'function' 对象没有属性 'assert_call_once_with'

2022-01-08 00:00:00 python python-3.x mocking pytest

问题描述

我正在尝试使用 pytest 和 pytest_mock 运行以下测试

I'm trying to run the following test using pytest and pytest_mock

def rm(filename):
    helper(filename, 5)

def helper(filename):
    pass

def test_unix_fs(mocker):
    mocker.patch('module.helper')
    rm('file')
    helper.assert_called_once_with('file', 5)

但我得到异常 AttributeError: 'function' object has no attribute 'assert_called_once_with'

我做错了什么?

解决方案

你不能在 vanilla 函数上执行 .assert_call_once_with 函数:你首先需要包装它与 mock.create_autospec 装饰器.比如:

You can not perform a .assert_called_once_with function on a vanilla function: you first need to wrap it with the mock.create_autospec decorator. So for instance:

import unittest.mock as mock

def rm(filename):
    helper(filename, 5)

def helper(filename):
    pass

helper = mock.create_autospec(helper)

def test_unix_fs(mocker):
    mocker.patch('module.helper')
    rm('file')
    helper.assert_called_once_with('file', 5)

或者更优雅:

import unittest.mock as mock

def rm(filename):
    helper(filename, 5)

@mock.create_autospec
def helper(filename):
    pass

def test_unix_fs(mocker):
    mocker.patch('module.helper')
    rm('file')
    helper.assert_called_once_with('file', 5)

请注意，断言将失败，因为您仅使用 'file' 调用它.所以一个有效的测试是:

Note that the assertion will fail, since you call it only with 'file'. So a valid test would be:

import unittest.mock as mock

def rm(filename):
    helper(filename, 5)

@mock.create_autospec
def helper(filename):
    pass

def test_unix_fs(mocker):
    mocker.patch('module.helper')
    rm('file')
    helper.assert_called_once_with('file')

编辑:如果函数是在某个模块中定义的，您可以将其包装在本地的装饰器中.例如:

EDIT: In case the function is defined in some module, you can wrap it in a decorator locally. For example:

import unittest.mock as mock
from some_module import some_function

some_function = mock.create_autospec(some_function)

def test_unix_fs(mocker):
    some_function('file')
    some_function.assert_called_once_with('file')

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