public void Cant_add_two_same_guests()
{
var duration = new DayDuration(new DateTime(2016, 2, 10), new DateTime(2016, 2, 11));
var reservation = new Reservation(null, null, duration);
var guestOne = new Guest("Test", "Test");
var guestTwo = new Guest("Test", "Test");
reservation.AddGuest(guestOne);
reservation.Invoking(x => x.AddGuest(guestTwo)).ShouldThrow<InvalidOperationException>();
}
