Issue #3319045: Assert that all expected package manager events are fired during build tests.

package_manager/tests/modules/package_manager_test_event_logger/src/EventSubscriber/EventLogSubscriber.php

+<?php
+
+declare(strict_types = 1);
+
+namespace Drupal\package_manager_test_event_logger\EventSubscriber;
+
+use Drupal\package_manager\Event\PostApplyEvent;
+use Drupal\package_manager\Event\PostCreateEvent;
+use Drupal\package_manager\Event\PostDestroyEvent;
+use Drupal\package_manager\Event\PostRequireEvent;
+use Drupal\package_manager\Event\PreApplyEvent;
+use Drupal\package_manager\Event\PreCreateEvent;
+use Drupal\package_manager\Event\PreDestroyEvent;
+use Drupal\package_manager\Event\PreRequireEvent;
+use Drupal\package_manager\Event\StageEvent;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+/**
+ * Defines an event subscriber to test logging during events in Package Manager.
+ */
+final class EventLogSubscriber implements EventSubscriberInterface {
+
+  /**
+   * Logs all events in the stage life cycle.
+   *
+   * @param \Drupal\package_manager\Event\StageEvent $event
+   *   The event object.
+   */
+  public function logEventInfo(StageEvent $event): void {
+    \Drupal::logger('package_manager_test_event_logger')->info('package_manager_test_event_logger-start: Event: ' . get_class($event) . ', Stage instance of: ' . get_class($event->getStage()) . ':package_manager_test_event_logger-end');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getSubscribedEvents(): array {
+    return [
+      PreCreateEvent::class => ['logEventInfo'],
+      PostCreateEvent::class => ['logEventInfo'],
+      PreRequireEvent::class => ['logEventInfo'],
+      PostRequireEvent::class => ['logEventInfo'],
+      PreApplyEvent::class => ['logEventInfo'],
+      PostApplyEvent::class => ['logEventInfo'],
+      PreDestroyEvent::class => ['logEventInfo'],
+      PostDestroyEvent::class => ['logEventInfo'],
+    ];
+  }
+
+}