How do you test your ROMs?

For ASM changes, I first test if my change does not break the game. After that I check it does what it should do and test other possible cases that could be problematic. A debugger can be helpful for troubleshooting. There are changes that don't require testing, like stuff you do with FF3usME except maybe monster AI.

FF3usME isn't what I was worried about (besides Gogo's sprite replacement haha), moreso the bigger changes and events I'm hoping to start making.