Can anyone tell me why this isn't working?
>>> 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)
Perhaps someone could suggest a better way?
Another option is to use
https://github.com/spulec/freezegun/
Install it:
pip install freezegun
And use it:
from freezegun import freeze_time
#freeze_time("2012-01-01")
def test_something():
from datetime import datetime
print(datetime.now()) # 2012-01-01 00:00:00
from datetime import date
print(date.today()) # 2012-01-01
It also affects other datetime calls in method calls from other modules:
other_module.py:
from datetime import datetime
def other_method():
print(datetime.now())
main.py:
from freezegun import freeze_time
#freeze_time("2012-01-01")
def test_something():
import other_module
other_module.other_method()
And finally:
$ python main.py
# 2012-01-01
For what it's worth, the Mock docs talk about datetime.date.today specifically, and it's possible to do this without having to create a dummy class:
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)
...
There are a few problems.
First of all, the way you're using mock.patch isn't quite right. When used as a decorator, it replaces the given function/class (in this case, datetime.date.today) with a Mock object only within the decorated function. So, only within your today() will datetime.date.today be a different function, which doesn't appear to be what you want.
What you really want seems to be more like this:
#mock.patch('datetime.date.today')
def test():
datetime.date.today.return_value = date(2010, 1, 1)
print datetime.date.today()
Unfortunately, this won't work:
>>> 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'
This fails because Python built-in types are immutable - see this answer for more details.
In this case, I would subclass datetime.date myself and create the right function:
import datetime
class NewDate(datetime.date):
#classmethod
def today(cls):
return cls(2010, 1, 1)
datetime.date = NewDate
And now you could do:
>>> datetime.date.today()
NewDate(2010, 1, 1)
I guess I came a little late for this but I think the main problem here is that you're patching datetime.date.today directly and, according to the documentation, this is wrong.
You should patch the reference imported in the file where the tested function is, for example.
Let's say you have a functions.py file where you have the following:
import datetime
def get_today():
return datetime.date.today()
then, in your test, you should have something like this
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...
Hope this helps a little bit.
Here's another way to mock datetime.date.today() with an added bonus that the rest of datetime functions continue to work, as the mock object is configured to wrap the original datetime module:
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
Note the wraps=datetime argument to mock.patch() – when the foo_module uses other datetime functions besides date.today() they will be forwarded to the original wrapped datetime module.
To add to Daniel G's solution:
from datetime import date
class FakeDate(date):
"A manipulable date replacement"
def __new__(cls, *args, **kwargs):
return date.__new__(date, *args, **kwargs)
This creates a class which, when instantiated, will return a normal datetime.date object, but which is also able to be changed.
#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)
The easiest way for me is doing this:
import datetime
from unittest.mock import Mock, patch
def test():
datetime_mock = Mock(wraps=datetime.datetime)
datetime_mock.now.return_value = datetime.datetime(1999, 1, 1)
with patch('datetime.datetime', new=datetime_mock):
assert datetime.datetime.now() == datetime.datetime(1999, 1, 1)
CAUTION for this solution: all functionality from datetime module from the target_module will stop working.
I faced the same situation a couple of days ago, and my solution was to define a function in the module to test and just mock that:
def get_date_now():
return datetime.datetime.now()
Today I found out about FreezeGun, and it seems to cover this case beautifully
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)
You can use the following approach, based on Daniel G solution. This one has advantage of not breaking type checking with isinstance(d, datetime.date).
import mock
def fixed_today(today):
from datetime import date
class FakeDateType(type):
def __instancecheck__(self, instance):
return isinstance(instance, date)
class FakeDate(date):
__metaclass__ = FakeDateType
def __new__(cls, *args, **kwargs):
return date.__new__(date, *args, **kwargs)
#staticmethod
def today():
return today
return mock.patch("datetime.date", FakeDate)
Basically, we replace C-based datetime.date class with our own python subclass, that produces original datetime.date instances and responds to isinstance() queries exactly as native datetime.date.
Use it as context manager in your tests:
with fixed_today(datetime.date(2013, 11, 22)):
# run the code under test
# note, that these type checks will not break when patch is active:
assert isinstance(datetime.date.today(), datetime.date)
Similar approach can be used to mock datetime.datetime.now() function.
CPython actually implements the datetime module using both a pure-Python Lib/datetime.py and a C-optimized Modules/_datetimemodule.c. The C-optimized version cannot be patched but the pure-Python version can.
