How to test multipart with SSE response?

[MeikelLP]

As previously asked in #2354

I now need to adjust the response not only to capture the request but also mock the response.
I've looked at https://www.reactiveui.net/documentation/refit/testing/streaming/ but didn't find an example on how to mock SSE in Reply.From

[kgeminicdev]

Reply.From can return any HttpResponseMessage. Refit chooses the stream framing from the response Content-Type alone, so a body with media type text/event-stream is parsed as SSE. Reply.ServerSentEvents(...) and StreamSource can't be combined with a responder, so write the SSE text yourself:

var parts = new Dictionary<string, string>();
using var http = new StubHttp
{
    { Route.Post("/upload"), Reply.From(async request =>
        {
            foreach (var part in (MultipartFormDataContent)request.Content!)
                parts[part.Headers.ContentDisposition!.Name!] = await part.ReadAsStringAsync();

            const string sse =
                "data: {\"id\":1,\"name\":\"Ada\"}\n\n" +
                "data: {\"id\":2,\"name\":\"Grace\"}\n\n";

            return new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new StringContent(sse, Encoding.UTF8, "text/event-stream"),
            };
        }) },
};
http.RequestCapture = RequestCapture.None;

var api = http.CreateClient<IUploadApi>("https://api.test");
var people = new List<Person>();
await foreach (var p in api.Upload(new StreamPart(stream, "a.txt", "text/plain"), "my file"))
    people.Add(p);

Assert.Equal("my file", parts["description"]);
Assert.Equal(2, people.Count);

Here Upload is declared as IAsyncEnumerable<Person> on a [Multipart] [Post("/upload")] method.

Each event is a data: <json> line followed by a blank line. That is the same framing Reply.ServerSentEvents produces. If a test doesn't need to look at the request, use Reply.ServerSentEvents(new[] { new Person(1, "Ada"), ... }), which serializes the items with the client's serializer.

[MeikelLP]

Thanks I didn't know how to put SSE in the HttpResponseMessage and thought this was some magic.