21 files changed, 448 insertions, 352 deletions
diff --git a/guides/source/3_0_release_notes.md b/guides/source/3_0_release_notes.md
index 46be2613ab..e985f1ab4b 100644
--- a/guides/source/3_0_release_notes.md
+++ b/guides/source/3_0_release_notes.md
@@ -138,7 +138,7 @@ More Information: - [Rails Edge Architecture](http://yehudakatz.com/2009/06/11/r
 
 [Arel](http://github.com/brynary/arel) (or Active Relation) has been taken on as the underpinnings of Active Record and is now required for Rails. Arel provides an SQL abstraction that simplifies out Active Record and provides the underpinnings for the relation functionality in Active Record.
 
-More information: - [Why I wrote Arel](http://magicscalingsprinkles.wordpress.com/2010/01/28/why-i-wrote-arel/.)
+More information: - [Why I wrote Arel](https://web.archive.org/web/20120718093140/http://magicscalingsprinkles.wordpress.com/2010/01/28/why-i-wrote-arel/)
 
 
 ### Mail Extraction
@@ -298,7 +298,7 @@ Deprecations
 
 More Information:
 * [The Rails 3 Router: Rack it Up](http://yehudakatz.com/2009/12/26/the-rails-3-router-rack-it-up/)
-* [Revamped Routes in Rails 3](http://rizwanreza.com/2009/12/20/revamped-routes-in-rails-3)
+* [Revamped Routes in Rails 3](https://medium.com/fusion-of-thoughts/revamped-routes-in-rails-3-b6d00654e5b0)
 * [Generic Actions in Rails 3](http://yehudakatz.com/2009/12/20/generic-actions-in-rails-3/)
 
 
diff --git a/guides/source/4_1_release_notes.md b/guides/source/4_1_release_notes.md
index 52a5acb75e..c7877a9cb5 100644
--- a/guides/source/4_1_release_notes.md
+++ b/guides/source/4_1_release_notes.md
@@ -136,7 +136,7 @@ end
 
 ### Action Mailer Previews
 
-Action Mailer previews provide a way to visually see how emails look by visiting
+Action Mailer previews provide a way to see how emails look by visiting
 a special URL that renders them.
 
 You implement a preview class whose methods return the mail object you'd like
diff --git a/guides/source/4_2_release_notes.md b/guides/source/4_2_release_notes.md
index d9f49aac55..737922c283 100644
--- a/guides/source/4_2_release_notes.md
+++ b/guides/source/4_2_release_notes.md
@@ -3,21 +3,19 @@ Ruby on Rails 4.2 Release Notes
 
 Highlights in Rails 4.2:
 
-* Active Job, Action Mailer #deliver_later
+* Active Job
+* Asynchronous mails
 * Adequate Record
 * Web Console
 * Foreign key support
 
-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/master) in the main Rails
-repository on GitHub.
+These release notes cover only the major changes. To learn about other
+features, bug fixes, and changes, please refer to the changelogs or check out
+the [list of commits](https://github.com/rails/rails/commits/4-2-stable) in
+the main Rails repository on GitHub.
 
 --------------------------------------------------------------------------------
 
-NOTE: This document is a work in progress, please help to improve this by sending
-a [pull request](https://github.com/rails/rails/edit/master/guides/source/4_2_release_notes.md).
-
 Upgrading to Rails 4.2
 ----------------------
 
@@ -25,96 +23,112 @@ 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 4.1 in case you
 haven't and make sure your application still runs as expected before attempting
 to upgrade to Rails 4.2. A list of things to watch out for when upgrading is
-available in the guide: [Upgrading Ruby on
-Rails](upgrading_ruby_on_rails.html#upgrading-from-rails-4-1-to-rails-4-2)
+available in the guide [Upgrading Ruby on
+Rails](upgrading_ruby_on_rails.html#upgrading-from-rails-4-1-to-rails-4-2).
 
 
 Major Features
 --------------
 
-### Active Job, Action Mailer #deliver_later
+### Active Job
 
-Active Job is a new framework in Rails 4.2. It is an adapter layer on top of
+Active Job is a new framework in Rails 4.2. It is a common interface on top of
 queuing systems like [Resque](https://github.com/resque/resque), [Delayed
 Job](https://github.com/collectiveidea/delayed_job),
 [Sidekiq](https://github.com/mperham/sidekiq), and more.
 
-You can write your jobs with the Active Job API, and it'll run on all these
-queues with no changes (it comes pre-configured with an inline runner).
+Jobs written with the Active Job API run on any of the supported queues thanks
+to their respective adapters. Active Job comes pre-configured with an inline
+runner that executes jobs right away.
+
+Jobs often need to take Active Record objects as arguments. Active Job passes
+object references as URIs (uniform resource identifiers) instead of marshaling
+the object itself. The new [Global ID](https://github.com/rails/globalid)
+library builds URIs and looks up the objects they reference. Passing Active
+Record objects as job arguments just works by using Global ID internally.
 
-Building on top of Active Job, Action Mailer now comes with a `#deliver_later`
-method, which adds your email to be sent as a job to a queue, so it doesn't
-bog down the controller or model.
+For example, if `trashable` is an Active Record object, then this job runs
+just fine with no serialization involved:
 
-The new GlobalID library makes it easy to pass Active Record objects to jobs by
-serializing them in a generic form. This means you no longer have to manually
-pack and unpack your Active Records by passing ids. Just give the job the
-straight Active Record object, and it'll serialize it using GlobalID, and
-deserialize it at run time.
+```ruby
+class TrashableCleanupJob < ActiveJob::Base
+  def perform(trashable, depth)
+    trashable.cleanup(depth)
+  end
+end
+```
+
+See the [Active Job Basics](active_job_basics.html) guide for more
+information.
+
+### Asynchronous Mails
+
+Building on top of Active Job, Action Mailer now comes with a `deliver_later`
+method that sends emails via the queue, so it doesn't block the controller or
+model if the queue is asynchronous (the default inline queue blocks).
+
+Sending emails right away is still possible with `deliver_now`.
 
 ### Adequate Record
 
-Adequate Record is a set of refactorings that make Active Record `find` and
-`find_by` methods and some association queries upto 2x faster.
+Adequate Record is a set of performance improvements in Active Record that makes
+common `find` and `find_by` calls and some association queries up to 2x faster.
 
-It works by caching SQL query patterns while executing the Active Record calls.
-The cache helps skip parts of the computation involved in the transformation of
-the calls into SQL queries. More details in [Aaron Patterson's
+It works by caching common SQL queries as prepared statements and reusing them
+on similar calls, skipping most of the query-generation work on subsequent
+calls. For more details, please refer to [Aaron Patterson's blog
 post](http://tenderlovemaking.com/2014/02/19/adequaterecord-pro-like-activerecord.html).
 
-Nothing special has to be done to activate this feature. Most `find` and
-`find_by` calls and association queries will use it automatically. Examples:
+Active Record will automatically take advantage of this feature on
+supported operations without any user involvement or code changes. Here are
+some examples of supported operations:
 
 ```ruby
-Post.find 1  # caches query pattern
-Post.find 2  # uses the cached pattern
+Post.find(1)  # First call generates and cache the prepared statement
+Post.find(2)  # Subsequent calls reuse the cached prepared statement
 
-Post.find_by_title 'first post'  # caches query pattern
-Post.find_by_title 'second post' # uses the cached pattern
+Post.find_by_title('first post')
+Post.find_by_title('second post')
 
-post.comments        # caches query pattern
-post.comments(true)  # uses cached pattern
+post.comments
+post.comments(true)
 ```
 
-The caching is not used in the following scenarios:
+It's important to highlight that, as the examples above suggest, the prepared
+statements do not cache the values passed in the method calls; rather, they
+have placeholders for them.
+
+Caching is not used in the following scenarios:
 
 - The model has a default scope
-- The model uses single table inheritance to inherit from another model
-- `find` with a list of ids. eg:
+- The model uses single table inheritance
+- `find` with a list of ids, e.g.:
 
   ```ruby
-  Post.find(1,2,3)
-  OR
-  Post.find [1,2]
+  # not cached
+  Post.find(1, 2, 3)
+  Post.find([1,2])
   ```
 
-- `find_by` with sql fragments:
+- `find_by` with SQL fragments:
 
   ```ruby
-  Post.find_by "published_at < ?", 2.weeks.ago
+  Post.find_by('published_at < ?', 2.weeks.ago)
   ```
 
 ### Web Console
 
-New applications generated from Rails 4.2 now come with the Web Console gem by
-default.
+New applications generated with Rails 4.2 now come with the [Web
+Console](https://github.com/rails/web-console) gem by default. Web Console adds
+an interactive Ruby console on every error page and provides a `console` view
+and controller helpers.
 
-Web Console is a set of debugging tools for your Rails application. It will add
-an interactive console on every error page, a `console` view helper and a VT100
-compatible terminal.
+The interactive console on error pages lets you execute code in the context of
+the place where the exception originated. The `console` helper, if called
+anywhere in a view or controller, launches an interactive console with the final
+context, once rendering has completed.
 
-The interactive console on the error pages lets you execute code where the
-exception originated. It's quite handy to introspect the state that led to the
-error.
-
-The `console` view helper launches an interactive console within the context of
-the view where it is invoked.
-
-Finally, you can launch a VT100 terminal that runs `rails console`. If you need
-to create or modify existing test data, you can do that straight from the
-browser.
-
-### Foreign key support
+### Foreign Key Support
 
 The migration DSL now supports adding and removing foreign keys. They are dumped
 to `schema.rb` as well. At this time, only the `mysql`, `mysql2` and `postgresql`
@@ -149,18 +163,18 @@ individual components for new deprecations in this release.
 
 The following changes may require immediate action upon upgrade.
 
