This book is about testing object-oriented software. It addresses various aspects of object-oriented software techniques with respect to their impact on testing. It argues that the testing of object-oriented software is not restricted to a single phase of software development. Instead, it runs concurrently with other development activities. This book concentrates heavily on the testing of classes and of components or sub-systems. A major part of the book is devoted towards testing of classes, the basic unit of composition for object-oriented software programs. C++ is the language used in this book. The book is intended for software practitioners, managers, researchers, students, or anyone interested in object-oriented technology and its impacts throughout the software engineering life-cycle.