diff -u b/core/modules/media/tests/src/Kernel/OEmbedSourceTest.php b/core/modules/media/tests/src/Kernel/OEmbedSourceTest.php
--- b/core/modules/media/tests/src/Kernel/OEmbedSourceTest.php
+++ b/core/modules/media/tests/src/Kernel/OEmbedSourceTest.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\Tests\media\Kernel;
 
+use Drupal\Component\Utility\Crypt;
 use Drupal\Core\Url;
 use Drupal\media\Entity\Media;
 use Drupal\media\OEmbed\Resource;
@@ -82,9 +83,8 @@
     // Get the local thumbnail URI and ensure that it does not contain any
     // query string.
     $local_thumbnail_uri = $media_type->getSource()->getMetadata($media, 'thumbnail_uri');
-    $this->assertStringStartsWith('public://oembed_thumbnails/', $local_thumbnail_uri);
-    $this->assertStringNotContainsString('?', $local_thumbnail_uri);
-    $this->assertStringNotContainsString('foo=bar', $local_thumbnail_uri);
+    $expected_uri = 'public://oembed_thumbnails/' . Crypt::hashBase64('/core/misc/druplicon.png') . '.png';
+    $this->assertSame($expected_uri, $local_thumbnail_uri);
   }
 
 }