This volume contains the conference proceedings of the IFIP 28th International Conference on Testing Software and Systems, which was held October 17-19, 2016. The International Conference on Testing Software and Systems (ICTSS) addresses the conceptual, theoretic, and practical problems of testing software systems, including communication protocols, services, distributed platforms, middleware, embedded- and cyber-physical systems, and security infrastructures. ICTSS is the successor of previous (joint) conferences TESTCOM and FATES and aims to be a forum for researchers, developers, testers, and users to review, discuss, and learn about new approaches, concepts, theories, methodologies, tools, and experience in the field of testing communicating systems and software