diff -u b/core/tests/Drupal/KernelTests/Core/File/DirectoryTest.php b/core/tests/Drupal/KernelTests/Core/File/DirectoryTest.php
--- b/core/tests/Drupal/KernelTests/Core/File/DirectoryTest.php
+++ b/core/tests/Drupal/KernelTests/Core/File/DirectoryTest.php
@@ -37,7 +37,7 @@
     $child_path = $parent_path . DIRECTORY_SEPARATOR . $child;
     /** @var \Drupal\Core\File\FileSystemInterface $file_system */
     $file_system = \Drupal::service('file_system');
-    $this->assertTrue($file_system->mkdir($child_path, 0775, TRUE), t('No error reported when creating new local directories.'), 'File');
+    $this->assertTrue($file_system->mkdir($child_path, 0775, TRUE), 'No error reported when creating new local directories.');
 
     // Ensure new directories also exist.
     $this->assertDirectoryExists($parent_path);
@@ -52,7 +52,7 @@
 
     // Check creating a directory using an absolute path.
     $absolute_path = $file_system->realpath($directory) . DIRECTORY_SEPARATOR . $this->randomMachineName() . DIRECTORY_SEPARATOR . $this->randomMachineName();
-    $this->assertTrue($file_system->mkdir($child_path, 0775, TRUE), 'No error reported when creating new local directories.');
+    $this->assertTrue($file_system->mkdir($absolute_path, 0775, TRUE), 'No error reported when creating new absolute directories.', 'File');
     $this->assertDirectoryPermissions($absolute_path, 0775);
   }