GAE 测试以验证 ndb 实体**未**放入数据存储区

Question

非常简单，我想运行一些代码并验证 没有实体 MyEntity(ndb.Model) 被放入数据存储区。

我尝试过MyEntity.query().fetch(keys_only=True)，但这似乎不是高度一致的（即它没有显示我刚刚添加的一个实体），因此返回一个空列表并不是真正的确认。 （我应该补充一点，我正在使用testbed.init_datastore_v3_stub，我已经尝试过datastore_stub_util.PseudoRandomHRConsistencyPolicy(probability=1) 和MasterSlaveConsistencyPolicy()，但没有成功。）

我认为有一种方法可以对一种类型的所有键执行高度一致的“获取”，但现在我找不到任何文档来支持这一点。

我知道如果我有一个密钥，我可以进行强一致的获取，但是这将如何转化为验证实体是否未添加，因此没有获取密钥？

Answer 1

好吧，除了normal unit testing testbeds 之外，我终于通过disabling the ndb cache via global context（How to Clear/Invalidate NDB Cache in Tests 提示）让它工作了。

还得到了以下帮助：

• What's the equivalent of Entity.all(keys_only=True).fetch(20) in NDB?
• How to fetch the latest data in GAE Python NDB

Helper Mixin：

class NdbTestbedNoCachingStronglyConsistentMixin(unittest.TestCase):
    def setUp(self):
        self.testbed = testbed.Testbed()
        self.testbed.activate()
        policy = None
        # policy = datastore_stub_util.MasterSlaveConsistencyPolicy()
        # policy = datastore_stub_util.PseudoRandomHRConsistencyPolicy(probability=1.0)
        self.testbed.init_datastore_v3_stub(consistency_policy=policy)
        # self.testbed.init_memcache_stub()

        # It's not enough (or necessary) to use stubs for datastore and memcache -
        # we also need to change ndb policy to ensure that datastore queries
        # are strongly-consistent
        cxt = ndb.get_context()

        def disallow(*args, **kwargs):
            return False

        cxt.set_cache_policy(disallow)
        cxt.set_memcache_policy(disallow)
        super(NdbTestbedNoCachingStronglyConsistentMixin, self).setUp()

    def tearDown(self):
        super(NdbTestbedNoCachingStronglyConsistentMixin, self).tearDown()
        self.testbed.deactivate()

这样使用（省略了一些不相关的代码）：

def _get_entity_keys():
    return MyNdbEntity.query().fetch(keys_only=True)


class TestMyEntity(NdbTestbedNoCachingStronglyConsistentMixin):

    def tearDown(self):
        super(TestMyEntity, self).tearDown()

        # Verify our assumptions that no entities persist between tests
        assert MyNdbEntity.get_by_identifier(self.account, TEST_IDENTIFIER) is None
        assert not _get_entity_keys()

    def test_get_uri_should_retrieve_existing_entity(self):
        provider.get_uri(TEST_IDENTIFIER)  # creates entity
        all_assets_keys = _get_entity_keys()
        created_asset = MyNdbEntity.get_by_identifier(self.account, TEST_IDENTIFIER)

        self.assertIn(created_asset.key, all_assets_keys)

        provider.get_uri(TEST_IDENTIFIER)
        all_assets_keys_after_get = _get_entity_keys()

        self.assertSequenceEqual(all_assets_keys_after_get, all_assets_keys)


    def test_get_uri_should_create_entity_and_prefix_identifier_with_security_id(self):
        expected_identifier = TEST_SECURITY_ID + '-' + TEST_IDENTIFIER
        expected_uri = VIEWER_IMAGE_BASE_URI % expected_identifier

        uri = provider.get_uri(TEST_IDENTIFIER)
        image = _get_entity_keys()[0].get()

        self.assertEqual(image.identifier, expected_identifier)
        self.assertEqual(uri, expected_uri)