        );
      }, `${commandName} at ${initialHTMLWithClass.replace(/\n/g, "\\n")}`);
    }
  }

  if (leftWhiteSpaceClass !== null) {
    // Replace style attribute with class attribute.
    const initialHTMLWithClass =
      t.initialHTML.replace(
        leftStyleAttr,
        `class="${leftWhiteSpaceClass}"`
      );
    if (initialHTMLWithClass != t.initialHTML) {
      promise_test(async () => {
        utils.setupEditingHost(initialHTMLWithClass);
        await (testingBackspace ? utils.sendBackspa