删除model-mommy实例

Question

我正在使用model-mommy生成测试数据，如此

class AuthorDetailViewTests(TestCase):

    def setUp(self):
        # set bio manually to avoid error being thrown by template tag markdown_format
        self.author = mommy.make('author.Author', bio='Some bio text')

    def tearDown(self):
        self.author.delete()

setUp()方法运行正常。问题是tearDown()方法实际上并没有删除创建的author实例。有没有办法实现这个目标？感谢