1 files changed, 148 insertions, 0 deletions
diff --git a/activerecord/test/cases/associations/eager_singularization_test.rb b/activerecord/test/cases/associations/eager_singularization_test.rb
new file mode 100644
index 0000000000..420a5a805b
--- /dev/null
+++ b/activerecord/test/cases/associations/eager_singularization_test.rb
@@ -0,0 +1,148 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+
+class EagerSingularizationTest < ActiveRecord::TestCase
+  class Virus < ActiveRecord::Base
+    belongs_to :octopus
+  end
+
+  class Octopus < ActiveRecord::Base
+    has_one :virus
+  end
+
+  class Pass < ActiveRecord::Base
+    belongs_to :bus
+  end
+
+  class Bus < ActiveRecord::Base
+    has_many :passes
+  end
+
+  class Mess < ActiveRecord::Base
+    has_and_belongs_to_many :crises
+  end
+
+  class Crisis < ActiveRecord::Base
+    has_and_belongs_to_many :messes
+    has_many :analyses, dependent: :destroy
+    has_many :successes, through: :analyses
+    has_many :dresses, dependent: :destroy
+    has_many :compresses, through: :dresses
+  end
+
+  class Analysis < ActiveRecord::Base
+    belongs_to :crisis
+    belongs_to :success
+  end
+
+  class Success < ActiveRecord::Base
+    has_many :analyses, dependent: :destroy
+    has_many :crises, through: :analyses
+  end
+
+  class Dress < ActiveRecord::Base
+    belongs_to :crisis
+    has_many :compresses
+  end
+
+  class Compress < ActiveRecord::Base
+    belongs_to :dress
+  end
+
+  def setup
+    connection.create_table :viri do |t|
+      t.column :octopus_id, :integer
+      t.column :species, :string
+    end
+    connection.create_table :octopi do |t|
+      t.column :species, :string
+    end
+    connection.create_table :passes do |t|
+      t.column :bus_id, :integer
+      t.column :rides, :integer
+    end
+    connection.create_table :buses do |t|
+      t.column :name, :string
+    end
+    connection.create_table :crises_messes, id: false do |t|
+      t.column :crisis_id, :integer
+      t.column :mess_id, :integer
+    end
+    connection.create_table :messes do |t|
+      t.column :name, :string
+    end
+    connection.create_table :crises do |t|
+      t.column :name, :string
+    end
+    connection.create_table :successes do |t|
+      t.column :name, :string
+    end
+    connection.create_table :analyses do |t|
+      t.column :crisis_id, :integer
+      t.column :success_id, :integer
+    end
+    connection.create_table :dresses do |t|
+      t.column :crisis_id, :integer
+    end
+    connection.create_table :compresses do |t|
+      t.column :dress_id, :integer
+    end
+  end
+
+  teardown do
+    connection.drop_table :viri
+    connection.drop_table :octopi
+    connection.drop_table :passes
+    connection.drop_table :buses
+    connection.drop_table :crises_messes
+    connection.drop_table :messes
+    connection.drop_table :crises
+    connection.drop_table :successes
+    connection.drop_table :analyses
+    connection.drop_table :dresses
+    connection.drop_table :compresses
+  end
+
+  def test_eager_no_extra_singularization_belongs_to
+    assert_nothing_raised do
+      Virus.all.merge!(includes: :octopus).to_a
+    end
+  end
+
+  def test_eager_no_extra_singularization_has_one
+    assert_nothing_raised do
+      Octopus.all.merge!(includes: :virus).to_a
+    end
+  end
+
+  def test_eager_no_extra_singularization_has_many
+    assert_nothing_raised do
+      Bus.all.merge!(includes: :passes).to_a
+    end
+  end
+
+  def test_eager_no_extra_singularization_has_and_belongs_to_many
+    assert_nothing_raised do
+      Crisis.all.merge!(includes: :messes).to_a
+      Mess.all.merge!(includes: :crises).to_a
+    end
+  end
+
+  def test_eager_no_extra_singularization_has_many_through_belongs_to
+    assert_nothing_raised do
+      Crisis.all.merge!(includes: :successes).to_a
+    end
+  end
+
+  def test_eager_no_extra_singularization_has_many_through_has_many
+    assert_nothing_raised do
+      Crisis.all.merge!(includes: :compresses).to_a
+    end
+  end
+
+  private
+    def connection
+      ActiveRecord::Base.connection
+    end
+end