Our testers use FitNesse (fitnesse.org) to describe their test cases. These include PowerCenter workflows.
For this purpose we've created a FitNesse Fixture in Java that accesses the PowerCenter Web Service Hub to run workflows. It is used very successfully by several projects, and include functional, non-functional and regression test support.
I am looking into creating a block here at communities and am wondering if anyone would be interested.
In a later phase, together with a business analyst, we would extend the solution to also include the specification in FitNesse, using the Specification By Example approach.
Let me know what you think.