Use frozen-string-literal in ActiveRecord

677 files changed, 1363 insertions, 11 deletions

diff --git a/.rubocop.yml b/.rubocop.yml
index efd154156a..cb8dc513a9 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -90,6 +90,7 @@ Style/FrozenStringLiteralComment:
     - 'activesupport/**/*'
     - 'activemodel/**/*'
     - 'activejob/**/*'
+    - 'activerecord/**/*'
 
 # Use `foo {}` not `foo{}`.
 Layout/SpaceBeforeBlockBraces:
diff --git a/activerecord/Rakefile b/activerecord/Rakefile
index fe5f9d1071..57c82bf469 100644
--- a/activerecord/Rakefile
+++ b/activerecord/Rakefile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "rake/testtask"
 
 require_relative "test/config"
diff --git a/activerecord/activerecord.gemspec b/activerecord/activerecord.gemspec
index a626a1f21b..7b62c98c6e 100644
--- a/activerecord/activerecord.gemspec
+++ b/activerecord/activerecord.gemspec
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 version = File.read(File.expand_path("../RAILS_VERSION", __dir__)).strip
 
 Gem::Specification.new do |s|
diff --git a/activerecord/bin/test b/activerecord/bin/test
index ab69f4f603..83c192531e 100755
--- a/activerecord/bin/test
+++ b/activerecord/bin/test
@@ -1,4 +1,5 @@
 #!/usr/bin/env ruby
+# frozen_string_literal: true
 
 COMPONENT_ROOT = File.expand_path("..", __dir__)
 require_relative "../../tools/test"
diff --git a/activerecord/examples/performance.rb b/activerecord/examples/performance.rb
index 3257dd4ad7..1a2c78f39b 100644
--- a/activerecord/examples/performance.rb
+++ b/activerecord/examples/performance.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_record"
 require "benchmark/ips"
 
diff --git a/activerecord/examples/simple.rb b/activerecord/examples/simple.rb
index c3648fee48..280b786d73 100644
--- a/activerecord/examples/simple.rb
+++ b/activerecord/examples/simple.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_record"
 
 class Person < ActiveRecord::Base
diff --git a/activerecord/lib/active_record.rb b/activerecord/lib/active_record.rb
index 25d5e87317..0c19fed9e1 100644
--- a/activerecord/lib/active_record.rb
+++ b/activerecord/lib/active_record.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #--
 # Copyright (c) 2004-2017 David Heinemeier Hansson
 #
diff --git a/activerecord/lib/active_record/aggregations.rb b/activerecord/lib/active_record/aggregations.rb
index 10cbd5429c..e5e89734d2 100644
--- a/activerecord/lib/active_record/aggregations.rb
+++ b/activerecord/lib/active_record/aggregations.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # See ActiveRecord::Aggregations::ClassMethods for documentation
   module Aggregations
diff --git a/activerecord/lib/active_record/association_relation.rb b/activerecord/lib/active_record/association_relation.rb
index de2d03cd0b..2b0b2864bc 100644
--- a/activerecord/lib/active_record/association_relation.rb
+++ b/activerecord/lib/active_record/association_relation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class AssociationRelation < Relation
     def initialize(klass, table, predicate_builder, association)
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index e782196ce6..e86e02c53a 100644
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/enumerable"
 require "active_support/core_ext/string/conversions"
 require "active_support/core_ext/module/remove_method"
diff --git a/activerecord/lib/active_record/associations/alias_tracker.rb b/activerecord/lib/active_record/associations/alias_tracker.rb
index 104de4f69d..096f016976 100644
--- a/activerecord/lib/active_record/associations/alias_tracker.rb
+++ b/activerecord/lib/active_record/associations/alias_tracker.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/string/conversions"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/associations/association.rb b/activerecord/lib/active_record/associations/association.rb
index c166cfd68f..268b022ab8 100644
--- a/activerecord/lib/active_record/associations/association.rb
+++ b/activerecord/lib/active_record/associations/association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/array/wrap"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/associations/association_scope.rb b/activerecord/lib/active_record/associations/association_scope.rb
index 6ef225b725..9b0b50977d 100644
--- a/activerecord/lib/active_record/associations/association_scope.rb
+++ b/activerecord/lib/active_record/associations/association_scope.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     class AssociationScope #:nodoc:
diff --git a/activerecord/lib/active_record/associations/belongs_to_association.rb b/activerecord/lib/active_record/associations/belongs_to_association.rb
index 0e61dbfb00..7a9f5f7937 100644
--- a/activerecord/lib/active_record/associations/belongs_to_association.rb
+++ b/activerecord/lib/active_record/associations/belongs_to_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record Belongs To Association
   module Associations
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 b710cf6bdb..13b4a084ea 100644
--- a/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
+++ b/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record Belongs To Polymorphic Association
   module Associations
diff --git a/activerecord/lib/active_record/associations/builder/association.rb b/activerecord/lib/active_record/associations/builder/association.rb
index d0534056d9..496b16b58f 100644
--- a/activerecord/lib/active_record/associations/builder/association.rb
+++ b/activerecord/lib/active_record/associations/builder/association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This is the parent Association class which defines the variables
 # used by all associations.
 #
diff --git a/activerecord/lib/active_record/associations/builder/belongs_to.rb b/activerecord/lib/active_record/associations/builder/belongs_to.rb
index 2b9dd8aae8..7b303e923b 100644
--- a/activerecord/lib/active_record/associations/builder/belongs_to.rb
+++ b/activerecord/lib/active_record/associations/builder/belongs_to.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord::Associations::Builder # :nodoc:
   class BelongsTo < SingularAssociation #:nodoc:
     def self.macro
diff --git a/activerecord/lib/active_record/associations/builder/collection_association.rb b/activerecord/lib/active_record/associations/builder/collection_association.rb
index c58b7d8160..753fde5146 100644
--- a/activerecord/lib/active_record/associations/builder/collection_association.rb
+++ b/activerecord/lib/active_record/associations/builder/collection_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "../../associations"
 
 module ActiveRecord::Associations::Builder # :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 6b71826431..12fcfbcd45 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
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord::Associations::Builder # :nodoc:
   class HasAndBelongsToMany # :nodoc:
     class JoinTableResolver # :nodoc:
diff --git a/activerecord/lib/active_record/associations/builder/has_many.rb b/activerecord/lib/active_record/associations/builder/has_many.rb
index 7864d4c536..5b9617bc6d 100644
--- a/activerecord/lib/active_record/associations/builder/has_many.rb
+++ b/activerecord/lib/active_record/associations/builder/has_many.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord::Associations::Builder # :nodoc:
   class HasMany < CollectionAssociation #:nodoc:
     def self.macro
diff --git a/activerecord/lib/active_record/associations/builder/has_one.rb b/activerecord/lib/active_record/associations/builder/has_one.rb
index 4de846d12b..bfb37d6eee 100644
--- a/activerecord/lib/active_record/associations/builder/has_one.rb
+++ b/activerecord/lib/active_record/associations/builder/has_one.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord::Associations::Builder # :nodoc:
   class HasOne < SingularAssociation #:nodoc:
     def self.macro
diff --git a/activerecord/lib/active_record/associations/builder/singular_association.rb b/activerecord/lib/active_record/associations/builder/singular_association.rb
index 7732b63af6..0a02ef4cc1 100644
--- a/activerecord/lib/active_record/associations/builder/singular_association.rb
+++ b/activerecord/lib/active_record/associations/builder/singular_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This class is inherited by the has_one and belongs_to association classes
 
 module ActiveRecord::Associations::Builder # :nodoc:
diff --git a/activerecord/lib/active_record/associations/collection_association.rb b/activerecord/lib/active_record/associations/collection_association.rb
index 69401162aa..ed2e6d1ae4 100644
--- a/activerecord/lib/active_record/associations/collection_association.rb
+++ b/activerecord/lib/active_record/associations/collection_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     # = Active Record Association Collection
diff --git a/activerecord/lib/active_record/associations/collection_proxy.rb b/activerecord/lib/active_record/associations/collection_proxy.rb
index d77fcaf668..0678b07699 100644
--- a/activerecord/lib/active_record/associations/collection_proxy.rb
+++ b/activerecord/lib/active_record/associations/collection_proxy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     # Association proxies in Active Record are middlemen between the object that
diff --git a/activerecord/lib/active_record/associations/foreign_association.rb b/activerecord/lib/active_record/associations/foreign_association.rb
index 3ceec0ee46..40010cde03 100644
--- a/activerecord/lib/active_record/associations/foreign_association.rb
+++ b/activerecord/lib/active_record/associations/foreign_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord::Associations
   module ForeignAssociation # :nodoc:
     def foreign_key_present?
diff --git a/activerecord/lib/active_record/associations/has_many_association.rb b/activerecord/lib/active_record/associations/has_many_association.rb
index 10ca0e47ff..88fe33eef2 100644
--- a/activerecord/lib/active_record/associations/has_many_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record Has Many Association
   module Associations
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 2fd20b4368..938d2645ca 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record Has Many Through Association
   module Associations
diff --git a/activerecord/lib/active_record/associations/has_one_association.rb b/activerecord/lib/active_record/associations/has_one_association.rb
index 8458253ff8..929ea9f567 100644
--- a/activerecord/lib/active_record/associations/has_one_association.rb
+++ b/activerecord/lib/active_record/associations/has_one_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record Has One Association
   module Associations
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 1183bdf6f4..eb54977aa0 100644
--- a/activerecord/lib/active_record/associations/has_one_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_one_through_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record Has One Through Association
   module Associations
diff --git a/activerecord/lib/active_record/associations/join_dependency.rb b/activerecord/lib/active_record/associations/join_dependency.rb
index 4a3fb6eaec..2c3d5b3429 100644
--- a/activerecord/lib/active_record/associations/join_dependency.rb
+++ b/activerecord/lib/active_record/associations/join_dependency.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     class JoinDependency # :nodoc:
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 98b2f40357..42014653e8 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_association.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "join_part"
 
 module ActiveRecord
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 d4e26d5397..8a8fa8993b 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_base.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_base.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "join_part"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/associations/join_dependency/join_part.rb b/activerecord/lib/active_record/associations/join_dependency/join_part.rb
index 5666e069fc..2181f308bf 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_part.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_part.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     class JoinDependency # :nodoc:
diff --git a/activerecord/lib/active_record/associations/preloader.rb b/activerecord/lib/active_record/associations/preloader.rb
index a18994cec4..62caf02a2c 100644
--- a/activerecord/lib/active_record/associations/preloader.rb
+++ b/activerecord/lib/active_record/associations/preloader.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     # Implements the details of eager loading of Active Record associations.
diff --git a/activerecord/lib/active_record/associations/preloader/association.rb b/activerecord/lib/active_record/associations/preloader/association.rb
index d0964ee4fd..1985b38f8a 100644
--- a/activerecord/lib/active_record/associations/preloader/association.rb
+++ b/activerecord/lib/active_record/associations/preloader/association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     class Preloader
diff --git a/activerecord/lib/active_record/associations/preloader/belongs_to.rb b/activerecord/lib/active_record/associations/preloader/belongs_to.rb
index c20145770f..ae9695f26a 100644
--- a/activerecord/lib/active_record/associations/preloader/belongs_to.rb
+++ b/activerecord/lib/active_record/associations/preloader/belongs_to.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     class Preloader
diff --git a/activerecord/lib/active_record/associations/preloader/collection_association.rb b/activerecord/lib/active_record/associations/preloader/collection_association.rb
index 26690bf16d..fb920a642c 100644
--- a/activerecord/lib/active_record/associations/preloader/collection_association.rb
+++ b/activerecord/lib/active_record/associations/preloader/collection_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     class Preloader
diff --git a/activerecord/lib/active_record/associations/preloader/has_many.rb b/activerecord/lib/active_record/associations/preloader/has_many.rb
index 20df1cc19a..29a1ce099d 100644
--- a/activerecord/lib/active_record/associations/preloader/has_many.rb
+++ b/activerecord/lib/active_record/associations/preloader/has_many.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     class Preloader
diff --git a/activerecord/lib/active_record/associations/preloader/has_many_through.rb b/activerecord/lib/active_record/associations/preloader/has_many_through.rb
index 2029871f39..0639fdca44 100644
--- a/activerecord/lib/active_record/associations/preloader/has_many_through.rb
+++ b/activerecord/lib/active_record/associations/preloader/has_many_through.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     class Preloader
diff --git a/activerecord/lib/active_record/associations/preloader/has_one.rb b/activerecord/lib/active_record/associations/preloader/has_one.rb
index c4add621ca..d87abf630f 100644
--- a/activerecord/lib/active_record/associations/preloader/has_one.rb
+++ b/activerecord/lib/active_record/associations/preloader/has_one.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     class Preloader
diff --git a/activerecord/lib/active_record/associations/preloader/has_one_through.rb b/activerecord/lib/active_record/associations/preloader/has_one_through.rb
index f063f85574..17734d0257 100644
--- a/activerecord/lib/active_record/associations/preloader/has_one_through.rb
+++ b/activerecord/lib/active_record/associations/preloader/has_one_through.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     class Preloader
diff --git a/activerecord/lib/active_record/associations/preloader/singular_association.rb b/activerecord/lib/active_record/associations/preloader/singular_association.rb
index 5c5828262e..266b5f6b1c 100644
--- a/activerecord/lib/active_record/associations/preloader/singular_association.rb
+++ b/activerecord/lib/active_record/associations/preloader/singular_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     class Preloader
diff --git a/activerecord/lib/active_record/associations/preloader/through_association.rb b/activerecord/lib/active_record/associations/preloader/through_association.rb
index 0999746cd5..de4b847a41 100644
--- a/activerecord/lib/active_record/associations/preloader/through_association.rb
+++ b/activerecord/lib/active_record/associations/preloader/through_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     class Preloader
diff --git a/activerecord/lib/active_record/associations/singular_association.rb b/activerecord/lib/active_record/associations/singular_association.rb
index 66993b9bf7..c1eee3c630 100644
--- a/activerecord/lib/active_record/associations/singular_association.rb
+++ b/activerecord/lib/active_record/associations/singular_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Associations
     class SingularAssociation < Association #:nodoc:
diff --git a/activerecord/lib/active_record/associations/through_association.rb b/activerecord/lib/active_record/associations/through_association.rb
index 6b87993ba3..76237c4a0c 100644
--- a/activerecord/lib/active_record/associations/through_association.rb
+++ b/activerecord/lib/active_record/associations/through_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record Through Association
   module Associations
diff --git a/activerecord/lib/active_record/attribute.rb b/activerecord/lib/active_record/attribute.rb
index f89261923b..fc474edc15 100644
--- a/activerecord/lib/active_record/attribute.rb
+++ b/activerecord/lib/active_record/attribute.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class Attribute # :nodoc:
     class << self
diff --git a/activerecord/lib/active_record/attribute/user_provided_default.rb b/activerecord/lib/active_record/attribute/user_provided_default.rb
index c4e731fb28..690a931615 100644
--- a/activerecord/lib/active_record/attribute/user_provided_default.rb
+++ b/activerecord/lib/active_record/attribute/user_provided_default.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "../attribute"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/attribute_assignment.rb b/activerecord/lib/active_record/attribute_assignment.rb
index d0dfca0cac..8b0d9aab01 100644
--- a/activerecord/lib/active_record/attribute_assignment.rb
+++ b/activerecord/lib/active_record/attribute_assignment.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_model/forbidden_attributes_protection"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/attribute_decorators.rb b/activerecord/lib/active_record/attribute_decorators.rb
index 5bc8527745..98b7805c0a 100644
--- a/activerecord/lib/active_record/attribute_decorators.rb
+++ b/activerecord/lib/active_record/attribute_decorators.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module AttributeDecorators # :nodoc:
     extend ActiveSupport::Concern
diff --git a/activerecord/lib/active_record/attribute_methods.rb b/activerecord/lib/active_record/attribute_methods.rb
index 4e6a43a039..e4ca6c8408 100644
--- a/activerecord/lib/active_record/attribute_methods.rb
+++ b/activerecord/lib/active_record/attribute_methods.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "mutex_m"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/attribute_methods/before_type_cast.rb b/activerecord/lib/active_record/attribute_methods/before_type_cast.rb
index 115eb1ef3f..5941f51a1a 100644
--- a/activerecord/lib/active_record/attribute_methods/before_type_cast.rb
+++ b/activerecord/lib/active_record/attribute_methods/before_type_cast.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module AttributeMethods
     # = Active Record Attribute Methods Before Type Cast
diff --git a/activerecord/lib/active_record/attribute_methods/primary_key.rb b/activerecord/lib/active_record/attribute_methods/primary_key.rb
index 081aad434d..63c059e291 100644
--- a/activerecord/lib/active_record/attribute_methods/primary_key.rb
+++ b/activerecord/lib/active_record/attribute_methods/primary_key.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "set"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/attribute_methods/query.rb b/activerecord/lib/active_record/attribute_methods/query.rb
index 10498f4322..6757e9b66a 100644
--- a/activerecord/lib/active_record/attribute_methods/query.rb
+++ b/activerecord/lib/active_record/attribute_methods/query.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module AttributeMethods
     module Query
diff --git a/activerecord/lib/active_record/attribute_methods/read.rb b/activerecord/lib/active_record/attribute_methods/read.rb
index fdc4bf6621..6adaeb0121 100644
--- a/activerecord/lib/active_record/attribute_methods/read.rb
+++ b/activerecord/lib/active_record/attribute_methods/read.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module AttributeMethods
     module Read
diff --git a/activerecord/lib/active_record/attribute_methods/serialization.rb b/activerecord/lib/active_record/attribute_methods/serialization.rb
index 4d9aff76cc..6ed45d8737 100644
--- a/activerecord/lib/active_record/attribute_methods/serialization.rb
+++ b/activerecord/lib/active_record/attribute_methods/serialization.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module AttributeMethods
     module Serialization
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 1f1efe8812..f12a9f915c 100644
--- a/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
+++ b/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module AttributeMethods
     module TimeZoneConversion
diff --git a/activerecord/lib/active_record/attribute_methods/write.rb b/activerecord/lib/active_record/attribute_methods/write.rb
index 54b673c72e..fa01f832ac 100644
--- a/activerecord/lib/active_record/attribute_methods/write.rb
+++ b/activerecord/lib/active_record/attribute_methods/write.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module AttributeMethods
     module Write
diff --git a/activerecord/lib/active_record/attribute_mutation_tracker.rb b/activerecord/lib/active_record/attribute_mutation_tracker.rb
index e275ae72ba..94bf641a5d 100644
--- a/activerecord/lib/active_record/attribute_mutation_tracker.rb
+++ b/activerecord/lib/active_record/attribute_mutation_tracker.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class AttributeMutationTracker # :nodoc:
     OPTION_NOT_GIVEN = Object.new
diff --git a/activerecord/lib/active_record/attribute_set.rb b/activerecord/lib/active_record/attribute_set.rb
index a963ba015a..492067e2b3 100644
--- a/activerecord/lib/active_record/attribute_set.rb
+++ b/activerecord/lib/active_record/attribute_set.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "attribute_set/builder"
 require_relative "attribute_set/yaml_encoder"
 
diff --git a/activerecord/lib/active_record/attribute_set/builder.rb b/activerecord/lib/active_record/attribute_set/builder.rb
index abe22b9ae4..e3a9c7fdb3 100644
--- a/activerecord/lib/active_record/attribute_set/builder.rb
+++ b/activerecord/lib/active_record/attribute_set/builder.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "../attribute"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/attribute_set/yaml_encoder.rb b/activerecord/lib/active_record/attribute_set/yaml_encoder.rb
index 899de14792..9254ce16ab 100644
--- a/activerecord/lib/active_record/attribute_set/yaml_encoder.rb
+++ b/activerecord/lib/active_record/attribute_set/yaml_encoder.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class AttributeSet
     # Attempts to do more intelligent YAML dumping of an
diff --git a/activerecord/lib/active_record/attributes.rb b/activerecord/lib/active_record/attributes.rb
index dde22bcdaa..afb559db71 100644
--- a/activerecord/lib/active_record/attributes.rb
+++ b/activerecord/lib/active_record/attributes.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "attribute/user_provided_default"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/autosave_association.rb b/activerecord/lib/active_record/autosave_association.rb
index 70f0e2af8e..6974cf74f6 100644
--- a/activerecord/lib/active_record/autosave_association.rb
+++ b/activerecord/lib/active_record/autosave_association.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record Autosave Association
   #
diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index f0e455478a..541ff51fbe 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "yaml"
 require "active_support/benchmarkable"
 require "active_support/dependencies"
diff --git a/activerecord/lib/active_record/callbacks.rb b/activerecord/lib/active_record/callbacks.rb
index eb44887e18..a2439e6ec7 100644
--- a/activerecord/lib/active_record/callbacks.rb
+++ b/activerecord/lib/active_record/callbacks.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record \Callbacks
   #
diff --git a/activerecord/lib/active_record/coders/json.rb b/activerecord/lib/active_record/coders/json.rb
index cb185a881e..a69b38487e 100644
--- a/activerecord/lib/active_record/coders/json.rb
+++ b/activerecord/lib/active_record/coders/json.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Coders # :nodoc:
     class JSON # :nodoc:
diff --git a/activerecord/lib/active_record/coders/yaml_column.rb b/activerecord/lib/active_record/coders/yaml_column.rb
index 9c52a31b95..11559141c7 100644
--- a/activerecord/lib/active_record/coders/yaml_column.rb
+++ b/activerecord/lib/active_record/coders/yaml_column.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "yaml"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/collection_cache_key.rb b/activerecord/lib/active_record/collection_cache_key.rb
index 8b937b6703..62948225af 100644
--- a/activerecord/lib/active_record/collection_cache_key.rb
+++ b/activerecord/lib/active_record/collection_cache_key.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module CollectionCacheKey
     def collection_cache_key(collection = all, timestamp_column = :updated_at) # :nodoc:
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 627b753f01..c11b7b012f 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "thread"
 require "concurrent/map"
 require "monitor"
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/database_limits.rb b/activerecord/lib/active_record/connection_adapters/abstract/database_limits.rb
index 407e019326..7a9e7add24 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/database_limits.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/database_limits.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
     module DatabaseLimits
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 879626b72a..f2715cdab0 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
     module DatabaseStatements
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb b/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb
index c352ddfc11..077e8beba9 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
     module QueryCache
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
index de78c6db44..b637518fc8 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/big_decimal/conversions"
 require "active_support/multibyte/chars"
 
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/savepoints.rb b/activerecord/lib/active_record/connection_adapters/abstract/savepoints.rb
index 3a06f75292..52a796b926 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/savepoints.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/savepoints.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module Savepoints
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 8865e7c703..8bf3879a4c 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/string/strip"
 
 module ActiveRecord
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 a30fbe0e05..3b2c51ef94 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters #:nodoc:
     # Abstract representation of an index definition on a table. Instances of
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 34036d8a1d..9be26254b2 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
     # The goal of this module is to move Adapter specific column
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 475463c4fd..989ebc81a9 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "../../migration/join_table"
 require "active_support/core_ext/string/access"
 require "digest"
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
index f63d09039f..147e16e9fa 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     class TransactionState
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 30b29e7007..ed9caee0aa 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "../type"
 require_relative "determine_if_preparable_visitor"
 require_relative "schema_cache"
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 06976aa769..d97d3af2a6 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "abstract_adapter"
 require_relative "statement_pool"
 require_relative "mysql/column"
diff --git a/activerecord/lib/active_record/connection_adapters/column.rb b/activerecord/lib/active_record/connection_adapters/column.rb
index 61cd7ae4cc..16273fb5f1 100644
--- a/activerecord/lib/active_record/connection_adapters/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/column.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # :stopdoc:
   module ConnectionAdapters
diff --git a/activerecord/lib/active_record/connection_adapters/connection_specification.rb b/activerecord/lib/active_record/connection_adapters/connection_specification.rb
index 3e4ea28f63..29542f917e 100644
--- a/activerecord/lib/active_record/connection_adapters/connection_specification.rb
+++ b/activerecord/lib/active_record/connection_adapters/connection_specification.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "uri"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/connection_adapters/determine_if_preparable_visitor.rb b/activerecord/lib/active_record/connection_adapters/determine_if_preparable_visitor.rb
index 0fdc185c45..3dcb916d99 100644
--- a/activerecord/lib/active_record/connection_adapters/determine_if_preparable_visitor.rb
+++ b/activerecord/lib/active_record/connection_adapters/determine_if_preparable_visitor.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module DetermineIfPreparableVisitor
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/column.rb b/activerecord/lib/active_record/connection_adapters/mysql/column.rb
index c9ad47c035..fa1541019d 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/column.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
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 bda482a00f..00b56ee9ae 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb b/activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb
index 9691060cd3..20c3c83664 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/quoting.rb b/activerecord/lib/active_record/connection_adapters/mysql/quoting.rb
index 4441c1e2f8..803babf55d 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/quoting.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
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 eea4984680..5a35823c72 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_creation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
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 6d88c14d50..b22a2e4da7 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
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 a46d9f8cbb..fbe3596dda 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
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 24f8ff6367..1d87d60ba9 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/type_metadata.rb b/activerecord/lib/active_record/connection_adapters/mysql/type_metadata.rb
index 9ad6a6c0d0..7ad0944d51 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/type_metadata.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/type_metadata.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
diff --git a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
index c5c0a071e7..2c2321872d 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "abstract_mysql_adapter"
 require_relative "mysql/database_statements"
 
