TDD - 我应该在我的域模型中测试数据库约束吗？

我应该在域对象中测试数据库约束吗？例如。如果数据库中的字段是varchar（500）并且是必需的，我应该在我的代码中对此进行测试吗？或者我应该只依靠try / catch。这是一项相当大的工作开销 - 如果可以避免的话。即

//partial method for a class generated by the Entity framework
[MetadataType(typeof(UserMetaData))]
public partial class User
{

}

public class UserMetaData
{
    [Required]
    [StringLength(500)]
    public string FirstName { get; set; }
}

// My domain object tests
// This test in particular will throw an expected exception, saying that the first name cannot be found
[TestFixture]
public class UserTest
{
    [Test]
    [ExpectedException(typeof(ValidationException), ExpectedMessage = "The FirstName field is required.")]
    public void user_should_require_first_name()
    {
        User user = new User();
        user.Id = 0;
        user.MiddleName = "x";
        user.IsAdmin = true;
        user.LastName = "James";
        user.Password = "password";
        user.Title = "Mr";
        user.Username = "jamesbrown";
        user.Email = "jamesbrown@somewebsite.com";

        TestsHelper.ValidateObject(user);
    }
}