous_packet = total_sql_chunks.last
+            sql << ";\n"
+            if max_allowed_packet_reached?(sql, previous_packet) || total_sql_chunks.empty?
+              total_sql_chunks << sql
+            else
+              previous_packet << sql
+            end
+          end
+        end
+
+        def max_allowed_packet_reached?(current_packet, previous_packet)
+          if current_packet.bytesize > max_allowed_packet
+            raise ActiveRecordError, "Fixtures set is too large #{current_packet.bytesize}. Consider increasing the max_allowed_packet variable."
+          elsif previous_packet.nil?
+            false
+          else
+            (current_packet.bytesize + previous_packet.bytesize) > max_allowed_packet
+          end
+        end
 
-        def without_sql_mode(mode)
-          result = execute("SELECT @@SESSION.sql_mode")
-          current_mode = result.first[0]
-          return yield unless current_mode.include?(mode)
+        def max_allowed_packet
+          bytes_margin = 2
+          @max_allowed_packet ||= (show_variable("max_allowed_packet") - bytes_margin)
+        end
+
+        def with_multi_statements
+          previous_flags = @config[:flags]
+          @config[:flags] = Mysql2::Client::MULTI_STATEMENTS
+          reconnect!
 
-          sql_mode = "REPLACE(@@sql_mode, '#{mode}', '')"
-          execute("SET @@SESSION.sql_mode = #{sql_mode}")
           yield
         ensure
-          sql_mode = "CONCAT(@@sql_mode, ',#{mode}')"
-          execute("SET @@SESSION.sql_mode = #{sql_mode}")
+          @config[:flags] = previous_flags
+          reconnect!
         end
 
         def initialize_type_map(m = type_map)
@@ -557,7 +584,6 @@ module ActiveRecord
           m.register_type %r(longblob)i,   Type::Binary.new(limit: 2**32 - 1)
           m.register_type %r(^float)i,     Type::Float.new(limit: 24)
           m.register_type %r(^double)i,    Type::Float.new(limit: 53)
-          m.register_type %r(^json)i,      Type::Json.new
 
           register_integer_type m, %r(^bigint)i,    limit: 8
           register_integer_type m, %r(^int)i,       limit: 4
@@ -600,25 +626,6 @@ module ActiveRecord
           end
         end
 
-        def add_index_length(quoted_columns, **options)
-          if length = options[:length]
-            case length
-            when Hash
-              length = length.symbolize_keys
-              quoted_columns.each { |name, column| column << "(#{length[name]})" if length[name].present? }
-            when Integer
-              quoted_columns.each { |name, column| column << "(#{length})" }
-            end
-          end
-
-          quoted_columns
-        end
-
-        def add_options_for_index_columns(quoted_columns, **options)
-          quoted_columns = add_index_length(quoted_columns, options)
-          super
-        end
-
         # See https://dev.mysql.com/doc/refman/5.7/en/error-messages-server.html
         ER_DUP_ENTRY            = 1062
         ER_NOT_NULL_VIOLATION   = 1048
@@ -630,6 +637,8 @@ module ActiveRecord
         ER_CANNOT_ADD_FOREIGN   = 1215
         ER_CANNOT_CREATE_TABLE  = 1005
         ER_LOCK_WAIT_TIMEOUT    = 1205
+        ER_QUERY_INTERRUPTED    = 1317
+        ER_QUERY_TIMEOUT        = 3024
 
         def translate_exception(exception, message)
           case error_number(exception)
@@ -654,20 +663,19 @@ module ActiveRecord
           when ER_LOCK_DEADLOCK
             Deadlocked.new(message)
           when ER_LOCK_WAIT_TIMEOUT
-            TransactionTimeout.new(message)
+            LockWaitTimeout.new(message)
+          when ER_QUERY_TIMEOUT
+            StatementTimeout.new(message)
+          when ER_QUERY_INTERRUPTED
+            QueryCanceled.new(message)
           else
             super
           end
         end
 
-        def add_column_sql(table_name, column_name, type, options = {})
-          td = create_table_definition(table_name)
-          cd = td.new_column_definition(column_name, type, options)
-          schema_creation.accept(AddColumnDefinition.new(cd))
-        end
-
-        def change_column_sql(table_name, column_name, type, options = {})
+        def change_column_for_alter(table_name, column_name, type, options = {})
           column = column_for(table_name, column_name)
+          type ||= column.sql_type
 
           unless options.key?(:default)
             options[:default] = column.default
@@ -686,7 +694,7 @@ module ActiveRecord
           schema_creation.accept(ChangeColumnDefinition.new(cd, column.name))
         end
 
-        def rename_column_sql(table_name, column_name, new_column_name)
+        def rename_column_for_alter(table_name, column_name, new_column_name)
           column  = column_for(table_name, column_name)
           options = {
             default: column.default,
@@ -700,31 +708,23 @@ module ActiveRecord
           schema_creation.accept(ChangeColumnDefinition.new(cd, column.name))
         end
 
-        def remove_column_sql(table_name, column_name, type = nil, options = {})
-          "DROP #{quote_column_name(column_name)}"
-        end
-
-        def remove_columns_sql(table_name, *column_names)
-          column_names.map { |column_name| remove_column_sql(table_name, column_name) }
-        end
-
-        def add_index_sql(table_name, column_name, options = {})
+        def add_index_for_alter(table_name, column_name, options = {})
           index_name, index_type, index_columns, _, index_algorithm, index_using = add_index_options(table_name, column_name, options)
           index_algorithm[0, 0] = ", " if index_algorithm.present?
           "ADD #{index_type} INDEX #{quote_column_name(index_name)} #{index_using} (#{index_columns})#{index_algorithm}"
         end
 
-        def remove_index_sql(table_name, options = {})
+        def remove_index_for_alter(table_name, options = {})
           index_name = index_name_for_remove(table_name, options)
-          "DROP INDEX #{index_name}"
+          "DROP INDEX #{quote_column_name(index_name)}"
         end
 
-        def add_timestamps_sql(table_name, options = {})
-          [add_column_sql(table_name, :created_at, :datetime, options), add_column_sql(table_name, :updated_at, :datetime, options)]
+        def add_timestamps_for_alter(table_name, options = {})
+          [add_column_for_alter(table_name, :created_at, :datetime, options), add_column_for_alter(table_name, :updated_at, :datetime, options)]
         end
 
-        def remove_timestamps_sql(table_name, options = {})
-          [remove_column_sql(table_name, :updated_at), remove_column_sql(table_name, :created_at)]
+        def remove_timestamps_for_alter(table_name, options = {})
+          [remove_column_for_alter(table_name, :updated_at), remove_column_for_alter(table_name, :created_at)]
         end
 
         # MySQL is too stupid to create a temporary table for use subquery, so we have
@@ -737,7 +737,8 @@ module ActiveRecord
           # to work with MySQL 5.7.6 which sets optimizer_switch='derived_merge=on'
           subselect.distinct unless select.limit || select.offset || select.orders.any?
 
-          Arel::SelectManager.new(subselect.as("__active_record_temp")).project(Arel.sql(key.name))
+          key_name = quote_column_name(key.name)
+          Arel::SelectManager.new(subselect.as("__active_record_temp")).project(Arel.sql(key_name))
         end
 
         def supports_rename_index?
diff --git a/activerecord/lib/active_record/connection_adapters/column.rb b/activerecord/lib/active_record/connection_adapters/column.rb
index 16273fb5f1..5d81de9fe1 100644
--- a/activerecord/lib/active_record/connection_adapters/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/column.rb
@@ -11,11 +11,11 @@ module ActiveRecord
 
       # Instantiates a new column in the table.
       #
-      # +name+ is the column's name, such as <tt>supplier_id</tt> in <tt>supplier_id int</tt>.
+      # +name+ is the column's name, such as <tt>supplier_id</tt> in <tt>supplier_id bigint</tt>.
       # +default+ is the type-casted default value, such as +new+ in <tt>sales_stage varchar(20) default 'new'</tt>.
       # +sql_type_metadata+ is various information about the type of the column
       # +null+ determines if this column allows +NULL+ values.
-      def initialize(name, default, sql_type_metadata = nil, null = true, table_name = nil, default_function = nil, collation = nil, comment: nil)
+      def initialize(name, default, sql_type_metadata = nil, null = true, table_name = nil, default_function = nil, collation = nil, comment: nil, **)
         @name = name.freeze
         @table_name = table_name
         @sql_type_metadata = sql_type_metadata
diff --git a/activerecord/lib/active_record/connection_adapters/connection_specification.rb b/activerecord/lib/active_record/connection_adapters/connection_specification.rb
index 29542f917e..901717ae3d 100644
--- a/activerecord/lib/active_record/connection_adapters/connection_specification.rb
+++ b/activerecord/lib/active_record/connection_adapters/connection_specification.rb
@@ -156,7 +156,6 @@ module ActiveRecord
             env_config = config[env] if config[env].is_a?(Hash) && !(config[env].key?("adapter") || config[env].key?("url"))
           end
 
-          config.reject! { |k, v| v.is_a?(Hash) && !(v.key?("adapter") || v.key?("url")) }
           config.merge! env_config if env_config
 
           config.each do |key, value|
@@ -183,13 +182,25 @@ module ActiveRecord
 
           raise(AdapterNotSpecified, "database configuration does not specify adapter") unless spec.key?(:adapter)
 
+          # Require the adapter itself and give useful feedback about
+          #   1. Missing adapter gems and
+          #   2. Adapter gems' missing dependencies.
           path_to_adapter = "active_record/connection_adapters/#{spec[:adapter]}_adapter"
           begin
             require path_to_adapter
-          rescue Gem::LoadError => e
-            raise Gem::LoadError, "Specified '#{spec[:adapter]}' for database adapter, but the gem is not loaded. Add `gem '#{e.name}'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord)."
           rescue LoadError => e
-            raise LoadError, "Could not load '#{path_to_adapter}'. Make sure that the adapter in config/database.yml is valid. If you use an adapter other than 'mysql2', 'postgresql' or 'sqlite3' add the necessary adapter gem to the Gemfile.", e.backtrace
+            # We couldn't require the adapter itself. Raise an exception that
+            # points out config typos and missing gems.
+            if e.path == path_to_adapter
+              # We can assume that a non-builtin adapter was specified, so it's
+              # either misspelled or missing from Gemfile.
+              raise e.class, "Could not load the '#{spec[:adapter]}' Active Record adapter. Ensure that the adapter is spelled correctly in config/database.yml and that you've added the necessary adapter gem to your Gemfile.", e.backtrace
+
+            # Bubbled up from the adapter require. Prefix the exception message
+            # with some guidance about how to address it and reraise.
+            else
+              raise e.class, "Error loading the '#{spec[:adapter]}' Active Record adapter. Missing a gem it depends on? #{e.message}", e.backtrace
+            end
           end
 
           adapter_method = "#{spec[:adapter]}_connection"
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb b/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
index a058a72872..4106ce01be 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
@@ -11,7 +11,7 @@ module ActiveRecord
           else
             super
           end
-          @connection.next_result while @connection.more_results?
+          discard_remaining_results
           result
         end
 
@@ -50,11 +50,18 @@ module ActiveRecord
         alias :exec_update :exec_delete
 
         private
+          def default_insert_value(column)
+            Arel.sql("DEFAULT") unless column.auto_increment?
+          end
 
           def last_inserted_id(result)
             @connection.last_id
           end
 
+          def discard_remaining_results
+            @connection.abandon_results!
+          end
+
           def exec_stmt_and_free(sql, name, binds, cache_stmt: false)
             # make sure we carry over any changes to ActiveRecord::Base.default_timezone that have been
             # made since we established the connection
@@ -64,10 +71,7 @@ module ActiveRecord
 
             log(sql, name, binds, type_casted_binds) do
               if cache_stmt
-                cache = @statements[sql] ||= {
-                  stmt: @connection.prepare(sql)
-                }
-                stmt = cache[:stmt]
+                stmt = @statements[sql] ||= @connection.prepare(sql)
               else
                 stmt = @connection.prepare(sql)
               end
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_creation.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_creation.rb
index 75377693c6..c9ea653b77 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_creation.rb
@@ -4,8 +4,7 @@ module ActiveRecord
   module ConnectionAdapters
     module MySQL
       class SchemaCreation < AbstractAdapter::SchemaCreation # :nodoc:
-        delegate :add_sql_comment!, :mariadb?, to: :@conn
-        private :add_sql_comment!, :mariadb?
+        delegate :add_sql_comment!, :mariadb?, to: :@conn, private: true
 
         private
 
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
index b22a2e4da7..2ed4ad16ae 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
@@ -4,11 +4,6 @@ module ActiveRecord
   module ConnectionAdapters
     module MySQL
       module ColumnMethods
-        def primary_key(name, type = :primary_key, **options)
-          options[:auto_increment] = true if [:integer, :bigint].include?(type) && !options.key?(:default)
-          super
-        end
-
         def blob(*args, **options)
           args.each { |name| column(name, :blob, options) }
         end
@@ -37,10 +32,6 @@ module ActiveRecord
           args.each { |name| column(name, :longtext, options) }
         end
 
-        def json(*args, **options)
-          args.each { |name| column(name, :json, options) }
-        end
-
         def unsigned_integer(*args, **options)
           args.each { |name| column(name, :unsigned_integer, options) }
         end
@@ -68,7 +59,6 @@ module ActiveRecord
           when :primary_key
             type = :integer
             options[:limit] ||= 8
-            options[:auto_increment] = true
             options[:primary_key] = true
           when /\Aunsigned_(?<type>.+)\z/
             type = $~[:type].to_sym
@@ -82,6 +72,11 @@ module ActiveRecord
           def aliased_types(name, fallback)
             fallback
           end
+
+          def integer_like_primary_key_type(type, options)
+            options[:auto_increment] = true
+            type
+          end
       end
 
       class Table < ActiveRecord::ConnectionAdapters::Table
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
index 95eb77aea4..d23178e43c 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
@@ -8,6 +8,7 @@ module ActiveRecord
           def prepare_column_options(column)
             spec = super
             spec[:unsigned] = "true" if column.unsigned?
+            spec[:auto_increment] = "true" if column.auto_increment?
 
             if @connection.supports_virtual_columns? && column.virtual?
               spec[:as] = extract_expression_for_virtual_column(column)
@@ -18,6 +19,12 @@ module ActiveRecord
             spec
           end
 
+          def column_spec_for_primary_key(column)
+            spec = super
+            spec.delete(:auto_increment) if column.type == :integer && column.auto_increment?
+            spec
+          end
+
           def default_primary_key?(column)
             super && column.auto_increment? && !column.unsigned?
           end
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
index 759493e3bd..ce50590651 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
@@ -5,13 +5,7 @@ module ActiveRecord
     module MySQL
       module SchemaStatements # :nodoc:
         # Returns an array of indexes for the given table.
-        def indexes(table_name, name = nil)
-          if name
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Passing name to #indexes is deprecated without replacement.
-            MSG
-          end
-
+        def indexes(table_name)
           indexes = []
           current_index = nil
           execute_and_free("SHOW KEYS FROM #{quote_table_name(table_name)}", "SCHEMA") do |result|
@@ -28,23 +22,26 @@ module ActiveRecord
                   index_using = mysql_index_type
                 end
 
-                indexes << IndexDefinition.new(
+                indexes << [
                   row[:Table],
                   row[:Key_name],
                   row[:Non_unique].to_i == 0,
+                  [],
+                  lengths: {},
+                  orders: {},
                   type: index_type,
                   using: index_using,
                   comment: row[:Index_comment].presence
-                )
+                ]
               end
 
-              indexes.last.columns << row[:Column_name]
-              indexes.last.lengths.merge!(row[:Column_name] => row[:Sub_part].to_i) if row[:Sub_part]
-              indexes.last.orders.merge!(row[:Column_name] => :desc) if row[:Collation] == "D"
+              indexes.last[-2] << row[:Column_name]
+              indexes.last[-1][:lengths].merge!(row[:Column_name] => row[:Sub_part].to_i) if row[:Sub_part]
+              indexes.last[-1][:orders].merge!(row[:Column_name] => :desc) if row[:Collation] == "D"
             end
           end
 
-          indexes
+          indexes.map { |index| IndexDefinition.new(*index) }
         end
 
         def remove_column(table_name, column_name, type = nil, options = {})
@@ -109,6 +106,18 @@ module ActiveRecord
             super unless specifier == "RESTRICT"
           end
 
+          def add_index_length(quoted_columns, **options)
+            lengths = options_for_index_columns(options[:length])
+            quoted_columns.each do |name, column|
+              column << "(#{lengths[name]})" if lengths[name].present?
+            end
+          end
+
+          def add_options_for_index_columns(quoted_columns, **options)
+            quoted_columns = add_index_length(quoted_columns, options)
+            super
+          end
+
           def data_source_sql(name = nil, type: nil)
             scope = quoted_scope(name, type: type)
 
diff --git a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
index 2c2321872d..4c57bd48ab 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
@@ -1,11 +1,10 @@
 # frozen_string_literal: true
 
-require_relative "abstract_mysql_adapter"
-require_relative "mysql/database_statements"
+require "active_record/connection_adapters/abstract_mysql_adapter"
+require "active_record/connection_adapters/mysql/database_statements"
 
-gem "mysql2", ">= 0.3.18", "< 0.5"
+gem "mysql2", ">= 0.4.4", "< 0.6.0"
 require "mysql2"
-raise "mysql2 0.4.3 is not supported. Please upgrade to 0.4.4+" if Mysql2::VERSION == "0.4.3"
 
 module ActiveRecord
   module ConnectionHandling # :nodoc:
@@ -105,6 +104,11 @@ module ActiveRecord
         @connection.close
       end
 
+      def discard! # :nodoc:
+        @connection.automatic_close = false
+        @connection = nil
+      end
+
       private
 
         def connect
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/column.rb b/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
index 1b67cee24b..3ccc7271ab 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
@@ -7,11 +7,37 @@ module ActiveRecord
       delegate :array, :oid, :fmod, to: :sql_type_metadata
       alias :array? :array
 
+      def initialize(*, max_identifier_length: 63, **)
+        super
+        @max_identifier_length = max_identifier_length
+      end
+
       def serial?
         return unless default_function
 
-        %r{\Anextval\('"?#{table_name}_#{name}_seq"?'::regclass\)\z} === default_function
+        if %r{\Anextval\('"?(?<sequence_name>.+_(?<suffix>seq\d*))"?'::regclass\)\z} =~ default_function
+          sequence_name_from_parts(table_name, name, suffix) == sequence_name
+        end
       end
+
+      private
+        attr_reader :max_identifier_length
+
+        def sequence_name_from_parts(table_name, column_name, suffix)
+          over_length = [table_name, column_name, suffix].map(&:length).sum + 2 - max_identifier_length
+
+          if over_length > 0
+            column_name_length = [(max_identifier_length - suffix.length - 2) / 2, column_name.length].min
+            over_length -= column_name.length - column_name_length
+            column_name = column_name[0, column_name_length - [over_length, 0].min]
+          end
+
+          if over_length > 0
+            table_name = table_name[0, table_name.length - over_length]
+          end
+
+          "#{table_name}_#{column_name}_#{suffix}"
+        end
     end
   end
 end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
index b28418d74f..247a25054e 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
@@ -1,27 +1,28 @@
 # frozen_string_literal: true
 
-require_relative "oid/array"
-require_relative "oid/bit"
-require_relative "oid/bit_varying"
-require_relative "oid/bytea"
-require_relative "oid/cidr"
-require_relative "oid/date_time"
-require_relative "oid/decimal"
-require_relative "oid/enum"
-require_relative "oid/hstore"
-require_relative "oid/inet"
-require_relative "oid/jsonb"
-require_relative "oid/money"
-require_relative "oid/oid"
-require_relative "oid/point"
-require_relative "oid/legacy_point"
-require_relative "oid/range"
-require_relative "oid/specialized_string"
-require_relative "oid/uuid"
-require_relative "oid/vector"
-require_relative "oid/xml"
+require "active_record/connection_adapters/postgresql/oid/array"
+require "active_record/connection_adapters/postgresql/oid/bit"
+require "active_record/connection_adapters/postgresql/oid/bit_varying"
+require "active_record/connection_adapters/postgresql/oid/bytea"
+require "active_record/connection_adapters/postgresql/oid/cidr"
+require "active_record/connection_adapters/postgresql/oid/date"
+require "active_record/connection_adapters/postgresql/oid/date_time"
+require "active_record/connection_adapters/postgresql/oid/decimal"
+require "active_record/connection_adapters/postgresql/oid/enum"
+require "active_record/connection_adapters/postgresql/oid/hstore"
+require "active_record/connection_adapters/postgresql/oid/inet"
+require "active_record/connection_adapters/postgresql/oid/jsonb"
+require "active_record/connection_adapters/postgresql/oid/money"
+require "active_record/connection_adapters/postgresql/oid/oid"
+require "active_record/connection_adapters/postgresql/oid/point"
+require "active_record/connection_adapters/postgresql/oid/legacy_point"
+require "active_record/connection_adapters/postgresql/oid/range"
+require "active_record/connection_adapters/postgresql/oid/specialized_string"
+require "active_record/connection_adapters/postgresql/oid/uuid"
+require "active_record/connection_adapters/postgresql/oid/vector"
+require "active_record/connection_adapters/postgresql/oid/xml"
 
-require_relative "oid/type_map_initializer"
+require "active_record/connection_adapters/postgresql/oid/type_map_initializer"
 
 module ActiveRecord
   module ConnectionAdapters
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit.rb
index 587e95d192..e9a79526f9 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit.rb
@@ -43,10 +43,7 @@ module ActiveRecord
               /\A[0-9A-F]*\Z/i.match?(value)
             end
 
-            # TODO Change this to private once we've dropped Ruby 2.2 support.
-            # Workaround for Ruby 2.2 "private attribute?" warning.
-            protected
-
+            private
               attr_reader :value
           end
         end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/date.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/date.rb
new file mode 100644
index 0000000000..24a1daa95a
--- /dev/null
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/date.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+module ActiveRecord
+  module ConnectionAdapters
+    module PostgreSQL
+      module OID # :nodoc:
+        class Date < Type::Date # :nodoc:
+          def cast_value(value)
+            case value
+            when "infinity" then ::Float::INFINITY
+            when "-infinity" then -::Float::INFINITY
+            when / BC$/
+              astronomical_year = format("%04d", -value[/^\d+/].to_i + 1)
+              super(value.sub(/ BC$/, "").sub(/^\d+/, astronomical_year))
+            else
+              super
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/decimal.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/decimal.rb
index 879dba7afd..e7d33855c4 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/decimal.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/decimal.rb
@@ -6,7 +6,7 @@ module ActiveRecord
       module OID # :nodoc:
         class Decimal < Type::Decimal # :nodoc:
           def infinity(options = {})
-            BigDecimal.new("Infinity") * (options[:negative] ? -1 : 1)
+            BigDecimal("Infinity") * (options[:negative] ? -1 : 1)
           end
         end
       end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb
index 7d5d7d91e6..6edb7cfd3c 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb
@@ -35,7 +35,7 @@ module ActiveRecord
             if value.is_a?(::Range)
               from = type_cast_single_for_database(value.begin)
               to = type_cast_single_for_database(value.end)
-              "[#{from},#{to}#{value.exclude_end? ? ')' : ']'}"
+              ::Range.new(from, to, value.exclude_end?)
             else
               super
             end
@@ -60,7 +60,7 @@ module ActiveRecord
             end
 
             def type_cast_single_for_database(value)
-              infinity?(value) ? "" : @subtype.serialize(value)
+              infinity?(value) ? value : @subtype.serialize(value)
             end
 
             def extract_bounds(value)
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb b/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
index fc458d0c73..e75202b0be 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
@@ -64,7 +64,7 @@ module ActiveRecord
         def quote_default_expression(value, column) # :nodoc:
           if value.is_a?(Proc)
             value.call
-          elsif column.type == :uuid && /\(\)/.match?(value)
+          elsif column.type == :uuid && value.is_a?(String) && /\(\)/.match?(value)
             value # Does not quote function default values for UUID columns
           elsif column.respond_to?(:array?)
             value = type_cast_from_column(column, value)
@@ -101,6 +101,8 @@ module ActiveRecord
               end
             when OID::Array::Data
               _quote(encode_array(value))
+            when Range
+              _quote(encode_range(value))
             else
               super
             end
@@ -117,6 +119,8 @@ module ActiveRecord
               value.to_s
             when OID::Array::Data
               encode_array(value)
+            when Range
+              encode_range(value)
             else
               super
             end
@@ -133,6 +137,10 @@ module ActiveRecord
             result
           end
 
+          def encode_range(range)
+            "[#{type_cast_range_value(range.first)},#{type_cast_range_value(range.last)}#{range.exclude_end? ? ')' : ']'}"
+          end
+
           def determine_encoding_of_strings_in_array(value)
             case value
             when ::Array then determine_encoding_of_strings_in_array(value.first)
@@ -146,6 +154,14 @@ module ActiveRecord
             else _type_cast(values)
             end
           end
+
+          def type_cast_range_value(value)
+            infinity?(value) ? "" : type_cast(value)
+          end
+
+          def infinity?(value)
+            value.respond_to?(:infinite?) && value.infinite?
+          end
       end
     end
   end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb b/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb
index 386d22a9bd..8df91c988b 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb
@@ -4,26 +4,21 @@ module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
       module ReferentialIntegrity # :nodoc:
-        def supports_disable_referential_integrity? # :nodoc:
-          true
-        end
-
         def disable_referential_integrity # :nodoc:
-          if supports_disable_referential_integrity?
-            original_exception = nil
+          original_exception = nil
 
-            begin
-              transaction(requires_new: true) do
-                execute(tables.collect { |name| "ALTER TABLE #{quote_table_name(name)} DISABLE TRIGGER ALL" }.join(";"))
-              end
-            rescue ActiveRecord::ActiveRecordError => e
-              original_exception = e
+          begin
+            transaction(requires_new: true) do
+              execute(tables.collect { |name| "ALTER TABLE #{quote_table_name(name)} DISABLE TRIGGER ALL" }.join(";"))
             end
+          rescue ActiveRecord::ActiveRecordError => e
+            original_exception = e
+          end
 
-            begin
-              yield
-            rescue ActiveRecord::InvalidForeignKey => e
-              warn <<-WARNING
+          begin
+            yield
+          rescue ActiveRecord::InvalidForeignKey => e
+            warn <<-WARNING
 WARNING: Rails was not able to disable referential integrity.
 
 This is most likely caused due to missing permissions.
@@ -32,17 +27,14 @@ Rails needs superuser privileges to disable referential integrity.
     cause: #{original_exception.try(:message)}
 
               WARNING
-              raise e
-            end
+            raise e
+          end
 
-            begin
-              transaction(requires_new: true) do
-                execute(tables.collect { |name| "ALTER TABLE #{quote_table_name(name)} ENABLE TRIGGER ALL" }.join(";"))
-              end
-            rescue ActiveRecord::ActiveRecordError
+          begin
+            transaction(requires_new: true) do
+              execute(tables.collect { |name| "ALTER TABLE #{quote_table_name(name)} ENABLE TRIGGER ALL" }.join(";"))
             end
-          else
-            yield
+          rescue ActiveRecord::ActiveRecordError
           end
         end
       end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb
index 59f661da25..8e381a92cf 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb
@@ -5,6 +5,18 @@ module ActiveRecord
     module PostgreSQL
       class SchemaCreation < AbstractAdapter::SchemaCreation # :nodoc:
         private
+          def visit_AlterTable(o)
+            super << o.constraint_validations.map { |fk| visit_ValidateConstraint fk }.join(" ")
+          end
+
+          def visit_AddForeignKey(o)
+            super.dup.tap { |sql| sql << " NOT VALID" unless o.validate? }
+          end
+
+          def visit_ValidateConstraint(name)
+            "VALIDATE CONSTRAINT #{quote_column_name(name)}"
+          end
+
           def add_column_options!(sql, options)
             if options[:collation]
               sql << " COLLATE \"#{options[:collation]}\""
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb
index f1489e4d69..6047217fcd 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb
@@ -44,15 +44,8 @@ module ActiveRecord
         # a record (as primary keys cannot be +nil+). This might be done via the
         # +SecureRandom.uuid+ method and a +before_save+ callback, for instance.
         def primary_key(name, type = :primary_key, **options)
-          options[:auto_increment] = true if [:integer, :bigint].include?(type) && !options.key?(:default)
           if type == :uuid
             options[:default] = options.fetch(:default, "gen_random_uuid()")
-          elsif options.delete(:auto_increment) == true && %i(integer bigint).include?(type)
-            type = if type == :bigint || options[:limit] == 8
-              :bigserial
-            else
-              :serial
-            end
           end
 
           super
@@ -102,10 +95,6 @@ module ActiveRecord
           args.each { |name| column(name, :int8range, options) }
         end
 
-        def json(*args, **options)
-          args.each { |name| column(name, :json, options) }
-        end
-
         def jsonb(*args, **options)
           args.each { |name| column(name, :jsonb, options) }
         end
@@ -185,11 +174,33 @@ module ActiveRecord
 
       class TableDefinition < ActiveRecord::ConnectionAdapters::TableDefinition
         include ColumnMethods
+
+        private
+          def integer_like_primary_key_type(type, options)
+            if type == :bigint || options[:limit] == 8
+              :bigserial
+            else
+              :serial
+            end
+          end
       end
 
       class Table < ActiveRecord::ConnectionAdapters::Table
         include ColumnMethods
       end
+
+      class AlterTable < ActiveRecord::ConnectionAdapters::AlterTable
+        attr_reader :constraint_validations
+
+        def initialize(td)
+          super
+          @constraint_validations = []
+        end
+
+        def validate_constraint(name)
+          @constraint_validations << name
+        end
+      end
     end
   end
 end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb
index c0dbb166b7..84643d20da 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb
@@ -5,6 +5,18 @@ module ActiveRecord
     module PostgreSQL
       class SchemaDumper < ConnectionAdapters::SchemaDumper # :nodoc:
         private
+
+          def extensions(stream)
+            extensions = @connection.extensions
+            if extensions.any?
+              stream.puts "  # These are extensions that must be enabled in order to support this database"
+              extensions.sort.each do |extension|
+                stream.puts "  enable_extension #{extension.inspect}"
+              end
+              stream.puts
+            end
+          end
+
           def prepare_column_options(column)
             spec = super
             spec[:array] = "true" if column.array?
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
index 9e2f61e6ce..e20e5f2914 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/string/strip"
-
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
@@ -40,7 +38,7 @@ module ActiveRecord
                       " TABLESPACE = \"#{value}\""
                     when :connection_limit
                       " CONNECTION LIMIT = #{value}"
-            else
+                    else
                       ""
             end
           end
@@ -66,12 +64,7 @@ module ActiveRecord
         end
 
         # Verifies existence of an index with a given name.
-        def index_name_exists?(table_name, index_name, default = nil)
-          unless default.nil?
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Passing default to #index_name_exists? is deprecated without replacement.
-            MSG
-          end
+        def index_name_exists?(table_name, index_name)
           table = quoted_scope(table_name)
           index = quoted_scope(index_name)
 
@@ -89,21 +82,12 @@ module ActiveRecord
         end
 
         # Returns an array of indexes for the given table.
-        def indexes(table_name, name = nil) # :nodoc:
-          if name
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Passing name to #indexes is deprecated without replacement.
-            MSG
-          end
-
+        def indexes(table_name) # :nodoc:
           scope = quoted_scope(table_name)
 
           result = query(<<-SQL, "SCHEMA")
             SELECT distinct i.relname, d.indisunique, d.indkey, pg_get_indexdef(d.indexrelid), t.oid,
-                            pg_catalog.obj_description(i.oid, 'pg_class') AS comment,
-            (SELECT COUNT(*) FROM pg_opclass o
-               JOIN (SELECT unnest(string_to_array(d.indclass::text, ' '))::int oid) c
-                 ON o.oid = c.oid WHERE o.opcdefault = 'f')
+                            pg_catalog.obj_description(i.oid, 'pg_class') AS comment
             FROM pg_class t
             INNER JOIN pg_index d ON t.oid = d.indrelid
             INNER JOIN pg_class i ON d.indexrelid = i.oid
@@ -122,24 +106,32 @@ module ActiveRecord
             inddef = row[3]
             oid = row[4]
             comment = row[5]
-            opclass = row[6]
 
-            using, expressions, where = inddef.scan(/ USING (\w+?) \((.+?)\)(?: WHERE (.+))?\z/).flatten
+            using, expressions, where = inddef.scan(/ USING (\w+?) \((.+?)\)(?: WHERE (.+))?\z/m).flatten
 
-            if indkey.include?(0) || opclass > 0
+            orders = {}
+            opclasses = {}
+
+            if indkey.include?(0)
               columns = expressions
             else
-              columns = Hash[query(<<-SQL.strip_heredoc, "SCHEMA")].values_at(*indkey).compact
+              columns = Hash[query(<<~SQL, "SCHEMA")].values_at(*indkey).compact
                 SELECT a.attnum, a.attname
                 FROM pg_attribute a
                 WHERE a.attrelid = #{oid}
                 AND a.attnum IN (#{indkey.join(",")})
               SQL
 
-              # add info on sort order for columns (only desc order is explicitly specified, asc is the default)
-              orders = Hash[
-                expressions.scan(/(\w+) DESC/).flatten.map { |order_column| [order_column, :desc] }
-              ]
+              # add info on sort order (only desc order is explicitly specified, asc is the default)
+              # and non-default opclasses
+              expressions.scan(/(?<column>\w+)\s?(?<opclass>\w+_ops)?\s?(?<desc>DESC)?\s?(?<nulls>NULLS (?:FIRST|LAST))?/).each do |column, opclass, desc, nulls|
+                opclasses[column] = opclass.to_sym if opclass
+                if nulls
+                  orders[column] = [desc, nulls].compact.join(" ")
+                else
+                  orders[column] = :desc if desc
+                end
+              end
             end
 
             IndexDefinition.new(
@@ -148,6 +140,7 @@ module ActiveRecord
               unique,
               columns,
               orders: orders,
+              opclasses: opclasses,
               where: where,
               using: using.to_sym,
               comment: comment.presence
@@ -165,7 +158,7 @@ module ActiveRecord
         def table_comment(table_name) # :nodoc:
           scope = quoted_scope(table_name, type: "BASE TABLE")
           if scope[:name]
-            query_value(<<-SQL.strip_heredoc, "SCHEMA")
+            query_value(<<~SQL, "SCHEMA")
               SELECT pg_catalog.obj_description(c.oid, 'pg_class')
               FROM pg_catalog.pg_class c
                 LEFT JOIN pg_namespace n ON n.oid = c.relnamespace
@@ -360,7 +353,7 @@ module ActiveRecord
         end
 
         def primary_keys(table_name) # :nodoc:
-          query_values(<<-SQL.strip_heredoc, "SCHEMA")
+          query_values(<<~SQL, "SCHEMA")
             SELECT a.attname
               FROM (
                      SELECT indrelid, indkey, generate_subscripts(indkey, 1) idx
@@ -375,6 +368,31 @@ module ActiveRecord
           SQL
         end
 
+        def bulk_change_table(table_name, operations)
+          sql_fragments = []
+          non_combinable_operations = []
+
+          operations.each do |command, args|
+            table, arguments = args.shift, args
+            method = :"#{command}_for_alter"
+
+            if respond_to?(method, true)
+              sqls, procs = Array(send(method, table, *arguments)).partition { |v| v.is_a?(String) }
+              sql_fragments << sqls
+              non_combinable_operations.concat(procs)
+            else
+              execute "ALTER TABLE #{quote_table_name(table_name)} #{sql_fragments.join(", ")}" unless sql_fragments.empty?
+              non_combinable_operations.each(&:call)
+              sql_fragments = []
+              non_combinable_operations = []
+              send(command, table, *arguments)
+            end
+          end
+
+          execute "ALTER TABLE #{quote_table_name(table_name)} #{sql_fragments.join(", ")}" unless sql_fragments.empty?
+          non_combinable_operations.each(&:call)
+        end
+
         # Renames a table.
         # Also renames a table's primary key sequence if the sequence name exists and
         # matches the Active Record default.
@@ -405,50 +423,23 @@ module ActiveRecord
 
         def change_column(table_name, column_name, type, options = {}) #:nodoc:
           clear_cache!
-          quoted_table_name = quote_table_name(table_name)
-          quoted_column_name = quote_column_name(column_name)
-          sql_type = type_to_sql(type, options)
-          sql = "ALTER TABLE #{quoted_table_name} ALTER COLUMN #{quoted_column_name} TYPE #{sql_type}".dup
-          if options[:collation]
-            sql << " COLLATE \"#{options[:collation]}\""
-          end
-          if options[:using]
-            sql << " USING #{options[:using]}"
-          elsif options[:cast_as]
-            cast_as_type = type_to_sql(options[:cast_as], options)
-            sql << " USING CAST(#{quoted_column_name} AS #{cast_as_type})"
-          end
-          execute sql
-
-          change_column_default(table_name, column_name, options[:default]) if options.key?(:default)
-          change_column_null(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
-          change_column_comment(table_name, column_name, options[:comment]) if options.key?(:comment)
+          sqls, procs = Array(change_column_for_alter(table_name, column_name, type, options)).partition { |v| v.is_a?(String) }
+          execute "ALTER TABLE #{quote_table_name(table_name)} #{sqls.join(", ")}"
+          procs.each(&:call)
         end
 
         # Changes the default value of a table column.
         def change_column_default(table_name, column_name, default_or_changes) # :nodoc:
-          clear_cache!
-          column = column_for(table_name, column_name)
-          return unless column
-
-          default = extract_new_default_value(default_or_changes)
-          alter_column_query = "ALTER TABLE #{quote_table_name(table_name)} ALTER COLUMN #{quote_column_name(column_name)} %s"
-          if default.nil?
-            # <tt>DEFAULT NULL</tt> results in the same behavior as <tt>DROP DEFAULT</tt>. However, PostgreSQL will
-            # cast the default to the columns type, which leaves us with a default like "default NULL::character varying".
-            execute alter_column_query % "DROP DEFAULT"
-          else
-            execute alter_column_query % "SET DEFAULT #{quote_default_expression(default, column)}"
-          end
+          execute "ALTER TABLE #{quote_table_name(table_name)} #{change_column_default_for_alter(table_name, column_name, default_or_changes)}"
         end
 
         def change_column_null(table_name, column_name, null, default = nil) #:nodoc:
           clear_cache!
           unless null || default.nil?
             column = column_for(table_name, column_name)
-            execute("UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote_default_expression(default, column)} WHERE #{quote_column_name(column_name)} IS NULL") if column
+            execute "UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote_default_expression(default, column)} WHERE #{quote_column_name(column_name)} IS NULL" if column
           end
-          execute("ALTER TABLE #{quote_table_name(table_name)} ALTER #{quote_column_name(column_name)} #{null ? 'DROP' : 'SET'} NOT NULL")
+          execute "ALTER TABLE #{quote_table_name(table_name)} #{change_column_null_for_alter(table_name, column_name, null, default)}"
         end
 
         # Adds comment for given table column or drops it if +comment+ is a +nil+
@@ -471,8 +462,8 @@ module ActiveRecord
         end
 
         def add_index(table_name, column_name, options = {}) #:nodoc:
-          index_name, index_type, index_columns, index_options, index_algorithm, index_using, comment = add_index_options(table_name, column_name, options)
-          execute("CREATE #{index_type} INDEX #{index_algorithm} #{quote_column_name(index_name)} ON #{quote_table_name(table_name)} #{index_using} (#{index_columns})#{index_options}").tap do
+          index_name, index_type, index_columns_and_opclasses, index_options, index_algorithm, index_using, comment = add_index_options(table_name, column_name, options)
+          execute("CREATE #{index_type} INDEX #{index_algorithm} #{quote_column_name(index_name)} ON #{quote_table_name(table_name)} #{index_using} (#{index_columns_and_opclasses})#{index_options}").tap do
             execute "COMMENT ON INDEX #{quote_column_name(index_name)} IS #{quote(comment)}" if comment
           end
         end
@@ -511,8 +502,8 @@ module ActiveRecord
 
         def foreign_keys(table_name)
           scope = quoted_scope(table_name)
-          fk_info = exec_query(<<-SQL.strip_heredoc, "SCHEMA")
-            SELECT t2.oid::regclass::text AS to_table, a1.attname AS column, a2.attname AS primary_key, c.conname AS name, c.confupdtype AS on_update, c.confdeltype AS on_delete
+          fk_info = exec_query(<<~SQL, "SCHEMA")
+            SELECT t2.oid::regclass::text AS to_table, a1.attname AS column, a2.attname AS primary_key, c.conname AS name, c.confupdtype AS on_update, c.confdeltype AS on_delete, c.convalidated AS valid
             FROM pg_constraint c
             JOIN pg_class t1 ON c.conrelid = t1.oid
             JOIN pg_class t2 ON c.confrelid = t2.oid
@@ -534,11 +525,20 @@ module ActiveRecord
 
             options[:on_delete] = extract_foreign_key_action(row["on_delete"])
             options[:on_update] = extract_foreign_key_action(row["on_update"])
+            options[:validate] = row["valid"]
 
             ForeignKeyDefinition.new(table_name, row["to_table"], options)
           end
         end
 
+        def foreign_tables
+          query_values(data_source_sql(type: "FOREIGN TABLE"), "SCHEMA")
+        end
+
+        def foreign_table_exists?(table_name)
+          query_values(data_source_sql(table_name, type: "FOREIGN TABLE"), "SCHEMA").any? if table_name.present?
+        end
+
         # Maps logical Rails types to PostgreSQL-specific data types.
         def type_to_sql(type, limit: nil, precision: nil, scale: nil, array: nil, **) # :nodoc:
           sql = \
@@ -583,7 +583,7 @@ module ActiveRecord
                .gsub(/\s+NULLS\s+(?:FIRST|LAST)\b/i, "")
             }.reject(&:blank?).map.with_index { |column, i| "#{column} AS alias_#{i}" }
 
-          [super, *order_columns].join(", ")
+          (order_columns << super).join(", ")
         end
 
         def update_table_definition(table_name, base) # :nodoc:
@@ -594,6 +594,43 @@ module ActiveRecord
           PostgreSQL::SchemaDumper.create(self, options)
         end
 
+        # Validates the given constraint.
+        #
+        # Validates the constraint named +constraint_name+ on +accounts+.
+        #
+        #   validate_constraint :accounts, :constraint_name
+        def validate_constraint(table_name, constraint_name)
+          return unless supports_validate_constraints?
+
+          at = create_alter_table table_name
+          at.validate_constraint constraint_name
+
+          execute schema_creation.accept(at)
+        end
+
+        # Validates the given foreign key.
+        #
+        # Validates the foreign key on +accounts.branch_id+.
+        #
+        #   validate_foreign_key :accounts, :branches
+        #
+        # Validates the foreign key on +accounts.owner_id+.
+        #
+        #   validate_foreign_key :accounts, column: :owner_id
+        #
+        # Validates the foreign key named +special_fk_name+ on the +accounts+ table.
+        #
+        #   validate_foreign_key :accounts, name: :special_fk_name
+        #
+        # The +options+ hash accepts the same keys as SchemaStatements#add_foreign_key.
+        def validate_foreign_key(from_table, options_or_to_table = {})
+          return unless supports_validate_constraints?
+
+          fk_name_to_validate = foreign_key_for!(from_table, options_or_to_table).name
+
+          validate_constraint from_table, fk_name_to_validate
+        end
+
         private
           def schema_creation
             PostgreSQL::SchemaCreation.new(self)
@@ -603,6 +640,10 @@ module ActiveRecord
             PostgreSQL::TableDefinition.new(*args)
           end
 
+          def create_alter_table(name)
+            PostgreSQL::AlterTable.new create_table_definition(name)
+          end
+
           def new_column_from_field(table_name, field)
             column_name, type, default, notnull, oid, fmod, collation, comment = field
             type_metadata = fetch_type_metadata(column_name, type, oid.to_i, fmod.to_i)
@@ -617,7 +658,8 @@ module ActiveRecord
               table_name,
               default_function,
               collation,
-              comment: comment.presence
+              comment: comment.presence,
+              max_identifier_length: max_identifier_length
             )
           end
 
@@ -641,9 +683,75 @@ module ActiveRecord
             end
           end
 
+          def change_column_sql(table_name, column_name, type, options = {})
+            quoted_column_name = quote_column_name(column_name)
+            sql_type = type_to_sql(type, options)
+            sql = "ALTER COLUMN #{quoted_column_name} TYPE #{sql_type}".dup
+            if options[:collation]
+              sql << " COLLATE \"#{options[:collation]}\""
+            end
+            if options[:using]
+              sql << " USING #{options[:using]}"
+            elsif options[:cast_as]
+              cast_as_type = type_to_sql(options[:cast_as], options)
+              sql << " USING CAST(#{quoted_column_name} AS #{cast_as_type})"
+            end
+
+            sql
+          end
+
+          def change_column_for_alter(table_name, column_name, type, options = {})
+            sqls = [change_column_sql(table_name, column_name, type, options)]
+            sqls << change_column_default_for_alter(table_name, column_name, options[:default]) if options.key?(:default)
+            sqls << change_column_null_for_alter(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
+            sqls << Proc.new { change_column_comment(table_name, column_name, options[:comment]) } if options.key?(:comment)
+            sqls
+          end
+
+
+          # Changes the default value of a table column.
+          def change_column_default_for_alter(table_name, column_name, default_or_changes) # :nodoc:
+            column = column_for(table_name, column_name)
+            return unless column
+
+            default = extract_new_default_value(default_or_changes)
+            alter_column_query = "ALTER COLUMN #{quote_column_name(column_name)} %s"
+            if default.nil?
+              # <tt>DEFAULT NULL</tt> results in the same behavior as <tt>DROP DEFAULT</tt>. However, PostgreSQL will
+              # cast the default to the columns type, which leaves us with a default like "default NULL::character varying".
+              alter_column_query % "DROP DEFAULT"
+            else
+              alter_column_query % "SET DEFAULT #{quote_default_expression(default, column)}"
+            end
+          end
+
+          def change_column_null_for_alter(table_name, column_name, null, default = nil) #:nodoc:
+            "ALTER #{quote_column_name(column_name)} #{null ? 'DROP' : 'SET'} NOT NULL"
+          end
+
+          def add_timestamps_for_alter(table_name, options = {})
+            [add_column_for_alter(table_name, :created_at, :datetime, options), add_column_for_alter(table_name, :updated_at, :datetime, options)]
+          end
+
+          def remove_timestamps_for_alter(table_name, options = {})
+            [remove_column_for_alter(table_name, :updated_at), remove_column_for_alter(table_name, :created_at)]
+          end
+
+          def add_index_opclass(quoted_columns, **options)
+            opclasses = options_for_index_columns(options[:opclass])
+            quoted_columns.each do |name, column|
+              column << " #{opclasses[name]}" if opclasses[name].present?
+            end
+          end
+
+          def add_options_for_index_columns(quoted_columns, **options)
+            quoted_columns = add_index_opclass(quoted_columns, options)
+            super
+          end
+
           def data_source_sql(name = nil, type: nil)
             scope = quoted_scope(name, type: type)
-            scope[:type] ||= "'r','v','m'" # (r)elation/table, (v)iew, (m)aterialized view
+            scope[:type] ||= "'r','v','m','f'" # (r)elation/table, (v)iew, (m)aterialized view, (f)oreign table
 
             sql = "SELECT c.relname FROM pg_class c LEFT JOIN pg_namespace n ON n.oid = c.relnamespace".dup
             sql << " WHERE n.nspname = #{scope[:schema]}"
@@ -660,6 +768,8 @@ module ActiveRecord
                 "'r'"
               when "VIEW"
                 "'v','m'"
+              when "FOREIGN TABLE"
+                "'f'"
               end
             scope = {}
             scope[:schema] = schema ? quote(schema) : "ANY (current_schemas(false))"
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/type_metadata.rb b/activerecord/lib/active_record/connection_adapters/postgresql/type_metadata.rb
index b252a76caa..ffd3be26b0 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/type_metadata.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/type_metadata.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 module ActiveRecord
+  # :stopdoc:
   module ConnectionAdapters
     class PostgreSQLTypeMetadata < DelegateClass(SqlTypeMetadata)
       undef to_yaml if method_defined?(:to_yaml)
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 4d37a292d6..fdf6f75108 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -1,23 +1,23 @@
 # frozen_string_literal: true
 
 # Make sure we're using pg high enough for type casts and Ruby 2.2+ compatibility
-gem "pg", "~> 0.18"
+gem "pg", ">= 0.18", "< 2.0"
 require "pg"
 
-require_relative "abstract_adapter"
-require_relative "statement_pool"
-require_relative "postgresql/column"
-require_relative "postgresql/database_statements"
-require_relative "postgresql/explain_pretty_printer"
-require_relative "postgresql/oid"
-require_relative "postgresql/quoting"
-require_relative "postgresql/referential_integrity"
-require_relative "postgresql/schema_creation"
-require_relative "postgresql/schema_definitions"
-require_relative "postgresql/schema_dumper"
-require_relative "postgresql/schema_statements"
-require_relative "postgresql/type_metadata"
-require_relative "postgresql/utils"
+require "active_record/connection_adapters/abstract_adapter"
+require "active_record/connection_adapters/statement_pool"
+require "active_record/connection_adapters/postgresql/column"
+require "active_record/connection_adapters/postgresql/database_statements"
+require "active_record/connection_adapters/postgresql/explain_pretty_printer"
+require "active_record/connection_adapters/postgresql/oid"
+require "active_record/connection_adapters/postgresql/quoting"
+require "active_record/connection_adapters/postgresql/referential_integrity"
+require "active_record/connection_adapters/postgresql/schema_creation"
+require "active_record/connection_adapters/postgresql/schema_definitions"
+require "active_record/connection_adapters/postgresql/schema_dumper"
+require "active_record/connection_adapters/postgresql/schema_statements"
+require "active_record/connection_adapters/postgresql/type_metadata"
+require "active_record/connection_adapters/postgresql/utils"
 
 module ActiveRecord
   module ConnectionHandling # :nodoc:
@@ -122,6 +122,10 @@ module ActiveRecord
       include PostgreSQL::SchemaStatements
       include PostgreSQL::DatabaseStatements
 
+      def supports_bulk_alter?
+        true
+      end
+
       def supports_index_sort_order?
         true
       end
@@ -142,6 +146,10 @@ module ActiveRecord
         true
       end
 
+      def supports_validate_constraints?
+        true
+      end
+
       def supports_views?
         true
       end
@@ -166,7 +174,7 @@ module ActiveRecord
         { concurrently: "CONCURRENTLY" }
       end
 
-      class StatementPool < ConnectionAdapters::StatementPool
+      class StatementPool < ConnectionAdapters::StatementPool # :nodoc:
         def initialize(connection, max)
           super(max)
           @connection = connection
@@ -182,7 +190,6 @@ module ActiveRecord
         end
 
         private
-
           def dealloc(key)
             @connection.query "DEALLOCATE #{key}" if connection_active?
           rescue PG::Error
@@ -273,6 +280,11 @@ module ActiveRecord
         end
       end
 
+      def discard! # :nodoc:
+        @connection.socket_io.reopen(IO::NULL) rescue nil
+        @connection = nil
+      end
+
       def native_database_types #:nodoc:
         NATIVE_DATABASE_TYPES
       end
@@ -306,20 +318,24 @@ module ActiveRecord
         postgresql_version >= 90300
       end
 
+      def supports_foreign_tables?
+        postgresql_version >= 90300
+      end
+
       def supports_pgcrypto_uuid?
         postgresql_version >= 90400
       end
 
       def get_advisory_lock(lock_id) # :nodoc:
         unless lock_id.is_a?(Integer) && lock_id.bit_length <= 63
-          raise(ArgumentError, "Postgres requires advisory lock ids to be a signed 64 bit integer")
+          raise(ArgumentError, "PostgreSQL requires advisory lock ids to be a signed 64 bit integer")
         end
         query_value("SELECT pg_try_advisory_lock(#{lock_id})")
       end
 
       def release_advisory_lock(lock_id) # :nodoc:
         unless lock_id.is_a?(Integer) && lock_id.bit_length <= 63
-          raise(ArgumentError, "Postgres requires advisory lock ids to be a signed 64 bit integer")
+          raise(ArgumentError, "PostgreSQL requires advisory lock ids to be a signed 64 bit integer")
         end
         query_value("SELECT pg_advisory_unlock(#{lock_id})")
       end
@@ -337,25 +353,20 @@ module ActiveRecord
       end
 
       def extension_enabled?(name)
-        if supports_extensions?
-          res = exec_query("SELECT EXISTS(SELECT * FROM pg_available_extensions WHERE name = '#{name}' AND installed_version IS NOT NULL) as enabled", "SCHEMA")
-          res.cast_values.first
-        end
+        res = exec_query("SELECT EXISTS(SELECT * FROM pg_available_extensions WHERE name = '#{name}' AND installed_version IS NOT NULL) as enabled", "SCHEMA")
+        res.cast_values.first
       end
 
       def extensions
-        if supports_extensions?
-          exec_query("SELECT extname FROM pg_extension", "SCHEMA").cast_values
-        else
-          super
-        end
+        exec_query("SELECT extname FROM pg_extension", "SCHEMA").cast_values
       end
 
       # Returns the configured supported identifier length supported by PostgreSQL
-      def table_alias_length
+      def max_identifier_length
         @max_identifier_length ||= query_value("SHOW max_identifier_length", "SCHEMA").to_i
       end
-      alias index_name_length table_alias_length
+      alias table_alias_length max_identifier_length
+      alias index_name_length max_identifier_length
 
       # Set the authorized user for this session
       def session_auth=(user)
@@ -387,7 +398,6 @@ module ActiveRecord
       end
 
       private
-
         # See https://www.postgresql.org/docs/current/static/errcodes-appendix.html
         VALUE_LIMIT_VIOLATION = "22001"
         NUMERIC_VALUE_OUT_OF_RANGE = "22003"
@@ -396,6 +406,8 @@ module ActiveRecord
         UNIQUE_VIOLATION      = "23505"
         SERIALIZATION_FAILURE = "40001"
         DEADLOCK_DETECTED     = "40P01"
+        LOCK_NOT_AVAILABLE    = "55P03"
+        QUERY_CANCELED        = "57014"
 
         def translate_exception(exception, message)
           return exception unless exception.respond_to?(:result)
@@ -415,6 +427,10 @@ module ActiveRecord
             SerializationFailure.new(message)
           when DEADLOCK_DETECTED
             Deadlocked.new(message)
+          when LOCK_NOT_AVAILABLE
+            LockWaitTimeout.new(message)
+          when QUERY_CANCELED
+            QueryCanceled.new(message)
           else
             super
           end
@@ -449,7 +465,7 @@ module ActiveRecord
           register_class_with_limit m, "bit", OID::Bit
           register_class_with_limit m, "varbit", OID::BitVarying
           m.alias_type "timestamptz", "timestamp"
-          m.register_type "date", Type::Date.new
+          m.register_type "date", OID::Date.new
 
           m.register_type "money", OID::Money.new
           m.register_type "bytea", OID::Bytea.new
@@ -821,6 +837,7 @@ module ActiveRecord
         ActiveRecord::Type.register(:bit_varying, OID::BitVarying, adapter: :postgresql)
         ActiveRecord::Type.register(:binary, OID::Bytea, adapter: :postgresql)
         ActiveRecord::Type.register(:cidr, OID::Cidr, adapter: :postgresql)
+        ActiveRecord::Type.register(:date, OID::Date, adapter: :postgresql)
         ActiveRecord::Type.register(:datetime, OID::DateTime, adapter: :postgresql)
         ActiveRecord::Type.register(:decimal, OID::Decimal, adapter: :postgresql)
         ActiveRecord::Type.register(:enum, OID::Enum, adapter: :postgresql)
diff --git a/activerecord/lib/active_record/connection_adapters/schema_cache.rb b/activerecord/lib/active_record/connection_adapters/schema_cache.rb
index f34b6733da..c29cf1f9a1 100644
--- a/activerecord/lib/active_record/connection_adapters/schema_cache.rb
+++ b/activerecord/lib/active_record/connection_adapters/schema_cache.rb
@@ -28,7 +28,7 @@ module ActiveRecord
         coder["columns_hash"] = @columns_hash
         coder["primary_keys"] = @primary_keys
         coder["data_sources"] = @data_sources
-        coder["version"] = ActiveRecord::Migrator.current_version
+        coder["version"] = connection.migration_context.current_version
       end
 
       def init_with(coder)
@@ -100,7 +100,7 @@ module ActiveRecord
 
       def marshal_dump
         # if we get current version during initialization, it happens stack over flow.
-        @version = ActiveRecord::Migrator.current_version
+        @version = connection.migration_context.current_version
         [@version, @columns, @columns_hash, @primary_keys, @data_sources]
       end
 
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
index 8042dbfea2..70de96326c 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
@@ -17,7 +17,7 @@ module ActiveRecord
         end
 
         def quoted_time(value)
-          quoted_date(value)
+          quoted_date(value).sub(/\A\d\d\d\d-\d\d-\d\d /, "2000-01-01 ")
         end
 
         def quoted_binary(value)
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_definitions.rb
index 501f17dbad..c9855019c1 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_definitions.rb
@@ -3,27 +3,16 @@
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
-      module ColumnMethods
-        def primary_key(name, type = :primary_key, **options)
-          if %i(integer bigint).include?(type) && (options.delete(:auto_increment) == true || !options.key?(:default))
-            type = :primary_key
-          end
-
-          super
-        end
-      end
-
       class TableDefinition < ActiveRecord::ConnectionAdapters::TableDefinition
-        include ColumnMethods
-
         def references(*args, **options)
           super(*args, type: :integer, **options)
         end
         alias :belongs_to :references
-      end
 
-      class Table < ActiveRecord::ConnectionAdapters::Table
-        include ColumnMethods
+        private
+          def integer_like_primary_key_type(type, options)
+            :primary_key
+          end
       end
     end
   end
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
index a512702b7b..58e5138e02 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
@@ -5,13 +5,7 @@ module ActiveRecord
     module SQLite3
       module SchemaStatements # :nodoc:
         # Returns an array of indexes for the given table.
-        def indexes(table_name, name = nil)
-          if name
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Passing name to #indexes is deprecated without replacement.
-            MSG
-          end
-
+        def indexes(table_name)
           exec_query("PRAGMA index_list(#{quote_table_name(table_name)})", "SCHEMA").map do |row|
             index_sql = query_value(<<-SQL, "SCHEMA")
               SELECT sql
@@ -29,20 +23,26 @@ module ActiveRecord
               col["name"]
             end
 
+            # Add info on sort order for columns (only desc order is explicitly specified, asc is
+            # the default)
+            orders = {}
+            if index_sql # index_sql can be null in case of primary key indexes
+              index_sql.scan(/"(\w+)" DESC/).flatten.each { |order_column|
+                orders[order_column] = :desc
+              }
+            end
+
             IndexDefinition.new(
               table_name,
               row["name"],
               row["unique"] != 0,
               columns,
-              where: where
+              where: where,
+              orders: orders
             )
           end
         end
 
-        def update_table_definition(table_name, base)
-          SQLite3::Table.new(table_name, base)
-        end
-
         def create_schema_dumper(options)
           SQLite3::SchemaDumper.create(self, options)
         end
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index d6f357bcc3..544374586c 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -1,13 +1,13 @@
 # frozen_string_literal: true
 
-require_relative "abstract_adapter"
-require_relative "statement_pool"
-require_relative "sqlite3/explain_pretty_printer"
-require_relative "sqlite3/quoting"
-require_relative "sqlite3/schema_creation"
-require_relative "sqlite3/schema_definitions"
-require_relative "sqlite3/schema_dumper"
-require_relative "sqlite3/schema_statements"
+require "active_record/connection_adapters/abstract_adapter"
+require "active_record/connection_adapters/statement_pool"
+require "active_record/connection_adapters/sqlite3/explain_pretty_printer"
+require "active_record/connection_adapters/sqlite3/quoting"
+require "active_record/connection_adapters/sqlite3/schema_creation"
+require "active_record/connection_adapters/sqlite3/schema_definitions"
+require "active_record/connection_adapters/sqlite3/schema_dumper"
+require "active_record/connection_adapters/sqlite3/schema_statements"
 
 gem "sqlite3", "~> 1.3.6"
 require "sqlite3"
@@ -60,7 +60,7 @@ module ActiveRecord
       include SQLite3::SchemaStatements
 
       NATIVE_DATABASE_TYPES = {
-        primary_key:  "INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL",
+        primary_key:  "integer PRIMARY KEY AUTOINCREMENT NOT NULL",
         string:       { name: "varchar" },
         text:         { name: "text" },
         integer:      { name: "integer" },
@@ -70,13 +70,14 @@ module ActiveRecord
         time:         { name: "time" },
         date:         { name: "date" },
         binary:       { name: "blob" },
-        boolean:      { name: "boolean" }
+        boolean:      { name: "boolean" },
+        json:         { name: "json" },
       }
 
       ##
       # :singleton-method:
       # Indicates whether boolean values are stored in sqlite3 databases as 1
-      # and 0 or 't' and 'f'. Leaving `ActiveRecord::ConnectionAdapters::SQLite3Adapter.represent_boolean_as_integer`
+      # and 0 or 't' and 'f'. Leaving <tt>ActiveRecord::ConnectionAdapters::SQLite3Adapter.represent_boolean_as_integer</tt>
       # set to false is deprecated. SQLite databases have used 't' and 'f' to
       # serialize boolean values and must have old data converted to 1 and 0
       # (its native boolean serialization) before setting this flag to true.
@@ -85,25 +86,28 @@ module ActiveRecord
       #   ExampleModel.where("boolean_column = 't'").update_all(boolean_column: 1)
       #   ExampleModel.where("boolean_column = 'f'").update_all(boolean_column: 0)
       # for all models and all boolean columns, after which the flag must be set
-      # to true by adding the following to your application.rb file:
+      # to true by adding the following to your <tt>application.rb</tt> file:
       #
       #   Rails.application.config.active_record.sqlite3.represent_boolean_as_integer = true
       class_attribute :represent_boolean_as_integer, default: false
 
-      class StatementPool < ConnectionAdapters::StatementPool
+      class StatementPool < ConnectionAdapters::StatementPool # :nodoc:
         private
-
           def dealloc(stmt)
-            stmt[:stmt].close unless stmt[:stmt].closed?
+            stmt.close unless stmt.closed?
           end
       end
 
       def initialize(connection, logger, connection_options, config)
         super(connection, logger, config)
 
-        @active     = nil
+        @active     = true
         @statements = StatementPool.new(self.class.type_cast_config_to_integer(config[:statement_limit]))
 
+        if sqlite_version < "3.8.0"
+          raise "Your version of SQLite (#{sqlite_version}) is too old. Active Record supports SQLite >= 3.8."
+        end
+
         configure_connection
       end
 
@@ -116,7 +120,7 @@ module ActiveRecord
       end
 
       def supports_partial_index?
-        sqlite_version >= "3.8.0"
+        true
       end
 
       def requires_reloading?
@@ -124,7 +128,7 @@ module ActiveRecord
       end
 
       def supports_foreign_keys_in_create?
-        sqlite_version >= "3.6.19"
+        true
       end
 
       def supports_views?
@@ -135,12 +139,12 @@ module ActiveRecord
         true
       end
 
-      def supports_multi_insert?
-        sqlite_version >= "3.7.11"
+      def supports_json?
+        true
       end
 
       def active?
-        @active != false
+        @active
       end
 
       # Disconnects from the database if already connected. Otherwise, this
@@ -183,13 +187,16 @@ module ActiveRecord
       # REFERENTIAL INTEGRITY ====================================
 
       def disable_referential_integrity # :nodoc:
-        old = query_value("PRAGMA foreign_keys")
+        old_foreign_keys = query_value("PRAGMA foreign_keys")
+        old_defer_foreign_keys = query_value("PRAGMA defer_foreign_keys")
 
         begin
+          execute("PRAGMA defer_foreign_keys = ON")
           execute("PRAGMA foreign_keys = OFF")
           yield
         ensure
-          execute("PRAGMA foreign_keys = #{old}")
+          execute("PRAGMA defer_foreign_keys = #{old_defer_foreign_keys}")
+          execute("PRAGMA foreign_keys = #{old_foreign_keys}")
         end
       end
 
@@ -220,11 +227,8 @@ module ActiveRecord
                 stmt.close
               end
             else
-              cache = @statements[sql] ||= {
-                stmt: @connection.prepare(sql)
-              }
-              stmt = cache[:stmt]
-              cols = cache[:cols] ||= stmt.columns
+              stmt = @statements[sql] ||= @connection.prepare(sql)
+              cols = stmt.columns
               stmt.reset!
               stmt.bind_params(type_casted_binds)
               records = stmt.to_a
@@ -286,19 +290,18 @@ module ActiveRecord
         rename_table_indexes(table_name, new_name)
       end
 
-      # See: https://www.sqlite.org/lang_altertable.html
-      # SQLite has an additional restriction on the ALTER TABLE statement
-      def valid_alter_table_type?(type)
-        type.to_sym != :primary_key
+      def valid_alter_table_type?(type, options = {})
+        !invalid_alter_table_type?(type, options)
       end
+      deprecate :valid_alter_table_type?
 
       def add_column(table_name, column_name, type, options = {}) #:nodoc:
-        if valid_alter_table_type?(type)
-          super(table_name, column_name, type, options)
-        else
+        if invalid_alter_table_type?(type, options)
           alter_table(table_name) do |definition|
             definition.column(column_name, type, options)
           end
+        else
+          super
         end
       end
 
@@ -364,12 +367,30 @@ module ActiveRecord
       end
 
       def insert_fixtures(rows, table_name)
-        rows.each do |row|
-          insert_fixture(row, table_name)
+        ActiveSupport::Deprecation.warn(<<-MSG.squish)
+          `insert_fixtures` is deprecated and will be removed in the next version of Rails.
+          Consider using `insert_fixtures_set` for performance improvement.
+        MSG
+        insert_fixtures_set(table_name => rows)
+      end
+
+      def insert_fixtures_set(fixture_set, tables_to_delete = [])
+        disable_referential_integrity do
+          transaction(requires_new: true) do
+            tables_to_delete.each { |table| delete "DELETE FROM #{quote_table_name(table)}", "Fixture Delete" }
+
+            fixture_set.each do |table_name, rows|
+              rows.each { |row| insert_fixture(row, table_name) }
+            end
+          end
         end
       end
 
       private
+        def initialize_type_map(m = type_map)
+          super
+          register_class_with_limit m, %r(int)i, SQLite3Integer
+        end
 
         def table_structure(table_name)
           structure = exec_query("PRAGMA table_info(#{quote_table_name(table_name)})", "SCHEMA")
@@ -378,14 +399,22 @@ module ActiveRecord
         end
         alias column_definitions table_structure
 
+        # See: https://www.sqlite.org/lang_altertable.html
+        # SQLite has an additional restriction on the ALTER TABLE statement
+        def invalid_alter_table_type?(type, options)
+          type.to_sym == :primary_key || options[:primary_key]
+        end
+
         def alter_table(table_name, options = {})
           altered_table_name = "a#{table_name}"
           caller = lambda { |definition| yield definition if block_given? }
 
           transaction do
-            move_table(table_name, altered_table_name,
-              options.merge(temporary: true))
-            move_table(altered_table_name, table_name, &caller)
+            disable_referential_integrity do
+              move_table(table_name, altered_table_name,
+                options.merge(temporary: true))
+              move_table(altered_table_name, table_name, &caller)
+            end
           end
         end
 
@@ -399,18 +428,21 @@ module ActiveRecord
           options[:id] = false
           create_table(to, options) do |definition|
             @definition = definition
-            @definition.primary_key(from_primary_key) if from_primary_key.present?
+            if from_primary_key.is_a?(Array)
+              @definition.primary_keys from_primary_key
+            end
             columns(from).each do |column|
               column_name = options[:rename] ?
                 (options[:rename][column.name] ||
                  options[:rename][column.name.to_sym] ||
                  column.name) : column.name
-              next if column_name == from_primary_key
 
               @definition.column(column_name, column.type,
                 limit: column.limit, default: column.default,
                 precision: column.precision, scale: column.scale,
-                null: column.null, collation: column.collation)
+                null: column.null, collation: column.collation,
+                primary_key: column_name == from_primary_key
+              )
             end
             yield @definition if block_given?
           end
@@ -423,6 +455,9 @@ module ActiveRecord
         def copy_table_indexes(from, to, rename = {})
           indexes(from).each do |index|
             name = index.name
+            # indexes sqlite creates for internal use start with `sqlite_` and
+            # don't need to be copied
+            next if name.starts_with?("sqlite_")
             if to == "a#{from}"
               name = "t#{name}"
             elsif from == "a#{to}"
@@ -438,6 +473,7 @@ module ActiveRecord
               # index name can't be the same
               opts = { name: name.gsub(/(^|_)(#{from})_/, "\\1#{to}_"), internal: true }
               opts[:unique] = true if index.unique
+              opts[:where] = index.where if index.where
               add_index(to, columns, opts)
             end
           end
@@ -525,6 +561,17 @@ module ActiveRecord
         def configure_connection
           execute("PRAGMA foreign_keys = ON", "SCHEMA")
         end
+
+        class SQLite3Integer < Type::Integer # :nodoc:
+          private
+            def _limit
+              # INTEGER storage class can be stored 8 bytes value.
+              # See https://www.sqlite.org/datatype3.html#storage_classes_and_datatypes
+              limit || 8
+            end
+        end
+
+        ActiveRecord::Type.register(:integer, SQLite3Integer, adapter: :sqlite3)
     end
     ActiveSupport.run_load_hooks(:active_record_sqlite3adapter, SQLite3Adapter)
   end
diff --git a/activerecord/lib/active_record/connection_handling.rb b/activerecord/lib/active_record/connection_handling.rb
index 9a47edfba4..ee0e651912 100644
--- a/activerecord/lib/active_record/connection_handling.rb
+++ b/activerecord/lib/active_record/connection_handling.rb
@@ -57,6 +57,10 @@ module ActiveRecord
       spec = resolver.resolve(config).symbolize_keys
       spec[:name] = spec_name
 
+      # use the primary config if a config is not passed in and
+      # it's a three tier config
+      spec = spec[spec_name.to_sym] if spec[spec_name.to_sym]
+
       connection_handler.establish_connection(spec)
     end
 
@@ -140,6 +144,6 @@ module ActiveRecord
     end
 
     delegate :clear_active_connections!, :clear_reloadable_connections!,
-      :clear_all_connections!, to: :connection_handler
+      :clear_all_connections!, :flush_idle_connections!, to: :connection_handler
   end
 end
diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index 945c4eca78..e1a0b2ecf8 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -18,6 +18,13 @@ module ActiveRecord
       mattr_accessor :logger, instance_writer: false
 
       ##
+      # :singleton-method:
+      #
+      # Specifies if the methods calling database queries should be logged below
+      # their relevant queries. Defaults to false.
+      mattr_accessor :verbose_query_logs, instance_writer: false, default: false
+
+      ##
       # Contains the database configuration - as is typically stored in config/database.yml -
       # as a Hash.
       #
@@ -76,25 +83,13 @@ module ActiveRecord
       # scope being ignored is error-worthy, rather than a warning.
       mattr_accessor :error_on_ignored_order, instance_writer: false, default: false
 
-      def self.error_on_ignored_order_or_limit
-        ActiveSupport::Deprecation.warn(<<-MSG.squish)
-          The flag error_on_ignored_order_or_limit is deprecated. Limits are
-          now supported. Please use error_on_ignored_order instead.
-        MSG
-        error_on_ignored_order
-      end
-
-      def error_on_ignored_order_or_limit
-        self.class.error_on_ignored_order_or_limit
-      end
-
-      def self.error_on_ignored_order_or_limit=(value)
-        ActiveSupport::Deprecation.warn(<<-MSG.squish)
-          The flag error_on_ignored_order_or_limit is deprecated. Limits are
-          now supported. Please use error_on_ignored_order= instead.
-        MSG
-        self.error_on_ignored_order = value
-      end
+      # :singleton-method:
+      # Specify the behavior for unsafe raw query methods. Values are as follows
+      #   deprecated - Warnings are logged when unsafe raw SQL is passed to
+      #                query methods.
+      #   disabled   - Unsafe raw SQL passed to query methods results in
+      #                UnknownAttributeReference exception.
+      mattr_accessor :allow_unsafe_raw_sql, instance_writer: false, default: :deprecated
 
       ##
       # :singleton-method:
@@ -286,10 +281,11 @@ module ActiveRecord
         end
 
         def relation
-          relation = Relation.create(self, arel_table, predicate_builder)
+          relation = Relation.create(self)
 
           if finder_needs_type_condition? && !ignore_default_scope?
-            relation.where(type_condition).create_with(inheritance_column.to_s => sti_name)
+            relation.where!(type_condition)
+            relation.create_with!(inheritance_column.to_s => sti_name)
           else
             relation
           end
@@ -386,8 +382,10 @@ module ActiveRecord
 
       _run_initialize_callbacks
 
-      @new_record  = true
-      @destroyed   = false
+      @new_record               = true
+      @destroyed                = false
+      @_start_transaction_state = {}
+      @transaction_state        = nil
 
       super
     end
diff --git a/activerecord/lib/active_record/counter_cache.rb b/activerecord/lib/active_record/counter_cache.rb
index 5005d58f1c..ee4f818cbf 100644
--- a/activerecord/lib/active_record/counter_cache.rb
+++ b/activerecord/lib/active_record/counter_cache.rb
@@ -53,7 +53,7 @@ module ActiveRecord
           unscoped.where(primary_key => object.id).update_all(updates)
         end
 
-        return true
+        true
       end
 
       # A generic "counter updater" implementation, intended primarily to be
diff --git a/activerecord/lib/active_record/database_configurations.rb b/activerecord/lib/active_record/database_configurations.rb
new file mode 100644
index 0000000000..ffeed45030
--- /dev/null
+++ b/activerecord/lib/active_record/database_configurations.rb
@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+module ActiveRecord
+  module DatabaseConfigurations # :nodoc:
+    class DatabaseConfig
+      attr_reader :env_name, :spec_name, :config
+
+      def initialize(env_name, spec_name, config)
+        @env_name = env_name
+        @spec_name = spec_name
+        @config = config
+      end
+    end
+
+    # Selects the config for the specified environment and specification name
+    #
+    # For example if passed :development, and :animals it will select the database
+    # under the :development and :animals configuration level
+    def self.config_for_env_and_spec(environment, specification_name, configs = ActiveRecord::Base.configurations) # :nodoc:
+      configs_for(environment, configs).find do |db_config|
+        db_config.spec_name == specification_name
+      end
+    end
+
+    # Collects the configs for the environment passed in.
+    #
+    # If a block is given returns the specification name and configuration
+    # otherwise returns an array of DatabaseConfig structs for the environment.
+    def self.configs_for(env, configs = ActiveRecord::Base.configurations, &blk) # :nodoc:
+      env_with_configs = db_configs(configs).select do |db_config|
+        db_config.env_name == env
+      end
+
+      if block_given?
+        env_with_configs.each do |env_with_config|
+          yield env_with_config.spec_name, env_with_config.config
+        end
+      else
+        env_with_configs
+      end
+    end
+
+    # Given an env, spec and config creates DatabaseConfig structs with
+    # each attribute set.
+    def self.walk_configs(env_name, spec_name, config) # :nodoc:
+      if config["database"] || config["url"] || config["adapter"]
+        DatabaseConfig.new(env_name, spec_name, config)
+      else
+        config.each_pair.map do |sub_spec_name, sub_config|
+          walk_configs(env_name, sub_spec_name, sub_config)
+        end
+      end
+    end
+
+    # Walks all the configs passed in and returns an array
+    # of DatabaseConfig structs for each configuration.
+    def self.db_configs(configs = ActiveRecord::Base.configurations) # :nodoc:
+      configs.each_pair.flat_map do |env_name, config|
+        walk_configs(env_name, "primary", config)
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/define_callbacks.rb b/activerecord/lib/active_record/define_callbacks.rb
index 2c8783dcc9..87ecd7cec5 100644
--- a/activerecord/lib/active_record/define_callbacks.rb
+++ b/activerecord/lib/active_record/define_callbacks.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
 module ActiveRecord
-  # This module exists because `ActiveRecord::AttributeMethods::Dirty` needs to
-  # define callbacks, but continue to have its version of `save` be the super
-  # method of `ActiveRecord::Callbacks`. This will be removed when the removal
+  # This module exists because ActiveRecord::AttributeMethods::Dirty needs to
+  # define callbacks, but continue to have its version of +save+ be the super
+  # method of ActiveRecord::Callbacks. This will be removed when the removal
   # of deprecated code removes this need.
   module DefineCallbacks
     extend ActiveSupport::Concern
diff --git a/activerecord/lib/active_record/enum.rb b/activerecord/lib/active_record/enum.rb
index f373b98035..23ecb24542 100644
--- a/activerecord/lib/active_record/enum.rb
+++ b/activerecord/lib/active_record/enum.rb
@@ -141,10 +141,7 @@ module ActiveRecord
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
+      private
         attr_reader :name, :mapping, :subtype
     end
 
@@ -221,6 +218,8 @@ module ActiveRecord
       def detect_enum_conflict!(enum_name, method_name, klass_method = false)
         if klass_method && dangerous_class_method?(method_name)
           raise_conflict_error(enum_name, method_name, type: "class")
+        elsif klass_method && method_defined_within?(method_name, Relation)
+          raise_conflict_error(enum_name, method_name, type: "class", source: Relation.name)
         elsif !klass_method && dangerous_attribute_method?(method_name)
           raise_conflict_error(enum_name, method_name)
         elsif !klass_method && method_defined_within?(method_name, _enum_methods_module, Module)
diff --git a/activerecord/lib/active_record/errors.rb b/activerecord/lib/active_record/errors.rb
index 9ef3316393..c2a180c939 100644
--- a/activerecord/lib/active_record/errors.rb
+++ b/activerecord/lib/active_record/errors.rb
@@ -120,13 +120,13 @@ module ActiveRecord
     def initialize(adapter = nil, message: nil, table: nil, foreign_key: nil, target_table: nil, primary_key: nil)
       @adapter = adapter
       if table
-        msg = <<-EOM.strip_heredoc
+        msg = +<<~EOM
           Column `#{foreign_key}` on table `#{table}` has a type of `#{column_type(table, foreign_key)}`.
           This does not match column `#{primary_key}` on `#{target_table}`, which has type `#{column_type(target_table, primary_key)}`.
           To resolve this issue, change the type of the `#{foreign_key}` column on `#{table}` to be :integer. (For example `t.integer #{foreign_key}`).
         EOM
       else
-        msg = <<-EOM
+        msg = +<<~EOM
           There is a mismatch between the foreign key and primary key column types.
           Verify that the foreign key column type and the primary key of the associated table match types.
         EOM
@@ -335,8 +335,40 @@ module ActiveRecord
   class IrreversibleOrderError < ActiveRecordError
   end
 
-  # TransactionTimeout will be raised when lock wait timeout expires.
-  # Wait time value is set by innodb_lock_wait_timeout.
-  class TransactionTimeout < StatementInvalid
+  # LockWaitTimeout will be raised when lock wait timeout exceeded.
+  class LockWaitTimeout < StatementInvalid
+  end
+
+  # StatementTimeout will be raised when statement timeout exceeded.
+  class StatementTimeout < StatementInvalid
+  end
+
+  # QueryCanceled will be raised when canceling statement due to user request.
+  class QueryCanceled < StatementInvalid
+  end
+
+  # UnknownAttributeReference is raised when an unknown and potentially unsafe
+  # value is passed to a query method when allow_unsafe_raw_sql is set to
+  # :disabled. For example, passing a non column name value to a relation's
+  # #order method might cause this exception.
+  #
+  # When working around this exception, caution should be taken to avoid SQL
+  # injection vulnerabilities when passing user-provided values to query
+  # methods. Known-safe values can be passed to query methods by wrapping them
+  # in Arel.sql.
+  #
+  # For example, with allow_unsafe_raw_sql set to :disabled, the following
+  # code would raise this exception:
+  #
+  #   Post.order("length(title)").first
+  #
+  # The desired result can be accomplished by wrapping the known-safe string
+  # in Arel.sql:
+  #
+  #   Post.order(Arel.sql("length(title)")).first
+  #
+  # Again, such a workaround should *not* be used when passing user-provided
+  # values, such as request parameters or model attributes to query methods.
+  class UnknownAttributeReference < ActiveRecordError
   end
 end
diff --git a/activerecord/lib/active_record/explain.rb b/activerecord/lib/active_record/explain.rb
index 8bb54a24b7..7ccb938888 100644
--- a/activerecord/lib/active_record/explain.rb
+++ b/activerecord/lib/active_record/explain.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "explain_registry"
+require "active_record/explain_registry"
 
 module ActiveRecord
   module Explain
diff --git a/activerecord/lib/active_record/explain_subscriber.rb b/activerecord/lib/active_record/explain_subscriber.rb
index 9252fa3fed..a86217abc0 100644
--- a/activerecord/lib/active_record/explain_subscriber.rb
+++ b/activerecord/lib/active_record/explain_subscriber.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/notifications"
-require_relative "explain_registry"
+require "active_record/explain_registry"
 
 module ActiveRecord
   class ExplainSubscriber # :nodoc:
diff --git a/activerecord/lib/active_record/fixtures.rb b/activerecord/lib/active_record/fixtures.rb
index 4940e122f4..8f022ff7a7 100644
--- a/activerecord/lib/active_record/fixtures.rb
+++ b/activerecord/lib/active_record/fixtures.rb
@@ -6,8 +6,8 @@ require "zlib"
 require "set"
 require "active_support/dependencies"
 require "active_support/core_ext/digest/uuid"
-require_relative "fixture_set/file"
-require_relative "errors"
+require "active_record/fixture_set/file"
+require "active_record/errors"
 
 module ActiveRecord
   class FixtureClassNotFound < ActiveRecord::ActiveRecordError #:nodoc:
@@ -147,7 +147,7 @@ module ActiveRecord
   # unwanted inter-test dependencies. Methods used by multiple fixtures should be defined in a module
   # that is included in ActiveRecord::FixtureSet.context_class.
   #
-  # - define a helper method in `test_helper.rb`
+  # - define a helper method in <tt>test_helper.rb</tt>
   #     module FixtureFileHelpers
   #       def file_sha(path)
   #         Digest::SHA2.hexdigest(File.read(Rails.root.join('test/fixtures', path)))
@@ -169,13 +169,13 @@ module ActiveRecord
   #     self.use_transactional_tests = true
   #
   #     test "godzilla" do
-  #       assert !Foo.all.empty?
+  #       assert_not_empty Foo.all
   #       Foo.destroy_all
-  #       assert Foo.all.empty?
+  #       assert_empty Foo.all
   #     end
   #
   #     test "godzilla aftermath" do
-  #       assert !Foo.all.empty?
+  #       assert_not_empty Foo.all
   #     end
   #   end
   #
@@ -540,47 +540,38 @@ module ActiveRecord
       }
 
       unless files_to_read.empty?
-        connection.disable_referential_integrity do
-          fixtures_map = {}
-
-          fixture_sets = files_to_read.map do |fs_name|
-            klass = class_names[fs_name]
-            conn = klass ? klass.connection : connection
-            fixtures_map[fs_name] = new( # ActiveRecord::FixtureSet.new
-              conn,
-              fs_name,
-              klass,
-              ::File.join(fixtures_directory, fs_name))
-          end
-
-          update_all_loaded_fixtures fixtures_map
-
-          connection.transaction(requires_new: true) do
-            deleted_tables = Hash.new { |h, k| h[k] = Set.new }
-            fixture_sets.each do |fs|
-              conn = fs.model_class.respond_to?(:connection) ? fs.model_class.connection : connection
-              table_rows = fs.table_rows
+        fixtures_map = {}
+
+        fixture_sets = files_to_read.map do |fs_name|
+          klass = class_names[fs_name]
+          conn = klass ? klass.connection : connection
+          fixtures_map[fs_name] = new( # ActiveRecord::FixtureSet.new
+            conn,
+            fs_name,
+            klass,
+            ::File.join(fixtures_directory, fs_name))
+        end
 
-              table_rows.each_key do |table|
-                unless deleted_tables[conn].include? table
-                  conn.delete "DELETE FROM #{conn.quote_table_name(table)}", "Fixture Delete"
-                end
-                deleted_tables[conn] << table
-              end
+        update_all_loaded_fixtures fixtures_map
+        fixture_sets_by_connection = fixture_sets.group_by { |fs| fs.model_class ? fs.model_class.connection : connection }
 
-              table_rows.each do |fixture_set_name, rows|
-                conn.insert_fixtures(rows, fixture_set_name)
-              end
+        fixture_sets_by_connection.each do |conn, set|
+          table_rows_for_connection = Hash.new { |h, k| h[k] = [] }
 
-              # Cap primary key sequences to max(pk).
-              if conn.respond_to?(:reset_pk_sequence!)
-                conn.reset_pk_sequence!(fs.table_name)
-              end
+          set.each do |fs|
+            fs.table_rows.each do |table, rows|
+              table_rows_for_connection[table].unshift(*rows)
             end
           end
+          conn.insert_fixtures_set(table_rows_for_connection, table_rows_for_connection.keys)
 
-          cache_fixtures(connection, fixtures_map)
+          # Cap primary key sequences to max(pk).
+          if conn.respond_to?(:reset_pk_sequence!)
+            set.each { |fs| conn.reset_pk_sequence!(fs.table_name) }
+          end
         end
+
+        cache_fixtures(connection, fixtures_map)
       end
       cached_fixtures(connection, fixture_set_names)
     end
@@ -883,6 +874,7 @@ module ActiveRecord
       class_attribute :use_instantiated_fixtures, default: false # true, false, or :no_instances
       class_attribute :pre_loaded_fixtures, default: false
       class_attribute :config, default: ActiveRecord::Base
+      class_attribute :lock_threads, default: true
     end
 
     module ClassMethods
@@ -982,7 +974,7 @@ module ActiveRecord
         @fixture_connections = enlist_fixture_connections
         @fixture_connections.each do |connection|
           connection.begin_transaction joinable: false
-          connection.pool.lock_thread = true
+          connection.pool.lock_thread = true if lock_threads
         end
 
         # When connections are established in the future, begin a transaction too
@@ -998,7 +990,7 @@ module ActiveRecord
 
             if connection && !@fixture_connections.include?(connection)
               connection.begin_transaction joinable: false
-              connection.pool.lock_thread = true
+              connection.pool.lock_thread = true if lock_threads
               @fixture_connections << connection
             end
           end
diff --git a/activerecord/lib/active_record/gem_version.rb b/activerecord/lib/active_record/gem_version.rb
index 7ccb57b305..72035a986b 100644
--- a/activerecord/lib/active_record/gem_version.rb
+++ b/activerecord/lib/active_record/gem_version.rb
@@ -7,8 +7,8 @@ module ActiveRecord
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
     PRE   = "alpha"
 
diff --git a/activerecord/lib/active_record/inheritance.rb b/activerecord/lib/active_record/inheritance.rb
index 0715c11473..6891c575c7 100644
--- a/activerecord/lib/active_record/inheritance.rb
+++ b/activerecord/lib/active_record/inheritance.rb
@@ -47,22 +47,21 @@ module ActiveRecord
       # Determines if one of the attributes passed in is the inheritance column,
       # and if the inheritance column is attr accessible, it initializes an
       # instance of the given subclass instead of the base class.
-      def new(*args, &block)
+      def new(attributes = nil, &block)
         if abstract_class? || self == Base
           raise NotImplementedError, "#{self} is an abstract class and cannot be instantiated."
         end
 
-        attrs = args.first
         if has_attribute?(inheritance_column)
-          subclass = subclass_from_attributes(attrs)
+          subclass = subclass_from_attributes(attributes)
 
-          if subclass.nil? && base_class == self
+          if subclass.nil? && base_class?
             subclass = subclass_from_attributes(column_defaults)
           end
         end
 
         if subclass && subclass != self
-          subclass.new(*args, &block)
+          subclass.new(attributes, &block)
         else
           super
         end
@@ -105,21 +104,53 @@ module ActiveRecord
         end
       end
 
-      # Set this to true if this is an abstract class (see <tt>abstract_class?</tt>).
-      # If you are using inheritance with ActiveRecord and don't want child classes
-      # to utilize the implied STI table name of the parent class, this will need to be true.
-      # For example, given the following:
+      # Returns whether the class is a base class.
+      # See #base_class for more information.
+      def base_class?
+        base_class == self
+      end
+
+      # Set this to +true+ if this is an abstract class (see
+      # <tt>abstract_class?</tt>).
+      # If you are using inheritance with Active Record and don't want a class
+      # to be considered as part of the STI hierarchy, you must set this to
+      # true.
+      # +ApplicationRecord+, for example, is generated as an abstract class.
+      #
+      # Consider the following default behaviour:
+      #
+      #   Shape = Class.new(ActiveRecord::Base)
+      #   Polygon = Class.new(Shape)
+      #   Square = Class.new(Polygon)
+      #
+      #   Shape.table_name   # => "shapes"
+      #   Polygon.table_name # => "shapes"
+      #   Square.table_name  # => "shapes"
+      #   Shape.create!      # => #<Shape id: 1, type: nil>
+      #   Polygon.create!    # => #<Polygon id: 2, type: "Polygon">
+      #   Square.create!     # => #<Square id: 3, type: "Square">
       #
-      #   class SuperClass < ActiveRecord::Base
+      # However, when using <tt>abstract_class</tt>, +Shape+ is omitted from
+      # the hierarchy:
+      #
+      #   class Shape < ActiveRecord::Base
       #     self.abstract_class = true
       #   end
-      #   class Child < SuperClass
-      #     self.table_name = 'the_table_i_really_want'
-      #   end
-      #
+      #   Polygon = Class.new(Shape)
+      #   Square = Class.new(Polygon)
       #
-      # <tt>self.abstract_class = true</tt> is required to make <tt>Child<.find,.create, or any Arel method></tt> use <tt>the_table_i_really_want</tt> instead of a table called <tt>super_classes</tt>
+      #   Shape.table_name   # => nil
+      #   Polygon.table_name # => "polygons"
+      #   Square.table_name  # => "polygons"
+      #   Shape.create!      # => NotImplementedError: Shape is an abstract class and cannot be instantiated.
+      #   Polygon.create!    # => #<Polygon id: 1, type: nil>
+      #   Square.create!     # => #<Square id: 2, type: "Square">
       #
+      # Note that in the above example, to disallow the creation of a plain
+      # +Polygon+, you should use <tt>validates :type, presence: true</tt>,
+      # instead of setting it as an abstract class. This way, +Polygon+ will
+      # stay in the hierarchy, and Active Record will continue to correctly
+      # derive the table name.
       attr_accessor :abstract_class
 
       # Returns whether this class is an abstract class or not.
@@ -131,6 +162,10 @@ module ActiveRecord
         store_full_sti_class ? name : name.demodulize
       end
 
+      def polymorphic_name
+        base_class.name
+      end
+
       def inherited(subclass)
         subclass.instance_variable_set(:@_type_candidates_cache, Concurrent::Map.new)
         super
diff --git a/activerecord/lib/active_record/internal_metadata.rb b/activerecord/lib/active_record/internal_metadata.rb
index 14795cc815..3626a13d7c 100644
--- a/activerecord/lib/active_record/internal_metadata.rb
+++ b/activerecord/lib/active_record/internal_metadata.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "scoping/default"
-require_relative "scoping/named"
+require "active_record/scoping/default"
+require "active_record/scoping/named"
 
 module ActiveRecord
   # This class is used to create a table that keeps track of values and keys such
@@ -17,7 +17,7 @@ module ActiveRecord
       end
 
       def []=(key, value)
-        find_or_initialize_by(key: key).update_attributes!(value: value)
+        find_or_initialize_by(key: key).update!(value: value)
       end
 
       def [](key)
diff --git a/activerecord/lib/active_record/legacy_yaml_adapter.rb b/activerecord/lib/active_record/legacy_yaml_adapter.rb
index 23644aab8f..ffa095dd94 100644
--- a/activerecord/lib/active_record/legacy_yaml_adapter.rb
+++ b/activerecord/lib/active_record/legacy_yaml_adapter.rb
@@ -8,7 +8,7 @@ module ActiveRecord
       case coder["active_record_yaml_version"]
       when 1, 2 then coder
       else
-        if coder["attributes"].is_a?(AttributeSet)
+        if coder["attributes"].is_a?(ActiveModel::AttributeSet)
           Rails420.convert(klass, coder)
         else
           Rails41.convert(klass, coder)
diff --git a/activerecord/lib/active_record/locking/optimistic.rb b/activerecord/lib/active_record/locking/optimistic.rb
index e1e24e2814..7f096bb532 100644
--- a/activerecord/lib/active_record/locking/optimistic.rb
+++ b/activerecord/lib/active_record/locking/optimistic.rb
@@ -61,13 +61,6 @@ module ActiveRecord
       end
 
       private
-
-        def increment_lock
-          lock_col = self.class.locking_column
-          previous_lock_value = send(lock_col)
-          send("#{lock_col}=", previous_lock_value + 1)
-        end
-
         def _create_record(attribute_names = self.attribute_names, *)
           if locking_enabled?
             # We always want to persist the locking version, even if we don't detect
@@ -77,63 +70,56 @@ module ActiveRecord
           super
         end
 
-        def _update_record(attribute_names = self.attribute_names)
+        def _touch_row(attribute_names, time)
+          super
+        ensure
+          clear_attribute_change(self.class.locking_column) if locking_enabled?
+        end
+
+        def _update_row(attribute_names, attempted_action = "update")
           return super unless locking_enabled?
-          return 0 if attribute_names.empty?
 
           begin
-            lock_col = self.class.locking_column
-
-            previous_lock_value = read_attribute_before_type_cast(lock_col)
-
-            increment_lock
-
-            attribute_names.push(lock_col)
+            locking_column = self.class.locking_column
+            previous_lock_value = read_attribute_before_type_cast(locking_column)
+            attribute_names << locking_column
 
-            relation = self.class.unscoped
+            self[locking_column] += 1
 
-            affected_rows = relation.where(
-              self.class.primary_key => id,
-              lock_col => previous_lock_value
-            ).update_all(
-              attributes_for_update(attribute_names).map do |name|
-                [name, _read_attribute(name)]
-              end.to_h
+            affected_rows = self.class._update_record(
+              attributes_with_values(attribute_names),
+              self.class.primary_key => id_in_database,
+              locking_column => previous_lock_value
             )
 
-            unless affected_rows == 1
-              raise ActiveRecord::StaleObjectError.new(self, "update")
+            if affected_rows != 1
+              raise ActiveRecord::StaleObjectError.new(self, attempted_action)
             end
 
             affected_rows
 
           # If something went wrong, revert the locking_column value.
           rescue Exception
-            send("#{lock_col}=", previous_lock_value.to_i)
-
+            self[locking_column] = previous_lock_value.to_i
             raise
           end
         end
 
         def destroy_row
-          affected_rows = super
-
-          if locking_enabled? && affected_rows != 1
-            raise ActiveRecord::StaleObjectError.new(self, "destroy")
-          end
+          return super unless locking_enabled?
 
-          affected_rows
-        end
+          locking_column = self.class.locking_column
 
-        def relation_for_destroy
-          relation = super
+          affected_rows = self.class._delete_record(
+            self.class.primary_key => id_in_database,
+            locking_column => read_attribute_before_type_cast(locking_column)
+          )
 
-          if locking_enabled?
-            locking_column = self.class.locking_column
-            relation = relation.where(locking_column => read_attribute_before_type_cast(locking_column))
+          if affected_rows != 1
+            raise ActiveRecord::StaleObjectError.new(self, "destroy")
           end
 
-          relation
+          affected_rows
         end
 
         module ClassMethods
diff --git a/activerecord/lib/active_record/locking/pessimistic.rb b/activerecord/lib/active_record/locking/pessimistic.rb
index 72bccd4906..5d1d15c94d 100644
--- a/activerecord/lib/active_record/locking/pessimistic.rb
+++ b/activerecord/lib/active_record/locking/pessimistic.rb
@@ -62,13 +62,14 @@ module ActiveRecord
       # the locked record.
       def lock!(lock = true)
         if persisted?
-          if changed?
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Locking a record with unpersisted changes is deprecated and will raise an
-              exception in Rails 5.2. Use `save` to persist the changes, or `reload` to
-              discard them explicitly.
+          if has_changes_to_save?
+            raise(<<-MSG.squish)
+              Locking a record with unpersisted changes is not supported. Use
+              `save` to persist the changes, or `reload` to discard them
+              explicitly.
             MSG
           end
+
           reload(lock: lock)
         end
         self
diff --git a/activerecord/lib/active_record/log_subscriber.rb b/activerecord/lib/active_record/log_subscriber.rb
index 405f3a30c6..cf884bc6da 100644
--- a/activerecord/lib/active_record/log_subscriber.rb
+++ b/activerecord/lib/active_record/log_subscriber.rb
@@ -90,6 +90,47 @@ module ActiveRecord
       def logger
         ActiveRecord::Base.logger
       end
+
+      def debug(progname = nil, &block)
+        return unless super
+
+        if ActiveRecord::Base.verbose_query_logs
+          log_query_source
+        end
+      end
+
+      def log_query_source
+        source_line, line_number = extract_callstack(caller_locations)
+
+        if source_line
+          if defined?(::Rails.root)
+            app_root = "#{::Rails.root}/"
+            source_line = source_line.sub(app_root, "")
+          end
+
+          logger.debug("  ↳ #{ source_line }:#{ line_number }")
+        end
+      end
+
+      def extract_callstack(callstack)
+        line = callstack.find do |frame|
+          frame.absolute_path && !ignored_callstack(frame.absolute_path)
+        end
+
+        offending_line = line || callstack.first
+
+        [
+          offending_line.path,
+          offending_line.lineno
+        ]
+      end
+
+      RAILS_GEM_ROOT = File.expand_path("../../..", __dir__) + "/"
+
+      def ignored_callstack(path)
+        path.start_with?(RAILS_GEM_ROOT) ||
+        path.start_with?(RbConfig::CONFIG["rubylibdir"])
+      end
   end
 end
 
diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index 52ca4671c2..025201c20b 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require "benchmark"
 require "set"
 require "zlib"
 require "active_support/core_ext/module/attribute_accessors"
@@ -140,6 +141,7 @@ module ActiveRecord
 
   class ConcurrentMigrationError < MigrationError #:nodoc:
     DEFAULT_MESSAGE = "Cannot run migrations because another migration process is currently running.".freeze
+    RELEASE_LOCK_FAILED_MESSAGE = "Failed to release advisory lock".freeze
 
     def initialize(message = DEFAULT_MESSAGE)
       super
@@ -354,9 +356,9 @@ module ActiveRecord
   # to match the structure of your database.
   #
   # To roll the database back to a previous migration version, use
-  # <tt>rails db:migrate VERSION=X</tt> where <tt>X</tt> is the version to which
+  # <tt>rails db:rollback VERSION=X</tt> where <tt>X</tt> is the version to which
   # you wish to downgrade. Alternatively, you can also use the STEP option if you
-  # wish to rollback last few migrations. <tt>rails db:migrate STEP=2</tt> will rollback
+  # wish to rollback last few migrations. <tt>rails db:rollback STEP=2</tt> will rollback
   # the latest two migrations.
   #
   # If any of the migrations throw an <tt>ActiveRecord::IrreversibleMigration</tt> exception,
@@ -550,7 +552,7 @@ module ActiveRecord
       end
 
       def call(env)
-        mtime = ActiveRecord::Migrator.last_migration.mtime.to_i
+        mtime = ActiveRecord::Base.connection.migration_context.last_migration.mtime.to_i
         if @last_check < mtime
           ActiveRecord::Migration.check_pending!(connection)
           @last_check = mtime
@@ -575,13 +577,14 @@ module ActiveRecord
 
       # Raises <tt>ActiveRecord::PendingMigrationError</tt> error if any migrations are pending.
       def check_pending!(connection = Base.connection)
-        raise ActiveRecord::PendingMigrationError if ActiveRecord::Migrator.needs_migration?(connection)
+        raise ActiveRecord::PendingMigrationError if connection.migration_context.needs_migration?
       end
 
       def load_schema_if_pending!
-        if ActiveRecord::Migrator.needs_migration? || !ActiveRecord::Migrator.any_migrations?
+        if Base.connection.migration_context.needs_migration? || !Base.connection.migration_context.any_migrations?
           # Roundtrip to Rake to allow plugins to hook into database initialization.
-          FileUtils.cd Rails.root do
+          root = defined?(ENGINE_ROOT) ? ENGINE_ROOT : Rails.root
+          FileUtils.cd(root) do
             current_config = Base.connection_config
             Base.clear_all_connections!
             system("bin/rails db:test:prepare")
@@ -733,6 +736,24 @@ module ActiveRecord
       execute_block { yield helper }
     end
 
+    # Used to specify an operation that is only run when migrating up
+    # (for example, populating a new column with its initial values).
+    #
+    # In the following example, the new column +published+ will be given
+    # the value +true+ for all existing records.
+    #
+    #    class AddPublishedToPosts < ActiveRecord::Migration[5.2]
+    #      def change
+    #        add_column :posts, :published, :boolean, default: false
+    #        up_only do
+    #          execute "update posts set published = 'true'"
+    #        end
+    #      end
+    #    end
+    def up_only
+      execute_block { yield } unless reverting?
+    end
+
     # Runs the given migration classes.
     # Last argument can specify options:
     # - :direction (default is :up)
@@ -857,10 +878,10 @@ module ActiveRecord
 
       FileUtils.mkdir_p(destination) unless File.exist?(destination)
 
-      destination_migrations = ActiveRecord::Migrator.migrations(destination)
+      destination_migrations = ActiveRecord::MigrationContext.new(destination).migrations
       last = destination_migrations.last
       sources.each do |scope, path|
-        source_migrations = ActiveRecord::Migrator.migrations(path)
+        source_migrations = ActiveRecord::MigrationContext.new(path).migrations
 
         source_migrations.each do |migration|
           source = File.binread(migration.filename)
@@ -978,136 +999,147 @@ module ActiveRecord
     end
   end
 
-  class Migrator#:nodoc:
-    class << self
-      attr_writer :migrations_paths
-      alias :migrations_path= :migrations_paths=
-
-      def migrate(migrations_paths, target_version = nil, &block)
-        case
-        when target_version.nil?
-          up(migrations_paths, target_version, &block)
-        when current_version == 0 && target_version == 0
-          []
-        when current_version > target_version
-          down(migrations_paths, target_version, &block)
-        else
-          up(migrations_paths, target_version, &block)
-        end
-      end
+  class MigrationContext # :nodoc:
+    attr_reader :migrations_paths
 
-      def rollback(migrations_paths, steps = 1)
-        move(:down, migrations_paths, steps)
-      end
+    def initialize(migrations_paths)
+      @migrations_paths = migrations_paths
+    end
 
-      def forward(migrations_paths, steps = 1)
-        move(:up, migrations_paths, steps)
+    def migrate(target_version = nil, &block)
+      case
+      when target_version.nil?
+        up(target_version, &block)
+      when current_version == 0 && target_version == 0
+        []
+      when current_version > target_version
+        down(target_version, &block)
+      else
+        up(target_version, &block)
       end
+    end
+
+    def rollback(steps = 1)
+      move(:down, steps)
+    end
 
-      def up(migrations_paths, target_version = nil)
-        migrations = migrations(migrations_paths)
-        migrations.select! { |m| yield m } if block_given?
+    def forward(steps = 1)
+      move(:up, steps)
+    end
 
-        new(:up, migrations, target_version).migrate
+    def up(target_version = nil)
+      selected_migrations = if block_given?
+        migrations.select { |m| yield m }
+      else
+        migrations
       end
 
-      def down(migrations_paths, target_version = nil)
-        migrations = migrations(migrations_paths)
-        migrations.select! { |m| yield m } if block_given?
+      Migrator.new(:up, selected_migrations, target_version).migrate
+    end
 
-        new(:down, migrations, target_version).migrate
+    def down(target_version = nil)
+      selected_migrations = if block_given?
+        migrations.select { |m| yield m }
+      else
+        migrations
       end
 
-      def run(direction, migrations_paths, target_version)
-        new(direction, migrations(migrations_paths), target_version).run
-      end
+      Migrator.new(:down, selected_migrations, target_version).migrate
+    end
 
-      def open(migrations_paths)
-        new(:up, migrations(migrations_paths), nil)
-      end
+    def run(direction, target_version)
+      Migrator.new(direction, migrations, target_version).run
+    end
 
-      def schema_migrations_table_name
-        SchemaMigration.table_name
-      end
-      deprecate :schema_migrations_table_name
+    def open
+      Migrator.new(:up, migrations, nil)
+    end
 
-      def get_all_versions(connection = Base.connection)
-        if SchemaMigration.table_exists?
-          SchemaMigration.all_versions.map(&:to_i)
-        else
-          []
-        end
+    def get_all_versions
+      if SchemaMigration.table_exists?
+        SchemaMigration.all_versions.map(&:to_i)
+      else
+        []
       end
+    end
 
-      def current_version(connection = Base.connection)
-        get_all_versions(connection).max || 0
-      end
+    def current_version
+      get_all_versions.max || 0
+    rescue ActiveRecord::NoDatabaseError
+    end
 
-      def needs_migration?(connection = Base.connection)
-        (migrations(migrations_paths).collect(&:version) - get_all_versions(connection)).size > 0
-      end
+    def needs_migration?
+      (migrations.collect(&:version) - get_all_versions).size > 0
+    end
 
-      def any_migrations?
-        migrations(migrations_paths).any?
-      end
+    def any_migrations?
+      migrations.any?
+    end
 
-      def last_migration #:nodoc:
-        migrations(migrations_paths).last || NullMigration.new
-      end
+    def last_migration #:nodoc:
+      migrations.last || NullMigration.new
+    end
 
-      def migrations_paths
-        @migrations_paths ||= ["db/migrate"]
-        # just to not break things if someone uses: migrations_path = some_string
-        Array(@migrations_paths)
-      end
+    def parse_migration_filename(filename) # :nodoc:
+      File.basename(filename).scan(Migration::MigrationFilenameRegexp).first
+    end
+
+    def migrations
+      migrations = migration_files.map do |file|
+        version, name, scope = parse_migration_filename(file)
+        raise IllegalMigrationNameError.new(file) unless version
+        version = version.to_i
+        name = name.camelize
 
-      def parse_migration_filename(filename) # :nodoc:
-        File.basename(filename).scan(Migration::MigrationFilenameRegexp).first
+        MigrationProxy.new(name, version, file, scope)
       end
 
-      def migrations(paths)
-        paths = Array(paths)
+      migrations.sort_by(&:version)
+    end
 
-        migrations = migration_files(paths).map do |file|
-          version, name, scope = parse_migration_filename(file)
-          raise IllegalMigrationNameError.new(file) unless version
-          version = version.to_i
-          name = name.camelize
+    def migrations_status
+      db_list = ActiveRecord::SchemaMigration.normalized_versions
 
-          MigrationProxy.new(name, version, file, scope)
-        end
+      file_list = migration_files.map do |file|
+        version, name, scope = parse_migration_filename(file)
+        raise IllegalMigrationNameError.new(file) unless version
+        version = ActiveRecord::SchemaMigration.normalize_migration_number(version)
+        status = db_list.delete(version) ? "up" : "down"
+        [status, version, (name + scope).humanize]
+      end.compact
 
-        migrations.sort_by(&:version)
+      db_list.map! do |version|
+        ["up", version, "********** NO FILE **********"]
       end
 
-      def migrations_status(paths)
-        paths = Array(paths)
-
-        db_list = ActiveRecord::SchemaMigration.normalized_versions
+      (db_list + file_list).sort_by { |_, version, _| version }
+    end
 
-        file_list = migration_files(paths).map do |file|
-          version, name, scope = parse_migration_filename(file)
-          raise IllegalMigrationNameError.new(file) unless version
-          version = ActiveRecord::SchemaMigration.normalize_migration_number(version)
-          status = db_list.delete(version) ? "up" : "down"
-          [status, version, (name + scope).humanize]
-        end.compact
+    def migration_files
+      paths = Array(migrations_paths)
+      Dir[*paths.flat_map { |path| "#{path}/**/[0-9]*_*.rb" }]
+    end
 
-        db_list.map! do |version|
-          ["up", version, "********** NO FILE **********"]
-        end
+    def current_environment
+      ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
+    end
 
-        (db_list + file_list).sort_by { |_, version, _| version }
-      end
+    def protected_environment?
+      ActiveRecord::Base.protected_environments.include?(last_stored_environment) if last_stored_environment
+    end
 
-      def migration_files(paths)
-        Dir[*paths.flat_map { |path| "#{path}/**/[0-9]*_*.rb" }]
-      end
+    def last_stored_environment
+      return nil if current_version == 0
+      raise NoEnvironmentInSchemaError unless ActiveRecord::InternalMetadata.table_exists?
 
-      private
+      environment = ActiveRecord::InternalMetadata[:environment]
+      raise NoEnvironmentInSchemaError unless environment
+      environment
+    end
 
-      def move(direction, migrations_paths, steps)
-        migrator = new(direction, migrations(migrations_paths))
+    private
+      def move(direction, steps)
+        migrator = Migrator.new(direction, migrations)
 
         if current_version != 0 && !migrator.current_migration
           raise UnknownMigrationVersionError.new(current_version)
@@ -1122,10 +1154,29 @@ module ActiveRecord
 
         finish = migrator.migrations[start_index + steps]
         version = finish ? finish.version : 0
-        send(direction, migrations_paths, version)
+        send(direction, version)
+      end
+  end
+
+  class Migrator # :nodoc:
+    class << self
+      attr_accessor :migrations_paths
+
+      def migrations_path=(path)
+        ActiveSupport::Deprecation.warn \
+          "ActiveRecord::Migrator.migrations_paths= is now deprecated and will be removed in Rails 6.0." \
+          "You can set the `migrations_paths` on the `connection` instead through the `database.yml`."
+        self.migrations_paths = [path]
+      end
+
+      # For cases where a table doesn't exist like loading from schema cache
+      def current_version
+        MigrationContext.new(migrations_paths).current_version
       end
     end
 
+    self.migrations_paths = ["db/migrate"]
+
     def initialize(direction, migrations, target_version = nil)
       @direction         = direction
       @target_version    = target_version
@@ -1188,7 +1239,7 @@ module ActiveRecord
     end
 
     def load_migrated
-      @migrated_versions = Set.new(self.class.get_all_versions)
+      @migrated_versions = Set.new(Base.connection.migration_context.get_all_versions)
     end
 
     private
@@ -1220,7 +1271,7 @@ module ActiveRecord
       # Stores the current environment in the database.
       def record_environment
         return if down?
-        ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Migrator.current_environment
+        ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Base.connection.migration_context.current_environment
       end
 
       def ran?(migration)
@@ -1229,7 +1280,7 @@ module ActiveRecord
 
       # Return true if a valid version is not provided.
       def invalid_target?
-        !target && @target_version && @target_version > 0
+        @target_version && @target_version != 0 && !target
       end
 
       def execute_migration_in_transaction(migration, direction)
@@ -1262,10 +1313,10 @@ module ActiveRecord
       end
 
       def validate(migrations)
-        name , = migrations.group_by(&:name).find { |_, v| v.length > 1 }
+        name, = migrations.group_by(&:name).find { |_, v| v.length > 1 }
         raise DuplicateMigrationNameError.new(name) if name
 
-        version , = migrations.group_by(&:version).find { |_, v| v.length > 1 }
+        version, = migrations.group_by(&:version).find { |_, v| v.length > 1 }
         raise DuplicateMigrationVersionError.new(version) if version
       end
 
@@ -1279,23 +1330,6 @@ module ActiveRecord
         end
       end
 
-      def self.last_stored_environment
-        return nil if current_version == 0
-        raise NoEnvironmentInSchemaError unless ActiveRecord::InternalMetadata.table_exists?
-
-        environment = ActiveRecord::InternalMetadata[:environment]
-        raise NoEnvironmentInSchemaError unless environment
-        environment
-      end
-
-      def self.current_environment
-        ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
-      end
-
-      def self.protected_environment?
-        ActiveRecord::Base.protected_environments.include?(last_stored_environment) if last_stored_environment
-      end
-
       def up?
         @direction == :up
       end
@@ -1323,12 +1357,17 @@ module ActiveRecord
 
       def with_advisory_lock
         lock_id = generate_migrator_advisory_lock_id
-        got_lock = Base.connection.get_advisory_lock(lock_id)
+        connection = Base.connection
+        got_lock = connection.get_advisory_lock(lock_id)
         raise ConcurrentMigrationError unless got_lock
         load_migrated # reload schema_migrations to be sure it wasn't changed by another process before we got the lock
         yield
       ensure
-        Base.connection.release_advisory_lock(lock_id) if got_lock
+        if got_lock && !connection.release_advisory_lock(lock_id)
+          raise ConcurrentMigrationError.new(
+            ConcurrentMigrationError::RELEASE_LOCK_FAILED_MESSAGE
+          )
+        end
       end
 
       MIGRATOR_SALT = 2053462845
diff --git a/activerecord/lib/active_record/migration/command_recorder.rb b/activerecord/lib/active_record/migration/command_recorder.rb
index a3a5e0fa16..087632b10f 100644
--- a/activerecord/lib/active_record/migration/command_recorder.rb
+++ b/activerecord/lib/active_record/migration/command_recorder.rb
@@ -85,7 +85,7 @@ module ActiveRecord
       # invert the +command+.
       def inverse_of(command, args, &block)
         method = :"invert_#{command}"
-        raise IrreversibleMigration, <<-MSG.strip_heredoc unless respond_to?(method, true)
+        raise IrreversibleMigration, <<~MSG unless respond_to?(method, true)
           This migration uses #{command}, which is not automatically reversible.
           To make the migration reversible you can either:
           1. Define #up and #down methods in place of the #change method.
@@ -110,7 +110,7 @@ module ActiveRecord
 
       private
 
-        module StraightReversions
+        module StraightReversions # :nodoc:
           private
             { transaction:       :transaction,
               execute_block:     :execute_block,
@@ -161,8 +161,8 @@ module ActiveRecord
           table, columns, options = *args
           options ||= {}
 
-          index_name = options[:name]
-          options_hash = index_name ? { name: index_name } : { column: columns }
+          options_hash = options.slice(:name, :algorithm)
+          options_hash[:column] = columns if !options_hash[:name]
 
           [:remove_index, [table, options_hash]]
         end
diff --git a/activerecord/lib/active_record/migration/compatibility.rb b/activerecord/lib/active_record/migration/compatibility.rb
index 784292f3f9..0edaaa0cf9 100644
--- a/activerecord/lib/active_record/migration/compatibility.rb
+++ b/activerecord/lib/active_record/migration/compatibility.rb
@@ -13,13 +13,41 @@ module ActiveRecord
         const_get(name)
       end
 
-      V5_2 = Current
+      V6_0 = Current
+
+      class V5_2 < V6_0
+      end
 
       class V5_1 < V5_2
+        def change_column(table_name, column_name, type, options = {})
+          if adapter_name == "PostgreSQL"
+            clear_cache!
+            sql = connection.send(:change_column_sql, table_name, column_name, type, options)
+            execute "ALTER TABLE #{quote_table_name(table_name)} #{sql}"
+            change_column_default(table_name, column_name, options[:default]) if options.key?(:default)
+            change_column_null(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
+            change_column_comment(table_name, column_name, options[:comment]) if options.key?(:comment)
+          else
+            super
+          end
+        end
+
+        def create_table(table_name, options = {})
+          if adapter_name == "Mysql2"
+            super(table_name, options: "ENGINE=InnoDB", **options)
+          else
+            super
+          end
+        end
       end
 
       class V5_0 < V5_1
         module TableDefinition
+          def primary_key(name, type = :primary_key, **options)
+            type = :integer if type == :primary_key
+            super
+          end
+
           def references(*args, **options)
             super(*args, type: :integer, **options)
           end
@@ -47,11 +75,8 @@ module ActiveRecord
           end
 
           if block_given?
-            super(table_name, options) do |t|
-              class << t
-                prepend TableDefinition
-              end
-              yield t
+            super do |t|
+              yield compatible_table_definition(t)
             end
           else
             super
@@ -60,21 +85,46 @@ module ActiveRecord
 
         def change_table(table_name, options = {})
           if block_given?
-            super(table_name, options) do |t|
-              class << t
-                prepend TableDefinition
-              end
-              yield t
+            super do |t|
+              yield compatible_table_definition(t)
             end
           else
             super
           end
         end
 
+        def create_join_table(table_1, table_2, column_options: {}, **options)
+          column_options.reverse_merge!(type: :integer)
+
+          if block_given?
+            super do |t|
+              yield compatible_table_definition(t)
+            end
+          else
+            super
+          end
+        end
+
+        def add_column(table_name, column_name, type, options = {})
+          if type == :primary_key
+            type = :integer
+            options[:primary_key] = true
+          end
+          super
+        end
+
         def add_reference(table_name, ref_name, **options)
           super(table_name, ref_name, type: :integer, **options)
         end
         alias :add_belongs_to :add_reference
+
+        private
+          def compatible_table_definition(t)
+            class << t
+              prepend TableDefinition
+            end
+            t
+          end
       end
 
       class V4_2 < V5_0
@@ -93,11 +143,8 @@ module ActiveRecord
 
         def create_table(table_name, options = {})
           if block_given?
-            super(table_name, options) do |t|
-              class << t
-                prepend TableDefinition
-              end
-              yield t
+            super do |t|
+              yield compatible_table_definition(t)
             end
           else
             super
@@ -106,11 +153,8 @@ module ActiveRecord
 
         def change_table(table_name, options = {})
           if block_given?
-            super(table_name, options) do |t|
-              class << t
-                prepend TableDefinition
-              end
-              yield t
+            super do |t|
+              yield compatible_table_definition(t)
             end
           else
             super
@@ -146,6 +190,12 @@ module ActiveRecord
         end
 
         private
+          def compatible_table_definition(t)
+            class << t
+              prepend TableDefinition
+            end
+            super
+          end
 
           def index_name_for_remove(table_name, options = {})
             index_name = index_name(table_name, options)
diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index 34c0ef4e75..694ff85fa1 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -87,19 +87,6 @@ module ActiveRecord
     # Sets the name of the internal metadata table.
 
     ##
-    # :singleton-method: protected_environments
-    # :call-seq: protected_environments
-    #
-    # The array of names of environments where destructive actions should be prohibited. By default,
-    # the value is <tt>["production"]</tt>.
-
-    ##
-    # :singleton-method: protected_environments=
-    # :call-seq: protected_environments=(environments)
-    #
-    # Sets an array of names of environments where destructive actions should be prohibited.
-
-    ##
     # :singleton-method: pluralize_table_names
     # :call-seq: pluralize_table_names
     #
@@ -115,20 +102,6 @@ module ActiveRecord
     # If true, the default table name for a Product class will be "products". If false, it would just be "product".
     # See table_name for the full rules on table/class naming. This is true, by default.
 
-    ##
-    # :singleton-method: ignored_columns
-    # :call-seq: ignored_columns
-    #
-    # The list of columns names the model should ignore. Ignored columns won't have attribute
-    # accessors defined, and won't be referenced in SQL queries.
-
-    ##
-    # :singleton-method: ignored_columns=
-    # :call-seq: ignored_columns=(columns)
-    #
-    # Sets the columns names the model should ignore. Ignored columns won't have attribute
-    # accessors defined, and won't be referenced in SQL queries.
-
     included do
       mattr_accessor :primary_key_prefix_type, instance_writer: false
 
@@ -136,11 +109,11 @@ module ActiveRecord
       class_attribute :table_name_suffix, instance_writer: false, default: ""
       class_attribute :schema_migrations_table_name, instance_accessor: false, default: "schema_migrations"
       class_attribute :internal_metadata_table_name, instance_accessor: false, default: "ar_internal_metadata"
-      class_attribute :protected_environments, instance_accessor: false, default: [ "production" ]
       class_attribute :pluralize_table_names, instance_writer: false, default: true
-      class_attribute :ignored_columns, instance_accessor: false, default: [].freeze
 
+      self.protected_environments = ["production"]
       self.inheritance_column = "type"
+      self.ignored_columns = [].freeze
 
       delegate :type_for_attribute, to: :class
 
@@ -252,6 +225,21 @@ module ActiveRecord
         (parents.detect { |p| p.respond_to?(:table_name_suffix) } || self).table_name_suffix
       end
 
+      # The array of names of environments where destructive actions should be prohibited. By default,
+      # the value is <tt>["production"]</tt>.
+      def protected_environments
+        if defined?(@protected_environments)
+          @protected_environments
+        else
+          superclass.protected_environments
+        end
+      end
+
+      # Sets an array of names of environments where destructive actions should be prohibited.
+      def protected_environments=(environments)
+        @protected_environments = environments.map(&:to_s)
+      end
+
       # Defines the name of the table column which will store the class name on single-table
       # inheritance situations.
       #
@@ -271,8 +259,24 @@ module ActiveRecord
         @explicit_inheritance_column = true
       end
 
+      # The list of columns names the model should ignore. Ignored columns won't have attribute
+      # accessors defined, and won't be referenced in SQL queries.
+      def ignored_columns
+        if defined?(@ignored_columns)
+          @ignored_columns
+        else
+          superclass.ignored_columns
+        end
+      end
+
+      # Sets the columns names the model should ignore. Ignored columns won't have attribute
+      # accessors defined, and won't be referenced in SQL queries.
+      def ignored_columns=(columns)
+        @ignored_columns = columns.map(&:to_s)
+      end
+
       def sequence_name
-        if base_class == self
+        if base_class?
           @sequence_name ||= reset_sequence_name
         else
           (@sequence_name ||= nil) || base_class.sequence_name
@@ -321,11 +325,11 @@ module ActiveRecord
       end
 
       def attributes_builder # :nodoc:
-        @attributes_builder ||= AttributeSet::Builder.new(attribute_types, primary_key) do |name|
-          unless columns_hash.key?(name)
-            _default_attributes[name].dup
-          end
+        unless defined?(@attributes_builder) && @attributes_builder
+          defaults = _default_attributes.except(*(column_names - [primary_key]))
+          @attributes_builder = ActiveModel::AttributeSet::Builder.new(attribute_types, defaults)
         end
+        @attributes_builder
       end
 
       def columns_hash # :nodoc:
@@ -344,7 +348,7 @@ module ActiveRecord
       end
 
       def yaml_encoder # :nodoc:
-        @yaml_encoder ||= AttributeSet::YAMLEncoder.new(attribute_types)
+        @yaml_encoder ||= ActiveModel::AttributeSet::YAMLEncoder.new(attribute_types)
       end
 
       # Returns the type of the attribute with the given name, after applying
@@ -357,8 +361,9 @@ module ActiveRecord
       # it).
       #
       # +attr_name+ The name of the attribute to retrieve the type for. Must be
-      # a string
+      # a string or a symbol.
       def type_for_attribute(attr_name, &block)
+        attr_name = attr_name.to_s
         if block
           attribute_types.fetch(attr_name, &block)
         else
@@ -374,7 +379,8 @@ module ActiveRecord
       end
 
       def _default_attributes # :nodoc:
-        @default_attributes ||= AttributeSet.new({})
+        load_schema
+        @default_attributes ||= ActiveModel::AttributeSet.new({})
       end
 
       # Returns an array of column names as strings.
@@ -421,7 +427,7 @@ module ActiveRecord
       #  end
       def reset_column_information
         connection.clear_cache!
-        undefine_attribute_methods
+        ([self] + descendants).each(&:undefine_attribute_methods)
         connection.schema_cache.clear_data_source_cache!(table_name)
 
         reload_schema_from_cache
@@ -495,8 +501,7 @@ module ActiveRecord
 
         # Computes and returns a table name according to default conventions.
         def compute_table_name
-          base = base_class
-          if self == base
+          if base_class?
             # Nested classes are prefixed with singular parent table name.
             if parent < Base && !parent.abstract_class?
               contained = parent.table_name
@@ -507,7 +512,7 @@ module ActiveRecord
             "#{full_table_name_prefix}#{contained}#{undecorated_table_name(name)}#{full_table_name_suffix}"
           else
             # STI subclasses always use their superclass' table.
-            base.table_name
+            base_class.table_name
           end
         end
     end
diff --git a/activerecord/lib/active_record/nested_attributes.rb b/activerecord/lib/active_record/nested_attributes.rb
index 1864ca5ad2..fa20bce3a9 100644
--- a/activerecord/lib/active_record/nested_attributes.rb
+++ b/activerecord/lib/active_record/nested_attributes.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/hash/except"
+require "active_support/core_ext/module/redefine_method"
 require "active_support/core_ext/object/try"
 require "active_support/core_ext/hash/indifferent_access"
 
@@ -62,6 +63,18 @@ module ActiveRecord
     #   member.update params[:member]
     #   member.avatar.icon # => 'sad'
     #
+    # If you want to update the current avatar without providing the id, you must add <tt>:update_only</tt> option.
+    #
+    #   class Member < ActiveRecord::Base
+    #     has_one :avatar
+    #     accepts_nested_attributes_for :avatar, update_only: true
+    #   end
+    #
+    #   params = { member: { avatar_attributes: { icon: 'sad' } } }
+    #   member.update params[:member]
+    #   member.avatar.id # => 2
+    #   member.avatar.icon # => 'sad'
+    #
     # By default you will only be able to set and update attributes on the
     # associated model. If you want to destroy the associated model through the
     # attributes hash, you have to enable it first using the
@@ -355,9 +368,7 @@ module ActiveRecord
         # associations are just regular associations.
         def generate_association_writer(association_name, type)
           generated_association_methods.module_eval <<-eoruby, __FILE__, __LINE__ + 1
-            if method_defined?(:#{association_name}_attributes=)
-              remove_method(:#{association_name}_attributes=)
-            end
+            silence_redefinition_of_method :#{association_name}_attributes=
             def #{association_name}_attributes=(attributes)
               assign_nested_attributes_for_#{type}_association(:#{association_name}, attributes)
             end
diff --git a/activerecord/lib/active_record/no_touching.rb b/activerecord/lib/active_record/no_touching.rb
index c573deb63a..754c891884 100644
--- a/activerecord/lib/active_record/no_touching.rb
+++ b/activerecord/lib/active_record/no_touching.rb
@@ -6,7 +6,7 @@ module ActiveRecord
     extend ActiveSupport::Concern
 
     module ClassMethods
-      # Lets you selectively disable calls to `touch` for the
+      # Lets you selectively disable calls to +touch+ for the
       # duration of a block.
       #
       # ==== Examples
diff --git a/activerecord/lib/active_record/persistence.rb b/activerecord/lib/active_record/persistence.rb
index 1297e0cde7..a0d5f1ee9f 100644
--- a/activerecord/lib/active_record/persistence.rb
+++ b/activerecord/lib/active_record/persistence.rb
@@ -71,6 +71,142 @@ module ActiveRecord
         klass.allocate.init_with("attributes" => attributes, "new_record" => false, &block)
       end
 
+      # Updates an object (or multiple objects) and saves it to the database, if validations pass.
+      # The resulting object is returned whether the object was saved successfully to the database or not.
+      #
+      # ==== Parameters
+      #
+      # * +id+ - This should be the id or an array of ids to be updated.
+      # * +attributes+ - This should be a hash of attributes or an array of hashes.
+      #
+      # ==== Examples
+      #
+      #   # Updates one record
+      #   Person.update(15, user_name: "Samuel", group: "expert")
+      #
+      #   # Updates multiple records
+      #   people = { 1 => { "first_name" => "David" }, 2 => { "first_name" => "Jeremy" } }
+      #   Person.update(people.keys, people.values)
+      #
+      #   # Updates multiple records from the result of a relation
+      #   people = Person.where(group: "expert")
+      #   people.update(group: "masters")
+      #
+      # Note: Updating a large number of records will run an UPDATE
+      # query for each record, which may cause a performance issue.
+      # When running callbacks is not needed for each record update,
+      # it is preferred to use {update_all}[rdoc-ref:Relation#update_all]
+      # for updating all records in a single query.
+      def update(id = :all, attributes)
+        if id.is_a?(Array)
+          id.map { |one_id| find(one_id) }.each_with_index { |object, idx|
+            object.update(attributes[idx])
+          }
+        elsif id == :all
+          all.each { |record| record.update(attributes) }
+        else
+          if ActiveRecord::Base === id
+            raise ArgumentError,
+              "You are passing an instance of ActiveRecord::Base to `update`. " \
+              "Please pass the id of the object by calling `.id`."
+          end
+          object = find(id)
+          object.update(attributes)
+          object
+        end
+      end
+
+      # Destroy an object (or multiple objects) that has the given id. The object is instantiated first,
+      # therefore all callbacks and filters are fired off before the object is deleted. This method is
+      # less efficient than #delete but allows cleanup methods and other actions to be run.
+      #
+      # This essentially finds the object (or multiple objects) with the given id, creates a new object
+      # from the attributes, and then calls destroy on it.
+      #
+      # ==== Parameters
+      #
+      # * +id+ - This should be the id or an array of ids to be destroyed.
+      #
+      # ==== Examples
+      #
+      #   # Destroy a single object
+      #   Todo.destroy(1)
+      #
+      #   # Destroy multiple objects
+      #   todos = [1,2,3]
+      #   Todo.destroy(todos)
+      def destroy(id)
+        if id.is_a?(Array)
+          find(id).each(&:destroy)
+        else
+          find(id).destroy
+        end
+      end
+
+      # Deletes the row with a primary key matching the +id+ argument, using a
+      # SQL +DELETE+ statement, and returns the number of rows deleted. Active
+      # Record objects are not instantiated, so the object's callbacks are not
+      # executed, including any <tt>:dependent</tt> association options.
+      #
+      # You can delete multiple rows at once by passing an Array of <tt>id</tt>s.
+      #
+      # Note: Although it is often much faster than the alternative, #destroy,
+      # skipping callbacks might bypass business logic in your application
+      # that ensures referential integrity or performs other essential jobs.
+      #
+      # ==== Examples
+      #
+      #   # Delete a single row
+      #   Todo.delete(1)
+      #
+      #   # Delete multiple rows
+      #   Todo.delete([2,3,4])
+      def delete(id_or_array)
+        where(primary_key => id_or_array).delete_all
+      end
+
+      def _insert_record(values) # :nodoc:
+        primary_key_value = nil
+
+        if primary_key && Hash === values
+          primary_key_value = values[primary_key]
+
+          if !primary_key_value && prefetch_primary_key?
+            primary_key_value = next_sequence_value
+            values[primary_key] = primary_key_value
+          end
+        end
+
+        if values.empty?
+          im = arel_table.compile_insert(connection.empty_insert_statement_value(primary_key))
+          im.into arel_table
+        else
+          im = arel_table.compile_insert(_substitute_values(values))
+        end
+
+        connection.insert(im, "#{self} Create", primary_key || false, primary_key_value)
+      end
+
+      def _update_record(values, constraints) # :nodoc:
+        constraints = _substitute_values(constraints).map { |attr, bind| attr.eq(bind) }
+
+        um = arel_table.where(
+          constraints.reduce(&:and)
+        ).compile_update(_substitute_values(values), primary_key)
+
+        connection.update(um, "#{self} Update")
+      end
+
+      def _delete_record(constraints) # :nodoc:
+        constraints = _substitute_values(constraints).map { |attr, bind| attr.eq(bind) }
+
+        dm = Arel::DeleteManager.new
+        dm.from(arel_table)
+        dm.wheres = constraints
+
+        connection.delete(dm, "#{self} Destroy")
+      end
+
       private
         # Called by +instantiate+ to decide which class to use for a new
         # record instance.
@@ -80,6 +216,14 @@ module ActiveRecord
         def discriminate_class_for_record(record)
           self
         end
+
+        def _substitute_values(values)
+          values.map do |name, value|
+            attr = arel_attribute(name)
+            bind = predicate_builder.build_bind_attribute(name, value)
+            [attr, bind]
+          end
+        end
     end
 
     # Returns true if this object hasn't been saved yet -- that is, a record
@@ -177,7 +321,7 @@ module ActiveRecord
     # callbacks or any <tt>:dependent</tt> association
     # options, use <tt>#destroy</tt>.
     def delete
-      _relation_for_itself.delete_all if persisted?
+      _delete_row if persisted?
       @destroyed = true
       freeze
     end
@@ -226,9 +370,10 @@ module ActiveRecord
     # Any change to the attributes on either instance will affect both instances.
     # If you want to change the sti column as well, use #becomes! instead.
     def becomes(klass)
-      became = klass.new
+      became = klass.allocate
+      became.send(:initialize)
       became.instance_variable_set("@attributes", @attributes)
-      became.instance_variable_set("@mutation_tracker", @mutation_tracker) if defined?(@mutation_tracker)
+      became.instance_variable_set("@mutations_from_database", @mutations_from_database ||= nil)
       became.instance_variable_set("@changed_attributes", attributes_changed_by_setter)
       became.instance_variable_set("@new_record", new_record?)
       became.instance_variable_set("@destroyed", destroyed?)
@@ -269,11 +414,7 @@ module ActiveRecord
       verify_readonly_attribute(name)
       public_send("#{name}=", value)
 
-      if has_changes_to_save?
-        save(validate: false)
-      else
-        true
-      end
+      save(validate: false)
     end
 
     # Updates the attributes of the model from the passed-in hash and saves the
@@ -289,6 +430,7 @@ module ActiveRecord
     end
 
     alias update_attributes update
+    deprecate :update_attributes
 
     # Updates its receiver just like #update but calls #save! instead
     # of +save+, so an exception is raised if the record is invalid and saving will fail.
@@ -302,6 +444,7 @@ module ActiveRecord
     end
 
     alias update_attributes! update!
+    deprecate :update_attributes!
 
     # Equivalent to <code>update_columns(name => value)</code>.
     def update_column(name, value)
@@ -332,13 +475,16 @@ module ActiveRecord
         verify_readonly_attribute(key.to_s)
       end
 
-      updated_count = _relation_for_itself.update_all(attributes)
+      affected_rows = self.class._update_record(
+        attributes,
+        self.class.primary_key => id_in_database
+      )
 
       attributes.each do |k, v|
         write_attribute_without_type_cast(k, v)
       end
 
-      updated_count == 1
+      affected_rows == 1
     end
 
     # Initializes +attribute+ to zero if +nil+ and adds the value passed as +by+ (default is 1).
@@ -353,7 +499,7 @@ module ActiveRecord
     # Wrapper around #increment that writes the update to the database.
     # Only +attribute+ is updated; the record itself is not saved.
     # This means that any other modified attributes will still be dirty.
-    # Validations and callbacks are skipped. Supports the `touch` option from
+    # Validations and callbacks are skipped. Supports the +touch+ option from
     # +update_counters+, see that for more.
     # Returns +self+.
     def increment!(attribute, by = 1, touch: nil)
@@ -374,7 +520,7 @@ module ActiveRecord
     # Wrapper around #decrement that writes the update to the database.
     # Only +attribute+ is updated; the record itself is not saved.
     # This means that any other modified attributes will still be dirty.
-    # Validations and callbacks are skipped. Supports the `touch` option from
+    # Validations and callbacks are skipped. Supports the +touch+ option from
     # +update_counters+, see that for more.
     # Returns +self+.
     def decrement!(attribute, by = 1, touch: nil)
@@ -511,35 +657,12 @@ module ActiveRecord
         MSG
       end
 
-      time ||= current_time_from_proper_timezone
-      attributes = timestamp_attributes_for_update_in_model
-      attributes.concat(names)
-
-      unless attributes.empty?
-        changes = {}
-
-        attributes.each do |column|
-          column = column.to_s
-          changes[column] = write_attribute(column, time)
-        end
-
-        scope = _relation_for_itself
-
-        if locking_enabled?
-          locking_column = self.class.locking_column
-          scope = scope.where(locking_column => read_attribute_before_type_cast(locking_column))
-          changes[locking_column] = increment_lock
-        end
-
-        clear_attribute_changes(changes.keys)
-        result = scope.update_all(changes) == 1
+      attribute_names = timestamp_attributes_for_update_in_model
+      attribute_names |= names.map(&:to_s)
 
-        if !result && locking_enabled?
-          raise ActiveRecord::StaleObjectError.new(self, "touch")
-        end
-
-        @_trigger_update_callback = result
-        result
+      unless attribute_names.empty?
+        affected_rows = _touch_row(attribute_names, time)
+        @_trigger_update_callback = affected_rows == 1
       else
         true
       end
@@ -552,19 +675,34 @@ module ActiveRecord
     end
 
     def destroy_row
-      relation_for_destroy.delete_all
+      _delete_row
     end
 
-    def relation_for_destroy
-      _relation_for_itself
+    def _delete_row
+      self.class._delete_record(self.class.primary_key => id_in_database)
     end
 
-    def _relation_for_itself
-      self.class.unscoped.where(self.class.primary_key => id)
+    def _touch_row(attribute_names, time)
+      time ||= current_time_from_proper_timezone
+
+      attribute_names.each do |attr_name|
+        write_attribute(attr_name, time)
+        clear_attribute_change(attr_name)
+      end
+
+      _update_row(attribute_names, "touch")
+    end
+
+    def _update_row(attribute_names, attempted_action = "update")
+      self.class._update_record(
+        attributes_with_values(attribute_names),
+        self.class.primary_key => id_in_database
+      )
     end
 
     def create_or_update(*args, &block)
       _raise_readonly_record_error if readonly?
+      return false if destroyed?
       result = new_record? ? _create_record(&block) : _update_record(*args, &block)
       result != false
     end
@@ -572,26 +710,29 @@ module ActiveRecord
     # Updates the associated record with values matching those of the instance attributes.
     # Returns the number of affected rows.
     def _update_record(attribute_names = self.attribute_names)
-      attributes_values = arel_attributes_with_values_for_update(attribute_names)
-      if attributes_values.empty?
-        rows_affected = 0
+      attribute_names &= self.class.column_names
+      attribute_names = attributes_for_update(attribute_names)
+
+      if attribute_names.empty?
+        affected_rows = 0
         @_trigger_update_callback = true
       else
-        rows_affected = self.class.unscoped._update_record attributes_values, id, id_in_database
-        @_trigger_update_callback = rows_affected > 0
+        affected_rows = _update_row(attribute_names)
+        @_trigger_update_callback = affected_rows == 1
       end
 
       yield(self) if block_given?
 
-      rows_affected
+      affected_rows
     end
 
     # Creates a record with values matching those of the instance attributes
     # and returns its id.
     def _create_record(attribute_names = self.attribute_names)
-      attributes_values = arel_attributes_with_values_for_create(attribute_names)
+      attribute_names &= self.class.column_names
+      attributes_values = attributes_with_values_for_create(attribute_names)
 
-      new_id = self.class.unscoped.insert attributes_values
+      new_id = self.class._insert_record(attributes_values)
       self.id ||= new_id if self.class.primary_key
 
       @new_record = false
diff --git a/activerecord/lib/active_record/query_cache.rb b/activerecord/lib/active_record/query_cache.rb
index 3d5babb8b7..28194c7c46 100644
--- a/activerecord/lib/active_record/query_cache.rb
+++ b/activerecord/lib/active_record/query_cache.rb
@@ -7,35 +7,31 @@ module ActiveRecord
       # Enable the query cache within the block if Active Record is configured.
       # If it's not, it will execute the given block.
       def cache(&block)
-        if configurations.empty?
-          yield
-        else
+        if connected? || !configurations.empty?
           connection.cache(&block)
+        else
+          yield
         end
       end
 
       # Disable the query cache within the block if Active Record is configured.
       # If it's not, it will execute the given block.
       def uncached(&block)
-        if configurations.empty?
-          yield
-        else
+        if connected? || !configurations.empty?
           connection.uncached(&block)
+        else
+          yield
         end
       end
     end
 
     def self.run
-      caching_pool = ActiveRecord::Base.connection_pool
-      caching_was_enabled = caching_pool.query_cache_enabled
-
-      caching_pool.enable_query_cache!
-
-      [caching_pool, caching_was_enabled]
+      ActiveRecord::Base.connection_handler.connection_pool_list.
+        reject { |p| p.query_cache_enabled }.each { |p| p.enable_query_cache! }
     end
 
-    def self.complete((caching_pool, caching_was_enabled))
-      caching_pool.disable_query_cache! unless caching_was_enabled
+    def self.complete(pools)
+      pools.each { |pool| pool.disable_query_cache! }
 
       ActiveRecord::Base.connection_handler.connection_pool_list.each do |pool|
         pool.release_connection if pool.active_connection? && !pool.connection.transaction_open?
diff --git a/activerecord/lib/active_record/querying.rb b/activerecord/lib/active_record/querying.rb
index f780538319..d33d36ac02 100644
--- a/activerecord/lib/active_record/querying.rb
+++ b/activerecord/lib/active_record/querying.rb
@@ -5,15 +5,15 @@ module ActiveRecord
     delegate :find, :take, :take!, :first, :first!, :last, :last!, :exists?, :any?, :many?, :none?, :one?, to: :all
     delegate :second, :second!, :third, :third!, :fourth, :fourth!, :fifth, :fifth!, :forty_two, :forty_two!, :third_to_last, :third_to_last!, :second_to_last, :second_to_last!, to: :all
     delegate :first_or_create, :first_or_create!, :first_or_initialize, to: :all
-    delegate :find_or_create_by, :find_or_create_by!, :find_or_initialize_by, to: :all
+    delegate :find_or_create_by, :find_or_create_by!, :create_or_find_by, :create_or_find_by!, :find_or_initialize_by, to: :all
     delegate :find_by, :find_by!, to: :all
-    delegate :destroy, :destroy_all, :delete, :delete_all, :update, :update_all, to: :all
+    delegate :destroy_all, :delete_all, :update_all, to: :all
     delegate :find_each, :find_in_batches, :in_batches, to: :all
     delegate :select, :group, :order, :except, :reorder, :limit, :offset, :joins, :left_joins, :left_outer_joins, :or,
              :where, :rewhere, :preload, :eager_load, :includes, :from, :lock, :readonly, :extending,
              :having, :create_with, :distinct, :references, :none, :unscope, :merge, to: :all
     delegate :count, :average, :minimum, :maximum, :sum, :calculate, to: :all
-    delegate :pluck, :ids, to: :all
+    delegate :pluck, :pick, :ids, to: :all
 
     # Executes a custom SQL query against your database and returns all the results. The results will
     # be returned as an array with columns requested encapsulated as attributes of the model you call
diff --git a/activerecord/lib/active_record/railtie.rb b/activerecord/lib/active_record/railtie.rb
index ead42d64ec..6ab80a654d 100644
--- a/activerecord/lib/active_record/railtie.rb
+++ b/activerecord/lib/active_record/railtie.rb
@@ -53,16 +53,17 @@ module ActiveRecord
     # to avoid cross references when loading a constant for the
     # first time. Also, make it output to STDERR.
     console do |app|
-      require_relative "railties/console_sandbox" if app.sandbox?
-      require_relative "base"
+      require "active_record/railties/console_sandbox" if app.sandbox?
+      require "active_record/base"
       unless ActiveSupport::Logger.logger_outputs_to?(Rails.logger, STDERR, STDOUT)
         console = ActiveSupport::Logger.new(STDERR)
         Rails.logger.extend ActiveSupport::Logger.broadcast console
       end
+      ActiveRecord::Base.verbose_query_logs = false
     end
 
     runner do
-      require_relative "base"
+      require "active_record/base"
     end
 
     initializer "active_record.initialize_timezone" do
@@ -90,12 +91,16 @@ module ActiveRecord
             filename = File.join(app.config.paths["db"].first, "schema_cache.yml")
 
             if File.file?(filename)
+              current_version = ActiveRecord::Migrator.current_version
+
+              next if current_version.nil?
+
               cache = YAML.load(File.read(filename))
-              if cache.version == ActiveRecord::Migrator.current_version
+              if cache.version == current_version
                 connection.schema_cache = cache
                 connection_pool.schema_cache = cache.dup
               else
-                warn "Ignoring db/schema_cache.yml because it has expired. The current schema version is #{ActiveRecord::Migrator.current_version}, but the one in the cache is #{cache.version}."
+                warn "Ignoring db/schema_cache.yml because it has expired. The current schema version is #{current_version}, but the one in the cache is #{cache.version}."
               end
             end
           end
@@ -106,7 +111,7 @@ module ActiveRecord
     initializer "active_record.warn_on_records_fetched_greater_than" do
       if config.active_record.warn_on_records_fetched_greater_than
         ActiveSupport.on_load(:active_record) do
-          require_relative "relation/record_fetch_warning"
+          require "active_record/relation/record_fetch_warning"
         end
       end
     end
@@ -146,12 +151,19 @@ end_warning
 
     # Expose database runtime to controller for logging.
     initializer "active_record.log_runtime" do
-      require_relative "railties/controller_runtime"
+      require "active_record/railties/controller_runtime"
       ActiveSupport.on_load(:action_controller) do
         include ActiveRecord::Railties::ControllerRuntime
       end
     end
 
+    initializer "active_record.collection_cache_association_loading" do
+      require "active_record/railties/collection_cache_association_loading"
+      ActiveSupport.on_load(:action_view) do
+        ActionView::PartialRenderer.prepend(ActiveRecord::Railties::CollectionCacheAssociationLoading)
+      end
+    end
+
     initializer "active_record.set_reloader_hooks" do
       ActiveSupport.on_load(:active_record) do
         ActiveSupport::Reloader.before_class_unload do
@@ -177,7 +189,16 @@ end_warning
     initializer "active_record.clear_active_connections" do
       config.after_initialize do
         ActiveSupport.on_load(:active_record) do
+          # Ideally the application doesn't connect to the database during boot,
+          # but sometimes it does. In case it did, we want to empty out the
+          # connection pools so that a non-database-using process (e.g. a master
+          # process in a forking server model) doesn't retain a needless
+          # connection. If it was needed, the incremental cost of reestablishing
+          # this connection is trivial: the rest of the pool would need to be
+          # populated anyway.
+
           clear_active_connections!
+          flush_idle_connections!
         end
       end
     end
diff --git a/activerecord/lib/active_record/railties/collection_cache_association_loading.rb b/activerecord/lib/active_record/railties/collection_cache_association_loading.rb
new file mode 100644
index 0000000000..b5129e4239
--- /dev/null
+++ b/activerecord/lib/active_record/railties/collection_cache_association_loading.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module ActiveRecord
+  module Railties # :nodoc:
+    module CollectionCacheAssociationLoading #:nodoc:
+      def setup(context, options, block)
+        @relation = relation_from_options(options)
+
+        super
+      end
+
+      def relation_from_options(cached: nil, partial: nil, collection: nil, **_)
+        return unless cached
+
+        relation = partial if partial.is_a?(ActiveRecord::Relation)
+        relation ||= collection if collection.is_a?(ActiveRecord::Relation)
+
+        if relation && !relation.loaded?
+          relation.skip_preloading!
+        end
+      end
+
+      def collection_without_template
+        @relation.preload_associations(@collection) if @relation
+        super
+      end
+
+      def collection_with_template
+        @relation.preload_associations(@collection) if @relation
+        super
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/railties/controller_runtime.rb b/activerecord/lib/active_record/railties/controller_runtime.rb
index 3cf66980a5..309441a057 100644
--- a/activerecord/lib/active_record/railties/controller_runtime.rb
+++ b/activerecord/lib/active_record/railties/controller_runtime.rb
@@ -1,56 +1,51 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/module/attr_internal"
-require_relative "../log_subscriber"
+require "active_record/log_subscriber"
 
 module ActiveRecord
   module Railties # :nodoc:
     module ControllerRuntime #:nodoc:
       extend ActiveSupport::Concern
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
-    protected
-
-      attr_internal :db_runtime
-
-    private
-
-      def process_action(action, *args)
-        # We also need to reset the runtime before each action
-        # because of queries in middleware or in cases we are streaming
-        # and it won't be cleaned up by the method below.
-        ActiveRecord::LogSubscriber.reset_runtime
-        super
+      module ClassMethods # :nodoc:
+        def log_process_action(payload)
+          messages, db_runtime = super, payload[:db_runtime]
+          messages << ("ActiveRecord: %.1fms" % db_runtime.to_f) if db_runtime
+          messages
+        end
       end
 
-      def cleanup_view_runtime
-        if logger && logger.info? && ActiveRecord::Base.connected?
-          db_rt_before_render = ActiveRecord::LogSubscriber.reset_runtime
-          self.db_runtime = (db_runtime || 0) + db_rt_before_render
-          runtime = super
-          db_rt_after_render = ActiveRecord::LogSubscriber.reset_runtime
-          self.db_runtime += db_rt_after_render
-          runtime - db_rt_after_render
-        else
+      private
+        attr_internal :db_runtime
+
+        def process_action(action, *args)
+          # We also need to reset the runtime before each action
+          # because of queries in middleware or in cases we are streaming
+          # and it won't be cleaned up by the method below.
+          ActiveRecord::LogSubscriber.reset_runtime
           super
         end
-      end
 
-      def append_info_to_payload(payload)
-        super
-        if ActiveRecord::Base.connected?
-          payload[:db_runtime] = (db_runtime || 0) + ActiveRecord::LogSubscriber.reset_runtime
+        def cleanup_view_runtime
+          if logger && logger.info? && ActiveRecord::Base.connected?
+            db_rt_before_render = ActiveRecord::LogSubscriber.reset_runtime
+            self.db_runtime = (db_runtime || 0) + db_rt_before_render
+            runtime = super
+            db_rt_after_render = ActiveRecord::LogSubscriber.reset_runtime
+            self.db_runtime += db_rt_after_render
+            runtime - db_rt_after_render
+          else
+            super
+          end
         end
-      end
 
-      module ClassMethods # :nodoc:
-        def log_process_action(payload)
-          messages, db_runtime = super, payload[:db_runtime]
-          messages << ("ActiveRecord: %.1fms" % db_runtime.to_f) if db_runtime
-          messages
+        def append_info_to_payload(payload)
+          super
+          if ActiveRecord::Base.connected?
+            payload[:db_runtime] = (db_runtime || 0) + ActiveRecord::LogSubscriber.reset_runtime
+          end
         end
-      end
     end
   end
 end
diff --git a/activerecord/lib/active_record/railties/databases.rake b/activerecord/lib/active_record/railties/databases.rake
index 691b3612d8..24449e8df3 100644
--- a/activerecord/lib/active_record/railties/databases.rake
+++ b/activerecord/lib/active_record/railties/databases.rake
@@ -4,16 +4,16 @@ require "active_record"
 
 db_namespace = namespace :db do
   desc "Set the environment value for the database"
-  task "environment:set" => [:environment, :load_config] do
+  task "environment:set" => :load_config do
     ActiveRecord::InternalMetadata.create_table
-    ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Migrator.current_environment
+    ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Base.connection.migration_context.current_environment
   end
 
-  task check_protected_environments: [:environment, :load_config] do
+  task check_protected_environments: :load_config do
     ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
   end
 
-  task :load_config do
+  task load_config: :environment do
     ActiveRecord::Base.configurations       = ActiveRecord::Tasks::DatabaseTasks.database_configuration || {}
     ActiveRecord::Migrator.migrations_paths = ActiveRecord::Tasks::DatabaseTasks.migrations_paths
   end
@@ -22,6 +22,14 @@ db_namespace = namespace :db do
     task all: :load_config do
       ActiveRecord::Tasks::DatabaseTasks.create_all
     end
+
+    ActiveRecord::Tasks::DatabaseTasks.for_each do |spec_name|
+      desc "Create #{spec_name} database for current environment"
+      task spec_name => :load_config do
+        db_config = ActiveRecord::DatabaseConfigurations.config_for_env_and_spec(Rails.env, spec_name)
+        ActiveRecord::Tasks::DatabaseTasks.create(db_config.config)
+      end
+    end
   end
 
   desc "Creates the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:create:all to create all databases in the config). Without RAILS_ENV or when RAILS_ENV is development, it defaults to creating the development and test databases."
@@ -33,6 +41,14 @@ db_namespace = namespace :db do
     task all: [:load_config, :check_protected_environments] do
       ActiveRecord::Tasks::DatabaseTasks.drop_all
     end
+
+    ActiveRecord::Tasks::DatabaseTasks.for_each do |spec_name|
+      desc "Drop #{spec_name} database for current environment"
+      task spec_name => [:load_config, :check_protected_environments] do
+        db_config = ActiveRecord::DatabaseConfigurations.config_for_env_and_spec(Rails.env, spec_name)
+        ActiveRecord::Tasks::DatabaseTasks.drop(db_config.config)
+      end
+    end
   end
 
   desc "Drops the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:drop:all to drop all databases in the config). Without RAILS_ENV or when RAILS_ENV is development, it defaults to dropping the development and test databases."
@@ -56,8 +72,11 @@ db_namespace = namespace :db do
   end
 
   desc "Migrate the database (options: VERSION=x, VERBOSE=false, SCOPE=blog)."
-  task migrate: [:environment, :load_config] do
-    ActiveRecord::Tasks::DatabaseTasks.migrate
+  task migrate: :load_config do
+    ActiveRecord::DatabaseConfigurations.configs_for(Rails.env) do |spec_name, config|
+      ActiveRecord::Base.establish_connection(config)
+      ActiveRecord::Tasks::DatabaseTasks.migrate
+    end
     db_namespace["_dump"].invoke
   end
 
@@ -77,8 +96,17 @@ db_namespace = namespace :db do
   end
 
   namespace :migrate do
+    ActiveRecord::Tasks::DatabaseTasks.for_each do |spec_name|
+      desc "Migrate #{spec_name} database for current environment"
+      task spec_name => :load_config do
+        db_config = ActiveRecord::DatabaseConfigurations.config_for_env_and_spec(Rails.env, spec_name)
+        ActiveRecord::Base.establish_connection(db_config.config)
+        ActiveRecord::Tasks::DatabaseTasks.migrate
+      end
+    end
+
     # desc  'Rollbacks the database one migration and re migrate up (options: STEP=x, VERSION=x).'
-    task redo: [:environment, :load_config] do
+    task redo: :load_config do
       raise "Empty VERSION provided" if ENV["VERSION"] && ENV["VERSION"].empty?
 
       if ENV["VERSION"]
@@ -94,24 +122,33 @@ db_namespace = namespace :db do
     task reset: ["db:drop", "db:create", "db:migrate"]
 
     # desc 'Runs the "up" for a given migration VERSION.'
-    task up: [:environment, :load_config] do
+    task up: :load_config do
       raise "VERSION is required" if !ENV["VERSION"] || ENV["VERSION"].empty?
 
-      version = ENV["VERSION"] ? ENV["VERSION"].to_i : nil
-      ActiveRecord::Migrator.run(:up, ActiveRecord::Tasks::DatabaseTasks.migrations_paths, version)
+      ActiveRecord::Tasks::DatabaseTasks.check_target_version
+
+      ActiveRecord::Base.connection.migration_context.run(
+        :up,
+        ActiveRecord::Tasks::DatabaseTasks.target_version
+      )
       db_namespace["_dump"].invoke
     end
 
     # desc 'Runs the "down" for a given migration VERSION.'
-    task down: [:environment, :load_config] do
+    task down: :load_config do
       raise "VERSION is required - To go down one migration, use db:rollback" if !ENV["VERSION"] || ENV["VERSION"].empty?
-      version = ENV["VERSION"] ? ENV["VERSION"].to_i : nil
-      ActiveRecord::Migrator.run(:down, ActiveRecord::Tasks::DatabaseTasks.migrations_paths, version)
+
+      ActiveRecord::Tasks::DatabaseTasks.check_target_version
+
+      ActiveRecord::Base.connection.migration_context.run(
+        :down,
+        ActiveRecord::Tasks::DatabaseTasks.target_version
+      )
       db_namespace["_dump"].invoke
     end
 
     desc "Display status of migrations"
-    task status: [:environment, :load_config] do
+    task status: :load_config do
       unless ActiveRecord::SchemaMigration.table_exists?
         abort "Schema migrations table does not exist yet."
       end
@@ -120,8 +157,7 @@ db_namespace = namespace :db do
       puts "\ndatabase: #{ActiveRecord::Base.connection_config[:database]}\n\n"
       puts "#{'Status'.center(8)}  #{'Migration ID'.ljust(14)}  Migration Name"
       puts "-" * 50
-      paths = ActiveRecord::Tasks::DatabaseTasks.migrations_paths
-      ActiveRecord::Migrator.migrations_status(paths).each do |status, version, name|
+      ActiveRecord::Base.connection.migration_context.migrations_status.each do |status, version, name|
         puts "#{status.center(8)}  #{version.ljust(14)}  #{name}"
       end
       puts
@@ -129,16 +165,16 @@ db_namespace = namespace :db do
   end
 
   desc "Rolls the schema back to the previous version (specify steps w/ STEP=n)."
-  task rollback: [:environment, :load_config] do
+  task rollback: :load_config do
     step = ENV["STEP"] ? ENV["STEP"].to_i : 1
-    ActiveRecord::Migrator.rollback(ActiveRecord::Tasks::DatabaseTasks.migrations_paths, step)
+    ActiveRecord::Base.connection.migration_context.rollback(step)
     db_namespace["_dump"].invoke
   end
 
   # desc 'Pushes the schema to the next version (specify steps w/ STEP=n).'
-  task forward: [:environment, :load_config] do
+  task forward: :load_config do
     step = ENV["STEP"] ? ENV["STEP"].to_i : 1
-    ActiveRecord::Migrator.forward(ActiveRecord::Tasks::DatabaseTasks.migrations_paths, step)
+    ActiveRecord::Base.connection.migration_context.forward(step)
     db_namespace["_dump"].invoke
   end
 
@@ -146,12 +182,12 @@ db_namespace = namespace :db do
   task reset: [ "db:drop", "db:setup" ]
 
   # desc "Retrieves the charset for the current environment's database"
-  task charset: [:environment, :load_config] do
+  task charset: :load_config do
     puts ActiveRecord::Tasks::DatabaseTasks.charset_current
   end
 
   # desc "Retrieves the collation for the current environment's database"
-  task collation: [:environment, :load_config] do
+  task collation: :load_config do
     begin
       puts ActiveRecord::Tasks::DatabaseTasks.collation_current
     rescue NoMethodError
@@ -160,13 +196,13 @@ db_namespace = namespace :db do
   end
 
   desc "Retrieves the current schema version number"
-  task version: [:environment, :load_config] do
-    puts "Current version: #{ActiveRecord::Migrator.current_version}"
+  task version: :load_config do
+    puts "Current version: #{ActiveRecord::Base.connection.migration_context.current_version}"
   end
 
   # desc "Raises an error if there are pending migrations"
-  task abort_if_pending_migrations: [:environment, :load_config] do
-    pending_migrations = ActiveRecord::Migrator.open(ActiveRecord::Tasks::DatabaseTasks.migrations_paths).pending_migrations
+  task abort_if_pending_migrations: :load_config do
+    pending_migrations = ActiveRecord::Base.connection.migration_context.open.pending_migrations
 
     if pending_migrations.any?
       puts "You have #{pending_migrations.size} pending #{pending_migrations.size > 1 ? 'migrations:' : 'migration:'}"
@@ -188,8 +224,8 @@ db_namespace = namespace :db do
 
   namespace :fixtures do
     desc "Loads fixtures into the current environment's database. Load specific fixtures using FIXTURES=x,y. Load from subdirectory in test/fixtures using FIXTURES_DIR=z. Specify an alternative path (eg. spec/fixtures) using FIXTURES_PATH=spec/fixtures."
-    task load: [:environment, :load_config] do
-      require_relative "../fixtures"
+    task load: :load_config do
+      require "active_record/fixtures"
 
       base_dir = ActiveRecord::Tasks::DatabaseTasks.fixtures_path
 
@@ -210,8 +246,8 @@ db_namespace = namespace :db do
     end
 
     # desc "Search for a fixture given a LABEL or ID. Specify an alternative path (eg. spec/fixtures) using FIXTURES_PATH=spec/fixtures."
-    task identify: [:environment, :load_config] do
-      require_relative "../fixtures"
+    task identify: :load_config do
+      require "active_record/fixtures"
 
       label, id = ENV["LABEL"], ENV["ID"]
       raise "LABEL or ID required" if label.blank? && id.blank?
@@ -221,7 +257,7 @@ db_namespace = namespace :db do
       base_dir = ActiveRecord::Tasks::DatabaseTasks.fixtures_path
 
       Dir["#{base_dir}/**/*.yml"].each do |file|
-        if data = YAML::load(ERB.new(IO.read(file)).result)
+        if data = YAML.load(ERB.new(IO.read(file)).result)
           data.each_key do |key|
             key_id = ActiveRecord::FixtureSet.identify(key)
 
@@ -236,17 +272,22 @@ db_namespace = namespace :db do
 
   namespace :schema do
     desc "Creates a db/schema.rb file that is portable against any DB supported by Active Record"
-    task dump: [:environment, :load_config] do
-      require_relative "../schema_dumper"
-      filename = ENV["SCHEMA"] || File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, "schema.rb")
-      File.open(filename, "w:utf-8") do |file|
-        ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, file)
+    task dump: :load_config do
+      require "active_record/schema_dumper"
+
+      ActiveRecord::DatabaseConfigurations.configs_for(Rails.env) do |spec_name, config|
+        filename = ActiveRecord::Tasks::DatabaseTasks.dump_filename(spec_name, :ruby)
+        File.open(filename, "w:utf-8") do |file|
+          ActiveRecord::Base.establish_connection(config)
+          ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, file)
+        end
       end
+
       db_namespace["schema:dump"].reenable
     end
 
     desc "Loads a schema.rb file into the database"
-    task load: [:environment, :load_config, :check_protected_environments] do
+    task load: [:load_config, :check_protected_environments] do
       ActiveRecord::Tasks::DatabaseTasks.load_schema_current(:ruby, ENV["SCHEMA"])
     end
 
@@ -256,39 +297,41 @@ db_namespace = namespace :db do
 
     namespace :cache do
       desc "Creates a db/schema_cache.yml file."
-      task dump: [:environment, :load_config] do
+      task dump: :load_config do
         conn = ActiveRecord::Base.connection
         filename = File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, "schema_cache.yml")
         ActiveRecord::Tasks::DatabaseTasks.dump_schema_cache(conn, filename)
       end
 
       desc "Clears a db/schema_cache.yml file."
-      task clear: [:environment, :load_config] do
+      task clear: :load_config do
         filename = File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, "schema_cache.yml")
         rm_f filename, verbose: false
       end
     end
-
   end
 
   namespace :structure do
     desc "Dumps the database structure to db/structure.sql. Specify another file with SCHEMA=db/my_structure.sql"
-    task dump: [:environment, :load_config] do
-      filename = ENV["SCHEMA"] || File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, "structure.sql")
-      current_config = ActiveRecord::Tasks::DatabaseTasks.current_config
-      ActiveRecord::Tasks::DatabaseTasks.structure_dump(current_config, filename)
-
-      if ActiveRecord::SchemaMigration.table_exists?
-        File.open(filename, "a") do |f|
-          f.puts ActiveRecord::Base.connection.dump_schema_information
-          f.print "\n"
+    task dump: :load_config do
+      ActiveRecord::DatabaseConfigurations.configs_for(Rails.env) do |spec_name, config|
+        ActiveRecord::Base.establish_connection(config)
+        filename = ActiveRecord::Tasks::DatabaseTasks.dump_filename(spec_name, :sql)
+        ActiveRecord::Tasks::DatabaseTasks.structure_dump(config, filename)
+
+        if ActiveRecord::SchemaMigration.table_exists?
+          File.open(filename, "a") do |f|
+            f.puts ActiveRecord::Base.connection.dump_schema_information
+            f.print "\n"
+          end
         end
       end
+
       db_namespace["structure:dump"].reenable
     end
 
     desc "Recreates the databases from the structure.sql file"
-    task load: [:environment, :load_config, :check_protected_environments] do
+    task load: [:load_config, :check_protected_environments] do
       ActiveRecord::Tasks::DatabaseTasks.load_schema_current(:sql, ENV["SCHEMA"])
     end
 
@@ -313,7 +356,7 @@ db_namespace = namespace :db do
       begin
         should_reconnect = ActiveRecord::Base.connection_pool.active_connection?
         ActiveRecord::Schema.verbose = false
-        ActiveRecord::Tasks::DatabaseTasks.load_schema ActiveRecord::Base.configurations["test"], :ruby, ENV["SCHEMA"]
+        ActiveRecord::Tasks::DatabaseTasks.load_schema ActiveRecord::Base.configurations["test"], :ruby, ENV["SCHEMA"], "test"
       ensure
         if should_reconnect
           ActiveRecord::Base.establish_connection(ActiveRecord::Base.configurations[ActiveRecord::Tasks::DatabaseTasks.env])
@@ -323,16 +366,16 @@ db_namespace = namespace :db do
 
     # desc "Recreate the test database from an existent structure.sql file"
     task load_structure: %w(db:test:purge) do
-      ActiveRecord::Tasks::DatabaseTasks.load_schema ActiveRecord::Base.configurations["test"], :sql, ENV["SCHEMA"]
+      ActiveRecord::Tasks::DatabaseTasks.load_schema ActiveRecord::Base.configurations["test"], :sql, ENV["SCHEMA"], "test"
     end
 
     # desc "Empty the test database"
-    task purge: %w(environment load_config check_protected_environments) do
+    task purge: %w(load_config check_protected_environments) do
       ActiveRecord::Tasks::DatabaseTasks.purge ActiveRecord::Base.configurations["test"]
     end
 
     # desc 'Load the test schema'
-    task prepare: %w(environment load_config) do
+    task prepare: :load_config do
       unless ActiveRecord::Base.configurations.blank?
         db_namespace["test:load"].invoke
       end
diff --git a/activerecord/lib/active_record/railties/jdbcmysql_error.rb b/activerecord/lib/active_record/railties/jdbcmysql_error.rb
deleted file mode 100644
index 72c75ddd52..0000000000
--- a/activerecord/lib/active_record/railties/jdbcmysql_error.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-# frozen_string_literal: true
-
-#FIXME Remove if ArJdbcMysql will give.
-module ArJdbcMySQL #:nodoc:
-  class Error < StandardError #:nodoc:
-    attr_accessor :error_number, :sql_state
-
-    def initialize(msg)
-      super
-      @error_number = nil
-      @sql_state    = nil
-    end
-
-    # Mysql gem compatibility
-    alias_method :errno, :error_number
-    alias_method :error, :message
-  end
-end
diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index e35049bb41..22d195c9a4 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/string/filters"
-require "active_support/deprecation"
 require "concurrent/map"
 
 module ActiveRecord
@@ -35,7 +34,8 @@ module ActiveRecord
 
     def self.add_reflection(ar, name, reflection)
       ar.clear_reflections_cache
-      ar._reflections = ar._reflections.merge(name.to_s => reflection)
+      name = name.to_s
+      ar._reflections = ar._reflections.except(name).merge!(name => reflection)
     end
 
     def self.add_aggregate_reflection(ar, name, reflection)
@@ -138,7 +138,7 @@ module ActiveRecord
     #         HasAndBelongsToManyReflection
     #     ThroughReflection
     #     PolymorphicReflection
-    #       RuntimeReflection
+    #     RuntimeReflection
     class AbstractReflection # :nodoc:
       def through_reflection?
         false
@@ -154,14 +154,6 @@ module ActiveRecord
         klass.new(attributes, &block)
       end
 
-      def quoted_table_name
-        klass.quoted_table_name
-      end
-
-      def primary_key_type
-        klass.type_for_attribute(klass.primary_key)
-      end
-
       # Returns the class name for the macro.
       #
       # <tt>composed_of :balance, class_name: 'Money'</tt> returns <tt>'Money'</tt>
@@ -182,11 +174,6 @@ module ActiveRecord
         scope ? [scope] : []
       end
 
-      def scope_chain
-        chain.map(&:scopes)
-      end
-      deprecate :scope_chain
-
       def build_join_constraint(table, foreign_table)
         key         = join_keys.key
         foreign_key = join_keys.foreign_key
@@ -206,7 +193,7 @@ module ActiveRecord
         klass_scope       = klass_join_scope(table, predicate_builder)
 
         if type
-          klass_scope.where!(type => foreign_klass.base_class.sti_name)
+          klass_scope.where!(type => foreign_klass.polymorphic_name)
         end
 
         scope_chain_items.inject(klass_scope, &:merge!)
@@ -214,7 +201,7 @@ module ActiveRecord
 
       def join_scopes(table, predicate_builder) # :nodoc:
         if scope
-          [build_scope(table, predicate_builder).instance_exec(&scope)]
+          [scope_for(build_scope(table, predicate_builder))]
         else
           []
         end
@@ -300,11 +287,19 @@ module ActiveRecord
       end
 
       def get_join_keys(association_klass)
-        JoinKeys.new(join_pk(association_klass), join_foreign_key)
+        JoinKeys.new(join_primary_key(association_klass), join_foreign_key)
       end
 
       def build_scope(table, predicate_builder = predicate_builder(table))
-        Relation.create(klass, table, predicate_builder)
+        Relation.create(
+          klass,
+          table: table,
+          predicate_builder: predicate_builder
+        )
+      end
+
+      def join_primary_key(*)
+        foreign_key
       end
 
       def join_foreign_key
@@ -321,10 +316,6 @@ module ActiveRecord
           PredicateBuilder.new(TableMetadata.new(klass, table))
         end
 
-        def join_pk(_)
-          foreign_key
-        end
-
         def primary_key(klass)
           klass.primary_key || raise(UnknownPrimaryKey.new(klass))
         end
@@ -373,6 +364,17 @@ module ActiveRecord
       #
       # <tt>composed_of :balance, class_name: 'Money'</tt> returns the Money class
       # <tt>has_many :clients</tt> returns the Client class
+      #
+      #   class Company < ActiveRecord::Base
+      #     has_many :clients
+      #   end
+      #
+      #   Company.reflect_on_association(:clients).klass
+      #   # => Client
+      #
+      # <b>Note:</b> Do not call +klass.new+ or +klass.create+ to instantiate
+      # a new association object. Use +build_association+ or +create_association+
+      # instead. This allows plugins to hook into association object creation.
       def klass
         @klass ||= compute_class(class_name)
       end
@@ -391,8 +393,8 @@ module ActiveRecord
           active_record == other_aggregation.active_record
       end
 
-      def scope_for(klass)
-        scope ? klass.unscoped.instance_exec(nil, &scope) : klass.unscoped
+      def scope_for(relation, owner = nil)
+        relation.instance_exec(owner, &scope) || relation
       end
 
       private
@@ -413,23 +415,10 @@ module ActiveRecord
     # Holds all the metadata about an association as it was specified in the
     # Active Record class.
     class AssociationReflection < MacroReflection #:nodoc:
-      # Returns the target association's class.
-      #
-      #   class Author < ActiveRecord::Base
-      #     has_many :books
-      #   end
-      #
-      #   Author.reflect_on_association(:books).klass
-      #   # => Book
-      #
-      # <b>Note:</b> Do not call +klass.new+ or +klass.create+ to instantiate
-      # a new association object. Use +build_association+ or +create_association+
-      # instead. This allows plugins to hook into association object creation.
-      def klass
-        @klass ||= compute_class(class_name)
-      end
-
       def compute_class(name)
+        if polymorphic?
+          raise ArgumentError, "Polymorphic associations do not support computing the class."
+        end
         active_record.send(:compute_type, name)
       end
 
@@ -438,21 +427,13 @@ module ActiveRecord
 
       def initialize(name, scope, options, active_record)
         super
-        @automatic_inverse_of = nil
         @type         = options[:as] && (options[:foreign_type] || "#{options[:as]}_type")
-        @foreign_type = options[:foreign_type] || "#{name}_type"
+        @foreign_type = options[:polymorphic] && (options[:foreign_type] || "#{name}_type")
         @constructable = calculate_constructable(macro, options)
         @association_scope_cache = Concurrent::Map.new
 
         if options[:class_name] && options[:class_name].class == Class
-          ActiveSupport::Deprecation.warn(<<-MSG.squish)
-            Passing a class to the `class_name` is deprecated and will raise
-            an ArgumentError in Rails 5.2. It eagerloads more classes than
-            necessary and potentially creates circular dependencies.
-
-            Please pass the class name as a string:
-            `#{macro} :#{name}, class_name: '#{options[:class_name]}'`
-          MSG
+          raise ArgumentError, "A class was passed to `:class_name` but we are expecting a string."
         end
       end
 
@@ -485,10 +466,6 @@ module ActiveRecord
         options[:primary_key] || primary_key(klass || self.klass)
       end
 
-      def association_primary_key_type
-        klass.type_for_attribute(association_primary_key.to_s)
-      end
-
       def active_record_primary_key
         @active_record_primary_key ||= options[:primary_key] || primary_key(active_record)
       end
@@ -594,7 +571,7 @@ module ActiveRecord
       end
 
       VALID_AUTOMATIC_INVERSE_MACROS = [:has_many, :has_one, :belongs_to]
-      INVALID_AUTOMATIC_INVERSE_OPTIONS = [:conditions, :through, :foreign_key]
+      INVALID_AUTOMATIC_INVERSE_OPTIONS = [:through, :foreign_key]
 
       def add_as_source(seed)
         seed
@@ -622,12 +599,14 @@ module ActiveRecord
         # If it cannot find a suitable inverse association name, it returns
         # +nil+.
         def inverse_name
-          options.fetch(:inverse_of) do
-            @automatic_inverse_of ||= automatic_inverse_of
+          unless defined?(@inverse_name)
+            @inverse_name = options.fetch(:inverse_of) { automatic_inverse_of }
           end
+
+          @inverse_name
         end
 
-        # returns either false or the inverse association name that it finds.
+        # returns either +nil+ or the inverse association name that it finds.
         def automatic_inverse_of
           if can_find_inverse_of_automatically?(self)
             inverse_name = ActiveSupport::Inflector.underscore(options[:as] || active_record.name.demodulize).to_sym
@@ -644,17 +623,12 @@ module ActiveRecord
               return inverse_name
             end
           end
-
-          false
         end
 
         # Checks if the inverse reflection that is returned from the
         # +automatic_inverse_of+ method is a valid reflection. We must
         # make sure that the reflection's active_record name matches up
         # with the current reflection's klass name.
-        #
-        # Note: klass will always be valid because when there's a NameError
-        # from calling +klass+, +reflection+ will already be set to false.
         def valid_inverse_reflection?(reflection)
           reflection &&
             klass <= reflection.active_record &&
@@ -749,19 +723,22 @@ module ActiveRecord
         end
       end
 
+      def join_primary_key(klass = nil)
+        polymorphic? ? association_primary_key(klass) : association_primary_key
+      end
+
       def join_foreign_key
         foreign_key
       end
 
       private
+        def can_find_inverse_of_automatically?(_)
+          !polymorphic? && super
+        end
 
         def calculate_constructable(macro, options)
           !polymorphic?
         end
-
-        def join_pk(klass)
-          polymorphic? ? association_primary_key(klass) : association_primary_key
-        end
     end
 
     class HasAndBelongsToManyReflection < AssociationReflection # :nodoc:
@@ -866,10 +843,6 @@ module ActiveRecord
         source_reflection.join_scopes(table, predicate_builder) + super
       end
 
-      def source_type_scope
-        through_reflection.klass.where(foreign_type => options[:source_type])
-      end
-
       def has_scope?
         scope || options[:source_type] ||
           source_reflection.has_scope? ||
@@ -890,10 +863,6 @@ module ActiveRecord
         actual_source_reflection.options[:primary_key] || primary_key(klass || self.klass)
       end
 
-      def association_primary_key_type
-        klass.type_for_attribute(association_primary_key.to_s)
-      end
-
       # Gets an array of possible <tt>:through</tt> source reflection names in both singular and plural form.
       #
       #   class Post < ActiveRecord::Base
@@ -996,16 +965,14 @@ module ActiveRecord
         collect_join_reflections(seed + [self])
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
       protected
-        attr_reader :delegate_reflection
-
         def actual_source_reflection # FIXME: this is a horrible name
           source_reflection.actual_source_reflection
         end
 
       private
+        attr_reader :delegate_reflection
+
         def collect_join_reflections(seed)
           a = source_reflection.add_as_source seed
           if options[:source_type]
@@ -1029,63 +996,32 @@ module ActiveRecord
     end
 
     class PolymorphicReflection < AbstractReflection # :nodoc:
+      delegate :klass, :scope, :plural_name, :type, :get_join_keys, :scope_for, to: :@reflection
+
       def initialize(reflection, previous_reflection)
         @reflection = reflection
         @previous_reflection = previous_reflection
       end
 
-      def scopes
-        scopes = @previous_reflection.scopes
-        if @previous_reflection.options[:source_type]
-          scopes + [@previous_reflection.source_type_scope]
-        else
-          scopes
-        end
-      end
-
       def join_scopes(table, predicate_builder) # :nodoc:
         scopes = @previous_reflection.join_scopes(table, predicate_builder) + super
-        if @previous_reflection.options[:source_type]
-          scopes + [@previous_reflection.source_type_scope]
-        else
-          scopes
-        end
-      end
-
-      def klass
-        @reflection.klass
-      end
-
-      def scope
-        @reflection.scope
-      end
-
-      def plural_name
-        @reflection.plural_name
-      end
-
-      def type
-        @reflection.type
+        scopes << build_scope(table, predicate_builder).instance_exec(nil, &source_type_scope)
       end
 
       def constraints
-        @reflection.constraints + [source_type_info]
-      end
-
-      def get_join_keys(association_klass)
-        @reflection.get_join_keys(association_klass)
+        @reflection.constraints + [source_type_scope]
       end
 
       private
-        def source_type_info
+        def source_type_scope
           type = @previous_reflection.foreign_type
           source_type = @previous_reflection.options[:source_type]
           lambda { |object| where(type => source_type) }
         end
     end
 
-    class RuntimeReflection < PolymorphicReflection # :nodoc:
-      attr_accessor :next
+    class RuntimeReflection < AbstractReflection # :nodoc:
+      delegate :scope, :type, :constraints, :get_join_keys, to: :@reflection
 
       def initialize(reflection, association)
         @reflection = reflection
@@ -1096,16 +1032,8 @@ module ActiveRecord
         @association.klass
       end
 
-      def constraints
-        @reflection.constraints
-      end
-
-      def alias_candidate(name)
-        "#{plural_name}_#{name}_join"
-      end
-
-      def alias_name
-        Arel::Table.new(table_name, type_caster: klass.type_caster)
+      def aliased_table
+        @aliased_table ||= Arel::Table.new(table_name, type_caster: klass.type_caster)
       end
 
       def all_includes; yield; end
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 012bc838b1..c055b97061 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -9,8 +9,9 @@ module ActiveRecord
 
     SINGLE_VALUE_METHODS = [:limit, :offset, :lock, :readonly, :reordering,
                             :reverse_order, :distinct, :create_with, :skip_query_cache]
+
     CLAUSE_METHODS = [:where, :having, :from]
-    INVALID_METHODS_FOR_DELETE_ALL = [:limit, :distinct, :offset, :group, :having]
+    INVALID_METHODS_FOR_DELETE_ALL = [:distinct, :group, :having]
 
     VALUE_METHODS = MULTI_VALUE_METHODS + SINGLE_VALUE_METHODS + CLAUSE_METHODS
 
@@ -18,17 +19,19 @@ module ActiveRecord
     include FinderMethods, Calculations, SpawnMethods, QueryMethods, Batches, Explain, Delegation
 
     attr_reader :table, :klass, :loaded, :predicate_builder
+    attr_accessor :skip_preloading_value
     alias :model :klass
     alias :loaded? :loaded
     alias :locked? :lock_value
 
-    def initialize(klass, table, predicate_builder, values = {})
+    def initialize(klass, table: klass.arel_table, predicate_builder: klass.predicate_builder, values: {})
       @klass  = klass
       @table  = table
       @values = values
       @offsets = {}
       @loaded = false
       @predicate_builder = predicate_builder
+      @delegate_to_klass = false
     end
 
     def initialize_copy(other)
@@ -36,67 +39,6 @@ module ActiveRecord
       reset
     end
 
-    def insert(values) # :nodoc:
-      primary_key_value = nil
-
-      if primary_key && Hash === values
-        primary_key_value = values[values.keys.find { |k|
-          k.name == primary_key
-        }]
-
-        if !primary_key_value && klass.prefetch_primary_key?
-          primary_key_value = klass.next_sequence_value
-          values[arel_attribute(klass.primary_key)] = primary_key_value
-        end
-      end
-
-      im = arel.create_insert
-      im.into @table
-
-      substitutes = substitute_values values
-
-      if values.empty? # empty insert
-        im.values = Arel.sql(connection.empty_insert_statement_value)
-      else
-        im.insert substitutes
-      end
-
-      @klass.connection.insert(
-        im,
-        "SQL",
-        primary_key || false,
-        primary_key_value,
-        nil,
-      )
-    end
-
-    def _update_record(values, id, id_was) # :nodoc:
-      substitutes = substitute_values values
-
-      scope = @klass.unscoped
-
-      if @klass.finder_needs_type_condition?
-        scope.unscope!(where: @klass.inheritance_column)
-      end
-
-      relation = scope.where(@klass.primary_key => (id_was || id))
-      um = relation
-        .arel
-        .compile_update(substitutes, @klass.primary_key)
-
-      @klass.connection.update(
-        um,
-        "SQL",
-      )
-    end
-
-    def substitute_values(values) # :nodoc:
-      values.map do |arel_attr, value|
-        bind = predicate_builder.build_bind_attribute(arel_attr.name, value)
-        [arel_attr, bind]
-      end
-    end
-
     def arel_attribute(name) # :nodoc:
       klass.arel_attribute(name, table)
     end
@@ -113,8 +55,8 @@ module ActiveRecord
     #
     #   user = users.new { |user| user.name = 'Oscar' }
     #   user.name # => Oscar
-    def new(*args, &block)
-      scoping { @klass.new(*args, &block) }
+    def new(attributes = nil, &block)
+      scoping { klass.new(scope_for_create(attributes), &block) }
     end
 
     alias build new
@@ -138,8 +80,12 @@ module ActiveRecord
     #
     #   users.create(name: nil) # validation on name
     #   # => #<User id: nil, name: nil, ...>
-    def create(*args, &block)
-      scoping { @klass.create(*args, &block) }
+    def create(attributes = nil, &block)
+      if attributes.is_a?(Array)
+        attributes.collect { |attr| create(attr, &block) }
+      else
+        scoping { klass.create(scope_for_create(attributes), &block) }
+      end
     end
 
     # Similar to #create, but calls
@@ -148,8 +94,12 @@ module ActiveRecord
     #
     # Expects arguments in the same format as
     # {ActiveRecord::Base.create!}[rdoc-ref:Persistence::ClassMethods#create!].
-    def create!(*args, &block)
-      scoping { @klass.create!(*args, &block) }
+    def create!(attributes = nil, &block)
+      if attributes.is_a?(Array)
+        attributes.collect { |attr| create!(attr, &block) }
+      else
+        scoping { klass.create!(scope_for_create(attributes), &block) }
+      end
     end
 
     def first_or_create(attributes = nil, &block) # :nodoc:
@@ -195,23 +145,12 @@ module ActiveRecord
     # failed due to validation errors it won't be persisted, you get what
     # #create returns in such situation.
     #
-    # Please note *this method is not atomic*, it runs first a SELECT, and if
+    # Please note <b>this method is not atomic</b>, it runs first a SELECT, and if
     # there are no results an INSERT is attempted. If there are other threads
     # or processes there is a race condition between both calls and it could
     # be the case that you end up with two similar records.
     #
-    # Whether that is a problem or not depends on the logic of the
-    # application, but in the particular case in which rows have a UNIQUE
-    # constraint an exception may be raised, just retry:
-    #
-    #  begin
-    #    CreditAccount.transaction(requires_new: true) do
-    #      CreditAccount.find_or_create_by(user_id: user.id)
-    #    end
-    #  rescue ActiveRecord::RecordNotUnique
-    #    retry
-    #  end
-    #
+    # If this might be a problem for your application, please see #create_or_find_by.
     def find_or_create_by(attributes, &block)
       find_by(attributes) || create(attributes, &block)
     end
@@ -223,6 +162,47 @@ module ActiveRecord
       find_by(attributes) || create!(attributes, &block)
     end
 
+    # Attempts to create a record with the given attributes in a table that has a unique constraint
+    # on one or several of its columns. If a row already exists with one or several of these
+    # unique constraints, the exception such an insertion would normally raise is caught,
+    # and the existing record with those attributes is found using #find_by.
+    #
+    # This is similar to #find_or_create_by, but avoids the problem of stale reads between the SELECT
+    # and the INSERT, as that method needs to first query the table, then attempt to insert a row
+    # if none is found.
+    #
+    # There are several drawbacks to #create_or_find_by, though:
+    #
+    # * The underlying table must have the relevant columns defined with unique constraints.
+    # * A unique constraint violation may be triggered by only one, or at least less than all,
+    #   of the given attributes. This means that the subsequent #find_by may fail to find a
+    #   matching record, which will then raise an <tt>ActiveRecord::RecordNotFound</tt> exception,
+    #   rather than a record with the given attributes.
+    # * While we avoid the race condition between SELECT -> INSERT from #find_or_create_by,
+    #   we actually have another race condition between INSERT -> SELECT, which can be triggered
+    #   if a DELETE between those two statements is run by another client. But for most applications,
+    #   that's a significantly less likely condition to hit.
+    # * It relies on exception handling to handle control flow, which may be marginally slower.
+    #
+    # This method will return a record if all given attributes are covered by unique constraints
+    # (unless the INSERT -> DELETE -> SELECT race condition is triggered), but if creation was attempted
+    # and failed due to validation errors it won't be persisted, you get what #create returns in
+    # such situation.
+    def create_or_find_by(attributes, &block)
+      transaction(requires_new: true) { create(attributes, &block) }
+    rescue ActiveRecord::RecordNotUnique
+      find_by!(attributes)
+    end
+
+    # Like #create_or_find_by, but calls
+    # {create!}[rdoc-ref:Persistence::ClassMethods#create!] so an exception
+    # is raised if the created record is invalid.
+    def create_or_find_by!(attributes, &block)
+      transaction(requires_new: true) { create!(attributes, &block) }
+    rescue ActiveRecord::RecordNotUnique
+      find_by!(attributes)
+    end
+
     # Like #find_or_create_by, but calls {new}[rdoc-ref:Core#new]
     # instead of {create}[rdoc-ref:Persistence::ClassMethods#create].
     def find_or_initialize_by(attributes, &block)
@@ -243,9 +223,10 @@ module ActiveRecord
     end
 
     # Converts relation objects to Array.
-    def to_a
+    def to_ary
       records.dup
     end
+    alias to_a to_ary
 
     def records # :nodoc:
       load
@@ -334,6 +315,13 @@ module ActiveRecord
       klass.current_scope = previous
     end
 
+    def _exec_scope(*args, &block) # :nodoc:
+      @delegate_to_klass = true
+      instance_exec(*args, &block) || self
+    ensure
+      @delegate_to_klass = false
+    end
+
     # Updates all records in the current relation with details given. This method constructs a single SQL UPDATE
     # statement and sends it straight to the database. It does not instantiate the involved models and it does not
     # trigger Active Record callbacks or validations. However, values passed to #update_all will still go through
@@ -359,12 +347,17 @@ module ActiveRecord
     def update_all(updates)
       raise ArgumentError, "Empty list of attributes to change" if updates.blank?
 
+      if eager_loading?
+        relation = apply_join_dependency
+        return relation.update_all(updates)
+      end
+
       stmt = Arel::UpdateManager.new
 
-      stmt.set Arel.sql(@klass.send(:sanitize_sql_for_assignment, updates))
+      stmt.set Arel.sql(@klass.sanitize_sql_for_assignment(updates))
       stmt.table(table)
 
-      if has_join_values?
+      if has_join_values? || offset_value
         @klass.connection.join_to_update(stmt, arel, arel_attribute(primary_key))
       else
         stmt.key = arel_attribute(primary_key)
@@ -373,51 +366,44 @@ module ActiveRecord
         stmt.wheres = arel.constraints
       end
 
-      @klass.connection.update stmt, "SQL"
+      @klass.connection.update stmt, "#{@klass} Update All"
     end
 
-    # Updates an object (or multiple objects) and saves it to the database, if validations pass.
-    # The resulting object is returned whether the object was saved successfully to the database or not.
+    # Touches all records in the current relation without instantiating records first with the updated_at/on attributes
+    # set to the current time or the time specified.
+    # This method can be passed attribute names and an optional time argument.
+    # If attribute names are passed, they are updated along with updated_at/on attributes.
+    # If no time argument is passed, the current time is used as default.
     #
-    # ==== Parameters
+    # === Examples
     #
-    # * +id+ - This should be the id or an array of ids to be updated.
-    # * +attributes+ - This should be a hash of attributes or an array of hashes.
+    #   # Touch all records
+    #   Person.all.touch_all
+    #   # => "UPDATE \"people\" SET \"updated_at\" = '2018-01-04 22:55:23.132670'"
     #
-    # ==== Examples
+    #   # Touch multiple records with a custom attribute
+    #   Person.all.touch_all(:created_at)
+    #   # => "UPDATE \"people\" SET \"updated_at\" = '2018-01-04 22:55:23.132670', \"created_at\" = '2018-01-04 22:55:23.132670'"
     #
-    #   # Updates one record
-    #   Person.update(15, user_name: 'Samuel', group: 'expert')
-    #
-    #   # Updates multiple records
-    #   people = { 1 => { "first_name" => "David" }, 2 => { "first_name" => "Jeremy" } }
-    #   Person.update(people.keys, people.values)
-    #
-    #   # Updates multiple records from the result of a relation
-    #   people = Person.where(group: 'expert')
-    #   people.update(group: 'masters')
-    #
-    # Note: Updating a large number of records will run an
-    # UPDATE query for each record, which may cause a performance
-    # issue. When running callbacks is not needed for each record update,
-    # it is preferred to use #update_all for updating all records
-    # in a single query.
-    def update(id = :all, attributes)
-      if id.is_a?(Array)
-        id.map.with_index { |one_id, idx| update(one_id, attributes[idx]) }
-      elsif id == :all
-        records.each { |record| record.update(attributes) }
-      else
-        if ActiveRecord::Base === id
-          raise ArgumentError, <<-MSG.squish
-            You are passing an instance of ActiveRecord::Base to `update`.
-            Please pass the id of the object by calling `.id`.
-          MSG
-        end
-        object = find(id)
-        object.update(attributes)
-        object
+    #   # Touch multiple records with a specified time
+    #   Person.all.touch_all(time: Time.new(2020, 5, 16, 0, 0, 0))
+    #   # => "UPDATE \"people\" SET \"updated_at\" = '2020-05-16 00:00:00'"
+    #
+    #   # Touch records with scope
+    #   Person.where(name: 'David').touch_all
+    #   # => "UPDATE \"people\" SET \"updated_at\" = '2018-01-04 22:55:23.132670' WHERE \"people\".\"name\" = 'David'"
+    def touch_all(*names, time: nil)
+      attributes = Array(names) + klass.timestamp_attributes_for_update_in_model
+      time ||= klass.current_time_from_proper_timezone
+      updates = {}
+      attributes.each { |column| updates[column] = time }
+
+      if klass.locking_enabled?
+        quoted_locking_column = connection.quote_column_name(klass.locking_column)
+        updates = sanitize_sql_for_assignment(updates) + ", #{quoted_locking_column} = COALESCE(#{quoted_locking_column}, 0) + 1"
       end
+
+      update_all(updates)
     end
 
     # Destroys the records by instantiating each
@@ -440,33 +426,6 @@ module ActiveRecord
       records.each(&:destroy).tap { reset }
     end
 
-    # Destroy an object (or multiple objects) that has the given id. The object is instantiated first,
-    # therefore all callbacks and filters are fired off before the object is deleted. This method is
-    # less efficient than #delete but allows cleanup methods and other actions to be run.
-    #
-    # This essentially finds the object (or multiple objects) with the given id, creates a new object
-    # from the attributes, and then calls destroy on it.
-    #
-    # ==== Parameters
-    #
-    # * +id+ - Can be either an Integer or an Array of Integers.
-    #
-    # ==== Examples
-    #
-    #   # Destroy a single object
-    #   Todo.destroy(1)
-    #
-    #   # Destroy multiple objects
-    #   todos = [1,2,3]
-    #   Todo.destroy(todos)
-    def destroy(id)
-      if id.is_a?(Array)
-        id.map { |one_id| destroy(one_id) }
-      else
-        find(id).destroy
-      end
-    end
-
     # Deletes the records without instantiating the records
     # first, and hence not calling the {#destroy}[rdoc-ref:Persistence#destroy]
     # method nor invoking callbacks.
@@ -483,8 +442,8 @@ module ActiveRecord
     #
     # If an invalid method is supplied, #delete_all raises an ActiveRecordError:
     #
-    #   Post.limit(100).delete_all
-    #   # => ActiveRecord::ActiveRecordError: delete_all doesn't support limit
+    #   Post.distinct.delete_all
+    #   # => ActiveRecord::ActiveRecordError: delete_all doesn't support distinct
     def delete_all
       invalid_methods = INVALID_METHODS_FOR_DELETE_ALL.select do |method|
         value = get_value(method)
@@ -494,44 +453,26 @@ module ActiveRecord
         raise ActiveRecordError.new("delete_all doesn't support #{invalid_methods.join(', ')}")
       end
 
+      if eager_loading?
+        relation = apply_join_dependency
+        return relation.delete_all
+      end
+
       stmt = Arel::DeleteManager.new
       stmt.from(table)
 
-      if has_join_values?
+      if has_join_values? || has_limit_or_offset?
         @klass.connection.join_to_delete(stmt, arel, arel_attribute(primary_key))
       else
         stmt.wheres = arel.constraints
       end
 
-      affected = @klass.connection.delete(stmt, "SQL")
+      affected = @klass.connection.delete(stmt, "#{@klass} Destroy")
 
       reset
       affected
     end
 
-    # Deletes the row with a primary key matching the +id+ argument, using a
-    # SQL +DELETE+ statement, and returns the number of rows deleted. Active
-    # Record objects are not instantiated, so the object's callbacks are not
-    # executed, including any <tt>:dependent</tt> association options.
-    #
-    # You can delete multiple rows at once by passing an Array of <tt>id</tt>s.
-    #
-    # Note: Although it is often much faster than the alternative,
-    # #destroy, skipping callbacks might bypass business logic in
-    # your application that ensures referential integrity or performs other
-    # essential jobs.
-    #
-    # ==== Examples
-    #
-    #   # Delete a single row
-    #   Todo.delete(1)
-    #
-    #   # Delete multiple rows
-    #   Todo.delete([2,3,4])
-    def delete(id_or_array)
-      where(primary_key => id_or_array).delete_all
-    end
-
     # Causes the records to be loaded from the database if they have not
     # been loaded already. You can use this if for some reason you need
     # to explicitly load some records before actually using them. The
@@ -551,6 +492,7 @@ module ActiveRecord
     end
 
     def reset
+      @delegate_to_klass = false
       @to_sql = @arel = @loaded = @should_eager_load = nil
       @records = [].freeze
       @offsets = {}
@@ -566,7 +508,7 @@ module ActiveRecord
                     relation = self
 
                     if eager_loading?
-                      find_with_associations { |rel, _| relation = rel }
+                      apply_join_dependency { |rel, _| relation = rel }
                     end
 
                     conn = klass.connection
@@ -580,12 +522,14 @@ module ActiveRecord
     #
     #   User.where(name: 'Oscar').where_values_hash
     #   # => {name: "Oscar"}
-    def where_values_hash(relation_table_name = table_name)
+    def where_values_hash(relation_table_name = klass.table_name)
       where_clause.to_h(relation_table_name)
     end
 
-    def scope_for_create
-      where_values_hash.merge!(create_with_value.stringify_keys)
+    def scope_for_create(attributes = nil)
+      scope = where_values_hash.merge!(create_with_value.stringify_keys)
+      scope.merge!(attributes) if attributes
+      scope
     end
 
     # Returns true if relation needs eager loading.
@@ -645,6 +589,21 @@ module ActiveRecord
       limit_value || offset_value
     end
 
+    def alias_tracker(joins = [], aliases = nil) # :nodoc:
+      joins += [aliases] if aliases
+      ActiveRecord::Associations::AliasTracker.create(connection, table.name, joins)
+    end
+
+    def preload_associations(records) # :nodoc:
+      preload = preload_values
+      preload += includes_values unless eager_loading?
+      preloader = nil
+      preload.each do |associations|
+        preloader ||= build_preloader
+        preloader.preload records, associations
+      end
+    end
+
     protected
 
       def load_records(records)
@@ -662,7 +621,7 @@ module ActiveRecord
         skip_query_cache_if_necessary do
           @records =
             if eager_loading?
-              find_with_associations do |relation, join_dependency|
+              apply_join_dependency do |relation, join_dependency|
                 if ActiveRecord::NullRelation === relation
                   []
                 else
@@ -674,13 +633,7 @@ module ActiveRecord
               klass.find_by_sql(arel, &block).freeze
             end
 
-          preload = preload_values
-          preload += includes_values unless eager_loading?
-          preloader = nil
-          preload.each do |associations|
-            preloader ||= build_preloader
-            preloader.preload @records, associations
-          end
+          preload_associations(@records) unless skip_preloading_value
 
           @records.each(&:readonly!) if readonly_value
 
diff --git a/activerecord/lib/active_record/relation/batches.rb b/activerecord/lib/active_record/relation/batches.rb
index fa19c679cf..ec4bb06c57 100644
--- a/activerecord/lib/active_record/relation/batches.rb
+++ b/activerecord/lib/active_record/relation/batches.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "batches/batch_enumerator"
+require "active_record/relation/batches/batch_enumerator"
 
 module ActiveRecord
   module Batches
@@ -251,20 +251,33 @@ module ActiveRecord
           end
         end
 
-        batch_relation = relation.where(arel_attribute(primary_key).gt(primary_key_offset))
+        bind = primary_key_bind(primary_key_offset)
+        batch_relation = relation.where(arel_attribute(primary_key).gt(bind))
       end
     end
 
     private
 
       def apply_limits(relation, start, finish)
-        relation = relation.where(arel_attribute(primary_key).gteq(start)) if start
-        relation = relation.where(arel_attribute(primary_key).lteq(finish)) if finish
+        relation = apply_start_limit(relation, start) if start
+        relation = apply_finish_limit(relation, finish) if finish
         relation
       end
 
+      def apply_start_limit(relation, start)
+        relation.where(arel_attribute(primary_key).gteq(primary_key_bind(start)))
+      end
+
+      def apply_finish_limit(relation, finish)
+        relation.where(arel_attribute(primary_key).lteq(primary_key_bind(finish)))
+      end
+
+      def primary_key_bind(value)
+        predicate_builder.build_bind_attribute(primary_key, value)
+      end
+
       def batch_order
-        "#{quoted_table_name}.#{quoted_primary_key} ASC"
+        arel_attribute(primary_key).asc
       end
 
       def act_on_ignored_order(error_on_ignore)
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 42d43224fa..f215c95f51 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -130,8 +130,15 @@ module ActiveRecord
     #      end
     def calculate(operation, column_name)
       if has_include?(column_name)
-        relation = construct_relation_for_association_calculations
-        relation.distinct! if operation.to_s.downcase == "count"
+        relation = apply_join_dependency
+
+        if operation.to_s.downcase == "count"
+          relation.distinct!
+          # PostgreSQL: ORDER BY expressions must appear in SELECT list when using DISTINCT
+          if (column_name == :all || column_name.nil?) && select_values.empty?
+            relation.order_values = []
+          end
+        end
 
         relation.calculate(operation, column_name)
       else
@@ -180,8 +187,10 @@ module ActiveRecord
       end
 
       if has_include?(column_names.first)
-        construct_relation_for_association_calculations.pluck(*column_names)
+        relation = apply_join_dependency
+        relation.pluck(*column_names)
       else
+        enforce_raw_sql_whitelist(column_names)
         relation = spawn
         relation.select_values = column_names.map { |cn|
           @klass.has_attribute?(cn) || @klass.attribute_alias?(cn) ? arel_attribute(cn) : cn
@@ -191,6 +200,24 @@ module ActiveRecord
       end
     end
 
+    # Pick the value(s) from the named column(s) in the current relation.
+    # This is short-hand for <tt>relation.limit(1).pluck(*column_names).first</tt>, and is primarily useful
+    # when you have a relation that's already narrowed down to a single row.
+    #
+    # Just like #pluck, #pick will only load the actual value, not the entire record object, so it's also
+    # more efficient. The value is, again like with pluck, typecast by the column type.
+    #
+    #   Person.where(id: 1).pick(:name)
+    #   # SELECT people.name FROM people WHERE id = 1 LIMIT 1
+    #   # => 'David'
+    #
+    #   Person.where(id: 1).pick(:name, :email_address)
+    #   # SELECT people.name, people.email_address FROM people WHERE id = 1 LIMIT 1
+    #   # => [ 'David', 'david@loudthinking.com' ]
+    def pick(*column_names)
+      limit(1).pluck(*column_names).first
+    end
+
     # Pluck all the ID's for the relation using the table's primary key
     #
     #   Person.ids # SELECT people.id FROM people
@@ -215,7 +242,7 @@ module ActiveRecord
         if operation == "count"
           column_name ||= select_for_count
           if column_name == :all
-            if distinct && !(has_limit_or_offset? && order_values.any?)
+            if distinct && (group_values.any? || select_values.empty? && order_values.empty?)
               column_name = primary_key
             end
           elsif column_name =~ /\s*DISTINCT[\s(]+/i
@@ -233,7 +260,7 @@ module ActiveRecord
       def aggregate_column(column_name)
         return column_name if Arel::Expressions === column_name
 
-        if @klass.has_attribute?(column_name.to_s) || @klass.attribute_alias?(column_name.to_s)
+        if @klass.has_attribute?(column_name) || @klass.attribute_alias?(column_name)
           @klass.arel_attribute(column_name)
         else
           Arel.sql(column_name == :all ? "*" : column_name.to_s)
@@ -247,7 +274,7 @@ module ActiveRecord
       def execute_simple_calculation(operation, column_name, distinct) #:nodoc:
         column_alias = column_name
 
-        if operation == "count" && has_limit_or_offset?
+        if operation == "count" && (column_name == :all && distinct || has_limit_or_offset?)
           # Shortcut when limit is zero.
           return 0 if limit_value == 0
 
@@ -389,14 +416,12 @@ module ActiveRecord
       end
 
       def build_count_subquery(relation, column_name, distinct)
-        relation.select_values = [
-          if column_name == :all
-            distinct ? table[Arel.star] : Arel.sql("1")
-          else
-            column_alias = Arel.sql("count_column")
-            aggregate_column(column_name).as(column_alias)
-          end
-        ]
+        if column_name == :all
+          relation.select_values = [ Arel.sql(FinderMethods::ONE_AS_ONE) ] unless distinct
+        else
+          column_alias = Arel.sql("count_column")
+          relation.select_values = [ aggregate_column(column_name).as(column_alias) ]
+        end
 
         subquery = relation.arel.as(Arel.sql("subquery_for_count"))
         select_value = operation_over_aggregate_column(column_alias || Arel.star, "count", false)
diff --git a/activerecord/lib/active_record/relation/delegation.rb b/activerecord/lib/active_record/relation/delegation.rb
index 4793f2a49b..488f71cdde 100644
--- a/activerecord/lib/active_record/relation/delegation.rb
+++ b/activerecord/lib/active_record/relation/delegation.rb
@@ -38,13 +38,12 @@ module ActiveRecord
     # may vary depending on the klass of a relation, so we create a subclass of Relation
     # for each different klass, and the delegations are compiled into that subclass only.
 
-    delegate :to_xml, :encode_with, :length, :each, :uniq, :to_ary, :join,
-             :[], :&, :|, :+, :-, :sample, :reverse, :compact, :in_groups, :in_groups_of,
+    delegate :to_xml, :encode_with, :length, :each, :join,
+             :[], :&, :|, :+, :-, :sample, :reverse, :rotate, :compact, :in_groups, :in_groups_of,
              :to_sentence, :to_formatted_s, :as_json,
-             :shuffle, :split, :index, to: :records
+             :shuffle, :split, :slice, :index, :rindex, to: :records
 
-    delegate :table_name, :quoted_table_name, :primary_key, :quoted_primary_key,
-             :connection, :columns_hash, to: :klass
+    delegate :primary_key, :connection, to: :klass
 
     module ClassSpecificRelation # :nodoc:
       extend ActiveSupport::Concern
@@ -75,13 +74,6 @@ module ActiveRecord
             end
           end
         end
-
-        def delegate(method, opts = {})
-          @delegation_mutex.synchronize do
-            return if method_defined?(method)
-            super
-          end
-        end
       end
 
       private
@@ -90,10 +82,14 @@ module ActiveRecord
           if @klass.respond_to?(method)
             self.class.delegate_to_scoped_klass(method)
             scoping { @klass.public_send(method, *args, &block) }
+          elsif @delegate_to_klass && @klass.respond_to?(method, true)
+            ActiveSupport::Deprecation.warn \
+              "Delegating missing #{method} method to #{@klass}. " \
+              "Accessibility of private/protected class methods in :scope is deprecated and will be removed in Rails 6.0."
+            @klass.send(method, *args, &block)
           elsif arel.respond_to?(method)
             ActiveSupport::Deprecation.warn \
               "Delegating #{method} to arel is deprecated and will be removed in Rails 6.0."
-            self.class.delegate method, to: :arel
             arel.public_send(method, *args, &block)
           else
             super
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index 2aed941916..f7613a187d 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -18,9 +18,10 @@ module ActiveRecord
     #   Person.find([1])        # returns an array for the object with ID = 1
     #   Person.where("administrator = 1").order("created_on DESC").find(1)
     #
-    # NOTE: The returned records may not be in the same order as the ids you
-    # provide since database rows are unordered. You will need to provide an explicit QueryMethods#order
-    # option if you want the results to be sorted.
+    # NOTE: The returned records are in the same order as the ids you provide.
+    # If you want the results to be sorted by database, you can use ActiveRecord::QueryMethods#where
+    # method and provide an explicit ActiveRecord::QueryMethods#order option.
+    # But ActiveRecord::QueryMethods#where method doesn't raise ActiveRecord::RecordNotFound.
     #
     # ==== Find with lock
     #
@@ -88,7 +89,7 @@ module ActiveRecord
       where(arg, *args).take!
     rescue ::RangeError
       raise RecordNotFound.new("Couldn't find #{@klass.name} with an out of range value",
-                               @klass.name)
+                               @klass.name, @klass.primary_key)
     end
 
     # Gives a record (or N records if a parameter is supplied) without any implied
@@ -147,7 +148,7 @@ module ActiveRecord
     #
     #   [#<Person id:4>, #<Person id:3>, #<Person id:2>]
     def last(limit = nil)
-      return find_last(limit) if loaded? || limit_value
+      return find_last(limit) if loaded? || has_limit_or_offset?
 
       result = ordered_relation.limit(limit)
       result = result.reverse_order!
@@ -284,7 +285,7 @@ module ActiveRecord
     # * Hash - Finds the record that matches these +find+-style conditions
     #   (such as <tt>{name: 'David'}</tt>).
     # * +false+ - Returns always +false+.
-    # * No args - Returns +false+ if the table is empty, +true+ otherwise.
+    # * No args - Returns +false+ if the relation is empty, +true+ otherwise.
     #
     # For more information about specifying conditions as a hash or array,
     # see the Conditions section in the introduction to ActiveRecord::Base.
@@ -300,6 +301,7 @@ module ActiveRecord
     #   Person.exists?(name: 'David')
     #   Person.exists?(false)
     #   Person.exists?
+    #   Person.where(name: 'Spartacus', rating: 4).exists?
     def exists?(conditions = :none)
       if Base === conditions
         raise ArgumentError, <<-MSG.squish
@@ -310,12 +312,12 @@ module ActiveRecord
 
       return false if !conditions || limit_value == 0
 
-      relation = self unless eager_loading?
-      relation ||= apply_join_dependency(self, construct_join_dependency(eager_loading: false))
-
-      return false if ActiveRecord::NullRelation === relation
+      if eager_loading?
+        relation = apply_join_dependency(eager_loading: false)
+        return relation.exists?(conditions)
+      end
 
-      relation = construct_relation_for_exists(relation, conditions)
+      relation = construct_relation_for_exists(conditions)
 
       skip_query_cache_if_necessary { connection.select_value(relation.arel, "#{name} Exists") } ? true : false
     rescue ::RangeError
@@ -338,7 +340,7 @@ module ActiveRecord
       if ids.nil?
         error = "Couldn't find #{name}".dup
         error << " with#{conditions}" if conditions
-        raise RecordNotFound.new(error, name)
+        raise RecordNotFound.new(error, name, key)
       elsif Array(ids).size == 1
         error = "Couldn't find #{name} with '#{key}'=#{ids}#{conditions}"
         raise RecordNotFound.new(error, name, key, ids)
@@ -346,7 +348,7 @@ module ActiveRecord
         error = "Couldn't find all #{name.pluralize} with '#{key}': ".dup
         error << "(#{ids.join(", ")})#{conditions} (found #{result_size} results, but was looking for #{expected_size})."
         error << " Couldn't find #{name.pluralize(not_found_ids.size)} with #{key.to_s.pluralize(not_found_ids.size)} #{not_found_ids.join(', ')}." if not_found_ids
-        raise RecordNotFound.new(error, name, primary_key, ids)
+        raise RecordNotFound.new(error, name, key, ids)
       end
     end
 
@@ -356,27 +358,8 @@ module ActiveRecord
         offset_value || 0
       end
 
-      def find_with_associations
-        # NOTE: the JoinDependency constructed here needs to know about
-        #       any joins already present in `self`, so pass them in
-        #
-        # failing to do so means that in cases like activerecord/test/cases/associations/inner_join_association_test.rb:136
-        # incorrect SQL is generated. In that case, the join dependency for
-        # SpecialCategorizations is constructed without knowledge of the
-        # preexisting join in joins_values to categorizations (by way of
-        # the `has_many :through` for categories).
-        #
-        join_dependency = construct_join_dependency(joins_values)
-
-        aliases  = join_dependency.aliases
-        relation = select aliases.columns
-        relation = apply_join_dependency(relation, join_dependency)
-
-        yield relation, join_dependency
-      end
-
-      def construct_relation_for_exists(relation, conditions)
-        relation = relation.except(:select, :distinct, :order)._select!(ONE_AS_ONE).limit!(1)
+      def construct_relation_for_exists(conditions)
+        relation = except(:select, :distinct, :order)._select!(ONE_AS_ONE).limit!(1)
 
         case conditions
         when Array, Hash
@@ -388,32 +371,39 @@ module ActiveRecord
         relation
       end
 
-      def construct_join_dependency(joins = [], eager_loading: true)
+      def construct_join_dependency
         including = eager_load_values + includes_values
-        ActiveRecord::Associations::JoinDependency.new(klass, table, including, joins, eager_loading: eager_loading)
+        joins = joins_values.select { |join| join.is_a?(Arel::Nodes::Join) }
+        ActiveRecord::Associations::JoinDependency.new(
+          klass, table, including, alias_tracker(joins)
+        )
       end
 
-      def construct_relation_for_association_calculations
-        apply_join_dependency(self, construct_join_dependency(joins_values))
-      end
-
-      def apply_join_dependency(relation, join_dependency)
-        relation = relation.except(:includes, :eager_load, :preload).joins!(join_dependency)
+      def apply_join_dependency(eager_loading: true)
+        join_dependency = construct_join_dependency
+        relation = except(:includes, :eager_load, :preload).joins!(join_dependency)
 
-        if using_limitable_reflections?(join_dependency.reflections)
-          relation
-        else
-          if relation.limit_value
+        if eager_loading && !using_limitable_reflections?(join_dependency.reflections)
+          if has_limit_or_offset?
             limited_ids = limited_ids_for(relation)
             limited_ids.empty? ? relation.none! : relation.where!(primary_key => limited_ids)
           end
-          relation.except(:limit, :offset)
+          relation.limit_value = relation.offset_value = nil
+        end
+
+        if block_given?
+          relation._select!(join_dependency.aliases.columns)
+          yield relation, join_dependency
+        else
+          relation
         end
       end
 
       def limited_ids_for(relation)
         values = @klass.connection.columns_for_distinct(
-          "#{quoted_table_name}.#{quoted_primary_key}", relation.order_values)
+          connection.column_name_from_arel_node(arel_attribute(primary_key)),
+          relation.order_values
+        )
 
         relation = relation.except(:select).select(values).distinct!
 
@@ -433,9 +423,12 @@ module ActiveRecord
 
         ids = ids.flatten.compact.uniq
 
+        model_name = @klass.name
+
         case ids.size
         when 0
-          raise RecordNotFound, "Couldn't find #{@klass.name} without an ID"
+          error_message = "Couldn't find #{model_name} without an ID"
+          raise RecordNotFound.new(error_message, model_name, primary_key)
         when 1
           result = find_one(ids.first)
           expects_array ? [ result ] : result
@@ -443,7 +436,8 @@ module ActiveRecord
           find_some(ids)
         end
       rescue ::RangeError
-        raise RecordNotFound, "Couldn't find #{@klass.name} with an out of range ID"
+        error_message = "Couldn't find #{model_name} with an out of range ID"
+        raise RecordNotFound.new(error_message, model_name, primary_key, ids)
       end
 
       def find_one(id)
@@ -527,7 +521,11 @@ module ActiveRecord
         else
           relation = ordered_relation
 
-          if limit_value.nil? || index < limit_value
+          if limit_value
+            limit = [limit_value - index, limit].min
+          end
+
+          if limit > 0
             relation = relation.offset(offset_index + index) unless index.zero?
             relation.limit(limit).to_a
           else
@@ -542,12 +540,11 @@ module ActiveRecord
         else
           relation = ordered_relation
 
-          relation.to_a[-index]
-          # TODO: can be made more performant on large result sets by
-          # for instance, last(index)[-index] (which would require
-          # refactoring the last(n) finder method to make test suite pass),
-          # or by using a combination of reverse_order, limit, and offset,
-          # e.g., reverse_order.offset(index-1).first
+          if equal?(relation) || has_limit_or_offset?
+            relation.records[-index]
+          else
+            relation.last(index)[-index]
+          end
         end
       end
 
diff --git a/activerecord/lib/active_record/relation/merger.rb b/activerecord/lib/active_record/relation/merger.rb
index 03824ffff9..25510d4a57 100644
--- a/activerecord/lib/active_record/relation/merger.rb
+++ b/activerecord/lib/active_record/relation/merger.rb
@@ -23,7 +23,11 @@ module ActiveRecord
       # build a relation to merge in rather than directly merging
       # the values.
       def other
-        other = Relation.create(relation.klass, relation.table, relation.predicate_builder)
+        other = Relation.create(
+          relation.klass,
+          table: relation.table,
+          predicate_builder: relation.predicate_builder
+        )
         hash.each { |k, v|
           if k == :joins
             if Hash === v
@@ -52,7 +56,7 @@ module ActiveRecord
 
       NORMAL_VALUES = Relation::VALUE_METHODS -
                       Relation::CLAUSE_METHODS -
-                      [:includes, :preload, :joins, :order, :reverse_order, :lock, :create_with, :reordering] # :nodoc:
+                      [:includes, :preload, :joins, :left_outer_joins, :order, :reverse_order, :lock, :create_with, :reordering] # :nodoc:
 
       def normal_values
         NORMAL_VALUES
@@ -79,6 +83,7 @@ module ActiveRecord
         merge_clauses
         merge_preloads
         merge_joins
+        merge_outer_joins
 
         relation
       end
@@ -112,22 +117,43 @@ module ActiveRecord
           if other.klass == relation.klass
             relation.joins!(*other.joins_values)
           else
-            joins_dependency, rest = other.joins_values.partition do |join|
+            alias_tracker = nil
+            joins_dependency = other.joins_values.map do |join|
               case join
               when Hash, Symbol, Array
-                true
+                alias_tracker ||= other.alias_tracker
+                ActiveRecord::Associations::JoinDependency.new(
+                  other.klass, other.table, join, alias_tracker
+                )
               else
-                false
+                join
               end
             end
 
-            join_dependency = ActiveRecord::Associations::JoinDependency.new(
-              other.klass, other.table, joins_dependency, []
-            )
+            relation.joins!(*joins_dependency)
+          end
+        end
+
+        def merge_outer_joins
+          return if other.left_outer_joins_values.blank?
 
-            relation.joins! rest
+          if other.klass == relation.klass
+            relation.left_outer_joins!(*other.left_outer_joins_values)
+          else
+            alias_tracker = nil
+            joins_dependency = other.left_outer_joins_values.map do |join|
+              case join
+              when Hash, Symbol, Array
+                alias_tracker ||= other.alias_tracker
+                ActiveRecord::Associations::JoinDependency.new(
+                  other.klass, other.table, join, alias_tracker
+                )
+              else
+                join
+              end
+            end
 
-            @relation = relation.joins join_dependency
+            relation.left_outer_joins!(*joins_dependency)
           end
         end
 
diff --git a/activerecord/lib/active_record/relation/predicate_builder.rb b/activerecord/lib/active_record/relation/predicate_builder.rb
index 5c42414072..7a0edcbc33 100644
--- a/activerecord/lib/active_record/relation/predicate_builder.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder.rb
@@ -13,6 +13,7 @@ module ActiveRecord
       register_handler(Range, RangeHandler.new(self))
       register_handler(Relation, RelationHandler.new)
       register_handler(Array, ArrayHandler.new(self))
+      register_handler(Set, ArrayHandler.new(self))
     end
 
     def build_from_hash(attributes)
@@ -56,9 +57,6 @@ module ActiveRecord
     end
 
     protected
-
-      attr_reader :table
-
       def expand_from_hash(attributes)
         return ["1=0"] if attributes.empty?
 
@@ -85,6 +83,18 @@ module ActiveRecord
               expand_from_hash(query).reduce(&:and)
             end
             queries.reduce(&:or)
+          elsif table.aggregated_with?(key)
+            mapping = table.reflect_on_aggregation(key).mapping
+            queries = Array.wrap(value).map do |object|
+              mapping.map do |field_attr, aggregate_attr|
+                if mapping.size == 1 && !object.respond_to?(aggregate_attr)
+                  build(table.arel_attribute(field_attr), object)
+                else
+                  build(table.arel_attribute(field_attr), object.send(aggregate_attr))
+                end
+              end.reduce(&:and)
+            end
+            queries.reduce(&:or)
           # FIXME: Deprecate this and provide a public API to force equality
           elsif (value.is_a?(Range) || value.is_a?(Array)) &&
             table.type(key.to_s).respond_to?(:subtype)
@@ -96,6 +106,7 @@ module ActiveRecord
       end
 
     private
+      attr_reader :table
 
       def associated_predicate_builder(association_name)
         self.class.new(table.associated_table(association_name))
@@ -123,11 +134,11 @@ module ActiveRecord
   end
 end
 
-require_relative "predicate_builder/array_handler"
-require_relative "predicate_builder/base_handler"
-require_relative "predicate_builder/basic_object_handler"
-require_relative "predicate_builder/range_handler"
-require_relative "predicate_builder/relation_handler"
+require "active_record/relation/predicate_builder/array_handler"
+require "active_record/relation/predicate_builder/base_handler"
+require "active_record/relation/predicate_builder/basic_object_handler"
+require "active_record/relation/predicate_builder/range_handler"
+require "active_record/relation/predicate_builder/relation_handler"
 
-require_relative "predicate_builder/association_query_value"
-require_relative "predicate_builder/polymorphic_array_value"
+require "active_record/relation/predicate_builder/association_query_value"
+require "active_record/relation/predicate_builder/polymorphic_array_value"
diff --git a/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
index 2fd75c8958..64bf83e3c1 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
@@ -34,8 +34,7 @@ module ActiveRecord
         array_predicates.inject(&:or)
       end
 
-      protected
-
+      private
         attr_reader :predicate_builder
 
         module NullPredicate # :nodoc:
diff --git a/activerecord/lib/active_record/relation/predicate_builder/association_query_value.rb b/activerecord/lib/active_record/relation/predicate_builder/association_query_value.rb
index 0255a65bfe..88cd71cf69 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/association_query_value.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/association_query_value.rb
@@ -12,12 +12,9 @@ module ActiveRecord
         [associated_table.association_join_foreign_key.to_s => ids]
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
+      private
         attr_reader :associated_table, :value
 
-      private
         def ids
           case value
           when Relation
@@ -30,7 +27,7 @@ module ActiveRecord
         end
 
         def primary_key
-          associated_table.association_join_keys.key
+          associated_table.association_join_primary_key
         end
 
         def convert_to_id(value)
diff --git a/activerecord/lib/active_record/relation/predicate_builder/base_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/base_handler.rb
index 112821135f..10c5c1a66a 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/base_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/base_handler.rb
@@ -11,8 +11,7 @@ module ActiveRecord
         predicate_builder.build(attribute, value.id)
       end
 
-      protected
-
+      private
         attr_reader :predicate_builder
     end
   end
diff --git a/activerecord/lib/active_record/relation/predicate_builder/basic_object_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/basic_object_handler.rb
index 34db266f05..e8c9f60860 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/basic_object_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/basic_object_handler.rb
@@ -12,8 +12,7 @@ module ActiveRecord
         attribute.eq(bind)
       end
 
-      protected
-
+      private
         attr_reader :predicate_builder
     end
   end
diff --git a/activerecord/lib/active_record/relation/predicate_builder/polymorphic_array_value.rb b/activerecord/lib/active_record/relation/predicate_builder/polymorphic_array_value.rb
index b87b5c36dd..aae04d9348 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/polymorphic_array_value.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/polymorphic_array_value.rb
@@ -17,27 +17,26 @@ module ActiveRecord
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
+      private
         attr_reader :associated_table, :values
 
-      private
         def type_to_ids_mapping
           default_hash = Hash.new { |hsh, key| hsh[key] = [] }
-          values.each_with_object(default_hash) { |value, hash| hash[base_class(value).name] << convert_to_id(value) }
+          values.each_with_object(default_hash) do |value, hash|
+            hash[klass(value).polymorphic_name] << convert_to_id(value)
+          end
         end
 
         def primary_key(value)
-          associated_table.association_primary_key(base_class(value))
+          associated_table.association_join_primary_key(klass(value))
         end
 
-        def base_class(value)
+        def klass(value)
           case value
           when Base
-            value.class.base_class
+            value.class
           when Relation
-            value.klass.base_class
+            value.klass
           end
         end
 
diff --git a/activerecord/lib/active_record/relation/predicate_builder/range_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/range_handler.rb
index 6d16579708..44bb2c7ab6 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/range_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/range_handler.rb
@@ -16,15 +16,16 @@ module ActiveRecord
       def call(attribute, value)
         begin_bind = predicate_builder.build_bind_attribute(attribute.name, value.begin)
         end_bind = predicate_builder.build_bind_attribute(attribute.name, value.end)
-        if value.begin.respond_to?(:infinite?) && value.begin.infinite?
-          if value.end.respond_to?(:infinite?) && value.end.infinite?
+
+        if begin_bind.value.infinity?
+          if end_bind.value.infinity?
             attribute.not_in([])
           elsif value.exclude_end?
             attribute.lt(end_bind)
           else
             attribute.lteq(end_bind)
           end
-        elsif value.end.respond_to?(:infinite?) && value.end.infinite?
+        elsif end_bind.value.infinity?
           attribute.gteq(begin_bind)
         elsif value.exclude_end?
           attribute.gteq(begin_bind).and(attribute.lt(end_bind))
@@ -33,8 +34,7 @@ module ActiveRecord
         end
       end
 
-      protected
-
+      private
         attr_reader :predicate_builder
     end
   end
diff --git a/activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb
index f51ea4fde0..c8bbfa5051 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb
@@ -4,6 +4,10 @@ module ActiveRecord
   class PredicateBuilder
     class RelationHandler # :nodoc:
       def call(attribute, value)
+        if value.eager_loading?
+          value = value.send(:apply_join_dependency)
+        end
+
         if value.select_values.empty?
           value = value.select(value.arel_attribute(value.klass.primary_key))
         end
diff --git a/activerecord/lib/active_record/relation/query_attribute.rb b/activerecord/lib/active_record/relation/query_attribute.rb
index 5a9a7fd432..f64bd30d38 100644
--- a/activerecord/lib/active_record/relation/query_attribute.rb
+++ b/activerecord/lib/active_record/relation/query_attribute.rb
@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
-require_relative "../attribute"
+require "active_model/attribute"
 
 module ActiveRecord
   class Relation
-    class QueryAttribute < Attribute # :nodoc:
+    class QueryAttribute < ActiveModel::Attribute # :nodoc:
       def type_cast(value)
         value
       end
@@ -21,6 +21,23 @@ module ActiveRecord
         !value_before_type_cast.is_a?(StatementCache::Substitute) &&
           (value_before_type_cast.nil? || value_for_database.nil?)
       end
+
+      def boundable?
+        return @_boundable if defined?(@_boundable)
+        nil?
+        @_boundable = true
+      rescue ::RangeError
+        @_boundable = false
+      end
+
+      def infinity?
+        _infinity?(value_before_type_cast) || boundable? && _infinity?(value_for_database)
+      end
+
+      private
+        def _infinity?(value)
+          value.respond_to?(:infinite?) && value.infinite?
+        end
     end
   end
 end
diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index bdc5c27328..db9101a168 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-require_relative "from_clause"
-require_relative "query_attribute"
-require_relative "where_clause"
-require_relative "where_clause_factory"
+require "active_record/relation/from_clause"
+require "active_record/relation/query_attribute"
+require "active_record/relation/where_clause"
+require "active_record/relation/where_clause_factory"
 require "active_model/forbidden_attributes_protection"
 
 module ActiveRecord
@@ -231,6 +231,7 @@ module ActiveRecord
     end
 
     def _select!(*fields) # :nodoc:
+      fields.reject!(&:blank?)
       fields.flatten!
       fields.map! do |field|
         klass.attribute_alias?(field) ? klass.attribute_alias(field).to_sym : field
@@ -295,6 +296,7 @@ module ActiveRecord
       spawn.order!(*args)
     end
 
+    # Same as #order but operates on relation in-place instead of copying.
     def order!(*args) # :nodoc:
       preprocess_order_args(args)
 
@@ -316,6 +318,7 @@ module ActiveRecord
       spawn.reorder!(*args)
     end
 
+    # Same as #reorder but operates on relation in-place instead of copying.
     def reorder!(*args) # :nodoc:
       preprocess_order_args(args)
 
@@ -325,8 +328,8 @@ module ActiveRecord
     end
 
     VALID_UNSCOPING_VALUES = Set.new([:where, :select, :group, :order, :lock,
-                                     :limit, :offset, :joins, :includes, :from,
-                                     :readonly, :having])
+                                     :limit, :offset, :joins, :left_outer_joins,
+                                     :includes, :from, :readonly, :having])
 
     # Removes an unwanted relation that is already defined on a chain of relations.
     # This is useful when passing around chains of relations and would like to
@@ -373,10 +376,11 @@ module ActiveRecord
       args.each do |scope|
         case scope
         when Symbol
+          scope = :left_outer_joins if scope == :left_joins
           if !VALID_UNSCOPING_VALUES.include?(scope)
             raise ArgumentError, "Called unscope() with invalid unscoping argument ':#{scope}'. Valid arguments are :#{VALID_UNSCOPING_VALUES.to_a.join(", :")}."
           end
-          set_value(scope, nil)
+          set_value(scope, DEFAULT_VALUES[scope])
         when Hash
           scope.each do |key, target_value|
             if key != :where
@@ -441,16 +445,14 @@ module ActiveRecord
     #   => SELECT "users".* FROM "users" LEFT OUTER JOIN "posts" ON "posts"."user_id" = "users"."id"
     #
     def left_outer_joins(*args)
-      check_if_method_has_arguments!(:left_outer_joins, args)
-
-      args.compact!
-      args.flatten!
-
+      check_if_method_has_arguments!(__callee__, args)
       spawn.left_outer_joins!(*args)
     end
     alias :left_joins :left_outer_joins
 
     def left_outer_joins!(*args) # :nodoc:
+      args.compact!
+      args.flatten!
       self.left_outer_joins_values += args
       self
     end
@@ -892,21 +894,27 @@ module ActiveRecord
       self
     end
 
-    def skip_query_cache! # :nodoc:
-      self.skip_query_cache_value = true
+    def skip_query_cache!(value = true) # :nodoc:
+      self.skip_query_cache_value = value
+      self
+    end
+
+    def skip_preloading! # :nodoc:
+      self.skip_preloading_value = true
       self
     end
 
     # Returns the Arel object associated with the relation.
-    def arel # :nodoc:
-      @arel ||= build_arel
+    def arel(aliases = nil) # :nodoc:
+      @arel ||= build_arel(aliases)
+    end
+
+    # Returns a relation value with a given name
+    def get_value(name) # :nodoc:
+      @values.fetch(name, DEFAULT_VALUES[name])
     end
 
     protected
-      # Returns a relation value with a given name
-      def get_value(name) # :nodoc:
-        @values[name] || default_value_for(name)
-      end
 
       # Sets the relation value with the given name
       def set_value(name, value) # :nodoc:
@@ -921,16 +929,16 @@ module ActiveRecord
         raise ImmutableRelation if defined?(@arel) && @arel
       end
 
-      def build_arel
+      def build_arel(aliases)
         arel = Arel::SelectManager.new(table)
 
-        build_joins(arel, joins_values.flatten) unless joins_values.empty?
-        build_left_outer_joins(arel, left_outer_joins_values.flatten) unless left_outer_joins_values.empty?
+        aliases = build_joins(arel, joins_values.flatten, aliases) unless joins_values.empty?
+        build_left_outer_joins(arel, left_outer_joins_values.flatten, aliases) unless left_outer_joins_values.empty?
 
         arel.where(where_clause.ast) unless where_clause.empty?
         arel.having(having_clause.ast) unless having_clause.empty?
         if limit_value
-          limit_attribute = Attribute.with_cast_value(
+          limit_attribute = ActiveModel::Attribute.with_cast_value(
             "LIMIT".freeze,
             connection.sanitize_limit(limit_value),
             Type.default_value,
@@ -938,7 +946,7 @@ module ActiveRecord
           arel.take(Arel::Nodes::BindParam.new(limit_attribute))
         end
         if offset_value
-          offset_attribute = Attribute.with_cast_value(
+          offset_attribute = ActiveModel::Attribute.with_cast_value(
             "OFFSET".freeze,
             offset_value.to_i,
             Type.default_value,
@@ -963,6 +971,9 @@ module ActiveRecord
         name = from_clause.name
         case opts
         when Relation
+          if opts.eager_loading?
+            opts = opts.send(:apply_join_dependency)
+          end
           name ||= "subquery"
           opts.arel.as(name.to_s)
         else
@@ -970,20 +981,22 @@ module ActiveRecord
         end
       end
 
-      def build_left_outer_joins(manager, outer_joins)
+      def build_left_outer_joins(manager, outer_joins, aliases)
         buckets = outer_joins.group_by do |join|
           case join
           when Hash, Symbol, Array
             :association_join
+          when ActiveRecord::Associations::JoinDependency
+            :stashed_join
           else
             raise ArgumentError, "only Hash, Symbol and Array are allowed"
           end
         end
 
-        build_join_query(manager, buckets, Arel::Nodes::OuterJoin)
+        build_join_query(manager, buckets, Arel::Nodes::OuterJoin, aliases)
       end
 
-      def build_joins(manager, joins)
+      def build_joins(manager, joins, aliases)
         buckets = joins.group_by do |join|
           case join
           when String
@@ -999,10 +1012,10 @@ module ActiveRecord
           end
         end
 
-        build_join_query(manager, buckets, Arel::Nodes::InnerJoin)
+        build_join_query(manager, buckets, Arel::Nodes::InnerJoin, aliases)
       end
 
-      def build_join_query(manager, buckets, join_type)
+      def build_join_query(manager, buckets, join_type, aliases)
         buckets.default = []
 
         association_joins         = buckets[:association_join]
@@ -1010,10 +1023,11 @@ module ActiveRecord
         join_nodes                = buckets[:join_node].uniq
         string_joins              = buckets[:string_join].map(&:strip).uniq
 
-        join_list = join_nodes + convert_join_strings_to_ast(manager, string_joins)
+        join_list = join_nodes + convert_join_strings_to_ast(string_joins)
+        alias_tracker = alias_tracker(join_list, aliases)
 
         join_dependency = ActiveRecord::Associations::JoinDependency.new(
-          klass, table, association_joins, join_list
+          klass, table, association_joins, alias_tracker
         )
 
         joins = join_dependency.join_constraints(stashed_association_joins, join_type)
@@ -1021,10 +1035,10 @@ module ActiveRecord
 
         manager.join_sources.concat(join_list)
 
-        manager
+        alias_tracker.aliases
       end
 
-      def convert_join_strings_to_ast(table, joins)
+      def convert_join_strings_to_ast(joins)
         joins
           .flatten
           .reject(&:blank?)
@@ -1034,6 +1048,8 @@ module ActiveRecord
       def build_select(arel)
         if select_values.any?
           arel.project(*arel_columns(select_values.uniq))
+        elsif klass.ignored_columns.any?
+          arel.project(*klass.column_names.map { |field| arel_attribute(field) })
         else
           arel.project(table[Arel.star])
         end
@@ -1070,7 +1086,7 @@ module ActiveRecord
             end
             o.split(",").map! do |s|
               s.strip!
-              s.gsub!(/\sasc\Z/i, " DESC") || s.gsub!(/\sdesc\Z/i, " ASC") || s.concat(" DESC")
+              s.gsub!(/\sasc\Z/i, " DESC") || s.gsub!(/\sdesc\Z/i, " ASC") || (s << " DESC")
             end
           else
             o
@@ -1079,6 +1095,10 @@ module ActiveRecord
       end
 
       def does_not_support_reverse?(order)
+        # Account for String subclasses like Arel::Nodes::SqlLiteral that
+        # override methods like #count.
+        order = String.new(order) unless order.instance_of?(String)
+
         # Uses SQL function with multiple arguments.
         (order.include?(",") && order.split(",").find { |section| section.count("(") != section.count(")") }) ||
           # Uses "nulls first" like construction.
@@ -1109,9 +1129,15 @@ module ActiveRecord
 
       def preprocess_order_args(order_args)
         order_args.map! do |arg|
-          klass.send(:sanitize_sql_for_order, arg)
+          klass.sanitize_sql_for_order(arg)
         end
         order_args.flatten!
+
+        @klass.enforce_raw_sql_whitelist(
+          order_args.flat_map { |a| a.is_a?(Hash) ? a.keys : a },
+          whitelist: AttributeMethods::ClassMethods::COLUMN_NAME_ORDER_WHITELIST
+        )
+
         validate_order_args(order_args)
 
         references = order_args.grep(String)
@@ -1172,23 +1198,15 @@ module ActiveRecord
       end
       alias having_clause_factory where_clause_factory
 
-      def default_value_for(name)
-        case name
-        when :create_with
-          FROZEN_EMPTY_HASH
-        when :readonly
-          false
-        when :where, :having
-          Relation::WhereClause.empty
-        when :from
-          Relation::FromClause.empty
-        when *Relation::MULTI_VALUE_METHODS
-          FROZEN_EMPTY_ARRAY
-        when *Relation::SINGLE_VALUE_METHODS
-          nil
-        else
-          raise ArgumentError, "unknown relation value #{name.inspect}"
-        end
+      DEFAULT_VALUES = {
+        create_with: FROZEN_EMPTY_HASH,
+        where: Relation::WhereClause.empty,
+        having: Relation::WhereClause.empty,
+        from: Relation::FromClause.empty
+      }
+
+      Relation::MULTI_VALUE_METHODS.each do |value|
+        DEFAULT_VALUES[value] ||= FROZEN_EMPTY_ARRAY
       end
   end
 end
diff --git a/activerecord/lib/active_record/relation/spawn_methods.rb b/activerecord/lib/active_record/relation/spawn_methods.rb
index 424894f835..b092399657 100644
--- a/activerecord/lib/active_record/relation/spawn_methods.rb
+++ b/activerecord/lib/active_record/relation/spawn_methods.rb
@@ -2,7 +2,7 @@
 
 require "active_support/core_ext/hash/except"
 require "active_support/core_ext/hash/slice"
-require_relative "merger"
+require "active_record/relation/merger"
 
 module ActiveRecord
   module SpawnMethods
@@ -10,6 +10,7 @@ module ActiveRecord
     def spawn #:nodoc:
       clone
     end
+    alias :all :spawn
 
     # Merges in the conditions from <tt>other</tt>, if <tt>other</tt> is an ActiveRecord::Relation.
     # Returns an array representing the intersection of the resulting records with <tt>other</tt>, if <tt>other</tt> is an array.
@@ -69,7 +70,7 @@ module ActiveRecord
     private
 
       def relation_with(values)
-        result = Relation.create(klass, table, predicate_builder, values)
+        result = Relation.create(klass, values: values)
         result.extend(*extending_values) if extending_values.any?
         result
       end
diff --git a/activerecord/lib/active_record/relation/where_clause.rb b/activerecord/lib/active_record/relation/where_clause.rb
index 752bb38481..a502713e56 100644
--- a/activerecord/lib/active_record/relation/where_clause.rb
+++ b/activerecord/lib/active_record/relation/where_clause.rb
@@ -47,7 +47,7 @@ module ActiveRecord
       end
 
       def to_h(table_name = nil)
-        equalities = predicates.grep(Arel::Nodes::Equality)
+        equalities = equalities(predicates)
         if table_name
           equalities = equalities.select do |node|
             node.left.relation.name == table_name
@@ -90,6 +90,20 @@ module ActiveRecord
         end
 
       private
+        def equalities(predicates)
+          equalities = []
+
+          predicates.each do |node|
+            case node
+            when Arel::Nodes::Equality
+              equalities << node
+            when Arel::Nodes::And
+              equalities.concat equalities(node.children)
+            end
+          end
+
+          equalities
+        end
 
         def predicates_unreferenced_by(other)
           predicates.reject do |n|
@@ -121,7 +135,7 @@ module ActiveRecord
         end
 
         def except_predicates(columns)
-          self.predicates.reject do |node|
+          predicates.reject do |node|
             case node
             when Arel::Nodes::Between, Arel::Nodes::In, Arel::Nodes::NotIn, Arel::Nodes::Equality, Arel::Nodes::NotEqual, Arel::Nodes::LessThan, Arel::Nodes::LessThanOrEqual, Arel::Nodes::GreaterThan, Arel::Nodes::GreaterThanOrEqual
               subrelation = (node.left.kind_of?(Arel::Attributes::Attribute) ? node.left : node.right)
diff --git a/activerecord/lib/active_record/relation/where_clause_factory.rb b/activerecord/lib/active_record/relation/where_clause_factory.rb
index 1374785354..c1b3eea9df 100644
--- a/activerecord/lib/active_record/relation/where_clause_factory.rb
+++ b/activerecord/lib/active_record/relation/where_clause_factory.rb
@@ -11,10 +11,9 @@ module ActiveRecord
       def build(opts, other)
         case opts
         when String, Array
-          parts = [klass.send(:sanitize_sql, other.empty? ? opts : ([opts] + other))]
+          parts = [klass.sanitize_sql(other.empty? ? opts : ([opts] + other))]
         when Hash
           attributes = predicate_builder.resolve_column_aliases(opts)
-          attributes = klass.send(:expand_hash_conditions_for_aggregates, attributes)
           attributes.stringify_keys!
 
           parts = predicate_builder.build_from_hash(attributes)
@@ -27,8 +26,7 @@ module ActiveRecord
         WhereClause.new(parts)
       end
 
-      protected
-
+      private
         attr_reader :klass, :predicate_builder
     end
   end
diff --git a/activerecord/lib/active_record/sanitization.rb b/activerecord/lib/active_record/sanitization.rb
index 91a4f1fad6..c6c268855e 100644
--- a/activerecord/lib/active_record/sanitization.rb
+++ b/activerecord/lib/active_record/sanitization.rb
@@ -5,72 +5,135 @@ module ActiveRecord
     extend ActiveSupport::Concern
 
     module ClassMethods
-      private
-
-        # Accepts an array or string of SQL conditions and sanitizes
-        # them into a valid SQL fragment for a WHERE clause.
-        #
-        #   sanitize_sql_for_conditions(["name=? and group_id=?", "foo'bar", 4])
-        #   # => "name='foo''bar' and group_id=4"
-        #
-        #   sanitize_sql_for_conditions(["name=:name and group_id=:group_id", name: "foo'bar", group_id: 4])
-        #   # => "name='foo''bar' and group_id='4'"
-        #
-        #   sanitize_sql_for_conditions(["name='%s' and group_id='%s'", "foo'bar", 4])
-        #   # => "name='foo''bar' and group_id='4'"
-        #
-        #   sanitize_sql_for_conditions("name='foo''bar' and group_id='4'")
-        #   # => "name='foo''bar' and group_id='4'"
-        def sanitize_sql_for_conditions(condition) # :doc:
-          return nil if condition.blank?
-
-          case condition
-          when Array; sanitize_sql_array(condition)
-          else        condition
-          end
+      # Accepts an array or string of SQL conditions and sanitizes
+      # them into a valid SQL fragment for a WHERE clause.
+      #
+      #   sanitize_sql_for_conditions(["name=? and group_id=?", "foo'bar", 4])
+      #   # => "name='foo''bar' and group_id=4"
+      #
+      #   sanitize_sql_for_conditions(["name=:name and group_id=:group_id", name: "foo'bar", group_id: 4])
+      #   # => "name='foo''bar' and group_id='4'"
+      #
+      #   sanitize_sql_for_conditions(["name='%s' and group_id='%s'", "foo'bar", 4])
+      #   # => "name='foo''bar' and group_id='4'"
+      #
+      #   sanitize_sql_for_conditions("name='foo''bar' and group_id='4'")
+      #   # => "name='foo''bar' and group_id='4'"
+      def sanitize_sql_for_conditions(condition)
+        return nil if condition.blank?
+
+        case condition
+        when Array; sanitize_sql_array(condition)
+        else        condition
         end
-        alias :sanitize_sql :sanitize_sql_for_conditions
-        alias :sanitize_conditions :sanitize_sql
-        deprecate sanitize_conditions: :sanitize_sql
-
-        # Accepts an array, hash, or string of SQL conditions and sanitizes
-        # them into a valid SQL fragment for a SET clause.
-        #
-        #   sanitize_sql_for_assignment(["name=? and group_id=?", nil, 4])
-        #   # => "name=NULL and group_id=4"
-        #
-        #   sanitize_sql_for_assignment(["name=:name and group_id=:group_id", name: nil, group_id: 4])
-        #   # => "name=NULL and group_id=4"
-        #
-        #   Post.send(:sanitize_sql_for_assignment, { name: nil, group_id: 4 })
-        #   # => "`posts`.`name` = NULL, `posts`.`group_id` = 4"
-        #
-        #   sanitize_sql_for_assignment("name=NULL and group_id='4'")
-        #   # => "name=NULL and group_id='4'"
-        def sanitize_sql_for_assignment(assignments, default_table_name = table_name) # :doc:
-          case assignments
-          when Array; sanitize_sql_array(assignments)
-          when Hash;  sanitize_sql_hash_for_assignment(assignments, default_table_name)
-          else        assignments
-          end
+      end
+      alias :sanitize_sql :sanitize_sql_for_conditions
+
+      # Accepts an array, hash, or string of SQL conditions and sanitizes
+      # them into a valid SQL fragment for a SET clause.
+      #
+      #   sanitize_sql_for_assignment(["name=? and group_id=?", nil, 4])
+      #   # => "name=NULL and group_id=4"
+      #
+      #   sanitize_sql_for_assignment(["name=:name and group_id=:group_id", name: nil, group_id: 4])
+      #   # => "name=NULL and group_id=4"
+      #
+      #   Post.sanitize_sql_for_assignment({ name: nil, group_id: 4 })
+      #   # => "`posts`.`name` = NULL, `posts`.`group_id` = 4"
+      #
+      #   sanitize_sql_for_assignment("name=NULL and group_id='4'")
+      #   # => "name=NULL and group_id='4'"
+      def sanitize_sql_for_assignment(assignments, default_table_name = table_name)
+        case assignments
+        when Array; sanitize_sql_array(assignments)
+        when Hash;  sanitize_sql_hash_for_assignment(assignments, default_table_name)
+        else        assignments
         end
-
-        # Accepts an array, or string of SQL conditions and sanitizes
-        # them into a valid SQL fragment for an ORDER clause.
-        #
-        #   sanitize_sql_for_order(["field(id, ?)", [1,3,2]])
-        #   # => "field(id, 1,3,2)"
-        #
-        #   sanitize_sql_for_order("id ASC")
-        #   # => "id ASC"
-        def sanitize_sql_for_order(condition) # :doc:
-          if condition.is_a?(Array) && condition.first.to_s.include?("?")
-            sanitize_sql_array(condition)
-          else
-            condition
+      end
+
+      # Accepts an array, or string of SQL conditions and sanitizes
+      # them into a valid SQL fragment for an ORDER clause.
+      #
+      #   sanitize_sql_for_order(["field(id, ?)", [1,3,2]])
+      #   # => "field(id, 1,3,2)"
+      #
+      #   sanitize_sql_for_order("id ASC")
+      #   # => "id ASC"
+      def sanitize_sql_for_order(condition)
+        if condition.is_a?(Array) && condition.first.to_s.include?("?")
+          enforce_raw_sql_whitelist([condition.first],
+            whitelist: AttributeMethods::ClassMethods::COLUMN_NAME_ORDER_WHITELIST
+          )
+
+          # Ensure we aren't dealing with a subclass of String that might
+          # override methods we use (eg. Arel::Nodes::SqlLiteral).
+          if condition.first.kind_of?(String) && !condition.first.instance_of?(String)
+            condition = [String.new(condition.first), *condition[1..-1]]
           end
+
+          Arel.sql(sanitize_sql_array(condition))
+        else
+          condition
         end
+      end
+
+      # Sanitizes a hash of attribute/value pairs into SQL conditions for a SET clause.
+      #
+      #   sanitize_sql_hash_for_assignment({ status: nil, group_id: 1 }, "posts")
+      #   # => "`posts`.`status` = NULL, `posts`.`group_id` = 1"
+      def sanitize_sql_hash_for_assignment(attrs, table)
+        c = connection
+        attrs.map do |attr, value|
+          type = type_for_attribute(attr)
+          value = type.serialize(type.cast(value))
+          "#{c.quote_table_name_for_assignment(table, attr)} = #{c.quote(value)}"
+        end.join(", ")
+      end
+
+      # Sanitizes a +string+ so that it is safe to use within an SQL
+      # LIKE statement. This method uses +escape_character+ to escape all occurrences of "\", "_" and "%".
+      #
+      #   sanitize_sql_like("100%")
+      #   # => "100\\%"
+      #
+      #   sanitize_sql_like("snake_cased_string")
+      #   # => "snake\\_cased\\_string"
+      #
+      #   sanitize_sql_like("100%", "!")
+      #   # => "100!%"
+      #
+      #   sanitize_sql_like("snake_cased_string", "!")
+      #   # => "snake!_cased!_string"
+      def sanitize_sql_like(string, escape_character = "\\")
+        pattern = Regexp.union(escape_character, "%", "_")
+        string.gsub(pattern) { |x| [escape_character, x].join }
+      end
+
+      # Accepts an array of conditions. The array has each value
+      # sanitized and interpolated into the SQL statement.
+      #
+      #   sanitize_sql_array(["name=? and group_id=?", "foo'bar", 4])
+      #   # => "name='foo''bar' and group_id=4"
+      #
+      #   sanitize_sql_array(["name=:name and group_id=:group_id", name: "foo'bar", group_id: 4])
+      #   # => "name='foo''bar' and group_id=4"
+      #
+      #   sanitize_sql_array(["name='%s' and group_id='%s'", "foo'bar", 4])
+      #   # => "name='foo''bar' and group_id='4'"
+      def sanitize_sql_array(ary)
+        statement, *values = ary
+        if values.first.is_a?(Hash) && /:\w+/.match?(statement)
+          replace_named_bind_variables(statement, values.first)
+        elsif statement.include?("?")
+          replace_bind_variables(statement, values)
+        elsif statement.blank?
+          statement
+        else
+          statement % values.collect { |value| connection.quote_string(value.to_s) }
+        end
+      end
 
+      private
         # Accepts a hash of SQL conditions and replaces those attributes
         # that correspond to a {#composed_of}[rdoc-ref:Aggregations::ClassMethods#composed_of]
         # relationship with their expanded aggregate attribute values.
@@ -92,10 +155,12 @@ module ActiveRecord
             if aggregation = reflect_on_aggregation(attr.to_sym)
               mapping = aggregation.mapping
               mapping.each do |field_attr, aggregate_attr|
-                if mapping.size == 1 && !value.respond_to?(aggregate_attr)
-                  expanded_attrs[field_attr] = value
+                expanded_attrs[field_attr] = if value.is_a?(Array)
+                  value.map { |it| it.send(aggregate_attr) }
+                elsif mapping.size == 1 && !value.respond_to?(aggregate_attr)
+                  value
                 else
-                  expanded_attrs[field_attr] = value.send(aggregate_attr)
+                  value.send(aggregate_attr)
                 end
               end
             else
@@ -104,61 +169,7 @@ module ActiveRecord
           end
           expanded_attrs
         end
-
-        # Sanitizes a hash of attribute/value pairs into SQL conditions for a SET clause.
-        #
-        #   sanitize_sql_hash_for_assignment({ status: nil, group_id: 1 }, "posts")
-        #   # => "`posts`.`status` = NULL, `posts`.`group_id` = 1"
-        def sanitize_sql_hash_for_assignment(attrs, table) # :doc:
-          c = connection
-          attrs.map do |attr, value|
-            value = type_for_attribute(attr.to_s).serialize(value)
-            "#{c.quote_table_name_for_assignment(table, attr)} = #{c.quote(value)}"
-          end.join(", ")
-        end
-
-        # Sanitizes a +string+ so that it is safe to use within an SQL
-        # LIKE statement. This method uses +escape_character+ to escape all occurrences of "\", "_" and "%".
-        #
-        #   sanitize_sql_like("100%")
-        #   # => "100\\%"
-        #
-        #   sanitize_sql_like("snake_cased_string")
-        #   # => "snake\\_cased\\_string"
-        #
-        #   sanitize_sql_like("100%", "!")
-        #   # => "100!%"
-        #
-        #   sanitize_sql_like("snake_cased_string", "!")
-        #   # => "snake!_cased!_string"
-        def sanitize_sql_like(string, escape_character = "\\") # :doc:
-          pattern = Regexp.union(escape_character, "%", "_")
-          string.gsub(pattern) { |x| [escape_character, x].join }
-        end
-
-        # Accepts an array of conditions. The array has each value
-        # sanitized and interpolated into the SQL statement.
-        #
-        #   sanitize_sql_array(["name=? and group_id=?", "foo'bar", 4])
-        #   # => "name='foo''bar' and group_id=4"
-        #
-        #   sanitize_sql_array(["name=:name and group_id=:group_id", name: "foo'bar", group_id: 4])
-        #   # => "name='foo''bar' and group_id=4"
-        #
-        #   sanitize_sql_array(["name='%s' and group_id='%s'", "foo'bar", 4])
-        #   # => "name='foo''bar' and group_id='4'"
-        def sanitize_sql_array(ary) # :doc:
-          statement, *values = ary
-          if values.first.is_a?(Hash) && /:\w+/.match?(statement)
-            replace_named_bind_variables(statement, values.first)
-          elsif statement.include?("?")
-            replace_bind_variables(statement, values)
-          elsif statement.blank?
-            statement
-          else
-            statement % values.collect { |value| connection.quote_string(value.to_s) }
-          end
-        end
+        deprecate :expand_hash_conditions_for_aggregates
 
         def replace_bind_variables(statement, values)
           raise_if_bind_arity_mismatch(statement, statement.count("?"), values.size)
@@ -207,10 +218,5 @@ module ActiveRecord
           end
         end
     end
-
-    def quoted_id # :nodoc:
-      self.class.connection.quote(@attributes[self.class.primary_key].value_for_database)
-    end
-    deprecate :quoted_id
   end
 end
diff --git a/activerecord/lib/active_record/schema.rb b/activerecord/lib/active_record/schema.rb
index 1e121f2a09..216359867c 100644
--- a/activerecord/lib/active_record/schema.rb
+++ b/activerecord/lib/active_record/schema.rb
@@ -55,7 +55,7 @@ module ActiveRecord
       end
 
       ActiveRecord::InternalMetadata.create_table
-      ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Migrator.current_environment
+      ActiveRecord::InternalMetadata[:environment] = connection.migration_context.current_environment
     end
 
     private
diff --git a/activerecord/lib/active_record/schema_dumper.rb b/activerecord/lib/active_record/schema_dumper.rb
index d2e1892ae7..d475e77444 100644
--- a/activerecord/lib/active_record/schema_dumper.rb
+++ b/activerecord/lib/active_record/schema_dumper.rb
@@ -17,6 +17,12 @@ module ActiveRecord
     # Only strings are accepted if ActiveRecord::Base.schema_format == :sql.
     cattr_accessor :ignore_tables, default: []
 
+    ##
+    # :singleton-method:
+    # Specify a custom regular expression matching foreign keys which name
+    # should not be dumped to db/schema.rb.
+    cattr_accessor :fk_ignore_pattern, default: /^fk_rails_[0-9a-f]{10}$/
+
     class << self
       def dump(connection = ActiveRecord::Base.connection, stream = STDOUT, config = ActiveRecord::Base)
         connection.create_schema_dumper(generate_options(config)).dump(stream)
@@ -44,7 +50,7 @@ module ActiveRecord
 
       def initialize(connection, options = {})
         @connection = connection
-        @version = Migrator::current_version rescue nil
+        @version = connection.migration_context.current_version rescue nil
         @options = options
       end
 
@@ -65,11 +71,11 @@ module ActiveRecord
 # of editing this file, please use the migrations feature of Active Record to
 # incrementally modify your database, and then regenerate this schema definition.
 #
-# Note that this schema.rb definition is the authoritative source for your
-# database schema. If you need to create the application database on another
-# system, you should be using db:schema:load, not running all the migrations
-# from scratch. The latter is a flawed and unsustainable approach (the more migrations
-# you'll amass, the slower it'll run and the greater likelihood for issues).
+# This file is the source Rails uses to define your schema when running `rails
+# db:schema:load`. When creating a new database, `rails db:schema:load` tends to
+# be faster and is potentially less error prone than running all of your
+# migrations from scratch. Old migrations may fail to apply correctly if those
+# migrations use external dependencies or application code.
 #
 # It's strongly recommended that you check this file into your version control system.
 
@@ -82,16 +88,8 @@ HEADER
         stream.puts "end"
       end
 
+      # extensions are only supported by PostgreSQL
       def extensions(stream)
-        return unless @connection.supports_extensions?
-        extensions = @connection.extensions
-        if extensions.any?
-          stream.puts "  # These are extensions that must be enabled in order to support this database"
-          extensions.sort.each do |extension|
-            stream.puts "  enable_extension #{extension.inspect}"
-          end
-          stream.puts
-        end
       end
 
       def tables(stream)
@@ -132,14 +130,13 @@ HEADER
           else
             tbl.print ", id: false"
           end
-          tbl.print ", force: :cascade"
 
           table_options = @connection.table_options(table)
           if table_options.present?
             tbl.print ", #{format_options(table_options)}"
           end
 
-          tbl.puts " do |t|"
+          tbl.puts ", force: :cascade do |t|"
 
           # then dump all non-primary key columns
           columns.each do |column|
@@ -193,8 +190,9 @@ HEADER
           "name: #{index.name.inspect}",
         ]
         index_parts << "unique: true" if index.unique
-        index_parts << "length: { #{format_options(index.lengths)} }" if index.lengths.present?
-        index_parts << "order: { #{format_options(index.orders)} }" if index.orders.present?
+        index_parts << "length: #{format_index_parts(index.lengths)}" if index.lengths.present?
+        index_parts << "order: #{format_index_parts(index.orders)}" if index.orders.present?
+        index_parts << "opclass: #{format_index_parts(index.opclasses)}" if index.opclasses.present?
         index_parts << "where: #{index.where.inspect}" if index.where
         index_parts << "using: #{index.using.inspect}" if !@connection.default_index_type?(index)
         index_parts << "type: #{index.type.inspect}" if index.type
@@ -218,7 +216,7 @@ HEADER
               parts << "primary_key: #{foreign_key.primary_key.inspect}"
             end
 
-            if foreign_key.name !~ /^fk_rails_[0-9a-f]{10}$/
+            if foreign_key.export_name_on_schema_dump?
               parts << "name: #{foreign_key.name.inspect}"
             end
 
@@ -240,6 +238,14 @@ HEADER
         options.map { |key, value| "#{key}: #{value.inspect}" }.join(", ")
       end
 
+      def format_index_parts(options)
+        if options.is_a?(Hash)
+          "{ #{format_options(options)} }"
+        else
+          options.inspect
+        end
+      end
+
       def remove_prefix_and_suffix(table)
         prefix = Regexp.escape(@options[:table_name_prefix].to_s)
         suffix = Regexp.escape(@options[:table_name_suffix].to_s)
diff --git a/activerecord/lib/active_record/schema_migration.rb b/activerecord/lib/active_record/schema_migration.rb
index 339a5334a8..f2d8b038fa 100644
--- a/activerecord/lib/active_record/schema_migration.rb
+++ b/activerecord/lib/active_record/schema_migration.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "scoping/default"
-require_relative "scoping/named"
+require "active_record/scoping/default"
+require "active_record/scoping/named"
 
 module ActiveRecord
   # This class is used to create a table that keeps track of which migrations
diff --git a/activerecord/lib/active_record/scoping.rb b/activerecord/lib/active_record/scoping.rb
index da585a9562..01ac56570a 100644
--- a/activerecord/lib/active_record/scoping.rb
+++ b/activerecord/lib/active_record/scoping.rb
@@ -11,23 +11,23 @@ module ActiveRecord
       include Named
     end
 
-    module ClassMethods
-      def current_scope(skip_inherited_scope = false) # :nodoc:
+    module ClassMethods # :nodoc:
+      def current_scope(skip_inherited_scope = false)
         ScopeRegistry.value_for(:current_scope, self, skip_inherited_scope)
       end
 
-      def current_scope=(scope) #:nodoc:
+      def current_scope=(scope)
         ScopeRegistry.set_value_for(:current_scope, self, scope)
       end
 
       # Collects attributes from scopes that should be applied when creating
       # an AR instance for the particular class this is called on.
-      def scope_attributes # :nodoc:
+      def scope_attributes
         all.scope_for_create
       end
 
       # Are there attributes associated with this scope?
-      def scope_attributes? # :nodoc:
+      def scope_attributes?
         current_scope
       end
     end
diff --git a/activerecord/lib/active_record/scoping/default.rb b/activerecord/lib/active_record/scoping/default.rb
index 86ae374318..8c612df27a 100644
--- a/activerecord/lib/active_record/scoping/default.rb
+++ b/activerecord/lib/active_record/scoping/default.rb
@@ -111,7 +111,7 @@ module ActiveRecord
               # The user has defined their own default scope method, so call that
               evaluate_default_scope do
                 if scope = default_scope
-                  (base_rel ||= relation).merge(scope)
+                  (base_rel ||= relation).merge!(scope)
                 end
               end
             elsif default_scopes.any?
@@ -119,7 +119,7 @@ module ActiveRecord
               evaluate_default_scope do
                 default_scopes.inject(base_rel) do |default_scope, scope|
                   scope = scope.respond_to?(:to_proc) ? scope : scope.method(:call)
-                  default_scope.merge(base_rel.instance_exec(&scope))
+                  default_scope.merge!(base_rel.instance_exec(&scope))
                 end
               end
             end
diff --git a/activerecord/lib/active_record/scoping/named.rb b/activerecord/lib/active_record/scoping/named.rb
index 6fa096c1fe..a784001587 100644
--- a/activerecord/lib/active_record/scoping/named.rb
+++ b/activerecord/lib/active_record/scoping/named.rb
@@ -24,8 +24,14 @@ module ActiveRecord
         # You can define a scope that applies to all finders using
         # {default_scope}[rdoc-ref:Scoping::Default::ClassMethods#default_scope].
         def all
+          current_scope = self.current_scope
+
           if current_scope
-            current_scope.clone
+            if self == current_scope.klass
+              current_scope.clone
+            else
+              relation.merge!(current_scope)
+            end
           else
             default_scoped
           end
@@ -165,13 +171,19 @@ module ActiveRecord
               "a class method with the same name."
           end
 
+          if method_defined_within?(name, Relation)
+            raise ArgumentError, "You tried to define a scope named \"#{name}\" " \
+              "on the model \"#{self.name}\", but ActiveRecord::Relation already defined " \
+              "an instance method with the same name."
+          end
+
           valid_scope_name?(name)
           extension = Module.new(&block) if block
 
           if body.respond_to?(:to_proc)
             singleton_class.send(:define_method, name) do |*args|
               scope = all
-              scope = scope.instance_exec(*args, &body) || scope
+              scope = scope._exec_scope(*args, &body)
               scope = scope.extending(extension) if extension
               scope
             end
diff --git a/activerecord/lib/active_record/statement_cache.rb b/activerecord/lib/active_record/statement_cache.rb
index 59acd63a0f..b41d3504fd 100644
--- a/activerecord/lib/active_record/statement_cache.rb
+++ b/activerecord/lib/active_record/statement_cache.rb
@@ -114,8 +114,7 @@ module ActiveRecord
       end
     end
 
-    protected
-
+    private
       attr_reader :query_builder, :bind_map, :klass
   end
 end
diff --git a/activerecord/lib/active_record/store.rb b/activerecord/lib/active_record/store.rb
index 202b82fa61..8d628359c3 100644
--- a/activerecord/lib/active_record/store.rb
+++ b/activerecord/lib/active_record/store.rb
@@ -17,8 +17,8 @@ module ActiveRecord
   # You can set custom coder to encode/decode your serialized attributes to/from different formats.
   # JSON, YAML, Marshal are supported out of the box. Generally it can be any wrapper that provides +load+ and +dump+.
   #
-  # NOTE: If you are using PostgreSQL specific columns like +hstore+ or +json+ there is no need for
-  # the serialization provided by {.store}[rdoc-ref:rdoc-ref:ClassMethods#store].
+  # NOTE: If you are using structured database data types (eg. PostgreSQL +hstore+/+json+, or MySQL 5.7+
+  # +json+) there is no need for the serialization provided by {.store}[rdoc-ref:rdoc-ref:ClassMethods#store].
   # Simply use {.store_accessor}[rdoc-ref:ClassMethods#store_accessor] instead to generate
   # the accessor methods. Be aware that these columns use a string keyed hash and do not allow access
   # using a symbol.
@@ -31,10 +31,14 @@ module ActiveRecord
   #
   #   class User < ActiveRecord::Base
   #     store :settings, accessors: [ :color, :homepage ], coder: JSON
+  #     store :parent, accessors: [ :name ], coder: JSON, prefix: true
+  #     store :spouse, accessors: [ :name ], coder: JSON, prefix: :partner
   #   end
   #
-  #   u = User.new(color: 'black', homepage: '37signals.com')
+  #   u = User.new(color: 'black', homepage: '37signals.com', parent_name: 'Mary', partner_name: 'Lily')
   #   u.color                          # Accessor stored attribute
+  #   u.parent_name                    # Accessor stored attribute with prefix
+  #   u.partner_name                   # Accessor stored attribute with custom prefix
   #   u.settings[:country] = 'Denmark' # Any attribute, even if not specified with an accessor
   #
   #   # There is no difference between strings and symbols for accessing custom attributes
@@ -44,6 +48,7 @@ module ActiveRecord
   #   # Add additional accessors to an existing store through store_accessor
   #   class SuperUser < User
   #     store_accessor :settings, :privileges, :servants
+  #     store_accessor :parent, :birthday, prefix: true
   #   end
   #
   # The stored attribute names can be retrieved using {.stored_attributes}[rdoc-ref:rdoc-ref:ClassMethods#stored_attributes].
@@ -81,19 +86,29 @@ module ActiveRecord
     module ClassMethods
       def store(store_attribute, options = {})
         serialize store_attribute, IndifferentCoder.new(store_attribute, options[:coder])
-        store_accessor(store_attribute, options[:accessors]) if options.has_key? :accessors
+        store_accessor(store_attribute, options[:accessors], prefix: options[:prefix]) if options.has_key? :accessors
       end
 
-      def store_accessor(store_attribute, *keys)
+      def store_accessor(store_attribute, *keys, prefix: nil)
         keys = keys.flatten
 
+        accessor_prefix =
+          case prefix
+          when String, Symbol
+            "#{prefix}_"
+          when TrueClass
+            "#{store_attribute}_"
+          else
+            ""
+          end
+
         _store_accessors_module.module_eval do
           keys.each do |key|
-            define_method("#{key}=") do |value|
+            define_method("#{accessor_prefix}#{key}=") do |value|
               write_store_attribute(store_attribute, key, value)
             end
 
-            define_method(key) do
+            define_method("#{accessor_prefix}#{key}") do
               read_store_attribute(store_attribute, key)
             end
           end
@@ -135,7 +150,7 @@ module ActiveRecord
       end
 
       def store_accessor_for(store_attribute)
-        type_for_attribute(store_attribute.to_s).accessor
+        type_for_attribute(store_attribute).accessor
       end
 
       class HashAccessor # :nodoc:
diff --git a/activerecord/lib/active_record/table_metadata.rb b/activerecord/lib/active_record/table_metadata.rb
index a5187efc84..b67479fb6a 100644
--- a/activerecord/lib/active_record/table_metadata.rb
+++ b/activerecord/lib/active_record/table_metadata.rb
@@ -2,8 +2,7 @@
 
 module ActiveRecord
   class TableMetadata # :nodoc:
-    delegate :foreign_type, :foreign_key, :join_keys, :join_foreign_key, to: :association, prefix: true
-    delegate :association_primary_key, to: :association
+    delegate :foreign_type, :foreign_key, :join_primary_key, :join_foreign_key, to: :association, prefix: true
 
     def initialize(klass, arel_table, association = nil)
       @klass = klass
@@ -31,7 +30,7 @@ module ActiveRecord
 
     def type(column_name)
       if klass
-        klass.type_for_attribute(column_name.to_s)
+        klass.type_for_attribute(column_name)
       else
         Type.default_value
       end
@@ -66,10 +65,15 @@ module ActiveRecord
       association && association.polymorphic?
     end
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
-    protected
+    def aggregated_with?(aggregation_name)
+      klass && reflect_on_aggregation(aggregation_name)
+    end
+
+    def reflect_on_aggregation(aggregation_name)
+      klass.reflect_on_aggregation(aggregation_name)
+    end
 
+    private
       attr_reader :klass, :arel_table, :association
   end
 end
diff --git a/activerecord/lib/active_record/tasks/database_tasks.rb b/activerecord/lib/active_record/tasks/database_tasks.rb
index 0f3f84ca08..521375954b 100644
--- a/activerecord/lib/active_record/tasks/database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/database_tasks.rb
@@ -54,10 +54,10 @@ module ActiveRecord
 
       def check_protected_environments!
         unless ENV["DISABLE_DATABASE_ENVIRONMENT_CHECK"]
-          current = ActiveRecord::Migrator.current_environment
-          stored  = ActiveRecord::Migrator.last_stored_environment
+          current = ActiveRecord::Base.connection.migration_context.current_environment
+          stored  = ActiveRecord::Base.connection.migration_context.last_stored_environment
 
-          if ActiveRecord::Migrator.protected_environment?
+          if ActiveRecord::Base.connection.migration_context.protected_environment?
             raise ActiveRecord::ProtectedEnvironmentError.new(stored)
           end
 
@@ -117,9 +117,9 @@ module ActiveRecord
       def create(*arguments)
         configuration = arguments.first
         class_for_adapter(configuration["adapter"]).new(*arguments).create
-        $stdout.puts "Created database '#{configuration['database']}'"
+        $stdout.puts "Created database '#{configuration['database']}'" if verbose?
       rescue DatabaseAlreadyExists
-        $stderr.puts "Database '#{configuration['database']}' already exists"
+        $stderr.puts "Database '#{configuration['database']}' already exists" if verbose?
       rescue Exception => error
         $stderr.puts error
         $stderr.puts "Couldn't create database for #{configuration.inspect}"
@@ -134,6 +134,18 @@ module ActiveRecord
         end
       end
 
+      def for_each
+        databases = Rails.application.config.load_database_yaml
+        database_configs = ActiveRecord::DatabaseConfigurations.configs_for(Rails.env, databases)
+
+        # if this is a single database application we don't want tasks for each primary database
+        return if database_configs.count == 1
+
+        database_configs.each do |db_config|
+          yield db_config.spec_name
+        end
+      end
+
       def create_current(environment = env)
         each_current_configuration(environment) { |configuration|
           create configuration
@@ -144,7 +156,7 @@ module ActiveRecord
       def drop(*arguments)
         configuration = arguments.first
         class_for_adapter(configuration["adapter"]).new(*arguments).drop
-        $stdout.puts "Dropped database '#{configuration['database']}'"
+        $stdout.puts "Dropped database '#{configuration['database']}'" if verbose?
       rescue ActiveRecord::NoDatabaseError
         $stderr.puts "Database '#{configuration['database']}' does not exist"
       rescue Exception => error
@@ -164,13 +176,11 @@ module ActiveRecord
       end
 
       def migrate
-        raise "Empty VERSION provided" if ENV["VERSION"] && ENV["VERSION"].empty?
+        check_target_version
 
-        verbose = ENV["VERBOSE"] ? ENV["VERBOSE"] != "false" : true
-        version = ENV["VERSION"] ? ENV["VERSION"].to_i : nil
         scope = ENV["SCOPE"]
-        verbose_was, Migration.verbose = Migration.verbose, verbose
-        Migrator.migrate(migrations_paths, version) do |migration|
+        verbose_was, Migration.verbose = Migration.verbose, verbose?
+        Base.connection.migration_context.migrate(target_version) do |migration|
           scope.blank? || scope == migration.scope
         end
         ActiveRecord::Base.clear_cache!
@@ -178,6 +188,16 @@ module ActiveRecord
         Migration.verbose = verbose_was
       end
 
+      def check_target_version
+        if target_version && !(Migration::MigrationFilenameRegexp.match?(ENV["VERSION"]) || /\A\d+\z/.match?(ENV["VERSION"]))
+          raise "Invalid format of target version: `VERSION=#{ENV['VERSION']}`"
+        end
+      end
+
+      def target_version
+        ENV["VERSION"].to_i if ENV["VERSION"] && !ENV["VERSION"].empty?
+      end
+
       def charset_current(environment = env)
         charset ActiveRecord::Base.configurations[environment]
       end
@@ -225,36 +245,50 @@ module ActiveRecord
         class_for_adapter(configuration["adapter"]).new(*arguments).structure_load(filename, structure_load_flags)
       end
 
-      def load_schema(configuration, format = ActiveRecord::Base.schema_format, file = nil) # :nodoc:
-        file ||= schema_file(format)
+      def load_schema(configuration, format = ActiveRecord::Base.schema_format, file = nil, environment = env, spec_name = "primary") # :nodoc:
+        file ||= dump_filename(spec_name, format)
+
+        check_schema_file(file)
+        ActiveRecord::Base.establish_connection(configuration)
 
         case format
         when :ruby
-          check_schema_file(file)
-          ActiveRecord::Base.establish_connection(configuration)
           load(file)
         when :sql
-          check_schema_file(file)
           structure_load(configuration, file)
         else
           raise ArgumentError, "unknown format #{format.inspect}"
         end
         ActiveRecord::InternalMetadata.create_table
-        ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Migrator.current_environment
+        ActiveRecord::InternalMetadata[:environment] = environment
       end
 
       def schema_file(format = ActiveRecord::Base.schema_format)
+        File.join(db_dir, schema_file_type(format))
+      end
+
+      def schema_file_type(format = ActiveRecord::Base.schema_format)
         case format
         when :ruby
-          File.join(db_dir, "schema.rb")
+          "schema.rb"
         when :sql
-          File.join(db_dir, "structure.sql")
+          "structure.sql"
+        end
+      end
+
+      def dump_filename(namespace, format = ActiveRecord::Base.schema_format)
+        filename = if namespace == "primary"
+          schema_file_type(format)
+        else
+          "#{namespace}_#{schema_file_type(format)}"
         end
+
+        ENV["SCHEMA"] || File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, filename)
       end
 
       def load_schema_current(format = ActiveRecord::Base.schema_format, file = nil, environment = env)
-        each_current_configuration(environment) { |configuration|
-          load_schema configuration, format, file
+        each_current_configuration(environment) { |configuration, spec_name, env|
+          load_schema(configuration, format, file, env, spec_name)
         }
         ActiveRecord::Base.establish_connection(environment.to_sym)
       end
@@ -288,6 +322,9 @@ module ActiveRecord
       end
 
       private
+        def verbose?
+          ENV["VERBOSE"] ? ENV["VERBOSE"] != "false" : true
+        end
 
         def class_for_adapter(adapter)
           _key, task = @tasks.each_pair.detect { |pattern, _task| adapter[pattern] }
@@ -301,9 +338,10 @@ module ActiveRecord
           environments = [environment]
           environments << "test" if environment == "development"
 
-          configurations = ActiveRecord::Base.configurations.values_at(*environments)
-          configurations.compact.each do |configuration|
-            yield configuration unless configuration["database"].blank?
+          environments.each do |env|
+            ActiveRecord::DatabaseConfigurations.configs_for(env) do |spec_name, configuration|
+              yield configuration, spec_name, env
+            end
           end
         end
 
diff --git a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
index 84265aa9e3..e697fa6def 100644
--- a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
@@ -3,8 +3,6 @@
 module ActiveRecord
   module Tasks # :nodoc:
     class MySQLDatabaseTasks # :nodoc:
-      ACCESS_DENIED_ERROR = 1045
-
       delegate :connection, :establish_connection, to: ActiveRecord::Base
 
       def initialize(configuration)
@@ -21,20 +19,6 @@ module ActiveRecord
         else
           raise
         end
-      rescue error_class => error
-        if error.respond_to?(:errno) && error.errno == ACCESS_DENIED_ERROR
-          $stdout.print error.message
-          establish_connection root_configuration_without_database
-          connection.create_database configuration["database"], creation_options
-          if configuration["username"] != "root"
-            connection.execute grant_statement.gsub(/\s+/, " ").strip
-          end
-          establish_connection configuration
-        else
-          $stderr.puts error.inspect
-          $stderr.puts "Couldn't create database for #{configuration.inspect}, #{creation_options.inspect}"
-          $stderr.puts "(If you set the charset manually, make sure you have a matching collation)" if configuration["encoding"]
-        end
       end
 
       def drop
@@ -99,37 +83,6 @@ module ActiveRecord
           end
         end
 
-        def error_class
-          if configuration["adapter"].include?("jdbc")
-            require_relative "../railties/jdbcmysql_error"
-            ArJdbcMySQL::Error
-          elsif defined?(Mysql2)
-            Mysql2::Error
-          else
-            StandardError
-          end
-        end
-
-        def grant_statement
-          <<-SQL
-GRANT ALL PRIVILEGES ON `#{configuration['database']}`.*
-  TO '#{configuration['username']}'@'localhost'
-IDENTIFIED BY '#{configuration['password']}' WITH GRANT OPTION;
-          SQL
-        end
-
-        def root_configuration_without_database
-          configuration_without_database.merge(
-            "username" => "root",
-            "password" => root_password
-          )
-        end
-
-        def root_password
-          $stdout.print "Please provide the root password for your MySQL installation\n>"
-          $stdin.gets.strip
-        end
-
         def prepare_command_options
           args = {
             "host"      => "--host",
diff --git a/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb b/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
index 5681ccdd23..647e066137 100644
--- a/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
@@ -117,7 +117,7 @@ module ActiveRecord
         end
 
         def run_cmd_error(cmd, args, action)
-          msg = "failed to execute:\n"
+          msg = "failed to execute:\n".dup
           msg << "#{cmd} #{args.join(' ')}\n\n"
           msg << "Please check the output above for any errors and make sure that `#{cmd}` is installed in your PATH and has proper permissions.\n\n"
           msg
diff --git a/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb b/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
index abdd6db64a..dfe599c4dd 100644
--- a/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
@@ -73,7 +73,7 @@ module ActiveRecord
         end
 
         def run_cmd_error(cmd, args)
-          msg = "failed to execute:\n"
+          msg = "failed to execute:\n".dup
           msg << "#{cmd} #{args.join(' ')}\n\n"
           msg << "Please check the output above for any errors and make sure that `#{cmd}` is installed in your PATH and has proper permissions.\n\n"
           msg
diff --git a/activerecord/lib/active_record/test_databases.rb b/activerecord/lib/active_record/test_databases.rb
new file mode 100644
index 0000000000..606a3b0fb5
--- /dev/null
+++ b/activerecord/lib/active_record/test_databases.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+require "active_support/testing/parallelization"
+
+module ActiveRecord
+  module TestDatabases # :nodoc:
+    ActiveSupport::Testing::Parallelization.after_fork_hook do |i|
+      create_and_migrate(i, spec_name: Rails.env)
+    end
+
+    ActiveSupport::Testing::Parallelization.run_cleanup_hook do |i|
+      drop(i, spec_name: Rails.env)
+    end
+
+    def self.create_and_migrate(i, spec_name:)
+      old, ENV["VERBOSE"] = ENV["VERBOSE"], "false"
+
+      connection_spec = ActiveRecord::Base.configurations[spec_name]
+
+      connection_spec["database"] += "-#{i}"
+      ActiveRecord::Tasks::DatabaseTasks.create(connection_spec)
+      ActiveRecord::Base.establish_connection(connection_spec)
+      ActiveRecord::Tasks::DatabaseTasks.migrate
+    ensure
+      ActiveRecord::Base.establish_connection(ActiveRecord::Base.configurations[Rails.env])
+      ENV["VERBOSE"] = old
+    end
+
+    def self.drop(i, spec_name:)
+      old, ENV["VERBOSE"] = ENV["VERBOSE"], "false"
+      connection_spec = ActiveRecord::Base.configurations[spec_name]
+
+      ActiveRecord::Tasks::DatabaseTasks.drop(connection_spec)
+    ensure
+      ENV["VERBOSE"] = old
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/timestamp.rb b/activerecord/lib/active_record/timestamp.rb
index 5da3759e5a..e47f06bf3a 100644
--- a/activerecord/lib/active_record/timestamp.rb
+++ b/activerecord/lib/active_record/timestamp.rb
@@ -52,16 +52,20 @@ module ActiveRecord
       clear_timestamp_attributes
     end
 
-    class_methods do
+    module ClassMethods # :nodoc:
+      def timestamp_attributes_for_update_in_model
+        timestamp_attributes_for_update.select { |c| column_names.include?(c) }
+      end
+
+      def current_time_from_proper_timezone
+        default_timezone == :utc ? Time.now.utc : Time.now
+      end
+
       private
         def timestamp_attributes_for_create_in_model
           timestamp_attributes_for_create.select { |c| column_names.include?(c) }
         end
 
-        def timestamp_attributes_for_update_in_model
-          timestamp_attributes_for_update.select { |c| column_names.include?(c) }
-        end
-
         def all_timestamp_attributes_in_model
           timestamp_attributes_for_create_in_model + timestamp_attributes_for_update_in_model
         end
@@ -73,10 +77,6 @@ module ActiveRecord
         def timestamp_attributes_for_update
           ["updated_at", "updated_on"]
         end
-
-        def current_time_from_proper_timezone
-          default_timezone == :utc ? Time.now.utc : Time.now
-        end
     end
 
   private
@@ -116,7 +116,7 @@ module ActiveRecord
     end
 
     def timestamp_attributes_for_update_in_model
-      self.class.send(:timestamp_attributes_for_update_in_model)
+      self.class.timestamp_attributes_for_update_in_model
     end
 
     def all_timestamp_attributes_in_model
@@ -124,7 +124,7 @@ module ActiveRecord
     end
 
     def current_time_from_proper_timezone
-      self.class.send(:current_time_from_proper_timezone)
+      self.class.current_time_from_proper_timezone
     end
 
     def max_updated_column_timestamp(timestamp_names = timestamp_attributes_for_update_in_model)
diff --git a/activerecord/lib/active_record/transactions.rb b/activerecord/lib/active_record/transactions.rb
index 6761f2da25..82adb19f5b 100644
--- a/activerecord/lib/active_record/transactions.rb
+++ b/activerecord/lib/active_record/transactions.rb
@@ -285,7 +285,7 @@ module ActiveRecord
             fire_on = Array(options[:on])
             assert_valid_transaction_action(fire_on)
             options[:if] = Array(options[:if])
-            options[:if].unshift("transaction_include_any_action?(#{fire_on})")
+            options[:if].unshift(-> { transaction_include_any_action?(fire_on) })
           end
         end
 
@@ -306,9 +306,7 @@ module ActiveRecord
     end
 
     def save(*) #:nodoc:
-      rollback_active_record_state! do
-        with_transaction_returning_status { super }
-      end
+      with_transaction_returning_status { super }
     end
 
     def save!(*) #:nodoc:
@@ -319,17 +317,6 @@ module ActiveRecord
       with_transaction_returning_status { super }
     end
 
-    # Reset id and @new_record if the transaction rolls back.
-    def rollback_active_record_state!
-      remember_transaction_record_state
-      yield
-    rescue Exception
-      restore_transaction_record_state
-      raise
-    ensure
-      clear_transaction_record_state
-    end
-
     def before_committed! # :nodoc:
       _run_before_commit_without_transaction_enrollment_callbacks
       _run_before_commit_callbacks
@@ -340,7 +327,7 @@ module ActiveRecord
     # Ensure that it is not called if the object was never persisted (failed create),
     # but call it after the commit of a destroyed object.
     def committed!(should_run_callbacks: true) #:nodoc:
-      if should_run_callbacks && destroyed? || persisted?
+      if should_run_callbacks && (destroyed? || persisted?)
         _run_commit_without_transaction_enrollment_callbacks
         _run_commit_callbacks
       end
@@ -382,13 +369,7 @@ module ActiveRecord
       status = nil
       self.class.transaction do
         add_to_transaction
-        begin
-          status = yield
-        rescue ActiveRecord::Rollback
-          clear_transaction_record_state
-          status = nil
-        end
-
+        status = yield
         raise ActiveRecord::Rollback unless status
       end
       status
@@ -402,8 +383,8 @@ module ActiveRecord
 
       # Save the new record state and id of a record so it can be restored later if a transaction fails.
       def remember_transaction_record_state
-        @_start_transaction_state[:id] = id
         @_start_transaction_state.reverse_merge!(
+          id: id,
           new_record: @new_record,
           destroyed: @destroyed,
           frozen?: frozen?,
@@ -491,7 +472,8 @@ module ActiveRecord
 
       def update_attributes_from_transaction_state(transaction_state)
         if transaction_state && transaction_state.finalized?
-          restore_transaction_record_state if transaction_state.rolledback?
+          restore_transaction_record_state(transaction_state.fully_rolledback?) if transaction_state.rolledback?
+          force_clear_transaction_record_state if transaction_state.fully_committed?
           clear_transaction_record_state if transaction_state.fully_completed?
         end
       end
diff --git a/activerecord/lib/active_record/translation.rb b/activerecord/lib/active_record/translation.rb
index 3cf70eafb8..82661a328a 100644
--- a/activerecord/lib/active_record/translation.rb
+++ b/activerecord/lib/active_record/translation.rb
@@ -10,7 +10,7 @@ module ActiveRecord
       classes = [klass]
       return classes if klass == ActiveRecord::Base
 
-      while klass != klass.base_class
+      while !klass.base_class?
         classes << klass = klass.superclass
       end
       classes
diff --git a/activerecord/lib/active_record/type.rb b/activerecord/lib/active_record/type.rb
index fa22df92b8..c303186ef2 100644
--- a/activerecord/lib/active_record/type.rb
+++ b/activerecord/lib/active_record/type.rb
@@ -2,21 +2,21 @@
 
 require "active_model/type"
 
-require_relative "type/internal/timezone"
+require "active_record/type/internal/timezone"
 
-require_relative "type/date"
-require_relative "type/date_time"
-require_relative "type/decimal_without_scale"
-require_relative "type/json"
-require_relative "type/time"
-require_relative "type/text"
-require_relative "type/unsigned_integer"
+require "active_record/type/date"
+require "active_record/type/date_time"
+require "active_record/type/decimal_without_scale"
+require "active_record/type/json"
+require "active_record/type/time"
+require "active_record/type/text"
+require "active_record/type/unsigned_integer"
 
-require_relative "type/serialized"
-require_relative "type/adapter_specific_registry"
+require "active_record/type/serialized"
+require "active_record/type/adapter_specific_registry"
 
-require_relative "type/type_map"
-require_relative "type/hash_lookup_type_map"
+require "active_record/type/type_map"
+require "active_record/type/hash_lookup_type_map"
 
 module ActiveRecord
   module Type
diff --git a/activerecord/lib/active_record/type/adapter_specific_registry.rb b/activerecord/lib/active_record/type/adapter_specific_registry.rb
index e7468aa542..b300fdfa05 100644
--- a/activerecord/lib/active_record/type/adapter_specific_registry.rb
+++ b/activerecord/lib/active_record/type/adapter_specific_registry.rb
@@ -52,8 +52,6 @@ module ActiveRecord
         priority <=> other.priority
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
       protected
 
         attr_reader :name, :block, :adapter, :override
@@ -114,13 +112,8 @@ module ActiveRecord
         super | 4
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-        attr_reader :options, :klass
-
       private
+        attr_reader :options, :klass
 
         def matches_options?(**kwargs)
           options.all? do |key, value|
diff --git a/activerecord/lib/active_record/type_caster.rb b/activerecord/lib/active_record/type_caster.rb
index ed2e4fb79c..2e5f45fa3d 100644
--- a/activerecord/lib/active_record/type_caster.rb
+++ b/activerecord/lib/active_record/type_caster.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "type_caster/map"
-require_relative "type_caster/connection"
+require "active_record/type_caster/map"
+require "active_record/type_caster/connection"
 
 module ActiveRecord
   module TypeCaster # :nodoc:
diff --git a/activerecord/lib/active_record/type_caster/connection.rb b/activerecord/lib/active_record/type_caster/connection.rb
index af4e4e37e2..7cf8181d8e 100644
--- a/activerecord/lib/active_record/type_caster/connection.rb
+++ b/activerecord/lib/active_record/type_caster/connection.rb
@@ -14,15 +14,10 @@ module ActiveRecord
         connection.type_cast_from_column(column, value)
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
+      private
         attr_reader :table_name
         delegate :connection, to: :@klass
 
-      private
-
         def column_for(attribute_name)
           if connection.schema_cache.data_source_exists?(table_name)
             connection.schema_cache.columns_hash(table_name)[attribute_name.to_s]
diff --git a/activerecord/lib/active_record/type_caster/map.rb b/activerecord/lib/active_record/type_caster/map.rb
index d51350ba83..663cdadb03 100644
--- a/activerecord/lib/active_record/type_caster/map.rb
+++ b/activerecord/lib/active_record/type_caster/map.rb
@@ -9,14 +9,11 @@ module ActiveRecord
 
       def type_cast_for_database(attr_name, value)
         return value if value.is_a?(Arel::Nodes::BindParam)
-        type = types.type_for_attribute(attr_name.to_s)
+        type = types.type_for_attribute(attr_name)
         type.serialize(value)
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
+      private
         attr_reader :types
     end
   end
diff --git a/activerecord/lib/active_record/validations.rb b/activerecord/lib/active_record/validations.rb
index 3f5c879f2f..ca27a3f0ab 100644
--- a/activerecord/lib/active_record/validations.rb
+++ b/activerecord/lib/active_record/validations.rb
@@ -86,8 +86,8 @@ module ActiveRecord
   end
 end
 
-require_relative "validations/associated"
-require_relative "validations/uniqueness"
-require_relative "validations/presence"
-require_relative "validations/absence"
-require_relative "validations/length"
+require "active_record/validations/associated"
+require "active_record/validations/uniqueness"
+require "active_record/validations/presence"
+require "active_record/validations/absence"
+require "active_record/validations/length"
diff --git a/activerecord/lib/active_record/validations/uniqueness.rb b/activerecord/lib/active_record/validations/uniqueness.rb
index f4ad58c087..5a1dbc8e53 100644
--- a/activerecord/lib/active_record/validations/uniqueness.rb
+++ b/activerecord/lib/active_record/validations/uniqueness.rb
@@ -23,7 +23,7 @@ module ActiveRecord
         relation = build_relation(finder_class, attribute, value)
         if record.persisted?
           if finder_class.primary_key
-            relation = relation.where.not(finder_class.primary_key => record.id_in_database || record.id)
+            relation = relation.where.not(finder_class.primary_key => record.id_in_database)
           else
             raise UnknownPrimaryKey.new(finder_class, "Can not validate uniqueness for persisted record without primary key.")
           end
@@ -205,9 +205,7 @@ module ActiveRecord
       #                                      | # Boom! We now have a duplicate
       #                                      | # title!
       #
-      # This could even happen if you use transactions with the 'serializable'
-      # isolation level. The best way to work around this problem is to add a unique
-      # index to the database table using
+      # The best way to work around this problem is to add a unique index to the database table using
       # {connection.add_index}[rdoc-ref:ConnectionAdapters::SchemaStatements#add_index].
       # In the rare case that a race condition occurs, the database will guarantee
       # the field's uniqueness.
diff --git a/activerecord/lib/arel.rb b/activerecord/lib/arel.rb
new file mode 100644
index 0000000000..7d04e1cac6
--- /dev/null
+++ b/activerecord/lib/arel.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require "arel/errors"
+
+require "arel/crud"
+require "arel/factory_methods"
+
+require "arel/expressions"
+require "arel/predications"
+require "arel/window_predications"
+require "arel/math"
+require "arel/alias_predication"
+require "arel/order_predications"
+require "arel/table"
+require "arel/attributes"
+require "arel/compatibility/wheres"
+
+require "arel/visitors"
+require "arel/collectors/sql_string"
+
+require "arel/tree_manager"
+require "arel/insert_manager"
+require "arel/select_manager"
+require "arel/update_manager"
+require "arel/delete_manager"
+require "arel/nodes"
+
+module Arel # :nodoc: all
+  VERSION = "10.0.0"
+
+  def self.sql(raw_sql)
+    Arel::Nodes::SqlLiteral.new raw_sql
+  end
+
+  def self.star
+    sql "*"
+  end
+  ## Convenience Alias
+  Node = Arel::Nodes::Node
+end
diff --git a/activerecord/lib/arel/alias_predication.rb b/activerecord/lib/arel/alias_predication.rb
new file mode 100644
index 0000000000..4abbbb7ef6
--- /dev/null
+++ b/activerecord/lib/arel/alias_predication.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module AliasPredication
+    def as(other)
+      Nodes::As.new self, Nodes::SqlLiteral.new(other)
+    end
+  end
+end
diff --git a/activerecord/lib/arel/attributes.rb b/activerecord/lib/arel/attributes.rb
new file mode 100644
index 0000000000..35d586c948
--- /dev/null
+++ b/activerecord/lib/arel/attributes.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require "arel/attributes/attribute"
+
+module Arel # :nodoc: all
+  module Attributes
+    ###
+    # Factory method to wrap a raw database +column+ to an Arel Attribute.
+    def self.for(column)
+      case column.type
+      when :string, :text, :binary             then String
+      when :integer                            then Integer
+      when :float                              then Float
+      when :decimal                            then Decimal
+      when :date, :datetime, :timestamp, :time then Time
+      when :boolean                            then Boolean
+      else
+        Undefined
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/attributes/attribute.rb b/activerecord/lib/arel/attributes/attribute.rb
new file mode 100644
index 0000000000..ecf499a23e
--- /dev/null
+++ b/activerecord/lib/arel/attributes/attribute.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Attributes
+    class Attribute < Struct.new :relation, :name
+      include Arel::Expressions
+      include Arel::Predications
+      include Arel::AliasPredication
+      include Arel::OrderPredications
+      include Arel::Math
+
+      ###
+      # Create a node for lowering this attribute
+      def lower
+        relation.lower self
+      end
+
+      def type_cast_for_database(value)
+        relation.type_cast_for_database(name, value)
+      end
+
+      def able_to_type_cast?
+        relation.able_to_type_cast?
+      end
+    end
+
+    class String    < Attribute; end
+    class Time      < Attribute; end
+    class Boolean   < Attribute; end
+    class Decimal   < Attribute; end
+    class Float     < Attribute; end
+    class Integer   < Attribute; end
+    class Undefined < Attribute; end
+  end
+
+  Attribute = Attributes::Attribute
+end
diff --git a/activerecord/lib/arel/collectors/bind.rb b/activerecord/lib/arel/collectors/bind.rb
new file mode 100644
index 0000000000..6f8912575d
--- /dev/null
+++ b/activerecord/lib/arel/collectors/bind.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Collectors
+    class Bind
+      def initialize
+        @binds = []
+      end
+
+      def <<(str)
+        self
+      end
+
+      def add_bind(bind)
+        @binds << bind
+        self
+      end
+
+      def value
+        @binds
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/collectors/composite.rb b/activerecord/lib/arel/collectors/composite.rb
new file mode 100644
index 0000000000..d040d8598d
--- /dev/null
+++ b/activerecord/lib/arel/collectors/composite.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Collectors
+    class Composite
+      def initialize(left, right)
+        @left = left
+        @right = right
+      end
+
+      def <<(str)
+        left << str
+        right << str
+        self
+      end
+
+      def add_bind(bind, &block)
+        left.add_bind bind, &block
+        right.add_bind bind, &block
+        self
+      end
+
+      def value
+        [left.value, right.value]
+      end
+
+      protected
+
+        attr_reader :left, :right
+    end
+  end
+end
diff --git a/activerecord/lib/arel/collectors/plain_string.rb b/activerecord/lib/arel/collectors/plain_string.rb
new file mode 100644
index 0000000000..687d7fbf2f
--- /dev/null
+++ b/activerecord/lib/arel/collectors/plain_string.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Collectors
+    class PlainString
+      def initialize
+        @str = "".dup
+      end
+
+      def value
+        @str
+      end
+
+      def <<(str)
+        @str << str
+        self
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/collectors/sql_string.rb b/activerecord/lib/arel/collectors/sql_string.rb
new file mode 100644
index 0000000000..c293a89a74
--- /dev/null
+++ b/activerecord/lib/arel/collectors/sql_string.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+require "arel/collectors/plain_string"
+
+module Arel # :nodoc: all
+  module Collectors
+    class SQLString < PlainString
+      def initialize(*)
+        super
+        @bind_index = 1
+      end
+
+      def add_bind(bind)
+        self << yield(@bind_index)
+        @bind_index += 1
+        self
+      end
+
+      def compile(bvs)
+        value
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/collectors/substitute_binds.rb b/activerecord/lib/arel/collectors/substitute_binds.rb
new file mode 100644
index 0000000000..3f40eec8a8
--- /dev/null
+++ b/activerecord/lib/arel/collectors/substitute_binds.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Collectors
+    class SubstituteBinds
+      def initialize(quoter, delegate_collector)
+        @quoter = quoter
+        @delegate = delegate_collector
+      end
+
+      def <<(str)
+        delegate << str
+        self
+      end
+
+      def add_bind(bind)
+        self << quoter.quote(bind)
+      end
+
+      def value
+        delegate.value
+      end
+
+      protected
+
+        attr_reader :quoter, :delegate
+    end
+  end
+end
diff --git a/activerecord/lib/arel/compatibility/wheres.rb b/activerecord/lib/arel/compatibility/wheres.rb
new file mode 100644
index 0000000000..c8a73f0dae
--- /dev/null
+++ b/activerecord/lib/arel/compatibility/wheres.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Compatibility # :nodoc:
+    class Wheres # :nodoc:
+      include Enumerable
+
+      module Value # :nodoc:
+        attr_accessor :visitor
+        def value
+          visitor.accept self
+        end
+
+        def name
+          super.to_sym
+        end
+      end
+
+      def initialize(engine, collection)
+        @engine     = engine
+        @collection = collection
+      end
+
+      def each
+        to_sql = Visitors::ToSql.new @engine
+
+        @collection.each { |c|
+          c.extend(Value)
+          c.visitor = to_sql
+          yield c
+        }
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/crud.rb b/activerecord/lib/arel/crud.rb
new file mode 100644
index 0000000000..e8a563ca4a
--- /dev/null
+++ b/activerecord/lib/arel/crud.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  ###
+  # FIXME hopefully we can remove this
+  module Crud
+    def compile_update(values, pk)
+      um = UpdateManager.new
+
+      if Nodes::SqlLiteral === values
+        relation = @ctx.from
+      else
+        relation = values.first.first.relation
+      end
+      um.key = pk
+      um.table relation
+      um.set values
+      um.take @ast.limit.expr if @ast.limit
+      um.order(*@ast.orders)
+      um.wheres = @ctx.wheres
+      um
+    end
+
+    def compile_insert(values)
+      im = create_insert
+      im.insert values
+      im
+    end
+
+    def create_insert
+      InsertManager.new
+    end
+
+    def compile_delete
+      dm = DeleteManager.new
+      dm.take @ast.limit.expr if @ast.limit
+      dm.wheres = @ctx.wheres
+      dm.from @ctx.froms
+      dm
+    end
+  end
+end
diff --git a/activerecord/lib/arel/delete_manager.rb b/activerecord/lib/arel/delete_manager.rb
new file mode 100644
index 0000000000..2def581009
--- /dev/null
+++ b/activerecord/lib/arel/delete_manager.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  class DeleteManager < Arel::TreeManager
+    def initialize
+      super
+      @ast = Nodes::DeleteStatement.new
+      @ctx = @ast
+    end
+
+    def from(relation)
+      @ast.relation = relation
+      self
+    end
+
+    def take(limit)
+      @ast.limit = Nodes::Limit.new(Nodes.build_quoted(limit)) if limit
+      self
+    end
+
+    def wheres=(list)
+      @ast.wheres = list
+    end
+  end
+end
diff --git a/activerecord/lib/arel/errors.rb b/activerecord/lib/arel/errors.rb
new file mode 100644
index 0000000000..2f8d5e3c02
--- /dev/null
+++ b/activerecord/lib/arel/errors.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  class ArelError < StandardError
+  end
+
+  class EmptyJoinError < ArelError
+  end
+end
diff --git a/activerecord/lib/arel/expressions.rb b/activerecord/lib/arel/expressions.rb
new file mode 100644
index 0000000000..da8afb338c
--- /dev/null
+++ b/activerecord/lib/arel/expressions.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Expressions
+    def count(distinct = false)
+      Nodes::Count.new [self], distinct
+    end
+
+    def sum
+      Nodes::Sum.new [self]
+    end
+
+    def maximum
+      Nodes::Max.new [self]
+    end
+
+    def minimum
+      Nodes::Min.new [self]
+    end
+
+    def average
+      Nodes::Avg.new [self]
+    end
+
+    def extract(field)
+      Nodes::Extract.new [self], field
+    end
+  end
+end
diff --git a/activerecord/lib/arel/factory_methods.rb b/activerecord/lib/arel/factory_methods.rb
new file mode 100644
index 0000000000..b828bc274e
--- /dev/null
+++ b/activerecord/lib/arel/factory_methods.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  ###
+  # Methods for creating various nodes
+  module FactoryMethods
+    def create_true
+      Arel::Nodes::True.new
+    end
+
+    def create_false
+      Arel::Nodes::False.new
+    end
+
+    def create_table_alias(relation, name)
+      Nodes::TableAlias.new(relation, name)
+    end
+
+    def create_join(to, constraint = nil, klass = Nodes::InnerJoin)
+      klass.new(to, constraint)
+    end
+
+    def create_string_join(to)
+      create_join to, nil, Nodes::StringJoin
+    end
+
+    def create_and(clauses)
+      Nodes::And.new clauses
+    end
+
+    def create_on(expr)
+      Nodes::On.new expr
+    end
+
+    def grouping(expr)
+      Nodes::Grouping.new expr
+    end
+
+    ###
+    # Create a LOWER() function
+    def lower(column)
+      Nodes::NamedFunction.new "LOWER", [Nodes.build_quoted(column)]
+    end
+  end
+end
diff --git a/activerecord/lib/arel/insert_manager.rb b/activerecord/lib/arel/insert_manager.rb
new file mode 100644
index 0000000000..c90fc33a48
--- /dev/null
+++ b/activerecord/lib/arel/insert_manager.rb
@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  class InsertManager < Arel::TreeManager
+    def initialize
+      super
+      @ast = Nodes::InsertStatement.new
+    end
+
+    def into(table)
+      @ast.relation = table
+      self
+    end
+
+    def columns; @ast.columns end
+    def values=(val); @ast.values = val; end
+
+    def select(select)
+      @ast.select = select
+    end
+
+    def insert(fields)
+      return if fields.empty?
+
+      if String === fields
+        @ast.values = Nodes::SqlLiteral.new(fields)
+      else
+        @ast.relation ||= fields.first.first.relation
+
+        values = []
+
+        fields.each do |column, value|
+          @ast.columns << column
+          values << value
+        end
+        @ast.values = create_values values, @ast.columns
+      end
+      self
+    end
+
+    def create_values(values, columns)
+      Nodes::Values.new values, columns
+    end
+
+    def create_values_list(rows)
+      Nodes::ValuesList.new(rows)
+    end
+  end
+end
diff --git a/activerecord/lib/arel/math.rb b/activerecord/lib/arel/math.rb
new file mode 100644
index 0000000000..2359f13148
--- /dev/null
+++ b/activerecord/lib/arel/math.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Math
+    def *(other)
+      Arel::Nodes::Multiplication.new(self, other)
+    end
+
+    def +(other)
+      Arel::Nodes::Grouping.new(Arel::Nodes::Addition.new(self, other))
+    end
+
+    def -(other)
+      Arel::Nodes::Grouping.new(Arel::Nodes::Subtraction.new(self, other))
+    end
+
+    def /(other)
+      Arel::Nodes::Division.new(self, other)
+    end
+
+    def &(other)
+      Arel::Nodes::Grouping.new(Arel::Nodes::BitwiseAnd.new(self, other))
+    end
+
+    def |(other)
+      Arel::Nodes::Grouping.new(Arel::Nodes::BitwiseOr.new(self, other))
+    end
+
+    def ^(other)
+      Arel::Nodes::Grouping.new(Arel::Nodes::BitwiseXor.new(self, other))
+    end
+
+    def <<(other)
+      Arel::Nodes::Grouping.new(Arel::Nodes::BitwiseShiftLeft.new(self, other))
+    end
+
+    def >>(other)
+      Arel::Nodes::Grouping.new(Arel::Nodes::BitwiseShiftRight.new(self, other))
+    end
+
+    def ~@
+      Arel::Nodes::BitwiseNot.new(self)
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes.rb b/activerecord/lib/arel/nodes.rb
new file mode 100644
index 0000000000..5af0e532e2
--- /dev/null
+++ b/activerecord/lib/arel/nodes.rb
@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+# node
+require "arel/nodes/node"
+require "arel/nodes/node_expression"
+require "arel/nodes/select_statement"
+require "arel/nodes/select_core"
+require "arel/nodes/insert_statement"
+require "arel/nodes/update_statement"
+require "arel/nodes/bind_param"
+
+# terminal
+
+require "arel/nodes/terminal"
+require "arel/nodes/true"
+require "arel/nodes/false"
+
+# unary
+require "arel/nodes/unary"
+require "arel/nodes/grouping"
+require "arel/nodes/ascending"
+require "arel/nodes/descending"
+require "arel/nodes/unqualified_column"
+require "arel/nodes/with"
+
+# binary
+require "arel/nodes/binary"
+require "arel/nodes/equality"
+require "arel/nodes/in" # Why is this subclassed from equality?
+require "arel/nodes/join_source"
+require "arel/nodes/delete_statement"
+require "arel/nodes/table_alias"
+require "arel/nodes/infix_operation"
+require "arel/nodes/unary_operation"
+require "arel/nodes/over"
+require "arel/nodes/matches"
+require "arel/nodes/regexp"
+
+# nary
+require "arel/nodes/and"
+
+# function
+# FIXME: Function + Alias can be rewritten as a Function and Alias node.
+# We should make Function a Unary node and deprecate the use of "aliaz"
+require "arel/nodes/function"
+require "arel/nodes/count"
+require "arel/nodes/extract"
+require "arel/nodes/values"
+require "arel/nodes/values_list"
+require "arel/nodes/named_function"
+
+# windows
+require "arel/nodes/window"
+
+# conditional expressions
+require "arel/nodes/case"
+
+# joins
+require "arel/nodes/full_outer_join"
+require "arel/nodes/inner_join"
+require "arel/nodes/outer_join"
+require "arel/nodes/right_outer_join"
+require "arel/nodes/string_join"
+
+require "arel/nodes/sql_literal"
+
+require "arel/nodes/casted"
diff --git a/activerecord/lib/arel/nodes/and.rb b/activerecord/lib/arel/nodes/and.rb
new file mode 100644
index 0000000000..c530a77bfb
--- /dev/null
+++ b/activerecord/lib/arel/nodes/and.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class And < Arel::Nodes::Node
+      attr_reader :children
+
+      def initialize(children)
+        super()
+        @children = children
+      end
+
+      def left
+        children.first
+      end
+
+      def right
+        children[1]
+      end
+
+      def hash
+        children.hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.children == other.children
+      end
+      alias :== :eql?
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/ascending.rb b/activerecord/lib/arel/nodes/ascending.rb
new file mode 100644
index 0000000000..8b617f4df5
--- /dev/null
+++ b/activerecord/lib/arel/nodes/ascending.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Ascending < Ordering
+      def reverse
+        Descending.new(expr)
+      end
+
+      def direction
+        :asc
+      end
+
+      def ascending?
+        true
+      end
+
+      def descending?
+        false
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/binary.rb b/activerecord/lib/arel/nodes/binary.rb
new file mode 100644
index 0000000000..e184e99c73
--- /dev/null
+++ b/activerecord/lib/arel/nodes/binary.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Binary < Arel::Nodes::NodeExpression
+      attr_accessor :left, :right
+
+      def initialize(left, right)
+        super()
+        @left  = left
+        @right = right
+      end
+
+      def initialize_copy(other)
+        super
+        @left  = @left.clone if @left
+        @right = @right.clone if @right
+      end
+
+      def hash
+        [self.class, @left, @right].hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.left == other.left &&
+          self.right == other.right
+      end
+      alias :== :eql?
+    end
+
+    %w{
+      As
+      Assignment
+      Between
+      GreaterThan
+      GreaterThanOrEqual
+      Join
+      LessThan
+      LessThanOrEqual
+      NotEqual
+      NotIn
+      Or
+      Union
+      UnionAll
+      Intersect
+      Except
+    }.each do |name|
+      const_set name, Class.new(Binary)
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/bind_param.rb b/activerecord/lib/arel/nodes/bind_param.rb
new file mode 100644
index 0000000000..53c5563d93
--- /dev/null
+++ b/activerecord/lib/arel/nodes/bind_param.rb
@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class BindParam < Node
+      attr_accessor :value
+
+      def initialize(value)
+        @value = value
+        super()
+      end
+
+      def hash
+        [self.class, self.value].hash
+      end
+
+      def eql?(other)
+        other.is_a?(BindParam) &&
+          value == other.value
+      end
+      alias :== :eql?
+
+      def nil?
+        value.nil?
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/case.rb b/activerecord/lib/arel/nodes/case.rb
new file mode 100644
index 0000000000..654a54825e
--- /dev/null
+++ b/activerecord/lib/arel/nodes/case.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Case < Arel::Nodes::Node
+      attr_accessor :case, :conditions, :default
+
+      def initialize(expression = nil, default = nil)
+        @case = expression
+        @conditions = []
+        @default = default
+      end
+
+      def when(condition, expression = nil)
+        @conditions << When.new(Nodes.build_quoted(condition), expression)
+        self
+      end
+
+      def then(expression)
+        @conditions.last.right = Nodes.build_quoted(expression)
+        self
+      end
+
+      def else(expression)
+        @default = Else.new Nodes.build_quoted(expression)
+        self
+      end
+
+      def initialize_copy(other)
+        super
+        @case = @case.clone if @case
+        @conditions = @conditions.map { |x| x.clone }
+        @default = @default.clone if @default
+      end
+
+      def hash
+        [@case, @conditions, @default].hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.case == other.case &&
+          self.conditions == other.conditions &&
+          self.default == other.default
+      end
+      alias :== :eql?
+    end
+
+    class When < Binary # :nodoc:
+    end
+
+    class Else < Unary # :nodoc:
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/casted.rb b/activerecord/lib/arel/nodes/casted.rb
new file mode 100644
index 0000000000..c1e6e97d6d
--- /dev/null
+++ b/activerecord/lib/arel/nodes/casted.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Casted < Arel::Nodes::NodeExpression # :nodoc:
+      attr_reader :val, :attribute
+      def initialize(val, attribute)
+        @val       = val
+        @attribute = attribute
+        super()
+      end
+
+      def nil?; @val.nil?; end
+
+      def hash
+        [self.class, val, attribute].hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+            self.val == other.val &&
+            self.attribute == other.attribute
+      end
+      alias :== :eql?
+    end
+
+    class Quoted < Arel::Nodes::Unary # :nodoc:
+      alias :val :value
+      def nil?; val.nil?; end
+    end
+
+    def self.build_quoted(other, attribute = nil)
+      case other
+      when Arel::Nodes::Node, Arel::Attributes::Attribute, Arel::Table, Arel::Nodes::BindParam, Arel::SelectManager, Arel::Nodes::Quoted, Arel::Nodes::SqlLiteral
+        other
+      else
+        case attribute
+        when Arel::Attributes::Attribute
+          Casted.new other, attribute
+        else
+          Quoted.new other
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/count.rb b/activerecord/lib/arel/nodes/count.rb
new file mode 100644
index 0000000000..880464639d
--- /dev/null
+++ b/activerecord/lib/arel/nodes/count.rb
@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Count < Arel::Nodes::Function
+      def initialize(expr, distinct = false, aliaz = nil)
+        super(expr, aliaz)
+        @distinct = distinct
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/delete_statement.rb b/activerecord/lib/arel/nodes/delete_statement.rb
new file mode 100644
index 0000000000..eaac05e2f6
--- /dev/null
+++ b/activerecord/lib/arel/nodes/delete_statement.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class DeleteStatement < Arel::Nodes::Node
+      attr_accessor :left, :right
+      attr_accessor :limit
+
+      alias :relation :left
+      alias :relation= :left=
+      alias :wheres :right
+      alias :wheres= :right=
+
+      def initialize(relation = nil, wheres = [])
+        super()
+        @left = relation
+        @right = wheres
+      end
+
+      def initialize_copy(other)
+        super
+        @left  = @left.clone if @left
+        @right = @right.clone if @right
+      end
+
+      def hash
+        [self.class, @left, @right].hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.left == other.left &&
+          self.right == other.right
+      end
+      alias :== :eql?
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/descending.rb b/activerecord/lib/arel/nodes/descending.rb
new file mode 100644
index 0000000000..f3f6992ca8
--- /dev/null
+++ b/activerecord/lib/arel/nodes/descending.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Descending < Ordering
+      def reverse
+        Ascending.new(expr)
+      end
+
+      def direction
+        :desc
+      end
+
+      def ascending?
+        false
+      end
+
+      def descending?
+        true
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/equality.rb b/activerecord/lib/arel/nodes/equality.rb
new file mode 100644
index 0000000000..2aa85a977e
--- /dev/null
+++ b/activerecord/lib/arel/nodes/equality.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Equality < Arel::Nodes::Binary
+      def operator; :== end
+      alias :operand1 :left
+      alias :operand2 :right
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/extract.rb b/activerecord/lib/arel/nodes/extract.rb
new file mode 100644
index 0000000000..5799ee9b8f
--- /dev/null
+++ b/activerecord/lib/arel/nodes/extract.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Extract < Arel::Nodes::Unary
+      attr_accessor :field
+
+      def initialize(expr, field)
+        super(expr)
+        @field = field
+      end
+
+      def hash
+        super ^ @field.hash
+      end
+
+      def eql?(other)
+        super &&
+          self.field == other.field
+      end
+      alias :== :eql?
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/false.rb b/activerecord/lib/arel/nodes/false.rb
new file mode 100644
index 0000000000..1e5bf04be5
--- /dev/null
+++ b/activerecord/lib/arel/nodes/false.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class False < Arel::Nodes::NodeExpression
+      def hash
+        self.class.hash
+      end
+
+      def eql?(other)
+        self.class == other.class
+      end
+      alias :== :eql?
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/full_outer_join.rb b/activerecord/lib/arel/nodes/full_outer_join.rb
new file mode 100644
index 0000000000..91bb81f2e3
--- /dev/null
+++ b/activerecord/lib/arel/nodes/full_outer_join.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class FullOuterJoin < Arel::Nodes::Join
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/function.rb b/activerecord/lib/arel/nodes/function.rb
new file mode 100644
index 0000000000..0a439b39f5
--- /dev/null
+++ b/activerecord/lib/arel/nodes/function.rb
@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Function < Arel::Nodes::NodeExpression
+      include Arel::WindowPredications
+      attr_accessor :expressions, :alias, :distinct
+
+      def initialize(expr, aliaz = nil)
+        super()
+        @expressions = expr
+        @alias       = aliaz && SqlLiteral.new(aliaz)
+        @distinct    = false
+      end
+
+      def as(aliaz)
+        self.alias = SqlLiteral.new(aliaz)
+        self
+      end
+
+      def hash
+        [@expressions, @alias, @distinct].hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.expressions == other.expressions &&
+          self.alias == other.alias &&
+          self.distinct == other.distinct
+      end
+      alias :== :eql?
+    end
+
+    %w{
+      Sum
+      Exists
+      Max
+      Min
+      Avg
+    }.each do |name|
+      const_set(name, Class.new(Function))
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/grouping.rb b/activerecord/lib/arel/nodes/grouping.rb
new file mode 100644
index 0000000000..4d0bd69d4d
--- /dev/null
+++ b/activerecord/lib/arel/nodes/grouping.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Grouping < Unary
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/in.rb b/activerecord/lib/arel/nodes/in.rb
new file mode 100644
index 0000000000..2be45d6f99
--- /dev/null
+++ b/activerecord/lib/arel/nodes/in.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class In < Equality
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/infix_operation.rb b/activerecord/lib/arel/nodes/infix_operation.rb
new file mode 100644
index 0000000000..bc7e20dcc6
--- /dev/null
+++ b/activerecord/lib/arel/nodes/infix_operation.rb
@@ -0,0 +1,80 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class InfixOperation < Binary
+      include Arel::Expressions
+      include Arel::Predications
+      include Arel::OrderPredications
+      include Arel::AliasPredication
+      include Arel::Math
+
+      attr_reader :operator
+
+      def initialize(operator, left, right)
+        super(left, right)
+        @operator = operator
+      end
+    end
+
+    class Multiplication < InfixOperation
+      def initialize(left, right)
+        super(:*, left, right)
+      end
+    end
+
+    class Division < InfixOperation
+      def initialize(left, right)
+        super(:/, left, right)
+      end
+    end
+
+    class Addition < InfixOperation
+      def initialize(left, right)
+        super(:+, left, right)
+      end
+    end
+
+    class Subtraction < InfixOperation
+      def initialize(left, right)
+        super(:-, left, right)
+      end
+    end
+
+    class Concat < InfixOperation
+      def initialize(left, right)
+        super("||", left, right)
+      end
+    end
+
+    class BitwiseAnd < InfixOperation
+      def initialize(left, right)
+        super(:&, left, right)
+      end
+    end
+
+    class BitwiseOr < InfixOperation
+      def initialize(left, right)
+        super(:|, left, right)
+      end
+    end
+
+    class BitwiseXor < InfixOperation
+      def initialize(left, right)
+        super(:^, left, right)
+      end
+    end
+
+    class BitwiseShiftLeft < InfixOperation
+      def initialize(left, right)
+        super(:<<, left, right)
+      end
+    end
+
+    class BitwiseShiftRight < InfixOperation
+      def initialize(left, right)
+        super(:>>, left, right)
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/inner_join.rb b/activerecord/lib/arel/nodes/inner_join.rb
new file mode 100644
index 0000000000..519fafad09
--- /dev/null
+++ b/activerecord/lib/arel/nodes/inner_join.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class InnerJoin < Arel::Nodes::Join
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/insert_statement.rb b/activerecord/lib/arel/nodes/insert_statement.rb
new file mode 100644
index 0000000000..d28fd1f6c8
--- /dev/null
+++ b/activerecord/lib/arel/nodes/insert_statement.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class InsertStatement < Arel::Nodes::Node
+      attr_accessor :relation, :columns, :values, :select
+
+      def initialize
+        super()
+        @relation = nil
+        @columns  = []
+        @values   = nil
+        @select   = nil
+      end
+
+      def initialize_copy(other)
+        super
+        @columns = @columns.clone
+        @values =  @values.clone if @values
+        @select =  @select.clone if @select
+      end
+
+      def hash
+        [@relation, @columns, @values, @select].hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.relation == other.relation &&
+          self.columns == other.columns &&
+          self.select == other.select &&
+          self.values == other.values
+      end
+      alias :== :eql?
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/join_source.rb b/activerecord/lib/arel/nodes/join_source.rb
new file mode 100644
index 0000000000..abf0944623
--- /dev/null
+++ b/activerecord/lib/arel/nodes/join_source.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    ###
+    # Class that represents a join source
+    #
+    #   http://www.sqlite.org/syntaxdiagrams.html#join-source
+
+    class JoinSource < Arel::Nodes::Binary
+      def initialize(single_source, joinop = [])
+        super
+      end
+
+      def empty?
+        !left && right.empty?
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/matches.rb b/activerecord/lib/arel/nodes/matches.rb
new file mode 100644
index 0000000000..fd5734f4bd
--- /dev/null
+++ b/activerecord/lib/arel/nodes/matches.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Matches < Binary
+      attr_reader :escape
+      attr_accessor :case_sensitive
+
+      def initialize(left, right, escape = nil, case_sensitive = false)
+        super(left, right)
+        @escape = escape && Nodes.build_quoted(escape)
+        @case_sensitive = case_sensitive
+      end
+    end
+
+    class DoesNotMatch < Matches; end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/named_function.rb b/activerecord/lib/arel/nodes/named_function.rb
new file mode 100644
index 0000000000..126462d6d6
--- /dev/null
+++ b/activerecord/lib/arel/nodes/named_function.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class NamedFunction < Arel::Nodes::Function
+      attr_accessor :name
+
+      def initialize(name, expr, aliaz = nil)
+        super(expr, aliaz)
+        @name = name
+      end
+
+      def hash
+        super ^ @name.hash
+      end
+
+      def eql?(other)
+        super && self.name == other.name
+      end
+      alias :== :eql?
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/node.rb b/activerecord/lib/arel/nodes/node.rb
new file mode 100644
index 0000000000..2b9b1e9828
--- /dev/null
+++ b/activerecord/lib/arel/nodes/node.rb
@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    ###
+    # Abstract base class for all AST nodes
+    class Node
+      include Arel::FactoryMethods
+      include Enumerable
+
+      if $DEBUG
+        def _caller
+          @caller
+        end
+
+        def initialize
+          @caller = caller.dup
+        end
+      end
+
+      ###
+      # Factory method to create a Nodes::Not node that has the recipient of
+      # the caller as a child.
+      def not
+        Nodes::Not.new self
+      end
+
+      ###
+      # Factory method to create a Nodes::Grouping node that has an Nodes::Or
+      # node as a child.
+      def or(right)
+        Nodes::Grouping.new Nodes::Or.new(self, right)
+      end
+
+      ###
+      # Factory method to create an Nodes::And node.
+      def and(right)
+        Nodes::And.new [self, right]
+      end
+
+      # FIXME: this method should go away.  I don't like people calling
+      # to_sql on non-head nodes.  This forces us to walk the AST until we
+      # can find a node that has a "relation" member.
+      #
+      # Maybe we should just use `Table.engine`?  :'(
+      def to_sql(engine = Table.engine)
+        collector = Arel::Collectors::SQLString.new
+        collector = engine.connection.visitor.accept self, collector
+        collector.value
+      end
+
+      # Iterate through AST, nodes will be yielded depth-first
+      def each(&block)
+        return enum_for(:each) unless block_given?
+
+        ::Arel::Visitors::DepthFirst.new(block).accept self
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/node_expression.rb b/activerecord/lib/arel/nodes/node_expression.rb
new file mode 100644
index 0000000000..cbcfaba37c
--- /dev/null
+++ b/activerecord/lib/arel/nodes/node_expression.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class NodeExpression < Arel::Nodes::Node
+      include Arel::Expressions
+      include Arel::Predications
+      include Arel::AliasPredication
+      include Arel::OrderPredications
+      include Arel::Math
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/outer_join.rb b/activerecord/lib/arel/nodes/outer_join.rb
new file mode 100644
index 0000000000..0a3042be61
--- /dev/null
+++ b/activerecord/lib/arel/nodes/outer_join.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class OuterJoin < Arel::Nodes::Join
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/over.rb b/activerecord/lib/arel/nodes/over.rb
new file mode 100644
index 0000000000..91176764a9
--- /dev/null
+++ b/activerecord/lib/arel/nodes/over.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Over < Binary
+      include Arel::AliasPredication
+
+      def initialize(left, right = nil)
+        super(left, right)
+      end
+
+      def operator; "OVER" end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/regexp.rb b/activerecord/lib/arel/nodes/regexp.rb
new file mode 100644
index 0000000000..7c25095569
--- /dev/null
+++ b/activerecord/lib/arel/nodes/regexp.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Regexp < Binary
+      attr_accessor :case_sensitive
+
+      def initialize(left, right, case_sensitive = true)
+        super(left, right)
+        @case_sensitive = case_sensitive
+      end
+    end
+
+    class NotRegexp < Regexp; end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/right_outer_join.rb b/activerecord/lib/arel/nodes/right_outer_join.rb
new file mode 100644
index 0000000000..04ed4aaa78
--- /dev/null
+++ b/activerecord/lib/arel/nodes/right_outer_join.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class RightOuterJoin < Arel::Nodes::Join
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/select_core.rb b/activerecord/lib/arel/nodes/select_core.rb
new file mode 100644
index 0000000000..2defe61974
--- /dev/null
+++ b/activerecord/lib/arel/nodes/select_core.rb
@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class SelectCore < Arel::Nodes::Node
+      attr_accessor :top, :projections, :wheres, :groups, :windows
+      attr_accessor :havings, :source, :set_quantifier
+
+      def initialize
+        super()
+        @source         = JoinSource.new nil
+        @top            = nil
+
+        # https://ronsavage.github.io/SQL/sql-92.bnf.html#set%20quantifier
+        @set_quantifier = nil
+        @projections    = []
+        @wheres         = []
+        @groups         = []
+        @havings        = []
+        @windows        = []
+      end
+
+      def from
+        @source.left
+      end
+
+      def from=(value)
+        @source.left = value
+      end
+
+      alias :froms= :from=
+      alias :froms :from
+
+      def initialize_copy(other)
+        super
+        @source      = @source.clone if @source
+        @projections = @projections.clone
+        @wheres      = @wheres.clone
+        @groups      = @groups.clone
+        @havings     = @havings.clone
+        @windows     = @windows.clone
+      end
+
+      def hash
+        [
+          @source, @top, @set_quantifier, @projections,
+          @wheres, @groups, @havings, @windows
+        ].hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.source == other.source &&
+          self.top == other.top &&
+          self.set_quantifier == other.set_quantifier &&
+          self.projections == other.projections &&
+          self.wheres == other.wheres &&
+          self.groups == other.groups &&
+          self.havings == other.havings &&
+          self.windows == other.windows
+      end
+      alias :== :eql?
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/select_statement.rb b/activerecord/lib/arel/nodes/select_statement.rb
new file mode 100644
index 0000000000..eff5dad939
--- /dev/null
+++ b/activerecord/lib/arel/nodes/select_statement.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class SelectStatement < Arel::Nodes::NodeExpression
+      attr_reader :cores
+      attr_accessor :limit, :orders, :lock, :offset, :with
+
+      def initialize(cores = [SelectCore.new])
+        super()
+        @cores          = cores
+        @orders         = []
+        @limit          = nil
+        @lock           = nil
+        @offset         = nil
+        @with           = nil
+      end
+
+      def initialize_copy(other)
+        super
+        @cores  = @cores.map { |x| x.clone }
+        @orders = @orders.map { |x| x.clone }
+      end
+
+      def hash
+        [@cores, @orders, @limit, @lock, @offset, @with].hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.cores == other.cores &&
+          self.orders == other.orders &&
+          self.limit == other.limit &&
+          self.lock == other.lock &&
+          self.offset == other.offset &&
+          self.with == other.with
+      end
+      alias :== :eql?
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/sql_literal.rb b/activerecord/lib/arel/nodes/sql_literal.rb
new file mode 100644
index 0000000000..d25a8521b7
--- /dev/null
+++ b/activerecord/lib/arel/nodes/sql_literal.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class SqlLiteral < String
+      include Arel::Expressions
+      include Arel::Predications
+      include Arel::AliasPredication
+      include Arel::OrderPredications
+
+      def encode_with(coder)
+        coder.scalar = self.to_s
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/string_join.rb b/activerecord/lib/arel/nodes/string_join.rb
new file mode 100644
index 0000000000..86027fcab7
--- /dev/null
+++ b/activerecord/lib/arel/nodes/string_join.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class StringJoin < Arel::Nodes::Join
+      def initialize(left, right = nil)
+        super
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/table_alias.rb b/activerecord/lib/arel/nodes/table_alias.rb
new file mode 100644
index 0000000000..f95ca16a3d
--- /dev/null
+++ b/activerecord/lib/arel/nodes/table_alias.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class TableAlias < Arel::Nodes::Binary
+      alias :name :right
+      alias :relation :left
+      alias :table_alias :name
+
+      def [](name)
+        Attribute.new(self, name)
+      end
+
+      def table_name
+        relation.respond_to?(:name) ? relation.name : name
+      end
+
+      def type_cast_for_database(*args)
+        relation.type_cast_for_database(*args)
+      end
+
+      def able_to_type_cast?
+        relation.respond_to?(:able_to_type_cast?) && relation.able_to_type_cast?
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/terminal.rb b/activerecord/lib/arel/nodes/terminal.rb
new file mode 100644
index 0000000000..d84c453f1a
--- /dev/null
+++ b/activerecord/lib/arel/nodes/terminal.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Distinct < Arel::Nodes::NodeExpression
+      def hash
+        self.class.hash
+      end
+
+      def eql?(other)
+        self.class == other.class
+      end
+      alias :== :eql?
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/true.rb b/activerecord/lib/arel/nodes/true.rb
new file mode 100644
index 0000000000..c891012969
--- /dev/null
+++ b/activerecord/lib/arel/nodes/true.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class True < Arel::Nodes::NodeExpression
+      def hash
+        self.class.hash
+      end
+
+      def eql?(other)
+        self.class == other.class
+      end
+      alias :== :eql?
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/unary.rb b/activerecord/lib/arel/nodes/unary.rb
new file mode 100644
index 0000000000..a3c0045897
--- /dev/null
+++ b/activerecord/lib/arel/nodes/unary.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Unary < Arel::Nodes::NodeExpression
+      attr_accessor :expr
+      alias :value :expr
+
+      def initialize(expr)
+        super()
+        @expr = expr
+      end
+
+      def hash
+        @expr.hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.expr == other.expr
+      end
+      alias :== :eql?
+    end
+
+    %w{
+      Bin
+      Cube
+      DistinctOn
+      Group
+      GroupingElement
+      GroupingSet
+      Lateral
+      Limit
+      Lock
+      Not
+      Offset
+      On
+      Ordering
+      RollUp
+      Top
+    }.each do |name|
+      const_set(name, Class.new(Unary))
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/unary_operation.rb b/activerecord/lib/arel/nodes/unary_operation.rb
new file mode 100644
index 0000000000..524282ac84
--- /dev/null
+++ b/activerecord/lib/arel/nodes/unary_operation.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class UnaryOperation < Unary
+      attr_reader :operator
+
+      def initialize(operator, operand)
+        super(operand)
+        @operator = operator
+      end
+    end
+
+    class BitwiseNot < UnaryOperation
+      def initialize(operand)
+        super(:~, operand)
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/unqualified_column.rb b/activerecord/lib/arel/nodes/unqualified_column.rb
new file mode 100644
index 0000000000..7c3e0720d7
--- /dev/null
+++ b/activerecord/lib/arel/nodes/unqualified_column.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class UnqualifiedColumn < Arel::Nodes::Unary
+      alias :attribute :expr
+      alias :attribute= :expr=
+
+      def relation
+        @expr.relation
+      end
+
+      def column
+        @expr.column
+      end
+
+      def name
+        @expr.name
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/update_statement.rb b/activerecord/lib/arel/nodes/update_statement.rb
new file mode 100644
index 0000000000..5184b1180f
--- /dev/null
+++ b/activerecord/lib/arel/nodes/update_statement.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class UpdateStatement < Arel::Nodes::Node
+      attr_accessor :relation, :wheres, :values, :orders, :limit
+      attr_accessor :key
+
+      def initialize
+        @relation = nil
+        @wheres   = []
+        @values   = []
+        @orders   = []
+        @limit    = nil
+        @key      = nil
+      end
+
+      def initialize_copy(other)
+        super
+        @wheres = @wheres.clone
+        @values = @values.clone
+      end
+
+      def hash
+        [@relation, @wheres, @values, @orders, @limit, @key].hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.relation == other.relation &&
+          self.wheres == other.wheres &&
+          self.values == other.values &&
+          self.orders == other.orders &&
+          self.limit == other.limit &&
+          self.key == other.key
+      end
+      alias :== :eql?
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/values.rb b/activerecord/lib/arel/nodes/values.rb
new file mode 100644
index 0000000000..650248dc04
--- /dev/null
+++ b/activerecord/lib/arel/nodes/values.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Values < Arel::Nodes::Binary
+      alias :expressions :left
+      alias :expressions= :left=
+      alias :columns :right
+      alias :columns= :right=
+
+      def initialize(exprs, columns = [])
+        super
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/values_list.rb b/activerecord/lib/arel/nodes/values_list.rb
new file mode 100644
index 0000000000..27109848e4
--- /dev/null
+++ b/activerecord/lib/arel/nodes/values_list.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class ValuesList < Node
+      attr_reader :rows
+
+      def initialize(rows)
+        @rows = rows
+        super()
+      end
+
+      def hash
+        @rows.hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.rows == other.rows
+      end
+      alias :== :eql?
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/window.rb b/activerecord/lib/arel/nodes/window.rb
new file mode 100644
index 0000000000..4916fc7fbe
--- /dev/null
+++ b/activerecord/lib/arel/nodes/window.rb
@@ -0,0 +1,126 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Window < Arel::Nodes::Node
+      attr_accessor :orders, :framing, :partitions
+
+      def initialize
+        @orders = []
+        @partitions = []
+        @framing = nil
+      end
+
+      def order(*expr)
+        # FIXME: We SHOULD NOT be converting these to SqlLiteral automatically
+        @orders.concat expr.map { |x|
+          String === x || Symbol === x ? Nodes::SqlLiteral.new(x.to_s) : x
+        }
+        self
+      end
+
+      def partition(*expr)
+        # FIXME: We SHOULD NOT be converting these to SqlLiteral automatically
+        @partitions.concat expr.map { |x|
+          String === x || Symbol === x ? Nodes::SqlLiteral.new(x.to_s) : x
+        }
+        self
+      end
+
+      def frame(expr)
+        @framing = expr
+      end
+
+      def rows(expr = nil)
+        if @framing
+          Rows.new(expr)
+        else
+          frame(Rows.new(expr))
+        end
+      end
+
+      def range(expr = nil)
+        if @framing
+          Range.new(expr)
+        else
+          frame(Range.new(expr))
+        end
+      end
+
+      def initialize_copy(other)
+        super
+        @orders = @orders.map { |x| x.clone }
+      end
+
+      def hash
+        [@orders, @framing].hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.orders == other.orders &&
+          self.framing == other.framing &&
+          self.partitions == other.partitions
+      end
+      alias :== :eql?
+    end
+
+    class NamedWindow < Window
+      attr_accessor :name
+
+      def initialize(name)
+        super()
+        @name = name
+      end
+
+      def initialize_copy(other)
+        super
+        @name = other.name.clone
+      end
+
+      def hash
+        super ^ @name.hash
+      end
+
+      def eql?(other)
+        super && self.name == other.name
+      end
+      alias :== :eql?
+    end
+
+    class Rows < Unary
+      def initialize(expr = nil)
+        super(expr)
+      end
+    end
+
+    class Range < Unary
+      def initialize(expr = nil)
+        super(expr)
+      end
+    end
+
+    class CurrentRow < Node
+      def hash
+        self.class.hash
+      end
+
+      def eql?(other)
+        self.class == other.class
+      end
+      alias :== :eql?
+    end
+
+    class Preceding < Unary
+      def initialize(expr = nil)
+        super(expr)
+      end
+    end
+
+    class Following < Unary
+      def initialize(expr = nil)
+        super(expr)
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/nodes/with.rb b/activerecord/lib/arel/nodes/with.rb
new file mode 100644
index 0000000000..157bdcaa08
--- /dev/null
+++ b/activerecord/lib/arel/nodes/with.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class With < Arel::Nodes::Unary
+      alias children expr
+    end
+
+    class WithRecursive < With; end
+  end
+end
diff --git a/activerecord/lib/arel/order_predications.rb b/activerecord/lib/arel/order_predications.rb
new file mode 100644
index 0000000000..d785bbba92
--- /dev/null
+++ b/activerecord/lib/arel/order_predications.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module OrderPredications
+    def asc
+      Nodes::Ascending.new self
+    end
+
+    def desc
+      Nodes::Descending.new self
+    end
+  end
+end
diff --git a/activerecord/lib/arel/predications.rb b/activerecord/lib/arel/predications.rb
new file mode 100644
index 0000000000..e83a6f162f
--- /dev/null
+++ b/activerecord/lib/arel/predications.rb
@@ -0,0 +1,241 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Predications
+    def not_eq(other)
+      Nodes::NotEqual.new self, quoted_node(other)
+    end
+
+    def not_eq_any(others)
+      grouping_any :not_eq, others
+    end
+
+    def not_eq_all(others)
+      grouping_all :not_eq, others
+    end
+
+    def eq(other)
+      Nodes::Equality.new self, quoted_node(other)
+    end
+
+    def eq_any(others)
+      grouping_any :eq, others
+    end
+
+    def eq_all(others)
+      grouping_all :eq, quoted_array(others)
+    end
+
+    def between(other)
+      if equals_quoted?(other.begin, -Float::INFINITY)
+        if equals_quoted?(other.end, Float::INFINITY)
+          not_in([])
+        elsif other.exclude_end?
+          lt(other.end)
+        else
+          lteq(other.end)
+        end
+      elsif equals_quoted?(other.end, Float::INFINITY)
+        gteq(other.begin)
+      elsif other.exclude_end?
+        gteq(other.begin).and(lt(other.end))
+      else
+        left = quoted_node(other.begin)
+        right = quoted_node(other.end)
+        Nodes::Between.new(self, left.and(right))
+      end
+    end
+
+    def in(other)
+      case other
+      when Arel::SelectManager
+        Arel::Nodes::In.new(self, other.ast)
+      when Range
+        if $VERBOSE
+          warn <<-eowarn
+Passing a range to `#in` is deprecated. Call `#between`, instead.
+          eowarn
+        end
+        between(other)
+      when Enumerable
+        Nodes::In.new self, quoted_array(other)
+      else
+        Nodes::In.new self, quoted_node(other)
+      end
+    end
+
+    def in_any(others)
+      grouping_any :in, others
+    end
+
+    def in_all(others)
+      grouping_all :in, others
+    end
+
+    def not_between(other)
+      if equals_quoted?(other.begin, -Float::INFINITY)
+        if equals_quoted?(other.end, Float::INFINITY)
+          self.in([])
+        elsif other.exclude_end?
+          gteq(other.end)
+        else
+          gt(other.end)
+        end
+      elsif equals_quoted?(other.end, Float::INFINITY)
+        lt(other.begin)
+      else
+        left = lt(other.begin)
+        right = if other.exclude_end?
+          gteq(other.end)
+        else
+          gt(other.end)
+        end
+        left.or(right)
+      end
+    end
+
+    def not_in(other)
+      case other
+      when Arel::SelectManager
+        Arel::Nodes::NotIn.new(self, other.ast)
+      when Range
+        if $VERBOSE
+          warn <<-eowarn
+Passing a range to `#not_in` is deprecated. Call `#not_between`, instead.
+          eowarn
+        end
+        not_between(other)
+      when Enumerable
+        Nodes::NotIn.new self, quoted_array(other)
+      else
+        Nodes::NotIn.new self, quoted_node(other)
+      end
+    end
+
+    def not_in_any(others)
+      grouping_any :not_in, others
+    end
+
+    def not_in_all(others)
+      grouping_all :not_in, others
+    end
+
+    def matches(other, escape = nil, case_sensitive = false)
+      Nodes::Matches.new self, quoted_node(other), escape, case_sensitive
+    end
+
+    def matches_regexp(other, case_sensitive = true)
+      Nodes::Regexp.new self, quoted_node(other), case_sensitive
+    end
+
+    def matches_any(others, escape = nil, case_sensitive = false)
+      grouping_any :matches, others, escape, case_sensitive
+    end
+
+    def matches_all(others, escape = nil, case_sensitive = false)
+      grouping_all :matches, others, escape, case_sensitive
+    end
+
+    def does_not_match(other, escape = nil, case_sensitive = false)
+      Nodes::DoesNotMatch.new self, quoted_node(other), escape, case_sensitive
+    end
+
+    def does_not_match_regexp(other, case_sensitive = true)
+      Nodes::NotRegexp.new self, quoted_node(other), case_sensitive
+    end
+
+    def does_not_match_any(others, escape = nil)
+      grouping_any :does_not_match, others, escape
+    end
+
+    def does_not_match_all(others, escape = nil)
+      grouping_all :does_not_match, others, escape
+    end
+
+    def gteq(right)
+      Nodes::GreaterThanOrEqual.new self, quoted_node(right)
+    end
+
+    def gteq_any(others)
+      grouping_any :gteq, others
+    end
+
+    def gteq_all(others)
+      grouping_all :gteq, others
+    end
+
+    def gt(right)
+      Nodes::GreaterThan.new self, quoted_node(right)
+    end
+
+    def gt_any(others)
+      grouping_any :gt, others
+    end
+
+    def gt_all(others)
+      grouping_all :gt, others
+    end
+
+    def lt(right)
+      Nodes::LessThan.new self, quoted_node(right)
+    end
+
+    def lt_any(others)
+      grouping_any :lt, others
+    end
+
+    def lt_all(others)
+      grouping_all :lt, others
+    end
+
+    def lteq(right)
+      Nodes::LessThanOrEqual.new self, quoted_node(right)
+    end
+
+    def lteq_any(others)
+      grouping_any :lteq, others
+    end
+
+    def lteq_all(others)
+      grouping_all :lteq, others
+    end
+
+    def when(right)
+      Nodes::Case.new(self).when quoted_node(right)
+    end
+
+    def concat(other)
+      Nodes::Concat.new self, other
+    end
+
+    private
+
+      def grouping_any(method_id, others, *extras)
+        nodes = others.map { |expr| send(method_id, expr, *extras) }
+        Nodes::Grouping.new nodes.inject { |memo, node|
+          Nodes::Or.new(memo, node)
+        }
+      end
+
+      def grouping_all(method_id, others, *extras)
+        nodes = others.map { |expr| send(method_id, expr, *extras) }
+        Nodes::Grouping.new Nodes::And.new(nodes)
+      end
+
+      def quoted_node(other)
+        Nodes.build_quoted(other, self)
+      end
+
+      def quoted_array(others)
+        others.map { |v| quoted_node(v) }
+      end
+
+      def equals_quoted?(maybe_quoted, value)
+        if maybe_quoted.is_a?(Nodes::Quoted)
+          maybe_quoted.val == value
+        else
+          maybe_quoted == value
+        end
+      end
+  end
+end
diff --git a/activerecord/lib/arel/select_manager.rb b/activerecord/lib/arel/select_manager.rb
new file mode 100644
index 0000000000..22a04b00c6
--- /dev/null
+++ b/activerecord/lib/arel/select_manager.rb
@@ -0,0 +1,273 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  class SelectManager < Arel::TreeManager
+    include Arel::Crud
+
+    STRING_OR_SYMBOL_CLASS = [Symbol, String]
+
+    def initialize(table = nil)
+      super()
+      @ast = Nodes::SelectStatement.new
+      @ctx = @ast.cores.last
+      from table
+    end
+
+    def initialize_copy(other)
+      super
+      @ctx = @ast.cores.last
+    end
+
+    def limit
+      @ast.limit && @ast.limit.expr
+    end
+    alias :taken :limit
+
+    def constraints
+      @ctx.wheres
+    end
+
+    def offset
+      @ast.offset && @ast.offset.expr
+    end
+
+    def skip(amount)
+      if amount
+        @ast.offset = Nodes::Offset.new(amount)
+      else
+        @ast.offset = nil
+      end
+      self
+    end
+    alias :offset= :skip
+
+    ###
+    # Produces an Arel::Nodes::Exists node
+    def exists
+      Arel::Nodes::Exists.new @ast
+    end
+
+    def as(other)
+      create_table_alias grouping(@ast), Nodes::SqlLiteral.new(other)
+    end
+
+    def lock(locking = Arel.sql("FOR UPDATE"))
+      case locking
+      when true
+        locking = Arel.sql("FOR UPDATE")
+      when Arel::Nodes::SqlLiteral
+      when String
+        locking = Arel.sql locking
+      end
+
+      @ast.lock = Nodes::Lock.new(locking)
+      self
+    end
+
+    def locked
+      @ast.lock
+    end
+
+    def on(*exprs)
+      @ctx.source.right.last.right = Nodes::On.new(collapse(exprs))
+      self
+    end
+
+    def group(*columns)
+      columns.each do |column|
+        # FIXME: backwards compat
+        column = Nodes::SqlLiteral.new(column) if String === column
+        column = Nodes::SqlLiteral.new(column.to_s) if Symbol === column
+
+        @ctx.groups.push Nodes::Group.new column
+      end
+      self
+    end
+
+    def from(table)
+      table = Nodes::SqlLiteral.new(table) if String === table
+
+      case table
+      when Nodes::Join
+        @ctx.source.right << table
+      else
+        @ctx.source.left = table
+      end
+
+      self
+    end
+
+    def froms
+      @ast.cores.map { |x| x.from }.compact
+    end
+
+    def join(relation, klass = Nodes::InnerJoin)
+      return self unless relation
+
+      case relation
+      when String, Nodes::SqlLiteral
+        raise EmptyJoinError if relation.empty?
+        klass = Nodes::StringJoin
+      end
+
+      @ctx.source.right << create_join(relation, nil, klass)
+      self
+    end
+
+    def outer_join(relation)
+      join(relation, Nodes::OuterJoin)
+    end
+
+    def having(expr)
+      @ctx.havings << expr
+      self
+    end
+
+    def window(name)
+      window = Nodes::NamedWindow.new(name)
+      @ctx.windows.push window
+      window
+    end
+
+    def project(*projections)
+      # FIXME: converting these to SQLLiterals is probably not good, but
+      # rails tests require it.
+      @ctx.projections.concat projections.map { |x|
+        STRING_OR_SYMBOL_CLASS.include?(x.class) ? Nodes::SqlLiteral.new(x.to_s) : x
+      }
+      self
+    end
+
+    def projections
+      @ctx.projections
+    end
+
+    def projections=(projections)
+      @ctx.projections = projections
+    end
+
+    def distinct(value = true)
+      if value
+        @ctx.set_quantifier = Arel::Nodes::Distinct.new
+      else
+        @ctx.set_quantifier = nil
+      end
+      self
+    end
+
+    def distinct_on(value)
+      if value
+        @ctx.set_quantifier = Arel::Nodes::DistinctOn.new(value)
+      else
+        @ctx.set_quantifier = nil
+      end
+      self
+    end
+
+    def order(*expr)
+      # FIXME: We SHOULD NOT be converting these to SqlLiteral automatically
+      @ast.orders.concat expr.map { |x|
+        STRING_OR_SYMBOL_CLASS.include?(x.class) ? Nodes::SqlLiteral.new(x.to_s) : x
+      }
+      self
+    end
+
+    def orders
+      @ast.orders
+    end
+
+    def where_sql(engine = Table.engine)
+      return if @ctx.wheres.empty?
+
+      viz = Visitors::WhereSql.new(engine.connection.visitor, engine.connection)
+      Nodes::SqlLiteral.new viz.accept(@ctx, Collectors::SQLString.new).value
+    end
+
+    def union(operation, other = nil)
+      if other
+        node_class = Nodes.const_get("Union#{operation.to_s.capitalize}")
+      else
+        other = operation
+        node_class = Nodes::Union
+      end
+
+      node_class.new self.ast, other.ast
+    end
+
+    def intersect(other)
+      Nodes::Intersect.new ast, other.ast
+    end
+
+    def except(other)
+      Nodes::Except.new ast, other.ast
+    end
+    alias :minus :except
+
+    def lateral(table_name = nil)
+      base = table_name.nil? ? ast : as(table_name)
+      Nodes::Lateral.new(base)
+    end
+
+    def with(*subqueries)
+      if subqueries.first.is_a? Symbol
+        node_class = Nodes.const_get("With#{subqueries.shift.to_s.capitalize}")
+      else
+        node_class = Nodes::With
+      end
+      @ast.with = node_class.new(subqueries.flatten)
+
+      self
+    end
+
+    def take(limit)
+      if limit
+        @ast.limit = Nodes::Limit.new(limit)
+        @ctx.top   = Nodes::Top.new(limit)
+      else
+        @ast.limit = nil
+        @ctx.top   = nil
+      end
+      self
+    end
+    alias limit= take
+
+    def join_sources
+      @ctx.source.right
+    end
+
+    def source
+      @ctx.source
+    end
+
+    class Row < Struct.new(:data) # :nodoc:
+      def id
+        data["id"]
+      end
+
+      def method_missing(name, *args)
+        name = name.to_s
+        return data[name] if data.key?(name)
+        super
+      end
+    end
+
+    private
+      def collapse(exprs, existing = nil)
+        exprs = exprs.unshift(existing.expr) if existing
+        exprs = exprs.compact.map { |expr|
+          if String === expr
+            # FIXME: Don't do this automatically
+            Arel.sql(expr)
+          else
+            expr
+          end
+        }
+
+        if exprs.length == 1
+          exprs.first
+        else
+          create_and exprs
+        end
+      end
+  end
+end
diff --git a/activerecord/lib/arel/table.rb b/activerecord/lib/arel/table.rb
new file mode 100644
index 0000000000..686fcdf962
--- /dev/null
+++ b/activerecord/lib/arel/table.rb
@@ -0,0 +1,111 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  class Table
+    include Arel::Crud
+    include Arel::FactoryMethods
+
+    @engine = nil
+    class << self; attr_accessor :engine; end
+
+    attr_accessor :name, :table_alias
+
+    # TableAlias and Table both have a #table_name which is the name of the underlying table
+    alias :table_name :name
+
+    def initialize(name, as: nil, type_caster: nil)
+      @name = name.to_s
+      @type_caster = type_caster
+
+      # Sometime AR sends an :as parameter to table, to let the table know
+      # that it is an Alias.  We may want to override new, and return a
+      # TableAlias node?
+      if as.to_s == @name
+        as = nil
+      end
+      @table_alias = as
+    end
+
+    def alias(name = "#{self.name}_2")
+      Nodes::TableAlias.new(self, name)
+    end
+
+    def from
+      SelectManager.new(self)
+    end
+
+    def join(relation, klass = Nodes::InnerJoin)
+      return from unless relation
+
+      case relation
+      when String, Nodes::SqlLiteral
+        raise EmptyJoinError if relation.empty?
+        klass = Nodes::StringJoin
+      end
+
+      from.join(relation, klass)
+    end
+
+    def outer_join(relation)
+      join(relation, Nodes::OuterJoin)
+    end
+
+    def group(*columns)
+      from.group(*columns)
+    end
+
+    def order(*expr)
+      from.order(*expr)
+    end
+
+    def where(condition)
+      from.where condition
+    end
+
+    def project(*things)
+      from.project(*things)
+    end
+
+    def take(amount)
+      from.take amount
+    end
+
+    def skip(amount)
+      from.skip amount
+    end
+
+    def having(expr)
+      from.having expr
+    end
+
+    def [](name)
+      ::Arel::Attribute.new self, name
+    end
+
+    def hash
+      # Perf note: aliases and table alias is excluded from the hash
+      #  aliases can have a loop back to this table breaking hashes in parent
+      #  relations, for the vast majority of cases @name is unique to a query
+      @name.hash
+    end
+
+    def eql?(other)
+      self.class == other.class &&
+        self.name == other.name &&
+        self.table_alias == other.table_alias
+    end
+    alias :== :eql?
+
+    def type_cast_for_database(attribute_name, value)
+      type_caster.type_cast_for_database(attribute_name, value)
+    end
+
+    def able_to_type_cast?
+      !type_caster.nil?
+    end
+
+    protected
+
+      attr_reader :type_caster
+  end
+end
diff --git a/activerecord/lib/arel/tree_manager.rb b/activerecord/lib/arel/tree_manager.rb
new file mode 100644
index 0000000000..ed47b09a37
--- /dev/null
+++ b/activerecord/lib/arel/tree_manager.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  class TreeManager
+    include Arel::FactoryMethods
+
+    attr_reader :ast
+
+    def initialize
+      @ctx = nil
+    end
+
+    def to_dot
+      collector = Arel::Collectors::PlainString.new
+      collector = Visitors::Dot.new.accept @ast, collector
+      collector.value
+    end
+
+    def to_sql(engine = Table.engine)
+      collector = Arel::Collectors::SQLString.new
+      collector = engine.connection.visitor.accept @ast, collector
+      collector.value
+    end
+
+    def initialize_copy(other)
+      super
+      @ast = @ast.clone
+    end
+
+    def where(expr)
+      if Arel::TreeManager === expr
+        expr = expr.ast
+      end
+      @ctx.wheres << expr
+      self
+    end
+  end
+end
diff --git a/activerecord/lib/arel/update_manager.rb b/activerecord/lib/arel/update_manager.rb
new file mode 100644
index 0000000000..fe444343ba
--- /dev/null
+++ b/activerecord/lib/arel/update_manager.rb
@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  class UpdateManager < Arel::TreeManager
+    def initialize
+      super
+      @ast = Nodes::UpdateStatement.new
+      @ctx = @ast
+    end
+
+    def take(limit)
+      @ast.limit = Nodes::Limit.new(Nodes.build_quoted(limit)) if limit
+      self
+    end
+
+    def key=(key)
+      @ast.key = Nodes.build_quoted(key)
+    end
+
+    def key
+      @ast.key
+    end
+
+    def order(*expr)
+      @ast.orders = expr
+      self
+    end
+
+    ###
+    # UPDATE +table+
+    def table(table)
+      @ast.relation = table
+      self
+    end
+
+    def wheres=(exprs)
+      @ast.wheres = exprs
+    end
+
+    def where(expr)
+      @ast.wheres << expr
+      self
+    end
+
+    def set(values)
+      if String === values
+        @ast.values = [values]
+      else
+        @ast.values = values.map { |column, value|
+          Nodes::Assignment.new(
+            Nodes::UnqualifiedColumn.new(column),
+            value
+          )
+        }
+      end
+      self
+    end
+  end
+end
diff --git a/activerecord/lib/arel/visitors.rb b/activerecord/lib/arel/visitors.rb
new file mode 100644
index 0000000000..e350f52e65
--- /dev/null
+++ b/activerecord/lib/arel/visitors.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require "arel/visitors/visitor"
+require "arel/visitors/depth_first"
+require "arel/visitors/to_sql"
+require "arel/visitors/sqlite"
+require "arel/visitors/postgresql"
+require "arel/visitors/mysql"
+require "arel/visitors/mssql"
+require "arel/visitors/oracle"
+require "arel/visitors/oracle12"
+require "arel/visitors/where_sql"
+require "arel/visitors/dot"
+require "arel/visitors/ibm_db"
+require "arel/visitors/informix"
+
+module Arel # :nodoc: all
+  module Visitors
+  end
+end
diff --git a/activerecord/lib/arel/visitors/depth_first.rb b/activerecord/lib/arel/visitors/depth_first.rb
new file mode 100644
index 0000000000..bcf8f8f980
--- /dev/null
+++ b/activerecord/lib/arel/visitors/depth_first.rb
@@ -0,0 +1,200 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Visitors
+    class DepthFirst < Arel::Visitors::Visitor
+      def initialize(block = nil)
+        @block = block || Proc.new
+        super()
+      end
+
+      private
+
+        def visit(o)
+          super
+          @block.call o
+        end
+
+        def unary(o)
+          visit o.expr
+        end
+        alias :visit_Arel_Nodes_Else              :unary
+        alias :visit_Arel_Nodes_Group             :unary
+        alias :visit_Arel_Nodes_Cube              :unary
+        alias :visit_Arel_Nodes_RollUp            :unary
+        alias :visit_Arel_Nodes_GroupingSet       :unary
+        alias :visit_Arel_Nodes_GroupingElement   :unary
+        alias :visit_Arel_Nodes_Grouping          :unary
+        alias :visit_Arel_Nodes_Having            :unary
+        alias :visit_Arel_Nodes_Lateral           :unary
+        alias :visit_Arel_Nodes_Limit             :unary
+        alias :visit_Arel_Nodes_Not               :unary
+        alias :visit_Arel_Nodes_Offset            :unary
+        alias :visit_Arel_Nodes_On                :unary
+        alias :visit_Arel_Nodes_Ordering          :unary
+        alias :visit_Arel_Nodes_Ascending         :unary
+        alias :visit_Arel_Nodes_Descending        :unary
+        alias :visit_Arel_Nodes_Top               :unary
+        alias :visit_Arel_Nodes_UnqualifiedColumn :unary
+
+        def function(o)
+          visit o.expressions
+          visit o.alias
+          visit o.distinct
+        end
+        alias :visit_Arel_Nodes_Avg    :function
+        alias :visit_Arel_Nodes_Exists :function
+        alias :visit_Arel_Nodes_Max    :function
+        alias :visit_Arel_Nodes_Min    :function
+        alias :visit_Arel_Nodes_Sum    :function
+
+        def visit_Arel_Nodes_NamedFunction(o)
+          visit o.name
+          visit o.expressions
+          visit o.distinct
+          visit o.alias
+        end
+
+        def visit_Arel_Nodes_Count(o)
+          visit o.expressions
+          visit o.alias
+          visit o.distinct
+        end
+
+        def visit_Arel_Nodes_Case(o)
+          visit o.case
+          visit o.conditions
+          visit o.default
+        end
+
+        def nary(o)
+          o.children.each { |child| visit child }
+        end
+        alias :visit_Arel_Nodes_And :nary
+
+        def binary(o)
+          visit o.left
+          visit o.right
+        end
+        alias :visit_Arel_Nodes_As                 :binary
+        alias :visit_Arel_Nodes_Assignment         :binary
+        alias :visit_Arel_Nodes_Between            :binary
+        alias :visit_Arel_Nodes_Concat             :binary
+        alias :visit_Arel_Nodes_DeleteStatement    :binary
+        alias :visit_Arel_Nodes_DoesNotMatch       :binary
+        alias :visit_Arel_Nodes_Equality           :binary
+        alias :visit_Arel_Nodes_FullOuterJoin      :binary
+        alias :visit_Arel_Nodes_GreaterThan        :binary
+        alias :visit_Arel_Nodes_GreaterThanOrEqual :binary
+        alias :visit_Arel_Nodes_In                 :binary
+        alias :visit_Arel_Nodes_InfixOperation     :binary
+        alias :visit_Arel_Nodes_JoinSource         :binary
+        alias :visit_Arel_Nodes_InnerJoin          :binary
+        alias :visit_Arel_Nodes_LessThan           :binary
+        alias :visit_Arel_Nodes_LessThanOrEqual    :binary
+        alias :visit_Arel_Nodes_Matches            :binary
+        alias :visit_Arel_Nodes_NotEqual           :binary
+        alias :visit_Arel_Nodes_NotIn              :binary
+        alias :visit_Arel_Nodes_NotRegexp          :binary
+        alias :visit_Arel_Nodes_Or                 :binary
+        alias :visit_Arel_Nodes_OuterJoin          :binary
+        alias :visit_Arel_Nodes_Regexp             :binary
+        alias :visit_Arel_Nodes_RightOuterJoin     :binary
+        alias :visit_Arel_Nodes_TableAlias         :binary
+        alias :visit_Arel_Nodes_Values             :binary
+        alias :visit_Arel_Nodes_When               :binary
+
+        def visit_Arel_Nodes_StringJoin(o)
+          visit o.left
+        end
+
+        def visit_Arel_Attribute(o)
+          visit o.relation
+          visit o.name
+        end
+        alias :visit_Arel_Attributes_Integer :visit_Arel_Attribute
+        alias :visit_Arel_Attributes_Float :visit_Arel_Attribute
+        alias :visit_Arel_Attributes_String :visit_Arel_Attribute
+        alias :visit_Arel_Attributes_Time :visit_Arel_Attribute
+        alias :visit_Arel_Attributes_Boolean :visit_Arel_Attribute
+        alias :visit_Arel_Attributes_Attribute :visit_Arel_Attribute
+        alias :visit_Arel_Attributes_Decimal :visit_Arel_Attribute
+
+        def visit_Arel_Table(o)
+          visit o.name
+        end
+
+        def terminal(o)
+        end
+        alias :visit_ActiveSupport_Multibyte_Chars :terminal
+        alias :visit_ActiveSupport_StringInquirer  :terminal
+        alias :visit_Arel_Nodes_Lock               :terminal
+        alias :visit_Arel_Nodes_Node               :terminal
+        alias :visit_Arel_Nodes_SqlLiteral         :terminal
+        alias :visit_Arel_Nodes_BindParam          :terminal
+        alias :visit_Arel_Nodes_Window             :terminal
+        alias :visit_Arel_Nodes_True               :terminal
+        alias :visit_Arel_Nodes_False              :terminal
+        alias :visit_BigDecimal                    :terminal
+        alias :visit_Bignum                        :terminal
+        alias :visit_Class                         :terminal
+        alias :visit_Date                          :terminal
+        alias :visit_DateTime                      :terminal
+        alias :visit_FalseClass                    :terminal
+        alias :visit_Fixnum                        :terminal
+        alias :visit_Float                         :terminal
+        alias :visit_Integer                       :terminal
+        alias :visit_NilClass                      :terminal
+        alias :visit_String                        :terminal
+        alias :visit_Symbol                        :terminal
+        alias :visit_Time                          :terminal
+        alias :visit_TrueClass                     :terminal
+
+        def visit_Arel_Nodes_InsertStatement(o)
+          visit o.relation
+          visit o.columns
+          visit o.values
+        end
+
+        def visit_Arel_Nodes_SelectCore(o)
+          visit o.projections
+          visit o.source
+          visit o.wheres
+          visit o.groups
+          visit o.windows
+          visit o.havings
+        end
+
+        def visit_Arel_Nodes_SelectStatement(o)
+          visit o.cores
+          visit o.orders
+          visit o.limit
+          visit o.lock
+          visit o.offset
+        end
+
+        def visit_Arel_Nodes_UpdateStatement(o)
+          visit o.relation
+          visit o.values
+          visit o.wheres
+          visit o.orders
+          visit o.limit
+        end
+
+        def visit_Array(o)
+          o.each { |i| visit i }
+        end
+        alias :visit_Set :visit_Array
+
+        def visit_Hash(o)
+          o.each { |k, v| visit(k); visit(v) }
+        end
+
+        DISPATCH = dispatch_cache
+
+        def get_dispatch_cache
+          DISPATCH
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/visitors/dot.rb b/activerecord/lib/arel/visitors/dot.rb
new file mode 100644
index 0000000000..d352b81914
--- /dev/null
+++ b/activerecord/lib/arel/visitors/dot.rb
@@ -0,0 +1,292 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Visitors
+    class Dot < Arel::Visitors::Visitor
+      class Node # :nodoc:
+        attr_accessor :name, :id, :fields
+
+        def initialize(name, id, fields = [])
+          @name   = name
+          @id     = id
+          @fields = fields
+        end
+      end
+
+      class Edge < Struct.new :name, :from, :to # :nodoc:
+      end
+
+      def initialize
+        super()
+        @nodes      = []
+        @edges      = []
+        @node_stack = []
+        @edge_stack = []
+        @seen       = {}
+      end
+
+      def accept(object, collector)
+        visit object
+        collector << to_dot
+      end
+
+      private
+
+        def visit_Arel_Nodes_Ordering(o)
+          visit_edge o, "expr"
+        end
+
+        def visit_Arel_Nodes_TableAlias(o)
+          visit_edge o, "name"
+          visit_edge o, "relation"
+        end
+
+        def visit_Arel_Nodes_Count(o)
+          visit_edge o, "expressions"
+          visit_edge o, "distinct"
+        end
+
+        def visit_Arel_Nodes_Values(o)
+          visit_edge o, "expressions"
+        end
+
+        def visit_Arel_Nodes_StringJoin(o)
+          visit_edge o, "left"
+        end
+
+        def visit_Arel_Nodes_InnerJoin(o)
+          visit_edge o, "left"
+          visit_edge o, "right"
+        end
+        alias :visit_Arel_Nodes_FullOuterJoin  :visit_Arel_Nodes_InnerJoin
+        alias :visit_Arel_Nodes_OuterJoin      :visit_Arel_Nodes_InnerJoin
+        alias :visit_Arel_Nodes_RightOuterJoin :visit_Arel_Nodes_InnerJoin
+
+        def visit_Arel_Nodes_DeleteStatement(o)
+          visit_edge o, "relation"
+          visit_edge o, "wheres"
+        end
+
+        def unary(o)
+          visit_edge o, "expr"
+        end
+        alias :visit_Arel_Nodes_Group             :unary
+        alias :visit_Arel_Nodes_Cube              :unary
+        alias :visit_Arel_Nodes_RollUp            :unary
+        alias :visit_Arel_Nodes_GroupingSet       :unary
+        alias :visit_Arel_Nodes_GroupingElement   :unary
+        alias :visit_Arel_Nodes_Grouping          :unary
+        alias :visit_Arel_Nodes_Having            :unary
+        alias :visit_Arel_Nodes_Limit             :unary
+        alias :visit_Arel_Nodes_Not               :unary
+        alias :visit_Arel_Nodes_Offset            :unary
+        alias :visit_Arel_Nodes_On                :unary
+        alias :visit_Arel_Nodes_Top               :unary
+        alias :visit_Arel_Nodes_UnqualifiedColumn :unary
+        alias :visit_Arel_Nodes_Preceding         :unary
+        alias :visit_Arel_Nodes_Following         :unary
+        alias :visit_Arel_Nodes_Rows              :unary
+        alias :visit_Arel_Nodes_Range             :unary
+
+        def window(o)
+          visit_edge o, "partitions"
+          visit_edge o, "orders"
+          visit_edge o, "framing"
+        end
+        alias :visit_Arel_Nodes_Window            :window
+
+        def named_window(o)
+          visit_edge o, "partitions"
+          visit_edge o, "orders"
+          visit_edge o, "framing"
+          visit_edge o, "name"
+        end
+        alias :visit_Arel_Nodes_NamedWindow       :named_window
+
+        def function(o)
+          visit_edge o, "expressions"
+          visit_edge o, "distinct"
+          visit_edge o, "alias"
+        end
+        alias :visit_Arel_Nodes_Exists :function
+        alias :visit_Arel_Nodes_Min    :function
+        alias :visit_Arel_Nodes_Max    :function
+        alias :visit_Arel_Nodes_Avg    :function
+        alias :visit_Arel_Nodes_Sum    :function
+
+        def extract(o)
+          visit_edge o, "expressions"
+          visit_edge o, "alias"
+        end
+        alias :visit_Arel_Nodes_Extract :extract
+
+        def visit_Arel_Nodes_NamedFunction(o)
+          visit_edge o, "name"
+          visit_edge o, "expressions"
+          visit_edge o, "distinct"
+          visit_edge o, "alias"
+        end
+
+        def visit_Arel_Nodes_InsertStatement(o)
+          visit_edge o, "relation"
+          visit_edge o, "columns"
+          visit_edge o, "values"
+        end
+
+        def visit_Arel_Nodes_SelectCore(o)
+          visit_edge o, "source"
+          visit_edge o, "projections"
+          visit_edge o, "wheres"
+          visit_edge o,  "windows"
+        end
+
+        def visit_Arel_Nodes_SelectStatement(o)
+          visit_edge o, "cores"
+          visit_edge o, "limit"
+          visit_edge o, "orders"
+          visit_edge o, "offset"
+        end
+
+        def visit_Arel_Nodes_UpdateStatement(o)
+          visit_edge o, "relation"
+          visit_edge o, "wheres"
+          visit_edge o, "values"
+        end
+
+        def visit_Arel_Table(o)
+          visit_edge o, "name"
+        end
+
+        def visit_Arel_Nodes_Casted(o)
+          visit_edge o, "val"
+          visit_edge o, "attribute"
+        end
+
+        def visit_Arel_Attribute(o)
+          visit_edge o, "relation"
+          visit_edge o, "name"
+        end
+        alias :visit_Arel_Attributes_Integer :visit_Arel_Attribute
+        alias :visit_Arel_Attributes_Float :visit_Arel_Attribute
+        alias :visit_Arel_Attributes_String :visit_Arel_Attribute
+        alias :visit_Arel_Attributes_Time :visit_Arel_Attribute
+        alias :visit_Arel_Attributes_Boolean :visit_Arel_Attribute
+        alias :visit_Arel_Attributes_Attribute :visit_Arel_Attribute
+
+        def nary(o)
+          o.children.each_with_index do |x, i|
+            edge(i) { visit x }
+          end
+        end
+        alias :visit_Arel_Nodes_And :nary
+
+        def binary(o)
+          visit_edge o, "left"
+          visit_edge o, "right"
+        end
+        alias :visit_Arel_Nodes_As                 :binary
+        alias :visit_Arel_Nodes_Assignment         :binary
+        alias :visit_Arel_Nodes_Between            :binary
+        alias :visit_Arel_Nodes_Concat             :binary
+        alias :visit_Arel_Nodes_DoesNotMatch       :binary
+        alias :visit_Arel_Nodes_Equality           :binary
+        alias :visit_Arel_Nodes_GreaterThan        :binary
+        alias :visit_Arel_Nodes_GreaterThanOrEqual :binary
+        alias :visit_Arel_Nodes_In                 :binary
+        alias :visit_Arel_Nodes_JoinSource         :binary
+        alias :visit_Arel_Nodes_LessThan           :binary
+        alias :visit_Arel_Nodes_LessThanOrEqual    :binary
+        alias :visit_Arel_Nodes_Matches            :binary
+        alias :visit_Arel_Nodes_NotEqual           :binary
+        alias :visit_Arel_Nodes_NotIn              :binary
+        alias :visit_Arel_Nodes_Or                 :binary
+        alias :visit_Arel_Nodes_Over               :binary
+
+        def visit_String(o)
+          @node_stack.last.fields << o
+        end
+        alias :visit_Time :visit_String
+        alias :visit_Date :visit_String
+        alias :visit_DateTime :visit_String
+        alias :visit_NilClass :visit_String
+        alias :visit_TrueClass :visit_String
+        alias :visit_FalseClass :visit_String
+        alias :visit_Integer :visit_String
+        alias :visit_Fixnum :visit_String
+        alias :visit_BigDecimal :visit_String
+        alias :visit_Float :visit_String
+        alias :visit_Symbol :visit_String
+        alias :visit_Arel_Nodes_SqlLiteral :visit_String
+
+        def visit_Arel_Nodes_BindParam(o); end
+
+        def visit_Hash(o)
+          o.each_with_index do |pair, i|
+            edge("pair_#{i}")   { visit pair }
+          end
+        end
+
+        def visit_Array(o)
+          o.each_with_index do |x, i|
+            edge(i) { visit x }
+          end
+        end
+        alias :visit_Set :visit_Array
+
+        def visit_edge(o, method)
+          edge(method) { visit o.send(method) }
+        end
+
+        def visit(o)
+          if node = @seen[o.object_id]
+            @edge_stack.last.to = node
+            return
+          end
+
+          node = Node.new(o.class.name, o.object_id)
+          @seen[node.id] = node
+          @nodes << node
+          with_node node do
+            super
+          end
+        end
+
+        def edge(name)
+          edge = Edge.new(name, @node_stack.last)
+          @edge_stack.push edge
+          @edges << edge
+          yield
+          @edge_stack.pop
+        end
+
+        def with_node(node)
+          if edge = @edge_stack.last
+            edge.to = node
+          end
+
+          @node_stack.push node
+          yield
+          @node_stack.pop
+        end
+
+        def quote(string)
+          string.to_s.gsub('"', '\"')
+        end
+
+        def to_dot
+          "digraph \"Arel\" {\nnode [width=0.375,height=0.25,shape=record];\n" +
+            @nodes.map { |node|
+              label = "<f0>#{node.name}"
+
+              node.fields.each_with_index do |field, i|
+                label += "|<f#{i + 1}>#{quote field}"
+              end
+
+              "#{node.id} [label=\"#{label}\"];"
+            }.join("\n") + "\n" + @edges.map { |edge|
+              "#{edge.from.id} -> #{edge.to.id} [label=\"#{edge.name}\"];"
+            }.join("\n") + "\n}"
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/visitors/ibm_db.rb b/activerecord/lib/arel/visitors/ibm_db.rb
new file mode 100644
index 0000000000..0a06aef60b
--- /dev/null
+++ b/activerecord/lib/arel/visitors/ibm_db.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Visitors
+    class IBM_DB < Arel::Visitors::ToSql
+      private
+
+        def visit_Arel_Nodes_Limit(o, collector)
+          collector << "FETCH FIRST "
+          collector = visit o.expr, collector
+          collector << " ROWS ONLY"
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/visitors/informix.rb b/activerecord/lib/arel/visitors/informix.rb
new file mode 100644
index 0000000000..0a9713794e
--- /dev/null
+++ b/activerecord/lib/arel/visitors/informix.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Visitors
+    class Informix < Arel::Visitors::ToSql
+      private
+        def visit_Arel_Nodes_SelectStatement(o, collector)
+          collector << "SELECT "
+          collector = maybe_visit o.offset, collector
+          collector = maybe_visit o.limit, collector
+          collector = o.cores.inject(collector) { |c, x|
+            visit_Arel_Nodes_SelectCore x, c
+          }
+          if o.orders.any?
+            collector << "ORDER BY "
+            collector = inject_join o.orders, collector, ", "
+          end
+          collector = maybe_visit o.lock, collector
+        end
+        def visit_Arel_Nodes_SelectCore(o, collector)
+          collector = inject_join o.projections, collector, ", "
+          if o.source && !o.source.empty?
+            collector << " FROM "
+            collector = visit o.source, collector
+          end
+
+          if o.wheres.any?
+            collector << " WHERE "
+            collector = inject_join o.wheres, collector, " AND "
+          end
+
+          if o.groups.any?
+            collector << "GROUP BY "
+            collector = inject_join o.groups, collector, ", "
+          end
+
+          if o.havings.any?
+            collector << " HAVING "
+            collector = inject_join o.havings, collector, " AND "
+          end
+          collector
+        end
+
+        def visit_Arel_Nodes_Offset(o, collector)
+          collector << "SKIP "
+          visit o.expr, collector
+        end
+        def visit_Arel_Nodes_Limit(o, collector)
+          collector << "FIRST "
+          visit o.expr, collector
+          collector << " "
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/visitors/mssql.rb b/activerecord/lib/arel/visitors/mssql.rb
new file mode 100644
index 0000000000..9aedc51d15
--- /dev/null
+++ b/activerecord/lib/arel/visitors/mssql.rb
@@ -0,0 +1,125 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Visitors
+    class MSSQL < Arel::Visitors::ToSql
+      RowNumber = Struct.new :children
+
+      def initialize(*)
+        @primary_keys = {}
+        super
+      end
+
+      private
+
+        # `top` wouldn't really work here. I.e. User.select("distinct first_name").limit(10) would generate
+        # "select top 10 distinct first_name from users", which is invalid query! it should be
+        # "select distinct top 10 first_name from users"
+        def visit_Arel_Nodes_Top(o)
+          ""
+        end
+
+        def visit_Arel_Visitors_MSSQL_RowNumber(o, collector)
+          collector << "ROW_NUMBER() OVER (ORDER BY "
+          inject_join(o.children, collector, ", ") << ") as _row_num"
+        end
+
+        def visit_Arel_Nodes_SelectStatement(o, collector)
+          if !o.limit && !o.offset
+            return super
+          end
+
+          is_select_count = false
+          o.cores.each { |x|
+            core_order_by = row_num_literal determine_order_by(o.orders, x)
+            if select_count? x
+              x.projections = [core_order_by]
+              is_select_count = true
+            else
+              x.projections << core_order_by
+            end
+          }
+
+          if is_select_count
+            # fixme count distinct wouldn't work with limit or offset
+            collector << "SELECT COUNT(1) as count_id FROM ("
+          end
+
+          collector << "SELECT _t.* FROM ("
+          collector = o.cores.inject(collector) { |c, x|
+            visit_Arel_Nodes_SelectCore x, c
+          }
+          collector << ") as _t WHERE #{get_offset_limit_clause(o)}"
+
+          if is_select_count
+            collector << ") AS subquery"
+          else
+            collector
+          end
+        end
+
+        def get_offset_limit_clause(o)
+          first_row = o.offset ? o.offset.expr.to_i + 1 : 1
+          last_row  = o.limit ? o.limit.expr.to_i - 1 + first_row : nil
+          if last_row
+            " _row_num BETWEEN #{first_row} AND #{last_row}"
+          else
+            " _row_num >= #{first_row}"
+          end
+        end
+
+        def visit_Arel_Nodes_DeleteStatement(o, collector)
+          collector << "DELETE "
+          if o.limit
+            collector << "TOP ("
+            visit o.limit.expr, collector
+            collector << ") "
+          end
+          collector << "FROM "
+          collector = visit o.relation, collector
+          if o.wheres.any?
+            collector << " WHERE "
+            inject_join o.wheres, collector, AND
+          else
+            collector
+          end
+        end
+
+        def determine_order_by(orders, x)
+          if orders.any?
+            orders
+          elsif x.groups.any?
+            x.groups
+          else
+            pk = find_left_table_pk(x.froms)
+            pk ? [pk] : []
+          end
+        end
+
+        def row_num_literal(order_by)
+          RowNumber.new order_by
+        end
+
+        def select_count?(x)
+          x.projections.length == 1 && Arel::Nodes::Count === x.projections.first
+        end
+
+        # FIXME raise exception of there is no pk?
+        def find_left_table_pk(o)
+          if o.kind_of?(Arel::Nodes::Join)
+            find_left_table_pk(o.left)
+          elsif o.instance_of?(Arel::Table)
+            find_primary_key(o)
+          end
+        end
+
+        def find_primary_key(o)
+          @primary_keys[o.name] ||= begin
+            primary_key_name = @connection.primary_key(o.name)
+            # some tables might be without primary key
+            primary_key_name && o[primary_key_name]
+          end
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/visitors/mysql.rb b/activerecord/lib/arel/visitors/mysql.rb
new file mode 100644
index 0000000000..37bfb661f0
--- /dev/null
+++ b/activerecord/lib/arel/visitors/mysql.rb
@@ -0,0 +1,87 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Visitors
+    class MySQL < Arel::Visitors::ToSql
+      private
+        def visit_Arel_Nodes_Union(o, collector, suppress_parens = false)
+          unless suppress_parens
+            collector << "( "
+          end
+
+          collector =   case o.left
+                        when Arel::Nodes::Union
+                          visit_Arel_Nodes_Union o.left, collector, true
+                        else
+                          visit o.left, collector
+          end
+
+          collector << " UNION "
+
+          collector =    case o.right
+                         when Arel::Nodes::Union
+                           visit_Arel_Nodes_Union o.right, collector, true
+                         else
+                           visit o.right, collector
+          end
+
+          if suppress_parens
+            collector
+          else
+            collector << " )"
+          end
+        end
+
+        def visit_Arel_Nodes_Bin(o, collector)
+          collector << "BINARY "
+          visit o.expr, collector
+        end
+
+        ###
+        # :'(
+        # http://dev.mysql.com/doc/refman/5.0/en/select.html#id3482214
+        def visit_Arel_Nodes_SelectStatement(o, collector)
+          if o.offset && !o.limit
+            o.limit = Arel::Nodes::Limit.new(18446744073709551615)
+          end
+          super
+        end
+
+        def visit_Arel_Nodes_SelectCore(o, collector)
+          o.froms ||= Arel.sql("DUAL")
+          super
+        end
+
+        def visit_Arel_Nodes_UpdateStatement(o, collector)
+          collector << "UPDATE "
+          collector = visit o.relation, collector
+
+          unless o.values.empty?
+            collector << " SET "
+            collector = inject_join o.values, collector, ", "
+          end
+
+          unless o.wheres.empty?
+            collector << " WHERE "
+            collector = inject_join o.wheres, collector, " AND "
+          end
+
+          unless o.orders.empty?
+            collector << " ORDER BY "
+            collector = inject_join o.orders, collector, ", "
+          end
+
+          maybe_visit o.limit, collector
+        end
+
+        def visit_Arel_Nodes_Concat(o, collector)
+          collector << " CONCAT("
+          visit o.left, collector
+          collector << ", "
+          visit o.right, collector
+          collector << ") "
+          collector
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/visitors/oracle.rb b/activerecord/lib/arel/visitors/oracle.rb
new file mode 100644
index 0000000000..30a1529d46
--- /dev/null
+++ b/activerecord/lib/arel/visitors/oracle.rb
@@ -0,0 +1,153 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Visitors
+    class Oracle < Arel::Visitors::ToSql
+      private
+
+        def visit_Arel_Nodes_SelectStatement(o, collector)
+          o = order_hacks(o)
+
+          # if need to select first records without ORDER BY and GROUP BY and without DISTINCT
+          # then can use simple ROWNUM in WHERE clause
+          if o.limit && o.orders.empty? && o.cores.first.groups.empty? && !o.offset && o.cores.first.set_quantifier.class.to_s !~ /Distinct/
+            o.cores.last.wheres.push Nodes::LessThanOrEqual.new(
+              Nodes::SqlLiteral.new("ROWNUM"), o.limit.expr
+            )
+            return super
+          end
+
+          if o.limit && o.offset
+            o        = o.dup
+            limit    = o.limit.expr
+            offset   = o.offset
+            o.offset = nil
+            collector << "
+                SELECT * FROM (
+                  SELECT raw_sql_.*, rownum raw_rnum_
+                  FROM ("
+
+            collector = super(o, collector)
+
+            if offset.expr.is_a? Nodes::BindParam
+              collector << ") raw_sql_ WHERE rownum <= ("
+              collector = visit offset.expr, collector
+              collector << " + "
+              collector = visit limit, collector
+              collector << ") ) WHERE raw_rnum_ > "
+              collector = visit offset.expr, collector
+              return collector
+            else
+              collector << ") raw_sql_
+                  WHERE rownum <= #{offset.expr.to_i + limit}
+                )
+                WHERE "
+              return visit(offset, collector)
+            end
+          end
+
+          if o.limit
+            o       = o.dup
+            limit   = o.limit.expr
+            collector << "SELECT * FROM ("
+            collector = super(o, collector)
+            collector << ") WHERE ROWNUM <= "
+            return visit limit, collector
+          end
+
+          if o.offset
+            o        = o.dup
+            offset   = o.offset
+            o.offset = nil
+            collector << "SELECT * FROM (
+                  SELECT raw_sql_.*, rownum raw_rnum_
+                  FROM ("
+            collector = super(o, collector)
+            collector << ") raw_sql_
+                )
+                WHERE "
+            return visit offset, collector
+          end
+
+          super
+        end
+
+        def visit_Arel_Nodes_Limit(o, collector)
+          collector
+        end
+
+        def visit_Arel_Nodes_Offset(o, collector)
+          collector << "raw_rnum_ > "
+          visit o.expr, collector
+        end
+
+        def visit_Arel_Nodes_Except(o, collector)
+          collector << "( "
+          collector = infix_value o, collector, " MINUS "
+          collector << " )"
+        end
+
+        def visit_Arel_Nodes_UpdateStatement(o, collector)
+          # Oracle does not allow ORDER BY/LIMIT in UPDATEs.
+          if o.orders.any? && o.limit.nil?
+            # However, there is no harm in silently eating the ORDER BY clause if no LIMIT has been provided,
+            # otherwise let the user deal with the error
+            o = o.dup
+            o.orders = []
+          end
+
+          super
+        end
+
+        ###
+        # Hacks for the order clauses specific to Oracle
+        def order_hacks(o)
+          return o if o.orders.empty?
+          return o unless o.cores.any? do |core|
+            core.projections.any? do |projection|
+              /FIRST_VALUE/ === projection
+            end
+          end
+          # Previous version with join and split broke ORDER BY clause
+          # if it contained functions with several arguments (separated by ',').
+          #
+          # orders   = o.orders.map { |x| visit x }.join(', ').split(',')
+          orders   = o.orders.map do |x|
+            string = visit(x, Arel::Collectors::SQLString.new).value
+            if string.include?(",")
+              split_order_string(string)
+            else
+              string
+            end
+          end.flatten
+          o.orders = []
+          orders.each_with_index do |order, i|
+            o.orders <<
+              Nodes::SqlLiteral.new("alias_#{i}__#{' DESC' if /\bdesc$/i === order}")
+          end
+          o
+        end
+
+        # Split string by commas but count opening and closing brackets
+        # and ignore commas inside brackets.
+        def split_order_string(string)
+          array = []
+          i = 0
+          string.split(",").each do |part|
+            if array[i]
+              array[i] << "," << part
+            else
+              # to ensure that array[i] will be String and not Arel::Nodes::SqlLiteral
+              array[i] = part.to_s
+            end
+            i += 1 if array[i].count("(") == array[i].count(")")
+          end
+          array
+        end
+
+        def visit_Arel_Nodes_BindParam(o, collector)
+          collector.add_bind(o.value) { |i| ":a#{i}" }
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/visitors/oracle12.rb b/activerecord/lib/arel/visitors/oracle12.rb
new file mode 100644
index 0000000000..7061f06087
--- /dev/null
+++ b/activerecord/lib/arel/visitors/oracle12.rb
@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Visitors
+    class Oracle12 < Arel::Visitors::ToSql
+      private
+
+        def visit_Arel_Nodes_SelectStatement(o, collector)
+          # Oracle does not allow LIMIT clause with select for update
+          if o.limit && o.lock
+            raise ArgumentError, <<-MSG
+            'Combination of limit and lock is not supported.
+            because generated SQL statements
+            `SELECT FOR UPDATE and FETCH FIRST n ROWS` generates ORA-02014.`
+          MSG
+          end
+          super
+        end
+
+        def visit_Arel_Nodes_SelectOptions(o, collector)
+          collector = maybe_visit o.offset, collector
+          collector = maybe_visit o.limit, collector
+          collector = maybe_visit o.lock, collector
+        end
+
+        def visit_Arel_Nodes_Limit(o, collector)
+          collector << "FETCH FIRST "
+          collector = visit o.expr, collector
+          collector << " ROWS ONLY"
+        end
+
+        def visit_Arel_Nodes_Offset(o, collector)
+          collector << "OFFSET "
+          visit o.expr, collector
+          collector << " ROWS"
+        end
+
+        def visit_Arel_Nodes_Except(o, collector)
+          collector << "( "
+          collector = infix_value o, collector, " MINUS "
+          collector << " )"
+        end
+
+        def visit_Arel_Nodes_UpdateStatement(o, collector)
+          # Oracle does not allow ORDER BY/LIMIT in UPDATEs.
+          if o.orders.any? && o.limit.nil?
+            # However, there is no harm in silently eating the ORDER BY clause if no LIMIT has been provided,
+            # otherwise let the user deal with the error
+            o = o.dup
+            o.orders = []
+          end
+
+          super
+        end
+
+        def visit_Arel_Nodes_BindParam(o, collector)
+          collector.add_bind(o.value) { |i| ":a#{i}" }
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/visitors/postgresql.rb b/activerecord/lib/arel/visitors/postgresql.rb
new file mode 100644
index 0000000000..108ee431ee
--- /dev/null
+++ b/activerecord/lib/arel/visitors/postgresql.rb
@@ -0,0 +1,104 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Visitors
+    class PostgreSQL < Arel::Visitors::ToSql
+      CUBE = "CUBE"
+      ROLLUP = "ROLLUP"
+      GROUPING_SET = "GROUPING SET"
+      LATERAL = "LATERAL"
+
+      private
+
+        def visit_Arel_Nodes_Matches(o, collector)
+          op = o.case_sensitive ? " LIKE " : " ILIKE "
+          collector = infix_value o, collector, op
+          if o.escape
+            collector << " ESCAPE "
+            visit o.escape, collector
+          else
+            collector
+          end
+        end
+
+        def visit_Arel_Nodes_DoesNotMatch(o, collector)
+          op = o.case_sensitive ? " NOT LIKE " : " NOT ILIKE "
+          collector = infix_value o, collector, op
+          if o.escape
+            collector << " ESCAPE "
+            visit o.escape, collector
+          else
+            collector
+          end
+        end
+
+        def visit_Arel_Nodes_Regexp(o, collector)
+          op = o.case_sensitive ? " ~ " : " ~* "
+          infix_value o, collector, op
+        end
+
+        def visit_Arel_Nodes_NotRegexp(o, collector)
+          op = o.case_sensitive ? " !~ " : " !~* "
+          infix_value o, collector, op
+        end
+
+        def visit_Arel_Nodes_DistinctOn(o, collector)
+          collector << "DISTINCT ON ( "
+          visit(o.expr, collector) << " )"
+        end
+
+        def visit_Arel_Nodes_BindParam(o, collector)
+          collector.add_bind(o.value) { |i| "$#{i}" }
+        end
+
+        def visit_Arel_Nodes_GroupingElement(o, collector)
+          collector << "( "
+          visit(o.expr, collector) << " )"
+        end
+
+        def visit_Arel_Nodes_Cube(o, collector)
+          collector << CUBE
+          grouping_array_or_grouping_element o, collector
+        end
+
+        def visit_Arel_Nodes_RollUp(o, collector)
+          collector << ROLLUP
+          grouping_array_or_grouping_element o, collector
+        end
+
+        def visit_Arel_Nodes_GroupingSet(o, collector)
+          collector << GROUPING_SET
+          grouping_array_or_grouping_element o, collector
+        end
+
+        def visit_Arel_Nodes_Lateral(o, collector)
+          collector << LATERAL
+          collector << SPACE
+          grouping_parentheses o, collector
+        end
+
+        # Used by Lateral visitor to enclose select queries in parentheses
+        def grouping_parentheses(o, collector)
+          if o.expr.is_a? Nodes::SelectStatement
+            collector << "("
+            visit o.expr, collector
+            collector << ")"
+          else
+            visit o.expr, collector
+          end
+        end
+
+        # Utilized by GroupingSet, Cube & RollUp visitors to
+        # handle grouping aggregation semantics
+        def grouping_array_or_grouping_element(o, collector)
+          if o.expr.is_a? Array
+            collector << "( "
+            visit o.expr, collector
+            collector << " )"
+          else
+            visit o.expr, collector
+          end
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/visitors/sqlite.rb b/activerecord/lib/arel/visitors/sqlite.rb
new file mode 100644
index 0000000000..cb1d2424ad
--- /dev/null
+++ b/activerecord/lib/arel/visitors/sqlite.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Visitors
+    class SQLite < Arel::Visitors::ToSql
+      private
+
+        # Locks are not supported in SQLite
+        def visit_Arel_Nodes_Lock(o, collector)
+          collector
+        end
+
+        def visit_Arel_Nodes_SelectStatement(o, collector)
+          o.limit = Arel::Nodes::Limit.new(-1) if o.offset && !o.limit
+          super
+        end
+
+        def visit_Arel_Nodes_True(o, collector)
+          collector << "1"
+        end
+
+        def visit_Arel_Nodes_False(o, collector)
+          collector << "0"
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/visitors/to_sql.rb b/activerecord/lib/arel/visitors/to_sql.rb
new file mode 100644
index 0000000000..5986fd5576
--- /dev/null
+++ b/activerecord/lib/arel/visitors/to_sql.rb
@@ -0,0 +1,847 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Visitors
+    class UnsupportedVisitError < StandardError
+      def initialize(object)
+        super "Unsupported argument type: #{object.class.name}. Construct an Arel node instead."
+      end
+    end
+
+    class ToSql < Arel::Visitors::Visitor
+      ##
+      # This is some roflscale crazy stuff.  I'm roflscaling this because
+      # building SQL queries is a hotspot.  I will explain the roflscale so that
+      # others will not rm this code.
+      #
+      # In YARV, string literals in a method body will get duped when the byte
+      # code is executed.  Let's take a look:
+      #
+      # > puts RubyVM::InstructionSequence.new('def foo; "bar"; end').disasm
+      #
+      #   == disasm: <RubyVM::InstructionSequence:foo@<compiled>>=====
+      #    0000 trace            8
+      #    0002 trace            1
+      #    0004 putstring        "bar"
+      #    0006 trace            16
+      #    0008 leave
+      #
+      # The `putstring` bytecode will dup the string and push it on the stack.
+      # In many cases in our SQL visitor, that string is never mutated, so there
+      # is no need to dup the literal.
+      #
+      # If we change to a constant lookup, the string will not be duped, and we
+      # can reduce the objects in our system:
+      #
+      # > puts RubyVM::InstructionSequence.new('BAR = "bar"; def foo; BAR; end').disasm
+      #
+      #  == disasm: <RubyVM::InstructionSequence:foo@<compiled>>========
+      #  0000 trace            8
+      #  0002 trace            1
+      #  0004 getinlinecache   11, <ic:0>
+      #  0007 getconstant      :BAR
+      #  0009 setinlinecache   <ic:0>
+      #  0011 trace            16
+      #  0013 leave
+      #
+      # `getconstant` should be a hash lookup, and no object is duped when the
+      # value of the constant is pushed on the stack.  Hence the crazy
+      # constants below.
+      #
+      # `matches` and `doesNotMatch` operate case-insensitively via Visitor subclasses
+      # specialized for specific databases when necessary.
+      #
+
+      WHERE    = " WHERE "    # :nodoc:
+      SPACE    = " "          # :nodoc:
+      COMMA    = ", "         # :nodoc:
+      GROUP_BY = " GROUP BY " # :nodoc:
+      ORDER_BY = " ORDER BY " # :nodoc:
+      WINDOW   = " WINDOW "   # :nodoc:
+      AND      = " AND "      # :nodoc:
+
+      DISTINCT = "DISTINCT"   # :nodoc:
+
+      def initialize(connection)
+        super()
+        @connection = connection
+      end
+
+      def compile(node, &block)
+        accept(node, Arel::Collectors::SQLString.new, &block).value
+      end
+
+      private
+
+        def visit_Arel_Nodes_DeleteStatement(o, collector)
+          collector << "DELETE FROM "
+          collector = visit o.relation, collector
+          if o.wheres.any?
+            collector << WHERE
+            collector = inject_join o.wheres, collector, AND
+          end
+
+          maybe_visit o.limit, collector
+        end
+
+        # FIXME: we should probably have a 2-pass visitor for this
+        def build_subselect(key, o)
+          stmt             = Nodes::SelectStatement.new
+          core             = stmt.cores.first
+          core.froms       = o.relation
+          core.wheres      = o.wheres
+          core.projections = [key]
+          stmt.limit       = o.limit
+          stmt.orders      = o.orders
+          stmt
+        end
+
+        def visit_Arel_Nodes_UpdateStatement(o, collector)
+          if o.orders.empty? && o.limit.nil?
+            wheres = o.wheres
+          else
+            wheres = [Nodes::In.new(o.key, [build_subselect(o.key, o)])]
+          end
+
+          collector << "UPDATE "
+          collector = visit o.relation, collector
+          unless o.values.empty?
+            collector << " SET "
+            collector = inject_join o.values, collector, ", "
+          end
+
+          unless wheres.empty?
+            collector << " WHERE "
+            collector = inject_join wheres, collector, " AND "
+          end
+
+          collector
+        end
+
+        def visit_Arel_Nodes_InsertStatement(o, collector)
+          collector << "INSERT INTO "
+          collector = visit o.relation, collector
+          if o.columns.any?
+            collector << " (#{o.columns.map { |x|
+              quote_column_name x.name
+            }.join ', '})"
+          end
+
+          if o.values
+            maybe_visit o.values, collector
+          elsif o.select
+            maybe_visit o.select, collector
+          else
+            collector
+          end
+        end
+
+        def visit_Arel_Nodes_Exists(o, collector)
+          collector << "EXISTS ("
+          collector = visit(o.expressions, collector) << ")"
+          if o.alias
+            collector << " AS "
+            visit o.alias, collector
+          else
+            collector
+          end
+        end
+
+        def visit_Arel_Nodes_Casted(o, collector)
+          collector << quoted(o.val, o.attribute).to_s
+        end
+
+        def visit_Arel_Nodes_Quoted(o, collector)
+          collector << quoted(o.expr, nil).to_s
+        end
+
+        def visit_Arel_Nodes_True(o, collector)
+          collector << "TRUE"
+        end
+
+        def visit_Arel_Nodes_False(o, collector)
+          collector << "FALSE"
+        end
+
+        def visit_Arel_Nodes_ValuesList(o, collector)
+          collector << "VALUES "
+
+          len = o.rows.length - 1
+          o.rows.each_with_index { |row, i|
+            collector << "("
+            row_len = row.length - 1
+            row.each_with_index do |value, k|
+              case value
+              when Nodes::SqlLiteral, Nodes::BindParam
+                collector = visit(value, collector)
+              else
+                collector << quote(value)
+              end
+              collector << COMMA unless k == row_len
+            end
+            collector << ")"
+            collector << COMMA unless i == len
+          }
+          collector
+        end
+
+        def visit_Arel_Nodes_Values(o, collector)
+          collector << "VALUES ("
+
+          len = o.expressions.length - 1
+          o.expressions.each_with_index { |value, i|
+            case value
+            when Nodes::SqlLiteral, Nodes::BindParam
+              collector = visit value, collector
+            else
+              collector << quote(value).to_s
+            end
+            unless i == len
+              collector << COMMA
+            end
+          }
+
+          collector << ")"
+        end
+
+        def visit_Arel_Nodes_SelectStatement(o, collector)
+          if o.with
+            collector = visit o.with, collector
+            collector << SPACE
+          end
+
+          collector = o.cores.inject(collector) { |c, x|
+            visit_Arel_Nodes_SelectCore(x, c)
+          }
+
+          unless o.orders.empty?
+            collector << ORDER_BY
+            len = o.orders.length - 1
+            o.orders.each_with_index { |x, i|
+              collector = visit(x, collector)
+              collector << COMMA unless len == i
+            }
+          end
+
+          visit_Arel_Nodes_SelectOptions(o, collector)
+
+          collector
+        end
+
+        def visit_Arel_Nodes_SelectOptions(o, collector)
+          collector = maybe_visit o.limit, collector
+          collector = maybe_visit o.offset, collector
+          collector = maybe_visit o.lock, collector
+        end
+
+        def visit_Arel_Nodes_SelectCore(o, collector)
+          collector << "SELECT"
+
+          collector = maybe_visit o.top, collector
+
+          collector = maybe_visit o.set_quantifier, collector
+
+          collect_nodes_for o.projections, collector, SPACE
+
+          if o.source && !o.source.empty?
+            collector << " FROM "
+            collector = visit o.source, collector
+          end
+
+          collect_nodes_for o.wheres, collector, WHERE, AND
+          collect_nodes_for o.groups, collector, GROUP_BY
+          unless o.havings.empty?
+            collector << " HAVING "
+            inject_join o.havings, collector, AND
+          end
+          collect_nodes_for o.windows, collector, WINDOW
+
+          collector
+        end
+
+        def collect_nodes_for(nodes, collector, spacer, connector = COMMA)
+          unless nodes.empty?
+            collector << spacer
+            len = nodes.length - 1
+            nodes.each_with_index do |x, i|
+              collector = visit(x, collector)
+              collector << connector unless len == i
+            end
+          end
+        end
+
+        def visit_Arel_Nodes_Bin(o, collector)
+          visit o.expr, collector
+        end
+
+        def visit_Arel_Nodes_Distinct(o, collector)
+          collector << DISTINCT
+        end
+
+        def visit_Arel_Nodes_DistinctOn(o, collector)
+          raise NotImplementedError, "DISTINCT ON not implemented for this db"
+        end
+
+        def visit_Arel_Nodes_With(o, collector)
+          collector << "WITH "
+          inject_join o.children, collector, COMMA
+        end
+
+        def visit_Arel_Nodes_WithRecursive(o, collector)
+          collector << "WITH RECURSIVE "
+          inject_join o.children, collector, COMMA
+        end
+
+        def visit_Arel_Nodes_Union(o, collector)
+          collector << "( "
+          infix_value(o, collector, " UNION ") << " )"
+        end
+
+        def visit_Arel_Nodes_UnionAll(o, collector)
+          collector << "( "
+          infix_value(o, collector, " UNION ALL ") << " )"
+        end
+
+        def visit_Arel_Nodes_Intersect(o, collector)
+          collector << "( "
+          infix_value(o, collector, " INTERSECT ") << " )"
+        end
+
+        def visit_Arel_Nodes_Except(o, collector)
+          collector << "( "
+          infix_value(o, collector, " EXCEPT ") << " )"
+        end
+
+        def visit_Arel_Nodes_NamedWindow(o, collector)
+          collector << quote_column_name(o.name)
+          collector << " AS "
+          visit_Arel_Nodes_Window o, collector
+        end
+
+        def visit_Arel_Nodes_Window(o, collector)
+          collector << "("
+
+          if o.partitions.any?
+            collector << "PARTITION BY "
+            collector = inject_join o.partitions, collector, ", "
+          end
+
+          if o.orders.any?
+            collector << SPACE if o.partitions.any?
+            collector << "ORDER BY "
+            collector = inject_join o.orders, collector, ", "
+          end
+
+          if o.framing
+            collector << SPACE if o.partitions.any? || o.orders.any?
+            collector = visit o.framing, collector
+          end
+
+          collector << ")"
+        end
+
+        def visit_Arel_Nodes_Rows(o, collector)
+          if o.expr
+            collector << "ROWS "
+            visit o.expr, collector
+          else
+            collector << "ROWS"
+          end
+        end
+
+        def visit_Arel_Nodes_Range(o, collector)
+          if o.expr
+            collector << "RANGE "
+            visit o.expr, collector
+          else
+            collector << "RANGE"
+          end
+        end
+
+        def visit_Arel_Nodes_Preceding(o, collector)
+          collector = if o.expr
+            visit o.expr, collector
+          else
+            collector << "UNBOUNDED"
+          end
+
+          collector << " PRECEDING"
+        end
+
+        def visit_Arel_Nodes_Following(o, collector)
+          collector = if o.expr
+            visit o.expr, collector
+          else
+            collector << "UNBOUNDED"
+          end
+
+          collector << " FOLLOWING"
+        end
+
+        def visit_Arel_Nodes_CurrentRow(o, collector)
+          collector << "CURRENT ROW"
+        end
+
+        def visit_Arel_Nodes_Over(o, collector)
+          case o.right
+          when nil
+            visit(o.left, collector) << " OVER ()"
+          when Arel::Nodes::SqlLiteral
+            infix_value o, collector, " OVER "
+          when String, Symbol
+            visit(o.left, collector) << " OVER #{quote_column_name o.right.to_s}"
+          else
+            infix_value o, collector, " OVER "
+          end
+        end
+
+        def visit_Arel_Nodes_Offset(o, collector)
+          collector << "OFFSET "
+          visit o.expr, collector
+        end
+
+        def visit_Arel_Nodes_Limit(o, collector)
+          collector << "LIMIT "
+          visit o.expr, collector
+        end
+
+        # FIXME: this does nothing on most databases, but does on MSSQL
+        def visit_Arel_Nodes_Top(o, collector)
+          collector
+        end
+
+        def visit_Arel_Nodes_Lock(o, collector)
+          visit o.expr, collector
+        end
+
+        def visit_Arel_Nodes_Grouping(o, collector)
+          if o.expr.is_a? Nodes::Grouping
+            visit(o.expr, collector)
+          else
+            collector << "("
+            visit(o.expr, collector) << ")"
+          end
+        end
+
+        def visit_Arel_SelectManager(o, collector)
+          collector << "("
+          visit(o.ast, collector) << ")"
+        end
+
+        def visit_Arel_Nodes_Ascending(o, collector)
+          visit(o.expr, collector) << " ASC"
+        end
+
+        def visit_Arel_Nodes_Descending(o, collector)
+          visit(o.expr, collector) << " DESC"
+        end
+
+        def visit_Arel_Nodes_Group(o, collector)
+          visit o.expr, collector
+        end
+
+        def visit_Arel_Nodes_NamedFunction(o, collector)
+          collector << o.name
+          collector << "("
+          collector << "DISTINCT " if o.distinct
+          collector = inject_join(o.expressions, collector, ", ") << ")"
+          if o.alias
+            collector << " AS "
+            visit o.alias, collector
+          else
+            collector
+          end
+        end
+
+        def visit_Arel_Nodes_Extract(o, collector)
+          collector << "EXTRACT(#{o.field.to_s.upcase} FROM "
+          visit(o.expr, collector) << ")"
+        end
+
+        def visit_Arel_Nodes_Count(o, collector)
+          aggregate "COUNT", o, collector
+        end
+
+        def visit_Arel_Nodes_Sum(o, collector)
+          aggregate "SUM", o, collector
+        end
+
+        def visit_Arel_Nodes_Max(o, collector)
+          aggregate "MAX", o, collector
+        end
+
+        def visit_Arel_Nodes_Min(o, collector)
+          aggregate "MIN", o, collector
+        end
+
+        def visit_Arel_Nodes_Avg(o, collector)
+          aggregate "AVG", o, collector
+        end
+
+        def visit_Arel_Nodes_TableAlias(o, collector)
+          collector = visit o.relation, collector
+          collector << " "
+          collector << quote_table_name(o.name)
+        end
+
+        def visit_Arel_Nodes_Between(o, collector)
+          collector = visit o.left, collector
+          collector << " BETWEEN "
+          visit o.right, collector
+        end
+
+        def visit_Arel_Nodes_GreaterThanOrEqual(o, collector)
+          collector = visit o.left, collector
+          collector << " >= "
+          visit o.right, collector
+        end
+
+        def visit_Arel_Nodes_GreaterThan(o, collector)
+          collector = visit o.left, collector
+          collector << " > "
+          visit o.right, collector
+        end
+
+        def visit_Arel_Nodes_LessThanOrEqual(o, collector)
+          collector = visit o.left, collector
+          collector << " <= "
+          visit o.right, collector
+        end
+
+        def visit_Arel_Nodes_LessThan(o, collector)
+          collector = visit o.left, collector
+          collector << " < "
+          visit o.right, collector
+        end
+
+        def visit_Arel_Nodes_Matches(o, collector)
+          collector = visit o.left, collector
+          collector << " LIKE "
+          collector = visit o.right, collector
+          if o.escape
+            collector << " ESCAPE "
+            visit o.escape, collector
+          else
+            collector
+          end
+        end
+
+        def visit_Arel_Nodes_DoesNotMatch(o, collector)
+          collector = visit o.left, collector
+          collector << " NOT LIKE "
+          collector = visit o.right, collector
+          if o.escape
+            collector << " ESCAPE "
+            visit o.escape, collector
+          else
+            collector
+          end
+        end
+
+        def visit_Arel_Nodes_JoinSource(o, collector)
+          if o.left
+            collector = visit o.left, collector
+          end
+          if o.right.any?
+            collector << SPACE if o.left
+            collector = inject_join o.right, collector, SPACE
+          end
+          collector
+        end
+
+        def visit_Arel_Nodes_Regexp(o, collector)
+          raise NotImplementedError, "~ not implemented for this db"
+        end
+
+        def visit_Arel_Nodes_NotRegexp(o, collector)
+          raise NotImplementedError, "!~ not implemented for this db"
+        end
+
+        def visit_Arel_Nodes_StringJoin(o, collector)
+          visit o.left, collector
+        end
+
+        def visit_Arel_Nodes_FullOuterJoin(o, collector)
+          collector << "FULL OUTER JOIN "
+          collector = visit o.left, collector
+          collector << SPACE
+          visit o.right, collector
+        end
+
+        def visit_Arel_Nodes_OuterJoin(o, collector)
+          collector << "LEFT OUTER JOIN "
+          collector = visit o.left, collector
+          collector << " "
+          visit o.right, collector
+        end
+
+        def visit_Arel_Nodes_RightOuterJoin(o, collector)
+          collector << "RIGHT OUTER JOIN "
+          collector = visit o.left, collector
+          collector << SPACE
+          visit o.right, collector
+        end
+
+        def visit_Arel_Nodes_InnerJoin(o, collector)
+          collector << "INNER JOIN "
+          collector = visit o.left, collector
+          if o.right
+            collector << SPACE
+            visit(o.right, collector)
+          else
+            collector
+          end
+        end
+
+        def visit_Arel_Nodes_On(o, collector)
+          collector << "ON "
+          visit o.expr, collector
+        end
+
+        def visit_Arel_Nodes_Not(o, collector)
+          collector << "NOT ("
+          visit(o.expr, collector) << ")"
+        end
+
+        def visit_Arel_Table(o, collector)
+          if o.table_alias
+            collector << "#{quote_table_name o.name} #{quote_table_name o.table_alias}"
+          else
+            collector << quote_table_name(o.name)
+          end
+        end
+
+        def visit_Arel_Nodes_In(o, collector)
+          if Array === o.right && o.right.empty?
+            collector << "1=0"
+          else
+            collector = visit o.left, collector
+            collector << " IN ("
+            visit(o.right, collector) << ")"
+          end
+        end
+
+        def visit_Arel_Nodes_NotIn(o, collector)
+          if Array === o.right && o.right.empty?
+            collector << "1=1"
+          else
+            collector = visit o.left, collector
+            collector << " NOT IN ("
+            collector = visit o.right, collector
+            collector << ")"
+          end
+        end
+
+        def visit_Arel_Nodes_And(o, collector)
+          inject_join o.children, collector, " AND "
+        end
+
+        def visit_Arel_Nodes_Or(o, collector)
+          collector = visit o.left, collector
+          collector << " OR "
+          visit o.right, collector
+        end
+
+        def visit_Arel_Nodes_Assignment(o, collector)
+          case o.right
+          when Arel::Nodes::UnqualifiedColumn, Arel::Attributes::Attribute, Arel::Nodes::BindParam
+            collector = visit o.left, collector
+            collector << " = "
+            visit o.right, collector
+          else
+            collector = visit o.left, collector
+            collector << " = "
+            collector << quote(o.right).to_s
+          end
+        end
+
+        def visit_Arel_Nodes_Equality(o, collector)
+          right = o.right
+
+          collector = visit o.left, collector
+
+          if right.nil?
+            collector << " IS NULL"
+          else
+            collector << " = "
+            visit right, collector
+          end
+        end
+
+        def visit_Arel_Nodes_NotEqual(o, collector)
+          right = o.right
+
+          collector = visit o.left, collector
+
+          if right.nil?
+            collector << " IS NOT NULL"
+          else
+            collector << " != "
+            visit right, collector
+          end
+        end
+
+        def visit_Arel_Nodes_As(o, collector)
+          collector = visit o.left, collector
+          collector << " AS "
+          visit o.right, collector
+        end
+
+        def visit_Arel_Nodes_Case(o, collector)
+          collector << "CASE "
+          if o.case
+            visit o.case, collector
+            collector << " "
+          end
+          o.conditions.each do |condition|
+            visit condition, collector
+            collector << " "
+          end
+          if o.default
+            visit o.default, collector
+            collector << " "
+          end
+          collector << "END"
+        end
+
+        def visit_Arel_Nodes_When(o, collector)
+          collector << "WHEN "
+          visit o.left, collector
+          collector << " THEN "
+          visit o.right, collector
+        end
+
+        def visit_Arel_Nodes_Else(o, collector)
+          collector << "ELSE "
+          visit o.expr, collector
+        end
+
+        def visit_Arel_Nodes_UnqualifiedColumn(o, collector)
+          collector << "#{quote_column_name o.name}"
+          collector
+        end
+
+        def visit_Arel_Attributes_Attribute(o, collector)
+          join_name = o.relation.table_alias || o.relation.name
+          collector << "#{quote_table_name join_name}.#{quote_column_name o.name}"
+        end
+        alias :visit_Arel_Attributes_Integer :visit_Arel_Attributes_Attribute
+        alias :visit_Arel_Attributes_Float :visit_Arel_Attributes_Attribute
+        alias :visit_Arel_Attributes_Decimal :visit_Arel_Attributes_Attribute
+        alias :visit_Arel_Attributes_String :visit_Arel_Attributes_Attribute
+        alias :visit_Arel_Attributes_Time :visit_Arel_Attributes_Attribute
+        alias :visit_Arel_Attributes_Boolean :visit_Arel_Attributes_Attribute
+
+        def literal(o, collector); collector << o.to_s; end
+
+        def visit_Arel_Nodes_BindParam(o, collector)
+          collector.add_bind(o.value) { "?" }
+        end
+
+        alias :visit_Arel_Nodes_SqlLiteral :literal
+        alias :visit_Bignum                :literal
+        alias :visit_Fixnum                :literal
+        alias :visit_Integer               :literal
+
+        def quoted(o, a)
+          if a && a.able_to_type_cast?
+            quote(a.type_cast_for_database(o))
+          else
+            quote(o)
+          end
+        end
+
+        def unsupported(o, collector)
+          raise UnsupportedVisitError.new(o)
+        end
+
+        alias :visit_ActiveSupport_Multibyte_Chars :unsupported
+        alias :visit_ActiveSupport_StringInquirer  :unsupported
+        alias :visit_BigDecimal                    :unsupported
+        alias :visit_Class                         :unsupported
+        alias :visit_Date                          :unsupported
+        alias :visit_DateTime                      :unsupported
+        alias :visit_FalseClass                    :unsupported
+        alias :visit_Float                         :unsupported
+        alias :visit_Hash                          :unsupported
+        alias :visit_NilClass                      :unsupported
+        alias :visit_String                        :unsupported
+        alias :visit_Symbol                        :unsupported
+        alias :visit_Time                          :unsupported
+        alias :visit_TrueClass                     :unsupported
+
+        def visit_Arel_Nodes_InfixOperation(o, collector)
+          collector = visit o.left, collector
+          collector << " #{o.operator} "
+          visit o.right, collector
+        end
+
+        alias :visit_Arel_Nodes_Addition       :visit_Arel_Nodes_InfixOperation
+        alias :visit_Arel_Nodes_Subtraction    :visit_Arel_Nodes_InfixOperation
+        alias :visit_Arel_Nodes_Multiplication :visit_Arel_Nodes_InfixOperation
+        alias :visit_Arel_Nodes_Division       :visit_Arel_Nodes_InfixOperation
+
+        def visit_Arel_Nodes_UnaryOperation(o, collector)
+          collector << " #{o.operator} "
+          visit o.expr, collector
+        end
+
+        def visit_Array(o, collector)
+          inject_join o, collector, ", "
+        end
+        alias :visit_Set :visit_Array
+
+        def quote(value)
+          return value if Arel::Nodes::SqlLiteral === value
+          @connection.quote value
+        end
+
+        def quote_table_name(name)
+          return name if Arel::Nodes::SqlLiteral === name
+          @connection.quote_table_name(name)
+        end
+
+        def quote_column_name(name)
+          return name if Arel::Nodes::SqlLiteral === name
+          @connection.quote_column_name(name)
+        end
+
+        def maybe_visit(thing, collector)
+          return collector unless thing
+          collector << " "
+          visit thing, collector
+        end
+
+        def inject_join(list, collector, join_str)
+          len = list.length - 1
+          list.each_with_index.inject(collector) { |c, (x, i)|
+            if i == len
+              visit x, c
+            else
+              visit(x, c) << join_str
+            end
+          }
+        end
+
+        def infix_value(o, collector, value)
+          collector = visit o.left, collector
+          collector << value
+          visit o.right, collector
+        end
+
+        def aggregate(name, o, collector)
+          collector << "#{name}("
+          if o.distinct
+            collector << "DISTINCT "
+          end
+          collector = inject_join(o.expressions, collector, ", ") << ")"
+          if o.alias
+            collector << " AS "
+            visit o.alias, collector
+          else
+            collector
+          end
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/visitors/visitor.rb b/activerecord/lib/arel/visitors/visitor.rb
new file mode 100644
index 0000000000..1c17184e86
--- /dev/null
+++ b/activerecord/lib/arel/visitors/visitor.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Visitors
+    class Visitor
+      def initialize
+        @dispatch = get_dispatch_cache
+      end
+
+      def accept(object, *args)
+        visit object, *args
+      end
+
+      private
+
+        attr_reader :dispatch
+
+        def self.dispatch_cache
+          Hash.new do |hash, klass|
+            hash[klass] = "visit_#{(klass.name || '').gsub('::', '_')}"
+          end
+        end
+
+        def get_dispatch_cache
+          self.class.dispatch_cache
+        end
+
+        def visit(object, *args)
+          dispatch_method = dispatch[object.class]
+          send dispatch_method, object, *args
+        rescue NoMethodError => e
+          raise e if respond_to?(dispatch_method, true)
+          superklass = object.class.ancestors.find { |klass|
+            respond_to?(dispatch[klass], true)
+          }
+          raise(TypeError, "Cannot visit #{object.class}") unless superklass
+          dispatch[object.class] = dispatch[superklass]
+          retry
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/visitors/where_sql.rb b/activerecord/lib/arel/visitors/where_sql.rb
new file mode 100644
index 0000000000..c6caf5e7c9
--- /dev/null
+++ b/activerecord/lib/arel/visitors/where_sql.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Visitors
+    class WhereSql < Arel::Visitors::ToSql
+      def initialize(inner_visitor, *args, &block)
+        @inner_visitor = inner_visitor
+        super(*args, &block)
+      end
+
+      private
+
+        def visit_Arel_Nodes_SelectCore(o, collector)
+          collector << "WHERE "
+          wheres = o.wheres.map do |where|
+            Nodes::SqlLiteral.new(@inner_visitor.accept(where, collector.class.new).value)
+          end
+
+          inject_join wheres, collector, " AND "
+        end
+    end
+  end
+end
diff --git a/activerecord/lib/arel/window_predications.rb b/activerecord/lib/arel/window_predications.rb
new file mode 100644
index 0000000000..3a8ee41f8a
--- /dev/null
+++ b/activerecord/lib/arel/window_predications.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module WindowPredications
+    def over(expr = nil)
+      Nodes::Over.new(self, expr)
+    end
+  end
+end
diff --git a/activerecord/lib/rails/generators/active_record/application_record/templates/application_record.rb b/activerecord/lib/rails/generators/active_record/application_record/templates/application_record.rb.tt
index 60050e0bf8..60050e0bf8 100644
--- a/activerecord/lib/rails/generators/active_record/application_record/templates/application_record.rb
+++ b/activerecord/lib/rails/generators/active_record/application_record/templates/application_record.rb.tt
diff --git a/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb b/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb
index 856fcc5897..a07b00ef79 100644
--- a/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb
+++ b/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb
@@ -15,12 +15,8 @@ module ActiveRecord
         migration_template @migration_template, File.join(db_migrate_path, "#{file_name}.rb")
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-        attr_reader :migration_action, :join_tables
-
       private
+        attr_reader :migration_action, :join_tables
 
         # Sets the default migration template that is being used for the generation of the migration.
         # Depending on command line arguments, the migration template and the table name instance
diff --git a/activerecord/lib/rails/generators/active_record/migration/templates/create_table_migration.rb b/activerecord/lib/rails/generators/active_record/migration/templates/create_table_migration.rb.tt
index 5f7201cfe1..5f7201cfe1 100644
--- a/activerecord/lib/rails/generators/active_record/migration/templates/create_table_migration.rb
+++ b/activerecord/lib/rails/generators/active_record/migration/templates/create_table_migration.rb.tt
diff --git a/activerecord/lib/rails/generators/active_record/migration/templates/migration.rb b/activerecord/lib/rails/generators/active_record/migration/templates/migration.rb.tt
index 481c70201b..481c70201b 100644
--- a/activerecord/lib/rails/generators/active_record/migration/templates/migration.rb
+++ b/activerecord/lib/rails/generators/active_record/migration/templates/migration.rb.tt
diff --git a/activerecord/lib/rails/generators/active_record/model/templates/model.rb b/activerecord/lib/rails/generators/active_record/model/templates/model.rb.tt
index 55dc65c8ad..55dc65c8ad 100644
--- a/activerecord/lib/rails/generators/active_record/model/templates/model.rb
+++ b/activerecord/lib/rails/generators/active_record/model/templates/model.rb.tt
diff --git a/activerecord/lib/rails/generators/active_record/model/templates/module.rb b/activerecord/lib/rails/generators/active_record/model/templates/module.rb.tt
index a3bf1c37b6..a3bf1c37b6 100644
--- a/activerecord/lib/rails/generators/active_record/model/templates/module.rb
+++ b/activerecord/lib/rails/generators/active_record/model/templates/module.rb.tt
diff --git a/activerecord/test/.gitignore b/activerecord/test/.gitignore
deleted file mode 100644
index a0ec5967dd..0000000000
--- a/activerecord/test/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-/config.yml
diff --git a/activerecord/test/cases/adapter_test.rb b/activerecord/test/cases/adapter_test.rb
index 9aaa2852d0..79642f5871 100644
--- a/activerecord/test/cases/adapter_test.rb
+++ b/activerecord/test/cases/adapter_test.rb
@@ -20,7 +20,7 @@ module ActiveRecord
         b = Book.create(name: "my \x00 book")
         b.reload
         assert_equal "my \x00 book", b.name
-        b.update_attributes(name: "my other \x00 book")
+        b.update(name: "my other \x00 book")
         b.reload
         assert_equal "my other \x00 book", b.name
       end
@@ -78,13 +78,13 @@ module ActiveRecord
       idx_name = "accounts_idx"
 
       indexes = @connection.indexes("accounts")
-      assert indexes.empty?
+      assert_empty indexes
 
       @connection.add_index :accounts, :firm_id, name: idx_name
       indexes = @connection.indexes("accounts")
       assert_equal "accounts", indexes.first.table
       assert_equal idx_name, indexes.first.name
-      assert !indexes.first.unique
+      assert_not indexes.first.unique
       assert_equal ["firm_id"], indexes.first.columns
     ensure
       @connection.remove_index(:accounts, name: idx_name) rescue nil
@@ -295,6 +295,10 @@ module ActiveRecord
         assert_equal "ы", error.message
       end
     end
+
+    def test_supports_multi_insert_is_deprecated
+      assert_deprecated { @connection.supports_multi_insert? }
+    end
   end
 
   class AdapterForeignKeyTest < ActiveRecord::TestCase
@@ -368,16 +372,16 @@ module ActiveRecord
     unless in_memory_db?
       test "transaction state is reset after a reconnect" do
         @connection.begin_transaction
-        assert @connection.transaction_open?
+        assert_predicate @connection, :transaction_open?
         @connection.reconnect!
-        assert !@connection.transaction_open?
+        assert_not_predicate @connection, :transaction_open?
       end
 
       test "transaction state is reset after a disconnect" do
         @connection.begin_transaction
-        assert @connection.transaction_open?
+        assert_predicate @connection, :transaction_open?
         @connection.disconnect!
-        assert !@connection.transaction_open?
+        assert_not_predicate @connection, :transaction_open?
       end
     end
 
diff --git a/activerecord/test/cases/adapters/mysql2/active_schema_test.rb b/activerecord/test/cases/adapters/mysql2/active_schema_test.rb
index a6b83ec377..976c5dde58 100644
--- a/activerecord/test/cases/adapters/mysql2/active_schema_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/active_schema_test.rb
@@ -9,7 +9,7 @@ class Mysql2ActiveSchemaTest < ActiveRecord::Mysql2TestCase
   def setup
     ActiveRecord::Base.connection.singleton_class.class_eval do
       alias_method :execute_without_stub, :execute
-      def execute(sql, name = nil) return sql end
+      def execute(sql, name = nil) sql end
     end
   end
 
@@ -68,14 +68,14 @@ class Mysql2ActiveSchemaTest < ActiveRecord::Mysql2TestCase
     def (ActiveRecord::Base.connection).data_source_exists?(*); false; end
 
     %w(SPATIAL FULLTEXT UNIQUE).each do |type|
-      expected = "CREATE TABLE `people` (#{type} INDEX `index_people_on_last_name`  (`last_name`)) ENGINE=InnoDB"
+      expected = "CREATE TABLE `people` (#{type} INDEX `index_people_on_last_name`  (`last_name`))"
       actual = ActiveRecord::Base.connection.create_table(:people, id: false) do |t|
         t.index :last_name, type: type
       end
       assert_equal expected, actual
     end
 
-    expected = "CREATE TABLE `people` ( INDEX `index_people_on_last_name` USING btree (`last_name`(10))) ENGINE=InnoDB"
+    expected = "CREATE TABLE `people` ( INDEX `index_people_on_last_name` USING btree (`last_name`(10)))"
     actual = ActiveRecord::Base.connection.create_table(:people, id: false) do |t|
       t.index :last_name, length: 10, using: :btree
     end
@@ -108,7 +108,7 @@ class Mysql2ActiveSchemaTest < ActiveRecord::Mysql2TestCase
   def test_create_mysql_database_with_encoding
     assert_equal "CREATE DATABASE `matt` DEFAULT CHARACTER SET `utf8`", create_database(:matt)
     assert_equal "CREATE DATABASE `aimonetti` DEFAULT CHARACTER SET `latin1`", create_database(:aimonetti, charset: "latin1")
-    assert_equal "CREATE DATABASE `matt_aimonetti` DEFAULT CHARACTER SET `big5` COLLATE `big5_chinese_ci`", create_database(:matt_aimonetti, charset: :big5, collation: :big5_chinese_ci)
+    assert_equal "CREATE DATABASE `matt_aimonetti` DEFAULT COLLATE `utf8mb4_bin`", create_database(:matt_aimonetti, collation: "utf8mb4_bin")
   end
 
   def test_recreate_mysql_database_with_encoding
@@ -148,8 +148,8 @@ class Mysql2ActiveSchemaTest < ActiveRecord::Mysql2TestCase
           t.timestamps null: true
         end
         ActiveRecord::Base.connection.remove_timestamps :delete_me, null: true
-        assert !column_present?("delete_me", "updated_at", "datetime")
-        assert !column_present?("delete_me", "created_at", "datetime")
+        assert_not column_present?("delete_me", "updated_at", "datetime")
+        assert_not column_present?("delete_me", "created_at", "datetime")
       ensure
         ActiveRecord::Base.connection.drop_table :delete_me rescue nil
       end
@@ -160,7 +160,7 @@ class Mysql2ActiveSchemaTest < ActiveRecord::Mysql2TestCase
     ActiveRecord::Base.connection.stubs(:data_source_exists?).with(:temp).returns(false)
     ActiveRecord::Base.connection.stubs(:index_name_exists?).with(:index_temp_on_zip).returns(false)
 
-    expected = "CREATE TEMPORARY TABLE `temp` ( INDEX `index_temp_on_zip`  (`zip`)) ENGINE=InnoDB AS SELECT id, name, zip FROM a_really_complicated_query"
+    expected = "CREATE TEMPORARY TABLE `temp` ( INDEX `index_temp_on_zip`  (`zip`)) AS SELECT id, name, zip FROM a_really_complicated_query"
     actual = ActiveRecord::Base.connection.create_table(:temp, temporary: true, as: "SELECT id, name, zip FROM a_really_complicated_query") do |t|
       t.index :zip
     end
diff --git a/activerecord/test/cases/adapters/mysql2/auto_increment_test.rb b/activerecord/test/cases/adapters/mysql2/auto_increment_test.rb
new file mode 100644
index 0000000000..4c67633946
--- /dev/null
+++ b/activerecord/test/cases/adapters/mysql2/auto_increment_test.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "support/schema_dumping_helper"
+
+class Mysql2AutoIncrementTest < ActiveRecord::Mysql2TestCase
+  include SchemaDumpingHelper
+
+  def setup
+    @connection = ActiveRecord::Base.connection
+  end
+
+  def teardown
+    @connection.drop_table :auto_increments, if_exists: true
+  end
+
+  def test_auto_increment_without_primary_key
+    @connection.create_table :auto_increments, id: false, force: true do |t|
+      t.integer :id, null: false, auto_increment: true
+      t.index :id
+    end
+    output = dump_table_schema("auto_increments")
+    assert_match(/t\.integer\s+"id",\s+null: false,\s+auto_increment: true$/, output)
+  end
+
+  def test_auto_increment_with_composite_primary_key
+    @connection.create_table :auto_increments, primary_key: [:id, :created_at], force: true do |t|
+      t.integer :id, null: false, auto_increment: true
+      t.datetime :created_at, null: false
+    end
+    output = dump_table_schema("auto_increments")
+    assert_match(/t\.integer\s+"id",\s+null: false,\s+auto_increment: true$/, output)
+  end
+end
diff --git a/activerecord/test/cases/adapters/mysql2/case_sensitivity_test.rb b/activerecord/test/cases/adapters/mysql2/case_sensitivity_test.rb
index fd5f712f1a..aa870349be 100644
--- a/activerecord/test/cases/adapters/mysql2/case_sensitivity_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/case_sensitivity_test.rb
@@ -14,8 +14,8 @@ class Mysql2CaseSensitivityTest < ActiveRecord::Mysql2TestCase
   end
 
   def test_case_sensitive
-    assert !CollationTest.columns_hash["string_ci_column"].case_sensitive?
-    assert CollationTest.columns_hash["string_cs_column"].case_sensitive?
+    assert_not_predicate CollationTest.columns_hash["string_ci_column"], :case_sensitive?
+    assert_predicate CollationTest.columns_hash["string_cs_column"], :case_sensitive?
   end
 
   def test_case_insensitive_comparison_for_ci_column
diff --git a/activerecord/test/cases/adapters/mysql2/connection_test.rb b/activerecord/test/cases/adapters/mysql2/connection_test.rb
index 9d81d506a0..726f58d58e 100644
--- a/activerecord/test/cases/adapters/mysql2/connection_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/connection_test.rb
@@ -40,41 +40,29 @@ class Mysql2ConnectionTest < ActiveRecord::Mysql2TestCase
   end
 
   def test_no_automatic_reconnection_after_timeout
-    assert @connection.active?
+    assert_predicate @connection, :active?
     @connection.update("set @@wait_timeout=1")
     sleep 2
-    assert !@connection.active?
+    assert_not_predicate @connection, :active?
   ensure
     # Repair all fixture connections so other tests won't break.
     @fixture_connections.each(&:verify!)
   end
 
   def test_successful_reconnection_after_timeout_with_manual_reconnect
-    assert @connection.active?
+    assert_predicate @connection, :active?
     @connection.update("set @@wait_timeout=1")
     sleep 2
     @connection.reconnect!
-    assert @connection.active?
+    assert_predicate @connection, :active?
   end
 
   def test_successful_reconnection_after_timeout_with_verify
-    assert @connection.active?
+    assert_predicate @connection, :active?
     @connection.update("set @@wait_timeout=1")
     sleep 2
     @connection.verify!
-    assert @connection.active?
-  end
-
-  def test_verify_with_args_is_deprecated
-    assert_deprecated do
-      @connection.verify!(option: true)
-    end
-    assert_deprecated do
-      @connection.verify!([])
-    end
-    assert_deprecated do
-      @connection.verify!({})
-    end
+    assert_predicate @connection, :active?
   end
 
   def test_execute_after_disconnect
@@ -186,10 +174,10 @@ class Mysql2ConnectionTest < ActiveRecord::Mysql2TestCase
     assert_equal "SCHEMA", @subscriber.logged[0][1]
   end
 
-  def test_logs_name_rename_column_sql
+  def test_logs_name_rename_column_for_alter
     @connection.execute "CREATE TABLE `bar_baz` (`foo` varchar(255))"
     @subscriber.logged.clear
-    @connection.send(:rename_column_sql, "bar_baz", "foo", "foo2")
+    @connection.send(:rename_column_for_alter, "bar_baz", "foo", "foo2")
     assert_equal "SCHEMA", @subscriber.logged[0][1]
   ensure
     @connection.execute "DROP TABLE `bar_baz`"
diff --git a/activerecord/test/cases/adapters/mysql2/enum_test.rb b/activerecord/test/cases/adapters/mysql2/enum_test.rb
index 108bec832c..832f5d61d1 100644
--- a/activerecord/test/cases/adapters/mysql2/enum_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/enum_test.rb
@@ -13,11 +13,11 @@ class Mysql2EnumTest < ActiveRecord::Mysql2TestCase
 
   def test_should_not_be_unsigned
     column = EnumTest.columns_hash["enum_column"]
-    assert_not column.unsigned?
+    assert_not_predicate column, :unsigned?
   end
 
   def test_should_not_be_bigint
     column = EnumTest.columns_hash["enum_column"]
-    assert_not column.bigint?
+    assert_not_predicate column, :bigint?
   end
 end
diff --git a/activerecord/test/cases/adapters/mysql2/explain_test.rb b/activerecord/test/cases/adapters/mysql2/explain_test.rb
index 2736f7cf0e..b8e778f0b0 100644
--- a/activerecord/test/cases/adapters/mysql2/explain_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/explain_test.rb
@@ -1,23 +1,23 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "models/developer"
-require "models/computer"
+require "models/author"
+require "models/post"
 
 class Mysql2ExplainTest < ActiveRecord::Mysql2TestCase
-  fixtures :developers
+  fixtures :authors
 
   def test_explain_for_one_query
-    explain = Developer.where(id: 1).explain
-    assert_match %(EXPLAIN for: SELECT `developers`.* FROM `developers` WHERE `developers`.`id` = 1), explain
-    assert_match %r(developers |.* const), explain
+    explain = Author.where(id: 1).explain
+    assert_match %(EXPLAIN for: SELECT `authors`.* FROM `authors` WHERE `authors`.`id` = 1), explain
+    assert_match %r(authors |.* const), explain
   end
 
   def test_explain_with_eager_loading
-    explain = Developer.where(id: 1).includes(:audit_logs).explain
-    assert_match %(EXPLAIN for: SELECT `developers`.* FROM `developers` WHERE `developers`.`id` = 1), explain
-    assert_match %r(developers |.* const), explain
-    assert_match %(EXPLAIN for: SELECT `audit_logs`.* FROM `audit_logs` WHERE `audit_logs`.`developer_id` = 1), explain
-    assert_match %r(audit_logs |.* ALL), explain
+    explain = Author.where(id: 1).includes(:posts).explain
+    assert_match %(EXPLAIN for: SELECT `authors`.* FROM `authors` WHERE `authors`.`id` = 1), explain
+    assert_match %r(authors |.* const), explain
+    assert_match %(EXPLAIN for: SELECT `posts`.* FROM `posts` WHERE `posts`.`author_id` = 1), explain
+    assert_match %r(posts |.* ALL), explain
   end
 end
diff --git a/activerecord/test/cases/adapters/mysql2/mysql2_adapter_test.rb b/activerecord/test/cases/adapters/mysql2/mysql2_adapter_test.rb
index d18fb97e05..0719baaa23 100644
--- a/activerecord/test/cases/adapters/mysql2/mysql2_adapter_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/mysql2_adapter_test.rb
@@ -25,25 +25,25 @@ class Mysql2AdapterTest < ActiveRecord::Mysql2TestCase
   end
 
   def test_columns_for_distinct_one_order
-    assert_equal "posts.id, posts.created_at AS alias_0",
+    assert_equal "posts.created_at AS alias_0, posts.id",
       @conn.columns_for_distinct("posts.id", ["posts.created_at desc"])
   end
 
   def test_columns_for_distinct_few_orders
-    assert_equal "posts.id, posts.created_at AS alias_0, posts.position AS alias_1",
+    assert_equal "posts.created_at AS alias_0, posts.position AS alias_1, posts.id",
       @conn.columns_for_distinct("posts.id", ["posts.created_at desc", "posts.position asc"])
   end
 
   def test_columns_for_distinct_with_case
     assert_equal(
-      "posts.id, CASE WHEN author.is_active THEN UPPER(author.name) ELSE UPPER(author.email) END AS alias_0",
+      "CASE WHEN author.is_active THEN UPPER(author.name) ELSE UPPER(author.email) END AS alias_0, posts.id",
       @conn.columns_for_distinct("posts.id",
         ["CASE WHEN author.is_active THEN UPPER(author.name) ELSE UPPER(author.email) END"])
     )
   end
 
   def test_columns_for_distinct_blank_not_nil_orders
-    assert_equal "posts.id, posts.created_at AS alias_0",
+    assert_equal "posts.created_at AS alias_0, posts.id",
       @conn.columns_for_distinct("posts.id", ["posts.created_at desc", "", "   "])
   end
 
@@ -52,7 +52,7 @@ class Mysql2AdapterTest < ActiveRecord::Mysql2TestCase
     def order.to_sql
       "posts.created_at desc"
     end
-    assert_equal "posts.id, posts.created_at AS alias_0",
+    assert_equal "posts.created_at AS alias_0, posts.id",
       @conn.columns_for_distinct("posts.id", [order])
   end
 
diff --git a/activerecord/test/cases/adapters/mysql2/schema_migrations_test.rb b/activerecord/test/cases/adapters/mysql2/schema_migrations_test.rb
index 62abd694bb..d7d9a2d732 100644
--- a/activerecord/test/cases/adapters/mysql2/schema_migrations_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/schema_migrations_test.rb
@@ -36,7 +36,7 @@ class SchemaMigrationsTest < ActiveRecord::Mysql2TestCase
       assert connection.column_exists?(table_name, :key, :string)
     end
   ensure
-    ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Migrator.current_environment
+    ActiveRecord::InternalMetadata[:environment] = connection.migration_context.current_environment
   end
 
   private
diff --git a/activerecord/test/cases/adapters/mysql2/schema_test.rb b/activerecord/test/cases/adapters/mysql2/schema_test.rb
index b587e756cf..1283b0642c 100644
--- a/activerecord/test/cases/adapters/mysql2/schema_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/schema_test.rb
@@ -67,7 +67,7 @@ module ActiveRecord
       end
 
       def test_data_source_exists_wrong_schema
-        assert(!@connection.data_source_exists?("#{@db_name}.zomg"), "data_source should not exist")
+        assert_not(@connection.data_source_exists?("#{@db_name}.zomg"), "data_source should not exist")
       end
 
       def test_dump_indexes
diff --git a/activerecord/test/cases/adapters/mysql2/table_options_test.rb b/activerecord/test/cases/adapters/mysql2/table_options_test.rb
index 6183d66b63..1c92df940f 100644
--- a/activerecord/test/cases/adapters/mysql2/table_options_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/table_options_test.rb
@@ -17,28 +17,103 @@ class Mysql2TableOptionsTest < ActiveRecord::Mysql2TestCase
   test "table options with ENGINE" do
     @connection.create_table "mysql_table_options", force: true, options: "ENGINE=MyISAM"
     output = dump_table_schema("mysql_table_options")
-    options = %r{create_table "mysql_table_options", force: :cascade, options: "(?<options>.*)"}.match(output)[:options]
+    options = %r{create_table "mysql_table_options", options: "(?<options>.*)"}.match(output)[:options]
     assert_match %r{ENGINE=MyISAM}, options
   end
 
   test "table options with ROW_FORMAT" do
     @connection.create_table "mysql_table_options", force: true, options: "ROW_FORMAT=REDUNDANT"
     output = dump_table_schema("mysql_table_options")
-    options = %r{create_table "mysql_table_options", force: :cascade, options: "(?<options>.*)"}.match(output)[:options]
+    options = %r{create_table "mysql_table_options", options: "(?<options>.*)"}.match(output)[:options]
     assert_match %r{ROW_FORMAT=REDUNDANT}, options
   end
 
   test "table options with CHARSET" do
     @connection.create_table "mysql_table_options", force: true, options: "CHARSET=utf8mb4"
     output = dump_table_schema("mysql_table_options")
-    options = %r{create_table "mysql_table_options", force: :cascade, options: "(?<options>.*)"}.match(output)[:options]
+    options = %r{create_table "mysql_table_options", options: "(?<options>.*)"}.match(output)[:options]
     assert_match %r{CHARSET=utf8mb4}, options
   end
 
   test "table options with COLLATE" do
     @connection.create_table "mysql_table_options", force: true, options: "COLLATE=utf8mb4_bin"
     output = dump_table_schema("mysql_table_options")
-    options = %r{create_table "mysql_table_options", force: :cascade, options: "(?<options>.*)"}.match(output)[:options]
+    options = %r{create_table "mysql_table_options", options: "(?<options>.*)"}.match(output)[:options]
     assert_match %r{COLLATE=utf8mb4_bin}, options
   end
 end
+
+class Mysql2DefaultEngineOptionSchemaDumpTest < ActiveRecord::Mysql2TestCase
+  include SchemaDumpingHelper
+  self.use_transactional_tests = false
+
+  def setup
+    @verbose_was = ActiveRecord::Migration.verbose
+    ActiveRecord::Migration.verbose = false
+  end
+
+  def teardown
+    ActiveRecord::Base.connection.drop_table "mysql_table_options", if_exists: true
+    ActiveRecord::Migration.verbose = @verbose_was
+    ActiveRecord::SchemaMigration.delete_all rescue nil
+  end
+
+  test "schema dump includes ENGINE=InnoDB if not provided" do
+    ActiveRecord::Base.connection.create_table "mysql_table_options", force: true
+
+    output  = dump_table_schema("mysql_table_options")
+    options = %r{create_table "mysql_table_options", options: "(?<options>.*)"}.match(output)[:options]
+    assert_match %r{ENGINE=InnoDB}, options
+  end
+
+  test "schema dump includes ENGINE=InnoDB in legacy migrations" do
+    migration = Class.new(ActiveRecord::Migration[5.1]) do
+      def migrate(x)
+        create_table "mysql_table_options", force: true
+      end
+    end.new
+
+    ActiveRecord::Migrator.new(:up, [migration]).migrate
+
+    output  = dump_table_schema("mysql_table_options")
+    options = %r{create_table "mysql_table_options", options: "(?<options>.*)"}.match(output)[:options]
+    assert_match %r{ENGINE=InnoDB}, options
+  end
+end
+
+class Mysql2DefaultEngineOptionSqlOutputTest < ActiveRecord::Mysql2TestCase
+  self.use_transactional_tests = false
+
+  def setup
+    @logger_was  = ActiveRecord::Base.logger
+    @log         = StringIO.new
+    @verbose_was = ActiveRecord::Migration.verbose
+    ActiveRecord::Base.logger = ActiveSupport::Logger.new(@log)
+    ActiveRecord::Migration.verbose = false
+  end
+
+  def teardown
+    ActiveRecord::Base.logger       = @logger_was
+    ActiveRecord::Migration.verbose = @verbose_was
+    ActiveRecord::Base.connection.drop_table "mysql_table_options", if_exists: true
+    ActiveRecord::SchemaMigration.delete_all rescue nil
+  end
+
+  test "new migrations do not contain default ENGINE=InnoDB option" do
+    ActiveRecord::Base.connection.create_table "mysql_table_options", force: true
+
+    assert_no_match %r{ENGINE=InnoDB}, @log.string
+  end
+
+  test "legacy migrations contain default ENGINE=InnoDB option" do
+    migration = Class.new(ActiveRecord::Migration[5.1]) do
+      def migrate(x)
+        create_table "mysql_table_options", force: true
+      end
+    end.new
+
+    ActiveRecord::Migrator.new(:up, [migration]).migrate
+
+    assert_match %r{ENGINE=InnoDB}, @log.string
+  end
+end
diff --git a/activerecord/test/cases/adapters/mysql2/transaction_test.rb b/activerecord/test/cases/adapters/mysql2/transaction_test.rb
index 25d9f69a89..52e283f247 100644
--- a/activerecord/test/cases/adapters/mysql2/transaction_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/transaction_test.rb
@@ -13,6 +13,7 @@ module ActiveRecord
 
     setup do
       @abort, Thread.abort_on_exception = Thread.abort_on_exception, false
+      Thread.report_on_exception, @original_report_on_exception = false, Thread.report_on_exception
 
       @connection = ActiveRecord::Base.connection
       @connection.clear_cache!
@@ -31,6 +32,7 @@ module ActiveRecord
       @connection.drop_table "samples", if_exists: true
 
       Thread.abort_on_exception = @abort
+      Thread.report_on_exception = @original_report_on_exception
     end
 
     test "raises Deadlocked when a deadlock is encountered" do
@@ -44,7 +46,7 @@ module ActiveRecord
           Sample.transaction do
             s1.lock!
             barrier.wait
-            s2.update_attributes value: 1
+            s2.update value: 1
           end
         end
 
@@ -52,7 +54,7 @@ module ActiveRecord
           Sample.transaction do
             s2.lock!
             barrier.wait
-            s1.update_attributes value: 2
+            s1.update value: 2
           end
         ensure
           thread.join
@@ -60,9 +62,87 @@ module ActiveRecord
       end
     end
 
-    test "raises TransactionTimeout when mysql raises ER_LOCK_WAIT_TIMEOUT" do
-      assert_raises(ActiveRecord::TransactionTimeout) do
-        ActiveRecord::Base.connection.execute("SIGNAL SQLSTATE 'HY000' SET MESSAGE_TEXT = 'Testing error', MYSQL_ERRNO = 1205;")
+    test "raises LockWaitTimeout when lock wait timeout exceeded" do
+      assert_raises(ActiveRecord::LockWaitTimeout) do
+        s = Sample.create!(value: 1)
+        latch1 = Concurrent::CountDownLatch.new
+        latch2 = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch1.count_down
+            latch2.wait
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch1.wait
+            Sample.connection.execute("SET innodb_lock_wait_timeout = 1")
+            Sample.lock.find(s.id)
+          end
+        ensure
+          Sample.connection.execute("SET innodb_lock_wait_timeout = DEFAULT")
+          latch2.count_down
+          thread.join
+        end
+      end
+    end
+
+    test "raises StatementTimeout when statement timeout exceeded" do
+      skip unless ActiveRecord::Base.connection.show_variable("max_execution_time")
+      assert_raises(ActiveRecord::StatementTimeout) do
+        s = Sample.create!(value: 1)
+        latch1 = Concurrent::CountDownLatch.new
+        latch2 = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch1.count_down
+            latch2.wait
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch1.wait
+            Sample.connection.execute("SET max_execution_time = 1")
+            Sample.lock.find(s.id)
+          end
+        ensure
+          Sample.connection.execute("SET max_execution_time = DEFAULT")
+          latch2.count_down
+          thread.join
+        end
+      end
+    end
+
+    test "raises QueryCanceled when canceling statement due to user request" do
+      assert_raises(ActiveRecord::QueryCanceled) do
+        s = Sample.create!(value: 1)
+        latch = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch.count_down
+            sleep(0.5)
+            conn = Sample.connection
+            pid = conn.query_value("SELECT id FROM information_schema.processlist WHERE info LIKE '% FOR UPDATE'")
+            conn.execute("KILL QUERY #{pid}")
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch.wait
+            Sample.lock.find(s.id)
+          end
+        ensure
+          thread.join
+        end
       end
     end
   end
diff --git a/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb b/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb
index d0a09f6481..97da96003d 100644
--- a/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb
@@ -54,7 +54,7 @@ class Mysql2UnsignedTypeTest < ActiveRecord::Mysql2TestCase
     end
 
     @connection.columns("unsigned_types").select { |c| /^unsigned_/.match?(c.name) }.each do |column|
-      assert column.unsigned?
+      assert_predicate column, :unsigned?
     end
   end
 
@@ -62,7 +62,7 @@ class Mysql2UnsignedTypeTest < ActiveRecord::Mysql2TestCase
     schema = dump_table_schema "unsigned_types"
     assert_match %r{t\.integer\s+"unsigned_integer",\s+unsigned: true$}, schema
     assert_match %r{t\.bigint\s+"unsigned_bigint",\s+unsigned: true$}, schema
-    assert_match %r{t\.float\s+"unsigned_float",\s+limit: 24,\s+unsigned: true$}, schema
+    assert_match %r{t\.float\s+"unsigned_float",\s+unsigned: true$}, schema
     assert_match %r{t\.decimal\s+"unsigned_decimal",\s+precision: 10,\s+scale: 2,\s+unsigned: true$}, schema
   end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/active_schema_test.rb b/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
index 9929237546..308ad1d854 100644
--- a/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
@@ -59,6 +59,15 @@ class PostgresqlActiveSchemaTest < ActiveRecord::PostgreSQLTestCase
       assert_equal expected, add_index(:people, "lower(last_name)", using: type, unique: true)
     end
 
+    expected = %(CREATE  INDEX  "index_people_on_last_name" ON "people" USING gist ("last_name" bpchar_pattern_ops))
+    assert_equal expected, add_index(:people, :last_name, using: :gist, opclass: { last_name: :bpchar_pattern_ops })
+
+    expected = %(CREATE  INDEX  "index_people_on_last_name_and_first_name" ON "people"  ("last_name" DESC NULLS LAST, "first_name" ASC))
+    assert_equal expected, add_index(:people, [:last_name, :first_name], order: { last_name: "DESC NULLS LAST", first_name: :asc })
+
+    expected = %(CREATE  INDEX  "index_people_on_last_name" ON "people"  ("last_name" NULLS FIRST))
+    assert_equal expected, add_index(:people, :last_name, order: "NULLS FIRST")
+
     assert_raise ArgumentError do
       add_index(:people, :last_name, algorithm: :copy)
     end
diff --git a/activerecord/test/cases/adapters/postgresql/array_test.rb b/activerecord/test/cases/adapters/postgresql/array_test.rb
index 0e9e86f425..42618c2ec3 100644
--- a/activerecord/test/cases/adapters/postgresql/array_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/array_test.rb
@@ -39,12 +39,12 @@ class PostgresqlArrayTest < ActiveRecord::PostgreSQLTestCase
   def test_column
     assert_equal :string, @column.type
     assert_equal "character varying(255)", @column.sql_type
-    assert @column.array?
-    assert_not @type.binary?
+    assert_predicate @column, :array?
+    assert_not_predicate @type, :binary?
 
     ratings_column = PgArray.columns_hash["ratings"]
     assert_equal :integer, ratings_column.type
-    assert ratings_column.array?
+    assert_predicate ratings_column, :array?
   end
 
   def test_not_compatible_with_serialize_array
@@ -109,7 +109,7 @@ class PostgresqlArrayTest < ActiveRecord::PostgreSQLTestCase
 
     assert_equal :text, column.type
     assert_equal [], PgArray.column_defaults["snippets"]
-    assert column.array?
+    assert_predicate column, :array?
   end
 
   def test_change_column_cant_make_non_array_column_to_array
@@ -228,7 +228,9 @@ class PostgresqlArrayTest < ActiveRecord::PostgreSQLTestCase
 
   def test_insert_fixtures
     tag_values = ["val1", "val2", "val3_with_'_multiple_quote_'_chars"]
-    @connection.insert_fixtures([{ "tags" => tag_values }], "pg_arrays")
+    assert_deprecated do
+      @connection.insert_fixtures([{ "tags" => tag_values }], "pg_arrays")
+    end
     assert_equal(PgArray.last.tags, tag_values)
   end
 
@@ -255,7 +257,7 @@ class PostgresqlArrayTest < ActiveRecord::PostgreSQLTestCase
     x = PgArray.create!(tags: tags)
     x.reload
 
-    refute x.changed?
+    assert_not_predicate x, :changed?
   end
 
   def test_quoting_non_standard_delimiters
@@ -277,7 +279,7 @@ class PostgresqlArrayTest < ActiveRecord::PostgreSQLTestCase
     x.reload
 
     assert_equal %w(one two three), x.tags
-    assert_not x.changed?
+    assert_not_predicate x, :changed?
   end
 
   def test_mutate_value_in_array
@@ -288,7 +290,7 @@ class PostgresqlArrayTest < ActiveRecord::PostgreSQLTestCase
     x.reload
 
     assert_equal [{ "a" => "c" }, { "b" => "b" }], x.hstores
-    assert_not x.changed?
+    assert_not_predicate x, :changed?
   end
 
   def test_datetime_with_timezone_awareness
@@ -351,7 +353,7 @@ class PostgresqlArrayTest < ActiveRecord::PostgreSQLTestCase
     assert e1.persisted?, "Saving e1"
 
     e2 = klass.create("tags" => ["black", "blue"])
-    assert !e2.persisted?, "e2 shouldn't be valid"
+    assert_not e2.persisted?, "e2 shouldn't be valid"
     assert e2.errors[:tags].any?, "Should have errors for tags"
     assert_equal ["has already been taken"], e2.errors[:tags], "Should have uniqueness message for tags"
   end
diff --git a/activerecord/test/cases/adapters/postgresql/bit_string_test.rb b/activerecord/test/cases/adapters/postgresql/bit_string_test.rb
index df04299569..c8e728bbb6 100644
--- a/activerecord/test/cases/adapters/postgresql/bit_string_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/bit_string_test.rb
@@ -29,20 +29,20 @@ class PostgresqlBitStringTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlBitString.columns_hash["a_bit"]
     assert_equal :bit, column.type
     assert_equal "bit(8)", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlBitString.type_for_attribute("a_bit")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_bit_string_varying_column
     column = PostgresqlBitString.columns_hash["a_bit_varying"]
     assert_equal :bit_varying, column.type
     assert_equal "bit varying(4)", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlBitString.type_for_attribute("a_bit_varying")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_default
diff --git a/activerecord/test/cases/adapters/postgresql/bytea_test.rb b/activerecord/test/cases/adapters/postgresql/bytea_test.rb
index a6bee113ff..64bb6906cd 100644
--- a/activerecord/test/cases/adapters/postgresql/bytea_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/bytea_test.rb
@@ -75,7 +75,7 @@ class PostgresqlByteaTest < ActiveRecord::PostgreSQLTestCase
   def test_write_value
     data = "\u001F"
     record = ByteaDataType.create(payload: data)
-    assert_not record.new_record?
+    assert_not_predicate record, :new_record?
     assert_equal(data, record.payload)
   end
 
@@ -101,14 +101,14 @@ class PostgresqlByteaTest < ActiveRecord::PostgreSQLTestCase
     data = File.read(File.join(__dir__, "..", "..", "..", "assets", "example.log"))
     assert(data.size > 1)
     record = ByteaDataType.create(payload: data)
-    assert_not record.new_record?
+    assert_not_predicate record, :new_record?
     assert_equal(data, record.payload)
     assert_equal(data, ByteaDataType.where(id: record.id).first.payload)
   end
 
   def test_write_nil
     record = ByteaDataType.create(payload: nil)
-    assert_not record.new_record?
+    assert_not_predicate record, :new_record?
     assert_nil(record.payload)
     assert_nil(ByteaDataType.where(id: record.id).first.payload)
   end
diff --git a/activerecord/test/cases/adapters/postgresql/change_schema_test.rb b/activerecord/test/cases/adapters/postgresql/change_schema_test.rb
index adf461a9cc..6dba4f3e14 100644
--- a/activerecord/test/cases/adapters/postgresql/change_schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/change_schema_test.rb
@@ -33,7 +33,7 @@ module ActiveRecord
         connection.change_column :strings, :somedate, :timestamp, array: true, cast_as: :timestamp
         column = connection.columns(:strings).find { |c| c.name == "somedate" }
         assert_equal :datetime, column.type
-        assert column.array?
+        assert_predicate column, :array?
       end
     end
   end
diff --git a/activerecord/test/cases/adapters/postgresql/citext_test.rb b/activerecord/test/cases/adapters/postgresql/citext_test.rb
index 050614cade..9eb0b7d99c 100644
--- a/activerecord/test/cases/adapters/postgresql/citext_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/citext_test.rb
@@ -3,78 +3,76 @@
 require "cases/helper"
 require "support/schema_dumping_helper"
 
-if ActiveRecord::Base.connection.supports_extensions?
-  class PostgresqlCitextTest < ActiveRecord::PostgreSQLTestCase
-    include SchemaDumpingHelper
-    class Citext < ActiveRecord::Base
-      self.table_name = "citexts"
-    end
-
-    def setup
-      @connection = ActiveRecord::Base.connection
+class PostgresqlCitextTest < ActiveRecord::PostgreSQLTestCase
+  include SchemaDumpingHelper
+  class Citext < ActiveRecord::Base
+    self.table_name = "citexts"
+  end
 
-      enable_extension!("citext", @connection)
+  def setup
+    @connection = ActiveRecord::Base.connection
 
-      @connection.create_table("citexts") do |t|
-        t.citext "cival"
-      end
-    end
+    enable_extension!("citext", @connection)
 
-    teardown do
-      @connection.drop_table "citexts", if_exists: true
-      disable_extension!("citext", @connection)
+    @connection.create_table("citexts") do |t|
+      t.citext "cival"
     end
+  end
 
-    def test_citext_enabled
-      assert @connection.extension_enabled?("citext")
-    end
+  teardown do
+    @connection.drop_table "citexts", if_exists: true
+    disable_extension!("citext", @connection)
+  end
 
-    def test_column
-      column = Citext.columns_hash["cival"]
-      assert_equal :citext, column.type
-      assert_equal "citext", column.sql_type
-      assert_not column.array?
+  def test_citext_enabled
+    assert @connection.extension_enabled?("citext")
+  end
 
-      type = Citext.type_for_attribute("cival")
-      assert_not type.binary?
-    end
+  def test_column
+    column = Citext.columns_hash["cival"]
+    assert_equal :citext, column.type
+    assert_equal "citext", column.sql_type
+    assert_not_predicate column, :array?
 
