<!DOCTYPE html>
<script src="../include.js"></script>
<script>
    test(() => {
        const HTMLNS = "http://www.w3.org/1999/xhtml";
        const uppercaseElement = document.createElementNS(HTMLNS, "DIV");
        println(`document.createElementNS(HTMLNS, "DIV") is instance of HTMLUnknownElement: ${uppercaseElement instanceof HTMLUnknownElement}`);
        const lowercaseElement = document.createElementNS(HTMLNS, "div");
        println(`document.createElementNS(HTMLNS, "div") is instance of HTMLDivEleme