Perhaps in development, but the stuff that tends to make it into the release of games seems to be gameplay related. Npc behaviors not lining up, the developer literally not implementing certain stats in the game (looking at you, Diablo 4), graphical bugs caused by something not loading or loading too slowly, performance issues from something loading 1000 copies of itself etc.
And where do you think many of those bugs come from? Usually utility code that isn't working in some edge case, those types of things can be easy to pull out and test in their own independent of the game
