We use Postman[0] for all our API testing. Postman has Jetpacks which is great way to write tests for any kind of APIs. Here's a recent blogpost on their blog - http://blog.getpostman.com/index.php/2014/03/07/writing-auto....
To top it all, the team just released Newman[1] which is a free and open-source command line collection / test runner for APIs that can be directly integrated into your build system.
[0] - http://getpostman.com