I recently had big problems to unit test the UnityWebRequest and started to write my own solution based on NSubstitute and a wrapper class, I uploaded the source code to a repository: https://github.com/goedleIO/unity_http_mocking
I'm happy for feedback. I anyone has an easier way to mock the UnityWebRequest. I also wrote a blog post about it, with a detailed description: https://blog.goedle.io/2018/08/06/mocking-web-requests-in-unity-fake-it-until-you-make-it/
How to mock UnityWebRequest in Unity 3d for unit test | Heykuki News