-    def test_change_table_supports_json
-      @connection.transaction do
-        @connection.change_table("citexts") do |t|
-          t.citext "username"
-        end
-        Citext.reset_column_information
-        column = Citext.columns_hash["username"]
-        assert_equal :citext, column.type
+    type = Citext.type_for_attribute("cival")
+    assert_not_predicate type, :binary?
+  end
 
-        raise ActiveRecord::Rollback # reset the schema change
+  def test_change_table_supports_json
+    @connection.transaction do
+      @connection.change_table("citexts") do |t|
+        t.citext "username"
       end
-    ensure
       Citext.reset_column_information
+      column = Citext.columns_hash["username"]
+      assert_equal :citext, column.type
+
+      raise ActiveRecord::Rollback # reset the schema change
     end
+  ensure
+    Citext.reset_column_information
+  end
 
-    def test_write
-      x = Citext.new(cival: "Some CI Text")
-      x.save!
-      citext = Citext.first
-      assert_equal "Some CI Text", citext.cival
+  def test_write
+    x = Citext.new(cival: "Some CI Text")
+    x.save!
+    citext = Citext.first
+    assert_equal "Some CI Text", citext.cival
 
-      citext.cival = "Some NEW CI Text"
-      citext.save!
+    citext.cival = "Some NEW CI Text"
+    citext.save!
 
-      assert_equal "Some NEW CI Text", citext.reload.cival
-    end
+    assert_equal "Some NEW CI Text", citext.reload.cival
+  end
 
-    def test_select_case_insensitive
-      @connection.execute "insert into citexts (cival) values('Cased Text')"
-      x = Citext.where(cival: "cased text").first
-      assert_equal "Cased Text", x.cival
-    end
+  def test_select_case_insensitive
+    @connection.execute "insert into citexts (cival) values('Cased Text')"
+    x = Citext.where(cival: "cased text").first
+    assert_equal "Cased Text", x.cival
+  end
 
-    def test_schema_dump_with_shorthand
-      output = dump_table_schema("citexts")
-      assert_match %r[t\.citext "cival"], output
-    end
+  def test_schema_dump_with_shorthand
+    output = dump_table_schema("citexts")
+    assert_match %r[t\.citext "cival"], output
   end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/composite_test.rb b/activerecord/test/cases/adapters/postgresql/composite_test.rb
index 5da95f7e2c..b0ce2694a3 100644
--- a/activerecord/test/cases/adapters/postgresql/composite_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/composite_test.rb
@@ -51,10 +51,10 @@ class PostgresqlCompositeTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlComposite.columns_hash["address"]
     assert_nil column.type
     assert_equal "full_address", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlComposite.type_for_attribute("address")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_composite_mapping
@@ -113,10 +113,10 @@ class PostgresqlCompositeWithCustomOIDTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlComposite.columns_hash["address"]
     assert_equal :full_address, column.type
     assert_equal "full_address", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlComposite.type_for_attribute("address")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_composite_mapping
diff --git a/activerecord/test/cases/adapters/postgresql/connection_test.rb b/activerecord/test/cases/adapters/postgresql/connection_test.rb
index 2bb217a8b1..d1b3c434e1 100644
--- a/activerecord/test/cases/adapters/postgresql/connection_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/connection_test.rb
@@ -103,7 +103,7 @@ module ActiveRecord
     end
 
     def test_indexes_logs_name
-      assert_deprecated { @connection.indexes("items", "hello") }
+      @connection.indexes("items")
       assert_equal "SCHEMA", @subscriber.logged[0][1]
     end
 
@@ -157,7 +157,7 @@ module ActiveRecord
       original_connection_pid = @connection.query("select pg_backend_pid()")
 
       # Sanity check.
-      assert @connection.active?
+      assert_predicate @connection, :active?
 
       if @connection.send(:postgresql_version) >= 90200
         secondary_connection = ActiveRecord::Base.connection_pool.checkout
@@ -176,7 +176,7 @@ module ActiveRecord
 
       @connection.verify!
 
-      assert @connection.active?
+      assert_predicate @connection, :active?
 
       # If we get no exception here, then either we re-connected successfully, or
       # we never actually got disconnected.
diff --git a/activerecord/test/cases/adapters/postgresql/date_test.rb b/activerecord/test/cases/adapters/postgresql/date_test.rb
new file mode 100644
index 0000000000..a86abac2be
--- /dev/null
+++ b/activerecord/test/cases/adapters/postgresql/date_test.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/topic"
+
+class PostgresqlDateTest < ActiveRecord::PostgreSQLTestCase
+  def test_load_infinity_and_beyond
+    topic = Topic.find_by_sql("SELECT 'infinity'::date AS last_read").first
+    assert topic.last_read.infinite?, "timestamp should be infinite"
+    assert_operator topic.last_read, :>, 0
+
+    topic = Topic.find_by_sql("SELECT '-infinity'::date AS last_read").first
+    assert topic.last_read.infinite?, "timestamp should be infinite"
+    assert_operator topic.last_read, :<, 0
+  end
+
+  def test_save_infinity_and_beyond
+    topic = Topic.create!(last_read: 1.0 / 0.0)
+    assert_equal(1.0 / 0.0, topic.last_read)
+
+    topic = Topic.create!(last_read: -1.0 / 0.0)
+    assert_equal(-1.0 / 0.0, topic.last_read)
+  end
+
+  def test_bc_date
+    date = Date.new(0) - 1.week
+    topic = Topic.create!(last_read: date)
+    assert_equal date, Topic.find(topic.id).last_read
+  end
+
+  def test_bc_date_leap_year
+    date = Time.utc(-4, 2, 29).to_date
+    topic = Topic.create!(last_read: date)
+    assert_equal date, Topic.find(topic.id).last_read
+  end
+
+  def test_bc_date_year_zero
+    date = Time.utc(0, 4, 7).to_date
+    topic = Topic.create!(last_read: date)
+    assert_equal date, Topic.find(topic.id).last_read
+  end
+end
diff --git a/activerecord/test/cases/adapters/postgresql/domain_test.rb b/activerecord/test/cases/adapters/postgresql/domain_test.rb
index 9c3817e2ad..eeaad94c27 100644
--- a/activerecord/test/cases/adapters/postgresql/domain_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/domain_test.rb
@@ -30,10 +30,10 @@ class PostgresqlDomainTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlDomain.columns_hash["price"]
     assert_equal :decimal, column.type
     assert_equal "custom_money", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlDomain.type_for_attribute("price")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_domain_acts_like_basetype
@@ -44,6 +44,6 @@ class PostgresqlDomainTest < ActiveRecord::PostgreSQLTestCase
     record.price = "34.15"
     record.save!
 
-    assert_equal BigDecimal.new("34.15"), record.reload.price
+    assert_equal BigDecimal("34.15"), record.reload.price
   end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/enum_test.rb b/activerecord/test/cases/adapters/postgresql/enum_test.rb
index 3d3cbe11a3..6789ff63e7 100644
--- a/activerecord/test/cases/adapters/postgresql/enum_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/enum_test.rb
@@ -32,10 +32,10 @@ class PostgresqlEnumTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlEnum.columns_hash["current_mood"]
     assert_equal :enum, column.type
     assert_equal "mood", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlEnum.type_for_attribute("current_mood")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_enum_defaults
@@ -73,7 +73,7 @@ class PostgresqlEnumTest < ActiveRecord::PostgreSQLTestCase
     @connection.execute "INSERT INTO postgresql_enums VALUES (1, 'sad');"
     stderr_output = capture(:stderr) { PostgresqlEnum.first }
 
-    assert stderr_output.blank?
+    assert_predicate stderr_output, :blank?
   end
 
   def test_enum_type_cast
diff --git a/activerecord/test/cases/adapters/postgresql/explain_test.rb b/activerecord/test/cases/adapters/postgresql/explain_test.rb
index 16fec94ede..be525383e9 100644
--- a/activerecord/test/cases/adapters/postgresql/explain_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/explain_test.rb
@@ -1,22 +1,22 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "models/developer"
-require "models/computer"
+require "models/author"
+require "models/post"
 
 class PostgreSQLExplainTest < ActiveRecord::PostgreSQLTestCase
-  fixtures :developers
+  fixtures :authors
 
   def test_explain_for_one_query
-    explain = Developer.where(id: 1).explain
-    assert_match %r(EXPLAIN for: SELECT "developers"\.\* FROM "developers" WHERE "developers"\."id" = (?:\$1 \[\["id", 1\]\]|1)), explain
+    explain = Author.where(id: 1).explain
+    assert_match %r(EXPLAIN for: SELECT "authors"\.\* FROM "authors" WHERE "authors"\."id" = (?:\$1 \[\["id", 1\]\]|1)), explain
     assert_match %(QUERY PLAN), explain
   end
 
   def test_explain_with_eager_loading
-    explain = Developer.where(id: 1).includes(:audit_logs).explain
+    explain = Author.where(id: 1).includes(:posts).explain
     assert_match %(QUERY PLAN), explain
-    assert_match %r(EXPLAIN for: SELECT "developers"\.\* FROM "developers" WHERE "developers"\."id" = (?:\$1 \[\["id", 1\]\]|1)), explain
-    assert_match %r(EXPLAIN for: SELECT "audit_logs"\.\* FROM "audit_logs" WHERE "audit_logs"\."developer_id" = (?:\$1 \[\["developer_id", 1\]\]|1)), explain
+    assert_match %r(EXPLAIN for: SELECT "authors"\.\* FROM "authors" WHERE "authors"\."id" = (?:\$1 \[\["id", 1\]\]|1)), explain
+    assert_match %r(EXPLAIN for: SELECT "posts"\.\* FROM "posts" WHERE "posts"\."author_id" = (?:\$1 \[\["author_id", 1\]\]|1)), explain
   end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/extension_migration_test.rb b/activerecord/test/cases/adapters/postgresql/extension_migration_test.rb
index e589e3ab1b..df97ab11e7 100644
--- a/activerecord/test/cases/adapters/postgresql/extension_migration_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/extension_migration_test.rb
@@ -22,10 +22,6 @@ class PostgresqlExtensionMigrationTest < ActiveRecord::PostgreSQLTestCase
 
     @connection = ActiveRecord::Base.connection
 
-    unless @connection.supports_extensions?
-      return skip("no extension support")
-    end
-
     @old_schema_migration_table_name = ActiveRecord::SchemaMigration.table_name
     @old_table_name_prefix = ActiveRecord::Base.table_name_prefix
     @old_table_name_suffix = ActiveRecord::Base.table_name_suffix
diff --git a/activerecord/test/cases/adapters/postgresql/foreign_table_test.rb b/activerecord/test/cases/adapters/postgresql/foreign_table_test.rb
new file mode 100644
index 0000000000..4fa315ad23
--- /dev/null
+++ b/activerecord/test/cases/adapters/postgresql/foreign_table_test.rb
@@ -0,0 +1,109 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/professor"
+
+if ActiveRecord::Base.connection.supports_foreign_tables?
+  class ForeignTableTest < ActiveRecord::TestCase
+    self.use_transactional_tests = false
+
+    class ForeignProfessor < ActiveRecord::Base
+      self.table_name = "foreign_professors"
+    end
+
+    class ForeignProfessorWithPk < ForeignProfessor
+      self.primary_key = "id"
+    end
+
+    def setup
+      @professor = Professor.create(name: "Nicola")
+
+      @connection = ActiveRecord::Base.connection
+      enable_extension!("postgres_fdw", @connection)
+
+      foreign_db_config = ARTest.connection_config["arunit2"]
+      @connection.execute <<-SQL
+        CREATE SERVER foreign_server
+          FOREIGN DATA WRAPPER postgres_fdw
+          OPTIONS (dbname '#{foreign_db_config["database"]}')
+      SQL
+
+      @connection.execute <<-SQL
+        CREATE USER MAPPING FOR CURRENT_USER
+          SERVER foreign_server
+      SQL
+
+      @connection.execute <<-SQL
+        CREATE FOREIGN TABLE foreign_professors (
+          id    int,
+          name  character varying NOT NULL
+        ) SERVER foreign_server OPTIONS (
+          table_name 'professors'
+        )
+      SQL
+    end
+
+    def teardown
+      disable_extension!("postgres_fdw", @connection)
+      @connection.execute <<-SQL
+        DROP SERVER IF EXISTS foreign_server CASCADE
+      SQL
+    end
+
+    def test_table_exists
+      table_name = ForeignProfessor.table_name
+      assert_not ActiveRecord::Base.connection.table_exists?(table_name)
+    end
+
+    def test_foreign_tables_are_valid_data_sources
+      table_name = ForeignProfessor.table_name
+      assert @connection.data_source_exists?(table_name), "'#{table_name}' should be a data source"
+    end
+
+    def test_foreign_tables
+      assert_equal ["foreign_professors"], @connection.foreign_tables
+    end
+
+    def test_foreign_table_exists
+      assert @connection.foreign_table_exists?("foreign_professors")
+      assert @connection.foreign_table_exists?(:foreign_professors)
+      assert_not @connection.foreign_table_exists?("nonexistingtable")
+      assert_not @connection.foreign_table_exists?("'")
+      assert_not @connection.foreign_table_exists?(nil)
+    end
+
+    def test_attribute_names
+      assert_equal ["id", "name"], ForeignProfessor.attribute_names
+    end
+
+    def test_attributes
+      professor = ForeignProfessorWithPk.find(@professor.id)
+      assert_equal @professor.attributes, professor.attributes
+    end
+
+    def test_does_not_have_a_primary_key
+      assert_nil ForeignProfessor.primary_key
+    end
+
+    def test_insert_record
+      # Explicit `id` here to avoid complex configurations to implicitly work with remote table
+      ForeignProfessorWithPk.create!(id: 100, name: "Leonardo")
+
+      professor = ForeignProfessorWithPk.last
+      assert_equal "Leonardo", professor.name
+    end
+
+    def test_update_record
+      professor = ForeignProfessorWithPk.find(@professor.id)
+      professor.name = "Albert"
+      professor.save!
+      professor.reload
+      assert_equal "Albert", professor.name
+    end
+
+    def test_delete_record
+      professor = ForeignProfessorWithPk.find(@professor.id)
+      assert_difference("ForeignProfessor.count", -1) { professor.destroy }
+    end
+  end
+end
diff --git a/activerecord/test/cases/adapters/postgresql/full_text_test.rb b/activerecord/test/cases/adapters/postgresql/full_text_test.rb
index c6f1e1727f..95dee3bf44 100644
--- a/activerecord/test/cases/adapters/postgresql/full_text_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/full_text_test.rb
@@ -22,10 +22,10 @@ class PostgresqlFullTextTest < ActiveRecord::PostgreSQLTestCase
     column = Tsvector.columns_hash["text_vector"]
     assert_equal :tsvector, column.type
     assert_equal "tsvector", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = Tsvector.type_for_attribute("text_vector")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_update_tsvector
diff --git a/activerecord/test/cases/adapters/postgresql/geometric_test.rb b/activerecord/test/cases/adapters/postgresql/geometric_test.rb
index e1ba00e07b..8c6f046553 100644
--- a/activerecord/test/cases/adapters/postgresql/geometric_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/geometric_test.rb
@@ -39,10 +39,10 @@ class PostgresqlPointTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlPoint.columns_hash["x"]
     assert_equal :point, column.type
     assert_equal "point", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlPoint.type_for_attribute("x")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_default
@@ -79,7 +79,7 @@ class PostgresqlPointTest < ActiveRecord::PostgreSQLTestCase
     p.reload
 
     assert_equal ActiveRecord::Point.new(10.0, 25.0), p.x
-    assert_not p.changed?
+    assert_not_predicate p, :changed?
   end
 
   def test_array_assignment
@@ -117,10 +117,10 @@ class PostgresqlPointTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlPoint.columns_hash["legacy_x"]
     assert_equal :point, column.type
     assert_equal "point", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlPoint.type_for_attribute("legacy_x")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_legacy_default
@@ -157,7 +157,7 @@ class PostgresqlPointTest < ActiveRecord::PostgreSQLTestCase
     p.reload
 
     assert_equal [10.0, 25.0], p.legacy_x
-    assert_not p.changed?
+    assert_not_predicate p, :changed?
   end
 end
 
diff --git a/activerecord/test/cases/adapters/postgresql/hstore_test.rb b/activerecord/test/cases/adapters/postgresql/hstore_test.rb
index 97a8a257c5..4b061a9375 100644
--- a/activerecord/test/cases/adapters/postgresql/hstore_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/hstore_test.rb
@@ -3,378 +3,376 @@
 require "cases/helper"
 require "support/schema_dumping_helper"
 
-if ActiveRecord::Base.connection.supports_extensions?
-  class PostgresqlHstoreTest < ActiveRecord::PostgreSQLTestCase
-    include SchemaDumpingHelper
-    class Hstore < ActiveRecord::Base
-      self.table_name = "hstores"
+class PostgresqlHstoreTest < ActiveRecord::PostgreSQLTestCase
+  include SchemaDumpingHelper
+  class Hstore < ActiveRecord::Base
+    self.table_name = "hstores"
 
-      store_accessor :settings, :language, :timezone
-    end
+    store_accessor :settings, :language, :timezone
+  end
 
-    class FakeParameters
-      def to_unsafe_h
-        { "hi" => "hi" }
-      end
+  class FakeParameters
+    def to_unsafe_h
+      { "hi" => "hi" }
     end
+  end
 
-    def setup
-      @connection = ActiveRecord::Base.connection
+  def setup
+    @connection = ActiveRecord::Base.connection
 
-      enable_extension!("hstore", @connection)
+    enable_extension!("hstore", @connection)
 
-      @connection.transaction do
-        @connection.create_table("hstores") do |t|
-          t.hstore "tags", default: ""
-          t.hstore "payload", array: true
-          t.hstore "settings"
-        end
+    @connection.transaction do
+      @connection.create_table("hstores") do |t|
+        t.hstore "tags", default: ""
+        t.hstore "payload", array: true
+        t.hstore "settings"
       end
-      Hstore.reset_column_information
-      @column = Hstore.columns_hash["tags"]
-      @type = Hstore.type_for_attribute("tags")
-    end
-
-    teardown do
-      @connection.drop_table "hstores", if_exists: true
-      disable_extension!("hstore", @connection)
     end
+    Hstore.reset_column_information
+    @column = Hstore.columns_hash["tags"]
+    @type = Hstore.type_for_attribute("tags")
+  end
 
-    def test_hstore_included_in_extensions
-      assert @connection.respond_to?(:extensions), "connection should have a list of extensions"
-      assert_includes @connection.extensions, "hstore", "extension list should include hstore"
-    end
+  teardown do
+    @connection.drop_table "hstores", if_exists: true
+    disable_extension!("hstore", @connection)
+  end
 
-    def test_disable_enable_hstore
-      assert @connection.extension_enabled?("hstore")
-      @connection.disable_extension "hstore"
-      assert_not @connection.extension_enabled?("hstore")
-      @connection.enable_extension "hstore"
-      assert @connection.extension_enabled?("hstore")
-    ensure
-      # Restore column(s) dropped by `drop extension hstore cascade;`
-      load_schema
-    end
+  def test_hstore_included_in_extensions
+    assert_respond_to @connection, :extensions
+    assert_includes @connection.extensions, "hstore", "extension list should include hstore"
+  end
 
-    def test_column
-      assert_equal :hstore, @column.type
-      assert_equal "hstore", @column.sql_type
-      assert_not @column.array?
+  def test_disable_enable_hstore
+    assert @connection.extension_enabled?("hstore")
+    @connection.disable_extension "hstore"
+    assert_not @connection.extension_enabled?("hstore")
+    @connection.enable_extension "hstore"
+    assert @connection.extension_enabled?("hstore")
+  ensure
+    # Restore column(s) dropped by `drop extension hstore cascade;`
+    load_schema
+  end
 
-      assert_not @type.binary?
-    end
+  def test_column
+    assert_equal :hstore, @column.type
+    assert_equal "hstore", @column.sql_type
+    assert_not_predicate @column, :array?
 
-    def test_default
-      @connection.add_column "hstores", "permissions", :hstore, default: '"users"=>"read", "articles"=>"write"'
-      Hstore.reset_column_information
+    assert_not_predicate @type, :binary?
+  end
 
-      assert_equal({ "users" => "read", "articles" => "write" }, Hstore.column_defaults["permissions"])
-      assert_equal({ "users" => "read", "articles" => "write" }, Hstore.new.permissions)
-    ensure
-      Hstore.reset_column_information
-    end
+  def test_default
+    @connection.add_column "hstores", "permissions", :hstore, default: '"users"=>"read", "articles"=>"write"'
+    Hstore.reset_column_information
 
-    def test_change_table_supports_hstore
-      @connection.transaction do
-        @connection.change_table("hstores") do |t|
-          t.hstore "users", default: ""
-        end
-        Hstore.reset_column_information
-        column = Hstore.columns_hash["users"]
-        assert_equal :hstore, column.type
+    assert_equal({ "users" => "read", "articles" => "write" }, Hstore.column_defaults["permissions"])
+    assert_equal({ "users" => "read", "articles" => "write" }, Hstore.new.permissions)
+  ensure
+    Hstore.reset_column_information
+  end
 
-        raise ActiveRecord::Rollback # reset the schema change
+  def test_change_table_supports_hstore
+    @connection.transaction do
+      @connection.change_table("hstores") do |t|
+        t.hstore "users", default: ""
       end
-    ensure
       Hstore.reset_column_information
+      column = Hstore.columns_hash["users"]
+      assert_equal :hstore, column.type
+
+      raise ActiveRecord::Rollback # reset the schema change
     end
+  ensure
+    Hstore.reset_column_information
+  end
 
-    def test_hstore_migration
-      hstore_migration = Class.new(ActiveRecord::Migration::Current) do
-        def change
-          change_table("hstores") do |t|
-            t.hstore :keys
-          end
+  def test_hstore_migration
+    hstore_migration = Class.new(ActiveRecord::Migration::Current) do
+      def change
+        change_table("hstores") do |t|
+          t.hstore :keys
         end
       end
-
-      hstore_migration.new.suppress_messages do
-        hstore_migration.migrate(:up)
-        assert_includes @connection.columns(:hstores).map(&:name), "keys"
-        hstore_migration.migrate(:down)
-        assert_not_includes @connection.columns(:hstores).map(&:name), "keys"
-      end
     end
 
-    def test_cast_value_on_write
-      x = Hstore.new tags: { "bool" => true, "number" => 5 }
-      assert_equal({ "bool" => true, "number" => 5 }, x.tags_before_type_cast)
-      assert_equal({ "bool" => "true", "number" => "5" }, x.tags)
-      x.save
-      assert_equal({ "bool" => "true", "number" => "5" }, x.reload.tags)
+    hstore_migration.new.suppress_messages do
+      hstore_migration.migrate(:up)
+      assert_includes @connection.columns(:hstores).map(&:name), "keys"
+      hstore_migration.migrate(:down)
+      assert_not_includes @connection.columns(:hstores).map(&:name), "keys"
     end
+  end
 
-    def test_type_cast_hstore
-      assert_equal({ "1" => "2" }, @type.deserialize("\"1\"=>\"2\""))
-      assert_equal({}, @type.deserialize(""))
-      assert_equal({ "key" => nil }, @type.deserialize("key => NULL"))
-      assert_equal({ "c" => "}", '"a"' => 'b "a b' }, @type.deserialize(%q(c=>"}", "\"a\""=>"b \"a b")))
-    end
+  def test_cast_value_on_write
+    x = Hstore.new tags: { "bool" => true, "number" => 5 }
+    assert_equal({ "bool" => true, "number" => 5 }, x.tags_before_type_cast)
+    assert_equal({ "bool" => "true", "number" => "5" }, x.tags)
+    x.save
+    assert_equal({ "bool" => "true", "number" => "5" }, x.reload.tags)
+  end
 
-    def test_with_store_accessors
-      x = Hstore.new(language: "fr", timezone: "GMT")
-      assert_equal "fr", x.language
-      assert_equal "GMT", x.timezone
+  def test_type_cast_hstore
+    assert_equal({ "1" => "2" }, @type.deserialize("\"1\"=>\"2\""))
+    assert_equal({}, @type.deserialize(""))
+    assert_equal({ "key" => nil }, @type.deserialize("key => NULL"))
+    assert_equal({ "c" => "}", '"a"' => 'b "a b' }, @type.deserialize(%q(c=>"}", "\"a\""=>"b \"a b")))
+  end
 
-      x.save!
-      x = Hstore.first
-      assert_equal "fr", x.language
-      assert_equal "GMT", x.timezone
+  def test_with_store_accessors
+    x = Hstore.new(language: "fr", timezone: "GMT")
+    assert_equal "fr", x.language
+    assert_equal "GMT", x.timezone
 
-      x.language = "de"
-      x.save!
+    x.save!
+    x = Hstore.first
+    assert_equal "fr", x.language
+    assert_equal "GMT", x.timezone
 
-      x = Hstore.first
-      assert_equal "de", x.language
-      assert_equal "GMT", x.timezone
-    end
+    x.language = "de"
+    x.save!
 
-    def test_duplication_with_store_accessors
-      x = Hstore.new(language: "fr", timezone: "GMT")
-      assert_equal "fr", x.language
-      assert_equal "GMT", x.timezone
+    x = Hstore.first
+    assert_equal "de", x.language
+    assert_equal "GMT", x.timezone
+  end
 
-      y = x.dup
-      assert_equal "fr", y.language
-      assert_equal "GMT", y.timezone
-    end
+  def test_duplication_with_store_accessors
+    x = Hstore.new(language: "fr", timezone: "GMT")
+    assert_equal "fr", x.language
+    assert_equal "GMT", x.timezone
 
-    def test_yaml_round_trip_with_store_accessors
-      x = Hstore.new(language: "fr", timezone: "GMT")
-      assert_equal "fr", x.language
-      assert_equal "GMT", x.timezone
+    y = x.dup
+    assert_equal "fr", y.language
+    assert_equal "GMT", y.timezone
+  end
 
-      y = YAML.load(YAML.dump(x))
-      assert_equal "fr", y.language
-      assert_equal "GMT", y.timezone
-    end
+  def test_yaml_round_trip_with_store_accessors
+    x = Hstore.new(language: "fr", timezone: "GMT")
+    assert_equal "fr", x.language
+    assert_equal "GMT", x.timezone
 
-    def test_changes_in_place
-      hstore = Hstore.create!(settings: { "one" => "two" })
-      hstore.settings["three"] = "four"
-      hstore.save!
-      hstore.reload
+    y = YAML.load(YAML.dump(x))
+    assert_equal "fr", y.language
+    assert_equal "GMT", y.timezone
+  end
 
-      assert_equal "four", hstore.settings["three"]
-      assert_not hstore.changed?
-    end
+  def test_changes_in_place
+    hstore = Hstore.create!(settings: { "one" => "two" })
+    hstore.settings["three"] = "four"
+    hstore.save!
+    hstore.reload
 
-    def test_dirty_from_user_equal
-      settings = { "alongkey" => "anything", "key" => "value" }
-      hstore = Hstore.create!(settings: settings)
+    assert_equal "four", hstore.settings["three"]
+    assert_not_predicate hstore, :changed?
+  end
 
-      hstore.settings = { "key" => "value", "alongkey" => "anything" }
-      assert_equal settings, hstore.settings
-      refute hstore.changed?
-    end
+  def test_dirty_from_user_equal
+    settings = { "alongkey" => "anything", "key" => "value" }
+    hstore = Hstore.create!(settings: settings)
 
-    def test_hstore_dirty_from_database_equal
-      settings = { "alongkey" => "anything", "key" => "value" }
-      hstore = Hstore.create!(settings: settings)
-      hstore.reload
+    hstore.settings = { "key" => "value", "alongkey" => "anything" }
+    assert_equal settings, hstore.settings
+    assert_not_predicate hstore, :changed?
+  end
 
-      assert_equal settings, hstore.settings
-      hstore.settings = settings
-      refute hstore.changed?
-    end
+  def test_hstore_dirty_from_database_equal
+    settings = { "alongkey" => "anything", "key" => "value" }
+    hstore = Hstore.create!(settings: settings)
+    hstore.reload
 
-    def test_gen1
-      assert_equal('" "=>""', @type.serialize(" " => ""))
-    end
+    assert_equal settings, hstore.settings
+    hstore.settings = settings
+    assert_not_predicate hstore, :changed?
+  end
 
-    def test_gen2
-      assert_equal('","=>""', @type.serialize("," => ""))
-    end
+  def test_gen1
+    assert_equal('" "=>""', @type.serialize(" " => ""))
+  end
 
-    def test_gen3
-      assert_equal('"="=>""', @type.serialize("=" => ""))
-    end
+  def test_gen2
+    assert_equal('","=>""', @type.serialize("," => ""))
+  end
 
-    def test_gen4
-      assert_equal('">"=>""', @type.serialize(">" => ""))
-    end
+  def test_gen3
+    assert_equal('"="=>""', @type.serialize("=" => ""))
+  end
 
-    def test_parse1
-      assert_equal({ "a" => nil, "b" => nil, "c" => "NuLl", "null" => "c" }, @type.deserialize('a=>null,b=>NuLl,c=>"NuLl",null=>c'))
-    end
+  def test_gen4
+    assert_equal('">"=>""', @type.serialize(">" => ""))
+  end
 
-    def test_parse2
-      assert_equal({ " " => " " },  @type.deserialize("\\ =>\\ "))
-    end
+  def test_parse1
+    assert_equal({ "a" => nil, "b" => nil, "c" => "NuLl", "null" => "c" }, @type.deserialize('a=>null,b=>NuLl,c=>"NuLl",null=>c'))
+  end
 
-    def test_parse3
-      assert_equal({ "=" => ">" },  @type.deserialize("==>>"))
-    end
+  def test_parse2
+    assert_equal({ " " => " " },  @type.deserialize("\\ =>\\ "))
+  end
 
-    def test_parse4
-      assert_equal({ "=a" => "q=w" },   @type.deserialize('\=a=>q=w'))
-    end
+  def test_parse3
+    assert_equal({ "=" => ">" },  @type.deserialize("==>>"))
+  end
 
-    def test_parse5
-      assert_equal({ "=a" => "q=w" },   @type.deserialize('"=a"=>q\=w'))
-    end
+  def test_parse4
+    assert_equal({ "=a" => "q=w" },   @type.deserialize('\=a=>q=w'))
+  end
 
-    def test_parse6
-      assert_equal({ "\"a" => "q>w" },  @type.deserialize('"\"a"=>q>w'))
-    end
+  def test_parse5
+    assert_equal({ "=a" => "q=w" },   @type.deserialize('"=a"=>q\=w'))
+  end
 
-    def test_parse7
-      assert_equal({ "\"a" => "q\"w" }, @type.deserialize('\"a=>q"w'))
-    end
+  def test_parse6
+    assert_equal({ "\"a" => "q>w" },  @type.deserialize('"\"a"=>q>w'))
+  end
 
-    def test_rewrite
-      @connection.execute "insert into hstores (tags) VALUES ('1=>2')"
-      x = Hstore.first
-      x.tags = { '"a\'' => "b" }
-      assert x.save!
-    end
+  def test_parse7
+    assert_equal({ "\"a" => "q\"w" }, @type.deserialize('\"a=>q"w'))
+  end
 
-    def test_select
-      @connection.execute "insert into hstores (tags) VALUES ('1=>2')"
-      x = Hstore.first
-      assert_equal({ "1" => "2" }, x.tags)
-    end
+  def test_rewrite
+    @connection.execute "insert into hstores (tags) VALUES ('1=>2')"
+    x = Hstore.first
+    x.tags = { '"a\'' => "b" }
+    assert x.save!
+  end
 
-    def test_array_cycle
-      assert_array_cycle([{ "AA" => "BB", "CC" => "DD" }, { "AA" => nil }])
-    end
+  def test_select
+    @connection.execute "insert into hstores (tags) VALUES ('1=>2')"
+    x = Hstore.first
+    assert_equal({ "1" => "2" }, x.tags)
+  end
 
-    def test_array_strings_with_quotes
-      assert_array_cycle([{ "this has" => 'some "s that need to be escaped"' }])
-    end
+  def test_array_cycle
+    assert_array_cycle([{ "AA" => "BB", "CC" => "DD" }, { "AA" => nil }])
+  end
 
-    def test_array_strings_with_commas
-      assert_array_cycle([{ "this,has" => "many,values" }])
-    end
+  def test_array_strings_with_quotes
+    assert_array_cycle([{ "this has" => 'some "s that need to be escaped"' }])
+  end
 
-    def test_array_strings_with_array_delimiters
-      assert_array_cycle(["{" => "}"])
-    end
+  def test_array_strings_with_commas
+    assert_array_cycle([{ "this,has" => "many,values" }])
+  end
 
-    def test_array_strings_with_null_strings
-      assert_array_cycle([{ "NULL" => "NULL" }])
-    end
+  def test_array_strings_with_array_delimiters
+    assert_array_cycle(["{" => "}"])
+  end
 
-    def test_contains_nils
-      assert_array_cycle([{ "NULL" => nil }])
-    end
+  def test_array_strings_with_null_strings
+    assert_array_cycle([{ "NULL" => "NULL" }])
+  end
 
-    def test_select_multikey
-      @connection.execute "insert into hstores (tags) VALUES ('1=>2,2=>3')"
-      x = Hstore.first
-      assert_equal({ "1" => "2", "2" => "3" }, x.tags)
-    end
+  def test_contains_nils
+    assert_array_cycle([{ "NULL" => nil }])
+  end
 
-    def test_create
-      assert_cycle("a" => "b", "1" => "2")
-    end
+  def test_select_multikey
+    @connection.execute "insert into hstores (tags) VALUES ('1=>2,2=>3')"
+    x = Hstore.first
+    assert_equal({ "1" => "2", "2" => "3" }, x.tags)
+  end
 
-    def test_nil
-      assert_cycle("a" => nil)
-    end
+  def test_create
+    assert_cycle("a" => "b", "1" => "2")
+  end
 
-    def test_quotes
-      assert_cycle("a" => 'b"ar', '1"foo' => "2")
-    end
+  def test_nil
+    assert_cycle("a" => nil)
+  end
 
-    def test_whitespace
-      assert_cycle("a b" => "b ar", '1"foo' => "2")
-    end
+  def test_quotes
+    assert_cycle("a" => 'b"ar', '1"foo' => "2")
+  end
 
-    def test_backslash
-      assert_cycle('a\\b' => 'b\\ar', '1"foo' => "2")
-    end
+  def test_whitespace
+    assert_cycle("a b" => "b ar", '1"foo' => "2")
+  end
 
-    def test_comma
-      assert_cycle("a, b" => "bar", '1"foo' => "2")
-    end
+  def test_backslash
+    assert_cycle('a\\b' => 'b\\ar', '1"foo' => "2")
+  end
 
-    def test_arrow
-      assert_cycle("a=>b" => "bar", '1"foo' => "2")
-    end
+  def test_comma
+    assert_cycle("a, b" => "bar", '1"foo' => "2")
+  end
 
-    def test_quoting_special_characters
-      assert_cycle("ca" => "cà", "ac" => "àc")
-    end
+  def test_arrow
+    assert_cycle("a=>b" => "bar", '1"foo' => "2")
+  end
 
-    def test_multiline
-      assert_cycle("a\nb" => "c\nd")
-    end
+  def test_quoting_special_characters
+    assert_cycle("ca" => "cà", "ac" => "àc")
+  end
 
-    class TagCollection
-      def initialize(hash); @hash = hash end
-      def to_hash; @hash end
-      def self.load(hash); new(hash) end
-      def self.dump(object); object.to_hash end
-    end
+  def test_multiline
+    assert_cycle("a\nb" => "c\nd")
+  end
 
-    class HstoreWithSerialize < Hstore
-      serialize :tags, TagCollection
-    end
+  class TagCollection
+    def initialize(hash); @hash = hash end
+    def to_hash; @hash end
+    def self.load(hash); new(hash) end
+    def self.dump(object); object.to_hash end
+  end
 
-    def test_hstore_with_serialized_attributes
-      HstoreWithSerialize.create! tags: TagCollection.new("one" => "two")
-      record = HstoreWithSerialize.first
-      assert_instance_of TagCollection, record.tags
-      assert_equal({ "one" => "two" }, record.tags.to_hash)
-      record.tags = TagCollection.new("three" => "four")
-      record.save!
-      assert_equal({ "three" => "four" }, HstoreWithSerialize.first.tags.to_hash)
-    end
+  class HstoreWithSerialize < Hstore
+    serialize :tags, TagCollection
+  end
 
-    def test_clone_hstore_with_serialized_attributes
-      HstoreWithSerialize.create! tags: TagCollection.new("one" => "two")
-      record = HstoreWithSerialize.first
-      dupe = record.dup
-      assert_equal({ "one" => "two" }, dupe.tags.to_hash)
-    end
+  def test_hstore_with_serialized_attributes
+    HstoreWithSerialize.create! tags: TagCollection.new("one" => "two")
+    record = HstoreWithSerialize.first
+    assert_instance_of TagCollection, record.tags
+    assert_equal({ "one" => "two" }, record.tags.to_hash)
+    record.tags = TagCollection.new("three" => "four")
+    record.save!
+    assert_equal({ "three" => "four" }, HstoreWithSerialize.first.tags.to_hash)
+  end
 
-    def test_schema_dump_with_shorthand
-      output = dump_table_schema("hstores")
-      assert_match %r[t\.hstore "tags",\s+default: {}], output
-    end
+  def test_clone_hstore_with_serialized_attributes
+    HstoreWithSerialize.create! tags: TagCollection.new("one" => "two")
+    record = HstoreWithSerialize.first
+    dupe = record.dup
+    assert_equal({ "one" => "two" }, dupe.tags.to_hash)
+  end
+
+  def test_schema_dump_with_shorthand
+    output = dump_table_schema("hstores")
+    assert_match %r[t\.hstore "tags",\s+default: {}], output
+  end
+
+  def test_supports_to_unsafe_h_values
+    assert_equal("\"hi\"=>\"hi\"", @type.serialize(FakeParameters.new))
+  end
 
-    def test_supports_to_unsafe_h_values
-      assert_equal("\"hi\"=>\"hi\"", @type.serialize(FakeParameters.new))
+  private
+    def assert_array_cycle(array)
+      # test creation
+      x = Hstore.create!(payload: array)
+      x.reload
+      assert_equal(array, x.payload)
+
+      # test updating
+      x = Hstore.create!(payload: [])
+      x.payload = array
+      x.save!
+      x.reload
+      assert_equal(array, x.payload)
     end
 
-    private
-      def assert_array_cycle(array)
-        # test creation
-        x = Hstore.create!(payload: array)
-        x.reload
-        assert_equal(array, x.payload)
-
-        # test updating
-        x = Hstore.create!(payload: [])
-        x.payload = array
-        x.save!
-        x.reload
-        assert_equal(array, x.payload)
-      end
+    def assert_cycle(hash)
+      # test creation
+      x = Hstore.create!(tags: hash)
+      x.reload
+      assert_equal(hash, x.tags)
 
-      def assert_cycle(hash)
-        # test creation
-        x = Hstore.create!(tags: hash)
-        x.reload
-        assert_equal(hash, x.tags)
-
-        # test updating
-        x = Hstore.create!(tags: {})
-        x.tags = hash
-        x.save!
-        x.reload
-        assert_equal(hash, x.tags)
-      end
-  end
+      # test updating
+      x = Hstore.create!(tags: {})
+      x.tags = hash
+      x.save!
+      x.reload
+      assert_equal(hash, x.tags)
+    end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/infinity_test.rb b/activerecord/test/cases/adapters/postgresql/infinity_test.rb
index 0b18c0c9d7..5e56ce8427 100644
--- a/activerecord/test/cases/adapters/postgresql/infinity_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/infinity_test.rb
@@ -13,6 +13,7 @@ class PostgresqlInfinityTest < ActiveRecord::PostgreSQLTestCase
     @connection.create_table(:postgresql_infinities) do |t|
       t.float :float
       t.datetime :datetime
+      t.date :date
     end
   end
 
@@ -43,11 +44,25 @@ class PostgresqlInfinityTest < ActiveRecord::PostgreSQLTestCase
   end
 
   test "type casting infinity on a datetime column" do
+    record = PostgresqlInfinity.create!(datetime: "infinity")
+    record.reload
+    assert_equal Float::INFINITY, record.datetime
+
     record = PostgresqlInfinity.create!(datetime: Float::INFINITY)
     record.reload
     assert_equal Float::INFINITY, record.datetime
   end
 
+  test "type casting infinity on a date column" do
+    record = PostgresqlInfinity.create!(date: "infinity")
+    record.reload
+    assert_equal Float::INFINITY, record.date
+
+    record = PostgresqlInfinity.create!(date: Float::INFINITY)
+    record.reload
+    assert_equal Float::INFINITY, record.date
+  end
+
   test "update_all with infinity on a datetime column" do
     record = PostgresqlInfinity.create!
     PostgresqlInfinity.update_all(datetime: Float::INFINITY)
@@ -68,4 +83,28 @@ class PostgresqlInfinityTest < ActiveRecord::PostgreSQLTestCase
       PostgresqlInfinity.reset_column_information
     end
   end
+
+  test "where clause with infinite range on a datetime column" do
+    record = PostgresqlInfinity.create!(datetime: Time.current)
+
+    string = PostgresqlInfinity.where(datetime: "-infinity".."infinity")
+    assert_equal record, string.take
+
+    infinity = PostgresqlInfinity.where(datetime: -::Float::INFINITY..::Float::INFINITY)
+    assert_equal record, infinity.take
+
+    assert_equal infinity.to_sql, string.to_sql
+  end
+
+  test "where clause with infinite range on a date column" do
+    record = PostgresqlInfinity.create!(date: Date.current)
+
+    string = PostgresqlInfinity.where(date: "-infinity".."infinity")
+    assert_equal record, string.take
+
+    infinity = PostgresqlInfinity.where(date: -::Float::INFINITY..::Float::INFINITY)
+    assert_equal record, infinity.take
+
+    assert_equal infinity.to_sql, string.to_sql
+  end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/ltree_test.rb b/activerecord/test/cases/adapters/postgresql/ltree_test.rb
index eca29f2892..8349ee6ee2 100644
--- a/activerecord/test/cases/adapters/postgresql/ltree_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/ltree_test.rb
@@ -31,10 +31,10 @@ class PostgresqlLtreeTest < ActiveRecord::PostgreSQLTestCase
     column = Ltree.columns_hash["path"]
     assert_equal :ltree, column.type
     assert_equal "ltree", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = Ltree.type_for_attribute("path")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_write
diff --git a/activerecord/test/cases/adapters/postgresql/money_test.rb b/activerecord/test/cases/adapters/postgresql/money_test.rb
index 563f0bbfae..be3590e8dd 100644
--- a/activerecord/test/cases/adapters/postgresql/money_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/money_test.rb
@@ -26,15 +26,15 @@ class PostgresqlMoneyTest < ActiveRecord::PostgreSQLTestCase
     assert_equal :money, column.type
     assert_equal "money", column.sql_type
     assert_equal 2, column.scale
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlMoney.type_for_attribute("wealth")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_default
-    assert_equal BigDecimal.new("150.55"), PostgresqlMoney.column_defaults["depth"]
-    assert_equal BigDecimal.new("150.55"), PostgresqlMoney.new.depth
+    assert_equal BigDecimal("150.55"), PostgresqlMoney.column_defaults["depth"]
+    assert_equal BigDecimal("150.55"), PostgresqlMoney.new.depth
   end
 
   def test_money_values
@@ -65,7 +65,7 @@ class PostgresqlMoneyTest < ActiveRecord::PostgreSQLTestCase
     money = PostgresqlMoney.create(wealth: "987.65".dup)
     assert_equal 987.65, money.wealth
 
-    new_value = BigDecimal.new("123.45")
+    new_value = BigDecimal("123.45")
     money.wealth = new_value
     money.save!
     money.reload
diff --git a/activerecord/test/cases/adapters/postgresql/network_test.rb b/activerecord/test/cases/adapters/postgresql/network_test.rb
index f461544a85..736570451b 100644
--- a/activerecord/test/cases/adapters/postgresql/network_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/network_test.rb
@@ -24,30 +24,30 @@ class PostgresqlNetworkTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlNetworkAddress.columns_hash["cidr_address"]
     assert_equal :cidr, column.type
     assert_equal "cidr", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlNetworkAddress.type_for_attribute("cidr_address")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_inet_column
     column = PostgresqlNetworkAddress.columns_hash["inet_address"]
     assert_equal :inet, column.type
     assert_equal "inet", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlNetworkAddress.type_for_attribute("inet_address")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_macaddr_column
     column = PostgresqlNetworkAddress.columns_hash["mac_address"]
     assert_equal :macaddr, column.type
     assert_equal "macaddr", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlNetworkAddress.type_for_attribute("mac_address")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_network_types
diff --git a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
index f199519d86..cbb6cd42b5 100644
--- a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
@@ -248,12 +248,12 @@ module ActiveRecord
 
       def test_index_with_opclass
         with_example_table do
-          @connection.add_index "ex", "data varchar_pattern_ops"
-          index = @connection.indexes("ex").find { |idx| idx.name == "index_ex_on_data_varchar_pattern_ops" }
-          assert_equal "data varchar_pattern_ops", index.columns
+          @connection.add_index "ex", "data", opclass: "varchar_pattern_ops"
+          index = @connection.indexes("ex").find { |idx| idx.name == "index_ex_on_data" }
+          assert_equal ["data"], index.columns
 
-          @connection.remove_index "ex", "data varchar_pattern_ops"
-          assert_not @connection.indexes("ex").find { |idx| idx.name == "index_ex_on_data_varchar_pattern_ops" }
+          @connection.remove_index "ex", "data"
+          assert_not @connection.indexes("ex").find { |idx| idx.name == "index_ex_on_data" }
         end
       end
 
@@ -263,25 +263,25 @@ module ActiveRecord
       end
 
       def test_columns_for_distinct_one_order
-        assert_equal "posts.id, posts.created_at AS alias_0",
+        assert_equal "posts.created_at AS alias_0, posts.id",
           @connection.columns_for_distinct("posts.id", ["posts.created_at desc"])
       end
 
       def test_columns_for_distinct_few_orders
-        assert_equal "posts.id, posts.created_at AS alias_0, posts.position AS alias_1",
+        assert_equal "posts.created_at AS alias_0, posts.position AS alias_1, posts.id",
           @connection.columns_for_distinct("posts.id", ["posts.created_at desc", "posts.position asc"])
       end
 
       def test_columns_for_distinct_with_case
         assert_equal(
-          "posts.id, CASE WHEN author.is_active THEN UPPER(author.name) ELSE UPPER(author.email) END AS alias_0",
+          "CASE WHEN author.is_active THEN UPPER(author.name) ELSE UPPER(author.email) END AS alias_0, posts.id",
           @connection.columns_for_distinct("posts.id",
             ["CASE WHEN author.is_active THEN UPPER(author.name) ELSE UPPER(author.email) END"])
         )
       end
 
       def test_columns_for_distinct_blank_not_nil_orders
-        assert_equal "posts.id, posts.created_at AS alias_0",
+        assert_equal "posts.created_at AS alias_0, posts.id",
           @connection.columns_for_distinct("posts.id", ["posts.created_at desc", "", "   "])
       end
 
@@ -290,23 +290,23 @@ module ActiveRecord
         def order.to_sql
           "posts.created_at desc"
         end
-        assert_equal "posts.id, posts.created_at AS alias_0",
+        assert_equal "posts.created_at AS alias_0, posts.id",
           @connection.columns_for_distinct("posts.id", [order])
       end
 
       def test_columns_for_distinct_with_nulls
-        assert_equal "posts.title, posts.updater_id AS alias_0", @connection.columns_for_distinct("posts.title", ["posts.updater_id desc nulls first"])
-        assert_equal "posts.title, posts.updater_id AS alias_0", @connection.columns_for_distinct("posts.title", ["posts.updater_id desc nulls last"])
+        assert_equal "posts.updater_id AS alias_0, posts.title", @connection.columns_for_distinct("posts.title", ["posts.updater_id desc nulls first"])
+        assert_equal "posts.updater_id AS alias_0, posts.title", @connection.columns_for_distinct("posts.title", ["posts.updater_id desc nulls last"])
       end
 
       def test_columns_for_distinct_without_order_specifiers
-        assert_equal "posts.title, posts.updater_id AS alias_0",
+        assert_equal "posts.updater_id AS alias_0, posts.title",
           @connection.columns_for_distinct("posts.title", ["posts.updater_id"])
 
-        assert_equal "posts.title, posts.updater_id AS alias_0",
+        assert_equal "posts.updater_id AS alias_0, posts.title",
           @connection.columns_for_distinct("posts.title", ["posts.updater_id nulls last"])
 
-        assert_equal "posts.title, posts.updater_id AS alias_0",
+        assert_equal "posts.updater_id AS alias_0, posts.title",
           @connection.columns_for_distinct("posts.title", ["posts.updater_id nulls first"])
       end
 
diff --git a/activerecord/test/cases/adapters/postgresql/range_test.rb b/activerecord/test/cases/adapters/postgresql/range_test.rb
index b4a776d04d..261c24634e 100644
--- a/activerecord/test/cases/adapters/postgresql/range_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/range_test.rb
@@ -134,10 +134,10 @@ _SQL
     end
 
     def test_numrange_values
-      assert_equal BigDecimal.new("0.1")..BigDecimal.new("0.2"), @first_range.num_range
-      assert_equal BigDecimal.new("0.1")...BigDecimal.new("0.2"), @second_range.num_range
-      assert_equal BigDecimal.new("0.1")...BigDecimal.new("Infinity"), @third_range.num_range
-      assert_equal BigDecimal.new("-Infinity")...BigDecimal.new("Infinity"), @fourth_range.num_range
+      assert_equal BigDecimal("0.1")..BigDecimal("0.2"), @first_range.num_range
+      assert_equal BigDecimal("0.1")...BigDecimal("0.2"), @second_range.num_range
+      assert_equal BigDecimal("0.1")...BigDecimal("Infinity"), @third_range.num_range
+      assert_equal BigDecimal("-Infinity")...BigDecimal("Infinity"), @fourth_range.num_range
       assert_nil @empty_range.num_range
     end
 
@@ -232,16 +232,67 @@ _SQL
       end
     end
 
+    def test_create_tstzrange_preserve_usec
+      tstzrange = Time.parse("2010-01-01 14:30:00.670277 +0100")...Time.parse("2011-02-02 14:30:00.745125 CDT")
+      round_trip(@new_range, :tstz_range, tstzrange)
+      assert_equal @new_range.tstz_range, tstzrange
+      assert_equal @new_range.tstz_range, Time.parse("2010-01-01 13:30:00.670277 UTC")...Time.parse("2011-02-02 19:30:00.745125 UTC")
+    end
+
+    def test_update_tstzrange_preserve_usec
+      assert_equal_round_trip(@first_range, :tstz_range,
+                              Time.parse("2010-01-01 14:30:00.245124 CDT")...Time.parse("2011-02-02 14:30:00.451274 CET"))
+      assert_nil_round_trip(@first_range, :tstz_range,
+                            Time.parse("2010-01-01 14:30:00.245124 +0100")...Time.parse("2010-01-01 13:30:00.245124 +0000"))
+    end
+
+    def test_create_tsrange_preseve_usec
+      tz = ::ActiveRecord::Base.default_timezone
+      assert_equal_round_trip(@new_range, :ts_range,
+                              Time.send(tz, 2010, 1, 1, 14, 30, 0, 125435)...Time.send(tz, 2011, 2, 2, 14, 30, 0, 225435))
+    end
+
+    def test_update_tsrange_preserve_usec
+      tz = ::ActiveRecord::Base.default_timezone
+      assert_equal_round_trip(@first_range, :ts_range,
+                              Time.send(tz, 2010, 1, 1, 14, 30, 0, 142432)...Time.send(tz, 2011, 2, 2, 14, 30, 0, 224242))
+      assert_nil_round_trip(@first_range, :ts_range,
+                            Time.send(tz, 2010, 1, 1, 14, 30, 0, 142432)...Time.send(tz, 2010, 1, 1, 14, 30, 0, 142432))
+    end
+
+    def test_timezone_awareness_tsrange_preserve_usec
+      tz = "Pacific Time (US & Canada)"
+
+      in_time_zone tz do
+        PostgresqlRange.reset_column_information
+        time_string = "2017-09-26 07:30:59.132451 -0700"
+        time = Time.zone.parse(time_string)
+        assert time.usec > 0
+
+        record = PostgresqlRange.new(ts_range: time_string..time_string)
+        assert_equal time..time, record.ts_range
+        assert_equal ActiveSupport::TimeZone[tz], record.ts_range.begin.time_zone
+        assert_equal time.usec, record.ts_range.begin.usec
+
+        record.save!
+        record.reload
+
+        assert_equal time..time, record.ts_range
+        assert_equal ActiveSupport::TimeZone[tz], record.ts_range.begin.time_zone
+        assert_equal time.usec, record.ts_range.begin.usec
+      end
+    end
+
     def test_create_numrange
       assert_equal_round_trip(@new_range, :num_range,
-                              BigDecimal.new("0.5")...BigDecimal.new("1"))
+                              BigDecimal("0.5")...BigDecimal("1"))
     end
 
     def test_update_numrange
       assert_equal_round_trip(@first_range, :num_range,
-                              BigDecimal.new("0.5")...BigDecimal.new("1"))
+                              BigDecimal("0.5")...BigDecimal("1"))
       assert_nil_round_trip(@first_range, :num_range,
-                            BigDecimal.new("0.5")...BigDecimal.new("0.5"))
+                            BigDecimal("0.5")...BigDecimal("0.5"))
     end
 
     def test_create_daterange
@@ -307,6 +358,18 @@ _SQL
       end
     end
 
+    def test_infinity_values
+      PostgresqlRange.create!(int4_range: 1..Float::INFINITY,
+                              int8_range: -Float::INFINITY..0,
+                              float_range: -Float::INFINITY..Float::INFINITY)
+
+      record = PostgresqlRange.first
+
+      assert_equal(1...Float::INFINITY, record.int4_range)
+      assert_equal(-Float::INFINITY...1, record.int8_range)
+      assert_equal(-Float::INFINITY...Float::INFINITY, record.float_range)
+    end
+
     private
       def assert_equal_round_trip(range, attribute, value)
         round_trip(range, attribute, value)
diff --git a/activerecord/test/cases/adapters/postgresql/schema_test.rb b/activerecord/test/cases/adapters/postgresql/schema_test.rb
index 5a64da028b..a36d066c80 100644
--- a/activerecord/test/cases/adapters/postgresql/schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/schema_test.rb
@@ -204,12 +204,12 @@ class SchemaTest < ActiveRecord::PostgreSQLTestCase
 
   def test_data_source_exists_when_not_on_schema_search_path
     with_schema_search_path("PUBLIC") do
-      assert(!@connection.data_source_exists?(TABLE_NAME), "data_source exists but should not be found")
+      assert_not(@connection.data_source_exists?(TABLE_NAME), "data_source exists but should not be found")
     end
   end
 
   def test_data_source_exists_wrong_schema
-    assert(!@connection.data_source_exists?("foo.things"), "data_source should not exist")
+    assert_not(@connection.data_source_exists?("foo.things"), "data_source should not exist")
   end
 
   def test_data_source_exists_quoted_names
@@ -459,7 +459,7 @@ class SchemaTest < ActiveRecord::PostgreSQLTestCase
         assert_equal :btree, index_d.using
         assert_equal :gin,   index_e.using
 
-        assert_equal :desc,  index_d.orders[INDEX_D_COLUMN]
+        assert_equal :desc,  index_d.orders
       end
     end
 
@@ -500,6 +500,66 @@ class SchemaForeignKeyTest < ActiveRecord::PostgreSQLTestCase
   end
 end
 
+class SchemaIndexOpclassTest < ActiveRecord::PostgreSQLTestCase
+  include SchemaDumpingHelper
+
+  setup do
+    @connection = ActiveRecord::Base.connection
+    @connection.create_table "trains" do |t|
+      t.string :name
+      t.text :description
+    end
+  end
+
+  teardown do
+    @connection.drop_table "trains", if_exists: true
+  end
+
+  def test_string_opclass_is_dumped
+    @connection.execute "CREATE INDEX trains_name_and_description ON trains USING btree(name text_pattern_ops, description text_pattern_ops)"
+
+    output = dump_table_schema "trains"
+
+    assert_match(/opclass: :text_pattern_ops/, output)
+  end
+
+  def test_non_default_opclass_is_dumped
+    @connection.execute "CREATE INDEX trains_name_and_description ON trains USING btree(name, description text_pattern_ops)"
+
+    output = dump_table_schema "trains"
+
+    assert_match(/opclass: \{ description: :text_pattern_ops \}/, output)
+  end
+end
+
+class SchemaIndexNullsOrderTest < ActiveRecord::PostgreSQLTestCase
+  include SchemaDumpingHelper
+
+  setup do
+    @connection = ActiveRecord::Base.connection
+    @connection.create_table "trains" do |t|
+      t.string :name
+      t.text :description
+    end
+  end
+
+  teardown do
+    @connection.drop_table "trains", if_exists: true
+  end
+
+  def test_nulls_order_is_dumped
+    @connection.execute "CREATE INDEX trains_name_and_description ON trains USING btree(name NULLS FIRST, description)"
+    output = dump_table_schema "trains"
+    assert_match(/order: \{ name: "NULLS FIRST" \}/, output)
+  end
+
+  def test_non_default_order_with_nulls_is_dumped
+    @connection.execute "CREATE INDEX trains_name_and_desc ON trains USING btree(name DESC NULLS LAST, description)"
+    output = dump_table_schema "trains"
+    assert_match(/order: \{ name: "DESC NULLS LAST" \}/, output)
+  end
+end
+
 class DefaultsUsingMultipleSchemasAndDomainTest < ActiveRecord::PostgreSQLTestCase
   setup do
     @connection = ActiveRecord::Base.connection
@@ -534,7 +594,7 @@ class DefaultsUsingMultipleSchemasAndDomainTest < ActiveRecord::PostgreSQLTestCa
   end
 
   def test_decimal_defaults_in_new_schema_when_overriding_domain
-    assert_equal BigDecimal.new("3.14159265358979323846"), Default.new.decimal_col, "Default of decimal column was not correctly parsed"
+    assert_equal BigDecimal("3.14159265358979323846"), Default.new.decimal_col, "Default of decimal column was not correctly parsed"
   end
 
   def test_bpchar_defaults_in_new_schema_when_overriding_domain
diff --git a/activerecord/test/cases/adapters/postgresql/serial_test.rb b/activerecord/test/cases/adapters/postgresql/serial_test.rb
index 3c020a88d0..83ea86be6d 100644
--- a/activerecord/test/cases/adapters/postgresql/serial_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/serial_test.rb
@@ -24,14 +24,14 @@ class PostgresqlSerialTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlSerial.columns_hash["seq"]
     assert_equal :integer, column.type
     assert_equal "integer", column.sql_type
-    assert column.serial?
+    assert_predicate column, :serial?
   end
 
   def test_not_serial_column
     column = PostgresqlSerial.columns_hash["serials_id"]
     assert_equal :integer, column.type
     assert_equal "integer", column.sql_type
-    assert_not column.serial?
+    assert_not_predicate column, :serial?
   end
 
   def test_schema_dump_with_shorthand
@@ -66,14 +66,14 @@ class PostgresqlBigSerialTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlBigSerial.columns_hash["seq"]
     assert_equal :integer, column.type
     assert_equal "bigint", column.sql_type
-    assert column.serial?
+    assert_predicate column, :serial?
   end
 
   def test_not_bigserial_column
     column = PostgresqlBigSerial.columns_hash["serials_id"]
     assert_equal :integer, column.type
     assert_equal "bigint", column.sql_type
-    assert_not column.serial?
+    assert_not_predicate column, :serial?
   end
 
   def test_schema_dump_with_shorthand
@@ -86,3 +86,71 @@ class PostgresqlBigSerialTest < ActiveRecord::PostgreSQLTestCase
     assert_match %r{t\.bigint\s+"serials_id",\s+default: -> \{ "nextval\('postgresql_big_serials_id_seq'::regclass\)" \}$}, output
   end
 end
+
+module SequenceNameDetectionTestCases
+  class CollidedSequenceNameTest < ActiveRecord::PostgreSQLTestCase
+    include SchemaDumpingHelper
+
+    def setup
+      @connection = ActiveRecord::Base.connection
+      @connection.create_table :foo_bar, force: true do |t|
+        t.serial :baz_id
+      end
+      @connection.create_table :foo, force: true do |t|
+        t.serial :bar_id
+        t.bigserial :bar_baz_id
+      end
+    end
+
+    def teardown
+      @connection.drop_table :foo_bar, if_exists: true
+      @connection.drop_table :foo, if_exists: true
+    end
+
+    def test_serial_columns
+      columns = @connection.columns(:foo)
+      columns.each do |column|
+        assert_equal :integer, column.type
+        assert_predicate column, :serial?
+      end
+    end
+
+    def test_schema_dump_with_collided_sequence_name
+      output = dump_table_schema "foo"
+      assert_match %r{t\.serial\s+"bar_id",\s+null: false$}, output
+      assert_match %r{t\.bigserial\s+"bar_baz_id",\s+null: false$}, output
+    end
+  end
+
+  class LongerSequenceNameDetectionTest < ActiveRecord::PostgreSQLTestCase
+    include SchemaDumpingHelper
+
+    def setup
+      @table_name = "long_table_name_to_test_sequence_name_detection_for_serial_cols"
+      @connection = ActiveRecord::Base.connection
+      @connection.create_table @table_name, force: true do |t|
+        t.serial :seq
+        t.bigserial :bigseq
+      end
+    end
+
+    def teardown
+      @connection.drop_table @table_name, if_exists: true
+    end
+
+    def test_serial_columns
+      columns = @connection.columns(@table_name)
+      columns.each do |column|
+        assert_equal :integer, column.type
+        assert_predicate column, :serial?
+      end
+    end
+
+    def test_schema_dump_with_long_table_name
+      output = dump_table_schema @table_name
+      assert_match %r{create_table "#{@table_name}", force: :cascade}, output
+      assert_match %r{t\.serial\s+"seq",\s+null: false$}, output
+      assert_match %r{t\.bigserial\s+"bigseq",\s+null: false$}, output
+    end
+  end
+end
diff --git a/activerecord/test/cases/adapters/postgresql/statement_pool_test.rb b/activerecord/test/cases/adapters/postgresql/statement_pool_test.rb
index a3eb4f9e67..fef4b02b04 100644
--- a/activerecord/test/cases/adapters/postgresql/statement_pool_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/statement_pool_test.rb
@@ -23,7 +23,7 @@ module ActiveRecord
             assert_equal "bar", cache["foo"]
 
             pid = fork {
-              lookup = cache["foo"];
+              lookup = cache["foo"]
               exit!(!lookup)
             }
 
diff --git a/activerecord/test/cases/adapters/postgresql/transaction_test.rb b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
index f56adf4a5e..984b2f5ea4 100644
--- a/activerecord/test/cases/adapters/postgresql/transaction_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
@@ -14,6 +14,7 @@ module ActiveRecord
 
     setup do
       @abort, Thread.abort_on_exception = Thread.abort_on_exception, false
+      Thread.report_on_exception, @original_report_on_exception = false, Thread.report_on_exception
 
       @connection = ActiveRecord::Base.connection
 
@@ -31,6 +32,7 @@ module ActiveRecord
       @connection.drop_table "samples", if_exists: true
 
       Thread.abort_on_exception = @abort
+      Thread.report_on_exception = @original_report_on_exception
     end
 
     test "raises SerializationFailure when a serialization failure occurs" do
@@ -74,7 +76,7 @@ module ActiveRecord
             Sample.transaction do
               s1.lock!
               barrier.wait
-              s2.update_attributes value: 1
+              s2.update value: 1
             end
           end
 
@@ -82,7 +84,7 @@ module ActiveRecord
             Sample.transaction do
               s2.lock!
               barrier.wait
-              s1.update_attributes value: 2
+              s1.update value: 2
             end
           ensure
             thread.join
@@ -91,6 +93,90 @@ module ActiveRecord
       end
     end
 
+    test "raises LockWaitTimeout when lock wait timeout exceeded" do
+      skip unless ActiveRecord::Base.connection.postgresql_version >= 90300
+      assert_raises(ActiveRecord::LockWaitTimeout) do
+        s = Sample.create!(value: 1)
+        latch1 = Concurrent::CountDownLatch.new
+        latch2 = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch1.count_down
+            latch2.wait
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch1.wait
+            Sample.connection.execute("SET lock_timeout = 1")
+            Sample.lock.find(s.id)
+          end
+        ensure
+          Sample.connection.execute("SET lock_timeout = DEFAULT")
+          latch2.count_down
+          thread.join
+        end
+      end
+    end
+
+    test "raises QueryCanceled when statement timeout exceeded" do
+      assert_raises(ActiveRecord::QueryCanceled) do
+        s = Sample.create!(value: 1)
+        latch1 = Concurrent::CountDownLatch.new
+        latch2 = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch1.count_down
+            latch2.wait
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch1.wait
+            Sample.connection.execute("SET statement_timeout = 1")
+            Sample.lock.find(s.id)
+          end
+        ensure
+          Sample.connection.execute("SET statement_timeout = DEFAULT")
+          latch2.count_down
+          thread.join
+        end
+      end
+    end
+
+    test "raises QueryCanceled when canceling statement due to user request" do
+      assert_raises(ActiveRecord::QueryCanceled) do
+        s = Sample.create!(value: 1)
+        latch = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch.count_down
+            sleep(0.5)
+            conn = Sample.connection
+            pid = conn.query_value("SELECT pid FROM pg_stat_activity WHERE query LIKE '% FOR UPDATE'")
+            conn.execute("SELECT pg_cancel_backend(#{pid})")
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch.wait
+            Sample.lock.find(s.id)
+          end
+        ensure
+          thread.join
+        end
+      end
+    end
+
     private
 
       def with_warning_suppression
diff --git a/activerecord/test/cases/adapters/postgresql/type_lookup_test.rb b/activerecord/test/cases/adapters/postgresql/type_lookup_test.rb
index 449023b6eb..8212ed4263 100644
--- a/activerecord/test/cases/adapters/postgresql/type_lookup_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/type_lookup_test.rb
@@ -30,6 +30,6 @@ class PostgresqlTypeLookupTest < ActiveRecord::PostgreSQLTestCase
     big_range = 0..123456789123456789
 
     assert_raises(ActiveModel::RangeError) { int_range.serialize(big_range) }
-    assert_equal "[0,123456789123456789]", bigint_range.serialize(big_range)
+    assert_equal "[0,123456789123456789]", @connection.type_cast(bigint_range.serialize(big_range))
   end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/uuid_test.rb b/activerecord/test/cases/adapters/postgresql/uuid_test.rb
index 76cb1bc354..71d07e2f4c 100644
--- a/activerecord/test/cases/adapters/postgresql/uuid_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/uuid_test.rb
@@ -76,14 +76,27 @@ class PostgresqlUUIDTest < ActiveRecord::PostgreSQLTestCase
     assert_nil column.default
   end
 
+  def test_add_column_with_default_array
+    connection.add_column :uuid_data_type, :thingy, :uuid, array: true, default: []
+
+    UUIDType.reset_column_information
+    column = UUIDType.columns_hash["thingy"]
+
+    assert_predicate column, :array?
+    assert_equal "{}", column.default
+
+    schema = dump_table_schema "uuid_data_type"
+    assert_match %r{t\.uuid "thingy", default: \[\], array: true$}, schema
+  end
+
   def test_data_type_of_uuid_types
     column = UUIDType.columns_hash["guid"]
     assert_equal :uuid, column.type
     assert_equal "uuid", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = UUIDType.type_for_attribute("guid")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_treat_blank_uuid_as_nil
@@ -165,7 +178,7 @@ class PostgresqlUUIDTest < ActiveRecord::PostgreSQLTestCase
     duplicate = klass.new(guid: record.guid)
 
     assert record.guid.present? # Ensure we actually are testing a UUID
-    assert_not duplicate.valid?
+    assert_not_predicate duplicate, :valid?
   end
 end
 
@@ -209,68 +222,66 @@ class PostgresqlUUIDGenerationTest < ActiveRecord::PostgreSQLTestCase
     connection.execute "DROP FUNCTION IF EXISTS my_uuid_generator();"
   end
 
-  if ActiveRecord::Base.connection.supports_extensions?
-    def test_id_is_uuid
-      assert_equal :uuid, UUID.columns_hash["id"].type
-      assert UUID.primary_key
-    end
+  def test_id_is_uuid
+    assert_equal :uuid, UUID.columns_hash["id"].type
+    assert UUID.primary_key
+  end
 
-    def test_id_has_a_default
-      u = UUID.create
-      assert_not_nil u.id
-    end
+  def test_id_has_a_default
+    u = UUID.create
+    assert_not_nil u.id
+  end
 
-    def test_auto_create_uuid
-      u = UUID.create
-      u.reload
-      assert_not_nil u.other_uuid
-    end
+  def test_auto_create_uuid
+    u = UUID.create
+    u.reload
+    assert_not_nil u.other_uuid
+  end
 
-    def test_pk_and_sequence_for_uuid_primary_key
-      pk, seq = connection.pk_and_sequence_for("pg_uuids")
-      assert_equal "id", pk
-      assert_nil seq
-    end
+  def test_pk_and_sequence_for_uuid_primary_key
+    pk, seq = connection.pk_and_sequence_for("pg_uuids")
+    assert_equal "id", pk
+    assert_nil seq
+  end
 
-    def test_schema_dumper_for_uuid_primary_key
-      schema = dump_table_schema "pg_uuids"
-      assert_match(/\bcreate_table "pg_uuids", id: :uuid, default: -> { "uuid_generate_v1\(\)" }/, schema)
-      assert_match(/t\.uuid "other_uuid", default: -> { "uuid_generate_v4\(\)" }/, schema)
-    end
+  def test_schema_dumper_for_uuid_primary_key
+    schema = dump_table_schema "pg_uuids"
+    assert_match(/\bcreate_table "pg_uuids", id: :uuid, default: -> { "uuid_generate_v1\(\)" }/, schema)
+    assert_match(/t\.uuid "other_uuid", default: -> { "uuid_generate_v4\(\)" }/, schema)
+  end
+
+  def test_schema_dumper_for_uuid_primary_key_with_custom_default
+    schema = dump_table_schema "pg_uuids_2"
+    assert_match(/\bcreate_table "pg_uuids_2", id: :uuid, default: -> { "my_uuid_generator\(\)" }/, schema)
+    assert_match(/t\.uuid "other_uuid_2", default: -> { "my_uuid_generator\(\)" }/, schema)
+  end
 
-    def test_schema_dumper_for_uuid_primary_key_with_custom_default
-      schema = dump_table_schema "pg_uuids_2"
-      assert_match(/\bcreate_table "pg_uuids_2", id: :uuid, default: -> { "my_uuid_generator\(\)" }/, schema)
-      assert_match(/t\.uuid "other_uuid_2", default: -> { "my_uuid_generator\(\)" }/, schema)
+  def test_schema_dumper_for_uuid_primary_key_default
+    schema = dump_table_schema "pg_uuids_3"
+    if connection.supports_pgcrypto_uuid?
+      assert_match(/\bcreate_table "pg_uuids_3", id: :uuid, default: -> { "gen_random_uuid\(\)" }/, schema)
+    else
+      assert_match(/\bcreate_table "pg_uuids_3", id: :uuid, default: -> { "uuid_generate_v4\(\)" }/, schema)
     end
+  end
+
+  def test_schema_dumper_for_uuid_primary_key_default_in_legacy_migration
+    @verbose_was = ActiveRecord::Migration.verbose
+    ActiveRecord::Migration.verbose = false
 
-    def test_schema_dumper_for_uuid_primary_key_default
-      schema = dump_table_schema "pg_uuids_3"
-      if connection.supports_pgcrypto_uuid?
-        assert_match(/\bcreate_table "pg_uuids_3", id: :uuid, default: -> { "gen_random_uuid\(\)" }/, schema)
-      else
-        assert_match(/\bcreate_table "pg_uuids_3", id: :uuid, default: -> { "uuid_generate_v4\(\)" }/, schema)
+    migration = Class.new(ActiveRecord::Migration[5.0]) do
+      def version; 101 end
+      def migrate(x)
+        create_table("pg_uuids_4", id: :uuid)
       end
-    end
+    end.new
+    ActiveRecord::Migrator.new(:up, [migration]).migrate
 
-    def test_schema_dumper_for_uuid_primary_key_default_in_legacy_migration
-      @verbose_was = ActiveRecord::Migration.verbose
-      ActiveRecord::Migration.verbose = false
-
-      migration = Class.new(ActiveRecord::Migration[5.0]) do
-        def version; 101 end
-        def migrate(x)
-          create_table("pg_uuids_4", id: :uuid)
-        end
-      end.new
-      ActiveRecord::Migrator.new(:up, [migration]).migrate
-
-      schema = dump_table_schema "pg_uuids_4"
-      assert_match(/\bcreate_table "pg_uuids_4", id: :uuid, default: -> { "uuid_generate_v4\(\)" }/, schema)
-    ensure
-      drop_table "pg_uuids_4"
-      ActiveRecord::Migration.verbose = @verbose_was
-    end
+    schema = dump_table_schema "pg_uuids_4"
+    assert_match(/\bcreate_table "pg_uuids_4", id: :uuid, default: -> { "uuid_generate_v4\(\)" }/, schema)
+  ensure
+    drop_table "pg_uuids_4"
+    ActiveRecord::Migration.verbose = @verbose_was
   end
 end
 
@@ -289,38 +300,36 @@ class PostgresqlUUIDTestNilDefault < ActiveRecord::PostgreSQLTestCase
     drop_table "pg_uuids"
   end
 
-  if ActiveRecord::Base.connection.supports_extensions?
-    def test_id_allows_default_override_via_nil
-      col_desc = connection.execute("SELECT pg_get_expr(d.adbin, d.adrelid) as default
-                                    FROM pg_attribute a
-                                    LEFT JOIN pg_attrdef d ON a.attrelid = d.adrelid AND a.attnum = d.adnum
-                                    WHERE a.attname='id' AND a.attrelid = 'pg_uuids'::regclass").first
-      assert_nil col_desc["default"]
-    end
+  def test_id_allows_default_override_via_nil
+    col_desc = connection.execute("SELECT pg_get_expr(d.adbin, d.adrelid) as default
+                                  FROM pg_attribute a
+                                  LEFT JOIN pg_attrdef d ON a.attrelid = d.adrelid AND a.attnum = d.adnum
+                                  WHERE a.attname='id' AND a.attrelid = 'pg_uuids'::regclass").first
+    assert_nil col_desc["default"]
+  end
 
-    def test_schema_dumper_for_uuid_primary_key_with_default_override_via_nil
-      schema = dump_table_schema "pg_uuids"
-      assert_match(/\bcreate_table "pg_uuids", id: :uuid, default: nil/, schema)
-    end
+  def test_schema_dumper_for_uuid_primary_key_with_default_override_via_nil
+    schema = dump_table_schema "pg_uuids"
+    assert_match(/\bcreate_table "pg_uuids", id: :uuid, default: nil/, schema)
+  end
 
-    def test_schema_dumper_for_uuid_primary_key_with_default_nil_in_legacy_migration
-      @verbose_was = ActiveRecord::Migration.verbose
-      ActiveRecord::Migration.verbose = false
-
-      migration = Class.new(ActiveRecord::Migration[5.0]) do
-        def version; 101 end
-        def migrate(x)
-          create_table("pg_uuids_4", id: :uuid, default: nil)
-        end
-      end.new
-      ActiveRecord::Migrator.new(:up, [migration]).migrate
-
-      schema = dump_table_schema "pg_uuids_4"
-      assert_match(/\bcreate_table "pg_uuids_4", id: :uuid, default: nil/, schema)
-    ensure
-      drop_table "pg_uuids_4"
-      ActiveRecord::Migration.verbose = @verbose_was
-    end
+  def test_schema_dumper_for_uuid_primary_key_with_default_nil_in_legacy_migration
+    @verbose_was = ActiveRecord::Migration.verbose
+    ActiveRecord::Migration.verbose = false
+
+    migration = Class.new(ActiveRecord::Migration[5.0]) do
+      def version; 101 end
+      def migrate(x)
+        create_table("pg_uuids_4", id: :uuid, default: nil)
+      end
+    end.new
+    ActiveRecord::Migrator.new(:up, [migration]).migrate
+
+    schema = dump_table_schema "pg_uuids_4"
+    assert_match(/\bcreate_table "pg_uuids_4", id: :uuid, default: nil/, schema)
+  ensure
+    drop_table "pg_uuids_4"
+    ActiveRecord::Migration.verbose = @verbose_was
   end
 end
 
@@ -354,23 +363,21 @@ class PostgresqlUUIDTestInverseOf < ActiveRecord::PostgreSQLTestCase
     drop_table "pg_uuid_posts"
   end
 
-  if ActiveRecord::Base.connection.supports_extensions?
-    def test_collection_association_with_uuid
-      post    = UuidPost.create!
-      comment = post.uuid_comments.create!
-      assert post.uuid_comments.find(comment.id)
-    end
+  def test_collection_association_with_uuid
+    post    = UuidPost.create!
+    comment = post.uuid_comments.create!
+    assert post.uuid_comments.find(comment.id)
+  end
 
-    def test_find_with_uuid
-      UuidPost.create!
-      assert_raise ActiveRecord::RecordNotFound do
-        UuidPost.find(123456)
-      end
+  def test_find_with_uuid
+    UuidPost.create!
+    assert_raise ActiveRecord::RecordNotFound do
+      UuidPost.find(123456)
     end
+  end
 
-    def test_find_by_with_uuid
-      UuidPost.create!
-      assert_nil UuidPost.find_by(id: 789)
-    end
+  def test_find_by_with_uuid
+    UuidPost.create!
+    assert_nil UuidPost.find_by(id: 789)
   end
 end
diff --git a/activerecord/test/cases/adapters/sqlite3/explain_test.rb b/activerecord/test/cases/adapters/sqlite3/explain_test.rb
index 3b081d34e1..b6d2ccdb53 100644
--- a/activerecord/test/cases/adapters/sqlite3/explain_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/explain_test.rb
@@ -1,23 +1,23 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "models/developer"
-require "models/computer"
+require "models/author"
+require "models/post"
 
 class SQLite3ExplainTest < ActiveRecord::SQLite3TestCase
-  fixtures :developers
+  fixtures :authors
 
   def test_explain_for_one_query
-    explain = Developer.where(id: 1).explain
-    assert_match %r(EXPLAIN for: SELECT "developers"\.\* FROM "developers" WHERE "developers"\."id" = (?:\? \[\["id", 1\]\]|1)), explain
-    assert_match(/(SEARCH )?TABLE developers USING (INTEGER )?PRIMARY KEY/, explain)
+    explain = Author.where(id: 1).explain
+    assert_match %r(EXPLAIN for: SELECT "authors"\.\* FROM "authors" WHERE "authors"\."id" = (?:\? \[\["id", 1\]\]|1)), explain
+    assert_match(/(SEARCH )?TABLE authors USING (INTEGER )?PRIMARY KEY/, explain)
   end
 
   def test_explain_with_eager_loading
-    explain = Developer.where(id: 1).includes(:audit_logs).explain
-    assert_match %r(EXPLAIN for: SELECT "developers"\.\* FROM "developers" WHERE "developers"\."id" = (?:\? \[\["id", 1\]\]|1)), explain
-    assert_match(/(SEARCH )?TABLE developers USING (INTEGER )?PRIMARY KEY/, explain)
-    assert_match %r(EXPLAIN for: SELECT "audit_logs"\.\* FROM "audit_logs" WHERE "audit_logs"\."developer_id" = (?:\? \[\["developer_id", 1\]\]|1)), explain
-    assert_match(/(SCAN )?TABLE audit_logs/, explain)
+    explain = Author.where(id: 1).includes(:posts).explain
+    assert_match %r(EXPLAIN for: SELECT "authors"\.\* FROM "authors" WHERE "authors"\."id" = (?:\? \[\["id", 1\]\]|1)), explain
+    assert_match(/(SEARCH )?TABLE authors USING (INTEGER )?PRIMARY KEY/, explain)
+    assert_match %r(EXPLAIN for: SELECT "posts"\.\* FROM "posts" WHERE "posts"\."author_id" = (?:\? \[\["author_id", 1\]\]|1)), explain
+    assert_match(/(SCAN )?TABLE posts/, explain)
   end
 end
diff --git a/activerecord/test/cases/adapters/sqlite3/json_test.rb b/activerecord/test/cases/adapters/sqlite3/json_test.rb
new file mode 100644
index 0000000000..6f247fcd22
--- /dev/null
+++ b/activerecord/test/cases/adapters/sqlite3/json_test.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "cases/json_shared_test_cases"
+
+class SQLite3JSONTest < ActiveRecord::SQLite3TestCase
+  include JSONSharedTestCases
+
+  def setup
+    super
+    @connection.create_table("json_data_type") do |t|
+      t.json "payload", default: {}
+      t.json "settings"
+    end
+  end
+
+  def test_default
+    @connection.add_column "json_data_type", "permissions", column_type, default: { "users": "read", "posts": ["read", "write"] }
+    klass.reset_column_information
+
+    assert_equal({ "users" => "read", "posts" => ["read", "write"] }, klass.column_defaults["permissions"])
+    assert_equal({ "users" => "read", "posts" => ["read", "write"] }, klass.new.permissions)
+  end
+
+  private
+    def column_type
+      :json
+    end
+end
diff --git a/activerecord/test/cases/adapters/sqlite3/quoting_test.rb b/activerecord/test/cases/adapters/sqlite3/quoting_test.rb
index de422fad23..1c85ff5674 100644
--- a/activerecord/test/cases/adapters/sqlite3/quoting_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/quoting_test.rb
@@ -38,7 +38,7 @@ class SQLite3QuotingTest < ActiveRecord::SQLite3TestCase
   end
 
   def test_type_cast_bigdecimal
-    bd = BigDecimal.new "10.0"
+    bd = BigDecimal "10.0"
     assert_equal bd.to_f, @conn.type_cast(bd)
   end
 
@@ -55,4 +55,11 @@ class SQLite3QuotingTest < ActiveRecord::SQLite3TestCase
 
     assert_equal "'2000-01-01 12:30:00.999999'", @conn.quote(type.serialize(value))
   end
+
+  def test_quoted_time_normalizes_date_qualified_time
+    value = ::Time.utc(2018, 3, 11, 12, 30, 0, 999999)
+    type = ActiveRecord::Type::Time.new
+
+    assert_equal "'2000-01-01 12:30:00.999999'", @conn.quote(type.serialize(value))
+  end
 end
diff --git a/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb b/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
index 2b51a32db6..ad155c7492 100644
--- a/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
@@ -61,7 +61,7 @@ module ActiveRecord
           WHERE  #{Owner.primary_key} = #{owner.id}
         esql
 
-        assert(!result.rows.first.include?("blob"), "should not store blobs")
+        assert_not(result.rows.first.include?("blob"), "should not store blobs")
       ensure
         owner.delete
       end
@@ -269,14 +269,6 @@ module ActiveRecord
         end
       end
 
-      def test_indexes_logs_name
-        with_example_table do
-          assert_logged [["PRAGMA index_list(\"ex\")", "SCHEMA", []]] do
-            assert_deprecated { @conn.indexes("ex", "hello") }
-          end
-        end
-      end
-
       def test_table_exists_logs_name
         with_example_table do
           sql = <<-SQL
@@ -368,16 +360,126 @@ module ActiveRecord
         end
       end
 
+      class Barcode < ActiveRecord::Base
+        self.primary_key = "code"
+      end
+
+      def test_copy_table_with_existing_records_have_custom_primary_key
+        connection = Barcode.connection
+        connection.create_table(:barcodes, primary_key: "code", id: :string, limit: 42, force: true) do |t|
+          t.text :other_attr
+        end
+        code = "214fe0c2-dd47-46df-b53b-66090b3c1d40"
+        Barcode.create!(code: code, other_attr: "xxx")
+
+        connection.remove_column("barcodes", "other_attr")
+
+        assert_equal code, Barcode.first.id
+      ensure
+        Barcode.reset_column_information
+      end
+
+      def test_copy_table_with_composite_primary_keys
+        connection = Barcode.connection
+        connection.create_table(:barcodes, primary_key: ["region", "code"], force: true) do |t|
+          t.string :region
+          t.string :code
+          t.text :other_attr
+        end
+        region = "US"
+        code = "214fe0c2-dd47-46df-b53b-66090b3c1d40"
+        Barcode.create!(region: region, code: code, other_attr: "xxx")
+
+        connection.remove_column("barcodes", "other_attr")
+
+        assert_equal ["region", "code"], connection.primary_keys("barcodes")
+
+        barcode = Barcode.first
+        assert_equal region, barcode.region
+        assert_equal code, barcode.code
+      ensure
+        Barcode.reset_column_information
+      end
+
+      def test_custom_primary_key_in_create_table
+        connection = Barcode.connection
+        connection.create_table :barcodes, id: false, force: true do |t|
+          t.primary_key :id, :string
+        end
+
+        assert_equal "id", connection.primary_key("barcodes")
+
+        custom_pk = Barcode.columns_hash["id"]
+
+        assert_equal :string, custom_pk.type
+        assert_not custom_pk.null
+      ensure
+        Barcode.reset_column_information
+      end
+
+      def test_custom_primary_key_in_change_table
+        connection = Barcode.connection
+        connection.create_table :barcodes, id: false, force: true do |t|
+          t.integer :dummy
+        end
+        connection.change_table :barcodes do |t|
+          t.primary_key :id, :string
+        end
+
+        assert_equal "id", connection.primary_key("barcodes")
+
+        custom_pk = Barcode.columns_hash["id"]
+
+        assert_equal :string, custom_pk.type
+        assert_not custom_pk.null
+      ensure
+        Barcode.reset_column_information
+      end
+
+      def test_add_column_with_custom_primary_key
+        connection = Barcode.connection
+        connection.create_table :barcodes, id: false, force: true do |t|
+          t.integer :dummy
+        end
+        connection.add_column :barcodes, :id, :string, primary_key: true
+
+        assert_equal "id", connection.primary_key("barcodes")
+
+        custom_pk = Barcode.columns_hash["id"]
+
+        assert_equal :string, custom_pk.type
+        assert_not custom_pk.null
+      ensure
+        Barcode.reset_column_information
+      end
+
+      def test_remove_column_preserves_partial_indexes
+        connection = Barcode.connection
+        connection.create_table :barcodes, force: true do |t|
+          t.string :code
+          t.string :region
+          t.boolean :bool_attr
+
+          t.index :code, unique: true, where: :bool_attr, name: "partial"
+        end
+        connection.remove_column :barcodes, :region
+
+        index = connection.indexes("barcodes").find { |idx| idx.name == "partial" }
+        assert_equal "bool_attr", index.where
+      ensure
+        Barcode.reset_column_information
+      end
+
       def test_supports_extensions
         assert_not @conn.supports_extensions?, "does not support extensions"
       end
 
       def test_respond_to_enable_extension
-        assert @conn.respond_to?(:enable_extension)
+        assert_respond_to @conn, :enable_extension
       end
 
       def test_respond_to_disable_extension
-        assert @conn.respond_to?(:disable_extension)
+        assert_respond_to @conn, :disable_extension
       end
 
       def test_statement_closed
@@ -398,6 +500,10 @@ module ActiveRecord
         end
       end
 
+      def test_deprecate_valid_alter_table_type
+        assert_deprecated { @conn.valid_alter_table_type?(:string) }
+      end
+
       private
 
         def assert_logged(logs)
diff --git a/activerecord/test/cases/adapters/sqlite3/statement_pool_test.rb b/activerecord/test/cases/adapters/sqlite3/statement_pool_test.rb
index 42b3841d41..61002435a4 100644
--- a/activerecord/test/cases/adapters/sqlite3/statement_pool_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/statement_pool_test.rb
@@ -10,7 +10,7 @@ class SQLite3StatementPoolTest < ActiveRecord::SQLite3TestCase
       assert_equal "bar", cache["foo"]
 
       pid = fork {
-        lookup = cache["foo"];
+        lookup = cache["foo"]
         exit!(!lookup)
       }
 
diff --git a/activerecord/test/cases/aggregations_test.rb b/activerecord/test/cases/aggregations_test.rb
index 7f654ec6f6..fbdf2ada4b 100644
--- a/activerecord/test/cases/aggregations_test.rb
+++ b/activerecord/test/cases/aggregations_test.rb
@@ -27,7 +27,7 @@ class AggregationsTest < ActiveRecord::TestCase
 
   def test_immutable_value_objects
     customers(:david).balance = Money.new(100)
-    assert_raise(RuntimeError) { customers(:david).balance.instance_eval { @amount = 20 } }
+    assert_raise(frozen_error_class) { customers(:david).balance.instance_eval { @amount = 20 } }
   end
 
   def test_inferred_mapping
diff --git a/activerecord/test/cases/ar_schema_test.rb b/activerecord/test/cases/ar_schema_test.rb
index 83974f327e..f05dcac7dd 100644
--- a/activerecord/test/cases/ar_schema_test.rb
+++ b/activerecord/test/cases/ar_schema_test.rb
@@ -48,7 +48,7 @@ class ActiveRecordSchemaTest < ActiveRecord::TestCase
 
     assert_nothing_raised { @connection.select_all "SELECT * FROM fruits" }
     assert_nothing_raised { @connection.select_all "SELECT * FROM schema_migrations" }
-    assert_equal 7, ActiveRecord::Migrator::current_version
+    assert_equal 7, @connection.migration_context.current_version
   end
 
   def test_schema_define_w_table_name_prefix
@@ -64,7 +64,7 @@ class ActiveRecordSchemaTest < ActiveRecord::TestCase
         t.column :flavor, :string
       end
     end
-    assert_equal 7, ActiveRecord::Migrator::current_version
+    assert_equal 7, @connection.migration_context.current_version
   ensure
     ActiveRecord::Base.table_name_prefix = old_table_name_prefix
     ActiveRecord::SchemaMigration.table_name = table_name
@@ -116,8 +116,8 @@ class ActiveRecordSchemaTest < ActiveRecord::TestCase
       end
     end
 
-    assert !@connection.columns(:has_timestamps).find { |c| c.name == "created_at" }.null
-    assert !@connection.columns(:has_timestamps).find { |c| c.name == "updated_at" }.null
+    assert_not @connection.columns(:has_timestamps).find { |c| c.name == "created_at" }.null
+    assert_not @connection.columns(:has_timestamps).find { |c| c.name == "updated_at" }.null
   end
 
   def test_timestamps_without_null_set_null_to_false_on_change_table
@@ -129,8 +129,8 @@ class ActiveRecordSchemaTest < ActiveRecord::TestCase
       end
     end
 
-    assert !@connection.columns(:has_timestamps).find { |c| c.name == "created_at" }.null
-    assert !@connection.columns(:has_timestamps).find { |c| c.name == "updated_at" }.null
+    assert_not @connection.columns(:has_timestamps).find { |c| c.name == "created_at" }.null
+    assert_not @connection.columns(:has_timestamps).find { |c| c.name == "updated_at" }.null
   end
 
   def test_timestamps_without_null_set_null_to_false_on_add_timestamps
@@ -139,7 +139,7 @@ class ActiveRecordSchemaTest < ActiveRecord::TestCase
       add_timestamps :has_timestamps, default: Time.now
     end
 
-    assert !@connection.columns(:has_timestamps).find { |c| c.name == "created_at" }.null
-    assert !@connection.columns(:has_timestamps).find { |c| c.name == "updated_at" }.null
+    assert_not @connection.columns(:has_timestamps).find { |c| c.name == "created_at" }.null
+    assert_not @connection.columns(:has_timestamps).find { |c| c.name == "updated_at" }.null
   end
 end
diff --git a/activerecord/test/cases/arel/attributes/attribute_test.rb b/activerecord/test/cases/arel/attributes/attribute_test.rb
new file mode 100644
index 0000000000..671e273543
--- /dev/null
+++ b/activerecord/test/cases/arel/attributes/attribute_test.rb
@@ -0,0 +1,1015 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+require "ostruct"
+
+module Arel
+  module Attributes
+    class AttributeTest < Arel::Spec
+      describe "#not_eq" do
+        it "should create a NotEqual node" do
+          relation = Table.new(:users)
+          relation[:id].not_eq(10).must_be_kind_of Nodes::NotEqual
+        end
+
+        it "should generate != in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].not_eq(10)
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE "users"."id" != 10
+          }
+        end
+
+        it "should handle nil" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].not_eq(nil)
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE "users"."id" IS NOT NULL
+          }
+        end
+      end
+
+      describe "#not_eq_any" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].not_eq_any([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ORs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].not_eq_any([1, 2])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" != 1 OR "users"."id" != 2)
+          }
+        end
+      end
+
+      describe "#not_eq_all" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].not_eq_all([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ANDs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].not_eq_all([1, 2])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" != 1 AND "users"."id" != 2)
+          }
+        end
+      end
+
+      describe "#gt" do
+        it "should create a GreaterThan node" do
+          relation = Table.new(:users)
+          relation[:id].gt(10).must_be_kind_of Nodes::GreaterThan
+        end
+
+        it "should generate > in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].gt(10)
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE "users"."id" > 10
+          }
+        end
+
+        it "should handle comparing with a subquery" do
+          users = Table.new(:users)
+
+          avg = users.project(users[:karma].average)
+          mgr = users.project(Arel.star).where(users[:karma].gt(avg))
+
+          mgr.to_sql.must_be_like %{
+            SELECT * FROM "users" WHERE "users"."karma" > (SELECT AVG("users"."karma") FROM "users")
+          }
+        end
+
+        it "should accept various data types." do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:name].gt("fake_name")
+          mgr.to_sql.must_match %{"users"."name" > 'fake_name'}
+
+          current_time = ::Time.now
+          mgr.where relation[:created_at].gt(current_time)
+          mgr.to_sql.must_match %{"users"."created_at" > '#{current_time}'}
+        end
+      end
+
+      describe "#gt_any" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].gt_any([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ORs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].gt_any([1, 2])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" > 1 OR "users"."id" > 2)
+          }
+        end
+      end
+
+      describe "#gt_all" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].gt_all([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ANDs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].gt_all([1, 2])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" > 1 AND "users"."id" > 2)
+          }
+        end
+      end
+
+      describe "#gteq" do
+        it "should create a GreaterThanOrEqual node" do
+          relation = Table.new(:users)
+          relation[:id].gteq(10).must_be_kind_of Nodes::GreaterThanOrEqual
+        end
+
+        it "should generate >= in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].gteq(10)
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE "users"."id" >= 10
+          }
+        end
+
+        it "should accept various data types." do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:name].gteq("fake_name")
+          mgr.to_sql.must_match %{"users"."name" >= 'fake_name'}
+
+          current_time = ::Time.now
+          mgr.where relation[:created_at].gteq(current_time)
+          mgr.to_sql.must_match %{"users"."created_at" >= '#{current_time}'}
+        end
+      end
+
+      describe "#gteq_any" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].gteq_any([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ORs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].gteq_any([1, 2])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" >= 1 OR "users"."id" >= 2)
+          }
+        end
+      end
+
+      describe "#gteq_all" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].gteq_all([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ANDs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].gteq_all([1, 2])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" >= 1 AND "users"."id" >= 2)
+          }
+        end
+      end
+
+      describe "#lt" do
+        it "should create a LessThan node" do
+          relation = Table.new(:users)
+          relation[:id].lt(10).must_be_kind_of Nodes::LessThan
+        end
+
+        it "should generate < in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].lt(10)
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE "users"."id" < 10
+          }
+        end
+
+        it "should accept various data types." do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:name].lt("fake_name")
+          mgr.to_sql.must_match %{"users"."name" < 'fake_name'}
+
+          current_time = ::Time.now
+          mgr.where relation[:created_at].lt(current_time)
+          mgr.to_sql.must_match %{"users"."created_at" < '#{current_time}'}
+        end
+      end
+
+      describe "#lt_any" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].lt_any([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ORs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].lt_any([1, 2])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" < 1 OR "users"."id" < 2)
+          }
+        end
+      end
+
+      describe "#lt_all" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].lt_all([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ANDs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].lt_all([1, 2])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" < 1 AND "users"."id" < 2)
+          }
+        end
+      end
+
+      describe "#lteq" do
+        it "should create a LessThanOrEqual node" do
+          relation = Table.new(:users)
+          relation[:id].lteq(10).must_be_kind_of Nodes::LessThanOrEqual
+        end
+
+        it "should generate <= in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].lteq(10)
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE "users"."id" <= 10
+          }
+        end
+
+        it "should accept various data types." do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:name].lteq("fake_name")
+          mgr.to_sql.must_match %{"users"."name" <= 'fake_name'}
+
+          current_time = ::Time.now
+          mgr.where relation[:created_at].lteq(current_time)
+          mgr.to_sql.must_match %{"users"."created_at" <= '#{current_time}'}
+        end
+      end
+
+      describe "#lteq_any" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].lteq_any([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ORs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].lteq_any([1, 2])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" <= 1 OR "users"."id" <= 2)
+          }
+        end
+      end
+
+      describe "#lteq_all" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].lteq_all([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ANDs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].lteq_all([1, 2])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" <= 1 AND "users"."id" <= 2)
+          }
+        end
+      end
+
+      describe "#average" do
+        it "should create a AVG node" do
+          relation = Table.new(:users)
+          relation[:id].average.must_be_kind_of Nodes::Avg
+        end
+
+        it "should generate the proper SQL" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id].average
+          mgr.to_sql.must_be_like %{
+            SELECT AVG("users"."id")
+            FROM "users"
+          }
+        end
+      end
+
+      describe "#maximum" do
+        it "should create a MAX node" do
+          relation = Table.new(:users)
+          relation[:id].maximum.must_be_kind_of Nodes::Max
+        end
+
+        it "should generate proper SQL" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id].maximum
+          mgr.to_sql.must_be_like %{
+            SELECT MAX("users"."id")
+            FROM "users"
+          }
+        end
+      end
+
+      describe "#minimum" do
+        it "should create a Min node" do
+          relation = Table.new(:users)
+          relation[:id].minimum.must_be_kind_of Nodes::Min
+        end
+
+        it "should generate proper SQL" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id].minimum
+          mgr.to_sql.must_be_like %{
+            SELECT MIN("users"."id")
+            FROM "users"
+          }
+        end
+      end
+
+      describe "#sum" do
+        it "should create a SUM node" do
+          relation = Table.new(:users)
+          relation[:id].sum.must_be_kind_of Nodes::Sum
+        end
+
+        it "should generate the proper SQL" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id].sum
+          mgr.to_sql.must_be_like %{
+            SELECT SUM("users"."id")
+            FROM "users"
+          }
+        end
+      end
+
+      describe "#count" do
+        it "should return a count node" do
+          relation = Table.new(:users)
+          relation[:id].count.must_be_kind_of Nodes::Count
+        end
+
+        it "should take a distinct param" do
+          relation = Table.new(:users)
+          count = relation[:id].count(nil)
+          count.must_be_kind_of Nodes::Count
+          count.distinct.must_be_nil
+        end
+      end
+
+      describe "#eq" do
+        it "should return an equality node" do
+          attribute = Attribute.new nil, nil
+          equality = attribute.eq 1
+          equality.left.must_equal attribute
+          equality.right.val.must_equal 1
+          equality.must_be_kind_of Nodes::Equality
+        end
+
+        it "should generate = in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].eq(10)
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE "users"."id" = 10
+          }
+        end
+
+        it "should handle nil" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].eq(nil)
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE "users"."id" IS NULL
+          }
+        end
+      end
+
+      describe "#eq_any" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].eq_any([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ORs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].eq_any([1, 2])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" = 1 OR "users"."id" = 2)
+          }
+        end
+
+        it "should not eat input" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          values = [1, 2]
+          mgr.where relation[:id].eq_any(values)
+          values.must_equal [1, 2]
+        end
+      end
+
+      describe "#eq_all" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].eq_all([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ANDs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].eq_all([1, 2])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" = 1 AND "users"."id" = 2)
+          }
+        end
+
+        it "should not eat input" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          values = [1, 2]
+          mgr.where relation[:id].eq_all(values)
+          values.must_equal [1, 2]
+        end
+      end
+
+      describe "#matches" do
+        it "should create a Matches node" do
+          relation = Table.new(:users)
+          relation[:name].matches("%bacon%").must_be_kind_of Nodes::Matches
+        end
+
+        it "should generate LIKE in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:name].matches("%bacon%")
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE "users"."name" LIKE '%bacon%'
+          }
+        end
+      end
+
+      describe "#matches_any" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:name].matches_any(["%chunky%", "%bacon%"]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ORs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:name].matches_any(["%chunky%", "%bacon%"])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."name" LIKE '%chunky%' OR "users"."name" LIKE '%bacon%')
+          }
+        end
+      end
+
+      describe "#matches_all" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:name].matches_all(["%chunky%", "%bacon%"]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ANDs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:name].matches_all(["%chunky%", "%bacon%"])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."name" LIKE '%chunky%' AND "users"."name" LIKE '%bacon%')
+          }
+        end
+      end
+
+      describe "#does_not_match" do
+        it "should create a DoesNotMatch node" do
+          relation = Table.new(:users)
+          relation[:name].does_not_match("%bacon%").must_be_kind_of Nodes::DoesNotMatch
+        end
+
+        it "should generate NOT LIKE in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:name].does_not_match("%bacon%")
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE "users"."name" NOT LIKE '%bacon%'
+          }
+        end
+      end
+
+      describe "#does_not_match_any" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:name].does_not_match_any(["%chunky%", "%bacon%"]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ORs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:name].does_not_match_any(["%chunky%", "%bacon%"])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."name" NOT LIKE '%chunky%' OR "users"."name" NOT LIKE '%bacon%')
+          }
+        end
+      end
+
+      describe "#does_not_match_all" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:name].does_not_match_all(["%chunky%", "%bacon%"]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ANDs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:name].does_not_match_all(["%chunky%", "%bacon%"])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."name" NOT LIKE '%chunky%' AND "users"."name" NOT LIKE '%bacon%')
+          }
+        end
+      end
+
+      describe "with a range" do
+        it "can be constructed with a standard range" do
+          attribute = Attribute.new nil, nil
+          node = attribute.between(1..3)
+
+          node.must_equal Nodes::Between.new(
+            attribute,
+            Nodes::And.new([
+              Nodes::Casted.new(1, attribute),
+              Nodes::Casted.new(3, attribute)
+            ])
+          )
+        end
+
+        it "can be constructed with a range starting from -Infinity" do
+          attribute = Attribute.new nil, nil
+          node = attribute.between(-::Float::INFINITY..3)
+
+          node.must_equal Nodes::LessThanOrEqual.new(
+            attribute,
+            Nodes::Casted.new(3, attribute)
+          )
+        end
+
+        it "can be constructed with a quoted range starting from -Infinity" do
+          attribute = Attribute.new nil, nil
+          node = attribute.between(quoted_range(-::Float::INFINITY, 3, false))
+
+          node.must_equal Nodes::LessThanOrEqual.new(
+            attribute,
+            Nodes::Quoted.new(3)
+          )
+        end
+
+        it "can be constructed with an exclusive range starting from -Infinity" do
+          attribute = Attribute.new nil, nil
+          node = attribute.between(-::Float::INFINITY...3)
+
+          node.must_equal Nodes::LessThan.new(
+            attribute,
+            Nodes::Casted.new(3, attribute)
+          )
+        end
+
+        it "can be constructed with a quoted exclusive range starting from -Infinity" do
+          attribute = Attribute.new nil, nil
+          node = attribute.between(quoted_range(-::Float::INFINITY, 3, true))
+
+          node.must_equal Nodes::LessThan.new(
+            attribute,
+            Nodes::Quoted.new(3)
+          )
+        end
+
+        it "can be constructed with an infinite range" do
+          attribute = Attribute.new nil, nil
+          node = attribute.between(-::Float::INFINITY..::Float::INFINITY)
+
+          node.must_equal Nodes::NotIn.new(attribute, [])
+        end
+
+        it "can be constructed with a quoted infinite range" do
+          attribute = Attribute.new nil, nil
+          node = attribute.between(quoted_range(-::Float::INFINITY, ::Float::INFINITY, false))
+
+          node.must_equal Nodes::NotIn.new(attribute, [])
+        end
+
+
+        it "can be constructed with a range ending at Infinity" do
+          attribute = Attribute.new nil, nil
+          node = attribute.between(0..::Float::INFINITY)
+
+          node.must_equal Nodes::GreaterThanOrEqual.new(
+            attribute,
+            Nodes::Casted.new(0, attribute)
+          )
+        end
+
+        it "can be constructed with a quoted range ending at Infinity" do
+          attribute = Attribute.new nil, nil
+          node = attribute.between(quoted_range(0, ::Float::INFINITY, false))
+
+          node.must_equal Nodes::GreaterThanOrEqual.new(
+            attribute,
+            Nodes::Quoted.new(0)
+          )
+        end
+
+        it "can be constructed with an exclusive range" do
+          attribute = Attribute.new nil, nil
+          node = attribute.between(0...3)
+
+          node.must_equal Nodes::And.new([
+            Nodes::GreaterThanOrEqual.new(
+              attribute,
+              Nodes::Casted.new(0, attribute)
+            ),
+            Nodes::LessThan.new(
+              attribute,
+              Nodes::Casted.new(3, attribute)
+            )
+          ])
+        end
+
+        def quoted_range(begin_val, end_val, exclude)
+          OpenStruct.new(
+            begin: Nodes::Quoted.new(begin_val),
+            end: Nodes::Quoted.new(end_val),
+            exclude_end?: exclude,
+          )
+        end
+      end
+
+      describe "#in" do
+        it "can be constructed with a subquery" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:name].does_not_match_all(["%chunky%", "%bacon%"])
+          attribute = Attribute.new nil, nil
+
+          node = attribute.in(mgr)
+
+          node.must_equal Nodes::In.new(attribute, mgr.ast)
+        end
+
+        it "can be constructed with a list" do
+          attribute = Attribute.new nil, nil
+          node = attribute.in([1, 2, 3])
+
+          node.must_equal Nodes::In.new(
+            attribute,
+            [
+              Nodes::Casted.new(1, attribute),
+              Nodes::Casted.new(2, attribute),
+              Nodes::Casted.new(3, attribute),
+            ]
+          )
+        end
+
+        it "can be constructed with a random object" do
+          attribute = Attribute.new nil, nil
+          random_object = Object.new
+          node = attribute.in(random_object)
+
+          node.must_equal Nodes::In.new(
+            attribute,
+            Nodes::Casted.new(random_object, attribute)
+          )
+        end
+
+        it "should generate IN in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].in([1, 2, 3])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE "users"."id" IN (1, 2, 3)
+          }
+        end
+      end
+
+      describe "#in_any" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].in_any([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ORs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].in_any([[1, 2], [3, 4]])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" IN (1, 2) OR "users"."id" IN (3, 4))
+          }
+        end
+      end
+
+      describe "#in_all" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].in_all([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ANDs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].in_all([[1, 2], [3, 4]])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" IN (1, 2) AND "users"."id" IN (3, 4))
+          }
+        end
+      end
+
+      describe "with a range" do
+        it "can be constructed with a standard range" do
+          attribute = Attribute.new nil, nil
+          node = attribute.not_between(1..3)
+
+          node.must_equal Nodes::Grouping.new(Nodes::Or.new(
+                                                Nodes::LessThan.new(
+                                                  attribute,
+                                                  Nodes::Casted.new(1, attribute)
+                                                ),
+            Nodes::GreaterThan.new(
+              attribute,
+              Nodes::Casted.new(3, attribute)
+            )
+          ))
+        end
+
+        it "can be constructed with a range starting from -Infinity" do
+          attribute = Attribute.new nil, nil
+          node = attribute.not_between(-::Float::INFINITY..3)
+
+          node.must_equal Nodes::GreaterThan.new(
+            attribute,
+            Nodes::Casted.new(3, attribute)
+          )
+        end
+
+        it "can be constructed with an exclusive range starting from -Infinity" do
+          attribute = Attribute.new nil, nil
+          node = attribute.not_between(-::Float::INFINITY...3)
+
+          node.must_equal Nodes::GreaterThanOrEqual.new(
+            attribute,
+            Nodes::Casted.new(3, attribute)
+          )
+        end
+
+        it "can be constructed with an infinite range" do
+          attribute = Attribute.new nil, nil
+          node = attribute.not_between(-::Float::INFINITY..::Float::INFINITY)
+
+          node.must_equal Nodes::In.new(attribute, [])
+        end
+
+        it "can be constructed with a range ending at Infinity" do
+          attribute = Attribute.new nil, nil
+          node = attribute.not_between(0..::Float::INFINITY)
+
+          node.must_equal Nodes::LessThan.new(
+            attribute,
+            Nodes::Casted.new(0, attribute)
+          )
+        end
+
+        it "can be constructed with an exclusive range" do
+          attribute = Attribute.new nil, nil
+          node = attribute.not_between(0...3)
+
+          node.must_equal Nodes::Grouping.new(Nodes::Or.new(
+                                                Nodes::LessThan.new(
+                                                  attribute,
+                                                  Nodes::Casted.new(0, attribute)
+                                                ),
+            Nodes::GreaterThanOrEqual.new(
+              attribute,
+              Nodes::Casted.new(3, attribute)
+            )
+          ))
+        end
+      end
+
+      describe "#not_in" do
+        it "can be constructed with a subquery" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:name].does_not_match_all(["%chunky%", "%bacon%"])
+          attribute = Attribute.new nil, nil
+
+          node = attribute.not_in(mgr)
+
+          node.must_equal Nodes::NotIn.new(attribute, mgr.ast)
+        end
+
+        it "can be constructed with a Union" do
+          relation = Table.new(:users)
+          mgr1 = relation.project(relation[:id])
+          mgr2 = relation.project(relation[:id])
+
+          union = mgr1.union(mgr2)
+          node = relation[:id].in(union)
+          node.to_sql.must_be_like %{
+            "users"."id" IN (( SELECT "users"."id" FROM "users" UNION SELECT "users"."id" FROM "users" ))
+          }
+        end
+
+        it "can be constructed with a list" do
+          attribute = Attribute.new nil, nil
+          node = attribute.not_in([1, 2, 3])
+
+          node.must_equal Nodes::NotIn.new(
+            attribute,
+            [
+              Nodes::Casted.new(1, attribute),
+              Nodes::Casted.new(2, attribute),
+              Nodes::Casted.new(3, attribute),
+            ]
+          )
+        end
+
+        it "can be constructed with a random object" do
+          attribute = Attribute.new nil, nil
+          random_object = Object.new
+          node = attribute.not_in(random_object)
+
+          node.must_equal Nodes::NotIn.new(
+            attribute,
+            Nodes::Casted.new(random_object, attribute)
+          )
+        end
+
+        it "should generate NOT IN in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].not_in([1, 2, 3])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE "users"."id" NOT IN (1, 2, 3)
+          }
+        end
+      end
+
+      describe "#not_in_any" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].not_in_any([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ORs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].not_in_any([[1, 2], [3, 4]])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" NOT IN (1, 2) OR "users"."id" NOT IN (3, 4))
+          }
+        end
+      end
+
+      describe "#not_in_all" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].not_in_all([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ANDs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].not_in_all([[1, 2], [3, 4]])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" NOT IN (1, 2) AND "users"."id" NOT IN (3, 4))
+          }
+        end
+      end
+
+      describe "#eq_all" do
+        it "should create a Grouping node" do
+          relation = Table.new(:users)
+          relation[:id].eq_all([1, 2]).must_be_kind_of Nodes::Grouping
+        end
+
+        it "should generate ANDs in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.where relation[:id].eq_all([1, 2])
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" WHERE ("users"."id" = 1 AND "users"."id" = 2)
+          }
+        end
+      end
+
+      describe "#asc" do
+        it "should create an Ascending node" do
+          relation = Table.new(:users)
+          relation[:id].asc.must_be_kind_of Nodes::Ascending
+        end
+
+        it "should generate ASC in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.order relation[:id].asc
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" ORDER BY "users"."id" ASC
+          }
+        end
+      end
+
+      describe "#desc" do
+        it "should create a Descending node" do
+          relation = Table.new(:users)
+          relation[:id].desc.must_be_kind_of Nodes::Descending
+        end
+
+        it "should generate DESC in sql" do
+          relation = Table.new(:users)
+          mgr = relation.project relation[:id]
+          mgr.order relation[:id].desc
+          mgr.to_sql.must_be_like %{
+            SELECT "users"."id" FROM "users" ORDER BY "users"."id" DESC
+          }
+        end
+      end
+
+      describe "equality" do
+        describe "#to_sql" do
+          it "should produce sql" do
+            table = Table.new :users
+            condition = table["id"].eq 1
+            condition.to_sql.must_equal '"users"."id" = 1'
+          end
+        end
+      end
+
+      describe "type casting" do
+        it "does not type cast by default" do
+          table = Table.new(:foo)
+          condition = table["id"].eq("1")
+
+          assert_not table.able_to_type_cast?
+          condition.to_sql.must_equal %("foo"."id" = '1')
+        end
+
+        it "type casts when given an explicit caster" do
+          fake_caster = Object.new
+          def fake_caster.type_cast_for_database(attr_name, value)
+            if attr_name == "id"
+              value.to_i
+            else
+              value
+            end
+          end
+          table = Table.new(:foo, type_caster: fake_caster)
+          condition = table["id"].eq("1").and(table["other_id"].eq("2"))
+
+          assert table.able_to_type_cast?
+          condition.to_sql.must_equal %("foo"."id" = 1 AND "foo"."other_id" = '2')
+        end
+
+        it "does not type cast SqlLiteral nodes" do
+          fake_caster = Object.new
+          def fake_caster.type_cast_for_database(attr_name, value)
+            value.to_i
+          end
+          table = Table.new(:foo, type_caster: fake_caster)
+          condition = table["id"].eq(Arel.sql("(select 1)"))
+
+          assert table.able_to_type_cast?
+          condition.to_sql.must_equal %("foo"."id" = (select 1))
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/attributes/math_test.rb b/activerecord/test/cases/arel/attributes/math_test.rb
new file mode 100644
index 0000000000..f3aabe4f60
--- /dev/null
+++ b/activerecord/test/cases/arel/attributes/math_test.rb
@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Attributes
+    class MathTest < Arel::Spec
+      %i[* /].each do |math_operator|
+        it "average should be compatiable with #{math_operator}" do
+          table = Arel::Table.new :users
+          (table[:id].average.public_send(math_operator, 2)).to_sql.must_be_like %{
+            AVG("users"."id") #{math_operator} 2
+          }
+        end
+
+        it "count should be compatiable with #{math_operator}" do
+          table = Arel::Table.new :users
+          (table[:id].count.public_send(math_operator, 2)).to_sql.must_be_like %{
+            COUNT("users"."id") #{math_operator} 2
+          }
+        end
+
+        it "maximum should be compatiable with #{math_operator}" do
+          table = Arel::Table.new :users
+          (table[:id].maximum.public_send(math_operator, 2)).to_sql.must_be_like %{
+            MAX("users"."id") #{math_operator} 2
+          }
+        end
+
+        it "minimum should be compatiable with #{math_operator}" do
+          table = Arel::Table.new :users
+          (table[:id].minimum.public_send(math_operator, 2)).to_sql.must_be_like %{
+            MIN("users"."id") #{math_operator} 2
+          }
+        end
+
+        it "attribute node should be compatiable with #{math_operator}" do
+          table = Arel::Table.new :users
+          (table[:id].public_send(math_operator, 2)).to_sql.must_be_like %{
+            "users"."id" #{math_operator} 2
+          }
+        end
+      end
+
+      %i[+ - & | ^ << >>].each do |math_operator|
+        it "average should be compatiable with #{math_operator}" do
+          table = Arel::Table.new :users
+          (table[:id].average.public_send(math_operator, 2)).to_sql.must_be_like %{
+            (AVG("users"."id") #{math_operator} 2)
+          }
+        end
+
+        it "count should be compatiable with #{math_operator}" do
+          table = Arel::Table.new :users
+          (table[:id].count.public_send(math_operator, 2)).to_sql.must_be_like %{
+            (COUNT("users"."id") #{math_operator} 2)
+          }
+        end
+
+        it "maximum should be compatiable with #{math_operator}" do
+          table = Arel::Table.new :users
+          (table[:id].maximum.public_send(math_operator, 2)).to_sql.must_be_like %{
+            (MAX("users"."id") #{math_operator} 2)
+          }
+        end
+
+        it "minimum should be compatiable with #{math_operator}" do
+          table = Arel::Table.new :users
+          (table[:id].minimum.public_send(math_operator, 2)).to_sql.must_be_like %{
+            (MIN("users"."id") #{math_operator} 2)
+          }
+        end
+
+        it "attribute node should be compatiable with #{math_operator}" do
+          table = Arel::Table.new :users
+          (table[:id].public_send(math_operator, 2)).to_sql.must_be_like %{
+            ("users"."id" #{math_operator} 2)
+          }
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/attributes_test.rb b/activerecord/test/cases/arel/attributes_test.rb
new file mode 100644
index 0000000000..b00af4bd29
--- /dev/null
+++ b/activerecord/test/cases/arel/attributes_test.rb
@@ -0,0 +1,68 @@
+# frozen_string_literal: true
+
+require_relative "helper"
+
+module Arel
+  describe "Attributes" do
+    it "responds to lower" do
+      relation  = Table.new(:users)
+      attribute = relation[:foo]
+      node      = attribute.lower
+      assert_equal "LOWER", node.name
+      assert_equal [attribute], node.expressions
+    end
+
+    describe "equality" do
+      it "is equal with equal ivars" do
+        array = [Attribute.new("foo", "bar"), Attribute.new("foo", "bar")]
+        assert_equal 1, array.uniq.size
+      end
+
+      it "is not equal with different ivars" do
+        array = [Attribute.new("foo", "bar"), Attribute.new("foo", "baz")]
+        assert_equal 2, array.uniq.size
+      end
+    end
+
+    describe "for" do
+      it "deals with unknown column types" do
+        column = Struct.new(:type).new :crazy
+        Attributes.for(column).must_equal Attributes::Undefined
+      end
+
+      it "returns the correct constant for strings" do
+        [:string, :text, :binary].each do |type|
+          column = Struct.new(:type).new type
+          Attributes.for(column).must_equal Attributes::String
+        end
+      end
+
+      it "returns the correct constant for ints" do
+        column = Struct.new(:type).new :integer
+        Attributes.for(column).must_equal Attributes::Integer
+      end
+
+      it "returns the correct constant for floats" do
+        column = Struct.new(:type).new :float
+        Attributes.for(column).must_equal Attributes::Float
+      end
+
+      it "returns the correct constant for decimals" do
+        column = Struct.new(:type).new :decimal
+        Attributes.for(column).must_equal Attributes::Decimal
+      end
+
+      it "returns the correct constant for boolean" do
+        column = Struct.new(:type).new :boolean
+        Attributes.for(column).must_equal Attributes::Boolean
+      end
+
+      it "returns the correct constant for time" do
+        [:date, :datetime, :timestamp, :time].each do |type|
+          column = Struct.new(:type).new type
+          Attributes.for(column).must_equal Attributes::Time
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/collectors/bind_test.rb b/activerecord/test/cases/arel/collectors/bind_test.rb
new file mode 100644
index 0000000000..ffa9b15f66
--- /dev/null
+++ b/activerecord/test/cases/arel/collectors/bind_test.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+require "arel/collectors/bind"
+
+module Arel
+  module Collectors
+    class TestBind < Arel::Test
+      def setup
+        @conn = FakeRecord::Base.new
+        @visitor = Visitors::ToSql.new @conn.connection
+        super
+      end
+
+      def collect(node)
+        @visitor.accept(node, Collectors::Bind.new)
+      end
+
+      def compile(node)
+        collect(node).value
+      end
+
+      def ast_with_binds(bvs)
+        table = Table.new(:users)
+        manager = Arel::SelectManager.new table
+        manager.where(table[:age].eq(Nodes::BindParam.new(bvs.shift)))
+        manager.where(table[:name].eq(Nodes::BindParam.new(bvs.shift)))
+        manager.ast
+      end
+
+      def test_compile_gathers_all_bind_params
+        binds = compile(ast_with_binds(["hello", "world"]))
+        assert_equal ["hello", "world"], binds
+
+        binds = compile(ast_with_binds(["hello2", "world3"]))
+        assert_equal ["hello2", "world3"], binds
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/collectors/composite_test.rb b/activerecord/test/cases/arel/collectors/composite_test.rb
new file mode 100644
index 0000000000..545637496f
--- /dev/null
+++ b/activerecord/test/cases/arel/collectors/composite_test.rb
@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+require "arel/collectors/bind"
+require "arel/collectors/composite"
+
+module Arel
+  module Collectors
+    class TestComposite < Arel::Test
+      def setup
+        @conn = FakeRecord::Base.new
+        @visitor = Visitors::ToSql.new @conn.connection
+        super
+      end
+
+      def collect(node)
+        sql_collector = Collectors::SQLString.new
+        bind_collector = Collectors::Bind.new
+        collector = Collectors::Composite.new(sql_collector, bind_collector)
+        @visitor.accept(node, collector)
+      end
+
+      def compile(node)
+        collect(node).value
+      end
+
+      def ast_with_binds(bvs)
+        table = Table.new(:users)
+        manager = Arel::SelectManager.new table
+        manager.where(table[:age].eq(Nodes::BindParam.new(bvs.shift)))
+        manager.where(table[:name].eq(Nodes::BindParam.new(bvs.shift)))
+        manager.ast
+      end
+
+      def test_composite_collector_performs_multiple_collections_at_once
+        sql, binds = compile(ast_with_binds(["hello", "world"]))
+        assert_equal 'SELECT FROM "users" WHERE "users"."age" = ? AND "users"."name" = ?', sql
+        assert_equal ["hello", "world"], binds
+
+        sql, binds = compile(ast_with_binds(["hello2", "world3"]))
+        assert_equal 'SELECT FROM "users" WHERE "users"."age" = ? AND "users"."name" = ?', sql
+        assert_equal ["hello2", "world3"], binds
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/collectors/sql_string_test.rb b/activerecord/test/cases/arel/collectors/sql_string_test.rb
new file mode 100644
index 0000000000..380573494d
--- /dev/null
+++ b/activerecord/test/cases/arel/collectors/sql_string_test.rb
@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Collectors
+    class TestSqlString < Arel::Test
+      def setup
+        @conn = FakeRecord::Base.new
+        @visitor = Visitors::ToSql.new @conn.connection
+        super
+      end
+
+      def collect(node)
+        @visitor.accept(node, Collectors::SQLString.new)
+      end
+
+      def compile(node)
+        collect(node).value
+      end
+
+      def ast_with_binds(bv)
+        table = Table.new(:users)
+        manager = Arel::SelectManager.new table
+        manager.where(table[:age].eq(bv))
+        manager.where(table[:name].eq(bv))
+        manager.ast
+      end
+
+      def test_compile
+        bv = Nodes::BindParam.new(1)
+        collector = collect ast_with_binds bv
+
+        sql = collector.compile ["hello", "world"]
+        assert_equal 'SELECT FROM "users" WHERE "users"."age" = ? AND "users"."name" = ?', sql
+      end
+
+      def test_returned_sql_uses_utf8_encoding
+        bv = Nodes::BindParam.new(1)
+        collector = collect ast_with_binds bv
+
+        sql = collector.compile ["hello", "world"]
+        assert_equal sql.encoding, Encoding::UTF_8
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/collectors/substitute_bind_collector_test.rb b/activerecord/test/cases/arel/collectors/substitute_bind_collector_test.rb
new file mode 100644
index 0000000000..255c8e79e9
--- /dev/null
+++ b/activerecord/test/cases/arel/collectors/substitute_bind_collector_test.rb
@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+require "arel/collectors/substitute_binds"
+require "arel/collectors/sql_string"
+
+module Arel
+  module Collectors
+    class TestSubstituteBindCollector < Arel::Test
+      def setup
+        @conn = FakeRecord::Base.new
+        @visitor = Visitors::ToSql.new @conn.connection
+        super
+      end
+
+      def ast_with_binds
+        table = Table.new(:users)
+        manager = Arel::SelectManager.new table
+        manager.where(table[:age].eq(Nodes::BindParam.new("hello")))
+        manager.where(table[:name].eq(Nodes::BindParam.new("world")))
+        manager.ast
+      end
+
+      def compile(node, quoter)
+        collector = Collectors::SubstituteBinds.new(quoter, Collectors::SQLString.new)
+        @visitor.accept(node, collector).value
+      end
+
+      def test_compile
+        quoter = Object.new
+        def quoter.quote(val)
+          val.to_s
+        end
+        sql = compile(ast_with_binds, quoter)
+        assert_equal 'SELECT FROM "users" WHERE "users"."age" = hello AND "users"."name" = world', sql
+      end
+
+      def test_quoting_is_delegated_to_quoter
+        quoter = Object.new
+        def quoter.quote(val)
+          val.inspect
+        end
+        sql = compile(ast_with_binds, quoter)
+        assert_equal 'SELECT FROM "users" WHERE "users"."age" = "hello" AND "users"."name" = "world"', sql
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/crud_test.rb b/activerecord/test/cases/arel/crud_test.rb
new file mode 100644
index 0000000000..f3cdd8927f
--- /dev/null
+++ b/activerecord/test/cases/arel/crud_test.rb
@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+require_relative "helper"
+
+module Arel
+  class FakeCrudder < SelectManager
+    class FakeEngine
+      attr_reader :calls, :connection_pool, :spec, :config
+
+      def initialize
+        @calls = []
+        @connection_pool = self
+        @spec = self
+        @config = { adapter: "sqlite3" }
+      end
+
+      def connection; self end
+
+      def method_missing(name, *args)
+        @calls << [name, args]
+      end
+    end
+
+    include Crud
+
+    attr_reader :engine
+    attr_accessor :ctx
+
+    def initialize(engine = FakeEngine.new)
+      super
+    end
+  end
+
+  describe "crud" do
+    describe "insert" do
+      it "should call insert on the connection" do
+        table = Table.new :users
+        fc = FakeCrudder.new
+        fc.from table
+        im = fc.compile_insert [[table[:id], "foo"]]
+        assert_instance_of Arel::InsertManager, im
+      end
+    end
+
+    describe "update" do
+      it "should call update on the connection" do
+        table = Table.new :users
+        fc = FakeCrudder.new
+        fc.from table
+        stmt = fc.compile_update [[table[:id], "foo"]], Arel::Attributes::Attribute.new(table, "id")
+        assert_instance_of Arel::UpdateManager, stmt
+      end
+    end
+
+    describe "delete" do
+      it "should call delete on the connection" do
+        table = Table.new :users
+        fc = FakeCrudder.new
+        fc.from table
+        stmt = fc.compile_delete
+        assert_instance_of Arel::DeleteManager, stmt
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/delete_manager_test.rb b/activerecord/test/cases/arel/delete_manager_test.rb
new file mode 100644
index 0000000000..17a5271039
--- /dev/null
+++ b/activerecord/test/cases/arel/delete_manager_test.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+require_relative "helper"
+
+module Arel
+  class DeleteManagerTest < Arel::Spec
+    describe "new" do
+      it "takes an engine" do
+        Arel::DeleteManager.new
+      end
+    end
+
+    it "handles limit properly" do
+      table = Table.new(:users)
+      dm = Arel::DeleteManager.new
+      dm.take 10
+      dm.from table
+      assert_match(/LIMIT 10/, dm.to_sql)
+    end
+
+    describe "from" do
+      it "uses from" do
+        table = Table.new(:users)
+        dm = Arel::DeleteManager.new
+        dm.from table
+        dm.to_sql.must_be_like %{ DELETE FROM "users" }
+      end
+
+      it "chains" do
+        table = Table.new(:users)
+        dm = Arel::DeleteManager.new
+        dm.from(table).must_equal dm
+      end
+    end
+
+    describe "where" do
+      it "uses where values" do
+        table = Table.new(:users)
+        dm = Arel::DeleteManager.new
+        dm.from table
+        dm.where table[:id].eq(10)
+        dm.to_sql.must_be_like %{ DELETE FROM "users" WHERE "users"."id" = 10}
+      end
+
+      it "chains" do
+        table = Table.new(:users)
+        dm = Arel::DeleteManager.new
+        dm.where(table[:id].eq(10)).must_equal dm
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/factory_methods_test.rb b/activerecord/test/cases/arel/factory_methods_test.rb
new file mode 100644
index 0000000000..26d2cdd08d
--- /dev/null
+++ b/activerecord/test/cases/arel/factory_methods_test.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require_relative "helper"
+
+module Arel
+  module FactoryMethods
+    class TestFactoryMethods < Arel::Test
+      class Factory
+        include Arel::FactoryMethods
+      end
+
+      def setup
+        @factory = Factory.new
+      end
+
+      def test_create_join
+        join = @factory.create_join :one, :two
+        assert_kind_of Nodes::Join, join
+        assert_equal :two, join.right
+      end
+
+      def test_create_on
+        on = @factory.create_on :one
+        assert_instance_of Nodes::On, on
+        assert_equal :one, on.expr
+      end
+
+      def test_create_true
+        true_node = @factory.create_true
+        assert_instance_of Nodes::True, true_node
+      end
+
+      def test_create_false
+        false_node = @factory.create_false
+        assert_instance_of Nodes::False, false_node
+      end
+
+      def test_lower
+        lower = @factory.lower :one
+        assert_instance_of Nodes::NamedFunction, lower
+        assert_equal "LOWER", lower.name
+        assert_equal [:one], lower.expressions.map(&:expr)
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/helper.rb b/activerecord/test/cases/arel/helper.rb
new file mode 100644
index 0000000000..f8ce658440
--- /dev/null
+++ b/activerecord/test/cases/arel/helper.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+require "active_support"
+require "minitest/autorun"
+require "arel"
+
+require_relative "support/fake_record"
+
+class Object
+  def must_be_like(other)
+    gsub(/\s+/, " ").strip.must_equal other.gsub(/\s+/, " ").strip
+  end
+end
+
+module Arel
+  class Test < ActiveSupport::TestCase
+    def setup
+      super
+      @arel_engine = Arel::Table.engine
+      Arel::Table.engine = FakeRecord::Base.new
+    end
+
+    def teardown
+      Arel::Table.engine = @arel_engine if defined? @arel_engine
+      super
+    end
+  end
+
+  class Spec < Minitest::Spec
+    before do
+      @arel_engine = Arel::Table.engine
+      Arel::Table.engine = FakeRecord::Base.new
+    end
+
+    after do
+      Arel::Table.engine = @arel_engine if defined? @arel_engine
+    end
+    include ActiveSupport::Testing::Assertions
+
+    # test/unit backwards compatibility methods
+    alias :assert_no_match :refute_match
+    alias :assert_not_equal :refute_equal
+    alias :assert_not_same :refute_same
+  end
+end
diff --git a/activerecord/test/cases/arel/insert_manager_test.rb b/activerecord/test/cases/arel/insert_manager_test.rb
new file mode 100644
index 0000000000..ae10ccf56c
--- /dev/null
+++ b/activerecord/test/cases/arel/insert_manager_test.rb
@@ -0,0 +1,244 @@
+# frozen_string_literal: true
+
+require_relative "helper"
+
+module Arel
+  class InsertManagerTest < Arel::Spec
+    describe "new" do
+      it "takes an engine" do
+        Arel::InsertManager.new
+      end
+    end
+
+    describe "insert" do
+      it "can create a Values node" do
+        manager = Arel::InsertManager.new
+        values  = manager.create_values %w{ a b }, %w{ c d }
+
+        assert_kind_of Arel::Nodes::Values, values
+        assert_equal %w{ a b }, values.left
+        assert_equal %w{ c d }, values.right
+      end
+
+      it "allows sql literals" do
+        manager = Arel::InsertManager.new
+        manager.into Table.new(:users)
+        manager.values = manager.create_values [Arel.sql("*")], %w{ a }
+        manager.to_sql.must_be_like %{
+          INSERT INTO \"users\" VALUES (*)
+        }
+      end
+
+      it "works with multiple values" do
+        table = Table.new(:users)
+        manager = Arel::InsertManager.new
+        manager.into table
+
+        manager.columns << table[:id]
+        manager.columns << table[:name]
+
+        manager.values = manager.create_values_list([
+          %w{1 david},
+          %w{2 kir},
+          ["3", Arel.sql("DEFAULT")],
+        ])
+
+        manager.to_sql.must_be_like %{
+          INSERT INTO \"users\" (\"id\", \"name\") VALUES ('1', 'david'), ('2', 'kir'), ('3', DEFAULT)
+        }
+      end
+
+      it "literals in multiple values are not escaped" do
+        table = Table.new(:users)
+        manager = Arel::InsertManager.new
+        manager.into table
+
+        manager.columns << table[:name]
+
+        manager.values = manager.create_values_list([
+          [Arel.sql("*")],
+          [Arel.sql("DEFAULT")],
+        ])
+
+        manager.to_sql.must_be_like %{
+          INSERT INTO \"users\" (\"name\") VALUES (*), (DEFAULT)
+        }
+      end
+
+      it "works with multiple single values" do
+        table = Table.new(:users)
+        manager = Arel::InsertManager.new
+        manager.into table
+
+        manager.columns << table[:name]
+
+        manager.values = manager.create_values_list([
+          %w{david},
+          %w{kir},
+          [Arel.sql("DEFAULT")],
+        ])
+
+        manager.to_sql.must_be_like %{
+          INSERT INTO \"users\" (\"name\") VALUES ('david'), ('kir'), (DEFAULT)
+        }
+      end
+
+      it "inserts false" do
+        table = Table.new(:users)
+        manager = Arel::InsertManager.new
+
+        manager.insert [[table[:bool], false]]
+        manager.to_sql.must_be_like %{
+          INSERT INTO "users" ("bool") VALUES ('f')
+        }
+      end
+
+      it "inserts null" do
+        table = Table.new(:users)
+        manager = Arel::InsertManager.new
+        manager.insert [[table[:id], nil]]
+        manager.to_sql.must_be_like %{
+          INSERT INTO "users" ("id") VALUES (NULL)
+        }
+      end
+
+      it "inserts time" do
+        table = Table.new(:users)
+        manager = Arel::InsertManager.new
+
+        time = Time.now
+        attribute = table[:created_at]
+
+        manager.insert [[attribute, time]]
+        manager.to_sql.must_be_like %{
+          INSERT INTO "users" ("created_at") VALUES (#{Table.engine.connection.quote time})
+        }
+      end
+
+      it "takes a list of lists" do
+        table = Table.new(:users)
+        manager = Arel::InsertManager.new
+        manager.into table
+        manager.insert [[table[:id], 1], [table[:name], "aaron"]]
+        manager.to_sql.must_be_like %{
+          INSERT INTO "users" ("id", "name") VALUES (1, 'aaron')
+        }
+      end
+
+      it "defaults the table" do
+        table = Table.new(:users)
+        manager = Arel::InsertManager.new
+        manager.insert [[table[:id], 1], [table[:name], "aaron"]]
+        manager.to_sql.must_be_like %{
+          INSERT INTO "users" ("id", "name") VALUES (1, 'aaron')
+        }
+      end
+
+      it "noop for empty list" do
+        table = Table.new(:users)
+        manager = Arel::InsertManager.new
+        manager.insert [[table[:id], 1]]
+        manager.insert []
+        manager.to_sql.must_be_like %{
+          INSERT INTO "users" ("id") VALUES (1)
+        }
+      end
+
+      it "is chainable" do
+        table = Table.new(:users)
+        manager = Arel::InsertManager.new
+        insert_result = manager.insert [[table[:id], 1]]
+        assert_equal manager, insert_result
+      end
+    end
+
+    describe "into" do
+      it "takes a Table and chains" do
+        manager = Arel::InsertManager.new
+        manager.into(Table.new(:users)).must_equal manager
+      end
+
+      it "converts to sql" do
+        table   = Table.new :users
+        manager = Arel::InsertManager.new
+        manager.into table
+        manager.to_sql.must_be_like %{
+          INSERT INTO "users"
+        }
+      end
+    end
+
+    describe "columns" do
+      it "converts to sql" do
+        table   = Table.new :users
+        manager = Arel::InsertManager.new
+        manager.into table
+        manager.columns << table[:id]
+        manager.to_sql.must_be_like %{
+          INSERT INTO "users" ("id")
+        }
+      end
+    end
+
+    describe "values" do
+      it "converts to sql" do
+        table   = Table.new :users
+        manager = Arel::InsertManager.new
+        manager.into table
+
+        manager.values = Nodes::Values.new [1]
+        manager.to_sql.must_be_like %{
+          INSERT INTO "users" VALUES (1)
+        }
+      end
+
+      it "accepts sql literals" do
+        table   = Table.new :users
+        manager = Arel::InsertManager.new
+        manager.into table
+
+        manager.values = Arel.sql("DEFAULT VALUES")
+        manager.to_sql.must_be_like %{
+          INSERT INTO "users" DEFAULT VALUES
+        }
+      end
+    end
+
+    describe "combo" do
+      it "combines columns and values list in order" do
+        table   = Table.new :users
+        manager = Arel::InsertManager.new
+        manager.into table
+
+        manager.values = Nodes::Values.new [1, "aaron"]
+        manager.columns << table[:id]
+        manager.columns << table[:name]
+        manager.to_sql.must_be_like %{
+          INSERT INTO "users" ("id", "name") VALUES (1, 'aaron')
+        }
+      end
+    end
+
+    describe "select" do
+
+      it "accepts a select query in place of a VALUES clause" do
+        table   = Table.new :users
+
+        manager = Arel::InsertManager.new
+        manager.into table
+
+        select = Arel::SelectManager.new
+        select.project Arel.sql("1")
+        select.project Arel.sql('"aaron"')
+
+        manager.select select
+        manager.columns << table[:id]
+        manager.columns << table[:name]
+        manager.to_sql.must_be_like %{
+          INSERT INTO "users" ("id", "name") (SELECT 1, "aaron")
+        }
+      end
+
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/and_test.rb b/activerecord/test/cases/arel/nodes/and_test.rb
new file mode 100644
index 0000000000..eff54abd91
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/and_test.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    describe "And" do
+      describe "equality" do
+        it "is equal with equal ivars" do
+          array = [And.new(["foo", "bar"]), And.new(["foo", "bar"])]
+          assert_equal 1, array.uniq.size
+        end
+
+        it "is not equal with different ivars" do
+          array = [And.new(["foo", "bar"]), And.new(["foo", "baz"])]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/as_test.rb b/activerecord/test/cases/arel/nodes/as_test.rb
new file mode 100644
index 0000000000..1169ea11c9
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/as_test.rb
@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    describe "As" do
+      describe "#as" do
+        it "makes an AS node" do
+          attr = Table.new(:users)[:id]
+          as = attr.as(Arel.sql("foo"))
+          assert_equal attr, as.left
+          assert_equal "foo", as.right
+        end
+
+        it "converts right to SqlLiteral if a string" do
+          attr = Table.new(:users)[:id]
+          as = attr.as("foo")
+          assert_kind_of Arel::Nodes::SqlLiteral, as.right
+        end
+      end
+
+      describe "equality" do
+        it "is equal with equal ivars" do
+          array = [As.new("foo", "bar"), As.new("foo", "bar")]
+          assert_equal 1, array.uniq.size
+        end
+
+        it "is not equal with different ivars" do
+          array = [As.new("foo", "bar"), As.new("foo", "baz")]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/ascending_test.rb b/activerecord/test/cases/arel/nodes/ascending_test.rb
new file mode 100644
index 0000000000..4811e6ff5b
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/ascending_test.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    class TestAscending < Arel::Test
+      def test_construct
+        ascending = Ascending.new "zomg"
+        assert_equal "zomg", ascending.expr
+      end
+
+      def test_reverse
+        ascending = Ascending.new "zomg"
+        descending = ascending.reverse
+        assert_kind_of Descending, descending
+        assert_equal ascending.expr, descending.expr
+      end
+
+      def test_direction
+        ascending = Ascending.new "zomg"
+        assert_equal :asc, ascending.direction
+      end
+
+      def test_ascending?
+        ascending = Ascending.new "zomg"
+        assert ascending.ascending?
+      end
+
+      def test_descending?
+        ascending = Ascending.new "zomg"
+        assert_not ascending.descending?
+      end
+
+      def test_equality_with_same_ivars
+        array = [Ascending.new("zomg"), Ascending.new("zomg")]
+        assert_equal 1, array.uniq.size
+      end
+
+      def test_inequality_with_different_ivars
+        array = [Ascending.new("zomg"), Ascending.new("zomg!")]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/bin_test.rb b/activerecord/test/cases/arel/nodes/bin_test.rb
new file mode 100644
index 0000000000..ee2ec3cf2f
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/bin_test.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    class TestBin < Arel::Test
+      def test_new
+        assert Arel::Nodes::Bin.new("zomg")
+      end
+
+      def test_default_to_sql
+        viz  = Arel::Visitors::ToSql.new Table.engine.connection_pool
+        node = Arel::Nodes::Bin.new(Arel.sql("zomg"))
+        assert_equal "zomg", viz.accept(node, Collectors::SQLString.new).value
+      end
+
+      def test_mysql_to_sql
+        viz  = Arel::Visitors::MySQL.new Table.engine.connection_pool
+        node = Arel::Nodes::Bin.new(Arel.sql("zomg"))
+        assert_equal "BINARY zomg", viz.accept(node, Collectors::SQLString.new).value
+      end
+
+      def test_equality_with_same_ivars
+        array = [Bin.new("zomg"), Bin.new("zomg")]
+        assert_equal 1, array.uniq.size
+      end
+
+      def test_inequality_with_different_ivars
+        array = [Bin.new("zomg"), Bin.new("zomg!")]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/binary_test.rb b/activerecord/test/cases/arel/nodes/binary_test.rb
new file mode 100644
index 0000000000..d160e7cd9d
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/binary_test.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    class NodesTest < Arel::Spec
+      describe "Binary" do
+        describe "#hash" do
+          it "generates a hash based on its value" do
+            eq = Equality.new("foo", "bar")
+            eq2 = Equality.new("foo", "bar")
+            eq3 = Equality.new("bar", "baz")
+
+            assert_equal eq.hash, eq2.hash
+            assert_not_equal eq.hash, eq3.hash
+          end
+
+          it "generates a hash specific to its class" do
+            eq = Equality.new("foo", "bar")
+            neq = NotEqual.new("foo", "bar")
+
+            assert_not_equal eq.hash, neq.hash
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/bind_param_test.rb b/activerecord/test/cases/arel/nodes/bind_param_test.rb
new file mode 100644
index 0000000000..37a362ece4
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/bind_param_test.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    describe "BindParam" do
+      it "is equal to other bind params with the same value" do
+        BindParam.new(1).must_equal(BindParam.new(1))
+        BindParam.new("foo").must_equal(BindParam.new("foo"))
+      end
+
+      it "is not equal to other nodes" do
+        BindParam.new(nil).wont_equal(Node.new)
+      end
+
+      it "is not equal to bind params with different values" do
+        BindParam.new(1).wont_equal(BindParam.new(2))
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/case_test.rb b/activerecord/test/cases/arel/nodes/case_test.rb
new file mode 100644
index 0000000000..89861488df
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/case_test.rb
@@ -0,0 +1,86 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    class NodesTest < Arel::Spec
+      describe "Case" do
+        describe "#initialize" do
+          it "sets case expression from first argument" do
+            node = Case.new "foo"
+
+            assert_equal "foo", node.case
+          end
+
+          it "sets default case from second argument" do
+            node = Case.new nil, "bar"
+
+            assert_equal "bar", node.default
+          end
+        end
+
+        describe "#clone" do
+          it "clones case, conditions and default" do
+            foo = Nodes.build_quoted "foo"
+
+            node = Case.new
+            node.case = foo
+            node.conditions = [When.new(foo, foo)]
+            node.default = foo
+
+            dolly = node.clone
+
+            assert_equal dolly.case, node.case
+            assert_not_same dolly.case, node.case
+
+            assert_equal dolly.conditions, node.conditions
+            assert_not_same dolly.conditions, node.conditions
+
+            assert_equal dolly.default, node.default
+            assert_not_same dolly.default, node.default
+          end
+        end
+
+        describe "equality" do
+          it "is equal with equal ivars" do
+            foo = Nodes.build_quoted "foo"
+            one = Nodes.build_quoted 1
+            zero = Nodes.build_quoted 0
+
+            case1 = Case.new foo
+            case1.conditions = [When.new(foo, one)]
+            case1.default = Else.new zero
+
+            case2 = Case.new foo
+            case2.conditions = [When.new(foo, one)]
+            case2.default = Else.new zero
+
+            array = [case1, case2]
+
+            assert_equal 1, array.uniq.size
+          end
+
+          it "is not equal with different ivars" do
+            foo = Nodes.build_quoted "foo"
+            bar = Nodes.build_quoted "bar"
+            one = Nodes.build_quoted 1
+            zero = Nodes.build_quoted 0
+
+            case1 = Case.new foo
+            case1.conditions = [When.new(foo, one)]
+            case1.default = Else.new zero
+
+            case2 = Case.new foo
+            case2.conditions = [When.new(bar, one)]
+            case2.default = Else.new zero
+
+            array = [case1, case2]
+
+            assert_equal 2, array.uniq.size
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/casted_test.rb b/activerecord/test/cases/arel/nodes/casted_test.rb
new file mode 100644
index 0000000000..e27f58a4e2
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/casted_test.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    describe Casted do
+      describe "#hash" do
+        it "is equal when eql? returns true" do
+          one = Casted.new 1, 2
+          also_one = Casted.new 1, 2
+
+          assert_equal one.hash, also_one.hash
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/count_test.rb b/activerecord/test/cases/arel/nodes/count_test.rb
new file mode 100644
index 0000000000..daabea6c4c
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/count_test.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+class Arel::Nodes::CountTest < Arel::Spec
+  describe "as" do
+    it "should alias the count" do
+      table = Arel::Table.new :users
+      table[:id].count.as("foo").to_sql.must_be_like %{
+        COUNT("users"."id") AS foo
+      }
+    end
+  end
+
+  describe "eq" do
+    it "should compare the count" do
+      table = Arel::Table.new :users
+      table[:id].count.eq(2).to_sql.must_be_like %{
+        COUNT("users"."id") = 2
+      }
+    end
+  end
+
+  describe "equality" do
+    it "is equal with equal ivars" do
+      array = [Arel::Nodes::Count.new("foo"), Arel::Nodes::Count.new("foo")]
+      assert_equal 1, array.uniq.size
+    end
+
+    it "is not equal with different ivars" do
+      array = [Arel::Nodes::Count.new("foo"), Arel::Nodes::Count.new("foo!")]
+      assert_equal 2, array.uniq.size
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/delete_statement_test.rb b/activerecord/test/cases/arel/nodes/delete_statement_test.rb
new file mode 100644
index 0000000000..3f078063a4
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/delete_statement_test.rb
@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+describe Arel::Nodes::DeleteStatement do
+  describe "#clone" do
+    it "clones wheres" do
+      statement = Arel::Nodes::DeleteStatement.new
+      statement.wheres = %w[a b c]
+
+      dolly = statement.clone
+      dolly.wheres.must_equal statement.wheres
+      dolly.wheres.wont_be_same_as statement.wheres
+    end
+  end
+
+  describe "equality" do
+    it "is equal with equal ivars" do
+      statement1 = Arel::Nodes::DeleteStatement.new
+      statement1.wheres = %w[a b c]
+      statement2 = Arel::Nodes::DeleteStatement.new
+      statement2.wheres = %w[a b c]
+      array = [statement1, statement2]
+      assert_equal 1, array.uniq.size
+    end
+
+    it "is not equal with different ivars" do
+      statement1 = Arel::Nodes::DeleteStatement.new
+      statement1.wheres = %w[a b c]
+      statement2 = Arel::Nodes::DeleteStatement.new
+      statement2.wheres = %w[1 2 3]
+      array = [statement1, statement2]
+      assert_equal 2, array.uniq.size
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/descending_test.rb b/activerecord/test/cases/arel/nodes/descending_test.rb
new file mode 100644
index 0000000000..5f1747e1da
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/descending_test.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    class TestDescending < Arel::Test
+      def test_construct
+        descending = Descending.new "zomg"
+        assert_equal "zomg", descending.expr
+      end
+
+      def test_reverse
+        descending = Descending.new "zomg"
+        ascending = descending.reverse
+        assert_kind_of Ascending, ascending
+        assert_equal descending.expr, ascending.expr
+      end
+
+      def test_direction
+        descending = Descending.new "zomg"
+        assert_equal :desc, descending.direction
+      end
+
+      def test_ascending?
+        descending = Descending.new "zomg"
+        assert_not descending.ascending?
+      end
+
+      def test_descending?
+        descending = Descending.new "zomg"
+        assert descending.descending?
+      end
+
+      def test_equality_with_same_ivars
+        array = [Descending.new("zomg"), Descending.new("zomg")]
+        assert_equal 1, array.uniq.size
+      end
+
+      def test_inequality_with_different_ivars
+        array = [Descending.new("zomg"), Descending.new("zomg!")]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/distinct_test.rb b/activerecord/test/cases/arel/nodes/distinct_test.rb
new file mode 100644
index 0000000000..de5f0ee588
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/distinct_test.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    describe "Distinct" do
+      describe "equality" do
+        it "is equal to other distinct nodes" do
+          array = [Distinct.new, Distinct.new]
+          assert_equal 1, array.uniq.size
+        end
+
+        it "is not equal with other nodes" do
+          array = [Distinct.new, Node.new]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/equality_test.rb b/activerecord/test/cases/arel/nodes/equality_test.rb
new file mode 100644
index 0000000000..e173720e86
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/equality_test.rb
@@ -0,0 +1,86 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    describe "equality" do
+      # FIXME: backwards compat
+      describe "backwards compat" do
+        describe "operator" do
+          it "returns :==" do
+            attr = Table.new(:users)[:id]
+            left = attr.eq(10)
+            left.operator.must_equal :==
+          end
+        end
+
+        describe "operand1" do
+          it "should equal left" do
+            attr = Table.new(:users)[:id]
+            left = attr.eq(10)
+            left.left.must_equal left.operand1
+          end
+        end
+
+        describe "operand2" do
+          it "should equal right" do
+            attr = Table.new(:users)[:id]
+            left = attr.eq(10)
+            left.right.must_equal left.operand2
+          end
+        end
+
+        describe "to_sql" do
+          it "takes an engine" do
+            engine = FakeRecord::Base.new
+            engine.connection.extend Module.new {
+              attr_accessor :quote_count
+              def quote(*args) @quote_count += 1; super; end
+              def quote_column_name(*args) @quote_count += 1; super; end
+              def quote_table_name(*args) @quote_count += 1; super; end
+            }
+            engine.connection.quote_count = 0
+
+            attr = Table.new(:users)[:id]
+            test = attr.eq(10)
+            test.to_sql engine
+            engine.connection.quote_count.must_equal 3
+          end
+        end
+      end
+
+      describe "or" do
+        it "makes an OR node" do
+          attr = Table.new(:users)[:id]
+          left  = attr.eq(10)
+          right = attr.eq(11)
+          node  = left.or right
+          node.expr.left.must_equal left
+          node.expr.right.must_equal right
+        end
+      end
+
+      describe "and" do
+        it "makes and AND node" do
+          attr = Table.new(:users)[:id]
+          left  = attr.eq(10)
+          right = attr.eq(11)
+          node  = left.and right
+          node.left.must_equal left
+          node.right.must_equal right
+        end
+      end
+
+      it "is equal with equal ivars" do
+        array = [Equality.new("foo", "bar"), Equality.new("foo", "bar")]
+        assert_equal 1, array.uniq.size
+      end
+
+      it "is not equal with different ivars" do
+        array = [Equality.new("foo", "bar"), Equality.new("foo", "baz")]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/extract_test.rb b/activerecord/test/cases/arel/nodes/extract_test.rb
new file mode 100644
index 0000000000..8fc1e04d67
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/extract_test.rb
@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+class Arel::Nodes::ExtractTest < Arel::Spec
+  it "should extract field" do
+    table = Arel::Table.new :users
+    table[:timestamp].extract("date").to_sql.must_be_like %{
+      EXTRACT(DATE FROM "users"."timestamp")
+    }
+  end
+
+  describe "as" do
+    it "should alias the extract" do
+      table = Arel::Table.new :users
+      table[:timestamp].extract("date").as("foo").to_sql.must_be_like %{
+        EXTRACT(DATE FROM "users"."timestamp") AS foo
+      }
+    end
+
+    it "should not mutate the extract" do
+      table = Arel::Table.new :users
+      extract = table[:timestamp].extract("date")
+      before = extract.dup
+      extract.as("foo")
+      assert_equal extract, before
+    end
+  end
+
+  describe "equality" do
+    it "is equal with equal ivars" do
+      table = Arel::Table.new :users
+      array = [table[:attr].extract("foo"), table[:attr].extract("foo")]
+      assert_equal 1, array.uniq.size
+    end
+
+    it "is not equal with different ivars" do
+      table = Arel::Table.new :users
+      array = [table[:attr].extract("foo"), table[:attr].extract("bar")]
+      assert_equal 2, array.uniq.size
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/false_test.rb b/activerecord/test/cases/arel/nodes/false_test.rb
new file mode 100644
index 0000000000..4ecf8e332e
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/false_test.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    describe "False" do
+      describe "equality" do
+        it "is equal to other false nodes" do
+          array = [False.new, False.new]
+          assert_equal 1, array.uniq.size
+        end
+
+        it "is not equal with other nodes" do
+          array = [False.new, Node.new]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/grouping_test.rb b/activerecord/test/cases/arel/nodes/grouping_test.rb
new file mode 100644
index 0000000000..03d5c142d5
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/grouping_test.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    class GroupingTest < Arel::Spec
+      it "should create Equality nodes" do
+        grouping = Grouping.new(Nodes.build_quoted("foo"))
+        grouping.eq("foo").to_sql.must_be_like "('foo') = 'foo'"
+      end
+
+      describe "equality" do
+        it "is equal with equal ivars" do
+          array = [Grouping.new("foo"), Grouping.new("foo")]
+          assert_equal 1, array.uniq.size
+        end
+
+        it "is not equal with different ivars" do
+          array = [Grouping.new("foo"), Grouping.new("bar")]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/infix_operation_test.rb b/activerecord/test/cases/arel/nodes/infix_operation_test.rb
new file mode 100644
index 0000000000..dcf2200c12
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/infix_operation_test.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    class TestInfixOperation < Arel::Test
+      def test_construct
+        operation = InfixOperation.new :+, 1, 2
+        assert_equal :+, operation.operator
+        assert_equal 1, operation.left
+        assert_equal 2, operation.right
+      end
+
+      def test_operation_alias
+        operation = InfixOperation.new :+, 1, 2
+        aliaz = operation.as("zomg")
+        assert_kind_of As, aliaz
+        assert_equal operation, aliaz.left
+        assert_equal "zomg", aliaz.right
+      end
+
+      def test_operation_ordering
+        operation = InfixOperation.new :+, 1, 2
+        ordering = operation.desc
+        assert_kind_of Descending, ordering
+        assert_equal operation, ordering.expr
+        assert ordering.descending?
+      end
+
+      def test_equality_with_same_ivars
+        array = [InfixOperation.new(:+, 1, 2), InfixOperation.new(:+, 1, 2)]
+        assert_equal 1, array.uniq.size
+      end
+
+      def test_inequality_with_different_ivars
+        array = [InfixOperation.new(:+, 1, 2), InfixOperation.new(:+, 1, 3)]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/insert_statement_test.rb b/activerecord/test/cases/arel/nodes/insert_statement_test.rb
new file mode 100644
index 0000000000..252a0d0d0b
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/insert_statement_test.rb
@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+describe Arel::Nodes::InsertStatement do
+  describe "#clone" do
+    it "clones columns and values" do
+      statement = Arel::Nodes::InsertStatement.new
+      statement.columns = %w[a b c]
+      statement.values  = %w[x y z]
+
+      dolly = statement.clone
+      dolly.columns.must_equal statement.columns
+      dolly.values.must_equal statement.values
+
+      dolly.columns.wont_be_same_as statement.columns
+      dolly.values.wont_be_same_as statement.values
+    end
+  end
+
+  describe "equality" do
+    it "is equal with equal ivars" do
+      statement1 = Arel::Nodes::InsertStatement.new
+      statement1.columns = %w[a b c]
+      statement1.values  = %w[x y z]
+      statement2 = Arel::Nodes::InsertStatement.new
+      statement2.columns = %w[a b c]
+      statement2.values  = %w[x y z]
+      array = [statement1, statement2]
+      assert_equal 1, array.uniq.size
+    end
+
+    it "is not equal with different ivars" do
+      statement1 = Arel::Nodes::InsertStatement.new
+      statement1.columns = %w[a b c]
+      statement1.values  = %w[x y z]
+      statement2 = Arel::Nodes::InsertStatement.new
+      statement2.columns = %w[a b c]
+      statement2.values  = %w[1 2 3]
+      array = [statement1, statement2]
+      assert_equal 2, array.uniq.size
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/named_function_test.rb b/activerecord/test/cases/arel/nodes/named_function_test.rb
new file mode 100644
index 0000000000..dbd7ae43be
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/named_function_test.rb
@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    class TestNamedFunction < Arel::Test
+      def test_construct
+        function = NamedFunction.new "omg", "zomg"
+        assert_equal "omg", function.name
+        assert_equal "zomg", function.expressions
+      end
+
+      def test_function_alias
+        function = NamedFunction.new "omg", "zomg"
+        function = function.as("wth")
+        assert_equal "omg", function.name
+        assert_equal "zomg", function.expressions
+        assert_kind_of SqlLiteral, function.alias
+        assert_equal "wth", function.alias
+      end
+
+      def test_construct_with_alias
+        function = NamedFunction.new "omg", "zomg", "wth"
+        assert_equal "omg", function.name
+        assert_equal "zomg", function.expressions
+        assert_kind_of SqlLiteral, function.alias
+        assert_equal "wth", function.alias
+      end
+
+      def test_equality_with_same_ivars
+        array = [
+          NamedFunction.new("omg", "zomg", "wth"),
+          NamedFunction.new("omg", "zomg", "wth")
+        ]
+        assert_equal 1, array.uniq.size
+      end
+
+      def test_inequality_with_different_ivars
+        array = [
+          NamedFunction.new("omg", "zomg", "wth"),
+          NamedFunction.new("zomg", "zomg", "wth")
+        ]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/node_test.rb b/activerecord/test/cases/arel/nodes/node_test.rb
new file mode 100644
index 0000000000..f4f07ef2c5
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/node_test.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  class TestNode < Arel::Test
+    def test_includes_factory_methods
+      assert Node.new.respond_to?(:create_join)
+    end
+
+    def test_all_nodes_are_nodes
+      Nodes.constants.map { |k|
+        Nodes.const_get(k)
+      }.grep(Class).each do |klass|
+        next if Nodes::SqlLiteral == klass
+        next if Nodes::BindParam == klass
+        next if klass.name =~ /^Arel::Nodes::(?:Test|.*Test$)/
+        assert klass.ancestors.include?(Nodes::Node), klass.name
+      end
+    end
+
+    def test_each
+      list = []
+      node = Nodes::Node.new
+      node.each { |n| list << n }
+      assert_equal [node], list
+    end
+
+    def test_generator
+      list = []
+      node = Nodes::Node.new
+      node.each.each { |n| list << n }
+      assert_equal [node], list
+    end
+
+    def test_enumerable
+      node = Nodes::Node.new
+      assert_kind_of Enumerable, node
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/not_test.rb b/activerecord/test/cases/arel/nodes/not_test.rb
new file mode 100644
index 0000000000..481e678700
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/not_test.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    describe "not" do
+      describe "#not" do
+        it "makes a NOT node" do
+          attr = Table.new(:users)[:id]
+          expr  = attr.eq(10)
+          node  = expr.not
+          node.must_be_kind_of Not
+          node.expr.must_equal expr
+        end
+      end
+
+      describe "equality" do
+        it "is equal with equal ivars" do
+          array = [Not.new("foo"), Not.new("foo")]
+          assert_equal 1, array.uniq.size
+        end
+
+        it "is not equal with different ivars" do
+          array = [Not.new("foo"), Not.new("baz")]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/or_test.rb b/activerecord/test/cases/arel/nodes/or_test.rb
new file mode 100644
index 0000000000..93f826740d
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/or_test.rb
@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    describe "or" do
+      describe "#or" do
+        it "makes an OR node" do
+          attr = Table.new(:users)[:id]
+          left  = attr.eq(10)
+          right = attr.eq(11)
+          node  = left.or right
+          node.expr.left.must_equal left
+          node.expr.right.must_equal right
+
+          oror = node.or(right)
+          oror.expr.left.must_equal node
+          oror.expr.right.must_equal right
+        end
+      end
+
+      describe "equality" do
+        it "is equal with equal ivars" do
+          array = [Or.new("foo", "bar"), Or.new("foo", "bar")]
+          assert_equal 1, array.uniq.size
+        end
+
+        it "is not equal with different ivars" do
+          array = [Or.new("foo", "bar"), Or.new("foo", "baz")]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/over_test.rb b/activerecord/test/cases/arel/nodes/over_test.rb
new file mode 100644
index 0000000000..981ec2e34b
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/over_test.rb
@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+class Arel::Nodes::OverTest < Arel::Spec
+  describe "as" do
+    it "should alias the expression" do
+      table = Arel::Table.new :users
+      table[:id].count.over.as("foo").to_sql.must_be_like %{
+        COUNT("users"."id") OVER () AS foo
+      }
+    end
+  end
+
+  describe "with literal" do
+    it "should reference the window definition by name" do
+      table = Arel::Table.new :users
+      table[:id].count.over("foo").to_sql.must_be_like %{
+        COUNT("users"."id") OVER "foo"
+      }
+    end
+  end
+
+  describe "with SQL literal" do
+    it "should reference the window definition by name" do
+      table = Arel::Table.new :users
+      table[:id].count.over(Arel.sql("foo")).to_sql.must_be_like %{
+        COUNT("users"."id") OVER foo
+      }
+    end
+  end
+
+  describe "with no expression" do
+    it "should use empty definition" do
+      table = Arel::Table.new :users
+      table[:id].count.over.to_sql.must_be_like %{
+        COUNT("users"."id") OVER ()
+      }
+    end
+  end
+
+  describe "with expression" do
+    it "should use definition in sub-expression" do
+      table = Arel::Table.new :users
+      window = Arel::Nodes::Window.new.order(table["foo"])
+      table[:id].count.over(window).to_sql.must_be_like %{
+        COUNT("users"."id") OVER (ORDER BY \"users\".\"foo\")
+      }
+    end
+  end
+
+  describe "equality" do
+    it "is equal with equal ivars" do
+      array = [
+        Arel::Nodes::Over.new("foo", "bar"),
+        Arel::Nodes::Over.new("foo", "bar")
+      ]
+      assert_equal 1, array.uniq.size
+    end
+
+    it "is not equal with different ivars" do
+      array = [
+        Arel::Nodes::Over.new("foo", "bar"),
+        Arel::Nodes::Over.new("foo", "baz")
+      ]
+      assert_equal 2, array.uniq.size
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/select_core_test.rb b/activerecord/test/cases/arel/nodes/select_core_test.rb
new file mode 100644
index 0000000000..0b698205ff
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/select_core_test.rb
@@ -0,0 +1,71 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    class TestSelectCore < Arel::Test
+      def test_clone
+        core = Arel::Nodes::SelectCore.new
+        core.froms       = %w[a b c]
+        core.projections = %w[d e f]
+        core.wheres      = %w[g h i]
+
+        dolly = core.clone
+
+        assert_equal core.froms, dolly.froms
+        assert_equal core.projections, dolly.projections
+        assert_equal core.wheres, dolly.wheres
+
+        assert_not_same core.froms, dolly.froms
+        assert_not_same core.projections, dolly.projections
+        assert_not_same core.wheres, dolly.wheres
+      end
+
+      def test_set_quantifier
+        core = Arel::Nodes::SelectCore.new
+        core.set_quantifier = Arel::Nodes::Distinct.new
+        viz = Arel::Visitors::ToSql.new Table.engine.connection_pool
+        assert_match "DISTINCT", viz.accept(core, Collectors::SQLString.new).value
+      end
+
+      def test_equality_with_same_ivars
+        core1 = SelectCore.new
+        core1.froms       = %w[a b c]
+        core1.projections = %w[d e f]
+        core1.wheres      = %w[g h i]
+        core1.groups      = %w[j k l]
+        core1.windows     = %w[m n o]
+        core1.havings     = %w[p q r]
+        core2 = SelectCore.new
+        core2.froms       = %w[a b c]
+        core2.projections = %w[d e f]
+        core2.wheres      = %w[g h i]
+        core2.groups      = %w[j k l]
+        core2.windows     = %w[m n o]
+        core2.havings     = %w[p q r]
+        array = [core1, core2]
+        assert_equal 1, array.uniq.size
+      end
+
+      def test_inequality_with_different_ivars
+        core1 = SelectCore.new
+        core1.froms       = %w[a b c]
+        core1.projections = %w[d e f]
+        core1.wheres      = %w[g h i]
+        core1.groups      = %w[j k l]
+        core1.windows     = %w[m n o]
+        core1.havings     = %w[p q r]
+        core2 = SelectCore.new
+        core2.froms       = %w[a b c]
+        core2.projections = %w[d e f]
+        core2.wheres      = %w[g h i]
+        core2.groups      = %w[j k l]
+        core2.windows     = %w[m n o]
+        core2.havings     = %w[l o l]
+        array = [core1, core2]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/select_statement_test.rb b/activerecord/test/cases/arel/nodes/select_statement_test.rb
new file mode 100644
index 0000000000..a91605de3e
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/select_statement_test.rb
@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+describe Arel::Nodes::SelectStatement do
+  describe "#clone" do
+    it "clones cores" do
+      statement = Arel::Nodes::SelectStatement.new %w[a b c]
+
+      dolly = statement.clone
+      dolly.cores.must_equal      statement.cores
+      dolly.cores.wont_be_same_as statement.cores
+    end
+  end
+
+  describe "equality" do
+    it "is equal with equal ivars" do
+      statement1 = Arel::Nodes::SelectStatement.new %w[a b c]
+      statement1.offset = 1
+      statement1.limit  = 2
+      statement1.lock   = false
+      statement1.orders = %w[x y z]
+      statement1.with   = "zomg"
+      statement2 = Arel::Nodes::SelectStatement.new %w[a b c]
+      statement2.offset = 1
+      statement2.limit  = 2
+      statement2.lock   = false
+      statement2.orders = %w[x y z]
+      statement2.with   = "zomg"
+      array = [statement1, statement2]
+      assert_equal 1, array.uniq.size
+    end
+
+    it "is not equal with different ivars" do
+      statement1 = Arel::Nodes::SelectStatement.new %w[a b c]
+      statement1.offset = 1
+      statement1.limit  = 2
+      statement1.lock   = false
+      statement1.orders = %w[x y z]
+      statement1.with   = "zomg"
+      statement2 = Arel::Nodes::SelectStatement.new %w[a b c]
+      statement2.offset = 1
+      statement2.limit  = 2
+      statement2.lock   = false
+      statement2.orders = %w[x y z]
+      statement2.with   = "wth"
+      array = [statement1, statement2]
+      assert_equal 2, array.uniq.size
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/sql_literal_test.rb b/activerecord/test/cases/arel/nodes/sql_literal_test.rb
new file mode 100644
index 0000000000..3b95fed1f4
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/sql_literal_test.rb
@@ -0,0 +1,75 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+require "yaml"
+
+module Arel
+  module Nodes
+    class SqlLiteralTest < Arel::Spec
+      before do
+        @visitor = Visitors::ToSql.new Table.engine.connection
+      end
+
+      def compile(node)
+        @visitor.accept(node, Collectors::SQLString.new).value
+      end
+
+      describe "sql" do
+        it "makes a sql literal node" do
+          sql = Arel.sql "foo"
+          sql.must_be_kind_of Arel::Nodes::SqlLiteral
+        end
+      end
+
+      describe "count" do
+        it "makes a count node" do
+          node = SqlLiteral.new("*").count
+          compile(node).must_be_like %{ COUNT(*) }
+        end
+
+        it "makes a distinct node" do
+          node = SqlLiteral.new("*").count true
+          compile(node).must_be_like %{ COUNT(DISTINCT *) }
+        end
+      end
+
+      describe "equality" do
+        it "makes an equality node" do
+          node = SqlLiteral.new("foo").eq(1)
+          compile(node).must_be_like %{ foo = 1 }
+        end
+
+        it "is equal with equal contents" do
+          array = [SqlLiteral.new("foo"), SqlLiteral.new("foo")]
+          assert_equal 1, array.uniq.size
+        end
+
+        it "is not equal with different contents" do
+          array = [SqlLiteral.new("foo"), SqlLiteral.new("bar")]
+          assert_equal 2, array.uniq.size
+        end
+      end
+
+      describe 'grouped "or" equality' do
+        it "makes a grouping node with an or node" do
+          node = SqlLiteral.new("foo").eq_any([1, 2])
+          compile(node).must_be_like %{ (foo = 1 OR foo = 2) }
+        end
+      end
+
+      describe 'grouped "and" equality' do
+        it "makes a grouping node with an and node" do
+          node = SqlLiteral.new("foo").eq_all([1, 2])
+          compile(node).must_be_like %{ (foo = 1 AND foo = 2) }
+        end
+      end
+
+      describe "serialization" do
+        it "serializes into YAML" do
+          yaml_literal = SqlLiteral.new("foo").to_yaml
+          assert_equal("foo", YAML.load(yaml_literal))
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/sum_test.rb b/activerecord/test/cases/arel/nodes/sum_test.rb
new file mode 100644
index 0000000000..5015964951
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/sum_test.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+class Arel::Nodes::SumTest < Arel::Spec
+  describe "as" do
+    it "should alias the sum" do
+      table = Arel::Table.new :users
+      table[:id].sum.as("foo").to_sql.must_be_like %{
+        SUM("users"."id") AS foo
+      }
+    end
+  end
+
+  describe "equality" do
+    it "is equal with equal ivars" do
+      array = [Arel::Nodes::Sum.new("foo"), Arel::Nodes::Sum.new("foo")]
+      assert_equal 1, array.uniq.size
+    end
+
+    it "is not equal with different ivars" do
+      array = [Arel::Nodes::Sum.new("foo"), Arel::Nodes::Sum.new("foo!")]
+      assert_equal 2, array.uniq.size
+    end
+  end
+
+  describe "order" do
+    it "should order the sum" do
+      table = Arel::Table.new :users
+      table[:id].sum.desc.to_sql.must_be_like %{
+        SUM("users"."id") DESC
+      }
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/table_alias_test.rb b/activerecord/test/cases/arel/nodes/table_alias_test.rb
new file mode 100644
index 0000000000..c661b6771e
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/table_alias_test.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    describe "table alias" do
+      describe "equality" do
+        it "is equal with equal ivars" do
+          relation1 = Table.new(:users)
+          node1     = TableAlias.new relation1, :foo
+          relation2 = Table.new(:users)
+          node2     = TableAlias.new relation2, :foo
+          array = [node1, node2]
+          assert_equal 1, array.uniq.size
+        end
+
+        it "is not equal with different ivars" do
+          relation1 = Table.new(:users)
+          node1     = TableAlias.new relation1, :foo
+          relation2 = Table.new(:users)
+          node2     = TableAlias.new relation2, :bar
+          array = [node1, node2]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/true_test.rb b/activerecord/test/cases/arel/nodes/true_test.rb
new file mode 100644
index 0000000000..1e85fe7d48
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/true_test.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    describe "True" do
+      describe "equality" do
+        it "is equal to other true nodes" do
+          array = [True.new, True.new]
+          assert_equal 1, array.uniq.size
+        end
+
+        it "is not equal with other nodes" do
+          array = [True.new, Node.new]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/unary_operation_test.rb b/activerecord/test/cases/arel/nodes/unary_operation_test.rb
new file mode 100644
index 0000000000..f0dd0c625c
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/unary_operation_test.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    class TestUnaryOperation < Arel::Test
+      def test_construct
+        operation = UnaryOperation.new :-, 1
+        assert_equal :-, operation.operator
+        assert_equal 1, operation.expr
+      end
+
+      def test_operation_alias
+        operation = UnaryOperation.new :-, 1
+        aliaz = operation.as("zomg")
+        assert_kind_of As, aliaz
+        assert_equal operation, aliaz.left
+        assert_equal "zomg", aliaz.right
+      end
+
+      def test_operation_ordering
+        operation = UnaryOperation.new :-, 1
+        ordering = operation.desc
+        assert_kind_of Descending, ordering
+        assert_equal operation, ordering.expr
+        assert ordering.descending?
+      end
+
+      def test_equality_with_same_ivars
+        array = [UnaryOperation.new(:-, 1), UnaryOperation.new(:-, 1)]
+        assert_equal 1, array.uniq.size
+      end
+
+      def test_inequality_with_different_ivars
+        array = [UnaryOperation.new(:-, 1), UnaryOperation.new(:-, 2)]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/update_statement_test.rb b/activerecord/test/cases/arel/nodes/update_statement_test.rb
new file mode 100644
index 0000000000..a83ce32f68
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/update_statement_test.rb
@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+describe Arel::Nodes::UpdateStatement do
+  describe "#clone" do
+    it "clones wheres and values" do
+      statement = Arel::Nodes::UpdateStatement.new
+      statement.wheres = %w[a b c]
+      statement.values = %w[x y z]
+
+      dolly = statement.clone
+      dolly.wheres.must_equal statement.wheres
+      dolly.wheres.wont_be_same_as statement.wheres
+
+      dolly.values.must_equal statement.values
+      dolly.values.wont_be_same_as statement.values
+    end
+  end
+
+  describe "equality" do
+    it "is equal with equal ivars" do
+      statement1 = Arel::Nodes::UpdateStatement.new
+      statement1.relation = "zomg"
+      statement1.wheres   = 2
+      statement1.values   = false
+      statement1.orders   = %w[x y z]
+      statement1.limit    = 42
+      statement1.key      = "zomg"
+      statement2 = Arel::Nodes::UpdateStatement.new
+      statement2.relation = "zomg"
+      statement2.wheres   = 2
+      statement2.values   = false
+      statement2.orders   = %w[x y z]
+      statement2.limit    = 42
+      statement2.key      = "zomg"
+      array = [statement1, statement2]
+      assert_equal 1, array.uniq.size
+    end
+
+    it "is not equal with different ivars" do
+      statement1 = Arel::Nodes::UpdateStatement.new
+      statement1.relation = "zomg"
+      statement1.wheres   = 2
+      statement1.values   = false
+      statement1.orders   = %w[x y z]
+      statement1.limit    = 42
+      statement1.key      = "zomg"
+      statement2 = Arel::Nodes::UpdateStatement.new
+      statement2.relation = "zomg"
+      statement2.wheres   = 2
+      statement2.values   = false
+      statement2.orders   = %w[x y z]
+      statement2.limit    = 42
+      statement2.key      = "wth"
+      array = [statement1, statement2]
+      assert_equal 2, array.uniq.size
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/window_test.rb b/activerecord/test/cases/arel/nodes/window_test.rb
new file mode 100644
index 0000000000..729b0556a4
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/window_test.rb
@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Nodes
+    describe "Window" do
+      describe "equality" do
+        it "is equal with equal ivars" do
+          window1 = Window.new
+          window1.orders = [1, 2]
+          window1.partitions = [1]
+          window1.frame 3
+          window2 = Window.new
+          window2.orders = [1, 2]
+          window2.partitions = [1]
+          window2.frame 3
+          array = [window1, window2]
+          assert_equal 1, array.uniq.size
+        end
+
+        it "is not equal with different ivars" do
+          window1 = Window.new
+          window1.orders = [1, 2]
+          window1.partitions = [1]
+          window1.frame 3
+          window2 = Window.new
+          window2.orders = [1, 2]
+          window1.partitions = [1]
+          window2.frame 4
+          array = [window1, window2]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+
+    describe "NamedWindow" do
+      describe "equality" do
+        it "is equal with equal ivars" do
+          window1 = NamedWindow.new "foo"
+          window1.orders = [1, 2]
+          window1.partitions = [1]
+          window1.frame 3
+          window2 = NamedWindow.new "foo"
+          window2.orders = [1, 2]
+          window2.partitions = [1]
+          window2.frame 3
+          array = [window1, window2]
+          assert_equal 1, array.uniq.size
+        end
+
+        it "is not equal with different ivars" do
+          window1 = NamedWindow.new "foo"
+          window1.orders = [1, 2]
+          window1.partitions = [1]
+          window1.frame 3
+          window2 = NamedWindow.new "bar"
+          window2.orders = [1, 2]
+          window2.partitions = [1]
+          window2.frame 3
+          array = [window1, window2]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+
+    describe "CurrentRow" do
+      describe "equality" do
+        it "is equal to other current row nodes" do
+          array = [CurrentRow.new, CurrentRow.new]
+          assert_equal 1, array.uniq.size
+        end
+
+        it "is not equal with other nodes" do
+          array = [CurrentRow.new, Node.new]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes_test.rb b/activerecord/test/cases/arel/nodes_test.rb
new file mode 100644
index 0000000000..9021de0d20
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes_test.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require_relative "helper"
+
+module Arel
+  module Nodes
+    class TestNodes < Arel::Test
+      def test_every_arel_nodes_have_hash_eql_eqeq_from_same_class
+        # #descendants code from activesupport
+        node_descendants = []
+        ObjectSpace.each_object(Arel::Nodes::Node.singleton_class) do |k|
+          next if k.respond_to?(:singleton_class?) && k.singleton_class?
+          node_descendants.unshift k unless k == self
+        end
+        node_descendants.delete(Arel::Nodes::Node)
+        node_descendants.delete(Arel::Nodes::NodeExpression)
+
+        bad_node_descendants = node_descendants.reject do |subnode|
+          eqeq_owner = subnode.instance_method(:==).owner
+          eql_owner = subnode.instance_method(:eql?).owner
+          hash_owner = subnode.instance_method(:hash).owner
+
+          eqeq_owner < Arel::Nodes::Node &&
+              eqeq_owner == eql_owner &&
+              eqeq_owner == hash_owner
+        end
+
+        problem_msg = "Some subclasses of Arel::Nodes::Node do not have a" \
+            " #== or #eql? or #hash defined from the same class as the others"
+        assert_empty bad_node_descendants, problem_msg
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/select_manager_test.rb b/activerecord/test/cases/arel/select_manager_test.rb
new file mode 100644
index 0000000000..f318577b94
--- /dev/null
+++ b/activerecord/test/cases/arel/select_manager_test.rb
@@ -0,0 +1,1236 @@
+# frozen_string_literal: true
+
+require_relative "helper"
+
+module Arel
+  class SelectManagerTest < Arel::Spec
+    def test_join_sources
+      manager = Arel::SelectManager.new
+      manager.join_sources << Arel::Nodes::StringJoin.new(Nodes.build_quoted("foo"))
+      assert_equal "SELECT FROM 'foo'", manager.to_sql
+    end
+
+    describe "backwards compatibility" do
+      describe "project" do
+        it "accepts symbols as sql literals" do
+          table   = Table.new :users
+          manager = Arel::SelectManager.new
+          manager.project :id
+          manager.from table
+          manager.to_sql.must_be_like %{
+            SELECT id FROM "users"
+          }
+        end
+      end
+
+      describe "order" do
+        it "accepts symbols" do
+          table   = Table.new :users
+          manager = Arel::SelectManager.new
+          manager.project Nodes::SqlLiteral.new "*"
+          manager.from table
+          manager.order :foo
+          manager.to_sql.must_be_like %{ SELECT * FROM "users" ORDER BY foo }
+        end
+      end
+
+      describe "group" do
+        it "takes a symbol" do
+          table   = Table.new :users
+          manager = Arel::SelectManager.new
+          manager.from table
+          manager.group :foo
+          manager.to_sql.must_be_like %{ SELECT FROM "users" GROUP BY foo }
+        end
+      end
+
+      describe "as" do
+        it "makes an AS node by grouping the AST" do
+          manager = Arel::SelectManager.new
+          as = manager.as(Arel.sql("foo"))
+          assert_kind_of Arel::Nodes::Grouping, as.left
+          assert_equal manager.ast, as.left.expr
+          assert_equal "foo", as.right
+        end
+
+        it "converts right to SqlLiteral if a string" do
+          manager = Arel::SelectManager.new
+          as = manager.as("foo")
+          assert_kind_of Arel::Nodes::SqlLiteral, as.right
+        end
+
+        it "can make a subselect" do
+          manager = Arel::SelectManager.new
+          manager.project Arel.star
+          manager.from Arel.sql("zomg")
+          as = manager.as(Arel.sql("foo"))
+
+          manager = Arel::SelectManager.new
+          manager.project Arel.sql("name")
+          manager.from as
+          manager.to_sql.must_be_like "SELECT name FROM (SELECT * FROM zomg) foo"
+        end
+      end
+
+      describe "from" do
+        it "ignores strings when table of same name exists" do
+          table   = Table.new :users
+          manager = Arel::SelectManager.new
+
+          manager.from table
+          manager.from "users"
+          manager.project table["id"]
+          manager.to_sql.must_be_like 'SELECT "users"."id" FROM users'
+        end
+
+        it "should support any ast" do
+          table = Table.new :users
+          manager1 = Arel::SelectManager.new
+
+          manager2 = Arel::SelectManager.new
+          manager2.project(Arel.sql("*"))
+          manager2.from table
+
+          manager1.project Arel.sql("lol")
+          as = manager2.as Arel.sql("omg")
+          manager1.from(as)
+
+          manager1.to_sql.must_be_like %{
+            SELECT lol FROM (SELECT * FROM "users") omg
+          }
+        end
+      end
+
+      describe "having" do
+        it "converts strings to SQLLiterals" do
+          table = Table.new :users
+          mgr = table.from
+          mgr.having Arel.sql("foo")
+          mgr.to_sql.must_be_like %{ SELECT FROM "users" HAVING foo }
+        end
+
+        it "can have multiple items specified separately" do
+          table = Table.new :users
+          mgr = table.from
+          mgr.having Arel.sql("foo")
+          mgr.having Arel.sql("bar")
+          mgr.to_sql.must_be_like %{ SELECT FROM "users" HAVING foo AND bar }
+        end
+
+        it "can receive any node" do
+          table = Table.new :users
+          mgr = table.from
+          mgr.having Arel::Nodes::And.new([Arel.sql("foo"), Arel.sql("bar")])
+          mgr.to_sql.must_be_like %{ SELECT FROM "users" HAVING foo AND bar }
+        end
+      end
+
+      describe "on" do
+        it "converts to sqlliterals" do
+          table = Table.new :users
+          right = table.alias
+          mgr   = table.from
+          mgr.join(right).on("omg")
+          mgr.to_sql.must_be_like %{ SELECT  FROM "users" INNER JOIN "users" "users_2" ON omg }
+        end
+
+        it "converts to sqlliterals with multiple items" do
+          table = Table.new :users
+          right = table.alias
+          mgr   = table.from
+          mgr.join(right).on("omg", "123")
+          mgr.to_sql.must_be_like %{ SELECT  FROM "users" INNER JOIN "users" "users_2" ON omg AND 123 }
+        end
+      end
+    end
+
+    describe "clone" do
+      it "creates new cores" do
+        table = Table.new :users, as: "foo"
+        mgr = table.from
+        m2 = mgr.clone
+        m2.project "foo"
+        mgr.to_sql.wont_equal m2.to_sql
+      end
+
+      it "makes updates to the correct copy" do
+        table = Table.new :users, as: "foo"
+        mgr = table.from
+        m2 = mgr.clone
+        m3 = m2.clone
+        m2.project "foo"
+        mgr.to_sql.wont_equal m2.to_sql
+        m3.to_sql.must_equal mgr.to_sql
+      end
+    end
+
+    describe "initialize" do
+      it "uses alias in sql" do
+        table = Table.new :users, as: "foo"
+        mgr = table.from
+        mgr.skip 10
+        mgr.to_sql.must_be_like %{ SELECT FROM "users" "foo" OFFSET 10 }
+      end
+    end
+
+    describe "skip" do
+      it "should add an offset" do
+        table = Table.new :users
+        mgr = table.from
+        mgr.skip 10
+        mgr.to_sql.must_be_like %{ SELECT FROM "users" OFFSET 10 }
+      end
+
+      it "should chain" do
+        table = Table.new :users
+        mgr = table.from
+        mgr.skip(10).to_sql.must_be_like %{ SELECT FROM "users" OFFSET 10 }
+      end
+    end
+
+    describe "offset" do
+      it "should add an offset" do
+        table = Table.new :users
+        mgr = table.from
+        mgr.offset = 10
+        mgr.to_sql.must_be_like %{ SELECT FROM "users" OFFSET 10 }
+      end
+
+      it "should remove an offset" do
+        table = Table.new :users
+        mgr = table.from
+        mgr.offset = 10
+        mgr.to_sql.must_be_like %{ SELECT FROM "users" OFFSET 10 }
+
+        mgr.offset = nil
+        mgr.to_sql.must_be_like %{ SELECT FROM "users" }
+      end
+
+      it "should return the offset" do
+        table = Table.new :users
+        mgr = table.from
+        mgr.offset = 10
+        assert_equal 10, mgr.offset
+      end
+    end
+
+    describe "exists" do
+      it "should create an exists clause" do
+        table = Table.new(:users)
+        manager = Arel::SelectManager.new table
+        manager.project Nodes::SqlLiteral.new "*"
+        m2 = Arel::SelectManager.new
+        m2.project manager.exists
+        m2.to_sql.must_be_like %{ SELECT EXISTS (#{manager.to_sql}) }
+      end
+
+      it "can be aliased" do
+        table = Table.new(:users)
+        manager = Arel::SelectManager.new table
+        manager.project Nodes::SqlLiteral.new "*"
+        m2 = Arel::SelectManager.new
+        m2.project manager.exists.as("foo")
+        m2.to_sql.must_be_like %{ SELECT EXISTS (#{manager.to_sql}) AS foo }
+      end
+    end
+
+    describe "union" do
+      before do
+        table = Table.new :users
+        @m1 = Arel::SelectManager.new table
+        @m1.project Arel.star
+        @m1.where(table[:age].lt(18))
+
+        @m2 = Arel::SelectManager.new table
+        @m2.project Arel.star
+        @m2.where(table[:age].gt(99))
+
+
+      end
+
+      it "should union two managers" do
+        # FIXME should this union "managers" or "statements" ?
+        # FIXME this probably shouldn't return a node
+        node = @m1.union @m2
+
+        # maybe FIXME: decide when wrapper parens are needed
+        node.to_sql.must_be_like %{
+          ( SELECT * FROM "users"  WHERE "users"."age" < 18 UNION SELECT * FROM "users"  WHERE "users"."age" > 99 )
+        }
+      end
+
+      it "should union all" do
+        node = @m1.union :all, @m2
+
+        node.to_sql.must_be_like %{
+          ( SELECT * FROM "users"  WHERE "users"."age" < 18 UNION ALL SELECT * FROM "users"  WHERE "users"."age" > 99 )
+        }
+      end
+
+    end
+
+    describe "intersect" do
+      before do
+        table = Table.new :users
+        @m1 = Arel::SelectManager.new table
+        @m1.project Arel.star
+        @m1.where(table[:age].gt(18))
+
+        @m2 = Arel::SelectManager.new table
+        @m2.project Arel.star
+        @m2.where(table[:age].lt(99))
+
+
+      end
+
+      it "should interect two managers" do
+        # FIXME should this intersect "managers" or "statements" ?
+        # FIXME this probably shouldn't return a node
+        node = @m1.intersect @m2
+
+        # maybe FIXME: decide when wrapper parens are needed
+        node.to_sql.must_be_like %{
+          ( SELECT * FROM "users"  WHERE "users"."age" > 18 INTERSECT SELECT * FROM "users"  WHERE "users"."age" < 99 )
+        }
+      end
+
+    end
+
+    describe "except" do
+      before do
+        table = Table.new :users
+        @m1 = Arel::SelectManager.new table
+        @m1.project Arel.star
+        @m1.where(table[:age].between(18..60))
+
+        @m2 = Arel::SelectManager.new table
+        @m2.project Arel.star
+        @m2.where(table[:age].between(40..99))
+      end
+
+      it "should except two managers" do
+        # FIXME should this except "managers" or "statements" ?
+        # FIXME this probably shouldn't return a node
+        node = @m1.except @m2
+
+        # maybe FIXME: decide when wrapper parens are needed
+        node.to_sql.must_be_like %{
+          ( SELECT * FROM "users"  WHERE "users"."age" BETWEEN 18 AND 60 EXCEPT SELECT * FROM "users"  WHERE "users"."age" BETWEEN 40 AND 99 )
+        }
+      end
+
+    end
+
+    describe "with" do
+      it "should support basic WITH" do
+        users          = Table.new(:users)
+        users_top      = Table.new(:users_top)
+        comments       = Table.new(:comments)
+
+        top            = users.project(users[:id]).where(users[:karma].gt(100))
+        users_as       = Arel::Nodes::As.new(users_top, top)
+        select_manager = comments.project(Arel.star).with(users_as)
+                          .where(comments[:author_id].in(users_top.project(users_top[:id])))
+
+        select_manager.to_sql.must_be_like %{
+          WITH "users_top" AS (SELECT "users"."id" FROM "users" WHERE "users"."karma" > 100) SELECT * FROM "comments" WHERE "comments"."author_id" IN (SELECT "users_top"."id" FROM "users_top")
+        }
+      end
+
+      it "should support WITH RECURSIVE" do
+        comments           = Table.new(:comments)
+        comments_id        = comments[:id]
+        comments_parent_id = comments[:parent_id]
+
+        replies            = Table.new(:replies)
+        replies_id         = replies[:id]
+
+        recursive_term = Arel::SelectManager.new
+        recursive_term.from(comments).project(comments_id, comments_parent_id).where(comments_id.eq 42)
+
+        non_recursive_term = Arel::SelectManager.new
+        non_recursive_term.from(comments).project(comments_id, comments_parent_id).join(replies).on(comments_parent_id.eq replies_id)
+
+        union = recursive_term.union(non_recursive_term)
+
+        as_statement = Arel::Nodes::As.new replies, union
+
+        manager = Arel::SelectManager.new
+        manager.with(:recursive, as_statement).from(replies).project(Arel.star)
+
+        sql = manager.to_sql
+        sql.must_be_like %{
+          WITH RECURSIVE "replies" AS (
+              SELECT "comments"."id", "comments"."parent_id" FROM "comments" WHERE "comments"."id" = 42
+            UNION
+              SELECT "comments"."id", "comments"."parent_id" FROM "comments" INNER JOIN "replies" ON "comments"."parent_id" = "replies"."id"
+          )
+          SELECT * FROM "replies"
+        }
+      end
+    end
+
+    describe "ast" do
+      it "should return the ast" do
+        table = Table.new :users
+        mgr = table.from
+        assert mgr.ast
+      end
+
+      it "should allow orders to work when the ast is grepped" do
+        table = Table.new :users
+        mgr = table.from
+        mgr.project Arel.sql "*"
+        mgr.from table
+        mgr.orders << Arel::Nodes::Ascending.new(Arel.sql("foo"))
+        mgr.ast.grep(Arel::Nodes::OuterJoin)
+        mgr.to_sql.must_be_like %{ SELECT * FROM "users" ORDER BY foo ASC }
+      end
+    end
+
+    describe "taken" do
+      it "should return limit" do
+        manager = Arel::SelectManager.new
+        manager.take 10
+        manager.taken.must_equal 10
+      end
+    end
+
+    describe "lock" do
+      # This should fail on other databases
+      it "adds a lock node" do
+        table = Table.new :users
+        mgr = table.from
+        mgr.lock.to_sql.must_be_like %{ SELECT FROM "users" FOR UPDATE }
+      end
+    end
+
+    describe "orders" do
+      it "returns order clauses" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        order = table[:id]
+        manager.order table[:id]
+        manager.orders.must_equal [order]
+      end
+    end
+
+    describe "order" do
+      it "generates order clauses" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.project Nodes::SqlLiteral.new "*"
+        manager.from table
+        manager.order table[:id]
+        manager.to_sql.must_be_like %{
+          SELECT * FROM "users" ORDER BY "users"."id"
+        }
+      end
+
+      # FIXME: I would like to deprecate this
+      it "takes *args" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.project Nodes::SqlLiteral.new "*"
+        manager.from table
+        manager.order table[:id], table[:name]
+        manager.to_sql.must_be_like %{
+          SELECT * FROM "users" ORDER BY "users"."id", "users"."name"
+        }
+      end
+
+      it "chains" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.order(table[:id]).must_equal manager
+      end
+
+      it "has order attributes" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.project Nodes::SqlLiteral.new "*"
+        manager.from table
+        manager.order table[:id].desc
+        manager.to_sql.must_be_like %{
+          SELECT * FROM "users" ORDER BY "users"."id" DESC
+        }
+      end
+    end
+
+    describe "on" do
+      it "takes two params" do
+        left      = Table.new :users
+        right     = left.alias
+        predicate = left[:id].eq(right[:id])
+        manager   = Arel::SelectManager.new
+
+        manager.from left
+        manager.join(right).on(predicate, predicate)
+        manager.to_sql.must_be_like %{
+           SELECT FROM "users"
+             INNER JOIN "users" "users_2"
+               ON "users"."id" = "users_2"."id" AND
+               "users"."id" = "users_2"."id"
+        }
+      end
+
+      it "takes three params" do
+        left      = Table.new :users
+        right     = left.alias
+        predicate = left[:id].eq(right[:id])
+        manager   = Arel::SelectManager.new
+
+        manager.from left
+        manager.join(right).on(
+          predicate,
+          predicate,
+          left[:name].eq(right[:name])
+        )
+        manager.to_sql.must_be_like %{
+           SELECT FROM "users"
+             INNER JOIN "users" "users_2"
+               ON "users"."id" = "users_2"."id" AND
+               "users"."id" = "users_2"."id" AND
+               "users"."name" = "users_2"."name"
+        }
+      end
+    end
+
+    it "should hand back froms" do
+      relation = Arel::SelectManager.new
+      assert_equal [], relation.froms
+    end
+
+    it "should create and nodes" do
+      relation = Arel::SelectManager.new
+      children = ["foo", "bar", "baz"]
+      clause = relation.create_and children
+      assert_kind_of Arel::Nodes::And, clause
+      assert_equal children, clause.children
+    end
+
+    it "should create insert managers" do
+      relation = Arel::SelectManager.new
+      insert = relation.create_insert
+      assert_kind_of Arel::InsertManager, insert
+    end
+
+    it "should create join nodes" do
+      relation = Arel::SelectManager.new
+      join = relation.create_join "foo", "bar"
+      assert_kind_of Arel::Nodes::InnerJoin, join
+      assert_equal "foo", join.left
+      assert_equal "bar", join.right
+    end
+
+    it "should create join nodes with a full outer join klass" do
+      relation = Arel::SelectManager.new
+      join = relation.create_join "foo", "bar", Arel::Nodes::FullOuterJoin
+      assert_kind_of Arel::Nodes::FullOuterJoin, join
+      assert_equal "foo", join.left
+      assert_equal "bar", join.right
+    end
+
+    it "should create join nodes with a outer join klass" do
+      relation = Arel::SelectManager.new
+      join = relation.create_join "foo", "bar", Arel::Nodes::OuterJoin
+      assert_kind_of Arel::Nodes::OuterJoin, join
+      assert_equal "foo", join.left
+      assert_equal "bar", join.right
+    end
+
+    it "should create join nodes with a right outer join klass" do
+      relation = Arel::SelectManager.new
+      join = relation.create_join "foo", "bar", Arel::Nodes::RightOuterJoin
+      assert_kind_of Arel::Nodes::RightOuterJoin, join
+      assert_equal "foo", join.left
+      assert_equal "bar", join.right
+    end
+
+    describe "join" do
+      it "responds to join" do
+        left      = Table.new :users
+        right     = left.alias
+        predicate = left[:id].eq(right[:id])
+        manager   = Arel::SelectManager.new
+
+        manager.from left
+        manager.join(right).on(predicate)
+        manager.to_sql.must_be_like %{
+           SELECT FROM "users"
+             INNER JOIN "users" "users_2"
+               ON "users"."id" = "users_2"."id"
+        }
+      end
+
+      it "takes a class" do
+        left      = Table.new :users
+        right     = left.alias
+        predicate = left[:id].eq(right[:id])
+        manager   = Arel::SelectManager.new
+
+        manager.from left
+        manager.join(right, Nodes::OuterJoin).on(predicate)
+        manager.to_sql.must_be_like %{
+           SELECT FROM "users"
+             LEFT OUTER JOIN "users" "users_2"
+               ON "users"."id" = "users_2"."id"
+        }
+      end
+
+      it "takes the full outer join class" do
+        left      = Table.new :users
+        right     = left.alias
+        predicate = left[:id].eq(right[:id])
+        manager   = Arel::SelectManager.new
+
+        manager.from left
+        manager.join(right, Nodes::FullOuterJoin).on(predicate)
+        manager.to_sql.must_be_like %{
+           SELECT FROM "users"
+             FULL OUTER JOIN "users" "users_2"
+               ON "users"."id" = "users_2"."id"
+        }
+      end
+
+      it "takes the right outer join class" do
+        left      = Table.new :users
+        right     = left.alias
+        predicate = left[:id].eq(right[:id])
+        manager   = Arel::SelectManager.new
+
+        manager.from left
+        manager.join(right, Nodes::RightOuterJoin).on(predicate)
+        manager.to_sql.must_be_like %{
+           SELECT FROM "users"
+             RIGHT OUTER JOIN "users" "users_2"
+               ON "users"."id" = "users_2"."id"
+        }
+      end
+
+      it "noops on nil" do
+        manager = Arel::SelectManager.new
+        manager.join(nil).must_equal manager
+      end
+
+      it "raises EmptyJoinError on empty" do
+        left      = Table.new :users
+        manager   = Arel::SelectManager.new
+
+        manager.from left
+        assert_raises(EmptyJoinError) do
+          manager.join("")
+        end
+      end
+    end
+
+    describe "outer join" do
+      it "responds to join" do
+        left      = Table.new :users
+        right     = left.alias
+        predicate = left[:id].eq(right[:id])
+        manager   = Arel::SelectManager.new
+
+        manager.from left
+        manager.outer_join(right).on(predicate)
+        manager.to_sql.must_be_like %{
+           SELECT FROM "users"
+             LEFT OUTER JOIN "users" "users_2"
+               ON "users"."id" = "users_2"."id"
+        }
+      end
+
+      it "noops on nil" do
+        manager = Arel::SelectManager.new
+        manager.outer_join(nil).must_equal manager
+      end
+    end
+
+    describe "joins" do
+
+      it "returns inner join sql" do
+        table   = Table.new :users
+        aliaz   = table.alias
+        manager = Arel::SelectManager.new
+        manager.from Nodes::InnerJoin.new(aliaz, table[:id].eq(aliaz[:id]))
+        assert_match 'INNER JOIN "users" "users_2" "users"."id" = "users_2"."id"',
+                     manager.to_sql
+      end
+
+      it "returns outer join sql" do
+        table   = Table.new :users
+        aliaz   = table.alias
+        manager = Arel::SelectManager.new
+        manager.from Nodes::OuterJoin.new(aliaz, table[:id].eq(aliaz[:id]))
+        assert_match 'LEFT OUTER JOIN "users" "users_2" "users"."id" = "users_2"."id"',
+                     manager.to_sql
+      end
+
+      it "can have a non-table alias as relation name" do
+        users    = Table.new :users
+        comments = Table.new :comments
+
+        counts = comments.from.
+          group(comments[:user_id]).
+          project(
+            comments[:user_id].as("user_id"),
+            comments[:user_id].count.as("count")
+          ).as("counts")
+
+        joins = users.join(counts).on(counts[:user_id].eq(10))
+        joins.to_sql.must_be_like %{
+          SELECT FROM "users" INNER JOIN (SELECT "comments"."user_id" AS user_id, COUNT("comments"."user_id") AS count FROM "comments" GROUP BY "comments"."user_id") counts ON counts."user_id" = 10
+        }
+      end
+
+      it "joins itself" do
+        left      = Table.new :users
+        right     = left.alias
+        predicate = left[:id].eq(right[:id])
+
+        mgr = left.join(right)
+        mgr.project Nodes::SqlLiteral.new("*")
+        mgr.on(predicate).must_equal mgr
+
+        mgr.to_sql.must_be_like %{
+           SELECT * FROM "users"
+             INNER JOIN "users" "users_2"
+               ON "users"."id" = "users_2"."id"
+        }
+      end
+
+      it "returns string join sql" do
+        manager = Arel::SelectManager.new
+        manager.from Nodes::StringJoin.new(Nodes.build_quoted("hello"))
+        assert_match "'hello'", manager.to_sql
+      end
+    end
+
+    describe "group" do
+      it "takes an attribute" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.group table[:id]
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" GROUP BY "users"."id"
+        }
+      end
+
+      it "chains" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.group(table[:id]).must_equal manager
+      end
+
+      it "takes multiple args" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.group table[:id], table[:name]
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" GROUP BY "users"."id", "users"."name"
+        }
+      end
+
+      # FIXME: backwards compat
+      it "makes strings literals" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.group "foo"
+        manager.to_sql.must_be_like %{ SELECT FROM "users" GROUP BY foo }
+      end
+    end
+
+    describe "window definition" do
+      it "can be empty" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window")
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS ()
+        }
+      end
+
+      it "takes an order" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").order(table["foo"].asc)
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (ORDER BY "users"."foo" ASC)
+        }
+      end
+
+      it "takes an order with multiple columns" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").order(table["foo"].asc, table["bar"].desc)
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (ORDER BY "users"."foo" ASC, "users"."bar" DESC)
+        }
+      end
+
+      it "takes a partition" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").partition(table["bar"])
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (PARTITION BY "users"."bar")
+        }
+      end
+
+      it "takes a partition and an order" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").partition(table["foo"]).order(table["foo"].asc)
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (PARTITION BY "users"."foo"
+            ORDER BY "users"."foo" ASC)
+        }
+      end
+
+      it "takes a partition with multiple columns" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").partition(table["bar"], table["baz"])
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (PARTITION BY "users"."bar", "users"."baz")
+        }
+      end
+
+      it "takes a rows frame, unbounded preceding" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").rows(Arel::Nodes::Preceding.new)
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (ROWS UNBOUNDED PRECEDING)
+        }
+      end
+
+      it "takes a rows frame, bounded preceding" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").rows(Arel::Nodes::Preceding.new(5))
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (ROWS 5 PRECEDING)
+        }
+      end
+
+      it "takes a rows frame, unbounded following" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").rows(Arel::Nodes::Following.new)
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (ROWS UNBOUNDED FOLLOWING)
+        }
+      end
+
+      it "takes a rows frame, bounded following" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").rows(Arel::Nodes::Following.new(5))
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (ROWS 5 FOLLOWING)
+        }
+      end
+
+      it "takes a rows frame, current row" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").rows(Arel::Nodes::CurrentRow.new)
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (ROWS CURRENT ROW)
+        }
+      end
+
+      it "takes a rows frame, between two delimiters" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        window = manager.window("a_window")
+        window.frame(
+          Arel::Nodes::Between.new(
+            window.rows,
+            Nodes::And.new([
+              Arel::Nodes::Preceding.new,
+              Arel::Nodes::CurrentRow.new
+            ])))
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)
+        }
+      end
+
+      it "takes a range frame, unbounded preceding" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").range(Arel::Nodes::Preceding.new)
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (RANGE UNBOUNDED PRECEDING)
+        }
+      end
+
+      it "takes a range frame, bounded preceding" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").range(Arel::Nodes::Preceding.new(5))
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (RANGE 5 PRECEDING)
+        }
+      end
+
+      it "takes a range frame, unbounded following" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").range(Arel::Nodes::Following.new)
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (RANGE UNBOUNDED FOLLOWING)
+        }
+      end
+
+      it "takes a range frame, bounded following" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").range(Arel::Nodes::Following.new(5))
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (RANGE 5 FOLLOWING)
+        }
+      end
+
+      it "takes a range frame, current row" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.window("a_window").range(Arel::Nodes::CurrentRow.new)
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (RANGE CURRENT ROW)
+        }
+      end
+
+      it "takes a range frame, between two delimiters" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        window = manager.window("a_window")
+        window.frame(
+          Arel::Nodes::Between.new(
+            window.range,
+            Nodes::And.new([
+              Arel::Nodes::Preceding.new,
+              Arel::Nodes::CurrentRow.new
+            ])))
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" WINDOW "a_window" AS (RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)
+        }
+      end
+    end
+
+    describe "delete" do
+      it "copies from" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        stmt = manager.compile_delete
+
+        stmt.to_sql.must_be_like %{ DELETE FROM "users" }
+      end
+
+      it "copies where" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.where table[:id].eq 10
+        stmt = manager.compile_delete
+
+        stmt.to_sql.must_be_like %{
+          DELETE FROM "users" WHERE "users"."id" = 10
+        }
+      end
+    end
+
+    describe "where_sql" do
+      it "gives me back the where sql" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.where table[:id].eq 10
+        manager.where_sql.must_be_like %{ WHERE "users"."id" = 10 }
+      end
+
+      it "joins wheres with AND" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.where table[:id].eq 10
+        manager.where table[:id].eq 11
+        manager.where_sql.must_be_like %{ WHERE "users"."id" = 10 AND "users"."id" = 11}
+      end
+
+      it "handles database specific statements" do
+        old_visitor = Table.engine.connection.visitor
+        Table.engine.connection.visitor = Visitors::PostgreSQL.new Table.engine.connection
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.where table[:id].eq 10
+        manager.where table[:name].matches "foo%"
+        manager.where_sql.must_be_like %{ WHERE "users"."id" = 10 AND "users"."name" ILIKE 'foo%' }
+        Table.engine.connection.visitor = old_visitor
+      end
+
+      it "returns nil when there are no wheres" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.where_sql.must_be_nil
+      end
+    end
+
+    describe "update" do
+
+      it "creates an update statement" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        stmt = manager.compile_update({ table[:id] => 1 }, Arel::Attributes::Attribute.new(table, "id"))
+
+        stmt.to_sql.must_be_like %{
+          UPDATE "users" SET "id" = 1
+        }
+      end
+
+      it "takes a string" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        stmt = manager.compile_update(Nodes::SqlLiteral.new("foo = bar"), Arel::Attributes::Attribute.new(table, "id"))
+
+        stmt.to_sql.must_be_like %{ UPDATE "users" SET foo = bar }
+      end
+
+      it "copies limits" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.take 1
+        stmt = manager.compile_update(Nodes::SqlLiteral.new("foo = bar"), Arel::Attributes::Attribute.new(table, "id"))
+        stmt.key = table["id"]
+
+        stmt.to_sql.must_be_like %{
+          UPDATE "users" SET foo = bar
+          WHERE "users"."id" IN (SELECT "users"."id" FROM "users" LIMIT 1)
+        }
+      end
+
+      it "copies order" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from table
+        manager.order :foo
+        stmt = manager.compile_update(Nodes::SqlLiteral.new("foo = bar"), Arel::Attributes::Attribute.new(table, "id"))
+        stmt.key = table["id"]
+
+        stmt.to_sql.must_be_like %{
+          UPDATE "users" SET foo = bar
+          WHERE "users"."id" IN (SELECT "users"."id" FROM "users" ORDER BY foo)
+        }
+      end
+
+      it "copies where clauses" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.where table[:id].eq 10
+        manager.from table
+        stmt = manager.compile_update({ table[:id] => 1 }, Arel::Attributes::Attribute.new(table, "id"))
+
+        stmt.to_sql.must_be_like %{
+          UPDATE "users" SET "id" = 1 WHERE "users"."id" = 10
+        }
+      end
+
+      it "copies where clauses when nesting is triggered" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.where table[:foo].eq 10
+        manager.take 42
+        manager.from table
+        stmt = manager.compile_update({ table[:id] => 1 }, Arel::Attributes::Attribute.new(table, "id"))
+
+        stmt.to_sql.must_be_like %{
+          UPDATE "users" SET "id" = 1 WHERE "users"."id" IN (SELECT "users"."id" FROM "users" WHERE "users"."foo" = 10 LIMIT 42)
+        }
+      end
+
+    end
+
+    describe "project" do
+      it "takes sql literals" do
+        manager = Arel::SelectManager.new
+        manager.project Nodes::SqlLiteral.new "*"
+        manager.to_sql.must_be_like %{ SELECT * }
+      end
+
+      it "takes multiple args" do
+        manager = Arel::SelectManager.new
+        manager.project Nodes::SqlLiteral.new("foo"),
+          Nodes::SqlLiteral.new("bar")
+        manager.to_sql.must_be_like %{ SELECT foo, bar }
+      end
+
+      it "takes strings" do
+        manager = Arel::SelectManager.new
+        manager.project "*"
+        manager.to_sql.must_be_like %{ SELECT * }
+      end
+
+    end
+
+    describe "projections" do
+      it "reads projections" do
+        manager = Arel::SelectManager.new
+        manager.project Arel.sql("foo"), Arel.sql("bar")
+        manager.projections.must_equal [Arel.sql("foo"), Arel.sql("bar")]
+      end
+    end
+
+    describe "projections=" do
+      it "overwrites projections" do
+        manager = Arel::SelectManager.new
+        manager.project Arel.sql("foo")
+        manager.projections = [Arel.sql("bar")]
+        manager.to_sql.must_be_like %{ SELECT bar }
+      end
+    end
+
+    describe "take" do
+      it "knows take" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from(table).project(table["id"])
+        manager.where(table["id"].eq(1))
+        manager.take 1
+
+        manager.to_sql.must_be_like %{
+          SELECT "users"."id"
+          FROM "users"
+          WHERE "users"."id" = 1
+          LIMIT 1
+        }
+      end
+
+      it "chains" do
+        manager = Arel::SelectManager.new
+        manager.take(1).must_equal manager
+      end
+
+      it "removes LIMIT when nil is passed" do
+        manager = Arel::SelectManager.new
+        manager.limit = 10
+        assert_match("LIMIT", manager.to_sql)
+
+        manager.limit = nil
+        assert_no_match("LIMIT", manager.to_sql)
+      end
+    end
+
+    describe "where" do
+      it "knows where" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from(table).project(table["id"])
+        manager.where(table["id"].eq(1))
+        manager.to_sql.must_be_like %{
+          SELECT "users"."id"
+          FROM "users"
+          WHERE "users"."id" = 1
+        }
+      end
+
+      it "chains" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from(table)
+        manager.project(table["id"]).where(table["id"].eq 1).must_equal manager
+      end
+    end
+
+    describe "from" do
+      it "makes sql" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+
+        manager.from table
+        manager.project table["id"]
+        manager.to_sql.must_be_like 'SELECT "users"."id" FROM "users"'
+      end
+
+      it "chains" do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new
+        manager.from(table).project(table["id"]).must_equal manager
+        manager.to_sql.must_be_like 'SELECT "users"."id" FROM "users"'
+      end
+    end
+
+    describe "source" do
+      it "returns the join source of the select core" do
+        manager = Arel::SelectManager.new
+        manager.source.must_equal manager.ast.cores.last.source
+      end
+    end
+
+    describe "distinct" do
+      it "sets the quantifier" do
+        manager = Arel::SelectManager.new
+
+        manager.distinct
+        manager.ast.cores.last.set_quantifier.class.must_equal Arel::Nodes::Distinct
+
+        manager.distinct(false)
+        manager.ast.cores.last.set_quantifier.must_be_nil
+      end
+
+      it "chains" do
+        manager = Arel::SelectManager.new
+        manager.distinct.must_equal manager
+        manager.distinct(false).must_equal manager
+      end
+    end
+
+    describe "distinct_on" do
+      it "sets the quantifier" do
+        manager = Arel::SelectManager.new
+        table = Table.new :users
+
+        manager.distinct_on(table["id"])
+        manager.ast.cores.last.set_quantifier.must_equal Arel::Nodes::DistinctOn.new(table["id"])
+
+        manager.distinct_on(false)
+        manager.ast.cores.last.set_quantifier.must_be_nil
+      end
+
+      it "chains" do
+        manager = Arel::SelectManager.new
+        table = Table.new :users
+
+        manager.distinct_on(table["id"]).must_equal manager
+        manager.distinct_on(false).must_equal manager
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/support/fake_record.rb b/activerecord/test/cases/arel/support/fake_record.rb
new file mode 100644
index 0000000000..559ff5d4e6
--- /dev/null
+++ b/activerecord/test/cases/arel/support/fake_record.rb
@@ -0,0 +1,129 @@
+# frozen_string_literal: true
+
+require "date"
+module FakeRecord
+  class Column < Struct.new(:name, :type)
+  end
+
+  class Connection
+    attr_reader :tables
+    attr_accessor :visitor
+
+    def initialize(visitor = nil)
+      @tables = %w{ users photos developers products}
+      @columns = {
+        "users" => [
+          Column.new("id", :integer),
+          Column.new("name", :string),
+          Column.new("bool", :boolean),
+          Column.new("created_at", :date)
+        ],
+        "products" => [
+          Column.new("id", :integer),
+          Column.new("price", :decimal)
+        ]
+      }
+      @columns_hash = {
+        "users" => Hash[@columns["users"].map { |x| [x.name, x] }],
+        "products" => Hash[@columns["products"].map { |x| [x.name, x] }]
+      }
+      @primary_keys = {
+        "users" => "id",
+        "products" => "id"
+      }
+      @visitor = visitor
+    end
+
+    def columns_hash(table_name)
+      @columns_hash[table_name]
+    end
+
+    def primary_key(name)
+      @primary_keys[name.to_s]
+    end
+
+    def data_source_exists?(name)
+      @tables.include? name.to_s
+    end
+
+    def columns(name, message = nil)
+      @columns[name.to_s]
+    end
+
+    def quote_table_name(name)
+      "\"#{name}\""
+    end
+
+    def quote_column_name(name)
+      "\"#{name}\""
+    end
+
+    def schema_cache
+      self
+    end
+
+    def quote(thing)
+      case thing
+      when DateTime
+        "'#{thing.strftime("%Y-%m-%d %H:%M:%S")}'"
+      when Date
+        "'#{thing.strftime("%Y-%m-%d")}'"
+      when true
+        "'t'"
+      when false
+        "'f'"
+      when nil
+        "NULL"
+      when Numeric
+        thing
+      else
+        "'#{thing.to_s.gsub("'", "\\\\'")}'"
+      end
+    end
+  end
+
+  class ConnectionPool
+    class Spec < Struct.new(:config)
+    end
+
+    attr_reader :spec, :connection
+
+    def initialize
+      @spec = Spec.new(adapter: "america")
+      @connection = Connection.new
+      @connection.visitor = Arel::Visitors::ToSql.new(connection)
+    end
+
+    def with_connection
+      yield connection
+    end
+
+    def table_exists?(name)
+      connection.tables.include? name.to_s
+    end
+
+    def columns_hash
+      connection.columns_hash
+    end
+
+    def schema_cache
+      connection
+    end
+
+    def quote(thing)
+      connection.quote thing
+    end
+  end
+
+  class Base
+    attr_accessor :connection_pool
+
+    def initialize
+      @connection_pool = ConnectionPool.new
+    end
+
+    def connection
+      connection_pool.connection
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/table_test.rb b/activerecord/test/cases/arel/table_test.rb
new file mode 100644
index 0000000000..91b7a5a480
--- /dev/null
+++ b/activerecord/test/cases/arel/table_test.rb
@@ -0,0 +1,216 @@
+# frozen_string_literal: true
+
+require_relative "helper"
+
+module Arel
+  class TableTest < Arel::Spec
+    before do
+      @relation = Table.new(:users)
+    end
+
+    it "should create join nodes" do
+      join = @relation.create_string_join "foo"
+      assert_kind_of Arel::Nodes::StringJoin, join
+      assert_equal "foo", join.left
+    end
+
+    it "should create join nodes" do
+      join = @relation.create_join "foo", "bar"
+      assert_kind_of Arel::Nodes::InnerJoin, join
+      assert_equal "foo", join.left
+      assert_equal "bar", join.right
+    end
+
+    it "should create join nodes with a klass" do
+      join = @relation.create_join "foo", "bar", Arel::Nodes::FullOuterJoin
+      assert_kind_of Arel::Nodes::FullOuterJoin, join
+      assert_equal "foo", join.left
+      assert_equal "bar", join.right
+    end
+
+    it "should create join nodes with a klass" do
+      join = @relation.create_join "foo", "bar", Arel::Nodes::OuterJoin
+      assert_kind_of Arel::Nodes::OuterJoin, join
+      assert_equal "foo", join.left
+      assert_equal "bar", join.right
+    end
+
+    it "should create join nodes with a klass" do
+      join = @relation.create_join "foo", "bar", Arel::Nodes::RightOuterJoin
+      assert_kind_of Arel::Nodes::RightOuterJoin, join
+      assert_equal "foo", join.left
+      assert_equal "bar", join.right
+    end
+
+    it "should return an insert manager" do
+      im = @relation.compile_insert "VALUES(NULL)"
+      assert_kind_of Arel::InsertManager, im
+      im.into Table.new(:users)
+      assert_equal "INSERT INTO \"users\" VALUES(NULL)", im.to_sql
+    end
+
+    describe "skip" do
+      it "should add an offset" do
+        sm = @relation.skip 2
+        sm.to_sql.must_be_like "SELECT FROM \"users\" OFFSET 2"
+      end
+    end
+
+    describe "having" do
+      it "adds a having clause" do
+        mgr = @relation.having @relation[:id].eq(10)
+        mgr.to_sql.must_be_like %{
+         SELECT FROM "users" HAVING "users"."id" = 10
+        }
+      end
+    end
+
+    describe "backwards compat" do
+      describe "join" do
+        it "noops on nil" do
+          mgr = @relation.join nil
+
+          mgr.to_sql.must_be_like %{ SELECT FROM "users" }
+        end
+
+        it "raises EmptyJoinError on empty" do
+          assert_raises(EmptyJoinError) do
+            @relation.join ""
+          end
+        end
+
+        it "takes a second argument for join type" do
+          right     = @relation.alias
+          predicate = @relation[:id].eq(right[:id])
+          mgr = @relation.join(right, Nodes::OuterJoin).on(predicate)
+
+          mgr.to_sql.must_be_like %{
+           SELECT FROM "users"
+             LEFT OUTER JOIN "users" "users_2"
+               ON "users"."id" = "users_2"."id"
+          }
+        end
+      end
+
+      describe "join" do
+        it "creates an outer join" do
+          right     = @relation.alias
+          predicate = @relation[:id].eq(right[:id])
+          mgr = @relation.outer_join(right).on(predicate)
+
+          mgr.to_sql.must_be_like %{
+            SELECT FROM "users"
+              LEFT OUTER JOIN "users" "users_2"
+                ON "users"."id" = "users_2"."id"
+          }
+        end
+      end
+    end
+
+    describe "group" do
+      it "should create a group" do
+        manager = @relation.group @relation[:id]
+        manager.to_sql.must_be_like %{
+          SELECT FROM "users" GROUP BY "users"."id"
+        }
+      end
+    end
+
+    describe "alias" do
+      it "should create a node that proxies to a table" do
+        node = @relation.alias
+        node.name.must_equal "users_2"
+        node[:id].relation.must_equal node
+      end
+    end
+
+    describe "new" do
+      it "should accept a hash" do
+        rel = Table.new :users, as: "foo"
+        rel.table_alias.must_equal "foo"
+      end
+
+      it "ignores as if it equals name" do
+        rel = Table.new :users, as: "users"
+        rel.table_alias.must_be_nil
+      end
+    end
+
+    describe "order" do
+      it "should take an order" do
+        manager = @relation.order "foo"
+        manager.to_sql.must_be_like %{ SELECT FROM "users" ORDER BY foo }
+      end
+    end
+
+    describe "take" do
+      it "should add a limit" do
+        manager = @relation.take 1
+        manager.project Nodes::SqlLiteral.new "*"
+        manager.to_sql.must_be_like %{ SELECT * FROM "users" LIMIT 1 }
+      end
+    end
+
+    describe "project" do
+      it "can project" do
+        manager = @relation.project Nodes::SqlLiteral.new "*"
+        manager.to_sql.must_be_like %{ SELECT * FROM "users" }
+      end
+
+      it "takes multiple parameters" do
+        manager = @relation.project Nodes::SqlLiteral.new("*"), Nodes::SqlLiteral.new("*")
+        manager.to_sql.must_be_like %{ SELECT *, * FROM "users" }
+      end
+    end
+
+    describe "where" do
+      it "returns a tree manager" do
+        manager = @relation.where @relation[:id].eq 1
+        manager.project @relation[:id]
+        manager.must_be_kind_of TreeManager
+        manager.to_sql.must_be_like %{
+          SELECT "users"."id"
+          FROM "users"
+          WHERE "users"."id" = 1
+        }
+      end
+    end
+
+    it "should have a name" do
+      @relation.name.must_equal "users"
+    end
+
+    it "should have a table name" do
+      @relation.table_name.must_equal "users"
+    end
+
+    describe "[]" do
+      describe "when given a Symbol" do
+        it "manufactures an attribute if the symbol names an attribute within the relation" do
+          column = @relation[:id]
+          column.name.must_equal :id
+        end
+      end
+    end
+
+    describe "equality" do
+      it "is equal with equal ivars" do
+        relation1 = Table.new(:users)
+        relation1.table_alias = "zomg"
+        relation2 = Table.new(:users)
+        relation2.table_alias = "zomg"
+        array = [relation1, relation2]
+        assert_equal 1, array.uniq.size
+      end
+
+      it "is not equal with different ivars" do
+        relation1 = Table.new(:users)
+        relation1.table_alias = "zomg"
+        relation2 = Table.new(:users)
+        relation2.table_alias = "zomg2"
+        array = [relation1, relation2]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/update_manager_test.rb b/activerecord/test/cases/arel/update_manager_test.rb
new file mode 100644
index 0000000000..cc1b9ac5b3
--- /dev/null
+++ b/activerecord/test/cases/arel/update_manager_test.rb
@@ -0,0 +1,126 @@
+# frozen_string_literal: true
+
+require_relative "helper"
+
+module Arel
+  class UpdateManagerTest < Arel::Spec
+    describe "new" do
+      it "takes an engine" do
+        Arel::UpdateManager.new
+      end
+    end
+
+    it "should not quote sql literals" do
+      table = Table.new(:users)
+      um = Arel::UpdateManager.new
+      um.table table
+      um.set [[table[:name], Arel::Nodes::BindParam.new(1)]]
+      um.to_sql.must_be_like %{ UPDATE "users" SET "name" =  ? }
+    end
+
+    it "handles limit properly" do
+      table = Table.new(:users)
+      um = Arel::UpdateManager.new
+      um.key = "id"
+      um.take 10
+      um.table table
+      um.set [[table[:name], nil]]
+      assert_match(/LIMIT 10/, um.to_sql)
+    end
+
+    describe "set" do
+      it "updates with null" do
+        table = Table.new(:users)
+        um = Arel::UpdateManager.new
+        um.table table
+        um.set [[table[:name], nil]]
+        um.to_sql.must_be_like %{ UPDATE "users" SET "name" =  NULL }
+      end
+
+      it "takes a string" do
+        table = Table.new(:users)
+        um = Arel::UpdateManager.new
+        um.table table
+        um.set Nodes::SqlLiteral.new "foo = bar"
+        um.to_sql.must_be_like %{ UPDATE "users" SET foo = bar }
+      end
+
+      it "takes a list of lists" do
+        table = Table.new(:users)
+        um = Arel::UpdateManager.new
+        um.table table
+        um.set [[table[:id], 1], [table[:name], "hello"]]
+        um.to_sql.must_be_like %{
+          UPDATE "users" SET "id" = 1, "name" =  'hello'
+        }
+      end
+
+      it "chains" do
+        table = Table.new(:users)
+        um = Arel::UpdateManager.new
+        um.set([[table[:id], 1], [table[:name], "hello"]]).must_equal um
+      end
+    end
+
+    describe "table" do
+      it "generates an update statement" do
+        um = Arel::UpdateManager.new
+        um.table Table.new(:users)
+        um.to_sql.must_be_like %{ UPDATE "users" }
+      end
+
+      it "chains" do
+        um = Arel::UpdateManager.new
+        um.table(Table.new(:users)).must_equal um
+      end
+
+      it "generates an update statement with joins" do
+        um = Arel::UpdateManager.new
+
+        table = Table.new(:users)
+        join_source = Arel::Nodes::JoinSource.new(
+          table,
+          [table.create_join(Table.new(:posts))]
+        )
+
+        um.table join_source
+        um.to_sql.must_be_like %{ UPDATE "users" INNER JOIN "posts" }
+      end
+    end
+
+    describe "where" do
+      it "generates a where clause" do
+        table = Table.new :users
+        um = Arel::UpdateManager.new
+        um.table table
+        um.where table[:id].eq(1)
+        um.to_sql.must_be_like %{
+          UPDATE "users" WHERE "users"."id" = 1
+        }
+      end
+
+      it "chains" do
+        table = Table.new :users
+        um = Arel::UpdateManager.new
+        um.table table
+        um.where(table[:id].eq(1)).must_equal um
+      end
+    end
+
+    describe "key" do
+      before do
+        @table = Table.new :users
+        @um = Arel::UpdateManager.new
+        @um.key = @table[:foo]
+      end
+
+      it "can be set" do
+        @um.ast.key.must_equal @table[:foo]
+      end
+
+      it "can be accessed" do
+        @um.key.must_equal @table[:foo]
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/visitors/depth_first_test.rb b/activerecord/test/cases/arel/visitors/depth_first_test.rb
new file mode 100644
index 0000000000..3baccc7316
--- /dev/null
+++ b/activerecord/test/cases/arel/visitors/depth_first_test.rb
@@ -0,0 +1,271 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Visitors
+    class TestDepthFirst < Arel::Test
+      Collector = Struct.new(:calls) do
+        def call(object)
+          calls << object
+        end
+      end
+
+      def setup
+        @collector = Collector.new []
+        @visitor = Visitors::DepthFirst.new @collector
+      end
+
+      def test_raises_with_object
+        assert_raises(TypeError) do
+          @visitor.accept(Object.new)
+        end
+      end
+
+
+      # unary ops
+      [
+        Arel::Nodes::Not,
+        Arel::Nodes::Group,
+        Arel::Nodes::On,
+        Arel::Nodes::Grouping,
+        Arel::Nodes::Offset,
+        Arel::Nodes::Ordering,
+        Arel::Nodes::StringJoin,
+        Arel::Nodes::UnqualifiedColumn,
+        Arel::Nodes::Top,
+        Arel::Nodes::Limit,
+        Arel::Nodes::Else,
+      ].each do |klass|
+        define_method("test_#{klass.name.gsub('::', '_')}") do
+          op = klass.new(:a)
+          @visitor.accept op
+          assert_equal [:a, op], @collector.calls
+        end
+      end
+
+      # functions
+      [
+        Arel::Nodes::Exists,
+        Arel::Nodes::Avg,
+        Arel::Nodes::Min,
+        Arel::Nodes::Max,
+        Arel::Nodes::Sum,
+      ].each do |klass|
+        define_method("test_#{klass.name.gsub('::', '_')}") do
+          func = klass.new(:a, "b")
+          @visitor.accept func
+          assert_equal [:a, "b", false, func], @collector.calls
+        end
+      end
+
+      def test_named_function
+        func = Arel::Nodes::NamedFunction.new(:a, :b, "c")
+        @visitor.accept func
+        assert_equal [:a, :b, false, "c", func], @collector.calls
+      end
+
+      def test_lock
+        lock = Nodes::Lock.new true
+        @visitor.accept lock
+        assert_equal [lock], @collector.calls
+      end
+
+      def test_count
+        count = Nodes::Count.new :a, :b, "c"
+        @visitor.accept count
+        assert_equal [:a, "c", :b, count], @collector.calls
+      end
+
+      def test_inner_join
+        join = Nodes::InnerJoin.new :a, :b
+        @visitor.accept join
+        assert_equal [:a, :b, join], @collector.calls
+      end
+
+      def test_full_outer_join
+        join = Nodes::FullOuterJoin.new :a, :b
+        @visitor.accept join
+        assert_equal [:a, :b, join], @collector.calls
+      end
+
+      def test_outer_join
+        join = Nodes::OuterJoin.new :a, :b
+        @visitor.accept join
+        assert_equal [:a, :b, join], @collector.calls
+      end
+
+      def test_right_outer_join
+        join = Nodes::RightOuterJoin.new :a, :b
+        @visitor.accept join
+        assert_equal [:a, :b, join], @collector.calls
+      end
+
+      [
+        Arel::Nodes::Assignment,
+        Arel::Nodes::Between,
+        Arel::Nodes::Concat,
+        Arel::Nodes::DoesNotMatch,
+        Arel::Nodes::Equality,
+        Arel::Nodes::GreaterThan,
+        Arel::Nodes::GreaterThanOrEqual,
+        Arel::Nodes::In,
+        Arel::Nodes::LessThan,
+        Arel::Nodes::LessThanOrEqual,
+        Arel::Nodes::Matches,
+        Arel::Nodes::NotEqual,
+        Arel::Nodes::NotIn,
+        Arel::Nodes::Or,
+        Arel::Nodes::TableAlias,
+        Arel::Nodes::Values,
+        Arel::Nodes::As,
+        Arel::Nodes::DeleteStatement,
+        Arel::Nodes::JoinSource,
+        Arel::Nodes::When,
+      ].each do |klass|
+        define_method("test_#{klass.name.gsub('::', '_')}") do
+          binary = klass.new(:a, :b)
+          @visitor.accept binary
+          assert_equal [:a, :b, binary], @collector.calls
+        end
+      end
+
+      def test_Arel_Nodes_InfixOperation
+        binary = Arel::Nodes::InfixOperation.new(:o, :a, :b)
+        @visitor.accept binary
+        assert_equal [:a, :b, binary], @collector.calls
+      end
+
+      # N-ary
+      [
+        Arel::Nodes::And,
+      ].each do |klass|
+        define_method("test_#{klass.name.gsub('::', '_')}") do
+          binary = klass.new([:a, :b, :c])
+          @visitor.accept binary
+          assert_equal [:a, :b, :c, binary], @collector.calls
+        end
+      end
+
+      [
+        Arel::Attributes::Integer,
+        Arel::Attributes::Float,
+        Arel::Attributes::String,
+        Arel::Attributes::Time,
+        Arel::Attributes::Boolean,
+        Arel::Attributes::Attribute
+      ].each do |klass|
+        define_method("test_#{klass.name.gsub('::', '_')}") do
+          binary = klass.new(:a, :b)
+          @visitor.accept binary
+          assert_equal [:a, :b, binary], @collector.calls
+        end
+      end
+
+      def test_table
+        relation = Arel::Table.new(:users)
+        @visitor.accept relation
+        assert_equal ["users", relation], @collector.calls
+      end
+
+      def test_array
+        node = Nodes::Or.new(:a, :b)
+        list = [node]
+        @visitor.accept list
+        assert_equal [:a, :b, node, list], @collector.calls
+      end
+
+      def test_set
+        node = Nodes::Or.new(:a, :b)
+        set  = Set.new([node])
+        @visitor.accept set
+        assert_equal [:a, :b, node, set], @collector.calls
+      end
+
+      def test_hash
+        node = Nodes::Or.new(:a, :b)
+        hash = { node => node }
+        @visitor.accept hash
+        assert_equal [:a, :b, node, :a, :b, node, hash], @collector.calls
+      end
+
+      def test_update_statement
+        stmt = Nodes::UpdateStatement.new
+        stmt.relation = :a
+        stmt.values << :b
+        stmt.wheres << :c
+        stmt.orders << :d
+        stmt.limit = :e
+
+        @visitor.accept stmt
+        assert_equal [:a, :b, stmt.values, :c, stmt.wheres, :d, stmt.orders,
+          :e, stmt], @collector.calls
+      end
+
+      def test_select_core
+        core = Nodes::SelectCore.new
+        core.projections << :a
+        core.froms = :b
+        core.wheres << :c
+        core.groups << :d
+        core.windows << :e
+        core.havings << :f
+
+        @visitor.accept core
+        assert_equal [
+          :a, core.projections,
+          :b, [],
+          core.source,
+          :c, core.wheres,
+          :d, core.groups,
+          :e, core.windows,
+          :f, core.havings,
+          core], @collector.calls
+      end
+
+      def test_select_statement
+        ss = Nodes::SelectStatement.new
+        ss.cores.replace [:a]
+        ss.orders << :b
+        ss.limit = :c
+        ss.lock = :d
+        ss.offset = :e
+
+        @visitor.accept ss
+        assert_equal [
+          :a, ss.cores,
+          :b, ss.orders,
+          :c,
+          :d,
+          :e,
+          ss], @collector.calls
+      end
+
+      def test_insert_statement
+        stmt = Nodes::InsertStatement.new
+        stmt.relation = :a
+        stmt.columns << :b
+        stmt.values = :c
+
+        @visitor.accept stmt
+        assert_equal [:a, :b, stmt.columns, :c, stmt], @collector.calls
+      end
+
+      def test_case
+        node = Arel::Nodes::Case.new
+        node.case = :a
+        node.conditions << :b
+        node.default = :c
+
+        @visitor.accept node
+        assert_equal [:a, :b, node.conditions, :c, node], @collector.calls
+      end
+
+      def test_node
+        node = Nodes::Node.new
+        @visitor.accept node
+        assert_equal [node], @collector.calls
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/visitors/dispatch_contamination_test.rb b/activerecord/test/cases/arel/visitors/dispatch_contamination_test.rb
new file mode 100644
index 0000000000..a07a1a050a
--- /dev/null
+++ b/activerecord/test/cases/arel/visitors/dispatch_contamination_test.rb
@@ -0,0 +1,72 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+require "concurrent"
+
+module Arel
+  module Visitors
+    class DummyVisitor < Visitor
+      def initialize
+        super
+        @barrier = Concurrent::CyclicBarrier.new(2)
+      end
+
+      def visit_Arel_Visitors_DummySuperNode(node)
+        42
+      end
+
+      # This is terrible, but it's the only way to reliably reproduce
+      # the possible race where two threads attempt to correct the
+      # dispatch hash at the same time.
+      def send(*args)
+        super
+      rescue
+        # Both threads try (and fail) to dispatch to the subclass's name
+        @barrier.wait
+        raise
+      ensure
+        # Then one thread successfully completes (updating the dispatch
+        # table in the process) before the other finishes raising its
+        # exception.
+        Thread.current[:delay].wait if Thread.current[:delay]
+      end
+    end
+
+    class DummySuperNode
+    end
+
+    class DummySubNode < DummySuperNode
+    end
+
+    class DispatchContaminationTest < Arel::Spec
+      before do
+        @connection = Table.engine.connection
+        @table = Table.new(:users)
+      end
+
+      it "dispatches properly after failing upwards" do
+        node = Nodes::Union.new(Nodes::True.new, Nodes::False.new)
+        assert_equal "( TRUE UNION FALSE )", node.to_sql
+
+        node.first # from Nodes::Node's Enumerable mixin
+
+        assert_equal "( TRUE UNION FALSE )", node.to_sql
+      end
+
+      it "is threadsafe when implementing superclass fallback" do
+        visitor = DummyVisitor.new
+        main_thread_finished = Concurrent::Event.new
+
+        racing_thread = Thread.new do
+          Thread.current[:delay] = main_thread_finished
+          visitor.accept DummySubNode.new
+        end
+
+        assert_equal 42, visitor.accept(DummySubNode.new)
+        main_thread_finished.set
+
+        assert_equal 42, racing_thread.value
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/visitors/dot_test.rb b/activerecord/test/cases/arel/visitors/dot_test.rb
new file mode 100644
index 0000000000..98f3bab620
--- /dev/null
+++ b/activerecord/test/cases/arel/visitors/dot_test.rb
@@ -0,0 +1,84 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Visitors
+    class TestDot < Arel::Test
+      def setup
+        @visitor = Visitors::Dot.new
+      end
+
+      # functions
+      [
+        Nodes::Sum,
+        Nodes::Exists,
+        Nodes::Max,
+        Nodes::Min,
+        Nodes::Avg,
+      ].each do |klass|
+        define_method("test_#{klass.name.gsub('::', '_')}") do
+          op = klass.new(:a, "z")
+          @visitor.accept op, Collectors::PlainString.new
+        end
+      end
+
+      def test_named_function
+        func = Nodes::NamedFunction.new "omg", "omg"
+        @visitor.accept func, Collectors::PlainString.new
+      end
+
+      # unary ops
+      [
+        Arel::Nodes::Not,
+        Arel::Nodes::Group,
+        Arel::Nodes::On,
+        Arel::Nodes::Grouping,
+        Arel::Nodes::Offset,
+        Arel::Nodes::Ordering,
+        Arel::Nodes::UnqualifiedColumn,
+        Arel::Nodes::Top,
+        Arel::Nodes::Limit,
+      ].each do |klass|
+        define_method("test_#{klass.name.gsub('::', '_')}") do
+          op = klass.new(:a)
+          @visitor.accept op, Collectors::PlainString.new
+        end
+      end
+
+      # binary ops
+      [
+        Arel::Nodes::Assignment,
+        Arel::Nodes::Between,
+        Arel::Nodes::DoesNotMatch,
+        Arel::Nodes::Equality,
+        Arel::Nodes::GreaterThan,
+        Arel::Nodes::GreaterThanOrEqual,
+        Arel::Nodes::In,
+        Arel::Nodes::LessThan,
+        Arel::Nodes::LessThanOrEqual,
+        Arel::Nodes::Matches,
+        Arel::Nodes::NotEqual,
+        Arel::Nodes::NotIn,
+        Arel::Nodes::Or,
+        Arel::Nodes::TableAlias,
+        Arel::Nodes::Values,
+        Arel::Nodes::As,
+        Arel::Nodes::DeleteStatement,
+        Arel::Nodes::JoinSource,
+        Arel::Nodes::Casted,
+      ].each do |klass|
+        define_method("test_#{klass.name.gsub('::', '_')}") do
+          binary = klass.new(:a, :b)
+          @visitor.accept binary, Collectors::PlainString.new
+        end
+      end
+
+      def test_Arel_Nodes_BindParam
+        node = Arel::Nodes::BindParam.new(1)
+        collector = Collectors::PlainString.new
+        assert_match '[label="<f0>Arel::Nodes::BindParam"]', @visitor.accept(node, collector).value
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/visitors/ibm_db_test.rb b/activerecord/test/cases/arel/visitors/ibm_db_test.rb
new file mode 100644
index 0000000000..7163cb34d3
--- /dev/null
+++ b/activerecord/test/cases/arel/visitors/ibm_db_test.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Visitors
+    class IbmDbTest < Arel::Spec
+      before do
+        @visitor = IBM_DB.new Table.engine.connection
+      end
+
+      def compile(node)
+        @visitor.accept(node, Collectors::SQLString.new).value
+      end
+
+      it "uses FETCH FIRST n ROWS to limit results" do
+        stmt = Nodes::SelectStatement.new
+        stmt.limit = Nodes::Limit.new(1)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT FETCH FIRST 1 ROWS ONLY"
+      end
+
+      it "uses FETCH FIRST n ROWS in updates with a limit" do
+        table = Table.new(:users)
+        stmt = Nodes::UpdateStatement.new
+        stmt.relation = table
+        stmt.limit = Nodes::Limit.new(Nodes.build_quoted(1))
+        stmt.key = table[:id]
+        sql = compile(stmt)
+        sql.must_be_like "UPDATE \"users\" WHERE \"users\".\"id\" IN (SELECT \"users\".\"id\" FROM \"users\" FETCH FIRST 1 ROWS ONLY)"
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/visitors/informix_test.rb b/activerecord/test/cases/arel/visitors/informix_test.rb
new file mode 100644
index 0000000000..b0b031cca3
--- /dev/null
+++ b/activerecord/test/cases/arel/visitors/informix_test.rb
@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Visitors
+    class InformixTest < Arel::Spec
+      before do
+        @visitor = Informix.new Table.engine.connection
+      end
+
+      def compile(node)
+        @visitor.accept(node, Collectors::SQLString.new).value
+      end
+
+      it "uses FIRST n to limit results" do
+        stmt = Nodes::SelectStatement.new
+        stmt.limit = Nodes::Limit.new(1)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT FIRST 1"
+      end
+
+      it "uses FIRST n in updates with a limit" do
+        table = Table.new(:users)
+        stmt = Nodes::UpdateStatement.new
+        stmt.relation = table
+        stmt.limit = Nodes::Limit.new(Nodes.build_quoted(1))
+        stmt.key = table[:id]
+        sql = compile(stmt)
+        sql.must_be_like "UPDATE \"users\" WHERE \"users\".\"id\" IN (SELECT FIRST 1 \"users\".\"id\" FROM \"users\")"
+      end
+
+      it "uses SKIP n to jump results" do
+        stmt = Nodes::SelectStatement.new
+        stmt.offset = Nodes::Offset.new(10)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT SKIP 10"
+      end
+
+      it "uses SKIP before FIRST" do
+        stmt = Nodes::SelectStatement.new
+        stmt.limit = Nodes::Limit.new(1)
+        stmt.offset = Nodes::Offset.new(1)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT SKIP 1 FIRST 1"
+      end
+
+      it "uses INNER JOIN to perform joins" do
+        core = Nodes::SelectCore.new
+        table = Table.new(:posts)
+        core.source = Nodes::JoinSource.new(table, [table.create_join(Table.new(:comments))])
+
+        stmt = Nodes::SelectStatement.new([core])
+        sql = compile(stmt)
+        sql.must_be_like 'SELECT FROM "posts" INNER JOIN "comments"'
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/visitors/mssql_test.rb b/activerecord/test/cases/arel/visitors/mssql_test.rb
new file mode 100644
index 0000000000..340376c3d6
--- /dev/null
+++ b/activerecord/test/cases/arel/visitors/mssql_test.rb
@@ -0,0 +1,99 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Visitors
+    class MssqlTest < Arel::Spec
+      before do
+        @visitor = MSSQL.new Table.engine.connection
+        @table = Arel::Table.new "users"
+      end
+
+      def compile(node)
+        @visitor.accept(node, Collectors::SQLString.new).value
+      end
+
+      it "should not modify query if no offset or limit" do
+        stmt = Nodes::SelectStatement.new
+        sql = compile(stmt)
+        sql.must_be_like "SELECT"
+      end
+
+      it "should go over table PK if no .order() or .group()" do
+        stmt = Nodes::SelectStatement.new
+        stmt.cores.first.from = @table
+        stmt.limit = Nodes::Limit.new(10)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT _t.* FROM (SELECT ROW_NUMBER() OVER (ORDER BY \"users\".\"id\") as _row_num FROM \"users\") as _t WHERE _row_num BETWEEN 1 AND 10"
+      end
+
+      it "caches the PK lookup for order" do
+        connection = Minitest::Mock.new
+        connection.expect(:primary_key, ["id"], ["users"])
+
+        # We don't care how many times these methods are called
+        def connection.quote_table_name(*); ""; end
+        def connection.quote_column_name(*); ""; end
+
+        @visitor = MSSQL.new(connection)
+        stmt = Nodes::SelectStatement.new
+        stmt.cores.first.from = @table
+        stmt.limit = Nodes::Limit.new(10)
+
+        compile(stmt)
+        compile(stmt)
+
+        connection.verify
+      end
+
+      it "should use TOP for limited deletes" do
+        stmt = Nodes::DeleteStatement.new
+        stmt.relation = @table
+        stmt.limit = Nodes::Limit.new(10)
+        sql = compile(stmt)
+
+        sql.must_be_like "DELETE TOP (10) FROM \"users\""
+      end
+
+      it "should go over query ORDER BY if .order()" do
+        stmt = Nodes::SelectStatement.new
+        stmt.limit = Nodes::Limit.new(10)
+        stmt.orders << Nodes::SqlLiteral.new("order_by")
+        sql = compile(stmt)
+        sql.must_be_like "SELECT _t.* FROM (SELECT ROW_NUMBER() OVER (ORDER BY order_by) as _row_num) as _t WHERE _row_num BETWEEN 1 AND 10"
+      end
+
+      it "should go over query GROUP BY if no .order() and there is .group()" do
+        stmt = Nodes::SelectStatement.new
+        stmt.cores.first.groups << Nodes::SqlLiteral.new("group_by")
+        stmt.limit = Nodes::Limit.new(10)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT _t.* FROM (SELECT ROW_NUMBER() OVER (ORDER BY group_by) as _row_num GROUP BY group_by) as _t WHERE _row_num BETWEEN 1 AND 10"
+      end
+
+      it "should use BETWEEN if both .limit() and .offset" do
+        stmt = Nodes::SelectStatement.new
+        stmt.limit = Nodes::Limit.new(10)
+        stmt.offset = Nodes::Offset.new(20)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT _t.* FROM (SELECT ROW_NUMBER() OVER (ORDER BY ) as _row_num) as _t WHERE _row_num BETWEEN 21 AND 30"
+      end
+
+      it "should use >= if only .offset" do
+        stmt = Nodes::SelectStatement.new
+        stmt.offset = Nodes::Offset.new(20)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT _t.* FROM (SELECT ROW_NUMBER() OVER (ORDER BY ) as _row_num) as _t WHERE _row_num >= 21"
+      end
+
+      it "should generate subquery for .count" do
+        stmt = Nodes::SelectStatement.new
+        stmt.limit = Nodes::Limit.new(10)
+        stmt.cores.first.projections << Nodes::Count.new("*")
+        sql = compile(stmt)
+        sql.must_be_like "SELECT COUNT(1) as count_id FROM (SELECT _t.* FROM (SELECT ROW_NUMBER() OVER (ORDER BY ) as _row_num) as _t WHERE _row_num BETWEEN 1 AND 10) AS subquery"
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/visitors/mysql_test.rb b/activerecord/test/cases/arel/visitors/mysql_test.rb
new file mode 100644
index 0000000000..9d3bad8516
--- /dev/null
+++ b/activerecord/test/cases/arel/visitors/mysql_test.rb
@@ -0,0 +1,80 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Visitors
+    class MysqlTest < Arel::Spec
+      before do
+        @visitor = MySQL.new Table.engine.connection
+      end
+
+      def compile(node)
+        @visitor.accept(node, Collectors::SQLString.new).value
+      end
+
+      it "squashes parenthesis on multiple unions" do
+        subnode = Nodes::Union.new Arel.sql("left"), Arel.sql("right")
+        node    = Nodes::Union.new subnode, Arel.sql("topright")
+        assert_equal 1, compile(node).scan("(").length
+
+        subnode = Nodes::Union.new Arel.sql("left"), Arel.sql("right")
+        node    = Nodes::Union.new Arel.sql("topleft"), subnode
+        assert_equal 1, compile(node).scan("(").length
+      end
+
+      ###
+      # :'(
+      # http://dev.mysql.com/doc/refman/5.0/en/select.html#id3482214
+      it "defaults limit to 18446744073709551615" do
+        stmt = Nodes::SelectStatement.new
+        stmt.offset = Nodes::Offset.new(1)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT FROM DUAL LIMIT 18446744073709551615 OFFSET 1"
+      end
+
+      it "should escape LIMIT" do
+        sc = Arel::Nodes::UpdateStatement.new
+        sc.relation = Table.new(:users)
+        sc.limit = Nodes::Limit.new(Nodes.build_quoted("omg"))
+        assert_equal("UPDATE \"users\" LIMIT 'omg'", compile(sc))
+      end
+
+      it "uses DUAL for empty from" do
+        stmt = Nodes::SelectStatement.new
+        sql = compile(stmt)
+        sql.must_be_like "SELECT FROM DUAL"
+      end
+
+      describe "locking" do
+        it "defaults to FOR UPDATE when locking" do
+          node = Nodes::Lock.new(Arel.sql("FOR UPDATE"))
+          compile(node).must_be_like "FOR UPDATE"
+        end
+
+        it "allows a custom string to be used as a lock" do
+          node = Nodes::Lock.new(Arel.sql("LOCK IN SHARE MODE"))
+          compile(node).must_be_like "LOCK IN SHARE MODE"
+        end
+      end
+
+      describe "concat" do
+        it "concats columns" do
+          @table = Table.new(:users)
+          query = @table[:name].concat(@table[:name])
+          compile(query).must_be_like %{
+            CONCAT("users"."name", "users"."name")
+          }
+        end
+
+        it "concats a string" do
+          @table = Table.new(:users)
+          query = @table[:name].concat(Nodes.build_quoted("abc"))
+          compile(query).must_be_like %{
+            CONCAT("users"."name", 'abc')
+          }
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/visitors/oracle12_test.rb b/activerecord/test/cases/arel/visitors/oracle12_test.rb
new file mode 100644
index 0000000000..83a2ee36ca
--- /dev/null
+++ b/activerecord/test/cases/arel/visitors/oracle12_test.rb
@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Visitors
+    class Oracle12Test < Arel::Spec
+      before do
+        @visitor = Oracle12.new Table.engine.connection
+        @table = Table.new(:users)
+      end
+
+      def compile(node)
+        @visitor.accept(node, Collectors::SQLString.new).value
+      end
+
+      it "modified except to be minus" do
+        left = Nodes::SqlLiteral.new("SELECT * FROM users WHERE age > 10")
+        right = Nodes::SqlLiteral.new("SELECT * FROM users WHERE age > 20")
+        sql = compile Nodes::Except.new(left, right)
+        sql.must_be_like %{
+          ( SELECT * FROM users WHERE age > 10 MINUS SELECT * FROM users WHERE age > 20 )
+        }
+      end
+
+      it "generates select options offset then limit" do
+        stmt = Nodes::SelectStatement.new
+        stmt.offset = Nodes::Offset.new(1)
+        stmt.limit = Nodes::Limit.new(10)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT OFFSET 1 ROWS FETCH FIRST 10 ROWS ONLY"
+      end
+
+      describe "locking" do
+        it "generates ArgumentError if limit and lock are used" do
+          stmt = Nodes::SelectStatement.new
+          stmt.limit = Nodes::Limit.new(10)
+          stmt.lock = Nodes::Lock.new(Arel.sql("FOR UPDATE"))
+          assert_raises ArgumentError do
+            compile(stmt)
+          end
+        end
+
+        it "defaults to FOR UPDATE when locking" do
+          node = Nodes::Lock.new(Arel.sql("FOR UPDATE"))
+          compile(node).must_be_like "FOR UPDATE"
+        end
+      end
+
+      describe "Nodes::BindParam" do
+        it "increments each bind param" do
+          query = @table[:name].eq(Arel::Nodes::BindParam.new(1))
+            .and(@table[:id].eq(Arel::Nodes::BindParam.new(1)))
+          compile(query).must_be_like %{
+            "users"."name" = :a1 AND "users"."id" = :a2
+          }
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/visitors/oracle_test.rb b/activerecord/test/cases/arel/visitors/oracle_test.rb
new file mode 100644
index 0000000000..e1dfe40cf9
--- /dev/null
+++ b/activerecord/test/cases/arel/visitors/oracle_test.rb
@@ -0,0 +1,197 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Visitors
+    class OracleTest < Arel::Spec
+      before do
+        @visitor = Oracle.new Table.engine.connection
+        @table = Table.new(:users)
+      end
+
+      def compile(node)
+        @visitor.accept(node, Collectors::SQLString.new).value
+      end
+
+      it "modifies order when there is distinct and first value" do
+        # *sigh*
+        select = "DISTINCT foo.id, FIRST_VALUE(projects.name) OVER (foo) AS alias_0__"
+        stmt = Nodes::SelectStatement.new
+        stmt.cores.first.projections << Nodes::SqlLiteral.new(select)
+        stmt.orders << Nodes::SqlLiteral.new("foo")
+        sql = compile(stmt)
+        sql.must_be_like %{
+          SELECT #{select} ORDER BY alias_0__
+        }
+      end
+
+      it "is idempotent with crazy query" do
+        # *sigh*
+        select = "DISTINCT foo.id, FIRST_VALUE(projects.name) OVER (foo) AS alias_0__"
+        stmt = Nodes::SelectStatement.new
+        stmt.cores.first.projections << Nodes::SqlLiteral.new(select)
+        stmt.orders << Nodes::SqlLiteral.new("foo")
+
+        sql = compile(stmt)
+        sql2 = compile(stmt)
+        sql.must_equal sql2
+      end
+
+      it "splits orders with commas" do
+        # *sigh*
+        select = "DISTINCT foo.id, FIRST_VALUE(projects.name) OVER (foo) AS alias_0__"
+        stmt = Nodes::SelectStatement.new
+        stmt.cores.first.projections << Nodes::SqlLiteral.new(select)
+        stmt.orders << Nodes::SqlLiteral.new("foo, bar")
+        sql = compile(stmt)
+        sql.must_be_like %{
+          SELECT #{select} ORDER BY alias_0__, alias_1__
+        }
+      end
+
+      it "splits orders with commas and function calls" do
+        # *sigh*
+        select = "DISTINCT foo.id, FIRST_VALUE(projects.name) OVER (foo) AS alias_0__"
+        stmt = Nodes::SelectStatement.new
+        stmt.cores.first.projections << Nodes::SqlLiteral.new(select)
+        stmt.orders << Nodes::SqlLiteral.new("NVL(LOWER(bar, foo), foo) DESC, UPPER(baz)")
+        sql = compile(stmt)
+        sql.must_be_like %{
+          SELECT #{select} ORDER BY alias_0__ DESC, alias_1__
+        }
+      end
+
+      describe "Nodes::SelectStatement" do
+        describe "limit" do
+          it "adds a rownum clause" do
+            stmt = Nodes::SelectStatement.new
+            stmt.limit = Nodes::Limit.new(10)
+            sql = compile stmt
+            sql.must_be_like %{ SELECT WHERE ROWNUM <= 10 }
+          end
+
+          it "is idempotent" do
+            stmt = Nodes::SelectStatement.new
+            stmt.orders << Nodes::SqlLiteral.new("foo")
+            stmt.limit = Nodes::Limit.new(10)
+            sql = compile stmt
+            sql2 = compile stmt
+            sql.must_equal sql2
+          end
+
+          it "creates a subquery when there is order_by" do
+            stmt = Nodes::SelectStatement.new
+            stmt.orders << Nodes::SqlLiteral.new("foo")
+            stmt.limit = Nodes::Limit.new(10)
+            sql = compile stmt
+            sql.must_be_like %{
+              SELECT * FROM (SELECT ORDER BY foo ) WHERE ROWNUM <= 10
+            }
+          end
+
+          it "creates a subquery when there is group by" do
+            stmt = Nodes::SelectStatement.new
+            stmt.cores.first.groups << Nodes::SqlLiteral.new("foo")
+            stmt.limit = Nodes::Limit.new(10)
+            sql = compile stmt
+            sql.must_be_like %{
+              SELECT * FROM (SELECT GROUP BY foo ) WHERE ROWNUM <= 10
+            }
+          end
+
+          it "creates a subquery when there is DISTINCT" do
+            stmt = Nodes::SelectStatement.new
+            stmt.cores.first.set_quantifier = Arel::Nodes::Distinct.new
+            stmt.cores.first.projections << Nodes::SqlLiteral.new("id")
+            stmt.limit = Arel::Nodes::Limit.new(10)
+            sql = compile stmt
+            sql.must_be_like %{
+              SELECT * FROM (SELECT DISTINCT id ) WHERE ROWNUM <= 10
+            }
+          end
+
+          it "creates a different subquery when there is an offset" do
+            stmt = Nodes::SelectStatement.new
+            stmt.limit = Nodes::Limit.new(10)
+            stmt.offset = Nodes::Offset.new(10)
+            sql = compile stmt
+            sql.must_be_like %{
+              SELECT * FROM (
+                SELECT raw_sql_.*, rownum raw_rnum_
+                FROM (SELECT ) raw_sql_
+                 WHERE rownum <= 20
+              )
+              WHERE raw_rnum_ > 10
+            }
+          end
+
+          it "creates a subquery when there is limit and offset with BindParams" do
+            stmt = Nodes::SelectStatement.new
+            stmt.limit = Nodes::Limit.new(Nodes::BindParam.new(1))
+            stmt.offset = Nodes::Offset.new(Nodes::BindParam.new(1))
+            sql = compile stmt
+            sql.must_be_like %{
+              SELECT * FROM (
+                SELECT raw_sql_.*, rownum raw_rnum_
+                FROM (SELECT ) raw_sql_
+                 WHERE rownum <= (:a1 + :a2)
+              )
+              WHERE raw_rnum_ > :a3
+            }
+          end
+
+          it "is idempotent with different subquery" do
+            stmt = Nodes::SelectStatement.new
+            stmt.limit = Nodes::Limit.new(10)
+            stmt.offset = Nodes::Offset.new(10)
+            sql = compile stmt
+            sql2 = compile stmt
+            sql.must_equal sql2
+          end
+        end
+
+        describe "only offset" do
+          it "creates a select from subquery with rownum condition" do
+            stmt = Nodes::SelectStatement.new
+            stmt.offset = Nodes::Offset.new(10)
+            sql = compile stmt
+            sql.must_be_like %{
+              SELECT * FROM (
+                SELECT raw_sql_.*, rownum raw_rnum_
+                FROM (SELECT) raw_sql_
+              )
+              WHERE raw_rnum_ > 10
+            }
+          end
+        end
+      end
+
+      it "modified except to be minus" do
+        left = Nodes::SqlLiteral.new("SELECT * FROM users WHERE age > 10")
+        right = Nodes::SqlLiteral.new("SELECT * FROM users WHERE age > 20")
+        sql = compile Nodes::Except.new(left, right)
+        sql.must_be_like %{
+          ( SELECT * FROM users WHERE age > 10 MINUS SELECT * FROM users WHERE age > 20 )
+        }
+      end
+
+      describe "locking" do
+        it "defaults to FOR UPDATE when locking" do
+          node = Nodes::Lock.new(Arel.sql("FOR UPDATE"))
+          compile(node).must_be_like "FOR UPDATE"
+        end
+      end
+
+      describe "Nodes::BindParam" do
+        it "increments each bind param" do
+          query = @table[:name].eq(Arel::Nodes::BindParam.new(1))
+            .and(@table[:id].eq(Arel::Nodes::BindParam.new(1)))
+          compile(query).must_be_like %{
+            "users"."name" = :a1 AND "users"."id" = :a2
+          }
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/visitors/postgres_test.rb b/activerecord/test/cases/arel/visitors/postgres_test.rb
new file mode 100644
index 0000000000..ba37afecfb
--- /dev/null
+++ b/activerecord/test/cases/arel/visitors/postgres_test.rb
@@ -0,0 +1,281 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Visitors
+    class PostgresTest < Arel::Spec
+      before do
+        @visitor = PostgreSQL.new Table.engine.connection
+        @table = Table.new(:users)
+        @attr = @table[:id]
+      end
+
+      def compile(node)
+        @visitor.accept(node, Collectors::SQLString.new).value
+      end
+
+      describe "locking" do
+        it "defaults to FOR UPDATE" do
+          compile(Nodes::Lock.new(Arel.sql("FOR UPDATE"))).must_be_like %{
+            FOR UPDATE
+          }
+        end
+
+        it "allows a custom string to be used as a lock" do
+          node = Nodes::Lock.new(Arel.sql("FOR SHARE"))
+          compile(node).must_be_like %{
+            FOR SHARE
+          }
+        end
+      end
+
+      it "should escape LIMIT" do
+        sc = Arel::Nodes::SelectStatement.new
+        sc.limit = Nodes::Limit.new(Nodes.build_quoted("omg"))
+        sc.cores.first.projections << Arel.sql("DISTINCT ON")
+        sc.orders << Arel.sql("xyz")
+        sql = compile(sc)
+        assert_match(/LIMIT 'omg'/, sql)
+        assert_equal 1, sql.scan(/LIMIT/).length, "should have one limit"
+      end
+
+      it "should support DISTINCT ON" do
+        core = Arel::Nodes::SelectCore.new
+        core.set_quantifier = Arel::Nodes::DistinctOn.new(Arel.sql("aaron"))
+        assert_match "DISTINCT ON ( aaron )", compile(core)
+      end
+
+      it "should support DISTINCT" do
+        core = Arel::Nodes::SelectCore.new
+        core.set_quantifier = Arel::Nodes::Distinct.new
+        assert_equal "SELECT DISTINCT", compile(core)
+      end
+
+      it "encloses LATERAL queries in parens" do
+        subquery = @table.project(:id).where(@table[:name].matches("foo%"))
+        compile(subquery.lateral).must_be_like %{
+          LATERAL (SELECT id FROM "users" WHERE "users"."name" ILIKE 'foo%')
+        }
+      end
+
+      it "produces LATERAL queries with alias" do
+        subquery = @table.project(:id).where(@table[:name].matches("foo%"))
+        compile(subquery.lateral("bar")).must_be_like %{
+          LATERAL (SELECT id FROM "users" WHERE "users"."name" ILIKE 'foo%') bar
+        }
+      end
+
+      describe "Nodes::Matches" do
+        it "should know how to visit" do
+          node = @table[:name].matches("foo%")
+          node.must_be_kind_of Nodes::Matches
+          node.case_sensitive.must_equal(false)
+          compile(node).must_be_like %{
+            "users"."name" ILIKE 'foo%'
+          }
+        end
+
+        it "should know how to visit case sensitive" do
+          node = @table[:name].matches("foo%", nil, true)
+          node.case_sensitive.must_equal(true)
+          compile(node).must_be_like %{
+            "users"."name" LIKE 'foo%'
+          }
+        end
+
+        it "can handle ESCAPE" do
+          node = @table[:name].matches("foo!%", "!")
+          compile(node).must_be_like %{
+            "users"."name" ILIKE 'foo!%' ESCAPE '!'
+          }
+        end
+
+        it "can handle subqueries" do
+          subquery = @table.project(:id).where(@table[:name].matches("foo%"))
+          node = @attr.in subquery
+          compile(node).must_be_like %{
+            "users"."id" IN (SELECT id FROM "users" WHERE "users"."name" ILIKE 'foo%')
+          }
+        end
+      end
+
+      describe "Nodes::DoesNotMatch" do
+        it "should know how to visit" do
+          node = @table[:name].does_not_match("foo%")
+          node.must_be_kind_of Nodes::DoesNotMatch
+          node.case_sensitive.must_equal(false)
+          compile(node).must_be_like %{
+            "users"."name" NOT ILIKE 'foo%'
+          }
+        end
+
+        it "should know how to visit case sensitive" do
+          node = @table[:name].does_not_match("foo%", nil, true)
+          node.case_sensitive.must_equal(true)
+          compile(node).must_be_like %{
+            "users"."name" NOT LIKE 'foo%'
+          }
+        end
+
+        it "can handle ESCAPE" do
+          node = @table[:name].does_not_match("foo!%", "!")
+          compile(node).must_be_like %{
+            "users"."name" NOT ILIKE 'foo!%' ESCAPE '!'
+          }
+        end
+
+        it "can handle subqueries" do
+          subquery = @table.project(:id).where(@table[:name].does_not_match("foo%"))
+          node = @attr.in subquery
+          compile(node).must_be_like %{
+            "users"."id" IN (SELECT id FROM "users" WHERE "users"."name" NOT ILIKE 'foo%')
+          }
+        end
+      end
+
+      describe "Nodes::Regexp" do
+        it "should know how to visit" do
+          node = @table[:name].matches_regexp("foo.*")
+          node.must_be_kind_of Nodes::Regexp
+          node.case_sensitive.must_equal(true)
+          compile(node).must_be_like %{
+            "users"."name" ~ 'foo.*'
+          }
+        end
+
+        it "can handle case insensitive" do
+          node = @table[:name].matches_regexp("foo.*", false)
+          node.must_be_kind_of Nodes::Regexp
+          node.case_sensitive.must_equal(false)
+          compile(node).must_be_like %{
+            "users"."name" ~* 'foo.*'
+          }
+        end
+
+        it "can handle subqueries" do
+          subquery = @table.project(:id).where(@table[:name].matches_regexp("foo.*"))
+          node = @attr.in subquery
+          compile(node).must_be_like %{
+            "users"."id" IN (SELECT id FROM "users" WHERE "users"."name" ~ 'foo.*')
+          }
+        end
+      end
+
+      describe "Nodes::NotRegexp" do
+        it "should know how to visit" do
+          node = @table[:name].does_not_match_regexp("foo.*")
+          node.must_be_kind_of Nodes::NotRegexp
+          node.case_sensitive.must_equal(true)
+          compile(node).must_be_like %{
+            "users"."name" !~ 'foo.*'
+          }
+        end
+
+        it "can handle case insensitive" do
+          node = @table[:name].does_not_match_regexp("foo.*", false)
+          node.case_sensitive.must_equal(false)
+          compile(node).must_be_like %{
+            "users"."name" !~* 'foo.*'
+          }
+        end
+
+        it "can handle subqueries" do
+          subquery = @table.project(:id).where(@table[:name].does_not_match_regexp("foo.*"))
+          node = @attr.in subquery
+          compile(node).must_be_like %{
+            "users"."id" IN (SELECT id FROM "users" WHERE "users"."name" !~ 'foo.*')
+          }
+        end
+      end
+
+      describe "Nodes::BindParam" do
+        it "increments each bind param" do
+          query = @table[:name].eq(Arel::Nodes::BindParam.new(1))
+            .and(@table[:id].eq(Arel::Nodes::BindParam.new(1)))
+          compile(query).must_be_like %{
+            "users"."name" = $1 AND "users"."id" = $2
+          }
+        end
+      end
+
+      describe "Nodes::Cube" do
+        it "should know how to visit with array arguments" do
+          node = Arel::Nodes::Cube.new([@table[:name], @table[:bool]])
+          compile(node).must_be_like %{
+            CUBE( "users"."name", "users"."bool" )
+          }
+        end
+
+        it "should know how to visit with CubeDimension Argument" do
+          dimensions = Arel::Nodes::GroupingElement.new([@table[:name], @table[:bool]])
+          node = Arel::Nodes::Cube.new(dimensions)
+          compile(node).must_be_like %{
+            CUBE( "users"."name", "users"."bool" )
+          }
+        end
+
+        it "should know how to generate paranthesis when supplied with many Dimensions" do
+          dim1 = Arel::Nodes::GroupingElement.new(@table[:name])
+          dim2 = Arel::Nodes::GroupingElement.new([@table[:bool], @table[:created_at]])
+          node = Arel::Nodes::Cube.new([dim1, dim2])
+          compile(node).must_be_like %{
+            CUBE( ( "users"."name" ), ( "users"."bool", "users"."created_at" ) )
+          }
+        end
+      end
+
+      describe "Nodes::GroupingSet" do
+        it "should know how to visit with array arguments" do
+          node = Arel::Nodes::GroupingSet.new([@table[:name], @table[:bool]])
+          compile(node).must_be_like %{
+            GROUPING SET( "users"."name", "users"."bool" )
+          }
+        end
+
+        it "should know how to visit with CubeDimension Argument" do
+          group = Arel::Nodes::GroupingElement.new([@table[:name], @table[:bool]])
+          node = Arel::Nodes::GroupingSet.new(group)
+          compile(node).must_be_like %{
+            GROUPING SET( "users"."name", "users"."bool" )
+          }
+        end
+
+        it "should know how to generate paranthesis when supplied with many Dimensions" do
+          group1 = Arel::Nodes::GroupingElement.new(@table[:name])
+          group2 = Arel::Nodes::GroupingElement.new([@table[:bool], @table[:created_at]])
+          node = Arel::Nodes::GroupingSet.new([group1, group2])
+          compile(node).must_be_like %{
+            GROUPING SET( ( "users"."name" ), ( "users"."bool", "users"."created_at" ) )
+          }
+        end
+      end
+
+      describe "Nodes::RollUp" do
+        it "should know how to visit with array arguments" do
+          node = Arel::Nodes::RollUp.new([@table[:name], @table[:bool]])
+          compile(node).must_be_like %{
+            ROLLUP( "users"."name", "users"."bool" )
+          }
+        end
+
+        it "should know how to visit with CubeDimension Argument" do
+          group = Arel::Nodes::GroupingElement.new([@table[:name], @table[:bool]])
+          node = Arel::Nodes::RollUp.new(group)
+          compile(node).must_be_like %{
+            ROLLUP( "users"."name", "users"."bool" )
+          }
+        end
+
+        it "should know how to generate paranthesis when supplied with many Dimensions" do
+          group1 = Arel::Nodes::GroupingElement.new(@table[:name])
+          group2 = Arel::Nodes::GroupingElement.new([@table[:bool], @table[:created_at]])
+          node = Arel::Nodes::RollUp.new([group1, group2])
+          compile(node).must_be_like %{
+            ROLLUP( ( "users"."name" ), ( "users"."bool", "users"."created_at" ) )
+          }
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/visitors/sqlite_test.rb b/activerecord/test/cases/arel/visitors/sqlite_test.rb
new file mode 100644
index 0000000000..6650b6ff3a
--- /dev/null
+++ b/activerecord/test/cases/arel/visitors/sqlite_test.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+
+module Arel
+  module Visitors
+    class SqliteTest < Arel::Spec
+      before do
+        @visitor = SQLite.new Table.engine.connection_pool
+      end
+
+      it "defaults limit to -1" do
+        stmt = Nodes::SelectStatement.new
+        stmt.offset = Nodes::Offset.new(1)
+        sql = @visitor.accept(stmt, Collectors::SQLString.new).value
+        sql.must_be_like "SELECT LIMIT -1 OFFSET 1"
+      end
+
+      it "does not support locking" do
+        node = Nodes::Lock.new(Arel.sql("FOR UPDATE"))
+        assert_equal "", @visitor.accept(node, Collectors::SQLString.new).value
+      end
+
+      it "does not support boolean" do
+        node = Nodes::True.new()
+        assert_equal "1", @visitor.accept(node, Collectors::SQLString.new).value
+        node = Nodes::False.new()
+        assert_equal "0", @visitor.accept(node, Collectors::SQLString.new).value
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/visitors/to_sql_test.rb b/activerecord/test/cases/arel/visitors/to_sql_test.rb
new file mode 100644
index 0000000000..ce836eded7
--- /dev/null
+++ b/activerecord/test/cases/arel/visitors/to_sql_test.rb
@@ -0,0 +1,654 @@
+# frozen_string_literal: true
+
+require_relative "../helper"
+require "bigdecimal"
+
+module Arel
+  module Visitors
+    describe "the to_sql visitor" do
+      before do
+        @conn = FakeRecord::Base.new
+        @visitor = ToSql.new @conn.connection
+        @table = Table.new(:users)
+        @attr = @table[:id]
+      end
+
+      def compile(node)
+        @visitor.accept(node, Collectors::SQLString.new).value
+      end
+
+      it "works with BindParams" do
+        node = Nodes::BindParam.new(1)
+        sql = compile node
+        sql.must_be_like "?"
+      end
+
+      it "does not quote BindParams used as part of a Values" do
+        bp = Nodes::BindParam.new(1)
+        values = Nodes::Values.new([bp])
+        sql = compile values
+        sql.must_be_like "VALUES (?)"
+      end
+
+      it "can define a dispatch method" do
+        visited = false
+        viz = Class.new(Arel::Visitors::Visitor) {
+          define_method(:hello) do |node, c|
+            visited = true
+          end
+
+          def dispatch
+            { Arel::Table => "hello" }
+          end
+        }.new
+
+        viz.accept(@table, Collectors::SQLString.new)
+        assert visited, "hello method was called"
+      end
+
+      it "should not quote sql literals" do
+        node = @table[Arel.star]
+        sql = compile node
+        sql.must_be_like '"users".*'
+      end
+
+      it "should visit named functions" do
+        function = Nodes::NamedFunction.new("omg", [Arel.star])
+        assert_equal "omg(*)", compile(function)
+      end
+
+      it "should chain predications on named functions" do
+        function = Nodes::NamedFunction.new("omg", [Arel.star])
+        sql = compile(function.eq(2))
+        sql.must_be_like %{ omg(*) = 2 }
+      end
+
+      it "should handle nil with named functions" do
+        function = Nodes::NamedFunction.new("omg", [Arel.star])
+        sql = compile(function.eq(nil))
+        sql.must_be_like %{ omg(*) IS NULL }
+      end
+
+      it "should visit built-in functions" do
+        function = Nodes::Count.new([Arel.star])
+        assert_equal "COUNT(*)", compile(function)
+
+        function = Nodes::Sum.new([Arel.star])
+        assert_equal "SUM(*)", compile(function)
+
+        function = Nodes::Max.new([Arel.star])
+        assert_equal "MAX(*)", compile(function)
+
+        function = Nodes::Min.new([Arel.star])
+        assert_equal "MIN(*)", compile(function)
+
+        function = Nodes::Avg.new([Arel.star])
+        assert_equal "AVG(*)", compile(function)
+      end
+
+      it "should visit built-in functions operating on distinct values" do
+        function = Nodes::Count.new([Arel.star])
+        function.distinct = true
+        assert_equal "COUNT(DISTINCT *)", compile(function)
+
+        function = Nodes::Sum.new([Arel.star])
+        function.distinct = true
+        assert_equal "SUM(DISTINCT *)", compile(function)
+
+        function = Nodes::Max.new([Arel.star])
+        function.distinct = true
+        assert_equal "MAX(DISTINCT *)", compile(function)
+
+        function = Nodes::Min.new([Arel.star])
+        function.distinct = true
+        assert_equal "MIN(DISTINCT *)", compile(function)
+
+        function = Nodes::Avg.new([Arel.star])
+        function.distinct = true
+        assert_equal "AVG(DISTINCT *)", compile(function)
+      end
+
+      it "works with lists" do
+        function = Nodes::NamedFunction.new("omg", [Arel.star, Arel.star])
+        assert_equal "omg(*, *)", compile(function)
+      end
+
+      describe "Nodes::Equality" do
+        it "should escape strings" do
+          test = Table.new(:users)[:name].eq "Aaron Patterson"
+          compile(test).must_be_like %{
+            "users"."name" = 'Aaron Patterson'
+          }
+        end
+
+        it "should handle false" do
+          table = Table.new(:users)
+          val = Nodes.build_quoted(false, table[:active])
+          sql = compile Nodes::Equality.new(val, val)
+          sql.must_be_like %{ 'f' = 'f' }
+        end
+
+        it "should handle nil" do
+          sql = compile Nodes::Equality.new(@table[:name], nil)
+          sql.must_be_like %{ "users"."name" IS NULL }
+        end
+      end
+
+      describe "Nodes::Grouping" do
+        it "wraps nested groupings in brackets only once" do
+          sql = compile Nodes::Grouping.new(Nodes::Grouping.new(Nodes.build_quoted("foo")))
+          sql.must_equal "('foo')"
+        end
+      end
+
+      describe "Nodes::NotEqual" do
+        it "should handle false" do
+          val = Nodes.build_quoted(false, @table[:active])
+          sql = compile Nodes::NotEqual.new(@table[:active], val)
+          sql.must_be_like %{ "users"."active" != 'f' }
+        end
+
+        it "should handle nil" do
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::NotEqual.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NOT NULL }
+        end
+      end
+
+      it "should visit string subclass" do
+        [
+          Class.new(String).new(":'("),
+          Class.new(Class.new(String)).new(":'("),
+        ].each do |obj|
+          val = Nodes.build_quoted(obj, @table[:active])
+          sql = compile Nodes::NotEqual.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" != ':\\'(' }
+        end
+      end
+
+      it "should visit_Class" do
+        compile(Nodes.build_quoted(DateTime)).must_equal "'DateTime'"
+      end
+
+      it "should escape LIMIT" do
+        sc = Arel::Nodes::SelectStatement.new
+        sc.limit = Arel::Nodes::Limit.new(Nodes.build_quoted("omg"))
+        assert_match(/LIMIT 'omg'/, compile(sc))
+      end
+
+      it "should contain a single space before ORDER BY" do
+        table = Table.new(:users)
+        test = table.order(table[:name])
+        sql = compile test
+        assert_match(/"users" ORDER BY/, sql)
+      end
+
+      it "should quote LIMIT without column type coercion" do
+        table = Table.new(:users)
+        sc = table.where(table[:name].eq(0)).take(1).ast
+        assert_match(/WHERE "users"."name" = 0 LIMIT 1/, compile(sc))
+      end
+
+      it "should visit_DateTime" do
+        dt = DateTime.now
+        table = Table.new(:users)
+        test = table[:created_at].eq dt
+        sql = compile test
+
+        sql.must_be_like %{"users"."created_at" = '#{dt.strftime("%Y-%m-%d %H:%M:%S")}'}
+      end
+
+      it "should visit_Float" do
+        test = Table.new(:products)[:price].eq 2.14
+        sql = compile test
+        sql.must_be_like %{"products"."price" = 2.14}
+      end
+
+      it "should visit_Not" do
+        sql = compile Nodes::Not.new(Arel.sql("foo"))
+        sql.must_be_like "NOT (foo)"
+      end
+
+      it "should apply Not to the whole expression" do
+        node = Nodes::And.new [@attr.eq(10), @attr.eq(11)]
+        sql = compile Nodes::Not.new(node)
+        sql.must_be_like %{NOT ("users"."id" = 10 AND "users"."id" = 11)}
+      end
+
+      it "should visit_As" do
+        as = Nodes::As.new(Arel.sql("foo"), Arel.sql("bar"))
+        sql = compile as
+        sql.must_be_like "foo AS bar"
+      end
+
+      it "should visit_Bignum" do
+        compile 8787878092
+      end
+
+      it "should visit_Hash" do
+        compile(Nodes.build_quoted(a: 1))
+      end
+
+      it "should visit_Set" do
+        compile Nodes.build_quoted(Set.new([1, 2]))
+      end
+
+      it "should visit_BigDecimal" do
+        compile Nodes.build_quoted(BigDecimal("2.14"))
+      end
+
+      it "should visit_Date" do
+        dt = Date.today
+        table = Table.new(:users)
+        test = table[:created_at].eq dt
+        sql = compile test
+
+        sql.must_be_like %{"users"."created_at" = '#{dt.strftime("%Y-%m-%d")}'}
+      end
+
+      it "should visit_NilClass" do
+        compile(Nodes.build_quoted(nil)).must_be_like "NULL"
+      end
+
+      it "unsupported input should raise UnsupportedVisitError" do
+        error = assert_raises(UnsupportedVisitError) { compile(nil) }
+        assert_match(/\AUnsupported/, error.message)
+      end
+
+      it "should visit_Arel_SelectManager, which is a subquery" do
+        mgr = Table.new(:foo).project(:bar)
+        compile(mgr).must_be_like '(SELECT bar FROM "foo")'
+      end
+
+      it "should visit_Arel_Nodes_And" do
+        node = Nodes::And.new [@attr.eq(10), @attr.eq(11)]
+        compile(node).must_be_like %{
+          "users"."id" = 10 AND "users"."id" = 11
+        }
+      end
+
+      it "should visit_Arel_Nodes_Or" do
+        node = Nodes::Or.new @attr.eq(10), @attr.eq(11)
+        compile(node).must_be_like %{
+          "users"."id" = 10 OR "users"."id" = 11
+        }
+      end
+
+      it "should visit_Arel_Nodes_Assignment" do
+        column = @table["id"]
+        node = Nodes::Assignment.new(
+          Nodes::UnqualifiedColumn.new(column),
+          Nodes::UnqualifiedColumn.new(column)
+        )
+        compile(node).must_be_like %{
+          "id" = "id"
+        }
+      end
+
+      it "should visit visit_Arel_Attributes_Time" do
+        attr = Attributes::Time.new(@attr.relation, @attr.name)
+        compile attr
+      end
+
+      it "should visit_TrueClass" do
+        test = Table.new(:users)[:bool].eq(true)
+        compile(test).must_be_like %{ "users"."bool" = 't' }
+      end
+
+      describe "Nodes::Matches" do
+        it "should know how to visit" do
+          node = @table[:name].matches("foo%")
+          compile(node).must_be_like %{
+            "users"."name" LIKE 'foo%'
+          }
+        end
+
+        it "can handle ESCAPE" do
+          node = @table[:name].matches("foo!%", "!")
+          compile(node).must_be_like %{
+            "users"."name" LIKE 'foo!%' ESCAPE '!'
+          }
+        end
+
+        it "can handle subqueries" do
+          subquery = @table.project(:id).where(@table[:name].matches("foo%"))
+          node = @attr.in subquery
+          compile(node).must_be_like %{
+            "users"."id" IN (SELECT id FROM "users" WHERE "users"."name" LIKE 'foo%')
+          }
+        end
+      end
+
+      describe "Nodes::DoesNotMatch" do
+        it "should know how to visit" do
+          node = @table[:name].does_not_match("foo%")
+          compile(node).must_be_like %{
+            "users"."name" NOT LIKE 'foo%'
+          }
+        end
+
+        it "can handle ESCAPE" do
+          node = @table[:name].does_not_match("foo!%", "!")
+          compile(node).must_be_like %{
+            "users"."name" NOT LIKE 'foo!%' ESCAPE '!'
+          }
+        end
+
+        it "can handle subqueries" do
+          subquery = @table.project(:id).where(@table[:name].does_not_match("foo%"))
+          node = @attr.in subquery
+          compile(node).must_be_like %{
+            "users"."id" IN (SELECT id FROM "users" WHERE "users"."name" NOT LIKE 'foo%')
+          }
+        end
+      end
+
+      describe "Nodes::Ordering" do
+        it "should know how to visit" do
+          node = @attr.desc
+          compile(node).must_be_like %{
+            "users"."id" DESC
+          }
+        end
+      end
+
+      describe "Nodes::In" do
+        it "should know how to visit" do
+          node = @attr.in [1, 2, 3]
+          compile(node).must_be_like %{
+            "users"."id" IN (1, 2, 3)
+          }
+        end
+
+        it "should return 1=0 when empty right which is always false" do
+          node = @attr.in []
+          compile(node).must_equal "1=0"
+        end
+
+        it "can handle two dot ranges" do
+          node = @attr.between 1..3
+          compile(node).must_be_like %{
+            "users"."id" BETWEEN 1 AND 3
+          }
+        end
+
+        it "can handle three dot ranges" do
+          node = @attr.between 1...3
+          compile(node).must_be_like %{
+            "users"."id" >= 1 AND "users"."id" < 3
+          }
+        end
+
+        it "can handle ranges bounded by infinity" do
+          node = @attr.between 1..Float::INFINITY
+          compile(node).must_be_like %{
+            "users"."id" >= 1
+          }
+          node = @attr.between(-Float::INFINITY..3)
+          compile(node).must_be_like %{
+            "users"."id" <= 3
+          }
+          node = @attr.between(-Float::INFINITY...3)
+          compile(node).must_be_like %{
+            "users"."id" < 3
+          }
+          node = @attr.between(-Float::INFINITY..Float::INFINITY)
+          compile(node).must_be_like %{1=1}
+        end
+
+        it "can handle subqueries" do
+          table = Table.new(:users)
+          subquery = table.project(:id).where(table[:name].eq("Aaron"))
+          node = @attr.in subquery
+          compile(node).must_be_like %{
+            "users"."id" IN (SELECT id FROM "users" WHERE "users"."name" = 'Aaron')
+          }
+        end
+      end
+
+      describe "Nodes::InfixOperation" do
+        it "should handle Multiplication" do
+          node = Arel::Attributes::Decimal.new(Table.new(:products), :price) * Arel::Attributes::Decimal.new(Table.new(:currency_rates), :rate)
+          compile(node).must_equal %("products"."price" * "currency_rates"."rate")
+        end
+
+        it "should handle Division" do
+          node = Arel::Attributes::Decimal.new(Table.new(:products), :price) / 5
+          compile(node).must_equal %("products"."price" / 5)
+        end
+
+        it "should handle Addition" do
+          node = Arel::Attributes::Decimal.new(Table.new(:products), :price) + 6
+          compile(node).must_equal %(("products"."price" + 6))
+        end
+
+        it "should handle Subtraction" do
+          node = Arel::Attributes::Decimal.new(Table.new(:products), :price) - 7
+          compile(node).must_equal %(("products"."price" - 7))
+        end
+
+        it "should handle Concatination" do
+          table = Table.new(:users)
+          node = table[:name].concat(table[:name])
+          compile(node).must_equal %("users"."name" || "users"."name")
+        end
+
+        it "should handle BitwiseAnd" do
+          node = Arel::Attributes::Integer.new(Table.new(:products), :bitmap) & 16
+          compile(node).must_equal %(("products"."bitmap" & 16))
+        end
+
+        it "should handle BitwiseOr" do
+          node = Arel::Attributes::Integer.new(Table.new(:products), :bitmap) | 16
+          compile(node).must_equal %(("products"."bitmap" | 16))
+        end
+
+        it "should handle BitwiseXor" do
+          node = Arel::Attributes::Integer.new(Table.new(:products), :bitmap) ^ 16
+          compile(node).must_equal %(("products"."bitmap" ^ 16))
+        end
+
+        it "should handle BitwiseShiftLeft" do
+          node = Arel::Attributes::Integer.new(Table.new(:products), :bitmap) << 4
+          compile(node).must_equal %(("products"."bitmap" << 4))
+        end
+
+        it "should handle BitwiseShiftRight" do
+          node = Arel::Attributes::Integer.new(Table.new(:products), :bitmap) >> 4
+          compile(node).must_equal %(("products"."bitmap" >> 4))
+        end
+
+        it "should handle arbitrary operators" do
+          node = Arel::Nodes::InfixOperation.new(
+            "&&",
+            Arel::Attributes::String.new(Table.new(:products), :name),
+            Arel::Attributes::String.new(Table.new(:products), :name)
+          )
+          compile(node).must_equal %("products"."name" && "products"."name")
+        end
+      end
+
+      describe "Nodes::UnaryOperation" do
+        it "should handle BitwiseNot" do
+          node = ~ Arel::Attributes::Integer.new(Table.new(:products), :bitmap)
+          compile(node).must_equal %( ~ "products"."bitmap")
+        end
+
+        it "should handle arbitrary operators" do
+          node = Arel::Nodes::UnaryOperation.new("!", Arel::Attributes::String.new(Table.new(:products), :active))
+          compile(node).must_equal %( ! "products"."active")
+        end
+      end
+
+      describe "Nodes::NotIn" do
+        it "should know how to visit" do
+          node = @attr.not_in [1, 2, 3]
+          compile(node).must_be_like %{
+            "users"."id" NOT IN (1, 2, 3)
+          }
+        end
+
+        it "should return 1=1 when empty right which is always true" do
+          node = @attr.not_in []
+          compile(node).must_equal "1=1"
+        end
+
+        it "can handle two dot ranges" do
+          node = @attr.not_between 1..3
+          compile(node).must_equal(
+            %{("users"."id" < 1 OR "users"."id" > 3)}
+          )
+        end
+
+        it "can handle three dot ranges" do
+          node = @attr.not_between 1...3
+          compile(node).must_equal(
+            %{("users"."id" < 1 OR "users"."id" >= 3)}
+          )
+        end
+
+        it "can handle ranges bounded by infinity" do
+          node = @attr.not_between 1..Float::INFINITY
+          compile(node).must_be_like %{
+            "users"."id" < 1
+          }
+          node = @attr.not_between(-Float::INFINITY..3)
+          compile(node).must_be_like %{
+            "users"."id" > 3
+          }
+          node = @attr.not_between(-Float::INFINITY...3)
+          compile(node).must_be_like %{
+            "users"."id" >= 3
+          }
+          node = @attr.not_between(-Float::INFINITY..Float::INFINITY)
+          compile(node).must_be_like %{1=0}
+        end
+
+        it "can handle subqueries" do
+          table = Table.new(:users)
+          subquery = table.project(:id).where(table[:name].eq("Aaron"))
+          node = @attr.not_in subquery
+          compile(node).must_be_like %{
+            "users"."id" NOT IN (SELECT id FROM "users" WHERE "users"."name" = 'Aaron')
+          }
+        end
+      end
+
+      describe "Constants" do
+        it "should handle true" do
+          test = Table.new(:users).create_true
+          compile(test).must_be_like %{
+            TRUE
+          }
+        end
+
+        it "should handle false" do
+          test = Table.new(:users).create_false
+          compile(test).must_be_like %{
+            FALSE
+          }
+        end
+      end
+
+      describe "TableAlias" do
+        it "should use the underlying table for checking columns" do
+          test = Table.new(:users).alias("zomgusers")[:id].eq "3"
+          compile(test).must_be_like %{
+            "zomgusers"."id" = '3'
+          }
+        end
+      end
+
+      describe "distinct on" do
+        it "raises not implemented error" do
+          core = Arel::Nodes::SelectCore.new
+          core.set_quantifier = Arel::Nodes::DistinctOn.new(Arel.sql("aaron"))
+
+          assert_raises(NotImplementedError) do
+            compile(core)
+          end
+        end
+      end
+
+      describe "Nodes::Regexp" do
+        it "raises not implemented error" do
+          node = Arel::Nodes::Regexp.new(@table[:name], Nodes.build_quoted("foo%"))
+
+          assert_raises(NotImplementedError) do
+            compile(node)
+          end
+        end
+      end
+
+      describe "Nodes::NotRegexp" do
+        it "raises not implemented error" do
+          node = Arel::Nodes::NotRegexp.new(@table[:name], Nodes.build_quoted("foo%"))
+
+          assert_raises(NotImplementedError) do
+            compile(node)
+          end
+        end
+      end
+
+      describe "Nodes::Case" do
+        it "supports simple case expressions" do
+          node = Arel::Nodes::Case.new(@table[:name])
+            .when("foo").then(1)
+            .else(0)
+
+          compile(node).must_be_like %{
+            CASE "users"."name" WHEN 'foo' THEN 1 ELSE 0 END
+          }
+        end
+
+        it "supports extended case expressions" do
+          node = Arel::Nodes::Case.new
+            .when(@table[:name].in(%w(foo bar))).then(1)
+            .else(0)
+
+          compile(node).must_be_like %{
+            CASE WHEN "users"."name" IN ('foo', 'bar') THEN 1 ELSE 0 END
+          }
+        end
+
+        it "works without default branch" do
+          node = Arel::Nodes::Case.new(@table[:name])
+            .when("foo").then(1)
+
+          compile(node).must_be_like %{
+            CASE "users"."name" WHEN 'foo' THEN 1 END
+          }
+        end
+
+        it "allows chaining multiple conditions" do
+          node = Arel::Nodes::Case.new(@table[:name])
+            .when("foo").then(1)
+            .when("bar").then(2)
+            .else(0)
+
+          compile(node).must_be_like %{
+            CASE "users"."name" WHEN 'foo' THEN 1 WHEN 'bar' THEN 2 ELSE 0 END
+          }
+        end
+
+        it "supports #when with two arguments and no #then" do
+          node = Arel::Nodes::Case.new @table[:name]
+
+          { foo: 1, bar: 0 }.reduce(node) { |_node, pair| _node.when(*pair) }
+
+          compile(node).must_be_like %{
+            CASE "users"."name" WHEN 'foo' THEN 1 WHEN 'bar' THEN 0 END
+          }
+        end
+
+        it "can be chained as a predicate" do
+          node = @table[:name].when("foo").then("bar").else("baz")
+
+          compile(node).must_be_like %{
+            CASE "users"."name" WHEN 'foo' THEN 'bar' ELSE 'baz' END
+          }
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/associations/belongs_to_associations_test.rb b/activerecord/test/cases/associations/belongs_to_associations_test.rb
index 0f7a249bf3..5011a9bbde 100644
--- a/activerecord/test/cases/associations/belongs_to_associations_test.rb
+++ b/activerecord/test/cases/associations/belongs_to_associations_test.rb
@@ -37,6 +37,13 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     assert_equal companies(:first_firm).name, firm.name
   end
 
+  def test_assigning_belongs_to_on_destroyed_object
+    client = Client.create!(name: "Client")
+    client.destroy!
+    assert_raise(frozen_error_class) { client.firm = nil }
+    assert_raise(frozen_error_class) { client.firm = Firm.new(name: "Firm") }
+  end
+
   def test_missing_attribute_error_is_raised_when_no_foreign_key_attribute
     assert_raises(ActiveModel::MissingAttributeError) { Client.select(:id).first.firm }
   end
@@ -79,7 +86,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     end
 
     account = model.new
-    assert account.valid?
+    assert_predicate account, :valid?
   ensure
     ActiveRecord::Base.belongs_to_required_by_default = original_value
   end
@@ -95,7 +102,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     end
 
     account = model.new
-    assert_not account.valid?
+    assert_not_predicate account, :valid?
     assert_equal [{ error: :blank }], account.errors.details[:company]
   ensure
     ActiveRecord::Base.belongs_to_required_by_default = original_value
@@ -112,7 +119,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     end
 
     account = model.new
-    assert_not account.valid?
+    assert_not_predicate account, :valid?
     assert_equal [{ error: :blank }], account.errors.details[:company]
   ensure
     ActiveRecord::Base.belongs_to_required_by_default = original_value
@@ -246,14 +253,14 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     Firm.create("name" => "Apple")
     Client.create("name" => "Citibank", :firm_name => "Apple")
     citibank_result = Client.all.merge!(where: { name: "Citibank" }, includes: :firm_with_primary_key).first
-    assert citibank_result.association(:firm_with_primary_key).loaded?
+    assert_predicate citibank_result.association(:firm_with_primary_key), :loaded?
   end
 
   def test_eager_loading_with_primary_key_as_symbol
     Firm.create("name" => "Apple")
     Client.create("name" => "Citibank", :firm_name => "Apple")
     citibank_result = Client.all.merge!(where: { name: "Citibank" }, includes: :firm_with_primary_key_symbols).first
-    assert citibank_result.association(:firm_with_primary_key_symbols).loaded?
+    assert_predicate citibank_result.association(:firm_with_primary_key_symbols), :loaded?
   end
 
   def test_creating_the_belonging_object
@@ -265,6 +272,15 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     assert_equal apple, citibank.firm
   end
 
+  def test_creating_the_belonging_object_from_new_record
+    citibank = Account.new("credit_limit" => 10)
+    apple    = citibank.create_firm("name" => "Apple")
+    assert_equal apple, citibank.firm
+    citibank.save
+    citibank.reload
+    assert_equal apple, citibank.firm
+  end
+
   def test_creating_the_belonging_object_with_primary_key
     client = Client.create(name: "Primary key client")
     apple  = client.create_firm_with_primary_key("name" => "Apple")
@@ -320,7 +336,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     client  = Client.create!(name: "Jimmy")
     account = client.create_account!(credit_limit: 10)
     assert_equal account, client.account
-    assert account.persisted?
+    assert_predicate account, :persisted?
     client.save
     client.reload
     assert_equal account, client.account
@@ -330,7 +346,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     client = Client.create!(name: "Jimmy")
     assert_raise(ActiveRecord::RecordInvalid) { client.create_account! }
     assert_not_nil client.account
-    assert client.account.new_record?
+    assert_predicate client.account, :new_record?
   end
 
   def test_reloading_the_belonging_object
@@ -627,10 +643,10 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     final_cut = Client.new("name" => "Final Cut")
     firm = Firm.find(1)
     final_cut.firm = firm
-    assert !final_cut.persisted?
+    assert_not_predicate final_cut, :persisted?
     assert final_cut.save
-    assert final_cut.persisted?
-    assert firm.persisted?
+    assert_predicate final_cut, :persisted?
+    assert_predicate firm, :persisted?
     assert_equal firm, final_cut.firm
     final_cut.association(:firm).reload
     assert_equal firm, final_cut.firm
@@ -640,10 +656,10 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     final_cut = Client.new("name" => "Final Cut")
     firm = Firm.find(1)
     final_cut.firm_with_primary_key = firm
-    assert !final_cut.persisted?
+    assert_not_predicate final_cut, :persisted?
     assert final_cut.save
-    assert final_cut.persisted?
-    assert firm.persisted?
+    assert_predicate final_cut, :persisted?
+    assert_predicate firm, :persisted?
     assert_equal firm, final_cut.firm_with_primary_key
     final_cut.association(:firm_with_primary_key).reload
     assert_equal firm, final_cut.firm_with_primary_key
@@ -790,7 +806,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
 
   def test_cant_save_readonly_association
     assert_raise(ActiveRecord::ReadOnlyRecord) { companies(:first_client).readonly_firm.save! }
-    assert companies(:first_client).readonly_firm.readonly?
+    assert_predicate companies(:first_client).readonly_firm, :readonly?
   end
 
   def test_polymorphic_assignment_foreign_key_type_string
@@ -931,6 +947,30 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     assert_equal error.message, "The :dependent option must be one of [:destroy, :delete], but is :nullify"
   end
 
+  class DestroyableBook < ActiveRecord::Base
+    self.table_name = "books"
+    belongs_to :author, class_name: "UndestroyableAuthor", dependent: :destroy
+  end
+
+  class UndestroyableAuthor < ActiveRecord::Base
+    self.table_name = "authors"
+    has_one :book, class_name: "DestroyableBook", foreign_key: "author_id"
+    before_destroy :dont
+
+    def dont
+      throw(:abort)
+    end
+  end
+
+  def test_dependency_should_halt_parent_destruction
+    author = UndestroyableAuthor.create!(name: "Test")
+    book = DestroyableBook.create!(author: author)
+
+    assert_no_difference ["UndestroyableAuthor.count", "DestroyableBook.count"] do
+      assert_not book.destroy
+    end
+  end
+
   def test_attributes_are_being_set_when_initialized_from_belongs_to_association_with_where_clause
     new_firm = accounts(:signals37).build_firm(name: "Apple")
     assert_equal new_firm.name, "Apple"
@@ -949,15 +989,15 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     firm_proxy                = client.send(:association_instance_get, :firm)
     firm_with_condition_proxy = client.send(:association_instance_get, :firm_with_condition)
 
-    assert !firm_proxy.stale_target?
-    assert !firm_with_condition_proxy.stale_target?
+    assert_not_predicate firm_proxy, :stale_target?
+    assert_not_predicate firm_with_condition_proxy, :stale_target?
     assert_equal companies(:first_firm), client.firm
     assert_equal companies(:first_firm), client.firm_with_condition
 
     client.client_of = companies(:another_firm).id
 
-    assert firm_proxy.stale_target?
-    assert firm_with_condition_proxy.stale_target?
+    assert_predicate firm_proxy, :stale_target?
+    assert_predicate firm_with_condition_proxy, :stale_target?
     assert_equal companies(:another_firm), client.firm
     assert_equal companies(:another_firm), client.firm_with_condition
   end
@@ -968,12 +1008,12 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     sponsor.sponsorable
     proxy = sponsor.send(:association_instance_get, :sponsorable)
 
-    assert !proxy.stale_target?
+    assert_not_predicate proxy, :stale_target?
     assert_equal members(:groucho), sponsor.sponsorable
 
     sponsor.sponsorable_id = members(:some_other_guy).id
 
-    assert proxy.stale_target?
+    assert_predicate proxy, :stale_target?
     assert_equal members(:some_other_guy), sponsor.sponsorable
   end
 
@@ -983,12 +1023,12 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     sponsor.sponsorable
     proxy = sponsor.send(:association_instance_get, :sponsorable)
 
-    assert !proxy.stale_target?
+    assert_not_predicate proxy, :stale_target?
     assert_equal members(:groucho), sponsor.sponsorable
 
     sponsor.sponsorable_type = "Firm"
 
-    assert proxy.stale_target?
+    assert_predicate proxy, :stale_target?
     assert_equal companies(:first_firm), sponsor.sponsorable
   end
 
@@ -1122,7 +1162,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     comment.post_id = 9223372036854775808 # out of range in the bigint
 
     assert_nil comment.post
-    assert_not comment.valid?
+    assert_not_predicate comment, :valid?
     assert_equal [{ error: :blank }], comment.errors.details[:post]
   end
 
@@ -1142,7 +1182,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
 
     citibank.firm_id = apple.id.to_s
 
-    assert !citibank.association(:firm).stale_target?
+    assert_not_predicate citibank.association(:firm), :stale_target?
   end
 
   def test_reflect_the_most_recent_change
diff --git a/activerecord/test/cases/associations/callbacks_test.rb b/activerecord/test/cases/associations/callbacks_test.rb
index e096cd4a0b..25d55dc4c9 100644
--- a/activerecord/test/cases/associations/callbacks_test.rb
+++ b/activerecord/test/cases/associations/callbacks_test.rb
@@ -15,7 +15,7 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
     @david = authors(:david)
     @thinking = posts(:thinking)
     @authorless = posts(:authorless)
-    assert @david.post_log.empty?
+    assert_empty @david.post_log
   end
 
   def test_adding_macro_callbacks
@@ -96,7 +96,7 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
   def test_has_and_belongs_to_many_add_callback
     david = developers(:david)
     ar = projects(:active_record)
-    assert ar.developers_log.empty?
+    assert_empty ar.developers_log
     ar.developers_with_callbacks << david
     assert_equal ["before_adding#{david.id}", "after_adding#{david.id}"], ar.developers_log
     ar.developers_with_callbacks << david
@@ -122,12 +122,12 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
     assert_equal alice, dev
     assert_not_nil new_dev
     assert new_dev, "record should not have been saved"
-    assert_not alice.new_record?
+    assert_not_predicate alice, :new_record?
   end
 
   def test_has_and_belongs_to_many_after_add_called_after_save
     ar = projects(:active_record)
-    assert ar.developers_log.empty?
+    assert_empty ar.developers_log
     alice = Developer.new(name: "alice")
     ar.developers_with_callbacks << alice
     assert_equal "after_adding#{alice.id}", ar.developers_log.last
@@ -143,7 +143,7 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
     david = developers(:david)
     jamis = developers(:jamis)
     activerecord = projects(:active_record)
-    assert activerecord.developers_log.empty?
+    assert_empty activerecord.developers_log
     activerecord.developers_with_callbacks.delete(david)
     assert_equal ["before_removing#{david.id}", "after_removing#{david.id}"], activerecord.developers_log
 
@@ -154,7 +154,7 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
 
   def test_has_and_belongs_to_many_does_not_fire_callbacks_on_clear
     activerecord = projects(:active_record)
-    assert activerecord.developers_log.empty?
+    assert_empty activerecord.developers_log
     if activerecord.developers_with_callbacks.size == 0
       activerecord.developers << developers(:david)
       activerecord.developers << developers(:jamis)
@@ -163,7 +163,7 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
     end
     activerecord.developers_with_callbacks.flat_map { |d| ["before_removing#{d.id}", "after_removing#{d.id}"] }.sort
     assert activerecord.developers_with_callbacks.clear
-    assert_predicate activerecord.developers_log, :empty?
+    assert_empty activerecord.developers_log
   end
 
   def test_has_many_and_belongs_to_many_callbacks_for_save_on_parent
@@ -183,7 +183,7 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
       @david.unchangeable_posts << @authorless
     rescue Exception
     end
-    assert @david.post_log.empty?
+    assert_empty @david.post_log
     assert_not_includes @david.unchangeable_posts, @authorless
     @david.reload
     assert_not_includes @david.unchangeable_posts, @authorless
diff --git a/activerecord/test/cases/associations/cascaded_eager_loading_test.rb b/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
index e69cfe5e52..e717621928 100644
--- a/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
+++ b/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
@@ -37,7 +37,7 @@ class CascadedEagerLoadingTest < ActiveRecord::TestCase
 
   def test_eager_association_loading_with_hmt_does_not_table_name_collide_when_joining_associations
     authors = Author.joins(:posts).eager_load(:comments).where(posts: { tags_count: 1 }).to_a
-    assert_equal 1, assert_no_queries { authors.size }
+    assert_equal 3, assert_no_queries { authors.size }
     assert_equal 10, assert_no_queries { authors[0].comments.size }
   end
 
@@ -136,7 +136,7 @@ class CascadedEagerLoadingTest < ActiveRecord::TestCase
   end
 
   def test_eager_association_loading_with_multiple_stis_and_order
-    author = Author.all.merge!(includes: { posts: [ :special_comments , :very_special_comment ] }, order: ["authors.name", "comments.body", "very_special_comments_posts.body"], where: "posts.id = 4").first
+    author = Author.all.merge!(includes: { posts: [ :special_comments, :very_special_comment ] }, order: ["authors.name", "comments.body", "very_special_comments_posts.body"], where: "posts.id = 4").first
     assert_equal authors(:david), author
     assert_no_queries do
       author.posts.first.special_comments
diff --git a/activerecord/test/cases/associations/eager_load_includes_full_sti_class_test.rb b/activerecord/test/cases/associations/eager_load_includes_full_sti_class_test.rb
index 8754889143..5fca972aee 100644
--- a/activerecord/test/cases/associations/eager_load_includes_full_sti_class_test.rb
+++ b/activerecord/test/cases/associations/eager_load_includes_full_sti_class_test.rb
@@ -8,37 +8,81 @@ module Namespaced
   class Post < ActiveRecord::Base
     self.table_name = "posts"
     has_one :tagging, as: :taggable, class_name: "Tagging"
+
+    def self.polymorphic_name
+      sti_name
+    end
   end
 end
 
-class EagerLoadIncludeFullStiClassNamesTest < ActiveRecord::TestCase
+module PolymorphicFullStiClassNamesSharedTest
   def setup
+    @old_store_full_sti_class = ActiveRecord::Base.store_full_sti_class
+    ActiveRecord::Base.store_full_sti_class = store_full_sti_class
+
     post = Namespaced::Post.create(title: "Great stuff", body: "This is not", author_id: 1)
     @tagging = Tagging.create(taggable: post)
-    @old = ActiveRecord::Base.store_full_sti_class
   end
 
   def teardown
-    ActiveRecord::Base.store_full_sti_class = @old
+    ActiveRecord::Base.store_full_sti_class = @old_store_full_sti_class
+  end
+
+  def test_class_names
+    ActiveRecord::Base.store_full_sti_class = !store_full_sti_class
+    post = Namespaced::Post.find_by_title("Great stuff")
+    assert_nil post.tagging
+
+    ActiveRecord::Base.store_full_sti_class = store_full_sti_class
+    post = Namespaced::Post.find_by_title("Great stuff")
+    assert_equal @tagging, post.tagging
   end
 
   def test_class_names_with_includes
-    ActiveRecord::Base.store_full_sti_class = false
+    ActiveRecord::Base.store_full_sti_class = !store_full_sti_class
     post = Namespaced::Post.includes(:tagging).find_by_title("Great stuff")
     assert_nil post.tagging
 
-    ActiveRecord::Base.store_full_sti_class = true
+    ActiveRecord::Base.store_full_sti_class = store_full_sti_class
     post = Namespaced::Post.includes(:tagging).find_by_title("Great stuff")
     assert_equal @tagging, post.tagging
   end
 
   def test_class_names_with_eager_load
-    ActiveRecord::Base.store_full_sti_class = false
+    ActiveRecord::Base.store_full_sti_class = !store_full_sti_class
     post = Namespaced::Post.eager_load(:tagging).find_by_title("Great stuff")
     assert_nil post.tagging
 
-    ActiveRecord::Base.store_full_sti_class = true
+    ActiveRecord::Base.store_full_sti_class = store_full_sti_class
     post = Namespaced::Post.eager_load(:tagging).find_by_title("Great stuff")
     assert_equal @tagging, post.tagging
   end
+
+  def test_class_names_with_find_by
+    post = Namespaced::Post.find_by_title("Great stuff")
+
+    ActiveRecord::Base.store_full_sti_class = !store_full_sti_class
+    assert_nil Tagging.find_by(taggable: post)
+
+    ActiveRecord::Base.store_full_sti_class = store_full_sti_class
+    assert_equal @tagging, Tagging.find_by(taggable: post)
+  end
+end
+
+class PolymorphicFullStiClassNamesTest < ActiveRecord::TestCase
+  include PolymorphicFullStiClassNamesSharedTest
+
+  private
+    def store_full_sti_class
+      true
+    end
+end
+
+class PolymorphicNonFullStiClassNamesTest < ActiveRecord::TestCase
+  include PolymorphicFullStiClassNamesSharedTest
+
+  private
+    def store_full_sti_class
+      false
+    end
 end
diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index 44bf7f7d2f..f46be8734b 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -284,7 +284,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
   end
 
   def test_loading_from_an_association_that_has_a_hash_of_conditions
-    assert !Author.all.merge!(includes: :hello_posts_with_hash_conditions).find(authors(:david).id).hello_posts.empty?
+    assert_not_empty Author.all.merge!(includes: :hello_posts_with_hash_conditions).find(authors(:david).id).hello_posts
   end
 
   def test_loading_with_no_associations
@@ -427,7 +427,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
   def test_eager_association_loading_with_belongs_to_and_order_string_with_quoted_table_name
     quoted_posts_id = Comment.connection.quote_table_name("posts") + "." + Comment.connection.quote_column_name("id")
     assert_nothing_raised do
-      Comment.includes(:post).references(:posts).order(quoted_posts_id)
+      Comment.includes(:post).references(:posts).order(Arel.sql(quoted_posts_id))
     end
   end
 
@@ -530,6 +530,14 @@ class EagerAssociationTest < ActiveRecord::TestCase
     assert_equal [comments(:does_it_hurt)], assert_no_queries { author.special_post_comments }
   end
 
+  def test_preloading_has_many_through_with_implicit_source
+    authors = Author.includes(:very_special_comments).to_a
+    assert_no_queries do
+      special_comment_authors = authors.map { |author| [author.name, author.very_special_comments.size] }
+      assert_equal [["David", 1], ["Mary", 0], ["Bob", 0]], special_comment_authors
+    end
+  end
+
   def test_eager_with_has_many_through_an_sti_join_model_with_conditions_on_both
     author = Author.all.merge!(includes: :special_nonexistent_post_comments, order: "authors.id").first
     assert_equal [], author.special_nonexistent_post_comments
@@ -779,7 +787,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
     Tagging.create!(taggable_type: "Post", taggable_id: post2.id, tag: tag)
 
     tag_with_includes = OrderedTag.includes(:tagged_posts).find(tag.id)
-    assert_equal(tag_with_includes.taggings.map(&:taggable).map(&:title), tag_with_includes.tagged_posts.map(&:title))
+    assert_equal tag_with_includes.ordered_taggings.map(&:taggable).map(&:title), tag_with_includes.tagged_posts.map(&:title)
   end
 
   def test_eager_has_many_through_multiple_with_order
@@ -861,23 +869,19 @@ class EagerAssociationTest < ActiveRecord::TestCase
     end
   end
 
-  def find_all_ordered(className, include = nil)
-    className.all.merge!(order: "#{className.table_name}.#{className.primary_key}", includes: include).to_a
-  end
-
   def test_limited_eager_with_order
     assert_equal(
       posts(:thinking, :sti_comments),
       Post.all.merge!(
         includes: [:author, :comments], where: { "authors.name" => "David" },
-        order: "UPPER(posts.title)", limit: 2, offset: 1
+        order: Arel.sql("UPPER(posts.title)"), limit: 2, offset: 1
       ).to_a
     )
     assert_equal(
       posts(:sti_post_and_comments, :sti_comments),
       Post.all.merge!(
         includes: [:author, :comments], where: { "authors.name" => "David" },
-        order: "UPPER(posts.title) DESC", limit: 2, offset: 1
+        order: Arel.sql("UPPER(posts.title) DESC"), limit: 2, offset: 1
       ).to_a
     )
   end
@@ -887,14 +891,14 @@ class EagerAssociationTest < ActiveRecord::TestCase
       posts(:thinking, :sti_comments),
       Post.all.merge!(
         includes: [:author, :comments], where: { "authors.name" => "David" },
-        order: ["UPPER(posts.title)", "posts.id"], limit: 2, offset: 1
+        order: [Arel.sql("UPPER(posts.title)"), "posts.id"], limit: 2, offset: 1
       ).to_a
     )
     assert_equal(
       posts(:sti_post_and_comments, :sti_comments),
       Post.all.merge!(
         includes: [:author, :comments], where: { "authors.name" => "David" },
-        order: ["UPPER(posts.title) DESC", "posts.id"], limit: 2, offset: 1
+        order: [Arel.sql("UPPER(posts.title) DESC"), "posts.id"], limit: 2, offset: 1
       ).to_a
     )
   end
@@ -1069,7 +1073,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
   end
 
   def test_load_with_sti_sharing_association
-    assert_queries(2) do #should not do 1 query per subclass
+    assert_queries(2) do # should not do 1 query per subclass
       Comment.includes(:post).to_a
     end
   end
@@ -1214,6 +1218,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
 
     client = assert_queries(2) { Client.preload(:firm).find(c.id) }
     assert_no_queries { assert_nil client.firm }
+    assert_equal c.client_of, client.client_of
   end
 
   def test_preloading_empty_belongs_to_polymorphic
@@ -1221,6 +1226,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
 
     tagging = assert_queries(2) { Tagging.preload(:taggable).find(t.id) }
     assert_no_queries { assert_nil tagging.taggable }
+    assert_equal t.taggable_id, tagging.taggable_id
   end
 
   def test_preloading_through_empty_belongs_to
@@ -1299,6 +1305,11 @@ class EagerAssociationTest < ActiveRecord::TestCase
     assert_equal projects.last.mentor.developers.first.contracts, projects.last.developers.last.contracts
   end
 
+  def test_preloading_has_many_through_with_custom_scope
+    project = Project.includes(:developers_named_david_with_hash_conditions).find(projects(:active_record).id)
+    assert_equal [developers(:david)], project.developers_named_david_with_hash_conditions
+  end
+
   test "scoping with a circular preload" do
     assert_equal Comment.find(1), Comment.preload(post: :comments).scoping { Comment.find(1) }
   end
@@ -1435,51 +1446,51 @@ class EagerAssociationTest < ActiveRecord::TestCase
   test "preloading readonly association" do
     # has-one
     firm = Firm.where(id: "1").preload(:readonly_account).first!
-    assert firm.readonly_account.readonly?
+    assert_predicate firm.readonly_account, :readonly?
 
     # has_and_belongs_to_many
     project = Project.where(id: "2").preload(:readonly_developers).first!
-    assert project.readonly_developers.first.readonly?
+    assert_predicate project.readonly_developers.first, :readonly?
 
     # has-many :through
     david = Author.where(id: "1").preload(:readonly_comments).first!
-    assert david.readonly_comments.first.readonly?
+    assert_predicate david.readonly_comments.first, :readonly?
   end
 
   test "eager-loading non-readonly association" do
     # has_one
     firm = Firm.where(id: "1").eager_load(:account).first!
-    assert_not firm.account.readonly?
+    assert_not_predicate firm.account, :readonly?
 
     # has_and_belongs_to_many
     project = Project.where(id: "2").eager_load(:developers).first!
-    assert_not project.developers.first.readonly?
+    assert_not_predicate project.developers.first, :readonly?
 
     # has_many :through
     david = Author.where(id: "1").eager_load(:comments).first!
-    assert_not david.comments.first.readonly?
+    assert_not_predicate david.comments.first, :readonly?
 
     # belongs_to
     post = Post.where(id: "1").eager_load(:author).first!
-    assert_not post.author.readonly?
+    assert_not_predicate post.author, :readonly?
   end
 
   test "eager-loading readonly association" do
     # has-one
     firm = Firm.where(id: "1").eager_load(:readonly_account).first!
-    assert firm.readonly_account.readonly?
+    assert_predicate firm.readonly_account, :readonly?
 
     # has_and_belongs_to_many
     project = Project.where(id: "2").eager_load(:readonly_developers).first!
-    assert project.readonly_developers.first.readonly?
+    assert_predicate project.readonly_developers.first, :readonly?
 
     # has-many :through
     david = Author.where(id: "1").eager_load(:readonly_comments).first!
-    assert david.readonly_comments.first.readonly?
+    assert_predicate david.readonly_comments.first, :readonly?
 
     # belongs_to
     post = Post.where(id: "1").eager_load(:readonly_author).first!
-    assert post.readonly_author.readonly?
+    assert_predicate post.readonly_author, :readonly?
   end
 
   test "preloading a polymorphic association with references to the associated table" do
@@ -1492,9 +1503,49 @@ class EagerAssociationTest < ActiveRecord::TestCase
     assert_equal posts(:welcome), post
   end
 
+  test "eager-loading with a polymorphic association won't work consistently" do
+    assert_raise(ActiveRecord::EagerLoadPolymorphicError) { authors(:david).essays.eager_load(:writer).to_a }
+    assert_raise(ActiveRecord::EagerLoadPolymorphicError) { authors(:david).essays.eager_load(:writer).count }
+    assert_raise(ActiveRecord::EagerLoadPolymorphicError) { authors(:david).essays.eager_load(:writer).exists? }
+  end
+
   # CollectionProxy#reader is expensive, so the preloader avoids calling it.
   test "preloading has_many_through association avoids calling association.reader" do
     ActiveRecord::Associations::HasManyAssociation.any_instance.expects(:reader).never
     Author.preload(:readonly_comments).first!
   end
+
+  test "preloading through a polymorphic association doesn't require the association to exist" do
+    sponsors = []
+    assert_queries 5 do
+      sponsors = Sponsor.where(sponsorable_id: 1).preload(sponsorable: [:post, :membership]).to_a
+    end
+    # check the preload worked
+    assert_queries 0 do
+      sponsors.map(&:sponsorable).map { |s| s.respond_to?(:posts) ? s.post.author : s.membership }
+    end
+  end
+
+  test "preloading a regular association through a polymorphic association doesn't require the association to exist on all types" do
+    sponsors = []
+    assert_queries 6 do
+      sponsors = Sponsor.where(sponsorable_id: 1).preload(sponsorable: [{ post: :first_comment }, :membership]).to_a
+    end
+    # check the preload worked
+    assert_queries 0 do
+      sponsors.map(&:sponsorable).map { |s| s.respond_to?(:posts) ? s.post.author : s.membership }
+    end
+  end
+
+  test "preloading a regular association with a typo through a polymorphic association still raises" do
+    # this test contains an intentional typo of first -> fist
+    assert_raises(ActiveRecord::AssociationNotFoundError) do
+      Sponsor.where(sponsorable_id: 1).preload(sponsorable: [{ post: :fist_comment }, :membership]).to_a
+    end
+  end
+
+  private
+    def find_all_ordered(klass, include = nil)
+      klass.order("#{klass.table_name}.#{klass.primary_key}").includes(include).to_a
+    end
 end
diff --git a/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb b/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
index 979dd986de..5d9735d98a 100644
--- a/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
@@ -88,12 +88,6 @@ class DeveloperWithSymbolClassName < Developer
   has_and_belongs_to_many :projects, class_name: :ProjectWithSymbolsForKeys
 end
 
-ActiveSupport::Deprecation.silence do
-  class DeveloperWithConstantClassName < Developer
-    has_and_belongs_to_many :projects, class_name: ProjectWithSymbolsForKeys
-  end
-end
-
 class DeveloperWithExtendOption < Developer
   module NamedExtension
     def category
@@ -186,11 +180,11 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
   def test_has_and_belongs_to_many
     david = Developer.find(1)
 
-    assert !david.projects.empty?
+    assert_not_empty david.projects
     assert_equal 2, david.projects.size
 
     active_record = Project.find(1)
-    assert !active_record.developers.empty?
+    assert_not_empty active_record.developers
     assert_equal 3, active_record.developers.size
     assert_includes active_record.developers, david
   end
@@ -268,10 +262,10 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     no_of_projects = Project.count
     aredridel = Developer.new("name" => "Aredridel")
     aredridel.projects.concat([Project.find(1), p = Project.new("name" => "Projekt")])
-    assert !aredridel.persisted?
-    assert !p.persisted?
+    assert_not_predicate aredridel, :persisted?
+    assert_not_predicate p, :persisted?
     assert aredridel.save
-    assert aredridel.persisted?
+    assert_predicate aredridel, :persisted?
     assert_equal no_of_devels + 1, Developer.count
     assert_equal no_of_projects + 1, Project.count
     assert_equal 2, aredridel.projects.size
@@ -317,14 +311,14 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
   def test_build
     devel = Developer.find(1)
     proj = assert_no_queries(ignore_none: false) { devel.projects.build("name" => "Projekt") }
-    assert !devel.projects.loaded?
+    assert_not_predicate devel.projects, :loaded?
 
     assert_equal devel.projects.last, proj
-    assert devel.projects.loaded?
+    assert_predicate devel.projects, :loaded?
 
-    assert !proj.persisted?
+    assert_not_predicate proj, :persisted?
     devel.save
-    assert proj.persisted?
+    assert_predicate proj, :persisted?
     assert_equal devel.projects.last, proj
     assert_equal Developer.find(1).projects.sort_by(&:id).last, proj  # prove join table is updated
   end
@@ -332,14 +326,14 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
   def test_new_aliased_to_build
     devel = Developer.find(1)
     proj = assert_no_queries(ignore_none: false) { devel.projects.new("name" => "Projekt") }
-    assert !devel.projects.loaded?
+    assert_not_predicate devel.projects, :loaded?
 
     assert_equal devel.projects.last, proj
-    assert devel.projects.loaded?
+    assert_predicate devel.projects, :loaded?
 
-    assert !proj.persisted?
+    assert_not_predicate proj, :persisted?
     devel.save
-    assert proj.persisted?
+    assert_predicate proj, :persisted?
     assert_equal devel.projects.last, proj
     assert_equal Developer.find(1).projects.sort_by(&:id).last, proj  # prove join table is updated
   end
@@ -349,10 +343,10 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     devel.projects.build(name: "Make bed")
     proj2 = devel.projects.build(name: "Lie in it")
     assert_equal devel.projects.last, proj2
-    assert !proj2.persisted?
+    assert_not_predicate proj2, :persisted?
     devel.save
-    assert devel.persisted?
-    assert proj2.persisted?
+    assert_predicate devel, :persisted?
+    assert_predicate proj2, :persisted?
     assert_equal devel.projects.last, proj2
     assert_equal Developer.find_by_name("Marcel").projects.last, proj2  # prove join table is updated
   end
@@ -360,12 +354,12 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
   def test_create
     devel = Developer.find(1)
     proj = devel.projects.create("name" => "Projekt")
-    assert !devel.projects.loaded?
+    assert_not_predicate devel.projects, :loaded?
 
     assert_equal devel.projects.last, proj
-    assert !devel.projects.loaded?
+    assert_not_predicate devel.projects, :loaded?
 
-    assert proj.persisted?
+    assert_predicate proj, :persisted?
     assert_equal Developer.find(1).projects.sort_by(&:id).last, proj  # prove join table is updated
   end
 
@@ -373,14 +367,14 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     # in Oracle '' is saved as null therefore need to save ' ' in not null column
     post = categories(:general).post_with_conditions.build(body: " ")
 
-    assert        post.save
-    assert_equal  "Yet Another Testing Title", post.title
+    assert post.save
+    assert_equal "Yet Another Testing Title", post.title
 
     # in Oracle '' is saved as null therefore need to save ' ' in not null column
     another_post = categories(:general).post_with_conditions.create(body: " ")
 
-    assert        another_post.persisted?
-    assert_equal  "Yet Another Testing Title", another_post.title
+    assert_predicate another_post, :persisted?
+    assert_equal "Yet Another Testing Title", another_post.title
   end
 
   def test_distinct_after_the_fact
@@ -447,10 +441,10 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
 
   def test_removing_associations_on_destroy
     david = DeveloperWithBeforeDestroyRaise.find(1)
-    assert !david.projects.empty?
+    assert_not_empty david.projects
     david.destroy
-    assert david.projects.empty?
-    assert DeveloperWithBeforeDestroyRaise.connection.select_all("SELECT * FROM developers_projects WHERE developer_id = 1").empty?
+    assert_empty david.projects
+    assert_empty DeveloperWithBeforeDestroyRaise.connection.select_all("SELECT * FROM developers_projects WHERE developer_id = 1")
   end
 
   def test_destroying
@@ -465,7 +459,7 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     end
 
     join_records = Developer.connection.select_all("SELECT * FROM developers_projects WHERE developer_id = #{david.id} AND project_id = #{project.id}")
-    assert join_records.empty?
+    assert_empty join_records
 
     assert_equal 1, david.reload.projects.size
     assert_equal 1, david.projects.reload.size
@@ -481,7 +475,7 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     end
 
     join_records = Developer.connection.select_all("SELECT * FROM developers_projects WHERE developer_id = #{david.id}")
-    assert join_records.empty?
+    assert_empty join_records
 
     assert_equal 0, david.reload.projects.size
     assert_equal 0, david.projects.reload.size
@@ -490,23 +484,23 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
   def test_destroy_all
     david = Developer.find(1)
     david.projects.reload
-    assert !david.projects.empty?
+    assert_not_empty david.projects
 
     assert_no_difference "Project.count" do
       david.projects.destroy_all
     end
 
     join_records = Developer.connection.select_all("SELECT * FROM developers_projects WHERE developer_id = #{david.id}")
-    assert join_records.empty?
+    assert_empty join_records
 
-    assert david.projects.empty?
-    assert david.projects.reload.empty?
+    assert_empty david.projects
+    assert_empty david.projects.reload
   end
 
   def test_destroy_associations_destroys_multiple_associations
     george = parrots(:george)
-    assert !george.pirates.empty?
-    assert !george.treasures.empty?
+    assert_not_empty george.pirates
+    assert_not_empty george.treasures
 
     assert_no_difference "Pirate.count" do
       assert_no_difference "Treasure.count" do
@@ -515,12 +509,12 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     end
 
     join_records = Parrot.connection.select_all("SELECT * FROM parrots_pirates WHERE parrot_id = #{george.id}")
-    assert join_records.empty?
-    assert george.pirates.reload.empty?
+    assert_empty join_records
+    assert_empty george.pirates.reload
 
     join_records = Parrot.connection.select_all("SELECT * FROM parrots_treasures WHERE parrot_id = #{george.id}")
-    assert join_records.empty?
-    assert george.treasures.reload.empty?
+    assert_empty join_records
+    assert_empty george.treasures.reload
   end
 
   def test_associations_with_conditions
@@ -553,7 +547,7 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     developer = project.developers.first
 
     assert_no_queries(ignore_none: false) do
-      assert project.developers.loaded?
+      assert_predicate project.developers, :loaded?
       assert_includes project.developers, developer
     end
   end
@@ -563,19 +557,19 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     developer = project.developers.first
 
     project.reload
-    assert ! project.developers.loaded?
+    assert_not_predicate project.developers, :loaded?
     assert_queries(1) do
       assert_includes project.developers, developer
     end
-    assert ! project.developers.loaded?
+    assert_not_predicate project.developers, :loaded?
   end
 
   def test_include_returns_false_for_non_matching_record_to_verify_scoping
     project = projects(:active_record)
     developer = Developer.create name: "Bryan", salary: 50_000
 
-    assert ! project.developers.loaded?
-    assert ! project.developers.include?(developer)
+    assert_not_predicate project.developers, :loaded?
+    assert_not project.developers.include?(developer)
   end
 
   def test_find_with_merged_options
@@ -668,7 +662,7 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     assert_includes developer.sym_special_projects, sp
   end
 
-  def test_update_attributes_after_push_without_duplicate_join_table_rows
+  def test_update_columns_after_push_without_duplicate_join_table_rows
     developer = Developer.new("name" => "Kano")
     project = SpecialProject.create("name" => "Special Project")
     assert developer.save
@@ -769,9 +763,9 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
 
   def test_get_ids_for_unloaded_associations_does_not_load_them
     developer = developers(:david)
-    assert !developer.projects.loaded?
+    assert_not_predicate developer.projects, :loaded?
     assert_equal projects(:active_record, :action_controller).map(&:id).sort, developer.project_ids.sort
-    assert !developer.projects.loaded?
+    assert_not_predicate developer.projects, :loaded?
   end
 
   def test_assign_ids
@@ -954,13 +948,6 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     end
   end
 
-  def test_with_constant_class_name
-    assert_nothing_raised do
-      developer = DeveloperWithConstantClassName.new
-      developer.projects
-    end
-  end
-
   def test_alternate_database
     professor = Professor.create(name: "Plum")
     course = Course.create(name: "Forensics")
diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index 6bd11a5d81..cc8f33f142 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -57,7 +57,7 @@ class HasManyAssociationsTestPrimaryKeys < ActiveRecord::TestCase
 
   def test_custom_primary_key_on_new_record_should_fetch_with_query
     subscriber = Subscriber.new(nick: "webster132")
-    assert !subscriber.subscriptions.loaded?
+    assert_not_predicate subscriber.subscriptions, :loaded?
 
     assert_queries 1 do
       assert_equal 2, subscriber.subscriptions.size
@@ -68,7 +68,7 @@ class HasManyAssociationsTestPrimaryKeys < ActiveRecord::TestCase
 
   def test_association_primary_key_on_new_record_should_fetch_with_query
     author = Author.new(name: "David")
-    assert !author.essays.loaded?
+    assert_not_predicate author.essays, :loaded?
 
     assert_queries 1 do
       assert_equal 1, author.essays.size
@@ -103,7 +103,7 @@ class HasManyAssociationsTestPrimaryKeys < ActiveRecord::TestCase
 
   def test_blank_custom_primary_key_on_new_record_should_not_run_queries
     author = Author.new
-    assert !author.essays.loaded?
+    assert_not_predicate author.essays, :loaded?
 
     assert_queries 0 do
       assert_equal 0, author.essays.size
@@ -201,7 +201,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     part.reload
 
     assert_nil part.ship
-    assert !part.updated_at_changed?
+    assert_not_predicate part, :updated_at_changed?
   end
 
   def test_create_from_association_should_respect_default_scope
@@ -444,7 +444,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       new_clients << company.clients_of_firm.build(name: "Another Client III")
     end
 
-    assert_not company.clients_of_firm.loaded?
+    assert_not_predicate company.clients_of_firm, :loaded?
     assert_queries(1) do
       assert_same new_clients[0], company.clients_of_firm.third
       assert_same new_clients[1], company.clients_of_firm.fourth
@@ -464,7 +464,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       new_clients << company.clients_of_firm.build(name: "Another Client III")
     end
 
-    assert_not company.clients_of_firm.loaded?
+    assert_not_predicate company.clients_of_firm, :loaded?
     assert_queries(1) do
       assert_same new_clients[0], company.clients_of_firm.third!
       assert_same new_clients[1], company.clients_of_firm.fourth!
@@ -497,8 +497,6 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     person = Person.new
     person.first_name = "Naruto"
     person.references << Reference.new
-    person.id = 10
-    person.references
     person.save!
     assert_equal 1, person.references.update_all(favourite: true)
   end
@@ -507,8 +505,6 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     person = Person.new
     person.first_name = "Sasuke"
     person.references << Reference.new
-    person.id = 10
-    person.references
     person.save!
     assert_predicate person.references, :exists?
   end
@@ -587,14 +583,14 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     # taking from unloaded Relation
     bob = klass.find(authors(:bob).id)
     new_post = bob.posts.build
-    assert_not bob.posts.loaded?
+    assert_not_predicate bob.posts, :loaded?
     assert_equal [posts(:misc_by_bob)], bob.posts.take(1)
     assert_equal [posts(:misc_by_bob), posts(:other_by_bob)], bob.posts.take(2)
     assert_equal [posts(:misc_by_bob), posts(:other_by_bob), new_post], bob.posts.take(3)
 
     # taking from loaded Relation
     bob.posts.load
-    assert bob.posts.loaded?
+    assert_predicate bob.posts, :loaded?
     assert_equal [posts(:misc_by_bob)], bob.posts.take(1)
     assert_equal [posts(:misc_by_bob), posts(:other_by_bob)], bob.posts.take(2)
     assert_equal [posts(:misc_by_bob), posts(:other_by_bob), new_post], bob.posts.take(3)
@@ -713,13 +709,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_find_each
     firm = companies(:first_firm)
 
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
 
     assert_queries(4) do
       firm.clients.find_each(batch_size: 1) { |c| assert_equal firm.id, c.firm_id }
     end
 
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_find_each_with_conditions
@@ -732,13 +728,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       end
     end
 
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_find_in_batches
     firm = companies(:first_firm)
 
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
 
     assert_queries(2) do
       firm.clients.find_in_batches(batch_size: 2) do |clients|
@@ -746,7 +742,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       end
     end
 
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_find_all_sanitized
@@ -831,7 +827,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   end
 
   def test_find_scoped_grouped_having
-    assert_equal 1, authors(:david).popular_grouped_posts.length
+    assert_equal 2, authors(:david).popular_grouped_posts.length
     assert_equal 0, authors(:mary).popular_grouped_posts.length
   end
 
@@ -955,20 +951,20 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_new_aliased_to_build
     company = companies(:first_firm)
     new_client = assert_no_queries(ignore_none: false) { company.clients_of_firm.new("name" => "Another Client") }
-    assert !company.clients_of_firm.loaded?
+    assert_not_predicate company.clients_of_firm, :loaded?
 
     assert_equal "Another Client", new_client.name
-    assert !new_client.persisted?
+    assert_not_predicate new_client, :persisted?
     assert_equal new_client, company.clients_of_firm.last
   end
 
   def test_build
     company = companies(:first_firm)
     new_client = assert_no_queries(ignore_none: false) { company.clients_of_firm.build("name" => "Another Client") }
-    assert !company.clients_of_firm.loaded?
+    assert_not_predicate company.clients_of_firm, :loaded?
 
     assert_equal "Another Client", new_client.name
-    assert !new_client.persisted?
+    assert_not_predicate new_client, :persisted?
     assert_equal new_client, company.clients_of_firm.last
   end
 
@@ -982,9 +978,29 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
 
   def test_collection_not_empty_after_building
     company = companies(:first_firm)
-    assert_predicate company.contracts, :empty?
+    assert_empty company.contracts
     company.contracts.build
-    assert_not_predicate company.contracts, :empty?
+    assert_not_empty company.contracts
+  end
+
+  def test_collection_size_with_dirty_target
+    post = posts(:thinking)
+    assert_equal [], post.reader_ids
+    assert_equal 0, post.readers.size
+    post.readers.reset
+    post.readers.build
+    assert_equal [nil], post.reader_ids
+    assert_equal 1, post.readers.size
+  end
+
+  def test_collection_empty_with_dirty_target
+    post = posts(:thinking)
+    assert_equal [], post.reader_ids
+    assert_empty post.readers
+    post.readers.reset
+    post.readers.build
+    assert_equal [nil], post.reader_ids
+    assert_not_empty post.readers
   end
 
   def test_collection_size_twice_for_regressions
@@ -1008,7 +1024,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_build_followed_by_save_does_not_load_target
     companies(:first_firm).clients_of_firm.build("name" => "Another Client")
     assert companies(:first_firm).save
-    assert !companies(:first_firm).clients_of_firm.loaded?
+    assert_not_predicate companies(:first_firm).clients_of_firm, :loaded?
   end
 
   def test_build_without_loading_association
@@ -1028,10 +1044,10 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_build_via_block
     company = companies(:first_firm)
     new_client = assert_no_queries(ignore_none: false) { company.clients_of_firm.build { |client| client.name = "Another Client" } }
-    assert !company.clients_of_firm.loaded?
+    assert_not_predicate company.clients_of_firm, :loaded?
 
     assert_equal "Another Client", new_client.name
-    assert !new_client.persisted?
+    assert_not_predicate new_client, :persisted?
     assert_equal new_client, company.clients_of_firm.last
   end
 
@@ -1069,7 +1085,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_predicate companies(:first_firm).clients_of_firm, :loaded?
 
     new_client = companies(:first_firm).clients_of_firm.create("name" => "Another Client")
-    assert new_client.persisted?
+    assert_predicate new_client, :persisted?
     assert_equal new_client, companies(:first_firm).clients_of_firm.last
     assert_equal new_client, companies(:first_firm).clients_of_firm.reload.last
   end
@@ -1082,7 +1098,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_create_followed_by_save_does_not_load_target
     companies(:first_firm).clients_of_firm.create("name" => "Another Client")
     assert companies(:first_firm).save
-    assert !companies(:first_firm).clients_of_firm.loaded?
+    assert_not_predicate companies(:first_firm).clients_of_firm, :loaded?
   end
 
   def test_deleting
@@ -1108,7 +1124,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     # option is not given on the association.
     ship = Ship.create(name: "Countless", treasures_count: 10)
 
-    assert_not Ship.reflect_on_association(:treasures).has_cached_counter?
+    assert_not_predicate Ship.reflect_on_association(:treasures), :has_cached_counter?
 
     # Count should come from sql count() of treasures rather than treasures_count attribute
     assert_equal ship.treasures.size, 0
@@ -1199,7 +1215,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_calling_empty_with_counter_cache
     post = posts(:welcome)
     assert_queries(0) do
-      assert_not post.comments.empty?
+      assert_not_empty post.comments
     end
   end
 
@@ -1211,20 +1227,20 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     end
   end
 
-  def test_calling_update_attributes_on_id_changes_the_counter_cache
+  def test_calling_update_on_id_changes_the_counter_cache
     topic = Topic.order("id ASC").first
     original_count = topic.replies.to_a.size
     assert_equal original_count, topic.replies_count
 
     first_reply = topic.replies.first
-    first_reply.update_attributes(parent_id: nil)
+    first_reply.update(parent_id: nil)
     assert_equal original_count - 1, topic.reload.replies_count
 
-    first_reply.update_attributes(parent_id: topic.id)
+    first_reply.update(parent_id: topic.id)
     assert_equal original_count, topic.reload.replies_count
   end
 
-  def test_calling_update_attributes_changing_ids_doesnt_change_counter_cache
+  def test_calling_update_changing_ids_doesnt_change_counter_cache
     topic1 = Topic.find(1)
     topic2 = Topic.find(3)
     original_count1 = topic1.replies.to_a.size
@@ -1233,11 +1249,11 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     reply1 = topic1.replies.first
     reply2 = topic2.replies.first
 
-    reply1.update_attributes(parent_id: topic2.id)
+    reply1.update(parent_id: topic2.id)
     assert_equal original_count1 - 1, topic1.reload.replies_count
     assert_equal original_count2 + 1, topic2.reload.replies_count
 
-    reply2.update_attributes(parent_id: topic1.id)
+    reply2.update(parent_id: topic1.id)
     assert_equal original_count1, topic1.reload.replies_count
     assert_equal original_count2, topic2.reload.replies_count
   end
@@ -1441,13 +1457,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_creation_respects_hash_condition
     ms_client = companies(:first_firm).clients_like_ms_with_hash_conditions.build
 
-    assert        ms_client.save
-    assert_equal  "Microsoft", ms_client.name
+    assert ms_client.save
+    assert_equal "Microsoft", ms_client.name
 
     another_ms_client = companies(:first_firm).clients_like_ms_with_hash_conditions.create
 
-    assert        another_ms_client.persisted?
-    assert_equal  "Microsoft", another_ms_client.name
+    assert_predicate another_ms_client, :persisted?
+    assert_equal "Microsoft", another_ms_client.name
   end
 
   def test_clearing_without_initial_access
@@ -1558,7 +1574,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_predicate companies(:first_firm).clients_of_firm, :loaded?
 
     clients = companies(:first_firm).clients_of_firm.to_a
-    assert !clients.empty?, "37signals has clients after load"
+    assert_not clients.empty?, "37signals has clients after load"
     destroyed = companies(:first_firm).clients_of_firm.destroy_all
     assert_equal clients.sort_by(&:id), destroyed.sort_by(&:id)
     assert destroyed.all?(&:frozen?), "destroyed clients should be frozen"
@@ -1570,7 +1586,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     firm = companies(:first_firm)
     assert_equal 3, firm.clients.size
     firm.destroy
-    assert Client.all.merge!(where: "firm_id=#{firm.id}").to_a.empty?
+    assert_empty Client.all.merge!(where: "firm_id=#{firm.id}").to_a
   end
 
   def test_dependence_for_associations_with_hash_condition
@@ -1633,7 +1649,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     firm = RestrictedWithExceptionFirm.create!(name: "restrict")
     firm.companies.create(name: "child")
 
-    assert !firm.companies.empty?
+    assert_not_empty firm.companies
     assert_raise(ActiveRecord::DeleteRestrictionError) { firm.destroy }
     assert RestrictedWithExceptionFirm.exists?(name: "restrict")
     assert firm.companies.exists?(name: "child")
@@ -1643,11 +1659,11 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     firm = RestrictedWithErrorFirm.create!(name: "restrict")
     firm.companies.create(name: "child")
 
-    assert !firm.companies.empty?
+    assert_not_empty firm.companies
 
     firm.destroy
 
-    assert !firm.errors.empty?
+    assert_not_empty firm.errors
 
     assert_equal "Cannot delete record because dependent companies exist", firm.errors[:base].first
     assert RestrictedWithErrorFirm.exists?(name: "restrict")
@@ -1660,11 +1676,11 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     firm = RestrictedWithErrorFirm.create!(name: "restrict")
     firm.companies.create(name: "child")
 
-    assert !firm.companies.empty?
+    assert_not_empty firm.companies
 
     firm.destroy
 
-    assert !firm.errors.empty?
+    assert_not_empty firm.errors
 
     assert_equal "Cannot delete record because dependent client companies exist", firm.errors[:base].first
     assert RestrictedWithErrorFirm.exists?(name: "restrict")
@@ -1716,8 +1732,8 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     account = Account.new
     orig_accounts = firm.accounts.to_a
 
-    assert !account.valid?
-    assert !orig_accounts.empty?
+    assert_not_predicate account, :valid?
+    assert_not_empty orig_accounts
     error = assert_raise ActiveRecord::RecordNotSaved do
       firm.accounts = [account]
     end
@@ -1775,9 +1791,9 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
 
   def test_get_ids_for_unloaded_associations_does_not_load_them
     company = companies(:first_firm)
-    assert !company.clients.loaded?
+    assert_not_predicate company.clients, :loaded?
     assert_equal [companies(:first_client).id, companies(:second_client).id, companies(:another_first_firm_client).id], company.client_ids
-    assert !company.clients.loaded?
+    assert_not_predicate company.clients, :loaded?
   end
 
   def test_counter_cache_on_unloaded_association
@@ -1842,6 +1858,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     ].each { |block| assert_raise(ActiveRecord::HasManyThroughCantAssociateThroughHasOneOrManyReflection, &block) }
   end
 
+  def test_associations_order_should_be_priority_over_throughs_order
+    david = authors(:david)
+    expected = [12, 10, 9, 8, 7, 6, 5, 3, 2, 1]
+    assert_equal expected, david.comments_desc.map(&:id)
+    assert_equal expected, Author.includes(:comments_desc).find(david.id).comments_desc.map(&:id)
+  end
+
   def test_dynamic_find_should_respect_association_order_for_through
     assert_equal Comment.find(10), authors(:david).comments_desc.where("comments.type = 'SpecialComment'").first
     assert_equal Comment.find(10), authors(:david).comments_desc.find_by_type("SpecialComment")
@@ -1859,7 +1882,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     client = firm.clients.first
 
     assert_no_queries do
-      assert firm.clients.loaded?
+      assert_predicate firm.clients, :loaded?
       assert_equal true, firm.clients.include?(client)
     end
   end
@@ -1869,18 +1892,18 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     client = firm.clients.first
 
     firm.reload
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
     assert_queries(1) do
       assert_equal true, firm.clients.include?(client)
     end
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_include_returns_false_for_non_matching_record_to_verify_scoping
     firm = companies(:first_firm)
     client = Client.create!(name: "Not Associated")
 
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
     assert_equal false, firm.clients.include?(client)
   end
 
@@ -1889,13 +1912,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     firm.clients.first
     firm.clients.second
     firm.clients.last
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_calling_first_or_last_on_loaded_association_should_not_fetch_with_query
     firm = companies(:first_firm)
     firm.clients.load_target
-    assert firm.clients.loaded?
+    assert_predicate firm.clients, :loaded?
 
     assert_no_queries(ignore_none: false) do
       firm.clients.first
@@ -1908,7 +1931,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_calling_first_or_last_on_existing_record_with_build_should_load_association
     firm = companies(:first_firm)
     firm.clients.build(name: "Foo")
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
 
     assert_queries 1 do
       firm.clients.first
@@ -1916,13 +1939,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       firm.clients.last
     end
 
-    assert firm.clients.loaded?
+    assert_predicate firm.clients, :loaded?
   end
 
   def test_calling_first_nth_or_last_on_existing_record_with_create_should_not_load_association
     firm = companies(:first_firm)
     firm.clients.create(name: "Foo")
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
 
     assert_queries 3 do
       firm.clients.first
@@ -1930,7 +1953,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       firm.clients.last
     end
 
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_calling_first_nth_or_last_on_new_record_should_not_run_queries
@@ -1946,14 +1969,14 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_calling_first_or_last_with_integer_on_association_should_not_load_association
     firm = companies(:first_firm)
     firm.clients.create(name: "Foo")
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
 
     assert_queries 2 do
       firm.clients.first(2)
       firm.clients.last(2)
     end
 
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_calling_many_should_count_instead_of_loading_association
@@ -1961,7 +1984,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_queries(1) do
       firm.clients.many?  # use count query
     end
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_calling_many_on_loaded_association_should_not_use_query
@@ -1973,25 +1996,26 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_calling_many_should_defer_to_collection_if_using_a_block
     firm = companies(:first_firm)
     assert_queries(1) do
-      firm.clients.expects(:size).never
-      firm.clients.many? { true }
+      assert_not_called(firm.clients, :size) do
+        firm.clients.many? { true }
+      end
     end
-    assert firm.clients.loaded?
+    assert_predicate firm.clients, :loaded?
   end
 
   def test_calling_many_should_return_false_if_none_or_one
     firm = companies(:another_firm)
-    assert !firm.clients_like_ms.many?
+    assert_not_predicate firm.clients_like_ms, :many?
     assert_equal 0, firm.clients_like_ms.size
 
     firm = companies(:first_firm)
-    assert !firm.limited_clients.many?
+    assert_not_predicate firm.limited_clients, :many?
     assert_equal 1, firm.limited_clients.size
   end
 
   def test_calling_many_should_return_true_if_more_than_one
     firm = companies(:first_firm)
-    assert firm.clients.many?
+    assert_predicate firm.clients, :many?
     assert_equal 3, firm.clients.size
   end
 
@@ -2000,33 +2024,34 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_queries(1) do
       firm.clients.none?  # use count query
     end
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_calling_none_on_loaded_association_should_not_use_query
     firm = companies(:first_firm)
     firm.clients.load  # force load
-    assert_no_queries { assert ! firm.clients.none? }
+    assert_no_queries { assert_not firm.clients.none? }
   end
 
   def test_calling_none_should_defer_to_collection_if_using_a_block
     firm = companies(:first_firm)
     assert_queries(1) do
-      firm.clients.expects(:size).never
-      firm.clients.none? { true }
+      assert_not_called(firm.clients, :size) do
+        firm.clients.none? { true }
+      end
     end
-    assert firm.clients.loaded?
+    assert_predicate firm.clients, :loaded?
   end
 
   def test_calling_none_should_return_true_if_none
     firm = companies(:another_firm)
-    assert firm.clients_like_ms.none?
+    assert_predicate firm.clients_like_ms, :none?
     assert_equal 0, firm.clients_like_ms.size
   end
 
   def test_calling_none_should_return_false_if_any
     firm = companies(:first_firm)
-    assert !firm.limited_clients.none?
+    assert_not_predicate firm.limited_clients, :none?
     assert_equal 1, firm.limited_clients.size
   end
 
@@ -2035,39 +2060,40 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_queries(1) do
       firm.clients.one?  # use count query
     end
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_calling_one_on_loaded_association_should_not_use_query
     firm = companies(:first_firm)
     firm.clients.load  # force load
-    assert_no_queries { assert ! firm.clients.one? }
+    assert_no_queries { assert_not firm.clients.one? }
   end
 
   def test_calling_one_should_defer_to_collection_if_using_a_block
     firm = companies(:first_firm)
     assert_queries(1) do
-      firm.clients.expects(:size).never
-      firm.clients.one? { true }
+      assert_not_called(firm.clients, :size) do
+        firm.clients.one? { true }
+      end
     end
-    assert firm.clients.loaded?
+    assert_predicate firm.clients, :loaded?
   end
 
   def test_calling_one_should_return_false_if_zero
     firm = companies(:another_firm)
-    assert ! firm.clients_like_ms.one?
+    assert_not_predicate firm.clients_like_ms, :one?
     assert_equal 0, firm.clients_like_ms.size
   end
 
   def test_calling_one_should_return_true_if_one
     firm = companies(:first_firm)
-    assert firm.limited_clients.one?
+    assert_predicate firm.limited_clients, :one?
     assert_equal 1, firm.limited_clients.size
   end
 
   def test_calling_one_should_return_false_if_more_than_one
     firm = companies(:first_firm)
-    assert ! firm.clients.one?
+    assert_not_predicate firm.clients, :one?
     assert_equal 3, firm.clients.size
   end
 
@@ -2089,9 +2115,10 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   end
 
   def test_association_proxy_transaction_method_starts_transaction_in_association_class
-    Comment.expects(:transaction)
-    Post.first.comments.transaction do
-      # nothing
+    assert_called(Comment, :transaction) do
+      Post.first.comments.transaction do
+        # nothing
+      end
     end
   end
 
@@ -2287,7 +2314,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     post = posts(:welcome)
 
     assert post.taggings_with_delete_all.count > 0
-    assert !post.taggings_with_delete_all.loaded?
+    assert_not_predicate post.taggings_with_delete_all, :loaded?
 
     # 2 queries: one DELETE and another to update the counter cache
     assert_queries(2) do
@@ -2309,7 +2336,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
 
   test "collection proxy respects default scope" do
     author = authors(:mary)
-    assert !author.first_posts.exists?
+    assert_not_predicate author.first_posts, :exists?
   end
 
   test "association with extend option" do
@@ -2350,7 +2377,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
 
   test "does not duplicate associations when used with natural primary keys" do
     speedometer = Speedometer.create!(id: "4")
-    speedometer.minivans.create!(minivan_id: "a-van-red" , name: "a van", color: "red")
+    speedometer.minivans.create!(minivan_id: "a-van-red", name: "a van", color: "red")
 
     assert_equal 1, speedometer.minivans.to_a.size, "Only one association should be present:\n#{speedometer.minivans.to_a}"
     assert_equal 1, speedometer.reload.minivans.to_a.size
@@ -2428,7 +2455,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     pirate = FamousPirate.new
     pirate.famous_ships << ship = FamousShip.new
 
-    assert pirate.valid?
+    assert_predicate pirate, :valid?
     assert_not pirate.valid?(:conference)
     assert_equal "can't be blank", ship.errors[:name].first
   end
@@ -2509,6 +2536,15 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_same car, new_bulb.car
   end
 
+  test "reattach to new objects replaces inverse association and foreign key" do
+    bulb = Bulb.create!(car: Car.create!)
+    assert bulb.car_id
+    car = Car.new
+    car.bulbs << bulb
+    assert_equal car, bulb.car
+    assert_nil bulb.car_id
+  end
+
   test "in memory replacement maintains order" do
     first_bulb = Bulb.create!
     second_bulb = Bulb.create!
@@ -2520,6 +2556,14 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_equal [first_bulb, second_bulb], car.bulbs
   end
 
+  test "association size calculation works with default scoped selects when not previously fetched" do
+    firm = Firm.create!(name: "Firm")
+    5.times { firm.developers_with_select << Developer.create!(name: "Developer") }
+
+    same_firm = Firm.find(firm.id)
+    assert_equal 5, same_firm.developers_with_select.size
+  end
+
   test "prevent double insertion of new object when the parent association loaded in the after save callback" do
     reset_callbacks(:save, Bulb) do
       Bulb.after_save { |record| record.car.bulbs.load }
@@ -2543,6 +2587,70 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     end
   end
 
+  test "calling size on an association that has not been loaded performs a query" do
+    car = Car.create!
+    Bulb.create(car_id: car.id)
+
+    car_two = Car.create!
+
+    assert_queries(1) do
+      assert_equal 1, car.bulbs.size
+    end
+
+    assert_queries(1) do
+      assert_equal 0, car_two.bulbs.size
+    end
+  end
+
+  test "calling size on an association that has been loaded does not perform query" do
+    car = Car.create!
+    Bulb.create(car_id: car.id)
+    car.bulb_ids
+
+    car_two = Car.create!
+    car_two.bulb_ids
+
+    assert_no_queries do
+      assert_equal 1, car.bulbs.size
+    end
+
+    assert_no_queries do
+      assert_equal 0, car_two.bulbs.size
+    end
+  end
+
+  test "calling empty on an association that has not been loaded performs a query" do
+    car = Car.create!
+    Bulb.create(car_id: car.id)
+
+    car_two = Car.create!
+
+    assert_queries(1) do
+      assert_not_empty car.bulbs
+    end
+
+    assert_queries(1) do
+      assert_empty car_two.bulbs
+    end
+  end
+
+  test "calling empty on an association that has been loaded does not performs query" do
+    car = Car.create!
+    Bulb.create(car_id: car.id)
+    car.bulb_ids
+
+    car_two = Car.create!
+    car_two.bulb_ids
+
+    assert_no_queries do
+      assert_not_empty car.bulbs
+    end
+
+    assert_no_queries do
+      assert_empty car_two.bulbs
+    end
+  end
+
   class AuthorWithErrorDestroyingAssociation < ActiveRecord::Base
     self.table_name = "authors"
     has_many :posts_with_error_destroying,
diff --git a/activerecord/test/cases/associations/has_many_through_associations_test.rb b/activerecord/test/cases/associations/has_many_through_associations_test.rb
index f8ea51225a..0facc286da 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -46,6 +46,11 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     Reader.create person_id: 0, post_id: 0
   end
 
+  def test_marshal_dump
+    preloaded = Post.includes(:first_blue_tags).first
+    assert_equal preloaded, Marshal.load(Marshal.dump(preloaded))
+  end
+
   def test_preload_sti_rhs_class
     developers = Developer.includes(:firms).all.to_a
     assert_no_queries do
@@ -353,10 +358,10 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     end
 
     assert_queries(1) do
-      assert posts(:welcome).people.empty?
+      assert_empty posts(:welcome).people
     end
 
-    assert posts(:welcome).reload.people.reload.empty?
+    assert_empty posts(:welcome).reload.people.reload
   end
 
   def test_destroy_association
@@ -366,8 +371,8 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
       end
     end
 
-    assert posts(:welcome).reload.people.empty?
-    assert posts(:welcome).people.reload.empty?
+    assert_empty posts(:welcome).reload.people
+    assert_empty posts(:welcome).people.reload
   end
 
   def test_destroy_all
@@ -377,8 +382,8 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
       end
     end
 
-    assert posts(:welcome).reload.people.empty?
-    assert posts(:welcome).people.reload.empty?
+    assert_empty posts(:welcome).reload.people
+    assert_empty posts(:welcome).people.reload
   end
 
   def test_should_raise_exception_for_destroying_mismatching_records
@@ -538,6 +543,16 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     end
   end
 
+  def test_update_counter_caches_on_destroy_with_indestructible_through_record
+    post = posts(:welcome)
+    tag  = post.indestructible_tags.create!(name: "doomed")
+    post.update_columns(indestructible_tags_count: post.indestructible_tags.count)
+
+    assert_no_difference "post.reload.indestructible_tags_count" do
+      posts(:welcome).indestructible_tags.destroy(tag)
+    end
+  end
+
   def test_replace_association
     assert_queries(4) { posts(:welcome);people(:david);people(:michael); posts(:welcome).people.reload }
 
@@ -675,10 +690,10 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     end
 
     assert_queries(0) do
-      assert posts(:welcome).people.empty?
+      assert_empty posts(:welcome).people
     end
 
-    assert posts(:welcome).reload.people.reload.empty?
+    assert_empty posts(:welcome).reload.people.reload
   end
 
   def test_association_callback_ordering
@@ -760,9 +775,9 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
 
   def test_get_ids_for_unloaded_associations_does_not_load_them
     person = people(:michael)
-    assert !person.posts.loaded?
+    assert_not_predicate person.posts, :loaded?
     assert_equal [posts(:welcome).id, posts(:authorless).id].sort, person.post_ids.sort
-    assert !person.posts.loaded?
+    assert_not_predicate person.posts, :loaded?
   end
 
   def test_association_proxy_transaction_method_starts_transaction_in_association_class
@@ -851,8 +866,8 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     author   = authors(:mary)
     category = author.named_categories.create(name: "Primary")
     author.named_categories.delete(category)
-    assert !Categorization.exists?(author_id: author.id, named_category_name: category.name)
-    assert author.named_categories.reload.empty?
+    assert_not Categorization.exists?(author_id: author.id, named_category_name: category.name)
+    assert_empty author.named_categories.reload
   end
 
   def test_collection_singular_ids_getter_with_string_primary_keys
@@ -869,6 +884,14 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     assert_equal [dev], company.developers
   end
 
+  def test_collection_singular_ids_setter_with_required_type_cast
+    company = companies(:rails_core)
+    dev = Developer.first
+
+    company.developer_ids = [dev.id.to_s]
+    assert_equal [dev], company.developers
+  end
+
   def test_collection_singular_ids_setter_with_string_primary_keys
     assert_nothing_raised do
       book = books(:awdr)
@@ -926,8 +949,8 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
   end
 
   def test_through_association_readonly_should_be_false
-    assert !people(:michael).posts.first.readonly?
-    assert !people(:michael).posts.to_a.first.readonly?
+    assert_not_predicate people(:michael).posts.first, :readonly?
+    assert_not_predicate people(:michael).posts.to_a.first, :readonly?
   end
 
   def test_can_update_through_association
@@ -1016,12 +1039,12 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     post.author_categorizations
     proxy = post.send(:association_instance_get, :author_categorizations)
 
-    assert !proxy.stale_target?
+    assert_not_predicate proxy, :stale_target?
     assert_equal authors(:mary).categorizations.sort_by(&:id), post.author_categorizations.sort_by(&:id)
 
     post.author_id = authors(:david).id
 
-    assert proxy.stale_target?
+    assert_predicate proxy, :stale_target?
     assert_equal authors(:david).categorizations.sort_by(&:id), post.author_categorizations.sort_by(&:id)
   end
 
@@ -1038,7 +1061,7 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
 
     assert_includes post.author_addresses, address
     post.author_addresses.delete(address)
-    assert post[:author_count].nil?
+    assert_predicate post[:author_count], :nil?
   end
 
   def test_primary_key_option_on_source
@@ -1250,6 +1273,18 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     TenantMembership.current_member = nil
   end
 
+  def test_has_many_through_with_scope_that_has_joined_same_table_with_parent_relation
+    assert_equal authors(:david), Author.joins(:comments_for_first_author).take
+  end
+
+  def test_has_many_through_with_unscope_should_affect_to_through_scope
+    assert_equal [comments(:eager_other_comment1)], authors(:mary).unordered_comments
+  end
+
+  def test_has_many_through_with_scope_should_accept_string_and_hash_join
+    assert_equal authors(:david), Author.joins({ comments_for_first_author: :post }, "inner join posts posts_alias on authors.id = posts_alias.author_id").eager_load(:categories).take
+  end
+
   def test_has_many_through_with_scope_should_respect_table_alias
     family = Family.create!
     users = 3.times.map { User.create! }
@@ -1288,6 +1323,70 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     end
   end
 
+  def test_has_many_through_update_ids_with_conditions
+    author = Author.create!(name: "Bill")
+    category = categories(:general)
+
+    author.update(
+      special_categories_with_condition_ids: [category.id],
+      nonspecial_categories_with_condition_ids: [category.id]
+    )
+
+    assert_equal [category.id], author.special_categories_with_condition_ids
+    assert_equal [category.id], author.nonspecial_categories_with_condition_ids
+
+    author.update(nonspecial_categories_with_condition_ids: [])
+    author.reload
+
+    assert_equal [category.id], author.special_categories_with_condition_ids
+    assert_equal [], author.nonspecial_categories_with_condition_ids
+  end
+
+  def test_single_has_many_through_association_with_unpersisted_parent_instance
+    post_with_single_has_many_through = Class.new(Post) do
+      def self.name; "PostWithSingleHasManyThrough"; end
+      has_many :subscriptions, through: :author
+    end
+    post = post_with_single_has_many_through.new
+
+    post.author = authors(:mary)
+    book1 = Book.create!(name: "essays on single has many through associations 1")
+    post.author.books << book1
+    subscription1 = Subscription.first
+    book1.subscriptions << subscription1
+    assert_equal [subscription1], post.subscriptions.to_a
+
+    post.author = authors(:bob)
+    book2 = Book.create!(name: "essays on single has many through associations 2")
+    post.author.books << book2
+    subscription2 = Subscription.second
+    book2.subscriptions << subscription2
+    assert_equal [subscription2], post.subscriptions.to_a
+  end
+
+  def test_nested_has_many_through_association_with_unpersisted_parent_instance
+    post_with_nested_has_many_through = Class.new(Post) do
+      def self.name; "PostWithNestedHasManyThrough"; end
+      has_many :books, through: :author
+      has_many :subscriptions, through: :books
+    end
+    post = post_with_nested_has_many_through.new
+
+    post.author = authors(:mary)
+    book1 = Book.create!(name: "essays on nested has many through associations 1")
+    post.author.books << book1
+    subscription1 = Subscription.first
+    book1.subscriptions << subscription1
+    assert_equal [subscription1], post.subscriptions.to_a
+
+    post.author = authors(:bob)
+    book2 = Book.create!(name: "essays on nested has many through associations 2")
+    post.author.books << book2
+    subscription2 = Subscription.second
+    book2.subscriptions << subscription2
+    assert_equal [subscription2], post.subscriptions.to_a
+  end
+
   private
     def make_model(name)
       Class.new(ActiveRecord::Base) { define_singleton_method(:name) { name } }
diff --git a/activerecord/test/cases/associations/has_one_associations_test.rb b/activerecord/test/cases/associations/has_one_associations_test.rb
index 2a9ebd19ed..d7e898a1c0 100644
--- a/activerecord/test/cases/associations/has_one_associations_test.rb
+++ b/activerecord/test/cases/associations/has_one_associations_test.rb
@@ -30,7 +30,8 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     ActiveRecord::SQLCounter.clear_log
     companies(:first_firm).account
   ensure
-    assert ActiveRecord::SQLCounter.log_all.all? { |sql| /order by/i !~ sql }, "ORDER BY was used in the query"
+    log_all = ActiveRecord::SQLCounter.log_all
+    assert log_all.all? { |sql| /order by/i !~ sql }, "ORDER BY was used in the query: #{log_all}"
   end
 
   def test_has_one_cache_nils
@@ -113,8 +114,8 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     developer = Developer.create!(name: "Someone")
     ship = Ship.create!(name: "Planet Caravan", developer: developer)
     ship.destroy
-    assert !ship.persisted?
-    assert !developer.persisted?
+    assert_not_predicate ship, :persisted?
+    assert_not_predicate developer, :persisted?
   end
 
   def test_natural_assignment_to_nil_after_destroy
@@ -185,7 +186,7 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
 
     assert_raise(ActiveRecord::DeleteRestrictionError) { firm.destroy }
     assert RestrictedWithExceptionFirm.exists?(name: "restrict")
-    assert firm.account.present?
+    assert_predicate firm.account, :present?
   end
 
   def test_restrict_with_error
@@ -196,10 +197,10 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
 
     firm.destroy
 
-    assert !firm.errors.empty?
+    assert_not_empty firm.errors
     assert_equal "Cannot delete record because a dependent account exists", firm.errors[:base].first
     assert RestrictedWithErrorFirm.exists?(name: "restrict")
-    assert firm.account.present?
+    assert_predicate firm.account, :present?
   end
 
   def test_restrict_with_error_with_locale
@@ -212,10 +213,10 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
 
     firm.destroy
 
-    assert !firm.errors.empty?
+    assert_not_empty firm.errors
     assert_equal "Cannot delete record because a dependent firm account exists", firm.errors[:base].first
     assert RestrictedWithErrorFirm.exists?(name: "restrict")
-    assert firm.account.present?
+    assert_predicate firm.account, :present?
   ensure
     I18n.backend.reload!
   end
@@ -376,7 +377,7 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
   def test_assignment_before_child_saved
     firm = Firm.find(1)
     firm.account = a = Account.new("credit_limit" => 1000)
-    assert a.persisted?
+    assert_predicate a, :persisted?
     assert_equal a, firm.account
     assert_equal a, firm.account
     firm.association(:account).reload
@@ -394,7 +395,7 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
 
   def test_cant_save_readonly_association
     assert_raise(ActiveRecord::ReadOnlyRecord) { companies(:first_firm).readonly_account.save!  }
-    assert companies(:first_firm).readonly_account.readonly?
+    assert_predicate companies(:first_firm).readonly_account, :readonly?
   end
 
   def test_has_one_proxy_should_not_respond_to_private_methods
@@ -432,7 +433,7 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
 
   def test_create_respects_hash_condition
     account = companies(:first_firm).create_account_limit_500_with_hash_conditions
-    assert       account.persisted?
+    assert_predicate account, :persisted?
     assert_equal 500, account.credit_limit
   end
 
@@ -449,9 +450,9 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     new_ship = pirate.create_ship
     assert_not_equal ships(:black_pearl), new_ship
     assert_equal new_ship, pirate.ship
-    assert new_ship.new_record?
+    assert_predicate new_ship, :new_record?
     assert_nil orig_ship.pirate_id
-    assert !orig_ship.changed? # check it was saved
+    assert_not orig_ship.changed? # check it was saved
   end
 
   def test_creation_failure_with_dependent_option
@@ -459,8 +460,8 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     orig_ship = pirate.dependent_ship
 
     new_ship = pirate.create_dependent_ship
-    assert new_ship.new_record?
-    assert orig_ship.destroyed?
+    assert_predicate new_ship, :new_record?
+    assert_predicate orig_ship, :destroyed?
   end
 
   def test_creation_failure_due_to_new_record_should_raise_error
@@ -480,7 +481,7 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     pirate = pirates(:blackbeard)
     pirate.ship.name = nil
 
-    assert !pirate.ship.valid?
+    assert_not_predicate pirate.ship, :valid?
     error = assert_raise(ActiveRecord::RecordNotSaved) do
       pirate.ship = ships(:interceptor)
     end
@@ -587,7 +588,7 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     ship.save!
 
     ship.name = "new name"
-    assert ship.changed?
+    assert_predicate ship, :changed?
     assert_queries(1) do
       # One query for updating name, not triggering query for updating pirate_id
       pirate.ship = ship
@@ -677,7 +678,7 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     book = SpecialBook.create!(status: "published")
     author.book = book
 
-    refute_equal 0, SpecialAuthor.joins(:book).where(books: { status: "published" }).count
+    assert_not_equal 0, SpecialAuthor.joins(:book).where(books: { status: "published" }).count
   end
 
   def test_association_enum_works_properly_with_nested_join
@@ -724,4 +725,28 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
 
     assert_not DestroyByParentBook.exists?(book.id)
   end
+
+  class UndestroyableBook < ActiveRecord::Base
+    self.table_name = "books"
+    belongs_to :author, class_name: "DestroyableAuthor"
+    before_destroy :dont
+
+    def dont
+      throw(:abort)
+    end
+  end
+
+  class DestroyableAuthor < ActiveRecord::Base
+    self.table_name = "authors"
+    has_one :book, class_name: "UndestroyableBook", foreign_key: "author_id", dependent: :destroy
+  end
+
+  def test_dependency_should_halt_parent_destruction
+    author = DestroyableAuthor.create!(name: "Test")
+    UndestroyableBook.create!(author: author)
+
+    assert_no_difference ["DestroyableAuthor.count", "UndestroyableBook.count"] do
+      assert_not author.destroy
+    end
+  end
 end
diff --git a/activerecord/test/cases/associations/has_one_through_associations_test.rb b/activerecord/test/cases/associations/has_one_through_associations_test.rb
index fe24c465b2..0309663943 100644
--- a/activerecord/test/cases/associations/has_one_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_one_through_associations_test.rb
@@ -42,6 +42,18 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
     assert_not_nil new_member.club
   end
 
+  def test_creating_association_builds_through_record
+    new_member = Member.create(name: "Chris")
+    new_club = new_member.association(:club).build
+    assert new_member.current_membership
+    assert_equal new_club, new_member.club
+    assert_predicate new_club, :new_record?
+    assert_predicate new_member.current_membership, :new_record?
+    assert new_member.save
+    assert_predicate new_club, :persisted?
+    assert_predicate new_member.current_membership, :persisted?
+  end
+
   def test_creating_association_builds_through_record_for_new
     new_member = Member.new(name: "Jane")
     new_member.club = clubs(:moustache_club)
@@ -52,6 +64,24 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
     assert_equal clubs(:moustache_club), new_member.club
   end
 
+  def test_building_multiple_associations_builds_through_record
+    member_type = MemberType.create!
+    member = Member.create!
+    member_detail_with_one_association = MemberDetail.new(member_type: member_type)
+    assert_predicate member_detail_with_one_association.member, :new_record?
+    member_detail_with_two_associations = MemberDetail.new(member_type: member_type, admittable: member)
+    assert_predicate member_detail_with_two_associations.member, :new_record?
+  end
+
+  def test_creating_multiple_associations_creates_through_record
+    member_type = MemberType.create!
+    member = Member.create!
+    member_detail_with_one_association = MemberDetail.create!(member_type: member_type)
+    assert_not_predicate member_detail_with_one_association.member, :new_record?
+    member_detail_with_two_associations = MemberDetail.create!(member_type: member_type, admittable: member)
+    assert_not_predicate member_detail_with_two_associations.member, :new_record?
+  end
+
   def test_creating_association_sets_both_parent_ids_for_new
     member = Member.new(name: "Sean Griffin")
     club = Club.new(name: "Da Club")
@@ -100,7 +130,7 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
   end
 
   def test_has_one_through_eager_loading
-    members = assert_queries(3) do #base table, through table, clubs table
+    members = assert_queries(3) do # base table, through table, clubs table
       Member.all.merge!(includes: :club, where: ["name = ?", "Groucho Marx"]).to_a
     end
     assert_equal 1, members.size
@@ -108,7 +138,7 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
   end
 
   def test_has_one_through_eager_loading_through_polymorphic
-    members = assert_queries(3) do #base table, through table, clubs table
+    members = assert_queries(3) do # base table, through table, clubs table
       Member.all.merge!(includes: :sponsor_club, where: ["name = ?", "Groucho Marx"]).to_a
     end
     assert_equal 1, members.size
@@ -139,7 +169,7 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
 
   def test_has_one_through_nonpreload_eagerloading
     members = assert_queries(1) do
-      Member.all.merge!(includes: :club, where: ["members.name = ?", "Groucho Marx"], order: "clubs.name").to_a #force fallback
+      Member.all.merge!(includes: :club, where: ["members.name = ?", "Groucho Marx"], order: "clubs.name").to_a # force fallback
     end
     assert_equal 1, members.size
     assert_not_nil assert_no_queries { members[0].club }
@@ -147,7 +177,7 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
 
   def test_has_one_through_nonpreload_eager_loading_through_polymorphic
     members = assert_queries(1) do
-      Member.all.merge!(includes: :sponsor_club, where: ["members.name = ?", "Groucho Marx"], order: "clubs.name").to_a #force fallback
+      Member.all.merge!(includes: :sponsor_club, where: ["members.name = ?", "Groucho Marx"], order: "clubs.name").to_a # force fallback
     end
     assert_equal 1, members.size
     assert_not_nil assert_no_queries { members[0].sponsor_club }
@@ -156,7 +186,7 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
   def test_has_one_through_nonpreload_eager_loading_through_polymorphic_with_more_than_one_through_record
     Sponsor.new(sponsor_club: clubs(:crazy_club), sponsorable: members(:groucho)).save!
     members = assert_queries(1) do
-      Member.all.merge!(includes: :sponsor_club, where: ["members.name = ?", "Groucho Marx"], order: "clubs.name DESC").to_a #force fallback
+      Member.all.merge!(includes: :sponsor_club, where: ["members.name = ?", "Groucho Marx"], order: "clubs.name DESC").to_a # force fallback
     end
     assert_equal 1, members.size
     assert_not_nil assert_no_queries { members[0].sponsor_club }
@@ -229,7 +259,7 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
       MemberDetail.all.merge!(includes: :member_type).to_a
     end
     @new_detail = @member_details[0]
-    assert @new_detail.send(:association, :member_type).loaded?
+    assert_predicate @new_detail.send(:association, :member_type), :loaded?
     assert_no_queries { @new_detail.member_type }
   end
 
@@ -317,12 +347,12 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
     minivan.dashboard
     proxy = minivan.send(:association_instance_get, :dashboard)
 
-    assert !proxy.stale_target?
+    assert_not_predicate proxy, :stale_target?
     assert_equal dashboards(:cool_first), minivan.dashboard
 
     minivan.speedometer_id = speedometers(:second).id
 
-    assert proxy.stale_target?
+    assert_predicate proxy, :stale_target?
     assert_equal dashboards(:second), minivan.dashboard
   end
 
@@ -334,7 +364,7 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
 
     minivan.speedometer_id = speedometers(:second).id
 
-    assert proxy.stale_target?
+    assert_predicate proxy, :stale_target?
     assert_equal dashboards(:second), minivan.dashboard
   end
 
diff --git a/activerecord/test/cases/associations/inner_join_association_test.rb b/activerecord/test/cases/associations/inner_join_association_test.rb
index 23be344419..c33dcdee61 100644
--- a/activerecord/test/cases/associations/inner_join_association_test.rb
+++ b/activerecord/test/cases/associations/inner_join_association_test.rb
@@ -27,6 +27,24 @@ class InnerJoinAssociationTest < ActiveRecord::TestCase
     end
   end
 
+  def test_construct_finder_sql_does_not_table_name_collide_on_duplicate_associations_with_left_outer_joins
+    sql = Person.joins(agents: :agents).left_outer_joins(agents: :agents).to_sql
+    assert_match(/agents_people_4/i, sql)
+  end
+
+  def test_construct_finder_sql_does_not_table_name_collide_with_string_joins
+    sql = Person.joins(:agents).joins("JOIN people agents_people ON agents_people.primary_contact_id = people.id").to_sql
+    assert_match(/agents_people_2/i, sql)
+  end
+
+  def test_construct_finder_sql_does_not_table_name_collide_with_aliased_joins
+    people = Person.arel_table
+    agents = people.alias("agents_people")
+    constraint = agents[:primary_contact_id].eq(people[:id])
+    sql = Person.joins(:agents).joins(agents.create_join(agents, agents.create_on(constraint))).to_sql
+    assert_match(/agents_people_2/i, sql)
+  end
+
   def test_construct_finder_sql_ignores_empty_joins_hash
     sql = Author.joins({}).to_sql
     assert_no_match(/JOIN/i, sql)
@@ -61,19 +79,19 @@ class InnerJoinAssociationTest < ActiveRecord::TestCase
 
   def test_find_with_implicit_inner_joins_honors_readonly_with_select
     authors = Author.joins(:posts).select("authors.*").to_a
-    assert !authors.empty?, "expected authors to be non-empty"
+    assert_not authors.empty?, "expected authors to be non-empty"
     assert authors.all? { |a| !a.readonly? }, "expected no authors to be readonly"
   end
 
   def test_find_with_implicit_inner_joins_honors_readonly_false
     authors = Author.joins(:posts).readonly(false).to_a
-    assert !authors.empty?, "expected authors to be non-empty"
+    assert_not authors.empty?, "expected authors to be non-empty"
     assert authors.all? { |a| !a.readonly? }, "expected no authors to be readonly"
   end
 
   def test_find_with_implicit_inner_joins_does_not_set_associations
     authors = Author.joins(:posts).select("authors.*").to_a
-    assert !authors.empty?, "expected authors to be non-empty"
+    assert_not authors.empty?, "expected authors to be non-empty"
     assert authors.all? { |a| !a.instance_variable_defined?(:@posts) }, "expected no authors to have the @posts association loaded"
   end
 
@@ -97,19 +115,19 @@ class InnerJoinAssociationTest < ActiveRecord::TestCase
     scope = Post.joins(:special_comments).where(id: posts(:sti_comments).id)
 
     # The join should match SpecialComment and its subclasses only
-    assert scope.where("comments.type" => "Comment").empty?
-    assert !scope.where("comments.type" => "SpecialComment").empty?
-    assert !scope.where("comments.type" => "SubSpecialComment").empty?
+    assert_empty scope.where("comments.type" => "Comment")
+    assert_not_empty scope.where("comments.type" => "SpecialComment")
+    assert_not_empty scope.where("comments.type" => "SubSpecialComment")
   end
 
   def test_find_with_conditions_on_reflection
-    assert !posts(:welcome).comments.empty?
+    assert_not_empty posts(:welcome).comments
     assert Post.joins(:nonexistent_comments).where(id: posts(:welcome).id).empty? # [sic!]
   end
 
   def test_find_with_conditions_on_through_reflection
-    assert !posts(:welcome).tags.empty?
-    assert Post.joins(:misc_tags).where(id: posts(:welcome).id).empty?
+    assert_not_empty posts(:welcome).tags
+    assert_empty Post.joins(:misc_tags).where(id: posts(:welcome).id)
   end
 
   test "the default scope of the target is applied when joining associations" do
diff --git a/activerecord/test/cases/associations/inverse_associations_test.rb b/activerecord/test/cases/associations/inverse_associations_test.rb
index e13cf93dcf..da3a42e2b5 100644
--- a/activerecord/test/cases/associations/inverse_associations_test.rb
+++ b/activerecord/test/cases/associations/inverse_associations_test.rb
@@ -119,17 +119,17 @@ class AutomaticInverseFindingTests < ActiveRecord::TestCase
   def test_polymorphic_and_has_many_through_relationships_should_not_have_inverses
     sponsor_reflection = Sponsor.reflect_on_association(:sponsorable)
 
-    assert !sponsor_reflection.has_inverse?, "A polymorphic association should not find an inverse automatically"
+    assert_not sponsor_reflection.has_inverse?, "A polymorphic association should not find an inverse automatically"
 
     club_reflection = Club.reflect_on_association(:members)
 
-    assert !club_reflection.has_inverse?, "A has_many_through association should not find an inverse automatically"
+    assert_not club_reflection.has_inverse?, "A has_many_through association should not find an inverse automatically"
   end
 
   def test_polymorphic_has_one_should_find_inverse_automatically
     man_reflection = Man.reflect_on_association(:polymorphic_face_without_inverse)
 
-    assert man_reflection.has_inverse?
+    assert_predicate man_reflection, :has_inverse?
   end
 end
 
@@ -150,22 +150,22 @@ class InverseAssociationTests < ActiveRecord::TestCase
 
   def test_should_be_able_to_ask_a_reflection_if_it_has_an_inverse
     has_one_with_inverse_ref = Man.reflect_on_association(:face)
-    assert has_one_with_inverse_ref.has_inverse?
+    assert_predicate has_one_with_inverse_ref, :has_inverse?
 
     has_many_with_inverse_ref = Man.reflect_on_association(:interests)
-    assert has_many_with_inverse_ref.has_inverse?
+    assert_predicate has_many_with_inverse_ref, :has_inverse?
 
     belongs_to_with_inverse_ref = Face.reflect_on_association(:man)
-    assert belongs_to_with_inverse_ref.has_inverse?
+    assert_predicate belongs_to_with_inverse_ref, :has_inverse?
 
     has_one_without_inverse_ref = Club.reflect_on_association(:sponsor)
-    assert !has_one_without_inverse_ref.has_inverse?
+    assert_not_predicate has_one_without_inverse_ref, :has_inverse?
 
     has_many_without_inverse_ref = Club.reflect_on_association(:memberships)
-    assert !has_many_without_inverse_ref.has_inverse?
+    assert_not_predicate has_many_without_inverse_ref, :has_inverse?
 
     belongs_to_without_inverse_ref = Sponsor.reflect_on_association(:sponsor_club)
-    assert !belongs_to_without_inverse_ref.has_inverse?
+    assert_not_predicate belongs_to_without_inverse_ref, :has_inverse?
   end
 
   def test_inverse_of_method_should_supply_the_actual_reflection_instance_it_is_the_inverse_of
@@ -190,6 +190,16 @@ class InverseAssociationTests < ActiveRecord::TestCase
     assert_nil belongs_to_ref.inverse_of
   end
 
+  def test_polymorphic_associations_dont_attempt_to_find_inverse_of
+    belongs_to_ref = Sponsor.reflect_on_association(:sponsor)
+    assert_raise(ArgumentError) { belongs_to_ref.klass }
+    assert_nil belongs_to_ref.inverse_of
+
+    belongs_to_ref = Face.reflect_on_association(:human)
+    assert_raise(ArgumentError) { belongs_to_ref.klass }
+    assert_nil belongs_to_ref.inverse_of
+  end
+
   def test_this_inverse_stuff
     firm = Firm.create!(name: "Adequate Holdings")
     Project.create!(name: "Project 1", firm: firm)
@@ -464,7 +474,7 @@ class InverseHasManyTests < ActiveRecord::TestCase
     interest = Interest.create!(man: man)
 
     man.interests.find(interest.id)
-    assert_not man.interests.loaded?
+    assert_not_predicate man.interests, :loaded?
   end
 
   def test_raise_record_not_found_error_when_invalid_ids_are_passed
@@ -484,7 +494,10 @@ class InverseHasManyTests < ActiveRecord::TestCase
   def test_raise_record_not_found_error_when_no_ids_are_passed
     man = Man.create!
 
