Haha! Well, 'way back when I was a student, my thesis adviser strongly urged each of us to take a clinically related course. I chose human testing. We had to actually administer a relatively eclectic battery of tests to an adult and a child and justify why we'd chosen this set of tests.
As I recall the most important thing we learned was to be very skeptical about what the tests purported to measure, and to look at the whole rather than the results of a single test. Also, we used the IQ test as a diagnostic tool rather than simply a measure of basic intelligence. Those tests really only measure potential to succeed in an academic environment anyway.
There may be tests that measure critical thinking but it would take a long, long time and too many able people would likely slip through the cracks.