Question

嘿，我刚刚开始使用Python中的单元测试和模拟。尝试测试一个采用单列数据帧并在根据数据帧值进行一些计算后返回浮点数的函数。

import unittest
from unittest.mock import MagicMock

def avg_annual_fcf_growth_rate(fcf_data_frame):
    delta = fcf_data_frame.iloc[9][0] - fcf_data_frame.iloc[0][0]
    avg_growth_rate = (delta**(1/9))-1 
    return avg_growth_rate

class Test_DCF(unittest.TestCase):

    def test_fcf_calculation(self):
        mock_fcf = MagicMock()
        mock_fcf.iloc[9][0].return_value = 100
        mock_fcf.iloc[0][0].return_value = 10
        result = avg_annual_fcf_growth_rate(mock_fcf)
        expected = ((100-10)**(1/9)) - 1
        self.assertEqual(result, expected)

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

#Sample dataframe 
         Free Cash Flow USD Mil
2008-12                  5114.0
2009-12                 10909.0
2010-12                 11915.0
2011-12                 12285.0
2012-12                 11175.0
2013-12                 16617.0
2014-12                 16825.0
2015-12                 15409.0
2016-12                 19581.0
2017-12                 34068.0

我遇到了一个问题，即结果是MagicMock对象而不是float。我尝试寻找答案，但是无法正确设置模拟对象的返回值。

运行测试的输出。

F
======================================================================
FAIL: test_fcf_calculation (__main__.Test_DCF)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "path/to/intrinsic_value_dcf_test.py", line 18, in test_fcf_calculation
    self.assertEqual(result, expected)
AssertionError: <MagicMock name='mock.iloc.__getitem__().[56 chars]104'> != 0.6486864043382532

----------------------------------------------------------------------
Ran 1 test in 0.004s

FAILED (failures=1)

Answer 1

据我所知，问题反复出现在__getitem__电话中。但是，可以进行以下操作：

def test_fcf_calculation(self):
    mock_fcf = MagicMock()

    mock_fcf.iloc.__getitem__.return_value = MagicMock(**{'__getitem__.side_effect': [100, 10]})

    result = avg_annual_fcf_growth_rate(mock_fcf)
    expected = ((100-10)**(1/9)) - 1
    print(mock_fcf.mock_calls)
    self.assertEqual(result, expected)

如何在MagicMock obj上设置值。这样被测函数不会返回MagicMock对象

1 个答案: