Faulty Interaction Localization (FIL) is a process to identify which combination of input parameter values induced test failures in combinatorial testing. An accurate and fast FIL provides helpful information to fix defects causing the test failure. One type of conventional FIL approach, which analyzes test results of whole test cases and estimates the suspiciousness of each combination, has two main concerns; (1) the accuracy is not enough, (2) the huge time cost is sometimes needed. In this paper, we propose two novel approaches to improve those concerns. FROGa attempts to estimate suspiciousness more accurately using logistic regression analysis. FROGb attempts to estimate failure-inducing combinations at high speed by estimating the subsets of them using logistic regression analysis and exploring just their supersets. Through evaluation experiments using a large number of artificial test results based on several real software systems, we observed that FROGa has very high accuracy, and FROGb can drastically reduce time cost for targets that have been difficult to complete by the conventional method.

Traditional just-in-time defect prediction approaches have been using changed lines of software to predict defective-changes in software development. However, they disregard information around the changed lines. Our main hypothesis is that such information has an impact on the likelihood that the change is defective. To take advantage of this infor- mation in defect prediction, we consider n-lines (n = 1, 2, . . . ) that precede and follow the changed lines (which we call context lines), and propose metrics that measure them, which we call “Context Metrics.” Specifically, these context metrics are defined as the num- ber of words/keywords in the context lines. In a large-scale empirical study using six open source software projects, we compare the performance of using our context metrics, tradi- tional code churn metrics (e.g., the number of modified subsystems), our extended context metrics which measure not only context lines but also changed lines, and combination met- rics that use two extended context metrics at a prediction model for defect prediction. The results show that context metrics that consider the context lines of added-lines achieve the best median value in all cases in terms of a statistical test. Moreover, using few number of context lines is suitable for context metric that considers words, and using more number of context lines is suitable for context metric that considers keywords. Finally, the combination metrics of two extended context metrics significantly outperform all studied metrics in all studied projects w. r. t. the area under the receiver operation characteristic curve (AUC) and Matthews correlation coefficient (MCC).

There have been many bug prediction models built with historical metrics, which are mined from version histories of software modules. Many studies have reported the effectiveness of these historical metrics. For prediction levels, most studies have targeted package and file levels. Prediction on a fine-grained level, which represents the method level, is required because there may be interesting results compared to coarse-grained (package and file levels) prediction. These results include good performance when considering quality assurance efforts, and new findings about the correlations between bugs and histories. However, fine-grained prediction has been a challenge because obtaining method histories from existing version control systems is a difficult problem. To tackle this problem, we have developed a fine-grained version control system for Java, Historage. With this system, we target Java software and conduct fine-grained prediction with well- known historical metrics. The results indicate that fine-grained (method-level) prediction outperforms coarse-grained (package and file levels) prediction when taking the efforts necessary to find bugs into account. Using a correlation analysis, we show that past bug information does not contribute to method-level bug prediction.