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
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
一般来说,你会有datetime或datetime。将日期导入某个模块。模拟该方法的一种更有效的方法是在导入它的模块上修补它。例子:
a.py
from datetime import date
def my_method():
return date.today()
然后,对于您的测试,模拟对象本身将作为参数传递给测试方法。您将使用所需的结果值设置模拟,然后调用测试中的方法。然后您可以断言您的方法完成了您想要的。
>>> import mock
>>> import a
>>> @mock.patch('a.date')
... def test_my_method(date_mock):
... date_mock.today.return_value = mock.sentinel.today
... result = a.my_method()
... print result
... date_mock.today.assert_called_once_with()
... assert mock.sentinel.today == result
...
>>> test_my_method()
sentinel.today
警告一句。很有可能嘲讽得过火了。当您这样做时,它会使您的测试更长、更难理解,并且不可能维护。在模拟像datetime.date这样简单的方法之前。今天,问问自己是否真的需要嘲笑它。如果您的测试短小精干,并且在不模拟函数的情况下运行良好,那么您可能只看到了正在测试的代码的内部细节,而不是需要模拟的对象。
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)
...
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
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):
....