Testing DataAnnotation-based validation in ASP.NET MVC

UPDATE: Aaron Jensen pointed out that this only works for .NET 4. The DataAnnotation.Validator class mentioned in the post does not exist in .NET 3.5, so this method does not work. With .NET Framework 3.5 SP1 came DataAnnotations, and with ASP.NET MVC 2 Preview 1 came built-in support for DataAnnotation validation. This makes basic validation, like required fields, number intervals and so on, very simple. In order to be able to test this validation, though, you have to mimic some of the work th...