diff --git a/core/lib/Drupal/Core/ProxyClass/File/MimeType/MimeTypeMapper.php b/core/lib/Drupal/Core/ProxyClass/File/MimeType/MimeTypeMapper.php
index 519cd95..7066840 100644
--- a/core/lib/Drupal/Core/ProxyClass/File/MimeType/MimeTypeMapper.php
+++ b/core/lib/Drupal/Core/ProxyClass/File/MimeType/MimeTypeMapper.php
@@ -1,9 +1,5 @@
 <?php
-
-/**
- * @file
- * Contains Drupal\Core\ProxyClass\File\MimeType\MimeTypeMapper.
- */
+// @codingStandardsIgnoreFile
 
 /**
  * This file was generated via php core/scripts/generate-proxy-class.php 'Drupal\Core\File\MimeType\MimeTypeMapper' "core/lib/Drupal/Core".
@@ -82,6 +78,14 @@ public function alterMapping(\Drupal\Core\Extension\ModuleHandlerInterface $modu
         /**
          * {@inheritdoc}
          */
+        public function setMapping(array $mapping)
+        {
+            return $this->lazyLoadItself()->setMapping($mapping);
+        }
+
+        /**
+         * {@inheritdoc}
+         */
         public function addMapping($mimetype, $extension)
         {
             return $this->lazyLoadItself()->addMapping($mimetype, $extension);
diff --git a/core/tests/Drupal/KernelTests/Core/File/MimeTypeTest.php b/core/tests/Drupal/KernelTests/Core/File/MimeTypeTest.php
index 7c34554..f507aed 100644
--- a/core/tests/Drupal/KernelTests/Core/File/MimeTypeTest.php
+++ b/core/tests/Drupal/KernelTests/Core/File/MimeTypeTest.php
@@ -105,7 +105,7 @@ public function testFileMimeTypeDetection() {
     // a MIME type.
     foreach ($test_case as $input => $expected) {
       $extensions = $mime_type_mapper->getExtensionsForMimeType($input);
-      $this->assertIdentical($extensions, $expected);
+      $this->assertIdentical($expected, $extensions);
     }
 
     // Now test mapping removals.