In attempting to AJAX-ize the site, I had the desire to handle JSON as if it were form post data. Queue a Rack middleware solution. rack-contrib contains a bunch of common middleware extensions, one being the horribly named PostBodyContentTypeParser. To get this working I added:

require 'rack/contrib'

with all of the rest of the required files.

Added:

use Rack::PostBodyContentTypeParser

to my application class

And went about over testing it like so:

def test_json_creates_params_hash
  params_hash={"user"=>{"username"=>"testuser","email"=>"test@test.com","password"=>"pass1","password_confirmation"=>"pass1"}}
  post '/test_json', params_hash
  assert !last_request.params.blank?
  assert_equal params_hash, last_request.params
  assert last_response.ok?
  json_string="{\"user\":{\"password_confirmation\":\"pass1\",\"username\":\"testuser\",\"password\":\"pass1\",\"email\":\"test@test.com\"}}"
  post '/test_json', JSON(json_string)
  assert !last_request.params.blank?
  assert_equal params_hash, last_request.params
  assert last_response.ok?
  post '/test_json', json_string, "CONTENT_TYPE"=>"application/json"
  assert_equal last_request.env["CONTENT_TYPE"], "application/json"
  assert !last_request.params.blank?
  assert_equal params_hash, last_request.params
  assert last_response.ok?
end