在python中，如何为打开文件的函数编写单元测试？

Question

这是获取版本并与 open 一起使用以从文件路径位置读取文件的函数。

def get_version(self):
    try:
        with open("file_path") as openfile:
            for line in openfile:
                sline = line.split()
                for row, column in enumerate(sline):
                    if column == "version=":
                        version = sline[row+1].strip('"')
    return version

Answer 1

您可以使用unittest.mock.mock_open(mock=None, read_data=None)来模拟该open函数。

例如

main.py:

class MyClass:
    def get_version(self):
        version = ''
        with open("file_path") as openfile:
            for line in openfile:
                sline = line.split()
                for row, column in enumerate(sline):
                    if column == "version=":
                        version = sline[row+1].strip('"')

        return version

test_main.py:

from main import MyClass
import unittest
from unittest.mock import mock_open, patch


class TestMain(unittest.TestCase):
    def test_get_version(self):
        m = mock_open(read_data='version= 1.0.0')
        with patch('builtins.open', m) as mocked_open:
            myclass_instace = MyClass()
            version = myclass_instace.get_version()
            self.assertEqual(version, '1.0.0')
            m.assert_called_with('file_path')


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

100%覆盖率的单元测试结果：

.
----------------------------------------------------------------------
Ran 1 test in 0.011s

OK
Name                                      Stmts   Miss  Cover   Missing
-----------------------------------------------------------------------
src/stackoverflow/60183706/main.py           10      0   100%
src/stackoverflow/60183706/test_main.py      14      0   100%
-----------------------------------------------------------------------
TOTAL                                        24      0   100%

Python版本：Python 3.7.5