'A trigger removed with L{IReactorCore.removeSystemEventTrigger} should
not be called when the event fires.'

def test_removeSystemEventTrigger(self):

    eventType = 'test'
    events = []
    def firstBeforeTrigger():
        events.append('first')
    def secondBeforeTrigger():
        events.append('second')
    self.addTrigger('before', eventType, firstBeforeTrigger)
    self.removeTrigger(self.addTrigger('before', eventType, secondBeforeTrigger))
    self.assertEqual(events, [])
    reactor.fireSystemEvent(eventType)
    self.assertEqual(events, ['first'])
