Crucible is a flexible, layered set of tools for pulling down software from the web, building it, running tests on it, and reporting any unusual behaviors back to the parent project.
But since every testing project is unique, we strive to structure Crucible as a set of distinct tools that can be used independently or in other frameworks. Thus, if you're working on your own test harness, we hope you can cherry pick something of use to you from Crucible. :-)