e[jsAttributeName] = validValue1;
    let logEntries = element.takeLog();
    assert_array_equals(logEntries.types(), ['attributeChanged']);
    assert_attribute_log_entry(
      logEntries.last(),
      { name: contentAttributeName, oldValue: null,
        newValue: contentValue1, namespace: null
      }
    );
  }, name + ' must enqueue an attributeChanged reaction when adding a new attribute');

  test(() => {
    let element = define_build_in_custom_element(
      [contentAttributeName], interfaceName, 