Adjust `Module.parent_name` to work when frozen; fixes #27637

1 files changed, 37 insertions, 0 deletions

diff --git a/activesupport/test/core_ext/module/introspection_test.rb b/activesupport/test/core_ext/module/introspection_test.rb
new file mode 100644
index 0000000000..db383850cd
--- /dev/null
+++ b/activesupport/test/core_ext/module/introspection_test.rb
@@ -0,0 +1,37 @@
+require "abstract_unit"
+require "active_support/core_ext/module/introspection"
+
+module ParentA
+  module B
+    module C; end
+    module FrozenC; end
+    FrozenC.freeze
+  end
+
+  module FrozenB; end
+  FrozenB.freeze
+end
+
+class IntrospectionTest < ActiveSupport::TestCase
+  def test_parent_name
+    assert_equal "ParentA", ParentA::B.parent_name
+    assert_equal "ParentA::B", ParentA::B::C.parent_name
+    assert_nil ParentA.parent_name
+  end
+
+  def test_parent_name_when_frozen
+    assert_equal "ParentA", ParentA::FrozenB.parent_name
+    assert_equal "ParentA::B", ParentA::B::FrozenC.parent_name
+  end
+
+  def test_parent
+    assert_equal ParentA::B, ParentA::B::C.parent
+    assert_equal ParentA, ParentA::B.parent
+    assert_equal Object, ParentA.parent
+  end
+
+  def test_parents
+    assert_equal [ParentA::B, ParentA, Object], ParentA::B::C.parents
+    assert_equal [ParentA, Object], ParentA::B.parents
+  end
+end