Xml Encoding UTF8 and Hidden BOM Byte

TestingUt8EncodingAndHiddenBOM.cs

using System;
using System.IO;
using System.Text;
using System.Xml;
using System.Xml.Linq;
using FluentAssertions;
using NUnit.Framework;

namespace TestingUt8EncodingAndHiddenBOM
{
    [TestFixture]
    class Utf8BomTests
    {
        private const string ExpectedXml = @"<xml><node></node><thing></thing></xml>";

        [Test]
        public void ShouldWorkAsItWillUseDefaultEncoding()
        {
            const string outerXml = @"<xml><node></node>{0}</xml>";
            const string innerXml = @"<thing></thing>";

            var result = PrettyPrintXmlDefaultEncoding(string.Format(outerXml, PrettyPrintXmlDefaultEncoding(innerXml)));

            result.Should().Be(PrettyPrintXmlDefaultEncoding(ExpectedXml));
        }

        [Test]
        public void ShouldFailAsItWillAddTheBOMAtBeginningAndInMiddleOfFile()
        {
            const string outerXml = @"<xml><node></node>{0}</xml>";
            const string innerXml = @"<thing></thing>";

            var result = PrettyPrintXmlUtf8Busted(string.Format(outerXml, PrettyPrintXmlUtf8Busted(innerXml)));

            FlattenXml(result).Should().Be(FlattenXml(PrettyPrintXmlUtf8Busted(ExpectedXml)));
        }

        [Test]
        public void ShouldWorkAsNoBOMIsIncluded()
        {
            const string outerXml = @"<xml><node></node>{0}</xml>";
            const string innerXml = @"<thing></thing>";

            var result = PrettyPrintXmlUtf8Working(string.Format(outerXml, PrettyPrintXmlUtf8Working(innerXml)));

            FlattenXml(result).Should().Be(FlattenXml(PrettyPrintXmlUtf8Working(ExpectedXml)));
        }

        private string FlattenXml(string input)
        {
            byte[] encodedString = Encoding.UTF8.GetBytes(input);

            // Put the byte array into a stream and rewind it to the beginning
            var ms = new MemoryStream(encodedString);
            ms.Flush();
            ms.Position = 0;

            // Build the XmlDocument from the MemorySteam of UTF-8 encoded bytes
            var xmlDoc = new XmlDocument();
            xmlDoc.Load(ms);
            return xmlDoc.OuterXml;
        }

        private string PrettyPrintXmlDefaultEncoding(string input)
        {
            var doc = XDocument.Parse(input);
            var xml = doc.ToString();
            Console.WriteLine(xml);
            return xml;
        }

        private string PrettyPrintXmlUtf8Working(string input)
        {
            var doc = XDocument.Parse(input);
            var ms = new MemoryStream();
            var encoding = new UTF8Encoding(false);
            using (var writer = XmlWriter.Create(ms, new XmlWriterSettings
            {
                Indent = true,
                Encoding = encoding,
                OmitXmlDeclaration = true,
            }))
            {
                doc.Save(writer);
            }

            return encoding.GetString(ms.ToArray());
        }

        private string PrettyPrintXmlUtf8Busted(string input)
        {
            var doc = XDocument.Parse(input);
            var ms = new MemoryStream();
            using (var writer = XmlWriter.Create(ms, new XmlWriterSettings
                {
                    Indent  = true, 
                    Encoding = Encoding.UTF8,
                    OmitXmlDeclaration = true,
                } ))
            {
                doc.Save(writer);
            }
            
            return Encoding.UTF8.GetString(ms.ToArray());
        }

    }
}