1 files changed, 28 insertions, 0 deletions
diff --git a/activesupport/test/core_ext/object_and_class_ext_test.rb b/activesupport/test/core_ext/object_and_class_ext_test.rb
index 9daf8d0ac4..e48d87a198 100644
--- a/activesupport/test/core_ext/object_and_class_ext_test.rb
+++ b/activesupport/test/core_ext/object_and_class_ext_test.rb
@@ -96,6 +96,34 @@ class ObjectTests < Test::Unit::TestCase
     assert object.respond_to?(:baz)
   end
 
+  class DuckTime
+    def acts_like_time?
+      true
+    end
+  end
+
+  def test_duck_typing
+    object = Object.new
+    time   = Time.now
+    date   = Date.today
+    dt     = DateTime.new
+    duck   = DuckTime.new
+
+    assert !object.acts_like?(:time)
+    assert !object.acts_like?(:date)
+
+    assert time.acts_like?(:time)
+    assert !time.acts_like?(:date)
+
+    assert !date.acts_like?(:time)
+    assert date.acts_like?(:date)
+
+    assert dt.acts_like?(:time)
+    assert dt.acts_like?(:date)
+
+    assert duck.acts_like?(:time)
+    assert !duck.acts_like?(:date)
+  end
 end
 
 class ObjectInstanceVariableTest < Test::Unit::TestCase