-### `render` with a String argument
+### `render` with a String Argument
 
-Previously, calling `render "foo/bar"` in a controller action is equivalent to
-`render file: "foo/bar"`. In Rails 4.2, this has been changed to mean `render template: "foo/bar"`
-instead. If you need to render a file, please change your code to use the
-explicit form (`render file: "foo/bar"`) instead.
+Previously, calling `render "foo/bar"` in a controller action was equivalent to
+`render file: "foo/bar"`. In Rails 4.2, this has been changed to mean
+`render template: "foo/bar"` instead. If you need to render a file, please
+change your code to use the explicit form (`render file: "foo/bar"`) instead.
 
-### `respond_with` / class-level `respond_to`
+### `respond_with` / Class-Level `respond_to`
 
-`respond_with` and the corresponding class-level `respond_to` have been moved to
-the `responders` gem. To use the following, add `gem 'responders', '~> 2.0'` to
-your Gemfile:
+`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:
 
 ```ruby
 # app/controllers/users_controller.rb
@@ -191,61 +205,47 @@ class UsersController < ApplicationController
 end
 ```
 
-### Default host for `rails server`
+### Default Host for `rails server`
 
 Due to a [change in Rack](https://github.com/rack/rack/commit/28b014484a8ac0bbb388e7eaeeef159598ec64fc),
 `rails server` now listens on `localhost` instead of `0.0.0.0` by default. This
-should have minimal impact on the standard development workflow as both http://127.0.0.1:3000
-and http://localhost:3000 would continue to work as before on your own machine.
+should have minimal impact on the standard development workflow as both
+http://127.0.0.1:3000 and http://localhost:3000 will continue to work as before
+on your own machine.
 
-However, with this change you would no longer be able to access the Rails server
-from a different machine (e.g. your development environment is in a virtual
-machine and you would like to access it from the host machine), you would need
-to start the server with `rails server -b 0.0.0.0` to restore the old behavior.
+However, with this change you will no longer be able to access the Rails
+server from a different machine, for example if your development environment
+is in a virtual machine and you would like to access it from the host machine.
+In such cases, please start the server with `rails server -b 0.0.0.0` to
+restore the old behavior.
 
 If you do this, be sure to configure your firewall properly such that only
 trusted machines on your network can access your development server.
 
-### Production logging
-
-The default log level in the `production` environment is now `:debug`. This
-makes it consistent with the other environments, and ensures plenty of
-information is available to diagnose problems.
-
-It can be returned to the previous level, `:info`, in the environment
-configuration:
-
-```ruby
-# config/environments/production.rb
-
-# Decrease the log volume.
-config.log_level = :info
-```
-
 ### HTML Sanitizer
 
 The HTML sanitizer has been replaced with a new, more robust, implementation
-built upon Loofah and Nokogiri. The new sanitizer is more secure and its
-sanitization is more powerful and flexible.
+built upon [Loofah](https://github.com/flavorjones/loofah) and
+[Nokogiri](https://github.com/sparklemotion/nokogiri). The new sanitizer is
+more secure and its sanitization is more powerful and flexible.
 
-With a new sanitization algorithm, the sanitized output will change for certain
+Due to the new algorithm, the sanitized output may be different for certain
 pathological inputs.
 
-If you have particular need for the exact output of the old sanitizer, you can
-add `rails-deprecated_sanitizer` to your Gemfile, and it will automatically
-replace the new implementation. Because it is opt-in, the legacy gem will not
-give deprecation warnings.
+If you have a particular need for the exact output of the old sanitizer, you
+can add the [rails-deprecated_sanitizer](https://github.com/kaspth/rails-deprecated_sanitizer)
+gem to the `Gemfile`, to have the old behavior. The gem does not issue
+deprecation warnings because it is opt-in.
 
 `rails-deprecated_sanitizer` will be supported for Rails 4.2 only; it will not
 be maintained for Rails 5.0.
 
-See [the blog post](http://blog.plataformatec.com.br/2014/07/the-new-html-sanitizer-in-rails-4-2/)
-for more detail on the changes in the new sanitizer.
+See [this blog post](http://blog.plataformatec.com.br/2014/07/the-new-html-sanitizer-in-rails-4-2/)
+for more details on the changes in the new sanitizer.
 
 ### `assert_select`
 
-`assert_select` is now based on Nokogiri, making it (TODO: betterer).
-
+`assert_select` is now based on [Nokogiri](https://github.com/sparklemotion/nokogiri).
 As a result, some previously-valid selectors are now unsupported. If your
 application is using any of these spellings, you will need to update them:
 
@@ -253,8 +253,13 @@ application is using any of these spellings, you will need to update them:
     non-alphanumeric characters.
 
     ```
-    a[href=/]      =>     a[href="/"]
-    a[href$=/]     =>     a[href$="/"]
+    # before
+    a[href=/]
+    a[href$=/]
+
+    # now
+    a[href="/"]
+    a[href$="/"]
     ```
 
 *   DOMs built from HTML source containing invalid HTML with improperly
@@ -300,11 +305,24 @@ Please refer to the [Changelog][railties] for detailed changes.
 
 ### Removals
 
+*   The `--skip-action-view` option has been removed from the
+    app generator. ([Pull Request](https://github.com/rails/rails/pull/17042))
+
 *   The `rails application` command has been removed without replacement.
     ([Pull Request](https://github.com/rails/rails/pull/11616))
 
 ### Deprecations
 
+*   Deprecated missing `config.log_level` for production environments.
+    ([Pull Request](https://github.com/rails/rails/pull/16622))
+
+*   Deprecated `rake test:all` in favor of `rake test` as it now run all tests
+    in the `test` folder.
+    ([Pull Request](https://github.com/rails/rails/pull/17348))
+
+*   Deprecated `rake test:all:db` in favor of `rake test:db`.
+    ([Pull Request](https://github.com/rails/rails/pull/17348))
+
 *   Deprecated `Rails::Rack::LogTailer` without replacement.
     ([Commit](https://github.com/rails/rails/commit/84a13e019e93efaa8994b3f8303d635a7702dbce))
 
@@ -316,9 +334,6 @@ Please refer to the [Changelog][railties] for detailed changes.
 *   Added a `required` option to the model generator for associations.
     ([Pull Request](https://github.com/rails/rails/pull/16062))
 
-*   Introduced an `after_bundle` callback for use in Rails templates.
-    ([Pull Request](https://github.com/rails/rails/pull/16359))
-
 *   Introduced the `x` namespace for defining custom configuration options:
 
     ```ruby
@@ -358,20 +373,23 @@ Please refer to the [Changelog][railties] for detailed changes.
 
     ([Pull Request](https://github.com/rails/rails/pull/16129))
 
-*   Introduced a `--skip-gems` option in the app generator to skip gems such as
-    `turbolinks` and `coffee-rails` that do not have their own specific flags.
-    ([Commit](https://github.com/rails/rails/commit/10565895805887d4faf004a6f71219da177f78b7))
+*   Introduced a `--skip-turbolinks` option in the app generator to not generate
+    turbolinks integration.
+    ([Commit](https://github.com/rails/rails/commit/bf17c8a531bc8059d50ad731398002a3e7162a7d))
 
-*   Introduced a `bin/setup` script to enable automated setup code when
+*   Introduced a `bin/setup` script as a convention for automated setup code when
     bootstrapping an application.
     ([Pull Request](https://github.com/rails/rails/pull/15189))
 
-*   Changed default value for `config.assets.digest` to `true` in development.
+*   Changed the default value for `config.assets.digest` to `true` in development.
     ([Pull Request](https://github.com/rails/rails/pull/15155))
 
 *   Introduced an API to register new extensions for `rake notes`.
     ([Pull Request](https://github.com/rails/rails/pull/14379))
 
+*   Introduced an `after_bundle` callback for use in Rails templates.
+    ([Pull Request](https://github.com/rails/rails/pull/16359))
+
 *   Introduced `Rails.gem_version` as a convenience method to return
     `Gem::Version.new(Rails.version)`.
     ([Pull Request](https://github.com/rails/rails/pull/14101))
@@ -384,10 +402,11 @@ Please refer to the [Changelog][action-pack] for detailed changes.
 
 ### Removals
 
-*   `respond_with` and the class-level `respond_to` were removed from Rails and
+*   `respond_with` and the class-level `respond_to` have been removed from Rails and
     moved to the `responders` gem (version 2.0). Add `gem 'responders', '~> 2.0'`
     to your `Gemfile` to continue using these features.
-    ([Pull Request](https://github.com/rails/rails/pull/16526))
+    ([Pull Request](https://github.com/rails/rails/pull/16526),
+     [More Details](http://guides.rubyonrails.org/upgrading_ruby_on_rails.html#responders))
 
 *   Removed deprecated `AbstractController::Helpers::ClassMethods::MissingHelperError`
     in favor of `AbstractController::Helpers::MissingHelperError`.
@@ -403,7 +422,7 @@ Please refer to the [Changelog][action-pack] for detailed changes.
     ([Commit](https://github.com/rails/rails-dom-testing/commit/b12850bc5ff23ba4b599bf2770874dd4f11bf750))
 
 *   Deprecated support for setting the `:to` option of a router to a symbol or a
-    string that does not contain a `#` character:
+    string that does not contain a "#" character:
 
     ```ruby
     get '/posts', to: MyRackApp    => (No change necessary)
@@ -414,22 +433,22 @@ Please refer to the [Changelog][action-pack] for detailed changes.
 
