public void SuceedsWhenSmaller()
        {
            ValidationRule <int> sut = GetSut(3, "a");

            sut.AtMost(4);
        }
        public void SuceedsWhenEqual()
        {
            ValidationRule <int> sut = GetSut(3, "a");

            sut.AtMost(3);
        }
        public void ItThrowsWhenValueIsToBig()
        {
            ValidationRule <int> sut = GetSut(4, "a");

            Assert.Throws <ArgumentOutOfRangeException>(() => sut.AtMost(2));
        }