new_contents: import os
  import unittest
  
  from chainer import dataset
  from chainer import testing
  
  
  class TestGetSetDatasetRoot(unittest.TestCase):
  
      def test_set_dataset_root(self):
          orig_root = dataset.get_dataset_root()
          new_root = '/tmp/dataset_root'
          try:
              dataset.set_dataset_root(new_root)
              self.assertEqual(dataset.get_dataset_root(), new_root)
          finally:
              dataset.set_dataset_root(orig_root)
  
  
  class TestGetDatasetDirectory(unittest.TestCase):
  
      def test_get_dataset_directory(self):
          root = dataset.get_dataset_root()
          path = dataset.get_dataset_directory('test', False)
          self.assertEqual(path, os.path.join(root, 'test'))
  
  
  testing.run_module(__name__, __file__)
  
subject: Add some tests on download.py