EnvironmentCleaner example

'delete_dir' => [
            'delete.me' => 'I am gone.',
          ],
          'delete_me.too' => 'delete this file.',
        ],
      ],
    ]);

    $connection = $this->prophesize(Connection::class);
    $test_run_results_storage = $this->prophesize(TestRunResultsStorageInterface::class);

    $cleaner = new EnvironmentCleaner(
      vfsStream::url('cleanup_test'),
      $connection->reveal(),
      $test_run_results_storage->reveal(),
      new NullOutput(),
      \Drupal::service('file_system')
    );

    $do_cleanup_ref = new \ReflectionMethod($cleaner, 'doCleanTemporaryDirectories');

    $this->assertFileExists(vfsStream::url('cleanup_test/sites/simpletest/delete_dir/delete.me'));
    $this->assertFileExists(vfsStream::url('cleanup_test/sites/simpletest/delete_me.too'));