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 technologyNo developer wants to waste time making sure every application feature still works whenever they push new code to production. Thankfully, automated testing delivers quick and precise feedback on whether your application still functions correctly every time you update it. With automated testing, you can validate your application with a single command—and unlike humans, machines don’t forget steps or make mistakes! about the book Testing JavaScript Applications  is a guide to creating JavaScript tests that are targeted to your application’s specific needs. Dripping with the insight author Lucas da Costa has developed as a core contributor to some of the most popular JS testing libraries, this book offers dozens of detailed code samples that you can apply to your own projects. You’ll learn how to write tests for both backend and frontend applications, covering the full spectrum of testing types so you can pick an approach that’s right for you. Taking on the role of a developer for a bakery’s web store, you’ll learn to validate different aspects including databases, third-party services, and how to spin-up a real browser instance to interact with the entire application. All examples are delivered using the popular testing tool Jest and modern packages of the JavaScript ecosystem.   what's inside Writing practical tests that make a real business contribution Writing tests for both front-end and back-end applications Managing the costs and complexity of your tests Practicing test-driven development Dealing with external dependencies, like databases or third-party APIs Supporting tests by creating a 'culture of quality' about the readerFor junior JavaScript developers. No testing experience required. 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. He has also contributed to Jest and other relevant open-source projects. Lucas is committed to a culture of sharing and has spoken at major software engineering conferences, including JSConf Colombia, FluentConf, HolyJS, CityJSConf London, and many others.