Add a basic integration test to cover the happy path of SubscriberLinkTokens

[MAILPOET-4345]

mailpoet/tests/integration/Cron/Workers/SubscriberLinkTokensTest.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace MailPoet\Cron\Workers;
+
+use MailPoet\Entities\ScheduledTaskEntity;
+use MailPoet\Entities\SubscriberEntity;
+use MailPoet\Test\DataFactories\Subscriber as SubscriberFactory;
+
+class SubscriberLinkTokensTest extends \MailPoetTest {
+  /** @var SubscriberLinkTokens */
+  private $worker;
+
+  public function _before() {
+    parent::_before();
+    $this->worker = $this->diContainer->get(SubscriberLinkTokens::class);
+  }
+
+  public function testItCanSetLinkTokensWhenFieldIsNull() {
+    $linkToken = 'some link token';
+    $subscriberWithLinkToken = (new SubscriberFactory())->withLinkToken($linkToken)->create();
+    $subscriberWithoutLinkToken1 = (new SubscriberFactory())->create();
+    $subscriberWithoutLinkToken2 = (new SubscriberFactory())->create();
+
+    $this->assertNull($subscriberWithoutLinkToken1->getLinkToken());
+    $this->assertNull($subscriberWithoutLinkToken2->getLinkToken());
+
+    $this->worker->processTaskStrategy(new ScheduledTaskEntity(), microtime(true));
+
+    $this->entityManager->refresh($subscriberWithLinkToken);
+    $this->entityManager->refresh($subscriberWithoutLinkToken1);
+    $this->entityManager->refresh($subscriberWithoutLinkToken2);
+
+    $this->assertSame($linkToken, $subscriberWithLinkToken->getLinkToken());
+    $this->assertIsString($subscriberWithoutLinkToken1->getLinkToken());
+    $this->assertIsString($subscriberWithoutLinkToken2->getLinkToken());
+  }
+
+  public function _after(): void {
+    $this->truncateEntity(SubscriberEntity::class);
+  }
+}
+