A little Arduino program for the sqfmi Watchy (watchy.sqfmi.com) that makes it easy to test the buttons.
Thanks to the people on discord, especially @mayanki (who pointed me at things) and @aliceafterall who created a version of this that only uses the Watchy display (but is a bit slower because of that).
Create a new sketch in Arduino, select ESP32 Dev module as target, connect watchy, select the correct port and upload!