You might be working in an agile or waterfall environment. Maybe you have well-defined procedures that were battle-tested through years of hard work, or maybe you just started your own start-up. No matter what the situation was, you likely faced at least one, if not more, of the following pains, problems, or causes for unsuccessful delivery:

• Part of your team is kept out of the loop during the creation of requirements, specifications, or user stories
• Most, if not all, of your tests are manual, or you don't have tests at all
• Even though you have automated tests, they do not detect real problems
• Automated tests are written and executed when it's too late for them to provide any real value to the project
• There is always something more urgent than dedicating time to testing
• Teams are split between testing, development, and functional analysis departments, and they are often out of sync
• There is an inability to refactor the code because of the fear that something will be broken
• The maintenance cost is too high
• The time to market is too big
• Clients do not feel that what was delivered is what they asked for
• Documentation is never up-to-date
• You're afraid to deploy to production because the result is unknown
• You're often not able to deploy to production because regression tests take too long to run
• The team is spending too much time trying to figure out what some method or a class does

TDD does not magically solve all of these problems. Instead, it puts us on the way towards the solution. There is no silver bullet, but if there is one development practice that can make a difference on so many levels, that practice is TDD.

TDD speeds up the time to market, enables easier refactoring, helps to create better design, and fosters looser coupling.

On top of the direct benefits, TDD is a prerequisite for many other practices (continuous delivery being one of them). Better design, well-written code, faster TTM, up-to-date documentation, and solid test coverage, are some of the results you will accomplish by applying TDD.

It's not an easy thing to master TDD. Even after learning all the theory and going through best practices and anti-patterns, the journey is only just beginning. TDD requires time and a lot of practice. It's a long trip that does not stop with this book. As a matter of fact, it never truly ends. There are always new ways to become more proficient and faster. However, even though the cost is high, the benefits are even higher. People who have spent enough time with TDD claim that there is no other way to develop a software. We are one of them and we're sure that you will be too.

We are strong believers that the best way to learn some coding technique is by coding. You won't be able to finish this book by reading it in a metro on the way to work. It's not a book that one can read in bed. You'll have to get your hands dirty and code.

In this chapter, we'll go through basics; starting from the next, you'll be learning by reading, writing, and running code. We'd like to say that by the time you're finished with this book, you'll be an experienced TDD programmer, but this is not true. By the end of this book, you'll be comfortable with TDD and you'll have a strong base in both theory and practice. The rest is up to you and the experience you'll be building by applying it in your day-to-day job.