PhD Oral Exam - Emad Fallahzadeh, Computer Science

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Effective software testing is essential for successful software releases, and numerous test optimization techniques have been proposed to enhance this process. However, existing research primarily concentrates on small datasets, resulting in impractical solutions for large-scale projects. Flaky tests, which significantly affect test optimization results, are often overlooked, and unrealistic approaches are employed to identify them. Furthermore, there is limited research on the impact of parallelization on test optimization techniques, particularly batching, and a lack of comprehensive comparisons among different techniques, including batching, which is an effective but often neglected approach.

To address research gaps, we analyzed the Chrome release process and collected a dataset of 276 million test results. In addition to evaluating established test optimization algorithms, we introduced two new algorithms. We also examined the impact of parallelism by varying the number of machines used. Our assessment covered various metrics, including feedback time, failing test detection speed, test execution time, and machine utilization.

Our investigation reveals that a significant portion of failures in testing is attributed to flaky tests, resulting in an inflated performance of test prioritization algorithms. Additionally, we observed that test parallelization has a non-linear impact on feedback time, as delays accumulate throughout the entire test queue. When it comes to optimizing feedback time, batching algorithms with adaptive batch sizes prove to be more effective compared to those with constant batch sizes, achieving execution reductions of up to 91%. Furthermore, our findings indicate that the batching technique is on par with the test selection algorithm in terms of effectiveness, while maintaining the advantage of not missing any failures.

Practitioners are encouraged to adopt adaptive batching techniques to minimize the number of machines required for testing and reduce feedback time, while effectively managing flaky tests. Analyzing historical data is crucial for determining the threshold at which adding more machines has minimal impact on feedback time, enabling optimization of testing efficiency and resource utilization.