System.Text.Tests.StringBuilderTests.Append_String C# (CSharp) Method

        public static void Append_String(string original, string value, int startIndex, int count, string expected)
        {
            StringBuilder builder;
            if (startIndex == 0 && count == (value?.Length ?? 0))
            {
                // Use Append(string)
                builder = new StringBuilder(original);
                builder.Append(value);
                Assert.Equal(expected, builder.ToString());
            }
            // Use Append(string, int, int)
            builder = new StringBuilder(original);
            builder.Append(value, startIndex, count);
            Assert.Equal(expected, builder.ToString());
        }