testing-strategy

# Testing Strategy > Examples use vitest, but the patterns apply to Jest, Mocha, pytest, Go testing, > and any mainstream test runner. ## When to Activate Read this skill when you are: - writing or reviewing tests (unit, integration, E2E multi-process, chaos) in any mainstream runner; - designing a test strategy for a new module or auditing coverage gaps; - setting up or hardening a CI pipeline that gates deploy on tests; - evaluating test QUALITY (mutation score, planted-bug reviewer evals), not just test quantity; - writing behavior-focused tests for React components, custom hooks, or pages (see `references/react-component-testing.md`); - running a test-first RED/GREEN/REFACTOR cycle for a new feature or bug fix (see `references/tdd-red-green-cycle.md`); - editing files matched by the machine triggers in the frontmatter (`**/test_*.py`, `**/*.test.{ts,tsx,js,jsx}`). The machine-first `activation_triggers` frontmatter remains the canonical auto-load rule; this section is its human-scannable mirror. ## Current State | Metric | Value | Assessment | |--------|-------|-----------| | Total tests | (measure) | Track passing/failing | | Test files | (measure) | In `src/__tests__/` or equivalent | | TypeScript errors | 0 target | `tsc --noEmit` clean | | Framework | vitest 4.x | Fast, ESM-native | | E2E multi-process tests | (measure) | Often a gap | | Stress/chaos tests | (measure) | Often a gap | | CI test execution | required | Tests must run before deploy | | Mu...