According to [this guide](http://guides.rubyonrails.org/action_controller_overview.html), we were populating the parameters above incorrectly.
> 9.1.1 path_parameters, query_parameters, and request_parameters

> Rails collects all of the parameters sent along with the request in the params hash, whether they are sent as part of the query string or the post body. The request object has three accessors that give you access to these parameters depending on where they came from. The query_parameters hash contains parameters that were sent as part of the query string while the request_parameters hash contains parameters sent as part of the post body. The path_parameters hash contains parameters that were recognized by the routing as being part of the path leading to this particular controller and action.