Trying to mock datetime date today but not working

Question

Can anyone tell me why this isn t working    gt  gt  gt  import mock  gt  gt  gt   mock patch  datetime date today       def today cls        return date 2010  1  1       gt  gt  gt  from datetime import date  gt  gt  gt  date today   datetime date 2010  12  19    Perhaps someone could suggest a better way

User · Answer

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

User · Answer

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    gt  gt  gt  import mock  gt  gt  gt  import a  gt  gt  gt   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      gt  gt  gt  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

User · Answer

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   gt  gt  gt  from datetime import date  gt  gt  gt  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

User · Answer

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  amp  Python3 compatible metaclass     MockedDatetime   DatetimeSubclassMeta  datetime    BaseMockedDatetime             return mock patch object dt   datetime   MockedDatetime    Use as   with mock datetime now target  datetime

User · Answer

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  - gt  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

User · Answer

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

User · Answer

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

User · Answer

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    gt  gt  gt  test   Traceback  most recent call last     File   lt stdin gt    line 1  in  lt module gt    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    gt  gt  gt  datetime date today   NewDate 2010  1  1

User · Answer

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

User · Answer

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 quot name  name  quot   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     quot name 2019-01-01 quot

User · Answer

For those of you using pytest with mocker 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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

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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       lt -- 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  quot  datetime quot     None importlib reload datetime   By setting sys modules  quot  datetime quot     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

User · Answer

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

User · Answer

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

User · Answer

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

[python] Trying to mock datetime.date.today(), but not working

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