200 in 1: Elfland
This game has debugging material.
200-in-1: Elfland is an NES multicart named after its first game, Elfland (mistakenly called "Elf Load" on the multicart menu).
An internal selftest program can be accessed by pressing Select + Start on the main menu. It performs a test of the CHR data, PRG data, mirroring support, and banking support. It is almost identical to the ROM/PCB test in 150-in-1, with only the palette and multicart's name changed. Both carts likely share similar menu code.