Almost all successful companies have some sort of verifiable hiring programs. facebook has their puzzles as a screener test. It is not a universal test but it helps. If you are able to solve the puzzles, there should be a higher probability that you are a better employee to the company than someone who can't solve the puzzles.
All they need to do is verify if those puzzles are good at screening good hires. If yes, well done then. They've got themselves a great hiring tool.
I'm not asking for the one almighty test that can screen if an employee is good or bad. I'm asking for tests that can help in increasing the probability of hiring good employees. For eg. for a sales job, you absolutely have to do a personality test. If the test indicate that you are introverted and have bad people skills, that you are not likely to be a good hire. Is the personality test a universal test? No, it's not. But it helps.