JBPM will not actually persist anything if the process runs and completes. (There is no state to save.) However, if you turn on history logging, you will see some data in some of those tables. Or, if your process does not finish (gets to a save/wait state) you will see some state in the DB.
Here is a way to log history:
JPAWorkingMemoryDbLogger logger = new JPAWorkingMemoryDbLogger(session);
HTH