@Override
    public List<? extends Instance> listAllInstances(String namespaceId, String serviceName) throws NacosException {
        Service service = getService(namespaceId, serviceName, true);
        return serviceStorage.getData(service).getHosts();
    }
@Test
    void testListAllInstances() throws NacosException {
        ServiceInfo serviceInfo = new ServiceInfo();
        serviceInfo.setHosts(Collections.emptyList());
        
        when(serviceStorage.getData(Mockito.any())).thenReturn(serviceInfo);
        
        List<? extends Instance> instances = instanceOperatorClient.listAllInstances("A", "C");
        
        assertEquals(0, instances.size());
    }