How can I test an EventStream?

[RemiBardon]

I have a route which returns an EventStream, how can I get the events in tests?

rocket::local::asynchronous::LocalRequest::dispatch returns a LocalResponse and I see no way to read events from it. Getting the response body returns an empty string, and there is no other API to get the stream AFAIK.

I tried sleeping before reading the body, it doesn't work either.
Edit: I tried yielding a static event in the EventStream and I see it in the response body. I can probably decode a list of events then.

[the10thWiz]

Yes. You will want to take advantage of Body's impl of AsyncRead. You can use AsyncReadExt (rocket::tokio::io::AsyncReadExt) to read raw bytes (and decode to a list of events), or Body's into_string or into_bytes to read the full data.

If you didn't use rocket::tokio::time::sleep to sleep, the request may not be able to make any progress. This would have prevented the handler from sending any events.

[RemiBardon]

I could read the body but now I'm trying to figure out how to parse the events.

Also yes I used rocket::tokio::time::sleep to make sure the thread is not blocked. I wasn't receiving any event because of a panic!() inside the EventStream! which wasn't logged 🤦🏻‍♂️

[SergioBenitez]

Also yes I used rocket::tokio::time::sleep to make sure the thread is not blocked. I wasn't receiving any event because of a panic!() inside the EventStream! which wasn't logged 🤦🏻‍♂️

That sounds odd. A panic is logged at a very low level, so it would be quite peculiar if that were the case. Do you have a reproducible example?

[RemiBardon]

No I don't and honestly it doesn't surprise me. I'm using cucumber to run BDD tests and it doesn't integrate well with Rocket's logging and system logs. I still have to improve this one day, it's quite annoying.

[the10thWiz]

I'm trying to figure out how to parse the events.

Obviously, it depends on what format the events are in, but serde_json provides a StreamDeserializer that deserializes a stream of multiple JSON objects. I think this might be an opportunity to improve Rocket's testing functionality, and provide methods to stream events from the async local response.

[the10thWiz]

That sounds odd. A panic is logged at a very low level, so it would be quite peculiar if that were the case. Do you have a reproducible example?

Panics inside EventStream are not caught (or logged) by Rocket, so they would presumably be logged to stderr, while Rocket normally logs to stdout. If the framework (cucumber) doesn't track stderr, the panic would be lost.