Unittest-mock os.listdir未在testfunction中使用/返回错误的值

Question

我想测试下面的函数，但仍然很难找到测试I/O操作的最佳实践。

def get_weight_file(path: Union[Path, str]) -> str:
"""Finds weights (.model) file in a directory
Parameters
----------
path: Union[Path, str]
Path where to find the weights file
Returns
-------
str
Filename of the weights (.model) file
"""
only_files = [
file for file in os.listdir(path) if os.path.isfile(os.path.join(path, file))
]
model_file = [file for file in only_files if file.endswith(".model")]
if len(model_file) == 0:
raise FileNotFoundError("No weights file found in current directory")
if len(model_file) > 1:
raise MultipleFilesError("Please provide a single weights file")
return model_file[0]

我试着嘲笑os.listdir.

@mock.patch("os.listdir", return_value=["test.model", "test.txt", "text.yaml"])
def test_get_weight_file(listdir):
assert get_weight_file(path="./") == "test.model"

这就是错误：

if len(model_file) == 0:
>           raise FileNotFoundError("No weights file found in current directory")
E           FileNotFoundError: No weights file found in current directory

函数似乎无法检索"；test.model"；文件无论如何，它不起作用，我不知道为什么，我也怀疑我解决这个问题的方法是最佳实践。有人能告诉我怎么解决这个问题吗？

Answer 1

实际上，您应该修补@mock.patch('os.listdir')，看看在哪里进行修补。

此外，我还修补了os.path.isfile()方法，因为我的真实文件系统上没有这些目录文件，所以我模拟它对True的返回值。

例如

get_weight_file.py:

import os

def get_weight_file(path):
only_files = [
file for file in os.listdir(path) if os.path.isfile(os.path.join(path, file))
]
print('os.listdir(path): ', os.listdir(path))
model_file = [file for file in only_files if file.endswith(".model")]
return model_file[0]

test_get_weight_file.py:

from unittest import TestCase, mock
import unittest
from get_weight_file import get_weight_file

class TestGetWeightFile(TestCase):
@mock.patch("os.path.isfile", return_value=True)
@mock.patch("os.listdir", return_value=["test.model", "test.txt", "text.yaml"])
def test_get_weight_file(self, mock_listdir, mock_isfile):
print('mock_isfile: ', mock_isfile.return_value)
print('mock_listdir: ', mock_listdir.return_value)
assert get_weight_file(path="./") == "test.model"

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

测试结果：

mock_isfile:  True
mock_listdir:  ['test.model', 'test.txt', 'text.yaml']
os.listdir(path):  ['test.model', 'test.txt', 'text.yaml']
.
----------------------------------------------------------------------
Ran 1 test in 0.001s
OK