     ([Commit](https://github.com/rails/rails/commit/cc26b6b7bccf0eea2e2c1a9ebdcc9d30ca7390d9))
 
-### Notable changes
+*   Deprecated support for string keys in URL helpers:
 
-*   Rails will now automatically include the template's digest in ETags.
-    ([Pull Request](https://github.com/rails/rails/pull/16527))
+    ```ruby
+    # bad
+    root_path('controller' => 'posts', 'action' => 'index')
 
-*   `render nothing: true` or rendering a `nil` body no longer add a single
-    space padding to the response body.
-    ([Pull Request](https://github.com/rails/rails/pull/14883))
+    # good
+    root_path(controller: 'posts', action: 'index')
+    ```
 
-*   Introduced the `always_permitted_parameters` option to configure which
-    parameters are permitted globally. The default value of this configuration
-    is `['controller', 'action']`.
-    ([Pull Request](https://github.com/rails/rails/pull/15933))
+    ([Pull Request](https://github.com/rails/rails/pull/17743))
+
+### Notable changes
 
-*   The `*_filter` family methods have been removed from the documentation. Their
-    usage is discouraged in favor of the `*_action` family methods:
+*   The `*_filter` family of methods have been removed from the documentation. Their
+    usage is discouraged in favor of the `*_action` family of methods:
 
     ```
     after_filter          => after_action
@@ -454,16 +473,28 @@ Please refer to the [Changelog][action-pack] for detailed changes.
     (Commit [1](https://github.com/rails/rails/commit/6c5f43bab8206747a8591435b2aa0ff7051ad3de),
     [2](https://github.com/rails/rails/commit/489a8f2a44dc9cea09154ee1ee2557d1f037c7d4))
 
-*   Added HTTP method `MKCALENDAR` from RFC-4791
+*   `render nothing: true` or rendering a `nil` body no longer add a single
+    space padding to the response body.
+    ([Pull Request](https://github.com/rails/rails/pull/14883))
+
+*   Rails now automatically includes the template's digest in ETags.
+    ([Pull Request](https://github.com/rails/rails/pull/16527))
+
+*   Segments that are passed into URL helpers are now automatically escaped.
+    ([Commit](https://github.com/rails/rails/commit/5460591f0226a9d248b7b4f89186bd5553e7768f))
+
+*   Introduced the `always_permitted_parameters` option to configure which
+    parameters are permitted globally. The default value of this configuration
+    is `['controller', 'action']`.
+    ([Pull Request](https://github.com/rails/rails/pull/15933))
+
+*   Added the HTTP method `MKCALENDAR` from [RFC 4791](https://tools.ietf.org/html/rfc4791).
     ([Pull Request](https://github.com/rails/rails/pull/15121))
 
 *   `*_fragment.action_controller` notifications now include the controller
     and action name in the payload.
     ([Pull Request](https://github.com/rails/rails/pull/14137))
 
-*   Segments that are passed into URL helpers are now automatically escaped.
-    ([Commit](https://github.com/rails/rails/commit/5460591f0226a9d248b7b4f89186bd5553e7768f))
-
 *   Improved the Routing Error page with fuzzy matching for route search.
     ([Pull Request](https://github.com/rails/rails/pull/14619))
 
@@ -471,28 +502,15 @@ Please refer to the [Changelog][action-pack] for detailed changes.
     ([Pull Request](https://github.com/rails/rails/pull/14280))
 
 *   When the Rails server is set to serve static assets, gzip assets will now be
-    served if the client supports it and a pre-generated gzip file (.gz) is on disk.
+    served if the client supports it and a pre-generated gzip file (`.gz`) is on disk.
     By default the asset pipeline generates `.gz` files for all compressible assets.
     Serving gzip files minimizes data transfer and speeds up asset requests. Always
     [use a CDN](http://guides.rubyonrails.org/asset_pipeline.html#cdns) if you are
     serving assets from your Rails server in production.
     ([Pull Request](https://github.com/rails/rails/pull/16466))
 
-*   The way `assert_select` works has changed; specifically a different library
-    is used to interpret css selectors, build the transient DOM that the
-    selectors are applied against, and to extract the data from that DOM. These
-    changes should only affect edge cases. Examples:
-    *  Values in attribute selectors may need to be quoted if they contain
-       non-alphanumeric characters.
-    *  DOMs built from HTML source containing invalid HTML with improperly
-       nested elements may differ.
-    *  If the data selected contains entities, the value selected for comparison
-       used to be raw (e.g. `AT&amp;T`), and now is evaluated
-       (e.g. `AT&T`).
-
-
 Action View
--------------
+-----------
 
 Please refer to the [Changelog][action-view] for detailed changes.
 
@@ -513,16 +531,16 @@ Please refer to the [Changelog][action-view] for detailed changes.
     `render file: "foo/bar"`.
     ([Pull Request](https://github.com/rails/rails/pull/16888))
 
-*   Introduced a `#{partial_name}_iteration` special local variable for use with
-    partials that are rendered with a collection. It provides access to the
-    current state of the iteration via the `#index`, `#size`, `#first?` and
-    `#last?` methods.
-    ([Pull Request](https://github.com/rails/rails/pull/7698))
-
 *   The form helpers no longer generate a `<div>` element with inline CSS around
     the hidden fields.
     ([Pull Request](https://github.com/rails/rails/pull/14738))
 
+*   Introduced a `#{partial_name}_iteration` special local variable for use with
+    partials that are rendered with a collection. It provides access to the
+    current state of the iteration via the `index`, `size`, `first?` and
+    `last?` methods.
+    ([Pull Request](https://github.com/rails/rails/pull/7698))
+
 *   Placeholder I18n follows the same convention as `label` I18n.
     ([Pull Request](https://github.com/rails/rails/pull/16438))
 
@@ -537,11 +555,15 @@ Please refer to the [Changelog][action-mailer] for detailed changes.
 *   Deprecated `*_path` helpers in mailers. Always use `*_url` helpers instead.
     ([Pull Request](https://github.com/rails/rails/pull/15840))
 
-*   Deprecated `deliver` / `deliver!` in favour of `deliver_now` / `deliver_now!`.
+*   Deprecated `deliver` / `deliver!` in favor of `deliver_now` / `deliver_now!`.
     ([Pull Request](https://github.com/rails/rails/pull/16582))
 
 ### Notable changes
 
+*   `link_to` and `url_for` generate absolute URLs by default in templates,
+    it is no longer needed to pass `only_path: false`.
+    ([Commit](https://github.com/rails/rails/commit/9685080a7677abfa5d288a81c3e078368c6bb67c))
+
 *   Introduced `deliver_later` which enqueues a job on the application's queue
     to deliver emails asynchronously.
     ([Pull Request](https://github.com/rails/rails/pull/16485))
@@ -570,7 +592,7 @@ Please refer to the [Changelog][active-record] for detailed changes.
 
 *   Removed unused `:timestamp` type. Transparently alias it to `:datetime`
     in all cases. Fixes inconsistencies when column types are sent outside of
-    `ActiveRecord`, such as for XML serialization.
+    Active Record, such as for XML serialization.
     ([Pull Request](https://github.com/rails/rails/pull/15184))
 
 ### Deprecations
@@ -578,112 +600,116 @@ Please refer to the [Changelog][active-record] for detailed changes.
 *   Deprecated swallowing of errors inside `after_commit` and `after_rollback`.
     ([Pull Request](https://github.com/rails/rails/pull/16537))
 
-*   Deprecated calling `DatabaseTasks.load_schema` without a connection. Use
-    `DatabaseTasks.load_schema_current` instead.
-    ([Commit](https://github.com/rails/rails/commit/f15cef67f75e4b52fd45655d7c6ab6b35623c608))
-
-*   Deprecated `Reflection#source_macro` without replacement as it is no longer
-    needed in Active Record.
-    ([Pull Request](https://github.com/rails/rails/pull/16373))
-
 *   Deprecated broken support for automatic detection of counter caches on
     `has_many :through` associations. You should instead manually specify the
     counter cache on the `has_many` and `belongs_to` associations for the
     through records.
     ([Pull Request](https://github.com/rails/rails/pull/15754))
 
-*   Deprecated `serialized_attributes` without replacement.
-    ([Pull Request](https://github.com/rails/rails/pull/15704))
-
-*   Deprecated returning `nil` from `column_for_attribute` when no column
-    exists. It will return a null object in Rails 5.0
-    ([Pull Request](https://github.com/rails/rails/pull/15878))
-
-*   Deprecated using `.joins`, `.preload` and `.eager_load` with associations
-    that depends on the instance state (i.e. those defined with a scope that
-    takes an argument) without replacement.
-    ([Commit](https://github.com/rails/rails/commit/ed56e596a0467390011bc9d56d462539776adac1))
-
 *   Deprecated passing Active Record objects to `.find` or `.exists?`. Call
-    `#id` on the objects first.
+    `id` on the objects first.
     (Commit [1](https://github.com/rails/rails/commit/d92ae6ccca3bcfd73546d612efaea011270bd270),
     [2](https://github.com/rails/rails/commit/d35f0033c7dec2b8d8b52058fb8db495d49596f7))
 
 *   Deprecated half-baked support for PostgreSQL range values with excluding
     beginnings. We currently map PostgreSQL ranges to Ruby ranges. This conversion
-    is not fully possible because the Ruby range does not support excluded
-    beginnings.
+    is not fully possible because Ruby ranges do not support excluded beginnings.
 