-    assert_raise(ActiveRecord::RecordNotFound) { man.interests.find() }
+    exception = assert_raise(ActiveRecord::RecordNotFound) { man.interests.load.find() }
+
+    assert_equal exception.model, "Interest"
+    assert_equal exception.primary_key, "id"
   end
 
   def test_trying_to_use_inverses_that_dont_exist_should_raise_an_error
@@ -501,16 +514,16 @@ class InverseHasManyTests < ActiveRecord::TestCase
     i.man.name = "Charles"
     assert_equal i.man.name, man.name
 
-    assert !man.persisted?
+    assert_not_predicate man, :persisted?
   end
 
   def test_inverse_instance_should_be_set_before_find_callbacks_are_run
     reset_callbacks(Interest, :find) do
       Interest.after_find { raise unless association(:man).loaded? && man.present? }
 
-      assert Man.first.interests.reload.any?
-      assert Man.includes(:interests).first.interests.any?
-      assert Man.joins(:interests).includes(:interests).first.interests.any?
+      assert_predicate Man.first.interests.reload, :any?
+      assert_predicate Man.includes(:interests).first.interests, :any?
+      assert_predicate Man.joins(:interests).includes(:interests).first.interests, :any?
     end
   end
 
@@ -518,9 +531,9 @@ class InverseHasManyTests < ActiveRecord::TestCase
     reset_callbacks(Interest, :initialize) do
       Interest.after_initialize { raise unless association(:man).loaded? && man.present? }
 
-      assert Man.first.interests.reload.any?
-      assert Man.includes(:interests).first.interests.any?
-      assert Man.joins(:interests).includes(:interests).first.interests.any?
+      assert_predicate Man.first.interests.reload, :any?
+      assert_predicate Man.includes(:interests).first.interests, :any?
+      assert_predicate Man.joins(:interests).includes(:interests).first.interests, :any?
     end
   end
 
@@ -672,6 +685,16 @@ class InversePolymorphicBelongsToTests < ActiveRecord::TestCase
     assert_equal old_inversed_man.object_id, new_inversed_man.object_id
   end
 
+  def test_inversed_instance_should_not_be_reloaded_after_stale_state_changed_with_validation
+    face = Face.new man: Man.new
+
+    old_inversed_man = face.man
+    face.save!
+    new_inversed_man = face.man
+
+    assert_equal old_inversed_man.object_id, new_inversed_man.object_id
+  end
+
   def test_should_not_try_to_set_inverse_instances_when_the_inverse_is_a_has_many
     i = interests(:llama_wrangling)
     m = i.polymorphic_man
diff --git a/activerecord/test/cases/associations/join_model_test.rb b/activerecord/test/cases/associations/join_model_test.rb
index 3abdcf3564..9d1c73c33b 100644
--- a/activerecord/test/cases/associations/join_model_test.rb
+++ b/activerecord/test/cases/associations/join_model_test.rb
@@ -44,11 +44,11 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
 
   def test_has_many_distinct_through_count
     author = authors(:mary)
-    assert !authors(:mary).unique_categorized_posts.loaded?
+    assert_not_predicate authors(:mary).unique_categorized_posts, :loaded?
     assert_queries(1) { assert_equal 1, author.unique_categorized_posts.count }
     assert_queries(1) { assert_equal 1, author.unique_categorized_posts.count(:title) }
     assert_queries(1) { assert_equal 0, author.unique_categorized_posts.where(title: nil).count(:title) }
-    assert !authors(:mary).unique_categorized_posts.loaded?
+    assert_not_predicate authors(:mary).unique_categorized_posts, :loaded?
   end
 
   def test_has_many_distinct_through_find
@@ -369,7 +369,7 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
     Tag.has_many :null_taggings, -> { none }, class_name: :Tagging
     Tag.has_many :null_tagged_posts, through: :null_taggings, source: "taggable", source_type: "Post"
     assert_equal [], tags(:general).null_tagged_posts
-    refute_equal [], tags(:general).tagged_posts
+    assert_not_equal [], tags(:general).tagged_posts
   end
 
   def test_eager_has_many_polymorphic_with_source_type
@@ -454,8 +454,8 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
 
   def test_has_many_through_uses_conditions_specified_on_the_has_many_association
     author = Author.first
-    assert author.comments.present?
-    assert author.nonexistent_comments.blank?
+    assert_predicate author.comments, :present?
+    assert_predicate author.nonexistent_comments, :blank?
   end
 
   def test_has_many_through_uses_correct_attributes
@@ -467,27 +467,27 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
     new_tag = Tag.new(name: "new")
 
     saved_post.tags << new_tag
-    assert new_tag.persisted? #consistent with habtm!
-    assert saved_post.persisted?
+    assert new_tag.persisted? # consistent with habtm!
+    assert_predicate saved_post, :persisted?
     assert_includes saved_post.tags, new_tag
 
-    assert new_tag.persisted?
+    assert_predicate new_tag, :persisted?
     assert_includes saved_post.reload.tags.reload, new_tag
 
     new_post = Post.new(title: "Association replacement works!", body: "You best believe it.")
     saved_tag = tags(:general)
 
     new_post.tags << saved_tag
-    assert !new_post.persisted?
-    assert saved_tag.persisted?
+    assert_not_predicate new_post, :persisted?
+    assert_predicate saved_tag, :persisted?
     assert_includes new_post.tags, saved_tag
 
     new_post.save!
-    assert new_post.persisted?
+    assert_predicate new_post, :persisted?
     assert_includes new_post.reload.tags.reload, saved_tag
 
-    assert !posts(:thinking).tags.build.persisted?
-    assert !posts(:thinking).tags.new.persisted?
+    assert_not_predicate posts(:thinking).tags.build, :persisted?
+    assert_not_predicate posts(:thinking).tags.new, :persisted?
   end
 
   def test_create_associate_when_adding_to_has_many_through
@@ -496,25 +496,25 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
     post_thinking = posts(:thinking)
     assert_nothing_raised { post_thinking.tags << push }
     assert_nil(wrong = post_thinking.tags.detect { |t| t.class != Tag },
-                message = "Expected a Tag in tags collection, got #{wrong.class}.")
+               "Expected a Tag in tags collection, got #{wrong.class}.")
     assert_nil(wrong = post_thinking.taggings.detect { |t| t.class != Tagging },
-                message = "Expected a Tagging in taggings collection, got #{wrong.class}.")
+               "Expected a Tagging in taggings collection, got #{wrong.class}.")
     assert_equal(count + 1, post_thinking.reload.tags.size)
     assert_equal(count + 1, post_thinking.tags.reload.size)
 
     assert_kind_of Tag, post_thinking.tags.create!(name: "foo")
     assert_nil(wrong = post_thinking.tags.detect { |t| t.class != Tag },
-                message = "Expected a Tag in tags collection, got #{wrong.class}.")
+               "Expected a Tag in tags collection, got #{wrong.class}.")
     assert_nil(wrong = post_thinking.taggings.detect { |t| t.class != Tagging },
-                message = "Expected a Tagging in taggings collection, got #{wrong.class}.")
+               "Expected a Tagging in taggings collection, got #{wrong.class}.")
     assert_equal(count + 2, post_thinking.reload.tags.size)
     assert_equal(count + 2, post_thinking.tags.reload.size)
 
     assert_nothing_raised { post_thinking.tags.concat(Tag.create!(name: "abc"), Tag.create!(name: "def")) }
     assert_nil(wrong = post_thinking.tags.detect { |t| t.class != Tag },
-                message = "Expected a Tag in tags collection, got #{wrong.class}.")
+               "Expected a Tag in tags collection, got #{wrong.class}.")
     assert_nil(wrong = post_thinking.taggings.detect { |t| t.class != Tagging },
-                message = "Expected a Tagging in taggings collection, got #{wrong.class}.")
+               "Expected a Tagging in taggings collection, got #{wrong.class}.")
     assert_equal(count + 4, post_thinking.reload.tags.size)
     assert_equal(count + 4, post_thinking.tags.reload.size)
 
@@ -529,14 +529,14 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
   def test_has_many_through_collection_size_doesnt_load_target_if_not_loaded
     author = authors(:david)
     assert_equal 10, author.comments.size
-    assert !author.comments.loaded?
+    assert_not_predicate author.comments, :loaded?
   end
 
   def test_has_many_through_collection_size_uses_counter_cache_if_it_exists
     c = categories(:general)
     c.categorizations_count = 100
     assert_equal 100, c.categorizations.size
-    assert !c.categorizations.loaded?
+    assert_not_predicate c.categorizations, :loaded?
   end
 
   def test_adding_junk_to_has_many_through_should_raise_type_mismatch
@@ -710,7 +710,7 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
     category = david.categories.first
 
     assert_no_queries do
-      assert david.categories.loaded?
+      assert_predicate david.categories, :loaded?
       assert_includes david.categories, category
     end
   end
@@ -720,19 +720,19 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
     category = david.categories.first
 
     david.reload
-    assert ! david.categories.loaded?
+    assert_not_predicate david.categories, :loaded?
     assert_queries(1) do
       assert_includes david.categories, category
     end
-    assert ! david.categories.loaded?
+    assert_not_predicate david.categories, :loaded?
   end
 
   def test_has_many_through_include_returns_false_for_non_matching_record_to_verify_scoping
     david = authors(:david)
     category = Category.create!(name: "Not Associated")
 
-    assert ! david.categories.loaded?
-    assert ! david.categories.include?(category)
+    assert_not_predicate david.categories, :loaded?
+    assert_not david.categories.include?(category)
   end
 
   def test_has_many_through_goes_through_all_sti_classes
diff --git a/activerecord/test/cases/associations/left_outer_join_association_test.rb b/activerecord/test/cases/associations/left_outer_join_association_test.rb
index c95d0425cd..0e54e8c1b0 100644
--- a/activerecord/test/cases/associations/left_outer_join_association_test.rb
+++ b/activerecord/test/cases/associations/left_outer_join_association_test.rb
@@ -5,6 +5,7 @@ require "models/post"
 require "models/comment"
 require "models/author"
 require "models/essay"
+require "models/category"
 require "models/categorization"
 require "models/person"
 
@@ -69,15 +70,15 @@ class LeftOuterJoinAssociationTest < ActiveRecord::TestCase
     scope = Post.left_outer_joins(:special_comments).where(id: posts(:sti_comments).id)
 
     # The join should match SpecialComment and its subclasses only
-    assert scope.where("comments.type" => "Comment").empty?
-    assert !scope.where("comments.type" => "SpecialComment").empty?
-    assert !scope.where("comments.type" => "SubSpecialComment").empty?
+    assert_empty scope.where("comments.type" => "Comment")
+    assert_not_empty scope.where("comments.type" => "SpecialComment")
+    assert_not_empty scope.where("comments.type" => "SubSpecialComment")
   end
 
   def test_does_not_override_select
     authors = Author.select("authors.name, #{%{(authors.author_address_id || ' ' || authors.author_address_extra_id) as addr_id}}").left_outer_joins(:posts)
-    assert authors.any?
-    assert authors.first.respond_to?(:addr_id)
+    assert_predicate authors, :any?
+    assert_respond_to authors.first, :addr_id
   end
 
   test "the default scope of the target is applied when joining associations" do
diff --git a/activerecord/test/cases/associations/nested_through_associations_test.rb b/activerecord/test/cases/associations/nested_through_associations_test.rb
index 3e37e512ca..03ed1c1d47 100644
--- a/activerecord/test/cases/associations/nested_through_associations_test.rb
+++ b/activerecord/test/cases/associations/nested_through_associations_test.rb
@@ -24,6 +24,11 @@ require "models/category"
 require "models/categorization"
 require "models/membership"
 require "models/essay"
+require "models/hotel"
+require "models/department"
+require "models/chef"
+require "models/cake_designer"
+require "models/drink_designer"
 
 class NestedThroughAssociationsTest < ActiveRecord::TestCase
   fixtures :authors, :author_addresses, :books, :posts, :subscriptions, :subscribers, :tags, :taggings,
@@ -73,7 +78,7 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
 
     # This ensures that the polymorphism of taggings is being observed correctly
     authors = Author.joins(:tags).where("taggings.taggable_type" => "FakeModel")
-    assert authors.empty?
+    assert_empty authors
   end
 
   # has_many through
@@ -172,7 +177,7 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
 
     members = Member.joins(:organization_member_details).
                      where("member_details.id" => 9)
-    assert members.empty?
+    assert_empty members
   end
 
   # has_many through
@@ -204,7 +209,7 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
 
     members = Member.joins(:organization_member_details_2).
                      where("member_details.id" => 9)
-    assert members.empty?
+    assert_empty members
   end
 
   # has_many through
@@ -420,9 +425,14 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
 
     # Check the polymorphism of taggings is being observed correctly (in both joins)
     authors = Author.joins(:similar_posts).where("taggings.taggable_type" => "FakeModel")
-    assert authors.empty?
+    assert_empty authors
     authors = Author.joins(:similar_posts).where("taggings_authors_join.taggable_type" => "FakeModel")
-    assert authors.empty?
+    assert_empty authors
+  end
+
+  def test_nested_has_many_through_with_scope_on_polymorphic_reflection
+    authors = Author.joins(:ordered_posts).where("posts.id" => posts(:misc_by_bob).id)
+    assert_equal [authors(:mary), authors(:bob)], authors.distinct.sort_by(&:id)
   end
 
   def test_has_many_through_with_foreign_key_option_on_through_reflection
@@ -446,9 +456,9 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
 
     # Ensure STI is respected in the join
     scope = Post.joins(:special_comments_ratings).where(id: posts(:sti_comments).id)
-    assert scope.where("comments.type" => "Comment").empty?
-    assert !scope.where("comments.type" => "SpecialComment").empty?
-    assert !scope.where("comments.type" => "SubSpecialComment").empty?
+    assert_empty scope.where("comments.type" => "Comment")
+    assert_not_empty scope.where("comments.type" => "SpecialComment")
+    assert_not_empty scope.where("comments.type" => "SubSpecialComment")
   end
 
   def test_has_many_through_with_sti_on_nested_through_reflection
@@ -456,8 +466,8 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
     assert_equal [taggings(:special_comment_rating)], taggings
 
     scope = Post.joins(:special_comments_ratings_taggings).where(id: posts(:sti_comments).id)
-    assert scope.where("comments.type" => "Comment").empty?
-    assert !scope.where("comments.type" => "SpecialComment").empty?
+    assert_empty scope.where("comments.type" => "Comment")
+    assert_not_empty scope.where("comments.type" => "SpecialComment")
   end
 
   def test_nested_has_many_through_writers_should_raise_error
@@ -507,7 +517,7 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
   end
 
   def test_nested_has_many_through_with_conditions_on_through_associations_preload
-    assert Author.where("tags.id" => 100).joins(:misc_post_first_blue_tags).empty?
+    assert_empty Author.where("tags.id" => 100).joins(:misc_post_first_blue_tags)
 
     authors = assert_queries(3) { Author.includes(:misc_post_first_blue_tags).to_a.sort_by(&:id) }
     blue = tags(:blue)
@@ -564,9 +574,40 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
     c = Categorization.new
     c.author = authors(:david)
     c.post_taggings.to_a
-    assert !c.post_taggings.empty?
+    assert_not_empty c.post_taggings
     c.save
-    assert !c.post_taggings.empty?
+    assert_not_empty c.post_taggings
+  end
+
+  def test_polymorphic_has_many_through_when_through_association_has_not_loaded
+    cake_designer = CakeDesigner.create!(chef: Chef.new)
+    drink_designer = DrinkDesigner.create!(chef: Chef.new)
+    department = Department.create!(chefs: [cake_designer.chef, drink_designer.chef])
+    Hotel.create!(departments: [department])
+    hotel = Hotel.includes(:cake_designers, :drink_designers).take
+
+    assert_equal [cake_designer], hotel.cake_designers
+    assert_equal [drink_designer], hotel.drink_designers
+  end
+
+  def test_polymorphic_has_many_through_when_through_association_has_already_loaded
+    cake_designer = CakeDesigner.create!(chef: Chef.new)
+    drink_designer = DrinkDesigner.create!(chef: Chef.new)
+    department = Department.create!(chefs: [cake_designer.chef, drink_designer.chef])
+    Hotel.create!(departments: [department])
+    hotel = Hotel.includes(:chefs, :cake_designers, :drink_designers).take
+
+    assert_equal [cake_designer], hotel.cake_designers
+    assert_equal [drink_designer], hotel.drink_designers
+  end
+
+  def test_polymorphic_has_many_through_joined_different_table_twice
+    cake_designer = CakeDesigner.create!(chef: Chef.new)
+    drink_designer = DrinkDesigner.create!(chef: Chef.new)
+    department = Department.create!(chefs: [cake_designer.chef, drink_designer.chef])
+    hotel = Hotel.create!(departments: [department])
+
+    assert_equal hotel, Hotel.joins(:cake_designers, :drink_designers).take
   end
 
   private
diff --git a/activerecord/test/cases/associations_test.rb b/activerecord/test/cases/associations_test.rb
index 9d1999bcb1..739eb02e0c 100644
--- a/activerecord/test/cases/associations_test.rb
+++ b/activerecord/test/cases/associations_test.rb
@@ -47,7 +47,7 @@ class AssociationsTest < ActiveRecord::TestCase
     ship = Ship.create!(name: "The good ship Dollypop")
     part = ship.parts.create!(name: "Mast")
     part.mark_for_destruction
-    assert ship.parts[0].marked_for_destruction?
+    assert_predicate ship.parts[0], :marked_for_destruction?
   end
 
   def test_loading_the_association_target_should_load_most_recent_attributes_for_child_records_marked_for_destruction
@@ -92,7 +92,7 @@ class AssociationsTest < ActiveRecord::TestCase
 
     firm.clients.reload
 
-    assert !firm.clients.empty?, "New firm should have reloaded client objects"
+    assert_not firm.clients.empty?, "New firm should have reloaded client objects"
     assert_equal 1, firm.clients.size, "New firm should have reloaded clients count"
   end
 
@@ -102,8 +102,8 @@ class AssociationsTest < ActiveRecord::TestCase
     has_many_reflections = [Tag.reflect_on_association(:taggings), Developer.reflect_on_association(:projects)]
     mixed_reflections = (belongs_to_reflections + has_many_reflections).uniq
     assert using_limitable_reflections.call(belongs_to_reflections), "Belong to associations are limitable"
-    assert !using_limitable_reflections.call(has_many_reflections), "All has many style associations are not limitable"
-    assert !using_limitable_reflections.call(mixed_reflections), "No collection associations (has many style) should pass"
+    assert_not using_limitable_reflections.call(has_many_reflections), "All has many style associations are not limitable"
+    assert_not using_limitable_reflections.call(mixed_reflections), "No collection associations (has many style) should pass"
   end
 
   def test_association_with_references
@@ -119,7 +119,7 @@ class AssociationProxyTest < ActiveRecord::TestCase
     david = authors(:david)
 
     david.posts << (post = Post.new(title: "New on Edge", body: "More cool stuff!"))
-    assert !david.posts.loaded?
+    assert_not_predicate david.posts, :loaded?
     assert_includes david.posts, post
   end
 
@@ -127,7 +127,7 @@ class AssociationProxyTest < ActiveRecord::TestCase
     david = authors(:david)
 
     david.categories << categories(:technology)
-    assert !david.categories.loaded?
+    assert_not_predicate david.categories, :loaded?
     assert_includes david.categories, categories(:technology)
   end
 
@@ -135,23 +135,23 @@ class AssociationProxyTest < ActiveRecord::TestCase
     david = authors(:david)
 
     david.posts << (post = Post.new(title: "New on Edge", body: "More cool stuff!"))
-    assert !david.posts.loaded?
+    assert_not_predicate david.posts, :loaded?
     david.save
-    assert !david.posts.loaded?
+    assert_not_predicate david.posts, :loaded?
     assert_includes david.posts, post
   end
 
   def test_push_does_not_lose_additions_to_new_record
     josh = Author.new(name: "Josh")
     josh.posts << Post.new(title: "New on Edge", body: "More cool stuff!")
-    assert josh.posts.loaded?
+    assert_predicate josh.posts, :loaded?
     assert_equal 1, josh.posts.size
   end
 
   def test_append_behaves_like_push
     josh = Author.new(name: "Josh")
     josh.posts.append Post.new(title: "New on Edge", body: "More cool stuff!")
-    assert josh.posts.loaded?
+    assert_predicate josh.posts, :loaded?
     assert_equal 1, josh.posts.size
   end
 
@@ -163,22 +163,22 @@ class AssociationProxyTest < ActiveRecord::TestCase
   def test_save_on_parent_does_not_load_target
     david = developers(:david)
 
-    assert !david.projects.loaded?
+    assert_not_predicate david.projects, :loaded?
     david.update_columns(created_at: Time.now)
-    assert !david.projects.loaded?
+    assert_not_predicate david.projects, :loaded?
   end
 
   def test_load_does_load_target
     david = developers(:david)
 
-    assert !david.projects.loaded?
+    assert_not_predicate david.projects, :loaded?
     david.projects.load
-    assert david.projects.loaded?
+    assert_predicate david.projects, :loaded?
   end
 
   def test_inspect_does_not_reload_a_not_yet_loaded_target
     andreas = Developer.new name: "Andreas", log: "new developer added"
-    assert !andreas.audit_logs.loaded?
+    assert_not_predicate andreas.audit_logs, :loaded?
     assert_match(/message: "new developer added"/, andreas.audit_logs.inspect)
   end
 
@@ -247,25 +247,25 @@ class AssociationProxyTest < ActiveRecord::TestCase
 
   test "first! works on loaded associations" do
     david = authors(:david)
-    assert_equal david.posts.first, david.posts.reload.first!
-    assert david.posts.loaded?
-    assert_no_queries { david.posts.first! }
+    assert_equal david.first_posts.first, david.first_posts.reload.first!
+    assert_predicate david.first_posts, :loaded?
+    assert_no_queries { david.first_posts.first! }
   end
 
   def test_pluck_uses_loaded_target
     david = authors(:david)
-    assert_equal david.posts.pluck(:title), david.posts.load.pluck(:title)
-    assert david.posts.loaded?
-    assert_no_queries { david.posts.pluck(:title) }
+    assert_equal david.first_posts.pluck(:title), david.first_posts.load.pluck(:title)
+    assert_predicate david.first_posts, :loaded?
+    assert_no_queries { david.first_posts.pluck(:title) }
   end
 
   def test_reset_unloads_target
     david = authors(:david)
     david.posts.reload
 
-    assert david.posts.loaded?
+    assert_predicate david.posts, :loaded?
     david.posts.reset
-    assert !david.posts.loaded?
+    assert_not_predicate david.posts, :loaded?
   end
 end
 
diff --git a/activerecord/test/cases/attribute_methods/read_test.rb b/activerecord/test/cases/attribute_methods/read_test.rb
index 0170a6e98d..54512068ee 100644
--- a/activerecord/test/cases/attribute_methods/read_test.rb
+++ b/activerecord/test/cases/attribute_methods/read_test.rb
@@ -12,7 +12,7 @@ module ActiveRecord
       def setup
         @klass = Class.new(Class.new { def self.initialize_generated_modules; end }) do
           def self.superclass; Base; end
-          def self.base_class; self; end
+          def self.base_class?; true; end
           def self.decorate_matching_attribute_types(*); end
 
           include ActiveRecord::DefineCallbacks
diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index 0ea8ef5cea..434d32846c 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -63,8 +63,8 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     t.author_name = ""
     assert t.attribute_present?("title")
     assert t.attribute_present?("written_on")
-    assert !t.attribute_present?("content")
-    assert !t.attribute_present?("author_name")
+    assert_not t.attribute_present?("content")
+    assert_not t.attribute_present?("author_name")
   end
 
   test "attribute_present with booleans" do
@@ -77,7 +77,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     assert b2.attribute_present?(:value)
 
     b3 = Boolean.new
-    assert !b3.attribute_present?(:value)
+    assert_not b3.attribute_present?(:value)
 
     b4 = Boolean.new
     b4.value = false
@@ -99,8 +99,8 @@ class AttributeMethodsTest < ActiveRecord::TestCase
   end
 
   test "boolean attributes" do
-    assert !Topic.find(1).approved?
-    assert Topic.find(2).approved?
+    assert_not_predicate Topic.find(1), :approved?
+    assert_predicate Topic.find(2), :approved?
   end
 
   test "set attributes" do
@@ -142,16 +142,16 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     assert_respond_to topic, :title=
     assert_respond_to topic, "author_name"
     assert_respond_to topic, "attribute_names"
-    assert !topic.respond_to?("nothingness")
-    assert !topic.respond_to?(:nothingness)
+    assert_not_respond_to topic, "nothingness"
+    assert_not_respond_to topic, :nothingness
   end
 
   test "respond_to? with a custom primary key" do
     keyboard = Keyboard.create
     assert_not_nil keyboard.key_number
     assert_equal keyboard.key_number, keyboard.id
-    assert keyboard.respond_to?("key_number")
-    assert keyboard.respond_to?("id")
+    assert_respond_to keyboard, "key_number"
+    assert_respond_to keyboard, "id"
   end
 
   test "id_before_type_cast with a custom primary key" do
@@ -170,8 +170,8 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     end
 
     topic = klass.allocate
-    assert !topic.respond_to?("nothingness")
-    assert !topic.respond_to?(:nothingness)
+    assert_not_respond_to topic, "nothingness"
+    assert_not_respond_to topic, :nothingness
     assert_respond_to topic, "title"
     assert_respond_to topic, :title
   end
@@ -200,12 +200,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
   if current_adapter?(:Mysql2Adapter)
     test "read attributes_before_type_cast on a boolean" do
       bool = Boolean.create!("value" => false)
-      if RUBY_PLATFORM.include?("java")
-        # JRuby will return the value before typecast as string.
-        assert_equal "0", bool.reload.attributes_before_type_cast["value"]
-      else
-        assert_equal 0, bool.reload.attributes_before_type_cast["value"]
-      end
+      assert_equal 0, bool.reload.attributes_before_type_cast["value"]
     end
   end
 
@@ -359,9 +354,9 @@ class AttributeMethodsTest < ActiveRecord::TestCase
   test "read_attribute when false" do
     topic = topics(:first)
     topic.approved = false
-    assert !topic.approved?, "approved should be false"
+    assert_not topic.approved?, "approved should be false"
     topic.approved = "false"
-    assert !topic.approved?, "approved should be false"
+    assert_not topic.approved?, "approved should be false"
   end
 
   test "read_attribute when true" do
@@ -375,10 +370,10 @@ class AttributeMethodsTest < ActiveRecord::TestCase
   test "boolean attributes writing and reading" do
     topic = Topic.new
     topic.approved = "false"
-    assert !topic.approved?, "approved should be false"
+    assert_not topic.approved?, "approved should be false"
 
     topic.approved = "false"
-    assert !topic.approved?, "approved should be false"
+    assert_not topic.approved?, "approved should be false"
 
     topic.approved = "true"
     assert topic.approved?, "approved should be true"
@@ -462,30 +457,30 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     SQL
 
     assert_equal "Firm", object.string_value
-    assert object.string_value?
+    assert_predicate object, :string_value?
 
     object.string_value = "  "
-    assert !object.string_value?
+    assert_not_predicate object, :string_value?
 
     assert_equal 1, object.int_value.to_i
-    assert object.int_value?
+    assert_predicate object, :int_value?
 
     object.int_value = "0"
-    assert !object.int_value?
+    assert_not_predicate object, :int_value?
   end
 
   test "non-attribute read and write" do
     topic = Topic.new
-    assert !topic.respond_to?("mumbo")
+    assert_not_respond_to topic, "mumbo"
     assert_raise(NoMethodError) { topic.mumbo }
     assert_raise(NoMethodError) { topic.mumbo = 5 }
   end
 
   test "undeclared attribute method does not affect respond_to? and method_missing" do
     topic = @target.new(title: "Budget")
-    assert topic.respond_to?("title")
+    assert_respond_to topic, "title"
     assert_equal "Budget", topic.title
-    assert !topic.respond_to?("title_hello_world")
+    assert_not_respond_to topic, "title_hello_world"
     assert_raise(NoMethodError) { topic.title_hello_world }
   end
 
@@ -496,7 +491,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
       @target.attribute_method_prefix prefix
 
       meth = "#{prefix}title"
-      assert topic.respond_to?(meth)
+      assert_respond_to topic, meth
       assert_equal ["title"], topic.send(meth)
       assert_equal ["title", "a"], topic.send(meth, "a")
       assert_equal ["title", 1, 2, 3], topic.send(meth, 1, 2, 3)
@@ -510,7 +505,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
       topic = @target.new(title: "Budget")
 
       meth = "title#{suffix}"
-      assert topic.respond_to?(meth)
+      assert_respond_to topic, meth
       assert_equal ["title"], topic.send(meth)
       assert_equal ["title", "a"], topic.send(meth, "a")
       assert_equal ["title", 1, 2, 3], topic.send(meth, 1, 2, 3)
@@ -524,7 +519,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
       topic = @target.new(title: "Budget")
 
       meth = "#{prefix}title#{suffix}"
-      assert topic.respond_to?(meth)
+      assert_respond_to topic, meth
       assert_equal ["title"], topic.send(meth)
       assert_equal ["title", "a"], topic.send(meth, "a")
       assert_equal ["title", 1, 2, 3], topic.send(meth, 1, 2, 3)
@@ -546,7 +541,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     else
       topic = Topic.all.merge!(select: "topics.*, 1=2 as is_test").first
     end
-    assert !topic.is_test?
+    assert_not_predicate topic, :is_test?
   end
 
   test "typecast attribute from select to true" do
@@ -557,7 +552,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     else
       topic = Topic.all.merge!(select: "topics.*, 2=2 as is_test").first
     end
-    assert topic.is_test?
+    assert_predicate topic, :is_test?
   end
 
   test "raises ActiveRecord::DangerousAttributeError when defining an AR method in a model" do
@@ -741,6 +736,16 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     end
   end
 
+  test "setting invalid string to a zone-aware time attribute" do
+    in_time_zone "Pacific Time (US & Canada)" do
+      record = @target.new
+      time_string = "ABC"
+
+      record.bonus_time = time_string
+      assert_nil record.bonus_time
+    end
+  end
+
   test "removing time zone-aware types" do
     with_time_zone_aware_types(:datetime) do
       in_time_zone "Pacific Time (US & Canada)" do
@@ -748,7 +753,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
         expected_time = Time.utc(2000, 01, 01, 10)
 
         assert_equal expected_time, record.bonus_time
-        assert record.bonus_time.utc?
+        assert_predicate record.bonus_time, :utc?
       end
     end
   end
@@ -772,7 +777,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     privatize("title")
 
     topic = @target.new(title: "The pros and cons of programming naked.")
-    assert !topic.respond_to?(:title)
+    assert_not_respond_to topic, :title
     exception = assert_raise(NoMethodError) { topic.title }
     assert_includes exception.message, "private method"
     assert_equal "I'm private", topic.send(:title)
@@ -782,7 +787,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     privatize("title=(value)")
 
     topic = @target.new
-    assert !topic.respond_to?(:title=)
+    assert_not_respond_to topic, :title=
     exception = assert_raise(NoMethodError) { topic.title = "Pants" }
     assert_includes exception.message, "private method"
     topic.send(:title=, "Very large pants")
@@ -792,7 +797,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     privatize("title?")
 
     topic = @target.new(title: "Isaac Newton's pants")
-    assert !topic.respond_to?(:title?)
+    assert_not_respond_to topic, :title?
     exception = assert_raise(NoMethodError) { topic.title? }
     assert_includes exception.message, "private method"
     assert topic.send(:title?)
@@ -832,7 +837,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
       self.table_name = "computers"
     end
 
-    assert !klass.instance_method_already_implemented?(:system)
+    assert_not klass.instance_method_already_implemented?(:system)
     computer = klass.new
     assert_nil computer.system
   end
@@ -846,8 +851,8 @@ class AttributeMethodsTest < ActiveRecord::TestCase
       self.table_name = "computers"
     end
 
-    assert !klass.instance_method_already_implemented?(:system)
-    assert !subklass.instance_method_already_implemented?(:system)
+    assert_not klass.instance_method_already_implemented?(:system)
+    assert_not subklass.instance_method_already_implemented?(:system)
     computer = subklass.new
     assert_nil computer.system
   end
@@ -984,9 +989,9 @@ class AttributeMethodsTest < ActiveRecord::TestCase
   test "came_from_user?" do
     model = @target.first
 
-    assert_not model.id_came_from_user?
+    assert_not_predicate model, :id_came_from_user?
     model.id = "omg"
-    assert model.id_came_from_user?
+    assert_predicate model, :id_came_from_user?
   end
 
   test "accessed_fields" do
@@ -999,6 +1004,11 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     assert_equal ["title"], model.accessed_fields
   end
 
+  test "generated attribute methods ancestors have correct class" do
+    mod = Topic.send(:generated_attribute_methods)
+    assert_match %r(GeneratedAttributeMethods), mod.inspect
+  end
+
   private
 
     def new_topic_like_ar_class(&block)
@@ -1019,14 +1029,6 @@ class AttributeMethodsTest < ActiveRecord::TestCase
       ActiveRecord::Base.time_zone_aware_types = old_types
     end
 
-    def cached_columns
-      Topic.columns.map(&:name)
-    end
-
-    def time_related_columns_on_topic
-      Topic.columns.select { |c| [:time, :date, :datetime, :timestamp].include?(c.type) }
-    end
-
     def privatize(method_signature)
       @target.class_eval(<<-private_method, __FILE__, __LINE__ + 1)
         private
diff --git a/activerecord/test/cases/attributes_test.rb b/activerecord/test/cases/attributes_test.rb
index 29a25b4461..3bc56694be 100644
--- a/activerecord/test/cases/attributes_test.rb
+++ b/activerecord/test/cases/attributes_test.rb
@@ -59,7 +59,7 @@ module ActiveRecord
     test "nonexistent attribute" do
       data = OverloadedType.new(non_existent_decimal: 1)
 
-      assert_equal BigDecimal.new(1), data.non_existent_decimal
+      assert_equal BigDecimal(1), data.non_existent_decimal
       assert_raise ActiveRecord::UnknownAttributeError do
         UnoverloadedType.new(non_existent_decimal: 1)
       end
@@ -108,12 +108,14 @@ module ActiveRecord
 
       assert_equal 6, klass.attribute_types.length
       assert_equal 6, klass.column_defaults.length
+      assert_equal 6, klass.attribute_names.length
       assert_not klass.attribute_types.include?("wibble")
 
       klass.attribute :wibble, Type::Value.new
 
       assert_equal 7, klass.attribute_types.length
       assert_equal 7, klass.column_defaults.length
+      assert_equal 7, klass.attribute_names.length
       assert_includes klass.attribute_types, "wibble"
     end
 
@@ -209,7 +211,7 @@ module ActiveRecord
     end
 
     test "attributes not backed by database columns are not dirty when unchanged" do
-      refute OverloadedType.new.non_existent_decimal_changed?
+      assert_not_predicate OverloadedType.new, :non_existent_decimal_changed?
     end
 
     test "attributes not backed by database columns are always initialized" do
@@ -243,13 +245,13 @@ module ActiveRecord
 
       model.foo << "asdf"
       assert_equal "lolasdf", model.foo
-      assert model.foo_changed?
+      assert_predicate model, :foo_changed?
 
       model.reload
       assert_equal "lol", model.foo
 
       model.foo = "lol"
-      refute model.changed?
+      assert_not_predicate model, :changed?
     end
 
     test "attributes not backed by database columns appear in inspect" do
diff --git a/activerecord/test/cases/autosave_association_test.rb b/activerecord/test/cases/autosave_association_test.rb
index da5e830ebc..7355f4cd62 100644
--- a/activerecord/test/cases/autosave_association_test.rb
+++ b/activerecord/test/cases/autosave_association_test.rb
@@ -5,6 +5,7 @@ require "models/bird"
 require "models/post"
 require "models/comment"
 require "models/company"
+require "models/contract"
 require "models/customer"
 require "models/developer"
 require "models/computer"
@@ -12,9 +13,7 @@ require "models/invoice"
 require "models/line_item"
 require "models/order"
 require "models/parrot"
-require "models/person"
 require "models/pirate"
-require "models/reader"
 require "models/ship"
 require "models/ship_part"
 require "models/tag"
@@ -51,8 +50,8 @@ class TestAutosaveAssociationsInGeneral < ActiveRecord::TestCase
     }
 
     u = person.create!(first_name: "cool")
-    u.update_attributes!(first_name: "nah") # still valid because validation only applies on 'create'
-    assert reference.create!(person: u).persisted?
+    u.update!(first_name: "nah") # still valid because validation only applies on 'create'
+    assert_predicate reference.create!(person: u), :persisted?
   end
 
   def test_should_not_add_the_same_callbacks_multiple_times_for_has_one
@@ -75,7 +74,7 @@ class TestAutosaveAssociationsInGeneral < ActiveRecord::TestCase
     ship = ShipWithoutNestedAttributes.new
     ship.prisoners.build
 
-    assert_not ship.valid?
+    assert_not_predicate ship, :valid?
     assert_equal 1, ship.errors[:name].length
   end
 
@@ -100,35 +99,35 @@ class TestDefaultAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCas
 
   def test_should_save_parent_but_not_invalid_child
     firm = Firm.new(name: "GlobalMegaCorp")
-    assert firm.valid?
+    assert_predicate firm, :valid?
 
     firm.build_account_using_primary_key
-    assert !firm.build_account_using_primary_key.valid?
+    assert_not_predicate firm.build_account_using_primary_key, :valid?
 
     assert firm.save
-    assert !firm.account_using_primary_key.persisted?
+    assert_not_predicate firm.account_using_primary_key, :persisted?
   end
 
   def test_save_fails_for_invalid_has_one
     firm = Firm.first
-    assert firm.valid?
+    assert_predicate firm, :valid?
 
     firm.build_account
 
-    assert !firm.account.valid?
-    assert !firm.valid?
-    assert !firm.save
+    assert_not_predicate firm.account, :valid?
+    assert_not_predicate firm, :valid?
+    assert_not firm.save
     assert_equal ["is invalid"], firm.errors["account"]
   end
 
   def test_save_succeeds_for_invalid_has_one_with_validate_false
     firm = Firm.first
-    assert firm.valid?
+    assert_predicate firm, :valid?
 
     firm.build_unvalidated_account
 
-    assert !firm.unvalidated_account.valid?
-    assert firm.valid?
+    assert_not_predicate firm.unvalidated_account, :valid?
+    assert_predicate firm, :valid?
     assert firm.save
   end
 
@@ -137,10 +136,10 @@ class TestDefaultAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCas
 
     account = firm.build_account("credit_limit" => 1000)
     assert_equal account, firm.account
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
     assert firm.save
     assert_equal account, firm.account
-    assert account.persisted?
+    assert_predicate account, :persisted?
   end
 
   def test_build_before_either_saved
@@ -148,16 +147,16 @@ class TestDefaultAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCas
 
     firm.account = account = Account.new("credit_limit" => 1000)
     assert_equal account, firm.account
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
     assert firm.save
     assert_equal account, firm.account
-    assert account.persisted?
+    assert_predicate account, :persisted?
   end
 
   def test_assignment_before_parent_saved
     firm = Firm.new("name" => "GlobalMegaCorp")
     firm.account = a = Account.find(1)
-    assert !firm.persisted?
+    assert_not_predicate firm, :persisted?
     assert_equal a, firm.account
     assert firm.save
     assert_equal a, firm.account
@@ -168,12 +167,12 @@ class TestDefaultAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCas
   def test_assignment_before_either_saved
     firm = Firm.new("name" => "GlobalMegaCorp")
     firm.account = a = Account.new("credit_limit" => 1000)
-    assert !firm.persisted?
-    assert !a.persisted?
+    assert_not_predicate firm, :persisted?
+    assert_not_predicate a, :persisted?
     assert_equal a, firm.account
     assert firm.save
-    assert firm.persisted?
-    assert a.persisted?
+    assert_predicate firm, :persisted?
+    assert_predicate a, :persisted?
     assert_equal a, firm.account
     firm.association(:account).reload
     assert_equal a, firm.account
@@ -222,13 +221,13 @@ class TestDefaultAutosaveAssociationOnABelongsToAssociation < ActiveRecord::Test
 
   def test_should_save_parent_but_not_invalid_child
     client = Client.new(name: "Joe (the Plumber)")
-    assert client.valid?
+    assert_predicate client, :valid?
 
     client.build_firm
-    assert !client.firm.valid?
+    assert_not_predicate client.firm, :valid?
 
     assert client.save
-    assert !client.firm.persisted?
+    assert_not_predicate client.firm, :persisted?
   end
 
   def test_save_fails_for_invalid_belongs_to
@@ -236,9 +235,9 @@ class TestDefaultAutosaveAssociationOnABelongsToAssociation < ActiveRecord::Test
     assert log = AuditLog.create(developer_id: 0, message: " ")
 
     log.developer = Developer.new
-    assert !log.developer.valid?
-    assert !log.valid?
-    assert !log.save
+    assert_not_predicate log.developer, :valid?
+    assert_not_predicate log, :valid?
+    assert_not log.save
     assert_equal ["is invalid"], log.errors["developer"]
   end
 
@@ -247,8 +246,8 @@ class TestDefaultAutosaveAssociationOnABelongsToAssociation < ActiveRecord::Test
     assert log = AuditLog.create(developer_id: 0, message: " ")
 
     log.unvalidated_developer = Developer.new
-    assert !log.unvalidated_developer.valid?
-    assert log.valid?
+    assert_not_predicate log.unvalidated_developer, :valid?
+    assert_predicate log, :valid?
     assert log.save
   end
 
@@ -257,10 +256,10 @@ class TestDefaultAutosaveAssociationOnABelongsToAssociation < ActiveRecord::Test
     apple = Firm.new("name" => "Apple")
     client.firm = apple
     assert_equal apple, client.firm
-    assert !apple.persisted?
+    assert_not_predicate apple, :persisted?
     assert client.save
     assert apple.save
-    assert apple.persisted?
+    assert_predicate apple, :persisted?
     assert_equal apple, client.firm
     client.association(:firm).reload
     assert_equal apple, client.firm
@@ -270,11 +269,11 @@ class TestDefaultAutosaveAssociationOnABelongsToAssociation < ActiveRecord::Test
     final_cut = Client.new("name" => "Final Cut")
     apple = Firm.new("name" => "Apple")
     final_cut.firm = apple
-    assert !final_cut.persisted?
-    assert !apple.persisted?
+    assert_not_predicate final_cut, :persisted?
+    assert_not_predicate apple, :persisted?
     assert final_cut.save
-    assert final_cut.persisted?
-    assert apple.persisted?
+    assert_predicate final_cut, :persisted?
+    assert_predicate apple, :persisted?
     assert_equal apple, final_cut.firm
     final_cut.association(:firm).reload
     assert_equal apple, final_cut.firm
@@ -383,7 +382,7 @@ class TestDefaultAutosaveAssociationOnABelongsToAssociation < ActiveRecord::Test
     auditlog.developer    = invalid_developer
     auditlog.developer_id = valid_developer.id
 
-    assert auditlog.valid?
+    assert_predicate auditlog, :valid?
   end
 end
 
@@ -396,8 +395,8 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttrib
     molecule.electrons = [valid_electron, invalid_electron]
     molecule.save
 
-    assert_not invalid_electron.valid?
-    assert valid_electron.valid?
+    assert_not_predicate invalid_electron, :valid?
+    assert_predicate valid_electron, :valid?
     assert_not molecule.persisted?, "Molecule should not be persisted when its electrons are invalid"
   end
 
@@ -409,9 +408,9 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttrib
 
     guitar.tuning_pegs = [tuning_peg_valid, tuning_peg_invalid]
 
-    assert_not tuning_peg_invalid.valid?
-    assert tuning_peg_valid.valid?
-    assert_not guitar.valid?
+    assert_not_predicate tuning_peg_invalid, :valid?
+    assert_predicate tuning_peg_valid, :valid?
+    assert_not_predicate guitar, :valid?
     assert_equal ["is not a number"], guitar.errors["tuning_pegs[1].pitch"]
     assert_not_equal ["is not a number"], guitar.errors["tuning_pegs.pitch"]
   end
@@ -426,9 +425,9 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttrib
 
     molecule.electrons = [valid_electron, invalid_electron]
 
-    assert_not invalid_electron.valid?
-    assert valid_electron.valid?
-    assert_not molecule.valid?
+    assert_not_predicate invalid_electron, :valid?
+    assert_predicate valid_electron, :valid?
+    assert_not_predicate molecule, :valid?
     assert_equal ["can't be blank"], molecule.errors["electrons[1].name"]
     assert_not_equal ["can't be blank"], molecule.errors["electrons.name"]
   ensure
@@ -442,9 +441,9 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttrib
 
     molecule.electrons = [valid_electron, invalid_electron]
 
-    assert_not invalid_electron.valid?
-    assert valid_electron.valid?
-    assert_not molecule.valid?
+    assert_not_predicate invalid_electron, :valid?
+    assert_predicate valid_electron, :valid?
+    assert_not_predicate molecule, :valid?
     assert_equal [{ error: :blank }], molecule.errors.details[:"electrons.name"]
   end
 
@@ -456,9 +455,9 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttrib
 
     guitar.tuning_pegs = [tuning_peg_valid, tuning_peg_invalid]
 
-    assert_not tuning_peg_invalid.valid?
-    assert tuning_peg_valid.valid?
-    assert_not guitar.valid?
+    assert_not_predicate tuning_peg_invalid, :valid?
+    assert_predicate tuning_peg_valid, :valid?
+    assert_not_predicate guitar, :valid?
     assert_equal [{ error: :not_a_number, value: nil }], guitar.errors.details[:"tuning_pegs[1].pitch"]
     assert_equal [], guitar.errors.details[:"tuning_pegs.pitch"]
   end
@@ -473,9 +472,9 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttrib
 
     molecule.electrons = [valid_electron, invalid_electron]
 
-    assert_not invalid_electron.valid?
-    assert valid_electron.valid?
-    assert_not molecule.valid?
+    assert_not_predicate invalid_electron, :valid?
+    assert_predicate valid_electron, :valid?
+    assert_not_predicate molecule, :valid?
     assert_equal [{ error: :blank }], molecule.errors.details[:"electrons[1].name"]
     assert_equal [], molecule.errors.details[:"electrons.name"]
   ensure
@@ -489,33 +488,45 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttrib
     molecule.electrons = [valid_electron]
     molecule.save
 
-    assert valid_electron.valid?
-    assert molecule.persisted?
+    assert_predicate valid_electron, :valid?
+    assert_predicate molecule, :persisted?
     assert_equal 1, molecule.electrons.count
   end
 end
 
 class TestDefaultAutosaveAssociationOnAHasManyAssociation < ActiveRecord::TestCase
-  fixtures :companies, :people
+  fixtures :companies, :developers
 
   def test_invalid_adding
     firm = Firm.find(1)
-    assert !(firm.clients_of_firm << c = Client.new)
-    assert !c.persisted?
-    assert !firm.valid?
-    assert !firm.save
-    assert !c.persisted?
+    assert_not (firm.clients_of_firm << c = Client.new)
+    assert_not_predicate c, :persisted?
+    assert_not_predicate firm, :valid?
+    assert_not firm.save
+    assert_not_predicate c, :persisted?
   end
 
   def test_invalid_adding_before_save
     new_firm = Firm.new("name" => "A New Firm, Inc")
     new_firm.clients_of_firm.concat([c = Client.new, Client.new("name" => "Apple")])
-    assert !c.persisted?
-    assert !c.valid?
-    assert !new_firm.valid?
-    assert !new_firm.save
-    assert !c.persisted?
-    assert !new_firm.persisted?
+    assert_not_predicate c, :persisted?
+    assert_not_predicate c, :valid?
+    assert_not_predicate new_firm, :valid?
+    assert_not new_firm.save
+    assert_not_predicate c, :persisted?
+    assert_not_predicate new_firm, :persisted?
+  end
+
+  def test_adding_unsavable_association
+    new_firm = Firm.new("name" => "A New Firm, Inc")
+    client = new_firm.clients.new("name" => "Apple")
+    client.throw_on_save = true
+
+    assert_predicate client, :valid?
+    assert_predicate new_firm, :valid?
+    assert_not new_firm.save
+    assert_not_predicate new_firm, :persisted?
+    assert_not_predicate client, :persisted?
   end
 
   def test_invalid_adding_with_validate_false
@@ -523,10 +534,10 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociation < ActiveRecord::TestCa
     client = Client.new
     firm.unvalidated_clients_of_firm << client
 
-    assert firm.valid?
-    assert !client.valid?
+    assert_predicate firm, :valid?
+    assert_not_predicate client, :valid?
     assert firm.save
-    assert !client.persisted?
+    assert_not_predicate client, :persisted?
   end
 
   def test_valid_adding_with_validate_false
@@ -535,24 +546,24 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociation < ActiveRecord::TestCa
     firm = Firm.first
     client = Client.new("name" => "Apple")
 
-    assert firm.valid?
-    assert client.valid?
-    assert !client.persisted?
+    assert_predicate firm, :valid?
+    assert_predicate client, :valid?
+    assert_not_predicate client, :persisted?
 
     firm.unvalidated_clients_of_firm << client
 
     assert firm.save
-    assert client.persisted?
+    assert_predicate client, :persisted?
     assert_equal no_of_clients + 1, Client.count
   end
 
   def test_invalid_build
     new_client = companies(:first_firm).clients_of_firm.build
-    assert !new_client.persisted?
-    assert !new_client.valid?
+    assert_not_predicate new_client, :persisted?
+    assert_not_predicate new_client, :valid?
     assert_equal new_client, companies(:first_firm).clients_of_firm.last
-    assert !companies(:first_firm).save
-    assert !new_client.persisted?
+    assert_not companies(:first_firm).save
+    assert_not_predicate new_client, :persisted?
     assert_equal 2, companies(:first_firm).clients_of_firm.reload.size
   end
 
@@ -571,8 +582,8 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociation < ActiveRecord::TestCa
     assert_equal no_of_firms, Firm.count      # Firm was not saved to database.
     assert_equal no_of_clients, Client.count  # Clients were not saved to database.
     assert new_firm.save
-    assert new_firm.persisted?
-    assert c.persisted?
+    assert_predicate new_firm, :persisted?
+    assert_predicate c, :persisted?
     assert_equal new_firm, c.firm
     assert_equal no_of_firms + 1, Firm.count      # Firm was saved to database.
     assert_equal no_of_clients + 2, Client.count  # Clients were saved to database.
@@ -591,22 +602,22 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociation < ActiveRecord::TestCa
   end
 
   def test_assign_ids_for_through_a_belongs_to
-    post = Post.new(title: "Assigning IDs works!", body: "You heard it here first, folks!")
-    post.person_ids = [people(:david).id, people(:michael).id]
-    post.save
-    post.reload
-    assert_equal 2, post.people.length
-    assert_includes post.people, people(:david)
+    firm = Firm.new("name" => "Apple")
+    firm.developer_ids = [developers(:david).id, developers(:jamis).id]
+    firm.save
+    firm.reload
+    assert_equal 2, firm.developers.length
+    assert_includes firm.developers, developers(:david)
   end
 
   def test_build_before_save
     company = companies(:first_firm)
     new_client = assert_no_queries(ignore_none: false) { company.clients_of_firm.build("name" => "Another Client") }
-    assert !company.clients_of_firm.loaded?
+    assert_not_predicate company.clients_of_firm, :loaded?
 
     company.name += "-changed"
     assert_queries(2) { assert company.save }
-    assert new_client.persisted?
+    assert_predicate new_client, :persisted?
     assert_equal 3, company.clients_of_firm.reload.size
   end
 
@@ -622,11 +633,11 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociation < ActiveRecord::TestCa
   def test_build_via_block_before_save
     company = companies(:first_firm)
     new_client = assert_no_queries(ignore_none: false) { company.clients_of_firm.build { |client| client.name = "Another Client" } }
-    assert !company.clients_of_firm.loaded?
+    assert_not_predicate company.clients_of_firm, :loaded?
 
     company.name += "-changed"
     assert_queries(2) { assert company.save }
-    assert new_client.persisted?
+    assert_predicate new_client, :persisted?
     assert_equal 3, company.clients_of_firm.reload.size
   end
 
@@ -658,62 +669,62 @@ class TestDefaultAutosaveAssociationOnNewRecord < ActiveRecord::TestCase
     new_account = Account.new("credit_limit" => 1000)
     new_firm = Firm.new("name" => "some firm")
 
-    assert !new_firm.persisted?
+    assert_not_predicate new_firm, :persisted?
     new_account.firm = new_firm
     new_account.save!
 
-    assert new_firm.persisted?
+    assert_predicate new_firm, :persisted?
 
     new_account = Account.new("credit_limit" => 1000)
     new_autosaved_firm = Firm.new("name" => "some firm")
 
-    assert !new_autosaved_firm.persisted?
+    assert_not_predicate new_autosaved_firm, :persisted?
     new_account.unautosaved_firm = new_autosaved_firm
     new_account.save!
 
-    assert !new_autosaved_firm.persisted?
+    assert_not_predicate new_autosaved_firm, :persisted?
   end
 
   def test_autosave_new_record_on_has_one_can_be_disabled_per_relationship
     firm = Firm.new("name" => "some firm")
     account = Account.new("credit_limit" => 1000)
 
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
     firm.account = account
     firm.save!
 
-    assert account.persisted?
+    assert_predicate account, :persisted?
 
     firm = Firm.new("name" => "some firm")
     account = Account.new("credit_limit" => 1000)
 
     firm.unautosaved_account = account
 
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
     firm.unautosaved_account = account
     firm.save!
 
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
   end
 
   def test_autosave_new_record_on_has_many_can_be_disabled_per_relationship
     firm = Firm.new("name" => "some firm")
     account = Account.new("credit_limit" => 1000)
 
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
     firm.accounts << account
 
     firm.save!
-    assert account.persisted?
+    assert_predicate account, :persisted?
 
     firm = Firm.new("name" => "some firm")
     account = Account.new("credit_limit" => 1000)
 
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
     firm.unautosaved_accounts << account
 
     firm.save!
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
   end
 
   def test_autosave_new_record_with_after_create_callback
@@ -746,18 +757,18 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
     @pirate.mark_for_destruction
     @pirate.ship.mark_for_destruction
 
-    assert !@pirate.reload.marked_for_destruction?
-    assert !@pirate.ship.reload.marked_for_destruction?
+    assert_not_predicate @pirate.reload, :marked_for_destruction?
+    assert_not_predicate @pirate.ship.reload, :marked_for_destruction?
   end
 
   # has_one
   def test_should_destroy_a_child_association_as_part_of_the_save_transaction_if_it_was_marked_for_destruction
-    assert !@pirate.ship.marked_for_destruction?
+    assert_not_predicate @pirate.ship, :marked_for_destruction?
 
     @pirate.ship.mark_for_destruction
     id = @pirate.ship.id
 
-    assert @pirate.ship.marked_for_destruction?
+    assert_predicate @pirate.ship, :marked_for_destruction?
     assert Ship.find_by_id(id)
 
     @pirate.save
@@ -767,11 +778,12 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
 
   def test_should_skip_validation_on_a_child_association_if_marked_for_destruction
     @pirate.ship.name = ""
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
 
     @pirate.ship.mark_for_destruction
-    @pirate.ship.expects(:valid?).never
-    assert_difference("Ship.count", -1) { @pirate.save! }
+    assert_not_called(@pirate.ship, :valid?) do
+      assert_difference("Ship.count", -1) { @pirate.save! }
+    end
   end
 
   def test_a_child_marked_for_destruction_should_not_be_destroyed_twice
@@ -796,7 +808,7 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
     @ship.pirate.catchphrase = "Changed Catchphrase"
     @ship.name_will_change!
 
-    assert_raise(RuntimeError) { assert !@pirate.save }
+    assert_raise(RuntimeError) { assert_not @pirate.save }
     assert_not_nil @pirate.reload.ship
   end
 
@@ -807,18 +819,19 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
   end
 
   def test_should_not_save_changed_has_one_unchanged_object_if_child_is_saved
-    @pirate.ship.expects(:save).never
-    assert @pirate.save
+    assert_not_called(@pirate.ship, :save) do
+      assert @pirate.save
+    end
   end
 
   # belongs_to
   def test_should_destroy_a_parent_association_as_part_of_the_save_transaction_if_it_was_marked_for_destruction
-    assert !@ship.pirate.marked_for_destruction?
+    assert_not_predicate @ship.pirate, :marked_for_destruction?
 
     @ship.pirate.mark_for_destruction
     id = @ship.pirate.id
 
-    assert @ship.pirate.marked_for_destruction?
+    assert_predicate @ship.pirate, :marked_for_destruction?
     assert Pirate.find_by_id(id)
 
     @ship.save
@@ -828,11 +841,12 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
 
   def test_should_skip_validation_on_a_parent_association_if_marked_for_destruction
     @ship.pirate.catchphrase = ""
-    assert !@ship.valid?
+    assert_not_predicate @ship, :valid?
 
     @ship.pirate.mark_for_destruction
-    @ship.pirate.expects(:valid?).never
-    assert_difference("Pirate.count", -1) { @ship.save! }
+    assert_not_called(@ship.pirate, :valid?) do
+      assert_difference("Pirate.count", -1) { @ship.save! }
+    end
   end
 
   def test_a_parent_marked_for_destruction_should_not_be_destroyed_twice
@@ -856,7 +870,7 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
 
     @ship.pirate.catchphrase = "Changed Catchphrase"
 
-    assert_raise(RuntimeError) { assert !@ship.save }
+    assert_raise(RuntimeError) { assert_not @ship.save }
     assert_not_nil @ship.reload.pirate
   end
 
@@ -872,7 +886,7 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
   def test_should_destroy_has_many_as_part_of_the_save_transaction_if_they_were_marked_for_destruction
     2.times { |i| @pirate.birds.create!(name: "birds_#{i}") }
 
-    assert !@pirate.birds.any?(&:marked_for_destruction?)
+    assert_not @pirate.birds.any?(&:marked_for_destruction?)
 
     @pirate.birds.each(&:mark_for_destruction)
     klass = @pirate.birds.first.class
@@ -882,7 +896,7 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
     ids.each { |id| assert klass.find_by_id(id) }
 
     @pirate.save
-    assert @pirate.reload.birds.empty?
+    assert_empty @pirate.reload.birds
     ids.each { |id| assert_nil klass.find_by_id(id) }
   end
 
@@ -890,30 +904,32 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
     @pirate.birds.create!(name: :parrot)
     @pirate.birds.first.destroy
     @pirate.save!
-    assert @pirate.reload.birds.empty?
+    assert_empty @pirate.reload.birds
   end
 
   def test_should_skip_validation_on_has_many_if_marked_for_destruction
     2.times { |i| @pirate.birds.create!(name: "birds_#{i}") }
 
     @pirate.birds.each { |bird| bird.name = "" }
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
 
-    @pirate.birds.each do |bird|
-      bird.mark_for_destruction
-      bird.expects(:valid?).never
+    @pirate.birds.each(&:mark_for_destruction)
+
+    assert_not_called(@pirate.birds.first, :valid?) do
+      assert_not_called(@pirate.birds.last, :valid?) do
+        assert_difference("Bird.count", -2) { @pirate.save! }
+      end
     end
-    assert_difference("Bird.count", -2) { @pirate.save! }
   end
 
   def test_should_skip_validation_on_has_many_if_destroyed
     @pirate.birds.create!(name: "birds_1")
 
     @pirate.birds.each { |bird| bird.name = "" }
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
 
     @pirate.birds.each(&:destroy)
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
   end
 
   def test_a_child_marked_for_destruction_should_not_be_destroyed_twice_while_saving_has_many
@@ -922,8 +938,11 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
     @pirate.birds.each(&:mark_for_destruction)
     assert @pirate.save
 
-    @pirate.birds.each { |bird| bird.expects(:destroy).never }
-    assert @pirate.save
+    @pirate.birds.each do |bird|
+      assert_not_called(bird, :destroy) do
+        assert @pirate.save
+      end
+    end
   end
 
   def test_should_rollback_destructions_if_an_exception_occurred_while_saving_has_many
@@ -938,7 +957,7 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
       end
     end
 
-    assert_raise(RuntimeError) { assert !@pirate.save }
+    assert_raise(RuntimeError) { assert_not @pirate.save }
     assert_equal before, @pirate.reload.birds
   end
 
@@ -1004,42 +1023,44 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
   def test_should_destroy_habtm_as_part_of_the_save_transaction_if_they_were_marked_for_destruction
     2.times { |i| @pirate.parrots.create!(name: "parrots_#{i}") }
 
-    assert !@pirate.parrots.any?(&:marked_for_destruction?)
+    assert_not @pirate.parrots.any?(&:marked_for_destruction?)
     @pirate.parrots.each(&:mark_for_destruction)
 
     assert_no_difference "Parrot.count" do
       @pirate.save
     end
 
-    assert @pirate.reload.parrots.empty?
+    assert_empty @pirate.reload.parrots
 
     join_records = Pirate.connection.select_all("SELECT * FROM parrots_pirates WHERE pirate_id = #{@pirate.id}")
-    assert join_records.empty?
+    assert_empty join_records
   end
 
   def test_should_skip_validation_on_habtm_if_marked_for_destruction
     2.times { |i| @pirate.parrots.create!(name: "parrots_#{i}") }
 
     @pirate.parrots.each { |parrot| parrot.name = "" }
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
+
+    @pirate.parrots.each { |parrot| parrot.mark_for_destruction }
 
-    @pirate.parrots.each do |parrot|
-      parrot.mark_for_destruction
-      parrot.expects(:valid?).never
+    assert_not_called(@pirate.parrots.first, :valid?) do
+      assert_not_called(@pirate.parrots.last, :valid?) do
+        @pirate.save!
+      end
     end
 
-    @pirate.save!
-    assert @pirate.reload.parrots.empty?
+    assert_empty @pirate.reload.parrots
   end
 
   def test_should_skip_validation_on_habtm_if_destroyed
     @pirate.parrots.create!(name: "parrots_1")
 
     @pirate.parrots.each { |parrot| parrot.name = "" }
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
 
     @pirate.parrots.each(&:destroy)
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
   end
 
   def test_a_child_marked_for_destruction_should_not_be_destroyed_twice_while_saving_habtm
@@ -1066,7 +1087,7 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
       end
     end
 
-    assert_raise(RuntimeError) { assert !@pirate.save }
+    assert_raise(RuntimeError) { assert_not @pirate.save }
     assert_equal before, @pirate.reload.parrots
   end
 
@@ -1146,16 +1167,16 @@ class TestAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCase
 
   def test_should_automatically_validate_the_associated_model
     @pirate.ship.name = ""
-    assert @pirate.invalid?
-    assert @pirate.errors[:"ship.name"].any?
+    assert_predicate @pirate, :invalid?
+    assert_predicate @pirate.errors[:"ship.name"], :any?
   end
 
   def test_should_merge_errors_on_the_associated_models_onto_the_parent_even_if_it_is_not_valid
     @pirate.ship.name   = nil
     @pirate.catchphrase = nil
-    assert @pirate.invalid?
-    assert @pirate.errors[:"ship.name"].any?
-    assert @pirate.errors[:catchphrase].any?
+    assert_predicate @pirate, :invalid?
+    assert_predicate @pirate.errors[:"ship.name"], :any?
+    assert_predicate @pirate.errors[:catchphrase], :any?
   end
 
   def test_should_not_ignore_different_error_messages_on_the_same_attribute
@@ -1164,7 +1185,7 @@ class TestAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCase
     Ship.validates_format_of :name, with: /\w/
     @pirate.ship.name   = ""
     @pirate.catchphrase = nil
-    assert @pirate.invalid?
+    assert_predicate @pirate, :invalid?
     assert_equal ["can't be blank", "is invalid"], @pirate.errors[:"ship.name"]
   ensure
     Ship._validators = old_validators if old_validators
@@ -1214,7 +1235,7 @@ class TestAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCase
 
     assert_no_difference "Pirate.count" do
       assert_no_difference "Ship.count" do
-        assert !pirate.save
+        assert_not pirate.save
       end
     end
   end
@@ -1233,7 +1254,7 @@ class TestAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCase
       end
     end
 
-    assert_raise(RuntimeError) { assert !@pirate.save }
+    assert_raise(RuntimeError) { assert_not @pirate.save }
     assert_equal before, [@pirate.reload.catchphrase, @pirate.ship.name]
   end
 
@@ -1245,7 +1266,7 @@ class TestAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCase
     ship = ShipWithoutNestedAttributes.new(name: "The Black Flag")
     ship.parts.build.mark_for_destruction
 
-    assert_not ship.valid?
+    assert_not_predicate ship, :valid?
   end
 end
 
@@ -1300,16 +1321,16 @@ class TestAutosaveAssociationOnABelongsToAssociation < ActiveRecord::TestCase
 
   def test_should_automatically_validate_the_associated_model
     @ship.pirate.catchphrase = ""
-    assert @ship.invalid?
-    assert @ship.errors[:"pirate.catchphrase"].any?
+    assert_predicate @ship, :invalid?
+    assert_predicate @ship.errors[:"pirate.catchphrase"], :any?
   end
 
   def test_should_merge_errors_on_the_associated_model_onto_the_parent_even_if_it_is_not_valid
     @ship.name = nil
     @ship.pirate.catchphrase = nil
-    assert @ship.invalid?
-    assert @ship.errors[:name].any?
-    assert @ship.errors[:"pirate.catchphrase"].any?
+    assert_predicate @ship, :invalid?
+    assert_predicate @ship.errors[:name], :any?
+    assert_predicate @ship.errors[:"pirate.catchphrase"], :any?
   end
 
   def test_should_still_allow_to_bypass_validations_on_the_associated_model
@@ -1338,7 +1359,7 @@ class TestAutosaveAssociationOnABelongsToAssociation < ActiveRecord::TestCase
 
     assert_no_difference "Ship.count" do
       assert_no_difference "Pirate.count" do
-        assert !ship.save
+        assert_not ship.save
       end
     end
   end
@@ -1357,7 +1378,7 @@ class TestAutosaveAssociationOnABelongsToAssociation < ActiveRecord::TestCase
       end
     end
 
-    assert_raise(RuntimeError) { assert !@ship.save }
+    assert_raise(RuntimeError) { assert_not @ship.save }
     assert_equal before, [@ship.pirate.reload.catchphrase, @ship.reload.name]
   end
 
@@ -1404,17 +1425,17 @@ module AutosaveAssociationOnACollectionAssociationTests
   def test_should_automatically_validate_the_associated_models
     @pirate.send(@association_name).each { |child| child.name = "" }
 
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
     assert_equal ["can't be blank"], @pirate.errors["#{@association_name}.name"]
-    assert @pirate.errors[@association_name].empty?
+    assert_empty @pirate.errors[@association_name]
   end
 
   def test_should_not_use_default_invalid_error_on_associated_models
     @pirate.send(@association_name).build(name: "")
 
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
     assert_equal ["can't be blank"], @pirate.errors["#{@association_name}.name"]
-    assert @pirate.errors[@association_name].empty?
+    assert_empty @pirate.errors[@association_name]
   end
 
   def test_should_default_invalid_error_from_i18n
@@ -1424,10 +1445,10 @@ module AutosaveAssociationOnACollectionAssociationTests
 
     @pirate.send(@association_name).build(name: "")
 
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
     assert_equal ["cannot be blank"], @pirate.errors["#{@association_name}.name"]
     assert_equal ["#{@association_name.to_s.humanize} name cannot be blank"], @pirate.errors.full_messages
-    assert @pirate.errors[@association_name].empty?
+    assert_empty @pirate.errors[@association_name]
   ensure
     I18n.backend = I18n::Backend::Simple.new
   end
@@ -1436,9 +1457,9 @@ module AutosaveAssociationOnACollectionAssociationTests
     @pirate.send(@association_name).each { |child| child.name = "" }
     @pirate.catchphrase = nil
 
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
     assert_equal ["can't be blank"], @pirate.errors["#{@association_name}.name"]
-    assert @pirate.errors[:catchphrase].any?
+    assert_predicate @pirate.errors[:catchphrase], :any?
   end
 
   def test_should_allow_to_bypass_validations_on_the_associated_models_on_update
@@ -1481,7 +1502,7 @@ module AutosaveAssociationOnACollectionAssociationTests
     @child_1.name = "Changed"
     @child_1.cancel_save_from_callback = true
 
-    assert !@pirate.save
+    assert_not @pirate.save
     assert_equal "Don' botharrr talkin' like one, savvy?", @pirate.reload.catchphrase
     assert_equal "Posideons Killer", @child_1.reload.name
 
@@ -1491,7 +1512,7 @@ module AutosaveAssociationOnACollectionAssociationTests
 
     assert_no_difference "Pirate.count" do
       assert_no_difference "#{new_child.class.name}.count" do
-        assert !new_pirate.save
+        assert_not new_pirate.save
       end
     end
   end
@@ -1511,7 +1532,7 @@ module AutosaveAssociationOnACollectionAssociationTests
       end
     end
 
-    assert_raise(RuntimeError) { assert !@pirate.save }
+    assert_raise(RuntimeError) { assert_not @pirate.save }
     assert_equal before, [@pirate.reload.catchphrase, *@pirate.send(@association_name).map(&:name)]
   end
 
@@ -1596,10 +1617,10 @@ class TestAutosaveAssociationValidationsOnAHasManyAssociation < ActiveRecord::Te
   end
 
   test "should automatically validate associations" do
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
     @pirate.birds.each { |bird| bird.name = "" }
 
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
   end
 end
 
@@ -1614,15 +1635,15 @@ class TestAutosaveAssociationValidationsOnAHasOneAssociation < ActiveRecord::Tes
   end
 
   test "should automatically validate associations with :validate => true" do
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
     @pirate.ship.name = ""
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
   end
 
   test "should not automatically add validate associations without :validate => true" do
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
     @pirate.non_validated_ship.name = ""
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
   end
 end
 
@@ -1635,15 +1656,15 @@ class TestAutosaveAssociationValidationsOnABelongsToAssociation < ActiveRecord::
   end
 
   test "should automatically validate associations with :validate => true" do
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
     @pirate.parrot = Parrot.new(name: "")
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
   end
 
   test "should not automatically validate associations without :validate => true" do
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
     @pirate.non_validated_parrot = Parrot.new(name: "")
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
   end
 end
 
@@ -1656,17 +1677,17 @@ class TestAutosaveAssociationValidationsOnAHABTMAssociation < ActiveRecord::Test
   end
 
   test "should automatically validate associations with :validate => true" do
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
     @pirate.parrots = [ Parrot.new(name: "popuga") ]
     @pirate.parrots.each { |parrot| parrot.name = "" }
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
   end
 
   test "should not automatically validate associations without :validate => true" do
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
     @pirate.non_validated_parrots = [ Parrot.new(name: "popuga") ]
     @pirate.non_validated_parrots.each { |parrot| parrot.name = "" }
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
   end
 end
 
@@ -1687,7 +1708,7 @@ class TestAutosaveAssociationValidationMethodsGeneration < ActiveRecord::TestCas
   end
 
   test "should not generate validation methods for has_one associations without :validate => true" do
-    assert !@pirate.respond_to?(:validate_associated_records_for_non_validated_ship)
+    assert_not_respond_to @pirate, :validate_associated_records_for_non_validated_ship
   end
 
   test "should generate validation methods for belongs_to associations with :validate => true" do
@@ -1695,7 +1716,7 @@ class TestAutosaveAssociationValidationMethodsGeneration < ActiveRecord::TestCas
   end
 
   test "should not generate validation methods for belongs_to associations without :validate => true" do
-    assert !@pirate.respond_to?(:validate_associated_records_for_non_validated_parrot)
+    assert_not_respond_to @pirate, :validate_associated_records_for_non_validated_parrot
   end
 
   test "should generate validation methods for HABTM associations with :validate => true" do
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index 1a1d4ce039..fcfab074a2 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -104,7 +104,7 @@ class BasicsTest < ActiveRecord::TestCase
     pk = Author.columns_hash["id"]
     ref = Post.columns_hash["author_id"]
 
-    assert_equal pk.bigint?, ref.bigint?
+    assert_equal pk.sql_type, ref.sql_type
   end
 
   def test_many_mutations
@@ -147,8 +147,8 @@ class BasicsTest < ActiveRecord::TestCase
   end
 
   def test_table_exists
-    assert !NonExistentTable.table_exists?
-    assert Topic.table_exists?
+    assert_not_predicate NonExistentTable, :table_exists?
+    assert_predicate Topic, :table_exists?
   end
 
   def test_preserving_date_objects
@@ -307,7 +307,7 @@ class BasicsTest < ActiveRecord::TestCase
     assert_equal "Dude", cbs[0].name
     assert_equal "Bob", cbs[1].name
     assert cbs[0].frickinawesome
-    assert !cbs[1].frickinawesome
+    assert_not cbs[1].frickinawesome
   end
 
   def test_load
@@ -450,7 +450,7 @@ class BasicsTest < ActiveRecord::TestCase
 
   def test_default_values
     topic = Topic.new
-    assert topic.approved?
+    assert_predicate topic, :approved?
     assert_nil topic.written_on
     assert_nil topic.bonus_time
     assert_nil topic.last_read
@@ -458,7 +458,7 @@ class BasicsTest < ActiveRecord::TestCase
     topic.save
 
     topic = Topic.find(topic.id)
-    assert topic.approved?
+    assert_predicate topic, :approved?
     assert_nil topic.last_read
 
     # Oracle has some funky default handling, so it requires a bit of
@@ -629,7 +629,7 @@ class BasicsTest < ActiveRecord::TestCase
   end
 
   def test_readonly_attributes
-    assert_equal Set.new([ "title" , "comments_count" ]), ReadonlyTitlePost.readonly_attributes
+    assert_equal Set.new([ "title", "comments_count" ]), ReadonlyTitlePost.readonly_attributes
 
     post = ReadonlyTitlePost.create(title: "cannot change this", body: "changeable")
     post.reload
@@ -727,9 +727,9 @@ class BasicsTest < ActiveRecord::TestCase
     b_nil = Boolean.find(nil_id)
     assert_nil b_nil.value
     b_false = Boolean.find(false_id)
-    assert !b_false.value?
+    assert_not_predicate b_false, :value?
     b_true = Boolean.find(true_id)
-    assert b_true.value?
+    assert_predicate b_true, :value?
   end
 
   def test_boolean_without_questionmark
@@ -753,9 +753,9 @@ class BasicsTest < ActiveRecord::TestCase
     b_blank = Boolean.find(blank_id)
     assert_nil b_blank.value
     b_false = Boolean.find(false_id)
-    assert !b_false.value?
+    assert_not_predicate b_false, :value?
     b_true = Boolean.find(true_id)
-    assert b_true.value?
+    assert_predicate b_true, :value?
   end
 
   def test_new_record_returns_boolean
@@ -768,7 +768,7 @@ class BasicsTest < ActiveRecord::TestCase
     duped_topic = nil
     assert_nothing_raised { duped_topic = topic.dup }
     assert_equal topic.title, duped_topic.title
-    assert !duped_topic.persisted?
+    assert_not_predicate duped_topic, :persisted?
 
     # test if the attributes have been duped
     topic.title = "a"
@@ -786,7 +786,7 @@ class BasicsTest < ActiveRecord::TestCase
 
     # test if saved clone object differs from original
     duped_topic.save
-    assert duped_topic.persisted?
+    assert_predicate duped_topic, :persisted?
     assert_not_equal duped_topic.id, topic.id
 
     duped_topic.reload
@@ -807,7 +807,7 @@ class BasicsTest < ActiveRecord::TestCase
     assert_nothing_raised { dup = dev.dup }
     assert_kind_of DeveloperSalary, dup.salary
     assert_equal dev.salary.amount, dup.salary.amount
-    assert !dup.persisted?
+    assert_not_predicate dup, :persisted?
 
     # test if the attributes have been duped
     original_amount = dup.salary.amount
@@ -815,7 +815,7 @@ class BasicsTest < ActiveRecord::TestCase
     assert_equal original_amount, dup.salary.amount
 
     assert dup.save
-    assert dup.persisted?
+    assert_predicate dup, :persisted?
     assert_not_equal dup.id, dev.id
   end
 
@@ -835,52 +835,52 @@ class BasicsTest < ActiveRecord::TestCase
 
   def test_clone_of_new_object_with_defaults
     developer = Developer.new
-    assert !developer.name_changed?
-    assert !developer.salary_changed?
+    assert_not_predicate developer, :name_changed?
+    assert_not_predicate developer, :salary_changed?
 
     cloned_developer = developer.clone
-    assert !cloned_developer.name_changed?
-    assert !cloned_developer.salary_changed?
+    assert_not_predicate cloned_developer, :name_changed?
+    assert_not_predicate cloned_developer, :salary_changed?
   end
 
   def test_clone_of_new_object_marks_attributes_as_dirty
     developer = Developer.new name: "Bjorn", salary: 100000
-    assert developer.name_changed?
-    assert developer.salary_changed?
+    assert_predicate developer, :name_changed?
+    assert_predicate developer, :salary_changed?
 
     cloned_developer = developer.clone
-    assert cloned_developer.name_changed?
-    assert cloned_developer.salary_changed?
+    assert_predicate cloned_developer, :name_changed?
+    assert_predicate cloned_developer, :salary_changed?
   end
 
   def test_clone_of_new_object_marks_as_dirty_only_changed_attributes
     developer = Developer.new name: "Bjorn"
     assert developer.name_changed?            # obviously
-    assert !developer.salary_changed?         # attribute has non-nil default value, so treated as not changed
+    assert_not developer.salary_changed?         # attribute has non-nil default value, so treated as not changed
 
     cloned_developer = developer.clone
-    assert cloned_developer.name_changed?
-    assert !cloned_developer.salary_changed?  # ... and cloned instance should behave same
+    assert_predicate cloned_developer, :name_changed?
+    assert_not cloned_developer.salary_changed?  # ... and cloned instance should behave same
   end
 
   def test_dup_of_saved_object_marks_attributes_as_dirty
     developer = Developer.create! name: "Bjorn", salary: 100000
-    assert !developer.name_changed?
-    assert !developer.salary_changed?
+    assert_not_predicate developer, :name_changed?
+    assert_not_predicate developer, :salary_changed?
 
     cloned_developer = developer.dup
     assert cloned_developer.name_changed?     # both attributes differ from defaults
-    assert cloned_developer.salary_changed?
+    assert_predicate cloned_developer, :salary_changed?
   end
 
   def test_dup_of_saved_object_marks_as_dirty_only_changed_attributes
     developer = Developer.create! name: "Bjorn"
-    assert !developer.name_changed?           # both attributes of saved object should be treated as not changed
-    assert !developer.salary_changed?
+    assert_not developer.name_changed?           # both attributes of saved object should be treated as not changed
+    assert_not_predicate developer, :salary_changed?
 
     cloned_developer = developer.dup
     assert cloned_developer.name_changed?     # ... but on cloned object should be
-    assert !cloned_developer.salary_changed?  # ... BUT salary has non-nil default which should be treated as not changed on cloned instance
+    assert_not cloned_developer.salary_changed?  # ... BUT salary has non-nil default which should be treated as not changed on cloned instance
   end
 
   def test_bignum
@@ -891,11 +891,9 @@ class BasicsTest < ActiveRecord::TestCase
     assert_equal 2147483648, company.rating
   end
 
-  unless current_adapter?(:SQLite3Adapter)
-    def test_bignum_pk
-      company = Company.create!(id: 2147483648, name: "foo")
-      assert_equal company, Company.find(company.id)
-    end
+  def test_bignum_pk
+    company = Company.create!(id: 2147483648, name: "foo")
+    assert_equal company, Company.find(company.id)
   end
 
   # TODO: extend defaults tests to other databases!
@@ -953,14 +951,14 @@ class BasicsTest < ActiveRecord::TestCase
   end
 
   def test_toggle_attribute
-    assert !topics(:first).approved?
+    assert_not_predicate topics(:first), :approved?
     topics(:first).toggle!(:approved)
-    assert topics(:first).approved?
+    assert_predicate topics(:first), :approved?
     topic = topics(:first)
     topic.toggle(:approved)
-    assert !topic.approved?
+    assert_not_predicate topic, :approved?
     topic.reload
-    assert topic.approved?
+    assert_predicate topic, :approved?
   end
 
   def test_reload
@@ -984,7 +982,7 @@ class BasicsTest < ActiveRecord::TestCase
     end
   end
 
-  def test_clear_cash_when_setting_table_name
+  def test_clear_cache_when_setting_table_name
     original_table_name = Joke.table_name
 
     Joke.table_name = "funny_jokes"
@@ -1433,28 +1431,92 @@ class BasicsTest < ActiveRecord::TestCase
   test "resetting column information doesn't remove attribute methods" do
     topic = topics(:first)
 
-    assert_not topic.id_changed?
+    assert_not_predicate topic, :id_changed?
 
     Topic.reset_column_information
 
-    assert_not topic.id_changed?
+    assert_not_predicate topic, :id_changed?
   end
 
   test "ignored columns are not present in columns_hash" do
     cache_columns = Developer.connection.schema_cache.columns_hash(Developer.table_name)
     assert_includes cache_columns.keys, "first_name"
     assert_not_includes Developer.columns_hash.keys, "first_name"
+    assert_not_includes SubDeveloper.columns_hash.keys, "first_name"
+    assert_not_includes SymbolIgnoredDeveloper.columns_hash.keys, "first_name"
   end
 
   test "ignored columns have no attribute methods" do
-    refute Developer.new.respond_to?(:first_name)
-    refute Developer.new.respond_to?(:first_name=)
-    refute Developer.new.respond_to?(:first_name?)
+    assert_not_respond_to Developer.new, :first_name
+    assert_not_respond_to Developer.new, :first_name=
+    assert_not_respond_to Developer.new, :first_name?
+    assert_not_respond_to SubDeveloper.new, :first_name
+    assert_not_respond_to SubDeveloper.new, :first_name=
+    assert_not_respond_to SubDeveloper.new, :first_name?
+    assert_not_respond_to SymbolIgnoredDeveloper.new, :first_name
+    assert_not_respond_to SymbolIgnoredDeveloper.new, :first_name=
+    assert_not_respond_to SymbolIgnoredDeveloper.new, :first_name?
   end
 
   test "ignored columns don't prevent explicit declaration of attribute methods" do
-    assert Developer.new.respond_to?(:last_name)
-    assert Developer.new.respond_to?(:last_name=)
-    assert Developer.new.respond_to?(:last_name?)
+    assert_respond_to Developer.new, :last_name
+    assert_respond_to Developer.new, :last_name=
+    assert_respond_to Developer.new, :last_name?
+    assert_respond_to SubDeveloper.new, :last_name
+    assert_respond_to SubDeveloper.new, :last_name=
+    assert_respond_to SubDeveloper.new, :last_name?
+    assert_respond_to SymbolIgnoredDeveloper.new, :last_name
+    assert_respond_to SymbolIgnoredDeveloper.new, :last_name=
+    assert_respond_to SymbolIgnoredDeveloper.new, :last_name?
+  end
+
+  test "ignored columns are stored as an array of string" do
+    assert_equal(%w(first_name last_name), Developer.ignored_columns)
+    assert_equal(%w(first_name last_name), SymbolIgnoredDeveloper.ignored_columns)
+  end
+
+  test "when #reload called, ignored columns' attribute methods are not defined" do
+    developer = Developer.create!(name: "Developer")
+    assert_not_respond_to developer, :first_name
+    assert_not_respond_to developer, :first_name=
+
+    developer.reload
+
+    assert_not_respond_to developer, :first_name
+    assert_not_respond_to developer, :first_name=
+  end
+
+  test "ignored columns not included in SELECT" do
+    query = Developer.all.to_sql.downcase
+
+    # ignored column
+    assert_not query.include?("first_name")
+
+    # regular column
+    assert query.include?("name")
+  end
+
+  test "column names are quoted when using #from clause and model has ignored columns" do
+    assert_not_empty Developer.ignored_columns
+    query = Developer.from("developers").to_sql
+    quoted_id = "#{Developer.quoted_table_name}.#{Developer.quoted_primary_key}"
+
+    assert_match(/SELECT #{Regexp.escape(quoted_id)}.* FROM developers/, query)
+  end
+
+  test "using table name qualified column names unless having SELECT list explicitly" do
+    assert_equal developers(:david), Developer.from("developers").joins(:shared_computers).take
+  end
+
+  test "protected environments by default is an array with production" do
+    assert_equal ["production"], ActiveRecord::Base.protected_environments
+  end
+
+  def test_protected_environments_are_stored_as_an_array_of_string
+    previous_protected_environments = ActiveRecord::Base.protected_environments
+    ActiveRecord::Base.protected_environments = [:staging, "production"]
+    assert_equal ["staging", "production"], ActiveRecord::Base.protected_environments
+  ensure
+    ActiveRecord::Base.protected_environments = previous_protected_environments
   end
 end
diff --git a/activerecord/test/cases/batches_test.rb b/activerecord/test/cases/batches_test.rb
index 53c1e61ad1..c8163901c6 100644
--- a/activerecord/test/cases/batches_test.rb
+++ b/activerecord/test/cases/batches_test.rb
@@ -313,7 +313,7 @@ class EachTest < ActiveRecord::TestCase
   def test_in_batches_each_record_should_yield_record_if_block_is_given
     assert_queries(6) do
       Post.in_batches(of: 2).each_record do |post|
-        assert post.title.present?
+        assert_predicate post.title, :present?
         assert_kind_of Post, post
       end
     end
@@ -322,7 +322,7 @@ class EachTest < ActiveRecord::TestCase
   def test_in_batches_each_record_should_return_enumerator_if_no_block_given
     assert_queries(6) do
       Post.in_batches(of: 2).each_record.with_index do |post, i|
-        assert post.title.present?
+        assert_predicate post.title, :present?
         assert_kind_of Post, post
       end
     end
@@ -353,24 +353,24 @@ class EachTest < ActiveRecord::TestCase
 
   def test_in_batches_should_not_be_loaded
     Post.in_batches(of: 1) do |relation|
-      assert_not relation.loaded?
+      assert_not_predicate relation, :loaded?
     end
 
     Post.in_batches(of: 1, load: false) do |relation|
-      assert_not relation.loaded?
+      assert_not_predicate relation, :loaded?
     end
   end
 
   def test_in_batches_should_be_loaded
     Post.in_batches(of: 1, load: true) do |relation|
-      assert relation.loaded?
+      assert_predicate relation, :loaded?
     end
   end
 
   def test_in_batches_if_not_loaded_executes_more_queries
     assert_queries(@total + 1) do
       Post.in_batches(of: 1, load: false) do |relation|
-        assert_not relation.loaded?
+        assert_not_predicate relation, :loaded?
       end
     end
   end
@@ -508,7 +508,7 @@ class EachTest < ActiveRecord::TestCase
   def test_in_batches_relations_update_all_should_not_affect_matching_records_in_other_batches
     Post.update_all(author_id: 0)
     person = Post.last
-    person.update_attributes(author_id: 1)
+    person.update(author_id: 1)
 
     Post.in_batches(of: 2) do |batch|
       batch.where("author_id >= 1").update_all("author_id = author_id + 1")
@@ -586,32 +586,19 @@ class EachTest < ActiveRecord::TestCase
     end
   end
 
-  test ".error_on_ignored_order_or_limit= is deprecated" do
-    begin
-      prev = ActiveRecord::Base.error_on_ignored_order
-      assert_deprecated "Please use error_on_ignored_order= instead." do
-        ActiveRecord::Base.error_on_ignored_order_or_limit = true
-      end
-      assert ActiveRecord::Base.error_on_ignored_order
-    ensure
-      ActiveRecord::Base.error_on_ignored_order = prev
-    end
-  end
-
-  test ".error_on_ignored_order_or_limit is deprecated" do
-    expected = ActiveRecord::Base.error_on_ignored_order
-    actual = assert_deprecated "Please use error_on_ignored_order instead." do
-      ActiveRecord::Base.error_on_ignored_order_or_limit
-    end
-    assert_equal expected, actual
-  end
+  test ".find_each respects table alias" do
+    assert_queries(1) do
+      table_alias = Post.arel_table.alias("omg_posts")
+      table_metadata = ActiveRecord::TableMetadata.new(Post, table_alias)
+      predicate_builder = ActiveRecord::PredicateBuilder.new(table_metadata)
 
-  test "#error_on_ignored_order_or_limit is deprecated" do
-    expected = ActiveRecord::Base.error_on_ignored_order
-    actual = assert_deprecated "Please use error_on_ignored_order instead." do
-      Post.new.error_on_ignored_order_or_limit
+      posts = ActiveRecord::Relation.create(
+        Post,
+        table: table_alias,
+        predicate_builder: predicate_builder
+      )
+      posts.find_each {}
     end
-    assert_equal expected, actual
   end
 
   test ".find_each bypasses the query cache for its own queries" do
diff --git a/activerecord/test/cases/cache_key_test.rb b/activerecord/test/cases/cache_key_test.rb
index 8f2f2c6186..3a569f226e 100644
--- a/activerecord/test/cases/cache_key_test.rb
+++ b/activerecord/test/cases/cache_key_test.rb
@@ -38,8 +38,8 @@ module ActiveRecord
     end
 
     test "cache_version is only there when versioning is on" do
-      assert CacheMeWithVersion.create.cache_version.present?
-      assert_not CacheMe.create.cache_version.present?
+      assert_predicate CacheMeWithVersion.create.cache_version, :present?
+      assert_not_predicate CacheMe.create.cache_version, :present?
     end
 
     test "cache_key_with_version always has both key and version" do
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index 39dff19b78..080d2a54bc 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -21,7 +21,7 @@ require "models/comment"
 require "models/rating"
 
 class CalculationsTest < ActiveRecord::TestCase
-  fixtures :companies, :accounts, :topics, :speedometers, :minivans, :books
+  fixtures :companies, :accounts, :topics, :speedometers, :minivans, :books, :posts, :comments
 
   def test_should_sum_field
     assert_equal 318, Account.sum(:credit_limit)
@@ -236,6 +236,24 @@ class CalculationsTest < ActiveRecord::TestCase
     end
   end
 
+  def test_count_with_eager_loading_and_custom_order
+    posts = Post.includes(:comments).order("comments.id")
+    assert_queries(1) { assert_equal 11, posts.count }
+    assert_queries(1) { assert_equal 11, posts.count(:all) }
+  end
+
+  def test_count_with_eager_loading_and_custom_order_and_distinct
+    posts = Post.includes(:comments).order("comments.id").distinct
+    assert_queries(1) { assert_equal 11, posts.count }
+    assert_queries(1) { assert_equal 11, posts.count(:all) }
+  end
+
+  def test_distinct_count_all_with_custom_select_and_order
+    accounts = Account.distinct.select("credit_limit % 10").order(Arel.sql("credit_limit % 10"))
+    assert_queries(1) { assert_equal 3, accounts.count(:all) }
+    assert_queries(1) { assert_equal 3, accounts.load.size }
+  end
+
   def test_distinct_count_with_order_and_limit
     assert_equal 4, Account.distinct.order(:firm_id).limit(4).count
   end
@@ -260,6 +278,10 @@ class CalculationsTest < ActiveRecord::TestCase
     assert_equal 3, Account.joins(:firm).distinct.order(:firm_id).limit(3).offset(2).count
   end
 
+  def test_distinct_count_with_group_by_and_order_and_limit
+    assert_equal({ 6 => 2 }, Account.group(:firm_id).distinct.order("1 DESC").limit(1).count)
+  end
+
   def test_should_group_by_summed_field_having_condition
     c = Account.group(:firm_id).having("sum(credit_limit) > 50").sum(:credit_limit)
     assert_nil        c[1]
@@ -518,8 +540,7 @@ class CalculationsTest < ActiveRecord::TestCase
   end
 
   def test_should_sum_expression
-    # Oracle adapter returns floating point value 636.0 after SUM
-    if current_adapter?(:OracleAdapter)
+    if current_adapter?(:SQLite3Adapter, :Mysql2Adapter, :PostgreSQLAdapter, :OracleAdapter)
       assert_equal 636, Account.sum("2 * credit_limit")
     else
       assert_equal 636, Account.sum("2 * credit_limit").to_i
@@ -660,14 +681,14 @@ class CalculationsTest < ActiveRecord::TestCase
   end
 
   def test_pluck_with_selection_clause
-    assert_equal [50, 53, 55, 60], Account.pluck("DISTINCT credit_limit").sort
-    assert_equal [50, 53, 55, 60], Account.pluck("DISTINCT accounts.credit_limit").sort
-    assert_equal [50, 53, 55, 60], Account.pluck("DISTINCT(credit_limit)").sort
+    assert_equal [50, 53, 55, 60], Account.pluck(Arel.sql("DISTINCT credit_limit")).sort
+    assert_equal [50, 53, 55, 60], Account.pluck(Arel.sql("DISTINCT accounts.credit_limit")).sort
+    assert_equal [50, 53, 55, 60], Account.pluck(Arel.sql("DISTINCT(credit_limit)")).sort
 
     # MySQL returns "SUM(DISTINCT(credit_limit))" as the column name unless
     # an alias is provided.  Without the alias, the column cannot be found
     # and properly typecast.
-    assert_equal [50 + 53 + 55 + 60], Account.pluck("SUM(DISTINCT(credit_limit)) as credit_limit")
+    assert_equal [50 + 53 + 55 + 60], Account.pluck(Arel.sql("SUM(DISTINCT(credit_limit)) as credit_limit"))
   end
 
   def test_plucks_with_ids
@@ -679,6 +700,11 @@ class CalculationsTest < ActiveRecord::TestCase
     assert_equal [], Topic.includes(:replies).limit(1).where("0 = 1").pluck(:id)
   end
 
+  def test_pluck_with_includes_offset
+    assert_equal [5], Topic.includes(:replies).order(:id).offset(4).pluck(:id)
+    assert_equal [], Topic.includes(:replies).order(:id).offset(5).pluck(:id)
+  end
+
   def test_pluck_not_auto_table_name_prefix_if_column_included
     Company.create!(name: "test", contracts: [Contract.new(developer_id: 7)])
     ids = Company.includes(:contracts).pluck(:developer_id)
@@ -769,10 +795,27 @@ class CalculationsTest < ActiveRecord::TestCase
     companies = Company.order(:name).limit(3).load
 
     assert_queries 1 do
-      assert_equal ["37signals", "Apex", "Ex Nihilo"], companies.pluck("DISTINCT name")
+      assert_equal ["37signals", "Apex", "Ex Nihilo"], companies.pluck(Arel.sql("DISTINCT name"))
     end
   end
 
+  def test_pick_one
+    assert_equal "The First Topic", Topic.order(:id).pick(:heading)
+    assert_nil Topic.none.pick(:heading)
+    assert_nil Topic.where("1=0").pick(:heading)
+  end
+
+  def test_pick_two
+    assert_equal ["David", "david@loudthinking.com"], Topic.order(:id).pick(:author_name, :author_email_address)
+    assert_nil Topic.none.pick(:author_name, :author_email_address)
+    assert_nil Topic.where("1=0").pick(:author_name, :author_email_address)
+  end
+
+  def test_pick_delegate_to_all
+    cool_first = minivans(:cool_first)
+    assert_equal cool_first.color, Minivan.pick(:color)
+  end
+
   def test_grouped_calculation_with_polymorphic_relation
     part = ShipPart.create!(name: "has trinket")
     part.trinkets.create!
diff --git a/activerecord/test/cases/callbacks_test.rb b/activerecord/test/cases/callbacks_test.rb
index 55c7475f46..b9ba51c730 100644
--- a/activerecord/test/cases/callbacks_test.rb
+++ b/activerecord/test/cases/callbacks_test.rb
@@ -385,60 +385,60 @@ class CallbacksTest < ActiveRecord::TestCase
   end
 
   def assert_save_callbacks_not_called(someone)
-    assert !someone.after_save_called
-    assert !someone.after_create_called
-    assert !someone.after_update_called
+    assert_not someone.after_save_called
+    assert_not someone.after_create_called
+    assert_not someone.after_update_called
   end
   private :assert_save_callbacks_not_called
 
   def test_before_create_throwing_abort
     someone = CallbackHaltedDeveloper.new
     someone.cancel_before_create = true
-    assert someone.valid?
-    assert !someone.save
+    assert_predicate someone, :valid?
+    assert_not someone.save
     assert_save_callbacks_not_called(someone)
   end
 
   def test_before_save_throwing_abort
     david = DeveloperWithCanceledCallbacks.find(1)
-    assert david.valid?
-    assert !david.save
+    assert_predicate david, :valid?
+    assert_not david.save
     exc = assert_raise(ActiveRecord::RecordNotSaved) { david.save! }
     assert_equal david, exc.record
 
     david = DeveloperWithCanceledCallbacks.find(1)
     david.salary = 10_000_000
-    assert !david.valid?
-    assert !david.save
+    assert_not_predicate david, :valid?
+    assert_not david.save
     assert_raise(ActiveRecord::RecordInvalid) { david.save! }
 
     someone = CallbackHaltedDeveloper.find(1)
     someone.cancel_before_save = true
-    assert someone.valid?
-    assert !someone.save
+    assert_predicate someone, :valid?
+    assert_not someone.save
     assert_save_callbacks_not_called(someone)
   end
 
   def test_before_update_throwing_abort
     someone = CallbackHaltedDeveloper.find(1)
     someone.cancel_before_update = true
-    assert someone.valid?
-    assert !someone.save
+    assert_predicate someone, :valid?
+    assert_not someone.save
     assert_save_callbacks_not_called(someone)
   end
 
   def test_before_destroy_throwing_abort
     david = DeveloperWithCanceledCallbacks.find(1)
-    assert !david.destroy
+    assert_not david.destroy
     exc = assert_raise(ActiveRecord::RecordNotDestroyed) { david.destroy! }
     assert_equal david, exc.record
     assert_not_nil ImmutableDeveloper.find_by_id(1)
 
     someone = CallbackHaltedDeveloper.find(1)
     someone.cancel_before_destroy = true
-    assert !someone.destroy
+    assert_not someone.destroy
     assert_raise(ActiveRecord::RecordNotDestroyed) { someone.destroy! }
-    assert !someone.after_destroy_called
+    assert_not someone.after_destroy_called
   end
 
   def test_callback_throwing_abort
@@ -467,12 +467,12 @@ class CallbacksTest < ActiveRecord::TestCase
 
   def test_inheritance_of_callbacks
     parent = ParentDeveloper.new
-    assert !parent.after_save_called
+    assert_not parent.after_save_called
     parent.save
     assert parent.after_save_called
 
     child = ChildDeveloper.new
-    assert !child.after_save_called
+    assert_not child.after_save_called
     child.save
     assert child.after_save_called
   end
diff --git a/activerecord/test/cases/clone_test.rb b/activerecord/test/cases/clone_test.rb
index 3187e6aed5..eea36ee736 100644
--- a/activerecord/test/cases/clone_test.rb
+++ b/activerecord/test/cases/clone_test.rb
@@ -12,7 +12,7 @@ module ActiveRecord
       cloned = topic.clone
       assert topic.persisted?, "topic persisted"
       assert cloned.persisted?, "topic persisted"
-      assert !cloned.new_record?, "topic is not new"
+      assert_not cloned.new_record?, "topic is not new"
     end
 
     def test_stays_frozen
@@ -21,7 +21,7 @@ module ActiveRecord
 
       cloned = topic.clone
       assert cloned.persisted?, "topic persisted"
-      assert !cloned.new_record?, "topic is not new"
+      assert_not cloned.new_record?, "topic is not new"
       assert cloned.frozen?, "topic should be frozen"
     end
 
@@ -36,7 +36,7 @@ module ActiveRecord
       cloned = Topic.new
       clone = cloned.clone
       cloned.freeze
-      assert_not clone.frozen?
+      assert_not_predicate clone, :frozen?
     end
   end
 end
diff --git a/activerecord/test/cases/collection_cache_key_test.rb b/activerecord/test/cases/collection_cache_key_test.rb
index dbe6857487..a5d908344a 100644
--- a/activerecord/test/cases/collection_cache_key_test.rb
+++ b/activerecord/test/cases/collection_cache_key_test.rb
@@ -24,7 +24,7 @@ module ActiveRecord
 
       /\Adevelopers\/query-(\h+)-(\d+)-(\d+)\z/ =~ developers.cache_key
 
-      assert_equal Digest::MD5.hexdigest(developers.to_sql), $1
+      assert_equal ActiveSupport::Digest.hexdigest(developers.to_sql), $1
       assert_equal developers.count.to_s, $2
       assert_equal last_developer_timestamp.to_s(ActiveRecord::Base.cache_timestamp_format), $3
     end
@@ -37,7 +37,7 @@ module ActiveRecord
 
       /\Adevelopers\/query-(\h+)-(\d+)-(\d+)\z/ =~ developers.cache_key
 
-      assert_equal Digest::MD5.hexdigest(developers.to_sql), $1
+      assert_equal ActiveSupport::Digest.hexdigest(developers.to_sql), $1
       assert_equal developers.count.to_s, $2
       assert_equal last_developer_timestamp.to_s(ActiveRecord::Base.cache_timestamp_format), $3
     end
@@ -50,11 +50,43 @@ module ActiveRecord
 
       /\Adevelopers\/query-(\h+)-(\d+)-(\d+)\z/ =~ developers.cache_key
 
-      assert_equal Digest::MD5.hexdigest(developers.to_sql), $1
+      assert_equal ActiveSupport::Digest.hexdigest(developers.to_sql), $1
       assert_equal developers.count.to_s, $2
       assert_equal last_developer_timestamp.to_s(ActiveRecord::Base.cache_timestamp_format), $3
     end
 
+    test "cache_key for relation with table alias" do
+      table_alias = Developer.arel_table.alias("omg_developers")
+      table_metadata = ActiveRecord::TableMetadata.new(Developer, table_alias)
+      predicate_builder = ActiveRecord::PredicateBuilder.new(table_metadata)
+
+      developers = ActiveRecord::Relation.create(
+        Developer,
+        table: table_alias,
+        predicate_builder: predicate_builder
+      )
+      developers = developers.where(salary: 100000).order(updated_at: :desc)
+      last_developer_timestamp = developers.first.updated_at
+
+      assert_match(/\Adevelopers\/query-(\h+)-(\d+)-(\d+)\z/, developers.cache_key)
+
+      /\Adevelopers\/query-(\h+)-(\d+)-(\d+)\z/ =~ developers.cache_key
+
+      assert_equal ActiveSupport::Digest.hexdigest(developers.to_sql), $1
+      assert_equal developers.count.to_s, $2
+      assert_equal last_developer_timestamp.to_s(ActiveRecord::Base.cache_timestamp_format), $3
+    end
+
+    test "cache_key for relation with includes" do
+      comments = Comment.includes(:post).where("posts.type": "Post")
+      assert_match(/\Acomments\/query-(\h+)-(\d+)-(\d+)\z/, comments.cache_key)
+    end
+
+    test "cache_key for loaded relation with includes" do
+      comments = Comment.includes(:post).where("posts.type": "Post").load
+      assert_match(/\Acomments\/query-(\h+)-(\d+)-(\d+)\z/, comments.cache_key)
+    end
+
     test "it triggers at most one query" do
       developers = Developer.where(name: "David")
 
@@ -113,5 +145,17 @@ module ActiveRecord
 
       assert_match(/\Adevelopers\/query-(\h+)-(\d+)-(\d+)\z/, developers.cache_key)
     end
+
+    test "cache_key with a relation having distinct and order" do
+      developers = Developer.distinct.order(:salary).limit(5)
+
+      assert_match(/\Adevelopers\/query-(\h+)-(\d+)-(\d+)\z/, developers.cache_key)
+    end
+
+    test "cache_key with a relation having custom select and order" do
+      developers = Developer.select("name AS dev_name").order("dev_name DESC").limit(5)
+
+      assert_match(/\Adevelopers\/query-(\h+)-(\d+)-(\d+)\z/, developers.cache_key)
+    end
   end
 end
diff --git a/activerecord/test/cases/comment_test.rb b/activerecord/test/cases/comment_test.rb
index f2ec5d6518..584e03d196 100644
--- a/activerecord/test/cases/comment_test.rb
+++ b/activerecord/test/cases/comment_test.rb
@@ -111,7 +111,7 @@ if ActiveRecord::Base.connection.supports_comments?
 
       # And check that these changes are reflected in dump
       output = dump_table_schema "commenteds"
-      assert_match %r[create_table "commenteds",.+\s+comment: "A table with comment"], output
+      assert_match %r[create_table "commenteds",.*\s+comment: "A table with comment"], output
       assert_match %r[t\.string\s+"name",\s+comment: "Comment should help clarify the column purpose"], output
       assert_match %r[t\.string\s+"obvious"\n], output
       assert_match %r[t\.string\s+"content",\s+comment: "Whoa, content describes itself!"], output
@@ -142,5 +142,27 @@ if ActiveRecord::Base.connection.supports_comments?
       assert_match %r[t\.string\s+"absent_comment"\n], output
       assert_no_match %r[t\.string\s+"absent_comment", comment:\n], output
     end
+
+    def test_change_table_comment
+      @connection.change_table_comment :commenteds, "Edited table comment"
+      assert_equal "Edited table comment", @connection.table_comment("commenteds")
+    end
+
+    def test_change_table_comment_to_nil
+      @connection.change_table_comment :commenteds, nil
+      assert_nil @connection.table_comment("commenteds")
+    end
+
+    def test_change_column_comment
+      @connection.change_column_comment :commenteds, :name, "Edited column comment"
+      column = Commented.columns_hash["name"]
+      assert_equal "Edited column comment", column.comment
+    end
+
+    def test_change_column_comment_to_nil
+      @connection.change_column_comment :commenteds, :name, nil
+      column = Commented.columns_hash["name"]
+      assert_nil column.comment
+    end
   end
 end
diff --git a/activerecord/test/cases/connection_adapters/adapter_leasing_test.rb b/activerecord/test/cases/connection_adapters/adapter_leasing_test.rb
index 82c6cf8dea..72838ff56b 100644
--- a/activerecord/test/cases/connection_adapters/adapter_leasing_test.rb
+++ b/activerecord/test/cases/connection_adapters/adapter_leasing_test.rb
@@ -45,11 +45,11 @@ module ActiveRecord
 
         # Make sure the pool marks the connection in use
         assert_equal @adapter, pool.connection
-        assert @adapter.in_use?
+        assert_predicate @adapter, :in_use?
 
         # Close should put the adapter back in the pool
         @adapter.close
-        assert_not @adapter.in_use?
+        assert_not_predicate @adapter, :in_use?
 
         assert_equal @adapter, pool.connection
       end
diff --git a/activerecord/test/cases/connection_adapters/connection_handler_test.rb b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
index 74d0ed348e..b8e623f17b 100644
--- a/activerecord/test/cases/connection_adapters/connection_handler_test.rb
+++ b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
@@ -1,10 +1,15 @@
 # frozen_string_literal: true
 
 require "cases/helper"
+require "models/person"
 
 module ActiveRecord
   module ConnectionAdapters
     class ConnectionHandlerTest < ActiveRecord::TestCase
+      self.use_transactional_tests = false
+
+      fixtures :people
+
       def setup
         @handler = ConnectionHandler.new
         @spec_name = "primary"
@@ -66,6 +71,56 @@ module ActiveRecord
         ENV["RAILS_ENV"] = previous_env
       end
 
+      unless in_memory_db?
+        def test_establish_connection_using_3_level_config_defaults_to_default_env_primary_db
+          previous_env, ENV["RAILS_ENV"] = ENV["RAILS_ENV"], "default_env"
+
+          config = {
+            "default_env" => {
+              "primary"  => { "adapter" => "sqlite3", "database" => "db/primary.sqlite3" },
+              "readonly" => { "adapter" => "sqlite3", "database" => "db/readonly.sqlite3" }
+            },
+            "another_env" => {
+              "primary"  => { "adapter" => "sqlite3", "database" => "db/another-primary.sqlite3" },
+              "readonly" => { "adapter" => "sqlite3", "database" => "db/another-readonly.sqlite3" }
+            }
+          }
+          @prev_configs, ActiveRecord::Base.configurations = ActiveRecord::Base.configurations, config
+
+          ActiveRecord::Base.establish_connection
+
+          assert_match "db/primary.sqlite3", ActiveRecord::Base.connection.pool.spec.config[:database]
+        ensure
+          ActiveRecord::Base.configurations = @prev_configs
+          ENV["RAILS_ENV"] = previous_env
+          ActiveRecord::Base.establish_connection(:arunit)
+          FileUtils.rm_rf "db"
+        end
+
+        def test_establish_connection_using_2_level_config_defaults_to_default_env_primary_db
+          previous_env, ENV["RAILS_ENV"] = ENV["RAILS_ENV"], "default_env"
+
+          config = {
+            "default_env" => {
+              "adapter" => "sqlite3", "database" => "db/primary.sqlite3"
+            },
+            "another_env" => {
+              "adapter" => "sqlite3", "database" => "db/bad-primary.sqlite3"
+            }
+          }
+          @prev_configs, ActiveRecord::Base.configurations = ActiveRecord::Base.configurations, config
+
+          ActiveRecord::Base.establish_connection
+
+          assert_match "db/primary.sqlite3", ActiveRecord::Base.connection.pool.spec.config[:database]
+        ensure
+          ActiveRecord::Base.configurations = @prev_configs
+          ENV["RAILS_ENV"] = previous_env
+          ActiveRecord::Base.establish_connection(:arunit)
+          FileUtils.rm_rf "db"
+        end
+      end
+
       def test_establish_connection_using_two_level_configurations
         config = { "development" => { "adapter" => "sqlite3", "database" => "db/primary.sqlite3" } }
         @prev_configs, ActiveRecord::Base.configurations = ActiveRecord::Base.configurations, config
@@ -98,11 +153,11 @@ module ActiveRecord
       end
 
       def test_active_connections?
-        assert !@handler.active_connections?
+        assert_not_predicate @handler, :active_connections?
         assert @handler.retrieve_connection(@spec_name)
-        assert @handler.active_connections?
+        assert_predicate @handler, :active_connections?
         @handler.clear_active_connections!
-        assert !@handler.active_connections?
+        assert_not_predicate @handler, :active_connections?
       end
 
       def test_retrieve_connection_pool
@@ -139,6 +194,75 @@ module ActiveRecord
           rd.close
         end
 
+        def test_forked_child_doesnt_mangle_parent_connection
+          object_id = ActiveRecord::Base.connection.object_id
+          assert_predicate ActiveRecord::Base.connection, :active?
+
+          rd, wr = IO.pipe
+          rd.binmode
+          wr.binmode
+
+          pid = fork {
+            rd.close
+            if ActiveRecord::Base.connection.active?
+              wr.write Marshal.dump ActiveRecord::Base.connection.object_id
+            end
+            wr.close
+
+            exit # allow finalizers to run
+          }
+
+          wr.close
+
+          Process.waitpid pid
+          assert_not_equal object_id, Marshal.load(rd.read)
+          rd.close
+
+          assert_equal 3, ActiveRecord::Base.connection.select_value("SELECT COUNT(*) FROM people")
+        end
+
+        unless in_memory_db?
+          def test_forked_child_recovers_from_disconnected_parent
+            object_id = ActiveRecord::Base.connection.object_id
+            assert_predicate ActiveRecord::Base.connection, :active?
+
+            rd, wr = IO.pipe
+            rd.binmode
+            wr.binmode
+
+            outer_pid = fork {
+              ActiveRecord::Base.connection.disconnect!
+
+              pid = fork {
+                rd.close
+                if ActiveRecord::Base.connection.active?
+                  pair = [ActiveRecord::Base.connection.object_id,
+                          ActiveRecord::Base.connection.select_value("SELECT COUNT(*) FROM people")]
+                  wr.write Marshal.dump pair
+                end
+                wr.close
+
+                exit # allow finalizers to run
+              }
+
+              Process.waitpid pid
+            }
+
+            wr.close
+
+            Process.waitpid outer_pid
+            child_id, child_count = Marshal.load(rd.read)
+
+            assert_not_equal object_id, child_id
+            rd.close
+
+            assert_equal 3, child_count
+
+            # Outer connection is unaffected
+            assert_equal 6, ActiveRecord::Base.connection.select_value("SELECT 2 * COUNT(*) FROM people")
+          end
+        end
+
         def test_retrieve_connection_pool_copies_schema_cache_from_ancestor_pool
           @pool.schema_cache = @pool.connection.schema_cache
           @pool.schema_cache.add("posts")
@@ -200,15 +324,15 @@ module ActiveRecord
         def test_a_class_using_custom_pool_and_switching_back_to_primary
           klass2 = Class.new(Base) { def self.name; "klass2"; end }
 
-          assert_equal klass2.connection.object_id, ActiveRecord::Base.connection.object_id
+          assert_same klass2.connection, ActiveRecord::Base.connection
 
           pool = klass2.establish_connection(ActiveRecord::Base.connection_pool.spec.config)
-          assert_equal klass2.connection.object_id, pool.connection.object_id
-          refute_equal klass2.connection.object_id, ActiveRecord::Base.connection.object_id
+          assert_same klass2.connection, pool.connection
+          assert_not_same klass2.connection, ActiveRecord::Base.connection
 
           klass2.remove_connection
 
-          assert_equal klass2.connection.object_id, ActiveRecord::Base.connection.object_id
+          assert_same klass2.connection, ActiveRecord::Base.connection
         end
 
         def test_connection_specification_name_should_fallback_to_parent
@@ -223,8 +347,8 @@ module ActiveRecord
         def test_remove_connection_should_not_remove_parent
           klass2 = Class.new(Base) { def self.name; "klass2"; end }
           klass2.remove_connection
-          refute_nil ActiveRecord::Base.connection.object_id
-          assert_equal klass2.connection.object_id, ActiveRecord::Base.connection.object_id
+          assert_not_nil ActiveRecord::Base.connection
+          assert_same klass2.connection, ActiveRecord::Base.connection
         end
       end
     end
diff --git a/activerecord/test/cases/connection_adapters/schema_cache_test.rb b/activerecord/test/cases/connection_adapters/schema_cache_test.rb
index 006be9e65d..67496381d1 100644
--- a/activerecord/test/cases/connection_adapters/schema_cache_test.rb
+++ b/activerecord/test/cases/connection_adapters/schema_cache_test.rb
@@ -22,8 +22,8 @@ module ActiveRecord
 
         new_cache = YAML.load(YAML.dump(@cache))
         assert_no_queries do
-          assert_equal 11, new_cache.columns("posts").size
-          assert_equal 11, new_cache.columns_hash("posts").size
+          assert_equal 12, new_cache.columns("posts").size
+          assert_equal 12, new_cache.columns_hash("posts").size
           assert new_cache.data_sources("posts")
           assert_equal "id", new_cache.primary_keys("posts")
         end
@@ -75,8 +75,8 @@ module ActiveRecord
         @cache = Marshal.load(Marshal.dump(@cache))
 
         assert_no_queries do
-          assert_equal 11, @cache.columns("posts").size
-          assert_equal 11, @cache.columns_hash("posts").size
+          assert_equal 12, @cache.columns("posts").size
+          assert_equal 12, @cache.columns_hash("posts").size
           assert @cache.data_sources("posts")
           assert_equal "id", @cache.primary_keys("posts")
         end
diff --git a/activerecord/test/cases/connection_adapters/type_lookup_test.rb b/activerecord/test/cases/connection_adapters/type_lookup_test.rb
index 917a04ebc3..1c79d776f0 100644
--- a/activerecord/test/cases/connection_adapters/type_lookup_test.rb
+++ b/activerecord/test/cases/connection_adapters/type_lookup_test.rb
@@ -82,11 +82,11 @@ unless current_adapter?(:PostgreSQLAdapter) # PostgreSQL does not use type strin
         end
 
         def test_bigint_limit
-          cast_type = @connection.send(:type_map).lookup("bigint")
+          limit = @connection.send(:type_map).lookup("bigint").send(:_limit)
           if current_adapter?(:OracleAdapter)
-            assert_equal 19, cast_type.limit
+            assert_equal 19, limit
           else
-            assert_equal 8, cast_type.limit
+            assert_equal 8, limit
           end
         end
 
diff --git a/activerecord/test/cases/connection_management_test.rb b/activerecord/test/cases/connection_management_test.rb
index 9d6ecbde78..0941ee3309 100644
--- a/activerecord/test/cases/connection_management_test.rb
+++ b/activerecord/test/cases/connection_management_test.rb
@@ -27,7 +27,7 @@ module ActiveRecord
 
         # make sure we have an active connection
         assert ActiveRecord::Base.connection
-        assert ActiveRecord::Base.connection_handler.active_connections?
+        assert_predicate ActiveRecord::Base.connection_handler, :active_connections?
       end
 
       def test_app_delegation
@@ -47,14 +47,14 @@ module ActiveRecord
       def test_connections_are_cleared_after_body_close
         _, _, body = @management.call(@env)
         body.close
-        assert !ActiveRecord::Base.connection_handler.active_connections?
+        assert_not_predicate ActiveRecord::Base.connection_handler, :active_connections?
       end
 
       def test_active_connections_are_not_cleared_on_body_close_during_transaction
         ActiveRecord::Base.transaction do
           _, _, body = @management.call(@env)
           body.close
-          assert ActiveRecord::Base.connection_handler.active_connections?
+          assert_predicate ActiveRecord::Base.connection_handler, :active_connections?
         end
       end
 
@@ -62,7 +62,7 @@ module ActiveRecord
         app       = Class.new(App) { def call(env); raise NotImplementedError; end }.new
         explosive = middleware(app)
         assert_raises(NotImplementedError) { explosive.call(@env) }
-        assert !ActiveRecord::Base.connection_handler.active_connections?
+        assert_not_predicate ActiveRecord::Base.connection_handler, :active_connections?
       end
 
       def test_connections_not_closed_if_exception_inside_transaction
@@ -70,14 +70,14 @@ module ActiveRecord
           app               = Class.new(App) { def call(env); raise RuntimeError; end }.new
           explosive         = middleware(app)
           assert_raises(RuntimeError) { explosive.call(@env) }
-          assert ActiveRecord::Base.connection_handler.active_connections?
+          assert_predicate ActiveRecord::Base.connection_handler, :active_connections?
         end
       end
 
       test "doesn't clear active connections when running in a test case" do
         executor.wrap do
           @management.call(@env)
-          assert ActiveRecord::Base.connection_handler.active_connections?
+          assert_predicate ActiveRecord::Base.connection_handler, :active_connections?
         end
       end
 
@@ -85,7 +85,7 @@ module ActiveRecord
         body = Class.new(String) { def to_path; "/path"; end }.new
         app = lambda { |_| [200, {}, body] }
         response_body = middleware(app).call(@env)[2]
-        assert response_body.respond_to?(:to_path)
+        assert_respond_to response_body, :to_path
         assert_equal "/path", response_body.to_path
       end
 
diff --git a/activerecord/test/cases/connection_pool_test.rb b/activerecord/test/cases/connection_pool_test.rb
index 2bfe490602..9ac03629c3 100644
--- a/activerecord/test/cases/connection_pool_test.rb
+++ b/activerecord/test/cases/connection_pool_test.rb
@@ -35,12 +35,12 @@ module ActiveRecord
 
       def test_checkout_after_close
         connection = pool.connection
-        assert connection.in_use?
+        assert_predicate connection, :in_use?
 
         connection.close
-        assert !connection.in_use?
+        assert_not_predicate connection, :in_use?
 
-        assert pool.connection.in_use?
+        assert_predicate pool.connection, :in_use?
       end
 
       def test_released_connection_moves_between_threads
@@ -80,18 +80,18 @@ module ActiveRecord
       end
 
       def test_active_connection_in_use
-        assert !pool.active_connection?
+        assert_not_predicate pool, :active_connection?
         main_thread = pool.connection
 
-        assert pool.active_connection?
+        assert_predicate pool, :active_connection?
 
         main_thread.close
 
-        assert !pool.active_connection?
+        assert_not_predicate pool, :active_connection?
       end
 
       def test_full_pool_exception
-        @pool.size.times { @pool.checkout }
+        @pool.size.times { assert @pool.checkout }
         assert_raises(ConnectionTimeoutError) do
           @pool.checkout
         end
@@ -156,13 +156,60 @@ module ActiveRecord
         @pool.connections.each { |conn| conn.close if conn.in_use? }
       end
 
+      def test_flush
+        idle_conn = @pool.checkout
+        recent_conn = @pool.checkout
+        active_conn = @pool.checkout
+
+        @pool.checkin idle_conn
+        @pool.checkin recent_conn
+
+        assert_equal 3, @pool.connections.length
+
+        def idle_conn.seconds_idle
+          1000
+        end
+
+        @pool.flush(30)
+
+        assert_equal 2, @pool.connections.length
+
+        assert_equal [recent_conn, active_conn].sort_by(&:__id__), @pool.connections.sort_by(&:__id__)
+      ensure
+        @pool.checkin active_conn
+      end
+
+      def test_flush_bang
+        idle_conn = @pool.checkout
+        recent_conn = @pool.checkout
+        active_conn = @pool.checkout
+        _dead_conn = Thread.new { @pool.checkout }.join
+
+        @pool.checkin idle_conn
+        @pool.checkin recent_conn
+
+        assert_equal 4, @pool.connections.length
+
+        def idle_conn.seconds_idle
+          1000
+        end
+
+        @pool.flush!
+
+        assert_equal 1, @pool.connections.length
+
+        assert_equal [active_conn].sort_by(&:__id__), @pool.connections.sort_by(&:__id__)
+      ensure
+        @pool.checkin active_conn
+      end
+
       def test_remove_connection
         conn = @pool.checkout
-        assert conn.in_use?
+        assert_predicate conn, :in_use?
 
         length = @pool.connections.length
         @pool.remove conn
-        assert conn.in_use?
+        assert_predicate conn, :in_use?
         assert_equal(length - 1, @pool.connections.length)
       ensure
         conn.close
@@ -177,11 +224,11 @@ module ActiveRecord
       end
 
       def test_active_connection?
-        assert !@pool.active_connection?
+        assert_not_predicate @pool, :active_connection?
         assert @pool.connection
-        assert @pool.active_connection?
+        assert_predicate @pool, :active_connection?
         @pool.release_connection
-        assert !@pool.active_connection?
+        assert_not_predicate @pool, :active_connection?
       end
 
       def test_checkout_behaviour
@@ -205,6 +252,14 @@ module ActiveRecord
         end.join
       end
 
+      def test_checkout_order_is_lifo
+        conn1 = @pool.checkout
+        conn2 = @pool.checkout
+        @pool.checkin conn1
+        @pool.checkin conn2
+        assert_equal [conn2, conn1], 2.times.map { @pool.checkout }
+      end
+
       # The connection pool is "fair" if threads waiting for
       # connections receive them in the order in which they began
       # waiting.  This ensures that we don't timeout one HTTP request
@@ -414,6 +469,7 @@ module ActiveRecord
       end
 
       def test_non_bang_disconnect_and_clear_reloadable_connections_throw_exception_if_threads_dont_return_their_conns
+        Thread.report_on_exception, original_report_on_exception = false, Thread.report_on_exception
         @pool.checkout_timeout = 0.001 # no need to delay test suite by waiting the whole full default timeout
         [:disconnect, :clear_reloadable_connections].each do |group_action_method|
           @pool.with_connection do |connection|
@@ -422,6 +478,8 @@ module ActiveRecord
             end
           end
         end
+      ensure
+        Thread.report_on_exception = original_report_on_exception
       end
 
       def test_disconnect_and_clear_reloadable_connections_attempt_to_wait_for_threads_to_return_their_conns
@@ -438,7 +496,7 @@ module ActiveRecord
               assert_nil timed_join_result
 
               # assert that since this is within default timeout our connection hasn't been forcefully taken away from us
-              assert @pool.active_connection?
+              assert_predicate @pool, :active_connection?
             end
           ensure
             thread.join if thread && !timed_join_result # clean up the other thread
@@ -452,7 +510,7 @@ module ActiveRecord
           @pool.with_connection do |connection|
             Thread.new { @pool.send(group_action_method) }.join
             # assert connection has been forcefully taken away from us
-            assert_not @pool.active_connection?
+            assert_not_predicate @pool, :active_connection?
 
             # make a new connection for with_connection to clean up
             @pool.connection
diff --git a/activerecord/test/cases/connection_specification/resolver_test.rb b/activerecord/test/cases/connection_specification/resolver_test.rb
index 3fa0ca8366..5b80f16a44 100644
--- a/activerecord/test/cases/connection_specification/resolver_test.rb
+++ b/activerecord/test/cases/connection_specification/resolver_test.rb
@@ -19,7 +19,7 @@ module ActiveRecord
             spec "ridiculous://foo?encoding=utf8"
           end
 
-          assert_match "Could not load 'active_record/connection_adapters/ridiculous_adapter'", error.message
+          assert_match "Could not load the 'ridiculous' Active Record adapter. Ensure that the adapter is spelled correctly in config/database.yml and that you've added the necessary adapter gem to your Gemfile.", error.message
         end
 
         # The abstract adapter is used simply to bypass the bit of code that
diff --git a/activerecord/test/cases/core_test.rb b/activerecord/test/cases/core_test.rb
index 356afdbd2b..6e7ae2efb4 100644
--- a/activerecord/test/cases/core_test.rb
+++ b/activerecord/test/cases/core_test.rb
@@ -4,7 +4,6 @@ require "cases/helper"
 require "models/person"
 require "models/topic"
 require "pp"
-require "active_support/core_ext/string/strip"
 
 class NonExistentTable < ActiveRecord::Base; end
 
@@ -39,26 +38,26 @@ class CoreTest < ActiveRecord::TestCase
     topic = Topic.new
     actual = "".dup
     PP.pp(topic, StringIO.new(actual))
-    expected = <<-PRETTY.strip_heredoc
-    #<Topic:0xXXXXXX
-     id: nil,
-     title: nil,
-     author_name: nil,
-     author_email_address: "test@test.com",
-     written_on: nil,
-     bonus_time: nil,
-     last_read: nil,
-     content: nil,
-     important: nil,
-     approved: true,
-     replies_count: 0,
-     unique_replies_count: 0,
-     parent_id: nil,
-     parent_title: nil,
-     type: nil,
-     group: nil,
-     created_at: nil,
-     updated_at: nil>
+    expected = <<~PRETTY
+      #<Topic:0xXXXXXX
+       id: nil,
+       title: nil,
+       author_name: nil,
+       author_email_address: "test@test.com",
+       written_on: nil,
+       bonus_time: nil,
+       last_read: nil,
+       content: nil,
+       important: nil,
+       approved: true,
+       replies_count: 0,
+       unique_replies_count: 0,
+       parent_id: nil,
+       parent_title: nil,
+       type: nil,
+       group: nil,
+       created_at: nil,
+       updated_at: nil>
     PRETTY
     assert actual.start_with?(expected.split("XXXXXX").first)
     assert actual.end_with?(expected.split("XXXXXX").last)
@@ -68,26 +67,26 @@ class CoreTest < ActiveRecord::TestCase
     topic = topics(:first)
     actual = "".dup
     PP.pp(topic, StringIO.new(actual))
-    expected = <<-PRETTY.strip_heredoc
-    #<Topic:0x\\w+
-     id: 1,
-     title: "The First Topic",
-     author_name: "David",
-     author_email_address: "david@loudthinking.com",
-     written_on: 2003-07-16 14:28:11 UTC,
-     bonus_time: 2000-01-01 14:28:00 UTC,
-     last_read: Thu, 15 Apr 2004,
-     content: "Have a nice day",
-     important: nil,
-     approved: false,
-     replies_count: 1,
-     unique_replies_count: 0,
-     parent_id: nil,
-     parent_title: nil,
-     type: nil,
-     group: nil,
-     created_at: [^,]+,
-     updated_at: [^,>]+>
+    expected = <<~PRETTY
+      #<Topic:0x\\w+
+       id: 1,
+       title: "The First Topic",
+       author_name: "David",
+       author_email_address: "david@loudthinking.com",
+       written_on: 2003-07-16 14:28:11 UTC,
+       bonus_time: 2000-01-01 14:28:00 UTC,
+       last_read: Thu, 15 Apr 2004,
+       content: "Have a nice day",
+       important: nil,
+       approved: false,
+       replies_count: 1,
+       unique_replies_count: 0,
+       parent_id: nil,
+       parent_title: nil,
+       type: nil,
+       group: nil,
+       created_at: [^,]+,
+       updated_at: [^,>]+>
     PRETTY
     assert_match(/\A#{expected}\z/, actual)
   end
diff --git a/activerecord/test/cases/date_time_precision_test.rb b/activerecord/test/cases/date_time_precision_test.rb
index 51f6164138..e64a8372d0 100644
--- a/activerecord/test/cases/date_time_precision_test.rb
+++ b/activerecord/test/cases/date_time_precision_test.rb
@@ -27,6 +27,24 @@ if subsecond_precision_supported?
       assert_equal 5, Foo.columns_hash["updated_at"].precision
     end
 
+    def test_datetime_precision_is_truncated_on_assignment
+      @connection.create_table(:foos, force: true)
+      @connection.add_column :foos, :created_at,  :datetime, precision: 0
+      @connection.add_column :foos, :updated_at, :datetime, precision: 6
+
+      time = ::Time.now.change(nsec: 123456789)
+      foo = Foo.new(created_at: time, updated_at: time)
+
+      assert_equal 0, foo.created_at.nsec
+      assert_equal 123456000, foo.updated_at.nsec
+
+      foo.save!
+      foo.reload
+
+      assert_equal 0, foo.created_at.nsec
+      assert_equal 123456000, foo.updated_at.nsec
+    end
+
     def test_timestamps_helper_with_custom_precision
       @connection.create_table(:foos, force: true) do |t|
         t.timestamps precision: 4
diff --git a/activerecord/test/cases/defaults_test.rb b/activerecord/test/cases/defaults_test.rb
index 4690682cd8..1c96aaabe2 100644
--- a/activerecord/test/cases/defaults_test.rb
+++ b/activerecord/test/cases/defaults_test.rb
@@ -9,7 +9,7 @@ class DefaultTest < ActiveRecord::TestCase
   def test_nil_defaults_for_not_null_columns
     %w(id name course_id).each do |name|
       column = Entrant.columns_hash[name]
-      assert !column.null, "#{name} column should be NOT NULL"
+      assert_not column.null, "#{name} column should be NOT NULL"
       assert_not column.default, "#{name} column should be DEFAULT 'nil'"
     end
   end
@@ -53,7 +53,7 @@ class DefaultNumbersTest < ActiveRecord::TestCase
 
   def test_default_decimal_number
     record = DefaultNumber.new
-    assert_equal BigDecimal.new("2.78"), record.decimal_number
+    assert_equal BigDecimal("2.78"), record.decimal_number
     assert_equal "2.78", record.decimal_number_before_type_cast
   end
 end
diff --git a/activerecord/test/cases/dirty_test.rb b/activerecord/test/cases/dirty_test.rb
index a602f83d8c..83cc2aa319 100644
--- a/activerecord/test/cases/dirty_test.rb
+++ b/activerecord/test/cases/dirty_test.rb
@@ -24,18 +24,18 @@ class DirtyTest < ActiveRecord::TestCase
 
     # Change catchphrase.
     pirate.catchphrase = "arrr"
-    assert pirate.catchphrase_changed?
+    assert_predicate pirate, :catchphrase_changed?
     assert_nil pirate.catchphrase_was
     assert_equal [nil, "arrr"], pirate.catchphrase_change
 
     # Saved - no changes.
     pirate.save!
-    assert !pirate.catchphrase_changed?
+    assert_not_predicate pirate, :catchphrase_changed?
     assert_nil pirate.catchphrase_change
 
     # Same value - no changes.
     pirate.catchphrase = "arrr"
-    assert !pirate.catchphrase_changed?
+    assert_not_predicate pirate, :catchphrase_changed?
     assert_nil pirate.catchphrase_change
   end
 
@@ -46,23 +46,23 @@ class DirtyTest < ActiveRecord::TestCase
 
       # New record - no changes.
       pirate = target.new
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
       assert_nil pirate.created_on_change
 
       # Saved - no changes.
       pirate.catchphrase = "arrrr, time zone!!"
       pirate.save!
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
       assert_nil pirate.created_on_change
 
       # Change created_on.
       old_created_on = pirate.created_on
       pirate.created_on = Time.now - 1.day
-      assert pirate.created_on_changed?
+      assert_predicate pirate, :created_on_changed?
       assert_kind_of ActiveSupport::TimeWithZone, pirate.created_on_was
       assert_equal old_created_on, pirate.created_on_was
       pirate.created_on = old_created_on
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
     end
   end
 
@@ -73,7 +73,7 @@ class DirtyTest < ActiveRecord::TestCase
 
       pirate = target.create!
       pirate.created_on = pirate.created_on
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
     end
   end
 
@@ -86,19 +86,19 @@ class DirtyTest < ActiveRecord::TestCase
 
       # New record - no changes.
       pirate = target.new
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
       assert_nil pirate.created_on_change
 
       # Saved - no changes.
       pirate.catchphrase = "arrrr, time zone!!"
       pirate.save!
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
       assert_nil pirate.created_on_change
 
       # Change created_on.
       old_created_on = pirate.created_on
       pirate.created_on = Time.now + 1.day
-      assert pirate.created_on_changed?
+      assert_predicate pirate, :created_on_changed?
       # kind_of does not work because
       # ActiveSupport::TimeWithZone.name == 'Time'
       assert_instance_of Time, pirate.created_on_was
@@ -113,19 +113,19 @@ class DirtyTest < ActiveRecord::TestCase
 
       # New record - no changes.
       pirate = target.new
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
       assert_nil pirate.created_on_change
 
       # Saved - no changes.
       pirate.catchphrase = "arrrr, time zone!!"
       pirate.save!
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
       assert_nil pirate.created_on_change
 
       # Change created_on.
       old_created_on = pirate.created_on
       pirate.created_on = Time.now + 1.day
-      assert pirate.created_on_changed?
+      assert_predicate pirate, :created_on_changed?
       # kind_of does not work because
       # ActiveSupport::TimeWithZone.name == 'Time'
       assert_instance_of Time, pirate.created_on_was
@@ -137,11 +137,11 @@ class DirtyTest < ActiveRecord::TestCase
     # the actual attribute here is name, title is an
     # alias setup via alias_attribute
     parrot = Parrot.new
-    assert !parrot.title_changed?
+    assert_not_predicate parrot, :title_changed?
     assert_nil parrot.title_change
 
     parrot.name = "Sam"
-    assert parrot.title_changed?
+    assert_predicate parrot, :title_changed?
     assert_nil parrot.title_was
     assert_equal parrot.name_change, parrot.title_change
   end
@@ -153,7 +153,7 @@ class DirtyTest < ActiveRecord::TestCase
     pirate.restore_catchphrase!
     assert_equal "Yar!", pirate.catchphrase
     assert_equal Hash.new, pirate.changes
-    assert !pirate.catchphrase_changed?
+    assert_not_predicate pirate, :catchphrase_changed?
   end
 
   def test_nullable_number_not_marked_as_changed_if_new_value_is_blank
@@ -161,7 +161,7 @@ class DirtyTest < ActiveRecord::TestCase
 
     ["", nil].each do |value|
       pirate.parrot_id = value
-      assert !pirate.parrot_id_changed?
+      assert_not_predicate pirate, :parrot_id_changed?
       assert_nil pirate.parrot_id_change
     end
   end
@@ -171,7 +171,7 @@ class DirtyTest < ActiveRecord::TestCase
 
     ["", nil].each do |value|
       numeric_data.bank_balance = value
-      assert !numeric_data.bank_balance_changed?
+      assert_not_predicate numeric_data, :bank_balance_changed?
       assert_nil numeric_data.bank_balance_change
     end
   end
@@ -181,7 +181,7 @@ class DirtyTest < ActiveRecord::TestCase
 
     ["", nil].each do |value|
       numeric_data.temperature = value
-      assert !numeric_data.temperature_changed?
+      assert_not_predicate numeric_data, :temperature_changed?
       assert_nil numeric_data.temperature_change
     end
   end
@@ -197,7 +197,7 @@ class DirtyTest < ActiveRecord::TestCase
       ["", nil].each do |value|
         topic.written_on = value
         assert_nil topic.written_on
-        assert !topic.written_on_changed?
+        assert_not_predicate topic, :written_on_changed?
       end
     end
   end
@@ -208,10 +208,10 @@ class DirtyTest < ActiveRecord::TestCase
     pirate.catchphrase = "arrr"
     assert pirate.save!
 
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
 
     pirate.parrot_id = "0"
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
   end
 
   def test_integer_zero_to_integer_zero_not_marked_as_changed
@@ -220,17 +220,17 @@ class DirtyTest < ActiveRecord::TestCase
     pirate.catchphrase = "arrr"
     assert pirate.save!
 
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
 
     pirate.parrot_id = 0
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
   end
 
   def test_float_zero_to_string_zero_not_marked_as_changed
     data = NumericData.new temperature: 0.0
     data.save!
 
-    assert_not data.changed?
+    assert_not_predicate data, :changed?
 
     data.temperature = "0"
     assert_empty data.changes
@@ -251,38 +251,38 @@ class DirtyTest < ActiveRecord::TestCase
     # check the change from 1 to ''
     pirate = Pirate.find_by_catchphrase("Yarrrr, me hearties")
     pirate.parrot_id = ""
-    assert pirate.parrot_id_changed?
+    assert_predicate pirate, :parrot_id_changed?
     assert_equal([1, nil], pirate.parrot_id_change)
     pirate.save
 
     # check the change from nil to 0
     pirate = Pirate.find_by_catchphrase("Yarrrr, me hearties")
     pirate.parrot_id = 0
-    assert pirate.parrot_id_changed?
+    assert_predicate pirate, :parrot_id_changed?
     assert_equal([nil, 0], pirate.parrot_id_change)
     pirate.save
 
     # check the change from 0 to ''
     pirate = Pirate.find_by_catchphrase("Yarrrr, me hearties")
     pirate.parrot_id = ""
-    assert pirate.parrot_id_changed?
+    assert_predicate pirate, :parrot_id_changed?
     assert_equal([0, nil], pirate.parrot_id_change)
   end
 
   def test_object_should_be_changed_if_any_attribute_is_changed
     pirate = Pirate.new
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
     assert_equal [], pirate.changed
     assert_equal Hash.new, pirate.changes
 
     pirate.catchphrase = "arrr"
-    assert pirate.changed?
+    assert_predicate pirate, :changed?
     assert_nil pirate.catchphrase_was
     assert_equal %w(catchphrase), pirate.changed
     assert_equal({ "catchphrase" => [nil, "arrr"] }, pirate.changes)
 
     pirate.save
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
     assert_equal [], pirate.changed
     assert_equal Hash.new, pirate.changes
   end
@@ -290,40 +290,40 @@ class DirtyTest < ActiveRecord::TestCase
   def test_attribute_will_change!
     pirate = Pirate.create!(catchphrase: "arr")
 
-    assert !pirate.catchphrase_changed?
+    assert_not_predicate pirate, :catchphrase_changed?
     assert pirate.catchphrase_will_change!
-    assert pirate.catchphrase_changed?
+    assert_predicate pirate, :catchphrase_changed?
     assert_equal ["arr", "arr"], pirate.catchphrase_change
 
     pirate.catchphrase << " matey!"
-    assert pirate.catchphrase_changed?
+    assert_predicate pirate, :catchphrase_changed?
     assert_equal ["arr", "arr matey!"], pirate.catchphrase_change
   end
 
   def test_virtual_attribute_will_change
     parrot = Parrot.create!(name: "Ruby")
     parrot.send(:attribute_will_change!, :cancel_save_from_callback)
-    assert parrot.has_changes_to_save?
+    assert_predicate parrot, :has_changes_to_save?
   end
 
   def test_association_assignment_changes_foreign_key
     pirate = Pirate.create!(catchphrase: "jarl")
     pirate.parrot = Parrot.create!(name: "Lorre")
-    assert pirate.changed?
+    assert_predicate pirate, :changed?
     assert_equal %w(parrot_id), pirate.changed
   end
 
   def test_attribute_should_be_compared_with_type_cast
     topic = Topic.new
-    assert topic.approved?
-    assert !topic.approved_changed?
+    assert_predicate topic, :approved?
+    assert_not_predicate topic, :approved_changed?
 
     # Coming from web form.
     params = { topic: { approved: 1 } }
     # In the controller.
     topic.attributes = params[:topic]
-    assert topic.approved?
-    assert !topic.approved_changed?
+    assert_predicate topic, :approved?
+    assert_not_predicate topic, :approved_changed?
   end
 
   def test_partial_update
@@ -366,7 +366,7 @@ class DirtyTest < ActiveRecord::TestCase
   def test_changed_attributes_should_be_preserved_if_save_failure
     pirate = Pirate.new
     pirate.parrot_id = 1
-    assert !pirate.save
+    assert_not pirate.save
     check_pirate_after_save_failure(pirate)
 
     pirate = Pirate.new
@@ -378,9 +378,9 @@ class DirtyTest < ActiveRecord::TestCase
   def test_reload_should_clear_changed_attributes
     pirate = Pirate.create!(catchphrase: "shiver me timbers")
     pirate.catchphrase = "*hic*"
-    assert pirate.changed?
+    assert_predicate pirate, :changed?
     pirate.reload
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
   end
 
   def test_dup_objects_should_not_copy_dirty_flag_from_creator
@@ -388,17 +388,17 @@ class DirtyTest < ActiveRecord::TestCase
     pirate_dup = pirate.dup
     pirate_dup.restore_catchphrase!
     pirate.catchphrase = "I love Rum"
-    assert pirate.catchphrase_changed?
-    assert !pirate_dup.catchphrase_changed?
+    assert_predicate pirate, :catchphrase_changed?
+    assert_not_predicate pirate_dup, :catchphrase_changed?
   end
 
   def test_reverted_changes_are_not_dirty
     phrase = "shiver me timbers"
     pirate = Pirate.create!(catchphrase: phrase)
     pirate.catchphrase = "*hic*"
-    assert pirate.changed?
+    assert_predicate pirate, :changed?
     pirate.catchphrase = phrase
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
   end
 
   def test_reverted_changes_are_not_dirty_after_multiple_changes
@@ -406,40 +406,40 @@ class DirtyTest < ActiveRecord::TestCase
     pirate = Pirate.create!(catchphrase: phrase)
     10.times do |i|
       pirate.catchphrase = "*hic*" * i
-      assert pirate.changed?
+      assert_predicate pirate, :changed?
     end
-    assert pirate.changed?
+    assert_predicate pirate, :changed?
     pirate.catchphrase = phrase
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
   end
 
   def test_reverted_changes_are_not_dirty_going_from_nil_to_value_and_back
     pirate = Pirate.create!(catchphrase: "Yar!")
 
     pirate.parrot_id = 1
-    assert pirate.changed?
-    assert pirate.parrot_id_changed?
-    assert !pirate.catchphrase_changed?
+    assert_predicate pirate, :changed?
+    assert_predicate pirate, :parrot_id_changed?
+    assert_not_predicate pirate, :catchphrase_changed?
 
     pirate.parrot_id = nil
-    assert !pirate.changed?
-    assert !pirate.parrot_id_changed?
-    assert !pirate.catchphrase_changed?
+    assert_not_predicate pirate, :changed?
+    assert_not_predicate pirate, :parrot_id_changed?
+    assert_not_predicate pirate, :catchphrase_changed?
   end
 
   def test_save_should_store_serialized_attributes_even_with_partial_writes
     with_partial_writes(Topic) do
       topic = Topic.create!(content: { a: "a" })
 
-      assert_not topic.changed?
+      assert_not_predicate topic, :changed?
 
       topic.content[:b] = "b"
 
-      assert topic.changed?
+      assert_predicate topic, :changed?
 
       topic.save!
 
-      assert_not topic.changed?
+      assert_not_predicate topic, :changed?
       assert_equal "b", topic.content[:b]
 
       topic.reload
@@ -473,6 +473,14 @@ class DirtyTest < ActiveRecord::TestCase
     end
   end
 
+  def test_changes_to_save_should_not_mutate_array_of_hashes
+    topic = Topic.new(author_name: "Bill", content: [{ a: "a" }])
+
+    topic.changes_to_save
+
+    assert_equal [{ a: "a" }], topic.content
+  end
+
   def test_previous_changes
     # original values should be in previous_changes
     pirate = Pirate.new
@@ -488,7 +496,7 @@ class DirtyTest < ActiveRecord::TestCase
     assert_not_nil pirate.previous_changes["updated_on"][1]
     assert_nil pirate.previous_changes["created_on"][0]
     assert_not_nil pirate.previous_changes["created_on"][1]
-    assert !pirate.previous_changes.key?("parrot_id")
+    assert_not pirate.previous_changes.key?("parrot_id")
 
     # original values should be in previous_changes
     pirate = Pirate.new
@@ -502,7 +510,7 @@ class DirtyTest < ActiveRecord::TestCase
     assert_equal [nil, pirate.id], pirate.previous_changes["id"]
     assert_includes pirate.previous_changes, "updated_on"
     assert_includes pirate.previous_changes, "created_on"
-    assert !pirate.previous_changes.key?("parrot_id")
+    assert_not pirate.previous_changes.key?("parrot_id")
 
     pirate.catchphrase = "Yar!!"
     pirate.reload
@@ -519,8 +527,8 @@ class DirtyTest < ActiveRecord::TestCase
     assert_equal ["arrr", "Me Maties!"], pirate.previous_changes["catchphrase"]
     assert_not_nil pirate.previous_changes["updated_on"][0]
     assert_not_nil pirate.previous_changes["updated_on"][1]
-    assert !pirate.previous_changes.key?("parrot_id")
-    assert !pirate.previous_changes.key?("created_on")
+    assert_not pirate.previous_changes.key?("parrot_id")
+    assert_not pirate.previous_changes.key?("created_on")
 
     pirate = Pirate.find_by_catchphrase("Me Maties!")
 
@@ -533,8 +541,8 @@ class DirtyTest < ActiveRecord::TestCase
     assert_equal ["Me Maties!", "Thar She Blows!"], pirate.previous_changes["catchphrase"]
     assert_not_nil pirate.previous_changes["updated_on"][0]
     assert_not_nil pirate.previous_changes["updated_on"][1]
-    assert !pirate.previous_changes.key?("parrot_id")
-    assert !pirate.previous_changes.key?("created_on")
+    assert_not pirate.previous_changes.key?("parrot_id")
+    assert_not pirate.previous_changes.key?("created_on")
 
     travel(1.second)
 
@@ -545,8 +553,8 @@ class DirtyTest < ActiveRecord::TestCase
     assert_equal ["Thar She Blows!", "Ahoy!"], pirate.previous_changes["catchphrase"]
     assert_not_nil pirate.previous_changes["updated_on"][0]
     assert_not_nil pirate.previous_changes["updated_on"][1]
-    assert !pirate.previous_changes.key?("parrot_id")
-    assert !pirate.previous_changes.key?("created_on")
+    assert_not pirate.previous_changes.key?("parrot_id")
+    assert_not pirate.previous_changes.key?("created_on")
 
     travel(1.second)
 
@@ -557,8 +565,8 @@ class DirtyTest < ActiveRecord::TestCase
     assert_equal ["Ahoy!", "Ninjas suck!"], pirate.previous_changes["catchphrase"]
     assert_not_nil pirate.previous_changes["updated_on"][0]
     assert_not_nil pirate.previous_changes["updated_on"][1]
-    assert !pirate.previous_changes.key?("parrot_id")
-    assert !pirate.previous_changes.key?("created_on")
+    assert_not pirate.previous_changes.key?("parrot_id")
+    assert_not pirate.previous_changes.key?("created_on")
   ensure
     travel_back
   end
@@ -596,7 +604,7 @@ class DirtyTest < ActiveRecord::TestCase
     pirate = Pirate.create!(catchphrase: "rrrr", created_on: time_in_paris)
 
     pirate.created_on = pirate.created_on.in_time_zone("Tokyo").to_s
-    assert !pirate.created_on_changed?
+    assert_not_predicate pirate, :created_on_changed?
   end
 
   test "partial insert" do
@@ -627,7 +635,7 @@ class DirtyTest < ActiveRecord::TestCase
     pirate = Pirate.create!(catchphrase: "arrrr")
     pirate.catchphrase << " matey!"
 
-    assert pirate.catchphrase_changed?
+    assert_predicate pirate, :catchphrase_changed?
     expected_changes = {
       "catchphrase" => ["arrrr", "arrrr matey!"]
     }
@@ -641,7 +649,7 @@ class DirtyTest < ActiveRecord::TestCase
     pirate.reload
 
     assert_equal "arrrr matey!", pirate.catchphrase
-    assert_not pirate.changed?
+    assert_not_predicate pirate, :changed?
   end
 
   test "in place mutation for binary" do
@@ -652,19 +660,19 @@ class DirtyTest < ActiveRecord::TestCase
 
     binary = klass.create!(data: "\\\\foo")
 
-    assert_not binary.changed?
+    assert_not_predicate binary, :changed?
 
     binary.data = binary.data.dup
 
-    assert_not binary.changed?
+    assert_not_predicate binary, :changed?
 
     binary = klass.last
 
-    assert_not binary.changed?
+    assert_not_predicate binary, :changed?
 
     binary.data << "bar"
 
-    assert binary.changed?
+    assert_predicate binary, :changed?
   end
 
   test "changes is correct for subclass" do
@@ -679,7 +687,7 @@ class DirtyTest < ActiveRecord::TestCase
     new_catchphrase = "arrrr matey!"
 
     pirate.catchphrase = new_catchphrase
-    assert pirate.catchphrase_changed?
+    assert_predicate pirate, :catchphrase_changed?
 
     expected_changes = {
       "catchphrase" => ["arrrr", new_catchphrase]
@@ -698,7 +706,7 @@ class DirtyTest < ActiveRecord::TestCase
     new_catchphrase = "arrrr matey!"
 
     pirate.catchphrase = new_catchphrase
-    assert pirate.catchphrase_changed?
+    assert_predicate pirate, :catchphrase_changed?
 
     expected_changes = {
       "catchphrase" => ["arrrr", new_catchphrase]
@@ -720,7 +728,7 @@ class DirtyTest < ActiveRecord::TestCase
     end
 
     model = klass.new(first_name: "Jim")
-    assert model.first_name_changed?
+    assert_predicate model, :first_name_changed?
   end
 
   test "attribute_will_change! doesn't try to save non-persistable attributes" do
@@ -732,10 +740,28 @@ class DirtyTest < ActiveRecord::TestCase
     record = klass.new(first_name: "Sean")
     record.non_persisted_attribute_will_change!
 
-    assert record.non_persisted_attribute_changed?
+    assert_predicate record, :non_persisted_attribute_changed?
     assert record.save
   end
 
+  test "virtual attributes are not written with partial_writes off" do
+    with_partial_writes(ActiveRecord::Base, false) do
+      klass = Class.new(ActiveRecord::Base) do
+        self.table_name = "people"
+        attribute :non_persisted_attribute, :string
+      end
+
+      record = klass.new(first_name: "Sean")
+      record.non_persisted_attribute_will_change!
+
+      assert record.save
+
+      record.non_persisted_attribute_will_change!
+
+      assert record.save
+    end
+  end
+
   test "mutating and then assigning doesn't remove the change" do
     pirate = Pirate.create!(catchphrase: "arrrr")
     pirate.catchphrase << " matey!"
@@ -762,26 +788,33 @@ class DirtyTest < ActiveRecord::TestCase
 
   test "attributes assigned but not selected are dirty" do
     person = Person.select(:id).first
-    refute person.changed?
+    assert_not_predicate person, :changed?
 
     person.first_name = "Sean"
-    assert person.changed?
+    assert_predicate person, :changed?
 
     person.first_name = nil
-    assert person.changed?
+    assert_predicate person, :changed?
+  end
+
+  test "attributes not selected are still missing after save" do
+    person = Person.select(:id).first
+    assert_raises(ActiveModel::MissingAttributeError) { person.first_name }
+    assert person.save # calls forget_attribute_assignments
+    assert_raises(ActiveModel::MissingAttributeError) { person.first_name }
   end
 
   test "saved_change_to_attribute? returns whether a change occurred in the last save" do
     person = Person.create!(first_name: "Sean")
 
-    assert person.saved_change_to_first_name?
-    refute person.saved_change_to_gender?
+    assert_predicate person, :saved_change_to_first_name?
+    assert_not_predicate person, :saved_change_to_gender?
     assert person.saved_change_to_first_name?(from: nil, to: "Sean")
     assert person.saved_change_to_first_name?(from: nil)
     assert person.saved_change_to_first_name?(to: "Sean")
-    refute person.saved_change_to_first_name?(from: "Jim", to: "Sean")
-    refute person.saved_change_to_first_name?(from: "Jim")
-    refute person.saved_change_to_first_name?(to: "Jim")
+    assert_not person.saved_change_to_first_name?(from: "Jim", to: "Sean")
+    assert_not person.saved_change_to_first_name?(from: "Jim")
+    assert_not person.saved_change_to_first_name?(to: "Jim")
   end
 
   test "saved_change_to_attribute returns the change that occurred in the last save" do
@@ -816,11 +849,11 @@ class DirtyTest < ActiveRecord::TestCase
   test "saved_changes? returns whether the last call to save changed anything" do
     person = Person.create!(first_name: "Sean")
 
-    assert person.saved_changes?
+    assert_predicate person, :saved_changes?
 
     person.save
 
-    refute person.saved_changes?
+    assert_not_predicate person, :saved_changes?
   end
 
   test "saved_changes returns a hash of all the changes that occurred" do
@@ -850,7 +883,7 @@ class DirtyTest < ActiveRecord::TestCase
     end
 
     person = klass.create!(first_name: "Sean")
-    refute person.changed?
+    assert_not_predicate person, :changed?
   end
 
   private
@@ -863,8 +896,8 @@ class DirtyTest < ActiveRecord::TestCase
     end
 
     def check_pirate_after_save_failure(pirate)
-      assert pirate.changed?
-      assert pirate.parrot_id_changed?
+      assert_predicate pirate, :changed?
+      assert_predicate pirate, :parrot_id_changed?
       assert_equal %w(parrot_id), pirate.changed
       assert_nil pirate.parrot_id_was
     end
diff --git a/activerecord/test/cases/dup_test.rb b/activerecord/test/cases/dup_test.rb
index 2fefdbf204..a2efbf89f9 100644
--- a/activerecord/test/cases/dup_test.rb
+++ b/activerecord/test/cases/dup_test.rb
@@ -3,20 +3,21 @@
 require "cases/helper"
 require "models/reply"
 require "models/topic"
+require "models/movie"
 
 module ActiveRecord
   class DupTest < ActiveRecord::TestCase
     fixtures :topics
 
     def test_dup
-      assert !Topic.new.freeze.dup.frozen?
+      assert_not_predicate Topic.new.freeze.dup, :frozen?
     end
 
     def test_not_readonly
       topic = Topic.first
 
       duped = topic.dup
-      assert !duped.readonly?, "should not be readonly"
+      assert_not duped.readonly?, "should not be readonly"
     end
 
     def test_is_readonly
@@ -31,7 +32,7 @@ module ActiveRecord
       topic = Topic.first
       duped = topic.dup
 
-      assert !duped.persisted?, "topic not persisted"
+      assert_not duped.persisted?, "topic not persisted"
       assert duped.new_record?, "topic is new"
     end
 
@@ -40,7 +41,7 @@ module ActiveRecord
       topic.destroy
 
       duped = topic.dup
-      assert_not duped.destroyed?
+      assert_not_predicate duped, :destroyed?
     end
 
     def test_dup_has_no_id
@@ -62,10 +63,10 @@ module ActiveRecord
 
       topic.attributes = dbtopic.attributes.except("id")
 
-      #duped has no timestamp values
+      # duped has no timestamp values
       duped = dbtopic.dup
 
-      #clear topic timestamp values
+      # clear topic timestamp values
       topic.send(:clear_timestamp_attributes)
 
       assert_equal topic.changes, duped.changes
@@ -100,7 +101,7 @@ module ActiveRecord
       # temporary change to the topic object
       topic.updated_at -= 3.days
 
-      #dup should not preserve the timestamps if present
+      # dup should not preserve the timestamps if present
       new_topic = topic.dup
       assert_nil new_topic.updated_at
       assert_nil new_topic.created_at
@@ -126,12 +127,12 @@ module ActiveRecord
 
         duped = topic.dup
         duped.title = nil
-        assert duped.invalid?
+        assert_predicate duped, :invalid?
 
         topic.title = nil
         duped.title = "Mathematics"
-        assert topic.invalid?
-        assert duped.valid?
+        assert_predicate topic, :invalid?
+        assert_predicate duped, :valid?
       end
     end
 
@@ -139,7 +140,7 @@ module ActiveRecord
       prev_default_scopes = Topic.default_scopes
       Topic.default_scopes = [proc { Topic.where(approved: true) }]
       topic = Topic.new(approved: false)
-      assert !topic.dup.approved?, "should not be overridden by default scopes"
+      assert_not topic.dup.approved?, "should not be overridden by default scopes"
     ensure
       Topic.default_scopes = prev_default_scopes
     end
@@ -157,5 +158,20 @@ module ActiveRecord
         record.dup
       end
     end
+
+    def test_dup_record_not_persisted_after_rollback_transaction
+      movie = Movie.new(name: "test")
+
+      assert_raises(ActiveRecord::RecordInvalid) do
+        Movie.transaction do
+          movie.save!
+          duped = movie.dup
+          duped.name = nil
+          duped.save!
+        end
+      end
+
+      assert_not movie.persisted?
+    end
   end
 end
diff --git a/activerecord/test/cases/enum_test.rb b/activerecord/test/cases/enum_test.rb
index 78cb89ccc5..d5a1d11e12 100644
--- a/activerecord/test/cases/enum_test.rb
+++ b/activerecord/test/cases/enum_test.rb
@@ -12,16 +12,16 @@ class EnumTest < ActiveRecord::TestCase
   end
 
   test "query state by predicate" do
-    assert @book.published?
-    assert_not @book.written?
-    assert_not @book.proposed?
+    assert_predicate @book, :published?
+    assert_not_predicate @book, :written?
+    assert_not_predicate @book, :proposed?
 
-    assert @book.read?
-    assert @book.in_english?
-    assert @book.author_visibility_visible?
-    assert @book.illustrator_visibility_visible?
-    assert @book.with_medium_font_size?
-    assert @book.medium_to_read?
+    assert_predicate @book, :read?
+    assert_predicate @book, :in_english?
+    assert_predicate @book, :author_visibility_visible?
+    assert_predicate @book, :illustrator_visibility_visible?
+    assert_predicate @book, :with_medium_font_size?
+    assert_predicate @book, :medium_to_read?
   end
 
   test "query state with strings" do
@@ -76,46 +76,46 @@ class EnumTest < ActiveRecord::TestCase
   end
 
   test "build from scope" do
-    assert Book.written.build.written?
-    assert_not Book.written.build.proposed?
+    assert_predicate Book.written.build, :written?
+    assert_not_predicate Book.written.build, :proposed?
   end
 
   test "build from where" do
-    assert Book.where(status: Book.statuses[:written]).build.written?
-    assert_not Book.where(status: Book.statuses[:written]).build.proposed?
-    assert Book.where(status: :written).build.written?
-    assert_not Book.where(status: :written).build.proposed?
-    assert Book.where(status: "written").build.written?
-    assert_not Book.where(status: "written").build.proposed?
+    assert_predicate Book.where(status: Book.statuses[:written]).build, :written?
+    assert_not_predicate Book.where(status: Book.statuses[:written]).build, :proposed?
+    assert_predicate Book.where(status: :written).build, :written?
+    assert_not_predicate Book.where(status: :written).build, :proposed?
+    assert_predicate Book.where(status: "written").build, :written?
+    assert_not_predicate Book.where(status: "written").build, :proposed?
   end
 
   test "update by declaration" do
     @book.written!
-    assert @book.written?
+    assert_predicate @book, :written?
     @book.in_english!
-    assert @book.in_english?
+    assert_predicate @book, :in_english?
     @book.author_visibility_visible!
-    assert @book.author_visibility_visible?
+    assert_predicate @book, :author_visibility_visible?
   end
 
   test "update by setter" do
     @book.update! status: :written
-    assert @book.written?
+    assert_predicate @book, :written?
   end
 
   test "enum methods are overwritable" do
     assert_equal "do publish work...", @book.published!
-    assert @book.published?
+    assert_predicate @book, :published?
   end
 
   test "direct assignment" do
     @book.status = :written
-    assert @book.written?
+    assert_predicate @book, :written?
   end
 
   test "assign string value" do
     @book.status = "written"
-    assert @book.written?
+    assert_predicate @book, :written?
   end
 
   test "enum changed attributes" do
@@ -242,17 +242,17 @@ class EnumTest < ActiveRecord::TestCase
   end
 
   test "building new objects with enum scopes" do
-    assert Book.written.build.written?
-    assert Book.read.build.read?
-    assert Book.in_spanish.build.in_spanish?
-    assert Book.illustrator_visibility_invisible.build.illustrator_visibility_invisible?
+    assert_predicate Book.written.build, :written?
+    assert_predicate Book.read.build, :read?
+    assert_predicate Book.in_spanish.build, :in_spanish?
+    assert_predicate Book.illustrator_visibility_invisible.build, :illustrator_visibility_invisible?
   end
 
   test "creating new objects with enum scopes" do
-    assert Book.written.create.written?
-    assert Book.read.create.read?
-    assert Book.in_spanish.create.in_spanish?
-    assert Book.illustrator_visibility_invisible.create.illustrator_visibility_invisible?
+    assert_predicate Book.written.create, :written?
+    assert_predicate Book.read.create, :read?
+    assert_predicate Book.in_spanish.create, :in_spanish?
+    assert_predicate Book.illustrator_visibility_invisible.create, :illustrator_visibility_invisible?
   end
 
   test "_before_type_cast" do
@@ -308,6 +308,24 @@ class EnumTest < ActiveRecord::TestCase
     end
   end
 
+  test "reserved enum values for relation" do
+    relation_method_samples = [
+      :records,
+      :to_ary,
+      :scope_for_create
+    ]
+
+    relation_method_samples.each do |value|
+      e = assert_raises(ArgumentError, "enum value `#{value}` should not be allowed") do
+        Class.new(ActiveRecord::Base) do
+          self.table_name = "books"
+          enum category: [:other, value]
+        end
+      end
+      assert_match(/You tried to define an enum named .* on the model/, e.message)
+    end
+  end
+
   test "overriding enum method should not raise" do
     assert_nothing_raised do
       Class.new(ActiveRecord::Base) do
@@ -337,9 +355,9 @@ class EnumTest < ActiveRecord::TestCase
     klass.delete_all
     klass.create!(status: "proposed")
     book = klass.new(status: "written")
-    assert book.valid?
+    assert_predicate book, :valid?
     book.status = "proposed"
-    assert_not book.valid?
+    assert_not_predicate book, :valid?
   end
 
   test "validate inclusion of value in array" do
@@ -350,9 +368,9 @@ class EnumTest < ActiveRecord::TestCase
     end
     klass.delete_all
     invalid_book = klass.new(status: "proposed")
-    assert_not invalid_book.valid?
+    assert_not_predicate invalid_book, :valid?
     valid_book = klass.new(status: "written")
-    assert valid_book.valid?
+    assert_predicate valid_book, :valid?
   end
 
   test "enums are distinct per class" do
@@ -399,10 +417,10 @@ class EnumTest < ActiveRecord::TestCase
     end
 
     book1 = klass.proposed.create!
-    assert book1.proposed?
+    assert_predicate book1, :proposed?
 
     book2 = klass.single.create!
-    assert book2.single?
+    assert_predicate book2, :single?
   end
 
   test "enum with alias_attribute" do
@@ -413,62 +431,62 @@ class EnumTest < ActiveRecord::TestCase
     end
 
     book = klass.proposed.create!
-    assert book.proposed?
+    assert_predicate book, :proposed?
     assert_equal "proposed", book.aliased_status
 
     book = klass.find(book.id)
-    assert book.proposed?
+    assert_predicate book, :proposed?
     assert_equal "proposed", book.aliased_status
   end
 
   test "query state by predicate with prefix" do
-    assert @book.author_visibility_visible?
-    assert_not @book.author_visibility_invisible?
-    assert @book.illustrator_visibility_visible?
-    assert_not @book.illustrator_visibility_invisible?
+    assert_predicate @book, :author_visibility_visible?
+    assert_not_predicate @book, :author_visibility_invisible?
+    assert_predicate @book, :illustrator_visibility_visible?
+    assert_not_predicate @book, :illustrator_visibility_invisible?
   end
 
   test "query state by predicate with custom prefix" do
-    assert @book.in_english?
-    assert_not @book.in_spanish?
-    assert_not @book.in_french?
+    assert_predicate @book, :in_english?
+    assert_not_predicate @book, :in_spanish?
+    assert_not_predicate @book, :in_french?
   end
 
   test "query state by predicate with custom suffix" do
-    assert     @book.medium_to_read?
-    assert_not @book.easy_to_read?
-    assert_not @book.hard_to_read?
+    assert_predicate @book, :medium_to_read?
+    assert_not_predicate @book, :easy_to_read?
+    assert_not_predicate @book, :hard_to_read?
   end
 
   test "enum methods with custom suffix defined" do
-    assert @book.class.respond_to?(:easy_to_read)
-    assert @book.class.respond_to?(:medium_to_read)
-    assert @book.class.respond_to?(:hard_to_read)
+    assert_respond_to @book.class, :easy_to_read
+    assert_respond_to @book.class, :medium_to_read
+    assert_respond_to @book.class, :hard_to_read
 
-    assert @book.respond_to?(:easy_to_read?)
-    assert @book.respond_to?(:medium_to_read?)
-    assert @book.respond_to?(:hard_to_read?)
+    assert_respond_to @book, :easy_to_read?
+    assert_respond_to @book, :medium_to_read?
+    assert_respond_to @book, :hard_to_read?
 
-    assert @book.respond_to?(:easy_to_read!)
-    assert @book.respond_to?(:medium_to_read!)
-    assert @book.respond_to?(:hard_to_read!)
+    assert_respond_to @book, :easy_to_read!
+    assert_respond_to @book, :medium_to_read!
+    assert_respond_to @book, :hard_to_read!
   end
 
   test "update enum attributes with custom suffix" do
     @book.medium_to_read!
-    assert_not @book.easy_to_read?
-    assert     @book.medium_to_read?
-    assert_not @book.hard_to_read?
+    assert_not_predicate @book, :easy_to_read?
+    assert_predicate @book, :medium_to_read?
+    assert_not_predicate @book, :hard_to_read?
 
     @book.easy_to_read!
-    assert     @book.easy_to_read?
-    assert_not @book.medium_to_read?
-    assert_not @book.hard_to_read?
+    assert_predicate @book, :easy_to_read?
+    assert_not_predicate @book, :medium_to_read?
+    assert_not_predicate @book, :hard_to_read?
 
     @book.hard_to_read!
-    assert_not @book.easy_to_read?
-    assert_not @book.medium_to_read?
-    assert     @book.hard_to_read?
+    assert_not_predicate @book, :easy_to_read?
+    assert_not_predicate @book, :medium_to_read?
+    assert_predicate @book, :hard_to_read?
   end
 
   test "uses default status when no status is provided in fixtures" do
@@ -479,12 +497,12 @@ class EnumTest < ActiveRecord::TestCase
 
   test "uses default value from database on initialization" do
     book = Book.new
-    assert book.proposed?
+    assert_predicate book, :proposed?
   end
 
   test "uses default value from database on initialization when using custom mapping" do
     book = Book.new
-    assert book.hard?
+    assert_predicate book, :hard?
   end
 
   test "data type of Enum type" do
diff --git a/activerecord/test/cases/explain_subscriber_test.rb b/activerecord/test/cases/explain_subscriber_test.rb
index fb698c47cd..82cc891970 100644
--- a/activerecord/test/cases/explain_subscriber_test.rb
+++ b/activerecord/test/cases/explain_subscriber_test.rb
@@ -15,20 +15,20 @@ if ActiveRecord::Base.connection.supports_explain?
 
     def test_collects_nothing_if_the_payload_has_an_exception
       SUBSCRIBER.finish(nil, nil, exception: Exception.new)
-      assert queries.empty?
+      assert_empty queries
     end
 
     def test_collects_nothing_for_ignored_payloads
       ActiveRecord::ExplainSubscriber::IGNORED_PAYLOADS.each do |ip|
         SUBSCRIBER.finish(nil, nil, name: ip)
       end
-      assert queries.empty?
+      assert_empty queries
     end
 
     def test_collects_nothing_if_collect_is_false
       ActiveRecord::ExplainRegistry.collect = false
       SUBSCRIBER.finish(nil, nil, name: "SQL", sql: "select 1 from users", binds: [1, 2])
-      assert queries.empty?
+      assert_empty queries
     end
 
     def test_collects_pairs_of_queries_and_binds
@@ -42,12 +42,12 @@ if ActiveRecord::Base.connection.supports_explain?
 
     def test_collects_nothing_if_the_statement_is_not_whitelisted
       SUBSCRIBER.finish(nil, nil, name: "SQL", sql: "SHOW max_identifier_length")
-      assert queries.empty?
+      assert_empty queries
     end
 
     def test_collects_nothing_if_the_statement_is_only_partially_matched
       SUBSCRIBER.finish(nil, nil, name: "SQL", sql: "select_db yo_mama")
-      assert queries.empty?
+      assert_empty queries
     end
 
     def test_collects_cte_queries
diff --git a/activerecord/test/cases/explain_test.rb b/activerecord/test/cases/explain_test.rb
index 17654027a9..a0e75f4e89 100644
--- a/activerecord/test/cases/explain_test.rb
+++ b/activerecord/test/cases/explain_test.rb
@@ -2,7 +2,6 @@
 
 require "cases/helper"
 require "models/car"
-require "active_support/core_ext/string/strip"
 
 if ActiveRecord::Base.connection.supports_explain?
   class ExplainTest < ActiveRecord::TestCase
@@ -53,7 +52,7 @@ if ActiveRecord::Base.connection.supports_explain?
       queries = sqls.zip(binds)
 
       stub_explain_for_query_plans(["query plan foo\n", "query plan bar\n"]) do
-        expected = <<-SQL.strip_heredoc
+        expected = <<~SQL
           EXPLAIN for: #{sqls[0]} [["wadus", 1]]
           query plan foo
 
diff --git a/activerecord/test/cases/finder_respond_to_test.rb b/activerecord/test/cases/finder_respond_to_test.rb
index 4039af66d0..59af4e6961 100644
--- a/activerecord/test/cases/finder_respond_to_test.rb
+++ b/activerecord/test/cases/finder_respond_to_test.rb
@@ -8,7 +8,7 @@ class FinderRespondToTest < ActiveRecord::TestCase
 
   def test_should_preserve_normal_respond_to_behaviour_on_base
     assert_respond_to ActiveRecord::Base, :new
-    assert !ActiveRecord::Base.respond_to?(:find_by_something)
+    assert_not_respond_to ActiveRecord::Base, :find_by_something
   end
 
   def test_should_preserve_normal_respond_to_behaviour_and_respond_to_newly_added_method
@@ -43,14 +43,14 @@ class FinderRespondToTest < ActiveRecord::TestCase
   end
 
   def test_should_not_respond_to_find_by_one_missing_attribute
-    assert !Topic.respond_to?(:find_by_undertitle)
+    assert_not_respond_to Topic, :find_by_undertitle
   end
 
   def test_should_not_respond_to_find_by_invalid_method_syntax
-    assert !Topic.respond_to?(:fail_to_find_by_title)
-    assert !Topic.respond_to?(:find_by_title?)
-    assert !Topic.respond_to?(:fail_to_find_or_create_by_title)
-    assert !Topic.respond_to?(:find_or_create_by_title?)
+    assert_not_respond_to Topic, :fail_to_find_by_title
+    assert_not_respond_to Topic, :find_by_title?
+    assert_not_respond_to Topic, :fail_to_find_or_create_by_title
+    assert_not_respond_to Topic, :find_or_create_by_title?
   end
 
   private
diff --git a/activerecord/test/cases/finder_test.rb b/activerecord/test/cases/finder_test.rb
index 55496147c1..8324b26ad3 100644
--- a/activerecord/test/cases/finder_test.rb
+++ b/activerecord/test/cases/finder_test.rb
@@ -9,6 +9,7 @@ require "models/company"
 require "models/tagging"
 require "models/topic"
 require "models/reply"
+require "models/rating"
 require "models/entrant"
 require "models/project"
 require "models/developer"
@@ -119,6 +120,21 @@ class FinderTest < ActiveRecord::TestCase
     assert_equal "The Fourth Topic of the day", records[2].title
   end
 
+  def test_find_with_ids_with_no_id_passed
+    exception = assert_raises(ActiveRecord::RecordNotFound) { Topic.find }
+    assert_equal exception.model, "Topic"
+    assert_equal exception.primary_key, "id"
+  end
+
+  def test_find_with_ids_with_id_out_of_range
+    exception = assert_raises(ActiveRecord::RecordNotFound) do
+      Topic.find("9999999999999999999999999999999")
+    end
+
+    assert_equal exception.model, "Topic"
+    assert_equal exception.primary_key, "id"
+  end
+
   def test_find_passing_active_record_object_is_not_permitted
     assert_raises(ArgumentError) do
       Topic.find(Topic.last)
@@ -156,6 +172,32 @@ class FinderTest < ActiveRecord::TestCase
     assert_raise(NoMethodError) { Topic.exists?([1, 2]) }
   end
 
+  def test_exists_with_scope
+    davids = Author.where(name: "David")
+    assert_equal true, davids.exists?
+    assert_equal true, davids.exists?(authors(:david).id)
+    assert_equal false, davids.exists?(authors(:mary).id)
+    assert_equal false, davids.exists?("42")
+    assert_equal false, davids.exists?(42)
+    assert_equal false, davids.exists?(davids.new.id)
+
+    fake = Author.where(name: "fake author")
+    assert_equal false, fake.exists?
+    assert_equal false, fake.exists?(authors(:david).id)
+  end
+
+  def test_exists_uses_existing_scope
+    post = authors(:david).posts.first
+    authors = Author.includes(:posts).where(name: "David", posts: { id: post.id })
+    assert_equal true, authors.exists?(authors(:david).id)
+  end
+
+  def test_any_with_scope_on_hash_includes
+    post = authors(:david).posts.first
+    categories = Categorization.includes(author: :posts).where(posts: { id: post.id })
+    assert_equal true, categories.exists?
+  end
+
   def test_exists_with_polymorphic_relation
     post = Post.create!(title: "Post", body: "default", taggings: [Tagging.new(comment: "tagging comment")])
     relation = Post.tagged_with_comment("tagging comment")
@@ -212,7 +254,7 @@ class FinderTest < ActiveRecord::TestCase
 
   # Ensure +exists?+ runs without an error by excluding order value.
   def test_exists_with_order
-    assert_equal true, Topic.order("invalid sql here").exists?
+    assert_equal true, Topic.order(Arel.sql("invalid sql here")).exists?
   end
 
   def test_exists_with_joins
@@ -228,20 +270,27 @@ class FinderTest < ActiveRecord::TestCase
   end
 
   def test_exists_with_includes_limit_and_empty_result
-    assert_equal false, Topic.includes(:replies).limit(0).exists?
-    assert_equal false, Topic.includes(:replies).limit(1).where("0 = 1").exists?
+    assert_no_queries { assert_equal false, Topic.includes(:replies).limit(0).exists? }
+    assert_queries(1) { assert_equal false, Topic.includes(:replies).limit(1).where("0 = 1").exists? }
   end
 
   def test_exists_with_distinct_association_includes_and_limit
     author = Author.first
-    assert_equal false, author.unique_categorized_posts.includes(:special_comments).limit(0).exists?
-    assert_equal true, author.unique_categorized_posts.includes(:special_comments).limit(1).exists?
+    unique_categorized_posts = author.unique_categorized_posts.includes(:special_comments)
+    assert_no_queries { assert_equal false, unique_categorized_posts.limit(0).exists? }
+    assert_queries(1) { assert_equal true, unique_categorized_posts.limit(1).exists? }
   end
 
   def test_exists_with_distinct_association_includes_limit_and_order
     author = Author.first
-    assert_equal false, author.unique_categorized_posts.includes(:special_comments).order("comments.tags_count DESC").limit(0).exists?
-    assert_equal true, author.unique_categorized_posts.includes(:special_comments).order("comments.tags_count DESC").limit(1).exists?
+    unique_categorized_posts = author.unique_categorized_posts.includes(:special_comments).order("comments.tags_count DESC")
+    assert_no_queries { assert_equal false, unique_categorized_posts.limit(0).exists? }
+    assert_queries(1) { assert_equal true, unique_categorized_posts.limit(1).exists? }
+  end
+
+  def test_exists_should_reference_correct_aliases_while_joining_tables_of_has_many_through_association
+    ratings = developers(:david).ratings.includes(comment: :post).where(posts: { id: 1 })
+    assert_queries(1) { assert_not_predicate ratings.limit(1), :exists? }
   end
 
   def test_exists_with_empty_table_and_no_args_given
@@ -365,7 +414,7 @@ class FinderTest < ActiveRecord::TestCase
   end
 
   def test_take
-    assert_equal topics(:first), Topic.take
+    assert_equal topics(:first), Topic.where("title = 'The First Topic'").take
   end
 
   def test_take_failing
@@ -516,7 +565,7 @@ class FinderTest < ActiveRecord::TestCase
     assert_nil Topic.offset(4).second_to_last
     assert_nil Topic.offset(5).second_to_last
 
-    #test with limit
+    # test with limit
     assert_nil Topic.limit(1).second
     assert_nil Topic.limit(1).second_to_last
   end
@@ -599,13 +648,13 @@ class FinderTest < ActiveRecord::TestCase
   def test_last_with_integer_and_order_should_use_sql_limit
     relation = Topic.order("title")
     assert_queries(1) { relation.last(5) }
-    assert !relation.loaded?
+    assert_not_predicate relation, :loaded?
   end
 
   def test_last_with_integer_and_reorder_should_use_sql_limit
     relation = Topic.reorder("title")
     assert_queries(1) { relation.last(5) }
-    assert !relation.loaded?
+    assert_not_predicate relation, :loaded?
   end
 
   def test_last_on_loaded_relation_should_not_use_sql
@@ -618,7 +667,7 @@ class FinderTest < ActiveRecord::TestCase
 
   def test_last_with_irreversible_order
     assert_raises(ActiveRecord::IrreversibleOrderError) do
-      Topic.order("coalesce(author_name, title)").last
+      Topic.order(Arel.sql("coalesce(author_name, title)")).last
     end
   end
 
@@ -630,12 +679,34 @@ class FinderTest < ActiveRecord::TestCase
     assert_equal comments.limit(2).to_a.last(2), comments.limit(2).last(2)
     assert_equal comments.limit(2).to_a.last(3), comments.limit(2).last(3)
 
+    assert_equal comments.offset(2).to_a.last, comments.offset(2).last
+    assert_equal comments.offset(2).to_a.last(2), comments.offset(2).last(2)
+    assert_equal comments.offset(2).to_a.last(3), comments.offset(2).last(3)
+
     comments = comments.offset(1)
     assert_equal comments.limit(2).to_a.last, comments.limit(2).last
     assert_equal comments.limit(2).to_a.last(2), comments.limit(2).last(2)
     assert_equal comments.limit(2).to_a.last(3), comments.limit(2).last(3)
   end
 
+  def test_first_on_relation_with_limit_and_offset
+    post = posts("sti_comments")
+
+    comments = post.comments.order(id: :asc)
+    assert_equal comments.limit(2).to_a.first, comments.limit(2).first
+    assert_equal comments.limit(2).to_a.first(2), comments.limit(2).first(2)
+    assert_equal comments.limit(2).to_a.first(3), comments.limit(2).first(3)
+
+    assert_equal comments.offset(2).to_a.first, comments.offset(2).first
+    assert_equal comments.offset(2).to_a.first(2), comments.offset(2).first(2)
+    assert_equal comments.offset(2).to_a.first(3), comments.offset(2).first(3)
+
+    comments = comments.offset(1)
+    assert_equal comments.limit(2).to_a.first, comments.limit(2).first
+    assert_equal comments.limit(2).to_a.first(2), comments.limit(2).first(2)
+    assert_equal comments.limit(2).to_a.first(3), comments.limit(2).first(3)
+  end
+
   def test_take_and_first_and_last_with_integer_should_return_an_array
     assert_kind_of Array, Topic.take(5)
     assert_kind_of Array, Topic.first(5)
@@ -656,8 +727,8 @@ class FinderTest < ActiveRecord::TestCase
     assert_raise(ActiveModel::MissingAttributeError) { topic.title? }
     assert_nil topic.read_attribute("title")
     assert_equal "David", topic.author_name
-    assert !topic.attribute_present?("title")
-    assert !topic.attribute_present?(:title)
+    assert_not topic.attribute_present?("title")
+    assert_not topic.attribute_present?(:title)
     assert topic.attribute_present?("author_name")
     assert_respond_to topic, "author_name"
   end
@@ -741,6 +812,15 @@ class FinderTest < ActiveRecord::TestCase
     assert_equal [1, 2, 6, 7, 8], Comment.where(id: [1..2, 6..8]).to_a.map(&:id).sort
   end
 
+  def test_find_on_hash_conditions_with_open_ended_range
+    assert_equal [1, 2, 3], Comment.where(id: Float::INFINITY..3).to_a.map(&:id).sort
+  end
+
+  def test_find_on_hash_conditions_with_numeric_range_for_string
+    topic = Topic.create!(title: "12 Factor App")
+    assert_equal [topic], Topic.where(title: 10..2).to_a
+  end
+
   def test_find_on_multiple_hash_conditions
     assert Topic.where(author_name: "David", title: "The First Topic", replies_count: 1, approved: false).find(1)
     assert_raise(ActiveRecord::RecordNotFound) { Topic.where(author_name: "David", title: "The First Topic", replies_count: 1, approved: true).find(1) }
@@ -797,6 +877,25 @@ class FinderTest < ActiveRecord::TestCase
     assert_equal customers(:david), found_customer
   end
 
+  def test_hash_condition_find_with_aggregate_having_three_mappings_array
+    david_address = customers(:david).address
+    zaphod_address = customers(:zaphod).address
+    barney_address = customers(:barney).address
+    assert_kind_of Address, david_address
+    assert_kind_of Address, zaphod_address
+    found_customers = Customer.where(address: [david_address, zaphod_address, barney_address])
+    assert_equal [customers(:david), customers(:zaphod), customers(:barney)], found_customers.sort_by(&:id)
+  end
+
+  def test_hash_condition_find_with_aggregate_having_one_mapping_array
+    david_balance = customers(:david).balance
+    zaphod_balance = customers(:zaphod).balance
+    assert_kind_of Money, david_balance
+    assert_kind_of Money, zaphod_balance
+    found_customers = Customer.where(balance: [david_balance, zaphod_balance])
+    assert_equal [customers(:david), customers(:zaphod)], found_customers.sort_by(&:id)
+  end
+
   def test_hash_condition_find_with_aggregate_attribute_having_same_name_as_field_and_key_value_being_aggregate
     gps_location = customers(:david).gps_location
     assert_kind_of GpsLocation, gps_location
@@ -1002,14 +1101,6 @@ class FinderTest < ActiveRecord::TestCase
     assert_raise(ArgumentError) { Topic.find_by_title_and_author_name("The First Topic") }
   end
 
-  def test_find_last_with_offset
-    devs = Developer.order("id")
-
-    assert_equal devs[2], Developer.offset(2).first
-    assert_equal devs[-3], Developer.offset(2).last
-    assert_equal devs[-3], Developer.offset(2).order("id DESC").first
-  end
-
   def test_find_by_nil_attribute
     topic = Topic.find_by_last_read nil
     assert_not_nil topic
@@ -1098,6 +1189,11 @@ class FinderTest < ActiveRecord::TestCase
       order("author_addresses_authors.id DESC").limit(3).to_a.size
   end
 
+  def test_find_with_eager_loading_collection_and_ordering_by_collection_primary_key
+    assert_equal Post.first, Post.eager_load(comments: :ratings).
+      order("posts.id, ratings.id, comments.id").first
+  end
+
   def test_find_with_nil_inside_set_passed_for_one_attribute
     client_of = Company.
       where(client_of: [2, 1, nil],
@@ -1189,7 +1285,7 @@ class FinderTest < ActiveRecord::TestCase
 
   test "find_by with associations" do
     assert_equal authors(:david), Post.find_by(author: authors(:david)).author
-    assert_equal authors(:mary) , Post.find_by(author: authors(:mary)).author
+    assert_equal authors(:mary), Post.find_by(author: authors(:mary)).author
   end
 
   test "find_by doesn't have implicit ordering" do
@@ -1254,12 +1350,12 @@ class FinderTest < ActiveRecord::TestCase
 
   test "#skip_query_cache! for #exists? with a limited eager load" do
     Topic.cache do
-      assert_queries(2) do
+      assert_queries(1) do
         Topic.eager_load(:replies).limit(1).exists?
         Topic.eager_load(:replies).limit(1).exists?
       end
 
-      assert_queries(4) do
+      assert_queries(2) do
         Topic.eager_load(:replies).limit(1).skip_query_cache!.exists?
         Topic.eager_load(:replies).limit(1).skip_query_cache!.exists?
       end
diff --git a/activerecord/test/cases/fixtures_test.rb b/activerecord/test/cases/fixtures_test.rb
index b0b63f5203..ee88bd8144 100644
--- a/activerecord/test/cases/fixtures_test.rb
+++ b/activerecord/test/cases/fixtures_test.rb
@@ -79,6 +79,151 @@ class FixturesTest < ActiveRecord::TestCase
         ActiveSupport::Notifications.unsubscribe(subscription)
       end
     end
+
+    def test_bulk_insert_multiple_table_with_a_multi_statement_query
+      subscriber = InsertQuerySubscriber.new
+      subscription = ActiveSupport::Notifications.subscribe("sql.active_record", subscriber)
+
+      create_fixtures("bulbs", "authors", "computers")
+
+      expected_sql = <<~EOS.chop
+        INSERT INTO #{ActiveRecord::Base.connection.quote_table_name("bulbs")} .*
+        INSERT INTO #{ActiveRecord::Base.connection.quote_table_name("authors")} .*
+        INSERT INTO #{ActiveRecord::Base.connection.quote_table_name("computers")} .*
+      EOS
+      assert_equal 1, subscriber.events.size
+      assert_match(/#{expected_sql}/, subscriber.events.first)
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscription)
+    end
+
+    def test_bulk_insert_with_a_multi_statement_query_raises_an_exception_when_any_insert_fails
+      require "models/aircraft"
+
+      assert_equal false, Aircraft.columns_hash["wheels_count"].null
+      fixtures = {
+        "aircraft" => [
+          { "name" => "working_aircrafts", "wheels_count" => 2 },
+          { "name" => "broken_aircrafts", "wheels_count" => nil },
+        ]
+      }
+
+      assert_no_difference "Aircraft.count" do
+        assert_raises(ActiveRecord::NotNullViolation) do
+          ActiveRecord::Base.connection.insert_fixtures_set(fixtures)
+        end
+      end
+    end
+  end
+
+  if current_adapter?(:Mysql2Adapter)
+    def test_insert_fixtures_set_raises_an_error_when_max_allowed_packet_is_smaller_than_fixtures_set_size
+      conn = ActiveRecord::Base.connection
+      mysql_margin = 2
+      packet_size = 1024
+      bytes_needed_to_have_a_1024_bytes_fixture = 858
+      fixtures = {
+        "traffic_lights" => [
+          { "location" => "US", "state" => ["NY"], "long_state" => ["a" * bytes_needed_to_have_a_1024_bytes_fixture] },
+        ]
+      }
+
+      conn.stubs(:max_allowed_packet).returns(packet_size - mysql_margin)
+
+      error = assert_raises(ActiveRecord::ActiveRecordError) { conn.insert_fixtures_set(fixtures) }
+      assert_match(/Fixtures set is too large #{packet_size}\./, error.message)
+    end
+
+    def test_insert_fixture_set_when_max_allowed_packet_is_bigger_than_fixtures_set_size
+      conn = ActiveRecord::Base.connection
+      packet_size = 1024
+      fixtures = {
+        "traffic_lights" => [
+          { "location" => "US", "state" => ["NY"], "long_state" => ["a" * 51] },
+        ]
+      }
+
+      conn.stubs(:max_allowed_packet).returns(packet_size)
+
+      assert_difference "TrafficLight.count" do
+        conn.insert_fixtures_set(fixtures)
+      end
+    end
+
+    def test_insert_fixtures_set_split_the_total_sql_into_two_chunks_smaller_than_max_allowed_packet
+      subscriber = InsertQuerySubscriber.new
+      subscription = ActiveSupport::Notifications.subscribe("sql.active_record", subscriber)
+      conn = ActiveRecord::Base.connection
+      packet_size = 1024
+      fixtures = {
+        "traffic_lights" => [
+          { "location" => "US", "state" => ["NY"], "long_state" => ["a" * 450] },
+        ],
+        "comments" => [
+          { "post_id" => 1, "body" => "a" * 450 },
+        ]
+      }
+
+      conn.stubs(:max_allowed_packet).returns(packet_size)
+
+      conn.insert_fixtures_set(fixtures)
+      assert_equal 2, subscriber.events.size
+      assert_operator subscriber.events.first.bytesize, :<, packet_size
+      assert_operator subscriber.events.second.bytesize, :<, packet_size
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscription)
+    end
+
+    def test_insert_fixtures_set_concat_total_sql_into_a_single_packet_smaller_than_max_allowed_packet
+      subscriber = InsertQuerySubscriber.new
+      subscription = ActiveSupport::Notifications.subscribe("sql.active_record", subscriber)
+      conn = ActiveRecord::Base.connection
+      packet_size = 1024
+      fixtures = {
+        "traffic_lights" => [
+          { "location" => "US", "state" => ["NY"], "long_state" => ["a" * 200] },
+        ],
+        "comments" => [
+          { "post_id" => 1, "body" => "a" * 200 },
+        ]
+      }
+
+      conn.stubs(:max_allowed_packet).returns(packet_size)
+
+      assert_difference ["TrafficLight.count", "Comment.count"], +1 do
+        conn.insert_fixtures_set(fixtures)
+      end
+      assert_equal 1, subscriber.events.size
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscription)
+    end
+  end
+
+  def test_auto_value_on_primary_key
+    fixtures = [
+      { "name" => "first", "wheels_count" => 2 },
+      { "name" => "second", "wheels_count" => 3 }
+    ]
+    conn = ActiveRecord::Base.connection
+    assert_nothing_raised do
+      conn.insert_fixtures_set({ "aircraft" => fixtures }, ["aircraft"])
+    end
+    result = conn.select_all("SELECT name, wheels_count FROM aircraft ORDER BY id")
+    assert_equal fixtures, result.to_a
+  end
+
+  def test_deprecated_insert_fixtures
+    fixtures = [
+      { "name" => "first", "wheels_count" => 2 },
+      { "name" => "second", "wheels_count" => 3 }
+    ]
+    conn = ActiveRecord::Base.connection
+    conn.delete("DELETE FROM aircraft")
+    assert_deprecated do
+      conn.insert_fixtures(fixtures, "aircraft")
+    end
+    result = conn.select_all("SELECT name, wheels_count FROM aircraft ORDER BY id")
+    assert_equal fixtures, result.to_a
   end
 
   def test_broken_yaml_exception
@@ -247,8 +392,8 @@ class FixturesTest < ActiveRecord::TestCase
   def test_nonexistent_fixture_file
     nonexistent_fixture_path = FIXTURES_ROOT + "/imnothere"
 
-    #sanity check to make sure that this file never exists
-    assert Dir[nonexistent_fixture_path + "*"].empty?
+    # sanity check to make sure that this file never exists
+    assert_empty Dir[nonexistent_fixture_path + "*"]
 
     assert_raise(Errno::ENOENT) do
       ActiveRecord::FixtureSet.new(Account.connection, "companies", Company, nonexistent_fixture_path)
@@ -447,14 +592,14 @@ class FixturesWithoutInstantiationTest < ActiveRecord::TestCase
   fixtures :topics, :developers, :accounts
 
   def test_without_complete_instantiation
-    assert !defined?(@first)
-    assert !defined?(@topics)
-    assert !defined?(@developers)
-    assert !defined?(@accounts)
+    assert_not defined?(@first)
+    assert_not defined?(@topics)
+    assert_not defined?(@developers)
+    assert_not defined?(@accounts)
   end
 
   def test_fixtures_from_root_yml_without_instantiation
-    assert !defined?(@unknown), "@unknown is not defined"
+    assert_not defined?(@unknown), "@unknown is not defined"
   end
 
   def test_visibility_of_accessor_method
@@ -489,7 +634,7 @@ class FixturesWithoutInstanceInstantiationTest < ActiveRecord::TestCase
   fixtures :topics, :developers, :accounts
 
   def test_without_instance_instantiation
-    assert !defined?(@first), "@first is not defined"
+    assert_not defined?(@first), "@first is not defined"
   end
 end
 
@@ -937,13 +1082,13 @@ class FoxyFixturesTest < ActiveRecord::TestCase
   def test_supports_inline_habtm
     assert(parrots(:george).treasures.include?(treasures(:diamond)))
     assert(parrots(:george).treasures.include?(treasures(:sapphire)))
-    assert(!parrots(:george).treasures.include?(treasures(:ruby)))
+    assert_not(parrots(:george).treasures.include?(treasures(:ruby)))
   end
 
   def test_supports_inline_habtm_with_specified_id
     assert(parrots(:polly).treasures.include?(treasures(:ruby)))
     assert(parrots(:polly).treasures.include?(treasures(:sapphire)))
-    assert(!parrots(:polly).treasures.include?(treasures(:diamond)))
+    assert_not(parrots(:polly).treasures.include?(treasures(:diamond)))
   end
 
   def test_supports_yaml_arrays
@@ -998,10 +1143,10 @@ class FoxyFixturesTest < ActiveRecord::TestCase
   end
 
   def test_resolves_enums
-    assert books(:awdr).published?
-    assert books(:awdr).read?
-    assert books(:rfr).proposed?
-    assert books(:ddd).published?
+    assert_predicate books(:awdr), :published?
+    assert_predicate books(:awdr), :read?
+    assert_predicate books(:rfr), :proposed?
+    assert_predicate books(:ddd), :published?
   end
 end
 
@@ -1041,7 +1186,7 @@ class CustomNameForFixtureOrModelTest < ActiveRecord::TestCase
   end
 
   def test_table_name_is_defined_in_the_model
-    assert_equal "randomly_named_table2", ActiveRecord::FixtureSet::all_loaded_fixtures["admin/randomly_named_a9"].table_name
+    assert_equal "randomly_named_table2", ActiveRecord::FixtureSet.all_loaded_fixtures["admin/randomly_named_a9"].table_name
     assert_equal "randomly_named_table2", Admin::ClassNameThatDoesNotFollowCONVENTIONS1.table_name
   end
 end
diff --git a/activerecord/test/cases/habtm_destroy_order_test.rb b/activerecord/test/cases/habtm_destroy_order_test.rb
index 5e503272e1..b15e1b48c4 100644
--- a/activerecord/test/cases/habtm_destroy_order_test.rb
+++ b/activerecord/test/cases/habtm_destroy_order_test.rb
@@ -15,7 +15,7 @@ class HabtmDestroyOrderTest < ActiveRecord::TestCase
         sicp.destroy
       end
     end
-    assert !sicp.destroyed?
+    assert_not_predicate sicp, :destroyed?
   end
 
   test "should not raise error if have foreign key in the join table" do
@@ -42,7 +42,7 @@ class HabtmDestroyOrderTest < ActiveRecord::TestCase
       ben.lessons << sicp
       ben.save!
       ben.destroy
-      assert !ben.reload.lessons.empty?
+      assert_not_empty ben.reload.lessons
     ensure
       # get rid of it so Student is still like it was
       Student.reset_callbacks(:destroy)
@@ -58,6 +58,6 @@ class HabtmDestroyOrderTest < ActiveRecord::TestCase
     assert_raises LessonError do
       sicp.destroy
     end
-    assert !sicp.reload.students.empty?
+    assert_not_empty sicp.reload.students
   end
 end
diff --git a/activerecord/test/cases/helper.rb b/activerecord/test/cases/helper.rb
index 6ea02ac191..66f11fe5bd 100644
--- a/activerecord/test/cases/helper.rb
+++ b/activerecord/test/cases/helper.rb
@@ -184,4 +184,4 @@ module InTimeZone
     end
 end
 
-require "mocha/setup" # FIXME: stop using mocha
+require "mocha/minitest" # FIXME: stop using mocha
diff --git a/activerecord/test/cases/inheritance_test.rb b/activerecord/test/cases/inheritance_test.rb
index c931f7d21c..4a0ad0442a 100644
--- a/activerecord/test/cases/inheritance_test.rb
+++ b/activerecord/test/cases/inheritance_test.rb
@@ -130,61 +130,70 @@ class InheritanceTest < ActiveRecord::TestCase
   end
 
   def test_descends_from_active_record
-    assert !ActiveRecord::Base.descends_from_active_record?
+    assert_not_predicate ActiveRecord::Base, :descends_from_active_record?
 
     # Abstract subclass of AR::Base.
-    assert LoosePerson.descends_from_active_record?
+    assert_predicate LoosePerson, :descends_from_active_record?
 
     # Concrete subclass of an abstract class.
-    assert LooseDescendant.descends_from_active_record?
+    assert_predicate LooseDescendant, :descends_from_active_record?
 
     # Concrete subclass of AR::Base.
-    assert TightPerson.descends_from_active_record?
+    assert_predicate TightPerson, :descends_from_active_record?
 
     # Concrete subclass of a concrete class but has no type column.
-    assert TightDescendant.descends_from_active_record?
+    assert_predicate TightDescendant, :descends_from_active_record?
 
     # Concrete subclass of AR::Base.
-    assert Post.descends_from_active_record?
+    assert_predicate Post, :descends_from_active_record?
 
     # Concrete subclasses of a concrete class which has a type column.
-    assert !StiPost.descends_from_active_record?
-    assert !SubStiPost.descends_from_active_record?
+    assert_not_predicate StiPost, :descends_from_active_record?
+    assert_not_predicate SubStiPost, :descends_from_active_record?
 
     # Abstract subclass of a concrete class which has a type column.
     # This is pathological, as you'll never have Sub < Abstract < Concrete.
-    assert !AbstractStiPost.descends_from_active_record?
+    assert_not_predicate AbstractStiPost, :descends_from_active_record?
 
     # Concrete subclass of an abstract class which has a type column.
-    assert !SubAbstractStiPost.descends_from_active_record?
+    assert_not_predicate SubAbstractStiPost, :descends_from_active_record?
   end
 
   def test_company_descends_from_active_record
-    assert !ActiveRecord::Base.descends_from_active_record?
+    assert_not_predicate ActiveRecord::Base, :descends_from_active_record?
     assert AbstractCompany.descends_from_active_record?, "AbstractCompany should descend from ActiveRecord::Base"
     assert Company.descends_from_active_record?, "Company should descend from ActiveRecord::Base"
-    assert !Class.new(Company).descends_from_active_record?, "Company subclass should not descend from ActiveRecord::Base"
+    assert_not Class.new(Company).descends_from_active_record?, "Company subclass should not descend from ActiveRecord::Base"
   end
 
   def test_abstract_class
-    assert !ActiveRecord::Base.abstract_class?
-    assert LoosePerson.abstract_class?
-    assert !LooseDescendant.abstract_class?
+    assert_not_predicate ActiveRecord::Base, :abstract_class?
+    assert_predicate LoosePerson, :abstract_class?
+    assert_not_predicate LooseDescendant, :abstract_class?
   end
 
   def test_inheritance_base_class
     assert_equal Post, Post.base_class
+    assert_predicate Post, :base_class?
     assert_equal Post, SpecialPost.base_class
+    assert_not_predicate SpecialPost, :base_class?
     assert_equal Post, StiPost.base_class
+    assert_not_predicate StiPost, :base_class?
     assert_equal Post, SubStiPost.base_class
+    assert_not_predicate SubStiPost, :base_class?
     assert_equal SubAbstractStiPost, SubAbstractStiPost.base_class
+    assert_predicate SubAbstractStiPost, :base_class?
   end
 
   def test_abstract_inheritance_base_class
     assert_equal LoosePerson, LoosePerson.base_class
+    assert_predicate LoosePerson, :base_class?
     assert_equal LooseDescendant, LooseDescendant.base_class
+    assert_predicate LooseDescendant, :base_class?
     assert_equal TightPerson, TightPerson.base_class
+    assert_predicate TightPerson, :base_class?
     assert_equal TightPerson, TightDescendant.base_class
+    assert_not_predicate TightDescendant, :base_class?
   end
 
   def test_base_class_activerecord_error
@@ -280,6 +289,21 @@ class InheritanceTest < ActiveRecord::TestCase
     assert_equal Firm, firm.class
   end
 
+  def test_where_new_with_subclass
+    firm = Company.where(type: "Firm").new
+    assert_equal Firm, firm.class
+  end
+
+  def test_where_create_with_subclass
+    firm = Company.where(type: "Firm").create(name: "Basecamp")
+    assert_equal Firm, firm.class
+  end
+
+  def test_where_create_bang_with_subclass
+    firm = Company.where(type: "Firm").create!(name: "Basecamp")
+    assert_equal Firm, firm.class
+  end
+
   def test_new_with_abstract_class
     e = assert_raises(NotImplementedError) do
       AbstractCompany.new
@@ -302,6 +326,30 @@ class InheritanceTest < ActiveRecord::TestCase
     assert_raise(ActiveRecord::SubclassNotFound) { Company.new(type: "Account") }
   end
 
+  def test_where_new_with_invalid_type
+    assert_raise(ActiveRecord::SubclassNotFound) { Company.where(type: "InvalidType").new }
+  end
+
+  def test_where_new_with_unrelated_type
+    assert_raise(ActiveRecord::SubclassNotFound) { Company.where(type: "Account").new }
+  end
+
+  def test_where_create_with_invalid_type
+    assert_raise(ActiveRecord::SubclassNotFound) { Company.where(type: "InvalidType").create }
+  end
+
+  def test_where_create_with_unrelated_type
+    assert_raise(ActiveRecord::SubclassNotFound) { Company.where(type: "Account").create }
+  end
+
+  def test_where_create_bang_with_invalid_type
+    assert_raise(ActiveRecord::SubclassNotFound) { Company.where(type: "InvalidType").create! }
+  end
+
+  def test_where_create_bang_with_unrelated_type
+    assert_raise(ActiveRecord::SubclassNotFound) { Company.where(type: "Account").create! }
+  end
+
   def test_new_with_unrelated_namespaced_type
     without_store_full_sti_class do
       e = assert_raises ActiveRecord::SubclassNotFound do
diff --git a/activerecord/test/cases/instrumentation_test.rb b/activerecord/test/cases/instrumentation_test.rb
new file mode 100644
index 0000000000..e6e8468757
--- /dev/null
+++ b/activerecord/test/cases/instrumentation_test.rb
@@ -0,0 +1,72 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/book"
+
+module ActiveRecord
+  class InstrumentationTest < ActiveRecord::TestCase
+    def test_payload_name_on_load
+      Book.create(name: "test book")
+      subscriber = ActiveSupport::Notifications.subscribe("sql.active_record") do |*args|
+        event = ActiveSupport::Notifications::Event.new(*args)
+        if event.payload[:sql].match "SELECT"
+          assert_equal "Book Load", event.payload[:name]
+        end
+      end
+      Book.first
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscriber) if subscriber
+    end
+
+    def test_payload_name_on_create
+      subscriber = ActiveSupport::Notifications.subscribe("sql.active_record") do |*args|
+        event = ActiveSupport::Notifications::Event.new(*args)
+        if event.payload[:sql].match "INSERT"
+          assert_equal "Book Create", event.payload[:name]
+        end
+      end
+      Book.create(name: "test book")
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscriber) if subscriber
+    end
+
+    def test_payload_name_on_update
+      subscriber = ActiveSupport::Notifications.subscribe("sql.active_record") do |*args|
+        event = ActiveSupport::Notifications::Event.new(*args)
+        if event.payload[:sql].match "UPDATE"
+          assert_equal "Book Update", event.payload[:name]
+        end
+      end
+      book = Book.create(name: "test book")
+      book.update_attribute(:name, "new name")
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscriber) if subscriber
+    end
+
+    def test_payload_name_on_update_all
+      subscriber = ActiveSupport::Notifications.subscribe("sql.active_record") do |*args|
+        event = ActiveSupport::Notifications::Event.new(*args)
+        if event.payload[:sql].match "UPDATE"
+          assert_equal "Book Update All", event.payload[:name]
+        end
+      end
+      Book.create(name: "test book")
+      Book.update_all(name: "new name")
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscriber) if subscriber
+    end
+
+    def test_payload_name_on_destroy
+      subscriber = ActiveSupport::Notifications.subscribe("sql.active_record") do |*args|
+        event = ActiveSupport::Notifications::Event.new(*args)
+        if event.payload[:sql].match "DELETE"
+          assert_equal "Book Destroy", event.payload[:name]
+        end
+      end
+      book = Book.create(name: "test book")
+      book.destroy
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscriber) if subscriber
+    end
+  end
+end
diff --git a/activerecord/test/cases/invertible_migration_test.rb b/activerecord/test/cases/invertible_migration_test.rb
index 20e747142b..363beb4780 100644
--- a/activerecord/test/cases/invertible_migration_test.rb
+++ b/activerecord/test/cases/invertible_migration_test.rb
@@ -161,6 +161,15 @@ module ActiveRecord
       end
     end
 
+    class UpOnlyMigration < SilentMigration
+      def change
+        add_column :horses, :oldie, :integer, default: 0
+        up_only { execute "update horses set oldie = 1" }
+      end
+    end
+
+    self.use_transactional_tests = false
+
     setup do
       @verbose_was, ActiveRecord::Migration.verbose = ActiveRecord::Migration.verbose, false
     end
@@ -206,7 +215,7 @@ module ActiveRecord
       migration = InvertibleMigration.new
       migration.migrate :up
       migration.migrate :down
-      assert !migration.connection.table_exists?("horses")
+      assert_not migration.connection.table_exists?("horses")
     end
 
     def test_migrate_revert
@@ -214,11 +223,11 @@ module ActiveRecord
       revert = InvertibleRevertMigration.new
       migration.migrate :up
       revert.migrate :up
-      assert !migration.connection.table_exists?("horses")
+      assert_not migration.connection.table_exists?("horses")
       revert.migrate :down
       assert migration.connection.table_exists?("horses")
       migration.migrate :down
-      assert !migration.connection.table_exists?("horses")
+      assert_not migration.connection.table_exists?("horses")
     end
 
     def test_migrate_revert_by_part
@@ -232,12 +241,12 @@ module ActiveRecord
       }
       migration.migrate :up
       assert_equal [:both, :up], received
-      assert !migration.connection.table_exists?("horses")
+      assert_not migration.connection.table_exists?("horses")
       assert migration.connection.table_exists?("new_horses")
       migration.migrate :down
       assert_equal [:both, :up, :both, :down], received
       assert migration.connection.table_exists?("horses")
-      assert !migration.connection.table_exists?("new_horses")
+      assert_not migration.connection.table_exists?("new_horses")
     end
 
     def test_migrate_revert_whole_migration
@@ -246,11 +255,11 @@ module ActiveRecord
         revert = RevertWholeMigration.new(klass)
         migration.migrate :up
         revert.migrate :up
-        assert !migration.connection.table_exists?("horses")
+        assert_not migration.connection.table_exists?("horses")
         revert.migrate :down
         assert migration.connection.table_exists?("horses")
         migration.migrate :down
-        assert !migration.connection.table_exists?("horses")
+        assert_not migration.connection.table_exists?("horses")
       end
     end
 
@@ -259,7 +268,7 @@ module ActiveRecord
       revert.migrate :down
       assert revert.connection.table_exists?("horses")
       revert.migrate :up
-      assert !revert.connection.table_exists?("horses")
+      assert_not revert.connection.table_exists?("horses")
     end
 
     def test_migrate_revert_change_column_default
@@ -295,6 +304,8 @@ module ActiveRecord
 
         migration2.migrate(:down)
         assert_equal false, Horse.connection.extension_enabled?("hstore")
+      ensure
+        enable_extension!("hstore", ActiveRecord::Base.connection)
       end
     end
 
@@ -330,7 +341,7 @@ module ActiveRecord
     def test_legacy_down
       LegacyMigration.migrate :up
       LegacyMigration.migrate :down
-      assert !ActiveRecord::Base.connection.table_exists?("horses"), "horses should not exist"
+      assert_not ActiveRecord::Base.connection.table_exists?("horses"), "horses should not exist"
     end
 
     def test_up
@@ -341,7 +352,7 @@ module ActiveRecord
     def test_down
       LegacyMigration.up
       LegacyMigration.down
-      assert !ActiveRecord::Base.connection.table_exists?("horses"), "horses should not exist"
+      assert_not ActiveRecord::Base.connection.table_exists?("horses"), "horses should not exist"
     end
 
     def test_migrate_down_with_table_name_prefix
@@ -350,7 +361,7 @@ module ActiveRecord
       migration = InvertibleMigration.new
       migration.migrate(:up)
       assert_nothing_raised { migration.migrate(:down) }
-      assert !ActiveRecord::Base.connection.table_exists?("p_horses_s"), "p_horses_s should not exist"
+      assert_not ActiveRecord::Base.connection.table_exists?("p_horses_s"), "p_horses_s should not exist"
     ensure
       ActiveRecord::Base.table_name_prefix = ActiveRecord::Base.table_name_suffix = ""
     end
@@ -372,9 +383,27 @@ module ActiveRecord
         connection = ActiveRecord::Base.connection
         assert connection.index_exists?(:horses, :content),
                "index on content should exist"
-        assert !connection.index_exists?(:horses, :content, name: "horses_index_named"),
+        assert_not connection.index_exists?(:horses, :content, name: "horses_index_named"),
               "horses_index_named index should not exist"
       end
     end
+
+    def test_up_only
+      InvertibleMigration.new.migrate(:up)
+      horse1 = Horse.create
+      # populates existing horses with oldie = 1 but new ones have default 0
+      UpOnlyMigration.new.migrate(:up)
+      Horse.reset_column_information
+      horse1.reload
+      horse2 = Horse.create
+
+      assert 1, horse1.oldie # created before migration
+      assert 0, horse2.oldie # created after migration
+
+      UpOnlyMigration.new.migrate(:down) # should be no error
+      connection = ActiveRecord::Base.connection
+      assert_not connection.column_exists?(:horses, :oldie)
+      Horse.reset_column_information
+    end
   end
 end
diff --git a/activerecord/test/cases/json_attribute_test.rb b/activerecord/test/cases/json_attribute_test.rb
index 63f3c77fc3..afc39d0420 100644
--- a/activerecord/test/cases/json_attribute_test.rb
+++ b/activerecord/test/cases/json_attribute_test.rb
@@ -19,14 +19,14 @@ class JsonAttributeTest < ActiveRecord::TestCase
   def setup
     super
     @connection.create_table("json_data_type") do |t|
-      t.text "payload"
-      t.text "settings"
+      t.string "payload"
+      t.string "settings"
     end
   end
 
   private
     def column_type
-      :text
+      :string
     end
 
     def klass
diff --git a/activerecord/test/cases/json_serialization_test.rb b/activerecord/test/cases/json_serialization_test.rb
index 52fe488cd5..82cf281cff 100644
--- a/activerecord/test/cases/json_serialization_test.rb
+++ b/activerecord/test/cases/json_serialization_test.rb
@@ -252,7 +252,7 @@ class DatabaseConnectedJsonEncodingTest < ActiveRecord::TestCase
     def @david.favorite_quote; "Constraints are liberating"; end
     json = @david.to_json(include: :posts, methods: :favorite_quote)
 
-    assert !@david.posts.first.respond_to?(:favorite_quote)
+    assert_not_respond_to @david.posts.first, :favorite_quote
     assert_match %r{"favorite_quote":"Constraints are liberating"}, json
     assert_equal 1, %r{"favorite_quote":}.match(json).size
   end
diff --git a/activerecord/test/cases/json_shared_test_cases.rb b/activerecord/test/cases/json_shared_test_cases.rb
index 56ec8c8a82..9b79803503 100644
--- a/activerecord/test/cases/json_shared_test_cases.rb
+++ b/activerecord/test/cases/json_shared_test_cases.rb
@@ -23,10 +23,10 @@ module JSONSharedTestCases
   def test_column
     column = klass.columns_hash["payload"]
     assert_equal column_type, column.type
-    assert_equal column_type.to_s, column.sql_type
+    assert_type_match column_type, column.sql_type
 
     type = klass.type_for_attribute("payload")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_change_table_supports_json
@@ -36,7 +36,7 @@ module JSONSharedTestCases
     klass.reset_column_information
     column = klass.columns_hash["users"]
     assert_equal column_type, column.type
-    assert_equal column_type.to_s, column.sql_type
+    assert_type_match column_type, column.sql_type
   end
 
   def test_schema_dumping
@@ -66,26 +66,26 @@ module JSONSharedTestCases
   end
 
   def test_rewrite
-    @connection.execute(%q|insert into json_data_type (payload) VALUES ('{"k":"v"}')|)
+    @connection.execute(insert_statement_per_database('{"k":"v"}'))
     x = klass.first
     x.payload = { '"a\'' => "b" }
     assert x.save!
   end
 
   def test_select
-    @connection.execute(%q|insert into json_data_type (payload) VALUES ('{"k":"v"}')|)
+    @connection.execute(insert_statement_per_database('{"k":"v"}'))
     x = klass.first
     assert_equal({ "k" => "v" }, x.payload)
   end
 
   def test_select_multikey
-    @connection.execute(%q|insert into json_data_type (payload) VALUES ('{"k1":"v1", "k2":"v2", "k3":[1,2,3]}')|)
+    @connection.execute(insert_statement_per_database('{"k1":"v1", "k2":"v2", "k3":[1,2,3]}'))
     x = klass.first
     assert_equal({ "k1" => "v1", "k2" => "v2", "k3" => [1, 2, 3] }, x.payload)
   end
 
   def test_null_json
-    @connection.execute("insert into json_data_type (payload) VALUES(null)")
+    @connection.execute(insert_statement_per_database("null"))
     x = klass.first
     assert_nil(x.payload)
   end
@@ -101,19 +101,19 @@ module JSONSharedTestCases
     x = klass.where(payload: nil).first
     assert_nil(x)
 
-    json.update_attributes(payload: nil)
+    json.update(payload: nil)
     x = klass.where(payload: nil).first
     assert_equal(json.reload, x)
   end
 
   def test_select_array_json_value
-    @connection.execute(%q|insert into json_data_type (payload) VALUES ('["v0",{"k1":"v1"}]')|)
+    @connection.execute(insert_statement_per_database('["v0",{"k1":"v1"}]'))
     x = klass.first
     assert_equal(["v0", { "k1" => "v1" }], x.payload)
   end
 
   def test_rewrite_array_json_value
-    @connection.execute(%q|insert into json_data_type (payload) VALUES ('["v0",{"k1":"v1"}]')|)
+    @connection.execute(insert_statement_per_database('["v0",{"k1":"v1"}]'))
     x = klass.first
     x.payload = ["v1", { "k2" => "v2" }, "v3"]
     assert x.save!
@@ -152,42 +152,42 @@ module JSONSharedTestCases
 
   def test_changes_in_place
     json = klass.new
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
 
     json.payload = { "one" => "two" }
-    assert json.changed?
-    assert json.payload_changed?
+    assert_predicate json, :changed?
+    assert_predicate json, :payload_changed?
 
     json.save!
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
 
     json.payload["three"] = "four"
-    assert json.payload_changed?
+    assert_predicate json, :payload_changed?
 
     json.save!
     json.reload
 
     assert_equal({ "one" => "two", "three" => "four" }, json.payload)
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
   end
 
   def test_changes_in_place_ignores_key_order
     json = klass.new
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
 
     json.payload = { "three" => "four", "one" => "two" }
     json.save!
     json.reload
 
     json.payload = { "three" => "four", "one" => "two" }
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
 
     json.payload = [{ "three" => "four", "one" => "two" }, { "seven" => "eight", "five" => "six" }]
     json.save!
     json.reload
 
     json.payload = [{ "three" => "four", "one" => "two" }, { "seven" => "eight", "five" => "six" }]
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
   end
 
   def test_changes_in_place_with_ruby_object
@@ -195,10 +195,10 @@ module JSONSharedTestCases
     json = klass.create!(payload: time)
 
     json.reload
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
 
     json.payload = time
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
   end
 
   def test_assigning_string_literal
@@ -253,4 +253,17 @@ module JSONSharedTestCases
     def klass
       JsonDataType
     end
+
+    def assert_type_match(type, sql_type)
+      native_type = ActiveRecord::Base.connection.native_database_types[type][:name]
+      assert_match %r(\A#{native_type}\b), sql_type
+    end
+
+    def insert_statement_per_database(values)
+      if current_adapter?(:OracleAdapter)
+        "insert into json_data_type (id, payload) VALUES (json_data_type_seq.nextval, '#{values}')"
+      else
+        "insert into json_data_type (payload) VALUES ('#{values}')"
+      end
+    end
 end
diff --git a/activerecord/test/cases/locking_test.rb b/activerecord/test/cases/locking_test.rb
index 743680ba92..8513edb0ab 100644
--- a/activerecord/test/cases/locking_test.rb
+++ b/activerecord/test/cases/locking_test.rb
@@ -15,6 +15,7 @@ require "models/bulb"
 require "models/engine"
 require "models/wheel"
 require "models/treasure"
+require "models/frog"
 
 class LockWithoutDefault < ActiveRecord::Base; end
 
@@ -69,8 +70,8 @@ class OptimisticLockingTest < ActiveRecord::TestCase
     assert_raise(ActiveRecord::StaleObjectError) { s2.destroy }
 
     assert s1.destroy
-    assert s1.frozen?
-    assert s1.destroyed?
+    assert_predicate s1, :frozen?
+    assert_predicate s1, :destroyed?
     assert_raises(ActiveRecord::RecordNotFound) { StringKeyObject.find("record1") }
   end
 
@@ -104,8 +105,8 @@ class OptimisticLockingTest < ActiveRecord::TestCase
     assert_raises(ActiveRecord::StaleObjectError) { p2.destroy }
 
     assert p1.destroy
-    assert p1.frozen?
-    assert p1.destroyed?
+    assert_predicate p1, :frozen?
+    assert_predicate p1, :destroyed?
     assert_raises(ActiveRecord::RecordNotFound) { Person.find(1) }
   end
 
@@ -194,6 +195,45 @@ class OptimisticLockingTest < ActiveRecord::TestCase
     end
   end
 
+  def test_update_with_dirty_primary_key
+    assert_raises(ActiveRecord::RecordNotUnique) do
+      person = Person.find(1)
+      person.id = 2
+      person.save!
+    end
+
+    person = Person.find(1)
+    person.id = 42
+    person.save!
+
+    assert Person.find(42)
+    assert_raises(ActiveRecord::RecordNotFound) do
+      Person.find(1)
+    end
+  end
+
+  def test_delete_with_dirty_primary_key
+    person = Person.find(1)
+    person.id = 2
+    person.delete
+
+    assert Person.find(2)
+    assert_raises(ActiveRecord::RecordNotFound) do
+      Person.find(1)
+    end
+  end
+
+  def test_destroy_with_dirty_primary_key
+    person = Person.find(1)
+    person.id = 2
+    person.destroy
+
+    assert Person.find(2)
+    assert_raises(ActiveRecord::RecordNotFound) do
+      Person.find(1)
+    end
+  end
+
   def test_explicit_update_lock_column_raise_error
     person = Person.find(1)
 
@@ -201,7 +241,7 @@ class OptimisticLockingTest < ActiveRecord::TestCase
       person.first_name = "Douglas Adams"
       person.lock_version = 42
 
-      assert person.lock_version_changed?
+      assert_predicate person, :lock_version_changed?
 
       person.save
     end
@@ -399,25 +439,59 @@ class OptimisticLockingTest < ActiveRecord::TestCase
     end
   end
 
+  def test_counter_cache_with_touch_and_lock_version
+    car = Car.create!
+
+    assert_equal 0, car.wheels_count
+    assert_equal 0, car.lock_version
+
+    previously_car_updated_at = car.updated_at
+    travel(2.second) do
+      Wheel.create!(wheelable: car)
+    end
+
+    assert_equal 1, car.reload.wheels_count
+    assert_not_equal previously_car_updated_at, car.updated_at
+    assert_equal 1, car.lock_version
+
+    previously_car_updated_at = car.updated_at
+    travel(1.day) do
+      car.wheels.first.update(size: 42)
+    end
+
+    assert_equal 1, car.reload.wheels_count
+    assert_not_equal previously_car_updated_at, car.updated_at
+    assert_equal 2, car.lock_version
+
+    previously_car_updated_at = car.updated_at
+    travel(2.second) do
+      car.wheels.first.destroy!
+    end
+
+    assert_equal 0, car.reload.wheels_count
+    assert_not_equal previously_car_updated_at, car.updated_at
+    assert_equal 3, car.lock_version
+  end
+
   def test_polymorphic_destroy_with_dependencies_and_lock_version
     car = Car.create!
 
     assert_difference "car.wheels.count"  do
-      car.wheels << Wheel.create!
+      car.wheels.create
     end
     assert_difference "car.wheels.count", -1  do
       car.reload.destroy
     end
-    assert car.destroyed?
+    assert_predicate car, :destroyed?
   end
 
   def test_removing_has_and_belongs_to_many_associations_upon_destroy
     p = RichPerson.create! first_name: "Jon"
     p.treasures.create!
-    assert !p.treasures.empty?
+    assert_not_empty p.treasures
     p.destroy
-    assert p.treasures.empty?
-    assert RichPerson.connection.select_all("SELECT * FROM peoples_treasures WHERE rich_person_id = 1").empty?
+    assert_empty p.treasures
+    assert_empty RichPerson.connection.select_all("SELECT * FROM peoples_treasures WHERE rich_person_id = 1")
   end
 
   def test_yaml_dumping_with_lock_column
@@ -487,7 +561,7 @@ class OptimisticLockingWithSchemaChangeTest < ActiveRecord::TestCase
 
     t1.destroy
 
-    assert t1.destroyed?
+    assert_predicate t1, :destroyed?
   end
 
   def test_destroy_stale_object
@@ -500,7 +574,7 @@ class OptimisticLockingWithSchemaChangeTest < ActiveRecord::TestCase
       stale_object.destroy!
     end
 
-    refute stale_object.destroyed?
+    assert_not_predicate stale_object, :destroyed?
   end
 
   private
@@ -565,17 +639,27 @@ unless in_memory_db?
       end
     end
 
-    # Locking a record reloads it.
-    def test_sane_lock_method
+    def test_lock_does_not_raise_when_the_object_is_not_dirty
+      person = Person.find 1
       assert_nothing_raised do
-        Person.transaction do
-          person = Person.find 1
-          old, person.first_name = person.first_name, "fooman"
-          # Locking a dirty record is deprecated
-          assert_deprecated do
-            person.lock!
-          end
-          assert_equal old, person.first_name
+        person.lock!
+      end
+    end
+
+    def test_lock_raises_when_the_record_is_dirty
+      person = Person.find 1
+      person.first_name = "fooman"
+      assert_raises(RuntimeError) do
+        person.lock!
+      end
+    end
+
+    def test_locking_in_after_save_callback
+      assert_nothing_raised do
+        frog = ::Frog.create(name: "Old Frog")
+        frog.name = "New Frog"
+        assert_not_deprecated do
+          frog.save!
         end
       end
     end
@@ -611,14 +695,12 @@ unless in_memory_db?
       end
     end
 
-    if current_adapter?(:PostgreSQLAdapter, :OracleAdapter)
-      def test_no_locks_no_wait
-        first, second = duel { Person.find 1 }
-        assert first.end > second.end
-      end
-
-      private
+    def test_no_locks_no_wait
+      first, second = duel { Person.find 1 }
+      assert first.end > second.end
+    end
 
+    private
       def duel(zzz = 5)
         t0, t1, t2, t3 = nil, nil, nil, nil
 
@@ -646,6 +728,5 @@ unless in_memory_db?
         assert t3 > t2
         [t0.to_f..t1.to_f, t2.to_f..t3.to_f]
       end
-    end
   end
 end
diff --git a/activerecord/test/cases/log_subscriber_test.rb b/activerecord/test/cases/log_subscriber_test.rb
index 208e54ed0b..e2742ed33e 100644
--- a/activerecord/test/cases/log_subscriber_test.rb
+++ b/activerecord/test/cases/log_subscriber_test.rb
@@ -33,8 +33,9 @@ class LogSubscriberTest < ActiveRecord::TestCase
       super
     end
 
-    def debug(message)
-      @debugs << message
+    def debug(progname = nil, &block)
+      @debugs << progname
+      super
     end
   end
 
@@ -171,6 +172,22 @@ class LogSubscriberTest < ActiveRecord::TestCase
     assert_match(/SELECT .*?FROM .?developers.?/i, @logger.logged(:debug).last)
   end
 
+  def test_vebose_query_logs
+    ActiveRecord::Base.verbose_query_logs = true
+
+    logger = TestDebugLogSubscriber.new
+    logger.sql(Event.new(0, sql: "hi mom!"))
+    assert_match(/↳/, @logger.logged(:debug).last)
+  ensure
+    ActiveRecord::Base.verbose_query_logs = false
+  end
+
+  def test_verbose_query_logs_disabled_by_default
+    logger = TestDebugLogSubscriber.new
+    logger.sql(Event.new(0, sql: "hi mom!"))
+    assert_no_match(/↳/, @logger.logged(:debug).last)
+  end
+
   def test_cached_queries
     ActiveRecord::Base.cache do
       Developer.all.load
diff --git a/activerecord/test/cases/migration/change_schema_test.rb b/activerecord/test/cases/migration/change_schema_test.rb
index 7b0644e9c0..f4d16cb093 100644
--- a/activerecord/test/cases/migration/change_schema_test.rb
+++ b/activerecord/test/cases/migration/change_schema_test.rb
@@ -84,7 +84,7 @@ module ActiveRecord
           columns = connection.columns(:testings)
           array_column = columns.detect { |c| c.name == "foo" }
 
-          assert array_column.array?
+          assert_predicate array_column, :array?
         end
 
         def test_create_table_with_array_column
@@ -95,7 +95,7 @@ module ActiveRecord
           columns = connection.columns(:testings)
           array_column = columns.detect { |c| c.name == "foo" }
 
-          assert array_column.array?
+          assert_predicate array_column, :array?
         end
       end
 
@@ -205,8 +205,8 @@ module ActiveRecord
         created_at_column = created_columns.detect { |c| c.name == "created_at" }
         updated_at_column = created_columns.detect { |c| c.name == "updated_at" }
 
-        assert !created_at_column.null
-        assert !updated_at_column.null
+        assert_not created_at_column.null
+        assert_not updated_at_column.null
       end
 
       def test_create_table_with_timestamps_should_create_datetime_columns_with_options
@@ -264,19 +264,18 @@ module ActiveRecord
           t.column :foo, :timestamp
         end
 
-        klass = Class.new(ActiveRecord::Base)
-        klass.table_name = "testings"
+        column = connection.columns(:testings).find { |c| c.name == "foo" }
 
-        assert_equal :datetime, klass.columns_hash["foo"].type
+        assert_equal :datetime, column.type
 
         if current_adapter?(:PostgreSQLAdapter)
-          assert_equal "timestamp without time zone", klass.columns_hash["foo"].sql_type
+          assert_equal "timestamp without time zone", column.sql_type
         elsif current_adapter?(:Mysql2Adapter)
-          assert_equal "timestamp", klass.columns_hash["foo"].sql_type
+          assert_equal "timestamp", column.sql_type
         elsif current_adapter?(:OracleAdapter)
-          assert_equal "TIMESTAMP(6)", klass.columns_hash["foo"].sql_type
+          assert_equal "TIMESTAMP(6)", column.sql_type
         else
-          assert_equal klass.connection.type_to_sql("datetime"), klass.columns_hash["foo"].sql_type
+          assert_equal connection.type_to_sql("datetime"), column.sql_type
         end
       end
 
@@ -409,7 +408,7 @@ module ActiveRecord
         end
         connection.change_table :testings do |t|
           assert t.column_exists?(:foo)
-          assert !(t.column_exists?(:bar))
+          assert_not (t.column_exists?(:bar))
         end
       end
 
diff --git a/activerecord/test/cases/migration/column_attributes_test.rb b/activerecord/test/cases/migration/column_attributes_test.rb
index be6dc2acb1..3022121f4c 100644
--- a/activerecord/test/cases/migration/column_attributes_test.rb
+++ b/activerecord/test/cases/migration/column_attributes_test.rb
@@ -80,7 +80,7 @@ module ActiveRecord
           TestModel.delete_all
 
           # Now use the Rails insertion
-          TestModel.create wealth: BigDecimal.new("12345678901234567890.0123456789")
+          TestModel.create wealth: BigDecimal("12345678901234567890.0123456789")
 
           # SELECT
           row = TestModel.first
@@ -146,7 +146,7 @@ module ActiveRecord
 
           TestModel.create first_name: "bob", last_name: "bobsen",
             bio: "I was born ....", age: 18, height: 1.78,
-            wealth: BigDecimal.new("12345678901234567890.0123456789"),
+            wealth: BigDecimal("12345678901234567890.0123456789"),
             birthday: 18.years.ago, favorite_day: 10.days.ago,
             moment_of_truth: "1782-10-10 21:40:18", male: true
 
@@ -159,7 +159,7 @@ module ActiveRecord
           # Test for 30 significant digits (beyond the 16 of float), 10 of them
           # after the decimal place.
 
-          assert_equal BigDecimal.new("0012345678901234567890.0123456789"), bob.wealth
+          assert_equal BigDecimal("0012345678901234567890.0123456789"), bob.wealth
 
           assert_equal true, bob.male?
 
diff --git a/activerecord/test/cases/migration/column_positioning_test.rb b/activerecord/test/cases/migration/column_positioning_test.rb
index 23414419dc..1c62a68cf9 100644
--- a/activerecord/test/cases/migration/column_positioning_test.rb
+++ b/activerecord/test/cases/migration/column_positioning_test.rb
@@ -52,6 +52,16 @@ module ActiveRecord
           conn.change_column :testings, :second, :integer, after: :third
           assert_equal %w(first third second), conn.columns(:testings).map(&:name)
         end
+
+        def test_add_reference_with_positioning_first
+          conn.add_reference :testings, :new, polymorphic: true, first: true
+          assert_equal %w(new_id new_type first second third), conn.columns(:testings).map(&:name)
+        end
+
+        def test_add_reference_with_positioning_after
+          conn.add_reference :testings, :new, polymorphic: true, after: :first
+          assert_equal %w(first new_id new_type second third), conn.columns(:testings).map(&:name)
+        end
       end
     end
   end
diff --git a/activerecord/test/cases/migration/columns_test.rb b/activerecord/test/cases/migration/columns_test.rb
index 1b1d0af132..cedd9c44e3 100644
--- a/activerecord/test/cases/migration/columns_test.rb
+++ b/activerecord/test/cases/migration/columns_test.rb
@@ -67,7 +67,7 @@ module ActiveRecord
       if current_adapter?(:Mysql2Adapter)
         def test_mysql_rename_column_preserves_auto_increment
           rename_column "test_models", "id", "id_test"
-          assert connection.columns("test_models").find { |c| c.name == "id_test" }.auto_increment?
+          assert_predicate connection.columns("test_models").find { |c| c.name == "id_test" }, :auto_increment?
           TestModel.reset_column_information
         ensure
           rename_column "test_models", "id_test", "id"
@@ -142,6 +142,10 @@ module ActiveRecord
       end
 
       def test_remove_column_with_multi_column_index
+        # MariaDB starting with 10.2.8
+        # Dropping a column that is part of a multi-column UNIQUE constraint is not permitted.
+        skip if current_adapter?(:Mysql2Adapter) && connection.mariadb? && connection.version >= "10.2.8"
+
         add_column "test_models", :hat_size, :integer
         add_column "test_models", :hat_style, :string, limit: 100
         add_index "test_models", ["hat_style", "hat_size"], unique: true
@@ -219,31 +223,31 @@ module ActiveRecord
 
       def test_change_column_with_nil_default
         add_column "test_models", "contributor", :boolean, default: true
-        assert TestModel.new.contributor?
+        assert_predicate TestModel.new, :contributor?
 
         change_column "test_models", "contributor", :boolean, default: nil
         TestModel.reset_column_information
-        assert_not TestModel.new.contributor?
+        assert_not_predicate TestModel.new, :contributor?
         assert_nil TestModel.new.contributor
       end
 
       def test_change_column_to_drop_default_with_null_false
         add_column "test_models", "contributor", :boolean, default: true, null: false
-        assert TestModel.new.contributor?
+        assert_predicate TestModel.new, :contributor?
 
         change_column "test_models", "contributor", :boolean, default: nil, null: false
         TestModel.reset_column_information
-        assert_not TestModel.new.contributor?
+        assert_not_predicate TestModel.new, :contributor?
         assert_nil TestModel.new.contributor
       end
 
       def test_change_column_with_new_default
         add_column "test_models", "administrator", :boolean, default: true
-        assert TestModel.new.administrator?
+        assert_predicate TestModel.new, :administrator?
 
         change_column "test_models", "administrator", :boolean, default: false
         TestModel.reset_column_information
-        assert_not TestModel.new.administrator?
+        assert_not_predicate TestModel.new, :administrator?
       end
 
       def test_change_column_with_custom_index_name
diff --git a/activerecord/test/cases/migration/command_recorder_test.rb b/activerecord/test/cases/migration/command_recorder_test.rb
index 0b5e983f14..3a11bb081b 100644
--- a/activerecord/test/cases/migration/command_recorder_test.rb
+++ b/activerecord/test/cases/migration/command_recorder_test.rb
@@ -14,7 +14,7 @@ module ActiveRecord
         recorder = CommandRecorder.new(Class.new {
           def america; end
         }.new)
-        assert recorder.respond_to?(:america)
+        assert_respond_to recorder, :america
       end
 
       def test_send_calls_super
@@ -27,7 +27,7 @@ module ActiveRecord
         recorder = CommandRecorder.new(Class.new {
           def create_table(name); end
         }.new)
-        assert recorder.respond_to?(:create_table), "respond_to? create_table"
+        assert_respond_to recorder, :create_table
         recorder.send(:create_table, :horses)
         assert_equal [[:create_table, [:horses], nil]], recorder.commands
       end
@@ -213,6 +213,11 @@ module ActiveRecord
         assert_equal [:remove_index, [:table, { name: "new_index" }]], remove
       end
 
+      def test_invert_add_index_with_algorithm_option
+        remove = @recorder.inverse_of :add_index, [:table, :one, algorithm: :concurrently]
+        assert_equal [:remove_index, [:table, { column: :one, algorithm: :concurrently }]], remove
+      end
+
       def test_invert_remove_index
         add = @recorder.inverse_of :remove_index, [:table, :one]
         assert_equal [:add_index, [:table, :one]], add
diff --git a/activerecord/test/cases/migration/compatibility_test.rb b/activerecord/test/cases/migration/compatibility_test.rb
index cb3b02c02a..69a50674af 100644
--- a/activerecord/test/cases/migration/compatibility_test.rb
+++ b/activerecord/test/cases/migration/compatibility_test.rb
@@ -16,7 +16,7 @@ module ActiveRecord
         ActiveRecord::Migration.verbose = false
 
         connection.create_table :testings do |t|
-          t.column :foo, :string, limit: 100
+          t.column :foo, :string, limit: 5
           t.column :bar, :string, limit: 100
         end
       end
@@ -126,15 +126,32 @@ module ActiveRecord
         end
         assert_match(/LegacyMigration < ActiveRecord::Migration\[4\.2\]/, e.message)
       end
+
+      if current_adapter?(:PostgreSQLAdapter)
+        class Testing < ActiveRecord::Base
+        end
+
+        def test_legacy_change_column_with_null_executes_update
+          migration = Class.new(ActiveRecord::Migration[5.1]) {
+            def migrate(x)
+              change_column :testings, :foo, :string, limit: 10, null: false, default: "foobar"
+            end
+          }.new
+
+          Testing.create!
+          ActiveRecord::Migrator.new(:up, [migration]).migrate
+          assert_equal ["foobar"], Testing.all.map(&:foo)
+        ensure
+          ActiveRecord::Base.clear_cache!
+        end
+      end
     end
   end
 end
 
-class LegacyPrimaryKeyTest < ActiveRecord::TestCase
+module LegacyPrimaryKeyTestCases
   include SchemaDumpingHelper
 
-  self.use_transactional_tests = false
-
   class LegacyPrimaryKey < ActiveRecord::Base
   end
 
@@ -152,7 +169,7 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
   end
 
   def test_legacy_primary_key_should_be_auto_incremented
-    @migration = Class.new(ActiveRecord::Migration[5.0]) {
+    @migration = Class.new(migration_class) {
       def change
         create_table :legacy_primary_keys do |t|
           t.references :legacy_ref
@@ -162,12 +179,10 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
 
     @migration.migrate(:up)
 
-    legacy_pk = LegacyPrimaryKey.columns_hash["id"]
-    assert_not legacy_pk.bigint?
-    assert_not legacy_pk.null
+    assert_legacy_primary_key
 
     legacy_ref = LegacyPrimaryKey.columns_hash["legacy_ref_id"]
-    assert_not legacy_ref.bigint?
+    assert_not_predicate legacy_ref, :bigint?
 
     record1 = LegacyPrimaryKey.create!
     assert_not_nil record1.id
@@ -182,7 +197,7 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
   def test_legacy_integer_primary_key_should_not_be_auto_incremented
     skip if current_adapter?(:SQLite3Adapter)
 
-    @migration = Class.new(ActiveRecord::Migration[5.0]) {
+    @migration = Class.new(migration_class) {
       def change
         create_table :legacy_primary_keys, id: :integer do |t|
         end
@@ -199,9 +214,85 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
     assert_match %r{create_table "legacy_primary_keys", id: :integer, default: nil}, schema
   end
 
+  def test_legacy_primary_key_in_create_table_should_be_integer
+    @migration = Class.new(migration_class) {
+      def change
+        create_table :legacy_primary_keys, id: false do |t|
+          t.primary_key :id
+        end
+      end
+    }.new
+
+    @migration.migrate(:up)
+
+    assert_legacy_primary_key
+  end
+
+  def test_legacy_primary_key_in_change_table_should_be_integer
+    @migration = Class.new(migration_class) {
+      def change
+        create_table :legacy_primary_keys, id: false do |t|
+          t.integer :dummy
+        end
+        change_table :legacy_primary_keys do |t|
+          t.primary_key :id
+        end
+      end
+    }.new
+
+    @migration.migrate(:up)
+
+    assert_legacy_primary_key
+  end
+
+  def test_add_column_with_legacy_primary_key_should_be_integer
+    @migration = Class.new(migration_class) {
+      def change
+        create_table :legacy_primary_keys, id: false do |t|
+          t.integer :dummy
+        end
+        add_column :legacy_primary_keys, :id, :primary_key
+      end
+    }.new
+
+    @migration.migrate(:up)
+
+    assert_legacy_primary_key
+  end
+
+  def test_legacy_join_table_foreign_keys_should_be_integer
+    @migration = Class.new(migration_class) {
+      def change
+        create_join_table :apples, :bananas do |t|
+        end
+      end
+    }.new
+
+    @migration.migrate(:up)
+
+    schema = dump_table_schema "apples_bananas"
+    assert_match %r{integer "apple_id", null: false}, schema
+    assert_match %r{integer "banana_id", null: false}, schema
+  end
+
+  def test_legacy_join_table_column_options_should_be_overwritten
+    @migration = Class.new(migration_class) {
+      def change
+        create_join_table :apples, :bananas, column_options: { type: :bigint } do |t|
+        end
+      end
+    }.new
+
+    @migration.migrate(:up)
+
+    schema = dump_table_schema "apples_bananas"
+    assert_match %r{bigint "apple_id", null: false}, schema
+    assert_match %r{bigint "banana_id", null: false}, schema
+  end
+
   if current_adapter?(:Mysql2Adapter)
     def test_legacy_bigint_primary_key_should_be_auto_incremented
-      @migration = Class.new(ActiveRecord::Migration[5.0]) {
+      @migration = Class.new(migration_class) {
         def change
           create_table :legacy_primary_keys, id: :bigint
         end
@@ -210,15 +301,15 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
       @migration.migrate(:up)
 
       legacy_pk = LegacyPrimaryKey.columns_hash["id"]
-      assert legacy_pk.bigint?
-      assert legacy_pk.auto_increment?
+      assert_predicate legacy_pk, :bigint?
+      assert_predicate legacy_pk, :auto_increment?
 
       schema = dump_table_schema "legacy_primary_keys"
       assert_match %r{create_table "legacy_primary_keys", (?!id: :bigint, default: nil)}, schema
     end
   else
     def test_legacy_bigint_primary_key_should_not_be_auto_incremented
-      @migration = Class.new(ActiveRecord::Migration[5.0]) {
+      @migration = Class.new(migration_class) {
         def change
           create_table :legacy_primary_keys, id: :bigint do |t|
           end
@@ -235,4 +326,44 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
       assert_match %r{create_table "legacy_primary_keys", id: :bigint, default: nil}, schema
     end
   end
+
+  private
+    def assert_legacy_primary_key
+      assert_equal "id", LegacyPrimaryKey.primary_key
+
+      legacy_pk = LegacyPrimaryKey.columns_hash["id"]
+
+      assert_equal :integer, legacy_pk.type
+      assert_not_predicate legacy_pk, :bigint?
+      assert_not legacy_pk.null
+
+      if current_adapter?(:Mysql2Adapter, :PostgreSQLAdapter)
+        schema = dump_table_schema "legacy_primary_keys"
+        assert_match %r{create_table "legacy_primary_keys", id: :(?:integer|serial), (?!default: nil)}, schema
+      end
+    end
+end
+
+module LegacyPrimaryKeyTest
+  class V5_0 < ActiveRecord::TestCase
+    include LegacyPrimaryKeyTestCases
+
+    self.use_transactional_tests = false
+
+    private
+      def migration_class
+        ActiveRecord::Migration[5.0]
+      end
+  end
+
+  class V4_2 < ActiveRecord::TestCase
+    include LegacyPrimaryKeyTestCases
+
+    self.use_transactional_tests = false
+
+    private
+      def migration_class
+        ActiveRecord::Migration[4.2]
+      end
+  end
 end
diff --git a/activerecord/test/cases/migration/create_join_table_test.rb b/activerecord/test/cases/migration/create_join_table_test.rb
index 77d32a24a5..e0cbb29dcf 100644
--- a/activerecord/test/cases/migration/create_join_table_test.rb
+++ b/activerecord/test/cases/migration/create_join_table_test.rb
@@ -69,7 +69,7 @@ module ActiveRecord
       def test_create_join_table_without_indexes
         connection.create_join_table :artists, :musics
 
-        assert connection.indexes(:artists_musics).blank?
+        assert_predicate connection.indexes(:artists_musics), :blank?
       end
 
       def test_create_join_table_with_index
@@ -95,42 +95,42 @@ module ActiveRecord
         connection.create_join_table :artists, :musics
         connection.drop_join_table :artists, :musics
 
-        assert !connection.table_exists?("artists_musics")
+        assert_not connection.table_exists?("artists_musics")
       end
 
       def test_drop_join_table_with_strings
         connection.create_join_table :artists, :musics
         connection.drop_join_table "artists", "musics"
 
-        assert !connection.table_exists?("artists_musics")
+        assert_not connection.table_exists?("artists_musics")
       end
 
       def test_drop_join_table_with_the_proper_order
         connection.create_join_table :videos, :musics
         connection.drop_join_table :videos, :musics
 
-        assert !connection.table_exists?("musics_videos")
+        assert_not connection.table_exists?("musics_videos")
       end
 
       def test_drop_join_table_with_the_table_name
         connection.create_join_table :artists, :musics, table_name: :catalog
         connection.drop_join_table :artists, :musics, table_name: :catalog
 
-        assert !connection.table_exists?("catalog")
+        assert_not connection.table_exists?("catalog")
       end
 
       def test_drop_join_table_with_the_table_name_as_string
         connection.create_join_table :artists, :musics, table_name: "catalog"
         connection.drop_join_table :artists, :musics, table_name: "catalog"
 
-        assert !connection.table_exists?("catalog")
+        assert_not connection.table_exists?("catalog")
       end
 
       def test_drop_join_table_with_column_options
         connection.create_join_table :artists, :musics, column_options: { null: true }
         connection.drop_join_table :artists, :musics, column_options: { null: true }
 
-        assert !connection.table_exists?("artists_musics")
+        assert_not connection.table_exists?("artists_musics")
       end
 
       def test_create_and_drop_join_table_with_common_prefix
@@ -139,7 +139,7 @@ module ActiveRecord
           assert connection.table_exists?("audio_artists_musics")
 
           connection.drop_join_table "audio_artists", "audio_musics"
-          assert !connection.table_exists?("audio_artists_musics"), "Should have dropped join table, but didn't"
+          assert_not connection.table_exists?("audio_artists_musics"), "Should have dropped join table, but didn't"
         end
       end
 
diff --git a/activerecord/test/cases/migration/foreign_key_test.rb b/activerecord/test/cases/migration/foreign_key_test.rb
index 499d072de5..c471dd1106 100644
--- a/activerecord/test/cases/migration/foreign_key_test.rb
+++ b/activerecord/test/cases/migration/foreign_key_test.rb
@@ -19,6 +19,52 @@ if ActiveRecord::Base.connection.supports_foreign_keys_in_create?
           assert_equal "fk_name", fk.name unless current_adapter?(:SQLite3Adapter)
         end
       end
+
+      class ForeignKeyChangeColumnTest < ActiveRecord::TestCase
+        self.use_transactional_tests = false
+
+        class Rocket < ActiveRecord::Base
+          has_many :astronauts
+        end
+
+        class Astronaut < ActiveRecord::Base
+          belongs_to :rocket
+        end
+
+        setup do
+          @connection = ActiveRecord::Base.connection
+          @connection.create_table "rockets", force: true do |t|
+            t.string :name
+          end
+
+          @connection.create_table "astronauts", force: true do |t|
+            t.string :name
+            t.references :rocket, foreign_key: true
+          end
+          Rocket.reset_column_information
+          Astronaut.reset_column_information
+        end
+
+        teardown do
+          @connection.drop_table "astronauts", if_exists: true
+          @connection.drop_table "rockets", if_exists: true
+          Rocket.reset_column_information
+          Astronaut.reset_column_information
+        end
+
+        def test_change_column_of_parent_table
+          foreign_keys = ActiveRecord::Base.connection.foreign_keys("astronauts")
+          rocket = Rocket.create!(name: "myrocket")
+          rocket.astronauts << Astronaut.create!
+
+          @connection.change_column_null :rockets, :name, false
+
+          fk = foreign_keys.first
+          assert_equal "myrocket", Rocket.first.name
+          assert_equal "astronauts", fk.from_table
+          assert_equal "rockets", fk.to_table
+        end
+      end
     end
   end
 end
@@ -227,6 +273,74 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
           end
         end
 
+        if ActiveRecord::Base.connection.supports_validate_constraints?
+          def test_add_invalid_foreign_key
+            @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", validate: false
+
+            foreign_keys = @connection.foreign_keys("astronauts")
+            assert_equal 1, foreign_keys.size
+
+            fk = foreign_keys.first
+            assert_not_predicate fk, :validated?
+          end
+
+          def test_validate_foreign_key_infers_column
+            @connection.add_foreign_key :astronauts, :rockets, validate: false
+            assert_not_predicate @connection.foreign_keys("astronauts").first, :validated?
+
+            @connection.validate_foreign_key :astronauts, :rockets
+            assert_predicate @connection.foreign_keys("astronauts").first, :validated?
+          end
+
+          def test_validate_foreign_key_by_column
+            @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", validate: false
+            assert_not_predicate @connection.foreign_keys("astronauts").first, :validated?
+
+            @connection.validate_foreign_key :astronauts, column: "rocket_id"
+            assert_predicate @connection.foreign_keys("astronauts").first, :validated?
+          end
+
+          def test_validate_foreign_key_by_symbol_column
+            @connection.add_foreign_key :astronauts, :rockets, column: :rocket_id, validate: false
+            assert_not_predicate @connection.foreign_keys("astronauts").first, :validated?
+
+            @connection.validate_foreign_key :astronauts, column: :rocket_id
+            assert_predicate @connection.foreign_keys("astronauts").first, :validated?
+          end
+
+          def test_validate_foreign_key_by_name
+            @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", name: "fancy_named_fk", validate: false
+            assert_not_predicate @connection.foreign_keys("astronauts").first, :validated?
+
+            @connection.validate_foreign_key :astronauts, name: "fancy_named_fk"
+            assert_predicate @connection.foreign_keys("astronauts").first, :validated?
+          end
+
+          def test_validate_foreign_non_existing_foreign_key_raises
+            assert_raises ArgumentError do
+              @connection.validate_foreign_key :astronauts, :rockets
+            end
+          end
+
+          def test_validate_constraint_by_name
+            @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", name: "fancy_named_fk", validate: false
+
+            @connection.validate_constraint :astronauts, "fancy_named_fk"
+            assert_predicate @connection.foreign_keys("astronauts").first, :validated?
+          end
+        else
+          # Foreign key should still be created, but should not be invalid
+          def test_add_invalid_foreign_key
+            @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", validate: false
+
+            foreign_keys = @connection.foreign_keys("astronauts")
+            assert_equal 1, foreign_keys.size
+
+            fk = foreign_keys.first
+            assert_predicate fk, :validated?
+          end
+        end
+
         def test_schema_dumping
           @connection.add_foreign_key :astronauts, :rockets
           output = dump_table_schema "astronauts"
@@ -238,6 +352,17 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
           assert_match %r{\s+add_foreign_key "fk_test_has_fk", "fk_test_has_pk", column: "fk_id", primary_key: "pk_id", name: "fk_name"$}, output
         end
 
+        def test_schema_dumping_with_custom_fk_ignore_pattern
+          original_pattern = ActiveRecord::SchemaDumper.fk_ignore_pattern
+          ActiveRecord::SchemaDumper.fk_ignore_pattern = /^ignored_/
+          @connection.add_foreign_key :astronauts, :rockets, name: :ignored_fk_astronauts_rockets
+
+          output = dump_table_schema "astronauts"
+          assert_match %r{\s+add_foreign_key "astronauts", "rockets"$}, output
+
+          ActiveRecord::SchemaDumper.fk_ignore_pattern = original_pattern
+        end
+
         def test_schema_dumping_on_delete_and_on_update_options
           @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", on_delete: :nullify, on_update: :cascade
 
diff --git a/activerecord/test/cases/migration/index_test.rb b/activerecord/test/cases/migration/index_test.rb
index bf1ebdb4c5..f8fecc83cd 100644
--- a/activerecord/test/cases/migration/index_test.rb
+++ b/activerecord/test/cases/migration/index_test.rb
@@ -33,10 +33,8 @@ module ActiveRecord
         connection.add_index(table_name, [:foo], name: "old_idx")
         connection.rename_index(table_name, "old_idx", "new_idx")
 
-        assert_deprecated do
-          assert_not connection.index_name_exists?(table_name, "old_idx", false)
-          assert connection.index_name_exists?(table_name, "new_idx", true)
-        end
+        assert_not connection.index_name_exists?(table_name, "old_idx")
+        assert connection.index_name_exists?(table_name, "new_idx")
       end
 
       def test_rename_index_too_long
@@ -101,7 +99,7 @@ module ActiveRecord
         connection.add_index :testings, :foo
 
         assert connection.index_exists?(:testings, :foo)
-        assert !connection.index_exists?(:testings, :bar)
+        assert_not connection.index_exists?(:testings, :bar)
       end
 
       def test_index_exists_on_multiple_columns
@@ -133,15 +131,18 @@ module ActiveRecord
 
         assert connection.index_exists?(:testings, :foo)
         assert connection.index_exists?(:testings, :foo, name: "custom_index_name")
-        assert !connection.index_exists?(:testings, :foo, name: "other_index_name")
+        assert_not connection.index_exists?(:testings, :foo, name: "other_index_name")
       end
 
       def test_remove_named_index
-        connection.add_index :testings, :foo, name: "custom_index_name"
+        connection.add_index :testings, :foo, name: "index_testings_on_custom_index_name"
 
         assert connection.index_exists?(:testings, :foo)
+
+        assert_raise(ArgumentError) { connection.remove_index(:testings, "custom_index_name") }
+
         connection.remove_index :testings, :foo
-        assert !connection.index_exists?(:testings, :foo)
+        assert_not connection.index_exists?(:testings, :foo)
       end
 
       def test_add_index_attribute_length_limit
@@ -205,7 +206,7 @@ module ActiveRecord
           assert connection.index_exists?("testings", "last_name")
 
           connection.remove_index("testings", "last_name")
-          assert !connection.index_exists?("testings", "last_name")
+          assert_not connection.index_exists?("testings", "last_name")
         end
       end
 
diff --git a/activerecord/test/cases/migration/pending_migrations_test.rb b/activerecord/test/cases/migration/pending_migrations_test.rb
index d0066f68be..dedb5ea502 100644
--- a/activerecord/test/cases/migration/pending_migrations_test.rb
+++ b/activerecord/test/cases/migration/pending_migrations_test.rb
@@ -4,37 +4,37 @@ require "cases/helper"
 
 module ActiveRecord
   class Migration
-    class PendingMigrationsTest < ActiveRecord::TestCase
-      def setup
-        super
-        @connection = Minitest::Mock.new
-        @app = Minitest::Mock.new
-        conn = @connection
-        @pending = Class.new(CheckPending) {
-          define_method(:connection) { conn }
-        }.new(@app)
-        @pending.instance_variable_set :@last_check, -1 # Force checking
-      end
+    if current_adapter?(:SQLite3Adapter) && !in_memory_db?
+      class PendingMigrationsTest < ActiveRecord::TestCase
+        setup do
+          file = ActiveRecord::Base.connection.raw_connection.filename
+          @conn = ActiveRecord::Base.establish_connection adapter: "sqlite3", database: ":memory:", migrations_paths: MIGRATIONS_ROOT + "/valid"
+          source_db = SQLite3::Database.new file
+          dest_db = ActiveRecord::Base.connection.raw_connection
+          backup = SQLite3::Backup.new(dest_db, "main", source_db, "main")
+          backup.step(-1)
+          backup.finish
+        end
 
-      def teardown
-        assert @connection.verify
-        assert @app.verify
-        super
-      end
+        teardown do
+          @conn.release_connection if @conn
+          ActiveRecord::Base.establish_connection :arunit
+        end
+
+        def test_errors_if_pending
+          ActiveRecord::Base.connection.drop_table "schema_migrations", if_exists: true
 
-      def test_errors_if_pending
-        ActiveRecord::Migrator.stub :needs_migration?, true do
-          assert_raise ActiveRecord::PendingMigrationError do
-            @pending.call(nil)
+          assert_raises ActiveRecord::PendingMigrationError do
+            CheckPending.new(Proc.new {}).call({})
           end
         end
-      end
 
-      def test_checks_if_supported
-        @app.expect :call, nil, [:foo]
+        def test_checks_if_supported
+          ActiveRecord::SchemaMigration.create_table
+          migrator = Base.connection.migration_context
+          capture(:stdout) { migrator.migrate }
 
-        ActiveRecord::Migrator.stub :needs_migration?, false do
-          @pending.call(:foo)
+          assert_nil CheckPending.new(Proc.new {}).call({})
         end
       end
     end
diff --git a/activerecord/test/cases/migration/rename_table_test.rb b/activerecord/test/cases/migration/rename_table_test.rb
index dfce266253..a9deb92585 100644
--- a/activerecord/test/cases/migration/rename_table_test.rb
+++ b/activerecord/test/cases/migration/rename_table_test.rb
@@ -86,9 +86,9 @@ module ActiveRecord
           rename_table :cats, :felines
 
           assert connection.table_exists? :felines
-          refute connection.table_exists? :cats
+          assert_not connection.table_exists? :cats
 
-          primary_key_name = connection.select_values(<<-SQL.strip_heredoc, "SCHEMA")[0]
+          primary_key_name = connection.select_values(<<~SQL, "SCHEMA")[0]
             SELECT c.relname
               FROM pg_class c
               JOIN pg_index i
@@ -107,7 +107,7 @@ module ActiveRecord
           connection.create_table :cats, id: :uuid, default: "uuid_generate_v4()"
           assert_nothing_raised { rename_table :cats, :felines }
           assert connection.table_exists? :felines
-          refute connection.table_exists? :cats
+          assert_not connection.table_exists? :cats
         ensure
           connection.drop_table :cats, if_exists: true
           connection.drop_table :felines, if_exists: true
diff --git a/activerecord/test/cases/migration_test.rb b/activerecord/test/cases/migration_test.rb
index 07afa89779..d1292dc53d 100644
--- a/activerecord/test/cases/migration_test.rb
+++ b/activerecord/test/cases/migration_test.rb
@@ -71,6 +71,16 @@ class MigrationTest < ActiveRecord::TestCase
     ActiveRecord::Migration.verbose = @verbose_was
   end
 
+  def test_migrator_migrations_path_is_deprecated
+    assert_deprecated do
+      ActiveRecord::Migrator.migrations_path = "/whatever"
+    end
+  ensure
+    assert_deprecated do
+      ActiveRecord::Migrator.migrations_path = "db/migrate"
+    end
+  end
+
   def test_migration_version_matches_component_version
     assert_equal ActiveRecord::VERSION::STRING.to_f, ActiveRecord::Migration.current_version
   end
@@ -78,20 +88,20 @@ class MigrationTest < ActiveRecord::TestCase
   def test_migrator_versions
     migrations_path = MIGRATIONS_ROOT + "/valid"
     old_path = ActiveRecord::Migrator.migrations_paths
-    ActiveRecord::Migrator.migrations_paths = migrations_path
+    migrator = ActiveRecord::MigrationContext.new(migrations_path)
 
-    ActiveRecord::Migrator.up(migrations_path)
-    assert_equal 3, ActiveRecord::Migrator.current_version
-    assert_equal false, ActiveRecord::Migrator.needs_migration?
+    migrator.up
+    assert_equal 3, migrator.current_version
+    assert_equal false, migrator.needs_migration?
 
-    ActiveRecord::Migrator.down(MIGRATIONS_ROOT + "/valid")
-    assert_equal 0, ActiveRecord::Migrator.current_version
-    assert_equal true, ActiveRecord::Migrator.needs_migration?
+    migrator.down
+    assert_equal 0, migrator.current_version
+    assert_equal true, migrator.needs_migration?
 
     ActiveRecord::SchemaMigration.create!(version: 3)
-    assert_equal true, ActiveRecord::Migrator.needs_migration?
+    assert_equal true, migrator.needs_migration?
   ensure
-    ActiveRecord::Migrator.migrations_paths = old_path
+    ActiveRecord::MigrationContext.new(old_path)
   end
 
   def test_migration_detection_without_schema_migration_table
@@ -99,28 +109,31 @@ class MigrationTest < ActiveRecord::TestCase
 
     migrations_path = MIGRATIONS_ROOT + "/valid"
     old_path = ActiveRecord::Migrator.migrations_paths
-    ActiveRecord::Migrator.migrations_paths = migrations_path
+    migrator = ActiveRecord::MigrationContext.new(migrations_path)
 
-    assert_equal true, ActiveRecord::Migrator.needs_migration?
+    assert_equal true, migrator.needs_migration?
   ensure
-    ActiveRecord::Migrator.migrations_paths = old_path
+    ActiveRecord::MigrationContext.new(old_path)
   end
 
   def test_any_migrations
     old_path = ActiveRecord::Migrator.migrations_paths
-    ActiveRecord::Migrator.migrations_paths = MIGRATIONS_ROOT + "/valid"
+    migrator = ActiveRecord::MigrationContext.new(MIGRATIONS_ROOT + "/valid")
 
-    assert ActiveRecord::Migrator.any_migrations?
+    assert_predicate migrator, :any_migrations?
 
-    ActiveRecord::Migrator.migrations_paths = MIGRATIONS_ROOT + "/empty"
+    migrator_empty = ActiveRecord::MigrationContext.new(MIGRATIONS_ROOT + "/empty")
 
-    assert_not ActiveRecord::Migrator.any_migrations?
+    assert_not_predicate migrator_empty, :any_migrations?
   ensure
-    ActiveRecord::Migrator.migrations_paths = old_path
+    ActiveRecord::MigrationContext.new(old_path)
   end
 
   def test_migration_version
-    assert_nothing_raised { ActiveRecord::Migrator.run(:up, MIGRATIONS_ROOT + "/version_check", 20131219224947) }
+    migrator = ActiveRecord::MigrationContext.new(MIGRATIONS_ROOT + "/version_check")
+    assert_equal 0, migrator.current_version
+    migrator.up(20131219224947)
+    assert_equal 20131219224947, migrator.current_version
   end
 
   def test_create_table_with_force_true_does_not_drop_nonexisting_table
@@ -157,14 +170,14 @@ class MigrationTest < ActiveRecord::TestCase
   def test_add_table_with_decimals
     Person.connection.drop_table :big_numbers rescue nil
 
-    assert !BigNumber.table_exists?
+    assert_not_predicate BigNumber, :table_exists?
     GiveMeBigNumbers.up
     BigNumber.reset_column_information
 
     assert BigNumber.create(
       bank_balance: 1586.43,
       big_bank_balance: BigDecimal("1000234000567.95"),
-      world_population: 6000000000,
+      world_population: 2**62,
       my_house_population: 3,
       value_of_e: BigDecimal("2.7182818284590452353602875")
     )
@@ -178,10 +191,8 @@ class MigrationTest < ActiveRecord::TestCase
     assert_not_nil b.my_house_population
     assert_not_nil b.value_of_e
 
-    # TODO: set world_population >= 2**62 to cover 64-bit platforms and test
-    # is_a?(Bignum)
     assert_kind_of Integer, b.world_population
-    assert_equal 6000000000, b.world_population
+    assert_equal 2**62, b.world_population
     assert_kind_of Integer, b.my_house_population
     assert_equal 3, b.my_house_population
     assert_kind_of BigDecimal, b.bank_balance
@@ -216,15 +227,16 @@ class MigrationTest < ActiveRecord::TestCase
 
   def test_filtering_migrations
     assert_no_column Person, :last_name
-    assert !Reminder.table_exists?
+    assert_not_predicate Reminder, :table_exists?
 
     name_filter = lambda { |migration| migration.name == "ValidPeopleHaveLastNames" }
-    ActiveRecord::Migrator.up(MIGRATIONS_ROOT + "/valid", &name_filter)
+    migrator = ActiveRecord::MigrationContext.new(MIGRATIONS_ROOT + "/valid")
+    migrator.up(&name_filter)
 
     assert_column Person, :last_name
     assert_raise(ActiveRecord::StatementInvalid) { Reminder.first }
 
-    ActiveRecord::Migrator.down(MIGRATIONS_ROOT + "/valid", &name_filter)
+    migrator.down(&name_filter)
 
     assert_no_column Person, :last_name
     assert_raise(ActiveRecord::StatementInvalid) { Reminder.first }
@@ -250,21 +262,21 @@ class MigrationTest < ActiveRecord::TestCase
 
   def test_instance_based_migration_up
     migration = MockMigration.new
-    assert !migration.went_up, "have not gone up"
-    assert !migration.went_down, "have not gone down"
+    assert_not migration.went_up, "have not gone up"
+    assert_not migration.went_down, "have not gone down"
 
     migration.migrate :up
     assert migration.went_up, "have gone up"
-    assert !migration.went_down, "have not gone down"
+    assert_not migration.went_down, "have not gone down"
   end
 
   def test_instance_based_migration_down
     migration = MockMigration.new
-    assert !migration.went_up, "have not gone up"
-    assert !migration.went_down, "have not gone down"
+    assert_not migration.went_up, "have not gone up"
+    assert_not migration.went_down, "have not gone down"
 
     migration.migrate :down
-    assert !migration.went_up, "have gone up"
+    assert_not migration.went_up, "have gone up"
     assert migration.went_down, "have not gone down"
   end
 
@@ -382,9 +394,9 @@ class MigrationTest < ActiveRecord::TestCase
     current_env     = ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
     migrations_path = MIGRATIONS_ROOT + "/valid"
     old_path        = ActiveRecord::Migrator.migrations_paths
-    ActiveRecord::Migrator.migrations_paths = migrations_path
+    migrator = ActiveRecord::MigrationContext.new(migrations_path)
 
-    ActiveRecord::Migrator.up(migrations_path)
+    migrator.up
     assert_equal current_env, ActiveRecord::InternalMetadata[:environment]
 
     original_rails_env  = ENV["RAILS_ENV"]
@@ -392,16 +404,16 @@ class MigrationTest < ActiveRecord::TestCase
     ENV["RAILS_ENV"]    = ENV["RACK_ENV"] = "foofoo"
     new_env = ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
 
-    refute_equal current_env, new_env
+    assert_not_equal current_env, new_env
 
     sleep 1 # mysql by default does not store fractional seconds in the database
-    ActiveRecord::Migrator.up(migrations_path)
+    migrator.up
     assert_equal new_env, ActiveRecord::InternalMetadata[:environment]
   ensure
-    ActiveRecord::Migrator.migrations_paths = old_path
+    migrator = ActiveRecord::MigrationContext.new(old_path)
     ENV["RAILS_ENV"] = original_rails_env
     ENV["RACK_ENV"]  = original_rack_env
-    ActiveRecord::Migrator.up(migrations_path)
+    migrator.up
   end
 
   def test_internal_metadata_stores_environment_when_other_data_exists
@@ -411,14 +423,15 @@ class MigrationTest < ActiveRecord::TestCase
     current_env     = ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
     migrations_path = MIGRATIONS_ROOT + "/valid"
     old_path        = ActiveRecord::Migrator.migrations_paths
-    ActiveRecord::Migrator.migrations_paths = migrations_path
 
     current_env = ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
-    ActiveRecord::Migrator.up(migrations_path)
+    migrator = ActiveRecord::MigrationContext.new(migrations_path)
+    migrator.up
     assert_equal current_env, ActiveRecord::InternalMetadata[:environment]
     assert_equal "bar", ActiveRecord::InternalMetadata[:foo]
   ensure
-    ActiveRecord::Migrator.migrations_paths = old_path
+    migrator = ActiveRecord::MigrationContext.new(old_path)
+    migrator.up
   end
 
   def test_proper_table_name_on_migration
@@ -450,7 +463,7 @@ class MigrationTest < ActiveRecord::TestCase
   end
 
   def test_rename_table_with_prefix_and_suffix
-    assert !Thing.table_exists?
+    assert_not_predicate Thing, :table_exists?
     ActiveRecord::Base.table_name_prefix = "p_"
     ActiveRecord::Base.table_name_suffix = "_s"
     Thing.reset_table_name
@@ -471,7 +484,7 @@ class MigrationTest < ActiveRecord::TestCase
   end
 
   def test_add_drop_table_with_prefix_and_suffix
-    assert !Reminder.table_exists?
+    assert_not_predicate Reminder, :table_exists?
     ActiveRecord::Base.table_name_prefix = "prefix_"
     ActiveRecord::Base.table_name_suffix = "_suffix"
     Reminder.reset_table_name
@@ -535,7 +548,7 @@ class MigrationTest < ActiveRecord::TestCase
       end
       assert Person.connection.column_exists?(:something, :foo)
       assert_nothing_raised { Person.connection.remove_column :something, :foo, :bar }
-      assert !Person.connection.column_exists?(:something, :foo)
+      assert_not Person.connection.column_exists?(:something, :foo)
       assert Person.connection.column_exists?(:something, :name)
       assert Person.connection.column_exists?(:something, :number)
     ensure
@@ -678,6 +691,25 @@ class MigrationTest < ActiveRecord::TestCase
       assert_no_column Person, :last_name,
         "without an advisory lock, the Migrator should not make any changes, but it did."
     end
+
+    def test_with_advisory_lock_raises_the_right_error_when_it_fails_to_release_lock
+      migration = Class.new(ActiveRecord::Migration::Current).new
+      migrator = ActiveRecord::Migrator.new(:up, [migration], 100)
+      lock_id = migrator.send(:generate_migrator_advisory_lock_id)
+
+      e = assert_raises(ActiveRecord::ConcurrentMigrationError) do
+        silence_stream($stderr) do
+          migrator.send(:with_advisory_lock) do
+            ActiveRecord::Base.connection.release_advisory_lock(lock_id)
+          end
+        end
+      end
+
+      assert_match(
+        /#{ActiveRecord::ConcurrentMigrationError::RELEASE_LOCK_FAILED_MESSAGE}/,
+        e.message
+      )
+    end
   end
 
   private
@@ -790,7 +822,7 @@ if ActiveRecord::Base.connection.supports_bulk_alter?
         end
       end
 
-      [:qualification, :experience].each { |c| assert ! column(c) }
+      [:qualification, :experience].each { |c| assert_not column(c) }
       assert column(:qualification_experience)
     end
 
@@ -801,8 +833,15 @@ if ActiveRecord::Base.connection.supports_bulk_alter?
         t.integer :age
       end
 
-      # Adding an index fires a query every time to check if an index already exists or not
-      assert_queries(3) do
+      classname = ActiveRecord::Base.connection.class.name[/[^:]*$/]
+      expected_query_count = {
+        "Mysql2Adapter"     => 3, # Adding an index fires a query every time to check if an index already exists or not
+        "PostgreSQLAdapter" => 2,
+      }.fetch(classname) {
+        raise "need an expected query count for #{classname}"
+      }
+
+      assert_queries(expected_query_count) do
         with_bulk_change_table do |t|
           t.index :username, unique: true, name: :awesome_username_index
           t.index [:name, :age]
@@ -813,7 +852,7 @@ if ActiveRecord::Base.connection.supports_bulk_alter?
 
       name_age_index = index(:index_delete_me_on_name_and_age)
       assert_equal ["name", "age"].sort, name_age_index.columns.sort
-      assert ! name_age_index.unique
+      assert_not name_age_index.unique
 
       assert index(:awesome_username_index).unique
     end
@@ -826,14 +865,22 @@ if ActiveRecord::Base.connection.supports_bulk_alter?
 
       assert index(:index_delete_me_on_name)
 
-      assert_queries(3) do
+      classname = ActiveRecord::Base.connection.class.name[/[^:]*$/]
+      expected_query_count = {
+        "Mysql2Adapter"     => 3, # Adding an index fires a query every time to check if an index already exists or not
+        "PostgreSQLAdapter" => 2,
+      }.fetch(classname) {
+        raise "need an expected query count for #{classname}"
+      }
+
+      assert_queries(expected_query_count) do
         with_bulk_change_table do |t|
           t.remove_index :name
           t.index :name, name: :new_name_index, unique: true
         end
       end
 
-      assert ! index(:index_delete_me_on_name)
+      assert_not index(:index_delete_me_on_name)
 
       new_name_index = index(:new_name_index)
       assert new_name_index.unique
@@ -845,21 +892,27 @@ if ActiveRecord::Base.connection.supports_bulk_alter?
         t.date :birthdate
       end
 
-      assert ! column(:name).default
+      assert_not column(:name).default
       assert_equal :date, column(:birthdate).type
 
-      # One query for columns (delete_me table)
-      # One query for primary key (delete_me table)
-      # One query to do the bulk change
-      assert_queries(3, ignore_none: true) do
+      classname = ActiveRecord::Base.connection.class.name[/[^:]*$/]
+      expected_query_count = {
+        "Mysql2Adapter"     => 3, # one query for columns, one query for primary key, one query to do the bulk change
+        "PostgreSQLAdapter" => 3, # one query for columns, one for bulk change, one for comment
+      }.fetch(classname) {
+        raise "need an expected query count for #{classname}"
+      }
+
+      assert_queries(expected_query_count, ignore_none: true) do
         with_bulk_change_table do |t|
           t.change :name, :string, default: "NONAME"
-          t.change :birthdate, :datetime
+          t.change :birthdate, :datetime, comment: "This is a comment"
         end
       end
 
       assert_equal "NONAME", column(:name).default
       assert_equal :datetime, column(:birthdate).type
+      assert_equal "This is a comment", column(:birthdate).comment
     end
 
     private
@@ -919,7 +972,7 @@ class CopyMigrationsTest < ActiveRecord::TestCase
     files_count = Dir[@migrations_path + "/*.rb"].length
     copied = ActiveRecord::Migration.copy(@migrations_path, bukkits: MIGRATIONS_ROOT + "/to_copy")
     assert_equal files_count, Dir[@migrations_path + "/*.rb"].length
-    assert copied.empty?
+    assert_empty copied
   ensure
     clear
   end
@@ -960,7 +1013,7 @@ class CopyMigrationsTest < ActiveRecord::TestCase
       files_count = Dir[@migrations_path + "/*.rb"].length
       copied = ActiveRecord::Migration.copy(@migrations_path, bukkits: MIGRATIONS_ROOT + "/to_copy_with_timestamps")
       assert_equal files_count, Dir[@migrations_path + "/*.rb"].length
-      assert copied.empty?
+      assert_empty copied
     end
   ensure
     clear
@@ -1002,7 +1055,7 @@ class CopyMigrationsTest < ActiveRecord::TestCase
       files_count = Dir[@migrations_path + "/*.rb"].length
       copied = ActiveRecord::Migration.copy(@migrations_path, bukkits: MIGRATIONS_ROOT + "/to_copy_with_timestamps")
       assert_equal files_count, Dir[@migrations_path + "/*.rb"].length
-      assert copied.empty?
+      assert_empty copied
     end
   ensure
     clear
@@ -1023,7 +1076,7 @@ class CopyMigrationsTest < ActiveRecord::TestCase
     files_count = Dir[@migrations_path + "/*.rb"].length
     copied = ActiveRecord::Migration.copy(@migrations_path, bukkits: MIGRATIONS_ROOT + "/magic")
     assert_equal files_count, Dir[@migrations_path + "/*.rb"].length
-    assert copied.empty?
+    assert_empty copied
   ensure
     clear
   end
@@ -1106,17 +1159,4 @@ class CopyMigrationsTest < ActiveRecord::TestCase
   def test_unknown_migration_version_should_raise_an_argument_error
     assert_raise(ArgumentError) { ActiveRecord::Migration[1.0] }
   end
-
-  def test_deprecate_initialize_internal_tables
-    assert_deprecated { ActiveRecord::Base.connection.initialize_schema_migrations_table }
-    assert_deprecated { ActiveRecord::Base.connection.initialize_internal_metadata_table }
-  end
-
-  def test_deprecate_supports_migrations
-    assert_deprecated { ActiveRecord::Base.connection.supports_migrations? }
-  end
-
-  def test_deprecate_schema_migrations_table_name
-    assert_deprecated { ActiveRecord::Migrator.schema_migrations_table_name }
-  end
 end
diff --git a/activerecord/test/cases/migrator_test.rb b/activerecord/test/cases/migrator_test.rb
index ee10be119c..873455cf67 100644
--- a/activerecord/test/cases/migrator_test.rb
+++ b/activerecord/test/cases/migrator_test.rb
@@ -66,10 +66,30 @@ class MigratorTest < ActiveRecord::TestCase
       list = [ActiveRecord::Migration.new("Foo", 1), ActiveRecord::Migration.new("Bar", 2)]
       ActiveRecord::Migrator.new(:up, list, 3).run
     end
+
+    assert_raises(ActiveRecord::UnknownMigrationVersionError) do
+      list = [ActiveRecord::Migration.new("Foo", 1), ActiveRecord::Migration.new("Bar", 2)]
+      ActiveRecord::Migrator.new(:up, list, -1).run
+    end
+
+    assert_raises(ActiveRecord::UnknownMigrationVersionError) do
+      list = [ActiveRecord::Migration.new("Foo", 1), ActiveRecord::Migration.new("Bar", 2)]
+      ActiveRecord::Migrator.new(:up, list, 0).run
+    end
+
+    assert_raises(ActiveRecord::UnknownMigrationVersionError) do
+      list = [ActiveRecord::Migration.new("Foo", 1), ActiveRecord::Migration.new("Bar", 2)]
+      ActiveRecord::Migrator.new(:up, list, 3).migrate
+    end
+
+    assert_raises(ActiveRecord::UnknownMigrationVersionError) do
+      list = [ActiveRecord::Migration.new("Foo", 1), ActiveRecord::Migration.new("Bar", 2)]
+      ActiveRecord::Migrator.new(:up, list, -1).migrate
+    end
   end
 
   def test_finds_migrations
-    migrations = ActiveRecord::Migrator.migrations(MIGRATIONS_ROOT + "/valid")
+    migrations = ActiveRecord::MigrationContext.new(MIGRATIONS_ROOT + "/valid").migrations
 
     [[1, "ValidPeopleHaveLastNames"], [2, "WeNeedReminders"], [3, "InnocentJointable"]].each_with_index do |pair, i|
       assert_equal migrations[i].version, pair.first
@@ -78,7 +98,8 @@ class MigratorTest < ActiveRecord::TestCase
   end
 
   def test_finds_migrations_in_subdirectories
-    migrations = ActiveRecord::Migrator.migrations(MIGRATIONS_ROOT + "/valid_with_subdirectories")
+    migrations = ActiveRecord::MigrationContext.new(MIGRATIONS_ROOT + "/valid_with_subdirectories").migrations
+
 
     [[1, "ValidPeopleHaveLastNames"], [2, "WeNeedReminders"], [3, "InnocentJointable"]].each_with_index do |pair, i|
       assert_equal migrations[i].version, pair.first
@@ -88,7 +109,7 @@ class MigratorTest < ActiveRecord::TestCase
 
   def test_finds_migrations_from_two_directories
     directories = [MIGRATIONS_ROOT + "/valid_with_timestamps", MIGRATIONS_ROOT + "/to_copy_with_timestamps"]
-    migrations = ActiveRecord::Migrator.migrations directories
+    migrations = ActiveRecord::MigrationContext.new(directories).migrations
 
     [[20090101010101, "PeopleHaveHobbies"],
      [20090101010202, "PeopleHaveDescriptions"],
@@ -101,14 +122,14 @@ class MigratorTest < ActiveRecord::TestCase
   end
 
   def test_finds_migrations_in_numbered_directory
-    migrations = ActiveRecord::Migrator.migrations [MIGRATIONS_ROOT + "/10_urban"]
+    migrations = ActiveRecord::MigrationContext.new(MIGRATIONS_ROOT + "/10_urban").migrations
     assert_equal 9, migrations[0].version
     assert_equal "AddExpressions", migrations[0].name
   end
 
   def test_relative_migrations
     list = Dir.chdir(MIGRATIONS_ROOT) do
-      ActiveRecord::Migrator.migrations("valid")
+      ActiveRecord::MigrationContext.new("valid").migrations
     end
 
     migration_proxy = list.find { |item|
@@ -137,7 +158,7 @@ class MigratorTest < ActiveRecord::TestCase
       ["up",   "002", "We need reminders"],
       ["down", "003", "Innocent jointable"],
       ["up",   "010", "********** NO FILE **********"],
-    ], ActiveRecord::Migrator.migrations_status(path)
+    ], ActiveRecord::MigrationContext.new(path).migrations_status
   end
 
   def test_migrations_status_in_subdirectories
@@ -151,7 +172,7 @@ class MigratorTest < ActiveRecord::TestCase
       ["up",   "002", "We need reminders"],
       ["down", "003", "Innocent jointable"],
       ["up",   "010", "********** NO FILE **********"],
-    ], ActiveRecord::Migrator.migrations_status(path)
+    ], ActiveRecord::MigrationContext.new(path).migrations_status
   end
 
   def test_migrations_status_with_schema_define_in_subdirectories
@@ -166,7 +187,7 @@ class MigratorTest < ActiveRecord::TestCase
       ["up", "001", "Valid people have last names"],
       ["up", "002", "We need reminders"],
       ["up", "003", "Innocent jointable"],
-    ], ActiveRecord::Migrator.migrations_status(path)
+    ], ActiveRecord::MigrationContext.new(path).migrations_status
   ensure
     ActiveRecord::Migrator.migrations_paths = prev_paths
   end
@@ -184,7 +205,7 @@ class MigratorTest < ActiveRecord::TestCase
       ["down", "20100201010101", "Valid with timestamps we need reminders"],
       ["down", "20100301010101", "Valid with timestamps innocent jointable"],
       ["up",   "20160528010101", "********** NO FILE **********"],
-    ], ActiveRecord::Migrator.migrations_status(paths)
+    ], ActiveRecord::MigrationContext.new(paths).migrations_status
   end
 
   def test_migrator_interleaved_migrations
@@ -212,25 +233,28 @@ class MigratorTest < ActiveRecord::TestCase
 
   def test_up_calls_up
     migrations = [Sensor.new(nil, 0), Sensor.new(nil, 1), Sensor.new(nil, 2)]
-    ActiveRecord::Migrator.new(:up, migrations).migrate
+    migrator = ActiveRecord::Migrator.new(:up, migrations)
+    migrator.migrate
     assert migrations.all?(&:went_up)
     assert migrations.all? { |m| !m.went_down }
-    assert_equal 2, ActiveRecord::Migrator.current_version
+    assert_equal 2, migrator.current_version
   end
 
   def test_down_calls_down
     test_up_calls_up
 
     migrations = [Sensor.new(nil, 0), Sensor.new(nil, 1), Sensor.new(nil, 2)]
-    ActiveRecord::Migrator.new(:down, migrations).migrate
+    migrator = ActiveRecord::Migrator.new(:down, migrations)
+    migrator.migrate
     assert migrations.all? { |m| !m.went_up }
     assert migrations.all?(&:went_down)
-    assert_equal 0, ActiveRecord::Migrator.current_version
+    assert_equal 0, migrator.current_version
   end
 
   def test_current_version
     ActiveRecord::SchemaMigration.create!(version: "1000")
-    assert_equal 1000, ActiveRecord::Migrator.current_version
+    migrator = ActiveRecord::MigrationContext.new("db/migrate")
+    assert_equal 1000, migrator.current_version
   end
 
   def test_migrator_one_up
@@ -269,33 +293,36 @@ class MigratorTest < ActiveRecord::TestCase
 
   def test_migrator_double_up
     calls, migrations = sensors(3)
-    assert_equal(0, ActiveRecord::Migrator.current_version)
+    migrator = ActiveRecord::Migrator.new(:up, migrations, 1)
+    assert_equal(0, migrator.current_version)
 
-    ActiveRecord::Migrator.new(:up, migrations, 1).migrate
+    migrator.migrate
     assert_equal [[:up, 1]], calls
     calls.clear
 
-    ActiveRecord::Migrator.new(:up, migrations, 1).migrate
+    migrator.migrate
     assert_equal [], calls
   end
 
   def test_migrator_double_down
     calls, migrations = sensors(3)
+    migrator = ActiveRecord::Migrator.new(:up, migrations, 1)
 
-    assert_equal(0, ActiveRecord::Migrator.current_version)
+    assert_equal 0, migrator.current_version
 
-    ActiveRecord::Migrator.new(:up, migrations, 1).run
+    migrator.run
     assert_equal [[:up, 1]], calls
     calls.clear
 
-    ActiveRecord::Migrator.new(:down, migrations, 1).run
+    migrator = ActiveRecord::Migrator.new(:down, migrations, 1)
+    migrator.run
     assert_equal [[:down, 1]], calls
     calls.clear
 
-    ActiveRecord::Migrator.new(:down, migrations, 1).run
+    migrator.run
     assert_equal [], calls
 
-    assert_equal(0, ActiveRecord::Migrator.current_version)
+    assert_equal 0, migrator.current_version
   end
 
   def test_migrator_verbosity
@@ -341,78 +368,85 @@ class MigratorTest < ActiveRecord::TestCase
 
   def test_migrator_going_down_due_to_version_target
     calls, migrator = migrator_class(3)
+    migrator = migrator.new("valid")
 
-    migrator.up("valid", 1)
+    migrator.up(1)
     assert_equal [[:up, 1]], calls
     calls.clear
 
-    migrator.migrate("valid", 0)
+    migrator.migrate(0)
     assert_equal [[:down, 1]], calls
     calls.clear
 
-    migrator.migrate("valid")
+    migrator.migrate
     assert_equal [[:up, 1], [:up, 2], [:up, 3]], calls
   end
 
   def test_migrator_output_when_running_multiple_migrations
     _, migrator = migrator_class(3)
+    migrator = migrator.new("valid")
 
-    result = migrator.migrate("valid")
+    result = migrator.migrate
     assert_equal(3, result.count)
 
     # Nothing migrated from duplicate run
-    result = migrator.migrate("valid")
+    result = migrator.migrate
     assert_equal(0, result.count)
 
-    result = migrator.rollback("valid")
+    result = migrator.rollback
     assert_equal(1, result.count)
   end
 
   def test_migrator_output_when_running_single_migration
     _, migrator = migrator_class(1)
-    result = migrator.run(:up, "valid", 1)
+    migrator = migrator.new("valid")
+
+    result = migrator.run(:up, 1)
 
     assert_equal(1, result.version)
   end
 
   def test_migrator_rollback
     _, migrator = migrator_class(3)
+    migrator = migrator.new("valid")
 
-    migrator.migrate("valid")
-    assert_equal(3, ActiveRecord::Migrator.current_version)
+    migrator.migrate
+    assert_equal(3, migrator.current_version)
 
-    migrator.rollback("valid")
-    assert_equal(2, ActiveRecord::Migrator.current_version)
+    migrator.rollback
+    assert_equal(2, migrator.current_version)
 
-    migrator.rollback("valid")
-    assert_equal(1, ActiveRecord::Migrator.current_version)
+    migrator.rollback
+    assert_equal(1, migrator.current_version)
 
-    migrator.rollback("valid")
-    assert_equal(0, ActiveRecord::Migrator.current_version)
+    migrator.rollback
+    assert_equal(0, migrator.current_version)
 
-    migrator.rollback("valid")
-    assert_equal(0, ActiveRecord::Migrator.current_version)
+    migrator.rollback
+    assert_equal(0, migrator.current_version)
   end
 
   def test_migrator_db_has_no_schema_migrations_table
     _, migrator = migrator_class(3)
+    migrator = migrator.new("valid")
 
     ActiveRecord::Base.connection.drop_table "schema_migrations", if_exists: true
     assert_not ActiveRecord::Base.connection.table_exists?("schema_migrations")
-    migrator.migrate("valid", 1)
+    migrator.migrate(1)
     assert ActiveRecord::Base.connection.table_exists?("schema_migrations")
   end
 
   def test_migrator_forward
     _, migrator = migrator_class(3)
-    migrator.migrate("/valid", 1)
-    assert_equal(1, ActiveRecord::Migrator.current_version)
+    migrator = migrator.new("/valid")
+    migrator.migrate(1)
+    assert_equal(1, migrator.current_version)
 
-    migrator.forward("/valid", 2)
-    assert_equal(3, ActiveRecord::Migrator.current_version)
+    migrator.forward(2)
+    assert_equal(3, migrator.current_version)
 
-    migrator.forward("/valid")
-    assert_equal(3, ActiveRecord::Migrator.current_version)
+    migrator.forward
+    assert_equal(3, migrator.current_version)
   end
 
   def test_only_loads_pending_migrations
@@ -420,25 +454,27 @@ class MigratorTest < ActiveRecord::TestCase
     ActiveRecord::SchemaMigration.create!(version: "1")
 
     calls, migrator = migrator_class(3)
-    migrator.migrate("valid", nil)
+    migrator = migrator.new("valid")
+    migrator.migrate
 
     assert_equal [[:up, 2], [:up, 3]], calls
   end
 
   def test_get_all_versions
     _, migrator = migrator_class(3)
+    migrator = migrator.new("valid")
 
-    migrator.migrate("valid")
-    assert_equal([1, 2, 3], ActiveRecord::Migrator.get_all_versions)
+    migrator.migrate
+    assert_equal([1, 2, 3], migrator.get_all_versions)
 
-    migrator.rollback("valid")
-    assert_equal([1, 2], ActiveRecord::Migrator.get_all_versions)
+    migrator.rollback
+    assert_equal([1, 2], migrator.get_all_versions)
 
-    migrator.rollback("valid")
-    assert_equal([1], ActiveRecord::Migrator.get_all_versions)
+    migrator.rollback
+    assert_equal([1], migrator.get_all_versions)
 
-    migrator.rollback("valid")
-    assert_equal([], ActiveRecord::Migrator.get_all_versions)
+    migrator.rollback
+    assert_equal([], migrator.get_all_versions)
   end
 
   private
@@ -463,11 +499,11 @@ class MigratorTest < ActiveRecord::TestCase
     def migrator_class(count)
       calls, migrations = sensors(count)
 
-      migrator = Class.new(ActiveRecord::Migrator).extend(Module.new {
-        define_method(:migrations) { |paths|
+      migrator = Class.new(ActiveRecord::MigrationContext) {
+        define_method(:migrations) { |*|
           migrations
         }
-      })
+      }
       [calls, migrator]
     end
 end
diff --git a/activerecord/test/cases/modules_test.rb b/activerecord/test/cases/modules_test.rb
index 060d555607..87455e4fcb 100644
--- a/activerecord/test/cases/modules_test.rb
+++ b/activerecord/test/cases/modules_test.rb
@@ -32,7 +32,7 @@ class ModulesTest < ActiveRecord::TestCase
 
   def test_module_spanning_associations
     firm = MyApplication::Business::Firm.first
-    assert !firm.clients.empty?, "Firm should have clients"
+    assert_not firm.clients.empty?, "Firm should have clients"
     assert_nil firm.class.table_name.match("::"), "Firm shouldn't have the module appear in its table name"
   end
 
@@ -155,7 +155,7 @@ class ModulesTest < ActiveRecord::TestCase
     ActiveRecord::Base.store_full_sti_class = true
 
     collection = Shop::Collection.first
-    assert !collection.products.empty?, "Collection should have products"
+    assert_not collection.products.empty?, "Collection should have products"
     assert_nothing_raised { collection.destroy }
   ensure
     ActiveRecord::Base.store_full_sti_class = old
@@ -166,7 +166,7 @@ class ModulesTest < ActiveRecord::TestCase
     ActiveRecord::Base.store_full_sti_class = true
 
     product = Shop::Product.first
-    assert !product.variants.empty?, "Product should have variants"
+    assert_not product.variants.empty?, "Product should have variants"
     assert_nothing_raised { product.destroy }
   ensure
     ActiveRecord::Base.store_full_sti_class = old
diff --git a/activerecord/test/cases/multiparameter_attributes_test.rb b/activerecord/test/cases/multiparameter_attributes_test.rb
index 59be4dc5a8..6f3903eed4 100644
--- a/activerecord/test/cases/multiparameter_attributes_test.rb
+++ b/activerecord/test/cases/multiparameter_attributes_test.rb
@@ -227,7 +227,7 @@ class MultiParameterAttributeTest < ActiveRecord::TestCase
       topic = Topic.find(1)
       topic.attributes = attributes
       assert_equal Time.local(2004, 6, 24, 16, 24, 0), topic.written_on
-      assert_equal false, topic.written_on.respond_to?(:time_zone)
+      assert_not_respond_to topic.written_on, :time_zone
     end
   end
 
@@ -242,7 +242,7 @@ class MultiParameterAttributeTest < ActiveRecord::TestCase
       topic = Topic.find(1)
       topic.attributes = attributes
       assert_equal Time.utc(2004, 6, 24, 16, 24, 0), topic.written_on
-      assert_equal false, topic.written_on.respond_to?(:time_zone)
+      assert_not_respond_to topic.written_on, :time_zone
     end
   ensure
     Topic.skip_time_zone_conversion_for_attributes = []
@@ -261,7 +261,7 @@ class MultiParameterAttributeTest < ActiveRecord::TestCase
         topic = Topic.find(1)
         topic.attributes = attributes
         assert_equal Time.zone.local(2000, 1, 1, 16, 24, 0), topic.bonus_time
-        assert_not topic.bonus_time.utc?
+        assert_not_predicate topic.bonus_time, :utc?
 
         attributes = {
           "written_on(1i)" => "2000", "written_on(2i)" => "", "written_on(3i)" => "",
@@ -394,6 +394,6 @@ class MultiParameterAttributeTest < ActiveRecord::TestCase
       "written_on(4i)" => "13",
       "written_on(5i)" => "55",
     )
-    refute_predicate topic, :written_on_came_from_user?
+    assert_not_predicate topic, :written_on_came_from_user?
   end
 end
diff --git a/activerecord/test/cases/nested_attributes_test.rb b/activerecord/test/cases/nested_attributes_test.rb
index a2ccb603a9..32af90caef 100644
--- a/activerecord/test/cases/nested_attributes_test.rb
+++ b/activerecord/test/cases/nested_attributes_test.rb
@@ -36,7 +36,7 @@ class TestNestedAttributesInGeneral < ActiveRecord::TestCase
     pirate.birds_with_reject_all_blank_attributes = [{ name: "", color: "", _destroy: "0" }]
     pirate.save!
 
-    assert pirate.birds_with_reject_all_blank.empty?
+    assert_empty pirate.birds_with_reject_all_blank
   end
 
   def test_should_not_build_a_new_record_if_reject_all_blank_returns_false
@@ -44,7 +44,7 @@ class TestNestedAttributesInGeneral < ActiveRecord::TestCase
     pirate.birds_with_reject_all_blank_attributes = [{ name: "", color: "" }]
     pirate.save!
 
-    assert pirate.birds_with_reject_all_blank.empty?
+    assert_empty pirate.birds_with_reject_all_blank
   end
 
   def test_should_build_a_new_record_if_reject_all_blank_does_not_return_false
@@ -83,7 +83,7 @@ class TestNestedAttributesInGeneral < ActiveRecord::TestCase
 
   def test_a_model_should_respond_to_underscore_destroy_and_return_if_it_is_marked_for_destruction
     ship = Ship.create!(name: "Nights Dirty Lightning")
-    assert !ship._destroy
+    assert_not ship._destroy
     ship.mark_for_destruction
     assert ship._destroy
   end
@@ -152,7 +152,7 @@ class TestNestedAttributesInGeneral < ActiveRecord::TestCase
     man = Man.create(name: "Jon")
     interest = man.interests.create(topic: "the ladies")
     man.update(interests_attributes: { _destroy: "1", id: interest.id })
-    assert man.reload.interests.empty?
+    assert_empty man.reload.interests
   end
 
   def test_reject_if_is_not_short_circuited_if_allow_destroy_is_false
@@ -240,7 +240,7 @@ class TestNestedAttributesOnAHasOneAssociation < ActiveRecord::TestCase
     @ship.destroy
     @pirate.reload.ship_attributes = { name: "Davy Jones Gold Dagger" }
 
-    assert !@pirate.ship.persisted?
+    assert_not_predicate @pirate.ship, :persisted?
     assert_equal "Davy Jones Gold Dagger", @pirate.ship.name
   end
 
@@ -261,7 +261,7 @@ class TestNestedAttributesOnAHasOneAssociation < ActiveRecord::TestCase
   def test_should_replace_an_existing_record_if_there_is_no_id
     @pirate.reload.ship_attributes = { name: "Davy Jones Gold Dagger" }
 
-    assert !@pirate.ship.persisted?
+    assert_not_predicate @pirate.ship, :persisted?
     assert_equal "Davy Jones Gold Dagger", @pirate.ship.name
     assert_equal "Nights Dirty Lightning", @ship.name
   end
@@ -335,7 +335,7 @@ class TestNestedAttributesOnAHasOneAssociation < ActiveRecord::TestCase
   def test_should_also_work_with_a_HashWithIndifferentAccess
     @pirate.ship_attributes = ActiveSupport::HashWithIndifferentAccess.new(id: @ship.id, name: "Davy Jones Gold Dagger")
 
-    assert @pirate.ship.persisted?
+    assert_predicate @pirate.ship, :persisted?
     assert_equal "Davy Jones Gold Dagger", @pirate.ship.name
   end
 
@@ -350,12 +350,12 @@ class TestNestedAttributesOnAHasOneAssociation < ActiveRecord::TestCase
   def test_should_not_destroy_the_associated_model_until_the_parent_is_saved
     @pirate.attributes = { ship_attributes: { id: @ship.id, _destroy: "1" } }
 
-    assert !@pirate.ship.destroyed?
-    assert @pirate.ship.marked_for_destruction?
+    assert_not_predicate @pirate.ship, :destroyed?
+    assert_predicate @pirate.ship, :marked_for_destruction?
 
     @pirate.save
 
-    assert @pirate.ship.destroyed?
+    assert_predicate @pirate.ship, :destroyed?
     assert_nil @pirate.reload.ship
   end
 
@@ -424,7 +424,7 @@ class TestNestedAttributesOnABelongsToAssociation < ActiveRecord::TestCase
     @pirate.destroy
     @ship.reload.pirate_attributes = { catchphrase: "Arr" }
 
-    assert !@ship.pirate.persisted?
+    assert_not_predicate @ship.pirate, :persisted?
     assert_equal "Arr", @ship.pirate.catchphrase
   end
 
@@ -445,7 +445,7 @@ class TestNestedAttributesOnABelongsToAssociation < ActiveRecord::TestCase
   def test_should_replace_an_existing_record_if_there_is_no_id
     @ship.reload.pirate_attributes = { catchphrase: "Arr" }
 
-    assert !@ship.pirate.persisted?
+    assert_not_predicate @ship.pirate, :persisted?
     assert_equal "Arr", @ship.pirate.catchphrase
     assert_equal "Aye", @pirate.catchphrase
   end
@@ -550,7 +550,7 @@ class TestNestedAttributesOnABelongsToAssociation < ActiveRecord::TestCase
     @pirate.delete
     @ship.reload.attributes = { update_only_pirate_attributes: { catchphrase: "Arr" } }
 
-    assert !@ship.update_only_pirate.persisted?
+    assert_not_predicate @ship.update_only_pirate, :persisted?
   end
 
   def test_should_update_existing_when_update_only_is_true_and_no_id_is_given
@@ -632,10 +632,10 @@ module NestedAttributesOnACollectionAssociationTests
   def test_should_not_load_association_when_updating_existing_records
     @pirate.reload
     @pirate.send(association_setter, [{ id: @child_1.id, name: "Grace OMalley" }])
-    assert ! @pirate.send(@association_name).loaded?
+    assert_not_predicate @pirate.send(@association_name), :loaded?
 
     @pirate.save
-    assert ! @pirate.send(@association_name).loaded?
+    assert_not_predicate @pirate.send(@association_name), :loaded?
     assert_equal "Grace OMalley", @child_1.reload.name
   end
 
@@ -663,7 +663,7 @@ module NestedAttributesOnACollectionAssociationTests
   def test_should_not_remove_scheduled_destroys_when_loading_association
     @pirate.reload
     @pirate.send(association_setter, [{ id: @child_1.id, _destroy: "1" }])
-    assert @pirate.send(@association_name).load_target.find { |r| r.id == @child_1.id }.marked_for_destruction?
+    assert_predicate @pirate.send(@association_name).load_target.find { |r| r.id == @child_1.id }, :marked_for_destruction?
   end
 
   def test_should_take_a_hash_with_composite_id_keys_and_assign_the_attributes_to_the_associated_models
@@ -705,10 +705,10 @@ module NestedAttributesOnACollectionAssociationTests
       association_getter => { "foo" => { name: "Grace OMalley" }, "bar" => { name: "Privateers Greed" } }
     }
 
-    assert !@pirate.send(@association_name).first.persisted?
+    assert_not_predicate @pirate.send(@association_name).first, :persisted?
     assert_equal "Grace OMalley", @pirate.send(@association_name).first.name
 
-    assert !@pirate.send(@association_name).last.persisted?
+    assert_not_predicate @pirate.send(@association_name).last, :persisted?
     assert_equal "Privateers Greed", @pirate.send(@association_name).last.name
   end
 
@@ -835,7 +835,7 @@ module NestedAttributesOnACollectionAssociationTests
       man = Man.create(name: "John")
       interest = man.interests.create(topic: "bar", zine_id: 0)
       assert interest.save
-      assert !man.update(interests_attributes: { id: interest.id, zine_id: "foo" })
+      assert_not man.update(interests_attributes: { id: interest.id, zine_id: "foo" })
     end
   end
 
@@ -1091,7 +1091,7 @@ class TestHasManyAutosaveAssociationWhichItselfHasAutosaveAssociations < ActiveR
   test "nested singular associations are validated" do
     part = ShipPart.new(name: "Stern", ship_attributes: { name: nil })
 
-    assert_not part.valid?
+    assert_not_predicate part, :valid?
     assert_equal ["Ship name can't be blank"], part.errors.full_messages
   end
 end
diff --git a/activerecord/test/cases/nested_attributes_with_callbacks_test.rb b/activerecord/test/cases/nested_attributes_with_callbacks_test.rb
index f04c68b08f..1d26057fdc 100644
--- a/activerecord/test/cases/nested_attributes_with_callbacks_test.rb
+++ b/activerecord/test/cases/nested_attributes_with_callbacks_test.rb
@@ -63,7 +63,7 @@ class NestedAttributesWithCallbacksTest < ActiveRecord::TestCase
 
   # Characterizing when :before_add callback is called
   test ":before_add called for new bird when not loaded" do
-    assert_not @pirate.birds_with_add.loaded?
+    assert_not_predicate @pirate.birds_with_add, :loaded?
     @pirate.birds_with_add_attributes = new_bird_attributes
     assert_new_bird_with_callback_called
   end
@@ -80,7 +80,7 @@ class NestedAttributesWithCallbacksTest < ActiveRecord::TestCase
   end
 
   test ":before_add not called for identical assignment when not loaded" do
-    assert_not @pirate.birds_with_add.loaded?
+    assert_not_predicate @pirate.birds_with_add, :loaded?
     @pirate.birds_with_add_attributes = existing_birds_attributes
     assert_callbacks_not_called
   end
@@ -92,7 +92,7 @@ class NestedAttributesWithCallbacksTest < ActiveRecord::TestCase
   end
 
   test ":before_add not called for destroy assignment when not loaded" do
-    assert_not @pirate.birds_with_add.loaded?
+    assert_not_predicate @pirate.birds_with_add, :loaded?
     @pirate.birds_with_add_attributes = destroy_bird_attributes
     assert_callbacks_not_called
   end
@@ -111,7 +111,7 @@ class NestedAttributesWithCallbacksTest < ActiveRecord::TestCase
   # Ensuring that the records in the association target are updated,
   # whether the association is loaded before or not
   test "Assignment updates records in target when not loaded" do
-    assert_not @pirate.birds_with_add.loaded?
+    assert_not_predicate @pirate.birds_with_add, :loaded?
     @pirate.birds_with_add_attributes = update_new_and_destroy_bird_attributes
     assert_assignment_affects_records_in_target(:birds_with_add)
   end
@@ -124,7 +124,7 @@ class NestedAttributesWithCallbacksTest < ActiveRecord::TestCase
 
   test("Assignment updates records in target when not loaded" \
        " and callback loads target") do
-    assert_not @pirate.birds_with_add_load.loaded?
+    assert_not_predicate @pirate.birds_with_add_load, :loaded?
     @pirate.birds_with_add_load_attributes = update_new_and_destroy_bird_attributes
     assert_assignment_affects_records_in_target(:birds_with_add_load)
   end
diff --git a/activerecord/test/cases/numeric_data_test.rb b/activerecord/test/cases/numeric_data_test.rb
index f917c8f727..14db63890e 100644
--- a/activerecord/test/cases/numeric_data_test.rb
+++ b/activerecord/test/cases/numeric_data_test.rb
@@ -19,7 +19,7 @@ class NumericDataTest < ActiveRecord::TestCase
     m = NumericData.new(
       bank_balance: 1586.43,
       big_bank_balance: BigDecimal("1000234000567.95"),
-      world_population: 6000000000,
+      world_population: 2**62,
       my_house_population: 3
     )
     assert m.save
@@ -27,11 +27,8 @@ class NumericDataTest < ActiveRecord::TestCase
     m1 = NumericData.find(m.id)
     assert_not_nil m1
 
-    # As with migration_test.rb, we should make world_population >= 2**62
-    # to cover 64-bit platforms and test it is a Bignum, but the main thing
-    # is that it's an Integer.
     assert_kind_of Integer, m1.world_population
-    assert_equal 6000000000, m1.world_population
+    assert_equal 2**62, m1.world_population
 
     assert_kind_of Integer, m1.my_house_population
     assert_equal 3, m1.my_house_population
@@ -47,7 +44,7 @@ class NumericDataTest < ActiveRecord::TestCase
     m = NumericData.new(
       bank_balance: 1586.43122334,
       big_bank_balance: BigDecimal("234000567.952344"),
-      world_population: 6000000000,
+      world_population: 2**62,
       my_house_population: 3
     )
     assert m.save
@@ -55,11 +52,8 @@ class NumericDataTest < ActiveRecord::TestCase
     m1 = NumericData.find(m.id)
     assert_not_nil m1
 
-    # As with migration_test.rb, we should make world_population >= 2**62
-    # to cover 64-bit platforms and test it is a Bignum, but the main thing
-    # is that it's an Integer.
     assert_kind_of Integer, m1.world_population
-    assert_equal 6000000000, m1.world_population
+    assert_equal 2**62, m1.world_population
 
     assert_kind_of Integer, m1.my_house_population
     assert_equal 3, m1.my_house_population
diff --git a/activerecord/test/cases/persistence_test.rb b/activerecord/test/cases/persistence_test.rb
index 170fd02b6f..4c332e30aa 100644
--- a/activerecord/test/cases/persistence_test.rb
+++ b/activerecord/test/cases/persistence_test.rb
@@ -48,7 +48,7 @@ class PersistenceTest < ActiveRecord::TestCase
       end
 
       if test_update_with_order_succeeds.call("id DESC")
-        assert !test_update_with_order_succeeds.call("id ASC") # test that this wasn't a fluke and using an incorrect order results in an exception
+        assert_not test_update_with_order_succeeds.call("id ASC") # test that this wasn't a fluke and using an incorrect order results in an exception
       else
         # test that we're failing because the current Arel's engine doesn't support UPDATE ORDER BY queries is using subselects instead
         assert_sql(/\AUPDATE .+ \(SELECT .* ORDER BY id DESC\)\z/i) do
@@ -59,13 +59,42 @@ class PersistenceTest < ActiveRecord::TestCase
 
     def test_update_all_with_order_and_limit_updates_subset_only
       author = authors(:david)
-      assert_nothing_raised do
-        assert_equal 1, author.posts_sorted_by_id_limited.size
-        assert_equal 2, author.posts_sorted_by_id_limited.limit(2).to_a.size
-        assert_equal 1, author.posts_sorted_by_id_limited.update_all([ "body = ?", "bulk update!" ])
-        assert_equal "bulk update!", posts(:welcome).body
-        assert_not_equal "bulk update!", posts(:thinking).body
-      end
+      limited_posts = author.posts_sorted_by_id_limited
+      assert_equal 1, limited_posts.size
+      assert_equal 2, limited_posts.limit(2).size
+      assert_equal 1, limited_posts.update_all([ "body = ?", "bulk update!" ])
+      assert_equal "bulk update!", posts(:welcome).body
+      assert_not_equal "bulk update!", posts(:thinking).body
+    end
+
+    def test_update_all_with_order_and_limit_and_offset_updates_subset_only
+      author = authors(:david)
+      limited_posts = author.posts_sorted_by_id_limited.offset(1)
+      assert_equal 1, limited_posts.size
+      assert_equal 2, limited_posts.limit(2).size
+      assert_equal 1, limited_posts.update_all([ "body = ?", "bulk update!" ])
+      assert_equal "bulk update!", posts(:thinking).body
+      assert_not_equal "bulk update!", posts(:welcome).body
+    end
+
+    def test_delete_all_with_order_and_limit_deletes_subset_only
+      author = authors(:david)
+      limited_posts = Post.where(author: author).order(:id).limit(1)
+      assert_equal 1, limited_posts.size
+      assert_equal 2, limited_posts.limit(2).size
+      assert_equal 1, limited_posts.delete_all
+      assert_raise(ActiveRecord::RecordNotFound) { posts(:welcome) }
+      assert posts(:thinking)
+    end
+
+    def test_delete_all_with_order_and_limit_and_offset_deletes_subset_only
+      author = authors(:david)
+      limited_posts = Post.where(author: author).order(:id).limit(1).offset(1)
+      assert_equal 1, limited_posts.size
+      assert_equal 2, limited_posts.limit(2).size
+      assert_equal 1, limited_posts.delete_all
+      assert_raise(ActiveRecord::RecordNotFound) { posts(:thinking) }
+      assert posts(:welcome)
     end
   end
 
@@ -73,17 +102,39 @@ class PersistenceTest < ActiveRecord::TestCase
     topic_data = { 1 => { "content" => "1 updated" }, 2 => { "content" => "2 updated" } }
     updated = Topic.update(topic_data.keys, topic_data.values)
 
-    assert_equal 2, updated.size
+    assert_equal [1, 2], updated.map(&:id)
+    assert_equal "1 updated", Topic.find(1).content
+    assert_equal "2 updated", Topic.find(2).content
+  end
+
+  def test_update_many_with_duplicated_ids
+    updated = Topic.update([1, 1, 2], [
+      { "content" => "1 duplicated" }, { "content" => "1 updated" }, { "content" => "2 updated" }
+    ])
+
+    assert_equal [1, 1, 2], updated.map(&:id)
     assert_equal "1 updated", Topic.find(1).content
     assert_equal "2 updated", Topic.find(2).content
   end
 
+  def test_update_many_with_invalid_id
+    topic_data = { 1 => { "content" => "1 updated" }, 2 => { "content" => "2 updated" }, 99999 => {} }
+
+    assert_raise(ActiveRecord::RecordNotFound) do
+      Topic.update(topic_data.keys, topic_data.values)
+    end
+
+    assert_not_equal "1 updated", Topic.find(1).content
+    assert_not_equal "2 updated", Topic.find(2).content
+  end
+
   def test_class_level_update_is_affected_by_scoping
     topic_data = { 1 => { "content" => "1 updated" }, 2 => { "content" => "2 updated" } }
 
     assert_raise(ActiveRecord::RecordNotFound) do
       Topic.where("1=0").scoping { Topic.update(topic_data.keys, topic_data.values) }
     end
+
     assert_not_equal "1 updated", Topic.find(1).content
     assert_not_equal "2 updated", Topic.find(2).content
   end
@@ -95,27 +146,31 @@ class PersistenceTest < ActiveRecord::TestCase
   end
 
   def test_delete_all_with_joins_and_where_part_is_hash
-    where_args = { toys: { name: "Bone" } }
-    count = Pet.joins(:toys).where(where_args).count
+    pets = Pet.joins(:toys).where(toys: { name: "Bone" })
 
-    assert_equal count, 1
-    assert_equal count, Pet.joins(:toys).where(where_args).delete_all
+    assert_equal true, pets.exists?
+    assert_equal pets.count, pets.delete_all
+  end
+
+  def test_delete_all_with_joins_and_where_part_is_not_hash
+    pets = Pet.joins(:toys).where("toys.name = ?", "Bone")
+
+    assert_equal true, pets.exists?
+    assert_equal pets.count, pets.delete_all
   end
 
   def test_delete_all_with_left_joins
-    where_args = { toys: { name: "Bone" } }
-    count = Pet.left_joins(:toys).where(where_args).count
+    pets = Pet.left_joins(:toys).where(toys: { name: "Bone" })
 
-    assert_equal count, 1
-    assert_equal count, Pet.left_joins(:toys).where(where_args).delete_all
+    assert_equal true, pets.exists?
+    assert_equal pets.count, pets.delete_all
   end
 
-  def test_delete_all_with_joins_and_where_part_is_not_hash
-    where_args = ["toys.name = ?", "Bone"]
-    count = Pet.joins(:toys).where(where_args).count
+  def test_delete_all_with_includes
+    pets = Pet.includes(:toys).where(toys: { name: "Bone" })
 
-    assert_equal count, 1
-    assert_equal count, Pet.joins(:toys).where(where_args).delete_all
+    assert_equal true, pets.exists?
+    assert_equal pets.count, pets.delete_all
   end
 
   def test_increment_attribute
@@ -162,7 +217,7 @@ class PersistenceTest < ActiveRecord::TestCase
   def test_destroy_all
     conditions = "author_name = 'Mary'"
     topics_by_mary = Topic.all.merge!(where: conditions, order: "id").to_a
-    assert ! topics_by_mary.empty?
+    assert_not_empty topics_by_mary
 
     assert_difference("Topic.count", -topics_by_mary.size) do
       destroyed = Topic.where(conditions).destroy_all.sort_by(&:id)
@@ -172,23 +227,40 @@ class PersistenceTest < ActiveRecord::TestCase
   end
 
   def test_destroy_many
-    clients = Client.all.merge!(order: "id").find([2, 3])
+    clients = Client.find([2, 3])
 
     assert_difference("Client.count", -2) do
-      destroyed = Client.destroy([2, 3]).sort_by(&:id)
+      destroyed = Client.destroy([2, 3])
       assert_equal clients, destroyed
       assert destroyed.all?(&:frozen?), "destroyed clients should be frozen"
     end
   end
 
+  def test_destroy_many_with_invalid_id
+    clients = Client.find([2, 3])
+
+    assert_raise(ActiveRecord::RecordNotFound) do
+      Client.destroy([2, 3, 99999])
+    end
+
+    assert_equal clients, Client.find([2, 3])
+  end
+
   def test_becomes
     assert_kind_of Reply, topics(:first).becomes(Reply)
     assert_equal "The First Topic", topics(:first).becomes(Reply).title
   end
 
+  def test_becomes_after_reload_schema_from_cache
+    Reply.define_attribute_methods
+    Reply.serialize(:content) # invoke reload_schema_from_cache
+    assert_kind_of Reply, topics(:first).becomes(Reply)
+    assert_equal "The First Topic", topics(:first).becomes(Reply).title
+  end
+
   def test_becomes_includes_errors
     company = Company.new(name: nil)
-    assert !company.valid?
+    assert_not_predicate company, :valid?
     original_errors = company.errors
     client = company.becomes(Client)
     assert_equal original_errors.keys, client.errors.keys
@@ -218,6 +290,17 @@ class PersistenceTest < ActiveRecord::TestCase
     assert_equal "The First Topic", Topic.find(copy.id).title
   end
 
+  def test_becomes_wont_break_mutation_tracking
+    topic = topics(:first)
+    reply = topic.becomes(Reply)
+
+    assert_equal 1, topic.id_in_database
+    assert_empty topic.attributes_in_database
+
+    assert_equal 1, reply.id_in_database
+    assert_empty reply.attributes_in_database
+  end
+
   def test_becomes_includes_changed_attributes
     company = Company.new(name: "37signals")
     client = company.becomes(Client)
@@ -305,8 +388,8 @@ class PersistenceTest < ActiveRecord::TestCase
     developer.destroy
     new_developer = developer.dup
     new_developer.save
-    assert new_developer.persisted?
-    assert_not new_developer.destroyed?
+    assert_predicate new_developer, :persisted?
+    assert_not_predicate new_developer, :destroyed?
   end
 
   def test_create_many
@@ -317,12 +400,13 @@ class PersistenceTest < ActiveRecord::TestCase
 
   def test_create_columns_not_equal_attributes
     topic = Topic.instantiate(
-      "attributes" => {
-        "title"          => "Another New Topic",
-        "does_not_exist" => "test"
-      }
+      "title"          => "Another New Topic",
+      "does_not_exist" => "test"
     )
+    topic = topic.dup # reset @new_record
     assert_nothing_raised { topic.save }
+    assert_predicate topic, :persisted?
+    assert_equal "Another New Topic", topic.reload.title
   end
 
   def test_create_through_factory_with_block
@@ -369,6 +453,8 @@ class PersistenceTest < ActiveRecord::TestCase
     topic_reloaded = Topic.instantiate(topic.attributes.merge("does_not_exist" => "test"))
     topic_reloaded.title = "A New Topic"
     assert_nothing_raised { topic_reloaded.save }
+    assert_predicate topic_reloaded, :persisted?
+    assert_equal "A New Topic", topic_reloaded.reload.title
   end
 
   def test_update_for_record_with_only_primary_key
@@ -405,6 +491,22 @@ class PersistenceTest < ActiveRecord::TestCase
     assert_instance_of Reply, Reply.find(reply.id)
   end
 
+  def test_becomes_default_sti_subclass
+    original_type = Topic.columns_hash["type"].default
+    ActiveRecord::Base.connection.change_column_default :topics, :type, "Reply"
+    Topic.reset_column_information
+
+    reply = topics(:second)
+    assert_instance_of Reply, reply
+
+    topic = reply.becomes(Topic)
+    assert_instance_of Topic, topic
+
+  ensure
+    ActiveRecord::Base.connection.change_column_default :topics, :type, original_type
+    Topic.reset_column_information
+  end
+
   def test_update_after_create
     klass = Class.new(Topic) do
       def self.name; "Topic"; end
@@ -434,7 +536,7 @@ class PersistenceTest < ActiveRecord::TestCase
   def test_update_does_not_run_sql_if_record_has_not_changed
     topic = Topic.create(title: "Another New Topic")
     assert_queries(0) { assert topic.update(title: "Another New Topic") }
-    assert_queries(0) { assert topic.update_attributes(title: "Another New Topic") }
+    assert_queries(0) { assert topic.update(title: "Another New Topic") }
   end
 
   def test_delete
@@ -470,10 +572,18 @@ class PersistenceTest < ActiveRecord::TestCase
     assert_raise(ActiveRecord::RecordNotFound) { Topic.find(topic.id) }
   end
 
-  def test_record_not_found_exception
+  def test_find_raises_record_not_found_exception
     assert_raise(ActiveRecord::RecordNotFound) { Topic.find(99999) }
   end
 
+  def test_update_raises_record_not_found_exception
+    assert_raise(ActiveRecord::RecordNotFound) { Topic.update(99999, approved: true) }
+  end
+
+  def test_destroy_raises_record_not_found_exception
+    assert_raise(ActiveRecord::RecordNotFound) { Topic.destroy(99999) }
+  end
+
   def test_update_all
     assert_equal Topic.count, Topic.update_all("content = 'bulk updated!'")
     assert_equal "bulk updated!", Topic.find(1).content
@@ -497,17 +607,24 @@ class PersistenceTest < ActiveRecord::TestCase
   end
 
   def test_update_all_with_joins
-    where_args = { toys: { name: "Bone" } }
-    count = Pet.left_joins(:toys).where(where_args).count
+    pets = Pet.joins(:toys).where(toys: { name: "Bone" })
 
-    assert_equal count, Pet.joins(:toys).where(where_args).update_all(name: "Bob")
+    assert_equal true, pets.exists?
+    assert_equal pets.count, pets.update_all(name: "Bob")
   end
 
   def test_update_all_with_left_joins
-    where_args = { toys: { name: "Bone" } }
-    count = Pet.left_joins(:toys).where(where_args).count
+    pets = Pet.left_joins(:toys).where(toys: { name: "Bone" })
 
-    assert_equal count, Pet.left_joins(:toys).where(where_args).update_all(name: "Bob")
+    assert_equal true, pets.exists?
+    assert_equal pets.count, pets.update_all(name: "Bob")
+  end
+
+  def test_update_all_with_includes
+    pets = Pet.includes(:toys).where(toys: { name: "Bone" })
+
+    assert_equal true, pets.exists?
+    assert_equal pets.count, pets.update_all(name: "Bob")
   end
 
   def test_update_all_with_non_standard_table_name
@@ -516,40 +633,65 @@ class PersistenceTest < ActiveRecord::TestCase
   end
 
   def test_delete_new_record
-    client = Client.new
+    client = Client.new(name: "37signals")
     client.delete
-    assert client.frozen?
+    assert_predicate client, :frozen?
+
+    assert_not client.save
+    assert_raise(ActiveRecord::RecordNotSaved) { client.save! }
+
+    assert_predicate client, :frozen?
+    assert_raise(RuntimeError) { client.name = "something else" }
   end
 
   def test_delete_record_with_associations
     client = Client.find(3)
     client.delete
-    assert client.frozen?
+    assert_predicate client, :frozen?
     assert_kind_of Firm, client.firm
+
+    assert_not client.save
+    assert_raise(ActiveRecord::RecordNotSaved) { client.save! }
+
+    assert_predicate client, :frozen?
     assert_raise(RuntimeError) { client.name = "something else" }
   end
 
   def test_destroy_new_record
-    client = Client.new
+    client = Client.new(name: "37signals")
     client.destroy
-    assert client.frozen?
+    assert_predicate client, :frozen?
+
+    assert_not client.save
+    assert_raise(ActiveRecord::RecordNotSaved) { client.save! }
+
+    assert_predicate client, :frozen?
+    assert_raise(RuntimeError) { client.name = "something else" }
   end
 
   def test_destroy_record_with_associations
     client = Client.find(3)
     client.destroy
-    assert client.frozen?
+    assert_predicate client, :frozen?
     assert_kind_of Firm, client.firm
+
+    assert_not client.save
+    assert_raise(ActiveRecord::RecordNotSaved) { client.save! }
+
+    assert_predicate client, :frozen?
     assert_raise(RuntimeError) { client.name = "something else" }
   end
 
   def test_update_attribute
-    assert !Topic.find(1).approved?
+    assert_not_predicate Topic.find(1), :approved?
     Topic.find(1).update_attribute("approved", true)
-    assert Topic.find(1).approved?
+    assert_predicate Topic.find(1), :approved?
 
     Topic.find(1).update_attribute(:approved, false)
-    assert !Topic.find(1).approved?
+    assert_not_predicate Topic.find(1), :approved?
+
+    Topic.find(1).update_attribute(:change_approved_before_save, true)
+    assert_predicate Topic.find(1), :approved?
   end
 
   def test_update_attribute_for_readonly_attribute
@@ -561,8 +703,8 @@ class PersistenceTest < ActiveRecord::TestCase
     t = Topic.first
     t.update_attribute(:title, "super_title")
     assert_equal "super_title", t.title
-    assert !t.changed?, "topic should not have changed"
-    assert !t.title_changed?, "title should not have changed"
+    assert_not t.changed?, "topic should not have changed"
+    assert_not t.title_changed?, "title should not have changed"
     assert_nil t.title_change, "title change should be nil"
 
     t.reload
@@ -586,14 +728,14 @@ class PersistenceTest < ActiveRecord::TestCase
   def test_update_column
     topic = Topic.find(1)
     topic.update_column("approved", true)
-    assert topic.approved?
+    assert_predicate topic, :approved?
     topic.reload
-    assert topic.approved?
+    assert_predicate topic, :approved?
 
     topic.update_column(:approved, false)
-    assert !topic.approved?
+    assert_not_predicate topic, :approved?
     topic.reload
-    assert !topic.approved?
+    assert_not_predicate topic, :approved?
   end
 
   def test_update_column_should_not_use_setter_method
@@ -680,10 +822,10 @@ class PersistenceTest < ActiveRecord::TestCase
   def test_update_columns
     topic = Topic.find(1)
     topic.update_columns("approved" => true, title: "Sebastian Topic")
-    assert topic.approved?
+    assert_predicate topic, :approved?
     assert_equal "Sebastian Topic", topic.title
     topic.reload
-    assert topic.approved?
+    assert_predicate topic, :approved?
     assert_equal "Sebastian Topic", topic.title
   end
 
@@ -791,54 +933,45 @@ class PersistenceTest < ActiveRecord::TestCase
 
   def test_update
     topic = Topic.find(1)
-    assert !topic.approved?
+    assert_not_predicate topic, :approved?
     assert_equal "The First Topic", topic.title
 
     topic.update("approved" => true, "title" => "The First Topic Updated")
     topic.reload
-    assert topic.approved?
+    assert_predicate topic, :approved?
     assert_equal "The First Topic Updated", topic.title
 
     topic.update(approved: false, title: "The First Topic")
     topic.reload
-    assert !topic.approved?
-    assert_equal "The First Topic", topic.title
-  end
-
-  def test_update_attributes
-    topic = Topic.find(1)
-    assert !topic.approved?
-    assert_equal "The First Topic", topic.title
-
-    topic.update_attributes("approved" => true, "title" => "The First Topic Updated")
-    topic.reload
-    assert topic.approved?
-    assert_equal "The First Topic Updated", topic.title
-
-    topic.update_attributes(approved: false, title: "The First Topic")
-    topic.reload
-    assert !topic.approved?
+    assert_not_predicate topic, :approved?
     assert_equal "The First Topic", topic.title
 
     error = assert_raise(ActiveRecord::RecordNotUnique, ActiveRecord::StatementInvalid) do
-      topic.update_attributes(id: 3, title: "Hm is it possible?")
+      topic.update(id: 3, title: "Hm is it possible?")
     end
     assert_not_nil error.cause
     assert_not_equal "Hm is it possible?", Topic.find(3).title
 
-    topic.update_attributes(id: 1234)
+    topic.update(id: 1234)
     assert_nothing_raised { topic.reload }
     assert_equal topic.title, Topic.find(1234).title
   end
 
-  def test_update_attributes_parameters
+  def test_update_attributes
+    topic = Topic.find(1)
+    assert_deprecated do
+      topic.update_attributes("title" => "The First Topic Updated")
+    end
+  end
+
+  def test_update_parameters
     topic = Topic.find(1)
     assert_nothing_raised do
-      topic.update_attributes({})
+      topic.update({})
     end
 
     assert_raises(ArgumentError) do
-      topic.update_attributes(nil)
+      topic.update(nil)
     end
   end
 
@@ -864,24 +997,10 @@ class PersistenceTest < ActiveRecord::TestCase
   end
 
   def test_update_attributes!
-    Reply.validates_presence_of(:title)
     reply = Reply.find(2)
-    assert_equal "The Second Topic of the day", reply.title
-    assert_equal "Have a nice day", reply.content
-
-    reply.update_attributes!("title" => "The Second Topic of the day updated", "content" => "Have a nice evening")
-    reply.reload
-    assert_equal "The Second Topic of the day updated", reply.title
-    assert_equal "Have a nice evening", reply.content
-
-    reply.update_attributes!(title: "The Second Topic of the day", content: "Have a nice day")
-    reply.reload
-    assert_equal "The Second Topic of the day", reply.title
-    assert_equal "Have a nice day", reply.content
-
-    assert_raise(ActiveRecord::RecordInvalid) { reply.update_attributes!(title: nil, content: "Have a nice evening") }
-  ensure
-    Reply.clear_validators!
+    assert_deprecated do
+      reply.update_attributes!("title" => "The Second Topic of the day updated")
+    end
   end
 
   def test_destroyed_returns_boolean
@@ -917,7 +1036,9 @@ class PersistenceTest < ActiveRecord::TestCase
     should_be_destroyed_reply = Reply.create("title" => "hello", "content" => "world")
     Topic.find(1).replies << should_be_destroyed_reply
 
-    Topic.destroy(1)
+    topic = Topic.destroy(1)
+    assert_predicate topic, :destroyed?
+
     assert_raise(ActiveRecord::RecordNotFound) { Topic.find(1) }
     assert_raise(ActiveRecord::RecordNotFound) { Reply.find(should_be_destroyed_reply.id) }
   end
@@ -929,6 +1050,7 @@ class PersistenceTest < ActiveRecord::TestCase
     assert_raise(ActiveRecord::RecordNotFound) do
       Topic.where("1=0").scoping { Topic.destroy(1) }
     end
+
     assert_nothing_raised { Topic.find(1) }
     assert_nothing_raised { Reply.find(should_not_be_destroyed_reply.id) }
   end
@@ -995,13 +1117,13 @@ class PersistenceTest < ActiveRecord::TestCase
   def test_find_via_reload
     post = Post.new
 
-    assert post.new_record?
+    assert_predicate post, :new_record?
 
     post.id = 1
     post.reload
 
     assert_equal "Welcome to the weblog", post.title
-    assert_not post.new_record?
+    assert_not_predicate post, :new_record?
   end
 
   def test_reload_via_querycache
@@ -1049,13 +1171,18 @@ class PersistenceTest < ActiveRecord::TestCase
   end
 
   def test_reset_column_information_resets_children
-    child = Class.new(Topic)
-    child.new # force schema to load
+    child_class = Class.new(Topic)
+    child_class.new # force schema to load
 
     ActiveRecord::Base.connection.add_column(:topics, :foo, :string)
     Topic.reset_column_information
 
-    assert_equal "bar", child.new(foo: :bar).foo
+    # this should redefine attribute methods
+    child_class.new
+
+    assert child_class.instance_methods.include?(:foo)
+    assert child_class.instance_methods.include?(:foo_changed?)
+    assert_equal "bar", child_class.new(foo: :bar).foo
   ensure
     ActiveRecord::Base.connection.remove_column(:topics, :foo)
     Topic.reset_column_information
diff --git a/activerecord/test/cases/primary_keys_test.rb b/activerecord/test/cases/primary_keys_test.rb
index df83fe0ea1..60dac91ec9 100644
--- a/activerecord/test/cases/primary_keys_test.rb
+++ b/activerecord/test/cases/primary_keys_test.rb
@@ -156,10 +156,6 @@ class PrimaryKeysTest < ActiveRecord::TestCase
     assert_nothing_raised { MixedCaseMonkey.find(1).destroy }
   end
 
-  def test_deprecate_supports_primary_key
-    assert_deprecated { ActiveRecord::Base.connection.supports_primary_key? }
-  end
-
   def test_primary_key_returns_value_if_it_exists
     klass = Class.new(ActiveRecord::Base) do
       self.table_name = "developers"
@@ -211,13 +207,13 @@ class PrimaryKeysTest < ActiveRecord::TestCase
     def test_serial_with_quoted_sequence_name
       column = MixedCaseMonkey.columns_hash[MixedCaseMonkey.primary_key]
       assert_equal "nextval('\"mixed_case_monkeys_monkeyID_seq\"'::regclass)", column.default_function
-      assert column.serial?
+      assert_predicate column, :serial?
     end
 
     def test_serial_with_unquoted_sequence_name
       column = Topic.columns_hash[Topic.primary_key]
       assert_equal "nextval('topics_id_seq'::regclass)", column.default_function
-      assert column.serial?
+      assert_predicate column, :serial?
     end
   end
 end
@@ -302,6 +298,8 @@ class PrimaryKeyAnyTypeTest < ActiveRecord::TestCase
     assert_not column.null
     assert_equal :string, column.type
     assert_equal 42, column.limit
+  ensure
+    Barcode.reset_column_information
   end
 
   test "schema dump primary key includes type and options" do
@@ -334,16 +332,26 @@ class CompositePrimaryKeyTest < ActiveRecord::TestCase
       t.string :region
       t.integer :code
     end
+    @connection.create_table(:travels, primary_key: ["from", "to"], force: true) do |t|
+      t.string :from
+      t.string :to
+    end
   end
 
   def teardown
-    @connection.drop_table(:uber_barcodes, if_exists: true)
+    @connection.drop_table :uber_barcodes, if_exists: true
+    @connection.drop_table :barcodes_reverse, if_exists: true
+    @connection.drop_table :travels, if_exists: true
   end
 
   def test_composite_primary_key
     assert_equal ["region", "code"], @connection.primary_keys("uber_barcodes")
   end
 
+  def test_composite_primary_key_with_reserved_words
+    assert_equal ["from", "to"], @connection.primary_keys("travels")
+  end
+
   def test_composite_primary_key_out_of_order
     skip if current_adapter?(:SQLite3Adapter)
     assert_equal ["code", "region"], @connection.primary_keys("barcodes_reverse")
@@ -422,7 +430,7 @@ if current_adapter?(:PostgreSQLAdapter, :Mysql2Adapter)
       @connection.create_table(:widgets, id: @pk_type, force: true)
       column = @connection.columns(:widgets).find { |c| c.name == "id" }
       assert_equal :integer, column.type
-      assert_not column.bigint?
+      assert_not_predicate column, :bigint?
     end
 
     test "primary key with serial/integer are automatically numbered" do
@@ -434,32 +442,32 @@ if current_adapter?(:PostgreSQLAdapter, :Mysql2Adapter)
     test "schema dump primary key with serial/integer" do
       @connection.create_table(:widgets, id: @pk_type, force: true)
       schema = dump_table_schema "widgets"
-      assert_match %r{create_table "widgets", id: :#{@pk_type}, force: :cascade}, schema
+      assert_match %r{create_table "widgets", id: :#{@pk_type}, }, schema
     end
 
     if current_adapter?(:Mysql2Adapter)
       test "primary key column type with options" do
         @connection.create_table(:widgets, id: :primary_key, limit: 4, unsigned: true, force: true)
         column = @connection.columns(:widgets).find { |c| c.name == "id" }
-        assert column.auto_increment?
+        assert_predicate column, :auto_increment?
         assert_equal :integer, column.type
-        assert_not column.bigint?
-        assert column.unsigned?
+        assert_not_predicate column, :bigint?
+        assert_predicate column, :unsigned?
 
         schema = dump_table_schema "widgets"
-        assert_match %r{create_table "widgets", id: :integer, unsigned: true, force: :cascade}, schema
+        assert_match %r{create_table "widgets", id: :integer, unsigned: true, }, schema
       end
 
       test "bigint primary key with unsigned" do
         @connection.create_table(:widgets, id: :bigint, unsigned: true, force: true)
         column = @connection.columns(:widgets).find { |c| c.name == "id" }
-        assert column.auto_increment?
+        assert_predicate column, :auto_increment?
         assert_equal :integer, column.type
-        assert column.bigint?
-        assert column.unsigned?
+        assert_predicate column, :bigint?
+        assert_predicate column, :unsigned?
 
         schema = dump_table_schema "widgets"
-        assert_match %r{create_table "widgets", id: :bigint, unsigned: true, force: :cascade}, schema
+        assert_match %r{create_table "widgets", id: :bigint, unsigned: true, }, schema
       end
     end
   end
diff --git a/activerecord/test/cases/query_cache_test.rb b/activerecord/test/cases/query_cache_test.rb
index d3f4b5bf75..0f990bac9d 100644
--- a/activerecord/test/cases/query_cache_test.rb
+++ b/activerecord/test/cases/query_cache_test.rb
@@ -82,7 +82,7 @@ class QueryCacheTest < ActiveRecord::TestCase
           assert_cache :off, conn
         end
 
-        assert !ActiveRecord::Base.connection.nil?
+        assert_not_predicate ActiveRecord::Base.connection, :nil?
         assert_cache :off
 
         middleware {
@@ -283,7 +283,7 @@ class QueryCacheTest < ActiveRecord::TestCase
       payload[:sql].downcase!
     end
 
-    assert_raises RuntimeError do
+    assert_raises frozen_error_class do
       ActiveRecord::Base.cache do
         assert_queries(1) { Task.find(1); Task.find(1) }
       end
@@ -302,14 +302,10 @@ class QueryCacheTest < ActiveRecord::TestCase
     end
   end
 
-  def test_cache_does_not_wrap_string_results_in_arrays
+  def test_cache_does_not_wrap_results_in_arrays
     Task.cache do
-      # Oracle adapter returns count() as Integer or Float
-      if current_adapter?(:OracleAdapter)
-        assert_kind_of Numeric, Task.connection.select_value("SELECT count(*) AS count_all FROM tasks")
-      elsif current_adapter?(:SQLite3Adapter, :Mysql2Adapter, :PostgreSQLAdapter)
-        # Future versions of the sqlite3 adapter will return numeric
-        assert_instance_of 0.class, Task.connection.select_value("SELECT count(*) AS count_all FROM tasks")
+      if current_adapter?(:SQLite3Adapter, :Mysql2Adapter, :PostgreSQLAdapter, :OracleAdapter)
+        assert_equal 2, Task.connection.select_value("SELECT count(*) AS count_all FROM tasks")
       else
         assert_instance_of String, Task.connection.select_value("SELECT count(*) AS count_all FROM tasks")
       end
@@ -324,6 +320,17 @@ class QueryCacheTest < ActiveRecord::TestCase
     end
   end
 
+  def test_cache_is_available_when_connection_is_connected
+    conf = ActiveRecord::Base.configurations
+
+    ActiveRecord::Base.configurations = {}
+    Task.cache do
+      assert_queries(1) { Task.find(1); Task.find(1) }
+    end
+  ensure
+    ActiveRecord::Base.configurations = conf
+  end
+
   def test_cache_is_available_when_using_a_not_connected_connection
     skip "In-Memory DB can't test for using a not connected connection" if in_memory_db?
     with_temporary_connection_pool do
@@ -331,7 +338,7 @@ class QueryCacheTest < ActiveRecord::TestCase
       conf = ActiveRecord::Base.configurations["arunit"].merge("name" => "test2")
       ActiveRecord::Base.connection_handler.establish_connection(conf)
       Task.connection_specification_name = "test2"
-      refute Task.connected?
+      assert_not_predicate Task, :connected?
 
       Task.cache do
         begin
@@ -370,7 +377,7 @@ class QueryCacheTest < ActiveRecord::TestCase
     post = Post.first
 
     Post.transaction do
-      post.update_attributes(title: "rollback")
+      post.update(title: "rollback")
       assert_equal 1, Post.where(title: "rollback").to_a.count
       raise ActiveRecord::Rollback
     end
@@ -383,7 +390,7 @@ class QueryCacheTest < ActiveRecord::TestCase
 
     begin
       Post.transaction do
-        post.update_attributes(title: "rollback")
+        post.update(title: "rollback")
         assert_equal 1, Post.where(title: "rollback").to_a.count
         raise "broken"
       end
@@ -418,24 +425,25 @@ class QueryCacheTest < ActiveRecord::TestCase
   def test_query_cache_does_not_establish_connection_if_unconnected
     with_temporary_connection_pool do
       ActiveRecord::Base.clear_active_connections!
-      refute ActiveRecord::Base.connection_handler.active_connections? # sanity check
+      assert_not ActiveRecord::Base.connection_handler.active_connections? # sanity check
 
       middleware {
-        refute ActiveRecord::Base.connection_handler.active_connections?, "QueryCache forced ActiveRecord::Base to establish a connection in setup"
+        assert_not ActiveRecord::Base.connection_handler.active_connections?, "QueryCache forced ActiveRecord::Base to establish a connection in setup"
       }.call({})
 
-      refute ActiveRecord::Base.connection_handler.active_connections?, "QueryCache forced ActiveRecord::Base to establish a connection in cleanup"
+      assert_not ActiveRecord::Base.connection_handler.active_connections?, "QueryCache forced ActiveRecord::Base to establish a connection in cleanup"
     end
   end
 
   def test_query_cache_is_enabled_on_connections_established_after_middleware_runs
     with_temporary_connection_pool do
       ActiveRecord::Base.clear_active_connections!
-      refute ActiveRecord::Base.connection_handler.active_connections? # sanity check
+      assert_not ActiveRecord::Base.connection_handler.active_connections? # sanity check
 
       middleware {
-        assert ActiveRecord::Base.connection.query_cache_enabled, "QueryCache did not get lazily enabled"
+        assert_predicate ActiveRecord::Base.connection, :query_cache_enabled
       }.call({})
+      assert_not_predicate ActiveRecord::Base.connection, :query_cache_enabled
     end
   end
 
@@ -448,14 +456,23 @@ class QueryCacheTest < ActiveRecord::TestCase
         assert ActiveRecord::Base.connection.query_cache_enabled
 
         Thread.new {
-          refute ActiveRecord::Base.connection_pool.query_cache_enabled
-          refute ActiveRecord::Base.connection.query_cache_enabled
+          assert_not ActiveRecord::Base.connection_pool.query_cache_enabled
+          assert_not ActiveRecord::Base.connection.query_cache_enabled
         }.join
       }.call({})
 
     end
   end
 
+  def test_query_cache_is_enabled_on_all_connection_pools
+    middleware {
+      ActiveRecord::Base.connection_handler.connection_pool_list.each do |pool|
+        assert pool.query_cache_enabled
+        assert pool.connection.query_cache_enabled
+      end
+    }.call({})
+  end
+
   private
     def middleware(&app)
       executor = Class.new(ActiveSupport::Executor)
@@ -466,14 +483,14 @@ class QueryCacheTest < ActiveRecord::TestCase
     def assert_cache(state, connection = ActiveRecord::Base.connection)
       case state
       when :off
-        assert !connection.query_cache_enabled, "cache should be off"
+        assert_not connection.query_cache_enabled, "cache should be off"
         assert connection.query_cache.empty?, "cache should be empty"
       when :clean
         assert connection.query_cache_enabled, "cache should be on"
         assert connection.query_cache.empty?, "cache should be empty"
       when :dirty
         assert connection.query_cache_enabled, "cache should be on"
-        assert !connection.query_cache.empty?, "cache should be dirty"
+        assert_not connection.query_cache.empty?, "cache should be dirty"
       else
         raise "unknown state"
       end
@@ -501,19 +518,19 @@ class QueryCacheExpiryTest < ActiveRecord::TestCase
 
   def test_find
     assert_called(Task.connection, :clear_query_cache) do
-      assert !Task.connection.query_cache_enabled
+      assert_not Task.connection.query_cache_enabled
       Task.cache do
         assert Task.connection.query_cache_enabled
         Task.find(1)
 
         Task.uncached do
-          assert !Task.connection.query_cache_enabled
+          assert_not Task.connection.query_cache_enabled
           Task.find(1)
         end
 
         assert Task.connection.query_cache_enabled
       end
-      assert !Task.connection.query_cache_enabled
+      assert_not Task.connection.query_cache_enabled
     end
   end
 
@@ -557,7 +574,7 @@ class QueryCacheExpiryTest < ActiveRecord::TestCase
     assert_called(ActiveRecord::Base.connection, :clear_query_cache, times: 2) do
       ActiveRecord::Base.cache do
         p = Post.find(1)
-        assert p.categories.any?
+        assert_predicate p.categories, :any?
         p.categories.delete_all
       end
     end
diff --git a/activerecord/test/cases/quoting_test.rb b/activerecord/test/cases/quoting_test.rb
index 59d3bbb573..92eb0c814f 100644
--- a/activerecord/test/cases/quoting_test.rb
+++ b/activerecord/test/cases/quoting_test.rb
@@ -46,27 +46,60 @@ module ActiveRecord
         assert_equal t.to_s(:db), @quoter.quoted_date(t)
       end
 
-      def test_quoted_time_utc
+      def test_quoted_timestamp_utc
         with_timezone_config default: :utc do
           t = Time.now.change(usec: 0)
           assert_equal t.getutc.to_s(:db), @quoter.quoted_date(t)
         end
       end
 
-      def test_quoted_time_local
+      def test_quoted_timestamp_local
         with_timezone_config default: :local do
           t = Time.now.change(usec: 0)
           assert_equal t.getlocal.to_s(:db), @quoter.quoted_date(t)
         end
       end
 
-      def test_quoted_time_crazy
+      def test_quoted_timestamp_crazy
         with_timezone_config default: :asdfasdf do
           t = Time.now.change(usec: 0)
           assert_equal t.getlocal.to_s(:db), @quoter.quoted_date(t)
         end
       end
 
+      def test_quoted_time_utc
+        with_timezone_config default: :utc do
+          t = Time.now.change(usec: 0)
+
+          expected = t.getutc.change(year: 2000, month: 1, day: 1)
+          expected = expected.to_s(:db).sub("2000-01-01 ", "")
+
+          assert_equal expected, @quoter.quoted_time(t)
+        end
+      end
+
+      def test_quoted_time_local
+        with_timezone_config default: :local do
+          t = Time.now.change(usec: 0)
+
+          expected = t.change(year: 2000, month: 1, day: 1)
+          expected = expected.getlocal.to_s(:db).sub("2000-01-01 ", "")
+
+          assert_equal expected, @quoter.quoted_time(t)
+        end
+      end
+
+      def test_quoted_time_crazy
+        with_timezone_config default: :asdfasdf do
+          t = Time.now.change(usec: 0)
+
+          expected = t.change(year: 2000, month: 1, day: 1)
+          expected = expected.getlocal.to_s(:db).sub("2000-01-01 ", "")
+
+          assert_equal expected, @quoter.quoted_time(t)
+        end
+      end
+
       def test_quoted_datetime_utc
         with_timezone_config default: :utc do
           t = Time.now.change(usec: 0).to_datetime
@@ -83,23 +116,6 @@ module ActiveRecord
         end
       end
 
-      class QuotedOne
-        def quoted_id
-          1
-        end
-      end
-      class SubQuotedOne < QuotedOne
-      end
-      def test_quote_with_quoted_id
-        assert_deprecated(/defined on \S+::QuotedOne at .*quoting_test\.rb:[0-9]/) do
-          assert_equal 1, @quoter.quote(QuotedOne.new)
-        end
-
-        assert_deprecated(/defined on \S+::SubQuotedOne\(\S+::QuotedOne\) at .*quoting_test\.rb:[0-9]/) do
-          assert_equal 1, @quoter.quote(SubQuotedOne.new)
-        end
-      end
-
       def test_quote_nil
         assert_equal "NULL", @quoter.quote(nil)
       end
@@ -128,7 +144,7 @@ module ActiveRecord
       end
 
       def test_quote_bigdecimal
-        bigdec = BigDecimal.new((1 << 100).to_s)
+        bigdec = BigDecimal((1 << 100).to_s)
         assert_equal bigdec.to_s("F"), @quoter.quote(bigdec)
       end
 
@@ -207,26 +223,6 @@ module ActiveRecord
         obj = Class.new.new
         assert_raise(TypeError) { @conn.type_cast(obj) }
       end
-
-      def test_type_cast_object_which_responds_to_quoted_id
-        quoted_id_obj = Class.new {
-          def quoted_id
-            "'zomg'"
-          end
-
-          def id
-            10
-          end
-        }.new
-        assert_equal 10, @conn.type_cast(quoted_id_obj)
-
-        quoted_id_obj = Class.new {
-          def quoted_id
-            "'zomg'"
-          end
-        }.new
-        assert_raise(TypeError) { @conn.type_cast(quoted_id_obj) }
-      end
     end
 
     class QuoteBooleanTest < ActiveRecord::TestCase
diff --git a/activerecord/test/cases/readonly_test.rb b/activerecord/test/cases/readonly_test.rb
index d1b85cb4ef..059fa76132 100644
--- a/activerecord/test/cases/readonly_test.rb
+++ b/activerecord/test/cases/readonly_test.rb
@@ -16,14 +16,14 @@ class ReadOnlyTest < ActiveRecord::TestCase
 
   def test_cant_save_readonly_record
     dev = Developer.find(1)
-    assert !dev.readonly?
+    assert_not_predicate dev, :readonly?
 
     dev.readonly!
-    assert dev.readonly?
+    assert_predicate dev, :readonly?
 
     assert_nothing_raised do
       dev.name = "Luscious forbidden fruit."
-      assert !dev.save
+      assert_not dev.save
       dev.name = "Forbidden."
     end
 
@@ -38,8 +38,8 @@ class ReadOnlyTest < ActiveRecord::TestCase
   end
 
   def test_find_with_readonly_option
-    Developer.all.each { |d| assert !d.readonly? }
-    Developer.readonly(false).each { |d| assert !d.readonly? }
+    Developer.all.each { |d| assert_not d.readonly? }
+    Developer.readonly(false).each { |d| assert_not d.readonly? }
     Developer.readonly(true).each { |d| assert d.readonly? }
     Developer.readonly.each { |d| assert d.readonly? }
   end
@@ -54,56 +54,56 @@ class ReadOnlyTest < ActiveRecord::TestCase
 
   def test_has_many_find_readonly
     post = Post.find(1)
-    assert !post.comments.empty?
-    assert !post.comments.any?(&:readonly?)
-    assert !post.comments.to_a.any?(&:readonly?)
+    assert_not_empty post.comments
+    assert_not post.comments.any?(&:readonly?)
+    assert_not post.comments.to_a.any?(&:readonly?)
     assert post.comments.readonly(true).all?(&:readonly?)
   end
 
   def test_has_many_with_through_is_not_implicitly_marked_readonly
     assert people = Post.find(1).people
-    assert !people.any?(&:readonly?)
+    assert_not people.any?(&:readonly?)
   end
 
   def test_has_many_with_through_is_not_implicitly_marked_readonly_while_finding_by_id
-    assert !posts(:welcome).people.find(1).readonly?
+    assert_not_predicate posts(:welcome).people.find(1), :readonly?
   end
 
   def test_has_many_with_through_is_not_implicitly_marked_readonly_while_finding_first
-    assert !posts(:welcome).people.first.readonly?
+    assert_not_predicate posts(:welcome).people.first, :readonly?
   end
 
   def test_has_many_with_through_is_not_implicitly_marked_readonly_while_finding_last
-    assert !posts(:welcome).people.last.readonly?
+    assert_not_predicate posts(:welcome).people.last, :readonly?
   end
 
   def test_readonly_scoping
     Post.where("1=1").scoping do
-      assert !Post.find(1).readonly?
-      assert Post.readonly(true).find(1).readonly?
-      assert !Post.readonly(false).find(1).readonly?
+      assert_not_predicate Post.find(1), :readonly?
+      assert_predicate Post.readonly(true).find(1), :readonly?
+      assert_not_predicate Post.readonly(false).find(1), :readonly?
     end
 
     Post.joins("   ").scoping do
-      assert !Post.find(1).readonly?
-      assert Post.readonly.find(1).readonly?
-      assert !Post.readonly(false).find(1).readonly?
+      assert_not_predicate Post.find(1), :readonly?
+      assert_predicate Post.readonly.find(1), :readonly?
+      assert_not_predicate Post.readonly(false).find(1), :readonly?
     end
 
     # Oracle barfs on this because the join includes unqualified and
     # conflicting column names
     unless current_adapter?(:OracleAdapter)
       Post.joins(", developers").scoping do
-        assert_not Post.find(1).readonly?
-        assert Post.readonly.find(1).readonly?
-        assert !Post.readonly(false).find(1).readonly?
+        assert_not_predicate Post.find(1), :readonly?
+        assert_predicate Post.readonly.find(1), :readonly?
+        assert_not_predicate Post.readonly(false).find(1), :readonly?
       end
     end
 
     Post.readonly(true).scoping do
-      assert Post.find(1).readonly?
-      assert Post.readonly.find(1).readonly?
-      assert !Post.readonly(false).find(1).readonly?
+      assert_predicate Post.find(1), :readonly?
+      assert_predicate Post.readonly.find(1), :readonly?
+      assert_not_predicate Post.readonly(false).find(1), :readonly?
     end
   end
 
@@ -111,10 +111,10 @@ class ReadOnlyTest < ActiveRecord::TestCase
     developer = Developer.find(1)
     project   = Post.find(1)
 
-    assert !developer.projects.all_as_method.first.readonly?
-    assert !developer.projects.all_as_scope.first.readonly?
+    assert_not_predicate developer.projects.all_as_method.first, :readonly?
+    assert_not_predicate developer.projects.all_as_scope.first, :readonly?
 
-    assert !project.comments.all_as_method.first.readonly?
-    assert !project.comments.all_as_scope.first.readonly?
+    assert_not_predicate project.comments.all_as_method.first, :readonly?
+    assert_not_predicate project.comments.all_as_scope.first, :readonly?
   end
 end
diff --git a/activerecord/test/cases/reaper_test.rb b/activerecord/test/cases/reaper_test.rb
index 49170abe6f..b034fe3e3b 100644
--- a/activerecord/test/cases/reaper_test.rb
+++ b/activerecord/test/cases/reaper_test.rb
@@ -18,6 +18,7 @@ module ActiveRecord
 
       class FakePool
         attr_reader :reaped
+        attr_reader :flushed
 
         def initialize
           @reaped = false
@@ -26,20 +27,24 @@ module ActiveRecord
         def reap
           @reaped = true
         end
+
+        def flush
+          @flushed = true
+        end
       end
 
       # A reaper with nil time should never reap connections
       def test_nil_time
         fp = FakePool.new
-        assert !fp.reaped
+        assert_not fp.reaped
         reaper = ConnectionPool::Reaper.new(fp, nil)
         reaper.run
-        assert !fp.reaped
+        assert_not fp.reaped
       end
 
       def test_some_time
         fp = FakePool.new
-        assert !fp.reaped
+        assert_not fp.reaped
 
         reaper = ConnectionPool::Reaper.new(fp, 0.0001)
         reaper.run
@@ -47,6 +52,7 @@ module ActiveRecord
           Thread.pass
         end
         assert fp.reaped
+        assert fp.flushed
       end
 
       def test_pool_has_reaper
@@ -73,14 +79,14 @@ module ActiveRecord
         end
         Thread.pass while conn.nil?
 
-        assert conn.in_use?
+        assert_predicate conn, :in_use?
 
         child.terminate
 
         while conn.in_use?
           Thread.pass
         end
-        assert !conn.in_use?
+        assert_not_predicate conn, :in_use?
       end
     end
   end
diff --git a/activerecord/test/cases/reflection_test.rb b/activerecord/test/cases/reflection_test.rb
index 4cd2d3aedc..abadafbad4 100644
--- a/activerecord/test/cases/reflection_test.rb
+++ b/activerecord/test/cases/reflection_test.rb
@@ -25,7 +25,6 @@ require "models/chef"
 require "models/department"
 require "models/cake_designer"
 require "models/drink_designer"
-require "models/mocktail_designer"
 require "models/recipe"
 
 class ReflectionTest < ActiveRecord::TestCase
@@ -67,13 +66,16 @@ class ReflectionTest < ActiveRecord::TestCase
 
   def test_column_string_type_and_limit
     assert_equal :string, @first.column_for_attribute("title").type
+    assert_equal :string, @first.column_for_attribute(:title).type
+    assert_equal :string, @first.type_for_attribute("title").type
+    assert_equal :string, @first.type_for_attribute(:title).type
     assert_equal 250, @first.column_for_attribute("title").limit
   end
 
   def test_column_null_not_null
     subscriber = Subscriber.first
     assert subscriber.column_for_attribute("name").null
-    assert !subscriber.column_for_attribute("nick").null
+    assert_not subscriber.column_for_attribute("nick").null
   end
 
   def test_human_name_for_column
@@ -82,6 +84,9 @@ class ReflectionTest < ActiveRecord::TestCase
 
   def test_integer_columns
     assert_equal :integer, @first.column_for_attribute("id").type
+    assert_equal :integer, @first.column_for_attribute(:id).type
+    assert_equal :integer, @first.type_for_attribute("id").type
+    assert_equal :integer, @first.type_for_attribute(:id).type
   end
 
   def test_non_existent_columns_return_null_object
@@ -90,6 +95,9 @@ class ReflectionTest < ActiveRecord::TestCase
     assert_equal "attribute_that_doesnt_exist", column.name
     assert_nil column.sql_type
     assert_nil column.type
+
+    column = @first.column_for_attribute(:attribute_that_doesnt_exist)
+    assert_instance_of ActiveRecord::ConnectionAdapters::NullColumn, column
   end
 
   def test_non_existent_types_are_identity_types
@@ -99,6 +107,11 @@ class ReflectionTest < ActiveRecord::TestCase
     assert_equal object, type.deserialize(object)
     assert_equal object, type.cast(object)
     assert_equal object, type.serialize(object)
+
+    type = @first.type_for_attribute(:attribute_that_doesnt_exist)
+    assert_equal object, type.deserialize(object)
+    assert_equal object, type.cast(object)
+    assert_equal object, type.serialize(object)
   end
 
   def test_reflection_klass_for_nested_class_name
@@ -150,7 +163,7 @@ class ReflectionTest < ActiveRecord::TestCase
     expected = Pirate.reflect_on_all_associations.select { |r| r.options[:autosave] }
     received = Pirate.reflect_on_all_autosave_associations
 
-    assert !received.empty?
+    assert_not_empty received
     assert_not_equal Pirate.reflect_on_all_associations.length, received.length
     assert_equal expected, received
   end
@@ -254,50 +267,35 @@ class ReflectionTest < ActiveRecord::TestCase
     assert_equal expected, actual
   end
 
-  def test_scope_chain
-    expected = [
-      [Tagging.reflect_on_association(:tag).scope, Post.reflect_on_association(:first_blue_tags).scope],
-      [Post.reflect_on_association(:first_taggings).scope],
-      [Author.reflect_on_association(:misc_posts).scope]
-    ]
-    actual = assert_deprecated do
-      Author.reflect_on_association(:misc_post_first_blue_tags).scope_chain
-    end
-    assert_equal expected, actual
-
-    expected = [
-      [
-        Tagging.reflect_on_association(:blue_tag).scope,
-        Post.reflect_on_association(:first_blue_tags_2).scope,
-        Author.reflect_on_association(:misc_post_first_blue_tags_2).scope
-      ],
-      [],
-      []
-    ]
-    actual = assert_deprecated do
-      Author.reflect_on_association(:misc_post_first_blue_tags_2).scope_chain
-    end
-    assert_equal expected, actual
-  end
-
   def test_scope_chain_does_not_interfere_with_hmt_with_polymorphic_case
-    @hotel = Hotel.create!
-    @department = @hotel.departments.create!
-    @department.chefs.create!(employable: CakeDesigner.create!)
-    @department.chefs.create!(employable: DrinkDesigner.create!)
+    hotel = Hotel.create!
+    department = hotel.departments.create!
+    department.chefs.create!(employable: CakeDesigner.create!)
+    department.chefs.create!(employable: DrinkDesigner.create!)
 
-    assert_equal 1, @hotel.cake_designers.size
-    assert_equal 1, @hotel.drink_designers.size
-    assert_equal 2, @hotel.chefs.size
+    assert_equal 1, hotel.cake_designers.size
+    assert_equal 1, hotel.cake_designers.count
+    assert_equal 1, hotel.drink_designers.size
+    assert_equal 1, hotel.drink_designers.count
+    assert_equal 2, hotel.chefs.size
+    assert_equal 2, hotel.chefs.count
   end
 
   def test_scope_chain_does_not_interfere_with_hmt_with_polymorphic_case_and_sti
-    @hotel = Hotel.create!
-    @hotel.mocktail_designers << MocktailDesigner.create!
+    hotel = Hotel.create!
+    hotel.mocktail_designers << MocktailDesigner.create!
+
+    assert_equal 1, hotel.mocktail_designers.size
+    assert_equal 1, hotel.mocktail_designers.count
+    assert_equal 1, hotel.chef_lists.size
+    assert_equal 1, hotel.chef_lists.count
 
-    assert_equal 1, @hotel.mocktail_designers.size
-    assert_equal 1, @hotel.mocktail_designers.count
-    assert_equal 1, @hotel.chef_lists.size
+    hotel.mocktail_designers = []
+
+    assert_equal 0, hotel.mocktail_designers.size
+    assert_equal 0, hotel.mocktail_designers.count
+    assert_equal 0, hotel.chef_lists.size
+    assert_equal 0, hotel.chef_lists.count
   end
 
   def test_scope_chain_of_polymorphic_association_does_not_leak_into_other_hmt_associations
@@ -317,12 +315,12 @@ class ReflectionTest < ActiveRecord::TestCase
   end
 
   def test_nested?
-    assert !Author.reflect_on_association(:comments).nested?
-    assert Author.reflect_on_association(:tags).nested?
+    assert_not_predicate Author.reflect_on_association(:comments), :nested?
+    assert_predicate Author.reflect_on_association(:tags), :nested?
 
     # Only goes :through once, but the through_reflection is a has_and_belongs_to_many, so this is
     # a nested through association
-    assert Category.reflect_on_association(:post_comments).nested?
+    assert_predicate Category.reflect_on_association(:post_comments), :nested?
   end
 
   def test_association_primary_key
@@ -337,15 +335,6 @@ class ReflectionTest < ActiveRecord::TestCase
     assert_equal "custom_primary_key", Author.reflect_on_association(:tags_with_primary_key).association_primary_key.to_s # nested
   end
 
-  def test_association_primary_key_type
-    # Normal Association
-    assert_equal :integer, Author.reflect_on_association(:posts).association_primary_key_type.type
-    assert_equal :string,  Author.reflect_on_association(:essay).association_primary_key_type.type
-
-    # Through Association
-    assert_equal :string, Author.reflect_on_association(:essay_category).association_primary_key_type.type
-  end
-
   def test_association_primary_key_raises_when_missing_primary_key
     reflection = ActiveRecord::Reflection.create(:has_many, :edge, nil, {}, Author)
     assert_raises(ActiveRecord::UnknownPrimaryKey) { reflection.association_primary_key }
@@ -366,42 +355,49 @@ class ReflectionTest < ActiveRecord::TestCase
     assert_raises(ActiveRecord::UnknownPrimaryKey) { reflection.active_record_primary_key }
   end
 
+  def test_type
+    assert_equal "taggable_type", Post.reflect_on_association(:taggings).type.to_s
+    assert_equal "imageable_class", Post.reflect_on_association(:images).type.to_s
+    assert_nil Post.reflect_on_association(:readers).type
+  end
+
   def test_foreign_type
     assert_equal "sponsorable_type", Sponsor.reflect_on_association(:sponsorable).foreign_type.to_s
     assert_equal "sponsorable_type", Sponsor.reflect_on_association(:thing).foreign_type.to_s
+    assert_nil Sponsor.reflect_on_association(:sponsor_club).foreign_type
   end
 
   def test_collection_association
-    assert Pirate.reflect_on_association(:birds).collection?
-    assert Pirate.reflect_on_association(:parrots).collection?
+    assert_predicate Pirate.reflect_on_association(:birds), :collection?
+    assert_predicate Pirate.reflect_on_association(:parrots), :collection?
 
-    assert !Pirate.reflect_on_association(:ship).collection?
-    assert !Ship.reflect_on_association(:pirate).collection?
+    assert_not_predicate Pirate.reflect_on_association(:ship), :collection?
+    assert_not_predicate Ship.reflect_on_association(:pirate), :collection?
   end
 
   def test_default_association_validation
-    assert ActiveRecord::Reflection.create(:has_many, :clients, nil, {}, Firm).validate?
+    assert_predicate ActiveRecord::Reflection.create(:has_many, :clients, nil, {}, Firm), :validate?
 
