If you're using Hibernate for Domain rich models, Unit testing domain logic is as simple as testing a POJO and Hibernate doesn't get in your way. The only caveat here is, For bidirectional mappings, you might have to set the object on both sides for unit tests.
Integration testing with database is generally not done for simple mappings. However it is suggested in the case of exquisite mappings like Single table inheritance etc. The only thing to remember here is, you may have to explicitly flush to database sometimes.
