This special section of Software and Systems Modeling contains extended versions of selected papers from the 17th International Conference on Software Engineering and Formal Methods (SEFM), which was held in Oslo, Norway, in September 2019. SEFM'2019 was the seventeenth edition of an annual series of conferences that aims at bringing together leading researchers and practitioners from academia and industry to advance the state of the art in formal methods, to facilitate their uptake in the software industry, and to encourage their integration within practical software engineering methods and tools. The six articles of this special section present contributions in machine learning, session types, runtime verification, reproducible execution, and model-based testing.