How to pass in a mocked HttpClient in a .NET test?

Question

I have a service which uses Microsoft.Net.Http to retrieve some Json data. Great!

Of course, I don't want my unit test hitting the actual server (otherwise, that's an integration test).

Here's my service ctor (which uses dependency injection...)

public Foo(string name, HttpClient httpClient = null) { ... } 

I'm not sure how I can mock this with ... say .. Moq or FakeItEasy.

I want to make sure that when my service calls GetAsync or PostAsync .. then i can fake those calls.

Any suggestions how I can do that?

I'm -hoping- i don't need to make my own Wrapper .. cause that's crap :( Microsoft can't have made an oversight with this, right?

(yes, it's easy to make wrappers .. i've done them before ... but it's the point!)

Answer 1

You can replace the core HttpMessageHandler with a fake one. Something that looks like this...

public class FakeResponseHandler : DelegatingHandler {     private readonly Dictionary<Uri, HttpResponseMessage> _FakeResponses = new Dictionary<Uri, HttpResponseMessage>();      public void AddFakeResponse(Uri uri, HttpResponseMessage responseMessage)     {         _FakeResponses.Add(uri, responseMessage);     }      protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)     {         if (_FakeResponses.ContainsKey(request.RequestUri))         {             return Task.FromResult(_FakeResponses[request.RequestUri]);         }         else         {             return Task.FromResult(new HttpResponseMessage(HttpStatusCode.NotFound) { RequestMessage = request });         }     } } 

and then you can create a client that will use the fake handler.

var fakeResponseHandler = new FakeResponseHandler(); fakeResponseHandler.AddFakeResponse(new Uri("http://example.org/test"), new HttpResponseMessage(HttpStatusCode.OK));  var httpClient = new HttpClient(fakeResponseHandler);  var response1 = await httpClient.GetAsync("http://example.org/notthere"); var response2 = await httpClient.GetAsync("http://example.org/test");  Assert.Equal(response1.StatusCode,HttpStatusCode.NotFound); Assert.Equal(response2.StatusCode, HttpStatusCode.OK); 

Answer 2

I know that this is an old question but I stumbled with it during a search on this topic and found a very nice solution to make testing HttpClient easier.

It is available via nuget:

https://github.com/richardszalay/mockhttp

PM> Install-Package RichardSzalay.MockHttp 

Here is a quick look on the usage:

var mockHttp = new MockHttpMessageHandler();  // Setup a respond for the user api (including a wildcard in the URL) mockHttp.When("http://localost/api/user/*")         .Respond("application/json", "{'name' : 'Test McGee'}"); // Respond with JSON  // Inject the handler or client into your application code var client = new HttpClient(mockHttp);  var response = await client.GetAsync("http://localost/api/user/1234"); // or without await: var response = client.GetAsync("http://localost/api/user/1234").Result;  var json = await response.Content.ReadAsStringAsync();  // No network connection required Console.Write(json); // {'name' : 'Test McGee'} 

More info on the github project page. Hope this can be useful.