I maintain that there's a difference between a test drive and a road test.
Test drive = A thrash to see if a particular type of car is fun to drive.
Road test = A procedure to determine if a car has faults only noticable while driving.
Don't let anyone test drive your car.
If they want to check if there are faults that may make them not buy the car, then take them for a drive yourself. An agreement to purchase the car at a predetermined price should be reached before the drive provided no faults are found. I'm sick of people wanting to drive cars when they don't even have the dosh.