I have a c# solution with the following structure:
mySolution myProject myProject.MSTests References Microsoft.VisualStudio.QualityTools.UnitTe
Another one for googlers using NUnit, especially those who have migrated from MS Unit test to NUnit. Please remove the project type Guids that are identifying the project as MS Test project from the project file.
{3AC096D0-A1C2-E12C-1390-A8335801FDAB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}