I built a little system that tracks what’s in the house, suggests recipes from it, and helps fill a cart. For about a week it was magic. Then it started lying to me — confidently.
This is the post I most want non-engineers to read, because the failure was invisible.
The bug that looked like success
The bot kept returning cheerful, complete answers: recipes, quantities, a tidy cart. Nothing errored. Nothing turned red. But the cart wasn’t actually being created on the store’s side — the step that mattered was failing silently, and every other step happily reported “done.”
Everything said completed. Nothing was.
Why it happened
The piece that talked to the outside world (the store) had a path that only works one specific way. My automation was taking a different path and getting a polite non-answer back — which the next step interpreted as “fine, carry on.” A chain of optimistic assumptions, each one reasonable, adding up to a confident lie.
The fix, and the habit
The fix was technical and boring. The habit is the real takeaway:
- Make every step prove it worked. “No error” is not “success.” I now make the risky steps emit an explicit OK or FAIL marker, so a silent skip can’t masquerade as a win.
- Test the thing that touches the real world, separately. The internal logic was perfect. The bug lived entirely at the boundary where my system met someone else’s.
- Distrust anything that never fails. A week of flawless runs should have made me more suspicious, not less.
I run a household, a business, and a consulting practice off these little systems. The scary failures aren’t the loud ones — they’re the ones that smile and say everything’s fine.
Tagged #testing. The next time something works perfectly, I’m going to go looking for the lie.