I've had to take a number of personality assessments during job interviews. Each time I take one of these tests, I feel they are testing little more than our ability to b.s. our employers. Some of the questions are so ridiculous it would take an absolute idiot to "flunk." For instance, for a certain restaurant job one question asked if applicants felt entitled to steal, if they thought they would get away with it. Of course they didn't want to hire someone who would steal...but do you think a thief would have a moral problem with lying about being a thief?
Additionally, the questions are largely leading about how much you're a "people person" or have things like an outgoing personality and a cheerful disposition. These are easy to fake when facing a scale-of-one-to-ten bubble test. Anyone can pretend to be cheerful and outgoing, and those with common sense know that someone who answers honestly that they are gloomy, sarcastic, or lazy will not be hired.
So why give them? Employers are kidding themselves that this weeds out the bad candidates. Really all they are doing is indicating to potential employees that they expect and encourage them to lie, exaggerate, or fake their way through the job. Those who "pass" the test show little more than that they know what the employer expects and are willing to at least attempt to fit into that box.