How to unittest Flask websocket server (Flask-SocketIO)

I wonder how can I unittest on my flask websocket server. My application supports quite many interface on REST API(Flask-restful) and Web Socket(Flask-SocketIO). All of websocket "emit" are proceed on celery process. I have problem unit-testing those websocket logic.

1. Several guys said, First I have to seperate this rest-api + websocket application. Is it weird running whole application on a single server (logically)?

2. How to unit-testing websocket code?

Thank you