     The current solution of incrementing the beginning is not correct
     and is now deprecated. For subtypes where we don't know how to increment
-    (e.g. `#succ` is not defined) it will raise an `ArgumentError` for ranges
+    (e.g. `succ` is not defined) it will raise an `ArgumentError` for ranges
     with excluding beginnings.
-
     ([Commit](https://github.com/rails/rails/commit/91949e48cf41af9f3e4ffba3e5eecf9b0a08bfc3))
 
-### Notable changes
+*   Deprecated calling `DatabaseTasks.load_schema` without a connection. Use
+    `DatabaseTasks.load_schema_current` instead.
+    ([Commit](https://github.com/rails/rails/commit/f15cef67f75e4b52fd45655d7c6ab6b35623c608))
 
-*   The PostgreSQL adapter now supports the `JSONB` datatype in PostgreSQL 9.4+.
-    ([Pull Request](https://github.com/rails/rails/pull/16220))
+*   Deprecated `sanitize_sql_hash_for_conditions` without replacement. Using a
+    `Relation` for performing queries and updates is the preferred API.
+    ([Commit](https://github.com/rails/rails/commit/d5902c9e))
 
-*   The `#references` method in migrations now supports a `type` option for
-    specifying the type of the foreign key (e.g. `:uuid`).
-    ([Pull Request](https://github.com/rails/rails/pull/16231))
+*   Deprecated `Reflection#source_macro` without replacement as it is no longer
+    needed in Active Record.
+    ([Pull Request](https://github.com/rails/rails/pull/16373))
 
-*   Added a `:required` option to singular associations, which defines a
-    presence validation on the association.
-    ([Pull Request](https://github.com/rails/rails/pull/16056))
+*   Deprecated `serialized_attributes` without replacement.
+    ([Pull Request](https://github.com/rails/rails/pull/15704))
 
-*   Introduced `ActiveRecord::Base#validate!` that raises `RecordInvalid` if the
-    record is invalid.
-    ([Pull Request](https://github.com/rails/rails/pull/8639))
+*   Deprecated returning `nil` from `column_for_attribute` when no column
+    exists. It will return a null object in Rails 5.0.
+    ([Pull Request](https://github.com/rails/rails/pull/15878))
 
-*   `ActiveRecord::Base#reload` now behaves the same as `m = Model.find(m.id)`,
-    meaning that it no longer retains the extra attributes from custom
-    `select`s.
-    ([Pull Request](https://github.com/rails/rails/pull/15866))
+*   Deprecated using `.joins`, `.preload` and `.eager_load` with associations
+    that depend on the instance state (i.e. those defined with a scope that
+    takes an argument) without replacement.
+    ([Commit](https://github.com/rails/rails/commit/ed56e596a0467390011bc9d56d462539776adac1))
 
-*   Introduced the `bin/rake db:purge` task to empty the database for the
-    current environment.
-    ([Commit](https://github.com/rails/rails/commit/e2f232aba15937a4b9d14bd91e0392c6d55be58d))
+### Notable changes
+
+*   Added a `:required` option to singular associations, which defines a
+    presence validation on the association.
+    ([Pull Request](https://github.com/rails/rails/pull/16056))
 
 *   `ActiveRecord::Dirty` now detects in-place changes to mutable values.
-    Serialized attributes on ActiveRecord models will no longer save when
+    Serialized attributes on Active Record models are no longer saved when
     unchanged. This also works with other types such as string columns and json
     columns on PostgreSQL.
     (Pull Requests [1](https://github.com/rails/rails/pull/15674),
     [2](https://github.com/rails/rails/pull/15786),
     [3](https://github.com/rails/rails/pull/15788))
 
-*   Added support for `#pretty_print` in `ActiveRecord::Base` objects.
-    ([Pull Request](https://github.com/rails/rails/pull/15172))
+*   Introduced the `db:purge` Rake task to empty the database for the
+    current environment.
+    ([Commit](https://github.com/rails/rails/commit/e2f232aba15937a4b9d14bd91e0392c6d55be58d))
+
+*   Introduced `ActiveRecord::Base#validate!` that raises
+    `ActiveRecord::RecordInvalid` if the record is invalid.
+    ([Pull Request](https://github.com/rails/rails/pull/8639))
+
+*   Introduced `validate` as an alias for `valid?`.
+    ([Pull Request](https://github.com/rails/rails/pull/14456))
+
+*   `touch` now accepts multiple attributes to be touched at once.
+    ([Pull Request](https://github.com/rails/rails/pull/14423))
 
-*   PostgreSQL and SQLite adapters no longer add a default limit of 255
+*   The PostgreSQL adapter now supports the `jsonb` datatype in PostgreSQL 9.4+.
+    ([Pull Request](https://github.com/rails/rails/pull/16220))
+
+*   The PostgreSQL and SQLite adapters no longer add a default limit of 255
     characters on string columns.
     ([Pull Request](https://github.com/rails/rails/pull/14579))
 
+*   Added support for the `citext` column type in the PostgreSQL adapter.
+    ([Pull Request](https://github.com/rails/rails/pull/12523))
+
+*   Added support for user-created range types in the PostgreSQL adapter.
+    ([Commit](https://github.com/rails/rails/commit/4cb47167e747e8f9dc12b0ddaf82bdb68c03e032))
+
 *   `sqlite3:///some/path` now resolves to the absolute system path
     `/some/path`. For relative paths, use `sqlite3:some/path` instead.
     (Previously, `sqlite3:///some/path` resolved to the relative path
-    `some/path`. This behaviour was deprecated on Rails 4.1).
+    `some/path`. This behavior was deprecated on Rails 4.1).
     ([Pull Request](https://github.com/rails/rails/pull/14569))
 
-*   Introduced `#validate` as an alias for `#valid?`.
-    ([Pull Request](https://github.com/rails/rails/pull/14456))
-
-*   `#touch` now accepts multiple attributes to be touched at once.
-    ([Pull Request](https://github.com/rails/rails/pull/14423))
-
 *   Added support for fractional seconds for MySQL 5.6 and above.
     (Pull Request [1](https://github.com/rails/rails/pull/8240),
     [2](https://github.com/rails/rails/pull/14359))
 
-*   Added support for the `citext` column type in PostgreSQL adapter.
-    ([Pull Request](https://github.com/rails/rails/pull/12523))
+*   Added `ActiveRecord::Base#pretty_print` to pretty print models.
+    ([Pull Request](https://github.com/rails/rails/pull/15172))
 
-*   Added support for user-created range types in PostgreSQL adapter.
-    ([Commit](https://github.com/rails/rails/commit/4cb47167e747e8f9dc12b0ddaf82bdb68c03e032))
+*   `ActiveRecord::Base#reload` now behaves the same as `m = Model.find(m.id)`,
+    meaning that it no longer retains the extra attributes from custom
+    `SELECT`s.
+    ([Pull Request](https://github.com/rails/rails/pull/15866))
 
+*   `ActiveRecord::Base#reflections` now returns a hash with string keys instead
+    of symbol keys. ([Pull Request](https://github.com/rails/rails/pull/17718))
+
+*   The `references` method in migrations now supports a `type` option for
+    specifying the type of the foreign key (e.g. `:uuid`).
+    ([Pull Request](https://github.com/rails/rails/pull/16231))
 
 Active Model
 ------------
@@ -701,11 +727,14 @@ Please refer to the [Changelog][active-model] for detailed changes.
     ([Pull Request](https://github.com/rails/rails/pull/16180))
 
 *   Deprecated `ActiveModel::Dirty#reset_changes` in favor of
-    `#clear_changes_information`.
+    `clear_changes_information`.
     ([Pull Request](https://github.com/rails/rails/pull/16180))
 
 ### Notable changes
 
+*   Introduced `validate` as an alias for `valid?`.
+    ([Pull Request](https://github.com/rails/rails/pull/14456))
+
 *   Introduced the `restore_attributes` method in `ActiveModel::Dirty` to restore
     the changed (dirty) attributes to their previous values.
     (Pull Request [1](https://github.com/rails/rails/pull/14861),
@@ -719,10 +748,6 @@ Please refer to the [Changelog][active-model] for detailed changes.
     characters if validations are enabled.
     ([Pull Request](https://github.com/rails/rails/pull/15708))
 
-*   Introduced `#validate` as an alias for `#valid?`.
-    ([Pull Request](https://github.com/rails/rails/pull/14456))
-
-
 Active Support
 --------------
 
@@ -753,15 +778,15 @@ Please refer to the [Changelog][active-support] for detailed changes.
 
 ### Notable changes
 
-*   `Object#try` and `Object#try!` can now be used without an explicit receiver.
-    ([Commit](https://github.com/rails/rails/commit/5e51bdda59c9ba8e5faf86294e3e431bd45f1830),
-    [Pull Request](https://github.com/rails/rails/pull/17361))
-
-*   Introduced new configuration option `active_support.test_order` for
+*   Introduced a new configuration option `active_support.test_order` for
     specifying the order test cases are executed. This option currently defaults
     to `:sorted` but will be changed to `:random` in Rails 5.0.
     ([Commit](https://github.com/rails/rails/commit/53e877f7d9291b2bf0b8c425f9e32ef35829f35b))
 
+*   `Object#try` and `Object#try!` can now be used without an explicit receiver in the block.
+    ([Commit](https://github.com/rails/rails/commit/5e51bdda59c9ba8e5faf86294e3e431bd45f1830),
+    [Pull Request](https://github.com/rails/rails/pull/17361))
+
 *   The `travel_to` test helper now truncates the `usec` component to 0.
     ([Commit](https://github.com/rails/rails/commit/9f6e82ee4783e491c20f5244a613fdeb4024beb5))
 
@@ -769,7 +794,7 @@ Please refer to the [Changelog][active-support] for detailed changes.
     (Commit [1](https://github.com/rails/rails/commit/702ad710b57bef45b081ebf42e6fa70820fdd810),
     [2](https://github.com/rails/rails/commit/64d91122222c11ad3918cc8e2e3ebc4b0a03448a))
 
-*   `Object#with_options` can now be used without an explicit receiver.
+*   `Object#with_options` can now be used without an explicit receiver in the block.
     ([Pull Request](https://github.com/rails/rails/pull/16339))
 
