pytest 8.4.1: pytest

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify pytest in pkg:pypi/pytest@8.4.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:pypi/pytest@8.4.1
Demonstrate these symbols/APIs:
  - pytest

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:2aa505ac7e38c845d791efef35b5a81a0484dd5408449b423ecf9b454366d026","contract":["pytest.approx performs tolerant float comparisons for scalar, sequence, and dictionary structures with custom abs and rel tolerances","pytest.approx supports nan comparison when nan_ok is explicitly enabled","pytest.raises verifies expected exception types, matches error messages with regex, and yields ExceptionInfo","pytest.raises accepts multiple expected exceptions as a tuple and fails when no exception is raised","pytest.MonkeyPatch context manager safely modifies environment variables and restores them on exit","pytest.main executes test sessions programmatically and returns ExitCode enum values"],"goal":"verify pytest in pkg:pypi/pytest@8.4.1","kind":"HOW","packages":["pkg:pypi/pytest@8.4.1"],"schemaVersion":1,"symbols":["pytest"]},"contractCommand":["python","test/contract.py"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"pypi","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"pip","schemaVersion":1},"license":"MIT-0","packages":["pkg:pypi/pytest@8.4.1"],"schemaVersion":1,"subject":"pkg:pypi/pytest@8.4.1","symbols":["pytest"],"verifierAdapter":"python@1"}

iniconfig==2.3.0
packaging==26.3
pluggy==1.6.0
pygments==2.21.0
pytest==8.4.1

"""Sample demonstrating core pytest APIs including approx, raises, MonkeyPatch, and main."""

import os
from typing import Any, Dict, List
import pytest


def calculate_metrics(values: List[float]) -> Dict[str, float]:
    """Calculate mean and variance for a list of numbers."""
    if not values:
        raise ValueError("cannot calculate metrics for an empty list")
    mean = sum(values) / len(values)
    variance = sum((x - mean) ** 2 for x in values) / len(values)
    return {"mean": mean, "variance": variance}


def compare_floats(a: float, b: float, rel: float = 1e-6, abs_tol: float = 1e-12) -> bool:
    """Compare two floating point numbers using pytest.approx."""
    return a == pytest.approx(b, rel=rel, abs=abs_tol)


def compare_dict_metrics(actual: Dict[str, float], expected: Dict[str, float]) -> bool:
    """Compare dictionary of float metrics using pytest.approx."""
    return actual == pytest.approx(expected)


def read_env_setting(key: str, default: str = "") -> str:
    """Retrieve environment configuration value."""
    return os.environ.get(key, default)


def execute_test_target(test_target: str) -> pytest.ExitCode:
    """Run a test file programmatically using pytest.main."""
    return pytest.main(["-q", "--no-header", test_target])

{
  "schemaVersion": 1,
  "goal": "verify pytest in pkg:pypi/pytest@8.4.1",
  "kind": "HOW",
  "packages": [
    "pkg:pypi/pytest@8.4.1"
  ],
  "symbols": [
    "pytest"
  ]
}

import os
import sys
import tempfile

# Ensure project root is on sys.path for local imports
sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))

import pytest
from sample import (
    calculate_metrics,
    compare_dict_metrics,
    compare_floats,
    execute_test_target,
    read_env_setting,
)


def test_approx_scalar_sequence_dict():
    # Assertion 1: pytest.approx performs tolerant float comparisons for scalar, sequence, and dictionary structures with custom abs and rel tolerances
    assert compare_floats(0.1 + 0.2, 0.3, rel=1e-6)
    assert [1.0001, 2.0002] == pytest.approx([1.0, 2.0], abs=1e-3)

    metrics = calculate_metrics([1.0, 2.0, 3.0, 4.0, 5.0])
    assert compare_dict_metrics(metrics, {"mean": 3.0, "variance": 2.0})


def test_approx_nan_support():
    # Assertion 2: pytest.approx supports nan comparison when nan_ok is explicitly enabled
    nan_val = float("nan")
    assert nan_val != pytest.approx(nan_val)
    assert nan_val == pytest.approx(nan_val, nan_ok=True)


def test_raises_and_exception_info():
    # Assertion 3: pytest.raises verifies expected exception types, matches error messages with regex, and yields ExceptionInfo
    with pytest.raises(ValueError, match=r"^cannot calculate metrics for an empty list$") as exc_info:
        calculate_metrics([])

    assert exc_info.type is ValueError
    assert exc_info.errisinstance(ValueError)
    assert "empty list" in str(exc_info.value)


def test_raises_multiple_exceptions_and_no_raise_failure():
    # Assertion 4: pytest.raises accepts multiple expected exceptions as a tuple and fails when no exception is raised
    with pytest.raises((KeyError, ValueError)):
        calculate_metrics([])

    with pytest.raises(pytest.fail.Exception, match=r"DID NOT RAISE"):
        with pytest.raises(ValueError):
            pass


def test_monkeypatch_context():
    # Assertion 5: pytest.MonkeyPatch context manager safely modifies environment variables and restores them on exit
    test_key = "CSX_TEST_CONFIG_ENV"
    assert read_env_setting(test_key, "default") == "default"

    with pytest.MonkeyPatch.context() as mp:
        mp.setenv(test_key, "active_value")
        assert read_env_setting(test_key, "default") == "active_value"

    assert read_env_setting(test_key, "default") == "default"


def test_main_exit_code():
    # Assertion 6: pytest.main executes test sessions programmatically and returns ExitCode enum values
    with tempfile.NamedTemporaryFile(mode="w", suffix=".py", delete=False) as f:
        f.write("def test_ok(): assert 1 + 1 == 2\n")
        temp_file = f.name

    try:
        exit_code = execute_test_target(temp_file)
        assert exit_code == pytest.ExitCode.OK
        assert isinstance(exit_code, pytest.ExitCode)
    finally:
        if os.path.exists(temp_file):
            os.remove(temp_file)


def main():
    test_approx_scalar_sequence_dict()
    test_approx_nan_support()
    test_raises_and_exception_info()
    test_raises_multiple_exceptions_and_no_raise_failure()
    test_monkeypatch_context()
    test_main_exit_code()
    print("Contract verification passed.")


if __name__ == "__main__":
    main()