Under some circumstances, the error message reported is not very informative; try, for example, to
- define a user or role schema with unique flag
- create first user (or group) with certain value for such a schema
- attempt to create another user (or group) with same value
- error is raised (correctly) but message says "DataIntegrityViolation [The transaction has been rolled back. See the nested exceptions for details on the errors that occurred.]"
Besides this specific case, more tests should be added to check at least every case managed by RestServiceExceptionMapper.