 *   Introduced `String#truncate_words` to truncate a string by a number of words.
diff --git a/guides/source/_welcome.html.erb b/guides/source/_welcome.html.erb
index f2315bfe22..614d69ecdd 100644
--- a/guides/source/_welcome.html.erb
+++ b/guides/source/_welcome.html.erb
@@ -15,5 +15,5 @@
 </p>
 <% end %>
 <p>
-  The guides for earlier releases: <a href="http://guides.rubyonrails.org/v4.1.6/">Rails 4.1.6</a>, <a href="http://guides.rubyonrails.org/v4.0.10/">Rails 4.0.10</a>, <a href="http://guides.rubyonrails.org/v3.2.19/">Rails 3.2.19</a> and <a href="http://guides.rubyonrails.org/v2.3.11/">Rails 2.3.11</a>.
+  The guides for earlier releases: <a href="http://guides.rubyonrails.org/v4.1.8/">Rails 4.1.8</a>, <a href="http://guides.rubyonrails.org/v4.0.12/">Rails 4.0.12</a>, <a href="http://guides.rubyonrails.org/v3.2.21/">Rails 3.2.21</a> and <a href="http://guides.rubyonrails.org/v2.3.11/">Rails 2.3.11</a>.
 </p>
diff --git a/guides/source/action_mailer_basics.md b/guides/source/action_mailer_basics.md
index f6c974c87a..ba7c16aa1d 100644
--- a/guides/source/action_mailer_basics.md
+++ b/guides/source/action_mailer_basics.md
@@ -35,10 +35,26 @@ views.
 ```bash
 $ bin/rails generate mailer UserMailer
 create  app/mailers/user_mailer.rb
+create  app/mailers/application_mailer.rb
 invoke  erb
 create    app/views/user_mailer
+create    app/views/layouts/mailer.text.erb
+create    app/views/layouts/mailer.html.erb
 invoke  test_unit
 create    test/mailers/user_mailer_test.rb
+create    test/mailers/previews/user_mailer_preview.rb
+```
+
+```ruby
+# app/mailers/application_mailer.rb
+class ApplicationMailer < ActionMailer::Base
+  default "from@example.com"
+  layout 'mailer'
+end
+
+# app/mailers/user_mailer.rb
+class UserMailer < ApplicationMailer
+end
 ```
 
 As you can see, you can generate mailers just like you use other generators with
@@ -63,8 +79,7 @@ delivered via email.
 `app/mailers/user_mailer.rb` contains an empty mailer:
 
 ```ruby
-class UserMailer < ActionMailer::Base
-  default from: 'from@example.com'
+class UserMailer < ApplicationMailer
 end
 ```
 
@@ -72,7 +87,7 @@ Let's add a method called `welcome_email`, that will send an email to the user's
 registered email address:
 
 ```ruby
-class UserMailer < ActionMailer::Base
+class UserMailer < ApplicationMailer
   default from: 'notifications@example.com'
 
   def welcome_email(user)
@@ -348,7 +363,7 @@ for the HTML version and `welcome_email.text.erb` for the plain text version.
 To change the default mailer view for your action you do something like:
 
 ```ruby
-class UserMailer < ActionMailer::Base
+class UserMailer < ApplicationMailer
   default from: 'notifications@example.com'
 
   def welcome_email(user)
@@ -370,7 +385,7 @@ If you want more flexibility you can also pass a block and render specific
 templates or even render inline or text without using a template file:
 
 ```ruby
-class UserMailer < ActionMailer::Base
+class UserMailer < ApplicationMailer
   default from: 'notifications@example.com'
 
   def welcome_email(user)
@@ -400,7 +415,7 @@ layout.
 In order to use a different file, call `layout` in your mailer:
 
 ```ruby
-class UserMailer < ActionMailer::Base
+class UserMailer < ApplicationMailer
   layout 'awesome' # use awesome.(html|text).erb as the layout
 end
 ```
@@ -412,7 +427,7 @@ You can also pass in a `layout: 'layout_name'` option to the render call inside
 the format block to specify different layouts for different formats:
 
 ```ruby
-class UserMailer < ActionMailer::Base
+class UserMailer < ApplicationMailer
   def welcome_email(user)
     mail(to: user.email) do |format|
       format.html { render layout: 'my_layout' }
@@ -455,16 +470,7 @@ By using the full URL, your links will now work in your emails.
 
 #### generating URLs with `url_for`
 
-You need to pass the `only_path: false` option when using `url_for`. This will
-ensure that absolute URLs are generated because the `url_for` view helper will,
-by default, generate relative URLs when a `:host` option isn't explicitly
-provided.
-
-```erb
-<%= url_for(controller: 'welcome',
-            action: 'greeting',
-            only_path: false) %>
-```
+`url_for` generate full URL by default in templates.
 
 If you did not configure the `:host` option globally make sure to pass it to
 `url_for`.
@@ -476,9 +482,6 @@ If you did not configure the `:host` option globally make sure to pass it to
             action: 'greeting') %>
 ```
 
-NOTE: When you explicitly pass the `:host` Rails will always generate absolute
-URLs, so there is no need to pass `only_path: false`.
-
 #### generating URLs with named routes
 
 Email clients have no web context and so paths have no base URL to form complete
@@ -510,7 +513,7 @@ while delivering emails, you can do this using `delivery_method_options` in the
 mailer action.
 
 ```ruby
-class UserMailer < ActionMailer::Base
+class UserMailer < ApplicationMailer
   def welcome_email(user, company)
     @user = user
     @url  = user_url(@user)
@@ -532,7 +535,7 @@ option. In such cases don't forget to add the `:content_type` option. Rails
 will default to `text/plain` otherwise.
 
 ```ruby
-class UserMailer < ActionMailer::Base
+class UserMailer < ApplicationMailer
   def welcome_email(user, email_body)
     mail(to: user.email,
          body: email_body,
@@ -562,7 +565,7 @@ mailer, and pass the email object to the mailer `receive` instance
 method. Here's an example:
 
 ```ruby
-class UserMailer < ActionMailer::Base
+class UserMailer < ApplicationMailer
   def receive(email)
     page = Page.find_by(address: email.to.first)
     page.emails.create(
@@ -598,7 +601,7 @@ Action Mailer allows for you to specify a `before_action`, `after_action` and
   using instance variables set in your mailer action.
 
 ```ruby
-class UserMailer < ActionMailer::Base
+class UserMailer < ApplicationMailer
   after_action :set_delivery_options,
                :prevent_delivery_to_guests,
                :set_business_headers
diff --git a/guides/source/action_view_overview.md b/guides/source/action_view_overview.md
index 683e633668..f4d5bb8272 100644
--- a/guides/source/action_view_overview.md
+++ b/guides/source/action_view_overview.md
@@ -7,7 +7,6 @@ After reading this guide, you will know:
 * How best to use templates, partials, and layouts.
 * What helpers are provided by Action View and how to make your own.
 * How to use localized views.
-* How to use Action View outside of Rails.
 
 --------------------------------------------------------------------------------
 
diff --git a/guides/source/active_job_basics.md b/guides/source/active_job_basics.md
index ca851371a9..748467866d 100644
--- a/guides/source/active_job_basics.md
+++ b/guides/source/active_job_basics.md
@@ -23,7 +23,7 @@ clean-ups, to billing charges, to mailings. Anything that can be chopped up
 into small units of work and run in parallel, really.
 
 
-The Purpose of the Active Job
+The Purpose of Active Job
 -----------------------------
 The main point is to ensure that all Rails apps will have a job infrastructure
 in place, even if it's in the form of an "immediate runner". We can then have
@@ -56,9 +56,6 @@ You can also create a job that will run on a specific queue:
 $ bin/rails generate job guests_cleanup --queue urgent
 ```
 
-As you can see, you can generate jobs just like you use other generators with
-Rails.
-
 If you don't want to use a generator, you could create your own file inside of
 `app/jobs`, just make sure that it inherits from `ActiveJob::Base`.
 
@@ -107,14 +104,19 @@ 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).
 
-### Changing the Backend
+### Setting the Backend
 
-You can easily change your queueing backend:
+You can easily set your queueing backend:
 
 ```ruby
-# be sure to have the adapter gem in your Gemfile and follow
-# the adapter specific installation and deployment instructions
-config.active_job.queue_adapter = :sidekiq
+# config/application.rb
+module YourApp
+  class Application < Rails::Application
+    # Be sure to have the adapter's gem in your Gemfile and follow
+    # the adapter's specific installation and deployment instructions.
+    config.active_job.queue_adapter = :sidekiq
+  end
+end
 ```
 
 
@@ -149,7 +151,7 @@ class GuestsCleanupJob < ActiveJob::Base
 end
 
 # Now your job will run on queue production_low_priority on your
-# production environment and on beta_low_priority on your beta
+# production environment and on staging_low_priority on your staging
 # environment
 ```
 
@@ -248,7 +250,7 @@ end
 ```
 
 
-ActionMailer
+Action Mailer
 ------------
 
 One of the most common jobs in a modern web application is sending emails outside
diff --git a/guides/source/active_record_postgresql.md b/guides/source/active_record_postgresql.md
index 6c94218ef6..a2681a80e9 100644
--- a/guides/source/active_record_postgresql.md
+++ b/guides/source/active_record_postgresql.md
@@ -103,11 +103,6 @@ profile.settings # => {"color"=>"blue", "resolution"=>"800x600"}
 
 profile.settings = {"color" => "yellow", "resolution" => "1280x1024"}
 profile.save!
-
-## you need to call _will_change! if you are editing the store in place
-profile.settings["color"] = "green"
-profile.settings_will_change!
-profile.save!
 ```
 
 ### JSON
@@ -219,7 +214,7 @@ Currently there is no special support for enumerated types. They are mapped as
 normal text columns:
 
 ```ruby
-# db/migrate/20131220144913_create_events.rb
+# db/migrate/20131220144913_create_articles.rb
 execute <<-SQL
   CREATE TYPE article_status AS ENUM ('draft', 'published');
 SQL
@@ -281,7 +276,7 @@ end
 # Usage
 User.create settings: "01010011"
 user = User.first
-user.settings # => "(Paris,Champs-Élysées)"
+user.settings # => "01010011"
 user.settings = "0xAF"
 user.settings # => 10101111
 user.save!
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md
index f6f96b79c6..7b11092f3d 100644
--- a/guides/source/active_support_core_extensions.md
+++ b/guides/source/active_support_core_extensions.md
@@ -1011,7 +1011,7 @@ self.default_params = {
 }.freeze
 ```
 
-They can be also accessed and overridden at the instance level.
+They can also be accessed and overridden at the instance level.
 
