Debugging application crashes is an expensive and time-taking process, relying on the developer’s expertise, and requiring knowledge about the system. Over the years, the research community has developed several automated approaches to ease debugging. Among those approaches, search-based crash reproduction, which tries to generate a test case capable of reproducing a given crash to make it observable to the developers, solely based on the stack trace included in the crash report. We believe that this makes crash reproduction the perfect candidate to achieve end-to-end crash fault localization. In this thesis, we explore and empirically evaluate the usage of search-based crash reproduction combined with spectrum-based fault localization on 50 real-world crashes. Starting from a crash report, we generate crash-reproducing test cases and use them in conjunction with the existing or an automatically generated unit test suite as input for spectrum-based fault localization. Our results show that, although, hand-written test cases remain the most efficient in the general scenario, automatically generated crash-reproducing test cases still reduce the number of statements to be investigated by developers. Additionally, when considering the best-case scenario where only crash-reproducing test cases covering the fault are evaluated, we observe no statistically significant difference between the accuracy of fault localization when using hand-written or automatically generated test cases. Our results confirm the feasibility of end-to-end automated crash fault localization. The results also identify new challenges for both automated test case generation and fault localization, as well as when they are combined.

Various search-based test generation techniques have been proposed to automate the process of test generation to fulfill different criteria (e.g., line coverage, branch coverage, mutation score, etc.). Despite these techniques' undeniable accomplishments, they still suffer from a lack of guidance coming from the data gathered from the production phase, which makes the generation of complex test cases harder for the search process. Hence, previous studies introduced many strategies (such as dynamic symbolic execution or seeding) to address this issue. However, the test cases created by these techniques cannot assure the full coverage of the execution paths in software under test. Therefore, this thesis introduces common and uncommon behavior test generation (CUBTG) for search-based unit test generation. CUBTG uses the concept of commonality score, which is a measure of how close an execution path of a generated test case is from reproducing the same common and uncommon execution patterns observed during the real-world usage of the software. To evaluate the performance of CUBTG, we implemented it in EvoSuite and evaluated it on 150 classes from JabRef, an open-source application for managing bibliography references. We found that CUBTG managed to cover more common behaviors than plain MOSA in 75% of the cases, and more uncommon behaviors in 60% of the cases. In up to 10% of the cases CUBTG managed to find more mutants seeded by PIT by using method sequences that plain MOSA did not find.

Software applications inevitably crash, and it is time-consuming to recreate the crash conditions for debugging. Recently, researchers have developed frameworks relying on genetic algorithms, e.g. Botsing, for automated crash reproduction. However, the existing approaches process exceptions of different types as if they were the same. In this thesis, we study how the four most common types of Java exceptions are thrown and define specialised fitness functions for them. We have extended Botsing and carried out an evaluation against 52 real-world crashes from seven various open-source software applications. Our results show that our proposed fitness functions influence both the effectiveness and efficiency, negatively or positively depending on the type of the target exception. This thesis demonstrates how tailoring the fitness functions according to the exception type can improve search-based crash reproduction.

The majority of the courses in the Computer Science Bachelor at the Delft University of Technology use so called lab sessions to provide an opportunity for students to ask questions about course material and get feedback on their assignment. In order to optimally support the students, teaching assistants, or TAs, are appointed to assist the lecturer during the lab sessions. With the number of students in the Bachelor quickly growing, the process of manually recruiting students to become a TA and assigning the TAs to lab sessions is becoming infeasible.

This project aims to ease the process of gathering and scheduling TAs. In order to achieve this goal, the Teaching Assistant Management platform, or TAM, has been developed. All parties involved in the process of appointing TAs can use TAM to provide their input. Lecturers can register their courses on TAM, students are able to indicate their interest to help with different courses and representatives from Education and Student Affairs can validate the application of the interested students. Using this input, TAM is able to automatically create a schedule by assigning TAs to lab sessions. To provide an algorithm for the automatic generation of schedules, a model based on the minimumcost max flow problem is created. Due to complications with the implementation of the minimum-cost max flow model, the schedule generation is handled by a linear solver: Gurobi. By modeling the constrains for a schedule to be considered valid, Gurobi is used to process the input of the users into an optimized schedule.

TAM consists of three components: a MySQL database, a backend written using Spring, containing the business logic and the implementation of the scheduler, and a frontend website created with Vue to provide an interface to the users. The frontend and the backend are connected using a REST API.

A unique aspect of the project is the live deployment of TAM. At the end of the fourth week, the first version was deployed, allowing interested students to submit their course preferences. Subsequent features have been deployed iteratively. During the development, muliple problems have been encountered. The team underestimated the time required to learn the new technologies, as well as the time needed to maintain a system in production. Furthermore, configuring Single Sign-On required more time than expected.