book

Testing JavaScript Applications

by Lucas Fernandes da Costa

May 2021

Intermediate to advanced

512 pages

14h 47m

English

Manning Publications

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prefaceacknowledgmentsabout this bookWho should read this bookHow this book is organized: A roadmapAbout the codeSystem requirementsliveBook discussion forumabout the authorabout the cover illustration
1.1 What is an automated test?1.2 Why automated tests matter1.2.1 Predictability1.2.2 Reproducibility1.2.3 Collaboration1.2.4 SpeedSummary
2.1 The testing pyramid2.2 Unit tests2.3 Integration tests2.4 End-to-end tests2.4.1 Testing HTTP APIs2.4.2 Testing GUIs2.4.3 Acceptance tests and end-to-end tests are not the same2.5 Exploratory testing and the value of QA2.6 Tests, cost, and revenueSummary

3.1 Organizing test suites3.1.1 Breaking down tests3.1.2 Parallelism3.1.3 Global hooks3.1.4 Atomicity3.2 Writing good assertions3.2.1 Assertions and error handling3.2.2 Loose assertions3.2.3 Using custom matchers3.2.4 Circular assertions3.3 Test doubles: Mocks, stubs, and spies3.3.1 Mocking imports3.4 Choosing what to test3.4.1 Don’t test third-party software3.4.2 To mock, or not to mock: That’s the question3.4.3 When in doubt, choose integration tests3.5 Code coverage3.5.1 Automated coverage reports3.5.2 Coverage types3.5.3 What coverage is good for and what it isn’tSummary
4.1 Structuring a testing environment4.1.1 End-to-end testing4.1.2 Integration testing4.1.3 Unit testing4.2 Testing HTTP endpoints4.2.1 Testing middleware4.3 Dealing with external dependencies4.3.1 Integrations with databases4.3.2 Integrations with other APIsSummary
5.1 Eliminating nondeterminism5.1.1 Parallelism and shared resources5.1.2 Dealing with time5.2 Reducing costs while preserving quality5.2.1 Reducing overlap between tests5.2.2 Creating transitive guarantees5.2.3 Turning assertions into preconditionsSummary
6.1 Introducing JSDOM6.2 Asserting on the DOM6.2.1 Making it easier to find elements6.2.2 Writing better assertions6.3 Handling events6.4 Testing and browser APIs6.4.1 Testing a localStorage integration6.4.2 Testing a History API integration6.5 Dealing with WebSockets and HTTP requests6.5.1 Tests involving HTTP requests6.5.2 Tests involving WebSocketsSummary
7.1 Setting up a test environment for React7.1.1 Setting up a React application7.1.2 Setting up a testing environment7.2 An overview of React testing libraries7.2.1 Rendering components and the DOM7.2.2 React Testing Library7.2.3 Enzyme7.2.4 The React test rendererSummary
8.1 Testing component integration8.1.1 Stubbing components8.2 Snapshot testing8.2.1 Snapshots beyond components8.2.2 Serializers8.3 Testing styles8.4 Component-level acceptance tests and component stories8.4.1 Writing stories8.4.2 Writing documentationSummary
9.1 The philosophy behind test-driven development9.1.1 What test-driven development is9.1.2 Adjusting the size of your iterations9.1.3 Why adopt test-driven development?9.1.4 When not to apply test-driven development9.2 Writing a JavaScript module using TDD9.3 Testing top-down versus testing bottom-up9.3.1 What bottom-up and top-down testing mean9.3.2 How top-down and bottom-up approaches impact a test-driven workflow9.3.3 The pros and cons of bottom-up versus top-down approaches9.4 Balancing maintenance costs, delivery speed, and brittleness9.4.1 Test-driven implementation9.4.2 Test-driven maintenance9.5 Setting up an environment for TDD to succeed9.5.1 Teamwide adoption9.5.2 Keeping distinct lanes9.5.3 Pairing9.5.4 Supplementary testing9.6 TDD, BDD, validations, and specificationsBDD (behavior-driven development)Summary
10.1 What are UI-based end-to-end tests?10.2 When to write each type of test10.2.1 UI-based end-to-end tests10.2.2 Pure end-to-end tests10.2.3 Pure UI tests10.2.4 A note on acceptance testing and this chapter’s name10.3 An overview of end-to-end testing tools10.3.1 Selenium10.3.2 Puppeteer10.3.3 Cypress10.3.4 When to choose CypressSummary
11.1 Your first UI-based end-to-end tests11.1.1 Setting up a test environment11.1.2 Writing your first tests11.1.3 Sending HTTP requests11.1.4 Sequencing actions11.2 Best practices for end-to-end-tests11.2.1 Page objects11.2.2 Application actions11.3 Dealing with flakiness11.3.1 Avoiding waiting for fixed amounts of time11.3.2 Stubbing uncontrollable factors11.3.3 Retrying tests11.4 Running tests on multiple browsers11.4.1 Using a testing framework to run tests within a browser11.4.2 Running UI-based tests in multiple browsers11.5 Visual regression testsSummary
12.1 What are continuous integration and continuous delivery?12.1.1 Continuous integration12.1.2 Continuous delivery12.2 The role of automated tests in a CI/CD pipeline12.3 Version-control checksSummary
13.1 Using type systems to make invalid states unrepresentable13.2 Reviewing code to catch problems machines can’t13.3 Using linters and formatters to produce consistent code13.4 Monitoring your systems to understand how they actually behave13.5 Explaining your software with good documentationSummary

Overview

Automated testing will help you write high-quality software in less time, with more confidence, fewer bugs, and without constant manual oversight. Testing JavaScript Applications is a guide to building a comprehensive and reliable JS application testing suite, covering both how to write tests and how JS testing tools work under the hood. You’ll learn from Lucas de Costa, a core contributor to popular JS testing libraries, as he shares a quality mindset for making testing decisions that deliver a real contribution to your business. You’ll benefit from informative explanations and diagrams, easily-transferable code samples, and useful tips on using the latest and most consolidated libraries and frameworks of the JavaScript ecosystem.

About the Technology
Automated testing is essential to delivering good JavaScript applications every time. A complete testing strategy needs to cover functions in isolation, integration between different parts of your code, and correctness from the end user’s perspective. This book will teach you how to deliver reliable software quickly and confidently.

About the Book
Testing JavaScript Applications teaches you how to implement an automated testing plan for JavaScript-based web applications. It describes practical testing strategies, covers useful tools and libraries, and explains how to foster a culture of quality. In this clearly-written, example-rich book, you’ll explore approaches for both backend and frontend applications and learn how to validate your software much more quickly and reliably.

What's Inside

Unit, end-to-end, and integration testing
Managing test cost and complexity
Practicing test-driven development
Dealing with external dependencies
Tools like Jest and Cypress

About the Reader
For junior JavaScript developers.

About the Author
Lucas da Costa is a core maintainer of Chai and Sinon.JS, two of the most popular testing tools in the JavaScript ecosystem, and contributed to numerous other open-source projects, including Jest.

Quotes
If you thought you knew how to test JavaScript applications, this book will surprise you!
- Lucian Enache, Glencore

This book is your key to taming the wild frontier of JavaScript testing.
- Bryan Miller, Petrolitix

A detailed, insightful book on JavaScript testing for newcomers and experienced programmers.
- Satej Sahu, Honeywell

An up-to-date, practical book that covers the ground level details of writing real-world tests and testing suites.
- Raul Siles, DinoSec