BugMaps-Granger: a tool for visualizing and predicting bugs using Granger causality tests

Despite the increasing number of bug analysis tools for exploring bugs in software systems, there are no tools supporting the investigation of causality relationships between internal quality metrics and bugs. In this paper, we propose an extension of the BugMaps tool called BugMaps-Granger that allows the analysis of source code properties that are more likely to cause bugs. For this purpose, we relied on the Granger Causality Test to evaluate whether past changes to a given time series of source code metrics can be used to forecast changes in a time series of defects. Our tool extracts source code versions from version control platforms, calculates source code metrics and defects time series, computes Granger Test results, and provides interactive visualizations for causal analysis of bugs. We provide an example of use of BugMaps-Granger involving data from the Equinox Framework and Eclipse JDT Core systems collected during three years. For these systems, the tool was able to identify the modules with more bugs, the average lifetime and complexity of the bugs, and the source code properties that are more likely to cause bugs. With the results provided by the tool in hand, a maintainer can perform at least two main software quality assurance activities: (a) refactoring the source code properties that Granger-caused bugs and (b) improving unit tests coverage in classes with more bugs.