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

Saving to local storage via Redux middleware

In this section, we’ll update our app to save the current state to local storage, a persistent data store managed by the user’s web browser. We’ll do that by way of Redux middleware.

Each time a statement is executed in the Spec Logo environment, the entire set of parsed tokens will be saved via the browser’s LocalStorage API. When the user next opens the app, the tokens will be read and replayed through the parser.

The parseTokens function

As a reminder, the parser (in src/parser.js) has a parseTokens function. This is the function we’ll call from within our middleware, and in this section, we’ll build tests to assert that we’ve called this function.

We’ll write a new piece of Redux middleware for the task. The middleware will pull out two pieces of the script state: name and parsedTokens.

Before we begin, let’s review the browser LocalStorage API:

  • window...