def test_answerless(self):
        """
        If a query is responded to with no answers or nameserver records, the
        L{Deferred} returned by L{Resolver.lookupAddress} fires with
        L{ResolverError}.
        """
        servers = {
            ('1.1.2.3', 53): {
                (b'example.com', A): {
                    },
                },
            }
        resolver = self._getResolver(servers)
        d = resolver.lookupAddress(b'example.com')
        return self.assertFailure(d, ResolverError)

        If a query is responded to with no answers or nameserver records, the
        L{Deferred} returned by L{Resolver.lookupAddress} fires with
        L{ResolverError}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/test/test_rootresolve.py