Testing is one of the most frequently used techniques in practice to assure the quality and the reliability of software systems. It is used not only during the development of such systems but also during their operation. Over the last years, new testing technologies appeared for checking both functional and non-functional requirements of systems. Application areas of these technologies include but are not limited to communicating systems such as protocols, middleware, networks, web services, cloud computing systems, wireless applications, control systems, business information systems, embedded and real-time software, and software product lines.