public void AddClassIfMissing_Missing_Adds()
{
var dom = new XmlDocument();
dom.LoadXml(@"<div class='one three'/>");
HtmlDom.AddClassIfMissing((XmlElement)dom.FirstChild, "two");
AssertThatXmlIn.Dom(dom).HasSpecifiedNumberOfMatchesForXpath("div[@class='one three two']", 1);
}