Verification coverage for combining test and proof

Abstract

The V&V practices of safety-critical industries (e.g. avionics) are currently based on either unit testing or unit proof to verify that a function satisfies its low-level requirements in order to be compliant with the highest certification levels, [26] (e.g. DO-178C level A for avionic software). In this context, the verification engineer must assess sufficient coverage of both code (structural coverage) and specification (functional coverage). However, there is no shared method for test and proof to measure structural coverage. In practice, this prevents the verification engineer from combining test and automatic proof to verify low-level requirements of a common piece of code in order to mitigate the verification cost. This paper fills this gap between test and proof by introducing a new notion of verification coverage based on mutation coverage. It subsumes functional coverage and structural coverage for both unit testing and unit proof. Consequently, it allows the verification engineer to mix test tools and automatic provers in the verification process for the sake of reducing verification cost, in the sense that the more automation is used during the verification, the less resource is spent to verify the program.