Best way to inject IHttpClientFactory mock?

[Lexy2]

Having trouble injecting IHttpClientFactory.

The application under test does a lot of using var httpClient = _httpClientFactory.CreateClient();

Which means if I do

_mockHttpClient = new MockHttpClient();

var httpClientFactoryMock = IHttpClientFactory.Mock();
httpClientFactoryMock.CreateClient(Any()).Returns(_mockHttpClient);

then by the next httpClient invocation the mock will already be disposed, and I'll get an ObjectDisposedException.

If I do

var httpClientFactoryMock = IHttpClientFactory.Mock();
httpClientFactoryMock.CreateClient(Any()).Returns(() => { _mockHttpClient = new MockHttpClient(); return _mockHttpClient; });

then I'm losing information about invocations on the previous clients if there were a few usings down the road of the class being tested.

How do I preserve the information about HttpClient invocations?

Note that I'm not using TestWebApplicationFactory.

[vbreuss]

Can't you set the disposeHandler: false on the HttpClient and re-use it in your test?

[Lexy2]

I use TUnit's MockHttpClient that doesn't have the constructor overload with disposeHandler:false. So this would be something like

MockHttpHandler _handler = new MockHttpHandler();

var httpClientFactoryMock = IHttpClientFactory.Mock();
httpClientFactoryMock.CreateClient(Any()).Returns(new HttpClient(_handler, disposeHandler: false));

Even then, the underlying HttpClient gets disposed, and in trying to reuse it I get

[Test Failure] Cannot access a disposed object.
Object name: 'System.Net.Http.HttpClient'.

I guess, I'll need a MockHttpClientWrapper that would not dispose the underlying HttpClient and implement another method to dispose of it at the end of the test. Seems ugly.

Or return a new HttpClient every time, but with the same handler.

[Lexy2]

So this becomes

MockHttpHandler _handler = new MockHttpHandler();

var httpClientFactoryMock = IHttpClientFactory.Mock();
httpClientFactoryMock.CreateClient(Any()).Returns(() => new HttpClient(_handler, disposeHandler: false));

And then I can test invocations directly from the handler.

Thank you!

[Lexy2]

@thomhurst maybe you could implement a better support for IHttpClientFactory outside of TestWebApplicationFactory for such cases.

[thomhurst]

Just so I understand your flow better, can you explain this part?

then by the next httpClient invocation the mock will already be disposed, and I'll get an ObjectDisposedException.

What's disposing it?

[Lexy2]

using var httpClient = _httpClientFactory.CreateClient(); statement in the application code is disposing it.

https://learn.microsoft.com/en-us/dotnet/core/extensions/httpclient-factory#httpclient-lifetime-management

HttpClient instances created by IHttpClientFactory are intended to be short-lived.

[thomhurst]

@Lexy2 added a Mock.HttpClientFactory() if you wanna give it a go

[Lexy2]

Perfect, works like a charm, thank you, @thomhurst