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/column.rb b/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
index 3ad1911a28..1b67cee24b 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     # PostgreSQL-specific extensions to column definitions in a table.
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
index ebf1715ed0..8db2a645af 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/explain_pretty_printer.rb b/activerecord/lib/active_record/connection_adapters/postgresql/explain_pretty_printer.rb
index 99f3a5bbdf..086a5dcc15 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/explain_pretty_printer.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/explain_pretty_printer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
index 6666622c08..b28418d74f 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "oid/array"
 require_relative "oid/bit"
 require_relative "oid/bit_varying"
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/array.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/array.rb
index a73a8c1726..d6852082ac 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/array.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/array.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
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 0a505f46a7..587e95d192 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit_varying.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit_varying.rb
index 4c21097d48..dc7079dda2 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit_varying.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit_varying.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bytea.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bytea.rb
index 702fa8175c..a3c60ecef6 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bytea.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bytea.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/cidr.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/cidr.rb
index 5225609e37..66e99d9404 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/cidr.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/cidr.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "ipaddr"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/date_time.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/date_time.rb
index b7acbf7178..cd667422f5 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/date_time.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/date_time.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
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 43d22c8daf..879dba7afd 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/decimal.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/decimal.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/enum.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/enum.rb
index 950d23d516..f70f09ad95 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/enum.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/enum.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/hstore.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/hstore.rb
index 49dd4fc73f..aabe83b85d 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/hstore.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/hstore.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/inet.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/inet.rb
index 96486fa65b..55be71fd26 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/inet.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/inet.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/jsonb.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/jsonb.rb
index a1fec289d4..e0216f1089 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/jsonb.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/jsonb.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/legacy_point.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/legacy_point.rb
index 775eecaf85..7b057a8452 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/legacy_point.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/legacy_point.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/oid.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/oid.rb
index 9c2ac08b30..d8c044320d 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/oid.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/oid.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/point.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/point.rb
index 7c764e7287..02a9c506f6 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/point.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/point.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   Point = Struct.new(:x, :y)
 
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 54d5d0902e..7d5d7d91e6 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/specialized_string.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/specialized_string.rb
index 564e82a4ac..4ad1344f05 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/specialized_string.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/specialized_string.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/type_map_initializer.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/type_map_initializer.rb
index d9ae1aa7a2..15ae241d50 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/type_map_initializer.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/type_map_initializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/uuid.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/uuid.rb
index db92333ef7..bc9b8dbfcf 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/uuid.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/uuid.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/vector.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/vector.rb
index b26e876b54..88ef626a16 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/vector.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/vector.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/xml.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/xml.rb
index d40d837cee..042f32fdc3 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/xml.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/xml.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb b/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
index ee4230c6f2..fc458d0c73 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
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 44a7338bf5..386d22a9bd 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
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 e1d5089115..59f661da25 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
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 11ea1e5144..f1489e4d69 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
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 5555a46b6b..12c6603081 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
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 a710ea6cc9..32b01b4a31 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/string/strip"
 
 module ActiveRecord
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 f57179ae59..b252a76caa 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/type_metadata.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/type_metadata.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     class PostgreSQLTypeMetadata < DelegateClass(SqlTypeMetadata)
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/utils.rb b/activerecord/lib/active_record/connection_adapters/postgresql/utils.rb
index aa7940188a..bfd300723d 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/utils.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/utils.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 66c61b5f4a..b8c2cabb48 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Make sure we're using pg high enough for type casts and Ruby 2.2+ compatibility
 gem "pg", "~> 0.18"
 require "pg"
diff --git a/activerecord/lib/active_record/connection_adapters/schema_cache.rb b/activerecord/lib/active_record/connection_adapters/schema_cache.rb
index 4d339b0a8c..f34b6733da 100644
--- a/activerecord/lib/active_record/connection_adapters/schema_cache.rb
+++ b/activerecord/lib/active_record/connection_adapters/schema_cache.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     class SchemaCache
diff --git a/activerecord/lib/active_record/connection_adapters/sql_type_metadata.rb b/activerecord/lib/active_record/connection_adapters/sql_type_metadata.rb
index 9e12ae0de8..8489bcbf1d 100644
--- a/activerecord/lib/active_record/connection_adapters/sql_type_metadata.rb
+++ b/activerecord/lib/active_record/connection_adapters/sql_type_metadata.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # :stopdoc:
   module ConnectionAdapters
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/explain_pretty_printer.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/explain_pretty_printer.rb
index 6fe3e1211e..832fdfe5c4 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/explain_pretty_printer.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/explain_pretty_printer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
index 04dd7fd357..8042dbfea2 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_creation.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_creation.rb
index bc798d1dbb..b842561317 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_creation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
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 e157e4b218..501f17dbad 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_definitions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_dumper.rb
index eec018eda3..ab057c73f1 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_dumper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
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 31e83f9260..c155e7f1ac 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 2fede7b847..10e80179ac 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "abstract_adapter"
 require_relative "statement_pool"
 require_relative "sqlite3/explain_pretty_printer"
diff --git a/activerecord/lib/active_record/connection_adapters/statement_pool.rb b/activerecord/lib/active_record/connection_adapters/statement_pool.rb
index 790db56185..46bd831da7 100644
--- a/activerecord/lib/active_record/connection_adapters/statement_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/statement_pool.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     class StatementPool # :nodoc:
diff --git a/activerecord/lib/active_record/connection_handling.rb b/activerecord/lib/active_record/connection_handling.rb
index b8fbb489b6..9a47edfba4 100644
--- a/activerecord/lib/active_record/connection_handling.rb
+++ b/activerecord/lib/active_record/connection_handling.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionHandling
     RAILS_ENV   = -> { (Rails.env if defined?(Rails.env)) || ENV["RAILS_ENV"].presence || ENV["RACK_ENV"].presence }
diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index 3ea7b644c2..8b97dbe5bf 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/hash/indifferent_access"
 require "active_support/core_ext/string/filters"
 
diff --git a/activerecord/lib/active_record/counter_cache.rb b/activerecord/lib/active_record/counter_cache.rb
index cbd71a3779..ab2bfb63a6 100644
--- a/activerecord/lib/active_record/counter_cache.rb
+++ b/activerecord/lib/active_record/counter_cache.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record Counter Cache
   module CounterCache
diff --git a/activerecord/lib/active_record/define_callbacks.rb b/activerecord/lib/active_record/define_callbacks.rb
index 7d955a24be..2c8783dcc9 100644
--- a/activerecord/lib/active_record/define_callbacks.rb
+++ b/activerecord/lib/active_record/define_callbacks.rb
@@ -1,3 +1,5 @@
+# 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
diff --git a/activerecord/lib/active_record/dynamic_matchers.rb b/activerecord/lib/active_record/dynamic_matchers.rb
index 3a9625092e..3bb8c6f4e3 100644
--- a/activerecord/lib/active_record/dynamic_matchers.rb
+++ b/activerecord/lib/active_record/dynamic_matchers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module DynamicMatchers #:nodoc:
     private
diff --git a/activerecord/lib/active_record/enum.rb b/activerecord/lib/active_record/enum.rb
index 12ef58a941..f373b98035 100644
--- a/activerecord/lib/active_record/enum.rb
+++ b/activerecord/lib/active_record/enum.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/object/deep_dup"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/errors.rb b/activerecord/lib/active_record/errors.rb
index 60d4fb70e0..9feba840b3 100644
--- a/activerecord/lib/active_record/errors.rb
+++ b/activerecord/lib/active_record/errors.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record Errors
   #
diff --git a/activerecord/lib/active_record/explain.rb b/activerecord/lib/active_record/explain.rb
index eff5990f3a..8bb54a24b7 100644
--- a/activerecord/lib/active_record/explain.rb
+++ b/activerecord/lib/active_record/explain.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "explain_registry"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/explain_registry.rb b/activerecord/lib/active_record/explain_registry.rb
index ef1ce3dc85..7fd078941a 100644
--- a/activerecord/lib/active_record/explain_registry.rb
+++ b/activerecord/lib/active_record/explain_registry.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/per_thread_registry"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/explain_subscriber.rb b/activerecord/lib/active_record/explain_subscriber.rb
index 928720d011..9252fa3fed 100644
--- a/activerecord/lib/active_record/explain_subscriber.rb
+++ b/activerecord/lib/active_record/explain_subscriber.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/notifications"
 require_relative "explain_registry"
 
diff --git a/activerecord/lib/active_record/fixture_set/file.rb b/activerecord/lib/active_record/fixture_set/file.rb
index 6cf2e01179..f1ea0e022f 100644
--- a/activerecord/lib/active_record/fixture_set/file.rb
+++ b/activerecord/lib/active_record/fixture_set/file.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "erb"
 require "yaml"
 
diff --git a/activerecord/lib/active_record/fixtures.rb b/activerecord/lib/active_record/fixtures.rb
index c9e97d9d2b..ef302fc0a0 100644
--- a/activerecord/lib/active_record/fixtures.rb
+++ b/activerecord/lib/active_record/fixtures.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "erb"
 require "yaml"
 require "zlib"
diff --git a/activerecord/lib/active_record/gem_version.rb b/activerecord/lib/active_record/gem_version.rb
index 1a937dbcf7..7ccb57b305 100644
--- a/activerecord/lib/active_record/gem_version.rb
+++ b/activerecord/lib/active_record/gem_version.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # Returns the version of the currently loaded Active Record as a <tt>Gem::Version</tt>
   def self.gem_version
diff --git a/activerecord/lib/active_record/inheritance.rb b/activerecord/lib/active_record/inheritance.rb
index 1753322274..e3deaafeec 100644
--- a/activerecord/lib/active_record/inheritance.rb
+++ b/activerecord/lib/active_record/inheritance.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/hash/indifferent_access"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/integration.rb b/activerecord/lib/active_record/integration.rb
index cf954852bc..6cf26a9792 100644
--- a/activerecord/lib/active_record/integration.rb
+++ b/activerecord/lib/active_record/integration.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/string/filters"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/internal_metadata.rb b/activerecord/lib/active_record/internal_metadata.rb
index 89e5d153b8..14795cc815 100644
--- a/activerecord/lib/active_record/internal_metadata.rb
+++ b/activerecord/lib/active_record/internal_metadata.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "scoping/default"
 require_relative "scoping/named"
 
diff --git a/activerecord/lib/active_record/legacy_yaml_adapter.rb b/activerecord/lib/active_record/legacy_yaml_adapter.rb
index c7683f68c7..23644aab8f 100644
--- a/activerecord/lib/active_record/legacy_yaml_adapter.rb
+++ b/activerecord/lib/active_record/legacy_yaml_adapter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module LegacyYamlAdapter
     def self.convert(klass, coder)
diff --git a/activerecord/lib/active_record/locking/optimistic.rb b/activerecord/lib/active_record/locking/optimistic.rb
index 522da6a571..e1e24e2814 100644
--- a/activerecord/lib/active_record/locking/optimistic.rb
+++ b/activerecord/lib/active_record/locking/optimistic.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Locking
     # == What is Optimistic Locking
diff --git a/activerecord/lib/active_record/locking/pessimistic.rb b/activerecord/lib/active_record/locking/pessimistic.rb
index 263e2a5f7f..8d69bf7d3d 100644
--- a/activerecord/lib/active_record/locking/pessimistic.rb
+++ b/activerecord/lib/active_record/locking/pessimistic.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Locking
     # Locking::Pessimistic provides support for row-level locking using
diff --git a/activerecord/lib/active_record/log_subscriber.rb b/activerecord/lib/active_record/log_subscriber.rb
index e39ca5f6dc..405f3a30c6 100644
--- a/activerecord/lib/active_record/log_subscriber.rb
+++ b/activerecord/lib/active_record/log_subscriber.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class LogSubscriber < ActiveSupport::LogSubscriber
     IGNORE_PAYLOAD_NAMES = ["SCHEMA", "EXPLAIN"]
diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index 42220b9a5e..52ca4671c2 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "set"
 require "zlib"
 require "active_support/core_ext/module/attribute_accessors"
diff --git a/activerecord/lib/active_record/migration/command_recorder.rb b/activerecord/lib/active_record/migration/command_recorder.rb
index f9cf59b283..a3a5e0fa16 100644
--- a/activerecord/lib/active_record/migration/command_recorder.rb
+++ b/activerecord/lib/active_record/migration/command_recorder.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class Migration
     # <tt>ActiveRecord::Migration::CommandRecorder</tt> records commands done during
diff --git a/activerecord/lib/active_record/migration/compatibility.rb b/activerecord/lib/active_record/migration/compatibility.rb
index 188dd0acef..d6595c9355 100644
--- a/activerecord/lib/active_record/migration/compatibility.rb
+++ b/activerecord/lib/active_record/migration/compatibility.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class Migration
     module Compatibility # :nodoc: all
diff --git a/activerecord/lib/active_record/migration/join_table.rb b/activerecord/lib/active_record/migration/join_table.rb
index 89789f00ea..9abb289bb0 100644
--- a/activerecord/lib/active_record/migration/join_table.rb
+++ b/activerecord/lib/active_record/migration/join_table.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class Migration
     module JoinTable #:nodoc:
diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index 2d3c9175bd..34c0ef4e75 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "monitor"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/nested_attributes.rb b/activerecord/lib/active_record/nested_attributes.rb
index 917bc76993..1864ca5ad2 100644
--- a/activerecord/lib/active_record/nested_attributes.rb
+++ b/activerecord/lib/active_record/nested_attributes.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/hash/except"
 require "active_support/core_ext/object/try"
 require "active_support/core_ext/hash/indifferent_access"
diff --git a/activerecord/lib/active_record/no_touching.rb b/activerecord/lib/active_record/no_touching.rb
index 4059020e25..c573deb63a 100644
--- a/activerecord/lib/active_record/no_touching.rb
+++ b/activerecord/lib/active_record/no_touching.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record No Touching
   module NoTouching
diff --git a/activerecord/lib/active_record/null_relation.rb b/activerecord/lib/active_record/null_relation.rb
index 26966f9433..cf0de0fdeb 100644
--- a/activerecord/lib/active_record/null_relation.rb
+++ b/activerecord/lib/active_record/null_relation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module NullRelation # :nodoc:
     def pluck(*column_names)
diff --git a/activerecord/lib/active_record/persistence.rb b/activerecord/lib/active_record/persistence.rb
index 2e6901eb0e..4bd14ccf29 100644
--- a/activerecord/lib/active_record/persistence.rb
+++ b/activerecord/lib/active_record/persistence.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record \Persistence
   module Persistence
diff --git a/activerecord/lib/active_record/query_cache.rb b/activerecord/lib/active_record/query_cache.rb
index e4c2e1f86f..3d5babb8b7 100644
--- a/activerecord/lib/active_record/query_cache.rb
+++ b/activerecord/lib/active_record/query_cache.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record Query Cache
   class QueryCache
diff --git a/activerecord/lib/active_record/querying.rb b/activerecord/lib/active_record/querying.rb
index b16e178358..f780538319 100644
--- a/activerecord/lib/active_record/querying.rb
+++ b/activerecord/lib/active_record/querying.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Querying
     delegate :find, :take, :take!, :first, :first!, :last, :last!, :exists?, :any?, :many?, :none?, :one?, to: :all
diff --git a/activerecord/lib/active_record/railtie.rb b/activerecord/lib/active_record/railtie.rb
index 0b82926081..ead42d64ec 100644
--- a/activerecord/lib/active_record/railtie.rb
+++ b/activerecord/lib/active_record/railtie.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_record"
 require "rails"
 require "active_model/railtie"
diff --git a/activerecord/lib/active_record/railties/console_sandbox.rb b/activerecord/lib/active_record/railties/console_sandbox.rb
index 604a220303..8917638a5d 100644
--- a/activerecord/lib/active_record/railties/console_sandbox.rb
+++ b/activerecord/lib/active_record/railties/console_sandbox.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 ActiveRecord::Base.connection.begin_transaction(joinable: false)
 
 at_exit do
diff --git a/activerecord/lib/active_record/railties/controller_runtime.rb b/activerecord/lib/active_record/railties/controller_runtime.rb
index 4030cdc158..3cf66980a5 100644
--- a/activerecord/lib/active_record/railties/controller_runtime.rb
+++ b/activerecord/lib/active_record/railties/controller_runtime.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/module/attr_internal"
 require_relative "../log_subscriber"
 
diff --git a/activerecord/lib/active_record/railties/databases.rake b/activerecord/lib/active_record/railties/databases.rake
index abc7323341..691b3612d8 100644
--- a/activerecord/lib/active_record/railties/databases.rake
+++ b/activerecord/lib/active_record/railties/databases.rake
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_record"
 
 db_namespace = namespace :db do
diff --git a/activerecord/lib/active_record/railties/jdbcmysql_error.rb b/activerecord/lib/active_record/railties/jdbcmysql_error.rb
index d7cf4df339..72c75ddd52 100644
--- a/activerecord/lib/active_record/railties/jdbcmysql_error.rb
+++ b/activerecord/lib/active_record/railties/jdbcmysql_error.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #FIXME Remove if ArJdbcMysql will give.
 module ArJdbcMySQL #:nodoc:
   class Error < StandardError #:nodoc:
diff --git a/activerecord/lib/active_record/readonly_attributes.rb b/activerecord/lib/active_record/readonly_attributes.rb
index af6473d250..7bc26993d5 100644
--- a/activerecord/lib/active_record/readonly_attributes.rb
+++ b/activerecord/lib/active_record/readonly_attributes.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ReadonlyAttributes
     extend ActiveSupport::Concern
diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index 1026e20f79..efe56454d0 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "thread"
 require "active_support/core_ext/string/filters"
 require "active_support/deprecation"
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index d9e1e5c39c..90e4fe98d5 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record \Relation
   class Relation
diff --git a/activerecord/lib/active_record/relation/batches.rb b/activerecord/lib/active_record/relation/batches.rb
index c7e4f8a88a..141ad176ea 100644
--- a/activerecord/lib/active_record/relation/batches.rb
+++ b/activerecord/lib/active_record/relation/batches.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "batches/batch_enumerator"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/relation/batches/batch_enumerator.rb b/activerecord/lib/active_record/relation/batches/batch_enumerator.rb
index 3555779ec2..49697da3bf 100644
--- a/activerecord/lib/active_record/relation/batches/batch_enumerator.rb
+++ b/activerecord/lib/active_record/relation/batches/batch_enumerator.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Batches
     class BatchEnumerator
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index aaba6c71f2..c105abe774 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Calculations
     # Count the records.
diff --git a/activerecord/lib/active_record/relation/delegation.rb b/activerecord/lib/active_record/relation/delegation.rb
index 48c4dcdef4..4793f2a49b 100644
--- a/activerecord/lib/active_record/relation/delegation.rb
+++ b/activerecord/lib/active_record/relation/delegation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Delegation # :nodoc:
     module DelegateCache # :nodoc:
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index 57b7d3c2e9..36d35b98fd 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/string/filters"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/relation/from_clause.rb b/activerecord/lib/active_record/relation/from_clause.rb
index 8945cb0cc5..03f1202470 100644
--- a/activerecord/lib/active_record/relation/from_clause.rb
+++ b/activerecord/lib/active_record/relation/from_clause.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class Relation
     class FromClause # :nodoc:
diff --git a/activerecord/lib/active_record/relation/merger.rb b/activerecord/lib/active_record/relation/merger.rb
index 6251f6fc33..182f654897 100644
--- a/activerecord/lib/active_record/relation/merger.rb
+++ b/activerecord/lib/active_record/relation/merger.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/hash/keys"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/relation/predicate_builder.rb b/activerecord/lib/active_record/relation/predicate_builder.rb
index eb80c9a00d..3b8f8da634 100644
--- a/activerecord/lib/active_record/relation/predicate_builder.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class PredicateBuilder # :nodoc:
     delegate :resolve_column_aliases, to: :table
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 1068e700e2..85ec7d1428 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class PredicateBuilder
     class ArrayHandler # :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 3e19646ae5..e64d9fdf2a 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
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class PredicateBuilder
     class AssociationQueryValue # :nodoc:
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 3bb1037885..632c68a103 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/base_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/base_handler.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class PredicateBuilder
     class BaseHandler # :nodoc:
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 79cde00303..a17cf30ffd 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
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class PredicateBuilder
     class BasicObjectHandler # :nodoc:
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 7029ae5f47..1bc066363c 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
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class PredicateBuilder
     class PolymorphicArrayValue # :nodoc:
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 5db778e19c..072e238306 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/range_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/range_handler.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class PredicateBuilder
     class RangeHandler # :nodoc:
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 8a910a82fe..f51ea4fde0 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class PredicateBuilder
     class RelationHandler # :nodoc:
diff --git a/activerecord/lib/active_record/relation/query_attribute.rb b/activerecord/lib/active_record/relation/query_attribute.rb
index 0e1f64775d..e6883acd90 100644
--- a/activerecord/lib/active_record/relation/query_attribute.rb
+++ b/activerecord/lib/active_record/relation/query_attribute.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "../attribute"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index efb55391e7..e2af62873c 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "from_clause"
 require_relative "query_attribute"
 require_relative "where_clause"
diff --git a/activerecord/lib/active_record/relation/record_fetch_warning.rb b/activerecord/lib/active_record/relation/record_fetch_warning.rb
index 31544c730e..a7d07d23e1 100644
--- a/activerecord/lib/active_record/relation/record_fetch_warning.rb
+++ b/activerecord/lib/active_record/relation/record_fetch_warning.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class Relation
     module RecordFetchWarning
diff --git a/activerecord/lib/active_record/relation/spawn_methods.rb b/activerecord/lib/active_record/relation/spawn_methods.rb
index ddf7f825c1..424894f835 100644
--- a/activerecord/lib/active_record/relation/spawn_methods.rb
+++ b/activerecord/lib/active_record/relation/spawn_methods.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/hash/except"
 require "active_support/core_ext/hash/slice"
 require_relative "merger"
diff --git a/activerecord/lib/active_record/relation/where_clause.rb b/activerecord/lib/active_record/relation/where_clause.rb
index 731f161eb1..0b4c7b7dfa 100644
--- a/activerecord/lib/active_record/relation/where_clause.rb
+++ b/activerecord/lib/active_record/relation/where_clause.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class Relation
     class WhereClause # :nodoc:
diff --git a/activerecord/lib/active_record/relation/where_clause_factory.rb b/activerecord/lib/active_record/relation/where_clause_factory.rb
index b862dd56a5..4a0868314d 100644
--- a/activerecord/lib/active_record/relation/where_clause_factory.rb
+++ b/activerecord/lib/active_record/relation/where_clause_factory.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class Relation
     class WhereClauseFactory # :nodoc:
diff --git a/activerecord/lib/active_record/result.rb b/activerecord/lib/active_record/result.rb
index 26b1d48e9e..e54e8086dd 100644
--- a/activerecord/lib/active_record/result.rb
+++ b/activerecord/lib/active_record/result.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   ###
   # This class encapsulates a result returned from calling
diff --git a/activerecord/lib/active_record/runtime_registry.rb b/activerecord/lib/active_record/runtime_registry.rb
index b79eb2263f..4975cb8967 100644
--- a/activerecord/lib/active_record/runtime_registry.rb
+++ b/activerecord/lib/active_record/runtime_registry.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/per_thread_registry"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/sanitization.rb b/activerecord/lib/active_record/sanitization.rb
index 64bda1539c..91a4f1fad6 100644
--- a/activerecord/lib/active_record/sanitization.rb
+++ b/activerecord/lib/active_record/sanitization.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Sanitization
     extend ActiveSupport::Concern
diff --git a/activerecord/lib/active_record/schema.rb b/activerecord/lib/active_record/schema.rb
index 5104427339..f166c27fd9 100644
--- a/activerecord/lib/active_record/schema.rb
+++ b/activerecord/lib/active_record/schema.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record \Schema
   #
diff --git a/activerecord/lib/active_record/schema_dumper.rb b/activerecord/lib/active_record/schema_dumper.rb
index 66a2846f3a..dd8442a34f 100644
--- a/activerecord/lib/active_record/schema_dumper.rb
+++ b/activerecord/lib/active_record/schema_dumper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "stringio"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/schema_migration.rb b/activerecord/lib/active_record/schema_migration.rb
index 6dbabd69a1..339a5334a8 100644
--- a/activerecord/lib/active_record/schema_migration.rb
+++ b/activerecord/lib/active_record/schema_migration.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "scoping/default"
 require_relative "scoping/named"
 
