Why does visual studio 2012 not find my tests?

Question

I have some tests that use the built in Microsoft.VisualStudio.TestTools.UnitTesting, but can not get them to run.

I am using visual studio 2012 ultimat

Answer 1

These are all great answers, but there is one more reason that I know of; I just ran into it. In one of my tests I had a ReSharper message indicating that I had an unused private class. It was a class I'm going to use in an upcoming test. This actually caused all of my tests to disappear.