Pytest + mock：补丁在没有 with 子句的情况下不起作用

Question

我正在测试需要将中心事实 table 与 10-20 个更小维度的 table 结合起来的复杂逻辑。我想模拟 10-20 更小的 tables。

如何在 for 循环中修补方法 return 值？ 请参阅下面的代码。

tables.py:

class BaseClass(object):

  def load(path: str):
    ...

class SmallTable1(BaseClass):


  def load():
     super().load(self.path)

class SmallTable20(BaseClass):

  def load():
     super().load(self.path)

test_logic.py

# QUESTION - how to make it work
def test_not_work(datasets):
   for i in range(1, 21):
      table = 'SmallTable' + str(i)
      with mock.patch('some_package.tables.{}.load'.format(table)) as load_mock:
         load_mock.return_value = datasets[table]
      do_joins()  # here my mocks doesn't work


def test_works(datasets):
   with mock.patch('some_package.tables.SmallTable1.load'.format(i)) as load_mock_1:
       load_mock_1.return_value = datasets[SmallTable1]

       with mock.patch('some_package.tables.SmallTable2.load'.format(i)) as load_mock_2:
            load_mock_2.return_value = datasets[SmallTable2]

            .....  # repeat the same 8-18 times more

                                     do_joins()  # here my mocks do work, but with cumbersome code and huge right offset

P.S。或者我可以尝试模拟 BaseClass.load，但我不知道如何 return 不同的数据集用于不同的 table (class).

Answer 1

假设 do_join 应在 循环外 调用，所有表都已修补，您可以编写一个使用 contextlib.ExitStack 来设置的固定装置所有模拟：

from contextlib import ExitStack
from unittest import mock   
import pytest

from some_package import do_join


@pytest.fixture
def datasets():
    ...    

@pytest.fixture
def mock_tables(datasets):
    with ExitStack() as stack:
        for i in range(1, 21):
            table = 'SmallTable' + str(i)
            load_mock = stack.enter_context(
                mock.patch('some_package.tables.{}.load'.format(table)))
            load_mock.return_value = datasets[table]
        yield


def test_join(mock_tables):
    do_join()

这意味着所有 mock 在 yield 时仍然处于活动状态，并且只有在测试完成后才会被删除。

如果您安装了 pytest-mock，您可以改用 mocker 夹具：

@pytest.fixture
def mock_tables(datasets, mocker):
    for i in range(1, 21):
        table = 'SmallTable' + str(i)
        load_mock = mocker.patch('some_package.tables.{}.load'.format(table))
        load_mock.return_value = datasets[table]
    yield

Pytest + mock：补丁在没有 with 子句的情况下不起作用

Pytest + mock: patch does not work without with clause

python

mocking

pytest

python-mock