Our company, Connamara Systems, is positioned in the Financial Technology space to deliver made-to-measure software using agile and test driven development methodologies. A lot of that software depends on the QuickFIX apis, and we make heavy use of Cucumber for our acceptance testing. These libraries have been hardened by many development cycles that are now in production.
If you use BDD and FIX, these gems could be for you. Contributions encouraged!