Test websocket client

[romamik]

What is a good way to test websocket client?
One possible option is to run a simple test server during a test run, but what's the easiest way to achieve this?

[jofas]

What framework are you using? In actix-web you spin up a server during testing. The functionality is built into the framework. I don't know how other frameworks do this, but to me it seems a sensible approach to start a server and a client and let them communicate with each other in order to test that all works as you expect.

[romamik]

There is no framework. The actual server cannot be used for tests, so I need a test server. Even simple echo server will do.

[jofas]

Inside your test, you could start a thread that runs a server that accepts websocket connections (i.e. tungstenite). Then on your main thread you start your websocket client, connect it to the server and start sending messages.

Here pseudo-code of how I'd imagine something like this to look like:

use your_crate::WsClient;

use tungstenite::accept;

use std::net::TcpListener;
use std::thread;

#[test]
fn test_websocket_client() {
    thread::spawn(|| { 
        let server = TcpListener::bind("127.0.0.1:9001").unwrap();
        let conn = server.incoming().next().unwrap();
        let mut websocket = accept(conn.unwrap()).unwrap();
        
        // echo 10 messages before shutting down
        for _ in 0..10 {
            let msg = websocket.read_message().unwrap();

            // We do not want to send back ping/pong messages.
            if msg.is_binary() || msg.is_text() {
                websocket.write_message(msg).unwrap();
            }
        }
    });
    
    let client = WsClient::new("127.0.0.1:9001").unwrap();

    for _ in 0..10 {
        client.send("ping");
        assert_eq!(client.receive(), "ping");
    }
}