tdd-vitest

name	tdd-vitest
description	Use ONLY when working with TypeScript and Vitest test files in this project. Provides rules for test file creation, running tests via npm scripts, and TDD best practices.

TDD with TypeScript and Vitest

Test File Creation

1. Create specification file with .spec.ts extension
2. Import with explicit extensions for local modules (e.g., from "./module.js")
3. Use Vitest testing functions (describe, it, expect)
4. Follow TDD red-green-refactor cycle
5. Leverage TypeScript's type checking during development

Running Tests — CRITICAL REQUIREMENTS

🚨 ALWAYS use npm scripts defined in package.json

✅ CORRECT — Use npm scripts:

npm test                   # Run all tests (vitest run)
npm run test:watch         # Run tests in watch mode

❌ WRONG — DO NOT use these:

npx vitest                        # Don't call vitest directly
vitest --run SomeFile.spec.ts     # Don't call vitest directly
npx vitest SomeFile.spec.ts       # Don't use npx

Why This Matters

• npm scripts provide a consistent interface for running tests
• Configuration is managed centrally in package.json
• Consistency across development and CI environments

Example Test Template

// calculator.spec.ts
import { describe, it, expect } from "vitest";
import { calculate } from "./calculator.js";

describe("Calculator", () => {
  it.todo("should handle basic operations");
  it.todo("should validate input types");
  it.todo("should handle edge cases");
});