CustomPageExceptionHtmlSubscriber example

$this->accessUnawareRouter = $this->createMock('Symfony\Component\Routing\Matcher\UrlMatcherInterface');
    $this->accessUnawareRouter->expects($this->any())
      ->method('match')
      ->willReturn([
        '_controller' => 'mocked',
      ]);
    $this->accessManager = $this->createMock('Drupal\Core\Access\AccessManagerInterface');
    $this->accessManager->expects($this->any())
      ->method('checkNamedRoute')
      ->willReturn(AccessResult::allowed()->addCacheTags(['foo', 'bar']));

    $this->customPageSubscriber = new CustomPageExceptionHtmlSubscriber($this->configFactory, $this->kernel, $this->logger, $this->redirectDestination, $this->accessUnawareRouter, $this->accessManager);

    $path_validator = $this->createMock('Drupal\Core\Path\PathValidatorInterface');
    $path_validator->expects($this->any())
      ->method('getUrlIfValidWithoutAccessCheck')
      ->willReturn(Url::fromRoute('foo', ['foo' => 'bar']));
    $container = new ContainerBuilder();
    $container->set('path.validator', $path_validator);
    \Drupal::setContainer($container);

    // You can't create an exception in PHP without throwing it. Store the     // current error_log, and disable it temporarily.