public void ReverseTest3()
        {
            string input  = "";
            string actual = ReverseWordsHelper.ReverseSentense(input);

            Assert.AreEqual(actual, null);
        }
        public void ReverseTest4()
        {
            string input    = "   ";
            string actual   = ReverseWordsHelper.ReverseSentense(input);
            string expected = "   ";

            Assert.AreEqual(actual, expected);
        }
        public void ReverseTest1()
        {
            string input    = "I am a student.";
            string actual   = ReverseWordsHelper.ReverseSentense(input);
            string expected = "student. a am I";

            Assert.AreEqual(actual, expected);
        }
        public void ReverseTest5()
        {
            string actual = ReverseWordsHelper.ReverseSentense(null);

            Assert.AreEqual(actual, null);
        }