public function test_construct_placeholder() {
    do_action( 'customize_register', $this->wp_customize );
    $default = array(
      'title'            => 'Lorem',
      'description'      => 'ipsum',
      'menu_item_parent' => 123,
    );
    $setting = new WP_Customize_Nav_Menu_Item_Setting( $this->wp_customize, 'nav_menu_item[-5]', compact( 'default' ) );
    $this->assertSame( -5, $setting->post_id );
    $this->assertNull( $setting->previous_post_id );
    $this->assertSame( $default, $setting->default );
  }