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Mocking the HttpClient in .NET Core (with NSubstitute)

Lars Richter on June 16, 2019

The problem I was writing a client library for a webservice. Inside of the client I used the Microsoft HttpClient class to call the webs...

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Yaduraj Shakti • Nov 1 '21

This was really helpful. Thanks Lars!

Just want to add:-

If your implementation does not accepts HttpClient in constructor and creates HttpClient directly, then you may use IHttpClientFactory.CreateClient() in your code. Now mock this IHttpClientFactory.CreateClient() to return your HttpClient in test.

FrancescoReviso • Mar 23 '20

Thanks Lars, this have been really useful for me. Just a remark for a more general context, in your implementation Input = await request.Content.ReadAsStringAsync(); works for SendAsync but it will throw an exception in the case we use GetAsync, since the request will be null

Lars Richter • Mar 23 '20

Hi Francesco,
you are totally right. There is still a lot of room for improvement. But I'm happy that the post helped you. :-)
I just realized, that codemaker asked for the complete code 2 months ago. Shame on me. I will make a GitHub repo soon und I will take care for the GetAsync case as well.

Lars Richter • Mar 25 '20

Hi Francesco,
I finally had time to create a little sample app. You can check it out on my GitHub profile under github.com/n-develop/HttpClientMock

I also checked the problem with GetAsync and found the reason. Of course, in a GET request, we don't have a body. So I added a little if (request.Content != null) in the mock class. I also updated the code in the post.
Thanks again for pointing it out. Now it should work even better.

A • Jul 16 '24

Do you an example for

//Mock mockHandler = new Mock();
//mockHandler
//.Protected()
//.Setup>(
//"SendAsync",
//ItExpr.IsAny(),
//ItExpr.IsAny()
//)
//.Returns(() =>
//{
// throw new Exception("Http Client Exception Error");
//});

//return new HttpClient(mockHandler.Object);