To repro, you have to do the following:
- You create a solution, with a standard c# class library.
- You add a custom project to the solution that is based on MPF.
- Go to "Class1" class of the class library.
- Select "Create Unit Tests..." from the context menu of the class.
The window will be empty, and you cannot select Class1. If you unload the MPF-based project, the wizard works again.