def test_startReactorWithReactor(self):
        """
        L{Runner.startReactor} with the C{reactor} argument runs the given
        reactor.
        """
        reactor = MemoryReactor()
        runner = Runner(reactor=reactor)
        runner.startReactor()

        self.assertTrue(reactor.hasRun)

        L{Runner.startReactor} with the C{reactor} argument runs the given
        reactor.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/application/runner/test/test_runner.py