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

Migrating to Jest’s built-in test double support

So far in this chapter, you’ve built your own hand-crafted spy function, with support for stubbing values and with its own matcher. The purpose of that has been to teach you how test doubles work and to show the essential set of spy and stub patterns that you’ll use in your component tests.

However, our spy function and the toBeCalledWith matcher are far from complete. Rather than investing any more time in our hand-crafted versions, it makes sense to switch to Jest’s own functions now. These work in essentially the same way as our spy function but have a couple of subtle differences.

This section starts with a rundown of Jest’s test double functionality. Then, we’ll migrate the CustomerForm test suite away from our hand-crafted spy function. Finally, we’ll do a little more cleanup by extracting more test helpers.

Using Jest to spy and stub

Here’s a rundown of Jest test...