The purpose of the NUnit transformation is to create a Class with test methods for all public methods of an existing .Net compatible Class. The resulting Class can then be generated and the tests filled out and run by NUnit.
The C# model originally transformed from the PIM:
After transformation becomes the PSM:
Note that for each Class in the C# model, a corresponding test Class has been created. Each of these test Classes contains a test method for every public method in the source Class, plus the methods required to appropriately set up the tests. It is your responsibility to fill in the details of each test.