This last part of the book is small but important. The other chapters show you how to write a variety of tests for your application. But what good is a test if you never run it? Continuous integration (CI) systems automatically run your entire test suite with each change, allowing you to catch issues effortlessly as soon as they’re introduced.

Chapter 11 shows you how to set up two different kinds of CI systems. For the DIY-minded, we cover in depth how to configure Jenkins, a popular open-source CI tool, to run your unit and E2E tests. We also show you how to use CircleCI, a popular commercial CI service.