What is a psychological test? How can a test be optimally constructed? How can the quality of a test be determined? Answering these questions is central to many foundational and applied areas of psychology. This book provides a clear and application-oriented introduction to the theoretical foundations of test construction and analysis. It begins by addressing the fundamental ideas of testing in psychology and its significance for psychological diagnostics, as well as the quality criteria and international standards that guide test construction and analysis. The central steps of test construction are illustrated, and the most important item formats are described along with their advantages and disadvantages. The subsequent chapters present in detail the most significant psychometric models for dichotomous, ordinal, and metric analyses.