To the Attention of Mobile Software Developers: Guess What, Test your App!

Software testing is an important phase in the software development life-cycle because it helps in identifying bugs in a software system before it is shipped into the hand of its end users. There are numerous studies on how developers test general-purpose software applications. The idiosyncrasies of mobile software applications, however, set mobile apps apart from general-purpose systems (e.g., desktop, stand-alone applications, web services). This paper investigates working habits and challenges of mobile software developers with respect to testing. A key finding of our exhaustive study, using 1000 Android apps, demonstrates that mobile apps are still tested in a very ad hoc way, if tested at all. However, we show that, as in other types of software, testing increases the quality of apps (demonstrated in user ratings and number of code issues). Furthermore, we find evidence that tests are essential when it comes to engaging the community to contribute to mobile open source software. We discuss reasons and potential directions to address our findings. Yet another relevant finding of our study is that Continuous Integration and Continuous Deployment (CI/CD) pipelines are rare in the mobile apps world (only 26% of the apps are developed in projects employing CI/CD) --- we argue that one of the main reasons is due to the lack of exhaustive and automatic testing.Comment: Journal of Empirical Software Engineerin

An Analysis of Bug Distribution in Object Oriented Systems

We introduced a new approach to describe Java software as graph, where nodes represent a Java file - called compilation unit (CU) - and an edges represent a relations between them. The software system is characterized by the degree distribution of the graph properties, like in-or-out links, as well as by the distribution of Chidamber and Kemerer metrics computed on its CUs. Every CU can be related to one or more bugs during its life. We find a relationship among the software system and the bugs hitting its nodes. We found that the distribution of some metrics, and the number of bugs per CU, exhibit a power-law behavior in their tails, as well as the number of CUs influenced by a specific bug. We examine the evolution of software metrics across different releases to understand how relationships among CUs metrics and CUs faultness change with time.Comment: 17 pages, 8 figures, 10 table

Software systems as complex networks: structure, function, and evolvability of software collaboration graphs

Software systems emerge from mere keystrokes to form intricate functional networks connecting many collaborating modules, objects, classes, methods, and subroutines. Building on recent advances in the study of complex networks, I have examined software collaboration graphs contained within several open-source software systems, and have found them to reveal scale-free, small-world networks similar to those identified in other technological, sociological, and biological systems. I present several measures of these network topologies, and discuss their relationship to software engineering practices. I also present a simple model of software system evolution based on refactoring processes which captures some of the salient features of the observed systems. Some implications of object-oriented design for questions about network robustness, evolvability, degeneracy, and organization are discussed in the wake of these findings.Comment: 16 pages, 8 figures; changed content, corrected typo

Diversity, Productivity, and Growth of Open Source Developer Communities

The open source development model has become a paradigm shift from traditional in-house/closed-source software development model, with many successes. Traditionally, open source projects were characterized essentially by their individual volunteer developers. Such tradition has changed significantly with the participation of many organizations in particular. However, there exists a knowledge gap concerning how open source developer communities evolve. In this paper, we present some observations on open source developer communities. In particular, we analyze git repositories of 20 well-known open source projects, with over 3 million commit activities in total. The analysis has been carried out in three respects, productivity, diversity and growth using the Spearman's rank correlation coefficient, diversity index and the Gompertz/logistic curves, respectively. We find out that (a) the Spearman's rank correlation coefficient between active contributors and commit activities reveals how changes in the size of the developer community impacts the productivity of the community; (b) the diversity index of an open source developer community reveals the structure of the community; and (c) the growth of open source developer communities can be described using different phases of growth curves as in many organic matters.Comment: 10 pages, 6 figure

Advancing Economic Research on the Free and Open Source Software Mode of Production

Early contributions to the academic literature on free/libre and open source software (F/LOSS) movements have been directed primarily at identifying the motivations that account for the sustained and often intensive involvement of many people in this non-contractual and unremunerated productive activity. This issue has been particularly prominent in economists’ contributions to the literature, and it reflects a view that widespread voluntary participation in the creation of economically valuable goods that is to be distributed without charge constitutes a significant behavioral anomaly. Undoubtedly, the motivations of F/LOSS developers deserve to be studied more intensively, but not because their behaviors are unique, or historically unprecedented. In this essay we argue that other aspects of the “open source” phenomenon are just as intriguing, if not more so, and possibly are also more consequential topics for economic analysis. We describe the re-focusing and re-direction of empirical and theoretical research in an integrated international project (based at Stanford University/SIEPR) that aims at better understanding a set of less widely discussed topics: the modes of organization, governance and performance of F/LOSS development -- viewed as a collective distributed mode of production.. We discuss of the significance of tackling those questions in order to assess the potentialities of the “open source way of working” as a paradigm for a broader class of knowledge and information- goods production, and conclude with proposals for the trajectory of future research along that line.