 ```ruby
 A.x = 1
@@ -1447,7 +1447,7 @@ Returns the substring of the string starting at position `position`:
 "hello".from(0)  # => "hello"
 "hello".from(2)  # => "llo"
 "hello".from(-2) # => "lo"
-"hello".from(10) # => "" if < 1.9, nil in 1.9
+"hello".from(10) # => nil
 ```
 
 NOTE: Defined in `active_support/core_ext/string/access.rb`.
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md
index 61490ceb54..a12f5638e3 100644
--- a/guides/source/association_basics.md
+++ b/guides/source/association_basics.md
@@ -1532,8 +1532,6 @@ Controls what happens to the associated objects when their owner is destroyed:
 * `:restrict_with_exception` causes an exception to be raised if there are any associated records
 * `:restrict_with_error` causes an error to be added to the owner if there are any associated objects
 
-NOTE: This option is ignored when you use the `:through` option on the association.
-
 ##### `:foreign_key`
 
 By convention, Rails assumes that the column used to hold the foreign key on the other model is the name of this model with the suffix `_id` added. The `:foreign_key` option lets you set the name of the foreign key directly:
diff --git a/guides/source/command_line.md b/guides/source/command_line.md
index b9014724bd..e72bc81766 100644
--- a/guides/source/command_line.md
+++ b/guides/source/command_line.md
@@ -61,7 +61,7 @@ With no further work, `rails server` will run our new shiny Rails app:
 $ cd commandsapp
 $ bin/rails server
 => Booting WEBrick
-=> Rails 4.2.0 application starting in development on http://0.0.0.0:3000
+=> Rails 4.2.0 application starting in development on http://localhost:3000
 => Call with -d to detach
 => Ctrl-C to shutdown server
 [2013-08-07 02:00:01] INFO  WEBrick 1.3.1
@@ -79,7 +79,7 @@ The server can be run on a different port using the `-p` option. The default dev
 $ bin/rails server -e production -p 4000
 ```
 
-The `-b` option binds Rails to the specified IP, by default it is 0.0.0.0. You can run a server as a daemon by passing a `-d` option.
+The `-b` option binds Rails to the specified IP, by default it is localhost. You can run a server as a daemon by passing a `-d` option.
 
 ### `rails generate`
 
@@ -368,8 +368,7 @@ Rake is Ruby Make, a standalone Ruby utility that replaces the Unix utility 'mak
 
 You can get a list of Rake tasks available to you, which will often depend on your current directory, by typing `rake --tasks`. Each task has a description, and should help you find the thing you need.
 
-To get the full backtrace for running rake task you can pass the option
-```--trace``` to command line, for example ```rake db:create --trace```.
+To get the full backtrace for running rake task you can pass the option ```--trace``` to command line, for example ```rake db:create --trace```.
 
 ```bash
 $ bin/rake --tasks
@@ -394,16 +393,11 @@ INFO: You can also use ```rake -T```  to get the list of tasks.
 ```bash
 $ bin/rake about
 About your application's environment
+Rails version             4.2.0
 Ruby version              1.9.3 (x86_64-linux)
 RubyGems version          1.3.6
 Rack version              1.3
-Rails version             4.2.0
 JavaScript Runtime        Node.js (V8)
-Active Record version     4.2.0
-Action Pack version       4.2.0
-Action View version       4.2.0
-Action Mailer version     4.2.0
-Active Support version    4.2.0
 Middleware                Rack::Sendfile, ActionDispatch::Static, Rack::Lock, #<ActiveSupport::Cache::Strategy::LocalCache::Middleware:0x007ffd131a7c88>, Rack::Runtime, Rack::MethodOverride, ActionDispatch::RequestId, Rails::Rack::Logger, ActionDispatch::ShowExceptions, ActionDispatch::DebugExceptions, ActionDispatch::RemoteIp, ActionDispatch::Reloader, ActionDispatch::Callbacks, ActiveRecord::Migration::CheckPending, ActiveRecord::ConnectionAdapters::ConnectionManagement, ActiveRecord::QueryCache, ActionDispatch::Cookies, ActionDispatch::Session::CookieStore, ActionDispatch::Flash, ActionDispatch::ParamsParser, Rack::Head, Rack::ConditionalGet, Rack::ETag
 Application root          /home/foobar/commandsapp
 Environment               development
@@ -413,10 +407,7 @@ Database schema version   20110805173523
 
 ### `assets`
 
-You can precompile the assets in `app/assets` using `rake assets:precompile`,
-and remove older compiled assets using `rake assets:clean`. The `assets:clean`
-task allows for rolling deploys that may still be linking to an old asset while
-the new assets are being built.
+You can precompile the assets in `app/assets` using `rake assets:precompile`, and remove older compiled assets using `rake assets:clean`. The `assets:clean` task allows for rolling deploys that may still be linking to an old asset while the new assets are being built.
 
 If you want to clear `public/assets` completely, you can use `rake assets:clobber`.
 
@@ -503,7 +494,7 @@ Rails comes with a test suite called Minitest. Rails owes its stability to the u
 
 ### `tmp`
 
-The `Rails.root/tmp` directory is, like the *nix /tmp directory, the holding place for temporary files like sessions (if you're using a file store for files), process id files, and cached actions.
+The `Rails.root/tmp` directory is, like the *nix /tmp directory, the holding place for temporary files like sessions (if you're using a file store for sessions), process id files, and cached actions.
 
 The `tmp:` namespaced tasks will help you clear and create the `Rails.root/tmp` directory:
 
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index 58c3f217eb..7688962c01 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -153,7 +153,7 @@ pipeline is enabled. It is set to true by default.
 
 * `config.assets.manifest` defines the full path to be used for the asset precompiler's manifest file. Defaults to a file named `manifest-<random>.json` in the `config.assets.prefix` directory within the public folder.
 
-* `config.assets.digest` enables the use of MD5 fingerprints in asset names. Set to `true` by default in `production.rb`.
+* `config.assets.digest` enables the use of MD5 fingerprints in asset names. Set to `true` by default in `production.rb` and `development.rb`.
 
 * `config.assets.debug` disables the concatenation and compression of assets. Set to `true` by default in `development.rb`.
 
@@ -214,7 +214,7 @@ Every Rails application comes with a standard set of middleware which it uses in
 * `ActionDispatch::Flash` sets up the `flash` keys. Only available if `config.action_controller.session_store` is set to a value.
 * `ActionDispatch::ParamsParser` parses out parameters from the request into `params`.
 * `Rack::MethodOverride` allows the method to be overridden if `params[:_method]` is set. This is the middleware which supports the PATCH, PUT, and DELETE HTTP method types.
-* `ActionDispatch::Head` converts HEAD requests to GET requests and serves them as so.
+* `Rack::Head` converts HEAD requests to GET requests and serves them as so.
 
 Besides these usual middleware, you can add your own by using the `config.middleware.use` method:
 
@@ -225,13 +225,13 @@ config.middleware.use Magical::Unicorns
 This will put the `Magical::Unicorns` middleware on the end of the stack. You can use `insert_before` if you wish to add a middleware before another.
 
 ```ruby
-config.middleware.insert_before ActionDispatch::Head, Magical::Unicorns
+config.middleware.insert_before Rack::Head, Magical::Unicorns
 ```
 
 There's also `insert_after` which will insert a middleware after another:
 
 ```ruby
-config.middleware.insert_after ActionDispatch::Head, Magical::Unicorns
+config.middleware.insert_after Rack::Head, Magical::Unicorns
 ```
 
 Middlewares can also be completely swapped out and replaced with others:
diff --git a/guides/source/documents.yaml b/guides/source/documents.yaml
index 4c98d3e1d5..1b838201cc 100644
--- a/guides/source/documents.yaml
+++ b/guides/source/documents.yaml
@@ -171,7 +171,6 @@
       name: Ruby on Rails 4.2 Release Notes
       url: 4_2_release_notes.html
       description: Release notes for Rails 4.2.
-      work_in_progress: true
     -
       name: Ruby on Rails 4.1 Release Notes
       url: 4_1_release_notes.html
diff --git a/guides/source/engines.md b/guides/source/engines.md
index 21ac941ac0..a1f2da18ed 100644
--- a/guides/source/engines.md
+++ b/guides/source/engines.md
@@ -32,7 +32,7 @@ directory structure, and are both generated using the `rails plugin new`
 generator. The difference is that an engine is considered a "full plugin" by
 Rails (as indicated by the `--full` option that's passed to the generator
 command). We'll actually be using the `--mountable` option here, which includes
-all the features of `--full`, and then some. This guide will refer to these 
+all the features of `--full`, and then some. This guide will refer to these
 "full plugins" simply as "engines" throughout. An engine **can** be a plugin,
 and a plugin **can** be an engine.
 
@@ -1036,31 +1036,42 @@ functionality, especially controllers. This means that if you were to make a
 typical `GET` to a controller in a controller's functional test like this:
 
 ```ruby
-get :index
+module Blorgh
+  class FooControllerTest < ActionController::TestCase
+    def test_index
+      get :index
+      ...
+    end
+  end
+end
 ```
 
 It may not function correctly. This is because the application doesn't know how
 to route these requests to the engine unless you explicitly tell it **how**. To
-do this, you must also pass the `:use_route` option as a parameter on these
-requests:
+do this, you must set the `@routes` instance variable to the engine's route set
+in your setup code:
 
 ```ruby
-get :index, use_route: :blorgh
+module Blorgh
+  class FooControllerTest < ActionController::TestCase
+    setup do
+      @routes = Engine.routes
+    end
+
+    def test_index
+      get :index
+      ...
+    end
+  end
+end
 ```
 
 This tells the application that you still want to perform a `GET` request to the
 `index` action of this controller, but you want to use the engine's route to get
 there, rather than the application's one.
 
