I'm surprised longarm dealers don't do that automatically - I never really thought about it but I would have just assumed that's something they'd do.
My Janome dealer won't let even the least expensive machine go out the door without them test-sewing on it, making sure all the stitches work, and adjusting anything that needs adjusting. Maybe he's just extraordinarily thorough? He's the only dealer I've worked with so I just assumed that was a standard thing and part of the benefit you get by buying through a dealer vs. shopping online.