I would expect them to at least let me know they are taking it out. Whenever I hand my car over for any reason to a garage or the like I always take a quick snap of the dash readout with my phone, mileage etc. you could always reset the mpg readout too to see if they are thrashing it! But shakedown? I can do that myself, I would be annoyed if a garage handed it to some kid to thrash about town.