I was working with Visual Studio 2015 today, and ran into an issue running NUnit tests. The basic process to integrate NUnit into Visual Studio is to use the NuGet package manager and install the NUnit framework and the NUnit Test Adapter.
However, if you install the latest version (currently 3.0.1) the NUnit Test Adapter doesn’t discover your tests. I did a bit of research and the latest version isn’t supported.
If you run into this problem, uninstall NUnit Framework 3.0.1 and instead install version 2.6.4.