Software Testing has gained a phenomenal importance in the recent years in the System Development Life Cycle. Many learned people have worked on the topic and provided various techniques and methodologies for effective and efficient testing. Today, even though we have many books and articles on Software Test Engineering, many people are fallacious in understanding the underlying concepts of the subject. Software Testing Book (STGB) is an open source project aimed at bringing the technicalities of Software Testing into one place and arriving at a common understanding. This book has been authored by professionals who have been exposed to Testing various applications. We wanted to bring out a base knowledge bank where Testing enthusiasts can start to learn the science and art of Software Testing, and this is how this book has come out. This book does not provide any specific methodologies to be followed for Testing, instead provides a conceptual understanding of the same.