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

Test-driving callback props

In this section, we’ll introduce a new extension function, propsOf, that reaches into a mocked child component and returns the props that were passed to it. We’ll use this to get hold of the onSave callback prop value and invoke it from our test, mimicking what would happen if the real CustomerForm had been submitted.

It’s worth revisiting why this is something we’d like to do. Reaching into a component and calling the prop directly seems complicated. However, the alternative is more complicated and more brittle.

The test we want to write next is the one that asserts that the AppointmentFormLoader component is shown after CustomerForm has been submitted and a new customer has been saved:

it("displays the AppointmentFormLoader after the CustomerForm is submitted", async () => {
  // ...
});

Now, imagine that we wanted to test this without a mocked CustomerForm. We would need to fill in the real...