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

Testing the Relay environment

There are a few different ways to approach the integration of Relay into a React application. The method we’ll use in this book is the fetchQuery function, which is analogous to the global.fetch function we’ve already used for standard HTTP requests.

However, Relay’s fetchQuery function has a much more complicated setup than global.fetch.

One of the parameters of the fetchQuery function is the environment, and in this section, we’ll see what that is and how to construct it.

Why Do We Need to Construct an Environment?

The Relay environment is an extension point where all manner of functionality can be added. Data caching is one example. If you’re interested in how to do that, check out the Further reading section at the end of this chapter.

We will build a function named buildEnvironment, and then another named getEnvironment that provides a singleton instance of this environment so that the initialization...