Looking to mock out your favorite HttpClient API in .net. Well here is one way to go about it.
So if you want to mock out HttpClient, remember what the client was built on, a chain of responsibility pattern.
public class HttpClient : HttpMessageInvoker { public HttpClient(); public HttpClient(HttpMessageHandler handler); public HttpClient(HttpMessageHandler handler, bool disposeHandler); }
HttpClient has a constructor that takes an HttpMessageHandler. What you could do instead is create an HttpMessageHandler to intercept a message being sent and insert your code own code into it. Example:
class MockMessageHandler : HttpMessageHandler { public Func<httpRequestMessage, System.Threading.CancellationToken, Task> funcToOverride { get; private set; } private MockHttpMessageHandler() { } public MockHttpMessageHandler(Func sendFunc) { funcToOverride = (httpRequestMessage, cancellationToken) => { return Task.Factory.StartNew(sendFunc); }; } protected override Task SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) { return funcToOverride.Invoke(request, cancellationToken); } } </pre> So above, what you would do is pass in a Func that returns an HttpResponseMessage. This is like in Moq, where you would set up a function through setup. Now you can return a Mock HttpResponseMessage or exception, whatever you are trying to test in your code. Let’s see an example:
MockHttpMessageHandler helper = new MockHttpMessageHandler( () => new HttpResponseMessage(System.Net.HttpStatusCode.OK) { Content = new StringContent(JsonConvert.SerializeObject(document)) } ); MockHttpMessageHandler actual; using (HttpClient client = new HttpClient(helper)) { actual = client.GetAsync("/whatever"); } Assert.IsEqual(/\*your expected response message\*/, actual); This now allows you to short circuit the client from calling out to a web service and return data that you would expect in your api.