improvements-2.x-dev/modules/improvements_title/tests/modules/improvements_title_test/improvements_title_test.module

<?php

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\Routing\Route;

/**
 * Implements hook_page_title_alter().
 */
function improvements_title_test_page_title_alter(mixed &$title, Request $request, Route $route): void {
  $route_name = $request->get('_route');

  if ($route_name == 'improvements_title_test.altered_route_title') {
    $title = 'Altered route title';
  }
}