1 files changed, 139 insertions, 0 deletions
diff --git a/activesupport/test/concern_test.rb b/activesupport/test/concern_test.rb
new file mode 100644
index 0000000000..4b3cfcd1d2
--- /dev/null
+++ b/activesupport/test/concern_test.rb
@@ -0,0 +1,139 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "active_support/concern"
+
+class ConcernTest < ActiveSupport::TestCase
+  module Baz
+    extend ActiveSupport::Concern
+
+    class_methods do
+      def baz
+        "baz"
+      end
+
+      def included_ran=(value)
+        @@included_ran = value
+      end
+
+      def included_ran
+        @@included_ran
+      end
+    end
+
+    included do
+      self.included_ran = true
+    end
+
+    def baz
+      "baz"
+    end
+  end
+
+  module Bar
+    extend ActiveSupport::Concern
+
+    include Baz
+
+    module ClassMethods
+      def baz
+        "bar's baz + " + super
+      end
+    end
+
+    def bar
+      "bar"
+    end
+
+    def baz
+      "bar+" + super
+    end
+  end
+
+  module Foo
+    extend ActiveSupport::Concern
+
+    include Bar, Baz
+  end
+
+  module Qux
+    module ClassMethods
+    end
+  end
+
+  def setup
+    @klass = Class.new
+  end
+
+  def test_module_is_included_normally
+    @klass.include(Baz)
+    assert_equal "baz", @klass.new.baz
+    assert_includes @klass.included_modules, ConcernTest::Baz
+  end
+
+  def test_class_methods_are_extended
+    @klass.include(Baz)
+    assert_equal "baz", @klass.baz
+    assert_equal ConcernTest::Baz::ClassMethods, (class << @klass; included_modules; end)[0]
+  end
+
+  def test_class_methods_are_extended_only_on_expected_objects
+    ::Object.include(Qux)
+    Object.extend(Qux::ClassMethods)
+    # module needs to be created after Qux is included in Object or bug won't
+    # be triggered
+    test_module = Module.new do
+      extend ActiveSupport::Concern
+
+      class_methods do
+        def test
+        end
+      end
+    end
+    @klass.include test_module
+    assert_not_respond_to Object, :test
+    Qux.class_eval do
+      remove_const :ClassMethods
+    end
+  end
+
+  def test_included_block_is_ran
+    @klass.include(Baz)
+    assert_equal true, @klass.included_ran
+  end
+
+  def test_modules_dependencies_are_met
+    @klass.include(Bar)
+    assert_equal "bar", @klass.new.bar
+    assert_equal "bar+baz", @klass.new.baz
+    assert_equal "bar's baz + baz", @klass.baz
+    assert_includes @klass.included_modules, ConcernTest::Bar
+  end
+
+  def test_dependencies_with_multiple_modules
+    @klass.include(Foo)
+    assert_equal [ConcernTest::Foo, ConcernTest::Bar, ConcernTest::Baz], @klass.included_modules[0..2]
+  end
+
+  def test_raise_on_multiple_included_calls
+    assert_raises(ActiveSupport::Concern::MultipleIncludedBlocks) do
+      Module.new do
+        extend ActiveSupport::Concern
+
+        included do
+        end
+
+        included do
+        end
+      end
+    end
+  end
+
+  def test_no_raise_on_same_included_call
+    assert_nothing_raised do
+      2.times do
+        load File.expand_path("../fixtures/concern/some_concern.rb", __FILE__)
+      end
+    end
+  end
+end