def test_timedOut(self):
        """
        The L{defer.Deferred} by default errbacks with a L{defer.TimeoutError}
        if it times out before callbacking or errbacking.
        """
        clock = Clock()
        d = defer.Deferred()
        d.addTimeout(10, clock)
        self.assertNoResult(d)

        clock.advance(15)

        self.failureResultOf(d, defer.TimeoutError)

        The L{defer.Deferred} by default errbacks with a L{defer.TimeoutError}
        if it times out before callbacking or errbacking.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_defer.py