'L{_ThreePhaseEvent.removeTrigger} should accept an opaque object
previously returned by L{_ThreePhaseEvent.addTrigger} and remove the
associated trigger.'

def test_removeTrigger(self):

    handle = self.event.addTrigger('before', self.trigger, self.arg)
    self.event.removeTrigger(handle)
    self.assertEqual(self.event.before, [])
