Dont let anyone ride your bike unless they have a valid MC license, or it will be YOUR butt on the line.
Your insurance covers the bike, not the person, so if you let someone ride it you are covered.
Since they showed you their license, if they want a test ride, hold their license. If they dont come back you call the cops and you have their ID. And most likely their car is still in your driveway.
One sticky point is how they get the bike home if they buy it. I have driven my car that I just sold to other peoples homes, so they can get the car there with 'my plates'. Then I take the plates off and ride home with my wife or son. Dont let anyone ride off with your plates on the vehicle, because once money changes hands, its not yours anymore and the plates are not valid.
The thing to be aware of is how this all happens. If they ask YOU "will you drive it to my house?" they could be setting you up. If you ask them how they will get the bike home, and they come up empty, then you can offer to ride it there. Its up to you, and its on your terms that way.