def test_reactor(self):
        """
        The L{client.Resolver} included in the L{resolve.ResolverChain} returned
        by L{client.createResolver} uses the global reactor.
        """
        reactor = Clock()
        with AlternateReactor(reactor):
            resolver = client.createResolver()
        res = [r for r in resolver.resolvers if isinstance(r, client.Resolver)]
        self.assertEqual(1, len(res))
        self.assertIs(reactor, res[0]._reactor)

        The L{client.Resolver} included in the L{resolve.ResolverChain} returned
        by L{client.createResolver} uses the global reactor.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/test/test_client.py