def test_resolverFactoryArgumentAbsent(self):
        r = Resolver(hints=[None])
        self.assertIdentical(r._resolverFactory, client.Resolver)
L{root.Resolver.__init__} sets L{client.Resolver} as the
dataset/ETHPy150Open twisted/twisted/twisted/names/test/test_rootresolve.py/RootResolverResolverFactoryTests.test_resolverFactoryArgumentAbsent