Offline API Testing

I'm using the Dropbox HTTP API for development purposes and was curious as to if there was any type of library or capacity that would allow for offline testing. Meaning, is there potentially some type of python, ruby, etc. library that would properly emulate the responses returned from the Dropbox HTTP API? Granted, since the documentation provides the JSON structure returned from each individual HTTP endpoint, it wouldn't be too bad to create my own library that handles the HTTP requests and provides some dummy JSON data back in response. I just didn't know if such a library/capacity already existed to allow for testing of my development when not connected to the Internet or when I can't use the Dropbox API Explorer tool.