Just lots of testing. Obviously the scope for generating bugs in a game like this is a lot higher than in a RenPy game; in addition to the usual asset and logic bugs (which you can get in RenPy as well), you also get the unique bugs Unity itself brings to the table, and the bugs arising from stuff like the poker combat, Elsewhere, etc.
You can see the change-file, it's essentially documenting an epic running battle of man vs bugs.
You can see the change-file, it's essentially documenting an epic running battle of man vs bugs.