javascript-testing-patterns

What problem does it solve?

Building robust JavaScript/TypeScript applications requires comprehensive testing, but setting up effective unit, integration, and end-to-end tests with proper mocking can be complex. This Skill provides a detailed guide to modern testing frameworks and best practices.

Core Features & Use Cases

• Unit Testing: Covers patterns for testing pure functions, classes, and async functions with Jest/Vitest.
• Mocking Strategies: Explains how to mock modules, use dependency injection, and spy on functions.
• Integration Testing: Guides on API and database integration tests using tools like Supertest and pg.
• Frontend Testing: Provides patterns for testing React components and hooks with Testing Library.
• Use Case: When starting a new Node.js backend or React frontend project, this Skill helps you set up a robust testing infrastructure from scratch, ensuring high code quality and preventing regressions.

Quick Start

Example: Unit test a simple add function

This demonstrates a basic unit test for a pure function using Vitest.

import { describe, it, expect } from 'vitest'; import { add } from './calculator';

describe('Calculator', () => { describe('add', () => { it('should add two positive numbers', () => { expect(add(2, 3)).toBe(5); }); }); });