How to unittest a datetime function

file.py

import datetime
ENV_NUMBER_DAYS_RESERVED = 3

def check_date(entity):
    entity_created_date = entity.get('createdDatetime').date()
    utc_date = datetime.datetime.utcnow().date()

    print((utc_date - entity_created_date).days) #<MagicMock name='datetime.datetime.utcnow().date().__sub__().days' id='4899349456'>
    print(type((utc_date - entity_created_date).days))#<class 'unittest.mock.MagicMock'>


    return True if (utc_date - entity_created_date).days > int(ENV_NUMBER_DAYS_RESERVED) else False

test.py

import file

@patch('file.datetime')
def test_check_date_False(self, date_now):
    entity = MagicMock()
    entity.get.return_value = datetime.datetime(2022,1,1)
    date_now.datetime.utcnow.date.return_value = datetime.datetime(2022,1,1)

    self.assertFalse(check_date(entity=entity))

I get an Error: TypeError: ‘>’ not supported between instances of ‘MagicMock’ and ‘int’

Is there anyway to test this function?

Probably the problem is with this part of the last line: (utc_date - namespace_created_date).days

Answer

I could reproduce and fix.

Here is a working unittest file (assuming file.py is accessible):

import unittest
from unittest.mock import patch, MagicMock

import datetime
import file

class TestFile(unittest.TestCase):
    @patch('file.datetime')
    def test_check_date_False(self, date_now):
        entity = MagicMock()
        entity.get.return_value = datetime.datetime(2022,1,1)
        date_now.datetime.utcnow.return_value = datetime.datetime(2022,1,1)

        self.assertFalse(file.check_date(None, entity=entity))
    
unittest.main(verbosity=2)

If I use date_now.datetime.utcnow.date.return_value = datetime.datetime(2022,1,1) I have the same error as you have, but removing .date is enough to have the test to pass.