Asp.net Unit test model data annotation DataType.EmailAddress?

Question

How do I test DataType.EmailAddress?

I have a Customer model with an Email property with the following data annotations to validate:

[StringLength(100)]
[DataType(DataType.EmailAddress, ErrorMessage = "Email must be a valid email address")]
[Display(Name = "Email")]
[Required(ErrorMessage = "Email is required")]
public string email { get; set; }

I am writing unit tests to test validations. I have figured out how to test required and string length.

Here's my method that catches other errors, but doesn't handle the DataType validations:

private List<ValidationResult> ValidateModel<T>(T model)
{
    var context = new ValidationContext(model, null, null);
    var result = new List<ValidationResult>();
    var valid = Validator.TryValidateObject(model, context, result, true);

    return result;
}

I call it in a test method:

[TestMethod]
public void Invalid_email_addresses_throw_errors()
{
    var model = new Models.Customer();

    model.email = "";
    var results = ValidateModel(model);
    Assert.IsTrue(results.Any(v => v.ErrorMessage == "Email is required"));
}

How do I test DataType.EmailAddress - passing in an invalid value and receiving the an error as a result?

Answer 1

Use the [EmailAddress] DataTypeAttribute.

EmailAddressAttribute is derived from DataTypeAttribute and overrides the IsValid method which is what checks that the value is in fact a valid email.

Using

[DataType(DataType.EmailAddress, ErrorMessage = "Email must be a valid email address")]

does not do anything for email validation.

If you inspect the source code for DataTypeAttribute you will realize that it is primarily a base attribute used to create custom and targeted validation attribute.

The DataTypeAttribute in the original question is being used incorrectly. There is no other solution than to use the EmailAddressAttribute as demonstrated below in the following unit test.

[TestClass]
public class UnitTestExample {
    [TestMethod]
    public void Invalid_email_addresses_throw_errors() {
        //Arrange
        var badEmail = "1234_)(";
        var subject = new Customer { email = badEmail };

        //Act
        var results = ValidateModel(subject);

        //Assert
        Assert.IsTrue(results.Count > 0);
        Assert.IsTrue(results.Any(v => v.MemberNames.Contains("email")));
    }

    public class Customer {

        [StringLength(100)]            
        [Display(Name = "Email")]
        [Required(ErrorMessage = "Email is required")]
        [EmailAddress(ErrorMessage = "Email must be a valid email address")]
        public string email { get; set; }

    }

    private List<ValidationResult> ValidateModel<T>(T model) {
        var context = new ValidationContext(model, null, null);
        var result = new List<ValidationResult>();
        var valid = Validator.TryValidateObject(model, context, result, true);

        return result;
    }
}