Add App::uses()

lib/Cake/Test/test_app/Plugin/TestPlugin/Controller/TestPluginAppController.php

@@ -16,5 +16,8 @@
  * @since         CakePHP(tm) v 1.2.0.5432
  * @license       MIT License (http://www.opensource.org/licenses/mit-license.php)
  */
+
+App::uses('AppController', 'Controller');
+
 class TestPluginAppController extends AppController {
 }