Emission tests in my state for cars newer than 1996 is “On Board Diagnostics” OBD using the plug in the car, behind the dashboard. They check wipers, lights, horn and glass (including darkened windows – 80% transparency required)

Here is a description of the program.

Cars less than 25 years old require emissions testing every two years; my car is exempt because it is older than that. The other vehicle laws here are fairly lenient; cracked windshields are okay so long as you can still see out of them, and there are no non-emissions inspections.

NH is a different story. Emissions testing is not done (though a Check Engine light is an automatic fail; no registration possible until fixed) but the slightest chip in your windshield is also a fail, as is any inoperative bulb. I failed once because one of the two bulbs illuminating my rear license plate was out; the plate was still lit, but that dead bulb was a fail. The salt in the roads started rusting a hole in your fender? Rough metal is a fail. Front windows tinted at all? Fail. Exhaust can be heard more than ten feet away? Likely to fail though not automatic. Stored OBDII code in your ECU that didn’t trip the Check Engine Light? Guess what…

Same as @jerv