There are some test ROMs online, but at the moment I don't have a way to launch an arbitrary ROM to debug it. I'm using qemu to debug the transpiler on PC, which lets me step through the ARM code instruction-by-instruction to find bugs. But I don't yet have the ability to run this via the Playdate Simulator, so I can't use the existing ROM loading interface, and indeed I don't have an actual gameboy emulator connected to this (only an 'emulator' (transpiler) for gameboy CPU instructions.)