flaky-test-detection

name	flaky-test-detection
description	Detect, prevent, and fix flaky Jest unit tests in MetaMask Mobile before they reach CI. Use this skill when: reviewing a PR diff or changed test files for flakiness risk, fixing an intermittently failing Jest test, reproducing a flaky test locally, or auditing GitHub Actions history to rank historically flaky unit tests by failure rate.

Flaky Test Detection

Task → Which mode?
├─ Reviewing changed test files / PR diff for risk patterns  → Review mode
├─ Fixing a known flaky Jest unit test                       → Review mode + local reproduce loop
└─ Auditing CI history to rank flaky tests by failure rate   → open references/gh-analysis.md

Constraints

All proposed fixes must comply with mms-unit-testing and mms-coding-guidelines. Key rules:

• Use jest.mocked(fn) — never fn as jest.Mock
• Use toBeOnTheScreen() — never toBeTruthy() / toBeDefined() for element presence
• Use yarn commands — never npm or npx
• No toMatchSnapshot() — use explicit assertions or toMatchInlineSnapshot()

Review mode

1. Scan changed .test.ts(x) files against the pattern table (J1–J10).
2. Classify each hit (async / timing / isolation / mock / state).
3. Propose the fix for each hit using the ✅ pattern from the matching section — apply only on explicit confirmation.
4. Run the local reproduction loop to confirm the fix holds.

Audit mode

Query GitHub Actions run history to produce a ranked list of historically flaky unit test files with failure rates and suggested fix categories.

Open references/gh-analysis.md for the full procedure.