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 verified fix. Never propose fixes before completing the investigation phase.

Replace setTimeout and sleep calls with condition-based waiting that polls for the actual condition you need, 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 after three failed fixes and question the architecture rather than attempting a fourth fix. Repeated failures where each fix reveals new problems elsewhere indicate a fundamentally wrong pattern, so discuss architectural changes before continuing.

Trace backward from the immediate cause by asking what called each function and what values were passed, continuing until you find the original trigger. Add stack trace instrumentation with console.error before the failing operation when manual tracing is not possible.

Never. Simple bugs have root causes too, and the systematic process is fast for simple issues. Skipping investigation under time pressure leads to symptom fixes that guarantee rework and repeated failures.

Use the find-polluter.sh bisection script, which runs each test file individually and checks whether the unwanted file or state appears. It stops at the first polluting test and reports the file for investigation.