This book constitutes the refereed proceedings of the 278th IFIP WG 6.1 International Conference on Testing Software and Systems, ICTSS 2016, held in Graz, Austria, in October 2016. The 12 revised full papers and 6 short papers presented were carefully reviewed and selected from 41 submissions. The papers are organized in topical sections on testing methodologies, heuristics and non-determinism in testing, practical applications, and short contributions.