WebApi controller tests method not found

It looks like my problem is indeed DLL hell, more specifically the DLL hell referenced by https://github.com/dotnet/corefx/issues/25773. The issue is caused by other NuGet packages that contain references to the newer version of System.Net.Http (4.2.0.0). The current solution appears to be to add a binding redirect to downgrade the assembly version to the expected version (4.0.0.0), but so far that has not helped me.

The solution that did work for me was to install the latest NuGet package of System.Net.Http, and use assembly binding redirects in my test project to ensure that it used the 4.2.0.0 version instead of 4.0.0.0.