@Override
    public List<ServiceInstance> filter(String serviceName, List<ServiceInstance> serviceInstances) {
        return serviceInstances;
    }
@Test
    public void filter() {
        final DefaultServiceInstance instance = new DefaultServiceInstance("localhost", "127.0.0.1", 8080,
                Collections.emptyMap(), "zk");
        final InstanceFilter nopInstanceFilter = new NopInstanceFilter();
        final List<ServiceInstance> defaultServiceInstances = Collections.singletonList(instance);
        final List<ServiceInstance> test = nopInstanceFilter.filter("test", defaultServiceInstances);
        Assert.assertEquals(test, defaultServiceInstances);
    }