Python-сообщество

 import long_time_module as l
def main():
    print('Executing main function')
    
def optional():
    l.ltc.print_ok()
    
if __name__ == '__main__':
    main()
    optional()

 class LongTimeExecutingClass():
    def __init__(self) -> None:
        print('LongTimeExecutingClass - Long, Long init')
        
    def print_ok(self)->None:
        print ('LongTimeExecutingClass - print ok')
ltc = LongTimeExecutingClass()

 from unittest import TestCase
from unittest.mock import patch
class MyClass():
    def __init__(self) -> None:
        print('Mocking init')
        
    def print_ok(self) -> None:
        print ('Mocking class - print ok')
class TestAll(TestCase):
    
    @patch('main.l.ltc', MyClass(), spec=False)
    def test_main(self):
        import main
        main.main()
        main.optional()
        assert True

 def test_main(self):
        import main
        main.l.ltc = MyClass()
        main.main()
        main.optional()
        assert True