Add tests for routing and to ensure output format

This avoids the tests passing if the json output is an array of kv pairs,
instead of the desired hash of attributes.

app/controllers/api/user_preferences_controller.rb

@@ -10,7 +10,7 @@ module Api
     before_action :set_request_formats
 
     ##
-    # return all the preferences as an XML document
+    # return all the preferences
     def index
       @user_preferences = current_user.preferences
 

test/controllers/api/user_preferences_controller_test.rb

@@ -9,6 +9,10 @@ module Api
         { :path => "/api/0.6/user/preferences", :method => :get },
         { :controller => "api/user_preferences", :action => "index" }
       )
+      assert_routing(
+        { :path => "/api/0.6/user/preferences.json", :method => :get },
+        { :controller => "api/user_preferences", :action => "index", :format => "json" }
+      )
       assert_routing(
         { :path => "/api/0.6/user/preferences", :method => :put },
         { :controller => "api/user_preferences", :action => "update_all" }
@@ -71,6 +75,7 @@ module Api
       js = ActiveSupport::JSON.decode(@response.body)
       assert_not_nil js
       assert_equal 2, js["preferences"].count
+      assert_equal user_preference.v, js["preferences"][user_preference.k]
     end
 
     ##