public void IfTooLong()
        {
            var veryLong = "very long";

            Assert.Throws <DesignByContractViolationException>(
                () => Fail.IfToLong(veryLong, 3, nameof(veryLong))
                );

            Fail.IfToLong(null, 300, "null");
            Fail.IfToLong("aa", 300, "aa");
            Fail.IfToLong("aa", 2, "aa");
        }