How to test a websocket client-server interaction?

I'm writing an integration WebSocket layer for one service and would like to test the interaction between my code and the server by creating some integration type of tests.

There's a project called mockserver which allows you to start an HTTP server, specify the expected requests that are going to be sent by a client and mock the response when the client's request hits the server. Unfortunately, mockserver doesn't provide any tools to mock a Websocket client-server interaction.

Is there a library or a framework of some sort that would allow me to implement this type of tests? Or should write some wrapper code around some servlet container that provides WebSocket support, so I'd be able to test my client code?