ADR-015 — Vitest for unit/integration tests, Playwright for e2e

Status · Accepted Date · 2026-04-28 TA anchor · §stack

Context

The orbital math library, data client, and router need unit test coverage. Critical user journeys need end-to-end coverage. A testing framework must be chosen.

Decision

Vitest for unit and integration tests. Playwright for end-to-end tests. Both run in GitHub Actions CI.

Rationale

Vitest is Vite-native — same config, same transform pipeline, fast. SvelteKit's testing documentation recommends it. Playwright is the current standard for e2e testing: cross-browser, reliable, good SvelteKit integration. Together they cover the full testing pyramid without introducing a complex Jest configuration.

Alternatives considered

• Jest — more familiar; slower with Vite projects; requires babel transform; rejected.
• Cypress — valid for e2e; heavier than Playwright; slower CI; rejected.
• Testing Library — component testing; useful addition later; not needed for Slice 1.

Consequences

Positive: fast unit tests; reliable e2e; both CI-ready out of the box. Negative: Playwright requires browser binaries in CI (~300MB download); cached after first run.

Implementation notes

vitest in vite.config.ts. Playwright config at playwright.config.ts. Unit tests colocated with source: src/lib/orbital.test.ts. E2e tests in tests/. CI caches Playwright browsers between runs.