Thesis Talk Jan Smits – Mutator, the open-source mutation testing framework

Mutator, the open-source mutation testing framework

Stryker Mutator, the open-source mutation testing framework developed with Info Support, would like to introduce mutation levels to their framework. These levels allow selecting a subset of Stryker’s mutators. A level can then be optimized for either performance or testing thoroughness. My assignment will be to determine how the levels can be designed to do so. I will be classifying the mutators based on performance impact and testing thoroughness.


Together with two other students I have worked on project Weapon-regeX for a course at the University of Twente. Our goal was to create a regular expression mutator for either Stryker4s or StrykerJS. For this we took inspiration from the implementation of Pim Rheiter for Stryker.NET and used the mutators he defined. In the end we support both Stryker4s and StrykerJS, by implementing our solution in Scala and using Scala.JS to compile to JavaScript as well. The result forms a library that Stryker can then import and use to mutate the regular expressions it finds. You can try it out yourself on our demo page: The three of us are continuing to maintain Weapon-regeX in our free time.

Jan Smits

After my positive experience with Stryker through the Weapon-regeX project I decided to my graduation assignment with them as well. The mutation testing research field is a relatively small but interesting one and I am learning a lot by reading through it. As a result of this assignment, I hope to create a framework that can classify existing and future mutators for Stryker into three or more mutation levels. This framework will most likely use empirical methods using a test bed of example projects.