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

Refactoring the Test Suite

At this point, you’ve written a handful of tests. Although they may seem simple enough already, they can be simpler.

It’s extremely important to build a maintainable test suite: one that is quick and painless to build and adapt. One way to roughly gauge maintainability is to look at the number of lines of code in each test. To give some comparison to what you’ve seen so far, in the Ruby language, a test with more than three lines is considered a long test!

This chapter will take a look at some of the ways you can make your test suite more concise. We’ll do that by extracting common code into a module that can be reused across all your test suites. We’ll also create a custom Jest matcher.

When is the right time to pull out reusable code?

So far, you’ve written one module with two test suites within it. It’s arguably too early to be looking for opportunities to extract duplicated code. Outside of...