def test_delayDelayedCall(self):
        """
        If a delayed call is re-delayed, the timeout passed to
        C{doIteration} is based on the remaining time before the call would
        have been made and the additional amount of time passed to the delay
        method.
        """
        reactor = TimeoutReportReactor()
        call = reactor.callLater(50, lambda: None)
        reactor.now += 10
        call.delay(20)
        timeout = self._checkIterationTimeout(reactor)
        self.assertEqual(timeout, 60)

        If a delayed call is re-delayed, the timeout passed to
        C{doIteration} is based on the remaining time before the call would
        have been made and the additional amount of time passed to the delay
        method.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/test/test_posixbase.py