def testLeaderForEvaluator(self):
    cluster_spec = {
        "chief": ["127.0.0.1:1234"],
        "worker": ["127.0.0.1:8964", "127.0.0.1:2333"],
        "ps": ["127.0.0.1:1926", "127.0.0.1:3141"],
        "evaluator": ["127.0.0.1:2019"]
    }
    self.assertEqual(
        multi_worker_util.collective_leader(cluster_spec, "evaluator", 0), "")