ADR-005: Testing Strategy with Vitest

• Status: Accepted
• Date: 2025-12-30
• Deciders: Simon

Context and Problem Statement

As the game's logic grew more complex (physics, collisions, state management), manual testing became insufficient. A structured unit testing approach was needed to ensure the reliability and correctness of the game engine.

Decision Drivers

• Speed: Fast test execution for rapid development.
• Integration: Must work seamlessly with Vite (ADR-004) and TypeScript (ADR-007).
• Features: Built-in support for mocking, coverage, and assertion libraries.

Considered Options

1. Jest: Popular but potentially slower and more complex to integrate with Vite.
2. Mocha/Chai: Traditional but requires more configuration.
3. Vitest: Modern testing framework built on Vite.

Decision Outcome

Chosen option: Vitest (implemented in commit 88ead1b), because it provides a near-zero configuration for Vite-based projects and offers excellent performance and developer experience.

Consequences

• Positive: Extremely fast tests, easy mocking, and built-in coverage reporting.
• Negative: Adds a dependency and requires writing/maintaining test files.