Debug Room is a Location in Nier: Automata.
Once you've defeated the game 3 times, save the game. This new save file will let you access Chapter Select and Debug. From Chapter Select you can launch any part of the story you have unlocked. The menu will now show you your progression. Side Quest progression will carry over from playthrough to playthrough so you don't need to redo them. Debug Room lets you fight enemies in a room to practice combat.