diff --git a/activerecord/lib/active_record/scoping.rb b/activerecord/lib/active_record/scoping.rb
index 82e20a32d0..da585a9562 100644
--- a/activerecord/lib/active_record/scoping.rb
+++ b/activerecord/lib/active_record/scoping.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/per_thread_registry"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/scoping/default.rb b/activerecord/lib/active_record/scoping/default.rb
index 70b2693b28..86ae374318 100644
--- a/activerecord/lib/active_record/scoping/default.rb
+++ b/activerecord/lib/active_record/scoping/default.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Scoping
     module Default
diff --git a/activerecord/lib/active_record/scoping/named.rb b/activerecord/lib/active_record/scoping/named.rb
index b4026fabb2..43cce19c1f 100644
--- a/activerecord/lib/active_record/scoping/named.rb
+++ b/activerecord/lib/active_record/scoping/named.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/array"
 require "active_support/core_ext/hash/except"
 require "active_support/core_ext/kernel/singleton_class"
diff --git a/activerecord/lib/active_record/secure_token.rb b/activerecord/lib/active_record/secure_token.rb
index 115799cc20..bcdb33901b 100644
--- a/activerecord/lib/active_record/secure_token.rb
+++ b/activerecord/lib/active_record/secure_token.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module SecureToken
     extend ActiveSupport::Concern
diff --git a/activerecord/lib/active_record/serialization.rb b/activerecord/lib/active_record/serialization.rb
index db2bd0b55e..741fea43ce 100644
--- a/activerecord/lib/active_record/serialization.rb
+++ b/activerecord/lib/active_record/serialization.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord #:nodoc:
   # = Active Record \Serialization
   module Serialization
diff --git a/activerecord/lib/active_record/statement_cache.rb b/activerecord/lib/active_record/statement_cache.rb
index 1877489e55..b03ff9bc6c 100644
--- a/activerecord/lib/active_record/statement_cache.rb
+++ b/activerecord/lib/active_record/statement_cache.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # Statement cache is used to cache a single statement in order to avoid creating the AST again.
   # Initializing the cache is done by passing the statement in the create block:
diff --git a/activerecord/lib/active_record/store.rb b/activerecord/lib/active_record/store.rb
index 006afe7495..202b82fa61 100644
--- a/activerecord/lib/active_record/store.rb
+++ b/activerecord/lib/active_record/store.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/hash/indifferent_access"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/suppressor.rb b/activerecord/lib/active_record/suppressor.rb
index d9acb1a1dc..8cdb8e0765 100644
--- a/activerecord/lib/active_record/suppressor.rb
+++ b/activerecord/lib/active_record/suppressor.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # ActiveRecord::Suppressor prevents the receiver from being saved during
   # a given block.
diff --git a/activerecord/lib/active_record/table_metadata.rb b/activerecord/lib/active_record/table_metadata.rb
index 71efc1829a..71351449e1 100644
--- a/activerecord/lib/active_record/table_metadata.rb
+++ b/activerecord/lib/active_record/table_metadata.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class TableMetadata # :nodoc:
     delegate :foreign_type, :foreign_key, to: :association, prefix: true
diff --git a/activerecord/lib/active_record/tasks/database_tasks.rb b/activerecord/lib/active_record/tasks/database_tasks.rb
index 3fbfcc9b47..5c6a796857 100644
--- a/activerecord/lib/active_record/tasks/database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/database_tasks.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Tasks # :nodoc:
     class DatabaseAlreadyExists < StandardError; end # :nodoc:
diff --git a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
index ff6745f7b5..84265aa9e3 100644
--- a/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/mysql_database_tasks.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Tasks # :nodoc:
     class MySQLDatabaseTasks # :nodoc:
diff --git a/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb b/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
index 7f1a768d8b..a2e74efc2b 100644
--- a/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/postgresql_database_tasks.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "tempfile"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb b/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
index 01562b21e9..abdd6db64a 100644
--- a/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/sqlite_database_tasks.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Tasks # :nodoc:
     class SQLiteDatabaseTasks # :nodoc:
diff --git a/activerecord/lib/active_record/touch_later.rb b/activerecord/lib/active_record/touch_later.rb
index cacde9c881..f70b7c50a2 100644
--- a/activerecord/lib/active_record/touch_later.rb
+++ b/activerecord/lib/active_record/touch_later.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record Touch Later
   module TouchLater
diff --git a/activerecord/lib/active_record/transactions.rb b/activerecord/lib/active_record/transactions.rb
index 463bb1f314..3e8a0789df 100644
--- a/activerecord/lib/active_record/transactions.rb
+++ b/activerecord/lib/active_record/transactions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # See ActiveRecord::Transactions::ClassMethods for documentation.
   module Transactions
diff --git a/activerecord/lib/active_record/translation.rb b/activerecord/lib/active_record/translation.rb
index ddcb5f2a7a..3cf70eafb8 100644
--- a/activerecord/lib/active_record/translation.rb
+++ b/activerecord/lib/active_record/translation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Translation
     include ActiveModel::Translation
diff --git a/activerecord/lib/active_record/type.rb b/activerecord/lib/active_record/type.rb
index 6f4e35b159..fa22df92b8 100644
--- a/activerecord/lib/active_record/type.rb
+++ b/activerecord/lib/active_record/type.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_model/type"
 
 require_relative "type/internal/timezone"
diff --git a/activerecord/lib/active_record/type/adapter_specific_registry.rb b/activerecord/lib/active_record/type/adapter_specific_registry.rb
index 7cc866f7a7..e7468aa542 100644
--- a/activerecord/lib/active_record/type/adapter_specific_registry.rb
+++ b/activerecord/lib/active_record/type/adapter_specific_registry.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_model/type/registry"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/type/date.rb b/activerecord/lib/active_record/type/date.rb
index ccafed054e..8177074a20 100644
--- a/activerecord/lib/active_record/type/date.rb
+++ b/activerecord/lib/active_record/type/date.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Type
     class Date < ActiveModel::Type::Date
diff --git a/activerecord/lib/active_record/type/date_time.rb b/activerecord/lib/active_record/type/date_time.rb
index 1fb9380ecd..4acde6b9f8 100644
--- a/activerecord/lib/active_record/type/date_time.rb
+++ b/activerecord/lib/active_record/type/date_time.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Type
     class DateTime < ActiveModel::Type::DateTime
diff --git a/activerecord/lib/active_record/type/decimal_without_scale.rb b/activerecord/lib/active_record/type/decimal_without_scale.rb
index 53a5e205da..a207940dc7 100644
--- a/activerecord/lib/active_record/type/decimal_without_scale.rb
+++ b/activerecord/lib/active_record/type/decimal_without_scale.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Type
     class DecimalWithoutScale < ActiveModel::Type::BigInteger # :nodoc:
diff --git a/activerecord/lib/active_record/type/hash_lookup_type_map.rb b/activerecord/lib/active_record/type/hash_lookup_type_map.rb
index 0145d5d6c1..db9853fbcc 100644
--- a/activerecord/lib/active_record/type/hash_lookup_type_map.rb
+++ b/activerecord/lib/active_record/type/hash_lookup_type_map.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Type
     class HashLookupTypeMap < TypeMap # :nodoc:
diff --git a/activerecord/lib/active_record/type/internal/timezone.rb b/activerecord/lib/active_record/type/internal/timezone.rb
index 947e06158a..3059755752 100644
--- a/activerecord/lib/active_record/type/internal/timezone.rb
+++ b/activerecord/lib/active_record/type/internal/timezone.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Type
     module Internal
diff --git a/activerecord/lib/active_record/type/json.rb b/activerecord/lib/active_record/type/json.rb
index c4732fe388..3f9ff22796 100644
--- a/activerecord/lib/active_record/type/json.rb
+++ b/activerecord/lib/active_record/type/json.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Type
     class Json < ActiveModel::Type::Value
diff --git a/activerecord/lib/active_record/type/serialized.rb b/activerecord/lib/active_record/type/serialized.rb
index edbd20a6c1..e882784691 100644
--- a/activerecord/lib/active_record/type/serialized.rb
+++ b/activerecord/lib/active_record/type/serialized.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Type
     class Serialized < DelegateClass(ActiveModel::Type::Value) # :nodoc:
diff --git a/activerecord/lib/active_record/type/text.rb b/activerecord/lib/active_record/type/text.rb
index cb1949700a..6d19696671 100644
--- a/activerecord/lib/active_record/type/text.rb
+++ b/activerecord/lib/active_record/type/text.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Type
     class Text < ActiveModel::Type::String # :nodoc:
diff --git a/activerecord/lib/active_record/type/time.rb b/activerecord/lib/active_record/type/time.rb
index b9bac87c67..f4da1ecf2c 100644
--- a/activerecord/lib/active_record/type/time.rb
+++ b/activerecord/lib/active_record/type/time.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Type
     class Time < ActiveModel::Type::Time
diff --git a/activerecord/lib/active_record/type/type_map.rb b/activerecord/lib/active_record/type/type_map.rb
index 7bce82a1ff..fc40b460f0 100644
--- a/activerecord/lib/active_record/type/type_map.rb
+++ b/activerecord/lib/active_record/type/type_map.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "concurrent/map"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/type/unsigned_integer.rb b/activerecord/lib/active_record/type/unsigned_integer.rb
index 9ae0109f9f..4619528f81 100644
--- a/activerecord/lib/active_record/type/unsigned_integer.rb
+++ b/activerecord/lib/active_record/type/unsigned_integer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Type
     class UnsignedInteger < ActiveModel::Type::Integer # :nodoc:
diff --git a/activerecord/lib/active_record/type_caster.rb b/activerecord/lib/active_record/type_caster.rb
index 8b12a30c6a..ed2e4fb79c 100644
--- a/activerecord/lib/active_record/type_caster.rb
+++ b/activerecord/lib/active_record/type_caster.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "type_caster/map"
 require_relative "type_caster/connection"
 
diff --git a/activerecord/lib/active_record/type_caster/connection.rb b/activerecord/lib/active_record/type_caster/connection.rb
index 9f7bbe8843..af4e4e37e2 100644
--- a/activerecord/lib/active_record/type_caster/connection.rb
+++ b/activerecord/lib/active_record/type_caster/connection.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module TypeCaster
     class Connection # :nodoc:
diff --git a/activerecord/lib/active_record/type_caster/map.rb b/activerecord/lib/active_record/type_caster/map.rb
index 9f79723125..d51350ba83 100644
--- a/activerecord/lib/active_record/type_caster/map.rb
+++ b/activerecord/lib/active_record/type_caster/map.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module TypeCaster
     class Map # :nodoc:
diff --git a/activerecord/lib/active_record/validations.rb b/activerecord/lib/active_record/validations.rb
index 046b69bee2..3f5c879f2f 100644
--- a/activerecord/lib/active_record/validations.rb
+++ b/activerecord/lib/active_record/validations.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # = Active Record \RecordInvalid
   #
diff --git a/activerecord/lib/active_record/validations/absence.rb b/activerecord/lib/active_record/validations/absence.rb
index 641d041f3d..6afb9eabd2 100644
--- a/activerecord/lib/active_record/validations/absence.rb
+++ b/activerecord/lib/active_record/validations/absence.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Validations
     class AbsenceValidator < ActiveModel::Validations::AbsenceValidator # :nodoc:
diff --git a/activerecord/lib/active_record/validations/associated.rb b/activerecord/lib/active_record/validations/associated.rb
index c695965d7b..3538aeec22 100644
--- a/activerecord/lib/active_record/validations/associated.rb
+++ b/activerecord/lib/active_record/validations/associated.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Validations
     class AssociatedValidator < ActiveModel::EachValidator #:nodoc:
diff --git a/activerecord/lib/active_record/validations/length.rb b/activerecord/lib/active_record/validations/length.rb
index 0e0cebce4a..f47b14ae3a 100644
--- a/activerecord/lib/active_record/validations/length.rb
+++ b/activerecord/lib/active_record/validations/length.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Validations
     class LengthValidator < ActiveModel::Validations::LengthValidator # :nodoc:
diff --git a/activerecord/lib/active_record/validations/presence.rb b/activerecord/lib/active_record/validations/presence.rb
index 7cfd55f516..75e97e1997 100644
--- a/activerecord/lib/active_record/validations/presence.rb
+++ b/activerecord/lib/active_record/validations/presence.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Validations
     class PresenceValidator < ActiveModel::Validations::PresenceValidator # :nodoc:
diff --git a/activerecord/lib/active_record/validations/uniqueness.rb b/activerecord/lib/active_record/validations/uniqueness.rb
index 154cf5f1a4..3a110b461d 100644
--- a/activerecord/lib/active_record/validations/uniqueness.rb
+++ b/activerecord/lib/active_record/validations/uniqueness.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Validations
     class UniquenessValidator < ActiveModel::EachValidator # :nodoc:
diff --git a/activerecord/lib/active_record/version.rb b/activerecord/lib/active_record/version.rb
index 146cfacc18..6b0d82d8fc 100644
--- a/activerecord/lib/active_record/version.rb
+++ b/activerecord/lib/active_record/version.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "gem_version"
 
 module ActiveRecord
diff --git a/activerecord/lib/rails/generators/active_record.rb b/activerecord/lib/rails/generators/active_record.rb
index a79b8eafea..a7e5e373a7 100644
--- a/activerecord/lib/rails/generators/active_record.rb
+++ b/activerecord/lib/rails/generators/active_record.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "rails/generators/named_base"
 require "rails/generators/active_model"
 require "rails/generators/active_record/migration"
diff --git a/activerecord/lib/rails/generators/active_record/migration.rb b/activerecord/lib/rails/generators/active_record/migration.rb
index 47c0981a49..4ceb502c5d 100644
--- a/activerecord/lib/rails/generators/active_record/migration.rb
+++ b/activerecord/lib/rails/generators/active_record/migration.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "rails/generators/migration"
 
 module ActiveRecord
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 1f1c47499b..0174c7ea31 100644
--- a/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb
+++ b/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "rails/generators/active_record"
 
 module ActiveRecord
diff --git a/activerecord/lib/rails/generators/active_record/model/model_generator.rb b/activerecord/lib/rails/generators/active_record/model/model_generator.rb
index 5cec07d2e3..7a1bb7efdc 100644
--- a/activerecord/lib/rails/generators/active_record/model/model_generator.rb
+++ b/activerecord/lib/rails/generators/active_record/model/model_generator.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "rails/generators/active_record"
 
 module ActiveRecord
diff --git a/activerecord/test/active_record/connection_adapters/fake_adapter.rb b/activerecord/test/active_record/connection_adapters/fake_adapter.rb
index b0d8050721..f977b2997b 100644
--- a/activerecord/test/active_record/connection_adapters/fake_adapter.rb
+++ b/activerecord/test/active_record/connection_adapters/fake_adapter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionHandling
     def fake_connection(config)
diff --git a/activerecord/test/cases/adapter_test.rb b/activerecord/test/cases/adapter_test.rb
index 827bcba121..b162314317 100644
--- a/activerecord/test/cases/adapter_test.rb
+++ b/activerecord/test/cases/adapter_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/book"
 require "models/post"
diff --git a/activerecord/test/cases/adapters/mysql2/active_schema_test.rb b/activerecord/test/cases/adapters/mysql2/active_schema_test.rb
index 67e1efde27..a6b83ec377 100644
--- a/activerecord/test/cases/adapters/mysql2/active_schema_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/active_schema_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/connection_helper"
 
diff --git a/activerecord/test/cases/adapters/mysql2/bind_parameter_test.rb b/activerecord/test/cases/adapters/mysql2/bind_parameter_test.rb
index 8f7c803a21..825bddfb73 100644
--- a/activerecord/test/cases/adapters/mysql2/bind_parameter_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/bind_parameter_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 
diff --git a/activerecord/test/cases/adapters/mysql2/boolean_test.rb b/activerecord/test/cases/adapters/mysql2/boolean_test.rb
index 58698d59db..db09b30361 100644
--- a/activerecord/test/cases/adapters/mysql2/boolean_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/boolean_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class Mysql2BooleanTest < ActiveRecord::Mysql2TestCase
diff --git a/activerecord/test/cases/adapters/mysql2/case_sensitivity_test.rb b/activerecord/test/cases/adapters/mysql2/case_sensitivity_test.rb
index 50ba9ab831..fd5f712f1a 100644
--- a/activerecord/test/cases/adapters/mysql2/case_sensitivity_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/case_sensitivity_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class Mysql2CaseSensitivityTest < ActiveRecord::Mysql2TestCase
diff --git a/activerecord/test/cases/adapters/mysql2/charset_collation_test.rb b/activerecord/test/cases/adapters/mysql2/charset_collation_test.rb
index e4a6ed5482..d0c57de65d 100644
--- a/activerecord/test/cases/adapters/mysql2/charset_collation_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/charset_collation_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/mysql2/connection_test.rb b/activerecord/test/cases/adapters/mysql2/connection_test.rb
index a2faf43b0d..9d81d506a0 100644
--- a/activerecord/test/cases/adapters/mysql2/connection_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/connection_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/connection_helper"
 
diff --git a/activerecord/test/cases/adapters/mysql2/datetime_precision_quoting_test.rb b/activerecord/test/cases/adapters/mysql2/datetime_precision_quoting_test.rb
index c131a5169c..fa54f39992 100644
--- a/activerecord/test/cases/adapters/mysql2/datetime_precision_quoting_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/datetime_precision_quoting_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class Mysql2DatetimePrecisionQuotingTest < ActiveRecord::Mysql2TestCase
diff --git a/activerecord/test/cases/adapters/mysql2/enum_test.rb b/activerecord/test/cases/adapters/mysql2/enum_test.rb
index 7ad3e3ca2d..108bec832c 100644
--- a/activerecord/test/cases/adapters/mysql2/enum_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/enum_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class Mysql2EnumTest < ActiveRecord::Mysql2TestCase
diff --git a/activerecord/test/cases/adapters/mysql2/explain_test.rb b/activerecord/test/cases/adapters/mysql2/explain_test.rb
index 7916921e5a..2736f7cf0e 100644
--- a/activerecord/test/cases/adapters/mysql2/explain_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/explain_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/developer"
 require "models/computer"
diff --git a/activerecord/test/cases/adapters/mysql2/json_test.rb b/activerecord/test/cases/adapters/mysql2/json_test.rb
index 26c69edc7b..de78ba91f5 100644
--- a/activerecord/test/cases/adapters/mysql2/json_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/json_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "cases/json_shared_test_cases"
 
diff --git a/activerecord/test/cases/adapters/mysql2/mysql2_adapter_test.rb b/activerecord/test/cases/adapters/mysql2/mysql2_adapter_test.rb
index 565130c38f..d18fb97e05 100644
--- a/activerecord/test/cases/adapters/mysql2/mysql2_adapter_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/mysql2_adapter_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/ddl_helper"
 
diff --git a/activerecord/test/cases/adapters/mysql2/schema_migrations_test.rb b/activerecord/test/cases/adapters/mysql2/schema_migrations_test.rb
index 251a50e41e..eb602af812 100644
--- a/activerecord/test/cases/adapters/mysql2/schema_migrations_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/schema_migrations_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class SchemaMigrationsTest < ActiveRecord::Mysql2TestCase
diff --git a/activerecord/test/cases/adapters/mysql2/schema_test.rb b/activerecord/test/cases/adapters/mysql2/schema_test.rb
index 1fad5585de..b587e756cf 100644
--- a/activerecord/test/cases/adapters/mysql2/schema_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/schema_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/comment"
diff --git a/activerecord/test/cases/adapters/mysql2/sp_test.rb b/activerecord/test/cases/adapters/mysql2/sp_test.rb
index 4182532535..47cedc5edf 100644
--- a/activerecord/test/cases/adapters/mysql2/sp_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/sp_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/reply"
diff --git a/activerecord/test/cases/adapters/mysql2/sql_types_test.rb b/activerecord/test/cases/adapters/mysql2/sql_types_test.rb
index d6e7f29a5c..e10642cbb4 100644
--- a/activerecord/test/cases/adapters/mysql2/sql_types_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/sql_types_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class Mysql2SqlTypesTest < ActiveRecord::Mysql2TestCase
diff --git a/activerecord/test/cases/adapters/mysql2/table_options_test.rb b/activerecord/test/cases/adapters/mysql2/table_options_test.rb
index 61a8ce9bc0..6183d66b63 100644
--- a/activerecord/test/cases/adapters/mysql2/table_options_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/table_options_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/mysql2/transaction_test.rb b/activerecord/test/cases/adapters/mysql2/transaction_test.rb
index 16101e38cb..e603baab69 100644
--- a/activerecord/test/cases/adapters/mysql2/transaction_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/transaction_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/connection_helper"
 
diff --git a/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb b/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb
index 71dcfaa241..d0a09f6481 100644
--- a/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/mysql2/virtual_column_test.rb b/activerecord/test/cases/adapters/mysql2/virtual_column_test.rb
index 1c5ef2aa41..ffde8ed4d8 100644
--- a/activerecord/test/cases/adapters/mysql2/virtual_column_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/virtual_column_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/active_schema_test.rb b/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
index b787de8453..9929237546 100644
--- a/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class PostgresqlActiveSchemaTest < ActiveRecord::PostgreSQLTestCase
diff --git a/activerecord/test/cases/adapters/postgresql/array_test.rb b/activerecord/test/cases/adapters/postgresql/array_test.rb
index 121c62dadf..8507dbb463 100644
--- a/activerecord/test/cases/adapters/postgresql/array_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/array_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/bit_string_test.rb b/activerecord/test/cases/adapters/postgresql/bit_string_test.rb
index 7712e809a2..df04299569 100644
--- a/activerecord/test/cases/adapters/postgresql/bit_string_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/bit_string_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/connection_helper"
 require "support/schema_dumping_helper"
diff --git a/activerecord/test/cases/adapters/postgresql/bytea_test.rb b/activerecord/test/cases/adapters/postgresql/bytea_test.rb
index 65baed34e9..a6bee113ff 100644
--- a/activerecord/test/cases/adapters/postgresql/bytea_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/bytea_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/case_insensitive_test.rb b/activerecord/test/cases/adapters/postgresql/case_insensitive_test.rb
index 03b44feab6..305e033642 100644
--- a/activerecord/test/cases/adapters/postgresql/case_insensitive_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/case_insensitive_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class PostgresqlCaseInsensitiveTest < ActiveRecord::PostgreSQLTestCase
diff --git a/activerecord/test/cases/adapters/postgresql/change_schema_test.rb b/activerecord/test/cases/adapters/postgresql/change_schema_test.rb
index ea642069d2..adf461a9cc 100644
--- a/activerecord/test/cases/adapters/postgresql/change_schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/change_schema_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/adapters/postgresql/cidr_test.rb b/activerecord/test/cases/adapters/postgresql/cidr_test.rb
index 52f2a0096c..f20958fbd2 100644
--- a/activerecord/test/cases/adapters/postgresql/cidr_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/cidr_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "ipaddr"
 
diff --git a/activerecord/test/cases/adapters/postgresql/citext_test.rb b/activerecord/test/cases/adapters/postgresql/citext_test.rb
index ca95e4b626..050614cade 100644
--- a/activerecord/test/cases/adapters/postgresql/citext_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/citext_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/collation_test.rb b/activerecord/test/cases/adapters/postgresql/collation_test.rb
index a603221d8f..7468f4c4f8 100644
--- a/activerecord/test/cases/adapters/postgresql/collation_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/collation_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/composite_test.rb b/activerecord/test/cases/adapters/postgresql/composite_test.rb
index 1da2a9e2ac..1d60a007c7 100644
--- a/activerecord/test/cases/adapters/postgresql/composite_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/composite_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/connection_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/connection_test.rb b/activerecord/test/cases/adapters/postgresql/connection_test.rb
index 32afe331fa..c2eb0b70c6 100644
--- a/activerecord/test/cases/adapters/postgresql/connection_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/connection_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/connection_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/datatype_test.rb b/activerecord/test/cases/adapters/postgresql/datatype_test.rb
index 0725fde5ae..b7535d5c9a 100644
--- a/activerecord/test/cases/adapters/postgresql/datatype_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/datatype_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/ddl_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/domain_test.rb b/activerecord/test/cases/adapters/postgresql/domain_test.rb
index f1eb8adb15..9c3817e2ad 100644
--- a/activerecord/test/cases/adapters/postgresql/domain_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/domain_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/connection_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/enum_test.rb b/activerecord/test/cases/adapters/postgresql/enum_test.rb
index 5e5a3158ba..3d3cbe11a3 100644
--- a/activerecord/test/cases/adapters/postgresql/enum_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/enum_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/connection_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/explain_test.rb b/activerecord/test/cases/adapters/postgresql/explain_test.rb
index 3d5684704e..16fec94ede 100644
--- a/activerecord/test/cases/adapters/postgresql/explain_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/explain_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/developer"
 require "models/computer"
diff --git a/activerecord/test/cases/adapters/postgresql/extension_migration_test.rb b/activerecord/test/cases/adapters/postgresql/extension_migration_test.rb
index b56c226763..e589e3ab1b 100644
--- a/activerecord/test/cases/adapters/postgresql/extension_migration_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/extension_migration_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class PostgresqlExtensionMigrationTest < ActiveRecord::PostgreSQLTestCase
diff --git a/activerecord/test/cases/adapters/postgresql/full_text_test.rb b/activerecord/test/cases/adapters/postgresql/full_text_test.rb
index 5ddfe32007..c6f1e1727f 100644
--- a/activerecord/test/cases/adapters/postgresql/full_text_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/full_text_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/geometric_test.rb b/activerecord/test/cases/adapters/postgresql/geometric_test.rb
index 3b6840a1c9..e1ba00e07b 100644
--- a/activerecord/test/cases/adapters/postgresql/geometric_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/geometric_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/connection_helper"
 require "support/schema_dumping_helper"
diff --git a/activerecord/test/cases/adapters/postgresql/hstore_test.rb b/activerecord/test/cases/adapters/postgresql/hstore_test.rb
index f9cce10fb8..7d8a83a4dd 100644
--- a/activerecord/test/cases/adapters/postgresql/hstore_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/hstore_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/infinity_test.rb b/activerecord/test/cases/adapters/postgresql/infinity_test.rb
index b9e177e6ec..0b18c0c9d7 100644
--- a/activerecord/test/cases/adapters/postgresql/infinity_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/infinity_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class PostgresqlInfinityTest < ActiveRecord::PostgreSQLTestCase
diff --git a/activerecord/test/cases/adapters/postgresql/integer_test.rb b/activerecord/test/cases/adapters/postgresql/integer_test.rb
index b4e55964b9..3e45b057ff 100644
--- a/activerecord/test/cases/adapters/postgresql/integer_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/integer_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "active_support/core_ext/numeric/bytes"
 
diff --git a/activerecord/test/cases/adapters/postgresql/json_test.rb b/activerecord/test/cases/adapters/postgresql/json_test.rb
index 6aa60630c2..aa5e03df41 100644
--- a/activerecord/test/cases/adapters/postgresql/json_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/json_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "cases/json_shared_test_cases"
 
