public function test_available_items_template() {
    add_filter( 'customize_nav_menu_available_item_types', array( $this, 'filter_item_types' ) );
    do_action( 'customize_register', $this->wp_customize );
    $menus = new WP_Customize_Nav_Menus( $this->wp_customize );

    ob_start();
    $menus->available_items_template();
    $template = ob_get_clean();

    $expected = sprintf( 'Customizing ▸ %s', esc_html( $this->wp_customize->get_panel( 'nav_menus' )->title ) );

    $this->assertStringContainsString( $expected, $template );

    $post_types = get_post_types( array( 'show_in_nav_menus' => true ), 'object' );
    if ( $post_types ) {
      foreach ( $post_types as $type ) {
        $this->assertStringContainsString( 'available-menu-items-post_type-' . esc_attr( $type->name ), $template );
        $this->assertMatchesRegularExpression( '#<h4 class="accordion-section-title".*>\s*' . esc_html( $type->labels->name ) . '#', $template );
        $this->assertStringContainsString( 'data-type="post_type"', $template );
        $this->assertStringContainsString( 'data-object="' . esc_attr( $type->name ) . '"', $template );
        $this->assertStringContainsString( 'data-type_label="' . esc_attr( $type->labels->singular_name ) . '"', $template );
      }
    }

    $taxonomies = get_taxonomies( array( 'show_in_nav_menus' => true ), 'object' );
    if ( $taxonomies ) {
      foreach ( $taxonomies as $tax ) {
        $this->assertStringContainsString( 'available-menu-items-taxonomy-' . esc_attr( $tax->name ), $template );
        $this->assertMatchesRegularExpression( '#<h4 class="accordion-section-title".*>\s*' . esc_html( $tax->labels->name ) . '#', $template );
        $this->assertStringContainsString( 'data-type="taxonomy"', $template );
        $this->assertStringContainsString( 'data-object="' . esc_attr( $tax->name ) . '"', $template );
        $this->assertStringContainsString( 'data-type_label="' . esc_attr( $tax->labels->singular_name ) . '"', $template );
      }
    }

    $this->assertStringContainsString( 'available-menu-items-custom_type', $template );
    $this->assertMatchesRegularExpression( '#<h4 class="accordion-section-title".*>\s*Custom#', $template );
    $this->assertStringContainsString( 'data-type="custom_type"', $template );
    $this->assertStringContainsString( 'data-object="custom_object"', $template );
    $this->assertStringContainsString( 'data-type_label="Custom Type"', $template );
  }