def test_beforePreceedsDuring(self):
        """
        L{IReactorCore.addSystemEventTrigger} should call triggers added to the
        C{'before'} phase before it calls triggers added to the C{'during'}
        phase.
        """
        eventType = 'test'
        events = []
        def beforeTrigger():
            events.append('before')
        def duringTrigger():
            events.append('during')
        self.addTrigger('before', eventType, beforeTrigger)
        self.addTrigger('during', eventType, duringTrigger)
        self.assertEqual(events, [])
        reactor.fireSystemEvent(eventType)
        self.assertEqual(events, ['before', 'during'])

        L{IReactorCore.addSystemEventTrigger} should call triggers added to the
        C{'before'} phase before it calls triggers added to the C{'during'}
        phase.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_internet.py