Testing demo: pytest without classes failure

---

examples/testing-demo/test_with_pytest_failure.py

import mymath

def test_math():
    assert mymath.add(2, 2) == 4

def test_more_math():
    assert mymath.add(3, 3) == 6

=========================== test session starts ============================
platform linux -- Python 3.11.2, pytest-7.3.1, pluggy-1.0.0
rootdir: /home/gabor/work/slides/python/examples/testing-demo
plugins: anyio-3.6.2
collected 2 items

test_with_pytest_failure.py .F                                       [100%]

================================= FAILURES =================================
______________________________ test_more_math ______________________________

    def test_more_math():
>       assert mymath.add(3, 3) == 6
E       assert 9 == 6
E        +  where 9 = <function add at 0x7f764062cea0>(3, 3)
E        +    where <function add at 0x7f764062cea0> = mymath.add

test_with_pytest_failure.py:7: AssertionError
========================= short test summary info ==========================
FAILED test_with_pytest_failure.py::test_more_math - assert 9 == 6
======================= 1 failed, 1 passed in 0.08s ========================

$ pytest test_with_pytest.py
$ echo $?
1

> pytest test_with_pytest.py
> echo %ERRORLEVEL%
1