It's popular everywhere, but I'm concerned about how they want to use it. No test is to be used as a sole measure of whether or not someone can work, or as diagnostic in and of itself, or to make any kind of major decisions about someone's life. The MMPI is to be used as part of a comprehensive psychological evaluation, and must be interpreted by a qualified psychologist, in the proper context. I doubt that your employer has the right to information such as your MMPI scores, anyway. If your therapist, doctor, or other professional treating you assesses that you are ready to go back to work, I would have an issue with the employer requiring additional testing.