I've just put the Mockify code up on Github and it's free to use by anyone that wants to play with it. Right now it supports getting a single order and getting a list of orders (with all it's parameters).
Mockify imitates the Shopify API in a Development Environment. By pointing ActiveResources site method to a Mockify site a developer can send ActiveResource calls to Mockify with the same parameters and return expectations of Shopify. Test data is seeded with the use of the populater and faker gems.