gHost = contentDocument.querySelector("div[contenteditable]");
    const utils = new EditorTestUtils(editingHost, window);
    utils.setupEditingHost(curTest.editorInnerHTML);
    contentDocument.documentElement.scrollHeight;  // flush pending things
    if (typeof curTest.init == "function") {
      await curTest.init(contentWindow, contentDocument, editingHost);
    }
    const initialValue = editingHost.innerHTML;
    await curTest.run(contentWindow, contentDocument, editingHost);
    const newValue = ed