Spectral Debugging with Weights and Incremental Ranking

Software faults can be diagnosed using program spectra. The program spectra considered here provide information about which statements are executed in each one of a set of test cases. This information is used to compute a value for each statement which indicates how likely it is to be buggy, and the statements are ranked according to these values. We present two improvements to this method. First, we associate varying weights with failed test cases --- test cases which execute fewer statements are given more weight and have more influence on the ranking. This generally improves diagnosis accuracy, with little additional cost. Second, the ranking is computed incrementally. After the top-ranked statement is identified, the weights are adjusted in order to compute the rest of the ranking. This further improves accuracy. The cost is more significant, but not prohibitive.