1. Remove or delete the Facilities Field group and Test Filed group where you have defined them. Save the case.
2. Go to App Explorer and look for the Data-...- Facilities class and Data-...test class. Delete these classes as you have just created them (and are hopefully not referencing any other variables in other classes).
3. Repeat the process of going to the case again, configure View and Data etc.. and NOW define a test variable as a field group as you have in the screen shot. Be careful not to define another variable. Tab to the DropDown. Hit the down arrow and wait. You should the list of classes being populated and now you can choose Assets.