Testing if function prints something correctly in python 3 with unittest

function_prints_correctly.py

# Python 3.7
import io
import unittest
import unittest.mock


# -- function --
def print_hello_world() -> None:
    print('Hello World!')
    

#  - test-- 
class TestFunction(unittest.TestCase):
    def test_print_hello_world_prints_correctly_with(self):
        with unittest.mock.patch('sys.stdout', new_callable=io.StringIO) as mock_stdout:
            print_hello_world()
            self.assertEqual(
                mock_stdout.getvalue(),
                'Hello World!\n'  # It's important to remember about '\n'
            )

    @unittest.mock.patch('sys.stdout', new_callable=io.StringIO)
    def test_print_hello_world_prints_correctly_decorator(self, mock_stdout):
        print_hello_world()
        self.assertEqual(
            mock_stdout.getvalue(),
            'Hello World!\n'  # It's important to remember about '\n'
        )