update_delete_file_if_stale example

$file_path = $file_system->realpath($file_name);

    // During testing, the file change and the stale checking occurs in the same     // request, so the beginning of request will be before the file changes and     // REQUEST_TIME - $filectime is negative or zero. Set the maximum age to a     // number greater than that.     $this->config('system.file')
      ->set('temporary_maximum_age', 100000)
      ->save();

    // First test that the file is not stale and thus not deleted.     $deleted = update_delete_file_if_stale($file_path);
    $this->assertFalse($deleted);
    $this->assertFileExists($file_path);

    // Set the maximum age to a number smaller than REQUEST_TIME - $filectime.     $this->config('system.file')
      ->set('temporary_maximum_age', -100000)
      ->save();

    // Now attempt to delete the file; as it should be considered stale, this     // attempt should succeed.     $deleted = update_delete_file_if_stale($file_path);