setUnroutedUrlAssembler example

$this->moduleHandler->expects($this->once())
      ->method('alter')
      ->with('link', $this->isType('array'));

    $this->urlAssembler->expects($this->once())
      ->method('assemble')
      ->with('https://www.drupal.org', ['set_active_class' => TRUE, 'external' => TRUE] + $this->defaultOptions)
      ->willReturnArgument(0);

    $url = Url::fromUri('https://www.drupal.org');
    $url->setUrlGenerator($this->urlGenerator);
    $url->setUnroutedUrlAssembler($this->urlAssembler);
    $url->setOption('set_active_class', TRUE);

    $result = $this->linkGenerator->generate('Drupal', $url);
    $this->assertLink([
      'attributes' => [
        'href' => 'https://www.drupal.org',
      ],
      'content' => 'Drupal',
    ], $result);
  }