Testing with pytest

A pytest test is just a function named test_something that asserts things. Run the whole suite with pytest. No test framework boilerplate, no classes required — plain functions and assert statements are enough for almost everything.

import pytest

@pytest.fixture
def sample_todos():
    return [{"title": "milk", "done": False}]

@pytest.mark.parametrize("n,expected", [(2, 4), (3, 9), (5, 25)])
def test_square(n, expected):
    assert n * n == expected

A fixture is shared setup that pytest injects into any test that names it as a parameter — no copy-pasted setup code at the top of every test, and pytest handles teardown too if the fixture needs it. @pytest.mark.parametrize runs the same test body against a list of input/expected pairs, so five similar tests become one.