Thats why you ask them to show you cash before the test drive (most people will ask for a small deposit in case anything goes wrong, usually $500, lay out a set of conditions (don’t spin my tires, roast my clutch, launch my car hard, since its NOT yours yet) and if they roast your clutch or anything you keep the money.
You can’t just shut down the chance of test drives. That won’t sell a car.