A year ago I published my first book. I was excited, but also very frightened. The less confident part of my nature taunted me with visions of a complete disaster. Would anyone buy a book by an unknown author? Fortunately, though, things went better than expected: the book was well received. I got many positive comments, some friendly pats on the back, new twitter followers, invitations to training sessions and conference talks, and the virtual badge of "unit testing expert". It also turned out that some people are willing to pay for the work of a relative newcomer.

All of this has encouraged me to try the same thing once again and rewrite the original book so that it presents the JUnit testing framework (instead of TestNG, which was the hero of the first book). Circumstances have been on my side. Firstly, after spending several years involved in TestNG projects, I joined a new one using JUnit. Secondly, the JUnit framework, after a long period of stagnation, has regained its vigour and is, once again, being actively developed. Thirdly, I was not a novice anymore. I had already written one book, so I knew exactly what kind of task I was taking on.

As with the first book, there are also many people who have helped me to write it. The comments received after publishing the former version have, moreover, enabled me to improve the content. A typo fixed here, a better formatted code there, a slightly updated code example - all in all, this book is definitely better than its predecessor! Thanks to Konrad Szydlo, Will McQueen and many others who shared their comments and spotted mistakes.

Today the book is ready. I hope you enjoy it!