This volume contains lectures on leading-edge research in methods and tools for use in computer system engineering; at the 4th International School on Engineering Trustworthy Software Systems, SETSS 2018, held in April 2018 at Southwest University in Chongqing, China. The five chapters in this volume provide an overview of research in the frontier of theories, methods, and tools for software modelling, design, and verification. The topics covered in these chapter include Software Verification with Whiley, Learning Büchi Automata and Its Applications, Security in IoT Applications, Programming in Z3, and The Impact of Alan Turing: Formal Methods and Beyond. The volume provides a useful resource for postgraduate students, researchers, academics, and engineers in industry, who are interested in theory, methods, and tools for the development of trustworthy software.