如何在 for 循环中动态模拟 python 函数的结果？

Question

我正在尝试实施一些单元测试来验证包含 for 循环的方法。此方法接收项目列表，并针对其中的每个项目执行函数 foo()，并将该项目作为参数。

有谁知道如何模拟 foo() 函数以根据作为输入提供的元素动态提供模拟的返回值？

方法：

def foo(i):
    if i == 'this':
        return 'a'
    else:
        return 'b'

def bar(items):
    results = []
    for item in items:
        results.append(foo(item))
    return results

单元测试：

from unittest import TestCase
from mock import patch

class TestCaseBar(TestCase):

    @patch('my_module.foo')
    def test_bar(self, mock_foo):
        mock_foo.return_value = 'dummy'  # I would like to dinamically mock this.
        items = ['this', 'that']
        result = bar(items)
        self.assertEqual(result, ['a', 'b'])
        self.assertTrue(mock_foo.call_count, 2)

提前感谢您的回答。

Answer 1

您可以使用为模拟对象的 side_effect 属性分配一个函数。然后，你可以为它实现模拟细节。

A function to be called whenever the Mock is called. See the side_effect attribute. Useful for raising exceptions or dynamically changing return values.

例如

my_module_64443736.py:

def foo(i):
    if i == 'this':
        return 'a'
    else:
        return 'b'


def bar(items):
    results = []
    for item in items:
        results.append(foo(item))
    return results

test_my_module_64443736.py:

from unittest import TestCase, main
from unittest.mock import patch
from my_module_64443736 import bar


class TestCaseBar(TestCase):

    @patch('my_module_64443736.foo')
    def test_bar(self, mock_foo):
        def dynamicMock(i):
            if i == 'this':
                return 'teresa teng'
            else:
                return 'best singer'
        mock_foo.side_effect = dynamicMock
        items = ['this', 'that']
        result = bar(items)
        self.assertEqual(result, ['teresa teng', 'best singer'])
        self.assertTrue(mock_foo.call_count, 2)


if __name__ == '__main__':
    main()

单元测试结果：

.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK
Name                                                    Stmts   Miss  Cover   Missing
-------------------------------------------------------------------------------------
src/Whosebug/64443736/my_module_64443736.py            9      3    67%   2-5
src/Whosebug/64443736/test_my_module_64443736.py      16      0   100%
-------------------------------------------------------------------------------------
TOTAL                                                      25      3    88%

如何在 for 循环中动态模拟 python 函数的结果？

How to dynamically mock the result of a python function inside a for loop?

mocking

python-3.x

python-unittest