如何在 SQLAlchemy 中测试查询？例如假设我们有这个 models.py

from sqlalchemy import (
        Column,
        Integer,
        String,
)
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

class Panel(Base):
    __tablename__ = 'Panels'

    id = Column(Integer, primary_key=True)
    category = Column(Integer, nullable=False)
    platform = Column(String, nullable=False)
    region = Column(String, nullable=False)

    def __init__(self, category, platform, region):
        self.category = category
        self.platform = platform
        self.region = region


    def __repr__(self):
        return (
            "<Panel('{self.category}', '{self.platform}', "
            "'{self.region}')>".format(self=self)
        )

还有这个 tests.py

import unittest

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

from models import Base, Panel


class TestQuery(unittest.TestCase):

    engine = create_engine('sqlite:///:memory:')
    Session = sessionmaker(bind=engine)
    session = Session()

    def setUp(self):
        Base.metadata.create_all(self.engine)
        self.session.add(Panel(1, 'ion torrent', 'start'))
        self.session.commit()

    def tearDown(self):
        Base.metadata.drop_all(self.engine)

    def test_query_panel(self):
        expected = [Panel(1, 'ion torrent', 'start')]
        result = self.session.query(Panel).all()
        self.assertEqual(result, expected)

当我们尝试运行测试时，它失败了，即使两个面板看起来相同。

$ nosetests
F
======================================================================
FAIL: test_query_panel (tests.TestQuery)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/clasher/tmp/tests.py", line 31, in test_query_panel
    self.assertEqual(result, expected)
AssertionError: Lists differ: [<Panel('1', 'ion torrent', 's... != [<Panel('1', 'ion torrent', 's...

First differing element 0:
<Panel('1', 'ion torrent', 'start')>
<Panel('1', 'ion torrent', 'start')>

  [<Panel('1', 'ion torrent', 'start')>, <Panel('2', 'ion torrent', 'end')>]

----------------------------------------------------------------------
Ran 1 test in 0.063s

FAILED (failures=1)

我找到的一个解决方案是对我希望在查询中找到的每个实例进行查询:

class TestQuery(unittest.TestCase):

    ...

    def test_query_panel(self):
        expected = [
            (1, 'ion torrent', 'start'),
            (2, 'ion torrent', 'end')
        ]
        successful = True
        # Check to make sure every expected item is in the query
        try:
            for category, platform, region in expected:
                self.session.query(Panel).filter_by(
                        category=category, platform=platform,
                        region=region).one()
        except (NoResultFound, MultipleResultsFound):
            successful = False
        self.assertTrue(successful)
        # Check to make sure no unexpected items are in the query
        self.assertEqual(self.session.query(Panel).count(),
                         len(expected))

不过，这让我觉得非常难看，而且我什至没有达到我要测试的复杂过滤查询的地步。有没有更优雅的解决方案，还是我总是必须手动进行一堆单独的查询？

最佳答案

您的原始测试在正确的轨道上，您只需做以下两件事之一:要么确保两个 Panel具有相同主键标识的对象比较为 True :

import unittest

from sqlalchemy import create_engine
from sqlalchemy.orm import Session

from database.models import Base

class Panel(Base):
    # ...

    def __eq__(self, other):
        return isinstance(other, Panel) and other.id == self.id

或者你可以组织你的测试，确保你检查的是同一个 Panel实例(因为这里我们利用了 identity map ):

class TestQuery(unittest.TestCase):
    def setUp(self):
        self.engine = create_engine('sqlite:///:memory:')
        self.session = Session(self.engine)
        Base.metadata.create_all(self.engine)
        self.panel = Panel(1, 'ion torrent', 'start')
        self.session.add(self.panel)
        self.session.commit()

    def tearDown(self):
        Base.metadata.drop_all(self.engine)

    def test_query_panel(self):
        expected = [self.panel]
        result = self.session.query(Panel).all()
        self.assertEqual(result, expected)

就引擎/ session 设置/拆卸而言，我会选择一种模式，在这种模式下，您对所有测试都使用单一引擎，并假设您的架构是固定的，所有测试都使用单一架构，那么您要确保您使用的数据在可以回滚的事务中执行。 Session可以这样工作，例如调用 commit()通过将整个测试包装在显式 Transaction 中，实际上并没有提交“真正的”事务。 . https://docs.sqlalchemy.org/en/latest/orm/session_transaction.html#joining-a-session-into-an-external-transaction-such-as-for-test-suites 中的示例说明了这种用法。每个测试夹具上都有一个“:memory:”引擎会占用大量内存，并且不会真正扩展到除 SQLite 之外的其他数据库。

关于python - SQLAlchemy 中查询的单元测试，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/14719507/