(Research Assistant: Brian Mitchell)
Directed testing has been criticized for its 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.
We are working on a model that permits representative and directed testing to be used in conjunction. Representative testing can be used early, when their 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 ordered statistics to combine the observed failure rates of faults no matter how those faults were detected.