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

I had this problem when upgrading my solution from Microsoft Visual Studio 2012 Express for Web to Microsoft Visual Studio 2013.

I had created a Unit Tests project in 2012, and after opening in 2013 the Unit Test project wouldn't show any tests in the tests explorer. Everytime I tried to run or debug tests it failed, saying the following in the output window:

    Failed to initialize client proxy: 
    could not connect to vstest.discoveryengine.x86.exe

I also noticed that on debugging the tests, it was launching an instance of Visual Studio 2012. This clued me into the fact that the Unit Tests project was still referencing 2012. Looking at the test project reference I realised it was targeting the wrong Microsoft Visual Studio Unit Test Framework DLL for this version of Visual Studio:

C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE\PublicAssemblies\Microsoft.VisualStudio.QualityTools.UnitTestFramework.dll

I changed the version number from 11.0 to 12.0:

C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7\IDE\PublicAssemblies\Microsoft.VisualStudio.QualityTools.UnitTestFramework.dll

I rebuilt all and this fixed the issue - all tests were found in the Test Explorer and now all tests are found and running perfectly.