public void RegisterDefaultAdapter() { var oldFactory = DataAnnotationsModelValidatorProvider.DefaultAttributeFactory; try { // Arrange var metadata = ModelMetadataProviders.Current.GetMetadataForType(() => null, typeof(MyValidatedClass)); var context = new ControllerContext(); DataAnnotationsModelValidatorProvider.RegisterDefaultAdapter(typeof(MyDefaultValidationAttributeAdapter)); // Act var result = new DataAnnotationsModelValidatorProvider().GetValidators(metadata, context).Single(); // Assert Assert.AreEqual(typeof(MyDefaultValidationAttributeAdapter), result.GetType()); } finally { DataAnnotationsModelValidatorProvider.DefaultAttributeFactory = oldFactory; } }