I need to create an XML-RPC server on the iphone for testing purposes. Is there is a library I could leverage?
Check out eczarny / xmlrpc on github. It comes with a test server.
Writing such a server -- especially for test purposes -- is pretty trivial using either Ruby or Python. I'd bet Ruby on Rails has solved this problem (I don't know it well enough to say for sure).
For Python, there are about a dozen solutions. I've personally both used a dead simple server with the built in libraries and have also used Twisted if the server needs any kind of complexity.