public class when_validating_contact : ContextSpecification {

   protected ContactService    Service;
   protected bool              Result;
   protected Contact           Contact;

   protected override void Context() {
           
       Service = new ContactService();
       //initialize the contact with known and valid values
       Contact = new Contact {
           Email       = "e-mail",
           FirstName   = "fist-name",
           LastName    = "last-name"
       };
   }

   protected override void Because() {
       Result = Service.Validate(Contact);
   }

   [TestClass]
   public class with_empty_email : when_validating_contact {
       protected override void Context() {
           base.Context();
           //set email to an invalid value
           Contact.Email = string.Empty;
        }
   }

   [TestClass]
   public class with_empty_firstname : when_validating_contact {
       protected override void Context() {
           base.Context();
           //set firstname to an invalid value
           Contact.FirstName = string.Empty;
       }
   }

   [TestClass]
   public class with_empty_lastname : when_validating_contact {
       protected override void Context() {
           base.Context();
           //set lastname to an invalid value
           Contact.LastName = string.Empty;
       }
   }

   //note - this test method is part of the base class
   [TestMethod]
   public void should_not_be_valid() {
       Assert.IsFalse(Result);
   }
}