This book constitutes the refereed proceedings of the 30^th IFIP WG 6.1 International Conference on Testing Software and Systems, ICTSS 2018, held in Cádiz, Spain, in October 2018. The 8 regular and 6 short papers presented were carefully reviewed and selected from 29 submissions. ICTSS is a series of international conferences addressing 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.