Residual test coverage monitoring

Structural coverage criteria are often used as an indicator of the thoroughness of testing, but complete satisfaction of a criterion is seldom achieved. When a software product is released with less than 100% coverage, testers are explicitly or implicitly assuming that executions satisfying the remaining test obligations (the residue) are either infeasible or occur so rarely that they have negligible impact on quality. Violation of this assumption indicates shortcomings in the testing process.