python - 如何模拟作为函数输入的对象？

Question

通常当我模拟时，我有以下类型的设置

# my_script.py
import numpy as np

def my_func(x):
    out = np.power(x, 2)
    return out

然后在 my_script 中测试 numpy power 调用:

# test_myscript.py

import numpy as np
import unittest
import mock

from my_script import my_func


class TestMyScript(unittest.TestCase):

    @mock.patch("my_script.np")
    def test_my_func(self, mock_os):
        """Test that numpy.power was called"""
        a = np.array([1, 2, 3])
        my_func(a)
        mock_os.power.assert_called_with(a, 2)


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

这很好用。

但是现在如果情况发生变化，假设我将 numpy 模块作为一个参数 放入 my_func 中；在这种情况下，我不知道如何模拟 numpy。

我如何在下面的函数中模拟 numpy，就像在上面的 test_myscript 中模拟一样？

请注意，numpy 不会导入到 my_script.py 中，而是导入到运行 my_script.py 函数的单独脚本中>.

# my_script.py
# numpy NOT imported in this script!

def my_func(x, numpy):
    out = numpy.power(x, 2)
    return out

编辑:

根据@Daniel Roseman 的评论，我包含了更多代码以明确函数的调用方式

# main_script.py

import numpy as np

from my_script import my_func

def main():
    a = np.array([1, 2, 3])
    my_func(a, np)  # numpy is passed into `my_func`

然后为了测试，我正在尝试下面的

# test_myscript.py

import numpy as np
import unittest
import mock

from my_script import my_func

class TestMyScript(unittest.TestCase):

    @mock.patch("main_script.np")  # import from main_script since numpy is imported here
    def test_my_func(self, mock_os):
        """Test that numpy.power was called"""
        a = np.array([1, 2, 3])
        my_func(a)
        mock_os.power.assert_called_with(a, 2)


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

但这失败了

Ran 1 test in 0.154s
>>> FAILED (failures=1)
>>> AssertionError: Expected 'power' to have been called.

Answer 1

我发现在这里使用 unittest.mock.Mock 对象效果最好。

所以如果我们有:

# my_script.py

def my_func(x, numpy):
    out = numpy.power(x, 2)
    return out

然后为了测试它我们有:

# test_myscript.py

import numpy as np
import unittest
from unittest.mock import Mock

from my_script import my_func

numpy_mock = Mock()


class TestMyScript(unittest.TestCase):

    def test_my_func(self):
        """Test that numpy.power was called"""
        a = np.array([1, 2, 3])
        _ = my_func(a, numpy_mock)  # pass the mocked object here
        numpy_mock.power.assert_called_once_with(a, 2)


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

哪个通过了测试