Merge branch '5.4' into 6.2

* 5.4:
  [Notifier] Replace tests dummy instances by already in place mocks

Author: nicolas-grekas

Tests/GatewayApiTransportTest.php

@@ -17,9 +17,7 @@
 use Symfony\Component\Notifier\Message\SentMessage;
 use Symfony\Component\Notifier\Message\SmsMessage;
 use Symfony\Component\Notifier\Test\TransportTestCase;
-use Symfony\Component\Notifier\Tests\Fixtures\DummyHttpClient;
-use Symfony\Component\Notifier\Tests\Fixtures\DummyMessage;
-use Symfony\Component\Notifier\Transport\TransportInterface;
+use Symfony\Component\Notifier\Tests\Transport\DummyMessage;
 use Symfony\Contracts\HttpClient\HttpClientInterface;
 use Symfony\Contracts\HttpClient\ResponseInterface;
 
@@ -31,7 +29,7 @@ final class GatewayApiTransportTest extends TransportTestCase
 {
     public static function createTransport(HttpClientInterface $client = null): GatewayApiTransport
     {
-        return new GatewayApiTransport('authtoken', 'Symfony', $client ?? new DummyHttpClient());
+        return new GatewayApiTransport('authtoken', 'Symfony', $client ?? new MockHttpClient());
     }
 
     public static function toStringProvider(): iterable