private function mockResponse($status, $body = null)
 {
     $mock = new Mock();
     if ($status === 200) {
         $mock->addResponse(new Response($status, array(), $body === null ? null : Stream::factory($body)));
     } else {
         $mock->addException(new RequestException('Exception', new Request('GET', 'http://graph.facebook.com/xyz')));
     }
     $this->guzzleClient->getEmitter()->attach($mock);
 }