public function testDuplicateIdentifiersAreNotRegistered()
 {
     $events = new Zend_EventManager_EventManager(array(__CLASS__, get_class($this)));
     $identifiers = $events->getIdentifiers();
     $this->assertSame(count($identifiers), 1);
     $this->assertSame($identifiers[0], __CLASS__);
     $events->addIdentifiers(__CLASS__);
     $this->assertSame(count($identifiers), 1);
     $this->assertSame($identifiers[0], __CLASS__);
 }