Actualización

vendor/symfony/dependency-injection/Tests/Fixtures/TestServiceSubscriber.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace Symfony\Component\DependencyInjection\Tests\Fixtures;
+
+use Symfony\Component\DependencyInjection\ServiceSubscriberInterface;
+
+class TestServiceSubscriber implements ServiceSubscriberInterface
+{
+    public function __construct($container)
+    {
+    }
+
+    public static function getSubscribedServices()
+    {
+        return [
+            __CLASS__,
+            '?'.CustomDefinition::class,
+            'bar' => CustomDefinition::class,
+            'baz' => '?'.CustomDefinition::class,
+        ];
+    }
+}