As someone living in area with mandatory tests they amount to checking engine light, gas cap test, visual inspection for exhaust leaks and obd2 code read. Not sure about California they have stricter rules. As I've heard you can only use oem converter, the one car was certified with. Now to what extend it is enforced do not know, it probably depends on location. From what I've seen they are not very competent to say the least. Had car fail inspection for faulty starter code.