I don't think researching the dealer will prevent this happening, just because it's never been reported before doesn't mean it won't happen to yours - new employees with no respect for customers cars, people that have done it historically but never been pulled for it etc.
I'd say that leaving the car with them for the least amount of time (if possible) is the best way forward - i'd expect the service manager to be less willing for a tech to take it for a spin during works time (unless a test drive is absolutely required) than they would be for the techs to take it out on their lunch break or overnight (if it's going to be with them for a few days and it's roadworthy the whole time they have it). Letting them know that you know your mileage when you pass it over and you don't expect to see any frivolous miles on it is probably all you can do to let them know that someone taking your car for a joy ride won't go unchallenged. At the end of the day though, they still might not give a toss, especially if they're doing work that they'd just about be able to justify a test drive post-fix for.
