56 miles/90 km seems a bit high. No way to prove whether the car has been test driven before you bought it though it is possible it was driven from another dealership. While you'll never know, I doubt the dealer allowed someone taking a test drive to really push the car. Frankly I wouldn't worry about it, just enjoy the new car!
2011 Space Grey E90 M3, DCT, Comp. Pkg.
1997 Z3 2.8, Artic Silver, Tanin Red interior, MT
1974 2002tii, Inka, MT