If you're interested in improving your practice at programming in general, and Test Driven Development in particular, I'd suggest doing code katas is a good way to learn. There's a host of programmers around the world using code katas to hone their skills and learn from one another, in a coding dojo, at a code retreat, in a pair on a lunchbreak, or just by themselves. This book uses Code Katas to illustrate some modern coding techniques, so you can learn about, and practice them.

A code kata is a simple coding problem that may take a little effort to solve the first time, but the point is you don't only do it once. Start over from scratch and try it again, but think more carefully about how you're solving it. Can you work in small steps, refactoring often, and keep your design simple and clean? Can you write a good suite of automated tests that support your development and provide good regression protection for future maintenance work? The challenge in a Code Kata is to solve the problem well, and to demonstrate good practices in how you reach your solution. If you're using Code Katas like this, you'll find you build up a repertoire of katas that you know well, and can use to polish your coding technique.

Code Katas are also useful when you're trying out something new - a tool, technique or coding environment. Keep one variable the same - the problem to solve - and see how your coding experience, design, and tests are affected by the new element. It's this way of using Code Katas that is the focus of this book. I'm assuming you are familiar with each code kata, and can use it to show you a new technique.

In this book I'll show you examples including, but not limited to, Mocks Fakes and Stubs. I'll also discuss techniques like London School TDD, Outside-In development, and Approval testing. I'll begin each topic with a discussion of the theory, and follow it up with some code listings and sample tests. My aim is that it'll be a little like pair programming with someone experienced in the technique, who can explain what they mean both in theory and example, and give you some commentary about when you might choose to use it. You'll definitely be expected to put in some work yourself, learning the Code Katas, and trying the techniques out for yourself. It'll certainly be more fun if you can get a group together and start a Coding Dojo.

My first book, "The Coding Dojo Handbook", is full of practical advice about how to set up this kind of a space for learning. While I was working on that book, I found myself writing long passages about particular techniques, and how you could learn about them using some of the code katas listed in the catalogue in that book. In the end, I decided that material didn't belong in "The Coding Dojo Handbook", and that it would be better to start a new book.

The techniques in "Mocks, Fakes and Stubs" are all useful to practice in a Coding Dojo environment, but not exclusively. I've included examples taken from a range of programming languages, including Java, Python, C++ and C#. You can do a Code Kata in pretty much any language you feel like, and you'll find and starting code is available in many popular languages on my Github page. All the code katas used in this book are listed in the Kata Catalogue from "The Coding Dojo Handbook".