Stub is_a? not instance_of? here

railties/test/generators/app_generator_test.rb

@@ -114,7 +114,7 @@ def test_application_name_is_detected_if_it_exists_and_app_folder_renamed
 
     Rails.application.config.root = app_moved_root
     Rails.application.class.stubs(:name).returns("Myapp")
-    Rails.application.stubs(:instance_of?).returns(Rails::Application)
+    Rails.application.stubs(:is_a?).returns(Rails::Application)
 
     FileUtils.mv(app_root, app_moved_root)