Merge branch '6.2' into 6.3

* 6.2:
  [Notifier] Replace tests dummy instances by already in place mocks
  Use PHPUnit 9.6 to run Symfony's test suite
  [DependencyInjection] Add doc for RUNTIME_EXCEPTION_ON_INVALID_REFERENCE behavior

Author: nicolas-grekas

Tests/SmsapiTransportTest.php

@@ -16,19 +16,16 @@
 use Symfony\Component\Notifier\Bridge\Smsapi\SmsapiTransport;
 use Symfony\Component\Notifier\Exception\TransportException;
 use Symfony\Component\Notifier\Message\ChatMessage;
-use Symfony\Component\Notifier\Message\MessageInterface;
 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;
 
 final class SmsapiTransportTest extends TransportTestCase
 {
     public static function createTransport(HttpClientInterface $client = null, string $from = '', bool $fast = false, bool $test = false): SmsapiTransport
     {
-        return (new SmsapiTransport('testToken', $from, $client ?? new DummyHttpClient()))->setHost('test.host')->setFast($fast)->setTest($test);
+        return (new SmsapiTransport('testToken', $from, $client ?? new MockHttpClient()))->setHost('test.host')->setFast($fast)->setTest($test);
     }
 
     public static function toStringProvider(): iterable