public void IsEmpty()
        {
            string      input  = "";
            List <char> output = new List <char>();

            Assert.AreEqual(output, UniqueChar.UniqCharacters(input));
        }
        public void UpercaseLowercaseDifferent()
        {
            string      input  = "bAB";
            List <char> output = new List <char>();

            output.Add('a');
            Assert.AreEqual(output, UniqueChar.UniqCharacters(input));
        }
        public void IsText()
        {
            string      input  = "bab";
            List <char> output = new List <char>();

            output.Add('a');
            Assert.AreEqual(output, UniqueChar.UniqCharacters(input));
        }