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

After an idyllic childhood spent playing with BASIC on French 8-bit computers like the Thomson T-07 whose keys go "boop" when you press them, Harry spent a few years being deeply unhappy as a management consultant. Soon he rediscovered his true geek nature, and was lucky enough to fall in with a bunch of XP fanatics, working on the pioneering but sadly defunct Resolver One spreadsheet. He now works at PythonAnywhere LLP, and spreads the gospel of TDD world-wide at talks, workshops and conferences, with all the passion and enthusiasm of a recent convert.