How to mock/set system date in pytest?

问题

In some of my tests I am having a problem that they fail on Travis because of time and time zone problems, so I want to mock system time for my test. How can I do this?

回答1:

AFAIK, you can't mock builtin methods.

One approach I have often done is to change my code a bit to not use datetime directly to obtain the date, but a wrapper function somewhere:

# mymodule.py

def get_today():
   return datetime.date.today()

This makes it trivial to just mock it in your test:

def test_something():
    with mock.patch('mymodule.get_today', return_value=datetime.date(2014, 6, 2)):
        ...

You can also use the freezegun module.

回答2:

There are two ways you can accomplish that:

Create function which you will call instead of datetime.datetime.now() as suggested by Bruno, but here is different implementation:

import os
import datetime

def mytoday():
 if 'MYDATE' in os.environ:
     return datetime.datetime.strptime(os.getenv('MYDATE'), '%m-%d-%Y').date()
 else:
     return datetime.date.today()

Then, in your test, you just monkeypatch environment variable:

import datetime

def test_patched_date(monkeypatch):
    monkeytest.setenv('MYDATE', '05-31-2014')
    assert datetime.date.today() == datetime.date(2014, 5, 31)

Monkeypatch the datetime function:

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

回答3:

@Brian-Kruger's answer is the best one. I've voted to undelete it. In the meantime...

Use freezegun (repo).

From the README:

from freezegun import freeze_time

@freeze_time("2012-01-14")
def test():
    assert datetime.datetime.now() == datetime.datetime(2012, 1, 14)

来源：https://stackoverflow.com/questions/23988853/how-to-mock-set-system-date-in-pytest

标签

python

pytest