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

What is a test double?

A unit in unit testing refers to a single function or component that we focus on for the duration of that test. The Act phase of a test should involve just one action on one unit. But units don’t act in isolation: functions call other functions, and components render child components and call callback props passed in from parent components. Your application can be thought of as a web of dependencies, and test doubles help us to design and test those dependencies.

When we’re writing tests, we isolate the unit under test. Often, that means we avoid exercising any of the collaborating objects. Why? Firstly, it helps us work toward our goal of independent, laser-focused tests. Secondly, sometimes those collaborating objects have side effects that would complicate our tests.

To give one example, with React components, we sometimes want to avoid rendering child components because they perform network requests when they are mounted.

A test double...