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

Fetching data on mount with useEffect

The appointment data we’ll load comes from an endpoint that takes start and end dates. These values filter the result to a specific time range:

GET /appointments/<from>-<to>

Our new component is passed a today prop that is a Date object with the value of the current time. We will calculate the from and to dates from the today prop and construct a URL to pass to global.fetch.

To get there, first, we’ll cover a bit of theory on testing the useEffect hook. Then, we’ll implement a new renderAndWait function, which we’ll need because we’re invoking a promise when the component is mounted. Finally, we’ll use that function in our new tests, building out the complete useEffect implementation.

Understanding the useEffect hook

The useEffect hook is React’s way of running side effects. The idea is that you provide a function that will run each time any of the hook’s dependencies...