Here in Texas, you must either have computer hookup to OBD II '96 and later, or tailpipe test under load '95 and earlier. Test under load is strapped to a dyno which replicates load at 0-30 mph. Car is tested at 1500 rpm and 2500 rpm, and the sweep in rpm between those 2 is calculated in too. The OBD hookup is easier, although they can go in your computer deep, for instance, once when head was off car, I repaired and drove around 30 min. before stopping for the inspect, he could tell by drive cycle just completed that I had done something to the car. He was satisfied with the answer that I had just gotten it back together. They have the ability to refuse inspect to any thing that "looks wrong", in other words, they can refuse anything they don't like. On the other hand, I wrecked my Focus, repaired it myself, but did NOT replace the airbags, just covered the holes with covers from junkyard. The law here has not caught up with airbags yet, even if airbag light is on, they will pass it as long as car appears and drives like it is safe. I told him no bags and had defeated light because I didn't like it staring me in the face. He said it was OK. Car must be 20 years or older to escape one of those 2 tests. Then it's safety inspect only. It's really funny that they jump through real hoops to make sure that all gas caps have a positive seal under vacuum check but they don't spend a single second checking for leaks anywhere else in the evap system. Perhaps that's because when our wonderful president was the governor here, there was a change ratified by lawmakers that lead inspectors to "snooping" around under the hood with an HC sniffer. Just sticking it in all the crevices around a motor broke lots of vacuum lines that were about to go anyway. To test one car took 30-45 minutes, then people were screaming when the inspector showed them the newly broken lines and told them they failed test. To test program one tv station borrowed new cars off dealer's lot and they failed too, horror stories of 6-8 hour waits for inspect abounded. Legislature finally caved in after 3 months into program and deep sixed it, cost like 300 million in losses to taxpayers.