@Override
    public boolean isSubscribed(String serviceName, String groupName, String clusters) throws NacosException {
        return grpcClientProxy.isSubscribed(serviceName, groupName, clusters);
    }
@Test
    void testIsSubscribed() throws NacosException {
        String serviceName = "service1";
        String groupName = "group1";
        String clusters = "cluster1";
        assertFalse(delegate.isSubscribed(serviceName, groupName, clusters));
        when(mockGrpcClient.isSubscribed(serviceName, groupName, clusters)).thenReturn(true);
        assertTrue(delegate.isSubscribed(serviceName, groupName, clusters));
    }