They gave up on smog checks here in Michigan, but back when we had to do it, I knew an accommodating test station operator that'd simply input my car information while running some other car twice. I may have had the cleanest 427 in the county---at least on paper.
KS
I did that in California when I lived there, as tests were performed by licensed auto repair shops. My neighbor had one, and I used to run my '86 3.8 EFI Cougar through for 8 cars I actually had running and registered (amazing, huh). He did this for a lot of people. He was about to get busted for the third time, which would have meant a mandatory stay in the pokey, so he sold the biz to his manager and bailed to an acre lot in Cabo San Lucas, Mexico, he had bought a couple years before. Always one step ahead, he was.
Here in AZ all the testing is done by the state. No cheating.