I work in a bodyshop, and I quite often have to test drive customer's cars on the open road to make sure all suspension repairs, etc turned out oka, and also to verify wheel alignment, A/C recharged (if applicable) operation of turn signals, lights, horn, verify coolant is topped up if rad was changed, etc before we give the car back to the customer. The road test I usually take lasts no more than 4-7 minutes, covering a loop around the block of about 5-6Km.
The whole time I'm very carefull, because if I do smack up a car, I have to pay the deductable on the shop's insurance policy. Although it's very tempting to have a heavy right foot on a 3 block straight in an RX-8 (even though it was a crappy automatic with a brown interior) I always thing ofhow I would like my car driven if it was in the shop, and drive it accordingly. I wouldn't want someone else bagging on my car when it's in for repair, so why would I do it to theirs?