teElementNS(): ',
  (w, constructor, options) => {
    w.customElements.define('a-a', constructor, options);
    return w.document.createElementNS('http://www.w3.org/1999/xhtml', 'a-a');
  });

function test_create_element_synchronous(description, define_and_create_element) {
  test_with_window((w) => {
    let is_constructed = false;
    define_and_create_element(w, class extends w.HTMLElement {
      constructor() { super(); is_constructed = true; }
    });
    assert_true(is_constructed, 'custom construc