  Test resources are usually limited and therefore it is often not possible to
completely test an application before a release. Therefore, testers need to
focus their activities on the relevant code regions. In this paper, we
introduce an inverse defect prediction approach to identify methods that
contain hardly any faults. We applied our approach to six Java open-source
projects and show that on average 31.6% of the methods of a project have a low
fault risk; they contain in total, on average, only 5.8% of all faults.
Furthermore, the results suggest that, unlike defect prediction, our approach
can also be applied in cross-project prediction scenarios. Therefore, inverse
defect prediction can help prioritize untested code areas and guide testers to
increase the fault detection probability.
