We are developing a big plugin with a big xmlrpc interface, and sometimes it’s hard to test your functions, and see what are the results.
Googling a bit I found a very cool tool. It’s open source so you can download it and test it, or even better, you can edit and add the things you need!
It’s really easy to use, you need to input your site url, and the function you want to call (with or without parameters), and run it! You will get the results (or an error), just below the function.
Here is the code: http://code.google.com/p/xmlrpc-test/