delegate_to_missing doesn't delegate private methods

So we shouldn't claim they're there, even when asked explicitly.

activesupport/lib/active_support/core_ext/module/delegation.rb

@@ -267,7 +267,10 @@ class Module
 
     module_eval <<-RUBY, __FILE__, __LINE__ + 1
       def respond_to_missing?(name, include_private = false)
-        #{target}.respond_to?(name, include_private)
+        # It may look like an oversight, but we deliberately do not pass
+        # +include_private+, because they do not get delegated.
+
+        #{target}.respond_to?(name)
       end
 
       def method_missing(method, *args, &block)

activesupport/test/core_ext/module_test.rb

@@ -356,6 +356,16 @@ class ModuleTest < ActiveSupport::TestCase
     assert_match(/undefined method `my_fake_method' for/, e.message)
   end
 
+  def test_delegate_to_missing_affects_respond_to
+    assert DecoratedTester.new(@david).respond_to?(:name)
+    assert_not DecoratedTester.new(@david).respond_to?(:private_name)
+    assert_not DecoratedTester.new(@david).respond_to?(:my_fake_method)
+
+    assert DecoratedTester.new(@david).respond_to?(:name, true)
+    assert_not DecoratedTester.new(@david).respond_to?(:private_name, true)
+    assert_not DecoratedTester.new(@david).respond_to?(:my_fake_method, true)
+  end
+
   def test_delegate_with_case
     event = Event.new(Tester.new)
     assert_equal 1, event.foo