public void TestAppendToElement()
{
var content = new HElement("span", "Content");
var element = new HElement("div", "First Content");
Assert.Same(content, content.AppendTo(element));
Assert.Equal("<div>First Content<span>Content</span></div>", element.ToString());
Assert.Same(content, content.AppendTo(null));
content = null;
Assert.Null(content.AppendTo(element));
}