public void Problem020_Tests_1()
        {
            string s   = "()";
            bool   act = Problem020.IsValid(s);
            bool   exp = true;

            Assert.Equal(exp, act);
        }
        public void Problem020_Tests_5()
        {
            string s   = "]";
            bool   act = Problem020.IsValid(s);
            bool   exp = false;

            Assert.Equal(exp, act);
        }