pytest Cheat Sheet: Selectors, Fixtures & Markers

pytest selection, fixtures, and markers in one quick reference.

Run, select, and parametrize tests with pytest.

Run & select

Command	Does
pytest	Run all tests
pytest path/test.py::test_fn	Run one test
pytest -k "expr"	Filter by name expression
pytest -m marker	Run tests with a marker
pytest -x	Stop on first failure
pytest --lf	Re-run last failures
pytest -q / -v	Quiet / verbose
pytest -n auto	Parallel (pytest-xdist)

Fixtures & markers

Construct	Use
@pytest.fixture	Reusable setup/teardown
scope="session"	Share across the run
@pytest.mark.skip	Skip a test
@pytest.mark.skipif(cond)	Conditional skip
@pytest.mark.xfail	Expected failure
conftest.py	Shared fixtures/config

Parametrize & assert

test_example.py

import pytest

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

def test_raises():
    with pytest.raises(ValueError):
        int("x")

Key takeaways

-k filters by name; -m filters by marker.
--lf re-runs only the last failures for fast iteration.
conftest.py holds fixtures shared across a directory tree.

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