Data for Test Population

Summary

Looking for best practice on how to create a test population for training

Content

We use a test population that we create for all of our in person training as well as documentation for Compensation Planning.  As we make our planning cycle more robust year after year it is clear that our test population has limitations, all of which can be fixed with a little bit of time and effort (i.e. employee history).  I'd like to hear how others use/create a test population for similar situations.  Do you use current data and mask personal information?  Do you upload an entirely new set of employees and create history?  Something else?  Thanks!