I'm new to using applications to test backend APIs. I've always just manually tested using the front-end applications. What I would like to do is to use an app that is designed specifically for backend API testing. So far, I've been directed to SoapUI, Postman, and Runscope. But I'm at a loss as I am more of a test analyst than I am a programmer, despite having experience automated testing in Selenium with JavaScript, Python and Ruby. Any suggestions? Thoughts? Warnings?
(I posted this to the QA page, too, so sorry for the duplicate question)