Want some brutally truthful tests designed to see how competent you are?

Take the SAT test, , which measures math ability, and verbal ability. Find a few psychology tests that try and measure memorization ability(like, how quickly and well you can memorize a topic)

Why? Because real world success, in intellectual endeavors, is largely a combination of how large your fluid intelligence is+memorization ability+ work ethic. The rest is due to combos of other factors.

Besides the SAT, you can take the LSAT, and study for a few things on there that require specific knowledge. The test is the single largest predictive factor of success in law school, and blind tests of competence.

There are a few other tests you can take. I recommend the AMC, which requires studying some topics outside of the regular school curriculum, but not too much.

Or, you could play starcraft for 3 months, and see how high you end up ranking.

Beyond these,I don't know of many good tests to see how competent you are.