如何为每个单元测试正确设置单个 SQLAlchemy 会话？

Question

当使用 WebTest 测试我的 Pyramid 应用程序时，我无法在我的测试中 create/use 一个单独的 Session 而没有收到关于范围会话已经存在的警告。

这里是Pyramid应用的main()函数，这里是配置数据库的地方。

# __init__.py of Pyramid application

from pyramid_sqlalchemy import init_sqlalchemy
from sqlalchemy import create_engine


def main(global_config, **settings):
    ...
    db_url = 'some-url'
    engine = create_engine(db_url)
    init_sqlalchemy(engine)  # Warning thrown here.

这是测试代码。

# test.py (Functional tests)

import transaction
from unittest import TestCase
from pyramid.paster import get_appsettings
from pyramid_sqlalchemy import init_sqlalchemy, Session
from sqlalchemy import create_engine
from webtest import TestApp

from app import main
from app.models.users import User


class BaseTestCase(TestCase):
    def base_set_up(self):
        # Create app using WebTest
        settings = get_appsettings('test.ini', name='main')
        app = main({}, **settings)
        self.test_app = TestApp(app)

        # Create session for tests.
        db_url = 'same-url-as-above'
        engine = create_engine(db_url)
        init_sqlalchemy(engine)
        # Note: I've tried both using pyramid_sqlalchemy approach here and 
        # creating a "plain, old" SQLAlchemy session here using sessionmaker.

    def base_tear_down(self):
        Session.remove()


class MyTests(BaseTestCase):
    def setUp(self):
        self.base_set_up()

        with transaction.manager:
            self.user = User('user@email.com', 'John', 'Smith')
            Session.add(self.user)
            Session.flush()

            Session.expunge_all()
        ...

    def tearDown(self):
        self.base_tear_down()

    def test_1(self):
        # This is a typical workflow on my tests.
        response = self.test_app.patch_json('/users/{0}'.format(self.user.id), {'email': 'new.email@email.com')
        self.assertEqual(response.status_code, 200)

        user = Session.query(User).filter_by(id=self.user.id).first()
        self.assertEqual(user.email, 'new.email@email.com')
    ...
    def test_8(self):
        ...

运行测试给了我 8 个通过，7 个警告，其中除了第一个之外的每个测试都给出以下警告：

From Pyramid application: __init__.py -> main -> init_sqlalchemy(engine): sqlalchemy.exc.SAWarning: At least one scoped session is already present. configure() can not affect sessions that have already been created.

如果这有用，我相信我在这里看到了同样的问题，只是我使用的是 pyramid_sqlalchemy 而不是创建我自己的 DBSession。

https://github.com/Pylons/webtest/issues/5

Answer 1

回答我自己的问题：我不确定这是否是最好的方法，但对我有用。

我没有尝试在我的测试中创建一个单独的会话，而是使用在应用程序中配置的 pyramid_sqlalchemy 会话工厂。据我所知，在测试和应用程序代码 return 中调用 Session 相同注册 scoped_session.

我为测试创建单独会话的初衷是确认记录已写入数据库，而不仅仅是在活动的 SQLAlchemy 会话中更新。通过这种新方法，我通过在测试事务和应用程序事务之间转换的测试点发出 Session.expire_all() 设法避免了这些 "caching" 问题。

# test.py (Functional tests)

import transaction
from unittest import TestCase
from pyramid.paster import get_appsettings
from pyramid_sqlalchemy import Session
from webtest import TestApp

from app import main
from app.models.users import User


class BaseTestCase(TestCase):
    def base_set_up(self):
        # Create app using WebTest
        settings = get_appsettings('test.ini', name='main')
        app = main({}, **settings)
        self.test_app = TestApp(app)

        # Don't set up an additional session in the tests. Instead import
        # and use pyramid_sqlalchemy.Session, which is set up in the application.

    def base_tear_down(self):
        Session.remove()


class MyTests(BaseTestCase):
    def setUp(self):
        self.base_set_up()

        with transaction.manager:
            self.user = User('user@email.com', 'John', 'Smith')
            Session.add(self.user)
            Session.flush()

            Session.expunge_all()
            Session.expire_all()  # "Reset" your session.

    def tearDown(self):
        self.base_tear_down()

如何为每个单元测试正确设置单个 SQLAlchemy 会话？

How do I properly set up a single SQLAlchemy session for each unit test?

sqlalchemy

webtest

python-3.x

pyramid