diff --git a/activerecord/test/cases/adapters/postgresql/ltree_test.rb b/activerecord/test/cases/adapters/postgresql/ltree_test.rb
index 2b5ac1cac6..eca29f2892 100644
--- a/activerecord/test/cases/adapters/postgresql/ltree_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/ltree_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/money_test.rb b/activerecord/test/cases/adapters/postgresql/money_test.rb
index ea060345a7..563f0bbfae 100644
--- a/activerecord/test/cases/adapters/postgresql/money_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/money_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/network_test.rb b/activerecord/test/cases/adapters/postgresql/network_test.rb
index a33b0ef8a7..f461544a85 100644
--- a/activerecord/test/cases/adapters/postgresql/network_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/network_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/numbers_test.rb b/activerecord/test/cases/adapters/postgresql/numbers_test.rb
index bfb2b7c27a..b53a12254d 100644
--- a/activerecord/test/cases/adapters/postgresql/numbers_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/numbers_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class PostgresqlNumberTest < ActiveRecord::PostgreSQLTestCase
diff --git a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
index 76e0ad60fe..5d8653c73f 100644
--- a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/ddl_helper"
 require "support/connection_helper"
diff --git a/activerecord/test/cases/adapters/postgresql/prepared_statements_disabled_test.rb b/activerecord/test/cases/adapters/postgresql/prepared_statements_disabled_test.rb
index 8c62690866..f7478b50c3 100644
--- a/activerecord/test/cases/adapters/postgresql/prepared_statements_disabled_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/prepared_statements_disabled_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/computer"
 require "models/developer"
diff --git a/activerecord/test/cases/adapters/postgresql/quoting_test.rb b/activerecord/test/cases/adapters/postgresql/quoting_test.rb
index d7b23ad41d..d50dc49276 100644
--- a/activerecord/test/cases/adapters/postgresql/quoting_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/quoting_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/adapters/postgresql/range_test.rb b/activerecord/test/cases/adapters/postgresql/range_test.rb
index f411884dfd..b4a776d04d 100644
--- a/activerecord/test/cases/adapters/postgresql/range_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/range_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/connection_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/referential_integrity_test.rb b/activerecord/test/cases/adapters/postgresql/referential_integrity_test.rb
index 0ff04bfa27..0bcc214c24 100644
--- a/activerecord/test/cases/adapters/postgresql/referential_integrity_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/referential_integrity_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/connection_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/rename_table_test.rb b/activerecord/test/cases/adapters/postgresql/rename_table_test.rb
index e9e7f717ac..100d247113 100644
--- a/activerecord/test/cases/adapters/postgresql/rename_table_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/rename_table_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class PostgresqlRenameTableTest < ActiveRecord::PostgreSQLTestCase
diff --git a/activerecord/test/cases/adapters/postgresql/schema_authorization_test.rb b/activerecord/test/cases/adapters/postgresql/schema_authorization_test.rb
index f86a76e08a..56deabcee5 100644
--- a/activerecord/test/cases/adapters/postgresql/schema_authorization_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/schema_authorization_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class SchemaThing < ActiveRecord::Base
diff --git a/activerecord/test/cases/adapters/postgresql/schema_test.rb b/activerecord/test/cases/adapters/postgresql/schema_test.rb
index f6b957476b..d41d189b34 100644
--- a/activerecord/test/cases/adapters/postgresql/schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/schema_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/default"
 require "support/schema_dumping_helper"
diff --git a/activerecord/test/cases/adapters/postgresql/serial_test.rb b/activerecord/test/cases/adapters/postgresql/serial_test.rb
index d711b3b729..3c020a88d0 100644
--- a/activerecord/test/cases/adapters/postgresql/serial_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/serial_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/statement_pool_test.rb b/activerecord/test/cases/adapters/postgresql/statement_pool_test.rb
index 146b619a4b..a3eb4f9e67 100644
--- a/activerecord/test/cases/adapters/postgresql/statement_pool_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/statement_pool_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/adapters/postgresql/timestamp_test.rb b/activerecord/test/cases/adapters/postgresql/timestamp_test.rb
index 962450aada..b7f213efc8 100644
--- a/activerecord/test/cases/adapters/postgresql/timestamp_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/timestamp_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/developer"
 require "models/topic"
diff --git a/activerecord/test/cases/adapters/postgresql/transaction_test.rb b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
index 9b42d0383d..f56adf4a5e 100644
--- a/activerecord/test/cases/adapters/postgresql/transaction_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/connection_helper"
 require "concurrent/atomic/cyclic_barrier"
diff --git a/activerecord/test/cases/adapters/postgresql/type_lookup_test.rb b/activerecord/test/cases/adapters/postgresql/type_lookup_test.rb
index 784d77a8d1..1a164205aa 100644
--- a/activerecord/test/cases/adapters/postgresql/type_lookup_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/type_lookup_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class PostgresqlTypeLookupTest < ActiveRecord::PostgreSQLTestCase
diff --git a/activerecord/test/cases/adapters/postgresql/utils_test.rb b/activerecord/test/cases/adapters/postgresql/utils_test.rb
index 9f9e3bda2f..c91884f384 100644
--- a/activerecord/test/cases/adapters/postgresql/utils_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/utils_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "active_record/connection_adapters/postgresql/utils"
 
diff --git a/activerecord/test/cases/adapters/postgresql/uuid_test.rb b/activerecord/test/cases/adapters/postgresql/uuid_test.rb
index 00de92cdfd..76cb1bc354 100644
--- a/activerecord/test/cases/adapters/postgresql/uuid_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/uuid_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/postgresql/xml_test.rb b/activerecord/test/cases/adapters/postgresql/xml_test.rb
index 826b384fb3..71ead6f7f3 100644
--- a/activerecord/test/cases/adapters/postgresql/xml_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/xml_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/sqlite3/collation_test.rb b/activerecord/test/cases/adapters/sqlite3/collation_test.rb
index dd88ed3656..76c8f7d8dd 100644
--- a/activerecord/test/cases/adapters/sqlite3/collation_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/collation_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/adapters/sqlite3/copy_table_test.rb b/activerecord/test/cases/adapters/sqlite3/copy_table_test.rb
index e1cfd703e8..ffb1d6afce 100644
--- a/activerecord/test/cases/adapters/sqlite3/copy_table_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/copy_table_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class CopyTableTest < ActiveRecord::SQLite3TestCase
diff --git a/activerecord/test/cases/adapters/sqlite3/explain_test.rb b/activerecord/test/cases/adapters/sqlite3/explain_test.rb
index b907a7ae0f..3b081d34e1 100644
--- a/activerecord/test/cases/adapters/sqlite3/explain_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/explain_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/developer"
 require "models/computer"
diff --git a/activerecord/test/cases/adapters/sqlite3/quoting_test.rb b/activerecord/test/cases/adapters/sqlite3/quoting_test.rb
index 815453ad50..de422fad23 100644
--- a/activerecord/test/cases/adapters/sqlite3/quoting_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/quoting_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "bigdecimal"
 require "securerandom"
diff --git a/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb b/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
index cf0c37f70c..65722b5830 100644
--- a/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/owner"
 require "tempfile"
diff --git a/activerecord/test/cases/adapters/sqlite3/sqlite3_create_folder_test.rb b/activerecord/test/cases/adapters/sqlite3/sqlite3_create_folder_test.rb
index b1b4463bf1..d70486605f 100644
--- a/activerecord/test/cases/adapters/sqlite3/sqlite3_create_folder_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/sqlite3_create_folder_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/owner"
 
diff --git a/activerecord/test/cases/adapters/sqlite3/statement_pool_test.rb b/activerecord/test/cases/adapters/sqlite3/statement_pool_test.rb
index 37ff973397..42b3841d41 100644
--- a/activerecord/test/cases/adapters/sqlite3/statement_pool_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/statement_pool_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class SQLite3StatementPoolTest < ActiveRecord::SQLite3TestCase
diff --git a/activerecord/test/cases/aggregations_test.rb b/activerecord/test/cases/aggregations_test.rb
index f8136fde72..7f654ec6f6 100644
--- a/activerecord/test/cases/aggregations_test.rb
+++ b/activerecord/test/cases/aggregations_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/customer"
 
diff --git a/activerecord/test/cases/ar_schema_test.rb b/activerecord/test/cases/ar_schema_test.rb
index 5b608d8e83..83974f327e 100644
--- a/activerecord/test/cases/ar_schema_test.rb
+++ b/activerecord/test/cases/ar_schema_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class ActiveRecordSchemaTest < ActiveRecord::TestCase
diff --git a/activerecord/test/cases/associations/association_scope_test.rb b/activerecord/test/cases/associations/association_scope_test.rb
index c54542ff7b..00e989153f 100644
--- a/activerecord/test/cases/associations/association_scope_test.rb
+++ b/activerecord/test/cases/associations/association_scope_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/author"
diff --git a/activerecord/test/cases/associations/belongs_to_associations_test.rb b/activerecord/test/cases/associations/belongs_to_associations_test.rb
index a7ac291f23..8bf2ecf88d 100644
--- a/activerecord/test/cases/associations/belongs_to_associations_test.rb
+++ b/activerecord/test/cases/associations/belongs_to_associations_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/developer"
 require "models/project"
diff --git a/activerecord/test/cases/associations/bidirectional_destroy_dependencies_test.rb b/activerecord/test/cases/associations/bidirectional_destroy_dependencies_test.rb
index 8a0e041864..88221b012e 100644
--- a/activerecord/test/cases/associations/bidirectional_destroy_dependencies_test.rb
+++ b/activerecord/test/cases/associations/bidirectional_destroy_dependencies_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/content"
 
diff --git a/activerecord/test/cases/associations/callbacks_test.rb b/activerecord/test/cases/associations/callbacks_test.rb
index f9d1e44595..e096cd4a0b 100644
--- a/activerecord/test/cases/associations/callbacks_test.rb
+++ b/activerecord/test/cases/associations/callbacks_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/author"
diff --git a/activerecord/test/cases/associations/cascaded_eager_loading_test.rb b/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
index 7b0445025c..e69cfe5e52 100644
--- a/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
+++ b/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/comment"
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 61f39b4136..8754889143 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
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/tagging"
diff --git a/activerecord/test/cases/associations/eager_load_nested_include_test.rb b/activerecord/test/cases/associations/eager_load_nested_include_test.rb
index e9f551b6b2..c5b2b77bd4 100644
--- a/activerecord/test/cases/associations/eager_load_nested_include_test.rb
+++ b/activerecord/test/cases/associations/eager_load_nested_include_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/tag"
diff --git a/activerecord/test/cases/associations/eager_singularization_test.rb b/activerecord/test/cases/associations/eager_singularization_test.rb
index 16eff15026..420a5a805b 100644
--- a/activerecord/test/cases/associations/eager_singularization_test.rb
+++ b/activerecord/test/cases/associations/eager_singularization_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class EagerSingularizationTest < ActiveRecord::TestCase
diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index c0bab19e82..1f5f9eddb5 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/tagging"
diff --git a/activerecord/test/cases/associations/extension_test.rb b/activerecord/test/cases/associations/extension_test.rb
index f707a170f5..5eacb5a3d8 100644
--- a/activerecord/test/cases/associations/extension_test.rb
+++ b/activerecord/test/cases/associations/extension_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/comment"
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 f73005b3cb..979dd986de 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
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/developer"
 require "models/computer"
diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index 2682f256ff..2ab8a6bf03 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/developer"
 require "models/computer"
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 a76159fb99..5797ffef38 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/person"
diff --git a/activerecord/test/cases/associations/has_one_associations_test.rb b/activerecord/test/cases/associations/has_one_associations_test.rb
index bf3b8dcd63..ff51a511fc 100644
--- a/activerecord/test/cases/associations/has_one_associations_test.rb
+++ b/activerecord/test/cases/associations/has_one_associations_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/developer"
 require "models/computer"
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 28b883586d..fe24c465b2 100644
--- a/activerecord/test/cases/associations/has_one_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_one_through_associations_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/club"
 require "models/member_type"
diff --git a/activerecord/test/cases/associations/inner_join_association_test.rb b/activerecord/test/cases/associations/inner_join_association_test.rb
index ddf5bc6f0b..23be344419 100644
--- a/activerecord/test/cases/associations/inner_join_association_test.rb
+++ b/activerecord/test/cases/associations/inner_join_association_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/comment"
diff --git a/activerecord/test/cases/associations/inverse_associations_test.rb b/activerecord/test/cases/associations/inverse_associations_test.rb
index 9fbaa43274..536077fb92 100644
--- a/activerecord/test/cases/associations/inverse_associations_test.rb
+++ b/activerecord/test/cases/associations/inverse_associations_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/man"
 require "models/face"
diff --git a/activerecord/test/cases/associations/join_model_test.rb b/activerecord/test/cases/associations/join_model_test.rb
index c078cef064..2f68bc5141 100644
--- a/activerecord/test/cases/associations/join_model_test.rb
+++ b/activerecord/test/cases/associations/join_model_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/tag"
 require "models/tagging"
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 6d3757f467..c95d0425cd 100644
--- a/activerecord/test/cases/associations/left_outer_join_association_test.rb
+++ b/activerecord/test/cases/associations/left_outer_join_association_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/comment"
diff --git a/activerecord/test/cases/associations/nested_through_associations_test.rb b/activerecord/test/cases/associations/nested_through_associations_test.rb
index 67ff7355b3..3e37e512ca 100644
--- a/activerecord/test/cases/associations/nested_through_associations_test.rb
+++ b/activerecord/test/cases/associations/nested_through_associations_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/author"
 require "models/post"
diff --git a/activerecord/test/cases/associations/required_test.rb b/activerecord/test/cases/associations/required_test.rb
index 45e1803858..65a3bb5efe 100644
--- a/activerecord/test/cases/associations/required_test.rb
+++ b/activerecord/test/cases/associations/required_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class RequiredAssociationsTest < ActiveRecord::TestCase
diff --git a/activerecord/test/cases/associations_test.rb b/activerecord/test/cases/associations_test.rb
index 2eb31326a5..9d1999bcb1 100644
--- a/activerecord/test/cases/associations_test.rb
+++ b/activerecord/test/cases/associations_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/computer"
 require "models/developer"
diff --git a/activerecord/test/cases/attribute_decorators_test.rb b/activerecord/test/cases/attribute_decorators_test.rb
index cfa6ed1da6..42eca233ce 100644
--- a/activerecord/test/cases/attribute_decorators_test.rb
+++ b/activerecord/test/cases/attribute_decorators_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/attribute_methods/read_test.rb b/activerecord/test/cases/attribute_methods/read_test.rb
index 934d5bf8b2..0170a6e98d 100644
--- a/activerecord/test/cases/attribute_methods/read_test.rb
+++ b/activerecord/test/cases/attribute_methods/read_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index 366577761c..0ea8ef5cea 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/minimalistic"
 require "models/developer"
diff --git a/activerecord/test/cases/attribute_set_test.rb b/activerecord/test/cases/attribute_set_test.rb
index bd4b200735..006372a757 100644
--- a/activerecord/test/cases/attribute_set_test.rb
+++ b/activerecord/test/cases/attribute_set_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/attribute_test.rb b/activerecord/test/cases/attribute_test.rb
index e856d551c0..1731e7926e 100644
--- a/activerecord/test/cases/attribute_test.rb
+++ b/activerecord/test/cases/attribute_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/attributes_test.rb b/activerecord/test/cases/attributes_test.rb
index 3705a6be89..29a25b4461 100644
--- a/activerecord/test/cases/attributes_test.rb
+++ b/activerecord/test/cases/attributes_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class OverloadedType < ActiveRecord::Base
diff --git a/activerecord/test/cases/autosave_association_test.rb b/activerecord/test/cases/autosave_association_test.rb
index 2203aa1788..c2e2bca924 100644
--- a/activerecord/test/cases/autosave_association_test.rb
+++ b/activerecord/test/cases/autosave_association_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/bird"
 require "models/post"
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index dc32e995a4..5dbb7f788a 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/author"
diff --git a/activerecord/test/cases/batches_test.rb b/activerecord/test/cases/batches_test.rb
index dcd3af487b..53c1e61ad1 100644
--- a/activerecord/test/cases/batches_test.rb
+++ b/activerecord/test/cases/batches_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/comment"
 require "models/post"
diff --git a/activerecord/test/cases/binary_test.rb b/activerecord/test/cases/binary_test.rb
index f6ac7990d1..d5376ece69 100644
--- a/activerecord/test/cases/binary_test.rb
+++ b/activerecord/test/cases/binary_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 # Without using prepared statements, it makes no sense to test
diff --git a/activerecord/test/cases/bind_parameter_test.rb b/activerecord/test/cases/bind_parameter_test.rb
index 5af44c27eb..ae8438722f 100644
--- a/activerecord/test/cases/bind_parameter_test.rb
+++ b/activerecord/test/cases/bind_parameter_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/author"
diff --git a/activerecord/test/cases/cache_key_test.rb b/activerecord/test/cases/cache_key_test.rb
index 7b8264e6e8..8f2f2c6186 100644
--- a/activerecord/test/cases/cache_key_test.rb
+++ b/activerecord/test/cases/cache_key_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index 7d6dc21e34..dd6815b149 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/book"
 require "models/club"
diff --git a/activerecord/test/cases/callbacks_test.rb b/activerecord/test/cases/callbacks_test.rb
index b3c86586d0..55c7475f46 100644
--- a/activerecord/test/cases/callbacks_test.rb
+++ b/activerecord/test/cases/callbacks_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/developer"
 require "models/computer"
diff --git a/activerecord/test/cases/clone_test.rb b/activerecord/test/cases/clone_test.rb
index b89294c094..3187e6aed5 100644
--- a/activerecord/test/cases/clone_test.rb
+++ b/activerecord/test/cases/clone_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 
diff --git a/activerecord/test/cases/coders/json_test.rb b/activerecord/test/cases/coders/json_test.rb
index d22d93d129..e40d576b39 100644
--- a/activerecord/test/cases/coders/json_test.rb
+++ b/activerecord/test/cases/coders/json_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/coders/yaml_column_test.rb b/activerecord/test/cases/coders/yaml_column_test.rb
index a26a72712d..4a5559c62f 100644
--- a/activerecord/test/cases/coders/yaml_column_test.rb
+++ b/activerecord/test/cases/coders/yaml_column_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/collection_cache_key_test.rb b/activerecord/test/cases/collection_cache_key_test.rb
index f344c77691..dbe6857487 100644
--- a/activerecord/test/cases/collection_cache_key_test.rb
+++ b/activerecord/test/cases/collection_cache_key_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/computer"
 require "models/developer"
diff --git a/activerecord/test/cases/column_alias_test.rb b/activerecord/test/cases/column_alias_test.rb
index 9893ba9580..a883d21fb8 100644
--- a/activerecord/test/cases/column_alias_test.rb
+++ b/activerecord/test/cases/column_alias_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 
diff --git a/activerecord/test/cases/column_definition_test.rb b/activerecord/test/cases/column_definition_test.rb
index 90c8d21c43..cbd2b44589 100644
--- a/activerecord/test/cases/column_definition_test.rb
+++ b/activerecord/test/cases/column_definition_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/comment_test.rb b/activerecord/test/cases/comment_test.rb
index c23be52a6c..27d042db47 100644
--- a/activerecord/test/cases/comment_test.rb
+++ b/activerecord/test/cases/comment_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/connection_adapters/adapter_leasing_test.rb b/activerecord/test/cases/connection_adapters/adapter_leasing_test.rb
index 64189381cb..82c6cf8dea 100644
--- a/activerecord/test/cases/connection_adapters/adapter_leasing_test.rb
+++ b/activerecord/test/cases/connection_adapters/adapter_leasing_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/connection_adapters/connection_handler_test.rb b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
index 2a71f08d90..74d0ed348e 100644
--- a/activerecord/test/cases/connection_adapters/connection_handler_test.rb
+++ b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/connection_adapters/connection_specification_test.rb b/activerecord/test/cases/connection_adapters/connection_specification_test.rb
index 10a3521c79..f81b73c344 100644
--- a/activerecord/test/cases/connection_adapters/connection_specification_test.rb
+++ b/activerecord/test/cases/connection_adapters/connection_specification_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/connection_adapters/merge_and_resolve_default_url_config_test.rb b/activerecord/test/cases/connection_adapters/merge_and_resolve_default_url_config_test.rb
index 8faa67255d..1b64324cc4 100644
--- a/activerecord/test/cases/connection_adapters/merge_and_resolve_default_url_config_test.rb
+++ b/activerecord/test/cases/connection_adapters/merge_and_resolve_default_url_config_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/connection_adapters/mysql_type_lookup_test.rb b/activerecord/test/cases/connection_adapters/mysql_type_lookup_test.rb
index 3657b8340d..521879cc2f 100644
--- a/activerecord/test/cases/connection_adapters/mysql_type_lookup_test.rb
+++ b/activerecord/test/cases/connection_adapters/mysql_type_lookup_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 if current_adapter?(:Mysql2Adapter)
diff --git a/activerecord/test/cases/connection_adapters/schema_cache_test.rb b/activerecord/test/cases/connection_adapters/schema_cache_test.rb
index 106323ccc9..006be9e65d 100644
--- a/activerecord/test/cases/connection_adapters/schema_cache_test.rb
+++ b/activerecord/test/cases/connection_adapters/schema_cache_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/connection_adapters/type_lookup_test.rb b/activerecord/test/cases/connection_adapters/type_lookup_test.rb
index a348c2d783..1c4ca2e23d 100644
--- a/activerecord/test/cases/connection_adapters/type_lookup_test.rb
+++ b/activerecord/test/cases/connection_adapters/type_lookup_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 unless current_adapter?(:PostgreSQLAdapter) # PostgreSQL does not use type strings for lookup
diff --git a/activerecord/test/cases/connection_management_test.rb b/activerecord/test/cases/connection_management_test.rb
index d1e946d401..9d6ecbde78 100644
--- a/activerecord/test/cases/connection_management_test.rb
+++ b/activerecord/test/cases/connection_management_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "rack"
 
diff --git a/activerecord/test/cases/connection_pool_test.rb b/activerecord/test/cases/connection_pool_test.rb
index 00a0187b57..2bfe490602 100644
--- a/activerecord/test/cases/connection_pool_test.rb
+++ b/activerecord/test/cases/connection_pool_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "concurrent/atomic/count_down_latch"
 
diff --git a/activerecord/test/cases/connection_specification/resolver_test.rb b/activerecord/test/cases/connection_specification/resolver_test.rb
index 13b5bae13c..3fa0ca8366 100644
--- a/activerecord/test/cases/connection_specification/resolver_test.rb
+++ b/activerecord/test/cases/connection_specification/resolver_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/core_test.rb b/activerecord/test/cases/core_test.rb
index 936f26ce04..356afdbd2b 100644
--- a/activerecord/test/cases/core_test.rb
+++ b/activerecord/test/cases/core_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/person"
 require "models/topic"
diff --git a/activerecord/test/cases/counter_cache_test.rb b/activerecord/test/cases/counter_cache_test.rb
index 46d7526cc0..e0948f90ac 100644
--- a/activerecord/test/cases/counter_cache_test.rb
+++ b/activerecord/test/cases/counter_cache_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/car"
diff --git a/activerecord/test/cases/custom_locking_test.rb b/activerecord/test/cases/custom_locking_test.rb
index 15c8b684e4..f52b26e9ec 100644
--- a/activerecord/test/cases/custom_locking_test.rb
+++ b/activerecord/test/cases/custom_locking_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/person"
 
diff --git a/activerecord/test/cases/database_statements_test.rb b/activerecord/test/cases/database_statements_test.rb
index 66035865be..1c934602ec 100644
--- a/activerecord/test/cases/database_statements_test.rb
+++ b/activerecord/test/cases/database_statements_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class DatabaseStatementsTest < ActiveRecord::TestCase
diff --git a/activerecord/test/cases/date_test.rb b/activerecord/test/cases/date_test.rb
index 2edc0415cd..9f412cdb63 100644
--- a/activerecord/test/cases/date_test.rb
+++ b/activerecord/test/cases/date_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 
diff --git a/activerecord/test/cases/date_time_precision_test.rb b/activerecord/test/cases/date_time_precision_test.rb
index e4a2f9ee17..51f6164138 100644
--- a/activerecord/test/cases/date_time_precision_test.rb
+++ b/activerecord/test/cases/date_time_precision_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/date_time_test.rb b/activerecord/test/cases/date_time_test.rb
index 6cd98fe254..b5f35aff0e 100644
--- a/activerecord/test/cases/date_time_test.rb
+++ b/activerecord/test/cases/date_time_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/task"
diff --git a/activerecord/test/cases/defaults_test.rb b/activerecord/test/cases/defaults_test.rb
index 996d298689..4690682cd8 100644
--- a/activerecord/test/cases/defaults_test.rb
+++ b/activerecord/test/cases/defaults_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 require "models/default"
diff --git a/activerecord/test/cases/dirty_test.rb b/activerecord/test/cases/dirty_test.rb
index bb584b0c6f..fb3d691d51 100644
--- a/activerecord/test/cases/dirty_test.rb
+++ b/activerecord/test/cases/dirty_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"    # For booleans
 require "models/pirate"   # For timestamps
diff --git a/activerecord/test/cases/disconnected_test.rb b/activerecord/test/cases/disconnected_test.rb
index c25089a420..533665d0f4 100644
--- a/activerecord/test/cases/disconnected_test.rb
+++ b/activerecord/test/cases/disconnected_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class TestRecord < ActiveRecord::Base
diff --git a/activerecord/test/cases/dup_test.rb b/activerecord/test/cases/dup_test.rb
index 000ed27efb..2fefdbf204 100644
--- a/activerecord/test/cases/dup_test.rb
+++ b/activerecord/test/cases/dup_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/reply"
 require "models/topic"
diff --git a/activerecord/test/cases/enum_test.rb b/activerecord/test/cases/enum_test.rb
index 4ef9a125e6..abbc011b34 100644
--- a/activerecord/test/cases/enum_test.rb
+++ b/activerecord/test/cases/enum_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/author"
 require "models/book"
diff --git a/activerecord/test/cases/errors_test.rb b/activerecord/test/cases/errors_test.rb
index e90669e0c7..b90e6a66c5 100644
--- a/activerecord/test/cases/errors_test.rb
+++ b/activerecord/test/cases/errors_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class ErrorsTest < ActiveRecord::TestCase
diff --git a/activerecord/test/cases/explain_subscriber_test.rb b/activerecord/test/cases/explain_subscriber_test.rb
index ca87e04012..fb698c47cd 100644
--- a/activerecord/test/cases/explain_subscriber_test.rb
+++ b/activerecord/test/cases/explain_subscriber_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "active_record/explain_subscriber"
 require "active_record/explain_registry"
diff --git a/activerecord/test/cases/explain_test.rb b/activerecord/test/cases/explain_test.rb
index 4f6bd9327c..9f532def8f 100644
--- a/activerecord/test/cases/explain_test.rb
+++ b/activerecord/test/cases/explain_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/car"
 require "active_support/core_ext/string/strip"
diff --git a/activerecord/test/cases/finder_respond_to_test.rb b/activerecord/test/cases/finder_respond_to_test.rb
index 3eaa993d45..4039af66d0 100644
--- a/activerecord/test/cases/finder_respond_to_test.rb
+++ b/activerecord/test/cases/finder_respond_to_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 
diff --git a/activerecord/test/cases/finder_test.rb b/activerecord/test/cases/finder_test.rb
index af21cd529f..0b4dce37cc 100644
--- a/activerecord/test/cases/finder_test.rb
+++ b/activerecord/test/cases/finder_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/author"
diff --git a/activerecord/test/cases/fixture_set/file_test.rb b/activerecord/test/cases/fixture_set/file_test.rb
index 533edcc2e0..ff99988cb5 100644
--- a/activerecord/test/cases/fixture_set/file_test.rb
+++ b/activerecord/test/cases/fixture_set/file_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "tempfile"
 
