Python: MagicMock, Patch and Side effect

print_random.py

import time
import uuid


class PrintRandom(object):
    def execute(self) -> None:
        while True:
            self.print_number(uuid.uuid1().int)
            time.sleep(1)

    @staticmethod
    def print_number(number: int) -> None:
        print("Number is: {}".format(number))


if __name__ == "__main__":
    obj = PrintRandom()
    obj.execute()

test_print_random.py

import uuid

from print_random import PrintRandom
import unittest
from unittest.mock import MagicMock, patch


class TestPrintRandom(unittest.TestCase):
    def setUp(self) -> None:
        pass

    def test_print_random(self):
        random = PrintRandom()
        random.print_number = MagicMock(side_effect=self._side_effect_except())
        try:
            random.execute()
        except StopIteration as e:
            self.assertIsInstance(e, StopIteration)

    @staticmethod
    def _side_effect_except():
        return StopIteration

    @patch("print_random.PrintRandom.print_number")
    def test_print_random_again(self, mocked_print_number):
        mocked_print_number.side_effect = self.print_number
        random = PrintRandom()
        try:
            random.execute()
        except StopIteration as e:
            self.assertIsInstance(e, StopIteration)

    @staticmethod
    def print_number(number: int) -> None:
        print("Printing from patched print: {}".format(number))
        raise StopIteration