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
几天前我遇到了同样的情况,我的解决方案是在模块中定义一个函数来测试和模拟:
def get_date_now():
return datetime.datetime.now()
今天我发现了《FreezeGun》,它似乎很好地解决了这个问题
from freezegun import freeze_time
import datetime
import unittest
@freeze_time("2012-01-14")
def test():
assert datetime.datetime.now() == datetime.datetime(2012, 1, 14)
其他回答
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)
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)
对于那些在测试类中使用补丁程序的人,下面是我如何成功地修补datetime功能:
from datetime import datetime
import unittest
from unittest.mock import Mock, patch
# Replace with the proper path to the module you would
# like datetime to be mocked
from path.to.my_module
class MyTestCases(unittest.TestCase):
def setUp(self):
"""execute on class instantiation"""
# Record both times at the same moment
self.dt_now, self.dt_utcnow = datetime.now(), datetime.utcnow()
# After retrieving real (or hardcoded datetime values),
# proceed to mock them in desired module
self.patch_datetime_functions()
def patch_datetime_functions(self) -> None:
"""
Patch datetime.now() and datetime.utcnow() to prevent issues when
comparing expected dates
"""
# Create a patcher
self.patcher_dt = patch(
'path.to.my_module'
)
# Start but make sure cleanup always occurs
self.patcher_dt.start()
self.addCleanup(self.patcher_dt.stop)
# Perform the actual patch – use lambdas as mock functions
datetime_mock = Mock(wraps=datetime)
datetime_mock.now.return_value = self.dt_now
datetime_mock.utcnow.return_value = self.dt_utcnow
my_module.datetime = datetime_mock
# Here's what it will look like when testing:
def some_test(self):
curr_dt = self.dt_now
returned_dt = my_module.datetime.utcnow()
# Compare the dates
self.assertEqual(curr_dt, returned_dt,
'Datetime values should be equal'
)
可以在不添加side_effects的情况下模拟datetime模块中的函数
import mock
from datetime import datetime
from where_datetime_used import do
initial_date = datetime.strptime('2018-09-27', "%Y-%m-%d")
with mock.patch('where_datetime_used.datetime') as mocked_dt:
mocked_dt.now.return_value = initial_date
do()
下面是另一种模拟datetime.date.today()的方法,其额外的好处是其余的datetime函数继续工作,因为模拟对象被配置为包装原始的datetime模块:
from unittest import mock, TestCase
import foo_module
class FooTest(TestCase):
@mock.patch(f'{foo_module.__name__}.datetime', wraps=datetime)
def test_something(self, mock_datetime):
# mock only datetime.date.today()
mock_datetime.date.today.return_value = datetime.date(2019, 3, 15)
# other calls to datetime functions will be forwarded to original datetime
注意mock.patch()的wraps=datetime参数——当foo_module使用date.today()之外的其他datetime函数时,它们将被转发到原始包装的datetime模块。