Recently I have a project to perform penetration testing on Vaadin Web Application. This kind of web application is new for me, so I'm just wondering what should I prepare to perform penetration testing on this application or what should I do after gathering information about the application?

I have tried to intercept the request and response using Burp and it seems like the application using websocket to exchange data which is I haven't know such method exist before. if there is any tools that you think can help please let me know (Like JSON Beautifier, or vuln. scanner).

Thanks in advance.