Why is the response content in this streaming service example empty? - stream

Question

I could really use some help understanding why this unit test is failing. I suspect it's due to the way I'm handling the streams. I have a number of other tests that successfully use this self-hosting server setup, but they all read services that return primitives like strings.
Here's the test in question:
using System.Net.Http;
using System.Threading;
using System.Web.Http.SelfHost;
using AttributeRouting.Web.Http.SelfHost;
using NUnit.Framework;
[TestFixture]
public class StreamControllerTests
{
[Test]
public void Can_get_simple_streaming_service_to_respond()
{
using (var config = new HttpSelfHostConfiguration("http://in-memory"))
{
config.Routes.MapHttpAttributeRoutes();
using (var server = new HttpSelfHostServer(config))
{
// I get the same behavior if I use HttpClient
using (var client = new HttpMessageInvoker(server))
{
using (var request = new HttpRequestMessage(HttpMethod.Get, "http://in-memory/stream/notepad"))
{
using (HttpResponseMessage response = client.SendAsync(request, CancellationToken.None).Result)
{
Assert.IsNotNull(response.Content);
// FAILS, content length is 0
Assert.Greater(response.Content.Headers.ContentLength, 0);
}
}
}
}
}
And here is the controller that feeds the test:
using System;
using System.Drawing.Imaging;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using AttributeRouting.Web.Mvc;
using MyUnitTests.Properties;
[GET("stream/notepad")]
public HttpResponseMessage StreamAnImageFromResources()
{
var imageStream = new MemoryStream(); // closed when stream content is read
Resources.a_jpeg_in_resources.Save(imageStream, ImageFormat.Jpeg);
try
{
HttpResponseMessage response = Request.CreateResponse();
// at this point, imageStream contains about 120K bytes
response.Content = new StreamContent(imageStream);
return response;
}
catch (Exception e)
{
return Request.CreateErrorResponse(HttpStatusCode.ServiceUnavailable, e);
}
}

Answer 1

I don't see anything really wrong but your test is more complicated than it needs to be.
Try this,
[Test]
public void Can_get_simple_streaming_service_to_respond2()
{
var config = new HttpConfiguration();
config.Routes.MapHttpAttributeRoutes();
var server = new HttpServer(config);
var client = new HttpClient(server);
var request = new HttpRequestMessage(HttpMethod.Get, "http://in-memory/stream/notepad");
HttpResponseMessage response = client.SendAsync(request, CancellationToken.None).Result;
Assert.IsNotNull(response.Content);
// FAILS, content length is 0
Assert.Greater(response.Content.Headers.ContentLength, 0);
}
EDIT: In the comments, Darrel gave me the true answer, which I'm moving to the answer body for visibility:
Check the position of your image stream after doing Save. You need to reset it back to 0 before passing to StreamContent. Also, you might want to consider doing GetManifestResourceStream instead, it will save copying the bytes into managed memory.