I had a neighbor who was a psychologist and who had a contract with the county PD to evaluate potential recruits. One day over a beer he mentioned that he routinely washed out fully one-third of the applicants but, the rules he operated under meant that he could only reject the ones who were a 'clear and present danger.' He felt that if he were allowed to flunk the ones who showed tendencies of developing anti-social behaviors in the future it would have been 2/3. This was in the early 80's. He was primarily seeing alcoholism/ domestic violence / or potential suicides which were all present in police departments at the time.
So they can have tests and the tests can work. But you also have to determine the rules of engagement.
So they can have tests and the tests can work. But you also have to determine the rules of engagement.