Gump builds quite a few projects, interacting with quite a selection of different programmers. So, it has quite a few use cases, and complex ones at that.
Investigate and assign failure
[wiki:ImaginaryUsers Jason] is working on the next generation of some popular java-based publishing framework, and the build started failing last night, which he just found out (it's 8:45am) on opening his inbox. This is not good, since he's supposed to be cutting a release in two weeks. He wants to know what caused the problem (including who introduced it), file a description into the issue tracker, then assign it to someone.
Update descriptor for project split-up
[wiki:ImaginaryUsers Steve] is splitting up the EJB engine into small components, and replacing ant with maven as the build tool. This is a gradual process he's been at for weeks. They just made the logger pluggable and split it into SPI and implementation, now he wants to go in and update gump to know about the change, of course running a test build to make sure the changes work on a system other than his own.
Fix a repeating project incompatibility through trial and error
[wiki:ImaginaryUsers JD]s new YAML-based configuration toolkit has not been building for a week now, and he's determined to fix it in the next two hours. He has no idea what the problem is yet, but it seems someone introduced an incompatibility in the AOP library. Since that library doesn't have tests, he just employs a trial and error method for finding the bug. This requires small commits to both the config toolkit and the AOP library, and compiling the two projects branches he's doing this on after each change.