public void Should_pass_null_or_before_validation_when_date_is_null() { var obj = new { earlier = new K { Date = null }, later = new K { Date = new DateTime(1979, 01, 01) } }; Check.Result result = Check.That(obj).earlier.Date[Should.BeNullOrBefore(Check.That(obj).later.Date)]; Console.WriteLine(result.Reason); Assert.That(result.Success, Is.True, result.Reason); }