ADR-003: Vitest over Jest

Status: Accepted

Context

We need a fast, modern, and ESM-native unit testing framework with built-in code coverage support.

Decision

We chose Vitest.

Rationale

Vitest provides native ESM execution, blazing fast test performance with worker threads, seamless Vite plugin integration, and zero-configuration TypeScript support.

Consequences

Unit and component tests are organized within the top-level tests/unit/ directory mirroring the application structure. Code coverage is measured using @vitest/coverage-v8 with an 80% coverage threshold enforced across CI.