What's in a bug report?

Context: Bug reports are the primary means by which users of a system are able to communicate a problem to the developers, and their contents are important - not only to support developers in maintaining the system, but also as the basis of automated tools to assist in the challenging tasks of finding and fixing bugs. Goal: This paper aims to investigate how users report bugs in systems: what information is provided, how frequently, and the consequences of this. Method: The study examined the quality and quantity of information provided in 1600 bugs reports drawn from four open-source projects (Eclipse, Firefox, Apache HTTP, and Facebook API), recorded what information users actually provide, how and when users provide the information, and how this affects the outcome of the bug. Results: Of the recorded sources of information, only observed behaviour and expected results appeared in more than 50% of reports. Those sources deemed highly useful by developers and tools such as stack traces and test cases appeared very infrequently. However, no strong relationship was observed between the provided information and the outcome of the bug. Conclusions: The paper demonstrates a clear mismatch between the information that developers would wish to appear in a bug report, and the information that actually appears. Furthermore, the quality of bug reports has an important impact on research which might rely on extracting this information automatically.