Vitest is now adopted by all teams. The Macan team uses it for testing their data visualization components. Browser mode has enabled us to consolidate component integration tests that previously required Cypress, simplifying our testing infrastructure alongside Storybook's visual regression testing. All tests are written in TypeScript. Average CI test time across all projects is under 90 seconds.

Why Vitest Over Jest

We migrated from Jest to Vitest across all projects in Q2 2024. The primary drivers:

• Vite-native — our frontend projects already use Vite for bundling; Vitest reuses the same config and transform pipeline, eliminating the dual-config problem
• Speed — Vitest's worker-based architecture and smart file watching reduced local test runs by ~60% compared to Jest
• ESM-first — no more moduleNameMapper hacks for ESM packages; Vitest handles modern module formats natively
• Compatible API — migration was mostly mechanical; describe/it/expect patterns carried over directly

Testing Strategy

Our testing pyramid across all projects:

Browser mode (powered by Playwright under the hood) runs component tests in a real browser, catching DOM-specific issues that jsdom misses — particularly around CSS media queries, intersection observers, and Web Component rendering.

CI Integration

Every PR triggers the full test suite via GitHub Actions. Our reusable workflow:

1. Runs Vitest with --reporter=junit for GitHub Actions test summary
2. Collects coverage with @vitest/coverage-v8
3. Posts coverage diff as a PR comment (minimum 80% for new code)
4. Fails on any test.skip or test.todo — these must be resolved before merge