class DestructableServiceTest

class DestructableServiceTest extends BrowserTestBase {
  
  /**
   * {@inheritdoc}
   */
  protected static $modules = [
    'system',
    'destructable_test',
  ];
  
  /**
   * {@inheritdoc}
   */
  protected $defaultTheme = 'stark';
  public function testDestructableServiceExecutionOrder() : void {
    $file_system = $this->container
      ->get('file_system');
    assert($file_system instanceof FileSystemInterface);
    $semaphore = $file_system->tempnam($file_system->getTempDirectory(), 'destructable_semaphore');
    $this->drupalGet(Url::fromRoute('destructable', [], [
      'query' => [
        'semaphore' => $semaphore,
      ],
    ]));
    // This should be false as the response should flush before running the
    // test service.
    $this->assertEmpty(file_get_contents($semaphore), 'Destructable service did not run when response flushed to client.');
    // The destructable service will sleep for 3 seconds, then run.
    // To ensure no race conditions on slow test runners, wait another 3s.
    sleep(6);
    $this->assertTrue(file_get_contents($semaphore) === 'ran', 'Destructable service did run.');
  }

}