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

Building matchers for component mocks

In this section, we’ll introduce a new matcher, toBeRenderedWithProps, that simplifies the expectations for our mock spy object.

Recall that our expectations look like this:

  { appointments },

Imagine if you were working on a team that had tests like this. Would a new joiner understand what that second argument, expect.anything(), is doing? Will you understand what this is doing if you don’t go away for a while and forget how component mocks work?

Let’s wrap that into a matcher that allows us to hide the second property.

We need two matchers to cover the common use cases. The first, toBeRenderedWithProps, is the one we’ll work through in this chapter. The second, toBeFirstRenderedWithProps, is left as an exercise for you.

The matcher, toBeRenderedWithProps, will pass if the component is currently rendered with the...