code/python/pytest-init.py

"""Example pytest fixtures and test functions.

A small but realistic conftest-style module showing common pytest patterns:
fixtures with different scopes, parametrization, and skip/xfail markers.
"""
from __future__ import annotations

import os
import tempfile
from pathlib import Path

import pytest


@pytest.fixture(scope="session")
def session_tmpdir() -> Path:
    """Session-scoped temporary directory shared across all tests."""
    with tempfile.TemporaryDirectory(prefix="pytest-session-") as d:
        yield Path(d)


@pytest.fixture
def sample_config() -> dict[str, object]:
    """Per-test configuration dict."""
    return {"debug": True, "timeout": 30, "retries": 3}


@pytest.fixture
def env_var(monkeypatch: pytest.MonkeyPatch) -> str:
    """Set and restore an environment variable for one test."""
    monkeypatch.setenv("APP_MODE", "test")
    return os.environ["APP_MODE"]


@pytest.mark.parametrize("value,expected", [(1, 1), (2, 4), (3, 9), (4, 16)])
def test_square(value: int, expected: int) -> None:
    assert value * value == expected


def test_config_defaults(sample_config: dict[str, object]) -> None:
    assert sample_config["debug"] is True
    assert sample_config["timeout"] == 30


def test_env_override(env_var: str) -> None:
    assert env_var == "test"


@pytest.mark.skipif(os.name == "nt", reason="POSIX-only path semantics")
def test_session_dir_exists(session_tmpdir: Path) -> None:
    assert session_tmpdir.exists() and session_tmpdir.is_dir()