def test_applicationRunnerChoosesReactorIfNone(self):
        """
        L{ApplicationRunner} chooses a reactor if none is specified.
        """
        reactor = DummyReactor()
        self.patch(internet, 'reactor', reactor)
        runner = app.ApplicationRunner({
            "profile": False,
            "profiler": "profile",
            "debug": False})
        runner.startReactor(None, None, None)
        self.assertTrue(reactor.called)

        L{ApplicationRunner} chooses a reactor if none is specified.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_twistd.py