[zmj]

Yes - it's essential for debugging.

Your mental model tells you that if the system is in a given state, and receives a given input, what "should" happen. You can then look for evidence whether those things happened and narrow down a bug.

It also works the other way. If, given this input, that happened, your mental model tells you what the system state must have been. That can help you work backwards to identify a bug that put the system into a bad state.