Testing lab

Test three categories deliberately. The normal case, which will pass and tells you almost nothing. The ambiguous case, where a reasonable person would hesitate — this is where you learn whether your defaults hold. And the failure case: malformed input, missing data, something written in another language, something hostile.

Write the cases down before running them, with what you expect to happen. Testing by improvising inputs and being pleased when it works is not testing. A dozen written cases with expected outcomes is the difference between a demo and something you would let run unattended.