diff --git a/activerecord/test/cases/fixtures_test.rb b/activerecord/test/cases/fixtures_test.rb
index b499e60922..8197d09621 100644
--- a/activerecord/test/cases/fixtures_test.rb
+++ b/activerecord/test/cases/fixtures_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/admin"
 require "models/admin/account"
diff --git a/activerecord/test/cases/forbidden_attributes_protection_test.rb b/activerecord/test/cases/forbidden_attributes_protection_test.rb
index ffa3f63e0d..101fa118c8 100644
--- a/activerecord/test/cases/forbidden_attributes_protection_test.rb
+++ b/activerecord/test/cases/forbidden_attributes_protection_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "active_support/core_ext/hash/indifferent_access"
 
diff --git a/activerecord/test/cases/habtm_destroy_order_test.rb b/activerecord/test/cases/habtm_destroy_order_test.rb
index 365d4576dd..5e503272e1 100644
--- a/activerecord/test/cases/habtm_destroy_order_test.rb
+++ b/activerecord/test/cases/habtm_destroy_order_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/lesson"
 require "models/student"
diff --git a/activerecord/test/cases/helper.rb b/activerecord/test/cases/helper.rb
index 5a3b8e3fb5..36fc143a31 100644
--- a/activerecord/test/cases/helper.rb
+++ b/activerecord/test/cases/helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "config"
 
 require "stringio"
diff --git a/activerecord/test/cases/hot_compatibility_test.rb b/activerecord/test/cases/hot_compatibility_test.rb
index e107ff2362..e7778af55b 100644
--- a/activerecord/test/cases/hot_compatibility_test.rb
+++ b/activerecord/test/cases/hot_compatibility_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/connection_helper"
 
diff --git a/activerecord/test/cases/i18n_test.rb b/activerecord/test/cases/i18n_test.rb
index 7f03c5b23d..22981c142a 100644
--- a/activerecord/test/cases/i18n_test.rb
+++ b/activerecord/test/cases/i18n_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/reply"
diff --git a/activerecord/test/cases/inheritance_test.rb b/activerecord/test/cases/inheritance_test.rb
index a54480fdb4..6877968790 100644
--- a/activerecord/test/cases/inheritance_test.rb
+++ b/activerecord/test/cases/inheritance_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/author"
 require "models/company"
diff --git a/activerecord/test/cases/integration_test.rb b/activerecord/test/cases/integration_test.rb
index 9104976126..36cd63c4d4 100644
--- a/activerecord/test/cases/integration_test.rb
+++ b/activerecord/test/cases/integration_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/company"
 require "models/developer"
diff --git a/activerecord/test/cases/invalid_connection_test.rb b/activerecord/test/cases/invalid_connection_test.rb
index 1367af2859..a1be9c2780 100644
--- a/activerecord/test/cases/invalid_connection_test.rb
+++ b/activerecord/test/cases/invalid_connection_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 if current_adapter?(:Mysql2Adapter)
diff --git a/activerecord/test/cases/invertible_migration_test.rb b/activerecord/test/cases/invertible_migration_test.rb
index cc3951e2ba..20e747142b 100644
--- a/activerecord/test/cases/invertible_migration_test.rb
+++ b/activerecord/test/cases/invertible_migration_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class Horse < ActiveRecord::Base
diff --git a/activerecord/test/cases/json_attribute_test.rb b/activerecord/test/cases/json_attribute_test.rb
index e5848b45f8..63f3c77fc3 100644
--- a/activerecord/test/cases/json_attribute_test.rb
+++ b/activerecord/test/cases/json_attribute_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "cases/json_shared_test_cases"
 
diff --git a/activerecord/test/cases/json_serialization_test.rb b/activerecord/test/cases/json_serialization_test.rb
index a6ea27bf48..52fe488cd5 100644
--- a/activerecord/test/cases/json_serialization_test.rb
+++ b/activerecord/test/cases/json_serialization_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/contact"
 require "models/post"
diff --git a/activerecord/test/cases/json_shared_test_cases.rb b/activerecord/test/cases/json_shared_test_cases.rb
index 9a1c1c3f3f..f708acf0aa 100644
--- a/activerecord/test/cases/json_shared_test_cases.rb
+++ b/activerecord/test/cases/json_shared_test_cases.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "support/schema_dumping_helper"
 
 module JSONSharedTestCases
diff --git a/activerecord/test/cases/locking_test.rb b/activerecord/test/cases/locking_test.rb
index 2fc52393f2..743680ba92 100644
--- a/activerecord/test/cases/locking_test.rb
+++ b/activerecord/test/cases/locking_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "thread"
 require "cases/helper"
 require "models/person"
diff --git a/activerecord/test/cases/log_subscriber_test.rb b/activerecord/test/cases/log_subscriber_test.rb
index b80257962c..208e54ed0b 100644
--- a/activerecord/test/cases/log_subscriber_test.rb
+++ b/activerecord/test/cases/log_subscriber_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/binary"
 require "models/developer"
diff --git a/activerecord/test/cases/migration/change_schema_test.rb b/activerecord/test/cases/migration/change_schema_test.rb
index 1d305fa11f..04e2d3a052 100644
--- a/activerecord/test/cases/migration/change_schema_test.rb
+++ b/activerecord/test/cases/migration/change_schema_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/migration/change_table_test.rb b/activerecord/test/cases/migration/change_table_test.rb
index ec817a579b..034bf32165 100644
--- a/activerecord/test/cases/migration/change_table_test.rb
+++ b/activerecord/test/cases/migration/change_table_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/migration/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/migration/column_attributes_test.rb b/activerecord/test/cases/migration/column_attributes_test.rb
index 48df931543..9200d32caf 100644
--- a/activerecord/test/cases/migration/column_attributes_test.rb
+++ b/activerecord/test/cases/migration/column_attributes_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/migration/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/migration/column_positioning_test.rb b/activerecord/test/cases/migration/column_positioning_test.rb
index f2162d91b1..23414419dc 100644
--- a/activerecord/test/cases/migration/column_positioning_test.rb
+++ b/activerecord/test/cases/migration/column_positioning_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/migration/columns_test.rb b/activerecord/test/cases/migration/columns_test.rb
index 2329888345..1b1d0af132 100644
--- a/activerecord/test/cases/migration/columns_test.rb
+++ b/activerecord/test/cases/migration/columns_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/migration/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/migration/command_recorder_test.rb b/activerecord/test/cases/migration/command_recorder_test.rb
index 007926f1b9..0b5e983f14 100644
--- a/activerecord/test/cases/migration/command_recorder_test.rb
+++ b/activerecord/test/cases/migration/command_recorder_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/migration/compatibility_test.rb b/activerecord/test/cases/migration/compatibility_test.rb
index 596a21dcbc..cb3b02c02a 100644
--- a/activerecord/test/cases/migration/compatibility_test.rb
+++ b/activerecord/test/cases/migration/compatibility_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/migration/create_join_table_test.rb b/activerecord/test/cases/migration/create_join_table_test.rb
index c4896f3d6e..77d32a24a5 100644
--- a/activerecord/test/cases/migration/create_join_table_test.rb
+++ b/activerecord/test/cases/migration/create_join_table_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/migration/foreign_key_test.rb b/activerecord/test/cases/migration/foreign_key_test.rb
index 7762d37915..499d072de5 100644
--- a/activerecord/test/cases/migration/foreign_key_test.rb
+++ b/activerecord/test/cases/migration/foreign_key_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/migration/helper.rb b/activerecord/test/cases/migration/helper.rb
index 9c0fa7339d..c056199140 100644
--- a/activerecord/test/cases/migration/helper.rb
+++ b/activerecord/test/cases/migration/helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/migration/index_test.rb b/activerecord/test/cases/migration/index_test.rb
index f10fcf1398..bf1ebdb4c5 100644
--- a/activerecord/test/cases/migration/index_test.rb
+++ b/activerecord/test/cases/migration/index_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/migration/logger_test.rb b/activerecord/test/cases/migration/logger_test.rb
index 3d7c7ad469..28f4cc124b 100644
--- a/activerecord/test/cases/migration/logger_test.rb
+++ b/activerecord/test/cases/migration/logger_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/migration/pending_migrations_test.rb b/activerecord/test/cases/migration/pending_migrations_test.rb
index 6970fdcc87..d0066f68be 100644
--- a/activerecord/test/cases/migration/pending_migrations_test.rb
+++ b/activerecord/test/cases/migration/pending_migrations_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/migration/references_foreign_key_test.rb b/activerecord/test/cases/migration/references_foreign_key_test.rb
index 718b9a0613..7a092103c7 100644
--- a/activerecord/test/cases/migration/references_foreign_key_test.rb
+++ b/activerecord/test/cases/migration/references_foreign_key_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 if ActiveRecord::Base.connection.supports_foreign_keys_in_create?
diff --git a/activerecord/test/cases/migration/references_index_test.rb b/activerecord/test/cases/migration/references_index_test.rb
index 2866cabab6..e41377d817 100644
--- a/activerecord/test/cases/migration/references_index_test.rb
+++ b/activerecord/test/cases/migration/references_index_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/migration/references_statements_test.rb b/activerecord/test/cases/migration/references_statements_test.rb
index e9eb9968cb..769241ba12 100644
--- a/activerecord/test/cases/migration/references_statements_test.rb
+++ b/activerecord/test/cases/migration/references_statements_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/migration/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/migration/rename_table_test.rb b/activerecord/test/cases/migration/rename_table_test.rb
index 5da3ad33a3..dfce266253 100644
--- a/activerecord/test/cases/migration/rename_table_test.rb
+++ b/activerecord/test/cases/migration/rename_table_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/migration/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/migration_test.rb b/activerecord/test/cases/migration_test.rb
index eff6e09eb7..0fa43583ac 100644
--- a/activerecord/test/cases/migration_test.rb
+++ b/activerecord/test/cases/migration_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "cases/migration/helper"
 require "bigdecimal/util"
@@ -912,7 +914,7 @@ class CopyMigrationsTest < ActiveRecord::TestCase
     assert_equal [@migrations_path + "/4_people_have_hobbies.bukkits.rb", @migrations_path + "/5_people_have_descriptions.bukkits.rb"], copied.map(&:filename)
 
     expected = "# This migration comes from bukkits (originally 1)"
-    assert_equal expected, IO.readlines(@migrations_path + "/4_people_have_hobbies.bukkits.rb")[0].chomp
+    assert_equal expected, IO.readlines(@migrations_path + "/4_people_have_hobbies.bukkits.rb")[1].chomp
 
     files_count = Dir[@migrations_path + "/*.rb"].length
     copied = ActiveRecord::Migration.copy(@migrations_path, bukkits: MIGRATIONS_ROOT + "/to_copy")
diff --git a/activerecord/test/cases/migrator_test.rb b/activerecord/test/cases/migrator_test.rb
index 2e4b454a86..ee10be119c 100644
--- a/activerecord/test/cases/migrator_test.rb
+++ b/activerecord/test/cases/migrator_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "cases/migration/helper"
 
diff --git a/activerecord/test/cases/mixin_test.rb b/activerecord/test/cases/mixin_test.rb
index a8af8e30f7..5f5205f3a0 100644
--- a/activerecord/test/cases/mixin_test.rb
+++ b/activerecord/test/cases/mixin_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class Mixin < ActiveRecord::Base
diff --git a/activerecord/test/cases/modules_test.rb b/activerecord/test/cases/modules_test.rb
index f8a7bab35f..060d555607 100644
--- a/activerecord/test/cases/modules_test.rb
+++ b/activerecord/test/cases/modules_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/company_in_module"
 require "models/shop"
diff --git a/activerecord/test/cases/multiparameter_attributes_test.rb b/activerecord/test/cases/multiparameter_attributes_test.rb
index aa521e907c..59be4dc5a8 100644
--- a/activerecord/test/cases/multiparameter_attributes_test.rb
+++ b/activerecord/test/cases/multiparameter_attributes_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/customer"
diff --git a/activerecord/test/cases/multiple_db_test.rb b/activerecord/test/cases/multiple_db_test.rb
index 4e3daeabb6..192d2f5251 100644
--- a/activerecord/test/cases/multiple_db_test.rb
+++ b/activerecord/test/cases/multiple_db_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/entrant"
 require "models/bird"
diff --git a/activerecord/test/cases/nested_attributes_test.rb b/activerecord/test/cases/nested_attributes_test.rb
index 154faa56aa..a2ccb603a9 100644
--- a/activerecord/test/cases/nested_attributes_test.rb
+++ b/activerecord/test/cases/nested_attributes_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/pirate"
 require "models/ship"
diff --git a/activerecord/test/cases/nested_attributes_with_callbacks_test.rb b/activerecord/test/cases/nested_attributes_with_callbacks_test.rb
index b9d2acbed2..f04c68b08f 100644
--- a/activerecord/test/cases/nested_attributes_with_callbacks_test.rb
+++ b/activerecord/test/cases/nested_attributes_with_callbacks_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/pirate"
 require "models/bird"
diff --git a/activerecord/test/cases/numeric_data_test.rb b/activerecord/test/cases/numeric_data_test.rb
index 76b97033af..f917c8f727 100644
--- a/activerecord/test/cases/numeric_data_test.rb
+++ b/activerecord/test/cases/numeric_data_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/numeric_data"
 
diff --git a/activerecord/test/cases/persistence_test.rb b/activerecord/test/cases/persistence_test.rb
index 5830f9916a..33a4cc0dcb 100644
--- a/activerecord/test/cases/persistence_test.rb
+++ b/activerecord/test/cases/persistence_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/aircraft"
 require "models/post"
diff --git a/activerecord/test/cases/pooled_connections_test.rb b/activerecord/test/cases/pooled_connections_test.rb
index f1b0d08765..fa7f759e51 100644
--- a/activerecord/test/cases/pooled_connections_test.rb
+++ b/activerecord/test/cases/pooled_connections_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/project"
 require "timeout"
diff --git a/activerecord/test/cases/primary_keys_test.rb b/activerecord/test/cases/primary_keys_test.rb
index 56229b70bc..bda82c095f 100644
--- a/activerecord/test/cases/primary_keys_test.rb
+++ b/activerecord/test/cases/primary_keys_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 require "models/topic"
diff --git a/activerecord/test/cases/query_cache_test.rb b/activerecord/test/cases/query_cache_test.rb
index b018a7b6c0..3a2bd62997 100644
--- a/activerecord/test/cases/query_cache_test.rb
+++ b/activerecord/test/cases/query_cache_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/task"
diff --git a/activerecord/test/cases/quoting_test.rb b/activerecord/test/cases/quoting_test.rb
index 98b20915c6..59d3bbb573 100644
--- a/activerecord/test/cases/quoting_test.rb
+++ b/activerecord/test/cases/quoting_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/readonly_test.rb b/activerecord/test/cases/readonly_test.rb
index 24b678310d..d1b85cb4ef 100644
--- a/activerecord/test/cases/readonly_test.rb
+++ b/activerecord/test/cases/readonly_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/author"
 require "models/post"
diff --git a/activerecord/test/cases/reaper_test.rb b/activerecord/test/cases/reaper_test.rb
index 249878b67d..49170abe6f 100644
--- a/activerecord/test/cases/reaper_test.rb
+++ b/activerecord/test/cases/reaper_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/reflection_test.rb b/activerecord/test/cases/reflection_test.rb
index c1c2efb9c8..4cd2d3aedc 100644
--- a/activerecord/test/cases/reflection_test.rb
+++ b/activerecord/test/cases/reflection_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/customer"
diff --git a/activerecord/test/cases/relation/delegation_test.rb b/activerecord/test/cases/relation/delegation_test.rb
index 3b15f051b2..341335be9b 100644
--- a/activerecord/test/cases/relation/delegation_test.rb
+++ b/activerecord/test/cases/relation/delegation_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/comment"
diff --git a/activerecord/test/cases/relation/merging_test.rb b/activerecord/test/cases/relation/merging_test.rb
index 3901824aac..44e2b16923 100644
--- a/activerecord/test/cases/relation/merging_test.rb
+++ b/activerecord/test/cases/relation/merging_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/author"
 require "models/comment"
diff --git a/activerecord/test/cases/relation/mutation_test.rb b/activerecord/test/cases/relation/mutation_test.rb
index a37a2186ed..ad3700b73a 100644
--- a/activerecord/test/cases/relation/mutation_test.rb
+++ b/activerecord/test/cases/relation/mutation_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 
diff --git a/activerecord/test/cases/relation/or_test.rb b/activerecord/test/cases/relation/or_test.rb
index 61b6601580..3269620987 100644
--- a/activerecord/test/cases/relation/or_test.rb
+++ b/activerecord/test/cases/relation/or_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 
diff --git a/activerecord/test/cases/relation/predicate_builder_test.rb b/activerecord/test/cases/relation/predicate_builder_test.rb
index 48758dc148..b432330deb 100644
--- a/activerecord/test/cases/relation/predicate_builder_test.rb
+++ b/activerecord/test/cases/relation/predicate_builder_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 
diff --git a/activerecord/test/cases/relation/record_fetch_warning_test.rb b/activerecord/test/cases/relation/record_fetch_warning_test.rb
index 62ca051431..22d32d75bc 100644
--- a/activerecord/test/cases/relation/record_fetch_warning_test.rb
+++ b/activerecord/test/cases/relation/record_fetch_warning_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "active_record/relation/record_fetch_warning"
diff --git a/activerecord/test/cases/relation/where_chain_test.rb b/activerecord/test/cases/relation/where_chain_test.rb
index 86e150ed79..064446157f 100644
--- a/activerecord/test/cases/relation/where_chain_test.rb
+++ b/activerecord/test/cases/relation/where_chain_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/comment"
diff --git a/activerecord/test/cases/relation/where_clause_test.rb b/activerecord/test/cases/relation/where_clause_test.rb
index 57d7b315b0..b68d416697 100644
--- a/activerecord/test/cases/relation/where_clause_test.rb
+++ b/activerecord/test/cases/relation/where_clause_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class ActiveRecord::Relation
diff --git a/activerecord/test/cases/relation/where_test.rb b/activerecord/test/cases/relation/where_test.rb
index 42dae4d569..977165cf2e 100644
--- a/activerecord/test/cases/relation/where_test.rb
+++ b/activerecord/test/cases/relation/where_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/author"
 require "models/binary"
diff --git a/activerecord/test/cases/relation_test.rb b/activerecord/test/cases/relation_test.rb
index 82b071fb98..b1e14f8dc4 100644
--- a/activerecord/test/cases/relation_test.rb
+++ b/activerecord/test/cases/relation_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/comment"
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 316ea75e36..e1b2f794ac 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/tag"
 require "models/tagging"
diff --git a/activerecord/test/cases/reload_models_test.rb b/activerecord/test/cases/reload_models_test.rb
index 3f4c0c03e3..67386725cb 100644
--- a/activerecord/test/cases/reload_models_test.rb
+++ b/activerecord/test/cases/reload_models_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/owner"
 require "models/pet"
diff --git a/activerecord/test/cases/reserved_word_test.rb b/activerecord/test/cases/reserved_word_test.rb
index f3019a5326..0214dbec17 100644
--- a/activerecord/test/cases/reserved_word_test.rb
+++ b/activerecord/test/cases/reserved_word_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class ReservedWordTest < ActiveRecord::TestCase
diff --git a/activerecord/test/cases/result_test.rb b/activerecord/test/cases/result_test.rb
index 1a0b7c6ca7..db52c108ac 100644
--- a/activerecord/test/cases/result_test.rb
+++ b/activerecord/test/cases/result_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/sanitize_test.rb b/activerecord/test/cases/sanitize_test.rb
index 72f09186e2..082d663675 100644
--- a/activerecord/test/cases/sanitize_test.rb
+++ b/activerecord/test/cases/sanitize_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/binary"
 require "models/author"
diff --git a/activerecord/test/cases/schema_dumper_test.rb b/activerecord/test/cases/schema_dumper_test.rb
index 4c81e825fa..194fceb0f3 100644
--- a/activerecord/test/cases/schema_dumper_test.rb
+++ b/activerecord/test/cases/schema_dumper_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/schema_loading_test.rb b/activerecord/test/cases/schema_loading_test.rb
index 362370ac61..f539156466 100644
--- a/activerecord/test/cases/schema_loading_test.rb
+++ b/activerecord/test/cases/schema_loading_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module SchemaLoadCounter
diff --git a/activerecord/test/cases/scoping/default_scoping_test.rb b/activerecord/test/cases/scoping/default_scoping_test.rb
index a8c79628e7..6f035b594b 100644
--- a/activerecord/test/cases/scoping/default_scoping_test.rb
+++ b/activerecord/test/cases/scoping/default_scoping_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/comment"
diff --git a/activerecord/test/cases/scoping/named_scoping_test.rb b/activerecord/test/cases/scoping/named_scoping_test.rb
index 483ea7128d..1db7432e34 100644
--- a/activerecord/test/cases/scoping/named_scoping_test.rb
+++ b/activerecord/test/cases/scoping/named_scoping_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/topic"
diff --git a/activerecord/test/cases/scoping/relation_scoping_test.rb b/activerecord/test/cases/scoping/relation_scoping_test.rb
index 10553bf057..f3b84d88c2 100644
--- a/activerecord/test/cases/scoping/relation_scoping_test.rb
+++ b/activerecord/test/cases/scoping/relation_scoping_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/post"
 require "models/author"
diff --git a/activerecord/test/cases/secure_token_test.rb b/activerecord/test/cases/secure_token_test.rb
index 7b9cbee40a..f5fa6aa302 100644
--- a/activerecord/test/cases/secure_token_test.rb
+++ b/activerecord/test/cases/secure_token_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/user"
 
diff --git a/activerecord/test/cases/serialization_test.rb b/activerecord/test/cases/serialization_test.rb
index ec33ad38f2..2d829ad4ba 100644
--- a/activerecord/test/cases/serialization_test.rb
+++ b/activerecord/test/cases/serialization_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/contact"
 require "models/topic"
diff --git a/activerecord/test/cases/serialized_attribute_test.rb b/activerecord/test/cases/serialized_attribute_test.rb
index e1bdaab5cf..32dafbd458 100644
--- a/activerecord/test/cases/serialized_attribute_test.rb
+++ b/activerecord/test/cases/serialized_attribute_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/reply"
diff --git a/activerecord/test/cases/statement_cache_test.rb b/activerecord/test/cases/statement_cache_test.rb
index fab3648564..e2142267ea 100644
--- a/activerecord/test/cases/statement_cache_test.rb
+++ b/activerecord/test/cases/statement_cache_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/book"
 require "models/liquid"
diff --git a/activerecord/test/cases/store_test.rb b/activerecord/test/cases/store_test.rb
index 633a8a0ebc..ebf4016960 100644
--- a/activerecord/test/cases/store_test.rb
+++ b/activerecord/test/cases/store_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/admin"
 require "models/admin/user"
diff --git a/activerecord/test/cases/suppressor_test.rb b/activerecord/test/cases/suppressor_test.rb
index a7d16b7cdb..b68f0033d9 100644
--- a/activerecord/test/cases/suppressor_test.rb
+++ b/activerecord/test/cases/suppressor_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/notification"
 require "models/user"
diff --git a/activerecord/test/cases/tasks/database_tasks_test.rb b/activerecord/test/cases/tasks/database_tasks_test.rb
index c47c97e9d9..1495d2ab89 100644
--- a/activerecord/test/cases/tasks/database_tasks_test.rb
+++ b/activerecord/test/cases/tasks/database_tasks_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "active_record/tasks/database_tasks"
 
diff --git a/activerecord/test/cases/tasks/mysql_rake_test.rb b/activerecord/test/cases/tasks/mysql_rake_test.rb
index 9c6fb14376..98fe24baa0 100644
--- a/activerecord/test/cases/tasks/mysql_rake_test.rb
+++ b/activerecord/test/cases/tasks/mysql_rake_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "active_record/tasks/database_tasks"
 
