問題描述

我有一個定義類屬性的基類和一些依賴它的子類，例如

I have a base class that defines a class attribute and some child classes that depend on it, e.g.

class Base(object):
    assignment = dict(a=1, b=2, c=3)

我想用不同的作業對這個類進行單元測試，例如空字典，單項等.當然這非常簡化，不是重構我的類或測試的問題

I want to unittest this class with different assignments, e.g. empty dictionary, single item, etc. This is extremely simplified of course, it's not a matter of refactoring my classes or tests

我想出的(pytest)測試最終是有效的

The (pytest) tests I have come up with, eventually, that work are

from .base import Base

def test_empty(self):
    with mock.patch("base.Base.assignment") as a:
        a.__get__ = mock.Mock(return_value={})
        assert len(Base().assignment.values()) == 0

def test_single(self):
    with mock.patch("base.Base.assignment") as a:
        a.__get__ = mock.Mock(return_value={'a':1})
        assert len(Base().assignment.values()) == 1

這感覺相當復雜和 hacky - 我什至不完全理解它為什么起作用(雖然我熟悉描述符).mock 是否會自動將類屬性轉換為描述符?

This feels rather complicated and hacky - I don't even fully understand why it works (I am familiar with descriptors though). Does mock automagically transform class attributes into descriptors?

感覺更合乎邏輯的解決方案不起作用:

A solution that would feel more logical does not work:

def test_single(self):
    with mock.patch("base.Base") as a:
        a.assignment = mock.PropertyMock(return_value={'a':1})
        assert len(Base().assignment.values()) == 1

或者只是

def test_single(self):
    with mock.patch("base.Base") as a:
        a.assignment = {'a':1}
        assert len(Base().assignment.values()) == 1

我嘗試過的其他變體也不起作用(作業在測試中保持不變).

Other variants that I've tried don't work either (assignments remains unchanged in the test).

模擬類屬性的正確方法是什么?有沒有比上述更好/更容易理解的方法?

What's the proper way to mock a class attribute? Is there a better / more understandable way than the one above?

推薦答案

base.Base.assignment 被簡單地替換為 Mock 對象.您通過添加 __get__ 方法使其成為描述符.

base.Base.assignment is simply replaced with a Mock object. You made it a descriptor by adding a __get__ method.

這有點冗長，有點不必要；您可以直接設置 base.Base.assignment:

It's a little verbose and a little unnecessary; you could simply set base.Base.assignment directly:

def test_empty(self):
    Base.assignment = {}
    assert len(Base().assignment.values()) == 0

當然，這在使用測試并發時不太安全.

This isn't too safe when using test concurrency, of course.

要使用 PropertyMock，我會使用:

with patch('base.Base.assignment', new_callable=PropertyMock) as a:
    a.return_value = {'a': 1}

甚至:

with patch('base.Base.assignment', new_callable=PropertyMock, 
           return_value={'a': 1}):

這篇關于在 python 單元測試中模擬類屬性的更好方法的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！