public void Test_CountCharOccurences_CorrectlyCountsOccurencesOfEachCharacterInAString_WhenCalled()
        {
            // Arrange
            // Arrange
            StringSorter sorter = new StringSorter();
            string       message = "ddfffabb";
            int          dExpected = 2, fExpected = 3, aExpected = 1, bExpected = 2;

            // Act
            Dictionary <char, int> dictionaryResult = sorter.CountCharOccurences(message);

            int aResult, bResult, dResult, fResult;

            dictionaryResult.TryGetValue('a', out aResult);
            dictionaryResult.TryGetValue('b', out bResult);
            dictionaryResult.TryGetValue('d', out dResult);
            dictionaryResult.TryGetValue('f', out fResult);

            // Assert
            Assert.AreEqual(aExpected, aResult);
            Assert.AreEqual(bExpected, bResult);
            Assert.AreEqual(dExpected, dResult);
            Assert.AreEqual(fExpected, fResult);
        }