DirectoryTest::setUp PHP Method

    public function setUp()
    {
        $this->directory = Path::joinWithTemp('directory_class');
        mkdir($this->directory, 0777, true);
        file_put_contents(Path::join($this->directory, 'file1.txt'), 'test');
        file_put_contents(Path::join($this->directory, 'file2.txt'), 'some new file');
    }

 protected function setUp()
 {
     parent::setUp();
     \Drupal::config('system.file')->set('default_scheme', 'dummy-remote')->save();
 }