Kernel test example for TwigExtension function

<?php

declare(strict_types=1);

namespace Drupal\Tests\MYMODULE\Kernel;

use Drupal\Core\Render\Markup;
use Drupal\Core\Session\UserSession;
use Drupal\flag\Entity\Flagging;
use Drupal\MYMODULE\TwigExtension\FriendsViewsLinkTwigExtension;
use Drupal\KernelTests\KernelTestBase;
use Drupal\user\Entity\User;

/**
* Tests the FriendsViewsLinkTwigExtension.
*/
class FriendsViewsLinkTwigExtensionTest extends KernelTestBase {

 /**
  * {@inheritdoc}
  */
 protected static $modules = [
   'system',
   'user',
   'field',
   'text',
   'taxonomy',
   'views',
   'flag',
   'privatemsg',
   'MYMODULE',
 ];
 
 /**
  * The current user.
  *
  * @var \Drupal\Core\Session\AccountInterface|\PHPUnit\Framework\MockObject\MockObject
  */
 protected $currentUser;
 
 /**
  * The flag service.
  *
  * @var \Drupal\flag\FlagServiceInterface|\PHPUnit\Framework\MockObject\MockObject
  */
 protected $flagService;
 
 /**
  * The entity type manager.
  *
  * @var \Drupal\Core\Entity\EntityTypeManagerInterface|\PHPUnit\Framework\MockObject\MockObject
  */
 protected $entityTypeManager;
 
 /**
  * The renderer.
  *
  * @var \Drupal\Core\Render\RendererInterface|\PHPUnit\Framework\MockObject\MockObject
  */
 protected $renderer;
 
 /**
  * {@inheritdoc}
  */
 protected function setUp(): void {
   parent::setUp();
   $this->flagService = $this->container->get('flag');
   $this->entityTypeManager = $this->container->get('entity_type.manager');
   $this->renderer = $this->container->get('renderer');
   $this->container->get('current_user')->setAccount(new UserSession(['uid' => 1]));
   $this->installEntitySchema('user');
   $this->installEntitySchema('flagging');
   $this->installSchema('flag', ['flag_counts']);
   $this->installConfig(['MYMODULE']);
 }
 
 /**
  * Tests the renderFriendLink function.
  */
 public function testRenderFriendLink(): void {
   $extension = new FriendsViewsLinkTwigExtension(
     $this->container->get('current_user'),
     $this->flagService,
     $this->entityTypeManager,
     $this->renderer
   );
   // Test case where the UID is different from the current user's ID.
   $uid = Markup::create(2);
   $flagging_id = Markup::create(3);
   $expected = '<a href="/friends/add/2">Add to friends</a>';
   $this->assertEquals($expected, $extension->renderFriendLink($uid, $flagging_id)->__toString());
   // Test case where the UID is the same as the current user's ID.
   $uid = Markup::create(1);
   $flagging_id = Markup::create(3);
   $expected = 'Error. Broken link';
   $this->assertEquals($expected, $extension->renderFriendLink($uid, $flagging_id));
   // Test request removing link.
   $uid = Markup::create(1);
   $flagging_id = Markup::create(3);
   $flaggable_user = User::create([
     'uid' => 2,
     'name' => 'foobar',
     'mail' => 'foobar@example.com',
   ]);
   $flaggable_user->save();
   $flagging = Flagging::create([
     'id' => (int) $flagging_id->__toString(),
     'flag_id' => 'friendship_request',
     'entity_type' => 'user',
     'entity_id' => $flaggable_user->id(),
     'uid' => (int) $uid->__toString(),
     'global' => 0,
     'created' => \Drupal::time()->getCurrentTime(),
   ]);
   $flagging->save();
   $flag = $this->flagService->getFlagById('friendship_request');
   $link = $flag->getLinkTypePlugin()->getAsFlagLink($flag, $flaggable_user, 'full');
   $link['#title']['#markup'] = t('Remove request');
   $expected = $this->renderer->renderInIsolation($link);
   $this->assertEquals($expected, $extension->renderFriendLink($uid, $flagging_id));
 }
 
}