public function test_ajax_load_available_items_error_messages( $post_args, $expected_results ) {

    $_POST = array_merge(
      array(
        'action'                => 'load-available-menu-items-customizer',
        'customize-menus-nonce' => wp_create_nonce( 'customize-menus' ),
      ),
      $post_args
    );

    // Make the request.
    $this->make_ajax_call( 'load-available-menu-items-customizer' );

    // Get the results.
    $response = json_decode( $this->_last_response, true );

    $this->assertSame( $expected_results, $response );
  }