public void to_xml()
    {
      Assert.Throws<ArgumentNullException>(() => XmlExtensions.ToXml<object>(null));
      Assert.Throws<ArgumentNullException>(() => XmlExtensions.ToXml<object>(null, Stream.Null));
      Assert.Throws<ArgumentNullException>(() => new object().ToXml((Stream) null));
      Assert.Throws<ArgumentNullException>(() => XmlExtensions.ToXml<object>(null, TextWriter.Null));
      Assert.Throws<ArgumentNullException>(() => new object().ToXml((TextWriter) null));
      Assert.Throws<ArgumentNullException>(() => XmlExtensions.ToXml<object>(null, XmlWriter.Create(Stream.Null)));
      Assert.Throws<ArgumentNullException>(() => new object().ToXml((XmlWriter) null));

      var subject = Guid.NewGuid().ToString();

      var xml = subject.ToXml();
      var stringWriter = new StringWriter();
      stringWriter.XmlWriter().Write(writer =>
      {
        new XmlSerializer(subject.GetType()).Serialize(writer, subject);
        Assert.Equal(xml, stringWriter.ToString());
      });
      Assert.Equal(xml, subject.ToXml((Type[]) null));
      Assert.Equal(xml, subject.ToXml(Enumerable.Empty<Type>().ToArray()));
      Assert.Equal(xml, subject.ToXml((Type[]) null));

      using (var stream = new MemoryStream())
      {
        Assert.True(ReferenceEquals(subject.ToXml(stream, Encoding.Unicode), subject));
        Assert.Equal(xml, stream.Rewind().Text());
        Assert.True(stream.CanWrite);
      }

      using (var writer = new StringWriter())
      {
        Assert.True(ReferenceEquals(subject.ToXml(writer), subject));
        Assert.Equal(xml, writer.ToString());
        writer.WriteLine();
      }

      stringWriter = new StringWriter();
      using (var writer = stringWriter.XmlWriter())
      {
        Assert.True(ReferenceEquals(subject.ToXml(writer), subject));
        Assert.Equal(xml, stringWriter.ToString());
        stringWriter.WriteLine();
      }
    }
    public void write()
    {
      Assert.Throws<ArgumentNullException>(() => XmlExtensions.Write<XmlWriter>(null, writer => {}));
      Assert.Throws<ArgumentNullException>(() => XmlExtensions.Write(XmlWriter.Create(Path.GetTempFileName()), null));

      const string Xml = "<?xml version=\"1.0\" encoding=\"utf-16\"?><article>text</article>";
      var stringWriter = new StringWriter();
      var xmlWriter = stringWriter.XmlWriter(true, Encoding.Unicode);
      Assert.True(ReferenceEquals(xmlWriter.Write(writer =>
      {
        writer.WriteStartDocument();
        writer.WriteElementString("article", "text");
        writer.WriteEndDocument();
      }), xmlWriter));
      Assert.Throws<InvalidOperationException>(() => xmlWriter.WriteRaw(string.Empty));
      Assert.Equal(Xml, stringWriter.ToString());
      stringWriter.WriteLine();
    }
    public void xml_writer_text_writer()
    {
      Assert.Throws<ArgumentNullException>(() => ((TextWriter) null).XmlWriter());

      const string Xml = "<?xml version=\"1.0\" encoding=\"utf-16\"?><article>text</article>";

      var textWriter = new StringWriter();
      textWriter.XmlWriter().Write(writer =>
      {
        Assert.False(writer.Settings.CloseOutput);
        Assert.Equal(Encoding.Unicode.ToString(), writer.Settings.Encoding.ToString());
        Assert.False(writer.Settings.Indent);
        writer.WriteElementString("article", "text");
      });
      Assert.Equal(Xml, textWriter.ToString());
      textWriter.Write(string.Empty);
      textWriter.Close();

      textWriter = new StringWriter();
      textWriter.XmlWriter(true).Write(writer =>
      {
        Assert.True(writer.Settings.CloseOutput);
        Assert.Equal(Encoding.Unicode.ToString(), writer.Settings.Encoding.ToString());
        Assert.False(writer.Settings.Indent);
      });
      textWriter.Write(string.Empty);
    }