The integration of generative AI tools like ChatGPT into software engineering workflows opens up new opportunities to boost productivity in tasks such as unit test engineering. However, these AI-assisted workflows can also significantly alter the developer's role, raising concerns about control, output quality, and learning, particularly for novice developers. This study investigates how novice software developers with foundational knowledge in software testing interact with generative AI for engineering unit tests. Our goal is to examine the strategies they use, how heavily they rely on generative AI, and the benefits and challenges they perceive when using generative AI-assisted approaches for test engineering. We conducted an observational study involving 12 undergraduate students who worked with generative AI for unit testing tasks, using ChatGPT running the GPT-3.5 model. We identified four interaction strategies, defined by whether the test idea or the test implementation originated from generative AI or from the participant. Additionally, we singled out prompting styles that focused on one-shot or iterative test generation, which often aligned with the broader interaction strategy. Students reported benefits including time-saving, reduced cognitive load, and support for test ideation, but also noted drawbacks such as diminished trust, test quality concerns, and lack of ownership. While strategy and prompting styles influenced workflow dynamics, they did not significantly affect test effectiveness or test code quality as measured by mutation score or test smells.

Modern software systems are large, with a project like Chromium reaching more than 30 million lines of code. Analyzing these large-scale projects over multiple versions rapidly becomes very expensive, and creating tools that can work at this scale is a challenge. This paper presents the HyperAST approach, that exploits the locality and redundancy of source code, to maintain thousands of Syntax Tree (AST) versions in memory. In particular, we contribute a programmatic interface to HyperAST that helps define the incremental computation of code metrics and efficient explorations of the fine-grained abstract syntax representation of source code.

With the advent of fast software evolution and multistage releases, temporal code analysis is becoming useful for various purposes, such as bug cause identification, bug prediction or code evolution analysis. Temporal code analyses can consist in analyzing multiple Abstract Syntax Trees (ASTs) extracted from code evolutions, e.g. one AST for each commit or release. Core feature to temporal analysis is code differencing: the computation of the so-called Diff or edit script between two given versions of the code. However, jointly analyzing and computing the difference on thousands versions of code faces scalability issues. Mainly because of the cost of: 1) parsing the original and evolved code in two source and target ASTs; 2) wasting resources by not reusing intermediate computation results that can be shared between versions. This paper details a novel approach based on time-oriented data structures that makes code differencing scale up to large software codebases. In particular, we leverage on the HyperAST, a novel representation of code histories, to propose an incremental and memory efficient approach by lazifying the well known GumTree diffing algorithms, a mainstream code differencing algorithm and tool. We evaluated our approach on a curated list of 19 large software projects and compared it to GumTree. Our approach outperforms it in scalability both in time and memory. We observed an order-of-magnitude difference: 1) in CPU time from x1.2 to x12.7 for the total time of diff computation and up to x226 in intermediate phases of the diff computation, and 2) in memory footprint of x4.5 per AST node. The approach produced 99.3% of identical diffs with respect to GumTree.

Abstract Syntax Trees (ASTs) are widely used beyond compilers in many tools that measure and improve code quality, such as code analysis, bug detection, mining code metrics, refactoring. With the advent of fast software evolution and multistage releases, the temporal analysis of an AST history is becoming useful to understand and maintain code.

Version Control Systems are key elements of modern software development. They provide the history of software systems, serialized as lists of commits. Practitioners may rely on this history to understand and study the evolutions of software systems, including the co-evolution amongst strongly coupled development artifacts such as production code and their tests. However, a precise identification of code and test co-evolutions requires practitioners to manually untangle spaghetti of evolutions. In this paper, we propose an automated approach for detecting co-evolutions between code and test, independently of the commit history. The approach creates a sound knowledge base of code and test co-evolutions that practitioners can use for various purposes in their projects. We conducted an empirical study on a curated set of 45 open-source systems having Git histories. Our approach exhibits a precision of 100 % and an underestimated recall of 37.5 % in detecting the code and test co-evolutions. Our approach also spotted different kinds of code and test co-evolutions, including some of those researchers manually identified in previous work.