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

Reducing effort when constructing components

Let’s look at a couple of simple ways to reduce the amount of time and code needed for test suites like the one we’ve just built: first, extracting builder functions, and second, extracting objects to store sensible defaults for our component props.

Extracting test data builders for time and date functions

You’ve already seen how we can extract reusable functions into namespaces of their own, such as the render, click, and element DOM functions. A special case of this is the builder function, which constructs objects that you’ll use in the Arrange and Act phases of your test.

The purpose of these functions is not just to remove duplication but also for simplification and to aid with comprehension.

We already have one candidate in our test suite, which is the following code:

const today = new Date();
today.setHours(9, 0, 0, 0);

We’ll update our test suite so that it uses a builder function...