public void IsValidFail(IComparable value, IComparable maxValue, bool expected)
        {
            var attribute = new MustBeGreaterThanAttribute(maxValue);

            try
            {
                attribute.IsValid(value);

                Assert.Fail();
            }
            catch (FormatException ex)
            {
                Assert.AreEqual("Input string was not in a correct format.", ex.Message);
            }
        }
        public void IsValid(IComparable value, IComparable maxValue, bool expected)
        {
            var attribute = new MustBeGreaterThanAttribute(maxValue);

            Assert.AreEqual(expected, attribute.IsValid(value));
        }