ADR-003: Vitest over Jest

Status: Accepted

Context

We need a fast and modern unit testing framework compatible with Vite-based tooling.

Decision

We chose Vitest 4.1.6.

Rationale

Vitest is significantly faster than Jest, provides out-of-the-box ESM support, and shares configuration with Vite, simplifying the build pipeline.

Consequences

Tests are colocated with source files in __tests__ directories.