This page provides the downloadable ROM image (for emulators or burning to an EPROM), the schematic for a DIY test harness, and a legendary step-by-step text guide titled "So your Spectrum doesn't work..."

Specialized tools for the "Toastrack" and Amstrad-era Spectrums. Where to Buy Hardware Diagnostic Tools

A “test program” is a small piece of software designed to verify hardware, software interfaces, or specific system behaviors. On the Spectrum, test programs historically served several purposes:

Diagnostic programs feature a "Keyboard Map." If an entire diagonal line of keys doesn't work, it’s usually the membrane, not the software.