Before you can test calculations, consolidations, and reports, you need data in the database. During the design process, loading mocked-up data or a subset of real data provides flexibility and shortens the time required to test and analyze results.
If you are satisfied with your database design after the preliminary test, test load the complete set of real data with which you will populate the final database. Use the test rules files if possible. This final test may reveal source data problems that were not anticipated during earlier design process phases.