def test_make_subdirectory(self):
        """Test make_subdirectory method."""
        node = self.vgw.make_subdirectory(self.root.id, 'the file name')
        self.assertTrue(isinstance(node, DirectoryNode))
        self.assertEqual(node.name, 'the file name')
        self.assertEqual(node.parent_id, self.root.id)
        self.assertEqual(node.volume_id, self.root.volume_id)
        self.assertNotEqual(node.when_created, None)
        self.assertNotEqual(node.when_last_modified, None)
        self.vgw.make_file(self.root.id, 'duplicatename')
        self.assertRaises(
            errors.AlreadyExists,
            self.vgw.make_subdirectory, self.root.id, 'duplicatename')