Add ActiveSupport::DescendantsTracker.

1 files changed, 72 insertions, 0 deletions

diff --git a/activesupport/test/descendants_tracker_test.rb b/activesupport/test/descendants_tracker_test.rb
new file mode 100644
index 0000000000..57c97b45d2
--- /dev/null
+++ b/activesupport/test/descendants_tracker_test.rb
@@ -0,0 +1,72 @@
+require 'abstract_unit'
+require 'test/unit'
+require 'active_support'
+
+class DescendantsTrackerTest < Test::Unit::TestCase
+  class Parent
+    extend ActiveSupport::DescendantsTracker
+  end
+
+  class Child1 < Parent
+  end
+
+  class Child2 < Parent
+  end
+
+  class Grandchild1 < Child1
+  end
+
+  class Grandchild2 < Child1
+  end
+
+  def test_descendants
+    assert_equal [Child1, Grandchild1, Grandchild2, Child2], Parent.descendants
+    assert_equal [Grandchild1, Grandchild2], Child1.descendants
+    assert_equal [], Child2.descendants
+  end
+
+  def test_direct_descendants
+    assert_equal [Child1, Child2], Parent.direct_descendants
+    assert_equal [Grandchild1, Grandchild2], Child1.direct_descendants
+    assert_equal [], Child2.direct_descendants
+  end
+
+  def test_clear_with_autoloaded_parent_children_and_granchildren
+    mark_as_autoloaded Parent, Child1, Child2, Grandchild1, Grandchild2 do
+      ActiveSupport::DescendantsTracker.clear
+      assert_equal Hash.new, ActiveSupport::DescendantsTracker.descendants
+    end
+  end
+
+  def test_clear_with_autoloaded_children_and_granchildren
+    mark_as_autoloaded Child1, Grandchild1, Grandchild2 do
+      ActiveSupport::DescendantsTracker.clear
+      assert_equal [Child2], Parent.descendants
+      assert_equal [], Child2.descendants
+    end
+  end
+
+  def test_clear_with_autoloaded_granchildren
+    mark_as_autoloaded Grandchild1, Grandchild2 do
+      ActiveSupport::DescendantsTracker.clear
+      assert_equal [Child1, Child2], Parent.descendants
+      assert_equal [], Child1.descendants
+      assert_equal [], Child2.descendants
+    end
+  end
+
+  protected
+
+  def mark_as_autoloaded(*klasses)
+    old_autoloaded = ActiveSupport::Dependencies.autoloaded_constants.dup
+    ActiveSupport::Dependencies.autoloaded_constants = klasses.map(&:name)
+
+    old_descendants = ActiveSupport::DescendantsTracker.descendants.dup
+    old_descendants.each { |k, v| old_descendants[k] = v.dup }
+
+    yield
+  ensure
+    ActiveSupport::Dependencies.autoloaded_constants = old_autoloaded
+    ActiveSupport::DescendantsTracker.descendants = old_descendants
+  end
+end
\ No newline at end of file