This book constitutes the refereed proceedings of the 32nd IFIP WG 6.1 International Conference on Testing Software and Systems, ICTSS 2020, which was supposed to be held in Naples, Italy, in December 2020, but was held virtually due to the COVID-19 pandemic. The 17 regular papers and 4 short papers presented were carefully reviewed and selected from 43 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. The papers are organized in the topical sections named: model-based testing; security testing; testing methods and applications; testing methods and automation; and short contributions.