def test_list_dir(self):
    for i in range(10):
      with gfile.GFile('ram://a/b/%d.txt' % i, 'w') as f:
        f.write('')
      with gfile.GFile('ram://c/b/%d.txt' % i, 'w') as f:
        f.write('')

    matches = ['%d.txt' % i for i in range(10)]
    self.assertEqual(gfile.ListDirectory('ram://a/b/'), matches)