'function'对象没有属性'assert_called_once_with'

Question

我正在尝试使用pytest和pytest_mock

运行以下测试

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)

但我得到例外AttributeError: 'function' object has no attribute 'assert_called_once_with'

我做错了什么？

Answer 1

您无法在 vanilla 函数上执行.assert_called_once_with函数：首先需要使用mock.create_autospec装饰器将其包装起来。例如：

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，因为您只能使用'file'调用它。所以有效的测试将是：

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：如果在某个模块中定义了该函数，则可以在本地将它包装在装饰器中。例如：

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')

Answer 2

在面向对象案例中：

class Foo:
    def rm(self, filename):
        self.helper(filename, 5)

    def helper(self, filename, number):
        pass

def test_unix_fs(mocker):
    mocker.patch.object(Foo, 'helper')
    foo = Foo()
    foo.rm('file')
    helper.assert_called_once_with('file', 5)