Unit Testing http4s router websocket endpoints

Question

The idea is to be able to unit test websocket endpoints on a router service. Any other kind of endpoint is fairly easy to test with a Request, but I can't figure out a way of easily testing websocket responses, as hitting the endpoint with a Request will give you a 501 error since you don't have any corresponding socket to handshake with.

This is the router I'm using

def router(averages: IO[SomeAverages]): HttpRoutes[F] =
    HttpRoutes.of[F] {
        case GET -> Root =>
            val toClient: Stream[F, WebSocketFrame] = {
                Stream
                  .awakeEvery[F](5.seconds)
                  .map(_ => {
                      val avg = averages.unsafeRunSync
                      WebSocketFrame.Text(avg.toString)
                  })
            }
            val fromClient: Pipe[F, WebSocketFrame, Unit] = _.evalMap {
                case WebSocketFrame.Text(t, _) => F.delay(println(t))
                case f => F.delay(println(s"Unknown type: $f"))
            }
            WebSocketBuilder[F].build(toClient, fromClient)
    }

The idea is to get something akin to the below code to work with websockets

val server = Server.initServer[IO]
val router = server.router
val request = Request[IO](Method.GET, uri"/")

val io = router.orNotFound.run(request)

val response = io.unsafeRunSync

// response.status should be 200
// will return 501 if a websocket endpoint

I've tried variations of this such as adding headers like

val request = Request[IO](
    Method.GET,
    uri"/",
    Headers(Header("Connection", "Upgrade"), Header("Upgrade", "websocket")
)

Though any Request will return a 501.

I'm not sure where to go from here, so if anyone has any suggestions I'd be glad to hear. I think it has something to do with creating a websocket client, but I don't know of a way to do that in http4s.

Unit Testing http4s router websocket endpoints

0 Answers