Bug in the Fridge

Once you've been into Quality Assurance for 5+ years you start to notice bugs everywhere and develop a sixth sense for it. Today I found a bug in my Liebherr KBGB 3864 refrigerator, caused by what looks like a race-condition.

This appliance starts beeping in case the door is left open for more than 60 seconds. The alarm stops if door is closed or can be muted manually while the door is still open.

The Bug

It happened so that I had the door open for nearly one minute and as it was closing I heard a beep. This time however the beeping didn't stop after the door had closed. The alarm continued beeping with the door closed so I tried to re-open and close it again. It didn't stop! I had to open the door and manually mute the alarm for it to stop.

The Root Cause

While not entirely sure, I think the reason for this malfunction was a race-condition. The alarm went on at nearly the same time when the controlling timer should have gone off (when closing the door).

Steps To Reproduce

I tried reproducing several times afterwards by opening and closing the door at the last possible moment. I used a stop-watch to time my actions. However I wasn't able to reproduce twice. Every time I tried, there was only one single beep as the door was closing and no more.

I guess then, like we say in QE, WORKS FOR ME!