One skill that’s essential for any professional JavaScript developer is the ability to write testable code. This book shows you what writing and maintaining testable JavaScript for the client- or server-side actually entails, whether you’re creating a new application or rewriting legacy code. From methods to reduce code complexity to unit testing, code coverage, debugging, and automation, you’ll learn a holistic approach for writing JavaScript code that you and your colleagues can easily fix and maintain going forward. Testing JavaScript code is complicated. This book helps experienced JavaScript developers simply the process considerably. Get an overview of Agile, test-driven development, and behavior-driven development. Use patterns from static languages and standards-based JavaScript to reduce code complexity. Learn the advantages of event-based architectures, including modularity, loose coupling, and reusability. Explore tools for writing and running unit tests at the functional and application level. Generate code coverage to measure the scope and effectiveness of your tests. Conduct integration, performance, and load testing, using Selenium or CasperJS. Use tools for in-browser, Node.js, mobile, and production debugging. Understand what, when, and how to automate your development processes.