Python：如何模拟 SQLAlchemy 事件处理程序（使用 mock.unittest）

Question

所以我有一个带有事件侦听器的 SQLAlchemy 模型：

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)

@event.listens_for(User, "after_insert")
@event.listens_for(User, "after_update")
def do_something(mapper, connection, self):
    foo = SomeClass(self)
    foo.do_something_to_database()

我有一个单元测试需要 update/insert 模型

@patch('my_package.user.do_something')
def test_user(mock_do_something):
    user = User() # This insert will invoke 'do_something' via the event listener.
    assertSomething(user)

但是，我的测试失败了，因为 do_something 函数似乎仍在被调用并且尚未成功模拟。我尝试阅读如何修补 here (it is calling this function right?) and I have tried to look through the SQLAlchemy source code here 以找到要修补的适当模块（类似于 @patch('sqlalchemy.event.registrat._listen_fn')），但无济于事。

有没有人遇到过这种情况？

Answer 1

我找到了在单元测试中禁用事件的解决方法

import sqlalchemy as sa
from unittest import TestCase
from mypackage.models.user import User

class TestUser(TestCase):
    def setUp(self):
        super(TestUser, self).setUp()
        sa.event.remove(User, "after_insert", do_something)
        sa.event.remove(User, "after_update", do_something)

    def tearDown(self):
        super(TestUser, self).tearDown()
        sa.event.listen(User, "after_insert", do_something)
        sa.event.listen(User, "after_update", do_something)

    @patch('my_package.user.do_something')
    def test_user(mock_do_something):
        user = User() 
        assertSomething(user)

Answer 2

也许有一个上下文管理器 class 可以删除侦听器并在退出时再次添加它可以解决问题。

类似于：

class SADeListener(object):
    def __init__(self, class_, event, callable_):
        self.class_ = class_
        self.event = event
        self.callable_ = callable_

    def __enter__(self):
        sqlalchemy.event.remove(self.class_, self.event, self.callable_)

    def __exit__(self, type_, value, tb):
        sqlalchemy.event.listen(self.class_, self.event, self.callable_)

然后直接使用它：

with SADeListener(User, "after_insert", do_something),
   SADeListener(User, "after_update", do_something):
    .. code ...

Python：如何模拟 SQLAlchemy 事件处理程序（使用 mock.unittest）

Python: How to mock SQLAlchemy event handlers (using mock.unittest)

python

unit-testing

sqlalchemy

mocking

event-handling