Several files were edited close together, a bug shows up, and it’s not obvious which change is actually responsible – guessing based on how the code reads risks a wasted round of testing on the wrong theory.
When a Bug’s Cause Is Unclear Across Several Recently-Changed Files, Isolate One at a Time
Field Note #236
⚡ Quick Fix (TL;DR)
The Culprit: Code that looks structurally correct on review can still hide the actual cause, especially when several plausible suspects exist at once. Two fix attempts based on code review alone both missed the real cause in a recent case, before a more disciplined test finally isolated it.
The Fix: Reduce one file to completely empty (or comment out whole sections) while holding everything else constant, then retest. If the bug persists with that file doing nothing at all, its cause is proven to be somewhere else entirely – a definitive result from one round of testing, rather than another guess.
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