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
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):
....
其他回答
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)
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):
....
对于那些使用pytest和pytest-mock的人(关于pytest-mock的更多信息在最后),这里是我如何模拟datetime.datetime.now(),这与最初的问题非常相似。
test_get_now(mocker):
datetime_mock = mocker.patch("blackline_accounts_import.datetime",)
datetime_mock.datetime.now.return_value=datetime.datetime(2019,3,11,6,2,0,0)
now == function_being_tested() # run function
assert now == datetime.datetime(2019,3,11,6,2,0,0)
本质上,mock必须设置为返回指定的日期。您不能直接修补datetime的对象。
Pytest-mock是一个使模拟对象成为fixture的库。更多细节可以在这里找到
在Daniel G的解决方案中补充一点:
from datetime import date
class FakeDate(date):
"A manipulable date replacement"
def __new__(cls, *args, **kwargs):
return date.__new__(date, *args, **kwargs)
这将创建一个类,当实例化时,该类将返回一个正常的datetime。对象,但也可以更改。
@mock.patch('datetime.date', FakeDate)
def test():
from datetime import date
FakeDate.today = classmethod(lambda cls: date(2010, 1, 1))
return date.today()
test() # datetime.date(2010, 1, 1)