Testing TypeScript Applications: From Unit Tests to E2E

Modern web development is unthinkable without quality testing. The book "Testing TypeScript Applications" is a comprehensive guide that will take you from the basics of writing simple unit tests to building complex E2E scenarios for large TypeScript projects.

The author, Alexey Sokolov, a senior developer with 10 years of experience, shares proven practices and real-world cases from commercial development. You will learn how to properly organize a test infrastructure, which tools to choose, and how to avoid common mistakes.

What you will learn from the book:

• TypeScript basics for testing: types, generics, utility types
• Setting up Jest, Vitest, and Mocha for TypeScript projects
• Unit testing functions, classes, and modules
• Working with mocks, stubs, and spies (jest.mock, sinon, ts-mockito)
• Integration testing with real databases and APIs
• Testing React components with React Testing Library and Cypress Component Testing
• E2E testing with Playwright and Cypress
• Testing Node.js servers (Express, Fastify, NestJS)
• Code coverage, mutation testing (Stryker)
• CI/CD integration: GitHub Actions, GitLab CI, Jenkins

Who this book is for:

• Frontend and backend developers working with TypeScript
• Team leads and architects implementing testing in their teams
• Junior developers looking to learn testing from scratch
• QA engineers transitioning to automation with TypeScript

The book is structured from simple to complex. The first chapters cover basic concepts and environment setup. The middle section covers advanced mocking techniques and testing asynchronous code. The final chapters present full-fledged cases: testing microservice architecture, working with queues (RabbitMQ, Kafka), and load testing.

Special attention is given to TypeScript-specific aspects: testing types, working with conditional types, testing decorators and DI containers. You will learn to write not just tests, but reliable, maintainable test scenarios that will serve as documentation for your code.

Each chapter contains practical examples ready to run and checklists for implementation in real projects. After reading, you will be able to confidently cover any TypeScript application with tests — from a simple script to an enterprise solution.

The book is available on the PythonLib website in PDF, EPUB, and online versions with interactive examples.