-Another way to do this is to assign the `@routes` instance variable to `Engine.routes` in your test setup:
-
-```ruby
-setup do
-  @routes = Engine.routes
-end
-```
-
-This will also ensure url helpers for the engine will work as expected in your tests.
+This also ensures that the engine's URL helpers will work as expected in your
+tests.
 
 Improving engine functionality
 ------------------------------
@@ -1155,7 +1166,7 @@ end
 
 Using `Class#class_eval` is great for simple adjustments, but for more complex
 class modifications, you might want to consider using [`ActiveSupport::Concern`]
-(http://edgeapi.rubyonrails.org/classes/ActiveSupport/Concern.html).
+(http://api.rubyonrails.org/classes/ActiveSupport/Concern.html).
 ActiveSupport::Concern manages load order of interlinked dependent modules and
 classes at run time allowing you to significantly modularize your code.
 
diff --git a/guides/source/form_helpers.md b/guides/source/form_helpers.md
index cb45e38614..f3f7415b3c 100644
--- a/guides/source/form_helpers.md
+++ b/guides/source/form_helpers.md
@@ -96,7 +96,15 @@ form_tag({controller: "people", action: "search"}, method: "get", class: "nifty_
 
 ### Helpers for Generating Form Elements
 
-Rails provides a series of helpers for generating form elements such as checkboxes, text fields, and radio buttons. These basic helpers, with names ending in "_tag" (such as `text_field_tag` and `check_box_tag`), generate just a single `<input>` element. The first parameter to these is always the name of the input. When the form is submitted, the name will be passed along with the form data, and will make its way to the `params` hash in the controller with the value entered by the user for that field. For example, if the form contains `<%= text_field_tag(:query) %>`, then you would be able to get the value of this field in the controller with `params[:query]`.
+Rails provides a series of helpers for generating form elements such as
+checkboxes, text fields, and radio buttons. These basic helpers, with names
+ending in `_tag` (such as `text_field_tag` and `check_box_tag`), generate just a
+single `<input>` element. The first parameter to these is always the name of the
+input. When the form is submitted, the name will be passed along with the form
+data, and will make its way to the `params` hash in the controller with the
+value entered by the user for that field. For example, if the form contains `<%=
+text_field_tag(:query) %>`, then you would be able to get the value of this
+field in the controller with `params[:query]`.
 
 When naming inputs, Rails uses certain conventions that make it possible to submit parameters with non-scalar values such as arrays or hashes, which will also be accessible in `params`. You can read more about them in [chapter 7 of this guide](#understanding-parameter-naming-conventions). For details on the precise usage of these helpers, please refer to the [API documentation](http://api.rubyonrails.org/classes/ActionView/Helpers/FormTagHelper.html).
 
diff --git a/guides/source/getting_started.md b/guides/source/getting_started.md
index 1769448531..dc63ae62b1 100644
--- a/guides/source/getting_started.md
+++ b/guides/source/getting_started.md
@@ -101,7 +101,7 @@ If you don't have Ruby installed have a look at
 install Ruby on your platform.
 
 Many popular UNIX-like OSes ship with an acceptable version of SQLite3. Windows
-users and others can find installation instructions at [the SQLite3 website](https://www.sqlite.org).
+users and others can find installation instructions at the [SQLite3 website](https://www.sqlite.org).
 Verify that it is correctly installed and in your PATH:
 
 ```bash
@@ -165,7 +165,7 @@ of the files and folders that Rails created by default:
 |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.|
 |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](http://bundler.io).|
+|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](http://bundler.io).|
 |lib/|Extended modules for your application.|
 |log/|Application log files.|
 |public/|The only folder seen by the world as-is. Contains static files and compiled assets.|
@@ -195,8 +195,8 @@ TIP: Compiling CoffeeScript and JavaScript asset compression requires you
 have a JavaScript runtime available on your system, in the absence
 of a runtime you will see an `execjs` error during asset compilation.
 Usually Mac OS X and Windows come with a JavaScript runtime installed.
-Rails adds the `therubyracer` gem to the generated `Gemfile` in a 
-commented line for new apps and you can uncomment if you need it. 
+Rails adds the `therubyracer` gem to the generated `Gemfile` in a
+commented line for new apps and you can uncomment if you need it.
 `therubyrhino` is the recommended runtime for JRuby users and is added by
 default to the `Gemfile` in apps generated under JRuby. You can investigate
 all the supported runtimes at [ExecJS](https://github.com/sstephenson/execjs#readme).
@@ -338,8 +338,8 @@ 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
-resource. Here's what `config/routes.rb` should look like after the
-_article resource_ is declared.
+resource. You need to add the _article resource_ to the
+`config/routes.rb` as follows:
 
 ```ruby
 Rails.application.routes.draw do
@@ -833,7 +833,7 @@ class ArticlesController < ApplicationController
 
 A couple of things to note. We use `Article.find` to find the article we're
 interested in, passing in `params[:id]` to get the `:id` parameter from the
-request. We also use an instance variable (prefixed by `@`) to hold a
+request. We also use an instance variable (prefixed with `@`) to hold a
 reference to the article object. We do this because Rails will pass all instance
 variables to the view.
 
@@ -1279,7 +1279,7 @@ And here's how our app looks so far:
 Our `edit` page looks very similar to the `new` page; in fact, they
 both share the same code for displaying the form. Let's remove this
 duplication by using a view partial. By convention, partial files are
-prefixed by an underscore.
+prefixed with an underscore.
 
 TIP: You can read more about partials in the
 [Layouts and Rendering in Rails](layouts_and_rendering.html) guide.
@@ -2049,7 +2049,7 @@ command-line utility:
   in your web browser to explore the API documentation.
 
 TIP: To be able to generate the Rails Guides locally with the `doc:guides` rake
-task you need to install the RedCloth gem. Add it to your `Gemfile` and run
+task you need to install the RedCloth and Nokogiri gems. Add it to your `Gemfile` and run
 `bundle install` and you're ready to go.
 
 Configuration Gotchas
diff --git a/guides/source/i18n.md b/guides/source/i18n.md
index f6cbc1823a..75b5275245 100644
--- a/guides/source/i18n.md
+++ b/guides/source/i18n.md
@@ -626,7 +626,7 @@ entry[count == 1 ? 0 : 1]
 
 I.e. the translation denoted as `:one` is regarded as singular, the other is used as plural (including the count being zero).
 
-If the lookup for the key does not return a Hash suitable for pluralization, an `18n::InvalidPluralizationData` exception is raised.
+If the lookup for the key does not return a Hash suitable for pluralization, an `I18n::InvalidPluralizationData` exception is raised.
 
 ### Setting and Passing a Locale
 
diff --git a/guides/source/rails_on_rack.md b/guides/source/rails_on_rack.md
index 8bc2678d8f..0dec0e139b 100644
--- a/guides/source/rails_on_rack.md
+++ b/guides/source/rails_on_rack.md
@@ -277,7 +277,7 @@ Much of Action Controller's functionality is implemented as Middlewares. The fol
 
 **`ActionDispatch::Callbacks`**
 
-* Runs the prepare callbacks before serving the request.
+* Provides callbacks to be executed before and after dispatching the request.
 
 **`ActiveRecord::Migration::CheckPending`**
 
@@ -307,7 +307,7 @@ Much of Action Controller's functionality is implemented as Middlewares. The fol
 
 * Parses out parameters from the request into `params`.
 
-**`ActionDispatch::Head`**
+**`Rack::Head`**
 
 * Converts HEAD requests to `GET` requests and serves them as so.
 
diff --git a/guides/source/security.md b/guides/source/security.md
index 125dd82666..b1c5b22338 100644
--- a/guides/source/security.md
+++ b/guides/source/security.md
@@ -362,7 +362,7 @@ Refer to the Injection section for countermeasures against XSS. It is _recommend
 
 **CSRF** Cross-Site Request Forgery (CSRF), also known as Cross-Site Reference Forgery (XSRF), is a gigantic attack method, it allows the attacker to do everything the administrator or Intranet user may do. As you have already seen above how CSRF works, here are a few examples of what attackers can do in the Intranet or admin interface.
 
-A real-world example is a [router reconfiguration by CSRF](http://www.h-online.com/security/Symantec-reports-first-active-attack-on-a-DSL-router--/news/102352). The attackers sent a malicious e-mail, with CSRF in it, to Mexican users. The e-mail claimed there was an e-card waiting for them, but it also contained an image tag that resulted in a HTTP-GET request to reconfigure the user's router (which is a popular model in Mexico). The request changed the DNS-settings so that requests to a Mexico-based banking site would be mapped to the attacker's site. Everyone who accessed the banking site through that router saw the attacker's fake web site and had their credentials stolen.
+A real-world example is a [router reconfiguration by CSRF](http://www.h-online.com/security/news/item/Symantec-reports-first-active-attack-on-a-DSL-router-735883.html). The attackers sent a malicious e-mail, with CSRF in it, to Mexican users. The e-mail claimed there was an e-card waiting for them, but it also contained an image tag that resulted in a HTTP-GET request to reconfigure the user's router (which is a popular model in Mexico). The request changed the DNS-settings so that requests to a Mexico-based banking site would be mapped to the attacker's site. Everyone who accessed the banking site through that router saw the attacker's fake web site and had their credentials stolen.
 
