def test_idempotent(self):
        """
        Multiple calls to L{client.getResolver} return the same L{IResolver}
        implementation.
        """
        with AlternateReactor(Clock()):
            a = client.getResolver()
            b = client.getResolver()
        self.assertIs(a, b)

        Multiple calls to L{client.getResolver} return the same L{IResolver}
        implementation.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/test/test_client.py