At the bottom of the pure-Python implementation in Lib/datetime.py is this code:
try:
from _datetime import * # <-- Import from C-optimized module.
except ImportError:
pass
This code imports all the C-optimized definitions and effectively replaces all the pure-Python definitions. We can force CPython to use the pure-Python implementation of the datetime module by doing:
import datetime
import importlib
import sys
sys.modules["_datetime"] = None
importlib.reload(datetime)
By setting sys.modules["_datetime"] = None, we tell Python to ignore the C-optimized module. Then we reload the module which causes the import from _datetime to fail. Now the pure-Python definitions remain and can be patched normally.
If you're using Pytest then include the snippet above in conftest.py and you can patch datetime objects normally.
We can use pytest-mock (https://pypi.org/project/pytest-mock/) mocker object to mock datetime behaviour in a particular module
Let's say you want to mock date time in the following file
# File path - source_dir/x/a.py
import datetime
def name_function():
name = datetime.now()
return f"name_{name}"
In the test function, mocker will be added to the function when test runs
def test_name_function(mocker):
mocker.patch('x.a.datetime')
x.a.datetime.now.return_value = datetime(2019, 1, 1)
actual = name_function()
assert actual == "name_2019-01-01"
Generally speaking, you would have datetime or perhaps datetime.date imported into a module somewhere. A more effective way of mocking the method would be to patch it on the module that is importing it. Example:
a.py
from datetime import date
def my_method():
return date.today()
Then for your test, the mock object itself would be passed as an argument to the test method. You would set up the mock with the result value you want, and then call your method under test. Then you would assert that your method did what you want.
>>> 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
A word of warning. It is most certainly possible to go overboard with mocking. When you do, it makes your tests longer, harder to understand, and impossible to maintain. Before you mock a method as simple as datetime.date.today, ask yourself if you really need to mock it. If your test is short and to the point and works fine without mocking the function, you may just be looking at an internal detail of the code you're testing rather than an object you need to mock.
It's possible to mock functions from datetime module without adding side_effects
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()
The best approach for me is a combination of #Daniel G and #frx08 solutions:
class Test_mock_date:
class NewDate(datetime.datetime):
#classmethod
def now(cls, tz=None):
return cls(2021, 5, 12)
def test_mock_date(self):
with patch('datetime.datetime', new = self.NewDate):
assert datetime.datetime.now() == datetime.datetime(2021, 5, 12, 0, 0)
You can take a look at the following medium article I wrote with different examples about how to use MagicMock https://medium.com/#camposer/d2113513b365
For those of you using pytest with pytest-mock (more info on pytest-mock at the end) here is how I mocked datetime.datetime.now() which is very similar to the original question.
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)
Essentially the mock has to be set to return the specified date. You aren't able to patch over datetime's object directly.
Pytest-mock is a library that makes a mock object a fixture. More detail can be found here
Maybe you could use your own "today()" method that you will patch where needed. Example with mocking utcnow() can be found here: https://bitbucket.org/k_bx/blog/src/tip/source/en_posts/2012-07-13-double-call-hack.rst?at=default
I implemented #user3016183 method using a custom decorator:
def changeNow(func, newNow = datetime(2015, 11, 23, 12, 00, 00)):
"""decorator used to change datetime.datetime.now() in the tested function."""
def retfunc(self):
with mock.patch('mymodule.datetime') as mock_date:
mock_date.now.return_value = newNow
mock_date.side_effect = lambda *args, **kw: datetime(*args, **kw)
func(self)
return retfunc
I thought that might help someone one day...
Several solutions are discussed in http://blog.xelnor.net/python-mocking-datetime/. In summary:
Mock object - Simple and efficient but breaks isinstance() checks:
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())
Mock class
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)
Use as:
with mock_datetime_now(target, datetime):
....
I made this work by importing datetime as realdatetime and replacing the methods I needed in the mock with the real methods:
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)
You can mock datetime using this:
In the module sources.py:
import datetime
class ShowTime:
def current_date():
return datetime.date.today().strftime('%Y-%m-%d')
In your tests.py:
from unittest import TestCase, mock
import datetime
class TestShowTime(TestCase):
def setUp(self) -> None:
self.st = sources.ShowTime()
super().setUp()
#mock.patch('sources.datetime.date')
def test_current_date(self, date_mock):
date_mock.today.return_value = datetime.datetime(year=2019, month=10, day=1)
current_date = self.st.current_date()
self.assertEqual(current_date, '2019-10-01')
For those using patchers in a test class, here's how I'm successfully patching datetime functionality:
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'
)
Minimal working example with monkeypatch
This solution uses monkeypatch from the https://pypi.org/project/pytest-mock/ package.
Features:
mock only datetime.today(), but datetime.now() still works as expected
mock only in a specific scope (i.e. block)
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