How to test multipart?

[MeikelLP]

I'm rewriting our client generator to use Refit (via Refitter).

I'm using StubHttp to test most of my client code but I'm unable to validate requests using [MultiPart]. What's the recommended way?

[NotAFlightRisk]

Turn off StubHttp's body capture and read the parts inside Reply.From, while the request's still alive:

var parts = new Dictionary<string, string>();
var http = new StubHttp
{
    { Route.Post("/upload"), Reply.From(async request =>
        {
            var multipart = (MultipartFormDataContent)request.Content!;
            foreach (var part in multipart)
                parts[part.Headers.ContentDisposition!.Name!] = await part.ReadAsStringAsync();
            return new HttpResponseMessage(HttpStatusCode.OK);
        }) },
};
http.RequestCapture = RequestCapture.None;

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

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

With the default capture, StubHttp swaps the body for a buffered copy before your route sees it, so request.Content isn't a MultipartFormDataContent any more. Refit also disposes the request once the call returns, so http.Requests is no good for reading parts afterwards, and LastRequestBodyAsync<T> just hands the raw body to the client's serializer (JSON by default). RequestCapture.None leaves the original content alone for the reply code (remarks on RequestCapture).

For a file part, part.Headers.ContentDisposition.FileName, part.Headers.ContentType and ReadAsByteArrayAsync() give you the rest.

Checked on Refit and Refit.Testing 16.3.0.