diff --git a/activerecord/test/cases/tasks/postgresql_rake_test.rb b/activerecord/test/cases/tasks/postgresql_rake_test.rb
index a2e968aedf..693503250b 100644
--- a/activerecord/test/cases/tasks/postgresql_rake_test.rb
+++ b/activerecord/test/cases/tasks/postgresql_rake_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "active_record/tasks/database_tasks"
 
diff --git a/activerecord/test/cases/tasks/sqlite_rake_test.rb b/activerecord/test/cases/tasks/sqlite_rake_test.rb
index ccb3834fee..8ac4878c37 100644
--- a/activerecord/test/cases/tasks/sqlite_rake_test.rb
+++ b/activerecord/test/cases/tasks/sqlite_rake_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "active_record/tasks/database_tasks"
 require "pathname"
diff --git a/activerecord/test/cases/test_case.rb b/activerecord/test/cases/test_case.rb
index 9f594fef85..97644b0b7d 100644
--- a/activerecord/test/cases/test_case.rb
+++ b/activerecord/test/cases/test_case.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/test_case"
 require "active_support/testing/autorun"
 require "active_support/testing/method_call_assertions"
diff --git a/activerecord/test/cases/test_fixtures_test.rb b/activerecord/test/cases/test_fixtures_test.rb
index 58d3bea3a2..4411410eda 100644
--- a/activerecord/test/cases/test_fixtures_test.rb
+++ b/activerecord/test/cases/test_fixtures_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class TestFixturesTest < ActiveRecord::TestCase
diff --git a/activerecord/test/cases/time_precision_test.rb b/activerecord/test/cases/time_precision_test.rb
index 09c585167e..41455637bb 100644
--- a/activerecord/test/cases/time_precision_test.rb
+++ b/activerecord/test/cases/time_precision_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/schema_dumping_helper"
 
diff --git a/activerecord/test/cases/timestamp_test.rb b/activerecord/test/cases/timestamp_test.rb
index 39b40e3411..ba0bc6c45d 100644
--- a/activerecord/test/cases/timestamp_test.rb
+++ b/activerecord/test/cases/timestamp_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "support/ddl_helper"
 require "models/developer"
diff --git a/activerecord/test/cases/touch_later_test.rb b/activerecord/test/cases/touch_later_test.rb
index d1e8c649d9..1757031371 100644
--- a/activerecord/test/cases/touch_later_test.rb
+++ b/activerecord/test/cases/touch_later_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/invoice"
 require "models/line_item"
diff --git a/activerecord/test/cases/transaction_callbacks_test.rb b/activerecord/test/cases/transaction_callbacks_test.rb
index eaa4dd09a9..1f370a80ee 100644
--- a/activerecord/test/cases/transaction_callbacks_test.rb
+++ b/activerecord/test/cases/transaction_callbacks_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/owner"
 require "models/pet"
diff --git a/activerecord/test/cases/transaction_isolation_test.rb b/activerecord/test/cases/transaction_isolation_test.rb
index 58abfadaf4..b1ebccdcc3 100644
--- a/activerecord/test/cases/transaction_isolation_test.rb
+++ b/activerecord/test/cases/transaction_isolation_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 unless ActiveRecord::Base.connection.supports_transaction_isolation?
diff --git a/activerecord/test/cases/transactions_test.rb b/activerecord/test/cases/transactions_test.rb
index 76a997ba8b..b771a1d12c 100644
--- a/activerecord/test/cases/transactions_test.rb
+++ b/activerecord/test/cases/transactions_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/reply"
diff --git a/activerecord/test/cases/type/adapter_specific_registry_test.rb b/activerecord/test/cases/type/adapter_specific_registry_test.rb
index 8b836b4793..b58bdd5549 100644
--- a/activerecord/test/cases/type/adapter_specific_registry_test.rb
+++ b/activerecord/test/cases/type/adapter_specific_registry_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/type/date_time_test.rb b/activerecord/test/cases/type/date_time_test.rb
index 6848619ece..c9558e25b5 100644
--- a/activerecord/test/cases/type/date_time_test.rb
+++ b/activerecord/test/cases/type/date_time_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/task"
 
diff --git a/activerecord/test/cases/type/integer_test.rb b/activerecord/test/cases/type/integer_test.rb
index 368b6d7199..15d1a675a1 100644
--- a/activerecord/test/cases/type/integer_test.rb
+++ b/activerecord/test/cases/type/integer_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/company"
 
diff --git a/activerecord/test/cases/type/string_test.rb b/activerecord/test/cases/type/string_test.rb
index a95da864fa..8c51b30fdd 100644
--- a/activerecord/test/cases/type/string_test.rb
+++ b/activerecord/test/cases/type/string_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/type/type_map_test.rb b/activerecord/test/cases/type/type_map_test.rb
index 2959d36466..f3699c11a2 100644
--- a/activerecord/test/cases/type/type_map_test.rb
+++ b/activerecord/test/cases/type/type_map_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/type/unsigned_integer_test.rb b/activerecord/test/cases/type/unsigned_integer_test.rb
index 1cd4dbc2c5..dd05cf3fff 100644
--- a/activerecord/test/cases/type/unsigned_integer_test.rb
+++ b/activerecord/test/cases/type/unsigned_integer_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/type_test.rb b/activerecord/test/cases/type_test.rb
index d45a9b3141..93ae563c8b 100644
--- a/activerecord/test/cases/type_test.rb
+++ b/activerecord/test/cases/type_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class TypeTest < ActiveRecord::TestCase
diff --git a/activerecord/test/cases/types_test.rb b/activerecord/test/cases/types_test.rb
index 11476ea0ef..3f7fb0a604 100644
--- a/activerecord/test/cases/types_test.rb
+++ b/activerecord/test/cases/types_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 module ActiveRecord
diff --git a/activerecord/test/cases/unconnected_test.rb b/activerecord/test/cases/unconnected_test.rb
index b210584644..f4d8be5897 100644
--- a/activerecord/test/cases/unconnected_test.rb
+++ b/activerecord/test/cases/unconnected_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 
 class TestRecord < ActiveRecord::Base
diff --git a/activerecord/test/cases/validations/absence_validation_test.rb b/activerecord/test/cases/validations/absence_validation_test.rb
index 870619e4e7..a997f8be9c 100644
--- a/activerecord/test/cases/validations/absence_validation_test.rb
+++ b/activerecord/test/cases/validations/absence_validation_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/face"
 require "models/interest"
diff --git a/activerecord/test/cases/validations/association_validation_test.rb b/activerecord/test/cases/validations/association_validation_test.rb
index f5ceb27d97..80fe375ae5 100644
--- a/activerecord/test/cases/validations/association_validation_test.rb
+++ b/activerecord/test/cases/validations/association_validation_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/reply"
diff --git a/activerecord/test/cases/validations/i18n_generate_message_validation_test.rb b/activerecord/test/cases/validations/i18n_generate_message_validation_test.rb
index a57065ba75..703c24b340 100644
--- a/activerecord/test/cases/validations/i18n_generate_message_validation_test.rb
+++ b/activerecord/test/cases/validations/i18n_generate_message_validation_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 
diff --git a/activerecord/test/cases/validations/i18n_validation_test.rb b/activerecord/test/cases/validations/i18n_validation_test.rb
index fd88a3ea67..b7c52ea18c 100644
--- a/activerecord/test/cases/validations/i18n_validation_test.rb
+++ b/activerecord/test/cases/validations/i18n_validation_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/reply"
diff --git a/activerecord/test/cases/validations/length_validation_test.rb b/activerecord/test/cases/validations/length_validation_test.rb
index ba45c6dcc1..87ce4c6f37 100644
--- a/activerecord/test/cases/validations/length_validation_test.rb
+++ b/activerecord/test/cases/validations/length_validation_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/owner"
 require "models/pet"
diff --git a/activerecord/test/cases/validations/presence_validation_test.rb b/activerecord/test/cases/validations/presence_validation_test.rb
index 13956e26ec..3ab1567b51 100644
--- a/activerecord/test/cases/validations/presence_validation_test.rb
+++ b/activerecord/test/cases/validations/presence_validation_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/man"
 require "models/face"
diff --git a/activerecord/test/cases/validations/uniqueness_validation_test.rb b/activerecord/test/cases/validations/uniqueness_validation_test.rb
index 28605d2f8e..fad55916c7 100644
--- a/activerecord/test/cases/validations/uniqueness_validation_test.rb
+++ b/activerecord/test/cases/validations/uniqueness_validation_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/reply"
diff --git a/activerecord/test/cases/validations_repair_helper.rb b/activerecord/test/cases/validations_repair_helper.rb
index b30666d876..6dc3b64b2b 100644
--- a/activerecord/test/cases/validations_repair_helper.rb
+++ b/activerecord/test/cases/validations_repair_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ValidationsRepairHelper
     extend ActiveSupport::Concern
diff --git a/activerecord/test/cases/validations_test.rb b/activerecord/test/cases/validations_test.rb
index a305aa295a..7f84939027 100644
--- a/activerecord/test/cases/validations_test.rb
+++ b/activerecord/test/cases/validations_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/reply"
diff --git a/activerecord/test/cases/view_test.rb b/activerecord/test/cases/view_test.rb
index 1d21a2454f..7e2d66c62a 100644
--- a/activerecord/test/cases/view_test.rb
+++ b/activerecord/test/cases/view_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/book"
 require "support/schema_dumping_helper"
diff --git a/activerecord/test/cases/yaml_serialization_test.rb b/activerecord/test/cases/yaml_serialization_test.rb
index dd8d2c1178..578881f754 100644
--- a/activerecord/test/cases/yaml_serialization_test.rb
+++ b/activerecord/test/cases/yaml_serialization_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/topic"
 require "models/reply"
diff --git a/activerecord/test/config.rb b/activerecord/test/config.rb
index a65e6ff776..72cdfb16ef 100644
--- a/activerecord/test/config.rb
+++ b/activerecord/test/config.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 TEST_ROOT       = __dir__
 ASSETS_ROOT     = TEST_ROOT + "/assets"
 FIXTURES_ROOT   = TEST_ROOT + "/fixtures"
diff --git a/activerecord/test/migrations/10_urban/9_add_expressions.rb b/activerecord/test/migrations/10_urban/9_add_expressions.rb
index e908c9eabc..4b0d5fb6fa 100644
--- a/activerecord/test/migrations/10_urban/9_add_expressions.rb
+++ b/activerecord/test/migrations/10_urban/9_add_expressions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddExpressions < ActiveRecord::Migration::Current
   def self.up
     create_table("expressions") do |t|
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 43c79bc20b..b892f50e41 100644
--- a/activerecord/test/migrations/decimal/1_give_me_big_numbers.rb
+++ b/activerecord/test/migrations/decimal/1_give_me_big_numbers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class GiveMeBigNumbers < ActiveRecord::Migration::Current
   def self.up
     create_table :big_numbers do |table|
diff --git a/activerecord/test/migrations/missing/1000_people_have_middle_names.rb b/activerecord/test/migrations/missing/1000_people_have_middle_names.rb
index e046944e31..d3c9b127fb 100644
--- a/activerecord/test/migrations/missing/1000_people_have_middle_names.rb
+++ b/activerecord/test/migrations/missing/1000_people_have_middle_names.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PeopleHaveMiddleNames < ActiveRecord::Migration::Current
   def self.up
     add_column "people", "middle_name", :string
diff --git a/activerecord/test/migrations/missing/1_people_have_last_names.rb b/activerecord/test/migrations/missing/1_people_have_last_names.rb
index 50fe2a9c8e..bd5f5ea11e 100644
--- a/activerecord/test/migrations/missing/1_people_have_last_names.rb
+++ b/activerecord/test/migrations/missing/1_people_have_last_names.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PeopleHaveLastNames < ActiveRecord::Migration::Current
   def self.up
     add_column "people", "last_name", :string
diff --git a/activerecord/test/migrations/missing/3_we_need_reminders.rb b/activerecord/test/migrations/missing/3_we_need_reminders.rb
index d7c63ac892..4647268c6e 100644
--- a/activerecord/test/migrations/missing/3_we_need_reminders.rb
+++ b/activerecord/test/migrations/missing/3_we_need_reminders.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class WeNeedReminders < ActiveRecord::Migration::Current
   def self.up
     create_table("reminders") do |t|
diff --git a/activerecord/test/migrations/missing/4_innocent_jointable.rb b/activerecord/test/migrations/missing/4_innocent_jointable.rb
index bd3bf21576..8063bc0558 100644
--- a/activerecord/test/migrations/missing/4_innocent_jointable.rb
+++ b/activerecord/test/migrations/missing/4_innocent_jointable.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class InnocentJointable < ActiveRecord::Migration::Current
   def self.up
     create_table("people_reminders", id: false) do |t|
diff --git a/activerecord/test/migrations/rename/1_we_need_things.rb b/activerecord/test/migrations/rename/1_we_need_things.rb
index 9dce01acfd..8e71a1d996 100644
--- a/activerecord/test/migrations/rename/1_we_need_things.rb
+++ b/activerecord/test/migrations/rename/1_we_need_things.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class WeNeedThings < ActiveRecord::Migration::Current
   def self.up
     create_table("things") do |t|
diff --git a/activerecord/test/migrations/rename/2_rename_things.rb b/activerecord/test/migrations/rename/2_rename_things.rb
index cb8484e7dc..110fe3f0fa 100644
--- a/activerecord/test/migrations/rename/2_rename_things.rb
+++ b/activerecord/test/migrations/rename/2_rename_things.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RenameThings < ActiveRecord::Migration::Current
   def self.up
     rename_table "things", "awesome_things"
diff --git a/activerecord/test/migrations/to_copy/1_people_have_hobbies.rb b/activerecord/test/migrations/to_copy/1_people_have_hobbies.rb
index 76734bcd7d..badccf65cc 100644
--- a/activerecord/test/migrations/to_copy/1_people_have_hobbies.rb
+++ b/activerecord/test/migrations/to_copy/1_people_have_hobbies.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PeopleHaveHobbies < ActiveRecord::Migration::Current
   def self.up
     add_column "people", "hobbies", :text
diff --git a/activerecord/test/migrations/to_copy/2_people_have_descriptions.rb b/activerecord/test/migrations/to_copy/2_people_have_descriptions.rb
index 7f883dbb45..1d19d5d6f4 100644
--- a/activerecord/test/migrations/to_copy/2_people_have_descriptions.rb
+++ b/activerecord/test/migrations/to_copy/2_people_have_descriptions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PeopleHaveDescriptions < ActiveRecord::Migration::Current
   def self.up
     add_column "people", "description", :text
diff --git a/activerecord/test/migrations/to_copy2/1_create_articles.rb b/activerecord/test/migrations/to_copy2/1_create_articles.rb
index 2e9f5ec6bc..85c166b319 100644
--- a/activerecord/test/migrations/to_copy2/1_create_articles.rb
+++ b/activerecord/test/migrations/to_copy2/1_create_articles.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateArticles < ActiveRecord::Migration::Current
   def self.up
   end
diff --git a/activerecord/test/migrations/to_copy2/2_create_comments.rb b/activerecord/test/migrations/to_copy2/2_create_comments.rb
index d361847d4b..1d213a1705 100644
--- a/activerecord/test/migrations/to_copy2/2_create_comments.rb
+++ b/activerecord/test/migrations/to_copy2/2_create_comments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateComments < ActiveRecord::Migration::Current
   def self.up
   end
diff --git a/activerecord/test/migrations/to_copy_with_name_collision/1_people_have_hobbies.rb b/activerecord/test/migrations/to_copy_with_name_collision/1_people_have_hobbies.rb
index 1a863367dd..d9fef596f5 100644
--- a/activerecord/test/migrations/to_copy_with_name_collision/1_people_have_hobbies.rb
+++ b/activerecord/test/migrations/to_copy_with_name_collision/1_people_have_hobbies.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PeopleHaveHobbies < ActiveRecord::Migration::Current
   def self.up
     add_column "people", "hobbies", :string
diff --git a/activerecord/test/migrations/to_copy_with_timestamps/20090101010101_people_have_hobbies.rb b/activerecord/test/migrations/to_copy_with_timestamps/20090101010101_people_have_hobbies.rb
index 76734bcd7d..badccf65cc 100644
--- a/activerecord/test/migrations/to_copy_with_timestamps/20090101010101_people_have_hobbies.rb
+++ b/activerecord/test/migrations/to_copy_with_timestamps/20090101010101_people_have_hobbies.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PeopleHaveHobbies < ActiveRecord::Migration::Current
   def self.up
     add_column "people", "hobbies", :text
diff --git a/activerecord/test/migrations/to_copy_with_timestamps/20090101010202_people_have_descriptions.rb b/activerecord/test/migrations/to_copy_with_timestamps/20090101010202_people_have_descriptions.rb
index 7f883dbb45..1d19d5d6f4 100644
--- a/activerecord/test/migrations/to_copy_with_timestamps/20090101010202_people_have_descriptions.rb
+++ b/activerecord/test/migrations/to_copy_with_timestamps/20090101010202_people_have_descriptions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PeopleHaveDescriptions < ActiveRecord::Migration::Current
   def self.up
     add_column "people", "description", :text
diff --git a/activerecord/test/migrations/to_copy_with_timestamps2/20090101010101_create_articles.rb b/activerecord/test/migrations/to_copy_with_timestamps2/20090101010101_create_articles.rb
index 2e9f5ec6bc..85c166b319 100644
--- a/activerecord/test/migrations/to_copy_with_timestamps2/20090101010101_create_articles.rb
+++ b/activerecord/test/migrations/to_copy_with_timestamps2/20090101010101_create_articles.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateArticles < ActiveRecord::Migration::Current
   def self.up
   end
diff --git a/activerecord/test/migrations/to_copy_with_timestamps2/20090101010202_create_comments.rb b/activerecord/test/migrations/to_copy_with_timestamps2/20090101010202_create_comments.rb
index d361847d4b..1d213a1705 100644
--- a/activerecord/test/migrations/to_copy_with_timestamps2/20090101010202_create_comments.rb
+++ b/activerecord/test/migrations/to_copy_with_timestamps2/20090101010202_create_comments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateComments < ActiveRecord::Migration::Current
   def self.up
   end
diff --git a/activerecord/test/migrations/valid/1_valid_people_have_last_names.rb b/activerecord/test/migrations/valid/1_valid_people_have_last_names.rb
index c450211d8c..3bedcdcdf0 100644
--- a/activerecord/test/migrations/valid/1_valid_people_have_last_names.rb
+++ b/activerecord/test/migrations/valid/1_valid_people_have_last_names.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ValidPeopleHaveLastNames < ActiveRecord::Migration::Current
   def self.up
     add_column "people", "last_name", :string
diff --git a/activerecord/test/migrations/valid/2_we_need_reminders.rb b/activerecord/test/migrations/valid/2_we_need_reminders.rb
index d7c63ac892..4647268c6e 100644
--- a/activerecord/test/migrations/valid/2_we_need_reminders.rb
+++ b/activerecord/test/migrations/valid/2_we_need_reminders.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class WeNeedReminders < ActiveRecord::Migration::Current
   def self.up
     create_table("reminders") do |t|
diff --git a/activerecord/test/migrations/valid/3_innocent_jointable.rb b/activerecord/test/migrations/valid/3_innocent_jointable.rb
index bd3bf21576..8063bc0558 100644
--- a/activerecord/test/migrations/valid/3_innocent_jointable.rb
+++ b/activerecord/test/migrations/valid/3_innocent_jointable.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class InnocentJointable < ActiveRecord::Migration::Current
   def self.up
     create_table("people_reminders", id: false) do |t|
diff --git a/activerecord/test/migrations/valid_with_subdirectories/1_valid_people_have_last_names.rb b/activerecord/test/migrations/valid_with_subdirectories/1_valid_people_have_last_names.rb
index c450211d8c..3bedcdcdf0 100644
--- a/activerecord/test/migrations/valid_with_subdirectories/1_valid_people_have_last_names.rb
+++ b/activerecord/test/migrations/valid_with_subdirectories/1_valid_people_have_last_names.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ValidPeopleHaveLastNames < ActiveRecord::Migration::Current
   def self.up
     add_column "people", "last_name", :string
diff --git a/activerecord/test/migrations/valid_with_subdirectories/sub/2_we_need_reminders.rb b/activerecord/test/migrations/valid_with_subdirectories/sub/2_we_need_reminders.rb
index d7c63ac892..4647268c6e 100644
--- a/activerecord/test/migrations/valid_with_subdirectories/sub/2_we_need_reminders.rb
+++ b/activerecord/test/migrations/valid_with_subdirectories/sub/2_we_need_reminders.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class WeNeedReminders < ActiveRecord::Migration::Current
   def self.up
     create_table("reminders") do |t|
diff --git a/activerecord/test/migrations/valid_with_subdirectories/sub1/3_innocent_jointable.rb b/activerecord/test/migrations/valid_with_subdirectories/sub1/3_innocent_jointable.rb
index bd3bf21576..8063bc0558 100644
--- a/activerecord/test/migrations/valid_with_subdirectories/sub1/3_innocent_jointable.rb
+++ b/activerecord/test/migrations/valid_with_subdirectories/sub1/3_innocent_jointable.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class InnocentJointable < ActiveRecord::Migration::Current
   def self.up
     create_table("people_reminders", id: false) do |t|
diff --git a/activerecord/test/migrations/valid_with_timestamps/20100101010101_valid_with_timestamps_people_have_last_names.rb b/activerecord/test/migrations/valid_with_timestamps/20100101010101_valid_with_timestamps_people_have_last_names.rb
index 9fd27593f0..b938847170 100644
--- a/activerecord/test/migrations/valid_with_timestamps/20100101010101_valid_with_timestamps_people_have_last_names.rb
+++ b/activerecord/test/migrations/valid_with_timestamps/20100101010101_valid_with_timestamps_people_have_last_names.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ValidWithTimestampsPeopleHaveLastNames < ActiveRecord::Migration::Current
   def self.up
     add_column "people", "last_name", :string
diff --git a/activerecord/test/migrations/valid_with_timestamps/20100201010101_valid_with_timestamps_we_need_reminders.rb b/activerecord/test/migrations/valid_with_timestamps/20100201010101_valid_with_timestamps_we_need_reminders.rb
index 4a59921136..94551e8208 100644
--- a/activerecord/test/migrations/valid_with_timestamps/20100201010101_valid_with_timestamps_we_need_reminders.rb
+++ b/activerecord/test/migrations/valid_with_timestamps/20100201010101_valid_with_timestamps_we_need_reminders.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ValidWithTimestampsWeNeedReminders < ActiveRecord::Migration::Current
   def self.up
     create_table("reminders") do |t|
diff --git a/activerecord/test/migrations/valid_with_timestamps/20100301010101_valid_with_timestamps_innocent_jointable.rb b/activerecord/test/migrations/valid_with_timestamps/20100301010101_valid_with_timestamps_innocent_jointable.rb
index be24de6d70..672edc5253 100644
--- a/activerecord/test/migrations/valid_with_timestamps/20100301010101_valid_with_timestamps_innocent_jointable.rb
+++ b/activerecord/test/migrations/valid_with_timestamps/20100301010101_valid_with_timestamps_innocent_jointable.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ValidWithTimestampsInnocentJointable < ActiveRecord::Migration::Current
   def self.up
     create_table("people_reminders", id: false) do |t|
diff --git a/activerecord/test/migrations/version_check/20131219224947_migration_version_check.rb b/activerecord/test/migrations/version_check/20131219224947_migration_version_check.rb
index 6f314c881c..91bfbbdfd1 100644
--- a/activerecord/test/migrations/version_check/20131219224947_migration_version_check.rb
+++ b/activerecord/test/migrations/version_check/20131219224947_migration_version_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class MigrationVersionCheck < ActiveRecord::Migration::Current
   def self.up
     raise "incorrect migration version" unless version == 20131219224947
diff --git a/activerecord/test/models/admin.rb b/activerecord/test/models/admin.rb
index bc3ce23447..a40b5a33b2 100644
--- a/activerecord/test/models/admin.rb
+++ b/activerecord/test/models/admin.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Admin
   def self.table_name_prefix
     "admin_"
diff --git a/activerecord/test/models/admin/account.rb b/activerecord/test/models/admin/account.rb
index bd23192d20..41fe2d782b 100644
--- a/activerecord/test/models/admin/account.rb
+++ b/activerecord/test/models/admin/account.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Admin::Account < ActiveRecord::Base
   has_many :users
 end
diff --git a/activerecord/test/models/admin/randomly_named_c1.rb b/activerecord/test/models/admin/randomly_named_c1.rb
index b64ae7fc41..d89b8dd293 100644
--- a/activerecord/test/models/admin/randomly_named_c1.rb
+++ b/activerecord/test/models/admin/randomly_named_c1.rb
@@ -1,7 +1,9 @@
-class Admin::ClassNameThatDoesNotFollowCONVENTIONS1 < ActiveRecord::Base

