Quantification of Verification Progress

A key disadvantage of software verification over other quality assurance techniques, such as testing, is its unpredictable cost. A lot of people-hours have to be invested before correctness can be proved, and, in contrast to testing, there is no quantifiable evidence that incremental verification effort results in incremental quality improvements. On the other hand, the process of verifying code can be seen as a sort of audit or code-walk, so there is an intuition that the process itself improves quality, even before a proof can be computed. In this paper we discuss our first attempts to quantify the incremental quality improvements that are achieved during verification using a metric called verification coverage.