Abstract: In a distributed computer program, active software probes in the form of small functions built into an application are invoked by another application. When invoked, an active probe provides a positive response if the service being requested is available from the probed package. If the service is not available, the probe will fail alerting the software package installer that there is a problem. The active probes thus perform a functionality check for the software package, not a check merely based on the package's release number. Because the probe is active, it is capable of checking for subtending capabilities that the calling application may not realize are necessary for this service. This ensures full coverage of the test while hiding some implementation details from the calling application.