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

            sut.AtLeast(2);
        }
        public void SuceedsWhenEqual()
        {
            ValidationRule <int> sut = GetSut(3, "a");

            sut.AtLeast(3);
        }
        public void ItThrowsWhenValueIsTosmall()
        {
            ValidationRule <int> sut = GetSut(1, "a");

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