public void AddAndReturnChild_Elements_AddChildToParent()
{
var parent = new XsltElement("Parent");
var child = new XsltElement("Child");
var returnedElement = parent.AddAndReturnChild(child);
Assert.Same(child, returnedElement);
Assert.Contains(parent.Elements(), e => e == child);
Assert.Same(parent, child.Parent);
}
public static XsltElement GetPathPartElement(XsltElement parentElement, XsltElement pathPartElement) => parentElement.FirstOrDefaultXsltElement(pathPartElement) ?? parentElement.AddAndReturnChild(pathPartElement);