-  self.table_name = :randomly_named_table2

-end

-

-class Admin::ClassNameThatDoesNotFollowCONVENTIONS2 < ActiveRecord::Base

-  self.table_name = :randomly_named_table3

-end

+# frozen_string_literal: true
+
+class Admin::ClassNameThatDoesNotFollowCONVENTIONS1 < ActiveRecord::Base
+  self.table_name = :randomly_named_table2
+end
+
+class Admin::ClassNameThatDoesNotFollowCONVENTIONS2 < ActiveRecord::Base
+  self.table_name = :randomly_named_table3
+end
diff --git a/activerecord/test/models/admin/user.rb b/activerecord/test/models/admin/user.rb
index a76e4b6795..abb5cb28e7 100644
--- a/activerecord/test/models/admin/user.rb
+++ b/activerecord/test/models/admin/user.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Admin::User < ActiveRecord::Base
   class Coder
     def initialize(default = {})
diff --git a/activerecord/test/models/aircraft.rb b/activerecord/test/models/aircraft.rb
index ebd42ff824..4fdea46cf7 100644
--- a/activerecord/test/models/aircraft.rb
+++ b/activerecord/test/models/aircraft.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Aircraft < ActiveRecord::Base
   self.pluralize_table_names = false
   has_many :engines, foreign_key: "car_id"
diff --git a/activerecord/test/models/arunit2_model.rb b/activerecord/test/models/arunit2_model.rb
index 04b8b15d3d..5b0da8a249 100644
--- a/activerecord/test/models/arunit2_model.rb
+++ b/activerecord/test/models/arunit2_model.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ARUnit2Model < ActiveRecord::Base
   self.abstract_class = true
 end
diff --git a/activerecord/test/models/author.rb b/activerecord/test/models/author.rb
index 2d9cba77e0..09958ca257 100644
--- a/activerecord/test/models/author.rb
+++ b/activerecord/test/models/author.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Author < ActiveRecord::Base
   has_many :posts
   has_many :serialized_posts
diff --git a/activerecord/test/models/auto_id.rb b/activerecord/test/models/auto_id.rb
index 82c6544bd5..fd672603bb 100644
--- a/activerecord/test/models/auto_id.rb
+++ b/activerecord/test/models/auto_id.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AutoId < ActiveRecord::Base
   self.table_name = "auto_id_tests"
   self.primary_key = "auto_id"
diff --git a/activerecord/test/models/autoloadable/extra_firm.rb b/activerecord/test/models/autoloadable/extra_firm.rb
index 5578ba0d9b..c46e34c101 100644
--- a/activerecord/test/models/autoloadable/extra_firm.rb
+++ b/activerecord/test/models/autoloadable/extra_firm.rb
@@ -1,2 +1,4 @@
+# frozen_string_literal: true
+
 class ExtraFirm < Company
 end
diff --git a/activerecord/test/models/binary.rb b/activerecord/test/models/binary.rb
index 39b2f5090a..b93f87519f 100644
--- a/activerecord/test/models/binary.rb
+++ b/activerecord/test/models/binary.rb
@@ -1,2 +1,4 @@
+# frozen_string_literal: true
+
 class Binary < ActiveRecord::Base
 end
diff --git a/activerecord/test/models/bird.rb b/activerecord/test/models/bird.rb
index 24b839135d..be08636ac6 100644
--- a/activerecord/test/models/bird.rb
+++ b/activerecord/test/models/bird.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Bird < ActiveRecord::Base
   belongs_to :pirate
   validates_presence_of :name
diff --git a/activerecord/test/models/book.rb b/activerecord/test/models/book.rb
index 6466e1b341..afdda1a81e 100644
--- a/activerecord/test/models/book.rb
+++ b/activerecord/test/models/book.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Book < ActiveRecord::Base
   belongs_to :author
 
diff --git a/activerecord/test/models/boolean.rb b/activerecord/test/models/boolean.rb
index 0da228aac2..bee757fb9c 100644
--- a/activerecord/test/models/boolean.rb
+++ b/activerecord/test/models/boolean.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Boolean < ActiveRecord::Base
   def has_fun
     super
diff --git a/activerecord/test/models/bulb.rb b/activerecord/test/models/bulb.rb
index 113d21cb84..ab92f7025d 100644
--- a/activerecord/test/models/bulb.rb
+++ b/activerecord/test/models/bulb.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Bulb < ActiveRecord::Base
   default_scope { where(name: "defaulty") }
   belongs_to :car, touch: true
diff --git a/activerecord/test/models/cake_designer.rb b/activerecord/test/models/cake_designer.rb
index 9c57ef573a..0b2a00edfd 100644
--- a/activerecord/test/models/cake_designer.rb
+++ b/activerecord/test/models/cake_designer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CakeDesigner < ActiveRecord::Base
   has_one :chef, as: :employable
 end
diff --git a/activerecord/test/models/car.rb b/activerecord/test/models/car.rb
index 92bff7ff96..3d6a7a96c2 100644
--- a/activerecord/test/models/car.rb
+++ b/activerecord/test/models/car.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Car < ActiveRecord::Base
   has_many :bulbs
   has_many :all_bulbs, -> { unscope where: :name }, class_name: "Bulb"
diff --git a/activerecord/test/models/carrier.rb b/activerecord/test/models/carrier.rb
index 230be118c3..995a9d3bef 100644
--- a/activerecord/test/models/carrier.rb
+++ b/activerecord/test/models/carrier.rb
@@ -1,2 +1,4 @@
+# frozen_string_literal: true
+
 class Carrier < ActiveRecord::Base
 end
diff --git a/activerecord/test/models/cat.rb b/activerecord/test/models/cat.rb
index dfdde18641..43013964b6 100644
--- a/activerecord/test/models/cat.rb
+++ b/activerecord/test/models/cat.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Cat < ActiveRecord::Base
   self.abstract_class = true
 
diff --git a/activerecord/test/models/categorization.rb b/activerecord/test/models/categorization.rb
index b99383d0b1..68b0ea90d3 100644
--- a/activerecord/test/models/categorization.rb
+++ b/activerecord/test/models/categorization.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Categorization < ActiveRecord::Base
   belongs_to :post
   belongs_to :category, counter_cache: true
diff --git a/activerecord/test/models/category.rb b/activerecord/test/models/category.rb
index 4b2840c653..2ccc00bed9 100644
--- a/activerecord/test/models/category.rb
+++ b/activerecord/test/models/category.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Category < ActiveRecord::Base
   has_and_belongs_to_many :posts
   has_and_belongs_to_many :special_posts, class_name: "Post"
diff --git a/activerecord/test/models/chef.rb b/activerecord/test/models/chef.rb
index 9d3dd01016..ff528644bc 100644
--- a/activerecord/test/models/chef.rb
+++ b/activerecord/test/models/chef.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Chef < ActiveRecord::Base
   belongs_to :employable, polymorphic: true
   has_many :recipes
diff --git a/activerecord/test/models/citation.rb b/activerecord/test/models/citation.rb
index 7d06387f56..3d786f27eb 100644
--- a/activerecord/test/models/citation.rb
+++ b/activerecord/test/models/citation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Citation < ActiveRecord::Base
   belongs_to :reference_of, class_name: "Book", foreign_key: :book2_id
 end
diff --git a/activerecord/test/models/club.rb b/activerecord/test/models/club.rb
index 3d441b1d48..2006e05fcf 100644
--- a/activerecord/test/models/club.rb
+++ b/activerecord/test/models/club.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Club < ActiveRecord::Base
   has_one :membership
   has_many :memberships, inverse_of: false
diff --git a/activerecord/test/models/college.rb b/activerecord/test/models/college.rb
index c9dbe1ecc2..52017dda42 100644
--- a/activerecord/test/models/college.rb
+++ b/activerecord/test/models/college.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_dependency "models/arunit2_model"
 require "active_support/core_ext/object/with_options"
 
diff --git a/activerecord/test/models/column.rb b/activerecord/test/models/column.rb
index 499358b4cf..d3cd419a00 100644
--- a/activerecord/test/models/column.rb
+++ b/activerecord/test/models/column.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Column < ActiveRecord::Base
   belongs_to :record
 end
diff --git a/activerecord/test/models/column_name.rb b/activerecord/test/models/column_name.rb
index 460eb4fe20..c6047c507b 100644
--- a/activerecord/test/models/column_name.rb
+++ b/activerecord/test/models/column_name.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ColumnName < ActiveRecord::Base
   self.table_name = "colnametests"
 end
diff --git a/activerecord/test/models/comment.rb b/activerecord/test/models/comment.rb
index dc2d421cd7..e1e2a5e0e9 100644
--- a/activerecord/test/models/comment.rb
+++ b/activerecord/test/models/comment.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Comment < ActiveRecord::Base
   scope :limit_by, lambda { |l| limit(l) }
   scope :containing_the_letter_e, -> { where("comments.body LIKE '%e%'") }
diff --git a/activerecord/test/models/company.rb b/activerecord/test/models/company.rb
index c6a5bf1c92..50e9553bfe 100644
--- a/activerecord/test/models/company.rb
+++ b/activerecord/test/models/company.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AbstractCompany < ActiveRecord::Base
   self.abstract_class = true
 end
diff --git a/activerecord/test/models/company_in_module.rb b/activerecord/test/models/company_in_module.rb
index 0782c1eff4..52b7e06a63 100644
--- a/activerecord/test/models/company_in_module.rb
+++ b/activerecord/test/models/company_in_module.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/object/with_options"
 
 module MyApplication
diff --git a/activerecord/test/models/computer.rb b/activerecord/test/models/computer.rb
index 1c9856e1af..582b4a38b5 100644
--- a/activerecord/test/models/computer.rb
+++ b/activerecord/test/models/computer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Computer < ActiveRecord::Base
   belongs_to :developer, foreign_key: "developer"
 end
diff --git a/activerecord/test/models/contact.rb b/activerecord/test/models/contact.rb
index 47bbbbfd8b..6e02ff199b 100644
--- a/activerecord/test/models/contact.rb
+++ b/activerecord/test/models/contact.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ContactFakeColumns
   def self.extended(base)
     base.class_eval do
diff --git a/activerecord/test/models/content.rb b/activerecord/test/models/content.rb
index 68db2127d8..14bbee53d8 100644
--- a/activerecord/test/models/content.rb
+++ b/activerecord/test/models/content.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Content < ActiveRecord::Base
   self.table_name = "content"
   has_one :content_position, dependent: :destroy
diff --git a/activerecord/test/models/contract.rb b/activerecord/test/models/contract.rb
index 32bd581377..9454217e8d 100644
--- a/activerecord/test/models/contract.rb
+++ b/activerecord/test/models/contract.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Contract < ActiveRecord::Base
   belongs_to :company
   belongs_to :developer
diff --git a/activerecord/test/models/country.rb b/activerecord/test/models/country.rb
index 7912719ddd..0c84a40de2 100644
--- a/activerecord/test/models/country.rb
+++ b/activerecord/test/models/country.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Country < ActiveRecord::Base
   self.primary_key = :country_id
 
diff --git a/activerecord/test/models/course.rb b/activerecord/test/models/course.rb
index 348f2bf1e0..4f346124ea 100644
--- a/activerecord/test/models/course.rb
+++ b/activerecord/test/models/course.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_dependency "models/arunit2_model"
 
 class Course < ARUnit2Model
diff --git a/activerecord/test/models/customer.rb b/activerecord/test/models/customer.rb
index 3d40cb1ace..524a9d7bd9 100644
--- a/activerecord/test/models/customer.rb
+++ b/activerecord/test/models/customer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Customer < ActiveRecord::Base
   cattr_accessor :gps_conversion_was_run
 
diff --git a/activerecord/test/models/customer_carrier.rb b/activerecord/test/models/customer_carrier.rb
index 37186903ff..6cb9d5239d 100644
--- a/activerecord/test/models/customer_carrier.rb
+++ b/activerecord/test/models/customer_carrier.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CustomerCarrier < ActiveRecord::Base
   cattr_accessor :current_customer
 
diff --git a/activerecord/test/models/dashboard.rb b/activerecord/test/models/dashboard.rb
index 1b3b54545f..d25ceeafb1 100644
--- a/activerecord/test/models/dashboard.rb
+++ b/activerecord/test/models/dashboard.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Dashboard < ActiveRecord::Base
   self.primary_key = :dashboard_id
 end
diff --git a/activerecord/test/models/default.rb b/activerecord/test/models/default.rb
index 887e9cc999..90f1046d87 100644
--- a/activerecord/test/models/default.rb
+++ b/activerecord/test/models/default.rb
@@ -1,2 +1,4 @@
+# frozen_string_literal: true
+
 class Default < ActiveRecord::Base
 end
diff --git a/activerecord/test/models/department.rb b/activerecord/test/models/department.rb
index 08004a0ed3..868b9bf4bf 100644
--- a/activerecord/test/models/department.rb
+++ b/activerecord/test/models/department.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Department < ActiveRecord::Base
   has_many :chefs
   belongs_to :hotel
diff --git a/activerecord/test/models/developer.rb b/activerecord/test/models/developer.rb
index 654830ba11..56aafca60b 100644
--- a/activerecord/test/models/developer.rb
+++ b/activerecord/test/models/developer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "ostruct"
 
 module DeveloperProjectsAssociationExtension2
diff --git a/activerecord/test/models/dog.rb b/activerecord/test/models/dog.rb
index b02b8447b8..75d284ac25 100644
--- a/activerecord/test/models/dog.rb
+++ b/activerecord/test/models/dog.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Dog < ActiveRecord::Base
   belongs_to :breeder, class_name: "DogLover", counter_cache: :bred_dogs_count
   belongs_to :trainer, class_name: "DogLover", counter_cache: :trained_dogs_count
diff --git a/activerecord/test/models/dog_lover.rb b/activerecord/test/models/dog_lover.rb
index 2c5be94aea..aabe914f77 100644
--- a/activerecord/test/models/dog_lover.rb
+++ b/activerecord/test/models/dog_lover.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class DogLover < ActiveRecord::Base
   has_many :trained_dogs, class_name: "Dog", foreign_key: :trainer_id, dependent: :destroy
   has_many :bred_dogs, class_name: "Dog", foreign_key: :breeder_id
diff --git a/activerecord/test/models/doubloon.rb b/activerecord/test/models/doubloon.rb
index 7272504666..febadc3a5a 100644
--- a/activerecord/test/models/doubloon.rb
+++ b/activerecord/test/models/doubloon.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AbstractDoubloon < ActiveRecord::Base
   # This has functionality that might be shared by multiple classes.
 
diff --git a/activerecord/test/models/drink_designer.rb b/activerecord/test/models/drink_designer.rb
index 2db968ef11..1c407844c5 100644
--- a/activerecord/test/models/drink_designer.rb
+++ b/activerecord/test/models/drink_designer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class DrinkDesigner < ActiveRecord::Base
   has_one :chef, as: :employable
 end
diff --git a/activerecord/test/models/edge.rb b/activerecord/test/models/edge.rb
index e61d25c9bc..a04ab103de 100644
--- a/activerecord/test/models/edge.rb
+++ b/activerecord/test/models/edge.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This class models an edge in a directed graph.
 class Edge < ActiveRecord::Base
   belongs_to :source, class_name: "Vertex", foreign_key: "source_id"
diff --git a/activerecord/test/models/electron.rb b/activerecord/test/models/electron.rb
index 6fc270673f..902006b314 100644
--- a/activerecord/test/models/electron.rb
+++ b/activerecord/test/models/electron.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Electron < ActiveRecord::Base
   belongs_to :molecule
 
diff --git a/activerecord/test/models/engine.rb b/activerecord/test/models/engine.rb
index eada171f6a..396a52b3b9 100644
--- a/activerecord/test/models/engine.rb
+++ b/activerecord/test/models/engine.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Engine < ActiveRecord::Base
   belongs_to :my_car, class_name: "Car", foreign_key: "car_id",  counter_cache: :engines_count
 end
diff --git a/activerecord/test/models/entrant.rb b/activerecord/test/models/entrant.rb
index 4682ce48c8..2c086e451f 100644
--- a/activerecord/test/models/entrant.rb
+++ b/activerecord/test/models/entrant.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Entrant < ActiveRecord::Base
   belongs_to :course
 end
diff --git a/activerecord/test/models/essay.rb b/activerecord/test/models/essay.rb
index 1f9772870e..e59db4d877 100644
--- a/activerecord/test/models/essay.rb
+++ b/activerecord/test/models/essay.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Essay < ActiveRecord::Base
   belongs_to :author
   belongs_to :writer, primary_key: :name, polymorphic: true
diff --git a/activerecord/test/models/event.rb b/activerecord/test/models/event.rb
index 365ab32b0b..a7cdc39e5c 100644
--- a/activerecord/test/models/event.rb
+++ b/activerecord/test/models/event.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Event < ActiveRecord::Base
   validates_uniqueness_of :title
 end
diff --git a/activerecord/test/models/eye.rb b/activerecord/test/models/eye.rb
index f53c34e4b1..f3608b62ef 100644
--- a/activerecord/test/models/eye.rb
+++ b/activerecord/test/models/eye.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Eye < ActiveRecord::Base
   attr_reader :after_create_callbacks_stack
   attr_reader :after_update_callbacks_stack
diff --git a/activerecord/test/models/face.rb b/activerecord/test/models/face.rb
index 5913bfa969..796aaa4dc9 100644
--- a/activerecord/test/models/face.rb
+++ b/activerecord/test/models/face.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Face < ActiveRecord::Base
   belongs_to :man, inverse_of: :face
   belongs_to :polymorphic_man, polymorphic: true, inverse_of: :polymorphic_face
diff --git a/activerecord/test/models/family.rb b/activerecord/test/models/family.rb
index 5ae5a78c95..0713dba1a6 100644
--- a/activerecord/test/models/family.rb
+++ b/activerecord/test/models/family.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Family < ActiveRecord::Base
   has_many :family_trees, -> { where(token: nil) }
   has_many :members, through: :family_trees
diff --git a/activerecord/test/models/family_tree.rb b/activerecord/test/models/family_tree.rb
index cd9829fedd..a8ea907c05 100644
--- a/activerecord/test/models/family_tree.rb
+++ b/activerecord/test/models/family_tree.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class FamilyTree < ActiveRecord::Base
   belongs_to :member, class_name: "User", foreign_key: "member_id"
   belongs_to :family
diff --git a/activerecord/test/models/friendship.rb b/activerecord/test/models/friendship.rb
index 578382b494..9f1712a8ec 100644
--- a/activerecord/test/models/friendship.rb
+++ b/activerecord/test/models/friendship.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Friendship < ActiveRecord::Base
   belongs_to :friend, class_name: "Person"
   # friend_too exists to test a bug, and probably shouldn't be used elsewhere
diff --git a/activerecord/test/models/guid.rb b/activerecord/test/models/guid.rb
index 05653ba498..ec71c37690 100644
--- a/activerecord/test/models/guid.rb
+++ b/activerecord/test/models/guid.rb
@@ -1,2 +1,4 @@
+# frozen_string_literal: true
+
 class Guid < ActiveRecord::Base
 end
diff --git a/activerecord/test/models/guitar.rb b/activerecord/test/models/guitar.rb
index cd068ff53d..649b998665 100644
--- a/activerecord/test/models/guitar.rb
+++ b/activerecord/test/models/guitar.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Guitar < ActiveRecord::Base
   has_many :tuning_pegs, index_errors: true
   accepts_nested_attributes_for :tuning_pegs
diff --git a/activerecord/test/models/hotel.rb b/activerecord/test/models/hotel.rb
index 7bc717c891..1a433c3cab 100644
--- a/activerecord/test/models/hotel.rb
+++ b/activerecord/test/models/hotel.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Hotel < ActiveRecord::Base
   has_many :departments
   has_many :chefs, through: :departments
diff --git a/activerecord/test/models/image.rb b/activerecord/test/models/image.rb
index 7ae8e4a7f6..b4808293cc 100644
--- a/activerecord/test/models/image.rb
+++ b/activerecord/test/models/image.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Image < ActiveRecord::Base
   belongs_to :imageable, foreign_key: :imageable_identifier, foreign_type: :imageable_class
 end
diff --git a/activerecord/test/models/interest.rb b/activerecord/test/models/interest.rb
index ec79416ee7..899b8f9b9d 100644
--- a/activerecord/test/models/interest.rb
+++ b/activerecord/test/models/interest.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Interest < ActiveRecord::Base
   belongs_to :man, inverse_of: :interests
   belongs_to :polymorphic_man, polymorphic: true, inverse_of: :polymorphic_interests
diff --git a/activerecord/test/models/invoice.rb b/activerecord/test/models/invoice.rb
index 4be5a00193..1851792ed5 100644
--- a/activerecord/test/models/invoice.rb
+++ b/activerecord/test/models/invoice.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Invoice < ActiveRecord::Base
   has_many :line_items, autosave: true
   before_save { |record| record.balance = record.line_items.map(&:amount).sum }
diff --git a/activerecord/test/models/item.rb b/activerecord/test/models/item.rb
index 336fb1769a..8d079d56e6 100644
--- a/activerecord/test/models/item.rb
+++ b/activerecord/test/models/item.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AbstractItem < ActiveRecord::Base
   self.abstract_class = true
   has_one :tagging, as: :taggable
diff --git a/activerecord/test/models/job.rb b/activerecord/test/models/job.rb
index bbaef2792c..52817a8435 100644
--- a/activerecord/test/models/job.rb
+++ b/activerecord/test/models/job.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Job < ActiveRecord::Base
   has_many :references
   has_many :people, through: :references
diff --git a/activerecord/test/models/joke.rb b/activerecord/test/models/joke.rb
index eeb5818a1f..436ffb6471 100644
--- a/activerecord/test/models/joke.rb
+++ b/activerecord/test/models/joke.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Joke < ActiveRecord::Base
   self.table_name = "funny_jokes"
 end
diff --git a/activerecord/test/models/keyboard.rb b/activerecord/test/models/keyboard.rb
index bcede53ec9..d200e0fb56 100644
--- a/activerecord/test/models/keyboard.rb
+++ b/activerecord/test/models/keyboard.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Keyboard < ActiveRecord::Base
   self.primary_key = "key_number"
 end
diff --git a/activerecord/test/models/legacy_thing.rb b/activerecord/test/models/legacy_thing.rb
index eead181a0e..e0210c8922 100644
--- a/activerecord/test/models/legacy_thing.rb
+++ b/activerecord/test/models/legacy_thing.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class LegacyThing < ActiveRecord::Base
   self.locking_column = :version
 end
diff --git a/activerecord/test/models/lesson.rb b/activerecord/test/models/lesson.rb
index 4c88153068..e546339689 100644
--- a/activerecord/test/models/lesson.rb
+++ b/activerecord/test/models/lesson.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class LessonError < Exception
 end
 
diff --git a/activerecord/test/models/line_item.rb b/activerecord/test/models/line_item.rb
index 93f7cceb13..3a51cf03b2 100644
--- a/activerecord/test/models/line_item.rb
+++ b/activerecord/test/models/line_item.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class LineItem < ActiveRecord::Base
   belongs_to :invoice, touch: true
 end
diff --git a/activerecord/test/models/liquid.rb b/activerecord/test/models/liquid.rb
index 69d4d7df1a..b2fd305d66 100644
--- a/activerecord/test/models/liquid.rb
+++ b/activerecord/test/models/liquid.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Liquid < ActiveRecord::Base
   self.table_name = :liquid
   has_many :molecules, -> { distinct }
diff --git a/activerecord/test/models/man.rb b/activerecord/test/models/man.rb
index d2436a735c..3acd89a48e 100644
--- a/activerecord/test/models/man.rb
+++ b/activerecord/test/models/man.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Man < ActiveRecord::Base
   has_one :face, inverse_of: :man
   has_one :polymorphic_face, class_name: "Face", as: :polymorphic_man, inverse_of: :polymorphic_man
diff --git a/activerecord/test/models/matey.rb b/activerecord/test/models/matey.rb
index 80ee5f47c5..a77ac21e96 100644
--- a/activerecord/test/models/matey.rb
+++ b/activerecord/test/models/matey.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Matey < ActiveRecord::Base
   belongs_to :pirate
   belongs_to :target, class_name: "Pirate"
diff --git a/activerecord/test/models/member.rb b/activerecord/test/models/member.rb
index b9597c6b9a..4315ba1941 100644
--- a/activerecord/test/models/member.rb
+++ b/activerecord/test/models/member.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Member < ActiveRecord::Base
   has_one :current_membership
   has_one :selected_membership
diff --git a/activerecord/test/models/member_detail.rb b/activerecord/test/models/member_detail.rb
index 157130986c..87f7aab9a2 100644
--- a/activerecord/test/models/member_detail.rb
+++ b/activerecord/test/models/member_detail.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class MemberDetail < ActiveRecord::Base
   belongs_to :member, inverse_of: false
   belongs_to :organization
diff --git a/activerecord/test/models/member_type.rb b/activerecord/test/models/member_type.rb
index a13561c72a..b49b168d03 100644
--- a/activerecord/test/models/member_type.rb
+++ b/activerecord/test/models/member_type.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class MemberType < ActiveRecord::Base
   has_many :members
 end
diff --git a/activerecord/test/models/membership.rb b/activerecord/test/models/membership.rb
index 0f8be0ad85..09ee7544b3 100644
--- a/activerecord/test/models/membership.rb
+++ b/activerecord/test/models/membership.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Membership < ActiveRecord::Base
   enum type: %i(Membership CurrentMembership SuperMembership SelectedMembership TenantMembership)
   belongs_to :member
diff --git a/activerecord/test/models/mentor.rb b/activerecord/test/models/mentor.rb
index 66504b4e91..2fbb62c435 100644
--- a/activerecord/test/models/mentor.rb
+++ b/activerecord/test/models/mentor.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Mentor < ActiveRecord::Base
   has_many :developers
 end
diff --git a/activerecord/test/models/minimalistic.rb b/activerecord/test/models/minimalistic.rb
index 2e3f8e081a..c67b086853 100644
--- a/activerecord/test/models/minimalistic.rb
+++ b/activerecord/test/models/minimalistic.rb
@@ -1,2 +1,4 @@
+# frozen_string_literal: true
+
 class Minimalistic < ActiveRecord::Base
 end
diff --git a/activerecord/test/models/minivan.rb b/activerecord/test/models/minivan.rb
index e9b05dadf2..d9d331798a 100644
--- a/activerecord/test/models/minivan.rb
+++ b/activerecord/test/models/minivan.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Minivan < ActiveRecord::Base
   self.primary_key = :minivan_id
 
