如何用py.test monkeypatch python的datetime.datetime.now？

Question

我需要測試使用datetime.datetime.now()的函數。什麼是最簡單的方法來做到這一點？

Answer 1

您需要monkeypatch datetime.now函數。在下面的例子，我創建夾具，我以後可以在其他測試中重複使用：

import datetime 
import pytest 

FAKE_TIME = datetime.datetime(2020, 12, 25, 17, 05, 55) 

@pytest.fixture 
def patch_datetime_now(monkeypatch): 

    class mydatetime: 
     @classmethod 
     def now(cls): 
      return FAKE_TIME 

    monkeypatch.setattr(datetime, 'datetime', mydatetime) 


def test_patch_datetime(patch_datetime_now): 
    assert datetime.datetime.now() == FAKE_TIME 

Answer 2

這是我用現在覆蓋夾具（），但保持日期時間的其餘部分工作（RE：悟的問題）。

它沒有廣泛測試，但它確實解決了其他情況下使用datetime的問題。對我來說，保持Django ORM處理這些日期時間值非常重要（特別是isinstance(Freeze.now(), datetime.datetime) == True）。

@pytest.fixture 
def freeze(monkeypatch): 
    """ Now() manager patches datetime return a fixed, settable, value 
     (freezes time) 
    """ 
    import datetime 
    original = datetime.datetime 

    class FreezeMeta(type): 
     def __instancecheck__(self, instance): 
      if type(instance) == original or type(instance) == Freeze: 
       return True 

    class Freeze(datetime.datetime): 
     __metaclass__ = FreezeMeta 

     @classmethod 
     def freeze(cls, val): 
      cls.frozen = val 

     @classmethod 
     def now(cls): 
      return cls.frozen 

     @classmethod 
     def delta(cls, timedelta=None, **kwargs): 
      """ Moves time fwd/bwd by the delta""" 
      from datetime import timedelta as td 
      if not timedelta: 
       timedelta = td(**kwargs) 
      cls.frozen += timedelta 

    monkeypatch.setattr(datetime, 'datetime', Freeze) 
    Freeze.freeze(original.now()) 
    return Freeze 

也許脫離主題，但可能會派上用場的其他人到這個問題。該裝置，可「凍結」時間，然後隨意移動來回你的測試中：

def test_timesensitive(freeze): 
    freeze.freeze(2015, 1, 1) 
    foo.prepare() # Uses datetime.now() to prepare its state 
    freeze.delta(days=2) 
    # Does something that takes in consideration that 2 days have passed 
    # i.e. datetime.now() returns a date 2 days in the future 
    foo.do_something() 
    assert foo.result == expected_result_after_2_days 

Answer 3

有freezegun module：

from datetime import datetime 
from freezegun import freeze_time # $ pip install freezegun 

@freeze_time("Jan 14th, 2012") 
def test_nice_datetime(): 
    assert datetime.now() == datetime(2012, 1, 14) 

freeze_time()也可以用作上下文管理器。該模塊支持指定本地時區的UTC偏移量。

Answer 4

從其他的答案改編：

import datetime as dt 

@contextmanager 
def mocked_now(now): 
    class MockedDatetime(dt.datetime): 
     @classmethod 
     def now(cls): 
      return now 

    with patch("datetime.datetime", MockedDatetime): 
     yield 

使用，如：

def test_now(): 
    with mocked_now(dt.datetime(2017, 10, 21)): 
     assert dt.datetime.now() == dt.datetime(2017, 10, 21)