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

Updating the app

We’ve completed the work on building the sagas, but we have just a couple of adjustments to make in the rest of the app.

The MenuButtons component is already functionally complete, but we need to update the tests to properly exercise the middleware, in two ways: first, we must stub out the WebSocket constructor, and second, we need to fire off a TRY_START_WATCHING action as soon as the app starts:

  1. Open test/MenuButtons.test.js and start by importing the act function. We’ll need this to await our socket saga actions:
    import { act } from "react-dom/test-utils";
  2. Next, find the describe block named sharing button and insert the following beforeEach block, which is similar to the same stubbed constructor you used in the saga tests:
    describe("sharing button", () => {
      let socketSpyFactory;
      let socketSpy;
      beforeEach(() => {
        socketSpyFactory = jest.spyOn(