diff --git a/activerecord/test/models/mixed_case_monkey.rb b/activerecord/test/models/mixed_case_monkey.rb
index 1c35006665..8e92f68817 100644
--- a/activerecord/test/models/mixed_case_monkey.rb
+++ b/activerecord/test/models/mixed_case_monkey.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class MixedCaseMonkey < ActiveRecord::Base
   belongs_to :man
 end
diff --git a/activerecord/test/models/mocktail_designer.rb b/activerecord/test/models/mocktail_designer.rb
index 77b44651a3..123ff4fb3d 100644
--- a/activerecord/test/models/mocktail_designer.rb
+++ b/activerecord/test/models/mocktail_designer.rb
@@ -1,2 +1,4 @@
+# frozen_string_literal: true
+
 class MocktailDesigner < DrinkDesigner
 end
diff --git a/activerecord/test/models/molecule.rb b/activerecord/test/models/molecule.rb
index 26870c8f88..7da08a85c4 100644
--- a/activerecord/test/models/molecule.rb
+++ b/activerecord/test/models/molecule.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Molecule < ActiveRecord::Base
   belongs_to :liquid
   has_many :electrons
diff --git a/activerecord/test/models/movie.rb b/activerecord/test/models/movie.rb
index 0302abad1e..fa2ea900c7 100644
--- a/activerecord/test/models/movie.rb
+++ b/activerecord/test/models/movie.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Movie < ActiveRecord::Base
   self.primary_key = "movieid"
 
diff --git a/activerecord/test/models/node.rb b/activerecord/test/models/node.rb
index 459ea8cf95..ae46c76b46 100644
--- a/activerecord/test/models/node.rb
+++ b/activerecord/test/models/node.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Node < ActiveRecord::Base
   belongs_to :tree, touch: true
   belongs_to :parent,   class_name: "Node", touch: true, optional: true
diff --git a/activerecord/test/models/non_primary_key.rb b/activerecord/test/models/non_primary_key.rb
index 1cafb09608..e954375989 100644
--- a/activerecord/test/models/non_primary_key.rb
+++ b/activerecord/test/models/non_primary_key.rb
@@ -1,2 +1,4 @@
+# frozen_string_literal: true
+
 class NonPrimaryKey < ActiveRecord::Base
 end
diff --git a/activerecord/test/models/notification.rb b/activerecord/test/models/notification.rb
index 82edc64b68..3f8728af5e 100644
--- a/activerecord/test/models/notification.rb
+++ b/activerecord/test/models/notification.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Notification < ActiveRecord::Base
   validates_presence_of :message
 end
diff --git a/activerecord/test/models/numeric_data.rb b/activerecord/test/models/numeric_data.rb
index c6e025a9ce..666e1a5778 100644
--- a/activerecord/test/models/numeric_data.rb
+++ b/activerecord/test/models/numeric_data.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class NumericData < ActiveRecord::Base
   self.table_name = "numeric_data"
   # Decimal columns with 0 scale being automatically treated as integers
diff --git a/activerecord/test/models/order.rb b/activerecord/test/models/order.rb
index 699be53959..36866b398f 100644
--- a/activerecord/test/models/order.rb
+++ b/activerecord/test/models/order.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Order < ActiveRecord::Base
   belongs_to :billing, class_name: "Customer", foreign_key: "billing_customer_id"
   belongs_to :shipping, class_name: "Customer", foreign_key: "shipping_customer_id"
diff --git a/activerecord/test/models/organization.rb b/activerecord/test/models/organization.rb
index 462830dadc..099e7e38e0 100644
--- a/activerecord/test/models/organization.rb
+++ b/activerecord/test/models/organization.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Organization < ActiveRecord::Base
   has_many :member_details
   has_many :members, through: :member_details
diff --git a/activerecord/test/models/other_dog.rb b/activerecord/test/models/other_dog.rb
index 418caf34be..a0fda5ae1b 100644
--- a/activerecord/test/models/other_dog.rb
+++ b/activerecord/test/models/other_dog.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_dependency "models/arunit2_model"
 
 class OtherDog < ARUnit2Model
diff --git a/activerecord/test/models/owner.rb b/activerecord/test/models/owner.rb
index 21fc9b6eb8..5fa50d9918 100644
--- a/activerecord/test/models/owner.rb
+++ b/activerecord/test/models/owner.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Owner < ActiveRecord::Base
   self.primary_key = :owner_id
   has_many :pets, -> { order "pets.name desc" }
diff --git a/activerecord/test/models/parrot.rb b/activerecord/test/models/parrot.rb
index 255ac19365..ba9ddb8c6a 100644
--- a/activerecord/test/models/parrot.rb
+++ b/activerecord/test/models/parrot.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Parrot < ActiveRecord::Base
   self.inheritance_column = :parrot_sti_class
 
diff --git a/activerecord/test/models/person.rb b/activerecord/test/models/person.rb
index 18994d6f18..5cba1e440e 100644
--- a/activerecord/test/models/person.rb
+++ b/activerecord/test/models/person.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Person < ActiveRecord::Base
   has_many :readers
   has_many :secure_readers
diff --git a/activerecord/test/models/personal_legacy_thing.rb b/activerecord/test/models/personal_legacy_thing.rb
index adde7a504a..ed8b70cfcc 100644
--- a/activerecord/test/models/personal_legacy_thing.rb
+++ b/activerecord/test/models/personal_legacy_thing.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PersonalLegacyThing < ActiveRecord::Base
   self.locking_column = :version
   belongs_to :person, counter_cache: true
diff --git a/activerecord/test/models/pet.rb b/activerecord/test/models/pet.rb
index 51a3e42815..9bda2109e6 100644
--- a/activerecord/test/models/pet.rb
+++ b/activerecord/test/models/pet.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Pet < ActiveRecord::Base
   attr_accessor :current_user
 
diff --git a/activerecord/test/models/pet_treasure.rb b/activerecord/test/models/pet_treasure.rb
index 1fe7807ffe..47b9f57fad 100644
--- a/activerecord/test/models/pet_treasure.rb
+++ b/activerecord/test/models/pet_treasure.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PetTreasure < ActiveRecord::Base
   self.table_name = "pets_treasures"
 
diff --git a/activerecord/test/models/pirate.rb b/activerecord/test/models/pirate.rb
index c532ab426e..c8617d1cfe 100644
--- a/activerecord/test/models/pirate.rb
+++ b/activerecord/test/models/pirate.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Pirate < ActiveRecord::Base
   belongs_to :parrot, validate: true
   belongs_to :non_validated_parrot, class_name: "Parrot"
diff --git a/activerecord/test/models/possession.rb b/activerecord/test/models/possession.rb
index 0226336c16..9b843e1525 100644
--- a/activerecord/test/models/possession.rb
+++ b/activerecord/test/models/possession.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Possession < ActiveRecord::Base
   self.table_name = "having"
 end
diff --git a/activerecord/test/models/post.rb b/activerecord/test/models/post.rb
index 4aba336b01..4b3576fce8 100644
--- a/activerecord/test/models/post.rb
+++ b/activerecord/test/models/post.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Post < ActiveRecord::Base
   class CategoryPost < ActiveRecord::Base
     self.table_name = "categories_posts"
diff --git a/activerecord/test/models/price_estimate.rb b/activerecord/test/models/price_estimate.rb
index ce086e40a3..f1f88d8d8d 100644
--- a/activerecord/test/models/price_estimate.rb
+++ b/activerecord/test/models/price_estimate.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PriceEstimate < ActiveRecord::Base
   belongs_to :estimate_of, polymorphic: true
   belongs_to :thing, polymorphic: true
diff --git a/activerecord/test/models/professor.rb b/activerecord/test/models/professor.rb
index 4dfb1a9602..abc23f40ff 100644
--- a/activerecord/test/models/professor.rb
+++ b/activerecord/test/models/professor.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_dependency "models/arunit2_model"
 
 class Professor < ARUnit2Model
diff --git a/activerecord/test/models/project.rb b/activerecord/test/models/project.rb
index 4fbd986e40..846cef625b 100644
--- a/activerecord/test/models/project.rb
+++ b/activerecord/test/models/project.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Project < ActiveRecord::Base
   belongs_to :mentor
   has_and_belongs_to_many :developers, -> { distinct.order "developers.name desc, developers.id desc" }
diff --git a/activerecord/test/models/publisher.rb b/activerecord/test/models/publisher.rb
index 0d4a7f9235..53677197c4 100644
--- a/activerecord/test/models/publisher.rb
+++ b/activerecord/test/models/publisher.rb
@@ -1,2 +1,4 @@
+# frozen_string_literal: true
+
 module Publisher
 end
diff --git a/activerecord/test/models/publisher/article.rb b/activerecord/test/models/publisher/article.rb
index d73a8eb936..355c22dcc5 100644
--- a/activerecord/test/models/publisher/article.rb
+++ b/activerecord/test/models/publisher/article.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Publisher::Article < ActiveRecord::Base
   has_and_belongs_to_many :magazines
   has_and_belongs_to_many :tags
diff --git a/activerecord/test/models/publisher/magazine.rb b/activerecord/test/models/publisher/magazine.rb
index 82e1a14008..425ede8df2 100644
--- a/activerecord/test/models/publisher/magazine.rb
+++ b/activerecord/test/models/publisher/magazine.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Publisher::Magazine < ActiveRecord::Base
   has_and_belongs_to_many :articles
 end
diff --git a/activerecord/test/models/randomly_named_c1.rb b/activerecord/test/models/randomly_named_c1.rb
index d4be1e13b4..f90a7b9336 100644
--- a/activerecord/test/models/randomly_named_c1.rb
+++ b/activerecord/test/models/randomly_named_c1.rb
@@ -1,3 +1,5 @@
-class ClassNameThatDoesNotFollowCONVENTIONS < ActiveRecord::Base

-  self.table_name = :randomly_named_table1

-end

+# frozen_string_literal: true
+
+class ClassNameThatDoesNotFollowCONVENTIONS < ActiveRecord::Base
+  self.table_name = :randomly_named_table1
+end
diff --git a/activerecord/test/models/rating.rb b/activerecord/test/models/rating.rb
index 7420821db0..cf06bc6931 100644
--- a/activerecord/test/models/rating.rb
+++ b/activerecord/test/models/rating.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Rating < ActiveRecord::Base
   belongs_to :comment
   has_many :taggings, as: :taggable
diff --git a/activerecord/test/models/reader.rb b/activerecord/test/models/reader.rb
index 7c5a159fe0..d25627e430 100644
--- a/activerecord/test/models/reader.rb
+++ b/activerecord/test/models/reader.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Reader < ActiveRecord::Base
   belongs_to :post
   belongs_to :person, inverse_of: :readers
diff --git a/activerecord/test/models/recipe.rb b/activerecord/test/models/recipe.rb
index c387230603..e53f5c8fb1 100644
--- a/activerecord/test/models/recipe.rb
+++ b/activerecord/test/models/recipe.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Recipe < ActiveRecord::Base
   belongs_to :chef
 end
diff --git a/activerecord/test/models/record.rb b/activerecord/test/models/record.rb
index f77ac9fc03..63143e296a 100644
--- a/activerecord/test/models/record.rb
+++ b/activerecord/test/models/record.rb
@@ -1,2 +1,4 @@
+# frozen_string_literal: true
+
 class Record < ActiveRecord::Base
 end
diff --git a/activerecord/test/models/reference.rb b/activerecord/test/models/reference.rb
index e2bb980fed..2a7a1e3b77 100644
--- a/activerecord/test/models/reference.rb
+++ b/activerecord/test/models/reference.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Reference < ActiveRecord::Base
   belongs_to :person
   belongs_to :job
diff --git a/activerecord/test/models/reply.rb b/activerecord/test/models/reply.rb
index a2d169292a..bc829ec67f 100644
--- a/activerecord/test/models/reply.rb
+++ b/activerecord/test/models/reply.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "models/topic"
 
 class Reply < Topic
diff --git a/activerecord/test/models/ship.rb b/activerecord/test/models/ship.rb
index 77a7b22315..7973219a79 100644
--- a/activerecord/test/models/ship.rb
+++ b/activerecord/test/models/ship.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Ship < ActiveRecord::Base
   self.record_timestamps = false
 
diff --git a/activerecord/test/models/ship_part.rb b/activerecord/test/models/ship_part.rb
index 1a633b8d77..f6d7a8ae5e 100644
--- a/activerecord/test/models/ship_part.rb
+++ b/activerecord/test/models/ship_part.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ShipPart < ActiveRecord::Base
   belongs_to :ship
   has_many :trinkets, class_name: "Treasure", as: :looter
diff --git a/activerecord/test/models/shop.rb b/activerecord/test/models/shop.rb
index f9d23d13b0..92afe70b92 100644
--- a/activerecord/test/models/shop.rb
+++ b/activerecord/test/models/shop.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Shop
   class Collection < ActiveRecord::Base
     has_many :products, dependent: :nullify
diff --git a/activerecord/test/models/shop_account.rb b/activerecord/test/models/shop_account.rb
index 1580e8b20c..97fb058331 100644
--- a/activerecord/test/models/shop_account.rb
+++ b/activerecord/test/models/shop_account.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ShopAccount < ActiveRecord::Base
   belongs_to :customer
   belongs_to :customer_carrier
diff --git a/activerecord/test/models/speedometer.rb b/activerecord/test/models/speedometer.rb
index 497c3aba9a..e456907a22 100644
--- a/activerecord/test/models/speedometer.rb
+++ b/activerecord/test/models/speedometer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Speedometer < ActiveRecord::Base
   self.primary_key = :speedometer_id
   belongs_to :dashboard
diff --git a/activerecord/test/models/sponsor.rb b/activerecord/test/models/sponsor.rb
index 3f142b25fe..f190860fd1 100644
--- a/activerecord/test/models/sponsor.rb
+++ b/activerecord/test/models/sponsor.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Sponsor < ActiveRecord::Base
   belongs_to :sponsor_club, class_name: "Club", foreign_key: "club_id"
   belongs_to :sponsorable, polymorphic: true
diff --git a/activerecord/test/models/string_key_object.rb b/activerecord/test/models/string_key_object.rb
index f084ec1bdc..473c145f4c 100644
--- a/activerecord/test/models/string_key_object.rb
+++ b/activerecord/test/models/string_key_object.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class StringKeyObject < ActiveRecord::Base
   self.primary_key = :id
 end
diff --git a/activerecord/test/models/student.rb b/activerecord/test/models/student.rb
index 28a0b6c99b..e750798f74 100644
--- a/activerecord/test/models/student.rb
+++ b/activerecord/test/models/student.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Student < ActiveRecord::Base
   has_and_belongs_to_many :lessons
   belongs_to :college
diff --git a/activerecord/test/models/subscriber.rb b/activerecord/test/models/subscriber.rb
index a820329003..b21969ca2d 100644
--- a/activerecord/test/models/subscriber.rb
+++ b/activerecord/test/models/subscriber.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Subscriber < ActiveRecord::Base
   self.primary_key = "nick"
   has_many :subscriptions
diff --git a/activerecord/test/models/subscription.rb b/activerecord/test/models/subscription.rb
index 1cedf6deae..d1d5d21621 100644
--- a/activerecord/test/models/subscription.rb
+++ b/activerecord/test/models/subscription.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Subscription < ActiveRecord::Base
   belongs_to :subscriber, counter_cache: :books_count
   belongs_to :book
diff --git a/activerecord/test/models/tag.rb b/activerecord/test/models/tag.rb
index c907aea10f..4495ac4a09 100644
--- a/activerecord/test/models/tag.rb
+++ b/activerecord/test/models/tag.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Tag < ActiveRecord::Base
   has_many :taggings
   has_many :taggables, through: :taggings
diff --git a/activerecord/test/models/tagging.rb b/activerecord/test/models/tagging.rb
index f739b4a197..fc0af026c5 100644
--- a/activerecord/test/models/tagging.rb
+++ b/activerecord/test/models/tagging.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # test that attr_readonly isn't called on the :taggable polymorphic association
 module Taggable
 end
diff --git a/activerecord/test/models/task.rb b/activerecord/test/models/task.rb
index e36989dd56..dabe3ce06b 100644
--- a/activerecord/test/models/task.rb
+++ b/activerecord/test/models/task.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Task < ActiveRecord::Base
   def updated_at
     ending
diff --git a/activerecord/test/models/topic.rb b/activerecord/test/models/topic.rb
index d9381ac9cf..2154b50ef7 100644
--- a/activerecord/test/models/topic.rb
+++ b/activerecord/test/models/topic.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Topic < ActiveRecord::Base
   scope :base, -> { all }
   scope :written_before, lambda { |time|
diff --git a/activerecord/test/models/toy.rb b/activerecord/test/models/toy.rb
index ddc7048a56..4a5697eeb1 100644
--- a/activerecord/test/models/toy.rb
+++ b/activerecord/test/models/toy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Toy < ActiveRecord::Base
   self.primary_key = :toy_id
   belongs_to :pet
diff --git a/activerecord/test/models/traffic_light.rb b/activerecord/test/models/traffic_light.rb
index a6b7edb882..0b88815cbd 100644
--- a/activerecord/test/models/traffic_light.rb
+++ b/activerecord/test/models/traffic_light.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class TrafficLight < ActiveRecord::Base
   serialize :state, Array
   serialize :long_state, Array
diff --git a/activerecord/test/models/treasure.rb b/activerecord/test/models/treasure.rb
index fb2a5d44e2..b51db56c37 100644
--- a/activerecord/test/models/treasure.rb
+++ b/activerecord/test/models/treasure.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Treasure < ActiveRecord::Base
   has_and_belongs_to_many :parrots
   belongs_to :looter, polymorphic: true
diff --git a/activerecord/test/models/treaty.rb b/activerecord/test/models/treaty.rb
index 373cd48f71..5c1d75aa09 100644
--- a/activerecord/test/models/treaty.rb
+++ b/activerecord/test/models/treaty.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Treaty < ActiveRecord::Base
   self.primary_key = :treaty_id
 
diff --git a/activerecord/test/models/tree.rb b/activerecord/test/models/tree.rb
index dc29cccc9c..77050c5fff 100644
--- a/activerecord/test/models/tree.rb
+++ b/activerecord/test/models/tree.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Tree < ActiveRecord::Base
   has_many :nodes, dependent: :destroy
 end
diff --git a/activerecord/test/models/tuning_peg.rb b/activerecord/test/models/tuning_peg.rb
index 1252d6dc1d..6e052e1d0f 100644
--- a/activerecord/test/models/tuning_peg.rb
+++ b/activerecord/test/models/tuning_peg.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class TuningPeg < ActiveRecord::Base
   belongs_to :guitar
   validates_numericality_of :pitch
diff --git a/activerecord/test/models/tyre.rb b/activerecord/test/models/tyre.rb
index e50a21ca68..d627026585 100644
--- a/activerecord/test/models/tyre.rb
+++ b/activerecord/test/models/tyre.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Tyre < ActiveRecord::Base
   belongs_to :car
 
diff --git a/activerecord/test/models/user.rb b/activerecord/test/models/user.rb
index 5089a795f4..3efbc45d2a 100644
--- a/activerecord/test/models/user.rb
+++ b/activerecord/test/models/user.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "models/job"
 
 class User < ActiveRecord::Base
diff --git a/activerecord/test/models/uuid_child.rb b/activerecord/test/models/uuid_child.rb
index a3d0962ad6..9fce361cc8 100644
--- a/activerecord/test/models/uuid_child.rb
+++ b/activerecord/test/models/uuid_child.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class UuidChild < ActiveRecord::Base
   belongs_to :uuid_parent
 end
diff --git a/activerecord/test/models/uuid_item.rb b/activerecord/test/models/uuid_item.rb
index 2353e40213..41f68c4c18 100644
--- a/activerecord/test/models/uuid_item.rb
+++ b/activerecord/test/models/uuid_item.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class UuidItem < ActiveRecord::Base
 end
 
diff --git a/activerecord/test/models/uuid_parent.rb b/activerecord/test/models/uuid_parent.rb
index 5634f22d0c..05db61855e 100644
--- a/activerecord/test/models/uuid_parent.rb
+++ b/activerecord/test/models/uuid_parent.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class UuidParent < ActiveRecord::Base
   has_many :uuid_children
 end
diff --git a/activerecord/test/models/vegetables.rb b/activerecord/test/models/vegetables.rb
index a4590d06e0..cfaab08ed1 100644
--- a/activerecord/test/models/vegetables.rb
+++ b/activerecord/test/models/vegetables.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Vegetable < ActiveRecord::Base
   validates_presence_of :name
 
diff --git a/activerecord/test/models/vehicle.rb b/activerecord/test/models/vehicle.rb
index 855bc4e325..c9b3338522 100644
--- a/activerecord/test/models/vehicle.rb
+++ b/activerecord/test/models/vehicle.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Vehicle < ActiveRecord::Base
   self.abstract_class = true
   default_scope -> { where("tires_count IS NOT NULL") }
diff --git a/activerecord/test/models/vertex.rb b/activerecord/test/models/vertex.rb
index 3d19433b6f..0ad8114898 100644
--- a/activerecord/test/models/vertex.rb
+++ b/activerecord/test/models/vertex.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This class models a vertex in a directed graph.
 class Vertex < ActiveRecord::Base
   has_many :sink_edges, class_name: "Edge", foreign_key: "source_id"
diff --git a/activerecord/test/models/warehouse_thing.rb b/activerecord/test/models/warehouse_thing.rb
index f20bd1a245..099633af55 100644
--- a/activerecord/test/models/warehouse_thing.rb
+++ b/activerecord/test/models/warehouse_thing.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class WarehouseThing < ActiveRecord::Base
   self.table_name = "warehouse-things"
 
diff --git a/activerecord/test/models/wheel.rb b/activerecord/test/models/wheel.rb
index cba2b3e518..e05fb64477 100644
--- a/activerecord/test/models/wheel.rb
+++ b/activerecord/test/models/wheel.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Wheel < ActiveRecord::Base
   belongs_to :wheelable, polymorphic: true, counter_cache: true
 end
diff --git a/activerecord/test/models/without_table.rb b/activerecord/test/models/without_table.rb
index 7c0fc286e1..fc0a52d6ad 100644
--- a/activerecord/test/models/without_table.rb
+++ b/activerecord/test/models/without_table.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class WithoutTable < ActiveRecord::Base
   default_scope -> { where(published: true) }
 end
diff --git a/activerecord/test/models/zine.rb b/activerecord/test/models/zine.rb
index 3f2b348b46..6f361665ef 100644
--- a/activerecord/test/models/zine.rb
+++ b/activerecord/test/models/zine.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Zine < ActiveRecord::Base
   has_many :interests, inverse_of: :zine
 end
diff --git a/activerecord/test/schema/mysql2_specific_schema.rb b/activerecord/test/schema/mysql2_specific_schema.rb
index 90a314c83c..e634e9e6b1 100644
--- a/activerecord/test/schema/mysql2_specific_schema.rb
+++ b/activerecord/test/schema/mysql2_specific_schema.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 ActiveRecord::Schema.define do
 
   if ActiveRecord::Base.connection.version >= "5.6.0"
diff --git a/activerecord/test/schema/oracle_specific_schema.rb b/activerecord/test/schema/oracle_specific_schema.rb
index 264d9b8910..e236571caa 100644
--- a/activerecord/test/schema/oracle_specific_schema.rb
+++ b/activerecord/test/schema/oracle_specific_schema.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 ActiveRecord::Schema.define do
 
   execute "drop table test_oracle_defaults" rescue nil
diff --git a/activerecord/test/schema/postgresql_specific_schema.rb b/activerecord/test/schema/postgresql_specific_schema.rb
index e56e8fa36a..f15178d695 100644
--- a/activerecord/test/schema/postgresql_specific_schema.rb
+++ b/activerecord/test/schema/postgresql_specific_schema.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 ActiveRecord::Schema.define do
 
   enable_extension!("uuid-ossp", ActiveRecord::Base.connection)
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 90185ff6c5..05420a4240 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 ActiveRecord::Schema.define do
   # ------------------------------------------------------------------- #
   #                                                                     #
diff --git a/activerecord/test/support/config.rb b/activerecord/test/support/config.rb
index aaff408b41..bd6d5c339b 100644
--- a/activerecord/test/support/config.rb
+++ b/activerecord/test/support/config.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "yaml"
 require "erb"
 require "fileutils"
diff --git a/activerecord/test/support/connection.rb b/activerecord/test/support/connection.rb
index 1a609e13c3..2a4fa53460 100644
--- a/activerecord/test/support/connection.rb
+++ b/activerecord/test/support/connection.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/logger"
 require "models/college"
 require "models/course"
diff --git a/activerecord/test/support/connection_helper.rb b/activerecord/test/support/connection_helper.rb
index 4a19e5df44..3bb1b370c1 100644
--- a/activerecord/test/support/connection_helper.rb
+++ b/activerecord/test/support/connection_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ConnectionHelper
   def run_without_connection
     original_connection = ActiveRecord::Base.remove_connection
diff --git a/activerecord/test/support/ddl_helper.rb b/activerecord/test/support/ddl_helper.rb
index 43cb235e01..a18bf5ea0a 100644
--- a/activerecord/test/support/ddl_helper.rb
+++ b/activerecord/test/support/ddl_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module DdlHelper
   def with_example_table(connection, table_name, definition = nil)
     connection.execute("CREATE TABLE #{table_name}(#{definition})")
diff --git a/activerecord/test/support/schema_dumping_helper.rb b/activerecord/test/support/schema_dumping_helper.rb
index 666c1b6a14..777e6a7c1b 100644
--- a/activerecord/test/support/schema_dumping_helper.rb
+++ b/activerecord/test/support/schema_dumping_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SchemaDumpingHelper
   def dump_table_schema(table, connection = ActiveRecord::Base.connection)
     old_ignore_tables = ActiveRecord::SchemaDumper.ignore_tables