-    assert !ActiveRecord::Reflection.create(:has_one, :client, nil, {}, Firm).validate?
-    assert !ActiveRecord::Reflection.create(:belongs_to, :client, nil, {}, Firm).validate?
+    assert_not_predicate ActiveRecord::Reflection.create(:has_one, :client, nil, {}, Firm), :validate?
+    assert_not_predicate ActiveRecord::Reflection.create(:belongs_to, :client, nil, {}, Firm), :validate?
   end
 
   def test_always_validate_association_if_explicit
-    assert ActiveRecord::Reflection.create(:has_one, :client, nil, { validate: true }, Firm).validate?
-    assert ActiveRecord::Reflection.create(:belongs_to, :client, nil, { validate: true }, Firm).validate?
-    assert ActiveRecord::Reflection.create(:has_many, :clients, nil, { validate: true }, Firm).validate?
+    assert_predicate ActiveRecord::Reflection.create(:has_one, :client, nil, { validate: true }, Firm), :validate?
+    assert_predicate ActiveRecord::Reflection.create(:belongs_to, :client, nil, { validate: true }, Firm), :validate?
+    assert_predicate ActiveRecord::Reflection.create(:has_many, :clients, nil, { validate: true }, Firm), :validate?
   end
 
   def test_validate_association_if_autosave
-    assert ActiveRecord::Reflection.create(:has_one, :client, nil, { autosave: true }, Firm).validate?
-    assert ActiveRecord::Reflection.create(:belongs_to, :client, nil, { autosave: true }, Firm).validate?
-    assert ActiveRecord::Reflection.create(:has_many, :clients, nil, { autosave: true }, Firm).validate?
+    assert_predicate ActiveRecord::Reflection.create(:has_one, :client, nil, { autosave: true }, Firm), :validate?
+    assert_predicate ActiveRecord::Reflection.create(:belongs_to, :client, nil, { autosave: true }, Firm), :validate?
+    assert_predicate ActiveRecord::Reflection.create(:has_many, :clients, nil, { autosave: true }, Firm), :validate?
   end
 
   def test_never_validate_association_if_explicit
-    assert !ActiveRecord::Reflection.create(:has_one, :client, nil, { autosave: true, validate: false }, Firm).validate?
-    assert !ActiveRecord::Reflection.create(:belongs_to, :client, nil, { autosave: true, validate: false }, Firm).validate?
-    assert !ActiveRecord::Reflection.create(:has_many, :clients, nil, { autosave: true, validate: false }, Firm).validate?
+    assert_not_predicate ActiveRecord::Reflection.create(:has_one, :client, nil, { autosave: true, validate: false }, Firm), :validate?
+    assert_not_predicate ActiveRecord::Reflection.create(:belongs_to, :client, nil, { autosave: true, validate: false }, Firm), :validate?
+    assert_not_predicate ActiveRecord::Reflection.create(:has_many, :clients, nil, { autosave: true, validate: false }, Firm), :validate?
   end
 
   def test_foreign_key
@@ -409,26 +405,15 @@ class ReflectionTest < ActiveRecord::TestCase
     assert_equal "category_id", Post.reflect_on_association(:categorizations).foreign_key.to_s
   end
 
-  def test_through_reflection_scope_chain_does_not_modify_other_reflections
-    orig_conds = assert_deprecated do
-      Post.reflect_on_association(:first_blue_tags_2).scope_chain
-    end.inspect
-    assert_deprecated do
-      Author.reflect_on_association(:misc_post_first_blue_tags_2).scope_chain
-    end
-    assert_equal orig_conds, assert_deprecated {
-      Post.reflect_on_association(:first_blue_tags_2).scope_chain
-    }.inspect
-  end
-
   def test_symbol_for_class_name
     assert_equal Client, Firm.reflect_on_association(:unsorted_clients_with_symbol).klass
   end
 
   def test_class_for_class_name
-    assert_deprecated do
-      assert_predicate ActiveRecord::Reflection.create(:has_many, :clients, nil, { class_name: Client }, Firm), :validate?
+    error = assert_raises(ArgumentError) do
+      ActiveRecord::Reflection.create(:has_many, :clients, nil, { class_name: Client }, Firm)
     end
+    assert_equal "A class was passed to `:class_name` but we are expecting a string.", error.message
   end
 
   def test_join_table
diff --git a/activerecord/test/cases/relation/delegation_test.rb b/activerecord/test/cases/relation/delegation_test.rb
index 8ffb9f163b..3f3d41980c 100644
--- a/activerecord/test/cases/relation/delegation_test.rb
+++ b/activerecord/test/cases/relation/delegation_test.rb
@@ -10,8 +10,8 @@ module ActiveRecord
       :+, :-, :|, :&, :[], :shuffle,
       :all?, :collect, :compact, :detect, :each, :each_cons, :each_with_index,
       :exclude?, :find_all, :flat_map, :group_by, :include?, :length,
-      :map, :none?, :one?, :partition, :reject, :reverse,
-      :sample, :second, :sort, :sort_by, :third,
+      :map, :none?, :one?, :partition, :reject, :reverse, :rotate,
+      :sample, :second, :sort, :sort_by, :slice, :third, :index, :rindex,
       :to_ary, :to_set, :to_xml, :to_yaml, :join,
       :in_groups, :in_groups_of, :to_sentence, :to_formatted_s, :as_json
     ]
@@ -32,6 +32,7 @@ module ActiveRecord
     def test_deprecate_arel_delegation
       AREL_METHODS.each do |method|
         assert_deprecated { target.public_send(method) }
+        assert_deprecated { target.public_send(method) }
       end
     end
   end
@@ -53,4 +54,32 @@ module ActiveRecord
       Comment.all
     end
   end
+
+  class QueryingMethodsDelegationTest < ActiveRecord::TestCase
+    QUERYING_METHODS = [
+      :find, :take, :take!, :first, :first!, :last, :last!, :exists?, :any?, :many?, :none?, :one?,
+      :second, :second!, :third, :third!, :fourth, :fourth!, :fifth, :fifth!, :forty_two, :forty_two!, :third_to_last, :third_to_last!, :second_to_last, :second_to_last!,
+      :first_or_create, :first_or_create!, :first_or_initialize,
+      :find_or_create_by, :find_or_create_by!, :create_or_find_by, :create_or_find_by!, :find_or_initialize_by,
+      :find_by, :find_by!,
+      :destroy_all, :delete_all, :update_all,
+      :find_each, :find_in_batches, :in_batches,
+      :select, :group, :order, :except, :reorder, :limit, :offset, :joins, :left_joins, :left_outer_joins, :or,
+      :where, :rewhere, :preload, :eager_load, :includes, :from, :lock, :readonly, :extending,
+      :having, :create_with, :distinct, :references, :none, :unscope, :merge,
+      :count, :average, :minimum, :maximum, :sum, :calculate,
+      :pluck, :pick, :ids,
+    ]
+
+    def test_delegate_querying_methods
+      klass = Class.new(ActiveRecord::Base) do
+        self.table_name = "posts"
+      end
+
+      QUERYING_METHODS.each do |method|
+        assert_respond_to klass.all, method
+        assert_respond_to klass, method
+      end
+    end
+  end
 end
diff --git a/activerecord/test/cases/relation/merging_test.rb b/activerecord/test/cases/relation/merging_test.rb
index b68b3723f6..f53ef1fe35 100644
--- a/activerecord/test/cases/relation/merging_test.rb
+++ b/activerecord/test/cases/relation/merging_test.rb
@@ -58,7 +58,7 @@ class RelationMergingTest < ActiveRecord::TestCase
 
   def test_relation_merging_with_locks
     devs = Developer.lock.where("salary >= 80000").order("id DESC").merge(Developer.limit(2))
-    assert devs.locked?
+    assert_predicate devs, :locked?
   end
 
   def test_relation_merging_with_preload
@@ -72,6 +72,16 @@ class RelationMergingTest < ActiveRecord::TestCase
     assert_equal 1, comments.count
   end
 
+  def test_relation_merging_with_left_outer_joins
+    comments = Comment.joins(:post).where(body: "Thank you for the welcome").merge(Post.left_outer_joins(:author).where(body: "Such a lovely day"))
+
+    assert_equal 1, comments.count
+  end
+
+  def test_relation_merging_with_skip_query_cache
+    assert_equal Post.all.merge(Post.all.skip_query_cache!).skip_query_cache_value, true
+  end
+
   def test_relation_merging_with_association
     assert_queries(2) do  # one for loading post, and another one merged query
       post = Post.where(body: "Such a lovely day").first
@@ -107,9 +117,9 @@ class RelationMergingTest < ActiveRecord::TestCase
 
   def test_merging_with_from_clause
     relation = Post.all
-    assert relation.from_clause.empty?
+    assert_empty relation.from_clause
     relation = relation.merge(Post.from("posts"))
-    refute relation.from_clause.empty?
+    assert_not_empty relation.from_clause
   end
 end
 
diff --git a/activerecord/test/cases/relation/mutation_test.rb b/activerecord/test/cases/relation/mutation_test.rb
index ad3700b73a..f82ecd4449 100644
--- a/activerecord/test/cases/relation/mutation_test.rb
+++ b/activerecord/test/cases/relation/mutation_test.rb
@@ -25,7 +25,7 @@ module ActiveRecord
     test "#order! with symbol prepends the table name" do
       assert relation.order!(:name).equal?(relation)
       node = relation.order_values.first
-      assert node.ascending?
+      assert_predicate node, :ascending?
       assert_equal :name, node.expr.name
       assert_equal "posts", node.expr.relation.name
     end
@@ -88,7 +88,7 @@ module ActiveRecord
       assert relation.reorder!(:name).equal?(relation)
       node = relation.order_values.first
 
-      assert node.ascending?
+      assert_predicate node, :ascending?
       assert_equal :name, node.expr.name
       assert_equal "posts", node.expr.relation.name
     end
@@ -137,9 +137,14 @@ module ActiveRecord
       assert relation.skip_query_cache_value
     end
 
+    test "skip_preloading!" do
+      relation.skip_preloading!
+      assert relation.skip_preloading_value
+    end
+
     private
       def relation
-        @relation ||= Relation.new(FakeKlass, Post.arel_table, Post.predicate_builder)
+        @relation ||= Relation.new(FakeKlass)
       end
   end
 end
diff --git a/activerecord/test/cases/relation/or_test.rb b/activerecord/test/cases/relation/or_test.rb
index 955e9fc9ce..065819e0f1 100644
--- a/activerecord/test/cases/relation/or_test.rb
+++ b/activerecord/test/cases/relation/or_test.rb
@@ -31,7 +31,7 @@ module ActiveRecord
     end
 
     def test_or_with_bind_params
-      assert_equal Post.find([1, 2]), Post.where(id: 1).or(Post.where(id: 2)).to_a
+      assert_equal Post.find([1, 2]).sort_by(&:id), Post.where(id: 1).or(Post.where(id: 2)).sort_by(&:id)
     end
 
     def test_or_with_null_both
@@ -126,5 +126,12 @@ module ActiveRecord
       expected = Author.find(1).posts + Post.where(title: "I don't have any comments")
       assert_equal expected.sort_by(&:id), actual.sort_by(&:id)
     end
+
+    def test_or_with_scope_on_association
+      author = Author.first
+      assert_nothing_raised do
+        author.top_posts.or(author.other_top_posts)
+      end
+    end
   end
 end
diff --git a/activerecord/test/cases/relation/select_test.rb b/activerecord/test/cases/relation/select_test.rb
new file mode 100644
index 0000000000..0577e6bfdb
--- /dev/null
+++ b/activerecord/test/cases/relation/select_test.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/post"
+
+module ActiveRecord
+  class SelectTest < ActiveRecord::TestCase
+    fixtures :posts
+
+    def test_select_with_nil_agrument
+      expected = Post.select(:title).to_sql
+      assert_equal expected, Post.select(nil).select(:title).to_sql
+    end
+  end
+end
diff --git a/activerecord/test/cases/relation/where_clause_test.rb b/activerecord/test/cases/relation/where_clause_test.rb
index e5eb159d36..8703d238a0 100644
--- a/activerecord/test/cases/relation/where_clause_test.rb
+++ b/activerecord/test/cases/relation/where_clause_test.rb
@@ -75,8 +75,8 @@ class ActiveRecord::Relation
     end
 
     test "a clause knows if it is empty" do
-      assert WhereClause.empty.empty?
-      assert_not WhereClause.new(["anything"]).empty?
+      assert_empty WhereClause.empty
+      assert_not_empty WhereClause.new(["anything"])
     end
 
     test "invert cannot handle nil" do
diff --git a/activerecord/test/cases/relation/where_test.rb b/activerecord/test/cases/relation/where_test.rb
index d95a54a2fe..99797528b2 100644
--- a/activerecord/test/cases/relation/where_test.rb
+++ b/activerecord/test/cases/relation/where_test.rb
@@ -265,7 +265,7 @@ module ActiveRecord
     end
 
     def test_where_with_decimal_for_string_column
-      count = Post.where(title: BigDecimal.new(0)).count
+      count = Post.where(title: BigDecimal(0)).count
       assert_equal 0, count
     end
 
diff --git a/activerecord/test/cases/relation_test.rb b/activerecord/test/cases/relation_test.rb
index c1805aa592..93e2363025 100644
--- a/activerecord/test/cases/relation_test.rb
+++ b/activerecord/test/cases/relation_test.rb
@@ -11,30 +11,29 @@ module ActiveRecord
     fixtures :posts, :comments, :authors, :author_addresses, :ratings
 
     def test_construction
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass, table: :b)
       assert_equal FakeKlass, relation.klass
       assert_equal :b, relation.table
-      assert !relation.loaded, "relation is not loaded"
+      assert_not relation.loaded, "relation is not loaded"
     end
 
     def test_responds_to_model_and_returns_klass
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       assert_equal FakeKlass, relation.model
     end
 
     def test_initialize_single_values
-      relation = Relation.new(FakeKlass, :b, nil)
-      (Relation::SINGLE_VALUE_METHODS - [:create_with, :readonly]).each do |method|
+      relation = Relation.new(FakeKlass)
+      (Relation::SINGLE_VALUE_METHODS - [:create_with]).each do |method|
         assert_nil relation.send("#{method}_value"), method.to_s
       end
-      assert_equal false, relation.readonly_value
       value = relation.create_with_value
       assert_equal({}, value)
       assert_predicate value, :frozen?
     end
 
     def test_multi_value_initialize
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       Relation::MULTI_VALUE_METHODS.each do |method|
         values = relation.send("#{method}_values")
         assert_equal [], values, method.to_s
@@ -43,54 +42,49 @@ module ActiveRecord
     end
 
     def test_extensions
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       assert_equal [], relation.extensions
     end
 
     def test_empty_where_values_hash
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       assert_equal({}, relation.where_values_hash)
     end
 
     def test_has_values
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
+      relation = Relation.new(Post)
       relation.where!(id: 10)
       assert_equal({ "id" => 10 }, relation.where_values_hash)
     end
 
     def test_values_wrong_table
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
+      relation = Relation.new(Post)
       relation.where! Comment.arel_table[:id].eq(10)
       assert_equal({}, relation.where_values_hash)
     end
 
     def test_tree_is_not_traversed
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
+      relation = Relation.new(Post)
       left     = relation.table[:id].eq(10)
       right    = relation.table[:id].eq(10)
-      combine  = left.and right
+      combine  = left.or(right)
       relation.where! combine
       assert_equal({}, relation.where_values_hash)
     end
 
-    def test_table_name_delegates_to_klass
-      relation = Relation.new(FakeKlass, :b, Post.predicate_builder)
-      assert_equal "posts", relation.table_name
-    end
-
     def test_scope_for_create
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       assert_equal({}, relation.scope_for_create)
     end
 
     def test_create_with_value
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
+      relation = Relation.new(Post)
       relation.create_with_value = { hello: "world" }
       assert_equal({ "hello" => "world" }, relation.scope_for_create)
     end
 
     def test_create_with_value_with_wheres
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
+      relation = Relation.new(Post)
       assert_equal({}, relation.scope_for_create)
 
       relation.where!(id: 10)
@@ -101,11 +95,11 @@ module ActiveRecord
     end
 
     def test_empty_scope
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
-      assert relation.empty_scope?
+      relation = Relation.new(Post)
+      assert_predicate relation, :empty_scope?
 
       relation.merge!(relation)
-      assert relation.empty_scope?
+      assert_predicate relation, :empty_scope?
     end
 
     def test_bad_constants_raise_errors
@@ -115,31 +109,31 @@ module ActiveRecord
     end
 
     def test_empty_eager_loading?
-      relation = Relation.new(FakeKlass, :b, nil)
-      assert !relation.eager_loading?
+      relation = Relation.new(FakeKlass)
+      assert_not_predicate relation, :eager_loading?
     end
 
     def test_eager_load_values
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       relation.eager_load! :b
-      assert relation.eager_loading?
+      assert_predicate relation, :eager_loading?
     end
 
     def test_references_values
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       assert_equal [], relation.references_values
       relation = relation.references(:foo).references(:omg, :lol)
       assert_equal ["foo", "omg", "lol"], relation.references_values
     end
 
     def test_references_values_dont_duplicate
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       relation = relation.references(:foo).references(:foo)
       assert_equal ["foo"], relation.references_values
     end
 
     test "merging a hash into a relation" do
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
+      relation = Relation.new(Post)
       relation = relation.merge where: { name: :lol }, readonly: true
 
       assert_equal({ "name" => :lol }, relation.where_clause.to_h)
@@ -147,7 +141,7 @@ module ActiveRecord
     end
 
     test "merging an empty hash into a relation" do
-      assert_equal Relation::WhereClause.empty, Relation.new(FakeKlass, :b, nil).merge({}).where_clause
+      assert_equal Relation::WhereClause.empty, Relation.new(FakeKlass).merge({}).where_clause
     end
 
     test "merging a hash with unknown keys raises" do
@@ -155,7 +149,7 @@ module ActiveRecord
     end
 
     test "merging nil or false raises" do
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
 
       e = assert_raises(ArgumentError) do
         relation = relation.merge nil
@@ -171,7 +165,7 @@ module ActiveRecord
     end
 
     test "#values returns a dup of the values" do
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder).where!(name: :foo)
+      relation = Relation.new(Post).where!(name: :foo)
       values   = relation.values
 
       values[:where] = nil
@@ -179,7 +173,7 @@ module ActiveRecord
     end
 
     test "relations can be created with a values hash" do
-      relation = Relation.new(FakeKlass, :b, nil, select: [:foo])
+      relation = Relation.new(FakeKlass, values: { select: [:foo] })
       assert_equal [:foo], relation.select_values
     end
 
@@ -191,13 +185,13 @@ module ActiveRecord
         end
       end
 
-      relation = Relation.new(klass, :b, nil)
+      relation = Relation.new(klass)
       relation.merge!(where: ["foo = ?", "bar"])
       assert_equal Relation::WhereClause.new(["foo = bar"]), relation.where_clause
     end
 
     def test_merging_readonly_false
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       readonly_false_relation = relation.readonly(false)
       # test merging in both directions
       assert_equal false, relation.merge(readonly_false_relation).readonly_value
@@ -241,17 +235,17 @@ module ActiveRecord
 
     def test_merge_raises_with_invalid_argument
       assert_raises ArgumentError do
-        relation = Relation.new(FakeKlass, :b, nil)
+        relation = Relation.new(FakeKlass)
         relation.merge(true)
       end
     end
 
     def test_respond_to_for_non_selected_element
       post = Post.select(:title).first
-      assert_equal false, post.respond_to?(:body), "post should not respond_to?(:body) since invoking it raises exception"
+      assert_not_respond_to post, :body, "post should not respond_to?(:body) since invoking it raises exception"
 
       silence_warnings { post = Post.select("'title' as post_title").first }
-      assert_equal false, post.respond_to?(:title), "post should not respond_to?(:body) since invoking it raises exception"
+      assert_not_respond_to post, :title, "post should not respond_to?(:body) since invoking it raises exception"
     end
 
     def test_select_quotes_when_using_from_clause
@@ -279,18 +273,32 @@ module ActiveRecord
       assert_equal({ 2 => 1, 4 => 3, 5 => 1 }, authors(:david).posts.merge(posts_with_special_comments_with_ratings).count)
     end
 
+    def test_relation_merging_keeps_joining_order
+      authors  = Author.where(id: 1)
+      posts    = Post.joins(:author).merge(authors)
+      comments = Comment.joins(:post).merge(posts)
+      ratings  = Rating.joins(:comment).merge(comments)
+
+      assert_equal 3, ratings.count
+    end
+
     class EnsureRoundTripTypeCasting < ActiveRecord::Type::Value
       def type
         :string
       end
 
+      def cast(value)
+        raise value unless value == "value from user"
+        "cast value"
+      end
+
       def deserialize(value)
         raise value unless value == "type cast for database"
         "type cast from database"
       end
 
       def serialize(value)
-        raise value unless value == "value from user"
+        raise value unless value == "cast value"
         "type cast for database"
       end
     end
@@ -307,6 +315,14 @@ module ActiveRecord
       assert_equal "type cast from database", UpdateAllTestModel.first.body
     end
 
+    def test_skip_preloading_after_arel_has_been_generated
+      assert_nothing_raised do
+        relation = Comment.all
+        relation.arel
+        relation.skip_preloading!
+      end
+    end
+
     private
 
       def skip_if_sqlite3_version_includes_quoting_bug
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index ae1dc35bff..952d2dd5d9 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -9,6 +9,7 @@ require "models/comment"
 require "models/author"
 require "models/entrant"
 require "models/developer"
+require "models/person"
 require "models/computer"
 require "models/reply"
 require "models/company"
@@ -19,12 +20,13 @@ require "models/tyre"
 require "models/minivan"
 require "models/possession"
 require "models/reader"
+require "models/category"
 require "models/categorization"
 require "models/edge"
+require "models/subscriber"
 
 class RelationTest < ActiveRecord::TestCase
-  fixtures :authors, :author_addresses, :topics, :entrants, :developers, :companies, :developers_projects, :accounts, :categories, :categorizations, :posts, :comments,
-    :tags, :taggings, :cars, :minivans
+  fixtures :authors, :author_addresses, :topics, :entrants, :developers, :people, :companies, :developers_projects, :accounts, :categories, :categorizations, :categories_posts, :posts, :comments, :tags, :taggings, :cars, :minivans
 
   class TopicWithCallbacks < ActiveRecord::Base
     self.table_name = :topics
@@ -56,7 +58,7 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_dynamic_finder
     x = Post.where("author_id = ?", 1)
-    assert x.klass.respond_to?(:find_by_id), "@klass should handle dynamic finders"
+    assert_respond_to x.klass, :find_by_id
   end
 
   def test_multivalue_where
@@ -98,7 +100,7 @@ class RelationTest < ActiveRecord::TestCase
       2.times { assert_equal 5, topics.to_a.size }
     end
 
-    assert topics.loaded?
+    assert_predicate topics, :loaded?
   end
 
   def test_scoped_first
@@ -108,7 +110,7 @@ class RelationTest < ActiveRecord::TestCase
       2.times { assert_equal "The First Topic", topics.first.title }
     end
 
-    assert ! topics.loaded?
+    assert_not_predicate topics, :loaded?
   end
 
   def test_loaded_first
@@ -119,7 +121,7 @@ class RelationTest < ActiveRecord::TestCase
       assert_equal "The First Topic", topics.first.title
     end
 
-    assert topics.loaded?
+    assert_predicate topics, :loaded?
   end
 
   def test_loaded_first_with_limit
@@ -131,7 +133,7 @@ class RelationTest < ActiveRecord::TestCase
                     "The Second Topic of the day"], topics.first(2).map(&:title)
     end
 
-    assert topics.loaded?
+    assert_predicate topics, :loaded?
   end
 
   def test_first_get_more_than_available
@@ -152,14 +154,14 @@ class RelationTest < ActiveRecord::TestCase
       2.times { topics.to_a }
     end
 
-    assert topics.loaded?
+    assert_predicate topics, :loaded?
 
     original_size = topics.to_a.size
     Topic.create! title: "fake"
 
     assert_queries(1) { topics.reload }
     assert_equal original_size + 1, topics.size
-    assert topics.loaded?
+    assert_predicate topics, :loaded?
   end
 
   def test_finding_with_subquery
@@ -195,6 +197,18 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal(relation.map(&:post_count).sort, subquery.values.sort)
   end
 
+  def test_finding_with_subquery_with_eager_loading_in_from
+    relation = Comment.includes(:post).where("posts.type": "Post")
+    assert_equal relation.to_a, Comment.select("*").from(relation).to_a
+    assert_equal relation.to_a, Comment.select("subquery.*").from(relation).to_a
+    assert_equal relation.to_a, Comment.select("a.*").from(relation, :a).to_a
+  end
+
+  def test_finding_with_subquery_with_eager_loading_in_where
+    relation = Comment.includes(:post).where("posts.type": "Post")
+    assert_equal relation.sort_by(&:id), Comment.where(id: relation).sort_by(&:id)
+  end
+
   def test_finding_with_conditions
     assert_equal ["David"], Author.where(name: "David").map(&:name)
     assert_equal ["Mary"],  Author.where(["name = ?", "Mary"]).map(&:name)
@@ -238,7 +252,7 @@ class RelationTest < ActiveRecord::TestCase
   end
 
   def test_reverse_order_with_function
-    topics = Topic.order("length(title)").reverse_order
+    topics = Topic.order(Arel.sql("length(title)")).reverse_order
     assert_equal topics(:second).title, topics.first.title
   end
 
@@ -248,24 +262,24 @@ class RelationTest < ActiveRecord::TestCase
   end
 
   def test_reverse_order_with_function_other_predicates
-    topics = Topic.order("author_name, length(title), id").reverse_order
+    topics = Topic.order(Arel.sql("author_name, length(title), id")).reverse_order
     assert_equal topics(:second).title, topics.first.title
-    topics = Topic.order("length(author_name), id, length(title)").reverse_order
+    topics = Topic.order(Arel.sql("length(author_name), id, length(title)")).reverse_order
     assert_equal topics(:fifth).title, topics.first.title
   end
 
   def test_reverse_order_with_multiargument_function
     assert_raises(ActiveRecord::IrreversibleOrderError) do
-      Topic.order("concat(author_name, title)").reverse_order
+      Topic.order(Arel.sql("concat(author_name, title)")).reverse_order
     end
     assert_raises(ActiveRecord::IrreversibleOrderError) do
-      Topic.order("concat(lower(author_name), title)").reverse_order
+      Topic.order(Arel.sql("concat(lower(author_name), title)")).reverse_order
     end
     assert_raises(ActiveRecord::IrreversibleOrderError) do
-      Topic.order("concat(author_name, lower(title))").reverse_order
+      Topic.order(Arel.sql("concat(author_name, lower(title))")).reverse_order
     end
     assert_raises(ActiveRecord::IrreversibleOrderError) do
-      Topic.order("concat(lower(author_name), title, length(title)").reverse_order
+      Topic.order(Arel.sql("concat(lower(author_name), title, length(title)")).reverse_order
     end
   end
 
@@ -277,10 +291,10 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_reverse_order_with_nulls_first_or_last
     assert_raises(ActiveRecord::IrreversibleOrderError) do
-      Topic.order("title NULLS FIRST").reverse_order
+      Topic.order(Arel.sql("title NULLS FIRST")).reverse_order
     end
     assert_raises(ActiveRecord::IrreversibleOrderError) do
-      Topic.order("title nulls last").reverse_order
+      Topic.order(Arel.sql("title nulls last")).reverse_order
     end
   end
 
@@ -373,29 +387,29 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_finding_with_cross_table_order_and_limit
     tags = Tag.includes(:taggings).
-              order("tags.name asc", "taggings.taggable_id asc", "REPLACE('abc', taggings.taggable_type, taggings.taggable_type)").
+              order("tags.name asc", "taggings.taggable_id asc", Arel.sql("REPLACE('abc', taggings.taggable_type, taggings.taggable_type)")).
               limit(1).to_a
     assert_equal 1, tags.length
   end
 
   def test_finding_with_complex_order_and_limit
-    tags = Tag.includes(:taggings).references(:taggings).order("REPLACE('abc', taggings.taggable_type, taggings.taggable_type)").limit(1).to_a
+    tags = Tag.includes(:taggings).references(:taggings).order(Arel.sql("REPLACE('abc', taggings.taggable_type, taggings.taggable_type)")).limit(1).to_a
     assert_equal 1, tags.length
   end
 
   def test_finding_with_complex_order
-    tags = Tag.includes(:taggings).references(:taggings).order("REPLACE('abc', taggings.taggable_type, taggings.taggable_type)").to_a
+    tags = Tag.includes(:taggings).references(:taggings).order(Arel.sql("REPLACE('abc', taggings.taggable_type, taggings.taggable_type)")).to_a
     assert_equal 3, tags.length
   end
 
   def test_finding_with_sanitized_order
-    query = Tag.order(["field(id, ?)", [1, 3, 2]]).to_sql
+    query = Tag.order([Arel.sql("field(id, ?)"), [1, 3, 2]]).to_sql
     assert_match(/field\(id, 1,3,2\)/, query)
 
-    query = Tag.order(["field(id, ?)", []]).to_sql
+    query = Tag.order([Arel.sql("field(id, ?)"), []]).to_sql
     assert_match(/field\(id, NULL\)/, query)
 
-    query = Tag.order(["field(id, ?)", nil]).to_sql
+    query = Tag.order([Arel.sql("field(id, ?)"), nil]).to_sql
     assert_match(/field\(id, NULL\)/, query)
   end
 
@@ -489,16 +503,16 @@ class RelationTest < ActiveRecord::TestCase
     relation = Topic.all
 
     ["find_by_title", "find_by_title_and_author_name"].each do |method|
-      assert_respond_to relation, method, "Topic.all should respond to #{method.inspect}"
+      assert_respond_to relation, method
     end
   end
 
   def test_respond_to_class_methods_and_scopes
-    assert Topic.all.respond_to?(:by_lifo)
+    assert_respond_to Topic.all, :by_lifo
   end
 
   def test_find_with_readonly_option
-    Developer.all.each { |d| assert !d.readonly? }
+    Developer.all.each { |d| assert_not d.readonly? }
     Developer.all.readonly.each { |d| assert d.readonly? }
   end
 
@@ -589,7 +603,7 @@ class RelationTest < ActiveRecord::TestCase
     reader = Reader.create! post_id: post.id, person_id: 1
     comment = Comment.create! post_id: post.id, body: "body"
 
-    assert !comment.respond_to?(:readers)
+    assert_not_respond_to comment, :readers
 
     post_rel = Post.preload(:readers).joins(:readers).where(title: "Uhuu")
     result_comment = Comment.joins(:post).merge(post_rel).to_a.first
@@ -710,7 +724,7 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_find_in_empty_array
     authors = Author.all.where(id: [])
-    assert authors.to_a.blank?
+    assert_predicate authors.to_a, :blank?
   end
 
   def test_where_with_ar_object
@@ -768,8 +782,6 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_find_all_using_where_with_relation
     david = authors(:david)
-    # switching the lines below would succeed in current rails
-    # assert_queries(2) {
     assert_queries(1) {
       relation = Author.where(id: Author.where(id: david.id))
       assert_equal [david], relation.to_a
@@ -808,8 +820,6 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_find_all_using_where_with_relation_and_alternate_primary_key
     cool_first = minivans(:cool_first)
-    # switching the lines below would succeed in current rails
-    # assert_queries(2) {
     assert_queries(1) {
       relation = Minivan.where(minivan_id: Minivan.where(name: cool_first.name))
       assert_equal [cool_first], relation.to_a
@@ -845,32 +855,6 @@ class RelationTest < ActiveRecord::TestCase
     }
   end
 
-  def test_exists
-    davids = Author.where(name: "David")
-    assert davids.exists?
-    assert davids.exists?(authors(:david).id)
-    assert ! davids.exists?(authors(:mary).id)
-    assert ! davids.exists?("42")
-    assert ! davids.exists?(42)
-    assert ! davids.exists?(davids.new.id)
-
-    fake = Author.where(name: "fake author")
-    assert ! fake.exists?
-    assert ! fake.exists?(authors(:david).id)
-  end
-
-  def test_exists_uses_existing_scope
-    post = authors(:david).posts.first
-    authors = Author.includes(:posts).where(name: "David", posts: { id: post.id })
-    assert authors.exists?(authors(:david).id)
-  end
-
-  def test_any_with_scope_on_hash_includes
-    post = authors(:david).posts.first
-    categories = Categorization.includes(author: :posts).where(posts: { id: post.id })
-    assert categories.exists?
-  end
-
   def test_last
     authors = Author.all
     assert_equal authors(:bob), authors.last
@@ -881,19 +865,19 @@ class RelationTest < ActiveRecord::TestCase
 
     # Force load
     assert_equal [authors(:david)], davids.to_a
-    assert davids.loaded?
+    assert_predicate davids, :loaded?
 
     assert_difference("Author.count", -1) { davids.destroy_all }
 
     assert_equal [], davids.to_a
-    assert davids.loaded?
+    assert_predicate davids, :loaded?
   end
 
   def test_delete_all
     davids = Author.where(name: "David")
 
     assert_difference("Author.count", -1) { davids.delete_all }
-    assert ! davids.loaded?
+    assert_not_predicate davids, :loaded?
   end
 
   def test_delete_all_loaded
@@ -901,20 +885,18 @@ class RelationTest < ActiveRecord::TestCase
 
     # Force load
     assert_equal [authors(:david)], davids.to_a
-    assert davids.loaded?
+    assert_predicate davids, :loaded?
 
     assert_difference("Author.count", -1) { davids.delete_all }
 
     assert_equal [], davids.to_a
-    assert davids.loaded?
+    assert_predicate davids, :loaded?
   end
 
   def test_delete_all_with_unpermitted_relation_raises_error
-    assert_raises(ActiveRecord::ActiveRecordError) { Author.limit(10).delete_all }
     assert_raises(ActiveRecord::ActiveRecordError) { Author.distinct.delete_all }
     assert_raises(ActiveRecord::ActiveRecordError) { Author.group(:name).delete_all }
     assert_raises(ActiveRecord::ActiveRecordError) { Author.having("SUM(id) < 3").delete_all }
-    assert_raises(ActiveRecord::ActiveRecordError) { Author.offset(10).delete_all }
   end
 
   def test_select_with_aggregates
@@ -922,9 +904,9 @@ class RelationTest < ActiveRecord::TestCase
 
     assert_equal 11, posts.count(:all)
     assert_equal 11, posts.size
-    assert posts.any?
-    assert posts.many?
-    assert_not posts.empty?
+    assert_predicate posts, :any?
+    assert_predicate posts, :many?
+    assert_not_empty posts
   end
 
   def test_select_takes_a_variable_list_of_args
@@ -953,13 +935,13 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal 11, posts.count(:all)
     assert_equal 11, posts.count(:id)
 
-    assert_equal 1, posts.where("comments_count > 1").count
-    assert_equal 9, posts.where(comments_count: 0).count
+    assert_equal 3, posts.where("comments_count > 1").count
+    assert_equal 6, posts.where(comments_count: 0).count
   end
 
   def test_count_with_block
     posts = Post.all
-    assert_equal 10, posts.count { |p| p.comments_count.even? }
+    assert_equal 8, posts.count { |p| p.comments_count.even? }
   end
 
   def test_count_on_association_relation
@@ -970,19 +952,37 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal author.posts.where(author_id: author.id).size, posts.count
 
     assert_equal 0, author.posts.where(author_id: another_author.id).size
-    assert author.posts.where(author_id: another_author.id).empty?
+    assert_empty author.posts.where(author_id: another_author.id)
   end
 
   def test_count_with_distinct
     posts = Post.all
 
-    assert_equal 3, posts.distinct(true).count(:comments_count)
+    assert_equal 4, posts.distinct(true).count(:comments_count)
     assert_equal 11, posts.distinct(false).count(:comments_count)
 
-    assert_equal 3, posts.distinct(true).select(:comments_count).count
+    assert_equal 4, posts.distinct(true).select(:comments_count).count
     assert_equal 11, posts.distinct(false).select(:comments_count).count
   end
 
+  def test_size_with_distinct
+    posts = Post.distinct.select(:author_id, :comments_count)
+    assert_queries(1) { assert_equal 8, posts.size }
+    assert_queries(1) { assert_equal 8, posts.load.size }
+  end
+
+  def test_size_with_eager_loading_and_custom_order
+    posts = Post.includes(:comments).order("comments.id")
+    assert_queries(1) { assert_equal 11, posts.size }
+    assert_queries(1) { assert_equal 11, posts.load.size }
+  end
+
+  def test_size_with_eager_loading_and_custom_order_and_distinct
+    posts = Post.includes(:comments).order("comments.id").distinct
+    assert_queries(1) { assert_equal 11, posts.size }
+    assert_queries(1) { assert_equal 11, posts.load.size }
+  end
+
   def test_update_all_with_scope
     tag = Tag.first
     Post.tagged_with(tag.id).update_all title: "rofl"
@@ -1014,29 +1014,29 @@ class RelationTest < ActiveRecord::TestCase
     posts = Post.all
 
     assert_queries(1) { assert_equal 11, posts.size }
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
 
     best_posts = posts.where(comments_count: 0)
     best_posts.load # force load
-    assert_no_queries { assert_equal 9, best_posts.size }
+    assert_no_queries { assert_equal 6, best_posts.size }
   end
 
   def test_size_with_limit
     posts = Post.limit(10)
 
     assert_queries(1) { assert_equal 10, posts.size }
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
 
     best_posts = posts.where(comments_count: 0)
     best_posts.load # force load
-    assert_no_queries { assert_equal 9, best_posts.size }
+    assert_no_queries { assert_equal 6, best_posts.size }
   end
 
   def test_size_with_zero_limit
     posts = Post.limit(0)
 
     assert_no_queries { assert_equal 0, posts.size }
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
 
     posts.load # force load
     assert_no_queries { assert_equal 0, posts.size }
@@ -1046,13 +1046,13 @@ class RelationTest < ActiveRecord::TestCase
     posts = Post.limit(0)
 
     assert_no_queries { assert_equal true, posts.empty? }
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
   end
 
   def test_count_complex_chained_relations
     posts = Post.select("comments_count").where("id is not null").group("author_id").where("comments_count > 0")
 
-    expected = { 1 => 2 }
+    expected = { 1 => 4, 2 => 1 }
     assert_equal expected, posts.count
   end
 
@@ -1060,11 +1060,11 @@ class RelationTest < ActiveRecord::TestCase
     posts = Post.all
 
     assert_queries(1) { assert_equal false, posts.empty? }
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
 
     no_posts = posts.where(title: "")
     assert_queries(1) { assert_equal true, no_posts.empty? }
-    assert ! no_posts.loaded?
+    assert_not_predicate no_posts, :loaded?
 
     best_posts = posts.where(comments_count: 0)
     best_posts.load # force load
@@ -1075,11 +1075,11 @@ class RelationTest < ActiveRecord::TestCase
     posts = Post.select("comments_count").where("id is not null").group("author_id").where("comments_count > 0")
 
     assert_queries(1) { assert_equal false, posts.empty? }
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
 
     no_posts = posts.where(title: "")
     assert_queries(1) { assert_equal true, no_posts.empty? }
-    assert ! no_posts.loaded?
+    assert_not_predicate no_posts, :loaded?
   end
 
   def test_any
@@ -1095,13 +1095,13 @@ class RelationTest < ActiveRecord::TestCase
 
     assert_queries(3) do
       assert posts.any? # Uses COUNT()
-      assert ! posts.where(id: nil).any?
+      assert_not_predicate posts.where(id: nil), :any?
 
       assert posts.any? { |p| p.id > 0 }
-      assert ! posts.any? { |p| p.id <= 0 }
+      assert_not posts.any? { |p| p.id <= 0 }
     end
 
-    assert posts.loaded?
+    assert_predicate posts, :loaded?
   end
 
   def test_many
@@ -1110,49 +1110,49 @@ class RelationTest < ActiveRecord::TestCase
     assert_queries(2) do
       assert posts.many? # Uses COUNT()
       assert posts.many? { |p| p.id > 0 }
-      assert ! posts.many? { |p| p.id < 2 }
+      assert_not posts.many? { |p| p.id < 2 }
     end
 
-    assert posts.loaded?
+    assert_predicate posts, :loaded?
   end
 
   def test_many_with_limits
     posts = Post.all
 
-    assert posts.many?
-    assert ! posts.limit(1).many?
+    assert_predicate posts, :many?
+    assert_not_predicate posts.limit(1), :many?
   end
 
   def test_none?
     posts = Post.all
     assert_queries(1) do
-      assert ! posts.none? # Uses COUNT()
+      assert_not posts.none? # Uses COUNT()
     end
 
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
 
     assert_queries(1) do
       assert posts.none? { |p| p.id < 0 }
-      assert ! posts.none? { |p| p.id == 1 }
+      assert_not posts.none? { |p| p.id == 1 }
     end
 
-    assert posts.loaded?
+    assert_predicate posts, :loaded?
   end
 
   def test_one
     posts = Post.all
     assert_queries(1) do
-      assert ! posts.one? # Uses COUNT()
+      assert_not posts.one? # Uses COUNT()
     end
 
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
 
     assert_queries(1) do
-      assert ! posts.one? { |p| p.id < 3 }
+      assert_not posts.one? { |p| p.id < 3 }
       assert posts.one? { |p| p.id == 1 }
     end
 
-    assert posts.loaded?
+    assert_predicate posts, :loaded?
   end
 
   def test_to_a_should_dup_target
@@ -1185,10 +1185,10 @@ class RelationTest < ActiveRecord::TestCase
 
     sparrow = birds.create
     assert_kind_of Bird, sparrow
-    assert !sparrow.persisted?
+    assert_not_predicate sparrow, :persisted?
 
     hen = birds.where(name: "hen").create
-    assert hen.persisted?
+    assert_predicate hen, :persisted?
     assert_equal "hen", hen.name
   end
 
@@ -1199,34 +1199,43 @@ class RelationTest < ActiveRecord::TestCase
 
     hen = birds.where(name: "hen").create!
     assert_kind_of Bird, hen
-    assert hen.persisted?
+    assert_predicate hen, :persisted?
     assert_equal "hen", hen.name
   end
 
+  def test_create_with_polymorphic_association
+    author = authors(:david)
+    post = posts(:welcome)
+    comment = Comment.where(post: post, author: author).create!(body: "hello")
+
+    assert_equal author, comment.author
+    assert_equal post, comment.post
+  end
+
   def test_first_or_create
     parrot = Bird.where(color: "green").first_or_create(name: "parrot")
     assert_kind_of Bird, parrot
-    assert parrot.persisted?
+    assert_predicate parrot, :persisted?
     assert_equal "parrot", parrot.name
     assert_equal "green", parrot.color
 
     same_parrot = Bird.where(color: "green").first_or_create(name: "parakeet")
     assert_kind_of Bird, same_parrot
-    assert same_parrot.persisted?
+    assert_predicate same_parrot, :persisted?
     assert_equal parrot, same_parrot
   end
 
   def test_first_or_create_with_no_parameters
     parrot = Bird.where(color: "green").first_or_create
     assert_kind_of Bird, parrot
-    assert !parrot.persisted?
+    assert_not_predicate parrot, :persisted?
     assert_equal "green", parrot.color
   end
 
   def test_first_or_create_with_block
     parrot = Bird.where(color: "green").first_or_create { |bird| bird.name = "parrot" }
     assert_kind_of Bird, parrot
-    assert parrot.persisted?
+    assert_predicate parrot, :persisted?
     assert_equal "green", parrot.color
     assert_equal "parrot", parrot.name
 
@@ -1247,13 +1256,13 @@ class RelationTest < ActiveRecord::TestCase
   def test_first_or_create_bang_with_valid_options
     parrot = Bird.where(color: "green").first_or_create!(name: "parrot")
     assert_kind_of Bird, parrot
-    assert parrot.persisted?
+    assert_predicate parrot, :persisted?
     assert_equal "parrot", parrot.name
     assert_equal "green", parrot.color
 
     same_parrot = Bird.where(color: "green").first_or_create!(name: "parakeet")
     assert_kind_of Bird, same_parrot
-    assert same_parrot.persisted?
+    assert_predicate same_parrot, :persisted?
     assert_equal parrot, same_parrot
   end
 
@@ -1268,7 +1277,7 @@ class RelationTest < ActiveRecord::TestCase
   def test_first_or_create_bang_with_valid_block
     parrot = Bird.where(color: "green").first_or_create! { |bird| bird.name = "parrot" }
     assert_kind_of Bird, parrot
-    assert parrot.persisted?
+    assert_predicate parrot, :persisted?
     assert_equal "green", parrot.color
     assert_equal "parrot", parrot.name
 
@@ -1299,9 +1308,9 @@ class RelationTest < ActiveRecord::TestCase
   def test_first_or_initialize
     parrot = Bird.where(color: "green").first_or_initialize(name: "parrot")
     assert_kind_of Bird, parrot
-    assert !parrot.persisted?
-    assert parrot.valid?
-    assert parrot.new_record?
+    assert_not_predicate parrot, :persisted?
+    assert_predicate parrot, :valid?
+    assert_predicate parrot, :new_record?
     assert_equal "parrot", parrot.name
     assert_equal "green", parrot.color
   end
@@ -1309,18 +1318,18 @@ class RelationTest < ActiveRecord::TestCase
   def test_first_or_initialize_with_no_parameters
     parrot = Bird.where(color: "green").first_or_initialize
     assert_kind_of Bird, parrot
-    assert !parrot.persisted?
-    assert !parrot.valid?
-    assert parrot.new_record?
+    assert_not_predicate parrot, :persisted?
+    assert_not_predicate parrot, :valid?
+    assert_predicate parrot, :new_record?
     assert_equal "green", parrot.color
   end
 
   def test_first_or_initialize_with_block
     parrot = Bird.where(color: "green").first_or_initialize { |bird| bird.name = "parrot" }
     assert_kind_of Bird, parrot
-    assert !parrot.persisted?
-    assert parrot.valid?
-    assert parrot.new_record?
+    assert_not_predicate parrot, :persisted?
+    assert_predicate parrot, :valid?
+    assert_predicate parrot, :new_record?
     assert_equal "green", parrot.color
     assert_equal "parrot", parrot.name
   end
@@ -1329,7 +1338,7 @@ class RelationTest < ActiveRecord::TestCase
     assert_nil Bird.find_by(name: "bob")
 
     bird = Bird.find_or_create_by(name: "bob")
-    assert bird.persisted?
+    assert_predicate bird, :persisted?
 
     assert_equal bird, Bird.find_or_create_by(name: "bob")
   end
@@ -1338,7 +1347,7 @@ class RelationTest < ActiveRecord::TestCase
     assert_nil Bird.find_by(name: "bob")
 
     bird = Bird.create_with(color: "green").find_or_create_by(name: "bob")
-    assert bird.persisted?
+    assert_predicate bird, :persisted?
     assert_equal "green", bird.color
 
     assert_equal bird, Bird.create_with(color: "blue").find_or_create_by(name: "bob")
@@ -1348,11 +1357,39 @@ class RelationTest < ActiveRecord::TestCase
     assert_raises(ActiveRecord::RecordInvalid) { Bird.find_or_create_by!(color: "green") }
   end
 
+  def test_create_or_find_by
+    assert_nil Subscriber.find_by(nick: "bob")
+
+    subscriber = Subscriber.create!(nick: "bob")
+
+    assert_equal subscriber, Subscriber.create_or_find_by(nick: "bob")
+    assert_not_equal subscriber, Subscriber.create_or_find_by(nick: "cat")
+  end
+
+  def test_create_or_find_by_with_non_unique_attributes
+    Subscriber.create!(nick: "bob", name: "the builder")
+
+    assert_raises(ActiveRecord::RecordNotFound) do
+      Subscriber.create_or_find_by(nick: "bob", name: "the cat")
+    end
+  end
+
+  def test_create_or_find_by_within_transaction
+    assert_nil Subscriber.find_by(nick: "bob")
+
+    subscriber = Subscriber.create!(nick: "bob")
+
+    Subscriber.transaction do
+      assert_equal subscriber, Subscriber.create_or_find_by(nick: "bob")
+      assert_not_equal subscriber, Subscriber.create_or_find_by(nick: "cat")
+    end
+  end
+
   def test_find_or_initialize_by
     assert_nil Bird.find_by(name: "bob")
 
     bird = Bird.find_or_initialize_by(name: "bob")
-    assert bird.new_record?
+    assert_predicate bird, :new_record?
     bird.save!
 
     assert_equal bird, Bird.find_or_initialize_by(name: "bob")
@@ -1489,6 +1526,50 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal posts(:welcome),  comments(:greetings).post
   end
 
+  def test_touch_all_updates_records_timestamps
+    david = developers(:david)
+    david_previously_updated_at = david.updated_at
+    jamis = developers(:jamis)
+    jamis_previously_updated_at = jamis.updated_at
+    Developer.where(name: "David").touch_all
+
+    assert_not_equal david_previously_updated_at, david.reload.updated_at
+    assert_equal jamis_previously_updated_at, jamis.reload.updated_at
+  end
+
+  def test_touch_all_with_custom_timestamp
+    developer = developers(:david)
+    previously_created_at = developer.created_at
+    previously_updated_at = developer.updated_at
+    Developer.where(name: "David").touch_all(:created_at)
+    developer = developer.reload
+
+    assert_not_equal previously_created_at, developer.created_at
+    assert_not_equal previously_updated_at, developer.updated_at
+  end
+
+  def test_touch_all_with_given_time
+    developer = developers(:david)
+    previously_created_at = developer.created_at
+    previously_updated_at = developer.updated_at
+    new_time = Time.utc(2015, 2, 16, 4, 54, 0)
+    Developer.where(name: "David").touch_all(:created_at, time: new_time)
+    developer = developer.reload
+
+    assert_not_equal previously_created_at, developer.created_at
+    assert_not_equal previously_updated_at, developer.updated_at
+    assert_equal new_time, developer.created_at
+    assert_equal new_time, developer.updated_at
+  end
+
+  def test_touch_all_updates_locking_column
+    person = people(:david)
+
+    assert_difference -> { person.reload.lock_version }, +1 do
+      Person.where(first_name: "David").touch_all
+    end
+  end
+
   def test_update_on_relation
     topic1 = TopicWithCallbacks.create! title: "arel", author_name: nil
     topic2 = TopicWithCallbacks.create! title: "activerecord", author_name: nil
@@ -1527,10 +1608,10 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_doesnt_add_having_values_if_options_are_blank
     scope = Post.having("")
-    assert scope.having_clause.empty?
+    assert_empty scope.having_clause
 
     scope = Post.having([])
-    assert scope.having_clause.empty?
+    assert_empty scope.having_clause
   end
 
   def test_having_with_binds_for_both_where_and_having
@@ -1556,13 +1637,13 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_references_triggers_eager_loading
     scope = Post.includes(:comments)
-    assert !scope.eager_loading?
-    assert scope.references(:comments).eager_loading?
+    assert_not_predicate scope, :eager_loading?
+    assert_predicate scope.references(:comments), :eager_loading?
   end
 
   def test_references_doesnt_trigger_eager_loading_if_reference_not_included
     scope = Post.references(:comments)
-    assert !scope.eager_loading?
+    assert_not_predicate scope, :eager_loading?
   end
 
   def test_automatically_added_where_references
@@ -1593,7 +1674,7 @@ class RelationTest < ActiveRecord::TestCase
     scope = Post.order("comments.body")
     assert_equal ["comments"], scope.references_values
 
-    scope = Post.order("#{Comment.quoted_table_name}.#{Comment.quoted_primary_key}")
+    scope = Post.order(Arel.sql("#{Comment.quoted_table_name}.#{Comment.quoted_primary_key}"))
     if current_adapter?(:OracleAdapter)
       assert_equal ["COMMENTS"], scope.references_values
     else
@@ -1610,7 +1691,7 @@ class RelationTest < ActiveRecord::TestCase
     scope = Post.order("comments.body asc")
     assert_equal ["comments"], scope.references_values
 
-    scope = Post.order("foo(comments.body)")
+    scope = Post.order(Arel.sql("foo(comments.body)"))
     assert_equal [], scope.references_values
   end
 
@@ -1618,7 +1699,7 @@ class RelationTest < ActiveRecord::TestCase
     scope = Post.reorder("comments.body")
     assert_equal %w(comments), scope.references_values
 
-    scope = Post.reorder("#{Comment.quoted_table_name}.#{Comment.quoted_primary_key}")
+    scope = Post.reorder(Arel.sql("#{Comment.quoted_table_name}.#{Comment.quoted_primary_key}"))
     if current_adapter?(:OracleAdapter)
       assert_equal ["COMMENTS"], scope.references_values
     else
@@ -1635,7 +1716,7 @@ class RelationTest < ActiveRecord::TestCase
     scope = Post.reorder("comments.body asc")
     assert_equal %w(comments), scope.references_values
 
-    scope = Post.reorder("foo(comments.body)")
+    scope = Post.reorder(Arel.sql("foo(comments.body)"))
     assert_equal [], scope.references_values
   end
 
@@ -1660,7 +1741,7 @@ class RelationTest < ActiveRecord::TestCase
     # checking if there are topics is used before you actually display them,
     # thus it shouldn't invoke an extra count query.
     assert_no_queries { assert topics.present? }
-    assert_no_queries { assert !topics.blank? }
+    assert_no_queries { assert_not topics.blank? }
 
     # shows count of topics and loops after loading the query should not trigger extra queries either.
     assert_no_queries { topics.size }
@@ -1670,7 +1751,7 @@ class RelationTest < ActiveRecord::TestCase
     # count always trigger the COUNT query.
     assert_queries(1) { topics.count }
 
-    assert topics.loaded?
+    assert_predicate topics, :loaded?
   end
 
   test "find_by with hash conditions returns the first matching record" do
@@ -1806,6 +1887,14 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal post, custom_post_relation.joins(:author).where!(title: post.title).take
   end
 
+  test "arel_attribute respects a custom table" do
+    assert_equal [posts(:sti_comments)], custom_post_relation.ranked_by_comments.limit_by(1).to_a
+  end
+
+  test "alias_tracker respects a custom table" do
+    assert_equal posts(:welcome), custom_post_relation("categories_posts").joins(:categories).first
+  end
+
   test "#load" do
     relation = Post.all
     assert_queries(1) do
@@ -1837,7 +1926,7 @@ class RelationTest < ActiveRecord::TestCase
   test "delegations do not leak to other classes" do
     Topic.all.by_lifo
     assert Topic.all.class.method_defined?(:by_lifo)
-    assert !Post.all.respond_to?(:by_lifo)
+    assert_not_respond_to Post.all, :by_lifo
   end
 
   def test_unscope_with_subquery
@@ -1862,7 +1951,7 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_locked_should_not_build_arel
     posts = Post.locked
-    assert posts.locked?
+    assert_predicate posts, :locked?
     assert_nothing_raised { posts.lock!(false) }
   end
 
@@ -1912,12 +2001,29 @@ class RelationTest < ActiveRecord::TestCase
     end
   end
 
+  test "#where with set" do
+    david = authors(:david)
+    mary = authors(:mary)
+
+    authors = Author.where(name: ["David", "Mary"].to_set)
+    assert_equal [david, mary], authors
+  end
+
+  test "#where with empty set" do
+    authors = Author.where(name: Set.new)
+    assert_empty authors
+  end
+
   private
-    def custom_post_relation
-      table_alias = Post.arel_table.alias("omg_posts")
+    def custom_post_relation(alias_name = "omg_posts")
+      table_alias = Post.arel_table.alias(alias_name)
       table_metadata = ActiveRecord::TableMetadata.new(Post, table_alias)
       predicate_builder = ActiveRecord::PredicateBuilder.new(table_metadata)
 
-      ActiveRecord::Relation.create(Post, table_alias, predicate_builder)
+      ActiveRecord::Relation.create(
+        Post,
+        table: table_alias,
+        predicate_builder: predicate_builder
+      )
     end
 end
diff --git a/activerecord/test/cases/reserved_word_test.rb b/activerecord/test/cases/reserved_word_test.rb
index 0214dbec17..e32605fd11 100644
--- a/activerecord/test/cases/reserved_word_test.rb
+++ b/activerecord/test/cases/reserved_word_test.rb
@@ -39,7 +39,7 @@ class ReservedWordTest < ActiveRecord::TestCase
       t.string :order
       t.belongs_to :select
     end
-    @connection.create_table :values, force: true do |t|
+    @connection.create_table :values, primary_key: :as, force: true do |t|
       t.belongs_to :group
     end
   end
@@ -88,6 +88,13 @@ class ReservedWordTest < ActiveRecord::TestCase
     assert_equal x, Group.find(x.id)
   end
 
+  def test_delete_all_with_subselect
+    create_test_fixtures :values
+    assert_equal 1, Values.order(:as).limit(1).offset(1).delete_all
+    assert_raise(ActiveRecord::RecordNotFound) { Values.find(2) }
+    assert Values.find(1)
+  end
+
   def test_has_one_associations
     create_test_fixtures :group, :values
     v = Group.find(1).values
@@ -109,7 +116,7 @@ class ReservedWordTest < ActiveRecord::TestCase
   end
 
   def test_activerecord_introspection
-    assert Group.table_exists?
+    assert_predicate Group, :table_exists?
     assert_equal ["id", "order", "select_id"], Group.columns.map(&:name).sort
   end
 
diff --git a/activerecord/test/cases/sanitize_test.rb b/activerecord/test/cases/sanitize_test.rb
index 082d663675..778cf86ac3 100644
--- a/activerecord/test/cases/sanitize_test.rb
+++ b/activerecord/test/cases/sanitize_test.rb
@@ -4,6 +4,7 @@ require "cases/helper"
 require "models/binary"
 require "models/author"
 require "models/post"
+require "models/customer"
 
 class SanitizeTest < ActiveRecord::TestCase
   def setup
@@ -11,30 +12,30 @@ class SanitizeTest < ActiveRecord::TestCase
 
   def test_sanitize_sql_array_handles_string_interpolation
     quoted_bambi = ActiveRecord::Base.connection.quote_string("Bambi")
-    assert_equal "name='#{quoted_bambi}'", Binary.send(:sanitize_sql_array, ["name='%s'", "Bambi"])
-    assert_equal "name='#{quoted_bambi}'", Binary.send(:sanitize_sql_array, ["name='%s'", "Bambi".mb_chars])
+    assert_equal "name='#{quoted_bambi}'", Binary.sanitize_sql_array(["name='%s'", "Bambi"])
+    assert_equal "name='#{quoted_bambi}'", Binary.sanitize_sql_array(["name='%s'", "Bambi".mb_chars])
     quoted_bambi_and_thumper = ActiveRecord::Base.connection.quote_string("Bambi\nand\nThumper")
-    assert_equal "name='#{quoted_bambi_and_thumper}'", Binary.send(:sanitize_sql_array, ["name='%s'", "Bambi\nand\nThumper"])
-    assert_equal "name='#{quoted_bambi_and_thumper}'", Binary.send(:sanitize_sql_array, ["name='%s'", "Bambi\nand\nThumper".mb_chars])
+    assert_equal "name='#{quoted_bambi_and_thumper}'", Binary.sanitize_sql_array(["name='%s'", "Bambi\nand\nThumper"])
+    assert_equal "name='#{quoted_bambi_and_thumper}'", Binary.sanitize_sql_array(["name='%s'", "Bambi\nand\nThumper".mb_chars])
   end
 
   def test_sanitize_sql_array_handles_bind_variables
     quoted_bambi = ActiveRecord::Base.connection.quote("Bambi")
-    assert_equal "name=#{quoted_bambi}", Binary.send(:sanitize_sql_array, ["name=?", "Bambi"])
-    assert_equal "name=#{quoted_bambi}", Binary.send(:sanitize_sql_array, ["name=?", "Bambi".mb_chars])
+    assert_equal "name=#{quoted_bambi}", Binary.sanitize_sql_array(["name=?", "Bambi"])
+    assert_equal "name=#{quoted_bambi}", Binary.sanitize_sql_array(["name=?", "Bambi".mb_chars])
     quoted_bambi_and_thumper = ActiveRecord::Base.connection.quote("Bambi\nand\nThumper")
-    assert_equal "name=#{quoted_bambi_and_thumper}", Binary.send(:sanitize_sql_array, ["name=?", "Bambi\nand\nThumper"])
-    assert_equal "name=#{quoted_bambi_and_thumper}", Binary.send(:sanitize_sql_array, ["name=?", "Bambi\nand\nThumper".mb_chars])
+    assert_equal "name=#{quoted_bambi_and_thumper}", Binary.sanitize_sql_array(["name=?", "Bambi\nand\nThumper"])
+    assert_equal "name=#{quoted_bambi_and_thumper}", Binary.sanitize_sql_array(["name=?", "Bambi\nand\nThumper".mb_chars])
   end
 
   def test_sanitize_sql_array_handles_named_bind_variables
     quoted_bambi = ActiveRecord::Base.connection.quote("Bambi")
-    assert_equal "name=#{quoted_bambi}", Binary.send(:sanitize_sql_array, ["name=:name", name: "Bambi"])
-    assert_equal "name=#{quoted_bambi} AND id=1", Binary.send(:sanitize_sql_array, ["name=:name AND id=:id", name: "Bambi", id: 1])
+    assert_equal "name=#{quoted_bambi}", Binary.sanitize_sql_array(["name=:name", name: "Bambi"])
+    assert_equal "name=#{quoted_bambi} AND id=1", Binary.sanitize_sql_array(["name=:name AND id=:id", name: "Bambi", id: 1])
 
     quoted_bambi_and_thumper = ActiveRecord::Base.connection.quote("Bambi\nand\nThumper")
-    assert_equal "name=#{quoted_bambi_and_thumper}", Binary.send(:sanitize_sql_array, ["name=:name", name: "Bambi\nand\nThumper"])
-    assert_equal "name=#{quoted_bambi_and_thumper} AND name2=#{quoted_bambi_and_thumper}", Binary.send(:sanitize_sql_array, ["name=:name AND name2=:name", name: "Bambi\nand\nThumper"])
+    assert_equal "name=#{quoted_bambi_and_thumper}", Binary.sanitize_sql_array(["name=:name", name: "Bambi\nand\nThumper"])
+    assert_equal "name=#{quoted_bambi_and_thumper} AND name2=#{quoted_bambi_and_thumper}", Binary.sanitize_sql_array(["name=:name AND name2=:name", name: "Bambi\nand\nThumper"])
   end
 
   def test_sanitize_sql_array_handles_relations
@@ -43,42 +44,50 @@ class SanitizeTest < ActiveRecord::TestCase
 
     sub_query_pattern = /\(\bselect\b.*?\bwhere\b.*?\)/i
 
-    select_author_sql = Post.send(:sanitize_sql_array, ["id in (?)", david_posts])
+    select_author_sql = Post.sanitize_sql_array(["id in (?)", david_posts])
     assert_match(sub_query_pattern, select_author_sql, "should sanitize `Relation` as subquery for bind variables")
 
-    select_author_sql = Post.send(:sanitize_sql_array, ["id in (:post_ids)", post_ids: david_posts])
+    select_author_sql = Post.sanitize_sql_array(["id in (:post_ids)", post_ids: david_posts])
     assert_match(sub_query_pattern, select_author_sql, "should sanitize `Relation` as subquery for named bind variables")
   end
 
   def test_sanitize_sql_array_handles_empty_statement
-    select_author_sql = Post.send(:sanitize_sql_array, [""])
+    select_author_sql = Post.sanitize_sql_array([""])
     assert_equal("", select_author_sql)
   end
 
   def test_sanitize_sql_like
-    assert_equal '100\%', Binary.send(:sanitize_sql_like, "100%")
-    assert_equal 'snake\_cased\_string', Binary.send(:sanitize_sql_like, "snake_cased_string")
-    assert_equal 'C:\\\\Programs\\\\MsPaint', Binary.send(:sanitize_sql_like, 'C:\\Programs\\MsPaint')
-    assert_equal "normal string 42", Binary.send(:sanitize_sql_like, "normal string 42")
+    assert_equal '100\%', Binary.sanitize_sql_like("100%")
+    assert_equal 'snake\_cased\_string', Binary.sanitize_sql_like("snake_cased_string")
+    assert_equal 'C:\\\\Programs\\\\MsPaint', Binary.sanitize_sql_like('C:\\Programs\\MsPaint')
+    assert_equal "normal string 42", Binary.sanitize_sql_like("normal string 42")
   end
 
   def test_sanitize_sql_like_with_custom_escape_character
-    assert_equal "100!%", Binary.send(:sanitize_sql_like, "100%", "!")
-    assert_equal "snake!_cased!_string", Binary.send(:sanitize_sql_like, "snake_cased_string", "!")
-    assert_equal "great!!", Binary.send(:sanitize_sql_like, "great!", "!")
-    assert_equal 'C:\\Programs\\MsPaint', Binary.send(:sanitize_sql_like, 'C:\\Programs\\MsPaint', "!")
-    assert_equal "normal string 42", Binary.send(:sanitize_sql_like, "normal string 42", "!")
+    assert_equal "100!%", Binary.sanitize_sql_like("100%", "!")
+    assert_equal "snake!_cased!_string", Binary.sanitize_sql_like("snake_cased_string", "!")
+    assert_equal "great!!", Binary.sanitize_sql_like("great!", "!")
+    assert_equal 'C:\\Programs\\MsPaint', Binary.sanitize_sql_like('C:\\Programs\\MsPaint', "!")
+    assert_equal "normal string 42", Binary.sanitize_sql_like("normal string 42", "!")
   end
 
   def test_sanitize_sql_like_example_use_case
     searchable_post = Class.new(Post) do
-      def self.search(term)
+      def self.search_as_method(term)
         where("title LIKE ?", sanitize_sql_like(term, "!"))
       end
+
+      scope :search_as_scope, -> (term) {
+        where("title LIKE ?", sanitize_sql_like(term, "!"))
+      }
+    end
+
+    assert_sql(/LIKE '20!% !_reduction!_!!'/) do
+      searchable_post.search_as_method("20% _reduction_!").to_a
     end
 
     assert_sql(/LIKE '20!% !_reduction!_!!'/) do
-      searchable_post.search("20% _reduction_!").to_a
+      searchable_post.search_as_scope("20% _reduction_!").to_a
     end
   end
 
@@ -153,24 +162,18 @@ class SanitizeTest < ActiveRecord::TestCase
     assert_equal "name=#{quoted_bambi_and_thumper}", bind("name=?", "Bambi\nand\nThumper".mb_chars)
   end
 
-  def test_bind_record
-    o = Class.new {
-      def quoted_id
-        1
-      end
-    }.new
-    assert_deprecated { assert_equal "1", bind("?", o) }
-
-    os = [o] * 3
-    assert_deprecated { assert_equal "1,1,1", bind("?", os) }
-  end
-
   def test_named_bind_with_postgresql_type_casts
     l = Proc.new { bind(":a::integer '2009-01-01'::date", a: "10") }
     assert_nothing_raised(&l)
     assert_equal "#{ActiveRecord::Base.connection.quote('10')}::integer '2009-01-01'::date", l.call
   end
 
+  def test_deprecated_expand_hash_conditions_for_aggregates
+    assert_deprecated do
+      assert_equal({ "balance" => 50 }, Customer.send(:expand_hash_conditions_for_aggregates, balance: Money.new(50)))
+    end
+  end
+
   private
     def bind(statement, *vars)
       if vars.first.is_a?(Hash)
diff --git a/activerecord/test/cases/schema_dumper_test.rb b/activerecord/test/cases/schema_dumper_test.rb
index eb9b257da9..15f4cea1a6 100644
--- a/activerecord/test/cases/schema_dumper_test.rb
+++ b/activerecord/test/cases/schema_dumper_test.rb
@@ -37,24 +37,6 @@ class SchemaDumperTest < ActiveRecord::TestCase
     ActiveRecord::SchemaMigration.delete_all
   end
 
-  if current_adapter?(:SQLite3Adapter)
-    %w{3.7.8 3.7.11 3.7.12}.each do |version_string|
-      test "dumps schema version for sqlite version #{version_string}" do
-        version = ActiveRecord::ConnectionAdapters::SQLite3Adapter::Version.new(version_string)
-        ActiveRecord::Base.connection.stubs(:sqlite_version).returns(version)
-
-        versions = %w{ 20100101010101 20100201010101 20100301010101 }
-        versions.reverse_each do |v|
-          ActiveRecord::SchemaMigration.create!(version: v)
-        end
-
-        schema_info = ActiveRecord::Base.connection.dump_schema_information
-        assert_match(/20100201010101.*20100301010101/m, schema_info)
-        ActiveRecord::SchemaMigration.delete_all
-      end
-    end
-  end
-
   def test_schema_dump
     output = standard_dump
     assert_match %r{create_table "accounts"}, output
@@ -66,7 +48,7 @@ class SchemaDumperTest < ActiveRecord::TestCase
 
   def test_schema_dump_uses_force_cascade_on_create_table
     output = dump_table_schema "authors"
-    assert_match %r{create_table "authors", force: :cascade}, output
+    assert_match %r{create_table "authors",.* force: :cascade}, output
   end
 
   def test_schema_dump_excludes_sqlite_sequence
@@ -177,14 +159,14 @@ class SchemaDumperTest < ActiveRecord::TestCase
 
   def test_schema_dumps_index_columns_in_right_order
     index_definition = dump_table_schema("companies").split(/\n/).grep(/t\.index.*company_index/).first.strip
-    if current_adapter?(:PostgreSQLAdapter)
-      assert_equal 't.index ["firm_id", "type", "rating"], name: "company_index", order: { rating: :desc }', index_definition
-    elsif current_adapter?(:Mysql2Adapter)
+    if current_adapter?(:Mysql2Adapter)
       if ActiveRecord::Base.connection.supports_index_sort_order?
         assert_equal 't.index ["firm_id", "type", "rating"], name: "company_index", length: { type: 10 }, order: { rating: :desc }', index_definition
       else
         assert_equal 't.index ["firm_id", "type", "rating"], name: "company_index", length: { type: 10 }', index_definition
       end
+    elsif ActiveRecord::Base.connection.supports_index_sort_order?
+      assert_equal 't.index ["firm_id", "type", "rating"], name: "company_index", order: { rating: :desc }', index_definition
     else
       assert_equal 't.index ["firm_id", "type", "rating"], name: "company_index"', index_definition
     end
@@ -192,13 +174,31 @@ class SchemaDumperTest < ActiveRecord::TestCase
 
   def test_schema_dumps_partial_indices
     index_definition = dump_table_schema("companies").split(/\n/).grep(/t\.index.*company_partial_index/).first.strip
-    if current_adapter?(:PostgreSQLAdapter, :SQLite3Adapter) && ActiveRecord::Base.connection.supports_partial_index?
+    if ActiveRecord::Base.connection.supports_partial_index?
       assert_equal 't.index ["firm_id", "type"], name: "company_partial_index", where: "(rating > 10)"', index_definition
     else
       assert_equal 't.index ["firm_id", "type"], name: "company_partial_index"', index_definition
     end
   end
 
+  def test_schema_dumps_index_sort_order
+    index_definition = dump_table_schema("companies").split(/\n/).grep(/t\.index.*_name_and_rating/).first.strip
+    if ActiveRecord::Base.connection.supports_index_sort_order?
+      assert_equal 't.index ["name", "rating"], name: "index_companies_on_name_and_rating", order: :desc', index_definition
+    else
+      assert_equal 't.index ["name", "rating"], name: "index_companies_on_name_and_rating"', index_definition
+    end
+  end
+
+  def test_schema_dumps_index_length
+    index_definition = dump_table_schema("companies").split(/\n/).grep(/t\.index.*_name_and_description/).first.strip
+    if current_adapter?(:Mysql2Adapter)
+      assert_equal 't.index ["name", "description"], name: "index_companies_on_name_and_description", length: 10', index_definition
+    else
+      assert_equal 't.index ["name", "description"], name: "index_companies_on_name_and_description"', index_definition
+    end
+  end
+
   def test_schema_dump_should_honor_nonstandard_primary_keys
     output = standard_dump
     match = output.match(%r{create_table "movies"(.*)do})
@@ -207,20 +207,25 @@ class SchemaDumperTest < ActiveRecord::TestCase
   end
 
   def test_schema_dump_should_use_false_as_default
-    output = standard_dump
+    output = dump_table_schema "booleans"
     assert_match %r{t\.boolean\s+"has_fun",.+default: false}, output
   end
 
   def test_schema_dump_does_not_include_limit_for_text_field
-    output = standard_dump
+    output = dump_table_schema "admin_users"
     assert_match %r{t\.text\s+"params"$}, output
   end
 
   def test_schema_dump_does_not_include_limit_for_binary_field
-    output = standard_dump
+    output = dump_table_schema "binaries"
     assert_match %r{t\.binary\s+"data"$}, output
   end
 
+  def test_schema_dump_does_not_include_limit_for_float_field
+    output = dump_table_schema "numeric_data"
+    assert_match %r{t\.float\s+"temperature"$}, output
+  end
+
   if current_adapter?(:Mysql2Adapter)
     def test_schema_dump_includes_length_for_mysql_binary_fields
       output = standard_dump
@@ -275,7 +280,7 @@ class SchemaDumperTest < ActiveRecord::TestCase
 
     def test_schema_dump_expression_indices
       index_definition = dump_table_schema("companies").split(/\n/).grep(/t\.index.*company_expression_index/).first.strip
-      assert_equal 't.index "lower((name)::text)", name: "company_expression_index"', index_definition
+      assert_match %r{CASE.+lower\(\(name\)::text\)}i, index_definition
     end
 
     def test_schema_dump_interval_type
@@ -289,34 +294,32 @@ class SchemaDumperTest < ActiveRecord::TestCase
       assert_match %r{t\.oid\s+"obj_id"$}, output
     end
 
-    if ActiveRecord::Base.connection.supports_extensions?
-      def test_schema_dump_includes_extensions
-        connection = ActiveRecord::Base.connection
+    def test_schema_dump_includes_extensions
+      connection = ActiveRecord::Base.connection
 
-        connection.stubs(:extensions).returns(["hstore"])
-        output = perform_schema_dump
-        assert_match "# These are extensions that must be enabled", output
-        assert_match %r{enable_extension "hstore"}, output
+      connection.stubs(:extensions).returns(["hstore"])
+      output = perform_schema_dump
+      assert_match "# These are extensions that must be enabled", output
+      assert_match %r{enable_extension "hstore"}, output
 
-        connection.stubs(:extensions).returns([])
-        output = perform_schema_dump
-        assert_no_match "# These are extensions that must be enabled", output
-        assert_no_match %r{enable_extension}, output
-      end
+      connection.stubs(:extensions).returns([])
+      output = perform_schema_dump
+      assert_no_match "# These are extensions that must be enabled", output
+      assert_no_match %r{enable_extension}, output
+    end
 
-      def test_schema_dump_includes_extensions_in_alphabetic_order
-        connection = ActiveRecord::Base.connection
+    def test_schema_dump_includes_extensions_in_alphabetic_order
+      connection = ActiveRecord::Base.connection
 
-        connection.stubs(:extensions).returns(["hstore", "uuid-ossp", "xml2"])
-        output = perform_schema_dump
-        enabled_extensions = output.scan(%r{enable_extension "(.+)"}).flatten
-        assert_equal ["hstore", "uuid-ossp", "xml2"], enabled_extensions
+      connection.stubs(:extensions).returns(["hstore", "uuid-ossp", "xml2"])
+      output = perform_schema_dump
+      enabled_extensions = output.scan(%r{enable_extension "(.+)"}).flatten
+      assert_equal ["hstore", "uuid-ossp", "xml2"], enabled_extensions
 
-        connection.stubs(:extensions).returns(["uuid-ossp", "xml2", "hstore"])
-        output = perform_schema_dump
-        enabled_extensions = output.scan(%r{enable_extension "(.+)"}).flatten
-        assert_equal ["hstore", "uuid-ossp", "xml2"], enabled_extensions
-      end
+      connection.stubs(:extensions).returns(["uuid-ossp", "xml2", "hstore"])
+      output = perform_schema_dump
+      enabled_extensions = output.scan(%r{enable_extension "(.+)"}).flatten
+      assert_equal ["hstore", "uuid-ossp", "xml2"], enabled_extensions
     end
   end
 
@@ -448,7 +451,7 @@ class SchemaDumperTest < ActiveRecord::TestCase
     output = ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, stream).string
 
     assert_match %r{create_table "omg_cats"}, output
-    refute_match %r{create_table "cats"}, output
+    assert_no_match %r{create_table "cats"}, output
   ensure
     migration.migrate(:down)
     ActiveRecord::Base.table_name_prefix = original_table_name_prefix
diff --git a/activerecord/test/cases/scoping/default_scoping_test.rb b/activerecord/test/cases/scoping/default_scoping_test.rb
index 716ca29eda..e3a34aa50d 100644
--- a/activerecord/test/cases/scoping/default_scoping_test.rb
+++ b/activerecord/test/cases/scoping/default_scoping_test.rb
@@ -120,49 +120,49 @@ class DefaultScopingTest < ActiveRecord::TestCase
   def test_unscope_with_where_attributes
     expected = Developer.order("salary DESC").collect(&:name)
     received = DeveloperOrderedBySalary.where(name: "David").unscope(where: :name).collect(&:name)
-    assert_equal expected, received
+    assert_equal expected.sort, received.sort
 
     expected_2 = Developer.order("salary DESC").collect(&:name)
     received_2 = DeveloperOrderedBySalary.select("id").where("name" => "Jamis").unscope({ where: :name }, :select).collect(&:name)
-    assert_equal expected_2, received_2
+    assert_equal expected_2.sort, received_2.sort
 
     expected_3 = Developer.order("salary DESC").collect(&:name)
     received_3 = DeveloperOrderedBySalary.select("id").where("name" => "Jamis").unscope(:select, :where).collect(&:name)
-    assert_equal expected_3, received_3
+    assert_equal expected_3.sort, received_3.sort
 
     expected_4 = Developer.order("salary DESC").collect(&:name)
     received_4 = DeveloperOrderedBySalary.where.not("name" => "Jamis").unscope(where: :name).collect(&:name)
-    assert_equal expected_4, received_4
+    assert_equal expected_4.sort, received_4.sort
 
     expected_5 = Developer.order("salary DESC").collect(&:name)
     received_5 = DeveloperOrderedBySalary.where.not("name" => ["Jamis", "David"]).unscope(where: :name).collect(&:name)
-    assert_equal expected_5, received_5
+    assert_equal expected_5.sort, received_5.sort
 
     expected_6 = Developer.order("salary DESC").collect(&:name)
     received_6 = DeveloperOrderedBySalary.where(Developer.arel_table["name"].eq("David")).unscope(where: :name).collect(&:name)
-    assert_equal expected_6, received_6
+    assert_equal expected_6.sort, received_6.sort
 
     expected_7 = Developer.order("salary DESC").collect(&:name)
     received_7 = DeveloperOrderedBySalary.where(Developer.arel_table[:name].eq("David")).unscope(where: :name).collect(&:name)
-    assert_equal expected_7, received_7
+    assert_equal expected_7.sort, received_7.sort
   end
 
   def test_unscope_comparison_where_clauses
     # unscoped for WHERE (`developers`.`id` <= 2)
     expected = Developer.order("salary DESC").collect(&:name)
     received = DeveloperOrderedBySalary.where(id: -Float::INFINITY..2).unscope(where: :id).collect { |dev| dev.name }
-    assert_equal expected, received
+    assert_equal expected.sort, received.sort
 
     # unscoped for WHERE (`developers`.`id` < 2)
     expected = Developer.order("salary DESC").collect(&:name)
     received = DeveloperOrderedBySalary.where(id: -Float::INFINITY...2).unscope(where: :id).collect { |dev| dev.name }
-    assert_equal expected, received
+    assert_equal expected.sort, received.sort
   end
 
   def test_unscope_multiple_where_clauses
     expected = Developer.order("salary DESC").collect(&:name)
     received = DeveloperOrderedBySalary.where(name: "Jamis").where(id: 1).unscope(where: [:name, :id]).collect(&:name)
-    assert_equal expected, received
+    assert_equal expected.sort, received.sort
   end
 
   def test_unscope_string_where_clauses_involved
@@ -172,28 +172,28 @@ class DefaultScopingTest < ActiveRecord::TestCase
     dev_ordered_relation = DeveloperOrderedBySalary.where(name: "Jamis").where("created_at > ?", 1.year.ago)
     received = dev_ordered_relation.unscope(where: [:name]).collect(&:name)
 
-    assert_equal expected, received
+    assert_equal expected.sort, received.sort
   end
 
   def test_unscope_with_grouping_attributes
     expected = Developer.order("salary DESC").collect(&:name)
     received = DeveloperOrderedBySalary.group(:name).unscope(:group).collect(&:name)
-    assert_equal expected, received
+    assert_equal expected.sort, received.sort
 
     expected_2 = Developer.order("salary DESC").collect(&:name)
     received_2 = DeveloperOrderedBySalary.group("name").unscope(:group).collect(&:name)
-    assert_equal expected_2, received_2
+    assert_equal expected_2.sort, received_2.sort
   end
 
   def test_unscope_with_limit_in_query
     expected = Developer.order("salary DESC").collect(&:name)
     received = DeveloperOrderedBySalary.limit(1).unscope(:limit).collect(&:name)
-    assert_equal expected, received
+    assert_equal expected.sort, received.sort
   end
 
   def test_order_to_unscope_reordering
     scope = DeveloperOrderedBySalary.order("salary DESC, name ASC").reverse_order.unscope(:order)
-    assert !/order/i.match?(scope.to_sql)
+    assert_no_match(/order/i, scope.to_sql)
   end
 
   def test_unscope_reverse_order
@@ -224,6 +224,18 @@ class DefaultScopingTest < ActiveRecord::TestCase
     assert_equal expected, received
   end
 
+  def test_unscope_left_outer_joins
+    expected = Developer.all.collect(&:name)
+    received = Developer.left_outer_joins(:projects).select(:id).unscope(:left_outer_joins, :select).collect(&:name)
+    assert_equal expected, received
+  end
+
+  def test_unscope_left_joins
+    expected = Developer.all.collect(&:name)
+    received = Developer.left_joins(:projects).select(:id).unscope(:left_joins, :select).collect(&:name)
+    assert_equal expected, received
+  end
+
   def test_unscope_includes
     expected = Developer.all.collect(&:name)
     received = Developer.includes(:projects).select(:id).unscope(:includes, :select).collect(&:name)
@@ -290,8 +302,8 @@ class DefaultScopingTest < ActiveRecord::TestCase
 
   def test_unscope_merging
     merged = Developer.where(name: "Jamis").merge(Developer.unscope(:where))
-    assert merged.where_clause.empty?
-    assert !merged.where(name: "Jon").where_clause.empty?
+    assert_empty merged.where_clause
+    assert_not_empty merged.where(name: "Jon").where_clause
   end
 
   def test_order_in_default_scope_should_not_prevail
@@ -472,7 +484,7 @@ class DefaultScopingTest < ActiveRecord::TestCase
   test "a scope can remove the condition from the default scope" do
     scope = DeveloperCalledJamis.david2
     assert_equal 1, scope.where_clause.ast.children.length
-    assert_equal Developer.where(name: "David"), scope
+    assert_equal Developer.where(name: "David").map(&:id), scope.map(&:id)
   end
 
   def test_with_abstract_class_where_clause_should_not_be_duplicated
diff --git a/activerecord/test/cases/scoping/named_scoping_test.rb b/activerecord/test/cases/scoping/named_scoping_test.rb
index b0431a4e34..4214f347fb 100644
--- a/activerecord/test/cases/scoping/named_scoping_test.rb
+++ b/activerecord/test/cases/scoping/named_scoping_test.rb
@@ -13,7 +13,7 @@ class NamedScopingTest < ActiveRecord::TestCase
   fixtures :posts, :authors, :topics, :comments, :author_addresses
 
   def test_implements_enumerable
-    assert !Topic.all.empty?
+    assert_not_empty Topic.all
 
     assert_equal Topic.all.to_a, Topic.base
     assert_equal Topic.all.to_a, Topic.base.to_a
@@ -40,7 +40,7 @@ class NamedScopingTest < ActiveRecord::TestCase
   end
 
   def test_delegates_finds_and_calculations_to_the_base_class
-    assert !Topic.all.empty?
+    assert_not_empty Topic.all
 
     assert_equal Topic.all.to_a,                Topic.base.to_a
     assert_equal Topic.first,                   Topic.base.first
@@ -65,13 +65,13 @@ class NamedScopingTest < ActiveRecord::TestCase
   end
 
   def test_scope_should_respond_to_own_methods_and_methods_of_the_proxy
-    assert Topic.approved.respond_to?(:limit)
-    assert Topic.approved.respond_to?(:count)
-    assert Topic.approved.respond_to?(:length)
+    assert_respond_to Topic.approved, :limit
+    assert_respond_to Topic.approved, :count
+    assert_respond_to Topic.approved, :length
   end
 
   def test_scopes_with_options_limit_finds_to_those_matching_the_criteria_specified
-    assert !Topic.all.merge!(where: { approved: true }).to_a.empty?
+    assert_not_empty Topic.all.merge!(where: { approved: true }).to_a
 
     assert_equal Topic.all.merge!(where: { approved: true }).to_a, Topic.approved
     assert_equal Topic.where(approved: true).count, Topic.approved.count
@@ -86,8 +86,8 @@ class NamedScopingTest < ActiveRecord::TestCase
   def test_scopes_are_composable
     assert_equal((approved = Topic.all.merge!(where: { approved: true }).to_a), Topic.approved)
     assert_equal((replied = Topic.all.merge!(where: "replies_count > 0").to_a), Topic.replied)
-    assert !(approved == replied)
-    assert !(approved & replied).empty?
+    assert_not (approved == replied)
+    assert_not_empty (approved & replied)
 
     assert_equal approved & replied, Topic.approved.replied
   end
@@ -115,7 +115,7 @@ class NamedScopingTest < ActiveRecord::TestCase
 
   def test_has_many_associations_have_access_to_scopes
     assert_not_equal Post.containing_the_letter_a, authors(:david).posts
-    assert !Post.containing_the_letter_a.empty?
+    assert_not_empty Post.containing_the_letter_a
 
     expected = authors(:david).posts & Post.containing_the_letter_a
     assert_equal expected.sort_by(&:id), authors(:david).posts.containing_the_letter_a.sort_by(&:id)
@@ -128,15 +128,15 @@ class NamedScopingTest < ActiveRecord::TestCase
 
   def test_has_many_through_associations_have_access_to_scopes
     assert_not_equal Comment.containing_the_letter_e, authors(:david).comments
-    assert !Comment.containing_the_letter_e.empty?
+    assert_not_empty Comment.containing_the_letter_e
 
     expected = authors(:david).comments & Comment.containing_the_letter_e
     assert_equal expected.sort_by(&:id), authors(:david).comments.containing_the_letter_e.sort_by(&:id)
   end
 
   def test_scopes_honor_current_scopes_from_when_defined
-    assert !Post.ranked_by_comments.limit_by(5).empty?
-    assert !authors(:david).posts.ranked_by_comments.limit_by(5).empty?
+    assert_not_empty Post.ranked_by_comments.limit_by(5)
+    assert_not_empty authors(:david).posts.ranked_by_comments.limit_by(5)
     assert_not_equal Post.ranked_by_comments.limit_by(5), authors(:david).posts.ranked_by_comments.limit_by(5)
     assert_not_equal Post.top(5), authors(:david).posts.top(5)
     # Oracle sometimes sorts differently if WHERE condition is changed
@@ -151,15 +151,31 @@ class NamedScopingTest < ActiveRecord::TestCase
     assert_equal "The scope body needs to be callable.", e.message
   end
 
+  def test_scopes_name_is_relation_method
+    conflicts = [
+      :records,
+      :to_ary,
+      :to_sql,
+      :explain
+    ]
+
+    conflicts.each do |name|
+      e = assert_raises ArgumentError do
+        Class.new(Post).class_eval { scope name, -> { where(approved: true) } }
+      end
+      assert_match(/You tried to define a scope named \"#{name}\" on the model/, e.message)
+    end
+  end
+
   def test_active_records_have_scope_named__all__
-    assert !Topic.all.empty?
+    assert_not_empty Topic.all
 
     assert_equal Topic.all.to_a, Topic.base
   end
 
   def test_active_records_have_scope_named__scoped__
     scope = Topic.where("content LIKE '%Have%'")
-    assert !scope.empty?
+    assert_not_empty scope
 
     assert_equal scope, Topic.all.merge!(where: "content LIKE '%Have%'")
   end
@@ -212,9 +228,9 @@ class NamedScopingTest < ActiveRecord::TestCase
   end
 
   def test_model_class_should_respond_to_any
-    assert Topic.any?
+    assert_predicate Topic, :any?
     Topic.delete_all
-    assert !Topic.any?
+    assert_not_predicate Topic, :any?
   end
 
   def test_many_should_not_load_results
@@ -243,22 +259,22 @@ class NamedScopingTest < ActiveRecord::TestCase
 
   def test_many_should_return_false_if_none_or_one
     topics = Topic.base.where(id: 0)
-    assert !topics.many?
+    assert_not_predicate topics, :many?
     topics = Topic.base.where(id: 1)
-    assert !topics.many?
+    assert_not_predicate topics, :many?
   end
 
   def test_many_should_return_true_if_more_than_one
-    assert Topic.base.many?
+    assert_predicate Topic.base, :many?
   end
 
   def test_model_class_should_respond_to_many
     Topic.delete_all
-    assert !Topic.many?
+    assert_not_predicate Topic, :many?
     Topic.create!
-    assert !Topic.many?
+    assert_not_predicate Topic, :many?
     Topic.create!
-    assert Topic.many?
+    assert_predicate Topic, :many?
   end
 
   def test_should_build_on_top_of_scope
@@ -287,6 +303,13 @@ class NamedScopingTest < ActiveRecord::TestCase
     assert_equal "lifo", topic.author_name
   end
 
+  def test_deprecated_delegating_private_method
+    assert_deprecated do
+      scope = Topic.all.by_private_lifo
+      assert_not scope.instance_variable_get(:@delegate_to_klass)
+    end
+  end
+
   def test_reserved_scope_names
     klass = Class.new(ActiveRecord::Base) do
       self.table_name = "topics"
@@ -407,16 +430,16 @@ class NamedScopingTest < ActiveRecord::TestCase
 
   def test_chaining_applies_last_conditions_when_creating
     post = Topic.rejected.new
-    assert !post.approved?
+    assert_not_predicate post, :approved?
 
     post = Topic.rejected.approved.new
-    assert post.approved?
+    assert_predicate post, :approved?
 
     post = Topic.approved.rejected.new
-    assert !post.approved?
+    assert_not_predicate post, :approved?
 
     post = Topic.approved.rejected.approved.new
-    assert post.approved?
+    assert_predicate post, :approved?
   end
 
   def test_chaining_combines_conditions_when_searching
@@ -465,8 +488,9 @@ class NamedScopingTest < ActiveRecord::TestCase
 
     [:public_method, :protected_method, :private_method].each do |reserved_method|
       assert Topic.respond_to?(reserved_method, true)
-      ActiveRecord::Base.logger.expects(:warn)
-      silence_warnings { Topic.scope(reserved_method, -> {}) }
+      assert_called(ActiveRecord::Base.logger, :warn) do
+        silence_warnings { Topic.scope(reserved_method, -> {}) }
+      end
     end
   end
 
@@ -482,7 +506,7 @@ class NamedScopingTest < ActiveRecord::TestCase
   def test_index_on_scope
     approved = Topic.approved.order("id ASC")
     assert_equal topics(:second), approved[0]
-    assert approved.loaded?
+    assert_predicate approved, :loaded?
   end
 
   def test_nested_scopes_queries_size
@@ -562,16 +586,16 @@ class NamedScopingTest < ActiveRecord::TestCase
   end
 
   def test_model_class_should_respond_to_none
-    assert !Topic.none?
+    assert_not_predicate Topic, :none?
     Topic.delete_all
-    assert Topic.none?
+    assert_predicate Topic, :none?
   end
 
   def test_model_class_should_respond_to_one
-    assert !Topic.one?
+    assert_not_predicate Topic, :one?
     Topic.delete_all
-    assert !Topic.one?
+    assert_not_predicate Topic, :one?
     Topic.create!
-    assert Topic.one?
+    assert_predicate Topic, :one?
   end
 end
diff --git a/activerecord/test/cases/scoping/relation_scoping_test.rb b/activerecord/test/cases/scoping/relation_scoping_test.rb
index f3b84d88c2..f18f1ed981 100644
--- a/activerecord/test/cases/scoping/relation_scoping_test.rb
+++ b/activerecord/test/cases/scoping/relation_scoping_test.rb
@@ -105,7 +105,7 @@ class RelationScopingTest < ActiveRecord::TestCase
     Developer.select("id, name").scoping do
       developer = Developer.where("name = 'David'").first
       assert_equal "David", developer.name
-      assert !developer.has_attribute?(:salary)
+      assert_not developer.has_attribute?(:salary)
     end
   end
 
@@ -213,21 +213,21 @@ class RelationScopingTest < ActiveRecord::TestCase
 
   def test_current_scope_does_not_pollute_sibling_subclasses
     Comment.none.scoping do
-      assert_not SpecialComment.all.any?
-      assert_not VerySpecialComment.all.any?
-      assert_not SubSpecialComment.all.any?
+      assert_not_predicate SpecialComment.all, :any?
+      assert_not_predicate VerySpecialComment.all, :any?
+      assert_not_predicate SubSpecialComment.all, :any?
     end
 
     SpecialComment.none.scoping do
-      assert Comment.all.any?
-      assert VerySpecialComment.all.any?
-      assert_not SubSpecialComment.all.any?
+      assert_predicate Comment.all, :any?
+      assert_predicate VerySpecialComment.all, :any?
+      assert_not_predicate SubSpecialComment.all, :any?
     end
 
     SubSpecialComment.none.scoping do
-      assert Comment.all.any?
-      assert VerySpecialComment.all.any?
-      assert SpecialComment.all.any?
+      assert_predicate Comment.all, :any?
+      assert_predicate VerySpecialComment.all, :any?
+      assert_predicate SpecialComment.all, :any?
     end
   end
 
@@ -240,6 +240,20 @@ class RelationScopingTest < ActiveRecord::TestCase
     assert_nil SpecialComment.current_scope
   end
 
+  def test_scoping_respects_current_class
+    Comment.unscoped do
+      assert_equal "a comment...", Comment.all.what_are_you
+      assert_equal "a special comment...", SpecialComment.all.what_are_you
+    end
+  end
+
+  def test_scoping_respects_sti_constraint
+    Comment.unscoped do
+      assert_equal comments(:greetings), Comment.find(1)
+      assert_raises(ActiveRecord::RecordNotFound) { SpecialComment.find(1) }
+    end
+  end
+
   def test_circular_joins_with_scoping_does_not_crash
     posts = Post.joins(comments: :post).scoping do
       Post.first(10)
@@ -320,7 +334,7 @@ class NestedRelationScopingTest < ActiveRecord::TestCase
   def test_nested_exclusive_scope_for_create
     comment = Comment.create_with(body: "Hey guys, nested scopes are broken. Please fix!").scoping do
       Comment.unscoped.create_with(post_id: 1).scoping do
-        assert Comment.new.body.blank?
+        assert_predicate Comment.new.body, :blank?
         Comment.create body: "Hey guys"
       end
     end
diff --git a/activerecord/test/cases/serialization_test.rb b/activerecord/test/cases/serialization_test.rb
index 2d829ad4ba..932780bfef 100644
--- a/activerecord/test/cases/serialization_test.rb
+++ b/activerecord/test/cases/serialization_test.rb
@@ -67,8 +67,8 @@ class SerializationTest < ActiveRecord::TestCase
 
     klazz.include_root_in_json = false
     assert ActiveRecord::Base.include_root_in_json
-    assert !klazz.include_root_in_json
-    assert !klazz.new.include_root_in_json
+    assert_not klazz.include_root_in_json
+    assert_not klazz.new.include_root_in_json
   ensure
     ActiveRecord::Base.include_root_in_json = original_root_in_json
   end
diff --git a/activerecord/test/cases/serialized_attribute_test.rb b/activerecord/test/cases/serialized_attribute_test.rb
index 32dafbd458..7de5429cbb 100644
--- a/activerecord/test/cases/serialized_attribute_test.rb
+++ b/activerecord/test/cases/serialized_attribute_test.rb
@@ -279,7 +279,7 @@ class SerializedAttributeTest < ActiveRecord::TestCase
 
     topic = Topic.new(content: nil)
 
-    assert_not topic.content_changed?
+    assert_not_predicate topic, :content_changed?
   end
 
   def test_classes_without_no_arg_constructors_are_not_supported
@@ -349,7 +349,7 @@ class SerializedAttributeTest < ActiveRecord::TestCase
 
     topic = model.create!(foo: "bar")
     topic.foo
-    refute topic.changed?
+    assert_not_predicate topic, :changed?
   end
 
   def test_serialized_attribute_works_under_concurrent_initial_access
diff --git a/activerecord/test/cases/statement_cache_test.rb b/activerecord/test/cases/statement_cache_test.rb
index 1f715e41a6..e3c12f68fd 100644
--- a/activerecord/test/cases/statement_cache_test.rb
+++ b/activerecord/test/cases/statement_cache_test.rb
@@ -12,7 +12,6 @@ module ActiveRecord
       @connection = ActiveRecord::Base.connection
     end
 
-    #Cache v 1.1 tests
     def test_statement_cache
       Book.create(name: "my book")
       Book.create(name: "my other book")
@@ -51,8 +50,6 @@ module ActiveRecord
       assert_equal("my other book", b.name)
     end
 
-    #End
-
     def test_statement_cache_with_simple_statement
       cache = ActiveRecord::StatementCache.create(Book.connection) do |params|
         Book.where(name: "my book").where("author_id > 3")
@@ -105,7 +102,7 @@ module ActiveRecord
         Book.find_by(name: "my other book")
       end
 
-      refute_equal book, other_book
+      assert_not_equal book, other_book
     end
 
     def test_find_by_does_not_use_statement_cache_if_table_name_is_changed
diff --git a/activerecord/test/cases/store_test.rb b/activerecord/test/cases/store_test.rb
index ebf4016960..3bd480cfbd 100644
--- a/activerecord/test/cases/store_test.rb
+++ b/activerecord/test/cases/store_test.rb
@@ -8,7 +8,12 @@ class StoreTest < ActiveRecord::TestCase
   fixtures :'admin/users'
 
   setup do
-    @john = Admin::User.create!(name: "John Doe", color: "black", remember_login: true, height: "tall", is_a_good_guy: true)
+    @john = Admin::User.create!(
+      name: "John Doe", color: "black", remember_login: true,
+      height: "tall", is_a_good_guy: true,
+      parent_name: "Quinn", partner_name: "Dallas",
+      partner_birthday: "1997-11-1"
+    )
   end
 
   test "reading store attributes through accessors" do
@@ -24,6 +29,21 @@ class StoreTest < ActiveRecord::TestCase
     assert_equal "37signals.com", @john.homepage
   end
 
+  test "reading store attributes through accessors with prefix" do
+    assert_equal "Quinn", @john.parent_name
+    assert_nil @john.parent_birthday
+    assert_equal "Dallas", @john.partner_name
+    assert_equal "1997-11-1", @john.partner_birthday
+  end
+
+  test "writing store attributes through accessors with prefix" do
+    @john.partner_name = "River"
+    @john.partner_birthday = "1999-2-11"
+
+    assert_equal "River", @john.partner_name
+    assert_equal "1999-2-11", @john.partner_birthday
+  end
+
   test "accessing attributes not exposed by accessors" do
     @john.settings[:icecream] = "graeters"
     @john.save
@@ -45,7 +65,7 @@ class StoreTest < ActiveRecord::TestCase
 
   test "updating the store will mark it as changed" do
     @john.color = "red"
-    assert @john.settings_changed?
+    assert_predicate @john, :settings_changed?
   end
 
   test "updating the store populates the changed array correctly" do
@@ -56,7 +76,7 @@ class StoreTest < ActiveRecord::TestCase
 
   test "updating the store won't mark it as changed if an attribute isn't changed" do
     @john.color = @john.color
-    assert !@john.settings_changed?
+    assert_not_predicate @john, :settings_changed?
   end
 
   test "object initialization with not nullable column" do
@@ -137,7 +157,7 @@ class StoreTest < ActiveRecord::TestCase
 
   test "updating the store will mark it as changed encoded with JSON" do
     @john.height = "short"
-    assert @john.json_data_changed?
+    assert_predicate @john, :json_data_changed?
   end
 
   test "object initialization with not nullable column encoded with JSON" do
diff --git a/activerecord/test/cases/tasks/database_tasks_test.rb b/activerecord/test/cases/tasks/database_tasks_test.rb
index 1495d2ab89..60c7cb1bb4 100644
--- a/activerecord/test/cases/tasks/database_tasks_test.rb
+++ b/activerecord/test/cases/tasks/database_tasks_test.rb
@@ -28,15 +28,32 @@ module ActiveRecord
 
   class DatabaseTasksUtilsTask < ActiveRecord::TestCase
     def test_raises_an_error_when_called_with_protected_environment
-      ActiveRecord::Migrator.stubs(:current_version).returns(1)
+      ActiveRecord::MigrationContext.any_instance.stubs(:current_version).returns(1)
 
-      protected_environments = ActiveRecord::Base.protected_environments.dup
-      current_env            = ActiveRecord::Migrator.current_environment
+      protected_environments = ActiveRecord::Base.protected_environments
+      current_env            = ActiveRecord::Base.connection.migration_context.current_environment
       assert_not_includes protected_environments, current_env
       # Assert no error
       ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
 
-      ActiveRecord::Base.protected_environments << current_env
+      ActiveRecord::Base.protected_environments = [current_env]
+      assert_raise(ActiveRecord::ProtectedEnvironmentError) do
+        ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
+      end
+    ensure
+      ActiveRecord::Base.protected_environments = protected_environments
+    end
+
+    def test_raises_an_error_when_called_with_protected_environment_which_name_is_a_symbol
+      ActiveRecord::MigrationContext.any_instance.stubs(:current_version).returns(1)
+
+      protected_environments = ActiveRecord::Base.protected_environments
+      current_env            = ActiveRecord::Base.connection.migration_context.current_environment
+      assert_not_includes protected_environments, current_env
+      # Assert no error
+      ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
+
+      ActiveRecord::Base.protected_environments = [current_env.to_sym]
       assert_raise(ActiveRecord::ProtectedEnvironmentError) do
         ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
       end
@@ -46,7 +63,7 @@ module ActiveRecord
 
     def test_raises_an_error_if_no_migrations_have_been_made
       ActiveRecord::InternalMetadata.stubs(:table_exists?).returns(false)
-      ActiveRecord::Migrator.stubs(:current_version).returns(1)
+      ActiveRecord::MigrationContext.any_instance.stubs(:current_version).returns(1)
 
       assert_raise(ActiveRecord::NoEnvironmentInSchemaError) do
         ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
@@ -63,10 +80,11 @@ module ActiveRecord
       instance = klazz.new
 
       klazz.stubs(:new).returns instance
-      instance.expects(:structure_dump).with("awesome-file.sql", nil)
 
-      ActiveRecord::Tasks::DatabaseTasks.register_task(/foo/, klazz)
-      ActiveRecord::Tasks::DatabaseTasks.structure_dump({ "adapter" => :foo }, "awesome-file.sql")
+      assert_called_with(instance, :structure_dump, ["awesome-file.sql", nil]) do
+        ActiveRecord::Tasks::DatabaseTasks.register_task(/foo/, klazz)
+        ActiveRecord::Tasks::DatabaseTasks.structure_dump({ "adapter" => :foo }, "awesome-file.sql")
+      end
     end
 
     def test_unregistered_task
@@ -93,6 +111,7 @@ module ActiveRecord
       ActiveRecord::Tasks::DatabaseTasks.dump_schema_cache(ActiveRecord::Base.connection, path)
       assert File.file?(path)
     ensure
+      ActiveRecord::Base.clear_cache!
       FileUtils.rm_rf(path)
     end
   end
@@ -109,50 +128,50 @@ module ActiveRecord
     def test_ignores_configurations_without_databases
       @configurations["development"].merge!("database" => nil)
 
-      ActiveRecord::Tasks::DatabaseTasks.expects(:create).never
-
-      ActiveRecord::Tasks::DatabaseTasks.create_all
+      assert_not_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
+        ActiveRecord::Tasks::DatabaseTasks.create_all
+      end
     end
 
     def test_ignores_remote_databases
       @configurations["development"].merge!("host" => "my.server.tld")
       $stderr.stubs(:puts).returns(nil)
 
-      ActiveRecord::Tasks::DatabaseTasks.expects(:create).never
-
-      ActiveRecord::Tasks::DatabaseTasks.create_all
+      assert_not_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
+        ActiveRecord::Tasks::DatabaseTasks.create_all
+      end
     end
 
     def test_warning_for_remote_databases
       @configurations["development"].merge!("host" => "my.server.tld")
 
-      $stderr.expects(:puts).with("This task only modifies local databases. my-db is on a remote host.")
-
-      ActiveRecord::Tasks::DatabaseTasks.create_all
+      assert_called_with($stderr, :puts, ["This task only modifies local databases. my-db is on a remote host."]) do
+        ActiveRecord::Tasks::DatabaseTasks.create_all
+      end
     end
 
     def test_creates_configurations_with_local_ip
       @configurations["development"].merge!("host" => "127.0.0.1")
 
-      ActiveRecord::Tasks::DatabaseTasks.expects(:create)
-
-      ActiveRecord::Tasks::DatabaseTasks.create_all
+      assert_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
+        ActiveRecord::Tasks::DatabaseTasks.create_all
+      end
     end
 
     def test_creates_configurations_with_local_host
       @configurations["development"].merge!("host" => "localhost")
 
-      ActiveRecord::Tasks::DatabaseTasks.expects(:create)
-
-      ActiveRecord::Tasks::DatabaseTasks.create_all
+      assert_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
+        ActiveRecord::Tasks::DatabaseTasks.create_all
+      end
     end
 
     def test_creates_configurations_with_blank_hosts
       @configurations["development"].merge!("host" => nil)
 
-      ActiveRecord::Tasks::DatabaseTasks.expects(:create)
-
-      ActiveRecord::Tasks::DatabaseTasks.create_all
+      assert_called(ActiveRecord::Tasks::DatabaseTasks, :create) do
+        ActiveRecord::Tasks::DatabaseTasks.create_all
+      end
     end
   end
 
@@ -161,7 +180,7 @@ module ActiveRecord
       @configurations = {
         "development" => { "database" => "dev-db" },
         "test"        => { "database" => "test-db" },
-        "production"  => { "database" => "prod-db" }
+        "production"  => { "url" => "prod-db-url" }
       }
 
       ActiveRecord::Base.stubs(:configurations).returns(@configurations)
@@ -169,8 +188,96 @@ module ActiveRecord
     end
 
     def test_creates_current_environment_database
+      assert_called_with(
+        ActiveRecord::Tasks::DatabaseTasks,
+        :create,
+        ["database" => "test-db"],
+      ) do
+        ActiveRecord::Tasks::DatabaseTasks.create_current(
+          ActiveSupport::StringInquirer.new("test")
+        )
+      end
+    end
+
+    def test_creates_current_environment_database_with_url
+      assert_called_with(
+        ActiveRecord::Tasks::DatabaseTasks,
+        :create,
+        ["url" => "prod-db-url"],
+      ) do
+        ActiveRecord::Tasks::DatabaseTasks.create_current(
+          ActiveSupport::StringInquirer.new("production")
+        )
+      end
+    end
+
+    def test_creates_test_and_development_databases_when_env_was_not_specified
       ActiveRecord::Tasks::DatabaseTasks.expects(:create).
-        with("database" => "prod-db")
+        with("database" => "dev-db")
+      ActiveRecord::Tasks::DatabaseTasks.expects(:create).
+        with("database" => "test-db")
+
+      ActiveRecord::Tasks::DatabaseTasks.create_current(
+        ActiveSupport::StringInquirer.new("development")
+      )
+    end
+
+    def test_creates_test_and_development_databases_when_rails_env_is_development
+      old_env = ENV["RAILS_ENV"]
+      ENV["RAILS_ENV"] = "development"
+      ActiveRecord::Tasks::DatabaseTasks.expects(:create).
+        with("database" => "dev-db")
+      ActiveRecord::Tasks::DatabaseTasks.expects(:create).
+        with("database" => "test-db")
+
+      ActiveRecord::Tasks::DatabaseTasks.create_current(
+        ActiveSupport::StringInquirer.new("development")
+      )
+    ensure
+      ENV["RAILS_ENV"] = old_env
+    end
+
+    def test_establishes_connection_for_the_given_environments
+      ActiveRecord::Tasks::DatabaseTasks.stubs(:create).returns true
+
+      ActiveRecord::Base.expects(:establish_connection).with(:development)
+
+      ActiveRecord::Tasks::DatabaseTasks.create_current(
+        ActiveSupport::StringInquirer.new("development")
+      )
+    end
+  end
+
+  class DatabaseTasksCreateCurrentThreeTierTest < ActiveRecord::TestCase
+    def setup
+      @configurations = {
+        "development" => { "primary" => { "database" => "dev-db" }, "secondary" => { "database" => "secondary-dev-db" } },
+        "test" => { "primary" => { "database" => "test-db" }, "secondary" => { "database" => "secondary-test-db" } },
+        "production" => { "primary" => { "url" => "prod-db-url" }, "secondary" => { "url" => "secondary-prod-db-url" } }
+      }
+
+      ActiveRecord::Base.stubs(:configurations).returns(@configurations)
+      ActiveRecord::Base.stubs(:establish_connection).returns(true)
+    end
+
+    def test_creates_current_environment_database
+      ActiveRecord::Tasks::DatabaseTasks.expects(:create).
+        with("database" => "test-db")
+
+      ActiveRecord::Tasks::DatabaseTasks.expects(:create).
+        with("database" => "secondary-test-db")
+
+      ActiveRecord::Tasks::DatabaseTasks.create_current(
+        ActiveSupport::StringInquirer.new("test")
+      )
+    end
+
+    def test_creates_current_environment_database_with_url
+      ActiveRecord::Tasks::DatabaseTasks.expects(:create).
+        with("url" => "prod-db-url")
+
+      ActiveRecord::Tasks::DatabaseTasks.expects(:create).
+        with("url" => "secondary-prod-db-url")
 
       ActiveRecord::Tasks::DatabaseTasks.create_current(
         ActiveSupport::StringInquirer.new("production")
@@ -181,7 +288,11 @@ module ActiveRecord
       ActiveRecord::Tasks::DatabaseTasks.expects(:create).
         with("database" => "dev-db")
       ActiveRecord::Tasks::DatabaseTasks.expects(:create).
+        with("database" => "secondary-dev-db")
+      ActiveRecord::Tasks::DatabaseTasks.expects(:create).
         with("database" => "test-db")
+      ActiveRecord::Tasks::DatabaseTasks.expects(:create).
+        with("database" => "secondary-test-db")
 
       ActiveRecord::Tasks::DatabaseTasks.create_current(
         ActiveSupport::StringInquirer.new("development")
@@ -194,7 +305,11 @@ module ActiveRecord
       ActiveRecord::Tasks::DatabaseTasks.expects(:create).
         with("database" => "dev-db")
       ActiveRecord::Tasks::DatabaseTasks.expects(:create).
+        with("database" => "secondary-dev-db")
+      ActiveRecord::Tasks::DatabaseTasks.expects(:create).
         with("database" => "test-db")
+      ActiveRecord::Tasks::DatabaseTasks.expects(:create).
+        with("database" => "secondary-test-db")
 
       ActiveRecord::Tasks::DatabaseTasks.create_current(
         ActiveSupport::StringInquirer.new("development")
@@ -203,7 +318,7 @@ module ActiveRecord
       ENV["RAILS_ENV"] = old_env
     end
 
-    def test_establishes_connection_for_the_given_environment
+    def test_establishes_connection_for_the_given_environments_config
       ActiveRecord::Tasks::DatabaseTasks.stubs(:create).returns true
 
       ActiveRecord::Base.expects(:establish_connection).with(:development)
@@ -235,50 +350,54 @@ module ActiveRecord
     def test_ignores_configurations_without_databases
       @configurations[:development].merge!("database" => nil)
 
-      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).never
-
-      ActiveRecord::Tasks::DatabaseTasks.drop_all
+      assert_not_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
+        ActiveRecord::Tasks::DatabaseTasks.drop_all
+      end
     end
 
     def test_ignores_remote_databases
       @configurations[:development].merge!("host" => "my.server.tld")
       $stderr.stubs(:puts).returns(nil)
 
-      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).never
-
-      ActiveRecord::Tasks::DatabaseTasks.drop_all
+      assert_not_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
+        ActiveRecord::Tasks::DatabaseTasks.drop_all
+      end
     end
 
     def test_warning_for_remote_databases
       @configurations[:development].merge!("host" => "my.server.tld")
 
-      $stderr.expects(:puts).with("This task only modifies local databases. my-db is on a remote host.")
-
-      ActiveRecord::Tasks::DatabaseTasks.drop_all
+      assert_called_with(
+        $stderr,
+        :puts,
+        ["This task only modifies local databases. my-db is on a remote host."],
+      ) do
+        ActiveRecord::Tasks::DatabaseTasks.drop_all
+      end
     end
 
     def test_drops_configurations_with_local_ip
       @configurations[:development].merge!("host" => "127.0.0.1")
 
-      ActiveRecord::Tasks::DatabaseTasks.expects(:drop)
-
-      ActiveRecord::Tasks::DatabaseTasks.drop_all
+      assert_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
+        ActiveRecord::Tasks::DatabaseTasks.drop_all
+      end
     end
 
     def test_drops_configurations_with_local_host
       @configurations[:development].merge!("host" => "localhost")
 
-      ActiveRecord::Tasks::DatabaseTasks.expects(:drop)
-
-      ActiveRecord::Tasks::DatabaseTasks.drop_all
+      assert_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
+        ActiveRecord::Tasks::DatabaseTasks.drop_all
+      end
     end
 
     def test_drops_configurations_with_blank_hosts
       @configurations[:development].merge!("host" => nil)
 
-      ActiveRecord::Tasks::DatabaseTasks.expects(:drop)
-
-      ActiveRecord::Tasks::DatabaseTasks.drop_all
+      assert_called(ActiveRecord::Tasks::DatabaseTasks, :drop) do
+        ActiveRecord::Tasks::DatabaseTasks.drop_all
+      end
     end
   end
 
@@ -287,7 +406,7 @@ module ActiveRecord
       @configurations = {
         "development" => { "database" => "dev-db" },
         "test"        => { "database" => "test-db" },
-        "production"  => { "database" => "prod-db" }
+        "production"  => { "url" => "prod-db-url" }
       }
 
       ActiveRecord::Base.stubs(:configurations).returns(@configurations)
@@ -295,7 +414,16 @@ module ActiveRecord
 
     def test_drops_current_environment_database
       ActiveRecord::Tasks::DatabaseTasks.expects(:drop).
-        with("database" => "prod-db")
+        with("database" => "test-db")
+
+      ActiveRecord::Tasks::DatabaseTasks.drop_current(
+        ActiveSupport::StringInquirer.new("test")
+      )
+    end
+
+    def test_drops_current_environment_database_with_url
+      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).
+        with("url" => "prod-db-url")
 
       ActiveRecord::Tasks::DatabaseTasks.drop_current(
         ActiveSupport::StringInquirer.new("production")
@@ -329,56 +457,208 @@ module ActiveRecord
     end
   end
 
-  class DatabaseTasksMigrateTest < ActiveRecord::TestCase
-    self.use_transactional_tests = false
-
+  class DatabaseTasksDropCurrentThreeTierTest < ActiveRecord::TestCase
     def setup
-      ActiveRecord::Tasks::DatabaseTasks.migrations_paths = "custom/path"
+      @configurations = {
+        "development" => { "primary" => { "database" => "dev-db" }, "secondary" => { "database" => "secondary-dev-db" } },
+        "test" => { "primary" => { "database" => "test-db" }, "secondary" => { "database" => "secondary-test-db" } },
+        "production" => { "primary" => { "url" => "prod-db-url" }, "secondary" => { "url" => "secondary-prod-db-url" } }
+      }
+
+      ActiveRecord::Base.stubs(:configurations).returns(@configurations)
     end
 
-    def teardown
-      ActiveRecord::Tasks::DatabaseTasks.migrations_paths = nil
+    def test_drops_current_environment_database
+      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).
+        with("database" => "test-db")
+
+      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).
+        with("database" => "secondary-test-db")
+
+      ActiveRecord::Tasks::DatabaseTasks.drop_current(
+        ActiveSupport::StringInquirer.new("test")
+      )
     end
 
-    def test_migrate_receives_correct_env_vars
-      verbose, version = ENV["VERBOSE"], ENV["VERSION"]
+    def test_drops_current_environment_database_with_url
+      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).
+        with("url" => "prod-db-url")
 
-      ENV["VERBOSE"] = "false"
-      ENV["VERSION"] = "4"
-      ActiveRecord::Migrator.expects(:migrate).with("custom/path", 4)
-      ActiveRecord::Migration.expects(:verbose=).with(false)
-      ActiveRecord::Migration.expects(:verbose=).with(ActiveRecord::Migration.verbose)
-      ActiveRecord::Tasks::DatabaseTasks.migrate
+      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).
+        with("url" => "secondary-prod-db-url")
 
-      ENV.delete("VERBOSE")
-      ENV.delete("VERSION")
-      ActiveRecord::Migrator.expects(:migrate).with("custom/path", nil)
-      ActiveRecord::Migration.expects(:verbose=).with(true)
-      ActiveRecord::Migration.expects(:verbose=).with(ActiveRecord::Migration.verbose)
-      ActiveRecord::Tasks::DatabaseTasks.migrate
+      ActiveRecord::Tasks::DatabaseTasks.drop_current(
+        ActiveSupport::StringInquirer.new("production")
+      )
+    end
 
-      ENV["VERBOSE"] = "yes"
-      ENV["VERSION"] = "unknown"
-      ActiveRecord::Migrator.expects(:migrate).with("custom/path", 0)
-      ActiveRecord::Migration.expects(:verbose=).with(true)
-      ActiveRecord::Migration.expects(:verbose=).with(ActiveRecord::Migration.verbose)
-      ActiveRecord::Tasks::DatabaseTasks.migrate
+    def test_drops_test_and_development_databases_when_env_was_not_specified
+      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).
+        with("database" => "dev-db")
+      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).
+        with("database" => "secondary-dev-db")
+      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).
+        with("database" => "test-db")
+      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).
+        with("database" => "secondary-test-db")
+
+      ActiveRecord::Tasks::DatabaseTasks.drop_current(
+        ActiveSupport::StringInquirer.new("development")
+      )
+    end
+
+    def test_drops_testand_development_databases_when_rails_env_is_development
+      old_env = ENV["RAILS_ENV"]
+      ENV["RAILS_ENV"] = "development"
+      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).
+        with("database" => "dev-db")
+      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).
+        with("database" => "secondary-dev-db")
+      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).
+        with("database" => "test-db")
+      ActiveRecord::Tasks::DatabaseTasks.expects(:drop).
+        with("database" => "secondary-test-db")
+
+      ActiveRecord::Tasks::DatabaseTasks.drop_current(
+        ActiveSupport::StringInquirer.new("development")
+      )
     ensure
-      ENV["VERBOSE"], ENV["VERSION"] = verbose, version
+      ENV["RAILS_ENV"] = old_env
+    end
+  end
+
+  if current_adapter?(:SQLite3Adapter) && !in_memory_db?
+    class DatabaseTasksMigrateTest < ActiveRecord::TestCase
+      self.use_transactional_tests = false
+
+      # Use a memory db here to avoid having to rollback at the end
+      setup do
+        migrations_path = MIGRATIONS_ROOT + "/valid"
+        file = ActiveRecord::Base.connection.raw_connection.filename
+        @conn = ActiveRecord::Base.establish_connection adapter: "sqlite3",
+          database: ":memory:", migrations_paths: migrations_path
+        source_db = SQLite3::Database.new file
+        dest_db = ActiveRecord::Base.connection.raw_connection
+        backup = SQLite3::Backup.new(dest_db, "main", source_db, "main")
+        backup.step(-1)
+        backup.finish
+      end
+
+      teardown do
+        @conn.release_connection if @conn
+        ActiveRecord::Base.establish_connection :arunit
+      end
+
+      def test_migrate_set_and_unset_verbose_and_version_env_vars
+        verbose, version = ENV["VERBOSE"], ENV["VERSION"]
+        ENV["VERSION"] = "2"
+        ENV["VERBOSE"] = "false"
+
+        # run down migration because it was already run on copied db
+        assert_empty capture_migration_output
+
+        ENV.delete("VERSION")
+        ENV.delete("VERBOSE")
+
+        # re-run up migration
+        assert_includes capture_migration_output, "migrating"
+      ensure
+        ENV["VERBOSE"], ENV["VERSION"] = verbose, version
+      end
+
+      def test_migrate_set_and_unset_empty_values_for_verbose_and_version_env_vars
+        verbose, version = ENV["VERBOSE"], ENV["VERSION"]
+
+        ENV["VERSION"] = "2"
+        ENV["VERBOSE"] = "false"
+
+        # run down migration because it was already run on copied db
+        assert_empty capture_migration_output
+
+        ENV["VERBOSE"] = ""
+        ENV["VERSION"] = ""
+
+        # re-run up migration
+        assert_includes capture_migration_output, "migrating"
+      ensure
+        ENV["VERBOSE"], ENV["VERSION"] = verbose, version
+      end
+
+      def test_migrate_set_and_unset_nonsense_values_for_verbose_and_version_env_vars
+        verbose, version = ENV["VERBOSE"], ENV["VERSION"]
+
+        # run down migration because it was already run on copied db
+        ENV["VERSION"] = "2"
+        ENV["VERBOSE"] = "false"
+
+        assert_empty capture_migration_output
+
+        ENV["VERBOSE"] = "yes"
+        ENV["VERSION"] = "2"
+
+        # run no migration because 2 was already run
+        assert_empty capture_migration_output
+      ensure
+        ENV["VERBOSE"], ENV["VERSION"] = verbose, version
+      end
+
+      private
+        def capture_migration_output
+          capture(:stdout) do
+            ActiveRecord::Tasks::DatabaseTasks.migrate
+          end
+        end
     end
+  end
+
+  class DatabaseTasksMigrateErrorTest < ActiveRecord::TestCase
+    self.use_transactional_tests = false
 
-    def test_migrate_raise_error_on_empty_version
+    def test_migrate_raise_error_on_invalid_version_format
       version = ENV["VERSION"]
-      ENV["VERSION"] = ""
+
+      ENV["VERSION"] = "unknown"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "0.1.11"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1.1.11"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "0 "
       e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
-      assert_equal "Empty VERSION provided", e.message
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1."
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1_"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1_name"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_match(/Invalid format of target version/, e.message)
     ensure
       ENV["VERSION"] = version
     end
 
+    def test_migrate_raise_error_on_failed_check_target_version
+      ActiveRecord::Tasks::DatabaseTasks.stubs(:check_target_version).raises("foo")
+
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.migrate }
+      assert_equal "foo", e.message
+    end
+
     def test_migrate_clears_schema_cache_afterward
-      ActiveRecord::Base.expects(:clear_cache!)
-      ActiveRecord::Tasks::DatabaseTasks.migrate
+      assert_called(ActiveRecord::Base, :clear_cache!) do
+        ActiveRecord::Tasks::DatabaseTasks.migrate
+      end
     end
   end
 
@@ -404,9 +684,10 @@ module ActiveRecord
 
       ActiveRecord::Tasks::DatabaseTasks.expects(:purge).
         with("database" => "prod-db")
-      ActiveRecord::Base.expects(:establish_connection).with(:production)
 
-      ActiveRecord::Tasks::DatabaseTasks.purge_current("production")
+      assert_called_with(ActiveRecord::Base, :establish_connection, [:production]) do
+        ActiveRecord::Tasks::DatabaseTasks.purge_current("production")
+      end
     end
   end
 
@@ -444,6 +725,108 @@ module ActiveRecord
     end
   end
 
+  class DatabaseTaskTargetVersionTest < ActiveRecord::TestCase
+    def test_target_version_returns_nil_if_version_does_not_exist
+      version = ENV.delete("VERSION")
+      assert_nil ActiveRecord::Tasks::DatabaseTasks.target_version
+    ensure
+      ENV["VERSION"] = version
+    end
+
+    def test_target_version_returns_nil_if_version_is_empty
+      version = ENV["VERSION"]
+
+      ENV["VERSION"] = ""
+      assert_nil ActiveRecord::Tasks::DatabaseTasks.target_version
+    ensure
+      ENV["VERSION"] = version
+    end
+
+    def test_target_version_returns_converted_to_integer_env_version_if_version_exists
+      version = ENV["VERSION"]
+
+      ENV["VERSION"] = "0"
+      assert_equal ENV["VERSION"].to_i, ActiveRecord::Tasks::DatabaseTasks.target_version
+
+      ENV["VERSION"] = "42"
+      assert_equal ENV["VERSION"].to_i, ActiveRecord::Tasks::DatabaseTasks.target_version
+
+      ENV["VERSION"] = "042"
+      assert_equal ENV["VERSION"].to_i, ActiveRecord::Tasks::DatabaseTasks.target_version
+    ensure
+      ENV["VERSION"] = version
+    end
+  end
+
+  class DatabaseTaskCheckTargetVersionTest < ActiveRecord::TestCase
+    def test_check_target_version_does_not_raise_error_on_empty_version
+      version = ENV["VERSION"]
+      ENV["VERSION"] = ""
+      assert_nothing_raised { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+    ensure
+      ENV["VERSION"] = version
+    end
+
+    def test_check_target_version_does_not_raise_error_if_version_is_not_setted
+      version = ENV.delete("VERSION")
+      assert_nothing_raised { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+    ensure
+      ENV["VERSION"] = version
+    end
+
+    def test_check_target_version_raises_error_on_invalid_version_format
+      version = ENV["VERSION"]
+
+      ENV["VERSION"] = "unknown"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "0.1.11"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1.1.11"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "0 "
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1."
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1_"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+      assert_match(/Invalid format of target version/, e.message)
+
+      ENV["VERSION"] = "1_name"
+      e = assert_raise(RuntimeError) { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+      assert_match(/Invalid format of target version/, e.message)
+    ensure
+      ENV["VERSION"] = version
+    end
+
+    def test_check_target_version_does_not_raise_error_on_valid_version_format
+      version = ENV["VERSION"]
+
+      ENV["VERSION"] = "0"
+      assert_nothing_raised { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+
+      ENV["VERSION"] = "1"
+      assert_nothing_raised { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+
+      ENV["VERSION"] = "001"
+      assert_nothing_raised { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+
+      ENV["VERSION"] = "001_name.rb"
+      assert_nothing_raised { ActiveRecord::Tasks::DatabaseTasks.check_target_version }
+    ensure
+      ENV["VERSION"] = version
+    end
+  end
+
   class DatabaseTasksStructureDumpTest < ActiveRecord::TestCase
     include DatabaseTasksSetupper
 
@@ -468,8 +851,9 @@ module ActiveRecord
 
   class DatabaseTasksCheckSchemaFileTest < ActiveRecord::TestCase
     def test_check_schema_file
-      Kernel.expects(:abort).with(regexp_matches(/awesome-file.sql/))
-      ActiveRecord::Tasks::DatabaseTasks.check_schema_file("awesome-file.sql")
+      assert_called_with(Kernel, :abort, [/awesome-file.sql/]) do
+        ActiveRecord::Tasks::DatabaseTasks.check_schema_file("awesome-file.sql")
+      end
     end
   end
 
diff --git a/activerecord/test/cases/tasks/mysql_rake_test.rb b/activerecord/test/cases/tasks/mysql_rake_test.rb
index 98fe24baa0..6cddfaefeb 100644
--- a/activerecord/test/cases/tasks/mysql_rake_test.rb
+++ b/activerecord/test/cases/tasks/mysql_rake_test.rb
@@ -75,7 +75,7 @@ if current_adapter?(:Mysql2Adapter)
       end
     end
 
-    class MysqlDBCreateAsRootTest < ActiveRecord::TestCase
+    class MysqlDBCreateWithInvalidPermissionsTest < ActiveRecord::TestCase
       def setup
         @connection    = stub("Connection", create_database: true)
         @error         = Mysql2::Error.new("Invalid permissions")
@@ -86,13 +86,8 @@ if current_adapter?(:Mysql2Adapter)
           "password" => "wossname"
         }
 
-        $stdin.stubs(:gets).returns("secret\n")
-        $stdout.stubs(:print).returns(nil)
-        @error.stubs(:errno).returns(1045)
         ActiveRecord::Base.stubs(:connection).returns(@connection)
-        ActiveRecord::Base.stubs(:establish_connection).
-          raises(@error).
-          then.returns(true)
+        ActiveRecord::Base.stubs(:establish_connection).raises(@error)
 
         $stdout, @original_stdout = StringIO.new, $stdout
         $stderr, @original_stderr = StringIO.new, $stderr
@@ -102,75 +97,11 @@ if current_adapter?(:Mysql2Adapter)
         $stdout, $stderr = @original_stdout, @original_stderr
       end
 
-      def test_root_password_is_requested
-        assert_permissions_granted_for("pat")
-        $stdin.expects(:gets).returns("secret\n")
-
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
-      end
-
-      def test_connection_established_as_root
-        assert_permissions_granted_for("pat")
-        ActiveRecord::Base.expects(:establish_connection).with(
-          "adapter"  => "mysql2",
-          "database" => nil,
-          "username" => "root",
-          "password" => "secret"
-        )
-
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
-      end
-
-      def test_database_created_by_root
-        assert_permissions_granted_for("pat")
-        @connection.expects(:create_database).
-          with("my-app-db", {})
-
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
-      end
-
-      def test_grant_privileges_for_normal_user
-        assert_permissions_granted_for("pat")
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
-      end
-
-      def test_do_not_grant_privileges_for_root_user
-        @configuration["username"] = "root"
-        @configuration["password"] = ""
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
-      end
-
-      def test_connection_established_as_normal_user
-        assert_permissions_granted_for("pat")
-        ActiveRecord::Base.expects(:establish_connection).returns do
-          ActiveRecord::Base.expects(:establish_connection).with(
-            "adapter"  => "mysql2",
-            "database" => "my-app-db",
-            "username" => "pat",
-            "password" => "secret"
-          )
-
-          raise @error
+      def test_raises_error
+        assert_raises(Mysql2::Error) do
+          ActiveRecord::Tasks::DatabaseTasks.create @configuration
         end
-
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
       end
-
-      def test_sends_output_to_stderr_when_other_errors
-        @error.stubs(:errno).returns(42)
-
-        $stderr.expects(:puts).at_least_once.returns(nil)
-
-        ActiveRecord::Tasks::DatabaseTasks.create @configuration
-      end
-
-      private
-
-        def assert_permissions_granted_for(db_user)
-          db_name = @configuration["database"]
-          db_password = @configuration["password"]
-          @connection.expects(:execute).with("GRANT ALL PRIVILEGES ON `#{db_name}`.* TO '#{db_user}'@'localhost' IDENTIFIED BY '#{db_password}' WITH GRANT OPTION;")
-        end
     end
 
     class MySQLDBDropTest < ActiveRecord::TestCase
@@ -291,9 +222,14 @@ if current_adapter?(:Mysql2Adapter)
 
       def test_structure_dump
         filename = "awesome-file.sql"
-        Kernel.expects(:system).with("mysqldump", "--result-file", filename, "--no-data", "--routines", "--skip-comments", "test-db").returns(true)
-
-        ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, filename)
+        assert_called_with(
+          Kernel,
+          :system,
+          ["mysqldump", "--result-file", filename, "--no-data", "--routines", "--skip-comments", "test-db"],
+          returns: true
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, filename)
+        end
       end
 
       def test_structure_dump_with_extra_flags
@@ -311,39 +247,57 @@ if current_adapter?(:Mysql2Adapter)
         filename = "awesome-file.sql"
         ActiveRecord::SchemaDumper.expects(:ignore_tables).returns(["foo", "bar"])
 
-        Kernel.expects(:system).with("mysqldump", "--result-file", filename, "--no-data", "--routines", "--skip-comments", "--ignore-table=test-db.foo", "--ignore-table=test-db.bar", "test-db").returns(true)
-
-        ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, filename)
+        assert_called_with(
+          Kernel,
+          :system,
+          ["mysqldump", "--result-file", filename, "--no-data", "--routines", "--skip-comments", "--ignore-table=test-db.foo", "--ignore-table=test-db.bar", "test-db"],
+          returns: true
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, filename)
+        end
       end
 
       def test_warn_when_external_structure_dump_command_execution_fails
         filename = "awesome-file.sql"
-        Kernel.expects(:system)
-          .with("mysqldump", "--result-file", filename, "--no-data", "--routines", "--skip-comments", "test-db")
-          .returns(false)
-
-        e = assert_raise(RuntimeError) {
-          ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, filename)
-        }
-        assert_match(/^failed to execute: `mysqldump`$/, e.message)
+        assert_called_with(
+          Kernel,
+          :system,
+          ["mysqldump", "--result-file", filename, "--no-data", "--routines", "--skip-comments", "test-db"],
+          returns: false
+        ) do
+          e = assert_raise(RuntimeError) {
+            ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, filename)
+          }
+          assert_match(/^failed to execute: `mysqldump`$/, e.message)
+        end
       end
 
       def test_structure_dump_with_port_number
         filename = "awesome-file.sql"
-        Kernel.expects(:system).with("mysqldump", "--port=10000", "--result-file", filename, "--no-data", "--routines", "--skip-comments", "test-db").returns(true)
-
-        ActiveRecord::Tasks::DatabaseTasks.structure_dump(
-          @configuration.merge("port" => 10000),
-          filename)
+        assert_called_with(
+          Kernel,
+          :system,
+          ["mysqldump", "--port=10000", "--result-file", filename, "--no-data", "--routines", "--skip-comments", "test-db"],
+          returns: true
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.structure_dump(
+            @configuration.merge("port" => 10000),
+            filename)
+        end
       end
 
       def test_structure_dump_with_ssl
         filename = "awesome-file.sql"
-        Kernel.expects(:system).with("mysqldump", "--ssl-ca=ca.crt", "--result-file", filename, "--no-data", "--routines", "--skip-comments", "test-db").returns(true)
-
-        ActiveRecord::Tasks::DatabaseTasks.structure_dump(
-          @configuration.merge("sslca" => "ca.crt"),
-          filename)
+        assert_called_with(
+          Kernel,
+          :system,
+          ["mysqldump", "--ssl-ca=ca.crt", "--result-file", filename, "--no-data", "--routines", "--skip-comments", "test-db"],
+          returns: true
+        ) do
+            ActiveRecord::Tasks::DatabaseTasks.structure_dump(
+              @configuration.merge("sslca" => "ca.crt"),
+              filename)
+          end
       end
 
       private
diff --git a/activerecord/test/cases/tasks/postgresql_rake_test.rb b/activerecord/test/cases/tasks/postgresql_rake_test.rb
index 693503250b..a1a3700f07 100644
--- a/activerecord/test/cases/tasks/postgresql_rake_test.rb
+++ b/activerecord/test/cases/tasks/postgresql_rake_test.rb
@@ -229,7 +229,6 @@ if current_adapter?(:PostgreSQLAdapter)
 
         ActiveRecord::Base.stubs(:connection).returns(@connection)
         ActiveRecord::Base.stubs(:establish_connection).returns(true)
-        Kernel.stubs(:system)
       end
 
       def teardown
@@ -237,9 +236,14 @@ if current_adapter?(:PostgreSQLAdapter)
       end
 
       def test_structure_dump
-        Kernel.expects(:system).with("pg_dump", "-s", "-x", "-O", "-f", @filename, "my-app-db").returns(true)
-
-        ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, @filename)
+        assert_called_with(
+          Kernel,
+          :system,
+          ["pg_dump", "-s", "-x", "-O", "-f", @filename, "my-app-db"],
+          returns: true
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, @filename)
+        end
       end
 
       def test_structure_dump_header_comments_removed
@@ -262,36 +266,75 @@ if current_adapter?(:PostgreSQLAdapter)
       end
 
       def test_structure_dump_with_ignore_tables
-        ActiveRecord::SchemaDumper.expects(:ignore_tables).returns(["foo", "bar"])
-
-        Kernel.expects(:system).with("pg_dump", "-s", "-x", "-O", "-f", @filename, "-T", "foo", "-T", "bar", "my-app-db").returns(true)
-
-        ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, @filename)
+        assert_called(
+          ActiveRecord::SchemaDumper,
+          :ignore_tables,
+          returns: ["foo", "bar"]
+        ) do
+          assert_called_with(
+            Kernel,
+            :system,
+            ["pg_dump", "-s", "-x", "-O", "-f", @filename, "-T", "foo", "-T", "bar", "my-app-db"],
+            returns: true
+          ) do
+            ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, @filename)
+          end
+        end
       end
 
       def test_structure_dump_with_schema_search_path
         @configuration["schema_search_path"] = "foo,bar"
 
-        Kernel.expects(:system).with("pg_dump", "-s", "-x", "-O", "-f", @filename, "--schema=foo", "--schema=bar", "my-app-db").returns(true)
-
-        ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, @filename)
+        assert_called_with(
+          Kernel,
+          :system,
+          ["pg_dump", "-s", "-x", "-O", "-f", @filename, "--schema=foo", "--schema=bar", "my-app-db"],
+          returns: true
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, @filename)
+        end
       end
 
       def test_structure_dump_with_schema_search_path_and_dump_schemas_all
         @configuration["schema_search_path"] = "foo,bar"
 
-        Kernel.expects(:system).with("pg_dump", "-s", "-x", "-O", "-f", @filename,  "my-app-db").returns(true)
-
-        with_dump_schemas(:all) do
-          ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, @filename)
+        assert_called_with(
+          Kernel,
+          :system,
+          ["pg_dump", "-s", "-x", "-O", "-f", @filename,  "my-app-db"],
+          returns: true
+        ) do
+          with_dump_schemas(:all) do
+            ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, @filename)
+          end
         end
       end
 
       def test_structure_dump_with_dump_schemas_string
-        Kernel.expects(:system).with("pg_dump", "-s", "-x", "-O", "-f", @filename, "--schema=foo", "--schema=bar", "my-app-db").returns(true)
+        assert_called_with(
+          Kernel,
+          :system,
+          ["pg_dump", "-s", "-x", "-O", "-f", @filename, "--schema=foo", "--schema=bar", "my-app-db"],
+          returns: true
+        ) do
+          with_dump_schemas("foo,bar") do
+            ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, @filename)
+          end
+        end
+      end
 
-        with_dump_schemas("foo,bar") do
-          ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, @filename)
+      def test_structure_dump_execution_fails
+        filename = "awesome-file.sql"
+        assert_called_with(
+          Kernel,
+          :system,
+          ["pg_dump", "-s", "-x", "-O", "-f", filename, "my-app-db"],
+          returns: nil
+        ) do
+          e = assert_raise(RuntimeError) do
+            ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, filename)
+          end
+          assert_match("failed to execute:", e.message)
         end
       end
 
@@ -323,14 +366,18 @@ if current_adapter?(:PostgreSQLAdapter)
 
         ActiveRecord::Base.stubs(:connection).returns(@connection)
         ActiveRecord::Base.stubs(:establish_connection).returns(true)
-        Kernel.stubs(:system)
       end
 
       def test_structure_load
         filename = "awesome-file.sql"
-        Kernel.expects(:system).with("psql", "-v", "ON_ERROR_STOP=1", "-q", "-f", filename, @configuration["database"]).returns(true)
-
-        ActiveRecord::Tasks::DatabaseTasks.structure_load(@configuration, filename)
+        assert_called_with(
+          Kernel,
+          :system,
+          ["psql", "-v", "ON_ERROR_STOP=1", "-q", "-f", filename, @configuration["database"]],
+          returns: true
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.structure_load(@configuration, filename)
+        end
       end
 
       def test_structure_load_with_extra_flags
@@ -346,9 +393,14 @@ if current_adapter?(:PostgreSQLAdapter)
 
       def test_structure_load_accepts_path_with_spaces
         filename = "awesome file.sql"
-        Kernel.expects(:system).with("psql", "-v", "ON_ERROR_STOP=1", "-q", "-f", filename, @configuration["database"]).returns(true)
-
-        ActiveRecord::Tasks::DatabaseTasks.structure_load(@configuration, filename)
+        assert_called_with(
+          Kernel,
+          :system,
+          ["psql", "-v", "ON_ERROR_STOP=1", "-q", "-f", filename, @configuration["database"]],
+          returns: true
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.structure_load(@configuration, filename)
+        end
       end
 
       private
diff --git a/activerecord/test/cases/tasks/sqlite_rake_test.rb b/activerecord/test/cases/tasks/sqlite_rake_test.rb
index 8ac4878c37..d368a7a6ee 100644
--- a/activerecord/test/cases/tasks/sqlite_rake_test.rb
+++ b/activerecord/test/cases/tasks/sqlite_rake_test.rb
@@ -204,9 +204,9 @@ if current_adapter?(:SQLite3Adapter)
       def test_structure_dump_with_ignore_tables
         dbfile   = @database
         filename = "awesome-file.sql"
-        ActiveRecord::SchemaDumper.expects(:ignore_tables).returns(["foo"])
-
-        ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, filename, "/rails/root")
+        assert_called(ActiveRecord::SchemaDumper, :ignore_tables, returns: ["foo"]) do
+          ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, filename, "/rails/root")
+        end
         assert File.exist?(dbfile)
         assert File.exist?(filename)
         assert_match(/bar/, File.read(filename))
@@ -215,6 +215,36 @@ if current_adapter?(:SQLite3Adapter)
         FileUtils.rm_f(filename)
         FileUtils.rm_f(dbfile)
       end
+
+      def test_structure_dump_execution_fails
+        dbfile   = @database
+        filename = "awesome-file.sql"
+        assert_called_with(
+          Kernel,
+          :system,
+          ["sqlite3", "--noop", "db_create.sqlite3", ".schema", out: "awesome-file.sql"],
+          returns: nil
+        ) do
+          e = assert_raise(RuntimeError) do
+            with_structure_dump_flags(["--noop"]) do
+              quietly { ActiveRecord::Tasks::DatabaseTasks.structure_dump(@configuration, filename, "/rails/root") }
+            end
+          end
+          assert_match("failed to execute:", e.message)
+        end
+      ensure
+        FileUtils.rm_f(filename)
+        FileUtils.rm_f(dbfile)
+      end
+
+      private
+        def with_structure_dump_flags(flags)
+          old = ActiveRecord::Tasks::DatabaseTasks.structure_dump_flags
+          ActiveRecord::Tasks::DatabaseTasks.structure_dump_flags = flags
+          yield
+        ensure
+          ActiveRecord::Tasks::DatabaseTasks.structure_dump_flags = old
+        end
     end
 
     class SqliteStructureLoadTest < ActiveRecord::TestCase
diff --git a/activerecord/test/cases/test_case.rb b/activerecord/test/cases/test_case.rb
index e57ebf56c8..409b07e56c 100644
--- a/activerecord/test/cases/test_case.rb
+++ b/activerecord/test/cases/test_case.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require "active_support/test_case"
+require "active_support"
 require "active_support/testing/autorun"
 require "active_support/testing/method_call_assertions"
 require "active_support/testing/stream"
@@ -77,6 +77,10 @@ module ActiveRecord
       model.reset_column_information
       model.column_names.include?(column_name.to_s)
     end
+
+    def frozen_error_class
+      Object.const_defined?(:FrozenError) ? FrozenError : RuntimeError
+    end
   end
 
   class PostgreSQLTestCase < TestCase
@@ -110,9 +114,9 @@ module ActiveRecord
     # FIXME: this needs to be refactored so specific database can add their own
     # ignored SQL, or better yet, use a different notification for the queries
     # instead examining the SQL content.
-    oracle_ignored     = [/^select .*nextval/i, /^SAVEPOINT/, /^ROLLBACK TO/, /^\s*select .* from all_triggers/im, /^\s*select .* from all_constraints/im, /^\s*select .* from all_tab_cols/im]
+    oracle_ignored     = [/^select .*nextval/i, /^SAVEPOINT/, /^ROLLBACK TO/, /^\s*select .* from all_triggers/im, /^\s*select .* from all_constraints/im, /^\s*select .* from all_tab_cols/im, /^\s*select .* from all_sequences/im]
     mysql_ignored      = [/^SHOW FULL TABLES/i, /^SHOW FULL FIELDS/, /^SHOW CREATE TABLE /i, /^SHOW VARIABLES /, /^\s*SELECT (?:column_name|table_name)\b.*\bFROM information_schema\.(?:key_column_usage|tables)\b/im]
-    postgresql_ignored = [/^\s*select\b.*\bfrom\b.*pg_namespace\b/im, /^\s*select tablename\b.*from pg_tables\b/im, /^\s*select\b.*\battname\b.*\bfrom\b.*\bpg_attribute\b/im, /^SHOW search_path/i]
+    postgresql_ignored = [/^\s*select\b.*\bfrom\b.*pg_namespace\b/im, /^\s*select tablename\b.*from pg_tables\b/im, /^\s*select\b.*\battname\b.*\bfrom\b.*\bpg_attribute\b/im, /^SHOW search_path/i, /^\s*SELECT\b.*::regtype::oid\b/im]
     sqlite3_ignored =    [/^\s*SELECT name\b.*\bFROM sqlite_master/im, /^\s*SELECT sql\b.*\bFROM sqlite_master/im]
 
     [oracle_ignored, mysql_ignored, postgresql_ignored, sqlite3_ignored].each do |db_ignored_sql|
diff --git a/activerecord/test/cases/time_precision_test.rb b/activerecord/test/cases/time_precision_test.rb
index 41455637bb..086500de38 100644
--- a/activerecord/test/cases/time_precision_test.rb
+++ b/activerecord/test/cases/time_precision_test.rb
@@ -27,6 +27,24 @@ if subsecond_precision_supported?
       assert_equal 6, Foo.columns_hash["finish"].precision
     end
 
+    def test_time_precision_is_truncated_on_assignment
+      @connection.create_table(:foos, force: true)
+      @connection.add_column :foos, :start,  :time, precision: 0
+      @connection.add_column :foos, :finish, :time, precision: 6
+
+      time = ::Time.now.change(nsec: 123456789)
+      foo = Foo.new(start: time, finish: time)
+
+      assert_equal 0, foo.start.nsec
+      assert_equal 123456000, foo.finish.nsec
+
+      foo.save!
+      foo.reload
+
+      assert_equal 0, foo.start.nsec
+      assert_equal 123456000, foo.finish.nsec
+    end
+
     def test_passing_precision_to_time_does_not_set_limit
       @connection.create_table(:foos, force: true) do |t|
         t.time :start,  precision: 3
diff --git a/activerecord/test/cases/timestamp_test.rb b/activerecord/test/cases/timestamp_test.rb
index 5d3e2a175c..75ecd6fc40 100644
--- a/activerecord/test/cases/timestamp_test.rb
+++ b/activerecord/test/cases/timestamp_test.rb
@@ -90,12 +90,22 @@ class TimestampTest < ActiveRecord::TestCase
       @developer.touch(:created_at)
     end
 
-    assert !@developer.created_at_changed? , "created_at should not be changed"
-    assert !@developer.changed?, "record should not be changed"
+    assert_not @developer.created_at_changed?, "created_at should not be changed"
+    assert_not @developer.changed?, "record should not be changed"
     assert_not_equal previously_created_at, @developer.created_at
     assert_not_equal @previously_updated_at, @developer.updated_at
   end
 
+  def test_touching_update_at_attribute_as_symbol_updates_timestamp
+    travel(1.second) do
+      @developer.touch(:updated_at)
+    end
+
+    assert_not @developer.updated_at_changed?
+    assert_not @developer.changed?
+    assert_not_equal @previously_updated_at, @developer.updated_at
+  end
+
   def test_touching_an_attribute_updates_it
     task = Task.first
     previous_value = task.ending
@@ -139,13 +149,13 @@ class TimestampTest < ActiveRecord::TestCase
 
   def test_touching_a_no_touching_object
     Developer.no_touching do
-      assert @developer.no_touching?
-      assert !@owner.no_touching?
+      assert_predicate @developer, :no_touching?
+      assert_not_predicate @owner, :no_touching?
       @developer.touch
     end
 
-    assert !@developer.no_touching?
-    assert !@owner.no_touching?
+    assert_not_predicate @developer, :no_touching?
+    assert_not_predicate @owner, :no_touching?
     assert_equal @previously_updated_at, @developer.updated_at
   end
 
@@ -162,26 +172,26 @@ class TimestampTest < ActiveRecord::TestCase
 
   def test_global_no_touching
     ActiveRecord::Base.no_touching do
-      assert @developer.no_touching?
-      assert @owner.no_touching?
+      assert_predicate @developer, :no_touching?
+      assert_predicate @owner, :no_touching?
       @developer.touch
     end
 
-    assert !@developer.no_touching?
-    assert !@owner.no_touching?
+    assert_not_predicate @developer, :no_touching?
+    assert_not_predicate @owner, :no_touching?
     assert_equal @previously_updated_at, @developer.updated_at
   end
 
   def test_no_touching_threadsafe
     Thread.new do
       Developer.no_touching do
-        assert @developer.no_touching?
+        assert_predicate @developer, :no_touching?
 
         sleep(1)
       end
     end
 
-    assert !@developer.no_touching?
+    assert_not_predicate @developer, :no_touching?
   end
 
   def test_no_touching_with_callbacks
@@ -237,7 +247,7 @@ class TimestampTest < ActiveRecord::TestCase
     pet = Pet.new(owner: klass.new)
     pet.save!
 
-    assert pet.owner.new_record?
+    assert_predicate pet.owner, :new_record?
   end
 
   def test_saving_a_record_with_a_belongs_to_that_specifies_touching_a_specific_attribute_the_parent_should_update_that_attribute
diff --git a/activerecord/test/cases/touch_later_test.rb b/activerecord/test/cases/touch_later_test.rb
index 1757031371..925a4609a2 100644
--- a/activerecord/test/cases/touch_later_test.rb
+++ b/activerecord/test/cases/touch_later_test.rb
@@ -13,7 +13,7 @@ class TouchLaterTest < ActiveRecord::TestCase
   def test_touch_laster_raise_if_non_persisted
     invoice = Invoice.new
     Invoice.transaction do
-      assert_not invoice.persisted?
+      assert_not_predicate invoice, :persisted?
       assert_raises(ActiveRecord::ActiveRecordError) do
         invoice.touch_later
       end
@@ -23,7 +23,7 @@ class TouchLaterTest < ActiveRecord::TestCase
   def test_touch_later_dont_set_dirty_attributes
     invoice = Invoice.create!
     invoice.touch_later
-    assert_not invoice.changed?
+    assert_not_predicate invoice, :changed?
   end
 
   def test_touch_later_respects_no_touching_policy
diff --git a/activerecord/test/cases/transaction_callbacks_test.rb b/activerecord/test/cases/transaction_callbacks_test.rb
index 1f370a80ee..05941c75ac 100644
--- a/activerecord/test/cases/transaction_callbacks_test.rb
+++ b/activerecord/test/cases/transaction_callbacks_test.rb
@@ -158,13 +158,13 @@ class TransactionCallbacksTest < ActiveRecord::TestCase
 
   def test_only_call_after_commit_on_top_level_transactions
     @first.after_commit_block { |r| r.history << :after_commit }
-    assert @first.history.empty?
+    assert_empty @first.history
 
     @first.transaction do
       @first.transaction(requires_new: true) do
         @first.touch
       end
-      assert @first.history.empty?
+      assert_empty @first.history
     end
     assert_equal [:after_commit], @first.history
   end
@@ -367,6 +367,26 @@ class TransactionCallbacksTest < ActiveRecord::TestCase
     assert_match(/:on conditions for after_commit and after_rollback callbacks have to be one of \[:create, :destroy, :update\]/, e.message)
   end
 
+  def test_after_commit_chain_not_called_on_errors
+    record_1 = TopicWithCallbacks.create!
+    record_2 = TopicWithCallbacks.create!
+    record_3 = TopicWithCallbacks.create!
+    callbacks = []
+    record_1.after_commit_block { raise }
+    record_2.after_commit_block { callbacks << record_2.id }
+    record_3.after_commit_block { callbacks << record_3.id }
+    begin
+      TopicWithCallbacks.transaction do
+        record_1.save!
+        record_2.save!
+        record_3.save!
+      end
+    rescue
+      # From record_1.after_commit
+    end
+    assert_equal [], callbacks
+  end
+
   def test_saving_a_record_with_a_belongs_to_that_specifies_touching_the_parent_should_call_callbacks_on_the_parent_object
     pet   = Pet.first
     owner = pet.owner
@@ -394,6 +414,28 @@ class TransactionCallbacksTest < ActiveRecord::TestCase
     end
 end
 
+class TransactionAfterCommitCallbacksWithOptimisticLockingTest < ActiveRecord::TestCase
+  class PersonWithCallbacks < ActiveRecord::Base
+    self.table_name = :people
+
+    after_create_commit { |record| record.history << :commit_on_create }
+    after_update_commit { |record| record.history << :commit_on_update }
+    after_destroy_commit { |record| record.history << :commit_on_destroy }
+
+    def history
+      @history ||= []
+    end
+  end
+
+  def test_after_commit_callbacks_with_optimistic_locking
+    person = PersonWithCallbacks.create!(first_name: "first name")
+    person.update!(first_name: "another name")
+    person.destroy
+
+    assert_equal [:commit_on_create, :commit_on_update, :commit_on_destroy], person.history
+  end
+end
+
 class CallbacksOnMultipleActionsTest < ActiveRecord::TestCase
   self.use_transactional_tests = false
 
@@ -518,7 +560,7 @@ class TransactionEnrollmentCallbacksTest < ActiveRecord::TestCase
       @topic.content = "foo"
       @topic.save!
     end
-    assert @topic.history.empty?
+    assert_empty @topic.history
   end
 
   def test_commit_run_transactions_callbacks_with_explicit_enrollment
@@ -538,7 +580,7 @@ class TransactionEnrollmentCallbacksTest < ActiveRecord::TestCase
       @topic.save!
       raise ActiveRecord::Rollback
     end
-    assert @topic.history.empty?
+    assert_empty @topic.history
   end
 
   def test_rollback_run_transactions_callbacks_with_explicit_enrollment
diff --git a/activerecord/test/cases/transaction_isolation_test.rb b/activerecord/test/cases/transaction_isolation_test.rb
index b1ebccdcc3..eaafd13360 100644
--- a/activerecord/test/cases/transaction_isolation_test.rb
+++ b/activerecord/test/cases/transaction_isolation_test.rb
@@ -15,9 +15,7 @@ unless ActiveRecord::Base.connection.supports_transaction_isolation?
       end
     end
   end
-end
-
-if ActiveRecord::Base.connection.supports_transaction_isolation?
+else
   class TransactionIsolationTest < ActiveRecord::TestCase
     self.use_transactional_tests = false
 
diff --git a/activerecord/test/cases/transactions_test.rb b/activerecord/test/cases/transactions_test.rb
index 7fd125ab74..5b685ca564 100644
--- a/activerecord/test/cases/transactions_test.rb
+++ b/activerecord/test/cases/transactions_test.rb
@@ -20,22 +20,22 @@ class TransactionTest < ActiveRecord::TestCase
 
   def test_persisted_in_a_model_with_custom_primary_key_after_failed_save
     movie = Movie.create
-    assert !movie.persisted?
+    assert_not_predicate movie, :persisted?
   end
 
   def test_raise_after_destroy
-    assert_not @first.frozen?
+    assert_not_predicate @first, :frozen?
 
     assert_raises(RuntimeError) {
       Topic.transaction do
         @first.destroy
-        assert @first.frozen?
+        assert_predicate @first, :frozen?
         raise
       end
     }
 
     assert @first.reload
-    assert_not @first.frozen?
+    assert_not_predicate @first, :frozen?
   end
 
   def test_successful
@@ -47,7 +47,7 @@ class TransactionTest < ActiveRecord::TestCase
     end
 
     assert Topic.find(1).approved?, "First should have been approved"
-    assert !Topic.find(2).approved?, "Second should have been unapproved"
+    assert_not Topic.find(2).approved?, "Second should have been unapproved"
   end
 
   def transaction_with_return
@@ -80,7 +80,7 @@ class TransactionTest < ActiveRecord::TestCase
     assert committed
 
     assert Topic.find(1).approved?, "First should have been approved"
-    assert !Topic.find(2).approved?, "Second should have been unapproved"
+    assert_not Topic.find(2).approved?, "Second should have been unapproved"
   ensure
     Topic.connection.class_eval do
       remove_method :commit_db_transaction
@@ -121,7 +121,7 @@ class TransactionTest < ActiveRecord::TestCase
     end
 
     assert Topic.find(1).approved?, "First should have been approved"
-    assert !Topic.find(2).approved?, "Second should have been unapproved"
+    assert_not Topic.find(2).approved?, "Second should have been unapproved"
   end
 
   def test_failing_on_exception
@@ -138,9 +138,9 @@ class TransactionTest < ActiveRecord::TestCase
     end
 
     assert @first.approved?, "First should still be changed in the objects"
-    assert !@second.approved?, "Second should still be changed in the objects"
+    assert_not @second.approved?, "Second should still be changed in the objects"
 
-    assert !Topic.find(1).approved?, "First shouldn't have been approved"
+    assert_not Topic.find(1).approved?, "First shouldn't have been approved"
     assert Topic.find(2).approved?, "Second should still be approved"
   end
 
@@ -152,20 +152,20 @@ class TransactionTest < ActiveRecord::TestCase
     @first.approved = true
     e = assert_raises(RuntimeError) { @first.save }
     assert_equal "Make the transaction rollback", e.message
-    assert !Topic.find(1).approved?
+    assert_not_predicate Topic.find(1), :approved?
   end
 
   def test_rolling_back_in_a_callback_rollbacks_before_save
     def @first.before_save_for_transaction
       raise ActiveRecord::Rollback
     end
-    assert !@first.approved
+    assert_not @first.approved
 
     Topic.transaction do
       @first.approved = true
       @first.save!
     end
-    assert !Topic.find(@first.id).approved?, "Should not commit the approved flag"
+    assert_not Topic.find(@first.id).approved?, "Should not commit the approved flag"
   end
 
   def test_raising_exception_in_nested_transaction_restore_state_in_save
@@ -186,7 +186,7 @@ class TransactionTest < ActiveRecord::TestCase
     author = Author.create! name: "foo"
     author.name = nil
     assert_not author.save
-    assert_not author.new_record?
+    assert_not_predicate author, :new_record?
   end
 
   def test_update_should_rollback_on_failure
@@ -194,7 +194,7 @@ class TransactionTest < ActiveRecord::TestCase
     posts_count = author.posts.size
     assert posts_count > 0
     status = author.update(name: nil, post_ids: [])
-    assert !status
+    assert_not status
     assert_equal posts_count, author.posts.reload.size
   end
 
@@ -212,7 +212,7 @@ class TransactionTest < ActiveRecord::TestCase
     add_cancelling_before_destroy_with_db_side_effect_to_topic @first
     nbooks_before_destroy = Book.count
     status = @first.destroy
-    assert !status
+    assert_not status
     @first.reload
     assert_equal nbooks_before_destroy, Book.count
   end
@@ -224,7 +224,7 @@ class TransactionTest < ActiveRecord::TestCase
       original_author_name = @first.author_name
       @first.author_name += "_this_should_not_end_up_in_the_db"
       status = @first.save
-      assert !status
+      assert_not status
       assert_equal original_author_name, @first.reload.author_name
       assert_equal nbooks_before_save, Book.count
     end
@@ -288,7 +288,19 @@ class TransactionTest < ActiveRecord::TestCase
     }
 
     new_topic = topic.create(title: "A new topic")
-    assert !new_topic.persisted?, "The topic should not be persisted"
+    assert_not new_topic.persisted?, "The topic should not be persisted"
+    assert_nil new_topic.id, "The topic should not have an ID"
+  end
+
+  def test_callback_rollback_in_create_with_rollback_exception
+    topic = Class.new(Topic) {
+      def after_create_for_transaction
+        raise ActiveRecord::Rollback
+      end
+    }
+
+    new_topic = topic.create(title: "A new topic")
+    assert_not new_topic.persisted?, "The topic should not be persisted"
     assert_nil new_topic.id, "The topic should not have an ID"
   end
 
@@ -303,7 +315,7 @@ class TransactionTest < ActiveRecord::TestCase
     end
 
     assert Topic.find(1).approved?, "First should have been approved"
-    assert !Topic.find(2).approved?, "Second should have been unapproved"
+    assert_not Topic.find(2).approved?, "Second should have been unapproved"
   end
 
   def test_nested_transaction_with_new_transaction_applies_parent_state_on_rollback
@@ -323,8 +335,8 @@ class TransactionTest < ActiveRecord::TestCase
       raise ActiveRecord::Rollback
     end
 
-    refute_predicate topic_one, :persisted?
-    refute_predicate topic_two, :persisted?
+    assert_not_predicate topic_one, :persisted?
+    assert_not_predicate topic_two, :persisted?
   end
 
   def test_nested_transaction_without_new_transaction_applies_parent_state_on_rollback
@@ -344,8 +356,8 @@ class TransactionTest < ActiveRecord::TestCase
       raise ActiveRecord::Rollback
     end
 
-    refute_predicate topic_one, :persisted?
-    refute_predicate topic_two, :persisted?
+    assert_not_predicate topic_one, :persisted?
+    assert_not_predicate topic_two, :persisted?
   end
 
   def test_double_nested_transaction_applies_parent_state_on_rollback
@@ -371,9 +383,9 @@ class TransactionTest < ActiveRecord::TestCase
       raise ActiveRecord::Rollback
     end
 
-    refute_predicate topic_one, :persisted?
-    refute_predicate topic_two, :persisted?
-    refute_predicate topic_three, :persisted?
+    assert_not_predicate topic_one, :persisted?
+    assert_not_predicate topic_two, :persisted?
+    assert_not_predicate topic_three, :persisted?
   end
 
   def test_manually_rolling_back_a_transaction
@@ -387,9 +399,9 @@ class TransactionTest < ActiveRecord::TestCase
     end
 
     assert @first.approved?, "First should still be changed in the objects"
-    assert !@second.approved?, "Second should still be changed in the objects"
+    assert_not @second.approved?, "Second should still be changed in the objects"
 
-    assert !Topic.find(1).approved?, "First shouldn't have been approved"
+    assert_not Topic.find(1).approved?, "First shouldn't have been approved"
     assert Topic.find(2).approved?, "Second should still be approved"
   end
 
@@ -417,8 +429,8 @@ class TransactionTest < ActiveRecord::TestCase
       end
     end
 
-    assert @first.reload.approved?
-    assert !@second.reload.approved?
+    assert_predicate @first.reload, :approved?
+    assert_not_predicate @second.reload, :approved?
   end if Topic.connection.supports_savepoints?
 
   def test_force_savepoint_on_instance
@@ -438,8 +450,8 @@ class TransactionTest < ActiveRecord::TestCase
       end
     end
 
-    assert @first.reload.approved?
-    assert !@second.reload.approved?
+    assert_predicate @first.reload, :approved?
+    assert_not_predicate @second.reload, :approved?
   end if Topic.connection.supports_savepoints?
 
   def test_no_savepoint_in_nested_transaction_without_force
@@ -459,8 +471,8 @@ class TransactionTest < ActiveRecord::TestCase
       end
     end
 
-    assert !@first.reload.approved?
-    assert !@second.reload.approved?
+    assert_not_predicate @first.reload, :approved?
+    assert_not_predicate @second.reload, :approved?
   end if Topic.connection.supports_savepoints?
 
   def test_many_savepoints
@@ -516,12 +528,12 @@ class TransactionTest < ActiveRecord::TestCase
       @first.approved = false
       @first.save!
       Topic.connection.rollback_to_savepoint("first")
-      assert @first.reload.approved?
+      assert_predicate @first.reload, :approved?
 
       @first.approved = false
       @first.save!
       Topic.connection.release_savepoint("first")
-      assert_not @first.reload.approved?
+      assert_not_predicate @first.reload, :approved?
     end
   end if Topic.connection.supports_savepoints?
 
@@ -576,12 +588,12 @@ class TransactionTest < ActiveRecord::TestCase
   def test_rollback_when_saving_a_frozen_record
     topic = Topic.new(title: "test")
     topic.freeze
-    e = assert_raise(RuntimeError) { topic.save }
+    e = assert_raise(frozen_error_class) { topic.save }
     # Not good enough, but we can't do much
     # about it since there is no specific error
     # for frozen objects.
     assert_match(/frozen/i, e.message)
-    assert !topic.persisted?, "not persisted"
+    assert_not topic.persisted?, "not persisted"
     assert_nil topic.id
     assert topic.frozen?, "not frozen"
   end
@@ -608,9 +620,9 @@ class TransactionTest < ActiveRecord::TestCase
     thread.join
 
     assert @first.approved?, "First should still be changed in the objects"
-    assert !@second.approved?, "Second should still be changed in the objects"
+    assert_not @second.approved?, "Second should still be changed in the objects"
 
-    assert !Topic.find(1).approved?, "First shouldn't have been approved"
+    assert_not Topic.find(1).approved?, "First shouldn't have been approved"
     assert Topic.find(2).approved?, "Second should still be approved"
   end
 
@@ -641,15 +653,15 @@ class TransactionTest < ActiveRecord::TestCase
       raise ActiveRecord::Rollback
     end
 
-    assert !topic_1.persisted?, "not persisted"
+    assert_not topic_1.persisted?, "not persisted"
     assert_nil topic_1.id
-    assert !topic_2.persisted?, "not persisted"
+    assert_not topic_2.persisted?, "not persisted"
     assert_nil topic_2.id
-    assert !topic_3.persisted?, "not persisted"
+    assert_not topic_3.persisted?, "not persisted"
     assert_nil topic_3.id
     assert @first.persisted?, "persisted"
     assert_not_nil @first.id
-    assert !@second.destroyed?, "not destroyed"
+    assert_not @second.destroyed?, "not destroyed"
   end
 
   def test_restore_frozen_state_after_double_destroy
@@ -663,8 +675,38 @@ class TransactionTest < ActiveRecord::TestCase
       raise ActiveRecord::Rollback
     end
 
-    assert_not reply.frozen?
-    assert_not topic.frozen?
+    assert_not_predicate reply, :frozen?
+    assert_not_predicate topic, :frozen?
+  end
+
+  def test_restore_new_record_after_double_save
+    topic = Topic.new
+
+    Topic.transaction do
+      topic.save!
+      topic.save!
+      raise ActiveRecord::Rollback
+    end
+
+    assert_nil topic.id
+    assert_predicate topic, :new_record?
+  end
+
+  def test_dont_restore_new_record_in_subsequent_transaction
+    topic = Topic.new
+
+    Topic.transaction do
+      topic.save!
+      topic.save!
+    end
+
+    Topic.transaction do
+      topic.save!
+      raise ActiveRecord::Rollback
+    end
+
+    assert_predicate topic, :persisted?
+    assert_not_predicate topic, :new_record?
   end
 
   def test_restore_id_after_rollback
@@ -819,28 +861,28 @@ class TransactionTest < ActiveRecord::TestCase
     connection = Topic.connection
     transaction = ActiveRecord::ConnectionAdapters::TransactionManager.new(connection).begin_transaction
 
-    assert transaction.open?
-    assert !transaction.state.rolledback?
-    assert !transaction.state.committed?
+    assert_predicate transaction, :open?
+    assert_not_predicate transaction.state, :rolledback?
+    assert_not_predicate transaction.state, :committed?
 
     transaction.rollback
 
-    assert transaction.state.rolledback?
-    assert !transaction.state.committed?
+    assert_predicate transaction.state, :rolledback?
+    assert_not_predicate transaction.state, :committed?
   end
 
   def test_transactions_state_from_commit
     connection = Topic.connection
     transaction = ActiveRecord::ConnectionAdapters::TransactionManager.new(connection).begin_transaction
 
-    assert transaction.open?
-    assert !transaction.state.rolledback?
-    assert !transaction.state.committed?
+    assert_predicate transaction, :open?
+    assert_not_predicate transaction.state, :rolledback?
+    assert_not_predicate transaction.state, :committed?
 
     transaction.commit
 
-    assert !transaction.state.rolledback?
-    assert transaction.state.committed?
+    assert_not_predicate transaction.state, :rolledback?
+    assert_predicate transaction.state, :committed?
   end
 
   def test_set_state_method_is_deprecated
@@ -929,7 +971,7 @@ class TransactionsWithTransactionalFixturesTest < ActiveRecord::TestCase
         raise
       end
     rescue
-      assert !@first.reload.approved?
+      assert_not_predicate @first.reload, :approved?
     end
   end
 
@@ -950,31 +992,29 @@ class TransactionsWithTransactionalFixturesTest < ActiveRecord::TestCase
       end
     end
 
-    assert !@first.reload.approved?
+    assert_not_predicate @first.reload, :approved?
   end
 end if Topic.connection.supports_savepoints?
 
-if current_adapter?(:PostgreSQLAdapter)
+if ActiveRecord::Base.connection.supports_transaction_isolation?
   class ConcurrentTransactionTest < TransactionTest
     # This will cause transactions to overlap and fail unless they are performed on
     # separate database connections.
-    unless in_memory_db?
-      def test_transaction_per_thread
-        threads = 3.times.map do
-          Thread.new do
-            Topic.transaction do
-              topic = Topic.find(1)
-              topic.approved = !topic.approved?
-              assert topic.save!
-              topic.approved = !topic.approved?
-              assert topic.save!
-            end
-            Topic.connection.close
+    def test_transaction_per_thread
+      threads = 3.times.map do
+        Thread.new do
+          Topic.transaction do
+            topic = Topic.find(1)
+            topic.approved = !topic.approved?
+            assert topic.save!
+            topic.approved = !topic.approved?
+            assert topic.save!
           end
+          Topic.connection.close
         end
-
-        threads.each(&:join)
       end
+
+      threads.each(&:join)
     end
 
     # Test for dirty reads among simultaneous transactions.
diff --git a/activerecord/test/cases/type/string_test.rb b/activerecord/test/cases/type/string_test.rb
index 8c51b30fdd..9e7810a6a5 100644
--- a/activerecord/test/cases/type/string_test.rb
+++ b/activerecord/test/cases/type/string_test.rb
@@ -9,16 +9,16 @@ module ActiveRecord
       klass.table_name = "authors"
 
       author = klass.create!(name: "Sean")
-      assert_not author.changed?
+      assert_not_predicate author, :changed?
 
       author.name << " Griffin"
-      assert author.name_changed?
+      assert_predicate author, :name_changed?
 
       author.save!
       author.reload
 
       assert_equal "Sean Griffin", author.name
-      assert_not author.changed?
+      assert_not_predicate author, :changed?
     end
   end
 end
diff --git a/activerecord/test/cases/unconnected_test.rb b/activerecord/test/cases/unconnected_test.rb
index f4d8be5897..9eefc32745 100644
--- a/activerecord/test/cases/unconnected_test.rb
+++ b/activerecord/test/cases/unconnected_test.rb
@@ -30,6 +30,6 @@ class TestUnconnectedAdapter < ActiveRecord::TestCase
   end
 
   def test_underlying_adapter_no_longer_active
-    assert !@underlying.active?, "Removed adapter should no longer be active"
+    assert_not @underlying.active?, "Removed adapter should no longer be active"
   end
 end
diff --git a/activerecord/test/cases/unsafe_raw_sql_test.rb b/activerecord/test/cases/unsafe_raw_sql_test.rb
new file mode 100644
index 0000000000..d5d8f2a09a
--- /dev/null
+++ b/activerecord/test/cases/unsafe_raw_sql_test.rb
@@ -0,0 +1,319 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/post"
+require "models/comment"
+
+class UnsafeRawSqlTest < ActiveRecord::TestCase
+  fixtures :posts, :comments
+
+  test "order: allows string column name" do
+    ids_expected = Post.order(Arel.sql("title")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order("title").pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order("title").pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows symbol column name" do
+    ids_expected = Post.order(Arel.sql("title")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(:title).pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(:title).pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows downcase symbol direction" do
+    ids_expected = Post.order(Arel.sql("title") => Arel.sql("asc")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(title: :asc).pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(title: :asc).pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows upcase symbol direction" do
+    ids_expected = Post.order(Arel.sql("title") => Arel.sql("ASC")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(title: :ASC).pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(title: :ASC).pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows string direction" do
+    ids_expected = Post.order(Arel.sql("title") => Arel.sql("asc")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(title: "asc").pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(title: "asc").pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows multiple columns" do
+    ids_expected = Post.order(Arel.sql("author_id"), Arel.sql("title")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(:author_id, :title).pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(:author_id, :title).pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows mixed" do
+    ids_expected = Post.order(Arel.sql("author_id"), Arel.sql("title") => Arel.sql("asc")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(:author_id, title: :asc).pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(:author_id, title: :asc).pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows table and column name" do
+    ids_expected = Post.order(Arel.sql("title")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order("posts.title").pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order("posts.title").pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows column name and direction in string" do
+    ids_expected = Post.order(Arel.sql("title desc")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order("title desc").pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order("title desc").pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows table name, column name and direction in string" do
+    ids_expected = Post.order(Arel.sql("title desc")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order("posts.title desc").pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order("posts.title desc").pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: allows NULLS FIRST and NULLS LAST too" do
+    raise "precondition failed" if Post.count < 2
+
+    # Ensure there are NULL and non-NULL post types.
+    Post.first.update_column(:type, nil)
+    Post.last.update_column(:type, "Programming")
+
+    ["asc", "desc", ""].each do |direction|
+      %w(first last).each do |position|
+        ids_expected = Post.order(Arel.sql("type #{direction} nulls #{position}")).pluck(:id)
+
+        ids_depr     = with_unsafe_raw_sql_deprecated { Post.order("type #{direction} nulls #{position}").pluck(:id) }
+        ids_disabled = with_unsafe_raw_sql_disabled   { Post.order("type #{direction} nulls #{position}").pluck(:id) }
+
+        assert_equal ids_expected, ids_depr
+        assert_equal ids_expected, ids_disabled
+      end
+    end
+  end if current_adapter?(:PostgreSQLAdapter)
+
+  test "order: disallows invalid column name" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ActiveRecord::UnknownAttributeReference) do
+        Post.order("len(title) asc").pluck(:id)
+      end
+    end
+  end
+
+  test "order: disallows invalid direction" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ArgumentError) do
+        Post.order(title: :foo).pluck(:id)
+      end
+    end
+  end
+
+  test "order: disallows invalid column with direction" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ActiveRecord::UnknownAttributeReference) do
+        Post.order("len(title)" => :asc).pluck(:id)
+      end
+    end
+  end
+
+  test "order: always allows Arel" do
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(Arel.sql("length(title)")).pluck(:title) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(Arel.sql("length(title)")).pluck(:title) }
+
+    assert_equal ids_depr, ids_disabled
+  end
+
+  test "order: allows Arel.sql with binds" do
+    ids_expected = Post.order(Arel.sql("REPLACE(title, 'misc', 'zzzz'), id")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order([Arel.sql("REPLACE(title, ?, ?), id"), "misc", "zzzz"]).pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order([Arel.sql("REPLACE(title, ?, ?), id"), "misc", "zzzz"]).pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: disallows invalid bind statement" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ActiveRecord::UnknownAttributeReference) do
+        Post.order(["REPLACE(title, ?, ?), id", "misc", "zzzz"]).pluck(:id)
+      end
+    end
+  end
+
+  test "order: disallows invalid Array arguments" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ActiveRecord::UnknownAttributeReference) do
+        Post.order(["author_id", "length(title)"]).pluck(:id)
+      end
+    end
+  end
+
+  test "order: allows valid Array arguments" do
+    ids_expected = Post.order(Arel.sql("author_id, length(title)")).pluck(:id)
+
+    ids_depr     = with_unsafe_raw_sql_deprecated { Post.order(["author_id", Arel.sql("length(title)")]).pluck(:id) }
+    ids_disabled = with_unsafe_raw_sql_disabled   { Post.order(["author_id", Arel.sql("length(title)")]).pluck(:id) }
+
+    assert_equal ids_expected, ids_depr
+    assert_equal ids_expected, ids_disabled
+  end
+
+  test "order: logs deprecation warning for unrecognized column" do
+    with_unsafe_raw_sql_deprecated do
+      assert_deprecated(/Dangerous query method/) do
+        Post.order("length(title)")
+      end
+    end
+  end
+
+  test "pluck: allows string column name" do
+    titles_expected = Post.pluck(Arel.sql("title"))
+
+    titles_depr     = with_unsafe_raw_sql_deprecated { Post.pluck("title") }
+    titles_disabled = with_unsafe_raw_sql_disabled   { Post.pluck("title") }
+
+    assert_equal titles_expected, titles_depr
+    assert_equal titles_expected, titles_disabled
+  end
+
+  test "pluck: allows symbol column name" do
+    titles_expected = Post.pluck(Arel.sql("title"))
+
+    titles_depr     = with_unsafe_raw_sql_deprecated { Post.pluck(:title) }
+    titles_disabled = with_unsafe_raw_sql_disabled   { Post.pluck(:title) }
+
+    assert_equal titles_expected, titles_depr
+    assert_equal titles_expected, titles_disabled
+  end
+
+  test "pluck: allows multiple column names" do
+    values_expected = Post.pluck(Arel.sql("title"), Arel.sql("id"))
+
+    values_depr     = with_unsafe_raw_sql_deprecated { Post.pluck(:title, :id) }
+    values_disabled = with_unsafe_raw_sql_disabled   { Post.pluck(:title, :id) }
+
+    assert_equal values_expected, values_depr
+    assert_equal values_expected, values_disabled
+  end
+
+  test "pluck: allows column names with includes" do
+    values_expected = Post.includes(:comments).pluck(Arel.sql("title"), Arel.sql("id"))
+
+    values_depr     = with_unsafe_raw_sql_deprecated { Post.includes(:comments).pluck(:title, :id) }
+    values_disabled = with_unsafe_raw_sql_disabled   { Post.includes(:comments).pluck(:title, :id) }
+
+    assert_equal values_expected, values_depr
+    assert_equal values_expected, values_disabled
+  end
+
+  test "pluck: allows auto-generated attributes" do
+    values_expected = Post.pluck(Arel.sql("tags_count"))
+
+    values_depr     = with_unsafe_raw_sql_deprecated { Post.pluck(:tags_count) }
+    values_disabled = with_unsafe_raw_sql_disabled   { Post.pluck(:tags_count) }
+
+    assert_equal values_expected, values_depr
+    assert_equal values_expected, values_disabled
+  end
+
+  test "pluck: allows table and column names" do
+    titles_expected = Post.pluck(Arel.sql("title"))
+
+    titles_depr     = with_unsafe_raw_sql_deprecated { Post.pluck("posts.title") }
+    titles_disabled = with_unsafe_raw_sql_disabled   { Post.pluck("posts.title") }
+
+    assert_equal titles_expected, titles_depr
+    assert_equal titles_expected, titles_disabled
+  end
+
+  test "pluck: disallows invalid column name" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ActiveRecord::UnknownAttributeReference) do
+        Post.pluck("length(title)")
+      end
+    end
+  end
+
+  test "pluck: disallows invalid column name amongst valid names" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ActiveRecord::UnknownAttributeReference) do
+        Post.pluck(:title, "length(title)")
+      end
+    end
+  end
+
+  test "pluck: disallows invalid column names with includes" do
+    with_unsafe_raw_sql_disabled do
+      assert_raises(ActiveRecord::UnknownAttributeReference) do
+        Post.includes(:comments).pluck(:title, "length(title)")
+      end
+    end
+  end
+
+  test "pluck: always allows Arel" do
+    values_depr     = with_unsafe_raw_sql_deprecated { Post.includes(:comments).pluck(:title, Arel.sql("length(title)")) }
+    values_disabled = with_unsafe_raw_sql_disabled   { Post.includes(:comments).pluck(:title, Arel.sql("length(title)")) }
+
+    assert_equal values_depr, values_disabled
+  end
+
+  test "pluck: logs deprecation warning" do
+    with_unsafe_raw_sql_deprecated do
+      assert_deprecated(/Dangerous query method/) do
+        Post.includes(:comments).pluck(:title, "length(title)")
+      end
+    end
+  end
+
+  def with_unsafe_raw_sql_disabled(&blk)
+    with_config(:disabled, &blk)
+  end
+
+  def with_unsafe_raw_sql_deprecated(&blk)
+    with_config(:deprecated, &blk)
+  end
+
+  def with_config(new_value, &blk)
+    old_value = ActiveRecord::Base.allow_unsafe_raw_sql
+    ActiveRecord::Base.allow_unsafe_raw_sql = new_value
+    blk.call
+  ensure
+    ActiveRecord::Base.allow_unsafe_raw_sql = old_value
+  end
+end
diff --git a/activerecord/test/cases/validations/absence_validation_test.rb b/activerecord/test/cases/validations/absence_validation_test.rb
index a997f8be9c..8235a54d8a 100644
--- a/activerecord/test/cases/validations/absence_validation_test.rb
+++ b/activerecord/test/cases/validations/absence_validation_test.rb
@@ -13,8 +13,8 @@ class AbsenceValidationTest < ActiveRecord::TestCase
       validates_absence_of :name
     end
 
-    assert boy_klass.new.valid?
-    assert_not boy_klass.new(name: "Alex").valid?
+    assert_predicate boy_klass.new, :valid?
+    assert_not_predicate boy_klass.new(name: "Alex"), :valid?
   end
 
   def test_has_one_marked_for_destruction
@@ -44,7 +44,7 @@ class AbsenceValidationTest < ActiveRecord::TestCase
     assert_not boy.valid?, "should not be valid if has_many association is present"
 
     i2.mark_for_destruction
-    assert boy.valid?
+    assert_predicate boy, :valid?
   end
 
   def test_does_not_call_to_a_on_associations
@@ -65,11 +65,11 @@ class AbsenceValidationTest < ActiveRecord::TestCase
       Interest.validates_absence_of(:token)
 
       interest = Interest.create!(topic: "Thought Leadering")
-      assert interest.valid?
+      assert_predicate interest, :valid?
 
       interest.token = "tl"
 
-      assert interest.invalid?
+      assert_predicate interest, :invalid?
     end
   end
 end
diff --git a/activerecord/test/cases/validations/association_validation_test.rb b/activerecord/test/cases/validations/association_validation_test.rb
index 80fe375ae5..ce6d42b34b 100644
--- a/activerecord/test/cases/validations/association_validation_test.rb
+++ b/activerecord/test/cases/validations/association_validation_test.rb
@@ -16,14 +16,14 @@ class AssociationValidationTest < ActiveRecord::TestCase
     Reply.validates_presence_of(:content)
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     t.replies << [r = Reply.new("title" => "A reply"), r2 = Reply.new("title" => "Another reply", "content" => "non-empty"), r3 = Reply.new("title" => "Yet another reply"), r4 = Reply.new("title" => "The last reply", "content" => "non-empty")]
-    assert !t.valid?
-    assert t.errors[:replies].any?
+    assert_not_predicate t, :valid?
+    assert_predicate t.errors[:replies], :any?
     assert_equal 1, r.errors.count  # make sure all associated objects have been validated
     assert_equal 0, r2.errors.count
     assert_equal 1, r3.errors.count
     assert_equal 0, r4.errors.count
     r.content = r3.content = "non-empty"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_associated_one
@@ -31,10 +31,10 @@ class AssociationValidationTest < ActiveRecord::TestCase
     Topic.validates_presence_of(:content)
     r = Reply.new("title" => "A reply", "content" => "with content!")
     r.topic = Topic.create("title" => "uhohuhoh")
-    assert !r.valid?
-    assert r.errors[:topic].any?
+    assert_not_predicate r, :valid?
+    assert_predicate r.errors[:topic], :any?
     r.topic.content = "non-empty"
-    assert r.valid?
+    assert_predicate r, :valid?
   end
 
   def test_validates_associated_marked_for_destruction
@@ -42,9 +42,9 @@ class AssociationValidationTest < ActiveRecord::TestCase
     Reply.validates_presence_of(:content)
     t = Topic.new
     t.replies << Reply.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
     t.replies.first.mark_for_destruction
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_associated_without_marked_for_destruction
@@ -56,7 +56,7 @@ class AssociationValidationTest < ActiveRecord::TestCase
     Topic.validates_associated(:replies)
     t = Topic.new
     t.define_singleton_method(:replies) { [reply.new] }
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_associated_with_custom_message_using_quotes
@@ -71,11 +71,11 @@ class AssociationValidationTest < ActiveRecord::TestCase
   def test_validates_associated_missing
     Reply.validates_presence_of(:topic)
     r = Reply.create("title" => "A reply", "content" => "with content!")
-    assert !r.valid?
-    assert r.errors[:topic].any?
+    assert_not_predicate r, :valid?
+    assert_predicate r.errors[:topic], :any?
 
     r.topic = Topic.first
-    assert r.valid?
+    assert_predicate r, :valid?
   end
 
   def test_validates_presence_of_belongs_to_association__parent_is_new_record
diff --git a/activerecord/test/cases/validations/length_validation_test.rb b/activerecord/test/cases/validations/length_validation_test.rb
index 87ce4c6f37..1fbcdc271b 100644
--- a/activerecord/test/cases/validations/length_validation_test.rb
+++ b/activerecord/test/cases/validations/length_validation_test.rb
@@ -17,48 +17,48 @@ class LengthValidationTest < ActiveRecord::TestCase
   def test_validates_size_of_association
     assert_nothing_raised { @owner.validates_size_of :pets, minimum: 1 }
     o = @owner.new("name" => "nopets")
-    assert !o.save
-    assert o.errors[:pets].any?
+    assert_not o.save
+    assert_predicate o.errors[:pets], :any?
     o.pets.build("name" => "apet")
-    assert o.valid?
+    assert_predicate o, :valid?
   end
 
   def test_validates_size_of_association_using_within
     assert_nothing_raised { @owner.validates_size_of :pets, within: 1..2 }
     o = @owner.new("name" => "nopets")
-    assert !o.save
-    assert o.errors[:pets].any?
+    assert_not o.save
+    assert_predicate o.errors[:pets], :any?
 
     o.pets.build("name" => "apet")
-    assert o.valid?
+    assert_predicate o, :valid?
 
     2.times { o.pets.build("name" => "apet") }
-    assert !o.save
-    assert o.errors[:pets].any?
+    assert_not o.save
+    assert_predicate o.errors[:pets], :any?
   end
 
   def test_validates_size_of_association_utf8
     @owner.validates_size_of :pets, minimum: 1
     o = @owner.new("name" => "あいうえおかきくけこ")
-    assert !o.save
-    assert o.errors[:pets].any?
+    assert_not o.save
+    assert_predicate o.errors[:pets], :any?
     o.pets.build("name" => "あいうえおかきくけこ")
-    assert o.valid?
+    assert_predicate o, :valid?
   end
 
   def test_validates_size_of_respects_records_marked_for_destruction
     @owner.validates_size_of :pets, minimum: 1
     owner = @owner.new
     assert_not owner.save
-    assert owner.errors[:pets].any?
+    assert_predicate owner.errors[:pets], :any?
     pet = owner.pets.build
-    assert owner.valid?
+    assert_predicate owner, :valid?
     assert owner.save
 
     pet_count = Pet.count
-    assert_not owner.update_attributes pets_attributes: [ { _destroy: 1, id: pet.id } ]
-    assert_not owner.valid?
-    assert owner.errors[:pets].any?
+    assert_not owner.update pets_attributes: [ { _destroy: 1, id: pet.id } ]
+    assert_not_predicate owner, :valid?
+    assert_predicate owner.errors[:pets], :any?
     assert_equal pet_count, Pet.count
   end
 
@@ -70,11 +70,11 @@ class LengthValidationTest < ActiveRecord::TestCase
 
       pet = Pet.create!(name: "Fancy Pants", nickname: "Fancy")
 
-      assert pet.valid?
+      assert_predicate pet, :valid?
 
       pet.nickname = ""
 
-      assert pet.invalid?
+      assert_predicate pet, :invalid?
     end
   end
 end
diff --git a/activerecord/test/cases/validations/presence_validation_test.rb b/activerecord/test/cases/validations/presence_validation_test.rb
index 3ab1567b51..63c3f67da2 100644
--- a/activerecord/test/cases/validations/presence_validation_test.rb
+++ b/activerecord/test/cases/validations/presence_validation_test.rb
@@ -15,10 +15,10 @@ class PresenceValidationTest < ActiveRecord::TestCase
   def test_validates_presence_of_non_association
     Boy.validates_presence_of(:name)
     b = Boy.new
-    assert b.invalid?
+    assert_predicate b, :invalid?
 
     b.name = "Alex"
-    assert b.valid?
+    assert_predicate b, :valid?
   end
 
   def test_validates_presence_of_has_one
@@ -33,23 +33,23 @@ class PresenceValidationTest < ActiveRecord::TestCase
     b = Boy.new
     f = Face.new
     b.face = f
-    assert b.valid?
+    assert_predicate b, :valid?
 
     f.mark_for_destruction
-    assert b.invalid?
+    assert_predicate b, :invalid?
   end
 
   def test_validates_presence_of_has_many_marked_for_destruction
     Boy.validates_presence_of(:interests)
     b = Boy.new
     b.interests << [i1 = Interest.new, i2 = Interest.new]
-    assert b.valid?
+    assert_predicate b, :valid?
 
     i1.mark_for_destruction
-    assert b.valid?
+    assert_predicate b, :valid?
 
     i2.mark_for_destruction
-    assert b.invalid?
+    assert_predicate b, :invalid?
   end
 
   def test_validates_presence_doesnt_convert_to_array
@@ -74,11 +74,11 @@ class PresenceValidationTest < ActiveRecord::TestCase
       Interest.validates_presence_of(:abbreviation)
 
       interest = Interest.create!(topic: "Thought Leadering", abbreviation: "tl")
-      assert interest.valid?
+      assert_predicate interest, :valid?
 
       interest.abbreviation = ""
 
-      assert interest.invalid?
+      assert_predicate interest, :invalid?
     end
   end
 
diff --git a/activerecord/test/cases/validations/uniqueness_validation_test.rb b/activerecord/test/cases/validations/uniqueness_validation_test.rb
index a10567f066..8f6f47e5fb 100644
--- a/activerecord/test/cases/validations/uniqueness_validation_test.rb
+++ b/activerecord/test/cases/validations/uniqueness_validation_test.rb
@@ -62,7 +62,7 @@ class TopicWithAfterCreate < Topic
   after_create :set_author
 
   def set_author
-    update_attributes!(author_name: "#{title} #{id}")
+    update!(author_name: "#{title} #{id}")
   end
 end
 
@@ -83,8 +83,8 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert t.save, "Should still save t as unique"
 
     t2 = Topic.new("title" => "I'm uniqué!")
-    assert !t2.valid?, "Shouldn't be valid"
-    assert !t2.save, "Shouldn't save t2 as unique"
+    assert_not t2.valid?, "Shouldn't be valid"
+    assert_not t2.save, "Shouldn't save t2 as unique"
     assert_equal ["has already been taken"], t2.errors[:title]
 
     t2.title = "Now I am really also unique"
@@ -96,7 +96,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     Topic.validates_uniqueness_of(:new_title)
 
     topic = Topic.new(new_title: "abc")
-    assert topic.valid?
+    assert_predicate topic, :valid?
   end
 
   def test_validates_uniqueness_with_nil_value
@@ -106,8 +106,8 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert t.save, "Should save t as unique"
 
     t2 = Topic.new("title" => nil)
-    assert !t2.valid?, "Shouldn't be valid"
-    assert !t2.save, "Shouldn't save t2 as unique"
+    assert_not t2.valid?, "Shouldn't be valid"
+    assert_not t2.save, "Shouldn't save t2 as unique"
     assert_equal ["has already been taken"], t2.errors[:title]
   end
 
@@ -116,7 +116,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     Topic.create!("title" => "abc")
 
     t2 = Topic.new("title" => "abc")
-    assert !t2.valid?
+    assert_not_predicate t2, :valid?
     assert t2.errors[:title]
   end
 
@@ -146,7 +146,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert r1.valid?, "Saving r1"
 
     r2 = t.replies.create "title" => "r2", "content" => "hello world"
-    assert !r2.valid?, "Saving r2 first time"
+    assert_not r2.valid?, "Saving r2 first time"
 
     r2.content = "something else"
     assert r2.save, "Saving r2 second time"
@@ -172,7 +172,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert r1.valid?, "Saving r1"
 
     r2 = t.replies.create "title" => "r2", "content" => "hello world"
-    assert !r2.valid?, "Saving r2 first time"
+    assert_not r2.valid?, "Saving r2 first time"
   end
 
   def test_validate_uniqueness_with_polymorphic_object_scope
@@ -193,7 +193,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert r1.valid?, "Saving r1"
 
     r2 = ReplyWithTitleObject.create "title" => "r1", "content" => "hello world"
-    assert !r2.valid?, "Saving r2 first time"
+    assert_not r2.valid?, "Saving r2 first time"
   end
 
   def test_validate_uniqueness_with_object_arg
@@ -205,7 +205,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert r1.valid?, "Saving r1"
 
     r2 = t.replies.create "title" => "r2", "content" => "hello world"
-    assert !r2.valid?, "Saving r2 first time"
+    assert_not r2.valid?, "Saving r2 first time"
   end
 
   def test_validate_uniqueness_scoped_to_defining_class
@@ -215,7 +215,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert r1.valid?, "Saving r1"
 
     r2 = t.silly_unique_replies.create "title" => "r2", "content" => "a barrel of fun"
-    assert !r2.valid?, "Saving r2"
+    assert_not r2.valid?, "Saving r2"
 
     # Should succeed as validates_uniqueness_of only applies to
     # UniqueReply and its subclasses
@@ -232,19 +232,19 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert r1.valid?, "Saving r1"
 
     r2 = t.replies.create "author_name" => "jeremy", "author_email_address" => "jeremy@rubyonrails.com", "title" => "You're crazy!", "content" => "Crazy reply again..."
-    assert !r2.valid?, "Saving r2. Double reply by same author."
+    assert_not r2.valid?, "Saving r2. Double reply by same author."
 
     r2.author_email_address = "jeremy_alt_email@rubyonrails.com"
     assert r2.save, "Saving r2 the second time."
 
     r3 = t.replies.create "author_name" => "jeremy", "author_email_address" => "jeremy_alt_email@rubyonrails.com", "title" => "You're wrong", "content" => "It's cubic"
-    assert !r3.valid?, "Saving r3"
+    assert_not r3.valid?, "Saving r3"
 
     r3.author_name = "jj"
     assert r3.save, "Saving r3 the second time."
 
     r3.author_name = "jeremy"
-    assert !r3.save, "Saving r3 the third time."
+    assert_not r3.save, "Saving r3 the third time."
   end
 
   def test_validate_case_insensitive_uniqueness
@@ -257,17 +257,17 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert t.save, "Should still save t as unique"
 
     t2 = Topic.new("title" => "I'm UNIQUE!", :parent_id => 1)
-    assert !t2.valid?, "Shouldn't be valid"
-    assert !t2.save, "Shouldn't save t2 as unique"
-    assert t2.errors[:title].any?
-    assert t2.errors[:parent_id].any?
+    assert_not t2.valid?, "Shouldn't be valid"
+    assert_not t2.save, "Shouldn't save t2 as unique"
+    assert_predicate t2.errors[:title], :any?
+    assert_predicate t2.errors[:parent_id], :any?
     assert_equal ["has already been taken"], t2.errors[:title]
 
     t2.title = "I'm truly UNIQUE!"
-    assert !t2.valid?, "Shouldn't be valid"
-    assert !t2.save, "Shouldn't save t2 as unique"
-    assert t2.errors[:title].empty?
-    assert t2.errors[:parent_id].any?
+    assert_not t2.valid?, "Shouldn't be valid"
+    assert_not t2.save, "Shouldn't save t2 as unique"
+    assert_empty t2.errors[:title]
+    assert_predicate t2.errors[:parent_id], :any?
 
     t2.parent_id = 4
     assert t2.save, "Should now save t2 as unique"
@@ -283,8 +283,8 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     # If database hasn't UTF-8 character set, this test fails
     if Topic.all.merge!(select: "LOWER(title) AS title").find(t_utf8.id).title == "я тоже уникальный!"
       t2_utf8 = Topic.new("title" => "я тоже УНИКАЛЬНЫЙ!")
-      assert !t2_utf8.valid?, "Shouldn't be valid"
-      assert !t2_utf8.save, "Shouldn't save t2_utf8 as unique"
+      assert_not t2_utf8.valid?, "Shouldn't be valid"
+      assert_not t2_utf8.save, "Shouldn't save t2_utf8 as unique"
     end
   end
 
@@ -326,15 +326,15 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     t2 = Topic.new("title" => "I'M UNIQUE!")
     assert t2.valid?, "Should be valid"
     assert t2.save, "Should save t2 as unique"
-    assert t2.errors[:title].empty?
-    assert t2.errors[:parent_id].empty?
+    assert_empty t2.errors[:title]
+    assert_empty t2.errors[:parent_id]
     assert_not_equal ["has already been taken"], t2.errors[:title]
 
     t3 = Topic.new("title" => "I'M uNiQUe!")
     assert t3.valid?, "Should be valid"
     assert t3.save, "Should save t2 as unique"
-    assert t3.errors[:title].empty?
-    assert t3.errors[:parent_id].empty?
+    assert_empty t3.errors[:title]
+    assert_empty t3.errors[:parent_id]
     assert_not_equal ["has already been taken"], t3.errors[:title]
   end
 
@@ -343,13 +343,13 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     Topic.create!("title" => 101)
 
     t2 = Topic.new("title" => 101)
-    assert !t2.valid?
+    assert_not_predicate t2, :valid?
     assert t2.errors[:title]
   end
 
   def test_validate_uniqueness_with_non_standard_table_names
     i1 = WarehouseThing.create(value: 1000)
-    assert !i1.valid?, "i1 should not be valid"
+    assert_not i1.valid?, "i1 should not be valid"
     assert i1.errors[:value].any?, "Should not be empty"
   end
 
@@ -360,7 +360,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
       t1 = Topic.new("title" => "I'm unique!", "author_name" => "Mary")
       assert t1.save
       t2 = Topic.new("title" => "I'm unique!", "author_name" => "David")
-      assert !t2.valid?
+      assert_not_predicate t2, :valid?
     end
   end
 
@@ -417,12 +417,12 @@ class UniquenessValidationTest < ActiveRecord::TestCase
 
     # Should use validation from base class (which is abstract)
     w2 = IneptWizard.new(name: "Rincewind", city: "Quirm")
-    assert !w2.valid?, "w2 shouldn't be valid"
+    assert_not w2.valid?, "w2 shouldn't be valid"
     assert w2.errors[:name].any?, "Should have errors for name"
     assert_equal ["has already been taken"], w2.errors[:name], "Should have uniqueness message for name"
 
     w3 = Conjurer.new(name: "Rincewind", city: "Quirm")
-    assert !w3.valid?, "w3 shouldn't be valid"
+    assert_not w3.valid?, "w3 shouldn't be valid"
     assert w3.errors[:name].any?, "Should have errors for name"
     assert_equal ["has already been taken"], w3.errors[:name], "Should have uniqueness message for name"
 
@@ -430,12 +430,12 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert w4.valid?, "Saving w4"
 
     w5 = Thaumaturgist.new(name: "The Amazing Bonko", city: "Lancre")
-    assert !w5.valid?, "w5 shouldn't be valid"
+    assert_not w5.valid?, "w5 shouldn't be valid"
     assert w5.errors[:name].any?, "Should have errors for name"
     assert_equal ["has already been taken"], w5.errors[:name], "Should have uniqueness message for name"
 
     w6 = Thaumaturgist.new(name: "Mustrum Ridcully", city: "Quirm")
-    assert !w6.valid?, "w6 shouldn't be valid"
+    assert_not w6.valid?, "w6 shouldn't be valid"
     assert w6.errors[:city].any?, "Should have errors for city"
     assert_equal ["has already been taken"], w6.errors[:city], "Should have uniqueness message for city"
   end
@@ -446,7 +446,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     Topic.create("title" => "I'm an unapproved topic", "approved" => false)
 
     t3 = Topic.new("title" => "I'm a topic", "approved" => true)
-    assert !t3.valid?, "t3 shouldn't be valid"
+    assert_not t3.valid?, "t3 shouldn't be valid"
 
     t4 = Topic.new("title" => "I'm an unapproved topic", "approved" => false)
     assert t4.valid?, "t4 should be valid"
@@ -460,16 +460,16 @@ class UniquenessValidationTest < ActiveRecord::TestCase
 
   def test_validate_uniqueness_on_existing_relation
     event = Event.create
-    assert TopicWithUniqEvent.create(event: event).valid?
+    assert_predicate TopicWithUniqEvent.create(event: event), :valid?
 
     topic = TopicWithUniqEvent.new(event: event)
-    assert_not topic.valid?
+    assert_not_predicate topic, :valid?
     assert_equal ["has already been taken"], topic.errors[:event]
   end
 
   def test_validate_uniqueness_on_empty_relation
     topic = TopicWithUniqEvent.new
-    assert topic.valid?
+    assert_predicate topic, :valid?
   end
 
   def test_validate_uniqueness_of_custom_primary_key
@@ -488,7 +488,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     key2 = klass.create!(key_number: 11)
 
     key2.key_number = 10
-    assert_not key2.valid?
+    assert_not_predicate key2, :valid?
   end
 
   def test_validate_uniqueness_without_primary_key
@@ -501,8 +501,8 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     end
 
     abc = klass.create!(dashboard_id: "abc")
-    assert klass.new(dashboard_id: "xyz").valid?
-    assert_not klass.new(dashboard_id: "abc").valid?
+    assert_predicate klass.new(dashboard_id: "xyz"), :valid?
+    assert_not_predicate klass.new(dashboard_id: "abc"), :valid?
 
     abc.dashboard_id = "def"
 
@@ -530,7 +530,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert topic.author_name.start_with?("Title1")
 
     topic2 = TopicWithAfterCreate.new(title: "Title1")
-    refute topic2.valid?
+    assert_not_predicate topic2, :valid?
     assert_equal(["has already been taken"], topic2.errors[:title])
   end
 
@@ -550,7 +550,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert_empty item.errors
 
     item2 = CoolTopic.new(id: item.id, title: "MyItem2")
-    refute item2.valid?
+    assert_not_predicate item2, :valid?
 
     assert_equal(["has already been taken"], item2.errors[:id])
   end
diff --git a/activerecord/test/cases/validations_test.rb b/activerecord/test/cases/validations_test.rb
index 7f84939027..a33877f43a 100644
--- a/activerecord/test/cases/validations_test.rb
+++ b/activerecord/test/cases/validations_test.rb
@@ -19,7 +19,7 @@ class ValidationsTest < ActiveRecord::TestCase
   def test_valid_uses_create_context_when_new
     r = WrongReply.new
     r.title = "Wrong Create"
-    assert_not r.valid?
+    assert_not_predicate r, :valid?
     assert r.errors[:title].any?, "A reply with a bad title should mark that attribute as invalid"
     assert_equal ["is Wrong Create"], r.errors[:title], "A reply with a bad content should contain an error"
   end
@@ -39,7 +39,7 @@ class ValidationsTest < ActiveRecord::TestCase
 
   def test_valid_using_special_context
     r = WrongReply.new(title: "Valid title")
-    assert !r.valid?(:special_case)
+    assert_not r.valid?(:special_case)
     assert_equal "Invalid", r.errors[:author_name].join
 
     r.author_name = "secret"
@@ -125,7 +125,7 @@ class ValidationsTest < ActiveRecord::TestCase
 
   def test_save_without_validation
     reply = WrongReply.new
-    assert !reply.save
+    assert_not reply.save
     assert reply.save(validate: false)
   end
 
@@ -139,7 +139,7 @@ class ValidationsTest < ActiveRecord::TestCase
 
   def test_throw_away_typing
     d = Developer.new("name" => "David", "salary" => "100,000")
-    assert !d.valid?
+    assert_not_predicate d, :valid?
     assert_equal 100, d.salary
     assert_equal "100,000", d.salary_before_type_cast
   end
@@ -166,7 +166,7 @@ class ValidationsTest < ActiveRecord::TestCase
     topic = klass.new(wibble: "123-4567")
     topic.wibble.gsub!("-", "")
 
-    assert topic.valid?
+    assert_predicate topic, :valid?
   end
 
   def test_numericality_validation_checks_against_raw_value
@@ -175,12 +175,12 @@ class ValidationsTest < ActiveRecord::TestCase
         ActiveModel::Name.new(self, nil, "Topic")
       end
       attribute :wibble, :decimal, scale: 2, precision: 9
-      validates_numericality_of :wibble, greater_than_or_equal_to: BigDecimal.new("97.18")
+      validates_numericality_of :wibble, greater_than_or_equal_to: BigDecimal("97.18")
     end
 
-    assert_not klass.new(wibble: "97.179").valid?
-    assert_not klass.new(wibble: 97.179).valid?
-    assert_not klass.new(wibble: BigDecimal.new("97.179")).valid?
+    assert_not_predicate klass.new(wibble: "97.179"), :valid?
+    assert_not_predicate klass.new(wibble: 97.179), :valid?
+    assert_not_predicate klass.new(wibble: BigDecimal("97.179")), :valid?
   end
 
   def test_acceptance_validator_doesnt_require_db_connection
diff --git a/activerecord/test/cases/yaml_serialization_test.rb b/activerecord/test/cases/yaml_serialization_test.rb
index 578881f754..60ebdce178 100644
--- a/activerecord/test/cases/yaml_serialization_test.rb
+++ b/activerecord/test/cases/yaml_serialization_test.rb
@@ -96,7 +96,7 @@ class YamlSerializationTest < ActiveRecord::TestCase
   def test_deserializing_rails_41_yaml
     topic = YAML.load(yaml_fixture("rails_4_1"))
 
-    assert topic.new_record?
+    assert_predicate topic, :new_record?
     assert_nil topic.id
     assert_equal "The First Topic", topic.title
     assert_equal({ omg: :lol }, topic.content)
@@ -105,7 +105,7 @@ class YamlSerializationTest < ActiveRecord::TestCase
   def test_deserializing_rails_4_2_0_yaml
     topic = YAML.load(yaml_fixture("rails_4_2_0"))
 
-    assert_not topic.new_record?
+    assert_not_predicate topic, :new_record?
     assert_equal 1, topic.id
     assert_equal "The First Topic", topic.title
     assert_equal("Have a nice day", topic.content)
diff --git a/activerecord/test/fixtures/.gitignore b/activerecord/test/fixtures/.gitignore
deleted file mode 100644
index 885029a512..0000000000
--- a/activerecord/test/fixtures/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-*.sqlite*
-\ No newline at end of file
diff --git a/activerecord/test/fixtures/customers.yml b/activerecord/test/fixtures/customers.yml
index 0399ff83b9..7d6c1366d0 100644
--- a/activerecord/test/fixtures/customers.yml
+++ b/activerecord/test/fixtures/customers.yml
@@ -23,4 +23,13 @@ barney:
   address_street: Quiet Road
   address_city: Peaceful Town
   address_country: Tranquil Land
-  gps_location: NULL
-\ No newline at end of file
+  gps_location: NULL
+
+mary:
+  id: 4
+  name: Mary
+  balance: 1
+  address_street: Funny Street
+  address_city: Peaceful Town
+  address_country: Nation Land
+  gps_location: NULL
diff --git a/activerecord/test/fixtures/minimalistics.yml b/activerecord/test/fixtures/minimalistics.yml
index c3ec546209..83df0551bc 100644
--- a/activerecord/test/fixtures/minimalistics.yml
+++ b/activerecord/test/fixtures/minimalistics.yml
@@ -1,2 +1,5 @@
+zero:
+  id: 0
+
 first:
   id: 1
diff --git a/activerecord/test/fixtures/other_posts.yml b/activerecord/test/fixtures/other_posts.yml
index 39ff763547..3e11a33802 100644
--- a/activerecord/test/fixtures/other_posts.yml
+++ b/activerecord/test/fixtures/other_posts.yml
@@ -5,3 +5,4 @@ second_welcome:
   author_id: 1
   title: Welcome to the another weblog
   body: It's really nice today
+  comments_count: 1
diff --git a/activerecord/test/fixtures/posts.yml b/activerecord/test/fixtures/posts.yml
index 86d46f753a..8d7e1e0ae7 100644
--- a/activerecord/test/fixtures/posts.yml
+++ b/activerecord/test/fixtures/posts.yml
@@ -28,6 +28,7 @@ sti_comments:
   author_id: 1
   title: sti comments
   body: hello
+  comments_count: 5
   type: Post
 
 sti_post_and_comments:
@@ -35,6 +36,7 @@ sti_post_and_comments:
   author_id: 1
   title: sti me
   body: hello
+  comments_count: 2
   type: StiPost
 
 sti_habtm:
@@ -50,6 +52,8 @@ eager_other:
   title: eager loading with OR'd conditions
   body: hello
   type: Post
+  comments_count: 1
+  tags_count: 3
 
 misc_by_bob:
   id: 8
@@ -57,6 +61,7 @@ misc_by_bob:
   title: misc post by bob
   body: hello
   type: Post
+  tags_count: 1
 
 misc_by_mary:
   id: 9
@@ -64,6 +69,7 @@ misc_by_mary:
   title: misc post by mary
   body: hello
   type: Post
+  tags_count: 1
 
 other_by_bob:
   id: 10
@@ -71,6 +77,7 @@ other_by_bob:
   title: other post by bob
   body: hello
   type: Post
+  tags_count: 1
 
 other_by_mary:
   id: 11
@@ -78,3 +85,4 @@ other_by_mary:
   title: other post by mary
   body: hello
   type: Post
+  tags_count: 1
diff --git a/activerecord/test/fixtures/reserved_words/values.yml b/activerecord/test/fixtures/reserved_words/values.yml
index 7d109609ab..9ed9e5edc5 100644
--- a/activerecord/test/fixtures/reserved_words/values.yml
+++ b/activerecord/test/fixtures/reserved_words/values.yml
@@ -1,7 +1,7 @@
 values1:
-  id: 1
+  as: 1
   group_id: 2
 
 values2:
-  id: 2
+  as: 2
   group_id: 1
diff --git a/activerecord/test/fixtures/sponsors.yml b/activerecord/test/fixtures/sponsors.yml
index 2da541c539..02ddb8dd38 100644
--- a/activerecord/test/fixtures/sponsors.yml
+++ b/activerecord/test/fixtures/sponsors.yml
@@ -10,3 +10,6 @@ crazy_club_sponsor_for_groucho:
   sponsor_club: crazy_club
   sponsorable_id: 3
   sponsorable_type: Member
+sponsor_for_author_david:
+  sponsorable_id: 1
+  sponsorable_type: Author
diff --git a/activerecord/test/fixtures/teapots.yml b/activerecord/test/fixtures/teapots.yml
deleted file mode 100644
index ff515beb45..0000000000
--- a/activerecord/test/fixtures/teapots.yml
+++ /dev/null
@@ -1,3 +0,0 @@
-bob:
-  id: 1
-  name: Bob
diff --git a/activerecord/test/migrations/decimal/1_give_me_big_numbers.rb b/activerecord/test/migrations/decimal/1_give_me_big_numbers.rb
index b892f50e41..7d4233fe31 100644
--- a/activerecord/test/migrations/decimal/1_give_me_big_numbers.rb
+++ b/activerecord/test/migrations/decimal/1_give_me_big_numbers.rb
@@ -5,7 +5,7 @@ class GiveMeBigNumbers < ActiveRecord::Migration::Current
     create_table :big_numbers do |table|
       table.column :bank_balance, :decimal, precision: 10, scale: 2
       table.column :big_bank_balance, :decimal, precision: 15, scale: 2
-      table.column :world_population, :decimal, precision: 10
+      table.column :world_population, :decimal, precision: 20
       table.column :my_house_population, :decimal, precision: 2
       table.column :value_of_e, :decimal
     end
diff --git a/activerecord/test/migrations/empty/.gitkeep b/activerecord/test/migrations/empty/.gitkeep
deleted file mode 100644
index e69de29bb2..0000000000
--- a/activerecord/test/migrations/empty/.gitkeep
+++ /dev/null
diff --git a/actionpack/test/tmp/.gitignore b/activerecord/test/migrations/empty/.keep
index e69de29bb2..e69de29bb2 100644
--- a/actionpack/test/tmp/.gitignore
+++ b/activerecord/test/migrations/empty/.keep
diff --git a/activerecord/test/models/admin/user.rb b/activerecord/test/models/admin/user.rb
index abb5cb28e7..3f55364510 100644
--- a/activerecord/test/models/admin/user.rb
+++ b/activerecord/test/models/admin/user.rb
@@ -19,6 +19,9 @@ class Admin::User < ActiveRecord::Base
   store :params, accessors: [ :token ], coder: YAML
   store :settings, accessors: [ :color, :homepage ]
   store_accessor :settings, :favorite_food
+  store :parent, accessors: [:birthday, :name], prefix: true
+  store :spouse, accessors: [:birthday], prefix: :partner
+  store_accessor :spouse, :name, prefix: :partner
   store :preferences, accessors: [ :remember_login ]
   store :json_data, accessors: [ :height, :weight ], coder: Coder.new
   store :json_data_empty, accessors: [ :is_a_good_guy ], coder: Coder.new
diff --git a/activerecord/test/models/author.rb b/activerecord/test/models/author.rb
index 09958ca257..75932c7eb6 100644
--- a/activerecord/test/models/author.rb
+++ b/activerecord/test/models/author.rb
@@ -8,6 +8,7 @@ class Author < ActiveRecord::Base
   has_many :posts_with_comments, -> { includes(:comments) }, class_name: "Post"
   has_many :popular_grouped_posts, -> { includes(:comments).group("type").having("SUM(comments_count) > 1").select("type") }, class_name: "Post"
   has_many :posts_with_comments_sorted_by_comment_id, -> { includes(:comments).order("comments.id") }, class_name: "Post"
+  has_many :posts_sorted_by_id, -> { order(:id) }, class_name: "Post"
   has_many :posts_sorted_by_id_limited, -> { order("posts.id").limit(1) }, class_name: "Post"
   has_many :posts_with_categories, -> { includes(:categories) }, class_name: "Post"
   has_many :posts_with_comments_and_categories, -> { includes(:comments, :categories).order("posts.id") }, class_name: "Post"
@@ -21,7 +22,8 @@ class Author < ActiveRecord::Base
   end
   has_many :comments_containing_the_letter_e, through: :posts, source: :comments
   has_many :comments_with_order_and_conditions, -> { order("comments.body").where("comments.body like 'Thank%'") }, through: :posts, source: :comments
-  has_many :comments_with_include, -> { includes(:post) }, through: :posts, source: :comments
+  has_many :comments_with_include, -> { includes(:post).where(posts: { type: "Post" }) }, through: :posts, source: :comments
+  has_many :comments_for_first_author, -> { for_first_author }, through: :posts, source: :comments
 
   has_many :first_posts
   has_many :comments_on_first_posts, -> { order("posts.id desc, comments.id asc") }, through: :first_posts, source: :comments
@@ -39,7 +41,8 @@ class Author < ActiveRecord::Base
            -> { where(title: "Welcome to the weblog").where(Post.arel_table[:comments_count].gt(0)) },
            class_name: "Post"
 
-  has_many :comments_desc, -> { order("comments.id DESC") }, through: :posts, source: :comments
+  has_many :comments_desc, -> { order("comments.id DESC") }, through: :posts_sorted_by_id, source: :comments
+  has_many :unordered_comments, -> { unscope(:order).distinct }, through: :posts_sorted_by_id_limited, source: :comments
   has_many :funky_comments, through: :posts, source: :comments
   has_many :ordered_uniq_comments, -> { distinct.order("comments.id") }, through: :posts, source: :comments
   has_many :ordered_uniq_comments_desc, -> { distinct.order("comments.id DESC") }, through: :posts, source: :comments
@@ -78,7 +81,7 @@ class Author < ActiveRecord::Base
            after_add: [:log_after_adding,  Proc.new { |o, r| o.post_log << "after_adding_proc#{r.id || '<new>'}" }]
   has_many :unchangeable_posts, class_name: "Post", before_add: :raise_exception, after_add: :log_after_adding
 
-  has_many :categorizations
+  has_many :categorizations, -> {}
   has_many :categories, through: :categorizations
   has_many :named_categories, through: :categorizations
 
@@ -86,6 +89,9 @@ class Author < ActiveRecord::Base
   has_many :special_categories, through: :special_categorizations, source: :category
   has_one  :special_category,   through: :special_categorizations, source: :category
 
+  has_many :special_categories_with_conditions, -> { where(categorizations: { special: true }) }, through: :categorizations, source: :category
+  has_many :nonspecial_categories_with_conditions, -> { where(categorizations: { special: false }) }, through: :categorizations, source: :category
+
   has_many :categories_like_general, -> { where(name: "General") }, through: :categorizations, source: :category, class_name: "Category"
 
   has_many :categorized_posts, through: :categorizations, source: :post
@@ -99,10 +105,12 @@ class Author < ActiveRecord::Base
   has_many :taggings,        through: :posts, source: :taggings
   has_many :taggings_2,      through: :posts, source: :tagging
   has_many :tags,            through: :posts
+  has_many :ordered_tags,    through: :posts
   has_many :post_categories, through: :posts, source: :categories
   has_many :tagging_tags,    through: :taggings, source: :tag
 
   has_many :similar_posts, -> { distinct }, through: :tags, source: :tagged_posts
+  has_many :ordered_posts, -> { distinct }, through: :ordered_tags, source: :tagged_posts
   has_many :distinct_tags, -> { select("DISTINCT tags.*").order("tags.name") }, through: :posts, source: :tags
 
   has_many :tags_with_primary_key, through: :posts
@@ -154,6 +162,9 @@ class Author < ActiveRecord::Base
     def extension_method; end
   end
 
+  has_many :top_posts, -> { order(id: :asc) }, class_name: "Post"
+  has_many :other_top_posts, -> { order(id: :asc) }, class_name: "Post"
+
   attr_accessor :post_log
   after_initialize :set_post_log
 
diff --git a/activerecord/test/models/comment.rb b/activerecord/test/models/comment.rb
index 740aa593ac..f0f0576709 100644
--- a/activerecord/test/models/comment.rb
+++ b/activerecord/test/models/comment.rb
@@ -60,6 +60,10 @@ end
 
 class SpecialComment < Comment
   default_scope { where(deleted_at: nil) }
+
+  def self.what_are_you
+    "a special comment..."
+  end
 end
 
 class SubSpecialComment < SpecialComment
@@ -72,7 +76,7 @@ class CommentThatAutomaticallyAltersPostBody < Comment
   belongs_to :post, class_name: "PostThatLoadsCommentsInAnAfterSaveHook", foreign_key: :post_id
 
   after_save do |comment|
-    comment.post.update_attributes(body: "Automatically altered")
+    comment.post.update(body: "Automatically altered")
   end
 end
 
@@ -83,6 +87,6 @@ end
 
 class CommentWithAfterCreateUpdate < Comment
   after_create do
-    update_attributes(body: "bar")
+    update(body: "bar")
   end
 end
diff --git a/activerecord/test/models/company.rb b/activerecord/test/models/company.rb
index bbc5fc2b2d..6219f57fa1 100644
--- a/activerecord/test/models/company.rb
+++ b/activerecord/test/models/company.rb
@@ -87,6 +87,8 @@ class Firm < Company
 
   has_many :association_with_references, -> { references(:foo) }, class_name: "Client"
 
+  has_many :developers_with_select, -> { select("id, name, first_name") }, class_name: "Developer"
+
   has_one :lead_developer, class_name: "Developer"
   has_many :projects
 
@@ -143,6 +145,11 @@ class Client < Company
     raise RaisedOnSave if raise_on_save
   end
 
+  attr_accessor :throw_on_save
+  before_save do
+    throw :abort if throw_on_save
+  end
+
   class RaisedOnDestroy < RuntimeError; end
   attr_accessor :raise_on_destroy
   before_destroy do
diff --git a/activerecord/test/models/contract.rb b/activerecord/test/models/contract.rb
index 9454217e8d..f273badd85 100644
--- a/activerecord/test/models/contract.rb
+++ b/activerecord/test/models/contract.rb
@@ -2,7 +2,7 @@
 
 class Contract < ActiveRecord::Base
   belongs_to :company
-  belongs_to :developer
+  belongs_to :developer, primary_key: :id
   belongs_to :firm, foreign_key: "company_id"
 
   before_save :hi
diff --git a/activerecord/test/models/customer.rb b/activerecord/test/models/customer.rb
index 524a9d7bd9..bc501a5ce0 100644
--- a/activerecord/test/models/customer.rb
+++ b/activerecord/test/models/customer.rb
@@ -4,7 +4,7 @@ class Customer < ActiveRecord::Base
   cattr_accessor :gps_conversion_was_run
 
   composed_of :address, mapping: [ %w(address_street street), %w(address_city city), %w(address_country country) ], allow_nil: true
-  composed_of :balance, class_name: "Money", mapping: %w(balance amount), converter: Proc.new(&:to_money)
+  composed_of :balance, class_name: "Money", mapping: %w(balance amount)
   composed_of :gps_location, allow_nil: true
   composed_of :non_blank_gps_location, class_name: "GpsLocation", allow_nil: true, mapping: %w(gps_location gps_location),
               converter: lambda { |gps| self.gps_conversion_was_run = true; gps.blank? ? nil : GpsLocation.new(gps) }
diff --git a/activerecord/test/models/developer.rb b/activerecord/test/models/developer.rb
index 56aafca60b..8881c69368 100644
--- a/activerecord/test/models/developer.rb
+++ b/activerecord/test/models/developer.rb
@@ -87,6 +87,17 @@ class Developer < ActiveRecord::Base
   private :track_instance_count
 end
 
+class SubDeveloper < Developer
+end
+
+class SymbolIgnoredDeveloper < ActiveRecord::Base
+  self.table_name = "developers"
+  self.ignored_columns = [:first_name, :last_name]
+
+  attr_accessor :last_name
+  define_attribute_method "last_name"
+end
+
 class AuditLog < ActiveRecord::Base
   belongs_to :developer, validate: true
   belongs_to :unvalidated_developer, class_name: "Developer"
diff --git a/activerecord/test/models/drink_designer.rb b/activerecord/test/models/drink_designer.rb
index 1c407844c5..eb6701b84e 100644
--- a/activerecord/test/models/drink_designer.rb
+++ b/activerecord/test/models/drink_designer.rb
@@ -3,3 +3,6 @@
 class DrinkDesigner < ActiveRecord::Base
   has_one :chef, as: :employable
 end
+
+class MocktailDesigner < DrinkDesigner
+end
diff --git a/activerecord/test/models/face.rb b/activerecord/test/models/face.rb
index 796aaa4dc9..e900fd40fb 100644
--- a/activerecord/test/models/face.rb
+++ b/activerecord/test/models/face.rb
@@ -2,10 +2,15 @@
 
 class Face < ActiveRecord::Base
   belongs_to :man, inverse_of: :face
+  belongs_to :human, polymorphic: true
   belongs_to :polymorphic_man, polymorphic: true, inverse_of: :polymorphic_face
   # Oracle identifier length is limited to 30 bytes or less, `polymorphic` renamed `poly`
   belongs_to :poly_man_without_inverse, polymorphic: true
   # These is a "broken" inverse_of for the purposes of testing
   belongs_to :horrible_man, class_name: "Man", inverse_of: :horrible_face
   belongs_to :horrible_polymorphic_man, polymorphic: true, inverse_of: :horrible_polymorphic_face
+
+  validate do
+    man
+  end
 end
diff --git a/activerecord/test/models/frog.rb b/activerecord/test/models/frog.rb
new file mode 100644
index 0000000000..73601aacdd
--- /dev/null
+++ b/activerecord/test/models/frog.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+class Frog < ActiveRecord::Base
+  after_save do
+    with_lock do
+    end
+  end
+end
diff --git a/activerecord/test/models/man.rb b/activerecord/test/models/man.rb
index 3acd89a48e..e26920e951 100644
--- a/activerecord/test/models/man.rb
+++ b/activerecord/test/models/man.rb
@@ -11,3 +11,6 @@ class Man < ActiveRecord::Base
   has_many :secret_interests, class_name: "Interest", inverse_of: :secret_man
   has_one :mixed_case_monkey
 end
+
+class Human < Man
+end
diff --git a/activerecord/test/models/member_detail.rb b/activerecord/test/models/member_detail.rb
index 87f7aab9a2..e121a849d0 100644
--- a/activerecord/test/models/member_detail.rb
+++ b/activerecord/test/models/member_detail.rb
@@ -5,6 +5,7 @@ class MemberDetail < ActiveRecord::Base
   belongs_to :organization
   has_one :member_type, through: :member
   has_one :membership, through: :member
+  has_one :admittable, through: :member, source_type: "Member"
 
   has_many :organization_member_details, through: :organization, source: :member_details
 end
diff --git a/activerecord/test/models/mocktail_designer.rb b/activerecord/test/models/mocktail_designer.rb
deleted file mode 100644
index 123ff4fb3d..0000000000
--- a/activerecord/test/models/mocktail_designer.rb
+++ /dev/null
@@ -1,4 +0,0 @@
-# frozen_string_literal: true
-
-class MocktailDesigner < DrinkDesigner
-end
diff --git a/activerecord/test/models/post.rb b/activerecord/test/models/post.rb
index 4c8e847354..54eb5e6783 100644
--- a/activerecord/test/models/post.rb
+++ b/activerecord/test/models/post.rb
@@ -21,7 +21,7 @@ class Post < ActiveRecord::Base
 
   scope :containing_the_letter_a, -> { where("body LIKE '%a%'") }
   scope :titled_with_an_apostrophe, -> { where("title LIKE '%''%'") }
-  scope :ranked_by_comments,      -> { order("comments_count DESC") }
+  scope :ranked_by_comments, -> { order(arel_attribute(:comments_count).desc) }
 
   scope :limit_by, lambda { |l| limit(l) }
   scope :locked, -> { lock }
@@ -106,6 +106,9 @@ class Post < ActiveRecord::Base
     end
   end
 
+  has_many :indestructible_taggings, as: :taggable, counter_cache: :indestructible_tags_count
+  has_many :indestructible_tags, through: :indestructible_taggings, source: :tag
+
   has_many :taggings_with_delete_all, class_name: "Tagging", as: :taggable, dependent: :delete_all, counter_cache: :taggings_with_delete_all_count
   has_many :taggings_with_destroy, class_name: "Tagging", as: :taggable, dependent: :destroy, counter_cache: :taggings_with_destroy_count
 
@@ -115,6 +118,7 @@ class Post < ActiveRecord::Base
   has_many :misc_tags, -> { where tags: { name: "Misc" } }, through: :taggings, source: :tag
   has_many :funky_tags, through: :taggings, source: :tag
   has_many :super_tags, through: :taggings
+  has_many :ordered_tags, through: :taggings
   has_many :tags_with_primary_key, through: :taggings, source: :tag_with_primary_key
   has_one :tagging, as: :taggable
 
@@ -318,5 +322,17 @@ class FakeKlass
     def arel_attribute(name, table)
       table[name]
     end
+
+    def enforce_raw_sql_whitelist(*args)
+      # noop
+    end
+
+    def arel_table
+      Post.arel_table
+    end
+
+    def predicate_builder
+      Post.predicate_builder
+    end
   end
 end
diff --git a/activerecord/test/models/sponsor.rb b/activerecord/test/models/sponsor.rb
index f190860fd1..18ff103ffe 100644
--- a/activerecord/test/models/sponsor.rb
+++ b/activerecord/test/models/sponsor.rb
@@ -3,6 +3,7 @@
 class Sponsor < ActiveRecord::Base
   belongs_to :sponsor_club, class_name: "Club", foreign_key: "club_id"
   belongs_to :sponsorable, polymorphic: true
+  belongs_to :sponsor, polymorphic: true
   belongs_to :thing, polymorphic: true, foreign_type: :sponsorable_type, foreign_key: :sponsorable_id
   belongs_to :sponsorable_with_conditions, -> { where name: "Ernie" }, polymorphic: true,
              foreign_type: "sponsorable_type", foreign_key: "sponsorable_id"
diff --git a/activerecord/test/models/tag.rb b/activerecord/test/models/tag.rb
index 4495ac4a09..c1a8890a8a 100644
--- a/activerecord/test/models/tag.rb
+++ b/activerecord/test/models/tag.rb
@@ -11,5 +11,6 @@ end
 class OrderedTag < Tag
   self.table_name = "tags"
 
-  has_many :taggings, -> { order("taggings.id DESC") }, foreign_key: "tag_id"
+  has_many :ordered_taggings, -> { order("taggings.id DESC") }, foreign_key: "tag_id", class_name: "Tagging"
+  has_many :tagged_posts, through: :ordered_taggings, source: "taggable", source_type: "Post"
 end
diff --git a/activerecord/test/models/tagging.rb b/activerecord/test/models/tagging.rb
index fc0af026c5..6d4230f6f4 100644
--- a/activerecord/test/models/tagging.rb
+++ b/activerecord/test/models/tagging.rb
@@ -8,8 +8,13 @@ class Tagging < ActiveRecord::Base
   belongs_to :tag, -> { includes(:tagging) }
   belongs_to :super_tag,   class_name: "Tag", foreign_key: "super_tag_id"
   belongs_to :invalid_tag, class_name: "Tag", foreign_key: "tag_id"
+  belongs_to :ordered_tag, class_name: "OrderedTag", foreign_key: "tag_id"
   belongs_to :blue_tag, -> { where tags: { name: "Blue" } }, class_name: "Tag", foreign_key: :tag_id
   belongs_to :tag_with_primary_key, class_name: "Tag", foreign_key: :tag_id, primary_key: :custom_primary_key
   belongs_to :taggable, polymorphic: true, counter_cache: :tags_count
   has_many :things, through: :taggable
 end
+
+class IndestructibleTagging < Tagging
+  before_destroy { throw :abort }
+end
diff --git a/activerecord/test/models/topic.rb b/activerecord/test/models/topic.rb
index 2154b50ef7..2e386d7669 100644
--- a/activerecord/test/models/topic.rb
+++ b/activerecord/test/models/topic.rb
@@ -12,9 +12,17 @@ class Topic < ActiveRecord::Base
 
   scope :scope_with_lambda, lambda { all }
 
+  scope :by_private_lifo, -> { where(author_name: private_lifo) }
   scope :by_lifo, -> { where(author_name: "lifo") }
   scope :replied, -> { where "replies_count > 0" }
 
+  class << self
+    private
+      def private_lifo
+        "lifo"
+      end
+  end
+
   scope "approved_as_string", -> { where(approved: true) }
   scope :anonymous_extension, -> {} do
     def one
@@ -65,6 +73,9 @@ class Topic < ActiveRecord::Base
 
   after_initialize :set_email_address
 
+  attr_accessor :change_approved_before_save
+  before_save :change_approved_callback
+
   class_attribute :after_initialize_called
   after_initialize do
     self.class.after_initialize_called = true
@@ -86,7 +97,7 @@ class Topic < ActiveRecord::Base
     end
 
     def set_email_address
-      unless persisted?
+      unless persisted? || will_save_change_to_author_email_address?
         self.author_email_address = "test@test.com"
       end
     end
@@ -96,6 +107,10 @@ class Topic < ActiveRecord::Base
     def before_destroy_for_transaction; end
     def after_save_for_transaction; end
     def after_create_for_transaction; end
+
+    def change_approved_callback
+      self.approved = change_approved_before_save unless change_approved_before_save.nil?
+    end
 end
 
 class ImportantTopic < Topic
diff --git a/activerecord/test/models/wheel.rb b/activerecord/test/models/wheel.rb
index e05fb64477..8db57d181e 100644
--- a/activerecord/test/models/wheel.rb
+++ b/activerecord/test/models/wheel.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 class Wheel < ActiveRecord::Base
-  belongs_to :wheelable, polymorphic: true, counter_cache: true
+  belongs_to :wheelable, polymorphic: true, counter_cache: true, touch: true
 end
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 8f872c38ba..92ad25ef76 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -21,6 +21,8 @@ ActiveRecord::Schema.define do
   create_table :admin_users, force: true do |t|
     t.string :name
     t.string :settings, null: true, limit: 1024
+    t.string :parent, null: true, limit: 1024
+    t.string :spouse, null: true, limit: 1024
     # MySQL does not allow default values for blobs. Fake it out with a
     # big varchar below.
     t.string :preferences, null: true, default: "", limit: 1024
@@ -123,7 +125,7 @@ ActiveRecord::Schema.define do
   create_table :cars, force: true do |t|
     t.string  :name
     t.integer :engines_count
-    t.integer :wheels_count
+    t.integer :wheels_count, default: 0
     t.column :lock_version, :integer, null: false, default: 0
     t.timestamps null: false
   end
@@ -191,6 +193,7 @@ ActiveRecord::Schema.define do
     t.string :resource_id
     t.string :resource_type
     t.integer :developer_id
+    t.datetime :updated_at
     t.datetime :deleted_at
     t.integer :comments
   end
@@ -204,10 +207,12 @@ ActiveRecord::Schema.define do
     t.bigint :rating, default: 1
     t.integer :account_id
     t.string :description, default: ""
+    t.index [:name, :rating], order: :desc
+    t.index [:name, :description], length: 10
     t.index [:firm_id, :type, :rating], name: "company_index", length: { type: 10 }, order: { rating: :desc }
     t.index [:firm_id, :type], name: "company_partial_index", where: "(rating > 10)"
     t.index :name, name: "company_name_index", using: :btree
-    t.index "lower(name)", name: "company_expression_index" if supports_expression_index?
+    t.index "(CASE WHEN rating > 0 THEN lower(name) END)", name: "company_expression_index" if supports_expression_index?
   end
 
   create_table :content, force: true do |t|
@@ -342,6 +347,10 @@ ActiveRecord::Schema.define do
     t.string :token
   end
 
+  create_table :frogs, force: true do |t|
+    t.string :name
+  end
+
   create_table :funny_jokes, force: true do |t|
     t.string :name
   end
@@ -477,7 +486,8 @@ ActiveRecord::Schema.define do
 
   create_table :members, force: true do |t|
     t.string :name
-    t.integer :member_type_id
+    t.references :member_type, index: false
+    t.references :admittable, polymorphic: true, index: false
   end
 
   create_table :member_details, force: true do |t|
@@ -544,7 +554,7 @@ ActiveRecord::Schema.define do
   create_table :numeric_data, force: true do |t|
     t.decimal :bank_balance, precision: 10, scale: 2
     t.decimal :big_bank_balance, precision: 15, scale: 2
-    t.decimal :world_population, precision: 10, scale: 0
+    t.decimal :world_population, precision: 20, scale: 0
     t.decimal :my_house_population, precision: 2, scale: 0
     t.decimal :decimal_number_with_default, precision: 3, scale: 2, default: 2.78
     t.float   :temperature
@@ -687,6 +697,7 @@ ActiveRecord::Schema.define do
     t.integer :taggings_with_delete_all_count, default: 0
     t.integer :taggings_with_destroy_count, default: 0
     t.integer :tags_count, default: 0
+    t.integer :indestructible_tags_count, default: 0
     t.integer :tags_with_destroy_count, default: 0
     t.integer :tags_with_nullify_count, default: 0
   end
@@ -810,6 +821,7 @@ ActiveRecord::Schema.define do
   create_table :sponsors, force: true do |t|
     t.integer :club_id
     t.references :sponsorable, polymorphic: true, index: false
+    t.references :sponsor, polymorphic: true, index: false
   end
 
   create_table :string_key_objects, id: false, force: true do |t|
@@ -844,6 +856,7 @@ ActiveRecord::Schema.define do
     t.column :taggable_type, :string
     t.column :taggable_id, :integer
     t.string :comment
+    t.string :type
   end
 
   create_table :tasks, force: true do |t|
@@ -946,6 +959,7 @@ ActiveRecord::Schema.define do
     t.string  :poly_man_without_inverse_type
     t.integer :horrible_polymorphic_man_id
     t.string  :horrible_polymorphic_man_type
+    t.references :human, polymorphic: true, index: false
   end
 
   create_table :interests, force: true do |t|
@@ -961,6 +975,7 @@ ActiveRecord::Schema.define do
   end
 
   create_table :wheels, force: true do |t|
+    t.integer :size
     t.references :wheelable, polymorphic: true
   end
 
diff --git a/activestorage/.babelrc b/activestorage/.babelrc
index a8211d329f..ed751f8745 100644
--- a/activestorage/.babelrc
+++ b/activestorage/.babelrc
@@ -1,5 +1,8 @@
 {
   "presets": [
     ["env", { "modules": false } ]
+  ],
+  "plugins": [
+    "external-helpers"
   ]
 }
diff --git a/activestorage/.gitignore b/activestorage/.gitignore
index a532335bdd..3e78878ffc 100644
--- a/activestorage/.gitignore
+++ b/activestorage/.gitignore
@@ -1,6 +1,6 @@
-.byebug_history
-node_modules
-test/dummy/db/*.sqlite3
-test/dummy/db/*.sqlite3-journal
-test/dummy/log/*.log
-test/dummy/tmp/
+/src/
+/test/dummy/db/*.sqlite3
+/test/dummy/db/*.sqlite3-journal
+/test/dummy/log/*.log
+/test/dummy/tmp/
+/test/service/configurations.yml
diff --git a/activestorage/CHANGELOG.md b/activestorage/CHANGELOG.md
index 358552313f..c8911fe611 100644
--- a/activestorage/CHANGELOG.md
+++ b/activestorage/CHANGELOG.md
@@ -1,3 +1,66 @@
-*   Added to Rails.
+*   Variant arguments of `false` or `nil` will no longer be passed to the
+    processor. For example, the following will not have the monochrome
+    variation applied:
 
-    *DHH*
+    ```ruby
+      avatar.variant(monochrome: false)
+    ```
+
+    *Jacob Smith*
+
+*   Generated attachment getter and setter methods are created
+    within the model's `GeneratedAssociationMethods` module to
+    allow overriding and composition using `super`.
+
+    *Josh Susser*, *Jamon Douglas*
+
+*   Add `ActiveStorage::Blob#open`, which downloads a blob to a tempfile on disk
+    and yields the tempfile. Deprecate `ActiveStorage::Downloading`.
+
+    *David Robertson*, *George Claghorn*
+
+*   Pass in `identify: false` as an argument when providing a `content_type` for
+    `ActiveStorage::Attached::{One,Many}#attach` to bypass automatic content
+    type inference. For example:
+
+    ```ruby
+      @message.image.attach(
+        io: File.open('/path/to/file'),
+        filename: 'file.pdf',
+        content_type: 'application/pdf',
+        identify: false
+      )
+    ```
+
+    *Ryan Davidson*
+
+*   The Google Cloud Storage service properly supports streaming downloads.
+    It now requires version 1.11 or newer of the google-cloud-storage gem.
+
+    *George Claghorn*
+
+*   Use the [ImageProcessing](https://github.com/janko-m/image_processing) gem
+    for Active Storage variants, and deprecate the MiniMagick backend.
+
+    This means that variants are now automatically oriented if the original
+    image was rotated. Also, in addition to the existing ImageMagick
+    operations, variants can now use `:resize_to_fit`, `:resize_to_fill`, and
+    other ImageProcessing macros. These are now recommended over raw `:resize`,
+    as they also sharpen the thumbnail after resizing.
+
+    The ImageProcessing gem also comes with a backend implemented on
+    [libvips](http://jcupitt.github.io/libvips/), an alternative to
+    ImageMagick which has significantly better performance than
+    ImageMagick in most cases, both in terms of speed and memory usage. In
+    Active Storage it's now possible to switch to the libvips backend by
+    changing `Rails.application.config.active_storage.variant_processor` to
+    `:vips`.
+
+    *Janko Marohnić*
+
+*   Rails 6 requires Ruby 2.4.1 or newer.
+
+    *Jeremy Daer*
+
+
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/activestorage/CHANGELOG.md) for previous changes.
diff --git a/activestorage/MIT-LICENSE b/activestorage/MIT-LICENSE
index 4e1c6cad79..eed89ac398 100644
--- a/activestorage/MIT-LICENSE
+++ b/activestorage/MIT-LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2017 David Heinemeier Hansson, Basecamp
+Copyright (c) 2017-2018 David Heinemeier Hansson, Basecamp
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/activestorage/README.md b/activestorage/README.md
index 17d98978bb..b677721d95 100644
--- a/activestorage/README.md
+++ b/activestorage/README.md
@@ -1,10 +1,10 @@
 # Active Storage
 
-Active Storage makes it simple to upload and reference files in cloud services like Amazon S3, Google Cloud Storage, or Microsoft Azure Storage, and attach those files to Active Records. Supports having one main service and mirrors in other services for redundancy. It also provides a disk service for testing or local deployments, but the focus is on cloud storage.
+Active Storage makes it simple to upload and reference files in cloud services like [Amazon S3](https://aws.amazon.com/s3/), [Google Cloud Storage](https://cloud.google.com/storage/docs/), or [Microsoft Azure Storage](https://azure.microsoft.com/en-us/services/storage/), and attach those files to Active Records. Supports having one main service and mirrors in other services for redundancy. It also provides a disk service for testing or local deployments, but the focus is on cloud storage.
 
 Files can be uploaded from the server to the cloud or directly from the client to the cloud.
 
-Image files can furthermore be transformed using on-demand variants for quality, aspect ratio, size, or any other [MiniMagick](https://github.com/minimagick/minimagick) supported transformation.
+Image files can furthermore be transformed using on-demand variants for quality, aspect ratio, size, or any other [MiniMagick](https://github.com/minimagick/minimagick) or [Vips](http://www.rubydoc.info/gems/ruby-vips/Vips/Image) supported transformation.
 
 ## Compared to other storage solutions
 
@@ -12,6 +12,10 @@ A key difference to how Active Storage works compared to other attachment soluti
 
 `Blob` models store attachment metadata (filename, content-type, etc.), and their identifier key in the storage service. Blob models do not store the actual binary data. They are intended to be immutable in spirit. One file, one blob. You can associate the same blob with multiple application models as well. And if you want to do transformations of a given `Blob`, the idea is that you'll simply create a new one, rather than attempt to mutate the existing one (though of course you can delete the previous version later if you don't need it).
 
+## Installation
+
+Run `rails active_storage:install` to copy over active_storage migrations.
+
 ## Examples
 
 One attachment:
@@ -24,7 +28,7 @@ class User < ApplicationRecord
 end
 
 # Attach an avatar to the user.
-user.avatar.attach(io: File.open("~/face.jpg"), filename: "avatar.jpg", content_type: "image/jpg")
+user.avatar.attach(io: File.open("/path/to/face.jpg"), filename: "face.jpg", content_type: "image/jpg")
 
 # Does the user have an avatar?
 user.avatar.attached? # => true
@@ -63,7 +67,7 @@ end
 ```
 
 ```erb
-<%= form_with model: @message do |form| %>
+<%= form_with model: @message, local: true do |form| %>
   <%= form.text_field :title, placeholder: "Title" %><br>
   <%= form.text_area :content %><br><br>
 
@@ -95,7 +99,7 @@ Variation of image attachment:
 
 ```erb
 <%# Hitting the variant URL will lazy transform the original blob and then redirect to its new service location %>
-<%= image_tag user.avatar.variant(resize: "100x100") %>
+<%= image_tag user.avatar.variant(resize_to_fit: [100, 100]) %>
 ```
 
 ## Direct uploads
@@ -139,3 +143,17 @@ Active Storage, with its included JavaScript library, supports uploading directl
 ## License
 
 Active Storage is released under the [MIT License](https://opensource.org/licenses/MIT).
+
+## Support
+
+API documentation is at:
+
+* http://api.rubyonrails.org
+
+Bug reports for the Ruby on Rails project can be filed here:
+
+* https://github.com/rails/rails/issues
+
+Feature requests should be discussed on the rails-core mailing list here:
+
+* https://groups.google.com/forum/?fromgroups#!forum/rubyonrails-core
diff --git a/activestorage/Rakefile b/activestorage/Rakefile
index aa71a65f6e..2e86d3d860 100644
--- a/activestorage/Rakefile
+++ b/activestorage/Rakefile
@@ -4,11 +4,14 @@ require "bundler/setup"
 require "bundler/gem_tasks"
 require "rake/testtask"
 
-Rake::TestTask.new do |test|
-  test.libs << "app/controllers"
-  test.libs << "test"
-  test.test_files = FileList["test/**/*_test.rb"]
-  test.warning = false
+Rake::TestTask.new do |t|
+  t.libs << "app/controllers"
+  t.libs << "test"
+  t.test_files = FileList["test/**/*_test.rb"]
+  t.verbose = true
+  t.warning = true
 end
 
+task :package
+
 task default: :test
diff --git a/activestorage/activestorage.gemspec b/activestorage/activestorage.gemspec
index 911e1a0469..cb1bb00a25 100644
--- a/activestorage/activestorage.gemspec
+++ b/activestorage/activestorage.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Local and cloud file storage framework."
   s.description = "Attach cloud and local files in Rails applications."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
@@ -17,7 +17,7 @@ Gem::Specification.new do |s|
   s.email    = "david@loudthinking.com"
   s.homepage = "http://rubyonrails.org"
 
-  s.files        = Dir["CHANGELOG.md", "MIT-LICENSE", "README.md", "lib/**/*", "app/**/*", "config/**/*"]
+  s.files        = Dir["CHANGELOG.md", "MIT-LICENSE", "README.md", "lib/**/*", "app/**/*", "config/**/*", "db/**/*"]
   s.require_path = "lib"
 
   s.metadata = {
@@ -27,4 +27,6 @@ Gem::Specification.new do |s|
 
   s.add_dependency "actionpack", version
   s.add_dependency "activerecord", version
+
+  s.add_dependency "marcel", "~> 0.3.1"
 end
diff --git a/activestorage/app/assets/javascripts/activestorage.js b/activestorage/app/assets/javascripts/activestorage.js
index 33dc5cdc58..a22f644238 100644
--- a/activestorage/app/assets/javascripts/activestorage.js
+++ b/activestorage/app/assets/javascripts/activestorage.js
@@ -1 +1,930 @@
-!function(t,e){"object"==typeof exports&&"object"==typeof module?module.exports=e():"function"==typeof define&&define.amd?define([],e):"object"==typeof exports?exports.ActiveStorage=e():t.ActiveStorage=e()}(this,function(){return function(t){function e(n){if(r[n])return r[n].exports;var i=r[n]={i:n,l:!1,exports:{}};return t[n].call(i.exports,i,i.exports,e),i.l=!0,i.exports}var r={};return e.m=t,e.c=r,e.d=function(t,r,n){e.o(t,r)||Object.defineProperty(t,r,{configurable:!1,enumerable:!0,get:n})},e.n=function(t){var r=t&&t.__esModule?function(){return t.default}:function(){return t};return e.d(r,"a",r),r},e.o=function(t,e){return Object.prototype.hasOwnProperty.call(t,e)},e.p="",e(e.s=2)}([function(t,e,r){"use strict";function n(t){var e=a(document.head,'meta[name="'+t+'"]');if(e)return e.getAttribute("content")}function i(t,e){return"string"==typeof t&&(e=t,t=document),o(t.querySelectorAll(e))}function a(t,e){return"string"==typeof t&&(e=t,t=document),t.querySelector(e)}function u(t,e){var r=arguments.length>2&&void 0!==arguments[2]?arguments[2]:{},n=r.bubbles,i=r.cancelable,a=r.detail,u=document.createEvent("Event");return u.initEvent(e,n||!0,i||!0),u.detail=a||{},t.dispatchEvent(u),u}function o(t){return Array.isArray(t)?t:Array.from?Array.from(t):[].slice.call(t)}e.d=n,e.c=i,e.b=a,e.a=u,e.e=o},function(t,e,r){"use strict";function n(t,e){if(!(t instanceof e))throw new TypeError("Cannot call a class as a function")}function i(t,e){if(t&&"function"==typeof t[e]){for(var r=arguments.length,n=Array(r>2?r-2:0),i=2;i<r;i++)n[i-2]=arguments[i];return t[e].apply(t,n)}}r.d(e,"a",function(){return c});var a=r(6),u=r(8),o=r(9),s=function(){function t(t,e){for(var r=0;r<e.length;r++){var n=e[r];n.enumerable=n.enumerable||!1,n.configurable=!0,"value"in n&&(n.writable=!0),Object.defineProperty(t,n.key,n)}}return function(e,r,n){return r&&t(e.prototype,r),n&&t(e,n),e}}(),f=0,c=function(){function t(e,r,i){n(this,t),this.id=++f,this.file=e,this.url=r,this.delegate=i}return s(t,[{key:"create",value:function(t){var e=this;a.a.create(this.file,function(r,n){var a=new u.a(e.file,n,e.url);i(e.delegate,"directUploadWillCreateBlobWithXHR",a.xhr),a.create(function(r){if(r)t(r);else{var n=new o.a(a);i(e.delegate,"directUploadWillStoreFileWithXHR",n.xhr),n.create(function(e){e?t(e):t(null,a.toJSON())})}})})}}]),t}()},function(t,e,r){"use strict";function n(){window.ActiveStorage&&Object(i.a)()}Object.defineProperty(e,"__esModule",{value:!0});var i=r(3),a=r(1);r.d(e,"start",function(){return i.a}),r.d(e,"DirectUpload",function(){return a.a}),setTimeout(n,1)},function(t,e,r){"use strict";function n(){d||(d=!0,document.addEventListener("submit",i),document.addEventListener("ajax:before",a))}function i(t){u(t)}function a(t){"FORM"==t.target.tagName&&u(t)}function u(t){var e=t.target;if(e.hasAttribute(l))return void t.preventDefault();var r=new c.a(e),n=r.inputs;n.length&&(t.preventDefault(),e.setAttribute(l,""),n.forEach(s),r.start(function(t){e.removeAttribute(l),t?n.forEach(f):o(e)}))}function o(t){var e=Object(h.b)(t,"input[type=submit]");if(e){var r=e,n=r.disabled;e.disabled=!1,e.click(),e.disabled=n}else e=document.createElement("input"),e.type="submit",e.style="display:none",t.appendChild(e),e.click(),t.removeChild(e)}function s(t){t.disabled=!0}function f(t){t.disabled=!1}e.a=n;var c=r(4),h=r(0),l="data-direct-uploads-processing",d=!1},function(t,e,r){"use strict";function n(t,e){if(!(t instanceof e))throw new TypeError("Cannot call a class as a function")}r.d(e,"a",function(){return s});var i=r(5),a=r(0),u=function(){function t(t,e){for(var r=0;r<e.length;r++){var n=e[r];n.enumerable=n.enumerable||!1,n.configurable=!0,"value"in n&&(n.writable=!0),Object.defineProperty(t,n.key,n)}}return function(e,r,n){return 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-\ No newline at end of file
+(function(global, factory) {
+  typeof exports === "object" && typeof module !== "undefined" ? factory(exports) : typeof define === "function" && define.amd ? define([ "exports" ], factory) : factory(global.ActiveStorage = {});
+})(this, function(exports) {
+  "use strict";
+  function createCommonjsModule(fn, module) {
+    return module = {
+      exports: {}
+    }, fn(module, module.exports), module.exports;
+  }
+  var sparkMd5 = createCommonjsModule(function(module, exports) {
+    (function(factory) {
+      {
+        module.exports = factory();
+      }
+    })(function(undefined) {
+      var hex_chr = [ "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" ];
+      function md5cycle(x, k) {
+        var a = x[0], b = x[1], c = x[2], d = x[3];
+        a += (b & c | ~b & d) + k[0] - 680876936 | 0;
+        a = (a << 7 | a >>> 25) + b | 0;
+        d += (a & b | ~a & c) + k[1] - 389564586 | 0;
+        d = (d << 12 | d >>> 20) + a | 0;
+        c += (d & a | ~d & b) + k[2] + 606105819 | 0;
+        c = (c << 17 | c >>> 15) + d | 0;
+        b += (c & d | ~c & a) + k[3] - 1044525330 | 0;
+        b = (b << 22 | b >>> 10) + c | 0;
+        a += (b & c | ~b & d) + k[4] - 176418897 | 0;
+        a = (a << 7 | a >>> 25) + b | 0;
+        d += (a & b | ~a & c) + k[5] + 1200080426 | 0;
+        d = (d << 12 | d >>> 20) + a | 0;
+        c += (d & a | ~d & b) + k[6] - 1473231341 | 0;
+        c = (c << 17 | c >>> 15) + d | 0;
+        b += (c & d | ~c & a) + k[7] - 45705983 | 0;
+        b = (b << 22 | b >>> 10) + c | 0;
+        a += (b & c | ~b & d) + k[8] + 1770035416 | 0;
+        a = (a << 7 | a >>> 25) + b | 0;
+        d += (a & b | ~a & c) + k[9] - 1958414417 | 0;
+        d = (d << 12 | d >>> 20) + a | 0;
+        c += (d & a | ~d & b) + k[10] - 42063 | 0;
+        c = (c << 17 | c >>> 15) + d | 0;
+        b += (c & d | ~c & a) + k[11] - 1990404162 | 0;
+        b = (b << 22 | b >>> 10) + c | 0;
+        a += (b & c | ~b & d) + k[12] + 1804603682 | 0;
+        a = (a << 7 | a >>> 25) + b | 0;
+        d += (a & b | ~a & c) + k[13] - 40341101 | 0;
+        d = (d << 12 | d >>> 20) + a | 0;
+        c += (d & a | ~d & b) + k[14] - 1502002290 | 0;
+        c = (c << 17 | c >>> 15) + d | 0;
+        b += (c & d | ~c & a) + k[15] + 1236535329 | 0;
+        b = (b << 22 | b >>> 10) + c | 0;
+        a += (b & d | c & ~d) + k[1] - 165796510 | 0;
+        a = (a << 5 | a >>> 27) + b | 0;
+        d += (a & c | b & ~c) + k[6] - 1069501632 | 0;
+        d = (d << 9 | d >>> 23) + a | 0;
+        c += (d & b | a & ~b) + k[11] + 643717713 | 0;
+        c = (c << 14 | c >>> 18) + d | 0;
+        b += (c & a | d & ~a) + k[0] - 373897302 | 0;
+        b = (b << 20 | b >>> 12) + c | 0;
+        a += (b & d | c & ~d) + k[5] - 701558691 | 0;
+        a = (a << 5 | a >>> 27) + b | 0;
+        d += (a & c | b & ~c) + k[10] + 38016083 | 0;
+        d = (d << 9 | d >>> 23) + a | 0;
+        c += (d & b | a & ~b) + k[15] - 660478335 | 0;
+        c = (c << 14 | c >>> 18) + d | 0;
+        b += (c & a | d & ~a) + k[4] - 405537848 | 0;
+        b = (b << 20 | b >>> 12) + c | 0;
+        a += (b & d | c & ~d) + k[9] + 568446438 | 0;
+        a = (a << 5 | a >>> 27) + b | 0;
+        d += (a & c | b & ~c) + k[14] - 1019803690 | 0;
+        d = (d << 9 | d >>> 23) + a | 0;
+        c += (d & b | a & ~b) + k[3] - 187363961 | 0;
+        c = (c << 14 | c >>> 18) + d | 0;
+        b += (c & a | d & ~a) + k[8] + 1163531501 | 0;
+        b = (b << 20 | b >>> 12) + c | 0;
+        a += (b & d | c & ~d) + k[13] - 1444681467 | 0;
+        a = (a << 5 | a >>> 27) + b | 0;
+        d += (a & c | b & ~c) + k[2] - 51403784 | 0;
+        d = (d << 9 | d >>> 23) + a | 0;
+        c += (d & b | a & ~b) + k[7] + 1735328473 | 0;
+        c = (c << 14 | c >>> 18) + d | 0;
+        b += (c & a | d & ~a) + k[12] - 1926607734 | 0;
+        b = (b << 20 | b >>> 12) + c | 0;
+        a += (b ^ c ^ d) + k[5] - 378558 | 0;
+        a = (a << 4 | a >>> 28) + b | 0;
+        d += (a ^ b ^ c) + k[8] - 2022574463 | 0;
+        d = (d << 11 | d >>> 21) + a | 0;
+        c += (d ^ a ^ b) + k[11] + 1839030562 | 0;
+        c = (c << 16 | c >>> 16) + d | 0;
+        b += (c ^ d ^ a) + k[14] - 35309556 | 0;
+        b = (b << 23 | b >>> 9) + c | 0;
+        a += (b ^ c ^ d) + k[1] - 1530992060 | 0;
+        a = (a << 4 | a >>> 28) + b | 0;
+        d += (a ^ b ^ c) + k[4] + 1272893353 | 0;
+        d = (d << 11 | d >>> 21) + a | 0;
+        c += (d ^ a ^ b) + k[7] - 155497632 | 0;
+        c = (c << 16 | c >>> 16) + d | 0;
+        b += (c ^ d ^ a) + k[10] - 1094730640 | 0;
+        b = (b << 23 | b >>> 9) + c | 0;
+        a += (b ^ c ^ d) + k[13] + 681279174 | 0;
+        a = (a << 4 | a >>> 28) + b | 0;
+        d += (a ^ b ^ c) + k[0] - 358537222 | 0;
+        d = (d << 11 | d >>> 21) + a | 0;
+        c += (d ^ a ^ b) + k[3] - 722521979 | 0;
+        c = (c << 16 | c >>> 16) + d | 0;
+        b += (c ^ d ^ a) + k[6] + 76029189 | 0;
+        b = (b << 23 | b >>> 9) + c | 0;
+        a += (b ^ c ^ d) + k[9] - 640364487 | 0;
+        a = (a << 4 | a >>> 28) + b | 0;
+        d += (a ^ b ^ c) + k[12] - 421815835 | 0;
+        d = (d << 11 | d >>> 21) + a | 0;
+        c += (d ^ a ^ b) + k[15] + 530742520 | 0;
+        c = (c << 16 | c >>> 16) + d | 0;
+        b += (c ^ d ^ a) + k[2] - 995338651 | 0;
+        b = (b << 23 | b >>> 9) + c | 0;
+        a += (c ^ (b | ~d)) + k[0] - 198630844 | 0;
+        a = (a << 6 | a >>> 26) + b | 0;
+        d += (b ^ (a | ~c)) + k[7] + 1126891415 | 0;
+        d = (d << 10 | d >>> 22) + a | 0;
+        c += (a ^ (d | ~b)) + k[14] - 1416354905 | 0;
+        c = (c << 15 | c >>> 17) + d | 0;
+        b += (d ^ (c | ~a)) + k[5] - 57434055 | 0;
+        b = (b << 21 | b >>> 11) + c | 0;
+        a += (c ^ (b | ~d)) + k[12] + 1700485571 | 0;
+        a = (a << 6 | a >>> 26) + b | 0;
+        d += (b ^ (a | ~c)) + k[3] - 1894986606 | 0;
+        d = (d << 10 | d >>> 22) + a | 0;
+        c += (a ^ (d | ~b)) + k[10] - 1051523 | 0;
+        c = (c << 15 | c >>> 17) + d | 0;
+        b += (d ^ (c | ~a)) + k[1] - 2054922799 | 0;
+        b = (b << 21 | b >>> 11) + c | 0;
+        a += (c ^ (b | ~d)) + k[8] + 1873313359 | 0;
+        a = (a << 6 | a >>> 26) + b | 0;
+        d += (b ^ (a | ~c)) + k[15] - 30611744 | 0;
+        d = (d << 10 | d >>> 22) + a | 0;
+        c += (a ^ (d | ~b)) + k[6] - 1560198380 | 0;
+        c = (c << 15 | c >>> 17) + d | 0;
+        b += (d ^ (c | ~a)) + k[13] + 1309151649 | 0;
+        b = (b << 21 | b >>> 11) + c | 0;
+        a += (c ^ (b | ~d)) + k[4] - 145523070 | 0;
+        a = (a << 6 | a >>> 26) + b | 0;
+        d += (b ^ (a | ~c)) + k[11] - 1120210379 | 0;
+        d = (d << 10 | d >>> 22) + a | 0;
+        c += (a ^ (d | ~b)) + k[2] + 718787259 | 0;
+        c = (c << 15 | c >>> 17) + d | 0;
+        b += (d ^ (c | ~a)) + k[9] - 343485551 | 0;
+        b = (b << 21 | b >>> 11) + c | 0;
+        x[0] = a + x[0] | 0;
+        x[1] = b + x[1] | 0;
+        x[2] = c + x[2] | 0;
+        x[3] = d + x[3] | 0;
+      }
+      function md5blk(s) {
+        var md5blks = [], i;
+        for (i = 0; i < 64; i += 4) {
+          md5blks[i >> 2] = s.charCodeAt(i) + (s.charCodeAt(i + 1) << 8) + (s.charCodeAt(i + 2) << 16) + (s.charCodeAt(i + 3) << 24);
+        }
+        return md5blks;
+      }
+      function md5blk_array(a) {
+        var md5blks = [], i;
+        for (i = 0; i < 64; i += 4) {
+          md5blks[i >> 2] = a[i] + (a[i + 1] << 8) + (a[i + 2] << 16) + (a[i + 3] << 24);
+        }
+        return md5blks;
+      }
+      function md51(s) {
+        var n = s.length, state = [ 1732584193, -271733879, -1732584194, 271733878 ], i, length, tail, tmp, lo, hi;
+        for (i = 64; i <= n; i += 64) {
+          md5cycle(state, md5blk(s.substring(i - 64, i)));
+        }
+        s = s.substring(i - 64);
+        length = s.length;
+        tail = [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ];
+        for (i = 0; i < length; i += 1) {
+          tail[i >> 2] |= s.charCodeAt(i) << (i % 4 << 3);
+        }
+        tail[i >> 2] |= 128 << (i % 4 << 3);
+        if (i > 55) {
+          md5cycle(state, tail);
+          for (i = 0; i < 16; i += 1) {
+            tail[i] = 0;
+          }
+        }
+        tmp = n * 8;
+        tmp = tmp.toString(16).match(/(.*?)(.{0,8})$/);
+        lo = parseInt(tmp[2], 16);
+        hi = parseInt(tmp[1], 16) || 0;
+        tail[14] = lo;
+        tail[15] = hi;
+        md5cycle(state, tail);
+        return state;
+      }
+      function md51_array(a) {
+        var n = a.length, state = [ 1732584193, -271733879, -1732584194, 271733878 ], i, length, tail, tmp, lo, hi;
+        for (i = 64; i <= n; i += 64) {
+          md5cycle(state, md5blk_array(a.subarray(i - 64, i)));
+        }
+        a = i - 64 < n ? a.subarray(i - 64) : new Uint8Array(0);
+        length = a.length;
+        tail = [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ];
+        for (i = 0; i < length; i += 1) {
+          tail[i >> 2] |= a[i] << (i % 4 << 3);
+        }
+        tail[i >> 2] |= 128 << (i % 4 << 3);
+        if (i > 55) {
+          md5cycle(state, tail);
+          for (i = 0; i < 16; i += 1) {
+            tail[i] = 0;
+          }
+        }
+        tmp = n * 8;
+        tmp = tmp.toString(16).match(/(.*?)(.{0,8})$/);
+        lo = parseInt(tmp[2], 16);
+        hi = parseInt(tmp[1], 16) || 0;
+        tail[14] = lo;
+        tail[15] = hi;
+        md5cycle(state, tail);
+        return state;
+      }
+      function rhex(n) {
+        var s = "", j;
+        for (j = 0; j < 4; j += 1) {
+          s += hex_chr[n >> j * 8 + 4 & 15] + hex_chr[n >> j * 8 & 15];
+        }
+        return s;
+      }
+      function hex(x) {
+        var i;
+        for (i = 0; i < x.length; i += 1) {
+          x[i] = rhex(x[i]);
+        }
+        return x.join("");
+      }
+      if (hex(md51("hello")) !== "5d41402abc4b2a76b9719d911017c592") ;
+      if (typeof ArrayBuffer !== "undefined" && !ArrayBuffer.prototype.slice) {
+        (function() {
+          function clamp(val, length) {
+            val = val | 0 || 0;
+            if (val < 0) {
+              return Math.max(val + length, 0);
+            }
+            return Math.min(val, length);
+          }
+          ArrayBuffer.prototype.slice = function(from, to) {
+            var length = this.byteLength, begin = clamp(from, length), end = length, num, target, targetArray, sourceArray;
+            if (to !== undefined) {
+              end = clamp(to, length);
+            }
+            if (begin > end) {
+              return new ArrayBuffer(0);
+            }
+            num = end - begin;
+            target = new ArrayBuffer(num);
+            targetArray = new Uint8Array(target);
+            sourceArray = new Uint8Array(this, begin, num);
+            targetArray.set(sourceArray);
+            return target;
+          };
+        })();
+      }
+      function toUtf8(str) {
+        if (/[\u0080-\uFFFF]/.test(str)) {
+          str = unescape(encodeURIComponent(str));
+        }
+        return str;
+      }
+      function utf8Str2ArrayBuffer(str, returnUInt8Array) {
+        var length = str.length, buff = new ArrayBuffer(length), arr = new Uint8Array(buff), i;
+        for (i = 0; i < length; i += 1) {
+          arr[i] = str.charCodeAt(i);
+        }
+        return returnUInt8Array ? arr : buff;
+      }
+      function arrayBuffer2Utf8Str(buff) {
+        return String.fromCharCode.apply(null, new Uint8Array(buff));
+      }
+      function concatenateArrayBuffers(first, second, returnUInt8Array) {
+        var result = new Uint8Array(first.byteLength + second.byteLength);
+        result.set(new Uint8Array(first));
+        result.set(new Uint8Array(second), first.byteLength);
+        return returnUInt8Array ? result : result.buffer;
+      }
+      function hexToBinaryString(hex) {
+        var bytes = [], length = hex.length, x;
+        for (x = 0; x < length - 1; x += 2) {
+          bytes.push(parseInt(hex.substr(x, 2), 16));
+        }
+        return String.fromCharCode.apply(String, bytes);
+      }
+      function SparkMD5() {
+        this.reset();
+      }
+      SparkMD5.prototype.append = function(str) {
+        this.appendBinary(toUtf8(str));
+        return this;
+      };
+      SparkMD5.prototype.appendBinary = function(contents) {
+        this._buff += contents;
+        this._length += contents.length;
+        var length = this._buff.length, i;
+        for (i = 64; i <= length; i += 64) {
+          md5cycle(this._hash, md5blk(this._buff.substring(i - 64, i)));
+        }
+        this._buff = this._buff.substring(i - 64);
+        return this;
+      };
+      SparkMD5.prototype.end = function(raw) {
+        var buff = this._buff, length = buff.length, i, tail = [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ], ret;
+        for (i = 0; i < length; i += 1) {
+          tail[i >> 2] |= buff.charCodeAt(i) << (i % 4 << 3);
+        }
+        this._finish(tail, length);
+        ret = hex(this._hash);
+        if (raw) {
+          ret = hexToBinaryString(ret);
+        }
+        this.reset();
+        return ret;
+      };
+      SparkMD5.prototype.reset = function() {
+        this._buff = "";
+        this._length = 0;
+        this._hash = [ 1732584193, -271733879, -1732584194, 271733878 ];
+        return this;
+      };
+      SparkMD5.prototype.getState = function() {
+        return {
+          buff: this._buff,
+          length: this._length,
+          hash: this._hash
+        };
+      };
+      SparkMD5.prototype.setState = function(state) {
+        this._buff = state.buff;
+        this._length = state.length;
+        this._hash = state.hash;
+        return this;
+      };
+      SparkMD5.prototype.destroy = function() {
+        delete this._hash;
+        delete this._buff;
+        delete this._length;
+      };
+      SparkMD5.prototype._finish = function(tail, length) {
+        var i = length, tmp, lo, hi;
+        tail[i >> 2] |= 128 << (i % 4 << 3);
+        if (i > 55) {
+          md5cycle(this._hash, tail);
+          for (i = 0; i < 16; i += 1) {
+            tail[i] = 0;
+          }
+        }
+        tmp = this._length * 8;
+        tmp = tmp.toString(16).match(/(.*?)(.{0,8})$/);
+        lo = parseInt(tmp[2], 16);
+        hi = parseInt(tmp[1], 16) || 0;
+        tail[14] = lo;
+        tail[15] = hi;
+        md5cycle(this._hash, tail);
+      };
+      SparkMD5.hash = function(str, raw) {
+        return SparkMD5.hashBinary(toUtf8(str), raw);
+      };
+      SparkMD5.hashBinary = function(content, raw) {
+        var hash = md51(content), ret = hex(hash);
+        return raw ? hexToBinaryString(ret) : ret;
+      };
+      SparkMD5.ArrayBuffer = function() {
+        this.reset();
+      };
+      SparkMD5.ArrayBuffer.prototype.append = function(arr) {
+        var buff = concatenateArrayBuffers(this._buff.buffer, arr, true), length = buff.length, i;
+        this._length += arr.byteLength;
+        for (i = 64; i <= length; i += 64) {
+          md5cycle(this._hash, md5blk_array(buff.subarray(i - 64, i)));
+        }
+        this._buff = i - 64 < length ? new Uint8Array(buff.buffer.slice(i - 64)) : new Uint8Array(0);
+        return this;
+      };
+      SparkMD5.ArrayBuffer.prototype.end = function(raw) {
+        var buff = this._buff, length = buff.length, tail = [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ], i, ret;
+        for (i = 0; i < length; i += 1) {
+          tail[i >> 2] |= buff[i] << (i % 4 << 3);
+        }
+        this._finish(tail, length);
+        ret = hex(this._hash);
+        if (raw) {
+          ret = hexToBinaryString(ret);
+        }
+        this.reset();
+        return ret;
+      };
+      SparkMD5.ArrayBuffer.prototype.reset = function() {
+        this._buff = new Uint8Array(0);
+        this._length = 0;
+        this._hash = [ 1732584193, -271733879, -1732584194, 271733878 ];
+        return this;
+      };
+      SparkMD5.ArrayBuffer.prototype.getState = function() {
+        var state = SparkMD5.prototype.getState.call(this);
+        state.buff = arrayBuffer2Utf8Str(state.buff);
+        return state;
+      };
+      SparkMD5.ArrayBuffer.prototype.setState = function(state) {
+        state.buff = utf8Str2ArrayBuffer(state.buff, true);
+        return SparkMD5.prototype.setState.call(this, state);
+      };
+      SparkMD5.ArrayBuffer.prototype.destroy = SparkMD5.prototype.destroy;
+      SparkMD5.ArrayBuffer.prototype._finish = SparkMD5.prototype._finish;
+      SparkMD5.ArrayBuffer.hash = function(arr, raw) {
+        var hash = md51_array(new Uint8Array(arr)), ret = hex(hash);
+        return raw ? hexToBinaryString(ret) : ret;
+      };
+      return SparkMD5;
+    });
+  });
+  var classCallCheck = function(instance, Constructor) {
+    if (!(instance instanceof Constructor)) {
+      throw new TypeError("Cannot call a class as a function");
+    }
+  };
+  var createClass = function() {
+    function defineProperties(target, props) {
+      for (var i = 0; i < props.length; i++) {
+        var descriptor = props[i];
+        descriptor.enumerable = descriptor.enumerable || false;
+        descriptor.configurable = true;
+        if ("value" in descriptor) descriptor.writable = true;
+        Object.defineProperty(target, descriptor.key, descriptor);
+      }
+    }
+    return function(Constructor, protoProps, staticProps) {
+      if (protoProps) defineProperties(Constructor.prototype, protoProps);
+      if (staticProps) defineProperties(Constructor, staticProps);
+      return Constructor;
+    };
+  }();
+  var fileSlice = File.prototype.slice || File.prototype.mozSlice || File.prototype.webkitSlice;
+  var FileChecksum = function() {
+    createClass(FileChecksum, null, [ {
+      key: "create",
+      value: function create(file, callback) {
+        var instance = new FileChecksum(file);
+        instance.create(callback);
+      }
+    } ]);
+    function FileChecksum(file) {
+      classCallCheck(this, FileChecksum);
+      this.file = file;
+      this.chunkSize = 2097152;
+      this.chunkCount = Math.ceil(this.file.size / this.chunkSize);
+      this.chunkIndex = 0;
+    }
+    createClass(FileChecksum, [ {
+      key: "create",
+      value: function create(callback) {
+        var _this = this;
+        this.callback = callback;
+        this.md5Buffer = new sparkMd5.ArrayBuffer();
+        this.fileReader = new FileReader();
+        this.fileReader.addEventListener("load", function(event) {
+          return _this.fileReaderDidLoad(event);
+        });
+        this.fileReader.addEventListener("error", function(event) {
+          return _this.fileReaderDidError(event);
+        });
+        this.readNextChunk();
+      }
+    }, {
+      key: "fileReaderDidLoad",
+      value: function fileReaderDidLoad(event) {
+        this.md5Buffer.append(event.target.result);
+        if (!this.readNextChunk()) {
+          var binaryDigest = this.md5Buffer.end(true);
+          var base64digest = btoa(binaryDigest);
+          this.callback(null, base64digest);
+        }
+      }
+    }, {
+      key: "fileReaderDidError",
+      value: function fileReaderDidError(event) {
+        this.callback("Error reading " + this.file.name);
+      }
+    }, {
+      key: "readNextChunk",
+      value: function readNextChunk() {
+        if (this.chunkIndex < this.chunkCount) {
+          var start = this.chunkIndex * this.chunkSize;
+          var end = Math.min(start + this.chunkSize, this.file.size);
+          var bytes = fileSlice.call(this.file, start, end);
+          this.fileReader.readAsArrayBuffer(bytes);
+          this.chunkIndex++;
+          return true;
+        } else {
+          return false;
+        }
+      }
+    } ]);
+    return FileChecksum;
+  }();
+  function getMetaValue(name) {
+    var element = findElement(document.head, 'meta[name="' + name + '"]');
+    if (element) {
+      return element.getAttribute("content");
+    }
+  }
+  function findElements(root, selector) {
+    if (typeof root == "string") {
+      selector = root;
+      root = document;
+    }
+    var elements = root.querySelectorAll(selector);
+    return toArray$1(elements);
+  }
+  function findElement(root, selector) {
+    if (typeof root == "string") {
+      selector = root;
+      root = document;
+    }
+    return root.querySelector(selector);
+  }
+  function dispatchEvent(element, type) {
+    var eventInit = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : {};
+    var disabled = element.disabled;
+    var bubbles = eventInit.bubbles, cancelable = eventInit.cancelable, detail = eventInit.detail;
+    var event = document.createEvent("Event");
+    event.initEvent(type, bubbles || true, cancelable || true);
+    event.detail = detail || {};
+    try {
+      element.disabled = false;
+      element.dispatchEvent(event);
+    } finally {
+      element.disabled = disabled;
+    }
+    return event;
+  }
+  function toArray$1(value) {
+    if (Array.isArray(value)) {
+      return value;
+    } else if (Array.from) {
+      return Array.from(value);
+    } else {
+      return [].slice.call(value);
+    }
+  }
+  var BlobRecord = function() {
+    function BlobRecord(file, checksum, url) {
+      var _this = this;
+      classCallCheck(this, BlobRecord);
+      this.file = file;
+      this.attributes = {
+        filename: file.name,
+        content_type: file.type,
+        byte_size: file.size,
+        checksum: checksum
+      };
+      this.xhr = new XMLHttpRequest();
+      this.xhr.open("POST", url, true);
+      this.xhr.responseType = "json";
+      this.xhr.setRequestHeader("Content-Type", "application/json");
+      this.xhr.setRequestHeader("Accept", "application/json");
+      this.xhr.setRequestHeader("X-Requested-With", "XMLHttpRequest");
+      this.xhr.setRequestHeader("X-CSRF-Token", getMetaValue("csrf-token"));
+      this.xhr.addEventListener("load", function(event) {
+        return _this.requestDidLoad(event);
+      });
+      this.xhr.addEventListener("error", function(event) {
+        return _this.requestDidError(event);
+      });
+    }
+    createClass(BlobRecord, [ {
+      key: "create",
+      value: function create(callback) {
+        this.callback = callback;
+        this.xhr.send(JSON.stringify({
+          blob: this.attributes
+        }));
+      }
+    }, {
+      key: "requestDidLoad",
+      value: function requestDidLoad(event) {
+        if (this.status >= 200 && this.status < 300) {
+          var response = this.response;
+          var direct_upload = response.direct_upload;
+          delete response.direct_upload;
+          this.attributes = response;
+          this.directUploadData = direct_upload;
+          this.callback(null, this.toJSON());
+        } else {
+          this.requestDidError(event);
+        }
+      }
+    }, {
+      key: "requestDidError",
+      value: function requestDidError(event) {
+        this.callback('Error creating Blob for "' + this.file.name + '". Status: ' + this.status);
+      }
+    }, {
+      key: "toJSON",
+      value: function toJSON() {
+        var result = {};
+        for (var key in this.attributes) {
+          result[key] = this.attributes[key];
+        }
+        return result;
+      }
+    }, {
+      key: "status",
+      get: function get$$1() {
+        return this.xhr.status;
+      }
+    }, {
+      key: "response",
+      get: function get$$1() {
+        var _xhr = this.xhr, responseType = _xhr.responseType, response = _xhr.response;
+        if (responseType == "json") {
+          return response;
+        } else {
+          return JSON.parse(response);
+        }
+      }
+    } ]);
+    return BlobRecord;
+  }();
+  var BlobUpload = function() {
+    function BlobUpload(blob) {
+      var _this = this;
+      classCallCheck(this, BlobUpload);
+      this.blob = blob;
+      this.file = blob.file;
+      var _blob$directUploadDat = blob.directUploadData, url = _blob$directUploadDat.url, headers = _blob$directUploadDat.headers;
+      this.xhr = new XMLHttpRequest();
+      this.xhr.open("PUT", url, true);
+      this.xhr.responseType = "text";
+      for (var key in headers) {
+        this.xhr.setRequestHeader(key, headers[key]);
+      }
+      this.xhr.addEventListener("load", function(event) {
+        return _this.requestDidLoad(event);
+      });
+      this.xhr.addEventListener("error", function(event) {
+        return _this.requestDidError(event);
+      });
+    }
+    createClass(BlobUpload, [ {
+      key: "create",
+      value: function create(callback) {
+        this.callback = callback;
+        this.xhr.send(this.file.slice());
+      }
+    }, {
+      key: "requestDidLoad",
+      value: function requestDidLoad(event) {
+        var _xhr = this.xhr, status = _xhr.status, response = _xhr.response;
+        if (status >= 200 && status < 300) {
+          this.callback(null, response);
+        } else {
+          this.requestDidError(event);
+        }
+      }
+    }, {
+      key: "requestDidError",
+      value: function requestDidError(event) {
+        this.callback('Error storing "' + this.file.name + '". Status: ' + this.xhr.status);
+      }
+    } ]);
+    return BlobUpload;
+  }();
+  var id = 0;
+  var DirectUpload = function() {
+    function DirectUpload(file, url, delegate) {
+      classCallCheck(this, DirectUpload);
+      this.id = ++id;
+      this.file = file;
+      this.url = url;
+      this.delegate = delegate;
+    }
+    createClass(DirectUpload, [ {
+      key: "create",
+      value: function create(callback) {
+        var _this = this;
+        FileChecksum.create(this.file, function(error, checksum) {
+          if (error) {
+            callback(error);
+            return;
+          }
+          var blob = new BlobRecord(_this.file, checksum, _this.url);
+          notify(_this.delegate, "directUploadWillCreateBlobWithXHR", blob.xhr);
+          blob.create(function(error) {
+            if (error) {
+              callback(error);
+            } else {
+              var upload = new BlobUpload(blob);
+              notify(_this.delegate, "directUploadWillStoreFileWithXHR", upload.xhr);
+              upload.create(function(error) {
+                if (error) {
+                  callback(error);
+                } else {
+                  callback(null, blob.toJSON());
+                }
+              });
+            }
+          });
+        });
+      }
+    } ]);
+    return DirectUpload;
+  }();
+  function notify(object, methodName) {
+    if (object && typeof object[methodName] == "function") {
+      for (var _len = arguments.length, messages = Array(_len > 2 ? _len - 2 : 0), _key = 2; _key < _len; _key++) {
+        messages[_key - 2] = arguments[_key];
+      }
+      return object[methodName].apply(object, messages);
+    }
+  }
+  var DirectUploadController = function() {
+    function DirectUploadController(input, file) {
+      classCallCheck(this, DirectUploadController);
+      this.input = input;
+      this.file = file;
+      this.directUpload = new DirectUpload(this.file, this.url, this);
+      this.dispatch("initialize");
+    }
+    createClass(DirectUploadController, [ {
+      key: "start",
+      value: function start(callback) {
+        var _this = this;
+        var hiddenInput = document.createElement("input");
+        hiddenInput.type = "hidden";
+        hiddenInput.name = this.input.name;
+        this.input.insertAdjacentElement("beforebegin", hiddenInput);
+        this.dispatch("start");
+        this.directUpload.create(function(error, attributes) {
+          if (error) {
+            hiddenInput.parentNode.removeChild(hiddenInput);
+            _this.dispatchError(error);
+          } else {
+            hiddenInput.value = attributes.signed_id;
+          }
+          _this.dispatch("end");
+          callback(error);
+        });
+      }
+    }, {
+      key: "uploadRequestDidProgress",
+      value: function uploadRequestDidProgress(event) {
+        var progress = event.loaded / event.total * 100;
+        if (progress) {
+          this.dispatch("progress", {
+            progress: progress
+          });
+        }
+      }
+    }, {
+      key: "dispatch",
+      value: function dispatch(name) {
+        var detail = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {};
+        detail.file = this.file;
+        detail.id = this.directUpload.id;
+        return dispatchEvent(this.input, "direct-upload:" + name, {
+          detail: detail
+        });
+      }
+    }, {
+      key: "dispatchError",
+      value: function dispatchError(error) {
+        var event = this.dispatch("error", {
+          error: error
+        });
+        if (!event.defaultPrevented) {
+          alert(error);
+        }
+      }
+    }, {
+      key: "directUploadWillCreateBlobWithXHR",
+      value: function directUploadWillCreateBlobWithXHR(xhr) {
+        this.dispatch("before-blob-request", {
+          xhr: xhr
+        });
+      }
+    }, {
+      key: "directUploadWillStoreFileWithXHR",
+      value: function directUploadWillStoreFileWithXHR(xhr) {
+        var _this2 = this;
+        this.dispatch("before-storage-request", {
+          xhr: xhr
+        });
+        xhr.upload.addEventListener("progress", function(event) {
+          return _this2.uploadRequestDidProgress(event);
+        });
+      }
+    }, {
+      key: "url",
+      get: function get$$1() {
+        return this.input.getAttribute("data-direct-upload-url");
+      }
+    } ]);
+    return DirectUploadController;
+  }();
+  var inputSelector = "input[type=file][data-direct-upload-url]:not([disabled])";
+  var DirectUploadsController = function() {
+    function DirectUploadsController(form) {
+      classCallCheck(this, DirectUploadsController);
+      this.form = form;
+      this.inputs = findElements(form, inputSelector).filter(function(input) {
+        return input.files.length;
+      });
+    }
+    createClass(DirectUploadsController, [ {
+      key: "start",
+      value: function start(callback) {
+        var _this = this;
+        var controllers = this.createDirectUploadControllers();
+        var startNextController = function startNextController() {
+          var controller = controllers.shift();
+          if (controller) {
+            controller.start(function(error) {
+              if (error) {
+                callback(error);
+                _this.dispatch("end");
+              } else {
+                startNextController();
+              }
+            });
+          } else {
+            callback();
+            _this.dispatch("end");
+          }
+        };
+        this.dispatch("start");
+        startNextController();
+      }
+    }, {
+      key: "createDirectUploadControllers",
+      value: function createDirectUploadControllers() {
+        var controllers = [];
+        this.inputs.forEach(function(input) {
+          toArray$1(input.files).forEach(function(file) {
+            var controller = new DirectUploadController(input, file);
+            controllers.push(controller);
+          });
+        });
+        return controllers;
+      }
+    }, {
+      key: "dispatch",
+      value: function dispatch(name) {
+        var detail = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {};
+        return dispatchEvent(this.form, "direct-uploads:" + name, {
+          detail: detail
+        });
+      }
+    } ]);
+    return DirectUploadsController;
+  }();
+  var processingAttribute = "data-direct-uploads-processing";
+  var started = false;
+  function start() {
+    if (!started) {
+      started = true;
+      document.addEventListener("submit", didSubmitForm);
+      document.addEventListener("ajax:before", didSubmitRemoteElement);
+    }
+  }
+  function didSubmitForm(event) {
+    handleFormSubmissionEvent(event);
+  }
+  function didSubmitRemoteElement(event) {
+    if (event.target.tagName == "FORM") {
+      handleFormSubmissionEvent(event);
+    }
+  }
+  function handleFormSubmissionEvent(event) {
+    var form = event.target;
+    if (form.hasAttribute(processingAttribute)) {
+      event.preventDefault();
+      return;
+    }
+    var controller = new DirectUploadsController(form);
+    var inputs = controller.inputs;
+    if (inputs.length) {
+      event.preventDefault();
+      form.setAttribute(processingAttribute, "");
+      inputs.forEach(disable);
+      controller.start(function(error) {
+        form.removeAttribute(processingAttribute);
+        if (error) {
+          inputs.forEach(enable);
+        } else {
+          submitForm(form);
+        }
+      });
+    }
+  }
+  function submitForm(form) {
+    var button = findElement(form, "input[type=submit]");
+    if (button) {
+      var _button = button, disabled = _button.disabled;
+      button.disabled = false;
+      button.focus();
+      button.click();
+      button.disabled = disabled;
+    } else {
+      button = document.createElement("input");
+      button.type = "submit";
+      button.style.display = "none";
+      form.appendChild(button);
+      button.click();
+      form.removeChild(button);
+    }
+  }
+  function disable(input) {
+    input.disabled = true;
+  }
+  function enable(input) {
+    input.disabled = false;
+  }
+  function autostart() {
+    if (window.ActiveStorage) {
+      start();
+    }
+  }
+  setTimeout(autostart, 1);
+  exports.start = start;
+  exports.DirectUpload = DirectUpload;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
+});
diff --git a/activestorage/app/controllers/active_storage/base_controller.rb b/activestorage/app/controllers/active_storage/base_controller.rb
new file mode 100644
index 0000000000..59312ac8df
--- /dev/null
+++ b/activestorage/app/controllers/active_storage/base_controller.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+# The base controller for all ActiveStorage controllers.
+class ActiveStorage::BaseController < ActionController::Base
+  protect_from_forgery with: :exception
+
+  before_action do
+    ActiveStorage::Current.host = request.base_url
+  end
+end
diff --git a/activestorage/app/controllers/active_storage/blobs_controller.rb b/activestorage/app/controllers/active_storage/blobs_controller.rb
index 00aa8567c8..92e54c386d 100644
--- a/activestorage/app/controllers/active_storage/blobs_controller.rb
+++ b/activestorage/app/controllers/active_storage/blobs_controller.rb
@@ -4,22 +4,11 @@
 # Note: These URLs are publicly accessible. If you need to enforce access protection beyond the
 # security-through-obscurity factor of the signed blob references, you'll need to implement your own
 # authenticated redirection controller.
-class ActiveStorage::BlobsController < ActionController::Base
+class ActiveStorage::BlobsController < ActiveStorage::BaseController
+  include ActiveStorage::SetBlob
+
   def show
-    if blob = find_signed_blob
-      expires_in 5.minutes # service_url defaults to 5 minutes
-      redirect_to blob.service_url(disposition: disposition_param)
-    else
-      head :not_found
-    end
+    expires_in ActiveStorage::Blob.service.url_expires_in
+    redirect_to @blob.service_url(disposition: params[:disposition])
   end
-
-  private
-    def find_signed_blob
-      ActiveStorage::Blob.find_signed(params[:signed_id])
-    end
-
-    def disposition_param
-      params[:disposition].presence_in(%w( inline attachment )) || "inline"
-    end
 end
diff --git a/activestorage/app/controllers/active_storage/direct_uploads_controller.rb b/activestorage/app/controllers/active_storage/direct_uploads_controller.rb
index 205d173648..78b43fc94c 100644
--- a/activestorage/app/controllers/active_storage/direct_uploads_controller.rb
+++ b/activestorage/app/controllers/active_storage/direct_uploads_controller.rb
@@ -3,7 +3,7 @@
 # Creates a new blob on the server side in anticipation of a direct-to-service upload from the client side.
 # When the client-side upload is completed, the signed_blob_id can be submitted as part of the form to reference
 # the blob that was created up front.
-class ActiveStorage::DirectUploadsController < ActionController::Base
+class ActiveStorage::DirectUploadsController < ActiveStorage::BaseController
   def create
     blob = ActiveStorage::Blob.create_before_direct_upload!(blob_args)
     render json: direct_upload_json(blob)
@@ -15,7 +15,7 @@ class ActiveStorage::DirectUploadsController < ActionController::Base
     end
 
     def direct_upload_json(blob)
-      blob.as_json(methods: :signed_id).merge(direct_upload: {
+      blob.as_json(root: false, methods: :signed_id).merge(direct_upload: {
         url: blob.service_url_for_direct_upload,
         headers: blob.service_headers_for_direct_upload
       })
diff --git a/activestorage/app/controllers/active_storage/disk_controller.rb b/activestorage/app/controllers/active_storage/disk_controller.rb
index 41e6d61bff..63918eb6f4 100644
--- a/activestorage/app/controllers/active_storage/disk_controller.rb
+++ b/activestorage/app/controllers/active_storage/disk_controller.rb
@@ -4,20 +4,31 @@
 # This means using expiring, signed URLs that are meant for immediate access, not permanent linking.
 # Always go through the BlobsController, or your own authenticated controller, rather than directly
 # to the service url.
-class ActiveStorage::DiskController < ActionController::Base
+class ActiveStorage::DiskController < ActiveStorage::BaseController
+  include ActionController::Live
+
+  skip_forgery_protection
+
   def show
     if key = decode_verified_key
-      send_data disk_service.download(key),
-        disposition: disposition_param, content_type: params[:content_type]
+      response.headers["Content-Type"] = params[:content_type] || DEFAULT_SEND_FILE_TYPE
+      response.headers["Content-Disposition"] = params[:disposition] || DEFAULT_SEND_FILE_DISPOSITION
+
+      disk_service.download key do |chunk|
+        response.stream.write chunk
+      end
     else
       head :not_found
     end
+  ensure
+    response.stream.close
   end
 
   def update
     if token = decode_verified_token
       if acceptable_content?(token)
         disk_service.upload token[:key], request.body, checksum: token[:checksum]
+        head :no_content
       else
         head :unprocessable_entity
       end
@@ -26,6 +37,8 @@ class ActiveStorage::DiskController < ActionController::Base
     end
   rescue ActiveStorage::IntegrityError
     head :unprocessable_entity
+  ensure
+    response.stream.close
   end
 
   private
@@ -38,10 +51,6 @@ class ActiveStorage::DiskController < ActionController::Base
       ActiveStorage.verifier.verified(params[:encoded_key], purpose: :blob_key)
     end
 
-    def disposition_param
-      params[:disposition].presence || "inline"
-    end
-
 
     def decode_verified_token
       ActiveStorage.verifier.verified(params[:encoded_token], purpose: :blob_token)
diff --git a/activestorage/app/controllers/active_storage/representations_controller.rb b/activestorage/app/controllers/active_storage/representations_controller.rb
new file mode 100644
index 0000000000..ce9286db7d
--- /dev/null
+++ b/activestorage/app/controllers/active_storage/representations_controller.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+# Take a signed permanent reference for a blob representation and turn it into an expiring service URL for download.
+# Note: These URLs are publicly accessible. If you need to enforce access protection beyond the
+# security-through-obscurity factor of the signed blob and variation reference, you'll need to implement your own
+# authenticated redirection controller.
+class ActiveStorage::RepresentationsController < ActiveStorage::BaseController
+  include ActiveStorage::SetBlob
+
+  def show
+    expires_in ActiveStorage::Blob.service.url_expires_in
+    redirect_to @blob.representation(params[:variation_key]).processed.service_url(disposition: params[:disposition])
+  end
+end
diff --git a/activestorage/app/controllers/active_storage/variants_controller.rb b/activestorage/app/controllers/active_storage/variants_controller.rb
deleted file mode 100644
index 02e3010626..0000000000
--- a/activestorage/app/controllers/active_storage/variants_controller.rb
+++ /dev/null
@@ -1,29 +0,0 @@
-# frozen_string_literal: true
-
-# Take a signed permanent reference for a variant and turn it into an expiring service URL for download.
-# Note: These URLs are publicly accessible. If you need to enforce access protection beyond the
-# security-through-obscurity factor of the signed blob and variation reference, you'll need to implement your own
-# authenticated redirection controller.
-class ActiveStorage::VariantsController < ActionController::Base
-  def show
-    if blob = find_signed_blob
-      expires_in 5.minutes # service_url defaults to 5 minutes
-      redirect_to ActiveStorage::Variant.new(blob, decoded_variation).processed.service_url(disposition: disposition_param)
-    else
-      head :not_found
-    end
-  end
-
-  private
-    def find_signed_blob
-      ActiveStorage::Blob.find_signed(params[:signed_blob_id])
-    end
-
-    def decoded_variation
-      ActiveStorage::Variation.decode(params[:variation_key])
-    end
-
-    def disposition_param
-      params[:disposition].presence_in(%w( inline attachment )) || "inline"
-    end
-end
diff --git a/activestorage/app/controllers/concerns/active_storage/set_blob.rb b/activestorage/app/controllers/concerns/active_storage/set_blob.rb
new file mode 100644
index 0000000000..f072954d78
--- /dev/null
+++ b/activestorage/app/controllers/concerns/active_storage/set_blob.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module ActiveStorage::SetBlob #:nodoc:
+  extend ActiveSupport::Concern
+
+  included do
+    before_action :set_blob
+  end
+
+  private
+    def set_blob
+      @blob = ActiveStorage::Blob.find_signed(params[:signed_blob_id] || params[:signed_id])
+    rescue ActiveSupport::MessageVerifier::InvalidSignature
+      head :not_found
+    end
+end
diff --git a/activestorage/app/javascript/activestorage/blob_record.js b/activestorage/app/javascript/activestorage/blob_record.js
index 3c6e6b6ba1..ff847892b2 100644
--- a/activestorage/app/javascript/activestorage/blob_record.js
+++ b/activestorage/app/javascript/activestorage/blob_record.js
@@ -22,14 +22,28 @@ export class BlobRecord {
     this.xhr.addEventListener("error", event => this.requestDidError(event))
   }
 
+  get status() {
+    return this.xhr.status
+  }
+
+  get response() {
+    const { responseType, response } = this.xhr
+    if (responseType == "json") {
+      return response
+    } else {
+      // Shim for IE 11: https://connect.microsoft.com/IE/feedback/details/794808
+      return JSON.parse(response)
+    }
+  }
+
   create(callback) {
     this.callback = callback
     this.xhr.send(JSON.stringify({ blob: this.attributes }))
   }
 
   requestDidLoad(event) {
-    const { status, response } = this.xhr
-    if (status >= 200 && status < 300) {
+    if (this.status >= 200 && this.status < 300) {
+      const { response } = this
       const { direct_upload } = response
       delete response.direct_upload
       this.attributes = response
@@ -41,7 +55,7 @@ export class BlobRecord {
   }
 
   requestDidError(event) {
-    this.callback(`Error creating Blob for "${this.file.name}". Status: ${this.xhr.status}`)
+    this.callback(`Error creating Blob for "${this.file.name}". Status: ${this.status}`)
   }
 
   toJSON() {
diff --git a/activestorage/app/javascript/activestorage/blob_upload.js b/activestorage/app/javascript/activestorage/blob_upload.js
index 99bf0c9e30..277cc8ff8e 100644
--- a/activestorage/app/javascript/activestorage/blob_upload.js
+++ b/activestorage/app/javascript/activestorage/blob_upload.js
@@ -7,6 +7,7 @@ export class BlobUpload {
 
     this.xhr = new XMLHttpRequest
     this.xhr.open("PUT", url, true)
+    this.xhr.responseType = "text"
     for (const key in headers) {
       this.xhr.setRequestHeader(key, headers[key])
     }
@@ -16,7 +17,7 @@ export class BlobUpload {
 
   create(callback) {
     this.callback = callback
-    this.xhr.send(this.file)
+    this.xhr.send(this.file.slice())
   }
 
   requestDidLoad(event) {
diff --git a/activestorage/app/javascript/activestorage/direct_upload.js b/activestorage/app/javascript/activestorage/direct_upload.js
index 7085e0a4ab..c2eedf289b 100644
--- a/activestorage/app/javascript/activestorage/direct_upload.js
+++ b/activestorage/app/javascript/activestorage/direct_upload.js
@@ -14,8 +14,14 @@ export class DirectUpload {
 
   create(callback) {
     FileChecksum.create(this.file, (error, checksum) => {
+      if (error) {
+        callback(error)
+        return
+      }
+
       const blob = new BlobRecord(this.file, checksum, this.url)
       notify(this.delegate, "directUploadWillCreateBlobWithXHR", blob.xhr)
+
       blob.create(error => {
         if (error) {
           callback(error)
diff --git a/activestorage/app/javascript/activestorage/helpers.js b/activestorage/app/javascript/activestorage/helpers.js
index 52fec8f6f1..7e83c447e7 100644
--- a/activestorage/app/javascript/activestorage/helpers.js
+++ b/activestorage/app/javascript/activestorage/helpers.js
@@ -23,11 +23,20 @@ export function findElement(root, selector) {
 }
 
 export function dispatchEvent(element, type, eventInit = {}) {
+  const { disabled } = element
   const { bubbles, cancelable, detail } = eventInit
   const event = document.createEvent("Event")
+
   event.initEvent(type, bubbles || true, cancelable || true)
   event.detail = detail || {}
-  element.dispatchEvent(event)
+
+  try {
+    element.disabled = false
+    element.dispatchEvent(event)
+  } finally {
+    element.disabled = disabled
+  }
+
   return event
 }
 
diff --git a/activestorage/app/javascript/activestorage/ujs.js b/activestorage/app/javascript/activestorage/ujs.js
index a2ce2cfc58..08c535470d 100644
--- a/activestorage/app/javascript/activestorage/ujs.js
+++ b/activestorage/app/javascript/activestorage/ujs.js
@@ -53,12 +53,13 @@ function submitForm(form) {
   if (button) {
     const { disabled } = button
     button.disabled = false
+    button.focus()
     button.click()
     button.disabled = disabled
   } else {
     button = document.createElement("input")
     button.type = "submit"
-    button.style = "display:none"
+    button.style.display = "none"
     form.appendChild(button)
     button.click()
     form.removeChild(button)
diff --git a/activestorage/app/jobs/active_storage/analyze_job.rb b/activestorage/app/jobs/active_storage/analyze_job.rb
new file mode 100644
index 0000000000..2a952f9f74
--- /dev/null
+++ b/activestorage/app/jobs/active_storage/analyze_job.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+# Provides asynchronous analysis of ActiveStorage::Blob records via ActiveStorage::Blob#analyze_later.
+class ActiveStorage::AnalyzeJob < ActiveStorage::BaseJob
+  def perform(blob)
+    blob.analyze
+  end
+end
diff --git a/activestorage/app/jobs/active_storage/base_job.rb b/activestorage/app/jobs/active_storage/base_job.rb
new file mode 100644
index 0000000000..6caab42a2d
--- /dev/null
+++ b/activestorage/app/jobs/active_storage/base_job.rb
@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class ActiveStorage::BaseJob < ActiveJob::Base
+  queue_as { ActiveStorage.queue }
+end
diff --git a/activestorage/app/jobs/active_storage/purge_job.rb b/activestorage/app/jobs/active_storage/purge_job.rb
index 369c07929d..98874d2250 100644
--- a/activestorage/app/jobs/active_storage/purge_job.rb
+++ b/activestorage/app/jobs/active_storage/purge_job.rb
@@ -1,11 +1,11 @@
 # frozen_string_literal: true
 
-# Provides delayed purging of attachments or blobs using their +purge_later+ method.
-class ActiveStorage::PurgeJob < ActiveJob::Base
+# Provides asynchronous purging of ActiveStorage::Blob records via ActiveStorage::Blob#purge_later.
+class ActiveStorage::PurgeJob < ActiveStorage::BaseJob
   # FIXME: Limit this to a custom ActiveStorage error
   retry_on StandardError
 
-  def perform(attachment_or_blob)
-    attachment_or_blob.purge
+  def perform(blob)
+    blob.purge
   end
 end
diff --git a/activestorage/app/models/active_storage/attachment.rb b/activestorage/app/models/active_storage/attachment.rb
index ad43845e4e..c59877a9a5 100644
--- a/activestorage/app/models/active_storage/attachment.rb
+++ b/activestorage/app/models/active_storage/attachment.rb
@@ -9,22 +9,31 @@ require "active_support/core_ext/module/delegation"
 class ActiveStorage::Attachment < ActiveRecord::Base
   self.table_name = "active_storage_attachments"
 
-  belongs_to :record, polymorphic: true
+  belongs_to :record, polymorphic: true, touch: true
   belongs_to :blob, class_name: "ActiveStorage::Blob"
 
   delegate_missing_to :blob
 
-  # Purging an attachment will purge the blob (delete the file on the service, then destroy the record)
-  # and then destroy the attachment itself.
+  after_create_commit :analyze_blob_later, :identify_blob
+
+  # Synchronously purges the blob (deletes it from the configured service) and destroys the attachment.
   def purge
     blob.purge
     destroy
   end
 
-  # Purging an attachment means purging the blob, which means talking to the service, which means
-  # talking over the Internet. Whenever you're doing that, it's a good idea to put that work in a job,
-  # so it doesn't hold up other operations. That's what +purge_later+ provides.
+  # Destroys the attachment and asynchronously purges the blob (deletes it from the configured service).
   def purge_later
-    ActiveStorage::PurgeJob.perform_later(self)
+    blob.purge_later
+    destroy
   end
+
+  private
+    def identify_blob
+      blob.identify
+    end
+
+    def analyze_blob_later
+      blob.analyze_later unless blob.analyzed?
+    end
 end
diff --git a/activestorage/app/models/active_storage/blob.rb b/activestorage/app/models/active_storage/blob.rb
index 664a53a778..134d3bb2d9 100644
--- a/activestorage/app/models/active_storage/blob.rb
+++ b/activestorage/app/models/active_storage/blob.rb
@@ -1,10 +1,12 @@
 # frozen_string_literal: true
 
+require "active_storage/downloader"
+
 # A blob is a record that contains the metadata about a file and a key for where that file resides on the service.
 # Blobs can be created in two ways:
 #
-# 1) Subsequent to the file being uploaded server-side to the service via <tt>create_after_upload!</tt>.
-# 2) Ahead of the file being directly uploaded client-side to the service via <tt>create_before_direct_upload!</tt>.
+# 1. Subsequent to the file being uploaded server-side to the service via <tt>create_after_upload!</tt>.
+# 2. Ahead of the file being directly uploaded client-side to the service via <tt>create_before_direct_upload!</tt>.
 #
 # The first option doesn't require any client-side JavaScript integration, and can be used by any other back-end
 # service that deals with files. The second option is faster, since you're not using your own server as a staging
@@ -14,13 +16,25 @@
 # update a blob's metadata on a subsequent pass, but you should not update the key or change the uploaded file.
 # If you need to create a derivative or otherwise change the blob, simply create a new blob and purge the old one.
 class ActiveStorage::Blob < ActiveRecord::Base
+  require_dependency "active_storage/blob/analyzable"
+  require_dependency "active_storage/blob/identifiable"
+  require_dependency "active_storage/blob/representable"
+
+  include Analyzable
+  include Identifiable
+  include Representable
+
   self.table_name = "active_storage_blobs"
 
   has_secure_token :key
-  store :metadata, coder: JSON
+  store :metadata, accessors: [ :analyzed, :identified ], coder: ActiveRecord::Coders::JSON
 
   class_attribute :service
 
+  has_many :attachments
+
+  scope :unattached, -> { left_joins(:attachments).where(ActiveStorage::Attachment.table_name => { blob_id: nil }) }
+
   class << self
     # You can used the signed ID of a blob to refer to it on the client side without fear of tampering.
     # This is particularly helpful for direct uploads where the client-side needs to refer to the blob
@@ -32,21 +46,23 @@ class ActiveStorage::Blob < ActiveRecord::Base
     end
 
     # Returns a new, unsaved blob instance after the +io+ has been uploaded to the service.
-    def build_after_upload(io:, filename:, content_type: nil, metadata: nil)
+    # When providing a content type, pass <tt>identify: false</tt> to bypass automatic content type inference.
+    def build_after_upload(io:, filename:, content_type: nil, metadata: nil, identify: true)
       new.tap do |blob|
         blob.filename     = filename
         blob.content_type = content_type
         blob.metadata     = metadata
 
-        blob.upload io
+        blob.upload(io, identify: identify)
       end
     end
 
     # Returns a saved blob instance after the +io+ has been uploaded to the service. Note, the blob is first built,
     # then the +io+ is uploaded, then the blob is saved. This is done this way to avoid uploading (which may take
     # time), while having an open database transaction.
-    def create_after_upload!(io:, filename:, content_type: nil, metadata: nil)
-      build_after_upload(io: io, filename: filename, content_type: content_type, metadata: metadata).tap(&:save!)
+    # When providing a content type, pass <tt>identify: false</tt> to bypass automatic content type inference.
+    def create_after_upload!(io:, filename:, content_type: nil, metadata: nil, identify: true)
+      build_after_upload(io: io, filename: filename, content_type: content_type, metadata: metadata, identify: identify).tap(&:save!)
     end
 
     # Returns a saved blob _without_ uploading a file to the service. This blob will point to a key where there is
@@ -59,7 +75,6 @@ class ActiveStorage::Blob < ActiveRecord::Base
     end
   end
 
-
   # Returns a signed ID for this blob that's suitable for reference on the client-side without fear of tampering.
   # It uses the framework-wide verifier on <tt>ActiveStorage.verifier</tt>, but with a dedicated purpose.
   def signed_id
@@ -101,38 +116,21 @@ class ActiveStorage::Blob < ActiveRecord::Base
     content_type.start_with?("text")
   end
 
-  # Returns an ActiveStorage::Variant instance with the set of +transformations+
-  # passed in. This is only relevant for image files, and it allows any image to
-  # be transformed for size, colors, and the like. Example:
-  #
-  #   avatar.variant(resize: "100x100").processed.service_url
-  #
-  # This will create and process a variant of the avatar blob that's constrained to a height and width of 100.
-  # Then it'll upload said variant to the service according to a derivative key of the blob and the transformations.
-  #
-  # Frequently, though, you don't actually want to transform the variant right away. But rather simply refer to a
-  # specific variant that can be created by a controller on-demand. Like so:
-  #
-  #   <%= image_tag url_for(Current.user.avatar.variant(resize: "100x100")) %>
-  #
-  # This will create a URL for that specific blob with that specific variant, which the ActiveStorage::VariantsController
-  # can then produce on-demand.
-  def variant(transformations)
-    ActiveStorage::Variant.new(self, ActiveStorage::Variation.new(transformations))
-  end
-
 
   # Returns the URL of the blob on the service. This URL is intended to be short-lived for security and not used directly
   # with users. Instead, the +service_url+ should only be exposed as a redirect from a stable, possibly authenticated URL.
   # Hiding the +service_url+ behind a redirect also gives you the power to change services without updating all URLs. And
   # it allows permanent URLs that redirect to the +service_url+ to be cached in the view.
-  def service_url(expires_in: 5.minutes, disposition: :inline)
-    service.url key, expires_in: expires_in, disposition: "#{disposition}; #{filename.parameters}", filename: filename, content_type: content_type
+  def service_url(expires_in: service.url_expires_in, disposition: :inline, filename: nil, **options)
+    filename = ActiveStorage::Filename.wrap(filename || self.filename)
+
+    service.url key, expires_in: expires_in, filename: filename, content_type: content_type,
+      disposition: forcibly_serve_as_binary? ? :attachment : disposition, **options
   end
 
   # Returns a URL that can be used to directly upload a file for this blob on the service. This URL is intended to be
   # short-lived for security and only generated on-demand by the client-side JavaScript responsible for doing the uploading.
-  def service_url_for_direct_upload(expires_in: 5.minutes)
+  def service_url_for_direct_upload(expires_in: service.url_expires_in)
     service.url_for_direct_upload key, expires_in: expires_in, content_type: content_type, content_length: byte_size, checksum: checksum
   end
 
@@ -141,19 +139,23 @@ class ActiveStorage::Blob < ActiveRecord::Base
     service.headers_for_direct_upload key, filename: filename, content_type: content_type, content_length: byte_size, checksum: checksum
   end
 
+
   # Uploads the +io+ to the service on the +key+ for this blob. Blobs are intended to be immutable, so you shouldn't be
   # using this method after a file has already been uploaded to fit with a blob. If you want to create a derivative blob,
   # you should instead simply create a new blob based on the old one.
   #
   # Prior to uploading, we compute the checksum, which is sent to the service for transit integrity validation. If the
   # checksum does not match what the service receives, an exception will be raised. We also measure the size of the +io+
-  # and store that in +byte_size+ on the blob record.
+  # and store that in +byte_size+ on the blob record. The content type is automatically extracted from the +io+ unless
+  # you specify a +content_type+ and pass +identify+ as false.
   #
   # Normally, you do not have to call this method directly at all. Use the factory class methods of +build_after_upload+
   # and +create_after_upload!+.
-  def upload(io)
-    self.checksum  = compute_checksum_in_chunks(io)
-    self.byte_size = io.size
+  def upload(io, identify: true)
+    self.checksum     = compute_checksum_in_chunks(io)
+    self.content_type = extract_content_type(io) if content_type.nil? || identify
+    self.byte_size    = io.size
+    self.identified   = true
 
     service.upload(key, io, checksum: checksum)
   end
@@ -164,12 +166,18 @@ class ActiveStorage::Blob < ActiveRecord::Base
     service.download key, &block
   end
 
+  # Downloads the blob to a tempfile on disk. Yields the tempfile.
+  def open(tempdir: nil, &block)
+    ActiveStorage::Downloader.new(self, tempdir: tempdir).download_blob_to_tempfile(&block)
+  end
+
 
   # Deletes the file on the service that's associated with this blob. This should only be done if the blob is going to be
   # deleted as well or you will essentially have a dead reference. It's recommended to use the +#purge+ and +#purge_later+
   # methods in most circumstances.
   def delete
-    service.delete key
+    service.delete(key)
+    service.delete_prefixed("variants/#{key}/") if image?
   end
 
   # Deletes the file on the service and then destroys the blob record. This is the recommended way to dispose of unwanted
@@ -196,4 +204,14 @@ class ActiveStorage::Blob < ActiveRecord::Base
         io.rewind
       end.base64digest
     end
+
+    def extract_content_type(io)
+      Marcel::MimeType.for io, name: filename.to_s, declared_type: content_type
+    end
+
+    def forcibly_serve_as_binary?
+      ActiveStorage.content_types_to_serve_as_binary.include?(content_type)
+    end
+
+    ActiveSupport.run_load_hooks(:active_storage_blob, self)
 end
diff --git a/activestorage/app/models/active_storage/blob/analyzable.rb b/activestorage/app/models/active_storage/blob/analyzable.rb
new file mode 100644
index 0000000000..5bda6e6d73
--- /dev/null
+++ b/activestorage/app/models/active_storage/blob/analyzable.rb
@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+require "active_storage/analyzer/null_analyzer"
+
+module ActiveStorage::Blob::Analyzable
+  # Extracts and stores metadata from the file associated with this blob using a relevant analyzer. Active Storage comes
+  # with built-in analyzers for images and videos. See ActiveStorage::Analyzer::ImageAnalyzer and
+  # ActiveStorage::Analyzer::VideoAnalyzer for information about the specific attributes they extract and the third-party
+  # libraries they require.
+  #
+  # To choose the analyzer for a blob, Active Storage calls +accept?+ on each registered analyzer in order. It uses the
+  # first analyzer for which +accept?+ returns true when given the blob. If no registered analyzer accepts the blob, no
+  # metadata is extracted from it.
+  #
+  # In a Rails application, add or remove analyzers by manipulating +Rails.application.config.active_storage.analyzers+
+  # in an initializer:
+  #
+  #   # Add a custom analyzer for Microsoft Office documents:
+  #   Rails.application.config.active_storage.analyzers.append DOCXAnalyzer
+  #
+  #   # Remove the built-in video analyzer:
+  #   Rails.application.config.active_storage.analyzers.delete ActiveStorage::Analyzer::VideoAnalyzer
+  #
+  # Outside of a Rails application, manipulate +ActiveStorage.analyzers+ instead.
+  #
+  # You won't ordinarily need to call this method from a Rails application. New blobs are automatically and asynchronously
+  # analyzed via #analyze_later when they're attached for the first time.
+  def analyze
+    update! metadata: metadata.merge(extract_metadata_via_analyzer)
+  end
+
+  # Enqueues an ActiveStorage::AnalyzeJob which calls #analyze.
+  #
+  # This method is automatically called for a blob when it's attached for the first time. You can call it to analyze a blob
+  # again (e.g. if you add a new analyzer or modify an existing one).
+  def analyze_later
+    ActiveStorage::AnalyzeJob.perform_later(self)
+  end
+
+  # Returns true if the blob has been analyzed.
+  def analyzed?
+    analyzed
+  end
+
+  private
+    def extract_metadata_via_analyzer
+      analyzer.metadata.merge(analyzed: true)
+    end
+
+    def analyzer
+      analyzer_class.new(self)
+    end
+
+    def analyzer_class
+      ActiveStorage.analyzers.detect { |klass| klass.accept?(self) } || ActiveStorage::Analyzer::NullAnalyzer
+    end
+end
diff --git a/activestorage/app/models/active_storage/blob/identifiable.rb b/activestorage/app/models/active_storage/blob/identifiable.rb
new file mode 100644
index 0000000000..049e45dc3e
--- /dev/null
+++ b/activestorage/app/models/active_storage/blob/identifiable.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module ActiveStorage::Blob::Identifiable
+  def identify
+    update! content_type: identify_content_type, identified: true unless identified?
+  end
+
+  def identified?
+    identified
+  end
+
+  private
+    def identify_content_type
+      Marcel::MimeType.for download_identifiable_chunk, name: filename.to_s, declared_type: content_type
+    end
+
+    def download_identifiable_chunk
+      service.download_chunk key, 0...4.kilobytes
+    end
+end
diff --git a/activestorage/app/models/active_storage/blob/representable.rb b/activestorage/app/models/active_storage/blob/representable.rb
new file mode 100644
index 0000000000..03d5511481
--- /dev/null
+++ b/activestorage/app/models/active_storage/blob/representable.rb
@@ -0,0 +1,93 @@
+# frozen_string_literal: true
+
+module ActiveStorage::Blob::Representable
+  extend ActiveSupport::Concern
+
+  included do
+    has_one_attached :preview_image
+  end
+
+  # Returns an ActiveStorage::Variant instance with the set of +transformations+ provided. This is only relevant for image
+  # files, and it allows any image to be transformed for size, colors, and the like. Example:
+  #
+  #   avatar.variant(resize_to_fit: [100, 100]).processed.service_url
+  #
+  # This will create and process a variant of the avatar blob that's constrained to a height and width of 100px.
+  # Then it'll upload said variant to the service according to a derivative key of the blob and the transformations.
+  #
+  # Frequently, though, you don't actually want to transform the variant right away. But rather simply refer to a
+  # specific variant that can be created by a controller on-demand. Like so:
+  #
+  #   <%= image_tag Current.user.avatar.variant(resize_to_fit: [100, 100]) %>
+  #
+  # This will create a URL for that specific blob with that specific variant, which the ActiveStorage::RepresentationsController
+  # can then produce on-demand.
+  #
+  # Raises ActiveStorage::InvariableError if ImageMagick cannot transform the blob. To determine whether a blob is
+  # variable, call ActiveStorage::Blob#variable?.
+  def variant(transformations)
+    if variable?
+      ActiveStorage::Variant.new(self, transformations)
+    else
+      raise ActiveStorage::InvariableError
+    end
+  end
+
+  # Returns true if ImageMagick can transform the blob (its content type is in +ActiveStorage.variable_content_types+).
+  def variable?
+    ActiveStorage.variable_content_types.include?(content_type)
+  end
+
+
+  # Returns an ActiveStorage::Preview instance with the set of +transformations+ provided. A preview is an image generated
+  # from a non-image blob. Active Storage comes with built-in previewers for videos and PDF documents. The video previewer
+  # extracts the first frame from a video and the PDF previewer extracts the first page from a PDF document.
+  #
+  #   blob.preview(resize_to_fit: [100, 100]).processed.service_url
+  #
+  # Avoid processing previews synchronously in views. Instead, link to a controller action that processes them on demand.
+  # Active Storage provides one, but you may want to create your own (for example, if you need authentication). Here’s
+  # how to use the built-in version:
+  #
+  #   <%= image_tag video.preview(resize_to_fit: [100, 100]) %>
+  #
+  # This method raises ActiveStorage::UnpreviewableError if no previewer accepts the receiving blob. To determine
+  # whether a blob is accepted by any previewer, call ActiveStorage::Blob#previewable?.
+  def preview(transformations)
+    if previewable?
+      ActiveStorage::Preview.new(self, transformations)
+    else
+      raise ActiveStorage::UnpreviewableError
+    end
+  end
+
+  # Returns true if any registered previewer accepts the blob. By default, this will return true for videos and PDF documents.
+  def previewable?
+    ActiveStorage.previewers.any? { |klass| klass.accept?(self) }
+  end
+
+
+  # Returns an ActiveStorage::Preview for a previewable blob or an ActiveStorage::Variant for a variable image blob.
+  #
+  #   blob.representation(resize_to_fit: [100, 100]).processed.service_url
+  #
+  # Raises ActiveStorage::UnrepresentableError if the receiving blob is neither variable nor previewable. Call
+  # ActiveStorage::Blob#representable? to determine whether a blob is representable.
+  #
+  # See ActiveStorage::Blob#preview and ActiveStorage::Blob#variant for more information.
+  def representation(transformations)
+    case
+    when previewable?
+      preview transformations
+    when variable?
+      variant transformations
+    else
+      raise ActiveStorage::UnrepresentableError
+    end
+  end
+
+  # Returns true if the blob is variable or previewable.
+  def representable?
+    variable? || previewable?
+  end
+end
diff --git a/activestorage/app/models/active_storage/current.rb b/activestorage/app/models/active_storage/current.rb
new file mode 100644
index 0000000000..7e431d8462
--- /dev/null
+++ b/activestorage/app/models/active_storage/current.rb
@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class ActiveStorage::Current < ActiveSupport::CurrentAttributes #:nodoc:
+  attribute :host
+end
diff --git a/activestorage/app/models/active_storage/filename.rb b/activestorage/app/models/active_storage/filename.rb
index c2ad5c844c..bebb5e61b3 100644
--- a/activestorage/app/models/active_storage/filename.rb
+++ b/activestorage/app/models/active_storage/filename.rb
@@ -1,40 +1,66 @@
 # frozen_string_literal: true
 
-# Encapsulates a string representing a filename to provide convenience access to parts of it and a sanitized version.
-# This is what's returned by `ActiveStorage::Blob#filename`. A Filename instance is comparable so it can be used for sorting.
+# Encapsulates a string representing a filename to provide convenient access to parts of it and sanitization.
+# A Filename instance is returned by ActiveStorage::Blob#filename, and is comparable so it can be used for sorting.
 class ActiveStorage::Filename
+  require_dependency "active_storage/filename/parameters"
+
   include Comparable
 
+  class << self
+    # Returns a Filename instance based on the given filename. If the filename is a Filename, it is
+    # returned unmodified. If it is a String, it is passed to ActiveStorage::Filename.new.
+    def wrap(filename)
+      filename.kind_of?(self) ? filename : new(filename)
+    end
+  end
+
   def initialize(filename)
     @filename = filename
   end
 
-  # Filename.new("racecar.jpg").base # => "racecar"
+  # Returns the part of the filename preceding any extension.
+  #
+  #   ActiveStorage::Filename.new("racecar.jpg").base # => "racecar"
+  #   ActiveStorage::Filename.new("racecar").base     # => "racecar"
+  #   ActiveStorage::Filename.new(".gitignore").base  # => ".gitignore"
   def base
     File.basename @filename, extension_with_delimiter
   end
 
-  # Filename.new("racecar.jpg").extension_with_delimiter # => ".jpg"
+  # Returns the extension of the filename (i.e. the substring following the last dot, excluding a dot at the
+  # beginning) with the dot that precedes it. If the filename has no extension, an empty string is returned.
+  #
+  #   ActiveStorage::Filename.new("racecar.jpg").extension_with_delimiter # => ".jpg"
+  #   ActiveStorage::Filename.new("racecar").extension_with_delimiter     # => ""
+  #   ActiveStorage::Filename.new(".gitignore").extension_with_delimiter  # => ""
   def extension_with_delimiter
     File.extname @filename
   end
 
-  # Filename.new("racecar.jpg").extension_without_delimiter # => "jpg"
+  # Returns the extension of the filename (i.e. the substring following the last dot, excluding a dot at
+  # the beginning). If the filename has no extension, an empty string is returned.
+  #
+  #   ActiveStorage::Filename.new("racecar.jpg").extension_without_delimiter # => "jpg"
+  #   ActiveStorage::Filename.new("racecar").extension_without_delimiter     # => ""
+  #   ActiveStorage::Filename.new(".gitignore").extension_without_delimiter  # => ""
   def extension_without_delimiter
     extension_with_delimiter.from(1).to_s
   end
 
   alias_method :extension, :extension_without_delimiter
 
-  # Filename.new("foo:bar.jpg").sanitized # => "foo-bar.jpg"
-  # Filename.new("foo/bar.jpg").sanitized # => "foo-bar.jpg"
+  # Returns the sanitized filename.
+  #
+  #   ActiveStorage::Filename.new("foo:bar.jpg").sanitized # => "foo-bar.jpg"
+  #   ActiveStorage::Filename.new("foo/bar.jpg").sanitized # => "foo-bar.jpg"
   #
-  # ...and any other character unsafe for URLs or storage is converted or stripped.
+  # Characters considered unsafe for storage (e.g. \, $, and the RTL override character) are replaced with a dash.
   def sanitized
     @filename.encode(Encoding::UTF_8, invalid: :replace, undef: :replace, replace: "�").strip.tr("\u{202E}%$|:;/\t\r\n\\", "-")
   end
 
-  def parameters
+  def parameters #:nodoc:
     Parameters.new self
   end
 
diff --git a/activestorage/app/models/active_storage/filename/parameters.rb b/activestorage/app/models/active_storage/filename/parameters.rb
index 58ce198d38..fb9ea10e49 100644
--- a/activestorage/app/models/active_storage/filename/parameters.rb
+++ b/activestorage/app/models/active_storage/filename/parameters.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-class ActiveStorage::Filename::Parameters
+class ActiveStorage::Filename::Parameters #:nodoc:
   attr_reader :filename
 
   def initialize(filename)
diff --git a/activestorage/app/models/active_storage/preview.rb b/activestorage/app/models/active_storage/preview.rb
new file mode 100644
index 0000000000..de58763399
--- /dev/null
+++ b/activestorage/app/models/active_storage/preview.rb
@@ -0,0 +1,89 @@
+# frozen_string_literal: true
+
+# Some non-image blobs can be previewed: that is, they can be presented as images. A video blob can be previewed by
+# extracting its first frame, and a PDF blob can be previewed by extracting its first page.
+#
+# A previewer extracts a preview image from a blob. Active Storage provides previewers for videos and PDFs:
+# ActiveStorage::Previewer::VideoPreviewer and ActiveStorage::Previewer::PDFPreviewer. Build custom previewers by
+# subclassing ActiveStorage::Previewer and implementing the requisite methods. Consult the ActiveStorage::Previewer
+# documentation for more details on what's required of previewers.
+#
+# To choose the previewer for a blob, Active Storage calls +accept?+ on each registered previewer in order. It uses the
+# first previewer for which +accept?+ returns true when given the blob. In a Rails application, add or remove previewers
+# by manipulating +Rails.application.config.active_storage.previewers+ in an initializer:
+#
+#   Rails.application.config.active_storage.previewers
+#   # => [ ActiveStorage::Previewer::PDFPreviewer, ActiveStorage::Previewer::VideoPreviewer ]
+#
+#   # Add a custom previewer for Microsoft Office documents:
+#   Rails.application.config.active_storage.previewers << DOCXPreviewer
+#   # => [ ActiveStorage::Previewer::PDFPreviewer, ActiveStorage::Previewer::VideoPreviewer, DOCXPreviewer ]
+#
+# Outside of a Rails application, modify +ActiveStorage.previewers+ instead.
+#
+# The built-in previewers rely on third-party system libraries. Specifically, the built-in video previewer requires
+# {ffmpeg}[https://www.ffmpeg.org]. Two PDF previewers are provided: one requires {Poppler}[https://poppler.freedesktop.org],
+# and the other requires {mupdf}[https://mupdf.com] (version 1.8 or newer). To preview PDFs, install either Poppler or mupdf.
+#
+# These libraries are not provided by Rails. You must install them yourself to use the built-in previewers. Before you
+# install and use third-party software, make sure you understand the licensing implications of doing so.
+class ActiveStorage::Preview
+  class UnprocessedError < StandardError; end
+
+  attr_reader :blob, :variation
+
+  def initialize(blob, variation_or_variation_key)
+    @blob, @variation = blob, ActiveStorage::Variation.wrap(variation_or_variation_key)
+  end
+
+  # Processes the preview if it has not been processed yet. Returns the receiving Preview instance for convenience:
+  #
+  #   blob.preview(resize_to_fit: [100, 100]).processed.service_url
+  #
+  # Processing a preview generates an image from its blob and attaches the preview image to the blob. Because the preview
+  # image is stored with the blob, it is only generated once.
+  def processed
+    process unless processed?
+    self
+  end
+
+  # Returns the blob's attached preview image.
+  def image
+    blob.preview_image
+  end
+
+  # Returns the URL of the preview's variant on the service. Raises ActiveStorage::Preview::UnprocessedError if the
+  # preview has not been processed yet.
+  #
+  # This method synchronously processes a variant of the preview image, so do not call it in views. Instead, generate
+  # a stable URL that redirects to the short-lived URL returned by this method.
+  def service_url(**options)
+    if processed?
+      variant.service_url(options)
+    else
+      raise UnprocessedError
+    end
+  end
+
+  private
+    def processed?
+      image.attached?
+    end
+
+    def process
+      previewer.preview { |attachable| image.attach(attachable) }
+    end
+
+    def variant
+      ActiveStorage::Variant.new(image, variation).processed
+    end
+
+
+    def previewer
+      previewer_class.new(blob)
+    end
+
+    def previewer_class
+      ActiveStorage.previewers.detect { |klass| klass.accept?(blob) }
+    end
+end
diff --git a/activestorage/app/models/active_storage/variant.rb b/activestorage/app/models/active_storage/variant.rb
index 02bf32b352..1df36e37d9 100644
--- a/activestorage/app/models/active_storage/variant.rb
+++ b/activestorage/app/models/active_storage/variant.rb
@@ -4,42 +4,60 @@
 # These variants are used to create thumbnails, fixed-size avatars, or any other derivative image from the
 # original.
 #
-# Variants rely on {MiniMagick}[https://github.com/minimagick/minimagick] for the actual transformations
-# of the file, so you must add <tt>gem "mini_magick"</tt> to your Gemfile if you wish to use variants.
+# Variants rely on {ImageProcessing}[https://github.com/janko-m/image_processing] gem for the actual transformations
+# of the file, so you must add <tt>gem "image_processing"</tt> to your Gemfile if you wish to use variants. By
+# default, images will be processed with {ImageMagick}[http://imagemagick.org] using the
+# {MiniMagick}[https://github.com/minimagick/minimagick] gem, but you can also switch to the
+# {libvips}[http://jcupitt.github.io/libvips/] processor operated by the {ruby-vips}[https://github.com/jcupitt/ruby-vips]
+# gem).
 #
-# Note that to create a variant it's necessary to download the entire blob file from the service and load it
-# into memory. The larger the image, the more memory is used. Because of this process, you also want to be
-# considerate about when the variant is actually processed. You shouldn't be processing variants inline in a
-# template, for example. Delay the processing to an on-demand controller, like the one provided in
-# ActiveStorage::VariantsController.
+#   Rails.application.config.active_storage.variant_processor
+#   # => :mini_magick
+#
+#   Rails.application.config.active_storage.variant_processor = :vips
+#   # => :vips
+#
+# Note that to create a variant it's necessary to download the entire blob file from the service. Because of this process,
+# you also want to be considerate about when the variant is actually processed. You shouldn't be processing variants inline
+# in a template, for example. Delay the processing to an on-demand controller, like the one provided in
+# ActiveStorage::RepresentationsController.
 #
 # To refer to such a delayed on-demand variant, simply link to the variant through the resolved route provided
 # by Active Storage like so:
 #
-#   <%= image_tag url_for(Current.user.avatar.variant(resize: "100x100")) %>
+#   <%= image_tag Current.user.avatar.variant(resize_to_fit: [100, 100]) %>
 #
-# This will create a URL for that specific blob with that specific variant, which the ActiveStorage::VariantsController
+# This will create a URL for that specific blob with that specific variant, which the ActiveStorage::RepresentationsController
 # can then produce on-demand.
 #
 # When you do want to actually produce the variant needed, call +processed+. This will check that the variant
 # has already been processed and uploaded to the service, and, if so, just return that. Otherwise it will perform
 # the transformations, upload the variant to the service, and return itself again. Example:
 #
-#   avatar.variant(resize: "100x100").processed.service_url
+#   avatar.variant(resize_to_fit: [100, 100]).processed.service_url
 #
 # This will create and process a variant of the avatar blob that's constrained to a height and width of 100.
 # Then it'll upload said variant to the service according to a derivative key of the blob and the transformations.
 #
-# A list of all possible transformations is available at https://www.imagemagick.org/script/mogrify.php. You can
-# combine as many as you like freely:
+# You can combine any number of ImageMagick/libvips operations into a variant, as well as any macros provided by the
+# ImageProcessing gem (such as +resize_to_fit+):
+#
+#   avatar.variant(resize_to_fit: [800, 800], monochrome: true, rotate: "-90")
+#
+# Visit the following links for a list of available ImageProcessing commands and ImageMagick/libvips operations:
 #
-#   avatar.variant(resize: "100x100", monochrome: true, flip: "-90")
+# * {ImageProcessing::MiniMagick}[https://github.com/janko-m/image_processing/blob/master/doc/minimagick.md#methods]
+# * {ImageMagick reference}[https://www.imagemagick.org/script/mogrify.php]
+# * {ImageProcessing::Vips}[https://github.com/janko-m/image_processing/blob/master/doc/vips.md#methods]
+# * {ruby-vips reference}[http://www.rubydoc.info/gems/ruby-vips/Vips/Image]
 class ActiveStorage::Variant
+  WEB_IMAGE_CONTENT_TYPES = %w( image/png image/jpeg image/jpg image/gif )
+
   attr_reader :blob, :variation
   delegate :service, to: :blob
 
-  def initialize(blob, variation)
-    @blob, @variation = blob, variation
+  def initialize(blob, variation_or_variation_key)
+    @blob, @variation = blob, ActiveStorage::Variation.wrap(variation_or_variation_key)
   end
 
   # Returns the variant instance itself after it's been processed or an existing processing has been found on the service.
@@ -50,7 +68,7 @@ class ActiveStorage::Variant
 
   # Returns a combination key of the blob and the variation that together identifies a specific variant.
   def key
-    "variants/#{blob.key}/#{variation.key}"
+    "variants/#{blob.key}/#{Digest::SHA256.hexdigest(variation.key)}"
   end
 
   # Returns the URL of the variant on the service. This URL is intended to be short-lived for security and not used directly
@@ -59,12 +77,16 @@ class ActiveStorage::Variant
   # it allows permanent URLs that redirect to the +service_url+ to be cached in the view.
   #
   # Use <tt>url_for(variant)</tt> (or the implied form, like +link_to variant+ or +redirect_to variant+) to get the stable URL
-  # for a variant that points to the ActiveStorage::VariantsController, which in turn will use this +service_call+ method
+  # for a variant that points to the ActiveStorage::RepresentationsController, which in turn will use this +service_call+ method
   # for its redirection.
-  def service_url(expires_in: 5.minutes, disposition: :inline)
-    service.url key, expires_in: expires_in, disposition: disposition, filename: blob.filename, content_type: blob.content_type
+  def service_url(expires_in: service.url_expires_in, disposition: :inline)
+    service.url key, expires_in: expires_in, disposition: disposition, filename: filename, content_type: content_type
   end
 
+  # Returns the receiving variant. Allows ActiveStorage::Variant and ActiveStorage::Preview instances to be used interchangeably.
+  def image
+    self
+  end
 
   private
     def processed?
@@ -72,11 +94,38 @@ class ActiveStorage::Variant
     end
 
     def process
-      service.upload key, transform(service.download(blob.key))
+      blob.open do |image|
+        transform image do |output|
+          upload output
+        end
+      end
+    end
+
+
+    def filename
+      if WEB_IMAGE_CONTENT_TYPES.include?(blob.content_type)
+        blob.filename
+      else
+        ActiveStorage::Filename.new("#{blob.filename.base}.png")
+      end
+    end
+
+    def content_type
+      blob.content_type.presence_in(WEB_IMAGE_CONTENT_TYPES) || "image/png"
+    end
+
+    def transform(image)
+      format = "png" unless WEB_IMAGE_CONTENT_TYPES.include?(blob.content_type)
+      result = variation.transform(image, format: format)
+
+      begin
+        yield result
+      ensure
+        result.close!
+      end
     end
 
-    def transform(io)
-      require "mini_magick"
-      File.open MiniMagick::Image.read(io).tap { |image| variation.transform(image) }.path
+    def upload(file)
+      service.upload(key, file)
     end
 end
diff --git a/activestorage/app/models/active_storage/variation.rb b/activestorage/app/models/active_storage/variation.rb
index f657d90db4..806af6366d 100644
--- a/activestorage/app/models/active_storage/variation.rb
+++ b/activestorage/app/models/active_storage/variation.rb
@@ -1,21 +1,33 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/object/inclusion"
-
 # A set of transformations that can be applied to a blob to create a variant. This class is exposed via
-# the `ActiveStorage::Blob#variant` method and should rarely be used directly.
+# the ActiveStorage::Blob#variant method and should rarely be used directly.
 #
 # In case you do need to use this directly, it's instantiated using a hash of transformations where
 # the key is the command and the value is the arguments. Example:
 #
-#   ActiveStorage::Variation.new(resize: "100x100", monochrome: true, trim: true, rotate: "-90")
+#   ActiveStorage::Variation.new(resize_to_fit: [100, 100], monochrome: true, trim: true, rotate: "-90")
 #
-# A list of all possible transformations is available at https://www.imagemagick.org/script/mogrify.php.
+# The options map directly to {ImageProcessing}[https://github.com/janko-m/image_processing] commands.
 class ActiveStorage::Variation
   attr_reader :transformations
 
   class << self
-    # Returns a variation instance with the transformations that were encoded by +encode+.
+    # Returns a Variation instance based on the given variator. If the variator is a Variation, it is
+    # returned unmodified. If it is a String, it is passed to ActiveStorage::Variation.decode. Otherwise,
+    # it is assumed to be a transformations Hash and is passed directly to the constructor.
+    def wrap(variator)
+      case variator
+      when self
+        variator
+      when String
+        decode variator
+      else
+        new variator
+      end
+    end
+
+    # Returns a Variation instance with the transformations that were encoded by +encode+.
     def decode(key)
       new ActiveStorage.verifier.verify(key, purpose: :variation)
     end
@@ -31,14 +43,16 @@ class ActiveStorage::Variation
     @transformations = transformations
   end
 
-  # Accepts an open MiniMagick image instance, like what's returned by <tt>MiniMagick::Image.read(io)</tt>,
-  # and performs the +transformations+ against it. The transformed image instance is then returned.
-  def transform(image)
-    transformations.each do |(method, argument)|
-      if eligible_argument?(argument)
-        image.public_send(method, argument)
+  # Accepts a File object, performs the +transformations+ against it, and
+  # saves the transformed image into a temporary file. If +format+ is specified
+  # it will be the format of the result image, otherwise the result image
+  # retains the source format.
+  def transform(file, format: nil)
+    ActiveSupport::Notifications.instrument("transform.active_storage") do
+      if processor
+        image_processing_transform(file, format)
       else
-        image.public_send(method)
+        mini_magick_transform(file, format)
       end
     end
   end
@@ -49,7 +63,65 @@ class ActiveStorage::Variation
   end
 
   private
-    def eligible_argument?(argument)
-      argument.present? && argument != true
+    # Applies image transformations using the ImageProcessing gem.
+    def image_processing_transform(file, format)
+      operations = transformations.inject([]) do |list, (name, argument)|
+        list.tap do |list|
+          if name.to_s == "combine_options"
+            ActiveSupport::Deprecation.warn("The ImageProcessing ActiveStorage variant backend doesn't need :combine_options, as it already generates a single MiniMagick command. In Rails 6.1 :combine_options will not be supported anymore.")
+            list.concat argument.keep_if { |key, value| value.present? }.to_a
+          elsif argument.present?
+            list << [name, argument]
+          end
+        end
+      end
+
+      processor
+        .source(file)
+        .loader(page: 0)
+        .convert(format)
+        .apply(operations)
+        .call
+    end
+
+    # Applies image transformations using the MiniMagick gem.
+    def mini_magick_transform(file, format)
+      image = MiniMagick::Image.new(file.path, file)
+
+      transformations.each do |name, argument_or_subtransformations|
+        image.mogrify do |command|
+          if name.to_s == "combine_options"
+            argument_or_subtransformations.each do |subtransformation_name, subtransformation_argument|
+              pass_transform_argument(command, subtransformation_name, subtransformation_argument)
+            end
+          else
+            pass_transform_argument(command, name, argument_or_subtransformations)
+          end
+        end
+      end
+
+      image.format(format) if format
+
+      image.tempfile.tap(&:open)
+    end
+
+    # Returns the ImageProcessing processor class specified by `ActiveStorage.variant_processor`.
+    def processor
+      begin
+        require "image_processing"
+      rescue LoadError
+        ActiveSupport::Deprecation.warn("Using mini_magick gem directly is deprecated and will be removed in Rails 6.1. Please add `gem 'image_processing', '~> 1.2'` to your Gemfile.")
+        return nil
+      end
+
+      ImageProcessing.const_get(ActiveStorage.variant_processor.to_s.camelize) if ActiveStorage.variant_processor
+    end
+
+    def pass_transform_argument(command, method, argument)
+      if argument == true
+        command.public_send(method)
+      elsif argument.present?
+        command.public_send(method, argument)
+      end
     end
 end
diff --git a/activestorage/config/routes.rb b/activestorage/config/routes.rb
index 168788475c..20d19f334a 100644
--- a/activestorage/config/routes.rb
+++ b/activestorage/config/routes.rb
@@ -3,25 +3,26 @@
 Rails.application.routes.draw do
   get "/rails/active_storage/blobs/:signed_id/*filename" => "active_storage/blobs#show", as: :rails_service_blob
 
-  direct :rails_blob do |blob|
-    route_for(:rails_service_blob, blob.signed_id, blob.filename)
+  direct :rails_blob do |blob, options|
+    route_for(:rails_service_blob, blob.signed_id, blob.filename, options)
   end
 
-  resolve("ActiveStorage::Blob")       { |blob| route_for(:rails_blob, blob) }
-  resolve("ActiveStorage::Attachment") { |attachment| route_for(:rails_blob, attachment.blob) }
+  resolve("ActiveStorage::Blob")       { |blob, options| route_for(:rails_blob, blob, options) }
+  resolve("ActiveStorage::Attachment") { |attachment, options| route_for(:rails_blob, attachment.blob, options) }
 
 
-  get "/rails/active_storage/variants/:signed_blob_id/:variation_key/*filename" => "active_storage/variants#show", as: :rails_blob_variation
+  get "/rails/active_storage/representations/:signed_blob_id/:variation_key/*filename" => "active_storage/representations#show", as: :rails_blob_representation
 
-  direct :rails_variant do |variant|
-    signed_blob_id = variant.blob.signed_id
-    variation_key  = variant.variation.key
-    filename       = variant.blob.filename
+  direct :rails_representation do |representation, options|
+    signed_blob_id = representation.blob.signed_id
+    variation_key  = representation.variation.key
+    filename       = representation.blob.filename
 
-    route_for(:rails_blob_variation, signed_blob_id, variation_key, filename)
+    route_for(:rails_blob_representation, signed_blob_id, variation_key, filename, options)
   end
 
-  resolve("ActiveStorage::Variant") { |variant| route_for(:rails_variant, variant) }
+  resolve("ActiveStorage::Variant") { |variant, options| route_for(:rails_representation, variant, options) }
+  resolve("ActiveStorage::Preview") { |preview, options| route_for(:rails_representation, preview, options) }
 
 
   get  "/rails/active_storage/disk/:encoded_key/*filename" => "active_storage/disk#show", as: :rails_disk_service
diff --git a/activestorage/lib/active_storage.rb b/activestorage/lib/active_storage.rb
index ccc1d4a163..e1deee1d82 100644
--- a/activestorage/lib/active_storage.rb
+++ b/activestorage/lib/active_storage.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 #--
-# Copyright (c) 2017 David Heinemeier Hansson
+# Copyright (c) 2017-2018 David Heinemeier Hansson, Basecamp
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the
@@ -26,13 +26,27 @@
 require "active_record"
 require "active_support"
 require "active_support/rails"
-require_relative "active_storage/version"
+
+require "active_storage/version"
+require "active_storage/errors"
+
+require "marcel"
 
 module ActiveStorage
   extend ActiveSupport::Autoload
 
   autoload :Attached
   autoload :Service
+  autoload :Previewer
+  autoload :Analyzer
 
+  mattr_accessor :logger
   mattr_accessor :verifier
+  mattr_accessor :queue
+  mattr_accessor :previewers, default: []
+  mattr_accessor :analyzers, default: []
+  mattr_accessor :variant_processor, default: :mini_magick
+  mattr_accessor :paths, default: {}
+  mattr_accessor :variable_content_types, default: []
+  mattr_accessor :content_types_to_serve_as_binary, default: []
 end
diff --git a/activestorage/lib/active_storage/analyzer.rb b/activestorage/lib/active_storage/analyzer.rb
new file mode 100644
index 0000000000..caa25418a5
--- /dev/null
+++ b/activestorage/lib/active_storage/analyzer.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  # This is an abstract base class for analyzers, which extract metadata from blobs. See
+  # ActiveStorage::Analyzer::ImageAnalyzer for an example of a concrete subclass.
+  class Analyzer
+    attr_reader :blob
+
+    # Implement this method in a concrete subclass. Have it return true when given a blob from which
+    # the analyzer can extract metadata.
+    def self.accept?(blob)
+      false
+    end
+
+    def initialize(blob)
+      @blob = blob
+    end
+
+    # Override this method in a concrete subclass. Have it return a Hash of metadata.
+    def metadata
+      raise NotImplementedError
+    end
+
+    private
+      # Downloads the blob to a tempfile on disk. Yields the tempfile.
+      def download_blob_to_tempfile(&block) #:doc:
+        blob.open tempdir: tempdir, &block
+      end
+
+      def logger #:doc:
+        ActiveStorage.logger
+      end
+
+      def tempdir #:doc:
+        Dir.tmpdir
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/analyzer/image_analyzer.rb b/activestorage/lib/active_storage/analyzer/image_analyzer.rb
new file mode 100644
index 0000000000..3b39de91be
--- /dev/null
+++ b/activestorage/lib/active_storage/analyzer/image_analyzer.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  # Extracts width and height in pixels from an image blob.
+  #
+  # If the image contains EXIF data indicating its angle is 90 or 270 degrees, its width and height are swapped for convenience.
+  #
+  # Example:
+  #
+  #   ActiveStorage::Analyzer::ImageAnalyzer.new(blob).metadata
+  #   # => { width: 4104, height: 2736 }
+  #
+  # This analyzer relies on the third-party {MiniMagick}[https://github.com/minimagick/minimagick] gem. MiniMagick requires
+  # the {ImageMagick}[http://www.imagemagick.org] system library.
+  class Analyzer::ImageAnalyzer < Analyzer
+    def self.accept?(blob)
+      blob.image?
+    end
+
+    def metadata
+      read_image do |image|
+        if rotated_image?(image)
+          { width: image.height, height: image.width }
+        else
+          { width: image.width, height: image.height }
+        end
+      end
+    rescue LoadError
+      logger.info "Skipping image analysis because the mini_magick gem isn't installed"
+      {}
+    end
+
+    private
+      def read_image
+        download_blob_to_tempfile do |file|
+          require "mini_magick"
+          yield MiniMagick::Image.new(file.path)
+        end
+      end
+
+      def rotated_image?(image)
+        %w[ RightTop LeftBottom ].include?(image["%[orientation]"])
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/analyzer/null_analyzer.rb b/activestorage/lib/active_storage/analyzer/null_analyzer.rb
new file mode 100644
index 0000000000..8ff7ce48e5
--- /dev/null
+++ b/activestorage/lib/active_storage/analyzer/null_analyzer.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  class Analyzer::NullAnalyzer < Analyzer # :nodoc:
+    def self.accept?(blob)
+      true
+    end
+
+    def metadata
+      {}
+    end
+  end
+end
diff --git a/activestorage/lib/active_storage/analyzer/video_analyzer.rb b/activestorage/lib/active_storage/analyzer/video_analyzer.rb
new file mode 100644
index 0000000000..e31bdb0edb
--- /dev/null
+++ b/activestorage/lib/active_storage/analyzer/video_analyzer.rb
@@ -0,0 +1,118 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  # Extracts the following from a video blob:
+  #
+  # * Width (pixels)
+  # * Height (pixels)
+  # * Duration (seconds)
+  # * Angle (degrees)
+  # * Display aspect ratio
+  #
+  # Example:
+  #
+  #   ActiveStorage::VideoAnalyzer.new(blob).metadata
+  #   # => { width: 640.0, height: 480.0, duration: 5.0, angle: 0, display_aspect_ratio: [4, 3] }
+  #
+  # When a video's angle is 90 or 270 degrees, its width and height are automatically swapped for convenience.
+  #
+  # This analyzer requires the {ffmpeg}[https://www.ffmpeg.org] system library, which is not provided by Rails.
+  class Analyzer::VideoAnalyzer < Analyzer
+    def self.accept?(blob)
+      blob.video?
+    end
+
+    def metadata
+      { width: width, height: height, duration: duration, angle: angle, display_aspect_ratio: display_aspect_ratio }.compact
+    end
+
+    private
+      def width
+        if rotated?
+          computed_height || encoded_height
+        else
+          encoded_width
+        end
+      end
+
+      def height
+        if rotated?
+          encoded_width
+        else
+          computed_height || encoded_height
+        end
+      end
+
+      def duration
+        Float(video_stream["duration"]) if video_stream["duration"]
+      end
+
+      def angle
+        Integer(tags["rotate"]) if tags["rotate"]
+      end
+
+      def display_aspect_ratio
+        if descriptor = video_stream["display_aspect_ratio"]
+          if terms = descriptor.split(":", 2)
+            numerator   = Integer(terms[0])
+            denominator = Integer(terms[1])
+
+            [numerator, denominator] unless numerator == 0
+          end
+        end
+      end
+
+
+      def rotated?
+        angle == 90 || angle == 270
+      end
+
+      def computed_height
+        if encoded_width && display_height_scale
+          encoded_width * display_height_scale
+        end
+      end
+
+      def encoded_width
+        @encoded_width ||= Float(video_stream["width"]) if video_stream["width"]
+      end
+
+      def encoded_height
+        @encoded_height ||= Float(video_stream["height"]) if video_stream["height"]
+      end
+
+      def display_height_scale
+        @display_height_scale ||= Float(display_aspect_ratio.last) / display_aspect_ratio.first if display_aspect_ratio
+      end
+
+
+      def tags
+        @tags ||= video_stream["tags"] || {}
+      end
+
+      def video_stream
+        @video_stream ||= streams.detect { |stream| stream["codec_type"] == "video" } || {}
+      end
+
+      def streams
+        probe["streams"] || []
+      end
+
+      def probe
+        download_blob_to_tempfile { |file| probe_from(file) }
+      end
+
+      def probe_from(file)
+        IO.popen([ ffprobe_path, "-print_format", "json", "-show_streams", "-v", "error", file.path ]) do |output|
+          JSON.parse(output.read)
+        end
+      rescue Errno::ENOENT
+        logger.info "Skipping video analysis because ffmpeg isn't installed"
+        {}
+      end
+
+      def ffprobe_path
+        ActiveStorage.paths[:ffprobe] || "ffprobe"
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/attached.rb b/activestorage/lib/active_storage/attached.rb
index 9c4b6d5d1d..c08fd56652 100644
--- a/activestorage/lib/active_storage/attached.rb
+++ b/activestorage/lib/active_storage/attached.rb
@@ -8,10 +8,10 @@ module ActiveStorage
   # Abstract base class for the concrete ActiveStorage::Attached::One and ActiveStorage::Attached::Many
   # classes that both provide proxy access to the blob association for a record.
   class Attached
-    attr_reader :name, :record
+    attr_reader :name, :record, :dependent
 
-    def initialize(name, record)
-      @name, @record = name, record
+    def initialize(name, record, dependent:)
+      @name, @record, @dependent = name, record, dependent
     end
 
     private
diff --git a/activestorage/lib/active_storage/attached/macros.rb b/activestorage/lib/active_storage/attached/macros.rb
index f3879ee2e3..f99cf35680 100644
--- a/activestorage/lib/active_storage/attached/macros.rb
+++ b/activestorage/lib/active_storage/attached/macros.rb
@@ -12,6 +12,10 @@ module ActiveStorage
     # There is no column defined on the model side, Active Storage takes
     # care of the mapping between your records and the attachment.
     #
+    # To avoid N+1 queries, you can include the attached blobs in your query like so:
+    #
+    #   User.with_attached_avatar
+    #
     # Under the covers, this relationship is implemented as a +has_one+ association to a
     # ActiveStorage::Attachment record and a +has_one-through+ association to a
     # ActiveStorage::Blob record. These associations are available as +avatar_attachment+
@@ -24,17 +28,25 @@ module ActiveStorage
     # If the +:dependent+ option isn't set, the attachment will be purged
     # (i.e. destroyed) whenever the record is destroyed.
     def has_one_attached(name, dependent: :purge_later)
-      class_eval <<-CODE, __FILE__, __LINE__ + 1
+      generated_association_methods.class_eval <<-CODE, __FILE__, __LINE__ + 1
         def #{name}
-          @active_storage_attached_#{name} ||= ActiveStorage::Attached::One.new("#{name}", self)
+          @active_storage_attached_#{name} ||= ActiveStorage::Attached::One.new("#{name}", self, dependent: #{dependent == :purge_later ? ":purge_later" : "false"})
+        end
+
+        def #{name}=(attachable)
+          #{name}.attach(attachable)
         end
       CODE
 
-      has_one :"#{name}_attachment", -> { where(name: name) }, class_name: "ActiveStorage::Attachment", as: :record
+      has_one :"#{name}_attachment", -> { where(name: name) }, class_name: "ActiveStorage::Attachment", as: :record, inverse_of: :record, dependent: false
       has_one :"#{name}_blob", through: :"#{name}_attachment", class_name: "ActiveStorage::Blob", source: :blob
 
+      scope :"with_attached_#{name}", -> { includes("#{name}_attachment": :blob) }
+
       if dependent == :purge_later
-        before_destroy { public_send(name).purge_later }
+        after_destroy_commit { public_send(name).purge_later }
+      else
+        before_destroy { public_send(name).detach }
       end
     end
 
@@ -63,19 +75,35 @@ module ActiveStorage
     # If the +:dependent+ option isn't set, all the attachments will be purged
     # (i.e. destroyed) whenever the record is destroyed.
     def has_many_attached(name, dependent: :purge_later)
-      class_eval <<-CODE, __FILE__, __LINE__ + 1
+      generated_association_methods.class_eval <<-CODE, __FILE__, __LINE__ + 1
         def #{name}
-          @active_storage_attached_#{name} ||= ActiveStorage::Attached::Many.new("#{name}", self)
+          @active_storage_attached_#{name} ||= ActiveStorage::Attached::Many.new("#{name}", self, dependent: #{dependent == :purge_later ? ":purge_later" : "false"})
+        end
+
+        def #{name}=(attachables)
+          #{name}.attach(attachables)
         end
       CODE
 
-      has_many :"#{name}_attachments", -> { where(name: name) }, as: :record, class_name: "ActiveStorage::Attachment"
+      has_many :"#{name}_attachments", -> { where(name: name) }, as: :record, class_name: "ActiveStorage::Attachment", inverse_of: :record, dependent: false do
+        def purge
+          each(&:purge)
+          reset
+        end
+
+        def purge_later
+          each(&:purge_later)
+          reset
+        end
+      end
       has_many :"#{name}_blobs", through: :"#{name}_attachments", class_name: "ActiveStorage::Blob", source: :blob
 
       scope :"with_attached_#{name}", -> { includes("#{name}_attachments": :blob) }
 
       if dependent == :purge_later
-        before_destroy { public_send(name).purge_later }
+        after_destroy_commit { public_send(name).purge_later }
+      else
+        before_destroy { public_send(name).detach }
       end
     end
   end
diff --git a/activestorage/lib/active_storage/attached/many.rb b/activestorage/lib/active_storage/attached/many.rb
index 59b7d7d559..d61acb6fad 100644
--- a/activestorage/lib/active_storage/attached/many.rb
+++ b/activestorage/lib/active_storage/attached/many.rb
@@ -13,15 +13,18 @@ module ActiveStorage
     end
 
     # Associates one or several attachments with the current record, saving them to the database.
-    # Examples:
     #
     #   document.images.attach(params[:images]) # Array of ActionDispatch::Http::UploadedFile objects
     #   document.images.attach(params[:signed_blob_id]) # Signed reference to blob from direct upload
-    #   document.images.attach(io: File.open("~/racecar.jpg"), filename: "racecar.jpg", content_type: "image/jpg")
+    #   document.images.attach(io: File.open("/path/to/racecar.jpg"), filename: "racecar.jpg", content_type: "image/jpg")
     #   document.images.attach([ first_blob, second_blob ])
     def attach(*attachables)
       attachables.flatten.collect do |attachable|
-        attachments.create!(name: name, blob: create_blob_from(attachable))
+        if record.new_record?
+          attachments.build(record: record, blob: create_blob_from(attachable))
+        else
+          attachments.create!(record: record, blob: create_blob_from(attachable))
+        end
       end
     end
 
@@ -36,20 +39,21 @@ module ActiveStorage
       attachments.any?
     end
 
+    # Deletes associated attachments without purging them, leaving their respective blobs in place.
+    def detach
+      attachments.destroy_all if attached?
+    end
+
+    ##
+    # :method: purge
+    #
     # Directly purges each associated attachment (i.e. destroys the blobs and
     # attachments and deletes the files on the service).
-    def purge
-      if attached?
-        attachments.each(&:purge)
-        attachments.reload
-      end
-    end
 
+
+    ##
+    # :method: purge_later
+    #
     # Purges each associated attachment through the queuing system.
-    def purge_later
-      if attached?
-        attachments.each(&:purge_later)
-      end
-    end
   end
 end
diff --git a/activestorage/lib/active_storage/attached/one.rb b/activestorage/lib/active_storage/attached/one.rb
index 2e5831348e..f992cb5f84 100644
--- a/activestorage/lib/active_storage/attached/one.rb
+++ b/activestorage/lib/active_storage/attached/one.rb
@@ -13,19 +13,31 @@ module ActiveStorage
       record.public_send("#{name}_attachment")
     end
 
+    def blank?
+      attachment.blank?
+    end
+
     # Associates a given attachment with the current record, saving it to the database.
-    # Examples:
     #
     #   person.avatar.attach(params[:avatar]) # ActionDispatch::Http::UploadedFile object
     #   person.avatar.attach(params[:signed_blob_id]) # Signed reference to blob from direct upload
-    #   person.avatar.attach(io: File.open("~/face.jpg"), filename: "face.jpg", content_type: "image/jpg")
+    #   person.avatar.attach(io: File.open("/path/to/face.jpg"), filename: "face.jpg", content_type: "image/jpg")
     #   person.avatar.attach(avatar_blob) # ActiveStorage::Blob object
     def attach(attachable)
-      write_attachment \
-        ActiveStorage::Attachment.create!(record: record, name: name, blob: create_blob_from(attachable))
+      blob_was = blob if attached?
+      blob = create_blob_from(attachable)
+
+      unless blob == blob_was
+        transaction do
+          detach
+          write_attachment build_attachment(blob: blob)
+        end
+
+        blob_was.purge_later if blob_was && dependent == :purge_later
+      end
     end
 
-    # Returns true if an attachment has been made.
+    # Returns +true+ if an attachment has been made.
     #
     #   class User < ActiveRecord::Base
     #     has_one_attached :avatar
@@ -36,6 +48,14 @@ module ActiveStorage
       attachment.present?
     end
 
+    # Deletes the attachment without purging it, leaving its blob in place.
+    def detach
+      if attached?
+        attachment.destroy
+        write_attachment nil
+      end
+    end
+
     # Directly purges the attachment (i.e. destroys the blob and
     # attachment and deletes the file on the service).
     def purge
@@ -53,6 +73,12 @@ module ActiveStorage
     end
 
     private
+      delegate :transaction, to: :record
+
+      def build_attachment(blob:)
+        ActiveStorage::Attachment.new(record: record, name: name, blob: blob)
+      end
+
       def write_attachment(attachment)
         record.public_send("#{name}_attachment=", attachment)
       end
diff --git a/activestorage/lib/active_storage/downloader.rb b/activestorage/lib/active_storage/downloader.rb
new file mode 100644
index 0000000000..0e7039e104
--- /dev/null
+++ b/activestorage/lib/active_storage/downloader.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  class Downloader #:nodoc:
+    def initialize(blob, tempdir: nil)
+      @blob    = blob
+      @tempdir = tempdir
+    end
+
+    def download_blob_to_tempfile
+      open_tempfile do |file|
+        download_blob_to file
+        yield file
+      end
+    end
+
+    private
+      attr_reader :blob, :tempdir
+
+      def open_tempfile
+        file = Tempfile.open([ "ActiveStorage", tempfile_extension_with_delimiter ], tempdir)
+
+        begin
+          yield file
+        ensure
+          file.close!
+        end
+      end
+
+      def download_blob_to(file)
+        file.binmode
+        blob.download { |chunk| file.write(chunk) }
+        file.flush
+        file.rewind
+      end
+
+      def tempfile_extension_with_delimiter
+        blob.filename.extension_with_delimiter
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/downloading.rb b/activestorage/lib/active_storage/downloading.rb
new file mode 100644
index 0000000000..df820bc088
--- /dev/null
+++ b/activestorage/lib/active_storage/downloading.rb
@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require "tmpdir"
+require "active_support/core_ext/string/filters"
+
+module ActiveStorage
+  module Downloading
+    def self.included(klass)
+      ActiveSupport::Deprecation.warn <<~MESSAGE.squish, caller_locations(2)
+        ActiveStorage::Downloading is deprecated and will be removed in Active Storage 6.1.
+        Use ActiveStorage::Blob#open instead.
+      MESSAGE
+    end
+
+    private
+      # Opens a new tempfile in #tempdir and copies blob data into it. Yields the tempfile.
+      def download_blob_to_tempfile #:doc:
+        open_tempfile_for_blob do |file|
+          download_blob_to file
+          yield file
+        end
+      end
+
+      def open_tempfile_for_blob
+        tempfile = Tempfile.open([ "ActiveStorage", blob.filename.extension_with_delimiter ], tempdir)
+
+        begin
+          yield tempfile
+        ensure
+          tempfile.close!
+        end
+      end
+
+      # Efficiently downloads blob data into the given file.
+      def download_blob_to(file) #:doc:
+        file.binmode
+        blob.download { |chunk| file.write(chunk) }
+        file.flush
+        file.rewind
+      end
+
+      # Returns the directory in which tempfiles should be opened. Defaults to +Dir.tmpdir+.
+      def tempdir #:doc:
+        Dir.tmpdir
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/engine.rb b/activestorage/lib/active_storage/engine.rb
index a5562b32d3..99588cdd4b 100644
--- a/activestorage/lib/active_storage/engine.rb
+++ b/activestorage/lib/active_storage/engine.rb
@@ -3,19 +3,55 @@
 require "rails"
 require "active_storage"
 
+require "active_storage/previewer/poppler_pdf_previewer"
+require "active_storage/previewer/mupdf_previewer"
+require "active_storage/previewer/video_previewer"
+
+require "active_storage/analyzer/image_analyzer"
+require "active_storage/analyzer/video_analyzer"
+
 module ActiveStorage
   class Engine < Rails::Engine # :nodoc:
     isolate_namespace ActiveStorage
 
     config.active_storage = ActiveSupport::OrderedOptions.new
+    config.active_storage.previewers = [ ActiveStorage::Previewer::PopplerPDFPreviewer, ActiveStorage::Previewer::MuPDFPreviewer, ActiveStorage::Previewer::VideoPreviewer ]
+    config.active_storage.analyzers = [ ActiveStorage::Analyzer::ImageAnalyzer, ActiveStorage::Analyzer::VideoAnalyzer ]
+    config.active_storage.paths = ActiveSupport::OrderedOptions.new
 
-    config.eager_load_namespaces << ActiveStorage
+    config.active_storage.variable_content_types = %w(
+      image/png
+      image/gif
+      image/jpg
+      image/jpeg
+      image/vnd.adobe.photoshop
+      image/vnd.microsoft.icon
+    )
 
-    initializer "active_storage.logger" do
-      require "active_storage/service"
+    config.active_storage.content_types_to_serve_as_binary = %w(
+      text/html
+      text/javascript
+      image/svg+xml
+      application/postscript
+      application/x-shockwave-flash
+      text/xml
+      application/xml
+      application/xhtml+xml
+    )
 
+    config.eager_load_namespaces << ActiveStorage
+
+    initializer "active_storage.configs" do
       config.after_initialize do |app|
-        ActiveStorage::Service.logger = app.config.active_storage.logger || Rails.logger
+        ActiveStorage.logger            = app.config.active_storage.logger || Rails.logger
+        ActiveStorage.queue             = app.config.active_storage.queue
+        ActiveStorage.variant_processor = app.config.active_storage.variant_processor || :mini_magick
+        ActiveStorage.previewers        = app.config.active_storage.previewers || []
+        ActiveStorage.analyzers         = app.config.active_storage.analyzers || []
+        ActiveStorage.paths             = app.config.active_storage.paths || {}
+
+        ActiveStorage.variable_content_types = app.config.active_storage.variable_content_types || []
+        ActiveStorage.content_types_to_serve_as_binary = app.config.active_storage.content_types_to_serve_as_binary || []
       end
     end
 
@@ -29,14 +65,12 @@ module ActiveStorage
 
     initializer "active_storage.verifier" do
       config.after_initialize do |app|
-        if app.secrets.secret_key_base.present?
-          ActiveStorage.verifier = app.message_verifier("ActiveStorage")
-        end
+        ActiveStorage.verifier = app.message_verifier("ActiveStorage")
       end
     end
 
     initializer "active_storage.services" do
-      config.to_prepare do
+      ActiveSupport.on_load(:active_storage_blob) do
         if config_choice = Rails.configuration.active_storage.service
           configs = Rails.configuration.active_storage.service_configurations ||= begin
             config_file = Pathname.new(Rails.root.join("config/storage.yml"))
diff --git a/activestorage/lib/active_storage/errors.rb b/activestorage/lib/active_storage/errors.rb
new file mode 100644
index 0000000000..f099b13f5b
--- /dev/null
+++ b/activestorage/lib/active_storage/errors.rb
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  class InvariableError < StandardError; end
+  class UnpreviewableError < StandardError; end
+  class UnrepresentableError < StandardError; end
+end
diff --git a/activestorage/lib/active_storage/gem_version.rb b/activestorage/lib/active_storage/gem_version.rb
index e1d7b3493a..492620731b 100644
--- a/activestorage/lib/active_storage/gem_version.rb
+++ b/activestorage/lib/active_storage/gem_version.rb
@@ -7,8 +7,8 @@ module ActiveStorage
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
     PRE   = "alpha"
 
diff --git a/activestorage/lib/active_storage/log_subscriber.rb b/activestorage/lib/active_storage/log_subscriber.rb
index 0d00a75c0e..a4e148c1a5 100644
--- a/activestorage/lib/active_storage/log_subscriber.rb
+++ b/activestorage/lib/active_storage/log_subscriber.rb
@@ -18,6 +18,10 @@ module ActiveStorage
       info event, color("Deleted file from key: #{key_in(event)}", RED)
     end
 
+    def service_delete_prefixed(event)
+      info event, color("Deleted files by key prefix: #{event.payload[:prefix]}", RED)
+    end
+
     def service_exist(event)
       debug event, color("Checked if file exists at key: #{key_in(event)} (#{event.payload[:exist] ? "yes" : "no"})", BLUE)
     end
@@ -27,7 +31,7 @@ module ActiveStorage
     end
 
     def logger
-      ActiveStorage::Service.logger
+      ActiveStorage.logger
     end
 
     private
diff --git a/activestorage/lib/active_storage/previewer.rb b/activestorage/lib/active_storage/previewer.rb
new file mode 100644
index 0000000000..bff5e42d41
--- /dev/null
+++ b/activestorage/lib/active_storage/previewer.rb
@@ -0,0 +1,79 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  # This is an abstract base class for previewers, which generate images from blobs. See
+  # ActiveStorage::Previewer::PDFPreviewer and ActiveStorage::Previewer::VideoPreviewer for examples of
+  # concrete subclasses.
+  class Previewer
+    attr_reader :blob
+
+    # Implement this method in a concrete subclass. Have it return true when given a blob from which
+    # the previewer can generate an image.
+    def self.accept?(blob)
+      false
+    end
+
+    def initialize(blob)
+      @blob = blob
+    end
+
+    # Override this method in a concrete subclass. Have it yield an attachable preview image (i.e.
+    # anything accepted by ActiveStorage::Attached::One#attach).
+    def preview
+      raise NotImplementedError
+    end
+
+    private
+      # Downloads the blob to a tempfile on disk. Yields the tempfile.
+      def download_blob_to_tempfile(&block) #:doc:
+        blob.open tempdir: tempdir, &block
+      end
+
+      # Executes a system command, capturing its binary output in a tempfile. Yields the tempfile.
+      #
+      # Use this method to shell out to a system library (e.g. mupdf or ffmpeg) for preview image
+      # generation. The resulting tempfile can be used as the +:io+ value in an attachable Hash:
+      #
+      #   def preview
+      #     download_blob_to_tempfile do |input|
+      #       draw "my-drawing-command", input.path, "--format", "png", "-" do |output|
+      #         yield io: output, filename: "#{blob.filename.base}.png", content_type: "image/png"
+      #       end
+      #     end
+      #   end
+      #
+      # The output tempfile is opened in the directory returned by #tempdir.
+      def draw(*argv) #:doc:
+        ActiveSupport::Notifications.instrument("preview.active_storage") do
+          open_tempfile_for_drawing do |file|
+            capture(*argv, to: file)
+            yield file
+          end
+        end
+      end
+
+      def open_tempfile_for_drawing
+        tempfile = Tempfile.open("ActiveStorage", tempdir)
+
+        begin
+          yield tempfile
+        ensure
+          tempfile.close!
+        end
+      end
+
+      def capture(*argv, to:)
+        to.binmode
+        IO.popen(argv, err: File::NULL) { |out| IO.copy_stream(out, to) }
+        to.rewind
+      end
+
+      def logger #:doc:
+        ActiveStorage.logger
+      end
+
+      def tempdir #:doc:
+        Dir.tmpdir
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/previewer/mupdf_previewer.rb b/activestorage/lib/active_storage/previewer/mupdf_previewer.rb
new file mode 100644
index 0000000000..ae02a4889d
--- /dev/null
+++ b/activestorage/lib/active_storage/previewer/mupdf_previewer.rb
@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  class Previewer::MuPDFPreviewer < Previewer
+    class << self
+      def accept?(blob)
+        blob.content_type == "application/pdf" && mutool_exists?
+      end
+
+      def mutool_path
+        ActiveStorage.paths[:mutool] || "mutool"
+      end
+
+      def mutool_exists?
+        return @mutool_exists unless @mutool_exists.nil?
+
+        system mutool_path, out: File::NULL, err: File::NULL
+
+        @mutool_exists = $?.exitstatus == 1
+      end
+    end
+
+    def preview
+      download_blob_to_tempfile do |input|
+        draw_first_page_from input do |output|
+          yield io: output, filename: "#{blob.filename.base}.png", content_type: "image/png"
+        end
+      end
+    end
+
+    private
+      def draw_first_page_from(file, &block)
+        draw self.class.mutool_path, "draw", "-F", "png", "-o", "-", file.path, "1", &block
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/previewer/poppler_pdf_previewer.rb b/activestorage/lib/active_storage/previewer/poppler_pdf_previewer.rb
new file mode 100644
index 0000000000..2a787362cf
--- /dev/null
+++ b/activestorage/lib/active_storage/previewer/poppler_pdf_previewer.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  class Previewer::PopplerPDFPreviewer < Previewer
+    class << self
+      def accept?(blob)
+        blob.content_type == "application/pdf" && pdftoppm_exists?
+      end
+
+      def pdftoppm_path
+        ActiveStorage.paths[:pdftoppm] || "pdftoppm"
+      end
+
+      def pdftoppm_exists?
+        return @pdftoppm_exists unless @pdftoppm_exists.nil?
+
+        @pdftoppm_exists = system(pdftoppm_path, "-v", out: File::NULL, err: File::NULL)
+      end
+    end
+
+    def preview
+      download_blob_to_tempfile do |input|
+        draw_first_page_from input do |output|
+          yield io: output, filename: "#{blob.filename.base}.png", content_type: "image/png"
+        end
+      end
+    end
+
+    private
+      def draw_first_page_from(file, &block)
+        # use 72 dpi to match thumbnail  dimesions of the PDF
+        draw self.class.pdftoppm_path, "-singlefile", "-r", "72", "-png", file.path, &block
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/previewer/video_previewer.rb b/activestorage/lib/active_storage/previewer/video_previewer.rb
new file mode 100644
index 0000000000..50e13d202a
--- /dev/null
+++ b/activestorage/lib/active_storage/previewer/video_previewer.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  class Previewer::VideoPreviewer < Previewer
+    def self.accept?(blob)
+      blob.video?
+    end
+
+    def preview
+      download_blob_to_tempfile do |input|
+        draw_relevant_frame_from input do |output|
+          yield io: output, filename: "#{blob.filename.base}.jpg", content_type: "image/jpeg"
+        end
+      end
+    end
+
+    private
+      def draw_relevant_frame_from(file, &block)
+        draw ffmpeg_path, "-i", file.path, "-y", "-vframes", "1", "-f", "image2", "-", &block
+      end
+
+      def ffmpeg_path
+        ActiveStorage.paths[:ffmpeg] || "ffmpeg"
+      end
+  end
+end
diff --git a/activestorage/lib/active_storage/service.rb b/activestorage/lib/active_storage/service.rb
index ce736b8728..949969fc95 100644
--- a/activestorage/lib/active_storage/service.rb
+++ b/activestorage/lib/active_storage/service.rb
@@ -4,6 +4,7 @@ require "active_storage/log_subscriber"
 
 module ActiveStorage
   class IntegrityError < StandardError; end
+
   # Abstract class serving as an interface for concrete services.
   #
   # The available services are:
@@ -40,7 +41,7 @@ module ActiveStorage
     extend ActiveSupport::Autoload
     autoload :Configurator
 
-    class_attribute :logger
+    class_attribute :url_expires_in, default: 5.minutes
 
     class << self
       # Configure an Active Storage service by name from a set of configurations,
@@ -72,12 +73,22 @@ module ActiveStorage
       raise NotImplementedError
     end
 
+    # Return the partial content in the byte +range+ of the file at the +key+.
+    def download_chunk(key, range)
+      raise NotImplementedError
+    end
+
     # Delete the file at the +key+.
     def delete(key)
       raise NotImplementedError
     end
 
-    # Return true if a file exists at the +key+.
+    # Delete files at keys starting with the +prefix+.
+    def delete_prefixed(prefix)
+      raise NotImplementedError
+    end
+
+    # Return +true+ if a file exists at the +key+.
     def exist?(key)
       raise NotImplementedError
     end
@@ -91,7 +102,7 @@ module ActiveStorage
 
     # Returns a signed, temporary URL that a direct upload file can be PUT to on the +key+.
     # The URL will be valid for the amount of seconds specified in +expires_in+.
-    # You most also provide the +content_type+, +content_length+, and +checksum+ of the file
+    # You must also provide the +content_type+, +content_length+, and +checksum+ of the file
     # that will be uploaded. All these attributes will be validated by the service upon upload.
     def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
       raise NotImplementedError
@@ -103,15 +114,19 @@ module ActiveStorage
     end
 
     private
-      def instrument(operation, key, payload = {}, &block)
+      def instrument(operation, payload = {}, &block)
         ActiveSupport::Notifications.instrument(
           "service_#{operation}.active_storage",
-          payload.merge(key: key, service: service_name), &block)
+          payload.merge(service: service_name), &block)
       end
 
       def service_name
         # ActiveStorage::Service::DiskService => Disk
         self.class.name.split("::").third.remove("Service")
       end
+
+      def content_disposition_with(type: "inline", filename:)
+        (type.to_s.presence_in(%w( attachment inline )) || "inline") + "; #{filename.parameters}"
+      end
   end
 end
diff --git a/activestorage/lib/active_storage/service/azure_storage_service.rb b/activestorage/lib/active_storage/service/azure_storage_service.rb
index 895cc9c2f1..2867a4e441 100644
--- a/activestorage/lib/active_storage/service/azure_storage_service.rb
+++ b/activestorage/lib/active_storage/service/azure_storage_service.rb
@@ -8,18 +8,17 @@ module ActiveStorage
   # Wraps the Microsoft Azure Storage Blob Service as an Active Storage service.
   # See ActiveStorage::Service for the generic API documentation that applies to all services.
   class Service::AzureStorageService < Service
-    attr_reader :client, :path, :blobs, :container, :signer
+    attr_reader :client, :blobs, :container, :signer
 
-    def initialize(path:, storage_account_name:, storage_access_key:, container:)
+    def initialize(storage_account_name:, storage_access_key:, container:)
       @client = Azure::Storage::Client.create(storage_account_name: storage_account_name, storage_access_key: storage_access_key)
       @signer = Azure::Storage::Core::Auth::SharedAccessSignature.new(storage_account_name, storage_access_key)
       @blobs = client.blob_client
       @container = container
-      @path = path
     end
 
     def upload(key, io, checksum: nil)
-      instrument :upload, key, checksum: checksum do
+      instrument :upload, key: key, checksum: checksum do
         begin
           blobs.create_block_blob(container, key, io, content_md5: checksum)
         rescue Azure::Core::Http::HTTPError
@@ -28,31 +27,54 @@ module ActiveStorage
       end
     end
 
-    def download(key)
+    def download(key, &block)
       if block_given?
-        instrument :streaming_download, key do
+        instrument :streaming_download, key: key do
           stream(key, &block)
         end
       else
-        instrument :download, key do
+        instrument :download, key: key do
           _, io = blobs.get_blob(container, key)
           io.force_encoding(Encoding::BINARY)
         end
       end
     end
 
+    def download_chunk(key, range)
+      instrument :download_chunk, key: key, range: range do
+        _, io = blobs.get_blob(container, key, start_range: range.begin, end_range: range.exclude_end? ? range.end - 1 : range.end)
+        io.force_encoding(Encoding::BINARY)
+      end
+    end
+
     def delete(key)
-      instrument :delete, key do
+      instrument :delete, key: key do
         begin
           blobs.delete_blob(container, key)
         rescue Azure::Core::Http::HTTPError
-          false
+          # Ignore files already deleted
+        end
+      end
+    end
+
+    def delete_prefixed(prefix)
+      instrument :delete_prefixed, prefix: prefix do
+        marker = nil
+
+        loop do
+          results = blobs.list_blobs(container, prefix: prefix, marker: marker)
+
+          results.each do |blob|
+            blobs.delete_blob(container, blob.name)
+          end
+
+          break unless marker = results.continuation_token.presence
         end
       end
     end
 
     def exist?(key)
-      instrument :exist, key do |payload|
+      instrument :exist, key: key do |payload|
         answer = blob_for(key).present?
         payload[:exist] = answer
         answer
@@ -60,13 +82,13 @@ module ActiveStorage
     end
 
     def url(key, expires_in:, filename:, disposition:, content_type:)
-      instrument :url, key do |payload|
-        base_url = url_for(key)
+      instrument :url, key: key do |payload|
         generated_url = signer.signed_uri(
-          URI(base_url), false,
+          uri_for(key), false,
+          service: "b",
           permissions: "r",
           expiry: format_expiry(expires_in),
-          content_disposition: disposition,
+          content_disposition: content_disposition_with(type: disposition, filename: filename),
           content_type: content_type
         ).to_s
 
@@ -77,10 +99,13 @@ module ActiveStorage
     end
 
     def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
-      instrument :url, key do |payload|
-        base_url = url_for(key)
-        generated_url = signer.signed_uri(URI(base_url), false, permissions: "rw",
-          expiry: format_expiry(expires_in)).to_s
+      instrument :url, key: key do |payload|
+        generated_url = signer.signed_uri(
+          uri_for(key), false,
+          service: "b",
+          permissions: "rw",
+          expiry: format_expiry(expires_in)
+        ).to_s
 
         payload[:url] = generated_url
 
@@ -93,8 +118,8 @@ module ActiveStorage
     end
 
     private
-      def url_for(key)
-        "#{path}/#{container}/#{key}"
+      def uri_for(key)
+        blobs.generate_uri("#{container}/#{key}")
       end
 
       def blob_for(key)
@@ -108,15 +133,15 @@ module ActiveStorage
       end
 
       # Reads the object for the given key in chunks, yielding each to the block.
-      def stream(key, options = {}, &block)
+      def stream(key)
         blob = blob_for(key)
 
         chunk_size = 5.megabytes
         offset = 0
 
         while offset < blob.properties[:content_length]
-          _, io = blobs.get_blob(container, key, start_range: offset, end_range: offset + chunk_size - 1)
-          yield io
+          _, chunk = blobs.get_blob(container, key, start_range: offset, end_range: offset + chunk_size - 1)
+          yield chunk.force_encoding(Encoding::BINARY)
           offset += chunk_size
         end
       end
diff --git a/activestorage/lib/active_storage/service/disk_service.rb b/activestorage/lib/active_storage/service/disk_service.rb
index 5aa8d74a5a..b1b6f1ddcf 100644
--- a/activestorage/lib/active_storage/service/disk_service.rb
+++ b/activestorage/lib/active_storage/service/disk_service.rb
@@ -16,7 +16,7 @@ module ActiveStorage
     end
 
     def upload(key, io, checksum: nil)
-      instrument :upload, key, checksum: checksum do
+      instrument :upload, key: key, checksum: checksum do
         IO.copy_stream(io, make_path_for(key))
         ensure_integrity_of(key, checksum) if checksum
       end
@@ -24,22 +24,31 @@ module ActiveStorage
 
     def download(key)
       if block_given?
-        instrument :streaming_download, key do
+        instrument :streaming_download, key: key do
           File.open(path_for(key), "rb") do |file|
-            while data = file.read(64.kilobytes)
+            while data = file.read(5.megabytes)
               yield data
             end
           end
         end
       else
-        instrument :download, key do
+        instrument :download, key: key do
           File.binread path_for(key)
         end
       end
     end
 
+    def download_chunk(key, range)
+      instrument :download_chunk, key: key, range: range do
+        File.open(path_for(key), "rb") do |file|
+          file.seek range.begin
+          file.read range.size
+        end
+      end
+    end
+
     def delete(key)
-      instrument :delete, key do
+      instrument :delete, key: key do
         begin
           File.delete path_for(key)
         rescue Errno::ENOENT
@@ -48,8 +57,16 @@ module ActiveStorage
       end
     end
 
+    def delete_prefixed(prefix)
+      instrument :delete_prefixed, prefix: prefix do
+        Dir.glob(path_for("#{prefix}*")).each do |path|
+          FileUtils.rm_rf(path)
+        end
+      end
+    end
+
     def exist?(key)
-      instrument :exist, key do |payload|
+      instrument :exist, key: key do |payload|
         answer = File.exist? path_for(key)
         payload[:exist] = answer
         answer
@@ -57,17 +74,17 @@ module ActiveStorage
     end
 
     def url(key, expires_in:, filename:, disposition:, content_type:)
-      instrument :url, key do |payload|
+      instrument :url, key: key do |payload|
         verified_key_with_expiration = ActiveStorage.verifier.generate(key, expires_in: expires_in, purpose: :blob_key)
 
         generated_url =
-          if defined?(Rails.application)
-            Rails.application.routes.url_helpers.rails_disk_service_path \
-              verified_key_with_expiration,
-              filename: filename, disposition: disposition, content_type: content_type
-          else
-            "/rails/active_storage/disk/#{verified_key_with_expiration}/#{filename}?disposition=#{disposition}&content_type=#{content_type}"
-          end
+          url_helpers.rails_disk_service_url(
+            verified_key_with_expiration,
+            host: current_host,
+            filename: filename,
+            disposition: content_disposition_with(type: disposition, filename: filename),
+            content_type: content_type
+          )
 
         payload[:url] = generated_url
 
@@ -76,7 +93,7 @@ module ActiveStorage
     end
 
     def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
-      instrument :url, key do |payload|
+      instrument :url, key: key do |payload|
         verified_token_with_expiration = ActiveStorage.verifier.generate(
           {
             key: key,
@@ -88,12 +105,7 @@ module ActiveStorage
           purpose: :blob_token }
         )
 
-        generated_url =
-          if defined?(Rails.application)
-            Rails.application.routes.url_helpers.update_rails_disk_service_path verified_token_with_expiration
-          else
-            "/rails/active_storage/disk/#{verified_token_with_expiration}"
-          end
+        generated_url = url_helpers.update_rails_disk_service_url(verified_token_with_expiration, host: current_host)
 
         payload[:url] = generated_url
 
@@ -124,5 +136,13 @@ module ActiveStorage
           raise ActiveStorage::IntegrityError
         end
       end
+
+      def url_helpers
+        @url_helpers ||= Rails.application.routes.url_helpers
+      end
+
+      def current_host
+        ActiveStorage::Current.host
+      end
   end
 end
diff --git a/activestorage/lib/active_storage/service/gcs_service.rb b/activestorage/lib/active_storage/service/gcs_service.rb
index ebf24a36d7..38acef81f4 100644
--- a/activestorage/lib/active_storage/service/gcs_service.rb
+++ b/activestorage/lib/active_storage/service/gcs_service.rb
@@ -1,56 +1,83 @@
 # frozen_string_literal: true
 
+gem "google-cloud-storage", "~> 1.11"
+
 require "google/cloud/storage"
+require "net/http"
+
 require "active_support/core_ext/object/to_query"
+require "active_storage/filename"
 
 module ActiveStorage
   # Wraps the Google Cloud Storage as an Active Storage service. See ActiveStorage::Service for the generic API
   # documentation that applies to all services.
   class Service::GCSService < Service
-    attr_reader :client, :bucket
-
-    def initialize(project:, keyfile:, bucket:)
-      @client = Google::Cloud::Storage.new(project: project, keyfile: keyfile)
-      @bucket = @client.bucket(bucket)
+    def initialize(**config)
+      @config = config
     end
 
     def upload(key, io, checksum: nil)
-      instrument :upload, key, checksum: checksum do
+      instrument :upload, key: key, checksum: checksum do
         begin
-          bucket.create_file(io, key, md5: checksum)
+          # The official GCS client library doesn't allow us to create a file with no Content-Type metadata.
+          # We need the file we create to have no Content-Type so we can control it via the response-content-type
+          # param in signed URLs. Workaround: let the GCS client create the file with an inferred
+          # Content-Type (usually "application/octet-stream") then clear it.
+          bucket.create_file(io, key, md5: checksum).update do |file|
+            file.content_type = nil
+          end
         rescue Google::Cloud::InvalidArgumentError
           raise ActiveStorage::IntegrityError
         end
       end
     end
 
-    # FIXME: Add streaming when given a block
-    def download(key)
-      instrument :download, key do
-        io = file_for(key).download
-        io.rewind
-        io.read
+    def download(key, &block)
+      if block_given?
+        instrument :streaming_download, key: key do
+          stream(key, &block)
+        end
+      else
+        instrument :download, key: key do
+          file_for(key).download.string
+        end
+      end
+    end
+
+    def download_chunk(key, range)
+      instrument :download_chunk, key: key, range: range do
+        file_for(key).download(range: range).string
       end
     end
 
     def delete(key)
-      instrument :delete, key do
-        file_for(key).try(:delete)
+      instrument :delete, key: key do
+        begin
+          file_for(key).delete
+        rescue Google::Cloud::NotFoundError
+          # Ignore files already deleted
+        end
+      end
+    end
+
+    def delete_prefixed(prefix)
+      instrument :delete_prefixed, prefix: prefix do
+        bucket.files(prefix: prefix).all(&:delete)
       end
     end
 
     def exist?(key)
-      instrument :exist, key do |payload|
-        answer = file_for(key).present?
+      instrument :exist, key: key do |payload|
+        answer = file_for(key).exists?
         payload[:exist] = answer
         answer
       end
     end
 
     def url(key, expires_in:, filename:, content_type:, disposition:)
-      instrument :url, key do |payload|
+      instrument :url, key: key do |payload|
         generated_url = file_for(key).signed_url expires: expires_in, query: {
-          "response-content-disposition" => disposition,
+          "response-content-disposition" => content_disposition_with(type: disposition, filename: filename),
           "response-content-type" => content_type
         }
 
@@ -60,10 +87,9 @@ module ActiveStorage
       end
     end
 
-    def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
-      instrument :url, key do |payload|
-        generated_url = bucket.signed_url key, method: "PUT", expires: expires_in,
-          content_type: content_type, content_md5: checksum
+    def url_for_direct_upload(key, expires_in:, checksum:, **)
+      instrument :url, key: key do |payload|
+        generated_url = bucket.signed_url key, method: "PUT", expires: expires_in, content_md5: checksum
 
         payload[:url] = generated_url
 
@@ -71,13 +97,36 @@ module ActiveStorage
       end
     end
 
-    def headers_for_direct_upload(key, content_type:, checksum:, **)
-      { "Content-Type" => content_type, "Content-MD5" => checksum }
+    def headers_for_direct_upload(key, checksum:, **)
+      { "Content-MD5" => checksum }
     end
 
     private
-      def file_for(key)
-        bucket.file(key)
+      attr_reader :config
+
+      def file_for(key, skip_lookup: true)
+        bucket.file(key, skip_lookup: skip_lookup)
+      end
+
+      # Reads the file for the given key in chunks, yielding each to the block.
+      def stream(key)
+        file = file_for(key, skip_lookup: false)
+
+        chunk_size = 5.megabytes
+        offset = 0
+
+        while offset < file.size
+          yield file.download(range: offset..(offset + chunk_size - 1)).string
+          offset += chunk_size
+        end
+      end
+
+      def bucket
+        @bucket ||= client.bucket(config.fetch(:bucket))
+      end
+
+      def client
+        @client ||= Google::Cloud::Storage.new(config.except(:bucket))
       end
   end
 end
diff --git a/activestorage/lib/active_storage/service/mirror_service.rb b/activestorage/lib/active_storage/service/mirror_service.rb
index 39e922f7ab..6002ef5a00 100644
--- a/activestorage/lib/active_storage/service/mirror_service.rb
+++ b/activestorage/lib/active_storage/service/mirror_service.rb
@@ -9,7 +9,7 @@ module ActiveStorage
   class Service::MirrorService < Service
     attr_reader :primary, :mirrors
 
-    delegate :download, :exist?, :url, to: :primary
+    delegate :download, :download_chunk, :exist?, :url, to: :primary
 
     # Stitch together from named services.
     def self.build(primary:, mirrors:, configurator:, **options) #:nodoc:
@@ -35,6 +35,11 @@ module ActiveStorage
       perform_across_services :delete, key
     end
 
+    # Delete files at keys starting with the +prefix+ on all services.
+    def delete_prefixed(prefix)
+      perform_across_services :delete_prefixed, prefix
+    end
+
     private
       def each_service(&block)
         [ primary, *mirrors ].each(&block)
diff --git a/activestorage/lib/active_storage/service/s3_service.rb b/activestorage/lib/active_storage/service/s3_service.rb
index e5d1e56e05..0286e7ff21 100644
--- a/activestorage/lib/active_storage/service/s3_service.rb
+++ b/activestorage/lib/active_storage/service/s3_service.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require "aws-sdk"
+require "aws-sdk-s3"
 require "active_support/core_ext/numeric/bytes"
 
 module ActiveStorage
@@ -9,15 +9,15 @@ module ActiveStorage
   class Service::S3Service < Service
     attr_reader :client, :bucket, :upload_options
 
-    def initialize(access_key_id:, secret_access_key:, region:, bucket:, upload: {}, **options)
-      @client = Aws::S3::Resource.new(access_key_id: access_key_id, secret_access_key: secret_access_key, region: region, **options)
+    def initialize(bucket:, upload: {}, **options)
+      @client = Aws::S3::Resource.new(**options)
       @bucket = @client.bucket(bucket)
 
       @upload_options = upload
     end
 
     def upload(key, io, checksum: nil)
-      instrument :upload, key, checksum: checksum do
+      instrument :upload, key: key, checksum: checksum do
         begin
           object_for(key).put(upload_options.merge(body: io, content_md5: checksum))
         rescue Aws::S3::Errors::BadDigest
@@ -26,26 +26,38 @@ module ActiveStorage
       end
     end
 
-    def download(key)
+    def download(key, &block)
       if block_given?
-        instrument :streaming_download, key do
+        instrument :streaming_download, key: key do
           stream(key, &block)
         end
       else
-        instrument :download, key do
-          object_for(key).get.body.read.force_encoding(Encoding::BINARY)
+        instrument :download, key: key do
+          object_for(key).get.body.string.force_encoding(Encoding::BINARY)
         end
       end
     end
 
+    def download_chunk(key, range)
+      instrument :download_chunk, key: key, range: range do
+        object_for(key).get(range: "bytes=#{range.begin}-#{range.exclude_end? ? range.end - 1 : range.end}").body.read.force_encoding(Encoding::BINARY)
+      end
+    end
+
     def delete(key)
-      instrument :delete, key do
+      instrument :delete, key: key do
         object_for(key).delete
       end
     end
 
+    def delete_prefixed(prefix)
+      instrument :delete_prefixed, prefix: prefix do
+        bucket.objects(prefix: prefix).batch_delete!
+      end
+    end
+
     def exist?(key)
-      instrument :exist, key do |payload|
+      instrument :exist, key: key do |payload|
         answer = object_for(key).exists?
         payload[:exist] = answer
         answer
@@ -53,9 +65,9 @@ module ActiveStorage
     end
 
     def url(key, expires_in:, filename:, disposition:, content_type:)
-      instrument :url, key do |payload|
-        generated_url = object_for(key).presigned_url :get, expires_in: expires_in,
-          response_content_disposition: disposition,
+      instrument :url, key: key do |payload|
+        generated_url = object_for(key).presigned_url :get, expires_in: expires_in.to_i,
+          response_content_disposition: content_disposition_with(type: disposition, filename: filename),
           response_content_type: content_type
 
         payload[:url] = generated_url
@@ -65,8 +77,8 @@ module ActiveStorage
     end
 
     def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
-      instrument :url, key do |payload|
-        generated_url = object_for(key).presigned_url :put, expires_in: expires_in,
+      instrument :url, key: key do |payload|
+        generated_url = object_for(key).presigned_url :put, expires_in: expires_in.to_i,
           content_type: content_type, content_length: content_length, content_md5: checksum
 
         payload[:url] = generated_url
@@ -85,14 +97,14 @@ module ActiveStorage
       end
 
       # Reads the object for the given key in chunks, yielding each to the block.
-      def stream(key, options = {}, &block)
+      def stream(key)
         object = object_for(key)
 
         chunk_size = 5.megabytes
         offset = 0
 
         while offset < object.content_length
-          yield object.read(options.merge(range: "bytes=#{offset}-#{offset + chunk_size - 1}"))
+          yield object.get(range: "bytes=#{offset}-#{offset + chunk_size - 1}").body.read.force_encoding(Encoding::BINARY)
           offset += chunk_size
         end
       end
diff --git a/activestorage/lib/tasks/activestorage.rake b/activestorage/lib/tasks/activestorage.rake
index ef923e5926..296e91afa1 100644
--- a/activestorage/lib/tasks/activestorage.rake
+++ b/activestorage/lib/tasks/activestorage.rake
@@ -3,6 +3,10 @@
 namespace :active_storage do
   desc "Copy over the migration needed to the application"
   task install: :environment do
-    Rake::Task["active_storage:install:migrations"].invoke
+    if Rake::Task.task_defined?("active_storage:install:migrations")
+      Rake::Task["active_storage:install:migrations"].invoke
+    else
+      Rake::Task["app:active_storage:install:migrations"].invoke
+    end
   end
 end
diff --git a/activestorage/package.json b/activestorage/package.json
index b481295a8d..00876985cf 100644
--- a/activestorage/package.json
+++ b/activestorage/package.json
@@ -1,10 +1,11 @@
 {
   "name": "activestorage",
-  "version": "5.2.0.alpha",
+  "version": "6.0.0-alpha",
   "description": "Attach cloud and local files in Rails applications",
   "main": "app/assets/javascripts/activestorage.js",
   "files": [
-    "app/assets/javascripts/*.js"
+    "app/assets/javascripts/*.js",
+    "src/*.js"
   ],
   "homepage": "http://rubyonrails.org/",
   "repository": {
@@ -16,18 +17,25 @@
   },
   "author": "Javan Makhmali <javan@javan.us>",
   "license": "MIT",
+  "dependencies": {
+    "spark-md5": "^3.0.0"
+  },
   "devDependencies": {
     "babel-core": "^6.25.0",
-    "babel-loader": "^7.1.1",
+    "babel-plugin-external-helpers": "^6.22.0",
     "babel-preset-env": "^1.6.0",
     "eslint": "^4.3.0",
     "eslint-plugin-import": "^2.7.0",
-    "spark-md5": "^3.0.0",
-    "webpack": "^3.4.0"
+    "rollup": "^0.58.2",
+    "rollup-plugin-babel": "^3.0.4",
+    "rollup-plugin-commonjs": "^9.1.0",
+    "rollup-plugin-node-resolve": "^3.3.0",
+    "rollup-plugin-uglify": "^3.0.0"
   },
   "scripts": {
     "prebuild": "yarn lint",
-    "build": "webpack -p",
-    "lint": "eslint app/javascript"
+    "build": "rollup --config rollup.config.js",
+    "lint": "eslint app/javascript",
+    "prepublishOnly": "rm -rf src && cp -R app/javascript/activestorage src"
   }
 }
diff --git a/activestorage/rollup.config.js b/activestorage/rollup.config.js
new file mode 100644
index 0000000000..1b4f9477ab
--- /dev/null
+++ b/activestorage/rollup.config.js
@@ -0,0 +1,28 @@
+import resolve from "rollup-plugin-node-resolve"
+import commonjs from "rollup-plugin-commonjs"
+import babel from "rollup-plugin-babel"
+import uglify from "rollup-plugin-uglify"
+
+const uglifyOptions = {
+  mangle: false,
+  compress: false,
+  output: {
+    beautify: true,
+    indent_level: 2
+  }
+}
+
+export default {
+  input: "app/javascript/activestorage/index.js",
+  output: {
+    file: "app/assets/javascripts/activestorage.js",
+    format: "umd",
+    name: "ActiveStorage"
+  },
+  plugins: [
+    resolve(),
+    commonjs(),
+    babel(),
+    uglify(uglifyOptions)
+  ]
+}
diff --git a/activestorage/test/analyzer/image_analyzer_test.rb b/activestorage/test/analyzer/image_analyzer_test.rb
new file mode 100644
index 0000000000..55bb5e7280
--- /dev/null
+++ b/activestorage/test/analyzer/image_analyzer_test.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+require "active_storage/analyzer/image_analyzer"
+
+class ActiveStorage::Analyzer::ImageAnalyzerTest < ActiveSupport::TestCase
+  test "analyzing a JPEG image" do
+    blob = create_file_blob(filename: "racecar.jpg", content_type: "image/jpeg")
+    metadata = extract_metadata_from(blob)
+
+    assert_equal 4104, metadata[:width]
+    assert_equal 2736, metadata[:height]
+  end
+
+  test "analyzing a rotated JPEG image" do
+    blob = create_file_blob(filename: "racecar_rotated.jpg", content_type: "image/jpeg")
+    metadata = extract_metadata_from(blob)
+
+    assert_equal 2736, metadata[:width]
+    assert_equal 4104, metadata[:height]
+  end
+
+  test "analyzing an SVG image without an XML declaration" do
+    blob = create_file_blob(filename: "icon.svg", content_type: "image/svg+xml")
+    metadata = extract_metadata_from(blob)
+
+    assert_equal 792, metadata[:width]
+    assert_equal 584, metadata[:height]
+  end
+end
diff --git a/activestorage/test/analyzer/video_analyzer_test.rb b/activestorage/test/analyzer/video_analyzer_test.rb
new file mode 100644
index 0000000000..d30f49315a
--- /dev/null
+++ b/activestorage/test/analyzer/video_analyzer_test.rb
@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+require "active_storage/analyzer/video_analyzer"
+
+class ActiveStorage::Analyzer::VideoAnalyzerTest < ActiveSupport::TestCase
+  test "analyzing a video" do
+    blob = create_file_blob(filename: "video.mp4", content_type: "video/mp4")
+    metadata = extract_metadata_from(blob)
+
+    assert_equal 640, metadata[:width]
+    assert_equal 480, metadata[:height]
+    assert_equal [4, 3], metadata[:display_aspect_ratio]
+    assert_equal 5.166648, metadata[:duration]
+    assert_not_includes metadata, :angle
+  end
+
+  test "analyzing a rotated video" do
+    blob = create_file_blob(filename: "rotated_video.mp4", content_type: "video/mp4")
+    metadata = extract_metadata_from(blob)
+
+    assert_equal 480, metadata[:width]
+    assert_equal 640, metadata[:height]
+    assert_equal [4, 3], metadata[:display_aspect_ratio]
+    assert_equal 5.227975, metadata[:duration]
+    assert_equal 90, metadata[:angle]
+  end
+
+  test "analyzing a video with rectangular samples" do
+    blob = create_file_blob(filename: "video_with_rectangular_samples.mp4", content_type: "video/mp4")
+    metadata = extract_metadata_from(blob)
+
+    assert_equal 1280, metadata[:width]
+    assert_equal 720, metadata[:height]
+    assert_equal [16, 9], metadata[:display_aspect_ratio]
+  end
+
+  test "analyzing a video with an undefined display aspect ratio" do
+    blob = create_file_blob(filename: "video_with_undefined_display_aspect_ratio.mp4", content_type: "video/mp4")
+    metadata = extract_metadata_from(blob)
+
+    assert_equal 640, metadata[:width]
+    assert_equal 480, metadata[:height]
+    assert_nil metadata[:display_aspect_ratio]
+  end
+
+  test "analyzing a video without a video stream" do
+    blob = create_file_blob(filename: "video_without_video_stream.mp4", content_type: "video/mp4")
+    metadata = extract_metadata_from(blob)
+    assert_equal({ "analyzed" => true, "identified" => true }, metadata)
+  end
+end
diff --git a/activestorage/test/controllers/blobs_controller_test.rb b/activestorage/test/controllers/blobs_controller_test.rb
index c37b9c8a10..9c811df895 100644
--- a/activestorage/test/controllers/blobs_controller_test.rb
+++ b/activestorage/test/controllers/blobs_controller_test.rb
@@ -5,7 +5,12 @@ require "database/setup"
 
 class ActiveStorage::BlobsControllerTest < ActionDispatch::IntegrationTest
   setup do
-    @blob = create_image_blob filename: "racecar.jpg"
+    @blob = create_file_blob filename: "racecar.jpg"
+  end
+
+  test "showing blob with invalid signed ID" do
+    get rails_service_blob_url("invalid", "racecar.jpg")
+    assert_response :not_found
   end
 
   test "showing blob utilizes browser caching" do
diff --git a/activestorage/test/controllers/direct_uploads_controller_test.rb b/activestorage/test/controllers/direct_uploads_controller_test.rb
index 888767086c..1b16da17d9 100644
--- a/activestorage/test/controllers/direct_uploads_controller_test.rb
+++ b/activestorage/test/controllers/direct_uploads_controller_test.rb
@@ -27,7 +27,7 @@ if SERVICE_CONFIGURATIONS[:s3] && SERVICE_CONFIGURATIONS[:s3][:access_key_id].pr
         assert_equal checksum, details["checksum"]
         assert_equal "text/plain", details["content_type"]
         assert_match SERVICE_CONFIGURATIONS[:s3][:bucket], details["direct_upload"]["url"]
-        assert_match(/s3\.(\S+)?amazonaws\.com/, details["direct_upload"]["url"])
+        assert_match(/s3(-[-a-z0-9]+)?\.(\S+)?amazonaws\.com/, details["direct_upload"]["url"])
         assert_equal({ "Content-Type" => "text/plain", "Content-MD5" => checksum }, details["direct_upload"]["headers"])
       end
     end
@@ -62,7 +62,7 @@ if SERVICE_CONFIGURATIONS[:gcs]
         assert_equal checksum, details["checksum"]
         assert_equal "text/plain", details["content_type"]
         assert_match %r{storage\.googleapis\.com/#{@config[:bucket]}}, details["direct_upload"]["url"]
-        assert_equal({ "Content-Type" => "text/plain", "Content-MD5" => checksum }, details["direct_upload"]["headers"])
+        assert_equal({ "Content-MD5" => checksum }, details["direct_upload"]["headers"])
       end
     end
   end
@@ -121,4 +121,27 @@ class ActiveStorage::DiskDirectUploadsControllerTest < ActionDispatch::Integrati
       assert_equal({ "Content-Type" => "text/plain" }, details["direct_upload"]["headers"])
     end
   end
+
+  test "creating new direct upload does not include root in json" do
+    checksum = Digest::MD5.base64digest("Hello")
+
+    set_include_root_in_json(true) do
+      post rails_direct_uploads_url, params: { blob: {
+        filename: "hello.txt", byte_size: 6, checksum: checksum, content_type: "text/plain" } }
+    end
+
+    @response.parsed_body.tap do |details|
+      assert_nil details["blob"]
+      assert_not_nil details["id"]
+    end
+  end
+
+  private
+    def set_include_root_in_json(value)
+      original = ActiveRecord::Base.include_root_in_json
+      ActiveRecord::Base.include_root_in_json = value
+      yield
+    ensure
+      ActiveRecord::Base.include_root_in_json = original
+    end
 end
diff --git a/activestorage/test/controllers/disk_controller_test.rb b/activestorage/test/controllers/disk_controller_test.rb
index 940dbf5918..9af7c83bdf 100644
--- a/activestorage/test/controllers/disk_controller_test.rb
+++ b/activestorage/test/controllers/disk_controller_test.rb
@@ -8,16 +8,18 @@ class ActiveStorage::DiskControllerTest < ActionDispatch::IntegrationTest
     blob = create_blob
 
     get blob.service_url
-    assert_equal "inline; filename=\"hello.txt\"; filename*=UTF-8''hello.txt", @response.headers["Content-Disposition"]
-    assert_equal "text/plain", @response.headers["Content-Type"]
+    assert_equal "inline; filename=\"hello.txt\"; filename*=UTF-8''hello.txt", response.headers["Content-Disposition"]
+    assert_equal "text/plain", response.headers["Content-Type"]
+    assert_equal "Hello world!", response.body
   end
 
   test "showing blob as attachment" do
     blob = create_blob
 
     get blob.service_url(disposition: :attachment)
-    assert_equal "attachment; filename=\"hello.txt\"; filename*=UTF-8''hello.txt", @response.headers["Content-Disposition"]
-    assert_equal "text/plain", @response.headers["Content-Type"]
+    assert_equal "attachment; filename=\"hello.txt\"; filename*=UTF-8''hello.txt", response.headers["Content-Disposition"]
+    assert_equal "text/plain", response.headers["Content-Type"]
+    assert_equal "Hello world!", response.body
   end
 
 
diff --git a/activestorage/test/controllers/representations_controller_test.rb b/activestorage/test/controllers/representations_controller_test.rb
new file mode 100644
index 0000000000..2662cc5283
--- /dev/null
+++ b/activestorage/test/controllers/representations_controller_test.rb
@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+class ActiveStorage::RepresentationsControllerWithVariantsTest < ActionDispatch::IntegrationTest
+  setup do
+    @blob = create_file_blob filename: "racecar.jpg"
+  end
+
+  test "showing variant inline" do
+    get rails_blob_representation_url(
+      filename: @blob.filename,
+      signed_blob_id: @blob.signed_id,
+      variation_key: ActiveStorage::Variation.encode(resize: "100x100"))
+
+    assert_redirected_to(/racecar\.jpg\?.*disposition=inline/)
+
+    image = read_image(@blob.variant(resize: "100x100"))
+    assert_equal 100, image.width
+    assert_equal 67, image.height
+  end
+
+  test "showing variant with invalid signed blob ID" do
+    get rails_blob_representation_url(
+      filename: @blob.filename,
+      signed_blob_id: "invalid",
+      variation_key: ActiveStorage::Variation.encode(resize: "100x100"))
+
+    assert_response :not_found
+  end
+end
+
+class ActiveStorage::RepresentationsControllerWithPreviewsTest < ActionDispatch::IntegrationTest
+  setup do
+    @blob = create_file_blob filename: "report.pdf", content_type: "application/pdf"
+  end
+
+  test "showing preview inline" do
+    get rails_blob_representation_url(
+      filename: @blob.filename,
+      signed_blob_id: @blob.signed_id,
+      variation_key: ActiveStorage::Variation.encode(resize: "100x100"))
+
+    assert_predicate @blob.preview_image, :attached?
+    assert_redirected_to(/report\.png\?.*disposition=inline/)
+
+    image = read_image(@blob.preview_image.variant(resize: "100x100"))
+    assert_equal 77, image.width
+    assert_equal 100, image.height
+  end
+
+  test "showing preview with invalid signed blob ID" do
+    get rails_blob_representation_url(
+      filename: @blob.filename,
+      signed_blob_id: "invalid",
+      variation_key: ActiveStorage::Variation.encode(resize: "100x100"))
+
+    assert_response :not_found
+  end
+end
diff --git a/activestorage/test/controllers/variants_controller_test.rb b/activestorage/test/controllers/variants_controller_test.rb
deleted file mode 100644
index 0a049f3bc4..0000000000
--- a/activestorage/test/controllers/variants_controller_test.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-# frozen_string_literal: true
-
-require "test_helper"
-require "database/setup"
-
-class ActiveStorage::VariantsControllerTest < ActionDispatch::IntegrationTest
-  setup do
-    @blob = create_image_blob filename: "racecar.jpg"
-  end
-
-  test "showing variant inline" do
-    get rails_blob_variation_url(
-      filename: @blob.filename,
-      signed_blob_id: @blob.signed_id,
-      variation_key: ActiveStorage::Variation.encode(resize: "100x100"))
-
-    assert_redirected_to(/racecar\.jpg\?.*disposition=inline/)
-
-    image = read_image_variant(@blob.variant(resize: "100x100"))
-    assert_equal 100, image.width
-    assert_equal 67, image.height
-  end
-end
diff --git a/activestorage/test/database/setup.rb b/activestorage/test/database/setup.rb
index 87564499e6..daeeb5695b 100644
--- a/activestorage/test/database/setup.rb
+++ b/activestorage/test/database/setup.rb
@@ -3,5 +3,5 @@
 require_relative "create_users_migration"
 
 ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
-ActiveRecord::Migrator.migrate File.expand_path("../../../db/migrate", __FILE__)
+ActiveRecord::Base.connection.migration_context.migrate
 ActiveStorageCreateUsers.migrate(:up)
diff --git a/activestorage/test/dummy/bin/bundle b/activestorage/test/dummy/bin/bundle
index 277e128251..5015ba6f8b 100755
--- a/activestorage/test/dummy/bin/bundle
+++ b/activestorage/test/dummy/bin/bundle
@@ -1,5 +1,5 @@
 #!/usr/bin/env ruby
 # frozen_string_literal: true
 
-ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile", __FILE__)
+ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../Gemfile", __dir__)
 load Gem.bin_path("bundler", "bundle")
diff --git a/activestorage/test/dummy/config/application.rb b/activestorage/test/dummy/config/application.rb
index 7ee6625bb5..bd14ac0b1a 100644
--- a/activestorage/test/dummy/config/application.rb
+++ b/activestorage/test/dummy/config/application.rb
@@ -10,16 +10,12 @@ require "action_controller/railtie"
 require "action_view/railtie"
 require "sprockets/railtie"
 require "active_storage/engine"
-#require "action_mailer/railtie"
-#require "rails/test_unit/railtie"
-#require "action_cable/engine"
-
 
 Bundler.require(*Rails.groups)
 
 module Dummy
   class Application < Rails::Application
-    config.load_defaults 5.1
+    config.load_defaults 5.2
 
     config.active_storage.service = :local
   end
diff --git a/activestorage/test/dummy/config/environments/test.rb b/activestorage/test/dummy/config/environments/test.rb
index ce0889e8ae..74a802d98c 100644
--- a/activestorage/test/dummy/config/environments/test.rb
+++ b/activestorage/test/dummy/config/environments/test.rb
@@ -30,6 +30,9 @@ Rails.application.configure do
   # Print deprecation notices to the stderr.
   config.active_support.deprecation = :stderr
 
+  # Disable request forgery protection in test environment.
+  config.action_controller.allow_forgery_protection = false
+
   # Raises error for missing translations
   # config.action_view.raise_on_missing_translations = true
 end
diff --git a/activestorage/test/fixtures/files/favicon.ico b/activestorage/test/fixtures/files/favicon.ico
new file mode 100644
index 0000000000..87192a8a07
--- /dev/null
+++ b/activestorage/test/fixtures/files/favicon.ico
diff --git a/activestorage/test/fixtures/files/icon.psd b/activestorage/test/fixtures/files/icon.psd
new file mode 100644
index 0000000000..631fceeaab
--- /dev/null
+++ b/activestorage/test/fixtures/files/icon.psd
diff --git a/activestorage/test/fixtures/files/icon.svg b/activestorage/test/fixtures/files/icon.svg
new file mode 100644
index 0000000000..6cfb0e241e
--- /dev/null
+++ b/activestorage/test/fixtures/files/icon.svg
@@ -0,0 +1,13 @@
+<!-- The XML declaration is intentionally omitted. -->
+<svg width="792px" height="584px" viewBox="0 0 792 584" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+    <path d="M9.51802657,28.724593 C9.51802657,18.2155955 18.1343454,9.60822622 28.6542694,9.60822622 L763.245541,9.60822622 C773.765465,9.60822622 782.381784,18.2155955 782.381784,28.724593 L782.381784,584 L792,584 L792,28.724593 C792,12.911054 779.075522,0 763.245541,0 L28.7544592,0 C12.9244782,0 0,12.911054 0,28.724593 L0,584 L9.61821632,584 C9.51802657,584 9.51802657,28.724593 9.51802657,28.724593 L9.51802657,28.724593 Z" id="Shape" opacity="0.3" fill="#CCCCCC"></path>
+    <circle id="Oval" fill="#FFCC33" cx="119.1" cy="147.2" r="33"></circle>
+    <circle id="Oval" fill="#3399FF" cx="119.1" cy="281.1" r="33"></circle>
+    <circle id="Oval" fill="#FF3333" cx="676.1" cy="376.8" r="33"></circle>
+    <circle id="Oval" fill="#FFCC33" cx="119.1" cy="477.2" r="33"></circle>
+    <rect id="Rectangle-path" opacity="0.75" fill="#CCCCCC" x="176.5" y="130.5" width="442.1" height="33.5"></rect>
+    <rect id="Rectangle-path" opacity="0.75" fill="#CCCCCC" x="176.5" y="183.1" width="442.1" height="33.5"></rect>
+    <rect id="Rectangle-path" opacity="0.75" fill="#CCCCCC" x="176.5" y="265.8" width="442.1" height="33.5"></rect>
+    <rect id="Rectangle-path" opacity="0.75" fill="#CCCCCC" x="176.5" y="363.4" width="442.1" height="33.5"></rect>
+    <rect id="Rectangle-path" opacity="0.75" fill="#CCCCCC" x="176.5" y="465.3" width="442.1" height="33.5"></rect>
+</svg>
diff --git a/activestorage/test/fixtures/files/image.gif b/activestorage/test/fixtures/files/image.gif
new file mode 100644
index 0000000000..90c05f671c
--- /dev/null
+++ b/activestorage/test/fixtures/files/image.gif
diff --git a/activestorage/test/fixtures/files/racecar_rotated.jpg b/activestorage/test/fixtures/files/racecar_rotated.jpg
new file mode 100644
index 0000000000..89e6d54f98
--- /dev/null
+++ b/activestorage/test/fixtures/files/racecar_rotated.jpg
diff --git a/activestorage/test/fixtures/files/report.pdf b/activestorage/test/fixtures/files/report.pdf
new file mode 100644
index 0000000000..cccb9b5d64
--- /dev/null
+++ b/activestorage/test/fixtures/files/report.pdf
diff --git a/activestorage/test/fixtures/files/rotated_video.mp4 b/activestorage/test/fixtures/files/rotated_video.mp4
new file mode 100644
index 0000000000..4c7a4e9e57
--- /dev/null
+++ b/activestorage/test/fixtures/files/rotated_video.mp4
diff --git a/activestorage/test/fixtures/files/video.mp4 b/activestorage/test/fixtures/files/video.mp4
new file mode 100644
index 0000000000..8fb1c5b24d
--- /dev/null
+++ b/activestorage/test/fixtures/files/video.mp4
diff --git a/activestorage/test/fixtures/files/video_with_rectangular_samples.mp4 b/activestorage/test/fixtures/files/video_with_rectangular_samples.mp4
new file mode 100644
index 0000000000..12b04afc87
--- /dev/null
+++ b/activestorage/test/fixtures/files/video_with_rectangular_samples.mp4
diff --git a/activestorage/test/fixtures/files/video_with_undefined_display_aspect_ratio.mp4 b/activestorage/test/fixtures/files/video_with_undefined_display_aspect_ratio.mp4
new file mode 100644
index 0000000000..eb354e756f
--- /dev/null
+++ b/activestorage/test/fixtures/files/video_with_undefined_display_aspect_ratio.mp4
diff --git a/activestorage/test/fixtures/files/video_without_video_stream.mp4 b/activestorage/test/fixtures/files/video_without_video_stream.mp4
new file mode 100644
index 0000000000..e6a55f868b
--- /dev/null
+++ b/activestorage/test/fixtures/files/video_without_video_stream.mp4
diff --git a/activestorage/test/models/attached_test.rb b/activestorage/test/models/attached_test.rb
new file mode 100644
index 0000000000..14395e12df
--- /dev/null
+++ b/activestorage/test/models/attached_test.rb
@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
+  include ActiveJob::TestHelper
+
+  setup do
+    @user = User.create!(name: "Josh")
+  end
+
+  teardown { ActiveStorage::Blob.all.each(&:purge) }
+
+  test "overriding has_one_attached methods works" do
+    # attach blob before messing with getter, which breaks `#attach`
+    @user.avatar.attach create_blob(filename: "funky.jpg")
+
+    # inherited only
+    assert_equal "funky.jpg", @user.avatar.filename.to_s
+
+    User.class_eval do
+      def avatar
+        super.filename.to_s.reverse
+      end
+    end
+
+    # override with super
+    assert_equal "funky.jpg".reverse, @user.avatar
+
+    User.send(:remove_method, :avatar)
+  end
+
+  test "overriding has_many_attached methods works" do
+    # attach blobs before messing with getter, which breaks `#attach`
+    @user.highlights.attach create_blob(filename: "funky.jpg"), create_blob(filename: "wonky.jpg")
+
+    # inherited only
+    assert_equal "funky.jpg", @user.highlights.first.filename.to_s
+    assert_equal "wonky.jpg", @user.highlights.second.filename.to_s
+
+    User.class_eval do
+      def highlights
+        super.reverse
+      end
+    end
+
+    # override with super
+    assert_equal "wonky.jpg", @user.highlights.first.filename.to_s
+    assert_equal "funky.jpg", @user.highlights.second.filename.to_s
+
+    User.send(:remove_method, :highlights)
+  end
+end
diff --git a/activestorage/test/models/attachments_test.rb b/activestorage/test/models/attachments_test.rb
index 7cfd8683db..ce83ec27d2 100644
--- a/activestorage/test/models/attachments_test.rb
+++ b/activestorage/test/models/attachments_test.rb
@@ -15,7 +15,7 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     assert_equal "funky.jpg", @user.avatar.filename.to_s
   end
 
-  test "attach existing sgid blob" do
+  test "attach existing blob from a signed ID" do
     @user.avatar.attach create_blob(filename: "funky.jpg").signed_id
     assert_equal "funky.jpg", @user.avatar.filename.to_s
   end
@@ -27,10 +27,107 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
 
   test "attach new blob from an UploadedFile" do
     file = file_fixture "racecar.jpg"
-    @user.avatar.attach Rack::Test::UploadedFile.new file
+    @user.avatar.attach Rack::Test::UploadedFile.new file.to_s
     assert_equal "racecar.jpg", @user.avatar.filename.to_s
   end
 
+  test "replace attached blob" do
+    @user.avatar.attach create_blob(filename: "funky.jpg")
+
+    perform_enqueued_jobs do
+      assert_no_difference -> { ActiveStorage::Blob.count } do
+        @user.avatar.attach create_blob(filename: "town.jpg")
+      end
+    end
+
+    assert_equal "town.jpg", @user.avatar.filename.to_s
+  end
+
+  test "replace attached blob unsuccessfully" do
+    @user.avatar.attach create_blob(filename: "funky.jpg")
+
+    perform_enqueued_jobs do
+      assert_raises do
+        @user.avatar.attach nil
+      end
+    end
+
+    assert_equal "funky.jpg", @user.reload.avatar.filename.to_s
+    assert ActiveStorage::Blob.service.exist?(@user.avatar.key)
+  end
+
+  test "replace attached blob with itself" do
+    @user.avatar.attach create_blob(filename: "funky.jpg")
+
+    assert_no_changes -> { @user.reload.avatar.blob } do
+      assert_no_changes -> { @user.reload.avatar.attachment } do
+        assert_no_enqueued_jobs do
+          @user.avatar.attach @user.avatar.blob
+        end
+      end
+    end
+  end
+
+  test "replaced attached blob with itself by signed ID" do
+    @user.avatar.attach create_blob(filename: "funky.jpg")
+
+    assert_no_changes -> { @user.reload.avatar.blob } do
+      assert_no_changes -> { @user.reload.avatar.attachment } do
+        assert_no_enqueued_jobs do
+          @user.avatar.attach @user.avatar.blob.signed_id
+        end
+      end
+    end
+  end
+
+  test "replace independent attached blob" do
+    @user.cover_photo.attach create_blob(filename: "funky.jpg")
+
+    perform_enqueued_jobs do
+      assert_difference -> { ActiveStorage::Blob.count }, +1 do
+        assert_no_difference -> { ActiveStorage::Attachment.count } do
+          @user.cover_photo.attach create_blob(filename: "town.jpg")
+        end
+      end
+    end
+
+    assert_equal "town.jpg", @user.cover_photo.filename.to_s
+  end
+
+  test "attach blob to new record" do
+    user = User.new(name: "Jason")
+
+    assert_no_changes -> { user.new_record? } do
+      assert_no_difference -> { ActiveStorage::Attachment.count } do
+        user.avatar.attach create_blob(filename: "funky.jpg")
+      end
+    end
+
+    assert_predicate user.avatar, :attached?
+    assert_equal "funky.jpg", user.avatar.filename.to_s
+
+    assert_difference -> { ActiveStorage::Attachment.count }, +1 do
+      user.save!
+    end
+
+    assert_predicate user.reload.avatar, :attached?
+    assert_equal "funky.jpg", user.avatar.filename.to_s
+  end
+
+  test "build new record with attached blob" do
+    assert_no_difference -> { ActiveStorage::Attachment.count } do
+      @user = User.new(name: "Jason", avatar: { io: StringIO.new("STUFF"), filename: "town.jpg", content_type: "image/jpg" })
+    end
+
+    assert_predicate @user, :new_record?
+    assert_predicate @user.avatar, :attached?
+    assert_equal "town.jpg", @user.avatar.filename.to_s
+
+    @user.save!
+    assert_predicate @user.reload.avatar, :attached?
+    assert_equal "town.jpg", @user.avatar.filename.to_s
+  end
+
   test "access underlying associations of new blob" do
     @user.avatar.attach create_blob(filename: "funky.jpg")
     assert_equal @user, @user.avatar_attachment.record
@@ -38,12 +135,90 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     assert_equal "funky.jpg", @user.avatar_attachment.blob.filename.to_s
   end
 
+  test "identify newly-attached, directly-uploaded blob" do
+    blob = directly_upload_file_blob(content_type: "application/octet-stream")
+
+    @user.avatar.attach(blob)
+
+    assert_equal "image/jpeg", @user.avatar.reload.content_type
+    assert_predicate @user.avatar, :identified?
+  end
+
+  test "identify and analyze newly-attached, directly-uploaded blob" do
+    blob = directly_upload_file_blob(content_type: "application/octet-stream")
+
+    perform_enqueued_jobs do
+      @user.avatar.attach blob
+    end
+
+    assert_equal true, @user.avatar.reload.metadata[:identified]
+    assert_equal 4104, @user.avatar.metadata[:width]
+    assert_equal 2736, @user.avatar.metadata[:height]
+  end
+
+  test "identify newly-attached blob only once" do
+    blob = create_file_blob
+    assert_predicate blob, :identified?
+
+    # The blob's backing file is a PNG image. Fudge its content type so we can tell if it's identified when we attach it.
+    blob.update! content_type: "application/octet-stream"
+
+    @user.avatar.attach blob
+    assert_equal "application/octet-stream", blob.content_type
+  end
+
+  test "analyze newly-attached blob" do
+    perform_enqueued_jobs do
+      @user.avatar.attach create_file_blob
+    end
+
+    assert_equal 4104, @user.avatar.reload.metadata[:width]
+    assert_equal 2736, @user.avatar.metadata[:height]
+  end
+
+  test "analyze attached blob only once" do
+    blob = create_file_blob
+
+    perform_enqueued_jobs do
+      @user.avatar.attach blob
+    end
+
+    assert_predicate blob.reload, :analyzed?
+
+    @user.avatar.detach
+
+    assert_no_enqueued_jobs do
+      @user.reload.avatar.attach blob
+    end
+  end
+
+  test "preserve existing metadata when analyzing a newly-attached blob" do
+    blob = create_file_blob(metadata: { foo: "bar" })
+
+    perform_enqueued_jobs do
+      @user.avatar.attach blob
+    end
+
+    assert_equal "bar", blob.reload.metadata[:foo]
+  end
+
+  test "detach blob" do
+    @user.avatar.attach create_blob(filename: "funky.jpg")
+    avatar_blob_id = @user.avatar.blob.id
+    avatar_key = @user.avatar.key
+
+    @user.avatar.detach
+    assert_not_predicate @user.avatar, :attached?
+    assert ActiveStorage::Blob.exists?(avatar_blob_id)
+    assert ActiveStorage::Blob.service.exist?(avatar_key)
+  end
+
   test "purge attached blob" do
     @user.avatar.attach create_blob(filename: "funky.jpg")
     avatar_key = @user.avatar.key
 
     @user.avatar.purge
-    assert_not @user.avatar.attached?
+    assert_not_predicate @user.avatar, :attached?
     assert_not ActiveStorage::Blob.service.exist?(avatar_key)
   end
 
@@ -52,13 +227,33 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     avatar_key = @user.avatar.key
 
     perform_enqueued_jobs do
-      @user.destroy
+      @user.reload.destroy
 
       assert_nil ActiveStorage::Blob.find_by(key: avatar_key)
       assert_not ActiveStorage::Blob.service.exist?(avatar_key)
     end
   end
 
+  test "delete attachment for independent blob when record is destroyed" do
+    @user.cover_photo.attach create_blob(filename: "funky.jpg")
+
+    @user.destroy
+    assert_not ActiveStorage::Attachment.exists?(record: @user, name: "cover_photo")
+  end
+
+  test "find with attached blob" do
+    records = %w[alice bob].map do |name|
+      User.create!(name: name).tap do |user|
+        user.avatar.attach create_blob(filename: "#{name}.jpg")
+      end
+    end
+
+    users = User.where(id: records.map(&:id)).with_attached_avatar.all
+
+    assert_equal "alice.jpg", users.first.avatar.filename.to_s
+    assert_equal "bob.jpg", users.second.avatar.filename.to_s
+  end
+
 
   test "attach existing blobs" do
     @user.highlights.attach create_blob(filename: "funky.jpg"), create_blob(filename: "wonky.jpg")
@@ -76,6 +271,48 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     assert_equal "country.jpg", @user.highlights.second.filename.to_s
   end
 
+  test "attach blobs to new record" do
+    user = User.new(name: "Jason")
+
+    assert_no_changes -> { user.new_record? } do
+      assert_no_difference -> { ActiveStorage::Attachment.count } do
+        user.highlights.attach(
+          { io: StringIO.new("STUFF"), filename: "town.jpg", content_type: "image/jpg" },
+          { io: StringIO.new("IT"), filename: "country.jpg", content_type: "image/jpg" })
+      end
+    end
+
+    assert_predicate user.highlights, :attached?
+    assert_equal "town.jpg", user.highlights.first.filename.to_s
+    assert_equal "country.jpg", user.highlights.second.filename.to_s
+
+    assert_difference -> { ActiveStorage::Attachment.count }, +2 do
+      user.save!
+    end
+
+    assert_predicate user.reload.highlights, :attached?
+    assert_equal "town.jpg", user.highlights.first.filename.to_s
+    assert_equal "country.jpg", user.highlights.second.filename.to_s
+  end
+
+  test "build new record with attached blobs" do
+    assert_no_difference -> { ActiveStorage::Attachment.count } do
+      @user = User.new(name: "Jason", highlights: [
+        { io: StringIO.new("STUFF"), filename: "town.jpg", content_type: "image/jpg" },
+        { io: StringIO.new("IT"), filename: "country.jpg", content_type: "image/jpg" }])
+    end
+
+    assert_predicate @user, :new_record?
+    assert_predicate @user.highlights, :attached?
+    assert_equal "town.jpg", @user.highlights.first.filename.to_s
+    assert_equal "country.jpg", @user.highlights.second.filename.to_s
+
+    @user.save!
+    assert_predicate @user.reload.highlights, :attached?
+    assert_equal "town.jpg", @user.highlights.first.filename.to_s
+    assert_equal "country.jpg", @user.highlights.second.filename.to_s
+  end
+
   test "find attached blobs" do
     @user.highlights.attach(
       { io: StringIO.new("STUFF"), filename: "town.jpg", content_type: "image/jpg" },
@@ -97,13 +334,75 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     assert_equal "town.jpg", @user.highlights_attachments.first.blob.filename.to_s
   end
 
+  test "analyze newly-attached blobs" do
+    perform_enqueued_jobs do
+      @user.highlights.attach(
+        create_file_blob(filename: "racecar.jpg", content_type: "image/jpeg"),
+        create_file_blob(filename: "video.mp4", content_type: "video/mp4"))
+    end
+
+    assert_equal 4104, @user.highlights.first.metadata[:width]
+    assert_equal 2736, @user.highlights.first.metadata[:height]
+
+    assert_equal 640, @user.highlights.second.metadata[:width]
+    assert_equal 480, @user.highlights.second.metadata[:height]
+  end
+
+  test "analyze attached blobs only once" do
+    blobs = [
+      create_file_blob(filename: "racecar.jpg", content_type: "image/jpeg"),
+      create_file_blob(filename: "video.mp4", content_type: "video/mp4")
+    ]
+
+    perform_enqueued_jobs do
+      @user.highlights.attach(blobs)
+    end
+
+    assert blobs.each(&:reload).all?(&:analyzed?)
+
+    @user.highlights.attachments.destroy_all
+
+    assert_no_enqueued_jobs do
+      @user.highlights.attach(blobs)
+    end
+  end
+
+  test "preserve existing metadata when analyzing newly-attached blobs" do
+    blobs = [
+      create_file_blob(filename: "racecar.jpg", content_type: "image/jpeg", metadata: { foo: "bar" }),
+      create_file_blob(filename: "video.mp4", content_type: "video/mp4", metadata: { foo: "bar" })
+    ]
+
+    perform_enqueued_jobs do
+      @user.highlights.attach(blobs)
+    end
+
+    blobs.each do |blob|
+      assert_equal "bar", blob.reload.metadata[:foo]
+    end
+  end
+
+  test "detach blobs" do
+    @user.highlights.attach create_blob(filename: "funky.jpg"), create_blob(filename: "wonky.jpg")
+    highlight_blob_ids = @user.highlights.collect { |highlight| highlight.blob.id }
+    highlight_keys = @user.highlights.collect(&:key)
+
+    @user.highlights.detach
+    assert_not_predicate @user.highlights, :attached?
+
+    assert ActiveStorage::Blob.exists?(highlight_blob_ids.first)
+    assert ActiveStorage::Blob.exists?(highlight_blob_ids.second)
+
+    assert ActiveStorage::Blob.service.exist?(highlight_keys.first)
+    assert ActiveStorage::Blob.service.exist?(highlight_keys.second)
+  end
 
   test "purge attached blobs" do
     @user.highlights.attach create_blob(filename: "funky.jpg"), create_blob(filename: "wonky.jpg")
     highlight_keys = @user.highlights.collect(&:key)
 
     @user.highlights.purge
-    assert_not @user.highlights.attached?
+    assert_not_predicate @user.highlights, :attached?
     assert_not ActiveStorage::Blob.service.exist?(highlight_keys.first)
     assert_not ActiveStorage::Blob.service.exist?(highlight_keys.second)
   end
@@ -113,7 +412,7 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     highlight_keys = @user.highlights.collect(&:key)
 
     perform_enqueued_jobs do
-      @user.destroy
+      @user.reload.destroy
 
       assert_nil ActiveStorage::Blob.find_by(key: highlight_keys.first)
       assert_not ActiveStorage::Blob.service.exist?(highlight_keys.first)
@@ -122,4 +421,39 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
       assert_not ActiveStorage::Blob.service.exist?(highlight_keys.second)
     end
   end
+
+  test "delete attachments for independent blobs when the record is destroyed" do
+    @user.vlogs.attach create_blob(filename: "funky.mp4"), create_blob(filename: "wonky.mp4")
+
+    @user.destroy
+    assert_not ActiveStorage::Attachment.exists?(record: @user, name: "vlogs")
+  end
+
+  test "selectively purge one attached blob of many" do
+    first_blob  = create_blob(filename: "funky.jpg")
+    second_blob = create_blob(filename: "wonky.jpg")
+    attachments = @user.highlights.attach(first_blob, second_blob)
+
+    assert_difference -> { ActiveStorage::Blob.count }, -1 do
+      @user.highlights.where(id: attachments.first.id).purge
+    end
+
+    assert_not ActiveStorage::Blob.exists?(key: first_blob.key)
+    assert ActiveStorage::Blob.exists?(key: second_blob.key)
+  end
+
+  test "selectively purge one attached blob of many later" do
+    first_blob  = create_blob(filename: "funky.jpg")
+    second_blob = create_blob(filename: "wonky.jpg")
+    attachments = @user.highlights.attach(first_blob, second_blob)
+
+    perform_enqueued_jobs do
+      assert_difference -> { ActiveStorage::Blob.count }, -1 do
+        @user.highlights.where(id: attachments.first.id).purge_later
+      end
+    end
+
+    assert_not ActiveStorage::Blob.exists?(key: first_blob.key)
+    assert ActiveStorage::Blob.exists?(key: second_blob.key)
+  end
 end
diff --git a/activestorage/test/models/blob_test.rb b/activestorage/test/models/blob_test.rb
index 6e815997ba..a013b7a924 100644
--- a/activestorage/test/models/blob_test.rb
+++ b/activestorage/test/models/blob_test.rb
@@ -2,8 +2,28 @@
 
 require "test_helper"
 require "database/setup"
+require "active_support/testing/method_call_assertions"
 
 class ActiveStorage::BlobTest < ActiveSupport::TestCase
+  include ActiveSupport::Testing::MethodCallAssertions
+
+  test ".unattached scope returns not attached blobs" do
+    class UserWithHasOneAttachedDependentFalse < User
+      has_one_attached :avatar, dependent: false
+    end
+
+    ActiveStorage::Blob.delete_all
+    blob_1 = create_blob filename: "funky.jpg"
+    blob_2 = create_blob filename: "town.jpg"
+
+    user = UserWithHasOneAttachedDependentFalse.create!
+    user.avatar.attach blob_1
+
+    assert_equal [blob_2], ActiveStorage::Blob.unattached
+    user.destroy
+    assert_equal [blob_1, blob_2].map(&:id).sort, ActiveStorage::Blob.unattached.pluck(:id).sort
+  end
+
   test "create after upload sets byte size and checksum" do
     data = "Hello world!"
     blob = create_blob data: data
@@ -13,14 +33,46 @@ class ActiveStorage::BlobTest < ActiveSupport::TestCase
     assert_equal Digest::MD5.base64digest(data), blob.checksum
   end
 
+  test "create after upload extracts content type from data" do
+    blob = create_file_blob content_type: "application/octet-stream"
+    assert_equal "image/jpeg", blob.content_type
+  end
+
+  test "create after upload extracts content type from filename" do
+    blob = create_blob content_type: "application/octet-stream"
+    assert_equal "text/plain", blob.content_type
+  end
+
+  test "create after upload extracts content_type from io when no content_type given and identify: false" do
+    blob = create_blob content_type: nil, identify: false
+    assert_equal "text/plain", blob.content_type
+  end
+
+  test "create after upload uses content_type when identify: false" do
+    blob = create_blob data: "Article,dates,analysis\n1, 2, 3", filename: "table.csv", content_type: "text/csv", identify: false
+    assert_equal "text/csv", blob.content_type
+  end
+
+  test "image?" do
+    blob = create_file_blob filename: "racecar.jpg"
+    assert_predicate blob, :image?
+    assert_not_predicate blob, :audio?
+  end
+
+  test "video?" do
+    blob = create_file_blob(filename: "video.mp4", content_type: "video/mp4")
+    assert_predicate blob, :video?
+    assert_not_predicate blob, :audio?
+  end
+
   test "text?" do
     blob = create_blob data: "Hello world!"
-    assert blob.text?
-    assert_not blob.audio?
+    assert_predicate blob, :text?
+    assert_not_predicate blob, :audio?
   end
 
   test "download yields chunks" do
-    blob   = create_blob data: "a" * 75.kilobytes
+    blob   = create_blob data: "a" * 5.0625.megabytes
     chunks = []
 
     blob.download do |chunk|
@@ -28,8 +80,29 @@ class ActiveStorage::BlobTest < ActiveSupport::TestCase
     end
 
     assert_equal 2, chunks.size
-    assert_equal "a" * 64.kilobytes, chunks.first
-    assert_equal "a" * 11.kilobytes, chunks.second
+    assert_equal "a" * 5.megabytes, chunks.first
+    assert_equal "a" * 64.kilobytes, chunks.second
+  end
+
+  test "open" do
+    create_file_blob(filename: "racecar.jpg").open do |file|
+      assert file.binmode?
+      assert_equal 0, file.pos
+      assert_match(/\.jpg\z/, file.path)
+      assert_equal file_fixture("racecar.jpg").binread, file.read, "Expected downloaded file to match fixture file"
+    end
+  end
+
+  test "open in a custom tempdir" do
+    tempdir = Dir.mktmpdir
+
+    create_file_blob(filename: "racecar.jpg").open(tempdir: tempdir) do |file|
+      assert file.binmode?
+      assert_equal 0, file.pos
+      assert_match(/\.jpg\z/, file.path)
+      assert file.path.starts_with?(tempdir)
+      assert_equal file_fixture("racecar.jpg").binread, file.read, "Expected downloaded file to match fixture file"
+    end
   end
 
   test "urls expiring in 5 minutes" do
@@ -41,16 +114,63 @@ class ActiveStorage::BlobTest < ActiveSupport::TestCase
     end
   end
 
-  test "purge removes from external service" do
+  test "urls force attachment as content disposition for content types served as binary" do
+    blob = create_blob(content_type: "text/html")
+
+    freeze_time do
+      assert_equal expected_url_for(blob, disposition: :attachment), blob.service_url
+      assert_equal expected_url_for(blob, disposition: :attachment), blob.service_url(disposition: :inline)
+    end
+  end
+
+  test "urls allow for custom filename" do
+    blob = create_blob(filename: "original.txt")
+    new_filename = ActiveStorage::Filename.new("new.txt")
+
+    freeze_time do
+      assert_equal expected_url_for(blob), blob.service_url
+      assert_equal expected_url_for(blob, filename: new_filename), blob.service_url(filename: new_filename)
+      assert_equal expected_url_for(blob, filename: new_filename), blob.service_url(filename: "new.txt")
+      assert_equal expected_url_for(blob, filename: blob.filename), blob.service_url(filename: nil)
+    end
+  end
+
+  test "urls allow for custom options" do
+    blob = create_blob(filename: "original.txt")
+
+    options = [
+      blob.key,
+      expires_in: blob.service.url_expires_in,
+      disposition: :inline,
+      content_type: blob.content_type,
+      filename: blob.filename,
+      thumb_size: "300x300",
+      thumb_mode: "crop"
+    ]
+    assert_called_with(blob.service, :url, options) do
+      blob.service_url(thumb_size: "300x300", thumb_mode: "crop")
+    end
+  end
+
+  test "purge deletes file from external service" do
     blob = create_blob
 
     blob.purge
     assert_not ActiveStorage::Blob.service.exist?(blob.key)
   end
 
+  test "purge deletes variants from external service" do
+    blob = create_file_blob
+    variant = blob.variant(resize: "100>").processed
+
+    blob.purge
+    assert_not ActiveStorage::Blob.service.exist?(variant.key)
+  end
+
   private
-    def expected_url_for(blob, disposition: :inline)
-      query_string = { content_type: blob.content_type, disposition: "#{disposition}; #{blob.filename.parameters}" }.to_param
-      "/rails/active_storage/disk/#{ActiveStorage.verifier.generate(blob.key, expires_in: 5.minutes, purpose: :blob_key)}/#{blob.filename}?#{query_string}"
+    def expected_url_for(blob, disposition: :inline, filename: nil)
+      filename ||= blob.filename
+      query_string = { content_type: blob.content_type, disposition: "#{disposition}; #{filename.parameters}" }.to_param
+      "https://example.com/rails/active_storage/disk/#{ActiveStorage.verifier.generate(blob.key, expires_in: 5.minutes, purpose: :blob_key)}/#{filename}?#{query_string}"
     end
 end
diff --git a/activestorage/test/models/presence_validation_test.rb b/activestorage/test/models/presence_validation_test.rb
new file mode 100644
index 0000000000..aa804506dd
--- /dev/null
+++ b/activestorage/test/models/presence_validation_test.rb
@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+class ActiveStorage::PresenceValidationTest < ActiveSupport::TestCase
+  class Admin < User; end
+
+  teardown do
+    Admin.clear_validators!
+  end
+
+  test "validates_presence_of has_one_attached" do
+    Admin.validates_presence_of :avatar
+    a = Admin.new
+    assert_predicate a, :invalid?
+
+    a.avatar.attach create_blob(filename: "funky.jpg")
+    assert_predicate a, :valid?
+  end
+
+  test "validates_presence_of has_many_attached" do
+    Admin.validates_presence_of :highlights
+    a = Admin.new
+    assert_predicate a, :invalid?
+
+    a.highlights.attach create_blob(filename: "funky.jpg")
+    assert_predicate a, :valid?
+  end
+end
diff --git a/activestorage/test/models/preview_test.rb b/activestorage/test/models/preview_test.rb
new file mode 100644
index 0000000000..e7ae399fb7
--- /dev/null
+++ b/activestorage/test/models/preview_test.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+class ActiveStorage::PreviewTest < ActiveSupport::TestCase
+  test "previewing a PDF" do
+    blob = create_file_blob(filename: "report.pdf", content_type: "application/pdf")
+    preview = blob.preview(resize: "640x280").processed
+
+    assert_predicate preview.image, :attached?
+    assert_equal "report.png", preview.image.filename.to_s
+    assert_equal "image/png", preview.image.content_type
+
+    image = read_image(preview.image)
+    assert_equal 612, image.width
+    assert_equal 792, image.height
+  end
+
+  test "previewing an MP4 video" do
+    blob = create_file_blob(filename: "video.mp4", content_type: "video/mp4")
+    preview = blob.preview(resize: "640x280").processed
+
+    assert_predicate preview.image, :attached?
+    assert_equal "video.jpg", preview.image.filename.to_s
+    assert_equal "image/jpeg", preview.image.content_type
+
+    image = read_image(preview.image)
+    assert_equal 640, image.width
+    assert_equal 480, image.height
+  end
+
+  test "previewing an unpreviewable blob" do
+    blob = create_file_blob
+
+    assert_raises ActiveStorage::UnpreviewableError do
+      blob.preview resize: "640x280"
+    end
+  end
+end
diff --git a/activestorage/test/models/representation_test.rb b/activestorage/test/models/representation_test.rb
new file mode 100644
index 0000000000..2a06b31c77
--- /dev/null
+++ b/activestorage/test/models/representation_test.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+class ActiveStorage::RepresentationTest < ActiveSupport::TestCase
+  test "representing an image" do
+    blob = create_file_blob
+    representation = blob.representation(resize: "100x100").processed
+
+    image = read_image(representation.image)
+    assert_equal 100, image.width
+    assert_equal 67, image.height
+  end
+
+  test "representing a PDF" do
+    blob = create_file_blob(filename: "report.pdf", content_type: "application/pdf")
+    representation = blob.representation(resize: "640x280").processed
+
+    image = read_image(representation.image)
+    assert_equal 612, image.width
+    assert_equal 792, image.height
+  end
+
+  test "representing an MP4 video" do
+    blob = create_file_blob(filename: "video.mp4", content_type: "video/mp4")
+    representation = blob.representation(resize: "640x280").processed
+
+    image = read_image(representation.image)
+    assert_equal 640, image.width
+    assert_equal 480, image.height
+  end
+
+  test "representing an unrepresentable blob" do
+    blob = create_blob
+
+    assert_raises ActiveStorage::UnrepresentableError do
+      blob.representation resize: "100x100"
+    end
+  end
+end
diff --git a/activestorage/test/models/variant_test.rb b/activestorage/test/models/variant_test.rb
index ca112ab907..6577f1cd9f 100644
--- a/activestorage/test/models/variant_test.rb
+++ b/activestorage/test/models/variant_test.rb
@@ -4,26 +4,174 @@ require "test_helper"
 require "database/setup"
 
 class ActiveStorage::VariantTest < ActiveSupport::TestCase
-  setup do
-    @blob = create_image_blob filename: "racecar.jpg"
+  test "resized variation of JPEG blob" do
+    blob = create_file_blob(filename: "racecar.jpg")
+    variant = blob.variant(resize: "100x100").processed
+    assert_match(/racecar\.jpg/, variant.service_url)
+
+    image = read_image(variant)
+    assert_equal 100, image.width
+    assert_equal 67, image.height
   end
 
-  test "resized variation" do
-    variant = @blob.variant(resize: "100x100").processed
+  test "resized and monochrome variation of JPEG blob" do
+    blob = create_file_blob(filename: "racecar.jpg")
+    variant = blob.variant(resize: "100x100", monochrome: true).processed
     assert_match(/racecar\.jpg/, variant.service_url)
 
-    image = read_image_variant(variant)
+    image = read_image(variant)
     assert_equal 100, image.width
     assert_equal 67, image.height
+    assert_match(/Gray/, image.colorspace)
   end
 
-  test "resized and monochrome variation" do
-    variant = @blob.variant(resize: "100x100", monochrome: true).processed
+  test "monochrome with default variant_processor" do
+    begin
+      ActiveStorage.variant_processor = nil
+
+      blob = create_file_blob(filename: "racecar.jpg")
+      variant = blob.variant(monochrome: true).processed
+      image = read_image(variant)
+      assert_match(/Gray/, image.colorspace)
+    ensure
+      ActiveStorage.variant_processor = :mini_magick
+    end
+  end
+
+  test "disabled variation of JPEG blob" do
+    blob = create_file_blob(filename: "racecar.jpg")
+    variant = blob.variant(resize: "100x100", monochrome: false).processed
     assert_match(/racecar\.jpg/, variant.service_url)
 
