def test_domainEmptyArgument(self):
        """
        L{client.Resolver.parseConfig} treats a I{domain} line without an
        argument as indicating a domain of C{b""}.
        """
        resolver = client.Resolver(servers=[("127.0.0.1", 53)])
        resolver.parseConfig([b"domain\n"])
        self.assertEqual(b"", resolver.domain)

        L{client.Resolver.parseConfig} treats a I{domain} line without an
        argument as indicating a domain of C{b""}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/test/test_client.py