Usagi's going in for general health and power tests.

General health would probably showcase that she's a healthy sixteen year old girl (if not just a tad overweight from sweets).

Power-wise, there would be a lot to be explored since she's a magical girl with incredible power - the ability to manifest an outfit out of nowhere, the incredible healing power of the Silver Crystal, the remaining crystals containing the powers of Uranus, Neptune, Saturn and Pluto (Earth, Water, Destruction, Time), so she'll be there for awhile.