public static void Run(string text, IConsole console)
        {
            // Execute
            var charToCountMap = NumberOfOccurenceOfEachCharacter.Run(text);

            // Display result
            console.Out.WriteLine("Result:");
            foreach (char c in charToCountMap.Keys)
            {
                console.Out.WriteLine($"{ c }: { charToCountMap[c] }");
            }
        }
        public void Run_WhenTextIsNull_ThrowsArgumentNullException()
        {
            Action actual = () => NumberOfOccurenceOfEachCharacter.Run((string)null);

            Assert.Throws <ArgumentNullException>(actual);
        }
        public void Run_WhenTextIsNotNull_ReturnsValidResult(string text, Dictionary <char, int> expected)
        {
            var actual = NumberOfOccurenceOfEachCharacter.Run(text);

            Assert.Equal(expected, actual);
        }