Test-adequacy and statistical testing: combining different properties of a test-set

Dependability assessment of safety-critical or safety-related software components is an important issue for example within the nuclear industry, the avionics sector or the military. Statistical testing is one way of quantifying the dependability of a given software product. The use of sector-specific standards with their suggested test-criteria is another (nonquantitative) way of aiming at employing only components that are "dependable enough". Ideally, both, the acknowledged test criteria and statistical test methods should come into play when assessing software dependability. We want to - in the long-term - move towards this aim. Thus we investigate in this paper a model to combine the fault-detection power of a given test-set (a test-adequacy criterion) with the statistical power of the test-set, i.e. the number of statistical tests within the test-set. With this model we aim at drawing out of any given test-set - whether devised by a plant engineer or a statistician - the overall contribution it can make to dependability assessment.