systematic-debugging

Follow a four-phase process: investigate the root cause by reading errors and reproducing the issue, analyze patterns against working examples, form and test a single hypothesis, then implement one fix with a failing test case. Never propose fixes before completing the investigation phase.

Replace setTimeout and sleep calls with condition-based waiting that polls for the actual condition you care about, such as an event appearing or state changing. Poll every 10ms with a clear timeout error, which eliminates race conditions and typically speeds up test execution.

Stop and return to root cause investigation with the new information rather than stacking more fixes. If three or more fixes have failed, question the underlying architecture with your team instead of attempting a fourth fix.

Trace backward through the call chain by asking what called each function and what values were passed, until you find the original trigger. Add stack trace instrumentation with console.error before the failing operation if manual tracing is not possible.

Never, according to this methodology. Simple bugs have root causes too, and systematic investigation is faster than guess-and-check thrashing even during emergencies, since random fixes create new bugs and guarantee rework.

Use the included find-polluter.sh bisection script, which runs test files one by one and checks whether the unwanted file or directory appears after each run. It stops at the first polluting test and reports the file responsible.