def test_resolverOrder(self):
        """
        L{server.DNSServerFactory.resolver} contains an ordered list of
        authorities, caches and clients.
        """
        # Use classes here so that we can see meaningful names in test results
        class DummyAuthority(object):
            pass

        class DummyCache(object):
            pass

        class DummyClient(object):
            pass

        self.assertEqual(
            server.DNSServerFactory(
                authorities=[DummyAuthority],
                caches=[DummyCache],
                clients=[DummyClient]).resolver.resolvers,
            [DummyAuthority, DummyCache, DummyClient])

        L{server.DNSServerFactory.resolver} contains an ordered list of
        authorities, caches and clients.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/test/test_server.py