谁能告诉我为什么这行不通?
>>> import mock
>>> @mock.patch('datetime.date.today')
... def today(cls):
... return date(2010, 1, 1)
...
>>> from datetime import date
>>> date.today()
datetime.date(2010, 12, 19)
也许有人能提出一个更好的办法?
谁能告诉我为什么这行不通?
>>> import mock
>>> @mock.patch('datetime.date.today')
... def today(cls):
... return date(2010, 1, 1)
...
>>> from datetime import date
>>> date.today()
datetime.date(2010, 12, 19)
也许有人能提出一个更好的办法?
当前回答
我通过将datetime导入为realdatetime并将我在模拟中需要的方法替换为实际方法来完成这项工作:
import datetime as realdatetime
@mock.patch('datetime')
def test_method(self, mock_datetime):
mock_datetime.today = realdatetime.today
mock_datetime.now.return_value = realdatetime.datetime(2019, 8, 23, 14, 34, 8, 0)
其他回答
值得注意的是,Mock文档专门讨论了datetime.date.today,并且可以在不创建虚拟类的情况下做到这一点:
https://docs.python.org/3/library/unittest.mock-examples.html#partial-mocking
>>> from datetime import date
>>> with patch('mymodule.date') as mock_date:
... mock_date.today.return_value = date(2010, 10, 8)
... mock_date.side_effect = lambda *args, **kw: date(*args, **kw)
...
... assert mymodule.date.today() == date(2010, 10, 8)
... assert mymodule.date(2009, 6, 8) == date(2009, 6, 8)
...
我想我来晚了一点,但我认为这里的主要问题是您直接修补datetime.date.today,根据文档,这是错误的。
例如,您应该修补在测试函数所在的文件中导入的引用。
假设你有一个functions.py文件,其中包含以下内容:
import datetime
def get_today():
return datetime.date.today()
然后,在你的测试中,你应该有这样的东西
import datetime
import unittest
from functions import get_today
from mock import patch, Mock
class GetTodayTest(unittest.TestCase):
@patch('functions.datetime')
def test_get_today(self, datetime_mock):
datetime_mock.date.today = Mock(return_value=datetime.strptime('Jun 1 2005', '%b %d %Y'))
value = get_today()
# then assert your thing...
希望这能对你有所帮助。
monkeypatch的最小工作示例
这个解决方案使用https://pypi.org/project/pytest-mock/包中的monkeypatch。
特点:
仅模拟datetime.today(),但datetime.now()仍然可以正常工作 仅在特定范围内模拟(即块)
import sys
from datetime import datetime
MOCKED_DATETIME_TODAY = datetime(1900, 1, 1, 0, 0, 0)
class MockedDatetime(datetime):
@classmethod
def today(cls):
return MOCKED_DATETIME_TODAY
def test_mock_datetime_today(monkeypatch):
"""Only datetime.today() is mocked and returns some date in 1900. datetime.now() returns still the current date."""
with monkeypatch.context() as mpc:
mpc.setattr(sys.modules[__name__], 'datetime', MockedDatetime)
assert datetime.today() == MOCKED_DATETIME_TODAY # datetime.today() mocked
assert datetime.now() > MOCKED_DATETIME_TODAY # datetime.now() not mocked
assert datetime.today() > MOCKED_DATETIME_TODAY # not mocked anymore
有一些问题。
首先,你使用模拟的方式。帕奇说得不太对。当用作装饰器时,它只在被装饰的函数内用Mock对象替换给定的函数/类(在本例中为datetime.date.today)。因此,只有在today()中,datetime.date.today才会是一个不同的函数,这似乎不是你想要的。
你真正想要的似乎是这样的:
@mock.patch('datetime.date.today')
def test():
datetime.date.today.return_value = date(2010, 1, 1)
print datetime.date.today()
不幸的是,这行不通:
>>> test()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "build/bdist.macosx-10.6-universal/egg/mock.py", line 557, in patched
File "build/bdist.macosx-10.6-universal/egg/mock.py", line 620, in __enter__
TypeError: can't set attributes of built-in/extension type 'datetime.date'
这是失败的,因为Python内置类型是不可变的-更多细节请参阅这个答案。
在本例中,我将继承datetime的子类。日期自己,并创建正确的函数:
import datetime
class NewDate(datetime.date):
@classmethod
def today(cls):
return cls(2010, 1, 1)
datetime.date = NewDate
现在你可以这样做:
>>> datetime.date.today()
NewDate(2010, 1, 1)
http://blog.xelnor.net/python-mocking-datetime/中讨论了几种解决方案。总而言之:
模拟对象-简单有效,但打破isinstance()检查:
target = datetime.datetime(2009, 1, 1)
with mock.patch.object(datetime, 'datetime', mock.Mock(wraps=datetime.datetime)) as patched:
patched.now.return_value = target
print(datetime.datetime.now())
模拟类
import datetime
import mock
real_datetime_class = datetime.datetime
def mock_datetime_now(target, dt):
class DatetimeSubclassMeta(type):
@classmethod
def __instancecheck__(mcs, obj):
return isinstance(obj, real_datetime_class)
class BaseMockedDatetime(real_datetime_class):
@classmethod
def now(cls, tz=None):
return target.replace(tzinfo=tz)
@classmethod
def utcnow(cls):
return target
# Python2 & Python3 compatible metaclass
MockedDatetime = DatetimeSubclassMeta('datetime', (BaseMockedDatetime,), {})
return mock.patch.object(dt, 'datetime', MockedDatetime)
使用:
with mock_datetime_now(target, datetime):
....