5.2. Unittest Patch

5.2.1. Patch Randint

Code:

>>> from random import randint
>>>
>>>
>>> def throw_dice():
...     return randint(1,6)

Test:

>>> from unittest import TestCase
>>> from unittest.mock import patch
>>>
>>>
>>> class MyTest(TestCase):
...     def test_age(self):
...         with patch('random.randint', return_value=4) as randint:
...             result = throw_dice()
...         self.assertEqual(result, 4)

5.2.2. Patch Date in Different Files

• class User is in the myfile.py file

• tests are in the mytests.py file

• cannot patch('date.today', return_value=...) because it is immutable

Code in the myfile.py file:

>>> from datetime import date
>>>
>>>
>>> class User:
...     def __init__(self, firstname, lastname, birthdate):
...         self.firstname = firstname
...         self.lastname = lastname
...         self.birthdate = date.fromisoformat(birthdate)
...
...     def age(self):
...         td = date.today() - self.birthdate
...         return int(td.days / 365.25)

Tests in the mytests.py file:

>>> from datetime import date
>>> from unittest import TestCase
>>> from unittest.mock import patch
>>>
>>>
>>> class MyTest(TestCase):
...     def test_age(self):
...         mark = User('Mark', 'Watney', birthdate='2000-01-02')
...         with patch('myfile.date') as d:
...             d.today.return_value = date(2024, 1, 2)
...             age = mark.get_age()
...         self.assertIsInstance(age, int)
...         self.assertEqual(age, 24)

5.2.3. Patch Date in the Same File

• class User is in the myfile.py file

• tests are also in the myfile.py file

• mind additional import inside of a context manager

• this is due to the fact, that date will be mocked (date.today())

• and today.return_value is also a date object (date(2024, 1, 2))

Code and tests in the myfile.py file:

>>> from datetime import date
>>> from unittest import TestCase
>>> from unittest.mock import patch
>>>
>>>
>>> class User:
...     def __init__(self, firstname, lastname, birthdate):
...         self.firstname = firstname
...         self.lastname = lastname
...         self.birthdate = date.fromisoformat(birthdate)
...
...     def age(self):
...         td = date.today() - self.birthdate
...         return int(td.days / 365.25)
>>>
>>>
>>> class MyTest(TestCase):
...     def test_age(self):
...         mark = User('Mark', 'Watney', birthdate='2000-01-02')
...         with patch('myfile.date') as d:
...             from datetime import date
...             d.today.return_value = date(2024, 1, 2)
...             age = mark.age()
...         self.assertIsInstance(age, int)
...         self.assertEqual(age, 24)