Book Image

Mastering React Test-Driven Development

By : Daniel Irvine
Book Image

Mastering React Test-Driven Development

By: Daniel Irvine

Overview of this book

Many programmers are aware of TDD but struggle to apply it beyond basic examples. This book teaches how to build complex, real-world applications using Test-Driven Development (TDD). It takes a first principles approach to the TDD process using plain Jest and includes test-driving the integration of libraries including React Router, Redux, and Relay (GraphQL). Readers will practice systematic refactoring while building out their own test framework, gaining a deep understanding of TDD tools and techniques. They will learn how to test-drive features such as client- and server-side form validation, data filtering and searching, navigation and user workflow, undo/redo, animation, LocalStorage access, WebSocket communication, and querying GraphQL endpoints. The book covers refactoring codebases to use the React Router and Redux libraries. via TDD. Redux is explored in depth, with reducers, middleware, sagas, and connected React components. The book also covers acceptance testing using Cucumber and Puppeteer. The book is fully up to date with React 16.9 and has in-depth coverage of hooks and the ‘act’ test helper.
Table of Contents (21 chapters)
Free Chapter
1
Section 1: First Principles of TDD
6
Section 2: Building a Single-Page Application
12
Section 3: Interactivity
16
Section 4: Acceptance Testing with BDD

Accepting text input

The Git tag for this section is accepting-text-input.

Let's render an HTML text input field onto the page. Add the following test to test/CustomerForm.test.js:

it('renders the first name field as a text box', () => {
render(<CustomerForm />);
const field = form('customer').elements.firstName;
expect(field).not.toBeNull();
expect(field.tagName).toEqual('INPUT');
expect(field.type).toEqual('text');
});
This test makes use of the DOM form API: any form allows access to all of its input elements using the elements indexer. This is a simpler way of accessing form fields than CSS selectors, so I prefer to use it when it's an option.

There are three expectations in this test:

  • For there to be a form element with the name firstName
  • For it to be an input element
  • For it to have a type of text

Let's...