Total joke.
Good idea, but unusable implementation
However, the constant pop-up ad asking you to purchase the paid features interrupts the tests, and there is no exit option (you must click the “purchase” button, which takes you to a purchasing page and out of the test you were currently in the middle of!). This happens every few minutes and makes the free version of the app completely unusable, which absolutely pushes me away from even considering the paid version.
There is also a lack of explanation on what much of the app is offering. A quick help guide to explain the different tests, and what different abbreviations and symbols in the tests mean would help (you can likely figure it out after a while, but you may be incorrect or missing something).