'L{_ThreePhaseEvent.removeTrigger} should raise L{ValueError} the second
time it is called with an object returned by
L{_ThreePhaseEvent.addTrigger}.'

def test_removeRemovedTrigger(self):

    handle = self.event.addTrigger('before', self.trigger, self.arg)
    self.event.removeTrigger(handle)
    self.assertRaises(ValueError, self.event.removeTrigger, handle)
