In my country you leave a certain amount for the inspector somewhere in the dash area or in your vehicle booklet. At least in the past I've known some people to do it for older cars, there were ways to bypass emissions tests and ignore some minor issues. Also, I once failed the brake fluid check and I had to repeat the inspection. Since I didn't have time to do a full drain, I just went to a nearby garage to suck it out from the overflow container with a syringe and top it off with fresh fluid. This was just to pass the test and I would fully replace it later.