Family inspection
Repair the whole family of inputs the bug class corrupts — and calibration matters: not every weird line is a bug.
Family inspection. After repairing, ask the family question: inputs of the same shape — other empty inputs, other ties, other single-element cases — would this same bug class corrupt? Your repair must handle the whole family, not one specimen. This is why the hidden tests always include at least one sibling of the symptom case.
For the exam: debugging MCQs give you the snippet and FOUR proposed single-line fixes. The wrong options are other classes' fixes — plausible, well-written, and aimed at a different bug. Identifying the CLASS first eliminates three options without testing any of them. That is the lab's payout: taxonomy turns a search problem into a recognition problem.