I'm having this issue where I'm using NUnit 2.6.3 in my project, but after installing NUnit Test Adapter 1.0.0.0 (most recent version I can find) in Visual Studio Professional 2012, my tests still didn't show up in Test Explorer. I realized soon that the description of NUnit Test Adapter states that it is compatible with NUnit versions up to 2.6.2, but it turns out I'm using NUnit 2.6.3. Using NuGet, I can't find an older version of NUnit, and using Visual Studio's Extensions and Updates manager, I can't find a version of NUnit Test Adapter that supports 2.6.3.