Textbook in PDF format The third edition of this trusted guide demonstrates the practical advantages of test-driven development (TDD) with Python and describes how to develop a real web application. You'll learn how to write and run tests before building each part of your app and then develop the minimum amount of code required to pass those tests. The result? Clean code that works. In the process, author Harry Percival teaches software and web developers the basics of Django, Selenium, Git, JavaScript, and Mock libraries, along with current web development techniques. This book—updated for Python 3.14 and Django 4—clearly demonstrates how TDD encourages simple designs and inspires confidence. Fully updated, this third edition addresses: The TDD workflow, including the unit test/code cycle and refactoring Unit tests for classes and functions and functional tests for user interactions within the browser Mock objects and the pros and cons of isolated versus integrated tests Testing and automation of deployments with a staging server Tests applied to the third-party plug-ins you integrate into your site Automatic tests using a continuous integration environment Using TDD to build a REST API with a JavaScript frontend interface I’ve tried to write this book with beginners in mind, but if you’re new to programming, I’m assuming that you’ve already learned the basics of Python. If you’re an experienced programmer but new to Python, you should get along just fine. Python is joyously simple to understand. You should be able to follow this book on Mac, Windows, or Linux. Detailed installation instructions for each OS follow. This book was tested against Python 3.14. If you’re on an earlier version, you will find minor differences in the way things look in my command output listings. The book uses the Django framework, which is (probably) the most well-established web framework in the Python world. I’ve written this book assuming that the reader has no prior knowledge of Django, but if you’re new to Python and new to web development and new to testing, you may occasionally find that there’s just one too many topics and sets of concepts to try and take on board. There’s a little bit of JavaScript in the second half of the book. If you don’t know JavaScript, don’t worry about it until then. And if you find yourself a little confused, I’ll recommend a couple of guides at that point