public void AddGuidEmptyValidationPredicate()
{
// Arrange.
ValidatableArgument<Guid> argument =
new ValidatableArgument<Guid>("argument", Guid.NewGuid());
// Act.
argument.IsEmptyGuid();
// Assert.
Assert.AreEqual(1, argument.ValidationPredicates.Count());
Assert.IsInstanceOfType(argument.ValidationPredicates.First(), typeof(GuidEmptyValidationPredicate));
}