How to test WebSocket Subscription ? about graphql-spqr-spring-boot-starter HOT 2 OPEN

Connecting to ws://localhost:50123/graphql?query=subscription%20onCommentAdded%20%7B%20commentAdded%20%7B%20id%20postId%20content%20%7D%20%7D
2021-10-09 12:10:47.660 DEBUG 13324 --- [o-auto-1-exec-2] o.s.web.servlet.DispatcherServlet        : GET "/graphql?query=subscription%20onCommentAdded%20%7B%20commentAdded%20%7B%20id%20postId%20content%20%7D%20%7D", parameters={masked}
2021-10-09 12:10:47.667 DEBUG 13324 --- [o-auto-1-exec-2] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to io.leangen.graphql.spqr.spring.web.mvc.DefaultGraphQLController#executeGet(GraphQLRequest, Object)
2021-10-09 12:10:47.683 DEBUG 13324 --- [o-auto-1-exec-2] o.s.w.c.request.async.WebAsyncManager    : Started async request
2021-10-09 12:10:47.684 DEBUG 13324 --- [o-auto-1-exec-2] o.s.w.c.request.async.WebAsyncManager    : Async result set, dispatch to /graphql
2021-10-09 12:10:47.684 DEBUG 13324 --- [o-auto-1-exec-2] o.s.web.servlet.DispatcherServlet        : Exiting but response remains open for further handling
2021-10-09 12:10:47.685 DEBUG 13324 --- [o-auto-1-exec-2] o.s.web.servlet.DispatcherServlet        : "ASYNC" dispatch for GET "/graphql?query=subscription%20onCommentAdded%20%7B%20commentAdded%20%7B%20id%20postId%20content%20%7D%20%7D", parameters={masked}
2021-10-09 12:10:47.686 DEBUG 13324 --- [o-auto-1-exec-2] s.w.s.m.m.a.RequestMappingHandlerAdapter : Resume with async result [{data=graphql.execution.reactive.CompletionStageMappingPublisher@6997f06}]
2021-10-09 12:10:47.687 DEBUG 13324 --- [o-auto-1-exec-2] m.m.a.RequestResponseBodyMethodProcessor : Using 'application/json', given [*/*] and supported [application/json]
2021-10-09 12:10:47.687 DEBUG 13324 --- [o-auto-1-exec-2] m.m.a.RequestResponseBodyMethodProcessor : Writing [{data=graphql.execution.reactive.CompletionStageMappingPublisher@6997f06}]
2021-10-09 12:10:47.696 DEBUG 13324 --- [o-auto-1-exec-2] o.s.web.servlet.DispatcherServlet        : Exiting from "ASYNC" dispatch, status 200
2021-10-09 12:10:47.706  WARN 13324 --- [ctor-http-nio-3] r.netty.http.client.HttpClientConnect    : [id:60230589-1, L:/127.0.0.1:50125 - R:localhost/127.0.0.1:50123] The connection observed an error

io.netty.handler.codec.http.websocketx.WebSocketClientHandshakeException: Invalid handshake response getStatus: 200 
	at io.netty.handler.codec.http.websocketx.WebSocketClientHandshaker13.verify(WebSocketClientHandshaker13.java:272) ~[netty-codec-http-4.1.68.Final.jar:4.1.68.Final]
	at io.netty.handler.codec.http.websocketx.WebSocketClientHandshaker.finishHandshake(WebSocketClientHandshaker.java:304) ~[netty-codec-http-4.1.68.Final.jar:4.1.68.Final]
	at reactor.netty.http.client.WebsocketClientOperations.onInboundNext(WebsocketClientOperations.java:116) ~[reactor-netty-http-1.0.11.jar:1.0.11]