AppModel.php

    public function __construct($id = false, $table = null, $ds = null) {
        parent::__construct($id, $table, $ds);
        $activities = new ActivityListener();
	$this->getEventManager()->attach($activities);
    }

gistfile1.php

    public function setUp() {
	    parent::setUp();
	    $this->AppModel = ClassRegistry::init('AppModel');
	    $this->AppModel->useTable = false;
	    
		$this->AppModel = $this->getMockForModel('AppModel');
		// This is where the error happens
		$this->AppModel->UserComment = $this->getMockForModel('UserComment');
	}
	
	public function testGetTaskId(){
		$test_id = 'Pwf_task_7465';
		$id = $this->AppModel->get_task_id($test_id);
		$this->assertEqual($id, $test_id);
		
		$missing_id = 'Pwf_task_0000';
		$id = $this->AppModel->get_task_id($missing_id);
		$this->assertEqual($id, null);

		$test_id = 'Pwf_project_7777';
		$id = $this->AppModel->get_project_id($test_id);
		$this->assertEqual($id, $test_id);
		
		$missing_id = 'Pwf_project_0000';
		$id = $this->AppModel->get_project_id($missing_id);
		$this->assertEqual($id, null);
		
	}