I found the best way to troubleshoot this issue is to create a .proj msbuild file and add your unit test projects which you hare having an issue into this file and execute the tests using the command line version of mstest. I found a small configuration issue in my app.config which only appeared when running the tests from mstest - otherwise the test project built just fine. Also you will find any indirect reference issues with this method as well. Once you can run the Unit test from the command line using mstest you can then do a clean solution, rebuild solution and your test should be discovered properly.