通过用新方法替换模型类的实例方法答案

【问题标题】：Mock instance method of a model class by replacing it with a new method通过用新方法替换模型类的实例方法
【发布时间】：2020-02-07 04:00:40
【问题描述】：

我想通过模拟在单元测试中用新函数替换实例方法“set_email_id”。实例方法返回 email_id 字段，但我想要一个新函数来打印相同的字段。我不确定要使用哪个模拟功能。我阅读了有关 side_effect、mock.object 等的信息。我无法让它发挥作用。

脚本：

class Myclass(models.Model):

   email_id = models.CharField(max_length=128, null=True, blank=True)

   def return_email_id(self):
       return self.email_id

def run():
    my_class = Myclass()
    my_class.email_id = 1

    #want to moke this call
    my_class.return_email_id()

单元测试：

@patch('models.Myclass.return_email_id')
def test(self, mock_email_id):

    def new_method():
        # this should replace the instance method
        print(self.email_id)

    # I know this wouldn't work. I just wanted to show it as an example
    mock_email_id.side_effect = new_method()

【问题讨论】：

如果该实例仅用于测试，您可以使用任何可调用对象覆盖它：instance.set_email_id = lambda self: … 或您选择的 Mock。顺便说一句，如果您看到它的实际作用，该方法的名称会有些误导。
我更改了方法的名称。谢谢。你能详细说明覆盖实例吗？它不只是为了测试而存在。我基本上是在测试“run()”函数，我希望“my_class.return_email_id()”在实例中打印 email_id 字段。

标签： python unit-testing class mocking side-effects

【解决方案1】：

参考这个例子。

mook_2.py

from datetime import datetime

import requests
from constants import STATUS_ENDPOINT


class BuildStatus:
    """The CI status of a pull request."""

    @staticmethod
    def build_date() -> str:
        return datetime.utcnow().isoformat()

    @classmethod
    def notify(cls, merge_request_id, status):
        build_status = {
            "id": merge_request_id,
            "status": status,
            "built_at": cls.build_date(),
        }
        response = requests.post(STATUS_ENDPOINT, json=build_status)
        response.raise_for_status()
        return response

test_mook.py

from unittest import mock

from constants import STATUS_ENDPOINT
from mock_2 import BuildStatus


@mock.patch("mock_2.requests") # mock_2.requests를 호출하면 mock_requests 모의 객체가 대신할것
def test_build_notification_sent(mock_requests):
    build_date = "2018-01-01T00:00:01"
    with mock.patch("mock_2.BuildStatus.build_date", return_value=build_date): # build_date 호출시 설정한 날짜 반환하도록함,
        BuildStatus.notify(123, "OK")

    expected_payload = {"id": 123, "status": "OK", "built_at": build_date}
    mock_requests.post.assert_called_with(
        STATUS_ENDPOINT, json=expected_payload
    )

常量.py

"""Definitions"""

STATUS_ENDPOINT = "http://localhost:8080/mrstatus"

【讨论】：