The Impact of Human Factors on the Participation Decision of Reviewers in Modern Code Review

Modern Code Review (MCR) plays a key role in software quality practices. In MCR process, a new patch (i.e., a set of code changes) is encouraged to be examined by reviewers in order to identify weaknesses in source code prior to an integration into main software repositories. To mitigate the risk of having future defects, prior work suggests that MCR should be performed with sufficient review participation. Indeed, recent work shows that a low number of participated reviewers is associated with poor software quality. However, there is a likely case that a new patch still suffers from poor review participation even though reviewers were invited. Hence, in this paper, we set out to investigate the factors that are associated with the participation decision of an invited reviewer. Through a case study of 230,090 patches spread across the Android, LibreOffice, OpenStack and Qt systems, we find that (1) 16%-66% of patches have at least one invited reviewer who did not respond to the review invitation; (2) human factors play an important role in predicting whether or not an invited reviewer will participate in a review; (3) a review participation rate of an invited reviewers and code authoring experience of an invited reviewer are highly associated with the participation decision of an invited reviewer. These results can help practitioners better understand about how human factors associate with the participation decision of reviewers and serve as guidelines for inviting reviewers, leading to a better inviting decision and a better reviewer participation.Comment: 43 pages, under submission at Springer Journal of Empirical Software Engineering (EMSE

Scale-free law: network science and copyright

No description supplie

Exploring Software Reusability Metrics with Q&A Forum Data

Question and answer (Q&A) forums contain valuable information regarding software reuse, but they can be challenging to analyse due to their unstructured free text. Here we introduce a new approach (LANLAN), using word embeddings and machine learning, to harness information available in StackOverflow. Specifically, we consider two different kinds of user communication describing difficulties encountered in software reuse: 'problem reports' point to potential defects, while 'support requests' ask for clarification on software usage. Word embeddings were trained on 1.6 billion tokens from StackOverflow and applied to identify which Q&A forum messages (from two large open source projects: Eclipse and Bioconductor) correspond to problem reports or support requests. LANLAN achieved an area under the receiver operator curve (AUROC) of over 0.9; it can be used to explore the relationship between software reusability metrics and difficulties encountered by users, as well as predict the number of difficulties users will face in the future. Q&A forum data can help improve understanding of software reuse, and may be harnessed as an additional resource to evaluate software reusability metrics

The LaTeX project: A case study of open-source software

This is a case study of TeX, a typesetting software that was developed by Donald E. Knuth in the late 70's. Released with an open source license, it has become a reference in scientific publishing. TeX is now used to typeset and publish much of the world's scientific literature in physics and mathematics. This case study is part of a wider effort by academics to understand the open-source phenomenon. That development model is similar to the organization of the production of knowledge in academia; there is no set organization with a hierarchy, but free collaboration that is coordinated spontaneously and winds up generating complex products that are the property of all who can understand its functioning. The case study was led by gathering qualitative data via interviews with TeX developers and quantitative data on the TeX community -- the program's code, the software that is part of the TeX distribution, the newsgroups dedicated to the software, and many other indicators of the evolution and activity in that open-source project. The case study is aimed at economists who want to develop models to understand and analyze the open-source phenomenon. It is also geared towards policy-makers who would like to encourage or regulate open- source, and towards open-source developers who wonder what are the efficient strategies to make an open-source project successful.TeX, LaTeX, case study, open source, software, innovation, organisational structure, economic history, knowledge production, knowledge diffusion.

Empirical study of software quality evolution in open source projects using agile practices

We analyse the time evolution of two open source Java projects: Eclipse and Netbeans, both developed following agile practices, though to a different extent. Our study is centered on quality analysis of the systems, measured as defects absence, and its relation with software metrics evolution. The two projects are described through a software graph in which nodes are represented by Java files and edges describe the existing relation between nodes. We propose a metrics suite for Java files based on Chidamber and Kemerer suite, and use it to study software evolution and its relationship with bug count.Comment: 12 pages, 6 figures 2 table