-    image = read_image_variant(variant)
+    image = read_image(variant)
     assert_equal 100, image.width
     assert_equal 67, image.height
-    assert_match(/Gray/, image.colorspace)
+    assert_match(/RGB/, image.colorspace)
+  end
+
+  test "disabled variation of JPEG blob with :combine_options" do
+    blob = create_file_blob(filename: "racecar.jpg")
+    variant = ActiveSupport::Deprecation.silence do
+      blob.variant(combine_options: {
+        resize: "100x100",
+        monochrome: false
+      }).processed
+    end
+    assert_match(/racecar\.jpg/, variant.service_url)
+
+    image = read_image(variant)
+    assert_equal 100, image.width
+    assert_equal 67, image.height
+    assert_match(/RGB/, image.colorspace)
+  end
+
+  test "disabled variation using :combine_options" do
+    begin
+      ActiveStorage.variant_processor = nil
+      blob = create_file_blob(filename: "racecar.jpg")
+      variant = ActiveSupport::Deprecation.silence do
+        blob.variant(combine_options: {
+          crop: "100x100+0+0",
+          monochrome: false
+        }).processed
+      end
+      assert_match(/racecar\.jpg/, variant.service_url)
+
+      image = read_image(variant)
+      assert_equal 100, image.width
+      assert_equal 100, image.height
+      assert_match(/RGB/, image.colorspace)
+    ensure
+      ActiveStorage.variant_processor = :mini_magick
+    end
+  end
+
+  test "center-weighted crop of JPEG blob using :combine_options" do
+    begin
+      ActiveStorage.variant_processor = nil
+      blob = create_file_blob(filename: "racecar.jpg")
+      variant = ActiveSupport::Deprecation.silence do
+        blob.variant(combine_options: {
+          gravity: "center",
+          resize: "100x100^",
+          crop: "100x100+0+0",
+        }).processed
+      end
+      assert_match(/racecar\.jpg/, variant.service_url)
+
+      image = read_image(variant)
+      assert_equal 100, image.width
+      assert_equal 100, image.height
+    ensure
+      ActiveStorage.variant_processor = :mini_magick
+    end
+  end
+
+  test "center-weighted crop of JPEG blob using :resize_to_fill" do
+    blob = create_file_blob(filename: "racecar.jpg")
+    variant = blob.variant(resize_to_fill: [100, 100]).processed
+    assert_match(/racecar\.jpg/, variant.service_url)
+
+    image = read_image(variant)
+    assert_equal 100, image.width
+    assert_equal 100, image.height
+  end
+
+  test "resized variation of PSD blob" do
+    blob = create_file_blob(filename: "icon.psd", content_type: "image/vnd.adobe.photoshop")
+    variant = blob.variant(resize: "20x20").processed
+    assert_match(/icon\.png/, variant.service_url)
+
+    image = read_image(variant)
+    assert_equal "PNG", image.type
+    assert_equal 20, image.width
+    assert_equal 20, image.height
+  end
+
+  test "resized variation of ICO blob" do
+    blob = create_file_blob(filename: "favicon.ico", content_type: "image/vnd.microsoft.icon")
+    variant = blob.variant(resize: "20x20").processed
+    assert_match(/icon\.png/, variant.service_url)
+
+    image = read_image(variant)
+    assert_equal "PNG", image.type
+    assert_equal 20, image.width
+    assert_equal 20, image.height
+  end
+
+  test "optimized variation of GIF blob" do
+    blob = create_file_blob(filename: "image.gif", content_type: "image/gif")
+
+    assert_nothing_raised do
+      blob.variant(layers: "Optimize").processed
+    end
+  end
+
+  test "variation of invariable blob" do
+    assert_raises ActiveStorage::InvariableError do
+      create_file_blob(filename: "report.pdf", content_type: "application/pdf").variant(resize: "100x100")
+    end
+  end
+
+  test "service_url doesn't grow in length despite long variant options" do
+    blob = create_file_blob(filename: "racecar.jpg")
+    variant = blob.variant(font: "a" * 10_000).processed
+    assert_operator variant.service_url.length, :<, 525
+  end
+
+  test "works for vips processor" do
+    begin
+      ActiveStorage.variant_processor = :vips
+      blob = create_file_blob(filename: "racecar.jpg")
+      variant = blob.variant(thumbnail_image: 100).processed
+
+      image = read_image(variant)
+      assert_equal 100, image.width
+      assert_equal 67, image.height
+    rescue LoadError
+      # libvips not installed
+    ensure
+      ActiveStorage.variant_processor = :mini_magick
+    end
   end
 end
diff --git a/activestorage/test/previewer/mupdf_previewer_test.rb b/activestorage/test/previewer/mupdf_previewer_test.rb
new file mode 100644
index 0000000000..6c2db6fcbf
--- /dev/null
+++ b/activestorage/test/previewer/mupdf_previewer_test.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+require "active_storage/previewer/mupdf_previewer"
+
+class ActiveStorage::Previewer::MuPDFPreviewerTest < ActiveSupport::TestCase
+  setup do
+    @blob = create_file_blob(filename: "report.pdf", content_type: "application/pdf")
+  end
+
+  test "previewing a PDF document" do
+    ActiveStorage::Previewer::MuPDFPreviewer.new(@blob).preview do |attachable|
+      assert_equal "image/png", attachable[:content_type]
+      assert_equal "report.png", attachable[:filename]
+
+      image = MiniMagick::Image.read(attachable[:io])
+      assert_equal 612, image.width
+      assert_equal 792, image.height
+    end
+  end
+end
diff --git a/activestorage/test/previewer/poppler_pdf_previewer_test.rb b/activestorage/test/previewer/poppler_pdf_previewer_test.rb
new file mode 100644
index 0000000000..2b41c8b642
--- /dev/null
+++ b/activestorage/test/previewer/poppler_pdf_previewer_test.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+require "active_storage/previewer/poppler_pdf_previewer"
+
+class ActiveStorage::Previewer::PopplerPDFPreviewerTest < ActiveSupport::TestCase
+  setup do
+    @blob = create_file_blob(filename: "report.pdf", content_type: "application/pdf")
+  end
+
+  test "previewing a PDF document" do
+    ActiveStorage::Previewer::PopplerPDFPreviewer.new(@blob).preview do |attachable|
+      assert_equal "image/png", attachable[:content_type]
+      assert_equal "report.png", attachable[:filename]
+
+      image = MiniMagick::Image.read(attachable[:io])
+      assert_equal 612, image.width
+      assert_equal 792, image.height
+    end
+  end
+end
diff --git a/activestorage/test/previewer/video_previewer_test.rb b/activestorage/test/previewer/video_previewer_test.rb
new file mode 100644
index 0000000000..9dc350205b
--- /dev/null
+++ b/activestorage/test/previewer/video_previewer_test.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "database/setup"
+
+require "active_storage/previewer/video_previewer"
+
+class ActiveStorage::Previewer::VideoPreviewerTest < ActiveSupport::TestCase
+  setup do
+    @blob = create_file_blob(filename: "video.mp4", content_type: "video/mp4")
+  end
+
+  test "previewing an MP4 video" do
+    ActiveStorage::Previewer::VideoPreviewer.new(@blob).preview do |attachable|
+      assert_equal "image/jpeg", attachable[:content_type]
+      assert_equal "video.jpg", attachable[:filename]
+
+      image = MiniMagick::Image.read(attachable[:io])
+      assert_equal 640, image.width
+      assert_equal 480, image.height
+      assert_equal "image/jpeg", image.mime_type
+    end
+  end
+end
diff --git a/activestorage/test/service/azure_storage_service_test.rb b/activestorage/test/service/azure_storage_service_test.rb
index 4729bdfbc5..be31bbe858 100644
--- a/activestorage/test/service/azure_storage_service_test.rb
+++ b/activestorage/test/service/azure_storage_service_test.rb
@@ -11,9 +11,9 @@ if SERVICE_CONFIGURATIONS[:azure]
 
     test "signed URL generation" do
       url = @service.url(FIXTURE_KEY, expires_in: 5.minutes,
-        disposition: "inline; filename=\"avatar.png\"", filename: "avatar.png", content_type: "image/png")
+        disposition: :inline, filename: ActiveStorage::Filename.new("avatar.png"), content_type: "image/png")
 
-      assert_match(/(\S+)&rscd=inline%3B\+filename%3D%22avatar.png%22&rsct=image%2Fpng/, url)
+      assert_match(/(\S+)&rscd=inline%3B\+filename%3D%22avatar\.png%22%3B\+filename\*%3DUTF-8%27%27avatar\.png&rsct=image%2Fpng/, url)
       assert_match SERVICE_CONFIGURATIONS[:azure][:container], url
     end
   end
diff --git a/activestorage/test/service/configurations.yml b/activestorage/test/service/configurations.example.yml
index 56ed37be5d..a63aa33302 100644
--- a/activestorage/test/service/configurations.yml
+++ b/activestorage/test/service/configurations.example.yml
@@ -7,7 +7,7 @@
 #
 # gcs:
 #   service: GCS
-#   keyfile: {
+#   credentials: {
 #     type: "service_account",
 #     project_id: "",
 #     private_key_id: "",
@@ -24,7 +24,6 @@
 #
 # azure:
 #   service: AzureStorage
-#   path: ""
 #   storage_account_name: ""
 #   storage_access_key: ""
 #   container: ""
diff --git a/activestorage/test/service/configurations.yml.enc b/activestorage/test/service/configurations.yml.enc
index df11aac161..648924a562 100644
--- a/activestorage/test/service/configurations.yml.enc
+++ b/activestorage/test/service/configurations.yml.enc
diff --git a/activestorage/test/service/configurator_test.rb b/activestorage/test/service/configurator_test.rb
index a2fd035e02..1c9c5c3aa0 100644
--- a/activestorage/test/service/configurator_test.rb
+++ b/activestorage/test/service/configurator_test.rb
@@ -6,6 +6,7 @@ class ActiveStorage::Service::ConfiguratorTest < ActiveSupport::TestCase
   test "builds correct service instance based on service name" do
     service = ActiveStorage::Service::Configurator.build(:foo, foo: { service: "Disk", root: "path" })
     assert_instance_of ActiveStorage::Service::DiskService, service
+    assert_equal "path", service.root
   end
 
   test "raises error when passing non-existent service name" do
diff --git a/activestorage/test/service/disk_service_test.rb b/activestorage/test/service/disk_service_test.rb
index f57e44536a..a4f2f4765f 100644
--- a/activestorage/test/service/disk_service_test.rb
+++ b/activestorage/test/service/disk_service_test.rb
@@ -8,7 +8,11 @@ class ActiveStorage::Service::DiskServiceTest < ActiveSupport::TestCase
   include ActiveStorage::Service::SharedServiceTests
 
   test "url generation" do
-    assert_match(/rails\/active_storage\/disk\/.*\/avatar\.png\?.+disposition=inline/,
-      @service.url(FIXTURE_KEY, expires_in: 5.minutes, disposition: "inline; filename=\"avatar.png\"", filename: "avatar.png", content_type: "image/png"))
+    assert_match(/^https:\/\/example.com\/rails\/active_storage\/disk\/.*\/avatar\.png\?content_type=image%2Fpng&disposition=inline/,
+      @service.url(FIXTURE_KEY, expires_in: 5.minutes, disposition: :inline, filename: ActiveStorage::Filename.new("avatar.png"), content_type: "image/png"))
+  end
+
+  test "headers_for_direct_upload generation" do
+    assert_equal({ "Content-Type" => "application/json" }, @service.headers_for_direct_upload(FIXTURE_KEY, content_type: "application/json"))
   end
 end
diff --git a/activestorage/test/service/gcs_service_test.rb b/activestorage/test/service/gcs_service_test.rb
index f664cee90b..fc2d9d0fa7 100644
--- a/activestorage/test/service/gcs_service_test.rb
+++ b/activestorage/test/service/gcs_service_test.rb
@@ -19,7 +19,7 @@ if SERVICE_CONFIGURATIONS[:gcs]
         uri = URI.parse url
         request = Net::HTTP::Put.new uri.request_uri
         request.body = data
-        request.add_field "Content-Type", "text/plain"
+        request.add_field "Content-Type", ""
         request.add_field "Content-MD5", checksum
         Net::HTTP.start(uri.host, uri.port, use_ssl: true) do |http|
           http.request request
@@ -32,12 +32,21 @@ if SERVICE_CONFIGURATIONS[:gcs]
     end
 
     test "signed URL generation" do
-      freeze_time do
-        url = SERVICE.bucket.signed_url(FIXTURE_KEY, expires: 120) +
-          "&response-content-disposition=inline%3B+filename%3D%22test.txt%22" +
-          "&response-content-type=text%2Fplain"
+      assert_match(/storage\.googleapis\.com\/.*response-content-disposition=inline.*test\.txt.*response-content-type=text%2Fplain/,
+        @service.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: :inline, filename: ActiveStorage::Filename.new("test.txt"), content_type: "text/plain"))
+    end
+
+    test "signed URL response headers" do
+      begin
+        key  = SecureRandom.base58(24)
+        data = "Something else entirely!"
+        @service.upload(key, StringIO.new(data), checksum: Digest::MD5.base64digest(data))
 
-        assert_equal url, @service.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: "inline; filename=\"test.txt\"", filename: "test.txt", content_type: "text/plain")
+        url = @service.url(key, expires_in: 2.minutes, disposition: :inline, filename: ActiveStorage::Filename.new("test.txt"), content_type: "text/plain")
+        response = Net::HTTP.get_response(URI(url))
+        assert_equal "text/plain", response.header["Content-Type"]
+      ensure
+        @service.delete key
       end
     end
   end
diff --git a/activestorage/test/service/mirror_service_test.rb b/activestorage/test/service/mirror_service_test.rb
index 93e86eff70..87306644c5 100644
--- a/activestorage/test/service/mirror_service_test.rb
+++ b/activestorage/test/service/mirror_service_test.rb
@@ -10,8 +10,8 @@ class ActiveStorage::Service::MirrorServiceTest < ActiveSupport::TestCase
   end.to_h
 
   config = mirror_config.merge \
-    mirror:   { service: "Mirror", primary: "primary", mirrors: mirror_config.keys },
-    primary:  { service: "Disk", root: Dir.mktmpdir("active_storage_tests_primary") }
+    mirror:  { service: "Mirror", primary: "primary", mirrors: mirror_config.keys },
+    primary: { service: "Disk", root: Dir.mktmpdir("active_storage_tests_primary") }
 
   SERVICE = ActiveStorage::Service.configure :mirror, config
 
@@ -19,11 +19,16 @@ class ActiveStorage::Service::MirrorServiceTest < ActiveSupport::TestCase
 
   test "uploading to all services" do
     begin
-      data = "Something else entirely!"
-      key  = upload(data, to: @service)
+      key      = SecureRandom.base58(24)
+      data     = "Something else entirely!"
+      io       = StringIO.new(data)
+      checksum = Digest::MD5.base64digest(data)
 
-      assert_equal data, SERVICE.primary.download(key)
-      SERVICE.mirrors.each do |mirror|
+      @service.upload key, io.tap(&:read), checksum: checksum
+      assert_predicate io, :eof?
+
+      assert_equal data, @service.primary.download(key)
+      @service.mirrors.each do |mirror|
         assert_equal data, mirror.download(key)
       end
     ensure
@@ -32,14 +37,18 @@ class ActiveStorage::Service::MirrorServiceTest < ActiveSupport::TestCase
   end
 
   test "downloading from primary service" do
-    data = "Something else entirely!"
-    key  = upload(data, to: SERVICE.primary)
+    key      = SecureRandom.base58(24)
+    data     = "Something else entirely!"
+    checksum = Digest::MD5.base64digest(data)
+
+    @service.primary.upload key, StringIO.new(data), checksum: checksum
 
     assert_equal data, @service.download(key)
   end
 
   test "deleting from all services" do
     @service.delete FIXTURE_KEY
+
     assert_not SERVICE.primary.exist?(FIXTURE_KEY)
     SERVICE.mirrors.each do |mirror|
       assert_not mirror.exist?(FIXTURE_KEY)
@@ -47,18 +56,11 @@ class ActiveStorage::Service::MirrorServiceTest < ActiveSupport::TestCase
   end
 
   test "URL generation in primary service" do
+    filename = ActiveStorage::Filename.new("test.txt")
+
     freeze_time do
-      assert_equal SERVICE.primary.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: :inline, filename: "test.txt", content_type: "text/plain"),
-        @service.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: :inline, filename: "test.txt", content_type: "text/plain")
+      assert_equal @service.primary.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: :inline, filename: filename, content_type: "text/plain"),
+        @service.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: :inline, filename: filename, content_type: "text/plain")
     end
   end
-
-  private
-    def upload(data, to:)
-      SecureRandom.base58(24).tap do |key|
-        io = StringIO.new(data).tap(&:read)
-        @service.upload key, io, checksum: Digest::MD5.base64digest(data)
-        assert io.eof?
-      end
-    end
 end
diff --git a/activestorage/test/service/s3_service_test.rb b/activestorage/test/service/s3_service_test.rb
index c07d6396b1..7833e51122 100644
--- a/activestorage/test/service/s3_service_test.rb
+++ b/activestorage/test/service/s3_service_test.rb
@@ -3,7 +3,7 @@
 require "service/shared_service_tests"
 require "net/http"
 
-if SERVICE_CONFIGURATIONS[:s3] && SERVICE_CONFIGURATIONS[:s3][:access_key_id].present?
+if SERVICE_CONFIGURATIONS[:s3]
   class ActiveStorage::Service::S3ServiceTest < ActiveSupport::TestCase
     SERVICE = ActiveStorage::Service.configure(:s3, SERVICE_CONFIGURATIONS)
 
@@ -33,9 +33,9 @@ if SERVICE_CONFIGURATIONS[:s3] && SERVICE_CONFIGURATIONS[:s3][:access_key_id].pr
 
     test "signed URL generation" do
       url = @service.url(FIXTURE_KEY, expires_in: 5.minutes,
-        disposition: "inline; filename=\"avatar.png\"", filename: "avatar.png", content_type: "image/png")
+        disposition: :inline, filename: ActiveStorage::Filename.new("avatar.png"), content_type: "image/png")
 
-      assert_match(/s3\.(\S+)?amazonaws.com.*response-content-disposition=inline.*avatar\.png.*response-content-type=image%2Fpng/, url)
+      assert_match(/s3(-[-a-z0-9]+)?\.(\S+)?amazonaws.com.*response-content-disposition=inline.*avatar\.png.*response-content-type=image%2Fpng/, url)
       assert_match SERVICE_CONFIGURATIONS[:s3][:bucket], url
     end
 
diff --git a/activestorage/test/service/shared_service_tests.rb b/activestorage/test/service/shared_service_tests.rb
index a9e1cb6ce9..b9f352e460 100644
--- a/activestorage/test/service/shared_service_tests.rb
+++ b/activestorage/test/service/shared_service_tests.rb
@@ -50,6 +50,29 @@ module ActiveStorage::Service::SharedServiceTests
       assert_equal FIXTURE_DATA, @service.download(FIXTURE_KEY)
     end
 
+    test "downloading in chunks" do
+      key = SecureRandom.base58(24)
+      expected_chunks = [ "a" * 5.megabytes, "b" ]
+      actual_chunks = []
+
+      begin
+        @service.upload key, StringIO.new(expected_chunks.join)
+
+        @service.download key do |chunk|
+          actual_chunks << chunk
+        end
+
+        assert_equal expected_chunks, actual_chunks, "Downloaded chunks did not match uploaded data"
+      ensure
+        @service.delete key
+      end
+    end
+
+    test "downloading partially" do
+      assert_equal "\x10\x00\x00", @service.download_chunk(FIXTURE_KEY, 19..21)
+      assert_equal "\x10\x00\x00", @service.download_chunk(FIXTURE_KEY, 19...22)
+    end
+
     test "existing" do
       assert @service.exist?(FIXTURE_KEY)
       assert_not @service.exist?(FIXTURE_KEY + "nonsense")
@@ -65,5 +88,22 @@ module ActiveStorage::Service::SharedServiceTests
         @service.delete SecureRandom.base58(24)
       end
     end
+
+    test "deleting by prefix" do
+      begin
+        @service.upload("a/a/a", StringIO.new(FIXTURE_DATA))
+        @service.upload("a/a/b", StringIO.new(FIXTURE_DATA))
+        @service.upload("a/b/a", StringIO.new(FIXTURE_DATA))
+
+        @service.delete_prefixed("a/a/")
+        assert_not @service.exist?("a/a/a")
+        assert_not @service.exist?("a/a/b")
+        assert @service.exist?("a/b/a")
+      ensure
+        @service.delete("a/a/a")
+        @service.delete("a/a/b")
+        @service.delete("a/b/a")
+      end
+    end
   end
 end
diff --git a/activestorage/test/template/image_tag_test.rb b/activestorage/test/template/image_tag_test.rb
index dedc58452e..f0b166c225 100644
--- a/activestorage/test/template/image_tag_test.rb
+++ b/activestorage/test/template/image_tag_test.rb
@@ -7,7 +7,7 @@ class ActiveStorage::ImageTagTest < ActionView::TestCase
   tests ActionView::Helpers::AssetTagHelper
 
   setup do
-    @blob = create_image_blob filename: "racecar.jpg"
+    @blob = create_file_blob filename: "racecar.jpg"
   end
 
   test "blob" do
@@ -19,6 +19,12 @@ class ActiveStorage::ImageTagTest < ActionView::TestCase
     assert_dom_equal %(<img src="#{polymorphic_url variant}" />), image_tag(variant)
   end
 
+  test "preview" do
+    blob = create_file_blob(filename: "report.pdf", content_type: "application/pdf")
+    preview = blob.preview(resize: "100x100")
+    assert_dom_equal %(<img src="#{polymorphic_url preview}" />), image_tag(preview)
+  end
+
   test "attachment" do
     attachment = ActiveStorage::Attachment.new(blob: @blob)
     assert_dom_equal %(<img src="#{polymorphic_url attachment}" />), image_tag(attachment)
@@ -27,7 +33,7 @@ class ActiveStorage::ImageTagTest < ActionView::TestCase
   test "error when attachment's empty" do
     @user = User.create!(name: "DHH")
 
-    assert_not @user.avatar.attached?
+    assert_not_predicate @user.avatar, :attached?
     assert_raises(ArgumentError) { image_tag(@user.avatar) }
   end
 
diff --git a/activestorage/test/test_helper.rb b/activestorage/test/test_helper.rb
index 2a969fa326..573a8e0b0b 100644
--- a/activestorage/test/test_helper.rb
+++ b/activestorage/test/test_helper.rb
@@ -1,11 +1,13 @@
 # frozen_string_literal: true
 
-require File.expand_path("../../test/dummy/config/environment.rb", __FILE__)
+ENV["RAILS_ENV"] ||= "test"
+require_relative "dummy/config/environment.rb"
 
 require "bundler/setup"
 require "active_support"
 require "active_support/test_case"
 require "active_support/testing/autorun"
+require "image_processing/mini_magick"
 
 begin
   require "byebug"
@@ -22,7 +24,7 @@ Minitest.backtrace_filter = Minitest::BacktraceFilter.new
 
 require "yaml"
 SERVICE_CONFIGURATIONS = begin
-  erb = ERB.new(Pathname.new(File.expand_path("../service/configurations.yml", __FILE__)).read)
+  erb = ERB.new(Pathname.new(File.expand_path("service/configurations.yml", __dir__)).read)
   configuration = YAML.load(erb.result) || {}
   configuration.deep_symbolize_keys
 rescue Errno::ENOENT
@@ -32,30 +34,50 @@ end
 
 require "tmpdir"
 ActiveStorage::Blob.service = ActiveStorage::Service::DiskService.new(root: Dir.mktmpdir("active_storage_tests"))
-ActiveStorage::Service.logger = ActiveSupport::Logger.new(nil)
 
+ActiveStorage.logger = ActiveSupport::Logger.new(nil)
 ActiveStorage.verifier = ActiveSupport::MessageVerifier.new("Testing")
 
 class ActiveSupport::TestCase
-  self.file_fixture_path = File.expand_path("../fixtures/files", __FILE__)
+  self.file_fixture_path = File.expand_path("fixtures/files", __dir__)
+
+  setup do
+    ActiveStorage::Current.host = "https://example.com"
+  end
+
+  teardown do
+    ActiveStorage::Current.reset
+  end
 
   private
-    def create_blob(data: "Hello world!", filename: "hello.txt", content_type: "text/plain")
-      ActiveStorage::Blob.create_after_upload! io: StringIO.new(data), filename: filename, content_type: content_type
+    def create_blob(data: "Hello world!", filename: "hello.txt", content_type: "text/plain", identify: true)
+      ActiveStorage::Blob.create_after_upload! io: StringIO.new(data), filename: filename, content_type: content_type, identify: identify
     end
 
-    def create_image_blob(filename: "racecar.jpg", content_type: "image/jpeg")
-      ActiveStorage::Blob.create_after_upload! \
-        io: file_fixture(filename).open,
-        filename: filename, content_type: content_type
+    def create_file_blob(filename: "racecar.jpg", content_type: "image/jpeg", metadata: nil)
+      ActiveStorage::Blob.create_after_upload! io: file_fixture(filename).open, filename: filename, content_type: content_type, metadata: metadata
     end
 
     def create_blob_before_direct_upload(filename: "hello.txt", byte_size:, checksum:, content_type: "text/plain")
       ActiveStorage::Blob.create_before_direct_upload! filename: filename, byte_size: byte_size, checksum: checksum, content_type: content_type
     end
 
-    def read_image_variant(variant)
-      MiniMagick::Image.open variant.service.send(:path_for, variant.key)
+    def directly_upload_file_blob(filename: "racecar.jpg", content_type: "image/jpeg")
+      file = file_fixture(filename)
+      byte_size = file.size
+      checksum = Digest::MD5.file(file).base64digest
+
+      create_blob_before_direct_upload(filename: filename, byte_size: byte_size, checksum: checksum, content_type: content_type).tap do |blob|
+        ActiveStorage::Blob.service.upload(blob.key, file.open)
+      end
+    end
+
+    def read_image(blob_or_variant)
+      MiniMagick::Image.open blob_or_variant.service.send(:path_for, blob_or_variant.key)
+    end
+
+    def extract_metadata_from(blob)
+      blob.tap(&:analyze).metadata
     end
 end
 
@@ -65,5 +87,8 @@ ActiveRecord::Base.send :include, GlobalID::Identification
 
 class User < ActiveRecord::Base
   has_one_attached :avatar
+  has_one_attached :cover_photo, dependent: false
+
   has_many_attached :highlights
+  has_many_attached :vlogs, dependent: false
 end
diff --git a/activestorage/webpack.config.js b/activestorage/webpack.config.js
deleted file mode 100644
index 92c4530e7f..0000000000
--- a/activestorage/webpack.config.js
+++ /dev/null
@@ -1,27 +0,0 @@
-const webpack = require("webpack")
-const path = require("path")
-
-module.exports = {
-  entry: {
-    "activestorage": path.resolve(__dirname, "app/javascript/activestorage/index.js"),
-  },
-
-  output: {
-    filename: "[name].js",
-    path: path.resolve(__dirname, "app/assets/javascripts"),
-    library: "ActiveStorage",
-    libraryTarget: "umd"
-  },
-
-  module: {
-    rules: [
-      {
-        test: /\.js$/,
-        exclude: /node_modules/,
-        use: {
-          loader: "babel-loader"
-        }
-      }
-    ]
-  }
-}
diff --git a/activestorage/yarn.lock b/activestorage/yarn.lock
index dd09577445..44eae3c5b1 100644
--- a/activestorage/yarn.lock
+++ b/activestorage/yarn.lock
@@ -2,15 +2,13 @@
 # yarn lockfile v1
 
 
-abbrev@1:
-  version "1.1.0"
-  resolved "https://registry.yarnpkg.com/abbrev/-/abbrev-1.1.0.tgz#d0554c2256636e2f56e7c2e5ad183f859428d81f"
+"@types/estree@0.0.38":
+  version "0.0.38"
+  resolved "https://registry.yarnpkg.com/@types/estree/-/estree-0.0.38.tgz#c1be40aa933723c608820a99a373a16d215a1ca2"
 
-acorn-dynamic-import@^2.0.0:
-  version "2.0.2"
-  resolved "https://registry.yarnpkg.com/acorn-dynamic-import/-/acorn-dynamic-import-2.0.2.tgz#c752bd210bef679501b6c6cb7fc84f8f47158cc4"
-  dependencies:
-    acorn "^4.0.3"
+"@types/node@*":
+  version "9.6.6"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-9.6.6.tgz#439b91f9caf3983cad2eef1e11f6bedcbf9431d2"
 
 acorn-jsx@^3.0.0:
   version "3.0.1"
@@ -22,11 +20,7 @@ acorn@^3.0.4:
   version "3.3.0"
   resolved "https://registry.yarnpkg.com/acorn/-/acorn-3.3.0.tgz#45e37fb39e8da3f25baee3ff5369e2bb5f22017a"
 
-acorn@^4.0.3:
-  version "4.0.13"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-4.0.13.tgz#105495ae5361d697bd195c825192e1ad7f253787"
-
-acorn@^5.0.0, acorn@^5.0.1:
+acorn@^5.0.1:
   version "5.1.1"
   resolved "https://registry.yarnpkg.com/acorn/-/acorn-5.1.1.tgz#53fe161111f912ab999ee887a90a0bc52822fd75"
 
@@ -34,18 +28,14 @@ ajv-keywords@^1.0.0:
   version "1.5.1"
   resolved "https://registry.yarnpkg.com/ajv-keywords/-/ajv-keywords-1.5.1.tgz#314dd0a4b3368fad3dfcdc54ede6171b886daf3c"
 
-ajv-keywords@^2.0.0:
-  version "2.1.0"
-  resolved "https://registry.yarnpkg.com/ajv-keywords/-/ajv-keywords-2.1.0.tgz#a296e17f7bfae7c1ce4f7e0de53d29cb32162df0"
-
-ajv@^4.7.0, ajv@^4.9.1:
+ajv@^4.7.0:
   version "4.11.8"
   resolved "https://registry.yarnpkg.com/ajv/-/ajv-4.11.8.tgz#82ffb02b29e662ae53bdc20af15947706739c536"
   dependencies:
     co "^4.6.0"
     json-stable-stringify "^1.0.1"
 
-ajv@^5.1.5, ajv@^5.2.0:
+ajv@^5.2.0:
   version "5.2.2"
   resolved "https://registry.yarnpkg.com/ajv/-/ajv-5.2.2.tgz#47c68d69e86f5d953103b0074a9430dc63da5e39"
   dependencies:
@@ -54,14 +44,6 @@ ajv@^5.1.5, ajv@^5.2.0:
     json-schema-traverse "^0.3.0"
     json-stable-stringify "^1.0.1"
 
-align-text@^0.1.1, align-text@^0.1.3:
-  version "0.1.4"
-  resolved "https://registry.yarnpkg.com/align-text/-/align-text-0.1.4.tgz#0cd90a561093f35d0a99256c22b7069433fad117"
-  dependencies:
-    kind-of "^3.0.2"
-    longest "^1.0.1"
-    repeat-string "^1.5.2"
-
 ansi-escapes@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/ansi-escapes/-/ansi-escapes-2.0.0.tgz#5bae52be424878dd9783e8910e3fc2922e83c81b"
@@ -84,24 +66,6 @@ ansi-styles@^3.1.0:
   dependencies:
     color-convert "^1.9.0"
 
-anymatch@^1.3.0:
-  version "1.3.0"
-  resolved "https://registry.yarnpkg.com/anymatch/-/anymatch-1.3.0.tgz#a3e52fa39168c825ff57b0248126ce5a8ff95507"
-  dependencies:
-    arrify "^1.0.0"
-    micromatch "^2.1.5"
-
-aproba@^1.0.3:
-  version "1.1.2"
-  resolved "https://registry.yarnpkg.com/aproba/-/aproba-1.1.2.tgz#45c6629094de4e96f693ef7eab74ae079c240fc1"
-
-are-we-there-yet@~1.1.2:
-  version "1.1.4"
-  resolved "https://registry.yarnpkg.com/are-we-there-yet/-/are-we-there-yet-1.1.4.tgz#bb5dca382bb94f05e15194373d16fd3ba1ca110d"
-  dependencies:
-    delegates "^1.0.0"
-    readable-stream "^2.0.6"
-
 argparse@^1.0.7:
   version "1.0.9"
   resolved "https://registry.yarnpkg.com/argparse/-/argparse-1.0.9.tgz#73d83bc263f86e97f8cc4f6bae1b0e90a7d22c86"
@@ -136,54 +100,6 @@ arrify@^1.0.0:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/arrify/-/arrify-1.0.1.tgz#898508da2226f380df904728456849c1501a4b0d"
 
-asn1.js@^4.0.0:
-  version "4.9.1"
-  resolved "https://registry.yarnpkg.com/asn1.js/-/asn1.js-4.9.1.tgz#48ba240b45a9280e94748990ba597d216617fd40"
-  dependencies:
-    bn.js "^4.0.0"
-    inherits "^2.0.1"
-    minimalistic-assert "^1.0.0"
-
-asn1@~0.2.3:
-  version "0.2.3"
-  resolved "https://registry.yarnpkg.com/asn1/-/asn1-0.2.3.tgz#dac8787713c9966849fc8180777ebe9c1ddf3b86"
-
-assert-plus@1.0.0, assert-plus@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/assert-plus/-/assert-plus-1.0.0.tgz#f12e0f3c5d77b0b1cdd9146942e4e96c1e4dd525"
-
-assert-plus@^0.2.0:
-  version "0.2.0"
-  resolved "https://registry.yarnpkg.com/assert-plus/-/assert-plus-0.2.0.tgz#d74e1b87e7affc0db8aadb7021f3fe48101ab234"
-
-assert@^1.1.1:
-  version "1.4.1"
-  resolved "https://registry.yarnpkg.com/assert/-/assert-1.4.1.tgz#99912d591836b5a6f5b345c0f07eefc08fc65d91"
-  dependencies:
-    util "0.10.3"
-
-async-each@^1.0.0:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/async-each/-/async-each-1.0.1.tgz#19d386a1d9edc6e7c1c85d388aedbcc56d33602d"
-
-async@^2.1.2:
-  version "2.5.0"
-  resolved "https://registry.yarnpkg.com/async/-/async-2.5.0.tgz#843190fd6b7357a0b9e1c956edddd5ec8462b54d"
-  dependencies:
-    lodash "^4.14.0"
-
-asynckit@^0.4.0:
-  version "0.4.0"
-  resolved "https://registry.yarnpkg.com/asynckit/-/asynckit-0.4.0.tgz#c79ed97f7f34cb8f2ba1bc9790bcc366474b4b79"
-
-aws-sign2@~0.6.0:
-  version "0.6.0"
-  resolved "https://registry.yarnpkg.com/aws-sign2/-/aws-sign2-0.6.0.tgz#14342dd38dbcc94d0e5b87d763cd63612c0e794f"
-
-aws4@^1.2.1:
-  version "1.6.0"
-  resolved "https://registry.yarnpkg.com/aws4/-/aws4-1.6.0.tgz#83ef5ca860b2b32e4a0deedee8c771b9db57471e"
-
 babel-code-frame@^6.22.0:
   version "6.22.0"
   resolved "https://registry.yarnpkg.com/babel-code-frame/-/babel-code-frame-6.22.0.tgz#027620bee567a88c32561574e7fd0801d33118e4"
@@ -330,14 +246,6 @@ babel-helpers@^6.24.1:
     babel-runtime "^6.22.0"
     babel-template "^6.24.1"
 
-babel-loader@^7.1.1:
-  version "7.1.1"
-  resolved "https://registry.yarnpkg.com/babel-loader/-/babel-loader-7.1.1.tgz#b87134c8b12e3e4c2a94e0546085bc680a2b8488"
-  dependencies:
-    find-cache-dir "^1.0.0"
-    loader-utils "^1.0.2"
-    mkdirp "^0.5.1"
-
 babel-messages@^6.23.0:
   version "6.23.0"
   resolved "https://registry.yarnpkg.com/babel-messages/-/babel-messages-6.23.0.tgz#f3cdf4703858035b2a2951c6ec5edf6c62f2630e"
@@ -350,6 +258,12 @@ babel-plugin-check-es2015-constants@^6.22.0:
   dependencies:
     babel-runtime "^6.22.0"
 
+babel-plugin-external-helpers@^6.22.0:
+  version "6.22.0"
+  resolved "https://registry.yarnpkg.com/babel-plugin-external-helpers/-/babel-plugin-external-helpers-6.22.0.tgz#2285f48b02bd5dede85175caf8c62e86adccefa1"
+  dependencies:
+    babel-runtime "^6.22.0"
+
 babel-plugin-syntax-async-functions@^6.8.0:
   version "6.13.0"
   resolved "https://registry.yarnpkg.com/babel-plugin-syntax-async-functions/-/babel-plugin-syntax-async-functions-6.13.0.tgz#cad9cad1191b5ad634bf30ae0872391e0647be95"
@@ -654,40 +568,6 @@ balanced-match@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/balanced-match/-/balanced-match-1.0.0.tgz#89b4d199ab2bee49de164ea02b89ce462d71b767"
 
-base64-js@^1.0.2:
-  version "1.2.1"
-  resolved "https://registry.yarnpkg.com/base64-js/-/base64-js-1.2.1.tgz#a91947da1f4a516ea38e5b4ec0ec3773675e0886"
-
-bcrypt-pbkdf@^1.0.0:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/bcrypt-pbkdf/-/bcrypt-pbkdf-1.0.1.tgz#63bc5dcb61331b92bc05fd528953c33462a06f8d"
-  dependencies:
-    tweetnacl "^0.14.3"
-
-big.js@^3.1.3:
-  version "3.1.3"
-  resolved "https://registry.yarnpkg.com/big.js/-/big.js-3.1.3.tgz#4cada2193652eb3ca9ec8e55c9015669c9806978"
-
-binary-extensions@^1.0.0:
-  version "1.9.0"
-  resolved "https://registry.yarnpkg.com/binary-extensions/-/binary-extensions-1.9.0.tgz#66506c16ce6f4d6928a5b3cd6a33ca41e941e37b"
-
-block-stream@*:
-  version "0.0.9"
-  resolved "https://registry.yarnpkg.com/block-stream/-/block-stream-0.0.9.tgz#13ebfe778a03205cfe03751481ebb4b3300c126a"
-  dependencies:
-    inherits "~2.0.0"
-
-bn.js@^4.0.0, bn.js@^4.1.0, bn.js@^4.1.1, bn.js@^4.4.0:
-  version "4.11.7"
-  resolved "https://registry.yarnpkg.com/bn.js/-/bn.js-4.11.7.tgz#ddb048e50d9482790094c13eb3fcfc833ce7ab46"
-
-boom@2.x.x:
-  version "2.10.1"
-  resolved "https://registry.yarnpkg.com/boom/-/boom-2.10.1.tgz#39c8918ceff5799f83f9492a848f625add0c766f"
-  dependencies:
-    hoek "2.x.x"
-
 brace-expansion@^1.1.7:
   version "1.1.8"
   resolved "https://registry.yarnpkg.com/brace-expansion/-/brace-expansion-1.1.8.tgz#c07b211c7c952ec1f8efd51a77ef0d1d3990a292"
@@ -703,61 +583,6 @@ braces@^1.8.2:
     preserve "^0.2.0"
     repeat-element "^1.1.2"
 
-brorand@^1.0.1:
-  version "1.1.0"
-  resolved "https://registry.yarnpkg.com/brorand/-/brorand-1.1.0.tgz#12c25efe40a45e3c323eb8675a0a0ce57b22371f"
-
-browserify-aes@^1.0.0, browserify-aes@^1.0.4:
-  version "1.0.6"
-  resolved "https://registry.yarnpkg.com/browserify-aes/-/browserify-aes-1.0.6.tgz#5e7725dbdef1fd5930d4ebab48567ce451c48a0a"
-  dependencies:
-    buffer-xor "^1.0.2"
-    cipher-base "^1.0.0"
-    create-hash "^1.1.0"
-    evp_bytestokey "^1.0.0"
-    inherits "^2.0.1"
-
-browserify-cipher@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/browserify-cipher/-/browserify-cipher-1.0.0.tgz#9988244874bf5ed4e28da95666dcd66ac8fc363a"
-  dependencies:
-    browserify-aes "^1.0.4"
-    browserify-des "^1.0.0"
-    evp_bytestokey "^1.0.0"
-
-browserify-des@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/browserify-des/-/browserify-des-1.0.0.tgz#daa277717470922ed2fe18594118a175439721dd"
-  dependencies:
-    cipher-base "^1.0.1"
-    des.js "^1.0.0"
-    inherits "^2.0.1"
-
-browserify-rsa@^4.0.0:
-  version "4.0.1"
-  resolved "https://registry.yarnpkg.com/browserify-rsa/-/browserify-rsa-4.0.1.tgz#21e0abfaf6f2029cf2fafb133567a701d4135524"
-  dependencies:
-    bn.js "^4.1.0"
-    randombytes "^2.0.1"
-
-browserify-sign@^4.0.0:
-  version "4.0.4"
-  resolved "https://registry.yarnpkg.com/browserify-sign/-/browserify-sign-4.0.4.tgz#aa4eb68e5d7b658baa6bf6a57e630cbd7a93d298"
-  dependencies:
-    bn.js "^4.1.1"
-    browserify-rsa "^4.0.0"
-    create-hash "^1.1.0"
-    create-hmac "^1.1.2"
-    elliptic "^6.0.0"
-    inherits "^2.0.1"
-    parse-asn1 "^5.0.0"
-
-browserify-zlib@^0.1.4:
-  version "0.1.4"
-  resolved "https://registry.yarnpkg.com/browserify-zlib/-/browserify-zlib-0.1.4.tgz#bb35f8a519f600e0fa6b8485241c979d0141fb2d"
-  dependencies:
-    pako "~0.2.0"
-
 browserslist@^2.1.2:
   version "2.2.2"
   resolved "https://registry.yarnpkg.com/browserslist/-/browserslist-2.2.2.tgz#e9b4618b8a01c193f9786beea09f6fd10dbe31c3"
@@ -765,25 +590,13 @@ browserslist@^2.1.2:
     caniuse-lite "^1.0.30000704"
     electron-to-chromium "^1.3.16"
 
-buffer-xor@^1.0.2:
-  version "1.0.3"
-  resolved "https://registry.yarnpkg.com/buffer-xor/-/buffer-xor-1.0.3.tgz#26e61ed1422fb70dd42e6e36729ed51d855fe8d9"
-
-buffer@^4.3.0:
-  version "4.9.1"
-  resolved "https://registry.yarnpkg.com/buffer/-/buffer-4.9.1.tgz#6d1bb601b07a4efced97094132093027c95bc298"
-  dependencies:
-    base64-js "^1.0.2"
-    ieee754 "^1.1.4"
-    isarray "^1.0.0"
-
 builtin-modules@^1.0.0, builtin-modules@^1.1.1:
   version "1.1.1"
   resolved "https://registry.yarnpkg.com/builtin-modules/-/builtin-modules-1.1.1.tgz#270f076c5a72c02f5b65a47df94c5fe3a278892f"
 
-builtin-status-codes@^3.0.0:
-  version "3.0.0"
-  resolved "https://registry.yarnpkg.com/builtin-status-codes/-/builtin-status-codes-3.0.0.tgz#85982878e21b98e1c66425e03d0174788f569ee8"
+builtin-modules@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/builtin-modules/-/builtin-modules-2.0.0.tgz#60b7ef5ae6546bd7deefa74b08b62a43a232648e"
 
 caller-path@^0.1.0:
   version "0.1.0"
@@ -795,29 +608,10 @@ callsites@^0.2.0:
   version "0.2.0"
   resolved "https://registry.yarnpkg.com/callsites/-/callsites-0.2.0.tgz#afab96262910a7f33c19a5775825c69f34e350ca"
 
-camelcase@^1.0.2:
-  version "1.2.1"
-  resolved "https://registry.yarnpkg.com/camelcase/-/camelcase-1.2.1.tgz#9bb5304d2e0b56698b2c758b08a3eaa9daa58a39"
-
-camelcase@^4.1.0:
-  version "4.1.0"
-  resolved "https://registry.yarnpkg.com/camelcase/-/camelcase-4.1.0.tgz#d545635be1e33c542649c69173e5de6acfae34dd"
-
 caniuse-lite@^1.0.30000704:
   version "1.0.30000706"
   resolved "https://registry.yarnpkg.com/caniuse-lite/-/caniuse-lite-1.0.30000706.tgz#bc59abc41ba7d4a3634dda95befded6114e1f24e"
 
-caseless@~0.12.0:
-  version "0.12.0"
-  resolved "https://registry.yarnpkg.com/caseless/-/caseless-0.12.0.tgz#1b681c21ff84033c826543090689420d187151dc"
-
-center-align@^0.1.1:
-  version "0.1.3"
-  resolved "https://registry.yarnpkg.com/center-align/-/center-align-0.1.3.tgz#aa0d32629b6ee972200411cbd4461c907bc2b7ad"
-  dependencies:
-    align-text "^0.1.3"
-    lazy-cache "^1.0.3"
-
 chalk@^1.1.0, chalk@^1.1.1, chalk@^1.1.3:
   version "1.1.3"
   resolved "https://registry.yarnpkg.com/chalk/-/chalk-1.1.3.tgz#a8115c55e4a702fe4d150abd3872822a7e09fc98"
@@ -836,28 +630,6 @@ chalk@^2.0.0:
     escape-string-regexp "^1.0.5"
     supports-color "^4.0.0"
 
-chokidar@^1.7.0:
-  version "1.7.0"
-  resolved "https://registry.yarnpkg.com/chokidar/-/chokidar-1.7.0.tgz#798e689778151c8076b4b360e5edd28cda2bb468"
-  dependencies:
-    anymatch "^1.3.0"
-    async-each "^1.0.0"
-    glob-parent "^2.0.0"
-    inherits "^2.0.1"
-    is-binary-path "^1.0.0"
-    is-glob "^2.0.0"
-    path-is-absolute "^1.0.0"
-    readdirp "^2.0.0"
-  optionalDependencies:
-    fsevents "^1.0.0"
-
-cipher-base@^1.0.0, cipher-base@^1.0.1, cipher-base@^1.0.3:
-  version "1.0.4"
-  resolved "https://registry.yarnpkg.com/cipher-base/-/cipher-base-1.0.4.tgz#8760e4ecc272f4c363532f926d874aae2c1397de"
-  dependencies:
-    inherits "^2.0.1"
-    safe-buffer "^5.0.1"
-
 circular-json@^0.3.1:
   version "0.3.3"
   resolved "https://registry.yarnpkg.com/circular-json/-/circular-json-0.3.3.tgz#815c99ea84f6809529d2f45791bdf82711352d66"
@@ -872,30 +644,10 @@ cli-width@^2.0.0:
   version "2.1.0"
   resolved "https://registry.yarnpkg.com/cli-width/-/cli-width-2.1.0.tgz#b234ca209b29ef66fc518d9b98d5847b00edf00a"
 
-cliui@^2.1.0:
-  version "2.1.0"
-  resolved "https://registry.yarnpkg.com/cliui/-/cliui-2.1.0.tgz#4b475760ff80264c762c3a1719032e91c7fea0d1"
-  dependencies:
-    center-align "^0.1.1"
-    right-align "^0.1.1"
-    wordwrap "0.0.2"
-
-cliui@^3.2.0:
-  version "3.2.0"
-  resolved "https://registry.yarnpkg.com/cliui/-/cliui-3.2.0.tgz#120601537a916d29940f934da3b48d585a39213d"
-  dependencies:
-    string-width "^1.0.1"
-    strip-ansi "^3.0.1"
-    wrap-ansi "^2.0.0"
-
 co@^4.6.0:
   version "4.6.0"
   resolved "https://registry.yarnpkg.com/co/-/co-4.6.0.tgz#6ea6bdf3d853ae54ccb8e47bfa0bf3f9031fb184"
 
-code-point-at@^1.0.0:
-  version "1.1.0"
-  resolved "https://registry.yarnpkg.com/code-point-at/-/code-point-at-1.1.0.tgz#0d070b4d043a5bea33a2f1a40e2edb3d9a4ccf77"
-
 color-convert@^1.9.0:
   version "1.9.0"
   resolved "https://registry.yarnpkg.com/color-convert/-/color-convert-1.9.0.tgz#1accf97dd739b983bf994d56fec8f95853641b7a"
@@ -906,15 +658,9 @@ color-name@^1.1.1:
   version "1.1.3"
   resolved "https://registry.yarnpkg.com/color-name/-/color-name-1.1.3.tgz#a7d0558bd89c42f795dd42328f740831ca53bc25"
 
-combined-stream@^1.0.5, combined-stream@~1.0.5:
-  version "1.0.5"
-  resolved "https://registry.yarnpkg.com/combined-stream/-/combined-stream-1.0.5.tgz#938370a57b4a51dea2c77c15d5c5fdf895164009"
-  dependencies:
-    delayed-stream "~1.0.0"
-
-commondir@^1.0.1:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/commondir/-/commondir-1.0.1.tgz#ddd800da0c66127393cca5950ea968a3aaf1253b"
+commander@~2.13.0:
+  version "2.13.0"
+  resolved "https://registry.yarnpkg.com/commander/-/commander-2.13.0.tgz#6964bca67685df7c1f1430c584f07d7597885b9c"
 
 concat-map@0.0.1:
   version "0.0.1"
@@ -928,20 +674,6 @@ concat-stream@^1.6.0:
     readable-stream "^2.2.2"
     typedarray "^0.0.6"
 
-console-browserify@^1.1.0:
-  version "1.1.0"
-  resolved "https://registry.yarnpkg.com/console-browserify/-/console-browserify-1.1.0.tgz#f0241c45730a9fc6323b206dbf38edc741d0bb10"
-  dependencies:
-    date-now "^0.1.4"
-
-console-control-strings@^1.0.0, console-control-strings@~1.1.0:
-  version "1.1.0"
-  resolved "https://registry.yarnpkg.com/console-control-strings/-/console-control-strings-1.1.0.tgz#3d7cf4464db6446ea644bf4b39507f9851008e8e"
-
-constants-browserify@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/constants-browserify/-/constants-browserify-1.0.0.tgz#c20b96d8c617748aaf1c16021760cd27fcb8cb75"
-
 contains-path@^0.1.0:
   version "0.1.0"
   resolved "https://registry.yarnpkg.com/contains-path/-/contains-path-0.1.0.tgz#fe8cf184ff6670b6baef01a9d4861a5cbec4120a"
@@ -958,34 +690,7 @@ core-util-is@~1.0.0:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/core-util-is/-/core-util-is-1.0.2.tgz#b5fd54220aa2bc5ab57aab7140c940754503c1a7"
 
-create-ecdh@^4.0.0:
-  version "4.0.0"
-  resolved "https://registry.yarnpkg.com/create-ecdh/-/create-ecdh-4.0.0.tgz#888c723596cdf7612f6498233eebd7a35301737d"
-  dependencies:
-    bn.js "^4.1.0"
-    elliptic "^6.0.0"
-
-create-hash@^1.1.0, create-hash@^1.1.1, create-hash@^1.1.2:
-  version "1.1.3"
-  resolved "https://registry.yarnpkg.com/create-hash/-/create-hash-1.1.3.tgz#606042ac8b9262750f483caddab0f5819172d8fd"
-  dependencies:
-    cipher-base "^1.0.1"
-    inherits "^2.0.1"
-    ripemd160 "^2.0.0"
-    sha.js "^2.4.0"
-
-create-hmac@^1.1.0, create-hmac@^1.1.2, create-hmac@^1.1.4:
-  version "1.1.6"
-  resolved "https://registry.yarnpkg.com/create-hmac/-/create-hmac-1.1.6.tgz#acb9e221a4e17bdb076e90657c42b93e3726cf06"
-  dependencies:
-    cipher-base "^1.0.3"
-    create-hash "^1.1.0"
-    inherits "^2.0.1"
-    ripemd160 "^2.0.0"
-    safe-buffer "^5.0.1"
-    sha.js "^2.4.8"
-
-cross-spawn@^5.0.1, cross-spawn@^5.1.0:
+cross-spawn@^5.1.0:
   version "5.1.0"
   resolved "https://registry.yarnpkg.com/cross-spawn/-/cross-spawn-5.1.0.tgz#e8bd0efee58fcff6f8f94510a0a554bbfa235449"
   dependencies:
@@ -993,57 +698,12 @@ cross-spawn@^5.0.1, cross-spawn@^5.1.0:
     shebang-command "^1.2.0"
     which "^1.2.9"
 
-cryptiles@2.x.x:
-  version "2.0.5"
-  resolved "https://registry.yarnpkg.com/cryptiles/-/cryptiles-2.0.5.tgz#3bdfecdc608147c1c67202fa291e7dca59eaa3b8"
-  dependencies:
-    boom "2.x.x"
-
-crypto-browserify@^3.11.0:
-  version "3.11.1"
-  resolved "https://registry.yarnpkg.com/crypto-browserify/-/crypto-browserify-3.11.1.tgz#948945efc6757a400d6e5e5af47194d10064279f"
-  dependencies:
-    browserify-cipher "^1.0.0"
-    browserify-sign "^4.0.0"
-    create-ecdh "^4.0.0"
-    create-hash "^1.1.0"
-    create-hmac "^1.1.0"
-    diffie-hellman "^5.0.0"
-    inherits "^2.0.1"
-    pbkdf2 "^3.0.3"
-    public-encrypt "^4.0.0"
-    randombytes "^2.0.0"
-
-d@1:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/d/-/d-1.0.0.tgz#754bb5bfe55451da69a58b94d45f4c5b0462d58f"
-  dependencies:
-    es5-ext "^0.10.9"
-
-dashdash@^1.12.0:
-  version "1.14.1"
-  resolved "https://registry.yarnpkg.com/dashdash/-/dashdash-1.14.1.tgz#853cfa0f7cbe2fed5de20326b8dd581035f6e2f0"
-  dependencies:
-    assert-plus "^1.0.0"
-
-date-now@^0.1.4:
-  version "0.1.4"
-  resolved "https://registry.yarnpkg.com/date-now/-/date-now-0.1.4.tgz#eaf439fd4d4848ad74e5cc7dbef200672b9e345b"
-
 debug@^2.1.1, debug@^2.2.0, debug@^2.6.8:
   version "2.6.8"
   resolved "https://registry.yarnpkg.com/debug/-/debug-2.6.8.tgz#e731531ca2ede27d188222427da17821d68ff4fc"
   dependencies:
     ms "2.0.0"
 
-decamelize@^1.0.0, decamelize@^1.1.1:
-  version "1.2.0"
-  resolved "https://registry.yarnpkg.com/decamelize/-/decamelize-1.2.0.tgz#f6534d15148269b20352e7bee26f501f9a191290"
-
-deep-extend@~0.4.0:
-  version "0.4.2"
-  resolved "https://registry.yarnpkg.com/deep-extend/-/deep-extend-0.4.2.tgz#48b699c27e334bf89f10892be432f6e4c7d34a7f"
-
 deep-is@~0.1.3:
   version "0.1.3"
   resolved "https://registry.yarnpkg.com/deep-is/-/deep-is-0.1.3.tgz#b369d6fb5dbc13eecf524f91b070feedc357cf34"
@@ -1060,35 +720,12 @@ del@^2.0.2:
     pinkie-promise "^2.0.0"
     rimraf "^2.2.8"
 
-delayed-stream@~1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/delayed-stream/-/delayed-stream-1.0.0.tgz#df3ae199acadfb7d440aaae0b29e2272b24ec619"
-
-delegates@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/delegates/-/delegates-1.0.0.tgz#84c6e159b81904fdca59a0ef44cd870d31250f9a"
-
-des.js@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/des.js/-/des.js-1.0.0.tgz#c074d2e2aa6a8a9a07dbd61f9a15c2cd83ec8ecc"
-  dependencies:
-    inherits "^2.0.1"
-    minimalistic-assert "^1.0.0"
-
 detect-indent@^4.0.0:
   version "4.0.0"
   resolved "https://registry.yarnpkg.com/detect-indent/-/detect-indent-4.0.0.tgz#f76d064352cdf43a1cb6ce619c4ee3a9475de208"
   dependencies:
     repeating "^2.0.0"
 
-diffie-hellman@^5.0.0:
-  version "5.0.2"
-  resolved "https://registry.yarnpkg.com/diffie-hellman/-/diffie-hellman-5.0.2.tgz#b5835739270cfe26acf632099fded2a07f209e5e"
-  dependencies:
-    bn.js "^4.1.0"
-    miller-rabin "^4.0.0"
-    randombytes "^2.0.0"
-
 doctrine@1.5.0:
   version "1.5.0"
   resolved "https://registry.yarnpkg.com/doctrine/-/doctrine-1.5.0.tgz#379dce730f6166f76cefa4e6707a159b02c5a6fa"
@@ -1103,128 +740,20 @@ doctrine@^2.0.0:
     esutils "^2.0.2"
     isarray "^1.0.0"
 
-domain-browser@^1.1.1:
-  version "1.1.7"
-  resolved "https://registry.yarnpkg.com/domain-browser/-/domain-browser-1.1.7.tgz#867aa4b093faa05f1de08c06f4d7b21fdf8698bc"
-
-ecc-jsbn@~0.1.1:
-  version "0.1.1"
-  resolved "https://registry.yarnpkg.com/ecc-jsbn/-/ecc-jsbn-0.1.1.tgz#0fc73a9ed5f0d53c38193398523ef7e543777505"
-  dependencies:
-    jsbn "~0.1.0"
-
 electron-to-chromium@^1.3.16:
   version "1.3.16"
   resolved "https://registry.yarnpkg.com/electron-to-chromium/-/electron-to-chromium-1.3.16.tgz#d0e026735754770901ae301a21664cba45d92f7d"
 
-elliptic@^6.0.0:
-  version "6.4.0"
-  resolved "https://registry.yarnpkg.com/elliptic/-/elliptic-6.4.0.tgz#cac9af8762c85836187003c8dfe193e5e2eae5df"
-  dependencies:
-    bn.js "^4.4.0"
-    brorand "^1.0.1"
-    hash.js "^1.0.0"
-    hmac-drbg "^1.0.0"
-    inherits "^2.0.1"
-    minimalistic-assert "^1.0.0"
-    minimalistic-crypto-utils "^1.0.0"
-
-emojis-list@^2.0.0:
-  version "2.1.0"
-  resolved "https://registry.yarnpkg.com/emojis-list/-/emojis-list-2.1.0.tgz#4daa4d9db00f9819880c79fa457ae5b09a1fd389"
-
-enhanced-resolve@^3.4.0:
-  version "3.4.1"
-  resolved "https://registry.yarnpkg.com/enhanced-resolve/-/enhanced-resolve-3.4.1.tgz#0421e339fd71419b3da13d129b3979040230476e"
-  dependencies:
-    graceful-fs "^4.1.2"
-    memory-fs "^0.4.0"
-    object-assign "^4.0.1"
-    tapable "^0.2.7"
-
-errno@^0.1.3:
-  version "0.1.4"
-  resolved "https://registry.yarnpkg.com/errno/-/errno-0.1.4.tgz#b896e23a9e5e8ba33871fc996abd3635fc9a1c7d"
-  dependencies:
-    prr "~0.0.0"
-
 error-ex@^1.2.0:
   version "1.3.1"
   resolved "https://registry.yarnpkg.com/error-ex/-/error-ex-1.3.1.tgz#f855a86ce61adc4e8621c3cda21e7a7612c3a8dc"
   dependencies:
     is-arrayish "^0.2.1"
 
-es5-ext@^0.10.14, es5-ext@^0.10.9, es5-ext@~0.10.14:
-  version "0.10.24"
-  resolved "https://registry.yarnpkg.com/es5-ext/-/es5-ext-0.10.24.tgz#a55877c9924bc0c8d9bd3c2cbe17495ac1709b14"
-  dependencies:
-    es6-iterator "2"
-    es6-symbol "~3.1"
-
-es6-iterator@2, es6-iterator@^2.0.1, es6-iterator@~2.0.1:
-  version "2.0.1"
-  resolved "https://registry.yarnpkg.com/es6-iterator/-/es6-iterator-2.0.1.tgz#8e319c9f0453bf575d374940a655920e59ca5512"
-  dependencies:
-    d "1"
-    es5-ext "^0.10.14"
-    es6-symbol "^3.1"
-
-es6-map@^0.1.3:
-  version "0.1.5"
-  resolved "https://registry.yarnpkg.com/es6-map/-/es6-map-0.1.5.tgz#9136e0503dcc06a301690f0bb14ff4e364e949f0"
-  dependencies:
-    d "1"
-    es5-ext "~0.10.14"
-    es6-iterator "~2.0.1"
-    es6-set "~0.1.5"
-    es6-symbol "~3.1.1"
-    event-emitter "~0.3.5"
-
-es6-set@~0.1.5:
-  version "0.1.5"
-  resolved "https://registry.yarnpkg.com/es6-set/-/es6-set-0.1.5.tgz#d2b3ec5d4d800ced818db538d28974db0a73ccb1"
-  dependencies:
-    d "1"
-    es5-ext "~0.10.14"
-    es6-iterator "~2.0.1"
-    es6-symbol "3.1.1"
-    event-emitter "~0.3.5"
-
-es6-symbol@3.1.1, es6-symbol@^3.1, es6-symbol@^3.1.1, es6-symbol@~3.1, es6-symbol@~3.1.1:
-  version "3.1.1"
-  resolved "https://registry.yarnpkg.com/es6-symbol/-/es6-symbol-3.1.1.tgz#bf00ef4fdab6ba1b46ecb7b629b4c7ed5715cc77"
-  dependencies:
-    d "1"
-    es5-ext "~0.10.14"
-
-es6-weak-map@^2.0.1:
-  version "2.0.2"
-  resolved "https://registry.yarnpkg.com/es6-weak-map/-/es6-weak-map-2.0.2.tgz#5e3ab32251ffd1538a1f8e5ffa1357772f92d96f"
-  dependencies:
-    d "1"
-    es5-ext "^0.10.14"
-    es6-iterator "^2.0.1"
-    es6-symbol "^3.1.1"
-
 escape-string-regexp@^1.0.2, escape-string-regexp@^1.0.5:
   version "1.0.5"
   resolved "https://registry.yarnpkg.com/escape-string-regexp/-/escape-string-regexp-1.0.5.tgz#1b61c0562190a8dff6ae3bb2cf0200ca130b86d4"
 
-escope@^3.6.0:
-  version "3.6.0"
-  resolved "https://registry.yarnpkg.com/escope/-/escope-3.6.0.tgz#e01975e812781a163a6dadfdd80398dc64c889c3"
-  dependencies:
-    es6-map "^0.1.3"
-    es6-weak-map "^2.0.1"
-    esrecurse "^4.1.0"
-    estraverse "^4.1.1"
-
-eslint-config-airbnb-base@^11.3.1:
-  version "11.3.1"
-  resolved "https://registry.yarnpkg.com/eslint-config-airbnb-base/-/eslint-config-airbnb-base-11.3.1.tgz#c0ab108c9beed503cb999e4c60f4ef98eda0ed30"
-  dependencies:
-    eslint-restricted-globals "^0.1.1"
-
 eslint-import-resolver-node@^0.3.1:
   version "0.3.1"
   resolved "https://registry.yarnpkg.com/eslint-import-resolver-node/-/eslint-import-resolver-node-0.3.1.tgz#4422574cde66a9a7b099938ee4d508a199e0e3cc"
@@ -1254,10 +783,6 @@ eslint-plugin-import@^2.7.0:
     minimatch "^3.0.3"
     read-pkg-up "^2.0.0"
 
-eslint-restricted-globals@^0.1.1:
-  version "0.1.1"
-  resolved "https://registry.yarnpkg.com/eslint-restricted-globals/-/eslint-restricted-globals-0.1.1.tgz#35f0d5cbc64c2e3ed62e93b4b1a7af05ba7ed4d7"
-
 eslint-scope@^3.7.1:
   version "3.7.1"
   resolved "https://registry.yarnpkg.com/eslint-scope/-/eslint-scope-3.7.1.tgz#3d63c3edfda02e06e01a452ad88caacc7cdcb6e8"
@@ -1334,38 +859,21 @@ estraverse@^4.0.0, estraverse@^4.1.0, estraverse@^4.1.1, estraverse@^4.2.0:
   version "4.2.0"
   resolved "https://registry.yarnpkg.com/estraverse/-/estraverse-4.2.0.tgz#0dee3fed31fcd469618ce7342099fc1afa0bdb13"
 
-esutils@^2.0.2:
-  version "2.0.2"
-  resolved "https://registry.yarnpkg.com/esutils/-/esutils-2.0.2.tgz#0abf4f1caa5bcb1f7a9d8acc6dea4faaa04bac9b"
-
-event-emitter@~0.3.5:
-  version "0.3.5"
-  resolved "https://registry.yarnpkg.com/event-emitter/-/event-emitter-0.3.5.tgz#df8c69eef1647923c7157b9ce83840610b02cc39"
-  dependencies:
-    d "1"
-    es5-ext "~0.10.14"
+estree-walker@^0.2.1:
+  version "0.2.1"
+  resolved "https://registry.yarnpkg.com/estree-walker/-/estree-walker-0.2.1.tgz#bdafe8095383d8414d5dc2ecf4c9173b6db9412e"
 
-events@^1.0.0:
-  version "1.1.1"
-  resolved "https://registry.yarnpkg.com/events/-/events-1.1.1.tgz#9ebdb7635ad099c70dcc4c2a1f5004288e8bd924"
+estree-walker@^0.3.0:
+  version "0.3.1"
+  resolved "https://registry.yarnpkg.com/estree-walker/-/estree-walker-0.3.1.tgz#e6b1a51cf7292524e7237c312e5fe6660c1ce1aa"
 
-evp_bytestokey@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/evp_bytestokey/-/evp_bytestokey-1.0.0.tgz#497b66ad9fef65cd7c08a6180824ba1476b66e53"
-  dependencies:
-    create-hash "^1.1.1"
+estree-walker@^0.5.1:
+  version "0.5.1"
+  resolved "https://registry.yarnpkg.com/estree-walker/-/estree-walker-0.5.1.tgz#64fc375053abc6f57d73e9bd2f004644ad3c5854"
 
-execa@^0.7.0:
-  version "0.7.0"
-  resolved "https://registry.yarnpkg.com/execa/-/execa-0.7.0.tgz#944becd34cc41ee32a63a9faf27ad5a65fc59777"
-  dependencies:
-    cross-spawn "^5.0.1"
-    get-stream "^3.0.0"
-    is-stream "^1.1.0"
-    npm-run-path "^2.0.0"
-    p-finally "^1.0.0"
-    signal-exit "^3.0.0"
-    strip-eof "^1.0.0"
+esutils@^2.0.2:
+  version "2.0.2"
+  resolved "https://registry.yarnpkg.com/esutils/-/esutils-2.0.2.tgz#0abf4f1caa5bcb1f7a9d8acc6dea4faaa04bac9b"
 
 expand-brackets@^0.1.4:
   version "0.1.5"
@@ -1379,10 +887,6 @@ expand-range@^1.8.1:
   dependencies:
     fill-range "^2.1.0"
 
-extend@~3.0.0:
-  version "3.0.1"
-  resolved "https://registry.yarnpkg.com/extend/-/extend-3.0.1.tgz#a755ea7bc1adfcc5a31ce7e762dbaadc5e636444"
-
 external-editor@^2.0.4:
   version "2.0.4"
   resolved "https://registry.yarnpkg.com/external-editor/-/external-editor-2.0.4.tgz#1ed9199da9cbfe2ef2f7a31b2fde8b0d12368972"
@@ -1397,10 +901,6 @@ extglob@^0.3.1:
   dependencies:
     is-extglob "^1.0.0"
 
-extsprintf@1.0.2:
-  version "1.0.2"
-  resolved "https://registry.yarnpkg.com/extsprintf/-/extsprintf-1.0.2.tgz#e1080e0658e300b06294990cc70e1502235fd550"
-
 fast-deep-equal@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/fast-deep-equal/-/fast-deep-equal-1.0.0.tgz#96256a3bc975595eb36d82e9929d060d893439ff"
@@ -1436,14 +936,6 @@ fill-range@^2.1.0:
     repeat-element "^1.1.2"
     repeat-string "^1.5.2"
 
-find-cache-dir@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/find-cache-dir/-/find-cache-dir-1.0.0.tgz#9288e3e9e3cc3748717d39eade17cf71fc30ee6f"
-  dependencies:
-    commondir "^1.0.1"
-    make-dir "^1.0.0"
-    pkg-dir "^2.0.0"
-
 find-up@^1.0.0:
   version "1.1.2"
   resolved "https://registry.yarnpkg.com/find-up/-/find-up-1.1.2.tgz#6b2e9822b1a2ce0a60ab64d610eccad53cb24d0f"
@@ -1451,7 +943,7 @@ find-up@^1.0.0:
     path-exists "^2.0.0"
     pinkie-promise "^2.0.0"
 
-find-up@^2.0.0, find-up@^2.1.0:
+find-up@^2.0.0:
   version "2.1.0"
   resolved "https://registry.yarnpkg.com/find-up/-/find-up-2.1.0.tgz#45d1b7e506c717ddd482775a2b77920a3c0c57a7"
   dependencies:
@@ -1476,46 +968,10 @@ for-own@^0.1.4:
   dependencies:
     for-in "^1.0.1"
 
-forever-agent@~0.6.1:
-  version "0.6.1"
-  resolved "https://registry.yarnpkg.com/forever-agent/-/forever-agent-0.6.1.tgz#fbc71f0c41adeb37f96c577ad1ed42d8fdacca91"
-
-form-data@~2.1.1:
-  version "2.1.4"
-  resolved "https://registry.yarnpkg.com/form-data/-/form-data-2.1.4.tgz#33c183acf193276ecaa98143a69e94bfee1750d1"
-  dependencies:
-    asynckit "^0.4.0"
-    combined-stream "^1.0.5"
-    mime-types "^2.1.12"
-
 fs.realpath@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/fs.realpath/-/fs.realpath-1.0.0.tgz#1504ad2523158caa40db4a2787cb01411994ea4f"
 
-fsevents@^1.0.0:
-  version "1.1.2"
-  resolved "https://registry.yarnpkg.com/fsevents/-/fsevents-1.1.2.tgz#3282b713fb3ad80ede0e9fcf4611b5aa6fc033f4"
-  dependencies:
-    nan "^2.3.0"
-    node-pre-gyp "^0.6.36"
-
-fstream-ignore@^1.0.5:
-  version "1.0.5"
-  resolved "https://registry.yarnpkg.com/fstream-ignore/-/fstream-ignore-1.0.5.tgz#9c31dae34767018fe1d249b24dada67d092da105"
-  dependencies:
-    fstream "^1.0.0"
-    inherits "2"
-    minimatch "^3.0.0"
-
-fstream@^1.0.0, fstream@^1.0.10, fstream@^1.0.2:
-  version "1.0.11"
-  resolved "https://registry.yarnpkg.com/fstream/-/fstream-1.0.11.tgz#5c1fb1f117477114f0632a0eb4b71b3cb0fd3171"
-  dependencies:
-    graceful-fs "^4.1.2"
-    inherits "~2.0.0"
-    mkdirp ">=0.5 0"
-    rimraf "2"
-
 function-bind@^1.0.2:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/function-bind/-/function-bind-1.1.0.tgz#16176714c801798e4e8f2cf7f7529467bb4a5771"
@@ -1524,33 +980,6 @@ functional-red-black-tree@^1.0.1:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/functional-red-black-tree/-/functional-red-black-tree-1.0.1.tgz#1b0ab3bd553b2a0d6399d29c0e3ea0b252078327"
 
-gauge@~2.7.3:
-  version "2.7.4"
-  resolved "https://registry.yarnpkg.com/gauge/-/gauge-2.7.4.tgz#2c03405c7538c39d7eb37b317022e325fb018bf7"
-  dependencies:
-    aproba "^1.0.3"
-    console-control-strings "^1.0.0"
-    has-unicode "^2.0.0"
-    object-assign "^4.1.0"
-    signal-exit "^3.0.0"
-    string-width "^1.0.1"
-    strip-ansi "^3.0.1"
-    wide-align "^1.1.0"
-
-get-caller-file@^1.0.1:
-  version "1.0.2"
-  resolved "https://registry.yarnpkg.com/get-caller-file/-/get-caller-file-1.0.2.tgz#f702e63127e7e231c160a80c1554acb70d5047e5"
-
-get-stream@^3.0.0:
-  version "3.0.0"
-  resolved "https://registry.yarnpkg.com/get-stream/-/get-stream-3.0.0.tgz#8e943d1358dc37555054ecbe2edb05aa174ede14"
-
-getpass@^0.1.1:
-  version "0.1.7"
-  resolved "https://registry.yarnpkg.com/getpass/-/getpass-0.1.7.tgz#5eff8e3e684d569ae4cb2b1282604e8ba62149fa"
-  dependencies:
-    assert-plus "^1.0.0"
-
 glob-base@^0.3.0:
   version "0.3.0"
   resolved "https://registry.yarnpkg.com/glob-base/-/glob-base-0.3.0.tgz#dbb164f6221b1c0b1ccf82aea328b497df0ea3c4"
@@ -1594,17 +1023,6 @@ graceful-fs@^4.1.2:
   version "4.1.11"
   resolved "https://registry.yarnpkg.com/graceful-fs/-/graceful-fs-4.1.11.tgz#0e8bdfe4d1ddb8854d64e04ea7c00e2a026e5658"
 
-har-schema@^1.0.5:
-  version "1.0.5"
-  resolved "https://registry.yarnpkg.com/har-schema/-/har-schema-1.0.5.tgz#d263135f43307c02c602afc8fe95970c0151369e"
-
-har-validator@~4.2.1:
-  version "4.2.1"
-  resolved "https://registry.yarnpkg.com/har-validator/-/har-validator-4.2.1.tgz#33481d0f1bbff600dd203d75812a6a5fba002e2a"
-  dependencies:
-    ajv "^4.9.1"
-    har-schema "^1.0.5"
-
 has-ansi@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/has-ansi/-/has-ansi-2.0.0.tgz#34f5049ce1ecdf2b0649af3ef24e45ed35416d91"
@@ -1615,50 +1033,12 @@ has-flag@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/has-flag/-/has-flag-2.0.0.tgz#e8207af1cc7b30d446cc70b734b5e8be18f88d51"
 
-has-unicode@^2.0.0:
-  version "2.0.1"
-  resolved "https://registry.yarnpkg.com/has-unicode/-/has-unicode-2.0.1.tgz#e0e6fe6a28cf51138855e086d1691e771de2a8b9"
-
 has@^1.0.1:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/has/-/has-1.0.1.tgz#8461733f538b0837c9361e39a9ab9e9704dc2f28"
   dependencies:
     function-bind "^1.0.2"
 
-hash-base@^2.0.0:
-  version "2.0.2"
-  resolved "https://registry.yarnpkg.com/hash-base/-/hash-base-2.0.2.tgz#66ea1d856db4e8a5470cadf6fce23ae5244ef2e1"
-  dependencies:
-    inherits "^2.0.1"
-
-hash.js@^1.0.0, hash.js@^1.0.3:
-  version "1.1.3"
-  resolved "https://registry.yarnpkg.com/hash.js/-/hash.js-1.1.3.tgz#340dedbe6290187151c1ea1d777a3448935df846"
-  dependencies:
-    inherits "^2.0.3"
-    minimalistic-assert "^1.0.0"
-
-hawk@~3.1.3:
-  version "3.1.3"
-  resolved "https://registry.yarnpkg.com/hawk/-/hawk-3.1.3.tgz#078444bd7c1640b0fe540d2c9b73d59678e8e1c4"
-  dependencies:
-    boom "2.x.x"
-    cryptiles "2.x.x"
-    hoek "2.x.x"
-    sntp "1.x.x"
-
-hmac-drbg@^1.0.0:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/hmac-drbg/-/hmac-drbg-1.0.1.tgz#d2745701025a6c775a6c545793ed502fc0c649a1"
-  dependencies:
-    hash.js "^1.0.3"
-    minimalistic-assert "^1.0.0"
-    minimalistic-crypto-utils "^1.0.1"
-
-hoek@2.x.x:
-  version "2.16.3"
-  resolved "https://registry.yarnpkg.com/hoek/-/hoek-2.16.3.tgz#20bb7403d3cea398e91dc4710a8ff1b8274a25ed"
-
 home-or-tmp@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/home-or-tmp/-/home-or-tmp-2.0.0.tgz#e36c3f2d2cae7d746a857e38d18d5f32a7882db8"
@@ -1670,26 +1050,10 @@ hosted-git-info@^2.1.4:
   version "2.5.0"
   resolved "https://registry.yarnpkg.com/hosted-git-info/-/hosted-git-info-2.5.0.tgz#6d60e34b3abbc8313062c3b798ef8d901a07af3c"
 
-http-signature@~1.1.0:
-  version "1.1.1"
-  resolved "https://registry.yarnpkg.com/http-signature/-/http-signature-1.1.1.tgz#df72e267066cd0ac67fb76adf8e134a8fbcf91bf"
-  dependencies:
-    assert-plus "^0.2.0"
-    jsprim "^1.2.2"
-    sshpk "^1.7.0"
-
-https-browserify@0.0.1:
-  version "0.0.1"
-  resolved "https://registry.yarnpkg.com/https-browserify/-/https-browserify-0.0.1.tgz#3f91365cabe60b77ed0ebba24b454e3e09d95a82"
-
 iconv-lite@^0.4.17:
   version "0.4.18"
   resolved "https://registry.yarnpkg.com/iconv-lite/-/iconv-lite-0.4.18.tgz#23d8656b16aae6742ac29732ea8f0336a4789cf2"
 
-ieee754@^1.1.4:
-  version "1.1.8"
-  resolved "https://registry.yarnpkg.com/ieee754/-/ieee754-1.1.8.tgz#be33d40ac10ef1926701f6f08a2d86fbfd1ad3e4"
-
 ignore@^3.3.3:
   version "3.3.3"
   resolved "https://registry.yarnpkg.com/ignore/-/ignore-3.3.3.tgz#432352e57accd87ab3110e82d3fea0e47812156d"
@@ -1698,10 +1062,6 @@ imurmurhash@^0.1.4:
   version "0.1.4"
   resolved "https://registry.yarnpkg.com/imurmurhash/-/imurmurhash-0.1.4.tgz#9218b9b2b928a238b13dc4fb6b6d576f231453ea"
 
-indexof@0.0.1:
-  version "0.0.1"
-  resolved "https://registry.yarnpkg.com/indexof/-/indexof-0.0.1.tgz#82dc336d232b9062179d05ab3293a66059fd435d"
-
 inflight@^1.0.4:
   version "1.0.6"
   resolved "https://registry.yarnpkg.com/inflight/-/inflight-1.0.6.tgz#49bd6331d7d02d0c09bc910a1075ba8165b56df9"
@@ -1709,18 +1069,10 @@ inflight@^1.0.4:
     once "^1.3.0"
     wrappy "1"
 
-inherits@2, inherits@^2.0.1, inherits@^2.0.3, inherits@~2.0.0, inherits@~2.0.1, inherits@~2.0.3:
+inherits@2, inherits@^2.0.3, inherits@~2.0.3:
   version "2.0.3"
   resolved "https://registry.yarnpkg.com/inherits/-/inherits-2.0.3.tgz#633c2c83e3da42a502f52466022480f4208261de"
 
-inherits@2.0.1:
-  version "2.0.1"
-  resolved "https://registry.yarnpkg.com/inherits/-/inherits-2.0.1.tgz#b17d08d326b4423e568eff719f91b0b1cbdf69f1"
-
-ini@~1.3.0:
-  version "1.3.4"
-  resolved "https://registry.yarnpkg.com/ini/-/ini-1.3.4.tgz#0537cb79daf59b59a1a517dff706c86ec039162e"
-
 inquirer@^3.0.6:
   version "3.2.1"
   resolved "https://registry.yarnpkg.com/inquirer/-/inquirer-3.2.1.tgz#06ceb0f540f45ca548c17d6840959878265fa175"
@@ -1740,30 +1092,16 @@ inquirer@^3.0.6:
     strip-ansi "^4.0.0"
     through "^2.3.6"
 
-interpret@^1.0.0:
-  version "1.0.3"
-  resolved "https://registry.yarnpkg.com/interpret/-/interpret-1.0.3.tgz#cbc35c62eeee73f19ab7b10a801511401afc0f90"
-
 invariant@^2.2.0, invariant@^2.2.2:
   version "2.2.2"
   resolved "https://registry.yarnpkg.com/invariant/-/invariant-2.2.2.tgz#9e1f56ac0acdb6bf303306f338be3b204ae60360"
   dependencies:
     loose-envify "^1.0.0"
 
-invert-kv@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/invert-kv/-/invert-kv-1.0.0.tgz#104a8e4aaca6d3d8cd157a8ef8bfab2d7a3ffdb6"
-
 is-arrayish@^0.2.1:
   version "0.2.1"
   resolved "https://registry.yarnpkg.com/is-arrayish/-/is-arrayish-0.2.1.tgz#77c99840527aa8ecb1a8ba697b80645a7a926a9d"
 
-is-binary-path@^1.0.0:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/is-binary-path/-/is-binary-path-1.0.1.tgz#75f16642b480f187a711c814161fd3a4a7655898"
-  dependencies:
-    binary-extensions "^1.0.0"
-
 is-buffer@^1.1.5:
   version "1.1.5"
   resolved "https://registry.yarnpkg.com/is-buffer/-/is-buffer-1.1.5.tgz#1f3b26ef613b214b88cbca23cc6c01d87961eecc"
@@ -1798,12 +1136,6 @@ is-finite@^1.0.0:
   dependencies:
     number-is-nan "^1.0.0"
 
-is-fullwidth-code-point@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/is-fullwidth-code-point/-/is-fullwidth-code-point-1.0.0.tgz#ef9e31386f031a7f0d643af82fde50c457ef00cb"
-  dependencies:
-    number-is-nan "^1.0.0"
-
 is-fullwidth-code-point@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/is-fullwidth-code-point/-/is-fullwidth-code-point-2.0.0.tgz#a3b30a5c4f199183167aaab93beefae3ddfb654f"
@@ -1814,6 +1146,10 @@ is-glob@^2.0.0, is-glob@^2.0.1:
   dependencies:
     is-extglob "^1.0.0"
 
+is-module@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/is-module/-/is-module-1.0.0.tgz#3258fb69f78c14d5b815d664336b4cffb6441591"
+
 is-number@^2.1.0:
   version "2.1.0"
   resolved "https://registry.yarnpkg.com/is-number/-/is-number-2.1.0.tgz#01fcbbb393463a548f2f466cce16dece49db908f"
@@ -1860,14 +1196,6 @@ is-resolvable@^1.0.0:
   dependencies:
     tryit "^1.0.1"
 
-is-stream@^1.1.0:
-  version "1.1.0"
-  resolved "https://registry.yarnpkg.com/is-stream/-/is-stream-1.1.0.tgz#12d4a3dd4e68e0b79ceb8dbc84173ae80d91ca44"
-
-is-typedarray@~1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/is-typedarray/-/is-typedarray-1.0.0.tgz#e479c80858df0c1b11ddda6940f96011fcda4a9a"
-
 isarray@1.0.0, isarray@^1.0.0, isarray@~1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/isarray/-/isarray-1.0.0.tgz#bb935d48582cba168c06834957a54a3e07124f11"
@@ -1882,10 +1210,6 @@ isobject@^2.0.0:
   dependencies:
     isarray "1.0.0"
 
-isstream@~0.1.2:
-  version "0.1.2"
-  resolved "https://registry.yarnpkg.com/isstream/-/isstream-0.1.2.tgz#47e63f7af55afa6f92e1500e690eb8b8529c099a"
-
 js-tokens@^3.0.0:
   version "3.0.2"
   resolved "https://registry.yarnpkg.com/js-tokens/-/js-tokens-3.0.2.tgz#9866df395102130e38f7f996bceb65443209c25b"
@@ -1897,10 +1221,6 @@ js-yaml@^3.8.4:
     argparse "^1.0.7"
     esprima "^4.0.0"
 
-jsbn@~0.1.0:
-  version "0.1.1"
-  resolved "https://registry.yarnpkg.com/jsbn/-/jsbn-0.1.1.tgz#a5e654c2e5a2deb5f201d96cefbca80c0ef2f513"
-
 jschardet@^1.4.2:
   version "1.5.0"
   resolved "https://registry.yarnpkg.com/jschardet/-/jschardet-1.5.0.tgz#a61f310306a5a71188e1b1acd08add3cfbb08b1e"
@@ -1913,29 +1233,17 @@ jsesc@~0.5.0:
   version "0.5.0"
   resolved "https://registry.yarnpkg.com/jsesc/-/jsesc-0.5.0.tgz#e7dee66e35d6fc16f710fe91d5cf69f70f08911d"
 
-json-loader@^0.5.4:
-  version "0.5.7"
-  resolved "https://registry.yarnpkg.com/json-loader/-/json-loader-0.5.7.tgz#dca14a70235ff82f0ac9a3abeb60d337a365185d"
-
 json-schema-traverse@^0.3.0:
   version "0.3.1"
   resolved "https://registry.yarnpkg.com/json-schema-traverse/-/json-schema-traverse-0.3.1.tgz#349a6d44c53a51de89b40805c5d5e59b417d3340"
 
-json-schema@0.2.3:
-  version "0.2.3"
-  resolved "https://registry.yarnpkg.com/json-schema/-/json-schema-0.2.3.tgz#b480c892e59a2f05954ce727bd3f2a4e882f9e13"
-
 json-stable-stringify@^1.0.1:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/json-stable-stringify/-/json-stable-stringify-1.0.1.tgz#9a759d39c5f2ff503fd5300646ed445f88c4f9af"
   dependencies:
     jsonify "~0.0.0"
 
-json-stringify-safe@~5.0.1:
-  version "5.0.1"
-  resolved "https://registry.yarnpkg.com/json-stringify-safe/-/json-stringify-safe-5.0.1.tgz#1296a2d58fd45f19a0f6ce01d65701e2c735b6eb"
-
-json5@^0.5.0, json5@^0.5.1:
+json5@^0.5.0:
   version "0.5.1"
   resolved "https://registry.yarnpkg.com/json5/-/json5-0.5.1.tgz#1eade7acc012034ad84e2396767ead9fa5495821"
 
@@ -1943,15 +1251,6 @@ jsonify@~0.0.0:
   version "0.0.0"
   resolved "https://registry.yarnpkg.com/jsonify/-/jsonify-0.0.0.tgz#2c74b6ee41d93ca51b7b5aaee8f503631d252a73"
 
-jsprim@^1.2.2:
-  version "1.4.0"
-  resolved "https://registry.yarnpkg.com/jsprim/-/jsprim-1.4.0.tgz#a3b87e40298d8c380552d8cc7628a0bb95a22918"
-  dependencies:
-    assert-plus "1.0.0"
-    extsprintf "1.0.2"
-    json-schema "0.2.3"
-    verror "1.3.6"
-
 kind-of@^3.0.2:
   version "3.2.2"
   resolved "https://registry.yarnpkg.com/kind-of/-/kind-of-3.2.2.tgz#31ea21a734bab9bbb0f32466d893aea51e4a3c64"
@@ -1964,16 +1263,6 @@ kind-of@^4.0.0:
   dependencies:
     is-buffer "^1.1.5"
 
-lazy-cache@^1.0.3:
-  version "1.0.4"
-  resolved "https://registry.yarnpkg.com/lazy-cache/-/lazy-cache-1.0.4.tgz#a1d78fc3a50474cb80845d3b3b6e1da49a446e8e"
-
-lcid@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/lcid/-/lcid-1.0.0.tgz#308accafa0bc483a3867b4b6f2b9506251d1b835"
-  dependencies:
-    invert-kv "^1.0.0"
-
 levn@^0.3.0, levn@~0.3.0:
   version "0.3.0"
   resolved "https://registry.yarnpkg.com/levn/-/levn-0.3.0.tgz#3b09924edf9f083c0490fdd4c0bc4421e04764ee"
@@ -1990,18 +1279,6 @@ load-json-file@^2.0.0:
     pify "^2.0.0"
     strip-bom "^3.0.0"
 
-loader-runner@^2.3.0:
-  version "2.3.0"
-  resolved "https://registry.yarnpkg.com/loader-runner/-/loader-runner-2.3.0.tgz#f482aea82d543e07921700d5a46ef26fdac6b8a2"
-
-loader-utils@^1.0.2, loader-utils@^1.1.0:
-  version "1.1.0"
-  resolved "https://registry.yarnpkg.com/loader-utils/-/loader-utils-1.1.0.tgz#c98aef488bcceda2ffb5e2de646d6a754429f5cd"
-  dependencies:
-    big.js "^3.1.3"
-    emojis-list "^2.0.0"
-    json5 "^0.5.0"
-
 locate-path@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/locate-path/-/locate-path-2.0.0.tgz#2b568b265eec944c6d9c0de9c3dbbbca0354cd8e"
@@ -2013,14 +1290,10 @@ lodash.cond@^4.3.0:
   version "4.5.2"
   resolved "https://registry.yarnpkg.com/lodash.cond/-/lodash.cond-4.5.2.tgz#f471a1da486be60f6ab955d17115523dd1d255d5"
 
-lodash@^4.0.0, lodash@^4.14.0, lodash@^4.17.4, lodash@^4.2.0, lodash@^4.3.0:
+lodash@^4.0.0, lodash@^4.17.4, lodash@^4.2.0, lodash@^4.3.0:
   version "4.17.4"
   resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.4.tgz#78203a4d1c328ae1d86dca6460e369b57f4055ae"
 
-longest@^1.0.1:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/longest/-/longest-1.0.1.tgz#30a0b2da38f73770e8294a0d22e6625ed77d0097"
-
 loose-envify@^1.0.0:
   version "1.3.1"
   resolved "https://registry.yarnpkg.com/loose-envify/-/loose-envify-1.3.1.tgz#d1a8ad33fa9ce0e713d65fdd0ac8b748d478c848"
@@ -2034,26 +1307,13 @@ lru-cache@^4.0.1:
     pseudomap "^1.0.2"
     yallist "^2.1.2"
 
-make-dir@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/make-dir/-/make-dir-1.0.0.tgz#97a011751e91dd87cfadef58832ebb04936de978"
-  dependencies:
-    pify "^2.3.0"
-
-mem@^1.1.0:
-  version "1.1.0"
-  resolved "https://registry.yarnpkg.com/mem/-/mem-1.1.0.tgz#5edd52b485ca1d900fe64895505399a0dfa45f76"
+magic-string@^0.22.4:
+  version "0.22.5"
+  resolved "https://registry.yarnpkg.com/magic-string/-/magic-string-0.22.5.tgz#8e9cf5afddf44385c1da5bc2a6a0dbd10b03657e"
   dependencies:
-    mimic-fn "^1.0.0"
+    vlq "^0.2.2"
 
-memory-fs@^0.4.0, memory-fs@~0.4.1:
-  version "0.4.1"
-  resolved "https://registry.yarnpkg.com/memory-fs/-/memory-fs-0.4.1.tgz#3a9a20b8462523e447cfbc7e8bb80ed667bfc552"
-  dependencies:
-    errno "^0.1.3"
-    readable-stream "^2.0.1"
-
-micromatch@^2.1.5:
+micromatch@^2.3.11:
   version "2.3.11"
   resolved "https://registry.yarnpkg.com/micromatch/-/micromatch-2.3.11.tgz#86677c97d1720b363431d04d0d15293bd38c1565"
   dependencies:
@@ -2071,36 +1331,11 @@ micromatch@^2.1.5:
     parse-glob "^3.0.4"
     regex-cache "^0.4.2"
 
-miller-rabin@^4.0.0:
-  version "4.0.0"
-  resolved "https://registry.yarnpkg.com/miller-rabin/-/miller-rabin-4.0.0.tgz#4a62fb1d42933c05583982f4c716f6fb9e6c6d3d"
-  dependencies:
-    bn.js "^4.0.0"
-    brorand "^1.0.1"
-
-mime-db@~1.29.0:
-  version "1.29.0"
-  resolved "https://registry.yarnpkg.com/mime-db/-/mime-db-1.29.0.tgz#48d26d235589651704ac5916ca06001914266878"
-
-mime-types@^2.1.12, mime-types@~2.1.7:
-  version "2.1.16"
-  resolved "https://registry.yarnpkg.com/mime-types/-/mime-types-2.1.16.tgz#2b858a52e5ecd516db897ac2be87487830698e23"
-  dependencies:
-    mime-db "~1.29.0"
-
 mimic-fn@^1.0.0:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/mimic-fn/-/mimic-fn-1.1.0.tgz#e667783d92e89dbd342818b5230b9d62a672ad18"
 
-minimalistic-assert@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/minimalistic-assert/-/minimalistic-assert-1.0.0.tgz#702be2dda6b37f4836bcb3f5db56641b64a1d3d3"
-
-minimalistic-crypto-utils@^1.0.0, minimalistic-crypto-utils@^1.0.1:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/minimalistic-crypto-utils/-/minimalistic-crypto-utils-1.0.1.tgz#f6c00c1c0b082246e5c4d99dfb8c7c083b2b582a"
-
-minimatch@^3.0.0, minimatch@^3.0.2, minimatch@^3.0.3, minimatch@^3.0.4:
+minimatch@^3.0.2, minimatch@^3.0.3, minimatch@^3.0.4:
   version "3.0.4"
   resolved "https://registry.yarnpkg.com/minimatch/-/minimatch-3.0.4.tgz#5166e286457f03306064be5497e8dbb0c3d32083"
   dependencies:
@@ -2110,11 +1345,7 @@ minimist@0.0.8:
   version "0.0.8"
   resolved "https://registry.yarnpkg.com/minimist/-/minimist-0.0.8.tgz#857fcabfc3397d2625b8228262e86aa7a011b05d"
 
-minimist@^1.2.0:
-  version "1.2.0"
-  resolved "https://registry.yarnpkg.com/minimist/-/minimist-1.2.0.tgz#a35008b20f41383eec1fb914f4cd5df79a264284"
-
-"mkdirp@>=0.5 0", mkdirp@^0.5.1, mkdirp@~0.5.0:
+mkdirp@^0.5.1:
   version "0.5.1"
   resolved "https://registry.yarnpkg.com/mkdirp/-/mkdirp-0.5.1.tgz#30057438eac6cf7f8c4767f38648d6697d75c903"
   dependencies:
@@ -2128,63 +1359,10 @@ mute-stream@0.0.7:
   version "0.0.7"
   resolved "https://registry.yarnpkg.com/mute-stream/-/mute-stream-0.0.7.tgz#3075ce93bc21b8fab43e1bc4da7e8115ed1e7bab"
 
-nan@^2.3.0:
-  version "2.6.2"
-  resolved "https://registry.yarnpkg.com/nan/-/nan-2.6.2.tgz#e4ff34e6c95fdfb5aecc08de6596f43605a7db45"
-
 natural-compare@^1.4.0:
   version "1.4.0"
   resolved "https://registry.yarnpkg.com/natural-compare/-/natural-compare-1.4.0.tgz#4abebfeed7541f2c27acfb29bdbbd15c8d5ba4f7"
 
-node-libs-browser@^2.0.0:
-  version "2.0.0"
-  resolved "https://registry.yarnpkg.com/node-libs-browser/-/node-libs-browser-2.0.0.tgz#a3a59ec97024985b46e958379646f96c4b616646"
-  dependencies:
-    assert "^1.1.1"
-    browserify-zlib "^0.1.4"
-    buffer "^4.3.0"
-    console-browserify "^1.1.0"
-    constants-browserify "^1.0.0"
-    crypto-browserify "^3.11.0"
-    domain-browser "^1.1.1"
-    events "^1.0.0"
-    https-browserify "0.0.1"
-    os-browserify "^0.2.0"
-    path-browserify "0.0.0"
-    process "^0.11.0"
-    punycode "^1.2.4"
-    querystring-es3 "^0.2.0"
-    readable-stream "^2.0.5"
-    stream-browserify "^2.0.1"
-    stream-http "^2.3.1"
-    string_decoder "^0.10.25"
-    timers-browserify "^2.0.2"
-    tty-browserify "0.0.0"
-    url "^0.11.0"
-    util "^0.10.3"
-    vm-browserify "0.0.4"
-
-node-pre-gyp@^0.6.36:
-  version "0.6.36"
-  resolved "https://registry.yarnpkg.com/node-pre-gyp/-/node-pre-gyp-0.6.36.tgz#db604112cb74e0d477554e9b505b17abddfab786"
-  dependencies:
-    mkdirp "^0.5.1"
-    nopt "^4.0.1"
-    npmlog "^4.0.2"
-    rc "^1.1.7"
-    request "^2.81.0"
-    rimraf "^2.6.1"
-    semver "^5.3.0"
-    tar "^2.2.1"
-    tar-pack "^3.4.0"
-
-nopt@^4.0.1:
-  version "4.0.1"
-  resolved "https://registry.yarnpkg.com/nopt/-/nopt-4.0.1.tgz#d0d4685afd5415193c8c7505602d0d17cd64474d"
-  dependencies:
-    abbrev "1"
-    osenv "^0.1.4"
-
 normalize-package-data@^2.3.2:
   version "2.4.0"
   resolved "https://registry.yarnpkg.com/normalize-package-data/-/normalize-package-data-2.4.0.tgz#12f95a307d58352075a04907b84ac8be98ac012f"
@@ -2200,30 +1378,11 @@ normalize-path@^2.0.1:
   dependencies:
     remove-trailing-separator "^1.0.1"
 
-npm-run-path@^2.0.0:
-  version "2.0.2"
-  resolved "https://registry.yarnpkg.com/npm-run-path/-/npm-run-path-2.0.2.tgz#35a9232dfa35d7067b4cb2ddf2357b1871536c5f"
-  dependencies:
-    path-key "^2.0.0"
-
-npmlog@^4.0.2:
-  version "4.1.2"
-  resolved "https://registry.yarnpkg.com/npmlog/-/npmlog-4.1.2.tgz#08a7f2a8bf734604779a9efa4ad5cc717abb954b"
-  dependencies:
-    are-we-there-yet "~1.1.2"
-    console-control-strings "~1.1.0"
-    gauge "~2.7.3"
-    set-blocking "~2.0.0"
-
 number-is-nan@^1.0.0:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/number-is-nan/-/number-is-nan-1.0.1.tgz#097b602b53422a522c1afb8790318336941a011d"
 
-oauth-sign@~0.8.1:
-  version "0.8.2"
-  resolved "https://registry.yarnpkg.com/oauth-sign/-/oauth-sign-0.8.2.tgz#46a6ab7f0aead8deae9ec0565780b7d4efeb9d43"
-
-object-assign@^4.0.1, object-assign@^4.1.0:
+object-assign@^4.0.1:
   version "4.1.1"
   resolved "https://registry.yarnpkg.com/object-assign/-/object-assign-4.1.1.tgz#2109adc7965887cfc05cbbd442cac8bfbb360863"
 
@@ -2234,7 +1393,7 @@ object.omit@^2.0.0:
     for-own "^0.1.4"
     is-extendable "^0.1.1"
 
-once@^1.3.0, once@^1.3.3:
+once@^1.3.0:
   version "1.4.0"
   resolved "https://registry.yarnpkg.com/once/-/once-1.4.0.tgz#583b1aa775961d4b113ac17d9c50baef9dd76bd1"
   dependencies:
@@ -2257,37 +1416,14 @@ optionator@^0.8.2:
     type-check "~0.3.2"
     wordwrap "~1.0.0"
 
-os-browserify@^0.2.0:
-  version "0.2.1"
-  resolved "https://registry.yarnpkg.com/os-browserify/-/os-browserify-0.2.1.tgz#63fc4ccee5d2d7763d26bbf8601078e6c2e0044f"
-
 os-homedir@^1.0.0:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/os-homedir/-/os-homedir-1.0.2.tgz#ffbc4988336e0e833de0c168c7ef152121aa7fb3"
 
-os-locale@^2.0.0:
-  version "2.1.0"
-  resolved "https://registry.yarnpkg.com/os-locale/-/os-locale-2.1.0.tgz#42bc2900a6b5b8bd17376c8e882b65afccf24bf2"
-  dependencies:
-    execa "^0.7.0"
-    lcid "^1.0.0"
-    mem "^1.1.0"
-
-os-tmpdir@^1.0.0, os-tmpdir@^1.0.1, os-tmpdir@~1.0.1:
+os-tmpdir@^1.0.1, os-tmpdir@~1.0.1:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/os-tmpdir/-/os-tmpdir-1.0.2.tgz#bbe67406c79aa85c5cfec766fe5734555dfa1274"
 
-osenv@^0.1.4:
-  version "0.1.4"
-  resolved "https://registry.yarnpkg.com/osenv/-/osenv-0.1.4.tgz#42fe6d5953df06c8064be6f176c3d05aaaa34644"
-  dependencies:
-    os-homedir "^1.0.0"
-    os-tmpdir "^1.0.0"
-
-p-finally@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/p-finally/-/p-finally-1.0.0.tgz#3fbcfb15b899a44123b34b6dcc18b724336a2cae"
-
 p-limit@^1.1.0:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/p-limit/-/p-limit-1.1.0.tgz#b07ff2d9a5d88bec806035895a2bab66a27988bc"
@@ -2298,20 +1434,6 @@ p-locate@^2.0.0:
   dependencies:
     p-limit "^1.1.0"
 
-pako@~0.2.0:
-  version "0.2.9"
-  resolved "https://registry.yarnpkg.com/pako/-/pako-0.2.9.tgz#f3f7522f4ef782348da8161bad9ecfd51bf83a75"
-
-parse-asn1@^5.0.0:
-  version "5.1.0"
-  resolved "https://registry.yarnpkg.com/parse-asn1/-/parse-asn1-5.1.0.tgz#37c4f9b7ed3ab65c74817b5f2480937fbf97c712"
-  dependencies:
-    asn1.js "^4.0.0"
-    browserify-aes "^1.0.0"
-    create-hash "^1.1.0"
-    evp_bytestokey "^1.0.0"
-    pbkdf2 "^3.0.3"
-
 parse-glob@^3.0.4:
   version "3.0.4"
   resolved "https://registry.yarnpkg.com/parse-glob/-/parse-glob-3.0.4.tgz#b2c376cfb11f35513badd173ef0bb6e3a388391c"
@@ -2327,10 +1449,6 @@ parse-json@^2.2.0:
   dependencies:
     error-ex "^1.2.0"
 
-path-browserify@0.0.0:
-  version "0.0.0"
-  resolved "https://registry.yarnpkg.com/path-browserify/-/path-browserify-0.0.0.tgz#a0b870729aae214005b7d5032ec2cbbb0fb4451a"
-
 path-exists@^2.0.0:
   version "2.1.0"
   resolved "https://registry.yarnpkg.com/path-exists/-/path-exists-2.1.0.tgz#0feb6c64f0fc518d9a754dd5efb62c7022761f4b"
@@ -2349,10 +1467,6 @@ path-is-inside@^1.0.1, path-is-inside@^1.0.2:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/path-is-inside/-/path-is-inside-1.0.2.tgz#365417dede44430d1c11af61027facf074bdfc53"
 
-path-key@^2.0.0:
-  version "2.0.1"
-  resolved "https://registry.yarnpkg.com/path-key/-/path-key-2.0.1.tgz#411cadb574c5a140d3a4b1910d40d80cc9f40b40"
-
 path-parse@^1.0.5:
   version "1.0.5"
   resolved "https://registry.yarnpkg.com/path-parse/-/path-parse-1.0.5.tgz#3c1adf871ea9cd6c9431b6ea2bd74a0ff055c4c1"
@@ -2363,21 +1477,7 @@ path-type@^2.0.0:
   dependencies:
     pify "^2.0.0"
 
-pbkdf2@^3.0.3:
-  version "3.0.12"
-  resolved "https://registry.yarnpkg.com/pbkdf2/-/pbkdf2-3.0.12.tgz#be36785c5067ea48d806ff923288c5f750b6b8a2"
-  dependencies:
-    create-hash "^1.1.2"
-    create-hmac "^1.1.4"
-    ripemd160 "^2.0.1"
-    safe-buffer "^5.0.1"
-    sha.js "^2.4.8"
-
-performance-now@^0.2.0:
-  version "0.2.0"
-  resolved "https://registry.yarnpkg.com/performance-now/-/performance-now-0.2.0.tgz#33ef30c5c77d4ea21c5a53869d91b56d8f2555e5"
-
-pify@^2.0.0, pify@^2.3.0:
+pify@^2.0.0:
   version "2.3.0"
   resolved "https://registry.yarnpkg.com/pify/-/pify-2.3.0.tgz#ed141a6ac043a849ea588498e7dca8b15330e90c"
 
@@ -2397,12 +1497,6 @@ pkg-dir@^1.0.0:
   dependencies:
     find-up "^1.0.0"
 
-pkg-dir@^2.0.0:
-  version "2.0.0"
-  resolved "https://registry.yarnpkg.com/pkg-dir/-/pkg-dir-2.0.0.tgz#f6d5d1109e19d63edf428e0bd57e12777615334b"
-  dependencies:
-    find-up "^2.1.0"
-
 pluralize@^4.0.0:
   version "4.0.0"
   resolved "https://registry.yarnpkg.com/pluralize/-/pluralize-4.0.0.tgz#59b708c1c0190a2f692f1c7618c446b052fd1762"
@@ -2423,52 +1517,14 @@ process-nextick-args@~1.0.6:
   version "1.0.7"
   resolved "https://registry.yarnpkg.com/process-nextick-args/-/process-nextick-args-1.0.7.tgz#150e20b756590ad3f91093f25a4f2ad8bff30ba3"
 
-process@^0.11.0:
-  version "0.11.10"
-  resolved "https://registry.yarnpkg.com/process/-/process-0.11.10.tgz#7332300e840161bda3e69a1d1d91a7d4bc16f182"
-
 progress@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/progress/-/progress-2.0.0.tgz#8a1be366bf8fc23db2bd23f10c6fe920b4389d1f"
 
-prr@~0.0.0:
-  version "0.0.0"
-  resolved "https://registry.yarnpkg.com/prr/-/prr-0.0.0.tgz#1a84b85908325501411853d0081ee3fa86e2926a"
-
 pseudomap@^1.0.2:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/pseudomap/-/pseudomap-1.0.2.tgz#f052a28da70e618917ef0a8ac34c1ae5a68286b3"
 
-public-encrypt@^4.0.0:
-  version "4.0.0"
-  resolved "https://registry.yarnpkg.com/public-encrypt/-/public-encrypt-4.0.0.tgz#39f699f3a46560dd5ebacbca693caf7c65c18cc6"
-  dependencies:
-    bn.js "^4.1.0"
-    browserify-rsa "^4.0.0"
-    create-hash "^1.1.0"
-    parse-asn1 "^5.0.0"
-    randombytes "^2.0.1"
-
-punycode@1.3.2:
-  version "1.3.2"
-  resolved "https://registry.yarnpkg.com/punycode/-/punycode-1.3.2.tgz#9653a036fb7c1ee42342f2325cceefea3926c48d"
-
-punycode@^1.2.4, punycode@^1.4.1:
-  version "1.4.1"
-  resolved "https://registry.yarnpkg.com/punycode/-/punycode-1.4.1.tgz#c0d5a63b2718800ad8e1eb0fa5269c84dd41845e"
-
-qs@~6.4.0:
-  version "6.4.0"
-  resolved "https://registry.yarnpkg.com/qs/-/qs-6.4.0.tgz#13e26d28ad6b0ffaa91312cd3bf708ed351e7233"
-
-querystring-es3@^0.2.0:
-  version "0.2.1"
-  resolved "https://registry.yarnpkg.com/querystring-es3/-/querystring-es3-0.2.1.tgz#9ec61f79049875707d69414596fd907a4d711e73"
-
-querystring@0.2.0:
-  version "0.2.0"
-  resolved "https://registry.yarnpkg.com/querystring/-/querystring-0.2.0.tgz#b209849203bb25df820da756e747005878521620"
-
 randomatic@^1.1.3:
   version "1.1.7"
   resolved "https://registry.yarnpkg.com/randomatic/-/randomatic-1.1.7.tgz#c7abe9cc8b87c0baa876b19fde83fd464797e38c"
@@ -2476,21 +1532,6 @@ randomatic@^1.1.3:
     is-number "^3.0.0"
     kind-of "^4.0.0"
 
-randombytes@^2.0.0, randombytes@^2.0.1:
-  version "2.0.5"
-  resolved "https://registry.yarnpkg.com/randombytes/-/randombytes-2.0.5.tgz#dc009a246b8d09a177b4b7a0ae77bc570f4b1b79"
-  dependencies:
-    safe-buffer "^5.1.0"
-
-rc@^1.1.7:
-  version "1.2.1"
-  resolved "https://registry.yarnpkg.com/rc/-/rc-1.2.1.tgz#2e03e8e42ee450b8cb3dce65be1bf8974e1dfd95"
-  dependencies:
-    deep-extend "~0.4.0"
-    ini "~1.3.0"
-    minimist "^1.2.0"
-    strip-json-comments "~2.0.1"
-
 read-pkg-up@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/read-pkg-up/-/read-pkg-up-2.0.0.tgz#6b72a8048984e0c41e79510fd5e9fa99b3b549be"
@@ -2506,7 +1547,7 @@ read-pkg@^2.0.0:
     normalize-package-data "^2.3.2"
     path-type "^2.0.0"
 
-readable-stream@^2.0.1, readable-stream@^2.0.2, readable-stream@^2.0.5, readable-stream@^2.0.6, readable-stream@^2.1.4, readable-stream@^2.2.2, readable-stream@^2.2.6:
+readable-stream@^2.2.2:
   version "2.3.3"
   resolved "https://registry.yarnpkg.com/readable-stream/-/readable-stream-2.3.3.tgz#368f2512d79f9d46fdfc71349ae7878bbc1eb95c"
   dependencies:
@@ -2518,15 +1559,6 @@ readable-stream@^2.0.1, readable-stream@^2.0.2, readable-stream@^2.0.5, readable
     string_decoder "~1.0.3"
     util-deprecate "~1.0.1"
 
-readdirp@^2.0.0:
-  version "2.1.0"
-  resolved "https://registry.yarnpkg.com/readdirp/-/readdirp-2.1.0.tgz#4ed0ad060df3073300c48440373f72d1cc642d78"
-  dependencies:
-    graceful-fs "^4.1.2"
-    minimatch "^3.0.2"
-    readable-stream "^2.0.2"
-    set-immediate-shim "^1.0.1"
-
 regenerate@^1.2.1:
   version "1.3.2"
   resolved "https://registry.yarnpkg.com/regenerate/-/regenerate-1.3.2.tgz#d1941c67bad437e1be76433add5b385f95b19260"
@@ -2586,41 +1618,6 @@ repeating@^2.0.0:
   dependencies:
     is-finite "^1.0.0"
 
-request@^2.81.0:
-  version "2.81.0"
-  resolved "https://registry.yarnpkg.com/request/-/request-2.81.0.tgz#c6928946a0e06c5f8d6f8a9333469ffda46298a0"
-  dependencies:
-    aws-sign2 "~0.6.0"
-    aws4 "^1.2.1"
-    caseless "~0.12.0"
-    combined-stream "~1.0.5"
-    extend "~3.0.0"
-    forever-agent "~0.6.1"
-    form-data "~2.1.1"
-    har-validator "~4.2.1"
-    hawk "~3.1.3"
-    http-signature "~1.1.0"
-    is-typedarray "~1.0.0"
-    isstream "~0.1.2"
-    json-stringify-safe "~5.0.1"
-    mime-types "~2.1.7"
-    oauth-sign "~0.8.1"
-    performance-now "^0.2.0"
-    qs "~6.4.0"
-    safe-buffer "^5.0.1"
-    stringstream "~0.0.4"
-    tough-cookie "~2.3.0"
-    tunnel-agent "^0.6.0"
-    uuid "^3.0.0"
-
-require-directory@^2.1.1:
-  version "2.1.1"
-  resolved "https://registry.yarnpkg.com/require-directory/-/require-directory-2.1.1.tgz#8c64ad5fd30dab1c976e2344ffe7f792a6a6df42"
-
-require-main-filename@^1.0.1:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/require-main-filename/-/require-main-filename-1.0.1.tgz#97f717b69d48784f5f526a6c5aa8ffdda055a4d1"
-
 require-uncached@^1.0.3:
   version "1.0.3"
   resolved "https://registry.yarnpkg.com/require-uncached/-/require-uncached-1.0.3.tgz#4e0d56d6c9662fd31e43011c4b95aa49955421d3"
@@ -2632,6 +1629,12 @@ resolve-from@^1.0.0:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/resolve-from/-/resolve-from-1.0.1.tgz#26cbfe935d1aeeeabb29bc3fe5aeb01e93d44226"
 
+resolve@^1.1.6, resolve@^1.5.0:
+  version "1.7.1"
+  resolved "https://registry.yarnpkg.com/resolve/-/resolve-1.7.1.tgz#aadd656374fd298aee895bc026b8297418677fd3"
+  dependencies:
+    path-parse "^1.0.5"
+
 resolve@^1.2.0:
   version "1.4.0"
   resolved "https://registry.yarnpkg.com/resolve/-/resolve-1.4.0.tgz#a75be01c53da25d934a98ebd0e4c4a7312f92a86"
@@ -2645,24 +1648,61 @@ restore-cursor@^2.0.0:
     onetime "^2.0.0"
     signal-exit "^3.0.2"
 
-right-align@^0.1.1:
-  version "0.1.3"
-  resolved "https://registry.yarnpkg.com/right-align/-/right-align-0.1.3.tgz#61339b722fe6a3515689210d24e14c96148613ef"
-  dependencies:
-    align-text "^0.1.1"
-
-rimraf@2, rimraf@^2.2.8, rimraf@^2.5.1, rimraf@^2.6.1:
+rimraf@^2.2.8:
   version "2.6.1"
   resolved "https://registry.yarnpkg.com/rimraf/-/rimraf-2.6.1.tgz#c2338ec643df7a1b7fe5c54fa86f57428a55f33d"
   dependencies:
     glob "^7.0.5"
 
-ripemd160@^2.0.0, ripemd160@^2.0.1:
+rollup-plugin-babel@^3.0.4:
+  version "3.0.4"
+  resolved "https://registry.yarnpkg.com/rollup-plugin-babel/-/rollup-plugin-babel-3.0.4.tgz#41b3e762fe64450dd61da3105a2cf7ad76be4edc"
+  dependencies:
+    rollup-pluginutils "^1.5.0"
+
+rollup-plugin-commonjs@^9.1.0:
+  version "9.1.0"
+  resolved "https://registry.yarnpkg.com/rollup-plugin-commonjs/-/rollup-plugin-commonjs-9.1.0.tgz#468341aab32499123ee9a04b22f51d9bf26fdd94"
+  dependencies:
+    estree-walker "^0.5.1"
+    magic-string "^0.22.4"
+    resolve "^1.5.0"
+    rollup-pluginutils "^2.0.1"
+
+rollup-plugin-node-resolve@^3.3.0:
+  version "3.3.0"
+  resolved "https://registry.yarnpkg.com/rollup-plugin-node-resolve/-/rollup-plugin-node-resolve-3.3.0.tgz#c26d110a36812cbefa7ce117cadcd3439aa1c713"
+  dependencies:
+    builtin-modules "^2.0.0"
+    is-module "^1.0.0"
+    resolve "^1.1.6"
+
+rollup-plugin-uglify@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/rollup-plugin-uglify/-/rollup-plugin-uglify-3.0.0.tgz#a34eca24617709c6bf1778e9653baafa06099b86"
+  dependencies:
+    uglify-es "^3.3.7"
+
+rollup-pluginutils@^1.5.0:
+  version "1.5.2"
+  resolved "https://registry.yarnpkg.com/rollup-pluginutils/-/rollup-pluginutils-1.5.2.tgz#1e156e778f94b7255bfa1b3d0178be8f5c552408"
+  dependencies:
+    estree-walker "^0.2.1"
+    minimatch "^3.0.2"
+
+rollup-pluginutils@^2.0.1:
   version "2.0.1"
-  resolved "https://registry.yarnpkg.com/ripemd160/-/ripemd160-2.0.1.tgz#0f4584295c53a3628af7e6d79aca21ce57d1c6e7"
+  resolved "https://registry.yarnpkg.com/rollup-pluginutils/-/rollup-pluginutils-2.0.1.tgz#7ec95b3573f6543a46a6461bd9a7c544525d0fc0"
+  dependencies:
+    estree-walker "^0.3.0"
+    micromatch "^2.3.11"
+
+rollup@^0.58.2:
+  version "0.58.2"
+  resolved "https://registry.yarnpkg.com/rollup/-/rollup-0.58.2.tgz#2feddea8c0c022f3e74b35c48e3c21b3433803ce"
   dependencies:
-    hash-base "^2.0.0"
-    inherits "^2.0.1"
+    "@types/estree" "0.0.38"
+    "@types/node" "*"
 
 run-async@^2.2.0:
   version "2.3.0"
@@ -2680,7 +1720,7 @@ rx-lite@*, rx-lite@^4.0.8:
   version "4.0.8"
   resolved "https://registry.yarnpkg.com/rx-lite/-/rx-lite-4.0.8.tgz#0b1e11af8bc44836f04a6407e92da42467b79444"
 
-safe-buffer@^5.0.1, safe-buffer@^5.1.0, safe-buffer@~5.1.0, safe-buffer@~5.1.1:
+safe-buffer@~5.1.0, safe-buffer@~5.1.1:
   version "5.1.1"
   resolved "https://registry.yarnpkg.com/safe-buffer/-/safe-buffer-5.1.1.tgz#893312af69b2123def71f57889001671eeb2c853"
 
@@ -2688,24 +1728,6 @@ safe-buffer@^5.0.1, safe-buffer@^5.1.0, safe-buffer@~5.1.0, safe-buffer@~5.1.1:
   version "5.4.1"
   resolved "https://registry.yarnpkg.com/semver/-/semver-5.4.1.tgz#e059c09d8571f0540823733433505d3a2f00b18e"
 
-set-blocking@^2.0.0, set-blocking@~2.0.0:
-  version "2.0.0"
-  resolved "https://registry.yarnpkg.com/set-blocking/-/set-blocking-2.0.0.tgz#045f9782d011ae9a6803ddd382b24392b3d890f7"
-
-set-immediate-shim@^1.0.1:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/set-immediate-shim/-/set-immediate-shim-1.0.1.tgz#4b2b1b27eb808a9f8dcc481a58e5e56f599f3f61"
-
-setimmediate@^1.0.4:
-  version "1.0.5"
-  resolved "https://registry.yarnpkg.com/setimmediate/-/setimmediate-1.0.5.tgz#290cbb232e306942d7d7ea9b83732ab7856f8285"
-
-sha.js@^2.4.0, sha.js@^2.4.8:
-  version "2.4.8"
-  resolved "https://registry.yarnpkg.com/sha.js/-/sha.js-2.4.8.tgz#37068c2c476b6baf402d14a49c67f597921f634f"
-  dependencies:
-    inherits "^2.0.1"
-
 shebang-command@^1.2.0:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/shebang-command/-/shebang-command-1.2.0.tgz#44aac65b695b03398968c39f363fee5deafdf1ea"
@@ -2716,7 +1738,7 @@ shebang-regex@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/shebang-regex/-/shebang-regex-1.0.0.tgz#da42f49740c0b42db2ca9728571cb190c98efea3"
 
-signal-exit@^3.0.0, signal-exit@^3.0.2:
+signal-exit@^3.0.2:
   version "3.0.2"
   resolved "https://registry.yarnpkg.com/signal-exit/-/signal-exit-3.0.2.tgz#b5fdc08f1287ea1178628e415e25132b73646c6d"
 
@@ -2728,26 +1750,20 @@ slice-ansi@0.0.4:
   version "0.0.4"
   resolved "https://registry.yarnpkg.com/slice-ansi/-/slice-ansi-0.0.4.tgz#edbf8903f66f7ce2f8eafd6ceed65e264c831b35"
 
-sntp@1.x.x:
-  version "1.0.9"
-  resolved "https://registry.yarnpkg.com/sntp/-/sntp-1.0.9.tgz#6541184cc90aeea6c6e7b35e2659082443c66198"
-  dependencies:
-    hoek "2.x.x"
-
-source-list-map@^2.0.0:
-  version "2.0.0"
-  resolved "https://registry.yarnpkg.com/source-list-map/-/source-list-map-2.0.0.tgz#aaa47403f7b245a92fbc97ea08f250d6087ed085"
-
 source-map-support@^0.4.2:
   version "0.4.15"
   resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.4.15.tgz#03202df65c06d2bd8c7ec2362a193056fef8d3b1"
   dependencies:
     source-map "^0.5.6"
 
-source-map@^0.5.0, source-map@^0.5.3, source-map@^0.5.6, source-map@~0.5.1, source-map@~0.5.3:
+source-map@^0.5.0, source-map@^0.5.6:
   version "0.5.6"
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.5.6.tgz#75ce38f52bf0733c5a7f0c118d81334a2bb5f412"
 
+source-map@~0.6.1:
+  version "0.6.1"
+  resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.6.1.tgz#74722af32e9614e9c287a8d0bbde48b5e2f1a263"
+
 spark-md5@^3.0.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/spark-md5/-/spark-md5-3.0.0.tgz#3722227c54e2faf24b1dc6d933cc144e6f71bfef"
@@ -2770,45 +1786,6 @@ sprintf-js@~1.0.2:
   version "1.0.3"
   resolved "https://registry.yarnpkg.com/sprintf-js/-/sprintf-js-1.0.3.tgz#04e6926f662895354f3dd015203633b857297e2c"
 
-sshpk@^1.7.0:
-  version "1.13.1"
-  resolved "https://registry.yarnpkg.com/sshpk/-/sshpk-1.13.1.tgz#512df6da6287144316dc4c18fe1cf1d940739be3"
-  dependencies:
-    asn1 "~0.2.3"
-    assert-plus "^1.0.0"
-    dashdash "^1.12.0"
-    getpass "^0.1.1"
-  optionalDependencies:
-    bcrypt-pbkdf "^1.0.0"
-    ecc-jsbn "~0.1.1"
-    jsbn "~0.1.0"
-    tweetnacl "~0.14.0"
-
-stream-browserify@^2.0.1:
-  version "2.0.1"
-  resolved "https://registry.yarnpkg.com/stream-browserify/-/stream-browserify-2.0.1.tgz#66266ee5f9bdb9940a4e4514cafb43bb71e5c9db"
-  dependencies:
-    inherits "~2.0.1"
-    readable-stream "^2.0.2"
-
-stream-http@^2.3.1:
-  version "2.7.2"
-  resolved "https://registry.yarnpkg.com/stream-http/-/stream-http-2.7.2.tgz#40a050ec8dc3b53b33d9909415c02c0bf1abfbad"
-  dependencies:
-    builtin-status-codes "^3.0.0"
-    inherits "^2.0.1"
-    readable-stream "^2.2.6"
-    to-arraybuffer "^1.0.0"
-    xtend "^4.0.0"
-
-string-width@^1.0.1, string-width@^1.0.2:
-  version "1.0.2"
-  resolved "https://registry.yarnpkg.com/string-width/-/string-width-1.0.2.tgz#118bdf5b8cdc51a2a7e70d211e07e2b0b9b107d3"
-  dependencies:
-    code-point-at "^1.0.0"
-    is-fullwidth-code-point "^1.0.0"
-    strip-ansi "^3.0.0"
-
 string-width@^2.0.0, string-width@^2.1.0:
   version "2.1.1"
   resolved "https://registry.yarnpkg.com/string-width/-/string-width-2.1.1.tgz#ab93f27a8dc13d28cac815c462143a6d9012ae9e"
@@ -2816,21 +1793,13 @@ string-width@^2.0.0, string-width@^2.1.0:
     is-fullwidth-code-point "^2.0.0"
     strip-ansi "^4.0.0"
 
-string_decoder@^0.10.25:
-  version "0.10.31"
-  resolved "https://registry.yarnpkg.com/string_decoder/-/string_decoder-0.10.31.tgz#62e203bc41766c6c28c9fc84301dab1c5310fa94"
-
 string_decoder@~1.0.3:
   version "1.0.3"
   resolved "https://registry.yarnpkg.com/string_decoder/-/string_decoder-1.0.3.tgz#0fc67d7c141825de94282dd536bec6b9bce860ab"
   dependencies:
     safe-buffer "~5.1.0"
 
-stringstream@~0.0.4:
-  version "0.0.5"
-  resolved "https://registry.yarnpkg.com/stringstream/-/stringstream-0.0.5.tgz#4e484cd4de5a0bbbee18e46307710a8a81621878"
-
-strip-ansi@^3.0.0, strip-ansi@^3.0.1:
+strip-ansi@^3.0.0:
   version "3.0.1"
   resolved "https://registry.yarnpkg.com/strip-ansi/-/strip-ansi-3.0.1.tgz#6a385fb8853d952d5ff05d0e8aaf94278dc63dcf"
   dependencies:
@@ -2846,10 +1815,6 @@ strip-bom@^3.0.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/strip-bom/-/strip-bom-3.0.0.tgz#2334c18e9c759f7bdd56fdef7e9ae3d588e68ed3"
 
-strip-eof@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/strip-eof/-/strip-eof-1.0.0.tgz#bb43ff5598a6eb05d89b59fcd129c983313606bf"
-
 strip-json-comments@~2.0.1:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/strip-json-comments/-/strip-json-comments-2.0.1.tgz#3c531942e908c2697c0ec344858c286c7ca0a60a"
@@ -2858,7 +1823,7 @@ supports-color@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/supports-color/-/supports-color-2.0.0.tgz#535d045ce6b6363fa40117084629995e9df324c7"
 
-supports-color@^4.0.0, supports-color@^4.2.1:
+supports-color@^4.0.0:
   version "4.2.1"
   resolved "https://registry.yarnpkg.com/supports-color/-/supports-color-4.2.1.tgz#65a4bb2631e90e02420dba5554c375a4754bb836"
   dependencies:
@@ -2875,31 +1840,6 @@ table@^4.0.1:
     slice-ansi "0.0.4"
     string-width "^2.0.0"
 
-tapable@^0.2.7:
-  version "0.2.7"
-  resolved "https://registry.yarnpkg.com/tapable/-/tapable-0.2.7.tgz#e46c0daacbb2b8a98b9b0cea0f4052105817ed5c"
-
-tar-pack@^3.4.0:
-  version "3.4.0"
-  resolved "https://registry.yarnpkg.com/tar-pack/-/tar-pack-3.4.0.tgz#23be2d7f671a8339376cbdb0b8fe3fdebf317984"
-  dependencies:
-    debug "^2.2.0"
-    fstream "^1.0.10"
-    fstream-ignore "^1.0.5"
-    once "^1.3.3"
-    readable-stream "^2.1.4"
-    rimraf "^2.5.1"
-    tar "^2.2.1"
-    uid-number "^0.0.6"
-
-tar@^2.2.1:
-  version "2.2.1"
-  resolved "https://registry.yarnpkg.com/tar/-/tar-2.2.1.tgz#8e4d2a256c0e2185c6b18ad694aec968b83cb1d1"
-  dependencies:
-    block-stream "*"
-    fstream "^1.0.2"
-    inherits "2"
-
 text-table@~0.2.0:
   version "0.2.0"
   resolved "https://registry.yarnpkg.com/text-table/-/text-table-0.2.0.tgz#7f5ee823ae805207c00af2df4a84ec3fcfa570b4"
@@ -2908,32 +1848,16 @@ through@^2.3.6:
   version "2.3.8"
   resolved "https://registry.yarnpkg.com/through/-/through-2.3.8.tgz#0dd4c9ffaabc357960b1b724115d7e0e86a2e1f5"
 
-timers-browserify@^2.0.2:
-  version "2.0.2"
-  resolved "https://registry.yarnpkg.com/timers-browserify/-/timers-browserify-2.0.2.tgz#ab4883cf597dcd50af211349a00fbca56ac86b86"
-  dependencies:
-    setimmediate "^1.0.4"
-
 tmp@^0.0.31:
   version "0.0.31"
   resolved "https://registry.yarnpkg.com/tmp/-/tmp-0.0.31.tgz#8f38ab9438e17315e5dbd8b3657e8bfb277ae4a7"
   dependencies:
     os-tmpdir "~1.0.1"
 
-to-arraybuffer@^1.0.0:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/to-arraybuffer/-/to-arraybuffer-1.0.1.tgz#7d229b1fcc637e466ca081180836a7aabff83f43"
-
 to-fast-properties@^1.0.1:
   version "1.0.3"
   resolved "https://registry.yarnpkg.com/to-fast-properties/-/to-fast-properties-1.0.3.tgz#b83571fa4d8c25b82e231b06e3a3055de4ca1a47"
 
-tough-cookie@~2.3.0:
-  version "2.3.2"
-  resolved "https://registry.yarnpkg.com/tough-cookie/-/tough-cookie-2.3.2.tgz#f081f76e4c85720e6c37a5faced737150d84072a"
-  dependencies:
-    punycode "^1.4.1"
-
 trim-right@^1.0.1:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/trim-right/-/trim-right-1.0.1.tgz#cb2e1203067e0c8de1f614094b9fe45704ea6003"
@@ -2942,20 +1866,6 @@ tryit@^1.0.1:
   version "1.0.3"
   resolved "https://registry.yarnpkg.com/tryit/-/tryit-1.0.3.tgz#393be730a9446fd1ead6da59a014308f36c289cb"
 
-tty-browserify@0.0.0:
-  version "0.0.0"
-  resolved "https://registry.yarnpkg.com/tty-browserify/-/tty-browserify-0.0.0.tgz#a157ba402da24e9bf957f9aa69d524eed42901a6"
-
-tunnel-agent@^0.6.0:
-  version "0.6.0"
-  resolved "https://registry.yarnpkg.com/tunnel-agent/-/tunnel-agent-0.6.0.tgz#27a5dea06b36b04a0a9966774b290868f0fc40fd"
-  dependencies:
-    safe-buffer "^5.0.1"
-
-tweetnacl@^0.14.3, tweetnacl@~0.14.0:
-  version "0.14.5"
-  resolved "https://registry.yarnpkg.com/tweetnacl/-/tweetnacl-0.14.5.tgz#5ae68177f192d4456269d108afa93ff8743f4f64"
-
 type-check@~0.3.2:
   version "0.3.2"
   resolved "https://registry.yarnpkg.com/type-check/-/type-check-0.3.2.tgz#5884cab512cf1d355e3fb784f30804b2b520db72"
@@ -2966,52 +1876,17 @@ typedarray@^0.0.6:
   version "0.0.6"
   resolved "https://registry.yarnpkg.com/typedarray/-/typedarray-0.0.6.tgz#867ac74e3864187b1d3d47d996a78ec5c8830777"
 
-uglify-js@^2.8.29:
-  version "2.8.29"
-  resolved "https://registry.yarnpkg.com/uglify-js/-/uglify-js-2.8.29.tgz#29c5733148057bb4e1f75df35b7a9cb72e6a59dd"
-  dependencies:
-    source-map "~0.5.1"
-    yargs "~3.10.0"
-  optionalDependencies:
-    uglify-to-browserify "~1.0.0"
-
-uglify-to-browserify@~1.0.0:
-  version "1.0.2"
-  resolved "https://registry.yarnpkg.com/uglify-to-browserify/-/uglify-to-browserify-1.0.2.tgz#6e0924d6bda6b5afe349e39a6d632850a0f882b7"
-
-uglifyjs-webpack-plugin@^0.4.6:
-  version "0.4.6"
-  resolved "https://registry.yarnpkg.com/uglifyjs-webpack-plugin/-/uglifyjs-webpack-plugin-0.4.6.tgz#b951f4abb6bd617e66f63eb891498e391763e309"
+uglify-es@^3.3.7:
+  version "3.3.9"
+  resolved "https://registry.yarnpkg.com/uglify-es/-/uglify-es-3.3.9.tgz#0c1c4f0700bed8dbc124cdb304d2592ca203e677"
   dependencies:
-    source-map "^0.5.6"
-    uglify-js "^2.8.29"
-    webpack-sources "^1.0.1"
-
-uid-number@^0.0.6:
-  version "0.0.6"
-  resolved "https://registry.yarnpkg.com/uid-number/-/uid-number-0.0.6.tgz#0ea10e8035e8eb5b8e4449f06da1c730663baa81"
-
-url@^0.11.0:
-  version "0.11.0"
-  resolved "https://registry.yarnpkg.com/url/-/url-0.11.0.tgz#3838e97cfc60521eb73c525a8e55bfdd9e2e28f1"
-  dependencies:
-    punycode "1.3.2"
-    querystring "0.2.0"
+    commander "~2.13.0"
+    source-map "~0.6.1"
 
 util-deprecate@~1.0.1:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/util-deprecate/-/util-deprecate-1.0.2.tgz#450d4dc9fa70de732762fbd2d4a28981419a0ccf"
 
-util@0.10.3, util@^0.10.3:
-  version "0.10.3"
-  resolved "https://registry.yarnpkg.com/util/-/util-0.10.3.tgz#7afb1afe50805246489e3db7fe0ed379336ac0f9"
-  dependencies:
-    inherits "2.0.1"
-
-uuid@^3.0.0:
-  version "3.1.0"
-  resolved "https://registry.yarnpkg.com/uuid/-/uuid-3.1.0.tgz#3dd3d3e790abc24d7b0d3a034ffababe28ebbc04"
-
 validate-npm-package-license@^3.0.1:
   version "3.0.1"
   resolved "https://registry.yarnpkg.com/validate-npm-package-license/-/validate-npm-package-license-3.0.1.tgz#2804babe712ad3379459acfbe24746ab2c303fbc"
@@ -3019,63 +1894,9 @@ validate-npm-package-license@^3.0.1:
     spdx-correct "~1.0.0"
     spdx-expression-parse "~1.0.0"
 
-verror@1.3.6:
-  version "1.3.6"
-  resolved "https://registry.yarnpkg.com/verror/-/verror-1.3.6.tgz#cff5df12946d297d2baaefaa2689e25be01c005c"
-  dependencies:
-    extsprintf "1.0.2"
-
-vm-browserify@0.0.4:
-  version "0.0.4"
-  resolved "https://registry.yarnpkg.com/vm-browserify/-/vm-browserify-0.0.4.tgz#5d7ea45bbef9e4a6ff65f95438e0a87c357d5a73"
-  dependencies:
-    indexof "0.0.1"
-
-watchpack@^1.4.0:
-  version "1.4.0"
-  resolved "https://registry.yarnpkg.com/watchpack/-/watchpack-1.4.0.tgz#4a1472bcbb952bd0a9bb4036801f954dfb39faac"
-  dependencies:
-    async "^2.1.2"
-    chokidar "^1.7.0"
-    graceful-fs "^4.1.2"
-
-webpack-sources@^1.0.1:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/webpack-sources/-/webpack-sources-1.0.1.tgz#c7356436a4d13123be2e2426a05d1dad9cbe65cf"
-  dependencies:
-    source-list-map "^2.0.0"
-    source-map "~0.5.3"
-
-webpack@^3.4.0:
-  version "3.4.0"
-  resolved "https://registry.yarnpkg.com/webpack/-/webpack-3.4.0.tgz#e9465b660ad79dd2d33874d968b31746ea9a8e63"
-  dependencies:
-    acorn "^5.0.0"
-    acorn-dynamic-import "^2.0.0"
-    ajv "^5.1.5"
-    ajv-keywords "^2.0.0"
-    async "^2.1.2"
-    enhanced-resolve "^3.4.0"
-    escope "^3.6.0"
-    interpret "^1.0.0"
-    json-loader "^0.5.4"
-    json5 "^0.5.1"
-    loader-runner "^2.3.0"
-    loader-utils "^1.1.0"
-    memory-fs "~0.4.1"
-    mkdirp "~0.5.0"
-    node-libs-browser "^2.0.0"
-    source-map "^0.5.3"
-    supports-color "^4.2.1"
-    tapable "^0.2.7"
-    uglifyjs-webpack-plugin "^0.4.6"
-    watchpack "^1.4.0"
-    webpack-sources "^1.0.1"
-    yargs "^8.0.2"
-
-which-module@^2.0.0:
-  version "2.0.0"
-  resolved "https://registry.yarnpkg.com/which-module/-/which-module-2.0.0.tgz#d9ef07dce77b9902b8a3a8fa4b31c3e3f7e6e87a"
+vlq@^0.2.2:
+  version "0.2.3"
+  resolved "https://registry.yarnpkg.com/vlq/-/vlq-0.2.3.tgz#8f3e4328cf63b1540c0d67e1b2778386f8975b26"
 
 which@^1.2.9:
   version "1.2.14"
@@ -3083,31 +1904,10 @@ which@^1.2.9:
   dependencies:
     isexe "^2.0.0"
 
-wide-align@^1.1.0:
-  version "1.1.2"
-  resolved "https://registry.yarnpkg.com/wide-align/-/wide-align-1.1.2.tgz#571e0f1b0604636ebc0dfc21b0339bbe31341710"
-  dependencies:
-    string-width "^1.0.2"
-
-window-size@0.1.0:
-  version "0.1.0"
-  resolved "https://registry.yarnpkg.com/window-size/-/window-size-0.1.0.tgz#5438cd2ea93b202efa3a19fe8887aee7c94f9c9d"
-
-wordwrap@0.0.2:
-  version "0.0.2"
-  resolved "https://registry.yarnpkg.com/wordwrap/-/wordwrap-0.0.2.tgz#b79669bb42ecb409f83d583cad52ca17eaa1643f"
-
 wordwrap@~1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/wordwrap/-/wordwrap-1.0.0.tgz#27584810891456a4171c8d0226441ade90cbcaeb"
 
-wrap-ansi@^2.0.0:
-  version "2.1.0"
-  resolved "https://registry.yarnpkg.com/wrap-ansi/-/wrap-ansi-2.1.0.tgz#d8fc3d284dd05794fe84973caecdd1cf824fdd85"
-  dependencies:
-    string-width "^1.0.1"
-    strip-ansi "^3.0.1"
-
 wrappy@1:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/wrappy/-/wrappy-1.0.2.tgz#b5243d8f3ec1aa35f1364605bc0d1036e30ab69f"
@@ -3118,47 +1918,6 @@ write@^0.2.1:
   dependencies:
     mkdirp "^0.5.1"
 
-xtend@^4.0.0:
-  version "4.0.1"
-  resolved "https://registry.yarnpkg.com/xtend/-/xtend-4.0.1.tgz#a5c6d532be656e23db820efb943a1f04998d63af"
-
-y18n@^3.2.1:
-  version "3.2.1"
-  resolved "https://registry.yarnpkg.com/y18n/-/y18n-3.2.1.tgz#6d15fba884c08679c0d77e88e7759e811e07fa41"
-
 yallist@^2.1.2:
   version "2.1.2"
   resolved "https://registry.yarnpkg.com/yallist/-/yallist-2.1.2.tgz#1c11f9218f076089a47dd512f93c6699a6a81d52"
-
-yargs-parser@^7.0.0:
-  version "7.0.0"
-  resolved "https://registry.yarnpkg.com/yargs-parser/-/yargs-parser-7.0.0.tgz#8d0ac42f16ea55debd332caf4c4038b3e3f5dfd9"
-  dependencies:
-    camelcase "^4.1.0"
-
-yargs@^8.0.2:
-  version "8.0.2"
-  resolved "https://registry.yarnpkg.com/yargs/-/yargs-8.0.2.tgz#6299a9055b1cefc969ff7e79c1d918dceb22c360"
-  dependencies:
-    camelcase "^4.1.0"
-    cliui "^3.2.0"
-    decamelize "^1.1.1"
-    get-caller-file "^1.0.1"
-    os-locale "^2.0.0"
-    read-pkg-up "^2.0.0"
-    require-directory "^2.1.1"
-    require-main-filename "^1.0.1"
-    set-blocking "^2.0.0"
-    string-width "^2.0.0"
-    which-module "^2.0.0"
-    y18n "^3.2.1"
-    yargs-parser "^7.0.0"
-
-yargs@~3.10.0:
-  version "3.10.0"
-  resolved "https://registry.yarnpkg.com/yargs/-/yargs-3.10.0.tgz#f7ee7bd857dd7c1d2d38c0e74efbd681d1431fd1"
-  dependencies:
-    camelcase "^1.0.2"
-    cliui "^2.1.0"
-    decamelize "^1.0.0"
-    window-size "0.1.0"
diff --git a/activesupport/.gitignore b/activesupport/.gitignore
new file mode 100644
index 0000000000..8cde8514fd
--- /dev/null
+++ b/activesupport/.gitignore
@@ -0,0 +1 @@
+/test/fixtures/isolation_test/
diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index ac1043df78..91818c3112 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,190 +1,135 @@
-*   `Module#delegate_missing_to` now raises `DelegationError` if target is nil,
-    similar to `Module#delegate`.
+*   Allow Range#=== and Range#cover? on Range
 
-    *Anton Khamets*
+    `Range#cover?` can now accept a range argument like `Range#include?` and
+    `Range#===`. `Range#===` works correctly on Ruby 2.6. `Range#include?` is moved
+    into a new file, with these two methods.
 
-*   Update `String#camelize` to provide feedback when wrong option is passed
+    *Requiring active_support/core_ext/range/include_range is now deprecated.*
+    *Use `require "active_support/core_ext/range/compare_range"` instead.*
 
-    `String#camelize` was returning nil without any feedback when an
-    invalid option was passed as a parameter.
+    *utilum*
 
-    Previously:
+*   Add `index_with` to Enumerable.
 
-        'one_two'.camelize(true)
-        => nil
+    Allows creating a hash from an enumerable with the value from a passed block
+    or a default argument.
 
-    Now:
+        %i( title body ).index_with { |attr| post.public_send(attr) }
+        # => { title: "hey", body: "what's up?" }
 
-        'one_two'.camelize(true)
-        => ArgumentError: Invalid option, use either :upper or :lower.
+        %i( title body ).index_with(nil)
+        # => { title: nil, body: nil }
 
-    *Ricardo Díaz*
+    Closely linked with its brethen `index_by`.
 
-*   Fix modulo operations involving durations
+    *Kasper Timm Hansen*
 
-    Rails 5.1 introduced `ActiveSupport::Duration::Scalar` as a wrapper
-    around numeric values as a way of ensuring a duration was the outcome of
-    an expression. However, the implementation was missing support for modulo
-    operations. This support has now been added and should result in a duration
-    being returned from expressions involving modulo operations.
+*   Fix bug where `ActiveSupport::Timezone.all` would fail when tzinfo data for
+    any timezone defined in `ActiveSupport::TimeZone::MAPPING` is missing.
 
-    Prior to Rails 5.1:
+    *Dominik Sander*
 
-        5.minutes % 2.minutes
-        => 60
+*   Redis cache store: `delete_matched` no longer blocks the Redis server.
+    (Switches from evaled Lua to a batched SCAN + DEL loop.)
 
-    Now:
+    *Gleb Mazovetskiy*
 
-        5.minutes % 2.minutes
-        => 1 minute
+*   Fix bug where `ActiveSupport::Cache` will massively inflate the storage
+    size when compression is enabled (which is true by default). This patch
+    does not attempt to repair existing data: please manually flush the cache
+    to clear out the problematic entries.
 
-    Fixes #29603 and #29743.
+    *Godfrey Chan*
 
-    *Sayan Chakraborty*, *Andrew White*
+*   Fix bug where `URI.unscape` would fail with mixed Unicode/escaped character input:
 
-*   Fix division where a duration is the denominator
+        URI.unescape("\xe3\x83\x90")  # => "バ"
+        URI.unescape("%E3%83%90")  # => "バ"
+        URI.unescape("\xe3\x83\x90%E3%83%90")  # => Encoding::CompatibilityError
 
-    PR #29163 introduced a change in behavior when a duration was the denominator
-    in a calculation - this was incorrect as dividing by a duration should always
-    return a `Numeric`. The behavior of previous versions of Rails has been restored.
+    *Ashe Connor*, *Aaron Patterson*
 
-    Fixes #29592.
+*   Add `before?` and `after?` methods to `Date`, `DateTime`,
+    `Time`, and `TimeWithZone`.
 
-    *Andrew White*
+    *Nick Holden*
 
-*   Add purpose and expiry support to `ActiveSupport::MessageVerifier` &
-   `ActiveSupport::MessageEncryptor`.
+*   `ActiveSupport::Inflector#ordinal` and `ActiveSupport::Inflector#ordinalize` now support
+    translations through I18n.
 
-    For instance, to ensure a message is only usable for one intended purpose:
+        # locale/fr.rb
 
-        token = @verifier.generate("x", purpose: :shipping)
+        {
+          fr: {
+            number: {
+              nth: {
+                ordinals: lambda do |_key, number:, **_options|
+                  if number.to_i.abs == 1
+                    'er'
+                  else
+                    'e'
+                  end
+                end,
 
-        @verifier.verified(token, purpose: :shipping) # => "x"
-        @verifier.verified(token)                     # => nil
+                ordinalized: lambda do |_key, number:, **_options|
+                  "#{number}#{ActiveSupport::Inflector.ordinal(number)}"
+                end
+              }
+            }
+          }
+        }
 
-    Or make it expire after a set time:
 
-        @verifier.generate("x", expires_in: 1.month)
-        @verifier.generate("y", expires_at: Time.now.end_of_year)
+    *Christian Blais*
 
-    Showcased with `ActiveSupport::MessageVerifier`, but works the same for
-    `ActiveSupport::MessageEncryptor`'s `encrypt_and_sign` and `decrypt_and_verify`.
+*   Add `:private` option to ActiveSupport's `Module#delegate`
+    in order to delegate methods as private:
 
-    Pull requests: #29599, #29854
+        class User < ActiveRecord::Base
+          has_one :profile
+          delegate :date_of_birth, to: :profile, private: true
 
-    *Assain Jaleel*
+          def age
+            Date.today.year - date_of_birth.year
+          end
+        end
 
-*   Make the order of `Hash#reverse_merge!` consistent with `HashWithIndifferentAccess`.
+        # User.new.age  # => 29
+        # User.new.date_of_birth
+        # => NoMethodError: private method `date_of_birth' called for #<User:0x00000008221340>
 
-    *Erol Fornoles*
+    *Tomas Valent*
 
-*   Add `freeze_time` helper which freezes time to `Time.now` in tests.
-
-    *Prathamesh Sonpatki*
-
-*   Default `ActiveSupport::MessageEncryptor` to use AES 256 GCM encryption.
-
-    On for new Rails 5.2 apps. Upgrading apps can find the config as a new
-    framework default.
-
-    *Assain Jaleel*
-
-*   Cache: `write_multi`
-
-        Rails.cache.write_multi foo: 'bar', baz: 'qux'
-
-    Plus faster fetch_multi with stores that implement `write_multi_entries`.
-    Keys that aren't found may be written to the cache store in one shot
-    instead of separate writes.
-
-    The default implementation simply calls `write_entry` for each entry.
-    Stores may override if they're capable of one-shot bulk writes, like
-    Redis `MSET`.
+*   `String#truncate_bytes` to truncate a string to a maximum bytesize without
+    breaking multibyte characters or grapheme clusters like 👩‍👩‍👦‍👦.
 
     *Jeremy Daer*
 
-*   Add default option to module and class attribute accessors.
-
-        mattr_accessor :settings, default: {}
-
-    Works for `mattr_reader`, `mattr_writer`, `cattr_accessor`, `cattr_reader`,
-    and `cattr_writer` as well.
-
-    *Genadi Samokovarov*
-
-*   Add `Date#prev_occurring` and `Date#next_occurring` to return specified next/previous occurring day of week.
-
-    *Shota Iguchi*
-
-*   Add default option to `class_attribute`.
-
-    Before:
-
-        class_attribute :settings
-        self.settings = {}
-
-    Now:
+*   `String#strip_heredoc` preserves frozenness.
 
-        class_attribute :settings, default: {}
+        "foo".freeze.strip_heredoc.frozen?  # => true
 
-    *DHH*
+    Fixes that frozen string literals would inadvertently become unfrozen:
 
-*   `#singularize` and `#pluralize` now respect uncountables for the specified locale.
+        # frozen_string_literal: true
 
-    *Eilis Hamilton*
+        foo = <<-MSG.strip_heredoc
+          la la la
+        MSG
 
-*   Add `ActiveSupport::CurrentAttributes` to provide a thread-isolated attributes singleton.
-    Primary use case is keeping all the per-request attributes easily available to the whole system.
+        foo.frozen?  # => false !??
 
-    *DHH*
-
-*   Fix implicit coercion calculations with scalars and durations
-
-    Previously, calculations where the scalar is first would be converted to a duration
-    of seconds, but this causes issues with dates being converted to times, e.g:
-
-        Time.zone = "Beijing"           # => Asia/Shanghai
-        date = Date.civil(2017, 5, 20)  # => Mon, 20 May 2017
-        2 * 1.day                       # => 172800 seconds
-        date + 2 * 1.day                # => Mon, 22 May 2017 00:00:00 CST +08:00
-
-    Now, the `ActiveSupport::Duration::Scalar` calculation methods will try to maintain
-    the part structure of the duration where possible, e.g:
-
-        Time.zone = "Beijing"           # => Asia/Shanghai
-        date = Date.civil(2017, 5, 20)  # => Mon, 20 May 2017
-        2 * 1.day                       # => 2 days
-        date + 2 * 1.day                # => Mon, 22 May 2017
-
-    Fixes #29160, #28970.
-
-    *Andrew White*
-
-*   Add support for versioned cache entries. This enables the cache stores to recycle cache keys, greatly saving
-    on storage in cases with frequent churn. Works together with the separation of `#cache_key` and `#cache_version`
-    in Active Record and its use in Action Pack's fragment caching.
-
-    *DHH*
-
-*   Pass gem name and deprecation horizon to deprecation notifications.
-
-    *Willem van Bergen*
-
-*   Add support for `:offset` and `:zone` to `ActiveSupport::TimeWithZone#change`
-
-    *Andrew White*
-
-*   Add support for `:offset` to `Time#change`
+    *Jeremy Daer*
 
-    Fixes #28723.
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
-    *Andrew White*
+    *Jeremy Daer*
 
-*   Add `fetch_values` for `HashWithIndifferentAccess`
+*   Adds parallel testing to Rails.
 
-    The method was originally added to `Hash` in Ruby 2.3.0.
+    Parallelize your test suite with forked processes or threads.
 
-    *Josh Pencheon*
+    *Eileen M. Uchitelle*, *Aaron Patterson*
 
 
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/activesupport/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/activesupport/CHANGELOG.md) for previous changes.
diff --git a/activesupport/MIT-LICENSE b/activesupport/MIT-LICENSE
index 6b3cead1a7..8f769c0767 100644
--- a/activesupport/MIT-LICENSE
+++ b/activesupport/MIT-LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2005-2017 David Heinemeier Hansson
+Copyright (c) 2005-2018 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/activesupport/README.rdoc b/activesupport/README.rdoc
index 8b47933bd2..c770324be8 100644
--- a/activesupport/README.rdoc
+++ b/activesupport/README.rdoc
@@ -30,7 +30,7 @@ API documentation is at:
 
 * http://api.rubyonrails.org
 
-Bug reports can be filed for the Ruby on Rails project here:
+Bug reports for the Ruby on Rails project can be filed here:
 
 * https://github.com/rails/rails/issues
 
diff --git a/activesupport/Rakefile b/activesupport/Rakefile
index 8672ab1542..f10f19be0a 100644
--- a/activesupport/Rakefile
+++ b/activesupport/Rakefile
@@ -14,10 +14,30 @@ Rake::TestTask.new do |t|
   t.ruby_opts = ["--dev"] if defined?(JRUBY_VERSION)
 end
 
+Rake::Task[:test].enhance do
+  Rake::Task["test:cache_stores:redis:ruby"].invoke
+end
+
 namespace :test do
   task :isolated do
     Dir.glob("test/**/*_test.rb").all? do |file|
       sh(Gem.ruby, "-w", "-Ilib:test", file)
     end || raise("Failures")
   end
+
+  namespace :cache_stores do
+    namespace :redis do
+      %w[ ruby hiredis ].each do |driver|
+        task("env:#{driver}") { ENV["REDIS_DRIVER"] = driver }
+
+        Rake::TestTask.new(driver => "env:#{driver}") do |t|
+          t.libs << "test"
+          t.test_files = ["test/cache/stores/redis_cache_store_test.rb"]
+          t.warning = true
+          t.verbose = true
+          t.ruby_opts = ["--dev"] if defined?(JRUBY_VERSION)
+        end
+      end
+    end
+  end
 end
diff --git a/activesupport/activesupport.gemspec b/activesupport/activesupport.gemspec
index db801d2da2..aa695c98b2 100644
--- a/activesupport/activesupport.gemspec
+++ b/activesupport/activesupport.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "A toolkit of support libraries and Ruby core extensions extracted from the Rails framework."
   s.description = "A toolkit of support libraries and Ruby core extensions extracted from the Rails framework. Rich support for multibyte strings, internationalization, time zones, and testing."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
@@ -27,7 +27,7 @@ Gem::Specification.new do |s|
     "changelog_uri"   => "https://github.com/rails/rails/blob/v#{version}/activesupport/CHANGELOG.md"
   }
 
-  s.add_dependency "i18n",       "~> 0.7"
+  s.add_dependency "i18n",       ">= 0.7", "< 2"
   s.add_dependency "tzinfo",     "~> 1.1"
   s.add_dependency "minitest",   "~> 5.1"
   s.add_dependency "concurrent-ruby", "~> 1.0", ">= 1.0.2"
diff --git a/activesupport/bin/generate_tables b/activesupport/bin/generate_tables
deleted file mode 100755
index 18199b2171..0000000000
--- a/activesupport/bin/generate_tables
+++ /dev/null
@@ -1,141 +0,0 @@
-#!/usr/bin/env ruby
-# frozen_string_literal: true
-
-begin
-  $:.unshift(File.expand_path("../lib", __dir__))
-  require "active_support"
-rescue IOError
-end
-
-require "open-uri"
-require "tmpdir"
-require "fileutils"
-
-module ActiveSupport
-  module Multibyte
-    module Unicode
-      class UnicodeDatabase
-        def load; end
-      end
-
-      class DatabaseGenerator
-        BASE_URI = "http://www.unicode.org/Public/#{UNICODE_VERSION}/ucd/"
-        SOURCES = {
-          codepoints: BASE_URI + "UnicodeData.txt",
-          composition_exclusion: BASE_URI + "CompositionExclusions.txt",
-          grapheme_break_property: BASE_URI + "auxiliary/GraphemeBreakProperty.txt",
-          cp1252: "http://unicode.org/Public/MAPPINGS/VENDORS/MICSFT/WINDOWS/CP1252.TXT"
-        }
-
-        def initialize
-          @ucd = Unicode::UnicodeDatabase.new
-        end
-
-        def parse_codepoints(line)
-          codepoint = Codepoint.new
-          raise "Could not parse input." unless line =~ /^
-            ([0-9A-F]+);        # code
-            ([^;]+);            # name
-            ([A-Z]+);           # general category
-            ([0-9]+);           # canonical combining class
-            ([A-Z]+);           # bidi class
-            (<([A-Z]*)>)?       # decomposition type
-            ((\ ?[0-9A-F]+)*);  # decomposition mapping
-            ([0-9]*);           # decimal digit
-            ([0-9]*);           # digit
-            ([^;]*);            # numeric
-            ([YN]*);            # bidi mirrored
-            ([^;]*);            # unicode 1.0 name
-            ([^;]*);            # iso comment
-            ([0-9A-F]*);        # simple uppercase mapping
-            ([0-9A-F]*);        # simple lowercase mapping
-            ([0-9A-F]*)$/ix     # simple titlecase mapping
-          codepoint.code              = $1.hex
-          codepoint.combining_class   = Integer($4)
-          codepoint.decomp_type       = $7
-          codepoint.decomp_mapping    = ($8 == "") ? nil : $8.split.collect(&:hex)
-          codepoint.uppercase_mapping = ($16 == "") ? 0 : $16.hex
-          codepoint.lowercase_mapping = ($17 == "") ? 0 : $17.hex
-          @ucd.codepoints[codepoint.code] = codepoint
-        end
-
-        def parse_grapheme_break_property(line)
-          if line =~ /^([0-9A-F.]+)\s*;\s*([\w]+)\s*#/
-            type = $2.downcase.intern
-            @ucd.boundary[type] ||= []
-            if $1.include? ".."
-              parts = $1.split ".."
-              @ucd.boundary[type] << (parts[0].hex..parts[1].hex)
-            else
-              @ucd.boundary[type] << $1.hex
-            end
-          end
-        end
-
-        def parse_composition_exclusion(line)
-          if line =~ /^([0-9A-F]+)/i
-            @ucd.composition_exclusion << $1.hex
-          end
-        end
-
-        def parse_cp1252(line)
-          if line =~ /^([0-9A-Fx]+)\s([0-9A-Fx]+)/i
-            @ucd.cp1252[$1.hex] = $2.hex
-          end
-        end
-
-        def create_composition_map
-          @ucd.codepoints.each do |_, cp|
-            if !cp.nil? && cp.combining_class == 0 && cp.decomp_type.nil? && !cp.decomp_mapping.nil? && cp.decomp_mapping.length == 2 && @ucd.codepoints[cp.decomp_mapping[0]].combining_class == 0 && !@ucd.composition_exclusion.include?(cp.code)
-              @ucd.composition_map[cp.decomp_mapping[0]] ||= {}
-              @ucd.composition_map[cp.decomp_mapping[0]][cp.decomp_mapping[1]] = cp.code
-            end
-          end
-        end
-
-        def normalize_boundary_map
-          @ucd.boundary.each do |k, v|
-            if [:lf, :cr].include? k
-              @ucd.boundary[k] = v[0]
-            end
-          end
-        end
-
-        def parse
-          SOURCES.each do |type, url|
-            filename = File.join(Dir.tmpdir, UNICODE_VERSION, "#{url.split('/').last}")
-            unless File.exist?(filename)
-              $stderr.puts "Downloading #{url.split('/').last}"
-              FileUtils.mkdir_p(File.dirname(filename))
-              File.open(filename, "wb") do |target|
-                open(url) do |source|
-                  source.each_line { |line| target.write line }
-                end
-              end
-            end
-            File.open(filename) do |file|
-              file.each_line { |line| send "parse_#{type}".intern, line }
-            end
-          end
-          create_composition_map
-          normalize_boundary_map
-        end
-
-        def dump_to(filename)
-          File.open(filename, "wb") do |f|
-            f.write Marshal.dump([@ucd.codepoints, @ucd.composition_exclusion, @ucd.composition_map, @ucd.boundary, @ucd.cp1252])
-          end
-        end
-      end
-    end
-  end
-end
-
-if __FILE__ == $0
-  filename = ActiveSupport::Multibyte::Unicode::UnicodeDatabase.filename
-  generator = ActiveSupport::Multibyte::Unicode::DatabaseGenerator.new
-  generator.parse
-  print "Writing to: #{filename}"
-  generator.dump_to filename
-  puts " (#{File.size(filename)} bytes)"
-end
diff --git a/activesupport/lib/active_support.rb b/activesupport/lib/active_support.rb
index 79b12f36b9..a4fb697669 100644
--- a/activesupport/lib/active_support.rb
+++ b/activesupport/lib/active_support.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 #--
-# Copyright (c) 2005-2017 David Heinemeier Hansson
+# Copyright (c) 2005-2018 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the
@@ -24,11 +24,11 @@
 #++
 
 require "securerandom"
-require_relative "active_support/dependencies/autoload"
-require_relative "active_support/version"
-require_relative "active_support/logger"
-require_relative "active_support/lazy_load_hooks"
-require_relative "active_support/core_ext/date_and_time/compatibility"
+require "active_support/dependencies/autoload"
+require "active_support/version"
+require "active_support/logger"
+require "active_support/lazy_load_hooks"
+require "active_support/core_ext/date_and_time/compatibility"
 
 module ActiveSupport
   extend ActiveSupport::Autoload
@@ -53,6 +53,7 @@ module ActiveSupport
     autoload :Callbacks
     autoload :Configurable
     autoload :Deprecation
+    autoload :Digest
     autoload :Gzip
     autoload :Inflector
     autoload :JSON
@@ -82,18 +83,6 @@ module ActiveSupport
 
   cattr_accessor :test_order # :nodoc:
 
-  def self.halt_callback_chains_on_return_false
-    ActiveSupport::Deprecation.warn(<<-MSG.squish)
-      ActiveSupport.halt_callback_chains_on_return_false is deprecated and will be removed in Rails 5.2.
-    MSG
-  end
-
-  def self.halt_callback_chains_on_return_false=(value)
-    ActiveSupport::Deprecation.warn(<<-MSG.squish)
-      ActiveSupport.halt_callback_chains_on_return_false= is deprecated and will be removed in Rails 5.2.
-    MSG
-  end
-
   def self.to_time_preserves_timezone
     DateAndTime::Compatibility.preserve_timezone
   end
diff --git a/activesupport/lib/active_support/all.rb b/activesupport/lib/active_support/all.rb
index 6638b25419..4adf446af8 100644
--- a/activesupport/lib/active_support/all.rb
+++ b/activesupport/lib/active_support/all.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 require "active_support"
-require_relative "time"
-require_relative "core_ext"
+require "active_support/time"
+require "active_support/core_ext"
diff --git a/activesupport/lib/active_support/benchmarkable.rb b/activesupport/lib/active_support/benchmarkable.rb
index 5573f6750e..f481d68198 100644
--- a/activesupport/lib/active_support/benchmarkable.rb
+++ b/activesupport/lib/active_support/benchmarkable.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/benchmark"
-require_relative "core_ext/hash/keys"
+require "active_support/core_ext/benchmark"
+require "active_support/core_ext/hash/keys"
 
 module ActiveSupport
   module Benchmarkable
diff --git a/activesupport/lib/active_support/cache.rb b/activesupport/lib/active_support/cache.rb
index 49d8965cb1..d769e2c8ea 100644
--- a/activesupport/lib/active_support/cache.rb
+++ b/activesupport/lib/active_support/cache.rb
@@ -1,21 +1,22 @@
 # frozen_string_literal: true
 
 require "zlib"
-require_relative "core_ext/array/extract_options"
-require_relative "core_ext/array/wrap"
-require_relative "core_ext/module/attribute_accessors"
-require_relative "core_ext/numeric/bytes"
-require_relative "core_ext/numeric/time"
-require_relative "core_ext/object/to_param"
-require_relative "core_ext/string/inflections"
+require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/array/wrap"
+require "active_support/core_ext/module/attribute_accessors"
+require "active_support/core_ext/numeric/bytes"
+require "active_support/core_ext/numeric/time"
+require "active_support/core_ext/object/to_param"
+require "active_support/core_ext/string/inflections"
 
 module ActiveSupport
   # See ActiveSupport::Cache::Store for documentation.
   module Cache
-    autoload :FileStore,     "active_support/cache/file_store"
-    autoload :MemoryStore,   "active_support/cache/memory_store"
-    autoload :MemCacheStore, "active_support/cache/mem_cache_store"
-    autoload :NullStore,     "active_support/cache/null_store"
+    autoload :FileStore,        "active_support/cache/file_store"
+    autoload :MemoryStore,      "active_support/cache/memory_store"
+    autoload :MemCacheStore,    "active_support/cache/mem_cache_store"
+    autoload :NullStore,        "active_support/cache/null_store"
+    autoload :RedisCacheStore,  "active_support/cache/redis_cache_store"
 
     # These options mean something to all cache implementations. Individual cache
     # implementations may support additional options.
@@ -148,18 +149,34 @@ module ActiveSupport
     #   cache.namespace = -> { @last_mod_time }  # Set the namespace to a variable
     #   @last_mod_time = Time.now  # Invalidate the entire cache by changing namespace
     #
-    # Caches can also store values in a compressed format to save space and
-    # reduce time spent sending data. Since there is overhead, values must be
-    # large enough to warrant compression. To turn on compression either pass
-    # <tt>compress: true</tt> in the initializer or as an option to +fetch+
-    # or +write+. To specify the threshold at which to compress values, set the
-    # <tt>:compress_threshold</tt> option. The default threshold is 16K.
+    # Cached data larger than 1kB are compressed by default. To turn off
+    # compression, pass <tt>compress: false</tt> to the initializer or to
+    # individual +fetch+ or +write+ method calls. The 1kB compression
+    # threshold is configurable with the <tt>:compress_threshold</tt> option,
+    # specified in bytes.
     class Store
       cattr_accessor :logger, instance_writer: true
 
       attr_reader :silence, :options
       alias :silence? :silence
 
+      class << self
+        private
+          def retrieve_pool_options(options)
+            {}.tap do |pool_options|
+              pool_options[:size] = options.delete(:pool_size) if options[:pool_size]
+              pool_options[:timeout] = options.delete(:pool_timeout) if options[:pool_timeout]
+            end
+          end
+
+          def ensure_connection_pool_added!
+            require "connection_pool"
+          rescue LoadError => e
+            $stderr.puts "You don't have connection_pool installed in your application. Please add it to your Gemfile and run bundle install"
+            raise e
+          end
+      end
+
       # Creates a new cache. The options will be passed to any write method calls
       # except for <tt>:namespace</tt> which can be used to set the global
       # namespace for the cache.
@@ -212,8 +229,7 @@ module ActiveSupport
       # ask whether you should force a cache write. Otherwise, it's clearer to
       # just call <tt>Cache#write</tt>.
       #
-      # Setting <tt>:compress</tt> will store a large cache entry set by the call
-      # in a compressed format.
+      # Setting <tt>compress: false</tt> disables compression of the cache entry.
       #
       # Setting <tt>:expires_in</tt> will set an expiration time on the cache.
       # All caches support auto-expiring content after a specified number of
@@ -317,8 +333,9 @@ module ActiveSupport
       # the cache with the given key, then that data is returned. Otherwise,
       # +nil+ is returned.
       #
-      # Note, if data was written with the <tt>:expires_in<tt> or <tt>:version</tt> options,
-      # both of these conditions are applied before the data is returned.
+      # Note, if data was written with the <tt>:expires_in</tt> or
+      # <tt>:version</tt> options, both of these conditions are applied before
+      # the data is returned.
       #
       # Options are passed to the underlying cache implementation.
       def read(name, options = nil)
@@ -358,23 +375,11 @@ module ActiveSupport
         options = names.extract_options!
         options = merged_options(options)
 
-        results = {}
-        names.each do |name|
-          key     = normalize_key(name, options)
-          version = normalize_version(name, options)
-          entry   = read_entry(key, options)
-
-          if entry
-            if entry.expired?
-              delete_entry(key, options)
-            elsif entry.mismatched?(version)
-              # Skip mismatched versions
-            else
-              results[name] = entry.value
-            end
+        instrument :read_multi, names, options do |payload|
+          read_multi_entries(names, options).tap do |results|
+            payload[:hits] = results.keys
           end
         end
-        results
       end
 
       # Cache Storage API to write multiple values at once.
@@ -415,14 +420,19 @@ module ActiveSupport
         options = names.extract_options!
         options = merged_options(options)
 
-        read_multi(*names, options).tap do |results|
-          writes = {}
+        instrument :read_multi, names, options do |payload|
+          read_multi_entries(names, options).tap do |results|
+            payload[:hits] = results.keys
+            payload[:super_operation] = :fetch_multi
 
-          (names - results.keys).each do |name|
-            results[name] = writes[name] = yield(name)
-          end
+            writes = {}
+
+            (names - results.keys).each do |name|
+              results[name] = writes[name] = yield(name)
+            end
 
-          write_multi writes, options
+            write_multi writes, options
+          end
         end
       end
 
@@ -539,6 +549,28 @@ module ActiveSupport
           raise NotImplementedError.new
         end
 
+        # Reads multiple entries from the cache implementation. Subclasses MAY
+        # implement this method.
+        def read_multi_entries(names, options)
+          results = {}
+          names.each do |name|
+            key     = normalize_key(name, options)
+            version = normalize_version(name, options)
+            entry   = read_entry(key, options)
+
+            if entry
+              if entry.expired?
+                delete_entry(key, options)
+              elsif entry.mismatched?(version)
+                # Skip mismatched versions
+              else
+                results[name] = entry.value
+              end
+            end
+          end
+          results
+        end
+
         # Writes multiple entries to the cache implementation. Subclasses MAY
         # implement this method.
         def write_multi_entries(hash, options)
@@ -562,14 +594,34 @@ module ActiveSupport
           end
         end
 
-        # Prefixes a key with the namespace. Namespace and key will be delimited
-        # with a colon.
-        def normalize_key(key, options)
-          key = expanded_key(key)
-          namespace = options[:namespace] if options
-          prefix = namespace.is_a?(Proc) ? namespace.call : namespace
-          key = "#{prefix}:#{key}" if prefix
-          key
+        # Expands and namespaces the cache key. May be overridden by
+        # cache stores to do additional normalization.
+        def normalize_key(key, options = nil)
+          namespace_key expanded_key(key), options
+        end
+
+        # Prefix the key with a namespace string:
+        #
+        #   namespace_key 'foo', namespace: 'cache'
+        #   # => 'cache:foo'
+        #
+        # With a namespace block:
+        #
+        #   namespace_key 'foo', namespace: -> { 'cache' }
+        #   # => 'cache:foo'
+        def namespace_key(key, options = nil)
+          options = merged_options(options)
+          namespace = options[:namespace]
+
+          if namespace.respond_to?(:call)
+            namespace = namespace.call
+          end
+
+          if namespace
+            "#{namespace}:#{key}"
+          else
+            key
+          end
         end
 
         # Expands key to be a consistent string value. Invokes +cache_key+ if
@@ -658,22 +710,17 @@ module ActiveSupport
     class Entry # :nodoc:
       attr_reader :version
 
-      DEFAULT_COMPRESS_LIMIT = 16.kilobytes
+      DEFAULT_COMPRESS_LIMIT = 1.kilobyte
 
       # Creates a new cache entry for the specified value. Options supported are
-      # +:compress+, +:compress_threshold+, and +:expires_in+.
-      def initialize(value, options = {})
-        if should_compress?(value, options)
-          @value = compress(value)
-          @compressed = true
-        else
-          @value = value
-        end
-
-        @version    = options[:version]
+      # +:compress+, +:compress_threshold+, +:version+ and +:expires_in+.
+      def initialize(value, compress: true, compress_threshold: DEFAULT_COMPRESS_LIMIT, version: nil, expires_in: nil, **)
+        @value      = value
+        @version    = version
         @created_at = Time.now.to_f
-        @expires_in = options[:expires_in]
-        @expires_in = @expires_in.to_f if @expires_in
+        @expires_in = expires_in && expires_in.to_f
+
+        compress!(compress_threshold) if compress
       end
 
       def value
@@ -705,17 +752,13 @@ module ActiveSupport
       # Returns the size of the cached value. This could be less than
       # <tt>value.size</tt> if the data is compressed.
       def size
-        if defined?(@s)
-          @s
+        case value
+        when NilClass
+          0
+        when String
+          @value.bytesize
         else
-          case value
-          when NilClass
-            0
-          when String
-            @value.bytesize
-          else
-            @s = Marshal.dump(@value).bytesize
-          end
+          @s ||= Marshal.dump(@value).bytesize
         end
       end
 
@@ -732,23 +775,30 @@ module ActiveSupport
       end
 
       private
-        def should_compress?(value, options)
-          if value && options[:compress]
-            compress_threshold = options[:compress_threshold] || DEFAULT_COMPRESS_LIMIT
-            serialized_value_size = (value.is_a?(String) ? value : Marshal.dump(value)).bytesize
-
-            return true if serialized_value_size >= compress_threshold
+        def compress!(compress_threshold)
+          case @value
+          when nil, true, false, Numeric
+            uncompressed_size = 0
+          when String
+            uncompressed_size = @value.bytesize
+          else
+            serialized = Marshal.dump(@value)
+            uncompressed_size = serialized.bytesize
           end
 
-          false
-        end
+          if uncompressed_size >= compress_threshold
+            serialized ||= Marshal.dump(@value)
+            compressed = Zlib::Deflate.deflate(serialized)
 
-        def compressed?
-          defined?(@compressed) ? @compressed : false
+            if compressed.bytesize < uncompressed_size
+              @value = compressed
+              @compressed = true
+            end
+          end
         end
 
-        def compress(value)
-          Zlib::Deflate.deflate(Marshal.dump(value))
+        def compressed?
+          defined?(@compressed)
         end
 
         def uncompress(value)
diff --git a/activesupport/lib/active_support/cache/file_store.rb b/activesupport/lib/active_support/cache/file_store.rb
index 28df2c066e..a0f44aac0f 100644
--- a/activesupport/lib/active_support/cache/file_store.rb
+++ b/activesupport/lib/active_support/cache/file_store.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/marshal"
-require_relative "../core_ext/file/atomic"
-require_relative "../core_ext/string/conversions"
+require "active_support/core_ext/marshal"
+require "active_support/core_ext/file/atomic"
+require "active_support/core_ext/string/conversions"
 require "uri/common"
 
 module ActiveSupport
@@ -39,9 +39,8 @@ module ActiveSupport
       def cleanup(options = nil)
         options = merged_options(options)
         search_dir(cache_path) do |fname|
-          key = file_path_key(fname)
-          entry = read_entry(key, options)
-          delete_entry(key, options) if entry && entry.expired?
+          entry = read_entry(fname, options)
+          delete_entry(fname, options) if entry && entry.expired?
         end
       end
 
@@ -122,7 +121,7 @@ module ActiveSupport
           fname = URI.encode_www_form_component(key)
 
           if fname.size > FILEPATH_MAX_SIZE
-            fname = Digest::MD5.hexdigest(key)
+            fname = ActiveSupport::Digest.hexdigest(key)
           end
 
           hash = Zlib.adler32(fname)
diff --git a/activesupport/lib/active_support/cache/mem_cache_store.rb b/activesupport/lib/active_support/cache/mem_cache_store.rb
index d7bd914722..2840781dde 100644
--- a/activesupport/lib/active_support/cache/mem_cache_store.rb
+++ b/activesupport/lib/active_support/cache/mem_cache_store.rb
@@ -7,9 +7,8 @@ rescue LoadError => e
   raise e
 end
 
-require "digest/md5"
-require_relative "../core_ext/marshal"
-require_relative "../core_ext/array/extract_options"
+require "active_support/core_ext/marshal"
+require "active_support/core_ext/array/extract_options"
 
 module ActiveSupport
   module Cache
@@ -64,7 +63,14 @@ module ActiveSupport
         addresses = addresses.flatten
         options = addresses.extract_options!
         addresses = ["localhost:11211"] if addresses.empty?
-        Dalli::Client.new(addresses, options)
+        pool_options = retrieve_pool_options(options)
+
+        if pool_options.empty?
+          Dalli::Client.new(addresses, options)
+        else
+          ensure_connection_pool_added!
+          ConnectionPool.new(pool_options) { Dalli::Client.new(addresses, options.merge(threadsafe: false)) }
+        end
       end
 
       # Creates a new MemCacheStore object, with the given memcached server
@@ -92,28 +98,6 @@ module ActiveSupport
         end
       end
 
-      # Reads multiple values from the cache using a single call to the
-      # servers for all keys. Options can be passed in the last argument.
-      def read_multi(*names)
-        options = names.extract_options!
-        options = merged_options(options)
-
-        keys_to_names = Hash[names.map { |name| [normalize_key(name, options), name] }]
-
-        raw_values = @data.get_multi(keys_to_names.keys)
-        values = {}
-
-        raw_values.each do |key, value|
-          entry = deserialize_entry(value)
-
-          unless entry.expired? || entry.mismatched?(normalize_version(keys_to_names[key], options))
-            values[keys_to_names[key]] = entry.value
-          end
-        end
-
-        values
-      end
-
       # Increment a cached value. This method uses the memcached incr atomic
       # operator and can only be used on values written with the :raw option.
       # Calling it on a value not stored with :raw will initialize that value
@@ -122,7 +106,7 @@ module ActiveSupport
         options = merged_options(options)
         instrument(:increment, name, amount: amount) do
           rescue_error_with nil do
-            @data.incr(normalize_key(name, options), amount)
+            @data.with { |c| c.incr(normalize_key(name, options), amount, options[:expires_in]) }
           end
         end
       end
@@ -135,7 +119,7 @@ module ActiveSupport
         options = merged_options(options)
         instrument(:decrement, name, amount: amount) do
           rescue_error_with nil do
-            @data.decr(normalize_key(name, options), amount)
+            @data.with { |c| c.decr(normalize_key(name, options), amount, options[:expires_in]) }
           end
         end
       end
@@ -143,18 +127,18 @@ module ActiveSupport
       # Clear the entire cache on all memcached servers. This method should
       # be used with care when shared cache is being used.
       def clear(options = nil)
-        rescue_error_with(nil) { @data.flush_all }
+        rescue_error_with(nil) { @data.with { |c| c.flush_all } }
       end
 
       # Get the statistics from the memcached servers.
       def stats
-        @data.stats
+        @data.with { |c| c.stats }
       end
 
       private
         # Read an entry from the cache.
         def read_entry(key, options)
-          rescue_error_with(nil) { deserialize_entry(@data.get(key, options)) }
+          rescue_error_with(nil) { deserialize_entry(@data.with { |c| c.get(key, options) }) }
         end
 
         # Write an entry to the cache.
@@ -167,13 +151,31 @@ module ActiveSupport
             expires_in += 5.minutes
           end
           rescue_error_with false do
-            @data.send(method, key, value, expires_in, options)
+            @data.with { |c| c.send(method, key, value, expires_in, options) }
+          end
+        end
+
+        # Reads multiple entries from the cache implementation.
+        def read_multi_entries(names, options)
+          keys_to_names = Hash[names.map { |name| [normalize_key(name, options), name] }]
+
+          raw_values = @data.with { |c| c.get_multi(keys_to_names.keys) }
+          values = {}
+
+          raw_values.each do |key, value|
+            entry = deserialize_entry(value)
+
+            unless entry.expired? || entry.mismatched?(normalize_version(keys_to_names[key], options))
+              values[keys_to_names[key]] = entry.value
+            end
           end
+
+          values
         end
 
         # Delete an entry from the cache.
         def delete_entry(key, options)
-          rescue_error_with(false) { @data.delete(key) }
+          rescue_error_with(false) { @data.with { |c| c.delete(key) } }
         end
 
         # Memcache keys are binaries. So we need to force their encoding to binary
@@ -183,7 +185,7 @@ module ActiveSupport
           key = super.dup
           key = key.force_encoding(Encoding::ASCII_8BIT)
           key = key.gsub(ESCAPE_KEY_CHARS) { |match| "%#{match.getbyte(0).to_s(16).upcase}" }
-          key = "#{key[0, 213]}:md5:#{Digest::MD5.hexdigest(key)}" if key.size > 250
+          key = "#{key[0, 213]}:md5:#{ActiveSupport::Digest.hexdigest(key)}" if key.size > 250
           key
         end
 
diff --git a/activesupport/lib/active_support/cache/redis_cache_store.rb b/activesupport/lib/active_support/cache/redis_cache_store.rb
new file mode 100644
index 0000000000..11c574258f
--- /dev/null
+++ b/activesupport/lib/active_support/cache/redis_cache_store.rb
@@ -0,0 +1,460 @@
+# frozen_string_literal: true
+
+begin
+  gem "redis", ">= 4.0.1"
+  require "redis"
+  require "redis/distributed"
+rescue LoadError
+  warn "The Redis cache store requires the redis gem, version 4.0.1 or later. Please add it to your Gemfile: `gem \"redis\", \"~> 4.0\"`"
+  raise
+end
+
+# Prefer the hiredis driver but don't require it.
+begin
+  require "redis/connection/hiredis"
+rescue LoadError
+end
+
+require "digest/sha2"
+require "active_support/core_ext/marshal"
+
+module ActiveSupport
+  module Cache
+    module ConnectionPoolLike
+      def with
+        yield self
+      end
+    end
+
+    ::Redis.include(ConnectionPoolLike)
+    ::Redis::Distributed.include(ConnectionPoolLike)
+
+    # Redis cache store.
+    #
+    # Deployment note: Take care to use a *dedicated Redis cache* rather
+    # than pointing this at your existing Redis server. It won't cope well
+    # with mixed usage patterns and it won't expire cache entries by default.
+    #
+    # Redis cache server setup guide: https://redis.io/topics/lru-cache
+    #
+    # * Supports vanilla Redis, hiredis, and Redis::Distributed.
+    # * Supports Memcached-like sharding across Redises with Redis::Distributed.
+    # * Fault tolerant. If the Redis server is unavailable, no exceptions are
+    #   raised. Cache fetches are all misses and writes are dropped.
+    # * Local cache. Hot in-memory primary cache within block/middleware scope.
+    # * +read_multi+ and +write_multi+ support for Redis mget/mset. Use Redis::Distributed
+    #   4.0.1+ for distributed mget support.
+    # * +delete_matched+ support for Redis KEYS globs.
+    class RedisCacheStore < Store
+      # Keys are truncated with their own SHA2 digest if they exceed 1kB
+      MAX_KEY_BYTESIZE = 1024
+
+      DEFAULT_REDIS_OPTIONS = {
+        connect_timeout:    20,
+        read_timeout:       1,
+        write_timeout:      1,
+        reconnect_attempts: 0,
+      }
+
+      DEFAULT_ERROR_HANDLER = -> (method:, returning:, exception:) do
+        if logger
+          logger.error { "RedisCacheStore: #{method} failed, returned #{returning.inspect}: #{exception.class}: #{exception.message}" }
+        end
+      end
+
+      # The maximum number of entries to receive per SCAN call.
+      SCAN_BATCH_SIZE = 1000
+      private_constant :SCAN_BATCH_SIZE
+
+      # Support raw values in the local cache strategy.
+      module LocalCacheWithRaw # :nodoc:
+        private
+          def read_entry(key, options)
+            entry = super
+            if options[:raw] && local_cache && entry
+              entry = deserialize_entry(entry.value)
+            end
+            entry
+          end
+
+          def write_entry(key, entry, options)
+            if options[:raw] && local_cache
+              raw_entry = Entry.new(serialize_entry(entry, raw: true))
+              raw_entry.expires_at = entry.expires_at
+              super(key, raw_entry, options)
+            else
+              super
+            end
+          end
+
+          def write_multi_entries(entries, options)
+            if options[:raw] && local_cache
+              raw_entries = entries.map do |key, entry|
+                raw_entry = Entry.new(serialize_entry(entry, raw: true))
+                raw_entry.expires_at = entry.expires_at
+              end.to_h
+
+              super(raw_entries, options)
+            else
+              super
+            end
+          end
+      end
+
+      prepend Strategy::LocalCache
+      prepend LocalCacheWithRaw
+
+      class << self
+        # Factory method to create a new Redis instance.
+        #
+        # Handles four options: :redis block, :redis instance, single :url
+        # string, and multiple :url strings.
+        #
+        #   Option  Class       Result
+        #   :redis  Proc    ->  options[:redis].call
+        #   :redis  Object  ->  options[:redis]
+        #   :url    String  ->  Redis.new(url: …)
+        #   :url    Array   ->  Redis::Distributed.new([{ url: … }, { url: … }, …])
+        #
+        def build_redis(redis: nil, url: nil, **redis_options) #:nodoc:
+          urls = Array(url)
+
+          if redis.is_a?(Proc)
+            redis.call
+          elsif redis
+            redis
+          elsif urls.size > 1
+            build_redis_distributed_client urls: urls, **redis_options
+          else
+            build_redis_client url: urls.first, **redis_options
+          end
+        end
+
+        private
+          def build_redis_distributed_client(urls:, **redis_options)
+            ::Redis::Distributed.new([], DEFAULT_REDIS_OPTIONS.merge(redis_options)).tap do |dist|
+              urls.each { |u| dist.add_node url: u }
+            end
+          end
+
+          def build_redis_client(url:, **redis_options)
+            ::Redis.new DEFAULT_REDIS_OPTIONS.merge(redis_options.merge(url: url))
+          end
+      end
+
+      attr_reader :redis_options
+      attr_reader :max_key_bytesize
+
+      # Creates a new Redis cache store.
+      #
+      # Handles three options: block provided to instantiate, single URL
+      # provided, and multiple URLs provided.
+      #
+      #   :redis Proc   -> options[:redis].call
+      #   :url   String -> Redis.new(url: …)
+      #   :url   Array  -> Redis::Distributed.new([{ url: … }, { url: … }, …])
+      #
+      # No namespace is set by default. Provide one if the Redis cache
+      # server is shared with other apps: <tt>namespace: 'myapp-cache'</tt>.
+      #
+      # Compression is enabled by default with a 1kB threshold, so cached
+      # values larger than 1kB are automatically compressed. Disable by
+      # passing <tt>compress: false</tt> or change the threshold by passing
+      # <tt>compress_threshold: 4.kilobytes</tt>.
+      #
+      # No expiry is set on cache entries by default. Redis is expected to
+      # be configured with an eviction policy that automatically deletes
+      # least-recently or -frequently used keys when it reaches max memory.
+      # See https://redis.io/topics/lru-cache for cache server setup.
+      #
+      # Race condition TTL is not set by default. This can be used to avoid
+      # "thundering herd" cache writes when hot cache entries are expired.
+      # See <tt>ActiveSupport::Cache::Store#fetch</tt> for more.
+      def initialize(namespace: nil, compress: true, compress_threshold: 1.kilobyte, expires_in: nil, race_condition_ttl: nil, error_handler: DEFAULT_ERROR_HANDLER, **redis_options)
+        @redis_options = redis_options
+
+        @max_key_bytesize = MAX_KEY_BYTESIZE
+        @error_handler = error_handler
+
+        super namespace: namespace,
+          compress: compress, compress_threshold: compress_threshold,
+          expires_in: expires_in, race_condition_ttl: race_condition_ttl
+      end
+
+      def redis
+        @redis ||= begin
+          pool_options = self.class.send(:retrieve_pool_options, redis_options)
+
+          if pool_options.any?
+            self.class.send(:ensure_connection_pool_added!)
+            ::ConnectionPool.new(pool_options) { self.class.build_redis(**redis_options) }
+          else
+            self.class.build_redis(**redis_options)
+          end
+        end
+      end
+
+      def inspect
+        instance = @redis || @redis_options
+        "<##{self.class} options=#{options.inspect} redis=#{instance.inspect}>"
+      end
+
+      # Cache Store API implementation.
+      #
+      # Read multiple values at once. Returns a hash of requested keys ->
+      # fetched values.
+      def read_multi(*names)
+        if mget_capable?
+          instrument(:read_multi, names, options) do |payload|
+            read_multi_mget(*names).tap do |results|
+              payload[:hits] = results.keys
+            end
+          end
+        else
+          super
+        end
+      end
+
+      # Cache Store API implementation.
+      #
+      # Supports Redis KEYS glob patterns:
+      #
+      #   h?llo matches hello, hallo and hxllo
+      #   h*llo matches hllo and heeeello
+      #   h[ae]llo matches hello and hallo, but not hillo
+      #   h[^e]llo matches hallo, hbllo, ... but not hello
+      #   h[a-b]llo matches hallo and hbllo
+      #
+      # Use \ to escape special characters if you want to match them verbatim.
+      #
+      # See https://redis.io/commands/KEYS for more.
+      #
+      # Failsafe: Raises errors.
+      def delete_matched(matcher, options = nil)
+        instrument :delete_matched, matcher do
+          unless String === matcher
+            raise ArgumentError, "Only Redis glob strings are supported: #{matcher.inspect}"
+          end
+          redis.with do |c|
+            pattern = namespace_key(matcher, options)
+            cursor = "0"
+            # Fetch keys in batches using SCAN to avoid blocking the Redis server.
+            begin
+              cursor, keys = c.scan(cursor, match: pattern, count: SCAN_BATCH_SIZE)
+              c.del(*keys) unless keys.empty?
+            end until cursor == "0"
+          end
+        end
+      end
+
+      # Cache Store API implementation.
+      #
+      # Increment a cached value. This method uses the Redis incr atomic
+      # operator and can only be used on values written with the :raw option.
+      # Calling it on a value not stored with :raw will initialize that value
+      # to zero.
+      #
+      # Failsafe: Raises errors.
+      def increment(name, amount = 1, options = nil)
+        instrument :increment, name, amount: amount do
+          failsafe :increment do
+            redis.with { |c| c.incrby normalize_key(name, options), amount }
+          end
+        end
+      end
+
+      # Cache Store API implementation.
+      #
+      # Decrement a cached value. This method uses the Redis decr atomic
+      # operator and can only be used on values written with the :raw option.
+      # Calling it on a value not stored with :raw will initialize that value
+      # to zero.
+      #
+      # Failsafe: Raises errors.
+      def decrement(name, amount = 1, options = nil)
+        instrument :decrement, name, amount: amount do
+          failsafe :decrement do
+            redis.with { |c| c.decrby normalize_key(name, options), amount }
+          end
+        end
+      end
+
+      # Cache Store API implementation.
+      #
+      # Removes expired entries. Handled natively by Redis least-recently-/
+      # least-frequently-used expiry, so manual cleanup is not supported.
+      def cleanup(options = nil)
+        super
+      end
+
+      # Clear the entire cache on all Redis servers. Safe to use on
+      # shared servers if the cache is namespaced.
+      #
+      # Failsafe: Raises errors.
+      def clear(options = nil)
+        failsafe :clear do
+          if namespace = merged_options(options)[:namespace]
+            delete_matched "*", namespace: namespace
+          else
+            redis.with { |c| c.flushdb }
+          end
+        end
+      end
+
+      def mget_capable? #:nodoc:
+        set_redis_capabilities unless defined? @mget_capable
+        @mget_capable
+      end
+
+      def mset_capable? #:nodoc:
+        set_redis_capabilities unless defined? @mset_capable
+        @mset_capable
+      end
+
+      private
+        def set_redis_capabilities
+          case redis
+          when Redis::Distributed
+            @mget_capable = true
+            @mset_capable = false
+          else
+            @mget_capable = true
+            @mset_capable = true
+          end
+        end
+
+        # Store provider interface:
+        # Read an entry from the cache.
+        def read_entry(key, options = nil)
+          failsafe :read_entry do
+            deserialize_entry redis.with { |c| c.get(key) }
+          end
+        end
+
+        def read_multi_entries(names, _options)
+          if mget_capable?
+            read_multi_mget(*names)
+          else
+            super
+          end
+        end
+
+        def read_multi_mget(*names)
+          options = names.extract_options!
+          options = merged_options(options)
+
+          keys = names.map { |name| normalize_key(name, options) }
+
+          values = failsafe(:read_multi_mget, returning: {}) do
+            redis.with { |c| c.mget(*keys) }
+          end
+
+          names.zip(values).each_with_object({}) do |(name, value), results|
+            if value
+              entry = deserialize_entry(value)
+              unless entry.nil? || entry.expired? || entry.mismatched?(normalize_version(name, options))
+                results[name] = entry.value
+              end
+            end
+          end
+        end
+
+        # Write an entry to the cache.
+        #
+        # Requires Redis 2.6.12+ for extended SET options.
+        def write_entry(key, entry, unless_exist: false, raw: false, expires_in: nil, race_condition_ttl: nil, **options)
+          serialized_entry = serialize_entry(entry, raw: raw)
+
+          # If race condition TTL is in use, ensure that cache entries
+          # stick around a bit longer after they would have expired
+          # so we can purposefully serve stale entries.
+          if race_condition_ttl && expires_in && expires_in > 0 && !raw
+            expires_in += 5.minutes
+          end
+
+          failsafe :write_entry, returning: false do
+            if unless_exist || expires_in
+              modifiers = {}
+              modifiers[:nx] = unless_exist
+              modifiers[:px] = (1000 * expires_in.to_f).ceil if expires_in
+
+              redis.with { |c| c.set key, serialized_entry, modifiers }
+            else
+              redis.with { |c| c.set key, serialized_entry }
+            end
+          end
+        end
+
+        # Delete an entry from the cache.
+        def delete_entry(key, options)
+          failsafe :delete_entry, returning: false do
+            redis.with { |c| c.del key }
+          end
+        end
+
+        # Nonstandard store provider API to write multiple values at once.
+        def write_multi_entries(entries, expires_in: nil, **options)
+          if entries.any?
+            if mset_capable? && expires_in.nil?
+              failsafe :write_multi_entries do
+                redis.with { |c| c.mapped_mset(serialize_entries(entries, raw: options[:raw])) }
+              end
+            else
+              super
+            end
+          end
+        end
+
+        # Truncate keys that exceed 1kB.
+        def normalize_key(key, options)
+          truncate_key super.b
+        end
+
+        def truncate_key(key)
+          if key.bytesize > max_key_bytesize
+            suffix = ":sha2:#{::Digest::SHA2.hexdigest(key)}"
+            truncate_at = max_key_bytesize - suffix.bytesize
+            "#{key.byteslice(0, truncate_at)}#{suffix}"
+          else
+            key
+          end
+        end
+
+        def deserialize_entry(serialized_entry)
+          if serialized_entry
+            entry = Marshal.load(serialized_entry) rescue serialized_entry
+            entry.is_a?(Entry) ? entry : Entry.new(entry)
+          end
+        end
+
+        def serialize_entry(entry, raw: false)
+          if raw
+            entry.value.to_s
+          else
+            Marshal.dump(entry)
+          end
+        end
+
+        def serialize_entries(entries, raw: false)
+          entries.transform_values do |entry|
+            serialize_entry entry, raw: raw
+          end
+        end
+
+        def failsafe(method, returning: nil)
+          yield
+        rescue ::Redis::BaseConnectionError => e
+          handle_exception exception: e, method: method, returning: returning
+          returning
+        end
+
+        def handle_exception(exception:, method:, returning:)
+          if @error_handler
+            @error_handler.(method: method, exception: exception, returning: returning)
+          end
+        rescue => failsafe
+          warn "RedisCacheStore ignored exception in handle_exception: #{failsafe.class}: #{failsafe.message}\n  #{failsafe.backtrace.join("\n  ")}"
+        end
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/cache/strategy/local_cache.rb b/activesupport/lib/active_support/cache/strategy/local_cache.rb
index a3eef1190a..39b32fc7f6 100644
--- a/activesupport/lib/active_support/cache/strategy/local_cache.rb
+++ b/activesupport/lib/active_support/cache/strategy/local_cache.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../../core_ext/object/duplicable"
-require_relative "../../core_ext/string/inflections"
-require_relative "../../per_thread_registry"
+require "active_support/core_ext/object/duplicable"
+require "active_support/core_ext/string/inflections"
+require "active_support/per_thread_registry"
 
 module ActiveSupport
   module Cache
@@ -54,6 +54,17 @@ module ActiveSupport
             @data[key]
           end
 
+          def read_multi_entries(keys, options)
+            values = {}
+
+            keys.each do |name|
+              entry = read_entry(name, options)
+              values[name] = entry.value if entry
+            end
+
+            values
+          end
+
           def write_entry(key, value, options)
             @data[key] = value
             true
@@ -116,6 +127,19 @@ module ActiveSupport
             end
           end
 
+          def read_multi_entries(keys, options)
+            return super unless local_cache
+
+            local_entries = local_cache.read_multi_entries(keys, options)
+            missed_keys = keys - local_entries.keys
+
+            if missed_keys.any?
+              local_entries.merge!(super(missed_keys, options))
+            else
+              local_entries
+            end
+          end
+
           def write_entry(key, entry, options)
             if options[:unless_exist]
               local_cache.delete_entry(key, options) if local_cache
diff --git a/activesupport/lib/active_support/callbacks.rb b/activesupport/lib/active_support/callbacks.rb
index e1cbfc945c..a1b841ec3d 100644
--- a/activesupport/lib/active_support/callbacks.rb
+++ b/activesupport/lib/active_support/callbacks.rb
@@ -1,13 +1,13 @@
 # frozen_string_literal: true
 
-require_relative "concern"
-require_relative "descendants_tracker"
-require_relative "core_ext/array/extract_options"
-require_relative "core_ext/class/attribute"
-require_relative "core_ext/kernel/reporting"
-require_relative "core_ext/kernel/singleton_class"
-require_relative "core_ext/string/filters"
-require_relative "deprecation"
+require "active_support/concern"
+require "active_support/descendants_tracker"
+require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/class/attribute"
+require "active_support/core_ext/kernel/reporting"
+require "active_support/core_ext/kernel/singleton_class"
+require "active_support/core_ext/string/filters"
+require "active_support/deprecation"
 require "thread"
 
 module ActiveSupport
@@ -298,8 +298,8 @@ module ActiveSupport
           @kind    = kind
           @filter  = filter
           @key     = compute_identifier filter
-          @if      = Array(options[:if])
-          @unless  = Array(options[:unless])
+          @if      = check_conditionals(Array(options[:if]))
+          @unless  = check_conditionals(Array(options[:unless]))
         end
 
         def filter; @key; end
@@ -323,7 +323,7 @@ module ActiveSupport
 
         def duplicates?(other)
           case @filter
-          when Symbol, String
+          when Symbol
             matches?(other.kind, other.filter)
           else
             false
@@ -350,9 +350,21 @@ module ActiveSupport
         end
 
         private
+          def check_conditionals(conditionals)
+            if conditionals.any? { |c| c.is_a?(String) }
+              raise ArgumentError, <<-MSG.squish
+                Passing string to be evaluated in :if and :unless conditional
+                options is not supported. Pass a symbol for an instance method,
+                or a lambda, proc or block, instead.
+              MSG
+            end
+
+            conditionals
+          end
+
           def compute_identifier(filter)
             case filter
-            when String, ::Proc
+            when ::Proc
               filter.object_id
             else
               filter
@@ -427,7 +439,6 @@ module ActiveSupport
         # Filters support:
         #
         #   Symbols:: A method to call.
-        #   Strings:: Some content to evaluate.
         #   Procs::   A proc to call with the object.
         #   Objects:: An object with a <tt>before_foo</tt> method on it to call.
         #
@@ -437,8 +448,6 @@ module ActiveSupport
           case filter
           when Symbol
             new(nil, filter, [], nil)
-          when String
-            new(nil, :instance_exec, [:value], compile_lambda(filter))
           when Conditionals::Value
             new(filter, :call, [:target, :value], nil)
           when ::Proc
@@ -455,10 +464,6 @@ module ActiveSupport
             new(filter, method_to_call, [:target], nil)
           end
         end
-
-        def self.compile_lambda(filter)
-          eval("lambda { |value| #{filter} }")
-        end
       end
 
       # Execute before and after filters in a sequence instead of
@@ -651,26 +656,17 @@ module ActiveSupport
         #
         # ===== Options
         #
-        # * <tt>:if</tt> - A symbol, a string (deprecated) or an array of symbols,
-        #   each naming an instance method or a proc; the callback will be called
-        #   only when they all return a true value.
-        # * <tt>:unless</tt> - A symbol, a string (deprecated) or an array of symbols,
-        #   each naming an instance method or a proc; the callback will be called
-        #   only when they all return a false value.
+        # * <tt>:if</tt> - A symbol or an array of symbols, each naming an instance
+        #   method or a proc; the callback will be called only when they all return
+        #   a true value.
+        # * <tt>:unless</tt> - A symbol or an array of symbols, each naming an
+        #   instance method or a proc; the callback will be called only when they
+        #   all return a false value.
         # * <tt>:prepend</tt> - If +true+, the callback will be prepended to the
         #   existing chain rather than appended.
         def set_callback(name, *filter_list, &block)
           type, filters, options = normalize_callback_params(filter_list, block)
 
-          if options[:if].is_a?(String) || options[:unless].is_a?(String)
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Passing string to be evaluated in :if and :unless conditional
-              options is deprecated and will be removed in Rails 5.2 without
-              replacement. Pass a symbol for an instance method, or a lambda,
-              proc or block, instead.
-            MSG
-          end
-
           self_chain = get_callbacks name
           mapped = filters.map do |filter|
             Callback.build(self_chain, filter, type, options)
@@ -695,13 +691,6 @@ module ActiveSupport
         def skip_callback(name, *filter_list, &block)
           type, filters, options = normalize_callback_params(filter_list, block)
 
-          if options[:if].is_a?(String) || options[:unless].is_a?(String)
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Passing string to :if and :unless conditional options is deprecated
-              and will be removed in Rails 5.2 without replacement.
-            MSG
-          end
-
           options[:raise] = true unless options.key?(:raise)
 
           __update_callbacks(name) do |target, chain|
@@ -760,8 +749,8 @@ module ActiveSupport
         # * <tt>:skip_after_callbacks_if_terminated</tt> - Determines if after
         #   callbacks should be terminated by the <tt>:terminator</tt> option. By
         #   default after callbacks are executed no matter if callback chain was
-        #   terminated or not. This option makes sense only when <tt>:terminator</tt>
-        #   option is specified.
+        #   terminated or not. This option has no effect if <tt>:terminator</tt>
+        #   option is set to +nil+.
         #
         # * <tt>:scope</tt> - Indicates which methods should be executed when an
         #   object is used as a callback.
@@ -820,7 +809,9 @@ module ActiveSupport
           names.each do |name|
             name = name.to_sym
 
-            set_callbacks name, CallbackChain.new(name, options)
+            ([self] + ActiveSupport::DescendantsTracker.descendants(self)).each do |target|
+              target.set_callbacks name, CallbackChain.new(name, options)
+            end
 
             module_eval <<-RUBY, __FILE__, __LINE__ + 1
               def _run_#{name}_callbacks(&block)
diff --git a/activesupport/lib/active_support/concern.rb b/activesupport/lib/active_support/concern.rb
index 32b5ca986b..b0a0d845e5 100644
--- a/activesupport/lib/active_support/concern.rb
+++ b/activesupport/lib/active_support/concern.rb
@@ -113,7 +113,7 @@ module ActiveSupport
     def append_features(base)
       if base.instance_variable_defined?(:@_dependencies)
         base.instance_variable_get(:@_dependencies) << self
-        return false
+        false
       else
         return false if base < self
         @_dependencies.each { |dep| base.include(dep) }
diff --git a/activesupport/lib/active_support/concurrency/load_interlock_aware_monitor.rb b/activesupport/lib/active_support/concurrency/load_interlock_aware_monitor.rb
new file mode 100644
index 0000000000..a8455c0048
--- /dev/null
+++ b/activesupport/lib/active_support/concurrency/load_interlock_aware_monitor.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+require "monitor"
+
+module ActiveSupport
+  module Concurrency
+    # A monitor that will permit dependency loading while blocked waiting for
+    # the lock.
+    class LoadInterlockAwareMonitor < Monitor
+      # Enters an exclusive section, but allows dependency loading while blocked
+      def mon_enter
+        mon_try_enter ||
+          ActiveSupport::Dependencies.interlock.permit_concurrent_loads { super }
+      end
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/configurable.rb b/activesupport/lib/active_support/configurable.rb
index 8e8e27b4ec..4d6f7819bb 100644
--- a/activesupport/lib/active_support/configurable.rb
+++ b/activesupport/lib/active_support/configurable.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-require_relative "concern"
-require_relative "ordered_options"
-require_relative "core_ext/array/extract_options"
-require_relative "core_ext/regexp"
+require "active_support/concern"
+require "active_support/ordered_options"
+require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/regexp"
 
 module ActiveSupport
   # Configurable provides a <tt>config</tt> method to store and retrieve
diff --git a/activesupport/lib/active_support/core_ext/array.rb b/activesupport/lib/active_support/core_ext/array.rb
index fdc209ef68..6d83b76882 100644
--- a/activesupport/lib/active_support/core_ext/array.rb
+++ b/activesupport/lib/active_support/core_ext/array.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-require_relative "array/wrap"
-require_relative "array/access"
-require_relative "array/conversions"
-require_relative "array/extract_options"
-require_relative "array/grouping"
-require_relative "array/prepend_and_append"
-require_relative "array/inquiry"
+require "active_support/core_ext/array/wrap"
+require "active_support/core_ext/array/access"
+require "active_support/core_ext/array/conversions"
+require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/array/grouping"
+require "active_support/core_ext/array/prepend_and_append"
+require "active_support/core_ext/array/inquiry"
diff --git a/activesupport/lib/active_support/core_ext/array/access.rb b/activesupport/lib/active_support/core_ext/array/access.rb
index d67f99df0e..b7ff7a3907 100644
--- a/activesupport/lib/active_support/core_ext/array/access.rb
+++ b/activesupport/lib/active_support/core_ext/array/access.rb
@@ -35,8 +35,8 @@ class Array
   #   people.without "Aaron", "Todd"
   #   # => ["David", "Rafael"]
   #
-  # Note: This is an optimization of `Enumerable#without` that uses `Array#-`
-  # instead of `Array#reject` for performance reasons.
+  # Note: This is an optimization of <tt>Enumerable#without</tt> that uses <tt>Array#-</tt>
+  # instead of <tt>Array#reject</tt> for performance reasons.
   def without(*elements)
     self - elements
   end
diff --git a/activesupport/lib/active_support/core_ext/array/conversions.rb b/activesupport/lib/active_support/core_ext/array/conversions.rb
index 6e17a81f0f..ea688ed2ea 100644
--- a/activesupport/lib/active_support/core_ext/array/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/array/conversions.rb
@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
-require_relative "../../xml_mini"
-require_relative "../hash/keys"
-require_relative "../string/inflections"
-require_relative "../object/to_param"
-require_relative "../object/to_query"
+require "active_support/xml_mini"
+require "active_support/core_ext/hash/keys"
+require "active_support/core_ext/string/inflections"
+require "active_support/core_ext/object/to_param"
+require "active_support/core_ext/object/to_query"
 
 class Array
   # Converts the array to a comma-separated sentence where the last element is
@@ -181,7 +181,7 @@ class Array
   #   </messages>
   #
   def to_xml(options = {})
-    require_relative "../../builder" unless defined?(Builder)
+    require "active_support/builder" unless defined?(Builder)
 
     options = options.dup
     options[:indent]  ||= 2
diff --git a/activesupport/lib/active_support/core_ext/array/inquiry.rb b/activesupport/lib/active_support/core_ext/array/inquiry.rb
index 4f4a9fa361..92c61bf201 100644
--- a/activesupport/lib/active_support/core_ext/array/inquiry.rb
+++ b/activesupport/lib/active_support/core_ext/array/inquiry.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../array_inquirer"
+require "active_support/array_inquirer"
 
 class Array
   # Wraps the array in an +ArrayInquirer+ object, which gives a friendlier way
diff --git a/activesupport/lib/active_support/core_ext/big_decimal.rb b/activesupport/lib/active_support/core_ext/big_decimal.rb
index 5568db689b..9e6a9d6331 100644
--- a/activesupport/lib/active_support/core_ext/big_decimal.rb
+++ b/activesupport/lib/active_support/core_ext/big_decimal.rb
@@ -1,3 +1,3 @@
 # frozen_string_literal: true
 
-require_relative "big_decimal/conversions"
+require "active_support/core_ext/big_decimal/conversions"
diff --git a/activesupport/lib/active_support/core_ext/class.rb b/activesupport/lib/active_support/core_ext/class.rb
index 65e1d68399..1c110fd07b 100644
--- a/activesupport/lib/active_support/core_ext/class.rb
+++ b/activesupport/lib/active_support/core_ext/class.rb
@@ -1,4 +1,4 @@
 # frozen_string_literal: true
 
-require_relative "class/attribute"
-require_relative "class/subclasses"
+require "active_support/core_ext/class/attribute"
+require "active_support/core_ext/class/subclasses"
diff --git a/activesupport/lib/active_support/core_ext/class/attribute.rb b/activesupport/lib/active_support/core_ext/class/attribute.rb
index e5a52db36a..fa33ff945f 100644
--- a/activesupport/lib/active_support/core_ext/class/attribute.rb
+++ b/activesupport/lib/active_support/core_ext/class/attribute.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../kernel/singleton_class"
-require_relative "../module/remove_method"
-require_relative "../array/extract_options"
+require "active_support/core_ext/kernel/singleton_class"
+require "active_support/core_ext/module/redefine_method"
+require "active_support/core_ext/array/extract_options"
 
 class Class
   # Declare a class-level attribute whose value is inheritable by subclasses.
@@ -92,25 +92,23 @@ class Class
     default_value      = options.fetch(:default, nil)
 
     attrs.each do |name|
-      remove_possible_singleton_method(name)
+      singleton_class.silence_redefinition_of_method(name)
       define_singleton_method(name) { nil }
 
-      remove_possible_singleton_method("#{name}?")
+      singleton_class.silence_redefinition_of_method("#{name}?")
       define_singleton_method("#{name}?") { !!public_send(name) } if instance_predicate
 
-      ivar = "@#{name}"
+      ivar = "@#{name}".to_sym
 
-      remove_possible_singleton_method("#{name}=")
+      singleton_class.silence_redefinition_of_method("#{name}=")
       define_singleton_method("#{name}=") do |val|
         singleton_class.class_eval do
-          remove_possible_method(name)
-          define_method(name) { val }
+          redefine_method(name) { val }
         end
 
         if singleton_class?
           class_eval do
-            remove_possible_method(name)
-            define_method(name) do
+            redefine_method(name) do
               if instance_variable_defined? ivar
                 instance_variable_get ivar
               else
@@ -123,8 +121,7 @@ class Class
       end
 
       if instance_reader
-        remove_possible_method name
-        define_method(name) do
+        redefine_method(name) do
           if instance_variable_defined?(ivar)
             instance_variable_get ivar
           else
@@ -132,13 +129,13 @@ class Class
           end
         end
 
-        remove_possible_method "#{name}?"
-        define_method("#{name}?") { !!public_send(name) } if instance_predicate
+        redefine_method("#{name}?") { !!public_send(name) } if instance_predicate
       end
 
       if instance_writer
-        remove_possible_method "#{name}="
-        attr_writer name
+        redefine_method("#{name}=") do |val|
+          instance_variable_set ivar, val
+        end
       end
 
       unless default_value.nil?
diff --git a/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb b/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb
index b4dbcc6698..a77354e153 100644
--- a/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb
+++ b/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb
@@ -3,4 +3,4 @@
 # cattr_* became mattr_* aliases in 7dfbd91b0780fbd6a1dd9bfbc176e10894871d2d,
 # but we keep this around for libraries that directly require it knowing they
 # want cattr_*. No need to deprecate.
-require_relative "../module/attribute_accessors"
+require "active_support/core_ext/module/attribute_accessors"
diff --git a/activesupport/lib/active_support/core_ext/class/subclasses.rb b/activesupport/lib/active_support/core_ext/class/subclasses.rb
index 4c910feb44..75e65337b7 100644
--- a/activesupport/lib/active_support/core_ext/class/subclasses.rb
+++ b/activesupport/lib/active_support/core_ext/class/subclasses.rb
@@ -1,8 +1,5 @@
 # frozen_string_literal: true
 
-require_relative "../module/anonymous"
-require_relative "../module/reachable"
-
 class Class
   begin
     # Test if this Ruby supports each_object against singleton_class
diff --git a/activesupport/lib/active_support/core_ext/date.rb b/activesupport/lib/active_support/core_ext/date.rb
index 2a2ed5496f..cce73f2db2 100644
--- a/activesupport/lib/active_support/core_ext/date.rb
+++ b/activesupport/lib/active_support/core_ext/date.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "date/acts_like"
-require_relative "date/blank"
-require_relative "date/calculations"
-require_relative "date/conversions"
-require_relative "date/zones"
+require "active_support/core_ext/date/acts_like"
+require "active_support/core_ext/date/blank"
+require "active_support/core_ext/date/calculations"
+require "active_support/core_ext/date/conversions"
+require "active_support/core_ext/date/zones"
diff --git a/activesupport/lib/active_support/core_ext/date/acts_like.rb b/activesupport/lib/active_support/core_ext/date/acts_like.rb
index 81769129b5..c8077f3774 100644
--- a/activesupport/lib/active_support/core_ext/date/acts_like.rb
+++ b/activesupport/lib/active_support/core_ext/date/acts_like.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../object/acts_like"
+require "active_support/core_ext/object/acts_like"
 
 class Date
   # Duck-types as a Date-like class. See Object#acts_like?.
diff --git a/activesupport/lib/active_support/core_ext/date/calculations.rb b/activesupport/lib/active_support/core_ext/date/calculations.rb
index 1a19ee8b1e..1cd7acb05d 100644
--- a/activesupport/lib/active_support/core_ext/date/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date/calculations.rb
@@ -1,11 +1,11 @@
 # frozen_string_literal: true
 
 require "date"
-require_relative "../../duration"
-require_relative "../object/acts_like"
-require_relative "zones"
-require_relative "../time/zones"
-require_relative "../date_and_time/calculations"
+require "active_support/duration"
+require "active_support/core_ext/object/acts_like"
+require "active_support/core_ext/date/zones"
+require "active_support/core_ext/time/zones"
+require "active_support/core_ext/date_and_time/calculations"
 
 class Date
   include DateAndTime::Calculations
diff --git a/activesupport/lib/active_support/core_ext/date/conversions.rb b/activesupport/lib/active_support/core_ext/date/conversions.rb
index 000d6f61ca..870119dc7f 100644
--- a/activesupport/lib/active_support/core_ext/date/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/date/conversions.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
 require "date"
-require_relative "../../inflector/methods"
-require_relative "zones"
-require_relative "../module/remove_method"
+require "active_support/inflector/methods"
+require "active_support/core_ext/date/zones"
+require "active_support/core_ext/module/redefine_method"
 
 class Date
   DATE_FORMATS = {
@@ -19,14 +19,6 @@ class Date
     iso8601: lambda { |date| date.iso8601 }
   }
 
-  # Ruby 1.9 has Date#to_time which converts to localtime only.
-  remove_method :to_time
-
-  # Ruby 1.9 has Date#xmlschema which converts to a string without the time
-  # component. This removal may generate an issue on FreeBSD, that's why we
-  # need to use remove_possible_method here
-  remove_possible_method :xmlschema
-
   # Convert to a formatted string. See DATE_FORMATS for predefined formats.
   #
   # This method is aliased to <tt>to_s</tt>.
@@ -72,6 +64,8 @@ class Date
   alias_method :default_inspect, :inspect
   alias_method :inspect, :readable_inspect
 
+  silence_redefinition_of_method :to_time
+
   # Converts a Date instance to a Time, where the time is set to the beginning of the day.
   # The timezone can be either :local or :utc (default :local).
   #
@@ -89,6 +83,8 @@ class Date
     ::Time.send(form, year, month, day)
   end
 
+  silence_redefinition_of_method :xmlschema
+
   # Returns a string which represents the time in used time zone as DateTime
   # defined by XML Schema:
   #
diff --git a/activesupport/lib/active_support/core_ext/date/zones.rb b/activesupport/lib/active_support/core_ext/date/zones.rb
index 1aed070df0..2dcf97cff8 100644
--- a/activesupport/lib/active_support/core_ext/date/zones.rb
+++ b/activesupport/lib/active_support/core_ext/date/zones.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "date"
-require_relative "../date_and_time/zones"
+require "active_support/core_ext/date_and_time/zones"
 
 class Date
   include DateAndTime::Zones
diff --git a/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb b/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
index 8546f7e57b..de13f00e60 100644
--- a/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../object/try"
+require "active_support/core_ext/object/try"
 
 module DateAndTime
   module Calculations
@@ -20,9 +20,9 @@ module DateAndTime
       advance(days: -1)
     end
 
-    # Returns a new date/time representing the previous day.
-    def prev_day
-      advance(days: -1)
+    # Returns a new date/time the specified number of days ago.
+    def prev_day(days = 1)
+      advance(days: -days)
     end
 
     # Returns a new date/time representing tomorrow.
@@ -30,9 +30,9 @@ module DateAndTime
       advance(days: 1)
     end
 
-    # Returns a new date/time representing the next day.
-    def next_day
-      advance(days: 1)
+    # Returns a new date/time the specified number of days in the future.
+    def next_day(days = 1)
+      advance(days: days)
     end
 
     # Returns true if the date/time is today.
@@ -60,6 +60,16 @@ module DateAndTime
       !WEEKEND_DAYS.include?(wday)
     end
 
+    # Returns true if the date/time before <tt>date_or_time</tt>.
+    def before?(date_or_time)
+      self < date_or_time
+    end
+
+    # Returns true if the date/time after <tt>date_or_time</tt>.
+    def after?(date_or_time)
+      self > date_or_time
+    end
+
     # Returns a new date/time the specified number of days ago.
     def days_ago(days)
       advance(days: -days)
@@ -188,9 +198,9 @@ module DateAndTime
       end
     end
 
-    # Short-hand for months_since(1).
-    def next_month
-      months_since(1)
+    # Returns a new date/time the specified number of months in the future.
+    def next_month(months = 1)
+      advance(months: months)
     end
 
     # Short-hand for months_since(3)
@@ -198,9 +208,9 @@ module DateAndTime
       months_since(3)
     end
 
-    # Short-hand for years_since(1).
-    def next_year
-      years_since(1)
+    # Returns a new date/time the specified number of years in the future.
+    def next_year(years = 1)
+      advance(years: years)
     end
 
     # Returns a new date/time representing the given day in the previous week.
@@ -223,11 +233,15 @@ module DateAndTime
     end
     alias_method :last_weekday, :prev_weekday
 
+    # Returns a new date/time the specified number of months ago.
+    def prev_month(months = 1)
+      advance(months: -months)
+    end
+
     # Short-hand for months_ago(1).
-    def prev_month
+    def last_month
       months_ago(1)
     end
-    alias_method :last_month, :prev_month
 
     # Short-hand for months_ago(3).
     def prev_quarter
@@ -235,11 +249,15 @@ module DateAndTime
     end
     alias_method :last_quarter, :prev_quarter
 
+    # Returns a new date/time the specified number of years ago.
+    def prev_year(years = 1)
+      advance(years: -years)
+    end
+
     # Short-hand for years_ago(1).
-    def prev_year
+    def last_year
       years_ago(1)
     end
-    alias_method :last_year, :prev_year
 
     # Returns the number of days to the start of the week on the given day.
     # Week is assumed to start on +start_day+, default is
@@ -322,20 +340,28 @@ module DateAndTime
       beginning_of_year..end_of_year
     end
 
-    # Returns specific next occurring day of week
+    # Returns a new date/time representing the next occurrence of the specified day of week.
+    #
+    #   today = Date.today               # => Thu, 14 Dec 2017
+    #   today.next_occurring(:monday)    # => Mon, 18 Dec 2017
+    #   today.next_occurring(:thursday)  # => Thu, 21 Dec 2017
     def next_occurring(day_of_week)
       current_day_number = wday != 0 ? wday - 1 : 6
       from_now = DAYS_INTO_WEEK.fetch(day_of_week) - current_day_number
       from_now += 7 unless from_now > 0
-      since(from_now.days)
+      advance(days: from_now)
     end
 
-    # Returns specific previous occurring day of week
+    # Returns a new date/time representing the previous occurrence of the specified day of week.
+    #
+    #   today = Date.today               # => Thu, 14 Dec 2017
+    #   today.prev_occurring(:monday)    # => Mon, 11 Dec 2017
+    #   today.prev_occurring(:thursday)  # => Thu, 07 Dec 2017
     def prev_occurring(day_of_week)
       current_day_number = wday != 0 ? wday - 1 : 6
       ago = current_day_number - DAYS_INTO_WEEK.fetch(day_of_week)
       ago += 7 unless ago > 0
-      ago(ago.days)
+      advance(days: -ago)
     end
 
     private
diff --git a/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb b/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb
index 5b3aabf6a5..d33c36ef73 100644
--- a/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb
+++ b/activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../module/attribute_accessors"
+require "active_support/core_ext/module/attribute_accessors"
 
 module DateAndTime
   module Compatibility
diff --git a/activesupport/lib/active_support/core_ext/date_time.rb b/activesupport/lib/active_support/core_ext/date_time.rb
index b3d6773e4f..790dbeec1b 100644
--- a/activesupport/lib/active_support/core_ext/date_time.rb
+++ b/activesupport/lib/active_support/core_ext/date_time.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "date_time/acts_like"
-require_relative "date_time/blank"
-require_relative "date_time/calculations"
-require_relative "date_time/compatibility"
-require_relative "date_time/conversions"
+require "active_support/core_ext/date_time/acts_like"
+require "active_support/core_ext/date_time/blank"
+require "active_support/core_ext/date_time/calculations"
+require "active_support/core_ext/date_time/compatibility"
+require "active_support/core_ext/date_time/conversions"
diff --git a/activesupport/lib/active_support/core_ext/date_time/acts_like.rb b/activesupport/lib/active_support/core_ext/date_time/acts_like.rb
index 02acb5fe21..5dccdfe219 100644
--- a/activesupport/lib/active_support/core_ext/date_time/acts_like.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/acts_like.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "date"
-require_relative "../object/acts_like"
+require "active_support/core_ext/object/acts_like"
 
 class DateTime
   # Duck-types as a Date-like class. See Object#acts_like?.
diff --git a/activesupport/lib/active_support/core_ext/date_time/compatibility.rb b/activesupport/lib/active_support/core_ext/date_time/compatibility.rb
index 71da7be8ca..7600a067cc 100644
--- a/activesupport/lib/active_support/core_ext/date_time/compatibility.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/compatibility.rb
@@ -1,16 +1,16 @@
 # frozen_string_literal: true
 
-require_relative "../date_and_time/compatibility"
-require_relative "../module/remove_method"
+require "active_support/core_ext/date_and_time/compatibility"
+require "active_support/core_ext/module/redefine_method"
 
 class DateTime
   include DateAndTime::Compatibility
 
-  remove_possible_method :to_time
+  silence_redefinition_of_method :to_time
 
-  # Either return an instance of `Time` with the same UTC offset
-  # as +self+ or an instance of `Time` representing the same time
-  # in the the local system timezone depending on the setting of
+  # Either return an instance of +Time+ with the same UTC offset
+  # as +self+ or an instance of +Time+ representing the same time
+  # in the local system timezone depending on the setting of
   # on the setting of +ActiveSupport.to_time_preserves_timezone+.
   def to_time
     preserve_timezone ? getlocal(utc_offset) : getlocal
diff --git a/activesupport/lib/active_support/core_ext/date_time/conversions.rb b/activesupport/lib/active_support/core_ext/date_time/conversions.rb
index e4c8f9898d..29725c89f7 100644
--- a/activesupport/lib/active_support/core_ext/date_time/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/conversions.rb
@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
 require "date"
-require_relative "../../inflector/methods"
-require_relative "../time/conversions"
-require_relative "calculations"
-require_relative "../../values/time_zone"
+require "active_support/inflector/methods"
+require "active_support/core_ext/time/conversions"
+require "active_support/core_ext/date_time/calculations"
+require "active_support/values/time_zone"
 
 class DateTime
   # Convert to a formatted string. See Time::DATE_FORMATS for predefined formats.
diff --git a/activesupport/lib/active_support/core_ext/enumerable.rb b/activesupport/lib/active_support/core_ext/enumerable.rb
index 17733d955c..7713c52cb1 100644
--- a/activesupport/lib/active_support/core_ext/enumerable.rb
+++ b/activesupport/lib/active_support/core_ext/enumerable.rb
@@ -1,59 +1,50 @@
 # frozen_string_literal: true
 
 module Enumerable
+  INDEX_WITH_DEFAULT = Object.new
+  private_constant :INDEX_WITH_DEFAULT
+
   # Enumerable#sum was added in Ruby 2.4, but it only works with Numeric elements
   # when we omit an identity.
+
+  # We can't use Refinements here because Refinements with Module which will be prepended
+  # doesn't work well https://bugs.ruby-lang.org/issues/13446
+  alias :_original_sum_with_required_identity :sum # :nodoc:
+  private :_original_sum_with_required_identity
+
+  # Calculates a sum from the elements.
   #
-  # We tried shimming it to attempt the fast native method, rescue TypeError,
-  # and fall back to the compatible implementation, but that's much slower than
-  # just calling the compat method in the first place.
-  if Enumerable.instance_methods(false).include?(:sum) && !((?a..?b).sum rescue false)
-    # We can't use Refinements here because Refinements with Module which will be prepended
-    # doesn't work well https://bugs.ruby-lang.org/issues/13446
-    alias :_original_sum_with_required_identity :sum
-    private :_original_sum_with_required_identity
-    # Calculates a sum from the elements.
-    #
-    #  payments.sum { |p| p.price * p.tax_rate }
-    #  payments.sum(&:price)
-    #
-    # The latter is a shortcut for:
-    #
-    #  payments.inject(0) { |sum, p| sum + p.price }
-    #
-    # It can also calculate the sum without the use of a block.
-    #
-    #  [5, 15, 10].sum # => 30
-    #  ['foo', 'bar'].sum # => "foobar"
-    #  [[1, 2], [3, 1, 5]].sum # => [1, 2, 3, 1, 5]
-    #
-    # The default sum of an empty list is zero. You can override this default:
-    #
-    #  [].sum(Payment.new(0)) { |i| i.amount } # => Payment.new(0)
-    def sum(identity = nil, &block)
-      if identity
-        _original_sum_with_required_identity(identity, &block)
-      elsif block_given?
-        map(&block).sum(identity)
-      else
-        inject(:+) || 0
-      end
-    end
-  else
-    def sum(identity = nil, &block)
-      if block_given?
-        map(&block).sum(identity)
-      else
-        sum = identity ? inject(identity, :+) : inject(:+)
-        sum || identity || 0
-      end
+  #  payments.sum { |p| p.price * p.tax_rate }
+  #  payments.sum(&:price)
+  #
+  # The latter is a shortcut for:
+  #
+  #  payments.inject(0) { |sum, p| sum + p.price }
+  #
+  # It can also calculate the sum without the use of a block.
+  #
+  #  [5, 15, 10].sum # => 30
+  #  ['foo', 'bar'].sum # => "foobar"
+  #  [[1, 2], [3, 1, 5]].sum # => [1, 2, 3, 1, 5]
+  #
+  # The default sum of an empty list is zero. You can override this default:
+  #
+  #  [].sum(Payment.new(0)) { |i| i.amount } # => Payment.new(0)
+  def sum(identity = nil, &block)
+    if identity
+      _original_sum_with_required_identity(identity, &block)
+    elsif block_given?
+      map(&block).sum(identity)
+    else
+      inject(:+) || 0
     end
   end
 
-  # Convert an enumerable to a hash.
+  # Convert an enumerable to a hash keying it by the block return value.
   #
   #   people.index_by(&:login)
   #   # => { "nextangle" => <Person ...>, "chade-" => <Person ...>, ...}
+  #
   #   people.index_by { |person| "#{person.first_name} #{person.last_name}" }
   #   # => { "Chade- Fowlersburg-e" => <Person ...>, "David Heinemeier Hansson" => <Person ...>, ...}
   def index_by
@@ -66,6 +57,26 @@ module Enumerable
     end
   end
 
+  # Convert an enumerable to a hash keying it with the enumerable items and with the values returned in the block.
+  #
+  #   post = Post.new(title: "hey there", body: "what's up?")
+  #
+  #   %i( title body ).index_with { |attr_name| post.public_send(attr_name) }
+  #   # => { title: "hey there", body: "what's up?" }
+  def index_with(default = INDEX_WITH_DEFAULT)
+    if block_given?
+      result = {}
+      each { |elem| result[elem] = yield(elem) }
+      result
+    elsif default != INDEX_WITH_DEFAULT
+      result = {}
+      each { |elem| result[elem] = default }
+      result
+    else
+      to_enum(:index_with) { size if respond_to?(:size) }
+    end
+  end
+
   # Returns +true+ if the enumerable has more than 1 element. Functionally
   # equivalent to <tt>enum.to_a.size > 1</tt>. Can be called with a block too,
   # much like any?, so <tt>people.many? { |p| p.age > 26 }</tt> returns +true+
@@ -133,27 +144,21 @@ class Range #:nodoc:
   end
 end
 
-# Array#sum was added in Ruby 2.4 but it only works with Numeric elements.
-#
-# We tried shimming it to attempt the fast native method, rescue TypeError,
-# and fall back to the compatible implementation, but that's much slower than
-# just calling the compat method in the first place.
-if Array.instance_methods(false).include?(:sum) && !(%w[a].sum rescue false)
-  # Using Refinements here in order not to expose our internal method
-  using Module.new {
-    refine Array do
-      alias :orig_sum :sum
-    end
-  }
+# Using Refinements here in order not to expose our internal method
+using Module.new {
+  refine Array do
+    alias :orig_sum :sum
+  end
+}
 
-  class Array
-    def sum(init = nil, &block) #:nodoc:
-      if init.is_a?(Numeric) || first.is_a?(Numeric)
-        init ||= 0
-        orig_sum(init, &block)
-      else
-        super
-      end
+class Array #:nodoc:
+  # Array#sum was added in Ruby 2.4 but it only works with Numeric elements.
+  def sum(init = nil, &block)
+    if init.is_a?(Numeric) || first.is_a?(Numeric)
+      init ||= 0
+      orig_sum(init, &block)
+    else
+      super
     end
   end
 end
diff --git a/activesupport/lib/active_support/core_ext/file.rb b/activesupport/lib/active_support/core_ext/file.rb
index 3c2364167d..64553bfa4e 100644
--- a/activesupport/lib/active_support/core_ext/file.rb
+++ b/activesupport/lib/active_support/core_ext/file.rb
@@ -1,3 +1,3 @@
 # frozen_string_literal: true
 
-require_relative "file/atomic"
+require "active_support/core_ext/file/atomic"
diff --git a/activesupport/lib/active_support/core_ext/hash.rb b/activesupport/lib/active_support/core_ext/hash.rb
index a74a8c15a6..c4b9e5f1a0 100644
--- a/activesupport/lib/active_support/core_ext/hash.rb
+++ b/activesupport/lib/active_support/core_ext/hash.rb
@@ -1,11 +1,9 @@
 # frozen_string_literal: true
 
-require_relative "hash/compact"
-require_relative "hash/conversions"
-require_relative "hash/deep_merge"
-require_relative "hash/except"
-require_relative "hash/indifferent_access"
-require_relative "hash/keys"
-require_relative "hash/reverse_merge"
-require_relative "hash/slice"
-require_relative "hash/transform_values"
+require "active_support/core_ext/hash/conversions"
+require "active_support/core_ext/hash/deep_merge"
+require "active_support/core_ext/hash/except"
+require "active_support/core_ext/hash/indifferent_access"
+require "active_support/core_ext/hash/keys"
+require "active_support/core_ext/hash/reverse_merge"
+require "active_support/core_ext/hash/slice"
diff --git a/activesupport/lib/active_support/core_ext/hash/compact.rb b/activesupport/lib/active_support/core_ext/hash/compact.rb
index d6364dd9f3..28c8d86b9b 100644
--- a/activesupport/lib/active_support/core_ext/hash/compact.rb
+++ b/activesupport/lib/active_support/core_ext/hash/compact.rb
@@ -1,29 +1,5 @@
 # frozen_string_literal: true
 
-class Hash
-  unless Hash.instance_methods(false).include?(:compact)
-    # Returns a hash with non +nil+ values.
-    #
-    #   hash = { a: true, b: false, c: nil }
-    #   hash.compact        # => { a: true, b: false }
-    #   hash                # => { a: true, b: false, c: nil }
-    #   { c: nil }.compact  # => {}
-    #   { c: true }.compact # => { c: true }
-    def compact
-      select { |_, value| !value.nil? }
-    end
-  end
+require "active_support/deprecation"
 
-  unless Hash.instance_methods(false).include?(:compact!)
-    # Replaces current hash with non +nil+ values.
-    # Returns +nil+ if no changes were made, otherwise returns the hash.
-    #
-    #   hash = { a: true, b: false, c: nil }
-    #   hash.compact!        # => { a: true, b: false }
-    #   hash                 # => { a: true, b: false }
-    #   { c: true }.compact! # => nil
-    def compact!
-      reject! { |_, value| value.nil? }
-    end
-  end
-end
+ActiveSupport::Deprecation.warn "Ruby 2.4+ (required by Rails 6) provides Hash#compact and Hash#compact! natively, so requiring active_support/core_ext/hash/compact is no longer necessary. Requiring it will raise LoadError in Rails 6.1."
diff --git a/activesupport/lib/active_support/core_ext/hash/conversions.rb b/activesupport/lib/active_support/core_ext/hash/conversions.rb
index 0c0701134e..5b48254646 100644
--- a/activesupport/lib/active_support/core_ext/hash/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/hash/conversions.rb
@@ -1,13 +1,13 @@
 # frozen_string_literal: true
 
-require_relative "../../xml_mini"
-require_relative "../../time"
-require_relative "../object/blank"
-require_relative "../object/to_param"
-require_relative "../object/to_query"
-require_relative "../array/wrap"
-require_relative "reverse_merge"
-require_relative "../string/inflections"
+require "active_support/xml_mini"
+require "active_support/time"
+require "active_support/core_ext/object/blank"
+require "active_support/core_ext/object/to_param"
+require "active_support/core_ext/object/to_query"
+require "active_support/core_ext/array/wrap"
+require "active_support/core_ext/hash/reverse_merge"
+require "active_support/core_ext/string/inflections"
 
 class Hash
   # Returns a string containing an XML representation of its receiver:
@@ -73,7 +73,7 @@ class Hash
   # configure your own builder with the <tt>:builder</tt> option. The method also accepts
   # options like <tt>:dasherize</tt> and friends, they are forwarded to the builder.
   def to_xml(options = {})
-    require_relative "../../builder" unless defined?(Builder)
+    require "active_support/builder" unless defined?(Builder)
 
     options = options.dup
     options[:indent]  ||= 2
@@ -165,7 +165,7 @@ module ActiveSupport
           Hash[params.map { |k, v| [k.to_s.tr("-", "_"), normalize_keys(v)] } ]
         when Array
           params.map { |v| normalize_keys(v) }
-          else
+        else
           params
         end
       end
@@ -178,7 +178,7 @@ module ActiveSupport
           process_array(value)
         when String
           value
-          else
+        else
           raise "can't typecast #{value.class.name} - #{value.inspect}"
         end
       end
diff --git a/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb b/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb
index 4681d986db..a38f33f128 100644
--- a/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb
+++ b/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../hash_with_indifferent_access"
+require "active_support/hash_with_indifferent_access"
 
 class Hash
   # Returns an <tt>ActiveSupport::HashWithIndifferentAccess</tt> out of its receiver:
diff --git a/activesupport/lib/active_support/core_ext/hash/keys.rb b/activesupport/lib/active_support/core_ext/hash/keys.rb
index d291802b40..bdf196ec3d 100644
--- a/activesupport/lib/active_support/core_ext/hash/keys.rb
+++ b/activesupport/lib/active_support/core_ext/hash/keys.rb
@@ -18,7 +18,7 @@ class Hash
       result[yield(key)] = self[key]
     end
     result
-  end
+  end unless method_defined? :transform_keys
 
   # Destructively converts all keys using the +block+ operations.
   # Same as +transform_keys+ but modifies +self+.
@@ -28,7 +28,7 @@ class Hash
       self[yield(key)] = delete(key)
     end
     self
-  end
+  end unless method_defined? :transform_keys!
 
   # Returns a new hash with all keys converted to strings.
   #
diff --git a/activesupport/lib/active_support/core_ext/hash/slice.rb b/activesupport/lib/active_support/core_ext/hash/slice.rb
index 94dc225edb..2bd0a56ea4 100644
--- a/activesupport/lib/active_support/core_ext/hash/slice.rb
+++ b/activesupport/lib/active_support/core_ext/hash/slice.rb
@@ -21,9 +21,8 @@ class Hash
   #   valid_keys = [:mass, :velocity, :time]
   #   search(options.slice(*valid_keys))
   def slice(*keys)
-    keys.map! { |key| convert_key(key) } if respond_to?(:convert_key, true)
-    keys.each_with_object(self.class.new) { |k, hash| hash[k] = self[k] if has_key?(k) }
-  end
+    keys.each_with_object(Hash.new) { |k, hash| hash[k] = self[k] if has_key?(k) }
+  end unless method_defined?(:slice)
 
   # Replaces the hash with only the given keys.
   # Returns a hash containing the removed key/value pairs.
@@ -31,7 +30,6 @@ class Hash
   #   { a: 1, b: 2, c: 3, d: 4 }.slice!(:a, :b)
   #   # => {:c=>3, :d=>4}
   def slice!(*keys)
-    keys.map! { |key| convert_key(key) } if respond_to?(:convert_key, true)
     omit = slice(*self.keys - keys)
     hash = slice(*keys)
     hash.default      = default
diff --git a/activesupport/lib/active_support/core_ext/hash/transform_values.rb b/activesupport/lib/active_support/core_ext/hash/transform_values.rb
index 4b19c9fc1f..fc15130c9e 100644
--- a/activesupport/lib/active_support/core_ext/hash/transform_values.rb
+++ b/activesupport/lib/active_support/core_ext/hash/transform_values.rb
@@ -1,32 +1,5 @@
 # frozen_string_literal: true
 
-class Hash
-  # Returns a new hash with the results of running +block+ once for every value.
-  # The keys are unchanged.
-  #
-  #   { a: 1, b: 2, c: 3 }.transform_values { |x| x * 2 } # => { a: 2, b: 4, c: 6 }
-  #
-  # If you do not provide a +block+, it will return an Enumerator
-  # for chaining with other methods:
-  #
-  #   { a: 1, b: 2 }.transform_values.with_index { |v, i| [v, i].join.to_i } # => { a: 10, b: 21 }
-  def transform_values
-    return enum_for(:transform_values) { size } unless block_given?
-    return {} if empty?
-    result = self.class.new
-    each do |key, value|
-      result[key] = yield(value)
-    end
-    result
-  end unless method_defined? :transform_values
+require "active_support/deprecation"
 
-  # Destructively converts all values using the +block+ operations.
-  # Same as +transform_values+ but modifies +self+.
-  def transform_values!
-    return enum_for(:transform_values!) { size } unless block_given?
-    each do |key, value|
-      self[key] = yield(value)
-    end
-  end unless method_defined? :transform_values!
-  # TODO: Remove this file when supporting only Ruby 2.4+.
-end
+ActiveSupport::Deprecation.warn "Ruby 2.4+ (required by Rails 6) provides Hash#transform_values natively, so requiring active_support/core_ext/hash/transform_values is no longer necessary. Requiring it will raise LoadError in Rails 6.1."
diff --git a/activesupport/lib/active_support/core_ext/integer.rb b/activesupport/lib/active_support/core_ext/integer.rb
index df80e7ffdb..d22701306a 100644
--- a/activesupport/lib/active_support/core_ext/integer.rb
+++ b/activesupport/lib/active_support/core_ext/integer.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
-require_relative "integer/multiple"
-require_relative "integer/inflections"
-require_relative "integer/time"
+require "active_support/core_ext/integer/multiple"
+require "active_support/core_ext/integer/inflections"
+require "active_support/core_ext/integer/time"
diff --git a/activesupport/lib/active_support/core_ext/integer/inflections.rb b/activesupport/lib/active_support/core_ext/integer/inflections.rb
index 7192e92346..aef3266f28 100644
--- a/activesupport/lib/active_support/core_ext/integer/inflections.rb
+++ b/activesupport/lib/active_support/core_ext/integer/inflections.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../inflector"
+require "active_support/inflector"
 
 class Integer
   # Ordinalize turns a number into an ordinal string used to denote the
diff --git a/activesupport/lib/active_support/core_ext/integer/time.rb b/activesupport/lib/active_support/core_ext/integer/time.rb
index 30c8f3bcf2..5efb89cf9f 100644
--- a/activesupport/lib/active_support/core_ext/integer/time.rb
+++ b/activesupport/lib/active_support/core_ext/integer/time.rb
@@ -1,29 +1,20 @@
 # frozen_string_literal: true
 
-require_relative "../../duration"
-require_relative "../numeric/time"
+require "active_support/duration"
+require "active_support/core_ext/numeric/time"
 
 class Integer
-  # Enables the use of time calculations and declarations, like <tt>45.minutes +
-  # 2.hours + 4.years</tt>.
+  # Returns a Duration instance matching the number of months provided.
   #
-  # These methods use Time#advance for precise date calculations when using
-  # <tt>from_now</tt>, +ago+, etc. as well as adding or subtracting their
-  # results from a Time object.
-  #
-  #   # equivalent to Time.now.advance(months: 1)
-  #   1.month.from_now
-  #
-  #   # equivalent to Time.now.advance(years: 2)
-  #   2.years.from_now
-  #
-  #   # equivalent to Time.now.advance(months: 4, years: 5)
-  #   (4.months + 5.years).from_now
+  #   2.months # => 2 months
   def months
     ActiveSupport::Duration.months(self)
   end
   alias :month :months
 
+  # Returns a Duration instance matching the number of years provided.
+  #
+  #   2.years # => 2 years
   def years
     ActiveSupport::Duration.years(self)
   end
diff --git a/activesupport/lib/active_support/core_ext/kernel.rb b/activesupport/lib/active_support/core_ext/kernel.rb
index 30810ce315..0f4356fbdd 100644
--- a/activesupport/lib/active_support/core_ext/kernel.rb
+++ b/activesupport/lib/active_support/core_ext/kernel.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "kernel/agnostics"
-require_relative "kernel/concern"
-require_relative "kernel/reporting"
-require_relative "kernel/singleton_class"
+require "active_support/core_ext/kernel/agnostics"
+require "active_support/core_ext/kernel/concern"
+require "active_support/core_ext/kernel/reporting"
+require "active_support/core_ext/kernel/singleton_class"
diff --git a/activesupport/lib/active_support/core_ext/kernel/concern.rb b/activesupport/lib/active_support/core_ext/kernel/concern.rb
index 32af9981a5..0b2baed780 100644
--- a/activesupport/lib/active_support/core_ext/kernel/concern.rb
+++ b/activesupport/lib/active_support/core_ext/kernel/concern.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../module/concerning"
+require "active_support/core_ext/module/concerning"
 
 module Kernel
   module_function
diff --git a/activesupport/lib/active_support/core_ext/load_error.rb b/activesupport/lib/active_support/core_ext/load_error.rb
index 750f858fcc..6b0dcab905 100644
--- a/activesupport/lib/active_support/core_ext/load_error.rb
+++ b/activesupport/lib/active_support/core_ext/load_error.rb
@@ -4,6 +4,6 @@ class LoadError
   # Returns true if the given path name (except perhaps for the ".rb"
   # extension) is the missing file which caused the exception to be raised.
   def is_missing?(location)
-    location.sub(/\.rb$/, "".freeze) == path.sub(/\.rb$/, "".freeze)
+    location.sub(/\.rb$/, "".freeze) == path.to_s.sub(/\.rb$/, "".freeze)
   end
 end
diff --git a/activesupport/lib/active_support/core_ext/module.rb b/activesupport/lib/active_support/core_ext/module.rb
index da8f572c3b..d91e3fba6a 100644
--- a/activesupport/lib/active_support/core_ext/module.rb
+++ b/activesupport/lib/active_support/core_ext/module.rb
@@ -1,13 +1,14 @@
 # frozen_string_literal: true
 
-require_relative "module/aliasing"
-require_relative "module/introspection"
-require_relative "module/anonymous"
-require_relative "module/reachable"
-require_relative "module/attribute_accessors"
-require_relative "module/attribute_accessors_per_thread"
-require_relative "module/attr_internal"
-require_relative "module/concerning"
-require_relative "module/delegation"
-require_relative "module/deprecation"
-require_relative "module/remove_method"
+require "active_support/core_ext/module/aliasing"
+require "active_support/core_ext/module/introspection"
+require "active_support/core_ext/module/anonymous"
+require "active_support/core_ext/module/reachable"
+require "active_support/core_ext/module/attribute_accessors"
+require "active_support/core_ext/module/attribute_accessors_per_thread"
+require "active_support/core_ext/module/attr_internal"
+require "active_support/core_ext/module/concerning"
+require "active_support/core_ext/module/delegation"
+require "active_support/core_ext/module/deprecation"
+require "active_support/core_ext/module/redefine_method"
+require "active_support/core_ext/module/remove_method"
diff --git a/activesupport/lib/active_support/core_ext/module/attribute_accessors.rb b/activesupport/lib/active_support/core_ext/module/attribute_accessors.rb
index e667c1f4a4..01fee0fb74 100644
--- a/activesupport/lib/active_support/core_ext/module/attribute_accessors.rb
+++ b/activesupport/lib/active_support/core_ext/module/attribute_accessors.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../array/extract_options"
-require_relative "../regexp"
+require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/regexp"
 
 # Extends the module object with class/module and instance accessors for
 # class/module attributes, just like the native attr* accessors for instance
@@ -163,10 +163,10 @@ class Module
   # parent class. Similarly if parent class changes the value then that would
   # change the value of subclasses too.
   #
-  #   class Male < Person
+  #   class Citizen < Person
   #   end
   #
-  #   Male.new.hair_colors << :blue
+  #   Citizen.new.hair_colors << :blue
   #   Person.new.hair_colors # => [:brown, :black, :blonde, :red, :blue]
   #
   # To opt out of the instance writer method, pass <tt>instance_writer: false</tt>.
diff --git a/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb b/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
index 90a350c5dc..4b9b6ea9bd 100644
--- a/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
+++ b/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../array/extract_options"
-require_relative "../regexp"
+require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/regexp"
 
 # Extends the module object with class/module and instance accessors for
 # class/module attributes, just like the native attr* accessors for instance
diff --git a/activesupport/lib/active_support/core_ext/module/concerning.rb b/activesupport/lib/active_support/core_ext/module/concerning.rb
index 17c202a24a..7bbbf321ab 100644
--- a/activesupport/lib/active_support/core_ext/module/concerning.rb
+++ b/activesupport/lib/active_support/core_ext/module/concerning.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../concern"
+require "active_support/concern"
 
 class Module
   # = Bite-sized separation of concerns
@@ -22,7 +22,7 @@ class Module
   #
   # == Using comments:
   #
-  #   class Todo
+  #   class Todo < ApplicationRecord
   #     # Other todo implementation
   #     # ...
   #
@@ -30,7 +30,6 @@ class Module
   #     has_many :events
   #
   #     before_create :track_creation
-  #     after_destroy :track_deletion
   #
   #     private
   #       def track_creation
@@ -42,7 +41,7 @@ class Module
   #
   # Noisy syntax.
   #
-  #   class Todo
+  #   class Todo < ApplicationRecord
   #     # Other todo implementation
   #     # ...
   #
@@ -52,7 +51,6 @@ class Module
   #       included do
   #         has_many :events
   #         before_create :track_creation
-  #         after_destroy :track_deletion
   #       end
   #
   #       private
@@ -70,7 +68,7 @@ class Module
   # increased overhead can be a reasonable tradeoff even if it reduces our
   # at-a-glance perception of how things work.
   #
-  #   class Todo
+  #   class Todo < ApplicationRecord
   #     # Other todo implementation
   #     # ...
   #
@@ -82,7 +80,7 @@ class Module
   # By quieting the mix-in noise, we arrive at a natural, low-ceremony way to
   # separate bite-sized concerns.
   #
-  #   class Todo
+  #   class Todo < ApplicationRecord
   #     # Other todo implementation
   #     # ...
   #
@@ -90,7 +88,6 @@ class Module
   #       included do
   #         has_many :events
   #         before_create :track_creation
-  #         after_destroy :track_deletion
   #       end
   #
   #       private
@@ -101,7 +98,7 @@ class Module
   #   end
   #
   #   Todo.ancestors
-  #   # => [Todo, Todo::EventTracking, Object]
+  #   # => [Todo, Todo::EventTracking, ApplicationRecord, Object]
   #
   # This small step has some wonderful ripple effects. We can
   # * grok the behavior of our class in one glance,
diff --git a/activesupport/lib/active_support/core_ext/module/delegation.rb b/activesupport/lib/active_support/core_ext/module/delegation.rb
index 1840dc942f..7f42f44efb 100644
--- a/activesupport/lib/active_support/core_ext/module/delegation.rb
+++ b/activesupport/lib/active_support/core_ext/module/delegation.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "set"
-require_relative "../regexp"
+require "active_support/core_ext/regexp"
 
 class Module
   # Error generated by +delegate+ when a method is called on +nil+ and +allow_nil+
@@ -22,8 +22,9 @@ class Module
   # ==== Options
   # * <tt>:to</tt> - Specifies the target object
   # * <tt>:prefix</tt> - Prefixes the new method with the target name or a custom prefix
-  # * <tt>:allow_nil</tt> - if set to true, prevents a +Module::DelegationError+
+  # * <tt>:allow_nil</tt> - If set to true, prevents a +Module::DelegationError+
   #   from being raised
+  # * <tt>:private</tt> - If set to true, changes method visibility to private
   #
   # The macro receives one or more method names (specified as symbols or
   # strings) and the name of the target object via the <tt>:to</tt> option
@@ -114,12 +115,26 @@ class Module
   #   invoice.customer_name    # => 'John Doe'
   #   invoice.customer_address # => 'Vimmersvej 13'
   #
+  # The delegated methods are public by default.
+  # Pass <tt>private: true</tt> to change that.
+  #
+  #   class User < ActiveRecord::Base
+  #     has_one :profile
+  #     delegate :first_name, to: :profile
+  #     delegate :date_of_birth, to: :profile, private: true
+  #
+  #     def age
+  #       Date.today.year - date_of_birth.year
+  #     end
+  #   end
+  #
+  #   User.new.first_name # => "Tomas"
+  #   User.new.date_of_birth # => NoMethodError: private method `date_of_birth' called for #<User:0x00000008221340>
+  #   User.new.age # => 2
+  #
   # If the target is +nil+ and does not respond to the delegated method a
-  # +Module::DelegationError+ is raised, as with any other value. Sometimes,
-  # however, it makes sense to be robust to that situation and that is the
-  # purpose of the <tt>:allow_nil</tt> option: If the target is not +nil+, or it
-  # is and responds to the method, everything works as usual. But if it is +nil+
-  # and does not respond to the delegated method, +nil+ is returned.
+  # +Module::DelegationError+ is raised. If you wish to instead return +nil+,
+  # use the <tt>:allow_nil</tt> option.
   #
   #   class User < ActiveRecord::Base
   #     has_one :profile
@@ -154,7 +169,7 @@ class Module
   #   Foo.new("Bar").name # raises NoMethodError: undefined method `name'
   #
   # The target method must be public, otherwise it will raise +NoMethodError+.
-  def delegate(*methods, to: nil, prefix: nil, allow_nil: nil)
+  def delegate(*methods, to: nil, prefix: nil, allow_nil: nil, private: nil)
     unless to
       raise ArgumentError, "Delegation needs a target. Supply an options hash with a :to key as the last argument (e.g. delegate :hello, to: :greeter)."
     end
@@ -176,7 +191,7 @@ class Module
     to = to.to_s
     to = "self.#{to}" if DELEGATION_RESERVED_METHOD_NAMES.include?(to)
 
-    methods.map do |method|
+    method_names = methods.map do |method|
       # Attribute writer methods only accept one argument. Makes sure []=
       # methods still accept two arguments.
       definition = /[^\]]=$/.match?(method) ? "arg" : "*args, &block"
@@ -216,6 +231,9 @@ class Module
 
       module_eval(method_def, file, line)
     end
+
+    private(*method_names) if private
+    method_names
   end
 
   # When building decorators, a common pattern may emerge:
diff --git a/activesupport/lib/active_support/core_ext/module/introspection.rb b/activesupport/lib/active_support/core_ext/module/introspection.rb
index 540385ef6f..c5bb598bd1 100644
--- a/activesupport/lib/active_support/core_ext/module/introspection.rb
+++ b/activesupport/lib/active_support/core_ext/module/introspection.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../inflector"
+require "active_support/inflector"
 
 class Module
   # Returns the name of the module containing this one.
diff --git a/activesupport/lib/active_support/core_ext/module/reachable.rb b/activesupport/lib/active_support/core_ext/module/reachable.rb
index 91b230b46c..e9cbda5245 100644
--- a/activesupport/lib/active_support/core_ext/module/reachable.rb
+++ b/activesupport/lib/active_support/core_ext/module/reachable.rb
@@ -1,10 +1,11 @@
 # frozen_string_literal: true
 
-require_relative "anonymous"
-require_relative "../string/inflections"
+require "active_support/core_ext/module/anonymous"
+require "active_support/core_ext/string/inflections"
 
 class Module
   def reachable? #:nodoc:
     !anonymous? && name.safe_constantize.equal?(self)
   end
+  deprecate :reachable?
 end
diff --git a/activesupport/lib/active_support/core_ext/module/redefine_method.rb b/activesupport/lib/active_support/core_ext/module/redefine_method.rb
new file mode 100644
index 0000000000..5bd8e6e973
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/module/redefine_method.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+class Module
+  # Marks the named method as intended to be redefined, if it exists.
+  # Suppresses the Ruby method redefinition warning. Prefer
+  # #redefine_method where possible.
+  def silence_redefinition_of_method(method)
+    if method_defined?(method) || private_method_defined?(method)
+      # This suppresses the "method redefined" warning; the self-alias
+      # looks odd, but means we don't need to generate a unique name
+      alias_method method, method
+    end
+  end
+
+  # Replaces the existing method definition, if there is one, with the passed
+  # block as its body.
+  def redefine_method(method, &block)
+    visibility = method_visibility(method)
+    silence_redefinition_of_method(method)
+    define_method(method, &block)
+    send(visibility, method)
+  end
+
+  # Replaces the existing singleton method definition, if there is one, with
+  # the passed block as its body.
+  def redefine_singleton_method(method, &block)
+    singleton_class.redefine_method(method, &block)
+  end
+
+  def method_visibility(method) # :nodoc:
+    case
+    when private_method_defined?(method)
+      :private
+    when protected_method_defined?(method)
+      :protected
+    else
+      :public
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/core_ext/module/remove_method.rb b/activesupport/lib/active_support/core_ext/module/remove_method.rb
index bf0d686e16..97eb5f9eca 100644
--- a/activesupport/lib/active_support/core_ext/module/remove_method.rb
+++ b/activesupport/lib/active_support/core_ext/module/remove_method.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/module/redefine_method"
+
 class Module
   # Removes the named method, if it exists.
   def remove_possible_method(method)
@@ -10,28 +12,6 @@ class Module
 
   # Removes the named singleton method, if it exists.
   def remove_possible_singleton_method(method)
-    singleton_class.instance_eval do
-      remove_possible_method(method)
-    end
-  end
-
-  # Replaces the existing method definition, if there is one, with the passed
-  # block as its body.
-  def redefine_method(method, &block)
-    visibility = method_visibility(method)
-    remove_possible_method(method)
-    define_method(method, &block)
-    send(visibility, method)
-  end
-
-  def method_visibility(method) # :nodoc:
-    case
-    when private_method_defined?(method)
-      :private
-    when protected_method_defined?(method)
-      :protected
-    else
-      :public
-    end
+    singleton_class.remove_possible_method(method)
   end
 end
diff --git a/activesupport/lib/active_support/core_ext/name_error.rb b/activesupport/lib/active_support/core_ext/name_error.rb
index d4f1e01140..6d37cd9dfd 100644
--- a/activesupport/lib/active_support/core_ext/name_error.rb
+++ b/activesupport/lib/active_support/core_ext/name_error.rb
@@ -10,6 +10,11 @@ class NameError
   #   end
   #   # => "HelloWorld"
   def missing_name
+    # Since ruby v2.3.0 `did_you_mean` gem is loaded by default.
+    # It extends NameError#message with spell corrections which are SLOW.
+    # We should use original_message message instead.
+    message = respond_to?(:original_message) ? original_message : self.message
+
     if /undefined local variable or method/ !~ message
       $1 if /((::)?([A-Z]\w*)(::[A-Z]\w*)*)$/ =~ message
     end
diff --git a/activesupport/lib/active_support/core_ext/numeric.rb b/activesupport/lib/active_support/core_ext/numeric.rb
index 76e33a7cb0..fe778470f1 100644
--- a/activesupport/lib/active_support/core_ext/numeric.rb
+++ b/activesupport/lib/active_support/core_ext/numeric.rb
@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-require_relative "numeric/bytes"
-require_relative "numeric/time"
-require_relative "numeric/inquiry"
-require_relative "numeric/conversions"
+require "active_support/core_ext/numeric/bytes"
+require "active_support/core_ext/numeric/time"
+require "active_support/core_ext/numeric/conversions"
diff --git a/activesupport/lib/active_support/core_ext/numeric/conversions.rb b/activesupport/lib/active_support/core_ext/numeric/conversions.rb
index 05528f5069..7fcd0d0311 100644
--- a/activesupport/lib/active_support/core_ext/numeric/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/numeric/conversions.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../big_decimal/conversions"
-require_relative "../../number_helper"
-require_relative "../module/deprecation"
+require "active_support/core_ext/big_decimal/conversions"
+require "active_support/number_helper"
+require "active_support/core_ext/module/deprecation"
 
 module ActiveSupport::NumericWithFormat
   # Provides options for converting numbers into formatted strings.
@@ -108,19 +108,19 @@ module ActiveSupport::NumericWithFormat
     when Integer, String
       super(format)
     when :phone
-      return ActiveSupport::NumberHelper.number_to_phone(self, options || {})
+      ActiveSupport::NumberHelper.number_to_phone(self, options || {})
     when :currency
-      return ActiveSupport::NumberHelper.number_to_currency(self, options || {})
+      ActiveSupport::NumberHelper.number_to_currency(self, options || {})
     when :percentage
-      return ActiveSupport::NumberHelper.number_to_percentage(self, options || {})
+      ActiveSupport::NumberHelper.number_to_percentage(self, options || {})
     when :delimited
-      return ActiveSupport::NumberHelper.number_to_delimited(self, options || {})
+      ActiveSupport::NumberHelper.number_to_delimited(self, options || {})
     when :rounded
-      return ActiveSupport::NumberHelper.number_to_rounded(self, options || {})
+      ActiveSupport::NumberHelper.number_to_rounded(self, options || {})
     when :human
-      return ActiveSupport::NumberHelper.number_to_human(self, options || {})
+      ActiveSupport::NumberHelper.number_to_human(self, options || {})
     when :human_size
-      return ActiveSupport::NumberHelper.number_to_human_size(self, options || {})
+      ActiveSupport::NumberHelper.number_to_human_size(self, options || {})
     when Symbol
       super()
     else
@@ -129,12 +129,6 @@ module ActiveSupport::NumericWithFormat
   end
 end
 
-# Ruby 2.4+ unifies Fixnum & Bignum into Integer.
-if 0.class == Integer
-  Integer.prepend ActiveSupport::NumericWithFormat
-else
-  Fixnum.prepend ActiveSupport::NumericWithFormat
-  Bignum.prepend ActiveSupport::NumericWithFormat
-end
+Integer.prepend ActiveSupport::NumericWithFormat
 Float.prepend ActiveSupport::NumericWithFormat
 BigDecimal.prepend ActiveSupport::NumericWithFormat
diff --git a/activesupport/lib/active_support/core_ext/numeric/inquiry.rb b/activesupport/lib/active_support/core_ext/numeric/inquiry.rb
index 15334c91f1..e05e40825b 100644
--- a/activesupport/lib/active_support/core_ext/numeric/inquiry.rb
+++ b/activesupport/lib/active_support/core_ext/numeric/inquiry.rb
@@ -1,28 +1,5 @@
 # frozen_string_literal: true
 
-unless 1.respond_to?(:positive?) # TODO: Remove this file when we drop support to ruby < 2.3
-  class Numeric
-    # Returns true if the number is positive.
-    #
-    #   1.positive?  # => true
-    #   0.positive?  # => false
-    #   -1.positive? # => false
-    def positive?
-      self > 0
-    end
+require "active_support/deprecation"
 
-    # Returns true if the number is negative.
-    #
-    #   -1.negative? # => true
-    #   0.negative?  # => false
-    #   1.negative?  # => false
-    def negative?
-      self < 0
-    end
-  end
-
-  class Complex
-    undef :positive?
-    undef :negative?
-  end
-end
+ActiveSupport::Deprecation.warn "Ruby 2.4+ (required by Rails 6) provides Numeric#positive? and Numeric#negative? natively, so requiring active_support/core_ext/numeric/inquiry is no longer necessary. Requiring it will raise LoadError in Rails 6.1."
diff --git a/activesupport/lib/active_support/core_ext/numeric/time.rb b/activesupport/lib/active_support/core_ext/numeric/time.rb
index 0cee87cb86..bc4627f7a2 100644
--- a/activesupport/lib/active_support/core_ext/numeric/time.rb
+++ b/activesupport/lib/active_support/core_ext/numeric/time.rb
@@ -1,25 +1,15 @@
 # frozen_string_literal: true
 
-require_relative "../../duration"
-require_relative "../time/calculations"
-require_relative "../time/acts_like"
-require_relative "../date/calculations"
-require_relative "../date/acts_like"
+require "active_support/duration"
+require "active_support/core_ext/time/calculations"
+require "active_support/core_ext/time/acts_like"
+require "active_support/core_ext/date/calculations"
+require "active_support/core_ext/date/acts_like"
 
 class Numeric
-  # Enables the use of time calculations and declarations, like 45.minutes + 2.hours + 4.years.
+  # Returns a Duration instance matching the number of seconds provided.
   #
-  # These methods use Time#advance for precise date calculations when using from_now, ago, etc.
-  # as well as adding or subtracting their results from a Time object. For example:
-  #
-  #   # equivalent to Time.current.advance(months: 1)
-  #   1.month.from_now
-  #
-  #   # equivalent to Time.current.advance(years: 2)
-  #   2.years.from_now
-  #
-  #   # equivalent to Time.current.advance(months: 4, years: 5)
-  #   (4.months + 5.years).from_now
+  #   2.seconds # => 2 seconds
   def seconds
     ActiveSupport::Duration.seconds(self)
   end
@@ -66,10 +56,10 @@ class Numeric
   alias :fortnight :fortnights
 
   # Returns the number of milliseconds equivalent to the seconds provided.
-  # Used with the standard time durations, like 1.hour.in_milliseconds --
-  # so we can feed them to JavaScript functions like getTime().
+  # Used with the standard time durations.
   #
-  #   2.in_milliseconds # => 2_000
+  #   2.in_milliseconds # => 2000
+  #   1.hour.in_milliseconds # => 3600000
   def in_milliseconds
     self * 1000
   end
diff --git a/activesupport/lib/active_support/core_ext/object.rb b/activesupport/lib/active_support/core_ext/object.rb
index 23f5eec8c7..efd34cc692 100644
--- a/activesupport/lib/active_support/core_ext/object.rb
+++ b/activesupport/lib/active_support/core_ext/object.rb
@@ -1,16 +1,16 @@
 # frozen_string_literal: true
 
-require_relative "object/acts_like"
-require_relative "object/blank"
-require_relative "object/duplicable"
-require_relative "object/deep_dup"
-require_relative "object/try"
-require_relative "object/inclusion"
+require "active_support/core_ext/object/acts_like"
+require "active_support/core_ext/object/blank"
+require "active_support/core_ext/object/duplicable"
+require "active_support/core_ext/object/deep_dup"
+require "active_support/core_ext/object/try"
+require "active_support/core_ext/object/inclusion"
 
-require_relative "object/conversions"
-require_relative "object/instance_variables"
+require "active_support/core_ext/object/conversions"
+require "active_support/core_ext/object/instance_variables"
 
-require_relative "object/json"
-require_relative "object/to_param"
-require_relative "object/to_query"
-require_relative "object/with_options"
+require "active_support/core_ext/object/json"
+require "active_support/core_ext/object/to_param"
+require "active_support/core_ext/object/to_query"
+require "active_support/core_ext/object/with_options"
diff --git a/activesupport/lib/active_support/core_ext/object/acts_like.rb b/activesupport/lib/active_support/core_ext/object/acts_like.rb
index 2eb72f6b3a..403ee20e39 100644
--- a/activesupport/lib/active_support/core_ext/object/acts_like.rb
+++ b/activesupport/lib/active_support/core_ext/object/acts_like.rb
@@ -7,6 +7,15 @@ class Object
   # <tt>x.acts_like?(:date)</tt> to do duck-type-safe comparisons, since classes that
   # we want to act like Time simply need to define an <tt>acts_like_time?</tt> method.
   def acts_like?(duck)
-    respond_to? :"acts_like_#{duck}?"
+    case duck
+    when :time
+      respond_to? :acts_like_time?
+    when :date
+      respond_to? :acts_like_date?
+    when :string
+      respond_to? :acts_like_string?
+    else
+      respond_to? :"acts_like_#{duck}?"
+    end
   end
 end
diff --git a/activesupport/lib/active_support/core_ext/object/blank.rb b/activesupport/lib/active_support/core_ext/object/blank.rb
index 397adbdb5a..2ca431ab10 100644
--- a/activesupport/lib/active_support/core_ext/object/blank.rb
+++ b/activesupport/lib/active_support/core_ext/object/blank.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../regexp"
+require "active_support/core_ext/regexp"
+require "concurrent/map"
 
 class Object
   # An object is blank if it's false, empty, or a whitespace string.
@@ -102,6 +103,9 @@ end
 
 class String
   BLANK_RE = /\A[[:space:]]*\z/
+  ENCODED_BLANKS = Concurrent::Map.new do |h, enc|
+    h[enc] = Regexp.new(BLANK_RE.source.encode(enc), BLANK_RE.options | Regexp::FIXEDENCODING)
+  end
 
   # A string is blank if it's empty or contains whitespaces only:
   #
@@ -119,7 +123,12 @@ class String
     # The regexp that matches blank strings is expensive. For the case of empty
     # strings we can speed up this method (~3.5x) with an empty? call. The
     # penalty for the rest of strings is marginal.
-    empty? || BLANK_RE.match?(self)
+    empty? ||
+      begin
+        BLANK_RE.match?(self)
+      rescue Encoding::CompatibilityError
+        ENCODED_BLANKS[self.encoding].match?(self)
+      end
   end
 end
 
diff --git a/activesupport/lib/active_support/core_ext/object/conversions.rb b/activesupport/lib/active_support/core_ext/object/conversions.rb
index fdc154188a..624fb8d77c 100644
--- a/activesupport/lib/active_support/core_ext/object/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/object/conversions.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "to_param"
-require_relative "to_query"
-require_relative "../array/conversions"
-require_relative "../hash/conversions"
+require "active_support/core_ext/object/to_param"
+require "active_support/core_ext/object/to_query"
+require "active_support/core_ext/array/conversions"
+require "active_support/core_ext/hash/conversions"
diff --git a/activesupport/lib/active_support/core_ext/object/deep_dup.rb b/activesupport/lib/active_support/core_ext/object/deep_dup.rb
index 4021b15de6..c66c5eb2d9 100644
--- a/activesupport/lib/active_support/core_ext/object/deep_dup.rb
+++ b/activesupport/lib/active_support/core_ext/object/deep_dup.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "duplicable"
+require "active_support/core_ext/object/duplicable"
 
 class Object
   # Returns a deep copy of object if it's duplicable. If it's
diff --git a/activesupport/lib/active_support/core_ext/object/duplicable.rb b/activesupport/lib/active_support/core_ext/object/duplicable.rb
index 1744a44df6..c78ee6bbfc 100644
--- a/activesupport/lib/active_support/core_ext/object/duplicable.rb
+++ b/activesupport/lib/active_support/core_ext/object/duplicable.rb
@@ -75,8 +75,11 @@ end
 
 class Symbol
   begin
-    :symbol.dup # Ruby 2.4.x.
-    "symbol_from_string".to_sym.dup # Some symbols can't `dup` in Ruby 2.4.0.
+    :symbol.dup
+
+    # Some symbols couldn't be duped in Ruby 2.4.0 only, due to a bug.
+    # This feature check catches any regression.
+    "symbol_from_string".to_sym.dup
   rescue TypeError
 
     # Symbols are not duplicable:
@@ -108,8 +111,8 @@ require "bigdecimal"
 class BigDecimal
   # BigDecimals are duplicable:
   #
-  #   BigDecimal.new("1.2").duplicable? # => true
-  #   BigDecimal.new("1.2").dup         # => #<BigDecimal:...,'0.12E1',18(18)>
+  #   BigDecimal("1.2").duplicable? # => true
+  #   BigDecimal("1.2").dup         # => #<BigDecimal:...,'0.12E1',18(18)>
   def duplicable?
     true
   end
diff --git a/activesupport/lib/active_support/core_ext/object/json.rb b/activesupport/lib/active_support/core_ext/object/json.rb
index 30495313d2..416059d17b 100644
--- a/activesupport/lib/active_support/core_ext/object/json.rb
+++ b/activesupport/lib/active_support/core_ext/object/json.rb
@@ -5,15 +5,16 @@ require "json"
 require "bigdecimal"
 require "uri/generic"
 require "pathname"
-require_relative "../big_decimal/conversions" # for #to_s
-require_relative "../hash/except"
-require_relative "../hash/slice"
-require_relative "instance_variables"
+require "active_support/core_ext/big_decimal/conversions" # for #to_s
+require "active_support/core_ext/hash/except"
+require "active_support/core_ext/hash/slice"
+require "active_support/core_ext/object/instance_variables"
 require "time"
-require_relative "../time/conversions"
-require_relative "../date_time/conversions"
-require_relative "../date/conversions"
+require "active_support/core_ext/time/conversions"
+require "active_support/core_ext/date_time/conversions"
+require "active_support/core_ext/date/conversions"
 
+#--
 # The JSON gem adds a few modules to Ruby core classes containing :to_json definition, overwriting
 # their default behavior. That said, we need to define the basic to_json method in all of them,
 # otherwise they will always use to_json gem implementation, which is backwards incompatible in
@@ -135,6 +136,12 @@ module Enumerable
   end
 end
 
+class IO
+  def as_json(options = nil) #:nodoc:
+    to_s
+  end
+end
+
 class Range
   def as_json(options = nil) #:nodoc:
     to_s
diff --git a/activesupport/lib/active_support/core_ext/object/to_param.rb b/activesupport/lib/active_support/core_ext/object/to_param.rb
index c57488bcbc..6d2bdd70f3 100644
--- a/activesupport/lib/active_support/core_ext/object/to_param.rb
+++ b/activesupport/lib/active_support/core_ext/object/to_param.rb
@@ -1,3 +1,3 @@
 # frozen_string_literal: true
 
-require_relative "to_query"
+require "active_support/core_ext/object/to_query"
diff --git a/activesupport/lib/active_support/core_ext/object/with_options.rb b/activesupport/lib/active_support/core_ext/object/with_options.rb
index 47766f6012..2838fd76be 100644
--- a/activesupport/lib/active_support/core_ext/object/with_options.rb
+++ b/activesupport/lib/active_support/core_ext/object/with_options.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../option_merger"
+require "active_support/option_merger"
 
 class Object
   # An elegant way to factor duplication out of options passed to a series of
@@ -62,7 +62,7 @@ class Object
   #
   #   validates :content, length: { minimum: 50 }, if: -> { content.present? }
   #
-  # Hence the inherited default for `if` key is ignored.
+  # Hence the inherited default for +if+ key is ignored.
   #
   # NOTE: You cannot call class methods implicitly inside of with_options.
   # You can access these methods using the class name instead:
diff --git a/activesupport/lib/active_support/core_ext/range.rb b/activesupport/lib/active_support/core_ext/range.rb
index 89bbbfcb81..78814fd189 100644
--- a/activesupport/lib/active_support/core_ext/range.rb
+++ b/activesupport/lib/active_support/core_ext/range.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "range/conversions"
-require_relative "range/include_range"
-require_relative "range/overlaps"
-require_relative "range/each"
+require "active_support/core_ext/range/conversions"
+require "active_support/core_ext/range/compare_range"
+require "active_support/core_ext/range/include_time_with_zone"
+require "active_support/core_ext/range/overlaps"
+require "active_support/core_ext/range/each"
diff --git a/activesupport/lib/active_support/core_ext/range/compare_range.rb b/activesupport/lib/active_support/core_ext/range/compare_range.rb
new file mode 100644
index 0000000000..704041f6de
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/range/compare_range.rb
@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+module ActiveSupport
+  module CompareWithRange #:nodoc:
+    # Extends the default Range#=== to support range comparisons.
+    #  (1..5) === (1..5) # => true
+    #  (1..5) === (2..3) # => true
+    #  (1..5) === (2..6) # => false
+    #
+    # The native Range#=== behavior is untouched.
+    #  ('a'..'f') === ('c') # => true
+    #  (5..9) === (11) # => false
+    def ===(value)
+      if value.is_a?(::Range)
+        # 1...10 includes 1..9 but it does not include 1..10.
+        operator = exclude_end? && !value.exclude_end? ? :< : :<=
+        super(value.first) && value.last.send(operator, last)
+      else
+        super
+      end
+    end
+
+    # Extends the default Range#include? to support range comparisons.
+    #  (1..5).include?(1..5) # => true
+    #  (1..5).include?(2..3) # => true
+    #  (1..5).include?(2..6) # => false
+    #
+    # The native Range#include? behavior is untouched.
+    #  ('a'..'f').include?('c') # => true
+    #  (5..9).include?(11) # => false
+    def include?(value)
+      if value.is_a?(::Range)
+        # 1...10 includes 1..9 but it does not include 1..10.
+        operator = exclude_end? && !value.exclude_end? ? :< : :<=
+        super(value.first) && value.last.send(operator, last)
+      else
+        super
+      end
+    end
+
+    # Extends the default Range#cover? to support range comparisons.
+    #  (1..5).cover?(1..5) # => true
+    #  (1..5).cover?(2..3) # => true
+    #  (1..5).cover?(2..6) # => false
+    #
+    # The native Range#cover? behavior is untouched.
+    #  ('a'..'f').cover?('c') # => true
+    #  (5..9).cover?(11) # => false
+    def cover?(value)
+      if value.is_a?(::Range)
+        # 1...10 covers 1..9 but it does not cover 1..10.
+        operator = exclude_end? && !value.exclude_end? ? :< : :<=
+        super(value.first) && value.last.send(operator, last)
+      else
+        super
+      end
+    end
+  end
+end
+
+Range.prepend(ActiveSupport::CompareWithRange)
diff --git a/activesupport/lib/active_support/core_ext/range/conversions.rb b/activesupport/lib/active_support/core_ext/range/conversions.rb
index 37868f5875..8832fbcb3c 100644
--- a/activesupport/lib/active_support/core_ext/range/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/range/conversions.rb
@@ -2,7 +2,13 @@
 
 module ActiveSupport::RangeWithFormat
   RANGE_FORMATS = {
-    db: Proc.new { |start, stop| "BETWEEN '#{start.to_s(:db)}' AND '#{stop.to_s(:db)}'" }
+    db: -> (start, stop) do
+      case start
+      when String then "BETWEEN '#{start}' AND '#{stop}'"
+      else
+        "BETWEEN '#{start.to_s(:db)}' AND '#{stop.to_s(:db)}'"
+      end
+    end
   }
 
   # Convert range to a formatted string. See RANGE_FORMATS for predefined formats.
diff --git a/activesupport/lib/active_support/core_ext/range/each.rb b/activesupport/lib/active_support/core_ext/range/each.rb
index cdff6393d7..2f22cd0e92 100644
--- a/activesupport/lib/active_support/core_ext/range/each.rb
+++ b/activesupport/lib/active_support/core_ext/range/each.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/time_with_zone"
+
 module ActiveSupport
   module EachTimeWithZone #:nodoc:
     def each(&block)
@@ -15,7 +17,7 @@ module ActiveSupport
     private
 
       def ensure_iteration_allowed
-        raise TypeError, "can't iterate from #{first.class}" if first.is_a?(Time)
+        raise TypeError, "can't iterate from #{first.class}" if first.is_a?(TimeWithZone)
       end
   end
 end
diff --git a/activesupport/lib/active_support/core_ext/range/include_range.rb b/activesupport/lib/active_support/core_ext/range/include_range.rb
index 7ba1011921..2da2c587a3 100644
--- a/activesupport/lib/active_support/core_ext/range/include_range.rb
+++ b/activesupport/lib/active_support/core_ext/range/include_range.rb
@@ -1,25 +1,9 @@
 # frozen_string_literal: true
 
-module ActiveSupport
-  module IncludeWithRange #:nodoc:
-    # Extends the default Range#include? to support range comparisons.
-    #  (1..5).include?(1..5) # => true
-    #  (1..5).include?(2..3) # => true
-    #  (1..5).include?(2..6) # => false
-    #
-    # The native Range#include? behavior is untouched.
-    #  ('a'..'f').include?('c') # => true
-    #  (5..9).include?(11) # => false
-    def include?(value)
-      if value.is_a?(::Range)
-        # 1...10 includes 1..9 but it does not include 1..10.
-        operator = exclude_end? && !value.exclude_end? ? :< : :<=
-        super(value.first) && value.last.send(operator, last)
-      else
-        super
-      end
-    end
-  end
-end
+require "active_support/deprecation"
 
-Range.prepend(ActiveSupport::IncludeWithRange)
+ActiveSupport::Deprecation.warn "You have required `active_support/core_ext/range/include_range`. " \
+"This file will be removed in Rails 6.1. You should require `active_support/core_ext/range/compare_range` " \
+  "instead."
+
+require "active_support/core_ext/range/compare_range"
diff --git a/activesupport/lib/active_support/core_ext/range/include_time_with_zone.rb b/activesupport/lib/active_support/core_ext/range/include_time_with_zone.rb
new file mode 100644
index 0000000000..5f80acf68e
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/range/include_time_with_zone.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require "active_support/time_with_zone"
+
+module ActiveSupport
+  module IncludeTimeWithZone #:nodoc:
+    # Extends the default Range#include? to support ActiveSupport::TimeWithZone.
+    #
+    #   (1.hour.ago..1.hour.from_now).include?(Time.current) # => true
+    #
+    def include?(value)
+      if first.is_a?(TimeWithZone)
+        cover?(value)
+      elsif last.is_a?(TimeWithZone)
+        cover?(value)
+      else
+        super
+      end
+    end
+  end
+end
+
+Range.prepend(ActiveSupport::IncludeTimeWithZone)
diff --git a/activesupport/lib/active_support/core_ext/regexp.rb b/activesupport/lib/active_support/core_ext/regexp.rb
index efbd708aee..d92943c7ae 100644
--- a/activesupport/lib/active_support/core_ext/regexp.rb
+++ b/activesupport/lib/active_support/core_ext/regexp.rb
@@ -4,8 +4,4 @@ class Regexp #:nodoc:
   def multiline?
     options & MULTILINE == MULTILINE
   end
-
-  def match?(string, pos = 0)
-    !!match(string, pos)
-  end unless //.respond_to?(:match?)
 end
diff --git a/activesupport/lib/active_support/core_ext/string.rb b/activesupport/lib/active_support/core_ext/string.rb
index 491eec2fc9..757d15c51a 100644
--- a/activesupport/lib/active_support/core_ext/string.rb
+++ b/activesupport/lib/active_support/core_ext/string.rb
@@ -1,15 +1,15 @@
 # frozen_string_literal: true
 
-require_relative "string/conversions"
-require_relative "string/filters"
-require_relative "string/multibyte"
-require_relative "string/starts_ends_with"
-require_relative "string/inflections"
-require_relative "string/access"
-require_relative "string/behavior"
-require_relative "string/output_safety"
-require_relative "string/exclude"
-require_relative "string/strip"
-require_relative "string/inquiry"
-require_relative "string/indent"
-require_relative "string/zones"
+require "active_support/core_ext/string/conversions"
+require "active_support/core_ext/string/filters"
+require "active_support/core_ext/string/multibyte"
+require "active_support/core_ext/string/starts_ends_with"
+require "active_support/core_ext/string/inflections"
+require "active_support/core_ext/string/access"
+require "active_support/core_ext/string/behavior"
+require "active_support/core_ext/string/output_safety"
+require "active_support/core_ext/string/exclude"
+require "active_support/core_ext/string/strip"
+require "active_support/core_ext/string/inquiry"
+require "active_support/core_ext/string/indent"
+require "active_support/core_ext/string/zones"
diff --git a/activesupport/lib/active_support/core_ext/string/conversions.rb b/activesupport/lib/active_support/core_ext/string/conversions.rb
index f8f6524b2b..29a88b07ad 100644
--- a/activesupport/lib/active_support/core_ext/string/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/string/conversions.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "date"
-require_relative "../time/calculations"
+require "active_support/core_ext/time/calculations"
 
 class String
   # Converts a string to a Time value.
diff --git a/activesupport/lib/active_support/core_ext/string/filters.rb b/activesupport/lib/active_support/core_ext/string/filters.rb
index 66e721eea3..df0e79afa8 100644
--- a/activesupport/lib/active_support/core_ext/string/filters.rb
+++ b/activesupport/lib/active_support/core_ext/string/filters.rb
@@ -78,6 +78,47 @@ class String
     "#{self[0, stop]}#{omission}"
   end
 
+  # Truncates +text+ to at most <tt>bytesize</tt> bytes in length without
+  # breaking string encoding by splitting multibyte characters or breaking
+  # grapheme clusters ("perceptual characters") by truncating at combining
+  # characters.
+  #
+  #   >> "🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪".size
+  #   => 20
+  #   >> "🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪".bytesize
+  #   => 80
+  #   >> "🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪".truncate_bytes(20)
+  #   => "🔪🔪🔪🔪…"
+  #
+  # The truncated text ends with the <tt>:omission</tt> string, defaulting
+  # to "…", for a total length not exceeding <tt>bytesize</tt>.
+  def truncate_bytes(truncate_at, omission: "…")
+    omission ||= ""
+
+    case
+    when bytesize <= truncate_at
+      dup
+    when omission.bytesize > truncate_at
+      raise ArgumentError, "Omission #{omission.inspect} is #{omission.bytesize}, larger than the truncation length of #{truncate_at} bytes"
+    when omission.bytesize == truncate_at
+      omission.dup
+    else
+      self.class.new.tap do |cut|
+        cut_at = truncate_at - omission.bytesize
+
+        scan(/\X/) do |grapheme|
+          if cut.bytesize + grapheme.bytesize <= cut_at
+            cut << grapheme
+          else
+            break
+          end
+        end
+
+        cut << omission
+      end
+    end
+  end
+
   # Truncates a given +text+ after a given number of words (<tt>words_count</tt>):
   #
   #   'Once upon a time in a world far far away'.truncate_words(4)
diff --git a/activesupport/lib/active_support/core_ext/string/inflections.rb b/activesupport/lib/active_support/core_ext/string/inflections.rb
index b5bb385033..8af301734a 100644
--- a/activesupport/lib/active_support/core_ext/string/inflections.rb
+++ b/activesupport/lib/active_support/core_ext/string/inflections.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../../inflector/methods"
-require_relative "../../inflector/transliterate"
+require "active_support/inflector/methods"
+require "active_support/inflector/transliterate"
 
 # String inflections define new methods on the String class to transform names for different purposes.
 # For instance, you can figure out the name of a table from the name of a class.
@@ -174,7 +174,7 @@ class String
   #   <%= link_to(@person.name, person_path) %>
   #   # => <a href="/person/1-donald-e-knuth">Donald E. Knuth</a>
   #
-  # To preserve the case of the characters in a string, use the `preserve_case` argument.
+  # To preserve the case of the characters in a string, use the +preserve_case+ argument.
   #
   #   class Person
   #     def to_param
diff --git a/activesupport/lib/active_support/core_ext/string/inquiry.rb b/activesupport/lib/active_support/core_ext/string/inquiry.rb
index 92069981b6..a796d5fb4f 100644
--- a/activesupport/lib/active_support/core_ext/string/inquiry.rb
+++ b/activesupport/lib/active_support/core_ext/string/inquiry.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../string_inquirer"
+require "active_support/string_inquirer"
 
 class String
   # Wraps the current string in the <tt>ActiveSupport::StringInquirer</tt> class,
diff --git a/activesupport/lib/active_support/core_ext/string/multibyte.rb b/activesupport/lib/active_support/core_ext/string/multibyte.rb
index fba5b166a2..6cceb46507 100644
--- a/activesupport/lib/active_support/core_ext/string/multibyte.rb
+++ b/activesupport/lib/active_support/core_ext/string/multibyte.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../multibyte"
+require "active_support/multibyte"
 
 class String
   # == Multibyte proxy
@@ -11,11 +11,14 @@ class String
   # encapsulates the original string. A Unicode safe version of all the String methods are defined on this proxy
   # class. If the proxy class doesn't respond to a certain method, it's forwarded to the encapsulated string.
   #
-  #   >> "ǉ".upcase
-  #   => "ǉ"
   #   >> "ǉ".mb_chars.upcase.to_s
   #   => "Ǉ"
   #
+  # NOTE: Ruby 2.4 and later support native Unicode case mappings:
+  #
+  #   >> "ǉ".upcase
+  #   => "Ǉ"
+  #
   # == Method chaining
   #
   # All the methods on the Chars proxy which normally return a string will return a Chars object. This allows
diff --git a/activesupport/lib/active_support/core_ext/string/output_safety.rb b/activesupport/lib/active_support/core_ext/string/output_safety.rb
index adcd2b1dca..f3bdc2977e 100644
--- a/activesupport/lib/active_support/core_ext/string/output_safety.rb
+++ b/activesupport/lib/active_support/core_ext/string/output_safety.rb
@@ -1,8 +1,9 @@
 # frozen_string_literal: true
 
 require "erb"
-require_relative "../kernel/singleton_class"
-require_relative "../../multibyte/unicode"
+require "active_support/core_ext/kernel/singleton_class"
+require "active_support/core_ext/module/redefine_method"
+require "active_support/multibyte/unicode"
 
 class ERB
   module Util
@@ -14,22 +15,18 @@ class ERB
     # A utility method for escaping HTML tag characters.
     # This method is also aliased as <tt>h</tt>.
     #
-    # In your ERB templates, use this method to escape any unsafe content. For example:
-    #   <%= h @person.name %>
-    #
     #   puts html_escape('is a > 0 & a < 10?')
     #   # => is a &gt; 0 &amp; a &lt; 10?
     def html_escape(s)
       unwrapped_html_escape(s).html_safe
     end
 
-    # Aliasing twice issues a warning "discarding old...". Remove first to avoid it.
-    remove_method(:h)
+    silence_redefinition_of_method :h
     alias h html_escape
 
     module_function :h
 
-    singleton_class.send(:remove_method, :html_escape)
+    singleton_class.silence_redefinition_of_method :html_escape
     module_function :html_escape
 
     # HTML escapes strings but doesn't wrap them with an ActiveSupport::SafeBuffer.
@@ -253,7 +250,7 @@ class String
   # Marks a string as trusted safe. It will be inserted into HTML with no
   # additional escaping performed. It is your responsibility to ensure that the
   # string contains no malicious content. This method is equivalent to the
-  # `raw` helper in views. It is recommended that you use `sanitize` instead of
+  # +raw+ helper in views. It is recommended that you use +sanitize+ instead of
   # this method. It should never be called on user input.
   def html_safe
     ActiveSupport::SafeBuffer.new(self)
diff --git a/activesupport/lib/active_support/core_ext/string/strip.rb b/activesupport/lib/active_support/core_ext/string/strip.rb
index cc26274e4a..6f9834bb16 100644
--- a/activesupport/lib/active_support/core_ext/string/strip.rb
+++ b/activesupport/lib/active_support/core_ext/string/strip.rb
@@ -20,6 +20,8 @@ class String
   # Technically, it looks for the least indented non-empty line
   # in the whole string, and removes that amount of leading whitespace.
   def strip_heredoc
-    gsub(/^#{scan(/^[ \t]*(?=\S)/).min}/, "".freeze)
+    gsub(/^#{scan(/^[ \t]*(?=\S)/).min}/, "".freeze).tap do |stripped|
+      stripped.freeze if frozen?
+    end
   end
 end
diff --git a/activesupport/lib/active_support/core_ext/string/zones.rb b/activesupport/lib/active_support/core_ext/string/zones.rb
index db30c03a8e..55dc231464 100644
--- a/activesupport/lib/active_support/core_ext/string/zones.rb
+++ b/activesupport/lib/active_support/core_ext/string/zones.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "conversions"
-require_relative "../time/zones"
+require "active_support/core_ext/string/conversions"
+require "active_support/core_ext/time/zones"
 
 class String
   # Converts String to a TimeWithZone in the current zone if Time.zone or Time.zone_default
diff --git a/activesupport/lib/active_support/core_ext/time.rb b/activesupport/lib/active_support/core_ext/time.rb
index 4e16274443..c809def05f 100644
--- a/activesupport/lib/active_support/core_ext/time.rb
+++ b/activesupport/lib/active_support/core_ext/time.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "time/acts_like"
-require_relative "time/calculations"
-require_relative "time/compatibility"
-require_relative "time/conversions"
-require_relative "time/zones"
+require "active_support/core_ext/time/acts_like"
+require "active_support/core_ext/time/calculations"
+require "active_support/core_ext/time/compatibility"
+require "active_support/core_ext/time/conversions"
+require "active_support/core_ext/time/zones"
diff --git a/activesupport/lib/active_support/core_ext/time/acts_like.rb b/activesupport/lib/active_support/core_ext/time/acts_like.rb
index 309418df42..8572b49639 100644
--- a/activesupport/lib/active_support/core_ext/time/acts_like.rb
+++ b/activesupport/lib/active_support/core_ext/time/acts_like.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../object/acts_like"
+require "active_support/core_ext/object/acts_like"
 
 class Time
   # Duck-types as a Time-like class. See Object#acts_like?.
diff --git a/activesupport/lib/active_support/core_ext/time/calculations.rb b/activesupport/lib/active_support/core_ext/time/calculations.rb
index 0e51df44ef..120768dec5 100644
--- a/activesupport/lib/active_support/core_ext/time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/time/calculations.rb
@@ -1,11 +1,11 @@
 # frozen_string_literal: true
 
-require_relative "../../duration"
-require_relative "conversions"
-require_relative "../../time_with_zone"
-require_relative "zones"
-require_relative "../date_and_time/calculations"
-require_relative "../date/calculations"
+require "active_support/duration"
+require "active_support/core_ext/time/conversions"
+require "active_support/time_with_zone"
+require "active_support/core_ext/time/zones"
+require "active_support/core_ext/date_and_time/calculations"
+require "active_support/core_ext/date/calculations"
 
 class Time
   include DateAndTime::Calculations
diff --git a/activesupport/lib/active_support/core_ext/time/compatibility.rb b/activesupport/lib/active_support/core_ext/time/compatibility.rb
index 93840e93ca..495e4f307b 100644
--- a/activesupport/lib/active_support/core_ext/time/compatibility.rb
+++ b/activesupport/lib/active_support/core_ext/time/compatibility.rb
@@ -1,12 +1,12 @@
 # frozen_string_literal: true
 
-require_relative "../date_and_time/compatibility"
-require_relative "../module/remove_method"
+require "active_support/core_ext/date_and_time/compatibility"
+require "active_support/core_ext/module/redefine_method"
 
 class Time
   include DateAndTime::Compatibility
 
-  remove_possible_method :to_time
+  silence_redefinition_of_method :to_time
 
   # Either return +self+ or the time in the local system timezone depending
   # on the setting of +ActiveSupport.to_time_preserves_timezone+.
diff --git a/activesupport/lib/active_support/core_ext/time/conversions.rb b/activesupport/lib/active_support/core_ext/time/conversions.rb
index e3fc930ef6..345cb2832c 100644
--- a/activesupport/lib/active_support/core_ext/time/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/time/conversions.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../../inflector/methods"
-require_relative "../../values/time_zone"
+require "active_support/inflector/methods"
+require "active_support/values/time_zone"
 
 class Time
   DATE_FORMATS = {
diff --git a/activesupport/lib/active_support/core_ext/time/zones.rb b/activesupport/lib/active_support/core_ext/time/zones.rb
index c48edb135f..a5588fd488 100644
--- a/activesupport/lib/active_support/core_ext/time/zones.rb
+++ b/activesupport/lib/active_support/core_ext/time/zones.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../../time_with_zone"
-require_relative "acts_like"
-require_relative "../date_and_time/zones"
+require "active_support/time_with_zone"
+require "active_support/core_ext/time/acts_like"
+require "active_support/core_ext/date_and_time/zones"
 
 class Time
   include DateAndTime::Zones
@@ -55,10 +55,10 @@ class Time
     #     end
     #   end
     #
-    #  NOTE: This won't affect any <tt>ActiveSupport::TimeWithZone</tt>
-    #  objects that have already been created, e.g. any model timestamp
-    #  attributes that have been read before the block will remain in
-    #  the application's default timezone.
+    # NOTE: This won't affect any <tt>ActiveSupport::TimeWithZone</tt>
+    # objects that have already been created, e.g. any model timestamp
+    # attributes that have been read before the block will remain in
+    # the application's default timezone.
     def use_zone(time_zone)
       new_zone = find_zone!(time_zone)
       begin
diff --git a/activesupport/lib/active_support/core_ext/uri.rb b/activesupport/lib/active_support/core_ext/uri.rb
index 60fc7f084f..cdd81ae562 100644
--- a/activesupport/lib/active_support/core_ext/uri.rb
+++ b/activesupport/lib/active_support/core_ext/uri.rb
@@ -1,18 +1,17 @@
 # frozen_string_literal: true
 
 require "uri"
-str = "\xE6\x97\xA5\xE6\x9C\xAC\xE8\xAA\x9E" # Ni-ho-nn-go in UTF-8, means Japanese.
-parser = URI::Parser.new
 
-unless str == parser.unescape(parser.escape(str))
+if RUBY_VERSION < "2.6.0"
+  require "active_support/core_ext/module/redefine_method"
   URI::Parser.class_eval do
-    remove_method :unescape
+    silence_redefinition_of_method :unescape
     def unescape(str, escaped = /%[a-fA-F\d]{2}/)
       # TODO: Are we actually sure that ASCII == UTF-8?
       # YK: My initial experiments say yes, but let's be sure please
       enc = str.encoding
       enc = Encoding::UTF_8 if enc == Encoding::US_ASCII
-      str.gsub(escaped) { |match| [match[1, 2].hex].pack("C") }.force_encoding(enc)
+      str.dup.force_encoding(Encoding::ASCII_8BIT).gsub(escaped) { |match| [match[1, 2].hex].pack("C") }.force_encoding(enc)
     end
   end
 end
diff --git a/activesupport/lib/active_support/dependencies.rb b/activesupport/lib/active_support/dependencies.rb
index 3ffe21e559..a02cefc78e 100644
--- a/activesupport/lib/active_support/dependencies.rb
+++ b/activesupport/lib/active_support/dependencies.rb
@@ -4,17 +4,17 @@ require "set"
 require "thread"
 require "concurrent/map"
 require "pathname"
-require_relative "core_ext/module/aliasing"
-require_relative "core_ext/module/attribute_accessors"
-require_relative "core_ext/module/introspection"
-require_relative "core_ext/module/anonymous"
-require_relative "core_ext/object/blank"
-require_relative "core_ext/kernel/reporting"
-require_relative "core_ext/load_error"
-require_relative "core_ext/name_error"
-require_relative "core_ext/string/starts_ends_with"
-require_relative "dependencies/interlock"
-require_relative "inflector"
+require "active_support/core_ext/module/aliasing"
+require "active_support/core_ext/module/attribute_accessors"
+require "active_support/core_ext/module/introspection"
+require "active_support/core_ext/module/anonymous"
+require "active_support/core_ext/object/blank"
+require "active_support/core_ext/kernel/reporting"
+require "active_support/core_ext/load_error"
+require "active_support/core_ext/name_error"
+require "active_support/core_ext/string/starts_ends_with"
+require "active_support/dependencies/interlock"
+require "active_support/inflector"
 
 module ActiveSupport #:nodoc:
   module Dependencies #:nodoc:
@@ -85,7 +85,7 @@ module ActiveSupport #:nodoc:
     # handles the new constants.
     #
     # If child.rb is being autoloaded, its constants will be added to
-    # autoloaded_constants. If it was being `require`d, they will be discarded.
+    # autoloaded_constants. If it was being required, they will be discarded.
     #
     # This is handled by walking back up the watch stack and adding the constants
     # found by child.rb to the list of original constants in parent.rb.
@@ -224,6 +224,8 @@ module ActiveSupport #:nodoc:
         Dependencies.require_or_load(file_name)
       end
 
+      # :doc:
+
       # Interprets a file using <tt>mechanism</tt> and marks its defined
       # constants as autoloaded. <tt>file_name</tt> can be either a string or
       # respond to <tt>to_path</tt>.
@@ -242,6 +244,8 @@ module ActiveSupport #:nodoc:
         Dependencies.depend_on(file_name, message)
       end
 
+      # :nodoc:
+
       def load_dependency(file)
         if Dependencies.load? && Dependencies.constant_watch_stack.watching?
           Dependencies.new_constants_in(Object) { yield }
@@ -447,6 +451,7 @@ module ActiveSupport #:nodoc:
       mod = Module.new
       into.const_set const_name, mod
       autoloaded_constants << qualified_name unless autoload_once_paths.include?(base_path)
+      autoloaded_constants.uniq!
       mod
     end
 
@@ -615,7 +620,7 @@ module ActiveSupport #:nodoc:
       return false if desc.is_a?(Module) && desc.anonymous?
       name = to_constant_name desc
       return false unless qualified_const_defined?(name)
-      return autoloaded_constants.include?(name)
+      autoloaded_constants.include?(name)
     end
 
     # Will the provided constant descriptor be unloaded?
@@ -670,7 +675,7 @@ module ActiveSupport #:nodoc:
       when Module
         desc.name ||
           raise(ArgumentError, "Anonymous modules have no name to be referenced by")
-        else raise TypeError, "Not a valid constant descriptor: #{desc.inspect}"
+      else raise TypeError, "Not a valid constant descriptor: #{desc.inspect}"
       end
     end
 
diff --git a/activesupport/lib/active_support/dependencies/autoload.rb b/activesupport/lib/active_support/dependencies/autoload.rb
index 1c3775f5eb..1cee85d98f 100644
--- a/activesupport/lib/active_support/dependencies/autoload.rb
+++ b/activesupport/lib/active_support/dependencies/autoload.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../inflector/methods"
+require "active_support/inflector/methods"
 
 module ActiveSupport
   # Autoload and eager load conveniences for your library.
diff --git a/activesupport/lib/active_support/dependencies/interlock.rb b/activesupport/lib/active_support/dependencies/interlock.rb
index 4e9595ed42..948be75638 100644
--- a/activesupport/lib/active_support/dependencies/interlock.rb
+++ b/activesupport/lib/active_support/dependencies/interlock.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../concurrency/share_lock"
+require "active_support/concurrency/share_lock"
 
 module ActiveSupport #:nodoc:
   module Dependencies #:nodoc:
diff --git a/activesupport/lib/active_support/deprecation.rb b/activesupport/lib/active_support/deprecation.rb
index e6550fdcd0..7271ab565b 100644
--- a/activesupport/lib/active_support/deprecation.rb
+++ b/activesupport/lib/active_support/deprecation.rb
@@ -14,13 +14,13 @@ module ActiveSupport
     # a circular require warning for active_support/deprecation.rb.
     #
     # So, we define the constant first, and load dependencies later.
-    require_relative "deprecation/instance_delegator"
-    require_relative "deprecation/behaviors"
-    require_relative "deprecation/reporting"
-    require_relative "deprecation/constant_accessor"
-    require_relative "deprecation/method_wrappers"
-    require_relative "deprecation/proxy_wrappers"
-    require_relative "core_ext/module/deprecation"
+    require "active_support/deprecation/instance_delegator"
+    require "active_support/deprecation/behaviors"
+    require "active_support/deprecation/reporting"
+    require "active_support/deprecation/constant_accessor"
+    require "active_support/deprecation/method_wrappers"
+    require "active_support/deprecation/proxy_wrappers"
+    require "active_support/core_ext/module/deprecation"
 
     include Singleton
     include InstanceDelegator
@@ -35,7 +35,7 @@ module ActiveSupport
     # and the second is a library name.
     #
     #   ActiveSupport::Deprecation.new('2.0', 'MyLibrary')
-    def initialize(deprecation_horizon = "6.0", gem_name = "Rails")
+    def initialize(deprecation_horizon = "6.1", gem_name = "Rails")
       self.gem_name = gem_name
       self.deprecation_horizon = deprecation_horizon
       # By default, warnings are not silenced and debugging is off.
diff --git a/activesupport/lib/active_support/deprecation/behaviors.rb b/activesupport/lib/active_support/deprecation/behaviors.rb
index 967320bcb9..3abd25aa85 100644
--- a/activesupport/lib/active_support/deprecation/behaviors.rb
+++ b/activesupport/lib/active_support/deprecation/behaviors.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../notifications"
+require "active_support/notifications"
 
 module ActiveSupport
   # Raised when <tt>ActiveSupport::Deprecation::Behavior#behavior</tt> is set with <tt>:raise</tt>.
@@ -27,7 +27,7 @@ module ActiveSupport
             if defined?(Rails.logger) && Rails.logger
               Rails.logger
             else
-              require_relative "../logger"
+              require "active_support/logger"
               ActiveSupport::Logger.new($stderr)
             end
         logger.warn message
@@ -85,7 +85,7 @@ module ActiveSupport
       #   ActiveSupport::Deprecation.behavior = :stderr
       #   ActiveSupport::Deprecation.behavior = [:stderr, :log]
       #   ActiveSupport::Deprecation.behavior = MyCustomHandler
-      #   ActiveSupport::Deprecation.behavior = ->(message, callstack) {
+      #   ActiveSupport::Deprecation.behavior = ->(message, callstack, deprecation_horizon, gem_name) {
       #     # custom stuff
       #   }
       def behavior=(behavior)
@@ -94,6 +94,10 @@ module ActiveSupport
 
       private
         def arity_coerce(behavior)
+          unless behavior.respond_to?(:call)
+            raise ArgumentError, "#{behavior.inspect} is not a valid deprecation behavior."
+          end
+
           if behavior.arity == 4 || behavior.arity == -1
             behavior
           else
diff --git a/activesupport/lib/active_support/deprecation/constant_accessor.rb b/activesupport/lib/active_support/deprecation/constant_accessor.rb
index 0dfd96d134..1ed0015812 100644
--- a/activesupport/lib/active_support/deprecation/constant_accessor.rb
+++ b/activesupport/lib/active_support/deprecation/constant_accessor.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require_relative "../inflector/methods"
-
 module ActiveSupport
   class Deprecation
     # DeprecatedConstantAccessor transforms a constant into a deprecated one by
@@ -17,7 +15,7 @@ module ActiveSupport
     #
     #   PLANETS = %w(mercury venus earth mars jupiter saturn uranus neptune pluto)
     #
-    #   (In a later update, the original implementation of `PLANETS` has been removed.)
+    #   # (In a later update, the original implementation of `PLANETS` has been removed.)
     #
     #   PLANETS_POST_2006 = %w(mercury venus earth mars jupiter saturn uranus neptune)
     #   include ActiveSupport::Deprecation::DeprecatedConstantAccessor
@@ -29,6 +27,8 @@ module ActiveSupport
     #        ["Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune"]
     module DeprecatedConstantAccessor
       def self.included(base)
+        require "active_support/inflector/methods"
+
         extension = Module.new do
           def const_missing(missing_const_name)
             if class_variable_defined?(:@@_deprecated_constants)
diff --git a/activesupport/lib/active_support/deprecation/instance_delegator.rb b/activesupport/lib/active_support/deprecation/instance_delegator.rb
index 539357c83e..8beda373a2 100644
--- a/activesupport/lib/active_support/deprecation/instance_delegator.rb
+++ b/activesupport/lib/active_support/deprecation/instance_delegator.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/kernel/singleton_class"
-require_relative "../core_ext/module/delegation"
+require "active_support/core_ext/kernel/singleton_class"
+require "active_support/core_ext/module/delegation"
 
 module ActiveSupport
   class Deprecation
diff --git a/activesupport/lib/active_support/deprecation/method_wrappers.rb b/activesupport/lib/active_support/deprecation/method_wrappers.rb
index 8c942ed9a5..5be893d281 100644
--- a/activesupport/lib/active_support/deprecation/method_wrappers.rb
+++ b/activesupport/lib/active_support/deprecation/method_wrappers.rb
@@ -1,16 +1,14 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/module/aliasing"
-require_relative "../core_ext/array/extract_options"
+require "active_support/core_ext/module/aliasing"
+require "active_support/core_ext/array/extract_options"
 
 module ActiveSupport
   class Deprecation
     module MethodWrapper
       # Declare that a method has been deprecated.
       #
-      #   module Fred
-      #     extend self
-      #
+      #   class Fred
       #     def aaa; end
       #     def bbb; end
       #     def ccc; end
@@ -22,15 +20,15 @@ module ActiveSupport
       #   ActiveSupport::Deprecation.deprecate_methods(Fred, :aaa, bbb: :zzz, ccc: 'use Bar#ccc instead')
       #   # => Fred
       #
-      #   Fred.aaa
+      #   Fred.new.aaa
       #   # DEPRECATION WARNING: aaa is deprecated and will be removed from Rails 5.1. (called from irb_binding at (irb):10)
       #   # => nil
       #
-      #   Fred.bbb
+      #   Fred.new.bbb
       #   # DEPRECATION WARNING: bbb is deprecated and will be removed from Rails 5.1 (use zzz instead). (called from irb_binding at (irb):11)
       #   # => nil
       #
-      #   Fred.ccc
+      #   Fred.new.ccc
       #   # DEPRECATION WARNING: ccc is deprecated and will be removed from Rails 5.1 (use Bar#ccc instead). (called from irb_binding at (irb):12)
       #   # => nil
       #
@@ -39,7 +37,7 @@ module ActiveSupport
       #   ActiveSupport::Deprecation.deprecate_methods(Fred, ddd: :zzz, deprecator: custom_deprecator)
       #   # => [:ddd]
       #
-      #   Fred.ddd
+      #   Fred.new.ddd
       #   DEPRECATION WARNING: ddd is deprecated and will be removed from MyGem next-release (use zzz instead). (called from irb_binding at (irb):15)
       #   # => nil
       #
@@ -48,7 +46,7 @@ module ActiveSupport
       #   custom_deprecator.deprecate_methods(Fred, eee: :zzz)
       #   # => [:eee]
       #
-      #   Fred.eee
+      #   Fred.new.eee
       #   DEPRECATION WARNING: eee is deprecated and will be removed from MyGem next-release (use zzz instead). (called from irb_binding at (irb):18)
       #   # => nil
       def deprecate_methods(target_module, *method_names)
@@ -62,6 +60,13 @@ module ActiveSupport
               deprecator.deprecation_warning(method_name, options[method_name])
               super(*args, &block)
             end
+
+            case
+            when target_module.protected_method_defined?(method_name)
+              protected method_name
+            when target_module.private_method_defined?(method_name)
+              private method_name
+            end
           end
         end
 
diff --git a/activesupport/lib/active_support/deprecation/proxy_wrappers.rb b/activesupport/lib/active_support/deprecation/proxy_wrappers.rb
index 1920d75faf..896c0d2d8e 100644
--- a/activesupport/lib/active_support/deprecation/proxy_wrappers.rb
+++ b/activesupport/lib/active_support/deprecation/proxy_wrappers.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../inflector/methods"
-require_relative "../core_ext/regexp"
+require "active_support/core_ext/regexp"
 
 module ActiveSupport
   class Deprecation
@@ -114,7 +113,7 @@ module ActiveSupport
     #
     #   PLANETS = %w(mercury venus earth mars jupiter saturn uranus neptune pluto)
     #
-    #   (In a later update, the original implementation of `PLANETS` has been removed.)
+    #   # (In a later update, the original implementation of `PLANETS` has been removed.)
     #
     #   PLANETS_POST_2006 = %w(mercury venus earth mars jupiter saturn uranus neptune)
     #   PLANETS = ActiveSupport::Deprecation::DeprecatedConstantProxy.new('PLANETS', 'PLANETS_POST_2006')
@@ -125,6 +124,8 @@ module ActiveSupport
     #        ["Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune"]
     class DeprecatedConstantProxy < DeprecationProxy
       def initialize(old_const, new_const, deprecator = ActiveSupport::Deprecation.instance, message: "#{old_const} is deprecated! Use #{new_const} instead.")
+        require "active_support/inflector/methods"
+
         @old_const = old_const
         @new_const = new_const
         @deprecator = deprecator
diff --git a/activesupport/lib/active_support/deprecation/reporting.rb b/activesupport/lib/active_support/deprecation/reporting.rb
index 242e21b782..7075b5b869 100644
--- a/activesupport/lib/active_support/deprecation/reporting.rb
+++ b/activesupport/lib/active_support/deprecation/reporting.rb
@@ -61,7 +61,7 @@ module ActiveSupport
           case message
           when Symbol then "#{warning} (use #{message} instead)"
           when String then "#{warning} (#{message})"
-            else warning
+          else warning
           end
         end
 
@@ -104,7 +104,7 @@ module ActiveSupport
           end
         end
 
-        RAILS_GEM_ROOT = File.expand_path("../../../..", __dir__)
+        RAILS_GEM_ROOT = File.expand_path("../../../..", __dir__) + "/"
 
         def ignored_callstack(path)
           path.start_with?(RAILS_GEM_ROOT) || path.start_with?(RbConfig::CONFIG["rubylibdir"])
diff --git a/activesupport/lib/active_support/digest.rb b/activesupport/lib/active_support/digest.rb
new file mode 100644
index 0000000000..fba10fbdcf
--- /dev/null
+++ b/activesupport/lib/active_support/digest.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module ActiveSupport
+  class Digest #:nodoc:
+    class <<self
+      def hash_digest_class
+        @hash_digest_class ||= ::Digest::MD5
+      end
+
+      def hash_digest_class=(klass)
+        raise ArgumentError, "#{klass} is expected to implement hexdigest class method" unless klass.respond_to?(:hexdigest)
+        @hash_digest_class = klass
+      end
+
+      def hexdigest(arg)
+        hash_digest_class.hexdigest(arg)[0...32]
+      end
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/duration.rb b/activesupport/lib/active_support/duration.rb
index 34024fa8c6..88897f811e 100644
--- a/activesupport/lib/active_support/duration.rb
+++ b/activesupport/lib/active_support/duration.rb
@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/array/conversions"
-require_relative "core_ext/module/delegation"
-require_relative "core_ext/object/acts_like"
-require_relative "core_ext/string/filters"
-require_relative "deprecation"
+require "active_support/core_ext/array/conversions"
+require "active_support/core_ext/module/delegation"
+require "active_support/core_ext/object/acts_like"
+require "active_support/core_ext/string/filters"
+require "active_support/deprecation"
 
 module ActiveSupport
   # Provides accurate date and time measurements using Date#advance and
@@ -194,7 +194,6 @@ module ActiveSupport
         end
 
         parts[:seconds] = remainder
-        parts.reject! { |k, v| v.zero? }
 
         new(value, parts)
       end
@@ -211,6 +210,7 @@ module ActiveSupport
     def initialize(value, parts) #:nodoc:
       @value, @parts = value, parts.to_h
       @parts.default = 0
+      @parts.reject! { |k, v| v.zero? }
     end
 
     def coerce(other) #:nodoc:
@@ -370,6 +370,8 @@ module ActiveSupport
     alias :before :ago
 
     def inspect #:nodoc:
+      return "0 seconds" if parts.empty?
+
       parts.
         reduce(::Hash.new(0)) { |h, (l, r)| h[l] += r; h }.
         sort_by { |unit,  _ | PARTS.index(unit) }.
@@ -381,6 +383,14 @@ module ActiveSupport
       to_i
     end
 
+    def init_with(coder) #:nodoc:
+      initialize(coder["value"], coder["parts"])
+    end
+
+    def encode_with(coder) #:nodoc:
+      coder.map = { "value" => @value, "parts" => @parts }
+    end
+
     # Build ISO 8601 Duration string for this duration.
     # The +precision+ parameter can be used to limit seconds' precision of duration.
     def iso8601(precision: nil)
diff --git a/activesupport/lib/active_support/duration/iso8601_parser.rb b/activesupport/lib/active_support/duration/iso8601_parser.rb
index a002424cd9..1847eeaa86 100644
--- a/activesupport/lib/active_support/duration/iso8601_parser.rb
+++ b/activesupport/lib/active_support/duration/iso8601_parser.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "strscan"
-require_relative "../core_ext/regexp"
+require "active_support/core_ext/regexp"
 
 module ActiveSupport
   class Duration
@@ -118,7 +118,7 @@ module ActiveSupport
             raise_parsing_error "(only last part can be fractional)"
           end
 
-          return true
+          true
         end
     end
   end
diff --git a/activesupport/lib/active_support/duration/iso8601_serializer.rb b/activesupport/lib/active_support/duration/iso8601_serializer.rb
index 985eac113f..84ae29c1ec 100644
--- a/activesupport/lib/active_support/duration/iso8601_serializer.rb
+++ b/activesupport/lib/active_support/duration/iso8601_serializer.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/object/blank"
-require_relative "../core_ext/hash/transform_values"
+require "active_support/core_ext/object/blank"
 
 module ActiveSupport
   class Duration
diff --git a/activesupport/lib/active_support/encrypted_configuration.rb b/activesupport/lib/active_support/encrypted_configuration.rb
new file mode 100644
index 0000000000..3c6da10548
--- /dev/null
+++ b/activesupport/lib/active_support/encrypted_configuration.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+require "yaml"
+require "active_support/encrypted_file"
+require "active_support/ordered_options"
+require "active_support/core_ext/object/inclusion"
+require "active_support/core_ext/module/delegation"
+
+module ActiveSupport
+  class EncryptedConfiguration < EncryptedFile
+    delegate :[], :fetch, to: :config
+    delegate_missing_to :options
+
+    def initialize(config_path:, key_path:, env_key:, raise_if_missing_key:)
+      super content_path: config_path, key_path: key_path,
+        env_key: env_key, raise_if_missing_key: raise_if_missing_key
+    end
+
+    # Allow a config to be started without a file present
+    def read
+      super
+    rescue ActiveSupport::EncryptedFile::MissingContentError
+      ""
+    end
+
+    def write(contents)
+      deserialize(contents)
+
+      super
+    end
+
+    def config
+      @config ||= deserialize(read).deep_symbolize_keys
+    end
+
+    private
+      def options
+        @options ||= ActiveSupport::InheritableOptions.new(config)
+      end
+
+      def deserialize(config)
+        config.present? ? YAML.load(config, content_path) : {}
+      end
+  end
+end
diff --git a/activesupport/lib/active_support/encrypted_file.rb b/activesupport/lib/active_support/encrypted_file.rb
new file mode 100644
index 0000000000..c66f1b557e
--- /dev/null
+++ b/activesupport/lib/active_support/encrypted_file.rb
@@ -0,0 +1,99 @@
+# frozen_string_literal: true
+
+require "pathname"
+require "active_support/message_encryptor"
+
+module ActiveSupport
+  class EncryptedFile
+    class MissingContentError < RuntimeError
+      def initialize(content_path)
+        super "Missing encrypted content file in #{content_path}."
+      end
+    end
+
+    class MissingKeyError < RuntimeError
+      def initialize(key_path:, env_key:)
+        super \
+          "Missing encryption key to decrypt file with. " +
+          "Ask your team for your master key and write it to #{key_path} or put it in the ENV['#{env_key}']."
+      end
+    end
+
+    CIPHER = "aes-128-gcm"
+
+    def self.generate_key
+      SecureRandom.hex(ActiveSupport::MessageEncryptor.key_len(CIPHER))
+    end
+
+
+    attr_reader :content_path, :key_path, :env_key, :raise_if_missing_key
+
+    def initialize(content_path:, key_path:, env_key:, raise_if_missing_key:)
+      @content_path, @key_path = Pathname.new(content_path), Pathname.new(key_path)
+      @env_key, @raise_if_missing_key = env_key, raise_if_missing_key
+    end
+
+    def key
+      read_env_key || read_key_file || handle_missing_key
+    end
+
+    def read
+      if !key.nil? && content_path.exist?
+        decrypt content_path.binread
+      else
+        raise MissingContentError, content_path
+      end
+    end
+
+    def write(contents)
+      IO.binwrite "#{content_path}.tmp", encrypt(contents)
+      FileUtils.mv "#{content_path}.tmp", content_path
+    end
+
+    def change(&block)
+      writing read, &block
+    end
+
+
+    private
+      def writing(contents)
+        tmp_file = "#{Process.pid}.#{content_path.basename.to_s.chomp('.enc')}"
+        tmp_path = Pathname.new File.join(Dir.tmpdir, tmp_file)
+        tmp_path.binwrite contents
+
+        yield tmp_path
+
+        updated_contents = tmp_path.binread
+
+        write(updated_contents) if updated_contents != contents
+      ensure
+        FileUtils.rm(tmp_path) if tmp_path.exist?
+      end
+
+
+      def encrypt(contents)
+        encryptor.encrypt_and_sign contents
+      end
+
+      def decrypt(contents)
+        encryptor.decrypt_and_verify contents
+      end
+
+      def encryptor
+        @encryptor ||= ActiveSupport::MessageEncryptor.new([ key ].pack("H*"), cipher: CIPHER)
+      end
+
+
+      def read_env_key
+        ENV[env_key]
+      end
+
+      def read_key_file
+        key_path.binread.strip if key_path.exist?
+      end
+
+      def handle_missing_key
+        raise MissingKeyError, key_path: key_path, env_key: env_key if raise_if_missing_key
+      end
+  end
+end
diff --git a/activesupport/lib/active_support/execution_wrapper.rb b/activesupport/lib/active_support/execution_wrapper.rb
index fd87d84795..f48c586cad 100644
--- a/activesupport/lib/active_support/execution_wrapper.rb
+++ b/activesupport/lib/active_support/execution_wrapper.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "callbacks"
+require "active_support/callbacks"
 
 module ActiveSupport
   class ExecutionWrapper
diff --git a/activesupport/lib/active_support/executor.rb b/activesupport/lib/active_support/executor.rb
index e6487ba69d..ce391b07ec 100644
--- a/activesupport/lib/active_support/executor.rb
+++ b/activesupport/lib/active_support/executor.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "execution_wrapper"
+require "active_support/execution_wrapper"
 
 module ActiveSupport
   class Executor < ExecutionWrapper
diff --git a/activesupport/lib/active_support/file_update_checker.rb b/activesupport/lib/active_support/file_update_checker.rb
index bcf7b9de64..1a0bb10815 100644
--- a/activesupport/lib/active_support/file_update_checker.rb
+++ b/activesupport/lib/active_support/file_update_checker.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/time/calculations"
+require "active_support/core_ext/time/calculations"
 
 module ActiveSupport
   # FileUpdateChecker specifies the API used by Rails to watch files
diff --git a/activesupport/lib/active_support/gem_version.rb b/activesupport/lib/active_support/gem_version.rb
index 2a7ef2f820..c951ad16a3 100644
--- a/activesupport/lib/active_support/gem_version.rb
+++ b/activesupport/lib/active_support/gem_version.rb
@@ -7,8 +7,8 @@ module ActiveSupport
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
     PRE   = "alpha"
 
diff --git a/activesupport/lib/active_support/hash_with_indifferent_access.rb b/activesupport/lib/active_support/hash_with_indifferent_access.rb
index 12291af443..e4afc8af93 100644
--- a/activesupport/lib/active_support/hash_with_indifferent_access.rb
+++ b/activesupport/lib/active_support/hash_with_indifferent_access.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/hash/keys"
-require_relative "core_ext/hash/reverse_merge"
+require "active_support/core_ext/hash/keys"
+require "active_support/core_ext/hash/reverse_merge"
 
 module ActiveSupport
   # Implements a hash where keys <tt>:foo</tt> and <tt>"foo"</tt> are considered
@@ -177,20 +177,18 @@ module ActiveSupport
       super(convert_key(key), *extras)
     end
 
-    if Hash.new.respond_to?(:dig)
-      # Same as <tt>Hash#dig</tt> where the key passed as argument can be
-      # either a string or a symbol:
-      #
-      #   counters = ActiveSupport::HashWithIndifferentAccess.new
-      #   counters[:foo] = { bar: 1 }
-      #
-      #   counters.dig('foo', 'bar')     # => 1
-      #   counters.dig(:foo, :bar)       # => 1
-      #   counters.dig(:zoo)             # => nil
-      def dig(*args)
-        args[0] = convert_key(args[0]) if args.size > 0
-        super(*args)
-      end
+    # Same as <tt>Hash#dig</tt> where the key passed as argument can be
+    # either a string or a symbol:
+    #
+    #   counters = ActiveSupport::HashWithIndifferentAccess.new
+    #   counters[:foo] = { bar: 1 }
+    #
+    #   counters.dig('foo', 'bar')     # => 1
+    #   counters.dig(:foo, :bar)       # => 1
+    #   counters.dig(:zoo)             # => nil
+    def dig(*args)
+      args[0] = convert_key(args[0]) if args.size > 0
+      super(*args)
     end
 
     # Same as <tt>Hash#default</tt> where the key passed as argument can be
@@ -228,7 +226,7 @@ module ActiveSupport
     #   hash.fetch_values('a', 'c') # => KeyError: key not found: "c"
     def fetch_values(*indices, &block)
       indices.collect { |key| fetch(key, &block) }
-    end if Hash.method_defined?(:fetch_values)
+    end
 
     # Returns a shallow copy of the hash.
     #
@@ -306,6 +304,29 @@ module ActiveSupport
       dup.tap { |hash| hash.transform_values!(*args, &block) }
     end
 
+    def transform_keys(*args, &block)
+      return to_enum(:transform_keys) unless block_given?
+      dup.tap { |hash| hash.transform_keys!(*args, &block) }
+    end
+
+    def transform_keys!
+      return enum_for(:transform_keys!) { size } unless block_given?
+      keys.each do |key|
+        self[yield(key)] = delete(key)
+      end
+      self
+    end
+
+    def slice(*keys)
+      keys.map! { |key| convert_key(key) }
+      self.class.new(super)
+    end
+
+    def slice!(*keys)
+      keys.map! { |key| convert_key(key) }
+      super
+    end
+
     def compact
       dup.tap(&:compact!)
     end
diff --git a/activesupport/lib/active_support/i18n.rb b/activesupport/lib/active_support/i18n.rb
index 80f1475630..39dab1cc71 100644
--- a/activesupport/lib/active_support/i18n.rb
+++ b/activesupport/lib/active_support/i18n.rb
@@ -1,15 +1,16 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/hash/deep_merge"
-require_relative "core_ext/hash/except"
-require_relative "core_ext/hash/slice"
+require "active_support/core_ext/hash/deep_merge"
+require "active_support/core_ext/hash/except"
+require "active_support/core_ext/hash/slice"
 begin
   require "i18n"
 rescue LoadError => e
   $stderr.puts "The i18n gem is not available. Please add it to your Gemfile and run bundle install"
   raise e
 end
-require_relative "lazy_load_hooks"
+require "active_support/lazy_load_hooks"
 
 ActiveSupport.run_load_hooks(:i18n)
 I18n.load_path << File.expand_path("locale/en.yml", __dir__)
+I18n.load_path << File.expand_path("locale/en.rb", __dir__)
diff --git a/activesupport/lib/active_support/i18n_railtie.rb b/activesupport/lib/active_support/i18n_railtie.rb
index 369aecff69..ce8bfbfd8c 100644
--- a/activesupport/lib/active_support/i18n_railtie.rb
+++ b/activesupport/lib/active_support/i18n_railtie.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
 require "active_support"
-require_relative "file_update_checker"
-require_relative "core_ext/array/wrap"
+require "active_support/file_update_checker"
+require "active_support/core_ext/array/wrap"
 
 # :enddoc:
 
diff --git a/activesupport/lib/active_support/inflections.rb b/activesupport/lib/active_support/inflections.rb
index e8e1657111..baf1cb3038 100644
--- a/activesupport/lib/active_support/inflections.rb
+++ b/activesupport/lib/active_support/inflections.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "inflector/inflections"
+require "active_support/inflector/inflections"
 
 #--
 # Defines the standard inflection rules. These are the starting point for
diff --git a/activesupport/lib/active_support/inflector.rb b/activesupport/lib/active_support/inflector.rb
index a6adb15a18..d77f04c9c5 100644
--- a/activesupport/lib/active_support/inflector.rb
+++ b/activesupport/lib/active_support/inflector.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
 # in case active_support/inflector is required without the rest of active_support
-require_relative "inflector/inflections"
-require_relative "inflector/transliterate"
-require_relative "inflector/methods"
+require "active_support/inflector/inflections"
+require "active_support/inflector/transliterate"
+require "active_support/inflector/methods"
 
-require_relative "inflections"
-require_relative "core_ext/string/inflections"
+require "active_support/inflections"
+require "active_support/core_ext/string/inflections"
diff --git a/activesupport/lib/active_support/inflector/inflections.rb b/activesupport/lib/active_support/inflector/inflections.rb
index 36dfbc5f42..7e5dff1d6d 100644
--- a/activesupport/lib/active_support/inflector/inflections.rb
+++ b/activesupport/lib/active_support/inflector/inflections.rb
@@ -1,9 +1,10 @@
 # frozen_string_literal: true
 
 require "concurrent/map"
-require_relative "../core_ext/array/prepend_and_append"
-require_relative "../core_ext/regexp"
-require_relative "../i18n"
+require "active_support/core_ext/array/prepend_and_append"
+require "active_support/core_ext/regexp"
+require "active_support/i18n"
+require "active_support/deprecation"
 
 module ActiveSupport
   module Inflector
@@ -67,16 +68,21 @@ module ActiveSupport
       end
 
       attr_reader :plurals, :singulars, :uncountables, :humans, :acronyms, :acronym_regex
+      deprecate :acronym_regex
+
+      attr_reader :acronyms_camelize_regex, :acronyms_underscore_regex # :nodoc:
 
       def initialize
-        @plurals, @singulars, @uncountables, @humans, @acronyms, @acronym_regex = [], [], Uncountables.new, [], {}, /(?=a)b/
+        @plurals, @singulars, @uncountables, @humans, @acronyms = [], [], Uncountables.new, [], {}
+        define_acronym_regex_patterns
       end
 
       # Private, for the test suite.
       def initialize_dup(orig) # :nodoc:
-        %w(plurals singulars uncountables humans acronyms acronym_regex).each do |scope|
+        %w(plurals singulars uncountables humans acronyms).each do |scope|
           instance_variable_set("@#{scope}", orig.send(scope).dup)
         end
+        define_acronym_regex_patterns
       end
 
       # Specifies a new acronym. An acronym must be specified as it will appear
@@ -130,7 +136,7 @@ module ActiveSupport
       #   camelize 'mcdonald'   # => 'McDonald'
       def acronym(word)
         @acronyms[word.downcase] = word
-        @acronym_regex = /#{@acronyms.values.join("|")}/
+        define_acronym_regex_patterns
       end
 
       # Specifies a new pluralization rule and its replacement. The rule can
@@ -221,10 +227,18 @@ module ActiveSupport
         case scope
         when :all
           @plurals, @singulars, @uncountables, @humans = [], [], Uncountables.new, []
-          else
+        else
           instance_variable_set "@#{scope}", []
         end
       end
+
+      private
+
+        def define_acronym_regex_patterns
+          @acronym_regex             = @acronyms.empty? ? /(?=a)b/ : /#{@acronyms.values.join("|")}/
+          @acronyms_camelize_regex   = /^(?:#{@acronym_regex}(?=\b|[A-Z_])|\w)/
+          @acronyms_underscore_regex = /(?:(?<=([A-Za-z\d]))|\b)(#{@acronym_regex})(?=\b|[^a-z])/
+        end
     end
 
     # Yields a singleton instance of Inflector::Inflections so you can specify
diff --git a/activesupport/lib/active_support/inflector/methods.rb b/activesupport/lib/active_support/inflector/methods.rb
index 9398ed60a4..339b93b8da 100644
--- a/activesupport/lib/active_support/inflector/methods.rb
+++ b/activesupport/lib/active_support/inflector/methods.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../inflections"
-require_relative "../core_ext/regexp"
+require "active_support/inflections"
+require "active_support/core_ext/regexp"
 
 module ActiveSupport
   # The Inflector transforms words from singular to plural, class names to table
@@ -71,7 +71,7 @@ module ActiveSupport
       if uppercase_first_letter
         string = string.sub(/^[a-z\d]*/) { |match| inflections.acronyms[match] || match.capitalize }
       else
-        string = string.sub(/^(?:#{inflections.acronym_regex}(?=\b|[A-Z_])|\w)/) { |match| match.downcase }
+        string = string.sub(inflections.acronyms_camelize_regex) { |match| match.downcase }
       end
       string.gsub!(/(?:_|(\/))([a-z\d]*)/i) { "#{$1}#{inflections.acronyms[$2] || $2.capitalize}" }
       string.gsub!("/".freeze, "::".freeze)
@@ -92,7 +92,7 @@ module ActiveSupport
     def underscore(camel_cased_word)
       return camel_cased_word unless /[A-Z-]|::/.match?(camel_cased_word)
       word = camel_cased_word.to_s.gsub("::".freeze, "/".freeze)
-      word.gsub!(/(?:(?<=([A-Za-z\d]))|\b)(#{inflections.acronym_regex})(?=\b|[^a-z])/) { "#{$1 && '_'.freeze }#{$2.downcase}" }
+      word.gsub!(inflections.acronyms_underscore_regex) { "#{$1 && '_'.freeze }#{$2.downcase}" }
       word.gsub!(/([A-Z\d]+)([A-Z][a-z])/, '\1_\2'.freeze)
       word.gsub!(/([a-z\d])([A-Z])/, '\1_\2'.freeze)
       word.tr!("-".freeze, "_".freeze)
@@ -138,7 +138,7 @@ module ActiveSupport
       result.tr!("_".freeze, " ".freeze)
 
       result.gsub!(/([a-z\d]*)/i) do |match|
-        "#{inflections.acronyms[match] || match.downcase}"
+        "#{inflections.acronyms[match.downcase] || match.downcase}"
       end
 
       if capitalize
@@ -341,18 +341,7 @@ module ActiveSupport
     #   ordinal(-11)   # => "th"
     #   ordinal(-1021) # => "st"
     def ordinal(number)
-      abs_number = number.to_i.abs
-
-      if (11..13).include?(abs_number % 100)
-        "th"
-      else
-        case abs_number % 10
-        when 1; "st"
-        when 2; "nd"
-        when 3; "rd"
-          else    "th"
-        end
-      end
+      I18n.translate("number.nth.ordinals", number: number)
     end
 
     # Turns a number into an ordinal string used to denote the position in an
@@ -365,7 +354,7 @@ module ActiveSupport
     #   ordinalize(-11)   # => "-11th"
     #   ordinalize(-1021) # => "-1021st"
     def ordinalize(number)
-      "#{number}#{ordinal(number)}"
+      I18n.translate("number.nth.ordinalized", number: number)
     end
 
     private
diff --git a/activesupport/lib/active_support/inflector/transliterate.rb b/activesupport/lib/active_support/inflector/transliterate.rb
index aa7b21734e..6f2ca4999c 100644
--- a/activesupport/lib/active_support/inflector/transliterate.rb
+++ b/activesupport/lib/active_support/inflector/transliterate.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/string/multibyte"
-require_relative "../i18n"
+require "active_support/core_ext/string/multibyte"
+require "active_support/i18n"
 
 module ActiveSupport
   module Inflector
@@ -71,17 +71,23 @@ module ActiveSupport
     # a 'pretty' URL.
     #
     #   parameterize("Donald E. Knuth") # => "donald-e-knuth"
-    #   parameterize("^trés|Jolie-- ")  # => "tres-jolie"
+    #   parameterize("^très|Jolie-- ")  # => "tres-jolie"
     #
-    # To use a custom separator, override the `separator` argument.
+    # To use a custom separator, override the +separator+ argument.
     #
     #  parameterize("Donald E. Knuth", separator: '_') # => "donald_e_knuth"
-    #  parameterize("^trés|Jolie-- ", separator: '_')  # => "tres_jolie"
+    #  parameterize("^très|Jolie__ ", separator: '_')  # => "tres_jolie"
     #
-    # To preserve the case of the characters in a string, use the `preserve_case` argument.
+    # To preserve the case of the characters in a string, use the +preserve_case+ argument.
     #
     #   parameterize("Donald E. Knuth", preserve_case: true) # => "Donald-E-Knuth"
-    #   parameterize("^trés|Jolie-- ", preserve_case: true) # => "tres-Jolie"
+    #   parameterize("^très|Jolie-- ", preserve_case: true) # => "tres-Jolie"
+    #
+    # It preserves dashes and underscores unless they are used as separators:
+    #
+    #  parameterize("^très|Jolie__ ")                 # => "tres-jolie__"
+    #  parameterize("^très|Jolie-- ", separator: "_") # => "tres_jolie--"
+    #  parameterize("^très_Jolie-- ", separator: ".") # => "tres_jolie--"
     #
     def parameterize(string, separator: "-", preserve_case: false)
       # Replace accented chars with their ASCII equivalents.
diff --git a/activesupport/lib/active_support/json.rb b/activesupport/lib/active_support/json.rb
index b5672025fb..d7887175c0 100644
--- a/activesupport/lib/active_support/json.rb
+++ b/activesupport/lib/active_support/json.rb
@@ -1,4 +1,4 @@
 # frozen_string_literal: true
 
-require_relative "json/decoding"
-require_relative "json/encoding"
+require "active_support/json/decoding"
+require "active_support/json/encoding"
diff --git a/activesupport/lib/active_support/json/decoding.rb b/activesupport/lib/active_support/json/decoding.rb
index caa4082dde..8c0e016dc5 100644
--- a/activesupport/lib/active_support/json/decoding.rb
+++ b/activesupport/lib/active_support/json/decoding.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/module/attribute_accessors"
-require_relative "../core_ext/module/delegation"
+require "active_support/core_ext/module/attribute_accessors"
+require "active_support/core_ext/module/delegation"
 require "json"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/json/encoding.rb b/activesupport/lib/active_support/json/encoding.rb
index 4016d13364..de1b8ac8cf 100644
--- a/activesupport/lib/active_support/json/encoding.rb
+++ b/activesupport/lib/active_support/json/encoding.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/object/json"
-require_relative "../core_ext/module/delegation"
+require "active_support/core_ext/object/json"
+require "active_support/core_ext/module/delegation"
 
 module ActiveSupport
   class << self
@@ -54,9 +54,13 @@ module ActiveSupport
           class EscapedString < String #:nodoc:
             def to_json(*)
               if Encoding.escape_html_entities_in_json
-                super.gsub ESCAPE_REGEX_WITH_HTML_ENTITIES, ESCAPED_CHARS
+                s = super
+                s.gsub! ESCAPE_REGEX_WITH_HTML_ENTITIES, ESCAPED_CHARS
+                s
               else
-                super.gsub ESCAPE_REGEX_WITHOUT_HTML_ENTITIES, ESCAPED_CHARS
+                s = super
+                s.gsub! ESCAPE_REGEX_WITHOUT_HTML_ENTITIES, ESCAPED_CHARS
+                s
               end
             end
 
diff --git a/activesupport/lib/active_support/key_generator.rb b/activesupport/lib/active_support/key_generator.rb
index 31de37b400..78f7d7ca8d 100644
--- a/activesupport/lib/active_support/key_generator.rb
+++ b/activesupport/lib/active_support/key_generator.rb
@@ -59,7 +59,7 @@ module ActiveSupport
         if secret.blank?
           raise ArgumentError, "A secret is required to generate an integrity hash " \
             "for cookie session data. Set a secret_key_base of at least " \
-            "#{SECRET_MIN_LENGTH} characters in config/secrets.yml."
+            "#{SECRET_MIN_LENGTH} characters in via `bin/rails credentials:edit`."
         end
 
         if secret.length < SECRET_MIN_LENGTH
diff --git a/activesupport/lib/active_support/locale/en.rb b/activesupport/lib/active_support/locale/en.rb
new file mode 100644
index 0000000000..a2a7ea7ae1
--- /dev/null
+++ b/activesupport/lib/active_support/locale/en.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+{
+  en: {
+    number: {
+      nth: {
+        ordinals: lambda do |_key, number:, **_options|
+          case number
+          when 1; "st"
+          when 2; "nd"
+          when 3; "rd"
+          when 4, 5, 6, 7, 8, 9, 10, 11, 12, 13; "th"
+          else
+            num_modulo = number.to_i.abs % 100
+            num_modulo %= 10 if num_modulo > 13
+            case num_modulo
+            when 1; "st"
+            when 2; "nd"
+            when 3; "rd"
+            else    "th"
+            end
+          end
+        end,
+
+        ordinalized: lambda do |_key, number:, **_options|
+          "#{number}#{ActiveSupport::Inflector.ordinal(number)}"
+        end
+      }
+    }
+  }
+}
diff --git a/activesupport/lib/active_support/log_subscriber.rb b/activesupport/lib/active_support/log_subscriber.rb
index 05a11221bf..0f7be06c8e 100644
--- a/activesupport/lib/active_support/log_subscriber.rb
+++ b/activesupport/lib/active_support/log_subscriber.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/module/attribute_accessors"
-require_relative "core_ext/class/attribute"
-require_relative "subscriber"
+require "active_support/core_ext/module/attribute_accessors"
+require "active_support/core_ext/class/attribute"
+require "active_support/subscriber"
 
 module ActiveSupport
   # ActiveSupport::LogSubscriber is an object set to consume
diff --git a/activesupport/lib/active_support/log_subscriber/test_helper.rb b/activesupport/lib/active_support/log_subscriber/test_helper.rb
index 5b2abfc57c..3f19ef5009 100644
--- a/activesupport/lib/active_support/log_subscriber/test_helper.rb
+++ b/activesupport/lib/active_support/log_subscriber/test_helper.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../log_subscriber"
-require_relative "../logger"
-require_relative "../notifications"
+require "active_support/log_subscriber"
+require "active_support/logger"
+require "active_support/notifications"
 
 module ActiveSupport
   class LogSubscriber
diff --git a/activesupport/lib/active_support/logger.rb b/activesupport/lib/active_support/logger.rb
index 3397ac4c9f..8152a182b4 100644
--- a/activesupport/lib/active_support/logger.rb
+++ b/activesupport/lib/active_support/logger.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "logger_silence"
-require_relative "logger_thread_safe_level"
+require "active_support/logger_silence"
+require "active_support/logger_thread_safe_level"
 require "logger"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/logger_silence.rb b/activesupport/lib/active_support/logger_silence.rb
index 693c7a1947..89f32b6782 100644
--- a/activesupport/lib/active_support/logger_silence.rb
+++ b/activesupport/lib/active_support/logger_silence.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "concern"
-require_relative "core_ext/module/attribute_accessors"
+require "active_support/concern"
+require "active_support/core_ext/module/attribute_accessors"
 require "concurrent"
 
 module LoggerSilence
diff --git a/activesupport/lib/active_support/logger_thread_safe_level.rb b/activesupport/lib/active_support/logger_thread_safe_level.rb
index 3c7f53d92c..ba32813d3d 100644
--- a/activesupport/lib/active_support/logger_thread_safe_level.rb
+++ b/activesupport/lib/active_support/logger_thread_safe_level.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "concern"
+require "active_support/concern"
 
 module ActiveSupport
   module LoggerThreadSafeLevel # :nodoc:
diff --git a/activesupport/lib/active_support/message_encryptor.rb b/activesupport/lib/active_support/message_encryptor.rb
index 27620f56be..8b73270894 100644
--- a/activesupport/lib/active_support/message_encryptor.rb
+++ b/activesupport/lib/active_support/message_encryptor.rb
@@ -2,9 +2,10 @@
 
 require "openssl"
 require "base64"
-require_relative "core_ext/array/extract_options"
-require_relative "message_verifier"
-require_relative "messages/metadata"
+require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/module/attribute_accessors"
+require "active_support/message_verifier"
+require "active_support/messages/metadata"
 
 module ActiveSupport
   # MessageEncryptor is a simple way to encrypt values which get stored
@@ -54,10 +55,36 @@ module ActiveSupport
   #
   # Then the messages can be verified and returned upto the expire time.
   # Thereafter, verifying returns +nil+.
+  #
+  # === Rotating keys
+  #
+  # MessageEncryptor also supports rotating out old configurations by falling
+  # back to a stack of encryptors. Call +rotate+ to build and add an encryptor
+  # so +decrypt_and_verify+ will also try the fallback.
+  #
+  # By default any rotated encryptors use the values of the primary
+  # encryptor unless specified otherwise.
+  #
+  # You'd give your encryptor the new defaults:
+  #
+  #   crypt = ActiveSupport::MessageEncryptor.new(@secret, cipher: "aes-256-gcm")
+  #
+  # Then gradually rotate the old values out by adding them as fallbacks. Any message
+  # generated with the old values will then work until the rotation is removed.
+  #
+  #   crypt.rotate old_secret            # Fallback to an old secret instead of @secret.
+  #   crypt.rotate cipher: "aes-256-cbc" # Fallback to an old cipher instead of aes-256-gcm.
+  #
+  # Though if both the secret and the cipher was changed at the same time,
+  # the above should be combined into:
+  #
+  #   crypt.rotate old_secret, cipher: "aes-256-cbc"
   class MessageEncryptor
-    class << self
-      attr_accessor :use_authenticated_message_encryption #:nodoc:
+    prepend Messages::Rotator::Encryptor
+
+    cattr_accessor :use_authenticated_message_encryption, instance_accessor: false, default: false
 
+    class << self
       def default_cipher #:nodoc:
         if use_authenticated_message_encryption
           "aes-256-gcm"
@@ -126,7 +153,7 @@ module ActiveSupport
 
     # Decrypt and verify a message. We need to verify the message in order to
     # avoid padding attacks. Reference: https://www.limited-entropy.com/padding-oracle-attacks/.
-    def decrypt_and_verify(data, purpose: nil)
+    def decrypt_and_verify(data, purpose: nil, **)
       _decrypt(verifier.verify(data), purpose)
     end
 
diff --git a/activesupport/lib/active_support/message_verifier.rb b/activesupport/lib/active_support/message_verifier.rb
index 7110d6d2c9..83c39c0a86 100644
--- a/activesupport/lib/active_support/message_verifier.rb
+++ b/activesupport/lib/active_support/message_verifier.rb
@@ -1,9 +1,10 @@
 # frozen_string_literal: true
 
 require "base64"
-require_relative "core_ext/object/blank"
-require_relative "security_utils"
-require_relative "messages/metadata"
+require "active_support/core_ext/object/blank"
+require "active_support/security_utils"
+require "active_support/messages/metadata"
+require "active_support/messages/rotator"
 
 module ActiveSupport
   # +MessageVerifier+ makes it easy to generate and verify messages which are
@@ -30,7 +31,7 @@ module ActiveSupport
   #
   # +MessageVerifier+ creates HMAC signatures using SHA1 hash algorithm by default.
   # If you want to use a different hash algorithm, you can change it by providing
-  # `:digest` key as an option while initializing the verifier:
+  # +:digest+ key as an option while initializing the verifier:
   #
   #   @verifier = ActiveSupport::MessageVerifier.new('s3Krit', digest: 'SHA256')
   #
@@ -73,7 +74,33 @@ module ActiveSupport
   # Then the messages can be verified and returned upto the expire time.
   # Thereafter, the +verified+ method returns +nil+ while +verify+ raises
   # <tt>ActiveSupport::MessageVerifier::InvalidSignature</tt>.
+  #
+  # === Rotating keys
+  #
+  # MessageVerifier also supports rotating out old configurations by falling
+  # back to a stack of verifiers. Call +rotate+ to build and add a verifier to
+  # so either +verified+ or +verify+ will also try verifying with the fallback.
+  #
+  # By default any rotated verifiers use the values of the primary
+  # verifier unless specified otherwise.
+  #
+  # You'd give your verifier the new defaults:
+  #
+  #   verifier = ActiveSupport::MessageVerifier.new(@secret, digest: "SHA512", serializer: JSON)
+  #
+  # Then gradually rotate the old values out by adding them as fallbacks. Any message
+  # generated with the old values will then work until the rotation is removed.
+  #
+  #   verifier.rotate old_secret          # Fallback to an old secret instead of @secret.
+  #   verifier.rotate digest: "SHA256"    # Fallback to an old digest instead of SHA512.
+  #   verifier.rotate serializer: Marshal # Fallback to an old serializer instead of JSON.
+  #
+  # Though the above would most likely be combined into one rotation:
+  #
+  #   verifier.rotate old_secret, digest: "SHA256", serializer: Marshal
   class MessageVerifier
+    prepend Messages::Rotator::Verifier
+
     class InvalidSignature < StandardError; end
 
     def initialize(secret, options = {})
@@ -120,7 +147,7 @@ module ActiveSupport
     #
     #   incompatible_message = "test--dad7b06c94abba8d46a15fafaef56c327665d5ff"
     #   verifier.verified(incompatible_message) # => TypeError: incompatible marshal file format
-    def verified(signed_message, purpose: nil)
+    def verified(signed_message, purpose: nil, **)
       if valid_message?(signed_message)
         begin
           data = signed_message.split("--".freeze)[0]
@@ -145,8 +172,8 @@ module ActiveSupport
     #
     #   other_verifier = ActiveSupport::MessageVerifier.new 'd1ff3r3nt-s3Krit'
     #   other_verifier.verify(signed_message) # => ActiveSupport::MessageVerifier::InvalidSignature
-    def verify(signed_message, purpose: nil)
-      verified(signed_message, purpose: purpose) || raise(InvalidSignature)
+    def verify(*args)
+      verified(*args) || raise(InvalidSignature)
     end
 
     # Generates a signed message for the provided value.
diff --git a/activesupport/lib/active_support/messages/rotation_configuration.rb b/activesupport/lib/active_support/messages/rotation_configuration.rb
new file mode 100644
index 0000000000..bd50d6d348
--- /dev/null
+++ b/activesupport/lib/active_support/messages/rotation_configuration.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+module ActiveSupport
+  module Messages
+    class RotationConfiguration # :nodoc:
+      attr_reader :signed, :encrypted
+
+      def initialize
+        @signed, @encrypted = [], []
+      end
+
+      def rotate(kind, *args)
+        case kind
+        when :signed
+          @signed << args
+        when :encrypted
+          @encrypted << args
+        end
+      end
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/messages/rotator.rb b/activesupport/lib/active_support/messages/rotator.rb
new file mode 100644
index 0000000000..823a399d67
--- /dev/null
+++ b/activesupport/lib/active_support/messages/rotator.rb
@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+module ActiveSupport
+  module Messages
+    module Rotator # :nodoc:
+      def initialize(*, **options)
+        super
+
+        @options   = options
+        @rotations = []
+      end
+
+      def rotate(*secrets, **options)
+        @rotations << build_rotation(*secrets, @options.merge(options))
+      end
+
+      module Encryptor
+        include Rotator
+
+        def decrypt_and_verify(*args, on_rotation: nil, **options)
+          super
+        rescue MessageEncryptor::InvalidMessage, MessageVerifier::InvalidSignature
+          run_rotations(on_rotation) { |encryptor| encryptor.decrypt_and_verify(*args, options) } || raise
+        end
+
+        private
+          def build_rotation(secret = @secret, sign_secret = @sign_secret, options)
+            self.class.new(secret, sign_secret, options)
+          end
+      end
+
+      module Verifier
+        include Rotator
+
+        def verified(*args, on_rotation: nil, **options)
+          super || run_rotations(on_rotation) { |verifier| verifier.verified(*args, options) }
+        end
+
+        private
+          def build_rotation(secret = @secret, options)
+            self.class.new(secret, options)
+          end
+      end
+
+      private
+        def run_rotations(on_rotation)
+          @rotations.find do |rotation|
+            if message = yield(rotation) rescue next
+              on_rotation.call if on_rotation
+              return message
+            end
+          end
+        end
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/multibyte/chars.rb b/activesupport/lib/active_support/multibyte/chars.rb
index d676827e8e..8152b8fd22 100644
--- a/activesupport/lib/active_support/multibyte/chars.rb
+++ b/activesupport/lib/active_support/multibyte/chars.rb
@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
-require_relative "../json"
-require_relative "../core_ext/string/access"
-require_relative "../core_ext/string/behavior"
-require_relative "../core_ext/module/delegation"
-require_relative "../core_ext/regexp"
+require "active_support/json"
+require "active_support/core_ext/string/access"
+require "active_support/core_ext/string/behavior"
+require "active_support/core_ext/module/delegation"
+require "active_support/core_ext/regexp"
 
 module ActiveSupport #:nodoc:
   module Multibyte #:nodoc:
diff --git a/activesupport/lib/active_support/multibyte/unicode.rb b/activesupport/lib/active_support/multibyte/unicode.rb
index a64223c0e0..4f0e1165ef 100644
--- a/activesupport/lib/active_support/multibyte/unicode.rb
+++ b/activesupport/lib/active_support/multibyte/unicode.rb
@@ -11,7 +11,7 @@ module ActiveSupport
       NORMALIZATION_FORMS = [:c, :kc, :d, :kd]
 
       # The Unicode version that is supported by the implementation
-      UNICODE_VERSION = "9.0.0"
+      UNICODE_VERSION = RbConfig::CONFIG["UNICODE_VERSION"]
 
       # The default normalization used for operations that require
       # normalization. It can be set to any of the normalizations
@@ -21,96 +21,13 @@ module ActiveSupport
       attr_accessor :default_normalization_form
       @default_normalization_form = :kc
 
-      # Hangul character boundaries and properties
-      HANGUL_SBASE = 0xAC00
-      HANGUL_LBASE = 0x1100
-      HANGUL_VBASE = 0x1161
-      HANGUL_TBASE = 0x11A7
-      HANGUL_LCOUNT = 19
-      HANGUL_VCOUNT = 21
-      HANGUL_TCOUNT = 28
-      HANGUL_NCOUNT = HANGUL_VCOUNT * HANGUL_TCOUNT
-      HANGUL_SCOUNT = 11172
-      HANGUL_SLAST = HANGUL_SBASE + HANGUL_SCOUNT
-
-      # Detect whether the codepoint is in a certain character class. Returns
-      # +true+ when it's in the specified character class and +false+ otherwise.
-      # Valid character classes are: <tt>:cr</tt>, <tt>:lf</tt>, <tt>:l</tt>,
-      # <tt>:v</tt>, <tt>:lv</tt>, <tt>:lvt</tt> and <tt>:t</tt>.
-      #
-      # Primarily used by the grapheme cluster support.
-      def in_char_class?(codepoint, classes)
-        classes.detect { |c| database.boundary[c] === codepoint } ? true : false
-      end
-
       # Unpack the string at grapheme boundaries. Returns a list of character
       # lists.
       #
       #   Unicode.unpack_graphemes('क्षि') # => [[2325, 2381], [2359], [2367]]
       #   Unicode.unpack_graphemes('Café') # => [[67], [97], [102], [233]]
       def unpack_graphemes(string)
-        codepoints = string.codepoints.to_a
-        unpacked = []
-        pos = 0
-        marker = 0
-        eoc = codepoints.length
-        while (pos < eoc)
-          pos += 1
-          previous = codepoints[pos - 1]
-          current = codepoints[pos]
-
-          # See http://unicode.org/reports/tr29/#Grapheme_Cluster_Boundary_Rules
-          should_break =
-            if pos == eoc
-              true
-            # GB3. CR X LF
-            elsif previous == database.boundary[:cr] && current == database.boundary[:lf]
-              false
-            # GB4. (Control|CR|LF) ÷
-            elsif previous && in_char_class?(previous, [:control, :cr, :lf])
-              true
-            # GB5. ÷ (Control|CR|LF)
-            elsif in_char_class?(current, [:control, :cr, :lf])
-              true
-            # GB6. L X (L|V|LV|LVT)
-            elsif database.boundary[:l] === previous && in_char_class?(current, [:l, :v, :lv, :lvt])
-              false
-            # GB7. (LV|V) X (V|T)
-            elsif in_char_class?(previous, [:lv, :v]) && in_char_class?(current, [:v, :t])
-              false
-            # GB8. (LVT|T) X (T)
-            elsif in_char_class?(previous, [:lvt, :t]) && database.boundary[:t] === current
-              false
-            # GB9. X (Extend | ZWJ)
-            elsif in_char_class?(current, [:extend, :zwj])
-              false
-            # GB9a. X SpacingMark
-            elsif database.boundary[:spacingmark] === current
-              false
-            # GB9b. Prepend X
-            elsif database.boundary[:prepend] === previous
-              false
-            # GB10. (E_Base | EBG) Extend* X E_Modifier
-            elsif (marker...pos).any? { |i| in_char_class?(codepoints[i], [:e_base, :e_base_gaz]) && codepoints[i + 1...pos].all? { |c| database.boundary[:extend] === c } } && database.boundary[:e_modifier] === current
-              false
-            # GB11. ZWJ X (Glue_After_Zwj | EBG)
-            elsif database.boundary[:zwj] === previous && in_char_class?(current, [:glue_after_zwj, :e_base_gaz])
-              false
-            # GB12. ^ (RI RI)* RI X RI
-            # GB13. [^RI] (RI RI)* RI X RI
-            elsif codepoints[marker..pos].all? { |c| database.boundary[:regional_indicator] === c } && codepoints[marker..pos].count { |c| database.boundary[:regional_indicator] === c }.even?
-              false
-            # GB999. Any ÷ Any
-            else
-              true
-            end
-
-          if should_break
-            unpacked << codepoints[marker..pos - 1]
-            marker = pos
-          end
-        end
-        unpacked
+        string.scan(/\X/).map(&:codepoints)
       end
 
       # Reverse operation of unpack_graphemes.
@@ -120,100 +37,18 @@ module ActiveSupport
         unpacked.flatten.pack("U*")
       end
 
-      # Re-order codepoints so the string becomes canonical.
-      def reorder_characters(codepoints)
-        length = codepoints.length - 1
-        pos = 0
-        while pos < length do
-          cp1, cp2 = database.codepoints[codepoints[pos]], database.codepoints[codepoints[pos + 1]]
-          if (cp1.combining_class > cp2.combining_class) && (cp2.combining_class > 0)
-            codepoints[pos..pos + 1] = cp2.code, cp1.code
-            pos += (pos > 0 ? -1 : 1)
-          else
-            pos += 1
-          end
-        end
-        codepoints
-      end
-
       # Decompose composed characters to the decomposed form.
       def decompose(type, codepoints)
-        codepoints.inject([]) do |decomposed, cp|
-          # if it's a hangul syllable starter character
-          if HANGUL_SBASE <= cp && cp < HANGUL_SLAST
-            sindex = cp - HANGUL_SBASE
-            ncp = [] # new codepoints
-            ncp << HANGUL_LBASE + sindex / HANGUL_NCOUNT
-            ncp << HANGUL_VBASE + (sindex % HANGUL_NCOUNT) / HANGUL_TCOUNT
-            tindex = sindex % HANGUL_TCOUNT
-            ncp << (HANGUL_TBASE + tindex) unless tindex == 0
-            decomposed.concat ncp
-          # if the codepoint is decomposable in with the current decomposition type
-          elsif (ncp = database.codepoints[cp].decomp_mapping) && (!database.codepoints[cp].decomp_type || type == :compatibility)
-            decomposed.concat decompose(type, ncp.dup)
-          else
-            decomposed << cp
-          end
+        if type == :compatibility
+          codepoints.pack("U*").unicode_normalize(:nfkd).codepoints
+        else
+          codepoints.pack("U*").unicode_normalize(:nfd).codepoints
         end
       end
 
       # Compose decomposed characters to the composed form.
       def compose(codepoints)
-        pos = 0
-        eoa = codepoints.length - 1
-        starter_pos = 0
-        starter_char = codepoints[0]
-        previous_combining_class = -1
-        while pos < eoa
-          pos += 1
-          lindex = starter_char - HANGUL_LBASE
-          # -- Hangul
-          if 0 <= lindex && lindex < HANGUL_LCOUNT
-            vindex = codepoints[starter_pos + 1] - HANGUL_VBASE rescue vindex = -1
-            if 0 <= vindex && vindex < HANGUL_VCOUNT
-              tindex = codepoints[starter_pos + 2] - HANGUL_TBASE rescue tindex = -1
-              if 0 <= tindex && tindex < HANGUL_TCOUNT
-                j = starter_pos + 2
-                eoa -= 2
-              else
-                tindex = 0
-                j = starter_pos + 1
-                eoa -= 1
-              end
-              codepoints[starter_pos..j] = (lindex * HANGUL_VCOUNT + vindex) * HANGUL_TCOUNT + tindex + HANGUL_SBASE
-            end
-            starter_pos += 1
-            starter_char = codepoints[starter_pos]
-          # -- Other characters
-          else
-            current_char = codepoints[pos]
-            current = database.codepoints[current_char]
-            if current.combining_class > previous_combining_class
-              if ref = database.composition_map[starter_char]
-                composition = ref[current_char]
-              else
-                composition = nil
-              end
-              unless composition.nil?
-                codepoints[starter_pos] = composition
-                starter_char = composition
-                codepoints.delete_at pos
-                eoa -= 1
-                pos -= 1
-                previous_combining_class = -1
-              else
-                previous_combining_class = current.combining_class
-              end
-            else
-              previous_combining_class = current.combining_class
-            end
-            if current.combining_class == 0
-              starter_pos = pos
-              starter_char = codepoints[pos]
-            end
-          end
-        end
-        codepoints
+        codepoints.pack("U*").unicode_normalize(:nfc).codepoints
       end
 
       # Rubinius' String#scrub, however, doesn't support ASCII-incompatible chars.
@@ -266,129 +101,37 @@ module ActiveSupport
       def normalize(string, form = nil)
         form ||= @default_normalization_form
         # See http://www.unicode.org/reports/tr15, Table 1
-        codepoints = string.codepoints.to_a
         case form
         when :d
-          reorder_characters(decompose(:canonical, codepoints))
+          string.unicode_normalize(:nfd)
         when :c
-          compose(reorder_characters(decompose(:canonical, codepoints)))
+          string.unicode_normalize(:nfc)
         when :kd
-          reorder_characters(decompose(:compatibility, codepoints))
+          string.unicode_normalize(:nfkd)
         when :kc
-          compose(reorder_characters(decompose(:compatibility, codepoints)))
-          else
+          string.unicode_normalize(:nfkc)
+        else
           raise ArgumentError, "#{form} is not a valid normalization variant", caller
-        end.pack("U*".freeze)
+        end
       end
 
       def downcase(string)
-        apply_mapping string, :lowercase_mapping
+        string.downcase
       end
 
       def upcase(string)
-        apply_mapping string, :uppercase_mapping
+        string.upcase
       end
 
       def swapcase(string)
-        apply_mapping string, :swapcase_mapping
-      end
-
-      # Holds data about a codepoint in the Unicode database.
-      class Codepoint
-        attr_accessor :code, :combining_class, :decomp_type, :decomp_mapping, :uppercase_mapping, :lowercase_mapping
-
-        # Initializing Codepoint object with default values
-        def initialize
-          @combining_class = 0
-          @uppercase_mapping = 0
-          @lowercase_mapping = 0
-        end
-
-        def swapcase_mapping
-          uppercase_mapping > 0 ? uppercase_mapping : lowercase_mapping
-        end
-      end
-
-      # Holds static data from the Unicode database.
-      class UnicodeDatabase
-        ATTRIBUTES = :codepoints, :composition_exclusion, :composition_map, :boundary, :cp1252
-
-        attr_writer(*ATTRIBUTES)
-
-        def initialize
-          @codepoints = Hash.new(Codepoint.new)
-          @composition_exclusion = []
-          @composition_map = {}
-          @boundary = {}
-          @cp1252 = {}
-        end
-
-        # Lazy load the Unicode database so it's only loaded when it's actually used
-        ATTRIBUTES.each do |attr_name|
-          class_eval(<<-EOS, __FILE__, __LINE__ + 1)
-            def #{attr_name}     # def codepoints
-              load               #   load
-              @#{attr_name}      #   @codepoints
-            end                  # end
-          EOS
-        end
-
-        # Loads the Unicode database and returns all the internal objects of
-        # UnicodeDatabase.
-        def load
-          begin
-            @codepoints, @composition_exclusion, @composition_map, @boundary, @cp1252 = File.open(self.class.filename, "rb") { |f| Marshal.load f.read }
-          rescue => e
-            raise IOError.new("Couldn't load the Unicode tables for UTF8Handler (#{e.message}), ActiveSupport::Multibyte is unusable")
-          end
-
-          # Redefine the === method so we can write shorter rules for grapheme cluster breaks
-          @boundary.each_key do |k|
-            @boundary[k].instance_eval do
-              def ===(other)
-                detect { |i| i === other } ? true : false
-              end
-            end if @boundary[k].kind_of?(Array)
-          end
-
-          # define attr_reader methods for the instance variables
-          class << self
-            attr_reader(*ATTRIBUTES)
-          end
-        end
-
-        # Returns the directory in which the data files are stored.
-        def self.dirname
-          File.expand_path("../values", __dir__)
-        end
-
-        # Returns the filename for the data file for this version.
-        def self.filename
-          File.expand_path File.join(dirname, "unicode_tables.dat")
-        end
+        string.swapcase
       end
 
       private
 
-        def apply_mapping(string, mapping)
-          database.codepoints
-          string.each_codepoint.map do |codepoint|
-            cp = database.codepoints[codepoint]
-            if cp && (ncp = cp.send(mapping)) && ncp > 0
-              ncp
-            else
-              codepoint
-            end
-          end.pack("U*")
-        end
-
         def recode_windows1252_chars(string)
           string.encode(Encoding::UTF_8, Encoding::Windows_1252, invalid: :replace, undef: :replace)
         end
-
-        def database
-          @database ||= UnicodeDatabase.new
-        end
     end
   end
 end
diff --git a/activesupport/lib/active_support/notifications.rb b/activesupport/lib/active_support/notifications.rb
index 96a3463905..6207de8094 100644
--- a/activesupport/lib/active_support/notifications.rb
+++ b/activesupport/lib/active_support/notifications.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "notifications/instrumenter"
-require_relative "notifications/fanout"
-require_relative "per_thread_registry"
+require "active_support/notifications/instrumenter"
+require "active_support/notifications/fanout"
+require "active_support/per_thread_registry"
 
 module ActiveSupport
   # = Notifications
diff --git a/activesupport/lib/active_support/number_helper/number_converter.rb b/activesupport/lib/active_support/number_helper/number_converter.rb
index 5ea9c8f113..06ba797a13 100644
--- a/activesupport/lib/active_support/number_helper/number_converter.rb
+++ b/activesupport/lib/active_support/number_helper/number_converter.rb
@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/big_decimal/conversions"
-require_relative "../core_ext/object/blank"
-require_relative "../core_ext/hash/keys"
-require_relative "../i18n"
-require_relative "../core_ext/class/attribute"
+require "active_support/core_ext/big_decimal/conversions"
+require "active_support/core_ext/object/blank"
+require "active_support/core_ext/hash/keys"
+require "active_support/i18n"
+require "active_support/core_ext/class/attribute"
 
 module ActiveSupport
   module NumberHelper
diff --git a/activesupport/lib/active_support/number_helper/number_to_currency_converter.rb b/activesupport/lib/active_support/number_helper/number_to_currency_converter.rb
index 1943b9e295..a25e22cbd3 100644
--- a/activesupport/lib/active_support/number_helper/number_to_currency_converter.rb
+++ b/activesupport/lib/active_support/number_helper/number_to_currency_converter.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/numeric/inquiry"
-
 module ActiveSupport
   module NumberHelper
     class NumberToCurrencyConverter < NumberConverter # :nodoc:
diff --git a/activesupport/lib/active_support/number_helper/number_to_rounded_converter.rb b/activesupport/lib/active_support/number_helper/number_to_rounded_converter.rb
index 3b62fe6819..eb528a0583 100644
--- a/activesupport/lib/active_support/number_helper/number_to_rounded_converter.rb
+++ b/activesupport/lib/active_support/number_helper/number_to_rounded_converter.rb
@@ -37,26 +37,6 @@ module ActiveSupport
 
       private
 
-        def digits_and_rounded_number(precision)
-          if zero?
-            [1, 0]
-          else
-            digits = digit_count(number)
-            multiplier = 10**(digits - precision)
-            rounded_number = calculate_rounded_number(multiplier)
-            digits = digit_count(rounded_number) # After rounding, the number of digits may have changed
-            [digits, rounded_number]
-          end
-        end
-
-        def calculate_rounded_number(multiplier)
-          (number / BigDecimal.new(multiplier.to_f.to_s)).round * multiplier
-        end
-
-        def digit_count(number)
-          number.zero? ? 1 : (Math.log10(absolute_number(number)) + 1).floor
-        end
-
         def strip_insignificant_zeros
           options[:strip_insignificant_zeros]
         end
diff --git a/activesupport/lib/active_support/number_helper/rounding_helper.rb b/activesupport/lib/active_support/number_helper/rounding_helper.rb
index a5b28296a2..2ad8d49c4e 100644
--- a/activesupport/lib/active_support/number_helper/rounding_helper.rb
+++ b/activesupport/lib/active_support/number_helper/rounding_helper.rb
@@ -36,7 +36,7 @@ module ActiveSupport
           return 0 if number.zero?
           digits = digit_count(number)
           multiplier = 10**(digits - precision)
-          (number / BigDecimal.new(multiplier.to_f.to_s)).round * multiplier
+          (number / BigDecimal(multiplier.to_f.to_s)).round * multiplier
         end
 
         def convert_to_decimal(number)
diff --git a/activesupport/lib/active_support/option_merger.rb b/activesupport/lib/active_support/option_merger.rb
index 42cbbe7c42..ab9ca727f6 100644
--- a/activesupport/lib/active_support/option_merger.rb
+++ b/activesupport/lib/active_support/option_merger.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/hash/deep_merge"
+require "active_support/core_ext/hash/deep_merge"
 
 module ActiveSupport
   class OptionMerger #:nodoc:
diff --git a/activesupport/lib/active_support/ordered_options.rb b/activesupport/lib/active_support/ordered_options.rb
index fa7825b3ba..c4e419f546 100644
--- a/activesupport/lib/active_support/ordered_options.rb
+++ b/activesupport/lib/active_support/ordered_options.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 
 module ActiveSupport
   # Usually key value pairs are handled something like this:
@@ -24,7 +24,7 @@ module ActiveSupport
   # To raise an exception when the value is blank, append a
   # bang to the key name, like:
   #
-  #   h.dog! # => raises KeyError: key not found: :dog
+  #   h.dog! # => raises KeyError: :dog is blank
   #
   class OrderedOptions < Hash
     alias_method :_get, :[] # preserve the original #[] method
@@ -46,7 +46,7 @@ module ActiveSupport
         bangs = name_string.chomp!("!")
 
         if bangs
-          fetch(name_string.to_sym).presence || raise(KeyError.new("#{name_string} is blank."))
+          self[name_string].presence || raise(KeyError.new(":#{name_string} is blank"))
         else
           self[name_string]
         end
diff --git a/activesupport/lib/active_support/per_thread_registry.rb b/activesupport/lib/active_support/per_thread_registry.rb
index dd0cc6a604..eb92fb4371 100644
--- a/activesupport/lib/active_support/per_thread_registry.rb
+++ b/activesupport/lib/active_support/per_thread_registry.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/module/delegation"
+require "active_support/core_ext/module/delegation"
 
 module ActiveSupport
   # NOTE: This approach has been deprecated for end-user code in favor of {thread_mattr_accessor}[rdoc-ref:Module#thread_mattr_accessor] and friends.
diff --git a/activesupport/lib/active_support/rails.rb b/activesupport/lib/active_support/rails.rb
index fe82d1cc14..8b727a69ec 100644
--- a/activesupport/lib/active_support/rails.rb
+++ b/activesupport/lib/active_support/rails.rb
@@ -11,25 +11,19 @@
 # Rails and can change anytime.
 
