A reliability model combining representative and directed testing

Directed testing methods, such as functional or structural testing, have been criticized for a lack of quantifiable results. Representative testing permits reliability modeling, which provides the desired quantification. Over time, however, representative testing becomes inherently less effective as a means of improving the actual quality of the software under test. A model is presented which permits representative and directed testing to be used in conjunction. Representative testing can be used early, when the rate of fault revelation is high. Later results from directed testing can be used to update the reliability estimates conventionally associated with representative methods. The key to this combination is shifting the observed random variable from interfailure time to a post-mortem analysis of the debugged faults, using order statistics to combine the observed failure rates of faults no matter how those faults were detected.