mockhttp VS WireMock.Net

I'd say that without wanting to refactor the code a little bit (maybe moving those HttpClients into a service so that they are easily mocked) your best bet would be to use something like WireMock or MockHttp.

What is the need to create a wrapper around the HttpClient? If it's for mocking, you can use this MockedHttpClientHandler for you tests

Voilà! That's how to write tests with HttpClient and Moq. With some extension methods, we could have a small DSL to write more readable tests. For a more fully-featured alternative to write tests for HttpClient, check mockhttp, "a testing layer for Microsoft's HttpClient library."

So if you need to mock http client you may want to look into a library like https://github.com/richardszalay/mockhttp

I'd say that without wanting to refactor the code a little bit (maybe moving those HttpClients into a service so that they are easily mocked) your best bet would be to use something like WireMock or MockHttp.

WireMock

WiremockNet https://github.com/WireMock-Net/WireMock.Net

In this post, I'll explain how to create mocks for HTTP APIs in narrow integration tests using the WireMock.Net library.

Recently was pointed to WireMock for testing purposes.

I use WireMock (@ Java) to start a local webserver alongside the tests, this webserver will provide ‘real’ responses to the client. Here’s the C# equivalent: https://github.com/WireMock-Net/WireMock.Net

You could try out WireMock.Net: https://github.com/WireMock-Net/WireMock.Net/wiki/Using-WireMock-in-UnitTests

Use WireMock to mock responses from the endpoint that FooClient interacts with. This lets you exercise all of the code contained in FooClient in a realistic way, without using mocks, but still get the different responses you expect.