@Override
    public List<MicroServiceInstance> getServerList(String serviceId) {
        if (!isRegistered.get()) {
            LOGGER.warning("Query instance must be at the stage that finish registry!");
            return Collections.emptyList();
        }
        if (serviceId == null) {
            // Unable to perform a replacement
            LOGGER.warning("Can not acquire the name of service, the process to replace instance won't be finished!");
            return Collections.emptyList();
        }
        return RegisterManager.INSTANCE.getServerList(serviceId);
    }
@Test
    public void getServerList() {
        Assert.assertTrue(registerCenterService.getServerList("test").isEmpty());
    }