Minecraft wiki entry for Rube_Goldberg_machine, associated text: On the console edition, you can exit without saving after testing the RGM so you don't need to reset it.
Make backup copies on the PC version by copying the level folder. There is also a button in the Edit menu that allows you to save backups. If all else fails, closing the game with the Task Manager can save the RGM if it misfires.
You can reset an RGM machine with the /clone command, a copy of the RGM machine, and command blocks. You could also use structure blocks.