Model-based test generation is an approach to generate test cases based on a formal model. Although test generation methods have long existed, its timed counterpart is still a new field. In addition, most of the proposed solutions suffer from combinatory explosion which continues to limit their applicability in practice. Accordingly, it explains why there are so few automatic formal methods for testing generation, for both time and untimed systems. This book presents an overview about models, specification languages and test generation approches adressed to timed systems. In addition, it proposes a test generation approach using test-purposes and considering timed constraints. In order to evaluate the applicability and efficiency of the proposed method, two real industrial applications are used as case studies: a Railroad Crossing and a Vocal Service furnished by France Telecom.