I just ran across this story about situations in which personality testing can backfire. The news story itself is a year old, but the message is timeless, and the upshot is clear.
Personality tests are a fantastic tool for workplace learning, teambuilding, coaching and mentoring, conflict resolution, etc. When used properly, such tests can also provide useful information about job applicants, but such hiring applications are a delicate matter. Specifically, employers need to be careful that the test does not discriminate against a protected class. The article quotes an employment lawyer: "Are you using a test to screen out applicants, or to provide insights on people who [sic] you are interested in?" This is a subtle but important distinction, and worth bearing in mind.