For more details about my research interests, visit my publications page.


To find defects in software, one needs test cases that execute the software systematically, and oracles that assess the correctness of the observed behavior when running these test cases. EvoSuite is a tool that automatically generates test cases with assertions for classes written in Java code. To achieve this, EvoSuite applies a novel hybrid approach that generates and optimizes whole test suites towards satisfying a coverage criterion. For the produced test suites, EvoSuite suggests possible oracles by adding small and effective sets of assertions that concisely summarize the current behavior; these assertions allow the developer to detect deviations from expected behavior, and to capture the current behavior in order to protect against future defects breaking this behaviour.

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Test generation tools commonly aim to cover structural artefacts of software, such as the source code or the user interface. However, focusing only on source code can lead to unrealistic or irrelevant test cases, while exploring a user interface often misses much of the underlying program behavior. Our EXSYST tool takes a new approach by exploring user interfaces while aiming to maximize code coverage, thus combining the best of both worlds. Experiments show that such an approach can achieve high code coverage matching and exceeding the code coverage of traditional unit-based test generators; yet, by construction every test case is realistic and relevant, and every detected failure can be shown to be caused by a real sequence of input events.

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Code Defenders 

Mutation testing is endorsed by software testing researchers for its unique capability of providing pragmatic estimates of a test suite’s fault detection capability, and for guiding testers in improving their test suites. In practice, however, wide-spread adoption of mutation testing is hampered because any non-trivial program results in huge numbers of mutants, many of which are either trivial or equivalent, and thus useless. Trivial mutants reduce the motivation of developers in trusting and using the technique, while equivalent mutants are frustratingly difficult to handle. These problems are exacerbated by insufficient education on testing, which often means that mutation testing is not well understood in practice. These are examples of the types of problems that gamification aims to overcome by making such tedious activities competitive and entertaining. In this paper, we introduce the first steps towards building Code Defenders, a mutation testing game where players take the role of an attacker, who aims to create the most subtle non-equivalent mutants, or a defender, who aims to create strong tests to kill these mutants. The benefits of such an approach are manifold: The game can serve an educational role by engaging learners in mutation testing activities in a fun way. Experienced players will produce strong test suites, capable of detecting even the most subtle bugs that other players can conceive. Equivalent mutants are handled by making them a special part of the gameplay, where points are at stake in duels between attackers and defenders.

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