@Override
    public void subscribe(String serviceName, EventListener listener) throws NacosException {
        subscribe(serviceName, new ArrayList<>(), listener);
    }
@Test
    void testSubscribeWithNullListener() throws NacosException {
        String serviceName = "service1";
        String groupName = "group1";
        //when
        client.subscribe(serviceName, groupName, null);
        //then
        verify(changeNotifier, never()).registerListener(groupName, serviceName,
                new NamingSelectorWrapper(NamingSelectorFactory.newIpSelector(""), null));
        verify(proxy, never()).subscribe(serviceName, groupName, "");
        
    }