Fix failing Mongoid tests

- attr_accessible not set for test user model, making Serializable tests
  inaccurate
- Mongoid does not `include_root_in_json` by default, so enable this for
  consistency with AR tests
- Mark tests pending for Mongoid < 2.1 that fail there due to known bugs
- Add `:mongoid` key for i18n model labels
- Remove outdated shim of `update_attribute` that caused mass assignment
  security to be applied (ugh, that took awhile to find)

test/helpers/devise_helper_test.rb

@@ -2,13 +2,16 @@ require 'test_helper'
 
 class DeviseHelperTest < ActionController::IntegrationTest
   setup do
+    model_labels = { :models => { :user => "utilisateur" } }
+
     I18n.backend.store_translations :fr,
     {
       :errors => { :messages => { :not_saved => {
         :one => "Erreur lors de l'enregistrement de '%{resource}': 1 erreur.",
         :other => "Erreur lors de l'enregistrement de '%{resource}': %{count} erreurs."
       } } },
-      :activerecord => { :models => { :user => "utilisateur" } }
+      :activerecord => model_labels,
+      :mongoid => model_labels
     }
 
     I18n.locale = 'fr'
@@ -30,6 +33,10 @@ class DeviseHelperTest < ActionController::IntegrationTest
   end
 
   test 'test errors.messages.not_saved with multiple errors from i18n' do
+    # Dirty tracking behavior prevents email validations from being applied:
+    #    https://github.com/mongoid/mongoid/issues/756
+    (pending "Fails on Mongoid < 2.1"; break) if defined?(Mongoid) && Mongoid::VERSION.to_f < 2.1
+
     get new_user_registration_path
 
     fill_in 'email', :with => 'invalid_email'
@@ -40,4 +47,5 @@ class DeviseHelperTest < ActionController::IntegrationTest
     assert_have_selector '#error_explanation'
     assert_contain "Erreur lors de l'enregistrement de 'utilisateur': 2 erreurs"
   end
-end
+end
+