Covered Is Not Checked: Which Branch Outcomes Would Your Tests Notice?

Md Nafiu Rahman, Cemil Canbaz, Soneya Binta Hossain

Code coverage reports what tests execute, not whether tests detect faults. Checked coverage addresses this gap by tracing code that influences test oracles through dynamic slicing, but slicing is costly, and Java slicers struggle with modern language features and complex programs. We present Veritas, a slicing-free approach that directly tests whether covered behavior is checked. We target object branch coverage (OBC), a compiled-code structural criterion with fault-detection effectiveness comparable to source-level Modified Condition/Decision Coverage (MC/DC), which is required at the highest assurance level of DO-178C. For each covered object-branch outcome, Veritas forces the opposite outcome and credits checking only when the change is executed, a previously passing test fails, and the failure is attributable to that outcome. Thus, Veritas distinguishes execution from demonstrated fault detection without dynamic dependence analysis. We evaluated Veritas on eleven open-source Java projects containing 51,382 object-branch outcomes. We find that 18% of covered outcomes can be changed without failing any test, exposing weaknesses hidden by coverage. Among surviving mutants, about…