JavaScript Testing

This book is a practical guide to automated testing in JavaScript using Node.js. It is intended for developers who already have basic knowledge of JS and want to learn how to write reliable, maintainable tests for their projects.

The author systematically covers all key aspects of testing: from unit testing with Jest and Mocha to integration tests with Supertest, from end-to-end testing with Playwright to API testing. Special attention is given to the principles of TDD (Test-Driven Development) and BDD (Behavior-Driven Development), as well as patterns for organizing test code.

The book has 12 chapters. The first three introduce the basics: setting up the environment, choosing a framework, and writing the first tests. Chapters 4–6 cover mocks, stubs, spies, and testing asynchronous code. Chapters 7–9 examine testing databases, HTTP requests, and WebSockets. Chapter ten covers CI/CD and integrating tests into pipelines. Chapter eleven covers code coverage and quality metrics. Chapter twelve covers advanced techniques: property-based testing, snapshot testing, and performance testing.

The reader will learn: how to write clean tests that don't break during refactoring; how to test code that depends on external services; how to build a test architecture for large projects; how to automate test execution in CI; how to measure and improve code coverage. You will learn to distinguish good tests from bad ones and understand when testing is unnecessary.

Why should you read this book? It doesn't just teach the syntax of asserts — it builds a testing culture. All examples are based on real-world scenarios from commercial development. The book is relevant for Node.js 14+ and modern versions of Jest (27+), Mocha (9+), and Playwright (1.20+). After reading it, you will be able to confidently implement testing in any JavaScript project.

For whom: frontend and backend JavaScript developers who want to master testing; team leads implementing QA processes; students of technical specialties studying modern web development.