 # Defines Object#blank? and Object#present?.
-require_relative "core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 
 # Rails own autoload, eager_load, etc.
-require_relative "dependencies/autoload"
+require "active_support/dependencies/autoload"
 
 # Support for ClassMethods and the included macro.
-require_relative "concern"
+require "active_support/concern"
 
 # Defines Class#class_attribute.
-require_relative "core_ext/class/attribute"
+require "active_support/core_ext/class/attribute"
 
 # Defines Module#delegate.
-require_relative "core_ext/module/delegation"
+require "active_support/core_ext/module/delegation"
 
 # Defines ActiveSupport::Deprecation.
-require_relative "deprecation"
-
-# Defines Regexp#match?.
-#
-# This should be removed when Rails needs Ruby 2.4 or later, and the require
-# added where other Regexp extensions are being used (easy to grep).
-require_relative "core_ext/regexp"
+require "active_support/deprecation"
diff --git a/activesupport/lib/active_support/railtie.rb b/activesupport/lib/active_support/railtie.rb
index 2efe391d01..605b50d346 100644
--- a/activesupport/lib/active_support/railtie.rb
+++ b/activesupport/lib/active_support/railtie.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support"
-require_relative "i18n_railtie"
+require "active_support/i18n_railtie"
 
 module ActiveSupport
   class Railtie < Rails::Railtie # :nodoc:
@@ -10,9 +10,11 @@ module ActiveSupport
     config.eager_load_namespaces << ActiveSupport
 
     initializer "active_support.set_authenticated_message_encryption" do |app|
-      if app.config.active_support.respond_to?(:use_authenticated_message_encryption)
-        ActiveSupport::MessageEncryptor.use_authenticated_message_encryption =
-          app.config.active_support.use_authenticated_message_encryption
+      config.after_initialize do
+        unless app.config.active_support.use_authenticated_message_encryption.nil?
+          ActiveSupport::MessageEncryptor.use_authenticated_message_encryption =
+            app.config.active_support.use_authenticated_message_encryption
+        end
       end
     end
 
@@ -36,24 +38,43 @@ module ActiveSupport
       rescue TZInfo::DataSourceNotFound => e
         raise e.exception "tzinfo-data is not present. Please add gem 'tzinfo-data' to your Gemfile and run bundle install"
       end
-      require_relative "core_ext/time/zones"
+      require "active_support/core_ext/time/zones"
       Time.zone_default = Time.find_zone!(app.config.time_zone)
     end
 
     # Sets the default week start
     # If assigned value is not a valid day symbol (e.g. :sunday, :monday, ...), an exception will be raised.
     initializer "active_support.initialize_beginning_of_week" do |app|
-      require_relative "core_ext/date/calculations"
+      require "active_support/core_ext/date/calculations"
       beginning_of_week_default = Date.find_beginning_of_week!(app.config.beginning_of_week)
 
       Date.beginning_of_week_default = beginning_of_week_default
     end
 
+    initializer "active_support.require_master_key" do |app|
+      if app.config.respond_to?(:require_master_key) && app.config.require_master_key
+        begin
+          app.credentials.key
+        rescue ActiveSupport::EncryptedFile::MissingKeyError => error
+          $stderr.puts error.message
+          exit 1
+        end
+      end
+    end
+
     initializer "active_support.set_configs" do |app|
       app.config.active_support.each do |k, v|
         k = "#{k}="
         ActiveSupport.send(k, v) if ActiveSupport.respond_to? k
       end
     end
+
+    initializer "active_support.set_hash_digest_class" do |app|
+      config.after_initialize do
+        if app.config.active_support.use_sha1_digests
+          ActiveSupport::Digest.hash_digest_class = ::Digest::SHA1
+        end
+      end
+    end
   end
 end
diff --git a/activesupport/lib/active_support/reloader.rb b/activesupport/lib/active_support/reloader.rb
index 44062e3491..b26d9c3665 100644
--- a/activesupport/lib/active_support/reloader.rb
+++ b/activesupport/lib/active_support/reloader.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "execution_wrapper"
+require "active_support/execution_wrapper"
 
 module ActiveSupport
   #--
@@ -28,14 +28,17 @@ module ActiveSupport
 
     define_callbacks :class_unload
 
+    # Registers a callback that will run once at application startup and every time the code is reloaded.
     def self.to_prepare(*args, &block)
       set_callback(:prepare, *args, &block)
     end
 
+    # Registers a callback that will run immediately before the classes are unloaded.
     def self.before_class_unload(*args, &block)
       set_callback(:class_unload, *args, &block)
     end
 
+    # Registers a callback that will run immediately after the classes are unloaded.
     def self.after_class_unload(*args, &block)
       set_callback(:class_unload, :after, *args, &block)
     end
diff --git a/activesupport/lib/active_support/rescuable.rb b/activesupport/lib/active_support/rescuable.rb
index 2f6aeef48a..e0fa29cacb 100644
--- a/activesupport/lib/active_support/rescuable.rb
+++ b/activesupport/lib/active_support/rescuable.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "concern"
-require_relative "core_ext/class/attribute"
-require_relative "core_ext/string/inflections"
+require "active_support/concern"
+require "active_support/core_ext/class/attribute"
+require "active_support/core_ext/string/inflections"
 
 module ActiveSupport
   # Rescuable module adds support for easier exception handling.
diff --git a/activesupport/lib/active_support/security_utils.rb b/activesupport/lib/active_support/security_utils.rb
index 51870559ec..20b6b9cd3f 100644
--- a/activesupport/lib/active_support/security_utils.rb
+++ b/activesupport/lib/active_support/security_utils.rb
@@ -1,17 +1,15 @@
 # frozen_string_literal: true
 
-require "digest"
+require "digest/sha2"
 
 module ActiveSupport
   module SecurityUtils
-    # Constant time string comparison.
+    # Constant time string comparison, for fixed length strings.
     #
     # The values compared should be of fixed length, such as strings
-    # that have already been processed by HMAC. This should not be used
-    # on variable length plaintext strings because it could leak length info
-    # via timing attacks.
-    def secure_compare(a, b)
-      return false unless a.bytesize == b.bytesize
+    # that have already been processed by HMAC. Raises in case of length mismatch.
+    def fixed_length_secure_compare(a, b)
+      raise ArgumentError, "string length mismatch." unless a.bytesize == b.bytesize
 
       l = a.unpack "C#{a.bytesize}"
 
@@ -19,11 +17,15 @@ module ActiveSupport
       b.each_byte { |byte| res |= byte ^ l.shift }
       res == 0
     end
-    module_function :secure_compare
+    module_function :fixed_length_secure_compare
 
-    def variable_size_secure_compare(a, b) # :nodoc:
-      secure_compare(::Digest::SHA256.hexdigest(a), ::Digest::SHA256.hexdigest(b))
+    # Constant time string comparison, for variable length strings.
+    #
+    # The values are first processed by SHA256, so that we don't leak length info
+    # via timing attacks.
+    def secure_compare(a, b)
+      fixed_length_secure_compare(::Digest::SHA256.hexdigest(a), ::Digest::SHA256.hexdigest(b)) && a == b
     end
-    module_function :variable_size_secure_compare
+    module_function :secure_compare
   end
 end
diff --git a/activesupport/lib/active_support/subscriber.rb b/activesupport/lib/active_support/subscriber.rb
index 7913bb815e..8ad39f7a05 100644
--- a/activesupport/lib/active_support/subscriber.rb
+++ b/activesupport/lib/active_support/subscriber.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "per_thread_registry"
-require_relative "notifications"
+require "active_support/per_thread_registry"
+require "active_support/notifications"
 
 module ActiveSupport
   # ActiveSupport::Subscriber is an object set to consume
@@ -54,25 +54,20 @@ module ActiveSupport
         @@subscribers ||= []
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-      attr_reader :subscriber, :notifier, :namespace
-
       private
+        attr_reader :subscriber, :notifier, :namespace
 
-      def add_event_subscriber(event) # :doc:
-        return if %w{ start finish }.include?(event.to_s)
+        def add_event_subscriber(event) # :doc:
+          return if %w{ start finish }.include?(event.to_s)
 
-        pattern = "#{event}.#{namespace}"
+          pattern = "#{event}.#{namespace}"
 
-        # Don't add multiple subscribers (eg. if methods are redefined).
-        return if subscriber.patterns.include?(pattern)
+          # Don't add multiple subscribers (eg. if methods are redefined).
+          return if subscriber.patterns.include?(pattern)
 
-        subscriber.patterns << pattern
-        notifier.subscribe(pattern, subscriber)
-      end
+          subscriber.patterns << pattern
+          notifier.subscribe(pattern, subscriber)
+        end
     end
 
     attr_reader :patterns # :nodoc:
diff --git a/activesupport/lib/active_support/tagged_logging.rb b/activesupport/lib/active_support/tagged_logging.rb
index fe13eaed4e..b069ac94d4 100644
--- a/activesupport/lib/active_support/tagged_logging.rb
+++ b/activesupport/lib/active_support/tagged_logging.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-require_relative "core_ext/module/delegation"
-require_relative "core_ext/object/blank"
+require "active_support/core_ext/module/delegation"
+require "active_support/core_ext/object/blank"
 require "logger"
-require_relative "logger"
+require "active_support/logger"
 
 module ActiveSupport
   # Wraps any standard Logger object to provide tagging capabilities.
@@ -52,7 +52,9 @@ module ActiveSupport
 
       def tags_text
         tags = current_tags
-        if tags.any?
+        if tags.one?
+          "[#{tags[0]}] "
+        elsif tags.any?
           tags.collect { |tag| "[#{tag}] " }.join
         end
       end
diff --git a/activesupport/lib/active_support/test_case.rb b/activesupport/lib/active_support/test_case.rb
index bc42758f76..f17743b6db 100644
--- a/activesupport/lib/active_support/test_case.rb
+++ b/activesupport/lib/active_support/test_case.rb
@@ -2,16 +2,16 @@
 
 gem "minitest" # make sure we get the gem, not stdlib
 require "minitest"
-require_relative "testing/tagged_logging"
-require_relative "testing/setup_and_teardown"
-require_relative "testing/assertions"
-require_relative "testing/deprecation"
-require_relative "testing/declarative"
-require_relative "testing/isolation"
-require_relative "testing/constant_lookup"
-require_relative "testing/time_helpers"
-require_relative "testing/file_fixtures"
-require_relative "core_ext/kernel/reporting"
+require "active_support/testing/tagged_logging"
+require "active_support/testing/setup_and_teardown"
+require "active_support/testing/assertions"
+require "active_support/testing/deprecation"
+require "active_support/testing/declarative"
+require "active_support/testing/isolation"
+require "active_support/testing/constant_lookup"
+require "active_support/testing/time_helpers"
+require "active_support/testing/file_fixtures"
+require "active_support/testing/parallelization"
 
 module ActiveSupport
   class TestCase < ::Minitest::Test
@@ -40,12 +40,97 @@ module ActiveSupport
       def test_order
         ActiveSupport.test_order ||= :random
       end
+
+      # Parallelizes the test suite.
+      #
+      # Takes a +workers+ argument that controls how many times the process
+      # is forked. For each process a new database will be created suffixed
+      # with the worker number.
+      #
+      #   test-database-0
+      #   test-database-1
+      #
+      # If <tt>ENV["PARALLEL_WORKERS"]</tt> is set the workers argument will be ignored
+      # and the environment variable will be used instead. This is useful for CI
+      # environments, or other environments where you may need more workers than
+      # you do for local testing.
+      #
+      # If the number of workers is set to +1+ or fewer, the tests will not be
+      # parallelized.
+      #
+      # The default parallelization method is to fork processes. If you'd like to
+      # use threads instead you can pass <tt>with: :threads</tt> to the +parallelize+
+      # method. Note the threaded parallelization does not create multiple
+      # database and will not work with system tests at this time.
+      #
+      #   parallelize(workers: 2, with: :threads)
+      #
+      # The threaded parallelization uses Minitest's parallel executor directly.
+      # The processes parallelization uses a Ruby Drb server.
+      def parallelize(workers: 2, with: :processes)
+        workers = ENV["PARALLEL_WORKERS"].to_i if ENV["PARALLEL_WORKERS"]
+
+        return if workers <= 1
+
+        executor = case with
+                   when :processes
+                     Testing::Parallelization.new(workers)
+                   when :threads
+                     Minitest::Parallel::Executor.new(workers)
+                   else
+                     raise ArgumentError, "#{with} is not a supported parallelization executor."
+        end
+
+        self.lock_threads = false if defined?(self.lock_threads) && with == :threads
+
+        Minitest.parallel_executor = executor
+
+        parallelize_me!
+      end
+
+      # Set up hook for parallel testing. This can be used if you have multiple
+      # databases or any behavior that needs to be run after the process is forked
+      # but before the tests run.
+      #
+      # Note: this feature is not available with the threaded parallelization.
+      #
+      # In your +test_helper.rb+ add the following:
+      #
+      #   class ActiveSupport::TestCase
+      #     parallelize_setup do
+      #       # create databases
+      #     end
+      #   end
+      def parallelize_setup(&block)
+        ActiveSupport::Testing::Parallelization.after_fork_hook do |worker|
+          yield worker
+        end
+      end
+
+      # Clean up hook for parallel testing. This can be used to drop databases
+      # if your app uses multiple write/read databases or other clean up before
+      # the tests finish. This runs before the forked process is closed.
+      #
+      # Note: this feature is not available with the threaded parallelization.
+      #
+      # In your +test_helper.rb+ add the following:
+      #
+      #   class ActiveSupport::TestCase
+      #     parallelize_teardown do
+      #       # drop databases
+      #     end
+      #   end
+      def parallelize_teardown(&block)
+        ActiveSupport::Testing::Parallelization.run_cleanup_hook do |worker|
+          yield worker
+        end
+      end
     end
 
     alias_method :method_name, :name
 
     include ActiveSupport::Testing::TaggedLogging
-    include ActiveSupport::Testing::SetupAndTeardown
+    prepend ActiveSupport::Testing::SetupAndTeardown
     include ActiveSupport::Testing::Assertions
     include ActiveSupport::Testing::Deprecation
     include ActiveSupport::Testing::TimeHelpers
diff --git a/activesupport/lib/active_support/testing/assertions.rb b/activesupport/lib/active_support/testing/assertions.rb
index e2bc51ff7a..6a56da384f 100644
--- a/activesupport/lib/active_support/testing/assertions.rb
+++ b/activesupport/lib/active_support/testing/assertions.rb
@@ -58,6 +58,12 @@ module ActiveSupport
       #     post :create, params: { article: {...} }
       #   end
       #
+      # A hash of expressions/numeric differences can also be passed in and evaluated.
+      #
+      #   assert_difference ->{ Article.count } => 1, ->{ Notification.count } => 2 do
+      #     post :create, params: { article: {...} }
+      #   end
+      #
       # A lambda or a list of lambdas can be passed in and evaluated:
       #
       #   assert_difference ->{ Article.count }, 2 do
@@ -73,20 +79,28 @@ module ActiveSupport
       #   assert_difference 'Article.count', -1, 'An Article should be destroyed' do
       #     post :delete, params: { id: ... }
       #   end
-      def assert_difference(expression, difference = 1, message = nil, &block)
-        expressions = Array(expression)
-
-        exps = expressions.map { |e|
+      def assert_difference(expression, *args, &block)
+        expressions =
+          if expression.is_a?(Hash)
+            message = args[0]
+            expression
+          else
+            difference = args[0] || 1
+            message = args[1]
+            Hash[Array(expression).map { |e| [e, difference] }]
+          end
+
+        exps = expressions.keys.map { |e|
           e.respond_to?(:call) ? e : lambda { eval(e, block.binding) }
         }
         before = exps.map(&:call)
 
         retval = yield
 
-        expressions.zip(exps).each_with_index do |(code, e), i|
-          error  = "#{code.inspect} didn't change by #{difference}"
+        expressions.zip(exps, before) do |(code, diff), exp, before_value|
+          error  = "#{code.inspect} didn't change by #{diff}"
           error  = "#{message}.\n#{error}" if message
-          assert_equal(before[i] + difference, e.call, error)
+          assert_equal(before_value + diff, exp.call, error)
         end
 
         retval
@@ -156,12 +170,15 @@ module ActiveSupport
 
         after = exp.call
 
-        if to == UNTRACKED
-          error = "#{expression.inspect} didn't change"
-          error = "#{message}.\n#{error}" if message
-          assert_not_equal before, after, error
-        else
-          error = "#{expression.inspect} didn't change to #{to}"
+        error = "#{expression.inspect} didn't change"
+        error = "#{error}. It was already #{to}" if before == to
+        error = "#{message}.\n#{error}" if message
+        assert before != after, error
+
+        unless to == UNTRACKED
+          error = "#{expression.inspect} didn't change to as expected\n"
+          error = "#{error}Expected: #{to.inspect}\n"
+          error = "#{error}  Actual: #{after.inspect}"
           error = "#{message}.\n#{error}" if message
           assert to === after, error
         end
@@ -190,7 +207,7 @@ module ActiveSupport
 
         error = "#{expression.inspect} did change to #{after}"
         error = "#{message}.\n#{error}" if message
-        assert_equal before, after, error
+        assert before == after, error
 
         retval
       end
diff --git a/activesupport/lib/active_support/testing/constant_lookup.rb b/activesupport/lib/active_support/testing/constant_lookup.rb
index 0fedd486fb..51167e9237 100644
--- a/activesupport/lib/active_support/testing/constant_lookup.rb
+++ b/activesupport/lib/active_support/testing/constant_lookup.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../concern"
-require_relative "../inflector"
+require "active_support/concern"
+require "active_support/inflector"
 
 module ActiveSupport
   module Testing
diff --git a/activesupport/lib/active_support/testing/deprecation.rb b/activesupport/lib/active_support/testing/deprecation.rb
index 4fda4832cc..f655435729 100644
--- a/activesupport/lib/active_support/testing/deprecation.rb
+++ b/activesupport/lib/active_support/testing/deprecation.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../deprecation"
-require_relative "../core_ext/regexp"
+require "active_support/deprecation"
+require "active_support/core_ext/regexp"
 
 module ActiveSupport
   module Testing
diff --git a/activesupport/lib/active_support/testing/isolation.rb b/activesupport/lib/active_support/testing/isolation.rb
index 954197a3cc..652a10da23 100644
--- a/activesupport/lib/active_support/testing/isolation.rb
+++ b/activesupport/lib/active_support/testing/isolation.rb
@@ -45,7 +45,8 @@ module ActiveSupport
                   end
                 }
               end
-              result = Marshal.dump(dup)
+              test_result = defined?(Minitest::Result) ? Minitest::Result.from(self) : dup
+              result = Marshal.dump(test_result)
             end
 
             write.puts [result].pack("m")
@@ -55,7 +56,7 @@ module ActiveSupport
           write.close
           result = read.read
           Process.wait2(pid)
-          return result.unpack("m")[0]
+          result.unpack1("m")
         end
       end
 
@@ -69,8 +70,9 @@ module ActiveSupport
 
           if ENV["ISOLATION_TEST"]
             yield
+            test_result = defined?(Minitest::Result) ? Minitest::Result.from(self) : dup
             File.open(ENV["ISOLATION_OUTPUT"], "w") do |file|
-              file.puts [Marshal.dump(dup)].pack("m")
+              file.puts [Marshal.dump(test_result)].pack("m")
             end
             exit!
           else
@@ -96,7 +98,7 @@ module ActiveSupport
                 nil
               end
 
-              return tmpfile.read.unpack("m")[0]
+              return tmpfile.read.unpack1("m")
             end
           end
         end
diff --git a/activesupport/lib/active_support/testing/parallelization.rb b/activesupport/lib/active_support/testing/parallelization.rb
new file mode 100644
index 0000000000..59c8486f41
--- /dev/null
+++ b/activesupport/lib/active_support/testing/parallelization.rb
@@ -0,0 +1,102 @@
+# frozen_string_literal: true
+
+require "drb"
+require "drb/unix"
+
+module ActiveSupport
+  module Testing
+    class Parallelization # :nodoc:
+      class Server
+        include DRb::DRbUndumped
+
+        def initialize
+          @queue = Queue.new
+        end
+
+        def record(reporter, result)
+          reporter.synchronize do
+            reporter.record(result)
+          end
+        end
+
+        def <<(o)
+          @queue << o
+        end
+
+        def pop; @queue.pop; end
+      end
+
+      @after_fork_hooks = []
+
+      def self.after_fork_hook(&blk)
+        @after_fork_hooks << blk
+      end
+
+      def self.after_fork_hooks
+        @after_fork_hooks
+      end
+
+      @run_cleanup_hooks = []
+
+      def self.run_cleanup_hook(&blk)
+        @run_cleanup_hooks << blk
+      end
+
+      def self.run_cleanup_hooks
+        @run_cleanup_hooks
+      end
+
+      def initialize(queue_size)
+        @queue_size = queue_size
+        @queue      = Server.new
+        @pool       = []
+
+        @url = DRb.start_service("drbunix:", @queue).uri
+      end
+
+      def after_fork(worker)
+        self.class.after_fork_hooks.each do |cb|
+          cb.call(worker)
+        end
+      end
+
+      def run_cleanup(worker)
+        self.class.run_cleanup_hooks.each do |cb|
+          cb.call(worker)
+        end
+      end
+
+      def start
+        @pool = @queue_size.times.map do |worker|
+          fork do
+            DRb.stop_service
+
+            after_fork(worker)
+
+            queue = DRbObject.new_with_uri(@url)
+
+            while job = queue.pop
+              klass    = job[0]
+              method   = job[1]
+              reporter = job[2]
+              result   = Minitest.run_one_method(klass, method)
+
+              queue.record(reporter, result)
+            end
+
+            run_cleanup(worker)
+          end
+        end
+      end
+
+      def <<(work)
+        @queue << work
+      end
+
+      def shutdown
+        @queue_size.times { @queue << nil }
+        @pool.each { |pid| Process.waitpid pid }
+      end
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/testing/setup_and_teardown.rb b/activesupport/lib/active_support/testing/setup_and_teardown.rb
index 18de7185d9..35321cd157 100644
--- a/activesupport/lib/active_support/testing/setup_and_teardown.rb
+++ b/activesupport/lib/active_support/testing/setup_and_teardown.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../concern"
-require_relative "../callbacks"
+require "active_support/callbacks"
 
 module ActiveSupport
   module Testing
@@ -19,11 +18,10 @@ module ActiveSupport
     #     end
     #   end
     module SetupAndTeardown
-      extend ActiveSupport::Concern
-
-      included do
-        include ActiveSupport::Callbacks
-        define_callbacks :setup, :teardown
+      def self.prepended(klass)
+        klass.include ActiveSupport::Callbacks
+        klass.define_callbacks :setup, :teardown
+        klass.extend ClassMethods
       end
 
       module ClassMethods
@@ -44,7 +42,12 @@ module ActiveSupport
       end
 
       def after_teardown # :nodoc:
-        run_callbacks :teardown
+        begin
+          run_callbacks :teardown
+        rescue => e
+          self.failures << Minitest::UnexpectedError.new(e)
+        end
+
         super
       end
     end
diff --git a/activesupport/lib/active_support/testing/stream.rb b/activesupport/lib/active_support/testing/stream.rb
index d070a1793d..127cfe1e12 100644
--- a/activesupport/lib/active_support/testing/stream.rb
+++ b/activesupport/lib/active_support/testing/stream.rb
@@ -33,7 +33,7 @@ module ActiveSupport
           yield
 
           stream_io.rewind
-          return captured_stream.read
+          captured_stream.read
         ensure
           captured_stream.close
           captured_stream.unlink
diff --git a/activesupport/lib/active_support/testing/time_helpers.rb b/activesupport/lib/active_support/testing/time_helpers.rb
index fa5f46736c..801ea2909b 100644
--- a/activesupport/lib/active_support/testing/time_helpers.rb
+++ b/activesupport/lib/active_support/testing/time_helpers.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/string/strip" # for strip_heredoc
-require_relative "../core_ext/time/calculations"
+require "active_support/core_ext/module/redefine_method"
+require "active_support/core_ext/time/calculations"
 require "concurrent/map"
 
 module ActiveSupport
@@ -43,7 +43,7 @@ module ActiveSupport
 
         def unstub_object(stub)
           singleton_class = stub.object.singleton_class
-          singleton_class.send :undef_method, stub.method_name
+          singleton_class.send :silence_redefinition_of_method, stub.method_name
           singleton_class.send :alias_method, stub.method_name, stub.original_method
           singleton_class.send :undef_method, stub.original_method
         end
@@ -111,7 +111,7 @@ module ActiveSupport
       #   Time.current # => Sat, 09 Nov 2013 15:34:49 EST -05:00
       def travel_to(date_or_time)
         if block_given? && simple_stubs.stubbing(Time, :now)
-          travel_to_nested_block_call = <<-MSG.strip_heredoc
+          travel_to_nested_block_call = <<~MSG
 
       Calling `travel_to` with a block, when we have previously already made a call to `travel_to`, can lead to confusing time stubbing.
 
diff --git a/activesupport/lib/active_support/time.rb b/activesupport/lib/active_support/time.rb
index fb1c5cee1c..51854675bf 100644
--- a/activesupport/lib/active_support/time.rb
+++ b/activesupport/lib/active_support/time.rb
@@ -9,12 +9,12 @@ end
 require "date"
 require "time"
 
-require_relative "core_ext/time"
-require_relative "core_ext/date"
-require_relative "core_ext/date_time"
+require "active_support/core_ext/time"
+require "active_support/core_ext/date"
+require "active_support/core_ext/date_time"
 
-require_relative "core_ext/integer/time"
-require_relative "core_ext/numeric/time"
+require "active_support/core_ext/integer/time"
+require "active_support/core_ext/numeric/time"
 
-require_relative "core_ext/string/conversions"
-require_relative "core_ext/string/zones"
+require "active_support/core_ext/string/conversions"
+require "active_support/core_ext/string/zones"
diff --git a/activesupport/lib/active_support/time_with_zone.rb b/activesupport/lib/active_support/time_with_zone.rb
index 59cafa193e..7e71318404 100644
--- a/activesupport/lib/active_support/time_with_zone.rb
+++ b/activesupport/lib/active_support/time_with_zone.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-require_relative "duration"
-require_relative "values/time_zone"
-require_relative "core_ext/object/acts_like"
-require_relative "core_ext/date_and_time/compatibility"
+require "active_support/duration"
+require "active_support/values/time_zone"
+require "active_support/core_ext/object/acts_like"
+require "active_support/core_ext/date_and_time/compatibility"
 
 module ActiveSupport
   # A Time-like class that can represent a time in any time zone. Necessary
@@ -225,6 +225,8 @@ module ActiveSupport
     def <=>(other)
       utc <=> other
     end
+    alias_method :before?, :<
+    alias_method :after?, :>
 
     # Returns true if the current object's time is within the specified
     # +min+ and +max+ time.
diff --git a/activesupport/lib/active_support/values/time_zone.rb b/activesupport/lib/active_support/values/time_zone.rb
index c871f11422..5f709c5fd9 100644
--- a/activesupport/lib/active_support/values/time_zone.rb
+++ b/activesupport/lib/active_support/values/time_zone.rb
@@ -2,7 +2,6 @@
 
 require "tzinfo"
 require "concurrent/map"
-require_relative "../core_ext/object/blank"
 
 module ActiveSupport
   # The TimeZone class serves as a wrapper around TZInfo::Timezone instances.
@@ -30,7 +29,7 @@ module ActiveSupport
   class TimeZone
     # Keys are Rails TimeZone names, values are TZInfo identifiers.
     MAPPING = {
-      "International Date Line West" => "Pacific/Midway",
+      "International Date Line West" => "Etc/GMT+12",
       "Midway Island"                => "Pacific/Midway",
       "American Samoa"               => "Pacific/Pago_Pago",
       "Hawaii"                       => "Pacific/Honolulu",
@@ -238,7 +237,7 @@ module ActiveSupport
         when Numeric, ActiveSupport::Duration
           arg *= 3600 if arg.abs <= 13
           all.find { |z| z.utc_offset == arg.to_i }
-          else
+        else
           raise ArgumentError, "invalid argument to TimeZone[]: #{arg.inspect}"
         end
       end
@@ -256,22 +255,32 @@ module ActiveSupport
         @country_zones[code] ||= load_country_zones(code)
       end
 
+      def clear #:nodoc:
+        @lazy_zones_map = Concurrent::Map.new
+        @country_zones  = Concurrent::Map.new
+        @zones = nil
+        @zones_map = nil
+      end
+
       private
         def load_country_zones(code)
           country = TZInfo::Country.get(code)
           country.zone_identifiers.map do |tz_id|
             if MAPPING.value?(tz_id)
-              self[MAPPING.key(tz_id)]
+              MAPPING.inject([]) do |memo, (key, value)|
+                memo << self[key] if value == tz_id
+                memo
+              end
             else
               create(tz_id, nil, TZInfo::Timezone.new(tz_id))
             end
-          end.sort!
+          end.flatten(1).sort!
         end
 
         def zones_map
-          @zones_map ||= begin
-            MAPPING.each_key { |place| self[place] } # load all the zones
-            @lazy_zones_map
+          @zones_map ||= MAPPING.each_with_object({}) do |(name, _), zones|
+            timezone = self[name]
+            zones[name] = timezone if timezone
           end
         end
     end
@@ -506,7 +515,7 @@ module ActiveSupport
     # Available so that TimeZone instances respond like TZInfo::Timezone
     # instances.
     def period_for_local(time, dst = true)
-      tzinfo.period_for_local(time, dst)
+      tzinfo.period_for_local(time, dst) { |periods| periods.last }
     end
 
     def periods_for_local(time) #:nodoc:
diff --git a/activesupport/lib/active_support/values/unicode_tables.dat b/activesupport/lib/active_support/values/unicode_tables.dat
deleted file mode 100644
index f7d9c48bbe..0000000000
--- a/activesupport/lib/active_support/values/unicode_tables.dat
+++ /dev/null
diff --git a/activesupport/lib/active_support/xml_mini.rb b/activesupport/lib/active_support/xml_mini.rb
index d49ee4508e..e42eee07a3 100644
--- a/activesupport/lib/active_support/xml_mini.rb
+++ b/activesupport/lib/active_support/xml_mini.rb
@@ -3,9 +3,9 @@
 require "time"
 require "base64"
 require "bigdecimal"
-require_relative "core_ext/module/delegation"
-require_relative "core_ext/string/inflections"
-require_relative "core_ext/date_time/calculations"
+require "active_support/core_ext/module/delegation"
+require "active_support/core_ext/string/inflections"
+require "active_support/core_ext/date_time/calculations"
 
 module ActiveSupport
   # = XmlMini
@@ -48,10 +48,6 @@ module ActiveSupport
         "Array"      => "array",
         "Hash"       => "hash"
       }
-
-      # No need to map these on Ruby 2.4+
-      TYPE_NAMES["Fixnum"] = "integer" unless 0.class == Integer
-      TYPE_NAMES["Bignum"] = "integer" unless 0.class == Integer
     end
 
     FORMATTING = {
@@ -83,7 +79,7 @@ module ActiveSupport
         end,
         "boolean"      => Proc.new { |boolean| %w(1 true).include?(boolean.to_s.strip) },
         "string"       => Proc.new { |string|  string.to_s },
-        "yaml"         => Proc.new { |yaml|    YAML::load(yaml) rescue yaml },
+        "yaml"         => Proc.new { |yaml|    YAML.load(yaml) rescue yaml },
         "base64Binary" => Proc.new { |bin|     ::Base64.decode64(bin) },
         "binary"       => Proc.new { |bin, entity| _parse_binary(bin, entity) },
         "file"         => Proc.new { |file, entity| _parse_file(file, entity) }
@@ -199,7 +195,7 @@ module ActiveSupport
         if name.is_a?(Module)
           name
         else
-          require_relative "xml_mini/#{name.downcase}"
+          require "active_support/xml_mini/#{name.downcase}"
           ActiveSupport.const_get("XmlMini_#{name}")
         end
       end
diff --git a/activesupport/lib/active_support/xml_mini/jdom.rb b/activesupport/lib/active_support/xml_mini/jdom.rb
index ebed376c7a..7f94a64016 100644
--- a/activesupport/lib/active_support/xml_mini/jdom.rb
+++ b/activesupport/lib/active_support/xml_mini/jdom.rb
@@ -5,7 +5,7 @@ raise "JRuby is required to use the JDOM backend for XmlMini" unless RUBY_PLATFO
 require "jruby"
 include Java
 
-require_relative "../core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 
 java_import javax.xml.parsers.DocumentBuilder unless defined? DocumentBuilder
 java_import javax.xml.parsers.DocumentBuilderFactory unless defined? DocumentBuilderFactory
@@ -169,7 +169,7 @@ module ActiveSupport
       # element::
       #   XML element to be checked.
       def empty_content?(element)
-        text = ""
+        text = "".dup
         child_nodes = element.child_nodes
         (0...child_nodes.length).each do |i|
           item = child_nodes.item(i)
diff --git a/activesupport/lib/active_support/xml_mini/libxml.rb b/activesupport/lib/active_support/xml_mini/libxml.rb
index b1be38fadf..0b000fea60 100644
--- a/activesupport/lib/active_support/xml_mini/libxml.rb
+++ b/activesupport/lib/active_support/xml_mini/libxml.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "libxml"
-require_relative "../core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 require "stringio"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/xml_mini/libxmlsax.rb b/activesupport/lib/active_support/xml_mini/libxmlsax.rb
index 3ad494310d..dcf16e6084 100644
--- a/activesupport/lib/active_support/xml_mini/libxmlsax.rb
+++ b/activesupport/lib/active_support/xml_mini/libxmlsax.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "libxml"
-require_relative "../core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 require "stringio"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/xml_mini/nokogiri.rb b/activesupport/lib/active_support/xml_mini/nokogiri.rb
index 1987330c25..5ee6fc8159 100644
--- a/activesupport/lib/active_support/xml_mini/nokogiri.rb
+++ b/activesupport/lib/active_support/xml_mini/nokogiri.rb
@@ -6,7 +6,7 @@ rescue LoadError => e
   $stderr.puts "You don't have nokogiri installed in your application. Please add it to your Gemfile and run bundle install"
   raise e
 end
-require_relative "../core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 require "stringio"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/xml_mini/nokogirisax.rb b/activesupport/lib/active_support/xml_mini/nokogirisax.rb
index fb57eb8867..b01ed00a14 100644
--- a/activesupport/lib/active_support/xml_mini/nokogirisax.rb
+++ b/activesupport/lib/active_support/xml_mini/nokogirisax.rb
@@ -6,7 +6,7 @@ rescue LoadError => e
   $stderr.puts "You don't have nokogiri installed in your application. Please add it to your Gemfile and run bundle install"
   raise e
 end
-require_relative "../core_ext/object/blank"
+require "active_support/core_ext/object/blank"
 require "stringio"
 
 module ActiveSupport
diff --git a/activesupport/lib/active_support/xml_mini/rexml.rb b/activesupport/lib/active_support/xml_mini/rexml.rb
index 5fd8978fc0..32458d5b0d 100644
--- a/activesupport/lib/active_support/xml_mini/rexml.rb
+++ b/activesupport/lib/active_support/xml_mini/rexml.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../core_ext/kernel/reporting"
-require_relative "../core_ext/object/blank"
+require "active_support/core_ext/kernel/reporting"
+require "active_support/core_ext/object/blank"
 require "stringio"
 
 module ActiveSupport
diff --git a/activesupport/test/abstract_unit.rb b/activesupport/test/abstract_unit.rb
index 3ac11e0fe0..f214898145 100644
--- a/activesupport/test/abstract_unit.rb
+++ b/activesupport/test/abstract_unit.rb
@@ -38,4 +38,8 @@ class ActiveSupport::TestCase
   private def jruby_skip(message = "")
     skip message if defined?(JRUBY_VERSION)
   end
+
+  def frozen_error_class
+    Object.const_defined?(:FrozenError) ? FrozenError : RuntimeError
+  end
 end
diff --git a/activesupport/test/array_inquirer_test.rb b/activesupport/test/array_inquirer_test.rb
index d5419b862d..9a260edd8a 100644
--- a/activesupport/test/array_inquirer_test.rb
+++ b/activesupport/test/array_inquirer_test.rb
@@ -9,9 +9,9 @@ class ArrayInquirerTest < ActiveSupport::TestCase
   end
 
   def test_individual
-    assert @array_inquirer.mobile?
-    assert @array_inquirer.tablet?
-    assert_not @array_inquirer.desktop?
+    assert_predicate @array_inquirer, :mobile?
+    assert_predicate @array_inquirer, :tablet?
+    assert_not_predicate @array_inquirer, :desktop?
   end
 
   def test_any
diff --git a/activesupport/test/benchmarkable_test.rb b/activesupport/test/benchmarkable_test.rb
index 424da0a52c..cb7a69cccf 100644
--- a/activesupport/test/benchmarkable_test.rb
+++ b/activesupport/test/benchmarkable_test.rb
@@ -26,7 +26,7 @@ class BenchmarkableTest < ActiveSupport::TestCase
 
   def test_without_block
     assert_raise(LocalJumpError) { benchmark }
-    assert buffer.empty?
+    assert_empty buffer
   end
 
   def test_defaults
diff --git a/activesupport/test/cache/behaviors.rb b/activesupport/test/cache/behaviors.rb
index cb08a10bba..2d39976be3 100644
--- a/activesupport/test/cache/behaviors.rb
+++ b/activesupport/test/cache/behaviors.rb
@@ -3,7 +3,10 @@
 require_relative "behaviors/autoloading_cache_behavior"
 require_relative "behaviors/cache_delete_matched_behavior"
 require_relative "behaviors/cache_increment_decrement_behavior"
+require_relative "behaviors/cache_instrumentation_behavior"
 require_relative "behaviors/cache_store_behavior"
 require_relative "behaviors/cache_store_version_behavior"
+require_relative "behaviors/connection_pool_behavior"
 require_relative "behaviors/encoded_key_cache_behavior"
+require_relative "behaviors/failure_safety_behavior"
 require_relative "behaviors/local_cache_behavior"
diff --git a/activesupport/test/cache/behaviors/cache_delete_matched_behavior.rb b/activesupport/test/cache/behaviors/cache_delete_matched_behavior.rb
index 6f59ce48d2..ed8eba8fc2 100644
--- a/activesupport/test/cache/behaviors/cache_delete_matched_behavior.rb
+++ b/activesupport/test/cache/behaviors/cache_delete_matched_behavior.rb
@@ -7,9 +7,9 @@ module CacheDeleteMatchedBehavior
     @cache.write("foo/bar", "baz")
     @cache.write("fu/baz", "bar")
     @cache.delete_matched(/oo/)
-    assert !@cache.exist?("foo")
+    assert_not @cache.exist?("foo")
     assert @cache.exist?("fu")
-    assert !@cache.exist?("foo/bar")
+    assert_not @cache.exist?("foo/bar")
     assert @cache.exist?("fu/baz")
   end
 end
diff --git a/activesupport/test/cache/behaviors/cache_increment_decrement_behavior.rb b/activesupport/test/cache/behaviors/cache_increment_decrement_behavior.rb
index 2fa2d7af88..16b7abc679 100644
--- a/activesupport/test/cache/behaviors/cache_increment_decrement_behavior.rb
+++ b/activesupport/test/cache/behaviors/cache_increment_decrement_behavior.rb
@@ -8,7 +8,9 @@ module CacheIncrementDecrementBehavior
     assert_equal 2, @cache.read("foo").to_i
     assert_equal 3, @cache.increment("foo")
     assert_equal 3, @cache.read("foo").to_i
-    assert_nil @cache.increment("bar")
+
+    missing = @cache.increment("bar")
+    assert(missing.nil? || missing == 1)
   end
 
   def test_decrement
@@ -18,6 +20,8 @@ module CacheIncrementDecrementBehavior
     assert_equal 2, @cache.read("foo").to_i
     assert_equal 1, @cache.decrement("foo")
     assert_equal 1, @cache.read("foo").to_i
-    assert_nil @cache.decrement("bar")
+
+    missing = @cache.decrement("bar")
+    assert(missing.nil? || missing == -1)
   end
 end
diff --git a/activesupport/test/cache/cache_store_write_multi_test.rb b/activesupport/test/cache/behaviors/cache_instrumentation_behavior.rb
index 5b6fd678c5..4e8ff60eb3 100644
--- a/activesupport/test/cache/cache_store_write_multi_test.rb
+++ b/activesupport/test/cache/behaviors/cache_instrumentation_behavior.rb
@@ -1,28 +1,15 @@
 # frozen_string_literal: true
 
-require "abstract_unit"
-require "active_support/cache"
-
-class CacheStoreWriteMultiEntriesStoreProviderInterfaceTest < ActiveSupport::TestCase
-  setup do
-    @cache = ActiveSupport::Cache.lookup_store(:null_store)
-  end
-
-  test "fetch_multi uses write_multi_entries store provider interface" do
+module CacheInstrumentationBehavior
+  def test_fetch_multi_uses_write_multi_entries_store_provider_interface
     assert_called_with(@cache, :write_multi_entries) do
       @cache.fetch_multi "a", "b", "c" do |key|
         key * 2
       end
     end
   end
-end
 
-class CacheStoreWriteMultiInstrumentationTest < ActiveSupport::TestCase
-  setup do
-    @cache = ActiveSupport::Cache.lookup_store(:null_store)
-  end
-
-  test "instrumentation" do
+  def test_write_multi_instrumentation
     writes = { "a" => "aa", "b" => "bb" }
 
     events = with_instrumentation "write_multi" do
@@ -34,16 +21,27 @@ class CacheStoreWriteMultiInstrumentationTest < ActiveSupport::TestCase
     assert_equal({ "a" => "aa", "b" => "bb" }, events[0].payload[:key])
   end
 
-  test "instrumentation with fetch_multi as super operation" do
-    skip "fetch_multi isn't instrumented yet"
+  def test_instrumentation_with_fetch_multi_as_super_operation
+    @cache.write("b", "bb")
 
-    events = with_instrumentation "write_multi" do
+    events = with_instrumentation "read_multi" do
       @cache.fetch_multi("a", "b") { |key| key * 2 }
     end
 
-    assert_equal %w[ cache_write_multi.active_support ], events.map(&:name)
-    assert_nil events[0].payload[:super_operation]
-    assert !events[0].payload[:hit]
+    assert_equal %w[ cache_read_multi.active_support ], events.map(&:name)
+    assert_equal :fetch_multi, events[0].payload[:super_operation]
+    assert_equal ["b"], events[0].payload[:hits]
+  end
+
+  def test_read_multi_instrumentation
+    @cache.write("b", "bb")
+
+    events = with_instrumentation "read_multi" do
+      @cache.read_multi("a", "b") { |key| key * 2 }
+    end
+
+    assert_equal %w[ cache_read_multi.active_support ], events.map(&:name)
+    assert_equal ["b"], events[0].payload[:hits]
   end
 
   private
diff --git a/activesupport/test/cache/behaviors/cache_store_behavior.rb b/activesupport/test/cache/behaviors/cache_store_behavior.rb
index 582e902f72..f9153ffe2a 100644
--- a/activesupport/test/cache/behaviors/cache_store_behavior.rb
+++ b/activesupport/test/cache/behaviors/cache_store_behavior.rb
@@ -33,7 +33,7 @@ module CacheStoreBehavior
 
     cache_miss = false
     assert_equal 3, @cache.fetch("foo") { |key| cache_miss = true; key.length }
-    assert !cache_miss
+    assert_not cache_miss
   end
 
   def test_fetch_with_forced_cache_miss
@@ -113,6 +113,16 @@ module CacheStoreBehavior
     assert_equal("fufu", @cache.read("fu"))
   end
 
+  def test_fetch_multi_without_expires_in
+    @cache.write("foo", "bar")
+    @cache.write("fud", "biz")
+
+    values = @cache.fetch_multi("foo", "fu", "fud", expires_in: nil) { |value| value * 2 }
+
+    assert_equal({ "foo" => "bar", "fu" => "fufu", "fud" => "biz" }, values)
+    assert_equal("fufu", @cache.read("fu"))
+  end
+
   def test_multi_with_objects
     cache_struct = Struct.new(:cache_key, :title)
     foo = cache_struct.new("foo", "FOO!")
@@ -131,19 +141,111 @@ module CacheStoreBehavior
     end
   end
 
-  def test_read_and_write_compressed_small_data
-    @cache.write("foo", "bar", compress: true)
-    assert_equal "bar", @cache.read("foo")
+  # Use strings that are guarenteed to compress well, so we can easily tell if
+  # the compression kicked in or not.
+  SMALL_STRING = "0" * 100
+  LARGE_STRING = "0" * 2.kilobytes
+
+  SMALL_OBJECT = { data: SMALL_STRING }
+  LARGE_OBJECT = { data: LARGE_STRING }
+
+  def test_nil_with_default_compression_settings
+    assert_uncompressed(nil)
   end
 
-  def test_read_and_write_compressed_large_data
-    @cache.write("foo", "bar", compress: true, compress_threshold: 2)
-    assert_equal "bar", @cache.read("foo")
+  def test_nil_with_compress_true
+    assert_uncompressed(nil, compress: true)
   end
 
-  def test_read_and_write_compressed_nil
-    @cache.write("foo", nil, compress: true)
-    assert_nil @cache.read("foo")
+  def test_nil_with_compress_false
+    assert_uncompressed(nil, compress: false)
+  end
+
+  def test_nil_with_compress_low_compress_threshold
+    assert_uncompressed(nil, compress: true, compress_threshold: 1)
+  end
+
+  def test_small_string_with_default_compression_settings
+    assert_uncompressed(SMALL_STRING)
+  end
+
+  def test_small_string_with_compress_true
+    assert_uncompressed(SMALL_STRING, compress: true)
+  end
+
+  def test_small_string_with_compress_false
+    assert_uncompressed(SMALL_STRING, compress: false)
+  end
+
+  def test_small_string_with_low_compress_threshold
+    assert_compressed(SMALL_STRING, compress: true, compress_threshold: 1)
+  end
+
+  def test_small_object_with_default_compression_settings
+    assert_uncompressed(SMALL_OBJECT)
+  end
+
+  def test_small_object_with_compress_true
+    assert_uncompressed(SMALL_OBJECT, compress: true)
+  end
+
+  def test_small_object_with_compress_false
+    assert_uncompressed(SMALL_OBJECT, compress: false)
+  end
+
+  def test_small_object_with_low_compress_threshold
+    assert_compressed(SMALL_OBJECT, compress: true, compress_threshold: 1)
+  end
+
+  def test_large_string_with_default_compression_settings
+    assert_compressed(LARGE_STRING)
+  end
+
+  def test_large_string_with_compress_true
+    assert_compressed(LARGE_STRING, compress: true)
+  end
+
+  def test_large_string_with_compress_false
+    assert_uncompressed(LARGE_STRING, compress: false)
+  end
+
+  def test_large_string_with_high_compress_threshold
+    assert_uncompressed(LARGE_STRING, compress: true, compress_threshold: 1.megabyte)
+  end
+
+  def test_large_object_with_default_compression_settings
+    assert_compressed(LARGE_OBJECT)
+  end
+
+  def test_large_object_with_compress_true
+    assert_compressed(LARGE_OBJECT, compress: true)
+  end
+
+  def test_large_object_with_compress_false
+    assert_uncompressed(LARGE_OBJECT, compress: false)
+  end
+
+  def test_large_object_with_high_compress_threshold
+    assert_uncompressed(LARGE_OBJECT, compress: true, compress_threshold: 1.megabyte)
+  end
+
+  def test_incompressable_data
+    assert_uncompressed(nil, compress: true, compress_threshold: 1)
+    assert_uncompressed(true, compress: true, compress_threshold: 1)
+    assert_uncompressed(false, compress: true, compress_threshold: 1)
+    assert_uncompressed(0, compress: true, compress_threshold: 1)
+    assert_uncompressed(1.2345, compress: true, compress_threshold: 1)
+    assert_uncompressed("", compress: true, compress_threshold: 1)
+
+    incompressible = nil
+
+    # generate an incompressible string
+    loop do
+      incompressible = SecureRandom.random_bytes(1.kilobyte)
+      break if incompressible.bytesize < Zlib::Deflate.deflate(incompressible).bytesize
+    end
+
+    assert_uncompressed(incompressible, compress: true, compress_threshold: 1)
   end
 
   def test_cache_key
@@ -164,6 +266,18 @@ module CacheStoreBehavior
     assert_equal "bar", @cache.read("foo")
   end
 
+  def test_unversioned_cache_key
+    obj = Object.new
+    def obj.cache_key
+      "foo"
+    end
+    def obj.cache_key_with_version
+      "foo-v1"
+    end
+    @cache.write(obj, "bar")
+    assert_equal "bar", @cache.read("foo")
+  end
+
   def test_array_as_cache_key
     @cache.write([:fu, "foo"], "bar")
     assert_equal "bar", @cache.read("fu/foo")
@@ -194,7 +308,7 @@ module CacheStoreBehavior
     @cache.write("foo", "bar")
     assert @cache.exist?("foo")
     assert @cache.delete("foo")
-    assert !@cache.exist?("foo")
+    assert_not @cache.exist?("foo")
   end
 
   def test_original_store_objects_should_not_be_immutable
@@ -287,8 +401,7 @@ module CacheStoreBehavior
   end
 
   def test_really_long_keys
-    key = "".dup
-    900.times { key << "x" }
+    key = "x" * 2048
     assert @cache.write(key, "bar")
     assert_equal "bar", @cache.read(key)
     assert_equal "bar", @cache.fetch(key)
@@ -328,4 +441,41 @@ module CacheStoreBehavior
   ensure
     ActiveSupport::Notifications.unsubscribe "cache_read.active_support"
   end
+
+  private
+
+    def assert_compressed(value, **options)
+      assert_compression(true, value, **options)
+    end
+
+    def assert_uncompressed(value, **options)
+      assert_compression(false, value, **options)
+    end
+
+    def assert_compression(should_compress, value, **options)
+      freeze_time do
+        @cache.write("actual", value, options)
+        @cache.write("uncompressed", value, options.merge(compress: false))
+      end
+
+      if value.nil?
+        assert_nil @cache.read("actual")
+        assert_nil @cache.read("uncompressed")
+      else
+        assert_equal value, @cache.read("actual")
+        assert_equal value, @cache.read("uncompressed")
+      end
+
+      actual_entry = @cache.send(:read_entry, @cache.send(:normalize_key, "actual", {}), {})
+      uncompressed_entry = @cache.send(:read_entry, @cache.send(:normalize_key, "uncompressed", {}), {})
+
+      actual_size = Marshal.dump(actual_entry).bytesize
+      uncompressed_size = Marshal.dump(uncompressed_entry).bytesize
+
+      if should_compress
+        assert_operator actual_size, :<, uncompressed_size, "value should be compressed"
+      else
+        assert_equal uncompressed_size, actual_size, "value should not be compressed"
+      end
+    end
 end
diff --git a/activesupport/test/cache/behaviors/cache_store_version_behavior.rb b/activesupport/test/cache/behaviors/cache_store_version_behavior.rb
index c2e4d046af..805f061839 100644
--- a/activesupport/test/cache/behaviors/cache_store_version_behavior.rb
+++ b/activesupport/test/cache/behaviors/cache_store_version_behavior.rb
@@ -30,7 +30,7 @@ module CacheStoreVersionBehavior
 
   def test_exist_with_wrong_version_should_be_false
     @cache.write("foo", "bar", version: 1)
-    assert !@cache.exist?("foo", version: 2)
+    assert_not @cache.exist?("foo", version: 2)
   end
 
   def test_reading_and_writing_with_model_supporting_cache_version
@@ -65,7 +65,7 @@ module CacheStoreVersionBehavior
     m1v2 = ModelWithKeyAndVersion.new("model/1", 2)
 
     @cache.write(m1v1, "bar")
-    assert     @cache.exist?(m1v1)
+    assert @cache.exist?(m1v1)
     assert_not @cache.fetch(m1v2)
   end
 
diff --git a/activesupport/test/cache/behaviors/connection_pool_behavior.rb b/activesupport/test/cache/behaviors/connection_pool_behavior.rb
new file mode 100644
index 0000000000..4d1901a173
--- /dev/null
+++ b/activesupport/test/cache/behaviors/connection_pool_behavior.rb
@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+module ConnectionPoolBehavior
+  def test_connection_pool
+    Thread.report_on_exception, original_report_on_exception = false, Thread.report_on_exception
+
+    threads = []
+
+    emulating_latency do
+      begin
+        cache = ActiveSupport::Cache.lookup_store(store, { pool_size: 2, pool_timeout: 1 }.merge(store_options))
+        cache.clear
+
+        assert_raises Timeout::Error do
+          # One of the three threads will fail in 1 second because our pool size
+          # is only two.
+          3.times do
+            threads << Thread.new do
+              cache.read("latency")
+            end
+          end
+
+          threads.each(&:join)
+        end
+      ensure
+        threads.each(&:kill)
+      end
+    end
+  ensure
+    Thread.report_on_exception = original_report_on_exception
+  end
+
+  def test_no_connection_pool
+    threads = []
+
+    emulating_latency do
+      begin
+        cache = ActiveSupport::Cache.lookup_store(store, store_options)
+        cache.clear
+
+        assert_nothing_raised do
+          # Default connection pool size is 5, assuming 10 will make sure that
+          # the connection pool isn't used at all.
+          10.times do
+            threads << Thread.new do
+              cache.read("latency")
+            end
+          end
+
+          threads.each(&:join)
+        end
+      ensure
+        threads.each(&:kill)
+      end
+    end
+  end
+
+  private
+    def store_options; {}; end
+end
diff --git a/activesupport/test/cache/behaviors/failure_safety_behavior.rb b/activesupport/test/cache/behaviors/failure_safety_behavior.rb
new file mode 100644
index 0000000000..43b67d81db
--- /dev/null
+++ b/activesupport/test/cache/behaviors/failure_safety_behavior.rb
@@ -0,0 +1,91 @@
+# frozen_string_literal: true
+
+module FailureSafetyBehavior
+  def test_fetch_read_failure_returns_nil
+    @cache.write("foo", "bar")
+
+    emulating_unavailability do |cache|
+      assert_nil cache.fetch("foo")
+    end
+  end
+
+  def test_fetch_read_failure_does_not_attempt_to_write
+  end
+
+  def test_read_failure_returns_nil
+    @cache.write("foo", "bar")
+
+    emulating_unavailability do |cache|
+      assert_nil cache.read("foo")
+    end
+  end
+
+  def test_read_multi_failure_returns_empty_hash
+    @cache.write_multi("foo" => "bar", "baz" => "quux")
+
+    emulating_unavailability do |cache|
+      assert_equal Hash.new, cache.read_multi("foo", "baz")
+    end
+  end
+
+  def test_write_failure_returns_false
+    emulating_unavailability do |cache|
+      assert_equal false, cache.write("foo", "bar")
+    end
+  end
+
+  def test_write_multi_failure_not_raises
+    emulating_unavailability do |cache|
+      assert_nothing_raised do
+        cache.write_multi("foo" => "bar", "baz" => "quux")
+      end
+    end
+  end
+
+  def test_fetch_multi_failure_returns_fallback_results
+    @cache.write_multi("foo" => "bar", "baz" => "quux")
+
+    emulating_unavailability do |cache|
+      fetched = cache.fetch_multi("foo", "baz") { |k| "unavailable" }
+      assert_equal Hash["foo" => "unavailable", "baz" => "unavailable"], fetched
+    end
+  end
+
+  def test_delete_failure_returns_false
+    @cache.write("foo", "bar")
+
+    emulating_unavailability do |cache|
+      assert_equal false, cache.delete("foo")
+    end
+  end
+
+  def test_exist_failure_returns_false
+    @cache.write("foo", "bar")
+
+    emulating_unavailability do |cache|
+      assert_not cache.exist?("foo")
+    end
+  end
+
+  def test_increment_failure_returns_nil
+    @cache.write("foo", 1, raw: true)
+
+    emulating_unavailability do |cache|
+      assert_nil cache.increment("foo")
+    end
+  end
+
+  def test_decrement_failure_returns_nil
+    @cache.write("foo", 1, raw: true)
+
+    emulating_unavailability do |cache|
+      assert_nil cache.decrement("foo")
+    end
+  end
+
+  def test_clear_failure_returns_nil
+    emulating_unavailability do |cache|
+      assert_nil cache.clear
+    end
+  end
+end
diff --git a/activesupport/test/cache/behaviors/local_cache_behavior.rb b/activesupport/test/cache/behaviors/local_cache_behavior.rb
index 8dec8090b1..baa38ba6ac 100644
--- a/activesupport/test/cache/behaviors/local_cache_behavior.rb
+++ b/activesupport/test/cache/behaviors/local_cache_behavior.rb
@@ -20,7 +20,11 @@ module LocalCacheBehavior
   end
 
   def test_cleanup_clears_local_cache_but_not_remote_cache
-    skip unless @cache.class.instance_methods(false).include?(:cleanup)
+    begin
+      @cache.cleanup
+    rescue NotImplementedError
+      skip
+    end
 
     @cache.with_local_cache do
       @cache.write("foo", "bar")
@@ -115,6 +119,28 @@ module LocalCacheBehavior
     end
   end
 
+  def test_local_cache_of_fetch_multi
+    @cache.with_local_cache do
+      @cache.fetch_multi("foo", "bar") { |_key| true }
+      @peek.delete("foo")
+      @peek.delete("bar")
+      assert_equal true, @cache.read("foo")
+      assert_equal true, @cache.read("bar")
+    end
+  end
+
+  def test_local_cache_of_read_multi
+    @cache.with_local_cache do
+      @cache.write("foo", "foo", raw: true)
+      @cache.write("bar", "bar", raw: true)
+      values = @cache.read_multi("foo", "bar")
+      assert_equal "foo", @cache.read("foo")
+      assert_equal "bar", @cache.read("bar")
+      assert_equal "foo", values["foo"]
+      assert_equal "bar", values["bar"]
+    end
+  end
+
   def test_middleware
     app = lambda { |env|
       result = @cache.write("foo", "bar")
diff --git a/activesupport/test/cache/cache_entry_test.rb b/activesupport/test/cache/cache_entry_test.rb
index 51b214ad8f..ec20a288e1 100644
--- a/activesupport/test/cache/cache_entry_test.rb
+++ b/activesupport/test/cache/cache_entry_test.rb
@@ -6,25 +6,11 @@ require "active_support/cache"
 class CacheEntryTest < ActiveSupport::TestCase
   def test_expired
     entry = ActiveSupport::Cache::Entry.new("value")
-    assert !entry.expired?, "entry not expired"
+    assert_not entry.expired?, "entry not expired"
     entry = ActiveSupport::Cache::Entry.new("value", expires_in: 60)
-    assert !entry.expired?, "entry not expired"
+    assert_not entry.expired?, "entry not expired"
     Time.stub(:now, Time.now + 61) do
       assert entry.expired?, "entry is expired"
     end
   end
-
-  def test_compress_values
-    value = "value" * 100
-    entry = ActiveSupport::Cache::Entry.new(value, compress: true, compress_threshold: 1)
-    assert_equal value, entry.value
-    assert(value.bytesize > entry.size, "value is compressed")
-  end
-
-  def test_non_compress_values
-    value = "value" * 100
-    entry = ActiveSupport::Cache::Entry.new(value)
-    assert_equal value, entry.value
-    assert_equal value.bytesize, entry.size
-  end
 end
diff --git a/activesupport/test/cache/cache_store_logger_test.rb b/activesupport/test/cache/cache_store_logger_test.rb
index 1af6893cc9..4648b2d361 100644
--- a/activesupport/test/cache/cache_store_logger_test.rb
+++ b/activesupport/test/cache/cache_store_logger_test.rb
@@ -13,7 +13,7 @@ class CacheStoreLoggerTest < ActiveSupport::TestCase
 
   def test_logging
     @cache.fetch("foo") { "bar" }
-    assert @buffer.string.present?
+    assert_predicate @buffer.string, :present?
   end
 
   def test_log_with_string_namespace
@@ -31,6 +31,6 @@ class CacheStoreLoggerTest < ActiveSupport::TestCase
 
   def test_mute_logging
     @cache.mute { @cache.fetch("foo") { "bar" } }
-    assert @buffer.string.blank?
+    assert_predicate @buffer.string, :blank?
   end
 end
diff --git a/activesupport/test/cache/cache_store_namespace_test.rb b/activesupport/test/cache/cache_store_namespace_test.rb
index b52a61c500..dfdb3262f2 100644
--- a/activesupport/test/cache/cache_store_namespace_test.rb
+++ b/activesupport/test/cache/cache_store_namespace_test.rb
@@ -25,7 +25,7 @@ class CacheStoreNamespaceTest < ActiveSupport::TestCase
     cache.write("foo", "bar")
     cache.write("fu", "baz")
     cache.delete_matched(/^fo/)
-    assert !cache.exist?("foo")
+    assert_not cache.exist?("foo")
     assert cache.exist?("fu")
   end
 
@@ -34,7 +34,7 @@ class CacheStoreNamespaceTest < ActiveSupport::TestCase
     cache.write("foo", "bar")
     cache.write("fu", "baz")
     cache.delete_matched(/OO/i)
-    assert !cache.exist?("foo")
+    assert_not cache.exist?("foo")
     assert cache.exist?("fu")
   end
 end
diff --git a/activesupport/test/cache/stores/file_store_test.rb b/activesupport/test/cache/stores/file_store_test.rb
index 391ab60b3a..f6855bb308 100644
--- a/activesupport/test/cache/stores/file_store_test.rb
+++ b/activesupport/test/cache/stores/file_store_test.rb
@@ -30,6 +30,7 @@ class FileStoreTest < ActiveSupport::TestCase
   include LocalCacheBehavior
   include CacheDeleteMatchedBehavior
   include CacheIncrementDecrementBehavior
+  include CacheInstrumentationBehavior
   include AutoloadingCacheBehavior
 
   def test_clear
@@ -67,7 +68,9 @@ class FileStoreTest < ActiveSupport::TestCase
   def test_filename_max_size
     key = "#{'A' * ActiveSupport::Cache::FileStore::FILENAME_MAX_SIZE}"
     path = @cache.send(:normalize_key, key, {})
-    Dir::Tmpname.create(path) do |tmpname, n, opts|
+    basename = File.basename(path)
+    dirname = File.dirname(path)
+    Dir::Tmpname.create(basename, Dir.tmpdir + dirname) do |tmpname, n, opts|
       assert File.basename(tmpname + ".lock").length <= 255, "Temp filename too long: #{File.basename(tmpname + '.lock').length}"
     end
   end
@@ -98,13 +101,13 @@ class FileStoreTest < ActiveSupport::TestCase
     end
     assert File.exist?(cache_dir), "Parent of top level cache dir was deleted!"
     assert File.exist?(sub_cache_dir), "Top level cache dir was deleted!"
-    assert Dir.entries(sub_cache_dir).reject { |f| ActiveSupport::Cache::FileStore::EXCLUDED_DIRS.include?(f) }.empty?
+    assert_empty Dir.entries(sub_cache_dir).reject { |f| ActiveSupport::Cache::FileStore::EXCLUDED_DIRS.include?(f) }
   end
 
   def test_log_exception_when_cache_read_fails
     File.stub(:exist?, -> { raise StandardError.new("failed") }) do
       @cache.send(:read_entry, "winston", {})
-      assert @buffer.string.present?
+      assert_predicate @buffer.string, :present?
     end
   end
 
@@ -118,6 +121,7 @@ class FileStoreTest < ActiveSupport::TestCase
       assert_not @cache.exist?("foo")
       assert @cache.exist?("baz")
       assert @cache.exist?("quux")
+      assert_equal 2, Dir.glob(File.join(cache_dir, "**")).size
     end
   end
 
diff --git a/activesupport/test/cache/stores/mem_cache_store_test.rb b/activesupport/test/cache/stores/mem_cache_store_test.rb
index 1b73fb65eb..f426a37c66 100644
--- a/activesupport/test/cache/stores/mem_cache_store_test.rb
+++ b/activesupport/test/cache/stores/mem_cache_store_test.rb
@@ -5,6 +5,24 @@ require "active_support/cache"
 require_relative "../behaviors"
 require "dalli"
 
+# Emulates a latency on Dalli's back-end for the key latency to facilitate
+# connection pool testing.
+class SlowDalliClient < Dalli::Client
+  def get(key, options = {})
+    if key =~ /latency/
+      sleep 3
+    else
+      super
+    end
+  end
+end
+
+class UnavailableDalliServer < Dalli::Server
+  def alive?
+    false
+  end
+end
+
 class MemCacheStoreTest < ActiveSupport::TestCase
   begin
     ss = Dalli::Client.new("localhost:11211").stats
@@ -31,8 +49,11 @@ class MemCacheStoreTest < ActiveSupport::TestCase
   include CacheStoreVersionBehavior
   include LocalCacheBehavior
   include CacheIncrementDecrementBehavior
+  include CacheInstrumentationBehavior
   include EncodedKeyCacheBehavior
   include AutoloadingCacheBehavior
+  include ConnectionPoolBehavior
+  include FailureSafetyBehavior
 
   def test_raw_values
     cache = ActiveSupport::Cache.lookup_store(:mem_cache_store, raw: true)
@@ -57,6 +78,22 @@ class MemCacheStoreTest < ActiveSupport::TestCase
     end
   end
 
+  def test_increment_expires_in
+    cache = ActiveSupport::Cache.lookup_store(:mem_cache_store, raw: true)
+    cache.clear
+    assert_called_with cache.instance_variable_get(:@data), :incr, [ "foo", 1, 60 ] do
+      cache.increment("foo", 1, expires_in: 60)
+    end
+  end
+
+  def test_decrement_expires_in
+    cache = ActiveSupport::Cache.lookup_store(:mem_cache_store, raw: true)
+    cache.clear
+    assert_called_with cache.instance_variable_get(:@data), :decr, [ "foo", 1, 60 ] do
+      cache.decrement("foo", 1, expires_in: 60)
+    end
+  end
+
   def test_local_cache_raw_values_with_marshal
     cache = ActiveSupport::Cache.lookup_store(:mem_cache_store, raw: true)
     cache.clear
@@ -73,4 +110,30 @@ class MemCacheStoreTest < ActiveSupport::TestCase
     value << "bingo"
     assert_not_equal value, @cache.read("foo")
   end
+
+  private
+
+    def store
+      :mem_cache_store
+    end
+
+    def emulating_latency
+      old_client = Dalli.send(:remove_const, :Client)
+      Dalli.const_set(:Client, SlowDalliClient)
+
+      yield
+    ensure
+      Dalli.send(:remove_const, :Client)
+      Dalli.const_set(:Client, old_client)
+    end
+
+    def emulating_unavailability
+      old_server = Dalli.send(:remove_const, :Server)
+      Dalli.const_set(:Server, UnavailableDalliServer)
+
+      yield ActiveSupport::Cache::MemCacheStore.new
+    ensure
+      Dalli.send(:remove_const, :Server)
+      Dalli.const_set(:Server, old_server)
+    end
 end
diff --git a/activesupport/test/cache/stores/memory_store_test.rb b/activesupport/test/cache/stores/memory_store_test.rb
index 3981f05331..4c0a4f549d 100644
--- a/activesupport/test/cache/stores/memory_store_test.rb
+++ b/activesupport/test/cache/stores/memory_store_test.rb
@@ -6,14 +6,21 @@ require_relative "../behaviors"
 
 class MemoryStoreTest < ActiveSupport::TestCase
   def setup
-    @record_size = ActiveSupport::Cache.lookup_store(:memory_store).send(:cached_size, 1, ActiveSupport::Cache::Entry.new("aaaaaaaaaa"))
-    @cache = ActiveSupport::Cache.lookup_store(:memory_store, expires_in: 60, size: @record_size * 10 + 1)
+    @cache = ActiveSupport::Cache.lookup_store(:memory_store, expires_in: 60)
   end
 
   include CacheStoreBehavior
   include CacheStoreVersionBehavior
   include CacheDeleteMatchedBehavior
   include CacheIncrementDecrementBehavior
+  include CacheInstrumentationBehavior
+end
+
+class MemoryStorePruningTest < ActiveSupport::TestCase
+  def setup
+    @record_size = ActiveSupport::Cache.lookup_store(:memory_store).send(:cached_size, 1, ActiveSupport::Cache::Entry.new("aaaaaaaaaa"))
+    @cache = ActiveSupport::Cache.lookup_store(:memory_store, expires_in: 60, size: @record_size * 10 + 1)
+  end
 
   def test_prune_size
     @cache.write(1, "aaaaaaaaaa") && sleep(0.001)
@@ -26,9 +33,9 @@ class MemoryStoreTest < ActiveSupport::TestCase
     @cache.prune(@record_size * 3)
     assert @cache.exist?(5)
     assert @cache.exist?(4)
-    assert !@cache.exist?(3), "no entry"
+    assert_not @cache.exist?(3), "no entry"
     assert @cache.exist?(2)
-    assert !@cache.exist?(1), "no entry"
+    assert_not @cache.exist?(1), "no entry"
   end
 
   def test_prune_size_on_write
@@ -50,12 +57,12 @@ class MemoryStoreTest < ActiveSupport::TestCase
     assert @cache.exist?(9)
     assert @cache.exist?(8)
     assert @cache.exist?(7)
-    assert !@cache.exist?(6), "no entry"
-    assert !@cache.exist?(5), "no entry"
+    assert_not @cache.exist?(6), "no entry"
+    assert_not @cache.exist?(5), "no entry"
     assert @cache.exist?(4)
-    assert !@cache.exist?(3), "no entry"
+    assert_not @cache.exist?(3), "no entry"
     assert @cache.exist?(2)
-    assert !@cache.exist?(1), "no entry"
+    assert_not @cache.exist?(1), "no entry"
   end
 
   def test_prune_size_on_write_based_on_key_length
@@ -75,11 +82,11 @@ class MemoryStoreTest < ActiveSupport::TestCase
     assert @cache.exist?(8)
     assert @cache.exist?(7)
     assert @cache.exist?(6)
-    assert !@cache.exist?(5), "no entry"
-    assert !@cache.exist?(4), "no entry"
-    assert !@cache.exist?(3), "no entry"
-    assert !@cache.exist?(2), "no entry"
-    assert !@cache.exist?(1), "no entry"
+    assert_not @cache.exist?(5), "no entry"
+    assert_not @cache.exist?(4), "no entry"
+    assert_not @cache.exist?(3), "no entry"
+    assert_not @cache.exist?(2), "no entry"
+    assert_not @cache.exist?(1), "no entry"
   end
 
   def test_pruning_is_capped_at_a_max_time
@@ -97,7 +104,7 @@ class MemoryStoreTest < ActiveSupport::TestCase
     assert @cache.exist?(4)
     assert @cache.exist?(3)
     assert @cache.exist?(2)
-    assert !@cache.exist?(1)
+    assert_not @cache.exist?(1)
   end
 
   def test_write_with_unless_exist
diff --git a/activesupport/test/cache/stores/redis_cache_store_test.rb b/activesupport/test/cache/stores/redis_cache_store_test.rb
new file mode 100644
index 0000000000..24c4c5c481
--- /dev/null
+++ b/activesupport/test/cache/stores/redis_cache_store_test.rb
@@ -0,0 +1,242 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "active_support/cache"
+require "active_support/cache/redis_cache_store"
+require_relative "../behaviors"
+
+driver_name = %w[ ruby hiredis ].include?(ENV["REDIS_DRIVER"]) ? ENV["REDIS_DRIVER"] : "hiredis"
+driver = Object.const_get("Redis::Connection::#{driver_name.camelize}")
+
+Redis::Connection.drivers.clear
+Redis::Connection.drivers.append(driver)
+
+# Emulates a latency on Redis's back-end for the key latency to facilitate
+# connection pool testing.
+class SlowRedis < Redis
+  def get(key, options = {})
+    if key =~ /latency/
+      sleep 3
+    else
+      super
+    end
+  end
+end
+
+module ActiveSupport::Cache::RedisCacheStoreTests
+  DRIVER = %w[ ruby hiredis ].include?(ENV["REDIS_DRIVER"]) ? ENV["REDIS_DRIVER"] : "hiredis"
+
+  class LookupTest < ActiveSupport::TestCase
+    test "may be looked up as :redis_cache_store" do
+      assert_kind_of ActiveSupport::Cache::RedisCacheStore,
+        ActiveSupport::Cache.lookup_store(:redis_cache_store)
+    end
+  end
+
+  class InitializationTest < ActiveSupport::TestCase
+    test "omitted URL uses Redis client with default settings" do
+      assert_called_with Redis, :new, [
+        url: nil,
+        connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+        reconnect_attempts: 0, driver: DRIVER
+      ] do
+        build
+      end
+    end
+
+    test "no URLs uses Redis client with default settings" do
+      assert_called_with Redis, :new, [
+        url: nil,
+        connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+        reconnect_attempts: 0, driver: DRIVER
+      ] do
+        build url: []
+      end
+    end
+
+    test "singular URL uses Redis client" do
+      assert_called_with Redis, :new, [
+        url: "redis://localhost:6379/0",
+        connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+        reconnect_attempts: 0, driver: DRIVER
+      ] do
+        build url: "redis://localhost:6379/0"
+      end
+    end
+
+    test "one URL uses Redis client" do
+      assert_called_with Redis, :new, [
+        url: "redis://localhost:6379/0",
+        connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+        reconnect_attempts: 0, driver: DRIVER
+      ] do
+        build url: %w[ redis://localhost:6379/0 ]
+      end
+    end
+
+    test "multiple URLs uses Redis::Distributed client" do
+      assert_called_with Redis, :new, [
+        [ url: "redis://localhost:6379/0",
+          connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+          reconnect_attempts: 0, driver: DRIVER ],
+        [ url: "redis://localhost:6379/1",
+          connect_timeout: 20, read_timeout: 1, write_timeout: 1,
+          reconnect_attempts: 0, driver: DRIVER ],
+      ], returns: Redis.new do
+        @cache = build url: %w[ redis://localhost:6379/0 redis://localhost:6379/1 ]
+        assert_kind_of ::Redis::Distributed, @cache.redis
+      end
+    end
+
+    test "block argument uses yielded client" do
+      block = -> { :custom_redis_client }
+      assert_called block, :call do
+        build redis: block
+      end
+    end
+
+    test "instance of Redis uses given instance" do
+      redis_instance = Redis.new
+      @cache = build(redis: redis_instance)
+      assert_same @cache.redis, redis_instance
+    end
+
+    private
+      def build(**kwargs)
+        ActiveSupport::Cache::RedisCacheStore.new(driver: DRIVER, **kwargs).tap do |cache|
+          cache.redis
+        end
+      end
+  end
+
+  class StoreTest < ActiveSupport::TestCase
+    setup do
+      @namespace = "namespace"
+
+      @cache = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1, namespace: @namespace, expires_in: 60, driver: DRIVER)
+      # @cache.logger = Logger.new($stdout)  # For test debugging
+
+      # For LocalCacheBehavior tests
+      @peek = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1, namespace: @namespace, driver: DRIVER)
+    end
+
+    teardown do
+      @cache.clear
+      @cache.redis.disconnect!
+    end
+  end
+
+  class RedisCacheStoreCommonBehaviorTest < StoreTest
+    include CacheStoreBehavior
+    include CacheStoreVersionBehavior
+    include LocalCacheBehavior
+    include CacheIncrementDecrementBehavior
+    include CacheInstrumentationBehavior
+    include AutoloadingCacheBehavior
+
+    def test_fetch_multi_uses_redis_mget
+      assert_called(@cache.redis, :mget, returns: []) do
+        @cache.fetch_multi("a", "b", "c") do |key|
+          key * 2
+        end
+      end
+    end
+  end
+
+  class ConnectionPoolBehaviourTest < StoreTest
+    include ConnectionPoolBehavior
+
+    private
+
+      def store
+        :redis_cache_store
+      end
+
+      def emulating_latency
+        old_redis = Object.send(:remove_const, :Redis)
+        Object.const_set(:Redis, SlowRedis)
+
+        yield
+      ensure
+        Object.send(:remove_const, :Redis)
+        Object.const_set(:Redis, old_redis)
+      end
+  end
+
+  class RedisDistributedConnectionPoolBehaviourTest < ConnectionPoolBehaviourTest
+    private
+      def store_options
+        { url: %w[ redis://localhost:6379/0 redis://localhost:6379/0 ] }
+      end
+  end
+
+  # Separate test class so we can omit the namespace which causes expected,
+  # appropriate complaints about incompatible string encodings.
+  class KeyEncodingSafetyTest < StoreTest
+    include EncodedKeyCacheBehavior
+
+    setup do
+      @cache = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1, driver: DRIVER)
+      @cache.logger = nil
+    end
+  end
+
+  class StoreAPITest < StoreTest
+  end
+
+  class UnavailableRedisClient < Redis::Client
+    def ensure_connected
+      raise Redis::BaseConnectionError
+    end
+  end
+
+  class FailureSafetyTest < StoreTest
+    include FailureSafetyBehavior
+
+    private
+
+      def emulating_unavailability
+        old_client = Redis.send(:remove_const, :Client)
+        Redis.const_set(:Client, UnavailableRedisClient)
+
+        yield ActiveSupport::Cache::RedisCacheStore.new
+      ensure
+        Redis.send(:remove_const, :Client)
+        Redis.const_set(:Client, old_client)
+      end
+  end
+
+  class DeleteMatchedTest < StoreTest
+    test "deletes keys matching glob" do
+      @cache.write("foo", "bar")
+      @cache.write("fu", "baz")
+      @cache.delete_matched("foo*")
+      assert_not @cache.exist?("foo")
+      assert @cache.exist?("fu")
+    end
+
+    test "fails with regexp matchers" do
+      assert_raise ArgumentError do
+        @cache.delete_matched(/OO/i)
+      end
+    end
+  end
+
+  class ClearTest < StoreTest
+    test "clear all cache key" do
+      @cache.write("foo", "bar")
+      @cache.write("fu", "baz")
+      @cache.clear
+      assert_not @cache.exist?("foo")
+      assert_not @cache.exist?("fu")
+    end
+
+    test "only clear namespace cache key" do
+      @cache.write("foo", "bar")
+      @cache.redis.set("fu", "baz")
+      @cache.clear
+      assert_not @cache.exist?("foo")
+      assert @cache.redis.exists("fu")
+    end
+  end
+end
diff --git a/activesupport/test/callback_inheritance_test.rb b/activesupport/test/callback_inheritance_test.rb
index 67813a749e..5633b6e2b8 100644
--- a/activesupport/test/callback_inheritance_test.rb
+++ b/activesupport/test/callback_inheritance_test.rb
@@ -164,10 +164,10 @@ end
 class DynamicInheritedCallbacks < ActiveSupport::TestCase
   def test_callbacks_looks_to_the_superclass_before_running
     child = EmptyChild.new.dispatch
-    assert !child.performed?
+    assert_not_predicate child, :performed?
     EmptyParent.set_callback :dispatch, :before, :perform!
     child = EmptyChild.new.dispatch
-    assert child.performed?
+    assert_predicate child, :performed?
   end
 
   def test_callbacks_should_be_performed_once_in_child_class
@@ -176,3 +176,13 @@ class DynamicInheritedCallbacks < ActiveSupport::TestCase
     assert_equal 1, child.count
   end
 end
+
+class DynamicDefinedCallbacks < ActiveSupport::TestCase
+  def test_callbacks_should_be_performed_once_in_child_class_after_dynamic_define
+    GrandParent.define_callbacks(:foo)
+    GrandParent.set_callback(:foo, :before, :before1)
+    parent = Parent.new("foo")
+    parent.run_callbacks(:foo)
+    assert_equal %w(before1), parent.log
+  end
+end
diff --git a/activesupport/test/callbacks_test.rb b/activesupport/test/callbacks_test.rb
index 3902e41a60..5c9a3b29e7 100644
--- a/activesupport/test/callbacks_test.rb
+++ b/activesupport/test/callbacks_test.rb
@@ -77,7 +77,7 @@ module CallbacksTest
     skip_callback :save, :after,  :after_save_method, unless: :yes
     skip_callback :save, :after,  :after_save_method, if: :no
     skip_callback :save, :before, :before_save_method, unless: :no
-    skip_callback :save, :before, CallbackClass , if: :yes
+    skip_callback :save, :before, CallbackClass, if: :yes
     def yes; true; end
     def no; false; end
   end
@@ -193,13 +193,6 @@ module CallbacksTest
     before_save Proc.new { |r| r.history << "b00m" }, if: :no
     before_save Proc.new { |r| r.history << [:before_save, :symbol] }, unless: :no
     before_save Proc.new { |r| r.history << "b00m" }, unless: :yes
-    # string
-    ActiveSupport::Deprecation.silence do
-      before_save Proc.new { |r| r.history << [:before_save, :string] }, if: "yes"
-      before_save Proc.new { |r| r.history << "b00m" }, if: "no"
-      before_save Proc.new { |r| r.history << [:before_save, :string] }, unless: "no"
-      before_save Proc.new { |r| r.history << "b00m" }, unless: "yes"
-    end
     # Combined if and unless
     before_save Proc.new { |r| r.history << [:before_save, :combined_symbol] }, if: :yes, unless: :no
     before_save Proc.new { |r| r.history << "b00m" }, if: :yes, unless: :yes
@@ -489,10 +482,9 @@ module CallbacksTest
         "block in run_callbacks",
         "tweedle_dum",
         "block in run_callbacks",
-        ("call" if RUBY_VERSION < "2.3"),
         "run_callbacks",
         "save"
-      ].compact, call_stack.map(&:label)
+      ], call_stack.map(&:label)
     end
 
     def test_short_call_stack
@@ -592,8 +584,6 @@ module CallbacksTest
         [:before_save, :proc],
         [:before_save, :symbol],
         [:before_save, :symbol],
-        [:before_save, :string],
-        [:before_save, :string],
         [:before_save, :combined_symbol],
       ], person.history
     end
@@ -839,7 +829,7 @@ module CallbacksTest
     def test_block_never_called_if_terminated
       obj = CallbackTerminator.new
       obj.save
-      assert !obj.saved
+      assert_not obj.saved
     end
   end
 
@@ -867,7 +857,7 @@ module CallbacksTest
     def test_block_never_called_if_abort_is_thrown
       obj = CallbackDefaultTerminator.new
       obj.save
-      assert !obj.saved
+      assert_not obj.saved
     end
   end
 
@@ -1182,14 +1172,15 @@ module CallbacksTest
     end
   end
 
-  class DeprecatedWarningTest < ActiveSupport::TestCase
-    def test_deprecate_string_conditional_options
+  class NotSupportedStringConditionalTest < ActiveSupport::TestCase
+    def test_string_conditional_options
       klass = Class.new(Record)
 
-      assert_deprecated { klass.before_save :tweedle, if: "true" }
-      assert_deprecated { klass.after_save :tweedle, unless: "false" }
-      assert_deprecated { klass.skip_callback :save, :before, :tweedle, if: "true" }
-      assert_deprecated { klass.skip_callback :save, :after, :tweedle, unless: "false" }
+      assert_raises(ArgumentError) { klass.before_save :tweedle, if: ["true"] }
+      assert_raises(ArgumentError) { klass.before_save :tweedle, if: "true" }
+      assert_raises(ArgumentError) { klass.after_save :tweedle, unless: "false" }
+      assert_raises(ArgumentError) { klass.skip_callback :save, :before, :tweedle, if: "true" }
+      assert_raises(ArgumentError) { klass.skip_callback :save, :after, :tweedle, unless: "false" }
     end
   end
 
diff --git a/activesupport/test/class_cache_test.rb b/activesupport/test/class_cache_test.rb
index 7b97028e8c..1ef1939b4b 100644
--- a/activesupport/test/class_cache_test.rb
+++ b/activesupport/test/class_cache_test.rb
@@ -11,17 +11,17 @@ module ActiveSupport
       end
 
       def test_empty?
-        assert @cache.empty?
+        assert_empty @cache
         @cache.store(ClassCacheTest)
-        assert !@cache.empty?
+        assert_not_empty @cache
       end
 
       def test_clear!
-        assert @cache.empty?
+        assert_empty @cache
         @cache.store(ClassCacheTest)
-        assert !@cache.empty?
+        assert_not_empty @cache
         @cache.clear!
-        assert @cache.empty?
+        assert_empty @cache
       end
 
       def test_set_key
@@ -40,35 +40,35 @@ module ActiveSupport
       end
 
       def test_get_constantizes
-        assert @cache.empty?
+        assert_empty @cache
         assert_equal ClassCacheTest, @cache.get(ClassCacheTest.name)
       end
 
       def test_get_constantizes_fails_on_invalid_names
-        assert @cache.empty?
+        assert_empty @cache
         assert_raise NameError do
           @cache.get("OmgTotallyInvalidConstantName")
         end
       end
 
       def test_get_alias
-        assert @cache.empty?
+        assert_empty @cache
         assert_equal @cache[ClassCacheTest.name], @cache.get(ClassCacheTest.name)
       end
 
       def test_safe_get_constantizes
-        assert @cache.empty?
+        assert_empty @cache
         assert_equal ClassCacheTest, @cache.safe_get(ClassCacheTest.name)
       end
 
       def test_safe_get_constantizes_doesnt_fail_on_invalid_names
-        assert @cache.empty?
+        assert_empty @cache
         assert_nil @cache.safe_get("OmgTotallyInvalidConstantName")
       end
 
       def test_new_rejects_strings
         @cache.store ClassCacheTest.name
-        assert !@cache.key?(ClassCacheTest.name)
+        assert_not @cache.key?(ClassCacheTest.name)
       end
 
       def test_store_returns_self
diff --git a/activesupport/test/concern_test.rb b/activesupport/test/concern_test.rb
index ef75a320d1..98d8f3ee0d 100644
--- a/activesupport/test/concern_test.rb
+++ b/activesupport/test/concern_test.rb
@@ -91,7 +91,7 @@ class ConcernTest < ActiveSupport::TestCase
       end
     end
     @klass.include test_module
-    assert_equal false, Object.respond_to?(:test)
+    assert_not_respond_to Object, :test
     Qux.class_eval do
       remove_const :ClassMethods
     end
diff --git a/activesupport/test/concurrency/load_interlock_aware_monitor_test.rb b/activesupport/test/concurrency/load_interlock_aware_monitor_test.rb
new file mode 100644
index 0000000000..2d0f45ec5f
--- /dev/null
+++ b/activesupport/test/concurrency/load_interlock_aware_monitor_test.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "concurrent/atomic/count_down_latch"
+require "active_support/concurrency/load_interlock_aware_monitor"
+
+module ActiveSupport
+  module Concurrency
+    class LoadInterlockAwareMonitorTest < ActiveSupport::TestCase
+      def setup
+        @monitor = ActiveSupport::Concurrency::LoadInterlockAwareMonitor.new
+      end
+
+      def test_entering_with_no_blocking
+        assert @monitor.mon_enter
+      end
+
+      def test_entering_with_blocking
+        load_interlock_latch = Concurrent::CountDownLatch.new
+        monitor_latch = Concurrent::CountDownLatch.new
+
+        able_to_use_monitor = false
+        able_to_load = false
+
+        thread_with_load_interlock = Thread.new do
+          ActiveSupport::Dependencies.interlock.running do
+            load_interlock_latch.count_down
+            monitor_latch.wait
+
+            @monitor.synchronize do
+              able_to_use_monitor = true
+            end
+          end
+        end
+
+        thread_with_monitor_lock = Thread.new do
+          @monitor.synchronize do
+            monitor_latch.count_down
+            load_interlock_latch.wait
+
+            ActiveSupport::Dependencies.interlock.loading do
+              able_to_load = true
+            end
+          end
+        end
+
+        thread_with_load_interlock.join
+        thread_with_monitor_lock.join
+
+        assert able_to_use_monitor
+        assert able_to_load
+      end
+    end
+  end
+end
diff --git a/activesupport/test/configurable_test.rb b/activesupport/test/configurable_test.rb
index 10719596df..1cf40261dc 100644
--- a/activesupport/test/configurable_test.rb
+++ b/activesupport/test/configurable_test.rb
@@ -43,11 +43,11 @@ class ConfigurableActiveSupport < ActiveSupport::TestCase
   test "configuration accessors are not available on instance" do
     instance = Parent.new
 
-    assert !instance.respond_to?(:bar)
-    assert !instance.respond_to?(:bar=)
+    assert_not_respond_to instance, :bar
+    assert_not_respond_to instance, :bar=
 
-    assert !instance.respond_to?(:baz)
-    assert !instance.respond_to?(:baz=)
+    assert_not_respond_to instance, :baz
+    assert_not_respond_to instance, :baz=
   end
 
   test "configuration accessors can take a default value" do
diff --git a/activesupport/test/core_ext/array/conversions_test.rb b/activesupport/test/core_ext/array/conversions_test.rb
index 0f919efcb0..0a7c43d421 100644
--- a/activesupport/test/core_ext/array/conversions_test.rb
+++ b/activesupport/test/core_ext/array/conversions_test.rb
@@ -90,7 +90,7 @@ class ToXmlTest < ActiveSupport::TestCase
   def test_to_xml_with_hash_elements
     xml = [
       { name: "David", age: 26, age_in_millis: 820497600000 },
-      { name: "Jason", age: 31, age_in_millis: BigDecimal.new("1.0") }
+      { name: "Jason", age: 31, age_in_millis: BigDecimal("1.0") }
     ].to_xml(skip_instruct: true, indent: 0)
 
     assert_equal '<objects type="array"><object>', xml.first(30)
@@ -173,7 +173,7 @@ class ToXmlTest < ActiveSupport::TestCase
   def test_to_xml_with_instruct
     xml = [
       { name: "David", age: 26, age_in_millis: 820497600000 },
-      { name: "Jason", age: 31, age_in_millis: BigDecimal.new("1.0") }
+      { name: "Jason", age: 31, age_in_millis: BigDecimal("1.0") }
     ].to_xml(skip_instruct: false, indent: 0)
 
     assert_match(/^<\?xml [^>]*/, xml)
@@ -183,7 +183,7 @@ class ToXmlTest < ActiveSupport::TestCase
   def test_to_xml_with_block
     xml = [
       { name: "David", age: 26, age_in_millis: 820497600000 },
-      { name: "Jason", age: 31, age_in_millis: BigDecimal.new("1.0") }
+      { name: "Jason", age: 31, age_in_millis: BigDecimal("1.0") }
     ].to_xml(skip_instruct: true, indent: 0) do |builder|
       builder.count 2
     end
diff --git a/activesupport/test/core_ext/array/grouping_test.rb b/activesupport/test/core_ext/array/grouping_test.rb
index da9d4963d8..37111a5d7d 100644
--- a/activesupport/test/core_ext/array/grouping_test.rb
+++ b/activesupport/test/core_ext/array/grouping_test.rb
@@ -4,15 +4,6 @@ require "abstract_unit"
 require "active_support/core_ext/array"
 
 class GroupingTest < ActiveSupport::TestCase
-  def setup
-    # In Ruby < 2.4, test we avoid Integer#/ (redefined by mathn)
-    Fixnum.send :private, :/ unless 0.class == Integer
-  end
-
-  def teardown
-    Fixnum.send :public, :/ unless 0.class == Integer
-  end
-
   def test_in_groups_of_with_perfect_fit
     groups = []
     ("a".."i").to_a.in_groups_of(3) do |group|
@@ -116,7 +107,7 @@ class SplitTest < ActiveSupport::TestCase
   def test_split_with_block
     a = (1..10).to_a
     assert_equal [[1, 2], [4, 5], [7, 8], [10]], a.split { |i| i % 3 == 0 }
-    assert_equal [1, 2, 3, 4, 5, 6, 7, 8, 9 , 10], a
+    assert_equal [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], a
   end
 
   def test_split_with_edge_values
diff --git a/activesupport/test/core_ext/bigdecimal_test.rb b/activesupport/test/core_ext/bigdecimal_test.rb
index 66e81f1162..62588be33b 100644
--- a/activesupport/test/core_ext/bigdecimal_test.rb
+++ b/activesupport/test/core_ext/bigdecimal_test.rb
@@ -5,7 +5,7 @@ require "active_support/core_ext/big_decimal"
 
 class BigDecimalTest < ActiveSupport::TestCase
   def test_to_s
-    bd = BigDecimal.new "0.01"
+    bd = BigDecimal "0.01"
     assert_equal "0.01", bd.to_s
     assert_equal "+0.01", bd.to_s("+F")
     assert_equal "+0.0 1", bd.to_s("+1F")
diff --git a/activesupport/test/core_ext/class_test.rb b/activesupport/test/core_ext/class_test.rb
index 9cc006fc63..5ea288738e 100644
--- a/activesupport/test/core_ext/class_test.rb
+++ b/activesupport/test/core_ext/class_test.rb
@@ -30,11 +30,11 @@ class ClassTest < ActiveSupport::TestCase
 
   def test_descendants_excludes_singleton_classes
     klass = Parent.new.singleton_class
-    refute Parent.descendants.include?(klass), "descendants should not include singleton classes"
+    assert_not Parent.descendants.include?(klass), "descendants should not include singleton classes"
   end
 
   def test_subclasses_excludes_singleton_classes
     klass = Parent.new.singleton_class
-    refute Parent.subclasses.include?(klass), "subclasses should not include singleton classes"
+    assert_not Parent.subclasses.include?(klass), "subclasses should not include singleton classes"
   end
 end
diff --git a/activesupport/test/core_ext/date_and_time_behavior.rb b/activesupport/test/core_ext/date_and_time_behavior.rb
index 256353c309..b77ea22701 100644
--- a/activesupport/test/core_ext/date_and_time_behavior.rb
+++ b/activesupport/test/core_ext/date_and_time_behavior.rb
@@ -9,6 +9,11 @@ module DateAndTimeBehavior
   end
 
   def test_prev_day
+    assert_equal date_time_init(2005, 2, 24, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_day(-2)
+    assert_equal date_time_init(2005, 2, 23, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_day(-1)
+    assert_equal date_time_init(2005, 2, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_day(0)
+    assert_equal date_time_init(2005, 2, 21, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_day(1)
+    assert_equal date_time_init(2005, 2, 20, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_day(2)
     assert_equal date_time_init(2005, 2, 21, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_day
     assert_equal date_time_init(2005, 2, 28, 10, 10, 10), date_time_init(2005, 3, 2, 10, 10, 10).prev_day.prev_day
   end
@@ -19,6 +24,11 @@ module DateAndTimeBehavior
   end
 
   def test_next_day
+    assert_equal date_time_init(2005, 2, 20, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_day(-2)
+    assert_equal date_time_init(2005, 2, 21, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_day(-1)
+    assert_equal date_time_init(2005, 2, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_day(0)
+    assert_equal date_time_init(2005, 2, 23, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_day(1)
+    assert_equal date_time_init(2005, 2, 24, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_day(2)
     assert_equal date_time_init(2005, 2, 23, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_day
     assert_equal date_time_init(2005, 3, 2, 10, 10, 10),  date_time_init(2005, 2, 28, 10, 10, 10).next_day.next_day
   end
@@ -151,6 +161,16 @@ module DateAndTimeBehavior
     assert_equal date_time_init(2015, 1, 5, 15, 15, 10), date_time_init(2015, 1, 3, 15, 15, 10).next_weekday
   end
 
+  def test_next_month
+    assert_equal date_time_init(2004, 12, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_month(-2)
+    assert_equal date_time_init(2005, 1, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_month(-1)
+    assert_equal date_time_init(2005, 2, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_month(0)
+    assert_equal date_time_init(2005, 3, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_month(1)
+    assert_equal date_time_init(2005, 4, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_month(2)
+    assert_equal date_time_init(2005, 3, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_month
+    assert_equal date_time_init(2005, 4, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).next_month.next_month
+  end
+
   def test_next_month_on_31st
     assert_equal date_time_init(2005, 9, 30, 15, 15, 10), date_time_init(2005, 8, 31, 15, 15, 10).next_month
   end
@@ -160,7 +180,13 @@ module DateAndTimeBehavior
   end
 
   def test_next_year
+    assert_equal date_time_init(2003, 6, 5, 10, 10, 10), date_time_init(2005, 6, 5, 10, 10, 10).next_year(-2)
+    assert_equal date_time_init(2004, 6, 5, 10, 10, 10), date_time_init(2005, 6, 5, 10, 10, 10).next_year(-1)
+    assert_equal date_time_init(2005, 6, 5, 10, 10, 10), date_time_init(2005, 6, 5, 10, 10, 10).next_year(0)
+    assert_equal date_time_init(2006, 6, 5, 10, 10, 10), date_time_init(2005, 6, 5, 10, 10, 10).next_year(1)
+    assert_equal date_time_init(2007, 6, 5, 10, 10, 10), date_time_init(2005, 6, 5, 10, 10, 10).next_year(2)
     assert_equal date_time_init(2006, 6, 5, 10, 10, 10), date_time_init(2005, 6, 5, 10, 10, 10).next_year
+    assert_equal date_time_init(2007, 6, 5, 10, 10, 10), date_time_init(2005, 6, 5, 10, 10, 10).next_year.next_year
   end
 
   def test_prev_week
@@ -203,6 +229,16 @@ module DateAndTimeBehavior
     assert_equal date_time_init(2015, 1, 2, 15, 15, 10), date_time_init(2015, 1, 4, 15, 15, 10).prev_weekday
   end
 
+  def test_prev_month
+    assert_equal date_time_init(2005, 4, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_month(-2)
+    assert_equal date_time_init(2005, 3, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_month(-1)
+    assert_equal date_time_init(2005, 2, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_month(0)
+    assert_equal date_time_init(2005, 1, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_month(1)
+    assert_equal date_time_init(2004, 12, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_month(2)
+    assert_equal date_time_init(2005, 1, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_month
+    assert_equal date_time_init(2004, 12, 22, 10, 10, 10), date_time_init(2005, 2, 22, 10, 10, 10).prev_month.prev_month
+  end
+
   def test_prev_month_on_31st
     assert_equal date_time_init(2004, 2, 29, 10, 10, 10), date_time_init(2004, 3, 31, 10, 10, 10).prev_month
   end
@@ -212,7 +248,21 @@ module DateAndTimeBehavior
   end
 
   def test_prev_year
+    assert_equal date_time_init(2007, 6, 5, 10, 10, 10),  date_time_init(2005, 6, 5, 10, 10, 10).prev_year(-2)
+    assert_equal date_time_init(2006, 6, 5, 10, 10, 10),  date_time_init(2005, 6, 5, 10, 10, 10).prev_year(-1)
+    assert_equal date_time_init(2005, 6, 5, 10, 10, 10),  date_time_init(2005, 6, 5, 10, 10, 10).prev_year(0)
+    assert_equal date_time_init(2004, 6, 5, 10, 10, 10),  date_time_init(2005, 6, 5, 10, 10, 10).prev_year(1)
+    assert_equal date_time_init(2003, 6, 5, 10, 10, 10),  date_time_init(2005, 6, 5, 10, 10, 10).prev_year(2)
     assert_equal date_time_init(2004, 6, 5, 10, 10, 10),  date_time_init(2005, 6, 5, 10, 10, 10).prev_year
+    assert_equal date_time_init(2003, 6, 5, 10, 10, 10),  date_time_init(2005, 6, 5, 10, 10, 10).prev_year.prev_year
+  end
+
+  def test_last_month_on_31st
+    assert_equal date_time_init(2004, 2, 29, 0, 0, 0), date_time_init(2004, 3, 31, 0, 0, 0).last_month
+  end
+
+  def test_last_year
+    assert_equal date_time_init(2004, 6, 5, 10, 0, 0), date_time_init(2005, 6, 5, 10, 0, 0).last_year
   end
 
   def test_days_to_week_start
@@ -247,24 +297,24 @@ module DateAndTimeBehavior
 
   def test_beginning_of_week
     assert_equal date_time_init(2005, 1, 31, 0, 0, 0),  date_time_init(2005, 2, 4, 10, 10, 10).beginning_of_week
-    assert_equal date_time_init(2005, 11, 28, 0, 0, 0), date_time_init(2005, 11, 28, 0, 0, 0).beginning_of_week #monday
-    assert_equal date_time_init(2005, 11, 28, 0, 0, 0), date_time_init(2005, 11, 29, 0, 0, 0).beginning_of_week #tuesday
-    assert_equal date_time_init(2005, 11, 28, 0, 0, 0), date_time_init(2005, 11, 30, 0, 0, 0).beginning_of_week #wednesday
-    assert_equal date_time_init(2005, 11, 28, 0, 0, 0), date_time_init(2005, 12, 01, 0, 0, 0).beginning_of_week #thursday
-    assert_equal date_time_init(2005, 11, 28, 0, 0, 0), date_time_init(2005, 12, 02, 0, 0, 0).beginning_of_week #friday
-    assert_equal date_time_init(2005, 11, 28, 0, 0, 0), date_time_init(2005, 12, 03, 0, 0, 0).beginning_of_week #saturday
-    assert_equal date_time_init(2005, 11, 28, 0, 0, 0), date_time_init(2005, 12, 04, 0, 0, 0).beginning_of_week #sunday
+    assert_equal date_time_init(2005, 11, 28, 0, 0, 0), date_time_init(2005, 11, 28, 0, 0, 0).beginning_of_week # monday
+    assert_equal date_time_init(2005, 11, 28, 0, 0, 0), date_time_init(2005, 11, 29, 0, 0, 0).beginning_of_week # tuesday
+    assert_equal date_time_init(2005, 11, 28, 0, 0, 0), date_time_init(2005, 11, 30, 0, 0, 0).beginning_of_week # wednesday
+    assert_equal date_time_init(2005, 11, 28, 0, 0, 0), date_time_init(2005, 12, 01, 0, 0, 0).beginning_of_week # thursday
+    assert_equal date_time_init(2005, 11, 28, 0, 0, 0), date_time_init(2005, 12, 02, 0, 0, 0).beginning_of_week # friday
+    assert_equal date_time_init(2005, 11, 28, 0, 0, 0), date_time_init(2005, 12, 03, 0, 0, 0).beginning_of_week # saturday
+    assert_equal date_time_init(2005, 11, 28, 0, 0, 0), date_time_init(2005, 12, 04, 0, 0, 0).beginning_of_week # sunday
   end
 
   def test_end_of_week
     assert_equal date_time_init(2008, 1, 6, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 12, 31, 10, 10, 10).end_of_week
-    assert_equal date_time_init(2007, 9, 2, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 8, 27, 0, 0, 0).end_of_week #monday
-    assert_equal date_time_init(2007, 9, 2, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 8, 28, 0, 0, 0).end_of_week #tuesday
-    assert_equal date_time_init(2007, 9, 2, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 8, 29, 0, 0, 0).end_of_week #wednesday
-    assert_equal date_time_init(2007, 9, 2, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 8, 30, 0, 0, 0).end_of_week #thursday
-    assert_equal date_time_init(2007, 9, 2, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 8, 31, 0, 0, 0).end_of_week #friday
-    assert_equal date_time_init(2007, 9, 2, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 9, 01, 0, 0, 0).end_of_week #saturday
-    assert_equal date_time_init(2007, 9, 2, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 9, 02, 0, 0, 0).end_of_week #sunday
+    assert_equal date_time_init(2007, 9, 2, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 8, 27, 0, 0, 0).end_of_week # monday
+    assert_equal date_time_init(2007, 9, 2, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 8, 28, 0, 0, 0).end_of_week # tuesday
+    assert_equal date_time_init(2007, 9, 2, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 8, 29, 0, 0, 0).end_of_week # wednesday
+    assert_equal date_time_init(2007, 9, 2, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 8, 30, 0, 0, 0).end_of_week # thursday
+    assert_equal date_time_init(2007, 9, 2, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 8, 31, 0, 0, 0).end_of_week # friday
+    assert_equal date_time_init(2007, 9, 2, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 9, 01, 0, 0, 0).end_of_week # saturday
+    assert_equal date_time_init(2007, 9, 2, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 9, 02, 0, 0, 0).end_of_week # sunday
   end
 
   def test_end_of_month
@@ -278,6 +328,26 @@ module DateAndTimeBehavior
     assert_equal date_time_init(2007, 12, 31, 23, 59, 59, Rational(999999999, 1000)), date_time_init(2007, 12, 31, 10, 10, 10).end_of_year
   end
 
+  def test_next_occurring
+    assert_equal date_time_init(2017, 12, 18, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).next_occurring(:monday)
+    assert_equal date_time_init(2017, 12, 19, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).next_occurring(:tuesday)
+    assert_equal date_time_init(2017, 12, 20, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).next_occurring(:wednesday)
+    assert_equal date_time_init(2017, 12, 21, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).next_occurring(:thursday)
+    assert_equal date_time_init(2017, 12, 15, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).next_occurring(:friday)
+    assert_equal date_time_init(2017, 12, 16, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).next_occurring(:saturday)
+    assert_equal date_time_init(2017, 12, 17, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).next_occurring(:sunday)
+  end
+
+  def test_prev_occurring
+    assert_equal date_time_init(2017, 12, 11, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).prev_occurring(:monday)
+    assert_equal date_time_init(2017, 12, 12, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).prev_occurring(:tuesday)
+    assert_equal date_time_init(2017, 12, 13, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).prev_occurring(:wednesday)
+    assert_equal date_time_init(2017, 12,  7, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).prev_occurring(:thursday)
+    assert_equal date_time_init(2017, 12,  8, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).prev_occurring(:friday)
+    assert_equal date_time_init(2017, 12,  9, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).prev_occurring(:saturday)
+    assert_equal date_time_init(2017, 12, 10, 3, 14, 15), date_time_init(2017, 12, 14, 3, 14, 15).prev_occurring(:sunday)
+  end
+
   def test_monday_with_default_beginning_of_week_set
     with_bw_default(:saturday) do
       assert_equal date_time_init(2012, 9, 17, 0, 0, 0), date_time_init(2012, 9, 18, 0, 0, 0).monday
@@ -291,28 +361,40 @@ module DateAndTimeBehavior
   end
 
   def test_on_weekend_on_saturday
-    assert date_time_init(2015, 1, 3, 0, 0, 0).on_weekend?
-    assert date_time_init(2015, 1, 3, 15, 15, 10).on_weekend?
+    assert_predicate date_time_init(2015, 1, 3, 0, 0, 0), :on_weekend?
+    assert_predicate date_time_init(2015, 1, 3, 15, 15, 10), :on_weekend?
   end
 
   def test_on_weekend_on_sunday
-    assert date_time_init(2015, 1, 4, 0, 0, 0).on_weekend?
-    assert date_time_init(2015, 1, 4, 15, 15, 10).on_weekend?
+    assert_predicate date_time_init(2015, 1, 4, 0, 0, 0), :on_weekend?
+    assert_predicate date_time_init(2015, 1, 4, 15, 15, 10), :on_weekend?
   end
 
   def test_on_weekend_on_monday
-    assert_not date_time_init(2015, 1, 5, 0, 0, 0).on_weekend?
-    assert_not date_time_init(2015, 1, 5, 15, 15, 10).on_weekend?
+    assert_not_predicate date_time_init(2015, 1, 5, 0, 0, 0), :on_weekend?
+    assert_not_predicate date_time_init(2015, 1, 5, 15, 15, 10), :on_weekend?
   end
 
   def test_on_weekday_on_sunday
-    assert_not date_time_init(2015, 1, 4, 0, 0, 0).on_weekday?
-    assert_not date_time_init(2015, 1, 4, 15, 15, 10).on_weekday?
+    assert_not_predicate date_time_init(2015, 1, 4, 0, 0, 0), :on_weekday?
+    assert_not_predicate date_time_init(2015, 1, 4, 15, 15, 10), :on_weekday?
   end
 
   def test_on_weekday_on_monday
-    assert date_time_init(2015, 1, 5, 0, 0, 0).on_weekday?
-    assert date_time_init(2015, 1, 5, 15, 15, 10).on_weekday?
+    assert_predicate date_time_init(2015, 1, 5, 0, 0, 0), :on_weekday?
+    assert_predicate date_time_init(2015, 1, 5, 15, 15, 10), :on_weekday?
+  end
+
+  def test_before
+    assert_equal false, date_time_init(2017, 3, 6, 12, 0, 0).before?(date_time_init(2017, 3, 5, 12, 0, 0))
+    assert_equal false, date_time_init(2017, 3, 6, 12, 0, 0).before?(date_time_init(2017, 3, 6, 12, 0, 0))
+    assert_equal true, date_time_init(2017, 3, 6, 12, 0, 0).before?(date_time_init(2017, 3, 7, 12, 0, 0))
+  end
+
+  def test_after
+    assert_equal true, date_time_init(2017, 3, 6, 12, 0, 0).after?(date_time_init(2017, 3, 5, 12, 0, 0))
+    assert_equal false, date_time_init(2017, 3, 6, 12, 0, 0).after?(date_time_init(2017, 3, 6, 12, 0, 0))
+    assert_equal false, date_time_init(2017, 3, 6, 12, 0, 0).after?(date_time_init(2017, 3, 7, 12, 0, 0))
   end
 
   def with_bw_default(bw = :monday)
diff --git a/activesupport/test/core_ext/date_ext_test.rb b/activesupport/test/core_ext/date_ext_test.rb
index b8672eac4b..b8652884ce 100644
--- a/activesupport/test/core_ext/date_ext_test.rb
+++ b/activesupport/test/core_ext/date_ext_test.rb
@@ -95,11 +95,11 @@ class DateExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_beginning_of_week_in_calendar_reform
-    assert_equal Date.new(1582, 10, 1), Date.new(1582, 10, 15).beginning_of_week #friday
+    assert_equal Date.new(1582, 10, 1), Date.new(1582, 10, 15).beginning_of_week # friday
   end
 
   def test_end_of_week_in_calendar_reform
-    assert_equal Date.new(1582, 10, 17), Date.new(1582, 10, 4).end_of_week #thursday
+    assert_equal Date.new(1582, 10, 17), Date.new(1582, 10, 4).end_of_week # thursday
   end
 
   def test_end_of_year
@@ -120,10 +120,6 @@ class DateExtCalculationsTest < ActiveSupport::TestCase
     assert_equal Date.new(1582, 10, 4), Date.new(1583, 10, 14).prev_year
   end
 
-  def test_last_year
-    assert_equal Date.new(2004, 6, 5),  Date.new(2005, 6, 5).last_year
-  end
-
   def test_last_year_in_leap_years
     assert_equal Date.new(1999, 2, 28), Date.new(2000, 2, 29).last_year
   end
@@ -148,7 +144,7 @@ class DateExtCalculationsTest < ActiveSupport::TestCase
     assert_equal Date.new(2012, 9, 28), Date.new(2005, 2, 28).advance(years: 7, months: 7)
     assert_equal Date.new(2013, 10, 3), Date.new(2005, 2, 28).advance(years: 7, months: 19, days: 5)
     assert_equal Date.new(2013, 10, 17), Date.new(2005, 2, 28).advance(years: 7, months: 19, weeks: 2, days: 5)
-    assert_equal Date.new(2005, 2, 28), Date.new(2004, 2, 29).advance(years: 1) #leap day plus one year
+    assert_equal Date.new(2005, 2, 28), Date.new(2004, 2, 29).advance(years: 1) # leap day plus one year
   end
 
   def test_advance_does_first_years_and_then_days
@@ -185,10 +181,6 @@ class DateExtCalculationsTest < ActiveSupport::TestCase
     assert_equal Date.new(1582, 10, 18), Date.new(1582, 10, 4).next_week
   end
 
-  def test_last_month_on_31st
-    assert_equal Date.new(2004, 2, 29), Date.new(2004, 3, 31).last_month
-  end
-
   def test_last_quarter_on_31st
     assert_equal Date.new(2004, 2, 29), Date.new(2004, 5, 31).last_quarter
   end
@@ -394,11 +386,11 @@ end
 
 class DateExtBehaviorTest < ActiveSupport::TestCase
   def test_date_acts_like_date
-    assert Date.new.acts_like_date?
+    assert_predicate Date.new, :acts_like_date?
   end
 
   def test_blank?
-    assert_not Date.new.blank?
+    assert_not_predicate Date.new, :blank?
   end
 
   def test_freeze_doesnt_clobber_memoized_instance_methods
diff --git a/activesupport/test/core_ext/date_time_ext_test.rb b/activesupport/test/core_ext/date_time_ext_test.rb
index a3c2018a31..894fb80cba 100644
--- a/activesupport/test/core_ext/date_time_ext_test.rb
+++ b/activesupport/test/core_ext/date_time_ext_test.rb
@@ -30,28 +30,6 @@ class DateTimeExtCalculationsTest < ActiveSupport::TestCase
     end
   end
 
-  def test_next_occur
-    datetime = DateTime.new(2016, 9, 24, 0, 0) # saturday
-    assert_equal datetime.next_occurring(:monday), datetime.since(2.days)
-    assert_equal datetime.next_occurring(:tuesday), datetime.since(3.days)
-    assert_equal datetime.next_occurring(:wednesday), datetime.since(4.days)
-    assert_equal datetime.next_occurring(:thursday), datetime.since(5.days)
-    assert_equal datetime.next_occurring(:friday), datetime.since(6.days)
-    assert_equal datetime.next_occurring(:saturday), datetime.since(1.week)
-    assert_equal datetime.next_occurring(:sunday), datetime.since(1.day)
-  end
-
-  def test_prev_occur
-    datetime = DateTime.new(2016, 9, 24, 0, 0) # saturday
-    assert_equal datetime.prev_occurring(:monday), datetime.ago(5.days)
-    assert_equal datetime.prev_occurring(:tuesday), datetime.ago(4.days)
-    assert_equal datetime.prev_occurring(:wednesday), datetime.ago(3.days)
-    assert_equal datetime.prev_occurring(:thursday), datetime.ago(2.days)
-    assert_equal datetime.prev_occurring(:friday), datetime.ago(1.day)
-    assert_equal datetime.prev_occurring(:saturday), datetime.ago(1.week)
-    assert_equal datetime.prev_occurring(:sunday), datetime.ago(6.days)
-  end
-
   def test_readable_inspect
     datetime = DateTime.new(2005, 2, 21, 14, 30, 0)
     assert_equal "Mon, 21 Feb 2005 14:30:00 +0000", datetime.readable_inspect
@@ -162,10 +140,6 @@ class DateTimeExtCalculationsTest < ActiveSupport::TestCase
     assert_equal DateTime.civil(2005, 4, 30, 23, 59, Rational(59999999999, 1000000000)), DateTime.civil(2005, 4, 20, 10, 10, 10).end_of_month
   end
 
-  def test_last_year
-    assert_equal DateTime.civil(2004, 6, 5, 10),  DateTime.civil(2005, 6, 5, 10, 0, 0).last_year
-  end
-
   def test_ago
     assert_equal DateTime.civil(2005, 2, 22, 10, 10, 9),  DateTime.civil(2005, 2, 22, 10, 10, 10).ago(1)
     assert_equal DateTime.civil(2005, 2, 22, 9, 10, 10),  DateTime.civil(2005, 2, 22, 10, 10, 10).ago(3600)
@@ -213,7 +187,7 @@ class DateTimeExtCalculationsTest < ActiveSupport::TestCase
     assert_equal DateTime.civil(2013, 10, 3, 15, 15, 10),  DateTime.civil(2005, 2, 28, 15, 15, 10).advance(years: 7, months: 19, days: 5)
     assert_equal DateTime.civil(2013, 10, 17, 15, 15, 10), DateTime.civil(2005, 2, 28, 15, 15, 10).advance(years: 7, months: 19, weeks: 2, days: 5)
     assert_equal DateTime.civil(2001, 12, 27, 15, 15, 10), DateTime.civil(2005, 2, 28, 15, 15, 10).advance(years: -3, months: -2, days: -1)
-    assert_equal DateTime.civil(2005, 2, 28, 15, 15, 10),  DateTime.civil(2004, 2, 29, 15, 15, 10).advance(years: 1) #leap day plus one year
+    assert_equal DateTime.civil(2005, 2, 28, 15, 15, 10),  DateTime.civil(2004, 2, 29, 15, 15, 10).advance(years: 1) # leap day plus one year
     assert_equal DateTime.civil(2005, 2, 28, 20, 15, 10),  DateTime.civil(2005, 2, 28, 15, 15, 10).advance(hours: 5)
     assert_equal DateTime.civil(2005, 2, 28, 15, 22, 10),  DateTime.civil(2005, 2, 28, 15, 15, 10).advance(minutes: 7)
     assert_equal DateTime.civil(2005, 2, 28, 15, 15, 19),  DateTime.civil(2005, 2, 28, 15, 15, 10).advance(seconds: 9)
@@ -248,10 +222,6 @@ class DateTimeExtCalculationsTest < ActiveSupport::TestCase
     assert_equal DateTime.civil(2016, 2, 29), DateTime.civil(2016, 3, 7).last_week
   end
 
-  def test_last_month_on_31st
-    assert_equal DateTime.civil(2004, 2, 29), DateTime.civil(2004, 3, 31).last_month
-  end
-
   def test_last_quarter_on_31st
     assert_equal DateTime.civil(2004, 2, 29), DateTime.civil(2004, 5, 31).last_quarter
   end
@@ -345,15 +315,15 @@ class DateTimeExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_acts_like_date
-    assert DateTime.new.acts_like_date?
+    assert_predicate DateTime.new, :acts_like_date?
   end
 
   def test_acts_like_time
-    assert DateTime.new.acts_like_time?
+    assert_predicate DateTime.new, :acts_like_time?
   end
 
   def test_blank?
-    assert_not DateTime.new.blank?
+    assert_not_predicate DateTime.new, :blank?
   end
 
   def test_utc?
@@ -393,45 +363,45 @@ class DateTimeExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_compare_with_time
-    assert_equal  1, DateTime.civil(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59)
-    assert_equal  0, DateTime.civil(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0)
+    assert_equal 1, DateTime.civil(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59)
+    assert_equal 0, DateTime.civil(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0)
     assert_equal(-1, DateTime.civil(2000) <=> Time.utc(2000, 1, 1, 0, 0, 1))
   end
 
   def test_compare_with_datetime
-    assert_equal  1, DateTime.civil(2000) <=> DateTime.civil(1999, 12, 31, 23, 59, 59)
-    assert_equal  0, DateTime.civil(2000) <=> DateTime.civil(2000, 1, 1, 0, 0, 0)
+    assert_equal 1, DateTime.civil(2000) <=> DateTime.civil(1999, 12, 31, 23, 59, 59)
+    assert_equal 0, DateTime.civil(2000) <=> DateTime.civil(2000, 1, 1, 0, 0, 0)
     assert_equal(-1, DateTime.civil(2000) <=> DateTime.civil(2000, 1, 1, 0, 0, 1))
   end
 
   def test_compare_with_time_with_zone
-    assert_equal  1, DateTime.civil(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(1999, 12, 31, 23, 59, 59), ActiveSupport::TimeZone["UTC"])
-    assert_equal  0, DateTime.civil(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 0), ActiveSupport::TimeZone["UTC"])
+    assert_equal 1, DateTime.civil(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(1999, 12, 31, 23, 59, 59), ActiveSupport::TimeZone["UTC"])
+    assert_equal 0, DateTime.civil(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 0), ActiveSupport::TimeZone["UTC"])
     assert_equal(-1, DateTime.civil(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 1), ActiveSupport::TimeZone["UTC"]))
   end
 
   def test_compare_with_string
-    assert_equal   1, DateTime.civil(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59).to_s
-    assert_equal   0, DateTime.civil(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0).to_s
+    assert_equal 1, DateTime.civil(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59).to_s
+    assert_equal 0, DateTime.civil(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0).to_s
     assert_equal(-1, DateTime.civil(2000) <=> Time.utc(2000, 1, 1, 0, 0, 1).to_s)
     assert_nil DateTime.civil(2000) <=> "Invalid as Time"
   end
 
   def test_compare_with_integer
-    assert_equal  1, DateTime.civil(1970, 1, 1, 12, 0, 0) <=> 2440587
-    assert_equal  0, DateTime.civil(1970, 1, 1, 12, 0, 0) <=> 2440588
+    assert_equal 1, DateTime.civil(1970, 1, 1, 12, 0, 0) <=> 2440587
+    assert_equal 0, DateTime.civil(1970, 1, 1, 12, 0, 0) <=> 2440588
     assert_equal(-1, DateTime.civil(1970, 1, 1, 12, 0, 0) <=> 2440589)
   end
 
   def test_compare_with_float
-    assert_equal  1, DateTime.civil(1970) <=> 2440586.5
-    assert_equal  0, DateTime.civil(1970) <=> 2440587.5
+    assert_equal 1, DateTime.civil(1970) <=> 2440586.5
+    assert_equal 0, DateTime.civil(1970) <=> 2440587.5
     assert_equal(-1, DateTime.civil(1970) <=> 2440588.5)
   end
 
   def test_compare_with_rational
-    assert_equal  1, DateTime.civil(1970) <=> Rational(4881173, 2)
-    assert_equal  0, DateTime.civil(1970) <=> Rational(4881175, 2)
+    assert_equal 1, DateTime.civil(1970) <=> Rational(4881173, 2)
+    assert_equal 0, DateTime.civil(1970) <=> Rational(4881175, 2)
     assert_equal(-1, DateTime.civil(1970) <=> Rational(4881177, 2))
   end
 
diff --git a/activesupport/test/core_ext/duration_test.rb b/activesupport/test/core_ext/duration_test.rb
index b3e0cd8bd0..240ae3bde0 100644
--- a/activesupport/test/core_ext/duration_test.rb
+++ b/activesupport/test/core_ext/duration_test.rb
@@ -5,6 +5,7 @@ require "active_support/inflector"
 require "active_support/time"
 require "active_support/json"
 require "time_zone_test_helpers"
+require "yaml"
 
 class DurationTest < ActiveSupport::TestCase
   include TimeZoneTestHelpers
@@ -15,30 +16,30 @@ class DurationTest < ActiveSupport::TestCase
     assert_kind_of ActiveSupport::Duration, d
     assert_kind_of Numeric, d
     assert_kind_of Integer, d
-    assert !d.is_a?(Hash)
+    assert_not d.is_a?(Hash)
 
     k = Class.new
     class << k; undef_method :== end
-    assert !d.is_a?(k)
+    assert_not d.is_a?(k)
   end
 
   def test_instance_of
-    assert 1.minute.instance_of?(1.class)
+    assert 1.minute.instance_of?(Integer)
     assert 2.days.instance_of?(ActiveSupport::Duration)
-    assert !3.second.instance_of?(Numeric)
+    assert_not 3.second.instance_of?(Numeric)
   end
 
   def test_threequals
     assert ActiveSupport::Duration === 1.day
-    assert !(ActiveSupport::Duration === 1.day.to_i)
-    assert !(ActiveSupport::Duration === "foo")
+    assert_not (ActiveSupport::Duration === 1.day.to_i)
+    assert_not (ActiveSupport::Duration === "foo")
   end
 
   def test_equals
     assert 1.day == 1.day
     assert 1.day == 1.day.to_i
     assert 1.day.to_i == 1.day
-    assert !(1.day == "foo")
+    assert_not (1.day == "foo")
   end
 
   def test_to_s
@@ -52,11 +53,11 @@ class DurationTest < ActiveSupport::TestCase
     assert 1.minute.eql?(1.minute)
     assert 1.minute.eql?(60.seconds)
     assert 2.days.eql?(48.hours)
-    assert !1.second.eql?(1)
-    assert !1.eql?(1.second)
+    assert_not 1.second.eql?(1)
+    assert_not 1.eql?(1.second)
     assert 1.minute.eql?(180.seconds - 2.minutes)
-    assert !1.minute.eql?(60)
-    assert !1.minute.eql?("foo")
+    assert_not 1.minute.eql?(60)
+    assert_not 1.minute.eql?("foo")
   end
 
   def test_inspect
@@ -71,6 +72,8 @@ class DurationTest < ActiveSupport::TestCase
     assert_equal "7 days",                          7.days.inspect
     assert_equal "1 week",                          1.week.inspect
     assert_equal "2 weeks",                         1.fortnight.inspect
+    assert_equal "0 seconds",                       (10 % 5.seconds).inspect
+    assert_equal "10 minutes",                      (10.minutes + 0.seconds).inspect
   end
 
   def test_inspect_locale
@@ -160,7 +163,7 @@ class DurationTest < ActiveSupport::TestCase
   end
 
   def test_time_plus_duration_returns_same_time_datatype
-    twz = ActiveSupport::TimeWithZone.new(nil, ActiveSupport::TimeZone["Moscow"] , Time.utc(2016, 4, 28, 00, 45))
+    twz = ActiveSupport::TimeWithZone.new(nil, ActiveSupport::TimeZone["Moscow"], Time.utc(2016, 4, 28, 00, 45))
     now = Time.now.utc
     %w( second minute hour day week month year ).each do |unit|
       assert_equal((now + 1.send(unit)).class, Time, "Time + 1.#{unit} must be Time")
@@ -640,6 +643,12 @@ class DurationTest < ActiveSupport::TestCase
     assert_equal time + d1, time + d2
   end
 
+  def test_durations_survive_yaml_serialization
+    d1 = YAML.load(YAML.dump(10.minutes))
+    assert_equal 600, d1.to_i
+    assert_equal 660, (d1 + 60).to_i
+  end
+
   private
     def eastern_time_zone
       if Gem.win_platform?
diff --git a/activesupport/test/core_ext/enumerable_test.rb b/activesupport/test/core_ext/enumerable_test.rb
index 8d71320931..b63464a36a 100644
--- a/activesupport/test/core_ext/enumerable_test.rb
+++ b/activesupport/test/core_ext/enumerable_test.rb
@@ -179,6 +179,21 @@ class EnumerableTests < ActiveSupport::TestCase
                  payments.index_by.each(&:price))
   end
 
+  def test_index_with
+    payments = GenericEnumerable.new([ Payment.new(5), Payment.new(15), Payment.new(10) ])
+
+    assert_equal({ Payment.new(5) => 5, Payment.new(15) => 15, Payment.new(10) => 10 }, payments.index_with(&:price))
+
+    assert_equal({ title: nil, body: nil }, %i( title body ).index_with(nil))
+    assert_equal({ title: [], body: [] }, %i( title body ).index_with([]))
+    assert_equal({ title: {}, body: {} }, %i( title body ).index_with({}))
+
+    assert_equal Enumerator, payments.index_with.class
+    assert_nil payments.index_with.size
+    assert_equal 42, (1..42).index_with.size
+    assert_equal({ Payment.new(5) => 5, Payment.new(15) => 15, Payment.new(10) => 10 }, payments.index_with.each(&:price))
+  end
+
   def test_many
     assert_equal false, GenericEnumerable.new([]).many?
     assert_equal false, GenericEnumerable.new([ 1 ]).many?
diff --git a/activesupport/test/core_ext/file_test.rb b/activesupport/test/core_ext/file_test.rb
index 23e3c277cc..9c97700e5d 100644
--- a/activesupport/test/core_ext/file_test.rb
+++ b/activesupport/test/core_ext/file_test.rb
@@ -8,7 +8,7 @@ class AtomicWriteTest < ActiveSupport::TestCase
     contents = "Atomic Text"
     File.atomic_write(file_name, Dir.pwd) do |file|
       file.write(contents)
-      assert !File.exist?(file_name)
+      assert_not File.exist?(file_name)
     end
     assert File.exist?(file_name)
     assert_equal contents, File.read(file_name)
@@ -22,7 +22,7 @@ class AtomicWriteTest < ActiveSupport::TestCase
       raise "something bad"
     end
   rescue
-    assert !File.exist?(file_name)
+    assert_not File.exist?(file_name)
   end
 
   def test_atomic_write_preserves_file_permissions
@@ -50,7 +50,7 @@ class AtomicWriteTest < ActiveSupport::TestCase
     contents = "Atomic Text"
     File.atomic_write(file_name, Dir.pwd) do |file|
       file.write(contents)
-      assert !File.exist?(file_name)
+      assert_not File.exist?(file_name)
     end
     assert File.exist?(file_name)
     assert_equal File.probe_stat_in(Dir.pwd).mode, file_mode
diff --git a/activesupport/test/core_ext/hash/transform_values_test.rb b/activesupport/test/core_ext/hash/transform_values_test.rb
index d34b7fa7b9..e481b5e4a9 100644
--- a/activesupport/test/core_ext/hash/transform_values_test.rb
+++ b/activesupport/test/core_ext/hash/transform_values_test.rb
@@ -2,25 +2,16 @@
 
 require "abstract_unit"
 require "active_support/core_ext/hash/indifferent_access"
-require "active_support/core_ext/hash/transform_values"
 
-class TransformValuesTest < ActiveSupport::TestCase
-  test "transform_values returns a new hash with the values computed from the block" do
-    original = { a: "a", b: "b" }
-    mapped = original.transform_values { |v| v + "!" }
-
-    assert_equal({ a: "a", b: "b" }, original)
-    assert_equal({ a: "a!", b: "b!" }, mapped)
-  end
-
-  test "transform_values! modifies the values of the original" do
-    original = { a: "a", b: "b" }
-    mapped = original.transform_values! { |v| v + "!" }
-
-    assert_equal({ a: "a!", b: "b!" }, original)
-    assert_same original, mapped
+class TransformValuesDeprecatedRequireTest < ActiveSupport::TestCase
+  test "requiring transform_values is deprecated" do
+    assert_deprecated do
+      require "active_support/core_ext/hash/transform_values"
+    end
   end
+end
 
+class IndifferentTransformValuesTest < ActiveSupport::TestCase
   test "indifferent access is still indifferent after mapping values" do
     original = { a: "a", b: "b" }.with_indifferent_access
     mapped = original.transform_values { |v| v + "!" }
@@ -28,50 +19,4 @@ class TransformValuesTest < ActiveSupport::TestCase
     assert_equal "a!", mapped[:a]
     assert_equal "a!", mapped["a"]
   end
-
-  # This is to be consistent with the behavior of Ruby's built in methods
-  # (e.g. #select, #reject) as of 2.2
-  test "default values do not persist during mapping" do
-    original = Hash.new("foo")
-    original[:a] = "a"
-    mapped = original.transform_values { |v| v + "!" }
-
-    assert_equal "a!", mapped[:a]
-    assert_nil mapped[:b]
-  end
-
-  test "default procs do not persist after mapping" do
-    original = Hash.new { "foo" }
-    original[:a] = "a"
-    mapped = original.transform_values { |v| v + "!" }
-
-    assert_equal "a!", mapped[:a]
-    assert_nil mapped[:b]
-  end
-
-  test "transform_values returns a sized Enumerator if no block is given" do
-    original = { a: "a", b: "b" }
-    enumerator = original.transform_values
-    assert_equal original.size, enumerator.size
-    assert_equal Enumerator, enumerator.class
-  end
-
-  test "transform_values! returns a sized Enumerator if no block is given" do
-    original = { a: "a", b: "b" }
-    enumerator = original.transform_values!
-    assert_equal original.size, enumerator.size
-    assert_equal Enumerator, enumerator.class
-  end
-
-  test "transform_values is chainable with Enumerable methods" do
-    original = { a: "a", b: "b" }
-    mapped = original.transform_values.with_index { |v, i| [v, i].join }
-    assert_equal({ a: "a0", b: "b1" }, mapped)
-  end
-
-  test "transform_values! is chainable with Enumerable methods" do
-    original = { a: "a", b: "b" }
-    original.transform_values!.with_index { |v, i| [v, i].join }
-    assert_equal({ a: "a0", b: "b1" }, original)
-  end
 end
diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
index 746d7ad416..f4f0dd6b31 100644
--- a/activesupport/test/core_ext/hash_ext_test.rb
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -45,8 +45,6 @@ class HashExtTest < ActiveSupport::TestCase
     assert_respond_to h, :deep_stringify_keys!
     assert_respond_to h, :to_options
     assert_respond_to h, :to_options!
-    assert_respond_to h, :compact
-    assert_respond_to h, :compact!
     assert_respond_to h, :except
     assert_respond_to h, :except!
   end
@@ -446,7 +444,7 @@ class HashExtTest < ActiveSupport::TestCase
     original.freeze
     assert_nothing_raised { original.except(:a) }
 
-    assert_raise(RuntimeError) { original.except!(:a) }
+    assert_raise(frozen_error_class) { original.except!(:a) }
   end
 
   def test_except_does_not_delete_values_in_original
@@ -456,38 +454,10 @@ class HashExtTest < ActiveSupport::TestCase
     end
   end
 
-  def test_compact
-    hash_contain_nil_value = @symbols.merge(z: nil)
-    hash_with_only_nil_values = { a: nil, b: nil }
-
-    h = hash_contain_nil_value.dup
-    assert_equal(@symbols, h.compact)
-    assert_equal(hash_contain_nil_value, h)
-
-    h = hash_with_only_nil_values.dup
-    assert_equal({}, h.compact)
-    assert_equal(hash_with_only_nil_values, h)
-
-    h = @symbols.dup
-    assert_equal(@symbols, h.compact)
-    assert_equal(@symbols, h)
-  end
-
-  def test_compact!
-    hash_contain_nil_value = @symbols.merge(z: nil)
-    hash_with_only_nil_values = { a: nil, b: nil }
-
-    h = hash_contain_nil_value.dup
-    assert_equal(@symbols, h.compact!)
-    assert_equal(@symbols, h)
-
-    h = hash_with_only_nil_values.dup
-    assert_equal({}, h.compact!)
-    assert_equal({}, h)
-
-    h = @symbols.dup
-    assert_nil(h.compact!)
-    assert_equal(@symbols, h)
+  def test_requiring_compact_is_deprecated
+    assert_deprecated do
+      require "active_support/core_ext/hash/compact"
+    end
   end
 end
 
@@ -1061,7 +1031,7 @@ class HashToXmlTest < ActiveSupport::TestCase
       </alert>
     XML
     alert_at = Hash.from_xml(alert_xml)["alert"]["alert_at"]
-    assert alert_at.utc?
+    assert_predicate alert_at, :utc?
     assert_equal Time.utc(2008, 2, 10, 15, 30, 45), alert_at
   end
 
@@ -1072,7 +1042,7 @@ class HashToXmlTest < ActiveSupport::TestCase
       </alert>
     XML
     alert_at = Hash.from_xml(alert_xml)["alert"]["alert_at"]
-    assert alert_at.utc?
+    assert_predicate alert_at, :utc?
     assert_equal Time.utc(2008, 2, 10, 15, 30, 45), alert_at
   end
 
@@ -1083,7 +1053,7 @@ class HashToXmlTest < ActiveSupport::TestCase
       </alert>
     XML
     alert_at = Hash.from_xml(alert_xml)["alert"]["alert_at"]
-    assert alert_at.utc?
+    assert_predicate alert_at, :utc?
     assert_equal 2050,  alert_at.year
     assert_equal 2,     alert_at.month
     assert_equal 10,    alert_at.day
diff --git a/activesupport/test/core_ext/integer_ext_test.rb b/activesupport/test/core_ext/integer_ext_test.rb
index 14169b084d..5691dc5341 100644
--- a/activesupport/test/core_ext/integer_ext_test.rb
+++ b/activesupport/test/core_ext/integer_ext_test.rb
@@ -8,14 +8,14 @@ class IntegerExtTest < ActiveSupport::TestCase
 
   def test_multiple_of
     [ -7, 0, 7, 14 ].each { |i| assert i.multiple_of?(7) }
-    [ -7, 7, 14 ].each { |i| assert ! i.multiple_of?(6) }
+    [ -7, 7, 14 ].each { |i| assert_not i.multiple_of?(6) }
 
     # test the 0 edge case
     assert 0.multiple_of?(0)
-    assert !5.multiple_of?(0)
+    assert_not 5.multiple_of?(0)
 
     # test with a prime
-    [2, 3, 5, 7].each { |i| assert !PRIME.multiple_of?(i) }
+    [2, 3, 5, 7].each { |i| assert_not PRIME.multiple_of?(i) }
   end
 
   def test_ordinalize
diff --git a/activesupport/test/core_ext/load_error_test.rb b/activesupport/test/core_ext/load_error_test.rb
index 4fdd228ff8..126aa51cb4 100644
--- a/activesupport/test/core_ext/load_error_test.rb
+++ b/activesupport/test/core_ext/load_error_test.rb
@@ -5,15 +5,22 @@ require "active_support/core_ext/load_error"
 
 class TestLoadError < ActiveSupport::TestCase
   def test_with_require
-    assert_raise(LoadError) { require 'no_this_file_don\'t_exist' }
+    assert_raise(LoadError) { require "no_this_file_don't_exist" }
   end
+
   def test_with_load
     assert_raise(LoadError) { load "nor_does_this_one" }
   end
+
   def test_path
     begin load "nor/this/one.rb"
     rescue LoadError => e
       assert_equal "nor/this/one.rb", e.path
     end
   end
+
+  def test_is_missing_with_nil_path
+    error = LoadError.new(nil)
+    assert_nothing_raised { error.is_missing?("anything") }
+  end
 end
diff --git a/activesupport/test/core_ext/module/anonymous_test.rb b/activesupport/test/core_ext/module/anonymous_test.rb
index 606f22c9b5..e03c217015 100644
--- a/activesupport/test/core_ext/module/anonymous_test.rb
+++ b/activesupport/test/core_ext/module/anonymous_test.rb
@@ -5,12 +5,12 @@ require "active_support/core_ext/module/anonymous"
 
 class AnonymousTest < ActiveSupport::TestCase
   test "an anonymous class or module are anonymous" do
-    assert Module.new.anonymous?
-    assert Class.new.anonymous?
+    assert_predicate Module.new, :anonymous?
+    assert_predicate Class.new, :anonymous?
   end
 
   test "a named class or module are not anonymous" do
-    assert !Kernel.anonymous?
-    assert !Object.anonymous?
+    assert_not_predicate Kernel, :anonymous?
+    assert_not_predicate Object, :anonymous?
   end
 end
diff --git a/activesupport/test/core_ext/module/attr_internal_test.rb b/activesupport/test/core_ext/module/attr_internal_test.rb
index c2a28eced4..9a65f75497 100644
--- a/activesupport/test/core_ext/module/attr_internal_test.rb
+++ b/activesupport/test/core_ext/module/attr_internal_test.rb
@@ -12,7 +12,7 @@ class AttrInternalTest < ActiveSupport::TestCase
   def test_reader
     assert_nothing_raised { @target.attr_internal_reader :foo }
 
-    assert !@instance.instance_variable_defined?("@_foo")
+    assert_not @instance.instance_variable_defined?("@_foo")
     assert_raise(NoMethodError) { @instance.foo = 1 }
 
     @instance.instance_variable_set("@_foo", 1)
@@ -22,7 +22,7 @@ class AttrInternalTest < ActiveSupport::TestCase
   def test_writer
     assert_nothing_raised { @target.attr_internal_writer :foo }
 
-    assert !@instance.instance_variable_defined?("@_foo")
+    assert_not @instance.instance_variable_defined?("@_foo")
     assert_nothing_raised { assert_equal 1, @instance.foo = 1 }
 
     assert_equal 1, @instance.instance_variable_get("@_foo")
@@ -32,7 +32,7 @@ class AttrInternalTest < ActiveSupport::TestCase
   def test_accessor
     assert_nothing_raised { @target.attr_internal :foo }
 
-    assert !@instance.instance_variable_defined?("@_foo")
+    assert_not @instance.instance_variable_defined?("@_foo")
     assert_nothing_raised { assert_equal 1, @instance.foo = 1 }
 
     assert_equal 1, @instance.instance_variable_get("@_foo")
@@ -44,10 +44,10 @@ class AttrInternalTest < ActiveSupport::TestCase
     assert_nothing_raised { Module.attr_internal_naming_format = "@abc%sdef" }
     @target.attr_internal :foo
 
-    assert !@instance.instance_variable_defined?("@_foo")
-    assert !@instance.instance_variable_defined?("@abcfoodef")
+    assert_not @instance.instance_variable_defined?("@_foo")
+    assert_not @instance.instance_variable_defined?("@abcfoodef")
     assert_nothing_raised { @instance.foo = 1 }
-    assert !@instance.instance_variable_defined?("@_foo")
+    assert_not @instance.instance_variable_defined?("@_foo")
     assert @instance.instance_variable_defined?("@abcfoodef")
   ensure
     Module.attr_internal_naming_format = "@_%s"
diff --git a/activesupport/test/core_ext/module/attribute_accessor_per_thread_test.rb b/activesupport/test/core_ext/module/attribute_accessor_per_thread_test.rb
index e0fbd1002c..e0e331fc91 100644
--- a/activesupport/test/core_ext/module/attribute_accessor_per_thread_test.rb
+++ b/activesupport/test/core_ext/module/attribute_accessor_per_thread_test.rb
@@ -43,22 +43,22 @@ class ModuleAttributeAccessorPerThreadTest < ActiveSupport::TestCase
       assert_respond_to @class, :foo
       assert_respond_to @class, :foo=
       assert_respond_to @object, :bar
-      assert !@object.respond_to?(:bar=)
+      assert_not_respond_to @object, :bar=
     end.join
   end
 
   def test_should_not_create_instance_reader
     Thread.new do
       assert_respond_to @class, :shaq
-      assert !@object.respond_to?(:shaq)
+      assert_not_respond_to @object, :shaq
     end.join
   end
 
   def test_should_not_create_instance_accessors
     Thread.new do
       assert_respond_to @class, :camp
-      assert !@object.respond_to?(:camp)
-      assert !@object.respond_to?(:camp=)
+      assert_not_respond_to @object, :camp
+      assert_not_respond_to @object, :camp=
     end.join
   end
 
diff --git a/activesupport/test/core_ext/module/attribute_accessor_test.rb b/activesupport/test/core_ext/module/attribute_accessor_test.rb
index f1d6859a88..33c583947a 100644
--- a/activesupport/test/core_ext/module/attribute_accessor_test.rb
+++ b/activesupport/test/core_ext/module/attribute_accessor_test.rb
@@ -65,18 +65,18 @@ class ModuleAttributeAccessorTest < ActiveSupport::TestCase
     assert_respond_to @module, :foo
     assert_respond_to @module, :foo=
     assert_respond_to @object, :bar
-    assert !@object.respond_to?(:bar=)
+    assert_not_respond_to @object, :bar=
   end
 
   def test_should_not_create_instance_reader
     assert_respond_to @module, :shaq
-    assert !@object.respond_to?(:shaq)
+    assert_not_respond_to @object, :shaq
   end
 
   def test_should_not_create_instance_accessors
     assert_respond_to @module, :camp
-    assert !@object.respond_to?(:camp)
-    assert !@object.respond_to?(:camp=)
+    assert_not_respond_to @object, :camp
+    assert_not_respond_to @object, :camp=
   end
 
   def test_should_raise_name_error_if_attribute_name_is_invalid
diff --git a/activesupport/test/core_ext/module/attribute_aliasing_test.rb b/activesupport/test/core_ext/module/attribute_aliasing_test.rb
index 187a0f4da2..81aac224f9 100644
--- a/activesupport/test/core_ext/module/attribute_aliasing_test.rb
+++ b/activesupport/test/core_ext/module/attribute_aliasing_test.rb
@@ -30,15 +30,15 @@ class AttributeAliasingTest < ActiveSupport::TestCase
   def test_attribute_alias
     e = AttributeAliasing::Email.new
 
-    assert !e.subject?
+    assert_not_predicate e, :subject?
 
     e.title = "Upgrade computer"
     assert_equal "Upgrade computer", e.subject
-    assert e.subject?
+    assert_predicate e, :subject?
 
     e.subject = "We got a long way to go"
     assert_equal "We got a long way to go", e.title
-    assert e.title?
+    assert_predicate e, :title?
   end
 
   def test_aliasing_to_uppercase_attributes
@@ -47,15 +47,15 @@ class AttributeAliasingTest < ActiveSupport::TestCase
     # to more sensible ones, everything goes *foof*.
     e = AttributeAliasing::Email.new
 
-    assert !e.body?
-    assert !e.Data?
+    assert_not_predicate e, :body?
+    assert_not_predicate e, :Data?
 
     e.body = "No, really, this is not a joke."
     assert_equal "No, really, this is not a joke.", e.Data
-    assert e.Data?
+    assert_predicate e, :Data?
 
     e.Data = "Uppercased methods are the suck"
     assert_equal "Uppercased methods are the suck", e.body
-    assert e.body?
+    assert_predicate e, :body?
   end
 end
diff --git a/activesupport/test/core_ext/module/concerning_test.rb b/activesupport/test/core_ext/module/concerning_test.rb
index 192c3d5a9c..374114c11b 100644
--- a/activesupport/test/core_ext/module/concerning_test.rb
+++ b/activesupport/test/core_ext/module/concerning_test.rb
@@ -21,7 +21,7 @@ class ModuleConcernTest < ActiveSupport::TestCase
 
     # Declares a concern but doesn't include it
     assert klass.const_defined?(:Baz, false)
-    assert !ModuleConcernTest.const_defined?(:Baz)
+    assert_not ModuleConcernTest.const_defined?(:Baz)
     assert_kind_of ActiveSupport::Concern, klass::Baz
     assert_not_includes klass.ancestors, klass::Baz, klass.ancestors.inspect
 
@@ -55,10 +55,10 @@ class ModuleConcernTest < ActiveSupport::TestCase
   end
 
   def test_using_class_methods_blocks_instead_of_ClassMethods_module
-    assert !Foo.respond_to?(:will_be_orphaned)
-    assert Foo.respond_to?(:hacked_on)
-    assert Foo.respond_to?(:nicer_dsl)
-    assert Foo.respond_to?(:doesnt_clobber)
+    assert_not_respond_to Foo, :will_be_orphaned
+    assert_respond_to Foo, :hacked_on
+    assert_respond_to Foo, :nicer_dsl
+    assert_respond_to Foo, :doesnt_clobber
 
     # Orphan in Foo::ClassMethods, not Bar::ClassMethods.
     assert Foo.const_defined?(:ClassMethods)
diff --git a/activesupport/test/core_ext/module/reachable_test.rb b/activesupport/test/core_ext/module/reachable_test.rb
index a69fc6839e..f356d46957 100644
--- a/activesupport/test/core_ext/module/reachable_test.rb
+++ b/activesupport/test/core_ext/module/reachable_test.rb
@@ -5,13 +5,17 @@ require "active_support/core_ext/module/reachable"
 
 class AnonymousTest < ActiveSupport::TestCase
   test "an anonymous class or module is not reachable" do
-    assert !Module.new.reachable?
-    assert !Class.new.reachable?
+    assert_deprecated do
+      assert_not_predicate Module.new, :reachable?
+      assert_not_predicate Class.new, :reachable?
+    end
   end
 
   test "ordinary named classes or modules are reachable" do
-    assert Kernel.reachable?
-    assert Object.reachable?
+    assert_deprecated do
+      assert_predicate Kernel, :reachable?
+      assert_predicate Object, :reachable?
+    end
   end
 
   test "a named class or module whose constant has gone is not reachable" do
@@ -21,8 +25,10 @@ class AnonymousTest < ActiveSupport::TestCase
     self.class.send(:remove_const, :C)
     self.class.send(:remove_const, :M)
 
-    assert !c.reachable?
-    assert !m.reachable?
+    assert_deprecated do
+      assert_not_predicate c, :reachable?
+      assert_not_predicate m, :reachable?
+    end
   end
 
   test "a named class or module whose constants store different objects are not reachable" do
@@ -35,9 +41,11 @@ class AnonymousTest < ActiveSupport::TestCase
     eval "class C; end"
     eval "module M; end"
 
-    assert C.reachable?
-    assert M.reachable?
-    assert !c.reachable?
-    assert !m.reachable?
+    assert_deprecated do
+      assert_predicate C, :reachable?
+      assert_predicate M, :reachable?
+      assert_not_predicate c, :reachable?
+      assert_not_predicate m, :reachable?
+    end
   end
 end
diff --git a/activesupport/test/core_ext/module/remove_method_test.rb b/activesupport/test/core_ext/module/remove_method_test.rb
index dbf71b477d..a18fc0a5e4 100644
--- a/activesupport/test/core_ext/module/remove_method_test.rb
+++ b/activesupport/test/core_ext/module/remove_method_test.rb
@@ -6,22 +6,22 @@ require "active_support/core_ext/module/remove_method"
 module RemoveMethodTests
   class A
     def do_something
-      return 1
+      1
     end
 
     def do_something_protected
-      return 1
+      1
     end
     protected :do_something_protected
 
     def do_something_private
-      return 1
+      1
     end
     private :do_something_private
 
     class << self
       def do_something_else
-        return 2
+        2
       end
     end
   end
@@ -32,14 +32,14 @@ class RemoveMethodTest < ActiveSupport::TestCase
     RemoveMethodTests::A.class_eval {
       remove_possible_method(:do_something)
     }
-    assert !RemoveMethodTests::A.new.respond_to?(:do_something)
+    assert_not_respond_to RemoveMethodTests::A.new, :do_something
   end
 
   def test_remove_singleton_method_from_an_object
     RemoveMethodTests::A.class_eval {
       remove_possible_singleton_method(:do_something_else)
     }
-    assert !RemoveMethodTests::A.respond_to?(:do_something_else)
+    assert_not_respond_to RemoveMethodTests::A, :do_something_else
   end
 
   def test_redefine_method_in_an_object
diff --git a/activesupport/test/core_ext/module_test.rb b/activesupport/test/core_ext/module_test.rb
index e918823074..04692f1484 100644
--- a/activesupport/test/core_ext/module_test.rb
+++ b/activesupport/test/core_ext/module_test.rb
@@ -347,7 +347,7 @@ class ModuleTest < ActiveSupport::TestCase
 
   def test_delegation_with_method_arguments
     has_block = HasBlock.new(Block.new)
-    assert has_block.hello?
+    assert_predicate has_block, :hello?
   end
 
   def test_delegate_missing_to_with_method
@@ -383,9 +383,9 @@ class ModuleTest < ActiveSupport::TestCase
   end
 
   def test_delegate_missing_to_affects_respond_to
-    assert DecoratedTester.new(@david).respond_to?(:name)
-    assert_not DecoratedTester.new(@david).respond_to?(:private_name)
-    assert_not DecoratedTester.new(@david).respond_to?(:my_fake_method)
+    assert_respond_to DecoratedTester.new(@david), :name
+    assert_not_respond_to DecoratedTester.new(@david), :private_name
+    assert_not_respond_to DecoratedTester.new(@david), :my_fake_method
 
     assert DecoratedTester.new(@david).respond_to?(:name, true)
     assert_not DecoratedTester.new(@david).respond_to?(:private_name, true)
@@ -414,8 +414,8 @@ class ModuleTest < ActiveSupport::TestCase
 
     place = location.new(Somewhere.new("Such street", "Sad city"))
 
-    assert_not place.respond_to?(:street)
-    assert_not place.respond_to?(:city)
+    assert_not_respond_to place, :street
+    assert_not_respond_to place, :city
 
     assert place.respond_to?(:street, true) # Asking for private method
     assert place.respond_to?(:city, true)
@@ -432,12 +432,79 @@ class ModuleTest < ActiveSupport::TestCase
 
     place = location.new(Somewhere.new("Such street", "Sad city"))
 
-    assert_not place.respond_to?(:street)
-    assert_not place.respond_to?(:city)
+    assert_not_respond_to place, :street
+    assert_not_respond_to place, :city
 
-    assert_not place.respond_to?(:the_street)
+    assert_not_respond_to place, :the_street
     assert place.respond_to?(:the_street, true)
-    assert_not place.respond_to?(:the_city)
+    assert_not_respond_to place, :the_city
     assert place.respond_to?(:the_city, true)
   end
+
+  def test_private_delegate_with_private_option
+    location = Class.new do
+      def initialize(place)
+        @place = place
+      end
+
+      delegate(:street, :city, to: :@place, private: true)
+    end
+
+    place = location.new(Somewhere.new("Such street", "Sad city"))
+
+    assert_not_respond_to place, :street
+    assert_not_respond_to place, :city
+
+    assert place.respond_to?(:street, true) # Asking for private method
+    assert place.respond_to?(:city, true)
+  end
+
+  def test_some_public_some_private_delegate_with_private_option
+    location = Class.new do
+      def initialize(place)
+        @place = place
+      end
+
+      delegate(:street, to: :@place)
+      delegate(:city, to: :@place, private: true)
+    end
+
+    place = location.new(Somewhere.new("Such street", "Sad city"))
+
+    assert_respond_to place, :street
+    assert_not_respond_to place, :city
+
+    assert place.respond_to?(:city, true) # Asking for private method
+  end
+
+  def test_private_delegate_prefixed_with_private_option
+    location = Class.new do
+      def initialize(place)
+        @place = place
+      end
+
+      delegate(:street, :city, to: :@place, prefix: :the, private: true)
+    end
+
+    place = location.new(Somewhere.new("Such street", "Sad city"))
+
+    assert_not_respond_to place, :the_street
+    assert place.respond_to?(:the_street, true)
+    assert_not_respond_to place, :the_city
+    assert place.respond_to?(:the_city, true)
+  end
+
+  def test_delegate_with_private_option_returns_names_of_delegate_methods
+    location = Class.new do
+      def initialize(place)
+        @place = place
+      end
+    end
+
+    assert_equal [:street, :city],
+      location.delegate(:street, :city, to: :@place, private: true)
+
+    assert_equal [:the_street, :the_city],
+      location.delegate(:street, :city, to: :@place, prefix: :the, private: true)
+  end
 end
diff --git a/activesupport/test/core_ext/name_error_test.rb b/activesupport/test/core_ext/name_error_test.rb
index d1dace3713..5c6c12ffc7 100644
--- a/activesupport/test/core_ext/name_error_test.rb
+++ b/activesupport/test/core_ext/name_error_test.rb
@@ -17,7 +17,7 @@ class NameErrorTest < ActiveSupport::TestCase
     exc = assert_raise NameError do
       some_method_that_does_not_exist
     end
-    assert !exc.missing_name?(:Foo)
+    assert_not exc.missing_name?(:Foo)
     assert_nil exc.missing_name
   end
 end
diff --git a/activesupport/test/core_ext/numeric_ext_test.rb b/activesupport/test/core_ext/numeric_ext_test.rb
index d38124b214..5005b9febd 100644
--- a/activesupport/test/core_ext/numeric_ext_test.rb
+++ b/activesupport/test/core_ext/numeric_ext_test.rb
@@ -302,7 +302,7 @@ class NumericExtFormattingTest < ActiveSupport::TestCase
     assert_equal "40 KB",    41100.to_s(:human_size, precision: 2)
     assert_equal "1.0 KB",   kilobytes(1.0123).to_s(:human_size, precision: 2, strip_insignificant_zeros: false)
     assert_equal "1.012 KB", kilobytes(1.0123).to_s(:human_size, precision: 3, significant: false)
-    assert_equal "1 KB",     kilobytes(1.0123).to_s(:human_size, precision: 0, significant: true) #ignores significant it precision is 0
+    assert_equal "1 KB",     kilobytes(1.0123).to_s(:human_size, precision: 0, significant: true) # ignores significant it precision is 0
   end
 
   def test_to_s__human_size_with_custom_delimiter_and_separator
@@ -330,17 +330,17 @@ class NumericExtFormattingTest < ActiveSupport::TestCase
     assert_equal "489.0 Thousand", 489000.to_s(:human, precision: 4, strip_insignificant_zeros: false)
     assert_equal "1.2346 Million", 1234567.to_s(:human, precision: 4, significant: false)
     assert_equal "1,2 Million", 1234567.to_s(:human, precision: 1, significant: false, separator: ",")
-    assert_equal "1 Million", 1234567.to_s(:human, precision: 0, significant: true, separator: ",") #significant forced to false
+    assert_equal "1 Million", 1234567.to_s(:human, precision: 0, significant: true, separator: ",") # significant forced to false
   end
 
   def test_number_to_human_with_custom_units
-    #Only integers
+    # Only integers
     volume = { unit: "ml", thousand: "lt", million: "m3" }
     assert_equal "123 lt", 123456.to_s(:human, units: volume)
     assert_equal "12 ml", 12.to_s(:human, units: volume)
     assert_equal "1.23 m3", 1234567.to_s(:human, units: volume)
 
-    #Including fractionals
+    # Including fractionals
     distance = { mili: "mm", centi: "cm", deci: "dm", unit: "m", ten: "dam", hundred: "hm", thousand: "km" }
     assert_equal "1.23 mm", 0.00123.to_s(:human, units: distance)
     assert_equal "1.23 cm", 0.0123.to_s(:human, units: distance)
@@ -353,14 +353,14 @@ class NumericExtFormattingTest < ActiveSupport::TestCase
     assert_equal "1.23 km", 1230.to_s(:human, units: distance)
     assert_equal "12.3 km", 12300.to_s(:human, units: distance)
 
-    #The quantifiers don't need to be a continuous sequence
+    # The quantifiers don't need to be a continuous sequence
     gangster = { hundred: "hundred bucks", million: "thousand quids" }
     assert_equal "1 hundred bucks", 100.to_s(:human, units: gangster)
     assert_equal "25 hundred bucks", 2500.to_s(:human, units: gangster)
     assert_equal "25 thousand quids", 25000000.to_s(:human, units: gangster)
     assert_equal "12300 thousand quids", 12345000000.to_s(:human, units: gangster)
 
-    #Spaces are stripped from the resulting string
+    # Spaces are stripped from the resulting string
     assert_equal "4", 4.to_s(:human, units: { unit: "", ten: "tens " })
     assert_equal "4.5  tens", 45.to_s(:human, units: { unit: "", ten: " tens   " })
   end
@@ -406,86 +406,9 @@ class NumericExtFormattingTest < ActiveSupport::TestCase
     assert_equal 10_000, 10.seconds.in_milliseconds
   end
 
-  # TODO: Remove positive and negative tests when we drop support to ruby < 2.3
-  b = 2**64
-
-  T_ZERO = b.coerce(0).first
-  T_ONE  = b.coerce(1).first
-  T_MONE = b.coerce(-1).first
-
-  def test_positive
-    assert_predicate(1, :positive?)
-    assert_not_predicate(0, :positive?)
-    assert_not_predicate(-1, :positive?)
-    assert_predicate(+1.0, :positive?)
-    assert_not_predicate(+0.0, :positive?)
-    assert_not_predicate(-0.0, :positive?)
-    assert_not_predicate(-1.0, :positive?)
-    assert_predicate(+(0.0.next_float), :positive?)
-    assert_not_predicate(-(0.0.next_float), :positive?)
-    assert_predicate(Float::INFINITY, :positive?)
-    assert_not_predicate(-Float::INFINITY, :positive?)
-    assert_not_predicate(Float::NAN, :positive?)
-
-    a = Class.new(Numeric) do
-      def >(x); true; end
-    end.new
-    assert_predicate(a, :positive?)
-
-    a = Class.new(Numeric) do
-      def >(x); false; end
-    end.new
-    assert_not_predicate(a, :positive?)
-
-    assert_predicate(1 / 2r, :positive?)
-    assert_not_predicate(-1 / 2r, :positive?)
-
-    assert_predicate(T_ONE, :positive?)
-    assert_not_predicate(T_MONE, :positive?)
-    assert_not_predicate(T_ZERO, :positive?)
-
-    e = assert_raises(NoMethodError) do
-      Complex(1).positive?
+  def test_requiring_inquiry_is_deprecated
+    assert_deprecated do
+      require "active_support/core_ext/numeric/inquiry"
     end
-
-    assert_match(/positive\?/, e.message)
-  end
-
-  def test_negative
-    assert_predicate(-1, :negative?)
-    assert_not_predicate(0, :negative?)
-    assert_not_predicate(1, :negative?)
-    assert_predicate(-1.0, :negative?)
-    assert_not_predicate(-0.0, :negative?)
-    assert_not_predicate(+0.0, :negative?)
-    assert_not_predicate(+1.0, :negative?)
-    assert_predicate(-(0.0.next_float), :negative?)
-    assert_not_predicate(+(0.0.next_float), :negative?)
-    assert_predicate(-Float::INFINITY, :negative?)
-    assert_not_predicate(Float::INFINITY, :negative?)
-    assert_not_predicate(Float::NAN, :negative?)
-
-    a = Class.new(Numeric) do
-      def <(x); true; end
-    end.new
-    assert_predicate(a, :negative?)
-
-    a = Class.new(Numeric) do
-      def <(x); false; end
-    end.new
-    assert_not_predicate(a, :negative?)
-
-    assert_predicate(-1 / 2r, :negative?)
-    assert_not_predicate(1 / 2r, :negative?)
-
-    assert_not_predicate(T_ONE, :negative?)
-    assert_predicate(T_MONE, :negative?)
-    assert_not_predicate(T_ZERO, :negative?)
-
-    e = assert_raises(NoMethodError) do
-      Complex(1).negative?
-    end
-
-    assert_match(/negative\?/, e.message)
   end
 end
diff --git a/activesupport/test/core_ext/object/acts_like_test.rb b/activesupport/test/core_ext/object/acts_like_test.rb
index 9f7b81f7fc..31241caf0a 100644
--- a/activesupport/test/core_ext/object/acts_like_test.rb
+++ b/activesupport/test/core_ext/object/acts_like_test.rb
@@ -17,19 +17,19 @@ class ObjectTests < ActiveSupport::TestCase
     dt     = DateTime.new
     duck   = DuckTime.new
 
-    assert !object.acts_like?(:time)
-    assert !object.acts_like?(:date)
+    assert_not object.acts_like?(:time)
+    assert_not object.acts_like?(:date)
 
     assert time.acts_like?(:time)
-    assert !time.acts_like?(:date)
+    assert_not time.acts_like?(:date)
 
-    assert !date.acts_like?(:time)
+    assert_not date.acts_like?(:time)
     assert date.acts_like?(:date)
 
     assert dt.acts_like?(:time)
     assert dt.acts_like?(:date)
 
     assert duck.acts_like?(:time)
-    assert !duck.acts_like?(:date)
+    assert_not duck.acts_like?(:date)
   end
 end
diff --git a/activesupport/test/core_ext/object/blank_test.rb b/activesupport/test/core_ext/object/blank_test.rb
index 749e59ec00..954f415383 100644
--- a/activesupport/test/core_ext/object/blank_test.rb
+++ b/activesupport/test/core_ext/object/blank_test.rb
@@ -16,8 +16,8 @@ class BlankTest < ActiveSupport::TestCase
     end
   end
 
-  BLANK = [ EmptyTrue.new, nil, false, "", "   ", "  \n\t  \r ", "　", "\u00a0", [], {} ]
-  NOT   = [ EmptyFalse.new, Object.new, true, 0, 1, "a", [nil], { nil => 0 }, Time.now ]
+  BLANK = [ EmptyTrue.new, nil, false, "", "   ", "  \n\t  \r ", "　", "\u00a0", [], {}, " ".encode("UTF-16LE") ]
+  NOT   = [ EmptyFalse.new, Object.new, true, 0, 1, "a", [nil], { nil => 0 }, Time.now, "my value".encode("UTF-16LE") ]
 
   def test_blank
     BLANK.each { |v| assert_equal true, v.blank?,  "#{v.inspect} should be blank" }
diff --git a/activesupport/test/core_ext/object/deep_dup_test.rb b/activesupport/test/core_ext/object/deep_dup_test.rb
index 2486592441..1fb26ebac7 100644
--- a/activesupport/test/core_ext/object/deep_dup_test.rb
+++ b/activesupport/test/core_ext/object/deep_dup_test.rb
@@ -47,7 +47,7 @@ class DeepDupTest < ActiveSupport::TestCase
     object = Object.new
     dup = object.deep_dup
     dup.instance_variable_set(:@a, 1)
-    assert !object.instance_variable_defined?(:@a)
+    assert_not object.instance_variable_defined?(:@a)
     assert dup.instance_variable_defined?(:@a)
   end
 
diff --git a/activesupport/test/core_ext/object/duplicable_test.rb b/activesupport/test/core_ext/object/duplicable_test.rb
index 93f39b00bb..5203434ae6 100644
--- a/activesupport/test/core_ext/object/duplicable_test.rb
+++ b/activesupport/test/core_ext/object/duplicable_test.rb
@@ -8,16 +8,10 @@ require "active_support/core_ext/numeric/time"
 class DuplicableTest < ActiveSupport::TestCase
   if RUBY_VERSION >= "2.5.0"
     RAISE_DUP = [method(:puts)]
-    ALLOW_DUP = ["1", "symbol_from_string".to_sym, Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal.new("4.56"), nil, false, true, 1, 2.3, Complex(1), Rational(1)]
-  elsif RUBY_VERSION >= "2.4.1"
-    RAISE_DUP = [method(:puts), Complex(1), Rational(1)]
-    ALLOW_DUP = ["1", "symbol_from_string".to_sym, Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal.new("4.56"), nil, false, true, 1, 2.3]
-  elsif RUBY_VERSION >= "2.4.0"  # Due to 2.4.0 bug. This elsif cannot be removed unless we drop 2.4.0 support...
-    RAISE_DUP = [method(:puts), Complex(1), Rational(1), "symbol_from_string".to_sym]
-    ALLOW_DUP = ["1", Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal.new("4.56"), nil, false, true, 1, 2.3]
+    ALLOW_DUP = ["1", "symbol_from_string".to_sym, Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal("4.56"), nil, false, true, 1, 2.3, Complex(1), Rational(1)]
   else
-    RAISE_DUP = [nil, false, true, :symbol, 1, 2.3, method(:puts), Complex(1), Rational(1)]
-    ALLOW_DUP = ["1", Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal.new("4.56")]
+    RAISE_DUP = [method(:puts), Complex(1), Rational(1)]
+    ALLOW_DUP = ["1", "symbol_from_string".to_sym, Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal("4.56"), nil, false, true, 1, 2.3]
   end
 
   def test_duplicable
@@ -25,7 +19,7 @@ class DuplicableTest < ActiveSupport::TestCase
                   "* https://github.com/rubinius/rubinius/issues/3089"
 
     RAISE_DUP.each do |v|
-      assert !v.duplicable?, "#{ v.inspect } should not be duplicable"
+      assert_not v.duplicable?, "#{ v.inspect } should not be duplicable"
       assert_raises(TypeError, v.class.name) { v.dup }
     end
 
diff --git a/activesupport/test/core_ext/object/inclusion_test.rb b/activesupport/test/core_ext/object/inclusion_test.rb
index 52c21f2e8e..8cbb4f848f 100644
--- a/activesupport/test/core_ext/object/inclusion_test.rb
+++ b/activesupport/test/core_ext/object/inclusion_test.rb
@@ -6,30 +6,30 @@ require "active_support/core_ext/object/inclusion"
 class InTest < ActiveSupport::TestCase
   def test_in_array
     assert 1.in?([1, 2])
-    assert !3.in?([1, 2])
+    assert_not 3.in?([1, 2])
   end
 
   def test_in_hash
     h = { "a" => 100, "b" => 200 }
     assert "a".in?(h)
-    assert !"z".in?(h)
+    assert_not "z".in?(h)
   end
 
   def test_in_string
     assert "lo".in?("hello")
-    assert !"ol".in?("hello")
+    assert_not "ol".in?("hello")
     assert ?h.in?("hello")
   end
 
   def test_in_range
     assert 25.in?(1..50)
-    assert !75.in?(1..50)
+    assert_not 75.in?(1..50)
   end
 
   def test_in_set
     s = Set.new([1, 2])
     assert 1.in?(s)
-    assert !3.in?(s)
+    assert_not 3.in?(s)
   end
 
   module A
@@ -45,8 +45,8 @@ class InTest < ActiveSupport::TestCase
   def test_in_module
     assert A.in?(B)
     assert A.in?(C)
-    assert !A.in?(A)
-    assert !A.in?(D)
+    assert_not A.in?(A)
+    assert_not A.in?(D)
   end
 
   def test_no_method_catching
diff --git a/activesupport/test/core_ext/object/instance_variables_test.rb b/activesupport/test/core_ext/object/instance_variables_test.rb
index b9ec827954..a3d8daab5b 100644
--- a/activesupport/test/core_ext/object/instance_variables_test.rb
+++ b/activesupport/test/core_ext/object/instance_variables_test.rb
@@ -19,7 +19,7 @@ class ObjectInstanceVariableTest < ActiveSupport::TestCase
   end
 
   def test_instance_exec_passes_arguments_to_block
-    assert_equal %w(hello goodbye), "hello".instance_exec("goodbye") { |v| [self, v] }
+    assert_equal %w(hello goodbye), "hello".dup.instance_exec("goodbye") { |v| [self, v] }
   end
 
   def test_instance_exec_with_frozen_obj
@@ -27,7 +27,7 @@ class ObjectInstanceVariableTest < ActiveSupport::TestCase
   end
 
   def test_instance_exec_nested
-    assert_equal %w(goodbye olleh bar), "hello".instance_exec("goodbye") { |arg|
+    assert_equal %w(goodbye olleh bar), "hello".dup.instance_exec("goodbye") { |arg|
       [arg] + instance_exec("bar") { |v| [reverse, v] } }
   end
 end
diff --git a/activesupport/test/core_ext/object/try_test.rb b/activesupport/test/core_ext/object/try_test.rb
index fe68b24bf5..a838334034 100644
--- a/activesupport/test/core_ext/object/try_test.rb
+++ b/activesupport/test/core_ext/object/try_test.rb
@@ -10,25 +10,25 @@ class ObjectTryTest < ActiveSupport::TestCase
 
   def test_nonexisting_method
     method = :undefined_method
-    assert !@string.respond_to?(method)
+    assert_not_respond_to @string, method
     assert_nil @string.try(method)
   end
 
   def test_nonexisting_method_with_arguments
     method = :undefined_method
-    assert !@string.respond_to?(method)
+    assert_not_respond_to @string, method
     assert_nil @string.try(method, "llo", "y")
   end
 
   def test_nonexisting_method_bang
     method = :undefined_method
-    assert !@string.respond_to?(method)
+    assert_not_respond_to @string, method
     assert_raise(NoMethodError) { @string.try!(method) }
   end
 
   def test_nonexisting_method_with_arguments_bang
     method = :undefined_method
-    assert !@string.respond_to?(method)
+    assert_not_respond_to @string, method
     assert_raise(NoMethodError) { @string.try!(method, "llo", "y") }
   end
 
@@ -78,7 +78,6 @@ class ObjectTryTest < ActiveSupport::TestCase
   def test_try_with_private_method_bang
     klass = Class.new do
       private
-
         def private_method
           "private method"
         end
@@ -90,7 +89,6 @@ class ObjectTryTest < ActiveSupport::TestCase
   def test_try_with_private_method
     klass = Class.new do
       private
-
         def private_method
           "private method"
         end
@@ -109,7 +107,6 @@ class ObjectTryTest < ActiveSupport::TestCase
     end
 
     private
-
       def private_delegator_method
         "private delegator method"
       end
@@ -120,11 +117,11 @@ class ObjectTryTest < ActiveSupport::TestCase
   end
 
   def test_try_with_method_on_delegator_target
-    assert_equal 5, Decorator.new(@string).size
+    assert_equal 5, Decorator.new(@string).try(:size)
   end
 
   def test_try_with_overridden_method_on_delegator
-    assert_equal "overridden reverse", Decorator.new(@string).reverse
+    assert_equal "overridden reverse", Decorator.new(@string).try(:reverse)
   end
 
   def test_try_with_private_method_on_delegator
@@ -140,7 +137,6 @@ class ObjectTryTest < ActiveSupport::TestCase
   def test_try_with_private_method_on_delegator_target
     klass = Class.new do
       private
-
         def private_method
           "private method"
         end
@@ -152,7 +148,6 @@ class ObjectTryTest < ActiveSupport::TestCase
   def test_try_with_private_method_on_delegator_target_bang
     klass = Class.new do
       private
-
         def private_method
           "private method"
         end
diff --git a/activesupport/test/core_ext/range_ext_test.rb b/activesupport/test/core_ext/range_ext_test.rb
index a96e3d62e8..7c7a78f461 100644
--- a/activesupport/test/core_ext/range_ext_test.rb
+++ b/activesupport/test/core_ext/range_ext_test.rb
@@ -16,6 +16,11 @@ class RangeTest < ActiveSupport::TestCase
     assert_equal "BETWEEN '2005-12-10 15:30:00' AND '2005-12-10 17:30:00'", date_range.to_s(:db)
   end
 
+  def test_to_s_with_alphabets
+    alphabet_range = ("a".."z")
+    assert_equal "BETWEEN 'a' AND 'z'", alphabet_range.to_s(:db)
+  end
+
   def test_to_s_with_numeric
     number_range = (1..100)
     assert_equal "BETWEEN '1' AND '100'", number_range.to_s(:db)
@@ -32,7 +37,7 @@ class RangeTest < ActiveSupport::TestCase
   end
 
   def test_overlaps_last_exclusive
-    assert !(1...5).overlaps?(5..10)
+    assert_not (1...5).overlaps?(5..10)
   end
 
   def test_overlaps_first_inclusive
@@ -40,7 +45,7 @@ class RangeTest < ActiveSupport::TestCase
   end
 
   def test_overlaps_first_exclusive
-    assert !(5..10).overlaps?(1...5)
+    assert_not (5..10).overlaps?(1...5)
   end
 
   def test_should_include_identical_inclusive
@@ -97,28 +102,31 @@ class RangeTest < ActiveSupport::TestCase
   def test_no_overlaps_on_time
     time_range_1 = Time.utc(2005, 12, 10, 15, 30)..Time.utc(2005, 12, 10, 17, 30)
     time_range_2 = Time.utc(2005, 12, 10, 17, 31)..Time.utc(2005, 12, 10, 18, 00)
-    assert !time_range_1.overlaps?(time_range_2)
+    assert_not time_range_1.overlaps?(time_range_2)
   end
 
   def test_each_on_time_with_zone
-    twz = ActiveSupport::TimeWithZone.new(nil, ActiveSupport::TimeZone["Eastern Time (US & Canada)"] , Time.utc(2006, 11, 28, 10, 30))
+    twz = ActiveSupport::TimeWithZone.new(nil, ActiveSupport::TimeZone["Eastern Time (US & Canada)"], Time.utc(2006, 11, 28, 10, 30))
     assert_raises TypeError do
       ((twz - 1.hour)..twz).each {}
     end
   end
 
   def test_step_on_time_with_zone
-    twz = ActiveSupport::TimeWithZone.new(nil, ActiveSupport::TimeZone["Eastern Time (US & Canada)"] , Time.utc(2006, 11, 28, 10, 30))
+    twz = ActiveSupport::TimeWithZone.new(nil, ActiveSupport::TimeZone["Eastern Time (US & Canada)"], Time.utc(2006, 11, 28, 10, 30))
     assert_raises TypeError do
       ((twz - 1.hour)..twz).step(1) {}
     end
   end
 
   def test_include_on_time_with_zone
-    twz = ActiveSupport::TimeWithZone.new(nil, ActiveSupport::TimeZone["Eastern Time (US & Canada)"] , Time.utc(2006, 11, 28, 10, 30))
-    assert_raises TypeError do
-      ((twz - 1.hour)..twz).include?(twz)
-    end
+    twz = ActiveSupport::TimeWithZone.new(nil, ActiveSupport::TimeZone["Eastern Time (US & Canada)"], Time.utc(2006, 11, 28, 10, 30))
+    assert ((twz - 1.hour)..twz).include?(twz)
+  end
+
+  def test_case_equals_on_time_with_zone
+    twz = ActiveSupport::TimeWithZone.new(nil, ActiveSupport::TimeZone["Eastern Time (US & Canada)"], Time.utc(2006, 11, 28, 10, 30))
+    assert ((twz - 1.hour)..twz) === twz
   end
 
   def test_date_time_with_each
diff --git a/activesupport/test/core_ext/regexp_ext_test.rb b/activesupport/test/core_ext/regexp_ext_test.rb
index 5737bdafda..7d18297b64 100644
--- a/activesupport/test/core_ext/regexp_ext_test.rb
+++ b/activesupport/test/core_ext/regexp_ext_test.rb
@@ -9,28 +9,4 @@ class RegexpExtAccessTests < ActiveSupport::TestCase
     assert_equal false, //.multiline?
     assert_equal false, /(?m:)/.multiline?
   end
-
-  # Based on https://github.com/ruby/ruby/blob/trunk/test/ruby/test_regexp.rb.
-  def test_match_p
-    /back(...)/ =~ "backref"
-    # must match here, but not in a separate method, e.g., assert_send,
-    # to check if $~ is affected or not.
-    assert_equal false, //.match?(nil)
-    assert_equal true, //.match?("")
-    assert_equal true, /.../.match?(:abc)
-    assert_raise(TypeError) { /.../.match?(Object.new) }
-    assert_equal true, /b/.match?("abc")
-    assert_equal true, /b/.match?("abc", 1)
-    assert_equal true, /../.match?("abc", 1)
-    assert_equal true, /../.match?("abc", -2)
-    assert_equal false, /../.match?("abc", -4)
-    assert_equal false, /../.match?("abc", 4)
-    assert_equal true, /\z/.match?("")
-    assert_equal true, /\z/.match?("abc")
-    assert_equal true, /R.../.match?("Ruby")
-    assert_equal false, /R.../.match?("Ruby", 1)
-    assert_equal false, /P.../.match?("Ruby")
-    assert_equal "backref", $&
-    assert_equal "ref", $1
-  end
 end
diff --git a/activesupport/test/core_ext/string_ext_test.rb b/activesupport/test/core_ext/string_ext_test.rb
index 9fd6d8ac0f..b8de16cc5e 100644
--- a/activesupport/test/core_ext/string_ext_test.rb
+++ b/activesupport/test/core_ext/string_ext_test.rb
@@ -9,9 +9,9 @@ require "constantize_test_cases"
 require "active_support/inflector"
 require "active_support/core_ext/string"
 require "active_support/time"
-require "active_support/core_ext/string/strip"
 require "active_support/core_ext/string/output_safety"
 require "active_support/core_ext/string/indent"
+require "active_support/core_ext/string/strip"
 require "time_zone_test_helpers"
 require "yaml"
 
@@ -24,6 +24,10 @@ class StringInflectionsTest < ActiveSupport::TestCase
     assert_equal "", "".strip_heredoc
   end
 
+  def test_strip_heredoc_on_a_frozen_string
+    assert "".freeze.strip_heredoc.frozen?
+  end
+
   def test_strip_heredoc_on_a_string_with_no_lines
     assert_equal "x", "x".strip_heredoc
     assert_equal "x", "    x".strip_heredoc
@@ -197,7 +201,7 @@ class StringInflectionsTest < ActiveSupport::TestCase
   end
 
   def test_string_parameterized_underscore_preserve_case
-    StringToParameterizePreserceCaseWithUnderscore.each do |normal, slugged|
+    StringToParameterizePreserveCaseWithUnderscore.each do |normal, slugged|
       assert_equal(slugged, normal.parameterize(separator: "_", preserve_case: true))
     end
   end
@@ -233,11 +237,11 @@ class StringInflectionsTest < ActiveSupport::TestCase
     s = "hello"
     assert s.starts_with?("h")
     assert s.starts_with?("hel")
-    assert !s.starts_with?("el")
+    assert_not s.starts_with?("el")
 
     assert s.ends_with?("o")
     assert s.ends_with?("lo")
-    assert !s.ends_with?("el")
+    assert_not s.ends_with?("el")
   end
 
   def test_string_squish
@@ -259,8 +263,8 @@ class StringInflectionsTest < ActiveSupport::TestCase
   end
 
   def test_string_inquiry
-    assert "production".inquiry.production?
-    assert !"production".inquiry.development?
+    assert_predicate "production".inquiry, :production?
+    assert_not_predicate "production".inquiry, :development?
   end
 
   def test_truncate
@@ -281,6 +285,68 @@ class StringInflectionsTest < ActiveSupport::TestCase
     assert_equal "Hello Big[...]", "Hello Big World!".truncate(15, omission: "[...]", separator: /\s/)
   end
 
+  def test_truncate_bytes
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16)
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16, omission: nil)
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16, omission: " ")
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16, omission: "🖖")
+
+    assert_equal "👍👍👍…", "👍👍👍👍".truncate_bytes(15)
+    assert_equal "👍👍👍", "👍👍👍👍".truncate_bytes(15, omission: nil)
+    assert_equal "👍👍👍 ", "👍👍👍👍".truncate_bytes(15, omission: " ")
+    assert_equal "👍👍🖖", "👍👍👍👍".truncate_bytes(15, omission: "🖖")
+
+    assert_equal "…", "👍👍👍👍".truncate_bytes(5)
+    assert_equal "👍", "👍👍👍👍".truncate_bytes(5, omission: nil)
+    assert_equal "👍 ", "👍👍👍👍".truncate_bytes(5, omission: " ")
+    assert_equal "🖖", "👍👍👍👍".truncate_bytes(5, omission: "🖖")
+
+    assert_equal "…", "👍👍👍👍".truncate_bytes(4)
+    assert_equal "👍", "👍👍👍👍".truncate_bytes(4, omission: nil)
+    assert_equal " ", "👍👍👍👍".truncate_bytes(4, omission: " ")
+    assert_equal "🖖", "👍👍👍👍".truncate_bytes(4, omission: "🖖")
+
+    assert_raise ArgumentError do
+      "👍👍👍👍".truncate_bytes(3, omission: "🖖")
+    end
+  end
+
+  def test_truncate_bytes_preserves_codepoints
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16)
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16, omission: nil)
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16, omission: " ")
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16, omission: "🖖")
+
+    assert_equal "👍👍👍…", "👍👍👍👍".truncate_bytes(15)
+    assert_equal "👍👍👍", "👍👍👍👍".truncate_bytes(15, omission: nil)
+    assert_equal "👍👍👍 ", "👍👍👍👍".truncate_bytes(15, omission: " ")
+    assert_equal "👍👍🖖", "👍👍👍👍".truncate_bytes(15, omission: "🖖")
+
+    assert_equal "…", "👍👍👍👍".truncate_bytes(5)
+    assert_equal "👍", "👍👍👍👍".truncate_bytes(5, omission: nil)
+    assert_equal "👍 ", "👍👍👍👍".truncate_bytes(5, omission: " ")
+    assert_equal "🖖", "👍👍👍👍".truncate_bytes(5, omission: "🖖")
+
+    assert_equal "…", "👍👍👍👍".truncate_bytes(4)
+    assert_equal "👍", "👍👍👍👍".truncate_bytes(4, omission: nil)
+    assert_equal " ", "👍👍👍👍".truncate_bytes(4, omission: " ")
+    assert_equal "🖖", "👍👍👍👍".truncate_bytes(4, omission: "🖖")
+
+    assert_raise ArgumentError do
+      "👍👍👍👍".truncate_bytes(3, omission: "🖖")
+    end
+  end
+
+  def test_truncates_bytes_preserves_grapheme_clusters
+    assert_equal "a ", "a ❤️ b".truncate_bytes(2, omission: nil)
+    assert_equal "a ", "a ❤️ b".truncate_bytes(3, omission: nil)
+    assert_equal "a ", "a ❤️ b".truncate_bytes(7, omission: nil)
+    assert_equal "a ❤️", "a ❤️ b".truncate_bytes(8, omission: nil)
+
+    assert_equal "a ", "a 👩‍❤️‍👩".truncate_bytes(13, omission: nil)
+    assert_equal "", "👩‍❤️‍👩".truncate_bytes(13, omission: nil)
+  end
+
   def test_truncate_words
     assert_equal "Hello Big World!", "Hello Big World!".truncate_words(3)
     assert_equal "Hello Big...", "Hello Big World!".truncate_words(2)
@@ -317,7 +383,7 @@ class StringInflectionsTest < ActiveSupport::TestCase
   end
 
   def test_truncate_should_not_be_html_safe
-    assert !"Hello World!".truncate(12).html_safe?
+    assert_not_predicate "Hello World!".truncate(12), :html_safe?
   end
 
   def test_remove
@@ -639,7 +705,7 @@ end
 
 class StringBehaviourTest < ActiveSupport::TestCase
   def test_acts_like_string
-    assert "Bambi".acts_like_string?
+    assert_predicate "Bambi", :acts_like_string?
   end
 end
 
@@ -654,10 +720,10 @@ class CoreExtStringMultibyteTest < ActiveSupport::TestCase
   end
 
   def test_string_should_recognize_utf8_strings
-    assert UTF8_STRING.is_utf8?
-    assert ASCII_STRING.is_utf8?
-    assert !EUC_JP_STRING.is_utf8?
-    assert !INVALID_UTF8_STRING.is_utf8?
+    assert_predicate UTF8_STRING, :is_utf8?
+    assert_predicate ASCII_STRING, :is_utf8?
+    assert_not_predicate EUC_JP_STRING, :is_utf8?
+    assert_not_predicate INVALID_UTF8_STRING, :is_utf8?
   end
 
   def test_mb_chars_returns_instance_of_proxy_class
@@ -676,12 +742,12 @@ class OutputSafetyTest < ActiveSupport::TestCase
   end
 
   test "A string is unsafe by default" do
-    assert !@string.html_safe?
+    assert_not_predicate @string, :html_safe?
   end
 
   test "A string can be marked safe" do
     string = @string.html_safe
-    assert string.html_safe?
+    assert_predicate string, :html_safe?
   end
 
   test "Marking a string safe returns the string" do
@@ -689,15 +755,15 @@ class OutputSafetyTest < ActiveSupport::TestCase
   end
 
   test "An integer is safe by default" do
-    assert 5.html_safe?
+    assert_predicate 5, :html_safe?
   end
 
   test "a float is safe by default" do
-    assert 5.7.html_safe?
+    assert_predicate 5.7, :html_safe?
   end
 
   test "An object is unsafe by default" do
-    assert !@object.html_safe?
+    assert_not_predicate @object, :html_safe?
   end
 
   test "Adding an object to a safe string returns a safe string" do
@@ -705,7 +771,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string << @object
 
     assert_equal "helloother", string
-    assert string.html_safe?
+    assert_predicate string, :html_safe?
   end
 
   test "Adding a safe string to another safe string returns a safe string" do
@@ -714,7 +780,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     @combination = @other_string + string
 
     assert_equal "otherhello", @combination
-    assert @combination.html_safe?
+    assert_predicate @combination, :html_safe?
   end
 
   test "Adding an unsafe string to a safe string escapes it and returns a safe string" do
@@ -725,20 +791,20 @@ class OutputSafetyTest < ActiveSupport::TestCase
     assert_equal "other&lt;foo&gt;", @combination
     assert_equal "hello<foo>", @other_combination
 
-    assert @combination.html_safe?
-    assert !@other_combination.html_safe?
+    assert_predicate @combination, :html_safe?
+    assert_not_predicate @other_combination, :html_safe?
   end
 
   test "Prepending safe onto unsafe yields unsafe" do
     @string.prepend "other".html_safe
-    assert !@string.html_safe?
+    assert_not_predicate @string, :html_safe?
     assert_equal "otherhello", @string
   end
 
   test "Prepending unsafe onto safe yields escaped safe" do
     other = "other".html_safe
     other.prepend "<foo>"
-    assert other.html_safe?
+    assert_predicate other, :html_safe?
     assert_equal "&lt;foo&gt;other", other
   end
 
@@ -747,14 +813,14 @@ class OutputSafetyTest < ActiveSupport::TestCase
 
     string = @string.html_safe
     @other_string.concat(string)
-    assert !@other_string.html_safe?
+    assert_not_predicate @other_string, :html_safe?
   end
 
   test "Concatting unsafe onto safe yields escaped safe" do
     @other_string = "other".html_safe
     string = @other_string.concat("<foo>")
     assert_equal "other&lt;foo&gt;", string
-    assert string.html_safe?
+    assert_predicate string, :html_safe?
   end
 
   test "Concatting safe onto safe yields safe" do
@@ -762,7 +828,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string = @string.html_safe
 
     @other_string.concat(string)
-    assert @other_string.html_safe?
+    assert_predicate @other_string, :html_safe?
   end
 
   test "Concatting safe onto unsafe with << yields unsafe" do
@@ -770,14 +836,14 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string = @string.html_safe
 
     @other_string << string
-    assert !@other_string.html_safe?
+    assert_not_predicate @other_string, :html_safe?
   end
 
   test "Concatting unsafe onto safe with << yields escaped safe" do
     @other_string = "other".html_safe
     string = @other_string << "<foo>"
     assert_equal "other&lt;foo&gt;", string
-    assert string.html_safe?
+    assert_predicate string, :html_safe?
   end
 
   test "Concatting safe onto safe with << yields safe" do
@@ -785,7 +851,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string = @string.html_safe
 
     @other_string << string
-    assert @other_string.html_safe?
+    assert_predicate @other_string, :html_safe?
   end
 
   test "Concatting safe onto unsafe with % yields unsafe" do
@@ -793,7 +859,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string = @string.html_safe
 
     @other_string = @other_string % string
-    assert !@other_string.html_safe?
+    assert_not_predicate @other_string, :html_safe?
   end
 
   test "Concatting unsafe onto safe with % yields escaped safe" do
@@ -801,7 +867,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string = @other_string % "<foo>"
 
     assert_equal "other&lt;foo&gt;", string
-    assert string.html_safe?
+    assert_predicate string, :html_safe?
   end
 
   test "Concatting safe onto safe with % yields safe" do
@@ -809,7 +875,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string = @string.html_safe
 
     @other_string = @other_string % string
-    assert @other_string.html_safe?
+    assert_predicate @other_string, :html_safe?
   end
 
   test "Concatting with % doesn't modify a string" do
@@ -823,7 +889,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string = @string.html_safe
     string = string.concat(13)
     assert_equal "hello".dup.concat(13), string
-    assert string.html_safe?
+    assert_predicate string, :html_safe?
   end
 
   test "emits normal string yaml" do
@@ -832,8 +898,8 @@ class OutputSafetyTest < ActiveSupport::TestCase
 
   test "call to_param returns a normal string" do
     string = @string.html_safe
-    assert string.html_safe?
-    assert !string.to_param.html_safe?
+    assert_predicate string, :html_safe?
+    assert_not_predicate string.to_param, :html_safe?
   end
 
   test "ERB::Util.html_escape should escape unsafe characters" do
diff --git a/activesupport/test/core_ext/time_ext_test.rb b/activesupport/test/core_ext/time_ext_test.rb
index dc2f4c5ac7..e1cb22fda8 100644
--- a/activesupport/test/core_ext/time_ext_test.rb
+++ b/activesupport/test/core_ext/time_ext_test.rb
@@ -178,10 +178,6 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
     assert_equal Time.local(2005, 2, 4, 19, 30, 59, Rational(999999999, 1000)), Time.local(2005, 2, 4, 19, 30, 10).end_of_minute
   end
 
-  def test_last_year
-    assert_equal Time.local(2004, 6, 5, 10),  Time.local(2005, 6, 5, 10, 0, 0).last_year
-  end
-
   def test_ago
     assert_equal Time.local(2005, 2, 22, 10, 10, 9),  Time.local(2005, 2, 22, 10, 10, 10).ago(1)
     assert_equal Time.local(2005, 2, 22, 9, 10, 10),  Time.local(2005, 2, 22, 10, 10, 10).ago(3600)
@@ -455,7 +451,7 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
     assert_equal Time.local(2013, 10, 3, 15, 15, 10), Time.local(2005, 2, 28, 15, 15, 10).advance(years: 7, months: 19, days: 5)
     assert_equal Time.local(2013, 10, 17, 15, 15, 10), Time.local(2005, 2, 28, 15, 15, 10).advance(years: 7, months: 19, weeks: 2, days: 5)
     assert_equal Time.local(2001, 12, 27, 15, 15, 10), Time.local(2005, 2, 28, 15, 15, 10).advance(years: -3, months: -2, days: -1)
-    assert_equal Time.local(2005, 2, 28, 15, 15, 10), Time.local(2004, 2, 29, 15, 15, 10).advance(years: 1) #leap day plus one year
+    assert_equal Time.local(2005, 2, 28, 15, 15, 10), Time.local(2004, 2, 29, 15, 15, 10).advance(years: 1) # leap day plus one year
     assert_equal Time.local(2005, 2, 28, 20, 15, 10), Time.local(2005, 2, 28, 15, 15, 10).advance(hours: 5)
     assert_equal Time.local(2005, 2, 28, 15, 22, 10), Time.local(2005, 2, 28, 15, 15, 10).advance(minutes: 7)
     assert_equal Time.local(2005, 2, 28, 15, 15, 19), Time.local(2005, 2, 28, 15, 15, 10).advance(seconds: 9)
@@ -477,7 +473,7 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
     assert_equal Time.utc(2013, 10, 3, 15, 15, 10), Time.utc(2005, 2, 22, 15, 15, 10).advance(years: 7, months: 19, days: 11)
     assert_equal Time.utc(2013, 10, 17, 15, 15, 10), Time.utc(2005, 2, 28, 15, 15, 10).advance(years: 7, months: 19, weeks: 2, days: 5)
     assert_equal Time.utc(2001, 12, 27, 15, 15, 10), Time.utc(2005, 2, 28, 15, 15, 10).advance(years: -3, months: -2, days: -1)
-    assert_equal Time.utc(2005, 2, 28, 15, 15, 10), Time.utc(2004, 2, 29, 15, 15, 10).advance(years: 1) #leap day plus one year
+    assert_equal Time.utc(2005, 2, 28, 15, 15, 10), Time.utc(2004, 2, 29, 15, 15, 10).advance(years: 1) # leap day plus one year
     assert_equal Time.utc(2005, 2, 28, 20, 15, 10), Time.utc(2005, 2, 28, 15, 15, 10).advance(hours: 5)
     assert_equal Time.utc(2005, 2, 28, 15, 22, 10), Time.utc(2005, 2, 28, 15, 15, 10).advance(minutes: 7)
     assert_equal Time.utc(2005, 2, 28, 15, 15, 19), Time.utc(2005, 2, 28, 15, 15, 10).advance(seconds: 9)
@@ -499,7 +495,7 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
     assert_equal Time.new(2013, 10, 3, 15, 15, 10, "-08:00"), Time.new(2005, 2, 22, 15, 15, 10, "-08:00").advance(years: 7, months: 19, days: 11)
     assert_equal Time.new(2013, 10, 17, 15, 15, 10, "-08:00"), Time.new(2005, 2, 28, 15, 15, 10, "-08:00").advance(years: 7, months: 19, weeks: 2, days: 5)
     assert_equal Time.new(2001, 12, 27, 15, 15, 10, "-08:00"), Time.new(2005, 2, 28, 15, 15, 10, "-08:00").advance(years: -3, months: -2, days: -1)
-    assert_equal Time.new(2005, 2, 28, 15, 15, 10, "-08:00"), Time.new(2004, 2, 29, 15, 15, 10, "-08:00").advance(years: 1) #leap day plus one year
+    assert_equal Time.new(2005, 2, 28, 15, 15, 10, "-08:00"), Time.new(2004, 2, 29, 15, 15, 10, "-08:00").advance(years: 1) # leap day plus one year
     assert_equal Time.new(2005, 2, 28, 20, 15, 10, "-08:00"), Time.new(2005, 2, 28, 15, 15, 10, "-08:00").advance(hours: 5)
     assert_equal Time.new(2005, 2, 28, 15, 22, 10, "-08:00"), Time.new(2005, 2, 28, 15, 15, 10, "-08:00").advance(minutes: 7)
     assert_equal Time.new(2005, 2, 28, 15, 15, 19, "-08:00"), Time.new(2005, 2, 28, 15, 15, 10, "-08:00").advance(seconds: 9)
@@ -664,10 +660,6 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
     end
   end
 
-  def test_last_month_on_31st
-    assert_equal Time.local(2004, 2, 29), Time.local(2004, 3, 31).last_month
-  end
-
   def test_xmlschema_is_available
     assert_nothing_raised { Time.now.xmlschema }
   end
@@ -745,7 +737,7 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_acts_like_time
-    assert Time.new.acts_like_time?
+    assert_predicate Time.new, :acts_like_time?
   end
 
   def test_formatted_offset_with_utc
@@ -764,26 +756,26 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_compare_with_time
-    assert_equal  1, Time.utc(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59, 999)
-    assert_equal  0, Time.utc(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0)
+    assert_equal 1, Time.utc(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59, 999)
+    assert_equal 0, Time.utc(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0)
     assert_equal(-1, Time.utc(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0, 001))
   end
 
   def test_compare_with_datetime
-    assert_equal  1, Time.utc(2000) <=> DateTime.civil(1999, 12, 31, 23, 59, 59)
-    assert_equal  0, Time.utc(2000) <=> DateTime.civil(2000, 1, 1, 0, 0, 0)
+    assert_equal 1, Time.utc(2000) <=> DateTime.civil(1999, 12, 31, 23, 59, 59)
+    assert_equal 0, Time.utc(2000) <=> DateTime.civil(2000, 1, 1, 0, 0, 0)
     assert_equal(-1, Time.utc(2000) <=> DateTime.civil(2000, 1, 1, 0, 0, 1))
   end
 
   def test_compare_with_time_with_zone
-    assert_equal  1, Time.utc(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(1999, 12, 31, 23, 59, 59), ActiveSupport::TimeZone["UTC"])
-    assert_equal  0, Time.utc(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 0), ActiveSupport::TimeZone["UTC"])
+    assert_equal 1, Time.utc(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(1999, 12, 31, 23, 59, 59), ActiveSupport::TimeZone["UTC"])
+    assert_equal 0, Time.utc(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 0), ActiveSupport::TimeZone["UTC"])
     assert_equal(-1, Time.utc(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 1), ActiveSupport::TimeZone["UTC"]))
   end
 
   def test_compare_with_string
-    assert_equal   1, Time.utc(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59, 999).to_s
-    assert_equal   0, Time.utc(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0).to_s
+    assert_equal 1, Time.utc(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59, 999).to_s
+    assert_equal 0, Time.utc(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0).to_s
     assert_equal(-1, Time.utc(2000) <=> Time.utc(2000, 1, 1, 0, 0, 1, 0).to_s)
     assert_nil Time.utc(2000) <=> "Invalid as Time"
   end
@@ -871,11 +863,11 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_minus_with_time_with_zone
-    assert_equal  86_400.0, Time.utc(2000, 1, 2) - ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1), ActiveSupport::TimeZone["UTC"])
+    assert_equal 86_400.0, Time.utc(2000, 1, 2) - ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1), ActiveSupport::TimeZone["UTC"])
   end
 
   def test_minus_with_datetime
-    assert_equal  86_400.0, Time.utc(2000, 1, 2) - DateTime.civil(2000, 1, 1)
+    assert_equal 86_400.0, Time.utc(2000, 1, 2) - DateTime.civil(2000, 1, 1)
   end
 
   def test_time_created_with_local_constructor_cannot_represent_times_during_hour_skipped_by_dst
@@ -883,7 +875,7 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
       # On Apr 2 2006 at 2:00AM in US, clocks were moved forward to 3:00AM.
       # Therefore, 2AM EST doesn't exist for this date; Time.local fails over to 3:00AM EDT
       assert_equal Time.local(2006, 4, 2, 3), Time.local(2006, 4, 2, 2)
-      assert Time.local(2006, 4, 2, 2).dst?
+      assert_predicate Time.local(2006, 4, 2, 2), :dst?
     end
   end
 
diff --git a/activesupport/test/core_ext/time_with_zone_test.rb b/activesupport/test/core_ext/time_with_zone_test.rb
index 0f80a24758..e650209268 100644
--- a/activesupport/test/core_ext/time_with_zone_test.rb
+++ b/activesupport/test/core_ext/time_with_zone_test.rb
@@ -3,7 +3,6 @@
 require "abstract_unit"
 require "active_support/time"
 require "time_zone_test_helpers"
-require "active_support/core_ext/string/strip"
 require "yaml"
 
 class TimeWithZoneTest < ActiveSupport::TestCase
@@ -50,6 +49,12 @@ class TimeWithZoneTest < ActiveSupport::TestCase
     assert_raise(ArgumentError) { @twz.in_time_zone(Object.new) }
   end
 
+  def test_in_time_zone_with_ambiguous_time
+    with_env_tz "Europe/Moscow" do
+      assert_equal Time.utc(2014, 10, 25, 22, 0, 0), Time.local(2014, 10, 26, 1, 0, 0).in_time_zone("Moscow")
+    end
+  end
+
   def test_localtime
     assert_equal @twz.localtime, @twz.utc.getlocal
     assert_instance_of Time, @twz.localtime
@@ -78,7 +83,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
 
   def test_formatted_offset
     assert_equal "-05:00", @twz.formatted_offset
-    assert_equal "-04:00", ActiveSupport::TimeWithZone.new(Time.utc(2000, 6), @time_zone).formatted_offset #dst
+    assert_equal "-04:00", ActiveSupport::TimeWithZone.new(Time.utc(2000, 6), @time_zone).formatted_offset # dst
   end
 
   def test_dst?
@@ -88,7 +93,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
 
   def test_zone
     assert_equal "EST", @twz.zone
-    assert_equal "EDT", ActiveSupport::TimeWithZone.new(Time.utc(2000, 6), @time_zone).zone #dst
+    assert_equal "EDT", ActiveSupport::TimeWithZone.new(Time.utc(2000, 6), @time_zone).zone # dst
   end
 
   def test_nsec
@@ -157,7 +162,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_to_yaml
-    yaml = <<-EOF.strip_heredoc
+    yaml = <<~EOF
       --- !ruby/object:ActiveSupport::TimeWithZone
       utc: 2000-01-01 00:00:00.000000000 Z
       zone: !ruby/object:ActiveSupport::TimeZone
@@ -169,7 +174,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_ruby_to_yaml
-    yaml = <<-EOF.strip_heredoc
+    yaml = <<~EOF
       ---
       twz: !ruby/object:ActiveSupport::TimeWithZone
         utc: 2000-01-01 00:00:00.000000000 Z
@@ -182,7 +187,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_yaml_load
-    yaml = <<-EOF.strip_heredoc
+    yaml = <<~EOF
       --- !ruby/object:ActiveSupport::TimeWithZone
       utc: 2000-01-01 00:00:00.000000000 Z
       zone: !ruby/object:ActiveSupport::TimeZone
@@ -194,7 +199,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_ruby_yaml_load
-    yaml = <<-EOF.strip_heredoc
+    yaml = <<~EOF
       ---
       twz: !ruby/object:ActiveSupport::TimeWithZone
         utc: 2000-01-01 00:00:00.000000000 Z
@@ -215,20 +220,20 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_compare_with_time
-    assert_equal  1, @twz <=> Time.utc(1999, 12, 31, 23, 59, 59)
-    assert_equal  0, @twz <=> Time.utc(2000, 1, 1, 0, 0, 0)
+    assert_equal 1, @twz <=> Time.utc(1999, 12, 31, 23, 59, 59)
+    assert_equal 0, @twz <=> Time.utc(2000, 1, 1, 0, 0, 0)
     assert_equal(-1, @twz <=> Time.utc(2000, 1, 1, 0, 0, 1))
   end
 
   def test_compare_with_datetime
-    assert_equal  1, @twz <=> DateTime.civil(1999, 12, 31, 23, 59, 59)
-    assert_equal  0, @twz <=> DateTime.civil(2000, 1, 1, 0, 0, 0)
+    assert_equal 1, @twz <=> DateTime.civil(1999, 12, 31, 23, 59, 59)
+    assert_equal 0, @twz <=> DateTime.civil(2000, 1, 1, 0, 0, 0)
     assert_equal(-1, @twz <=> DateTime.civil(2000, 1, 1, 0, 0, 1))
   end
 
   def test_compare_with_time_with_zone
-    assert_equal  1, @twz <=> ActiveSupport::TimeWithZone.new(Time.utc(1999, 12, 31, 23, 59, 59), ActiveSupport::TimeZone["UTC"])
-    assert_equal  0, @twz <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 0), ActiveSupport::TimeZone["UTC"])
+    assert_equal 1, @twz <=> ActiveSupport::TimeWithZone.new(Time.utc(1999, 12, 31, 23, 59, 59), ActiveSupport::TimeZone["UTC"])
+    assert_equal 0, @twz <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 0), ActiveSupport::TimeZone["UTC"])
     assert_equal(-1, @twz <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 1), ActiveSupport::TimeZone["UTC"]))
   end
 
@@ -284,6 +289,20 @@ class TimeWithZoneTest < ActiveSupport::TestCase
     end
   end
 
+  def test_before
+    twz = ActiveSupport::TimeWithZone.new(Time.utc(2017, 3, 6, 12, 0, 0), @time_zone)
+    assert_equal false, twz.before?(ActiveSupport::TimeWithZone.new(Time.utc(2017, 3, 6, 11, 59, 59), @time_zone))
+    assert_equal false, twz.before?(ActiveSupport::TimeWithZone.new(Time.utc(2017, 3, 6, 12, 0, 0), @time_zone))
+    assert_equal true, twz.before?(ActiveSupport::TimeWithZone.new(Time.utc(2017, 3, 6, 12, 00, 1), @time_zone))
+  end
+
+  def test_after
+    twz = ActiveSupport::TimeWithZone.new(Time.utc(2017, 3, 6, 12, 0, 0), @time_zone)
+    assert_equal true, twz.after?(ActiveSupport::TimeWithZone.new(Time.utc(2017, 3, 6, 11, 59, 59), @time_zone))
+    assert_equal false, twz.after?(ActiveSupport::TimeWithZone.new(Time.utc(2017, 3, 6, 12, 0, 0), @time_zone))
+    assert_equal false, twz.after?(ActiveSupport::TimeWithZone.new(Time.utc(2017, 3, 6, 12, 00, 1), @time_zone))
+  end
+
   def test_eql?
     assert_equal true, @twz.eql?(@twz.dup)
     assert_equal true, @twz.eql?(Time.utc(2000))
@@ -301,13 +320,13 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_plus_with_integer
-    assert_equal Time.utc(1999, 12, 31, 19, 0 , 5), (@twz + 5).time
+    assert_equal Time.utc(1999, 12, 31, 19, 0, 5), (@twz + 5).time
   end
 
   def test_plus_with_integer_when_self_wraps_datetime
     datetime = DateTime.civil(2000, 1, 1, 0)
     twz = ActiveSupport::TimeWithZone.new(datetime, @time_zone)
-    assert_equal DateTime.civil(1999, 12, 31, 19, 0 , 5), (twz + 5).time
+    assert_equal DateTime.civil(1999, 12, 31, 19, 0, 5), (twz + 5).time
   end
 
   def test_plus_when_crossing_time_class_limit
@@ -316,31 +335,31 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_plus_with_duration
-    assert_equal Time.utc(2000, 1, 5, 19, 0 , 0), (@twz + 5.days).time
+    assert_equal Time.utc(2000, 1, 5, 19, 0, 0), (@twz + 5.days).time
   end
 
   def test_minus_with_integer
-    assert_equal Time.utc(1999, 12, 31, 18, 59 , 55), (@twz - 5).time
+    assert_equal Time.utc(1999, 12, 31, 18, 59, 55), (@twz - 5).time
   end
 
   def test_minus_with_integer_when_self_wraps_datetime
     datetime = DateTime.civil(2000, 1, 1, 0)
     twz = ActiveSupport::TimeWithZone.new(datetime, @time_zone)
-    assert_equal DateTime.civil(1999, 12, 31, 18, 59 , 55), (twz - 5).time
+    assert_equal DateTime.civil(1999, 12, 31, 18, 59, 55), (twz - 5).time
   end
 
   def test_minus_with_duration
-    assert_equal Time.utc(1999, 12, 26, 19, 0 , 0), (@twz - 5.days).time
+    assert_equal Time.utc(1999, 12, 26, 19, 0, 0), (@twz - 5.days).time
   end
 
   def test_minus_with_time
-    assert_equal  86_400.0,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - Time.utc(2000, 1, 1)
-    assert_equal  86_400.0,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2), ActiveSupport::TimeZone["Hawaii"]) - Time.utc(2000, 1, 1)
+    assert_equal 86_400.0,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - Time.utc(2000, 1, 1)
+    assert_equal 86_400.0,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2), ActiveSupport::TimeZone["Hawaii"]) - Time.utc(2000, 1, 1)
   end
 
   def test_minus_with_time_precision
-    assert_equal  86_399.999999998,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2, 23, 59, 59, Rational(999999999, 1000)), ActiveSupport::TimeZone["UTC"]) - Time.utc(2000, 1, 2, 0, 0, 0, Rational(1, 1000))
-    assert_equal  86_399.999999998,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2, 23, 59, 59, Rational(999999999, 1000)), ActiveSupport::TimeZone["Hawaii"]) - Time.utc(2000, 1, 2, 0, 0, 0, Rational(1, 1000))
+    assert_equal 86_399.999999998,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2, 23, 59, 59, Rational(999999999, 1000)), ActiveSupport::TimeZone["UTC"]) - Time.utc(2000, 1, 2, 0, 0, 0, Rational(1, 1000))
+    assert_equal 86_399.999999998,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2, 23, 59, 59, Rational(999999999, 1000)), ActiveSupport::TimeZone["Hawaii"]) - Time.utc(2000, 1, 2, 0, 0, 0, Rational(1, 1000))
   end
 
   def test_minus_with_time_with_zone
@@ -352,20 +371,20 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   def test_minus_with_time_with_zone_precision
     twz1 = ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 0, Rational(1, 1000)), ActiveSupport::TimeZone["UTC"])
     twz2 = ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 23, 59, 59, Rational(999999999, 1000)), ActiveSupport::TimeZone["UTC"])
-    assert_equal  86_399.999999998,  twz2 - twz1
+    assert_equal 86_399.999999998,  twz2 - twz1
   end
 
   def test_minus_with_datetime
-    assert_equal  86_400.0,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - DateTime.civil(2000, 1, 1)
+    assert_equal 86_400.0,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - DateTime.civil(2000, 1, 1)
   end
 
   def test_minus_with_datetime_precision
-    assert_equal  86_399.999999999,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 23, 59, 59, Rational(999999999, 1000)), ActiveSupport::TimeZone["UTC"]) - DateTime.civil(2000, 1, 1)
+    assert_equal 86_399.999999999,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 23, 59, 59, Rational(999999999, 1000)), ActiveSupport::TimeZone["UTC"]) - DateTime.civil(2000, 1, 1)
   end
 
   def test_minus_with_wrapped_datetime
-    assert_equal  86_400.0,  ActiveSupport::TimeWithZone.new(DateTime.civil(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - Time.utc(2000, 1, 1)
-    assert_equal  86_400.0,  ActiveSupport::TimeWithZone.new(DateTime.civil(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - DateTime.civil(2000, 1, 1)
+    assert_equal 86_400.0,  ActiveSupport::TimeWithZone.new(DateTime.civil(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - Time.utc(2000, 1, 1)
+    assert_equal 86_400.0,  ActiveSupport::TimeWithZone.new(DateTime.civil(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - DateTime.civil(2000, 1, 1)
   end
 
   def test_plus_and_minus_enforce_spring_dst_rules
@@ -475,7 +494,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_acts_like_time
-    assert @twz.acts_like_time?
+    assert_predicate @twz, :acts_like_time?
     assert @twz.acts_like?(:time)
     assert ActiveSupport::TimeWithZone.new(DateTime.civil(2000), @time_zone).acts_like?(:time)
   end
@@ -486,7 +505,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_blank?
-    assert_not @twz.blank?
+    assert_not_predicate @twz, :blank?
   end
 
   def test_is_a
@@ -501,17 +520,17 @@ class TimeWithZoneTest < ActiveSupport::TestCase
 
   def test_method_missing_with_time_return_value
     assert_instance_of ActiveSupport::TimeWithZone, @twz.months_since(1)
-    assert_equal Time.utc(2000, 1, 31, 19, 0 , 0), @twz.months_since(1).time
+    assert_equal Time.utc(2000, 1, 31, 19, 0, 0), @twz.months_since(1).time
   end
 
   def test_marshal_dump_and_load
     marshal_str = Marshal.dump(@twz)
     mtime = Marshal.load(marshal_str)
     assert_equal Time.utc(2000, 1, 1, 0), mtime.utc
-    assert mtime.utc.utc?
+    assert_predicate mtime.utc, :utc?
     assert_equal ActiveSupport::TimeZone["Eastern Time (US & Canada)"], mtime.time_zone
     assert_equal Time.utc(1999, 12, 31, 19), mtime.time
-    assert mtime.time.utc?
+    assert_predicate mtime.time, :utc?
     assert_equal @twz.inspect, mtime.inspect
   end
 
@@ -520,16 +539,16 @@ class TimeWithZoneTest < ActiveSupport::TestCase
     marshal_str = Marshal.dump(twz)
     mtime = Marshal.load(marshal_str)
     assert_equal Time.utc(2000, 1, 1, 0), mtime.utc
-    assert mtime.utc.utc?
+    assert_predicate mtime.utc, :utc?
     assert_equal "America/New_York", mtime.time_zone.name
     assert_equal Time.utc(1999, 12, 31, 19), mtime.time
-    assert mtime.time.utc?
+    assert_predicate mtime.time, :utc?
     assert_equal @twz.inspect, mtime.inspect
   end
 
   def test_freeze
     @twz.freeze
-    assert @twz.frozen?
+    assert_predicate @twz, :frozen?
   end
 
   def test_freeze_preloads_instance_variables
@@ -1029,8 +1048,8 @@ class TimeWithZoneMethodsForTimeAndDateTimeTest < ActiveSupport::TestCase
 
   def test_nil_time_zone
     Time.use_zone nil do
-      assert !@t.in_time_zone.respond_to?(:period), "no period method"
-      assert !@dt.in_time_zone.respond_to?(:period), "no period method"
+      assert_not_respond_to @t.in_time_zone, :period, "no period method"
+      assert_not_respond_to @dt.in_time_zone, :period, "no period method"
     end
   end
 
@@ -1218,7 +1237,7 @@ class TimeWithZoneMethodsForDate < ActiveSupport::TestCase
 
   def test_nil_time_zone
     with_tz_default nil do
-      assert !@d.in_time_zone.respond_to?(:period), "no period method"
+      assert_not_respond_to @d.in_time_zone, :period, "no period method"
     end
   end
 
@@ -1267,9 +1286,9 @@ class TimeWithZoneMethodsForString < ActiveSupport::TestCase
 
   def test_nil_time_zone
     with_tz_default nil do
-      assert !@s.in_time_zone.respond_to?(:period), "no period method"
-      assert !@u.in_time_zone.respond_to?(:period), "no period method"
-      assert !@z.in_time_zone.respond_to?(:period), "no period method"
+      assert_not_respond_to @s.in_time_zone, :period, "no period method"
+      assert_not_respond_to @u.in_time_zone, :period, "no period method"
+      assert_not_respond_to @z.in_time_zone, :period, "no period method"
     end
   end
 
@@ -1301,4 +1320,10 @@ class TimeWithZoneMethodsForString < ActiveSupport::TestCase
     assert_raise(ArgumentError) { @u.in_time_zone(Object.new) }
     assert_raise(ArgumentError) { @z.in_time_zone(Object.new) }
   end
+
+  def test_in_time_zone_with_ambiguous_time
+    with_tz_default "Moscow" do
+      assert_equal Time.utc(2014, 10, 25, 22, 0, 0), "2014-10-26 01:00:00".in_time_zone
+    end
+  end
 end
diff --git a/activesupport/test/core_ext/uri_ext_test.rb b/activesupport/test/core_ext/uri_ext_test.rb
index 8816b0d392..c0686bc720 100644
--- a/activesupport/test/core_ext/uri_ext_test.rb
+++ b/activesupport/test/core_ext/uri_ext_test.rb
@@ -9,6 +9,6 @@ class URIExtTest < ActiveSupport::TestCase
     str = "\xE6\x97\xA5\xE6\x9C\xAC\xE8\xAA\x9E" # Ni-ho-nn-go in UTF-8, means Japanese.
 
     parser = URI.parser
-    assert_equal str, parser.unescape(parser.escape(str))
+    assert_equal str + str, parser.unescape(str + parser.escape(str).encode(Encoding::UTF_8))
   end
 end
diff --git a/activesupport/test/dependencies_test.rb b/activesupport/test/dependencies_test.rb
index d636da46d2..84cb64a7c2 100644
--- a/activesupport/test/dependencies_test.rb
+++ b/activesupport/test/dependencies_test.rb
@@ -185,6 +185,61 @@ class DependenciesTest < ActiveSupport::TestCase
     end
   end
 
+  # Regression see https://github.com/rails/rails/issues/31694
+  def test_included_constant_that_changes_to_have_exception_then_back_does_not_loop_forever
+    # This constant references a nested constant whose namespace will be auto-generated
+    parent_constant = <<-RUBY
+      class ConstantReloadError
+        AnotherConstant::ReloadError
+      end
+    RUBY
+
+    # This constant's namespace will be auto-generated,
+    # also, we'll edit it to contain an error at load-time
+    child_constant = <<-RUBY
+      class AnotherConstant::ReloadError
+        # no_such_method_as_this
+      end
+    RUBY
+
+    # Create a version which contains an error during loading
+    child_constant_with_error = child_constant.sub("# no_such_method_as_this", "no_such_method_as_this")
+
+    fixtures_path = File.join(__dir__, "autoloading_fixtures")
+    Dir.mktmpdir(nil, fixtures_path) do |tmpdir|
+      # Set up the file structure where constants will be loaded from
+      child_constant_path = "#{tmpdir}/another_constant/reload_error.rb"
+      File.write("#{tmpdir}/constant_reload_error.rb", parent_constant)
+      Dir.mkdir("#{tmpdir}/another_constant")
+      File.write(child_constant_path, child_constant_with_error)
+
+      tmpdir_name = tmpdir.split("/").last
+      with_loading("autoloading_fixtures/#{tmpdir_name}") do
+        # Load the file, with the error:
+        assert_raises(NameError) {
+          ConstantReloadError
+        }
+
+        Timeout.timeout(0.1) do
+          # Remove the constant, as if Rails development middleware is reloading changed files:
+          ActiveSupport::Dependencies.remove_unloadable_constants!
+          assert_not defined?(AnotherConstant::ReloadError)
+        end
+
+        # Change the file, so that it is **correct** this time:
+        File.write(child_constant_path, child_constant)
+
+        # Again: Remove the constant, as if Rails development middleware is reloading changed files:
+        ActiveSupport::Dependencies.remove_unloadable_constants!
+        assert_not defined?(AnotherConstant::ReloadError)
+
+        # Now, reload the _fixed_ constant:
+        assert ConstantReloadError
+        assert AnotherConstant::ReloadError
+      end
+    end
+  end
+
   def test_module_loading
     with_autoloading_fixtures do
       assert_kind_of Module, A
@@ -480,9 +535,9 @@ class DependenciesTest < ActiveSupport::TestCase
 
   def test_qualified_const_defined_should_not_call_const_missing
     ModuleWithMissing.missing_count = 0
-    assert ! ActiveSupport::Dependencies.qualified_const_defined?("ModuleWithMissing::A")
+    assert_not ActiveSupport::Dependencies.qualified_const_defined?("ModuleWithMissing::A")
     assert_equal 0, ModuleWithMissing.missing_count
-    assert ! ActiveSupport::Dependencies.qualified_const_defined?("ModuleWithMissing::A::B")
+    assert_not ActiveSupport::Dependencies.qualified_const_defined?("ModuleWithMissing::A::B")
     assert_equal 0, ModuleWithMissing.missing_count
   end
 
@@ -492,13 +547,13 @@ class DependenciesTest < ActiveSupport::TestCase
 
   def test_autoloaded?
     with_autoloading_fixtures do
-      assert ! ActiveSupport::Dependencies.autoloaded?("ModuleFolder")
-      assert ! ActiveSupport::Dependencies.autoloaded?("ModuleFolder::NestedClass")
+      assert_not ActiveSupport::Dependencies.autoloaded?("ModuleFolder")
+      assert_not ActiveSupport::Dependencies.autoloaded?("ModuleFolder::NestedClass")
 
       assert ActiveSupport::Dependencies.autoloaded?(ModuleFolder)
 
       assert ActiveSupport::Dependencies.autoloaded?("ModuleFolder")
-      assert ! ActiveSupport::Dependencies.autoloaded?("ModuleFolder::NestedClass")
+      assert_not ActiveSupport::Dependencies.autoloaded?("ModuleFolder::NestedClass")
 
       assert ActiveSupport::Dependencies.autoloaded?(ModuleFolder::NestedClass)
 
@@ -509,11 +564,11 @@ class DependenciesTest < ActiveSupport::TestCase
       assert ActiveSupport::Dependencies.autoloaded?(:ModuleFolder)
 
       # Anonymous modules aren't autoloaded.
-      assert !ActiveSupport::Dependencies.autoloaded?(Module.new)
+      assert_not ActiveSupport::Dependencies.autoloaded?(Module.new)
 
       nil_name = Module.new
       def nil_name.name() nil end
-      assert !ActiveSupport::Dependencies.autoloaded?(nil_name)
+      assert_not ActiveSupport::Dependencies.autoloaded?(nil_name)
     end
   ensure
     remove_constants(:ModuleFolder)
@@ -700,7 +755,7 @@ class DependenciesTest < ActiveSupport::TestCase
     Object.const_set :EM, Class.new
     with_autoloading_fixtures do
       require_dependency "em"
-      assert ! ActiveSupport::Dependencies.autoloaded?(:EM), "EM shouldn't be marked autoloaded!"
+      assert_not ActiveSupport::Dependencies.autoloaded?(:EM), "EM shouldn't be marked autoloaded!"
       ActiveSupport::Dependencies.clear
     end
   ensure
@@ -723,11 +778,11 @@ class DependenciesTest < ActiveSupport::TestCase
       M.unloadable
 
       ActiveSupport::Dependencies.clear
-      assert ! defined?(M)
+      assert_not defined?(M)
 
       Object.const_set :M, Module.new
       ActiveSupport::Dependencies.clear
-      assert ! defined?(M), "Dependencies should unload unloadable constants each time"
+      assert_not defined?(M), "Dependencies should unload unloadable constants each time"
     end
   end
 
@@ -752,9 +807,9 @@ class DependenciesTest < ActiveSupport::TestCase
     Object.const_set :C, Class.new { def self.before_remove_const; end }
     C.unloadable
     assert_called(C, :before_remove_const, times: 1) do
-      assert C.respond_to?(:before_remove_const)
+      assert_respond_to C, :before_remove_const
       ActiveSupport::Dependencies.clear
-      assert !defined?(C)
+      assert_not defined?(C)
     end
   ensure
     remove_constants(:C)
@@ -925,10 +980,10 @@ class DependenciesTest < ActiveSupport::TestCase
 
   def test_autoload_doesnt_shadow_no_method_error_with_relative_constant
     with_autoloading_fixtures do
-      assert !defined?(::RaisesNoMethodError), "::RaisesNoMethodError is defined but it hasn't been referenced yet!"
+      assert_not defined?(::RaisesNoMethodError), "::RaisesNoMethodError is defined but it hasn't been referenced yet!"
       2.times do
         assert_raise(NoMethodError) { RaisesNoMethodError }
-        assert !defined?(::RaisesNoMethodError), "::RaisesNoMethodError is defined but it should have failed!"
+        assert_not defined?(::RaisesNoMethodError), "::RaisesNoMethodError is defined but it should have failed!"
       end
     end
   ensure
@@ -937,10 +992,10 @@ class DependenciesTest < ActiveSupport::TestCase
 
   def test_autoload_doesnt_shadow_no_method_error_with_absolute_constant
     with_autoloading_fixtures do
-      assert !defined?(::RaisesNoMethodError), "::RaisesNoMethodError is defined but it hasn't been referenced yet!"
+      assert_not defined?(::RaisesNoMethodError), "::RaisesNoMethodError is defined but it hasn't been referenced yet!"
       2.times do
         assert_raise(NoMethodError) { ::RaisesNoMethodError }
-        assert !defined?(::RaisesNoMethodError), "::RaisesNoMethodError is defined but it should have failed!"
+        assert_not defined?(::RaisesNoMethodError), "::RaisesNoMethodError is defined but it should have failed!"
       end
     end
   ensure
@@ -965,13 +1020,13 @@ class DependenciesTest < ActiveSupport::TestCase
           ::RaisesNameError::FooBarBaz.object_id
         end
         assert_equal "uninitialized constant RaisesNameError::FooBarBaz", e.message
-        assert !defined?(::RaisesNameError), "::RaisesNameError is defined but it should have failed!"
+        assert_not defined?(::RaisesNameError), "::RaisesNameError is defined but it should have failed!"
       end
 
-      assert !defined?(::RaisesNameError)
+      assert_not defined?(::RaisesNameError)
       2.times do
         assert_raise(NameError) { ::RaisesNameError }
-        assert !defined?(::RaisesNameError), "::RaisesNameError is defined but it should have failed!"
+        assert_not defined?(::RaisesNameError), "::RaisesNameError is defined but it should have failed!"
       end
     end
   ensure
diff --git a/activesupport/test/deprecation/method_wrappers_test.rb b/activesupport/test/deprecation/method_wrappers_test.rb
index 04e2325754..439e117c1d 100644
--- a/activesupport/test/deprecation/method_wrappers_test.rb
+++ b/activesupport/test/deprecation/method_wrappers_test.rb
@@ -8,6 +8,16 @@ class MethodWrappersTest < ActiveSupport::TestCase
     @klass = Class.new do
       def new_method; "abc" end
       alias_method :old_method, :new_method
+
+      protected
+
+        def new_protected_method; "abc" end
+        alias_method :old_protected_method, :new_protected_method
+
+      private
+
+        def new_private_method; "abc" end
+        alias_method :old_private_method, :new_private_method
     end
   end
 
@@ -33,4 +43,16 @@ class MethodWrappersTest < ActiveSupport::TestCase
 
     assert_deprecated(warning, deprecator) { assert_equal "abc", @klass.new.old_method }
   end
+
+  def test_deprecate_methods_protected_method
+    ActiveSupport::Deprecation.deprecate_methods(@klass, old_protected_method: :new_protected_method)
+
+    assert(@klass.protected_method_defined?(:old_protected_method))
+  end
+
+  def test_deprecate_methods_private_method
+    ActiveSupport::Deprecation.deprecate_methods(@klass, old_private_method: :new_private_method)
+
+    assert(@klass.private_method_defined?(:old_private_method))
+  end
 end
diff --git a/activesupport/test/deprecation/proxy_wrappers_test.rb b/activesupport/test/deprecation/proxy_wrappers_test.rb
index 2f866775f6..9e26052fb4 100644
--- a/activesupport/test/deprecation/proxy_wrappers_test.rb
+++ b/activesupport/test/deprecation/proxy_wrappers_test.rb
@@ -9,16 +9,16 @@ class ProxyWrappersTest < ActiveSupport::TestCase
 
   def test_deprecated_object_proxy_doesnt_wrap_falsy_objects
     proxy = ActiveSupport::Deprecation::DeprecatedObjectProxy.new(nil, "message")
-    assert !proxy
+    assert_not proxy
   end
 
   def test_deprecated_instance_variable_proxy_doesnt_wrap_falsy_objects
     proxy = ActiveSupport::Deprecation::DeprecatedInstanceVariableProxy.new(nil, :waffles)
-    assert !proxy
+    assert_not proxy
   end
 
   def test_deprecated_constant_proxy_doesnt_wrap_falsy_objects
     proxy = ActiveSupport::Deprecation::DeprecatedConstantProxy.new(Waffles, NewWaffles)
-    assert !proxy
+    assert_not proxy
   end
 end
diff --git a/activesupport/test/deprecation_test.rb b/activesupport/test/deprecation_test.rb
index f2267a822f..105153584d 100644
--- a/activesupport/test/deprecation_test.rb
+++ b/activesupport/test/deprecation_test.rb
@@ -158,7 +158,7 @@ class DeprecationTest < ActiveSupport::TestCase
     stderr_output = capture(:stderr) {
       assert_nil behavior.call("Some error!", ["call stack!"], "horizon", "gem")
     }
-    assert stderr_output.empty?
+    assert_empty stderr_output
   end
 
   def test_default_notify_behavior
@@ -182,6 +182,14 @@ class DeprecationTest < ActiveSupport::TestCase
     end
   end
 
+  def test_default_invalid_behavior
+    e = assert_raises(ArgumentError) do
+      ActiveSupport::Deprecation.behavior = :invalid
+    end
+
+    assert_equal ":invalid is not a valid deprecation behavior.", e.message
+  end
+
   def test_deprecated_instance_variable_proxy
     assert_not_deprecated { @dtc.request.size }
 
diff --git a/activesupport/test/descendants_tracker_test_cases.rb b/activesupport/test/descendants_tracker_test_cases.rb
index 1f8b4a8605..2c94c3c56c 100644
--- a/activesupport/test/descendants_tracker_test_cases.rb
+++ b/activesupport/test/descendants_tracker_test_cases.rb
@@ -37,7 +37,7 @@ module DescendantsTrackerTestCases
     mark_as_autoloaded(*ALL) do
       ActiveSupport::DescendantsTracker.clear
       ALL.each do |k|
-        assert ActiveSupport::DescendantsTracker.descendants(k).empty?
+        assert_empty ActiveSupport::DescendantsTracker.descendants(k)
       end
     end
   end
diff --git a/activesupport/test/descendants_tracker_with_autoloading_test.rb b/activesupport/test/descendants_tracker_with_autoloading_test.rb
index 7c396b7c8e..d4fedb5a67 100644
--- a/activesupport/test/descendants_tracker_with_autoloading_test.rb
+++ b/activesupport/test/descendants_tracker_with_autoloading_test.rb
@@ -12,7 +12,7 @@ class DescendantsTrackerWithAutoloadingTest < ActiveSupport::TestCase
     mark_as_autoloaded(*ALL) do
       ActiveSupport::DescendantsTracker.clear
       ALL.each do |k|
-        assert ActiveSupport::DescendantsTracker.descendants(k).empty?
+        assert_empty ActiveSupport::DescendantsTracker.descendants(k)
       end
     end
   end
diff --git a/activesupport/test/descendants_tracker_without_autoloading_test.rb b/activesupport/test/descendants_tracker_without_autoloading_test.rb
index f5c6a3045d..c65f69cba3 100644
--- a/activesupport/test/descendants_tracker_without_autoloading_test.rb
+++ b/activesupport/test/descendants_tracker_without_autoloading_test.rb
@@ -13,7 +13,7 @@ class DescendantsTrackerWithoutAutoloadingTest < ActiveSupport::TestCase
       parent_instance = Parent.new
       parent_instance.singleton_class.descendants
       ActiveSupport::DescendantsTracker.clear
-      assert !ActiveSupport::DescendantsTracker.class_variable_get(:@@direct_descendants).key?(parent_instance.singleton_class)
+      assert_not ActiveSupport::DescendantsTracker.class_variable_get(:@@direct_descendants).key?(parent_instance.singleton_class)
     end
   end
 end
diff --git a/activesupport/test/digest_test.rb b/activesupport/test/digest_test.rb
new file mode 100644
index 0000000000..83ff2a8d83
--- /dev/null
+++ b/activesupport/test/digest_test.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "openssl"
+
+class DigestTest < ActiveSupport::TestCase
+  class InvalidDigest; end
+  def test_with_default_hash_digest_class
+    assert_equal ::Digest::MD5.hexdigest("hello friend"), ActiveSupport::Digest.hexdigest("hello friend")
+  end
+
+  def test_with_custom_hash_digest_class
+    original_hash_digest_class = ActiveSupport::Digest.hash_digest_class
+
+    ActiveSupport::Digest.hash_digest_class = ::Digest::SHA1
+    digest = ActiveSupport::Digest.hexdigest("hello friend")
+
+    assert_equal 32, digest.length
+    assert_equal ::Digest::SHA1.hexdigest("hello friend")[0...32], digest
+  ensure
+    ActiveSupport::Digest.hash_digest_class = original_hash_digest_class
+  end
+
+  def test_should_raise_argument_error_if_custom_digest_is_missing_hexdigest_method
+    assert_raises(ArgumentError) { ActiveSupport::Digest.hash_digest_class = InvalidDigest }
+  end
+end
diff --git a/activesupport/test/encrypted_configuration_test.rb b/activesupport/test/encrypted_configuration_test.rb
new file mode 100644
index 0000000000..93ccf457de
--- /dev/null
+++ b/activesupport/test/encrypted_configuration_test.rb
@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "active_support/encrypted_configuration"
+
+class EncryptedConfigurationTest < ActiveSupport::TestCase
+  setup do
+    @credentials_config_path = File.join(Dir.tmpdir, "credentials.yml.enc")
+
+    @credentials_key_path = File.join(Dir.tmpdir, "master.key")
+    File.write(@credentials_key_path, ActiveSupport::EncryptedConfiguration.generate_key)
+
+    @credentials = ActiveSupport::EncryptedConfiguration.new(
+      config_path: @credentials_config_path, key_path: @credentials_key_path,
+      env_key: "RAILS_MASTER_KEY", raise_if_missing_key: true
+    )
+  end
+
+  teardown do
+    FileUtils.rm_rf @credentials_config_path
+    FileUtils.rm_rf @credentials_key_path
+  end
+
+  test "reading configuration by env key" do
+    FileUtils.rm_rf @credentials_key_path
+
+    begin
+      ENV["RAILS_MASTER_KEY"] = ActiveSupport::EncryptedConfiguration.generate_key
+      @credentials.write({ something: { good: true, bad: false } }.to_yaml)
+
+      assert @credentials[:something][:good]
+      assert_not @credentials.dig(:something, :bad)
+      assert_nil @credentials.fetch(:nothing, nil)
+    ensure
+      ENV["RAILS_MASTER_KEY"] = nil
+    end
+  end
+
+  test "reading configuration by key file" do
+    @credentials.write({ something: { good: true } }.to_yaml)
+
+    assert @credentials.something[:good]
+  end
+
+  test "change configuration by key file" do
+    @credentials.write({ something: { good: true } }.to_yaml)
+    @credentials.change do |config_file|
+      config = YAML.load(config_file.read)
+      config_file.write config.merge(new: "things").to_yaml
+    end
+
+    assert @credentials.something[:good]
+    assert_equal "things", @credentials[:new]
+  end
+
+  test "raise error when writing an invalid format value" do
+    assert_raise(Psych::SyntaxError) do
+      @credentials.change do |config_file|
+        config_file.write "login: *login\n  username: dummy"
+      end
+    end
+  end
+
+  test "raises key error when accessing config via bang method" do
+    assert_raise(KeyError) { @credentials.something! }
+  end
+end
diff --git a/activesupport/test/encrypted_file_test.rb b/activesupport/test/encrypted_file_test.rb
new file mode 100644
index 0000000000..ba3bbef903
--- /dev/null
+++ b/activesupport/test/encrypted_file_test.rb
@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "active_support/encrypted_file"
+
+class EncryptedFileTest < ActiveSupport::TestCase
+  setup do
+    @content = "One little fox jumped over the hedge"
+
+    @content_path = File.join(Dir.tmpdir, "content.txt.enc")
+
+    @key_path = File.join(Dir.tmpdir, "content.txt.key")
+    File.write(@key_path, ActiveSupport::EncryptedFile.generate_key)
+
+    @encrypted_file = ActiveSupport::EncryptedFile.new(
+      content_path: @content_path, key_path: @key_path, env_key: "CONTENT_KEY", raise_if_missing_key: true
+    )
+  end
+
+  teardown do
+    FileUtils.rm_rf @content_path
+    FileUtils.rm_rf @key_path
+  end
+
+  test "reading content by env key" do
+    FileUtils.rm_rf @key_path
+
+    begin
+      ENV["CONTENT_KEY"] = ActiveSupport::EncryptedFile.generate_key
+      @encrypted_file.write @content
+
+      assert_equal @content, @encrypted_file.read
+    ensure
+      ENV["CONTENT_KEY"] = nil
+    end
+  end
+
+  test "reading content by key file" do
+    @encrypted_file.write(@content)
+    assert_equal @content, @encrypted_file.read
+  end
+
+  test "change content by key file" do
+    @encrypted_file.write(@content)
+    @encrypted_file.change do |file|
+      file.write(file.read + " and went by the lake")
+    end
+
+    assert_equal "#{@content} and went by the lake", @encrypted_file.read
+  end
+
+  test "raise MissingKeyError when key is missing" do
+    assert_raise(ActiveSupport::EncryptedFile::MissingKeyError) do
+      ActiveSupport::EncryptedFile.new(
+        content_path: @content_path, key_path: "", env_key: "", raise_if_missing_key: true
+      ).read
+    end
+  end
+end
diff --git a/activesupport/test/evented_file_update_checker_test.rb b/activesupport/test/evented_file_update_checker_test.rb
index 9b560f7f42..d3af0dbef3 100644
--- a/activesupport/test/evented_file_update_checker_test.rb
+++ b/activesupport/test/evented_file_update_checker_test.rb
@@ -39,18 +39,18 @@ class EventedFileUpdateCheckerTest < ActiveSupport::TestCase
     FileUtils.touch(tmpfiles)
 
     checker = new_checker(tmpfiles) {}
-    assert !checker.updated?
+    assert_not_predicate checker, :updated?
 
     # Pipes used for flow control across fork.
     boot_reader,  boot_writer  = IO.pipe
     touch_reader, touch_writer = IO.pipe
 
     pid = fork do
-      assert checker.updated?
+      assert_predicate checker, :updated?
 
       # Clear previous check value.
       checker.execute
-      assert !checker.updated?
+      assert_not_predicate checker, :updated?
 
       # Fork is booted, ready for file to be touched
       # notify parent process.
@@ -60,7 +60,7 @@ class EventedFileUpdateCheckerTest < ActiveSupport::TestCase
       # has been touched.
       IO.select([touch_reader])
 
-      assert checker.updated?
+      assert_predicate checker, :updated?
     end
 
     assert pid
@@ -72,7 +72,7 @@ class EventedFileUpdateCheckerTest < ActiveSupport::TestCase
     # Notify fork that files have been touched.
     touch_writer.write("touched")
 
-    assert checker.updated?
+    assert_predicate checker, :updated?
 
     Process.wait(pid)
   end
diff --git a/activesupport/test/file_update_checker_shared_tests.rb b/activesupport/test/file_update_checker_shared_tests.rb
index f8266dac06..72683816b3 100644
--- a/activesupport/test/file_update_checker_shared_tests.rb
+++ b/activesupport/test/file_update_checker_shared_tests.rb
@@ -30,7 +30,7 @@ module FileUpdateCheckerSharedTests
 
     checker = new_checker { i += 1 }
 
-    assert !checker.execute_if_updated
+    assert_not checker.execute_if_updated
     assert_equal 0, i
   end
 
@@ -41,7 +41,7 @@ module FileUpdateCheckerSharedTests
 
     checker = new_checker(tmpfiles) { i += 1 }
 
-    assert !checker.execute_if_updated
+    assert_not checker.execute_if_updated
     assert_equal 0, i
   end
 
@@ -89,12 +89,12 @@ module FileUpdateCheckerSharedTests
     i = 0
 
     checker = new_checker(tmpfiles) { i += 1 }
-    assert !checker.updated?
+    assert_not_predicate checker, :updated?
 
     touch(tmpfiles)
     wait
 
-    assert checker.updated?
+    assert_predicate checker, :updated?
   end
 
   test "updated should become true when watched files are modified" do
@@ -103,12 +103,12 @@ module FileUpdateCheckerSharedTests
     FileUtils.touch(tmpfiles)
 
     checker = new_checker(tmpfiles) { i += 1 }
-    assert !checker.updated?
+    assert_not_predicate checker, :updated?
 
     touch(tmpfiles)
     wait
 
-    assert checker.updated?
+    assert_predicate checker, :updated?
   end
 
   test "updated should become true when watched files are deleted" do
@@ -117,12 +117,12 @@ module FileUpdateCheckerSharedTests
     FileUtils.touch(tmpfiles)
 
     checker = new_checker(tmpfiles) { i += 1 }
-    assert !checker.updated?
+    assert_not_predicate checker, :updated?
 
     rm_f(tmpfiles)
     wait
 
-    assert checker.updated?
+    assert_predicate checker, :updated?
   end
 
   test "should be robust to handle files with wrong modified time" do
@@ -164,14 +164,14 @@ module FileUpdateCheckerSharedTests
     i = 0
 
     checker = new_checker(tmpfiles) { i += 1 }
-    assert !checker.updated?
+    assert_not_predicate checker, :updated?
 
     touch(tmpfiles)
     wait
 
-    assert checker.updated?
+    assert_predicate checker, :updated?
     checker.execute
-    assert !checker.updated?
+    assert_not_predicate checker, :updated?
   end
 
   test "should execute the block if files change in a watched directory one extension" do
@@ -212,7 +212,7 @@ module FileUpdateCheckerSharedTests
     touch(tmpfile("foo.rb"))
     wait
 
-    assert !checker.execute_if_updated
+    assert_not checker.execute_if_updated
     assert_equal 0, i
   end
 
@@ -238,7 +238,7 @@ module FileUpdateCheckerSharedTests
     mkdir(subdir)
     wait
 
-    assert !checker.execute_if_updated
+    assert_not checker.execute_if_updated
     assert_equal 0, i
 
     touch(File.join(subdir, "nested.rb"))
@@ -259,7 +259,7 @@ module FileUpdateCheckerSharedTests
     touch(tmpfile("new.txt"))
     wait
 
-    assert !checker.execute_if_updated
+    assert_not checker.execute_if_updated
     assert_equal 0, i
 
     # subdir does not look for Ruby files, but its parent tmpdir does.
diff --git a/activesupport/test/gzip_test.rb b/activesupport/test/gzip_test.rb
index 05ce12fe86..3d790f69c4 100644
--- a/activesupport/test/gzip_test.rb
+++ b/activesupport/test/gzip_test.rb
@@ -18,7 +18,7 @@ class GzipTest < ActiveSupport::TestCase
     compressed = ActiveSupport::Gzip.compress("")
 
     assert_equal Encoding.find("binary"), compressed.encoding
-    assert !compressed.blank?, "a compressed blank string should not be blank"
+    assert_not compressed.blank?, "a compressed blank string should not be blank"
   end
 
   def test_compress_should_return_gzipped_string_by_compression_level
diff --git a/activesupport/test/hash_with_indifferent_access_test.rb b/activesupport/test/hash_with_indifferent_access_test.rb
index b3788ee65c..eebff18ef1 100644
--- a/activesupport/test/hash_with_indifferent_access_test.rb
+++ b/activesupport/test/hash_with_indifferent_access_test.rb
@@ -169,8 +169,6 @@ class HashWithIndifferentAccessTest < ActiveSupport::TestCase
   end
 
   def test_indifferent_fetch_values
-    skip unless Hash.method_defined?(:fetch_values)
-
     @mixed = @mixed.with_indifferent_access
 
     assert_equal [1, 2], @mixed.fetch_values("a", "b")
@@ -282,7 +280,7 @@ class HashWithIndifferentAccessTest < ActiveSupport::TestCase
     replaced = hash.replace(b: 12)
 
     assert hash.key?("b")
-    assert !hash.key?(:a)
+    assert_not hash.key?(:a)
     assert_equal 12, hash[:b]
     assert_same hash, replaced
   end
@@ -294,7 +292,7 @@ class HashWithIndifferentAccessTest < ActiveSupport::TestCase
     replaced = hash.replace(HashByConversion.new(b: 12))
 
     assert hash.key?("b")
-    assert !hash.key?(:a)
+    assert_not hash.key?(:a)
     assert_equal 12, hash[:b]
     assert_same hash, replaced
   end
@@ -399,6 +397,49 @@ class HashWithIndifferentAccessTest < ActiveSupport::TestCase
     assert_instance_of ActiveSupport::HashWithIndifferentAccess, indifferent_strings
   end
 
+  def test_indifferent_transform_keys
+    hash = ActiveSupport::HashWithIndifferentAccess.new(@strings).transform_keys { |k| k * 2 }
+
+    assert_equal({ "aa" => 1, "bb" => 2 }, hash)
+    assert_instance_of ActiveSupport::HashWithIndifferentAccess, hash
+
+    hash = ActiveSupport::HashWithIndifferentAccess.new(@strings).transform_keys { |k| k.to_sym }
+
+    assert_equal(1, hash[:a])
+    assert_equal(1, hash["a"])
+    assert_instance_of ActiveSupport::HashWithIndifferentAccess, hash
+  end
+
+  def test_indifferent_transform_keys_bang
+    indifferent_strings = ActiveSupport::HashWithIndifferentAccess.new(@strings)
+    indifferent_strings.transform_keys! { |k| k * 2 }
+
+    assert_equal({ "aa" => 1, "bb" => 2 }, indifferent_strings)
+    assert_instance_of ActiveSupport::HashWithIndifferentAccess, indifferent_strings
+
+    indifferent_strings = ActiveSupport::HashWithIndifferentAccess.new(@strings)
+    indifferent_strings.transform_keys! { |k| k.to_sym }
+
+    assert_equal(1, indifferent_strings[:a])
+    assert_equal(1, indifferent_strings["a"])
+    assert_instance_of ActiveSupport::HashWithIndifferentAccess, indifferent_strings
+  end
+
+  def test_indifferent_transform_values
+    hash = ActiveSupport::HashWithIndifferentAccess.new(@strings).transform_values { |v| v * 2 }
+
+    assert_equal({ "a" => 2, "b" => 4 }, hash)
+    assert_instance_of ActiveSupport::HashWithIndifferentAccess, hash
+  end
+
+  def test_indifferent_transform_values_bang
+    indifferent_strings = ActiveSupport::HashWithIndifferentAccess.new(@strings)
+    indifferent_strings.transform_values! { |v| v * 2 }
+
+    assert_equal({ "a" => 2, "b" => 4 }, indifferent_strings)
+    assert_instance_of ActiveSupport::HashWithIndifferentAccess, indifferent_strings
+  end
+
   def test_indifferent_compact
     hash_contain_nil_value = @strings.merge("z" => nil)
     hash = ActiveSupport::HashWithIndifferentAccess.new(hash_contain_nil_value)
@@ -532,7 +573,6 @@ class HashWithIndifferentAccessTest < ActiveSupport::TestCase
   end
 
   def test_nested_dig_indifferent_access
-    skip if RUBY_VERSION < "2.3.0"
     data = { "this" => { "views" => 1234 } }.with_indifferent_access
     assert_equal 1234, data.dig(:this, :views)
   end
@@ -566,7 +606,7 @@ class HashWithIndifferentAccessTest < ActiveSupport::TestCase
   def test_assorted_keys_not_stringified
     original = { Object.new => 2, 1 => 2, [] => true }
     indiff = original.with_indifferent_access
-    assert(!indiff.keys.any? { |k| k.kind_of? String }, "A key was converted to a string!")
+    assert_not(indiff.keys.any? { |k| k.kind_of? String }, "A key was converted to a string!")
   end
 
   def test_deep_merge_on_indifferent_access
diff --git a/activesupport/test/inflector_test.rb b/activesupport/test/inflector_test.rb
index eeec0ab1a5..5e50acf5db 100644
--- a/activesupport/test/inflector_test.rb
+++ b/activesupport/test/inflector_test.rb
@@ -224,6 +224,12 @@ class InflectorTest < ActiveSupport::TestCase
     assert_equal("json_html_api", ActiveSupport::Inflector.underscore("JSONHTMLAPI"))
   end
 
+  def test_acronym_regexp_is_deprecated
+    assert_deprecated do
+      ActiveSupport::Inflector.inflections.acronym_regex
+    end
+  end
+
   def test_underscore
     CamelToUnderscore.each do |camel, underscore|
       assert_equal(underscore, ActiveSupport::Inflector.underscore(camel))
@@ -356,6 +362,19 @@ class InflectorTest < ActiveSupport::TestCase
     assert_equal("Col rpted bugs", ActiveSupport::Inflector.humanize("COL_rpted_bugs"))
   end
 
+  def test_humanize_with_acronyms
+    ActiveSupport::Inflector.inflections do |inflect|
+      inflect.acronym "LAX"
+      inflect.acronym "SFO"
+    end
+    assert_equal("LAX roundtrip to SFO", ActiveSupport::Inflector.humanize("LAX ROUNDTRIP TO SFO"))
+    assert_equal("LAX roundtrip to SFO", ActiveSupport::Inflector.humanize("LAX ROUNDTRIP TO SFO", capitalize: false))
+    assert_equal("LAX roundtrip to SFO", ActiveSupport::Inflector.humanize("lax roundtrip to sfo"))
+    assert_equal("LAX roundtrip to SFO", ActiveSupport::Inflector.humanize("lax roundtrip to sfo", capitalize: false))
+    assert_equal("LAX roundtrip to SFO", ActiveSupport::Inflector.humanize("Lax Roundtrip To Sfo"))
+    assert_equal("LAX roundtrip to SFO", ActiveSupport::Inflector.humanize("Lax Roundtrip To Sfo", capitalize: false))
+  end
+
   def test_constantize
     run_constantize_tests_on do |string|
       ActiveSupport::Inflector.constantize(string)
@@ -441,12 +460,12 @@ class InflectorTest < ActiveSupport::TestCase
 
     ActiveSupport::Inflector.inflections(:es) { |inflect| inflect.clear }
 
-    assert ActiveSupport::Inflector.inflections(:es).plurals.empty?
-    assert ActiveSupport::Inflector.inflections(:es).singulars.empty?
-    assert ActiveSupport::Inflector.inflections(:es).uncountables.empty?
-    assert !ActiveSupport::Inflector.inflections.plurals.empty?
-    assert !ActiveSupport::Inflector.inflections.singulars.empty?
-    assert !ActiveSupport::Inflector.inflections.uncountables.empty?
+    assert_empty ActiveSupport::Inflector.inflections(:es).plurals
+    assert_empty ActiveSupport::Inflector.inflections(:es).singulars
+    assert_empty ActiveSupport::Inflector.inflections(:es).uncountables
+    assert_not_empty ActiveSupport::Inflector.inflections.plurals
+    assert_not_empty ActiveSupport::Inflector.inflections.singulars
+    assert_not_empty ActiveSupport::Inflector.inflections.uncountables
   end
 
   def test_clear_all
@@ -459,10 +478,10 @@ class InflectorTest < ActiveSupport::TestCase
 
       inflect.clear :all
 
-      assert inflect.plurals.empty?
-      assert inflect.singulars.empty?
-      assert inflect.uncountables.empty?
-      assert inflect.humans.empty?
+      assert_empty inflect.plurals
+      assert_empty inflect.singulars
+      assert_empty inflect.uncountables
+      assert_empty inflect.humans
     end
   end
 
@@ -476,10 +495,10 @@ class InflectorTest < ActiveSupport::TestCase
 
       inflect.clear
 
-      assert inflect.plurals.empty?
-      assert inflect.singulars.empty?
-      assert inflect.uncountables.empty?
-      assert inflect.humans.empty?
+      assert_empty inflect.plurals
+      assert_empty inflect.singulars
+      assert_empty inflect.uncountables
+      assert_empty inflect.humans
     end
   end
 
diff --git a/activesupport/test/inflector_test_cases.rb b/activesupport/test/inflector_test_cases.rb
index f1214671ce..689370cccf 100644
--- a/activesupport/test/inflector_test_cases.rb
+++ b/activesupport/test/inflector_test_cases.rb
@@ -221,7 +221,7 @@ module InflectorTestCases
     "Test with malformed utf8 \251"       => "test_with_malformed_utf8"
   }
 
-  StringToParameterizePreserceCaseWithUnderscore = {
+  StringToParameterizePreserveCaseWithUnderscore = {
     "Donald E. Knuth"                     => "Donald_E_Knuth",
     "Random text with *(bad)* characters" => "Random_text_with_bad_characters",
     "With-some-dashes"                    => "With-some-dashes",
diff --git a/activesupport/test/json/encoding_test.rb b/activesupport/test/json/encoding_test.rb
index eafa2e1712..340a2abf75 100644
--- a/activesupport/test/json/encoding_test.rb
+++ b/activesupport/test/json/encoding_test.rb
@@ -187,7 +187,7 @@ class TestJSONEncoding < ActiveSupport::TestCase
   def test_array_should_pass_encoding_options_to_children_in_as_json
     people = [
       { name: "John", address: { city: "London", country: "UK" } },
-      { name: "Jean", address: { city: "Paris" , country: "France" } }
+      { name: "Jean", address: { city: "Paris", country: "France" } }
     ]
     json = people.as_json only: [:address, :city]
     expected = [
@@ -201,7 +201,7 @@ class TestJSONEncoding < ActiveSupport::TestCase
   def test_array_should_pass_encoding_options_to_children_in_to_json
     people = [
       { name: "John", address: { city: "London", country: "UK" } },
-      { name: "Jean", address: { city: "Paris" , country: "France" } }
+      { name: "Jean", address: { city: "Paris", country: "France" } }
     ]
     json = people.to_json only: [:address, :city]
 
@@ -210,10 +210,10 @@ class TestJSONEncoding < ActiveSupport::TestCase
 
   People = Class.new(BasicObject) do
     include Enumerable
-    def initialize()
+    def initialize
       @people = [
         { name: "John", address: { city: "London", country: "UK" } },
-        { name: "Jean", address: { city: "Paris" , country: "France" } }
+        { name: "Jean", address: { city: "Paris", country: "France" } }
       ]
     end
     def each(*, &blk)
@@ -454,6 +454,10 @@ EXPECTED
     assert_equal '{"number":null}', NaNNumber.new.to_json
   end
 
+  def test_to_json_works_on_io_objects
+    assert_equal STDOUT.to_s.to_json, STDOUT.to_json
+  end
+
   private
 
     def object_keys(json_object)
diff --git a/activesupport/test/key_generator_test.rb b/activesupport/test/key_generator_test.rb
index a948cfbd8e..cdde2c573a 100644
--- a/activesupport/test/key_generator_test.rb
+++ b/activesupport/test/key_generator_test.rb
@@ -36,13 +36,13 @@ else
       # key would break.
 
       expected = "b129376f68f1ecae788d7433310249d65ceec090ecacd4c872a3a9e9ec78e055739be5cc6956345d5ae38e7e1daa66f1de587dc8da2bf9e8b965af4b3918a122"
-      assert_equal expected, ActiveSupport::KeyGenerator.new("0" * 64).generate_key("some_salt").unpack("H*").first
+      assert_equal expected, ActiveSupport::KeyGenerator.new("0" * 64).generate_key("some_salt").unpack1("H*")
 
       expected = "b129376f68f1ecae788d7433310249d65ceec090ecacd4c872a3a9e9ec78e055"
-      assert_equal expected, ActiveSupport::KeyGenerator.new("0" * 64).generate_key("some_salt", 32).unpack("H*").first
+      assert_equal expected, ActiveSupport::KeyGenerator.new("0" * 64).generate_key("some_salt", 32).unpack1("H*")
 
       expected = "cbea7f7f47df705967dc508f4e446fd99e7797b1d70011c6899cd39bbe62907b8508337d678505a7dc8184e037f1003ba3d19fc5d829454668e91d2518692eae"
-      assert_equal expected, ActiveSupport::KeyGenerator.new("0" * 64, iterations: 2).generate_key("some_salt").unpack("H*").first
+      assert_equal expected, ActiveSupport::KeyGenerator.new("0" * 64, iterations: 2).generate_key("some_salt").unpack1("H*")
     end
   end
 
diff --git a/activesupport/test/message_encryptor_test.rb b/activesupport/test/message_encryptor_test.rb
index 1fbe655642..9edf07f762 100644
--- a/activesupport/test/message_encryptor_test.rb
+++ b/activesupport/test/message_encryptor_test.rb
@@ -115,6 +115,72 @@ class MessageEncryptorTest < ActiveSupport::TestCase
     assert_equal "Ruby on Rails", encryptor.decrypt_and_verify(encrypted_message)
   end
 
+  def test_rotating_secret
+    old_message = ActiveSupport::MessageEncryptor.new(secrets[:old], cipher: "aes-256-gcm").encrypt_and_sign("old")
+
+    encryptor = ActiveSupport::MessageEncryptor.new(@secret, cipher: "aes-256-gcm")
+    encryptor.rotate secrets[:old]
+
+    assert_equal "old", encryptor.decrypt_and_verify(old_message)
+  end
+
+  def test_rotating_serializer
+    old_message = ActiveSupport::MessageEncryptor.new(secrets[:old], cipher: "aes-256-gcm", serializer: JSON).
+      encrypt_and_sign(ahoy: :hoy)
+
+    encryptor = ActiveSupport::MessageEncryptor.new(@secret, cipher: "aes-256-gcm", serializer: JSON)
+    encryptor.rotate secrets[:old]
+
+    assert_equal({ "ahoy" => "hoy" }, encryptor.decrypt_and_verify(old_message))
+  end
+
+  def test_rotating_aes_cbc_secrets
+    old_encryptor = ActiveSupport::MessageEncryptor.new(secrets[:old], "old sign", cipher: "aes-256-cbc")
+    old_message = old_encryptor.encrypt_and_sign("old")
+
+    encryptor = ActiveSupport::MessageEncryptor.new(@secret)
+    encryptor.rotate secrets[:old], "old sign", cipher: "aes-256-cbc"
+
+    assert_equal "old", encryptor.decrypt_and_verify(old_message)
+  end
+
+  def test_multiple_rotations
+    older_message = ActiveSupport::MessageEncryptor.new(secrets[:older], "older sign").encrypt_and_sign("older")
+    old_message = ActiveSupport::MessageEncryptor.new(secrets[:old], "old sign").encrypt_and_sign("old")
+
+    encryptor = ActiveSupport::MessageEncryptor.new(@secret)
+    encryptor.rotate secrets[:old], "old sign"
+    encryptor.rotate secrets[:older], "older sign"
+
+    assert_equal "new",   encryptor.decrypt_and_verify(encryptor.encrypt_and_sign("new"))
+    assert_equal "old",   encryptor.decrypt_and_verify(old_message)
+    assert_equal "older", encryptor.decrypt_and_verify(older_message)
+  end
+
+  def test_on_rotation_is_called_and_returns_modified_messages
+    older_message = ActiveSupport::MessageEncryptor.new(secrets[:older], "older sign").encrypt_and_sign(encoded: "message")
+
+    encryptor = ActiveSupport::MessageEncryptor.new(@secret)
+    encryptor.rotate secrets[:old]
+    encryptor.rotate secrets[:older], "older sign"
+
+    rotated = false
+    message = encryptor.decrypt_and_verify(older_message, on_rotation: proc { rotated = true })
+
+    assert_equal({ encoded: "message" }, message)
+    assert rotated
+  end
+
+  def test_with_rotated_metadata
+    old_message = ActiveSupport::MessageEncryptor.new(secrets[:old], cipher: "aes-256-gcm").
+      encrypt_and_sign("metadata", purpose: :rotation)
+
+    encryptor = ActiveSupport::MessageEncryptor.new(@secret, cipher: "aes-256-gcm")
+    encryptor.rotate secrets[:old]
+
+    assert_equal "metadata", encryptor.decrypt_and_verify(old_message, purpose: :rotation)
+  end
+
   private
     def assert_aead_not_decrypted(encryptor, value)
       assert_raise(ActiveSupport::MessageEncryptor::InvalidMessage) do
@@ -134,6 +200,10 @@ class MessageEncryptorTest < ActiveSupport::TestCase
       end
     end
 
+    def secrets
+      @secrets ||= Hash.new { |h, k| h[k] = SecureRandom.random_bytes(32) }
+    end
+
     def munge(base64_string)
       bits = ::Base64.strict_decode64(base64_string)
       bits.reverse!
diff --git a/activesupport/test/message_verifier_test.rb b/activesupport/test/message_verifier_test.rb
index fbeafca203..0fa53695e0 100644
--- a/activesupport/test/message_verifier_test.rb
+++ b/activesupport/test/message_verifier_test.rb
@@ -20,16 +20,17 @@ class MessageVerifierTest < ActiveSupport::TestCase
   def setup
     @verifier = ActiveSupport::MessageVerifier.new("Hey, I'm a secret!")
     @data = { some: "data", now: Time.utc(2010) }
+    @secret = SecureRandom.random_bytes(32)
   end
 
   def test_valid_message
     data, hash = @verifier.generate(@data).split("--")
-    assert !@verifier.valid_message?(nil)
-    assert !@verifier.valid_message?("")
-    assert !@verifier.valid_message?("\xff") # invalid encoding
-    assert !@verifier.valid_message?("#{data.reverse}--#{hash}")
-    assert !@verifier.valid_message?("#{data}--#{hash.reverse}")
-    assert !@verifier.valid_message?("purejunk")
+    assert_not @verifier.valid_message?(nil)
+    assert_not @verifier.valid_message?("")
+    assert_not @verifier.valid_message?("\xff") # invalid encoding
+    assert_not @verifier.valid_message?("#{data.reverse}--#{hash}")
+    assert_not @verifier.valid_message?("#{data}--#{hash.reverse}")
+    assert_not @verifier.valid_message?("purejunk")
   end
 
   def test_simple_round_tripping
@@ -39,7 +40,7 @@ class MessageVerifierTest < ActiveSupport::TestCase
   end
 
   def test_verified_returns_false_on_invalid_message
-    assert !@verifier.verified("purejunk")
+    assert_not @verifier.verified("purejunk")
   end
 
   def test_verify_exception_on_invalid_message
@@ -90,6 +91,51 @@ class MessageVerifierTest < ActiveSupport::TestCase
     signed_message = "BAh7BzoJc29tZUkiCWRhdGEGOgZFVDoIbm93SXU6CVRpbWUNIIAbgAAAAAAHOgtvZmZzZXRpADoJem9uZUkiCFVUQwY7BkY=--d03c52c91dfe4ccc5159417c660461bcce005e96"
     assert_equal @data, @verifier.verify(signed_message)
   end
+
+  def test_rotating_secret
+    old_message = ActiveSupport::MessageVerifier.new("old", digest: "SHA1").generate("old")
+
+    verifier = ActiveSupport::MessageVerifier.new(@secret, digest: "SHA1")
+    verifier.rotate "old"
+
+    assert_equal "old", verifier.verified(old_message)
+  end
+
+  def test_multiple_rotations
+    old_message   = ActiveSupport::MessageVerifier.new("old", digest: "SHA256").generate("old")
+    older_message = ActiveSupport::MessageVerifier.new("older", digest: "SHA1").generate("older")
+
+    verifier = ActiveSupport::MessageVerifier.new(@secret, digest: "SHA512")
+    verifier.rotate "old",   digest: "SHA256"
+    verifier.rotate "older", digest: "SHA1"
+
+    assert_equal "new",   verifier.verified(verifier.generate("new"))
+    assert_equal "old",   verifier.verified(old_message)
+    assert_equal "older", verifier.verified(older_message)
+  end
+
+  def test_on_rotation_is_called_and_verified_returns_message
+    older_message = ActiveSupport::MessageVerifier.new("older", digest: "SHA1").generate(encoded: "message")
+
+    verifier = ActiveSupport::MessageVerifier.new(@secret, digest: "SHA512")
+    verifier.rotate "old",   digest: "SHA256"
+    verifier.rotate "older", digest: "SHA1"
+
+    rotated = false
+    message = verifier.verified(older_message, on_rotation: proc { rotated = true })
+
+    assert_equal({ encoded: "message" }, message)
+    assert rotated
+  end
+
+  def test_rotations_with_metadata
+    old_message = ActiveSupport::MessageVerifier.new("old").generate("old", purpose: :rotation)
+
+    verifier = ActiveSupport::MessageVerifier.new(@secret)
+    verifier.rotate "old"
+
+    assert_equal "old", verifier.verified(old_message, purpose: :rotation)
+  end
 end
 
 class MessageVerifierMetadataTest < ActiveSupport::TestCase
diff --git a/activesupport/test/messages/rotation_configuration_test.rb b/activesupport/test/messages/rotation_configuration_test.rb
new file mode 100644
index 0000000000..2f6824ed21
--- /dev/null
+++ b/activesupport/test/messages/rotation_configuration_test.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "active_support/messages/rotation_configuration"
+
+class MessagesRotationConfiguration < ActiveSupport::TestCase
+  def setup
+    @config = ActiveSupport::Messages::RotationConfiguration.new
+  end
+
+  def test_signed_configurations
+    @config.rotate :signed, "older secret", salt: "salt", digest: "SHA1"
+    @config.rotate :signed, "old secret", salt: "salt", digest: "SHA256"
+
+    assert_equal [
+      [ "older secret", salt: "salt", digest: "SHA1" ],
+      [ "old secret", salt: "salt", digest: "SHA256" ] ], @config.signed
+  end
+
+  def test_encrypted_configurations
+    @config.rotate :encrypted, "old raw key", cipher: "aes-256-gcm"
+
+    assert_equal [ [ "old raw key", cipher: "aes-256-gcm" ] ], @config.encrypted
+  end
+end
diff --git a/activesupport/test/multibyte_chars_test.rb b/activesupport/test/multibyte_chars_test.rb
index f51fbe2671..061446c782 100644
--- a/activesupport/test/multibyte_chars_test.rb
+++ b/activesupport/test/multibyte_chars_test.rb
@@ -75,7 +75,7 @@ class MultibyteCharsTest < ActiveSupport::TestCase
   def test_consumes_utf8_strings
     assert @proxy_class.consumes?(UNICODE_STRING)
     assert @proxy_class.consumes?(ASCII_STRING)
-    assert !@proxy_class.consumes?(BYTE_STRING)
+    assert_not @proxy_class.consumes?(BYTE_STRING)
   end
 
   def test_concatenation_should_return_a_proxy_class_instance
@@ -148,7 +148,7 @@ class MultibyteCharsUTF8BehaviourTest < ActiveSupport::TestCase
   def test_identity
     assert_equal @chars, @chars
     assert @chars.eql?(@chars)
-    assert !@chars.eql?(UNICODE_STRING)
+    assert_not @chars.eql?(UNICODE_STRING)
   end
 
   def test_string_methods_are_chainable
@@ -469,10 +469,10 @@ class MultibyteCharsUTF8BehaviourTest < ActiveSupport::TestCase
   end
 
   def test_respond_to_knows_which_methods_the_proxy_responds_to
-    assert "".mb_chars.respond_to?(:slice) # Defined on Chars
-    assert "".mb_chars.respond_to?(:capitalize!) # Defined on Chars
-    assert "".mb_chars.respond_to?(:gsub) # Defined on String
-    assert !"".mb_chars.respond_to?(:undefined_method) # Not defined
+    assert_respond_to "".mb_chars, :slice # Defined on Chars
+    assert_respond_to "".mb_chars, :capitalize! # Defined on Chars
+    assert_respond_to "".mb_chars, :gsub # Defined on String
+    assert_not_respond_to "".mb_chars, :undefined_method # Not defined
   end
 
   def test_method_works_for_proxyed_methods
@@ -485,7 +485,7 @@ class MultibyteCharsUTF8BehaviourTest < ActiveSupport::TestCase
   end
 
   def test_acts_like_string
-    assert "Bambi".mb_chars.acts_like_string?
+    assert_predicate "Bambi".mb_chars, :acts_like_string?
   end
 end
 
diff --git a/activesupport/test/multibyte_unicode_database_test.rb b/activesupport/test/multibyte_unicode_database_test.rb
deleted file mode 100644
index 540a34493d..0000000000
--- a/activesupport/test/multibyte_unicode_database_test.rb
+++ /dev/null
@@ -1,26 +0,0 @@
-# frozen_string_literal: true
-
-require "abstract_unit"
-
-class MultibyteUnicodeDatabaseTest < ActiveSupport::TestCase
-  include ActiveSupport::Multibyte::Unicode
-
-  def setup
-    @ucd = UnicodeDatabase.new
-  end
-
-  UnicodeDatabase::ATTRIBUTES.each do |attribute|
-    define_method "test_lazy_loading_on_attribute_access_of_#{attribute}" do
-      assert_called(@ucd, :load) do
-        @ucd.send(attribute)
-      end
-    end
-  end
-
-  def test_load
-    @ucd.load
-    UnicodeDatabase::ATTRIBUTES.each do |attribute|
-      assert @ucd.send(attribute).length > 1
-    end
-  end
-end
diff --git a/activesupport/test/notifications/instrumenter_test.rb b/activesupport/test/notifications/instrumenter_test.rb
index 1d76c91d30..d5c9e82e9f 100644
--- a/activesupport/test/notifications/instrumenter_test.rb
+++ b/activesupport/test/notifications/instrumenter_test.rb
@@ -47,13 +47,13 @@ module ActiveSupport
       def test_start
         instrumenter.start("foo", payload)
         assert_equal [["foo", instrumenter.id, payload]], notifier.starts
-        assert_predicate notifier.finishes, :empty?
+        assert_empty notifier.finishes
       end
 
       def test_finish
         instrumenter.finish("foo", payload)
         assert_equal [["foo", instrumenter.id, payload]], notifier.finishes
-        assert_predicate notifier.starts, :empty?
+        assert_empty notifier.starts
       end
     end
   end
diff --git a/activesupport/test/notifications_test.rb b/activesupport/test/notifications_test.rb
index 5cfbd60131..d035f993f7 100644
--- a/activesupport/test/notifications_test.rb
+++ b/activesupport/test/notifications_test.rb
@@ -250,8 +250,8 @@ module Notifications
       time = Time.now
       event = event(:foo, time, time + 0.01, random_id, {})
 
-      assert_equal    :foo, event.name
-      assert_equal    time, event.time
+      assert_equal :foo, event.name
+      assert_equal time, event.time
       assert_in_delta 10.0, event.duration, 0.00001
     end
 
@@ -270,9 +270,9 @@ module Notifications
       parent.children << child
 
       assert parent.parent_of?(child)
-      assert !child.parent_of?(parent)
-      assert !parent.parent_of?(not_child)
-      assert !not_child.parent_of?(parent)
+      assert_not child.parent_of?(parent)
+      assert_not parent.parent_of?(not_child)
+      assert_not not_child.parent_of?(parent)
     end
 
     private
diff --git a/activesupport/test/number_helper_i18n_test.rb b/activesupport/test/number_helper_i18n_test.rb
index 6d6958be49..365fa96f4d 100644
--- a/activesupport/test/number_helper_i18n_test.rb
+++ b/activesupport/test/number_helper_i18n_test.rb
@@ -35,7 +35,7 @@ module ActiveSupport
               thousand: "t",
               million: "m",
               billion: "b",
-              trillion: "t" ,
+              trillion: "t",
               quadrillion: "q"
             }
           }
@@ -77,10 +77,10 @@ module ActiveSupport
     end
 
     def test_number_with_i18n_precision
-      #Delimiter was set to ""
+      # Delimiter was set to ""
       assert_equal("10000", number_to_rounded(10000, locale: "ts"))
 
-      #Precision inherited and significant was set
+      # Precision inherited and significant was set
       assert_equal("1.00", number_to_rounded(1.0, locale: "ts"))
     end
 
@@ -90,7 +90,7 @@ module ActiveSupport
     end
 
     def test_number_with_i18n_delimiter
-      #Delimiter "," and separator "."
+      # Delimiter "," and separator "."
       assert_equal("1,000,000.234", number_to_delimited(1000000.234, locale: "ts"))
     end
 
@@ -114,7 +114,7 @@ module ActiveSupport
     end
 
     def test_number_to_i18n_human_size
-      #b for bytes and k for kbytes
+      # b for bytes and k for kbytes
       assert_equal("2 k", number_to_human_size(2048, locale: "ts"))
       assert_equal("42 b", number_to_human_size(42, locale: "ts"))
     end
@@ -125,11 +125,11 @@ module ActiveSupport
     end
 
     def test_number_to_human_with_default_translation_scope
-      #Using t for thousand
+      # Using t for thousand
       assert_equal "2 t", number_to_human(2000, locale: "ts")
-      #Significant was set to true with precision 2, using b for billion
+      # Significant was set to true with precision 2, using b for billion
       assert_equal "1.2 b", number_to_human(1234567890, locale: "ts")
-      #Using pluralization (Ten/Tens and Tenth/Tenths)
+      # Using pluralization (Ten/Tens and Tenth/Tenths)
       assert_equal "1 Tenth", number_to_human(0.1, locale: "ts")
       assert_equal "1.3 Tenth", number_to_human(0.134, locale: "ts")
       assert_equal "2 Tenths", number_to_human(0.2, locale: "ts")
@@ -144,7 +144,7 @@ module ActiveSupport
     end
 
     def test_number_to_human_with_custom_translation_scope
-      #Significant was set to true with precision 2, with custom translated units
+      # Significant was set to true with precision 2, with custom translated units
       assert_equal "4.3 cm", number_to_human(0.0432, locale: "ts", units: :custom_units_for_number_to_human)
     end
   end
diff --git a/activesupport/test/number_helper_test.rb b/activesupport/test/number_helper_test.rb
index b4795b6ee1..16ccc5572c 100644
--- a/activesupport/test/number_helper_test.rb
+++ b/activesupport/test/number_helper_test.rb
@@ -260,7 +260,7 @@ module ActiveSupport
           assert_equal "40 KB", number_helper.number_to_human_size(41100, precision: 2)
           assert_equal "1.0 KB",   number_helper.number_to_human_size(kilobytes(1.0123), precision: 2, strip_insignificant_zeros: false)
           assert_equal "1.012 KB",   number_helper.number_to_human_size(kilobytes(1.0123), precision: 3, significant: false)
-          assert_equal "1 KB",   number_helper.number_to_human_size(kilobytes(1.0123), precision: 0, significant: true) #ignores significant it precision is 0
+          assert_equal "1 KB",   number_helper.number_to_human_size(kilobytes(1.0123), precision: 0, significant: true) # ignores significant it precision is 0
         end
       end
 
@@ -292,7 +292,7 @@ module ActiveSupport
           assert_equal "489.0 Thousand", number_helper.number_to_human(489000, precision: 4, strip_insignificant_zeros: false)
           assert_equal "1.2346 Million", number_helper.number_to_human(1234567, precision: 4, significant: false)
           assert_equal "1,2 Million", number_helper.number_to_human(1234567, precision: 1, significant: false, separator: ",")
-          assert_equal "1 Million", number_helper.number_to_human(1234567, precision: 0, significant: true, separator: ",") #significant forced to false
+          assert_equal "1 Million", number_helper.number_to_human(1234567, precision: 0, significant: true, separator: ",") # significant forced to false
           assert_equal "1 Million", number_helper.number_to_human(999999)
           assert_equal "1 Billion", number_helper.number_to_human(999999999)
         end
@@ -300,13 +300,13 @@ module ActiveSupport
 
       def test_number_to_human_with_custom_units
         [@instance_with_helpers, TestClassWithClassNumberHelpers, ActiveSupport::NumberHelper].each do |number_helper|
-          #Only integers
+          # Only integers
           volume = { unit: "ml", thousand: "lt", million: "m3" }
           assert_equal "123 lt", number_helper.number_to_human(123456, units: volume)
           assert_equal "12 ml", number_helper.number_to_human(12, units: volume)
           assert_equal "1.23 m3", number_helper.number_to_human(1234567, units: volume)
 
-          #Including fractionals
+          # Including fractionals
           distance = { mili: "mm", centi: "cm", deci: "dm", unit: "m", ten: "dam", hundred: "hm", thousand: "km" }
           assert_equal "1.23 mm", number_helper.number_to_human(0.00123, units: distance)
           assert_equal "1.23 cm", number_helper.number_to_human(0.0123, units: distance)
@@ -319,7 +319,7 @@ module ActiveSupport
           assert_equal "1.23 km", number_helper.number_to_human(1230, units: distance)
           assert_equal "12.3 km", number_helper.number_to_human(12300, units: distance)
 
-          #The quantifiers don't need to be a continuous sequence
+          # The quantifiers don't need to be a continuous sequence
           gangster = { hundred: "hundred bucks", million: "thousand quids" }
           assert_equal "1 hundred bucks", number_helper.number_to_human(100, units: gangster)
           assert_equal "25 hundred bucks", number_helper.number_to_human(2500, units: gangster)
@@ -329,11 +329,11 @@ module ActiveSupport
           assert_equal "25 thousand quids", number_helper.number_to_human(25000000, units: gangster)
           assert_equal "12300 thousand quids", number_helper.number_to_human(12345000000, units: gangster)
 
-          #Spaces are stripped from the resulting string
+          # Spaces are stripped from the resulting string
           assert_equal "4", number_helper.number_to_human(4, units: { unit: "", ten: "tens " })
           assert_equal "4.5  tens", number_helper.number_to_human(45, units: { unit: "", ten: " tens   " })
 
-          #Uses only the provided units and does not try to use larger ones
+          # Uses only the provided units and does not try to use larger ones
           assert_equal "1000 kilometers", number_helper.number_to_human(1_000_000, units: { unit: "meter", thousand: "kilometers" })
         end
       end
diff --git a/activesupport/test/ordered_options_test.rb b/activesupport/test/ordered_options_test.rb
index 7f2e774c02..90394fee0a 100644
--- a/activesupport/test/ordered_options_test.rb
+++ b/activesupport/test/ordered_options_test.rb
@@ -15,7 +15,7 @@ class OrderedOptionsTest < ActiveSupport::TestCase
 
     a[:allow_concurrency] = false
     assert_equal 1, a.size
-    assert !a[:allow_concurrency]
+    assert_not a[:allow_concurrency]
 
     a["else_where"] = 56
     assert_equal 2, a.size
@@ -47,7 +47,7 @@ class OrderedOptionsTest < ActiveSupport::TestCase
 
     a.allow_concurrency = false
     assert_equal 1, a.size
-    assert !a.allow_concurrency
+    assert_not a.allow_concurrency
 
     a.else_where = 56
     assert_equal 2, a.size
@@ -82,8 +82,8 @@ class OrderedOptionsTest < ActiveSupport::TestCase
 
   def test_introspection
     a = ActiveSupport::OrderedOptions.new
-    assert a.respond_to?(:blah)
-    assert a.respond_to?(:blah=)
+    assert_respond_to a, :blah
+    assert_respond_to a, :blah=
     assert_equal 42, a.method(:blah=).call(42)
     assert_equal 42, a.method(:blah).call
   end
@@ -91,7 +91,20 @@ class OrderedOptionsTest < ActiveSupport::TestCase
   def test_raises_with_bang
     a = ActiveSupport::OrderedOptions.new
     a[:foo] = :bar
-    assert a.respond_to?(:foo!)
+    assert_respond_to a, :foo!
+
+    assert_nothing_raised { a.foo! }
+    assert_equal a.foo, a.foo!
+
+    assert_raises(KeyError) do
+      a.foo = nil
+      a.foo!
+    end
+    assert_raises(KeyError) { a.non_existing_key! }
+  end
+
+  def test_inheritable_options_with_bang
+    a = ActiveSupport::InheritableOptions.new(foo: :bar)
 
     assert_nothing_raised { a.foo! }
     assert_equal a.foo, a.foo!
diff --git a/activesupport/test/reloader_test.rb b/activesupport/test/reloader_test.rb
index 3e4229eaf7..976917c1a1 100644
--- a/activesupport/test/reloader_test.rb
+++ b/activesupport/test/reloader_test.rb
@@ -8,18 +8,18 @@ class ReloaderTest < ActiveSupport::TestCase
     reloader.to_prepare { prepared = true }
     reloader.to_complete { completed = true }
 
-    assert !prepared
-    assert !completed
+    assert_not prepared
+    assert_not completed
     reloader.prepare!
     assert prepared
-    assert !completed
+    assert_not completed
 
     prepared = false
     reloader.wrap do
       assert prepared
       prepared = false
     end
-    assert !prepared
+    assert_not prepared
   end
 
   def test_prepend_prepare_callback
@@ -42,7 +42,7 @@ class ReloaderTest < ActiveSupport::TestCase
     invoked = false
     r.to_run { invoked = true }
     r.wrap {}
-    assert !invoked
+    assert_not invoked
   end
 
   def test_full_reload_sequence
diff --git a/activesupport/test/safe_buffer_test.rb b/activesupport/test/safe_buffer_test.rb
index 05c2fb59be..9456bb8753 100644
--- a/activesupport/test/safe_buffer_test.rb
+++ b/activesupport/test/safe_buffer_test.rb
@@ -39,7 +39,7 @@ class SafeBufferTest < ActiveSupport::TestCase
   end
 
   test "Should be considered safe" do
-    assert @buffer.html_safe?
+    assert_predicate @buffer, :html_safe?
   end
 
   test "Should return a safe buffer when calling to_s" do
@@ -78,13 +78,13 @@ class SafeBufferTest < ActiveSupport::TestCase
   test "Should not return safe buffer from gsub" do
     altered_buffer = @buffer.gsub("", "asdf")
     assert_equal "asdf", altered_buffer
-    assert !altered_buffer.html_safe?
+    assert_not_predicate altered_buffer, :html_safe?
   end
 
   test "Should not return safe buffer from gsub!" do
     @buffer.gsub!("", "asdf")
     assert_equal "asdf", @buffer
-    assert !@buffer.html_safe?
+    assert_not_predicate @buffer, :html_safe?
   end
 
   test "Should escape dirty buffers on add" do
@@ -101,13 +101,13 @@ class SafeBufferTest < ActiveSupport::TestCase
 
   test "Should preserve html_safe? status on copy" do
     @buffer.gsub!("", "<>")
-    assert !@buffer.dup.html_safe?
+    assert_not_predicate @buffer.dup, :html_safe?
   end
 
   test "Should return safe buffer when added with another safe buffer" do
     clean = "<script>".html_safe
     result_buffer = @buffer + clean
-    assert result_buffer.html_safe?
+    assert_predicate result_buffer, :html_safe?
     assert_equal "<script>", result_buffer
   end
 
@@ -127,8 +127,8 @@ class SafeBufferTest < ActiveSupport::TestCase
   end
 
   test "clone_empty keeps the original dirtyness" do
-    assert @buffer.clone_empty.html_safe?
-    assert !@buffer.gsub!("", "").clone_empty.html_safe?
+    assert_predicate @buffer.clone_empty, :html_safe?
+    assert_not_predicate @buffer.gsub!("", "").clone_empty, :html_safe?
   end
 
   test "Should be safe when sliced if original value was safe" do
@@ -141,13 +141,13 @@ class SafeBufferTest < ActiveSupport::TestCase
     x = "foo".html_safe.gsub!("f", '<script>alert("lolpwnd");</script>')
 
     # calling gsub! makes the dirty flag true
-    assert !x.html_safe?, "should not be safe"
+    assert_not x.html_safe?, "should not be safe"
 
     # getting a slice of it
     y = x[0..-1]
 
     # should still be unsafe
-    assert !y.html_safe?, "should not be safe"
+    assert_not y.html_safe?, "should not be safe"
   end
 
   test "Should work with interpolation (array argument)" do
diff --git a/activesupport/test/security_utils_test.rb b/activesupport/test/security_utils_test.rb
index efd2bcfa0f..fff9cc2a8d 100644
--- a/activesupport/test/security_utils_test.rb
+++ b/activesupport/test/security_utils_test.rb
@@ -9,8 +9,14 @@ class SecurityUtilsTest < ActiveSupport::TestCase
     assert_not ActiveSupport::SecurityUtils.secure_compare("a", "b")
   end
 
-  def test_variable_size_secure_compare_should_perform_string_comparison
-    assert ActiveSupport::SecurityUtils.variable_size_secure_compare("a", "a")
-    assert_not ActiveSupport::SecurityUtils.variable_size_secure_compare("a", "b")
+  def test_fixed_length_secure_compare_should_perform_string_comparison
+    assert ActiveSupport::SecurityUtils.fixed_length_secure_compare("a", "a")
+    assert_not ActiveSupport::SecurityUtils.fixed_length_secure_compare("a", "b")
+  end
+
+  def test_fixed_length_secure_compare_raise_on_length_mismatch
+    assert_raises(ArgumentError, "string length mismatch.") do
+      ActiveSupport::SecurityUtils.fixed_length_secure_compare("a", "ab")
+    end
   end
 end
diff --git a/activesupport/test/string_inquirer_test.rb b/activesupport/test/string_inquirer_test.rb
index bf8f878a32..09726b144a 100644
--- a/activesupport/test/string_inquirer_test.rb
+++ b/activesupport/test/string_inquirer_test.rb
@@ -8,11 +8,11 @@ class StringInquirerTest < ActiveSupport::TestCase
   end
 
   def test_match
-    assert @string_inquirer.production?
+    assert_predicate @string_inquirer, :production?
   end
 
   def test_miss
-    assert_not @string_inquirer.development?
+    assert_not_predicate @string_inquirer, :development?
   end
 
   def test_missing_question_mark
diff --git a/activesupport/test/tagged_logging_test.rb b/activesupport/test/tagged_logging_test.rb
index 5fd6a6b316..e2b41cf8ee 100644
--- a/activesupport/test/tagged_logging_test.rb
+++ b/activesupport/test/tagged_logging_test.rb
@@ -21,7 +21,7 @@ class TaggedLoggingTest < ActiveSupport::TestCase
     assert_nil logger.formatter
     ActiveSupport::TaggedLogging.new(logger)
     assert_not_nil logger.formatter
-    assert logger.formatter.respond_to?(:tagged)
+    assert_respond_to logger.formatter, :tagged
   end
 
   test "tagged once" do
@@ -74,11 +74,12 @@ class TaggedLoggingTest < ActiveSupport::TestCase
   test "keeps each tag in their own thread" do
     @logger.tagged("BCX") do
       Thread.new do
+        @logger.info "Dull story"
         @logger.tagged("OMG") { @logger.info "Cool story" }
       end.join
       @logger.info "Funky time"
     end
-    assert_equal "[OMG] Cool story\n[BCX] Funky time\n", @output.string
+    assert_equal "Dull story\n[OMG] Cool story\n[BCX] Funky time\n", @output.string
   end
 
   test "keeps each tag in their own instance" do
diff --git a/activesupport/test/test_case_test.rb b/activesupport/test/test_case_test.rb
index 8830c9b348..19901fad99 100644
--- a/activesupport/test/test_case_test.rb
+++ b/activesupport/test/test_case_test.rb
@@ -2,7 +2,7 @@
 
 require "abstract_unit"
 
-class AssertDifferenceTest < ActiveSupport::TestCase
+class AssertionsTest < ActiveSupport::TestCase
   def setup
     @object = Class.new do
       attr_accessor :num
@@ -87,7 +87,8 @@ class AssertDifferenceTest < ActiveSupport::TestCase
 
   def test_expression_is_evaluated_in_the_appropriate_scope
     silence_warnings do
-      local_scope = local_scope = "foo"
+      local_scope = "foo"
+      local_scope = local_scope  # to suppress unused variable warning
       assert_difference("local_scope; @object.num") { @object.increment }
     end
   end
@@ -114,6 +115,35 @@ class AssertDifferenceTest < ActiveSupport::TestCase
     end
   end
 
+  def test_hash_of_expressions
+    assert_difference "@object.num" => 1, "@object.num + 1" => 1 do
+      @object.increment
+    end
+  end
+
+  def test_hash_of_expressions_with_message
+    error = assert_raises Minitest::Assertion do
+      assert_difference({ "@object.num" => 0 }, "Object Changed") do
+        @object.increment
+      end
+    end
+    assert_equal "Object Changed.\n\"@object.num\" didn't change by 0.\nExpected: 0\n  Actual: 1", error.message
+  end
+
+  def test_hash_of_lambda_expressions
+    assert_difference -> { @object.num } => 1, -> { @object.num + 1 } => 1 do
+      @object.increment
+    end
+  end
+
+  def test_hash_of_expressions_identify_failure
+    assert_raises(Minitest::Assertion) do
+      assert_difference "@object.num" => 1, "1 + 1" => 1 do
+        @object.increment
+      end
+    end
+  end
+
   def test_assert_changes_pass
     assert_changes "@object.num" do
       @object.increment
@@ -155,6 +185,16 @@ class AssertDifferenceTest < ActiveSupport::TestCase
     end
   end
 
+  def test_assert_changes_with_to_option_but_no_change_has_special_message
+    error = assert_raises Minitest::Assertion do
+      assert_changes "@object.num", to: 0 do
+        # no changes
+      end
+    end
+
+    assert_equal "\"@object.num\" didn't change. It was already 0", error.message
+  end
+
   def test_assert_changes_with_wrong_to_option
     assert_raises Minitest::Assertion do
       assert_changes "@object.num", to: 2 do
@@ -178,6 +218,7 @@ class AssertDifferenceTest < ActiveSupport::TestCase
   end
 
   def test_assert_changes_works_with_any_object
+    # Silences: instance variable @new_object not initialized.
     retval = silence_warnings do
       assert_changes :@new_object, from: nil, to: 42 do
         @new_object = 42
@@ -200,7 +241,7 @@ class AssertDifferenceTest < ActiveSupport::TestCase
   def test_assert_changes_with_to_and_case_operator
     token = nil
 
-    assert_changes "token", to: /\w{32}/ do
+    assert_changes -> { token }, to: /\w{32}/ do
       token = SecureRandom.hex
     end
   end
@@ -208,7 +249,7 @@ class AssertDifferenceTest < ActiveSupport::TestCase
   def test_assert_changes_with_to_and_from_and_case_operator
     token = SecureRandom.hex
 
-    assert_changes "token", from: /\w{32}/, to: /\w{32}/ do
+    assert_changes -> { token }, from: /\w{32}/, to: /\w{32}/ do
       token = SecureRandom.hex
     end
   end
@@ -216,10 +257,11 @@ class AssertDifferenceTest < ActiveSupport::TestCase
   def test_assert_changes_with_message
     error = assert_raises Minitest::Assertion do
       assert_changes "@object.num", "@object.num should 1", to: 1 do
+        @object.decrement
       end
     end
 
-    assert_equal "@object.num should 1.\n\"@object.num\" didn't change to 1", error.message
+    assert_equal "@object.num should 1.\n\"@object.num\" didn't change to as expected\nExpected: 1\n  Actual: -1", error.message
   end
 
   def test_assert_no_changes_pass
@@ -235,7 +277,7 @@ class AssertDifferenceTest < ActiveSupport::TestCase
       end
     end
 
-    assert_equal "@object.num should not change.\n\"@object.num\" did change to 1.\nExpected: 0\n  Actual: 1", error.message
+    assert_equal "@object.num should not change.\n\"@object.num\" did change to 1", error.message
   end
 end
 
diff --git a/activesupport/test/testing/after_teardown_test.rb b/activesupport/test/testing/after_teardown_test.rb
new file mode 100644
index 0000000000..961af49479
--- /dev/null
+++ b/activesupport/test/testing/after_teardown_test.rb
@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+
+module OtherAfterTeardown
+  def after_teardown
+    super
+
+    @witness = true
+  end
+end
+
+class AfterTeardownTest < ActiveSupport::TestCase
+  include OtherAfterTeardown
+
+  attr_writer :witness
+
+  MyError = Class.new(StandardError)
+
+  teardown do
+    raise MyError, "Test raises an error, all after_teardown should still get called"
+  end
+
+  def after_teardown
+    assert_changes -> { failures.count }, from: 0, to: 1 do
+      super
+    end
+
+    assert_equal true, @witness
+    failures.clear
+  end
+
+  def test_teardown_raise_but_all_after_teardown_method_are_called
+    assert true
+  end
+end
diff --git a/activesupport/test/time_travel_test.rb b/activesupport/test/time_travel_test.rb
index 4172c18ead..9c2c635f43 100644
--- a/activesupport/test/time_travel_test.rb
+++ b/activesupport/test/time_travel_test.rb
@@ -98,7 +98,7 @@ class TimeTravelTest < ActiveSupport::TestCase
       travel_to outer_expected_time do
         e = assert_raises(RuntimeError) do
           travel_to(inner_expected_time) do
-            #noop
+            # noop
           end
         end
         assert_match(/Calling `travel_to` with a block, when we have previously already made a call to `travel_to`, can lead to confusing time stubbing\./, e.message)
diff --git a/activesupport/test/time_zone_test.rb b/activesupport/test/time_zone_test.rb
index acb0ecd226..b59f3e9405 100644
--- a/activesupport/test/time_zone_test.rb
+++ b/activesupport/test/time_zone_test.rb
@@ -32,6 +32,12 @@ class TimeZoneTest < ActiveSupport::TestCase
     end
   end
 
+  def test_period_for_local_with_ambigiuous_time
+    zone = ActiveSupport::TimeZone["Moscow"]
+    period = zone.period_for_local(Time.utc(2015, 1, 1))
+    assert_equal period, zone.period_for_local(Time.utc(2014, 10, 26, 1, 0, 0))
+  end
+
   def test_from_integer_to_map
     assert_instance_of ActiveSupport::TimeZone, ActiveSupport::TimeZone[-28800] # PST
   end
@@ -195,6 +201,11 @@ class TimeZoneTest < ActiveSupport::TestCase
     assert_equal "EDT", twz.zone
   end
 
+  def test_local_with_ambiguous_time
+    zone = ActiveSupport::TimeZone["Moscow"]
+    assert_equal Time.utc(2014, 10, 25, 22, 0, 0), zone.local(2014, 10, 26, 1, 0, 0)
+  end
+
   def test_at
     zone = ActiveSupport::TimeZone["Eastern Time (US & Canada)"]
     secs = 946684800.0
@@ -303,6 +314,11 @@ class TimeZoneTest < ActiveSupport::TestCase
     end
   end
 
+  def test_iso8601_with_ambiguous_time
+    zone = ActiveSupport::TimeZone["Moscow"]
+    assert_equal Time.utc(2014, 10, 25, 22, 0, 0), zone.parse("2014-10-26T01:00:00")
+  end
+
   def test_parse
     zone = ActiveSupport::TimeZone["Eastern Time (US & Canada)"]
     twz = zone.parse("1999-12-31 19:00:00")
@@ -412,6 +428,11 @@ class TimeZoneTest < ActiveSupport::TestCase
     assert_equal "argument out of range", exception.message
   end
 
+  def test_parse_with_ambiguous_time
+    zone = ActiveSupport::TimeZone["Moscow"]
+    assert_equal Time.utc(2014, 10, 25, 22, 0, 0), zone.parse("2014-10-26 01:00:00")
+  end
+
   def test_rfc3339
     zone = ActiveSupport::TimeZone["Eastern Time (US & Canada)"]
     twz = zone.rfc3339("1999-12-31T14:00:00-10:00")
@@ -604,6 +625,11 @@ class TimeZoneTest < ActiveSupport::TestCase
     end
   end
 
+  def test_strptime_with_ambiguous_time
+    zone = ActiveSupport::TimeZone["Moscow"]
+    assert_equal Time.utc(2014, 10, 25, 22, 0, 0), zone.strptime("2014-10-26 01:00:00", "%Y-%m-%d %H:%M:%S")
+  end
+
   def test_utc_offset_lazy_loaded_from_tzinfo_when_not_passed_in_to_initialize
     tzinfo = TZInfo::Timezone.get("America/New_York")
     zone = ActiveSupport::TimeZone.create(tzinfo.name, nil, tzinfo)
@@ -692,6 +718,28 @@ class TimeZoneTest < ActiveSupport::TestCase
     end
   end
 
+  def test_all_uninfluenced_by_time_zone_lookups_delegated_to_tzinfo
+    ActiveSupport::TimeZone.clear
+    galapagos = ActiveSupport::TimeZone["Pacific/Galapagos"]
+    all_zones = ActiveSupport::TimeZone.all
+    assert_not_includes all_zones, galapagos
+  end
+
+  def test_all_doesnt_raise_exception_with_missing_tzinfo_data
+    mappings = {
+      "Puerto Rico" => "America/Unknown",
+      "Pittsburgh"  => "America/New_York"
+    }
+
+    with_tz_mappings(mappings) do
+      assert_nil ActiveSupport::TimeZone["Puerto Rico"]
+      assert_nil ActiveSupport::TimeZone[-9]
+      assert_nothing_raised do
+        ActiveSupport::TimeZone.all
+      end
+    end
+  end
+
   def test_index
     assert_nil ActiveSupport::TimeZone["bogus"]
     assert_instance_of ActiveSupport::TimeZone, ActiveSupport::TimeZone["Central Time (US & Canada)"]
@@ -723,6 +771,16 @@ class TimeZoneTest < ActiveSupport::TestCase
     assert_not_includes ActiveSupport::TimeZone.country_zones(:ru), ActiveSupport::TimeZone["Kuala Lumpur"]
   end
 
+  def test_country_zones_with_and_without_mappings
+    assert_includes ActiveSupport::TimeZone.country_zones("au"), ActiveSupport::TimeZone["Adelaide"]
+    assert_includes ActiveSupport::TimeZone.country_zones("au"), ActiveSupport::TimeZone["Australia/Lord_Howe"]
+  end
+
+  def test_country_zones_with_multiple_mappings
+    assert_includes ActiveSupport::TimeZone.country_zones("gb"), ActiveSupport::TimeZone["Edinburgh"]
+    assert_includes ActiveSupport::TimeZone.country_zones("gb"), ActiveSupport::TimeZone["London"]
+  end
+
   def test_country_zones_without_mappings
     assert_includes ActiveSupport::TimeZone.country_zones(:sv), ActiveSupport::TimeZone["America/El_Salvador"]
   end
diff --git a/activesupport/test/time_zone_test_helpers.rb b/activesupport/test/time_zone_test_helpers.rb
index 051703a781..85ed727c9b 100644
--- a/activesupport/test/time_zone_test_helpers.rb
+++ b/activesupport/test/time_zone_test_helpers.rb
@@ -23,4 +23,17 @@ module TimeZoneTestHelpers
   ensure
     ActiveSupport.to_time_preserves_timezone = old_preserve_tz
   end
+
+  def with_tz_mappings(mappings)
+    old_mappings = ActiveSupport::TimeZone::MAPPING.dup
+    ActiveSupport::TimeZone.clear
+    ActiveSupport::TimeZone::MAPPING.clear
+    ActiveSupport::TimeZone::MAPPING.merge!(mappings)
+
+    yield
+  ensure
+    ActiveSupport::TimeZone.clear
+    ActiveSupport::TimeZone::MAPPING.clear
+    ActiveSupport::TimeZone::MAPPING.merge!(old_mappings)
+  end
 end
diff --git a/activesupport/test/xml_mini/libxml_engine_test.rb b/activesupport/test/xml_mini/libxml_engine_test.rb
index 5c13f493f1..3eef3946a3 100644
--- a/activesupport/test/xml_mini/libxml_engine_test.rb
+++ b/activesupport/test/xml_mini/libxml_engine_test.rb
@@ -6,7 +6,7 @@ XMLMiniEngineTest.run_with_gem("libxml") do
   class LibxmlEngineTest < XMLMiniEngineTest
     def setup
       super
-      LibXML::XML::Error.set_handler(&lambda { |error| }) #silence libxml, exceptions will do
+      LibXML::XML::Error.set_handler(&lambda { |error| }) # silence libxml, exceptions will do
     end
 
     private
diff --git a/activesupport/test/xml_mini_test.rb b/activesupport/test/xml_mini_test.rb
index 5e46406a7b..18a3f2ca66 100644
--- a/activesupport/test/xml_mini_test.rb
+++ b/activesupport/test/xml_mini_test.rb
@@ -114,7 +114,7 @@ module XmlMiniTest
     end
 
     test "#to_tag accepts decimal types" do
-      @xml.to_tag(:b, ::BigDecimal.new("1.2"), @options)
+      @xml.to_tag(:b, BigDecimal("1.2"), @options)
       assert_xml("<b type=\"decimal\">1.2</b>")
     end
 
diff --git a/ci/custom_cops/bin/test b/ci/custom_cops/bin/test
new file mode 100755
index 0000000000..495ffec83a
--- /dev/null
+++ b/ci/custom_cops/bin/test
@@ -0,0 +1,5 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+COMPONENT_ROOT = File.expand_path("..", __dir__)
+require_relative "../../../tools/test"
diff --git a/ci/custom_cops/lib/custom_cops.rb b/ci/custom_cops/lib/custom_cops.rb
new file mode 100644
index 0000000000..157b8247e4
--- /dev/null
+++ b/ci/custom_cops/lib/custom_cops.rb
@@ -0,0 +1,4 @@
+# frozen_string_literal: true
+
+require_relative "custom_cops/refute_not"
+require_relative "custom_cops/assert_not"
diff --git a/ci/custom_cops/lib/custom_cops/assert_not.rb b/ci/custom_cops/lib/custom_cops/assert_not.rb
new file mode 100644
index 0000000000..8b49d3eac2
--- /dev/null
+++ b/ci/custom_cops/lib/custom_cops/assert_not.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+module CustomCops
+  # Enforces the use of `assert_not` over `assert !`.
+  #
+  # @example
+  #   # bad
+  #   assert !x
+  #   assert ! x
+  #
+  #   # good
+  #   assert_not x
+  #
+  class AssertNot < RuboCop::Cop::Cop
+    MSG = "Prefer `assert_not` over `assert !`"
+
+    def_node_matcher :offensive?, "(send nil? :assert (send ... :!) ...)"
+
+    def on_send(node)
+      add_offense(node) if offensive?(node)
+    end
+
+    def autocorrect(node)
+      expression = node.loc.expression
+
+      ->(corrector) do
+        corrector.replace(
+          expression,
+          corrected_source(expression.source)
+        )
+      end
+    end
+
+    private
+
+      def corrected_source(source)
+        source.gsub(/^assert(\(| ) *! */, "assert_not\\1")
+      end
+  end
+end
diff --git a/ci/custom_cops/lib/custom_cops/refute_not.rb b/ci/custom_cops/lib/custom_cops/refute_not.rb
new file mode 100644
index 0000000000..3e89e0fd32
--- /dev/null
+++ b/ci/custom_cops/lib/custom_cops/refute_not.rb
@@ -0,0 +1,71 @@
+# frozen_string_literal: true
+
+module CustomCops
+  # Enforces the use of `#assert_not` methods over `#refute` methods.
+  #
+  # @example
+  #   # bad
+  #   refute false
+  #   refute_empty [1, 2, 3]
+  #   refute_equal true, false
+  #
+  #   # good
+  #   assert_not false
+  #   assert_not_empty [1, 2, 3]
+  #   assert_not_equal true, false
+  #
+  class RefuteNot < RuboCop::Cop::Cop
+    MSG = "Prefer `%<assert_method>s` over `%<refute_method>s`"
+
+    CORRECTIONS = {
+      refute:             "assert_not",
+      refute_empty:       "assert_not_empty",
+      refute_equal:       "assert_not_equal",
+      refute_in_delta:    "assert_not_in_delta",
+      refute_in_epsilon:  "assert_not_in_epsilon",
+      refute_includes:    "assert_not_includes",
+      refute_instance_of: "assert_not_instance_of",
+      refute_kind_of:     "assert_not_kind_of",
+      refute_nil:         "assert_not_nil",
+      refute_operator:    "assert_not_operator",
+      refute_predicate:   "assert_not_predicate",
+      refute_respond_to:  "assert_not_respond_to",
+      refute_same:        "assert_not_same",
+      refute_match:       "assert_no_match"
+    }.freeze
+
+    OFFENSIVE_METHODS = CORRECTIONS.keys.freeze
+
+    def_node_matcher :offensive?, "(send nil? #offensive_method? ...)"
+
+    def on_send(node)
+      return unless offensive?(node)
+
+      message = offense_message(node.method_name)
+      add_offense(node, location: :selector, message: message)
+    end
+
+    def autocorrect(node)
+      ->(corrector) do
+        corrector.replace(
+          node.loc.selector,
+          CORRECTIONS[node.method_name]
+        )
+      end
+    end
+
+    private
+
+      def offensive_method?(method_name)
+        OFFENSIVE_METHODS.include?(method_name)
+      end
+
+      def offense_message(method_name)
+        format(
+          MSG,
+          refute_method: method_name,
+          assert_method: CORRECTIONS[method_name]
+        )
+      end
+  end
+end
diff --git a/ci/custom_cops/test/custom_cops/assert_not_test.rb b/ci/custom_cops/test/custom_cops/assert_not_test.rb
new file mode 100644
index 0000000000..abb151aeb4
--- /dev/null
+++ b/ci/custom_cops/test/custom_cops/assert_not_test.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+require "support/cop_helper"
+require_relative "../../lib/custom_cops/assert_not"
+
+class AssertNotTest < ActiveSupport::TestCase
+  include CopHelper
+
+  setup do
+    @cop = CustomCops::AssertNot.new
+  end
+
+  test "rejects 'assert !'" do
+    inspect_source @cop, "assert !x"
+    assert_offense @cop, "^^^^^^^^^ Prefer `assert_not` over `assert !`"
+  end
+
+  test "rejects 'assert !' with a complex value" do
+    inspect_source @cop, "assert !a.b(c)"
+    assert_offense @cop, "^^^^^^^^^^^^^^ Prefer `assert_not` over `assert !`"
+  end
+
+  test "autocorrects `assert !`" do
+    corrected = autocorrect_source(@cop, "assert !false")
+    assert_equal "assert_not false", corrected
+  end
+
+  test "autocorrects `assert !` with extra spaces" do
+    corrected = autocorrect_source(@cop, "assert   !  false")
+    assert_equal "assert_not false", corrected
+  end
+
+  test "autocorrects `assert !` with parentheses" do
+    corrected = autocorrect_source(@cop, "assert(!false)")
+    assert_equal "assert_not(false)", corrected
+  end
+
+  test "accepts `assert_not`" do
+    inspect_source @cop, "assert_not x"
+    assert_empty @cop.offenses
+  end
+end
diff --git a/ci/custom_cops/test/custom_cops/refute_not_test.rb b/ci/custom_cops/test/custom_cops/refute_not_test.rb
new file mode 100644
index 0000000000..f0f6eaeda0
--- /dev/null
+++ b/ci/custom_cops/test/custom_cops/refute_not_test.rb
@@ -0,0 +1,66 @@
+# frozen_string_literal: true
+
+require "support/cop_helper"
+require_relative "../../lib/custom_cops/refute_not"
+
+class RefuteNotTest < ActiveSupport::TestCase
+  include CopHelper
+
+  setup do
+    @cop = CustomCops::RefuteNot.new
+  end
+
+  {
+    refute:             :assert_not,
+    refute_empty:       :assert_not_empty,
+    refute_equal:       :assert_not_equal,
+    refute_in_delta:    :assert_not_in_delta,
+    refute_in_epsilon:  :assert_not_in_epsilon,
+    refute_includes:    :assert_not_includes,
+    refute_instance_of: :assert_not_instance_of,
+    refute_kind_of:     :assert_not_kind_of,
+    refute_nil:         :assert_not_nil,
+    refute_operator:    :assert_not_operator,
+    refute_predicate:   :assert_not_predicate,
+    refute_respond_to:  :assert_not_respond_to,
+    refute_same:        :assert_not_same,
+    refute_match:       :assert_no_match
+  }.each do |refute_method, assert_method|
+    test "rejects `#{refute_method}` with a single argument" do
+      inspect_source(@cop, "#{refute_method} a")
+      assert_offense @cop, offense_message(refute_method, assert_method)
+    end
+
+    test "rejects `#{refute_method}` with multiple arguments" do
+      inspect_source(@cop, "#{refute_method} a, b, c")
+      assert_offense @cop, offense_message(refute_method, assert_method)
+    end
+
+    test "autocorrects `#{refute_method}` with a single argument" do
+      corrected = autocorrect_source(@cop, "#{refute_method} a")
+      assert_equal "#{assert_method} a", corrected
+    end
+
+    test "autocorrects `#{refute_method}` with multiple arguments" do
+      corrected = autocorrect_source(@cop, "#{refute_method} a, b, c")
+      assert_equal "#{assert_method} a, b, c", corrected
+    end
+
+    test "accepts `#{assert_method}` with a single argument" do
+      inspect_source(@cop, "#{assert_method} a")
+      assert_empty @cop.offenses
+    end
+
+    test "accepts `#{assert_method}` with multiple arguments" do
+      inspect_source(@cop, "#{assert_method} a, b, c")
+      assert_empty @cop.offenses
+    end
+  end
+
+  private
+
+    def offense_message(refute_method, assert_method)
+      carets = "^" * refute_method.to_s.length
+      "#{carets} Prefer `#{assert_method}` over `#{refute_method}`"
+    end
+end
diff --git a/ci/custom_cops/test/support/cop_helper.rb b/ci/custom_cops/test/support/cop_helper.rb
new file mode 100644
index 0000000000..c2c6b969dd
--- /dev/null
+++ b/ci/custom_cops/test/support/cop_helper.rb
@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require "rubocop"
+
+module CopHelper
+  def inspect_source(cop, source)
+    processed_source = parse_source(source)
+    raise "Error parsing example code" unless processed_source.valid_syntax?
+    investigate(cop, processed_source)
+    processed_source
+  end
+
+  def autocorrect_source(cop, source)
+    cop.instance_variable_get(:@options)[:auto_correct] = true
+    processed_source = inspect_source(cop, source)
+    rewrite(cop, processed_source)
+  end
+
+  def assert_offense(cop, expected_message)
+    assert_not_empty(
+      cop.offenses,
+      "Expected offense with message \"#{expected_message}\", but got no offense"
+    )
+
+    offense = cop.offenses.first
+    carets = "^" * offense.column_length
+
+    assert_equal expected_message, "#{carets} #{offense.message}"
+  end
+
+  private
+    TARGET_RUBY_VERSION = 2.4
+
+    def parse_source(source)
+      RuboCop::ProcessedSource.new(source, TARGET_RUBY_VERSION)
+    end
+
+    def rewrite(cop, processed_source)
+      RuboCop::Cop::Corrector.new(processed_source.buffer, cop.corrections)
+        .rewrite
+    end
+
+    def investigate(cop, processed_source)
+      RuboCop::Cop::Commissioner.new([cop], [], raise_error: true)
+        .investigate(processed_source)
+    end
+end
diff --git a/ci/phantomjs.js b/ci/phantomjs.js
deleted file mode 100644
index 7a33fb14a3..0000000000
--- a/ci/phantomjs.js
+++ /dev/null
@@ -1,149 +0,0 @@
-/*
- * PhantomJS Runner QUnit Plugin 1.2.0
- *
- * PhantomJS binaries: http://phantomjs.org/download.html
- * Requires PhantomJS 1.6+ (1.7+ recommended)
- *
- * Run with:
- *   phantomjs runner.js [url-of-your-qunit-testsuite]
- *
- * e.g.
- *   phantomjs runner.js http://localhost/qunit/test/index.html
- */
-
-/*global phantom:false, require:false, console:false, window:false, QUnit:false */
-
-(function() {
-	'use strict';
-
-	var url, page, timeout,
-		args = require('system').args;
-
-	// arg[0]: scriptName, args[1...]: arguments
-	if (args.length < 2 || args.length > 3) {
-		console.error('Usage:\n  phantomjs runner.js [url-of-your-qunit-testsuite] [timeout-in-seconds]');
-		phantom.exit(1);
-	}
-
-	url = args[1];
-	page = require('webpage').create();
-	if (args[2] !== undefined) {
-		timeout = parseInt(args[2], 10);
-	}
-
-	// Route `console.log()` calls from within the Page context to the main Phantom context (i.e. current `this`)
-	page.onConsoleMessage = function(msg) {
-		console.log(msg);
-	};
-
-	page.onInitialized = function() {
-		page.evaluate(addLogging);
-	};
-
-	page.onCallback = function(message) {
-		var result,
-			failed;
-
-		if (message) {
-			if (message.name === 'QUnit.done') {
-				result = message.data;
-				failed = !result || !result.total || result.failed;
-
-				if (!result.total) {
-					console.error('No tests were executed. Are you loading tests asynchronously?');
-				}
-
-				phantom.exit(failed ? 1 : 0);
-			}
-		}
-	};
-
-	page.open(url, function(status) {
-		if (status !== 'success') {
-			console.error('Unable to access network: ' + status);
-			phantom.exit(1);
-		} else {
-			// Cannot do this verification with the 'DOMContentLoaded' handler because it
-			// will be too late to attach it if a page does not have any script tags.
-			var qunitMissing = page.evaluate(function() { return (typeof QUnit === 'undefined' || !QUnit); });
-			if (qunitMissing) {
-				console.error('The `QUnit` object is not present on this page.');
-				phantom.exit(1);
-			}
-
-			// Set a timeout on the test running, otherwise tests with async problems will hang forever
-			if (typeof timeout === 'number') {
-				setTimeout(function() {
-					console.error('The specified timeout of ' + timeout + ' seconds has expired. Aborting...');
-					phantom.exit(1);
-				}, timeout * 1000);
-			}
-
-			// Do nothing... the callback mechanism will handle everything!
-		}
-	});
-
-	function addLogging() {
-		window.document.addEventListener('DOMContentLoaded', function() {
-			var currentTestAssertions = [];
-
-			QUnit.log(function(details) {
-				var response;
-
-				// Ignore passing assertions
-				if (details.result) {
-					return;
-				}
-
-				response = details.message || '';
-
-				if (typeof details.expected !== 'undefined') {
-					if (response) {
-						response += ', ';
-					}
-
-					response += 'expected: ' + details.expected + ', but was: ' + details.actual;
-				}
-
-				if (details.source) {
-					response += "\n" + details.source;
-				}
-
-				currentTestAssertions.push('Failed assertion: ' + response);
-			});
-
-			QUnit.testDone(function(result) {
-				var i,
-					len,
-					name = '';
-
-				if (result.module) {
-					name += result.module + ': ';
-				}
-				name += result.name;
-
-				if (result.failed) {
-					console.log('\n' + 'Test failed: ' + name);
-
-					for (i = 0, len = currentTestAssertions.length; i < len; i++) {
-						console.log('    ' + currentTestAssertions[i]);
-					}
-				}
-
-				currentTestAssertions.length = 0;
-			});
-
-			QUnit.done(function(result) {
-				console.log('\n' + 'Took ' + result.runtime +  'ms to run ' + result.total + ' tests. ' + result.passed + ' passed, ' + result.failed + ' failed.');
-
-				if (typeof window.callPhantom === 'function') {
-					window.callPhantom({
-						'name': 'QUnit.done',
-						'data': result
-					});
-				}
-			});
-		}, false);
-	}
-})();
-
diff --git a/ci/qunit-selenium-runner.rb b/ci/qunit-selenium-runner.rb
new file mode 100644
index 0000000000..05bcab8cdb
--- /dev/null
+++ b/ci/qunit-selenium-runner.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+require "qunit/selenium/test_runner"
+require "chromedriver/helper"
+
+driver_options = Selenium::WebDriver::Chrome::Options.new
+driver_options.add_argument("--headless")
+driver_options.add_argument("--disable-gpu")
+driver_options.add_argument("--no-sandbox")
+
+driver = ::Selenium::WebDriver.for(:chrome, options: driver_options)
+result = QUnit::Selenium::TestRunner.new(driver).open(ARGV[0], timeout: 60)
+driver.quit
+
+puts "Time: #{result.duration} seconds, Total: #{result.assertions[:total]}, Passed: #{result.assertions[:passed]}, Failed: #{result.assertions[:failed]}"
+exit(result.tests[:failed] > 0 ? 1 : 0)
diff --git a/ci/travis.rb b/ci/travis.rb
index b124358789..861063afa5 100755
--- a/ci/travis.rb
+++ b/ci/travis.rb
@@ -135,7 +135,7 @@ class Build
     if activesupport? && !isolated?
       # There is a known issue with the listen tests that causes files to be
       # incorrectly GC'ed even when they are still in-use. The current solution
-      # is to only run them in isolation to avoid randomly failing our test suite.
+      # is to only run them in isolation to avoid random failures of our test suite.
       { "LISTEN" => "0" }
     else
       {}
@@ -159,7 +159,7 @@ results = {}
 ENV["GEM"].split(",").each do |gem|
   [false, true].each do |isolated|
     next if ENV["TRAVIS_PULL_REQUEST"] && ENV["TRAVIS_PULL_REQUEST"] != "false" && isolated
-    next if RUBY_VERSION < "2.4" && isolated
+    next if RUBY_VERSION < "2.5" && isolated
     next if gem == "railties" && isolated
     next if gem == "ac" && isolated
     next if gem == "ac:integration" && isolated
diff --git a/guides/CHANGELOG.md b/guides/CHANGELOG.md
index d8b122d264..0307e06fd9 100644
--- a/guides/CHANGELOG.md
+++ b/guides/CHANGELOG.md
@@ -1 +1,6 @@
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/guides/CHANGELOG.md) for previous changes.
+*   Rails 6 requires Ruby 2.4.1 or newer.
+
+    *Jeremy Daer*
+
+
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/guides/CHANGELOG.md) for previous changes.
diff --git a/guides/assets/images/rails4_features.png b/guides/assets/images/4_0_release_notes/rails4_features.png
index ac73f05cf7..ac73f05cf7 100644
--- a/guides/assets/images/rails4_features.png
+++ b/guides/assets/images/4_0_release_notes/rails4_features.png
diff --git a/guides/assets/images/akshaysurve.jpg b/guides/assets/images/akshaysurve.jpg
deleted file mode 100644
index cfc3333958..0000000000
--- a/guides/assets/images/akshaysurve.jpg
+++ /dev/null
diff --git a/guides/assets/images/association_basics/belongs_to.png b/guides/assets/images/association_basics/belongs_to.png
new file mode 100644
index 0000000000..2b8c1d52ea
--- /dev/null
+++ b/guides/assets/images/association_basics/belongs_to.png
diff --git a/guides/assets/images/association_basics/habtm.png b/guides/assets/images/association_basics/habtm.png
new file mode 100644
index 0000000000..7e508cc1a6
--- /dev/null
+++ b/guides/assets/images/association_basics/habtm.png
diff --git a/guides/assets/images/association_basics/has_many.png b/guides/assets/images/association_basics/has_many.png
new file mode 100644
index 0000000000..36ccf9f0f6
--- /dev/null
+++ b/guides/assets/images/association_basics/has_many.png
diff --git a/guides/assets/images/association_basics/has_many_through.png b/guides/assets/images/association_basics/has_many_through.png
new file mode 100644
index 0000000000..9e9caabd73
--- /dev/null
+++ b/guides/assets/images/association_basics/has_many_through.png
diff --git a/guides/assets/images/association_basics/has_one.png b/guides/assets/images/association_basics/has_one.png
new file mode 100644
index 0000000000..c29c6b9c59
--- /dev/null
+++ b/guides/assets/images/association_basics/has_one.png
diff --git a/guides/assets/images/association_basics/has_one_through.png b/guides/assets/images/association_basics/has_one_through.png
new file mode 100644
index 0000000000..fdf13286c4
--- /dev/null
+++ b/guides/assets/images/association_basics/has_one_through.png
diff --git a/guides/assets/images/association_basics/polymorphic.png b/guides/assets/images/association_basics/polymorphic.png
new file mode 100644
index 0000000000..d630db9e01
--- /dev/null
+++ b/guides/assets/images/association_basics/polymorphic.png
diff --git a/guides/assets/images/belongs_to.png b/guides/assets/images/belongs_to.png
deleted file mode 100644
index 1a9926e578..0000000000
--- a/guides/assets/images/belongs_to.png
+++ /dev/null
diff --git a/guides/assets/images/credits_pic_blank.gif b/guides/assets/images/credits_pic_blank.gif
deleted file mode 100644
index a6b335d0c9..0000000000
--- a/guides/assets/images/credits_pic_blank.gif
+++ /dev/null
diff --git a/guides/assets/images/fxn.png b/guides/assets/images/fxn.png
deleted file mode 100644
index 733d380cba..0000000000
--- a/guides/assets/images/fxn.png
+++ /dev/null
diff --git a/guides/assets/images/getting_started/rails_welcome.png b/guides/assets/images/getting_started/rails_welcome.png
index 44f89ec8de..88efe34a9d 100644
--- a/guides/assets/images/getting_started/rails_welcome.png
+++ b/guides/assets/images/getting_started/rails_welcome.png
diff --git a/guides/assets/images/getting_started/routing_error_no_route_matches.png b/guides/assets/images/getting_started/routing_error_no_route_matches.png
deleted file mode 100644
index 08c54f921f..0000000000
--- a/guides/assets/images/getting_started/routing_error_no_route_matches.png
+++ /dev/null
diff --git a/guides/assets/images/habtm.png b/guides/assets/images/habtm.png
deleted file mode 100644
index 41013b743d..0000000000
--- a/guides/assets/images/habtm.png
+++ /dev/null
diff --git a/guides/assets/images/has_many.png b/guides/assets/images/has_many.png
deleted file mode 100644
index 0d67bea38b..0000000000
--- a/guides/assets/images/has_many.png
+++ /dev/null
diff --git a/guides/assets/images/has_many_through.png b/guides/assets/images/has_many_through.png
deleted file mode 100644
index b4da60e1fb..0000000000
--- a/guides/assets/images/has_many_through.png
+++ /dev/null
diff --git a/guides/assets/images/has_one.png b/guides/assets/images/has_one.png
deleted file mode 100644
index c70763856a..0000000000
--- a/guides/assets/images/has_one.png
+++ /dev/null
diff --git a/guides/assets/images/has_one_through.png b/guides/assets/images/has_one_through.png
deleted file mode 100644
index 888a02b775..0000000000
--- a/guides/assets/images/has_one_through.png
+++ /dev/null
diff --git a/guides/assets/images/header_backdrop.png b/guides/assets/images/header_backdrop.png
deleted file mode 100644
index 81f4d91774..0000000000
--- a/guides/assets/images/header_backdrop.png
+++ /dev/null
diff --git a/guides/assets/images/icons/README b/guides/assets/images/icons/README
deleted file mode 100644
index 09da77fc86..0000000000
--- a/guides/assets/images/icons/README
+++ /dev/null
@@ -1,5 +0,0 @@
-Replaced the plain DocBook XSL admonition icons with Jimmac's DocBook
-icons (http://jimmac.musichall.cz/ikony.php3). I dropped transparency
-from the Jimmac icons to get round MS IE and FOP PNG incompatibilities.
-
-Stuart Rackham
diff --git a/guides/assets/images/icons/callouts/1.png b/guides/assets/images/icons/callouts/1.png
deleted file mode 100644
index c5d02adcf4..0000000000
--- a/guides/assets/images/icons/callouts/1.png
+++ /dev/null
diff --git a/guides/assets/images/icons/callouts/10.png b/guides/assets/images/icons/callouts/10.png
deleted file mode 100644
index fe89f9ef83..0000000000
--- a/guides/assets/images/icons/callouts/10.png
+++ /dev/null
diff --git a/guides/assets/images/icons/callouts/11.png b/guides/assets/images/icons/callouts/11.png
deleted file mode 100644
index 3b7b9318e7..0000000000
--- a/guides/assets/images/icons/callouts/11.png
+++ /dev/null
diff --git a/guides/assets/images/icons/callouts/12.png b/guides/assets/images/icons/callouts/12.png
deleted file mode 100644
index 7b95925e9d..0000000000
--- a/guides/assets/images/icons/callouts/12.png
+++ /dev/null
diff --git a/guides/assets/images/icons/callouts/13.png b/guides/assets/images/icons/callouts/13.png
deleted file mode 100644
index 4b99fe8efc..0000000000
--- a/guides/assets/images/icons/callouts/13.png
+++ /dev/null
diff --git a/guides/assets/images/icons/callouts/14.png b/guides/assets/images/icons/callouts/14.png
deleted file mode 100644
index dbde9ca749..0000000000
--- a/guides/assets/images/icons/callouts/14.png
+++ /dev/null
diff --git a/guides/assets/images/icons/callouts/15.png b/guides/assets/images/icons/callouts/15.png
deleted file mode 100644
index 70e4bba615..0000000000
--- a/guides/assets/images/icons/callouts/15.png
+++ /dev/null
diff --git a/guides/assets/images/icons/callouts/2.png b/guides/assets/images/icons/callouts/2.png
deleted file mode 100644
index 8c57970ba9..0000000000
--- a/guides/assets/images/icons/callouts/2.png
+++ /dev/null
diff --git a/guides/assets/images/icons/callouts/3.png b/guides/assets/images/icons/callouts/3.png
deleted file mode 100644
index 57a33d15b4..0000000000
--- a/guides/assets/images/icons/callouts/3.png
+++ /dev/null
diff --git a/guides/assets/images/icons/callouts/4.png b/guides/assets/images/icons/callouts/4.png
deleted file mode 100644
index f061ab02b8..0000000000
--- a/guides/assets/images/icons/callouts/4.png
+++ /dev/null
diff --git a/guides/assets/images/icons/callouts/5.png b/guides/assets/images/icons/callouts/5.png
deleted file mode 100644
index b4de02da11..0000000000
--- a/guides/assets/images/icons/callouts/5.png
+++ /dev/null
diff --git a/guides/assets/images/icons/callouts/6.png b/guides/assets/images/icons/callouts/6.png
deleted file mode 100644
index 0e055eec1e..0000000000
--- a/guides/assets/images/icons/callouts/6.png
+++ /dev/null
diff --git a/guides/assets/images/icons/callouts/7.png b/guides/assets/images/icons/callouts/7.png
deleted file mode 100644
index 5ead87d040..0000000000
--- a/guides/assets/images/icons/callouts/7.png
+++ /dev/null
diff --git a/guides/assets/images/icons/callouts/8.png b/guides/assets/images/icons/callouts/8.png
deleted file mode 100644
index cb99545eb6..0000000000
--- a/guides/assets/images/icons/callouts/8.png
+++ /dev/null
diff --git a/guides/assets/images/icons/callouts/9.png b/guides/assets/images/icons/callouts/9.png
deleted file mode 100644
index 0ac03602f6..0000000000
--- a/guides/assets/images/icons/callouts/9.png
+++ /dev/null
diff --git a/guides/assets/images/icons/caution.png b/guides/assets/images/icons/caution.png
deleted file mode 100644
index 7227b54b32..0000000000
--- a/guides/assets/images/icons/caution.png
+++ /dev/null
diff --git a/guides/assets/images/icons/example.png b/guides/assets/images/icons/example.png
deleted file mode 100644
index a0e855befa..0000000000
--- a/guides/assets/images/icons/example.png
+++ /dev/null
diff --git a/guides/assets/images/icons/home.png b/guides/assets/images/icons/home.png
deleted file mode 100644
index e70e164522..0000000000
--- a/guides/assets/images/icons/home.png
+++ /dev/null
diff --git a/guides/assets/images/icons/important.png b/guides/assets/images/icons/important.png
deleted file mode 100644
index bab53bf3aa..0000000000
--- a/guides/assets/images/icons/important.png
+++ /dev/null
diff --git a/guides/assets/images/icons/next.png b/guides/assets/images/icons/next.png
deleted file mode 100644
index a158832725..0000000000
--- a/guides/assets/images/icons/next.png
+++ /dev/null
diff --git a/guides/assets/images/icons/note.png b/guides/assets/images/icons/note.png
deleted file mode 100644
index 62eec7845f..0000000000
--- a/guides/assets/images/icons/note.png
+++ /dev/null
diff --git a/guides/assets/images/icons/prev.png b/guides/assets/images/icons/prev.png
deleted file mode 100644
index 8a96960422..0000000000
--- a/guides/assets/images/icons/prev.png
+++ /dev/null
diff --git a/guides/assets/images/icons/tip.png b/guides/assets/images/icons/tip.png
deleted file mode 100644
index a5316d318f..0000000000
--- a/guides/assets/images/icons/tip.png
+++ /dev/null
diff --git a/guides/assets/images/icons/up.png b/guides/assets/images/icons/up.png
deleted file mode 100644
index 6cac818170..0000000000
--- a/guides/assets/images/icons/up.png
+++ /dev/null
diff --git a/guides/assets/images/icons/warning.png b/guides/assets/images/icons/warning.png
deleted file mode 100644
index 72a8a5d873..0000000000
--- a/guides/assets/images/icons/warning.png
+++ /dev/null
diff --git a/guides/assets/images/oscardelben.jpg b/guides/assets/images/oscardelben.jpg
deleted file mode 100644
index 9f3f67c2c7..0000000000
--- a/guides/assets/images/oscardelben.jpg
+++ /dev/null
diff --git a/guides/assets/images/polymorphic.png b/guides/assets/images/polymorphic.png
deleted file mode 100644
index e0a7f6d64a..0000000000
--- a/guides/assets/images/polymorphic.png
+++ /dev/null
diff --git a/guides/assets/images/radar.png b/guides/assets/images/radar.png
deleted file mode 100644
index 421b62b623..0000000000
--- a/guides/assets/images/radar.png
+++ /dev/null
diff --git a/guides/assets/images/rails_logo_remix.gif b/guides/assets/images/rails_logo_remix.gif
deleted file mode 100644
index 58960ee4f9..0000000000
--- a/guides/assets/images/rails_logo_remix.gif
+++ /dev/null
diff --git a/guides/assets/images/csrf.png b/guides/assets/images/security/csrf.png
index a8123d47c3..a8123d47c3 100644
--- a/guides/assets/images/csrf.png
+++ b/guides/assets/images/security/csrf.png
diff --git a/guides/assets/images/session_fixation.png b/guides/assets/images/security/session_fixation.png
index e009484f09..e009484f09 100644
--- a/guides/assets/images/session_fixation.png
+++ b/guides/assets/images/security/session_fixation.png
diff --git a/guides/assets/images/tab_yellow.png b/guides/assets/images/tab_yellow.png
deleted file mode 100644
index 053c807d28..0000000000
--- a/guides/assets/images/tab_yellow.png
+++ /dev/null
diff --git a/guides/assets/images/vijaydev.jpg b/guides/assets/images/vijaydev.jpg
deleted file mode 100644
index fe5e4f1cb4..0000000000
--- a/guides/assets/images/vijaydev.jpg
+++ /dev/null
diff --git a/guides/assets/javascripts/guides.js b/guides/assets/javascripts/guides.js
index e4d25dfb21..e39ac239cd 100644
--- a/guides/assets/javascripts/guides.js
+++ b/guides/assets/javascripts/guides.js
@@ -1,53 +1,54 @@
-$.fn.selectGuide = function(guide) {
-  $("select", this).val(guide);
-};
-
-var guidesIndex = {
-  bind: function() {
-    var currentGuidePath = window.location.pathname;
-    var currentGuide = currentGuidePath.substring(currentGuidePath.lastIndexOf("/")+1);
-    $(".guides-index-small").
-      on("change", "select", guidesIndex.navigate).
-      selectGuide(currentGuide);
-    $(document).on("click", ".more-info-button", function(e){
-      e.stopPropagation();
-      if ($(".more-info-links").is(":visible")) {
-        $(".more-info-links").addClass("s-hidden").unwrap();
-      } else {
-        $(".more-info-links").wrap("<div class='more-info-container'></div>").removeClass("s-hidden");
-      }
-    });
-    $("#guidesMenu").on("click", function(e) {
-      $("#guides").toggle();
-      return false;
+(function() {
+  "use strict";
+
+  this.syntaxhighlighterConfig = { autoLinks: false };
+
+  this.wrap = function(elem, wrapper) {
+    elem.parentNode.insertBefore(wrapper, elem);
+    wrapper.appendChild(elem);
+  }
+
+  this.unwrap = function(elem) {
+    var wrapper = elem.parentNode;
+    wrapper.parentNode.replaceChild(elem, wrapper);
+  }
+
+  this.createElement = function(tagName, className) {
+    var elem = document.createElement(tagName);
+    elem.classList.add(className);
+    return elem;
+  }
+
+  document.addEventListener("DOMContentLoaded", function() {
+    var guidesMenu = document.getElementById("guidesMenu");
+    var guides     = document.getElementById("guides");
+
+    guidesMenu.addEventListener("click", function(e) {
+      e.preventDefault();
+      guides.classList.toggle("visible");
     });
-    $(document).on("click", function(e){
-      e.stopPropagation();
-      var $button = $(".more-info-button");
-      var element;
 
-      // Cross browser find the element that had the event
-      if (e.target) element = e.target;
-      else if (e.srcElement) element = e.srcElement;
+    var guidesIndexItem   = document.querySelector("select.guides-index-item");
+    var currentGuidePath  = window.location.pathname;
+    guidesIndexItem.value = currentGuidePath.substring(currentGuidePath.lastIndexOf("/") + 1);
 
-      // Defeat the older Safari bug:
-      // http://www.quirksmode.org/js/events_properties.html
-      if (element.nodeType === 3) element = element.parentNode;
+    guidesIndexItem.addEventListener("change", function(e) {
+      window.location = e.target.value;
+    });
 
-      var $element = $(element);
+    var moreInfoButton = document.querySelector(".more-info-button");
+    var moreInfoLinks  = document.querySelector(".more-info-links");
 
-      var $container = $element.parents(".more-info-container");
+    moreInfoButton.addEventListener("click", function(e) {
+      e.preventDefault();
 
-      // We've captured a click outside the popup
-      if($container.length === 0){
-        $container = $button.next(".more-info-container");
-        $container.find(".more-info-links").addClass("s-hidden").unwrap();
+      if (moreInfoLinks.classList.contains("s-hidden")) {
+        wrap(moreInfoLinks, createElement("div", "more-info-container"));
+        moreInfoLinks.classList.remove("s-hidden");
+      } else {
+        moreInfoLinks.classList.add("s-hidden");
+        unwrap(moreInfoLinks);
       }
     });
-  },
-  navigate: function(e){
-    var $list = $(e.target);
-    var url = $list.val();
-    window.location = url;
-  }
-};
+  });
+}).call(this);
diff --git a/guides/assets/javascripts/jquery.min.js b/guides/assets/javascripts/jquery.min.js
deleted file mode 100644
index 93adea19fd..0000000000
--- a/guides/assets/javascripts/jquery.min.js
+++ /dev/null
@@ -1,4 +0,0 @@
-/*! jQuery v1.7.2 jquery.com | jquery.org/license */
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b,c,d,e=cq||cr(),g=!0,h=this.elem,i=this.options;if(a||e>=i.duration+this.startTime){this.now=this.end,this.pos=this.state=1,this.update(),i.animatedProperties[this.prop]=!0;for(b in i.animatedProperties)i.animatedProperties[b]!==!0&&(g=!1);if(g){i.overflow!=null&&!f.support.shrinkWrapBlocks&&f.each(["","X","Y"],function(a,b){h.style["overflow"+b]=i.overflow[a]}),i.hide&&f(h).hide();if(i.hide||i.show)for(b in i.animatedProperties)f.style(h,b,i.orig[b]),f.removeData(h,"fxshow"+b,!0),f.removeData(h,"toggle"+b,!0);d=i.complete,d&&(i.complete=!1,d.call(h))}return!1}i.duration==Infinity?this.now=e:(c=e-this.startTime,this.state=c/i.duration,this.pos=f.easing[i.animatedProperties[this.prop]](this.state,c,0,1,i.duration),this.now=this.start+(this.end-this.start)*this.pos),this.update();return!0}},f.extend(f.fx,{tick:function(){var a,b=f.timers,c=0;for(;c<b.length;c++)a=b[c],!a()&&b[c]===a&&b.splice(c--,1);b.length||f.fx.stop()},interval:13,stop:function(){clearInterval(co),co=null},speeds:{slow:600,fast:200,_default:400},step:{opacity:function(a){f.style(a.elem,"opacity",a.now)},_default:function(a){a.elem.style&&a.elem.style[a.prop]!=null?a.elem.style[a.prop]=a.now+a.unit:a.elem[a.prop]=a.now}}}),f.each(cp.concat.apply([],cp),function(a,b){b.indexOf("margin")&&(f.fx.step[b]=function(a){f.style(a.elem,b,Math.max(0,a.now)+a.unit)})}),f.expr&&f.expr.filters&&(f.expr.filters.animated=function(a){return f.grep(f.timers,function(b){return a===b.elem}).length});var cv,cw=/^t(?:able|d|h)$/i,cx=/^(?:body|html)$/i;"getBoundingClientRect"in c.documentElement?cv=function(a,b,c,d){try{d=a.getBoundingClientRect()}catch(e){}if(!d||!f.contains(c,a))return d?{top:d.top,left:d.left}:{top:0,left:0};var g=b.body,h=cy(b),i=c.clientTop||g.clientTop||0,j=c.clientLeft||g.clientLeft||0,k=h.pageYOffset||f.support.boxModel&&c.scrollTop||g.scrollTop,l=h.pageXOffset||f.support.boxModel&&c.scrollLeft||g.scrollLeft,m=d.top+k-i,n=d.left+l-j;return{top:m,left:n}}:cv=function(a,b,c){var d,e=a.offsetParent,g=a,h=b.body,i=b.defaultView,j=i?i.getComputedStyle(a,null):a.currentStyle,k=a.offsetTop,l=a.offsetLeft;while((a=a.parentNode)&&a!==h&&a!==c){if(f.support.fixedPosition&&j.position==="fixed")break;d=i?i.getComputedStyle(a,null):a.currentStyle,k-=a.scrollTop,l-=a.scrollLeft,a===e&&(k+=a.offsetTop,l+=a.offsetLeft,f.support.doesNotAddBorder&&(!f.support.doesAddBorderForTableAndCells||!cw.test(a.nodeName))&&(k+=parseFloat(d.borderTopWidth)||0,l+=parseFloat(d.borderLeftWidth)||0),g=e,e=a.offsetParent),f.support.subtractsBorderForOverflowNotVisible&&d.overflow!=="visible"&&(k+=parseFloat(d.borderTopWidth)||0,l+=parseFloat(d.borderLeftWidth)||0),j=d}if(j.position==="relative"||j.position==="static")k+=h.offsetTop,l+=h.offsetLeft;f.support.fixedPosition&&j.position==="fixed"&&(k+=Math.max(c.scrollTop,h.scrollTop),l+=Math.max(c.scrollLeft,h.scrollLeft));return{top:k,left:l}},f.fn.offset=function(a){if(arguments.length)return a===b?this:this.each(function(b){f.offset.setOffset(this,a,b)});var c=this[0],d=c&&c.ownerDocument;if(!d)return null;if(c===d.body)return f.offset.bodyOffset(c);return cv(c,d,d.documentElement)},f.offset={bodyOffset:function(a){var b=a.offsetTop,c=a.offsetLeft;f.support.doesNotIncludeMarginInBodyOffset&&(b+=parseFloat(f.css(a,"marginTop"))||0,c+=parseFloat(f.css(a,"marginLeft"))||0);return{top:b,left:c}},setOffset:function(a,b,c){var d=f.css(a,"position");d==="static"&&(a.style.position="relative");var e=f(a),g=e.offset(),h=f.css(a,"top"),i=f.css(a,"left"),j=(d==="absolute"||d==="fixed")&&f.inArray("auto",[h,i])>-1,k={},l={},m,n;j?(l=e.position(),m=l.top,n=l.left):(m=parseFloat(h)||0,n=parseFloat(i)||0),f.isFunction(b)&&(b=b.call(a,c,g)),b.top!=null&&(k.top=b.top-g.top+m),b.left!=null&&(k.left=b.left-g.left+n),"using"in b?b.using.call(a,k):e.css(k)}},f.fn.extend({position:function(){if(!this[0])return null;var a=this[0],b=this.offsetParent(),c=this.offset(),d=cx.test(b[0].nodeName)?{top:0,left:0}:b.offset();c.top-=parseFloat(f.css(a,"marginTop"))||0,c.left-=parseFloat(f.css(a,"marginLeft"))||0,d.top+=parseFloat(f.css(b[0],"borderTopWidth"))||0,d.left+=parseFloat(f.css(b[0],"borderLeftWidth"))||0;return{top:c.top-d.top,left:c.left-d.left}},offsetParent:function(){return this.map(function(){var a=this.offsetParent||c.body;while(a&&!cx.test(a.nodeName)&&f.css(a,"position")==="static")a=a.offsetParent;return a})}}),f.each({scrollLeft:"pageXOffset",scrollTop:"pageYOffset"},function(a,c){var d=/Y/.test(c);f.fn[a]=function(e){return f.access(this,function(a,e,g){var h=cy(a);if(g===b)return h?c in h?h[c]:f.support.boxModel&&h.document.documentElement[e]||h.document.body[e]:a[e];h?h.scrollTo(d?f(h).scrollLeft():g,d?g:f(h).scrollTop()):a[e]=g},a,e,arguments.length,null)}}),f.each({Height:"height",Width:"width"},function(a,c){var d="client"+a,e="scroll"+a,g="offset"+a;f.fn["inner"+a]=function(){var a=this[0];return a?a.style?parseFloat(f.css(a,c,"padding")):this[c]():null},f.fn["outer"+a]=function(a){var b=this[0];return b?b.style?parseFloat(f.css(b,c,a?"margin":"border")):this[c]():null},f.fn[c]=function(a){return f.access(this,function(a,c,h){var i,j,k,l;if(f.isWindow(a)){i=a.document,j=i.documentElement[d];return f.support.boxModel&&j||i.body&&i.body[d]||j}if(a.nodeType===9){i=a.documentElement;if(i[d]>=i[e])return i[d];return Math.max(a.body[e],i[e],a.body[g],i[g])}if(h===b){k=f.css(a,c),l=parseFloat(k);return f.isNumeric(l)?l:k}f(a).css(c,h)},c,a,arguments.length,null)}}),a.jQuery=a.$=f,typeof define=="function"&&define.amd&&define.amd.jQuery&&define("jquery",[],function(){return f})})(window);
-\ No newline at end of file
diff --git a/guides/assets/javascripts/responsive-tables.js b/guides/assets/javascripts/responsive-tables.js
index 8554a1343b..24906dddeb 100644
--- a/guides/assets/javascripts/responsive-tables.js
+++ b/guides/assets/javascripts/responsive-tables.js
@@ -1,43 +1,50 @@
-$(document).ready(function() {
+(function() {
+  "use strict";
+
   var switched = false;
-  $("table").not(".syntaxhighlighter").addClass("responsive");
+
+  // For old browsers
+  var each = function(node, callback) {
+    var array = Array.prototype.slice.call(node);
+    for(var i = 0; i < array.length; i++) callback(array[i]);
+  }
+
+  each(document.querySelectorAll(":not(.syntaxhighlighter)>table"), function(element) {
+    element.classList.add("responsive");
+  });
+
   var updateTables = function() {
-    if (($(window).width() < 767) && !switched ){
+    if (document.documentElement.clientWidth < 767 && !switched) {
       switched = true;
-      $("table.responsive").each(function(i, element) {
-        splitTable($(element));
-      });
-      return true;
-    }
-    else if (switched && ($(window).width() > 767)) {
+      each(document.querySelectorAll("table.responsive"), splitTable);
+    } else {
       switched = false;
-      $("table.responsive").each(function(i, element) {
-        unsplitTable($(element));
-      });
+      each(document.querySelectorAll(".table-wrapper table.responsive"), unsplitTable);
     }
-  };
-   
-  $(window).load(updateTables);
-  $(window).bind("resize", updateTables);
-   
-	
-	function splitTable(original)
-	{
-		original.wrap("<div class='table-wrapper' />");
-		
-		var copy = original.clone();
-		copy.find("td:not(:first-child), th:not(:first-child)").css("display", "none");
-		copy.removeClass("responsive");
-		
-		original.closest(".table-wrapper").append(copy);
-		copy.wrap("<div class='pinned' />");
-		original.wrap("<div class='scrollable' />");
-	}
-	
-	function unsplitTable(original) {
-    original.closest(".table-wrapper").find(".pinned").remove();
-    original.unwrap();
-    original.unwrap();
-	}
-
-});
+  }
+
+  document.addEventListener("DOMContentLoaded", updateTables);
+  window.addEventListener("resize", updateTables);
+
+  var splitTable = function(original) {
+    wrap(original, createElement("div", "table-wrapper"));
+
+    var copy = original.cloneNode(true);
+    each(copy.querySelectorAll("td:not(:first-child), th:not(:first-child)"), function(element) {
+      element.style.display = "none";
+    });
+    copy.classList.remove("responsive");
+
+    original.parentNode.append(copy);
+    wrap(copy, createElement("div", "pinned"))
+    wrap(original, createElement("div", "scrollable"));
+  }
+
+  var unsplitTable = function(original) {
+    each(document.querySelectorAll(".table-wrapper .pinned"), function(element) {
+      element.parentNode.removeChild(element);
+    });
+    unwrap(original.parentNode);
+    unwrap(original);
+  }
+}).call(this);
diff --git a/guides/assets/stylesheets/main.css b/guides/assets/stylesheets/main.css
index b27776745a..00d4bcb21e 100644
--- a/guides/assets/stylesheets/main.css
+++ b/guides/assets/stylesheets/main.css
@@ -70,7 +70,7 @@ table {
 }
 
 table th, table td {
-  padding: 0.25em 1em;
+  padding: 9px 10px;
   border: 1px solid #CCC;
   border-collapse: collapse;
 }
@@ -79,7 +79,6 @@ table th {
   border-bottom: 2px solid #CCC;
   background: #EEE;
   font-weight: bold;
-  padding: 0.5em 1em;
 }
 
 img {
@@ -265,8 +264,6 @@ body {
   }
 }
 
-#extraCol {display: none;}
-
 #footer {
   padding: 2em 0;
   background: #222 url(../images/footer_tile.gif) repeat-x;
@@ -410,6 +407,10 @@ a, a:link, a:visited {
   padding-top: 2em;
 }
 
+#guides.visible {
+  display: block !important;
+}
+
 #guides dt, #guides dd {
   font-weight: normal;
   font-size: 0.722em;
@@ -555,8 +556,6 @@ h6 {
   font-size: 1.2857em;
   padding: 0.125em 0 0.25em 0;
   margin-bottom: 0;
-  /*background: url(../images/book_icon.gif) no-repeat left top;
-  padding: 0.125em 0 0.25em 28px;*/
 }
 
 @media screen and (max-width: 480px) {
@@ -665,10 +664,8 @@ div.code_container {
   visibility: hidden;
 }
 
-.clearfix {display: inline-block;}
 * html .clearfix {height: 1%;}
 .clearfix {display: block;}
-.clear { clear:both; }
 
 /* Same bottom margin for special boxes than for regular paragraphs, this way
 intermediate whitespace looks uniform. */
@@ -696,9 +693,6 @@ div.important p, div.caution p, div.warning p, div.note p, div.info p {
 /* Foundation v2.1.4 http://foundation.zurb.com */
 /* Artfully masterminded by ZURB  */
 
-table th { font-weight: bold; }
-table td, table th { padding: 9px 10px; text-align: left; }
-
 /* Mobile */
 @media only screen and (max-width: 767px) {
   table.responsive { margin-bottom: 0; }
diff --git a/guides/assets/stylesheets/print.css b/guides/assets/stylesheets/print.css
index bdc8ec948d..6280422469 100644
--- a/guides/assets/stylesheets/print.css
+++ b/guides/assets/stylesheets/print.css
@@ -4,7 +4,7 @@
 /* Modified January 31, 2009
 --------------------------------------- */
 
-body, .wrapper, .note, .info, code, #topNav, .L, .R, #frame, #container, #header, #navigation, #footer, #feature, #mainCol, #subCol, #extraCol, .content {position: static; text-align: left; text-indent: 0; background: White; color: Black; border-color: Black; width: auto; height: auto; display: block; float: none; min-height: 0; margin: 0; padding: 0;}
+body, .wrapper, .note, .info, code, #topNav, .L, .R, #frame, #container, #header, #navigation, #footer, #feature, #mainCol, #subCol, .content {position: static; text-align: left; text-indent: 0; background: White; color: Black; border-color: Black; width: auto; height: auto; display: block; float: none; min-height: 0; margin: 0; padding: 0;}
 
 body {
   background: #FFF;
diff --git a/guides/assets/stylesheets/responsive-tables.css b/guides/assets/stylesheets/responsive-tables.css
deleted file mode 100644
index f5fbcbf948..0000000000
--- a/guides/assets/stylesheets/responsive-tables.css
+++ /dev/null
@@ -1,50 +0,0 @@
-/* Foundation v2.1.4 http://foundation.zurb.com */
-/* Artfully masterminded by ZURB  */
-
-/* -------------------------------------------------- 
-   Table of Contents
------------------------------------------------------
-:: Shared Styles
-:: Page Name 1
-:: Page Name 2
-*/
-
-
-/* -----------------------------------------
-   Shared Styles
------------------------------------------ */
-
-table th { font-weight: bold; }
-table td, table th { padding: 9px 10px; text-align: left; }
-
-/* Mobile */
-@media only screen and (max-width: 767px) {
-	
-	table { margin-bottom: 0; }
-	
-	.pinned { position: absolute; left: 0; top: 0; background: #fff; width: 35%; overflow: hidden; overflow-x: scroll; border-right: 1px solid #ccc; border-left: 1px solid #ccc; }
-	.pinned table { border-right: none; border-left: none; width: 100%; }
-	.pinned table th, .pinned table td { white-space: nowrap; }
-	.pinned td:last-child { border-bottom: 0; }
-	
-	div.table-wrapper { position: relative; margin-bottom: 20px; overflow: hidden; border-right: 1px solid #ccc; }
-	div.table-wrapper div.scrollable table { margin-left: 35%; }
-	div.table-wrapper div.scrollable { overflow: scroll; overflow-y: hidden; }	
-	
-	table td, table th { position: relative; white-space: nowrap; overflow: hidden; }
-	table th:first-child, table td:first-child, table td:first-child, table.pinned td { display: none; }
-	
-}
-
-/* -----------------------------------------
-   Page Name 1
------------------------------------------ */
-
-
-
-
-/* -----------------------------------------
-   Page Name 2
------------------------------------------ */
-
-
diff --git a/guides/bug_report_templates/action_controller_gem.rb b/guides/bug_report_templates/action_controller_gem.rb
index 4d8d8db3e5..e8b6ad19dd 100644
--- a/guides/bug_report_templates/action_controller_gem.rb
+++ b/guides/bug_report_templates/action_controller_gem.rb
@@ -9,8 +9,11 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   # Activate the gem you are reporting the issue against.
-  gem "rails", "5.1.0"
+  gem "rails", "5.2.0"
 end
 
 require "rack/test"
@@ -19,7 +22,6 @@ require "action_controller/railtie"
 class TestApp < Rails::Application
   config.root = __dir__
   config.session_store :cookie_store, key: "cookie_store_key"
-  secrets.secret_token    = "secret_token"
   secrets.secret_key_base = "secret_key_base"
 
   config.logger = Logger.new($stdout)
diff --git a/guides/bug_report_templates/action_controller_master.rb b/guides/bug_report_templates/action_controller_master.rb
index 1f862e07da..ffd81c0079 100644
--- a/guides/bug_report_templates/action_controller_master.rb
+++ b/guides/bug_report_templates/action_controller_master.rb
@@ -9,15 +9,16 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   gem "rails", github: "rails/rails"
-  gem "arel", github: "rails/arel"
 end
 
 require "action_controller/railtie"
 
 class TestApp < Rails::Application
   config.root = __dir__
-  secrets.secret_token    = "secret_token"
   secrets.secret_key_base = "secret_key_base"
 
   config.logger = Logger.new($stdout)
diff --git a/guides/bug_report_templates/active_job_gem.rb b/guides/bug_report_templates/active_job_gem.rb
index af777a86ef..720b7e9c51 100644
--- a/guides/bug_report_templates/active_job_gem.rb
+++ b/guides/bug_report_templates/active_job_gem.rb
@@ -9,8 +9,11 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   # Activate the gem you are reporting the issue against.
-  gem "activejob", "5.1.0"
+  gem "activejob", "5.2.0"
 end
 
 require "minitest/autorun"
diff --git a/guides/bug_report_templates/active_job_master.rb b/guides/bug_report_templates/active_job_master.rb
index 39fb3f60a6..4bcee07607 100644
--- a/guides/bug_report_templates/active_job_master.rb
+++ b/guides/bug_report_templates/active_job_master.rb
@@ -9,8 +9,10 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   gem "rails", github: "rails/rails"
-  gem "arel", github: "rails/arel"
 end
 
 require "active_job"
diff --git a/guides/bug_report_templates/active_record_gem.rb b/guides/bug_report_templates/active_record_gem.rb
index 168e2dcc66..c0d705239b 100644
--- a/guides/bug_report_templates/active_record_gem.rb
+++ b/guides/bug_report_templates/active_record_gem.rb
@@ -9,8 +9,11 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   # Activate the gem you are reporting the issue against.
-  gem "activerecord", "5.1.0"
+  gem "activerecord", "5.2.0"
   gem "sqlite3"
 end
 
diff --git a/guides/bug_report_templates/active_record_master.rb b/guides/bug_report_templates/active_record_master.rb
index cbd2cff2b8..914f04f51a 100644
--- a/guides/bug_report_templates/active_record_master.rb
+++ b/guides/bug_report_templates/active_record_master.rb
@@ -9,8 +9,10 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   gem "rails", github: "rails/rails"
-  gem "arel", github: "rails/arel"
   gem "sqlite3"
 end
 
diff --git a/guides/bug_report_templates/active_record_migrations_gem.rb b/guides/bug_report_templates/active_record_migrations_gem.rb
index b931ed0beb..f47cf08766 100644
--- a/guides/bug_report_templates/active_record_migrations_gem.rb
+++ b/guides/bug_report_templates/active_record_migrations_gem.rb
@@ -9,8 +9,11 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   # Activate the gem you are reporting the issue against.
-  gem "activerecord", "5.1.0"
+  gem "activerecord", "5.2.0"
   gem "sqlite3"
 end
 
@@ -34,7 +37,7 @@ end
 class Payment < ActiveRecord::Base
 end
 
-class ChangeAmountToAddScale < ActiveRecord::Migration[5.0]
+class ChangeAmountToAddScale < ActiveRecord::Migration[5.2]
   def change
     reversible do |dir|
       dir.up do
diff --git a/guides/bug_report_templates/active_record_migrations_master.rb b/guides/bug_report_templates/active_record_migrations_master.rb
index 2c009c0563..715dca98ba 100644
--- a/guides/bug_report_templates/active_record_migrations_master.rb
+++ b/guides/bug_report_templates/active_record_migrations_master.rb
@@ -9,8 +9,10 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   gem "rails", github: "rails/rails"
-  gem "arel", github: "rails/arel"
   gem "sqlite3"
 end
 
@@ -34,7 +36,7 @@ end
 class Payment < ActiveRecord::Base
 end
 
-class ChangeAmountToAddScale < ActiveRecord::Migration[5.0]
+class ChangeAmountToAddScale < ActiveRecord::Migration[6.0]
   def change
     reversible do |dir|
       dir.up do
diff --git a/guides/bug_report_templates/benchmark.rb b/guides/bug_report_templates/benchmark.rb
index d0f5a634bc..046572148b 100644
--- a/guides/bug_report_templates/benchmark.rb
+++ b/guides/bug_report_templates/benchmark.rb
@@ -9,8 +9,10 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   gem "rails", github: "rails/rails"
-  gem "arel", github: "rails/arel"
   gem "benchmark-ips"
 end
 
diff --git a/guides/bug_report_templates/generic_gem.rb b/guides/bug_report_templates/generic_gem.rb
index c990bda005..0935354bf4 100644
--- a/guides/bug_report_templates/generic_gem.rb
+++ b/guides/bug_report_templates/generic_gem.rb
@@ -9,10 +9,14 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   # Activate the gem you are reporting the issue against.
-  gem "activesupport", "5.1.0"
+  gem "activesupport", "5.2.0"
 end
 
+require "active_support"
 require "active_support/core_ext/object/blank"
 require "minitest/autorun"
 
diff --git a/guides/bug_report_templates/generic_master.rb b/guides/bug_report_templates/generic_master.rb
index 1a9b99b624..727f428960 100644
--- a/guides/bug_report_templates/generic_master.rb
+++ b/guides/bug_report_templates/generic_master.rb
@@ -9,8 +9,10 @@ end
 
 gemfile(true) do
   source "https://rubygems.org"
+
+  git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
   gem "rails", github: "rails/rails"
-  gem "arel", github: "rails/arel"
 end
 
 require "active_support"
diff --git a/guides/rails_guides/generator.rb b/guides/rails_guides/generator.rb
index 7205f37be7..c83538ad48 100644
--- a/guides/rails_guides/generator.rb
+++ b/guides/rails_guides/generator.rb
@@ -141,32 +141,34 @@ module RailsGuides
         puts "Generating #{guide} as #{output_file}"
         layout = @kindle ? "kindle/layout" : "layout"
 
-        File.open(output_path, "w") do |f|
-          view = ActionView::Base.new(
-            @source_dir,
-            edge:     @edge,
-            version:  @version,
-            mobi:     "kindle/#{mobi}",
-            language: @language
-          )
-          view.extend(Helpers)
-
-          if guide =~ /\.(\w+)\.erb$/
-            # Generate the special pages like the home.
-            # Passing a template handler in the template name is deprecated. So pass the file name without the extension.
-            result = view.render(layout: layout, formats: [$1], file: $`)
-          else
-            body = File.read("#{@source_dir}/#{guide}")
-            result = RailsGuides::Markdown.new(
-              view:    view,
-              layout:  layout,
-              edge:    @edge,
-              version: @version
-            ).render(body)
-
-            warn_about_broken_links(result)
-          end
+        view = ActionView::Base.new(
+          @source_dir,
+          edge:     @edge,
+          version:  @version,
+          mobi:     "kindle/#{mobi}",
+          language: @language
+        )
+        view.extend(Helpers)
+
+        if guide =~ /\.(\w+)\.erb$/
+          return if %w[_license _welcome layout].include?($`)
+
+          # Generate the special pages like the home.
+          # Passing a template handler in the template name is deprecated. So pass the file name without the extension.
+          result = view.render(layout: layout, formats: [$1], file: $`)
+        else
+          body = File.read("#{@source_dir}/#{guide}")
+          result = RailsGuides::Markdown.new(
+            view:    view,
+            layout:  layout,
+            edge:    @edge,
+            version: @version
+          ).render(body)
+
+          warn_about_broken_links(result)
+        end
 
+        File.open(output_path, "w") do |f|
           f.write(result)
         end
       end
diff --git a/guides/rails_guides/helpers.rb b/guides/rails_guides/helpers.rb
index a6970fb90c..5ab1388c29 100644
--- a/guides/rails_guides/helpers.rb
+++ b/guides/rails_guides/helpers.rb
@@ -38,15 +38,6 @@ module RailsGuides
       end
     end
 
-    def author(name, nick, image = "credits_pic_blank.gif", &block)
-      image = "images/#{image}"
-
-      result = tag(:img, src: image, class: "left pic", alt: name, width: 91, height: 91)
-      result << content_tag(:h3, name)
-      result << content_tag(:p, capture(&block))
-      content_tag(:div, result, class: "clearfix", id: nick)
-    end
-
     def code(&block)
       c = capture(&block)
       content_tag(:code, c)
diff --git a/guides/rails_guides/kindle.rb b/guides/rails_guides/kindle.rb
index 87a369a15a..d370541d2e 100644
--- a/guides/rails_guides/kindle.rb
+++ b/guides/rails_guides/kindle.rb
@@ -35,7 +35,7 @@ module Kindle
   def generate_front_matter(html_pages)
     frontmatter = []
     html_pages.delete_if { |x|
-      if x =~ /(toc|welcome|credits|copyright).html/
+      if x =~ /(toc|welcome|copyright).html/
         frontmatter << x unless x =~ /toc/
         true
       end
@@ -58,9 +58,9 @@ module Kindle
   end
 
   def generate_sections(html_pages)
-    FileUtils::rm_rf("sections/")
+    FileUtils.rm_rf("sections/")
     html_pages.each_with_index do |page, section_idx|
-      FileUtils::mkdir_p("sections/%03d" % section_idx)
+      FileUtils.mkdir_p("sections/%03d" % section_idx)
       doc = Nokogiri::HTML(File.open(page))
       title = doc.at("title").inner_text.gsub("Ruby on Rails Guides: ", "")
       title = page.capitalize.gsub(".html", "") if title.strip == ""
diff --git a/guides/rails_guides/levenshtein.rb b/guides/rails_guides/levenshtein.rb
index bafa6bfe9d..c48af797fa 100644
--- a/guides/rails_guides/levenshtein.rb
+++ b/guides/rails_guides/levenshtein.rb
@@ -38,7 +38,7 @@ module RailsGuides
         d[m] = x
       end
 
-      return x
+      x
     end
   end
 end
diff --git a/guides/rails_guides/markdown/renderer.rb b/guides/rails_guides/markdown/renderer.rb
index 1f2fe91ea1..78820a7856 100644
--- a/guides/rails_guides/markdown/renderer.rb
+++ b/guides/rails_guides/markdown/renderer.rb
@@ -75,7 +75,7 @@ HTML
           #
           # It is important that we do not eat more than one newline
           # because formatting may be wrong otherwise. For example,
-          # if a bulleted list follows the first item is not rendered
+          # if a bulleted list follows, the first item is not rendered
           # as a list item, but as a paragraph starting with a plain
           # asterisk.
           body.gsub(/^(TIP|IMPORTANT|CAUTION|WARNING|NOTE|INFO|TODO)[.:](.*?)(\n(?=\n)|\Z)/m) do
diff --git a/guides/source/2_2_release_notes.md b/guides/source/2_2_release_notes.md
index ac5833e069..005331977e 100644
--- a/guides/source/2_2_release_notes.md
+++ b/guides/source/2_2_release_notes.md
@@ -57,11 +57,10 @@ rake doc:guides
 
 This will put the guides inside `Rails.root/doc/guides` and you may start surfing straight away by opening `Rails.root/doc/guides/index.html` in your favourite browser.
 
-* Lead Contributors: [Rails Documentation Team](credits.html)
 * Major contributions from [Xavier Noria](http://advogato.org/person/fxn/diary.html) and [Hongli Lai](http://izumi.plan99.net/blog/).
 * More information:
     * [Rails Guides hackfest](http://hackfest.rubyonrails.org/guide)
-    * [Help improve Rails documentation on Git branch](http://weblog.rubyonrails.org/2008/5/2/help-improve-rails-documentation-on-git-branch)
+    * [Help improve Rails documentation on Git branch](https://weblog.rubyonrails.org/2008/5/2/help-improve-rails-documentation-on-git-branch)
 
 Better integration with HTTP : Out of the box ETag support
 ----------------------------------------------------------
@@ -113,7 +112,7 @@ config.threadsafe!
 
 * More information :
     * [Thread safety for your Rails](http://m.onkey.org/2008/10/23/thread-safety-for-your-rails)
-    * [Thread safety project announcement](http://weblog.rubyonrails.org/2008/8/16/josh-peek-officially-joins-the-rails-core)
+    * [Thread safety project announcement](https://weblog.rubyonrails.org/2008/8/16/josh-peek-officially-joins-the-rails-core)
     * [Q/A: What Thread-safe Rails Means](http://blog.headius.com/2008/08/qa-what-thread-safe-rails-means.html)
 
 Active Record
@@ -125,7 +124,7 @@ There are two big additions to talk about here: transactional migrations and poo
 
 Historically, multiple-step Rails migrations have been a source of trouble. If something went wrong during a migration, everything before the error changed the database and everything after the error wasn't applied. Also, the migration version was stored as having been executed, which means that it couldn't be simply rerun by `rake db:migrate:redo` after you fix the problem. Transactional migrations change this by wrapping migration steps in a DDL transaction, so that if any of them fail, the entire migration is undone. In Rails 2.2, transactional migrations are supported on PostgreSQL out of the box. The code is extensible to other database types in the future - and IBM has already extended it to support the DB2 adapter.
 
-* Lead Contributor: [Adam Wiggins](http://adam.heroku.com/)
+* Lead Contributor: [Adam Wiggins](http://about.adamwiggins.com/)
 * More information:
     * [DDL Transactions](http://adam.heroku.com/past/2008/9/3/ddl_transactions/)
     * [A major milestone for DB2 on Rails](http://db2onrails.com/2008/11/08/a-major-milestone-for-db2-on-rails/)
@@ -391,7 +390,7 @@ You can unpack or install a single gem by specifying `GEM=_gem_name_` on the com
 * Lead Contributor: [Matt Jones](https://github.com/al2o3cr)
 * More information:
     * [What's New in Edge Rails: Gem Dependencies](http://archives.ryandaigle.com/articles/2008/4/1/what-s-new-in-edge-rails-gem-dependencies)
-    * [Rails 2.1.2 and 2.2RC1: Update Your RubyGems](http://afreshcup.com/2008/10/25/rails-212-and-22rc1-update-your-rubygems/)
+    * [Rails 2.1.2 and 2.2RC1: Update Your RubyGems](https://afreshcup.com/home/2008/10/25/rails-212-and-22rc1-update-your-rubygems)
     * [Detailed discussion on Lighthouse](http://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/1128)
 
 ### Other Railties Changes
diff --git a/guides/source/2_3_release_notes.md b/guides/source/2_3_release_notes.md
index 3f5a3c7ade..2b8c9351e8 100644
--- a/guides/source/2_3_release_notes.md
+++ b/guides/source/2_3_release_notes.md
@@ -54,7 +54,7 @@ Documentation
 
 The [Ruby on Rails guides](http://guides.rubyonrails.org/) project has published several additional guides for Rails 2.3. In addition, a [separate site](http://edgeguides.rubyonrails.org/) maintains updated copies of the Guides for Edge Rails. Other documentation efforts include a relaunch of the [Rails wiki](http://newwiki.rubyonrails.org/) and early planning for a Rails Book.
 
-* More Information: [Rails Documentation Projects](http://weblog.rubyonrails.org/2009/1/15/rails-documentation-projects)
+* More Information: [Rails Documentation Projects](https://weblog.rubyonrails.org/2009/1/15/rails-documentation-projects)
 
 Ruby 1.9.1 Support
 ------------------
@@ -89,7 +89,7 @@ accepts_nested_attributes_for :author,
 ```
 
 * Lead Contributor: [Eloy Duran](http://superalloy.nl/)
-* More Information: [Nested Model Forms](http://weblog.rubyonrails.org/2009/1/26/nested-model-forms)
+* More Information: [Nested Model Forms](https://weblog.rubyonrails.org/2009/1/26/nested-model-forms)
 
 ### Nested Transactions
 
@@ -231,10 +231,10 @@ Rails chooses between file, template, and action depending on whether there is a
 
 ### Application Controller Renamed
 
-If you're one of the people who has always been bothered by the special-case naming of `application.rb`, rejoice! It's been reworked to be application_controller.rb in Rails 2.3. In addition, there's a new rake task, `rake rails:update:application_controller` to do this automatically for you - and it will be run as part of the normal `rake rails:update` process.
+If you're one of the people who has always been bothered by the special-case naming of `application.rb`, rejoice! It's been reworked to be `application_controller.rb` in Rails 2.3. In addition, there's a new rake task, `rake rails:update:application_controller` to do this automatically for you - and it will be run as part of the normal `rake rails:update` process.
 
 * More Information:
-    * [The Death of Application.rb](http://afreshcup.com/2008/11/17/rails-2x-the-death-of-applicationrb/)
+    * [The Death of Application.rb](https://afreshcup.com/home/2008/11/17/rails-2x-the-death-of-applicationrb)
     * [What's New in Edge Rails: Application.rb Duality is no More](http://archives.ryandaigle.com/articles/2008/11/19/what-s-new-in-edge-rails-application-rb-duality-is-no-more)
 
 ### HTTP Digest Authentication Support
@@ -304,7 +304,7 @@ Rails now keeps a per-request local cache of read from the remote cache stores,
 
 Rails can now provide localized views, depending on the locale that you have set. For example, suppose you have a `Posts` controller with a `show` action. By default, this will render `app/views/posts/show.html.erb`. But if you set `I18n.locale = :da`, it will render `app/views/posts/show.da.html.erb`. If the localized template isn't present, the undecorated version will be used. Rails also includes `I18n#available_locales` and `I18n::SimpleBackend#available_locales`, which return an array of the translations that are available in the current Rails project.
 
-In addition, you can use the same scheme to localize the rescue files in the `public` directory: `public/500.da.html` or `public/404.en.html` work, for example.
+In addition, you can use the same scheme to localize the rescue files in the public directory: `public/500.da.html` or `public/404.en.html` work, for example.
 
 ### Partial Scoping for Translations
 
@@ -376,7 +376,7 @@ You can write this view in Rails 2.3:
 
 * Lead Contributor: [Eloy Duran](http://superalloy.nl/)
 * More Information:
-    * [Nested Model Forms](http://weblog.rubyonrails.org/2009/1/26/nested-model-forms)
+    * [Nested Model Forms](https://weblog.rubyonrails.org/2009/1/26/nested-model-forms)
     * [complex-form-examples](https://github.com/alloy/complex-form-examples)
     * [What's New in Edge Rails: Nested Object Forms](http://archives.ryandaigle.com/articles/2009/2/1/what-s-new-in-edge-rails-nested-attributes)
 
@@ -468,7 +468,7 @@ options_from_collection_for_select(@product.sizes, :name, :id, :disabled => lamb
 ```
 
 * Lead Contributor: [Tekin Suleyman](http://tekin.co.uk/)
-* More Information: [New in rails 2.3 - disabled option tags and lambdas for selecting and disabling options from collections](http://tekin.co.uk/2009/03/new-in-rails-23-disabled-option-tags-and-lambdas-for-selecting-and-disabling-options-from-collections/)
+* More Information: [New in rails 2.3 - disabled option tags and lambdas for selecting and disabling options from collections](https://tekin.co.uk/2009/03/new-in-rails-23-disabled-option-tags-and-lambdas-for-selecting-and-disabling-options-from-collections)
 
 ### A Note About Template Loading
 
@@ -533,7 +533,7 @@ If you look up the spec on the "json.org" site, you'll discover that all keys in
 ### Other Active Support Changes
 
 * You can use `Enumerable#none?` to check that none of the elements match the supplied block.
-* If you're using Active Support [delegates](http://afreshcup.com/2008/10/19/coming-in-rails-22-delegate-prefixes/) the new `:allow_nil` option lets you return `nil` instead of raising an exception when the target object is nil.
+* If you're using Active Support [delegates](https://afreshcup.com/home/2008/10/19/coming-in-rails-22-delegate-prefixes) the new `:allow_nil` option lets you return `nil` instead of raising an exception when the target object is nil.
 * `ActiveSupport::OrderedHash`: now implements `each_key` and `each_value`.
 * `ActiveSupport::MessageEncryptor` provides a simple way to encrypt information for storage in an untrusted location (like cookies).
 * Active Support's `from_xml` no longer depends on XmlSimple. Instead, Rails now includes its own XmlMini implementation, with just the functionality that it requires. This lets Rails dispense with the bundled copy of XmlSimple that it's been carting around.
@@ -552,7 +552,7 @@ In addition to the Rack changes covered above, Railties (the core code of Rails
 Rails Metal is a new mechanism that provides superfast endpoints inside of your Rails applications. Metal classes bypass routing and Action Controller to give you raw speed (at the cost of all the things in Action Controller, of course). This builds on all of the recent foundation work to make Rails a Rack application with an exposed middleware stack. Metal endpoints can be loaded from your application or from plugins.
 
 * More Information:
-    * [Introducing Rails Metal](http://weblog.rubyonrails.org/2008/12/17/introducing-rails-metal)
+    * [Introducing Rails Metal](https://weblog.rubyonrails.org/2008/12/17/introducing-rails-metal)
     * [Rails Metal: a micro-framework with the power of Rails](http://soylentfoo.jnewland.com/articles/2008/12/16/rails-metal-a-micro-framework-with-the-power-of-rails-m)
     * [Metal: Super-fast Endpoints within your Rails Apps](http://www.railsinside.com/deployment/180-metal-super-fast-endpoints-within-your-rails-apps.html)
     * [What's New in Edge Rails: Rails Metal](http://archives.ryandaigle.com/articles/2008/12/18/what-s-new-in-edge-rails-rails-metal)
@@ -576,7 +576,7 @@ Building on thoughtbot's [Quiet Backtrace](https://github.com/thoughtbot/quietba
 
 ### Faster Boot Time in Development Mode with Lazy Loading/Autoload
 
-Quite a bit of work was done to make sure that bits of Rails (and its dependencies) are only brought into memory when they're actually needed. The core frameworks - Active Support, Active Record, Action Controller, Action Mailer and Action View - are now using `autoload` to lazy-load their individual classes. This work should help keep the memory footprint down and improve overall Rails performance.
+Quite a bit of work was done to make sure that bits of Rails (and its dependencies) are only brought into memory when they're actually needed. The core frameworks - Active Support, Active Record, Action Controller, Action Mailer, and Action View - are now using `autoload` to lazy-load their individual classes. This work should help keep the memory footprint down and improve overall Rails performance.
 
 You can also specify (by using the new `preload_frameworks` option) whether the core libraries should be autoloaded at startup. This defaults to `false` so that Rails autoloads itself piece-by-piece, but there are some circumstances where you still need to bring in everything at once - Passenger and JRuby both want to see all of Rails loaded together.
 
@@ -592,7 +592,7 @@ The internals of the various <code>rake gem</code> tasks have been substantially
 * Internal Rails testing has been switched from `Test::Unit::TestCase` to `ActiveSupport::TestCase`, and the Rails core requires Mocha to test.
 * The default `environment.rb` file has been decluttered.
 * The dbconsole script now lets you use an all-numeric password without crashing.
-* `Rails.root` now returns a `Pathname` object, which means you can use it directly with the `join` method to [clean up existing code](http://afreshcup.com/2008/12/05/a-little-rails_root-tidiness/) that uses `File.join`.
+* `Rails.root` now returns a `Pathname` object, which means you can use it directly with the `join` method to [clean up existing code](https://afreshcup.wordpress.com/2008/12/05/a-little-rails_root-tidiness/) that uses `File.join`.
 * Various files in /public that deal with CGI and FCGI dispatching are no longer generated in every Rails application by default (you can still get them if you need them by adding `--with-dispatchers` when you run the `rails` command, or add them later with `rake rails:update:generate_dispatchers`).
 * Rails Guides have been converted from AsciiDoc to Textile markup.
 * Scaffolded views and controllers have been cleaned up a bit.
@@ -605,7 +605,7 @@ Deprecated
 
 A few pieces of older code are deprecated in this release:
 
-* If you're one of the (fairly rare) Rails developers who deploys in a fashion that depends on the inspector, reaper, and spawner scripts, you'll need to know that those scripts are no longer included in core Rails. If you need them, you'll be able to pick up copies via the [irs_process_scripts](https://github.com/rails/irs_process_scripts/tree) plugin.
+* If you're one of the (fairly rare) Rails developers who deploys in a fashion that depends on the inspector, reaper, and spawner scripts, you'll need to know that those scripts are no longer included in core Rails. If you need them, you'll be able to pick up copies via the [irs_process_scripts](https://github.com/rails/irs_process_scripts) plugin.
 * `render_component` goes from "deprecated" to "nonexistent" in Rails 2.3. If you still need it, you can install the [render_component plugin](https://github.com/rails/render_component/tree/master).
 * Support for Rails components has been removed.
 * If you were one of the people who got used to running `script/performance/request` to look at performance based on integration tests, you need to learn a new trick: that script has been removed from core Rails now. There's a new request_profiler plugin that you can install to get the exact same functionality back.
diff --git a/guides/source/3_0_release_notes.md b/guides/source/3_0_release_notes.md
index f0e2cb3b63..f4b5eb3c4c 100644
--- a/guides/source/3_0_release_notes.md
+++ b/guides/source/3_0_release_notes.md
@@ -155,7 +155,7 @@ Documentation
 
 The documentation in the Rails tree is being updated with all the API changes, additionally, the [Rails Edge Guides](http://edgeguides.rubyonrails.org/) are being updated one by one to reflect the changes in Rails 3.0. The guides at [guides.rubyonrails.org](http://guides.rubyonrails.org/) however will continue to contain only the stable version of Rails (at this point, version 2.3.5, until 3.0 is released).
 
-More Information: - [Rails Documentation Projects](http://weblog.rubyonrails.org/2009/1/15/rails-documentation-projects)
+More Information: - [Rails Documentation Projects](https://weblog.rubyonrails.org/2009/1/15/rails-documentation-projects)
 
 
 Internationalization
@@ -174,7 +174,7 @@ More Information: - [Rails 3 I18n changes](http://blog.plataformatec.com.br/2010
 Railties
 --------
 
-With the decoupling of the main Rails frameworks, Railties got a huge overhaul so as to make linking up frameworks, engines or plugins as painless and extensible as possible:
+With the decoupling of the main Rails frameworks, Railties got a huge overhaul so as to make linking up frameworks, engines, or plugins as painless and extensible as possible:
 
 * Each application now has its own name space, application is started with `YourAppName.boot` for example, makes interacting with other applications a lot easier.
 * Anything under `Rails.root/app` is now added to the load path, so you can make `app/observers/user_observer.rb` and Rails will load it without any modifications.
@@ -213,7 +213,7 @@ Railties now deprecates:
 More information:
 
 * [Discovering Rails 3 generators](http://blog.plataformatec.com.br/2010/01/discovering-rails-3-generators)
-* [The Rails Module (in Rails 3)](http://litanyagainstfear.com/blog/2010/02/03/the-rails-module/)
+* [The Rails Module (in Rails 3)](http://quaran.to/blog/2010/02/03/the-rails-module/)
 
 Action Pack
 -----------
@@ -250,7 +250,7 @@ Deprecations:
 More Information:
 
 * [Render Options in Rails 3](https://blog.engineyard.com/2010/render-options-in-rails-3)
-* [Three reasons to love ActionController::Responder](http://weblog.rubyonrails.org/2009/8/31/three-reasons-love-responder)
+* [Three reasons to love ActionController::Responder](https://weblog.rubyonrails.org/2009/8/31/three-reasons-love-responder)
 
 
 ### Action Dispatch
@@ -422,7 +422,7 @@ More Information:
 Active Record
 -------------
 
-Active Record received a lot of attention in Rails 3.0, including abstraction into Active Model, a full update to the Query interface using Arel, validation updates and many enhancements and fixes. All of the Rails 2.x API will be usable through a compatibility layer that will be supported until version 3.1.
+Active Record received a lot of attention in Rails 3.0, including abstraction into Active Model, a full update to the Query interface using Arel, validation updates, and many enhancements and fixes. All of the Rails 2.x API will be usable through a compatibility layer that will be supported until version 3.1.
 
 
 ### Query Interface
diff --git a/guides/source/3_2_release_notes.md b/guides/source/3_2_release_notes.md
index 6570b19f97..ae6eb27f35 100644
--- a/guides/source/3_2_release_notes.md
+++ b/guides/source/3_2_release_notes.md
@@ -30,13 +30,13 @@ TIP: Note that Ruby 1.8.7 p248 and p249 have marshalling bugs that crash Rails.
 
 ### What to update in your apps
 
-* Update your Gemfile to depend on
+* Update your `Gemfile` to depend on
     * `rails = 3.2.0`
     * `sass-rails ~> 3.2.3`
     * `coffee-rails ~> 3.2.1`
     * `uglifier >= 1.0.3`
 
-* Rails 3.2 deprecates `vendor/plugins` and Rails 4.0 will remove them completely. You can start replacing these plugins by extracting them as gems and adding them in your Gemfile. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`.
+* Rails 3.2 deprecates `vendor/plugins` and Rails 4.0 will remove them completely. You can start replacing these plugins by extracting them as gems and adding them in your `Gemfile`. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`.
 
 * There are a couple of new configuration changes you'd want to add in `config/environments/development.rb`:
 
@@ -156,7 +156,7 @@ Railties
 
     will create indexes for `title` and `author` with the latter being a unique index. Some types such as decimal accept custom options. In the example, `price` will be a decimal column with precision and scale set to 7 and 2 respectively.
 
-* Turn gem has been removed from default Gemfile.
+* Turn gem has been removed from default `Gemfile`.
 
 * Remove old plugin generator `rails generate plugin` in favor of `rails plugin new` command.
 
diff --git a/guides/source/4_0_release_notes.md b/guides/source/4_0_release_notes.md
index 6f1b75a42b..a1a6a225b2 100644
--- a/guides/source/4_0_release_notes.md
+++ b/guides/source/4_0_release_notes.md
@@ -55,7 +55,7 @@ $ ruby /path/to/rails/railties/bin/rails new myapp --dev
 Major Features
 --------------
 
-[![Rails 4.0](images/rails4_features.png)](http://guides.rubyonrails.org/images/rails4_features.png)
+[![Rails 4.0](images/4_0_release_notes/rails4_features.png)](http://guides.rubyonrails.org/images/4_0_release_notes/rails4_features.png)
 
 ### Upgrade
 
@@ -66,7 +66,7 @@ Major Features
 * **ActiveRecord session store** ([commit](https://github.com/rails/rails/commit/0ffe19056c8e8b2f9ae9d487b896cad2ce9387ad)) - The ActiveRecord session store is extracted to a separate gem. Storing sessions in SQL is costly. Instead, use cookie sessions, memcache sessions, or a custom session store.
 * **ActiveModel mass assignment protection** ([commit](https://github.com/rails/rails/commit/f8c9a4d3e88181cee644f91e1342bfe896ca64c6)) - Rails 3 mass assignment protection is deprecated. Instead, use strong parameters.
 * **ActiveResource** ([commit](https://github.com/rails/rails/commit/f1637bf2bb00490203503fbd943b73406e043d1d)) - ActiveResource is extracted to a separate gem. ActiveResource was not widely used.
-* **vendor/plugins removed** ([commit](https://github.com/rails/rails/commit/853de2bd9ac572735fa6cf59fcf827e485a231c3)) - Use a Gemfile to manage installed gems.
+* **vendor/plugins removed** ([commit](https://github.com/rails/rails/commit/853de2bd9ac572735fa6cf59fcf827e485a231c3)) - Use a `Gemfile` to manage installed gems.
 
 ### ActionPack
 
diff --git a/guides/source/4_1_release_notes.md b/guides/source/4_1_release_notes.md
index 6bf65757ec..2c5e665e33 100644
--- a/guides/source/4_1_release_notes.md
+++ b/guides/source/4_1_release_notes.md
@@ -274,7 +274,7 @@ for detailed changes.
 * The [Spring application
   preloader](https://github.com/rails/spring) is now installed
   by default for new applications. It uses the development group of
-  the Gemfile, so will not be installed in
+  the `Gemfile`, so will not be installed in
   production. ([Pull Request](https://github.com/rails/rails/pull/12958))
 
 * `BACKTRACE` environment variable to show unfiltered backtraces for test
diff --git a/guides/source/4_2_release_notes.md b/guides/source/4_2_release_notes.md
index a30bfc458a..7105df5634 100644
--- a/guides/source/4_2_release_notes.md
+++ b/guides/source/4_2_release_notes.md
@@ -179,7 +179,7 @@ change your code to use the explicit form (`render file: "foo/bar"`) instead.
 
 `respond_with` and the corresponding class-level `respond_to` have been moved
 to the [responders](https://github.com/plataformatec/responders) gem. Add
-`gem 'responders', '~> 2.0'` to your Gemfile to use it:
+`gem 'responders', '~> 2.0'` to your `Gemfile` to use it:
 
 ```ruby
 # app/controllers/users_controller.rb
@@ -368,7 +368,7 @@ Please refer to the [Changelog][railties] for detailed changes.
 
 ### Notable changes
 
-*   Introduced `web-console` in the default application Gemfile.
+*   Introduced `web-console` in the default application `Gemfile`.
     ([Pull Request](https://github.com/rails/rails/pull/11667))
 
 *   Added a `required` option to the model generator for associations.
diff --git a/guides/source/5_0_release_notes.md b/guides/source/5_0_release_notes.md
index 6d53e1c2b4..04d4bd75cd 100644
--- a/guides/source/5_0_release_notes.md
+++ b/guides/source/5_0_release_notes.md
@@ -55,7 +55,7 @@ information.
 ### API Applications
 
 Rails can now be used to create slimmed down API only applications.
-This is useful for creating and serving APIs similar to [Twitter](https://dev.twitter.com) or [GitHub](https://developer.github.com) API, 
+This is useful for creating and serving APIs similar to [Twitter](https://dev.twitter.com) or [GitHub](https://developer.github.com) API,
 that can be used to serve public facing, as well as, for custom applications.
 
 You can generate a new api Rails app using:
@@ -73,11 +73,11 @@ This will do three main things:
   `ActionController::Base`. As with middleware, this will leave out any Action
   Controller modules that provide functionalities primarily used by browser
   applications.
-- Configure the generators to skip generating views, helpers and assets when
+- Configure the generators to skip generating views, helpers, and assets when
   you generate a new resource.
 
 The application provides a base for APIs,
-that can then be [configured to pull in functionality](api_app.html) as suitable for the application's needs.  
+that can then be [configured to pull in functionality](api_app.html) as suitable for the application's needs.
 
 See the [Using Rails for API-only Applications](api_app.html) guide for more
 information.
@@ -775,7 +775,7 @@ Please refer to the [Changelog][active-record] for detailed changes.
 
 *   Added prepared statements support to `mysql2` adapter, for mysql2 0.4.4+,
     Previously this was only supported on the deprecated `mysql` legacy adapter.
-    To enable, set `prepared_statements: true` in config/database.yml.
+    To enable, set `prepared_statements: true` in `config/database.yml`.
     ([Pull Request](https://github.com/rails/rails/pull/23461))
 
 *   Added ability to call `ActionRecord::Relation#update` on relation objects
@@ -997,7 +997,7 @@ Please refer to the [Changelog][active-support] for detailed changes.
 
 *   New config option
     `config.active_support.halt_callback_chains_on_return_false` to specify
-    whether ActiveRecord, ActiveModel and ActiveModel::Validations callback
+    whether ActiveRecord, ActiveModel, and ActiveModel::Validations callback
     chains can be halted by returning `false` in a 'before' callback.
     ([Pull Request](https://github.com/rails/rails/pull/17227))
 
diff --git a/guides/source/5_1_release_notes.md b/guides/source/5_1_release_notes.md
index fa92b9e5f8..68c120fd78 100644
--- a/guides/source/5_1_release_notes.md
+++ b/guides/source/5_1_release_notes.md
@@ -102,7 +102,7 @@ Secrets will be decrypted in production, using a key stored either in the
 [Pull Request](https://github.com/rails/rails/pull/27825)
 
 Allows specifying common parameters used for all methods in a mailer class in
-order to share instance variables, headers and other common setup.
+order to share instance variables, headers, and other common setup.
 
 ``` ruby
 class InvitationsMailer < ApplicationMailer
@@ -170,7 +170,7 @@ Before Rails 5.1, there were two interfaces for handling HTML forms:
 `form_for` for model instances and `form_tag` for custom URLs.
 
 Rails 5.1 combines both of these interfaces with `form_with`, and
-can generate form tags based on URLs, scopes or models.
+can generate form tags based on URLs, scopes, or models.
 
 Using just a URL:
 
@@ -350,6 +350,13 @@ Please refer to the [Changelog][action-pack] for detailed changes.
 
 *   Removed deprecated methods related to controller filters.
     ([Commit](https://github.com/rails/rails/commit/d7be30e8babf5e37a891522869e7b0191b79b757))
+    
+*   Removed deprecated support to `:text` and `:nothing` in `render`.
+    ([Commit](https://github.com/rails/rails/commit/79a5ea9eadb4d43b62afacedc0706cbe88c54496), 
+    [Commit](https://github.com/rails/rails/commit/57e1c99a280bdc1b324936a690350320a1cd8111))
+
+*   Removed deprecated support for calling `HashWithIndifferentAccess` methods on `ActionController::Parameters`.
+    ([Commit](https://github.com/rails/rails/pull/26746/commits/7093ceb480ad6a0a91b511832dad4c6a86981b93))
 
 ### Deprecations
 
@@ -602,7 +609,7 @@ Please refer to the [Changelog][active-support] for detailed changes.
     ([Pull Request](https://github.com/rails/rails/pull/28157))
 
 *   Deprecated passing string to `:if` and `:unless` conditional options on `set_callback` and `skip_callback`.
-    ([Commit](https://github.com/rails/rails/commit/0952552)
+    ([Commit](https://github.com/rails/rails/commit/0952552))
 
 ### Notable changes
 
diff --git a/guides/source/5_2_release_notes.md b/guides/source/5_2_release_notes.md
new file mode 100644
index 0000000000..ab24c7e590
--- /dev/null
+++ b/guides/source/5_2_release_notes.md
@@ -0,0 +1,861 @@
+**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.**
+
+Ruby on Rails 5.2 Release Notes
+===============================
+
+Highlights in Rails 5.2:
+
+* Active Storage
+* Redis Cache Store
+* HTTP/2 Early Hints
+* Credentials
+* Content Security Policy
+
+These release notes cover only the major changes. To learn about various bug
+fixes and changes, please refer to the change logs or check out the [list of
+commits](https://github.com/rails/rails/commits/5-2-stable) in the main Rails
+repository on GitHub.
+
+--------------------------------------------------------------------------------
+
+Upgrading to Rails 5.2
+----------------------
+
+If you're upgrading an existing application, it's a great idea to have good test
+coverage before going in. You should also first upgrade to Rails 5.1 in case you
+haven't and make sure your application still runs as expected before attempting
+an update to Rails 5.2. A list of things to watch out for when upgrading is
+available in the
+[Upgrading Ruby on Rails](upgrading_ruby_on_rails.html#upgrading-from-rails-5-1-to-rails-5-2)
+guide.
+
+Major Features
+--------------
+
+### Active Storage
+
+[Pull Request](https://github.com/rails/rails/pull/30020)
+
+[Active Storage](https://github.com/rails/rails/tree/5-2-stable/activestorage)
+facilitates uploading files to a cloud storage service like
+Amazon S3, Google Cloud Storage, or Microsoft Azure Storage and attaching
+those files to Active Record objects. It comes with a local disk-based service
+for development and testing and supports mirroring files to subordinate
+services for backups and migrations.
+You can read more about Active Storage in the
+[Active Storage Overview](active_storage_overview.html) guide.
+
+### Redis Cache Store
+
+[Pull Request](https://github.com/rails/rails/pull/31134)
+
+Rails 5.2 ships with built-in Redis cache store.
+You can read more about this in the
+[Caching with Rails: An Overview](caching_with_rails.html#activesupport-cache-rediscachestore)
+guide.
+
+### HTTP/2 Early Hints
+
+[Pull Request](https://github.com/rails/rails/pull/30744)
+
+Rails 5.2 supports [HTTP/2 Early Hints](https://tools.ietf.org/html/rfc8297).
+To start the server with Early Hints enabled pass `--early-hints`
+to `bin/rails server`.
+
+### Credentials
+
+[Pull Request](https://github.com/rails/rails/pull/30067)
+
+Added `config/credentials.yml.enc` file to store production app secrets.
+It allows saving any authentication credentials for third-party services
+directly in repository encrypted with a key in the `config/master.key` file or
+the `RAILS_MASTER_KEY` environment variable.
+This will eventually replace `Rails.application.secrets` and the encrypted
+secrets introduced in Rails 5.1.
+Furthermore, Rails 5.2
+[opens API underlying Credentials](https://github.com/rails/rails/pull/30940),
+so you can easily deal with other encrypted configurations, keys, and files.
+You can read more about this in the
+[Securing Rails Applications](security.html#custom-credentials)
+guide.
+
+### Content Security Policy
+
+[Pull Request](https://github.com/rails/rails/pull/31162)
+
+Rails 5.2 ships with a new DSL that allows you to configure a
+[Content Security Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy)
+for your application. You can configure a global default policy and then
+override it on a per-resource basis and even use lambdas to inject per-request
+values into the header such as account subdomains in a multi-tenant application.
+You can read more about this in the
+[Securing Rails Applications](security.html#content-security-policy)
+guide.
+
+Railties
+--------
+
+Please refer to the [Changelog][railties] for detailed changes.
+
+### Deprecations
+
+*   Deprecate `capify!` method in generators and templates.
+    ([Pull Request](https://github.com/rails/rails/pull/29493))
+
+*   Passing the environment's name as a regular argument to the
+    `rails dbconsole` and `rails console` commands is deprecated.
+    The `-e` option should be used instead.
+    ([Commit](https://github.com/rails/rails/commit/48b249927375465a7102acc71c2dfb8d49af8309))
+
+*   Deprecate using subclass of `Rails::Application` to start the Rails server.
+    ([Pull Request](https://github.com/rails/rails/pull/30127))
+
+*   Deprecate `after_bundle` callback in Rails plugin templates.
+    ([Pull Request](https://github.com/rails/rails/pull/29446))
+
+### Notable changes
+
+*   Added a shared section to `config/database.yml` that will be loaded for
+    all environments.
+    ([Pull Request](https://github.com/rails/rails/pull/28896))
+
+*   Add `railtie.rb` to the plugin generator.
+    ([Pull Request](https://github.com/rails/rails/pull/29576))
+
+*   Clear screenshot files in `tmp:clear` task.
+    ([Pull Request](https://github.com/rails/rails/pull/29534))
+
+*   Skip unused components when running `bin/rails app:update`.
+    If the initial app generation skipped Action Cable, Active Record etc.,
+    the update task honors those skips too.
+    ([Pull Request](https://github.com/rails/rails/pull/29645))
+
+*   Allow passing a custom connection name to the `rails dbconsole`
+    command when using a 3-level database configuration.
+    Example: `bin/rails dbconsole -c replica`.
+    ([Commit](https://github.com/rails/rails/commit/1acd9a6464668d4d54ab30d016829f60b70dbbeb))
+
+*   Properly expand shortcuts for environment's name running the `console`
+    and `dbconsole` commands.
+    ([Commit](https://github.com/rails/rails/commit/3777701f1380f3814bd5313b225586dec64d4104))
+
+*   Add `bootsnap` to default `Gemfile`.
+    ([Pull Request](https://github.com/rails/rails/pull/29313))
+
+*   Support `-` as a platform-agnostic way to run a script from stdin with
+    `rails runner`
+    ([Pull Request](https://github.com/rails/rails/pull/26343))
+
+*   Add `ruby x.x.x` version to `Gemfile` and create `.ruby-version`
+    root file containing the current Ruby version when new Rails applications
+    are created.
+    ([Pull Request](https://github.com/rails/rails/pull/30016))
+
+*   Add `--skip-action-cable` option to the plugin generator.
+    ([Pull Request](https://github.com/rails/rails/pull/30164))
+
+*   Add `git_source` to `Gemfile` for plugin generator.
+    ([Pull Request](https://github.com/rails/rails/pull/30110))
+
+*   Skip unused components when running `bin/rails` in Rails plugin.
+    ([Commit](https://github.com/rails/rails/commit/62499cb6e088c3bc32a9396322c7473a17a28640))
+
+*   Optimize indentation for generator actions.
+    ([Pull Request](https://github.com/rails/rails/pull/30166))
+
+*   Optimize routes indentation.
+    ([Pull Request](https://github.com/rails/rails/pull/30241))
+
+*   Add `--skip-yarn` option to the plugin generator.
+    ([Pull Request](https://github.com/rails/rails/pull/30238))
+
+*   Support multiple versions arguments for `gem` method of Generators.
+    ([Pull Request](https://github.com/rails/rails/pull/30323))
+
+*   Derive `secret_key_base` from the app name in development and test
+    environments.
+    ([Pull Request](https://github.com/rails/rails/pull/30067))
+
+*   Add `mini_magick` to default `Gemfile` as comment.
+    ([Pull Request](https://github.com/rails/rails/pull/30633))
+
+*   `rails new` and `rails plugin new` get `Active Storage` by default.
+     Add ability to skip `Active Storage` with `--skip-active-storage`
+     and do so automatically when `--skip-active-record` is used.
+    ([Pull Request](https://github.com/rails/rails/pull/30101))
+
+Action Cable
+------------
+
+Please refer to the [Changelog][action-cable] for detailed changes.
+
+### Removals
+
+*   Removed deprecated evented redis adapter.
+    ([Commit](https://github.com/rails/rails/commit/48766e32d31651606b9f68a16015ad05c3b0de2c))
+
+### Notable changes
+
+*   Add support for `host`, `port`, `db` and `password` options in cable.yml
+    ([Pull Request](https://github.com/rails/rails/pull/29528))
+
+*   Hash long stream identifiers when using PostgreSQL adapter.
+    ([Pull Request](https://github.com/rails/rails/pull/29297))
+
+Action Pack
+-----------
+
+Please refer to the [Changelog][action-pack] for detailed changes.
+
+### Removals
+
+*   Remove deprecated `ActionController::ParamsParser::ParseError`.
+    ([Commit](https://github.com/rails/rails/commit/e16c765ac6dcff068ff2e5554d69ff345c003de1))
+
+### Deprecations
+
+*   Deprecate `#success?`, `#missing?` and `#error?` aliases of
+    `ActionDispatch::TestResponse`.
+    ([Pull Request](https://github.com/rails/rails/pull/30104))
+
+### Notable changes
+
+*   Add support for recyclable cache keys with fragment caching.
+    ([Pull Request](https://github.com/rails/rails/pull/29092))
+
+*   Change the cache key format for fragments to make it easier to debug key
+    churn.
+    ([Pull Request](https://github.com/rails/rails/pull/29092))
+
+*   AEAD encrypted cookies and sessions with GCM.
+    ([Pull Request](https://github.com/rails/rails/pull/28132))
+
+*   Protect from forgery by default.
+    ([Pull Request](https://github.com/rails/rails/pull/29742))
+
+*   Enforce signed/encrypted cookie expiry server side.
+    ([Pull Request](https://github.com/rails/rails/pull/30121))
+
+*   Cookies `:expires` option supports `ActiveSupport::Duration` object.
+    ([Pull Request](https://github.com/rails/rails/pull/30121))
+
+*   Use Capybara registered `:puma` server config.
+    ([Pull Request](https://github.com/rails/rails/pull/30638))
+
+*   Simplify cookies middleware with key rotation support.
+    ([Pull Request](https://github.com/rails/rails/pull/29716))
+
+*   Add ability to enable Early Hints for HTTP/2.
+    ([Pull Request](https://github.com/rails/rails/pull/30744))
+
+*   Add headless chrome support to System Tests.
+    ([Pull Request](https://github.com/rails/rails/pull/30876))
+
+*   Add `:allow_other_host` option to `redirect_back` method.
+    ([Pull Request](https://github.com/rails/rails/pull/30850))
+
+*   Make `assert_recognizes` to traverse mounted engines.
+    ([Pull Request](https://github.com/rails/rails/pull/22435))
+
+*   Add DSL for configuring Content-Security-Policy header.
+    ([Pull Request](https://github.com/rails/rails/pull/31162),
+    [Commit](https://github.com/rails/rails/commit/619b1b6353a65e1635d10b8f8c6630723a5a6f1a),
+    [Commit](https://github.com/rails/rails/commit/4ec8bf68ff92f35e79232fbd605012ce1f4e1e6e))
+
+*   Register most popular audio/video/font mime types supported by modern
+    browsers.
+    ([Pull Request](https://github.com/rails/rails/pull/31251))
+
+*   Changed the default system test screenshot output from `inline` to `simple`.
+    ([Commit](https://github.com/rails/rails/commit/9d6e288ee96d6241f864dbf90211c37b14a57632))
+
+*   Add headless firefox support to System Tests.
+    ([Pull Request](https://github.com/rails/rails/pull/31365))
+
+*   Add secure `X-Download-Options` and `X-Permitted-Cross-Domain-Policies` to
+    default headers set.
+    ([Commit](https://github.com/rails/rails/commit/5d7b70f4336d42eabfc403e9f6efceb88b3eff44))
+
+*   Changed the system tests to set Puma as default server only when the
+    user haven't specified manually another server.
+    ([Pull Request](https://github.com/rails/rails/pull/31384))
+
+*   Add `Referrer-Policy` header to default headers set.
+    ([Commit](https://github.com/rails/rails/commit/428939be9f954d39b0c41bc53d85d0d106b9d1a1))
+
+*   Matches behavior of `Hash#each` in `ActionController::Parameters#each`.
+    ([Pull Request](https://github.com/rails/rails/pull/27790))
+
+*   Add support for automatic nonce generation for Rails UJS.
+    ([Commit](https://github.com/rails/rails/commit/b2f0a8945956cd92dec71ec4e44715d764990a49))
+
+*   Update the default HSTS max-age value to 31536000 seconds (1 year)
+    to meet the minimum max-age requirement for https://hstspreload.org/.
+    ([Commit](https://github.com/rails/rails/commit/30b5f469a1d30c60d1fb0605e84c50568ff7ed37))
+
+*   Add alias method `to_hash` to `to_h` for `cookies`.
+    Add alias method `to_h` to `to_hash` for `session`.
+    ([Commit](https://github.com/rails/rails/commit/50a62499e41dfffc2903d468e8b47acebaf9b500))
+
+Action View
+-----------
+
+Please refer to the [Changelog][action-view] for detailed changes.
+
+### Removals
+
+*   Remove deprecated Erubis ERB handler.
+    ([Commit](https://github.com/rails/rails/commit/7de7f12fd140a60134defe7dc55b5a20b2372d06))
+
+### Deprecations
+
+*   Deprecate `image_alt` helper which used to add default alt text to
+    the images generated by `image_tag`.
+    ([Pull Request](https://github.com/rails/rails/pull/30213))
+
+### Notable changes
+
+*   Add `:json` type to `auto_discovery_link_tag` to support
+    [JSON Feeds](https://jsonfeed.org/version/1).
+    ([Pull Request](https://github.com/rails/rails/pull/29158))
+
+*   Add `srcset` option to `image_tag` helper.
+    ([Pull Request](https://github.com/rails/rails/pull/29349))
+
+*   Fix issues with `field_error_proc` wrapping `optgroup` and
+    select divider `option`.
+    ([Pull Request](https://github.com/rails/rails/pull/31088))
+
+*   Change `form_with` to generates ids by default.
+    ([Commit](https://github.com/rails/rails/commit/260d6f112a0ffdbe03e6f5051504cb441c1e94cd))
+
+*   Add `preload_link_tag` helper.
+    ([Pull Request](https://github.com/rails/rails/pull/31251))
+
+*   Allow the use of callable objects as group methods for grouped selects.
+    ([Pull Request](https://github.com/rails/rails/pull/31578))
+
+Action Mailer
+-------------
+
+Please refer to the [Changelog][action-mailer] for detailed changes.
+
+### Notable changes
+
+*   Allow Action Mailer classes to configure their delivery job.
+    ([Pull Request](https://github.com/rails/rails/pull/29457))
+
+*   Add `assert_enqueued_email_with` test helper.
+    ([Pull Request](https://github.com/rails/rails/pull/30695))
+
+Active Record
+-------------
+
+Please refer to the [Changelog][active-record] for detailed changes.
+
+### Removals
+
+*   Remove deprecated `#migration_keys`.
+    ([Pull Request](https://github.com/rails/rails/pull/30337))
+
+*   Remove deprecated support to `quoted_id` when typecasting
+    an Active Record object.
+    ([Commit](https://github.com/rails/rails/commit/82472b3922bda2f337a79cef961b4760d04f9689))
+
+*   Remove deprecated argument `default` from `index_name_exists?`.
+    ([Commit](https://github.com/rails/rails/commit/8f5b34df81175e30f68879479243fbce966122d7))
+
+*   Remove deprecated support to passing a class to `:class_name`
+    on associations.
+    ([Commit](https://github.com/rails/rails/commit/e65aff70696be52b46ebe57207ebd8bb2cfcdbb6))
+
+*   Remove deprecated methods `initialize_schema_migrations_table` and
+    `initialize_internal_metadata_table`.
+    ([Commit](https://github.com/rails/rails/commit/c9660b5777707658c414b430753029cd9bc39934))
+
+*   Remove deprecated method `supports_migrations?`.
+    ([Commit](https://github.com/rails/rails/commit/9438c144b1893f2a59ec0924afe4d46bd8d5ffdd))
+
+*   Remove deprecated method `supports_primary_key?`.
+    ([Commit](https://github.com/rails/rails/commit/c56ff22fc6e97df4656ddc22909d9bf8b0c2cbb1))
+
+*   Remove deprecated method
+    `ActiveRecord::Migrator.schema_migrations_table_name`.
+    ([Commit](https://github.com/rails/rails/commit/7df6e3f3cbdea9a0460ddbab445c81fbb1cfd012))
+
+*   Remove deprecated argument `name` from `#indexes`.
+    ([Commit](https://github.com/rails/rails/commit/d6b779ecebe57f6629352c34bfd6c442ac8fba0e))
+
+*   Remove deprecated arguments from `#verify!`.
+    ([Commit](https://github.com/rails/rails/commit/9c6ee1bed0292fc32c23dc1c68951ae64fc510be))
+
+*   Remove deprecated configuration `.error_on_ignored_order_or_limit`.
+    ([Commit](https://github.com/rails/rails/commit/e1066f450d1a99c9a0b4d786b202e2ca82a4c3b3))
+
+*   Remove deprecated method `#scope_chain`.
+    ([Commit](https://github.com/rails/rails/commit/ef7784752c5c5efbe23f62d2bbcc62d4fd8aacab))
+
+*   Remove deprecated method `#sanitize_conditions`.
+    ([Commit](https://github.com/rails/rails/commit/8f5413b896099f80ef46a97819fe47a820417bc2))
+
+### Deprecations
+
+*   Deprecate `supports_statement_cache?`.
+    ([Pull Request](https://github.com/rails/rails/pull/28938))
+
+*   Deprecate passing arguments and block at the same time to
+    `count` and `sum` in `ActiveRecord::Calculations`.
+    ([Pull Request](https://github.com/rails/rails/pull/29262))
+
+*   Deprecate delegating to `arel` in `Relation`.
+    ([Pull Request](https://github.com/rails/rails/pull/29619))
+
+*   Deprecate `set_state` method in `TransactionState`.
+    ([Commit](https://github.com/rails/rails/commit/608ebccf8f6314c945444b400a37c2d07f21b253))
+
+*   Deprecate `expand_hash_conditions_for_aggregates` without replacement.
+    ([Commit](https://github.com/rails/rails/commit/7ae26885d96daee3809d0bd50b1a440c2f5ffb69))
+
+### Notable changes
+
+*   When calling the dynamic fixture accessor method with no arguments, it now
+    returns all fixtures of this type. Previously this method always returned
+    an empty array.
+    ([Pull Request](https://github.com/rails/rails/pull/28692))
+
+*   Fix inconsistency with changed attributes when overriding
+    Active Record attribute reader.
+    ([Pull Request](https://github.com/rails/rails/pull/28661))
+
+*   Support Descending Indexes for MySQL.
+    ([Pull Request](https://github.com/rails/rails/pull/28773))
+
+*   Fix `bin/rails db:forward` first migration.
+    ([Commit](https://github.com/rails/rails/commit/b77d2aa0c336492ba33cbfade4964ba0eda3ef84))
+
+*   Raise error `UnknownMigrationVersionError` on the movement of migrations
+    when the current migration does not exist.
+    ([Commit](https://github.com/rails/rails/commit/bb9d6eb094f29bb94ef1f26aa44f145f17b973fe))
+
+*   Respect `SchemaDumper.ignore_tables` in rake tasks for
+    databases structure dump.
+    ([Pull Request](https://github.com/rails/rails/pull/29077))
+
+*   Add `ActiveRecord::Base#cache_version` to support recyclable cache keys via
+    the new versioned entries in `ActiveSupport::Cache`. This also means that
+    `ActiveRecord::Base#cache_key` will now return a stable key that
+    does not include a timestamp any more.
+    ([Pull Request](https://github.com/rails/rails/pull/29092))
+
+*   Prevent creation of bind param if casted value is nil.
+    ([Pull Request](https://github.com/rails/rails/pull/29282))
+
+*   Use bulk INSERT to insert fixtures for better performance.
+    ([Pull Request](https://github.com/rails/rails/pull/29504))
+
+*   Merging two relations representing nested joins no longer transforms
+    the joins of the merged relation into LEFT OUTER JOIN.
+    ([Pull Request](https://github.com/rails/rails/pull/27063))
+
+*   Fix transactions to apply state to child transactions.
+    Previously, if you had a nested transaction and the outer transaction was
+    rolledback, the record from the inner transaction would still be marked
+    as persisted. It was fixed by applying the state of the parent
+    transaction to the child transaction when the parent transaction is
+    rolledback. This will correctly mark records from the inner transaction
+    as not persisted.
+    ([Commit](https://github.com/rails/rails/commit/0237da287eb4c507d10a0c6d94150093acc52b03))
+
+*   Fix eager loading/preloading association with scope including joins.
+    ([Pull Request](https://github.com/rails/rails/pull/29413))
+
+*   Prevent errors raised by `sql.active_record` notification subscribers
+    from being converted into `ActiveRecord::StatementInvalid` exceptions.
+    ([Pull Request](https://github.com/rails/rails/pull/29692))
+
+*   Skip query caching when working with batches of records
+    (`find_each`, `find_in_batches`, `in_batches`).
+    ([Commit](https://github.com/rails/rails/commit/b83852e6eed5789b23b13bac40228e87e8822b4d))
+
+*   Change sqlite3 boolean serialization to use 1 and 0.
+    SQLite natively recognizes 1 and 0 as true and false, but does not natively
+    recognize 't' and 'f' as was previously serialized.
+    ([Pull Request](https://github.com/rails/rails/pull/29699))
+
+*   Values constructed using multi-parameter assignment will now use the
+    post-type-cast value for rendering in single-field form inputs.
+    ([Commit](https://github.com/rails/rails/commit/1519e976b224871c7f7dd476351930d5d0d7faf6))
+
+*   `ApplicationRecord` is no longer generated when generating models. If you
+    need to generate it, it can be created with `rails g application_record`.
+    ([Pull Request](https://github.com/rails/rails/pull/29916))
+
+*   `Relation#or` now accepts two relations who have different values for
+    `references` only, as `references` can be implicitly called by `where`.
+    ([Commit](https://github.com/rails/rails/commit/ea6139101ccaf8be03b536b1293a9f36bc12f2f7))
+
+*   When using `Relation#or`, extract the common conditions and
+    put them before the OR condition.
+    ([Pull Request](https://github.com/rails/rails/pull/29950))
+
+*   Add `binary` fixture helper method.
+    ([Pull Request](https://github.com/rails/rails/pull/30073))
+
+*   Automatically guess the inverse associations for STI.
+    ([Pull Request](https://github.com/rails/rails/pull/23425))
+
+*   Add new error class `LockWaitTimeout` which will be raised
+    when lock wait timeout exceeded.
+    ([Pull Request](https://github.com/rails/rails/pull/30360))
+
+*   Update payload names for `sql.active_record` instrumentation to be
+    more descriptive.
+    ([Pull Request](https://github.com/rails/rails/pull/30619))
+
+*   Use given algorithm while removing index from database.
+    ([Pull Request](https://github.com/rails/rails/pull/24199))
+
+*   Passing a `Set` to `Relation#where` now behaves the same as passing
+    an array.
+    ([Commit](https://github.com/rails/rails/commit/9cf7e3494f5bd34f1382c1ff4ea3d811a4972ae2))
+
+*   PostgreSQL `tsrange` now preserves subsecond precision.
+    ([Pull Request](https://github.com/rails/rails/pull/30725))
+
+*   Raises when calling `lock!` in a dirty record.
+    ([Commit](https://github.com/rails/rails/commit/63cf15877bae859ff7b4ebaf05186f3ca79c1863))
+
+*   Fixed a bug where column orders for an index weren't written to
+    `db/schema.rb` when using the sqlite adapter.
+    ([Pull Request](https://github.com/rails/rails/pull/30970))
+
+*   Fix `bin/rails db:migrate` with specified `VERSION`.
+    `bin/rails db:migrate` with empty VERSION behaves as without `VERSION`.
+    Check a format of `VERSION`: Allow a migration version number
+    or name of a migration file. Raise error if format of `VERSION` is invalid.
+    Raise error if target migration doesn't exist.
+    ([Pull Request](https://github.com/rails/rails/pull/30714))
+
+*   Add new error class `StatementTimeout` which will be raised
+    when statement timeout exceeded.
+    ([Pull Request](https://github.com/rails/rails/pull/31129))
+
+*   `update_all` will now pass its values to `Type#cast` before passing them to
+    `Type#serialize`. This means that `update_all(foo: 'true')` will properly
+    persist a boolean.
+    ([Commit](https://github.com/rails/rails/commit/68fe6b08ee72cc47263e0d2c9ff07f75c4b42761))
+
+*   Require raw SQL fragments to be explicitly marked when used in
+    relation query methods.
+    ([Commit](https://github.com/rails/rails/commit/a1ee43d2170dd6adf5a9f390df2b1dde45018a48),
+    [Commit](https://github.com/rails/rails/commit/e4a921a75f8702a7dbaf41e31130fe884dea93f9))
+
+*   Add `#up_only` to database migrations for code that is only relevant when
+    migrating up, e.g. populating a new column.
+    ([Pull Request](https://github.com/rails/rails/pull/31082))
+
+*   Add new error class `QueryCanceled` which will be raised
+    when canceling statement due to user request.
+    ([Pull Request](https://github.com/rails/rails/pull/31235))
+
+*   Don't allow scopes to be defined which conflict with instance methods
+    on `Relation`.
+    ([Pull Request](https://github.com/rails/rails/pull/31179))
+
+*   Add support for PostgreSQL operator classes to `add_index`.
+    ([Pull Request](https://github.com/rails/rails/pull/19090))
+
+*   Log database query callers.
+    ([Pull Request](https://github.com/rails/rails/pull/26815),
+    [Pull Request](https://github.com/rails/rails/pull/31519),
+    [Pull Request](https://github.com/rails/rails/pull/31690))
+
+*   Undefine attribute methods on descendants when resetting column information.
+    ([Pull Request](https://github.com/rails/rails/pull/31475))
+
+*   Using subselect for `delete_all` with `limit` or `offset`.
+    ([Commit](https://github.com/rails/rails/commit/9e7260da1bdc0770cf4ac547120c85ab93ff3d48))
+
+*   Fixed inconsistency with `first(n)` when used with `limit()`.
+    The `first(n)` finder now respects the `limit()`, making it consistent
+    with `relation.to_a.first(n)`, and also with the behavior of `last(n)`.
+    ([Pull Request](https://github.com/rails/rails/pull/27597))
+
+*   Fix nested `has_many :through` associations on unpersisted parent instances.
+    ([Commit](https://github.com/rails/rails/commit/027f865fc8b262d9ba3ee51da3483e94a5489b66))
+
+*   Take into account association conditions when deleting through records.
+    ([Commit](https://github.com/rails/rails/commit/ae48c65e411e01c1045056562319666384bb1b63))
+
+*   Don't allow destroyed object mutation after `save` or `save!` is called.
+    ([Commit](https://github.com/rails/rails/commit/562dd0494a90d9d47849f052e8913f0050f3e494))
+
+*   Fix relation merger issue with `left_outer_joins`.
+    ([Pull Request](https://github.com/rails/rails/pull/27860))
+
+*   Support for PostgreSQL foreign tables.
+    ([Pull Request](https://github.com/rails/rails/pull/31549))
+
+*   Clear the transaction state when an Active Record object is duped.
+    ([Pull Request](https://github.com/rails/rails/pull/31751))
+
+*   Fix not expanded problem when passing an Array object as argument
+    to the where method using `composed_of` column.
+    ([Pull Request](https://github.com/rails/rails/pull/31724))
+
+*   Make `reflection.klass` raise if `polymorphic?` not to be misused.
+    ([Commit](https://github.com/rails/rails/commit/63fc1100ce054e3e11c04a547cdb9387cd79571a))
+
+*   Fix `#columns_for_distinct` of MySQL and PostgreSQL to make
+    `ActiveRecord::FinderMethods#limited_ids_for` use correct primary key values
+    even if `ORDER BY` columns include other table's primary key.
+    ([Commit](https://github.com/rails/rails/commit/851618c15750979a75635530200665b543561a44))
+
+*   Fix `dependent: :destroy` issue for has_one/belongs_to relationship where
+    the parent class was getting deleted when the child was not.
+    ([Commit](https://github.com/rails/rails/commit/b0fc04aa3af338d5a90608bf37248668d59fc881))
+
+Active Model
+------------
+
+Please refer to the [Changelog][active-model] for detailed changes.
+
+### Notable changes
+
+*   Fix methods `#keys`, `#values` in `ActiveModel::Errors`.
+    Change `#keys` to only return the keys that don't have empty messages.
+    Change `#values` to only return the not empty values.
+    ([Pull Request](https://github.com/rails/rails/pull/28584))
+
+*   Add method `#merge!` for `ActiveModel::Errors`.
+    ([Pull Request](https://github.com/rails/rails/pull/29714))
+
+*   Allow passing a Proc or Symbol to length validator options.
+    ([Pull Request](https://github.com/rails/rails/pull/30674))
+
+*   Execute `ConfirmationValidator` validation when `_confirmation`'s value
+    is `false`.
+    ([Pull Request](https://github.com/rails/rails/pull/31058))
+
+*   Models using the attributes API with a proc default can now be marshalled.
+    ([Commit](https://github.com/rails/rails/commit/0af36c62a5710e023402e37b019ad9982e69de4b))
+
+*   Do not lose all multiple `:includes` with options in serialization.
+    ([Commit](https://github.com/rails/rails/commit/853054bcc7a043eea78c97e7705a46abb603cc44))
+
+Active Support
+--------------
+
+Please refer to the [Changelog][active-support] for detailed changes.
+
+### Removals
+
+*   Remove deprecated `:if` and `:unless` string filter for callbacks.
+    ([Commit](https://github.com/rails/rails/commit/c792354adcbf8c966f274915c605c6713b840548))
+
+*   Remove deprecated `halt_callback_chains_on_return_false` option.
+    ([Commit](https://github.com/rails/rails/commit/19fbbebb1665e482d76cae30166b46e74ceafe29))
+
+### Deprecations
+
+*   Deprecate `Module#reachable?` method.
+    ([Pull Request](https://github.com/rails/rails/pull/30624))
+
+*   Deprecate `secrets.secret_token`.
+    ([Commit](https://github.com/rails/rails/commit/fbcc4bfe9a211e219da5d0bb01d894fcdaef0a0e))
+
+### Notable changes
+
+*   Add `fetch_values` for `HashWithIndifferentAccess`.
+    ([Pull Request](https://github.com/rails/rails/pull/28316))
+
+*   Add support for `:offset` to `Time#change`.
+    ([Commit](https://github.com/rails/rails/commit/851b7f866e13518d900407c78dcd6eb477afad06))
+
+*   Add support for `:offset` and `:zone`
+    to `ActiveSupport::TimeWithZone#change`.
+    ([Commit](https://github.com/rails/rails/commit/851b7f866e13518d900407c78dcd6eb477afad06))
+
+*   Pass gem name and deprecation horizon to deprecation notifications.
+    ([Pull Request](https://github.com/rails/rails/pull/28800))
+
+*   Add support for versioned cache entries. This enables the cache stores to
+    recycle cache keys, greatly saving on storage in cases with frequent churn.
+    Works together with the separation of `#cache_key` and `#cache_version`
+    in Active Record and its use in Action Pack's fragment caching.
+    ([Pull Request](https://github.com/rails/rails/pull/29092))
+
+*   Add `ActiveSupport::CurrentAttributes` to provide a thread-isolated
+    attributes singleton. Primary use case is keeping all the per-request
+    attributes easily available to the whole system.
+    ([Pull Request](https://github.com/rails/rails/pull/29180))
+
+*   `#singularize` and `#pluralize` now respect uncountables for
+    the specified locale.
+    ([Commit](https://github.com/rails/rails/commit/352865d0f835c24daa9a2e9863dcc9dde9e5371a))
+
+*   Add default option to `class_attribute`.
+    ([Pull Request](https://github.com/rails/rails/pull/29270))
+
+*   Add `Date#prev_occurring` and `Date#next_occurring` to return
+    specified next/previous occurring day of week.
+    ([Pull Request](https://github.com/rails/rails/pull/26600))
+
+*   Add default option to module and class attribute accessors.
+    ([Pull Request](https://github.com/rails/rails/pull/29294))
+
+*   Cache: `write_multi`.
+    ([Pull Request](https://github.com/rails/rails/pull/29366))
+
+*   Default `ActiveSupport::MessageEncryptor` to use AES 256 GCM encryption.
+    ([Pull Request](https://github.com/rails/rails/pull/29263))
+
+*   Add `freeze_time` helper which freezes time to `Time.now` in tests.
+    ([Pull Request](https://github.com/rails/rails/pull/29681))
+
+*   Make the order of `Hash#reverse_merge!` consistent
+    with `HashWithIndifferentAccess`.
+    ([Pull Request](https://github.com/rails/rails/pull/28077))
+
+*   Add purpose and expiry support to `ActiveSupport::MessageVerifier` and
+    `ActiveSupport::MessageEncryptor`.
+    ([Pull Request](https://github.com/rails/rails/pull/29892))
+
+*   Update `String#camelize` to provide feedback when wrong option is passed.
+    ([Pull Request](https://github.com/rails/rails/pull/30039))
+
+*   `Module#delegate_missing_to` now raises `DelegationError` if target is nil,
+    similar to `Module#delegate`.
+    ([Pull Request](https://github.com/rails/rails/pull/30191))
+
+*   Add `ActiveSupport::EncryptedFile` and
+    `ActiveSupport::EncryptedConfiguration`.
+    ([Pull Request](https://github.com/rails/rails/pull/30067))
+
+*   Add `config/credentials.yml.enc` to store production app secrets.
+    ([Pull Request](https://github.com/rails/rails/pull/30067))
+
+*   Add key rotation support to `MessageEncryptor` and `MessageVerifier`.
+    ([Pull Request](https://github.com/rails/rails/pull/29716))
+
+*   Return an instance of `HashWithIndifferentAccess` from
+    `HashWithIndifferentAccess#transform_keys`.
+    ([Pull Request](https://github.com/rails/rails/pull/30728))
+
+*   `Hash#slice` now falls back to Ruby 2.5+'s built-in definition if defined.
+    ([Commit](https://github.com/rails/rails/commit/01ae39660243bc5f0a986e20f9c9bff312b1b5f8))
+
+*   `IO#to_json` now returns the `to_s` representation, rather than
+    attempting to convert to an array. This fixes a bug where `IO#to_json`
+    would raise an `IOError` when called on an unreadable object.
+    ([Pull Request](https://github.com/rails/rails/pull/30953))
+
+*   Add same method signature for `Time#prev_day` and `Time#next_day`
+    in accordance with `Date#prev_day`, `Date#next_day`.
+    Allows pass argument for `Time#prev_day` and `Time#next_day`.
+    ([Commit](https://github.com/rails/rails/commit/61ac2167eff741bffb44aec231f4ea13d004134e))
+
+*   Add same method signature for `Time#prev_month` and `Time#next_month`
+    in accordance with `Date#prev_month`, `Date#next_month`.
+    Allows pass argument for `Time#prev_month` and `Time#next_month`.
+    ([Commit](https://github.com/rails/rails/commit/f2c1e3a793570584d9708aaee387214bc3543530))
+
+*   Add same method signature for `Time#prev_year` and `Time#next_year`
+    in accordance with `Date#prev_year`, `Date#next_year`.
+    Allows pass argument for `Time#prev_year` and `Time#next_year`.
+    ([Commit](https://github.com/rails/rails/commit/ee9d81837b5eba9d5ec869ae7601d7ffce763e3e))
+
+*   Fix acronym support in `humanize`.
+    ([Commit](https://github.com/rails/rails/commit/0ddde0a8fca6a0ca3158e3329713959acd65605d))
+
+*   Allow `Range#include?` on TWZ ranges.
+    ([Pull Request](https://github.com/rails/rails/pull/31081))
+
+*   Cache: Enable compression by default for values > 1kB.
+    ([Pull Request](https://github.com/rails/rails/pull/31147))
+
+*   Redis cache store.
+    ([Pull Request](https://github.com/rails/rails/pull/31134),
+    [Pull Request](https://github.com/rails/rails/pull/31866))
+
+*   Handle `TZInfo::AmbiguousTime` errors.
+    ([Pull Request](https://github.com/rails/rails/pull/31128))
+
+*   MemCacheStore: Support expiring counters.
+    ([Commit](https://github.com/rails/rails/commit/b22ee64b5b30c6d5039c292235e10b24b1057f6d))
+
+*   Make `ActiveSupport::TimeZone.all` return only time zones that are in
+    `ActiveSupport::TimeZone::MAPPING`.
+    ([Pull Request](https://github.com/rails/rails/pull/31176))
+
+*   Changed default behaviour of `ActiveSupport::SecurityUtils.secure_compare`,
+    to make it not leak length information even for variable length string.
+    Renamed old `ActiveSupport::SecurityUtils.secure_compare` to
+    `fixed_length_secure_compare`, and started raising `ArgumentError` in
+    case of length mismatch of passed strings.
+    ([Pull Request](https://github.com/rails/rails/pull/24510))
+
+*   Use SHA-1 to generate non-sensitive digests, such as the ETag header.
+    ([Pull Request](https://github.com/rails/rails/pull/31289),
+    [Pull Request](https://github.com/rails/rails/pull/31651))
+
+*   `assert_changes` will always assert that the expression changes,
+    regardless of `from:` and `to:` argument combinations.
+    ([Pull Request](https://github.com/rails/rails/pull/31011))
+
+*   Add missing instrumentation for `read_multi`
+    in `ActiveSupport::Cache::Store`.
+    ([Pull Request](https://github.com/rails/rails/pull/30268))
+
+*   Support hash as first argument in `assert_difference`.
+    This allows to specify multiple numeric differences in the same assertion.
+    ([Pull Request](https://github.com/rails/rails/pull/31600))
+
+*   Caching: MemCache and Redis `read_multi` and `fetch_multi` speedup.
+    Read from the local in-memory cache before consulting the backend.
+    ([Commit](https://github.com/rails/rails/commit/a2b97e4ffef971607a1be8fc7909f099b6840f36))
+
+Active Job
+----------
+
+Please refer to the [Changelog][active-job] for detailed changes.
+
+### Notable changes
+
+*   Allow block to be passed to `ActiveJob::Base.discard_on` to allow custom
+    handling of discard jobs.
+    ([Pull Request](https://github.com/rails/rails/pull/30622))
+
+Ruby on Rails Guides
+--------------------
+
+Please refer to the [Changelog][guides] for detailed changes.
+
+### Notable changes
+
+*   Add
+    [Threading and Code Execution in Rails](threading_and_code_execution.html)
+    Guide.
+    ([Pull Request](https://github.com/rails/rails/pull/27494))
+
+*   Add [Active Storage Overview](active_storage_overview.html) Guide.
+    ([Pull Request](https://github.com/rails/rails/pull/31037))
+
+Credits
+-------
+
+See the
+[full list of contributors to Rails](http://contributors.rubyonrails.org/)
+for the many people who spent many hours making Rails, the stable and robust
+framework it is. Kudos to all of them.
+
+[railties]:       https://github.com/rails/rails/blob/5-2-stable/railties/CHANGELOG.md
+[action-pack]:    https://github.com/rails/rails/blob/5-2-stable/actionpack/CHANGELOG.md
+[action-view]:    https://github.com/rails/rails/blob/5-2-stable/actionview/CHANGELOG.md
+[action-mailer]:  https://github.com/rails/rails/blob/5-2-stable/actionmailer/CHANGELOG.md
+[action-cable]:   https://github.com/rails/rails/blob/5-2-stable/actioncable/CHANGELOG.md
+[active-record]:  https://github.com/rails/rails/blob/5-2-stable/activerecord/CHANGELOG.md
+[active-model]:   https://github.com/rails/rails/blob/5-2-stable/activemodel/CHANGELOG.md
+[active-support]: https://github.com/rails/rails/blob/5-2-stable/activesupport/CHANGELOG.md
+[active-job]:     https://github.com/rails/rails/blob/5-2-stable/activejob/CHANGELOG.md
+[guides]:         https://github.com/rails/rails/blob/5-2-stable/guides/CHANGELOG.md
diff --git a/guides/source/_welcome.html.erb b/guides/source/_welcome.html.erb
index 8afec00018..5dd6bfdd23 100644
--- a/guides/source/_welcome.html.erb
+++ b/guides/source/_welcome.html.erb
@@ -10,16 +10,20 @@
 </p>
 <% else %>
 <p>
-  These are the new guides for Rails 5.1 based on <a href="https://github.com/rails/rails/tree/<%= @version %>"><%= @version %></a>.
+  These are the new guides for Rails 5.2 based on <a href="https://github.com/rails/rails/tree/<%= @version %>"><%= @version %></a>.
   These guides are designed to make you immediately productive with Rails, and to help you understand how all of the pieces fit together.
 </p>
 <% end %>
 <p>
 The guides for earlier releases:
+<a href="http://guides.rubyonrails.org/v5.2/">Rails 5.2</a>,
+<a href="http://guides.rubyonrails.org/v5.1/">Rails 5.1</a>,
 <a href="http://guides.rubyonrails.org/v5.0/">Rails 5.0</a>,
 <a href="http://guides.rubyonrails.org/v4.2/">Rails 4.2</a>,
 <a href="http://guides.rubyonrails.org/v4.1/">Rails 4.1</a>,
 <a href="http://guides.rubyonrails.org/v4.0/">Rails 4.0</a>,
-<a href="http://guides.rubyonrails.org/v3.2/">Rails 3.2</a>, and
+<a href="http://guides.rubyonrails.org/v3.2/">Rails 3.2</a>,
+<a href="http://guides.rubyonrails.org/v3.1/">Rails 3.1</a>,
+<a href="http://guides.rubyonrails.org/v3.0/">Rails 3.0</a>, and
 <a href="http://guides.rubyonrails.org/v2.3/">Rails 2.3</a>.
 </p>
diff --git a/guides/source/action_cable_overview.md b/guides/source/action_cable_overview.md
index 31151e0329..c250db2e0c 100644
--- a/guides/source/action_cable_overview.md
+++ b/guides/source/action_cable_overview.md
@@ -1,12 +1,14 @@
+**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.**
+
 Action Cable Overview
 =====================
 
-In this guide you will learn how Action Cable works and how to use WebSockets to
+In this guide, you will learn how Action Cable works and how to use WebSockets to
 incorporate real-time features into your Rails application.
 
 After reading this guide, you will know:
 
-* What Action Cable is and its integration on backend and frontend
+* What Action Cable is and its integration backend and frontend
 * How to setup Action Cable
 * How to setup channels
 * Deployment and Architecture setup for running Action Cable
@@ -129,7 +131,7 @@ subscriptions based on an identifier sent by the cable consumer.
 # app/channels/chat_channel.rb
 class ChatChannel < ApplicationCable::Channel
   # Called when the consumer has successfully
-  # become a subscriber of this channel.
+  # become a subscriber to this channel.
   def subscribed
   end
 end
@@ -225,7 +227,7 @@ A *broadcasting* is a pub/sub link where anything transmitted by a publisher
 is routed directly to the channel subscribers who are streaming that named
 broadcasting. Each channel can be streaming zero or more broadcastings.
 
-Broadcastings are purely an online queue and time dependent. If a consumer is
+Broadcastings are purely an online queue and time-dependent. If a consumer is
 not streaming (subscribed to a given channel), they'll not get the broadcast
 should they connect later.
 
@@ -515,8 +517,8 @@ user. For a user with an ID of 1, the broadcasting name would be
 The channel has been instructed to stream everything that arrives at
 `web_notifications:1` directly to the client by invoking the `received`
 callback. The data passed as argument is the hash sent as the second parameter
-to the server-side broadcast call, JSON encoded for the trip across the wire,
-and unpacked for the data argument arriving to `received`.
+to the server-side broadcast call, JSON encoded for the trip across the wire
+and unpacked for the data argument arriving as `received`.
 
 ### More Complete Examples
 
@@ -555,9 +557,8 @@ The async adapter is intended for development/testing and should not be used in
 
 ##### Redis Adapter
 
-Action Cable contains two Redis adapters: "normal" Redis and Evented Redis. Both
-of the adapters require users to provide a URL pointing to the Redis server.
-Additionally, a channel_prefix may be provided to avoid channel name collisions
+The Redis adapter requires users to provide a URL pointing to the Redis server.
+Additionally, a `channel_prefix` may be provided to avoid channel name collisions
 when using the same Redis server for multiple applications. See the [Redis PubSub documentation](https://redis.io/topics/pubsub#database-amp-scoping) for more details.
 
 ##### PostgreSQL Adapter
@@ -570,7 +571,7 @@ This may change in the future. [#27214](https://github.com/rails/rails/issues/27
 
 Action Cable will only accept requests from specified origins, which are
 passed to the server config as an array. The origins can be instances of
-strings or regular expressions, against which a check for match will be performed.
+strings or regular expressions, against which a check for the match will be performed.
 
 ```ruby
 config.action_cable.allowed_request_origins = ['http://rubyonrails.com', %r{http://ruby.*}]
@@ -593,7 +594,7 @@ environment configuration files.
 
 ### Other Configurations
 
-The other common option to configure, is the log tags applied to the
+The other common option to configure is the log tags applied to the
 per-connection logger. Here's an example that uses
 the user account id if available, else "no-account" while tagging:
 
@@ -608,7 +609,7 @@ config.action_cable.log_tags = [
 For a full list of all configuration options, see the
 `ActionCable::Server::Configuration` class.
 
-Also note that your server must provide at least the same number of database
+Also, note that your server must provide at least the same number of database
 connections as you have workers. The default worker pool size is set to 4, so
 that means you have to make at least that available. You can change that in
 `config/database.yml` through the `pool` attribute.
@@ -669,8 +670,8 @@ authentication. You can see one way of doing that with Devise in this [article](
 ## Dependencies
 
 Action Cable provides a subscription adapter interface to process its
-pubsub internals. By default, asynchronous, inline, PostgreSQL, evented
-Redis, and non-evented Redis adapters are included. The default adapter
+pubsub internals. By default, asynchronous, inline, PostgreSQL, and Redis
+adapters are included. The default adapter
 in new Rails applications is the asynchronous (`async`) adapter.
 
 The Ruby side of things is built on top of [websocket-driver](https://github.com/faye/websocket-driver-ruby),
diff --git a/guides/source/action_controller_overview.md b/guides/source/action_controller_overview.md
index b3b5f19b61..60a19542e6 100644
--- a/guides/source/action_controller_overview.md
+++ b/guides/source/action_controller_overview.md
@@ -21,9 +21,9 @@ After reading this guide, you will know:
 What Does a Controller Do?
 --------------------------
 
-Action Controller is the C in MVC. After the router has determined which controller to use for a request, the controller is responsible for making sense of the request and producing the appropriate output. Luckily, Action Controller does most of the groundwork for you and uses smart conventions to make this as straightforward as possible.
+Action Controller is the C in [MVC](https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller). After the router has determined which controller to use for a request, the controller is responsible for making sense of the request, and producing the appropriate output. Luckily, Action Controller does most of the groundwork for you and uses smart conventions to make this as straightforward as possible.
 
-For most conventional [RESTful](https://en.wikipedia.org/wiki/Representational_state_transfer) applications, the controller will receive the request (this is invisible to you as the developer), fetch or save data from a model and use a view to create HTML output. If your controller needs to do things a little differently, that's not a problem, this is just the most common way for a controller to work.
+For most conventional [RESTful](https://en.wikipedia.org/wiki/Representational_state_transfer) applications, the controller will receive the request (this is invisible to you as the developer), fetch or save data from a model, and use a view to create HTML output. If your controller needs to do things a little differently, that's not a problem, this is just the most common way for a controller to work.
 
 A controller can thus be thought of as a middleman between models and views. It makes the model data available to the view so it can display that data to the user, and it saves or updates user data to the model.
 
@@ -51,7 +51,7 @@ class ClientsController < ApplicationController
 end
 ```
 
-As an example, if a user goes to `/clients/new` in your application to add a new client, Rails will create an instance of `ClientsController` and call its `new` method. Note that the empty method from the example above would work just fine because Rails will by default render the `new.html.erb` view unless the action says otherwise. The `new` method could make available to the view a `@client` instance variable by creating a new `Client`:
+As an example, if a user goes to `/clients/new` in your application to add a new client, Rails will create an instance of `ClientsController` and call its `new` method. Note that the empty method from the example above would work just fine because Rails will by default render the `new.html.erb` view unless the action says otherwise. By creating a new `Client`, the `new` method can make a `@client` instance variable accessible in the view:
 
 ```ruby
 def new
@@ -397,34 +397,18 @@ You can also pass a `:domain` key and specify the domain name for the cookie:
 Rails.application.config.session_store :cookie_store, key: '_your_app_session', domain: ".example.com"
 ```
 
-Rails sets up (for the CookieStore) a secret key used for signing the session data. This can be changed in `config/secrets.yml`
+Rails sets up (for the CookieStore) a secret key used for signing the session data in `config/credentials.yml.enc`. This can be changed with `bin/rails credentials:edit`.
 
 ```ruby
-# Be sure to restart your server when you modify this file.
-
-# Your secret key is used for verifying the integrity of signed cookies.
-# If you change this key, all old signed cookies will become invalid!
-
-# Make sure the secret is at least 30 characters and all random,
-# no regular words or you'll be exposed to dictionary attacks.
-# You can use `rails secret` to generate a secure secret key.
-
-# Make sure the secrets in this file are kept private
-# if you're sharing your code publicly.
+# aws:
+#   access_key_id: 123
+#   secret_access_key: 345
 
-development:
-  secret_key_base: a75d...
-
-test:
-  secret_key_base: 492f...
-
-# Do not keep production secrets in the repository,
-# instead read values from the environment.
-production:
-  secret_key_base: <%= ENV["SECRET_KEY_BASE"] %>
+# Used as the base secret for all MessageVerifiers in Rails, including the one protecting cookies.
+secret_key_base: 492f...
 ```
 
-NOTE: Changing the secret when using the `CookieStore` will invalidate all existing sessions.
+NOTE: Changing the secret_key_base when using the `CookieStore` will invalidate all existing sessions.
 
 ### Accessing the Session
 
@@ -466,14 +450,16 @@ class LoginsController < ApplicationController
 end
 ```
 
-To remove something from the session, assign that key to be `nil`:
+To remove something from the session, delete the key/value pair:
 
 ```ruby
 class LoginsController < ApplicationController
   # "Delete" a login, aka "log the user out"
   def destroy
     # Remove the user id from the session
-    @_current_user = session[:current_user_id] = nil
+    session.delete(:current_user_id)
+    # Clear the memoized current user
+    @_current_user = nil
     redirect_to root_url
   end
 end
@@ -492,7 +478,7 @@ Let's use the act of logging out as an example. The controller can send a messag
 ```ruby
 class LoginsController < ApplicationController
   def destroy
-    session[:current_user_id] = nil
+    session.delete(:current_user_id)
     flash[:notice] = "You have successfully logged out."
     redirect_to root_url
   end
@@ -670,8 +656,8 @@ class UsersController < ApplicationController
     @users = User.all
     respond_to do |format|
       format.html # index.html.erb
-      format.xml  { render xml: @users}
-      format.json { render json: @users}
+      format.xml  { render xml: @users }
+      format.json { render json: @users }
     end
   end
 end
@@ -791,18 +777,18 @@ Again, this is not an ideal example for this filter, because it's not run in the
 Request Forgery Protection
 --------------------------
 
-Cross-site request forgery is a type of attack in which a site tricks a user into making requests on another site, possibly adding, modifying or deleting data on that site without the user's knowledge or permission.
+Cross-site request forgery is a type of attack in which a site tricks a user into making requests on another site, possibly adding, modifying, or deleting data on that site without the user's knowledge or permission.
 
-The first step to avoid this is to make sure all "destructive" actions (create, update and destroy) can only be accessed with non-GET requests. If you're following RESTful conventions you're already doing this. However, a malicious site can still send a non-GET request to your site quite easily, and that's where the request forgery protection comes in. As the name says, it protects from forged requests.
+The first step to avoid this is to make sure all "destructive" actions (create, update, and destroy) can only be accessed with non-GET requests. If you're following RESTful conventions you're already doing this. However, a malicious site can still send a non-GET request to your site quite easily, and that's where the request forgery protection comes in. As the name says, it protects from forged requests.
 
 The way this is done is to add a non-guessable token which is only known to your server to each request. This way, if a request comes in without the proper token, it will be denied access.
 
 If you generate a form like this:
 
 ```erb
-<%= form_for @user do |f| %>
-  <%= f.text_field :username %>
-  <%= f.text_field :password %>
+<%= form_with model: @user, local: true do |form| %>
+  <%= form.text_field :username %>
+  <%= form.text_field :password %>
 <% end %>
 ```
 
@@ -871,7 +857,7 @@ If you want to set custom headers for a response then `response.headers` is the
 response.headers["Content-Type"] = "application/pdf"
 ```
 
-Note: in the above case it would make more sense to use the `content_type` setter directly.
+NOTE: In the above case it would make more sense to use the `content_type` setter directly.
 
 HTTP Authentications
 --------------------
@@ -1132,7 +1118,7 @@ Rails default exception handling displays a "500 Server Error" message for all e
 
 ### The Default 500 and 404 Templates
 
-By default a production application will render either a 404 or a 500 error message, in the development environment all unhandled exceptions are raised. These messages are contained in static HTML files in the `public` folder, in `404.html` and `500.html` respectively. You can customize these files to add some extra information and style, but remember that they are static HTML; i.e. you can't use ERB, SCSS, CoffeeScript, or layouts for them.
+By default a production application will render either a 404 or a 500 error message, in the development environment all unhandled exceptions are raised. These messages are contained in static HTML files in the public folder, in `404.html` and `500.html` respectively. You can customize these files to add some extra information and style, but remember that they are static HTML; i.e. you can't use ERB, SCSS, CoffeeScript, or layouts for them.
 
 ### `rescue_from`
 
@@ -1197,22 +1183,6 @@ NOTE: Certain exceptions are only rescuable from the `ApplicationController` cla
 Force HTTPS protocol
 --------------------
 
-Sometime you might want to force a particular controller to only be accessible via an HTTPS protocol for security reasons. You can use the `force_ssl` method in your controller to enforce that:
-
-```ruby
-class DinnerController
-  force_ssl
-end
-```
-
-Just like the filter, you could also pass `:only` and `:except` to enforce the secure connection only to specific actions:
-
-```ruby
-class DinnerController
-  force_ssl only: :cheeseburger
-  # or
-  force_ssl except: :cheeseburger
-end
-```
-
-Please note that if you find yourself adding `force_ssl` to many controllers, you may want to force the whole application to use HTTPS instead. In that case, you can set the `config.force_ssl` in your environment file.
+If you'd like to ensure that communication to your controller is only possible
+via HTTPS, you should do so by enabling the `ActionDispatch::SSL` middleware via
+`config.force_ssl` in your environment configuration.
diff --git a/guides/source/action_mailer_basics.md b/guides/source/action_mailer_basics.md
index ba26c922be..86d06508b0 100644
--- a/guides/source/action_mailer_basics.md
+++ b/guides/source/action_mailer_basics.md
@@ -20,9 +20,18 @@ Introduction
 ------------
 
 Action Mailer allows you to send emails from your application using mailer classes
-and views. Mailers work very similarly to controllers. They inherit from
-`ActionMailer::Base` and live in `app/mailers`, and they have associated views
-that appear in `app/views`.
+and views.
+
+#### Mailers are similar to controllers
+
+They inherit from `ActionMailer::Base` and live in `app/mailers`. Mailers also work
+very similarly to controllers. Some examples of similarities are enumerated below.
+Mailers have:
+
+* Actions, and also, associated views that appear in `app/views`.
+* Instance variables that are accessible in views.
+* The ability to utilise layouts and partials.
+* The ability to access a params hash.
 
 Sending Emails
 --------------
@@ -60,8 +69,7 @@ end
 ```
 
 As you can see, you can generate mailers just like you use other generators with
-Rails. Mailers are conceptually similar to controllers, and so we get a mailer,
-a directory for views, and a test.
+Rails.
 
 If you didn't want to use a generator, you could create your own file inside of
 `app/mailers`, just make sure that it inherits from `ActionMailer::Base`:
@@ -73,10 +81,9 @@ end
 
 #### Edit the Mailer
 
-Mailers are very similar to Rails controllers. They also have methods called
-"actions" and use views to structure the content. Where a controller generates
-content like HTML to send back to the client, a Mailer creates a message to be
-delivered via email.
+Mailers have methods called "actions" and they use views to structure their content.
+Where a controller generates content like HTML to send back to the client, a Mailer
+creates a message to be delivered via email.
 
 `app/mailers/user_mailer.rb` contains an empty mailer:
 
@@ -92,8 +99,8 @@ registered email address:
 class UserMailer < ApplicationMailer
   default from: 'notifications@example.com'
 
-  def welcome_email(user)
-    @user = user
+  def welcome_email
+    @user = params[:user]
     @url  = 'http://example.com/login'
     mail(to: @user.email, subject: 'Welcome to My Awesome Site')
   end
@@ -110,9 +117,6 @@ messages in this class. This can be overridden on a per-email basis.
 * `mail` - The actual email message, we are passing the `:to` and `:subject`
 headers in.
 
-Just like controllers, any instance variables we define in the method become
-available for use in the views.
-
 #### Create a Mailer View
 
 Create a file called `welcome_email.html.erb` in `app/views/user_mailer/`. This
@@ -176,7 +180,7 @@ $ bin/rails db:migrate
 Now that we have a user model to play with, we will just edit the
 `app/controllers/users_controller.rb` make it instruct the `UserMailer` to deliver
 an email to the newly created user by editing the create action and inserting a
-call to `UserMailer.welcome_email` right after the user is successfully saved.
+call to `UserMailer.with(user: @user).welcome_email` right after the user is successfully saved.
 
 Action Mailer is nicely integrated with Active Job so you can send emails outside
 of the request-response cycle, so the user doesn't have to wait on it:
@@ -191,7 +195,7 @@ class UsersController < ApplicationController
     respond_to do |format|
       if @user.save
         # Tell the UserMailer to send a welcome email after save
-        UserMailer.welcome_email(@user).deliver_later
+        UserMailer.with(user: @user).welcome_email.deliver_later
 
         format.html { redirect_to(@user, notice: 'User was successfully created.') }
         format.json { render json: @user, status: :created, location: @user }
@@ -220,16 +224,21 @@ If you want to send emails right away (from a cronjob for example) just call
 class SendWeeklySummary
   def run
     User.find_each do |user|
-      UserMailer.weekly_summary(user).deliver_now
+      UserMailer.with(user: user).weekly_summary.deliver_now
     end
   end
 end
 ```
 
+Any key value pair passed to `with` just becomes the `params` for the mailer
+action. So `with(user: @user, account: @user.account)` makes `params[:user]` and
+`params[:account]` available in the mailer action. Just like controllers have
+params.
+
 The method `welcome_email` returns an `ActionMailer::MessageDelivery` object which
 can then just be told `deliver_now` or `deliver_later` to send itself out. The
 `ActionMailer::MessageDelivery` object is just a wrapper around a `Mail::Message`. If
-you want to inspect, alter or do anything else with the `Mail::Message` object you can
+you want to inspect, alter, or do anything else with the `Mail::Message` object you can
 access it with the `message` method on the `ActionMailer::MessageDelivery` object.
 
 ### Auto encoding header values
@@ -261,7 +270,7 @@ Action Mailer makes it very easy to add attachments.
 
 * Pass the file name and content and Action Mailer and the
   [Mail gem](https://github.com/mikel/mail) will automatically guess the
-  mime_type, set the encoding and create the attachment.
+  mime_type, set the encoding, and create the attachment.
 
     ```ruby
     attachments['filename.jpg'] = File.read('/path/to/filename.jpg')
@@ -331,7 +340,7 @@ with the addresses separated by commas.
 
 ```ruby
 class AdminMailer < ApplicationMailer
-  default to: Proc.new { Admin.pluck(:email) },
+  default to: -> { Admin.pluck(:email) },
           from: 'notification@example.com'
 
   def new_registration(user)
@@ -351,8 +360,8 @@ address when they receive the email. The trick to doing that is to format the
 email address in the format `"Full Name" <email>`.
 
 ```ruby
-def welcome_email(user)
-  @user = user
+def welcome_email
+  @user = params[:user]
   email_with_name = %("#{@user.name}" <#{@user.email}>)
   mail(to: email_with_name, subject: 'Welcome to My Awesome Site')
 end
@@ -372,8 +381,8 @@ To change the default mailer view for your action you do something like:
 class UserMailer < ApplicationMailer
   default from: 'notifications@example.com'
 
-  def welcome_email(user)
-    @user = user
+  def welcome_email
+    @user = params[:user]
     @url  = 'http://example.com/login'
     mail(to: @user.email,
          subject: 'Welcome to My Awesome Site',
@@ -394,8 +403,8 @@ templates or even render inline or text without using a template file:
 class UserMailer < ApplicationMailer
   default from: 'notifications@example.com'
 
-  def welcome_email(user)
-    @user = user
+  def welcome_email
+    @user = params[:user]
     @url  = 'http://example.com/login'
     mail(to: @user.email,
          subject: 'Welcome to My Awesome Site') do |format|
@@ -413,7 +422,7 @@ inside of Action Controller, so you can use all the same options, such as
 
 #### Caching mailer view
 
-You can do cache in mailer views like in application views using `cache` method.
+You can perform fragment caching in mailer views like in application views using the `cache` method.
 
 ```
 <% cache do %>
@@ -427,6 +436,9 @@ And in order to use this feature, you need to configure your application with th
   config.action_mailer.perform_caching = true
 ```
 
+Fragment caching is also supported in multipart emails.
+Read more about caching in the [Rails caching guide](caching_with_rails.html).
+
 ### Action Mailer Layouts
 
 Just like controller views, you can also have mailer layouts. The layout name
@@ -450,8 +462,8 @@ the format block to specify different layouts for different formats:
 
 ```ruby
 class UserMailer < ApplicationMailer
-  def welcome_email(user)
-    mail(to: user.email) do |format|
+  def welcome_email
+    mail(to: params[:user].email) do |format|
       format.html { render layout: 'my_layout' }
       format.text
     end
@@ -474,7 +486,7 @@ special URL that renders them. In the above example, the preview class for
 ```ruby
 class UserMailerPreview < ActionMailer::Preview
   def welcome_email
-    UserMailer.welcome_email(User.first)
+    UserMailer.with(user: User.first).welcome_email
   end
 end
 ```
@@ -591,12 +603,12 @@ mailer action.
 
 ```ruby
 class UserMailer < ApplicationMailer
-  def welcome_email(user, company)
-    @user = user
+  def welcome_email
+    @user = params[:user]
     @url  = user_url(@user)
-    delivery_options = { user_name: company.smtp_user,
-                         password: company.smtp_password,
-                         address: company.smtp_host }
+    delivery_options = { user_name: params[:company].smtp_user,
+                         password: params[:company].smtp_password,
+                         address: params[:company].smtp_host }
     mail(to: @user.email,
          subject: "Please see the Terms and Conditions attached",
          delivery_method_options: delivery_options)
@@ -613,9 +625,9 @@ will default to `text/plain` otherwise.
 
 ```ruby
 class UserMailer < ApplicationMailer
-  def welcome_email(user, email_body)
-    mail(to: user.email,
-         body: email_body,
+  def welcome_email
+    mail(to: params[:user].email,
+         body: params[:email_body],
          content_type: "text/html",
          subject: "Already rendered!")
   end
@@ -674,24 +686,43 @@ Action Mailer allows for you to specify a `before_action`, `after_action` and
 * You could use a `before_action` to populate the mail object with defaults,
   delivery_method_options or insert default headers and attachments.
 
+```ruby
+class InvitationsMailer < ApplicationMailer
+  before_action { @inviter, @invitee = params[:inviter], params[:invitee] }
+  before_action { @account = params[:inviter].account }
+
+  default to:       -> { @invitee.email_address },
+          from:     -> { common_address(@inviter) },
+          reply_to: -> { @inviter.email_address_with_name }
+
+  def account_invitation
+    mail subject: "#{@inviter.name} invited you to their Basecamp (#{@account.name})"
+  end
+
+  def project_invitation
+    @project    = params[:project]
+    @summarizer = ProjectInvitationSummarizer.new(@project.bucket)
+
+    mail subject: "#{@inviter.name.familiar} added you to a project in Basecamp (#{@account.name})"
+  end
+end
+```
+
 * You could use an `after_action` to do similar setup as a `before_action` but
   using instance variables set in your mailer action.
 
 ```ruby
 class UserMailer < ApplicationMailer
+  before_action { @business, @user = params[:business], params[:user] }
+
   after_action :set_delivery_options,
                :prevent_delivery_to_guests,
                :set_business_headers
 
-  def feedback_message(business, user)
-    @business = business
-    @user = user
-    mail
+  def feedback_message
   end
 
-  def campaign_message(business, user)
-    @business = business
-    @user = user
+  def campaign_message
   end
 
   private
@@ -778,9 +809,9 @@ config.action_mailer.smtp_settings = {
   user_name:            '<username>',
   password:             '<password>',
   authentication:       'plain',
-  enable_starttls_auto: true  }
+  enable_starttls_auto: true }
 ```
-Note: As of July 15, 2014, Google increased [its security measures](https://support.google.com/accounts/answer/6010255) and now blocks attempts from apps it deems less secure.
+NOTE: As of July 15, 2014, Google increased [its security measures](https://support.google.com/accounts/answer/6010255) and now blocks attempts from apps it deems less secure.
 You can change your Gmail settings [here](https://www.google.com/settings/security/lesssecureapps) to allow the attempts. If your Gmail account has 2-factor authentication enabled,
 then you will need to set an [app password](https://myaccount.google.com/apppasswords) and use that instead of your regular password. Alternatively, you can
 use another ESP to send email by replacing 'smtp.gmail.com' above with the address of your provider.
diff --git a/guides/source/action_view_overview.md b/guides/source/action_view_overview.md
index ea72567c03..b85568af5c 100644
--- a/guides/source/action_view_overview.md
+++ b/guides/source/action_view_overview.md
@@ -7,7 +7,7 @@ After reading this guide, you will know:
 
 * What Action View is and how to use it with Rails.
 * How best to use templates, partials, and layouts.
-* What helpers are provided by Action View and how to make your own.
+* What helpers are provided by Action View.
 * How to use localized views.
 
 --------------------------------------------------------------------------------
@@ -48,7 +48,7 @@ For example, the index controller action of the `articles_controller.rb` will us
 The complete HTML returned to the client is composed of a combination of this ERB file, a layout template that wraps it, and all the partials that the view may reference. Within this guide you will find more detailed documentation about each of these three components.
 
 
-Templates, Partials and Layouts
+Templates, Partials, and Layouts
 -------------------------------
 
 As mentioned, the final HTML output is a composition of three Rails elements: `Templates`, `Partials` and `Layouts`.
@@ -62,7 +62,7 @@ Rails supports multiple template systems and uses a file extension to distinguis
 
 #### ERB
 
-Within an ERB template, Ruby code can be included using both `<% %>` and `<%= %>` tags. The `<% %>` tags are used to execute Ruby code that does not return anything, such as conditions, loops or blocks, and the `<%= %>` tags are used when you want output.
+Within an ERB template, Ruby code can be included using both `<% %>` and `<%= %>` tags. The `<% %>` tags are used to execute Ruby code that does not return anything, such as conditions, loops, or blocks, and the `<%= %>` tags are used when you want output.
 
 Consider the following loop for names:
 
@@ -149,10 +149,10 @@ end
 
 #### Jbuilder
 [Jbuilder](https://github.com/rails/jbuilder) is a gem that's
-maintained by the Rails team and included in the default Rails Gemfile.
+maintained by the Rails team and included in the default Rails `Gemfile`.
 It's similar to Builder, but is used to generate JSON, instead of XML.
 
-If you don't have it, you can add the following to your Gemfile:
+If you don't have it, you can add the following to your `Gemfile`:
 
 ```ruby
 gem 'jbuilder'
@@ -490,7 +490,7 @@ stylesheet_link_tag "application" # => <link href="/assets/application.css" medi
 
 #### stylesheet_path
 
-Computes the path to a stylesheet asset in the `app/assets/stylesheets` directory. If the source filename has no extension, `.css` will be appended. Full paths from the document root will be passed through. Used internally by stylesheet_link_tag to build the stylesheet path.
+Computes the path to a stylesheet asset in the `app/assets/stylesheets` directory. If the source filename has no extension, `.css` will be appended. Full paths from the document root will be passed through. Used internally by `stylesheet_link_tag` to build the stylesheet path.
 
 ```ruby
 stylesheet_path "application" # => /assets/application.css
@@ -760,7 +760,7 @@ time_ago_in_words(3.minutes.from_now)  # => 3 minutes
 
 #### time_select
 
-Returns a set of select tags (one for hour, minute and optionally second) pre-selected for accessing a specified time-based attribute. The selects are prepared for multi-parameter assignment to an Active Record object.
+Returns a set of select tags (one for hour, minute, and optionally second) pre-selected for accessing a specified time-based attribute. The selects are prepared for multi-parameter assignment to an Active Record object.
 
