we have bi-annual testing in ontario. $35 for the test.
to address the potential socio-economic impact, if the car fails, there's an upper limit on the repair costs - if the vehicle repairs would exceed that, the owner can get a "conditional pass" good for 2 years until the next test (and presumably enough time to either fix the problem or get another car).
of course i was nervous when i brought in my old accord with 340,000+ kms on the clock. but it passed with flying colours, barely registering the emissions that were being tested (of course I kept it tuned within an inch of its life).
i watched from the waiting area as the mechanics in the shop passed around the print-out of my car's results. they were amazed that it did so well. (and it did just as well 2 years later with 370,000+ kms).
the only mod on the honda that i changed "back" for the test was the timing. i put it back to spec for the test, then advanced it again afterwards. i don't think it would have failed me, but didn't want to take a chance.