The HVC Controller Test is a test cartridge (kensa cassette) for maintenance use, more specifically for testing Famicom controllers (including internal MIC).
Rhis small program contains a hidden mini-game, similar to the American toy game Simon. To start it, hold B + Down on Controller II, then reset the console. After a while, both controllers on the screen will automatically pass all the checks and the mini-game will begin. The program will flash a button for you to press on Controller I, and you must press it as quickly as possible. If you press the correct button just in time, a sound will play; if you miss, a different sound will play. The game will then move to the next button. Your goal is to correctly press as many buttons as possible.
Even more interesting, the source code to this mini-game is present at the end of the program itself. In the sources, this game is called “Ura Asobi”, which means something like “End Game”.
HVC Controller Test