Question

In my unit tests, I would like to force the validation of a code first POCO that has DataAnnotations on it.

The MVC framework must be doing it behind the scenes, and basically I would like to know how, so I can hopefully make use of it.

Answer 1

The MVC framework bust be doing it behind the scenes, and basically I
would like to know how, so I can hopefully make use of it.

It’s the default model binder that is responsible for invoking the validation of the model once it has bound it from the request values.

You could invoke the validation process manually by using a ValidationContext.

Let’s suppose that you have a model:

public class Foo
{
    [Required(ErrorMessage = "the Bar is absolutely required")]
    public string Bar { get; set; }
}

and then you could unit test it:

[TestMethod]
public void The_Bar_Is_Required()
{
    // arrange
    var foo = new Foo();
    var results = new List<ValidationResult>();
    var context = new ValidationContext(foo, null, null);

    // act
    var actual = Validator.TryValidateObject(foo, context, results);

    // assert
    Assert.IsFalse(actual);
}

Alternatively to using DataAnnotations you could use FluentValidation.NET to perform validation on your view models. It integrates nicely with ASP.NET MVC and it allows you to unit test your validators in a very elegant way.