VS 2012: Can not show Test Explorer

For quite some time I was working with VS 2012 RC and everything was fine. But all of a sudden I could not open the Test Explorer. I got a MEF error message as shown below:

The main error message was

The composition produces a single composition error. The root cause is provided below. Review the CompositionException.Errors property for more detailed information. 

1) Value cannot be null.
Paramter name: testPlatform

Followed by further error messages. I tried to repair Visual Studio installation, installed different test platform adapters but nothing helped. I found the solution in at Stack Overflow, but very hidden down below, so I repeat it here:

Under C:\Users\Tobias\AppData\Local\Microsoft\VisualStudio\11.0\ComponentModelCache delete the Microsoft.VisualStudio.Default.cache file. That does the trick for me!

Thanks GertGregers and happy testing.