.NET Core HttpClient–Testing redirections

When testing a specific API I had to check if the user was redirected to the correct location. However although I thought that I had written my api correctly, the response code didn’t match.

	[ApiController]
	[Route("job")]
	public class JobController : ControllerBase
	{
	[HttpGet("{jobId}")]
	public IActionResult Job(Guid jobId)
	{
	//Return OK if job is still running/scheduled
	var job=_jobRepository.Get(jobId);
	if (job == null)
	return NotFound(jobId);
	if (job.Status == Status.Pending)
	return Ok();
	//Return 500 if job failed
	if (job.Status == Status.Failed)
	{
	return StatusCode(500);
	}
	//Return 302 when job is finished
	if (job.Status == Status.Succeeded)
	{
	return RedirectToAction(nameof(JobOutPut), new { jobId });
	}
	return NotFound(jobId);
	}
	}

view raw JobController.cs hosted with ❤ by GitHub

Here is the related test code:

	internal static class HttpClientExtensions
	{
	internal static async Task PollForResults(this HttpClient httpClient,Uri requestUri, Func<HttpResponseMessage, Task> successAction, Func<HttpResponseMessage, Task> failureAction = null)
	{
	int numberOfAttempts = 3;
	int attemptCount = 0;
	//Keep querying the URI until we get a 302 with a result
	while (attemptCount< numberOfAttempts)
	{
	var pollingResponse = await httpClient.GetAsync(requestUri);
	if (pollingResponse.StatusCode == System.Net.HttpStatusCode.OK)
	{
	attemptCount++;
	await Task.Delay(1000);
	}
	if (pollingResponse.StatusCode == System.Net.HttpStatusCode.InternalServerError)
	{
	if (pollingResponse.Content.Headers.ContentType.Equals(new MediaTypeHeaderValue("application/zip")))
	{
	if (failureAction == null)
	return;
	await failureAction(pollingResponse);
	}
	break;
	}
	if (pollingResponse.StatusCode == System.Net.HttpStatusCode.Redirect)
	{
	// Response should contain a location header with job output URI
	var jobOutputLocation = pollingResponse.Headers.Location;
	var outputResponse = await httpClient.GetAsync(jobOutputLocation);
	if (successAction == null)
	return;
	await successAction(outputResponse);
	break;
	}
	}
	}

view raw HttpClientExtensions.cs hosted with ❤ by GitHub

	public class JobApiTests : IClassFixture<SelfHostedApi>
	{
	public HttpClient Sut { get; }
	public GenerationApiTests(SelfHostedApi fixture)
	{
	Sut = fixture.CreateClient();
	}
	[Fact]
	public async Task API_Enables_Bulk_Processing_Files_On_URL_Path()
	{
	//Arrange
	var templateFile = new Uri("http://localhost/ExampleTemplate.docx");
	var xmlFile = "ExampleXML.xml";
	var targetFile = $"ExampleDocument-{Guid.NewGuid()}.zip";
	var form = new MultipartFormBuilder()
	.AddFile(xmlFile, "xmlFiles", "File1.xml")
	.AddFile(xmlFile, "xmlFiles", "File2.xml")
	.AddFile(xmlFile, "xmlFiles", "File3.xml")
	.Build();
	//Act
	var response = await Sut.PostAsync($"/job/bulk/uri?template={templateFile}", form);
	response.EnsureSuccessStatusCode();
	//Response should contain a location header with job id
	var jobLocation = response.Headers.Location;
	await Sut.PollForResults(jobLocation, successAction: response => response.WriteToFile(targetFile,checkStatusCode:false));
	//Assert
	Assert.True(File.Exists(targetFile));
	Assert.True(new FileInfo(targetFile).Length > 0);
	}
	}

view raw JobApiTests.cs hosted with ❤ by GitHub

Do you spot my mistake? Let’s have a look at the documentation:

	//
	// Summary:
	// Creates an instance of System.Net.Http.HttpClient that automatically follows
	// redirects and handles cookies.
	//
	// Returns:
	// The System.Net.Http.HttpClient.
	public HttpClient CreateClient()
	{
	return CreateClient(ClientOptions);
	}

view raw CreateClient.cs hosted with ❤ by GitHub

The default HttpClient will automatically handle redirects what makes it impossible to check for the 302 status code

To change this behavior, you need to create your own HttpHandler and use it when building up your HttpClient instance:

	public class JobnApiTests : IClassFixture<SelfHostedApi>
	{
	public HttpClient Sut { get; }
	public GenerationApiTests(SelfHostedApi fixture)
	{
	var handler = new HttpHandler();
	Sut = fixture.CreateDefaultClient(handler);
	}
	internal class HttpHandler : DelegatingHandler
	{
	public HttpHandler()
	{
	//We override the default handler to avoid automatic redirection
	//This makes it hard to detect the job completion in our tests
	this.InnerHandler = new HttpClientHandler()
	{
	AllowAutoRedirect = false
	};
	}
	}
	}

view raw JobApiTestsFixed.cs hosted with ❤ by GitHub