如何在单元测试期间验证Mock mock_calls列表中的.__ getitem __()调用

Question

当尝试单元测试返回元组的方法并且我试图查看代码是否访问正确的元组索引时,python尝试评估预期的调用并将其转换为字符串.

call().methodA().__getitem__(0)最终被转换成'().methodA' 我的expected_calls列表中的断言.

提供的示例代码导致输出和回溯:

expected_calls=[call().methodA(), '().methodA']
  result_calls=[call().methodA(), call().methodA().__getitem__(0)]
======================================================================
ERROR: test_methodB (badMockCalls.Test_UsingToBeMocked_methods)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\dev\workspace\TestCode\src\badMockCalls.py", line 43, in test_methodB
    self.assertListEqual(expected_calls, self.result_calls)
  File "C:\Python33\lib\unittest\case.py", line 844, in assertListEqual
    self.assertSequenceEqual(list1, list2, msg, seq_type=list)
  File "C:\Python33\lib\unittest\case.py", line 764, in assertSequenceEqual
    if seq1 == seq2:
  File "C:\Python33\lib\unittest\mock.py", line 1927, in __eq__
    first, second = other
ValueError: too many values to unpack (expected 2)

----------------------------------------------------------------------
Ran 1 test in 0.006s

FAILED (errors=1)

我如何判断methodB正在调用self.tbm.methodA()[0]？

示例代码(Python 3.3.2):

import unittest
from unittest.mock import call, patch
import logging

log = logging.getLogger(__name__)
log.setLevel(logging.DEBUG)
_ch = logging.StreamHandler()
_ch.setLevel(logging.DEBUG)
log.addHandler(_ch)

class ToBeMocked():  # external resource that can't be changed
    def methodA(self):
        return (1,)

class UsingToBeMocked():  # project code
    def __init__(self):
        self.tbm = ToBeMocked()

    def methodB(self):
        value = self.tbm.methodA()[0]
        return value

class Test_UsingToBeMocked_methods(unittest.TestCase):
    def setUp(self):
        self.patcher = patch(__name__ + '.ToBeMocked')
        self.mock_ToBeMocked = self.patcher.start()
        self.utbm = UsingToBeMocked()
        # clear out the mock_calls list from the constructor calls
        self.mock_ToBeMocked.mock_calls = []
        # set result to always point to the mock_calls that we are testing
        self.result_calls = self.mock_ToBeMocked.mock_calls

    def tearDown(self):
        self.patcher.stop()

    def test_methodB(self):
        self.utbm.methodB()
        # make sure the correct sequence of calls is made with correct parameters
        expected_calls = [call().methodA(),
                          call().methodA().__getitem__(0)]
        log.debug('expected_calls=' + str(expected_calls))
        log.debug('  result_calls=' + str(self.result_calls))
        self.assertListEqual(expected_calls, self.result_calls)

if __name__ == "__main__":
    unittest.main()

Answer 1

我刚刚偶然发现了同样的问题。我使用了这里的解决方案/解决方法：

http://www.voidspace.org.uk/python/mock/examples.html#mocking-a-dictionary-with-magicmock

即：

>> mock.__getitem__.call_args_list
[call('a'), call('c'), call('d'), call('b'), call('d')]

您可以跳过魔术函数名称的误解并检查其参数。