Mea culpa: How developers fix their own simple bugs differently from other developers

Reviewed by Greg Wilson / 2021-08-10
Keywords: Faults

This paper from Zhu and Godfrey looks at single-statement bug fixes in Java code: more specifically, at the differences between how bug are fixed by the people who created them and how they are fixed by other people. The authors found that people fix their own bugs more quickly than other people's, which falls under the heading of "I would have predicted that, but it's nice to have it validated".

What I wouldn't have predicted is that when people fix their own bugs, they tend to create larger commits that also address other issues; when they fix other people's bugs, their commits are smaller and more tightly focused. It's easy to say that this could have been predicted as well, but its opposite would have been just as plausible after the fact: if the authors had found that people are more focused when fixing their own small bugs, I would also have said, "Yeah, that makes sense." This is why I find empirical studies so valuable: in many cases "X" and "not X" are equally easy to rationalize, so we need evidence to help us decide which to believe.

Two more things to note about this paper. First, it relies on the SZZ algorithm to align bugs and code fixes, so the results discussed above depend on how well that algorithm does its job; a future post will dive into that. Second, the dataset used in this paper is available online at so that other people (like you) can explore it, reanalyze it, or use it in courses. The frequency with which researchers make data available like this is one of the biggest and most welcome changes in research during our four-year hiatus (the other being the trend toward open access publishing). We will try to link to datasets whenever we can; if we miss any, please contact us, file an issue, or submit a pull request to help us do better.

Zhu2021 Wenhan Zhu and Michael W. Godfrey: "Mea culpa: How developers fix their own simple bugs differently from other developers". 2021 IEEE/ACM 18th International Conference on Mining Software Repositories (MSR), 10.1109/msr52588.2021.00065.

In this work, we study how the authorship of code affects bug-fixing commits using the SStuBs dataset, a collection of single-statement bug fix changes in popular Java Maven projects. More specifically, we study the differences in characteristics between simple bug fixes by the original author—that is, the developer who submitted the bug-inducing commit—and by different developers (i.e., non-authors). Our study shows that nearly half (i.e., 44.3%) of simple bugs are fixed by a different developer. We found that bug fixes by the original author and by different developers differed qualitatively and quantitatively. We observed that bug-fixing time by authors is much shorter than that of other developers. We also found that bug-fixing commits by authors tended to be larger in size and scope, and address multiple issues, whereas bug-fixing commits by other developers tended to be smaller and more focused on the bug itself. Future research can further study the different patterns in bug-fixing and create more tailored tools based on the developer's needs.