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)
1
Part 1 – Exploring the TDD Workflow
10
Part 2 – Building Application Features
16
Part 3 – Interactivity
20
Part 4 – Behavior-Driven Development with Cucumber

Canceling animations with cancelAnimationFrame

The useEffect hook we’ve written has commandToAnimate and isDrawingLine in its dependency list. That means that when either of these values updates, the useEffect hook is torn down and will be restarted. But there are other occasions when we want to cancel the animation. One time this happens is when the user resets their screen.

If a command is currently animating when the user clicks the Reset button, we don’t want the current animation frame to continue. We want to clean that up.

Let’s add a test for that now:

  1. Add the following test at the bottom of test/Drawing.test.js:
    it("calls cancelAnimationFrame on reset", () => {
      renderWithStore(<Drawing />, {
        script: { drawCommands: [horizontalLine] }
      });
      renderWithStore(<Drawing />, {
        script: { drawCommands: [] }
      });
      expect(window...