 Another example changed Google Adsense's e-mail address and password by. If the victim was logged into Google Adsense, the administration interface for Google advertisements campaigns, an attacker could change their credentials. 
 
diff --git a/guides/source/testing.md b/guides/source/testing.md
index 6678db21f8..d54f431d54 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -82,7 +82,7 @@ Each fixture is given a name followed by an indented list of colon-separated key
 
 If you are working with [associations](/association_basics.html), you can simply
 define a reference node between two different fixtures. Here's an example with
-a belongs_to/has_many association:
+a `belongs_to`/`has_many` association:
 
 ```yaml
 # In fixtures/categories.yml
@@ -728,7 +728,7 @@ class UserFlowsTest < ActionDispatch::IntegrationTest
     https!(false)
     get "/articles/all"
     assert_response :success
-    assert assigns(:products)
+    assert assigns(:articles)
   end
 end
 ```
@@ -785,14 +785,13 @@ end
 Rake Tasks for Running your Tests
 ---------------------------------
 
-You don't need to set up and run your tests by hand on a test-by-test basis.
-Rails comes with a number of commands to help in testing.
-The table below lists all commands that come along in the default Rakefile
-when you initiate a Rails project.
+Rails comes with a number of built-in rake tasks to help with testing. The
+table below lists the commands included in the default Rakefile when a Rails
+project is created.
 
 | Tasks                   | Description |
 | ----------------------- | ----------- |
-| `rake test`             | Runs all unit, functional and integration tests. You can also simply run `rake` as Rails will run all the tests by default |
+| `rake test`             | Runs all tests in the `test` folder. You can also simply run `rake` as Rails will run all the tests by default |
 | `rake test:controllers` | Runs all the controller tests from `test/controllers` |
 | `rake test:functionals` | Runs all the functional tests from `test/controllers`, `test/mailers`, and `test/functional` |
 | `rake test:helpers`     | Runs all the helper tests from `test/helpers` |
@@ -801,11 +800,10 @@ when you initiate a Rails project.
 | `rake test:mailers`     | Runs all the mailer tests from `test/mailers` |
 | `rake test:models`      | Runs all the model tests from `test/models` |
 | `rake test:units`       | Runs all the unit tests from `test/models`, `test/helpers`, and `test/unit` |
-| `rake test:all`         | Runs all tests quickly by merging all types and not resetting db |
-| `rake test:all:db`      | Runs all tests quickly by merging all types and resetting db |
+| `rake test:db`          | Runs all tests in the `test` folder and resets the db |
 
 
-Brief Note About `Minitest`
+A Brief Note About Minitest
 -----------------------------
 
 Ruby ships with a vast Standard Library for all common use-cases including testing. Since version 1.9, Ruby provides `Minitest`, a framework for testing. All the basic assertions such as `assert_equal` discussed above are actually defined in `Minitest::Assertions`. The classes `ActiveSupport::TestCase`, `ActionController::TestCase`, `ActionMailer::TestCase`, `ActionView::TestCase` and `ActionDispatch::IntegrationTest` - which we have been inheriting in our test classes - include `Minitest::Assertions`, allowing us to use all of the basic assertions in our tests.
@@ -902,13 +900,17 @@ end
 Testing Routes
 --------------
 
-Like everything else in your Rails application, it is recommended that you test your routes. An example test for a route in the default `show` action of `Articles` controller above should look like:
+Like everything else in your Rails application, it is recommended that you test your routes. Below are example tests for the routes of default `show` and `create` action of `Articles` controller above and it should look like:
 
 ```ruby
 class ArticleRoutesTest < ActionController::TestCase
   test "should route to article" do
     assert_routing '/articles/1', { controller: "articles", action: "show", id: "1" }
   end
+
+  test "should route to create article" do
+    assert_routing({ method: 'post', path: '/articles' }, { controller: "articles", action: "create" })
+  end
 end
 ```
 
@@ -1045,6 +1047,68 @@ end
 Moreover, since the test class extends from `ActionView::TestCase`, you have
 access to Rails' helper methods such as `link_to` or `pluralize`.
 
+Testing Jobs
+------------
+
+Since your custom jobs can be queued at different levels inside your application,
+you'll need to test both jobs themselves (their behavior when they get enqueued)
+and that other entities correctly enqueue them.
+
+### A Basic Test Case
+
+By default, when you generate a job, an associated test will be generated as well
+under the `test/jobs` directory. Here's an example test with a billing job:
+
+```ruby
+require 'test_helper'
+
+class BillingJobTest < ActiveJob::TestCase
+  test 'that account is charged' do
+    BillingJob.perform_now(account, product)
+    assert account.reload.charged_for?(product)
+  end
+end
+```
+
+This test is pretty simple and only asserts that the job get the work done
+as expected.
+
+By default, `ActiveJob::TestCase` will set the queue adapter to `:test` so that
+your jobs are performed inline. It will also ensure that all previously performed
+and enqueued jobs are cleared before any test run so you can safely assume that
+no jobs have already been executed in the scope of each test.
+
+### Custom Assertions And Testing Jobs Inside Other Components
+
+Active Job ships with a bunch of custom assertions that can be used to lessen
+the verbosity of tests:
+
+| Assertion                              | Purpose |
+| -------------------------------------- | ------- |
+| `assert_enqueued_jobs(number)`         | Asserts that the number of enqueued jobs matches the given number. |
+| `assert_performed_jobs(number)`        | Asserts that the number of performed jobs matches the given number. |
+| `assert_no_enqueued_jobs { ... }`      | Asserts that no jobs have been enqueued. |
+| `assert_no_performed_jobs { ... }`     | Asserts that no jobs have been performed. |
+| `assert_enqueued_with([args]) { ... }` | Asserts that the job passed in the block has been enqueued with the given arguments. |
+| `assert_performed_with([args]) { ... }`| Asserts that the job passed in the block has been performed with the given arguments. |
+
+It's a good practice to ensure that your jobs correctly get enqueued or performed
+wherever you invoke them (e.g. inside your controllers). This is precisely where
+the custom assertions provided by Active Job are pretty useful. For instance,
+within a model:
+
+```ruby
+require 'test_helper'
+
+class ProductTest < ActiveSupport::TestCase
+  test 'billing job scheduling' do
+    assert_enqueued_with(job: BillingJob) do
+      product.charge(account)
+    end
+  end
+end
+```
+
 Other Testing Approaches
 ------------------------
 
@@ -1056,3 +1120,4 @@ The built-in `minitest` based testing is not the only way to test Rails applicat
 * [MiniTest::Spec Rails](https://github.com/metaskills/minitest-spec-rails), use the MiniTest::Spec DSL within your rails tests.
 * [Shoulda](http://www.thoughtbot.com/projects/shoulda), an extension to `test/unit` with additional helpers, macros, and assertions.
 * [RSpec](http://relishapp.com/rspec), a behavior-driven development framework
+* [Capybara](http://jnicklas.github.com/capybara/), Acceptance test framework for web applications
diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index aac2aef615..4ce61c282d 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -50,22 +50,10 @@ Don't forget to review the difference, to see if there were any unexpected chang
 Upgrading from Rails 4.1 to Rails 4.2
 -------------------------------------
 
-NOTE: This section is a work in progress, please help to improve this by sending
-a [pull request](https://github.com/rails/rails/edit/master/guides/source/upgrading_ruby_on_rails.md).
-
 ### 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.
 
-Additionally, you can tell Rails to automatically mount a VT100-compatible console on a predetermined path by setting the appropriate configuration flags in your development config:
-
-```ruby
-# config/environments/development.rb
-
-config.web_console.automount = true
-config.web_console.default_mount_path = '/terminal' # Optional, defaults to /console
-```
-
 ### 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:
@@ -145,6 +133,18 @@ assigning `nil` to a serialized attribute will save it to the database
 as `NULL` instead of passing the `nil` value through the coder (e.g. `"null"`
 when using the `JSON` coder).
 
+### Production log level
+
+In Rails 5, the default log level for the production environment will be changed
+to `:debug` (from `:info`). To preserve the current default, add the following
+line to your `production.rb`:
+
+```ruby
+# Set to `:info` to match the current default, or set to `:debug` to opt-into
+# the future default.
+config.log_level = :info
+```
+
 ### `after_bundle` in Rails templates
 
 If you have a Rails template that adds all the files in version control, it
@@ -181,7 +181,7 @@ end
 
 There's a new choice for sanitizing HTML fragments in your applications. The
 venerable html-scanner approach is now officially being deprecated in favor of
-[`Rails Html Sanitizer`](https://github.com/rails/rails-html-sanitizer).
+[`Rails HTML Sanitizer`](https://github.com/rails/rails-html-sanitizer).
 
 This means the methods `sanitize`, `sanitize_css`, `strip_tags` and
 `strip_links` are backed by a new implementation.
@@ -207,7 +207,7 @@ 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/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
@@ -421,7 +421,7 @@ class ReadOnlyModel < ActiveRecord::Base
 end
 ```
 
-This behaviour was never intentionally supported. Due to a change in the internals
+This behavior was never intentionally supported. Due to a change in the internals
 of `ActiveSupport::Callbacks`, this is no longer allowed in Rails 4.1. Using a
 `return` statement in an inline callback block causes a `LocalJumpError` to
 be raised when the callback is executed.
@@ -795,7 +795,7 @@ Rails 4.0 extracted Active Resource to its own gem. If you still need the featur
 
 * Rails 4.0 has changed how errors attach with the `ActiveModel::Validations::ConfirmationValidator`. Now when confirmation validations fail, the error will be attached to `:#{attribute}_confirmation` instead of `attribute`.
 
-* Rails 4.0 has changed `ActiveModel::Serializers::JSON.include_root_in_json` default value to `false`. Now, Active Model Serializers and Active Record objects have the same default behaviour. This means that you can comment or remove the following option in the `config/initializers/wrap_parameters.rb` file:
+* Rails 4.0 has changed `ActiveModel::Serializers::JSON.include_root_in_json` default value to `false`. Now, Active Model Serializers and Active Record objects have the same default behavior. This means that you can comment or remove the following option in the `config/initializers/wrap_parameters.rb` file:
 
 ```ruby
 # Disable root element in JSON by default.