I am using the new Web API bits in a project, and I have found that I cannot use the normal HttpMessageRequest
, as I need to add client certificates to the request. As a result, I am using the HttpClient
(so I can use WebRequestHandler
). This all works well, except that it isn't stub/mock friendly, at least for Rhino Mocks.
I would normally create a wrapper service around HttpClient
that I would use instead, but I would like to avoid this if possible, as there are a lot of methods that I would need to wrap. I am hoping that I have missing something—any suggestions on how to stub HttpClient
?
As an alternative to the excellent ideas already presented by @Raj, it may be possible to go a step lower and to mock/fake the HttpMessageHandler
instead.
If you make any class that needs an HttpClient
accept it as a dependency injection parameter in the constructor, then when unit testing you can pass in an HttpClient
that has been injected with your own HttpMessageHandler
. This simple class has only one abstract method that you need to implement, as follows:
public class FakeHttpMessageHandler : HttpMessageHandler
{
public HttpRequestMessage RequestMessage { get; private set; }
protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
RequestMessage = request;
return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK));
}
}
My trivial example just saves the HttpRequestMessage
in a public property for later inspection and returns HTTP 200 (OK), but you could augment this by adding a constructor that sets the result you want returned.
You'd use this class like this:
public void foo()
{
//Arrange
var fakeHandler = new FakeHttpMessageHandler();
var client = new HttpClient(fakeHandler);
var SUT = new ClassUnderTest(client);
//Act
SUT.DomSomething();
//Assert
fakeHandler.RequestMessage.Method.ShouldEqual(HttpMethod.Get); // etc...
}
There are limitations to this approach, for example in a method that makes multiple requests or needs to create multiple HttpClient
s, then the fake handler might start to become too complicated. However, it may be worth consideration for simple cases.