Using Rspec, how do I test the JSON format of my controller in Rails 3.0.11?

I realize that setting :format => :json is one solution (as noted above). However, I wanted to test the same conditions that the clients to my API would use. My clients would not be setting the :format parameter, instead they would be setting the Accept HTTP header. If you are interested in this solution, here is what I used:

# api/v1/test_controller_spec.rb
require 'spec_helper.rb'
describe Api::V1::TestController do
  render_views
  context "when request sets accept => application/json" do
    it "should return successful response" do
      request.accept = "application/json"
      get :test
      response.should be_success
    end
  end
end