I am a researcher at the Software Engineering Chair (of Prof. Zeller) at Saarland University. The central theme of my research is improving software quality, and my recent research concerns the prevention, detection, and removal of defects in software. I develop techniques to automatically generate system tests, achieving high coverage and real failures. At the same time, I strive to develop techniques that are both scalable to large-scale applications from the real-world and practically usable, yet preserve their strong formal foundation.