mastery-jest

A small learning project for mastering Jest with TypeScript.

Purpose

This repository is designed to help you practice and learn Jest testing in a TypeScript environment. It includes a simple source file and a test suite configured to run with ts-jest.

Setup

1. Install dependencies:

pnpm install

2. Run the test suite:

pnpm test

Roadmap

Basic

• Learn Jest test structure: describe, test, and expect
• Write simple unit tests for functions and return values
• Run Jest tests locally with pnpm test
• Use matchers like toBe, toEqual, toContain, and toHaveLength

Intermediate

• Test asynchronous code with async/await, resolves, and rejects
• Mock functions and modules using jest.fn() and jest.mock()
• Use setup and teardown hooks: beforeEach, afterEach, beforeAll, afterAll
• Organize test files and improve coverage with targeted cases

Advanced

• Explore spies, deep mocks, and custom matchers
• Test Express routes or API handlers in Node.js
• Use snapshot testing for component or object output validation
• Configure Jest with TypeScript via ts-jest and custom transformer settings

Mastery

• Write resilient tests that focus on behavior, not implementation
• Combine Jest with code coverage reports and continuous integration
• Use advanced mock behaviors for complex dependencies
• Debug failing tests and maintain a clean, stable test suite