A case study of refactoring large-scale industrial systems to efficiently improve source code quality

Refactoring source code has many benefits (e.g. improving maintainability, robustness and source code quality), but it takes time away from other implementation tasks, resulting in developers neglecting refactoring steps during the development process. But what happens when they know that the quality of their source code needs to be improved and they can get the extra time and money to refactor the code? What will they do? What will they consider the most important for improving source code quality? What sort of issues will they address first or last and how will they solve them? In our paper, we look for answers to these questions in a case study of refactoring large-scale industrial systems where developers participated in a project to improve the quality of their software systems. We collected empirical data of over a thousand refactoring patches for 5 systems with over 5 million lines of code in total, and we found that developers really optimized the refactoring process to significantly improve the quality of these systems. © 2014 Springer International Publishing

Behind the Scenes: On the Relationship Between Developer Experience and Refactoring

Refactoring is widely recognized as one of the efficient techniques to manage technical debt and maintain a healthy software project through enforcing best design practices, or coping with design defects. Previous refactoring surveys have shown that code refactoring activities are mainly executed by developers who have sufficient knowledge of the system’s design, and disposing of leadership roles in their development teams. However, these surveys were mainly limited to specific projects and companies. In this paper, we explore the generalizability of the previous results by analyzing 800 open-source projects. We mine their refactoring activities, and we identify their corresponding contributors. Then, we associate an experience score to each contributor in order to test various hypotheses related to whether developers with higher scores tend to 1) perform a higher number of refactoring operations 2) exhibit different motivations behind their refactoring, and 3) better document their refactoring activity. We found that (1) although refactoring is not restricted to a subset of developers, those with higher contribution score tend to perform more refactorings than others; (2) while there is no correlation between experience and motivation behind refactoring, top contributed developers are found to perform a wider variety of refactoring operations, regardless of their complexity; and (3) top contributed developer tend to document less their refactoring activity. Our qualitative analysis of three randomly sampled projects show that the developers who are responsible for the majority of refactoring activities are typically in advanced positions in their development teams, demonstrating their extensive knowledge of the design of the systems they contribute to

A Survey of Search-Based Refactoring for Software Maintenance

Abstract This survey reviews published materials related to the specific area of Search-Based Software Engineering that concerns software maintenance and, in particular, refactoring. The survey aims to give a comprehensive review of the use of search-based refactoring to maintain software. Fifty different papers have been selected from online databases to analyze and review the use of search-based refactoring in software engineering. The current state of the research is analyzed and patterns in the studies are investigated in order to assess gaps in the area and suggest opportunities for future research. The papers reviewed are tabulated in order to aid researchers in quickly referencing studies. The literature addresses different methods using search-based refactoring for software maintenance, as well as studies that investigate the optimization process and discuss components of the search. There are studies that analyze different software metrics, experiment with multi-objective techniques and propose refactoring tools for use. Analysis of the literature has indicated some opportunities for future research in the area. More experimentation of the techniques in an industrial environment and feedback from software developers is needed to support the approaches. Also, recent work with multi-objective techniques has shown that there are exciting possibilities for future research using these techniques with refactoring. This survey is beneficial as an introduction for any researchers aiming to work in the area of Search-Based Software Engineering with respect to software maintenance and will allow them to gain an understanding of the current landscape of the research and the insights gathered

Achieving Quality through Software Maintenance and Evolution: on the role of Agile Methodologies and Open Source Software

Agile methodologies, open source software development, and emerging new technologies are at the base of disruptive changes in software engineering. Being effort estimation pivotal for effective project management in the agile context, in the first part of the thesis we contribute to improve effort estimation by devising a real-time story point classifier, designed with the collaboration of an industrial partner and by exploiting publicly available data on open source projects. We demonstrate that, after an initial training on at least 300 issue reports, the classifier estimates a new issue in less than 15 seconds with a mean magnitude of relative error between 0.16 and 0.61. In addition, issue type, summary, description, and related components prove to be project-dependent features pivotal for story point estimation. Since story points are the most popular effort estimation metric in the agile context, in the second study presented in the thesis we investigate the role of agile methodologies in software maintenance and evolution, and prove its undoubted influence on the refactoring research field over the last 15 years. In the later part of the thesis, we focus on recent technologies to understand their impact on software engineering. We start by proposing a specialized blockchain-oriented software engineering, on the basis of the peculiar challenges the blockchain sector must confront with and statistical data retrieved from a corpus of open source blockchain-oriented software repositories, identified relying upon the 2016 Moody’s Blockchain Report. We advocate the need for new professional roles, enhanced security and reliability, novel modeling languages, and specialized metrics, along with new research directions focusing on collaboration among large teams, testing, and specialized tools for the creation of smart contracts. Along with the blockchain, in the later part of this work we also study the growing mobile sector. More specifically, we focus on the relationships between software defects and the use of the underlying system API, proving that our findings are aligned with those in the literature, namely, that the applications which are more connected to API classes are also more defect-prone. Finally, in the last work presented in the dissertation, we conducted a statistical analysis of 20 open source object-oriented systems, 10 written in the highly popular language Java and 10 in the rising language Python. We leveraged two statistical distribution functions–the log-normal and the double Pareto distributions–to provide good fits, both in Java and Python, for three metrics, namely, the NOLM, NOM, and NOS metrics. The study, among other findings, revealed that the variability of the number of methods used in Python classes is lower than in Java classes, and that Java classes, on average, feature fewer lines of code than Python classes