public function search_items( WP_REST_Request $request ) {
    $subtypes = $request[ WP_REST_Search_Controller::PROP_SUBTYPE ];
    if ( in_array( WP_REST_Search_Controller::TYPE_ANY, $subtypes, true ) ) {
      $subtypes = $this->subtypes;
    }

    $results = array();
    foreach ( $subtypes as $subtype ) {
      $results = array_merge( $results, wp_list_filter( array_values( $this->items ), array( 'test_type' => $subtype ) ) );
    }

    $results = wp_list_sort( $results, 'test_id', 'DESC' );

    $number = (int) $request['per_page'];
    $offset = (int) $request['per_page'] * ( (int) $request['page'] - 1 );

    $total = count( $results );

    $results = array_slice( $results, $offset, $number );

    return array(
      self::RESULT_IDS   => wp_list_pluck( $results, 'test_id' ),
      self::RESULT_TOTAL => $total,
    );
  }