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

Animating with requestAnimationFrame

In this section, you will use the useEffect hook in combination with window.requestAnimationFrame to adjust the positioning of AnimatedLine and Turtle.

The window.requestAnimationFrame function is used to animate visual properties. For example, you can use it to increase the length of a line from 0 units to 200 units over a given time period, such as 2 seconds.

To make this work, you provide it with a callback that will be run at the next repaint interval. This callback is provided with the current animation time when it’s called:

const myCallback = time => {
  // animating code here

If you know the start time of your animation, you can work out the elapsed animation time and use that to calculate the current value of your animated property.

The browser can invoke your callback at a very high refresh rate, such as 60 times per second. Because of these very small intervals...