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

Duplicating tests for multiple form fields

So far, we’ve written a set of tests that fully define the firstName text field. Now, we want to add two more fields, which are essentially the same as the firstName field but with different id values and labels.

Before you reach for copy and paste, stop and think about the duplication you could be about to add to both your tests and your production code. We have six tests that define the first name. This means we would end up with 18 tests to define three fields. That’s a lot of tests without any kind of grouping or abstraction.

So, let’s do both – that is, group our tests and abstract out a function that generates our tests for us.

Nesting describe blocks

We can nest describe blocks to break similar tests up into logical contexts. We can invent a convention for how to name these describe blocks. Whereas the top level is named after the form itself, the second-level describe blocks are named after the...