def test_overrideServers(self):
        """
        Servers passed to L{client.createResolver} are used in addition to any
        found in the file given by the I{resolvconf} parameter.
        """
        resolvconf = self.path()
        resolvconf.setContent(b"nameserver 127.1.2.3\n")
        with AlternateReactor(Clock()):
            resolver = client.createResolver(
                servers=[("127.3.2.1", 53)], resolvconf=resolvconf.path)
        res = [r for r in resolver.resolvers if isinstance(r, client.Resolver)]
        self.assertEqual(1, len(res))
        self.assertEqual([("127.3.2.1", 53)], res[0].servers)
        self.assertEqual([("127.1.2.3", 53)], res[0].dynServers)

        Servers passed to L{client.createResolver} are used in addition to any
        found in the file given by the I{resolvconf} parameter.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/test/test_client.py