Clear validators before and after each test

Or some tests fail when run in random order

activerecord/test/cases/validations/i18n_validation_test.rb

@@ -6,6 +6,7 @@ class I18nValidationTest < ActiveRecord::TestCase
   repair_validations(Topic, Reply)
 
   def setup
+    repair_validations(Topic, Reply)
     Reply.validates_presence_of(:title)
     @topic = Topic.new
     @old_load_path, @old_backend = I18n.load_path.dup, I18n.backend

activerecord/test/cases/validations_repair_helper.rb

@@ -13,7 +13,7 @@ def repair_validations(*model_classes)
     end
 
     def repair_validations(*model_classes)
-      yield
+      yield if block_given?
     ensure
       model_classes.each do |k|
         k.clear_validators!