public void TestReplaceAll()
{
var n1 = new HText("Content");
var n2 = new HElement("span", n1);
var n3 = new HElement("span", "Another content");
var n4 = new HElement("div", n2, n3);
var elements = new HElement[] { new HElement("p", "p 1"), null, new HElement("div", "div 2") };
Assert.Same(elements, elements.ReplaceAll(n3, n2));
Assert.Equal("<div><p>p 1</p><div>div 2</div><p>p 1</p><div>div 2</div></div>", n4.ToString());
elements = null;
Assert.Null(elements.ReplaceAll(n3, n2));
Assert.Equal("<div><p>p 1</p><div>div 2</div><p>p 1</p><div>div 2</div></div>", n4.ToString());
}