 ```ruby
 # Creates a time select tag that, when POSTed, will be stored in the order variable in the submitted attribute
@@ -807,20 +807,22 @@ The core method of this helper, `form_for`, gives you the ability to create a fo
 The HTML generated for this would be:
 
 ```html
-<form action="/people/create" method="post">
-  <input id="person_first_name" name="person[first_name]" type="text" />
-  <input id="person_last_name" name="person[last_name]" type="text" />
-  <input name="commit" type="submit" value="Create" />
+<form class="new_person" id="new_person" action="/people" accept-charset="UTF-8" method="post">
+  <input name="utf8" type="hidden" value="&#x2713;" />
+  <input type="hidden" name="authenticity_token" value="lTuvBzs7ANygT0NFinXj98tfw3Emfm65wwYLbUvoWsK2pngccIQSUorM2C035M9dZswXgWTvKwFS8W5TVblpYw==" />
+  <input type="text" name="person[first_name]" id="person_first_name" />
+  <input type="text" name="person[last_name]" id="person_last_name" />
+  <input type="submit" name="commit" value="Create" data-disable-with="Create" />
 </form>
 ```
 
 The params object created when this form is submitted would look like:
 
 ```ruby
-{ "action" => "create", "controller" => "people", "person" => { "first_name" => "William", "last_name" => "Smith" } }
+{"utf8" => "✓", "authenticity_token" => "lTuvBzs7ANygT0NFinXj98tfw3Emfm65wwYLbUvoWsK2pngccIQSUorM2C035M9dZswXgWTvKwFS8W5TVblpYw==", "person" => {"first_name" => "William", "last_name" => "Smith"}, "commit" => "Create", "controller" => "people", "action" => "create"}
 ```
 
-The params hash has a nested person value, which can therefore be accessed with params[:person] in the controller.
+The params hash has a nested person value, which can therefore be accessed with `params[:person]` in the controller.
 
 #### check_box
 
@@ -1100,7 +1102,7 @@ Possible output:
 </optgroup>
 ```
 
-Note: Only the `optgroup` and `option` tags are returned, so you still have to wrap the output in an appropriate `select` tag.
+NOTE: Only the `optgroup` and `option` tags are returned, so you still have to wrap the output in an appropriate `select` tag.
 
 #### options_for_select
 
@@ -1111,7 +1113,7 @@ options_for_select([ "VISA", "MasterCard" ])
 # => <option>VISA</option> <option>MasterCard</option>
 ```
 
-Note: Only the `option` tags are returned, you have to wrap this call in a regular HTML `select` tag.
+NOTE: Only the `option` tags are returned, you have to wrap this call in a regular HTML `select` tag.
 
 #### options_from_collection_for_select
 
@@ -1128,7 +1130,7 @@ options_from_collection_for_select(@project.people, "id", "name")
 # => <option value="#{person.id}">#{person.name}</option>
 ```
 
-Note: Only the `option` tags are returned, you have to wrap this call in a regular HTML `select` tag.
+NOTE: Only the `option` tags are returned, you have to wrap this call in a regular HTML `select` tag.
 
 #### select
 
@@ -1160,7 +1162,7 @@ Returns a string of option tags for pretty much any time zone in the world.
 Returns select and option tags for the given object and method, using `time_zone_options_for_select` to generate the list of option tags.
 
 ```ruby
-time_zone_select( "user", "time_zone")
+time_zone_select("user", "time_zone")
 ```
 
 #### date_field
@@ -1265,8 +1267,8 @@ password_field_tag 'pass'
 Creates a radio button; use groups of radio buttons named the same to allow users to select from a group of options.
 
 ```ruby
-radio_button_tag 'gender', 'male'
-# => <input id="gender_male" name="gender" type="radio" value="male" />
+radio_button_tag 'favorite_color', 'maroon'
+# => <input id="favorite_color_maroon" name="favorite_color" type="radio" value="maroon" />
 ```
 
 #### select_tag
diff --git a/guides/source/active_job_basics.md b/guides/source/active_job_basics.md
index 9fc95954bc..3183fccd4f 100644
--- a/guides/source/active_job_basics.md
+++ b/guides/source/active_job_basics.md
@@ -120,7 +120,7 @@ production apps will need to pick a persistent backend.
 ### Backends
 
 Active Job has built-in adapters for multiple queuing backends (Sidekiq,
-Resque, Delayed Job and others). To get an up-to-date list of the adapters
+Resque, Delayed Job, and others). To get an up-to-date list of the adapters
 see the API Documentation for [ActiveJob::QueueAdapters](http://api.rubyonrails.org/classes/ActiveJob/QueueAdapters.html).
 
 ### Setting the Backend
@@ -147,7 +147,7 @@ class GuestsCleanupJob < ApplicationJob
   #....
 end
 
-# Now your job will use `resque` as it's backend queue adapter overriding what
+# Now your job will use `resque` as its backend queue adapter overriding what
 # was configured in `config.active_job.queue_adapter`.
 ```
 
@@ -162,6 +162,7 @@ Here is a noncomprehensive list of documentation:
 
 - [Sidekiq](https://github.com/mperham/sidekiq/wiki/Active-Job)
 - [Resque](https://github.com/resque/resque/wiki/ActiveJob)
+- [Sneakers](https://github.com/jondot/sneakers/wiki/How-To:-Rails-Background-Jobs-with-ActiveJob)
 - [Sucker Punch](https://github.com/brandonhilkert/sucker_punch#active-job)
 - [Queue Classic](https://github.com/QueueClassic/queue_classic#active-job)
 
@@ -275,7 +276,7 @@ class GuestsCleanupJob < ApplicationJob
   end
 
   private
-    def around_cleanup(job)
+    def around_cleanup
       # Do something before perform
       yield
       # Do something after perform
@@ -289,7 +290,7 @@ For example, you could send metrics for every job enqueued:
 
 ```ruby
 class ApplicationJob
-  before_enqueue { |job| $statsd.increment "#{job.name.underscore}.enqueue" }
+  before_enqueue { |job| $statsd.increment "#{job.class.name.underscore}.enqueue" }
 end
 ```
 
@@ -338,8 +339,23 @@ UserMailer.welcome(@user).deliver_later # Email will be localized to Esperanto.
 ```
 
 
-GlobalID
---------
+Supported types for arguments
+----------------------------
+
+ActiveJob supports the following types of arguments by default:
+
+  - Basic types (`NilClass`, `String`, `Integer`, `Float`, `BigDecimal`, `TrueClass`, `FalseClass`)
+  - `Symbol`
+  - `Date`
+  - `Time`
+  - `DateTime`
+  - `ActiveSupport::TimeWithZone`
+  - `ActiveSupport::Duration`
+  - `Hash` (Keys should be of `String` or `Symbol` type)
+  - `ActiveSupport::HashWithIndifferentAccess`
+  - `Array`
+
+### GlobalID
 
 Active Job supports GlobalID for parameters. This makes it possible to pass live
 Active Record objects to your job instead of class/id pairs, which you then have
@@ -367,6 +383,39 @@ end
 This works with any class that mixes in `GlobalID::Identification`, which
 by default has been mixed into Active Record classes.
 
+### Serializers
+
+You can extend the list of supported argument types. You just need to define your own serializer:
+
+```ruby
+class MoneySerializer < ActiveJob::Serializers::ObjectSerializer
+  # Checks if an argument should be serialized by this serializer.
+  def serialize?(argument)
+    argument.is_a? Money
+  end
+
+  # Converts an object to a simpler representative using supported object types.
+  # The recommended representative is a Hash with a specific key. Keys can be of basic types only.
+  # You should call `super` to add the custom serializer type to the hash.
+  def serialize(money)
+    super(
+      "amount" => money.amount,
+      "currency" => money.currency
+    )
+  end
+
+  # Converts serialized value into a proper object.
+  def deserialize(hash)
+    Money.new(hash["amount"], hash["currency"])
+  end
+end
+```
+
+and add this serializer to the list:
+
+```ruby
+Rails.application.config.active_job.custom_serializers << MoneySerializer
+```
 
 Exceptions
 ----------
@@ -388,6 +437,25 @@ class GuestsCleanupJob < ApplicationJob
 end
 ```
 
+### Retrying or Discarding failed jobs
+
+It's also possible to retry or discard a job if an exception is raised during execution.
+For example:
+
+```ruby
+class RemoteServiceJob < ApplicationJob
+  retry_on CustomAppException # defaults to 3s wait, 5 attempts
+
+  discard_on ActiveJob::DeserializationError
+
+  def perform(*args)
+    # Might raise CustomAppException or ActiveJob::DeserializationError
+  end
+end
+```
+
+To get more details see the API Documentation for [ActiveJob::Exceptions](http://api.rubyonrails.org/classes/ActiveJob/Exceptions/ClassMethods.html).
+
 ### Deserialization
 
 GlobalID allows serializing full Active Record objects passed to `#perform`.
diff --git a/guides/source/active_model_basics.md b/guides/source/active_model_basics.md
index b8f076a27b..4b0ea32d7c 100644
--- a/guides/source/active_model_basics.md
+++ b/guides/source/active_model_basics.md
@@ -61,7 +61,7 @@ person.age_highest?  # => false
 
 `ActiveModel::Callbacks` gives Active Record style callbacks. This provides an
 ability to define callbacks which run at appropriate times.
-After defining callbacks, you can wrap them with before, after and around
+After defining callbacks, you can wrap them with before, after, and around
 custom methods.
 
 ```ruby
@@ -464,7 +464,7 @@ a `password` accessor with certain validations on it.
 #### Requirements
 
 `ActiveModel::SecurePassword` depends on [`bcrypt`](https://github.com/codahale/bcrypt-ruby 'BCrypt'),
-so include this gem in your Gemfile to use `ActiveModel::SecurePassword` correctly.
+so include this gem in your `Gemfile` to use `ActiveModel::SecurePassword` correctly.
 In order to make this work, the model must have an accessor named `password_digest`.
 The `has_secure_password` will add the following validations on the `password` accessor:
 
diff --git a/guides/source/active_record_basics.md b/guides/source/active_record_basics.md
index 11aefcb05f..182bc865f0 100644
--- a/guides/source/active_record_basics.md
+++ b/guides/source/active_record_basics.md
@@ -13,7 +13,7 @@ After reading this guide, you will know:
 * How to use Active Record models to manipulate data stored in a relational
   database.
 * Active Record schema naming conventions.
-* The concepts of database migrations, validations and callbacks.
+* The concepts of database migrations, validations, and callbacks.
 
 --------------------------------------------------------------------------------
 
@@ -38,13 +38,15 @@ object on how to write to and read from the database.
 
 ### Object Relational Mapping
 
-Object Relational Mapping, commonly referred to as its abbreviation ORM, is
+[Object Relational Mapping](https://en.wikipedia.org/wiki/Object-relational_mapping), commonly referred to as its abbreviation ORM, is
 a technique that connects the rich objects of an application to tables in
 a relational database management system. Using ORM, the properties and
 relationships of the objects in an application can be easily stored and
 retrieved from a database without writing SQL statements directly and with less
 overall database access code.
 
+NOTE: If you are not familiar enough with relational database management systems (RDBMS) or structured query language (SQL), please go through [this tutorial](https://www.w3schools.com/sql/default.asp) (or [this one](http://www.sqlcourse.com/)) or study them by other means. Understanding how relational databases work is crucial to understanding Active Records and Rails in general.
+
 ### Active Record as an ORM Framework
 
 Active Record gives us several mechanisms, the most important being the ability
@@ -142,7 +144,7 @@ end
 This will create a `Product` model, mapped to a `products` table at the
 database. By doing this you'll also have the ability to map the columns of each
 row in that table with the attributes of the instances of your model. Suppose
-that the `products` table was created using an SQL statement like:
+that the `products` table was created using an SQL (or one of its extensions) statement like:
 
 ```sql
 CREATE TABLE products (
@@ -152,8 +154,9 @@ CREATE TABLE products (
 );
 ```
 
-Following the table schema above, you would be able to write code like the
-following:
+Schema above declares a table with two columns: `id` and `name`. Each row of
+this table represents a certain product with these two parameters. Thus, you
+would be able to write code like the following:
 
 ```ruby
 p = Product.new
@@ -208,7 +211,7 @@ to allow an application to read and manipulate data stored within its tables.
 
 ### Create
 
-Active Record objects can be created from a hash, a block or have their
+Active Record objects can be created from a hash, a block, or have their
 attributes manually set after creation. The `new` method will return a new
 object while `create` will return the object and save it to the database.
 
@@ -304,13 +307,24 @@ user = User.find_by(name: 'David')
 user.destroy
 ```
 
+If you'd like to delete several records in bulk, you may use `destroy_all`
+method:
+
+```ruby
+# find and delete all users named David
+User.where(name: 'David').destroy_all
+
+# delete all users
+User.destroy_all
+```
+
 Validations
 -----------
 
 Active Record allows you to validate the state of a model before it gets written
 into the database. There are several methods that you can use to check your
 models and validate that an attribute value is not empty, is unique and not
-already in the database, follows a specific format and many more.
+already in the database, follows a specific format, and many more.
 
 Validation is a very important issue to consider when persisting to the database, so
 the methods `save` and `update` take it into account when
@@ -339,7 +353,7 @@ Callbacks
 Active Record callbacks allow you to attach code to certain events in the
 life-cycle of your models. This enables you to add behavior to your models by
 transparently executing code when those events occur, like when you create a new
-record, update it, destroy it and so on. You can learn more about callbacks in
+record, update it, destroy it, and so on. You can learn more about callbacks in
 the [Active Record Callbacks guide](active_record_callbacks.html).
 
 Migrations
@@ -373,5 +387,5 @@ provides rollback features. To actually create the table, you'd run `rails db:mi
 and to roll it back, `rails db:rollback`.
 
 Note that the above code is database-agnostic: it will run in MySQL,
-PostgreSQL, Oracle and others. You can learn more about migrations in the
+PostgreSQL, Oracle, and others. You can learn more about migrations in the
 [Active Record Migrations guide](active_record_migrations.html).
diff --git a/guides/source/active_record_callbacks.md b/guides/source/active_record_callbacks.md
index 53417f012e..0f74daace6 100644
--- a/guides/source/active_record_callbacks.md
+++ b/guides/source/active_record_callbacks.md
@@ -213,6 +213,7 @@ The following methods trigger callbacks:
 * `save!`
 * `save(validate: false)`
 * `toggle!`
+* `touch`
 * `update_attribute`
 * `update`
 * `update!`
@@ -245,7 +246,6 @@ Just as with validations, it is also possible to skip callbacks by using the fol
 * `increment`
 * `increment_counter`
 * `toggle`
-* `touch`
 * `update_column`
 * `update_columns`
 * `update_all`
@@ -264,7 +264,7 @@ The whole callback chain is wrapped in a transaction. If any callback raises an
 throw :abort
 ```
 
-WARNING. Any exception that is not `ActiveRecord::Rollback` or `ActiveRecord::RecordInvalid` will be re-raised by Rails after the callback chain is halted. Raising an exception other than `ActiveRecord::Rollback` or `ActiveRecord::RecordInvalid` may break code that does not expect methods like `save` and `update_attributes` (which normally try to return `true` or `false`) to raise an exception.
+WARNING. Any exception that is not `ActiveRecord::Rollback` or `ActiveRecord::RecordInvalid` will be re-raised by Rails after the callback chain is halted. Raising an exception other than `ActiveRecord::Rollback` or `ActiveRecord::RecordInvalid` may break code that does not expect methods like `save` and `update` (which normally try to return `true` or `false`) to raise an exception.
 
 Relational Callbacks
 --------------------
@@ -408,7 +408,7 @@ end
 NOTE: The `:on` option specifies when a callback will be fired. If you
 don't supply the `:on` option the callback will fire for every action.
 
-Since using `after_commit` callback only on create, update or delete is
+Since using `after_commit` callback only on create, update, or delete is
 common, there are aliases for those operations:
 
 * `after_create_commit`
diff --git a/guides/source/active_record_migrations.md b/guides/source/active_record_migrations.md
index f8f36bf600..dda87802bf 100644
--- a/guides/source/active_record_migrations.md
+++ b/guides/source/active_record_migrations.md
@@ -353,8 +353,7 @@ create_table :products, options: "ENGINE=BLACKHOLE" do |t|
 end
 ```
 
-will append `ENGINE=BLACKHOLE` to the SQL statement used to create the table
-(when using MySQL or MariaDB, the default is `ENGINE=InnoDB`).
+will append `ENGINE=BLACKHOLE` to the SQL statement used to create the table.
 
 Also you can pass the `:comment` option with any description for the table
 that will be stored in database itself and can be viewed with database administration
@@ -443,7 +442,7 @@ change_column_default :products, :approved, from: true, to: false
 This sets `:name` field on products to a `NOT NULL` column and the default
 value of the `:approved` field from true to false.
 
-Note: You could also write the above `change_column_default` migration as
+NOTE: You could also write the above `change_column_default` migration as
 `change_column_default :products, :approved, false`, but unlike the previous
 example, this would make your migration irreversible.
 
@@ -789,7 +788,7 @@ version to migrate to.
 
 ### Setup the Database
 
-The `rails db:setup` task will create the database, load the schema and initialize
+The `rails db:setup` task will create the database, load the schema, and initialize
 it with the seed data.
 
 ### Resetting the Database
@@ -897,7 +896,7 @@ Occasionally you will make a mistake when writing a migration. If you have
 already run the migration, then you cannot just edit the migration and run the
 migration again: Rails thinks it has already run the migration and so will do
 nothing when you run `rails db:migrate`. You must rollback the migration (for
-example with `bin/rails db:rollback`), edit your migration and then run
+example with `bin/rails db:rollback`), edit your migration, and then run
 `rails db:migrate` to run the corrected version.
 
 In general, editing existing migrations is not a good idea. You will be
@@ -918,35 +917,29 @@ Schema Dumping and You
 ### What are Schema Files for?
 
 Migrations, mighty as they may be, are not the authoritative source for your
-database schema. That role falls to either `db/schema.rb` or an SQL file which
-Active Record generates by examining the database. They are not designed to be
-edited, they just represent the current state of the database.
+database schema. Your database remains the authoritative source. By default,
+Rails generates `db/schema.rb` which attempts to capture the current state of
+your database schema.
 
-There is no need (and it is error prone) to deploy a new instance of an app by
-replaying the entire migration history. It is much simpler and faster to just
-load into the database a description of the current schema.
-
-For example, this is how the test database is created: the current development
-database is dumped (either to `db/schema.rb` or `db/structure.sql`) and then
-loaded into the test database.
+It tends to be faster and less error prone to create a new instance of your
+application's database by loading the schema file via `rails db:schema:load`
+than it is to replay the entire migration history. Old migrations may fail to
+apply correctly if those migrations use changing external dependencies or rely
+on application code which evolves separately from your migrations.
 
 Schema files are also useful if you want a quick look at what attributes an
 Active Record object has. This information is not in the model's code and is
 frequently spread across several migrations, but the information is nicely
-summed up in the schema file. The
-[annotate_models](https://github.com/ctran/annotate_models) gem automatically
-adds and updates comments at the top of each model summarizing the schema if
-you desire that functionality.
+summed up in the schema file.
 
 ### Types of Schema Dumps
 
-There are two ways to dump the schema. This is set in `config/application.rb`
-by the `config.active_record.schema_format` setting, which may be either `:sql`
-or `:ruby`.
+The format of the schema dump generated by Rails is controlled by the
+`config.active_record.schema_format` setting in `config/application.rb`. By
+default, the format is `:ruby`, but can also be set to `:sql`.
 
 If `:ruby` is selected, then the schema is stored in `db/schema.rb`. If you look
-at this file you'll find that it looks an awful lot like one very big
-migration:
+at this file you'll find that it looks an awful lot like one very big migration:
 
 ```ruby
 ActiveRecord::Schema.define(version: 20080906171750) do
@@ -968,36 +961,32 @@ end
 
 In many ways this is exactly what it is. This file is created by inspecting the
 database and expressing its structure using `create_table`, `add_index`, and so
-on. Because this is database-independent, it could be loaded into any database
-that Active Record supports. This could be very useful if you were to
-distribute an application that is able to run against multiple databases.
-
-NOTE: `db/schema.rb` cannot express database specific items such as triggers,
-sequences, stored procedures or check constraints, etc. Please note that while
-custom SQL statements can be run in migrations, these statements cannot be reconstituted
-by the schema dumper. If you are using features like this, then you
-should set the schema format to `:sql`.
-
-Instead of using Active Record's schema dumper, the database's structure will
-be dumped using a tool specific to the database (via the `db:structure:dump`
-rails task) into `db/structure.sql`. For example, for PostgreSQL, the `pg_dump`
-utility is used. For MySQL and MariaDB, this file will contain the output of
-`SHOW CREATE TABLE` for the various tables.
-
-Loading these schemas is simply a question of executing the SQL statements they
-contain. By definition, this will create a perfect copy of the database's
-structure. Using the `:sql` schema format will, however, prevent loading the
-schema into a RDBMS other than the one used to create it.
+on.
+
+`db/schema.rb` cannot express everything your database may support such as
+triggers, sequences, stored procedures, check constraints, etc. While migrations
+may use `execute` to create database constructs that are not supported by the
+Ruby migration DSL, these constructs may not be able to be reconstituted by the
+schema dumper. If you are using features like these, you should set the schema
+format to `:sql` in order to get an accurate schema file that is useful to
+create new database instances.
+
+When the schema format is set to `:sql`, the database structure will be dumped
+using a tool specific to the database into `db/structure.sql`. For example, for
+PostgreSQL, the `pg_dump` utility is used. For MySQL and MariaDB, this file will
+contain the output of `SHOW CREATE TABLE` for the various tables.
+
+To load the schema from `db/structure.sql`, run `rails db:structure:load`.
+Loading this file is done by executing the SQL statements it contains. By
+definition, this will create a perfect copy of the database's structure.
 
 ### Schema Dumps and Source Control
 
-Because schema dumps are the authoritative source for your database schema, it
-is strongly recommended that you check them into source control.
+Because schema files are commonly used to create new databases, it is strongly
+recommended that you check your schema file into source control.
 
-`db/schema.rb` contains the current version number of the database. This
-ensures conflicts are going to happen in the case of a merge where both
-branches touched the schema. When that happens, solve conflicts manually,
-keeping the highest version number of the two.
+Merge conflicts can occur in your schema file when two branches modify schema.
+To resolve these conflicts run `rails db:migrate` to regenerate the schema file.
 
 Active Record and Referential Integrity
 ---------------------------------------
diff --git a/guides/source/active_record_postgresql.md b/guides/source/active_record_postgresql.md
index 58c61f0864..796b65d6d4 100644
--- a/guides/source/active_record_postgresql.md
+++ b/guides/source/active_record_postgresql.md
@@ -84,7 +84,7 @@ Book.where("array_length(ratings, 1) >= 3")
 ### Hstore
 
 * [type definition](https://www.postgresql.org/docs/current/static/hstore.html)
-* [functions and operators](https://www.postgresql.org/docs/current/static/hstore.html#AEN179902)
+* [functions and operators](https://www.postgresql.org/docs/current/static/hstore.html#id-1.11.7.26.5)
 
 NOTE: You need to enable the `hstore` extension to use hstore.
 
@@ -290,7 +290,7 @@ SELECT n.nspname AS enum_schema,
 ### UUID
 
 * [type definition](https://www.postgresql.org/docs/current/static/datatype-uuid.html)
-* [pgcrypto generator function](https://www.postgresql.org/docs/current/static/pgcrypto.html#AEN182570)
+* [pgcrypto generator function](https://www.postgresql.org/docs/current/static/pgcrypto.html#id-1.11.7.35.7)
 * [uuid-ossp generator functions](https://www.postgresql.org/docs/current/static/uuid-ossp.html)
 
 NOTE: You need to enable the `pgcrypto` (only PostgreSQL >= 9.4) or `uuid-ossp`
@@ -349,7 +349,7 @@ create_table :users, force: true do |t|
   t.column :settings, "bit(8)"
 end
 
-# app/models/device.rb
+# app/models/user.rb
 class User < ApplicationRecord
 end
 
diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md
index 53cacfa6ea..944cee8a23 100644
--- a/guides/source/active_record_querying.md
+++ b/guides/source/active_record_querying.md
@@ -414,7 +414,7 @@ end
 `find_in_batches` works on model classes, as seen above, and also on relations:
 
 ```ruby
-Invoice.pending.find_in_batches do |invoice|
+Invoice.pending.find_in_batches do |invoices|
   pending_invoices_export.add_invoices(invoices)
 end
 ```
@@ -486,7 +486,7 @@ This makes for clearer readability if you have a large number of variable condit
 
 Active Record also allows you to pass in hash conditions which can increase the readability of your conditions syntax. With hash conditions, you pass in a hash with keys of the fields you want qualified and the values of how you want to qualify them:
 
-NOTE: Only equality, range and subset checking are possible with Hash conditions.
+NOTE: Only equality, range, and subset checking are possible with Hash conditions.
 
 #### Equality Conditions
 
@@ -801,7 +801,7 @@ The SQL that would be executed:
 SELECT * FROM articles WHERE id > 10 ORDER BY id DESC
 
 # Original query without `only`
-SELECT "articles".* FROM "articles" WHERE (id > 10) ORDER BY id desc LIMIT 20
+SELECT * FROM articles WHERE id > 10 ORDER BY id DESC LIMIT 20
 
 ```
 
@@ -820,14 +820,14 @@ Article.find(10).comments.reorder('name')
 The SQL that would be executed:
 
 ```sql
-SELECT * FROM articles WHERE id = 10
+SELECT * FROM articles WHERE id = 10 LIMIT 1
 SELECT * FROM comments WHERE article_id = 10 ORDER BY name
 ```
 
 In the case where the `reorder` clause is not used, the SQL executed would be:
 
 ```sql
-SELECT * FROM articles WHERE id = 10
+SELECT * FROM articles WHERE id = 10 LIMIT 1
 SELECT * FROM comments WHERE article_id = 10 ORDER BY posted_at DESC
 ```
 
@@ -1091,7 +1091,7 @@ This produces:
 
 ```sql
 SELECT articles.* FROM articles
-  INNER JOIN categories ON articles.category_id = categories.id
+  INNER JOIN categories ON categories.id = articles.category_id
   INNER JOIN comments ON comments.article_id = articles.id
 ```
 
@@ -1393,7 +1393,7 @@ end
 ```
 
 NOTE: The `default_scope` is also applied while creating/building a record
-when the scope arguments are given as a `Hash`. It is not applied while 
+when the scope arguments are given as a `Hash`. It is not applied while
 updating a record. E.g.:
 
 ```ruby
@@ -1712,10 +1712,10 @@ Client.find_by_sql("SELECT * FROM clients
 
 ### `select_all`
 
-`find_by_sql` has a close relative called `connection#select_all`. `select_all` will retrieve objects from the database using custom SQL just like `find_by_sql` but will not instantiate them. Instead, you will get an array of hashes where each hash indicates a record.
+`find_by_sql` has a close relative called `connection#select_all`. `select_all` will retrieve objects from the database using custom SQL just like `find_by_sql` but will not instantiate them. This method will return an instance of `ActiveRecord::Result` class and calling `to_hash` on this object would return you an array of hashes where each hash indicates a record.
 
 ```ruby
-Client.connection.select_all("SELECT first_name, created_at FROM clients WHERE id = '1'")
+Client.connection.select_all("SELECT first_name, created_at FROM clients WHERE id = '1'").to_hash
 # => [
 #   {"first_name"=>"Rafael", "created_at"=>"2012-11-10 23:23:45.281189"},
 #   {"first_name"=>"Eileen", "created_at"=>"2013-12-09 11:22:35.221282"}
@@ -1871,14 +1871,14 @@ All calculation methods work directly on a model:
 
 ```ruby
 Client.count
-# SELECT count(*) AS count_all FROM clients
+# SELECT COUNT(*) FROM clients
 ```
 
 Or on a relation:
 
 ```ruby
 Client.where(first_name: 'Ryan').count
-# SELECT count(*) AS count_all FROM clients WHERE (first_name = 'Ryan')
+# SELECT COUNT(*) FROM clients WHERE (first_name = 'Ryan')
 ```
 
 You can also use various finder methods on a relation for performing complex calculations:
@@ -1890,9 +1890,9 @@ Client.includes("orders").where(first_name: 'Ryan', orders: { status: 'received'
 Which will execute:
 
 ```sql
-SELECT count(DISTINCT clients.id) AS count_all FROM clients
-  LEFT OUTER JOIN orders ON orders.client_id = clients.id WHERE
-  (clients.first_name = 'Ryan' AND orders.status = 'received')
+SELECT COUNT(DISTINCT clients.id) FROM clients
+  LEFT OUTER JOIN orders ON orders.client_id = clients.id
+  WHERE (clients.first_name = 'Ryan' AND orders.status = 'received')
 ```
 
 ### Count
diff --git a/guides/source/active_record_validations.md b/guides/source/active_record_validations.md
index e9157f3db1..c7846a0283 100644
--- a/guides/source/active_record_validations.md
+++ b/guides/source/active_record_validations.md
@@ -745,7 +745,7 @@ class Person < ApplicationRecord
 end
 ```
 
-The block receives the record, the attribute's name and the attribute's value.
+The block receives the record, the attribute's name, and the attribute's value.
 You can do anything you like to check for valid data within the block. If your
 validation fails, you should add an error message to the model, therefore
 making it invalid.
@@ -953,7 +953,7 @@ should happen, an `Array` can be used. Moreover, you can apply both `:if` and
 ```ruby
 class Computer < ApplicationRecord
   validates :mouse, presence: true,
-                    if: [Proc.new  { |c| c.market.retail? }, :desktop?],
+                    if: [Proc.new { |c| c.market.retail? }, :desktop?],
                     unless: Proc.new { |c| c.trackpad.present? }
 end
 ```
diff --git a/guides/source/active_storage_overview.md b/guides/source/active_storage_overview.md
new file mode 100644
index 0000000000..91ad089d40
--- /dev/null
+++ b/guides/source/active_storage_overview.md
@@ -0,0 +1,748 @@
+**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.**
+
+Active Storage Overview
+=======================
+
+This guide covers how to attach files to your Active Record models.
+
+After reading this guide, you will know:
+
+* How to attach one or many files to a record.
+* How to delete an attached file.
+* How to link to an attached file.
+* How to use variants to transform images.
+* How to generate an image representation of a non-image file, such as a PDF or a video.
+* How to send file uploads directly from browsers to a storage service,
+  bypassing your application servers.
+* How to clean up files stored during testing.
+* How to implement support for additional storage services.
+
+--------------------------------------------------------------------------------
+
+What is Active Storage?
+-----------------------
+
+Active Storage facilitates uploading files to a cloud storage service like
+Amazon S3, Google Cloud Storage, or Microsoft Azure Storage and attaching those
+files to Active Record objects. It comes with a local disk-based service for
+development and testing and supports mirroring files to subordinate services for
+backups and migrations.
+
+Using Active Storage, an application can transform image uploads with
+[ImageMagick](https://www.imagemagick.org), generate image representations of
+non-image uploads like PDFs and videos, and extract metadata from arbitrary
+files.
+
+## Setup
+
+Active Storage uses two tables in your application’s database named
+`active_storage_blobs` and `active_storage_attachments`. After upgrading your
+application to Rails 5.2, run `rails active_storage:install` to generate a
+migration that creates these tables. Use `rails db:migrate` to run the
+migration.
+
+Declare Active Storage services in `config/storage.yml`. For each service your
+application uses, provide a name and the requisite configuration. The example
+below declares three services named `local`, `test`, and `amazon`:
+
+```yaml
+local:
+  service: Disk
+  root: <%= Rails.root.join("storage") %>
+
+test:
+  service: Disk
+  root: <%= Rails.root.join("tmp/storage") %>
+
+amazon:
+  service: S3
+  access_key_id: ""
+  secret_access_key: ""
+```
+
+Tell Active Storage which service to use by setting
+`Rails.application.config.active_storage.service`. Because each environment will
+likely use a different service, it is recommended to do this on a
+per-environment basis. To use the disk service from the previous example in the
+development environment, you would add the following to
+`config/environments/development.rb`:
+
+```ruby
+# Store files locally.
+config.active_storage.service = :local
+```
+
+To use the Amazon S3 service in production, you add the following to
+`config/environments/production.rb`:
+
+```ruby
+# Store files on Amazon S3.
+config.active_storage.service = :amazon
+```
+
+Continue reading for more information on the built-in service adapters (e.g.
+`Disk` and `S3`) and the configuration they require.
+
+### Disk Service
+
+Declare a Disk service in `config/storage.yml`:
+
+```yaml
+local:
+  service: Disk
+  root: <%= Rails.root.join("storage") %>
+```
+
+### Amazon S3 Service
+
+Declare an S3 service in `config/storage.yml`:
+
+```yaml
+amazon:
+  service: S3
+  access_key_id: ""
+  secret_access_key: ""
+  region: ""
+  bucket: ""
+```
+
+Add the [`aws-sdk-s3`](https://github.com/aws/aws-sdk-ruby) gem to your `Gemfile`:
+
+```ruby
+gem "aws-sdk-s3", require: false
+```
+
+NOTE: The core features of Active Storage require the following permissions: `s3:ListBucket`, `s3:PutObject`, `s3:GetObject`, and `s3:DeleteObject`. If you have additional upload options configured such as setting ACLs then additional permissions may be required.
+
+NOTE: If you want to use environment variables, standard SDK configuration files, profiles,
+IAM instance profiles or task roles, you can omit the `access_key_id`, `secret_access_key`,
+and `region` keys in the example above. The Amazon S3 Service supports all of the
+authentication options described in the [AWS SDK documentation]
+(https://docs.aws.amazon.com/sdk-for-ruby/v3/developer-guide/setup-config.html).
+
+
+### Microsoft Azure Storage Service
+
+Declare an Azure Storage service in `config/storage.yml`:
+
+```yaml
+azure:
+  service: AzureStorage
+  storage_account_name: ""
+  storage_access_key: ""
+  container: ""
+```
+
+Add the [`azure-storage`](https://github.com/Azure/azure-storage-ruby) gem to your `Gemfile`:
+
+```ruby
+gem "azure-storage", require: false
+```
+
+### Google Cloud Storage Service
+
+Declare a Google Cloud Storage service in `config/storage.yml`:
+
+```yaml
+google:
+  service: GCS
+  credentials: <%= Rails.root.join("path/to/keyfile.json") %>
+  project: ""
+  bucket: ""
+```
+
+Optionally provide a Hash of credentials instead of a keyfile path:
+
+```yaml
+google:
+  service: GCS
+  credentials:
+    type: "service_account"
+    project_id: ""
+    private_key_id: <%= Rails.application.credentials.dig(:gcs, :private_key_id) %>
+    private_key: <%= Rails.application.credentials.dig(:gcs, :private_key) %>
+    client_email: ""
+    client_id: ""
+    auth_uri: "https://accounts.google.com/o/oauth2/auth"
+    token_uri: "https://accounts.google.com/o/oauth2/token"
+    auth_provider_x509_cert_url: "https://www.googleapis.com/oauth2/v1/certs"
+    client_x509_cert_url: ""
+  project: ""
+  bucket: ""
+```
+
+Add the [`google-cloud-storage`](https://github.com/GoogleCloudPlatform/google-cloud-ruby/tree/master/google-cloud-storage) gem to your `Gemfile`:
+
+```ruby
+gem "google-cloud-storage", "~> 1.8", require: false
+```
+
+### Mirror Service
+
+You can keep multiple services in sync by defining a mirror service. When a file
+is uploaded or deleted, it's done across all the mirrored services. Mirrored
+services can be used to facilitate a migration between services in production.
+You can start mirroring to the new service, copy existing files from the old
+service to the new, then go all-in on the new service. Define each of the
+services you'd like to use as described above and reference them from a mirrored
+service.
+
+```yaml
+s3_west_coast:
+  service: S3
+  access_key_id: ""
+  secret_access_key: ""
+  region: ""
+  bucket: ""
+
+s3_east_coast:
+  service: S3
+  access_key_id: ""
+  secret_access_key: ""
+  region: ""
+  bucket: ""
+
+production:
+  service: Mirror
+  primary: s3_east_coast
+  mirrors:
+    - s3_west_coast
+```
+
+NOTE: Files are served from the primary service.
+
+Attaching Files to Records
+--------------------------
+
+### `has_one_attached`
+
+The `has_one_attached` macro sets up a one-to-one mapping between records and
+files. Each record can have one file attached to it.
+
+For example, suppose your application has a `User` model. If you want each user to
+have an avatar, define the `User` model like this:
+
+```ruby
+class User < ApplicationRecord
+  has_one_attached :avatar
+end
+```
+
+You can create a user with an avatar:
+
+```ruby
+class SignupController < ApplicationController
+  def create
+    user = User.create!(user_params)
+    session[:user_id] = user.id
+    redirect_to root_path
+  end
+
+  private
+    def user_params
+      params.require(:user).permit(:email_address, :password, :avatar)
+    end
+end
+```
+
+Call `avatar.attach` to attach an avatar to an existing user:
+
+```ruby
+Current.user.avatar.attach(params[:avatar])
+```
+
+Call `avatar.attached?` to determine whether a particular user has an avatar:
+
+```ruby
+Current.user.avatar.attached?
+```
+
+### `has_many_attached`
+
+The `has_many_attached` macro sets up a one-to-many relationship between records
+and files. Each record can have many files attached to it.
+
+For example, suppose your application has a `Message` model. If you want each
+message to have many images, define the `Message` model like this:
+
+```ruby
+class Message < ApplicationRecord
+  has_many_attached :images
+end
+```
+
+You can create a message with images:
+
+```ruby
+class MessagesController < ApplicationController
+  def create
+    message = Message.create!(message_params)
+    redirect_to message
+  end
+
+  private
+    def message_params
+      params.require(:message).permit(:title, :content, images: [])
+    end
+end
+```
+
+Call `images.attach` to add new images to an existing message:
+
+```ruby
+@message.images.attach(params[:images])
+```
+
+Call `images.attached?` to determine whether a particular message has any images:
+
+```ruby
+@message.images.attached?
+```
+
+### Attaching File/IO Objects
+
+Sometimes you need to attach a file that doesn’t arrive via an HTTP request.
+For example, you may want to attach a file you generated on disk or downloaded
+from a user-submitted URL. You may also want to attach a fixture file in a
+model test. To do that, provide a Hash containing at least an open IO object
+and a filename:
+
+```ruby
+@message.image.attach(io: File.open('/path/to/file'), filename: 'file.pdf')
+```
+
+When possible, provide a content type as well. Active Storage attempts to
+determine a file’s content type from its data. It falls back to the content
+type you provide if it can’t do that.
+
+```ruby
+@message.image.attach(io: File.open('/path/to/file'), filename: 'file.pdf', content_type: 'application/pdf')
+```
+
+You can bypass the content type inference from the data by passing in
+`identify: false` along with the `content_type`.
+
+```ruby
+@message.image.attach(
+  io: File.open('/path/to/file'),
+  filename: 'file.pdf',
+  content_type: 'application/pdf'
+  identify: false
+)
+```
+
+If you don’t provide a content type and Active Storage can’t determine the
+file’s content type automatically, it defaults to application/octet-stream.
+
+
+Removing Files
+--------------
+
+To remove an attachment from a model, call `purge` on the attachment. Removal
+can be done in the background if your application is setup to use Active Job.
+Purging deletes the blob and the file from the storage service.
+
+```ruby
+# Synchronously destroy the avatar and actual resource files.
+user.avatar.purge
+
+# Destroy the associated models and actual resource files async, via Active Job.
+user.avatar.purge_later
+```
+
+Linking to Files
+----------------
+
+Generate a permanent URL for the blob that points to the application. Upon
+access, a redirect to the actual service endpoint is returned. This indirection
+decouples the public URL from the actual one, and allows, for example, mirroring
+attachments in different services for high-availability. The redirection has an
+HTTP expiration of 5 min.
+
+```ruby
+url_for(user.avatar)
+```
+
+To create a download link, use the `rails_blob_{path|url}` helper. Using this
+helper allows you to set the disposition.
+
+```ruby
+rails_blob_path(user.avatar, disposition: "attachment")
+```
+
+If you need to create a link from outside of controller/view context (Background
+jobs, Cronjobs, etc.), you can access the rails_blob_path like this:
+
+```
+Rails.application.routes.url_helpers.rails_blob_path(user.avatar, only_path: true)
+```
+
+Downloading Files
+-----------------
+
+Sometimes you need to process a blob after it’s uploaded—for example, to convert
+it to a different format. Use `ActiveStorage::Blob#download` to read a blob’s
+binary data into memory:
+
+```ruby
+binary = user.avatar.download
+```
+
+You might want to download a blob to a file on disk so an external program (e.g.
+a virus scanner or media transcoder) can operate on it. Use
+`ActiveStorage::Blob#open` to download a blob to a tempfile on disk:
+
+```ruby
+message.video.open do |file|
+  system '/path/to/virus/scanner', file.path
+  # ...
+end
+```
+
+Transforming Images
+-------------------
+
+To create a variation of the image, call `variant` on the `Blob`. You can pass
+any transformation to the method supported by the processor. The default
+processor is [MiniMagick](https://github.com/minimagick/minimagick), but you
+can also use [Vips](http://www.rubydoc.info/gems/ruby-vips/Vips/Image).
+
+To enable variants, add the `image_processing` gem to your `Gemfile`:
+
+```ruby
+gem 'image_processing', '~> 1.2'
+```
+
+When the browser hits the variant URL, Active Storage will lazily transform the
+original blob into the specified format and redirect to its new service
+location.
+
+```erb
+<%= image_tag user.avatar.variant(resize_to_fit: [100, 100]) %>
+```
+
+To switch to the Vips processor, you would add the following to
+`config/application.rb`:
+
+```ruby
+# Use Vips for processing variants.
+config.active_storage.variant_processor = :vips
+```
+
+Previewing Files
+----------------
+
+Some non-image files can be previewed: that is, they can be presented as images.
+For example, a video file can be previewed by extracting its first frame. Out of
+the box, Active Storage supports previewing videos and PDF documents.
+
+```erb
+<ul>
+  <% @message.files.each do |file| %>
+    <li>
+      <%= image_tag file.preview(resize_to_limit: [100, 100]) %>
+    </li>
+  <% end %>
+</ul>
+```
+
+WARNING: Extracting previews requires third-party applications, `ffmpeg` for
+video and `mutool` for PDFs. These libraries are not provided by Rails. You must
+install them yourself to use the built-in previewers. Before you install and use
+third-party software, make sure you understand the licensing implications of
+doing so.
+
+Direct Uploads
+--------------
+
+Active Storage, with its included JavaScript library, supports uploading
+directly from the client to the cloud.
+
+### Direct upload installation
+
+1. Include `activestorage.js` in your application's JavaScript bundle.
+
+    Using the asset pipeline:
+
+    ```js
+    //= require activestorage
+
+    ```
+
+    Using the npm package:
+
+    ```js
+    import * as ActiveStorage from "activestorage"
+    ActiveStorage.start()
+    ```
+
+2. Annotate file inputs with the direct upload URL.
+
+    ```ruby
+    <%= form.file_field :attachments, multiple: true, direct_upload: true %>
+    ```
+3. That's it! Uploads begin upon form submission.
+
+### Direct upload JavaScript events
+
+| Event name | Event target | Event data (`event.detail`) | Description |
+| --- | --- | --- | --- |
+| `direct-uploads:start` | `<form>` | None | A form containing files for direct upload fields was submitted. |
+| `direct-upload:initialize` | `<input>` | `{id, file}` | Dispatched for every file after form submission. |
+| `direct-upload:start` | `<input>` | `{id, file}` | A direct upload is starting. |
+| `direct-upload:before-blob-request` | `<input>` | `{id, file, xhr}` | Before making a request to your application for direct upload metadata. |
+| `direct-upload:before-storage-request` | `<input>` | `{id, file, xhr}` | Before making a request to store a file. |
+| `direct-upload:progress` | `<input>` | `{id, file, progress}` | As requests to store files progress. |
+| `direct-upload:error` | `<input>` | `{id, file, error}` | An error occurred. An `alert` will display unless this event is canceled. |
+| `direct-upload:end` | `<input>` | `{id, file}` | A direct upload has ended. |
+| `direct-uploads:end` | `<form>` | None | All direct uploads have ended. |
+
+### Example
+
+You can use these events to show the progress of an upload.
+
+![direct-uploads](https://user-images.githubusercontent.com/5355/28694528-16e69d0c-72f8-11e7-91a7-c0b8cfc90391.gif)
+
+To show the uploaded files in a form:
+
+```js
+// direct_uploads.js
+
+addEventListener("direct-upload:initialize", event => {
+  const { target, detail } = event
+  const { id, file } = detail
+  target.insertAdjacentHTML("beforebegin", `
+    <div id="direct-upload-${id}" class="direct-upload direct-upload--pending">
+      <div id="direct-upload-progress-${id}" class="direct-upload__progress" style="width: 0%"></div>
+      <span class="direct-upload__filename">${file.name}</span>
+    </div>
+  `)
+})
+
+addEventListener("direct-upload:start", event => {
+  const { id } = event.detail
+  const element = document.getElementById(`direct-upload-${id}`)
+  element.classList.remove("direct-upload--pending")
+})
+
+addEventListener("direct-upload:progress", event => {
+  const { id, progress } = event.detail
+  const progressElement = document.getElementById(`direct-upload-progress-${id}`)
+  progressElement.style.width = `${progress}%`
+})
+
+addEventListener("direct-upload:error", event => {
+  event.preventDefault()
+  const { id, error } = event.detail
+  const element = document.getElementById(`direct-upload-${id}`)
+  element.classList.add("direct-upload--error")
+  element.setAttribute("title", error)
+})
+
+addEventListener("direct-upload:end", event => {
+  const { id } = event.detail
+  const element = document.getElementById(`direct-upload-${id}`)
+  element.classList.add("direct-upload--complete")
+})
+```
+
+Add styles:
+
+```css
+/* direct_uploads.css */
+
+.direct-upload {
+  display: inline-block;
+  position: relative;
+  padding: 2px 4px;
+  margin: 0 3px 3px 0;
+  border: 1px solid rgba(0, 0, 0, 0.3);
+  border-radius: 3px;
+  font-size: 11px;
+  line-height: 13px;
+}
+
+.direct-upload--pending {
+  opacity: 0.6;
+}
+
+.direct-upload__progress {
+  position: absolute;
+  top: 0;
+  left: 0;
+  bottom: 0;
+  opacity: 0.2;
+  background: #0076ff;
+  transition: width 120ms ease-out, opacity 60ms 60ms ease-in;
+  transform: translate3d(0, 0, 0);
+}
+
+.direct-upload--complete .direct-upload__progress {
+  opacity: 0.4;
+}
+
+.direct-upload--error {
+  border-color: red;
+}
+
+input[type=file][data-direct-upload-url][disabled] {
+  display: none;
+}
+```
+
+### Integrating with Libraries or Frameworks
+
+If you want to use the Direct Upload feature from a JavaScript framework, or
+you want to integrate custom drag and drop solutions, you can use the
+`DirectUpload` class for this purpose. Upon receiving a file from your library
+of choice, instantiate a DirectUpload and call its create method. Create takes
+a callback to invoke when the upload completes.
+
+```js
+import { DirectUpload } from "activestorage"
+
+const input = document.querySelector('input[type=file]')
+
+// Bind to file drop - use the ondrop on a parent element or use a
+//  library like Dropzone
+const onDrop = (event) => {
+  event.preventDefault()
+  const files = event.dataTransfer.files;
+  Array.from(files).forEach(file => uploadFile(file))
+}
+
+// Bind to normal file selection
+input.addEventListener('change', (event) => {
+  Array.from(input.files).forEach(file => uploadFile(file))
+  // you might clear the selected files from the input
+  input.value = null
+})
+
+const uploadFile = (file) {
+  // your form needs the file_field direct_upload: true, which
+  //  provides data-direct-upload-url
+  const url = input.dataset.directUploadUrl
+  const upload = new DirectUpload(file, url)
+
+  upload.create((error, blob) => {
+    if (error) {
+      // Handle the error
+    } else {
+      // Add an appropriately-named hidden input to the form with a
+      //  value of blob.signed_id so that the blob ids will be
+      //  transmitted in the normal upload flow
+      const hiddenField = document.createElement('input')
+      hiddenField.setAttribute("type", "hidden");
+      hiddenField.setAttribute("value", blob.signed_id);
+      hiddenField.name = input.name
+      document.querySelector('form').appendChild(hiddenField)
+    }
+  })
+}
+```
+
+If you need to track the progress of the file upload, you can pass a third
+parameter to the `DirectUpload` constructor. During the upload, DirectUpload
+will call the object's `directUploadWillStoreFileWithXHR` method. You can then
+bind your own progress handler on the XHR.
+
+```js
+import { DirectUpload } from "activestorage"
+
+class Uploader {
+  constructor(file, url) {
+    this.upload = new DirectUpload(this.file, this.url, this)
+  }
+
+  upload(file) {
+    this.upload.create((error, blob) => {
+      if (error) {
+        // Handle the error
+      } else {
+        // Add an appropriately-named hidden input to the form
+        // with a value of blob.signed_id
+      }
+    })
+  }
+
+  directUploadWillStoreFileWithXHR(request) {
+    request.upload.addEventListener("progress",
+      event => this.directUploadDidProgress(event))
+  }
+
+  directUploadDidProgress(event) {
+    // Use event.loaded and event.total to update the progress bar
+  }
+}
+```
+
+Discarding Files Stored During System Tests
+-------------------------------------------
+
+System tests clean up test data by rolling back a transaction. Because destroy
+is never called on an object, the attached files are never cleaned up. If you
+want to clear the files, you can do it in an `after_teardown` callback. Doing it
+here ensures that all connections created during the test are complete and
+you won't receive an error from Active Storage saying it can't find a file.
+
+```ruby
+class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
+  driven_by :selenium, using: :chrome, screen_size: [1400, 1400]
+
+  def remove_uploaded_files
+    FileUtils.rm_rf("#{Rails.root}/storage_test")
+  end
+
+  def after_teardown
+    super
+    remove_uploaded_files
+  end
+end
+```
+
+If your system tests verify the deletion of a model with attachments and you're
+using Active Job, set your test environment to use the inline queue adapter so
+the purge job is executed immediately rather at an unknown time in the future.
+
+You may also want to use a separate service definition for the test environment
+so your tests don't delete the files you create during development.
+
+```ruby
+# Use inline job processing to make things happen immediately
+config.active_job.queue_adapter = :inline
+
+# Separate file storage in the test environment
+config.active_storage.service = :local_test
+```
+
+Discarding Files Stored During Integration Tests
+-------------------------------------------
+
+Similarly to System Tests, files uploaded during Integration Tests will not be
+automatically cleaned up. If you want to clear the files, you can do it in an
+`after_teardown` callback. Doing it here ensures that all connections created
+during the test are complete and you won't receive an error from Active Storage
+saying it can't find a file.
+
+```ruby
+module ActionDispatch
+  class IntegrationTest
+    def remove_uploaded_files
+      FileUtils.rm_rf(Rails.root.join('tmp', 'storage'))
+    end
+
+    def after_teardown
+      super
+      remove_uploaded_files
+    end
+  end
+end
+```
+
+Implementing Support for Other Cloud Services
+---------------------------------------------
+
+If you need to support a cloud service other than these, you will need to
+implement the Service. Each service extends
+[`ActiveStorage::Service`](https://github.com/rails/rails/blob/master/activestorage/lib/active_storage/service.rb)
+by implementing the methods necessary to upload and download files to the cloud.
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md
index 20d09e65b3..057651e0cf 100644
--- a/guides/source/active_support_core_extensions.md
+++ b/guides/source/active_support_core_extensions.md
@@ -135,16 +135,14 @@ NOTE: Defined in `active_support/core_ext/object/blank.rb`.
 
 ### `duplicable?`
 
-In Ruby 2.4 most objects can be duplicated via `dup` or `clone` except 
-methods and certain numbers. Though Ruby 2.2 and 2.3 can't duplicate `nil`,
-`false`, `true`, and  symbols as well as instances `Float`, `Fixnum`, 
-and `Bignum` instances.
+As of Ruby 2.5, most objects can be duplicated via `dup` or `clone`:
 
 ```ruby
 "foo".dup           # => "foo"
 "".dup              # => ""
-1.method(:+).dup    # => TypeError: allocator undefined for Method
-Complex(0).dup      # => TypeError: can't copy Complex
+Rational(1).dup     # => (1/1)
+Complex(0).dup      # => (0+0i)
+1.method(:+).dup    # => TypeError (allocator undefined for Method)
 ```
 
 Active Support provides `duplicable?` to query an object about this:
@@ -152,35 +150,18 @@ Active Support provides `duplicable?` to query an object about this:
 ```ruby
 "foo".duplicable?           # => true
 "".duplicable?              # => true
-Rational(1).duplicable?     # => false
-Complex(1).duplicable?      # => false
+Rational(1).duplicable?     # => true
+Complex(1).duplicable?      # => true
 1.method(:+).duplicable?    # => false
 ```
 
-`duplicable?` matches Ruby's `dup` according to the Ruby version.
-
-So in 2.4:
+`duplicable?` matches the current Ruby version's `dup` behavior,
+so results will vary according the version of Ruby you're using.
+In Ruby 2.4, for example, Complex and Rational are not duplicable:
 
 ```ruby
-nil.dup                 # => nil
-:my_symbol.dup          # => :my_symbol
-1.dup                   # => 1
-
-nil.duplicable?         # => true
-:my_symbol.duplicable?  # => true
-1.duplicable?           # => true
-```
-
-Whereas in 2.2 and 2.3:
-
-```ruby
-nil.dup                 # => TypeError: can't dup NilClass
-:my_symbol.dup          # => TypeError: can't dup Symbol
-1.dup                   # => TypeError: can't dup Fixnum
-
-nil.duplicable?         # => false
-:my_symbol.duplicable?  # => false
-1.duplicable?           # => false
+Rational(1).duplicable?     # => false
+Complex(1).duplicable?      # => false
 ```
 
 WARNING: Any class can disallow duplication by removing `dup` and `clone` or raising exceptions from them. Thus only `rescue` can tell whether a given arbitrary object is duplicable. `duplicable?` depends on the hard-coded list above, but it is much faster than `rescue`. Use it only if you know the hard-coded list is enough in your use case.
@@ -634,7 +615,7 @@ NOTE: Defined in `active_support/core_ext/module/introspection.rb`.
 
 #### `parent_name`
 
-The `parent_name` method on a nested named module returns the fully-qualified name of the module that contains its corresponding constant:
+The `parent_name` method on a nested named module returns the fully qualified name of the module that contains its corresponding constant:
 
 ```ruby
 module X
@@ -674,44 +655,6 @@ M.parents       # => [X::Y, X, Object]
 
 NOTE: Defined in `active_support/core_ext/module/introspection.rb`.
 
-### Reachable
-
-A named module is reachable if it is stored in its corresponding constant. It means you can reach the module object via the constant.
-
-That is what ordinarily happens, if a module is called "M", the `M` constant exists and holds it:
-
-```ruby
-module M
-end
-
-M.reachable? # => true
-```
-
-But since constants and modules are indeed kind of decoupled, module objects can become unreachable:
-
-```ruby
-module M
-end
-
-orphan = Object.send(:remove_const, :M)
-
-# The module object is orphan now but it still has a name.
-orphan.name # => "M"
-
-# You cannot reach it via the constant M because it does not even exist.
-orphan.reachable? # => false
-
-# Let's define a module called "M" again.
-module M
-end
-
-# The constant M exists now again, and it stores a module
-# object called "M", but it is a new instance.
-orphan.reachable? # => false
-```
-
-NOTE: Defined in `active_support/core_ext/module/reachable.rb`.
-
 ### Anonymous
 
 A module may or may not have a name:
@@ -745,7 +688,6 @@ end
 
 m = Object.send(:remove_const, :M)
 
-m.reachable? # => false
 m.anonymous? # => false
 ```
 
@@ -837,6 +779,14 @@ delegate :size, to: :attachment, prefix: :avatar
 
 In the previous example the macro generates `avatar_size` rather than `size`.
 
+The option `:private` changes methods scope:
+
+```ruby
+delegate :date_of_birth, to: :profile, private: true
+```
+
+The delegated methods are public by default. Pass `private: true` to change that.
+
 NOTE: Defined in `active_support/core_ext/module/delegation.rb`
 
 #### `delegate_missing_to`
@@ -864,7 +814,11 @@ There are cases where you need to define a method with `define_method`, but don'
 
 The method `redefine_method` prevents such a potential warning, removing the existing method before if needed.
 
-NOTE: Defined in `active_support/core_ext/module/remove_method.rb`.
+You can also use `silence_redefinition_of_method` if you need to define
+the replacement method yourself (because you're using `delegate`, for
+example).
+
+NOTE: Defined in `active_support/core_ext/module/redefine_method.rb`.
 
 Extensions to `Class`
 ---------------------
@@ -960,6 +914,15 @@ The macros `cattr_reader`, `cattr_writer`, and `cattr_accessor` are analogous to
 ```ruby
 class MysqlAdapter < AbstractAdapter
   # Generates class methods to access @@emulate_booleans.
+  cattr_accessor :emulate_booleans
+end
+```
+
+Also, you can pass a block to `cattr_*` to set up the attribute with a default value:
+
+```ruby
+class MysqlAdapter < AbstractAdapter
+  # Generates class methods to access @@emulate_booleans with default value of true.
   cattr_accessor :emulate_booleans, default: true
 end
 ```
@@ -976,15 +939,6 @@ end
 
 we can access `field_error_proc` in views.
 
-Also, you can pass a block to `cattr_*` to set up the attribute with a default value:
-
-```ruby
-class MysqlAdapter < AbstractAdapter
-  # Generates class methods to access @@emulate_booleans with default value of true.
-  cattr_accessor :emulate_booleans, default: true
-end
-```
-
 The generation of the reader instance method can be prevented by setting `:instance_reader` to `false` and the generation of the writer instance method can be prevented by setting `:instance_writer` to `false`. Generation of both methods can be prevented by setting `:instance_accessor` to `false`. In all cases, the value must be exactly `false` and not any false value.
 
 ```ruby
@@ -1787,7 +1741,7 @@ The methods `to_date`, `to_time`, and `to_datetime` are basically convenience wr
 "2010-07-27 23:42:00".to_time(:local) # => 2010-07-27 23:42:00 +0200
 ```
 
-Default is `:utc`.
+Default is `:local`.
 
 Please refer to the documentation of `Date._parse` for further details.
 
@@ -1831,7 +1785,7 @@ NOTE: Defined in `active_support/core_ext/numeric/bytes.rb`.
 
 ### Time
 
-Enables the use of time calculations and declarations, like `45.minutes + 2.hours + 4.years`.
+Enables the use of time calculations and declarations, like `45.minutes + 2.hours + 4.weeks`.
 
 These methods use Time#advance for precise date calculations when using from_now, ago, etc.
 as well as adding or subtracting their results from a Time object. For example:
@@ -1840,13 +1794,15 @@ as well as adding or subtracting their results from a Time object. For example:
 # equivalent to Time.current.advance(months: 1)
 1.month.from_now
 
-# equivalent to Time.current.advance(years: 2)
-2.years.from_now
+# equivalent to Time.current.advance(weeks: 2)
+2.weeks.from_now
 
-# equivalent to Time.current.advance(months: 4, years: 5)
-(4.months + 5.years).from_now
+# equivalent to Time.current.advance(months: 4, weeks: 5)
+(4.months + 5.weeks).from_now
 ```
 
+WARNING. For other durations please refer to the time extensions to `Integer`.
+
 NOTE: Defined in `active_support/core_ext/numeric/time.rb`.
 
 ### Formatting
@@ -1982,6 +1938,28 @@ The method `ordinalize` returns the ordinal string corresponding to the receiver
 
 NOTE: Defined in `active_support/core_ext/integer/inflections.rb`.
 
+### Time
+
+Enables the use of time calculations and declarations, like `4.months + 5.years`.
+
+These methods use Time#advance for precise date calculations when using from_now, ago, etc.
+as well as adding or subtracting their results from a Time object. For example:
+
+```ruby
+# equivalent to Time.current.advance(months: 1)
+1.month.from_now
+
+# equivalent to Time.current.advance(years: 2)
+2.years.from_now
+
+# equivalent to Time.current.advance(months: 4, years: 5)
+(4.months + 5.years).from_now
+```
+
+WARNING. For other durations please refer to the time extensions to `Numeric`.
+
+NOTE: Defined in `active_support/core_ext/integer/time.rb`.
+
 Extensions to `BigDecimal`
 --------------------------
 ### `to_s`
@@ -1989,19 +1967,19 @@ Extensions to `BigDecimal`
 The method `to_s` provides a default specifier of "F". This means that a simple call to `to_s` will result in floating point representation instead of engineering notation:
 
 ```ruby
-BigDecimal.new(5.00, 6).to_s       # => "5.0"
+BigDecimal(5.00, 6).to_s       # => "5.0"
 ```
 
 and that symbol specifiers are also supported:
 
 ```ruby
-BigDecimal.new(5.00, 6).to_s(:db)  # => "5.0"
+BigDecimal(5.00, 6).to_s(:db)  # => "5.0"
 ```
 
 Engineering notation is still supported:
 
 ```ruby
-BigDecimal.new(5.00, 6).to_s("e")  # => "0.5E1"
+BigDecimal(5.00, 6).to_s("e")  # => "0.5E1"
 ```
 
 Extensions to `Enumerable`
@@ -2061,6 +2039,21 @@ WARNING. Keys should normally be unique. If the block returns the same value for
 
 NOTE: Defined in `active_support/core_ext/enumerable.rb`.
 
+### `index_with`
+
+The method `index_with` generates a hash with the elements of an enumerable as keys. The value
+is either a passed default or returned in a block.
+
+```ruby
+%i( title body created_at ).index_with { |attr_name| public_send(attr_name) }
+# => { title: "hey", body: "what's up?", … }
+
+WEEKDAYS.index_with([ Interval.all_day ])
+# => { monday: [ 0, 1440 ], … }
+```
+
+NOTE: Defined in `active_support/core_ext/enumerable.rb`.
+
 ### `many?`
 
 The method `many?` is shorthand for `collection.size > 1`:
@@ -2787,20 +2780,6 @@ Active Record does not accept unknown options when building associations, for ex
 
 NOTE: Defined in `active_support/core_ext/hash/keys.rb`.
 
-### Working with Values
-
-#### `transform_values` && `transform_values!`
-
-The method `transform_values` accepts a block and returns a hash that has applied the block operations to each of the values in the receiver.
-
-```ruby
-{ nil => nil, 1 => 1, :x => :a }.transform_values { |value| value.to_s.upcase }
-# => {nil=>"", 1=>"1", :x=>"A"}
-```
-There's also the bang variant `transform_values!` that applies the block operations to values in the very receiver.
-
-NOTE: Defined in `active_support/core_ext/hash/transform_values.rb`.
-
 ### Slicing
 
 Ruby has built-in support for taking slices out of strings and arrays. Active Support extends slicing to hashes:
@@ -2862,16 +2841,6 @@ The method `with_indifferent_access` returns an `ActiveSupport::HashWithIndiffer
 
 NOTE: Defined in `active_support/core_ext/hash/indifferent_access.rb`.
 
-### Compacting
-
-The methods `compact` and `compact!` return a Hash without items with `nil` value.
-
-```ruby
-{a: 1, b: 2, c: nil}.compact # => {a: 1, b: 2}
-```
-
-NOTE: Defined in `active_support/core_ext/hash/compact.rb`.
-
 Extensions to `Regexp`
 ----------------------
 
@@ -2901,24 +2870,6 @@ end
 
 NOTE: Defined in `active_support/core_ext/regexp.rb`.
 
-### `match?`
-
-Rails implements `Regexp#match?` for Ruby versions prior to 2.4:
-
-```ruby
-/oo/.match?('foo')    # => true
-/oo/.match?('bar')    # => false
-/oo/.match?('foo', 1) # => true
-```
-
-The backport has the same interface and lack of side-effects in the caller like
-not setting `$1` and friends, but it does not have the speed benefits. Its
-purpose is to be able to write 2.4 compatible code. Rails itself uses this
-predicate internally for example.
-
-Active Support defines `Regexp#match?` only if not present, so code running
-under 2.4 or later does run the original one and gets the performance boost.
-
 Extensions to `Range`
 ---------------------
 
@@ -2938,9 +2889,9 @@ As the example depicts, the `:db` format generates a `BETWEEN` SQL clause. That
 
 NOTE: Defined in `active_support/core_ext/range/conversions.rb`.
 
-### `include?`
+### `===`, `include?`, and `cover?`
 
-The methods `Range#include?` and `Range#===` say whether some value falls between the ends of a given instance:
+The methods `Range#===`, `Range#include?`, and `Range#cover?` say whether some value falls between the ends of a given instance:
 
 ```ruby
 (2..3).include?(Math::E) # => true
@@ -2949,18 +2900,23 @@ The methods `Range#include?` and `Range#===` say whether some value falls betwee
 Active Support extends these methods so that the argument may be another range in turn. In that case we test whether the ends of the argument range belong to the receiver themselves:
 
 ```ruby
+(1..10) === (3..7)  # => true
+(1..10) === (0..7)  # => false
+(1..10) === (3..11) # => false
+(1...9) === (3..9)  # => false
+
 (1..10).include?(3..7)  # => true
 (1..10).include?(0..7)  # => false
 (1..10).include?(3..11) # => false
 (1...9).include?(3..9)  # => false
 
-(1..10) === (3..7)  # => true
-(1..10) === (0..7)  # => false
-(1..10) === (3..11) # => false
-(1...9) === (3..9)  # => false
+(1..10).cover?(3..7)  # => true
+(1..10).cover?(0..7)  # => false
+(1..10).cover?(3..11) # => false
+(1...9).cover?(3..9)  # => false
 ```
 
-NOTE: Defined in `active_support/core_ext/range/include_range.rb`.
+NOTE: Defined in `active_support/core_ext/range/compare_range.rb`.
 
 ### `overlaps?`
 
@@ -2981,6 +2937,32 @@ Extensions to `Date`
 
 NOTE: All the following methods are defined in `active_support/core_ext/date/calculations.rb`.
 
+```ruby
+yesterday
+tomorrow
+beginning_of_week (at_beginning_of_week)
+end_of_week (at_end_of_week)
+monday
+sunday
+weeks_ago
+prev_week (last_week)
+next_week
+months_ago
+months_since
+beginning_of_month (at_beginning_of_month)
+end_of_month (at_end_of_month)
+last_month
+beginning_of_quarter (at_beginning_of_quarter)
+end_of_quarter (at_end_of_quarter)
+beginning_of_year (at_beginning_of_year)
+end_of_year (at_end_of_year)
+years_ago
+years_since
+last_year
+on_weekday?
+on_weekend?
+```
+
 INFO: The following calculation methods have edge cases in October 1582, since days 5..14 just do not exist. This guide does not document their behavior around those days for brevity, but it is enough to say that they do what you would expect. That is, `Date.new(1582, 10, 4).tomorrow` returns `Date.new(1582, 10, 15)` and so on. Please check `test/core_ext/date_ext_test.rb` in the Active Support test suite for expected behavior.
 
 #### `Date.current`
@@ -2991,68 +2973,6 @@ When making Date comparisons using methods which honor the user time zone, make
 
 #### Named dates
 
-##### `prev_year`, `next_year`
-
-In Ruby 1.9 `prev_year` and `next_year` return a date with the same day/month in the last or next year:
-
-```ruby
-d = Date.new(2010, 5, 8) # => Sat, 08 May 2010
-d.prev_year              # => Fri, 08 May 2009
-d.next_year              # => Sun, 08 May 2011
-```
-
-If date is the 29th of February of a leap year, you obtain the 28th:
-
-```ruby
-d = Date.new(2000, 2, 29) # => Tue, 29 Feb 2000
-d.prev_year               # => Sun, 28 Feb 1999
-d.next_year               # => Wed, 28 Feb 2001
-```
-
-`prev_year` is aliased to `last_year`.
-
-##### `prev_month`, `next_month`
-
-In Ruby 1.9 `prev_month` and `next_month` return the date with the same day in the last or next month:
-
-```ruby
-d = Date.new(2010, 5, 8) # => Sat, 08 May 2010
-d.prev_month             # => Thu, 08 Apr 2010
-d.next_month             # => Tue, 08 Jun 2010
-```
-
-If such a day does not exist, the last day of the corresponding month is returned:
-
-```ruby
-Date.new(2000, 5, 31).prev_month # => Sun, 30 Apr 2000
-Date.new(2000, 3, 31).prev_month # => Tue, 29 Feb 2000
-Date.new(2000, 5, 31).next_month # => Fri, 30 Jun 2000
-Date.new(2000, 1, 31).next_month # => Tue, 29 Feb 2000
-```
-
-`prev_month` is aliased to `last_month`.
-
-##### `prev_quarter`, `next_quarter`
-
-Same as `prev_month` and `next_month`. It returns the date with the same day in the previous or next quarter:
-
-```ruby
-t = Time.local(2010, 5, 8) # => Sat, 08 May 2010
-t.prev_quarter             # => Mon, 08 Feb 2010
-t.next_quarter             # => Sun, 08 Aug 2010
-```
-
-If such a day does not exist, the last day of the corresponding month is returned:
-
-```ruby
-Time.local(2000, 7, 31).prev_quarter  # => Sun, 30 Apr 2000
-Time.local(2000, 5, 31).prev_quarter  # => Tue, 29 Feb 2000
-Time.local(2000, 10, 31).prev_quarter # => Mon, 30 Oct 2000
-Time.local(2000, 11, 31).next_quarter # => Wed, 28 Feb 2001
-```
-
-`prev_quarter` is aliased to `last_quarter`.
-
 ##### `beginning_of_week`, `end_of_week`
 
 The methods `beginning_of_week` and `end_of_week` return the dates for the
@@ -3170,6 +3090,8 @@ Date.new(2012, 2, 29).years_ago(3)     # => Sat, 28 Feb 2009
 Date.new(2012, 2, 29).years_since(3)   # => Sat, 28 Feb 2015
 ```
 
+`last_year` is short-hand for `#years_ago(1)`.
+
 ##### `months_ago`, `months_since`
 
 The methods `months_ago` and `months_since` work analogously for months:
@@ -3186,6 +3108,8 @@ Date.new(2010, 4, 30).months_ago(2)    # => Sun, 28 Feb 2010
 Date.new(2009, 12, 31).months_since(2) # => Sun, 28 Feb 2010
 ```
 
+`last_month` is short-hand for `#months_ago(1)`.
+
 ##### `weeks_ago`
 
 The method `weeks_ago` works analogously for weeks:
@@ -3348,35 +3272,7 @@ WARNING: `DateTime` is not aware of DST rules and so some of these methods have
 
 NOTE: All the following methods are defined in `active_support/core_ext/date_time/calculations.rb`.
 
-The class `DateTime` is a subclass of `Date` so by loading `active_support/core_ext/date/calculations.rb` you inherit these methods and their aliases, except that they will always return datetimes:
-
-```ruby
-yesterday
-tomorrow
-beginning_of_week (at_beginning_of_week)
-end_of_week (at_end_of_week)
-monday
-sunday
-weeks_ago
-prev_week (last_week)
-next_week
-months_ago
-months_since
-beginning_of_month (at_beginning_of_month)
-end_of_month (at_end_of_month)
-prev_month (last_month)
-next_month
-beginning_of_quarter (at_beginning_of_quarter)
-end_of_quarter (at_end_of_quarter)
-beginning_of_year (at_beginning_of_year)
-end_of_year (at_end_of_year)
-years_ago
-years_since
-prev_year (last_year)
-next_year
-on_weekday?
-on_weekend?
-```
+The class `DateTime` is a subclass of `Date` so by loading `active_support/core_ext/date/calculations.rb` you inherit these methods and their aliases, except that they will always return datetimes.
 
 The following methods are reimplemented so you do **not** need to load `active_support/core_ext/date/calculations.rb` for these ones:
 
@@ -3524,8 +3420,6 @@ Extensions to `Time`
 
 NOTE: All the following methods are defined in `active_support/core_ext/time/calculations.rb`.
 
-Active Support adds to `Time` many of the methods available for `DateTime`:
-
 ```ruby
 past?
 today?
@@ -3537,6 +3431,8 @@ change
 advance
 ago
 since (in)
+prev_day
+next_day
 beginning_of_day (midnight, at_midnight, at_beginning_of_day)
 end_of_day
 beginning_of_hour (at_beginning_of_hour)
@@ -3552,15 +3448,17 @@ months_ago
 months_since
 beginning_of_month (at_beginning_of_month)
 end_of_month (at_end_of_month)
-prev_month (last_month)
+prev_month
 next_month
+last_month
 beginning_of_quarter (at_beginning_of_quarter)
 end_of_quarter (at_end_of_quarter)
 beginning_of_year (at_beginning_of_year)
 end_of_year (at_end_of_year)
 years_ago
 years_since
-prev_year (last_year)
+prev_year
+last_year
 next_year
 on_weekday?
 on_weekend?
@@ -3618,6 +3516,74 @@ now.all_year
 # => Fri, 01 Jan 2010 00:00:00 UTC +00:00..Fri, 31 Dec 2010 23:59:59 UTC +00:00
 ```
 
+#### `prev_day`, `next_day`
+
+In Ruby 1.9 `prev_day` and `next_day` return the date in the last or next day:
+
+```ruby
+d = Date.new(2010, 5, 8) # => Sat, 08 May 2010
+d.prev_day               # => Fri, 07 May 2010
+d.next_day               # => Sun, 09 May 2010
+```
+
+#### `prev_month`, `next_month`
+
+In Ruby 1.9 `prev_month` and `next_month` return the date with the same day in the last or next month:
+
+```ruby
+d = Date.new(2010, 5, 8) # => Sat, 08 May 2010
+d.prev_month             # => Thu, 08 Apr 2010
+d.next_month             # => Tue, 08 Jun 2010
+```
+
+If such a day does not exist, the last day of the corresponding month is returned:
+
+```ruby
+Date.new(2000, 5, 31).prev_month # => Sun, 30 Apr 2000
+Date.new(2000, 3, 31).prev_month # => Tue, 29 Feb 2000
+Date.new(2000, 5, 31).next_month # => Fri, 30 Jun 2000
+Date.new(2000, 1, 31).next_month # => Tue, 29 Feb 2000
+```
+
+#### `prev_year`, `next_year`
+
+In Ruby 1.9 `prev_year` and `next_year` return a date with the same day/month in the last or next year:
+
+```ruby
+d = Date.new(2010, 5, 8) # => Sat, 08 May 2010
+d.prev_year              # => Fri, 08 May 2009
+d.next_year              # => Sun, 08 May 2011
+```
+
+If date is the 29th of February of a leap year, you obtain the 28th:
+
+```ruby
+d = Date.new(2000, 2, 29) # => Tue, 29 Feb 2000
+d.prev_year               # => Sun, 28 Feb 1999
+d.next_year               # => Wed, 28 Feb 2001
+```
+
+#### `prev_quarter`, `next_quarter`
+
+`prev_quarter` and `next_quarter` return the date with the same day in the previous or next quarter:
+
+```ruby
+t = Time.local(2010, 5, 8) # => 2010-05-08 00:00:00 +0300
+t.prev_quarter             # => 2010-02-08 00:00:00 +0200
+t.next_quarter             # => 2010-08-08 00:00:00 +0300
+```
+
+If such a day does not exist, the last day of the corresponding month is returned:
+
+```ruby
+Time.local(2000, 7, 31).prev_quarter  # => 2000-04-30 00:00:00 +0300
+Time.local(2000, 5, 31).prev_quarter  # => 2000-02-29 00:00:00 +0200
+Time.local(2000, 10, 31).prev_quarter # => 2000-07-31 00:00:00 +0300
+Time.local(2000, 11, 31).next_quarter # => 2001-03-01 00:00:00 +0200
+```
+
+`prev_quarter` is aliased to `last_quarter`.
+
 ### Time Constructors
 
 Active Support defines `Time.current` to be `Time.zone.now` if there's a user time zone defined, with fallback to `Time.now`:
@@ -3704,9 +3670,9 @@ Extensions to `NameError`
 
 Active Support adds `missing_name?` to `NameError`, which tests whether the exception was raised because of the name passed as argument.
 
-The name may be given as a symbol or string. A symbol is tested against the bare constant name, a string is against the fully-qualified constant name.
+The name may be given as a symbol or string. A symbol is tested against the bare constant name, a string is against the fully qualified constant name.
 
-TIP: A symbol can represent a fully-qualified constant name as in `:"ActiveRecord::Base"`, so the behavior for symbols is defined for convenience, not because it has to be that way technically.
+TIP: A symbol can represent a fully qualified constant name as in `:"ActiveRecord::Base"`, so the behavior for symbols is defined for convenience, not because it has to be that way technically.
 
 For example, when an action of `ArticlesController` is called Rails tries optimistically to use `ArticlesHelper`. It is OK that the helper module does not exist, so if an exception for that constant name is raised it should be silenced. But it could be the case that `articles_helper.rb` raises a `NameError` due to an actual unknown constant. That should be reraised. The method `missing_name?` provides a way to distinguish both cases:
 
diff --git a/guides/source/active_support_instrumentation.md b/guides/source/active_support_instrumentation.md
index 03c9183eb3..ac40fda11d 100644
--- a/guides/source/active_support_instrumentation.md
+++ b/guides/source/active_support_instrumentation.md
@@ -3,7 +3,7 @@
 Active Support Instrumentation
 ==============================
 
-Active Support is a part of core Rails that provides Ruby language extensions, utilities and other things. One of the things it includes is an instrumentation API that can be used inside an application to measure certain actions that occur within Ruby code, such as that inside a Rails application or the framework itself. It is not limited to Rails, however. It can be used independently in other Ruby scripts if it is so desired.
+Active Support is a part of core Rails that provides Ruby language extensions, utilities, and other things. One of the things it includes is an instrumentation API that can be used inside an application to measure certain actions that occur within Ruby code, such as that inside a Rails application or the framework itself. It is not limited to Rails, however. It can be used independently in other Ruby scripts if it is so desired.
 
 In this guide, you will learn how to use the instrumentation API inside of Active Support to measure events inside of Rails and other Ruby code.
 
@@ -169,7 +169,7 @@ INFO. Additional keys may be added by the caller.
 
 ### send_data.action_controller
 
-`ActionController` does not had any specific information to the payload. All options are passed through to the payload.
+`ActionController` does not add any specific information to the payload. All options are passed through to the payload.
 
 ### redirect_to.action_controller
 
@@ -197,6 +197,12 @@ INFO. Additional keys may be added by the caller.
 }
 ```
 
+### unpermitted_parameters.action_controller
+
+| Key     | Value            |
+| ------- | ---------------- |
+| `:keys` | Unpermitted keys |
+
 Action View
 -----------
 
@@ -304,7 +310,7 @@ Action Mailer
   mailer: "Notification",
   message_id: "4f5b5491f1774_181b23fc3d4434d38138e5@mba.local.mail",
   subject: "Rails Guides",
-  to: ["users@rails.com", "ddh@rails.com"],
+  to: ["users@rails.com", "dhh@rails.com"],
   from: ["me@rails.com"],
   date: Sat, 10 Mar 2012 14:18:09 +0100,
   mail: "..." # omitted for brevity
@@ -330,13 +336,29 @@ Action Mailer
   mailer: "Notification",
   message_id: "4f5b5491f1774_181b23fc3d4434d38138e5@mba.local.mail",
   subject: "Rails Guides",
-  to: ["users@rails.com", "ddh@rails.com"],
+  to: ["users@rails.com", "dhh@rails.com"],
   from: ["me@rails.com"],
   date: Sat, 10 Mar 2012 14:18:09 +0100,
   mail: "..." # omitted for brevity
 }
 ```
 
+### process.action_mailer
+
+| Key           | Value                    |
+| ------------- | ------------------------ |
+| `:mailer`     | Name of the mailer class |
+| `:action`     | The action               |
+| `:args`       | The arguments            |
+
+```ruby
+{
+  mailer: "Notification",
+  action: "welcome_email",
+  args: []
+}
+```
+
 Active Support
 --------------
 
@@ -450,6 +472,99 @@ Active Job
 | `:adapter`   | QueueAdapter object processing the job |
 | `:job`       | Job object                             |
 
+Action Cable
+------------
+
+### perform_action.action_cable
+
+| Key              | Value                     |
+| ---------------- | ------------------------- |
+| `:channel_class` | Name of the channel class |
+| `:action`        | The action                |
+| `:data`          | A hash of data            |
+
+### transmit.action_cable
+
+| Key              | Value                     |
+| ---------------- | ------------------------- |
+| `:channel_class` | Name of the channel class |
+| `:data`          | A hash of data            |
+| `:via`           | Via                       |
+
+### transmit_subscription_confirmation.action_cable
+
+| Key              | Value                     |
+| ---------------- | ------------------------- |
+| `:channel_class` | Name of the channel class |
+
+### transmit_subscription_rejection.action_cable
+
+| Key              | Value                     |
+| ---------------- | ------------------------- |
+| `:channel_class` | Name of the channel class |
+
+### broadcast.action_cable
+
+| Key             | Value                |
+| --------------- | -------------------- |
+| `:broadcasting` | A named broadcasting |
+| `:message`      | A hash of message    |
+| `:coder`        | The coder            |
+
+Active Storage
+--------------
+
+### service_upload.active_storage
+
+| Key          | Value                        |
+| ------------ | ---------------------------- |
+| `:key`       | Secure token                 |
+| `:service`   | Name of the service          |
+| `:checksum`  | Checksum to ensure integrity |
+
+### service_streaming_download.active_storage
+
+| Key          | Value               |
+| ------------ | ------------------- |
+| `:key`       | Secure token        |
+| `:service`   | Name of the service |
+
+### service_download.active_storage
+
+| Key          | Value               |
+| ------------ | ------------------- |
+| `:key`       | Secure token        |
+| `:service`   | Name of the service |
+
+### service_delete.active_storage
+
+| Key          | Value               |
+| ------------ | ------------------- |
+| `:key`       | Secure token        |
+| `:service`   | Name of the service |
+
+### service_delete_prefixed.active_storage
+
+| Key          | Value               |
+| ------------ | ------------------- |
+| `:prefix`    | Key prefix          |
+| `:service`   | Name of the service |
+
+### service_exist.active_storage
+
+| Key          | Value                       |
+| ------------ | --------------------------- |
+| `:key`       | Secure token                |
+| `:service`   | Name of the service         |
+| `:exist`     | File or blob exists or not  |
+
+### service_url.active_storage
+
+| Key          | Value               |
+| ------------ | ------------------- |
+| `:key`       | Secure token        |
+| `:service`   | Name of the service |
+| `:url`       | Generated url       |
 
 Railties
 --------
@@ -549,4 +664,4 @@ end
 ```
 
 You should follow Rails conventions when defining your own events. The format is: `event.library`.
-If you application is sending Tweets, you should create an event named `tweet.twitter`.
+If your application is sending Tweets, you should create an event named `tweet.twitter`.
diff --git a/guides/source/api_app.md b/guides/source/api_app.md
index da1b7b25ef..d6b228b2f8 100644
--- a/guides/source/api_app.md
+++ b/guides/source/api_app.md
@@ -1,6 +1,5 @@
 **DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.**
 
-
 Using Rails for API-only Applications
 =====================================
 
@@ -25,7 +24,7 @@ With the advent of client-side frameworks, more developers are using Rails to
 build a back-end that is shared between their web application and other native
 applications.
 
-For example, Twitter uses its [public API](https://dev.twitter.com) in its web
+For example, Twitter uses its [public API](https://developer.twitter.com/) in its web
 application, which is built as a static site that consumes JSON resources.
 
 Instead of using Rails to generate HTML that communicates with the server
@@ -99,7 +98,7 @@ Handled at the Action Pack layer:
 - Header and Redirection Responses: `head :no_content` and
   `redirect_to user_url(current_user)` come in handy. Sure, you could manually
   add the response headers, but why?
-- Caching: Rails provides page, action and fragment caching. Fragment caching
+- Caching: Rails provides page, action, and fragment caching. Fragment caching
   is especially helpful when building up a nested JSON object.
 - Basic, Digest, and Token Authentication: Rails comes with out-of-the-box support
   for three kinds of HTTP authentication.
@@ -107,7 +106,7 @@ Handled at the Action Pack layer:
   handlers for a variety of events, such as action processing, sending a file or
   data, redirection, and database queries. The payload of each event comes with
   relevant information (for the action processing event, the payload includes
-  the controller, action, parameters, request format, request method and the
+  the controller, action, parameters, request format, request method, and the
   request's full path).
 - Generators: It is often handy to generate a resource and get your model,
   controller, test stubs, and routes created for you in a single command for
@@ -149,7 +148,7 @@ This will do three main things for you:
   `ActionController::Base`. As with middleware, this will leave out any Action
   Controller modules that provide functionalities primarily used by browser
   applications.
-- Configure the generators to skip generating views, helpers and assets when
+- Configure the generators to skip generating views, helpers, and assets when
   you generate a new resource.
 
 ### Changing an existing application
@@ -216,7 +215,6 @@ An API application comes with the following middleware by default:
 - `Rack::Head`
 - `Rack::ConditionalGet`
 - `Rack::ETag`
-- `MyApi::Application::Routes`
 
 See the [internal middleware](rails_on_rack.html#internal-middleware-stack)
 section of the Rack guide for further information on them.
@@ -377,7 +375,6 @@ controller modules by default:
 - `ActionController::ConditionalGet`: Support for `stale?`.
 - `ActionController::BasicImplicitRender`: Makes sure to return an empty response, if there isn't an explicit one.
 - `ActionController::StrongParameters`: Support for parameters white-listing in combination with Active Model mass assignment.
-- `ActionController::ForceSSL`: Support for `force_ssl`.
 - `ActionController::DataStreaming`: Support for `send_file` and `send_data`.
 - `AbstractController::Callbacks`: Support for `before_action` and
   similar helpers.
@@ -415,8 +412,10 @@ Some common modules you might want to add:
 
 - `AbstractController::Translation`: Support for the `l` and `t` localization
   and translation methods.
-- `ActionController::HttpAuthentication::Basic` (or `Digest` or `Token`): Support
-  for basic, digest or token HTTP authentication.
+- Support for basic, digest, or token HTTP authentication:
+  * `ActionController::HttpAuthentication::Basic::ControllerMethods`,
+  * `ActionController::HttpAuthentication::Digest::ControllerMethods`,
+  * `ActionController::HttpAuthentication::Token::ControllerMethods`
 - `ActionView::Layouts`: Support for layouts when rendering.
 - `ActionController::MimeResponds`: Support for `respond_to`.
 - `ActionController::Cookies`: Support for `cookies`, which includes
diff --git a/guides/source/api_documentation_guidelines.md b/guides/source/api_documentation_guidelines.md
index 2c153d3783..10b89433e7 100644
--- a/guides/source/api_documentation_guidelines.md
+++ b/guides/source/api_documentation_guidelines.md
@@ -16,7 +16,7 @@ RDoc
 ----
 
 The [Rails API documentation](http://api.rubyonrails.org) is generated with
-[RDoc](http://docs.seattlerb.org/rdoc/). To generate it, make sure you are
+[RDoc](https://ruby.github.io/rdoc/). To generate it, make sure you are
 in the rails root directory, run `bundle install` and execute:
 
 ```bash
@@ -26,9 +26,9 @@ in the rails root directory, run `bundle install` and execute:
 Resulting HTML files can be found in the ./doc/rdoc directory.
 
 Please consult the RDoc documentation for help with the
-[markup](http://docs.seattlerb.org/rdoc/RDoc/Markup.html),
+[markup](https://ruby.github.io/rdoc/RDoc/Markup.html),
 and also take into account these [additional
-directives](http://docs.seattlerb.org/rdoc/RDoc/Parser/Ruby.html).
+directives](https://ruby.github.io/rdoc/RDoc/Parser/Ruby.html).
 
 Wording
 -------
diff --git a/guides/source/asset_pipeline.md b/guides/source/asset_pipeline.md
index 17ab9c7600..5ac3586889 100644
--- a/guides/source/asset_pipeline.md
+++ b/guides/source/asset_pipeline.md
@@ -20,10 +20,9 @@ What is the Asset Pipeline?
 
 The asset pipeline provides a framework to concatenate and minify or compress
 JavaScript and CSS assets. It also adds the ability to write these assets in
-other languages and pre-processors such as CoffeeScript, Sass and ERB.
+other languages and pre-processors such as CoffeeScript, Sass, and ERB.
 It allows assets in your application to be automatically combined with assets
-from other gems. For example, jquery-rails includes a copy of jquery.js
-and enables AJAX features in Rails.
+from other gems.
 
 The asset pipeline is implemented by the
 [sprockets-rails](https://github.com/rails/sprockets-rails) gem,
@@ -35,7 +34,7 @@ rails new appname --skip-sprockets
 ```
 
 Rails automatically adds the `sass-rails`, `coffee-rails` and `uglifier`
-gems to your Gemfile, which are used by Sprockets for asset compression:
+gems to your `Gemfile`, which are used by Sprockets for asset compression:
 
 ```ruby
 gem 'sass-rails'
@@ -44,8 +43,8 @@ gem 'coffee-rails'
 ```
 
 Using the `--skip-sprockets` option will prevent Rails from adding
-them to your Gemfile, so if you later want to enable
-the asset pipeline you will have to add those gems to your Gemfile. Also,
+them to your `Gemfile`, so if you later want to enable
+the asset pipeline you will have to add those gems to your `Gemfile`. Also,
 creating an application with the `--skip-sprockets` option will generate
 a slightly different `config/application.rb` file, with a require statement
 for the sprockets railtie that is commented-out. You will have to remove
@@ -65,7 +64,7 @@ config.assets.js_compressor = :uglifier
 ```
 
 NOTE: The `sass-rails` gem is automatically used for CSS compression if included
-in the Gemfile and no `config.assets.css_compressor` option is set.
+in the `Gemfile` and no `config.assets.css_compressor` option is set.
 
 
 ### Main Features
@@ -154,7 +153,7 @@ environments. You can enable or disable it in your configuration through the
 
 More reading:
 
-* [Optimize caching](http://code.google.com/speed/page-speed/docs/caching.html)
+* [Optimize caching](https://developers.google.com/speed/docs/insights/LeverageBrowserCaching)
 * [Revving Filenames: don't use querystring](http://www.stevesouders.com/blog/2008/08/23/revving-filenames-dont-use-querystring/)
 
 
@@ -181,7 +180,7 @@ When you generate a scaffold or a controller, Rails also generates a JavaScript
 file (or CoffeeScript file if the `coffee-rails` gem is in the `Gemfile`) and a
 Cascading Style Sheet file (or SCSS file if `sass-rails` is in the `Gemfile`)
 for that controller. Additionally, when generating a scaffold, Rails generates
-the file scaffolds.css (or scaffolds.scss if `sass-rails` is in the
+the file `scaffolds.css` (or `scaffolds.scss` if `sass-rails` is in the
 `Gemfile`.)
 
 For example, if you generate a `ProjectsController`, Rails will also add a new
@@ -202,7 +201,7 @@ will result in your assets being included more than once.
 
 WARNING: When using asset precompilation, you will need to ensure that your
 controller assets will be precompiled when loading them on a per page basis. By
-default .coffee and .scss files will not be precompiled on their own. See
+default `.coffee` and `.scss` files will not be precompiled on their own. See
 [Precompiling Assets](#precompiling-assets) for more information on how
 precompiling works.
 
@@ -225,7 +224,7 @@ Pipeline assets can be placed inside an application in one of three locations:
 `app/assets`, `lib/assets` or `vendor/assets`.
 
 * `app/assets` is for assets that are owned by the application, such as custom
-images, JavaScript files or stylesheets.
+images, JavaScript files, or stylesheets.
 
 * `lib/assets` is for your own libraries' code that doesn't really fit into the
 scope of the application or those libraries which are shared across applications.
@@ -435,7 +434,7 @@ Sprockets uses manifest files to determine which assets to include and serve.
 These manifest files contain _directives_ - instructions that tell Sprockets
 which files to require in order to build a single CSS or JavaScript file. With
 these directives, Sprockets loads the files specified, processes them if
-necessary, concatenates them into one single file and then compresses them
+necessary, concatenates them into one single file, and then compresses them
 (based on value of `Rails.application.config.assets.js_compressor`). By serving
 one file rather than many, the load time of pages can be greatly reduced because
 the browser makes fewer requests. Compression also reduces file size, enabling
@@ -726,11 +725,11 @@ include, you can add them to the `precompile` array in `config/initializers/asse
 Rails.application.config.assets.precompile += %w( admin.js admin.css )
 ```
 
-NOTE. Always specify an expected compiled filename that ends with .js or .css,
+NOTE. Always specify an expected compiled filename that ends with `.js` or `.css`,
 even if you want to add Sass or CoffeeScript files to the precompile array.
 
-The task also generates a `.sprockets-manifest-md5hash.json` (where `md5hash` is
-an MD5 hash) that contains a list with all your assets and their respective
+The task also generates a `.sprockets-manifest-randomhex.json` (where `randomhex` is
+a 16-byte random hex string) that contains a list with all your assets and their respective
 fingerprints. This is used by the Rails helper methods to avoid handing the
 mapping requests back to Sprockets. A typical manifest file looks like:
 
@@ -846,11 +845,11 @@ signals all caches between your server and the client browser that this content
 number of requests for this asset from your server; the asset has a good chance
 of being in the local browser cache or some intermediate cache.
 
-This mode uses more memory, performs more poorly than the default and is not
+This mode uses more memory, performs more poorly than the default, and is not
 recommended.
 
 If you are deploying a production application to a system without any
-pre-existing JavaScript runtimes, you may want to add one to your Gemfile:
+pre-existing JavaScript runtimes, you may want to add one to your `Gemfile`:
 
 ```ruby
 group :production do
@@ -918,7 +917,7 @@ config.action_controller.asset_host = ENV['CDN_HOST']
 
 
 
-Note: You would need to set `CDN_HOST` on your server to `mycdnsubdomain
+NOTE: You would need to set `CDN_HOST` on your server to `mycdnsubdomain
 .fictional-cdn.com` for this to work.
 
 Once you have configured your server and your CDN when you serve a webpage that
@@ -1090,7 +1089,7 @@ Possible options for JavaScript compression are `:closure`, `:uglifier` and
 `:yui`. These require the use of the `closure-compiler`, `uglifier` or
 `yui-compressor` gems, respectively.
 
-The default Gemfile includes [uglifier](https://github.com/lautis/uglifier).
+The default `Gemfile` includes [uglifier](https://github.com/lautis/uglifier).
 This gem wraps [UglifyJS](https://github.com/mishoo/UglifyJS) (written for
 NodeJS) in Ruby. It compresses your code by removing white space and comments,
 shortening local variable names, and performing other micro-optimizations such
@@ -1205,10 +1204,10 @@ Adding Assets to Your Gems
 
 Assets can also come from external sources in the form of gems.
 
-A good example of this is the `jquery-rails` gem which comes with Rails as the
-standard JavaScript library gem. This gem contains an engine class which
-inherits from `Rails::Engine`. By doing this, Rails is informed that the
-directory for this gem may contain assets and the `app/assets`, `lib/assets` and
+A good example of this is the `jquery-rails` gem.
+This gem contains an engine class which inherits from `Rails::Engine`.
+By doing this, Rails is informed that the directory for this
+gem may contain assets and the `app/assets`, `lib/assets` and
 `vendor/assets` directories of this engine are added to the search path of
 Sprockets.
 
@@ -1219,7 +1218,7 @@ Sprockets uses Processors, Transformers, Compressors, and Exporters to extend
 Sprockets functionality. Have a look at
 [Extending Sprockets](https://github.com/rails/sprockets/blob/master/guides/extending_sprockets.md)
 to learn more. Here we registered a preprocessor to add a comment to the end
-of text/css (.css) files.
+of text/css (`.css`) files.
 
 ```ruby
 module AddComment
@@ -1244,11 +1243,7 @@ moving the files from `public/` to the new locations. See [Asset
 Organization](#asset-organization) above for guidance on the correct locations
 for different file types.
 
-Next will be avoiding duplicate JavaScript files. Since jQuery is the default
-JavaScript library from Rails 3.1 onwards, you don't need to copy `jquery.js`
-into `app/assets` and it will be included automatically.
-
-The third is updating the various environment files with the correct default
+Next is updating the various environment files with the correct default
 options.
 
 In `application.rb`:
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md
index b5bd24d027..e7408b5a7f 100644
--- a/guides/source/association_basics.md
+++ b/guides/source/association_basics.md
@@ -94,7 +94,7 @@ class Book < ApplicationRecord
 end
 ```
 
-![belongs_to Association Diagram](images/belongs_to.png)
+![belongs_to Association Diagram](images/association_basics/belongs_to.png)
 
 NOTE: `belongs_to` associations _must_ use the singular term. If you used the pluralized form in the above example for the `author` association in the `Book` model, you would be told that there was an "uninitialized constant Book::Authors". This is because Rails automatically infers the class name from the association name. If the association name is wrongly pluralized, then the inferred class will be wrongly pluralized too.
 
@@ -127,7 +127,7 @@ class Supplier < ApplicationRecord
 end
 ```
 
-![has_one Association Diagram](images/has_one.png)
+![has_one Association Diagram](images/association_basics/has_one.png)
 
 The corresponding migration might look like this:
 
@@ -171,7 +171,7 @@ end
 
 NOTE: The name of the other model is pluralized when declaring a `has_many` association.
 
-![has_many Association Diagram](images/has_many.png)
+![has_many Association Diagram](images/association_basics/has_many.png)
 
 The corresponding migration might look like this:
 
@@ -213,7 +213,7 @@ class Patient < ApplicationRecord
 end
 ```
 
-![has_many :through Association Diagram](images/has_many_through.png)
+![has_many :through Association Diagram](images/association_basics/has_many_through.png)
 
 The corresponding migration might look like this:
 
@@ -299,7 +299,7 @@ class AccountHistory < ApplicationRecord
 end
 ```
 
-![has_one :through Association Diagram](images/has_one_through.png)
+![has_one :through Association Diagram](images/association_basics/has_one_through.png)
 
 The corresponding migration might look like this:
 
@@ -340,7 +340,7 @@ class Part < ApplicationRecord
 end
 ```
 
-![has_and_belongs_to_many Association Diagram](images/habtm.png)
+![has_and_belongs_to_many Association Diagram](images/association_basics/habtm.png)
 
 The corresponding migration might look like this:
 
@@ -439,7 +439,7 @@ end
 
 The simplest rule of thumb is that you should set up a `has_many :through` relationship if you need to work with the relationship model as an independent entity. If you don't need to do anything with the relationship model, it may be simpler to set up a `has_and_belongs_to_many` relationship (though you'll need to remember to create the joining table in the database).
 
-You should use `has_many :through` if you need validations, callbacks or extra attributes on the join model.
+You should use `has_many :through` if you need validations, callbacks, or extra attributes on the join model.
 
 ### Polymorphic Associations
 
@@ -494,7 +494,7 @@ class CreatePictures < ActiveRecord::Migration[5.0]
 end
 ```
 
-![Polymorphic Association Diagram](images/polymorphic.png)
+![Polymorphic Association Diagram](images/association_basics/polymorphic.png)
 
 ### Self Joins
 
@@ -505,7 +505,7 @@ class Employee < ApplicationRecord
   has_many :subordinates, class_name: "Employee",
                           foreign_key: "manager_id"
 
-  belongs_to :manager, class_name: "Employee"
+  belongs_to :manager, class_name: "Employee", optional: true
 end
 ```
 
@@ -572,40 +572,32 @@ class Book < ApplicationRecord
 end
 ```
 
-This declaration needs to be backed up by the proper foreign key declaration on the books table:
+This declaration needs to be backed up by a corresponding foreign key column in the books table. For a brand new table, the migration might look something like this:
 
 ```ruby
 class CreateBooks < ActiveRecord::Migration[5.0]
   def change
     create_table :books do |t|
-      t.datetime :published_at
-      t.string   :book_number
-      t.integer  :author_id
+      t.datetime   :published_at
+      t.string     :book_number
+      t.references :author
     end
   end
 end
 ```
 
-If you create an association some time after you build the underlying model, you need to remember to create an `add_column` migration to provide the necessary foreign key.
-
-It's a good practice to add an index on the foreign key to improve queries
-performance and a foreign key constraint to ensure referential data integrity:
+Whereas for an existing table, it might look like this:
 
 ```ruby
-class CreateBooks < ActiveRecord::Migration[5.0]
+class AddAuthorToBooks < ActiveRecord::Migration[5.0]
   def change
-    create_table :books do |t|
-      t.datetime :published_at
-      t.string   :book_number
-      t.integer  :author_id
-    end
-
-    add_index :books, :author_id
-    add_foreign_key :books, :authors
+    add_reference :books, :author
   end
 end
 ```
 
+NOTE: If you wish to [enforce referential integrity at the database level](/active_record_migrations.html#foreign-keys), add the `foreign_key: true` option to the ‘reference’ column declarations above.
+
 #### Creating Join Tables for `has_and_belongs_to_many` Associations
 
 If you create a `has_and_belongs_to_many` association, you need to explicitly create the joining table. Unless the name of the join table is explicitly specified by using the `:join_table` option, Active Record creates the name by using the lexical book of the class names. So a join between author and book models will give the default join table name of "authors_books" because "a" outranks "b" in lexical ordering.
@@ -735,12 +727,9 @@ a.first_name = 'David'
 a.first_name == b.author.first_name # => true
 ```
 
-Active Record supports automatic identification for most associations with standard names. However, Active Record will not automatically identify bi-directional associations that contain any of the following options:
+Active Record supports automatic identification for most associations with standard names. However, Active Record will not automatically identify bi-directional associations that contain a scope or any of the following options:
 
-* `:conditions`
 * `:through`
-* `:polymorphic`
-* `:class_name`
 * `:foreign_key`
 
 For example, consider the following model declarations:
@@ -787,12 +776,6 @@ a.first_name = 'David'
 a.first_name == b.writer.first_name # => true
 ```
 
-There are a few limitations to `:inverse_of` support:
-
-* They do not work with `:through` associations.
-* They do not work with `:polymorphic` associations.
-* They do not work with `:as` associations.
-
 Detailed Association Reference
 ------------------------------
 
@@ -804,7 +787,7 @@ The `belongs_to` association creates a one-to-one match with another model. In d
 
 #### Methods Added by `belongs_to`
 
-When you declare a `belongs_to` association, the declaring class automatically gains five methods related to the association:
+When you declare a `belongs_to` association, the declaring class automatically gains 6 methods related to the association:
 
 * `association`
 * `association=(associate)`
@@ -906,7 +889,7 @@ The `belongs_to` association supports these options:
 
 ##### `:autosave`
 
-If you set the `:autosave` option to `true`, Rails will save any loaded members and destroy members that are marked for destruction whenever you save the parent object.
+If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved.
 
 ##### `:class_name`
 
@@ -1012,7 +995,7 @@ When we execute `@user.todos.create` then the `@todo` record will have its
 
 ##### `:inverse_of`
 
-The `:inverse_of` option specifies the name of the `has_many` or `has_one` association that is the inverse of this association. Does not work in combination with the `:polymorphic` options.
+The `:inverse_of` option specifies the name of the `has_many` or `has_one` association that is the inverse of this association.
 
 ```ruby
 class Author < ApplicationRecord
@@ -1082,7 +1065,7 @@ You can use any of the standard [querying methods](active_record_querying.html)
 The `where` method lets you specify the conditions that the associated object must meet.
 
 ```ruby
-class book < ApplicationRecord
+class Book < ApplicationRecord
   belongs_to :author, -> { where active: true }
 end
 ```
@@ -1155,7 +1138,7 @@ The `has_one` association creates a one-to-one match with another model. In data
 
 #### Methods Added by `has_one`
 
-When you declare a `has_one` association, the declaring class automatically gains five methods related to the association:
+When you declare a `has_one` association, the declaring class automatically gains 6 methods related to the association:
 
 * `association`
 * `association=(associate)`
@@ -1257,7 +1240,7 @@ Setting the `:as` option indicates that this is a polymorphic association. Polym
 
 ##### `:autosave`
 
-If you set the `:autosave` option to `true`, Rails will save any loaded members and destroy members that are marked for destruction whenever you save the parent object.
+If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved.
 
 ##### `:class_name`
 
@@ -1299,7 +1282,7 @@ TIP: In any case, Rails will not create foreign key columns for you. You need to
 
 ##### `:inverse_of`
 
-The `:inverse_of` option specifies the name of the `belongs_to` association that is the inverse of this association. Does not work in combination with the `:through` or `:as` options.
+The `:inverse_of` option specifies the name of the `belongs_to` association that is the inverse of this association.
 
 ```ruby
 class Supplier < ApplicationRecord
@@ -1428,7 +1411,7 @@ The `has_many` association creates a one-to-many relationship with another model
 
 #### Methods Added by `has_many`
 
-When you declare a `has_many` association, the declaring class automatically gains 16 methods related to the association:
+When you declare a `has_many` association, the declaring class automatically gains 17 methods related to the association:
 
 * `collection`
 * `collection<<(object, ...)`
@@ -1561,7 +1544,8 @@ The `collection.size` method returns the number of objects in the collection.
 
 ##### `collection.find(...)`
 
-The `collection.find` method finds objects within the collection. It uses the same syntax and options as `ActiveRecord::Base.find`.
+The `collection.find` method finds objects within the collection. It uses the same syntax and options as
+[`ActiveRecord::Base.find`](http://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find).
 
 ```ruby
 @available_book = @author.books.find(1)
@@ -1653,7 +1637,7 @@ Setting the `:as` option indicates that this is a polymorphic association, as di
 
 ##### `:autosave`
 
-If you set the `:autosave` option to `true`, Rails will save any loaded members and destroy members that are marked for destruction whenever you save the parent object.
+If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved.
 
 ##### `:class_name`
 
@@ -1693,7 +1677,7 @@ TIP: In any case, Rails will not create foreign key columns for you. You need to
 
 ##### `:inverse_of`
 
-The `:inverse_of` option specifies the name of the `belongs_to` association that is the inverse of this association. Does not work in combination with the `:through` or `:as` options.
+The `:inverse_of` option specifies the name of the `belongs_to` association that is the inverse of this association.
 
 ```ruby
 class Author < ApplicationRecord
@@ -1960,7 +1944,7 @@ The `has_and_belongs_to_many` association creates a many-to-many relationship wi
 
 #### Methods Added by `has_and_belongs_to_many`
 
-When you declare a `has_and_belongs_to_many` association, the declaring class automatically gains 16 methods related to the association:
+When you declare a `has_and_belongs_to_many` association, the declaring class automatically gains 17 methods related to the association:
 
 * `collection`
 * `collection<<(object, ...)`
@@ -2091,7 +2075,8 @@ The `collection.size` method returns the number of objects in the collection.
 
 ##### `collection.find(...)`
 
-The `collection.find` method finds objects within the collection. It uses the same syntax and options as `ActiveRecord::Base.find`. It also adds the additional condition that the object must be in the collection.
+The `collection.find` method finds objects within the collection. It uses the same syntax and options as
+[`ActiveRecord::Base.find`](http://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find).
 
 ```ruby
 @assembly = @part.assemblies.find(1)
@@ -2099,7 +2084,7 @@ The `collection.find` method finds objects within the collection. It uses the sa
 
 ##### `collection.where(...)`
 
-The `collection.where` method finds objects within the collection based on the conditions supplied but the objects are loaded lazily meaning that the database is queried only when the object(s) are accessed. It also adds the additional condition that the object must be in the collection.
+The `collection.where` method finds objects within the collection based on the conditions supplied but the objects are loaded lazily meaning that the database is queried only when the object(s) are accessed.
 
 ```ruby
 @new_assemblies = @part.assemblies.where("created_at > ?", 2.days.ago)
@@ -2176,7 +2161,7 @@ end
 
 ##### `:autosave`
 
-If you set the `:autosave` option to `true`, Rails will save any loaded members and destroy members that are marked for destruction whenever you save the parent object.
+If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved.
 
 ##### `:class_name`
 
@@ -2406,7 +2391,7 @@ Single Table Inheritance
 ------------------------
 
 Sometimes, you may want to share fields and behavior between different models.
-Let's say we have Car, Motorcycle and Bicycle models. We will want to share
+Let's say we have Car, Motorcycle, and Bicycle models. We will want to share
 the `color` and `price` fields and some methods for all of them, but having some
 specific behavior for each, and separated controllers too.
 
diff --git a/guides/source/autoloading_and_reloading_constants.md b/guides/source/autoloading_and_reloading_constants.md
index c62194faf4..767e158a7e 100644
--- a/guides/source/autoloading_and_reloading_constants.md
+++ b/guides/source/autoloading_and_reloading_constants.md
@@ -8,7 +8,7 @@ This guide documents how constant autoloading and reloading works.
 After reading this guide, you will know:
 
 * Key aspects of Ruby constants
-* What is `autoload_paths`
+* What are the `autoload_paths` and how does eager loading work in production?
 * How constant autoloading works
 * What is `require_dependency`
 * How constant reloading works
@@ -230,10 +230,12 @@ is not entirely equivalent to the one of the body of the definitions using the
 `class` and `module` keywords. But both idioms result in the same constant
 assignment.
 
-Thus, when one informally says "the `String` class", that really means: the
-class object stored in the constant called "String" in the class object stored
-in the `Object` constant. `String` is otherwise an ordinary Ruby constant and
-everything related to constants such as resolution algorithms applies to it.
+Thus, an informal expression like "the `String` class" technically means the
+class object stored in the constant called "String". That constant, in turn,
+belongs to the class object stored in the constant called "Object".
+
+`String` is an ordinary constant, and everything related to them such as
+resolution algorithms applies to it.
 
 Likewise, in the controller
 
@@ -330,11 +332,17 @@ its resolution next. Let's define *parent* to be that qualifying class or module
 object, that is, `Billing` in the example above. The algorithm for qualified
 constants goes like this:
 
-1. The constant is looked up in the parent and its ancestors.
+1. The constant is looked up in the parent and its ancestors. In Ruby >= 2.5,
+`Object` is skipped if present among the ancestors. `Kernel` and `BasicObject`
+are still checked though.
 
 2. If the lookup fails, `const_missing` is invoked in the parent. The default
 implementation of `const_missing` raises `NameError`, but it can be overridden.
 
+INFO. In Ruby < 2.5 `String::Hash` evaluates to `Hash` and the interpreter
+issues a warning: "toplevel constant Hash referenced by String::Hash". Starting
+with 2.5, `String::Hash` raises `NameError` because `Object` is skipped.
+
 As you see, this algorithm is simpler than the one for relative constants. In
 particular, the nesting plays no role here, and modules are not special-cased,
 if neither they nor their ancestors have the constants, `Object` is **not**
@@ -424,8 +432,8 @@ if `House` is still unknown when `app/models/beach_house.rb` is being eager
 loaded, Rails autoloads it.
 
 
-autoload_paths
---------------
+autoload_paths and eager_load_paths
+-----------------------------------
 
 As you probably know, when `require` gets a relative file name:
 
@@ -445,7 +453,7 @@ the idea is that when a constant like `Post` is hit and missing, if there's a
 `post.rb` file for example in `app/models` Rails is going to find it, evaluate
 it, and have `Post` defined as a side-effect.
 
-Alright, Rails has a collection of directories similar to `$LOAD_PATH` in which
+All right, Rails has a collection of directories similar to `$LOAD_PATH` in which
 to look up `post.rb`. That collection is called `autoload_paths` and by
 default it contains:
 
@@ -459,17 +467,22 @@ default it contains:
 
 * The directory `test/mailers/previews`.
 
-Also, this collection is configurable via `config.autoload_paths`. For example,
-`lib` was in the list years ago, but no longer is. An application can opt-in
-by adding this to `config/application.rb`:
+`eager_load_paths` is initially the `app` paths above
 
-```ruby
-config.autoload_paths << "#{Rails.root}/lib"
-```
+How files are autoloaded depends on `eager_load` and `cache_classes` config settings which typically vary in development, production, and test modes:
+ 
+ * In **development**, you want quicker startup with incremental loading of application code.  So `eager_load` should be set to `false`, and Rails will autoload files as needed (see [Autoloading Algorithms](#autoloading-algorithms) below) -- and then reload them when they change (see [Constant Reloading](#constant-reloading) below).
+ * In **production**, however you want consistency and thread-safety and can live with a longer boot time. So `eager_load` is set to `true`, and then during boot (before the app is ready to receive requests) Rails loads all files in the `eager_load_paths`  and then turns off auto loading (NB: autoloading may be needed during eager loading). Not autoloading after boot is a `good thing`, as autoloading can cause the app to be have thread-safety problems. 
+ * In **test**, for speed of execution (of individual tests) `eager_load` is `false`, so Rails follows development behaviour. 
+
+What is described above are the defaults with a newly generated Rails app. There are multiple ways this can be configured differently (see [Configuring Rails Applications](configuring.html#rails-general-configuration).
+). But using `autoload_paths` on its own  in the past (before Rails 5) developers might configure `autoload_paths` to add in extra locations (e.g. `lib` which used to be an autoload path list years ago, but no longer is).  However this is now discouraged for most purposes, as it is likely to lead to production-only errors. It is possible to add new locations to both `config.eager_load_paths` and `config.autoload_paths` but use at your own risk.
+
+See also [Autoloading in the Test Environment](#autoloading-in-the-test-environment).
 
 `config.autoload_paths` is not changeable from environment-specific configuration files.
 
-The value of `autoload_paths` can be inspected. In a just generated application
+The value of `autoload_paths` can be inspected. In a just-generated application
 it is (edited):
 
 ```
@@ -954,7 +967,7 @@ to work on some subclass, things get interesting.
 While working with `Polygon` you do not need to be aware of all its descendants,
 because anything in the table is by definition a polygon, but when working with
 subclasses Active Record needs to be able to enumerate the types it is looking
-for. Let’s see an example.
+for. Let's see an example.
 
 `Rectangle.all` only loads rectangles by adding a type constraint to the query:
 
@@ -963,7 +976,7 @@ SELECT "polygons".* FROM "polygons"
 WHERE "polygons"."type" IN ("Rectangle")
 ```
 
-Let’s introduce now a subclass of `Rectangle`:
+Let's introduce now a subclass of `Rectangle`:
 
 ```ruby
 # app/models/square.rb
@@ -978,7 +991,7 @@ SELECT "polygons".* FROM "polygons"
 WHERE "polygons"."type" IN ("Rectangle", "Square")
 ```
 
-But there’s a caveat here: How does Active Record know that the class `Square`
+But there's a caveat here: How does Active Record know that the class `Square`
 exists at all?
 
 Even if the file `app/models/square.rb` exists and defines the `Square` class,
@@ -1049,7 +1062,7 @@ end
 
 The purpose of this setup would be that the application uses the class that
 corresponds to the environment via `AUTH_SERVICE`. In development mode
-`MockedAuthService` gets autoloaded when the initializer runs. Let’s suppose
+`MockedAuthService` gets autoloaded when the initializer runs. Let's suppose
 we do some requests, change its implementation, and hit the application again.
 To our surprise the changes are not reflected. Why?
 
@@ -1178,6 +1191,8 @@ end
 
 #### Qualified References
 
+WARNING. This gotcha is only possible in Ruby < 2.5.
+
 Given
 
 ```ruby
@@ -1321,3 +1336,17 @@ class C < BasicObject
   end
 end
 ```
+
+### Autoloading in the Test Environment
+ 
+When configuring the `test` environment for autoloading you might consider multiple factors. 
+
+For example it might be worth running your tests with an identical setup to production (`config.eager_load = true`, `config.cache_classes = true`) in order to catch any problems before they hit production (this is compensation for the lack of dev-prod parity). However this will slow down the boot time for individual tests on a dev machine (and is not immediately compatible with spring see below). So one possibility is to do this on a 
+[CI](https://en.wikipedia.org/wiki/Continuous_integration) machine only (which should run without spring). 
+
+On a development machine you can then have your tests running with whatever is fastest (ideally `config.eager_load = false`). 
+
+With the [Spring](https://github.com/rails/spring) pre-loader (included with new Rails apps), you ideally keep `config.eager_load = false` as per development. Sometimes you may end up with a hybrid configuration (`config.eager_load = true`, `config.cache_classes = true` AND `config.enable_dependency_loading = true`), see [spring issue](https://github.com/rails/spring/issues/519#issuecomment-348324369). However it might be simpler to keep the same configuration as development, and work out whatever it is that is causing autoloading to fail (perhaps by the results of your CI test results). 
+
+Occasionally you may need to explicitly eager_load by using `Rails
+.application.eager_load!` in the setup of your tests -- this might occur if your [tests involve multithreading](https://stackoverflow.com/questions/25796409/in-rails-how-can-i-eager-load-all-code-before-a-specific-rspec-test). 
diff --git a/guides/source/caching_with_rails.md b/guides/source/caching_with_rails.md
index 6cdce5c2f4..f760f0a005 100644
--- a/guides/source/caching_with_rails.md
+++ b/guides/source/caching_with_rails.md
@@ -32,7 +32,7 @@ Basic Caching
 This is an introduction to three types of caching techniques: page, action and
 fragment caching. By default Rails provides fragment caching. In order to use
 page and action caching you will need to add `actionpack-page_caching` and
-`actionpack-action_caching` to your Gemfile.
+`actionpack-action_caching` to your `Gemfile`.
 
 By default, caching is only enabled in your production environment. To play
 around with caching locally you'll want to enable caching in your local
@@ -100,9 +100,9 @@ called key-based expiration.
 
 Cache fragments will also be expired when the view fragment changes (e.g., the
 HTML in the view changes). The string of characters at the end of the key is a
-template tree digest. It is an MD5 hash computed based on the contents of the
-view fragment you are caching. If you change the view fragment, the MD5 hash
-will change, expiring the existing file.
+template tree digest. It is a hash digest computed based on the contents of the
+view fragment you are caching. If you change the view fragment, the digest will
+change, expiring the existing file.
 
 TIP: Cache stores like Memcached will automatically delete old cache files.
 
@@ -175,10 +175,28 @@ class Game < ApplicationRecord
 end
 ```
 
-With `touch` set to true, any action which changes `updated_at` for a game
+With `touch` set to `true`, any action which changes `updated_at` for a game
 record will also change it for the associated product, thereby expiring the
 cache.
 
+### Shared Partial Caching
+
+It is possible to share partials and associated caching between files with different mime types. For example shared partial caching allows template writers to share a partial between HTML and JavaScript files. When templates are collected in the template resolver file paths they only include the template language extension and not the mime type. Because of this templates can be used for multiple mime types. Both HTML and JavaScript requests will respond to the following code:
+
+```ruby
+render(partial: 'hotels/hotel', collection: @hotels, cached: true)
+```
+
+Will load a file named `hotels/hotel.erb`.
+
+Another option is to include the full filename of the partial to render.
+
+```ruby
+render(partial: 'hotels/hotel.html.erb', collection: @hotels, cached: true)
+```
+
+Will load a file named `hotels/hotel.html.erb` in any file mime type, for example you could include this partial in a JavaScript file.
+
 ### Managing dependencies
 
 In order to correctly invalidate the cache, you need to properly define the
@@ -272,7 +290,7 @@ Sometimes you need to cache a particular value or query result instead of cachin
 
 The most efficient way to implement low-level caching is using the `Rails.cache.fetch` method. This method does both reading and writing to the cache. When passed only a single argument, the key is fetched and value from the cache is returned. If a block is passed, that block will be executed in the event of a cache miss. The return value of the block will be written to the cache under the given cache key, and that return value will be returned. In case of cache hit, the cached value will be returned without executing the block.
 
-Consider the following example. An application has a `Product` model with an instance method that looks up the product’s price on a competing website. The data returned by this method would be perfect for low-level caching:
+Consider the following example. An application has a `Product` model with an instance method that looks up the product's price on a competing website. The data returned by this method would be perfect for low-level caching:
 
 ```ruby
 class Product < ApplicationRecord
@@ -284,7 +302,7 @@ class Product < ApplicationRecord
 end
 ```
 
-NOTE: Notice that in this example we used the `cache_key` method, so the resulting cache-key will be something like `products/233-20140225082222765838000/competing_price`. `cache_key` generates a string based on the model’s `id` and `updated_at` attributes. This is a common convention and has the benefit of invalidating the cache whenever the product is updated. In general, when you use low-level caching for instance level information, you need to generate a cache key.
+NOTE: Notice that in this example we used the `cache_key` method, so the resulting cache key will be something like `products/233-20140225082222765838000/competing_price`. `cache_key` generates a string based on the model's `id` and `updated_at` attributes. This is a common convention and has the benefit of invalidating the cache whenever the product is updated. In general, when you use low-level caching for instance level information, you need to generate a cache key.
 
 ### SQL Caching
 
@@ -348,9 +366,9 @@ There are some common options used by all cache implementations. These can be pa
 
 * `:namespace` - This option can be used to create a namespace within the cache store. It is especially useful if your application shares a cache with other applications.
 
-* `:compress` - This option can be used to indicate that compression should be used in the cache. This can be useful for transferring large cache entries over a slow network.
+* `:compress` - Enabled by default. Compresses cache entries so more data can be stored in the same memory footprint, leading to fewer cache evictions and higher hit rates.
 
-* `:compress_threshold` - This option is used in conjunction with the `:compress` option to indicate a threshold under which cache entries should not be compressed. This defaults to 16 kilobytes.
+* `:compress_threshold` - Defaults to 1kB. Cache entries larger than this threshold, specified in bytes, are compressed.
 
 * `:expires_in` - This option sets an expiration time in seconds for the cache entry when it will be automatically removed from the cache.
 
@@ -387,10 +405,10 @@ store is not appropriate for large application deployments. However, it can
 work well for small, low traffic sites with only a couple of server processes,
 as well as development and test environments.
 
-New Rails projects are configured to use this implementation in development environment by default. 
+New Rails projects are configured to use this implementation in development environment by default.
 
-NOTE: Since processes will not share cache data when using `:memory_store`, 
-it will not be possible to manually read, write or expire the cache via the Rails console.
+NOTE: Since processes will not share cache data when using `:memory_store`,
+it will not be possible to manually read, write, or expire the cache via the Rails console.
 
 ### ActiveSupport::Cache::FileStore
 
@@ -426,6 +444,78 @@ The `write` and `fetch` methods on this cache accept two additional options that
 config.cache_store = :mem_cache_store, "cache-1.example.com", "cache-2.example.com"
 ```
 
+### ActiveSupport::Cache::RedisCacheStore
+
+The Redis cache store takes advantage of Redis support for automatic eviction
+when it reaches max memory, allowing it to behave much like a Memcached cache server.
+
+Deployment note: Redis doesn't expire keys by default, so take care to use a
+dedicated Redis cache server. Don't fill up your persistent-Redis server with
+volatile cache data! Read the
+[Redis cache server setup guide](https://redis.io/topics/lru-cache) in detail.
+
+For a cache-only Redis server, set `maxmemory-policy` to one of the variants of allkeys.
+Redis 4+ supports least-frequently-used eviction (`allkeys-lfu`), an excellent
+default choice. Redis 3 and earlier should use least-recently-used eviction (`allkeys-lru`).
+
+Set cache read and write timeouts relatively low. Regenerating a cached value
+is often faster than waiting more than a second to retrieve it. Both read and
+write timeouts default to 1 second, but may be set lower if your network is
+consistently low-latency.
+
+By default, the cache store will not attempt to reconnect to Redis if the
+connection fails during a request. If you experience frequent disconnects you
+may wish to enable reconnect attempts.
+
+Cache reads and writes never raise exceptions; they just return `nil` instead,
+behaving as if there was nothing in the cache. To gauge whether your cache is
+hitting exceptions, you may provide an `error_handler` to report to an
+exception gathering service. It must accept three keyword arguments: `method`,
+the cache store method that was originally called; `returning`, the value that
+was returned to the user, typically `nil`; and `exception`, the exception that
+was rescued.
+
+To get started, add the redis gem to your Gemfile:
+
+```ruby
+gem 'redis'
+```
+
+You can enable support for the faster [hiredis](https://github.com/redis/hiredis)
+connection library by additionally adding its ruby wrapper to your Gemfile:
+
+```ruby
+gem 'hiredis'
+```
+
+Redis cache store will automatically require & use hiredis if available. No further
+configuration is needed.
+
+Finally, add the configuration in the relevant `config/environments/*.rb` file:
+
+```ruby
+config.cache_store = :redis_cache_store, { url: ENV['REDIS_URL'] }
+```
+
+A more complex, production Redis cache store may look something like this:
+
+```ruby
+cache_servers = %w(redis://cache-01:6379/0 redis://cache-02:6379/0)
+config.cache_store = :redis_cache_store, { url: cache_servers,
+
+  connect_timeout:    30,  # Defaults to 20 seconds
+  read_timeout:       0.2, # Defaults to 1 second
+  write_timeout:      0.2, # Defaults to 1 second
+  reconnect_attempts: 1,   # Defaults to 0
+
+  error_handler: -> (method:, returning:, exception:) {
+    # Report errors to Sentry as warnings
+    Raven.capture_exception exception, level: 'warning',
+      tags: { method: method, returning: returning }
+  }
+}
+```
+
 ### ActiveSupport::Cache::NullStore
 
 This cache store implementation is meant to be used only in development or test environments and it never stores anything. This can be very useful in development when you have code that interacts directly with `Rails.cache` but caching may interfere with being able to see the results of code changes. With this cache store, all `fetch` and `read` operations will result in a miss.
@@ -580,7 +670,7 @@ Caching in Development
 ----------------------
 
 It's common to want to test the caching strategy of your application
-in development mode. Rails provides the rake task `dev:cache` to 
+in development mode. Rails provides the rake task `dev:cache` to
 easily toggle caching on/off.
 
 ```bash
diff --git a/guides/source/command_line.md b/guides/source/command_line.md
index 2cd8e02a77..58a2d6d30f 100644
--- a/guides/source/command_line.md
+++ b/guides/source/command_line.md
@@ -161,7 +161,7 @@ $ bin/rails generate controller Greetings hello
      create      app/assets/stylesheets/greetings.scss
 ```
 
-What all did this generate? It made sure a bunch of directories were in our application, and created a controller file, a view file, a functional test file, a helper for the view, a JavaScript file and a stylesheet file.
+What all did this generate? It made sure a bunch of directories were in our application, and created a controller file, a view file, a functional test file, a helper for the view, a JavaScript file, and a stylesheet file.
 
 Check out the controller and modify it a little (in `app/controllers/greetings_controller.rb`):
 
@@ -290,7 +290,7 @@ INFO: You can also use the alias "c" to invoke the console: `rails c`.
 You can specify the environment in which the `console` command should operate.
 
 ```bash
-$ bin/rails console staging
+$ bin/rails console -e staging
 ```
 
 If you wish to test out some code without changing any data, you can do that by invoking `rails console --sandbox`.
@@ -329,7 +329,7 @@ With the `helper` method it is possible to access Rails and your application's h
 
 ### `rails dbconsole`
 
-`rails dbconsole` figures out which database you're using and drops you into whichever command line interface you would use with it (and figures out the command line parameters to give to it, too!). It supports MySQL (including MariaDB), PostgreSQL and SQLite3.
+`rails dbconsole` figures out which database you're using and drops you into whichever command line interface you would use with it (and figures out the command line parameters to give to it, too!). It supports MySQL (including MariaDB), PostgreSQL, and SQLite3.
 
 INFO: You can also use the alias "db" to invoke the dbconsole: `rails db`.
 
@@ -431,16 +431,16 @@ INFO: You can also use `bin/rails -T`  to get the list of tasks.
 ```bash
 $ bin/rails about
 About your application's environment
-Rails version             5.1.0
-Ruby version              2.2.2 (x86_64-linux)
-RubyGems version          2.4.6
-Rack version              2.0.1
+Rails version             6.0.0
+Ruby version              2.5.0 (x86_64-linux)
+RubyGems version          2.7.3
+Rack version              2.0.4
 JavaScript Runtime        Node.js (V8)
 Middleware:               Rack::Sendfile, ActionDispatch::Static, ActionDispatch::Executor, ActiveSupport::Cache::Strategy::LocalCache::Middleware, Rack::Runtime, Rack::MethodOverride, ActionDispatch::RequestId, ActionDispatch::RemoteIp, Sprockets::Rails::QuietAssets, Rails::Rack::Logger, ActionDispatch::ShowExceptions, WebConsole::Middleware, ActionDispatch::DebugExceptions, ActionDispatch::Reloader, ActionDispatch::Callbacks, ActiveRecord::Migration::CheckPending, ActionDispatch::Cookies, ActionDispatch::Session::CookieStore, ActionDispatch::Flash, Rack::Head, Rack::ConditionalGet, Rack::ETag
 Application root          /home/foobar/commandsapp
 Environment               development
 Database adapter          sqlite3
-Database schema version   20110805173523
+Database schema version   20180205173523
 ```
 
 ### `assets`
@@ -457,7 +457,7 @@ More information about migrations can be found in the [Migrations](active_record
 
 ### `notes`
 
-`bin/rails notes` will search through your code for comments beginning with FIXME, OPTIMIZE or TODO. The search is done in files with extension `.builder`, `.rb`, `.rake`, `.yml`, `.yaml`, `.ruby`, `.css`, `.js` and `.erb` for both default and custom annotations.
+`bin/rails notes` will search through your code for comments beginning with FIXME, OPTIMIZE, or TODO. The search is done in files with extension `.builder`, `.rb`, `.rake`, `.yml`, `.yaml`, `.ruby`, `.css`, `.js`, and `.erb` for both default and custom annotations.
 
 ```bash
 $ bin/rails notes
@@ -500,7 +500,7 @@ app/models/article.rb:
 
 NOTE. When using specific annotations and custom annotations, the annotation name (FIXME, BUG etc) is not displayed in the output lines.
 
-By default, `rails notes` will look in the `app`, `config`, `db`, `lib` and `test` directories. If you would like to search other directories, you can configure them using `config.annotations.register_directories` option.
+By default, `rails notes` will look in the `app`, `config`, `db`, `lib`, and `test` directories. If you would like to search other directories, you can configure them using `config.annotations.register_directories` option.
 
 ```ruby
 config.annotations.register_directories("spec", "vendor")
@@ -537,8 +537,8 @@ The `tmp:` namespaced tasks will help you clear and create the `Rails.root/tmp`
 * `rails tmp:cache:clear` clears `tmp/cache`.
 * `rails tmp:sockets:clear` clears `tmp/sockets`.
 * `rails tmp:screenshots:clear` clears `tmp/screenshots`.
-* `rails tmp:clear` clears all cache, sockets and screenshot files.
-* `rails tmp:create` creates tmp directories for cache, sockets and pids.
+* `rails tmp:clear` clears all cache, sockets, and screenshot files.
+* `rails tmp:create` creates tmp directories for cache, sockets, and pids.
 
 ### Miscellaneous
 
@@ -587,7 +587,7 @@ $ bin/rails "task_name[value 1]" # entire argument string should be quoted
 $ bin/rails db:nothing
 ```
 
-NOTE: If your need to interact with your application models, perform database queries and so on, your task should depend on the `environment` task, which will load your application code.
+NOTE: If your need to interact with your application models, perform database queries, and so on, your task should depend on the `environment` task, which will load your application code.
 
 The Rails Advanced Command Line
 -------------------------------
@@ -659,6 +659,6 @@ development:
 ...
 ```
 
-It also generated some lines in our database.yml configuration corresponding to our choice of PostgreSQL for database.
+It also generated some lines in our `database.yml` configuration corresponding to our choice of PostgreSQL for database.
 
 NOTE. The only catch with using the SCM options is that you have to make your application's directory first, then initialize your SCM, then you can run the `rails new` command to generate the basis of your app.
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index d4e1d7b5dd..d4aa6546a7 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -62,12 +62,10 @@ These configuration methods are to be called on a `Rails::Railtie` object, such
 
 * `config.autoload_once_paths` accepts an array of paths from which Rails will autoload constants that won't be wiped per request. Relevant if `config.cache_classes` is `false`, which is the case in development mode by default. Otherwise, all autoloading happens only once. All elements of this array must also be in `autoload_paths`. Default is an empty array.
 
-* `config.autoload_paths` accepts an array of paths from which Rails will autoload constants. Default is all directories under `app`.
+* `config.autoload_paths` accepts an array of paths from which Rails will autoload constants. Default is all directories under `app`. It is no longer recommended to adjust this. See [Autoloading and Reloading Constants](autoloading_and_reloading_constants.html#autoload-paths-and-eager-load-paths)
 
 * `config.cache_classes` controls whether or not application classes and modules should be reloaded on each request. Defaults to `false` in development mode, and `true` in test and production modes.
 
-* `config.action_view.cache_template_loading` controls whether or not templates should be reloaded on each request. Defaults to whatever is set for `config.cache_classes`.
-
 * `config.beginning_of_week` sets the default beginning of week for the
 application. Accepts a valid week day symbol (e.g. `:monday`).
 
@@ -88,7 +86,7 @@ application. Accepts a valid week day symbol (e.g. `:monday`).
     end
     ```
 
-* `config.eager_load` when `true`, eager loads all registered `config.eager_load_namespaces`. This includes your application, engines, Rails frameworks and any other registered namespace.
+* `config.eager_load` when `true`, eager loads all registered `config.eager_load_namespaces`. This includes your application, engines, Rails frameworks, and any other registered namespace.
 
 * `config.eager_load_namespaces` registers namespaces that are eager loaded when `config.eager_load` is `true`. All namespaces in the list must respond to the `eager_load!` method.
 
@@ -138,7 +136,7 @@ defaults to `:debug` for all environments. The available log levels are: `:debug
 
 * `config.reload_classes_only_on_change` enables or disables reloading of classes only when tracked files change. By default tracks everything on autoload paths and is set to `true`. If `config.cache_classes` is `true`, this option is ignored.
 
-* `secrets.secret_key_base` is used for specifying a key which allows sessions for the application to be verified against a known secure key to prevent tampering. Applications get `secrets.secret_key_base` initialized to a random key present in `config/secrets.yml`.
+* `secret_key_base` is used for specifying a key which allows sessions for the application to be verified against a known secure key to prevent tampering. Applications get a random generated key in test and development environments, other environments should set one in `config/credentials.yml.enc`.
 
 * `config.public_file_server.enabled` configures Rails to serve static files from the public directory. This option defaults to `true`, but in the production environment it is set to `false` because the server software (e.g. NGINX or Apache) used to run the application should serve static files instead. If you are running or testing your app in production mode using WEBrick (it is not recommended to use WEBrick in production) set the option to `true.` Otherwise, you won't be able to use page caching and request for files that exist under the public directory.
 
@@ -202,6 +200,7 @@ The full set of methods that can be used in this block are as follows:
 * `force_plural` allows pluralized model names. Defaults to `false`.
 * `helper` defines whether or not to generate helpers. Defaults to `true`.
 * `integration_tool` defines which integration tool to use to generate integration tests. Defaults to `:test_unit`.
+* `system_tests` defines which integration tool to use to generate system tests. Defaults to `:test_unit`.
 * `javascripts` turns on the hook for JavaScript files in generators. Used in Rails for when the `scaffold` generator is run. Defaults to `true`.
 * `javascript_engine` configures the engine to be used (for eg. coffee) when generating assets. Defaults to `:js`.
 * `orm` defines which orm to use. Defaults to `false` and will use Active Record by default.
@@ -322,6 +321,10 @@ All these configuration options are delegated to the `I18n` library.
 
 * `config.active_record.schema_migrations_table_name` lets you set a string to be used as the name of the schema migrations table.
 
+* `config.active_record.internal_metadata_table_name` lets you set a string to be used as the name of the internal metadata table.
+
+* `config.active_record.protected_environments` lets you set an array of names of environments where destructive actions should be prohibited.
+
 * `config.active_record.pluralize_table_names` specifies whether Rails will look for singular or plural table names in the database. If set to `true` (the default), then the Customer class will use the `customers` table. If set to false, then the Customer class will use the `customer` table.
 
 * `config.active_record.default_timezone` determines whether to use `Time.local` (if set to `:local`) or `Time.utc` (if set to `:utc`) when pulling dates and times from the database. The default is `:utc`.
@@ -391,15 +394,21 @@ by setting up a Rake task which runs
     ```
 
   for all models and all boolean columns, after which the flag must be set to true
-by adding the following to your application.rb file:
+by adding the following to your `application.rb` file:
 
     ```ruby
     Rails.application.config.active_record.sqlite3.represent_boolean_as_integer = true
     ```
 
-The schema dumper adds one additional configuration option:
+The schema dumper adds two additional configuration options:
+
+* `ActiveRecord::SchemaDumper.ignore_tables` accepts an array of tables that should _not_ be included in any generated schema file.
 
-* `ActiveRecord::SchemaDumper.ignore_tables` accepts an array of tables that should _not_ be included in any generated schema file. This setting is ignored unless `config.active_record.schema_format == :ruby`.
+* `ActiveRecord::SchemaDumper.fk_ignore_pattern` allows setting a different regular
+  expression that will be used to decide whether a foreign key's name should be
+  dumped to db/schema.rb or not. By default, foreign key names starting with
+  `fk_rails_` are not exported to the database schema dump.
+  Defaults to `/^fk_rails_[0-9a-f]{10}$/`.
 
 ### Configuring Action Controller
 
@@ -459,7 +468,10 @@ The schema dumper adds one additional configuration option:
     config.action_dispatch.default_headers = {
       'X-Frame-Options' => 'SAMEORIGIN',
       'X-XSS-Protection' => '1; mode=block',
-      'X-Content-Type-Options' => 'nosniff'
+      'X-Content-Type-Options' => 'nosniff',
+      'X-Download-Options' => 'noopen',
+      'X-Permitted-Cross-Domain-Policies' => 'none',
+      'Referrer-Policy' => 'strict-origin-when-cross-origin'
     }
     ```
 
@@ -487,6 +499,19 @@ Defaults to `'signed cookie'`.
   authenticated encrypted cookie salt. Defaults to `'authenticated encrypted
   cookie'`.
 
+* `config.action_dispatch.encrypted_cookie_cipher` sets the cipher to be
+  used for encrypted cookies. This defaults to `"aes-256-gcm"`.
+
+* `config.action_dispatch.signed_cookie_digest` sets the digest to be
+  used for signed cookies. This defaults to `"SHA1"`.
+
+* `config.action_dispatch.cookies_rotations` allows rotating
+  secrets, ciphers, and digests for encrypted and signed cookies.
+
+* `config.action_dispatch.use_authenticated_cookie_encryption` controls whether
+  signed and encrypted cookies use the AES-256-GCM cipher or
+  the older AES-256-CBC cipher. It defaults to `true`.
+
 * `config.action_dispatch.perform_deep_munge` configures whether `deep_munge`
   method should be performed on the parameters. See [Security Guide](security.html#unsafe-query-generation)
   for more information. It defaults to `true`.
@@ -525,6 +550,8 @@ Defaults to `'signed cookie'`.
 
 `config.action_view` includes a small number of configuration settings:
 
+* `config.action_view.cache_template_loading` controls whether or not templates should be reloaded on each request. Defaults to whatever is set for `config.cache_classes`.
+
 * `config.action_view.field_error_proc` provides an HTML generator for displaying errors that come from Active Model. The default is
 
     ```ruby
@@ -563,12 +590,23 @@ Defaults to `'signed cookie'`.
   error should be raised for missing translations.
 
 * `config.action_view.automatically_disable_submit_tag` determines whether
-  submit_tag should automatically disable on click, this defaults to `true`.
+  `submit_tag` should automatically disable on click, this defaults to `true`.
 
 * `config.action_view.debug_missing_translation` determines whether to wrap the missing translations key in a `<span>` tag or not. This defaults to `true`.
 
 * `config.action_view.form_with_generates_remote_forms` determines whether `form_with` generates remote forms or not. This defaults to `true`.
 
+* `config.action_view.form_with_generates_ids` determines whether `form_with` generates ids on inputs. This defaults to `true`.
+
+* `config.action_view.default_enforce_utf8` determines whether forms are generated with a hidden tag that forces older versions of Internet Explorer to submit forms encoded in UTF-8. This defaults to `false`.
+
+* `config.action_view.finalize_compiled_template_methods` determines
+  whether the methods on `ActionView::CompiledTemplates` that templates
+  compile themselves to are removed when template instances are
+  destroyed by the garbage collector. This helps prevent memory leaks in
+  development mode, but for large test suites, disabling this option in
+  the test environment can improve performance. This defaults to `true`.
+
 ### Configuring Action Mailer
 
 There are a number of settings available on `config.action_mailer`:
@@ -657,6 +695,8 @@ There are a few configuration options available in Active Support:
 
 * `config.active_support.time_precision` sets the precision of JSON encoded time values. Defaults to `3`.
 
+* `config.active_support.use_sha1_digests` specifies whether to use SHA-1 instead of MD5 to generate non-sensitive digests, such as the ETag header. Defaults to false.
+
 * `ActiveSupport::Logger.silencer` is set to `false` to disable the ability to silence logging in a block. The default is `true`.
 
 * `ActiveSupport::Cache::Store.logger` specifies the logger to use within cache store operations.
@@ -720,6 +760,8 @@ There are a few configuration options available in Active Support:
 
 * `config.active_job.logger` accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then used to log information from Active Job. You can retrieve this logger by calling `logger` on either an Active Job class or an Active Job instance. Set to `nil` to disable logging.
 
+* `config.active_job.custom_serializers` allows to set custom argument serializers. Defaults to `[]`.
+
 ### Configuring Action Cable
 
 * `config.action_cable.url` accepts a string for the URL for where
@@ -731,6 +773,43 @@ main application.
 You can set this as nil to not mount Action Cable as part of your
 normal Rails server.
 
+
+### Configuring Active Storage
+
+`config.active_storage` provides the following configuration options:
+
+* `config.active_storage.variant_processor` accepts a symbol `:mini_magick` or `:vips`, specifying whether variant transformations will be performed with MiniMagick or ruby-vips. The default is `:mini_magick`.
+
+* `config.active_storage.analyzers` accepts an array of classes indicating the analyzers available for Active Storage blobs. The default is `[ActiveStorage::Analyzer::ImageAnalyzer, ActiveStorage::Analyzer::VideoAnalyzer]`. The former can extract width and height of an image blob; the latter can extract width, height, duration, angle, and aspect ratio of a video blob.
+
+* `config.active_storage.previewers` accepts an array of classes indicating the image previewers available in Active Storage blobs. The default is `[ActiveStorage::Previewer::PDFPreviewer, ActiveStorage::Previewer::VideoPreviewer]`. The former can generate a thumbnail from the first page of a PDF blob; the latter from the relevant frame of a video blob.
+
+* `config.active_storage.paths` accepts a hash of options indicating the locations of previewer/analyzer commands. The default is `{}`, meaning the commands will be looked for in the default path. Can include any of these options:
+    * `:ffprobe` - The location of the ffprobe executable.
+    * `:mutool` - The location of the mutool executable.
+    * `:ffmpeg` - The location of the ffmpeg executable.
+
+   ```ruby
+   config.active_storage.paths[:ffprobe] = '/usr/local/bin/ffprobe'
+   ```
+
+* `config.active_storage.variable_content_types` accepts an array of strings indicating the content types that Active Storage can transform through ImageMagick. The default is `%w(image/png image/gif image/jpg image/jpeg image/vnd.adobe.photoshop)`.
+
+* `config.active_storage.content_types_to_serve_as_binary` accepts an array of strings indicating the content types that Active Storage will always serve as an attachment, rather than inline. The default is `%w(text/html
+text/javascript image/svg+xml application/postscript application/x-shockwave-flash text/xml application/xml application/xhtml+xml)`.
+
+* `config.active_storage.queue` can be used to set the name of the Active Job queue used to perform jobs like analyzing the content of a blob or purging a blog.
+
+  ```ruby
+  config.active_job.queue = :low_priority
+  ```
+
+* `config.active_storage.logger` can be used to set the logger used by Active Storage. Accepts a logger conforming to the interface of Log4r or the default Ruby Logger class.
+
+  ```ruby
+  config.active_job.logger = ActiveSupport::Logger.new(STDOUT)
+  ```
+
 ### Configuring a Database
 
 Just about every Rails application will interact with a database. You can connect to the database by setting an environment variable `ENV['DATABASE_URL']` or by using a configuration file called `config/database.yml`.
@@ -964,7 +1043,7 @@ By default Rails ships with three environments: "development", "test", and "prod
 
 Imagine you have a server which mirrors the production environment but is only used for testing. Such a server is commonly called a "staging server". To define an environment called "staging" for this server, just create a file called `config/environments/staging.rb`. Please use the contents of any existing file in `config/environments` as a starting point and make the necessary changes from there.
 
-That environment is no different than the default ones, start a server with `rails server -e staging`, a console with `rails console staging`, `Rails.env.staging?` works, etc.
+That environment is no different than the default ones, start a server with `rails server -e staging`, a console with `rails console -e staging`, `Rails.env.staging?` works, etc.
 
 
 ### Deploy to a subdirectory (relative url root)
@@ -994,11 +1073,11 @@ Deploying your application using a reverse proxy has definite advantages over tr
 
 Many modern web servers can be used as a proxy server to balance third-party elements such as caching servers or application servers.
 
-One such application server you can use is [Unicorn](http://unicorn.bogomips.org/) to run behind a reverse proxy.
+One such application server you can use is [Unicorn](https://bogomips.org/unicorn/) to run behind a reverse proxy.
 
 In this case, you would need to configure the proxy server (NGINX, Apache, etc) to accept connections from your application server (Unicorn). By default Unicorn will listen for TCP connections on port 8080, but you can change the port or configure it to use sockets instead.
 
-You can find more information in the [Unicorn readme](http://unicorn.bogomips.org/README.html) and understand the [philosophy](http://unicorn.bogomips.org/PHILOSOPHY.html) behind it.
+You can find more information in the [Unicorn readme](https://bogomips.org/unicorn/README.html) and understand the [philosophy](https://bogomips.org/unicorn/PHILOSOPHY.html) behind it.
 
 Once you've configured the application server, you must proxy requests to it by configuring your web server appropriately. For example your NGINX config may include:
 
@@ -1026,7 +1105,7 @@ server {
 }
 ```
 
-Be sure to read the [NGINX documentation](http://nginx.org/en/docs/) for the most up-to-date information.
+Be sure to read the [NGINX documentation](https://nginx.org/en/docs/) for the most up-to-date information.
 
 
 Rails Environment Settings
@@ -1048,7 +1127,7 @@ After loading the framework and any gems in your application, Rails turns to loa
 
 NOTE: You can use subfolders to organize your initializers if you like, because Rails will look into the whole file hierarchy from the initializers folder on down.
 
-TIP: If you have any ordering dependency in your initializers, you can control the load order through naming. Initializer files are loaded in alphabetical order by their path. For example, `01_critical.rb` will be loaded before `02_normal.rb`.
+TIP: While Rails supports numbering of initializer file names for load ordering purposes, a better technique is to place any code that need to load in a specific order within the same file. This reduces file name churn, makes dependencies more explicit, and can help surface new concepts within your application.
 
 Initialization events
 ---------------------
@@ -1127,7 +1206,7 @@ Below is a comprehensive list of all the initializers found in Rails in the orde
 
 * `i18n.callbacks`: In the development environment, sets up a `to_prepare` callback which will call `I18n.reload!` if any of the locales have changed since the last request. In production mode this callback will only run on the first request.
 
-* `active_support.deprecation_behavior`: Sets up deprecation reporting for environments, defaulting to `:log` for development, `:notify` for production and `:stderr` for test. If a value isn't set for `config.active_support.deprecation` then this initializer will prompt the user to configure this line in the current environment's `config/environments` file. Can be set to an array of values.
+* `active_support.deprecation_behavior`: Sets up deprecation reporting for environments, defaulting to `:log` for development, `:notify` for production, and `:stderr` for test. If a value isn't set for `config.active_support.deprecation` then this initializer will prompt the user to configure this line in the current environment's `config/environments` file. Can be set to an array of values.
 
 * `active_support.initialize_time_zone`: Sets the default time zone for the application based on the `config.time_zone` setting, which defaults to "UTC".
 
@@ -1186,23 +1265,23 @@ Below is a comprehensive list of all the initializers found in Rails in the orde
 
 * `add_routing_paths`: Loads (by default) all `config/routes.rb` files (in the application and railties, including engines) and sets up the routes for the application.
 
-* `add_locales`: Adds the files in `config/locales` (from the application, railties and engines) to `I18n.load_path`, making available the translations in these files.
+* `add_locales`: Adds the files in `config/locales` (from the application, railties, and engines) to `I18n.load_path`, making available the translations in these files.
 
-* `add_view_paths`: Adds the directory `app/views` from the application, railties and engines to the lookup path for view files for the application.
+* `add_view_paths`: Adds the directory `app/views` from the application, railties, and engines to the lookup path for view files for the application.
 
 * `load_environment_config`: Loads the `config/environments` file for the current environment.
 
-* `prepend_helpers_path`: Adds the directory `app/helpers` from the application, railties and engines to the lookup path for helpers for the application.
+* `prepend_helpers_path`: Adds the directory `app/helpers` from the application, railties, and engines to the lookup path for helpers for the application.
 
-* `load_config_initializers`: Loads all Ruby files from `config/initializers` in the application, railties and engines. The files in this directory can be used to hold configuration settings that should be made after all of the frameworks are loaded.
+* `load_config_initializers`: Loads all Ruby files from `config/initializers` in the application, railties, and engines. The files in this directory can be used to hold configuration settings that should be made after all of the frameworks are loaded.
 
 * `engines_blank_point`: Provides a point-in-initialization to hook into if you wish to do anything before engines are loaded. After this point, all railtie and engine initializers are run.
 
-* `add_generator_templates`: Finds templates for generators at `lib/templates` for the application, railties and engines and adds these to the `config.generators.templates` setting, which will make the templates available for all generators to reference.
+* `add_generator_templates`: Finds templates for generators at `lib/templates` for the application, railties, and engines and adds these to the `config.generators.templates` setting, which will make the templates available for all generators to reference.
 
 * `ensure_autoload_once_paths_as_subset`: Ensures that the `config.autoload_once_paths` only contains paths from `config.autoload_paths`. If it contains extra paths, then an exception will be raised.
 
-* `add_to_prepare_blocks`: The block for every `config.to_prepare` call in the application, a railtie or engine is added to the `to_prepare` callbacks for Action Dispatch which will be run per request in development, or before the first request in production.
+* `add_to_prepare_blocks`: The block for every `config.to_prepare` call in the application, a railtie, or engine is added to the `to_prepare` callbacks for Action Dispatch which will be run per request in development, or before the first request in production.
 
 * `add_builtin_route`: If the application is running under the development environment then this will append the route for `rails/info/properties` to the application routes. This route provides the detailed information such as Rails and Ruby version for `public/index.html` in a default Rails application.
 
@@ -1210,7 +1289,7 @@ Below is a comprehensive list of all the initializers found in Rails in the orde
 
 * `eager_load!`: If `config.eager_load` is `true`, runs the `config.before_eager_load` hooks and then calls `eager_load!` which will load all `config.eager_load_namespaces`.
 
-* `finisher_hook`: Provides a hook for after the initialization of process of the application is complete, as well as running all the `config.after_initialize` blocks for the application, railties and engines.
+* `finisher_hook`: Provides a hook for after the initialization of process of the application is complete, as well as running all the `config.after_initialize` blocks for the application, railties, and engines.
 
 * `set_routes_reloader_hook`: Configures Action Dispatch to reload the routes file using `ActiveSupport::Callbacks.to_run`.
 
@@ -1302,13 +1381,13 @@ Search Engines Indexing
 -----------------------
 
 Sometimes, you may want to prevent some pages of your application to be visible
-on search sites like Google, Bing, Yahoo or Duck Duck Go. The robots that index
+on search sites like Google, Bing, Yahoo, or Duck Duck Go. The robots that index
 these sites will first analyze the `http://your-site.com/robots.txt` file to
 know which pages it is allowed to index.
 
 Rails creates this file for you inside the `/public` folder. By default, it allows
 search engines to index all pages of your application. If you want to block
-indexing on all pages of you application, use this:
+indexing on all pages of your application, use this:
 
 ```
 User-agent: *
diff --git a/guides/source/contributing_to_ruby_on_rails.md b/guides/source/contributing_to_ruby_on_rails.md
index 7424818757..ba5d7bbee8 100644
--- a/guides/source/contributing_to_ruby_on_rails.md
+++ b/guides/source/contributing_to_ruby_on_rails.md
@@ -23,7 +23,7 @@ README](https://github.com/rails/rails/blob/master/README.md), everyone interact
 Reporting an Issue
 ------------------
 
-Ruby on Rails uses [GitHub Issue Tracking](https://github.com/rails/rails/issues) to track issues (primarily bugs and contributions of new code). If you've found a bug in Ruby on Rails, this is the place to start. You'll need to create a (free) GitHub account in order to submit an issue, to comment on them or to create pull requests.
+Ruby on Rails uses [GitHub Issue Tracking](https://github.com/rails/rails/issues) to track issues (primarily bugs and contributions of new code). If you've found a bug in Ruby on Rails, this is the place to start. You'll need to create a (free) GitHub account in order to submit an issue, to comment on them, or to create pull requests.
 
 NOTE: Bugs in the most recent released version of Ruby on Rails are likely to get the most attention. Also, the Rails core team is always interested in feedback from those who can take the time to test _edge Rails_ (the code for the version of Rails that is currently under development). Later in this guide, you'll find out how to get edge Rails for testing.
 
@@ -37,7 +37,7 @@ Then, don't get your hopes up! Unless you have a "Code Red, Mission Critical, th
 
 ### Create an Executable Test Case
 
-Having a way to reproduce your issue will be very helpful for others to help confirm, investigate and ultimately fix your issue. You can do this by providing an executable test case. To make this process easier, we have prepared several bug report templates for you to use as a starting point:
+Having a way to reproduce your issue will be very helpful for others to help confirm, investigate, and ultimately fix your issue. You can do this by providing an executable test case. To make this process easier, we have prepared several bug report templates for you to use as a starting point:
 
 * Template for Active Record (models, database) issues: [gem](https://github.com/rails/rails/blob/master/guides/bug_report_templates/active_record_gem.rb) / [master](https://github.com/rails/rails/blob/master/guides/bug_report_templates/active_record_master.rb)
 * Template for testing Active Record (migration) issues: [gem](https://github.com/rails/rails/blob/master/guides/bug_report_templates/active_record_migrations_gem.rb) / [master](https://github.com/rails/rails/blob/master/guides/bug_report_templates/active_record_migrations_master.rb)
@@ -84,7 +84,9 @@ discussions new features require.
 Helping to Resolve Existing Issues
 ----------------------------------
 
-As a next step beyond reporting issues, you can help the core team resolve existing issues. If you check the [issues list](https://github.com/rails/rails/issues) in GitHub Issues, you'll find lots of issues already requiring attention. What can you do for these? Quite a bit, actually:
+As a next step beyond reporting issues, you can help the core team resolve existing ones by providing feedback about them. If you are new to Rails core development, that might be a great way to walk your first steps, you'll get familiar with the code base and the processes.
+
+If you check the [issues list](https://github.com/rails/rails/issues) in GitHub Issues, you'll find lots of issues already requiring attention. What can you do for these? Quite a bit, actually:
 
 ### Verifying Bug Reports
 
@@ -130,9 +132,10 @@ Contributing to the Rails Documentation
 Ruby on Rails has two main sets of documentation: the guides, which help you
 learn about Ruby on Rails, and the API, which serves as a reference.
 
-You can help improve the Rails guides by making them more coherent, consistent or readable, adding missing information, correcting factual errors, fixing typos, or bringing them up to date with the latest edge Rails.
+You can help improve the Rails guides by making them more coherent, consistent, or readable, adding missing information, correcting factual errors, fixing typos, or bringing them up to date with the latest edge Rails.
 
-To do so, open a pull request to [Rails](https://github.com/rails/rails) on GitHub.
+To do so, make changes to Rails guides source files (located [here](https://github.com/rails/rails/tree/master/guides/source) on GitHub). Then open a pull request to apply your
+changes to master branch.
 
 When working with documentation, please take into account the [API Documentation Guidelines](api_documentation_guidelines.html) and the [Ruby on Rails Guides Guidelines](ruby_on_rails_guides_guidelines.html).
 
@@ -381,7 +384,7 @@ $ RUBYOPT=-W0 bundle exec rake test
 
 The CHANGELOG is an important part of every release. It keeps the list of changes for every Rails version.
 
-You should add an entry **to the top** of the CHANGELOG of the framework that you modified if you're adding or removing a feature, committing a bug fix or adding deprecation notices. Refactorings and documentation changes generally should not go to the CHANGELOG.
+You should add an entry **to the top** of the CHANGELOG of the framework that you modified if you're adding or removing a feature, committing a bug fix, or adding deprecation notices. Refactorings and documentation changes generally should not go to the CHANGELOG.
 
 A CHANGELOG entry should summarize what was changed and should end with the author's name. You can use multiple lines if you need more space and you can attach code examples indented with 4 spaces. If a change is related to a specific issue, you should attach the issue's number. Here is an example CHANGELOG entry:
 
@@ -395,7 +398,7 @@ A CHANGELOG entry should summarize what was changed and should end with the auth
           end
         end
 
-    You can continue after the code example and you can attach issue number. GH#1234
+    You can continue after the code example and you can attach issue number. Fixes #1234.
 
     *Your Name*
 ```
diff --git a/guides/source/credits.html.erb b/guides/source/credits.html.erb
deleted file mode 100644
index 5adbd12ac0..0000000000
--- a/guides/source/credits.html.erb
+++ /dev/null
@@ -1,80 +0,0 @@
-<% content_for :page_title do %>
-Ruby on Rails Guides: Credits
-<% end %>
-
-<% content_for :header_section do %>
-<h2>Credits</h2>
-
-<p>We'd like to thank the following people for their tireless contributions to this project.</p>
-
-<% end %>
-
-<h3 class="section">Rails Guides Reviewers</h3>
-
-<%= author('Vijay Dev', 'vijaydev', 'vijaydev.jpg') do %>
-  Vijayakumar, found as Vijay Dev on the web, is a web applications developer and an open source enthusiast who lives in Chennai, India. He started using Rails in 2009 and began actively contributing to Rails documentation in late 2010. He <a href="https://twitter.com/vijay_dev">tweets</a> a lot and also <a href="http://vijaydev.wordpress.com">blogs</a>.
-<% end %>
-
-<%= author('Xavier Noria', 'fxn', 'fxn.png') do %>
-  Xavier Noria has been into Ruby on Rails since 2005. He is a Rails core team member and enjoys combining his passion for Rails and his past life as a proofreader of math textbooks. Xavier is currently an independent Ruby on Rails consultant. Oh, he also <a href="http://twitter.com/fxn">tweets</a> and can be found everywhere as &quot;fxn&quot;.
-<% end %>
-
-<h3 class="section">Rails Guides Designers</h3>
-
-<%= author('Jason Zimdars', 'jz') do %>
-  Jason Zimdars is an experienced creative director and web designer who has lead UI and UX design for numerous websites and web applications. You can see more of his design and writing at <a href="http://www.thinkcage.com/">Thinkcage.com</a> or follow him on <a href="https://twitter.com/jasonzimdars">Twitter</a>.
-<% end %>
-
-<h3 class="section">Rails Guides Authors</h3>
-
-<%= author('Ryan Bigg', 'radar', 'radar.png') do %>
-  Ryan Bigg works as a Rails developer at <a href="http://marketplacer.com">Marketplacer</a> and has been working with Rails since 2006. He's the author of <a href="https://leanpub.com/multi-tenancy-rails">Multi Tenancy With Rails</a> and co-author of <a href="http://manning.com/bigg2">Rails 4 in Action</a>. He's written many gems which can be seen on <a href="https://github.com/radar">his GitHub page</a> and he also tweets prolifically as <a href="http://twitter.com/ryanbigg">@ryanbigg</a>.
-<% end %>
-
-<%= author('Oscar Del Ben', 'oscardelben', 'oscardelben.jpg') do %>
-Oscar Del Ben is a software engineer at <a href="http://www.businessinsider.com/google-buys-wildfire-2012-8">Wildfire</a>. He's a regular open source contributor (<a href="https://github.com/oscardelben">GitHub account</a>) and tweets regularly at <a href="https://twitter.com/oscardelben">@oscardelben</a>.
-  <% end %>
-
-<%= author('Frederick Cheung', 'fcheung') do %>
-  Frederick Cheung is Chief Wizard at Texperts where he has been using Rails since 2006. He is based in Cambridge (UK) and when not consuming fine ales he blogs at <a href="http://www.spacevatican.org">spacevatican.org</a>.
-<% end %>
-
-<%= author('Tore Darell', 'toretore') do %>
-  Tore Darell is an independent developer based in Menton, France who specialises in cruft-free web applications using Ruby, Rails and unobtrusive JavaScript. You can follow him on <a href="http://twitter.com/toretore">Twitter</a>.
-<% end %>
-
-<%= author('Jeff Dean', 'zilkey') do %>
-  Jeff Dean is a software engineer with <a href="http://pivotallabs.com">Pivotal Labs</a>.
-<% end %>
-
-<%= author('Mike Gunderloy', 'mgunderloy') do %>
-  Mike Gunderloy is a consultant with <a href="http://www.actionrails.com">ActionRails</a>. He brings 25 years of experience in a variety of languages to bear on his current work with Rails. His near-daily links and other blogging can be found at <a href="http://afreshcup.com">A Fresh Cup</a> and he <a href="http://twitter.com/MikeG1">twitters</a> too much.
-<% end %>
-
-<%= author('Mikel Lindsaar', 'raasdnil') do %>
-  Mikel Lindsaar has been working with Rails since 2006 and is the author of the Ruby <a href="https://github.com/mikel/mail">Mail gem</a> and core contributor (he helped re-write Action Mailer's API). Mikel is the founder of <a href="http://rubyx.com/">RubyX</a>, has a <a href="http://lindsaar.net/">blog</a> and <a href="http://twitter.com/raasdnil">tweets</a>.
-<% end %>
-
-<%= author('Cássio Marques', 'cmarques') do %>
-  Cássio Marques is a Brazilian software developer working with different programming languages such as Ruby, JavaScript, CPP and Java, as an independent consultant. He blogs at <a href="http://cassiomarques.wordpress.com">/* CODIFICANDO */</a>, which is mainly written in Portuguese, but will soon get a new section for posts with English translation.
-<% end %>
-
-<%= author('James Miller', 'bensie') do %>
-  James Miller is a software developer for <a href="http://www.jk-tech.com">JK Tech</a> in San Diego, CA. You can find James on GitHub, Gmail, Twitter, and Freenode as &quot;bensie&quot;.
-<% end %>
-
-<%= author('Pratik Naik', 'lifo') do %>
-  Pratik Naik is a Ruby on Rails developer at <a href="https://basecamp.com/">Basecamp</a> and maintains a blog at <a href="http://m.onkey.org">has_many :bugs, :through =&gt; :rails</a>. He also has a semi-active <a href="http://twitter.com/lifo">twitter account</a>.
-<% end %>
-
-<%= author('Emilio Tagua', 'miloops') do %>
-  Emilio Tagua &mdash;a.k.a. miloops&mdash; is an Argentinian entrepreneur, developer, open source contributor and Rails evangelist. Cofounder of <a href="http://eventioz.com">Eventioz</a>. He has been using Rails since 2006 and contributing since early 2008. Can be found at gmail, twitter, freenode, everywhere as &quot;miloops&quot;.
-<% end %>
-
-<%= author('Heiko Webers', 'hawe') do %>
-  Heiko Webers is the founder of <a href="http://www.bauland42.de">bauland42</a>, a German web application security consulting and development company focused on Ruby on Rails. He blogs at the <a href="http://www.rorsecurity.info">Ruby on Rails Security Project</a>. After 10 years of desktop application development, Heiko has rarely looked back.
-<% end %>
-
-<%= author('Akshay Surve', 'startupjockey', 'akshaysurve.jpg') do %>
-  Akshay Surve is the Founder at <a href="http://www.deltax.com">DeltaX</a>, hackathon specialist, a midnight code junkie and occasionally writes prose. You can connect with him on <a href="https://twitter.com/akshaysurve">Twitter</a>, <a href="http://www.linkedin.com/in/akshaysurve">Linkedin</a>, <a href="http://www.akshaysurve.com/">Personal Blog</a> or <a href="http://www.quora.com/Akshay-Surve">Quora</a>.
-<% end %>
diff --git a/guides/source/debugging_rails_applications.md b/guides/source/debugging_rails_applications.md
index 07c78be3db..b7476a4ab2 100644
--- a/guides/source/debugging_rails_applications.md
+++ b/guides/source/debugging_rails_applications.md
@@ -147,7 +147,7 @@ TIP: The default Rails log level is `debug` in all environments.
 
 ### Sending Messages
 
-To write in the current log use the `logger.(debug|info|warn|error|fatal)` method from within a controller, model or mailer:
+To write in the current log use the `logger.(debug|info|warn|error|fatal)` method from within a controller, model, or mailer:
 
 ```ruby
 logger.debug "Person attributes hash: #{@person.attributes.inspect}"
@@ -485,7 +485,7 @@ stack frames.
 
 ### Threads
 
-The debugger can list, stop, resume and switch between running threads by using
+The debugger can list, stop, resume, and switch between running threads by using
 the `thread` command (or the abbreviated `th`). This command has a handful of
 options:
 
@@ -777,7 +777,7 @@ deleted when that breakpoint is reached.
 * `finish [n]`: execute until the selected stack frame returns. If no frame
 number is given, the application will run until the currently selected frame
 returns. The currently selected frame starts out the most-recent frame or 0 if
-no frame positioning (e.g up, down or frame) has been performed. If a frame
+no frame positioning (e.g up, down, or frame) has been performed. If a frame
 number is given it will run until the specified frame returns.
 
 ### Editing
@@ -875,7 +875,7 @@ location of the `console` call; it won't be rendered on the spot of its
 invocation but next to your HTML content.
 
 The console executes pure Ruby code: You can define and instantiate
-custom classes, create new models and inspect variables.
+custom classes, create new models, and inspect variables.
 
 NOTE: Only one console can be rendered per request. Otherwise `web-console`
 will raise an error on the second `console` invocation.
diff --git a/guides/source/documents.yaml b/guides/source/documents.yaml
index 59205ee465..5cddf79eeb 100644
--- a/guides/source/documents.yaml
+++ b/guides/source/documents.yaml
@@ -72,7 +72,7 @@
       url: active_support_core_extensions.html
       description: This guide documents the Ruby core extensions defined in Active Support.
     -
-      name: Rails Internationalization API
+      name: Rails Internationalization (I18n) API
       url: i18n.html
       description: This guide covers how to add internationalization to your applications. Your application will be able to translate content to different languages, change pluralization rules, use correct date formats for each country, and so on.
     -
@@ -84,6 +84,10 @@
       url: active_job_basics.html
       description: This guide provides you with all you need to get started creating, enqueuing, and executing background jobs.
     -
+      name: Active Storage Overview
+      url: active_storage_overview.html
+      description: This guide covers how to attach files to your Active Record models.
+    -
       name: Testing Rails Applications
       url: testing.html
       description: This is a rather comprehensive guide to the various testing facilities in Rails. It covers everything from 'What is a test?' to Integration Testing. Enjoy.
@@ -104,7 +108,7 @@
       url: command_line.html
       description: This guide covers the command line tools provided by Rails.
     -
-      name: Asset Pipeline
+      name: The Asset Pipeline
       url: asset_pipeline.html
       description: This guide documents the asset pipeline.
     -
@@ -151,7 +155,7 @@
       url: rails_on_rack.html
       description: This guide covers Rails integration with Rack and interfacing with other Rack components.
     -
-      name: Creating and Customizing Rails Generators
+      name: Creating and Customizing Rails Generators & Templates
       url: generators.html
       description: This guide covers the process of adding a brand new generator to your extension or providing an alternative to an element of a built-in Rails generator (such as providing alternative test stubs for the scaffold generator).
     -
@@ -159,6 +163,11 @@
       url: engines.html
       description: This guide explains how to write a mountable engine.
       work_in_progress: true
+    -
+      name: Threading and Code Execution in Rails
+      url: threading_and_code_execution.html
+      description: This guide describes the considerations needed and tools available when working directly with concurrency in a Rails application.
+      work_in_progress: true
 -
   name: Contributing to Ruby on Rails
   documents:
@@ -178,7 +187,7 @@
   name: Maintenance Policy
   documents:
     -
-      name: Maintenance Policy
+      name: Maintenance Policy for Ruby on Rails
       url: maintenance_policy.html
       description: What versions of Ruby on Rails are currently supported, and when to expect new versions.
 -
@@ -189,6 +198,10 @@
       url: upgrading_ruby_on_rails.html
       description: This guide helps in upgrading applications to latest Ruby on Rails versions.
     -
+      name: Ruby on Rails 5.2 Release Notes
+      url: 5_2_release_notes.html
+      description: Release notes for Rails 5.2.
+    -
       name: Ruby on Rails 5.1 Release Notes
       url: 5_1_release_notes.html
       description: Release notes for Rails 5.1.
diff --git a/guides/source/engines.md b/guides/source/engines.md
index c7331b6ca4..9dbce5d09b 100644
--- a/guides/source/engines.md
+++ b/guides/source/engines.md
@@ -63,7 +63,7 @@ authentication for its parent applications, or
 [Thredded](https://github.com/thredded/thredded), an engine that provides forum
 functionality. There's also [Spree](https://github.com/spree/spree) which
 provides an e-commerce platform, and
-[RefineryCMS](https://github.com/refinery/refinerycms), a CMS engine.
+[Refinery CMS](https://github.com/refinery/refinerycms), a CMS engine.
 
 Finally, engines would not have been possible without the work of James Adam,
 Piotr Sarnacki, the Rails Core Team, and a number of other people. If you ever
@@ -188,7 +188,7 @@ inside the application, performing tasks such as adding the `app` directory of
 the engine to the load path for models, mailers, controllers, and views.
 
 The `isolate_namespace` method here deserves special notice. This call is
-responsible for isolating the controllers, models, routes and other things into
+responsible for isolating the controllers, models, routes, and other things into
 their own namespace, away from similar components inside the application.
 Without this, there is a possibility that the engine's components could "leak"
 into the application, causing unwanted disruption, or that important engine
@@ -461,7 +461,7 @@ rather than visiting `/articles`. This means that instead of
 
 Now that the engine can create new articles, it only makes sense to add
 commenting functionality as well. To do this, you'll need to generate a comment
-model, a comment controller and then modify the articles scaffold to display
+model, a comment controller, and then modify the articles scaffold to display
 comments and allow people to create new ones.
 
 From the application root, run the model generator. Tell it to generate a
@@ -537,12 +537,12 @@ directory at `app/views/blorgh/comments` and in it a new file called
 
 ```html+erb
 <h3>New comment</h3>
-<%= form_for [@article, @article.comments.build] do |f| %>
+<%= form_with(model: [@article, @article.comments.build], local: true) do |form| %>
   <p>
-    <%= f.label :text %><br>
-    <%= f.text_area :text %>
+    <%= form.label :text %><br>
+    <%= form.text_area :text %>
   </p>
-  <%= f.submit %>
+  <%= form.submit %>
 <% end %>
 ```
 
@@ -653,7 +653,7 @@ there isn't an application handy to test this out in, generate one using the
 $ rails new unicorn
 ```
 
-Usually, specifying the engine inside the Gemfile would be done by specifying it
+Usually, specifying the engine inside the `Gemfile` would be done by specifying it
 as a normal, everyday gem.
 
 ```ruby
@@ -783,8 +783,8 @@ added above the `title` field with this code:
 
 ```html+erb
 <div class="field">
-  <%= f.label :author_name %><br>
-  <%= f.text_field :author_name %>
+  <%= form.label :author_name %><br>
+  <%= form.text_field :author_name %>
 </div>
 ```
 
@@ -921,7 +921,7 @@ engine:
 mattr_accessor :author_class
 ```
 
-This method works like its brothers, `attr_accessor` and `cattr_accessor`, but
+This method works like its siblings, `attr_accessor` and `cattr_accessor`, but
 provides a setter and getter method on the module with the specified name. To
 use it, it must be referenced using `Blorgh.author_class`.
 
@@ -982,7 +982,7 @@ Blorgh.author_class = "User"
 WARNING: It's very important here to use the `String` version of the class,
 rather than the class itself. If you were to use the class, Rails would attempt
 to load that class and then reference the related table. This could lead to
-problems if the table wasn't already existing. Therefore, a `String` should be
+problems if the table didn't already exist. Therefore, a `String` should be
 used and then converted to a class using `constantize` in the engine later on.
 
 Go ahead and try to create a new article. You will see that it works exactly in the
@@ -998,7 +998,7 @@ some sort of identifier by which it can be referenced.
 #### General Engine Configuration
 
 Within an engine, there may come a time where you wish to use things such as
-initializers, internationalization or other configuration options. The great
+initializers, internationalization, or other configuration options. The great
 news is that these things are entirely possible, because a Rails engine shares
 much the same functionality as a Rails application. In fact, a Rails
 application's functionality is actually a superset of what is provided by
@@ -1020,11 +1020,11 @@ Testing an engine
 When an engine is generated, there is a smaller dummy application created inside
 it at `test/dummy`. This application is used as a mounting point for the engine,
 to make testing the engine extremely simple. You may extend this application by
-generating controllers, models or views from within the directory, and then use
+generating controllers, models, or views from within the directory, and then use
 those to test your engine.
 
 The `test` directory should be treated like a typical Rails testing environment,
-allowing for unit, functional and integration tests.
+allowing for unit, functional, and integration tests.
 
 ### Functional Tests
 
@@ -1322,7 +1322,7 @@ engine.
 
 Assets within an engine work in an identical way to a full application. Because
 the engine class inherits from `Rails::Engine`, the application will know to
-look up assets in the engine's 'app/assets' and 'lib/assets' directories.
+look up assets in the engine's `app/assets` and `lib/assets` directories.
 
 Like all of the other components of an engine, the assets should be namespaced.
 This means that if you have an asset called `style.css`, it should be placed at
@@ -1361,7 +1361,7 @@ that only exists for your engine. In this case, the host application doesn't
 need to require `admin.css` or `admin.js`. Only the gem's admin layout needs
 these assets. It doesn't make sense for the host app to include
 `"blorgh/admin.css"` in its stylesheets. In this situation, you should
-explicitly define these assets for precompilation.  This tells sprockets to add
+explicitly define these assets for precompilation.  This tells Sprockets to add
 your engine assets when `bin/rails assets:precompile` is triggered.
 
 You can define assets for precompilation in `engine.rb`:
@@ -1501,6 +1501,7 @@ To hook into the initialization process of one of the following classes use the
 | `ActionController::Base`          | `action_controller`                  |
 | `ActionController::TestCase`      | `action_controller_test_case`        |
 | `ActionDispatch::IntegrationTest` | `action_dispatch_integration_test`   |
+| `ActionDispatch::SystemTestCase`  | `action_dispatch_system_test_case`   |
 | `ActionMailer::Base`              | `action_mailer`                      |
 | `ActionMailer::TestCase`          | `action_mailer_test_case`            |
 | `ActionView::Base`                | `action_view`                        |
@@ -1513,14 +1514,14 @@ To hook into the initialization process of one of the following classes use the
 
 ## Configuration hooks
 
-These are the available configuration hooks. They do not hook into any particular framework, instead they run in context of the entire application.
+These are the available configuration hooks. They do not hook into any particular framework, but instead they run in context of the entire application.
 
-| Hook                   | Use Case                                                                              |
-| ---------------------- | ------------------------------------------------------------------------------------- |
-| `before_configuration` | First configurable block to run. Called before any initializers are run.              |
-| `before_initialize`    | Second configurable block to run. Called before frameworks initialize.                |
-| `before_eager_load`    | Third configurable block to run. Does not run if `config.cache_classes` set to false. |
-| `after_initialize`     | Last configurable block to run. Called after frameworks initialize.                   |
+| Hook                   | Use Case                                                                           |
+| ---------------------- | ---------------------------------------------------------------------------------- |
+| `before_configuration` | First configurable block to run. Called before any initializers are run.           |
+| `before_initialize`    | Second configurable block to run. Called before frameworks initialize.             |
+| `before_eager_load`    | Third configurable block to run. Does not run if `config.eager_load` set to false. |
+| `after_initialize`     | Last configurable block to run. Called after frameworks initialize.                |
 
 ### Example
 
diff --git a/guides/source/form_helpers.md b/guides/source/form_helpers.md
index f46f1648b3..0ee64c855e 100644
--- a/guides/source/form_helpers.md
+++ b/guides/source/form_helpers.md
@@ -1,7 +1,7 @@
 **DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.**
 
-Form Helpers
-============
+Action View Form Helpers
+========================
 
 Forms in web applications are an essential interface for user input. However, form markup can quickly become tedious to write and maintain because of the need to handle form control naming and its numerous attributes. Rails does away with this complexity by providing view helpers for generating form markup. However, since these helpers have different use cases, developers need to know the differences between the helper methods before putting them to use.
 
@@ -165,7 +165,7 @@ make it easier for users to click the inputs.
 Other form controls worth mentioning are textareas, password fields,
 hidden fields, search fields, telephone fields, date fields, time fields,
 color fields, datetime-local fields, month fields, week fields,
-URL fields, email fields, number fields and range fields:
+URL fields, email fields, number fields, and range fields:
 
 ```erb
 <%= text_area_tag(:message, "Hi, nice site", size: "24x6") %>
@@ -208,7 +208,7 @@ Output:
 Hidden inputs are not shown to the user but instead hold data like any textual input. Values inside them can be changed with JavaScript.
 
 IMPORTANT: The search, telephone, date, time, color, datetime, datetime-local,
-month, week, URL, email, number and range inputs are HTML5 controls.
+month, week, URL, email, number, and range inputs are HTML5 controls.
 If you require your app to have a consistent experience in older browsers,
 you will need an HTML5 polyfill (provided by CSS and/or JavaScript).
 There is definitely [no shortage of solutions for this](https://github.com/Modernizr/Modernizr/wiki/HTML5-Cross-Browser-Polyfills), although a popular tool at the moment is
@@ -274,10 +274,12 @@ There are a few things to note here:
 The resulting HTML is:
 
 ```html
-<form accept-charset="UTF-8" action="/articles" method="post" class="nifty_form">
-  <input id="article_title" name="article[title]" type="text" />
-  <textarea id="article_body" name="article[body]" cols="60" rows="12"></textarea>
-  <input name="commit" type="submit" value="Create" />
+<form class="nifty_form" id="new_article" action="/articles" accept-charset="UTF-8" method="post">
+  <input name="utf8" type="hidden" value="&#x2713;" />
+  <input type="hidden" name="authenticity_token" value="NRkFyRWxdYNfUg7vYxLOp2SLf93lvnl+QwDWorR42Dp6yZXPhHEb6arhDOIWcqGit8jfnrPwL781/xlrzj63TA==" />
+  <input type="text" name="article[title]" id="article_title" />
+  <textarea name="article[body]" id="article_body" cols="60" rows="12"></textarea>
+  <input type="submit" name="commit" value="Create" data-disable-with="Create" />
 </form>
 ```
 
@@ -299,9 +301,11 @@ You can create a similar binding without actually creating `<form>` tags with th
 which produces the following output:
 
 ```html
-<form accept-charset="UTF-8" action="/people" class="new_person" id="new_person" method="post">
-  <input id="person_name" name="person[name]" type="text" />
-  <input id="contact_detail_phone_number" name="contact_detail[phone_number]" type="text" />
+<form class="new_person" id="new_person" action="/people" accept-charset="UTF-8" method="post">
+  <input name="utf8" type="hidden" value="&#x2713;" />
+  <input type="hidden" name="authenticity_token" value="bL13x72pldyDD8bgtkjKQakJCpd4A8JdXGbfksxBDHdf1uC0kCMqe2tvVdUYfidJt0fj3ihC4NxiVHv8GVYxJA==" />
+  <input type="text" name="person[name]" id="person_name" />
+  <input type="text" name="contact_detail[phone_number]" id="contact_detail_phone_number" />
 </form>
 ```
 
@@ -438,7 +442,7 @@ output:
 
 Whenever Rails sees that the internal value of an option being generated matches this value, it will add the `selected` attribute to that option.
 
-WARNING: When `:include_blank` or `:prompt` are not present, `:include_blank` is forced true if the select attribute `required` is true, display `size` is one and `multiple` is not true.
+WARNING: When `:include_blank` or `:prompt` are not present, `:include_blank` is forced true if the select attribute `required` is true, display `size` is one, and `multiple` is not true.
 
 You can add arbitrary attributes to the options using hashes:
 
@@ -705,7 +709,7 @@ Understanding Parameter Naming Conventions
 ------------------------------------------
 
 As you've seen in the previous sections, values from forms can be at the top level of the `params` hash or nested in another hash. For example, in a standard `create`
-action for a Person model, `params[:person]` would usually be a hash of all the attributes for the person to create. The `params` hash can also contain arrays, arrays of hashes and so on.
+action for a Person model, `params[:person]` would usually be a hash of all the attributes for the person to create. The `params` hash can also contain arrays, arrays of hashes, and so on.
 
 Fundamentally HTML forms don't know about any sort of structured data, all they generate is name-value pairs, where pairs are just plain strings. The arrays and hashes you see in your application are the result of some parameter naming conventions that Rails uses.
 
@@ -759,7 +763,7 @@ We can mix and match these two concepts. One element of a hash might be an array
 
 This would result in `params[:addresses]` being an array of hashes with keys `line1`, `line2` and `city`. Rails decides to start accumulating values in a new hash whenever it encounters an input name that already exists in the current hash.
 
-There's a restriction, however, while hashes can be nested arbitrarily, only one level of "arrayness" is allowed. Arrays can usually be replaced by hashes; for example, instead of having an array of model objects, one can have a hash of model objects keyed by their id, an array index or some other parameter.
+There's a restriction, however, while hashes can be nested arbitrarily, only one level of "arrayness" is allowed. Arrays can usually be replaced by hashes; for example, instead of having an array of model objects, one can have a hash of model objects keyed by their id, an array index, or some other parameter.
 
 WARNING: Array parameters do not play well with the `check_box` helper. According to the HTML specification unchecked checkboxes submit no value. However it is often convenient for a checkbox to always submit a value. The `check_box` helper fakes this by creating an auxiliary hidden input with the same name. If the checkbox is unchecked only the hidden input is submitted and if it is checked then both are submitted but the value submitted by the checkbox takes precedence. When working with array parameters this duplicate submission will confuse Rails since duplicate input names are how it decides when to start a new array element. It is preferable to either use `check_box_tag` or to use hashes instead of arrays.
 
@@ -819,7 +823,7 @@ will create inputs like
 <input id="person_address_primary_1_city" name="person[address][primary][1][city]" type="text" value="bologna" />
 ```
 
-As a general rule the final input name is the concatenation of the name given to `fields_for`/`form_for`, the index value and the name of the attribute. You can also pass an `:index` option directly to helpers such as `text_field`, but it is usually less repetitive to specify this at the form builder level rather than on individual input controls.
+As a general rule the final input name is the concatenation of the name given to `fields_for`/`form_for`, the index value, and the name of the attribute. You can also pass an `:index` option directly to helpers such as `text_field`, but it is usually less repetitive to specify this at the form builder level rather than on individual input controls.
 
 As a shortcut you can append [] to the name and omit the `:index` option. This is the same as specifying `index: address` so
 
@@ -869,7 +873,7 @@ Or if you don't want to render an `authenticity_token` field:
 Building Complex Forms
 ----------------------
 
-Many apps grow beyond simple forms editing a single object. For example, when creating a `Person` you might want to allow the user to (on the same form) create multiple address records (home, work, etc.). When later editing that person the user should be able to add, remove or amend addresses as necessary.
+Many apps grow beyond simple forms editing a single object. For example, when creating a `Person` you might want to allow the user to (on the same form) create multiple address records (home, work, etc.). When later editing that person the user should be able to add, remove, or amend addresses as necessary.
 
 ### Configuring the Model
 
@@ -886,7 +890,7 @@ class Address < ApplicationRecord
 end
 ```
 
-This creates an `addresses_attributes=` method on `Person` that allows you to create, update and (optionally) destroy addresses.
+This creates an `addresses_attributes=` method on `Person` that allows you to create, update, and (optionally) destroy addresses.
 
 ### Nested Forms
 
@@ -916,7 +920,7 @@ When an association accepts nested attributes `fields_for` renders its block onc
 ```ruby
 def new
   @person = Person.new
-  2.times { @person.addresses.build}
+  2.times { @person.addresses.build }
 end
 ```
 
diff --git a/guides/source/generators.md b/guides/source/generators.md
index b7b8262e4a..11fca5f9fb 100644
--- a/guides/source/generators.md
+++ b/guides/source/generators.md
@@ -221,7 +221,7 @@ If we want to avoid generating the default `app/assets/stylesheets/scaffolds.scs
   end
 ```
 
-The next customization on the workflow will be to stop generating stylesheet, JavaScript and test fixture files for scaffolds altogether. We can achieve that by changing our configuration to the following:
+The next customization on the workflow will be to stop generating stylesheet, JavaScript, and test fixture files for scaffolds altogether. We can achieve that by changing our configuration to the following:
 
 ```ruby
 config.generators do |g|
@@ -233,7 +233,7 @@ config.generators do |g|
 end
 ```
 
-If we generate another resource with the scaffold generator, we can see that stylesheet, JavaScript and fixture files are not created anymore. If you want to customize it further, for example to use DataMapper and RSpec instead of Active Record and TestUnit, it's just a matter of adding their gems to your application and configuring your generators.
+If we generate another resource with the scaffold generator, we can see that stylesheet, JavaScript, and fixture files are not created anymore. If you want to customize it further, for example to use DataMapper and RSpec instead of Active Record and TestUnit, it's just a matter of adding their gems to your application and configuring your generators.
 
 To demonstrate this, we are going to create a new helper generator that simply adds some instance variable readers. First, we create a generator within the rails namespace, as this is where rails searches for generators used as hooks:
 
diff --git a/guides/source/getting_started.md b/guides/source/getting_started.md
index 1e5c6fe3d0..de2c459cff 100644
--- a/guides/source/getting_started.md
+++ b/guides/source/getting_started.md
@@ -87,20 +87,18 @@ current version of Ruby installed:
 
 ```bash
 $ ruby -v
-ruby 2.3.1p112
+ruby 2.5.0
 ```
 
-Rails requires Ruby version 2.2.2 or later. If the version number returned is
+Rails requires Ruby version 2.4.1 or later. If the version number returned is
 less than that number, you'll need to install a fresh copy of Ruby.
 
-TIP: A number of tools exist to help you quickly install Ruby and Ruby
-on Rails on your system. Windows users can use [Rails Installer](http://railsinstaller.org),
-while macOS users can use [Tokaido](https://github.com/tokaido/tokaidoapp).
-For more installation methods for most Operating Systems take a look at
-[ruby-lang.org](https://www.ruby-lang.org/en/documentation/installation/).
+TIP: To quickly install Ruby and Ruby on Rails on your system in Windows, you can use 
+[Rails Installer](http://railsinstaller.org). For more installation methods for most 
+Operating Systems take a look at [ruby-lang.org](https://www.ruby-lang.org/en/documentation/installation/).
 
 If you are working on Windows, you should also install the
-[Ruby Installer Development Kit](http://rubyinstaller.org/downloads/).
+[Ruby Installer Development Kit](https://rubyinstaller.org/downloads/).
 
 You will also need an installation of the SQLite3 database.
 Many popular UNIX-like OSes ship with an acceptable version of SQLite3.
@@ -169,21 +167,24 @@ of the files and folders that Rails created by default:
 
 | File/Folder | Purpose |
 | ----------- | ------- |
-|app/|Contains the controllers, models, views, helpers, mailers, channels, jobs and assets for your application. You'll focus on this folder for the remainder of this guide.|
-|bin/|Contains the rails script that starts your app and can contain other scripts you use to setup, update, deploy or run your application.|
+|app/|Contains the controllers, models, views, helpers, mailers, channels, jobs, and assets for your application. You'll focus on this folder for the remainder of this guide.|
+|bin/|Contains the rails script that starts your app and can contain other scripts you use to setup, update, deploy, or run your application.|
 |config/|Configure your application's routes, database, and more. This is covered in more detail in [Configuring Rails Applications](configuring.html).|
-|config.ru|Rack configuration for Rack based servers used to start the application.|
+|config.ru|Rack configuration for Rack based servers used to start the application. For more information about Rack, see the [Rack website](https://rack.github.io/).|
 |db/|Contains your current database schema, as well as the database migrations.|
 |Gemfile<br>Gemfile.lock|These files allow you to specify what gem dependencies are needed for your Rails application. These files are used by the Bundler gem. For more information about Bundler, see the [Bundler website](https://bundler.io).|
 |lib/|Extended modules for your application.|
 |log/|Application log files.|
+|package.json|This file allows you to specify what npm dependencies are needed for your Rails application. This file is used by Yarn. For more information about Yarn, see the [Yarn website](https://yarnpkg.com/lang/en/).|
 |public/|The only folder seen by the world as-is. Contains static files and compiled assets.|
-|Rakefile|This file locates and loads tasks that can be run from the command line. The task definitions are defined throughout the components of Rails. Rather than changing Rakefile, you should add your own tasks by adding files to the `lib/tasks` directory of your application.|
+|Rakefile|This file locates and loads tasks that can be run from the command line. The task definitions are defined throughout the components of Rails. Rather than changing `Rakefile`, you should add your own tasks by adding files to the `lib/tasks` directory of your application.|
 |README.md|This is a brief instruction manual for your application. You should edit this file to tell others what your application does, how to set it up, and so on.|
+|storage/|Active Storage files for Disk Service. This is covered in [Active Storage Overview](active_storage_overview.html).|
 |test/|Unit tests, fixtures, and other test apparatus. These are covered in [Testing Rails Applications](testing.html).|
 |tmp/|Temporary files (like cache and pid files).|
 |vendor/|A place for all third-party code. In a typical Rails application this includes vendored gems.|
 |.gitignore|This file tells git which files (or patterns) it should ignore. See [GitHub - Ignoring files](https://help.github.com/articles/ignoring-files) for more info about ignoring files.
+|.ruby-version|This file contains the default Ruby version.|
 
 Hello, Rails!
 -------------
@@ -340,13 +341,13 @@ TIP: For more information about routing, refer to [Rails Routing from the Outsid
 Getting Up and Running
 ----------------------
 
-Now that you've seen how to create a controller, an action and a view, let's
+Now that you've seen how to create a controller, an action, and a view, let's
 create something with a bit more substance.
 
 In the Blog application, you will now create a new _resource_. A resource is the
-term used for a collection of similar objects, such as articles, people or
+term used for a collection of similar objects, such as articles, people, or
 animals.
-You can create, read, update and destroy items for a resource and these
+You can create, read, update, and destroy items for a resource and these
 operations are referred to as _CRUD_ operations.
 
 Rails provides a `resources` method which can be used to declare a standard REST
@@ -370,16 +371,17 @@ singular form `article` and makes meaningful use of the distinction.
 
 ```bash
 $ bin/rails routes
-      Prefix Verb   URI Pattern                  Controller#Action
-    articles GET    /articles(.:format)          articles#index
-             POST   /articles(.:format)          articles#create
- new_article GET    /articles/new(.:format)      articles#new
-edit_article GET    /articles/:id/edit(.:format) articles#edit
-     article GET    /articles/:id(.:format)      articles#show
-             PATCH  /articles/:id(.:format)      articles#update
-             PUT    /articles/:id(.:format)      articles#update
-             DELETE /articles/:id(.:format)      articles#destroy
-        root GET    /                            welcome#index
+       Prefix Verb   URI Pattern                  Controller#Action
+welcome_index GET    /welcome/index(.:format)     welcome#index
+     articles GET    /articles(.:format)          articles#index
+              POST   /articles(.:format)          articles#create
+  new_article GET    /articles/new(.:format)      articles#new
+ edit_article GET    /articles/:id/edit(.:format) articles#edit
+      article GET    /articles/:id(.:format)      articles#show
+              PATCH  /articles/:id(.:format)      articles#update
+              PUT    /articles/:id(.:format)      articles#update
+              DELETE /articles/:id(.:format)      articles#destroy
+         root GET    /                            welcome#index
 ```
 
 In the next section, you will add the ability to create new articles in your
@@ -459,8 +461,7 @@ You're getting this error now because Rails expects plain actions like this one
 to have views associated with them to display their information. With no view
 available, Rails will raise an exception.
 
-In the above image, the bottom line has been truncated. Let's see what the full
-error message looks like:
+Let's look at the full error message again:
 
 >ArticlesController#new is missing a template for this request format and variant. request.formats: ["text/html"] request.variant: [] NOTE! For XHR/Ajax or API requests, this action would normally respond with 204 No Content: an empty white screen. Since you're loading it in a web browser, we assume that you expected to actually render a template, not… nothing, so we're showing an error to be extra-clear. If you expect 204 No Content, carry on. That's what you'll get from an XHR or API request. Give it a shot.
 
@@ -502,7 +503,7 @@ write this content in it:
 ```
 
 When you refresh <http://localhost:3000/articles/new> you'll now see that the
-page has a title. The route, controller, action and view are now working
+page has a title. The route, controller, action, and view are now working
 harmoniously! It's time to create the form for a new article.
 
 ### The first form
@@ -565,15 +566,16 @@ To see what Rails will do with this, we look back at the output of
 ```bash
 $ bin/rails routes
       Prefix Verb   URI Pattern                  Controller#Action
-    articles GET    /articles(.:format)          articles#index
-             POST   /articles(.:format)          articles#create
- new_article GET    /articles/new(.:format)      articles#new
-edit_article GET    /articles/:id/edit(.:format) articles#edit
-     article GET    /articles/:id(.:format)      articles#show
-             PATCH  /articles/:id(.:format)      articles#update
-             PUT    /articles/:id(.:format)      articles#update
-             DELETE /articles/:id(.:format)      articles#destroy
-        root GET    /                            welcome#index
+welcome_index GET    /welcome/index(.:format)     welcome#index
+     articles GET    /articles(.:format)          articles#index
+              POST   /articles(.:format)          articles#create
+  new_article GET    /articles/new(.:format)      articles#new
+ edit_article GET    /articles/:id/edit(.:format) articles#edit
+      article GET    /articles/:id(.:format)      articles#show
+              PATCH  /articles/:id(.:format)      articles#update
+              PUT    /articles/:id(.:format)      articles#update
+              DELETE /articles/:id(.:format)      articles#destroy
+         root GET    /                            welcome#index
 ```
 
 The `articles_path` helper tells Rails to point the form to the URI Pattern
@@ -592,7 +594,7 @@ familiar error:
 You now need to create the `create` action within the `ArticlesController` for
 this to work.
 
-NOTE: by default `form_with` submits forms using Ajax thereby skipping full page
+NOTE: By default `form_with` submits forms using Ajax thereby skipping full page
 redirects. To make this guide easier to get into we've disabled that with
 `local: true` for now.
 
@@ -807,7 +809,7 @@ private
 
 TIP: For more information, refer to the reference above and
 [this blog article about Strong Parameters]
-(http://weblog.rubyonrails.org/2012/3/21/strong-parameters/).
+(https://weblog.rubyonrails.org/2012/3/21/strong-parameters/).
 
 ### Showing Articles
 
@@ -1119,10 +1121,10 @@ that otherwise `@article` would be `nil` in our view, and calling
 `@article.errors.any?` would throw an error.
 
 TIP: Rails automatically wraps fields that contain an error with a div
-with class `field_with_errors`. You can define a css rule to make them
+with class `field_with_errors`. You can define a CSS rule to make them
 standout.
 
-Now you'll get a nice error message when saving an article without title when
+Now you'll get a nice error message when saving an article without a title when
 you attempt to do just that on the new article form
 <http://localhost:3000/articles/new>:
 
@@ -1163,7 +1165,7 @@ it look as follows:
 ```html+erb
 <h1>Edit article</h1>
 
-<%= form_with(model: @article) do |form| %>
+<%= form_with(model: @article, local: true) do |form| %>
 
   <% if @article.errors.any? %>
     <div id="error_explanation">
@@ -1201,10 +1203,10 @@ it look as follows:
 This time we point the form to the `update` action, which is not defined yet
 but will be very soon.
 
-Passing the article object to the method, will automagically create url for submitting the edited article form.
-This option tells Rails that we want this form to be submitted
-via the `PATCH` HTTP method which is the HTTP method you're expected to use to
-**update** resources according to the REST protocol.
+Passing the article object to the method will automatically set the URL for
+submitting the edited article form. This option tells Rails that we want this
+form to be submitted via the `PATCH` HTTP method, which is the HTTP method you're
+expected to use to **update** resources according to the REST protocol.
 
 The arguments to `form_with` could be model objects, say, `model: @article` which would
 cause the helper to fill in the form with the fields of the object. Passing in a
@@ -1503,7 +1505,7 @@ appear.
 TIP: Learn more about Unobtrusive JavaScript on
 [Working With JavaScript in Rails](working_with_javascript_in_rails.html) guide.
 
-Congratulations, you can now create, show, list, update and destroy
+Congratulations, you can now create, show, list, update, and destroy
 articles.
 
 TIP: In general, Rails encourages using resources objects instead of
@@ -1519,7 +1521,7 @@ comments on articles.
 ### Generating a Model
 
 We're going to see the same generator that we used before when creating
-the `Article` model. This time we'll create a `Comment` model to hold
+the `Article` model. This time we'll create a `Comment` model to hold a
 reference to an article. Run this command in your terminal:
 
 ```bash
@@ -1766,7 +1768,7 @@ add that to the `app/views/articles/show.html.erb`.
 <% end %>
 
 <h2>Add a comment:</h2>
-<%= form_with(model: [ @article, @article.comments.build ]) do |form| %>
+<%= form_with(model: [ @article, @article.comments.build ], local: true) do |form| %>
   <p>
     <%= form.label :commenter %><br>
     <%= form.text_field :commenter %>
@@ -1832,7 +1834,7 @@ following:
 <%= render @article.comments %>
 
 <h2>Add a comment:</h2>
-<%= form_with(model: [ @article, @article.comments.build ]) do |form| %>
+<%= form_with(model: [ @article, @article.comments.build ], local: true) do |form| %>
   <p>
     <%= form.label :commenter %><br>
     <%= form.text_field :commenter %>
@@ -1854,7 +1856,7 @@ This will now render the partial in `app/views/comments/_comment.html.erb` once
 for each comment that is in the `@article.comments` collection. As the `render`
 method iterates over the `@article.comments` collection, it assigns each
 comment to a local variable named the same as the partial, in this case
-`comment` which is then available in the partial for us to show.
+`comment`, which is then available in the partial for us to show.
 
 ### Rendering a Partial Form
 
@@ -1862,7 +1864,7 @@ Let us also move that new comment section out to its own partial. Again, you
 create a file `app/views/comments/_form.html.erb` containing:
 
 ```html+erb
-<%= form_with(model: [ @article, @article.comments.build ]) do |form| %>
+<%= form_with(model: [ @article, @article.comments.build ], local: true) do |form| %>
   <p>
     <%= form.label :commenter %><br>
     <%= form.text_field :commenter %>
@@ -2057,13 +2059,13 @@ What's Next?
 Now that you've seen your first Rails application, you should feel free to
 update it and experiment on your own.
 
-Remember you don't have to do everything without help. As you need assistance
+Remember, you don't have to do everything without help. As you need assistance
 getting up and running with Rails, feel free to consult these support
 resources:
 
 * The [Ruby on Rails Guides](index.html)
-* The [Ruby on Rails Tutorial](http://railstutorial.org/book)
-* The [Ruby on Rails mailing list](http://groups.google.com/group/rubyonrails-talk)
+* The [Ruby on Rails Tutorial](https://www.railstutorial.org/book)
+* The [Ruby on Rails mailing list](https://groups.google.com/group/rubyonrails-talk)
 * The [#rubyonrails](irc://irc.freenode.net/#rubyonrails) channel on irc.freenode.net
 
 
diff --git a/guides/source/i18n.md b/guides/source/i18n.md
index dda16f755e..ec7582fa62 100644
--- a/guides/source/i18n.md
+++ b/guides/source/i18n.md
@@ -11,7 +11,7 @@ So, in the process of _internationalizing_ your Rails application you have to:
 
 * Ensure you have support for i18n.
 * Tell Rails where to find locale dictionaries.
-* Tell Rails how to set, preserve and switch locales.
+* Tell Rails how to set, preserve, and switch locales.
 
 In the process of _localizing_ your application you'll probably want to do the following three things:
 
@@ -42,6 +42,8 @@ Internationalization is a complex problem. Natural languages differ in so many w
 
 As part of this solution, **every static string in the Rails framework** - e.g. Active Record validation messages, time and date formats - **has been internationalized**. _Localization_ of a Rails application means defining translated values for these strings in desired languages.
 
+To localize store and update _content_ in your application (e.g. translate blog posts), see the [Translating model content](#translating-model-content) section.
+
 ### The Overall Architecture of the Library
 
 Thus, the Ruby I18n gem is split into two parts:
@@ -105,7 +107,7 @@ This means, that in the `:en` locale, the key _hello_ will map to the _Hello wor
 
 The I18n library will use **English** as a **default locale**, i.e. if a different locale is not set, `:en` will be used for looking up translations.
 
-NOTE: The i18n library takes a **pragmatic approach** to locale keys (after [some discussion](http://groups.google.com/group/rails-i18n/browse_thread/thread/14dede2c7dbe9470/80eec34395f64f3c?hl=en)), including only the _locale_ ("language") part, like `:en`, `:pl`, not the _region_ part, like `:en-US` or `:en-GB`, which are traditionally used for separating "languages" and "regional setting" or "dialects". Many international applications use only the "language" element of a locale such as `:cs`, `:th` or `:es` (for Czech, Thai and Spanish). However, there are also regional differences within different language groups that may be important. For instance, in the `:en-US` locale you would have $ as a currency symbol, while in `:en-GB`, you would have £. Nothing stops you from separating regional and other settings in this way: you just have to provide full "English - United Kingdom" locale in a `:en-GB` dictionary. Few gems such as [Globalize3](https://github.com/globalize/globalize) may help you implement it.
+NOTE: The i18n library takes a **pragmatic approach** to locale keys (after [some discussion](https://groups.google.com/forum/#!topic/rails-i18n/FN7eLH2-lHA)), including only the _locale_ ("language") part, like `:en`, `:pl`, not the _region_ part, like `:en-US` or `:en-GB`, which are traditionally used for separating "languages" and "regional setting" or "dialects". Many international applications use only the "language" element of a locale such as `:cs`, `:th`, or `:es` (for Czech, Thai, and Spanish). However, there are also regional differences within different language groups that may be important. For instance, in the `:en-US` locale you would have $ as a currency symbol, while in `:en-GB`, you would have £. Nothing stops you from separating regional and other settings in this way: you just have to provide full "English - United Kingdom" locale in a `:en-GB` dictionary.
 
 The **translations load path** (`I18n.load_path`) is an array of paths to files that will be loaded automatically. Configuring this path allows for customization of translations directory structure and file naming scheme.
 
@@ -313,7 +315,7 @@ In general, this approach is far less reliable than using the language header an
 WARNING: You may be tempted to store the chosen locale in a _session_ or a *cookie*. However, **do not do this**. The locale should be transparent and a part of the URL. This way you won't break people's basic assumptions about the web itself: if you send a URL to a friend, they should see the same page and content as you. A fancy word for this would be that you're being [*RESTful*](https://en.wikipedia.org/wiki/Representational_State_Transfer). Read more about the RESTful approach in [Stefan Tilkov's articles](https://www.infoq.com/articles/rest-introduction). Sometimes there are exceptions to this rule and those are discussed below.
 
 Internationalization and Localization
------------------------------------
+-------------------------------------
 
 OK! Now you've initialized I18n support for your Ruby on Rails application and told it which locale to use and how to preserve it between requests.
 
@@ -371,7 +373,7 @@ end
 
 ```html+erb
 # app/views/home/index.html.erb
-<h1><%=t :hello_world %></h1>
+<h1><%= t :hello_world %></h1>
 <p><%= flash[:notice] %></p>
 ```
 
@@ -416,7 +418,7 @@ If your translations are stored in YAML files, certain keys must be escaped. The
 
 Examples:
 
-```erb
+```yaml
 # config/locales/en.yml
 en:
   success:
@@ -430,12 +432,12 @@ en:
 ```
 
 ```ruby
-I18n.t 'success.true' # => 'True!'
-I18n.t 'success.on' # => 'On!'
+I18n.t 'success.true'  # => 'True!'
+I18n.t 'success.on'    # => 'On!'
 I18n.t 'success.false' # => 'False!'
 I18n.t 'failure.false' # => Translation Missing
-I18n.t 'failure.off' # => Translation Missing
-I18n.t 'failure.true' # => Translation Missing
+I18n.t 'failure.off'   # => Translation Missing
+I18n.t 'failure.true'  # => Translation Missing
 ```
 
 ### Passing Variables to Translations
@@ -502,7 +504,7 @@ OK! Now let's add a timestamp to the view, so we can demo the **date/time locali
 
 ```erb
 # app/views/home/index.html.erb
-<h1><%=t :hello_world %></h1>
+<h1><%= t :hello_world %></h1>
 <p><%= flash[:notice] %></p>
 <p><%= l Time.now, format: :short %></p>
 ```
@@ -594,7 +596,7 @@ Covered are features like these:
 
 ### Looking up Translations
 
-#### Basic Lookup, Scopes and Nested Keys
+#### Basic Lookup, Scopes, and Nested Keys
 
 Translations are looked up by keys which can be both Symbols or Strings, so these calls are equivalent:
 
@@ -827,14 +829,14 @@ For example when you add the following translations:
 en:
   activerecord:
     models:
-      user: Dude
+      user: Customer
     attributes:
       user:
         login: "Handle"
       # will translate User attribute "login" as "Handle"
 ```
 
-Then `User.model_name.human` will return "Dude" and `User.human_attribute_name("login")` will return "Handle".
+Then `User.model_name.human` will return "Customer" and `User.human_attribute_name("login")` will return "Handle".
 
 You can also set a plural form for model names, adding as following:
 
@@ -843,11 +845,11 @@ en:
   activerecord:
     models:
       user:
-        one: Dude
-        other: Dudes
+        one: Customer
+        other: Customers
 ```
 
-Then `User.model_name.human(count: 2)` will return "Dudes". With `count: 1` or without params will return "Dude".
+Then `User.model_name.human(count: 2)` will return "Customers". With `count: 1` or without params will return "Customer".
 
 In the event you need to access nested attributes within a given model, you should nest these under `model/attribute` at the model level of your translation file:
 
@@ -855,12 +857,12 @@ In the event you need to access nested attributes within a given model, you shou
 en:
   activerecord:
     attributes:
-      user/gender:
-        female: "Female"
-        male: "Male"
+      user/role:
+        admin: "Admin"
+        contributor: "Contributor"
 ```
 
-Then `User.human_attribute_name("gender.female")` will return "Female".
+Then `User.human_attribute_name("role.admin")` will return "Admin".
 
 NOTE: If you are using a class which includes `ActiveModel` and does not inherit from `ActiveRecord::Base`, replace `activerecord` with `activemodel` in the above key paths.
 
@@ -977,7 +979,7 @@ en:
 ```
 
 NOTE: In order to use this helper, you need to install [DynamicForm](https://github.com/joelmoss/dynamic_form)
-gem by adding this line to your Gemfile: `gem 'dynamic_form'`.
+gem by adding this line to your `Gemfile`: `gem 'dynamic_form'`.
 
 ### Translations for Action Mailer E-Mail Subjects
 
@@ -1050,7 +1052,7 @@ The Simple backend shipped with Active Support allows you to store translations
 
 For example a Ruby Hash providing translations can look like this:
 
-```yaml
+```ruby
 {
   pt: {
     foo: {
@@ -1099,13 +1101,11 @@ Customize your I18n Setup
 
 For several reasons the Simple backend shipped with Active Support only does the "simplest thing that could possibly work" _for Ruby on Rails_[^3] ... which means that it is only guaranteed to work for English and, as a side effect, languages that are very similar to English. Also, the simple backend is only capable of reading translations but cannot dynamically store them to any format.
 
-That does not mean you're stuck with these limitations, though. The Ruby I18n gem makes it very easy to exchange the Simple backend implementation with something else that fits better for your needs. E.g. you could exchange it with Globalize's Static backend:
+That does not mean you're stuck with these limitations, though. The Ruby I18n gem makes it very easy to exchange the Simple backend implementation with something else that fits better for your needs, by passing a backend instance to the `I18n.backend=` setter.
 
-```ruby
-I18n.backend = Globalize::Backend::Static.new
-```
+For example, you can replace the Simple backend with the the Chain backend to chain multiple backends together. This is useful when you want to use standard translations with a Simple backend but store custom application translations in a database or other backends.
 
-You can also use the Chain backend to chain multiple backends together. This is useful when you want to use standard translations with a Simple backend but store custom application translations in a database or other backends. For example, you could use the Active Record backend and fall back to the (default) Simple backend:
+With the Chain backend, you could use the Active Record backend and fall back to the (default) Simple backend:
 
 ```ruby
 I18n.backend = I18n::Backend::Chain.new(I18n::Backend::ActiveRecord.new, I18n.backend)
@@ -1166,28 +1166,37 @@ To do so, the helper forces `I18n#translate` to raise exceptions no matter what
 I18n.t :foo, raise: true # always re-raises exceptions from the backend
 ```
 
+Translating Model Content
+-------------------------
+
+The I18n API described in this guide is primarily intended for translating interface strings. If you are looking to translate model content (e.g. blog posts), you will need a different solution to help with this.
+
+Several gems can help with this:
+
+* [Globalize](https://github.com/globalize/globalize): Store translations on separate translation tables, one for each translated model
+* [Mobility](https://github.com/shioyama/mobility): Provides support for storing translations in many formats, including translation tables, json columns (Postgres), etc.
+* [Traco](https://github.com/barsoom/traco): Translatable columns for Rails 3 and 4, stored in the model table itself
+
 Conclusion
 ----------
 
 At this point you should have a good overview about how I18n support in Ruby on Rails works and are ready to start translating your project.
 
-If you want to discuss certain portions or have questions, please sign up to the [rails-i18n mailing list](http://groups.google.com/group/rails-i18n).
-
 
 Contributing to Rails I18n
 --------------------------
 
 I18n support in Ruby on Rails was introduced in the release 2.2 and is still evolving. The project follows the good Ruby on Rails development tradition of evolving solutions in gems and real applications first, and only then cherry-picking the best-of-breed of most widely useful features for inclusion in the core.
 
-Thus we encourage everybody to experiment with new ideas and features in gems or other libraries and make them available to the community. (Don't forget to announce your work on our [mailing list](http://groups.google.com/group/rails-i18n)!)
+Thus we encourage everybody to experiment with new ideas and features in gems or other libraries and make them available to the community. (Don't forget to announce your work on our [mailing list](https://groups.google.com/forum/#!forum/rails-i18n)!)
 
-If you find your own locale (language) missing from our [example translations data](https://github.com/svenfuchs/rails-i18n/tree/master/rails/locale) repository for Ruby on Rails, please [_fork_](https://github.com/guides/fork-a-project-and-submit-your-modifications) the repository, add your data and send a [pull request](https://help.github.com/articles/about-pull-requests/).
+If you find your own locale (language) missing from our [example translations data](https://github.com/svenfuchs/rails-i18n/tree/master/rails/locale) repository for Ruby on Rails, please [_fork_](https://github.com/guides/fork-a-project-and-submit-your-modifications) the repository, add your data, and send a [pull request](https://help.github.com/articles/about-pull-requests/).
 
 
 Resources
 ---------
 
-* [Google group: rails-i18n](http://groups.google.com/group/rails-i18n) - The project's mailing list.
+* [Google group: rails-i18n](https://groups.google.com/forum/#!forum/rails-i18n) - The project's mailing list.
 * [GitHub: rails-i18n](https://github.com/svenfuchs/rails-i18n) - Code repository and issue tracker for the rails-i18n project. Most importantly you can find lots of [example translations](https://github.com/svenfuchs/rails-i18n/tree/master/rails/locale) for Rails that should work for your application in most cases.
 * [GitHub: i18n](https://github.com/svenfuchs/i18n) - Code repository and issue tracker for the i18n gem.
 
diff --git a/guides/source/index.html.erb b/guides/source/index.html.erb
index 2fdf18a2e9..76f01fea0a 100644
--- a/guides/source/index.html.erb
+++ b/guides/source/index.html.erb
@@ -10,7 +10,9 @@ Ruby on Rails Guides
 <div id="subCol">
   <dl>
     <dt></dt>
-    <dd class="kindle">Rails Guides are also available for <%= link_to 'Kindle', @mobi %>.</dd>
+    <% unless @edge -%>
+      <dd class="kindle">Rails Guides are also available for <%= link_to 'Kindle', @mobi %>.</dd>
+    <% end -%>
     <dd class="work-in-progress">Guides marked with this icon are currently being worked on and will not be available in the Guides Index menu. While still useful, they may contain incomplete information and even errors. You can help by reviewing them and posting your comments and corrections.</dd>
   </dl>
 </div>
diff --git a/guides/source/initialization.md b/guides/source/initialization.md
index 0cfabe2a66..d3b122c7fe 100644
--- a/guides/source/initialization.md
+++ b/guides/source/initialization.md
@@ -93,7 +93,7 @@ require 'bundler/setup' # Set up gems listed in the Gemfile.
 
 In a standard Rails application, there's a `Gemfile` which declares all
 dependencies of the application. `config/boot.rb` sets
-`ENV['BUNDLE_GEMFILE']` to the location of this file. If the Gemfile
+`ENV['BUNDLE_GEMFILE']` to the location of this file. If the `Gemfile`
 exists, then `bundler/setup` is required. The require is used by Bundler to
 configure the load path for your Gemfile's dependencies.
 
@@ -116,8 +116,6 @@ A standard Rails application depends on several gems, specifically:
 * mail
 * mime-types
 * rack
-* rack-cache
-* rack-mount
 * rack-test
 * rails
 * railties
@@ -534,12 +532,12 @@ require "rails"
 
 %w(
   active_record/railtie
+  active_storage/engine
   action_controller/railtie
   action_view/railtie
   action_mailer/railtie
   active_job/railtie
   action_cable/engine
-  active_storage/engine
   rails/test_unit/railtie
   sprockets/railtie
 ).each do |railtie|
diff --git a/guides/source/kindle/rails_guides.opf.erb b/guides/source/kindle/rails_guides.opf.erb
index 63eeb007d7..1882ec1005 100644
--- a/guides/source/kindle/rails_guides.opf.erb
+++ b/guides/source/kindle/rails_guides.opf.erb
@@ -26,7 +26,7 @@
     <item id="<%= document['url'] %>" media-type="text/html" href="<%= document['url'] %>" />
   <% end %>
 
-  <% %w{toc.html credits.html welcome.html copyright.html}.each do |url| %>
+  <% %w{toc.html welcome.html copyright.html}.each do |url| %>
     <item id="<%= url %>" media-type="text/html" href="<%= url %>" />
   <% end %>
 
@@ -38,7 +38,6 @@
 <spine toc="toc">
   <itemref idref="toc.html" />
   <itemref idref="welcome.html" />
-  <itemref idref="credits.html" />
   <itemref idref="copyright.html" />
   <% documents_flat.each do |document| %>
     <itemref idref="<%= document['url'] %>" />
diff --git a/guides/source/kindle/toc.html.erb b/guides/source/kindle/toc.html.erb
index f310edd3a1..b77ac2e99d 100644
--- a/guides/source/kindle/toc.html.erb
+++ b/guides/source/kindle/toc.html.erb
@@ -14,11 +14,10 @@ Ruby on Rails Guides
         <% if document['work_in_progress']%>(WIP)<% end %>
       </li>
     <% end %>
-  </ul>  
+  </ul>
 <% end %>
 <hr />
 <ul>
-  <li><a href="credits.html">Credits</a></li>
   <li><a href="copyright.html">Copyright &amp; License</a></li>
 </ul>
 </div>
diff --git a/guides/source/kindle/toc.ncx.erb b/guides/source/kindle/toc.ncx.erb
index 5094fea4ca..9b73bc9bea 100644
--- a/guides/source/kindle/toc.ncx.erb
+++ b/guides/source/kindle/toc.ncx.erb
@@ -30,10 +30,6 @@
         </navLabel>
         <content src="welcome.html"/>
       </navPoint>
-      <navPoint class="article" id="credits" playOrder="3">
-        <navLabel><text>Credits</text></navLabel>
-        <content src="credits.html"/>
-      </navPoint>
       <navPoint class="article" id="copyright" playOrder="4">
         <navLabel><text>Copyright &amp; License</text></navLabel>
         <content src="copyright.html"/>
diff --git a/guides/source/layout.html.erb b/guides/source/layout.html.erb
index 334595e4d2..4ed2793fe3 100644
--- a/guides/source/layout.html.erb
+++ b/guides/source/layout.html.erb
@@ -29,7 +29,7 @@
         More Ruby on Rails
       </span>
       <ul class="more-info-links s-hidden">
-        <li class="more-info"><a href="http://weblog.rubyonrails.org/">Blog</a></li>
+        <li class="more-info"><a href="https://weblog.rubyonrails.org/">Blog</a></li>
         <li class="more-info"><a href="http://guides.rubyonrails.org/">Guides</a></li>
         <li class="more-info"><a href="http://api.rubyonrails.org/">API</a></li>
         <li class="more-info"><a href="https://stackoverflow.com/questions/tagged/ruby-on-rails">Ask for help</a></li>
@@ -59,7 +59,6 @@
           </div>
         </li>
         <li><a class="nav-item" href="contributing_to_ruby_on_rails.html">Contribute</a></li>
-        <li><a class="nav-item" href="credits.html">Credits</a></li>
         <li class="guides-index guides-index-small">
           <select class="guides-index-item nav-item">
             <option value="index.html">Guides Index</option>
@@ -99,9 +98,9 @@
           To get started, you can read our <%= link_to 'documentation contributions', 'http://edgeguides.rubyonrails.org/contributing_to_ruby_on_rails.html#contributing-to-the-rails-documentation' %> section.
         </p>
         <p>
-          You may also find incomplete content, or stuff that is not up to date.
+          You may also find incomplete content or stuff that is not up to date.
           Please do add any missing documentation for master. Make sure to check
-          <%= link_to 'Edge Guides','http://edgeguides.rubyonrails.org' %> first to verify
+          <%= link_to 'Edge Guides', 'http://edgeguides.rubyonrails.org' %> first to verify
           if the issues are already fixed or not on the master branch.
           Check the <%= link_to 'Ruby on Rails Guides Guidelines', 'ruby_on_rails_guides_guidelines.html' %>
           for style and conventions.
@@ -111,7 +110,7 @@
           <%= link_to 'open an issue', 'https://github.com/rails/rails/issues' %>.
         </p>
         <p>And last but not least, any kind of discussion regarding Ruby on Rails
-          documentation is very welcome in the <%= link_to 'rubyonrails-docs mailing list', 'https://groups.google.com/forum/#!forum/rubyonrails-docs' %>.
+          documentation is very welcome on the <%= link_to 'rubyonrails-docs mailing list', 'https://groups.google.com/forum/#!forum/rubyonrails-docs' %>.
         </p>
       </div>
     </div>
@@ -124,15 +123,8 @@
     </div>
   </div>
 
-  <script type="text/javascript" src="javascripts/jquery.min.js"></script>
-  <script type="text/javascript" src="javascripts/responsive-tables.js"></script>
-  <script type="text/javascript" src="javascripts/guides.js"></script>
   <script type="text/javascript" src="javascripts/syntaxhighlighter.js"></script>
-  <script type="text/javascript">
-    syntaxhighlighterConfig = {
-      autoLinks: false,
-    };
-    $(guidesIndex.bind);
-  </script>
+  <script type="text/javascript" src="javascripts/guides.js"></script>
+  <script type="text/javascript" src="javascripts/responsive-tables.js"></script>
 </body>
 </html>
diff --git a/guides/source/layouts_and_rendering.md b/guides/source/layouts_and_rendering.md
index 76b325d0bf..d7072a766b 100644
--- a/guides/source/layouts_and_rendering.md
+++ b/guides/source/layouts_and_rendering.md
@@ -71,23 +71,25 @@ If we want to display the properties of all the books in our view, we can do so
 <h1>Listing Books</h1>
 
 <table>
-  <tr>
-    <th>Title</th>
-    <th>Summary</th>
-    <th></th>
-    <th></th>
-    <th></th>
-  </tr>
-
-<% @books.each do |book| %>
-  <tr>
-    <td><%= book.title %></td>
-    <td><%= book.content %></td>
-    <td><%= link_to "Show", book %></td>
-    <td><%= link_to "Edit", edit_book_path(book) %></td>
-    <td><%= link_to "Remove", book, method: :delete, data: { confirm: "Are you sure?" } %></td>
-  </tr>
-<% end %>
+  <thead>
+    <tr>
+      <th>Title</th>
+      <th>Content</th>
+      <th colspan="3"></th>
+    </tr>
+  </thead>
+
+  <tbody>
+    <% @books.each do |book| %>
+      <tr>
+        <td><%= book.title %></td>
+        <td><%= book.content %></td>
+        <td><%= link_to "Show", book %></td>
+        <td><%= link_to "Edit", edit_book_path(book) %></td>
+        <td><%= link_to "Destroy", book, method: :delete, data: { confirm: "Are you sure?" } %></td>
+      </tr>
+    <% end %>
+  </tbody>
 </table>
 
 <br>
@@ -95,7 +97,7 @@ If we want to display the properties of all the books in our view, we can do so
 <%= link_to "New book", new_book_path %>
 ```
 
-NOTE: The actual rendering is done by subclasses of `ActionView::TemplateHandlers`. This guide does not dig into that process, but it's important to know that the file extension on your view controls the choice of template handler. Beginning with Rails 2, the standard extensions are `.erb` for ERB (HTML with embedded Ruby), and `.builder` for Builder (XML generator).
+NOTE: The actual rendering is done by nested classes of the module [`ActionView::Template::Handlers`](http://api.rubyonrails.org/classes/ActionView/Template/Handlers.html). This guide does not dig into that process, but it's important to know that the file extension on your view controls the choice of template handler.
 
 ### Using `render`
 
@@ -168,7 +170,7 @@ render a file, because Windows filenames do not have the same format as Unix fil
 
 #### Wrapping it up
 
-The above three ways of rendering (rendering another template within the controller, rendering a template within another controller and rendering an arbitrary file on the file system) are actually variants of the same action.
+The above three ways of rendering (rendering another template within the controller, rendering a template within another controller, and rendering an arbitrary file on the file system) are actually variants of the same action.
 
 In fact, in the BooksController class, inside of the update action where we want to render the edit template if the book does not update successfully, all of the following render calls would all render the `edit.html.erb` template in the `views/books` directory:
 
@@ -230,14 +232,14 @@ You can send an HTML string back to the browser by using the `:html` option to
 `render`:
 
 ```ruby
-render html: "<strong>Not Found</strong>".html_safe
+render html: helpers.tag.strong('Not Found')
 ```
 
 TIP: This is useful when you're rendering a small snippet of HTML code.
 However, you might want to consider moving it to a template file if the markup
 is complex.
 
-NOTE: When using `html:` option, HTML entities will be escaped if the string is not marked as HTML safe by using `html_safe` method.
+NOTE: When using `html:` option, HTML entities will be escaped if the string is not composed with `html_safe`-aware APIs.
 
 #### Rendering JSON
 
@@ -283,7 +285,7 @@ the response. Using `:plain` or `:html` might be more appropriate most of the
 time.
 
 NOTE: Unless overridden, your response returned from this render option will be
-`text/html`, as that is the default content type of Action Dispatch response.
+`text/plain`, as that is the default content type of Action Dispatch response.
 
 #### Options for `render`
 
@@ -401,7 +403,7 @@ Rails understands both numeric status codes and the corresponding symbols shown
 |                     | 511              | :network_authentication_required |
 
 NOTE:  If you try to render content along with a non-content status code
-(100-199, 204, 205 or 304), it will be dropped from the response.
+(100-199, 204, 205, or 304), it will be dropped from the response.
 
 ##### The `:formats` Option
 
@@ -1264,7 +1266,7 @@ You can also pass in arbitrary local variables to any partial you are rendering
 
 In this case, the partial will have access to a local variable `title` with the value "Products Page".
 
-TIP: Rails also makes a counter variable available within a partial called by the collection, named after the member of the collection followed by `_counter`. For example, if you're rendering `@products`, within the partial you can refer to `product_counter` to tell you how many times the partial has been rendered. This does not work in conjunction with the `as: :value` option.
+TIP: Rails also makes a counter variable available within a partial called by the collection, named after the title of the partial followed by `_counter`. For example, when rendering a collection `@products` the partial `_product.html.erb` can access the variable `product_counter` which indexes the number of times it has been rendered within the enclosing view.
 
 You can also specify a second partial to be rendered between instances of the main partial by using the `:spacer_template` option:
 
diff --git a/guides/source/maintenance_policy.md b/guides/source/maintenance_policy.md
index 1d6a4edb5b..2604d289e9 100644
--- a/guides/source/maintenance_policy.md
+++ b/guides/source/maintenance_policy.md
@@ -44,7 +44,7 @@ from.
 In special situations, where someone from the Core Team agrees to support more series,
 they are included in the list of supported series.
 
-**Currently included series:** `5.1.Z`.
+**Currently included series:** `5.2.Z`.
 
 Security Issues
 ---------------
@@ -59,16 +59,16 @@ be built from 1.2.2, and then added to the end of 1-2-stable. This means that
 security releases are easy to upgrade to if you're running the latest version
 of Rails.
 
-**Currently included series:** `5.1.Z`, `5.0.Z`.
+**Currently included series:** `5.2.Z`, `5.1.Z`.
 
 Severe Security Issues
 ----------------------
 
-For severe security issues we will provide new versions as above, and also the
+For severe security issues all releases in the current major series, and also the
 last major release series will receive patches and new versions. The
 classification of the security issue is judged by the core team.
 
-**Currently included series:** `5.1.Z`, `5.0.Z`, `4.2.Z`.
+**Currently included series:** `5.2.Z`, `5.1.Z`, `5.0.Z`, `4.2.Z`.
 
 Unsupported Release Series
 --------------------------
diff --git a/guides/source/plugins.md b/guides/source/plugins.md
index 0f0cde7634..5d18f8a1f4 100644
--- a/guides/source/plugins.md
+++ b/guides/source/plugins.md
@@ -135,7 +135,7 @@ To test that your method does what it says it does, run the unit tests with `bin
   2 runs, 2 assertions, 0 failures, 0 errors, 0 skips
 ```
 
-To see this in action, change to the `test/dummy` directory, fire up a console and start squawking:
+To see this in action, change to the `test/dummy` directory, fire up a console, and start squawking:
 
 ```bash
 $ bin/rails console
@@ -237,7 +237,7 @@ Finished in 0.004812s, 831.2949 runs/s, 415.6475 assertions/s.
 
 This tells us that we don't have the necessary models (Hickwall and Wickwall) that we are trying to test.
 We can easily generate these models in our "dummy" Rails application by running the following commands from the
-test/dummy directory:
+`test/dummy` directory:
 
 ```bash
 $ cd test/dummy
@@ -359,7 +359,7 @@ When you run `bin/test`, you should see the tests all pass:
 
 ### Add an Instance Method
 
-This plugin will add a method named 'squawk' to any Active Record object that calls 'acts_as_yaffle'. The 'squawk'
+This plugin will add a method named 'squawk' to any Active Record object that calls `acts_as_yaffle`. The 'squawk'
 method will simply set the value of one of the fields in the database.
 
 To start out, write a failing test that shows the behavior you'd like:
@@ -392,7 +392,7 @@ end
 ```
 
 Run the test to make sure the last two tests fail with an error that contains "NoMethodError: undefined method `squawk'",
-then update 'acts_as_yaffle.rb' to look like this:
+then update `acts_as_yaffle.rb` to look like this:
 
 ```ruby
 # yaffle/lib/yaffle/acts_as_yaffle.rb
@@ -446,7 +446,7 @@ Publishing Your Gem
 -------------------
 
 Gem plugins currently in development can easily be shared from any Git repository. To share the Yaffle gem with others, simply
-commit the code to a Git repository (like GitHub) and add a line to the Gemfile of the application in question:
+commit the code to a Git repository (like GitHub) and add a line to the `Gemfile` of the application in question:
 
 ```ruby
 gem "yaffle", git: "https://github.com/rails/yaffle.git"
diff --git a/guides/source/rails_on_rack.md b/guides/source/rails_on_rack.md
index aa1476ecc0..8d66942e31 100644
--- a/guides/source/rails_on_rack.md
+++ b/guides/source/rails_on_rack.md
@@ -13,12 +13,12 @@ After reading this guide, you will know:
 
 --------------------------------------------------------------------------------
 
-WARNING: This guide assumes a working knowledge of Rack protocol and Rack concepts such as middlewares, url maps and `Rack::Builder`.
+WARNING: This guide assumes a working knowledge of Rack protocol and Rack concepts such as middlewares, url maps, and `Rack::Builder`.
 
 Introduction to Rack
 --------------------
 
-Rack provides a minimal, modular and adaptable interface for developing web applications in Ruby. By wrapping HTTP requests and responses in the simplest way possible, it unifies and distills the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call.
+Rack provides a minimal, modular, and adaptable interface for developing web applications in Ruby. By wrapping HTTP requests and responses in the simplest way possible, it unifies and distills the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call.
 
 Explaining how Rack works is not really in the scope of this guide. In case you
 are not familiar with Rack's basics, you should check out the [Resources](#resources)
@@ -122,9 +122,11 @@ use ActiveRecord::Migration::CheckPending
 use ActionDispatch::Cookies
 use ActionDispatch::Session::CookieStore
 use ActionDispatch::Flash
+use ActionDispatch::ContentSecurityPolicy::Middleware
 use Rack::Head
 use Rack::ConditionalGet
 use Rack::ETag
+use Rack::TempfileReaper
 run MyApp::Application.routes
 ```
 
@@ -132,7 +134,7 @@ The default middlewares shown here (and some others) are each summarized in the
 
 ### Configuring Middleware Stack
 
-Rails provides a simple configuration interface `config.middleware` for adding, removing and modifying the middlewares in the middleware stack via `application.rb` or the environment specific configuration file `environments/<environment>.rb`.
+Rails provides a simple configuration interface `config.middleware` for adding, removing, and modifying the middlewares in the middleware stack via `application.rb` or the environment specific configuration file `environments/<environment>.rb`.
 
 #### Adding a Middleware
 
@@ -249,7 +251,7 @@ Much of Action Controller's functionality is implemented as Middlewares. The fol
 
 **`Rails::Rack::Logger`**
 
-* Notifies the logs that the request has began. After request is complete, flushes all the logs.
+* Notifies the logs that the request has begun. After the request is complete, flushes all the logs.
 
 **`ActionDispatch::ShowExceptions`**
 
@@ -283,18 +285,26 @@ Much of Action Controller's functionality is implemented as Middlewares. The fol
 
 * Sets up the flash keys. Only available if `config.action_controller.session_store` is set to a value.
 
+**`ActionDispatch::ContentSecurityPolicy::Middleware`**
+
+* Provides a DSL to configure a Content-Security-Policy header.
+
 **`Rack::Head`**
 
 * Converts HEAD requests to `GET` requests and serves them as so.
 
 **`Rack::ConditionalGet`**
 
-* Adds support for "Conditional `GET`" so that server responds with nothing if page wasn't changed.
+* Adds support for "Conditional `GET`" so that server responds with nothing if the page wasn't changed.
 
 **`Rack::ETag`**
 
 * Adds ETag header on all String bodies. ETags are used to validate cache.
 
+**`Rack::TempfileReaper`**
+
+* Cleans up tempfiles used to buffer multipart requests.
+
 TIP: It's possible to use any of the above middlewares in your custom Rack stack.
 
 Resources
diff --git a/guides/source/routing.md b/guides/source/routing.md
index 638f77be13..41f80a3814 100644
--- a/guides/source/routing.md
+++ b/guides/source/routing.md
@@ -36,6 +36,8 @@ get '/patients/:id', to: 'patients#show'
 
 the request is dispatched to the `patients` controller's `show` action with `{ id: '17' }` in `params`.
 
+NOTE: Rails uses snake_case for controller names here, if you have a multiple word controller like `MonsterTrucksController`, you want to use `monster_trucks#show` for example.
+
 ### Generating Paths and URLs from Code
 
 You can also generate paths and URLs. If the route above is modified to be:
@@ -58,6 +60,26 @@ and this in the corresponding view:
 
 then the router will generate the path `/patients/17`. This reduces the brittleness of your view and makes your code easier to understand. Note that the id does not need to be specified in the route helper.
 
+### Configuring the Rails Router
+
+The routes for your application or engine live in the file `config/routes.rb` and typically looks like this:
+
+```ruby
+Rails.application.routes.draw do
+  resources :brands, only: [:index, :show] do
+    resources :products, only: [:index, :show]
+  end
+
+  resource :basket, only: [:show, :update, :destroy]
+
+  resolve("Basket") { route_for(:basket) }
+end
+```
+
+Since this is a regular Ruby source file you can use all of its features to help you define your routes but be careful with variable names as they can clash with the DSL methods of the router.
+
+NOTE: The `Rails.application.routes.draw do ... end` block that wraps your route definitions is required to establish the scope for the router DSL and must not be deleted.
+
 Resource Routing: the Rails Default
 -----------------------------------
 
@@ -116,7 +138,7 @@ Creating a resourceful route will also expose a number of helpers to the control
 * `edit_photo_path(:id)` returns `/photos/:id/edit` (for instance, `edit_photo_path(10)` returns `/photos/10/edit`)
 * `photo_path(:id)` returns `/photos/:id` (for instance, `photo_path(10)` returns `/photos/10`)
 
-Each of these helpers has a corresponding `_url` helper (such as `photos_url`) which returns the same path prefixed with the current host, port and path prefix.
+Each of these helpers has a corresponding `_url` helper (such as `photos_url`) which returns the same path prefixed with the current host, port, and path prefix.
 
 ### Defining Multiple Resources at the Same Time
 
@@ -174,7 +196,7 @@ A singular resourceful route generates these helpers:
 * `edit_geocoder_path` returns `/geocoder/edit`
 * `geocoder_path` returns `/geocoder`
 
-As with plural resources, the same helpers ending in `_url` will also include the host, port and path prefix.
+As with plural resources, the same helpers ending in `_url` will also include the host, port, and path prefix.
 
 ### Controller Namespaces and Routing
 
@@ -549,7 +571,7 @@ In particular, simple routing makes it very easy to map legacy URLs to new Rails
 When you set up a regular route, you supply a series of symbols that Rails maps to parts of an incoming HTTP request. For example, consider this route:
 
 ```ruby
-get 'photos(/:id)', to: :display
+get 'photos(/:id)', to: 'photos#display'
 ```
 
 If an incoming request of `/photos/1` is processed by this route (because it hasn't matched any previous route in the file), then the result will be to invoke the `display` action of the `PhotosController`, and to make the final parameter `"1"` available as `params[:id]`. This route will also route the incoming request of `/photos` to `PhotosController#display`, since `:id` is an optional parameter, denoted by parentheses.
@@ -622,7 +644,7 @@ You can also use this to override routing methods defined by resources, like thi
 get ':username', to: 'users#show', as: :user
 ```
 
-This will define a `user_path` method that will be available in controllers, helpers and views that will go to a route such as `/bob`. Inside the `show` action of `UsersController`, `params[:username]` will contain the username for the user. Change `:username` in the route definition if you do not want your parameter name to be `:username`.
+This will define a `user_path` method that will be available in controllers, helpers, and views that will go to a route such as `/bob`. Inside the `show` action of `UsersController`, `params[:username]` will contain the username for the user. Change `:username` in the route definition if you do not want your parameter name to be `:username`.
 
 ### HTTP Verb Constraints
 
@@ -852,6 +874,49 @@ You can specify unicode character routes directly. For example:
 get 'こんにちは', to: 'welcome#index'
 ```
 
+### Direct routes
+
+You can create custom URL helpers directly. For example:
+
+```ruby
+direct :homepage do
+  "http://www.rubyonrails.org"
+end
+
+# >> homepage_url
+# => "http://www.rubyonrails.org"
+```
+
+The return value of the block must be a valid argument for the `url_for` method. So, you can pass a valid string URL, Hash, Array, an Active Model instance, or an Active Model class.
+
+```ruby
+direct :commentable do |model|
+  [ model, anchor: model.dom_id ]
+end
+
+direct :main do
+  { controller: 'pages', action: 'index', subdomain: 'www' }
+end
+```
+
+### Using `resolve`
+
+The `resolve` method allows customizing polymorphic mapping of models. For example:
+
+``` ruby
+resource :basket
+
+resolve("Basket") { [:basket] }
+```
+
+``` erb
+<%= form_for @basket do |form| %>
+  <!-- basket form -->
+<% end %>
+```
+
+This will generate the singular URL `/basket` instead of the usual `/baskets/:id`.
+
 Customizing Resourceful Routes
 ------------------------------
 
@@ -996,7 +1061,7 @@ scope ':username' do
 end
 ```
 
-This will provide you with URLs such as `/bob/articles/1` and will allow you to reference the `username` part of the path as `params[:username]` in controllers, helpers and views.
+This will provide you with URLs such as `/bob/articles/1` and will allow you to reference the `username` part of the path as `params[:username]` in controllers, helpers, and views.
 
 ### Restricting the Routes Created
 
@@ -1074,10 +1139,10 @@ resources :videos, param: :identifier
 ```
 
 ```
-     videos GET  /videos(.:format)                  videos#index
-            POST /videos(.:format)                  videos#create
- new_videos GET  /videos/new(.:format)              videos#new
-edit_videos GET  /videos/:identifier/edit(.:format) videos#edit
+    videos GET  /videos(.:format)                  videos#index
+           POST /videos(.:format)                  videos#create
+ new_video GET  /videos/new(.:format)              videos#new
+edit_video GET  /videos/:identifier/edit(.:format) videos#edit
 ```
 
 ```ruby
@@ -1095,7 +1160,7 @@ class Video < ApplicationRecord
 end
 
 video = Video.find_by(identifier: "Roman-Holiday")
-edit_videos_path(video) # => "/videos/Roman-Holiday"
+edit_video_path(video) # => "/videos/Roman-Holiday/edit"
 ```
 
 Inspecting and Testing Routes
@@ -1140,7 +1205,7 @@ $ bin/rails routes -c Comments
 $ bin/rails routes -c Articles::CommentsController
 ```
 
-TIP: You'll find that the output from `rails routes` is much more readable if you widen your terminal window until the output lines don't wrap.
+TIP: You'll find that the output from `rails routes` is much more readable if you widen your terminal window until the output lines don't wrap. You can also use --expanded option to turn on the expanded table formatting mode.
 
 ### Testing Routes
 
diff --git a/guides/source/security.md b/guides/source/security.md
index d0d7e12b0a..6e390d872f 100644
--- a/guides/source/security.md
+++ b/guides/source/security.md
@@ -1,7 +1,7 @@
 **DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.**
 
-Ruby on Rails Security Guide
-============================
+Securing Rails Applications
+===========================
 
 This manual describes common security problems in web applications and how to avoid them with Rails.
 
@@ -21,13 +21,13 @@ Introduction
 
 Web application frameworks are made to help developers build web applications. Some of them also help you with securing the web application. In fact one framework is not more secure than another: If you use it correctly, you will be able to build secure apps with many frameworks. Ruby on Rails has some clever helper methods, for example against SQL injection, so that this is hardly a problem.
 
-In general there is no such thing as plug-n-play security. Security depends on the people using the framework, and sometimes on the development method. And it depends on all layers of a web application environment: The back-end storage, the web server and the web application itself (and possibly other layers or applications).
+In general there is no such thing as plug-n-play security. Security depends on the people using the framework, and sometimes on the development method. And it depends on all layers of a web application environment: The back-end storage, the web server, and the web application itself (and possibly other layers or applications).
 
 The Gartner Group, however, estimates that 75% of attacks are at the web application layer, and found out "that out of 300 audited sites, 97% are vulnerable to attack". This is because web applications are relatively easy to attack, as they are simple to understand and manipulate, even by the lay person.
 
-The threats against web applications include user account hijacking, bypass of access control, reading or modifying sensitive data, or presenting fraudulent content. Or an attacker might be able to install a Trojan horse program or unsolicited e-mail sending software, aim at financial enrichment or cause brand name damage by modifying company resources. In order to prevent attacks, minimize their impact and remove points of attack, first of all, you have to fully understand the attack methods in order to find the correct countermeasures. That is what this guide aims at.
+The threats against web applications include user account hijacking, bypass of access control, reading or modifying sensitive data, or presenting fraudulent content. Or an attacker might be able to install a Trojan horse program or unsolicited e-mail sending software, aim at financial enrichment, or cause brand name damage by modifying company resources. In order to prevent attacks, minimize their impact and remove points of attack, first of all, you have to fully understand the attack methods in order to find the correct countermeasures. That is what this guide aims at.
 
-In order to develop secure web applications you have to keep up to date on all layers and know your enemies. To keep up to date subscribe to security mailing lists, read security blogs and make updating and security checks a habit (check the [Additional Resources](#additional-resources) chapter). It is done manually because that's how you find the nasty logical security problems.
+In order to develop secure web applications you have to keep up to date on all layers and know your enemies. To keep up to date subscribe to security mailing lists, read security blogs, and make updating and security checks a habit (check the [Additional Resources](#additional-resources) chapter). It is done manually because that's how you find the nasty logical security problems.
 
 Sessions
 --------
@@ -52,7 +52,7 @@ User.find(session[:user_id])
 
 NOTE: _The session ID is a 32-character random hex string._
 
-The session ID is generated using `SecureRandom.hex` which generates a random hex string using platform specific methods (such as OpenSSL, /dev/urandom or Win32) for generating cryptographically secure random numbers. Currently it is not feasible to brute-force Rails' session IDs.
+The session ID is generated using `SecureRandom.hex` which generates a random hex string using platform specific methods (such as OpenSSL, /dev/urandom or Win32 CryptoAPI) for generating cryptographically secure random numbers. Currently it is not feasible to brute-force Rails' session IDs.
 
 ### Session Hijacking
 
@@ -74,7 +74,7 @@ Hence, the cookie serves as temporary authentication for the web application. An
 
 * Instead of stealing a cookie unknown to the attacker, they fix a user's session identifier (in the cookie) known to them. Read more about this so-called session fixation later.
 
-The main objective of most attackers is to make money. The underground prices for stolen bank login accounts range from $10-$1000 (depending on the available amount of funds), $0.40-$20 for credit card numbers, $1-$8 for online auction site accounts and $4-$30 for email passwords, according to the [Symantec Global Internet Security Threat Report](http://eval.symantec.com/mktginfo/enterprise/white_papers/b-whitepaper_internet_security_threat_report_xiii_04-2008.en-us.pdf).
+The main objective of most attackers is to make money. The underground prices for stolen bank login accounts range from 0.5%-10% of account balance, $0.5-$30 for credit card numbers ($20-$60 with full details), $0.1-$1.5 for identities (Name, SSN & DOB), $20-$50 for retailer accounts, and $6-$10 for cloud service provider accounts, according to the [Symantec Internet Security Threat Report (2017)](https://www.symantec.com/content/dam/symantec/docs/reports/istr-22-2017-en.pdf).
 
 ### Session Guidelines
 
@@ -85,46 +85,117 @@ This will also be a good idea, if you modify the structure of an object and old
 
 * _Critical data should not be stored in session_. If the user clears their cookies or closes the browser, they will be lost. And with a client-side session storage, the user can read the data.
 
-### Session Storage
+### Encrypted Session Storage
 
 NOTE: _Rails provides several storage mechanisms for the session hashes. The most important is `ActionDispatch::Session::CookieStore`._
 
-Rails 2 introduced a new default session storage, CookieStore. CookieStore saves the session hash directly in a cookie on the client-side. The server retrieves the session hash from the cookie and eliminates the need for a session ID. That will greatly increase the speed of the application, but it is a controversial storage option and you have to think about the security implications of it:
+The `CookieStore` saves the session hash directly in a cookie on the
+client-side. The server retrieves the session hash from the cookie and
+eliminates the need for a session ID. That will greatly increase the
+speed of the application, but it is a controversial storage option and
+you have to think about the security implications and storage
+limitations of it:
+
+* Cookies imply a strict size limit of 4kB. This is fine as you should
+  not store large amounts of data in a session anyway, as described
+  before. Storing the current user's database id in a session is common
+  practice.
+
+* Session cookies do not invalidate themselves and can be maliciously
+  reused. It may be a good idea to have your application invalidate old
+  session cookies using a stored timestamp.
+
+The `CookieStore` uses the
+[encrypted](http://api.rubyonrails.org/classes/ActionDispatch/Cookies/ChainedCookieJars.html#method-i-encrypted)
+cookie jar to provide a secure, encrypted location to store session
+data. Cookie-based sessions thus provide both integrity as well as
+confidentiality to their contents. The encryption key, as well as the
+verification key used for
+[signed](http://api.rubyonrails.org/classes/ActionDispatch/Cookies/ChainedCookieJars.html#method-i-signed)
+cookies, is derived from the `secret_key_base` configuration value.
+
+As of Rails 5.2 encrypted cookies and sessions are protected using AES
+GCM encryption. This form of encryption is a type of Authenticated
+Encryption and couples authentication and encryption in single step
+while also producing shorter ciphertexts as compared to other
+algorithms previously used. The key for cookies encrypted with AES GCM
+are derived using a salt value defined by the
+`config.action_dispatch.authenticated_encrypted_cookie_salt`
+configuration value.
+
+Prior to this version, encrypted cookies were secured using AES in CBC
+mode with HMAC using SHA1 for authentication. The keys for this type of
+encryption and for HMAC verification were derived via the salts defined
+by `config.action_dispatch.encrypted_cookie_salt` and
+`config.action_dispatch.encrypted_signed_cookie_salt` respectively.
+
+Prior to Rails version 4 in both versions 2 and 3, session cookies were
+protected using only HMAC verification. As such, these session cookies
+only provided integrity to their content because the actual session data
+was stored in plaintext encoded as base64. This is how `signed` cookies
+work in the current version of Rails. These kinds of cookies are still
+useful for protecting the integrity of certain client-stored data and
+information.
+
+__Do not use a trivial secret for the `secret_key_base`, i.e. a word
+from a dictionary, or one which is shorter than 30 characters! Instead
+use `rails secret` to generate secret keys!__
+
+It is also important to use different salt values for encrypted and
+signed cookies. Using the same value for different salt configuration
+values may lead to the same derived key being used for different
+security features which in turn may weaken the strength of the key.
+
+In test and development applications get a `secret_key_base` derived from the app name. Other environments must use a random key present in `config/credentials.yml.enc`, shown here in its decrypted state:
+
+    secret_key_base: 492f...
 
-* Cookies imply a strict size limit of 4kB. This is fine as you should not store large amounts of data in a session anyway, as described before. _Storing the current user's database id in a session is usually ok_.
+If you have received an application where the secret was exposed (e.g. an application whose source was shared), strongly consider changing the secret.
 
-* The client can see everything you store in a session, because it is stored in clear-text (actually Base64-encoded, so not encrypted). So, of course, _you don't want to store any secrets here_. To prevent session hash tampering, a digest is calculated from the session with a server-side secret (`secrets.secret_token`) and inserted into the end of the cookie.
+### Rotating Encrypted and Signed Cookies Configurations
 
-In Rails 4, encrypted cookies through AES in CBC mode with HMAC using SHA1 for
-verification was introduced. This prevents the user from accessing and tampering
-the content of the cookie. Thus the session becomes a more secure place to store
-data. The encryption is performed using a server-side `secrets.secret_key_base`.
-Two salts are used when deriving keys for encryption and verification. These
-salts are set via the `config.action_dispatch.encrypted_cookie_salt` and
-`config.action_dispatch.encrypted_signed_cookie_salt` configuration values.
+Rotation is ideal for changing cookie configurations and ensuring old cookies
+aren't immediately invalid. Your users then have a chance to visit your site,
+get their cookie read with an old configuration and have it rewritten with the
+new change. The rotation can then be removed once you're comfortable enough
+users have had their chance to get their cookies upgraded.
 
-Rails 5.2 uses AES-GCM for the encryption which couples authentication
-and encryption in one faster step and produces shorter ciphertexts.
+It's possible to rotate the ciphers and digests used for encrypted and signed cookies.
 
-Encrypted cookies are automatically upgraded if the
-`config.action_dispatch.use_authenticated_cookie_encryption` is enabled.
+For instance to change the digest used for signed cookies from SHA1 to SHA256,
+you would first assign the new configuration value:
 
-_Do not use a trivial secret, i.e. a word from a dictionary, or one which is shorter than 30 characters! Instead use `rails secret` to generate secret keys!_
+```ruby
+Rails.application.config.action_dispatch.signed_cookie_digest = "SHA256"
+```
 
-Applications get `secrets.secret_key_base` initialized to a random key present in `config/secrets.yml`, e.g.:
+Now add a rotation for the old SHA1 digest so existing cookies are
+seamlessly upgraded to the new SHA256 digest.
 
-    development:
-      secret_key_base: a75d...
+```ruby
+Rails.application.config.action_dispatch.cookies_rotations.tap do |cookies|
+  cookies.rotate :signed, digest: "SHA1"
+end
+```
 
-    test:
-      secret_key_base: 492f...
+Then any written signed cookies will be digested with SHA256. Old cookies
+that were written with SHA1 can still be read, and if accessed will be written
+with the new digest so they're upgraded and won't be invalid when you remove the
+rotation.
 
-    production:
-      secret_key_base: <%= ENV["SECRET_KEY_BASE"] %>
+Once users with SHA1 digested signed cookies should no longer have a chance to
+have their cookies rewritten, remove the rotation.
 
-Older versions of Rails use CookieStore, which uses `secret_token` instead of `secret_key_base` that is used by EncryptedCookieStore. Read the upgrade documentation for more information.
+While you can setup as many rotations as you'd like it's not common to have many
+rotations going at any one time.
 
-If you have received an application where the secret was exposed (e.g. an application whose source was shared), strongly consider changing the secret.
+For more details on key rotation with encrypted and signed messages as
+well as the various options the `rotate` method accepts, please refer to
+the
+[MessageEncryptor API](http://api.rubyonrails.org/classes/ActiveSupport/MessageEncryptor.html)
+and
+[MessageVerifier API](http://api.rubyonrails.org/classes/ActiveSupport/MessageVerifier.html)
+documentation.
 
 ### Replay Attacks for CookieStore Sessions
 
@@ -146,7 +217,7 @@ The best _solution against it is not to store this kind of data in a session, bu
 
 NOTE: _Apart from stealing a user's session ID, the attacker may fix a session ID known to them. This is called session fixation._
 
-![Session fixation](images/session_fixation.png)
+![Session fixation](images/security/session_fixation.png)
 
 This attack focuses on fixing a user's session ID known to the attacker, and forcing the user's browser into using this ID. It is therefore not necessary for the attacker to steal the session ID afterwards. Here is how this attack works:
 
@@ -173,7 +244,7 @@ Another countermeasure is to _save user-specific properties in the session_, ver
 
 ### Session Expiry
 
-NOTE: _Sessions that never expire extend the time-frame for attacks such as cross-site request forgery (CSRF), session hijacking and session fixation._
+NOTE: _Sessions that never expire extend the time-frame for attacks such as cross-site request forgery (CSRF), session hijacking, and session fixation._
 
 One possibility is to set the expiry time-stamp of the cookie with the session ID. However the client can edit cookies that are stored in the web browser so expiring sessions on the server is safer. Here is an example of how to _expire sessions in a database table_. Call `Session.sweep("20 minutes")` to expire sessions that were used longer than 20 minutes ago.
 
@@ -189,7 +260,7 @@ class Session < ApplicationRecord
 end
 ```
 
-The section about session fixation introduced the problem of maintained sessions. An attacker maintaining a session every five minutes can keep the session alive forever, although you are expiring sessions. A simple solution for this would be to add a created_at column to the sessions table. Now you can delete sessions that were created a long time ago. Use this line in the sweep method above:
+The section about session fixation introduced the problem of maintained sessions. An attacker maintaining a session every five minutes can keep the session alive forever, although you are expiring sessions. A simple solution for this would be to add a `created_at` column to the sessions table. Now you can delete sessions that were created a long time ago. Use this line in the sweep method above:
 
 ```ruby
 delete_all "updated_at < '#{time.ago.to_s(:db)}' OR
@@ -201,7 +272,7 @@ Cross-Site Request Forgery (CSRF)
 
 This attack method works by including malicious code or a link in a page that accesses a web application that the user is believed to have authenticated. If the session for that web application has not timed out, an attacker may execute unauthorized commands.
 
-![](images/csrf.png)
+![](images/security/csrf.png)
 
 In the [session chapter](#sessions) you have learned that most Rails applications use cookie-based sessions. Either they store the session ID in the cookie and have a server-side session hash, or the entire session hash is on the client-side. In either case the browser will automatically send along the cookie on every request to a domain, if it can find a cookie for that domain. The controversial point is that if the request comes from a site of a different domain, it will also send the cookie. Let's start with an example:
 
@@ -211,7 +282,7 @@ In the [session chapter](#sessions) you have learned that most Rails application
 * The web application at `www.webapp.com` verifies the user information in the corresponding session hash and destroys the project with the ID 1. It then returns a result page which is an unexpected result for the browser, so it will not display the image.
 * Bob doesn't notice the attack - but a few days later he finds out that project number one is gone.
 
-It is important to notice that the actual crafted image or link doesn't necessarily have to be situated in the web application's domain, it can be anywhere - in a forum, blog post or email.
+It is important to notice that the actual crafted image or link doesn't necessarily have to be situated in the web application's domain, it can be anywhere - in a forum, blog post, or email.
 
 CSRF appears very rarely in CVE (Common Vulnerabilities and Exposures) - less than 0.1% in 2006 - but it really is a 'sleeping giant' [Grossman]. This is in stark contrast to the results in many security contract works - _CSRF is an important security issue_.
 
@@ -231,7 +302,7 @@ The HTTP protocol basically provides two main types of requests - GET and POST (
 * The interaction _changes the state_ of the resource in a way that the user would perceive (e.g., a subscription to a service), or
 * The user is _held accountable for the results_ of the interaction.
 
-If your web application is RESTful, you might be used to additional HTTP verbs, such as PATCH, PUT or DELETE. Some legacy web browsers, however, do not support them - only GET and POST. Rails uses a hidden `_method` field to handle these cases.
+If your web application is RESTful, you might be used to additional HTTP verbs, such as PATCH, PUT, or DELETE. Some legacy web browsers, however, do not support them - only GET and POST. Rails uses a hidden `_method` field to handle these cases.
 
 _POST requests can be sent automatically, too_. In this example, the link www.harmless.com is shown as the destination in the browser's status bar. But it has actually dynamically created a new form that sends a POST request.
 
@@ -254,7 +325,7 @@ Or the attacker places the code into the onmouseover event handler of an image:
 
 There are many other possibilities, like using a `<script>` tag to make a cross-site request to a URL with a JSONP or JavaScript response. The response is executable code that the attacker can find a way to run, possibly extracting sensitive data. To protect against this data leakage, we must disallow cross-site `<script>` tags. Ajax requests, however, obey the browser's same-origin policy (only your own site is allowed to initiate `XmlHttpRequest`) so we can safely allow them to return JavaScript responses.
 
-Note: We can't distinguish a `<script>` tag's origin—whether it's a tag on your own site or on some other malicious site—so we must block all `<script>` across the board, even if it's actually a safe same-origin script served from your own site. In these cases, explicitly skip CSRF protection on actions that serve JavaScript meant for a `<script>` tag.
+NOTE: We can't distinguish a `<script>` tag's origin—whether it's a tag on your own site or on some other malicious site—so we must block all `<script>` across the board, even if it's actually a safe same-origin script served from your own site. In these cases, explicitly skip CSRF protection on actions that serve JavaScript meant for a `<script>` tag.
 
 To protect against all other forged requests, we introduce a _required security token_ that our site knows but other sites don't know. We include the security token in requests and verify it on the server. This is a one-liner in your application controller, and is the default for newly created Rails applications:
 
@@ -321,7 +392,7 @@ This example is a Base64 encoded JavaScript which displays a simple message box.
 
 NOTE: _Make sure file uploads don't overwrite important files, and process media files asynchronously._
 
-Many web applications allow users to upload files. _File names, which the user may choose (partly), should always be filtered_ as an attacker could use a malicious file name to overwrite any file on the server. If you store file uploads at /var/www/uploads, and the user enters a file name like "../../../etc/passwd", it may overwrite an important file. Of course, the Ruby interpreter would need the appropriate permissions to do so - one more reason to run web servers, database servers and other programs as a less privileged Unix user.
+Many web applications allow users to upload files. _File names, which the user may choose (partly), should always be filtered_ as an attacker could use a malicious file name to overwrite any file on the server. If you store file uploads at /var/www/uploads, and the user enters a file name like "../../../etc/passwd", it may overwrite an important file. Of course, the Ruby interpreter would need the appropriate permissions to do so - one more reason to run web servers, database servers, and other programs as a less privileged Unix user.
 
 When filtering user input file names, _don't try to remove malicious parts_. Think of a situation where the web application removes all "../" in a file name and an attacker uses a string such as "....//" - the result will be "../". It is best to use a whitelist approach, which _checks for the validity of a file name with a set of accepted characters_. This is opposed to a blacklist approach which attempts to remove not allowed characters. In case it isn't a valid file name, reject it (or replace not accepted characters), but don't remove them. Here is the file name sanitizer from the [attachment_fu plugin](https://github.com/technoweenie/attachment_fu/tree/master):
 
@@ -391,7 +462,7 @@ A real-world example is a [router reconfiguration by CSRF](http://www.h-online.c
 
 Another example changed Google Adsense's e-mail address and password. If the victim was logged into Google Adsense, the administration interface for Google advertisement campaigns, an attacker could change the credentials of the victim. 
 
-Another popular attack is to spam your web application, your blog or forum to propagate malicious XSS. Of course, the attacker has to know the URL structure, but most Rails URLs are quite straightforward or they will be easy to find out, if it is an open-source application's admin interface. The attacker may even do 1,000 lucky guesses by just including malicious IMG-tags which try every possible combination.
+Another popular attack is to spam your web application, your blog, or forum to propagate malicious XSS. Of course, the attacker has to know the URL structure, but most Rails URLs are quite straightforward or they will be easy to find out, if it is an open-source application's admin interface. The attacker may even do 1,000 lucky guesses by just including malicious IMG-tags which try every possible combination.
 
 For _countermeasures against CSRF in administration interfaces and Intranet applications, refer to the countermeasures in the CSRF section_.
 
@@ -403,7 +474,7 @@ The common admin interface works like this: it's located at www.example.com/admi
 
 * Does the admin really have to access the interface from everywhere in the world? Think about _limiting the login to a bunch of source IP addresses_. Examine request.remote_ip to find out about the user's IP address. This is not bullet-proof, but a great barrier. Remember that there might be a proxy in use, though.
 
-* _Put the admin interface to a special sub-domain_ such as admin.application.com and make it a separate application with its own user management. This makes stealing an admin cookie from the usual domain, www.application.com, impossible. This is because of the same origin policy in your browser: An injected (XSS) script on www.application.com may not read the cookie for admin.application.com and vice-versa.
+* _Put the admin interface to a special subdomain_ such as admin.application.com and make it a separate application with its own user management. This makes stealing an admin cookie from the usual domain, www.application.com, impossible. This is because of the same origin policy in your browser: An injected (XSS) script on www.application.com may not read the cookie for admin.application.com and vice-versa.
 
 User Management
 ---------------
@@ -431,7 +502,7 @@ If the parameter was nil, the resulting SQL query will be
 SELECT * FROM users WHERE (users.activation_code IS NULL) LIMIT 1
 ```
 
-And thus it found the first user in the database, returned it and logged them in. You can find out more about it in [this blog post](http://www.rorsecurity.info/2007/10/28/restful_authentication-login-security/). _It is advisable to update your plug-ins from time to time_. Moreover, you can review your application to find more flaws like this.
+And thus it found the first user in the database, returned it, and logged them in. You can find out more about it in [this blog post](http://www.rorsecurity.info/2007/10/28/restful_authentication-login-security/). _It is advisable to update your plug-ins from time to time_. Moreover, you can review your application to find more flaws like this.
 
 ### Brute-Forcing Accounts
 
@@ -465,7 +536,7 @@ Depending on your web application, there may be more ways to hijack the user's a
 
 INFO: _A CAPTCHA is a challenge-response test to determine that the response is not generated by a computer. It is often used to protect registration forms from attackers and comment forms from automatic spam bots by asking the user to type the letters of a distorted image. This is the positive CAPTCHA, but there is also the negative CAPTCHA. The idea of a negative CAPTCHA is not for a user to prove that they are human, but reveal that a robot is a robot._
 
-A popular positive CAPTCHA API is [reCAPTCHA](http://recaptcha.net/) which displays two distorted images of words from old books. It also adds an angled line, rather than a distorted background and high levels of warping on the text as earlier CAPTCHAs did, because the latter were broken. As a bonus, using reCAPTCHA helps to digitize old books. [ReCAPTCHA](https://github.com/ambethia/recaptcha/) is also a Rails plug-in with the same name as the API.
+A popular positive CAPTCHA API is [reCAPTCHA](https://developers.google.com/recaptcha/) which displays two distorted images of words from old books. It also adds an angled line, rather than a distorted background and high levels of warping on the text as earlier CAPTCHAs did, because the latter were broken. As a bonus, using reCAPTCHA helps to digitize old books. [ReCAPTCHA](https://github.com/ambethia/recaptcha/) is also a Rails plug-in with the same name as the API.
 
 You will get two keys from the API, a public and a private key, which you have to put into your Rails environment. After that you can use the recaptcha_tags method in the view, and the verify_recaptcha method in the controller. Verify_recaptcha will return false if the validation fails.
 The problem with CAPTCHAs is that they have a negative impact on the user experience. Additionally, some visually impaired users have found certain kinds of distorted CAPTCHAs difficult to read. Still, positive CAPTCHAs are one of the best methods to prevent all kinds of bots from submitting forms.
@@ -480,7 +551,7 @@ Here are some ideas how to hide honeypot fields by JavaScript and/or CSS:
 * make the elements very small or color them the same as the background of the page
 * leave the fields displayed, but tell humans to leave them blank
 
-The most simple negative CAPTCHA is one hidden honeypot field. On the server side, you will check the value of the field: If it contains any text, it must be a bot. Then, you can either ignore the post or return a positive result, but not saving the post to the database. This way the bot will be satisfied and moves on. You can do this with annoying users, too.
+The most simple negative CAPTCHA is one hidden honeypot field. On the server side, you will check the value of the field: If it contains any text, it must be a bot. Then, you can either ignore the post or return a positive result, but not saving the post to the database. This way the bot will be satisfied and moves on.
 
 You can find more sophisticated negative CAPTCHAs in Ned Batchelder's [blog post](http://nedbatchelder.com/text/stopbots.html):
 
@@ -502,18 +573,6 @@ config.filter_parameters << :password
 
 NOTE: Provided parameters will be filtered out by partial matching regular expression. Rails adds default `:password` in the appropriate initializer (`initializers/filter_parameter_logging.rb`) and cares about typical application parameters `password` and `password_confirmation`.
 
-### Good Passwords
-
-INFO: _Do you find it hard to remember all your passwords? Don't write them down, but use the initial letters of each word in an easy to remember sentence._
-
-Bruce Schneier, a security technologist, [has analyzed](http://www.schneier.com/blog/archives/2006/12/realworld_passw.html) 34,000 real-world user names and passwords from the MySpace phishing attack mentioned [below](#examples-from-the-underground). It turns out that most of the passwords are quite easy to crack. The 20 most common passwords are:
-
-password1, abc123, myspace1, password, blink182, qwerty1, ****you, 123abc, baseball1, football1, 123456, soccer, monkey1, liverpool1, princess1, jordan23, slipknot1, superman1, iloveyou1, and monkey.
-
-It is interesting that only 4% of these passwords were dictionary words and the great majority is actually alphanumeric. However, password cracker dictionaries contain a large number of today's passwords, and they try out all kinds of (alphanumerical) combinations. If an attacker knows your user name and you use a weak password, your account will be easily cracked.
-
-A good password is a long alphanumeric combination of mixed cases. As this is quite hard to remember, it is advisable to enter only the _first letters of a sentence that you can easily remember_. For example "The quick brown fox jumps over the lazy dog" will be "Tqbfjotld". Note that this is just an example, you should not use well known phrases like these, as they might appear in cracker dictionaries, too.
-
 ### Regular Expressions
 
 INFO: _A common pitfall in Ruby's regular expressions is to match the string's beginning and end by ^ and $, instead of \A and \z._
@@ -580,13 +639,13 @@ Injection
 
 INFO: _Injection is a class of attacks that introduce malicious code or parameters into a web application in order to run it within its security context. Prominent examples of injection are cross-site scripting (XSS) and SQL injection._
 
-Injection is very tricky, because the same code or parameter can be malicious in one context, but totally harmless in another. A context can be a scripting, query or programming language, the shell or a Ruby/Rails method. The following sections will cover all important contexts where injection attacks may happen. The first section, however, covers an architectural decision in connection with Injection.
+Injection is very tricky, because the same code or parameter can be malicious in one context, but totally harmless in another. A context can be a scripting, query, or programming language, the shell, or a Ruby/Rails method. The following sections will cover all important contexts where injection attacks may happen. The first section, however, covers an architectural decision in connection with Injection.
 
 ### Whitelists versus Blacklists
 
-NOTE: _When sanitizing, protecting or verifying something, prefer whitelists over blacklists._
+NOTE: _When sanitizing, protecting, or verifying something, prefer whitelists over blacklists._
 
-A blacklist can be a list of bad e-mail addresses, non-public actions or bad HTML tags. This is opposed to a whitelist which lists the good e-mail addresses, public actions, good HTML tags and so on. Although sometimes it is not possible to create a whitelist (in a SPAM filter, for example), _prefer to use whitelist approaches_:
+A blacklist can be a list of bad e-mail addresses, non-public actions or bad HTML tags. This is opposed to a whitelist which lists the good e-mail addresses, public actions, good HTML tags, and so on. Although sometimes it is not possible to create a whitelist (in a SPAM filter, for example), _prefer to use whitelist approaches_:
 
 * Use before_action except: [...] instead of only: [...] for security-related actions. This way you don't forget to enable security checks for newly added actions.
 * Allow &lt;strong&gt; instead of removing &lt;script&gt; against Cross-Site Scripting (XSS). See below for details.
@@ -659,7 +718,7 @@ Also, the second query renames some columns with the AS statement so that the we
 
 #### Countermeasures
 
-Ruby on Rails has a built-in filter for special SQL characters, which will escape ' , " , NULL character and line breaks. *Using `Model.find(id)` or `Model.find_by_some thing(something)` automatically applies this countermeasure*. But in SQL fragments, especially *in conditions fragments (`where("...")`), the `connection.execute()` or `Model.find_by_sql()` methods, it has to be applied manually*.
+Ruby on Rails has a built-in filter for special SQL characters, which will escape ' , " , NULL character, and line breaks. *Using `Model.find(id)` or `Model.find_by_some thing(something)` automatically applies this countermeasure*. But in SQL fragments, especially *in conditions fragments (`where("...")`), the `connection.execute()` or `Model.find_by_sql()` methods, it has to be applied manually*.
 
 Instead of passing a string to the conditions option, you can pass an array to sanitize tainted strings like this:
 
@@ -683,7 +742,7 @@ INFO: _The most widespread, and one of the most devastating security vulnerabili
 
 An entry point is a vulnerable URL and its parameters where an attacker can start an attack.
 
-The most common entry points are message posts, user comments, and guest books, but project titles, document names and search result pages have also been vulnerable - just about everywhere where the user can input data. But the input does not necessarily have to come from input boxes on web sites, it can be in any URL parameter - obvious, hidden or internal. Remember that the user may intercept any traffic. Applications or client-site proxies make it easy to change requests. There are also other attack vectors like banner advertisements.
+The most common entry points are message posts, user comments, and guest books, but project titles, document names, and search result pages have also been vulnerable - just about everywhere where the user can input data. But the input does not necessarily have to come from input boxes on web sites, it can be in any URL parameter - obvious, hidden or internal. Remember that the user may intercept any traffic. Applications or client-site proxies make it easy to change requests. There are also other attack vectors like banner advertisements.
 
 XSS attacks work like this: An attacker injects some code, the web application saves it and displays it on a page, later presented to a victim. Most XSS examples simply display an alert box, but it is more powerful than that. XSS can steal the cookie, hijack the session, redirect the victim to a fake website, display advertisements for the benefit of the attacker, change elements on the web site to get confidential information or install malicious software through security holes in the web browser.
 
@@ -726,11 +785,11 @@ The log files on www.attacker.com will read like this:
 GET http://www.attacker.com/_app_session=836c1c25278e5b321d6bea4f19cb57e2
 ```
 
-You can mitigate these attacks (in the obvious way) by adding the **httpOnly** flag to cookies, so that document.cookie may not be read by JavaScript. HTTP only cookies can be used from IE v6.SP1, Firefox v2.0.0.5, Opera 9.5, Safari 4 and Chrome 1.0.154 onwards. But other, older browsers (such as WebTV and IE 5.5 on Mac) can actually cause the page to fail to load. Be warned that cookies [will still be visible using Ajax](https://www.owasp.org/index.php/HTTPOnly#Browsers_Supporting_HttpOnly), though.
+You can mitigate these attacks (in the obvious way) by adding the **httpOnly** flag to cookies, so that document.cookie may not be read by JavaScript. HTTP only cookies can be used from IE v6.SP1, Firefox v2.0.0.5, Opera 9.5, Safari 4, and Chrome 1.0.154 onwards. But other, older browsers (such as WebTV and IE 5.5 on Mac) can actually cause the page to fail to load. Be warned that cookies [will still be visible using Ajax](https://www.owasp.org/index.php/HTTPOnly#Browsers_Supporting_HttpOnly), though.
 
 ##### Defacement
 
-With web page defacement an attacker can do a lot of things, for example, present false information or lure the victim on the attackers web site to steal the cookie, login credentials or other sensitive data. The most popular way is to include code from external sources by iframes:
+With web page defacement an attacker can do a lot of things, for example, present false information or lure the victim on the attackers web site to steal the cookie, login credentials, or other sensitive data. The most popular way is to include code from external sources by iframes:
 
 ```html
 <iframe name="StatPage" src="http://58.xx.xxx.xxx" width=5 height=5 style="display:none"></iframe>
@@ -801,9 +860,9 @@ In December 2006, 34,000 actual user names and passwords were stolen in a [MySpa
 
 ### CSS Injection
 
-INFO: _CSS Injection is actually JavaScript injection, because some browsers (IE, some versions of Safari and others) allow JavaScript in CSS. Think twice about allowing custom CSS in your web application._
+INFO: _CSS Injection is actually JavaScript injection, because some browsers (IE, some versions of Safari, and others) allow JavaScript in CSS. Think twice about allowing custom CSS in your web application._
 
-CSS Injection is explained best by the well-known [MySpace Samy worm](https://samy.pl/popular/tech.html). This worm automatically sent a friend request to Samy (the attacker) simply by visiting his profile. Within several hours he had over 1 million friend requests, which created so much traffic that MySpace went offline. The following is a technical explanation of that worm.
+CSS Injection is explained best by the well-known [MySpace Samy worm](https://samy.pl/myspace/tech.html). This worm automatically sent a friend request to Samy (the attacker) simply by visiting his profile. Within several hours he had over 1 million friend requests, which created so much traffic that MySpace went offline. The following is a technical explanation of that worm.
 
 MySpace blocked many tags, but allowed CSS. So the worm's author put JavaScript into CSS like this:
 
@@ -890,9 +949,9 @@ system("/bin/echo","hello; rm *")
 
 ### Header Injection
 
-WARNING: _HTTP headers are dynamically generated and under certain circumstances user input may be injected. This can lead to false redirection, XSS or HTTP response splitting._
+WARNING: _HTTP headers are dynamically generated and under certain circumstances user input may be injected. This can lead to false redirection, XSS, or HTTP response splitting._
 
-HTTP request headers have a Referer, User-Agent (client software), and Cookie field, among others. Response headers for example have a status code, Cookie and Location (redirection target URL) field. All of them are user-supplied and may be manipulated with more or less effort. _Remember to escape these header fields, too._ For example when you display the user agent in an administration area.
+HTTP request headers have a Referer, User-Agent (client software), and Cookie field, among others. Response headers for example have a status code, Cookie, and Location (redirection target URL) field. All of them are user-supplied and may be manipulated with more or less effort. _Remember to escape these header fields, too._ For example when you display the user agent in an administration area.
 
 Besides that, it is _important to know what you are doing when building response headers partly based on user input._ For example you want to redirect the user back to a specific page. To do that you introduced a "referer" field in a form to redirect to the given address:
 
@@ -999,7 +1058,10 @@ Every HTTP response from your Rails application receives the following default s
 config.action_dispatch.default_headers = {
   'X-Frame-Options' => 'SAMEORIGIN',
   'X-XSS-Protection' => '1; mode=block',
-  'X-Content-Type-Options' => 'nosniff'
+  'X-Content-Type-Options' => 'nosniff',
+  'X-Download-Options' => 'noopen',
+  'X-Permitted-Cross-Domain-Policies' => 'none',
+  'Referrer-Policy' => 'strict-origin-when-cross-origin'
 }
 ```
 
@@ -1027,32 +1089,150 @@ Here is a list of common headers:
 * **Access-Control-Allow-Origin:** Used to control which sites are allowed to bypass same origin policies and send cross-origin requests.
 * **Strict-Transport-Security:** [Used to control if the browser is allowed to only access a site over a secure connection](https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security)
 
+### Content Security Policy
+
+Rails provides a DSL that allows you to configure a
+[Content Security Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy)
+for your application. You can configure a global default policy and then
+override it on a per-resource basis and even use lambdas to inject per-request
+values into the header such as account subdomains in a multi-tenant application.
+
+Example global policy:
+
+```ruby
+# config/initializers/content_security_policy.rb
+Rails.application.config.content_security_policy do |policy|
+  policy.default_src :self, :https
+  policy.font_src    :self, :https, :data
+  policy.img_src     :self, :https, :data
+  policy.object_src  :none
+  policy.script_src  :self, :https
+  policy.style_src   :self, :https
+
+  # Specify URI for violation reports
+  policy.report_uri "/csp-violation-report-endpoint"
+end
+```
+
+Example controller overrides:
+
+```ruby
+# Override policy inline
+class PostsController < ApplicationController
+  content_security_policy do |p|
+    p.upgrade_insecure_requests true
+  end
+end
+
+# Using literal values
+class PostsController < ApplicationController
+  content_security_policy do |p|
+    p.base_uri "https://www.example.com"
+  end
+end
+
+# Using mixed static and dynamic values
+class PostsController < ApplicationController
+  content_security_policy do |p|
+    p.base_uri :self, -> { "https://#{current_user.domain}.example.com" }
+  end
+end
+
+# Disabling the global CSP
+class LegacyPagesController < ApplicationController
+  content_security_policy false, only: :index
+end
+```
+
+Use the `content_security_policy_report_only`
+configuration attribute to set
+[Content-Security-Policy-Report-Only](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy-Report-Only)
+in order to report only content violations for migrating
+legacy content
+
+```ruby
+# config/initializers/content_security_policy.rb
+Rails.application.config.content_security_policy_report_only = true
+```
+
+```ruby
+# Controller override
+class PostsController < ApplicationController
+  content_security_policy_report_only only: :index
+end
+```
+
+You can enable automatic nonce generation:
+
+```ruby
+# config/initializers/content_security_policy.rb
+Rails.application.config.content_security_policy do |policy|
+  policy.script_src :self, :https
+end
+
+Rails.application.config.content_security_policy_nonce_generator = -> request { SecureRandom.base64(16) }
+```
+
+Then you can add an automatic nonce value by passing `nonce: true`
+as part of `html_options`. Example:
+
+```html+erb
+<%= javascript_tag nonce: true do -%>
+  alert('Hello, World!');
+<% end -%>
+```
+
+The same works with `javascript_include_tag`:
+
+```html+erb
+<%= javascript_include_tag "script", nonce: true %>
+```
+
+Use [`csp_meta_tag`](http://api.rubyonrails.org/classes/ActionView/Helpers/CspHelper.html#method-i-csp_meta_tag)
+helper to create a meta tag "csp-nonce" with the per-session nonce value
+for allowing inline `<script>` tags.
+
+```html+erb
+<head>
+  <%= csp_meta_tag %>
+</head>
+```
+
+This is used by the Rails UJS helper to create dynamically
+loaded inline `<script>` elements.
+
 Environmental Security
 ----------------------
 
 It is beyond the scope of this guide to inform you on how to secure your application code and environments. However, please secure your database configuration, e.g. `config/database.yml`, and your server-side secret, e.g. stored in `config/secrets.yml`. You may want to further restrict access, using environment-specific versions of these files and any others that may contain sensitive information.
 
-### Custom secrets
+### Custom credentials
+
+Rails generates a `config/credentials.yml.enc` to store third-party credentials
+within the repo. This is only viable because Rails encrypts the file with a master
+key that's generated into a version control ignored `config/master.key` — Rails
+will also look for that key in `ENV["RAILS_MASTER_KEY"]`. Rails also requires the
+key to boot in production, so the credentials can be read.
+
+To edit stored credentials use `bin/rails credentials:edit`.
 
-Rails generates a `config/secrets.yml`. By default, this file contains the
-application's `secret_key_base`, but it could also be used to store other
-secrets such as access keys for external APIs.
+By default, this file contains the application's
+`secret_key_base`, but it could also be used to store other credentials such as
+access keys for external APIs.
 
-The secrets added to this file are accessible via `Rails.application.secrets`.
-For example, with the following `config/secrets.yml`:
+The credentials added to this file are accessible via `Rails.application.credentials`.
+For example, with the following decrypted `config/credentials.yml.enc`:
 
-    development:
-      secret_key_base: 3b7cd727ee24e8444053437c36cc66c3
-      some_api_key: SOMEKEY
+    secret_key_base: 3b7cd727ee24e8444053437c36cc66c3
+    some_api_key: SOMEKEY
 
-`Rails.application.secrets.some_api_key` returns `SOMEKEY` in the development
-environment.
+`Rails.application.credentials.some_api_key` returns `SOMEKEY` in any environment.
 
 If you want an exception to be raised when some key is blank, use the bang
 version:
 
 ```ruby
-Rails.application.secrets.some_api_key! # => raises KeyError: key not found: :some_api_key
+Rails.application.credentials.some_api_key! # => raises KeyError: :some_api_key is blank
 ```
 
 Additional Resources
diff --git a/guides/source/testing.md b/guides/source/testing.md
index 4ee3267261..0a6d2d6555 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -1,7 +1,7 @@
 **DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.**
 
-A Guide to Testing Rails Applications
-=====================================
+Testing Rails Applications
+==========================
 
 This guide covers built-in mechanisms in Rails for testing your application.
 
@@ -33,8 +33,8 @@ Rails creates a `test` directory for you as soon as you create a Rails project u
 
 ```bash
 $ ls -F test
-controllers/           helpers/               mailers/               system/                test_helper.rb
-fixtures/              integration/           models/                application_system_test_case.rb
+application_system_test_case.rb  fixtures/                        integration/                     models/                          test_helper.rb
+controllers/                     helpers/                         mailers/                         system/
 ```
 
 The `helpers`, `mailers`, and `models` directories are meant to hold tests for view helpers, mailers, and models, respectively. The `controllers` directory is meant to hold tests for controllers, routes, and views. The `integration` directory is meant to hold tests for interactions between controllers.
@@ -319,6 +319,8 @@ specify to make your test failure messages clearer.
 | `assert_not_includes( collection, obj, [msg] )`                  | Ensures that `obj` is not in `collection`.|
 | `assert_in_delta( expected, actual, [delta], [msg] )`            | Ensures that the numbers `expected` and `actual` are within `delta` of each other.|
 | `assert_not_in_delta( expected, actual, [delta], [msg] )`        | Ensures that the numbers `expected` and `actual` are not within `delta` of each other.|
+| `assert_in_epsilon ( expected, actual, [epsilon], [msg] )`       | Ensures that the numbers `expected` and `actual` have a relative error less than `epsilon`.|
+| `assert_not_in_epsilon ( expected, actual, [epsilon], [msg] )`   | Ensures that the numbers `expected` and `actual` don't have a relative error less than `epsilon`.|
 | `assert_throws( symbol, [msg] ) { block }`                       | Ensures that the given block throws the symbol.|
 | `assert_raises( exception1, exception2, ... ) { block }`         | Ensures that the given block raises one of the given exceptions.|
 | `assert_instance_of( class, obj, [msg] )`                        | Ensures that `obj` is an instance of `class`.|
@@ -431,16 +433,8 @@ at the end of test run and so on. Check the documentation of the test runner as
 
 ```bash
 $ bin/rails test -h
-minitest options:
-    -h, --help                       Display this help.
-    -s, --seed SEED                  Sets random seed. Also via env. Eg: SEED=n rake
-    -v, --verbose                    Verbose. Show progress processing files.
-    -n, --name PATTERN               Filter run on /regexp/ or string.
-        --exclude PATTERN            Exclude /regexp/ or string from run.
-
-Known extensions: rails, pride
-
 Usage: bin/rails test [options] [files or directories]
+
 You can run a single test by appending a line number to a filename:
 
     bin/rails test test/models/user_test.rb:27
@@ -451,13 +445,105 @@ You can run multiple files and directories at the same time:
 
 By default test failures and errors are reported inline during a run.
 
-Rails options:
+minitest options:
+    -h, --help                       Display this help.
+        --no-plugins                 Bypass minitest plugin auto-loading (or set $MT_NO_PLUGINS).
+    -s, --seed SEED                  Sets random seed. Also via env. Eg: SEED=n rake
+    -v, --verbose                    Verbose. Show progress processing files.
+    -n, --name PATTERN               Filter run on /regexp/ or string.
+        --exclude PATTERN            Exclude /regexp/ or string from run.
+
+Known extensions: rails, pride
     -w, --warnings                   Run with Ruby warnings enabled
-    -e, --environment                Run tests in the ENV environment
+    -e, --environment ENV            Run tests in the ENV environment
     -b, --backtrace                  Show the complete backtrace
     -d, --defer-output               Output test failures and errors after the test run
     -f, --fail-fast                  Abort test run on first failure or error
     -c, --[no-]color                 Enable color in the output
+    -p, --pride                      Pride. Show your testing pride!
+```
+
+Parallel Testing
+----------------
+
+Parallel testing allows you to parallelize your test suite. While forking processes is the
+default method, threading is supported as well. Running tests in parallel reduces the time it
+takes your entire test suite to run.
+
+### Parallel testing with processes
+
+The default parallelization method is to fork processes using Ruby's DRb system. The processes
+are forked based on the number of workers provided. The default is 2, but can be changed by the
+number passed to the parallelize method. Active Record automatically handles creating and
+migrating a new database for each worker to use.
+
+To enable parallelization add the following to your `test_helper.rb`:
+
+```
+class ActiveSupport::TestCase
+  parallelize(workers: 2)
+end
+```
+
+The number of workers passed is the number of times the process will be forked. You may want to
+parallelize your local test suite differently from your CI, so an environment variable is provided
+to be able to easily change the number of workers a test run should use:
+
+```
+PARALLEL_WORKERS=15 bin/rails test
+```
+
+When parallelizing tests, Active Record automatically handles creating and migrating a database for each
+process. The databases will be suffixed with the number corresponding to the worker. For example, if you
+have 2 workers the tests will create `test-database-0` and `test-database-1` respectively.
+
+If the number of workers passed is 1 or fewer the processes will not be forked and the tests will not
+be parallelized and the tests will use the original `test-database` database.
+
+Two hooks are provided, one runs when the process is forked, and one runs before the processes are closed.
+These can be useful if your app uses multiple databases or perform other tasks that depend on the number of
+workers.
+
+The `parallelize_setup` method is called right after the processes are forked. The `parallelize_teardown` method
+is called right before the processes are closed.
+
+```
+class ActiveSupport::TestCase
+  parallelize_setup do |worker|
+    # setup databases
+  end
+
+  parallelize_teardown do |worker|
+    # cleanup database
+  end
+
+  parallelize(workers: 2)
+end
+```
+
+These methods are not needed or available when using parallel testing with threads.
+
+### Parallel testing with threads
+
+If you prefer using threads or are using JRuby, a threaded parallelization option is provided. The threaded
+parallelizer is backed by Minitest's `Parallel::Executor`.
+
+To change the parallelization method to use threads over forks put the following in your `test_helper.rb`
+
+```
+class ActiveSupport::TestCase
+  parallelize(workers: 2, with: :threads)
+end
+```
+
+Rails applications generated from JRuby will automatically include the `with: :threads` option.
+
+The number of workers passed to `parallelize` determines the number of threads the tests will use. You may
+want to parallelize your local test suite differently from your CI, so an environment variable is provided
+to be able to easily change the number of workers a test run should use:
+
+```
+PARALLEL_WORKERS=15 bin/rails test
 ```
 
 The Test Database
@@ -605,7 +691,7 @@ System Testing
 --------------
 
 System tests allow you to test user interactions with your application, running tests
-in either a real or a headless browser. System tests uses Capybara under the hood.
+in either a real or a headless browser. System tests use Capybara under the hood.
 
 For creating Rails system tests, you use the `test/system` directory in your
 application. Rails provides a generator to create a system test skeleton for you.
@@ -645,7 +731,7 @@ system tests should live.
 
 If you want to change the default settings you can change what the system
 tests are "driven by". Say you want to change the driver from Selenium to
-Poltergeist. First add the `poltergeist` gem to your Gemfile. Then in your
+Poltergeist. First add the `poltergeist` gem to your `Gemfile`. Then in your
 `application_system_test_case.rb` file do the following:
 
 ```ruby
@@ -671,6 +757,17 @@ class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
 end
 ```
 
+If you want to use a headless browser, you could use Headless Chrome or Headless Firefox by adding
+`headless_chrome` or `headless_firefox` in the `:using` argument.
+
+```ruby
+require "test_helper"
+
+class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
+  driven_by :selenium, using: :headless_chrome
+end
+```
+
 If your Capybara configuration requires more setup than provided by Rails, this
 additional configuration could be added into the `application_system_test_case.rb`
 file.
@@ -765,9 +862,37 @@ Then the test will fill in the title and body of the article with the specified
 text. Once the fields are filled in, "Create Article" is clicked on which will
 send a POST request to create the new article in the database.
 
-We will be redirected back to the the articles index page and there we assert
+We will be redirected back to the articles index page and there we assert
 that the text from the new article's title is on the articles index page.
 
+#### Testing for multiple screen sizes
+If you want to test for mobile sizes on top of testing for desktop,
+you can create another class that inherits from SystemTestCase and use in your
+test suite. In this example a file called `mobile_system_test_case.rb` is created
+in the `/test` directory with the following configuration.
+
+```ruby
+require "test_helper"
+
+class MobileSystemTestCase < ActionDispatch::SystemTestCase
+  driven_by :selenium, using: :chrome, screen_size: [375, 667]
+end
+```
+To use this configuration, create a test inside `test/system` that inherits from `MobileSystemTestCase`.
+Now you can test your app using multiple different configurations.
+
+```ruby
+require "mobile_system_test_case"
+
+class PostsTest < MobileSystemTestCase
+
+  test "visiting the index" do
+    visit posts_url
+    assert_selector "h1", text: "Posts"
+  end
+end
+```
+
 #### Taking it further
 
 The beauty of system testing is that it is similar to integration testing in
@@ -960,16 +1085,16 @@ The `get` method kicks off the web request and populates the results into the `@
 
 All of these keyword arguments are optional.
 
-Example: Calling the `:show` action, passing an `id` of 12 as the `params` and setting `HTTP_REFERER` header:
+Example: Calling the `:show` action for the first `Article`, passing in an `HTTP_REFERER` header:
 
 ```ruby
-get article_url, params: { id: 12 }, headers: { "HTTP_REFERER" => "http://example.com/home" }
+get article_url(Article.first), headers: { "HTTP_REFERER" => "http://example.com/home" }
 ```
 
-Another example: Calling the `:update` action, passing an `id` of 12 as the `params` as an Ajax request.
+Another example: Calling the `:update` action for the last `Article`, passing in new text for the `title` in `params`, as an Ajax request:
 
 ```ruby
-patch article_url, params: { id: 12 }, xhr: true
+patch article_url(Article.last), params: { article: { title: "updated" } }, xhr: true
 ```
 
 NOTE: If you try running `test_should_create_article` test from `articles_controller_test.rb` it will fail on account of the newly added model level validation and rightly so.
@@ -1006,7 +1131,7 @@ If you're familiar with the HTTP protocol, you'll know that `get` is a type of r
 * `head`
 * `delete`
 
-All of request types have equivalent methods that you can use. In a typical C.R.U.D. application you'll be using `get`, `post`, `put` and `delete` more often.
+All of request types have equivalent methods that you can use. In a typical C.R.U.D. application you'll be using `get`, `post`, `put`, and `delete` more often.
 
 NOTE: Functional tests do not verify whether the specified request type is accepted by the action, we're more concerned with the result. Request tests exist for this use case to make your tests more purposeful.
 
@@ -1360,7 +1485,7 @@ located under the `test/helpers` directory.
 Given we have the following helper:
 
 ```ruby
-module UserHelper
+module UsersHelper
   def link_to_user(user)
     link_to "#{user.first_name} #{user.last_name}", user
   end
@@ -1370,7 +1495,7 @@ end
 We can test the output of this method like this:
 
 ```ruby
-class UserHelperTest < ActionView::TestCase
+class UsersHelperTest < ActionView::TestCase
   test "should return the user's full name" do
     user = users(:david)
 
@@ -1471,12 +1596,12 @@ manually with: `ActionMailer::Base.deliveries.clear`
 
 ### Functional Testing
 
-Functional testing for mailers involves more than just checking that the email body, recipients and so forth are correct. In functional mail tests you call the mail deliver methods and check that the appropriate emails have been appended to the delivery list. It is fairly safe to assume that the deliver methods themselves do their job. You are probably more interested in whether your own business logic is sending emails when you expect them to go out. For example, you can check that the invite friend operation is sending an email appropriately:
+Functional testing for mailers involves more than just checking that the email body, recipients, and so forth are correct. In functional mail tests you call the mail deliver methods and check that the appropriate emails have been appended to the delivery list. It is fairly safe to assume that the deliver methods themselves do their job. You are probably more interested in whether your own business logic is sending emails when you expect them to go out. For example, you can check that the invite friend operation is sending an email appropriately:
 
 ```ruby
 require 'test_helper'
 
-class UserControllerTest < ActionDispatch::IntegrationTest
+class UsersControllerTest < ActionDispatch::IntegrationTest
   test "invite friend" do
     assert_difference 'ActionMailer::Base.deliveries.size', +1 do
       post invite_friend_url, params: { email: 'friend@example.com' }
@@ -1494,7 +1619,7 @@ Testing Jobs
 ------------
 
 Since your custom jobs can be queued at different levels inside your application,
-you'll need to test both, the jobs themselves (their behavior when they get enqueued)
+you'll need to test both the jobs themselves (their behavior when they get enqueued)
 and that other entities correctly enqueue them.
 
 ### A Basic Test Case
@@ -1513,7 +1638,7 @@ class BillingJobTest < ActiveJob::TestCase
 end
 ```
 
-This test is pretty simple and only asserts that the job get the work done
+This test is pretty simple and only asserts that the job got the work done
 as expected.
 
 By default, `ActiveJob::TestCase` will set the queue adapter to `:test` so that
diff --git a/guides/source/threading_and_code_execution.md b/guides/source/threading_and_code_execution.md
new file mode 100644
index 0000000000..e4febc7507
--- /dev/null
+++ b/guides/source/threading_and_code_execution.md
@@ -0,0 +1,324 @@
+**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.**
+
+Threading and Code Execution in Rails
+=====================================
+
+After reading this guide, you will know:
+
+* What code Rails will automatically execute concurrently
+* How to integrate manual concurrency with Rails internals
+* How to wrap all application code
+* How to affect application reloading
+
+--------------------------------------------------------------------------------
+
+Automatic Concurrency
+---------------------
+
+Rails automatically allows various operations to be performed at the same time.
+
+When using a threaded web server, such as the default Puma, multiple HTTP
+requests will be served simultaneously, with each request provided its own
+controller instance.
+
+Threaded Active Job adapters, including the built-in Async, will likewise
+execute several jobs at the same time. Action Cable channels are managed this
+way too.
+
+These mechanisms all involve multiple threads, each managing work for a unique
+instance of some object (controller, job, channel), while sharing the global
+process space (such as classes and their configurations, and global variables).
+As long as your code doesn't modify any of those shared things, it can mostly
+ignore that other threads exist.
+
+The rest of this guide describes the mechanisms Rails uses to make it "mostly
+ignorable", and how extensions and applications with special needs can use them.
+
+Executor
+--------
+
+The Rails Executor separates application code from framework code: any time the
+framework invokes code you've written in your application, it will be wrapped by
+the Executor.
+
+The Executor consists of two callbacks: `to_run` and `to_complete`. The Run
+callback is called before the application code, and the Complete callback is
+called after.
+
+### Default callbacks
+
+In a default Rails application, the Executor callbacks are used to:
+
+* track which threads are in safe positions for autoloading and reloading
+* enable and disable the Active Record query cache
+* return acquired Active Record connections to the pool
+* constrain internal cache lifetimes
+
+Prior to Rails 5.0, some of these were handled by separate Rack middleware
+classes (such as `ActiveRecord::ConnectionAdapters::ConnectionManagement`), or
+directly wrapping code with methods like
+`ActiveRecord::Base.connection_pool.with_connection`. The Executor replaces
+these with a single more abstract interface.
+
+### Wrapping application code
+
+If you're writing a library or component that will invoke application code, you
+should wrap it with a call to the executor:
+
+```ruby
+Rails.application.executor.wrap do
+  # call application code here
+end
+```
+
+TIP: If you repeatedly invoke application code from a long-running process, you
+may want to wrap using the Reloader instead.
+
+Each thread should be wrapped before it runs application code, so if your
+application manually delegates work to other threads, such as via `Thread.new`
+or Concurrent Ruby features that use thread pools, you should immediately wrap
+the block:
+
+```ruby
+Thread.new do
+  Rails.application.executor.wrap do
+    # your code here
+  end
+end
+```
+
+NOTE: Concurrent Ruby uses a `ThreadPoolExecutor`, which it sometimes configures
+with an `executor` option. Despite the name, it is unrelated.
+
+The Executor is safely re-entrant; if it is already active on the current
+thread, `wrap` is a no-op.
+
+If it's impractical to wrap the application code in a block (for
+example, the Rack API makes this problematic), you can also use the `run!` /
+`complete!` pair:
+
+```ruby
+Thread.new do
+  execution_context = Rails.application.executor.run!
+  # your code here
+ensure
+  execution_context.complete! if execution_context
+end
+```
+
+### Concurrency
+
+The Executor will put the current thread into `running` mode in the Load
+Interlock. This operation will block temporarily if another thread is currently
+either autoloading a constant or unloading/reloading the application.
+
+Reloader
+--------
+
+Like the Executor, the Reloader also wraps application code. If the Executor is
+not already active on the current thread, the Reloader will invoke it for you,
+so you only need to call one. This also guarantees that everything the Reloader
+does, including all its callback invocations, occurs wrapped inside the
+Executor.
+
+```ruby
+Rails.application.reloader.wrap do
+  # call application code here
+end
+```
+
+The Reloader is only suitable where a long-running framework-level process
+repeatedly calls into application code, such as for a web server or job queue.
+Rails automatically wraps web requests and Active Job workers, so you'll rarely
+need to invoke the Reloader for yourself. Always consider whether the Executor
+is a better fit for your use case.
+
+### Callbacks
+
+Before entering the wrapped block, the Reloader will check whether the running
+application needs to be reloaded -- for example, because a model's source file has
+been modified. If it determines a reload is required, it will wait until it's
+safe, and then do so, before continuing. When the application is configured to
+always reload regardless of whether any changes are detected, the reload is
+instead performed at the end of the block.
+
+The Reloader also provides `to_run` and `to_complete` callbacks; they are
+invoked at the same points as those of the Executor, but only when the current
+execution has initiated an application reload. When no reload is deemed
+necessary, the Reloader will invoke the wrapped block with no other callbacks.
+
+### Class Unload
+
+The most significant part of the reloading process is the Class Unload, where
+all autoloaded classes are removed, ready to be loaded again. This will occur
+immediately before either the Run or Complete callback, depending on the
+`reload_classes_only_on_change` setting.
+
+Often, additional reloading actions need to be performed either just before or
+just after the Class Unload, so the Reloader also provides `before_class_unload`
+and `after_class_unload` callbacks.
+
+### Concurrency
+
+Only long-running "top level" processes should invoke the Reloader, because if
+it determines a reload is needed, it will block until all other threads have
+completed any Executor invocations.
+
+If this were to occur in a "child" thread, with a waiting parent inside the
+Executor, it would cause an unavoidable deadlock: the reload must occur before
+the child thread is executed, but it cannot be safely performed while the parent
+thread is mid-execution. Child threads should use the Executor instead.
+
+Framework Behavior
+------------------
+
+The Rails framework components use these tools to manage their own concurrency
+needs too.
+
+`ActionDispatch::Executor` and `ActionDispatch::Reloader` are Rack middlewares
+that wraps the request with a supplied Executor or Reloader, respectively. They
+are automatically included in the default application stack. The Reloader will
+ensure any arriving HTTP request is served with a freshly-loaded copy of the
+application if any code changes have occurred.
+
+Active Job also wraps its job executions with the Reloader, loading the latest
+code to execute each job as it comes off the queue.
+
+Action Cable uses the Executor instead: because a Cable connection is linked to
+a specific instance of a class, it's not possible to reload for every arriving
+websocket message. Only the message handler is wrapped, though; a long-running
+Cable connection does not prevent a reload that's triggered by a new incoming
+request or job. Instead, Action Cable uses the Reloader's `before_class_unload`
+callback to disconnect all its connections. When the client automatically
+reconnects, it will be speaking to the new version of the code.
+
+The above are the entry points to the framework, so they are responsible for
+ensuring their respective threads are protected, and deciding whether a reload
+is necessary. Other components only need to use the Executor when they spawn
+additional threads.
+
+### Configuration
+
+The Reloader only checks for file changes when `cache_classes` is false and
+`reload_classes_only_on_change` is true (which is the default in the
+`development` environment).
+
+When `cache_classes` is true (in `production`, by default), the Reloader is only
+a pass-through to the Executor.
+
+The Executor always has important work to do, like database connection
+management. When `cache_classes` and `eager_load` are both true (`production`),
+no autoloading or class reloading will occur, so it does not need the Load
+Interlock. If either of those are false (`development`), then the Executor will
+use the Load Interlock to ensure constants are only loaded when it is safe.
+
+Load Interlock
+--------------
+
+The Load Interlock allows autoloading and reloading to be enabled in a
+multi-threaded runtime environment.
+
+When one thread is performing an autoload by evaluating the class definition
+from the appropriate file, it is important no other thread encounters a
+reference to the partially-defined constant.
+
+Similarly, it is only safe to perform an unload/reload when no application code
+is in mid-execution: after the reload, the `User` constant, for example, may
+point to a different class. Without this rule, a poorly-timed reload would mean
+`User.new.class == User`, or even `User == User`, could be false.
+
+Both of these constraints are addressed by the Load Interlock. It keeps track of
+which threads are currently running application code, loading a class, or
+unloading autoloaded constants.
+
+Only one thread may load or unload at a time, and to do either, it must wait
+until no other threads are running application code. If a thread is waiting to
+perform a load, it doesn't prevent other threads from loading (in fact, they'll
+cooperate, and each perform their queued load in turn, before all resuming
+running together).
+
+### `permit_concurrent_loads`
+
+The Executor automatically acquires a `running` lock for the duration of its
+block, and autoload knows when to upgrade to a `load` lock, and switch back to
+`running` again afterwards.
+
+Other blocking operations performed inside the Executor block (which includes
+all application code), however, can needlessly retain the `running` lock. If
+another thread encounters a constant it must autoload, this can cause a
+deadlock.
+
+For example, assuming `User` is not yet loaded, the following will deadlock:
+
+```ruby
+Rails.application.executor.wrap do
+  th = Thread.new do
+    Rails.application.executor.wrap do
+      User # inner thread waits here; it cannot load
+           # User while another thread is running
+    end
+  end
+
+  th.join # outer thread waits here, holding 'running' lock
+end
+```
+
+To prevent this deadlock, the outer thread can `permit_concurrent_loads`. By
+calling this method, the thread guarantees it will not dereference any
+possibly-autoloaded constant inside the supplied block. The safest way to meet
+that promise is to put it as close as possible to the blocking call:
+
+```ruby
+Rails.application.executor.wrap do
+  th = Thread.new do
+    Rails.application.executor.wrap do
+      User # inner thread can acquire the 'load' lock,
+           # load User, and continue
+    end
+  end
+
+  ActiveSupport::Dependencies.interlock.permit_concurrent_loads do
+    th.join # outer thread waits here, but has no lock
+  end
+end
+```
+
+Another example, using Concurrent Ruby:
+
+```ruby
+Rails.application.executor.wrap do
+  futures = 3.times.collect do |i|
+    Concurrent::Future.execute do
+      Rails.application.executor.wrap do
+        # do work here
+      end
+    end
+  end
+
+  values = ActiveSupport::Dependencies.interlock.permit_concurrent_loads do
+    futures.collect(&:value)
+  end
+end
+```
+
+
+### ActionDispatch::DebugLocks
+
+If your application is deadlocking and you think the Load Interlock may be
+involved, you can temporarily add the ActionDispatch::DebugLocks middleware to
+`config/application.rb`:
+
+```ruby
+config.middleware.insert_before Rack::Sendfile,
+                                  ActionDispatch::DebugLocks
+```
+
+If you then restart the application and re-trigger the deadlock condition,
+`/rails/locks` will show a summary of all threads currently known to the
+interlock, which lock level they are holding or awaiting, and their current
+backtrace.
+
+Generally a deadlock will be caused by the interlock conflicting with some other
+external lock or blocking I/O call. Once you find it, you can wrap it with
+`permit_concurrent_loads`.
+
diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index d932fc8d8f..55e78a47de 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -1,7 +1,7 @@
 **DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.**
 
-A Guide for Upgrading Ruby on Rails
-===================================
+Upgrading Ruby on Rails
+=======================
 
 This guide provides steps to be followed when you upgrade your applications to a newer version of Ruby on Rails. These steps are also available in individual release guides.
 
@@ -27,7 +27,7 @@ The process should go as follows:
 3. Fix tests and deprecated features.
 4. Move to the latest patch version of the next minor version.
 
-Repeat this process until you reach your target Rails version. Each time you move versions, you will need to change the Rails version number in the Gemfile (and possibly other gem versions) and run `bundle update`. Then run the Update task mentioned below to update configuration files, then run your tests.
+Repeat this process until you reach your target Rails version. Each time you move versions, you will need to change the Rails version number in the `Gemfile` (and possibly other gem versions) and run `bundle update`. Then run the Update task mentioned below to update configuration files, then run your tests.
 
 You can find a list of all released Rails versions [here](https://rubygems.org/gems/rails/versions).
 
@@ -35,6 +35,7 @@ You can find a list of all released Rails versions [here](https://rubygems.org/g
 
 Rails generally stays close to the latest released Ruby version when it's released:
 
+* Rails 6 requires Ruby 2.4.1 or newer.
 * Rails 5 requires Ruby 2.2.2 or newer.
 * Rails 4 prefers Ruby 2.0 and requires 1.9.3 or newer.
 * Rails 3.2.x is the last branch to support Ruby 1.8.7.
@@ -45,7 +46,7 @@ TIP: Ruby 1.8.7 p248 and p249 have marshaling bugs that crash Rails. Ruby Enterp
 ### The Update Task
 
 Rails provides the `app:update` task (`rake rails:update` on 4.2 and earlier). After updating the Rails version
-in the Gemfile, run this task.
+in the `Gemfile`, run this task.
 This will help you with the creation of new files and changes of old files in an
 interactive session.
 
@@ -65,6 +66,38 @@ Overwrite /myapp/config/application.rb? (enter "h" for help) [Ynaqdh]
 
 Don't forget to review the difference, to see if there were any unexpected changes.
 
+Upgrading from Rails 5.2 to Rails 6.0
+-------------------------------------
+
+### Force SSL
+
+The `force_ssl` method on controllers has been deprecated and will be removed in
+Rails 6.1. You are encouraged to enable `config.force_ssl` to enforce HTTPS
+connections throughout your application. If you need to exempt certain endpoints
+from redirection, you can use `config.ssl_options` to configure that behavior.
+
+
+Upgrading from Rails 5.1 to Rails 5.2
+-------------------------------------
+
+For more information on changes made to Rails 5.2 please see the [release notes](5_2_release_notes.html).
+
+### Bootsnap
+
+Rails 5.2 adds bootsnap gem in the [newly generated app's Gemfile](https://github.com/rails/rails/pull/29313).
+The `app:update` task sets it up in `boot.rb`. If you want to use it, then add it in the Gemfile,
+otherwise change the `boot.rb` to not use bootsnap.
+
+### Expiry in signed or encrypted cookie is now embedded in the cookies values
+
+To improve security, Rails now embeds the expiry information also in encrypted or signed cookies value.
+
+This new embed information make those cookies incompatible with versions of Rails older than 5.2.
+
+If you require your cookies to be read by 5.1 and older, or you are still validating your 5.2 deploy and want
+to allow you to rollback set
+`Rails.application.config.action_dispatch.use_authenticated_cookie_encryption` to `false`.
+
 Upgrading from Rails 5.0 to Rails 5.1
 -------------------------------------
 
@@ -72,7 +105,7 @@ For more information on changes made to Rails 5.1 please see the [release notes]
 
 ### Top-level `HashWithIndifferentAccess` is soft-deprecated
 
-If your application uses the the top-level `HashWithIndifferentAccess` class, you
+If your application uses the top-level `HashWithIndifferentAccess` class, you
 should slowly move your code to instead use `ActiveSupport::HashWithIndifferentAccess`.
 
 It is only soft-deprecated, which means that your code will not break at the
@@ -179,7 +212,7 @@ See [#19034](https://github.com/rails/rails/pull/19034) for more details.
 
 `assigns` and `assert_template` have been extracted to the `rails-controller-testing` gem. To
 continue using these methods in your controller tests, add `gem 'rails-controller-testing'` to
-your Gemfile.
+your `Gemfile`.
 
 If you are using Rspec for testing, please see the extra configuration required in the gem's
 documentation.
@@ -212,7 +245,7 @@ true.
 
 `ActiveModel::Serializers::Xml` has been extracted from Rails to the `activemodel-serializers-xml`
 gem. To continue using XML serialization in your application, add `gem 'activemodel-serializers-xml'`
-to your Gemfile.
+to your `Gemfile`.
 
 ### Removed Support for Legacy `mysql` Database Adapter
 
@@ -278,7 +311,7 @@ You can now just call the dependency once with a wildcard.
 
 ### `ActionView::Helpers::RecordTagHelper` moved to external gem (record_tag_helper)
 
-`content_tag_for` and `div_for` have been removed in favor of just using `content_tag`. To continue using the older methods, add the `record_tag_helper` gem to your Gemfile:
+`content_tag_for` and `div_for` have been removed in favor of just using `content_tag`. To continue using the older methods, add the `record_tag_helper` gem to your `Gemfile`:
 
 ```ruby
 gem 'record_tag_helper', '~> 1.0'
@@ -411,11 +444,11 @@ Upgrading from Rails 4.1 to Rails 4.2
 
 ### Web Console
 
-First, add `gem 'web-console', '~> 2.0'` to the `:development` group in your Gemfile and run `bundle install` (it won't have been included when you upgraded Rails). Once it's been installed, you can simply drop a reference to the console helper (i.e., `<%= console %>`) into any view you want to enable it for. A console will also be provided on any error page you view in your development environment.
+First, add `gem 'web-console', '~> 2.0'` to the `:development` group in your `Gemfile` and run `bundle install` (it won't have been included when you upgraded Rails). Once it's been installed, you can simply drop a reference to the console helper (i.e., `<%= console %>`) into any view you want to enable it for. A console will also be provided on any error page you view in your development environment.
 
 ### Responders
 
-`respond_with` and the class-level `respond_to` methods have been extracted to the `responders` gem. To use them, simply add `gem 'responders', '~> 2.0'` to your Gemfile. Calls to `respond_with` and `respond_to` (again, at the class level) will no longer work without having included the `responders` gem in your dependencies:
+`respond_with` and the class-level `respond_to` methods have been extracted to the `responders` gem. To use them, simply add `gem 'responders', '~> 2.0'` to your `Gemfile`. Calls to `respond_with` and `respond_to` (again, at the class level) will no longer work without having included the `responders` gem in your dependencies:
 
 ```ruby
 # app/controllers/users_controller.rb
@@ -559,7 +592,7 @@ Read the [gem's readme](https://github.com/rails/rails-html-sanitizer) for more
 The documentation for `PermitScrubber` and `TargetScrubber` explains how you
 can gain complete control over when and how elements should be stripped.
 
-If your application needs to use the old sanitizer implementation, include `rails-deprecated_sanitizer` in your Gemfile:
+If your application needs to use the old sanitizer implementation, include `rails-deprecated_sanitizer` in your `Gemfile`:
 
 ```ruby
 gem 'rails-deprecated_sanitizer'
@@ -567,7 +600,7 @@ gem 'rails-deprecated_sanitizer'
 
 ### Rails DOM Testing
 
-The [`TagAssertions` module](http://api.rubyonrails.org/classes/ActionDispatch/Assertions/TagAssertions.html) (containing methods such as `assert_tag`), [has been deprecated](https://github.com/rails/rails/blob/6061472b8c310158a2a2e8e9a6b81a1aef6b60fe/actionpack/lib/action_dispatch/testing/assertions/dom.rb) in favor of the `assert_select` methods from the `SelectorAssertions` module, which has been extracted into the [rails-dom-testing gem](https://github.com/rails/rails-dom-testing).
+The [`TagAssertions` module](http://api.rubyonrails.org/v4.1/classes/ActionDispatch/Assertions/TagAssertions.html) (containing methods such as `assert_tag`), [has been deprecated](https://github.com/rails/rails/blob/6061472b8c310158a2a2e8e9a6b81a1aef6b60fe/actionpack/lib/action_dispatch/testing/assertions/dom.rb) in favor of the `assert_select` methods from the `SelectorAssertions` module, which has been extracted into the [rails-dom-testing gem](https://github.com/rails/rails-dom-testing).
 
 
 ### Masked Authenticity Tokens
@@ -617,7 +650,7 @@ migration DSL counterpart.
 
 The migration procedure is as follows:
 
-1. remove `gem "foreigner"` from the Gemfile.
+1. remove `gem "foreigner"` from the `Gemfile`.
 2. run `bundle install`.
 3. run `bin/rake db:schema:dump`.
 4. make sure that `db/schema.rb` contains every foreign key definition with
@@ -648,7 +681,7 @@ xhr :get, :index, format: :js
 
 to explicitly test an `XmlHttpRequest`.
 
-Note: Your own `<script>` tags are treated as cross-origin and blocked by
+NOTE: Your own `<script>` tags are treated as cross-origin and blocked by
 default, too. If you really mean to load JavaScript from `<script>` tags,
 you must now explicitly skip CSRF protection on those actions.
 
@@ -769,7 +802,7 @@ and has been removed from Rails.
 
 If your application currently depends on MultiJSON directly, you have a few options:
 
-1. Add 'multi_json' to your Gemfile. Note that this might cease to work in the future
+1. Add 'multi_json' to your `Gemfile`. Note that this might cease to work in the future
 
 2. Migrate away from MultiJSON by using `obj.to_json`, and `JSON.parse(str)` instead.
 
@@ -810,7 +843,7 @@ part of the rewrite, the following features have been removed from the encoder:
 
 If your application depends on one of these features, you can get them back by
 adding the [`activesupport-json_encoder`](https://github.com/rails/activesupport-json_encoder)
-gem to your Gemfile.
+gem to your `Gemfile`.
 
 #### JSON representation of Time objects
 
@@ -1099,7 +1132,7 @@ being used, you can update your form to use the `PUT` method instead:
 <%= form_for [ :update_name, @user ], method: :put do |f| %>
 ```
 
-For more on PATCH and why this change was made, see [this post](http://weblog.rubyonrails.org/2012/2/26/edge-rails-patch-is-the-new-primary-http-method-for-updates/)
+For more on PATCH and why this change was made, see [this post](https://weblog.rubyonrails.org/2012/2/26/edge-rails-patch-is-the-new-primary-http-method-for-updates/)
 on the Rails blog.
 
 #### A note about media types
@@ -1135,8 +1168,8 @@ full support for the last few changes in the specification.
 
 ### Gemfile
 
-Rails 4.0 removed the `assets` group from Gemfile. You'd need to remove that
-line from your Gemfile when upgrading. You should also update your application
+Rails 4.0 removed the `assets` group from `Gemfile`. You'd need to remove that
+line from your `Gemfile` when upgrading. You should also update your application
 file (in `config/application.rb`):
 
 ```ruby
@@ -1147,7 +1180,7 @@ Bundler.require(*Rails.groups)
 
 ### vendor/plugins
 
-Rails 4.0 no longer supports loading plugins from `vendor/plugins`. You must replace any plugins by extracting them to gems and adding them to your Gemfile. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`.
+Rails 4.0 no longer supports loading plugins from `vendor/plugins`. You must replace any plugins by extracting them to gems and adding them to your `Gemfile`. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`.
 
 ### Active Record
 
@@ -1214,7 +1247,7 @@ end
 
 ### Active Resource
 
-Rails 4.0 extracted Active Resource to its own gem. If you still need the feature you can add the [Active Resource gem](https://github.com/rails/activeresource) in your Gemfile.
+Rails 4.0 extracted Active Resource to its own gem. If you still need the feature you can add the [Active Resource gem](https://github.com/rails/activeresource) in your `Gemfile`.
 
 ### Active Model
 
@@ -1414,7 +1447,7 @@ config.active_record.mass_assignment_sanitizer = :strict
 
 ### vendor/plugins
 
-Rails 3.2 deprecates `vendor/plugins` and Rails 4.0 will remove them completely. While it's not strictly necessary as part of a Rails 3.2 upgrade, you can start replacing any plugins by extracting them to gems and adding them to your Gemfile. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`.
+Rails 3.2 deprecates `vendor/plugins` and Rails 4.0 will remove them completely. While it's not strictly necessary as part of a Rails 3.2 upgrade, you can start replacing any plugins by extracting them to gems and adding them to your `Gemfile`. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`.
 
 ### Active Record
 
diff --git a/guides/source/working_with_javascript_in_rails.md b/guides/source/working_with_javascript_in_rails.md
index 6bce73ccad..a922bdc16b 100644
--- a/guides/source/working_with_javascript_in_rails.md
+++ b/guides/source/working_with_javascript_in_rails.md
@@ -24,11 +24,11 @@ In order to understand Ajax, you must first understand what a web browser does
 normally.
 
 When you type `http://localhost:3000` into your browser's address bar and hit
-'Go,' the browser (your 'client') makes a request to the server. It parses the
+'Go', the browser (your 'client') makes a request to the server. It parses the
 response, then fetches all associated assets, like JavaScript files,
 stylesheets and images. It then assembles the page. If you click a link, it
 does the same process: fetch the page, fetch the assets, put it all together,
-show you the results. This is called the 'request response cycle.'
+show you the results. This is called the 'request response cycle'.
 
 JavaScript can also make requests to the server, and parse the response. It
 also has the ability to update information on the page. Combining these two
@@ -57,7 +57,7 @@ will show you how Rails can help you write websites in this way, but it's
 all built on top of this fairly simple technique.
 
 Unobtrusive JavaScript
--------------------------------------
+----------------------
 
 Rails uses a technique called "Unobtrusive JavaScript" to handle attaching
 JavaScript to the DOM. This is generally considered to be a best-practice
@@ -139,7 +139,7 @@ JavaScript) in this style, and you can expect that many libraries will also
 follow this pattern.
 
 Built-in Helpers
-----------------------
+----------------
 
 ### Remote elements
 
@@ -174,7 +174,7 @@ passing the `:local` option `form_with`.
 This will generate the following HTML:
 
 ```html
-<form action="/articles" method="post" data-remote="true">
+<form action="/articles" accept-charset="UTF-8" method="post" data-remote="true">
   ...
 </form>
 ```
@@ -188,15 +188,20 @@ bind to the `ajax:success` event. On failure, use `ajax:error`. Check it out:
 
 ```coffeescript
 $(document).ready ->
-  $("#new_article").on("ajax:success", (e, data, status, xhr) ->
+  $("#new_article").on("ajax:success", (event) ->
+    [data, status, xhr] = event.detail
     $("#new_article").append xhr.responseText
-  ).on "ajax:error", (e, xhr, status, error) ->
+  ).on "ajax:error", (event) ->
     $("#new_article").append "<p>ERROR</p>"
 ```
 
 Obviously, you'll want to be a bit more sophisticated than that, but it's a
 start.
 
+NOTE: As of Rails 5.1 and the new `rails-ujs`, the parameters `data, status, xhr`
+have been bundled into `event.detail`. For information about the previously used
+`jquery-ujs` in Rails 5 and earlier, read the [`jquery-ujs` wiki](https://github.com/rails/jquery-ujs/wiki/ajax).
+
 #### link_to
 
 [`link_to`](http://api.rubyonrails.org/classes/ActionView/Helpers/UrlHelper.html#method-i-link_to)
@@ -225,7 +230,7 @@ and write some CoffeeScript like this:
 
 ```coffeescript
 $ ->
-  $("a[data-remote]").on "ajax:success", (e, data, status, xhr) ->
+  $("a[data-remote]").on "ajax:success", (event) ->
     alert "The article was deleted."
 ```
 
