A Game Boy Cartridge Diagnoses the Game Boy—and Prints Its Report on a Game Boy Printer
GB Test Lab is a diagnostic cartridge for the original Game Boy. It checks functions including memory, interrupts, cartridge-slot lines and button contacts, while its Quick Check runs several autonomous tests in under a minute.
Results can be stored per console, and a connected Game Boy Printer can produce a six-page report on thermal paper. The cartridge also contains twenty reference articles explaining Game Boy components and symptoms.
Details： Game Boy Museum ↗
The diagnostic tool for a Game Boy is itself a Game Boy cartridge, and even the final report comes out through the period-correct Game Boy Printer. The commitment is complete.