Metabor\Observer\Subject::attach PHP Method

    public function attach(\SplObserver $observer)
    {
        $this->observers->attach($observer);
    }

 public function testWillThrowAnExcpetionIfObserverIsNotAnEvent()
 {
     $command = $this->createTestInstance(array('__invoke'));
     $subject = new Subject();
     $subject->attach($command);
     $this->setExpectedException('\\Exception');
     $subject->notify();
 }