python - 使用 nosegae 运行的数据存储测试的意外测试结果

Question

我有一个我正在为其编写单元测试的 UserRepository 类

class UserRepository(object):
    """
    Repository that handles storage and retrieval of models.User objects
    in and from the datastore.

    """
    def create(self, user):
        """
        Create the given user in the datastore if it doesn't exist yet.

        Args:
            user: The user to create.

        Returns:
            The created user.

        Raises:
            exc.DuplicateEntity: If the desired phonenumber is
                already taken.

        """
        duplicate_user = models.User.query(models.User.phonenumber == user.phonenumber).fetch()
        if duplicate_user:
            raise exc.DuplicateEntity()

        user.put()
        return user

我有这些测试

class UserServiceTest(unittest.TestCase):
    """Tests for the UserService."""
    def setUp(self):
        """
        Called before tests are run.

        """
        self.user_repo = repositories.UserRepository()
        #self.policy = datastore_stub_util.PseudoRandomHRConsistencyPolicy(probability=1)

    def test_create(self):
        """
        Test if the create method creates a user.

        """
        ndb.delete_multi(models.User.query().fetch(keys_only=True))

        user = models.User(phonenumber='+31612345678#',
                           email='tim@castelijns.nl',
                           password='1234abcd')

        ret_user = self.user_repo.create(user)
        self.assertEqual(ret_user, user)

    def test_create_duplicate_fails(self):
        """
        Test if attempting to create a user with an existing phonenumber
        fails.

        """
        ndb.delete_multi(models.User.query().fetch(keys_only=True))

        user = models.User(phonenumber='+31612345678#',
                           email='tim@castelijns.nl',
                           password='1234abcd')

        self.user_repo.create(user)

        with self.assertRaises(exc.DuplicateEntity):
            self.user_repo.create(user)

ndb.delete_multi(models.User.query().fetch(keys_only=True)) 是为了从测试环境中清除现有用户，这样测试用例就不会相互影响.

这是自定义异常

class DuplicateEntity(Exception):
    """Exception to raise when trying to create a duplicate entity."""

我用

运行测试

$ nosetests --with-gae

输出

======================================================================
FAIL: Test if attempting to create a user with an existing phonenumber
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/tests/dal/test_repositories.py", line 53, in test_create_duplicate_fails
    self.user_repo.create(user)
AssertionError: DuplicateEntity not raised

----------------------------------------------------------------------
Ran 2 tests in 0.080s

FAILED (failures=1)

这是出乎意料的，因为此处对 .create 的第二次调用应该引发异常，因为已经有一个用户使用该电话号码。

我确信代码有效，因为我已经对其进行了实时测试。

同样奇怪的是，如果我在 with 语句上方添加对 .create 的调用，它确实会引发异常:

self.user_repo.create(user)
self.user_repo.create(user)

with self.assertRaises(exc.DuplicateEntity):
    self.user_repo.create(user)

所以它在第 3 次调用时被引发，但不是第 2 次。

我感觉它与数据存储一致性策略有关，如 here 所述:

The PseudoRandomHRConsistencyPolicy class lets you control the likelihood of a write applying before each global (non-ancestor) query. By setting the probability to 0%, we are instructing the datastore stub to operate with the maximum amount of eventual consistency. Maximum eventual consistency means writes will commit but always fail to apply, so global (non-ancestor) queries will consistently fail to see changes.

但是我不知道 nosegae 如何处理这个问题。它甚至是可配置的吗？ nosegae doesn't have alot of documentation .

我该如何解决(或解决)这个问题？

Answer 1

您的问题是您正在使用查询来测试重复项，但由于最终一致性，不能保证该查询有效。您会注意到，您引用的文档中的测试都使用确保一致性的祖先查询。

我的看法是，这是预期的正确行为(AssertionError: DuplicateEntity not raised error)并强调了你的模型/方法的问题。