I would like to thank my beloved Marta for showing extreme support, understanding, and encouragement during the creation of this book. I would also like to thank Tomasz Kaczanowski for the indispensable guidelines that allowed me to put the book on the right track. All the discussions with Brice Dutheil helped to deepen my understanding of the philosophy behind Mockito and testing as such. I would like to thank Jakub Nabrdalik, Maciej Zieliński, Kamil Trepczyński, and Michal Pasiński for the brainstorming sessions and reviews. Last but not least, I would like to express my gratitude to all of the official reviewers who helped to increase the quality of this book.