Software Testability Measurement for Assertion Placement and Fault Localization

Software testability the tendency for software to reveal its faults during testing is an important issue for veri cation and quality assurance Testability measurement can also be used to good advantage as a debugging aide In this paper we propose using testability measures for assertion place ment and fault isolation One measure of testability is a technique termed Sensitivity Analysis This technique analyzes how likely a test scheme is to propagate data state errors to the output space cause internal states to become corrupted when faults are exercised and exercise the code By knowing where small faults are likely to hide for a particular test scheme we have insight into where assertions are warranted and particularly bene cial Even without hints from assertions as to where a fault might be resident sensitivity analysis and a rough failure probability estimate for a program during test or operation provide enough information to formalize a testability based debugging paradigm that can be used to identify possible fault sites This model works well when hiding faults are of small size and causing infrequent failure