Question

我正在测试复杂的逻辑，这些逻辑需要将中央事实表与10-20个较小的维表连接在一起。我想模拟那10-20个较小的表。

如何在for循环中修补方法返回的值？请参见下面的代码。

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，但是然后我不知道如何为不同的表（类）返回不同的数据集。

Answer 1

假设do_join将在循环的外被调用，并修补了所有表，则可以编写一个使用contextlib.ExitStack来设置所有模拟的夹具：

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()

这意味着所有模拟在屈服时仍处于活动状态，并且仅在测试完成后才会删除。

如果已安装pytest-mock，则可以改用mocker固定装置：

@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 +模拟：没有with子句的补丁不起作用

1 个答案: