/**
  * @depends testSubscribesToTopic
  */
 public function testListsSubscriptions($subscriptionArn)
 {
     self::log('List subscriptions');
     $i = $this->sns->getIterator('ListSubscriptionsByTopic', array('TopicArn' => self::$topicArn));
     $data = iterator_to_array($i);
     self::log('Found the following subscriptions: ' . var_export($data, true));
     foreach ($data as $sub) {
         if ($sub['SubscriptionArn'] == self::$subscriptionArn) {
             return true;
         }
     }
     $this->fail('Did not find the subscription ARN of ' . self::$subscriptionArn);
 }