System.Tests.StringTests.LastIndexOf_SingleLetter C# (CSharp) Method

        public static void LastIndexOf_SingleLetter(string s, char value, int startIndex, int count, int expected)
        {
            if (count == s.Length)
            {
                if (startIndex == s.Length - 1)
                {
                    Assert.Equal(expected, s.LastIndexOf(value));
                    Assert.Equal(expected, s.LastIndexOf(value.ToString()));
                }
                Assert.Equal(expected, s.LastIndexOf(value, startIndex));
                Assert.Equal(expected, s.LastIndexOf(value.ToString(), startIndex));
            }
            Assert.Equal(expected, s.LastIndexOf(value, startIndex, count));
            Assert.Equal(expected, s.LastIndexOf(value.ToString(), startIndex, count));

            Assert.Equal(expected, s.LastIndexOf(value.ToString(), startIndex, count, StringComparison.CurrentCulture));
            Assert.Equal(expected, s.LastIndexOf(value.ToString(), startIndex, count, StringComparison.Ordinal));
            Assert.Equal(expected, s.LastIndexOf(value.ToString(), startIndex, count, StringComparison.OrdinalIgnoreCase));
        }