@Test
    public void testOnMessage() {
        doNothing().when(pluginDataSubscriber).onSubscribe(any());
        String json = GsonUtils.getInstance().toJson(websocketData);
        shenyuWebsocketClient.onMessage(json);
        verify(pluginDataSubscriber).onSubscribe(any());
    }
add test case for {@link ShenyuWebsocketClient}.
shenyu-sync-data-center/shenyu-sync-data-websocket/src/test/java/org/apache/shenyu/plugin/sync/data/websocket/client/ShenyuWebsocketClientTest.java