@@ -343,46 +348,13 @@ This generates a form with:
 <input data-disable-with="Saving..." type="submit">
 ```
 
-Dealing with Ajax events
-------------------------
-
-Here are the different events that are fired when you deal with elements
-that have a `data-remote` attribute:
-
-NOTE: All handlers bound to these events are always passed the event object as the
-first argument. The table below describes the extra parameters passed after the
-event argument. For example, if the extra parameters are listed as `xhr, settings`,
-then to access them, you would define your handler with `function(event, xhr, settings)`.
-
-| Event name          | Extra parameters | Fired                                                       |
-|---------------------|------------------|-------------------------------------------------------------|
-| `ajax:before`       |                  | Before the whole ajax business, aborts if stopped.          |
-| `ajax:beforeSend`   | xhr, options     | Before the request is sent, aborts if stopped.              |
-| `ajax:send`         | xhr              | When the request is sent.                                   |
-| `ajax:success`      | xhr, status, err | After completion, if the response was a success.            |
-| `ajax:error`        | xhr, status, err | After completion, if the response was an error.             |
-| `ajax:complete`     | xhr, status      | After the request has been completed, no matter the outcome.|
-| `ajax:aborted:file` | elements         | If there are non-blank file inputs, aborts if stopped.      |
-
-### Stoppable events
-
-If you stop `ajax:before` or `ajax:beforeSend` by returning false from the
-handler method, the Ajax request will never take place. The `ajax:before` event
-is also useful for manipulating form data before serialization. The
-`ajax:beforeSend` event is also useful for adding custom request headers.
-
-If you stop the `ajax:aborted:file` event, the default behavior of allowing the
-browser to submit the form via normal means (i.e. non-AJAX submission) will be
-canceled and the form will not be submitted at all. This is useful for
-implementing your own AJAX file upload workaround.
-
 ### Rails-ujs event handlers
 
 Rails 5.1 introduced rails-ujs and dropped jQuery as a dependency.
 As a result the Unobtrusive JavaScript (UJS) driver has been rewritten to operate without jQuery.
 These introductions cause small changes to `custom events` fired during the request:
 
-NOTE: Signature of calls to UJS’s event handlers has changed.
+NOTE: Signature of calls to UJS's event handlers has changed.
 Unlike the version with jQuery, all custom events return only one parameter: `event`.
 In this parameter, there is an additional attribute `detail` which contains an array of extra parameters.
 
@@ -401,10 +373,28 @@ Example usage:
 ```html
 document.body.addEventListener('ajax:success', function(event) {
   var detail = event.detail;
-  var data = detail[0], status = detail[1],  xhr = detail[2];
+  var data = detail[0], status = detail[1], xhr = detail[2];
 })
 ```
 
+NOTE: As of Rails 5.1 and the new `rails-ujs`, the parameters `data, status, xhr`
+have been bundled into `event.detail`. For information about the previously used
+`jquery-ujs` in Rails 5 and earlier, read the [`jquery-ujs` wiki](https://github.com/rails/jquery-ujs/wiki/ajax).
+
+### Stoppable events
+You can stop execution of the Ajax request by running `event.preventDefault()`
+from the handlers methods `ajax:before` or `ajax:beforeSend`.
+The `ajax:before` event can manipulate form data before serialization and the
+`ajax:beforeSend` event is useful for adding custom request headers.
+
+If you stop the `ajax:aborted:file` event, the default behavior of allowing the
+browser to submit the form via normal means (i.e. non-Ajax submission) will be
+canceled and the form will not be submitted at all. This is useful for
+implementing your own Ajax file upload workaround.
+
+Note, you should use `return false` to prevent event for `jquery-ujs` and
+`e.preventDefault()` for `rails-ujs`
+
 Server-Side Concerns
 --------------------
 
@@ -504,7 +494,7 @@ replace the entire `<body>` of the page with the `<body>` of the response. It
 will then use PushState to change the URL to the correct one, preserving
 refresh semantics and giving you pretty URLs.
 
-The only thing you have to do to enable Turbolinks is have it in your Gemfile,
+The only thing you have to do to enable Turbolinks is have it in your `Gemfile`,
 and put `//= require turbolinks` in your JavaScript manifest, which is usually
 `app/assets/javascripts/application.js`.
 
diff --git a/rails.gemspec b/rails.gemspec
index 4b57377871..709ce642f3 100644
--- a/rails.gemspec
+++ b/rails.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Full-stack web application framework."
   s.description = "Ruby on Rails is a full-stack web framework optimized for programmer happiness and sustainable productivity. It encourages beautiful code by favoring convention over configuration."
 
-  s.required_ruby_version     = ">= 2.2.2"
+  s.required_ruby_version     = ">= 2.4.1"
   s.required_rubygems_version = ">= 1.8.11"
 
   s.license = "MIT"
diff --git a/railties/.gitignore b/railties/.gitignore
index 80dd262d2f..c08562e016 100644
--- a/railties/.gitignore
+++ b/railties/.gitignore
@@ -1 +1,5 @@
-log/
+/log/
+/test/500.html
+/test/fixtures/tmp/
+/test/initializer/root/log/
+/tmp/
diff --git a/railties/CHANGELOG.md b/railties/CHANGELOG.md
index 7b720d6e18..83a57a8c6a 100644
--- a/railties/CHANGELOG.md
+++ b/railties/CHANGELOG.md
@@ -1,129 +1,78 @@
-*   Add `--skip-yarn` option to the plugin generator.
+*   Don't generate unused files in `app:update` task
 
-    *bogdanvlviv*
+     Skip the assets' initializer when sprockets isn't loaded.
 
-*   Optimize routes indentation.
+     Skip `config/spring.rb` when spring isn't loaded.
 
-    *Yoshiyuki Hirano*
+     Skip yarn's contents when yarn integration isn't used.
 
-*   Optimize indentation for generator actions.
-
-    *Yoshiyuki Hirano*
-
-*   Skip unused components when running `bin/rails` in Rails plugin.
-
-    *Yoshiyuki Hirano*
-
-*   Add `git_source` to `Gemfile` for plugin generator.
-
-    *Yoshiyuki Hirano*
-
-*   Add `--skip-action-cable` option to the plugin generator.
-
-    *bogdanvlviv*
-
-*   Deprecate support of use `Rails::Application` subclass to start Rails server.
-
-    *Yuji Yaginuma*
-
-*   Add `ruby x.x.x` version to `Gemfile` and create `.ruby-version`
-    root file containing the current Ruby version when new Rails applications are
-    created.
-
-    *Alberto Almagro*
-
-*   Support `-` as a platform-agnostic way to run a script from stdin with
-    `rails runner`
-
-    *Cody Cutrer*
-
-*   Add `bootsnap` to default `Gemfile`.
-
-    *Burke Libbey*
-
-*   Properly expand shortcuts for environment's name running the `console`
-    and `dbconsole` commands.
-
-    *Robin Dupret*
+    *Tsukuru Tanimichi*
 
-*   Passing the environment's name as a regular argument to the
-    `rails dbconsole` and `rails console` commands is deprecated.
-    The `-e` option should be used instead.
+*   Make the master.key file read-only for the owner upon generation on
+    POSIX-compliant systems.
 
     Previously:
 
-        $ bin/rails dbconsole production
+        $ ls -l config/master.key
+        -rw-r--r--   1 owner  group      32 Jan 1 00:00 master.key
 
     Now:
 
-        $ bin/rails dbconsole -e production
-
-    *Robin Dupret*, *Kasper Timm Hansen*
+        $ ls -l config/master.key
+        -rw-------   1 owner  group      32 Jan 1 00:00 master.key
 
-*   Allow passing a custom connection name to the `rails dbconsole`
-    command when using a 3-level database configuration.
+    Fixes #32604.
 
-        $ bin/rails dbconsole -c replica
+    *Jose Luis Duran*
 
-    *Robin Dupret*, *Jeremy Daer*
+*   Deprecate support for using the `HOST` environment to specify the server IP.
 
-*   Skip unused components when running `bin/rails app:update`.
+    The `BINDING` environment should be used instead.
 
-    If the initial app generation skipped Action Cable, Active Record etc.,
-    the update task honors those skips too.
+    Fixes #29516.
 
     *Yuji Yaginuma*
 
-*   Make Rails' test runner work better with minitest plugins.
+*   Deprecate passing Rack server name as a regular argument to `rails server`.
 
-    By demoting the Rails test runner to just another minitest plugin —
-    and thereby not eager loading it — we can co-exist much better with
-    other minitest plugins such as pride and minitest-focus.
-
-    *Kasper Timm Hansen*
-
-*   Load environment file in `dbconsole` command.
-
-    Fixes #29717.
-
-    *Yuji Yaginuma*
-
-*   Add `rails secrets:show` command.
-
-    *Yuji Yaginuma*
-
-*   Allow mounting the same engine several times in different locations.
-
-    Fixes #20204.
-
-    *David Rodríguez*
+    Previously:
 
-*   Clear screenshot files in `tmp:clear` task.
+        $ bin/rails server thin
 
-    *Yuji Yaginuma*
+    There wasn't an explicit option for the Rack server to use, now we have the
+    `--using` option with the `-u` short switch.
 
-*   Add `railtie.rb` to the plugin generator
-
-    *Tsukuru Tanimichi*
-
-*   Deprecate `capify!` method in generators and templates.
+    Now:
 
-    *Yuji Yaginuma*
+        $ bin/rails server -u thin
 
-*   Allow irb options to be passed from `rails console` command.
+    This change also improves the error message if a missing or mistyped rack
+    server is given.
 
-    Fixes #28988.
+    *Genadi Samokovarov*
 
-    *Yuji Yaginuma*
+*   Add "rails routes --expanded" option to output routes in expanded mode like
+    "psql --expanded". Result looks like:
 
-*   Added a shared section to `config/database.yml` that will be loaded for all environments.
+    ```
+    $ rails routes --expanded
+    --[ Route 1 ]------------------------------------------------------------
+    Prefix            | high_scores
+    Verb              | GET
+    URI               | /high_scores(.:format)
+    Controller#Action | high_scores#index
+    --[ Route 2 ]------------------------------------------------------------
+    Prefix            | new_high_score
+    Verb              | GET
+    URI               | /high_scores/new(.:format)
+    Controller#Action | high_scores#new
+    ```
 
-    *Pierre Schambacher*
+    *Benoit Tigeot*
 
-*   Namespace error pages' CSS selectors to stop the styles from bleeding into other pages
-    when using Turbolinks.
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
-    *Jan Krutisch*
+    *Jeremy Daer*
 
 
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/railties/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/railties/CHANGELOG.md) for previous changes.
diff --git a/railties/MIT-LICENSE b/railties/MIT-LICENSE
index f9e4444f07..cce00cbc3a 100644
--- a/railties/MIT-LICENSE
+++ b/railties/MIT-LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2004-2017 David Heinemeier Hansson
+Copyright (c) 2004-2018 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/railties/RDOC_MAIN.rdoc b/railties/RDOC_MAIN.rdoc
index 6b9a243593..a4a4b6b235 100644
--- a/railties/RDOC_MAIN.rdoc
+++ b/railties/RDOC_MAIN.rdoc
@@ -1,35 +1,57 @@
-== Welcome to \Rails
-
-\Rails is a web-application framework that includes everything needed to create
-database-backed web applications according to the {Model-View-Controller (MVC)}[https://en.wikipedia.org/wiki/Model-view-controller] pattern.
-
-Understanding the MVC pattern is key to understanding \Rails. MVC divides your application
-into three layers, each with a specific responsibility.
-
-The View layer is composed of "templates" that are responsible for providing
-appropriate representations of your application's resources. Templates
-can come in a variety of formats, but most view templates are \HTML with embedded Ruby
-code (.erb files).
-
-The Model layer represents your domain model (such as Account, Product, Person, Post)
-and encapsulates the business logic that is specific to your application. In \Rails,
-database-backed model classes are derived from ActiveRecord::Base. Active Record allows
-you to present the data from database rows as objects and embellish these data objects
-with business logic methods. Although most \Rails models are backed by a database, models
-can also be ordinary Ruby classes, or Ruby classes that implement a set of interfaces as
-provided by the ActiveModel module. You can read more about Active Record in its
-{README}[link:files/activerecord/README_rdoc.html].
-
-The Controller layer is responsible for handling incoming HTTP requests and providing a
-suitable response. Usually this means returning \HTML, but \Rails controllers can also
-generate XML, JSON, PDFs, mobile-specific views, and more. Controllers manipulate models
-and render view templates in order to generate the appropriate HTTP response.
-
-In \Rails, the Controller and View layers are handled together by Action Pack.
-These two layers are bundled in a single package due to their heavy interdependence.
-This is unlike the relationship between Active Record and Action Pack, which are
-independent. Each of these packages can be used independently outside of \Rails. You
-can read more about Action Pack in its {README}[link:files/actionpack/README_rdoc.html].
+= Welcome to \Rails
+
+== What's \Rails
+
+\Rails is a web-application framework that includes everything needed to
+create database-backed web applications according to the
+{Model-View-Controller (MVC)}[http://en.wikipedia.org/wiki/Model-view-controller]
+pattern.
+
+Understanding the MVC pattern is key to understanding \Rails. MVC divides your
+application into three layers: Model, View, and Controller, each with a specific responsibility.
+
+== Model layer
+
+The <em><b>Model layer</b></em> represents the domain model (such as Account, Product,
+Person, Post, etc.) and encapsulates the business logic specific to
+your application. In \Rails, database-backed model classes are derived from
+<tt>ActiveRecord::Base</tt>. {Active Record}[link:files/activerecord/README_rdoc.html] allows you to present the data from
+database rows as objects and embellish these data objects with business logic
+methods. Although most \Rails models are backed by a database, models can also be ordinary
+Ruby classes, or Ruby classes that implement a set of interfaces as provided by
+the {Active Model}[link:files/activemodel/README_rdoc.html] module.
+
+== Controller layer
+
+The <em><b>Controller layer</b></em> is responsible for handling incoming HTTP requests and
+providing a suitable response. Usually this means returning \HTML, but \Rails controllers
+can also generate XML, JSON, PDFs, mobile-specific views, and more. Controllers load and
+manipulate models, and render view templates in order to generate the appropriate HTTP response.
+In \Rails, incoming requests are routed by Action Dispatch to an appropriate controller, and
+controller classes are derived from <tt>ActionController::Base</tt>. Action Dispatch and Action Controller
+are bundled together in {Action Pack}[link:files/actionpack/README_rdoc.html].
+
+== View layer
+
+The <em><b>View layer</b></em> is composed of "templates" that are responsible for providing
+appropriate representations of your application's resources. Templates can
+come in a variety of formats, but most view templates are \HTML with embedded
+Ruby code (ERB files). Views are typically rendered to generate a controller response,
+or to generate the body of an email. In \Rails, View generation is handled by {Action View}[link:files/actionview/README_rdoc.html].
+
+== Frameworks and libraries
+
+{Active Record}[link:files/activerecord/README_rdoc.html], {Active Model}[link:files/activemodel/README_rdoc.html],
+{Action Pack}[link:files/actionpack/README_rdoc.html], and {Action View}[link:files/actionview/README_rdoc.html] can each be used independently outside \Rails.
+In addition to that, \Rails also comes with {Action Mailer}[link:files/actionmailer/README_rdoc.html], a library
+to generate and send emails; {Active Job}[link:files/activejob/README_md.html], a
+framework for declaring jobs and making them run on a variety of queueing
+backends; {Action Cable}[link:files/actioncable/README_md.html], a framework to
+integrate WebSockets with a \Rails application; {Active Storage}[link:files/activestorage/README_md.html],
+a library to attach cloud and local files to \Rails applications;
+and {Active Support}[link:files/activesupport/README_rdoc.html], a collection
+of utility classes and standard library extensions that are useful for \Rails,
+and may also be used independently outside \Rails.
 
 == Getting Started
 
@@ -45,28 +67,31 @@ can read more about Action Pack in its {README}[link:files/actionpack/README_rdo
 
 3. Change directory to +myapp+ and start the web server:
 
-    $ cd myapp; rails server
+    $ cd myapp
+    $ rails server
 
    Run with <tt>--help</tt> or <tt>-h</tt> for options.
 
-4. Go to http://localhost:3000 and you'll see:
-
-    "Yay! You’re on Rails!"
+4. Go to <tt>http://localhost:3000</tt> and you'll see: "Yay! You’re on \Rails!"
 
 5. Follow the guidelines to start developing your application. You may find the following resources handy:
 
-* The \README file created within your application.
-* {Getting Started with \Rails}[http://guides.rubyonrails.org/getting_started.html].
-* {Ruby on \Rails Tutorial}[https://www.railstutorial.org/book].
-* {Ruby on \Rails Guides}[http://guides.rubyonrails.org].
-* {The API Documentation}[http://api.rubyonrails.org].
+   * The \README file created within your application.
+   * {Getting Started with \Rails}[http://guides.rubyonrails.org/getting_started.html].
+   * {Ruby on \Rails Guides}[http://guides.rubyonrails.org].
+   * {The API Documentation}[http://api.rubyonrails.org].
+   * {Ruby on \Rails Tutorial}[https://www.railstutorial.org/book].
 
 == Contributing
 
-We encourage you to contribute to Ruby on \Rails! Please check out the {Contributing to Rails
-guide}[http://edgeguides.rubyonrails.org/contributing_to_ruby_on_rails.html] for guidelines about how
-to proceed. {Join us}[http://contributors.rubyonrails.org]!
+We encourage you to contribute to Ruby on \Rails! Please check out the
+{Contributing to Ruby on \Rails guide}[http://guides.rubyonrails.org/contributing_to_ruby_on_rails.html] for guidelines about how to proceed. {Join us!}[http://contributors.rubyonrails.org]
+
+Trying to report a possible security vulnerability in \Rails? Please
+check out our {security policy}[http://rubyonrails.org/security/] for
+guidelines about how to proceed.
 
+Everyone interacting in \Rails and its sub-projects' codebases, issue trackers, chat rooms, and mailing lists is expected to follow the \Rails {code of conduct}[http://rubyonrails.org/conduct/].
 
 == License
 
diff --git a/railties/Rakefile b/railties/Rakefile
index d41c6e7438..8251b2bb32 100644
--- a/railties/Rakefile
+++ b/railties/Rakefile
@@ -11,19 +11,61 @@ task test: "test:isolated"
 
 namespace :test do
   task :isolated do
+    dash_i = [
+      "test",
+      "lib",
+      "../activesupport/lib",
+      "../actionpack/lib",
+      "../actionview/lib",
+      "../activemodel/lib"
+    ].map { |dir| File.expand_path(dir, __dir__) }
+
+    dash_i.reverse_each do |x|
+      $:.unshift(x) unless $:.include?(x)
+    end
+    $-w = true
+
+    require "bundler/setup" unless defined?(Bundler)
+    require "active_support"
+
+    failing_files = []
+
     dirs = (ENV["TEST_DIR"] || ENV["TEST_DIRS"] || "**").split(",")
     test_files = dirs.map { |dir| "test/#{dir}/*_test.rb" }
     Dir[*test_files].each do |file|
-      next true if file.include?("fixtures")
-      dash_i = [
-        "test",
-        "lib",
-        "#{__dir__}/../activesupport/lib",
-        "#{__dir__}/../actionpack/lib",
-        "#{__dir__}/../actionview/lib",
-        "#{__dir__}/../activemodel/lib"
-      ]
-      ruby "-w", "-I#{dash_i.join ':'}", file
+      next true if file.start_with?("test/fixtures/")
+
+      fake_command = Shellwords.join([
+        FileUtils::RUBY,
+        "-w",
+        *dash_i.map { |dir| "-I#{Pathname.new(dir).relative_path_from(Pathname.pwd)}" },
+        file,
+      ])
+      puts fake_command
+
+      # We could run these in parallel, but pretty much all of the
+      # railties tests already run in parallel, so ¯\_(⊙︿⊙)_/¯
+      Process.waitpid fork {
+        ARGV.clear
+        Rake.application = nil
+
+        load file
+      }
+
+      unless $?.success?
+        failing_files << file
+      end
+    end
+
+    unless failing_files.empty?
+      puts
+      puts "Failed in:"
+      failing_files.each do |file|
+        puts "  #{file}"
+      end
+      puts
+
+      raise "Failure in isolated test runner"
     end
   end
 end
@@ -31,7 +73,7 @@ end
 Rake::TestTask.new("test:regular") do |t|
   t.libs << "test" << "#{__dir__}/../activesupport/lib"
   t.pattern = "test/**/*_test.rb"
-  t.warning = false
+  t.warning = true
   t.verbose = true
   t.ruby_opts = ["--dev"] if defined?(JRUBY_VERSION)
 end
diff --git a/railties/lib/minitest/rails_plugin.rb b/railties/lib/minitest/rails_plugin.rb
index 6901b0bbc8..6486fa1798 100644
--- a/railties/lib/minitest/rails_plugin.rb
+++ b/railties/lib/minitest/rails_plugin.rb
@@ -13,7 +13,7 @@ module Minitest
   end
 
   def self.plugin_rails_options(opts, options)
-    Rails::TestUnit::Runner.attach_before_load_options(opts)
+    ::Rails::TestUnit::Runner.attach_before_load_options(opts)
 
     opts.on("-b", "--backtrace", "Show the complete backtrace") do
       options[:full_backtrace] = true
@@ -43,10 +43,15 @@ module Minitest
       Minitest.backtrace_filter = ::Rails.backtrace_cleaner if ::Rails.respond_to?(:backtrace_cleaner)
     end
 
+    # Suppress summary reports when outputting inline rerun snippets.
+    if reporter.reporters.reject! { |reporter| reporter.kind_of?(SummaryReporter) }
+      reporter << SuppressedSummaryReporter.new(options[:io], options)
+    end
+
     # Replace progress reporter for colors.
-    reporter.reporters.delete_if { |reporter| reporter.kind_of?(SummaryReporter) || reporter.kind_of?(ProgressReporter) }
-    reporter << SuppressedSummaryReporter.new(options[:io], options)
-    reporter << ::Rails::TestUnitReporter.new(options[:io], options)
+    if reporter.reporters.reject! { |reporter| reporter.kind_of?(ProgressReporter) }
+      reporter << ::Rails::TestUnitReporter.new(options[:io], options)
+    end
   end
 
   # Backwardscompatibility with Rails 5.0 generated plugin test scripts
diff --git a/railties/lib/rails.rb b/railties/lib/rails.rb
index 04bb9ba94a..092105d502 100644
--- a/railties/lib/rails.rb
+++ b/railties/lib/rails.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "rails/ruby_version_check"
+require "rails/ruby_version_check"
 
 require "pathname"
 
@@ -11,8 +11,8 @@ require "active_support/core_ext/module/delegation"
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/object/blank"
 
-require_relative "rails/application"
-require_relative "rails/version"
+require "rails/application"
+require "rails/version"
 
 require "active_support/railtie"
 require "action_dispatch/railtie"
@@ -50,7 +50,7 @@ module Rails
     def backtrace_cleaner
       @backtrace_cleaner ||= begin
         # Relies on Active Support, so we have to lazy load to postpone definition until Active Support has been loaded
-        require_relative "rails/backtrace_cleaner"
+        require "rails/backtrace_cleaner"
         Rails::BacktraceCleaner.new
       end
     end
diff --git a/railties/lib/rails/all.rb b/railties/lib/rails/all.rb
index e55b2e2433..f5dccd2381 100644
--- a/railties/lib/rails/all.rb
+++ b/railties/lib/rails/all.rb
@@ -4,12 +4,12 @@ require "rails"
 
 %w(
   active_record/railtie
+  active_storage/engine
   action_controller/railtie
   action_view/railtie
   action_mailer/railtie
   active_job/railtie
   action_cable/engine
-  active_storage/engine
   rails/test_unit/railtie
   sprockets/railtie
 ).each do |railtie|
diff --git a/railties/lib/rails/api/generator.rb b/railties/lib/rails/api/generator.rb
index 6e5eec2e34..3405560b74 100644
--- a/railties/lib/rails/api/generator.rb
+++ b/railties/lib/rails/api/generator.rb
@@ -6,8 +6,11 @@ class RDoc::Generator::API < RDoc::Generator::SDoc # :nodoc:
   RDoc::RDoc.add_generator self
 
   def generate_class_tree_level(classes, visited = {})
-    # Only process core extensions on the first visit.
+    # Only process core extensions on the first visit and remove
+    # Active Storage duplicated classes that are at the top level
+    # since they aren't nested under a definition of the `ActiveStorage` module.
     if visited.empty?
+      classes = classes.reject { |klass| active_storage?(klass) }
       core_exts, classes = classes.partition { |klass| core_extension?(klass) }
 
       super.unshift([ "Core extensions", "", "", build_core_ext_subtree(core_exts, visited) ])
@@ -27,4 +30,8 @@ class RDoc::Generator::API < RDoc::Generator::SDoc # :nodoc:
     def core_extension?(klass)
       klass.name != "ActiveSupport" && klass.in_files.any? { |file| file.absolute_name.include?("core_ext") }
     end
+
+    def active_storage?(klass)
+      klass.name != "ActiveStorage" && klass.in_files.all? { |file| file.absolute_name.include?("active_storage") }
+    end
 end
diff --git a/railties/lib/rails/api/task.rb b/railties/lib/rails/api/task.rb
index 184f5b14f1..e7f0557584 100644
--- a/railties/lib/rails/api/task.rb
+++ b/railties/lib/rails/api/task.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "rdoc/task"
-require_relative "generator"
+require "rails/api/generator"
 
 module Rails
   module API
diff --git a/railties/lib/rails/app_loader.rb b/railties/lib/rails/app_loader.rb
index 3e9b3bd4bb..20eb75d95c 100644
--- a/railties/lib/rails/app_loader.rb
+++ b/railties/lib/rails/app_loader.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "pathname"
-require_relative "version"
+require "rails/version"
 
 module Rails
   module AppLoader # :nodoc:
@@ -56,7 +56,7 @@ EOS
             $stderr.puts(BUNDLER_WARNING)
             Object.const_set(:APP_PATH, File.expand_path("config/application", Dir.pwd))
             require File.expand_path("../boot", APP_PATH)
-            require_relative "commands"
+            require "rails/commands"
             break
           end
         end
diff --git a/railties/lib/rails/app_updater.rb b/railties/lib/rails/app_updater.rb
index c2436a69f9..a243968a39 100644
--- a/railties/lib/rails/app_updater.rb
+++ b/railties/lib/rails/app_updater.rb
@@ -21,11 +21,15 @@ module Rails
       private
         def generator_options
           options = { api: !!Rails.application.config.api_only, update: true }
-          options[:skip_active_record] = !defined?(ActiveRecord::Railtie)
-          options[:skip_action_mailer] = !defined?(ActionMailer::Railtie)
-          options[:skip_action_cable]  = !defined?(ActionCable::Engine)
-          options[:skip_sprockets]     = !defined?(Sprockets::Railtie)
-          options[:skip_puma]          = !defined?(Puma)
+          options[:skip_yarn] = !File.exist?(Rails.root.join("bin", "yarn"))
+          options[:skip_active_record]  = !defined?(ActiveRecord::Railtie)
+          options[:skip_active_storage] = !defined?(ActiveStorage::Engine) || !defined?(ActiveRecord::Railtie)
+          options[:skip_action_mailer]  = !defined?(ActionMailer::Railtie)
+          options[:skip_action_cable]   = !defined?(ActionCable::Engine)
+          options[:skip_sprockets]      = !defined?(Sprockets::Railtie)
+          options[:skip_puma]           = !defined?(Puma)
+          options[:skip_bootsnap]       = !defined?(Bootsnap)
+          options[:skip_spring]         = !defined?(Spring)
           options
         end
     end
diff --git a/railties/lib/rails/application.rb b/railties/lib/rails/application.rb
index 72f8bf0e14..e346d5cc3a 100644
--- a/railties/lib/rails/application.rb
+++ b/railties/lib/rails/application.rb
@@ -5,8 +5,10 @@ require "active_support/core_ext/hash/keys"
 require "active_support/core_ext/object/blank"
 require "active_support/key_generator"
 require "active_support/message_verifier"
-require_relative "engine"
-require_relative "secrets"
+require "active_support/encrypted_configuration"
+require "active_support/deprecation"
+require "rails/engine"
+require "rails/secrets"
 
 module Rails
   # An Engine with the responsibility of coordinating the whole boot process.
@@ -171,12 +173,10 @@ module Rails
       # number of iterations selected based on consultation with the google security
       # team. Details at https://github.com/rails/rails/pull/6952#issuecomment-7661220
       @caching_key_generator ||=
-        if secrets.secret_key_base
-          unless secrets.secret_key_base.kind_of?(String)
-            raise ArgumentError, "`secret_key_base` for #{Rails.env} environment must be a type of String, change this value in `config/secrets.yml`"
-          end
-          key_generator = ActiveSupport::KeyGenerator.new(secrets.secret_key_base, iterations: 1000)
-          ActiveSupport::CachingKeyGenerator.new(key_generator)
+        if secret_key_base
+          ActiveSupport::CachingKeyGenerator.new(
+            ActiveSupport::KeyGenerator.new(secret_key_base, iterations: 1000)
+          )
         else
           ActiveSupport::LegacyKeyGenerator.new(secrets.secret_token)
         end
@@ -246,13 +246,11 @@ module Rails
     # will be used by middlewares and engines to configure themselves.
     def env_config
       @app_env_config ||= begin
-        validate_secret_key_config!
-
         super.merge(
           "action_dispatch.parameter_filter" => config.filter_parameters,
           "action_dispatch.redirect_filter" => config.filter_redirect,
           "action_dispatch.secret_token" => secrets.secret_token,
-          "action_dispatch.secret_key_base" => secrets.secret_key_base,
+          "action_dispatch.secret_key_base" => secret_key_base,
           "action_dispatch.show_exceptions" => config.action_dispatch.show_exceptions,
           "action_dispatch.show_detailed_exceptions" => config.consider_all_requests_local,
           "action_dispatch.logger" => Rails.logger,
@@ -263,8 +261,15 @@ module Rails
           "action_dispatch.encrypted_cookie_salt" => config.action_dispatch.encrypted_cookie_salt,
           "action_dispatch.encrypted_signed_cookie_salt" => config.action_dispatch.encrypted_signed_cookie_salt,
           "action_dispatch.authenticated_encrypted_cookie_salt" => config.action_dispatch.authenticated_encrypted_cookie_salt,
+          "action_dispatch.use_authenticated_cookie_encryption" => config.action_dispatch.use_authenticated_cookie_encryption,
+          "action_dispatch.encrypted_cookie_cipher" => config.action_dispatch.encrypted_cookie_cipher,
+          "action_dispatch.signed_cookie_digest" => config.action_dispatch.signed_cookie_digest,
           "action_dispatch.cookies_serializer" => config.action_dispatch.cookies_serializer,
-          "action_dispatch.cookies_digest" => config.action_dispatch.cookies_digest
+          "action_dispatch.cookies_digest" => config.action_dispatch.cookies_digest,
+          "action_dispatch.cookies_rotations" => config.action_dispatch.cookies_rotations,
+          "action_dispatch.content_security_policy" => config.content_security_policy,
+          "action_dispatch.content_security_policy_report_only" => config.content_security_policy_report_only,
+          "action_dispatch.content_security_policy_nonce_generator" => config.content_security_policy_nonce_generator
         )
       end
     end
@@ -398,6 +403,12 @@ module Rails
         # Fallback to config.secret_token if secrets.secret_token isn't set
         secrets.secret_token ||= config.secret_token
 
+        if secrets.secret_token.present?
+          ActiveSupport::Deprecation.warn(
+            "`secrets.secret_token` is deprecated in favor of `secret_key_base` and will be removed in Rails 6.0."
+          )
+        end
+
         secrets
       end
     end
@@ -406,6 +417,67 @@ module Rails
       @secrets = secrets
     end
 
+    # The secret_key_base is used as the input secret to the application's key generator, which in turn
+    # is used to create all MessageVerifiers/MessageEncryptors, including the ones that sign and encrypt cookies.
+    #
+    # In test and development, this is simply derived as a MD5 hash of the application's name.
+    #
+    # In all other environments, we look for it first in ENV["SECRET_KEY_BASE"],
+    # then credentials.secret_key_base, and finally secrets.secret_key_base. For most applications,
+    # the correct place to store it is in the encrypted credentials file.
+    def secret_key_base
+      if Rails.env.test? || Rails.env.development?
+        secrets.secret_key_base || Digest::MD5.hexdigest(self.class.name)
+      else
+        validate_secret_key_base(
+          ENV["SECRET_KEY_BASE"] || credentials.secret_key_base || secrets.secret_key_base
+        )
+      end
+    end
+
+    # Decrypts the credentials hash as kept in +config/credentials.yml.enc+. This file is encrypted with
+    # the Rails master key, which is either taken from <tt>ENV["RAILS_MASTER_KEY"]</tt> or from loading
+    # +config/master.key+.
+    def credentials
+      @credentials ||= encrypted("config/credentials.yml.enc")
+    end
+
+    # Shorthand to decrypt any encrypted configurations or files.
+    #
+    # For any file added with <tt>bin/rails encrypted:edit</tt> call +read+ to decrypt
+    # the file with the master key.
+    # The master key is either stored in +config/master.key+ or <tt>ENV["RAILS_MASTER_KEY"]</tt>.
+    #
+    #   Rails.application.encrypted("config/mystery_man.txt.enc").read
+    #   # => "We've met before, haven't we?"
+    #
+    # It's also possible to interpret encrypted YAML files with +config+.
+    #
+    #   Rails.application.encrypted("config/credentials.yml.enc").config
+    #   # => { next_guys_line: "I don't think so. Where was it you think we met?" }
+    #
+    # Any top-level configs are also accessible directly on the return value:
+    #
+    #   Rails.application.encrypted("config/credentials.yml.enc").next_guys_line
+    #   # => "I don't think so. Where was it you think we met?"
+    #
+    # The files or configs can also be encrypted with a custom key. To decrypt with
+    # a key in the +ENV+, use:
+    #
+    #   Rails.application.encrypted("config/special_tokens.yml.enc", env_key: "SPECIAL_TOKENS")
+    #
+    # Or to decrypt with a file, that should be version control ignored, relative to +Rails.root+:
+    #
+    #   Rails.application.encrypted("config/special_tokens.yml.enc", key_path: "config/special_tokens.key")
+    def encrypted(path, key_path: "config/master.key", env_key: "RAILS_MASTER_KEY")
+      ActiveSupport::EncryptedConfiguration.new(
+        config_path: Rails.root.join(path),
+        key_path: Rails.root.join(key_path),
+        env_key: env_key,
+        raise_if_missing_key: config.require_master_key
+      )
+    end
+
     def to_app #:nodoc:
       self
     end
@@ -441,7 +513,7 @@ module Rails
     def run_tasks_blocks(app) #:nodoc:
       railties.each { |r| r.run_tasks_blocks(app) }
       super
-      require_relative "tasks"
+      require "rails/tasks"
       task :environment do
         ActiveSupport.on_load(:before_initialize) { config.eager_load = false }
 
@@ -504,14 +576,13 @@ module Rails
       default_stack.build_stack
     end
 
-    def validate_secret_key_config! #:nodoc:
-      if secrets.secret_key_base.blank?
-        ActiveSupport::Deprecation.warn "You didn't set `secret_key_base`. " \
-          "Read the upgrade documentation to learn more about this new config option."
-
-        if secrets.secret_token.blank?
-          raise "Missing `secret_key_base` for '#{Rails.env}' environment, set this value in `config/secrets.yml`"
-        end
+    def validate_secret_key_base(secret_key_base)
+      if secret_key_base.is_a?(String) && secret_key_base.present?
+        secret_key_base
+      elsif secret_key_base
+        raise ArgumentError, "`secret_key_base` for #{Rails.env} environment must be a type of String`"
+      elsif secrets.secret_token.blank?
+        raise ArgumentError, "Missing `secret_key_base` for '#{Rails.env}' environment, set this string with `rails credentials:edit`"
       end
     end
 
diff --git a/railties/lib/rails/application/bootstrap.rb b/railties/lib/rails/application/bootstrap.rb
index c24d4573a9..e3c0759f95 100644
--- a/railties/lib/rails/application/bootstrap.rb
+++ b/railties/lib/rails/application/bootstrap.rb
@@ -4,7 +4,7 @@ require "fileutils"
 require "active_support/notifications"
 require "active_support/dependencies"
 require "active_support/descendants_tracker"
-require_relative "../secrets"
+require "rails/secrets"
 
 module Rails
   class Application
diff --git a/railties/lib/rails/application/configuration.rb b/railties/lib/rails/application/configuration.rb
index 31e2a45bff..bba573499d 100644
--- a/railties/lib/rails/application/configuration.rb
+++ b/railties/lib/rails/application/configuration.rb
@@ -2,8 +2,8 @@
 
 require "active_support/core_ext/kernel/reporting"
 require "active_support/file_update_checker"
-require_relative "../engine/configuration"
-require_relative "../source_annotation_extractor"
+require "rails/engine/configuration"
+require "rails/source_annotation_extractor"
 
 module Rails
   class Application
@@ -16,44 +16,50 @@ module Rails
                     :ssl_options, :public_file_server,
                     :session_options, :time_zone, :reload_classes_only_on_change,
                     :beginning_of_week, :filter_redirect, :x, :enable_dependency_loading,
-                    :read_encrypted_secrets, :log_level
+                    :read_encrypted_secrets, :log_level, :content_security_policy_report_only,
+                    :content_security_policy_nonce_generator, :require_master_key
 
-      attr_reader :encoding, :api_only
+      attr_reader :encoding, :api_only, :loaded_config_version
 
       def initialize(*)
         super
-        self.encoding                    = Encoding::UTF_8
-        @allow_concurrency               = nil
-        @consider_all_requests_local     = false
-        @filter_parameters               = []
-        @filter_redirect                 = []
-        @helpers_paths                   = []
-        @public_file_server              = ActiveSupport::OrderedOptions.new
-        @public_file_server.enabled      = true
-        @public_file_server.index_name   = "index"
-        @force_ssl                       = false
-        @ssl_options                     = {}
-        @session_store                   = nil
-        @time_zone                       = "UTC"
-        @beginning_of_week               = :monday
-        @log_level                       = :debug
-        @generators                      = app_generators
-        @cache_store                     = [ :file_store, "#{root}/tmp/cache/" ]
-        @railties_order                  = [:all]
-        @relative_url_root               = ENV["RAILS_RELATIVE_URL_ROOT"]
-        @reload_classes_only_on_change   = true
-        @file_watcher                    = ActiveSupport::FileUpdateChecker
-        @exceptions_app                  = nil
-        @autoflush_log                   = true
-        @log_formatter                   = ActiveSupport::Logger::SimpleFormatter.new
-        @eager_load                      = nil
-        @secret_token                    = nil
-        @secret_key_base                 = nil
-        @api_only                        = false
-        @debug_exception_response_format = nil
-        @x                               = Custom.new
-        @enable_dependency_loading       = false
-        @read_encrypted_secrets          = false
+        self.encoding                            = Encoding::UTF_8
+        @allow_concurrency                       = nil
+        @consider_all_requests_local             = false
+        @filter_parameters                       = []
+        @filter_redirect                         = []
+        @helpers_paths                           = []
+        @public_file_server                      = ActiveSupport::OrderedOptions.new
+        @public_file_server.enabled              = true
+        @public_file_server.index_name           = "index"
+        @force_ssl                               = false
+        @ssl_options                             = {}
+        @session_store                           = nil
+        @time_zone                               = "UTC"
+        @beginning_of_week                       = :monday
+        @log_level                               = :debug
+        @generators                              = app_generators
+        @cache_store                             = [ :file_store, "#{root}/tmp/cache/" ]
+        @railties_order                          = [:all]
+        @relative_url_root                       = ENV["RAILS_RELATIVE_URL_ROOT"]
+        @reload_classes_only_on_change           = true
+        @file_watcher                            = ActiveSupport::FileUpdateChecker
+        @exceptions_app                          = nil
+        @autoflush_log                           = true
+        @log_formatter                           = ActiveSupport::Logger::SimpleFormatter.new
+        @eager_load                              = nil
+        @secret_token                            = nil
+        @secret_key_base                         = nil
+        @api_only                                = false
+        @debug_exception_response_format         = nil
+        @x                                       = Custom.new
+        @enable_dependency_loading               = false
+        @read_encrypted_secrets                  = false
+        @content_security_policy                 = nil
+        @content_security_policy_report_only     = false
+        @content_security_policy_nonce_generator = nil
+        @require_master_key                      = false
+        @loaded_config_version                   = nil
       end
 
       def load_defaults(target_version)
@@ -71,7 +77,6 @@ module Rails
           end
 
           self.ssl_options = { hsts: { subdomains: true } }
-
         when "5.1"
           load_defaults "5.0"
 
@@ -82,7 +87,6 @@ module Rails
           if respond_to?(:action_view)
             action_view.form_with_generates_remote_forms = true
           end
-
         when "5.2"
           load_defaults "5.1"
 
@@ -100,15 +104,27 @@ module Rails
 
           if respond_to?(:active_support)
             active_support.use_authenticated_message_encryption = true
+            active_support.use_sha1_digests = true
           end
 
           if respond_to?(:action_controller)
             action_controller.default_protect_from_forgery = true
           end
 
+          if respond_to?(:action_view)
+            action_view.form_with_generates_ids = true
+          end
+        when "6.0"
+          load_defaults "5.2"
+
+          if respond_to?(:action_view)
+            action_view.default_enforce_utf8 = false
+          end
         else
           raise "Unknown version #{target_version.to_s.inspect}"
         end
+
+        @loaded_config_version = target_version
       end
 
       def encoding=(value)
@@ -150,8 +166,20 @@ module Rails
         end
       end
 
+      # Loads the database YAML without evaluating ERB.  People seem to
+      # write ERB that makes the database configuration depend on
+      # Rails configuration.  But we want Rails configuration (specifically
+      # `rake` and `rails` tasks) to be generated based on information in
+      # the database yaml, so we need a method that loads the database
+      # yaml *without* the context of the Rails application.
+      def load_database_yaml # :nodoc:
+        path = paths["config/database"].existent.first
+        return {} unless path
+        YAML.load_file(path.to_s)
+      end
+
       # Loads and returns the entire raw configuration of database from
-      # values stored in `config/database.yml`.
+      # values stored in <tt>config/database.yml</tt>.
       def database_configuration
         path = paths["config/database"].existent.first
         yaml = Pathname.new(path) if path
@@ -225,7 +253,15 @@ module Rails
       end
 
       def annotations
-        SourceAnnotationExtractor::Annotation
+        Rails::SourceAnnotationExtractor::Annotation
+      end
+
+      def content_security_policy(&block)
+        if block_given?
+          @content_security_policy = ActionDispatch::ContentSecurityPolicy.new(&block)
+        else
+          @content_security_policy
+        end
       end
 
       class Custom #:nodoc:
diff --git a/railties/lib/rails/application/default_middleware_stack.rb b/railties/lib/rails/application/default_middleware_stack.rb
index ea2273c1f2..433a7ab41f 100644
--- a/railties/lib/rails/application/default_middleware_stack.rb
+++ b/railties/lib/rails/application/default_middleware_stack.rb
@@ -63,9 +63,15 @@ module Rails
             middleware.use ::ActionDispatch::Flash
           end
 
+          unless config.api_only
+            middleware.use ::ActionDispatch::ContentSecurityPolicy::Middleware
+          end
+
           middleware.use ::Rack::Head
           middleware.use ::Rack::ConditionalGet
           middleware.use ::Rack::ETag, "no-cache"
+
+          middleware.use ::Rack::TempfileReaper unless config.api_only
         end
       end
 
diff --git a/railties/lib/rails/application/finisher.rb b/railties/lib/rails/application/finisher.rb
index 3d938be951..c4b188aeee 100644
--- a/railties/lib/rails/application/finisher.rb
+++ b/railties/lib/rails/application/finisher.rb
@@ -58,7 +58,7 @@ module Rails
       end
 
       # This needs to happen before eager load so it happens
-      # in exactly the same point regardless of config.cache_classes
+      # in exactly the same point regardless of config.eager_load
       initializer :run_prepare_callbacks do |app|
         app.reloader.prepare!
       end
diff --git a/railties/lib/rails/application_controller.rb b/railties/lib/rails/application_controller.rb
index fa8793d81a..b3fe822218 100644
--- a/railties/lib/rails/application_controller.rb
+++ b/railties/lib/rails/application_controller.rb
@@ -4,6 +4,13 @@ class Rails::ApplicationController < ActionController::Base # :nodoc:
   self.view_paths = File.expand_path("templates", __dir__)
   layout "application"
 
+  before_action :disable_content_security_policy_nonce!
+
+  content_security_policy do |policy|
+    policy.script_src :unsafe_inline
+    policy.style_src :unsafe_inline
+  end
+
   private
 
     def require_local!
@@ -15,4 +22,8 @@ class Rails::ApplicationController < ActionController::Base # :nodoc:
     def local_request?
       Rails.application.config.consider_all_requests_local || request.local?
     end
+
+    def disable_content_security_policy_nonce!
+      request.content_security_policy_nonce_generator = nil
+    end
 end
diff --git a/railties/lib/rails/cli.rb b/railties/lib/rails/cli.rb
index 50a2ed30cf..e56e604fdc 100644
--- a/railties/lib/rails/cli.rb
+++ b/railties/lib/rails/cli.rb
@@ -1,15 +1,15 @@
 # frozen_string_literal: true
 
-require_relative "app_loader"
+require "rails/app_loader"
 
 # If we are inside a Rails application this method performs an exec and thus
 # the rest of this script is not run.
 Rails::AppLoader.exec_app
 
-require_relative "ruby_version_check"
+require "rails/ruby_version_check"
 Signal.trap("INT") { puts; exit(1) }
 
-require_relative "command"
+require "rails/command"
 
 if ARGV.first == "plugin"
   ARGV.shift
diff --git a/railties/lib/rails/code_statistics.rb b/railties/lib/rails/code_statistics.rb
index 7ceb86198f..9c447c366f 100644
--- a/railties/lib/rails/code_statistics.rb
+++ b/railties/lib/rails/code_statistics.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "code_statistics_calculator"
+require "rails/code_statistics_calculator"
 require "active_support/core_ext/enumerable"
 
 class CodeStatistics #:nodoc:
diff --git a/railties/lib/rails/command.rb b/railties/lib/rails/command.rb
index 812e846837..6d99ac9936 100644
--- a/railties/lib/rails/command.rb
+++ b/railties/lib/rails/command.rb
@@ -4,7 +4,6 @@ require "active_support"
 require "active_support/dependencies/autoload"
 require "active_support/core_ext/enumerable"
 require "active_support/core_ext/object/blank"
-require "active_support/core_ext/hash/transform_values"
 
 require "thor"
 
@@ -12,6 +11,7 @@ module Rails
   module Command
     extend ActiveSupport::Autoload
 
+    autoload :Spellchecker
     autoload :Behavior
     autoload :Base
 
diff --git a/railties/lib/rails/command/actions.rb b/railties/lib/rails/command/actions.rb
index 2f6827b7f4..cbb743346b 100644
--- a/railties/lib/rails/command/actions.rb
+++ b/railties/lib/rails/command/actions.rb
@@ -3,9 +3,9 @@
 module Rails
   module Command
     module Actions
-      # Change to the application's path if there is no config.ru file in current directory.
-      # This allows us to run `rails server` from other directories, but still get
-      # the main config.ru and properly set the tmp directory.
+      # Change to the application's path if there is no <tt>config.ru</tt> file in current directory.
+      # This allows us to run <tt>rails server</tt> from other directories, but still get
+      # the main <tt>config.ru</tt> and properly set the <tt>tmp</tt> directory.
       def set_application_directory!
         Dir.chdir(File.expand_path("../..", APP_PATH)) unless File.exist?(File.expand_path("config.ru"))
       end
diff --git a/railties/lib/rails/command/base.rb b/railties/lib/rails/command/base.rb
index e92b2042bd..fa462ef7e9 100644
--- a/railties/lib/rails/command/base.rb
+++ b/railties/lib/rails/command/base.rb
@@ -6,7 +6,7 @@ require "erb"
 require "active_support/core_ext/string/filters"
 require "active_support/core_ext/string/inflections"
 
-require_relative "actions"
+require "rails/command/actions"
 
 module Rails
   module Command
@@ -112,8 +112,8 @@ module Rails
         # Default file root to place extra files a command might need, placed
         # one folder above the command file.
         #
-        # For a `Rails::Command::TestCommand` placed in `rails/command/test_command.rb`
-        # would return `rails/test`.
+        # For a Rails::Command::TestCommand placed in <tt>rails/command/test_command.rb</tt>
+        # would return <tt>rails/test</tt>.
         def default_command_root
           path = File.expand_path(File.join("../commands", command_root_namespace), __dir__)
           path if File.exist?(path)
diff --git a/railties/lib/rails/command/behavior.rb b/railties/lib/rails/command/behavior.rb
index 7a6dd28e1a..718e2d9ab2 100644
--- a/railties/lib/rails/command/behavior.rb
+++ b/railties/lib/rails/command/behavior.rb
@@ -19,46 +19,6 @@ module Rails
         end
 
         private
-
-          # This code is based directly on the Text gem implementation.
-          # Copyright (c) 2006-2013 Paul Battley, Michael Neumann, Tim Fletcher.
-          #
-          # Returns a value representing the "cost" of transforming str1 into str2.
-          def levenshtein_distance(str1, str2) # :doc:
-            s = str1
-            t = str2
-            n = s.length
-            m = t.length
-
-            return m if (0 == n)
-            return n if (0 == m)
-
-            d = (0..m).to_a
-            x = nil
-
-            # avoid duplicating an enumerable object in the loop
-            str2_codepoint_enumerable = str2.each_codepoint
-
-            str1.each_codepoint.with_index do |char1, i|
-              e = i + 1
-
-              str2_codepoint_enumerable.with_index do |char2, j|
-                cost = (char1 == char2) ? 0 : 1
-                x = [
-                     d[j + 1] + 1, # insertion
-                     e + 1,      # deletion
-                     d[j] + cost # substitution
-                    ].min
-                d[j] = e
-                e = x
-              end
-
-              d[m] = x
-            end
-
-            x
-          end
-
           # Prints a list of generators.
           def print_list(base, namespaces)
             return if namespaces.empty?
diff --git a/railties/lib/rails/command/helpers/editor.rb b/railties/lib/rails/command/helpers/editor.rb
new file mode 100644
index 0000000000..6191d97672
--- /dev/null
+++ b/railties/lib/rails/command/helpers/editor.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+require "active_support/encrypted_file"
+
+module Rails
+  module Command
+    module Helpers
+      module Editor
+        private
+          def ensure_editor_available(command:)
+            if ENV["EDITOR"].to_s.empty?
+              say "No $EDITOR to open file in. Assign one like this:"
+              say ""
+              say %(EDITOR="mate --wait" #{command})
+              say ""
+              say "For editors that fork and exit immediately, it's important to pass a wait flag,"
+              say "otherwise the credentials will be saved immediately with no chance to edit."
+
+              false
+            else
+              true
+            end
+          end
+
+          def catch_editing_exceptions
+            yield
+          rescue Interrupt
+            say "Aborted changing file: nothing saved."
+          rescue ActiveSupport::EncryptedFile::MissingKeyError => error
+            say error.message
+          end
+      end
+    end
+  end
+end
diff --git a/railties/lib/rails/command/spellchecker.rb b/railties/lib/rails/command/spellchecker.rb
new file mode 100644
index 0000000000..04485097fa
--- /dev/null
+++ b/railties/lib/rails/command/spellchecker.rb
@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+module Rails
+  module Command
+    module Spellchecker # :nodoc:
+      class << self
+        def suggest(word, from:)
+          if defined?(DidYouMean::SpellChecker)
+            DidYouMean::SpellChecker.new(dictionary: from.map(&:to_s)).correct(word).first
+          else
+            from.sort_by { |w| levenshtein_distance(word, w) }.first
+          end
+        end
+
+        private
+
+          # This code is based directly on the Text gem implementation.
+          # Copyright (c) 2006-2013 Paul Battley, Michael Neumann, Tim Fletcher.
+          #
+          # Returns a value representing the "cost" of transforming str1 into str2.
+          def levenshtein_distance(str1, str2) # :doc:
+            s = str1
+            t = str2
+            n = s.length
+            m = t.length
+
+            return m if (0 == n)
+            return n if (0 == m)
+
+            d = (0..m).to_a
+            x = nil
+
+            # avoid duplicating an enumerable object in the loop
+            str2_codepoint_enumerable = str2.each_codepoint
+
+            str1.each_codepoint.with_index do |char1, i|
+              e = i + 1
+
+              str2_codepoint_enumerable.with_index do |char2, j|
+                cost = (char1 == char2) ? 0 : 1
+                x = [
+                  d[j + 1] + 1, # insertion
+                  e + 1,        # deletion
+                  d[j] + cost   # substitution
+                ].min
+                d[j] = e
+                e = x
+              end
+
+              d[m] = x
+            end
+
+            x
+          end
+      end
+    end
+  end
+end
diff --git a/railties/lib/rails/commands.rb b/railties/lib/rails/commands.rb
index 1aea1e1a96..77961a0292 100644
--- a/railties/lib/rails/commands.rb
+++ b/railties/lib/rails/commands.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "command"
+require "rails/command"
 
 aliases = {
   "g"  => "generate",
diff --git a/railties/lib/rails/commands/application/application_command.rb b/railties/lib/rails/commands/application/application_command.rb
index 13d47a63bc..f77553b830 100644
--- a/railties/lib/rails/commands/application/application_command.rb
+++ b/railties/lib/rails/commands/application/application_command.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../../generators"
-require_relative "../../generators/rails/app/app_generator"
+require "rails/generators"
+require "rails/generators/rails/app/app_generator"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/commands/console/console_command.rb b/railties/lib/rails/commands/console/console_command.rb
index 5dc695c240..e35faa5b01 100644
--- a/railties/lib/rails/commands/console/console_command.rb
+++ b/railties/lib/rails/commands/console/console_command.rb
@@ -3,7 +3,7 @@
 require "irb"
 require "irb/completion"
 
-require_relative "../../command/environment_argument"
+require "rails/command/environment_argument"
 
 module Rails
   class Console
diff --git a/railties/lib/rails/commands/credentials/USAGE b/railties/lib/rails/commands/credentials/USAGE
new file mode 100644
index 0000000000..85877c71b7
--- /dev/null
+++ b/railties/lib/rails/commands/credentials/USAGE
@@ -0,0 +1,40 @@
+=== Storing Encrypted Credentials in Source Control
+
+The Rails `credentials` commands provide access to encrypted credentials,
+so you can safely store access tokens, database passwords, and the like
+safely inside the app without relying on a mess of ENVs.
+
+This also allows for atomic deploys: no need to coordinate key changes
+to get everything working as the keys are shipped with the code.
+
+=== Setup
+
+Applications after Rails 5.2 automatically have a basic credentials file generated
+that just contains the secret_key_base used by MessageVerifiers/MessageEncryptors, like the ones
+signing and encrypting cookies.
+
+For applications created prior to Rails 5.2, we'll automatically generate a new
+credentials file in `config/credentials.yml.enc` the first time you run `bin/rails credentials:edit`.
+If you didn't have a master key saved in `config/master.key`, that'll be created too.
+
+Don't lose this master key! Put it in a password manager your team can access.
+Should you lose it no one, including you, will be able to access any encrypted
+credentials.
+
+Don't commit the key! Add `config/master.key` to your source control's
+ignore file. If you use Git, Rails handles this for you.
+
+Rails also looks for the master key in `ENV["RAILS_MASTER_KEY"]`, if that's easier to manage.
+
+You could prepend that to your server's start command like this:
+
+   RAILS_MASTER_KEY="very-secret-and-secure" server.start
+
+=== Editing Credentials
+
+This will open a temporary file in `$EDITOR` with the decrypted contents to edit
+the encrypted credentials.
+
+When the temporary file is next saved the contents are encrypted and written to
+`config/credentials.yml.enc` while the file itself is destroyed to prevent credentials
+from leaking.
diff --git a/railties/lib/rails/commands/credentials/credentials_command.rb b/railties/lib/rails/commands/credentials/credentials_command.rb
new file mode 100644
index 0000000000..fa54c0362a
--- /dev/null
+++ b/railties/lib/rails/commands/credentials/credentials_command.rb
@@ -0,0 +1,79 @@
+# frozen_string_literal: true
+
+require "active_support"
+require "rails/command/helpers/editor"
+
+module Rails
+  module Command
+    class CredentialsCommand < Rails::Command::Base # :nodoc:
+      include Helpers::Editor
+
+      no_commands do
+        def help
+          say "Usage:\n  #{self.class.banner}"
+          say ""
+          say self.class.desc
+        end
+      end
+
+      def edit
+        require_application_and_environment!
+
+        ensure_editor_available(command: "bin/rails credentials:edit") || (return)
+        ensure_master_key_has_been_added if Rails.application.credentials.key.nil?
+        ensure_credentials_have_been_added
+
+        catch_editing_exceptions do
+          change_credentials_in_system_editor
+        end
+
+        say "New credentials encrypted and saved."
+      end
+
+      def show
+        require_application_and_environment!
+
+        say Rails.application.credentials.read.presence || missing_credentials_message
+      end
+
+      private
+        def ensure_master_key_has_been_added
+          master_key_generator.add_master_key_file
+          master_key_generator.ignore_master_key_file
+        end
+
+        def ensure_credentials_have_been_added
+          credentials_generator.add_credentials_file_silently
+        end
+
+        def change_credentials_in_system_editor
+          Rails.application.credentials.change do |tmp_path|
+            system("#{ENV["EDITOR"]} #{tmp_path}")
+          end
+        end
+
+
+        def master_key_generator
+          require "rails/generators"
+          require "rails/generators/rails/master_key/master_key_generator"
+
+          Rails::Generators::MasterKeyGenerator.new
+        end
+
+        def credentials_generator
+          require "rails/generators"
+          require "rails/generators/rails/credentials/credentials_generator"
+
+          Rails::Generators::CredentialsGenerator.new
+        end
+
+        def missing_credentials_message
+          if Rails.application.credentials.key.nil?
+            "Missing master key to decrypt credentials. See bin/rails credentials:help"
+          else
+            "No credentials have been added yet. Use bin/rails credentials:edit to change that."
+          end
+        end
+    end
+  end
+end
diff --git a/railties/lib/rails/commands/dbconsole/dbconsole_command.rb b/railties/lib/rails/commands/dbconsole/dbconsole_command.rb
index 6296c95a87..806b7de6d6 100644
--- a/railties/lib/rails/commands/dbconsole/dbconsole_command.rb
+++ b/railties/lib/rails/commands/dbconsole/dbconsole_command.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../command/environment_argument"
+require "rails/command/environment_argument"
 
 module Rails
   class DBConsole
@@ -75,7 +75,7 @@ module Rails
         args += ["-P", "#{config['password']}"] if config["password"]
 
         if config["host"]
-          host_arg = "#{config['host']}"
+          host_arg = "#{config['host']}".dup
           host_arg << ":#{config['port']}" if config["port"]
           args += ["-S", host_arg]
         end
@@ -97,7 +97,7 @@ module Rails
         elsif configurations[environment].blank? && configurations[connection].blank?
           raise ActiveRecord::AdapterNotSpecified, "'#{environment}' database is not configured. Available configuration: #{configurations.inspect}"
         else
-          configurations[environment].presence || configurations[connection]
+          configurations[connection] || configurations[environment].presence
         end
       end
     end
diff --git a/railties/lib/rails/commands/destroy/destroy_command.rb b/railties/lib/rails/commands/destroy/destroy_command.rb
index 686193ddb9..dd432d28fd 100644
--- a/railties/lib/rails/commands/destroy/destroy_command.rb
+++ b/railties/lib/rails/commands/destroy/destroy_command.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../generators"
+require "rails/generators"
 
 module Rails
   module Command
diff --git a/railties/lib/rails/commands/encrypted/encrypted_command.rb b/railties/lib/rails/commands/encrypted/encrypted_command.rb
new file mode 100644
index 0000000000..3bc8f76ce4
--- /dev/null
+++ b/railties/lib/rails/commands/encrypted/encrypted_command.rb
@@ -0,0 +1,86 @@
+# frozen_string_literal: true
+
+require "pathname"
+require "active_support"
+require "rails/command/helpers/editor"
+
+module Rails
+  module Command
+    class EncryptedCommand < Rails::Command::Base # :nodoc:
+      include Helpers::Editor
+
+      class_option :key, aliases: "-k", type: :string,
+        default: "config/master.key", desc: "The Rails.root relative path to the encryption key"
+
+      no_commands do
+        def help
+          say "Usage:\n  #{self.class.banner}"
+          say ""
+        end
+      end
+
+      def edit(file_path)
+        require_application_and_environment!
+        encrypted = Rails.application.encrypted(file_path, key_path: options[:key])
+
+        ensure_editor_available(command: "bin/rails encrypted:edit") || (return)
+        ensure_encryption_key_has_been_added(options[:key]) if encrypted.key.nil?
+        ensure_encrypted_file_has_been_added(file_path, options[:key])
+
+        catch_editing_exceptions do
+          change_encrypted_file_in_system_editor(file_path, options[:key])
+        end
+
+        say "File encrypted and saved."
+      rescue ActiveSupport::MessageEncryptor::InvalidMessage
+        say "Couldn't decrypt #{file_path}. Perhaps you passed the wrong key?"
+      end
+
+      def show(file_path)
+        require_application_and_environment!
+        encrypted = Rails.application.encrypted(file_path, key_path: options[:key])
+
+        say encrypted.read.presence || missing_encrypted_message(key: encrypted.key, key_path: options[:key], file_path: file_path)
+      end
+
+      private
+        def ensure_encryption_key_has_been_added(key_path)
+          encryption_key_file_generator.add_key_file(key_path)
+          encryption_key_file_generator.ignore_key_file(key_path)
+        end
+
+        def ensure_encrypted_file_has_been_added(file_path, key_path)
+          encrypted_file_generator.add_encrypted_file_silently(file_path, key_path)
+        end
+
+        def change_encrypted_file_in_system_editor(file_path, key_path)
+          Rails.application.encrypted(file_path, key_path: key_path).change do |tmp_path|
+            system("#{ENV["EDITOR"]} #{tmp_path}")
+          end
+        end
+
+
+        def encryption_key_file_generator
+          require "rails/generators"
+          require "rails/generators/rails/encryption_key_file/encryption_key_file_generator"
+
+          Rails::Generators::EncryptionKeyFileGenerator.new
+        end
+
+        def encrypted_file_generator
+          require "rails/generators"
+          require "rails/generators/rails/encrypted_file/encrypted_file_generator"
+
+          Rails::Generators::EncryptedFileGenerator.new
+        end
+
+        def missing_encrypted_message(key:, key_path:, file_path:)
+          if key.nil?
+            "Missing '#{key_path}' to decrypt data. See bin/rails encrypted:help"
+          else
+            "File '#{file_path}' does not exist. Use bin/rails encrypted:edit #{file_path} to change that."
+          end
+        end
+    end
+  end
+end
diff --git a/railties/lib/rails/commands/generate/generate_command.rb b/railties/lib/rails/commands/generate/generate_command.rb
index 73f627637d..93d7a0ce3a 100644
--- a/railties/lib/rails/commands/generate/generate_command.rb
+++ b/railties/lib/rails/commands/generate/generate_command.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../generators"
+require "rails/generators"
 
 module Rails
   module Command
diff --git a/railties/lib/rails/commands/plugin/plugin_command.rb b/railties/lib/rails/commands/plugin/plugin_command.rb
index 5d3dfadf84..2b192abf9b 100644
--- a/railties/lib/rails/commands/plugin/plugin_command.rb
+++ b/railties/lib/rails/commands/plugin/plugin_command.rb
@@ -36,8 +36,8 @@ module Rails
 
       private
         def run_plugin_generator(plugin_args)
-          require_relative "../../generators"
-          require_relative "../../generators/rails/plugin/plugin_generator"
+          require "rails/generators"
+          require "rails/generators/rails/plugin/plugin_generator"
           Rails::Generators::PluginGenerator.start plugin_args
         end
     end
diff --git a/railties/lib/rails/commands/routes/routes_command.rb b/railties/lib/rails/commands/routes/routes_command.rb
new file mode 100644
index 0000000000..b592a5212f
--- /dev/null
+++ b/railties/lib/rails/commands/routes/routes_command.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+require "rails/command"
+
+module Rails
+  module Command
+    class RoutesCommand < Base # :nodoc:
+      class_option :controller, aliases: "-c", desc: "Filter by a specific controller, e.g. PostsController or Admin::PostsController."
+      class_option :grep, aliases: "-g", desc: "Grep routes by a specific pattern."
+      class_option :expanded, type: :boolean, aliases: "-E", desc: "Print routes expanded vertically with parts explained."
+
+      def perform(*)
+        require_application_and_environment!
+        require "action_dispatch/routing/inspector"
+
+        say inspector.format(formatter, routes_filter)
+      end
+
+      private
+        def inspector
+          ActionDispatch::Routing::RoutesInspector.new(Rails.application.routes.routes)
+        end
+
+        def formatter
+          if options.key?("expanded")
+            ActionDispatch::Routing::ConsoleFormatter::Expanded.new
+          else
+            ActionDispatch::Routing::ConsoleFormatter::Sheet.new
+          end
+        end
+
+        def routes_filter
+          options.symbolize_keys.slice(:controller, :grep)
+        end
+    end
+  end
+end
diff --git a/railties/lib/rails/commands/runner/runner_command.rb b/railties/lib/rails/commands/runner/runner_command.rb
index cd9462e08f..30fbf04982 100644
--- a/railties/lib/rails/commands/runner/runner_command.rb
+++ b/railties/lib/rails/commands/runner/runner_command.rb
@@ -32,13 +32,13 @@ module Rails
         ARGV.replace(command_argv)
 
         if code_or_file == "-"
-          eval($stdin.read, binding, "stdin")
+          eval($stdin.read, TOPLEVEL_BINDING, "stdin")
         elsif File.exist?(code_or_file)
           $0 = code_or_file
           Kernel.load code_or_file
         else
           begin
-            eval(code_or_file, binding, __FILE__, __LINE__)
+            eval(code_or_file, TOPLEVEL_BINDING, __FILE__, __LINE__)
           rescue SyntaxError, NameError => error
             $stderr.puts "Please specify a valid ruby command or the path of a script to run."
             $stderr.puts "Run '#{self.class.executable} -h' for help."
diff --git a/railties/lib/rails/commands/secrets/secrets_command.rb b/railties/lib/rails/commands/secrets/secrets_command.rb
index d93c4de74e..a36ccf314c 100644
--- a/railties/lib/rails/commands/secrets/secrets_command.rb
+++ b/railties/lib/rails/commands/secrets/secrets_command.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support"
-require_relative "../../secrets"
+require "rails/secrets"
 
 module Rails
   module Command
@@ -15,7 +15,7 @@ module Rails
       end
 
       def setup
-        generator.start
+        deprecate_in_favor_of_credentials_and_exit
       end
 
       def edit
@@ -42,11 +42,10 @@ module Rails
       rescue Rails::Secrets::MissingKeyError => error
         say error.message
       rescue Errno::ENOENT => error
-        raise unless error.message =~ /secrets\.yml\.enc/
-
-        Rails::Secrets.read_template_for_editing do |tmp_path|
-          system("#{ENV["EDITOR"]} #{tmp_path}")
-          generator.skip_secrets_file { setup }
+        if error.message =~ /secrets\.yml\.enc/
+          deprecate_in_favor_of_credentials_and_exit
+        else
+          raise
         end
       end
 
@@ -55,11 +54,11 @@ module Rails
       end
 
       private
-        def generator
-          require_relative "../../generators"
-          require_relative "../../generators/rails/encrypted_secrets/encrypted_secrets_generator"
+        def deprecate_in_favor_of_credentials_and_exit
+          say "Encrypted secrets is deprecated in favor of credentials. Run:"
+          say "bin/rails credentials:help"
 
-          Rails::Generators::EncryptedSecretsGenerator
+          exit 1
         end
     end
   end
diff --git a/railties/lib/rails/commands/server/server_command.rb b/railties/lib/rails/commands/server/server_command.rb
index 785265d766..77b6c1f65d 100644
--- a/railties/lib/rails/commands/server/server_command.rb
+++ b/railties/lib/rails/commands/server/server_command.rb
@@ -6,7 +6,7 @@ require "action_dispatch"
 require "rails"
 require "active_support/deprecation"
 require "active_support/core_ext/string/filters"
-require_relative "../../dev_caching"
+require "rails/dev_caching"
 
 module Rails
   class Server < ::Rack::Server
@@ -27,7 +27,7 @@ module Rails
         app = super
         if app.is_a?(Class)
           ActiveSupport::Deprecation.warn(<<-MSG.squish)
-            Use `Rails::Application` subclass to start the server is deprecated and will be removed in Rails 6.0.
+            Using `Rails::Application` subclass to start the server is deprecated and will be removed in Rails 6.0.
             Please change `run #{app}` to `run Rails.application` in config.ru.
           MSG
         end
@@ -43,18 +43,22 @@ module Rails
       ENV["RAILS_ENV"] ||= options[:environment]
     end
 
-    def start
-      print_boot_information
+    def start(after_stop_callback = nil)
       trap(:INT) { exit }
       create_tmp_directories
       setup_dev_caching
       log_to_stdout if options[:log_stdout]
 
-      super
+      super()
     ensure
-      # The '-h' option calls exit before @options is set.
-      # If we call 'options' with it unset, we get double help banners.
-      puts "Exiting" unless @options && options[:daemonize]
+      after_stop_callback.call if after_stop_callback
+    end
+
+    def serveable? # :nodoc:
+      server
+      true
+    rescue LoadError, NameError
+      false
     end
 
     def middleware
@@ -65,6 +69,10 @@ module Rails
       super.merge(@default_options)
     end
 
+    def served_url
+      "#{options[:SSLEnable] ? 'https' : 'http'}://#{options[:Host]}:#{options[:Port]}" unless use_puma?
+    end
+
     private
       def setup_dev_caching
         if options[:environment] == "development"
@@ -72,13 +80,6 @@ module Rails
         end
       end
 
-      def print_boot_information
-        url = "on #{options[:SSLEnable] ? 'https' : 'http'}://#{options[:Host]}:#{options[:Port]}" unless use_puma?
-        puts "=> Booting #{ActiveSupport::Inflector.demodulize(server)}"
-        puts "=> Rails #{Rails.version} application starting in #{Rails.env} #{url}"
-        puts "=> Run `rails server -h` for more startup options"
-      end
-
       def create_tmp_directories
         %w(cache pids sockets).each do |dir_to_make|
           FileUtils.mkdir_p(File.join(Rails.root, "tmp", dir_to_make))
@@ -108,9 +109,15 @@ module Rails
 
   module Command
     class ServerCommand < Base # :nodoc:
+      # Hard-coding a bunch of handlers here as we don't have a public way of
+      # querying them from the Rack::Handler registry.
+      RACK_SERVERS = %w(cgi fastcgi webrick lsws scgi thin puma unicorn)
+
       DEFAULT_PORT = 3000
       DEFAULT_PID_PATH = "tmp/pids/server.pid".freeze
 
+      argument :using, optional: true
+
       class_option :port, aliases: "-p", type: :numeric,
         desc: "Runs Rails on the specified port - defaults to 3000.", banner: :port
       class_option :binding, aliases: "-b", type: :string,
@@ -122,28 +129,39 @@ module Rails
         desc: "Runs server as a Daemon."
       class_option :environment, aliases: "-e", type: :string,
         desc: "Specifies the environment to run this server under (development/test/production).", banner: :name
+      class_option :using, aliases: "-u", type: :string,
+        desc: "Specifies the Rack server used to run the application (thin/puma/webrick).", banner: :name
       class_option :pid, aliases: "-P", type: :string, default: DEFAULT_PID_PATH,
         desc: "Specifies the PID file."
       class_option "dev-caching", aliases: "-C", type: :boolean, default: nil,
         desc: "Specifies whether to perform caching in development."
       class_option "restart", type: :boolean, default: nil, hide: true
+      class_option "early_hints", type: :boolean, default: nil, desc: "Enables HTTP/2 early hints."
 
       def initialize(args = [], local_options = {}, config = {})
         @original_options = local_options
         super
-        @server = self.args.shift
+        @using = deprecated_positional_rack_server(using) || options[:using]
         @log_stdout = options[:daemon].blank? && (options[:environment] || Rails.env) == "development"
       end
 
       def perform
         set_application_directory!
         prepare_restart
+
         Rails::Server.new(server_options).tap do |server|
           # Require application after server sets environment to propagate
           # the --environment option.
           require APP_PATH
           Dir.chdir(Rails.application.root)
-          server.start
+
+          if server.serveable?
+            print_boot_information(server.server, server.served_url)
+            after_stop_callback = -> { say "Exiting" unless options[:daemon] }
+            server.start(after_stop_callback)
+          else
+            say rack_server_suggestion(using)
+          end
         end
       end
 
@@ -151,7 +169,7 @@ module Rails
         def server_options
           {
             user_supplied_options: user_supplied_options,
-            server:                @server,
+            server:                using,
             log_stdout:            @log_stdout,
             Port:                  port,
             Host:                  host,
@@ -161,7 +179,8 @@ module Rails
             daemonize:             options[:daemon],
             pid:                   pid,
             caching:               options["dev-caching"],
-            restart_cmd:           restart_command
+            restart_cmd:           restart_command,
+            early_hints:           early_hints
           }
         end
       end
@@ -200,7 +219,7 @@ module Rails
                 user_supplied_options << name
               end
             end
-            user_supplied_options << :Host if ENV["HOST"]
+            user_supplied_options << :Host if ENV["HOST"] || ENV["BINDING"]
             user_supplied_options << :Port if ENV["PORT"]
             user_supplied_options.uniq
           end
@@ -215,7 +234,17 @@ module Rails
             options[:binding]
           else
             default_host = environment == "development" ? "localhost" : "0.0.0.0"
-            ENV.fetch("HOST", default_host)
+
+            if ENV["HOST"] && !ENV["BINDING"]
+              ActiveSupport::Deprecation.warn(<<-MSG.squish)
+                Using the `HOST` environment to specify the IP is deprecated and will be removed in Rails 6.1.
+                Please use `BINDING` environment instead.
+              MSG
+
+              return ENV["HOST"]
+            end
+
+            ENV.fetch("BINDING", default_host)
           end
         end
 
@@ -224,7 +253,11 @@ module Rails
         end
 
         def restart_command
-          "bin/rails server #{@server} #{@original_options.join(" ")} --restart"
+          "bin/rails server #{using} #{@original_options.join(" ")} --restart"
+        end
+
+        def early_hints
+          options[:early_hints]
         end
 
         def pid
@@ -232,12 +265,50 @@ module Rails
         end
 
         def self.banner(*)
-          "rails server [puma, thin etc] [options]"
+          "rails server [thin/puma/webrick] [options]"
         end
 
         def prepare_restart
           FileUtils.rm_f(options[:pid]) if options[:restart]
         end
+
+        def deprecated_positional_rack_server(value)
+          if value
+            ActiveSupport::Deprecation.warn(<<-MSG.squish)
+              Passing the Rack server name as a regular argument is deprecated
+              and will be removed in the next Rails version. Please, use the -u
+              option instead.
+            MSG
+            value
+          end
+        end
+
+        def rack_server_suggestion(server)
+          if server.in?(RACK_SERVERS)
+            <<~MSG
+              Could not load server "#{server}". Maybe you need to the add it to the Gemfile?
+
+                gem "#{server}"
+
+              Run `rails server --help` for more options.
+            MSG
+          else
+            suggestions = Rails::Command::Spellchecker.suggest(server, from: RACK_SERVERS)
+
+            <<~MSG
+              Could not find server "#{server}". Maybe you meant #{suggestions.inspect}?
+              Run `rails server --help` for more options.
+            MSG
+          end
+        end
+
+        def print_boot_information(server, url)
+          say <<~MSG
+            => Booting #{ActiveSupport::Inflector.demodulize(server)}
+            => Rails #{Rails.version} application starting in #{Rails.env} #{url}
+            => Run `rails server --help` for more startup options
+          MSG
+        end
     end
   end
 end
diff --git a/railties/lib/rails/commands/test/test_command.rb b/railties/lib/rails/commands/test/test_command.rb
index a2216553ca..00ea9ac4a6 100644
--- a/railties/lib/rails/commands/test/test_command.rb
+++ b/railties/lib/rails/commands/test/test_command.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative "../../command"
-require_relative "../../test_unit/runner"
-require_relative "../../test_unit/reporter"
+require "rails/command"
+require "rails/test_unit/runner"
+require "rails/test_unit/reporter"
 
 module Rails
   module Command
diff --git a/railties/lib/rails/configuration.rb b/railties/lib/rails/configuration.rb
index 70815d114d..d3a54d9364 100644
--- a/railties/lib/rails/configuration.rb
+++ b/railties/lib/rails/configuration.rb
@@ -2,8 +2,8 @@
 
 require "active_support/ordered_options"
 require "active_support/core_ext/object"
-require_relative "paths"
-require_relative "rack"
+require "rails/paths"
+require "rails/rack"
 
 module Rails
   module Configuration
diff --git a/railties/lib/rails/engine.rb b/railties/lib/rails/engine.rb
index cc2030d37d..6a13a84108 100644
--- a/railties/lib/rails/engine.rb
+++ b/railties/lib/rails/engine.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "railtie"
-require_relative "engine/railties"
+require "rails/railtie"
+require "rails/engine/railties"
 require "active_support/core_ext/module/delegation"
 require "pathname"
 require "thread"
@@ -439,8 +439,8 @@ module Rails
     # Load console and invoke the registered hooks.
     # Check <tt>Rails::Railtie.console</tt> for more info.
     def load_console(app = self)
-      require_relative "console/app"
-      require_relative "console/helpers"
+      require "rails/console/app"
+      require "rails/console/helpers"
       run_console_blocks(app)
       self
     end
@@ -463,7 +463,7 @@ module Rails
     # Load Rails generators and invoke the registered hooks.
     # Check <tt>Rails::Railtie.generators</tt> for more info.
     def load_generators(app = self)
-      require_relative "generators"
+      require "rails/generators"
       run_generators_blocks(app)
       Rails::Generators.configure!(app.config.generators)
       self
diff --git a/railties/lib/rails/engine/commands.rb b/railties/lib/rails/engine/commands.rb
index 3854907507..05218640c6 100644
--- a/railties/lib/rails/engine/commands.rb
+++ b/railties/lib/rails/engine/commands.rb
@@ -6,4 +6,4 @@ unless defined?(APP_PATH)
   end
 end
 
-require_relative "../commands"
+require "rails/commands"
diff --git a/railties/lib/rails/engine/configuration.rb b/railties/lib/rails/engine/configuration.rb
index 16ba7f9eb8..6bf0406b21 100644
--- a/railties/lib/rails/engine/configuration.rb
+++ b/railties/lib/rails/engine/configuration.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../railtie/configuration"
+require "rails/railtie/configuration"
 
 module Rails
   class Engine
diff --git a/railties/lib/rails/engine/updater.rb b/railties/lib/rails/engine/updater.rb
index 21a0fc5562..be7a47124a 100644
--- a/railties/lib/rails/engine/updater.rb
+++ b/railties/lib/rails/engine/updater.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../generators"
-require_relative "../generators/rails/plugin/plugin_generator"
+require "rails/generators"
+require "rails/generators/rails/plugin/plugin_generator"
 
 module Rails
   class Engine
diff --git a/railties/lib/rails/gem_version.rb b/railties/lib/rails/gem_version.rb
index 92b5e0392a..54bfbdd516 100644
--- a/railties/lib/rails/gem_version.rb
+++ b/railties/lib/rails/gem_version.rb
@@ -7,8 +7,8 @@ module Rails
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
     PRE   = "alpha"
 
diff --git a/railties/lib/rails/generators.rb b/railties/lib/rails/generators.rb
index a630d55e59..f8460bd4ee 100644
--- a/railties/lib/rails/generators.rb
+++ b/railties/lib/rails/generators.rb
@@ -4,7 +4,7 @@ activesupport_path = File.expand_path("../../../activesupport/lib", __dir__)
 $:.unshift(activesupport_path) if File.directory?(activesupport_path) && !$:.include?(activesupport_path)
 
 require "thor/group"
-require_relative "command"
+require "rails/command"
 
 require "active_support"
 require "active_support/core_ext/object/blank"
@@ -218,6 +218,10 @@ module Rails
         rails.delete("app")
         rails.delete("plugin")
         rails.delete("encrypted_secrets")
+        rails.delete("encrypted_file")
+        rails.delete("encryption_key_file")
+        rails.delete("master_key")
+        rails.delete("credentials")
 
         hidden_namespaces.each { |n| groups.delete(n.to_s) }
 
@@ -272,11 +276,11 @@ module Rails
           klass.start(args, config)
         else
           options     = sorted_groups.flat_map(&:last)
-          suggestions = options.sort_by { |suggested| levenshtein_distance(namespace.to_s, suggested) }.first(3)
-          msg =  "Could not find generator '#{namespace}'. ".dup
-          msg << "Maybe you meant #{ suggestions.map { |s| "'#{s}'" }.to_sentence(last_word_connector: " or ", locale: :en) }\n"
-          msg << "Run `rails generate --help` for more options."
-          puts msg
+          suggestion  = Rails::Command::Spellchecker.suggest(namespace.to_s, from: options)
+          puts <<~MSG
+            Could not find generator '#{namespace}'. Maybe you meant #{suggestion.inspect}?
+            Run `rails generate --help` for more options.
+          MSG
         end
       end
 
diff --git a/railties/lib/rails/generators/actions.rb b/railties/lib/rails/generators/actions.rb
index c773e07eba..d85bbfb03e 100644
--- a/railties/lib/rails/generators/actions.rb
+++ b/railties/lib/rails/generators/actions.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/string/strip"
+
 module Rails
   module Generators
     module Actions
@@ -13,17 +15,22 @@ module Rails
       #
       #   gem "rspec", group: :test
       #   gem "technoweenie-restful-authentication", lib: "restful-authentication", source: "http://gems.github.com/"
-      #   gem "rails", "3.0", git: "git://github.com/rails/rails"
+      #   gem "rails", "3.0", git: "https://github.com/rails/rails"
+      #   gem "RedCloth", ">= 4.1.0", "< 4.2.0"
       def gem(*args)
         options = args.extract_options!
-        name, version = args
+        name, *versions = args
 
         # Set the message to be shown in logs. Uses the git repo if one is given,
         # otherwise use name (version).
         parts, message = [ quote(name) ], name.dup
-        if version ||= options.delete(:version)
-          parts   << quote(version)
-          message << " (#{version})"
+
+        if versions = versions.any? ? versions : options.delete(:version)
+          _versions = Array(versions)
+          _versions.each do |version|
+            parts << quote(version)
+          end
+          message << " (#{_versions.join(", ")})"
         end
         message = options[:git] if options[:git]
 
@@ -216,6 +223,7 @@ module Rails
       #   rake("db:migrate")
       #   rake("db:migrate", env: "production")
       #   rake("gems:install", sudo: true)
+      #   rake("gems:install", capture: true)
       def rake(command, options = {})
         execute_command :rake, command, options
       end
@@ -225,6 +233,7 @@ module Rails
       #   rails_command("db:migrate")
       #   rails_command("db:migrate", env: "production")
       #   rails_command("gems:install", sudo: true)
+      #   rails_command("gems:install", capture: true)
       def rails_command(command, options = {})
         execute_command :rails, command, options
       end
@@ -287,7 +296,11 @@ module Rails
           log executor, command
           env  = options[:env] || ENV["RAILS_ENV"] || "development"
           sudo = options[:sudo] && !Gem.win_platform? ? "sudo " : ""
-          in_root { run("#{sudo}#{extify(executor)} #{command} RAILS_ENV=#{env}", verbose: false) }
+          config = { verbose: false }
+
+          config.merge!(capture: options[:capture]) if options[:capture]
+
+          in_root { run("#{sudo}#{extify(executor)} #{command} RAILS_ENV=#{env}", config) }
         end
 
         # Add an extension to the given name based on the platform.
diff --git a/railties/lib/rails/generators/app_base.rb b/railties/lib/rails/generators/app_base.rb
index c8688fb7f3..f51542f3ec 100644
--- a/railties/lib/rails/generators/app_base.rb
+++ b/railties/lib/rails/generators/app_base.rb
@@ -2,11 +2,10 @@
 
 require "fileutils"
 require "digest/md5"
-require "active_support/core_ext/string/strip"
-require_relative "../version" unless defined?(Rails::VERSION)
+require "rails/version" unless defined?(Rails::VERSION)
 require "open-uri"
 require "uri"
-require_relative "../generators"
+require "rails/generators"
 require "active_support/core_ext/array/extract_options"
 
 module Rails
@@ -26,75 +25,81 @@ module Rails
       end
 
       def self.add_shared_options_for(name)
-        class_option :template,           type: :string, aliases: "-m",
-                                          desc: "Path to some #{name} template (can be a filesystem path or URL)"
+        class_option :template,            type: :string, aliases: "-m",
+                                           desc: "Path to some #{name} template (can be a filesystem path or URL)"
 
-        class_option :database,           type: :string, aliases: "-d", default: "sqlite3",
-                                          desc: "Preconfigure for selected database (options: #{DATABASES.join('/')})"
+        class_option :database,            type: :string, aliases: "-d", default: "sqlite3",
+                                           desc: "Preconfigure for selected database (options: #{DATABASES.join('/')})"
 
-        class_option :skip_yarn,          type: :boolean, default: false,
-                                          desc: "Don't use Yarn for managing JavaScript dependencies"
+        class_option :skip_yarn,           type: :boolean, default: false,
+                                           desc: "Don't use Yarn for managing JavaScript dependencies"
 
-        class_option :skip_gemfile,       type: :boolean, default: false,
-                                          desc: "Don't create a Gemfile"
+        class_option :skip_gemfile,        type: :boolean, default: false,
+                                           desc: "Don't create a Gemfile"
 
-        class_option :skip_git,           type: :boolean, aliases: "-G", default: false,
-                                          desc: "Skip .gitignore file"
+        class_option :skip_git,            type: :boolean, aliases: "-G", default: false,
+                                           desc: "Skip .gitignore file"
 
-        class_option :skip_keeps,         type: :boolean, default: false,
-                                          desc: "Skip source control .keep files"
+        class_option :skip_keeps,          type: :boolean, default: false,
+                                           desc: "Skip source control .keep files"
 
-        class_option :skip_action_mailer, type: :boolean, aliases: "-M",
-                                          default: false,
-                                          desc: "Skip Action Mailer files"
+        class_option :skip_action_mailer,  type: :boolean, aliases: "-M",
+                                           default: false,
+                                           desc: "Skip Action Mailer files"
 
-        class_option :skip_active_record, type: :boolean, aliases: "-O", default: false,
-                                          desc: "Skip Active Record files"
+        class_option :skip_active_record,  type: :boolean, aliases: "-O", default: false,
+                                           desc: "Skip Active Record files"
 
-        class_option :skip_puma,          type: :boolean, aliases: "-P", default: false,
-                                          desc: "Skip Puma related files"
+        class_option :skip_active_storage, type: :boolean, default: false,
+                                           desc: "Skip Active Storage files"
 
-        class_option :skip_action_cable,  type: :boolean, aliases: "-C", default: false,
-                                          desc: "Skip Action Cable files"
+        class_option :skip_puma,           type: :boolean, aliases: "-P", default: false,
+                                           desc: "Skip Puma related files"
 
-        class_option :skip_sprockets,     type: :boolean, aliases: "-S", default: false,
-                                          desc: "Skip Sprockets files"
+        class_option :skip_action_cable,   type: :boolean, aliases: "-C", default: false,
+                                           desc: "Skip Action Cable files"
 
-        class_option :skip_spring,        type: :boolean, default: false,
-                                          desc: "Don't install Spring application preloader"
+        class_option :skip_sprockets,      type: :boolean, aliases: "-S", default: false,
+                                           desc: "Skip Sprockets files"
 
-        class_option :skip_listen,        type: :boolean, default: false,
-                                          desc: "Don't generate configuration that depends on the listen gem"
+        class_option :skip_spring,         type: :boolean, default: false,
+                                           desc: "Don't install Spring application preloader"
 
-        class_option :skip_coffee,        type: :boolean, default: false,
-                                          desc: "Don't use CoffeeScript"
+        class_option :skip_listen,         type: :boolean, default: false,
+                                           desc: "Don't generate configuration that depends on the listen gem"
 
-        class_option :skip_javascript,    type: :boolean, aliases: "-J", default: false,
-                                          desc: "Skip JavaScript files"
+        class_option :skip_coffee,         type: :boolean, default: false,
+                                           desc: "Don't use CoffeeScript"
 
-        class_option :skip_turbolinks,    type: :boolean, default: false,
-                                          desc: "Skip turbolinks gem"
+        class_option :skip_javascript,     type: :boolean, aliases: "-J", default: false,
+                                           desc: "Skip JavaScript files"
 
-        class_option :skip_test,          type: :boolean, aliases: "-T", default: false,
-                                          desc: "Skip test files"
+        class_option :skip_turbolinks,     type: :boolean, default: false,
+                                           desc: "Skip turbolinks gem"
 
-        class_option :skip_system_test,   type: :boolean, default: false,
-                                          desc: "Skip system test files"
+        class_option :skip_test,           type: :boolean, aliases: "-T", default: false,
+                                           desc: "Skip test files"
 
-        class_option :dev,                type: :boolean, default: false,
-                                          desc: "Setup the #{name} with Gemfile pointing to your Rails checkout"
+        class_option :skip_system_test,    type: :boolean, default: false,
+                                           desc: "Skip system test files"
 
-        class_option :edge,               type: :boolean, default: false,
-                                          desc: "Setup the #{name} with Gemfile pointing to Rails repository"
+        class_option :skip_bootsnap,       type: :boolean, default: false,
+                                           desc: "Skip bootsnap gem"
 
-        class_option :rc,                 type: :string, default: nil,
-                                          desc: "Path to file containing extra configuration options for rails command"
+        class_option :dev,                 type: :boolean, default: false,
+                                           desc: "Setup the #{name} with Gemfile pointing to your Rails checkout"
 
-        class_option :no_rc,              type: :boolean, default: false,
-                                          desc: "Skip loading of extra configuration options from .railsrc file"
+        class_option :edge,                type: :boolean, default: false,
+                                           desc: "Setup the #{name} with Gemfile pointing to Rails repository"
 
-        class_option :help,               type: :boolean, aliases: "-h", group: :rails,
-                                          desc: "Show this help message and quit"
+        class_option :rc,                  type: :string, default: nil,
+                                           desc: "Path to file containing extra configuration options for rails command"
+
+        class_option :no_rc,               type: :boolean, default: false,
+                                           desc: "Skip loading of extra configuration options from .railsrc file"
+
+        class_option :help,                type: :boolean, aliases: "-h", group: :rails,
+                                           desc: "Show this help message and quit"
       end
 
       def initialize(*args)
@@ -189,15 +194,33 @@ module Rails
       def webserver_gemfile_entry # :doc:
         return [] if options[:skip_puma]
         comment = "Use Puma as the app server"
-        GemfileEntry.new("puma", "~> 3.7", comment)
+        GemfileEntry.new("puma", "~> 3.11", comment)
       end
 
       def include_all_railties? # :doc:
-        options.values_at(:skip_active_record, :skip_action_mailer, :skip_test, :skip_sprockets, :skip_action_cable).none?
+        [
+          options.values_at(
+            :skip_active_record,
+            :skip_action_mailer,
+            :skip_test,
+            :skip_sprockets,
+            :skip_action_cable
+          ),
+          skip_active_storage?
+        ].flatten.none?
       end
 
       def comment_if(value) # :doc:
-        options[value] ? "# " : ""
+        question = "#{value}?"
+
+        comment =
+          if respond_to?(question, true)
+            send(question)
+          else
+            options[value]
+          end
+
+        comment ? "# " : ""
       end
 
       def keeps? # :doc:
@@ -208,6 +231,10 @@ module Rails
         !options[:skip_active_record] && options[:database] == "sqlite3"
       end
 
+      def skip_active_storage? # :doc:
+        options[:skip_active_storage] || options[:skip_active_record]
+      end
+
       class GemfileEntry < Struct.new(:name, :version, :comment, :options, :commented_out)
         def initialize(name, version, comment, options = {}, commented_out = false)
           super
@@ -241,17 +268,14 @@ module Rails
       end
 
       def rails_gemfile_entry
-        dev_edge_common = [
-          GemfileEntry.github("arel", "rails/arel"),
-        ]
         if options.dev?
           [
             GemfileEntry.path("rails", Rails::Generators::RAILS_DEV_PATH)
-          ] + dev_edge_common
+          ]
         elsif options.edge?
           [
             GemfileEntry.github("rails", "rails/rails")
-          ] + dev_edge_common
+          ]
         else
           [GemfileEntry.version("rails",
                             rails_version_specifier,
@@ -275,8 +299,8 @@ module Rails
       def gem_for_database
         # %w( mysql postgresql sqlite3 oracle frontbase ibm_db sqlserver jdbcmysql jdbcsqlite3 jdbcpostgresql )
         case options[:database]
-        when "mysql"          then ["mysql2", [">= 0.3.18", "< 0.5"]]
-        when "postgresql"     then ["pg", ["~> 0.18"]]
+        when "mysql"          then ["mysql2", [">= 0.4.4", "< 0.6.0"]]
+        when "postgresql"     then ["pg", [">= 0.18", "< 2.0"]]
         when "oracle"         then ["activerecord-oracle_enhanced-adapter", nil]
         when "frontbase"      then ["ruby-frontbase", nil]
         when "sqlserver"      then ["activerecord-sqlserver-adapter", nil]
@@ -290,11 +314,13 @@ module Rails
 
       def convert_database_option_for_jruby
         if defined?(JRUBY_VERSION)
-          case options[:database]
-          when "postgresql" then options[:database].replace "jdbcpostgresql"
-          when "mysql"      then options[:database].replace "jdbcmysql"
-          when "sqlite3"    then options[:database].replace "jdbcsqlite3"
+          opt = options.dup
+          case opt[:database]
+          when "postgresql" then opt[:database] = "jdbcpostgresql"
+          when "mysql"      then opt[:database] = "jdbcmysql"
+          when "sqlite3"    then opt[:database] = "jdbcsqlite3"
           end
+          self.options = opt.freeze
         end
       end
 
@@ -369,7 +395,7 @@ module Rails
         return [] if options[:skip_action_cable]
         comment = "Use Redis adapter to run Action Cable in production"
         gems = []
-        gems << GemfileEntry.new("redis", "~> 3.0", comment, {}, true)
+        gems << GemfileEntry.new("redis", "~> 4.0", comment, {}, true)
         gems
       end
 
@@ -413,6 +439,10 @@ module Rails
         !options[:skip_listen] && os_supports_listen_out_of_the_box?
       end
 
+      def depend_on_bootsnap?
+        !options[:skip_bootsnap] && !options[:dev] && !defined?(JRUBY_VERSION)
+      end
+
       def os_supports_listen_out_of_the_box?
         RbConfig::CONFIG["host_os"] =~ /darwin|linux/
       end
diff --git a/railties/lib/rails/generators/css/assets/assets_generator.rb b/railties/lib/rails/generators/css/assets/assets_generator.rb
index 5f7be769b2..f657d1e50f 100644
--- a/railties/lib/rails/generators/css/assets/assets_generator.rb
+++ b/railties/lib/rails/generators/css/assets/assets_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../named_base"
+require "rails/generators/named_base"
 
 module Css # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/css/scaffold/scaffold_generator.rb b/railties/lib/rails/generators/css/scaffold/scaffold_generator.rb
index 5996cb1483..89c560f382 100644
--- a/railties/lib/rails/generators/css/scaffold/scaffold_generator.rb
+++ b/railties/lib/rails/generators/css/scaffold/scaffold_generator.rb
@@ -1,17 +1,17 @@
 # frozen_string_literal: true
 
-require_relative "../../named_base"
+require "rails/generators/named_base"
 
 module Css # :nodoc:
   module Generators # :nodoc:
     class ScaffoldGenerator < Rails::Generators::NamedBase # :nodoc:
+      source_root Rails::Generators::ScaffoldGenerator.source_root
+
       # In order to allow the Sass generators to pick up the default Rails CSS and
       # transform it, we leave it in a standard location for the CSS stylesheet
       # generators to handle. For the simple, default case, just copy it over.
       def copy_stylesheet
-        dir = Rails::Generators::ScaffoldGenerator.source_root
-        file = File.join(dir, "scaffold.css")
-        create_file "app/assets/stylesheets/scaffold.css", File.read(file)
+        copy_file "scaffold.css", "app/assets/stylesheets/scaffold.css"
       end
     end
   end
diff --git a/railties/lib/rails/generators/erb.rb b/railties/lib/rails/generators/erb.rb
index 2c20834611..ba20bcd32a 100644
--- a/railties/lib/rails/generators/erb.rb
+++ b/railties/lib/rails/generators/erb.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "named_base"
+require "rails/generators/named_base"
 
 module Erb # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/erb/controller/controller_generator.rb b/railties/lib/rails/generators/erb/controller/controller_generator.rb
index 1a6c84288b..8e13744b2a 100644
--- a/railties/lib/rails/generators/erb/controller/controller_generator.rb
+++ b/railties/lib/rails/generators/erb/controller/controller_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../erb"
+require "rails/generators/erb"
 
 module Erb # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/erb/controller/templates/view.html.erb b/railties/lib/rails/generators/erb/controller/templates/view.html.erb.tt
index cd54d13d83..cd54d13d83 100644
--- a/railties/lib/rails/generators/erb/controller/templates/view.html.erb
+++ b/railties/lib/rails/generators/erb/controller/templates/view.html.erb.tt
diff --git a/railties/lib/rails/generators/erb/mailer/mailer_generator.rb b/railties/lib/rails/generators/erb/mailer/mailer_generator.rb
index 5774d86c8e..997602cb8c 100644
--- a/railties/lib/rails/generators/erb/mailer/mailer_generator.rb
+++ b/railties/lib/rails/generators/erb/mailer/mailer_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../erb"
+require "rails/generators/erb"
 
 module Erb # :nodoc:
   module Generators # :nodoc:
@@ -35,7 +35,7 @@ module Erb # :nodoc:
         end
 
         def file_name
-          @_file_name ||= super.gsub(/_mailer/i, "")
+          @_file_name ||= super.sub(/_mailer\z/i, "")
         end
     end
   end
diff --git a/railties/lib/rails/generators/erb/mailer/templates/view.html.erb b/railties/lib/rails/generators/erb/mailer/templates/view.html.erb.tt
index b5045671b3..b5045671b3 100644
--- a/railties/lib/rails/generators/erb/mailer/templates/view.html.erb
+++ b/railties/lib/rails/generators/erb/mailer/templates/view.html.erb.tt
diff --git a/railties/lib/rails/generators/erb/mailer/templates/view.text.erb b/railties/lib/rails/generators/erb/mailer/templates/view.text.erb.tt
index 342285df19..342285df19 100644
--- a/railties/lib/rails/generators/erb/mailer/templates/view.text.erb
+++ b/railties/lib/rails/generators/erb/mailer/templates/view.text.erb.tt
diff --git a/railties/lib/rails/generators/erb/scaffold/scaffold_generator.rb b/railties/lib/rails/generators/erb/scaffold/scaffold_generator.rb
index e80c6d4b7d..2fc04e4094 100644
--- a/railties/lib/rails/generators/erb/scaffold/scaffold_generator.rb
+++ b/railties/lib/rails/generators/erb/scaffold/scaffold_generator.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../../erb"
-require_relative "../../resource_helpers"
+require "rails/generators/erb"
+require "rails/generators/resource_helpers"
 
 module Erb # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/erb/scaffold/templates/_form.html.erb b/railties/lib/rails/generators/erb/scaffold/templates/_form.html.erb.tt
index 4f2e84f924..518cb1121e 100644
--- a/railties/lib/rails/generators/erb/scaffold/templates/_form.html.erb
+++ b/railties/lib/rails/generators/erb/scaffold/templates/_form.html.erb.tt
@@ -1,4 +1,4 @@
-<%%= form_with(model: <%= singular_table_name %>, local: true) do |form| %>
+<%%= form_with(model: <%= model_resource_name %>, local: true) do |form| %>
   <%% if <%= singular_table_name %>.errors.any? %>
     <div id="error_explanation">
       <h2><%%= pluralize(<%= singular_table_name %>.errors.count, "error") %> prohibited this <%= singular_table_name %> from being saved:</h2>
@@ -15,15 +15,15 @@
   <div class="field">
 <% if attribute.password_digest? -%>
     <%%= form.label :password %>
-    <%%= form.password_field :password, id: :<%= field_id(:password) %> %>
+    <%%= form.password_field :password %>
   </div>
 
   <div class="field">
     <%%= form.label :password_confirmation %>
-    <%%= form.password_field :password_confirmation, id: :<%= field_id(:password_confirmation) %> %>
+    <%%= form.password_field :password_confirmation %>
 <% else -%>
     <%%= form.label :<%= attribute.column_name %> %>
-    <%%= form.<%= attribute.field_type %> :<%= attribute.column_name %>, id: :<%= field_id(attribute.column_name) %> %>
+    <%%= form.<%= attribute.field_type %> :<%= attribute.column_name %> %>
 <% end -%>
   </div>
 
diff --git a/railties/lib/rails/generators/erb/scaffold/templates/edit.html.erb b/railties/lib/rails/generators/erb/scaffold/templates/edit.html.erb.tt
index 81329473d9..81329473d9 100644
--- a/railties/lib/rails/generators/erb/scaffold/templates/edit.html.erb
+++ b/railties/lib/rails/generators/erb/scaffold/templates/edit.html.erb.tt
diff --git a/railties/lib/rails/generators/erb/scaffold/templates/index.html.erb b/railties/lib/rails/generators/erb/scaffold/templates/index.html.erb.tt
index 5f4904fee1..e1ede7c713 100644
--- a/railties/lib/rails/generators/erb/scaffold/templates/index.html.erb
+++ b/railties/lib/rails/generators/erb/scaffold/templates/index.html.erb.tt
@@ -18,9 +18,9 @@
 <% attributes.reject(&:password_digest?).each do |attribute| -%>
         <td><%%= <%= singular_table_name %>.<%= attribute.name %> %></td>
 <% end -%>
-        <td><%%= link_to 'Show', <%= singular_table_name %> %></td>
-        <td><%%= link_to 'Edit', edit_<%= singular_table_name %>_path(<%= singular_table_name %>) %></td>
-        <td><%%= link_to 'Destroy', <%= singular_table_name %>, method: :delete, data: { confirm: 'Are you sure?' } %></td>
+        <td><%%= link_to 'Show', <%= model_resource_name %> %></td>
+        <td><%%= link_to 'Edit', edit_<%= singular_route_name %>_path(<%= singular_table_name %>) %></td>
+        <td><%%= link_to 'Destroy', <%= model_resource_name %>, method: :delete, data: { confirm: 'Are you sure?' } %></td>
       </tr>
     <%% end %>
   </tbody>
@@ -28,4 +28,4 @@
 
 <br>
 
-<%%= link_to 'New <%= singular_table_name.titleize %>', new_<%= singular_table_name %>_path %>
+<%%= link_to 'New <%= singular_table_name.titleize %>', new_<%= singular_route_name %>_path %>
diff --git a/railties/lib/rails/generators/erb/scaffold/templates/new.html.erb b/railties/lib/rails/generators/erb/scaffold/templates/new.html.erb.tt
index 9b2b2f4875..9b2b2f4875 100644
--- a/railties/lib/rails/generators/erb/scaffold/templates/new.html.erb
+++ b/railties/lib/rails/generators/erb/scaffold/templates/new.html.erb.tt
diff --git a/railties/lib/rails/generators/erb/scaffold/templates/show.html.erb b/railties/lib/rails/generators/erb/scaffold/templates/show.html.erb.tt
index 5e634153be..5e634153be 100644
--- a/railties/lib/rails/generators/erb/scaffold/templates/show.html.erb
+++ b/railties/lib/rails/generators/erb/scaffold/templates/show.html.erb.tt
diff --git a/railties/lib/rails/generators/generated_attribute.rb b/railties/lib/rails/generators/generated_attribute.rb
index 2728459968..f7fd30a5fb 100644
--- a/railties/lib/rails/generators/generated_attribute.rb
+++ b/railties/lib/rails/generators/generated_attribute.rb
@@ -75,7 +75,7 @@ module Rails
                         when :date                 then :date_select
                         when :text                 then :text_area
                         when :boolean              then :check_box
-          else
+                        else
                           :text_field
         end
       end
@@ -91,7 +91,7 @@ module Rails
                      when :text                        then "MyText"
                      when :boolean                     then false
                      when :references, :belongs_to     then nil
-          else
+                     else
                        ""
         end
       end
diff --git a/railties/lib/rails/generators/js/assets/assets_generator.rb b/railties/lib/rails/generators/js/assets/assets_generator.rb
index ea151aa04e..9d32c666dc 100644
--- a/railties/lib/rails/generators/js/assets/assets_generator.rb
+++ b/railties/lib/rails/generators/js/assets/assets_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../named_base"
+require "rails/generators/named_base"
 
 module Js # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/migration.rb b/railties/lib/rails/generators/migration.rb
index 7162b8c0b4..5081060895 100644
--- a/railties/lib/rails/generators/migration.rb
+++ b/railties/lib/rails/generators/migration.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/concern"
-require_relative "actions/create_migration"
+require "rails/generators/actions/create_migration"
 
 module Rails
   module Generators
@@ -63,7 +63,12 @@ module Rails
         numbered_destination = File.join(dir, ["%migration_number%", base].join("_"))
 
         create_migration numbered_destination, nil, config do
-          ERB.new(::File.binread(source), nil, "-", "@output_buffer").result(context)
+          match = ERB.version.match(/\Aerb\.rb \[(?<version>[^ ]+) /)
+          if match && match[:version] >= "2.2.0" # Ruby 2.6+
+            ERB.new(::File.binread(source), trim_mode: "-", eoutvar: "@output_buffer").result(context)
+          else
+            ERB.new(::File.binread(source), nil, "-", "@output_buffer").result(context)
+          end
         end
       end
     end
diff --git a/railties/lib/rails/generators/model_helpers.rb b/railties/lib/rails/generators/model_helpers.rb
index aa3564476a..50078404b3 100644
--- a/railties/lib/rails/generators/model_helpers.rb
+++ b/railties/lib/rails/generators/model_helpers.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "active_model"
+require "rails/generators/active_model"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/generators/named_base.rb b/railties/lib/rails/generators/named_base.rb
index fe8447be23..d6732f8ff1 100644
--- a/railties/lib/rails/generators/named_base.rb
+++ b/railties/lib/rails/generators/named_base.rb
@@ -1,8 +1,7 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/module/introspection"
-require_relative "base"
-require_relative "generated_attribute"
+require "rails/generators/base"
+require "rails/generators/generated_attribute"
 
 module Rails
   module Generators
@@ -32,12 +31,8 @@ module Rails
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-        attr_reader :file_name
-
       private
+        attr_reader :file_name
 
         # FIXME: We are avoiding to use alias because a bug on thor that make
         # this method public and add it to the task list.
@@ -100,11 +95,11 @@ module Rails
         end
 
         def index_helper # :doc:
-          uncountable? ? "#{plural_table_name}_index" : plural_table_name
+          uncountable? ? "#{plural_route_name}_index" : plural_route_name
         end
 
         def show_helper # :doc:
-          "#{singular_table_name}_url(@#{singular_table_name})"
+          "#{singular_route_name}_url(@#{singular_table_name})"
         end
 
         def edit_helper # :doc:
@@ -112,11 +107,7 @@ module Rails
         end
 
         def new_helper # :doc:
-          "new_#{singular_table_name}_url"
-        end
-
-        def field_id(attribute_name)
-          [singular_table_name, attribute_name].join("_")
+          "new_#{singular_route_name}_url"
         end
 
         def singular_table_name # :doc:
@@ -152,6 +143,35 @@ module Rails
           end
         end
 
+        def redirect_resource_name # :doc:
+          model_resource_name(prefix: "@")
+        end
+
+        def model_resource_name(prefix: "") # :doc:
+          resource_name = "#{prefix}#{singular_table_name}"
+          if options[:model_name]
+            "[#{controller_class_path.map { |name| ":" + name }.join(", ")}, #{resource_name}]"
+          else
+            resource_name
+          end
+        end
+
+        def singular_route_name # :doc:
+          if options[:model_name]
+            "#{controller_class_path.join('_')}_#{singular_table_name}"
+          else
+            singular_table_name
+          end
+        end
+
+        def plural_route_name # :doc:
+          if options[:model_name]
+            "#{controller_class_path.join('_')}_#{plural_table_name}"
+          else
+            plural_table_name
+          end
+        end
+
         def assign_names!(name)
           @class_path = name.include?("/") ? name.split("/") : name.split("::")
           @class_path.map!(&:underscore)
@@ -193,7 +213,7 @@ module Rails
         #
         def self.check_class_collision(options = {}) # :doc:
           define_method :check_class_collision do
-            name = if respond_to?(:controller_class_name) # for ScaffoldBase
+            name = if respond_to?(:controller_class_name) # for ResourceHelpers
               controller_class_name
             else
               class_name
diff --git a/railties/lib/rails/generators/rails/app/app_generator.rb b/railties/lib/rails/generators/rails/app/app_generator.rb
index 0f73cc4755..34067240d7 100644
--- a/railties/lib/rails/generators/rails/app/app_generator.rb
+++ b/railties/lib/rails/generators/rails/app/app_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../app_base"
+require "rails/generators/app_base"
 
 module Rails
   module ActionMethods # :nodoc:
@@ -69,7 +69,7 @@ module Rails
 
     def version_control
       if !options[:skip_git] && !options[:pretend]
-        run "git init"
+        run "git init", capture: options[:quiet]
       end
     end
 
@@ -95,11 +95,9 @@ module Rails
     end
 
     def bin_when_updating
-      bin_yarn_exist = File.exist?("bin/yarn")
-
       bin
 
-      if options[:api] && !bin_yarn_exist
+      if options[:skip_yarn]
         remove_file "bin/yarn"
       end
     end
@@ -111,11 +109,10 @@ module Rails
         template "routes.rb"
         template "application.rb"
         template "environment.rb"
-        template "secrets.yml"
         template "cable.yml" unless options[:skip_action_cable]
         template "puma.rb"   unless options[:skip_puma]
         template "spring.rb" if spring_install?
-        template "storage.yml"
+        template "storage.yml" unless skip_active_storage?
 
         directory "environments"
         directory "initializers"
@@ -129,6 +126,9 @@ module Rails
       active_storage_config_exist    = File.exist?("config/storage.yml")
       rack_cors_config_exist         = File.exist?("config/initializers/cors.rb")
       assets_config_exist            = File.exist?("config/initializers/assets.rb")
+      csp_config_exist               = File.exist?("config/initializers/content_security_policy.rb")
+
+      @config_target_version = Rails.application.config.loaded_config_version || "5.0"
 
       config
 
@@ -140,10 +140,14 @@ module Rails
         template "config/cable.yml"
       end
 
-      if !active_storage_config_exist
+      if !skip_active_storage? && !active_storage_config_exist
         template "config/storage.yml"
       end
 
+      if options[:skip_sprockets] && !assets_config_exist
+        remove_file "config/initializers/assets.rb"
+      end
+
       unless rack_cors_config_exist
         remove_file "config/initializers/cors.rb"
       end
@@ -153,12 +157,28 @@ module Rails
           remove_file "config/initializers/cookies_serializer.rb"
         end
 
-        unless assets_config_exist
-          remove_file "config/initializers/assets.rb"
+        unless csp_config_exist
+          remove_file "config/initializers/content_security_policy.rb"
         end
       end
     end
 
+    def master_key
+      return if options[:pretend] || options[:dummy_app]
+
+      require "rails/generators/rails/master_key/master_key_generator"
+      master_key_generator = Rails::Generators::MasterKeyGenerator.new([], quiet: options[:quiet], force: options[:force])
+      master_key_generator.add_master_key_file_silently
+      master_key_generator.ignore_master_key_file_silently
+    end
+
+    def credentials
+      return if options[:pretend] || options[:dummy_app]
+
+      require "rails/generators/rails/credentials/credentials_generator"
+      Rails::Generators::CredentialsGenerator.new([], quiet: options[:quiet]).add_credentials_file_silently
+    end
+
     def database_yml
       template "config/databases/#{options[:database]}.yml", "config/database.yml"
     end
@@ -213,6 +233,10 @@ module Rails
     def vendor
       empty_directory_with_keep_file "vendor"
     end
+
+    def config_target_version
+      defined?(@config_target_version) ? @config_target_version : Rails::VERSION::STRING.to_f
+    end
   end
 
   module Generators
@@ -222,7 +246,7 @@ module Rails
     RESERVED_NAMES = %w[application destroy plugin runner test]
 
     class AppGenerator < AppBase # :nodoc:
-      WEBPACKS = %w( react vue angular elm )
+      WEBPACKS = %w( react vue angular elm stimulus )
 
       add_shared_options_for "application"
 
@@ -289,6 +313,14 @@ module Rails
       end
       remove_task :update_config_files
 
+      def create_master_key
+        build(:master_key)
+      end
+
+      def create_credentials
+        build(:credentials)
+      end
+
       def display_upgrade_guide_info
         say "\nAfter this, check Rails upgrade guide at http://guides.rubyonrails.org/upgrading_ruby_on_rails.html for more details about upgrading your app."
       end
@@ -320,6 +352,14 @@ module Rails
         build(:public_directory)
       end
 
+      def create_tmp_files
+        build(:tmp)
+      end
+
+      def create_vendor_files
+        build(:vendor)
+      end
+
       def create_test_files
         build(:test) unless options[:skip_test]
       end
@@ -328,12 +368,8 @@ module Rails
         build(:system_test) if depends_on_system_test?
       end
 
-      def create_tmp_files
-        build(:tmp)
-      end
-
-      def create_vendor_files
-        build(:vendor)
+      def create_storage_files
+        build(:storage) unless skip_active_storage?
       end
 
       def delete_app_assets_if_api_option
@@ -351,9 +387,13 @@ module Rails
         end
       end
 
-      def delete_application_layout_file_if_api_option
+      def delete_app_views_if_api_option
         if options[:api]
-          remove_file "app/views/layouts/application.html.erb"
+          if options[:skip_action_mailer]
+            remove_dir "app/views"
+          else
+            remove_file "app/views/layouts/application.html.erb"
+          end
         end
       end
 
@@ -405,6 +445,7 @@ module Rails
       def delete_non_api_initializers_if_api_option
         if options[:api]
           remove_file "config/initializers/cookies_serializer.rb"
+          remove_file "config/initializers/content_security_policy.rb"
         end
       end
 
@@ -416,7 +457,7 @@ module Rails
 
       def delete_new_framework_defaults
         unless options[:update]
-          remove_file "config/initializers/new_framework_defaults_5_2.rb"
+          remove_file "config/initializers/new_framework_defaults_6_0.rb"
         end
       end
 
@@ -482,10 +523,6 @@ module Rails
         end
       end
 
-      def app_secret
-        SecureRandom.hex(64)
-      end
-
       def mysql_socket
         @mysql_socket ||= [
           "/tmp/mysql.sock",                        # default
@@ -532,7 +569,7 @@ module Rails
 
         def handle_version_request!(argument)
           if ["--version", "-v"].include?(argument)
-            require_relative "../../../version"
+            require "rails/version"
             puts "Rails #{Rails::VERSION::STRING}"
             exit(0)
           end
diff --git a/railties/lib/rails/generators/rails/app/templates/Gemfile b/railties/lib/rails/generators/rails/app/templates/Gemfile.tt
index 7b7bebc957..1567333023 100644
--- a/railties/lib/rails/generators/rails/app/templates/Gemfile
+++ b/railties/lib/rails/generators/rails/app/templates/Gemfile.tt
@@ -20,13 +20,20 @@ ruby <%= "'#{RUBY_VERSION}'" -%>
 
 # Use ActiveModel has_secure_password
 # gem 'bcrypt', '~> 3.1.7'
+<% unless skip_active_storage? -%>
+
+# Use ActiveStorage variant
+# gem 'image_processing', '~> 1.2'
+<% end -%>
 
 # Use Capistrano for deployment
 # gem 'capistrano-rails', group: :development
 
+<% if depend_on_bootsnap? -%>
 # Reduces boot times through caching; required in config/boot.rb
 gem 'bootsnap', '>= 1.1.0', require: false
 
+<%- end -%>
 <%- if options.api? -%>
 # Use Rack CORS for handling Cross-Origin Resource Sharing (CORS), making cross-origin AJAX possible
 # gem 'rack-cors'
@@ -36,11 +43,6 @@ gem 'bootsnap', '>= 1.1.0', require: false
 group :development, :test do
   # Call 'byebug' anywhere in the code to stop execution and get a debugger console
   gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
-  <%- if depends_on_system_test? -%>
-  # Adds support for Capybara system testing and selenium driver
-  gem 'capybara', '~> 2.13'
-  gem 'selenium-webdriver'
-  <%- end -%>
 end
 
 group :development do
@@ -63,6 +65,16 @@ group :development do
 <% end -%>
 <% end -%>
 end
+
+<%- if depends_on_system_test? -%>
+group :test do
+  # Adds support for Capybara system testing and selenium driver
+  gem 'capybara', '>= 2.15'
+  gem 'selenium-webdriver'
+  # Easy installation and use of chromedriver to run system tests with Chrome
+  gem 'chromedriver-helper'
+end
+<%- end -%>
 <% end -%>
 
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
diff --git a/railties/lib/rails/generators/rails/app/templates/README.md b/railties/lib/rails/generators/rails/app/templates/README.md.tt
index 7db80e4ca1..7db80e4ca1 100644
--- a/railties/lib/rails/generators/rails/app/templates/README.md
+++ b/railties/lib/rails/generators/rails/app/templates/README.md.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/Rakefile b/railties/lib/rails/generators/rails/app/templates/Rakefile.tt
index e85f913914..e85f913914 100644
--- a/railties/lib/rails/generators/rails/app/templates/Rakefile
+++ b/railties/lib/rails/generators/rails/app/templates/Rakefile.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/application.js.tt b/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/application.js.tt
index 62fd04f113..5183bcd256 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/application.js.tt
+++ b/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/application.js.tt
@@ -12,7 +12,9 @@
 //
 <% unless options[:skip_javascript] -%>
 //= require rails-ujs
+<% unless skip_active_storage? -%>
 //= require activestorage
+<% end -%>
 <% unless options[:skip_turbolinks] -%>
 //= require turbolinks
 <% end -%>
diff --git a/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/cable.js b/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/cable.js.tt
index 739aa5f022..739aa5f022 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/cable.js
+++ b/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/cable.js.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/assets/stylesheets/application.css b/railties/lib/rails/generators/rails/app/templates/app/assets/stylesheets/application.css.tt
index d05ea0f511..d05ea0f511 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/assets/stylesheets/application.css
+++ b/railties/lib/rails/generators/rails/app/templates/app/assets/stylesheets/application.css.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/channel.rb b/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/channel.rb.tt
index d672697283..d672697283 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/channel.rb
+++ b/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/channel.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/connection.rb b/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/connection.rb.tt
index 0ff5442f47..0ff5442f47 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/connection.rb
+++ b/railties/lib/rails/generators/rails/app/templates/app/channels/application_cable/connection.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/helpers/application_helper.rb b/railties/lib/rails/generators/rails/app/templates/app/helpers/application_helper.rb.tt
index de6be7945c..de6be7945c 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/helpers/application_helper.rb
+++ b/railties/lib/rails/generators/rails/app/templates/app/helpers/application_helper.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/jobs/application_job.rb b/railties/lib/rails/generators/rails/app/templates/app/jobs/application_job.rb.tt
index a009ace51c..a009ace51c 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/jobs/application_job.rb
+++ b/railties/lib/rails/generators/rails/app/templates/app/jobs/application_job.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/mailers/application_mailer.rb b/railties/lib/rails/generators/rails/app/templates/app/mailers/application_mailer.rb.tt
index 286b2239d1..286b2239d1 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/mailers/application_mailer.rb
+++ b/railties/lib/rails/generators/rails/app/templates/app/mailers/application_mailer.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/models/application_record.rb b/railties/lib/rails/generators/rails/app/templates/app/models/application_record.rb.tt
index 10a4cba84d..10a4cba84d 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/models/application_record.rb
+++ b/railties/lib/rails/generators/rails/app/templates/app/models/application_record.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt b/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt
index 5460155b3e..ef715f1368 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt
@@ -3,6 +3,7 @@
   <head>
     <title><%= camelized %></title>
     <%%= csrf_meta_tags %>
+    <%%= csp_meta_tag %>
 
     <%- if options[:skip_javascript] -%>
     <%%= stylesheet_link_tag    'application', media: 'all' %>
diff --git a/railties/lib/rails/generators/rails/app/templates/bin/bundle b/railties/lib/rails/generators/rails/app/templates/bin/bundle.tt
index a84f0afe47..a84f0afe47 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/bundle
+++ b/railties/lib/rails/generators/rails/app/templates/bin/bundle.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/bin/rails b/railties/lib/rails/generators/rails/app/templates/bin/rails.tt
index 513a2e0183..513a2e0183 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/rails
+++ b/railties/lib/rails/generators/rails/app/templates/bin/rails.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/bin/rake b/railties/lib/rails/generators/rails/app/templates/bin/rake.tt
index d14fc8395b..d14fc8395b 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/rake
+++ b/railties/lib/rails/generators/rails/app/templates/bin/rake.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/bin/update.tt b/railties/lib/rails/generators/rails/app/templates/bin/update.tt
index d744bec32f..70cc71d83b 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/update.tt
+++ b/railties/lib/rails/generators/rails/app/templates/bin/update.tt
@@ -15,6 +15,11 @@ chdir APP_ROOT do
   puts '== Installing dependencies =='
   system! 'gem install bundler --conservative'
   system('bundle check') || system!('bundle install')
+<% unless options.skip_yarn? -%>
+
+  # Install JavaScript dependencies if using Yarn
+  # system('bin/yarn')
+<% end -%>
 <% unless options.skip_active_record? -%>
 
   puts "\n== Updating database =="
diff --git a/railties/lib/rails/generators/rails/app/templates/bin/yarn b/railties/lib/rails/generators/rails/app/templates/bin/yarn.tt
index c2f9b6768a..90ddcc520e 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/yarn
+++ b/railties/lib/rails/generators/rails/app/templates/bin/yarn.tt
@@ -1,7 +1,7 @@
-VENDOR_PATH = File.expand_path('..', __dir__)
-Dir.chdir(VENDOR_PATH) do
+APP_ROOT = File.expand_path('..', __dir__)
+Dir.chdir(APP_ROOT) do
   begin
-    exec "yarnpkg #{ARGV.join(' ')}"
+    exec "yarnpkg", *ARGV
   rescue Errno::ENOENT
     $stderr.puts "Yarn executable was not detected in the system."
     $stderr.puts "Download Yarn at https://yarnpkg.com/en/docs/install"
diff --git a/railties/lib/rails/generators/rails/app/templates/config.ru b/railties/lib/rails/generators/rails/app/templates/config.ru.tt
index f7ba0b527b..f7ba0b527b 100644
--- a/railties/lib/rails/generators/rails/app/templates/config.ru
+++ b/railties/lib/rails/generators/rails/app/templates/config.ru.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/application.rb b/railties/lib/rails/generators/rails/app/templates/config/application.rb.tt
index dde09edb94..9a427113c7 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/application.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/application.rb.tt
@@ -8,10 +8,10 @@ require "rails"
 require "active_model/railtie"
 require "active_job/railtie"
 <%= comment_if :skip_active_record %>require "active_record/railtie"
+<%= comment_if :skip_active_storage %>require "active_storage/engine"
 require "action_controller/railtie"
 <%= comment_if :skip_action_mailer %>require "action_mailer/railtie"
 require "action_view/railtie"
-require "active_storage/engine"
 <%= comment_if :skip_action_cable %>require "action_cable/engine"
 <%= comment_if :skip_sprockets %>require "sprockets/railtie"
 <%= comment_if :skip_test %>require "rails/test_unit/railtie"
@@ -24,11 +24,12 @@ Bundler.require(*Rails.groups)
 module <%= app_const_base %>
   class Application < Rails::Application
     # Initialize configuration defaults for originally generated Rails version.
-    config.load_defaults <%= Rails::VERSION::STRING.to_f %>
+    config.load_defaults <%= build(:config_target_version) %>
 
     # Settings in config/environments/* take precedence over those specified here.
-    # Application configuration should go into files in config/initializers
-    # -- all .rb files in that directory are automatically loaded.
+    # Application configuration can go into files in config/initializers
+    # -- all .rb files in that directory are automatically loaded after loading
+    # the framework and any gems in your application.
 <%- if options.api? -%>
 
     # Only loads a smaller set of middleware suitable for API only apps.
diff --git a/railties/lib/rails/generators/rails/app/templates/config/boot.rb b/railties/lib/rails/generators/rails/app/templates/config/boot.rb.tt
index b9e460cef3..42d46b8175 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/boot.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/boot.rb.tt
@@ -1,4 +1,6 @@
 ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__)
 
 require 'bundler/setup' # Set up gems listed in the Gemfile.
+<% if depend_on_bootsnap? -%>
 require 'bootsnap/setup' # Speed up boot time by caching expensive operations.
+<%- end -%>
diff --git a/railties/lib/rails/generators/rails/app/templates/config/cable.yml b/railties/lib/rails/generators/rails/app/templates/config/cable.yml.tt
index 8e53156c71..8e53156c71 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/cable.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/cable.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/frontbase.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/frontbase.yml.tt
index 917b52e535..917b52e535 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/frontbase.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/frontbase.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/ibm_db.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/ibm_db.yml.tt
index d40117a27f..d40117a27f 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/ibm_db.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/ibm_db.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbc.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbc.yml.tt
index 563be77710..563be77710 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbc.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbc.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcmysql.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcmysql.yml.tt
index 2a67bdca25..2a67bdca25 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcmysql.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcmysql.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcpostgresql.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcpostgresql.yml.tt
index 70df04079d..70df04079d 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcpostgresql.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcpostgresql.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcsqlite3.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcsqlite3.yml.tt
index 371415e6a8..371415e6a8 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcsqlite3.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/jdbcsqlite3.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/mysql.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/mysql.yml.tt
index 04afaa0596..04afaa0596 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/mysql.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/mysql.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/oracle.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/oracle.yml.tt
index 6da0601b24..6da0601b24 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/oracle.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/oracle.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/postgresql.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/postgresql.yml.tt
index 145cfb7f74..145cfb7f74 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/postgresql.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/postgresql.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/sqlite3.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/sqlite3.yml.tt
index 9510568124..9510568124 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/sqlite3.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/sqlite3.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/databases/sqlserver.yml b/railties/lib/rails/generators/rails/app/templates/config/databases/sqlserver.yml.tt
index 049de65f22..049de65f22 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/databases/sqlserver.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/databases/sqlserver.yml.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/environment.rb b/railties/lib/rails/generators/rails/app/templates/config/environment.rb.tt
index 426333bb46..426333bb46 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environment.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/environment.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt
index 98689cc30d..3807c8a9aa 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt
@@ -14,7 +14,7 @@ Rails.application.configure do
 
   # Enable/disable caching. By default caching is disabled.
   # Run rails dev:cache to toggle caching.
-  if Rails.root.join('tmp/caching-dev.txt').exist?
+  if Rails.root.join('tmp', 'caching-dev.txt').exist?
     config.action_controller.perform_caching = true
 
     config.cache_store = :memory_store
@@ -26,9 +26,11 @@ Rails.application.configure do
 
     config.cache_store = :null_store
   end
+  <%- unless skip_active_storage? -%>
 
-  # Store uploaded files on the local file system (see config/storage.yml for options)
+  # Store uploaded files on the local file system (see config/storage.yml for options).
   config.active_storage.service = :local
+  <%- end -%>
   <%- unless options.skip_action_mailer? -%>
 
   # Don't care if the mailer can't send.
@@ -44,6 +46,9 @@ Rails.application.configure do
   # Raise an error on page load if there are pending migrations.
   config.active_record.migration_error = :page_load
 
+  # Highlight code that triggered database queries in logs.
+  config.active_record.verbose_query_logs = true
+
   <%- end -%>
   <%- unless options.skip_sprockets? -%>
   # Debug mode disables concatenation and preprocessing of assets.
@@ -55,7 +60,7 @@ Rails.application.configure do
   config.assets.quiet = true
   <%- end -%>
 
-  # Raises error for missing translations
+  # Raises error for missing translations.
   # config.action_view.raise_on_missing_translations = true
 
   # Use an evented file watcher to asynchronously detect changes in source code,
diff --git a/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
index f68e13aa8b..d646694477 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
@@ -14,10 +14,9 @@ Rails.application.configure do
   config.consider_all_requests_local       = false
   config.action_controller.perform_caching = true
 
-  # Attempt to read encrypted secrets from `config/secrets.yml.enc`.
-  # Requires an encryption key in `ENV["RAILS_MASTER_KEY"]` or
-  # `config/secrets.yml.key`.
-  config.read_encrypted_secrets = true
+  # Ensures that a master key has been made available in either ENV["RAILS_MASTER_KEY"]
+  # or in config/master.key. This key is used to decrypt credentials (and other encrypted files).
+  # config.require_master_key = true
 
   # Disable serving static files from the `/public` folder by default since
   # Apache or NGINX already handles this.
@@ -35,8 +34,6 @@ Rails.application.configure do
   # Do not fallback to assets pipeline if a precompiled asset is missed.
   config.assets.compile = false
 
-  # `config.assets.precompile` and `config.assets.version` have moved to config/initializers/assets.rb
-
   <%- end -%>
   # Enable serving of images, stylesheets, and JavaScripts from an asset server.
   # config.action_controller.asset_host = 'http://assets.example.com'
@@ -45,11 +42,13 @@ Rails.application.configure do
   # config.action_dispatch.x_sendfile_header = 'X-Sendfile' # for Apache
   # config.action_dispatch.x_sendfile_header = 'X-Accel-Redirect' # for NGINX
 
-  # Store uploaded files on the local file system (see config/storage.yml for options)
+  <%- unless skip_active_storage? -%>
+  # Store uploaded files on the local file system (see config/storage.yml for options).
   config.active_storage.service = :local
 
+  <%- end -%>
   <%- unless options[:skip_action_cable] -%>
-  # Mount Action Cable outside main process or domain
+  # Mount Action Cable outside main process or domain.
   # config.action_cable.mount_path = nil
   # config.action_cable.url = 'wss://example.com/cable'
   # config.action_cable.allowed_request_origins = [ 'http://example.com', /http:\/\/example.*/ ]
@@ -68,7 +67,7 @@ Rails.application.configure do
   # Use a different cache store in production.
   # config.cache_store = :mem_cache_store
 
-  # Use a real queuing backend for Active Job (and separate queues per environment)
+  # Use a real queuing backend for Active Job (and separate queues per environment).
   # config.active_job.queue_adapter     = :resque
   # config.active_job.queue_name_prefix = "<%= app_name %>_#{Rails.env}"
 
diff --git a/railties/lib/rails/generators/rails/app/templates/config/environments/test.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/environments/test.rb.tt
index a53978bc6e..82f2a8aebe 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environments/test.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/environments/test.rb.tt
@@ -28,8 +28,11 @@ Rails.application.configure do
   # Disable request forgery protection in test environment.
   config.action_controller.allow_forgery_protection = false
 
-  # Store uploaded files on the local file system in a temporary directory
+  <%- unless skip_active_storage? -%>
+  # Store uploaded files on the local file system in a temporary directory.
   config.active_storage.service = :test
+
+  <%- end -%>
   <%- unless options.skip_action_mailer? -%>
   config.action_mailer.perform_caching = false
 
@@ -37,11 +40,14 @@ Rails.application.configure do
   # The :test delivery method accumulates sent emails in the
   # ActionMailer::Base.deliveries array.
   config.action_mailer.delivery_method = :test
-  <%- end -%>
 
+  <%- end -%>
   # Print deprecation notices to the stderr.
   config.active_support.deprecation = :stderr
 
-  # Raises error for missing translations
+  # Raises error for missing translations.
   # config.action_view.raise_on_missing_translations = true
+
+  # Prevent expensive template finalization at end of test suite runs.
+  config.action_view.finalize_compiled_template_methods = false
 end
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/application_controller_renderer.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/application_controller_renderer.rb.tt
index 89d2efab2b..89d2efab2b 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/application_controller_renderer.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/application_controller_renderer.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/backtrace_silencers.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/backtrace_silencers.rb.tt
index 59385cdf37..59385cdf37 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/backtrace_silencers.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/backtrace_silencers.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt
new file mode 100644
index 0000000000..d3bcaa5ec8
--- /dev/null
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt
@@ -0,0 +1,25 @@
+# Be sure to restart your server when you modify this file.
+
+# Define an application-wide content security policy
+# For further information see the following documentation
+# https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy
+
+# Rails.application.config.content_security_policy do |policy|
+#   policy.default_src :self, :https
+#   policy.font_src    :self, :https, :data
+#   policy.img_src     :self, :https, :data
+#   policy.object_src  :none
+#   policy.script_src  :self, :https
+#   policy.style_src   :self, :https
+
+#   # Specify URI for violation reports
+#   # policy.report_uri "/csp-violation-report-endpoint"
+# end
+
+# If you are using UJS then enable automatic nonce generation
+# Rails.application.config.content_security_policy_nonce_generator = -> request { SecureRandom.base64(16) }
+
+# Report CSP violations to a specified URI
+# For further information see the following documentation:
+# https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy-Report-Only
+# Rails.application.config.content_security_policy_report_only = true
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/cookies_serializer.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/cookies_serializer.rb.tt
index 5a6a32d371..5a6a32d371 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/cookies_serializer.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/cookies_serializer.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/cors.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/cors.rb.tt
index 3b1c1b5ed1..3b1c1b5ed1 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/cors.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/cors.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/filter_parameter_logging.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/filter_parameter_logging.rb.tt
index 4a994e1e7b..4a994e1e7b 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/filter_parameter_logging.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/filter_parameter_logging.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/inflections.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/inflections.rb.tt
index ac033bf9dc..ac033bf9dc 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/inflections.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/inflections.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/mime_types.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/mime_types.rb.tt
index dc1899682b..dc1899682b 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/mime_types.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/mime_types.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_5_2.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_5_2.rb.tt
deleted file mode 100644
index 25dcddb27a..0000000000
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_5_2.rb.tt
+++ /dev/null
@@ -1,27 +0,0 @@
-# Be sure to restart your server when you modify this file.
-#
-# This file contains migration options to ease your Rails 5.2 upgrade.
-#
-# Once upgraded flip defaults one by one to migrate to the new default.
-#
-# Read the Guide for Upgrading Ruby on Rails for more info on each option.
-
-# Make Active Record use stable #cache_key alongside new #cache_version method.
-# This is needed for recyclable cache keys.
-# Rails.application.config.active_record.cache_versioning = true
-
-# Use AES 256 GCM authenticated encryption for encrypted cookies.
-# Existing cookies will be converted on read then written with the new scheme.
-# Rails.application.config.action_dispatch.use_authenticated_cookie_encryption = true
-
-# Use AES-256-GCM authenticated encryption as default cipher for encrypting messages
-# instead of AES-256-CBC, when use_authenticated_message_encryption is set to true.
-# Rails.application.config.active_support.use_authenticated_message_encryption = true
-
-# Add default protection from forgery to ActionController::Base instead of in
-# ApplicationController.
-# Rails.application.config.action_controller.default_protect_from_forgery = true
-
-# Store boolean values are in sqlite3 databases as 1 and 0 instead of 't' and
-# 'f' after migrating old data.
-# Rails.application.config.active_record.sqlite3.represent_boolean_as_integer = true
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_6_0.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_6_0.rb.tt
new file mode 100644
index 0000000000..179b97de4a
--- /dev/null
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_6_0.rb.tt
@@ -0,0 +1,10 @@
+# Be sure to restart your server when you modify this file.
+#
+# This file contains migration options to ease your Rails 6.0 upgrade.
+#
+# Once upgraded flip defaults one by one to migrate to the new default.
+#
+# Read the Guide for Upgrading Ruby on Rails for more info on each option.
+
+# Don't force requests from old versions of IE to be UTF-8 encoded
+# Rails.application.config.action_view.default_enforce_utf8 = false
diff --git a/railties/lib/rails/generators/rails/app/templates/config/puma.rb b/railties/lib/rails/generators/rails/app/templates/config/puma.rb.tt
index 1e19380dcb..a5eccf816b 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/puma.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/puma.rb.tt
@@ -26,31 +26,9 @@ environment ENV.fetch("RAILS_ENV") { "development" }
 # Use the `preload_app!` method when specifying a `workers` number.
 # This directive tells Puma to first boot the application and load code
 # before forking the application. This takes advantage of Copy On Write
-# process behavior so workers use less memory. If you use this option
-# you need to make sure to reconnect any threads in the `on_worker_boot`
-# block.
+# process behavior so workers use less memory.
 #
 # preload_app!
 
-# If you are preloading your application and using Active Record, it's
-# recommended that you close any connections to the database before workers
-# are forked to prevent connection leakage.
-#
-# before_fork do
-#   ActiveRecord::Base.connection_pool.disconnect! if defined?(ActiveRecord)
-# end
-
-# The code in the `on_worker_boot` will be called if you are using
-# clustered mode by specifying a number of `workers`. After each worker
-# process is booted, this block will be run. If you are using the `preload_app!`
-# option, you will want to use this block to reconnect to any threads
-# or connections that may have been created at application boot, as Ruby
-# cannot share connections between processes.
-#
-# on_worker_boot do
-#   ActiveRecord::Base.establish_connection if defined?(ActiveRecord)
-# end
-#
-
 # Allow puma to be restarted by `rails restart` command.
 plugin :tmp_restart
diff --git a/railties/lib/rails/generators/rails/app/templates/config/routes.rb b/railties/lib/rails/generators/rails/app/templates/config/routes.rb.tt
index 787824f888..787824f888 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/routes.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/routes.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/secrets.yml b/railties/lib/rails/generators/rails/app/templates/config/secrets.yml
deleted file mode 100644
index ea9d47396c..0000000000
--- a/railties/lib/rails/generators/rails/app/templates/config/secrets.yml
+++ /dev/null
@@ -1,32 +0,0 @@
-# Be sure to restart your server when you modify this file.
-
-# Your secret key is used for verifying the integrity of signed cookies.
-# If you change this key, all old signed cookies will become invalid!
-
-# Make sure the secret is at least 30 characters and all random,
-# no regular words or you'll be exposed to dictionary attacks.
-# You can use `rails secret` to generate a secure secret key.
-
-# Make sure the secrets in this file are kept private
-# if you're sharing your code publicly.
-
-# Shared secrets are available across all environments.
-
-# shared:
-#   api_key: a1B2c3D4e5F6
-
-# Environmental secrets are only available for that specific environment.
-
-development:
-  secret_key_base: <%= app_secret %>
-
-test:
-  secret_key_base: <%= app_secret %>
-
-# Do not keep production secrets in the unencrypted secrets file.
-# Instead, either read values from the environment.
-# Or, use `bin/rails secrets:setup` to configure encrypted secrets
-# and move the `production:` environment over there.
-
-production:
-  secret_key_base: <%%= ENV["SECRET_KEY_BASE"] %>
diff --git a/railties/lib/rails/generators/rails/app/templates/config/spring.rb b/railties/lib/rails/generators/rails/app/templates/config/spring.rb.tt
index db5bf1307a..db5bf1307a 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/spring.rb
+++ b/railties/lib/rails/generators/rails/app/templates/config/spring.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/config/storage.yml b/railties/lib/rails/generators/rails/app/templates/config/storage.yml.tt
index 089ed4567a..7207c75086 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/storage.yml
+++ b/railties/lib/rails/generators/rails/app/templates/config/storage.yml.tt
@@ -6,11 +6,11 @@ local:
   service: Disk
   root: <%%= Rails.root.join("storage") %>
 
-# Use rails secrets:edit to set the AWS secrets (as shared:aws:access_key_id|secret_access_key)
+# Use rails credentials:edit to set the AWS secrets (as aws:access_key_id|secret_access_key)
 # amazon:
 #   service: S3
-#   access_key_id: <%%= Rails.application.secrets.dig(:aws, :access_key_id) %>
-#   secret_access_key: <%%= Rails.application.secrets.dig(:aws, :secret_access_key) %>
+#   access_key_id: <%%= Rails.application.credentials.dig(:aws, :access_key_id) %>
+#   secret_access_key: <%%= Rails.application.credentials.dig(:aws, :secret_access_key) %>
 #   region: us-east-1
 #   bucket: your_own_bucket
 
@@ -18,15 +18,14 @@ local:
 # google:
 #   service: GCS
 #   project: your_project
-#   keyfile: <%%= Rails.root.join("path/to/gcs.keyfile") %>
+#   credentials: <%%= Rails.root.join("path/to/gcs.keyfile") %>
 #   bucket: your_own_bucket
 
-# Use rails secrets:edit to set the Azure Storage secret (as shared:azure_storage:storage_access_key)
+# Use rails credentials:edit to set the Azure Storage secret (as azure_storage:storage_access_key)
 # microsoft:
 #   service: AzureStorage
-#   path: your_azure_storage_path
 #   storage_account_name: your_account_name
-#   storage_access_key: <%%= Rails.application.secrets.dig(:azure_storage, :storage_access_key) %>
+#   storage_access_key: <%%= Rails.application.credentials.dig(:azure_storage, :storage_access_key) %>
 #   container: your_container_name
 
 # mirror:
diff --git a/railties/lib/rails/generators/rails/app/templates/gitignore b/railties/lib/rails/generators/rails/app/templates/gitignore.tt
index 83a7b211aa..4e114fb1d9 100644
--- a/railties/lib/rails/generators/rails/app/templates/gitignore
+++ b/railties/lib/rails/generators/rails/app/templates/gitignore.tt
@@ -21,14 +21,19 @@
 !/tmp/.keep
 <% end -%>
 
+<% unless skip_active_storage? -%>
 # Ignore uploaded files in development
 /storage/*
+<% if keeps? -%>
+!/storage/.keep
+<% end -%>
+<% end -%>
 
 <% unless options.skip_yarn? -%>
 /node_modules
 /yarn-error.log
-<% end -%>
 
+<% end -%>
 <% unless options.api? -%>
 /public/assets
 <% end -%>
diff --git a/railties/lib/rails/generators/rails/app/templates/package.json b/railties/lib/rails/generators/rails/app/templates/package.json.tt
index 46db57dcbe..46db57dcbe 100644
--- a/railties/lib/rails/generators/rails/app/templates/package.json
+++ b/railties/lib/rails/generators/rails/app/templates/package.json.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/ruby-version b/railties/lib/rails/generators/rails/app/templates/ruby-version
deleted file mode 100644
index c444f33b0f..0000000000
--- a/railties/lib/rails/generators/rails/app/templates/ruby-version
+++ /dev/null
@@ -1 +0,0 @@
-<%= RUBY_VERSION -%>
diff --git a/railties/lib/rails/generators/rails/app/templates/ruby-version.tt b/railties/lib/rails/generators/rails/app/templates/ruby-version.tt
new file mode 100644
index 0000000000..19f0d7f202
--- /dev/null
+++ b/railties/lib/rails/generators/rails/app/templates/ruby-version.tt
@@ -0,0 +1 @@
+<%= "#{RUBY_ENGINE}-#{RUBY_ENGINE_VERSION}" -%>
diff --git a/railties/lib/rails/generators/rails/app/templates/test/application_system_test_case.rb b/railties/lib/rails/generators/rails/app/templates/test/application_system_test_case.rb.tt
index d19212abd5..d19212abd5 100644
--- a/railties/lib/rails/generators/rails/app/templates/test/application_system_test_case.rb
+++ b/railties/lib/rails/generators/rails/app/templates/test/application_system_test_case.rb.tt
diff --git a/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb b/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt
index 6ad1f11781..c918b57eca 100644
--- a/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb
+++ b/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt
@@ -1,7 +1,15 @@
+ENV['RAILS_ENV'] ||= 'test'
 require_relative '../config/environment'
 require 'rails/test_help'
 
 class ActiveSupport::TestCase
+  # Run tests in parallel with specified workers
+<% if defined?(JRUBY_VERSION) -%>
+  parallelize(workers: 2, with: :threads)
+<%- else -%>
+  parallelize(workers: 2)
+<% end -%>
+
 <% unless options[:skip_active_record] -%>
   # Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
   fixtures :all
diff --git a/railties/lib/rails/generators/rails/assets/templates/stylesheet.css b/railties/lib/rails/generators/rails/assets/templates/stylesheet.css
index 7594abf268..afad32db02 100644
--- a/railties/lib/rails/generators/rails/assets/templates/stylesheet.css
+++ b/railties/lib/rails/generators/rails/assets/templates/stylesheet.css
@@ -1,4 +1,4 @@
-/* 
+/*
   Place all the styles related to the matching controller here.
   They will automatically be included in application.css.
 */
diff --git a/railties/lib/rails/generators/rails/controller/controller_generator.rb b/railties/lib/rails/generators/rails/controller/controller_generator.rb
index 6d45d6e8f8..eb75e7e661 100644
--- a/railties/lib/rails/generators/rails/controller/controller_generator.rb
+++ b/railties/lib/rails/generators/rails/controller/controller_generator.rb
@@ -16,13 +16,24 @@ module Rails
 
       def add_routes
         return if options[:skip_routes]
+        return if actions.empty?
         route generate_routing_code
       end
 
-      hook_for :template_engine, :test_framework, :helper, :assets
+      hook_for :template_engine, :test_framework, :helper, :assets do |generator|
+        invoke generator, [ remove_possible_suffix(name), actions ]
+      end
 
       private
 
+        def file_name
+          @_file_name ||= remove_possible_suffix(super)
+        end
+
+        def remove_possible_suffix(name)
+          name.sub(/_?controller$/i, "")
+        end
+
         # This method creates nested route entry for namespaced resources.
         # For eg. rails g controller foo/bar/baz index show
         # Will generate -
diff --git a/railties/lib/rails/generators/rails/controller/templates/controller.rb b/railties/lib/rails/generators/rails/controller/templates/controller.rb.tt
index 633e0b3177..633e0b3177 100644
--- a/railties/lib/rails/generators/rails/controller/templates/controller.rb
+++ b/railties/lib/rails/generators/rails/controller/templates/controller.rb.tt
diff --git a/railties/lib/rails/generators/rails/credentials/credentials_generator.rb b/railties/lib/rails/generators/rails/credentials/credentials_generator.rb
new file mode 100644
index 0000000000..719e0c1e4c
--- /dev/null
+++ b/railties/lib/rails/generators/rails/credentials/credentials_generator.rb
@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+require "rails/generators/base"
+require "rails/generators/rails/master_key/master_key_generator"
+require "active_support/encrypted_configuration"
+
+module Rails
+  module Generators
+    class CredentialsGenerator < Base # :nodoc:
+      def add_credentials_file
+        unless credentials.content_path.exist?
+          template = credentials_template
+
+          say "Adding #{credentials.content_path} to store encrypted credentials."
+          say ""
+          say "The following content has been encrypted with the Rails master key:"
+          say ""
+          say template, :on_green
+          say ""
+
+          add_credentials_file_silently(template)
+
+          say "You can edit encrypted credentials with `bin/rails credentials:edit`."
+          say ""
+        end
+      end
+
+      def add_credentials_file_silently(template = nil)
+        unless credentials.content_path.exist?
+          credentials.write(credentials_template)
+        end
+      end
+
+      private
+        def credentials
+          ActiveSupport::EncryptedConfiguration.new(
+            config_path: "config/credentials.yml.enc",
+            key_path: "config/master.key",
+            env_key: "RAILS_MASTER_KEY",
+            raise_if_missing_key: true
+          )
+        end
+
+        def credentials_template
+          <<~YAML
+            # aws:
+            #   access_key_id: 123
+            #   secret_access_key: 345
+
+            # Used as the base secret for all MessageVerifiers in Rails, including the one protecting cookies.
+            secret_key_base: #{SecureRandom.hex(64)}
+          YAML
+        end
+    end
+  end
+end
diff --git a/railties/lib/rails/generators/rails/encrypted_file/encrypted_file_generator.rb b/railties/lib/rails/generators/rails/encrypted_file/encrypted_file_generator.rb
new file mode 100644
index 0000000000..867e28c6db
--- /dev/null
+++ b/railties/lib/rails/generators/rails/encrypted_file/encrypted_file_generator.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require "rails/generators/base"
+require "active_support/encrypted_file"
+
+module Rails
+  module Generators
+    class EncryptedFileGenerator < Base # :nodoc:
+      def add_encrypted_file_silently(file_path, key_path, template = encrypted_file_template)
+        unless File.exist?(file_path)
+          setup = { content_path: file_path, key_path: key_path, env_key: "RAILS_MASTER_KEY", raise_if_missing_key: true }
+          ActiveSupport::EncryptedFile.new(setup).write(template)
+        end
+      end
+
+      private
+        def encrypted_file_template
+          <<~YAML
+            # aws:
+            #   access_key_id: 123
+            #   secret_access_key: 345
+
+          YAML
+        end
+    end
+  end
+end
diff --git a/railties/lib/rails/generators/rails/encrypted_secrets/encrypted_secrets_generator.rb b/railties/lib/rails/generators/rails/encrypted_secrets/encrypted_secrets_generator.rb
deleted file mode 100644
index d054e8cad2..0000000000
--- a/railties/lib/rails/generators/rails/encrypted_secrets/encrypted_secrets_generator.rb
+++ /dev/null
@@ -1,72 +0,0 @@
-# frozen_string_literal: true
-
-require_relative "../../base"
-require_relative "../../../secrets"
-
-module Rails
-  module Generators
-    class EncryptedSecretsGenerator < Base
-      def add_secrets_key_file
-        unless File.exist?("config/secrets.yml.key") || File.exist?("config/secrets.yml.enc")
-          key = Rails::Secrets.generate_key
-
-          say "Adding config/secrets.yml.key to store the encryption key: #{key}"
-          say ""
-          say "Save this in a password manager your team can access."
-          say ""
-          say "If you lose the key, no one, including you, can access any encrypted secrets."
-
-          say ""
-          create_file "config/secrets.yml.key", key
-          say ""
-        end
-      end
-
-      def ignore_key_file
-        if File.exist?(".gitignore")
-          unless File.read(".gitignore").include?(key_ignore)
-            say "Ignoring config/secrets.yml.key so it won't end up in Git history:"
-            say ""
-            append_to_file ".gitignore", key_ignore
-            say ""
-          end
-        else
-          say "IMPORTANT: Don't commit config/secrets.yml.key. Add this to your ignore file:"
-          say key_ignore, :on_green
-          say ""
-        end
-      end
-
-      def add_encrypted_secrets_file
-        unless (defined?(@@skip_secrets_file) && @@skip_secrets_file) || File.exist?("config/secrets.yml.enc")
-          say "Adding config/secrets.yml.enc to store secrets that needs to be encrypted."
-          say ""
-          say "For now the file contains this but it's been encrypted with the generated key:"
-          say ""
-          say Secrets.template, :on_green
-          say ""
-
-          Secrets.write(Secrets.template)
-
-          say "You can edit encrypted secrets with `bin/rails secrets:edit`."
-          say ""
-        end
-
-        say "Add this to your config/environments/production.rb:"
-        say "config.read_encrypted_secrets = true"
-      end
-
-      def self.skip_secrets_file
-        @@skip_secrets_file = true
-        yield
-      ensure
-        @@skip_secrets_file = false
-      end
-
-      private
-        def key_ignore
-          [ "", "# Ignore encrypted secrets key file.", "config/secrets.yml.key", "" ].join("\n")
-        end
-    end
-  end
-end
diff --git a/railties/lib/rails/generators/rails/encryption_key_file/encryption_key_file_generator.rb b/railties/lib/rails/generators/rails/encryption_key_file/encryption_key_file_generator.rb
new file mode 100644
index 0000000000..e2359e9ded
--- /dev/null
+++ b/railties/lib/rails/generators/rails/encryption_key_file/encryption_key_file_generator.rb
@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+require "pathname"
+require "rails/generators/base"
+require "active_support/encrypted_file"
+
+module Rails
+  module Generators
+    class EncryptionKeyFileGenerator < Base # :nodoc:
+      def add_key_file(key_path)
+        key_path = Pathname.new(key_path)
+
+        unless key_path.exist?
+          key = ActiveSupport::EncryptedFile.generate_key
+
+          log "Adding #{key_path} to store the encryption key: #{key}"
+          log ""
+          log "Save this in a password manager your team can access."
+          log ""
+          log "If you lose the key, no one, including you, can access anything encrypted with it."
+
+          log ""
+          add_key_file_silently(key_path, key)
+          log ""
+        end
+      end
+
+      def add_key_file_silently(key_path, key = nil)
+        create_file key_path, key || ActiveSupport::EncryptedFile.generate_key
+        key_path.chmod 0600
+      end
+
+      def ignore_key_file(key_path, ignore: key_ignore(key_path))
+        if File.exist?(".gitignore")
+          unless File.read(".gitignore").include?(ignore)
+            log "Ignoring #{key_path} so it won't end up in Git history:"
+            log ""
+            append_to_file ".gitignore", ignore
+            log ""
+          end
+        else
+          log "IMPORTANT: Don't commit #{key_path}. Add this to your ignore file:"
+          log ignore, :on_green
+          log ""
+        end
+      end
+
+      def ignore_key_file_silently(key_path, ignore: key_ignore(key_path))
+        append_to_file ".gitignore", ignore if File.exist?(".gitignore")
+      end
+
+      private
+        def key_ignore(key_path)
+          [ "", "/#{key_path}", "" ].join("\n")
+        end
+    end
+  end
+end
diff --git a/railties/lib/rails/generators/rails/helper/templates/helper.rb b/railties/lib/rails/generators/rails/helper/templates/helper.rb.tt
index b4173151b4..b4173151b4 100644
--- a/railties/lib/rails/generators/rails/helper/templates/helper.rb
+++ b/railties/lib/rails/generators/rails/helper/templates/helper.rb.tt
diff --git a/railties/lib/rails/generators/rails/master_key/master_key_generator.rb b/railties/lib/rails/generators/rails/master_key/master_key_generator.rb
new file mode 100644
index 0000000000..21664ea86d
--- /dev/null
+++ b/railties/lib/rails/generators/rails/master_key/master_key_generator.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+require "pathname"
+require "rails/generators/base"
+require "rails/generators/rails/encryption_key_file/encryption_key_file_generator"
+require "active_support/encrypted_file"
+
+module Rails
+  module Generators
+    class MasterKeyGenerator < Base # :nodoc:
+      MASTER_KEY_PATH = Pathname.new("config/master.key")
+
+      def add_master_key_file
+        unless MASTER_KEY_PATH.exist?
+          key = ActiveSupport::EncryptedFile.generate_key
+
+          log "Adding #{MASTER_KEY_PATH} to store the master encryption key: #{key}"
+          log ""
+          log "Save this in a password manager your team can access."
+          log ""
+          log "If you lose the key, no one, including you, can access anything encrypted with it."
+
+          log ""
+          add_master_key_file_silently(key)
+          log ""
+        end
+      end
+
+      def add_master_key_file_silently(key = nil)
+        unless MASTER_KEY_PATH.exist?
+          key_file_generator.add_key_file_silently(MASTER_KEY_PATH, key)
+        end
+      end
+
+      def ignore_master_key_file
+        key_file_generator.ignore_key_file(MASTER_KEY_PATH, ignore: key_ignore)
+      end
+
+      def ignore_master_key_file_silently
+        key_file_generator.ignore_key_file_silently(MASTER_KEY_PATH, ignore: key_ignore)
+      end
+
+      private
+        def key_file_generator
+          EncryptionKeyFileGenerator.new([], options)
+        end
+
+        def key_ignore
+          [ "", "# Ignore master key for decrypting credentials and more.", "/#{MASTER_KEY_PATH}", "" ].join("\n")
+        end
+    end
+  end
+end
diff --git a/railties/lib/rails/generators/rails/model/model_generator.rb b/railties/lib/rails/generators/rails/model/model_generator.rb
index 1dca03e0bb..de4de2cae2 100644
--- a/railties/lib/rails/generators/rails/model/model_generator.rb
+++ b/railties/lib/rails/generators/rails/model/model_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../model_helpers"
+require "rails/generators/model_helpers"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/generators/rails/plugin/plugin_generator.rb b/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
index eb941adf95..a83c911806 100644
--- a/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
+++ b/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/hash/slice"
-require_relative "../app/app_generator"
+require "rails/generators/rails/app/app_generator"
 require "date"
 
 module Rails
@@ -88,17 +87,18 @@ task default: :test
     end
 
     PASSTHROUGH_OPTIONS = [
-      :skip_active_record, :skip_action_mailer, :skip_javascript, :skip_action_cable, :skip_sprockets, :database,
+      :skip_active_record, :skip_active_storage, :skip_action_mailer, :skip_javascript, :skip_action_cable, :skip_sprockets, :database,
       :javascript, :skip_yarn, :api, :quiet, :pretend, :skip
     ]
 
     def generate_test_dummy(force = false)
-      opts = (options || {}).slice(*PASSTHROUGH_OPTIONS)
+      opts = (options.dup || {}).keep_if { |k, _| PASSTHROUGH_OPTIONS.map(&:to_s).include?(k) }
       opts[:force] = force
       opts[:skip_bundle] = true
       opts[:skip_listen] = true
       opts[:skip_git] = true
       opts[:skip_turbolinks] = true
+      opts[:dummy_app] = true
 
       invoke Rails::Generators::AppGenerator,
         [ File.expand_path(dummy_path, destination_root) ], opts
@@ -167,7 +167,7 @@ task default: :test
 
       gemfile_in_app_path = File.join(rails_app_path, "Gemfile")
       if File.exist? gemfile_in_app_path
-        entry = "gem '#{name}', path: '#{relative_path}'"
+        entry = "\ngem '#{name}', path: '#{relative_path}'"
         append_file gemfile_in_app_path, entry
       end
     end
@@ -263,6 +263,10 @@ task default: :test
       public_task :apply_rails_template
 
       def run_after_bundle_callbacks
+        unless @after_bundle_callbacks.empty?
+          ActiveSupport::Deprecation.warn("`after_bundle` is deprecated and will be removed in the next version of Rails. ")
+        end
+
         @after_bundle_callbacks.each do |callback|
           callback.call
         end
diff --git a/railties/lib/rails/generators/rails/plugin/templates/%name%.gemspec b/railties/lib/rails/generators/rails/plugin/templates/%name%.gemspec.tt
index 9a8c4bf098..9a8c4bf098 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/%name%.gemspec
+++ b/railties/lib/rails/generators/rails/plugin/templates/%name%.gemspec.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/Gemfile b/railties/lib/rails/generators/rails/plugin/templates/Gemfile.tt
index 290259b4db..290259b4db 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/Gemfile
+++ b/railties/lib/rails/generators/rails/plugin/templates/Gemfile.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/MIT-LICENSE b/railties/lib/rails/generators/rails/plugin/templates/MIT-LICENSE.tt
index ff2fb3ba4e..ff2fb3ba4e 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/MIT-LICENSE
+++ b/railties/lib/rails/generators/rails/plugin/templates/MIT-LICENSE.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/README.md b/railties/lib/rails/generators/rails/plugin/templates/README.md.tt
index 1632409bea..1632409bea 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/README.md
+++ b/railties/lib/rails/generators/rails/plugin/templates/README.md.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/Rakefile b/railties/lib/rails/generators/rails/plugin/templates/Rakefile.tt
index f3efe21cf1..f3efe21cf1 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/Rakefile
+++ b/railties/lib/rails/generators/rails/plugin/templates/Rakefile.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/controllers/%namespaced_name%/application_controller.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/controllers/%namespaced_name%/application_controller.rb.tt
index abbacd9bec..b86ef0f2f8 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/controllers/%namespaced_name%/application_controller.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/controllers/%namespaced_name%/application_controller.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class ApplicationController < ActionController::#{api? ? "API" : "Base"}
     #{ api? ? '# ' : '' }protect_from_forgery with: :exception
   end
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/helpers/%namespaced_name%/application_helper.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/helpers/%namespaced_name%/application_helper.rb.tt
index 25d692732d..be078f36de 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/helpers/%namespaced_name%/application_helper.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/helpers/%namespaced_name%/application_helper.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   module ApplicationHelper
   end
 rb
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/jobs/%namespaced_name%/application_job.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/jobs/%namespaced_name%/application_job.rb.tt
index bad1ff2d16..846863bc13 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/jobs/%namespaced_name%/application_job.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/jobs/%namespaced_name%/application_job.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class ApplicationJob < ActiveJob::Base
   end
 rb
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/mailers/%namespaced_name%/application_mailer.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/mailers/%namespaced_name%/application_mailer.rb.tt
index 09aac13f42..246e274348 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/mailers/%namespaced_name%/application_mailer.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/mailers/%namespaced_name%/application_mailer.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class ApplicationMailer < ActionMailer::Base
     default from: 'from@example.com'
     layout 'mailer'
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/models/%namespaced_name%/application_record.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/models/%namespaced_name%/application_record.rb.tt
index 8aa3de78f1..21465278be 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/models/%namespaced_name%/application_record.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/models/%namespaced_name%/application_record.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class ApplicationRecord < ActiveRecord::Base
     self.abstract_class = true
   end
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/views/layouts/%namespaced_name%/application.html.erb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/views/layouts/%namespaced_name%/application.html.erb.tt
index 6bc480161d..6e54a1ce9d 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/views/layouts/%namespaced_name%/application.html.erb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/views/layouts/%namespaced_name%/application.html.erb.tt
@@ -2,9 +2,13 @@
 <html>
 <head>
   <title><%= humanized %></title>
+  <%%= csrf_meta_tags %>
+  <%%= csp_meta_tag %>
+
   <%%= stylesheet_link_tag    "<%= namespaced_name %>/application", media: "all" %>
+  <%- unless options[:skip_javascript] -%>
   <%%= javascript_include_tag "<%= namespaced_name %>/application" %>
-  <%%= csrf_meta_tags %>
+  <%- end -%>
 </head>
 <body>
 
diff --git a/railties/lib/rails/generators/rails/plugin/templates/bin/rails.tt b/railties/lib/rails/generators/rails/plugin/templates/bin/rails.tt
index b3264509fc..ee8e469da2 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/bin/rails.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/bin/rails.tt
@@ -19,10 +19,10 @@ require "rails"
 require "active_model/railtie"
 require "active_job/railtie"
 <%= comment_if :skip_active_record %>require "active_record/railtie"
+<%= comment_if :skip_active_storage %>require "active_storage/engine"
 require "action_controller/railtie"
 <%= comment_if :skip_action_mailer %>require "action_mailer/railtie"
 require "action_view/railtie"
-require "active_storage/engine"
 <%= comment_if :skip_action_cable %>require "action_cable/engine"
 <%= comment_if :skip_sprockets %>require "sprockets/railtie"
 <%= comment_if :skip_test %>require "rails/test_unit/railtie"
diff --git a/railties/lib/rails/generators/rails/plugin/templates/config/routes.rb b/railties/lib/rails/generators/rails/plugin/templates/config/routes.rb.tt
index 154452bfe5..154452bfe5 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/config/routes.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/config/routes.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/gitignore b/railties/lib/rails/generators/rails/plugin/templates/gitignore.tt
index e15863d860..7a68da5c4b 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/gitignore
+++ b/railties/lib/rails/generators/rails/plugin/templates/gitignore.tt
@@ -11,5 +11,8 @@ pkg/
 <%= dummy_path %>/node_modules/
 <%= dummy_path %>/yarn-error.log
 <% end -%>
+<% unless skip_active_storage? -%>
+<%= dummy_path %>/storage/
+<% end -%>
 <%= dummy_path %>/tmp/
 <% end -%>
diff --git a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%.rb b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%.rb.tt
index 3285055eb7..3285055eb7 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb.tt
index 8938770fc4..4ec1804940 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class Engine < ::Rails::Engine
   #{mountable? ? '  isolate_namespace ' + camelized_modules : ' '}
   #{api? ? "  config.generators.api_only = true" : ' '}
diff --git a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb.tt
index 7bdf4ee5fb..b853fabcc3 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class Railtie < ::Rails::Railtie
   end
 rb
diff --git a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/version.rb b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/version.rb.tt
index b08f4ef9ae..b08f4ef9ae 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/version.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/version.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/lib/tasks/%namespaced_name%_tasks.rake b/railties/lib/rails/generators/rails/plugin/templates/lib/tasks/%namespaced_name%_tasks.rake.tt
index 88a2c4120f..88a2c4120f 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/lib/tasks/%namespaced_name%_tasks.rake
+++ b/railties/lib/rails/generators/rails/plugin/templates/lib/tasks/%namespaced_name%_tasks.rake.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/application.rb b/railties/lib/rails/generators/rails/plugin/templates/rails/application.rb.tt
index 47b56ae3df..06ffe2f1ed 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/rails/application.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/application.rb.tt
@@ -8,10 +8,10 @@ require "rails"
 require "active_model/railtie"
 require "active_job/railtie"
 <%= comment_if :skip_active_record %>require "active_record/railtie"
+<%= comment_if :skip_active_storage %>require "active_storage/engine"
 require "action_controller/railtie"
 <%= comment_if :skip_action_mailer %>require "action_mailer/railtie"
 require "action_view/railtie"
-require "active_storage/engine"
 <%= comment_if :skip_action_cable %>require "action_cable/engine"
 <%= comment_if :skip_sprockets %>require "sprockets/railtie"
 <%= comment_if :skip_test %>require "rails/test_unit/railtie"
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/boot.rb b/railties/lib/rails/generators/rails/plugin/templates/rails/boot.rb.tt
index c9aef85d40..c9aef85d40 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/rails/boot.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/boot.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/dummy_manifest.js b/railties/lib/rails/generators/rails/plugin/templates/rails/dummy_manifest.js.tt
index 03937cf8ff..03937cf8ff 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/rails/dummy_manifest.js
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/dummy_manifest.js.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/engine_manifest.js b/railties/lib/rails/generators/rails/plugin/templates/rails/engine_manifest.js.tt
index 2f23844f5e..2f23844f5e 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/rails/engine_manifest.js
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/engine_manifest.js.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js b/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js.tt
index e54c6461cc..51049826bf 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js.tt
@@ -10,4 +10,8 @@
 // Read Sprockets README (https://github.com/rails/sprockets#sprockets-directives) for details
 // about supported directives.
 //
+//= require rails-ujs
+<% unless skip_active_storage? -%>
+//= require activestorage
+<% end -%>
 //= require_tree .
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/routes.rb b/railties/lib/rails/generators/rails/plugin/templates/rails/routes.rb.tt
index 694510edc0..694510edc0 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/rails/routes.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/routes.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/test/%namespaced_name%_test.rb b/railties/lib/rails/generators/rails/plugin/templates/test/%namespaced_name%_test.rb.tt
index 1ee05d7871..1ee05d7871 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/test/%namespaced_name%_test.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/test/%namespaced_name%_test.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/test/application_system_test_case.rb b/railties/lib/rails/generators/rails/plugin/templates/test/application_system_test_case.rb.tt
index d19212abd5..d19212abd5 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/test/application_system_test_case.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/test/application_system_test_case.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/test/integration/navigation_test.rb b/railties/lib/rails/generators/rails/plugin/templates/test/integration/navigation_test.rb.tt
index 29e59d8407..29e59d8407 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/test/integration/navigation_test.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/test/integration/navigation_test.rb.tt
diff --git a/railties/lib/rails/generators/rails/plugin/templates/test/test_helper.rb b/railties/lib/rails/generators/rails/plugin/templates/test/test_helper.rb.tt
index 2af7e06041..755d19ef5d 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/test/test_helper.rb
+++ b/railties/lib/rails/generators/rails/plugin/templates/test/test_helper.rb.tt
@@ -1,3 +1,6 @@
+# Configure Rails Environment
+ENV["RAILS_ENV"] = "test"
+
 require_relative "<%= File.join('..', options[:dummy_path], 'config/environment') -%>"
 <% unless options[:skip_active_record] -%>
 ActiveRecord::Migrator.migrations_paths = [File.expand_path("../<%= options[:dummy_path] -%>/db/migrate", __dir__)]
@@ -12,6 +15,7 @@ require "rails/test_help"
 Minitest.backtrace_filter = Minitest::BacktraceFilter.new
 
 <% unless engine? -%>
+require "rails/test_unit/reporter"
 Rails::TestUnitReporter.executable = 'bin/test'
 <% end -%>
 
diff --git a/railties/lib/rails/generators/rails/resource/USAGE b/railties/lib/rails/generators/rails/resource/USAGE
index e359cd574f..66d0ee546a 100644
--- a/railties/lib/rails/generators/rails/resource/USAGE
+++ b/railties/lib/rails/generators/rails/resource/USAGE
@@ -1,6 +1,6 @@
 Description:
     Stubs out a new resource including an empty model and controller suitable
-    for a restful, resource-oriented application. Pass the singular model name,
+    for a RESTful, resource-oriented application. Pass the singular model name,
     either CamelCased or under_scored, as the first argument, and an optional
     list of attribute pairs.
 
diff --git a/railties/lib/rails/generators/rails/resource/resource_generator.rb b/railties/lib/rails/generators/rails/resource/resource_generator.rb
index 74b1574863..3ba25ef0fe 100644
--- a/railties/lib/rails/generators/rails/resource/resource_generator.rb
+++ b/railties/lib/rails/generators/rails/resource/resource_generator.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../../resource_helpers"
-require_relative "../model/model_generator"
+require "rails/generators/resource_helpers"
+require "rails/generators/rails/model/model_generator"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/generators/rails/scaffold/scaffold_generator.rb b/railties/lib/rails/generators/rails/scaffold/scaffold_generator.rb
index c0fb873d36..8beb7416c0 100644
--- a/railties/lib/rails/generators/rails/scaffold/scaffold_generator.rb
+++ b/railties/lib/rails/generators/rails/scaffold/scaffold_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../resource/resource_generator"
+require "rails/generators/rails/resource/resource_generator"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/generators/rails/scaffold_controller/scaffold_controller_generator.rb b/railties/lib/rails/generators/rails/scaffold_controller/scaffold_controller_generator.rb
index 601a4b3a6e..7030561a33 100644
--- a/railties/lib/rails/generators/rails/scaffold_controller/scaffold_controller_generator.rb
+++ b/railties/lib/rails/generators/rails/scaffold_controller/scaffold_controller_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../resource_helpers"
+require "rails/generators/resource_helpers"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/generators/rails/scaffold_controller/templates/api_controller.rb b/railties/lib/rails/generators/rails/scaffold_controller/templates/api_controller.rb.tt
index 400afec6dc..400afec6dc 100644
--- a/railties/lib/rails/generators/rails/scaffold_controller/templates/api_controller.rb
+++ b/railties/lib/rails/generators/rails/scaffold_controller/templates/api_controller.rb.tt
diff --git a/railties/lib/rails/generators/rails/scaffold_controller/templates/controller.rb b/railties/lib/rails/generators/rails/scaffold_controller/templates/controller.rb.tt
index 42b9e34274..05f1c2b2d3 100644
--- a/railties/lib/rails/generators/rails/scaffold_controller/templates/controller.rb
+++ b/railties/lib/rails/generators/rails/scaffold_controller/templates/controller.rb.tt
@@ -29,7 +29,7 @@ class <%= controller_class_name %>Controller < ApplicationController
     @<%= singular_table_name %> = <%= orm_class.build(class_name, "#{singular_table_name}_params") %>
 
     if @<%= orm_instance.save %>
-      redirect_to @<%= singular_table_name %>, notice: <%= "'#{human_name} was successfully created.'" %>
+      redirect_to <%= redirect_resource_name %>, notice: <%= "'#{human_name} was successfully created.'" %>
     else
       render :new
     end
@@ -38,7 +38,7 @@ class <%= controller_class_name %>Controller < ApplicationController
   # PATCH/PUT <%= route_url %>/1
   def update
     if @<%= orm_instance.update("#{singular_table_name}_params") %>
-      redirect_to @<%= singular_table_name %>, notice: <%= "'#{human_name} was successfully updated.'" %>
+      redirect_to <%= redirect_resource_name %>, notice: <%= "'#{human_name} was successfully updated.'" %>
     else
       render :edit
     end
diff --git a/railties/lib/rails/generators/rails/task/templates/task.rb b/railties/lib/rails/generators/rails/task/templates/task.rb.tt
index 1e3ed5f158..1e3ed5f158 100644
--- a/railties/lib/rails/generators/rails/task/templates/task.rb
+++ b/railties/lib/rails/generators/rails/task/templates/task.rb.tt
diff --git a/railties/lib/rails/generators/resource_helpers.rb b/railties/lib/rails/generators/resource_helpers.rb
index 8bd5110940..5675faff70 100644
--- a/railties/lib/rails/generators/resource_helpers.rb
+++ b/railties/lib/rails/generators/resource_helpers.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "active_model"
-require_relative "model_helpers"
+require "rails/generators/active_model"
+require "rails/generators/model_helpers"
 
 module Rails
   module Generators
@@ -25,13 +25,8 @@ module Rails
         assign_controller_names!(controller_name.pluralize)
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-        attr_reader :controller_name, :controller_file_name
-
       private
+        attr_reader :controller_name, :controller_file_name
 
         def controller_class_path
           if options[:model_name]
diff --git a/railties/lib/rails/generators/test_case.rb b/railties/lib/rails/generators/test_case.rb
index 9c06eed95a..5c71bf0be9 100644
--- a/railties/lib/rails/generators/test_case.rb
+++ b/railties/lib/rails/generators/test_case.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-require_relative "../generators"
-require_relative "testing/behaviour"
-require_relative "testing/setup_and_teardown"
-require_relative "testing/assertions"
+require "rails/generators"
+require "rails/generators/testing/behaviour"
+require "rails/generators/testing/setup_and_teardown"
+require "rails/generators/testing/assertions"
 require "fileutils"
 
 module Rails
diff --git a/railties/lib/rails/generators/test_unit.rb b/railties/lib/rails/generators/test_unit.rb
index 1aa03ace99..1005ac557c 100644
--- a/railties/lib/rails/generators/test_unit.rb
+++ b/railties/lib/rails/generators/test_unit.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "named_base"
+require "rails/generators/named_base"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/controller/controller_generator.rb b/railties/lib/rails/generators/test_unit/controller/controller_generator.rb
index 3947b74205..1a9ac6bf2a 100644
--- a/railties/lib/rails/generators/test_unit/controller/controller_generator.rb
+++ b/railties/lib/rails/generators/test_unit/controller/controller_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/controller/templates/functional_test.rb b/railties/lib/rails/generators/test_unit/controller/templates/functional_test.rb.tt
index 4efa977a89..ff41fef9e9 100644
--- a/railties/lib/rails/generators/test_unit/controller/templates/functional_test.rb
+++ b/railties/lib/rails/generators/test_unit/controller/templates/functional_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require 'test_helper'
 
 <% module_namespacing do -%>
diff --git a/railties/lib/rails/generators/test_unit/generator/generator_generator.rb b/railties/lib/rails/generators/test_unit/generator/generator_generator.rb
index 9f79e9eee1..19be4f2f51 100644
--- a/railties/lib/rails/generators/test_unit/generator/generator_generator.rb
+++ b/railties/lib/rails/generators/test_unit/generator/generator_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/generator/templates/generator_test.rb b/railties/lib/rails/generators/test_unit/generator/templates/generator_test.rb.tt
index e6fb6c5ff4..a7f1fc4fba 100644
--- a/railties/lib/rails/generators/test_unit/generator/templates/generator_test.rb
+++ b/railties/lib/rails/generators/test_unit/generator/templates/generator_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require 'test_helper'
 require '<%= generator_path %>'
 
diff --git a/railties/lib/rails/generators/test_unit/helper/helper_generator.rb b/railties/lib/rails/generators/test_unit/helper/helper_generator.rb
index 1c60c3573f..77308dcf7d 100644
--- a/railties/lib/rails/generators/test_unit/helper/helper_generator.rb
+++ b/railties/lib/rails/generators/test_unit/helper/helper_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/integration/integration_generator.rb b/railties/lib/rails/generators/test_unit/integration/integration_generator.rb
index c859ba5e4e..ae307c5cd9 100644
--- a/railties/lib/rails/generators/test_unit/integration/integration_generator.rb
+++ b/railties/lib/rails/generators/test_unit/integration/integration_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/integration/templates/integration_test.rb b/railties/lib/rails/generators/test_unit/integration/templates/integration_test.rb.tt
index 65708b6c3b..118e0f1271 100644
--- a/railties/lib/rails/generators/test_unit/integration/templates/integration_test.rb
+++ b/railties/lib/rails/generators/test_unit/integration/templates/integration_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require 'test_helper'
 
 <% module_namespacing do -%>
diff --git a/railties/lib/rails/generators/test_unit/job/job_generator.rb b/railties/lib/rails/generators/test_unit/job/job_generator.rb
index cbbcd1cd4e..1dae3cb6a5 100644
--- a/railties/lib/rails/generators/test_unit/job/job_generator.rb
+++ b/railties/lib/rails/generators/test_unit/job/job_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
@@ -8,8 +8,13 @@ module TestUnit # :nodoc:
       check_class_collision suffix: "JobTest"
 
       def create_test_file
-        template "unit_test.rb.erb", File.join("test/jobs", class_path, "#{file_name}_job_test.rb")
+        template "unit_test.rb", File.join("test/jobs", class_path, "#{file_name}_job_test.rb")
       end
+
+      private
+        def file_name
+          @_file_name ||= super.sub(/_job\z/i, "")
+        end
     end
   end
 end
diff --git a/railties/lib/rails/generators/test_unit/job/templates/unit_test.rb.erb b/railties/lib/rails/generators/test_unit/job/templates/unit_test.rb.tt
index f5351d0ec6..f5351d0ec6 100644
--- a/railties/lib/rails/generators/test_unit/job/templates/unit_test.rb.erb
+++ b/railties/lib/rails/generators/test_unit/job/templates/unit_test.rb.tt
diff --git a/railties/lib/rails/generators/test_unit/mailer/mailer_generator.rb b/railties/lib/rails/generators/test_unit/mailer/mailer_generator.rb
index 45f82158e9..ab8331f31c 100644
--- a/railties/lib/rails/generators/test_unit/mailer/mailer_generator.rb
+++ b/railties/lib/rails/generators/test_unit/mailer/mailer_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
@@ -21,7 +21,7 @@ module TestUnit # :nodoc:
 
       private
         def file_name
-          @_file_name ||= super.gsub(/_mailer/i, "")
+          @_file_name ||= super.sub(/_mailer\z/i, "")
         end
     end
   end
diff --git a/railties/lib/rails/generators/test_unit/mailer/templates/functional_test.rb b/railties/lib/rails/generators/test_unit/mailer/templates/functional_test.rb.tt
index 1ec3a2f360..a2f2d30de5 100644
--- a/railties/lib/rails/generators/test_unit/mailer/templates/functional_test.rb
+++ b/railties/lib/rails/generators/test_unit/mailer/templates/functional_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require 'test_helper'
 
 <% module_namespacing do -%>
diff --git a/railties/lib/rails/generators/test_unit/mailer/templates/preview.rb b/railties/lib/rails/generators/test_unit/mailer/templates/preview.rb.tt
index 9876210b6c..b063cbc47b 100644
--- a/railties/lib/rails/generators/test_unit/mailer/templates/preview.rb
+++ b/railties/lib/rails/generators/test_unit/mailer/templates/preview.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 <% module_namespacing do -%>
 # Preview all emails at http://localhost:3000/rails/mailers/<%= file_path %>_mailer
 class <%= class_name %>MailerPreview < ActionMailer::Preview
diff --git a/railties/lib/rails/generators/test_unit/model/model_generator.rb b/railties/lib/rails/generators/test_unit/model/model_generator.rb
index 2b1cc50c20..02d7502592 100644
--- a/railties/lib/rails/generators/test_unit/model/model_generator.rb
+++ b/railties/lib/rails/generators/test_unit/model/model_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/model/templates/fixtures.yml b/railties/lib/rails/generators/test_unit/model/templates/fixtures.yml.tt
index 0681780c97..0681780c97 100644
--- a/railties/lib/rails/generators/test_unit/model/templates/fixtures.yml
+++ b/railties/lib/rails/generators/test_unit/model/templates/fixtures.yml.tt
diff --git a/railties/lib/rails/generators/test_unit/model/templates/unit_test.rb b/railties/lib/rails/generators/test_unit/model/templates/unit_test.rb.tt
index 5f1ffeb33b..c9bc7d5b90 100644
--- a/railties/lib/rails/generators/test_unit/model/templates/unit_test.rb
+++ b/railties/lib/rails/generators/test_unit/model/templates/unit_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require 'test_helper'
 
 <% module_namespacing do -%>
diff --git a/railties/lib/rails/generators/test_unit/plugin/plugin_generator.rb b/railties/lib/rails/generators/test_unit/plugin/plugin_generator.rb
index 10fe27b2c3..0657bc2389 100644
--- a/railties/lib/rails/generators/test_unit/plugin/plugin_generator.rb
+++ b/railties/lib/rails/generators/test_unit/plugin/plugin_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/plugin/templates/test_helper.rb b/railties/lib/rails/generators/test_unit/plugin/templates/test_helper.rb
index 2147b09568..30a861f09d 100644
--- a/railties/lib/rails/generators/test_unit/plugin/templates/test_helper.rb
+++ b/railties/lib/rails/generators/test_unit/plugin/templates/test_helper.rb
@@ -1,4 +1,2 @@
-# frozen_string_literal: true
-
 require 'active_support/testing/autorun'
 require 'active_support'
diff --git a/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb b/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb
index 23d5c63614..e2e8b18eab 100644
--- a/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb
+++ b/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
-require_relative "../../resource_helpers"
+require "rails/generators/test_unit"
+require "rails/generators/resource_helpers"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
@@ -23,7 +23,7 @@ module TestUnit # :nodoc:
         template template_file,
                  File.join("test/controllers", controller_class_path, "#{controller_file_name}_controller_test.rb")
 
-        unless options.api? || options[:system_tests].nil?
+        if !options.api? && options[:system_tests]
           template "system_test.rb", File.join("test/system", class_path, "#{file_name.pluralize}_test.rb")
         end
       end
diff --git a/railties/lib/rails/generators/test_unit/scaffold/templates/api_functional_test.rb b/railties/lib/rails/generators/test_unit/scaffold/templates/api_functional_test.rb.tt
index 2ef93b8aea..f21861d8e6 100644
--- a/railties/lib/rails/generators/test_unit/scaffold/templates/api_functional_test.rb
+++ b/railties/lib/rails/generators/test_unit/scaffold/templates/api_functional_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require 'test_helper'
 
 <% module_namespacing do -%>
diff --git a/railties/lib/rails/generators/test_unit/scaffold/templates/functional_test.rb b/railties/lib/rails/generators/test_unit/scaffold/templates/functional_test.rb.tt
index bcf9392bd1..195d60be20 100644
--- a/railties/lib/rails/generators/test_unit/scaffold/templates/functional_test.rb
+++ b/railties/lib/rails/generators/test_unit/scaffold/templates/functional_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require 'test_helper'
 
 <% module_namespacing do -%>
diff --git a/railties/lib/rails/generators/test_unit/scaffold/templates/system_test.rb b/railties/lib/rails/generators/test_unit/scaffold/templates/system_test.rb.tt
index ba8bdc192e..f83f5a5c62 100644
--- a/railties/lib/rails/generators/test_unit/scaffold/templates/system_test.rb
+++ b/railties/lib/rails/generators/test_unit/scaffold/templates/system_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require "application_system_test_case"
 
 <% module_namespacing do -%>
diff --git a/railties/lib/rails/generators/test_unit/system/system_generator.rb b/railties/lib/rails/generators/test_unit/system/system_generator.rb
index d3acbfd738..08504d4124 100644
--- a/railties/lib/rails/generators/test_unit/system/system_generator.rb
+++ b/railties/lib/rails/generators/test_unit/system/system_generator.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../../test_unit"
+require "rails/generators/test_unit"
 
 module TestUnit # :nodoc:
   module Generators # :nodoc:
diff --git a/railties/lib/rails/generators/test_unit/system/templates/application_system_test_case.rb b/railties/lib/rails/generators/test_unit/system/templates/application_system_test_case.rb.tt
index c05709aff8..d19212abd5 100644
--- a/railties/lib/rails/generators/test_unit/system/templates/application_system_test_case.rb
+++ b/railties/lib/rails/generators/test_unit/system/templates/application_system_test_case.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require "test_helper"
 
 class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
diff --git a/railties/lib/rails/generators/test_unit/system/templates/system_test.rb b/railties/lib/rails/generators/test_unit/system/templates/system_test.rb.tt
index cfac061cd1..b5ce2ba5c8 100644
--- a/railties/lib/rails/generators/test_unit/system/templates/system_test.rb
+++ b/railties/lib/rails/generators/test_unit/system/templates/system_test.rb.tt
@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 require "application_system_test_case"
 
 class <%= class_name.pluralize %>Test < ApplicationSystemTestCase
diff --git a/railties/lib/rails/generators/testing/behaviour.rb b/railties/lib/rails/generators/testing/behaviour.rb
index 97a09c1166..6ab88bd59f 100644
--- a/railties/lib/rails/generators/testing/behaviour.rb
+++ b/railties/lib/rails/generators/testing/behaviour.rb
@@ -6,7 +6,7 @@ require "active_support/core_ext/hash/reverse_merge"
 require "active_support/core_ext/kernel/reporting"
 require "active_support/testing/stream"
 require "active_support/concern"
-require_relative "../../generators"
+require "rails/generators"
 
 module Rails
   module Generators
diff --git a/railties/lib/rails/info.rb b/railties/lib/rails/info.rb
index d8f361f524..d5c9973c6b 100644
--- a/railties/lib/rails/info.rb
+++ b/railties/lib/rails/info.rb
@@ -99,7 +99,7 @@ module Rails
     end
 
     property "Database schema version" do
-      ActiveRecord::Migrator.current_version rescue nil
+      ActiveRecord::Base.connection.migration_context.current_version rescue nil
     end
   end
 end
diff --git a/railties/lib/rails/info_controller.rb b/railties/lib/rails/info_controller.rb
index 6535b5b6ad..b4f4a5922a 100644
--- a/railties/lib/rails/info_controller.rb
+++ b/railties/lib/rails/info_controller.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "application_controller"
+require "rails/application_controller"
 require "action_dispatch/routing/inspector"
 
 class Rails::InfoController < Rails::ApplicationController # :nodoc:
diff --git a/railties/lib/rails/mailers_controller.rb b/railties/lib/rails/mailers_controller.rb
index 6bd3161fdd..0b0e802358 100644
--- a/railties/lib/rails/mailers_controller.rb
+++ b/railties/lib/rails/mailers_controller.rb
@@ -1,14 +1,14 @@
 # frozen_string_literal: true
 
-require_relative "application_controller"
+require "rails/application_controller"
 
 class Rails::MailersController < Rails::ApplicationController # :nodoc:
   prepend_view_path ActionDispatch::DebugExceptions::RESCUES_TEMPLATE_PATH
 
   before_action :require_local!, unless: :show_previews?
-  before_action :find_preview, only: :preview
+  before_action :find_preview, :set_locale, only: :preview
 
-  helper_method :part_query
+  helper_method :part_query, :locale_query
 
   def index
     @previews = ActionMailer::Preview.all
@@ -84,4 +84,12 @@ class Rails::MailersController < Rails::ApplicationController # :nodoc:
     def part_query(mime_type)
       request.query_parameters.merge(part: mime_type).to_query
     end
+
+    def locale_query(locale)
+      request.query_parameters.merge(locale: locale).to_query
+    end
+
+    def set_locale
+      I18n.locale = params[:locale] || I18n.default_locale
+    end
 end
diff --git a/railties/lib/rails/plugin/test.rb b/railties/lib/rails/plugin/test.rb
index 2426521e35..18b6fd1757 100644
--- a/railties/lib/rails/plugin/test.rb
+++ b/railties/lib/rails/plugin/test.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require_relative "../test_unit/runner"
-require_relative "../test_unit/reporter"
+require "rails/test_unit/runner"
+require "rails/test_unit/reporter"
 
 Rails::TestUnitReporter.executable = "bin/test"
 
diff --git a/railties/lib/rails/rack/logger.rb b/railties/lib/rails/rack/logger.rb
index ec5212ee76..4ea7e40319 100644
--- a/railties/lib/rails/rack/logger.rb
+++ b/railties/lib/rails/rack/logger.rb
@@ -35,9 +35,9 @@ module Rails
           instrumenter = ActiveSupport::Notifications.instrumenter
           instrumenter.start "request.action_dispatch", request: request
           logger.info { started_request_message(request) }
-          resp = @app.call(env)
-          resp[2] = ::Rack::BodyProxy.new(resp[2]) { finish(request) }
-          resp
+          status, headers, body = @app.call(env)
+          body = ::Rack::BodyProxy.new(body) { finish(request) }
+          [status, headers, body]
         rescue Exception
           finish(request)
           raise
diff --git a/railties/lib/rails/railtie.rb b/railties/lib/rails/railtie.rb
index 42c4a82b1b..88dd932370 100644
--- a/railties/lib/rails/railtie.rb
+++ b/railties/lib/rails/railtie.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "initializable"
+require "rails/initializable"
 require "active_support/inflector"
 require "active_support/core_ext/module/introspection"
 require "active_support/core_ext/module/delegation"
diff --git a/railties/lib/rails/railtie/configuration.rb b/railties/lib/rails/railtie/configuration.rb
index d9997759f2..70274b948c 100644
--- a/railties/lib/rails/railtie/configuration.rb
+++ b/railties/lib/rails/railtie/configuration.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../configuration"
+require "rails/configuration"
 
 module Rails
   class Railtie
@@ -55,7 +55,7 @@ module Rails
         ActiveSupport.on_load(:before_configuration, yield: true, &block)
       end
 
-      # Third configurable block to run. Does not run if +config.cache_classes+
+      # Third configurable block to run. Does not run if +config.eager_load+
       # set to false.
       def before_eager_load(&block)
         ActiveSupport.on_load(:before_eager_load, yield: true, &block)
diff --git a/railties/lib/rails/ruby_version_check.rb b/railties/lib/rails/ruby_version_check.rb
index 76b6b80d28..b2d44d9b8e 100644
--- a/railties/lib/rails/ruby_version_check.rb
+++ b/railties/lib/rails/ruby_version_check.rb
@@ -1,15 +1,15 @@
 # frozen_string_literal: true
 
-if RUBY_VERSION < "2.2.2" && RUBY_ENGINE == "ruby"
+if Gem::Version.new(RUBY_VERSION) < Gem::Version.new("2.4.1") && RUBY_ENGINE == "ruby"
   desc = defined?(RUBY_DESCRIPTION) ? RUBY_DESCRIPTION : "ruby #{RUBY_VERSION} (#{RUBY_RELEASE_DATE})"
   abort <<-end_message
 
-    Rails 5 requires Ruby 2.2.2 or newer.
+    Rails 6 requires Ruby 2.4.1 or newer.
 
     You're running
       #{desc}
 
-    Please upgrade to Ruby 2.2.2 or newer to continue.
+    Please upgrade to Ruby 2.4.1 or newer to continue.
 
   end_message
 end
diff --git a/railties/lib/rails/secrets.rb b/railties/lib/rails/secrets.rb
index 33821dd759..747cf31d7a 100644
--- a/railties/lib/rails/secrets.rb
+++ b/railties/lib/rails/secrets.rb
@@ -2,7 +2,6 @@
 
 require "yaml"
 require "active_support/message_encryptor"
-require "active_support/core_ext/string/strip"
 
 module Rails
   # Greatly inspired by Ara T. Howard's magnificent sekrets gem. 😘
@@ -32,23 +31,10 @@ module Rails
         end
       end
 
-      def generate_key
-        SecureRandom.hex(OpenSSL::Cipher.new(@cipher).key_len)
-      end
-
       def key
         ENV["RAILS_MASTER_KEY"] || read_key_file || handle_missing_key
       end
 
-      def template
-        <<-end_of_template.strip_heredoc
-          # See `secrets.yml` for tips on generating suitable keys.
-          # production:
-          #  external_api_key: 1466aac22e6a869134be3d09b9e89232fc2c2289
-
-        end_of_template
-      end
-
       def encrypt(data)
         encryptor.encrypt_and_sign(data)
       end
@@ -70,10 +56,6 @@ module Rails
         writing(read, &block)
       end
 
-      def read_template_for_editing(&block)
-        writing(template, &block)
-      end
-
       private
         def handle_missing_key
           raise MissingKeyError
diff --git a/railties/lib/rails/source_annotation_extractor.rb b/railties/lib/rails/source_annotation_extractor.rb
index 1db6c98537..7257aaeaae 100644
--- a/railties/lib/rails/source_annotation_extractor.rb
+++ b/railties/lib/rails/source_annotation_extractor.rb
@@ -1,141 +1,150 @@
 # frozen_string_literal: true
 
-# Implements the logic behind the rake tasks for annotations like
-#
-#   rails notes
-#   rails notes:optimize
-#
-# and friends. See <tt>rails -T notes</tt> and <tt>railties/lib/rails/tasks/annotations.rake</tt>.
-#
-# Annotation objects are triplets <tt>:line</tt>, <tt>:tag</tt>, <tt>:text</tt> that
-# represent the line where the annotation lives, its tag, and its text. Note
-# the filename is not stored.
-#
-# Annotations are looked for in comments and modulus whitespace they have to
-# start with the tag optionally followed by a colon. Everything up to the end
-# of the line (or closing ERB comment tag) is considered to be their text.
-class SourceAnnotationExtractor
-  Annotation = Struct.new(:line, :tag, :text) do
-    def self.directories
-      @@directories ||= %w(app config db lib test) + (ENV["SOURCE_ANNOTATION_DIRECTORIES"] || "").split(",")
-    end
+require "active_support/deprecation"
 
-    # Registers additional directories to be included
-    #   SourceAnnotationExtractor::Annotation.register_directories("spec", "another")
-    def self.register_directories(*dirs)
-      directories.push(*dirs)
-    end
+# Remove this deprecated class in the next minor version
+#:nodoc:
+SourceAnnotationExtractor = ActiveSupport::Deprecation::DeprecatedConstantProxy.
+  new("SourceAnnotationExtractor", "Rails::SourceAnnotationExtractor")
 
-    def self.extensions
-      @@extensions ||= {}
-    end
+module Rails
+  # Implements the logic behind the rake tasks for annotations like
+  #
+  #   rails notes
+  #   rails notes:optimize
+  #
+  # and friends. See <tt>rails -T notes</tt> and <tt>railties/lib/rails/tasks/annotations.rake</tt>.
+  #
+  # Annotation objects are triplets <tt>:line</tt>, <tt>:tag</tt>, <tt>:text</tt> that
+  # represent the line where the annotation lives, its tag, and its text. Note
+  # the filename is not stored.
+  #
+  # Annotations are looked for in comments and modulus whitespace they have to
+  # start with the tag optionally followed by a colon. Everything up to the end
+  # of the line (or closing ERB comment tag) is considered to be their text.
+  class SourceAnnotationExtractor
+    class Annotation < Struct.new(:line, :tag, :text)
+      def self.directories
+        @@directories ||= %w(app config db lib test) + (ENV["SOURCE_ANNOTATION_DIRECTORIES"] || "").split(",")
+      end
 
-    # Registers new Annotations File Extensions
-    #   SourceAnnotationExtractor::Annotation.register_extensions("css", "scss", "sass", "less", "js") { |tag| /\/\/\s*(#{tag}):?\s*(.*)$/ }
-    def self.register_extensions(*exts, &block)
-      extensions[/\.(#{exts.join("|")})$/] = block
-    end
+      # Registers additional directories to be included
+      #   Rails::SourceAnnotationExtractor::Annotation.register_directories("spec", "another")
+      def self.register_directories(*dirs)
+        directories.push(*dirs)
+      end
 
-    register_extensions("builder", "rb", "rake", "yml", "yaml", "ruby") { |tag| /#\s*(#{tag}):?\s*(.*)$/ }
-    register_extensions("css", "js") { |tag| /\/\/\s*(#{tag}):?\s*(.*)$/ }
-    register_extensions("erb") { |tag| /<%\s*#\s*(#{tag}):?\s*(.*?)\s*%>/ }
+      def self.extensions
+        @@extensions ||= {}
+      end
 
-    # Returns a representation of the annotation that looks like this:
+      # Registers new Annotations File Extensions
+      #   Rails::SourceAnnotationExtractor::Annotation.register_extensions("css", "scss", "sass", "less", "js") { |tag| /\/\/\s*(#{tag}):?\s*(.*)$/ }
+      def self.register_extensions(*exts, &block)
+        extensions[/\.(#{exts.join("|")})$/] = block
+      end
+
+      register_extensions("builder", "rb", "rake", "yml", "yaml", "ruby") { |tag| /#\s*(#{tag}):?\s*(.*)$/ }
+      register_extensions("css", "js") { |tag| /\/\/\s*(#{tag}):?\s*(.*)$/ }
+      register_extensions("erb") { |tag| /<%\s*#\s*(#{tag}):?\s*(.*?)\s*%>/ }
+
+      # Returns a representation of the annotation that looks like this:
+      #
+      #   [126] [TODO] This algorithm is simple and clearly correct, make it faster.
+      #
+      # If +options+ has a flag <tt>:tag</tt> the tag is shown as in the example above.
+      # Otherwise the string contains just line and text.
+      def to_s(options = {})
+        s = "[#{line.to_s.rjust(options[:indent])}] ".dup
+        s << "[#{tag}] " if options[:tag]
+        s << text
+      end
+    end
+
+    # Prints all annotations with tag +tag+ under the root directories +app+,
+    # +config+, +db+, +lib+, and +test+ (recursively).
     #
-    #   [126] [TODO] This algorithm is simple and clearly correct, make it faster.
+    # Additional directories may be added using a comma-delimited list set using
+    # <tt>ENV['SOURCE_ANNOTATION_DIRECTORIES']</tt>.
     #
-    # If +options+ has a flag <tt>:tag</tt> the tag is shown as in the example above.
-    # Otherwise the string contains just line and text.
-    def to_s(options = {})
-      s = "[#{line.to_s.rjust(options[:indent])}] ".dup
-      s << "[#{tag}] " if options[:tag]
-      s << text
+    # Directories may also be explicitly set using the <tt>:dirs</tt> key in +options+.
+    #
+    #   Rails::SourceAnnotationExtractor.enumerate 'TODO|FIXME', dirs: %w(app lib), tag: true
+    #
+    # If +options+ has a <tt>:tag</tt> flag, it will be passed to each annotation's +to_s+.
+    #
+    # See <tt>#find_in</tt> for a list of file extensions that will be taken into account.
+    #
+    # This class method is the single entry point for the rake tasks.
+    def self.enumerate(tag, options = {})
+      extractor = new(tag)
+      dirs = options.delete(:dirs) || Annotation.directories
+      extractor.display(extractor.find(dirs), options)
     end
-  end
 
-  # Prints all annotations with tag +tag+ under the root directories +app+,
-  # +config+, +db+, +lib+, and +test+ (recursively).
-  #
-  # Additional directories may be added using a comma-delimited list set using
-  # <tt>ENV['SOURCE_ANNOTATION_DIRECTORIES']</tt>.
-  #
-  # Directories may also be explicitly set using the <tt>:dirs</tt> key in +options+.
-  #
-  #   SourceAnnotationExtractor.enumerate 'TODO|FIXME', dirs: %w(app lib), tag: true
-  #
-  # If +options+ has a <tt>:tag</tt> flag, it will be passed to each annotation's +to_s+.
-  #
-  # See <tt>#find_in</tt> for a list of file extensions that will be taken into account.
-  #
-  # This class method is the single entry point for the rake tasks.
-  def self.enumerate(tag, options = {})
-    extractor = new(tag)
-    dirs = options.delete(:dirs) || Annotation.directories
-    extractor.display(extractor.find(dirs), options)
-  end
-
-  attr_reader :tag
-
-  def initialize(tag)
-    @tag = tag
-  end
+    attr_reader :tag
 
-  # Returns a hash that maps filenames under +dirs+ (recursively) to arrays
-  # with their annotations.
-  def find(dirs)
-    dirs.inject({}) { |h, dir| h.update(find_in(dir)) }
-  end
+    def initialize(tag)
+      @tag = tag
+    end
 
-  # Returns a hash that maps filenames under +dir+ (recursively) to arrays
-  # with their annotations. Only files with annotations are included. Files
-  # with extension +.builder+, +.rb+, +.rake+, +.yml+, +.yaml+, +.ruby+,
-  # +.css+, +.js+ and +.erb+ are taken into account.
-  def find_in(dir)
-    results = {}
-
-    Dir.glob("#{dir}/*") do |item|
-      next if File.basename(item)[0] == ?.
-
-      if File.directory?(item)
-        results.update(find_in(item))
-      else
-        extension = Annotation.extensions.detect do |regexp, _block|
-          regexp.match(item)
-        end
+    # Returns a hash that maps filenames under +dirs+ (recursively) to arrays
+    # with their annotations.
+    def find(dirs)
+      dirs.inject({}) { |h, dir| h.update(find_in(dir)) }
+    end
 
-        if extension
-          pattern = extension.last.call(tag)
-          results.update(extract_annotations_from(item, pattern)) if pattern
+    # Returns a hash that maps filenames under +dir+ (recursively) to arrays
+    # with their annotations. Files with extensions registered in
+    # <tt>Rails::SourceAnnotationExtractor::Annotation.extensions</tt> are
+    # taken into account. Only files with annotations are included.
+    def find_in(dir)
+      results = {}
+
+      Dir.glob("#{dir}/*") do |item|
+        next if File.basename(item)[0] == ?.
+
+        if File.directory?(item)
+          results.update(find_in(item))
+        else
+          extension = Annotation.extensions.detect do |regexp, _block|
+            regexp.match(item)
+          end
+
+          if extension
+            pattern = extension.last.call(tag)
+            results.update(extract_annotations_from(item, pattern)) if pattern
+          end
         end
       end
-    end
 
-    results
-  end
+      results
+    end
 
-  # If +file+ is the filename of a file that contains annotations this method returns
-  # a hash with a single entry that maps +file+ to an array of its annotations.
-  # Otherwise it returns an empty hash.
-  def extract_annotations_from(file, pattern)
-    lineno = 0
-    result = File.readlines(file, encoding: Encoding::BINARY).inject([]) do |list, line|
-      lineno += 1
-      next list unless line =~ pattern
-      list << Annotation.new(lineno, $1, $2)
+    # If +file+ is the filename of a file that contains annotations this method returns
+    # a hash with a single entry that maps +file+ to an array of its annotations.
+    # Otherwise it returns an empty hash.
+    def extract_annotations_from(file, pattern)
+      lineno = 0
+      result = File.readlines(file, encoding: Encoding::BINARY).inject([]) do |list, line|
+        lineno += 1
+        next list unless line =~ pattern
+        list << Annotation.new(lineno, $1, $2)
+      end
+      result.empty? ? {} : { file => result }
     end
-    result.empty? ? {} : { file => result }
-  end
 
-  # Prints the mapping from filenames to annotations in +results+ ordered by filename.
-  # The +options+ hash is passed to each annotation's +to_s+.
-  def display(results, options = {})
-    options[:indent] = results.flat_map { |f, a| a.map(&:line) }.max.to_s.size
-    results.keys.sort.each do |file|
-      puts "#{file}:"
-      results[file].each do |note|
-        puts "  * #{note.to_s(options)}"
+    # Prints the mapping from filenames to annotations in +results+ ordered by filename.
+    # The +options+ hash is passed to each annotation's +to_s+.
+    def display(results, options = {})
+      options[:indent] = results.flat_map { |f, a| a.map(&:line) }.max.to_s.size
+      results.keys.sort.each do |file|
+        puts "#{file}:"
+        results[file].each do |note|
+          puts "  * #{note.to_s(options)}"
+        end
+        puts
       end
-      puts
     end
   end
 end
diff --git a/railties/lib/rails/tasks.rb b/railties/lib/rails/tasks.rb
index 2f644a20c9..56f2eba312 100644
--- a/railties/lib/rails/tasks.rb
+++ b/railties/lib/rails/tasks.rb
@@ -12,7 +12,6 @@ require "rake"
   middleware
   misc
   restart
-  routes
   tmp
   yarn
 ).tap { |arr|
diff --git a/railties/lib/rails/tasks/annotations.rake b/railties/lib/rails/tasks/annotations.rake
index 931f81ac7e..60bcdc5e1b 100644
--- a/railties/lib/rails/tasks/annotations.rake
+++ b/railties/lib/rails/tasks/annotations.rake
@@ -1,22 +1,22 @@
 # frozen_string_literal: true
 
-require_relative "../source_annotation_extractor"
+require "rails/source_annotation_extractor"
 
 desc "Enumerate all annotations (use notes:optimize, :fixme, :todo for focus)"
 task :notes do
-  SourceAnnotationExtractor.enumerate "OPTIMIZE|FIXME|TODO", tag: true
+  Rails::SourceAnnotationExtractor.enumerate "OPTIMIZE|FIXME|TODO", tag: true
 end
 
 namespace :notes do
   ["OPTIMIZE", "FIXME", "TODO"].each do |annotation|
     # desc "Enumerate all #{annotation} annotations"
     task annotation.downcase.intern do
-      SourceAnnotationExtractor.enumerate annotation
+      Rails::SourceAnnotationExtractor.enumerate annotation
     end
   end
 
   desc "Enumerate a custom annotation, specify with ANNOTATION=CUSTOM"
   task :custom do
-    SourceAnnotationExtractor.enumerate ENV["ANNOTATION"]
+    Rails::SourceAnnotationExtractor.enumerate ENV["ANNOTATION"]
   end
 end
diff --git a/railties/lib/rails/tasks/dev.rake b/railties/lib/rails/tasks/dev.rake
index 90fd3ccd8b..5aea6f7dc5 100644
--- a/railties/lib/rails/tasks/dev.rake
+++ b/railties/lib/rails/tasks/dev.rake
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "../dev_caching"
+require "rails/dev_caching"
 
 namespace :dev do
   desc "Toggle development mode caching on/off"
diff --git a/railties/lib/rails/tasks/engine.rake b/railties/lib/rails/tasks/engine.rake
index 3ce49a1641..8d77904210 100644
--- a/railties/lib/rails/tasks/engine.rake
+++ b/railties/lib/rails/tasks/engine.rake
@@ -8,7 +8,7 @@ task "load_app" do
     task update: [ "update:bin" ]
 
     namespace :update do
-      require_relative "../engine/updater"
+      require "rails/engine/updater"
       # desc "Adds new executables to the engine bin/ directory"
       task :bin do
         Rails::Engine::Updater.run(:create_bin_files)
@@ -53,7 +53,7 @@ namespace :db do
   desc "Rolls the schema back to the previous version (specify steps w/ STEP=n)."
   app_task "rollback"
 
-  desc "Create a db/schema.rb file that can be portably used against any DB supported by Active Record"
+  desc "Create a db/schema.rb file that can be portably used against any database supported by Active Record"
   app_task "schema:dump"
 
   desc "Load a schema.rb file into the database"
@@ -62,7 +62,7 @@ namespace :db do
   desc "Load the seed data from db/seeds.rb"
   app_task "seed"
 
-  desc "Create the database, load the schema, and initialize with the seed data (use db:reset to also drop the db first)"
+  desc "Create the database, load the schema, and initialize with the seed data (use db:reset to also drop the database first)"
   app_task "setup"
 
   desc "Dump the database structure to an SQL file"
@@ -70,6 +70,9 @@ namespace :db do
 
   desc "Retrieves the current schema version number"
   app_task "version"
+
+  # desc 'Load the test schema'
+  app_task "test:prepare"
 end
 
 def find_engine_path(path)
diff --git a/railties/lib/rails/tasks/framework.rake b/railties/lib/rails/tasks/framework.rake
index 8931aabcda..1a3711c446 100644
--- a/railties/lib/rails/tasks/framework.rake
+++ b/railties/lib/rails/tasks/framework.rake
@@ -9,8 +9,8 @@ namespace :app do
     template = ENV["LOCATION"]
     raise "No LOCATION value given. Please set LOCATION either as path to a file or a URL" if template.blank?
     template = File.expand_path(template) if template !~ %r{\A[A-Za-z][A-Za-z0-9+\-\.]*://}
-    require_relative "../generators"
-    require_relative "../generators/rails/app/app_generator"
+    require "rails/generators"
+    require "rails/generators/rails/app/app_generator"
     generator = Rails::Generators::AppGenerator.new [Rails.root], {}, { destination_root: Rails.root }
     generator.apply template, verbose: false
   end
@@ -38,9 +38,9 @@ namespace :app do
   end
 
   namespace :update do
-    require_relative "../app_updater"
+    require "rails/app_updater"
 
-    # desc "Update config/boot.rb from your current rails install"
+    # desc "Update config files from your current rails install"
     task :configs do
       Rails::AppUpdater.invoke_from_app_generator :create_boot_file
       Rails::AppUpdater.invoke_from_app_generator :update_config_files
diff --git a/railties/lib/rails/tasks/routes.rake b/railties/lib/rails/tasks/routes.rake
deleted file mode 100644
index 403286d280..0000000000
--- a/railties/lib/rails/tasks/routes.rake
+++ /dev/null
@@ -1,31 +0,0 @@
-# frozen_string_literal: true
-
-require "optparse"
-
-desc "Print out all defined routes in match order, with names. Target specific controller with -c option, or grep routes using -g option"
-task routes: :environment do
-  all_routes = Rails.application.routes.routes
-  require "action_dispatch/routing/inspector"
-  inspector = ActionDispatch::Routing::RoutesInspector.new(all_routes)
-
-  routes_filter = nil
-
-  OptionParser.new do |opts|
-    opts.banner = "Usage: rails routes [options]"
-
-    Rake.application.standard_rake_options.each { |args| opts.on(*args) }
-
-    opts.on("-c CONTROLLER") do |controller|
-      routes_filter = { controller: controller }
-    end
-
-    opts.on("-g PATTERN") do |pattern|
-      routes_filter = pattern
-    end
-
-  end.parse!(ARGV.reject { |x| x == "routes" })
-
-  puts inspector.format(ActionDispatch::Routing::ConsoleFormatter.new, routes_filter)
-
-  exit 0 # ensure extra arguments aren't interpreted as Rake tasks
-end
diff --git a/railties/lib/rails/tasks/statistics.rake b/railties/lib/rails/tasks/statistics.rake
index 0449a13586..594db91eec 100644
--- a/railties/lib/rails/tasks/statistics.rake
+++ b/railties/lib/rails/tasks/statistics.rake
@@ -26,6 +26,6 @@ end.select { |name, dir| File.directory?(dir) }
 
 desc "Report code statistics (KLOCs, etc) from the application or engine"
 task :stats do
-  require_relative "../code_statistics"
+  require "rails/code_statistics"
   CodeStatistics.new(*STATS_DIRECTORIES).to_s
 end
diff --git a/railties/lib/rails/tasks/yarn.rake b/railties/lib/rails/tasks/yarn.rake
index 48da7ffc51..cf45a392e8 100644
--- a/railties/lib/rails/tasks/yarn.rake
+++ b/railties/lib/rails/tasks/yarn.rake
@@ -3,7 +3,13 @@
 namespace :yarn do
   desc "Install all JavaScript dependencies as specified via Yarn"
   task :install do
-    system("./bin/yarn install --no-progress --production")
+    # Install only production deps when for not usual envs.
+    valid_node_envs = %w[test development production]
+    node_env = ENV.fetch("NODE_ENV") do
+      rails_env = ENV["RAILS_ENV"]
+      valid_node_envs.include?(rails_env) ? rails_env : "production"
+    end
+    system({ "NODE_ENV" => node_env }, "./bin/yarn install --no-progress --frozen-lockfile")
   end
 end
 
diff --git a/railties/lib/rails/templates/rails/mailers/email.html.erb b/railties/lib/rails/templates/rails/mailers/email.html.erb
index 89c1129f90..e46364ba8a 100644
--- a/railties/lib/rails/templates/rails/mailers/email.html.erb
+++ b/railties/lib/rails/templates/rails/mailers/email.html.erb
@@ -95,11 +95,25 @@
       </dd>
     <% end %>
 
+    <dt>Format:</dt>
     <% if @email.multipart? %>
       <dd>
-        <select onchange="formatChanged(this);">
-          <option <%= request.format == Mime[:html] ? 'selected' : '' %> value="?<%= part_query('text/html') %>">View as HTML email</option>
-          <option <%= request.format == Mime[:text] ? 'selected' : '' %> value="?<%= part_query('text/plain') %>">View as plain-text email</option>
+        <select id="part" onchange="refreshBody(false);">
+          <option <%= request.format == Mime[:html] ? 'selected' : '' %> value="<%= part_query('text/html') %>">View as HTML email</option>
+          <option <%= request.format == Mime[:text] ? 'selected' : '' %> value="<%= part_query('text/plain') %>">View as plain-text email</option>
+        </select>
+      </dd>
+    <% else %>
+      <dd id="mime_type" data-mime-type="<%= part_query(@email.mime_type) %>"><%= @email.mime_type == 'text/html' ? 'HTML email' : 'plain-text email' %></dd>
+    <% end %>
+
+    <% if I18n.available_locales.count > 1 %>
+      <dt>Locale:</dt>
+      <dd>
+        <select id="locale" onchange="refreshBody(true);">
+          <% I18n.available_locales.each do |locale| %>
+            <option <%= I18n.locale == locale ? 'selected' : '' %> value="<%= locale_query(locale) %>"><%= locale %></option>
+          <% end %>
         </select>
       </dd>
     <% end %>
@@ -116,15 +130,30 @@
 <% end %>
 
 <script>
-  function formatChanged(form) {
-    var part_name = form.options[form.selectedIndex].value
-    var iframe =document.getElementsByName('messageBody')[0];
-    iframe.contentWindow.location.replace(part_name);
-
-    if (history.replaceState) {
-      var url    = location.pathname.replace(/\.(txt|html)$/, '');
-      var format = /html/.test(part_name) ? '.html' : '.txt';
-      window.history.replaceState({}, '', url + format);
+  function refreshBody(reload) {
+    var part_select = document.querySelector('select#part');
+    var locale_select = document.querySelector('select#locale');
+    var iframe = document.getElementsByName('messageBody')[0];
+    var part_param = part_select ?
+      part_select.options[part_select.selectedIndex].value :
+      document.querySelector('#mime_type').dataset.mimeType;
+    var locale_param = locale_select ? locale_select.options[locale_select.selectedIndex].value : null;
+    var fresh_location;
+    if (locale_param) {
+      fresh_location = '?' + part_param + '&' + locale_param;
+    } else {
+      fresh_location = '?' + part_param;
+    }
+    iframe.contentWindow.location = fresh_location;
+
+    var url = location.pathname.replace(/\.(txt|html)$/, '');
+    var format = /html/.test(part_param) ? '.html' : '.txt';
+    var state_to_replace = locale_param ? (url + format + '?' + locale_param) : (url + format);
+
+    if (reload) {
+      location.href = state_to_replace;
+    } else if (history.replaceState) {
+      window.history.replaceState({}, '', state_to_replace);
     }
   }
 </script>
diff --git a/railties/lib/rails/test_help.rb b/railties/lib/rails/test_help.rb
index f755474488..4bd7d74b04 100644
--- a/railties/lib/rails/test_help.rb
+++ b/railties/lib/rails/test_help.rb
@@ -8,7 +8,7 @@ require "active_support/test_case"
 require "action_controller"
 require "action_controller/test_case"
 require "action_dispatch/testing/integration"
-require_relative "generators/test_case"
+require "rails/generators/test_case"
 
 require "active_support/testing/autorun"
 
@@ -22,6 +22,7 @@ if defined?(ActiveRecord::Base)
 
   module ActiveSupport
     class TestCase
+      include ActiveRecord::TestDatabases
       include ActiveRecord::TestFixtures
       self.fixture_path = "#{Rails.root}/test/fixtures/"
       self.file_fixture_path = fixture_path + "files"
@@ -29,10 +30,6 @@ if defined?(ActiveRecord::Base)
   end
 
   ActionDispatch::IntegrationTest.fixture_path = ActiveSupport::TestCase.fixture_path
-
-  def create_fixtures(*fixture_set_names, &block)
-    FixtureSet.create_fixtures(ActiveSupport::TestCase.fixture_path, fixture_set_names, {}, &block)
-  end
 end
 
 # :enddoc:
diff --git a/railties/lib/rails/test_unit/railtie.rb b/railties/lib/rails/test_unit/railtie.rb
index 05f9a177d0..42b6daa3d1 100644
--- a/railties/lib/rails/test_unit/railtie.rb
+++ b/railties/lib/rails/test_unit/railtie.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "line_filtering"
+require "rails/test_unit/line_filtering"
 
 if defined?(Rake.application) && Rake.application.top_level_tasks.grep(/^(default$|test(:|$))/).any?
   ENV["RAILS_ENV"] ||= Rake.application.options.show_tasks ? "development" : "test"
diff --git a/railties/lib/rails/test_unit/reporter.rb b/railties/lib/rails/test_unit/reporter.rb
index 7d3164f1eb..28b93cee5a 100644
--- a/railties/lib/rails/test_unit/reporter.rb
+++ b/railties/lib/rails/test_unit/reporter.rb
@@ -64,11 +64,17 @@ module Rails
       end
 
       def format_line(result)
-        "%s#%s = %.2f s = %s" % [result.class, result.name, result.time, result.result_code]
+        klass = result.respond_to?(:klass) ? result.klass : result.class
+        "%s#%s = %.2f s = %s" % [klass, result.name, result.time, result.result_code]
       end
 
       def format_rerun_snippet(result)
-        location, line = result.method(result.name).source_location
+        location, line = if result.respond_to?(:source_location)
+          result.source_location
+        else
+          result.method(result.name).source_location
+        end
+
         "#{executable} #{relative_path_for(location)}:#{line}"
       end
 
diff --git a/railties/lib/rails/test_unit/runner.rb b/railties/lib/rails/test_unit/runner.rb
index 5c2f6451e2..de5744c662 100644
--- a/railties/lib/rails/test_unit/runner.rb
+++ b/railties/lib/rails/test_unit/runner.rb
@@ -13,7 +13,7 @@ module Rails
       class << self
         def attach_before_load_options(opts)
           opts.on("--warnings", "-w", "Run with Ruby warnings enabled") {}
-          opts.on("--environment", "-e", "Run tests in the ENV environment") {}
+          opts.on("-e", "--environment ENV", "Run tests in the ENV environment") {}
         end
 
         def parse_options(argv)
diff --git a/railties/lib/rails/test_unit/testing.rake b/railties/lib/rails/test_unit/testing.rake
index 18d699f806..32ac27a135 100644
--- a/railties/lib/rails/test_unit/testing.rake
+++ b/railties/lib/rails/test_unit/testing.rake
@@ -2,7 +2,7 @@
 
 gem "minitest"
 require "minitest"
-require_relative "runner"
+require "rails/test_unit/runner"
 
 task default: :test
 
diff --git a/railties/lib/rails/welcome_controller.rb b/railties/lib/rails/welcome_controller.rb
index 0cb43e0f31..5b84b57679 100644
--- a/railties/lib/rails/welcome_controller.rb
+++ b/railties/lib/rails/welcome_controller.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative "application_controller"
+require "rails/application_controller"
 
 class Rails::WelcomeController < Rails::ApplicationController # :nodoc:
   layout false
diff --git a/railties/railties.gemspec b/railties/railties.gemspec
index 4c665cd546..6fdb4648c2 100644
--- a/railties/railties.gemspec
+++ b/railties/railties.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Tools for creating, working with, and running Rails applications."
   s.description = "Rails internals: application bootup, plugins, generators, and rake tasks."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
@@ -34,7 +34,7 @@ Gem::Specification.new do |s|
   s.add_dependency "actionpack",    version
 
   s.add_dependency "rake", ">= 0.8.7"
-  s.add_dependency "thor", ">= 0.18.1", "< 2.0"
+  s.add_dependency "thor", ">= 0.19.0", "< 2.0"
   s.add_dependency "method_source"
 
   s.add_development_dependency "actionview", version
diff --git a/railties/test/abstract_unit.rb b/railties/test/abstract_unit.rb
index a63b7a8377..b42f37d6b9 100644
--- a/railties/test/abstract_unit.rb
+++ b/railties/test/abstract_unit.rb
@@ -15,7 +15,6 @@ require "rails/all"
 module TestApp
   class Application < Rails::Application
     config.root = __dir__
-    secrets.secret_key_base = "b3c631c314c0bbca50c1b2843150fe33"
   end
 end
 
diff --git a/railties/test/app_loader_test.rb b/railties/test/app_loader_test.rb
index bb556f1968..c7a6bdee1b 100644
--- a/railties/test/app_loader_test.rb
+++ b/railties/test/app_loader_test.rb
@@ -40,13 +40,13 @@ class AppLoaderTest < ActiveSupport::TestCase
     test "is not in a Rails application if #{exe} is not found in the current or parent directories" do
       def loader.find_executables; end
 
-      assert !loader.exec_app
+      assert_not loader.exec_app
     end
 
     test "is not in a Rails application if #{exe} exists but is a folder" do
       FileUtils.mkdir_p(exe)
 
-      assert !loader.exec_app
+      assert_not loader.exec_app
     end
 
     ["APP_PATH", "ENGINE_PATH"].each do |keyword|
@@ -61,7 +61,7 @@ class AppLoaderTest < ActiveSupport::TestCase
       test "is not in a Rails application if #{exe} exists but doesn't contain #{keyword}" do
         write exe
 
-        assert !loader.exec_app
+        assert_not loader.exec_app
       end
 
       test "is in a Rails application if parent directory has #{exe} containing #{keyword} and chdirs to the root directory" do
diff --git a/railties/test/application/asset_debugging_test.rb b/railties/test/application/asset_debugging_test.rb
index 128040262f..3e0f31860b 100644
--- a/railties/test/application/asset_debugging_test.rb
+++ b/railties/test/application/asset_debugging_test.rb
@@ -9,10 +9,7 @@ module ApplicationTests
     include Rack::Test::Methods
 
     def setup
-      # FIXME: shush Sass warning spam, not relevant to testing Railties
-      Kernel.silence_warnings do
-        build_app(initializers: true)
-      end
+      build_app(initializers: true)
 
       app_file "app/assets/javascripts/application.js", "//= require_tree ."
       app_file "app/assets/javascripts/xmlhr.js", "function f1() { alert(); }"
@@ -36,16 +33,10 @@ module ApplicationTests
       teardown_app
     end
 
-    # FIXME: shush Sass warning spam, not relevant to testing Railties
-    def get(*)
-      Kernel.silence_warnings { super }
-    end
-
     test "assets are concatenated when debug is off and compile is off either if debug_assets param is provided" do
       # config.assets.debug and config.assets.compile are false for production environment
       ENV["RAILS_ENV"] = "production"
-      output = Dir.chdir(app_path) { `bin/rails assets:precompile --trace 2>&1` }
-      assert $?.success?, output
+      rails "assets:precompile", "--trace"
 
       # Load app env
       app "production"
@@ -86,7 +77,8 @@ module ApplicationTests
         stylesheet_link_tag:    %r{<link rel="stylesheet" media="screen" href="/stylesheets/#{contents}.css" />},
         javascript_include_tag: %r{<script src="/javascripts/#{contents}.js">},
         audio_tag:              %r{<audio src="/audios/#{contents}"></audio>},
-        video_tag:              %r{<video src="/videos/#{contents}"></video>}
+        video_tag:              %r{<video src="/videos/#{contents}"></video>},
+        image_submit_tag:       %r{<input type="image" src="/images/#{contents}" />}
       }
 
       cases.each do |(view_method, tag_match)|
diff --git a/railties/test/application/assets_test.rb b/railties/test/application/assets_test.rb
index 99fe6749d9..4ca6d02b85 100644
--- a/railties/test/application/assets_test.rb
+++ b/railties/test/application/assets_test.rb
@@ -47,7 +47,7 @@ module ApplicationTests
     end
 
     def assert_no_file_exists(filename)
-      assert !File.exist?(filename), "#{filename} does exist"
+      assert_not File.exist?(filename), "#{filename} does exist"
     end
 
     test "assets routes have higher priority" do
@@ -62,10 +62,7 @@ module ApplicationTests
 
       add_to_env_config "development", "config.assets.digest = false"
 
-      # FIXME: shush Sass warning spam, not relevant to testing Railties
-      Kernel.silence_warnings do
-        require "#{app_path}/config/environment"
-      end
+      require "#{app_path}/config/environment"
 
       get "/assets/demo.js"
       assert_equal 'a = "/assets/rails.png";', last_response.body.strip
@@ -79,7 +76,7 @@ module ApplicationTests
       # Load app env
       app "production"
 
-      assert !defined?(Uglifier)
+      assert_not defined?(Uglifier)
       get "/assets/demo.js"
       assert_match "alert()", last_response.body
       assert defined?(Uglifier)
@@ -273,10 +270,10 @@ module ApplicationTests
       app "production"
 
       # Checking if Uglifier is defined we can know if Sprockets was reached or not
-      assert !defined?(Uglifier)
+      assert_not defined?(Uglifier)
       get "/assets/#{asset_path}"
       assert_match "alert()", last_response.body
-      assert !defined?(Uglifier)
+      assert_not defined?(Uglifier)
     end
 
     test "precompile properly refers files referenced with asset_path" do
diff --git a/railties/test/application/bin_setup_test.rb b/railties/test/application/bin_setup_test.rb
index a09c371033..54934dbe24 100644
--- a/railties/test/application/bin_setup_test.rb
+++ b/railties/test/application/bin_setup_test.rb
@@ -22,7 +22,7 @@ module ApplicationTests
           end
         RUBY
 
-        list_tables = lambda { `bin/rails runner 'p ActiveRecord::Base.connection.tables'`.strip }
+        list_tables = lambda { rails("runner", "p ActiveRecord::Base.connection.tables").strip }
         File.write("log/test.log", "zomg!")
 
         assert_equal "[]", list_tables.call
diff --git a/railties/test/application/configuration/custom_test.rb b/railties/test/application/configuration/custom_test.rb
index 05b17b4a7a..608bc2fbe3 100644
--- a/railties/test/application/configuration/custom_test.rb
+++ b/railties/test/application/configuration/custom_test.rb
@@ -33,7 +33,7 @@ module ApplicationTests
         assert_nil x.i_do_not_exist.zomg
 
         # test that custom configuration responds to all messages
-        assert_equal true, x.respond_to?(:i_do_not_exist)
+        assert_respond_to x, :i_do_not_exist
         assert_kind_of Method, x.method(:i_do_not_exist)
         assert_kind_of ActiveSupport::OrderedOptions, x.i_do_not_exist
       end
diff --git a/railties/test/application/configuration_test.rb b/railties/test/application/configuration_test.rb
index ebe019f6a9..c2699006f6 100644
--- a/railties/test/application/configuration_test.rb
+++ b/railties/test/application/configuration_test.rb
@@ -40,10 +40,7 @@ module ApplicationTests
       @app ||= begin
         ENV["RAILS_ENV"] = env
 
-        # FIXME: shush Sass warning spam, not relevant to testing Railties
-        Kernel.silence_warnings do
-          require "#{app_path}/config/environment"
-        end
+        require "#{app_path}/config/environment"
 
         Rails.application
       ensure
@@ -97,7 +94,7 @@ module ApplicationTests
 
       with_rails_env "development" do
         app "development"
-        assert Rails.application.config.log_tags.blank?
+        assert_predicate Rails.application.config.log_tags, :blank?
       end
     end
 
@@ -317,6 +314,7 @@ module ApplicationTests
     end
 
     test "the application can be eager loaded even when there are no frameworks" do
+      FileUtils.rm_rf("#{app_path}/app/jobs/application_job.rb")
       FileUtils.rm_rf("#{app_path}/app/models/application_record.rb")
       FileUtils.rm_rf("#{app_path}/app/mailers/application_mailer.rb")
       FileUtils.rm_rf("#{app_path}/config/environments")
@@ -363,7 +361,7 @@ module ApplicationTests
         end
       RUBY
 
-      assert !$prepared
+      assert_not $prepared
 
       app "development"
 
@@ -478,45 +476,61 @@ module ApplicationTests
 
     test "application message verifier can be used when the key_generator is ActiveSupport::LegacyKeyGenerator" do
       app_file "config/initializers/secret_token.rb", <<-RUBY
+        Rails.application.credentials.secret_key_base = nil
         Rails.application.config.secret_token = "b3c631c314c0bbca50c1b2843150fe33"
       RUBY
-      app_file "config/secrets.yml", <<-YAML
-        development:
-          secret_key_base:
-      YAML
 
-      app "development"
+      app "production"
 
-      assert_equal app.env_config["action_dispatch.key_generator"], Rails.application.key_generator
-      assert_equal app.env_config["action_dispatch.key_generator"].class, ActiveSupport::LegacyKeyGenerator
+      assert_kind_of ActiveSupport::LegacyKeyGenerator, Rails.application.key_generator
       message = app.message_verifier(:sensitive_value).generate("some_value")
       assert_equal "some_value", Rails.application.message_verifier(:sensitive_value).verify(message)
     end
 
-    test "warns when secrets.secret_key_base is blank and config.secret_token is set" do
+    test "config.secret_token is deprecated" do
       app_file "config/initializers/secret_token.rb", <<-RUBY
         Rails.application.config.secret_token = "b3c631c314c0bbca50c1b2843150fe33"
       RUBY
-      app_file "config/secrets.yml", <<-YAML
-        development:
-          secret_key_base:
-      YAML
 
-      app "development"
+      app "production"
 
-      assert_deprecated(/You didn't set `secret_key_base`./) do
-        app.env_config
+      assert_deprecated(/secret_token/) do
+        app.secrets
       end
     end
 
-    test "raise when secrets.secret_key_base is not a type of string" do
+    test "secrets.secret_token is deprecated" do
       app_file "config/secrets.yml", <<-YAML
-        development:
-          secret_key_base: 123
+        production:
+          secret_token: "b3c631c314c0bbca50c1b2843150fe33"
       YAML
 
+      app "production"
+
+      assert_deprecated(/secret_token/) do
+        app.secrets
+      end
+    end
+
+
+    test "raises when secret_key_base is blank" do
+      app_file "config/initializers/secret_token.rb", <<-RUBY
+        Rails.application.credentials.secret_key_base = nil
+      RUBY
+
+      error = assert_raise(ArgumentError) do
+        app "production"
+      end
+      assert_match(/Missing `secret_key_base`./, error.message)
+    end
+
+    test "raise when secret_key_base is not a type of string" do
+      add_to_config <<-RUBY
+        Rails.application.credentials.secret_key_base = 123
+      RUBY
+
       assert_raise(ArgumentError) do
-        app "development"
+        app "production"
       end
     end
 
@@ -536,7 +550,7 @@ module ApplicationTests
 
     test "application verifier can build different verifiers" do
       make_basic_app do |application|
-        application.secrets.secret_key_base = "b3c631c314c0bbca50c1b2843150fe33"
+        application.credentials.secret_key_base = "b3c631c314c0bbca50c1b2843150fe33"
         application.config.session_store :disabled
       end
 
@@ -562,6 +576,7 @@ module ApplicationTests
 
       app "development"
       assert_equal "3b7cd727ee24e8444053437c36cc66c3", app.secrets.secret_key_base
+      assert_equal "3b7cd727ee24e8444053437c36cc66c3", app.secret_key_base
     end
 
     test "secret_key_base is copied from config to secrets when not set" do
@@ -654,37 +669,15 @@ module ApplicationTests
 
     test "uses ActiveSupport::LegacyKeyGenerator as app.key_generator when secrets.secret_key_base is blank" do
       app_file "config/initializers/secret_token.rb", <<-RUBY
+        Rails.application.credentials.secret_key_base = nil
         Rails.application.config.secret_token = "b3c631c314c0bbca50c1b2843150fe33"
       RUBY
-      app_file "config/secrets.yml", <<-YAML
-        development:
-          secret_key_base:
-      YAML
 
-      app "development"
+      app "production"
 
       assert_equal "b3c631c314c0bbca50c1b2843150fe33", app.config.secret_token
-      assert_nil app.secrets.secret_key_base
-      assert_equal app.key_generator.class, ActiveSupport::LegacyKeyGenerator
-    end
-
-    test "uses ActiveSupport::LegacyKeyGenerator with config.secret_token as app.key_generator when secrets.secret_key_base is blank" do
-      app_file "config/initializers/secret_token.rb", <<-RUBY
-        Rails.application.config.secret_token = ""
-      RUBY
-      app_file "config/secrets.yml", <<-YAML
-        development:
-          secret_key_base:
-      YAML
-
-      app "development"
-
-      assert_equal "", app.config.secret_token
-      assert_nil app.secrets.secret_key_base
-      e = assert_raise ArgumentError do
-        app.key_generator
-      end
-      assert_match(/\AA secret is required/, e.message)
+      assert_nil app.credentials.secret_key_base
+      assert_kind_of ActiveSupport::LegacyKeyGenerator, app.key_generator
     end
 
     test "that nested keys are symbolized the same as parents for hashes more than one level deep" do
@@ -701,6 +694,28 @@ module ApplicationTests
       assert_equal "697361616320736c6f616e2028656c6f7265737429", app.secrets.smtp_settings[:password]
     end
 
+    test "require_master_key aborts app boot when missing key" do
+      skip "can't run without fork" unless Process.respond_to?(:fork)
+
+      remove_file "config/master.key"
+      add_to_config "config.require_master_key = true"
+
+      error = capture(:stderr) do
+        Process.wait(Process.fork { app "development" })
+      end
+
+      assert_equal 1, $?.exitstatus
+      assert_match(/Missing.*RAILS_MASTER_KEY/, error)
+    end
+
+    test "credentials does not raise error when require_master_key is false and master key does not exist" do
+      remove_file "config/master.key"
+      add_to_config "config.require_master_key = false"
+      app "development"
+
+      assert_not app.credentials.secret_key_base
+    end
+
     test "protect from forgery is the default in a new app" do
       make_basic_app
 
@@ -751,6 +766,68 @@ module ApplicationTests
       assert_match(/label/, last_response.body)
     end
 
+    test "form_with can be configured with form_with_generates_ids" do
+      app_file "config/initializers/form_builder.rb", <<-RUBY
+      Rails.configuration.action_view.form_with_generates_ids = false
+      RUBY
+
+      app_file "app/models/post.rb", <<-RUBY
+      class Post
+        include ActiveModel::Model
+        attr_accessor :name
+      end
+      RUBY
+
+      app_file "app/controllers/posts_controller.rb", <<-RUBY
+      class PostsController < ApplicationController
+        def index
+          render inline: "<%= begin; form_with(model: Post.new) {|f| f.text_field(:name)}; rescue => e; e.to_s; end %>"
+        end
+      end
+      RUBY
+
+      add_to_config <<-RUBY
+        routes.prepend do
+          resources :posts
+        end
+      RUBY
+
+      app "development"
+
+      get "/posts"
+
+      assert_no_match(/id=('|")post_name('|")/, last_response.body)
+    end
+
+    test "form_with outputs ids by default" do
+      app_file "app/models/post.rb", <<-RUBY
+      class Post
+        include ActiveModel::Model
+        attr_accessor :name
+      end
+      RUBY
+
+      app_file "app/controllers/posts_controller.rb", <<-RUBY
+      class PostsController < ApplicationController
+        def index
+          render inline: "<%= begin; form_with(model: Post.new) {|f| f.text_field(:name)}; rescue => e; e.to_s; end %>"
+        end
+      end
+      RUBY
+
+      add_to_config <<-RUBY
+        routes.prepend do
+          resources :posts
+        end
+      RUBY
+
+      app "development"
+
+      get "/posts"
+
+      assert_match(/id=('|")post_name('|")/, last_response.body)
+    end
+
     test "form_with can be configured with form_with_generates_remote_forms" do
       app_file "config/initializers/form_builder.rb", <<-RUBY
       Rails.configuration.action_view.form_with_generates_remote_forms = false
@@ -1249,7 +1326,7 @@ module ApplicationTests
       assert_equal 200, last_response.status
     end
 
-    test "config.action_controller.action_on_unpermitted_parameters is :log by default on development" do
+    test "config.action_controller.action_on_unpermitted_parameters is :log by default in development" do
       app "development"
 
       force_lazy_load_hooks { ActionController::Base }
@@ -1258,7 +1335,7 @@ module ApplicationTests
       assert_equal :log, ActionController::Parameters.action_on_unpermitted_parameters
     end
 
-    test "config.action_controller.action_on_unpermitted_parameters is :log by default on test" do
+    test "config.action_controller.action_on_unpermitted_parameters is :log by default in test" do
       app "test"
 
       force_lazy_load_hooks { ActionController::Base }
@@ -1267,7 +1344,7 @@ module ApplicationTests
       assert_equal :log, ActionController::Parameters.action_on_unpermitted_parameters
     end
 
-    test "config.action_controller.action_on_unpermitted_parameters is false by default on production" do
+    test "config.action_controller.action_on_unpermitted_parameters is false by default in production" do
       app "production"
 
       force_lazy_load_hooks { ActionController::Base }
@@ -1340,14 +1417,14 @@ module ApplicationTests
       assert_equal "XML", last_response.body
     end
 
-    test "Rails.application#env_config exists and include some existing parameters" do
+    test "Rails.application#env_config exists and includes some existing parameters" do
       make_basic_app
 
-      assert_equal      app.env_config["action_dispatch.parameter_filter"],  app.config.filter_parameters
-      assert_equal      app.env_config["action_dispatch.show_exceptions"],   app.config.action_dispatch.show_exceptions
-      assert_equal      app.env_config["action_dispatch.logger"],            Rails.logger
-      assert_equal      app.env_config["action_dispatch.backtrace_cleaner"], Rails.backtrace_cleaner
-      assert_equal      app.env_config["action_dispatch.key_generator"],     Rails.application.key_generator
+      assert_equal app.env_config["action_dispatch.parameter_filter"],  app.config.filter_parameters
+      assert_equal app.env_config["action_dispatch.show_exceptions"],   app.config.action_dispatch.show_exceptions
+      assert_equal app.env_config["action_dispatch.logger"],            Rails.logger
+      assert_equal app.env_config["action_dispatch.backtrace_cleaner"], Rails.backtrace_cleaner
+      assert_equal app.env_config["action_dispatch.key_generator"],     Rails.application.key_generator
     end
 
     test "config.colorize_logging default is true" do
@@ -1402,7 +1479,7 @@ module ApplicationTests
     test "respond_to? accepts include_private" do
       make_basic_app
 
-      assert_not Rails.configuration.respond_to?(:method_missing)
+      assert_not_respond_to Rails.configuration, :method_missing
       assert Rails.configuration.respond_to?(:method_missing, true)
     end
 
@@ -1414,12 +1491,18 @@ module ApplicationTests
       assert_not ActiveRecord::Base.dump_schema_after_migration
     end
 
-    test "config.active_record.dump_schema_after_migration is true by default on development" do
+    test "config.active_record.dump_schema_after_migration is true by default in development" do
       app "development"
 
       assert ActiveRecord::Base.dump_schema_after_migration
     end
 
+    test "config.active_record.verbose_query_logs is false by default in development" do
+      app "development"
+
+      assert_not ActiveRecord::Base.verbose_query_logs
+    end
+
     test "config.annotations wrapping SourceAnnotationExtractor::Annotation class" do
       make_basic_app do |application|
         application.config.annotations.register_extensions("coffee") do |tag|
@@ -1427,7 +1510,7 @@ module ApplicationTests
         end
       end
 
-      assert_not_nil SourceAnnotationExtractor::Annotation.extensions[/\.(coffee)$/]
+      assert_not_nil Rails::SourceAnnotationExtractor::Annotation.extensions[/\.(coffee)$/]
     end
 
     test "rake_tasks block works at instance level" do
@@ -1657,9 +1740,7 @@ module ApplicationTests
 
     test "default SQLite3Adapter.represent_boolean_as_integer for 5.1 is false" do
       remove_from_config '.*config\.load_defaults.*\n'
-      add_to_top_of_config <<-RUBY
-        config.load_defaults 5.1
-      RUBY
+
       app_file "app/models/post.rb", <<-RUBY
         class Post < ActiveRecord::Base
         end
@@ -1686,7 +1767,7 @@ module ApplicationTests
     test "represent_boolean_as_integer should be able to set via config.active_record.sqlite3.represent_boolean_as_integer" do
       remove_from_config '.*config\.load_defaults.*\n'
 
-      app_file "config/initializers/new_framework_defaults_5_2.rb", <<-RUBY
+      app_file "config/initializers/new_framework_defaults_6_0.rb", <<-RUBY
         Rails.application.config.active_record.sqlite3.represent_boolean_as_integer = true
       RUBY
 
@@ -1751,7 +1832,7 @@ module ApplicationTests
 
     test "api_only is false by default" do
       app "development"
-      refute Rails.application.config.api_only
+      assert_not Rails.application.config.api_only
     end
 
     test "api_only generator config is set when api_only is set" do
@@ -1808,6 +1889,113 @@ module ApplicationTests
       assert_equal "https://example.org/", last_response.location
     end
 
+    test "ActiveSupport::MessageEncryptor.use_authenticated_message_encryption is true by default for new apps" do
+      app "development"
+
+      assert_equal true, ActiveSupport::MessageEncryptor.use_authenticated_message_encryption
+    end
+
+    test "ActiveSupport::MessageEncryptor.use_authenticated_message_encryption is false by default for upgraded apps" do
+      remove_from_config '.*config\.load_defaults.*\n'
+
+      app "development"
+
+      assert_equal false, ActiveSupport::MessageEncryptor.use_authenticated_message_encryption
+    end
+
+    test "ActiveSupport::MessageEncryptor.use_authenticated_message_encryption can be configured via config.active_support.use_authenticated_message_encryption" do
+      remove_from_config '.*config\.load_defaults.*\n'
+
+      app_file "config/initializers/new_framework_defaults_6_0.rb", <<-RUBY
+        Rails.application.config.active_support.use_authenticated_message_encryption = true
+      RUBY
+
+      app "development"
+
+      assert_equal true, ActiveSupport::MessageEncryptor.use_authenticated_message_encryption
+    end
+
+    test "ActiveSupport::Digest.hash_digest_class is Digest::SHA1 by default for new apps" do
+      app "development"
+
+      assert_equal Digest::SHA1, ActiveSupport::Digest.hash_digest_class
+    end
+
+    test "ActiveSupport::Digest.hash_digest_class is Digest::MD5 by default for upgraded apps" do
+      remove_from_config '.*config\.load_defaults.*\n'
+
+      app "development"
+
+      assert_equal Digest::MD5, ActiveSupport::Digest.hash_digest_class
+    end
+
+    test "ActiveSupport::Digest.hash_digest_class can be configured via config.active_support.use_sha1_digests" do
+      remove_from_config '.*config\.load_defaults.*\n'
+
+      app_file "config/initializers/new_framework_defaults_6_0.rb", <<-RUBY
+        Rails.application.config.active_support.use_sha1_digests = true
+      RUBY
+
+      app "development"
+
+      assert_equal Digest::SHA1, ActiveSupport::Digest.hash_digest_class
+    end
+
+    test "custom serializers should be able to set via config.active_job.custom_serializers in an initializer" do
+      class ::DummySerializer < ActiveJob::Serializers::ObjectSerializer; end
+
+      app_file "config/initializers/custom_serializers.rb", <<-RUBY
+      Rails.application.config.active_job.custom_serializers << DummySerializer
+      RUBY
+
+      app "development"
+
+      assert_includes ActiveJob::Serializers.serializers, DummySerializer
+    end
+
+    test "ActionView::Helpers::FormTagHelper.default_enforce_utf8 is false by default" do
+      app "development"
+      assert_equal false, ActionView::Helpers::FormTagHelper.default_enforce_utf8
+    end
+
+    test "ActionView::Helpers::FormTagHelper.default_enforce_utf8 is true in an upgraded app" do
+      remove_from_config '.*config\.load_defaults.*\n'
+      add_to_config 'config.load_defaults "5.2"'
+
+      app "development"
+
+      assert_equal true, ActionView::Helpers::FormTagHelper.default_enforce_utf8
+    end
+
+    test "ActionView::Helpers::FormTagHelper.default_enforce_utf8 can be configured via config.action_view.default_enforce_utf8" do
+      remove_from_config '.*config\.load_defaults.*\n'
+
+      app_file "config/initializers/new_framework_defaults_6_0.rb", <<-RUBY
+        Rails.application.config.action_view.default_enforce_utf8 = true
+      RUBY
+
+      app "development"
+
+      assert_equal true, ActionView::Helpers::FormTagHelper.default_enforce_utf8
+    end
+
+    test "ActionView::Template.finalize_compiled_template_methods is true by default" do
+      app "test"
+      assert_equal true, ActionView::Template.finalize_compiled_template_methods
+    end
+
+    test "ActionView::Template.finalize_compiled_template_methods can be configured via config.action_view.finalize_compiled_template_methods" do
+      app_file "config/environments/test.rb", <<-RUBY
+      Rails.application.configure do
+        config.action_view.finalize_compiled_template_methods = false
+      end
+      RUBY
+
+      app "test"
+
+      assert_equal false, ActionView::Template.finalize_compiled_template_methods
+    end
+
     private
       def force_lazy_load_hooks
         yield # Tasty clarifying sugar, homie! We only need to reference a constant to load it.
diff --git a/railties/test/application/console_test.rb b/railties/test/application/console_test.rb
index 13164f49c2..4a14042cd3 100644
--- a/railties/test/application/console_test.rb
+++ b/railties/test/application/console_test.rb
@@ -73,7 +73,7 @@ class ConsoleTest < ActiveSupport::TestCase
     MODEL
 
     load_environment
-    assert User.new.respond_to?(:name)
+    assert_respond_to User.new, :name
 
     app_file "app/models/user.rb", <<-MODEL
       class User
@@ -81,9 +81,9 @@ class ConsoleTest < ActiveSupport::TestCase
       end
     MODEL
 
-    assert !User.new.respond_to?(:age)
+    assert_not_respond_to User.new, :age
     irb_context.reload!(false)
-    assert User.new.respond_to?(:age)
+    assert_respond_to User.new, :age
   end
 
   def test_access_to_helpers
diff --git a/railties/test/application/content_security_policy_test.rb b/railties/test/application/content_security_policy_test.rb
new file mode 100644
index 0000000000..0d28df16f8
--- /dev/null
+++ b/railties/test/application/content_security_policy_test.rb
@@ -0,0 +1,223 @@
+# frozen_string_literal: true
+
+require "isolation/abstract_unit"
+require "rack/test"
+
+module ApplicationTests
+  class ContentSecurityPolicyTest < ActiveSupport::TestCase
+    include ActiveSupport::Testing::Isolation
+    include Rack::Test::Methods
+
+    def setup
+      build_app
+    end
+
+    def teardown
+      teardown_app
+    end
+
+    test "default content security policy is nil" do
+      controller :pages, <<-RUBY
+        class PagesController < ApplicationController
+          def index
+            render html: "<h1>Welcome to Rails!</h1>"
+          end
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          root to: "pages#index"
+        end
+      RUBY
+
+      app("development")
+
+      get "/"
+      assert_nil last_response.headers["Content-Security-Policy"]
+    end
+
+    test "empty content security policy is generated" do
+      controller :pages, <<-RUBY
+        class PagesController < ApplicationController
+          def index
+            render html: "<h1>Welcome to Rails!</h1>"
+          end
+        end
+      RUBY
+
+      app_file "config/initializers/content_security_policy.rb", <<-RUBY
+        Rails.application.config.content_security_policy do |p|
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          root to: "pages#index"
+        end
+      RUBY
+
+      app("development")
+
+      get "/"
+      assert_policy ""
+    end
+
+    test "global content security policy in an initializer" do
+      controller :pages, <<-RUBY
+        class PagesController < ApplicationController
+          def index
+            render html: "<h1>Welcome to Rails!</h1>"
+          end
+        end
+      RUBY
+
+      app_file "config/initializers/content_security_policy.rb", <<-RUBY
+        Rails.application.config.content_security_policy do |p|
+          p.default_src :self, :https
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          root to: "pages#index"
+        end
+      RUBY
+
+      app("development")
+
+      get "/"
+      assert_policy "default-src 'self' https:"
+    end
+
+    test "global report only content security policy in an initializer" do
+      controller :pages, <<-RUBY
+        class PagesController < ApplicationController
+          def index
+            render html: "<h1>Welcome to Rails!</h1>"
+          end
+        end
+      RUBY
+
+      app_file "config/initializers/content_security_policy.rb", <<-RUBY
+        Rails.application.config.content_security_policy do |p|
+          p.default_src :self, :https
+        end
+
+        Rails.application.config.content_security_policy_report_only = true
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          root to: "pages#index"
+        end
+      RUBY
+
+      app("development")
+
+      get "/"
+      assert_policy "default-src 'self' https:", report_only: true
+    end
+
+    test "override content security policy in a controller" do
+      controller :pages, <<-RUBY
+        class PagesController < ApplicationController
+          content_security_policy do |p|
+            p.default_src "https://example.com"
+          end
+
+          def index
+            render html: "<h1>Welcome to Rails!</h1>"
+          end
+        end
+      RUBY
+
+      app_file "config/initializers/content_security_policy.rb", <<-RUBY
+        Rails.application.config.content_security_policy do |p|
+          p.default_src :self, :https
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          root to: "pages#index"
+        end
+      RUBY
+
+      app("development")
+
+      get "/"
+      assert_policy "default-src https://example.com"
+    end
+
+    test "override content security policy to report only in a controller" do
+      controller :pages, <<-RUBY
+        class PagesController < ApplicationController
+          content_security_policy_report_only
+
+          def index
+            render html: "<h1>Welcome to Rails!</h1>"
+          end
+        end
+      RUBY
+
+      app_file "config/initializers/content_security_policy.rb", <<-RUBY
+        Rails.application.config.content_security_policy do |p|
+          p.default_src :self, :https
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          root to: "pages#index"
+        end
+      RUBY
+
+      app("development")
+
+      get "/"
+      assert_policy "default-src 'self' https:", report_only: true
+    end
+
+    test "global content security policy added to rack app" do
+      app_file "config/initializers/content_security_policy.rb", <<-RUBY
+        Rails.application.config.content_security_policy do |p|
+          p.default_src :self, :https
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+
+          app = ->(env) {
+            [200, { "Content-Type" => "text/html" }, ["<p>Hello, World!</p>"]]
+          }
+
+          root to: app
+        end
+      RUBY
+
+      app("development")
+
+      get "/"
+      assert_policy "default-src 'self' https:"
+    end
+
+    private
+
+      def assert_policy(expected, report_only: false)
+        assert_equal 200, last_response.status
+
+        if report_only
+          expected_header = "Content-Security-Policy-Report-Only"
+          unexpected_header = "Content-Security-Policy"
+        else
+          expected_header = "Content-Security-Policy"
+          unexpected_header = "Content-Security-Policy-Report-Only"
+        end
+
+        assert_nil last_response.headers[unexpected_header]
+        assert_equal expected, last_response.headers[expected_header]
+      end
+  end
+end
diff --git a/railties/test/application/current_attributes_integration_test.rb b/railties/test/application/current_attributes_integration_test.rb
index 811721b331..146e96facc 100644
--- a/railties/test/application/current_attributes_integration_test.rb
+++ b/railties/test/application/current_attributes_integration_test.rb
@@ -39,6 +39,8 @@ class CurrentAttributesIntegrationTest < ActiveSupport::TestCase
 
     app_file "app/controllers/customers_controller.rb", <<-RUBY
       class CustomersController < ApplicationController
+        layout false
+
         def set_current_customer
           Current.customer = Customer.new("david")
           render :index
diff --git a/railties/test/application/dbconsole_test.rb b/railties/test/application/dbconsole_test.rb
index ba04c81b4d..8eb293c179 100644
--- a/railties/test/application/dbconsole_test.rb
+++ b/railties/test/application/dbconsole_test.rb
@@ -19,21 +19,19 @@ module ApplicationTests
     end
 
     def test_use_value_defined_in_environment_file_in_database_yml
-      Dir.chdir(app_path) do
-        app_file "config/database.yml", <<-YAML
-          development:
-             database: <%= Rails.application.config.database %>
-             adapter: sqlite3
-             pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
-             timeout: 5000
-        YAML
+      app_file "config/database.yml", <<-YAML
+        development:
+           database: <%= Rails.application.config.database %>
+           adapter: sqlite3
+           pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
+           timeout: 5000
+      YAML
 
-        app_file "config/environments/development.rb", <<-RUBY
-          Rails.application.configure do
-            config.database = "db/development.sqlite3"
-          end
-        RUBY
-      end
+      app_file "config/environments/development.rb", <<-RUBY
+        Rails.application.configure do
+          config.database = "db/development.sqlite3"
+        end
+      RUBY
 
       master, slave = PTY.open
       spawn_dbconsole(slave)
@@ -43,22 +41,20 @@ module ApplicationTests
     end
 
     def test_respect_environment_option
-      Dir.chdir(app_path) do
-        app_file "config/database.yml", <<-YAML
-          default: &default
-            adapter: sqlite3
-            pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
-            timeout: 5000
+      app_file "config/database.yml", <<-YAML
+        default: &default
+          adapter: sqlite3
+          pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
+          timeout: 5000
 
-          development:
-            <<: *default
-            database: db/development.sqlite3
+        development:
+          <<: *default
+          database: db/development.sqlite3
 
-          production:
-            <<: *default
-            database: db/production.sqlite3
-        YAML
-      end
+        production:
+          <<: *default
+          database: db/production.sqlite3
+      YAML
 
       master, slave = PTY.open
       spawn_dbconsole(slave, "-e production")
diff --git a/railties/test/application/generators_test.rb b/railties/test/application/generators_test.rb
index 58197a8f6b..e5e557d204 100644
--- a/railties/test/application/generators_test.rb
+++ b/railties/test/application/generators_test.rb
@@ -31,7 +31,7 @@ module ApplicationTests
     end
 
     test "allow running plugin new generator inside Rails app directory" do
-      FileUtils.cd(rails_root) { `ruby bin/rails plugin new vendor/plugins/bukkits` }
+      rails "plugin", "new", "vendor/plugins/bukkits"
       assert File.exist?(File.join(rails_root, "vendor/plugins/bukkits/test/dummy/config/application.rb"))
     end
 
@@ -167,13 +167,14 @@ module ApplicationTests
         config.api_only = true
       RUBY
 
-      FileUtils.cd(rails_root) { `bin/rails generate mailer notifier foo` }
+      rails "generate", "mailer", "notifier", "foo"
       assert File.exist?(File.join(rails_root, "app/views/notifier_mailer/foo.text.erb"))
       assert File.exist?(File.join(rails_root, "app/views/notifier_mailer/foo.html.erb"))
     end
 
     test "ARGV is mutated as expected" do
       require "#{app_path}/config/environment"
+      require "rails/command"
       Rails::Command.const_set("APP_PATH", "rails/all")
 
       FileUtils.cd(rails_root) do
@@ -187,12 +188,13 @@ module ApplicationTests
       Rails::Command.send(:remove_const, "APP_PATH")
     end
 
-    test "help does not show hidden namespaces" do
+    test "help does not show hidden namespaces and hidden commands" do
       FileUtils.cd(rails_root) do
-        output = `bin/rails generate --help`
+        output = rails("generate", "--help")
         assert_no_match "active_record:migration", output
+        assert_no_match "credentials", output
 
-        output = `bin/rails destroy --help`
+        output = rails("destroy", "--help")
         assert_no_match "active_record:migration", output
       end
     end
diff --git a/railties/test/application/help_test.rb b/railties/test/application/help_test.rb
index 3a9384b927..f728fc3b85 100644
--- a/railties/test/application/help_test.rb
+++ b/railties/test/application/help_test.rb
@@ -14,12 +14,12 @@ class HelpTest < ActiveSupport::TestCase
   end
 
   test "command works" do
-    output = Dir.chdir(app_path) { `bin/rails help` }
+    output = rails("help")
     assert_match "The most common rails commands are", output
   end
 
   test "short-cut alias works" do
-    output = Dir.chdir(app_path) { `bin/rails -h` }
+    output = rails("-h")
     assert_match "The most common rails commands are", output
   end
 end
diff --git a/railties/test/application/initializers/frameworks_test.rb b/railties/test/application/initializers/frameworks_test.rb
index d643c85181..1530ea82d6 100644
--- a/railties/test/application/initializers/frameworks_test.rb
+++ b/railties/test/application/initializers/frameworks_test.rb
@@ -211,26 +211,22 @@ module ApplicationTests
     test "database middleware doesn't initialize when activerecord is not in frameworks" do
       use_frameworks []
       require "#{app_path}/config/environment"
-      assert_nil defined?(ActiveRecord::Base)
+      assert !defined?(ActiveRecord::Base) || ActiveRecord.autoload?(:Base)
     end
 
     test "use schema cache dump" do
-      Dir.chdir(app_path) do
-        `rails generate model post title:string;
-         bin/rails db:migrate db:schema:cache:dump`
-      end
+      rails %w(generate model post title:string)
+      rails %w(db:migrate db:schema:cache:dump)
       require "#{app_path}/config/environment"
       ActiveRecord::Base.connection.drop_table("posts") # force drop posts table for test.
       assert ActiveRecord::Base.connection.schema_cache.data_sources("posts")
     end
 
     test "expire schema cache dump" do
-      Dir.chdir(app_path) do
-        `rails generate model post title:string;
-         bin/rails db:migrate db:schema:cache:dump db:rollback`
-      end
+      rails %w(generate model post title:string)
+      rails %w(db:migrate db:schema:cache:dump db:rollback)
       require "#{app_path}/config/environment"
-      assert !ActiveRecord::Base.connection.schema_cache.data_sources("posts")
+      assert_not ActiveRecord::Base.connection.schema_cache.data_sources("posts")
     end
 
     test "active record establish_connection uses Rails.env if DATABASE_URL is not set" do
@@ -270,7 +266,7 @@ module ApplicationTests
         ActiveRecord::Base.connection
       RUBY
       require "#{app_path}/config/environment"
-      assert !ActiveRecord::Base.connection_pool.active_connection?
+      assert_not_predicate ActiveRecord::Base.connection_pool, :active_connection?
     end
   end
 end
diff --git a/railties/test/application/initializers/notifications_test.rb b/railties/test/application/initializers/notifications_test.rb
index 23b20d578c..c65c955734 100644
--- a/railties/test/application/initializers/notifications_test.rb
+++ b/railties/test/application/initializers/notifications_test.rb
@@ -32,6 +32,7 @@ module ApplicationTests
 
       logger = ActiveSupport::LogSubscriber::TestHelper::MockLogger.new
       ActiveRecord::Base.logger = logger
+      ActiveRecord::Base.verbose_query_logs = false
 
       # Mimic Active Record notifications
       instrument "sql.active_record", name: "SQL", sql: "SHOW tables"
diff --git a/railties/test/application/integration_test_case_test.rb b/railties/test/application/integration_test_case_test.rb
index 88b54af8c8..c08761092b 100644
--- a/railties/test/application/integration_test_case_test.rb
+++ b/railties/test/application/integration_test_case_test.rb
@@ -1,10 +1,11 @@
 # frozen_string_literal: true
 
 require "isolation/abstract_unit"
+require "env_helpers"
 
 module ApplicationTests
   class IntegrationTestCaseTest < ActiveSupport::TestCase
-    include ActiveSupport::Testing::Isolation
+    include ActiveSupport::Testing::Isolation, EnvHelpers
 
     setup do
       build_app
@@ -15,7 +16,7 @@ module ApplicationTests
     end
 
     test "resets Action Mailer test deliveries" do
-      script("generate mailer BaseMailer welcome")
+      rails "generate", "mailer", "BaseMailer", "welcome"
 
       app_file "test/integration/mailer_integration_test.rb", <<-RUBY
         require 'test_helper'
@@ -39,14 +40,14 @@ module ApplicationTests
         end
       RUBY
 
-      output = Dir.chdir(app_path) { `bin/rails test 2>&1` }
-      assert_equal 0, $?.to_i, output
+      with_rails_env("test") { rails("db:migrate") }
+      output = rails("test")
       assert_match(/0 failures, 0 errors/, output)
     end
   end
 
   class IntegrationTestDefaultApp < ActiveSupport::TestCase
-    include ActiveSupport::Testing::Isolation
+    include ActiveSupport::Testing::Isolation, EnvHelpers
 
     setup do
       build_app
@@ -67,8 +68,8 @@ module ApplicationTests
         end
       RUBY
 
-      output = Dir.chdir(app_path) { `bin/rails test 2>&1` }
-      assert_equal 0, $?.to_i, output
+      with_rails_env("test") { rails("db:migrate") }
+      output = rails("test")
       assert_match(/0 failures, 0 errors/, output)
     end
   end
diff --git a/railties/test/application/loading_test.rb b/railties/test/application/loading_test.rb
index 11c886e991..889ad16fb8 100644
--- a/railties/test/application/loading_test.rb
+++ b/railties/test/application/loading_test.rb
@@ -300,7 +300,7 @@ class LoadingTest < ActiveSupport::TestCase
       end
     MIGRATION
 
-    Dir.chdir(app_path) { `rake db:migrate` }
+    rails("db:migrate")
     require "#{rails_root}/config/environment"
 
     get "/title"
@@ -314,7 +314,7 @@ class LoadingTest < ActiveSupport::TestCase
       end
     MIGRATION
 
-    Dir.chdir(app_path) { `rake db:migrate` }
+    rails("db:migrate")
 
     get "/body"
     assert_equal "BODY", last_response.body
@@ -352,11 +352,23 @@ class LoadingTest < ActiveSupport::TestCase
   def test_initialize_can_be_called_at_any_time
     require "#{app_path}/config/application"
 
-    assert !Rails.initialized?
-    assert !Rails.application.initialized?
+    assert_not_predicate Rails, :initialized?
+    assert_not_predicate Rails.application, :initialized?
     Rails.initialize!
-    assert Rails.initialized?
-    assert Rails.application.initialized?
+    assert_predicate Rails, :initialized?
+    assert_predicate Rails.application, :initialized?
+  end
+
+  test "frameworks aren't loaded during initialization" do
+    app_file "config/initializers/raise_when_frameworks_load.rb", <<-RUBY
+      %i(action_controller action_mailer active_job active_record).each do |framework|
+        ActiveSupport.on_load(framework) { raise "\#{framework} loaded!" }
+      end
+    RUBY
+
+    assert_nothing_raised do
+      require "#{app_path}/config/environment"
+    end
   end
 
   private
diff --git a/railties/test/application/mailer_previews_test.rb b/railties/test/application/mailer_previews_test.rb
index 4e77cece1b..ba186bda44 100644
--- a/railties/test/application/mailer_previews_test.rb
+++ b/railties/test/application/mailer_previews_test.rb
@@ -296,7 +296,7 @@ module ApplicationTests
     test "mailer preview not found" do
       app("development")
       get "/rails/mailers/notifier"
-      assert last_response.not_found?
+      assert_predicate last_response, :not_found?
       assert_match "Mailer preview &#39;notifier&#39; not found", last_response.body
     end
 
@@ -326,7 +326,7 @@ module ApplicationTests
       app("development")
 
       get "/rails/mailers/notifier/bar"
-      assert last_response.not_found?
+      assert_predicate last_response, :not_found?
       assert_match "Email &#39;bar&#39; not found in NotifierPreview", last_response.body
     end
 
@@ -382,7 +382,7 @@ module ApplicationTests
       app("development")
 
       get "/rails/mailers/notifier/foo?part=text%2Fhtml"
-      assert last_response.not_found?
+      assert_predicate last_response, :not_found?
       assert_match "Email part &#39;text/html&#39; not found in NotifierPreview#foo", last_response.body
     end
 
@@ -450,11 +450,67 @@ module ApplicationTests
 
       get "/rails/mailers/notifier/foo.html"
       assert_equal 200, last_response.status
-      assert_match '<option selected value="?part=text%2Fhtml">View as HTML email</option>', last_response.body
+      assert_match '<option selected value="part=text%2Fhtml">View as HTML email</option>', last_response.body
 
       get "/rails/mailers/notifier/foo.txt"
       assert_equal 200, last_response.status
-      assert_match '<option selected value="?part=text%2Fplain">View as plain-text email</option>', last_response.body
+      assert_match '<option selected value="part=text%2Fplain">View as plain-text email</option>', last_response.body
+    end
+
+    test "locale menu selects correct option" do
+      app_file "config/initializers/available_locales.rb", <<-RUBY
+        Rails.application.configure do
+          config.i18n.available_locales = %i[en ja]
+        end
+      RUBY
+
+      mailer "notifier", <<-RUBY
+        class Notifier < ActionMailer::Base
+          default from: "from@example.com"
+
+          def foo
+            mail to: "to@example.org"
+          end
+        end
+      RUBY
+
+      html_template "notifier/foo", <<-RUBY
+        <p>Hello, World!</p>
+      RUBY
+
+      text_template "notifier/foo", <<-RUBY
+        Hello, World!
+      RUBY
+
+      mailer_preview "notifier", <<-RUBY
+        class NotifierPreview < ActionMailer::Preview
+          def foo
+            Notifier.foo
+          end
+        end
+      RUBY
+
+      app("development")
+
+      get "/rails/mailers/notifier/foo.html"
+      assert_equal 200, last_response.status
+      assert_match '<option selected value="locale=en">en', last_response.body
+      assert_match '<option  value="locale=ja">ja', last_response.body
+
+      get "/rails/mailers/notifier/foo.html?locale=ja"
+      assert_equal 200, last_response.status
+      assert_match '<option  value="locale=en">en', last_response.body
+      assert_match '<option selected value="locale=ja">ja', last_response.body
+
+      get "/rails/mailers/notifier/foo.txt"
+      assert_equal 200, last_response.status
+      assert_match '<option selected value="locale=en">en', last_response.body
+      assert_match '<option  value="locale=ja">ja', last_response.body
+
+      get "/rails/mailers/notifier/foo.txt?locale=ja"
+      assert_equal 200, last_response.status
+      assert_match '<option  value="locale=en">en', last_response.body
+      assert_match '<option selected value="locale=ja">ja', last_response.body
     end
 
     test "mailer previews create correct links when loaded on a subdirectory" do
@@ -520,8 +576,8 @@ module ApplicationTests
       get "/rails/mailers/notifier/foo.txt"
       assert_equal 200, last_response.status
       assert_match '<iframe seamless name="messageBody" src="?part=text%2Fplain">', last_response.body
-      assert_match '<option selected value="?part=text%2Fplain">', last_response.body
-      assert_match '<option  value="?part=text%2Fhtml">', last_response.body
+      assert_match '<option selected value="part=text%2Fplain">', last_response.body
+      assert_match '<option  value="part=text%2Fhtml">', last_response.body
 
       get "/rails/mailers/notifier/foo?part=text%2Fplain"
       assert_equal 200, last_response.status
@@ -530,8 +586,8 @@ module ApplicationTests
       get "/rails/mailers/notifier/foo.html?name=Ruby"
       assert_equal 200, last_response.status
       assert_match '<iframe seamless name="messageBody" src="?name=Ruby&amp;part=text%2Fhtml">', last_response.body
-      assert_match '<option selected value="?name=Ruby&amp;part=text%2Fhtml">', last_response.body
-      assert_match '<option  value="?name=Ruby&amp;part=text%2Fplain">', last_response.body
+      assert_match '<option selected value="name=Ruby&amp;part=text%2Fhtml">', last_response.body
+      assert_match '<option  value="name=Ruby&amp;part=text%2Fplain">', last_response.body
 
       get "/rails/mailers/notifier/foo?name=Ruby&part=text%2Fhtml"
       assert_equal 200, last_response.status
diff --git a/railties/test/application/middleware/cache_test.rb b/railties/test/application/middleware/cache_test.rb
index 9822ec563d..3768d8ce2d 100644
--- a/railties/test/application/middleware/cache_test.rb
+++ b/railties/test/application/middleware/cache_test.rb
@@ -140,7 +140,7 @@ module ApplicationTests
       etag = last_response.headers["ETag"]
 
       get "/expires/expires_etag", { private: true }, { "HTTP_IF_NONE_MATCH" => etag }
-      assert_equal     "miss", last_response.headers["X-Rack-Cache"]
+      assert_equal "miss", last_response.headers["X-Rack-Cache"]
       assert_not_equal body,   last_response.body
     end
 
@@ -174,7 +174,7 @@ module ApplicationTests
       last = last_response.headers["Last-Modified"]
 
       get "/expires/expires_last_modified", { private: true }, { "HTTP_IF_MODIFIED_SINCE" => last }
-      assert_equal     "miss", last_response.headers["X-Rack-Cache"]
+      assert_equal "miss", last_response.headers["X-Rack-Cache"]
       assert_not_equal body,   last_response.body
     end
   end
diff --git a/railties/test/application/middleware/cookies_test.rb b/railties/test/application/middleware/cookies_test.rb
index 23f1ec3e35..ecb4ee3446 100644
--- a/railties/test/application/middleware/cookies_test.rb
+++ b/railties/test/application/middleware/cookies_test.rb
@@ -1,10 +1,12 @@
 # frozen_string_literal: true
 
 require "isolation/abstract_unit"
+require "rack/test"
 
 module ApplicationTests
   class CookiesTest < ActiveSupport::TestCase
     include ActiveSupport::Testing::Isolation
+    include Rack::Test::Methods
 
     def new_app
       File.expand_path("#{app_path}/../new_app")
@@ -15,6 +17,10 @@ module ApplicationTests
       FileUtils.rm_rf("#{app_path}/config/environments")
     end
 
+    def app
+      Rails.application
+    end
+
     def teardown
       teardown_app
       FileUtils.rm_rf(new_app) if File.directory?(new_app)
@@ -44,5 +50,144 @@ module ApplicationTests
       require "#{app_path}/config/environment"
       assert_equal false, ActionDispatch::Cookies::CookieJar.always_write_cookie
     end
+
+    test "signed cookies with SHA512 digest and rotated out SHA256 and SHA1 digests" do
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          get  ':controller(/:action)'
+          post ':controller(/:action)'
+        end
+      RUBY
+
+      controller :foo, <<-RUBY
+        class FooController < ActionController::Base
+          protect_from_forgery with: :null_session
+
+          def write_raw_cookie_sha1
+            cookies[:signed_cookie] = TestVerifiers.sha1.generate("signed cookie")
+            head :ok
+          end
+
+          def write_raw_cookie_sha256
+            cookies[:signed_cookie] = TestVerifiers.sha256.generate("signed cookie")
+            head :ok
+          end
+
+          def read_signed
+            render plain: cookies.signed[:signed_cookie].inspect
+          end
+
+          def read_raw_cookie
+            render plain: cookies[:signed_cookie]
+          end
+        end
+      RUBY
+
+      add_to_config <<-RUBY
+        sha1_secret   = Rails.application.key_generator.generate_key("sha1")
+        sha256_secret = Rails.application.key_generator.generate_key("sha256")
+
+        ::TestVerifiers = Class.new do
+          class_attribute :sha1, default: ActiveSupport::MessageVerifier.new(sha1_secret, digest: "SHA1")
+          class_attribute :sha256, default: ActiveSupport::MessageVerifier.new(sha256_secret, digest: "SHA256")
+        end
+
+        config.action_dispatch.signed_cookie_digest = "SHA512"
+        config.action_dispatch.signed_cookie_salt = "sha512 salt"
+
+        config.action_dispatch.cookies_rotations.tap do |cookies|
+          cookies.rotate :signed, sha1_secret,   digest: "SHA1"
+          cookies.rotate :signed, sha256_secret, digest: "SHA256"
+        end
+      RUBY
+
+      require "#{app_path}/config/environment"
+
+      verifier_sha512 = ActiveSupport::MessageVerifier.new(app.key_generator.generate_key("sha512 salt"), digest: :SHA512)
+
+      get "/foo/write_raw_cookie_sha1"
+      get "/foo/read_signed"
+      assert_equal "signed cookie".inspect, last_response.body
+
+      get "/foo/read_raw_cookie"
+      assert_equal "signed cookie", verifier_sha512.verify(last_response.body)
+
+      get "/foo/write_raw_cookie_sha256"
+      get "/foo/read_signed"
+      assert_equal "signed cookie".inspect, last_response.body
+
+      get "/foo/read_raw_cookie"
+      assert_equal "signed cookie", verifier_sha512.verify(last_response.body)
+    end
+
+    test "encrypted cookies rotating multiple encryption keys" do
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          get  ':controller(/:action)'
+          post ':controller(/:action)'
+        end
+      RUBY
+
+      controller :foo, <<-RUBY
+        class FooController < ActionController::Base
+          protect_from_forgery with: :null_session
+
+          def write_raw_cookie_one
+            cookies[:encrypted_cookie] = TestEncryptors.first_gcm.encrypt_and_sign("encrypted cookie")
+            head :ok
+          end
+
+          def write_raw_cookie_two
+            cookies[:encrypted_cookie] = TestEncryptors.second_gcm.encrypt_and_sign("encrypted cookie")
+            head :ok
+          end
+
+          def read_encrypted
+            render plain: cookies.encrypted[:encrypted_cookie].inspect
+          end
+
+          def read_raw_cookie
+            render plain: cookies[:encrypted_cookie]
+          end
+        end
+      RUBY
+
+      add_to_config <<-RUBY
+        first_secret  = Rails.application.key_generator.generate_key("first", 32)
+        second_secret = Rails.application.key_generator.generate_key("second", 32)
+
+        ::TestEncryptors = Class.new do
+          class_attribute :first_gcm,  default: ActiveSupport::MessageEncryptor.new(first_secret, cipher: "aes-256-gcm")
+          class_attribute :second_gcm, default: ActiveSupport::MessageEncryptor.new(second_secret, cipher: "aes-256-gcm")
+        end
+
+        config.action_dispatch.use_authenticated_cookie_encryption = true
+        config.action_dispatch.encrypted_cookie_cipher = "aes-256-gcm"
+        config.action_dispatch.authenticated_encrypted_cookie_salt = "salt"
+
+        config.action_dispatch.cookies_rotations.tap do |cookies|
+          cookies.rotate :encrypted, first_secret
+          cookies.rotate :encrypted, second_secret
+        end
+      RUBY
+
+      require "#{app_path}/config/environment"
+
+      encryptor = ActiveSupport::MessageEncryptor.new(app.key_generator.generate_key("salt", 32), cipher: "aes-256-gcm")
+
+      get "/foo/write_raw_cookie_one"
+      get "/foo/read_encrypted"
+      assert_equal "encrypted cookie".inspect, last_response.body
+
+      get "/foo/read_raw_cookie"
+      assert_equal "encrypted cookie", encryptor.decrypt_and_verify(last_response.body)
+
+      get "/foo/write_raw_cookie_sha256"
+      get "/foo/read_encrypted"
+      assert_equal "encrypted cookie".inspect, last_response.body
+
+      get "/foo/read_raw_cookie"
+      assert_equal "encrypted cookie", encryptor.decrypt_and_verify(last_response.body)
+    end
   end
 end
diff --git a/railties/test/application/middleware/exceptions_test.rb b/railties/test/application/middleware/exceptions_test.rb
index 75afeec905..2d659ade8d 100644
--- a/railties/test/application/middleware/exceptions_test.rb
+++ b/railties/test/application/middleware/exceptions_test.rb
@@ -102,7 +102,7 @@ module ApplicationTests
       end
     end
 
-    test "routing to an nonexistent controller when action_dispatch.show_exceptions and consider_all_requests_local are set shows diagnostics" do
+    test "routing to a nonexistent controller when action_dispatch.show_exceptions and consider_all_requests_local are set shows diagnostics" do
       app_file "config/routes.rb", <<-RUBY
         Rails.application.routes.draw do
           resources :articles
diff --git a/railties/test/application/middleware/sendfile_test.rb b/railties/test/application/middleware/sendfile_test.rb
index 4731396029..818ad61c64 100644
--- a/railties/test/application/middleware/sendfile_test.rb
+++ b/railties/test/application/middleware/sendfile_test.rb
@@ -15,10 +15,6 @@ module ApplicationTests
       teardown_app
     end
 
-    def app
-      @app ||= Rails.application
-    end
-
     define_method :simple_controller do
       class ::OmgController < ActionController::Base
         def index
@@ -33,7 +29,7 @@ module ApplicationTests
       simple_controller
 
       get "/"
-      assert !last_response.headers["X-Sendfile"]
+      assert_not last_response.headers["X-Sendfile"]
       assert_equal File.read(__FILE__), last_response.body
     end
 
diff --git a/railties/test/application/middleware/session_test.rb b/railties/test/application/middleware/session_test.rb
index 15acfe93e9..9182a63ab7 100644
--- a/railties/test/application/middleware/session_test.rb
+++ b/railties/test/application/middleware/session_test.rb
@@ -31,7 +31,7 @@ module ApplicationTests
       add_to_config "config.force_ssl = true"
       add_to_config "config.ssl_options = { secure_cookies: false }"
       require "#{app_path}/config/environment"
-      assert !app.config.session_options[:secure]
+      assert_not app.config.session_options[:secure]
     end
 
     test "session is not loaded if it's not used" do
@@ -51,7 +51,7 @@ module ApplicationTests
       get "/"
 
       assert last_request.env["HTTP_COOKIE"]
-      assert !last_response.headers["Set-Cookie"]
+      assert_not last_response.headers["Set-Cookie"]
     end
 
     test "session is empty and isn't saved on unverified request when using :null_session protect method" do
@@ -337,31 +337,37 @@ module ApplicationTests
 
       add_to_config <<-RUBY
         # Use a static key
-        secrets.secret_key_base = "known key base"
+        Rails.application.credentials.secret_key_base = "known key base"
 
         # Enable AEAD cookies
         config.action_dispatch.use_authenticated_cookie_encryption = true
       RUBY
 
-      require "#{app_path}/config/environment"
+      begin
+        old_rails_env, ENV["RAILS_ENV"] = ENV["RAILS_ENV"], "production"
 
-      get "/foo/write_raw_session"
-      get "/foo/read_session"
-      assert_equal "1", last_response.body
+        require "#{app_path}/config/environment"
 
-      get "/foo/write_session"
-      get "/foo/read_session"
-      assert_equal "2", last_response.body
+        get "/foo/write_raw_session"
+        get "/foo/read_session"
+        assert_equal "1", last_response.body
 
-      get "/foo/read_encrypted_cookie"
-      assert_equal "2", last_response.body
+        get "/foo/write_session"
+        get "/foo/read_session"
+        assert_equal "2", last_response.body
 
-      cipher = "aes-256-gcm"
-      secret = app.key_generator.generate_key("authenticated encrypted cookie")
-      encryptor = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len(cipher)], cipher: cipher)
+        get "/foo/read_encrypted_cookie"
+        assert_equal "2", last_response.body
 
-      get "/foo/read_raw_cookie"
-      assert_equal 2, encryptor.decrypt_and_verify(last_response.body)["foo"]
+        cipher = "aes-256-gcm"
+        secret = app.key_generator.generate_key("authenticated encrypted cookie")
+        encryptor = ActiveSupport::MessageEncryptor.new(secret[0, ActiveSupport::MessageEncryptor.key_len(cipher)], cipher: cipher)
+
+        get "/foo/read_raw_cookie"
+        assert_equal 2, encryptor.decrypt_and_verify(last_response.body)["foo"]
+      ensure
+        ENV["RAILS_ENV"] = old_rails_env
+      end
     end
 
     test "session upgrading legacy signed cookies to new signed cookies" do
@@ -400,26 +406,32 @@ module ApplicationTests
 
       add_to_config <<-RUBY
         secrets.secret_token = "3b7cd727ee24e8444053437c36cc66c4"
-        secrets.secret_key_base = nil
+        Rails.application.credentials.secret_key_base = nil
       RUBY
 
-      require "#{app_path}/config/environment"
+      begin
+        old_rails_env, ENV["RAILS_ENV"] = ENV["RAILS_ENV"], "production"
 
-      get "/foo/write_raw_session"
-      get "/foo/read_session"
-      assert_equal "1", last_response.body
+        require "#{app_path}/config/environment"
 
-      get "/foo/write_session"
-      get "/foo/read_session"
-      assert_equal "2", last_response.body
+        get "/foo/write_raw_session"
+        get "/foo/read_session"
+        assert_equal "1", last_response.body
 
-      get "/foo/read_signed_cookie"
-      assert_equal "2", last_response.body
+        get "/foo/write_session"
+        get "/foo/read_session"
+        assert_equal "2", last_response.body
 
-      verifier = ActiveSupport::MessageVerifier.new(app.secrets.secret_token)
+        get "/foo/read_signed_cookie"
+        assert_equal "2", last_response.body
 
-      get "/foo/read_raw_cookie"
-      assert_equal 2, verifier.verify(last_response.body)["foo"]
+        verifier = ActiveSupport::MessageVerifier.new(app.secrets.secret_token)
+
+        get "/foo/read_raw_cookie"
+        assert_equal 2, verifier.verify(last_response.body)["foo"]
+      ensure
+        ENV["RAILS_ENV"] = old_rails_env
+      end
     end
 
     test "calling reset_session on request does not trigger an error for API apps" do
diff --git a/railties/test/application/middleware_test.rb b/railties/test/application/middleware_test.rb
index 0a5a524692..5efaf841d4 100644
--- a/railties/test/application/middleware_test.rb
+++ b/railties/test/application/middleware_test.rb
@@ -42,9 +42,11 @@ module ApplicationTests
         "ActionDispatch::Cookies",
         "ActionDispatch::Session::CookieStore",
         "ActionDispatch::Flash",
+        "ActionDispatch::ContentSecurityPolicy::Middleware",
         "Rack::Head",
         "Rack::ConditionalGet",
-        "Rack::ETag"
+        "Rack::ETag",
+        "Rack::TempfileReaper"
       ], middleware
     end
 
@@ -248,7 +250,7 @@ module ApplicationTests
 
     test "can't change middleware after it's built" do
       boot!
-      assert_raise RuntimeError do
+      assert_raise frozen_error_class do
         app.config.middleware.use Rack::Config
       end
     end
diff --git a/railties/test/application/paths_test.rb b/railties/test/application/paths_test.rb
index 0abc5cc9aa..28a9206daa 100644
--- a/railties/test/application/paths_test.rb
+++ b/railties/test/application/paths_test.rb
@@ -37,7 +37,7 @@ module ApplicationTests
     end
 
     def assert_not_in_load_path(*path)
-      assert !$:.any? { |p| File.expand_path(p) == root(*path) }, "Load path includes '#{root(*path)}'. They are:\n-----\n #{$:.join("\n")}\n-----"
+      assert_not $:.any? { |p| File.expand_path(p) == root(*path) }, "Load path includes '#{root(*path)}'. They are:\n-----\n #{$:.join("\n")}\n-----"
     end
 
     test "booting up Rails yields a valid paths object" do
diff --git a/railties/test/application/per_request_digest_cache_test.rb b/railties/test/application/per_request_digest_cache_test.rb
index e9bc91785c..10d3313f6e 100644
--- a/railties/test/application/per_request_digest_cache_test.rb
+++ b/railties/test/application/per_request_digest_cache_test.rb
@@ -59,7 +59,7 @@ class PerRequestDigestCacheTest < ActiveSupport::TestCase
     assert_equal 200, last_response.status
 
     values = ActionView::LookupContext::DetailsKey.digest_caches.first.values
-    assert_equal [ "8ba099b7749542fe765ff34a6824d548" ], values
+    assert_equal [ "effc8928d0b33535c8a21d24ec617161" ], values
     assert_equal %w(david dingus), last_response.body.split.map(&:strip)
   end
 
diff --git a/railties/test/application/rake/dbs_test.rb b/railties/test/application/rake/dbs_test.rb
index db88eb0fd3..0594236b1f 100644
--- a/railties/test/application/rake/dbs_test.rb
+++ b/railties/test/application/rake/dbs_test.rb
@@ -26,15 +26,15 @@ module ApplicationTests
         FileUtils.rm_rf("#{app_path}/config/database.yml")
       end
 
-      def db_create_and_drop(expected_database)
+      def db_create_and_drop(expected_database, environment_loaded: true)
         Dir.chdir(app_path) do
-          output = `bin/rails db:create`
+          output = rails("db:create")
           assert_match(/Created database/, output)
           assert File.exist?(expected_database)
-          assert_equal expected_database, ActiveRecord::Base.connection_config[:database]
-          output = `bin/rails db:drop`
+          assert_equal expected_database, ActiveRecord::Base.connection_config[:database] if environment_loaded
+          output = rails("db:drop")
           assert_match(/Dropped database/, output)
-          assert !File.exist?(expected_database)
+          assert_not File.exist?(expected_database)
         end
       end
 
@@ -49,20 +49,35 @@ module ApplicationTests
         db_create_and_drop database_url_db_name
       end
 
+      test "db:create and db:drop respect environment setting" do
+        app_file "config/database.yml", <<-YAML
+          development:
+            database: <%= Rails.application.config.database %>
+            adapter: sqlite3
+        YAML
+
+        app_file "config/environments/development.rb", <<-RUBY
+          Rails.application.configure do
+            config.database = "db/development.sqlite3"
+          end
+        RUBY
+
+        db_create_and_drop "db/development.sqlite3", environment_loaded: false
+      end
+
       def with_database_existing
         Dir.chdir(app_path) do
           set_database_url
-          `bin/rails db:create`
+          rails "db:create"
           yield
-          `bin/rails db:drop`
+          rails "db:drop"
         end
       end
 
       test "db:create failure because database exists" do
         with_database_existing do
-          output = `bin/rails db:create 2>&1`
+          output = rails("db:create")
           assert_match(/already exists/, output)
-          assert_equal 0, $?.exitstatus
         end
       end
 
@@ -77,24 +92,35 @@ module ApplicationTests
 
       test "db:create failure because bad permissions" do
         with_bad_permissions do
-          output = `bin/rails db:create 2>&1`
+          output = rails("db:create", allow_failure: true)
           assert_match(/Couldn't create database/, output)
           assert_equal 1, $?.exitstatus
         end
       end
 
-      test "db:drop failure because database does not exist" do
-        Dir.chdir(app_path) do
-          output = `bin/rails db:drop:_unsafe --trace 2>&1`
-          assert_match(/does not exist/, output)
+      test "db:create works when schema cache exists and database does not exist" do
+        use_postgresql
+
+        begin
+          rails %w(db:create db:migrate db:schema:cache:dump)
+
+          rails "db:drop"
+          rails "db:create"
           assert_equal 0, $?.exitstatus
+        ensure
+          rails "db:drop" rescue nil
         end
       end
 
+      test "db:drop failure because database does not exist" do
+        output = rails("db:drop:_unsafe", "--trace")
+        assert_match(/does not exist/, output)
+      end
+
       test "db:drop failure because bad permissions" do
         with_database_existing do
           with_bad_permissions do
-            output = `bin/rails db:drop 2>&1`
+            output = rails("db:drop", allow_failure: true)
             assert_match(/Couldn't drop/, output)
             assert_equal 1, $?.exitstatus
           end
@@ -102,13 +128,11 @@ module ApplicationTests
       end
 
       def db_migrate_and_status(expected_database)
-        Dir.chdir(app_path) do
-          `bin/rails generate model book title:string;
-           bin/rails db:migrate`
-          output = `bin/rails db:migrate:status`
-          assert_match(%r{database:\s+\S*#{Regexp.escape(expected_database)}}, output)
-          assert_match(/up\s+\d{14}\s+Create books/, output)
-        end
+        rails "generate", "model", "book", "title:string"
+        rails "db:migrate"
+        output = rails("db:migrate:status")
+        assert_match(%r{database:\s+\S*#{Regexp.escape(expected_database)}}, output)
+        assert_match(/up\s+\d{14}\s+Create books/, output)
       end
 
       test "db:migrate and db:migrate:status without database_url" do
@@ -124,8 +148,8 @@ module ApplicationTests
 
       def db_schema_dump
         Dir.chdir(app_path) do
-          `bin/rails generate model book title:string;
-           bin/rails db:migrate db:schema:dump`
+          rails "generate", "model", "book", "title:string"
+          rails "db:migrate", "db:schema:dump"
           schema_dump = File.read("db/schema.rb")
           assert_match(/create_table \"books\"/, schema_dump)
         end
@@ -142,8 +166,8 @@ module ApplicationTests
 
       def db_fixtures_load(expected_database)
         Dir.chdir(app_path) do
-          `bin/rails generate model book title:string;
-           bin/rails db:migrate db:fixtures:load`
+          rails "generate", "model", "book", "title:string"
+          rails "db:migrate", "db:fixtures:load"
           assert_match expected_database, ActiveRecord::Base.connection_config[:database]
           require "#{app_path}/app/models/book"
           assert_equal 2, Book.count
@@ -163,24 +187,23 @@ module ApplicationTests
 
       test "db:fixtures:load with namespaced fixture" do
         require "#{app_path}/config/environment"
-        Dir.chdir(app_path) do
-          `bin/rails generate model admin::book title:string;
-           bin/rails db:migrate db:fixtures:load`
-          require "#{app_path}/app/models/admin/book"
-          assert_equal 2, Admin::Book.count
-        end
+
+        rails "generate", "model", "admin::book", "title:string"
+        rails "db:migrate", "db:fixtures:load"
+        require "#{app_path}/app/models/admin/book"
+        assert_equal 2, Admin::Book.count
       end
 
       def db_structure_dump_and_load(expected_database)
         Dir.chdir(app_path) do
-          `bin/rails generate model book title:string;
-           bin/rails db:migrate db:structure:dump`
+          rails "generate", "model", "book", "title:string"
+          rails "db:migrate", "db:structure:dump"
           structure_dump = File.read("db/structure.sql")
           assert_match(/CREATE TABLE (?:IF NOT EXISTS )?\"books\"/, structure_dump)
-          `bin/rails environment db:drop db:structure:load`
+          rails "environment", "db:drop", "db:structure:load"
           assert_match expected_database, ActiveRecord::Base.connection_config[:database]
           require "#{app_path}/app/models/book"
-          #if structure is not loaded correctly, exception would be raised
+          # if structure is not loaded correctly, exception would be raised
           assert_equal 0, Book.count
         end
       end
@@ -196,86 +219,86 @@ module ApplicationTests
         db_structure_dump_and_load database_url_db_name
       end
 
+      test "db:structure:dump and db:structure:load set ar_internal_metadata" do
+        require "#{app_path}/config/environment"
+        db_structure_dump_and_load ActiveRecord::Base.configurations[Rails.env]["database"]
+
+        assert_equal "test", rails("runner", "-e", "test", "puts ActiveRecord::InternalMetadata[:environment]").strip
+        assert_equal "development", rails("runner", "puts ActiveRecord::InternalMetadata[:environment]").strip
+      end
+
       test "db:structure:dump does not dump schema information when no migrations are used" do
-        Dir.chdir(app_path) do
-          # create table without migrations
-          `bin/rails runner 'ActiveRecord::Base.connection.create_table(:posts) {|t| t.string :title }'`
+        # create table without migrations
+        rails "runner", "ActiveRecord::Base.connection.create_table(:posts) {|t| t.string :title }"
 
-          stderr_output = capture(:stderr) { `bin/rails db:structure:dump` }
-          assert_empty stderr_output
-          structure_dump = File.read("db/structure.sql")
-          assert_match(/CREATE TABLE (?:IF NOT EXISTS )?\"posts\"/, structure_dump)
-        end
+        stderr_output = capture(:stderr) { rails("db:structure:dump", stderr: true, allow_failure: true) }
+        assert_empty stderr_output
+        structure_dump = File.read("#{app_path}/db/structure.sql")
+        assert_match(/CREATE TABLE (?:IF NOT EXISTS )?\"posts\"/, structure_dump)
       end
 
       test "db:schema:load and db:structure:load do not purge the existing database" do
-        Dir.chdir(app_path) do
-          `bin/rails runner 'ActiveRecord::Base.connection.create_table(:posts) {|t| t.string :title }'`
+        rails "runner", "ActiveRecord::Base.connection.create_table(:posts) {|t| t.string :title }"
 
-          app_file "db/schema.rb", <<-RUBY
-            ActiveRecord::Schema.define(version: 20140423102712) do
-              create_table(:comments) {}
-            end
-          RUBY
+        app_file "db/schema.rb", <<-RUBY
+          ActiveRecord::Schema.define(version: 20140423102712) do
+            create_table(:comments) {}
+          end
+        RUBY
 
-          list_tables = lambda { `bin/rails runner 'p ActiveRecord::Base.connection.tables'`.strip }
+        list_tables = lambda { rails("runner", "p ActiveRecord::Base.connection.tables").strip }
 
-          assert_equal '["posts"]', list_tables[]
-          `bin/rails db:schema:load`
-          assert_equal '["posts", "comments", "schema_migrations", "ar_internal_metadata"]', list_tables[]
+        assert_equal '["posts"]', list_tables[]
+        rails "db:schema:load"
+        assert_equal '["posts", "comments", "schema_migrations", "ar_internal_metadata"]', list_tables[]
 
-          app_file "db/structure.sql", <<-SQL
-            CREATE TABLE "users" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "name" varchar(255));
-          SQL
+        app_file "db/structure.sql", <<-SQL
+          CREATE TABLE "users" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "name" varchar(255));
+        SQL
 
-          `bin/rails db:structure:load`
-          assert_equal '["posts", "comments", "schema_migrations", "ar_internal_metadata", "users"]', list_tables[]
-        end
+        rails "db:structure:load"
+        assert_equal '["posts", "comments", "schema_migrations", "ar_internal_metadata", "users"]', list_tables[]
       end
 
       test "db:schema:load with inflections" do
-        Dir.chdir(app_path) do
-          app_file "config/initializers/inflection.rb", <<-RUBY
-            ActiveSupport::Inflector.inflections do |inflect|
-              inflect.irregular 'goose', 'geese'
-            end
-          RUBY
-          app_file "config/initializers/primary_key_table_name.rb", <<-RUBY
-            ActiveRecord::Base.primary_key_prefix_type = :table_name
-          RUBY
-          app_file "db/schema.rb", <<-RUBY
-            ActiveRecord::Schema.define(version: 20140423102712) do
-              create_table("goose".pluralize) do |t|
-                t.string :name
-              end
+        app_file "config/initializers/inflection.rb", <<-RUBY
+          ActiveSupport::Inflector.inflections do |inflect|
+            inflect.irregular 'goose', 'geese'
+          end
+        RUBY
+        app_file "config/initializers/primary_key_table_name.rb", <<-RUBY
+          ActiveRecord::Base.primary_key_prefix_type = :table_name
+        RUBY
+        app_file "db/schema.rb", <<-RUBY
+          ActiveRecord::Schema.define(version: 20140423102712) do
+            create_table("goose".pluralize) do |t|
+              t.string :name
             end
-          RUBY
+          end
+        RUBY
 
-          `bin/rails db:schema:load`
+        rails "db:schema:load"
 
-          tables = `bin/rails runner 'p ActiveRecord::Base.connection.tables'`.strip
-          assert_match(/"geese"/, tables)
+        tables = rails("runner", "p ActiveRecord::Base.connection.tables").strip
+        assert_match(/"geese"/, tables)
 
-          columns = `bin/rails runner 'p ActiveRecord::Base.connection.columns("geese").map(&:name)'`.strip
-          assert_equal columns, '["gooseid", "name"]'
-        end
+        columns = rails("runner", "p ActiveRecord::Base.connection.columns('geese').map(&:name)").strip
+        assert_equal columns, '["gooseid", "name"]'
       end
 
       test "db:schema:load fails if schema.rb doesn't exist yet" do
-        Dir.chdir(app_path) do
-          stderr_output = capture(:stderr) { `bin/rails db:schema:load` }
-          assert_match(/Run `rails db:migrate` to create it/, stderr_output)
-        end
+        stderr_output = capture(:stderr) { rails("db:schema:load", stderr: true, allow_failure: true) }
+        assert_match(/Run `rails db:migrate` to create it/, stderr_output)
       end
 
       def db_test_load_structure
         Dir.chdir(app_path) do
-          `bin/rails generate model book title:string;
-           bin/rails db:migrate db:structure:dump db:test:load_structure`
+          rails "generate", "model", "book", "title:string"
+          rails "db:migrate", "db:structure:dump", "db:test:load_structure"
           ActiveRecord::Base.configurations = Rails.application.config.database_configuration
           ActiveRecord::Base.establish_connection :test
           require "#{app_path}/app/models/book"
-          #if structure is not loaded correctly, exception would be raised
+          # if structure is not loaded correctly, exception would be raised
           assert_equal 0, Book.count
           assert_match ActiveRecord::Base.configurations["test"]["database"],
             ActiveRecord::Base.connection_config[:database]
@@ -306,15 +329,52 @@ module ApplicationTests
             puts ActiveRecord::Base.connection_config[:database]
           RUBY
 
-          Dir.chdir(app_path) do
-            database_path = `bin/rails db:setup`
-            assert_equal "development.sqlite3", File.basename(database_path.strip)
-          end
+          database_path = rails("db:setup")
+          assert_equal "development.sqlite3", File.basename(database_path.strip)
         ensure
           ENV["RAILS_ENV"] = @old_rails_env
           ENV["RACK_ENV"] = @old_rack_env
         end
       end
+
+      test "db:setup sets ar_internal_metadata" do
+        app_file "db/schema.rb", ""
+        rails "db:setup"
+
+        test_environment = lambda { rails("runner", "-e", "test", "puts ActiveRecord::InternalMetadata[:environment]").strip }
+        development_environment = lambda { rails("runner", "puts ActiveRecord::InternalMetadata[:environment]").strip }
+
+        assert_equal "test", test_environment.call
+        assert_equal "development", development_environment.call
+
+        app_file "db/structure.sql", ""
+        app_file "config/initializers/enable_sql_schema_format.rb", <<-RUBY
+          Rails.application.config.active_record.schema_format = :sql
+        RUBY
+
+        rails "db:setup"
+
+        assert_equal "test", test_environment.call
+        assert_equal "development", development_environment.call
+      end
+
+      test "db:test:prepare sets test ar_internal_metadata" do
+        app_file "db/schema.rb", ""
+        rails "db:test:prepare"
+
+        test_environment = lambda { rails("runner", "-e", "test", "puts ActiveRecord::InternalMetadata[:environment]").strip }
+
+        assert_equal "test", test_environment.call
+
+        app_file "db/structure.sql", ""
+        app_file "config/initializers/enable_sql_schema_format.rb", <<-RUBY
+          Rails.application.config.active_record.schema_format = :sql
+        RUBY
+
+        rails "db:test:prepare"
+
+        assert_equal "test", test_environment.call
+      end
     end
   end
 end
diff --git a/railties/test/application/rake/dev_test.rb b/railties/test/application/rake/dev_test.rb
index b25593ee1c..66e1ac9d99 100644
--- a/railties/test/application/rake/dev_test.rb
+++ b/railties/test/application/rake/dev_test.rb
@@ -17,7 +17,7 @@ module ApplicationTests
 
       test "dev:cache creates file and outputs message" do
         Dir.chdir(app_path) do
-          output = `rails dev:cache`
+          output = rails("dev:cache")
           assert File.exist?("tmp/caching-dev.txt")
           assert_match(/Development mode is now being cached/, output)
         end
@@ -25,8 +25,8 @@ module ApplicationTests
 
       test "dev:cache deletes file and outputs message" do
         Dir.chdir(app_path) do
-          `rails dev:cache` # Create caching file.
-          output = `rails dev:cache` # Delete caching file.
+          rails "dev:cache" # Create caching file.
+          output = rails("dev:cache") # Delete caching file.
           assert_not File.exist?("tmp/caching-dev.txt")
           assert_match(/Development mode is no longer being cached/, output)
         end
@@ -34,12 +34,12 @@ module ApplicationTests
 
       test "dev:cache touches tmp/restart.txt" do
         Dir.chdir(app_path) do
-          `rails dev:cache`
+          rails "dev:cache"
           assert File.exist?("tmp/restart.txt")
 
           prev_mtime = File.mtime("tmp/restart.txt")
           sleep(1)
-          `rails dev:cache`
+          rails "dev:cache"
           curr_mtime = File.mtime("tmp/restart.txt")
           assert_not_equal prev_mtime, curr_mtime
         end
diff --git a/railties/test/application/rake/log_test.rb b/railties/test/application/rake/log_test.rb
index c52be5f396..678f26db26 100644
--- a/railties/test/application/rake/log_test.rb
+++ b/railties/test/application/rake/log_test.rb
@@ -23,7 +23,7 @@ module ApplicationTests
           File.write("log/test.log", "test")
           File.write("log/dummy.log", "dummy")
 
-          `rails log:clear`
+          rails "log:clear"
 
           assert_equal 0, File.size("log/test.log")
           assert_equal 0, File.size("log/staging.log")
diff --git a/railties/test/application/rake/migrations_test.rb b/railties/test/application/rake/migrations_test.rb
index d130a58441..47c5ac105a 100644
--- a/railties/test/application/rake/migrations_test.rb
+++ b/railties/test/application/rake/migrations_test.rb
@@ -15,263 +15,416 @@ module ApplicationTests
       end
 
       test "running migrations with given scope" do
-        Dir.chdir(app_path) do
-          `bin/rails generate model user username:string password:string`
+        rails "generate", "model", "user", "username:string", "password:string"
 
-          app_file "db/migrate/01_a_migration.bukkits.rb", <<-MIGRATION
-            class AMigration < ActiveRecord::Migration::Current
-            end
-          MIGRATION
+        app_file "db/migrate/01_a_migration.bukkits.rb", <<-MIGRATION
+          class AMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
 
-          output = `bin/rails db:migrate SCOPE=bukkits`
-          assert_no_match(/create_table\(:users\)/, output)
-          assert_no_match(/CreateUsers/, output)
-          assert_no_match(/add_column\(:users, :email, :string\)/, output)
+        output = rails("db:migrate", "SCOPE=bukkits")
+        assert_no_match(/create_table\(:users\)/, output)
+        assert_no_match(/CreateUsers/, output)
+        assert_no_match(/add_column\(:users, :email, :string\)/, output)
 
-          assert_match(/AMigration: migrated/, output)
+        assert_match(/AMigration: migrated/, output)
 
-          output = `bin/rails db:migrate SCOPE=bukkits VERSION=0`
-          assert_no_match(/drop_table\(:users\)/, output)
-          assert_no_match(/CreateUsers/, output)
-          assert_no_match(/remove_column\(:users, :email\)/, output)
+        # run all the migrations to test scope for down
+        output = rails("db:migrate")
+        assert_match(/CreateUsers: migrated/, output)
 
-          assert_match(/AMigration: reverted/, output)
-        end
+        output = rails("db:migrate", "SCOPE=bukkits", "VERSION=0")
+        assert_no_match(/drop_table\(:users\)/, output)
+        assert_no_match(/CreateUsers/, output)
+        assert_no_match(/remove_column\(:users, :email\)/, output)
+
+        assert_match(/AMigration: reverted/, output)
+
+        output = rails("db:migrate", "VERSION=0")
+
+        assert_match(/CreateUsers: reverted/, output)
+      end
+
+      test "version outputs current version" do
+        app_file "db/migrate/01_one_migration.rb", <<-MIGRATION
+          class OneMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        rails "db:migrate"
+
+        output = rails("db:version")
+        assert_match(/Current version: 1/, output)
+      end
+
+      test "migrate with specified VERSION in different formats" do
+        app_file "db/migrate/01_one_migration.rb", <<-MIGRATION
+          class OneMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        app_file "db/migrate/02_two_migration.rb", <<-MIGRATION
+          class TwoMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        app_file "db/migrate/03_three_migration.rb", <<-MIGRATION
+          class ThreeMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        rails "db:migrate"
+
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
+        assert_match(/up\s+003\s+Three migration/, output)
+
+        rails "db:migrate", "VERSION=01_one_migration.rb"
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/down\s+002\s+Two migration/, output)
+        assert_match(/down\s+003\s+Three migration/, output)
+
+        rails "db:migrate", "VERSION=3"
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
+        assert_match(/up\s+003\s+Three migration/, output)
+
+        rails "db:migrate", "VERSION=001"
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/down\s+002\s+Two migration/, output)
+        assert_match(/down\s+003\s+Three migration/, output)
       end
 
       test "migration with empty version" do
-        Dir.chdir(app_path) do
-          output = `bin/rails db:migrate VERSION= 2>&1`
-          assert_match(/Empty VERSION provided/, output)
+        app_file "db/migrate/01_one_migration.rb", <<-MIGRATION
+          class OneMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
 
-          output = `bin/rails db:migrate:redo VERSION= 2>&1`
-          assert_match(/Empty VERSION provided/, output)
+        app_file "db/migrate/02_two_migration.rb", <<-MIGRATION
+          class TwoMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
 
-          output = `bin/rails db:migrate:up VERSION= 2>&1`
-          assert_match(/VERSION is required/, output)
+        rails("db:migrate", "VERSION=")
 
-          output = `bin/rails db:migrate:up 2>&1`
-          assert_match(/VERSION is required/, output)
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
 
-          output = `bin/rails db:migrate:down VERSION= 2>&1`
-          assert_match(/VERSION is required - To go down one migration, use db:rollback/, output)
+        output = rails("db:migrate:redo", "VERSION=", allow_failure: true)
+        assert_match(/Empty VERSION provided/, output)
 
-          output = `bin/rails db:migrate:down 2>&1`
-          assert_match(/VERSION is required - To go down one migration, use db:rollback/, output)
-        end
+        output = rails("db:migrate:up", "VERSION=", allow_failure: true)
+        assert_match(/VERSION is required/, output)
+
+        output = rails("db:migrate:up", allow_failure: true)
+        assert_match(/VERSION is required/, output)
+
+        output = rails("db:migrate:down", "VERSION=", allow_failure: true)
+        assert_match(/VERSION is required - To go down one migration, use db:rollback/, output)
+
+        output = rails("db:migrate:down", allow_failure: true)
+        assert_match(/VERSION is required - To go down one migration, use db:rollback/, output)
+
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
+      end
+
+      test "migration with 0 version" do
+        app_file "db/migrate/01_one_migration.rb", <<-MIGRATION
+          class OneMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        app_file "db/migrate/02_two_migration.rb", <<-MIGRATION
+          class TwoMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        rails "db:migrate"
+
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
+
+        rails "db:migrate", "VERSION=0"
+
+        output = rails("db:migrate:status")
+        assert_match(/down\s+001\s+One migration/, output)
+        assert_match(/down\s+002\s+Two migration/, output)
       end
 
       test "model and migration generator with change syntax" do
-        Dir.chdir(app_path) do
-          `bin/rails generate model user username:string password:string;
-           bin/rails generate migration add_email_to_users email:string`
-
-          output = `bin/rails db:migrate`
-          assert_match(/create_table\(:users\)/, output)
-          assert_match(/CreateUsers: migrated/, output)
-          assert_match(/add_column\(:users, :email, :string\)/, output)
-          assert_match(/AddEmailToUsers: migrated/, output)
-
-          output = `bin/rails db:rollback STEP=2`
-          assert_match(/drop_table\(:users\)/, output)
-          assert_match(/CreateUsers: reverted/, output)
-          assert_match(/remove_column\(:users, :email, :string\)/, output)
-          assert_match(/AddEmailToUsers: reverted/, output)
-        end
+        rails "generate", "model", "user", "username:string", "password:string"
+        rails "generate", "migration", "add_email_to_users", "email:string"
+
+        output = rails("db:migrate")
+        assert_match(/create_table\(:users\)/, output)
+        assert_match(/CreateUsers: migrated/, output)
+        assert_match(/add_column\(:users, :email, :string\)/, output)
+        assert_match(/AddEmailToUsers: migrated/, output)
+
+        output = rails("db:rollback", "STEP=2")
+        assert_match(/drop_table\(:users\)/, output)
+        assert_match(/CreateUsers: reverted/, output)
+        assert_match(/remove_column\(:users, :email, :string\)/, output)
+        assert_match(/AddEmailToUsers: reverted/, output)
       end
 
       test "migration status when schema migrations table is not present" do
-        output = Dir.chdir(app_path) { `bin/rails db:migrate:status 2>&1` }
+        output = rails("db:migrate:status", allow_failure: true)
         assert_equal "Schema migrations table does not exist yet.\n", output
       end
 
       test "migration status" do
-        Dir.chdir(app_path) do
-          `bin/rails generate model user username:string password:string;
-           bin/rails generate migration add_email_to_users email:string;
-           bin/rails db:migrate`
+        rails "generate", "model", "user", "username:string", "password:string"
+        rails "generate", "migration", "add_email_to_users", "email:string"
+        rails "db:migrate"
 
-          output = `bin/rails db:migrate:status`
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{14}\s+Create users/, output)
-          assert_match(/up\s+\d{14}\s+Add email to users/, output)
+        assert_match(/up\s+\d{14}\s+Create users/, output)
+        assert_match(/up\s+\d{14}\s+Add email to users/, output)
 
-          `bin/rails db:rollback STEP=1`
-          output = `bin/rails db:migrate:status`
+        rails "db:rollback", "STEP=1"
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{14}\s+Create users/, output)
-          assert_match(/down\s+\d{14}\s+Add email to users/, output)
-        end
+        assert_match(/up\s+\d{14}\s+Create users/, output)
+        assert_match(/down\s+\d{14}\s+Add email to users/, output)
       end
 
       test "migration status without timestamps" do
         add_to_config("config.active_record.timestamped_migrations = false")
 
-        Dir.chdir(app_path) do
-          `bin/rails generate model user username:string password:string;
-           bin/rails generate migration add_email_to_users email:string;
-           bin/rails db:migrate`
+        rails "generate", "model", "user", "username:string", "password:string"
+        rails "generate", "migration", "add_email_to_users", "email:string"
+        rails "db:migrate"
 
-          output = `bin/rails db:migrate:status`
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{3,}\s+Create users/, output)
-          assert_match(/up\s+\d{3,}\s+Add email to users/, output)
+        assert_match(/up\s+\d{3,}\s+Create users/, output)
+        assert_match(/up\s+\d{3,}\s+Add email to users/, output)
 
-          `bin/rails db:rollback STEP=1`
-          output = `bin/rails db:migrate:status`
+        rails "db:rollback", "STEP=1"
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{3,}\s+Create users/, output)
-          assert_match(/down\s+\d{3,}\s+Add email to users/, output)
-        end
+        assert_match(/up\s+\d{3,}\s+Create users/, output)
+        assert_match(/down\s+\d{3,}\s+Add email to users/, output)
       end
 
       test "migration status after rollback and redo" do
-        Dir.chdir(app_path) do
-          `bin/rails generate model user username:string password:string;
-           bin/rails generate migration add_email_to_users email:string;
-           bin/rails db:migrate`
+        rails "generate", "model", "user", "username:string", "password:string"
+        rails "generate", "migration", "add_email_to_users", "email:string"
+        rails "db:migrate"
 
-          output = `bin/rails db:migrate:status`
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{14}\s+Create users/, output)
-          assert_match(/up\s+\d{14}\s+Add email to users/, output)
+        assert_match(/up\s+\d{14}\s+Create users/, output)
+        assert_match(/up\s+\d{14}\s+Add email to users/, output)
 
-          `bin/rails db:rollback STEP=2`
-          output = `bin/rails db:migrate:status`
+        rails "db:rollback", "STEP=2"
+        output = rails("db:migrate:status")
 
-          assert_match(/down\s+\d{14}\s+Create users/, output)
-          assert_match(/down\s+\d{14}\s+Add email to users/, output)
+        assert_match(/down\s+\d{14}\s+Create users/, output)
+        assert_match(/down\s+\d{14}\s+Add email to users/, output)
 
-          `bin/rails db:migrate:redo`
-          output = `bin/rails db:migrate:status`
+        rails "db:migrate:redo"
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{14}\s+Create users/, output)
-          assert_match(/up\s+\d{14}\s+Add email to users/, output)
-        end
+        assert_match(/up\s+\d{14}\s+Create users/, output)
+        assert_match(/up\s+\d{14}\s+Add email to users/, output)
       end
 
       test "migration status after rollback and forward" do
-        Dir.chdir(app_path) do
-          `bin/rails generate model user username:string password:string;
-           bin/rails generate migration add_email_to_users email:string;
-           bin/rails db:migrate`
+        rails "generate", "model", "user", "username:string", "password:string"
+        rails "generate", "migration", "add_email_to_users", "email:string"
+        rails "db:migrate"
 
-          output = `bin/rails db:migrate:status`
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{14}\s+Create users/, output)
-          assert_match(/up\s+\d{14}\s+Add email to users/, output)
+        assert_match(/up\s+\d{14}\s+Create users/, output)
+        assert_match(/up\s+\d{14}\s+Add email to users/, output)
 
-          `bin/rails db:rollback STEP=2`
-          output = `bin/rails db:migrate:status`
+        rails "db:rollback", "STEP=2"
+        output = rails("db:migrate:status")
 
-          assert_match(/down\s+\d{14}\s+Create users/, output)
-          assert_match(/down\s+\d{14}\s+Add email to users/, output)
+        assert_match(/down\s+\d{14}\s+Create users/, output)
+        assert_match(/down\s+\d{14}\s+Add email to users/, output)
 
-          `bin/rails db:forward STEP=2`
-          output = `bin/rails db:migrate:status`
+        rails "db:forward", "STEP=2"
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{14}\s+Create users/, output)
-          assert_match(/up\s+\d{14}\s+Add email to users/, output)
-        end
+        assert_match(/up\s+\d{14}\s+Create users/, output)
+        assert_match(/up\s+\d{14}\s+Add email to users/, output)
       end
 
       test "raise error on any move when current migration does not exist" do
         Dir.chdir(app_path) do
-          `bin/rails generate model user username:string password:string;
-           bin/rails generate migration add_email_to_users email:string;
-           bin/rails db:migrate
-           rm db/migrate/*email*.rb`
+          rails "generate", "model", "user", "username:string", "password:string"
+          rails "generate", "migration", "add_email_to_users", "email:string"
+          rails "db:migrate"
+          `rm db/migrate/*email*.rb`
 
-          output = `bin/rails db:migrate:status`
+          output = rails("db:migrate:status")
           assert_match(/up\s+\d{14}\s+Create users/, output)
           assert_match(/up\s+\d{14}\s+\** NO FILE \**/, output)
 
-          output = `bin/rails db:rollback 2>&1`
+          output = rails("db:rollback", allow_failure: true)
           assert_match(/rails aborted!/, output)
           assert_match(/ActiveRecord::UnknownMigrationVersionError:/, output)
           assert_match(/No migration with version number\s\d{14}\./, output)
 
-          output = `bin/rails db:migrate:status`
+          output = rails("db:migrate:status")
           assert_match(/up\s+\d{14}\s+Create users/, output)
           assert_match(/up\s+\d{14}\s+\** NO FILE \**/, output)
 
-          output = `bin/rails db:forward 2>&1`
+          output = rails("db:forward", allow_failure: true)
           assert_match(/rails aborted!/, output)
           assert_match(/ActiveRecord::UnknownMigrationVersionError:/, output)
           assert_match(/No migration with version number\s\d{14}\./, output)
 
-          output = `bin/rails db:migrate:status`
+          output = rails("db:migrate:status")
           assert_match(/up\s+\d{14}\s+Create users/, output)
           assert_match(/up\s+\d{14}\s+\** NO FILE \**/, output)
         end
       end
 
+      test "raise error on any move when target migration does not exist" do
+        app_file "db/migrate/01_one_migration.rb", <<-MIGRATION
+          class OneMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        app_file "db/migrate/02_two_migration.rb", <<-MIGRATION
+          class TwoMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        rails "db:migrate"
+
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
+
+        output = rails("db:migrate", "VERSION=3", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/ActiveRecord::UnknownMigrationVersionError:/, output)
+        assert_match(/No migration with version number 3/, output)
+
+        output = rails("db:migrate:status")
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
+      end
+
+      test "raise error on any move when VERSION has invalid format" do
+        output = rails("db:migrate", "VERSION=unknown", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate", "VERSION=0.1.11", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate", "VERSION=1.1.11", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate", "VERSION='0 '", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate", "VERSION=1.", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate", "VERSION=1_", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate", "VERSION=1_name", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate:redo", "VERSION=unknown", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate:up", "VERSION=unknown", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+
+        output = rails("db:migrate:down", "VERSION=unknown", allow_failure: true)
+        assert_match(/rails aborted!/, output)
+        assert_match(/Invalid format of target version/, output)
+      end
+
       test "migration status after rollback and redo without timestamps" do
         add_to_config("config.active_record.timestamped_migrations = false")
 
-        Dir.chdir(app_path) do
-          `bin/rails generate model user username:string password:string;
-           bin/rails generate migration add_email_to_users email:string;
-           bin/rails db:migrate`
+        rails "generate", "model", "user", "username:string", "password:string"
+        rails "generate", "migration", "add_email_to_users", "email:string"
+        rails "db:migrate"
 
-          output = `bin/rails db:migrate:status`
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{3,}\s+Create users/, output)
-          assert_match(/up\s+\d{3,}\s+Add email to users/, output)
+        assert_match(/up\s+\d{3,}\s+Create users/, output)
+        assert_match(/up\s+\d{3,}\s+Add email to users/, output)
 
-          `bin/rails db:rollback STEP=2`
-          output = `bin/rails db:migrate:status`
+        rails "db:rollback", "STEP=2"
+        output = rails("db:migrate:status")
 
-          assert_match(/down\s+\d{3,}\s+Create users/, output)
-          assert_match(/down\s+\d{3,}\s+Add email to users/, output)
+        assert_match(/down\s+\d{3,}\s+Create users/, output)
+        assert_match(/down\s+\d{3,}\s+Add email to users/, output)
 
-          `bin/rails db:migrate:redo`
-          output = `bin/rails db:migrate:status`
+        rails "db:migrate:redo"
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+\d{3,}\s+Create users/, output)
-          assert_match(/up\s+\d{3,}\s+Add email to users/, output)
-        end
+        assert_match(/up\s+\d{3,}\s+Create users/, output)
+        assert_match(/up\s+\d{3,}\s+Add email to users/, output)
       end
 
       test "running migrations with not timestamp head migration files" do
-        Dir.chdir(app_path) do
-
-          app_file "db/migrate/1_one_migration.rb", <<-MIGRATION
-            class OneMigration < ActiveRecord::Migration::Current
-            end
-          MIGRATION
+        app_file "db/migrate/1_one_migration.rb", <<-MIGRATION
+          class OneMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
 
-          app_file "db/migrate/02_two_migration.rb", <<-MIGRATION
-            class TwoMigration < ActiveRecord::Migration::Current
-            end
-          MIGRATION
+        app_file "db/migrate/02_two_migration.rb", <<-MIGRATION
+          class TwoMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
 
-          `bin/rails db:migrate`
+        rails "db:migrate"
 
-          output = `bin/rails db:migrate:status`
+        output = rails("db:migrate:status")
 
-          assert_match(/up\s+001\s+One migration/, output)
-          assert_match(/up\s+002\s+Two migration/, output)
-        end
+        assert_match(/up\s+001\s+One migration/, output)
+        assert_match(/up\s+002\s+Two migration/, output)
       end
 
       test "schema generation when dump_schema_after_migration is set" do
         add_to_config("config.active_record.dump_schema_after_migration = false")
 
         Dir.chdir(app_path) do
-          `bin/rails generate model book title:string`
-          output = `bin/rails generate model author name:string`
+          rails "generate", "model", "book", "title:string"
+          output = rails("generate", "model", "author", "name:string")
           version = output =~ %r{[^/]+db/migrate/(\d+)_create_authors\.rb} && $1
 
-          `bin/rails db:migrate db:rollback db:forward db:migrate:up db:migrate:down VERSION=#{version}`
-          assert !File.exist?("db/schema.rb"), "should not dump schema when configured not to"
+          rails "db:migrate", "db:rollback", "db:forward", "db:migrate:up", "db:migrate:down", "VERSION=#{version}"
+          assert_not File.exist?("db/schema.rb"), "should not dump schema when configured not to"
         end
 
         add_to_config("config.active_record.dump_schema_after_migration = true")
 
         Dir.chdir(app_path) do
-          `bin/rails generate model reviews book_id:integer`
-          `bin/rails db:migrate`
+          rails "generate", "model", "reviews", "book_id:integer"
+          rails "db:migrate"
 
           structure_dump = File.read("db/schema.rb")
           assert_match(/create_table "reviews"/, structure_dump)
@@ -280,8 +433,8 @@ module ApplicationTests
 
       test "default schema generation after migration" do
         Dir.chdir(app_path) do
-          `bin/rails generate model book title:string;
-           bin/rails db:migrate`
+          rails "generate", "model", "book", "title:string"
+          rails "db:migrate"
 
           structure_dump = File.read("db/schema.rb")
           assert_match(/create_table "books"/, structure_dump)
@@ -290,12 +443,12 @@ module ApplicationTests
 
       test "migration status migrated file is deleted" do
         Dir.chdir(app_path) do
-          `bin/rails generate model user username:string password:string;
-           bin/rails generate migration add_email_to_users email:string;
-           bin/rails db:migrate
-           rm db/migrate/*email*.rb`
+          rails "generate", "model", "user", "username:string", "password:string"
+          rails "generate", "migration", "add_email_to_users", "email:string"
+          rails "db:migrate"
+          `rm db/migrate/*email*.rb`
 
-          output = `bin/rails db:migrate:status`
+          output = rails("db:migrate:status")
 
           assert_match(/up\s+\d{14}\s+Create users/, output)
           assert_match(/up\s+\d{14}\s+\** NO FILE \**/, output)
diff --git a/railties/test/application/rake/multi_dbs_test.rb b/railties/test/application/rake/multi_dbs_test.rb
new file mode 100644
index 0000000000..07d96fcb56
--- /dev/null
+++ b/railties/test/application/rake/multi_dbs_test.rb
@@ -0,0 +1,164 @@
+# frozen_string_literal: true
+
+require "isolation/abstract_unit"
+
+module ApplicationTests
+  module RakeTests
+    class RakeMultiDbsTest < ActiveSupport::TestCase
+      include ActiveSupport::Testing::Isolation
+
+      def setup
+        build_app(multi_db: true)
+        FileUtils.rm_rf("#{app_path}/config/environments")
+      end
+
+      def teardown
+        teardown_app
+      end
+
+      def db_create_and_drop(namespace, expected_database, environment_loaded: true)
+        Dir.chdir(app_path) do
+          output = rails("db:create")
+          assert_match(/Created database/, output)
+          assert_match_namespace(namespace, output)
+          assert File.exist?(expected_database)
+
+          output = rails("db:drop")
+          assert_match(/Dropped database/, output)
+          assert_match_namespace(namespace, output)
+          assert_not File.exist?(expected_database)
+        end
+      end
+
+      def db_create_and_drop_namespace(namespace, expected_database, environment_loaded: true)
+        Dir.chdir(app_path) do
+          output = rails("db:create:#{namespace}")
+          assert_match(/Created database/, output)
+          assert_match_namespace(namespace, output)
+          assert File.exist?(expected_database)
+
+          output = rails("db:drop:#{namespace}")
+          assert_match(/Dropped database/, output)
+          assert_match_namespace(namespace, output)
+          assert_not File.exist?(expected_database)
+        end
+      end
+
+      def assert_match_namespace(namespace, output)
+        if namespace == "primary"
+          assert_match(/#{Rails.env}.sqlite3/, output)
+        else
+          assert_match(/#{Rails.env}_#{namespace}.sqlite3/, output)
+        end
+      end
+
+      def db_migrate_and_schema_dump_and_load(namespace, expected_database, format)
+        Dir.chdir(app_path) do
+          rails "generate", "model", "book", "title:string"
+          rails "generate", "model", "dog", "name:string"
+          write_models_for_animals
+          rails "db:migrate", "db:#{format}:dump"
+
+          if format == "schema"
+            schema_dump = File.read("db/#{format}.rb")
+            schema_dump_animals = File.read("db/animals_#{format}.rb")
+            assert_match(/create_table \"books\"/, schema_dump)
+            assert_match(/create_table \"dogs\"/, schema_dump_animals)
+          else
+            schema_dump = File.read("db/#{format}.sql")
+            schema_dump_animals = File.read("db/animals_#{format}.sql")
+            assert_match(/CREATE TABLE (?:IF NOT EXISTS )?\"books\"/, schema_dump)
+            assert_match(/CREATE TABLE (?:IF NOT EXISTS )?\"dogs\"/, schema_dump_animals)
+          end
+
+          rails "db:#{format}:load"
+
+          ar_tables = lambda { rails("runner", "p ActiveRecord::Base.connection.tables").strip }
+          animals_tables = lambda { rails("runner", "p AnimalsBase.connection.tables").strip }
+
+          assert_equal '["schema_migrations", "ar_internal_metadata", "books"]', ar_tables[]
+          assert_equal '["schema_migrations", "ar_internal_metadata", "dogs"]', animals_tables[]
+        end
+      end
+
+      def db_migrate_namespaced(namespace, expected_database)
+        Dir.chdir(app_path) do
+          rails "generate", "model", "book", "title:string"
+          rails "generate", "model", "dog", "name:string"
+          write_models_for_animals
+          output = rails("db:migrate:#{namespace}")
+          if namespace == "primary"
+            assert_match(/CreateBooks: migrated/, output)
+          else
+            assert_match(/CreateDogs: migrated/, output)
+          end
+        end
+      end
+
+      def write_models_for_animals
+        # make a directory for the animals migration
+        FileUtils.mkdir_p("#{app_path}/db/animals_migrate")
+        # move the dogs migration if it unless it already lives there
+        FileUtils.mv(Dir.glob("#{app_path}/db/migrate/**/*dogs.rb").first, "db/animals_migrate/") unless Dir.glob("#{app_path}/db/animals_migrate/**/*dogs.rb").first
+        # delete the dogs migration if it's still present in the
+        # migrate folder. This is necessary because sometimes
+        # the code isn't fast enough and an extra migration gets made
+        FileUtils.rm(Dir.glob("#{app_path}/db/migrate/**/*dogs.rb").first) if Dir.glob("#{app_path}/db/migrate/**/*dogs.rb").first
+
+        # change the base of the dog model
+        app_path("/app/models/dog.rb") do |file_name|
+          file = File.read("#{app_path}/app/models/dog.rb")
+          file.sub!(/ApplicationRecord/, "AnimalsBase")
+          File.write(file_name, file)
+        end
+
+        # create the base model for dog to inherit from
+        File.open("#{app_path}/app/models/animals_base.rb", "w") do |file|
+          file.write(<<-EOS
+class AnimalsBase < ActiveRecord::Base
+  self.abstract_class = true
+
+  establish_connection :animals
+end
+EOS
+)
+        end
+      end
+
+      test "db:create and db:drop works on all databases for env" do
+        require "#{app_path}/config/environment"
+        ActiveRecord::Base.configurations[Rails.env].each do |namespace, config|
+          db_create_and_drop namespace, config["database"]
+        end
+      end
+
+      test "db:create:namespace and db:drop:namespace works on specified databases" do
+        require "#{app_path}/config/environment"
+        ActiveRecord::Base.configurations[Rails.env].each do |namespace, config|
+          db_create_and_drop_namespace namespace, config["database"]
+        end
+      end
+
+      test "db:migrate and db:schema:dump and db:schema:load works on all databases" do
+        require "#{app_path}/config/environment"
+        ActiveRecord::Base.configurations[Rails.env].each do |namespace, config|
+          db_migrate_and_schema_dump_and_load namespace, config["database"], "schema"
+        end
+      end
+
+      test "db:migrate and db:structure:dump and db:structure:load works on all databases" do
+        require "#{app_path}/config/environment"
+        ActiveRecord::Base.configurations[Rails.env].each do |namespace, config|
+          db_migrate_and_schema_dump_and_load namespace, config["database"], "structure"
+        end
+      end
+
+      test "db:migrate:namespace works" do
+        require "#{app_path}/config/environment"
+        ActiveRecord::Base.configurations[Rails.env].each do |namespace, config|
+          db_migrate_namespaced namespace, config["database"]
+        end
+      end
+    end
+  end
+end
diff --git a/railties/test/application/rake/notes_test.rb b/railties/test/application/rake/notes_test.rb
index 8e9fe9b6b4..d73e5cdfa3 100644
--- a/railties/test/application/rake/notes_test.rb
+++ b/railties/test/application/rake/notes_test.rb
@@ -101,7 +101,7 @@ module ApplicationTests
           task :notes_custom do
             tags = 'TODO|FIXME'
             opts = { dirs: %w(lib test), tag: true }
-            SourceAnnotationExtractor.enumerate(tags, opts)
+            Rails::SourceAnnotationExtractor.enumerate(tags, opts)
           end
         EOS
 
diff --git a/railties/test/application/rake/restart_test.rb b/railties/test/application/rake/restart_test.rb
index ed96dcb6b1..8614560bf2 100644
--- a/railties/test/application/rake/restart_test.rb
+++ b/railties/test/application/rake/restart_test.rb
@@ -17,12 +17,12 @@ module ApplicationTests
 
       test "rails restart touches tmp/restart.txt" do
         Dir.chdir(app_path) do
-          `bin/rails restart`
+          rails "restart"
           assert File.exist?("tmp/restart.txt")
 
           prev_mtime = File.mtime("tmp/restart.txt")
           sleep(1)
-          `bin/rails restart`
+          rails "restart"
           curr_mtime = File.mtime("tmp/restart.txt")
           assert_not_equal prev_mtime, curr_mtime
         end
@@ -31,7 +31,7 @@ module ApplicationTests
       test "rails restart should work even if tmp folder does not exist" do
         Dir.chdir(app_path) do
           FileUtils.remove_dir("tmp")
-          `bin/rails restart`
+          rails "restart"
           assert File.exist?("tmp/restart.txt")
         end
       end
diff --git a/railties/test/application/rake/tmp_test.rb b/railties/test/application/rake/tmp_test.rb
index 8641d140cb..048fd7adcc 100644
--- a/railties/test/application/rake/tmp_test.rb
+++ b/railties/test/application/rake/tmp_test.rb
@@ -26,7 +26,7 @@ module ApplicationTests
           FileUtils.mkdir_p("tmp/screenshots")
           FileUtils.touch("tmp/screenshots/fail.png")
 
-          `rails tmp:clear`
+          rails "tmp:clear"
 
           assert_not File.exist?("tmp/cache/cache_file")
           assert_not File.exist?("tmp/sockets/socket_file")
@@ -36,9 +36,7 @@ module ApplicationTests
 
       test "tmp:clear should work if folder missing" do
         FileUtils.remove_dir("#{app_path}/tmp")
-        errormsg = Dir.chdir(app_path) { `bin/rails tmp:clear` }
-        assert_predicate $?, :success?
-        assert_empty errormsg
+        rails "tmp:clear"
       end
     end
   end
diff --git a/railties/test/application/rake_test.rb b/railties/test/application/rake_test.rb
index fe59bed874..1522a2bbc5 100644
--- a/railties/test/application/rake_test.rb
+++ b/railties/test/application/rake_test.rb
@@ -1,11 +1,11 @@
 # frozen_string_literal: true
 
 require "isolation/abstract_unit"
-require "active_support/core_ext/string/strip"
+require "env_helpers"
 
 module ApplicationTests
   class RakeTest < ActiveSupport::TestCase
-    include ActiveSupport::Testing::Isolation
+    include ActiveSupport::Testing::Isolation, EnvHelpers
 
     def setup
       build_app
@@ -26,22 +26,22 @@ module ApplicationTests
     end
 
     test "task is protected when previous migration was production" do
-      Dir.chdir(app_path) do
-        output = `bin/rails generate model product name:string;
-         env RAILS_ENV=production bin/rails db:create db:migrate;
-         env RAILS_ENV=production bin/rails db:test:prepare test 2>&1`
+      with_rails_env "production" do
+        rails "generate", "model", "product", "name:string"
+        rails "db:create", "db:migrate"
+        output = rails("db:test:prepare", allow_failure: true)
 
         assert_match(/ActiveRecord::ProtectedEnvironmentError/, output)
       end
     end
 
     def test_not_protected_when_previous_migration_was_not_production
-      Dir.chdir(app_path) do
-        output = `bin/rails generate model product name:string;
-         env RAILS_ENV=test bin/rails db:create db:migrate;
-         env RAILS_ENV=test bin/rails db:test:prepare test 2>&1`
+      with_rails_env "test" do
+        rails "generate", "model", "product", "name:string"
+        rails "db:create", "db:migrate"
+        output = rails("db:test:prepare", "test")
 
-        refute_match(/ActiveRecord::ProtectedEnvironmentError/, output)
+        assert_no_match(/ActiveRecord::ProtectedEnvironmentError/, output)
       end
     end
 
@@ -56,7 +56,7 @@ module ApplicationTests
         Rails.application.initialize!
       RUBY
 
-      assert_match("SuperMiddleware", Dir.chdir(app_path) { `bin/rails middleware` })
+      assert_match("SuperMiddleware", rails("middleware"))
     end
 
     def test_initializers_are_executed_in_rake_tasks
@@ -71,7 +71,7 @@ module ApplicationTests
         end
       RUBY
 
-      output = Dir.chdir(app_path) { `bin/rails do_nothing` }
+      output = rails("do_nothing")
       assert_match "Doing something...", output
     end
 
@@ -92,7 +92,7 @@ module ApplicationTests
         end
       RUBY
 
-      output = Dir.chdir(app_path) { `bin/rails do_nothing` }
+      output = rails("do_nothing")
       assert_match "Hello world", output
     end
 
@@ -100,6 +100,7 @@ module ApplicationTests
       add_to_config <<-RUBY
         rake_tasks do
           task do_nothing: :environment do
+            puts 'There is nothing'
           end
         end
       RUBY
@@ -112,162 +113,13 @@ module ApplicationTests
         raise 'should not be pre-required for rake even eager_load=true'
       RUBY
 
-      Dir.chdir(app_path) do
-        assert system("bin/rails do_nothing RAILS_ENV=production"),
-               "should not be pre-required for rake even eager_load=true"
-      end
+      output = rails("do_nothing", "RAILS_ENV=production")
+      assert_match "There is nothing", output
     end
 
     def test_code_statistics_sanity
       assert_match "Code LOC: 25     Test LOC: 0     Code to Test Ratio: 1:0.0",
-        Dir.chdir(app_path) { `bin/rails stats` }
-    end
-
-    def test_rails_routes_calls_the_route_inspector
-      app_file "config/routes.rb", <<-RUBY
-        Rails.application.routes.draw do
-          get '/cart', to: 'cart#show'
-        end
-      RUBY
-
-      output = Dir.chdir(app_path) { `bin/rails routes` }
-      assert_equal <<-MESSAGE.strip_heredoc, output
-                         Prefix Verb URI Pattern                                                                       Controller#Action
-                           cart GET  /cart(.:format)                                                                   cart#show
-             rails_service_blob GET  /rails/active_storage/blobs/:signed_id/*filename(.:format)                        active_storage/blobs#show
-           rails_blob_variation GET  /rails/active_storage/variants/:signed_blob_id/:variation_key/*filename(.:format) active_storage/variants#show
-             rails_disk_service GET  /rails/active_storage/disk/:encoded_key/*filename(.:format)                       active_storage/disk#show
-      update_rails_disk_service PUT  /rails/active_storage/disk/:encoded_token(.:format)                               active_storage/disk#update
-           rails_direct_uploads POST /rails/active_storage/direct_uploads(.:format)                                    active_storage/direct_uploads#create
-      MESSAGE
-    end
-
-    def test_singular_resource_output_in_rake_routes
-      app_file "config/routes.rb", <<-RUBY
-        Rails.application.routes.draw do
-          resource :post
-        end
-      RUBY
-
-      expected_output = ["   Prefix Verb   URI Pattern          Controller#Action",
-                         " new_post GET    /post/new(.:format)  posts#new",
-                         "edit_post GET    /post/edit(.:format) posts#edit",
-                         "     post GET    /post(.:format)      posts#show",
-                         "          PATCH  /post(.:format)      posts#update",
-                         "          PUT    /post(.:format)      posts#update",
-                         "          DELETE /post(.:format)      posts#destroy",
-                         "          POST   /post(.:format)      posts#create\n"].join("\n")
-
-      output = Dir.chdir(app_path) { `bin/rails routes -c PostController` }
-      assert_equal expected_output, output
-    end
-
-    def test_rails_routes_with_global_search_key
-      app_file "config/routes.rb", <<-RUBY
-        Rails.application.routes.draw do
-          get '/cart', to: 'cart#show'
-          post '/cart', to: 'cart#create'
-          get '/basketballs', to: 'basketball#index'
-        end
-      RUBY
-
-      output = Dir.chdir(app_path) { `bin/rails routes -g show` }
-      assert_equal <<-MESSAGE.strip_heredoc, output
-                         Prefix Verb URI Pattern                                                                       Controller#Action
-                           cart GET  /cart(.:format)                                                                   cart#show
-             rails_service_blob GET  /rails/active_storage/blobs/:signed_id/*filename(.:format)                        active_storage/blobs#show
-           rails_blob_variation GET  /rails/active_storage/variants/:signed_blob_id/:variation_key/*filename(.:format) active_storage/variants#show
-             rails_disk_service GET  /rails/active_storage/disk/:encoded_key/*filename(.:format)                       active_storage/disk#show
-      MESSAGE
-
-      output = Dir.chdir(app_path) { `bin/rails routes -g POST` }
-      assert_equal <<-MESSAGE.strip_heredoc, output
-                         Prefix Verb URI Pattern                                    Controller#Action
-                                POST /cart(.:format)                                cart#create
-           rails_direct_uploads POST /rails/active_storage/direct_uploads(.:format) active_storage/direct_uploads#create
-      MESSAGE
-
-      output = Dir.chdir(app_path) { `bin/rails routes -g basketballs` }
-      assert_equal "     Prefix Verb URI Pattern            Controller#Action\n" \
-                   "basketballs GET  /basketballs(.:format) basketball#index\n", output
-    end
-
-    def test_rails_routes_with_controller_search_key
-      app_file "config/routes.rb", <<-RUBY
-        Rails.application.routes.draw do
-          get '/cart', to: 'cart#show'
-          get '/basketball', to: 'basketball#index'
-        end
-      RUBY
-
-      output = Dir.chdir(app_path) { `bin/rails routes -c cart` }
-      assert_equal "Prefix Verb URI Pattern     Controller#Action\n  cart GET  /cart(.:format) cart#show\n", output
-
-      output = Dir.chdir(app_path) { `bin/rails routes -c Cart` }
-      assert_equal "Prefix Verb URI Pattern     Controller#Action\n  cart GET  /cart(.:format) cart#show\n", output
-
-      output = Dir.chdir(app_path) { `bin/rails routes -c CartController` }
-      assert_equal "Prefix Verb URI Pattern     Controller#Action\n  cart GET  /cart(.:format) cart#show\n", output
-    end
-
-    def test_rails_routes_with_namespaced_controller_search_key
-      app_file "config/routes.rb", <<-RUBY
-        Rails.application.routes.draw do
-          namespace :admin do
-            resource :post
-          end
-        end
-      RUBY
-      expected_output = ["         Prefix Verb   URI Pattern                Controller#Action",
-                         " new_admin_post GET    /admin/post/new(.:format)  admin/posts#new",
-                         "edit_admin_post GET    /admin/post/edit(.:format) admin/posts#edit",
-                         "     admin_post GET    /admin/post(.:format)      admin/posts#show",
-                         "                PATCH  /admin/post(.:format)      admin/posts#update",
-                         "                PUT    /admin/post(.:format)      admin/posts#update",
-                         "                DELETE /admin/post(.:format)      admin/posts#destroy",
-                         "                POST   /admin/post(.:format)      admin/posts#create\n"].join("\n")
-
-      output = Dir.chdir(app_path) { `bin/rails routes -c Admin::PostController` }
-      assert_equal expected_output, output
-
-      output = Dir.chdir(app_path) { `bin/rails routes -c PostController` }
-      assert_equal expected_output, output
-    end
-
-    def test_rails_routes_displays_message_when_no_routes_are_defined
-      app_file "config/routes.rb", <<-RUBY
-        Rails.application.routes.draw do
-        end
-      RUBY
-
-      assert_equal <<-MESSAGE.strip_heredoc, Dir.chdir(app_path) { `bin/rails routes` }
-                         Prefix Verb URI Pattern                                                                       Controller#Action
-             rails_service_blob GET  /rails/active_storage/blobs/:signed_id/*filename(.:format)                        active_storage/blobs#show
-           rails_blob_variation GET  /rails/active_storage/variants/:signed_blob_id/:variation_key/*filename(.:format) active_storage/variants#show
-             rails_disk_service GET  /rails/active_storage/disk/:encoded_key/*filename(.:format)                       active_storage/disk#show
-      update_rails_disk_service PUT  /rails/active_storage/disk/:encoded_token(.:format)                               active_storage/disk#update
-           rails_direct_uploads POST /rails/active_storage/direct_uploads(.:format)                                    active_storage/direct_uploads#create
-      MESSAGE
-    end
-
-    def test_rake_routes_with_rake_options
-      app_file "config/routes.rb", <<-RUBY
-        Rails.application.routes.draw do
-          get '/cart', to: 'cart#show'
-        end
-      RUBY
-
-      output = Dir.chdir(app_path) { `bin/rake --rakefile Rakefile routes` }
-
-      assert_equal <<-MESSAGE.strip_heredoc, output
-                         Prefix Verb URI Pattern                                                                       Controller#Action
-                           cart GET  /cart(.:format)                                                                   cart#show
-             rails_service_blob GET  /rails/active_storage/blobs/:signed_id/*filename(.:format)                        active_storage/blobs#show
-           rails_blob_variation GET  /rails/active_storage/variants/:signed_blob_id/:variation_key/*filename(.:format) active_storage/variants#show
-             rails_disk_service GET  /rails/active_storage/disk/:encoded_key/*filename(.:format)                       active_storage/disk#show
-      update_rails_disk_service PUT  /rails/active_storage/disk/:encoded_token(.:format)                               active_storage/disk#update
-           rails_direct_uploads POST /rails/active_storage/direct_uploads(.:format)                                    active_storage/direct_uploads#create
-      MESSAGE
+        rails("stats")
     end
 
     def test_logger_is_flushed_when_exiting_production_rake_tasks
@@ -279,44 +131,37 @@ module ApplicationTests
         end
       RUBY
 
-      output = Dir.chdir(app_path) { `bin/rails log_something RAILS_ENV=production && cat log/production.log` }
-      assert_match "Sample log message", output
+      rails "log_something", "RAILS_ENV=production"
+      assert_match "Sample log message", File.read("#{app_path}/log/production.log")
     end
 
     def test_loading_specific_fixtures
-      Dir.chdir(app_path) do
-        `bin/rails generate model user username:string password:string;
-         bin/rails generate model product name:string;
-         bin/rails db:migrate`
-      end
+      rails "generate", "model", "user", "username:string", "password:string"
+      rails "generate", "model", "product", "name:string"
+      rails "db:migrate"
 
       require "#{rails_root}/config/environment"
 
       # loading a specific fixture
-      errormsg = Dir.chdir(app_path) { `bin/rails db:fixtures:load FIXTURES=products` }
-      assert $?.success?, errormsg
+      rails "db:fixtures:load", "FIXTURES=products"
 
       assert_equal 2, ::AppTemplate::Application::Product.count
       assert_equal 0, ::AppTemplate::Application::User.count
     end
 
     def test_loading_only_yml_fixtures
-      Dir.chdir(app_path) do
-        `bin/rails db:migrate`
-      end
+      rails "db:migrate"
 
       app_file "test/fixtures/products.csv", ""
 
       require "#{rails_root}/config/environment"
-      errormsg = Dir.chdir(app_path) { `bin/rails db:fixtures:load` }
-      assert $?.success?, errormsg
+      rails "db:fixtures:load"
     end
 
     def test_scaffold_tests_pass_by_default
-      output = Dir.chdir(app_path) do
-        `bin/rails generate scaffold user username:string password:string;
-         RAILS_ENV=test bin/rails db:migrate test`
-      end
+      rails "generate", "scaffold", "user", "username:string", "password:string"
+      with_rails_env("test") { rails("db:migrate") }
+      output = rails("test")
 
       assert_match(/7 runs, 9 assertions, 0 failures, 0 errors/, output)
       assert_no_match(/Errors running/, output)
@@ -332,22 +177,20 @@ module ApplicationTests
         end
       RUBY
 
-      output = Dir.chdir(app_path) do
-        `bin/rails generate scaffold user username:string password:string;
-         RAILS_ENV=test bin/rails db:migrate test`
-      end
+      rails "generate", "scaffold", "user", "username:string", "password:string"
+      with_rails_env("test") { rails("db:migrate") }
+      output = rails("test")
 
       assert_match(/5 runs, 7 assertions, 0 failures, 0 errors/, output)
       assert_no_match(/Errors running/, output)
     end
 
     def test_scaffold_with_references_columns_tests_pass_by_default
-      output = Dir.chdir(app_path) do
-        `bin/rails generate model Product;
-         bin/rails generate model Cart;
-         bin/rails generate scaffold LineItems product:references cart:belongs_to;
-         RAILS_ENV=test bin/rails db:migrate test`
-      end
+      rails "generate", "model", "Product"
+      rails "generate", "model", "Cart"
+      rails "generate", "scaffold", "LineItems", "product:references", "cart:belongs_to"
+      with_rails_env("test") { rails("db:migrate") }
+      output = rails("test")
 
       assert_match(/7 runs, 9 assertions, 0 failures, 0 errors/, output)
       assert_no_match(/Errors running/, output)
@@ -355,59 +198,47 @@ module ApplicationTests
 
     def test_db_test_prepare_when_using_sql_format
       add_to_config "config.active_record.schema_format = :sql"
-      output = Dir.chdir(app_path) do
-        `bin/rails generate scaffold user username:string;
-         bin/rails db:migrate;
-         bin/rails db:test:prepare 2>&1 --trace`
-      end
+      rails "generate", "scaffold", "user", "username:string"
+      rails "db:migrate"
+      output = rails("db:test:prepare", "--trace")
       assert_match(/Execute db:test:load_structure/, output)
     end
 
     def test_rake_dump_structure_should_respect_db_structure_env_variable
-      Dir.chdir(app_path) do
-        # ensure we have a schema_migrations table to dump
-        `bin/rails db:migrate db:structure:dump SCHEMA=db/my_structure.sql`
-      end
+      # ensure we have a schema_migrations table to dump
+      rails "db:migrate", "db:structure:dump", "SCHEMA=db/my_structure.sql"
       assert File.exist?(File.join(app_path, "db", "my_structure.sql"))
     end
 
     def test_rake_dump_structure_should_be_called_twice_when_migrate_redo
       add_to_config "config.active_record.schema_format = :sql"
 
-      output = Dir.chdir(app_path) do
-        `bin/rails g model post title:string;
-         bin/rails db:migrate:redo 2>&1 --trace;`
-      end
+      rails "g", "model", "post", "title:string"
+      output = rails("db:migrate:redo", "--trace")
 
       # expect only Invoke db:structure:dump (first_time)
       assert_no_match(/^\*\* Invoke db:structure:dump\s+$/, output)
     end
 
     def test_rake_dump_schema_cache
-      Dir.chdir(app_path) do
-        `bin/rails generate model post title:string;
-         bin/rails generate model product name:string;
-         bin/rails db:migrate db:schema:cache:dump`
-      end
+      rails "generate", "model", "post", "title:string"
+      rails "generate", "model", "product", "name:string"
+      rails "db:migrate", "db:schema:cache:dump"
       assert File.exist?(File.join(app_path, "db", "schema_cache.yml"))
     end
 
     def test_rake_clear_schema_cache
-      Dir.chdir(app_path) do
-        `bin/rails db:schema:cache:dump db:schema:cache:clear`
-      end
-      assert !File.exist?(File.join(app_path, "db", "schema_cache.yml"))
+      rails "db:schema:cache:dump", "db:schema:cache:clear"
+      assert_not File.exist?(File.join(app_path, "db", "schema_cache.yml"))
     end
 
     def test_copy_templates
-      Dir.chdir(app_path) do
-        `bin/rails app:templates:copy`
-        %w(controller mailer scaffold).each do |dir|
-          assert File.exist?(File.join(app_path, "lib", "templates", "erb", dir))
-        end
-        %w(controller helper scaffold_controller assets).each do |dir|
-          assert File.exist?(File.join(app_path, "lib", "templates", "rails", dir))
-        end
+      rails "app:templates:copy"
+      %w(controller mailer scaffold).each do |dir|
+        assert File.exist?(File.join(app_path, "lib", "templates", "erb", dir))
+      end
+      %w(controller helper scaffold_controller assets).each do |dir|
+        assert File.exist?(File.join(app_path, "lib", "templates", "rails", dir))
       end
     end
 
@@ -415,10 +246,7 @@ module ApplicationTests
       app_file "config/initializers/dummy.rb", "puts 'Hello, World!'"
       app_file "template.rb", ""
 
-      output = Dir.chdir(app_path) do
-        `bin/rails app:template LOCATION=template.rb`
-      end
-
+      output = rails("app:template", "LOCATION=template.rb")
       assert_match(/Hello, World!/, output)
     end
   end
diff --git a/railties/test/application/rendering_test.rb b/railties/test/application/rendering_test.rb
index 3724886c54..ab1591f388 100644
--- a/railties/test/application/rendering_test.rb
+++ b/railties/test/application/rendering_test.rb
@@ -4,7 +4,7 @@ require "isolation/abstract_unit"
 require "rack/test"
 
 module ApplicationTests
-  class RoutingTest < ActiveSupport::TestCase
+  class RenderingTest < ActiveSupport::TestCase
     include ActiveSupport::Testing::Isolation
     include Rack::Test::Methods
 
diff --git a/railties/test/application/runner_test.rb b/railties/test/application/runner_test.rb
index a66f288795..8f5f48c281 100644
--- a/railties/test/application/runner_test.rb
+++ b/railties/test/application/runner_test.rb
@@ -26,22 +26,19 @@ module ApplicationTests
     end
 
     def test_should_include_runner_in_shebang_line_in_help_without_option
-      assert_match "/rails runner", Dir.chdir(app_path) { `bin/rails runner` }
+      assert_match "/rails runner", rails("runner", allow_failure: true)
     end
 
     def test_should_include_runner_in_shebang_line_in_help
-      assert_match "/rails runner", Dir.chdir(app_path) { `bin/rails runner --help` }
+      assert_match "/rails runner", rails("runner", "--help")
     end
 
     def test_should_run_ruby_statement
-      assert_match "42", Dir.chdir(app_path) { `bin/rails runner "puts User.count"` }
+      assert_match "42", rails("runner", "puts User.count")
     end
 
     def test_should_set_argv_when_running_code
-      output = Dir.chdir(app_path) {
-        # Both long and short args, at start and end of ARGV
-        `bin/rails runner "puts ARGV.join(',')" --foo a1 -b a2 a3 --moo`
-      }
+      output = rails("runner", "puts ARGV.join(',')", "--foo", "a1", "-b", "a2", "a3", "--moo")
       assert_equal "--foo,a1,-b,a2,a3,--moo", output.chomp
     end
 
@@ -50,7 +47,7 @@ module ApplicationTests
       puts User.count
       SCRIPT
 
-      assert_match "42", Dir.chdir(app_path) { `bin/rails runner "bin/count_users.rb"` }
+      assert_match "42", rails("runner", "bin/count_users.rb")
     end
 
     def test_no_minitest_loaded_in_production_mode
@@ -67,7 +64,7 @@ module ApplicationTests
       puts $0
       SCRIPT
 
-      assert_match "bin/dollar0.rb", Dir.chdir(app_path) { `bin/rails runner "bin/dollar0.rb"` }
+      assert_match "bin/dollar0.rb", rails("runner", "bin/dollar0.rb")
     end
 
     def test_should_set_dollar_program_name_to_file
@@ -75,7 +72,7 @@ module ApplicationTests
       puts $PROGRAM_NAME
       SCRIPT
 
-      assert_match "bin/program_name.rb", Dir.chdir(app_path) { `bin/rails runner "bin/program_name.rb"` }
+      assert_match "bin/program_name.rb", rails("runner", "bin/program_name.rb")
     end
 
     def test_passes_extra_args_to_file
@@ -83,7 +80,7 @@ module ApplicationTests
       p ARGV
       SCRIPT
 
-      assert_match %w( a b ).to_s, Dir.chdir(app_path) { `bin/rails runner "bin/program_name.rb" a b` }
+      assert_match %w( a b ).to_s, rails("runner", "bin/program_name.rb", "a", "b")
     end
 
     def test_should_run_stdin
@@ -101,35 +98,47 @@ module ApplicationTests
         end
       RUBY
 
-      assert_match "true", Dir.chdir(app_path) { `bin/rails runner "puts Rails.application.config.ran"` }
+      assert_match "true", rails("runner", "puts Rails.application.config.ran")
     end
 
     def test_default_environment
-      assert_match "development", Dir.chdir(app_path) { `bin/rails runner "puts Rails.env"` }
+      assert_match "development", rails("runner", "puts Rails.env")
     end
 
     def test_runner_detects_syntax_errors
-      output = Dir.chdir(app_path) { `bin/rails runner "puts 'hello world" 2>&1` }
-      assert_not $?.success?
+      output = rails("runner", "puts 'hello world", allow_failure: true)
+      assert_not_predicate $?, :success?
       assert_match "unterminated string meets end of file", output
     end
 
     def test_runner_detects_bad_script_name
-      output = Dir.chdir(app_path) { `bin/rails runner "iuiqwiourowe" 2>&1` }
-      assert_not $?.success?
+      output = rails("runner", "iuiqwiourowe", allow_failure: true)
+      assert_not_predicate $?, :success?
       assert_match "undefined local variable or method `iuiqwiourowe' for", output
     end
 
     def test_environment_with_rails_env
       with_rails_env "production" do
-        assert_match "production", Dir.chdir(app_path) { `bin/rails runner "puts Rails.env"` }
+        assert_match "production", rails("runner", "puts Rails.env")
       end
     end
 
     def test_environment_with_rack_env
       with_rack_env "production" do
-        assert_match "production", Dir.chdir(app_path) { `bin/rails runner "puts Rails.env"` }
+        assert_match "production", rails("runner", "puts Rails.env")
       end
     end
+
+    def test_can_call_same_name_class_as_defined_in_thor
+      app_file "app/models/task.rb", <<-MODEL
+      class Task
+        def self.count
+          42
+        end
+      end
+      MODEL
+
+      assert_match "42", rails("runner", "puts Task.count")
+    end
   end
 end
diff --git a/railties/test/application/server_test.rb b/railties/test/application/server_test.rb
index 6db9a3b9e8..92b991dd05 100644
--- a/railties/test/application/server_test.rb
+++ b/railties/test/application/server_test.rb
@@ -29,12 +29,17 @@ module ApplicationTests
       server.app
 
       log = File.read(Rails.application.config.paths["log"].first)
-      assert_match(/DEPRECATION WARNING: Use `Rails::Application` subclass to start the server is deprecated/, log)
+      assert_match(/DEPRECATION WARNING: Using `Rails::Application` subclass to start the server is deprecated/, log)
     end
 
     test "restart rails server with custom pid file path" do
       skip "PTY unavailable" unless available_pty?
 
+      File.open("#{app_path}/config/boot.rb", "w") do |f|
+        f.puts "ENV['BUNDLE_GEMFILE'] = '#{Bundler.default_gemfile}'"
+        f.puts "require 'bundler/setup'"
+      end
+
       master, slave = PTY.open
       pid = nil
 
@@ -42,7 +47,7 @@ module ApplicationTests
         pid = Process.spawn("#{app_path}/bin/rails server -P tmp/dummy.pid", in: slave, out: slave, err: slave)
         assert_output("Listening", master)
 
-        Dir.chdir(app_path) { system("bin/rails restart") }
+        rails("restart")
 
         assert_output("Restarting", master)
         assert_output("Inherited", master)
diff --git a/railties/test/application/test_runner_test.rb b/railties/test/application/test_runner_test.rb
index 1eda2a5eaf..8e5ccf94cc 100644
--- a/railties/test/application/test_runner_test.rb
+++ b/railties/test/application/test_runner_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "isolation/abstract_unit"
-require "active_support/core_ext/string/strip"
 require "env_helpers"
 
 module ApplicationTests
@@ -59,7 +58,7 @@ module ApplicationTests
         def; end
       RUBY
 
-      error = capture(:stderr) { run_test_command("test/models/error_test.rb") }
+      error = capture(:stderr) { run_test_command("test/models/error_test.rb", stderr: true) }
       assert_match "syntax error", error
     end
 
@@ -91,13 +90,11 @@ module ApplicationTests
       create_test_file :unit, "baz_unit"
       create_test_file :controllers, "foobar_controller"
 
-      Dir.chdir(app_path) do
-        `bin/rails test:units`.tap do |output|
-          assert_match "FooTest", output
-          assert_match "BarHelperTest", output
-          assert_match "BazUnitTest", output
-          assert_match "3 runs, 3 assertions, 0 failures", output
-        end
+      rails("test:units").tap do |output|
+        assert_match "FooTest", output
+        assert_match "BarHelperTest", output
+        assert_match "BazUnitTest", output
+        assert_match "3 runs, 3 assertions, 0 failures", output
       end
     end
 
@@ -140,13 +137,11 @@ module ApplicationTests
       create_test_file :functional, "baz_functional"
       create_test_file :models, "foo"
 
-      Dir.chdir(app_path) do
-        `bin/rails test:functionals`.tap do |output|
-          assert_match "FooMailerTest", output
-          assert_match "BarControllerTest", output
-          assert_match "BazFunctionalTest", output
-          assert_match "3 runs, 3 assertions, 0 failures", output
-        end
+      rails("test:functionals").tap do |output|
+        assert_match "FooMailerTest", output
+        assert_match "BarControllerTest", output
+        assert_match "BazFunctionalTest", output
+        assert_match "3 runs, 3 assertions, 0 failures", output
       end
     end
 
@@ -506,10 +501,10 @@ module ApplicationTests
     end
 
     def test_output_inline_by_default
-      create_test_file :models, "post", pass: false
+      create_test_file :models, "post", pass: false, print: false
 
       output = run_test_command("test/models/post_test.rb")
-      expect = %r{Running:\n\nPostTest\nF\n\nFailure:\nPostTest#test_truth \[[^\]]+test/models/post_test.rb:6\]:\nwups!\n\nbin/rails test test/models/post_test.rb:4\n\n\n\n}
+      expect = %r{Running:\n\nF\n\nFailure:\nPostTest#test_truth \[[^\]]+test/models/post_test.rb:6\]:\nwups!\n\nbin/rails test test/models/post_test.rb:4\n\n\n\n}
       assert_match expect, output
     end
 
@@ -524,11 +519,33 @@ module ApplicationTests
       create_test_file :models, "post", pass: false
 
       assert_match(/Interrupt/,
-        capture(:stderr) { run_test_command("test/models/post_test.rb --fail-fast") })
+        capture(:stderr) { run_test_command("test/models/post_test.rb --fail-fast", stderr: true) })
+    end
+
+    def test_run_in_parallel_with_processes
+      file_name = create_parallel_processes_test_file
+
+      output = run_test_command(file_name)
+
+      assert_match %r{Finished in.*\n2 runs, 2 assertions}, output
+    end
+
+    def test_run_in_parallel_with_threads
+      app_path("/test/test_helper.rb") do |file_name|
+        file = File.read(file_name)
+        file.sub!(/parallelize\(([^\)]*)\)/, "parallelize(\\1, with: :threads)")
+        File.write(file_name, file)
+      end
+
+      file_name = create_parallel_threads_test_file
+
+      output = run_test_command(file_name)
+
+      assert_match %r{Finished in.*\n2 runs, 2 assertions}, output
     end
 
     def test_raise_error_when_specified_file_does_not_exist
-      error = capture(:stderr) { run_test_command("test/not_exists.rb") }
+      error = capture(:stderr) { run_test_command("test/not_exists.rb", stderr: true) }
       assert_match(%r{cannot load such file.+test/not_exists\.rb}, error)
     end
 
@@ -554,14 +571,16 @@ module ApplicationTests
 
     def test_rails_db_create_all_restores_db_connection
       create_test_file :models, "account"
-      output = Dir.chdir(app_path) { `bin/rails db:create:all db:migrate && echo ".tables" | rails dbconsole` }
+      rails "db:create:all", "db:migrate"
+      output = Dir.chdir(app_path) { `echo ".tables" | rails dbconsole` }
       assert_match "ar_internal_metadata", output, "tables should be dumped"
     end
 
     def test_rails_db_create_all_restores_db_connection_after_drop
       create_test_file :models, "account"
-      Dir.chdir(app_path) { `bin/rails db:create:all` } # create all to avoid warnings
-      output = Dir.chdir(app_path) { `bin/rails db:drop:all db:create:all db:migrate && echo ".tables" | rails dbconsole` }
+      rails "db:create:all" # create all to avoid warnings
+      rails "db:drop:all", "db:create:all", "db:migrate"
+      output = Dir.chdir(app_path) { `echo ".tables" | rails dbconsole` }
       assert_match "ar_internal_metadata", output, "tables should be dumped"
     end
 
@@ -571,6 +590,40 @@ module ApplicationTests
       assert_match "AccountTest#test_truth", output, "passing TEST= should run selected test"
     end
 
+    def test_running_with_ruby_gets_test_env_by_default
+      # Subshells inherit `ENV`, so we need to ensure `RAILS_ENV` is set to
+      # nil before we run the tests in the test app.
+      re, ENV["RAILS_ENV"] = ENV["RAILS_ENV"], nil
+
+      file = create_test_for_env("test")
+      results = Dir.chdir(app_path) {
+        `ruby -Ilib:test #{file}`.each_line.map { |line| JSON.parse line }
+      }
+      assert_equal 1, results.length
+      failures = results.first["failures"]
+      flunk(failures.first) unless failures.empty?
+
+    ensure
+      ENV["RAILS_ENV"] = re
+    end
+
+    def test_running_with_ruby_can_set_env_via_cmdline
+      # Subshells inherit `ENV`, so we need to ensure `RAILS_ENV` is set to
+      # nil before we run the tests in the test app.
+      re, ENV["RAILS_ENV"] = ENV["RAILS_ENV"], nil
+
+      file = create_test_for_env("development")
+      results = Dir.chdir(app_path) {
+        `RAILS_ENV=development ruby -Ilib:test #{file}`.each_line.map { |line| JSON.parse line }
+      }
+      assert_equal 1, results.length
+      failures = results.first["failures"]
+      flunk(failures.first) unless failures.empty?
+
+    ensure
+      ENV["RAILS_ENV"] = re
+    end
+
     def test_rake_passes_multiple_TESTOPTS_to_minitest
       create_test_file :models, "account"
       output = Dir.chdir(app_path) { `bin/rake test TESTOPTS='-v --seed=1234'` }
@@ -601,7 +654,7 @@ module ApplicationTests
         end
       RUBY
       assert_match(/warning: assigned but unused variable/,
-        capture(:stderr) { run_test_command("test/models/warnings_test.rb -w") })
+        capture(:stderr) { run_test_command("test/models/warnings_test.rb -w", stderr: true) })
     end
 
     def test_reset_sessions_before_rollback_on_system_tests
@@ -679,14 +732,14 @@ module ApplicationTests
     end
 
     private
-      def run_test_command(arguments = "test/unit/test_test.rb")
-        Dir.chdir(app_path) { `bin/rails t #{arguments}` }
+      def run_test_command(arguments = "test/unit/test_test.rb", **opts)
+        rails "t", *Shellwords.split(arguments), allow_failure: true, **opts
       end
 
       def create_model_with_fixture
-        script "generate model user name:string"
+        rails "generate", "model", "user", "name:string"
 
-        app_file "test/fixtures/users.yml", <<-YAML.strip_heredoc
+        app_file "test/fixtures/users.yml", <<~YAML
           vampire:
             id: 1
             name: Koyomi Araragi
@@ -729,19 +782,109 @@ module ApplicationTests
         app_file "db/schema.rb", ""
       end
 
-      def create_test_file(path = :unit, name = "test", pass: true)
+      def create_test_for_env(env)
+        app_file "test/models/environment_test.rb", <<-RUBY
+          require 'test_helper'
+          class JSONReporter < Minitest::AbstractReporter
+            def record(result)
+              puts JSON.dump(klass: result.class.name,
+                             name: result.name,
+                             failures: result.failures,
+                             assertions: result.assertions,
+                             time: result.time)
+            end
+          end
+
+          def Minitest.plugin_json_reporter_init(opts)
+            Minitest.reporter.reporters.clear
+            Minitest.reporter.reporters << JSONReporter.new
+          end
+
+          Minitest.extensions << "rails"
+          Minitest.extensions << "json_reporter"
+
+          # Minitest uses RubyGems to find plugins, and since RubyGems
+          # doesn't know about the Rails installation we're pointing at,
+          # Minitest won't require the Rails minitest plugin when we run
+          # these integration tests.  So we have to manually require the
+          # Minitest plugin here.
+          require 'minitest/rails_plugin'
+
+          class EnvironmentTest < ActiveSupport::TestCase
+            def test_environment
+              test_db = ActiveRecord::Base.configurations[#{env.dump}]["database"]
+              db_file = ActiveRecord::Base.connection_config[:database]
+              assert_match(test_db, db_file)
+              assert_equal #{env.dump}, ENV["RAILS_ENV"]
+            end
+          end
+        RUBY
+      end
+
+      def create_test_file(path = :unit, name = "test", pass: true, print: true)
         app_file "test/#{path}/#{name}_test.rb", <<-RUBY
           require 'test_helper'
 
           class #{name.camelize}Test < ActiveSupport::TestCase
             def test_truth
-              puts "#{name.camelize}Test"
+              puts "#{name.camelize}Test" if #{print}
               assert #{pass}, 'wups!'
             end
           end
         RUBY
       end
 
+      def create_parallel_processes_test_file
+        app_file "test/models/parallel_test.rb", <<-RUBY
+          require 'test_helper'
+
+          class ParallelTest < ActiveSupport::TestCase
+            RD1, WR1 = IO.pipe
+            RD2, WR2 = IO.pipe
+
+            test "one" do
+              WR1.close
+              assert_equal "x", RD1.read(1) # blocks until two runs
+
+              RD2.close
+              WR2.write "y" # Allow two to run
+              WR2.close
+            end
+
+            test "two" do
+              RD1.close
+              WR1.write "x" # Allow one to run
+              WR1.close
+
+              WR2.close
+              assert_equal "y", RD2.read(1) # blocks until one runs
+            end
+          end
+        RUBY
+      end
+
+      def create_parallel_threads_test_file
+        app_file "test/models/parallel_test.rb", <<-RUBY
+          require 'test_helper'
+
+          class ParallelTest < ActiveSupport::TestCase
+            Q1 = Queue.new
+            Q2 = Queue.new
+            test "one" do
+              assert_equal "x", Q1.pop # blocks until two runs
+
+              Q2 << "y"
+            end
+
+            test "two" do
+              Q1 << "x"
+
+              assert_equal "y", Q2.pop # blocks until one runs
+            end
+          end
+        RUBY
+      end
+
       def create_env_test
         app_file "test/unit/env_test.rb", <<-RUBY
           require 'test_helper'
@@ -755,17 +898,17 @@ module ApplicationTests
       end
 
       def create_scaffold
-        script "generate scaffold user name:string"
-        Dir.chdir(app_path) { File.exist?("app/models/user.rb") }
+        rails "generate", "scaffold", "user", "name:string"
+        assert File.exist?("#{app_path}/app/models/user.rb")
         run_migration
       end
 
       def create_controller
-        script "generate controller admin/dashboard index"
+        rails "generate", "controller", "admin/dashboard", "index"
       end
 
       def run_migration
-        Dir.chdir(app_path) { `bin/rails db:migrate` }
+        rails "db:migrate"
       end
   end
 end
diff --git a/railties/test/application/test_test.rb b/railties/test/application/test_test.rb
index 7e2364c0a6..fb43bebfbe 100644
--- a/railties/test/application/test_test.rb
+++ b/railties/test/application/test_test.rb
@@ -7,10 +7,15 @@ module ApplicationTests
     include ActiveSupport::Testing::Isolation
 
     def setup
+      @old = ENV["PARALLEL_WORKERS"]
+      ENV["PARALLEL_WORKERS"] = "0"
+
       build_app
     end
 
     def teardown
+      ENV["PARALLEL_WORKERS"] = @old
+
       teardown_app
     end
 
@@ -102,7 +107,7 @@ module ApplicationTests
     end
 
     test "ruby schema migrations" do
-      output  = script("generate model user name:string")
+      output  = rails("generate", "model", "user", "name:string")
       version = output.match(/(\d+)_create_users\.rb/)[1]
 
       app_file "test/models/user_test.rb", <<-RUBY
@@ -139,7 +144,7 @@ module ApplicationTests
     end
 
     test "sql structure migrations" do
-      output  = script("generate model user name:string")
+      output  = rails("generate", "model", "user", "name:string")
       version = output.match(/(\d+)_create_users\.rb/)[1]
 
       app_file "test/models/user_test.rb", <<-RUBY
@@ -178,7 +183,7 @@ module ApplicationTests
     end
 
     test "sql structure migrations when adding column to existing table" do
-      output_1  = script("generate model user name:string")
+      output_1  = rails("generate", "model", "user", "name:string")
       version_1 = output_1.match(/(\d+)_create_users\.rb/)[1]
 
       app_file "test/models/user_test.rb", <<-RUBY
@@ -203,7 +208,7 @@ module ApplicationTests
 
       assert_successful_test_run("models/user_test.rb")
 
-      output_2  = script("generate migration add_email_to_users")
+      output_2  = rails("generate", "migration", "add_email_to_users")
       version_2 = output_2.match(/(\d+)_add_email_to_users\.rb/)[1]
 
       app_file "test/models/user_test.rb", <<-RUBY
@@ -231,7 +236,7 @@ module ApplicationTests
     # For now, the user has to synchronize the schema manually.
     # This test-case serves as a reminder for this use-case.
     test "manually synchronize test schema after rollback" do
-      output  = script("generate model user name:string")
+      output  = rails("generate", "model", "user", "name:string")
       version = output.match(/(\d+)_create_users\.rb/)[1]
 
       app_file "test/models/user_test.rb", <<-RUBY
@@ -265,7 +270,7 @@ module ApplicationTests
 
       assert_successful_test_run "models/user_test.rb"
 
-      Dir.chdir(app_path) { `bin/rails db:test:prepare` }
+      rails "db:test:prepare"
 
       assert_unsuccessful_run "models/user_test.rb", <<-ASSERTION
 Expected: ["id", "name"]
@@ -274,7 +279,7 @@ Expected: ["id", "name"]
     end
 
     test "hooks for plugins" do
-      output  = script("generate model user name:string")
+      output  = rails("generate", "model", "user", "name:string")
       version = output.match(/(\d+)_create_users\.rb/)[1]
 
       app_file "lib/tasks/hooks.rake", <<-RUBY
@@ -334,7 +339,7 @@ Expected: ["id", "name"]
       end
 
       def run_test_file(name, options = {})
-        Dir.chdir(app_path) { `bin/rails test "#{app_path}/test/#{name}" 2>&1` }
+        rails "test", "#{app_path}/test/#{name}", allow_failure: true
       end
   end
 end
diff --git a/railties/test/application/url_generation_test.rb b/railties/test/application/url_generation_test.rb
index 4f962db6c4..f22b9fda3d 100644
--- a/railties/test/application/url_generation_test.rb
+++ b/railties/test/application/url_generation_test.rb
@@ -16,7 +16,6 @@ module ApplicationTests
       require "action_view/railtie"
 
       class MyApp < Rails::Application
-        secrets.secret_key_base = "3b7cd727ee24e8444053437c36cc66c4"
         config.session_store :cookie_store, key: "_myapp_session"
         config.active_support.deprecation = :log
         config.eager_load = false
diff --git a/railties/test/application/version_test.rb b/railties/test/application/version_test.rb
index 62d3c7b254..ae85cf8f05 100644
--- a/railties/test/application/version_test.rb
+++ b/railties/test/application/version_test.rb
@@ -15,12 +15,12 @@ class VersionTest < ActiveSupport::TestCase
   end
 
   test "command works" do
-    output = Dir.chdir(app_path) { `bin/rails version` }
+    output = rails("version")
     assert_equal "Rails #{Rails.gem_version}\n", output
   end
 
   test "short-cut alias works" do
-    output = Dir.chdir(app_path) { `bin/rails -v` }
+    output = rails("-v")
     assert_equal "Rails #{Rails.gem_version}\n", output
   end
 end
diff --git a/railties/test/command/spellchecker_test.rb b/railties/test/command/spellchecker_test.rb
new file mode 100644
index 0000000000..e6a7a3957c
--- /dev/null
+++ b/railties/test/command/spellchecker_test.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "rails/command/spellchecker"
+
+class Rails::Command::SpellcheckerTest < ActiveSupport::TestCase
+  test "suggests a word correction from dictionary" do
+    assert_equal "thin", Rails::Command::Spellchecker.suggest("tin", from: %w(puma thin cgi))
+  end
+end
diff --git a/railties/test/commands/console_test.rb b/railties/test/commands/console_test.rb
index 7eb26c355c..b7cdb8229e 100644
--- a/railties/test/commands/console_test.rb
+++ b/railties/test/commands/console_test.rb
@@ -20,30 +20,30 @@ class Rails::ConsoleTest < ActiveSupport::TestCase
 
   def test_sandbox_option
     console = Rails::Console.new(app, parse_arguments(["--sandbox"]))
-    assert console.sandbox?
+    assert_predicate console, :sandbox?
   end
 
   def test_short_version_of_sandbox_option
     console = Rails::Console.new(app, parse_arguments(["-s"]))
-    assert console.sandbox?
+    assert_predicate console, :sandbox?
   end
 
   def test_no_options
     console = Rails::Console.new(app, parse_arguments([]))
-    assert !console.sandbox?
+    assert_not_predicate console, :sandbox?
   end
 
   def test_start
     start
 
-    assert app.console.started?
+    assert_predicate app.console, :started?
     assert_match(/Loading \w+ environment \(Rails/, output)
   end
 
   def test_start_with_sandbox
     start ["--sandbox"]
 
-    assert app.console.started?
+    assert_predicate app.console, :started?
     assert app.sandbox
     assert_match(/Loading \w+ environment in sandbox \(Rails/, output)
   end
@@ -172,21 +172,8 @@ class Rails::ConsoleTest < ActiveSupport::TestCase
     end
 
     def parse_arguments(args)
-      Rails::Command::ConsoleCommand.class_eval do
-        alias_method :old_perform, :perform
-        define_method(:perform) do
-          extract_environment_option_from_argument
-
-          options
-        end
-      end
-
-      Rails::Command.invoke(:console, args)
-    ensure
-      Rails::Command::ConsoleCommand.class_eval do
-        undef_method :perform
-        alias_method :perform, :old_perform
-        undef_method :old_perform
-      end
+      command = Rails::Command::ConsoleCommand.new([], args)
+      command.send(:extract_environment_option_from_argument)
+      command.options
     end
 end
diff --git a/railties/test/commands/credentials_test.rb b/railties/test/commands/credentials_test.rb
new file mode 100644
index 0000000000..663ee73bcd
--- /dev/null
+++ b/railties/test/commands/credentials_test.rb
@@ -0,0 +1,86 @@
+# frozen_string_literal: true
+
+require "isolation/abstract_unit"
+require "env_helpers"
+require "rails/command"
+require "rails/commands/credentials/credentials_command"
+
+class Rails::Command::CredentialsCommandTest < ActiveSupport::TestCase
+  include ActiveSupport::Testing::Isolation, EnvHelpers
+
+  setup { build_app }
+
+  teardown { teardown_app }
+
+  test "edit without editor gives hint" do
+    run_edit_command(editor: "").tap do |output|
+      assert_match "No $EDITOR to open file in", output
+      assert_match "bin/rails credentials:edit", output
+    end
+  end
+
+  test "edit credentials" do
+    # Run twice to ensure credentials can be reread after first edit pass.
+    2.times do
+      assert_match(/access_key_id: 123/, run_edit_command)
+    end
+  end
+
+  test "edit command does not add master key to gitignore when already exist" do
+    run_edit_command
+
+    Dir.chdir(app_path) do
+      gitignore = File.read(".gitignore")
+      assert_equal 1, gitignore.scan(%r|config/master\.key|).length
+    end
+  end
+
+  test "edit command does not overwrite by default if credentials already exists" do
+    run_edit_command(editor: "eval echo api_key: abc >")
+    assert_match(/api_key: abc/, run_show_command)
+
+    run_edit_command
+    assert_match(/api_key: abc/, run_show_command)
+  end
+
+  test "edit command does not add master key when `RAILS_MASTER_KEY` env specified" do
+    Dir.chdir(app_path) do
+      key = IO.binread("config/master.key").strip
+      FileUtils.rm("config/master.key")
+
+      switch_env("RAILS_MASTER_KEY", key) do
+        run_edit_command
+        assert_not File.exist?("config/master.key")
+      end
+    end
+  end
+
+  test "show credentials" do
+    assert_match(/access_key_id: 123/, run_show_command)
+  end
+
+  test "show command raise error when require_master_key is specified and key does not exist" do
+    remove_file "config/master.key"
+    add_to_config "config.require_master_key = true"
+
+    assert_match(/Missing encryption key to decrypt file with/, run_show_command(allow_failure: true))
+  end
+
+  test "show command does not raise error when require_master_key is false and master key does not exist" do
+    remove_file "config/master.key"
+    add_to_config "config.require_master_key = false"
+
+    assert_match(/Missing master key to decrypt credentials/, run_show_command)
+  end
+
+  private
+    def run_edit_command(editor: "cat")
+      switch_env("EDITOR", editor) do
+        rails "credentials:edit"
+      end
+    end
+
+    def run_show_command(**options)
+      rails "credentials:show", **options
+    end
+end
diff --git a/railties/test/commands/dbconsole_test.rb b/railties/test/commands/dbconsole_test.rb
index e922a23e15..0aea21051a 100644
--- a/railties/test/commands/dbconsole_test.rb
+++ b/railties/test/commands/dbconsole_test.rb
@@ -123,31 +123,31 @@ class Rails::DBConsoleTest < ActiveSupport::TestCase
 
   def test_mysql
     start(adapter: "mysql2", database: "db")
-    assert !aborted
+    assert_not aborted
     assert_equal [%w[mysql mysql5], "db"], dbconsole.find_cmd_and_exec_args
   end
 
   def test_mysql_full
     start(adapter: "mysql2", database: "db", host: "locahost", port: 1234, socket: "socket", username: "user", password: "qwerty", encoding: "UTF-8")
-    assert !aborted
+    assert_not aborted
     assert_equal [%w[mysql mysql5], "--host=locahost", "--port=1234", "--socket=socket", "--user=user", "--default-character-set=UTF-8", "-p", "db"], dbconsole.find_cmd_and_exec_args
   end
 
   def test_mysql_include_password
     start({ adapter: "mysql2", database: "db", username: "user", password: "qwerty" }, ["-p"])
-    assert !aborted
+    assert_not aborted
     assert_equal [%w[mysql mysql5], "--user=user", "--password=qwerty", "db"], dbconsole.find_cmd_and_exec_args
   end
 
   def test_postgresql
     start(adapter: "postgresql", database: "db")
-    assert !aborted
+    assert_not aborted
     assert_equal ["psql", "db"], dbconsole.find_cmd_and_exec_args
   end
 
   def test_postgresql_full
     start(adapter: "postgresql", database: "db", username: "user", password: "q1w2e3", host: "host", port: 5432)
-    assert !aborted
+    assert_not aborted
     assert_equal ["psql", "db"], dbconsole.find_cmd_and_exec_args
     assert_equal "user", ENV["PGUSER"]
     assert_equal "host", ENV["PGHOST"]
@@ -157,7 +157,7 @@ class Rails::DBConsoleTest < ActiveSupport::TestCase
 
   def test_postgresql_include_password
     start({ adapter: "postgresql", database: "db", username: "user", password: "q1w2e3" }, ["-p"])
-    assert !aborted
+    assert_not aborted
     assert_equal ["psql", "db"], dbconsole.find_cmd_and_exec_args
     assert_equal "user", ENV["PGUSER"]
     assert_equal "q1w2e3", ENV["PGPASSWORD"]
@@ -165,13 +165,13 @@ class Rails::DBConsoleTest < ActiveSupport::TestCase
 
   def test_sqlite3
     start(adapter: "sqlite3", database: "db.sqlite3")
-    assert !aborted
+    assert_not aborted
     assert_equal ["sqlite3", Rails.root.join("db.sqlite3").to_s], dbconsole.find_cmd_and_exec_args
   end
 
   def test_sqlite3_mode
     start({ adapter: "sqlite3", database: "db.sqlite3" }, ["--mode", "html"])
-    assert !aborted
+    assert_not aborted
     assert_equal ["sqlite3", "-html", Rails.root.join("db.sqlite3").to_s], dbconsole.find_cmd_and_exec_args
   end
 
@@ -182,30 +182,36 @@ class Rails::DBConsoleTest < ActiveSupport::TestCase
 
   def test_sqlite3_db_absolute_path
     start(adapter: "sqlite3", database: "/tmp/db.sqlite3")
-    assert !aborted
+    assert_not aborted
     assert_equal ["sqlite3", "/tmp/db.sqlite3"], dbconsole.find_cmd_and_exec_args
   end
 
   def test_sqlite3_db_without_defined_rails_root
     Rails.stub(:respond_to?, false) do
       start(adapter: "sqlite3", database: "config/db.sqlite3")
-      assert !aborted
+      assert_not aborted
       assert_equal ["sqlite3", Rails.root.join("../config/db.sqlite3").to_s], dbconsole.find_cmd_and_exec_args
     end
   end
 
   def test_oracle
     start(adapter: "oracle", database: "db", username: "user", password: "secret")
-    assert !aborted
+    assert_not aborted
     assert_equal ["sqlplus", "user@db"], dbconsole.find_cmd_and_exec_args
   end
 
   def test_oracle_include_password
     start({ adapter: "oracle", database: "db", username: "user", password: "secret" }, ["-p"])
-    assert !aborted
+    assert_not aborted
     assert_equal ["sqlplus", "user/secret@db"], dbconsole.find_cmd_and_exec_args
   end
 
+  def test_sqlserver
+    start(adapter: "sqlserver", database: "db", username: "user", password: "secret", host: "localhost", port: 1433)
+    assert_not aborted
+    assert_equal ["sqsh", "-D", "db", "-U", "user", "-P", "secret", "-S", "localhost:1433"], dbconsole.find_cmd_and_exec_args
+  end
+
   def test_unknown_command_line_client
     start(adapter: "unknown", database: "db")
     assert aborted
diff --git a/railties/test/commands/encrypted_test.rb b/railties/test/commands/encrypted_test.rb
new file mode 100644
index 0000000000..9fc73d5f18
--- /dev/null
+++ b/railties/test/commands/encrypted_test.rb
@@ -0,0 +1,106 @@
+# frozen_string_literal: true
+
+require "isolation/abstract_unit"
+require "env_helpers"
+require "rails/command"
+require "rails/commands/encrypted/encrypted_command"
+
+class Rails::Command::EncryptedCommandTest < ActiveSupport::TestCase
+  include ActiveSupport::Testing::Isolation, EnvHelpers
+
+  setup :build_app
+  teardown :teardown_app
+
+  test "edit without editor gives hint" do
+    run_edit_command("config/tokens.yml.enc", editor: "").tap do |output|
+      assert_match "No $EDITOR to open file in", output
+      assert_match "bin/rails encrypted:edit", output
+    end
+  end
+
+  test "edit encrypted file" do
+    # Run twice to ensure file can be reread after first edit pass.
+    2.times do
+      assert_match(/access_key_id: 123/, run_edit_command("config/tokens.yml.enc"))
+    end
+  end
+
+  test "edit command does not add master key to gitignore when already exist" do
+    run_edit_command("config/tokens.yml.enc")
+
+    Dir.chdir(app_path) do
+      assert_match "/config/master.key", File.read(".gitignore")
+    end
+  end
+
+  test "edit command does not add master key when `RAILS_MASTER_KEY` env specified" do
+    Dir.chdir(app_path) do
+      key = IO.binread("config/master.key").strip
+      FileUtils.rm("config/master.key")
+
+      switch_env("RAILS_MASTER_KEY", key) do
+        run_edit_command("config/tokens.yml.enc")
+        assert_not File.exist?("config/master.key")
+      end
+    end
+  end
+
+  test "edit encrypts file with custom key" do
+    run_edit_command("config/tokens.yml.enc", key: "config/tokens.key")
+
+    Dir.chdir(app_path) do
+      assert File.exist?("config/tokens.yml.enc")
+      assert File.exist?("config/tokens.key")
+
+      assert_match "/config/tokens.key", File.read(".gitignore")
+    end
+
+    assert_match(/access_key_id: 123/, run_edit_command("config/tokens.yml.enc", key: "config/tokens.key"))
+  end
+
+  test "show encrypted file with custom key" do
+    run_edit_command("config/tokens.yml.enc", key: "config/tokens.key")
+
+    assert_match(/access_key_id: 123/, run_show_command("config/tokens.yml.enc", key: "config/tokens.key"))
+  end
+
+  test "show command raise error when require_master_key is specified and key does not exist" do
+    add_to_config "config.require_master_key = true"
+
+    assert_match(/Missing encryption key to decrypt file with/,
+      run_show_command("config/tokens.yml.enc", key: "unexist.key", allow_failure: true))
+  end
+
+  test "show command does not raise error when require_master_key is false and master key does not exist" do
+    remove_file "config/master.key"
+    add_to_config "config.require_master_key = false"
+
+    assert_match(/Missing 'config\/master\.key' to decrypt data/, run_show_command("config/tokens.yml.enc"))
+  end
+
+  test "won't corrupt encrypted file when passed wrong key" do
+    run_edit_command("config/tokens.yml.enc", key: "config/tokens.key")
+
+    assert_match "passed the wrong key",
+      run_edit_command("config/tokens.yml.enc", allow_failure: true)
+
+    assert_match(/access_key_id: 123/, run_show_command("config/tokens.yml.enc", key: "config/tokens.key"))
+  end
+
+  private
+    def run_edit_command(file, key: nil, editor: "cat", **options)
+      switch_env("EDITOR", editor) do
+        rails "encrypted:edit", prepare_args(file, key), **options
+      end
+    end
+
+    def run_show_command(file, key: nil, **options)
+      rails "encrypted:show", prepare_args(file, key), **options
+    end
+
+    def prepare_args(file, key)
+      args = [ file ]
+      args.push("--key", key) if key
+      args
+    end
+end
diff --git a/railties/test/commands/routes_test.rb b/railties/test/commands/routes_test.rb
new file mode 100644
index 0000000000..77ed2bda61
--- /dev/null
+++ b/railties/test/commands/routes_test.rb
@@ -0,0 +1,175 @@
+# frozen_string_literal: true
+
+require "isolation/abstract_unit"
+require "rails/command"
+require "rails/commands/routes/routes_command"
+require "io/console/size"
+
+class Rails::Command::RoutesTest < ActiveSupport::TestCase
+  setup :build_app
+  teardown :teardown_app
+
+  test "singular resource output in rails routes" do
+    app_file "config/routes.rb", <<-RUBY
+      Rails.application.routes.draw do
+        resource :post
+      end
+    RUBY
+
+    expected_output = ["   Prefix Verb   URI Pattern          Controller#Action",
+                       " new_post GET    /post/new(.:format)  posts#new",
+                       "edit_post GET    /post/edit(.:format) posts#edit",
+                       "     post GET    /post(.:format)      posts#show",
+                       "          PATCH  /post(.:format)      posts#update",
+                       "          PUT    /post(.:format)      posts#update",
+                       "          DELETE /post(.:format)      posts#destroy",
+                       "          POST   /post(.:format)      posts#create\n"].join("\n")
+
+    output = run_routes_command(["-c", "PostController"])
+    assert_equal expected_output, output
+  end
+
+  test "rails routes with global search key" do
+    app_file "config/routes.rb", <<-RUBY
+      Rails.application.routes.draw do
+        get '/cart', to: 'cart#show'
+        post '/cart', to: 'cart#create'
+        get '/basketballs', to: 'basketball#index'
+      end
+    RUBY
+
+    output = run_routes_command(["-g", "show"])
+    assert_equal <<~MESSAGE, output
+                         Prefix Verb URI Pattern                                                                              Controller#Action
+                           cart GET  /cart(.:format)                                                                          cart#show
+             rails_service_blob GET  /rails/active_storage/blobs/:signed_id/*filename(.:format)                               active_storage/blobs#show
+      rails_blob_representation GET  /rails/active_storage/representations/:signed_blob_id/:variation_key/*filename(.:format) active_storage/representations#show
+             rails_disk_service GET  /rails/active_storage/disk/:encoded_key/*filename(.:format)                              active_storage/disk#show
+    MESSAGE
+
+    output = run_routes_command(["-g", "POST"])
+    assert_equal <<~MESSAGE, output
+                    Prefix Verb URI Pattern                                    Controller#Action
+                           POST /cart(.:format)                                cart#create
+      rails_direct_uploads POST /rails/active_storage/direct_uploads(.:format) active_storage/direct_uploads#create
+    MESSAGE
+
+    output = run_routes_command(["-g", "basketballs"])
+    assert_equal "     Prefix Verb URI Pattern            Controller#Action\n" \
+                 "basketballs GET  /basketballs(.:format) basketball#index\n", output
+  end
+
+  test "rails routes with controller search key" do
+    app_file "config/routes.rb", <<-RUBY
+      Rails.application.routes.draw do
+        get '/cart', to: 'cart#show'
+        get '/basketball', to: 'basketball#index'
+      end
+    RUBY
+
+    output = run_routes_command(["-c", "cart"])
+    assert_equal "Prefix Verb URI Pattern     Controller#Action\n  cart GET  /cart(.:format) cart#show\n", output
+
+    output = run_routes_command(["-c", "Cart"])
+    assert_equal "Prefix Verb URI Pattern     Controller#Action\n  cart GET  /cart(.:format) cart#show\n", output
+
+    output = run_routes_command(["-c", "CartController"])
+    assert_equal "Prefix Verb URI Pattern     Controller#Action\n  cart GET  /cart(.:format) cart#show\n", output
+  end
+
+  test "rails routes with namespaced controller search key" do
+    app_file "config/routes.rb", <<-RUBY
+      Rails.application.routes.draw do
+        namespace :admin do
+          resource :post
+        end
+      end
+    RUBY
+
+    expected_output = ["         Prefix Verb   URI Pattern                Controller#Action",
+                       " new_admin_post GET    /admin/post/new(.:format)  admin/posts#new",
+                       "edit_admin_post GET    /admin/post/edit(.:format) admin/posts#edit",
+                       "     admin_post GET    /admin/post(.:format)      admin/posts#show",
+                       "                PATCH  /admin/post(.:format)      admin/posts#update",
+                       "                PUT    /admin/post(.:format)      admin/posts#update",
+                       "                DELETE /admin/post(.:format)      admin/posts#destroy",
+                       "                POST   /admin/post(.:format)      admin/posts#create\n"].join("\n")
+
+    output = run_routes_command(["-c", "Admin::PostController"])
+    assert_equal expected_output, output
+
+    output = run_routes_command(["-c", "PostController"])
+    assert_equal expected_output, output
+  end
+
+  test "rails routes displays message when no routes are defined" do
+    app_file "config/routes.rb", <<-RUBY
+      Rails.application.routes.draw do
+      end
+    RUBY
+
+    assert_equal <<~MESSAGE, run_routes_command
+                         Prefix Verb URI Pattern                                                                              Controller#Action
+             rails_service_blob GET  /rails/active_storage/blobs/:signed_id/*filename(.:format)                               active_storage/blobs#show
+      rails_blob_representation GET  /rails/active_storage/representations/:signed_blob_id/:variation_key/*filename(.:format) active_storage/representations#show
+             rails_disk_service GET  /rails/active_storage/disk/:encoded_key/*filename(.:format)                              active_storage/disk#show
+      update_rails_disk_service PUT  /rails/active_storage/disk/:encoded_token(.:format)                                      active_storage/disk#update
+           rails_direct_uploads POST /rails/active_storage/direct_uploads(.:format)                                           active_storage/direct_uploads#create
+    MESSAGE
+  end
+
+  test "rails routes with expanded option" do
+    begin
+      previous_console_winsize = IO.console.winsize
+      IO.console.winsize = [0, 27]
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          get '/cart', to: 'cart#show'
+        end
+      RUBY
+
+      output = run_routes_command(["--expanded"])
+
+      assert_equal <<~MESSAGE, output
+        --[ Route 1 ]--------------
+        Prefix            | cart
+        Verb              | GET
+        URI               | /cart(.:format)
+        Controller#Action | cart#show
+        --[ Route 2 ]--------------
+        Prefix            | rails_service_blob
+        Verb              | GET
+        URI               | /rails/active_storage/blobs/:signed_id/*filename(.:format)
+        Controller#Action | active_storage/blobs#show
+        --[ Route 3 ]--------------
+        Prefix            | rails_blob_representation
+        Verb              | GET
+        URI               | /rails/active_storage/representations/:signed_blob_id/:variation_key/*filename(.:format)
+        Controller#Action | active_storage/representations#show
+        --[ Route 4 ]--------------
+        Prefix            | rails_disk_service
+        Verb              | GET
+        URI               | /rails/active_storage/disk/:encoded_key/*filename(.:format)
+        Controller#Action | active_storage/disk#show
+        --[ Route 5 ]--------------
+        Prefix            | update_rails_disk_service
+        Verb              | PUT
+        URI               | /rails/active_storage/disk/:encoded_token(.:format)
+        Controller#Action | active_storage/disk#update
+        --[ Route 6 ]--------------
+        Prefix            | rails_direct_uploads
+        Verb              | POST
+        URI               | /rails/active_storage/direct_uploads(.:format)
+        Controller#Action | active_storage/direct_uploads#create
+      MESSAGE
+    ensure
+      IO.console.winsize = previous_console_winsize
+    end
+  end
+
+  private
+    def run_routes_command(args = [])
+      rails "routes", args
+    end
+end
diff --git a/railties/test/commands/secrets_test.rb b/railties/test/commands/secrets_test.rb
index a1213a57f8..6b9f284a0c 100644
--- a/railties/test/commands/secrets_test.rb
+++ b/railties/test/commands/secrets_test.rb
@@ -1,27 +1,45 @@
 # frozen_string_literal: true
 
 require "isolation/abstract_unit"
+require "env_helpers"
 require "rails/command"
 require "rails/commands/secrets/secrets_command"
 
 class Rails::Command::SecretsCommandTest < ActiveSupport::TestCase
-  include ActiveSupport::Testing::Isolation
+  include ActiveSupport::Testing::Isolation, EnvHelpers
 
-  def setup
-    build_app
+  setup :build_app
+  teardown :teardown_app
+
+  test "edit without editor gives hint" do
+    assert_match "No $EDITOR to open decrypted secrets in", run_edit_command(editor: "")
   end
 
-  def teardown
-    teardown_app
+  test "encrypted secrets are deprecated when using credentials" do
+    assert_match "Encrypted secrets is deprecated", run_setup_command
+    assert_equal 1, $?.exitstatus
+    assert_not File.exist?("config/secrets.yml.enc")
   end
 
-  test "edit without editor gives hint" do
-    assert_match "No $EDITOR to open decrypted secrets in", run_edit_command(editor: "")
+  test "encrypted secrets are deprecated when running edit without setup" do
+    assert_match "Encrypted secrets is deprecated", run_setup_command
+    assert_equal 1, $?.exitstatus
+    assert_not File.exist?("config/secrets.yml.enc")
+  end
+
+  test "encrypted secrets are deprecated for 5.1 config/secrets.yml apps" do
+    Dir.chdir(app_path) do
+      FileUtils.rm("config/credentials.yml.enc")
+      FileUtils.touch("config/secrets.yml")
+
+      assert_match "Encrypted secrets is deprecated", run_setup_command
+      assert_equal 1, $?.exitstatus
+      assert_not File.exist?("config/secrets.yml.enc")
+    end
   end
 
   test "edit secrets" do
-    # Runs setup before first edit.
-    assert_match(/Adding config\/secrets\.yml\.key to store the encryption key/, run_edit_command)
+    prevent_deprecation
 
     # Run twice to ensure encrypted secrets can be reread after first edit pass.
     2.times do
@@ -30,20 +48,30 @@ class Rails::Command::SecretsCommandTest < ActiveSupport::TestCase
   end
 
   test "show secrets" do
-    run_setup_command
+    prevent_deprecation
+
     assert_match(/external_api_key: 1466aac22e6a869134be3d09b9e89232fc2c2289/, run_show_command)
   end
 
   private
+    def prevent_deprecation
+      Dir.chdir(app_path) do
+        File.write("config/secrets.yml.key", "f731758c639da2604dfb6bf3d1025de8")
+        File.write("config/secrets.yml.enc", "sEB0mHxDbeP1/KdnMk00wyzPFACl9K6t0cZWn5/Mfx/YbTHvnI07vrneqHg9kaH3wOS7L6pIQteu1P077OtE4BSx/ZRc/sgQPHyWu/tXsrfHqnPNpayOF/XZqizE91JacSFItNMWpuPsp9ynbzz+7cGhoB1S4aPNIU6u0doMrzdngDbijsaAFJmsHIQh6t/QHoJx--8aMoE0PvUWmw1Iqz--ldFqnM/K0g9k17M8PKoN/Q==")
+      end
+    end
+
     def run_edit_command(editor: "cat")
-      Dir.chdir(app_path) { `EDITOR="#{editor}" bin/rails secrets:edit` }
+      switch_env("EDITOR", editor) do
+        rails "secrets:edit", allow_failure: true
+      end
     end
 
     def run_show_command
-      Dir.chdir(app_path) { `bin/rails secrets:show` }
+      rails "secrets:show", allow_failure: true
     end
 
     def run_setup_command
-      Dir.chdir(app_path) { `bin/rails secrets:setup` }
+      rails "secrets:setup", allow_failure: true
     end
 end
diff --git a/railties/test/commands/server_test.rb b/railties/test/commands/server_test.rb
index 556c2289e7..e7a56b3e6d 100644
--- a/railties/test/commands/server_test.rb
+++ b/railties/test/commands/server_test.rb
@@ -1,15 +1,15 @@
 # frozen_string_literal: true
 
-require "abstract_unit"
+require "isolation/abstract_unit"
 require "env_helpers"
 require "rails/command"
 require "rails/commands/server/server_command"
 
-class Rails::ServerTest < ActiveSupport::TestCase
+class Rails::Command::ServerCommandTest < ActiveSupport::TestCase
   include EnvHelpers
 
   def test_environment_with_server_option
-    args = ["thin", "-e", "production"]
+    args = ["-u", "thin", "-e", "production"]
     options = parse_arguments(args)
     assert_equal "production", options[:environment]
     assert_equal "thin", options[:server]
@@ -22,8 +22,38 @@ class Rails::ServerTest < ActiveSupport::TestCase
     assert_nil options[:server]
   end
 
+  def test_explicit_using_option
+    args = ["-u", "thin"]
+    options = parse_arguments(args)
+    assert_equal "thin", options[:server]
+  end
+
+  def test_using_server_mistype
+    assert_match(/Could not find server "tin". Maybe you meant "thin"?/, run_command("--using", "tin"))
+  end
+
+  def test_using_positional_argument_deprecation
+    assert_match(/DEPRECATION WARNING/, run_command("tin"))
+  end
+
+  def test_using_known_server_that_isnt_in_the_gemfile
+    assert_match(/Could not load server "unicorn". Maybe you need to the add it to the Gemfile/, run_command("-u", "unicorn"))
+  end
+
+  def test_daemon_with_option
+    args = ["-d"]
+    options = parse_arguments(args)
+    assert_equal true, options[:daemonize]
+  end
+
+  def test_daemon_without_option
+    args = []
+    options = parse_arguments(args)
+    assert_equal false, options[:daemonize]
+  end
+
   def test_server_option_without_environment
-    args = ["thin"]
+    args = ["-u", "thin"]
     with_rack_env nil do
       with_rails_env nil do
         options = parse_arguments(args)
@@ -60,6 +90,15 @@ class Rails::ServerTest < ActiveSupport::TestCase
 
   def test_environment_with_host
     switch_env "HOST", "1.2.3.4" do
+      assert_deprecated do
+        options = parse_arguments
+        assert_equal "1.2.3.4", options[:Host]
+      end
+    end
+  end
+
+  def test_environment_with_binding
+    switch_env "BINDING", "1.2.3.4" do
       options = parse_arguments
       assert_equal "1.2.3.4", options[:Host]
     end
@@ -81,6 +120,18 @@ class Rails::ServerTest < ActiveSupport::TestCase
     assert_equal false, options[:caching]
   end
 
+  def test_early_hints_with_option
+    args = ["--early-hints"]
+    options = parse_arguments(args)
+    assert_equal true, options[:early_hints]
+  end
+
+  def test_early_hints_is_nil_by_default
+    args = []
+    options = parse_arguments(args)
+    assert_nil options[:early_hints]
+  end
+
   def test_log_stdout
     with_rack_env nil do
       with_rails_env nil do
@@ -154,7 +205,7 @@ class Rails::ServerTest < ActiveSupport::TestCase
       assert_equal 3000, options[:Port]
     end
 
-    switch_env "HOST", "1.2.3.4" do
+    switch_env "BINDING", "1.2.3.4" do
       args = ["-b", "127.0.0.1"]
       options = parse_arguments(args)
       assert_equal "127.0.0.1", options[:Host]
@@ -173,6 +224,11 @@ class Rails::ServerTest < ActiveSupport::TestCase
 
     server_options = parse_arguments(["--port=3001"])
     assert_equal [:Port], server_options[:user_supplied_options]
+
+    switch_env "BINDING", "1.2.3.4" do
+      server_options = parse_arguments
+      assert_equal [:Host], server_options[:user_supplied_options]
+    end
   end
 
   def test_default_options
@@ -197,7 +253,20 @@ class Rails::ServerTest < ActiveSupport::TestCase
     ARGV.replace original_args
   end
 
+  def test_served_url
+    args = %w(-u webrick -b 127.0.0.1 -p 4567)
+    server = Rails::Server.new(parse_arguments(args))
+    assert_equal "http://127.0.0.1:4567", server.served_url
+  end
+
   private
+    def run_command(*args)
+      build_app
+      rails "server", *args
+    ensure
+      teardown_app
+    end
+
     def parse_arguments(args = [])
       Rails::Command::ServerCommand.new([], args).server_options
     end
diff --git a/railties/test/engine/test_test.rb b/railties/test/engine/test_test.rb
new file mode 100644
index 0000000000..18af85a0aa
--- /dev/null
+++ b/railties/test/engine/test_test.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+
+class Rails::Engine::TestTest < ActiveSupport::TestCase
+  setup do
+    @destination_root = Dir.mktmpdir("bukkits")
+    Dir.chdir(@destination_root) { `bundle exec rails plugin new bukkits --mountable` }
+  end
+
+  teardown do
+    FileUtils.rm_rf(@destination_root)
+  end
+
+  test "automatically synchronize test schema" do
+    Dir.chdir(plugin_path) do
+      # In order to confirm that migration files are loaded, generate multiple migration files.
+      `bin/rails generate model user name:string;
+       bin/rails generate model todo name:string;
+       RAILS_ENV=development bin/rails db:migrate`
+
+      output = `bin/rails test test/models/bukkits/user_test.rb`
+      assert_includes(output, "0 runs, 0 assertions, 0 failures, 0 errors, 0 skips")
+    end
+  end
+
+  private
+    def plugin_path
+      "#{@destination_root}/bukkits"
+    end
+end
diff --git a/railties/test/engine_test.rb b/railties/test/engine_test.rb
index 4bd8a07085..19379e200c 100644
--- a/railties/test/engine_test.rb
+++ b/railties/test/engine_test.rb
@@ -11,7 +11,7 @@ class EngineTest < ActiveSupport::TestCase
       end
     end
 
-    assert !engine.routes?
+    assert_not_predicate engine, :routes?
   end
 
   def test_application_can_be_subclassed
diff --git a/railties/test/fixtures/about_yml_plugins/bad_about_yml/about.yml b/railties/test/fixtures/about_yml_plugins/bad_about_yml/about.yml
deleted file mode 100644
index fe80872a16..0000000000
--- a/railties/test/fixtures/about_yml_plugins/bad_about_yml/about.yml
+++ /dev/null
@@ -1 +0,0 @@
-# an empty YAML file - any content in here seems to get parsed as a string
-\ No newline at end of file
diff --git a/railties/test/fixtures/about_yml_plugins/bad_about_yml/init.rb b/railties/test/fixtures/about_yml_plugins/bad_about_yml/init.rb
deleted file mode 100644
index 1a82a2bdd4..0000000000
--- a/railties/test/fixtures/about_yml_plugins/bad_about_yml/init.rb
+++ /dev/null
@@ -1,3 +0,0 @@
-# frozen_string_literal: true
-
-# intentionally empty
diff --git a/railties/test/fixtures/about_yml_plugins/plugin_without_about_yml/init.rb b/railties/test/fixtures/about_yml_plugins/plugin_without_about_yml/init.rb
deleted file mode 100644
index 1a82a2bdd4..0000000000
--- a/railties/test/fixtures/about_yml_plugins/plugin_without_about_yml/init.rb
+++ /dev/null
@@ -1,3 +0,0 @@
-# frozen_string_literal: true
-
-# intentionally empty
diff --git a/railties/test/generators/actions_test.rb b/railties/test/generators/actions_test.rb
index e2ff3c279c..a54a6dbc28 100644
--- a/railties/test/generators/actions_test.rb
+++ b/railties/test/generators/actions_test.rb
@@ -71,10 +71,17 @@ class ActionsTest < Rails::Generators::TestCase
 
   def test_gem_with_version_should_include_version_in_gemfile
     run_generator
-
-    action :gem, "rspec", ">=2.0.0.a5"
-
-    assert_file "Gemfile", /gem 'rspec', '>=2.0.0.a5'/
+    action :gem, "rspec", ">= 2.0.0.a5"
+    action :gem, "RedCloth", ">= 4.1.0", "< 4.2.0"
+    action :gem, "nokogiri", version: ">= 1.4.2"
+    action :gem, "faker", version: [">= 0.1.0", "< 0.3.0"]
+
+    assert_file "Gemfile" do |content|
+      assert_match(/gem 'rspec', '>= 2\.0\.0\.a5'/, content)
+      assert_match(/gem 'RedCloth', '>= 4\.1\.0', '< 4\.2\.0'/, content)
+      assert_match(/gem 'nokogiri', '>= 1\.4\.2'/, content)
+      assert_match(/gem 'faker', '>= 0\.1\.0', '< 0\.3\.0'/, content)
+    end
   end
 
   def test_gem_should_insert_on_separate_lines
@@ -301,6 +308,14 @@ class ActionsTest < Rails::Generators::TestCase
     end
   end
 
+  test "rake command with capture option should run rake command with capture" do
+    assert_called_with(generator, :run, ["rake log:clear RAILS_ENV=development", verbose: false, capture: true]) do
+      with_rails_env nil do
+        action :rake, "log:clear", capture: true
+      end
+    end
+  end
+
   test "rails command should run rails_command with default env" do
     assert_called_with(generator, :run, ["rails log:clear RAILS_ENV=development", verbose: false]) do
       with_rails_env nil do
@@ -339,6 +354,14 @@ class ActionsTest < Rails::Generators::TestCase
     end
   end
 
+  test "rails command with capture option should run rails_command with capture" do
+    assert_called_with(generator, :run, ["rails log:clear RAILS_ENV=development", verbose: false, capture: true]) do
+      with_rails_env nil do
+        action :rails_command, "log:clear", capture: true
+      end
+    end
+  end
+
   def test_capify_should_run_the_capify_command
     content = capture(:stderr) do
       assert_called_with(generator, :run, ["capify .", verbose: false]) do
@@ -380,7 +403,7 @@ class ActionsTest < Rails::Generators::TestCase
     content.gsub!(/^  \#.*\n/, "")
     content.gsub!(/^\n/, "")
 
-    File.open(route_path, "wb") { |file| file.write(content) }
+    File.write(route_path, content)
 
     routes = <<-F
 Rails.application.routes.draw do
diff --git a/railties/test/generators/api_app_generator_test.rb b/railties/test/generators/api_app_generator_test.rb
index d141b1d4b4..9c523ad372 100644
--- a/railties/test/generators/api_app_generator_test.rb
+++ b/railties/test/generators/api_app_generator_test.rb
@@ -13,7 +13,7 @@ class ApiAppGeneratorTest < Rails::Generators::TestCase
     Rails.application = TestApp::Application
     super
 
-    Kernel::silence_warnings do
+    Kernel.silence_warnings do
       Thor::Base.shell.send(:attr_accessor, :always_force)
       @shell = Thor::Base.shell.new
       @shell.send(:always_force=, true)
@@ -63,6 +63,23 @@ class ApiAppGeneratorTest < Rails::Generators::TestCase
     end
   end
 
+  def test_generator_if_skip_action_mailer_is_given
+    run_generator [destination_root, "--api", "--skip-action-mailer"]
+    assert_file "config/application.rb", /#\s+require\s+["']action_mailer\/railtie["']/
+    assert_file "config/environments/development.rb" do |content|
+      assert_no_match(/config\.action_mailer/, content)
+    end
+    assert_file "config/environments/test.rb" do |content|
+      assert_no_match(/config\.action_mailer/, content)
+    end
+    assert_file "config/environments/production.rb" do |content|
+      assert_no_match(/config\.action_mailer/, content)
+    end
+    assert_no_directory "app/mailers"
+    assert_no_directory "test/mailers"
+    assert_no_directory "app/views"
+  end
+
   def test_app_update_does_not_generate_unnecessary_config_files
     run_generator
 
@@ -72,6 +89,7 @@ class ApiAppGeneratorTest < Rails::Generators::TestCase
 
     assert_no_file "config/initializers/cookies_serializer.rb"
     assert_no_file "config/initializers/assets.rb"
+    assert_no_file "config/initializers/content_security_policy.rb"
   end
 
   def test_app_update_does_not_generate_unnecessary_bin_files
@@ -125,7 +143,7 @@ class ApiAppGeneratorTest < Rails::Generators::TestCase
         config/locales/en.yml
         config/puma.rb
         config/routes.rb
-        config/secrets.yml
+        config/credentials.yml.enc
         config/spring.rb
         config/storage.yml
         db
@@ -149,6 +167,7 @@ class ApiAppGeneratorTest < Rails::Generators::TestCase
          bin/yarn
          config/initializers/assets.rb
          config/initializers/cookies_serializer.rb
+         config/initializers/content_security_policy.rb
          lib/assets
          test/helpers
          tmp/cache/assets
diff --git a/railties/test/generators/app_generator_test.rb b/railties/test/generators/app_generator_test.rb
index f64ebf5f1f..3cb7d66bbb 100644
--- a/railties/test/generators/app_generator_test.rb
+++ b/railties/test/generators/app_generator_test.rb
@@ -56,6 +56,7 @@ DEFAULT_APP_FILES = %w(
   config/initializers/assets.rb
   config/initializers/backtrace_silencers.rb
   config/initializers/cookies_serializer.rb
+  config/initializers/content_security_policy.rb
   config/initializers/filter_parameter_logging.rb
   config/initializers/inflections.rb
   config/initializers/mime_types.rb
@@ -64,7 +65,7 @@ DEFAULT_APP_FILES = %w(
   config/locales/en.yml
   config/puma.rb
   config/routes.rb
-  config/secrets.yml
+  config/credentials.yml.enc
   config/spring.rb
   config/storage.yml
   db
@@ -75,6 +76,7 @@ DEFAULT_APP_FILES = %w(
   log
   package.json
   public
+  storage
   test/application_system_test_case.rb
   test/test_helper.rb
   test/fixtures
@@ -89,6 +91,7 @@ DEFAULT_APP_FILES = %w(
   tmp
   tmp/cache
   tmp/cache/assets
+  tmp/storage
 )
 
 class AppGeneratorTest < Rails::Generators::TestCase
@@ -102,6 +105,15 @@ class AppGeneratorTest < Rails::Generators::TestCase
     ::DEFAULT_APP_FILES
   end
 
+  def test_skip_bundle
+    assert_not_called(generator([destination_root], skip_bundle: true), :bundle_command) do
+      quietly { generator.invoke_all }
+      # skip_bundle is only about running bundle install, ensure the Gemfile is still
+      # generated.
+      assert_file "Gemfile"
+    end
+  end
+
   def test_assets
     run_generator
 
@@ -199,7 +211,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
   end
 
   def test_new_application_doesnt_need_defaults
-    assert_no_file "config/initializers/new_framework_defaults_5_2.rb"
+    assert_no_file "config/initializers/new_framework_defaults_6_0.rb"
   end
 
   def test_new_application_load_defaults
@@ -207,6 +219,8 @@ class AppGeneratorTest < Rails::Generators::TestCase
     run_generator [app_root]
     output = nil
 
+    assert_file "#{app_root}/config/application.rb", /\s+config\.load_defaults #{Rails::VERSION::STRING.to_f}/
+
     Dir.chdir(app_root) do
       output = `./bin/rails r "puts Rails.application.config.assets.unknown_asset_fallback"`
     end
@@ -245,14 +259,14 @@ class AppGeneratorTest < Rails::Generators::TestCase
     app_root = File.join(destination_root, "myapp")
     run_generator [app_root]
 
-    assert_no_file "#{app_root}/config/initializers/new_framework_defaults_5_2.rb"
+    assert_no_file "#{app_root}/config/initializers/new_framework_defaults_6_0.rb"
 
     stub_rails_application(app_root) do
       generator = Rails::Generators::AppGenerator.new ["rails"], { update: true }, { destination_root: app_root, shell: @shell }
       generator.send(:app_const)
       quietly { generator.send(:update_config_files) }
 
-      assert_file "#{app_root}/config/initializers/new_framework_defaults_5_2.rb"
+      assert_file "#{app_root}/config/initializers/new_framework_defaults_6_0.rb"
     end
   end
 
@@ -282,13 +296,56 @@ class AppGeneratorTest < Rails::Generators::TestCase
     end
   end
 
+  def test_app_update_does_not_generate_yarn_contents_when_bin_yarn_is_not_used
+    app_root = File.join(destination_root, "myapp")
+    run_generator [app_root, "--skip-yarn"]
+
+    stub_rails_application(app_root) do
+      generator = Rails::Generators::AppGenerator.new ["rails"], { update: true, skip_yarn: true }, { destination_root: app_root, shell: @shell }
+      generator.send(:app_const)
+      quietly { generator.send(:update_bin_files) }
+
+      assert_no_file "#{app_root}/bin/yarn"
+
+      assert_file "#{app_root}/bin/setup" do |content|
+        assert_no_match(/system\('bin\/yarn'\)/, content)
+      end
+
+      assert_file "#{app_root}/bin/update" do |content|
+        assert_no_match(/system\('bin\/yarn'\)/, content)
+      end
+    end
+  end
+
+  def test_app_update_does_not_generate_assets_initializer_when_skip_sprockets_is_given
+    app_root = File.join(destination_root, "myapp")
+    run_generator [app_root, "--skip-sprockets"]
+
+    stub_rails_application(app_root) do
+      generator = Rails::Generators::AppGenerator.new ["rails"], { update: true, skip_sprockets: true }, { destination_root: app_root, shell: @shell }
+      generator.send(:app_const)
+      quietly { generator.send(:update_config_files) }
+
+      assert_no_file "#{app_root}/config/initializers/assets.rb"
+    end
+  end
+
+  def test_app_update_does_not_generate_spring_contents_when_skip_spring_is_given
+    app_root = File.join(destination_root, "myapp")
+    run_generator [app_root, "--skip-spring"]
+
+    FileUtils.cd(app_root) do
+      quietly { system("bin/rails app:update") }
+    end
+
+    assert_no_file "#{app_root}/config/spring.rb"
+  end
+
   def test_app_update_does_not_generate_action_cable_contents_when_skip_action_cable_is_given
     app_root = File.join(destination_root, "myapp")
     run_generator [app_root, "--skip-action-cable"]
 
     FileUtils.cd(app_root) do
-      # For avoid conflict file
-      FileUtils.rm("#{app_root}/config/secrets.yml")
       quietly { system("bin/rails app:update") }
     end
 
@@ -298,6 +355,89 @@ class AppGeneratorTest < Rails::Generators::TestCase
     end
   end
 
+  def test_app_update_does_not_generate_bootsnap_contents_when_skip_bootsnap_is_given
+    app_root = File.join(destination_root, "myapp")
+    run_generator [app_root, "--skip-bootsnap"]
+
+    FileUtils.cd(app_root) do
+      quietly { system("bin/rails app:update") }
+    end
+
+    assert_file "#{app_root}/config/boot.rb" do |content|
+      assert_no_match(/require 'bootsnap\/setup'/, content)
+    end
+  end
+
+  def test_gem_for_active_storage
+    run_generator
+    assert_file "Gemfile", /^# gem 'image_processing'/
+  end
+
+  def test_gem_for_active_storage_when_skip_active_storage_is_given
+    run_generator [destination_root, "--skip-active-storage"]
+
+    assert_no_gem "image_processing"
+  end
+
+  def test_app_update_does_not_generate_active_storage_contents_when_skip_active_storage_is_given
+    app_root = File.join(destination_root, "myapp")
+    run_generator [app_root, "--skip-active-storage"]
+
+    FileUtils.cd(app_root) do
+      quietly { system("bin/rails app:update") }
+    end
+
+    assert_file "#{app_root}/config/environments/development.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{app_root}/config/environments/production.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{app_root}/config/environments/test.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_no_file "#{app_root}/config/storage.yml"
+  end
+
+  def test_app_update_does_not_generate_active_storage_contents_when_skip_active_record_is_given
+    app_root = File.join(destination_root, "myapp")
+    run_generator [app_root, "--skip-active-record"]
+
+    FileUtils.cd(app_root) do
+      quietly { system("bin/rails app:update") }
+    end
+
+    assert_file "#{app_root}/config/environments/development.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{app_root}/config/environments/production.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{app_root}/config/environments/test.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_no_file "#{app_root}/config/storage.yml"
+  end
+
+  def test_app_update_does_not_change_config_target_version
+    run_generator
+
+    FileUtils.cd(destination_root) do
+      config = "config/application.rb"
+      content = File.read(config)
+      File.write(config, content.gsub(/config\.load_defaults #{Rails::VERSION::STRING.to_f}/, "config.load_defaults 5.1"))
+      quietly { system("bin/rails app:update") }
+    end
+
+    assert_file "config/application.rb", /\s+config\.load_defaults 5\.1/
+  end
+
   def test_application_names_are_not_singularized
     run_generator [File.join(destination_root, "hats")]
     assert_file "hats/config/environment.rb", /Rails\.application\.initialize!/
@@ -323,13 +463,13 @@ class AppGeneratorTest < Rails::Generators::TestCase
     end
   end
 
-  def test_config_another_database
+  def test_config_mysql_database
     run_generator([destination_root, "-d", "mysql"])
     assert_file "config/database.yml", /mysql/
     if defined?(JRUBY_VERSION)
       assert_gem "activerecord-jdbcmysql-adapter"
     else
-      assert_gem "mysql2", "'>= 0.3.18', '< 0.5'"
+      assert_gem "mysql2", "'>= 0.4.4', '< 0.6.0'"
     end
   end
 
@@ -344,7 +484,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
     if defined?(JRUBY_VERSION)
       assert_gem "activerecord-jdbcpostgresql-adapter"
     else
-      assert_gem "pg", "'~> 0.18'"
+      assert_gem "pg", "'>= 0.18', '< 2.0'"
     end
   end
 
@@ -383,15 +523,13 @@ class AppGeneratorTest < Rails::Generators::TestCase
 
   def test_generator_defaults_to_puma_version
     run_generator [destination_root]
-    assert_gem "puma", "'~> 3.7'"
+    assert_gem "puma", "'~> 3.11'"
   end
 
   def test_generator_if_skip_puma_is_given
     run_generator [destination_root, "--skip-puma"]
     assert_no_file "config/puma.rb"
-    assert_file "Gemfile" do |content|
-      assert_no_match(/puma/, content)
-    end
+    assert_no_gem "puma"
   end
 
   def test_generator_has_assets_gems
@@ -411,20 +549,18 @@ class AppGeneratorTest < Rails::Generators::TestCase
 
     assert_file "config/application.rb", /#\s+require\s+["']rails\/test_unit\/railtie["']/
 
-    assert_file "Gemfile" do |content|
-      assert_no_match(/capybara/, content)
-      assert_no_match(/selenium-webdriver/, content)
-    end
+    assert_no_gem "capybara"
+    assert_no_gem "selenium-webdriver"
+    assert_no_gem "chromedriver-helper"
 
     assert_no_directory("test")
   end
 
   def test_generator_if_skip_system_test_is_given
     run_generator [destination_root, "--skip-system-test"]
-    assert_file "Gemfile" do |content|
-      assert_no_match(/capybara/, content)
-      assert_no_match(/selenium-webdriver/, content)
-    end
+    assert_no_gem "capybara"
+    assert_no_gem "selenium-webdriver"
+    assert_no_gem "chromedriver-helper"
 
     assert_directory("test")
 
@@ -470,10 +606,8 @@ class AppGeneratorTest < Rails::Generators::TestCase
       assert_no_match(/javascript_include_tag\s+'application' \%>/, contents)
     end
 
-    assert_file "Gemfile" do |content|
-      assert_no_match(/coffee-rails/, content)
-      assert_no_match(/uglifier/, content)
-    end
+    assert_no_gem "coffee-rails"
+    assert_no_gem "uglifier"
 
     assert_file "config/environments/production.rb" do |content|
       assert_no_match(/config\.assets\.js_compressor = :uglifier/, content)
@@ -497,9 +631,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
   def test_inclusion_of_a_debugger
     run_generator
     if defined?(JRUBY_VERSION) || RUBY_ENGINE == "rbx"
-      assert_file "Gemfile" do |content|
-        assert_no_match(/byebug/, content)
-      end
+      assert_no_gem "byebug"
     else
       assert_gem "byebug"
     end
@@ -562,6 +694,18 @@ class AppGeneratorTest < Rails::Generators::TestCase
     assert_no_match(/run  git init/, output)
   end
 
+  def test_quiet_option
+    output = run_generator [File.join(destination_root, "myapp"), "--quiet"]
+    assert_empty output
+  end
+
+  def test_force_option_overwrites_every_file_except_master_key
+    run_generator [File.join(destination_root, "myapp")]
+    output = run_generator [File.join(destination_root, "myapp"), "--force"]
+    assert_match(/force/, output)
+    assert_no_match("force  config/master.key", output)
+  end
+
   def test_application_name_with_spaces
     path = File.join(destination_root, "foo bar")
 
@@ -638,9 +782,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
     assert_called_with(Process, :respond_to?, [[:fork], [:fork]], returns: false) do
       run_generator
 
-      assert_file "Gemfile" do |content|
-        assert_no_match(/spring/, content)
-      end
+      assert_no_gem "spring"
     end
   end
 
@@ -648,25 +790,58 @@ class AppGeneratorTest < Rails::Generators::TestCase
     run_generator [destination_root, "--skip-spring"]
 
     assert_no_file "config/spring.rb"
-    assert_file "Gemfile" do |content|
-      assert_no_match(/spring/, content)
-    end
+    assert_no_gem "spring"
   end
 
   def test_spring_with_dev_option
     run_generator [destination_root, "--dev"]
 
-    assert_file "Gemfile" do |content|
-      assert_no_match(/spring/, content)
+    assert_no_gem "spring"
+  end
+
+  def test_webpack_option
+    command_check = -> command, *_ do
+      @called ||= 0
+      if command == "webpacker:install"
+        @called += 1
+        assert_equal 1, @called, "webpacker:install expected to be called once, but was called #{@called} times."
+      end
+    end
+
+    generator([destination_root], webpack: "webpack").stub(:rails_command, command_check) do
+      generator.stub :bundle_command, nil do
+        quietly { generator.invoke_all }
+      end
+    end
+
+    assert_gem "webpacker"
+  end
+
+  def test_webpack_option_with_js_framework
+    command_check = -> command, *_ do
+      case command
+      when "webpacker:install"
+        @webpacker ||= 0
+        @webpacker += 1
+        assert_equal 1, @webpacker, "webpacker:install expected to be called once, but was called #{@webpacker} times."
+      when "webpacker:install:react"
+        @react ||= 0
+        @react += 1
+        assert_equal 1, @react, "webpacker:install:react expected to be called once, but was called #{@react} times."
+      end
+    end
+
+    generator([destination_root], webpack: "react").stub(:rails_command, command_check) do
+      generator.stub :bundle_command, nil do
+        quietly { generator.invoke_all }
+      end
     end
   end
 
   def test_generator_if_skip_turbolinks_is_given
     run_generator [destination_root, "--skip-turbolinks"]
 
-    assert_file "Gemfile" do |content|
-      assert_no_match(/turbolinks/, content)
-    end
+    assert_no_gem "turbolinks"
     assert_file "app/views/layouts/application.html.erb" do |content|
       assert_no_match(/data-turbolinks-track/, content)
     end
@@ -675,6 +850,40 @@ class AppGeneratorTest < Rails::Generators::TestCase
     end
   end
 
+  def test_bootsnap
+    run_generator
+
+    unless defined?(JRUBY_VERSION)
+      assert_gem "bootsnap"
+      assert_file "config/boot.rb" do |content|
+        assert_match(/require 'bootsnap\/setup'/, content)
+      end
+    else
+      assert_no_gem "bootsnap"
+      assert_file "config/boot.rb" do |content|
+        assert_no_match(/require 'bootsnap\/setup'/, content)
+      end
+    end
+  end
+
+  def test_skip_bootsnap
+    run_generator [destination_root, "--skip-bootsnap"]
+
+    assert_no_gem "bootsnap"
+    assert_file "config/boot.rb" do |content|
+      assert_no_match(/require 'bootsnap\/setup'/, content)
+    end
+  end
+
+  def test_bootsnap_with_dev_option
+    run_generator [destination_root, "--dev"]
+
+    assert_no_gem "bootsnap"
+    assert_file "config/boot.rb" do |content|
+      assert_no_match(/require 'bootsnap\/setup'/, content)
+    end
+  end
+
   def test_inclusion_of_ruby_version
     run_generator
 
@@ -682,7 +891,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
       assert_match(/ruby '#{RUBY_VERSION}'/, content)
     end
     assert_file ".ruby-version" do |content|
-      assert_match(/#{RUBY_VERSION}/, content)
+      assert_match(/#{RUBY_ENGINE}-#{RUBY_ENGINE_VERSION}/, content)
     end
   end
 
@@ -739,7 +948,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
 
     sequence = ["git init", "install", "exec spring binstub --all", "echo ran after_bundle"]
     @sequence_step ||= 0
-    ensure_bundler_first = -> command do
+    ensure_bundler_first = -> command, options = nil do
       assert_equal sequence[@sequence_step], command, "commands should be called in sequence #{sequence}"
       @sequence_step += 1
     end
@@ -747,7 +956,9 @@ class AppGeneratorTest < Rails::Generators::TestCase
     generator([destination_root], template: path).stub(:open, check_open, template) do
       generator.stub(:bundle_command, ensure_bundler_first) do
         generator.stub(:run, ensure_bundler_first) do
-          quietly { generator.invoke_all }
+          generator.stub(:rails_command, ensure_bundler_first) do
+            quietly { generator.invoke_all }
+          end
         end
       end
     end
@@ -755,11 +966,28 @@ class AppGeneratorTest < Rails::Generators::TestCase
     assert_equal 4, @sequence_step
   end
 
+  def test_gitignore
+    run_generator
+
+    assert_file ".gitignore" do |content|
+      assert_match(/config\/master\.key/, content)
+    end
+  end
+
   def test_system_tests_directory_generated
     run_generator
 
-    assert_file("test/system/.keep")
     assert_directory("test/system")
+    assert_file("test/system/.keep")
+  end
+
+  unless Gem.win_platform?
+    def test_master_key_is_only_readable_by_the_owner
+      run_generator
+
+      stat = File.stat("config/master.key")
+      assert_equal "100600", sprintf("%o", stat.mode)
+    end
   end
 
   private
@@ -782,6 +1010,12 @@ class AppGeneratorTest < Rails::Generators::TestCase
       end
     end
 
+    def assert_no_gem(gem)
+      assert_file "Gemfile" do |content|
+        assert_no_match(gem, content)
+      end
+    end
+
     def assert_listen_related_configuration
       assert_gem "listen"
       assert_gem "spring-watcher-listen"
@@ -792,9 +1026,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
     end
 
     def assert_no_listen_related_configuration
-      assert_file "Gemfile" do |content|
-        assert_no_match(/listen/, content)
-      end
+      assert_no_gem "listen"
 
       assert_file "config/environments/development.rb" do |content|
         assert_match(/^\s*# config\.file_watcher = ActiveSupport::EventedFileUpdateChecker/, content)
diff --git a/railties/test/generators/argv_scrubber_test.rb b/railties/test/generators/argv_scrubber_test.rb
index 3f4c985a33..9ef61dc978 100644
--- a/railties/test/generators/argv_scrubber_test.rb
+++ b/railties/test/generators/argv_scrubber_test.rb
@@ -82,9 +82,8 @@ module Rails
         file.puts "--hello --world"
         file.flush
 
-        message = nil
         scrubber = Class.new(ARGVScrubber) {
-          define_method(:puts) { |msg| message = msg }
+          define_method(:puts) { |msg| }
         }.new ["new", "--rc=#{file.path}"]
         args = scrubber.prepare!
         assert_equal ["--hello", "--world"], args
diff --git a/railties/test/generators/channel_generator_test.rb b/railties/test/generators/channel_generator_test.rb
index e238197eba..e543cc11b8 100644
--- a/railties/test/generators/channel_generator_test.rb
+++ b/railties/test/generators/channel_generator_test.rb
@@ -76,4 +76,14 @@ class ChannelGeneratorTest < Rails::Generators::TestCase
     assert_file "app/channels/application_cable/connection.rb"
     assert_file "app/assets/javascripts/cable.js"
   end
+
+  def test_channel_suffix_is_not_duplicated
+    run_generator ["chat_channel"]
+
+    assert_no_file "app/channels/chat_channel_channel.rb"
+    assert_file "app/channels/chat_channel.rb"
+
+    assert_no_file "app/assets/javascripts/channels/chat_channel.js"
+    assert_file "app/assets/javascripts/channels/chat.js"
+  end
 end
diff --git a/railties/test/generators/controller_generator_test.rb b/railties/test/generators/controller_generator_test.rb
index a3218951a6..021004c9b8 100644
--- a/railties/test/generators/controller_generator_test.rb
+++ b/railties/test/generators/controller_generator_test.rb
@@ -109,4 +109,33 @@ class ControllerGeneratorTest < Rails::Generators::TestCase
       assert_match(/^  namespace :admin do\n    get 'dashboard\/index'\n    get 'dashboard\/show'\n  end$/, route)
     end
   end
+
+  def test_does_not_add_routes_when_action_is_not_specified
+    run_generator ["admin/dashboard"]
+    assert_file "config/routes.rb" do |routes|
+      assert_no_match(/namespace :admin/, routes)
+    end
+  end
+
+  def test_controller_suffix_is_not_duplicated
+    run_generator ["account_controller"]
+
+    assert_no_file "app/controllers/account_controller_controller.rb"
+    assert_file "app/controllers/account_controller.rb"
+
+    assert_no_file "app/views/account_controller/"
+    assert_file "app/views/account/"
+
+    assert_no_file "test/controllers/account_controller_controller_test.rb"
+    assert_file "test/controllers/account_controller_test.rb"
+
+    assert_no_file "app/helpers/account_controller_helper.rb"
+    assert_file "app/helpers/account_helper.rb"
+
+    assert_no_file "app/assets/javascripts/account_controller.js"
+    assert_file "app/assets/javascripts/account.js"
+
+    assert_no_file "app/assets/stylesheets/account_controller.css"
+    assert_file "app/assets/stylesheets/account.css"
+  end
 end
diff --git a/railties/test/generators/create_migration_test.rb b/railties/test/generators/create_migration_test.rb
index 3cb7fd6baa..2ae38045c5 100644
--- a/railties/test/generators/create_migration_test.rb
+++ b/railties/test/generators/create_migration_test.rb
@@ -70,7 +70,7 @@ class CreateMigrationTest < Rails::Generators::TestCase
     create_migration
 
     assert_match(/identical  db\/migrate\/1_create_articles\.rb\n/, invoke!)
-    assert @migration.identical?
+    assert_predicate @migration, :identical?
   end
 
   def test_invoke_when_exists_not_identical
diff --git a/railties/test/generators/encrypted_secrets_generator_test.rb b/railties/test/generators/encrypted_secrets_generator_test.rb
deleted file mode 100644
index 205827e498..0000000000
--- a/railties/test/generators/encrypted_secrets_generator_test.rb
+++ /dev/null
@@ -1,44 +0,0 @@
-# frozen_string_literal: true
-
-require "generators/generators_test_helper"
-require "rails/generators/rails/encrypted_secrets/encrypted_secrets_generator"
-
-class EncryptedSecretsGeneratorTest < Rails::Generators::TestCase
-  include GeneratorsTestHelper
-
-  def setup
-    super
-    cd destination_root
-  end
-
-  def test_generates_key_file_and_encrypted_secrets_file
-    run_generator
-
-    assert_file "config/secrets.yml.key", /\w+/
-
-    assert File.exist?("config/secrets.yml.enc")
-    assert_no_match(/production:\n#  external_api_key: \w+/, IO.binread("config/secrets.yml.enc"))
-    assert_match(/production:\n#  external_api_key: \w+/, Rails::Secrets.read)
-  end
-
-  def test_appends_to_gitignore
-    FileUtils.touch(".gitignore")
-
-    run_generator
-
-    assert_file ".gitignore", /config\/secrets.yml.key/, /(?!config\/secrets.yml.enc)/
-  end
-
-  def test_warns_when_ignore_is_missing
-    assert_match(/Add this to your ignore file/i, run_generator)
-  end
-
-  def test_doesnt_generate_a_new_key_file_if_already_opted_in_to_encrypted_secrets
-    FileUtils.mkdir("config")
-    File.open("config/secrets.yml.enc", "w") { |f| f.puts "already secrety" }
-
-    run_generator
-
-    assert_no_file "config/secrets.yml.key"
-  end
-end
diff --git a/railties/test/generators/generated_attribute_test.rb b/railties/test/generators/generated_attribute_test.rb
index c6f7bdeda1..772b4f6f0d 100644
--- a/railties/test/generators/generated_attribute_test.rb
+++ b/railties/test/generators/generated_attribute_test.rb
@@ -104,25 +104,25 @@ class GeneratedAttributeTest < Rails::Generators::TestCase
 
   def test_reference_is_true
     %w(references belongs_to).each do |attribute_type|
-      assert create_generated_attribute(attribute_type).reference?
+      assert_predicate create_generated_attribute(attribute_type), :reference?
     end
   end
 
   def test_reference_is_false
     %w(foo bar baz).each do |attribute_type|
-      assert !create_generated_attribute(attribute_type).reference?
+      assert_not_predicate create_generated_attribute(attribute_type), :reference?
     end
   end
 
   def test_polymorphic_reference_is_true
     %w(references belongs_to).each do |attribute_type|
-      assert create_generated_attribute("#{attribute_type}{polymorphic}").polymorphic?
+      assert_predicate create_generated_attribute("#{attribute_type}{polymorphic}"), :polymorphic?
     end
   end
 
   def test_polymorphic_reference_is_false
     %w(foo bar baz).each do |attribute_type|
-      assert !create_generated_attribute("#{attribute_type}{polymorphic}").polymorphic?
+      assert_not_predicate create_generated_attribute("#{attribute_type}{polymorphic}"), :polymorphic?
     end
   end
 
@@ -148,7 +148,7 @@ class GeneratedAttributeTest < Rails::Generators::TestCase
     att = Rails::Generators::GeneratedAttribute.parse("supplier:references{required}:index")
     assert_equal "supplier", att.name
     assert_equal :references, att.type
-    assert att.has_index?
-    assert att.required?
+    assert_predicate att, :has_index?
+    assert_predicate att, :required?
   end
 end
diff --git a/railties/test/generators/generators_test_helper.rb b/railties/test/generators/generators_test_helper.rb
index cb5d8da7b1..ad2a55f496 100644
--- a/railties/test/generators/generators_test_helper.rb
+++ b/railties/test/generators/generators_test_helper.rb
@@ -43,9 +43,9 @@ module GeneratorsTestHelper
   end
 
   def copy_routes
-    routes = File.expand_path("../../lib/rails/generators/rails/app/templates/config/routes.rb", __dir__)
+    routes = File.expand_path("../../lib/rails/generators/rails/app/templates/config/routes.rb.tt", __dir__)
     destination = File.join(destination_root, "config")
     FileUtils.mkdir_p(destination)
-    FileUtils.cp routes, destination
+    FileUtils.cp routes, File.join(destination, "routes.rb")
   end
 end
diff --git a/railties/test/generators/job_generator_test.rb b/railties/test/generators/job_generator_test.rb
index 13276fac65..234ba6dad7 100644
--- a/railties/test/generators/job_generator_test.rb
+++ b/railties/test/generators/job_generator_test.rb
@@ -35,4 +35,14 @@ class JobGeneratorTest < Rails::Generators::TestCase
       assert_match(/class ApplicationJob < ActiveJob::Base/, job)
     end
   end
+
+  def test_job_suffix_is_not_duplicated
+    run_generator ["notifier_job"]
+
+    assert_no_file "app/jobs/notifier_job_job.rb"
+    assert_file "app/jobs/notifier_job.rb"
+
+    assert_no_file "test/jobs/notifier_job_job_test.rb"
+    assert_file "test/jobs/notifier_job_test.rb"
+  end
 end
diff --git a/railties/test/generators/model_generator_test.rb b/railties/test/generators/model_generator_test.rb
index 516aa0704f..8d933e82c3 100644
--- a/railties/test/generators/model_generator_test.rb
+++ b/railties/test/generators/model_generator_test.rb
@@ -2,7 +2,6 @@
 
 require "generators/generators_test_helper"
 require "rails/generators/rails/model/model_generator"
-require "active_support/core_ext/string/strip"
 
 class ModelGeneratorTest < Rails::Generators::TestCase
   include GeneratorsTestHelper
@@ -379,10 +378,10 @@ class ModelGeneratorTest < Rails::Generators::TestCase
   def test_required_belongs_to_adds_required_association
     run_generator ["account", "supplier:references{required}"]
 
-    expected_file = <<-FILE.strip_heredoc
-    class Account < ApplicationRecord
-      belongs_to :supplier, required: true
-    end
+    expected_file = <<~FILE
+      class Account < ApplicationRecord
+        belongs_to :supplier, required: true
+      end
     FILE
     assert_file "app/models/account.rb", expected_file
   end
@@ -390,10 +389,10 @@ class ModelGeneratorTest < Rails::Generators::TestCase
   def test_required_polymorphic_belongs_to_generages_correct_model
     run_generator ["account", "supplier:references{required,polymorphic}"]
 
-    expected_file = <<-FILE.strip_heredoc
-    class Account < ApplicationRecord
-      belongs_to :supplier, polymorphic: true, required: true
-    end
+    expected_file = <<~FILE
+      class Account < ApplicationRecord
+        belongs_to :supplier, polymorphic: true, required: true
+      end
     FILE
     assert_file "app/models/account.rb", expected_file
   end
@@ -401,10 +400,10 @@ class ModelGeneratorTest < Rails::Generators::TestCase
   def test_required_and_polymorphic_are_order_independent
     run_generator ["account", "supplier:references{polymorphic.required}"]
 
-    expected_file = <<-FILE.strip_heredoc
-    class Account < ApplicationRecord
-      belongs_to :supplier, polymorphic: true, required: true
-    end
+    expected_file = <<~FILE
+      class Account < ApplicationRecord
+        belongs_to :supplier, polymorphic: true, required: true
+      end
     FILE
     assert_file "app/models/account.rb", expected_file
   end
@@ -452,11 +451,11 @@ class ModelGeneratorTest < Rails::Generators::TestCase
 
   def test_token_option_adds_has_secure_token
     run_generator ["user", "token:token", "auth_token:token"]
-    expected_file = <<-FILE.strip_heredoc
-    class User < ApplicationRecord
-      has_secure_token
-      has_secure_token :auth_token
-    end
+    expected_file = <<~FILE
+      class User < ApplicationRecord
+        has_secure_token
+        has_secure_token :auth_token
+      end
     FILE
     assert_file "app/models/user.rb", expected_file
   end
diff --git a/railties/test/generators/named_base_test.rb b/railties/test/generators/named_base_test.rb
index 67f05926e3..4e61b660d7 100644
--- a/railties/test/generators/named_base_test.rb
+++ b/railties/test/generators/named_base_test.rb
@@ -33,6 +33,17 @@ class NamedBaseTest < Rails::Generators::TestCase
     assert_name g, "foos",       :plural_name
     assert_name g, "admin.foo",  :i18n_scope
     assert_name g, "admin_foos", :table_name
+    assert_name g, "admin/foos", :controller_name
+    assert_name g, %w(admin),     :controller_class_path
+    assert_name g, "Admin::Foos", :controller_class_name
+    assert_name g, "admin/foos",  :controller_file_path
+    assert_name g, "foos",        :controller_file_name
+    assert_name g, "admin.foos",  :controller_i18n_scope
+    assert_name g, "admin_foo",  :singular_route_name
+    assert_name g, "admin_foos", :plural_route_name
+    assert_name g, "@admin_foo", :redirect_resource_name
+    assert_name g, "admin_foo",  :model_resource_name
+    assert_name g, "admin_foos", :index_helper
   end
 
   def test_named_generator_attributes_as_ruby
@@ -47,6 +58,17 @@ class NamedBaseTest < Rails::Generators::TestCase
     assert_name g, "foos",       :plural_name
     assert_name g, "admin.foo",  :i18n_scope
     assert_name g, "admin_foos", :table_name
+    assert_name g, "Admin::Foos", :controller_name
+    assert_name g, %w(admin),     :controller_class_path
+    assert_name g, "Admin::Foos", :controller_class_name
+    assert_name g, "admin/foos",  :controller_file_path
+    assert_name g, "foos",        :controller_file_name
+    assert_name g, "admin.foos",  :controller_i18n_scope
+    assert_name g, "admin_foo",  :singular_route_name
+    assert_name g, "admin_foos", :plural_route_name
+    assert_name g, "@admin_foo", :redirect_resource_name
+    assert_name g, "admin_foo",  :model_resource_name
+    assert_name g, "admin_foos", :index_helper
   end
 
   def test_named_generator_attributes_without_pluralized
@@ -59,7 +81,7 @@ class NamedBaseTest < Rails::Generators::TestCase
     ActiveRecord::Base.pluralize_table_names = original_pluralize_table_names
   end
 
-  def test_scaffold_plural_names
+  def test_namespaced_scaffold_plural_names
     g = generator ["admin/foo"]
     assert_name g, "admin/foos",  :controller_name
     assert_name g, %w(admin),     :controller_class_path
@@ -69,7 +91,7 @@ class NamedBaseTest < Rails::Generators::TestCase
     assert_name g, "admin.foos",  :controller_i18n_scope
   end
 
-  def test_scaffold_plural_names_as_ruby
+  def test_namespaced_scaffold_plural_names_as_ruby
     g = generator ["Admin::Foo"]
     assert_name g, "Admin::Foos", :controller_name
     assert_name g, %w(admin),     :controller_class_path
@@ -131,6 +153,19 @@ class NamedBaseTest < Rails::Generators::TestCase
     assert_name g, "admin/foos",  :controller_file_path
     assert_name g, "foos",        :controller_file_name
     assert_name g, "admin.foos",  :controller_i18n_scope
+    assert_name g, "admin_user",  :singular_route_name
+    assert_name g, "admin_users", :plural_route_name
+    assert_name g, "[:admin, @user]", :redirect_resource_name
+    assert_name g, "[:admin, user]",  :model_resource_name
+    assert_name g, "admin_users", :index_helper
+  end
+
+  def test_scaffold_plural_names
+    g = generator ["User"]
+    assert_name g, "@user", :redirect_resource_name
+    assert_name g, "user",  :model_resource_name
+    assert_name g, "user",  :singular_route_name
+    assert_name g, "users", :plural_route_name
   end
 
   private
diff --git a/railties/test/generators/namespaced_generators_test.rb b/railties/test/generators/namespaced_generators_test.rb
index 205014c80a..4b75a31f17 100644
--- a/railties/test/generators/namespaced_generators_test.rb
+++ b/railties/test/generators/namespaced_generators_test.rb
@@ -152,7 +152,7 @@ class NamespacedMailerGeneratorTest < NamespacedGeneratorTestCase
     assert_file "app/mailers/test_app/notifier_mailer.rb" do |mailer|
       assert_match(/module TestApp/, mailer)
       assert_match(/class NotifierMailer < ApplicationMailer/, mailer)
-      assert_no_match(/default from: "from@example.com"/, mailer)
+      assert_no_match(/default from: "from@example\.com"/, mailer)
     end
   end
 
diff --git a/railties/test/generators/plugin_generator_test.rb b/railties/test/generators/plugin_generator_test.rb
index 38130ceb68..28ac3611b7 100644
--- a/railties/test/generators/plugin_generator_test.rb
+++ b/railties/test/generators/plugin_generator_test.rb
@@ -82,11 +82,12 @@ class PluginGeneratorTest < Rails::Generators::TestCase
   end
 
   def test_generating_in_full_mode_with_almost_of_all_skip_options
-    run_generator [destination_root, "--full", "-M", "-O", "-C", "-S", "-T"]
+    run_generator [destination_root, "--full", "-M", "-O", "-C", "-S", "-T", "--skip-active-storage"]
     assert_file "bin/rails" do |content|
       assert_no_match(/\s+require\s+["']rails\/all["']/, content)
     end
     assert_file "bin/rails", /#\s+require\s+["']active_record\/railtie["']/
+    assert_file "bin/rails", /#\s+require\s+["']active_storage\/engine["']/
     assert_file "bin/rails", /#\s+require\s+["']action_mailer\/railtie["']/
     assert_file "bin/rails", /#\s+require\s+["']action_cable\/engine["']/
     assert_file "bin/rails", /#\s+require\s+["']sprockets\/railtie["']/
@@ -216,12 +217,22 @@ class PluginGeneratorTest < Rails::Generators::TestCase
 
   def test_javascripts_generation
     run_generator [destination_root, "--mountable"]
-    assert_file "app/assets/javascripts/bukkits/application.js"
+    assert_file "app/assets/javascripts/bukkits/application.js" do |content|
+      assert_match "//= require rails-ujs", content
+      assert_match "//= require activestorage", content
+      assert_match "//= require_tree .", content
+    end
+    assert_file "app/views/layouts/bukkits/application.html.erb" do |content|
+      assert_match "javascript_include_tag", content
+    end
   end
 
   def test_skip_javascripts
     run_generator [destination_root, "--skip-javascript", "--mountable"]
     assert_no_file "app/assets/javascripts/bukkits/application.js"
+    assert_file "app/views/layouts/bukkits/application.html.erb" do |content|
+      assert_no_match "javascript_include_tag", content
+    end
   end
 
   def test_template_from_dir_pwd
@@ -240,8 +251,7 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     run_generator [destination_root, "--full", "--skip_active_record"]
     FileUtils.cd destination_root
     quietly { system "bundle install" }
-    # FIXME: Active Storage will provoke a test error without ActiveRecord (fix by allowing to skip active storage)
-    assert_match(/1 runs, 0 assertions, 0 failures, 1 errors/, `bundle exec rake test 2>&1`)
+    assert_match(/1 runs, 1 assertions, 0 failures, 0 errors/, `bundle exec rake test 2>&1`)
   end
 
   def test_ensure_that_migration_tasks_work_with_mountable_option
@@ -321,8 +331,11 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_file "app/helpers/bukkits/application_helper.rb", /module Bukkits\n  module ApplicationHelper/
     assert_file "app/views/layouts/bukkits/application.html.erb" do |contents|
       assert_match "<title>Bukkits</title>", contents
+      assert_match "<%= csrf_meta_tags %>", contents
+      assert_match "<%= csp_meta_tag %>", contents
       assert_match(/stylesheet_link_tag\s+['"]bukkits\/application['"]/, contents)
       assert_match(/javascript_include_tag\s+['"]bukkits\/application['"]/, contents)
+      assert_match "<%= yield %>", contents
     end
     assert_file "test/test_helper.rb" do |content|
       assert_match(/ActiveRecord::Migrator\.migrations_paths.+\.\.\/test\/dummy\/db\/migrate/, content)
@@ -475,6 +488,8 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_no_file "test/dummy/Gemfile"
     assert_no_file "test/dummy/public/robots.txt"
     assert_no_file "test/dummy/README.md"
+    assert_no_file "test/dummy/config/master.key"
+    assert_no_file "test/dummy/config/credentials.yml.enc"
     assert_no_directory "test/dummy/lib/tasks"
     assert_no_directory "test/dummy/test"
     assert_no_directory "test/dummy/vendor"
@@ -514,10 +529,11 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     gemfile_path = "#{Rails.root}/Gemfile"
     Object.const_set("APP_PATH", Rails.root)
     FileUtils.touch gemfile_path
+    File.write(gemfile_path, "#foo")
 
     run_generator
 
-    assert_file gemfile_path, /gem 'bukkits', path: 'tmp\/bukkits'/
+    assert_file gemfile_path, /^gem 'bukkits', path: 'tmp\/bukkits'/
   ensure
     Object.send(:remove_const, "APP_PATH")
     FileUtils.rm gemfile_path
@@ -719,6 +735,38 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     Object.send(:remove_const, "ENGINE_ROOT")
   end
 
+  def test_after_bundle_callback
+    path = "http://example.org/rails_template"
+    template = %{ after_bundle { run "echo ran after_bundle" } }.dup
+    template.instance_eval "def read; self; end" # Make the string respond to read
+
+    check_open = -> *args do
+      assert_equal [ path, "Accept" => "application/x-thor-template" ], args
+      template
+    end
+
+    sequence = ["echo ran after_bundle"]
+    @sequence_step ||= 0
+    ensure_bundler_first = -> command do
+      assert_equal sequence[@sequence_step], command, "commands should be called in sequence #{sequence}"
+      @sequence_step += 1
+    end
+
+    content = nil
+    generator([destination_root], template: path).stub(:open, check_open, template) do
+      generator.stub(:bundle_command, ensure_bundler_first) do
+        generator.stub(:run, ensure_bundler_first) do
+          silence_stream($stdout) do
+            content = capture(:stderr) { generator.invoke_all }
+          end
+        end
+      end
+    end
+
+    assert_equal 1, @sequence_step
+    assert_match(/DEPRECATION WARNING: `after_bundle` is deprecated/, content)
+  end
+
   private
 
     def action(*args, &block)
diff --git a/railties/test/generators/plugin_test_runner_test.rb b/railties/test/generators/plugin_test_runner_test.rb
index 28a76f0617..89c3f1e496 100644
--- a/railties/test/generators/plugin_test_runner_test.rb
+++ b/railties/test/generators/plugin_test_runner_test.rb
@@ -105,6 +105,12 @@ class PluginTestRunnerTest < ActiveSupport::TestCase
       capture(:stderr) { run_test_command("test/models/warnings_test.rb -w") })
   end
 
+  def test_run_rake_test
+    create_test_file "foo"
+    result = Dir.chdir(plugin_path) { `rake test TEST=test/foo_test.rb` }
+    assert_match "1 runs, 1 assertions, 0 failures", result
+  end
+
   private
     def plugin_path
       "#{@destination_root}/bukkits"
diff --git a/railties/test/generators/scaffold_controller_generator_test.rb b/railties/test/generators/scaffold_controller_generator_test.rb
index 384524aba9..fd5aa817b4 100644
--- a/railties/test/generators/scaffold_controller_generator_test.rb
+++ b/railties/test/generators/scaffold_controller_generator_test.rb
@@ -174,6 +174,29 @@ class ScaffoldControllerGeneratorTest < Rails::Generators::TestCase
       assert_instance_method :index, content do |m|
         assert_match("@users = User.all", m)
       end
+
+      assert_instance_method :create, content do |m|
+        assert_match("redirect_to [:admin, @user]", m)
+      end
+
+      assert_instance_method :update, content do |m|
+        assert_match("redirect_to [:admin, @user]", m)
+      end
+    end
+
+    assert_file "app/views/admin/users/index.html.erb" do |content|
+      assert_match("'Show', [:admin, user]", content)
+      assert_match("'Edit', edit_admin_user_path(user)", content)
+      assert_match("'Destroy', [:admin, user]", content)
+      assert_match("'New User', new_admin_user_path", content)
+    end
+
+    assert_file "app/views/admin/users/new.html.erb" do |content|
+      assert_match("'Back', admin_users_path", content)
+    end
+
+    assert_file "app/views/admin/users/_form.html.erb" do |content|
+      assert_match("model: [:admin, user]", content)
     end
   end
 
@@ -184,6 +207,7 @@ class ScaffoldControllerGeneratorTest < Rails::Generators::TestCase
 
     Dir.chdir(engine_path) do
       quietly { `bin/rails g controller dashboard foo` }
+      quietly { `bin/rails db:migrate RAILS_ENV=test` }
       assert_match(/2 runs, 2 assertions, 0 failures, 0 errors/, `bin/rails test 2>&1`)
     end
   end
@@ -195,6 +219,7 @@ class ScaffoldControllerGeneratorTest < Rails::Generators::TestCase
 
     Dir.chdir(engine_path) do
       quietly { `bin/rails g controller dashboard foo` }
+      quietly { `bin/rails db:migrate RAILS_ENV=test` }
       assert_match(/2 runs, 2 assertions, 0 failures, 0 errors/, `bin/rails test 2>&1`)
     end
   end
diff --git a/railties/test/generators/scaffold_generator_test.rb b/railties/test/generators/scaffold_generator_test.rb
index 03322c1c59..3e631f6021 100644
--- a/railties/test/generators/scaffold_generator_test.rb
+++ b/railties/test/generators/scaffold_generator_test.rb
@@ -282,7 +282,14 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
                 /class Admin::RolesTest < ApplicationSystemTestCase/
 
     # Views
-    %w(index edit new show _form).each do |view|
+    assert_file "app/views/admin/roles/index.html.erb" do |content|
+      assert_match("'Show', admin_role", content)
+      assert_match("'Edit', edit_admin_role_path(admin_role)", content)
+      assert_match("'Destroy', admin_role", content)
+      assert_match("'New Admin Role', new_admin_role_path", content)
+    end
+
+    %w(edit new show _form).each do |view|
       assert_file "app/views/admin/roles/#{view}.html.erb"
     end
     assert_no_file "app/views/layouts/admin/roles.html.erb"
@@ -340,7 +347,7 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
     content = File.read(route_path).gsub(/\.routes\.draw do/) do |match|
       "#{match} |map|"
     end
-    File.open(route_path, "wb") { |file| file.write(content) }
+    File.write(route_path, content)
 
     run_generator ["product_line"], behavior: :revoke
 
@@ -357,7 +364,7 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
     content.gsub!(/^  \#.*\n/, "")
     content.gsub!(/^\n/, "")
 
-    File.open(route_path, "wb") { |file| file.write(content) }
+    File.write(route_path, content)
     assert_file "config/routes.rb", /\.routes\.draw do\n  resources :product_lines\nend\n\z/
 
     run_generator ["product_line"], behavior: :revoke
@@ -464,8 +471,8 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
     end
 
     assert_file "app/views/accounts/_form.html.erb" do |content|
-      assert_match(/^\W{4}<%= form\.text_field :name, id: :account_name %>/, content)
-      assert_match(/^\W{4}<%= form\.text_field :currency_id, id: :account_currency_id %>/, content)
+      assert_match(/^\W{4}<%= form\.text_field :name %>/, content)
+      assert_match(/^\W{4}<%= form\.text_field :currency_id %>/, content)
     end
   end
 
@@ -488,8 +495,8 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
     end
 
     assert_file "app/views/users/_form.html.erb" do |content|
-      assert_match(/<%= form\.password_field :password, id: :user_password %>/, content)
-      assert_match(/<%= form\.password_field :password_confirmation, id: :user_password_confirmation %>/, content)
+      assert_match(/<%= form\.password_field :password %>/, content)
+      assert_match(/<%= form\.password_field :password_confirmation %>/, content)
     end
 
     assert_file "app/views/users/index.html.erb" do |content|
diff --git a/railties/test/generators/shared_generator_tests.rb b/railties/test/generators/shared_generator_tests.rb
index 56c9b37e1b..aa577e4234 100644
--- a/railties/test/generators/shared_generator_tests.rb
+++ b/railties/test/generators/shared_generator_tests.rb
@@ -9,7 +9,7 @@ module SharedGeneratorTests
     super
     Rails::Generators::AppGenerator.instance_variable_set("@desc", nil)
 
-    Kernel::silence_warnings do
+    Kernel.silence_warnings do
       Thor::Base.shell.send(:attr_accessor, :always_force)
       @shell = Thor::Base.shell.new
       @shell.send(:always_force=, true)
@@ -92,7 +92,9 @@ module SharedGeneratorTests
     end
 
     generator([destination_root], template: path).stub(:open, check_open, template) do
-      quietly { assert_match(/It works!/, capture(:stdout) { generator.invoke_all }) }
+      generator.stub :bundle_command, nil do
+        quietly { assert_match(/It works!/, capture(:stdout) { generator.invoke_all }) }
+      end
     end
   end
 
@@ -103,15 +105,6 @@ module SharedGeneratorTests
     end
   end
 
-  def test_skip_bundle
-    assert_not_called(generator([destination_root], skip_bundle: true), :bundle_command) do
-      quietly { generator.invoke_all }
-      # skip_bundle is only about running bundle install, ensure the Gemfile is still
-      # generated.
-      assert_file "Gemfile"
-    end
-  end
-
   def test_skip_git
     run_generator [destination_root, "--skip-git", "--full"]
     assert_no_file(".gitignore")
@@ -129,13 +122,26 @@ module SharedGeneratorTests
   end
 
   def test_default_frameworks_are_required_when_others_are_removed
-    run_generator [destination_root, "--skip-active-record", "--skip-action-mailer", "--skip-action-cable", "--skip-sprockets"]
-    assert_file "#{application_path}/config/application.rb", /require\s+["']rails["']/
-    assert_file "#{application_path}/config/application.rb", /require\s+["']active_model\/railtie["']/
-    assert_file "#{application_path}/config/application.rb", /require\s+["']active_job\/railtie["']/
-    assert_file "#{application_path}/config/application.rb", /require\s+["']action_controller\/railtie["']/
-    assert_file "#{application_path}/config/application.rb", /require\s+["']action_view\/railtie["']/
-    assert_file "#{application_path}/config/application.rb", /require\s+["']active_storage\/engine["']/
+    run_generator [
+      destination_root,
+      "--skip-active-record",
+      "--skip-active-storage",
+      "--skip-action-mailer",
+      "--skip-action-cable",
+      "--skip-sprockets"
+    ]
+
+    assert_file "#{application_path}/config/application.rb", /^require\s+["']rails["']/
+    assert_file "#{application_path}/config/application.rb", /^require\s+["']active_model\/railtie["']/
+    assert_file "#{application_path}/config/application.rb", /^require\s+["']active_job\/railtie["']/
+    assert_file "#{application_path}/config/application.rb", /^# require\s+["']active_record\/railtie["']/
+    assert_file "#{application_path}/config/application.rb", /^# require\s+["']active_storage\/engine["']/
+    assert_file "#{application_path}/config/application.rb", /^require\s+["']action_controller\/railtie["']/
+    assert_file "#{application_path}/config/application.rb", /^# require\s+["']action_mailer\/railtie["']/
+    assert_file "#{application_path}/config/application.rb", /^require\s+["']action_view\/railtie["']/
+    assert_file "#{application_path}/config/application.rb", /^# require\s+["']action_cable\/engine["']/
+    assert_file "#{application_path}/config/application.rb", /^# require\s+["']sprockets\/railtie["']/
+    assert_file "#{application_path}/config/application.rb", /^require\s+["']rails\/test_unit\/railtie["']/
   end
 
   def test_generator_without_skips
@@ -149,7 +155,7 @@ module SharedGeneratorTests
     end
     assert_file "#{application_path}/config/environments/production.rb" do |content|
       assert_match(/# config\.action_mailer\.raise_delivery_errors = false/, content)
-      assert_match(/^  config\.read_encrypted_secrets = true/, content)
+      assert_match(/^  # config\.require_master_key = true/, content)
     end
   end
 
@@ -189,6 +195,94 @@ module SharedGeneratorTests
     end
   end
 
+  def test_generator_for_active_storage
+    run_generator
+
+    assert_file "#{application_path}/app/assets/javascripts/application.js" do |content|
+      assert_match(/^\/\/= require activestorage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/development.rb" do |content|
+      assert_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/production.rb" do |content|
+      assert_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/test.rb" do |content|
+      assert_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{application_path}/config/storage.yml"
+    assert_directory "#{application_path}/storage"
+    assert_directory "#{application_path}/tmp/storage"
+
+    assert_file ".gitignore" do |content|
+      assert_match(/\/storage\//, content)
+    end
+  end
+
+  def test_generator_if_skip_active_storage_is_given
+    run_generator [destination_root, "--skip-active-storage"]
+
+    assert_file "#{application_path}/config/application.rb", /#\s+require\s+["']active_storage\/engine["']/
+
+    assert_file "#{application_path}/app/assets/javascripts/application.js" do |content|
+      assert_no_match(/^\/\/= require activestorage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/development.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/production.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/test.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_no_file "#{application_path}/config/storage.yml"
+    assert_no_directory "#{application_path}/storage"
+    assert_no_directory "#{application_path}/tmp/storage"
+
+    assert_file ".gitignore" do |content|
+      assert_no_match(/\/storage\//, content)
+    end
+  end
+
+  def test_generator_does_not_generate_active_storage_contents_if_skip_active_record_is_given
+    run_generator [destination_root, "--skip-active-record"]
+
+    assert_file "#{application_path}/config/application.rb", /#\s+require\s+["']active_storage\/engine["']/
+
+    assert_file "#{application_path}/app/assets/javascripts/application.js" do |content|
+      assert_no_match(/^\/\/= require activestorage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/development.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/production.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_file "#{application_path}/config/environments/test.rb" do |content|
+      assert_no_match(/config\.active_storage/, content)
+    end
+
+    assert_no_file "#{application_path}/config/storage.yml"
+    assert_no_directory "#{application_path}/storage"
+    assert_no_directory "#{application_path}/tmp/storage"
+
+    assert_file ".gitignore" do |content|
+      assert_no_match(/\/storage\//, content)
+    end
+  end
+
   def test_generator_if_skip_action_mailer_is_given
     run_generator [destination_root, "--skip-action-mailer"]
     assert_file "#{application_path}/config/application.rb", /#\s+require\s+["']action_mailer\/railtie["']/
diff --git a/railties/test/generators_test.rb b/railties/test/generators_test.rb
index 28e7617d7f..a16a2d3f0a 100644
--- a/railties/test/generators_test.rb
+++ b/railties/test/generators_test.rb
@@ -33,13 +33,26 @@ class GeneratorsTest < Rails::Generators::TestCase
   def test_generator_suggestions
     name = :migrationz
     output = capture(:stdout) { Rails::Generators.invoke name }
-    assert_match "Maybe you meant 'migration'", output
+    assert_match 'Maybe you meant "migration"?', output
+  end
+
+  def test_generator_suggestions_except_en_locale
+    orig_available_locales = I18n.available_locales
+    orig_default_locale = I18n.default_locale
+    I18n.available_locales = :ja
+    I18n.default_locale = :ja
+    name = :tas
+    output = capture(:stdout) { Rails::Generators.invoke name }
+    assert_match 'Maybe you meant "task"?', output
+  ensure
+    I18n.available_locales = orig_available_locales
+    I18n.default_locale = orig_default_locale
   end
 
   def test_generator_multiple_suggestions
     name = :tas
     output = capture(:stdout) { Rails::Generators.invoke name }
-    assert_match "Maybe you meant 'task', 'job' or", output
+    assert_match 'Maybe you meant "task"?', output
   end
 
   def test_help_when_a_generator_with_required_arguments_is_invoked_without_arguments
@@ -51,7 +64,7 @@ class GeneratorsTest < Rails::Generators::TestCase
     assert File.exist?(File.join(@path, "generators", "model_generator.rb"))
     assert_called_with(Rails::Generators::ModelGenerator, :start, [["Account"], {}]) do
       warnings = capture(:stderr) { Rails::Generators.invoke :model, ["Account"] }
-      assert warnings.empty?
+      assert_empty warnings
     end
   end
 
diff --git a/railties/test/isolation/abstract_unit.rb b/railties/test/isolation/abstract_unit.rb
index e79bf09654..3cde7c03b0 100644
--- a/railties/test/isolation/abstract_unit.rb
+++ b/railties/test/isolation/abstract_unit.rb
@@ -38,7 +38,12 @@ module TestHelpers
     end
 
     def app_path(*args)
-      tmp_path(*%w[app] + args)
+      path = tmp_path(*%w[app] + args)
+      if block_given?
+        yield path
+      else
+        path
+      end
     end
 
     def framework_path
@@ -56,10 +61,7 @@ module TestHelpers
       @app ||= begin
         ENV["RAILS_ENV"] = env
 
-        # FIXME: shush Sass warning spam, not relevant to testing Railties
-        Kernel.silence_warnings do
-          require "#{app_path}/config/environment"
-        end
+        require "#{app_path}/config/environment"
 
         Rails.application
       end
@@ -85,22 +87,6 @@ module TestHelpers
       assert_match "charset=utf-8", resp[1]["Content-Type"]
       assert extract_body(resp).match(/Yay! You.*re on Rails!/)
     end
-
-    def assert_success(resp)
-      assert_equal 202, resp[0]
-    end
-
-    def assert_missing(resp)
-      assert_equal 404, resp[0]
-    end
-
-    def assert_header(key, value, resp)
-      assert_equal value, resp[1][key.to_s]
-    end
-
-    def assert_body(expected, resp)
-      assert_equal expected, extract_body(resp)
-    end
   end
 
   module Generation
@@ -108,7 +94,6 @@ module TestHelpers
     def build_app(options = {})
       @prev_rails_env = ENV["RAILS_ENV"]
       ENV["RAILS_ENV"] = "development"
-      ENV["SECRET_KEY_BASE"] ||= SecureRandom.hex(16)
 
       FileUtils.rm_rf(app_path)
       FileUtils.cp_r(app_template_path, app_path)
@@ -127,22 +112,57 @@ module TestHelpers
         end
       end
 
-      File.open("#{app_path}/config/database.yml", "w") do |f|
-        f.puts <<-YAML
-        default: &default
-          adapter: sqlite3
-          pool: 5
-          timeout: 5000
-        development:
-          <<: *default
-          database: db/development.sqlite3
-        test:
-          <<: *default
-          database: db/test.sqlite3
-        production:
-          <<: *default
-          database: db/production.sqlite3
-        YAML
+      if options[:multi_db]
+        File.open("#{app_path}/config/database.yml", "w") do |f|
+          f.puts <<-YAML
+          default: &default
+            adapter: sqlite3
+            pool: 5
+            timeout: 5000
+          development:
+            primary:
+              <<: *default
+              database: db/development.sqlite3
+            animals:
+              <<: *default
+              database: db/development_animals.sqlite3
+              migrations_paths: db/animals_migrate
+          test:
+            primary:
+              <<: *default
+              database: db/test.sqlite3
+            animals:
+              <<: *default
+              database: db/test_animals.sqlite3
+              migrations_paths: db/animals_migrate
+          production:
+            primary:
+              <<: *default
+              database: db/production.sqlite3
+            animals:
+              <<: *default
+              database: db/production_animals.sqlite3
+              migrations_paths: db/animals_migrate
+          YAML
+        end
+      else
+        File.open("#{app_path}/config/database.yml", "w") do |f|
+          f.puts <<-YAML
+          default: &default
+            adapter: sqlite3
+            pool: 5
+            timeout: 5000
+          development:
+            <<: *default
+            database: db/development.sqlite3
+          test:
+            <<: *default
+            database: db/test.sqlite3
+          production:
+            <<: *default
+            database: db/production.sqlite3
+          YAML
+        end
       end
 
       add_to_config <<-RUBY
@@ -157,6 +177,7 @@ module TestHelpers
 
     def teardown_app
       ENV["RAILS_ENV"] = @prev_rails_env if @prev_rails_env
+      FileUtils.rm_rf(tmp_path)
     end
 
     # Make a very basic app, without creating the whole directory structure.
@@ -166,9 +187,10 @@ module TestHelpers
       require "action_controller/railtie"
       require "action_view/railtie"
 
-      @app = Class.new(Rails::Application)
+      @app = Class.new(Rails::Application) do
+        def self.name; "RailtiesTestApp"; end
+      end
       @app.config.eager_load = false
-      @app.secrets.secret_key_base = "3b7cd727ee24e8444053437c36cc66c4"
       @app.config.session_store :cookie_store, key: "_myapp_session"
       @app.config.active_support.deprecation = :log
       @app.config.active_support.test_order = :random
@@ -236,10 +258,86 @@ module TestHelpers
       end
     end
 
-    def script(script)
-      Dir.chdir(app_path) do
-        `#{Gem.ruby} #{app_path}/bin/rails #{script}`
+    # Invoke a bin/rails command inside the app
+    #
+    # allow_failure:: true to return normally if the command exits with
+    #   a non-zero status. By default, this method will raise.
+    # stderr:: true to pass STDERR output straight to the "real" STDERR.
+    #   By default, the STDERR and STDOUT of the process will be
+    #   combined in the returned string.
+    def rails(*args, allow_failure: false, stderr: false)
+      args = args.flatten
+      fork = true
+
+      command = "bin/rails #{Shellwords.join args}#{' 2>&1' unless stderr}"
+
+      # Don't fork if the environment has disabled it
+      fork = false if ENV["NO_FORK"]
+
+      # Don't fork if the runtime isn't able to
+      fork = false if !Process.respond_to?(:fork)
+
+      # Don't fork if we're re-invoking minitest
+      fork = false if args.first == "t" || args.grep(/\Atest(:|\z)/).any?
+
+      if fork
+        out_read, out_write = IO.pipe
+        if stderr
+          err_read, err_write = IO.pipe
+        else
+          err_write = out_write
+        end
+
+        pid = fork do
+          out_read.close
+          err_read.close if err_read
+
+          $stdin.reopen(File::NULL, "r")
+          $stdout.reopen(out_write)
+          $stderr.reopen(err_write)
+
+          at_exit do
+            case $!
+            when SystemExit
+              exit! $!.status
+            when nil
+              exit! 0
+            else
+              err_write.puts "#{$!.class}: #{$!}"
+              exit! 1
+            end
+          end
+
+          Rails.instance_variable_set :@_env, nil
+
+          $-v = $-w = false
+          Dir.chdir app_path unless Dir.pwd == app_path
+
+          ARGV.replace(args)
+          load "./bin/rails"
+
+          exit! 0
+        end
+
+        out_write.close
+
+        if err_read
+          err_write.close
+
+          $stderr.write err_read.read
+        end
+
+        output = out_read.read
+
+        Process.waitpid pid
+
+      else
+        output = `cd #{app_path}; #{command}`
       end
+
+      raise "rails command failed (#{$?.exitstatus}): #{command}\n#{output}" unless allow_failure || $?.success?
+
+      output
     end
 
     def add_to_top_of_config(str)
@@ -284,10 +382,12 @@ module TestHelpers
     end
 
     def app_file(path, contents, mode = "w")
-      FileUtils.mkdir_p File.dirname("#{app_path}/#{path}")
-      File.open("#{app_path}/#{path}", mode) do |f|
+      file_name = "#{app_path}/#{path}"
+      FileUtils.mkdir_p File.dirname(file_name)
+      File.open(file_name, mode) do |f|
         f.puts contents
       end
+      file_name
     end
 
     def remove_file(path)
@@ -299,7 +399,7 @@ module TestHelpers
     end
 
     def use_frameworks(arr)
-      to_remove = [:actionmailer, :activerecord] - arr
+      to_remove = [:actionmailer, :activerecord, :activestorage, :activejob] - arr
 
       if to_remove.include?(:activerecord)
         remove_from_config "config.active_record.*"
@@ -307,6 +407,21 @@ module TestHelpers
 
       $:.reject! { |path| path =~ %r'/(#{to_remove.join('|')})/' }
     end
+
+    def use_postgresql
+      File.open("#{app_path}/config/database.yml", "w") do |f|
+        f.puts <<-YAML
+        default: &default
+          adapter: postgresql
+          pool: 5
+          database: railties_test
+        development:
+          <<: *default
+        test:
+          <<: *default
+        YAML
+      end
+    end
   end
 end
 
@@ -315,6 +430,10 @@ class ActiveSupport::TestCase
   include TestHelpers::Rack
   include TestHelpers::Generation
   include ActiveSupport::Testing::Stream
+
+  def frozen_error_class
+    Object.const_defined?(:FrozenError) ? FrozenError : RuntimeError
+  end
 end
 
 # Create a scope and build a fixture rails app
@@ -329,4 +448,25 @@ Module.new do
   File.open("#{app_template_path}/config/boot.rb", "w") do |f|
     f.puts "require 'rails/all'"
   end
+
+  # Fake 'Bundler.require' -- we run using the repo's Gemfile, not an
+  # app-specific one: we don't want to require every gem that lists.
+  contents = File.read("#{app_template_path}/config/application.rb")
+  contents.sub!(/^Bundler\.require.*/, "%w(turbolinks).each { |r| require r }")
+  File.write("#{app_template_path}/config/application.rb", contents)
+
+  require "rails"
+
+  require "active_model"
+  require "active_job"
+  require "active_record"
+  require "action_controller"
+  require "action_mailer"
+  require "action_view"
+  require "active_storage"
+  require "action_cable"
+  require "sprockets"
+
+  require "action_view/helpers"
+  require "action_dispatch/routing/route_set"
 end unless defined?(RAILS_ISOLATED_ENGINE)
diff --git a/railties/test/minitest/rails_plugin_test.rb b/railties/test/minitest/rails_plugin_test.rb
new file mode 100644
index 0000000000..7c3a2022a9
--- /dev/null
+++ b/railties/test/minitest/rails_plugin_test.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+
+class Minitest::RailsPluginTest < ActiveSupport::TestCase
+  setup do
+    @options = Minitest.process_args []
+    @output = StringIO.new("".encode("UTF-8"))
+  end
+
+  test "default reporters are replaced" do
+    with_reporter Minitest::CompositeReporter.new do |reporter|
+      reporter << Minitest::SummaryReporter.new(@output, @options)
+      reporter << Minitest::ProgressReporter.new(@output, @options)
+      reporter << Minitest::Reporter.new(@output, @options)
+
+      Minitest.plugin_rails_init({})
+
+      assert_equal 3, reporter.reporters.count
+      assert reporter.reporters.any? { |candidate| candidate.kind_of?(Minitest::SuppressedSummaryReporter) }
+      assert reporter.reporters.any? { |candidate| candidate.kind_of?(::Rails::TestUnitReporter) }
+      assert reporter.reporters.any? { |candidate| candidate.kind_of?(Minitest::Reporter) }
+    end
+  end
+
+  test "no custom reporters are added if nothing to replace" do
+    with_reporter Minitest::CompositeReporter.new do |reporter|
+      Minitest.plugin_rails_init({})
+
+      assert_empty reporter.reporters
+    end
+  end
+
+  private
+    def with_reporter(reporter)
+      old_reporter, Minitest.reporter = Minitest.reporter, reporter
+
+      yield reporter
+    ensure
+      Minitest.reporter = old_reporter
+    end
+end
diff --git a/railties/test/path_generation_test.rb b/railties/test/path_generation_test.rb
index d4dfa8e4a6..849b183b37 100644
--- a/railties/test/path_generation_test.rb
+++ b/railties/test/path_generation_test.rb
@@ -58,12 +58,14 @@ class PathGenerationTest < ActiveSupport::TestCase
     Rails.logger    = Logger.new nil
 
     app = Class.new(Rails::Application) {
+      def self.name; "ScriptNameTestApp"; end
+
       attr_accessor :controller
+
       def initialize
         super
         app = self
         @routes = TestSet.new ->(c) { app.controller = c }
-        secrets.secret_key_base = "foo"
         secrets.secret_token = "foo"
       end
       def app; routes; end
diff --git a/railties/test/paths_test.rb b/railties/test/paths_test.rb
index 854b4448a4..9f5bb37c20 100644
--- a/railties/test/paths_test.rb
+++ b/railties/test/paths_test.rb
@@ -104,7 +104,7 @@ class PathsTest < ActiveSupport::TestCase
     File.stub(:exist?, true) do
       @root.add "app", with: "/app"
       @root["app"].autoload_once!
-      assert @root["app"].autoload_once?
+      assert_predicate @root["app"], :autoload_once?
       assert_includes @root.autoload_once, @root["app"].expanded.first
     end
   end
@@ -112,17 +112,17 @@ class PathsTest < ActiveSupport::TestCase
   test "it is possible to remove a path that should be autoloaded only once" do
     @root["app"] = "/app"
     @root["app"].autoload_once!
-    assert @root["app"].autoload_once?
+    assert_predicate @root["app"], :autoload_once?
 
     @root["app"].skip_autoload_once!
-    assert !@root["app"].autoload_once?
+    assert_not_predicate @root["app"], :autoload_once?
     assert_not_includes @root.autoload_once, @root["app"].expanded.first
   end
 
   test "it is possible to add a path without assignment and specify it should be loaded only once" do
     File.stub(:exist?, true) do
       @root.add "app", with: "/app", autoload_once: true
-      assert @root["app"].autoload_once?
+      assert_predicate @root["app"], :autoload_once?
       assert_includes @root.autoload_once, "/app"
     end
   end
@@ -130,7 +130,7 @@ class PathsTest < ActiveSupport::TestCase
   test "it is possible to add multiple paths without assignment and specify it should be loaded only once" do
     File.stub(:exist?, true) do
       @root.add "app", with: ["/app", "/app2"], autoload_once: true
-      assert @root["app"].autoload_once?
+      assert_predicate @root["app"], :autoload_once?
       assert_includes @root.autoload_once, "/app"
       assert_includes @root.autoload_once, "/app2"
     end
@@ -158,7 +158,7 @@ class PathsTest < ActiveSupport::TestCase
     File.stub(:exist?, true) do
       @root["app"] = "/app"
       @root["app"].eager_load!
-      assert @root["app"].eager_load?
+      assert_predicate @root["app"], :eager_load?
       assert_includes @root.eager_load, @root["app"].to_a.first
     end
   end
@@ -166,17 +166,17 @@ class PathsTest < ActiveSupport::TestCase
   test "it is possible to skip a path from eager loading" do
     @root["app"] = "/app"
     @root["app"].eager_load!
-    assert @root["app"].eager_load?
+    assert_predicate @root["app"], :eager_load?
 
     @root["app"].skip_eager_load!
-    assert !@root["app"].eager_load?
+    assert_not_predicate @root["app"], :eager_load?
     assert_not_includes @root.eager_load, @root["app"].to_a.first
   end
 
   test "it is possible to add a path without assignment and mark it as eager" do
     File.stub(:exist?, true) do
       @root.add "app", with: "/app", eager_load: true
-      assert @root["app"].eager_load?
+      assert_predicate @root["app"], :eager_load?
       assert_includes @root.eager_load, "/app"
     end
   end
@@ -184,7 +184,7 @@ class PathsTest < ActiveSupport::TestCase
   test "it is possible to add multiple paths without assignment and mark them as eager" do
     File.stub(:exist?, true) do
       @root.add "app", with: ["/app", "/app2"], eager_load: true
-      assert @root["app"].eager_load?
+      assert_predicate @root["app"], :eager_load?
       assert_includes @root.eager_load, "/app"
       assert_includes @root.eager_load, "/app2"
     end
@@ -193,8 +193,8 @@ class PathsTest < ActiveSupport::TestCase
   test "it is possible to create a path without assignment and mark it both as eager and load once" do
     File.stub(:exist?, true) do
       @root.add "app", with: "/app", eager_load: true, autoload_once: true
-      assert @root["app"].eager_load?
-      assert @root["app"].autoload_once?
+      assert_predicate @root["app"], :eager_load?
+      assert_predicate @root["app"], :autoload_once?
       assert_includes @root.eager_load, "/app"
       assert_includes @root.autoload_once, "/app"
     end
@@ -254,7 +254,7 @@ class PathsTest < ActiveSupport::TestCase
   test "a path can be added to the load path on creation" do
     File.stub(:exist?, true) do
       @root.add "app", with: "/app", load_path: true
-      assert @root["app"].load_path?
+      assert_predicate @root["app"], :load_path?
       assert_equal ["/app"], @root.load_paths
     end
   end
@@ -271,7 +271,7 @@ class PathsTest < ActiveSupport::TestCase
   test "a path can be marked as autoload on creation" do
     File.stub(:exist?, true) do
       @root.add "app", with: "/app", autoload: true
-      assert @root["app"].autoload?
+      assert_predicate @root["app"], :autoload?
       assert_equal ["/app"], @root.autoload_paths
     end
   end
diff --git a/railties/test/rack_logger_test.rb b/railties/test/rack_logger_test.rb
index e47f30d5b6..6e8f333e1d 100644
--- a/railties/test/rack_logger_test.rb
+++ b/railties/test/rack_logger_test.rb
@@ -14,14 +14,21 @@ module Rails
 
         attr_reader :logger
 
-        def initialize(logger = NULL, taggers = nil, &block)
-          super(->(_) { block.call; [200, {}, []] }, taggers)
+        def initialize(logger = NULL, app: nil, taggers: nil, &block)
+          app ||= ->(_) { block.call; [200, {}, []] }
+          super(app, taggers)
           @logger = logger
         end
 
         def development?; false; end
       end
 
+      class TestApp < Struct.new(:response)
+        def call(_env)
+          response
+        end
+      end
+
       Subscriber = Struct.new(:starts, :finishes) do
         def initialize(starts = [], finishes = [])
           super
@@ -72,6 +79,17 @@ module Rails
           end
         end
       end
+
+      def test_logger_does_not_mutate_app_return
+        response = [].freeze
+        app = TestApp.new(response)
+        logger = TestLogger.new(app: app)
+        assert_no_changes("response") do
+          assert_nothing_raised do
+            logger.call("REQUEST_METHOD" => "GET")
+          end
+        end
+      end
     end
   end
 end
diff --git a/railties/test/rails_info_test.rb b/railties/test/rails_info_test.rb
index 227a739b71..50522c1be6 100644
--- a/railties/test/rails_info_test.rb
+++ b/railties/test/rails_info_test.rb
@@ -2,27 +2,14 @@
 
 require "abstract_unit"
 
-unless defined?(Rails) && defined?(Rails::Info)
-  module Rails
-    class Info; end
-  end
-end
-
-require "active_support/core_ext/kernel/reporting"
-
 class InfoTest < ActiveSupport::TestCase
-  def setup
-    Rails.send :remove_const, :Info
-    silence_warnings { load "rails/info.rb" }
-  end
-
   def test_property_with_block_swallows_exceptions_and_ignores_property
     assert_nothing_raised do
       Rails::Info.module_eval do
         property("Bogus") { raise }
       end
     end
-    assert !property_defined?("Bogus")
+    assert_not property_defined?("Bogus")
   end
 
   def test_property_with_string
diff --git a/railties/test/railties/engine_test.rb b/railties/test/railties/engine_test.rb
index e6964b4b18..9a3ddc8d5e 100644
--- a/railties/test/railties/engine_test.rb
+++ b/railties/test/railties/engine_test.rb
@@ -32,6 +32,11 @@ module RailtiesTest
       require "#{app_path}/config/environment"
     end
 
+    def migrations
+      migration_root = File.expand_path(ActiveRecord::Migrator.migrations_paths.first, app_path)
+      ActiveRecord::MigrationContext.new(migration_root).migrations
+    end
+
     test "serving sprocket's assets" do
       @plugin.write "app/assets/javascripts/engine.js.erb", "<%= :alert %>();"
       add_to_env_config "development", "config.assets.digest = false"
@@ -82,31 +87,32 @@ module RailtiesTest
         end
       RUBY
 
-      add_to_config "ActiveRecord::Base.timestamped_migrations = false"
-
       boot_rails
 
       Dir.chdir(app_path) do
+        # Install Active Storage migration file first so as not to affect test.
+        `bundle exec rake active_storage:install`
         output = `bundle exec rake bukkits:install:migrations`
 
-        assert File.exist?("#{app_path}/db/migrate/2_create_users.bukkits.rb")
-        assert File.exist?("#{app_path}/db/migrate/3_add_last_name_to_users.bukkits.rb")
-        assert_match(/Copied migration 2_create_users\.bukkits\.rb from bukkits/, output)
-        assert_match(/Copied migration 3_add_last_name_to_users\.bukkits\.rb from bukkits/, output)
-        assert_match(/NOTE: Migration 3_create_sessions\.rb from bukkits has been skipped/, output)
-        assert_equal 3, Dir["#{app_path}/db/migrate/*.rb"].length
-
-        output = `bundle exec rake railties:install:migrations`.split("\n")
+        ["CreateUsers", "AddLastNameToUsers", "CreateSessions"].each do |migration_name|
+          assert migrations.detect { |migration| migration.name == migration_name }
+        end
+        assert_match(/Copied migration \d+_create_users\.bukkits\.rb from bukkits/, output)
+        assert_match(/Copied migration \d+_add_last_name_to_users\.bukkits\.rb from bukkits/, output)
+        assert_match(/NOTE: Migration \d+_create_sessions\.rb from bukkits has been skipped/, output)
 
-        assert_no_match(/2_create_users/, output.join("\n"))
+        migrations_count = Dir["#{app_path}/db/migrate/*.rb"].length
 
-        bukkits_migration_order = output.index(output.detect { |o| /NOTE: Migration 3_create_sessions\.rb from bukkits has been skipped/ =~ o })
-        assert_not_nil bukkits_migration_order, "Expected migration to be skipped"
+        assert_equal migrations.length, migrations_count
 
-        migrations_count = Dir["#{app_path}/db/migrate/*.rb"].length
-        `bundle exec rake railties:install:migrations`
+        output = `bundle exec rake railties:install:migrations`.split("\n")
 
         assert_equal migrations_count, Dir["#{app_path}/db/migrate/*.rb"].length
+
+        assert_no_match(/\d+_create_users/, output.join("\n"))
+
+        bukkits_migration_order = output.index(output.detect { |o| /NOTE: Migration \d+_create_sessions\.rb from bukkits has been skipped/ =~ o })
+        assert_not_nil bukkits_migration_order, "Expected migration to be skipped"
       end
     end
 
@@ -171,10 +177,12 @@ module RailtiesTest
       boot_rails
 
       Dir.chdir(app_path) do
+        # Install Active Storage migration file first so as not to affect test.
+        `bundle exec rake active_storage:install`
         output = `bundle exec rake railties:install:migrations`.split("\n")
 
-        assert_match(/Copied migration \d+_create_users\.core_engine\.rb from core_engine/, output.second)
-        assert_match(/Copied migration \d+_create_keys\.api_engine\.rb from api_engine/, output.last)
+        assert_match(/Copied migration \d+_create_users\.core_engine\.rb from core_engine/, output.first)
+        assert_match(/Copied migration \d+_create_keys\.api_engine\.rb from api_engine/, output.second)
       end
     end
 
@@ -203,9 +211,12 @@ module RailtiesTest
 
       Dir.chdir(@plugin.path) do
         output = `bundle exec rake app:bukkits:install:migrations`
-        assert File.exist?("#{app_path}/db/migrate/0_add_first_name_to_users.bukkits.rb")
-        assert_match(/Copied migration 0_add_first_name_to_users\.bukkits\.rb from bukkits/, output)
-        assert_equal 1, Dir["#{app_path}/db/migrate/*.rb"].length
+
+        migration_with_engine_path = migrations.detect { |migration| migration.name == "AddFirstNameToUsers" }
+        assert migration_with_engine_path
+        assert_match(/\/db\/migrate\/\d+_add_first_name_to_users\.bukkits\.rb/, migration_with_engine_path.filename)
+        assert_match(/Copied migration \d+_add_first_name_to_users\.bukkits\.rb from bukkits/, output)
+        assert_equal migrations.length, Dir["#{app_path}/db/migrate/*.rb"].length
       end
     end
 
@@ -215,7 +226,7 @@ module RailtiesTest
       require "rdoc/task"
       require "rake/testtask"
       Rails.application.load_tasks
-      assert !Rake::Task.task_defined?("bukkits:install:migrations")
+      assert_not Rake::Task.task_defined?("bukkits:install:migrations")
     end
 
     test "puts its lib directory on load path" do
@@ -734,7 +745,7 @@ YAML
       assert_equal "bukkits", Bukkits::Engine.engine_name
       assert_equal Bukkits.railtie_namespace, Bukkits::Engine
       assert ::Bukkits::MyMailer.method_defined?(:foo_url)
-      assert !::Bukkits::MyMailer.method_defined?(:bar_url)
+      assert_not ::Bukkits::MyMailer.method_defined?(:bar_url)
 
       get("/bukkits/from_app")
       assert_equal "false", last_response.body
@@ -969,14 +980,14 @@ YAML
       boot_rails
 
       app_generators = Rails.application.config.generators.options[:rails]
-      assert_equal :mongoid  , app_generators[:orm]
-      assert_equal :liquid   , app_generators[:template_engine]
+      assert_equal :mongoid, app_generators[:orm]
+      assert_equal :liquid, app_generators[:template_engine]
       assert_equal :test_unit, app_generators[:test_framework]
 
       generators = Bukkits::Engine.config.generators.options[:rails]
       assert_equal :data_mapper, generators[:orm]
-      assert_equal :haml      , generators[:template_engine]
-      assert_equal :rspec     , generators[:test_framework]
+      assert_equal :haml, generators[:template_engine]
+      assert_equal :rspec, generators[:test_framework]
     end
 
     test "engine should get default generators with ability to overwrite them" do
@@ -992,10 +1003,10 @@ YAML
 
       generators = Bukkits::Engine.config.generators.options[:rails]
       assert_equal :active_record, generators[:orm]
-      assert_equal :rspec        , generators[:test_framework]
+      assert_equal :rspec, generators[:test_framework]
 
       app_generators = Rails.application.config.generators.options[:rails]
-      assert_equal :test_unit    , app_generators[:test_framework]
+      assert_equal :test_unit, app_generators[:test_framework]
     end
 
     test "do not create table_name_prefix method if it already exists" do
@@ -1468,6 +1479,21 @@ YAML
       assert_equal "/fruits/2/bukkits/posts", last_response.body
     end
 
+    test "active_storage:install task works within engine" do
+      @plugin.write "Rakefile", <<-RUBY
+        APP_RAKEFILE = '#{app_path}/Rakefile'
+        load 'rails/tasks/engine.rake'
+      RUBY
+
+      Dir.chdir(@plugin.path) do
+        output = `bundle exec rake app:active_storage:install`
+        assert $?.success?, output
+
+        active_storage_migration = migrations.detect { |migration| migration.name == "CreateActiveStorageTables" }
+        assert active_storage_migration
+      end
+    end
+
   private
     def app
       Rails.application
diff --git a/railties/test/railties/railtie_test.rb b/railties/test/railties/railtie_test.rb
index 359ab0fdae..7c3d1e3759 100644
--- a/railties/test/railties/railtie_test.rb
+++ b/railties/test/railties/railtie_test.rb
@@ -65,7 +65,7 @@ module RailtiesTest
     test "railtie can add to_prepare callbacks" do
       $to_prepare = false
       class Foo < Rails::Railtie ; config.to_prepare { $to_prepare = true } ; end
-      assert !$to_prepare
+      assert_not $to_prepare
       require "#{app_path}/config/environment"
       require "rack/test"
       extend Rack::Test::Methods
@@ -91,7 +91,7 @@ module RailtiesTest
     test "railtie can add after_initialize callbacks" do
       $after_initialize = false
       class Foo < Rails::Railtie ; config.after_initialize { $after_initialize = true } ; end
-      assert !$after_initialize
+      assert_not $after_initialize
       require "#{app_path}/config/environment"
       assert $after_initialize
     end
@@ -107,7 +107,7 @@ module RailtiesTest
 
       require "#{app_path}/config/environment"
 
-      assert !$ran_block
+      assert_not $ran_block
       require "rake"
       require "rake/testtask"
       require "rdoc/task"
@@ -151,7 +151,7 @@ module RailtiesTest
 
       require "#{app_path}/config/environment"
 
-      assert !$ran_block
+      assert_not $ran_block
       Rails.application.load_generators
       assert $ran_block
     end
@@ -167,7 +167,7 @@ module RailtiesTest
 
       require "#{app_path}/config/environment"
 
-      assert !$ran_block
+      assert_not $ran_block
       Rails.application.load_console
       assert $ran_block
     end
@@ -183,7 +183,7 @@ module RailtiesTest
 
       require "#{app_path}/config/environment"
 
-      assert !$ran_block
+      assert_not $ran_block
       Rails.application.load_runner
       assert $ran_block
     end
@@ -197,7 +197,7 @@ module RailtiesTest
         end
       end
 
-      assert !$ran_block
+      assert_not $ran_block
       require "#{app_path}/config/environment"
       assert $ran_block
     end
diff --git a/railties/test/secrets_test.rb b/railties/test/secrets_test.rb
index 445e216f16..06877bc76a 100644
--- a/railties/test/secrets_test.rb
+++ b/railties/test/secrets_test.rb
@@ -1,31 +1,24 @@
 # frozen_string_literal: true
 
-require "abstract_unit"
 require "isolation/abstract_unit"
-require "rails/generators"
-require "rails/generators/rails/encrypted_secrets/encrypted_secrets_generator"
 require "rails/secrets"
 
 class Rails::SecretsTest < ActiveSupport::TestCase
   include ActiveSupport::Testing::Isolation
 
-  def setup
-    build_app
-  end
-
-  def teardown
-    teardown_app
-  end
+  setup :build_app
+  teardown :teardown_app
 
   test "setting read to false skips parsing" do
     run_secrets_generator do
       Rails::Secrets.write(<<-end_of_secrets)
-        test:
+        production:
           yeah_yeah: lets-walk-in-the-cool-evening-light
       end_of_secrets
 
-      Rails.application.config.read_encrypted_secrets = false
-      Rails.application.instance_variable_set(:@secrets, nil) # Dance around caching 💃🕺
+      add_to_env_config("production", "config.read_encrypted_secrets = false")
+      app("production")
+
       assert_not Rails.application.secrets.yeah_yeah
     end
   end
@@ -47,7 +40,7 @@ class Rails::SecretsTest < ActiveSupport::TestCase
         ENV["RAILS_MASTER_KEY"] = IO.binread("config/secrets.yml.key").strip
         FileUtils.rm("config/secrets.yml.key")
 
-        assert_match "production:\n#  external_api_key", Rails::Secrets.read
+        assert_match "# production:\n#   external_api_key:", Rails::Secrets.read
       ensure
         ENV["RAILS_MASTER_KEY"] = old_key
       end
@@ -69,7 +62,7 @@ class Rails::SecretsTest < ActiveSupport::TestCase
       Rails::Secrets.read_for_editing do |tmp_path|
         decrypted_path = tmp_path
 
-        assert_match(/production:\n#  external_api_key/, File.read(tmp_path))
+        assert_match(/# production:\n#   external_api_key/, File.read(tmp_path))
 
         File.write(tmp_path, "Empty streets, empty nights. The Downtown Lights.")
       end
@@ -82,17 +75,18 @@ class Rails::SecretsTest < ActiveSupport::TestCase
   test "merging secrets with encrypted precedence" do
     run_secrets_generator do
       File.write("config/secrets.yml", <<-end_of_secrets)
-        test:
+        production:
           yeah_yeah: lets-go-walking-down-this-empty-street
       end_of_secrets
 
       Rails::Secrets.write(<<-end_of_secrets)
-        test:
+        production:
           yeah_yeah: lets-walk-in-the-cool-evening-light
       end_of_secrets
 
-      Rails.application.config.read_encrypted_secrets = true
-      Rails.application.instance_variable_set(:@secrets, nil) # Dance around caching 💃🕺
+      add_to_env_config("production", "config.read_encrypted_secrets = true")
+      app("production")
+
       assert_equal "lets-walk-in-the-cool-evening-light", Rails.application.secrets.yeah_yeah
     end
   end
@@ -108,7 +102,9 @@ class Rails::SecretsTest < ActiveSupport::TestCase
         config.dereferenced_secret = Rails.application.secrets.some_secret
       end_of_config
 
-      assert_equal "yeah yeah\n", `bin/rails runner -e production "puts Rails.application.config.dereferenced_secret"`
+      app("production")
+
+      assert_equal "yeah yeah", Rails.application.config.dereferenced_secret
     end
   end
 
@@ -141,7 +137,9 @@ class Rails::SecretsTest < ActiveSupport::TestCase
         assert_match(/production:\n\s*api_key: 00112233445566778899aabbccddeeff…\n/, File.read(tmp_path))
       end
 
-      assert_equal "00112233445566778899aabbccddeeff…\n", `bin/rails runner -e production "puts Rails.application.secrets.api_key"`
+      app("production")
+
+      assert_equal "00112233445566778899aabbccddeeff…", Rails.application.secrets.api_key
     end
   end
 
@@ -158,19 +156,21 @@ class Rails::SecretsTest < ActiveSupport::TestCase
         assert_equal(secrets.dup.force_encoding(Encoding::ASCII_8BIT), IO.binread(tmp_path))
       end
 
-      assert_equal "00112233445566778899aabbccddeeff…\n", `bin/rails runner -e production "puts Rails.application.secrets.api_key"`
+      app("production")
+
+      assert_equal "00112233445566778899aabbccddeeff…", Rails.application.secrets.api_key
     end
   end
 
   private
     def run_secrets_generator
       Dir.chdir(app_path) do
-        capture(:stdout) do
-          Rails::Generators::EncryptedSecretsGenerator.start
-        end
+        File.write("config/secrets.yml.key", "f731758c639da2604dfb6bf3d1025de8")
+        File.write("config/secrets.yml.enc", "sEB0mHxDbeP1/KdnMk00wyzPFACl9K6t0cZWn5/Mfx/YbTHvnI07vrneqHg9kaH3wOS7L6pIQteu1P077OtE4BSx/ZRc/sgQPHyWu/tXsrfHqnPNpayOF/XZqizE91JacSFItNMWpuPsp9ynbzz+7cGhoB1S4aPNIU6u0doMrzdngDbijsaAFJmsHIQh6t/QHoJx--8aMoE0PvUWmw1Iqz--ldFqnM/K0g9k17M8PKoN/Q==")
 
-        # Make config.paths["config/secrets"] to be relative to app_path
-        Rails.application.config.root = app_path
+        add_to_config <<-RUBY
+          config.read_encrypted_secrets = true
+        RUBY
 
         yield
       end
diff --git a/railties/test/test_unit/reporter_test.rb b/railties/test/test_unit/reporter_test.rb
index ad852d0f35..91cb47779b 100644
--- a/railties/test/test_unit/reporter_test.rb
+++ b/railties/test/test_unit/reporter_test.rb
@@ -163,7 +163,7 @@ class TestUnitReporterTest < ActiveSupport::TestCase
     end
 
     def failed_test
-      ft = ExampleTest.new(:woot)
+      ft = Minitest::Result.from(ExampleTest.new(:woot))
       ft.failures << begin
                        raise Minitest::Assertion, "boo"
                      rescue Minitest::Assertion => e
@@ -176,17 +176,17 @@ class TestUnitReporterTest < ActiveSupport::TestCase
       error = ArgumentError.new("wups")
       error.set_backtrace([ "some_test.rb:4" ])
 
-      et = ExampleTest.new(:woot)
+      et = Minitest::Result.from(ExampleTest.new(:woot))
       et.failures << Minitest::UnexpectedError.new(error)
       et
     end
 
     def passing_test
-      ExampleTest.new(:woot)
+      Minitest::Result.from(ExampleTest.new(:woot))
     end
 
     def skipped_test
-      st = ExampleTest.new(:woot)
+      st = Minitest::Result.from(ExampleTest.new(:woot))
       st.failures << begin
                        raise Minitest::Skip, "skipchurches, misstemples"
                      rescue Minitest::Assertion => e
diff --git a/tasks/release.rb b/tasks/release.rb
index aa8ba44c1a..cbda9a3798 100644
--- a/tasks/release.rb
+++ b/tasks/release.rb
@@ -6,7 +6,6 @@ FRAMEWORK_NAMES = Hash.new { |h, k| k.split(/(?<=active|action)/).map(&:capitali
 root    = File.expand_path("..", __dir__)
 version = File.read("#{root}/RAILS_VERSION").strip
 tag     = "v#{version}"
-gem_version = Gem::Version.new(version)
 
 directory "pkg"
 
@@ -108,7 +107,7 @@ namespace :changelog do
       header = "## Rails #{version} (#{Date.today.strftime('%B %d, %Y')}) ##\n\n"
       header += "*   No changes.\n\n\n" if current_contents =~ /\A##/
       contents = header + current_contents
-      File.open(fname, "wb") { |f| f.write contents }
+      File.write(fname, contents)
     end
   end
 
@@ -119,7 +118,7 @@ namespace :changelog do
       fname = File.join fw, "CHANGELOG.md"
 
       contents = File.read(fname).sub(/^(## Rails .*)\n/, replace)
-      File.open(fname, "wb") { |f| f.write contents }
+      File.write(fname, contents)
     end
   end
 
@@ -248,6 +247,12 @@ task :announce do
 
     require "erb"
     template = File.read("../tasks/release_announcement_draft.erb")
-    puts ERB.new(template, nil, "<>").result(binding)
+
+    match = ERB.version.match(/\Aerb\.rb \[(?<version>[^ ]+) /)
+    if match && match[:version] >= "2.2.0" # Ruby 2.6+
+      puts ERB.new(template, trim_mode: "<>").result(binding)
+    else
+      puts ERB.new(template, nil, "<>").result(binding)
+    end
   end
 end
diff --git a/version.rb b/version.rb
index 92b5e0392a..54bfbdd516 100644
--- a/version.rb
+++ b/version.rb
@@ -7,8 +7,8 @@ module Rails
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
     PRE   = "alpha"