[HttpClient] Fix response id property check in MockResponse

Author: fancyweb

Response/MockResponse.php

@@ -159,7 +159,7 @@ public static function fromRequest(string $method, string $url, array $options,
      */
     protected static function schedule(self $response, array &$runningResponses): void
     {
-        if (!$response->id) {
+        if (!isset($response->id)) {
             throw new InvalidArgumentException('MockResponse instances must be issued by MockHttpClient before processing.');
         }
 

Tests/Response/MockResponseTest.php

@@ -3,6 +3,7 @@
 namespace Symfony\Component\HttpClient\Tests\Response;
 
 use PHPUnit\Framework\TestCase;
+use Symfony\Component\HttpClient\Exception\InvalidArgumentException;
 use Symfony\Component\HttpClient\Exception\JsonException;
 use Symfony\Component\HttpClient\Exception\TransportException;
 use Symfony\Component\HttpClient\Response\MockResponse;
@@ -107,4 +108,12 @@ public function testErrorIsTakenIntoAccountInInitialization()
             'error' => 'ccc error',
         ]))->getStatusCode();
     }
+
+    public function testMustBeIssuedByMockHttpClient()
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('MockResponse instances must be issued by MockHttpClient before processing.');
+
+        (new MockResponse())->getContent();
+    }
 }