I do mystery shops that just ask if the air and/or water appear to be in working condition. If the instructions said I needed to actually check to see if they're working then the shops probably wouldn't be worth the fee they're paying me and I probably wouldn't do them, especially if I had to pay out of pocket for the air and water that I don't need.
@wwin is right that in California, you're supposed to get free air and water if you buy gas, but some of the gas station attendants don't know that: I've seen them argue with customers about it while doing my shops.
Shopper in California's Bay Area