Book Image

Mastering React Test-Driven Development - Second Edition

By : Daniel Irvine
Book Image

Mastering React Test-Driven Development - Second Edition

By: Daniel Irvine

Overview of this book

Test-driven development (TDD) is a programming workflow that helps you build your apps by specifying behavior as automated tests. The TDD workflow future-proofs apps so that they can be modified without fear of breaking existing functionality. Another benefit of TDD is that it helps software development teams communicate their intentions more clearly, by way of test specifications. This book teaches you how to apply TDD when building React apps. You’ll create a sample app using the same React libraries and tools that professional React developers use, such as Jest, React Router, Redux, Relay (GraphQL), Cucumber, and Puppeteer. The TDD workflow is supported by various testing techniques and patterns, which are useful even if you’re not following the TDD process. This book covers these techniques by walking you through the creation of a component test framework. You’ll learn automated testing theory which will help you work with any of the test libraries that are in standard usage today, such as React Testing Library. This second edition has been revised with a stronger focus on concise code examples and has been fully updated for React 18. By the end of this TDD book, you’ll be able to use React, Redux, and GraphQL to develop robust web apps.
Table of Contents (26 chapters)
Part 1 – Exploring the TDD Workflow
Part 2 – Building Application Features
Part 3 – Interactivity
Part 4 – Behavior-Driven Development with Cucumber

Creating a Jest matcher using TDD

In our tests so far, we’ve used a variety of matchers. These functions tack on to the end of the expect function call:


In this section, you’ll build a matcher using a test-driven approach to make sure it’s doing the right thing. You’ll learn about the Jest matcher API as you build your test suite.

You’ve seen quite a few matchers so far: toBeNull, toContain, toEqual, and toHaveLength. You’ve also seen how they can be negated with not.

Matchers are a powerful way of building expressive yet concise tests. You should take some time to learn all the matchers that Jest has to offer.

Jest matcher libraries

There are a lot of different matcher libraries available as npm packages. Although we won’t use them in this book (since we’re building everything up from first principles), you should make use of these libraries. See the Further reading...