Keep in mind that several copies of a satellite will be built during production. Some are mockups of a few subsystems (e.g. structure), some are used for tests (e.g. thermal, electrical, interference), often there's also a "flight spare" which is an exact copy of the satellite in case something goes wrong with the flight hardware (e.g. broken during testing, launch failure).

E.g. Curiosity has such a spare (I'm not sure if it's the same as the flight hardware or close enough) which will be sent in a future mission (I think 2017, though I don't have any sources at hand) with (some) different experiments on board.