public void HackerRankTest7()
        {
            // input string is 1000 chars long
            string s      = GetInputString(_sTestDataRootDir + "testcase7_input.txt");
            string result = SherlockAndTheValidString.isValid(s);

            Assert.AreEqual(result, "YES");
        }
        public void HackerRankTest4()
        {
            string res = SherlockAndTheValidString.isValid("aabbc");

            Assert.AreEqual("YES", res);
        }
        // [DataTestMethod]
        public void BigStringIsValid(string s)
        {
            string res = SherlockAndTheValidString.isValid(s);

            Assert.AreEqual("YES", res);
        }
        // [DataTestMethod]
        public void RemoveLastCharTest(string s)
        {
            string res = SherlockAndTheValidString.isValid(s);

            Assert.AreEqual("YES", res);
        }
        // [DataTestMethod]
        public void Trickey1Test(string s)
        {
            string res = SherlockAndTheValidString.isValid(s);

            Assert.AreEqual("NO", res);
        }
        public void FailIsValid()
        {
            string res = SherlockAndTheValidString.isValid("ebbccdda");

            Assert.AreEqual("NO", res);
        }