add engine's namespace to fixture name

railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb

@@ -15,6 +15,15 @@ def create_test_files
                  File.join("test/controllers", controller_class_path, "#{controller_file_name}_controller_test.rb")
       end
 
+      def fixture_name
+        @fixture_name ||=
+          if defined?(ENGINE_ROOT)
+            namespaced_path + "_" + table_name
+          else
+            table_name
+          end
+      end
+
       private
 
         def attributes_hash

railties/lib/rails/generators/test_unit/scaffold/templates/functional_test.rb

@@ -3,7 +3,7 @@
 <% module_namespacing do -%>
 class <%= controller_class_name %>ControllerTest < ActionController::TestCase
   setup do
-    @<%= singular_table_name %> = <%= table_name %>(:one)
+    @<%= singular_table_name %> = <%= fixture_name %>(:one)
 <% if defined?(ENGINE_ROOT) -%>
     @routes = Engine.routes
 <% end -%>

railties/test/generators/plugin_generator_test.rb

@@ -521,6 +521,7 @@ def test_generating_scaffold_controller_inside_mountable_engine
     end
 
     assert_file "test/controllers/bukkits/users_controller_test.rb" do |contents|
+      assert_match(/@user = bukkits_users\(:one\)/, contents)
       assert_match(/@routes = Engine.routes/, contents)
     end
   end