Trying to run Unit Tests on Visual Studio 2013

I'm just trying to run my UnitTests on Visual Studio 2013, but I still having this issue:

System.AppDomainUnloadedException: Tentativa de acesso a um AppDomain não carregado. This can happen if the test(s) started a thread but did not stop it. Make sure that all the threads started by the test(s) are stopped before completion.

I've searched in MSDN forums, but I have no anwsers. Someone passed this issue ?

Thanks for all =)