unit-tests skill

Overview

This skill configures fast, Jest-compatible unit testing using Bun's built-in test runner for TypeScript projects. It provides co-located test file conventions, mocking support, and a concise recipe to get tests running quickly in full stack AI apps. The setup focuses on production-ready patterns and repeatable steps.

How this skill works

The skill installs and configures Bun's test runner and applies a Jest-like API so existing tests require minimal changes. It places tests next to implementation files, enables built-in mocking and snapshot features, and includes a recipe URI for step-by-step instructions. The result is a lightweight test environment with fast startup and native TypeScript compatibility.

When to use it

• You need fast local unit test feedback for TypeScript services or libraries.
• You want to reuse Jest-style tests while moving to Bun for performance.
• You prefer co-located tests alongside implementation files for clarity.
• You need built-in mocking and snapshot capabilities without heavy tooling.
• You want a simple, reproducible recipe for CI and developer workstations.

Best practices

• Co-locate test files with implementation using .test.ts or .spec.ts suffixes.
• Keep tests focused and fast: mock external services and avoid slow integration calls.
• Use Bun's snapshot testing for UI-like outputs and stable string comparisons.
• Run tests locally with Bun and include the test command in CI pipelines.
• Maintain Jest-compatible APIs to ease migration and reuse existing test code.

Example use cases

• Adding unit tests to a new TypeScript service in a full stack AI app.
• Migrating existing Jest tests to Bun to reduce CI and developer test time.
• Creating fast feedback loops for model input validation and utility functions.
• Mocking external APIs and databases during component-level testing.
• Standardizing test layout across a monorepo using co-located test files.

FAQ