TDD - Should I test database constraints at my domain model?

Should I test database constraints in my domain object? E.g. If the field in the database is varchar(500) and required, should I have a test for this in my code? Or should I just rely on a try/catch.

It is a fairly large overhead of work to do - if it can be avoided.

I.e

//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_sh开发者_开发问答ould_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);
    }
}

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In general try...catch is the most efficient when dealing with exceptions to a rule. It also means you only need to change/add a rule in the DB - not in the DB and the code.

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IMHO, the domain model is the wrong place to do checks like this. If you want to provide the user with a more meaningful error message than the exception text from the database, add validation of input values to your UI layer, i.e. your ViewModel or Controller.