# pyproject.toml
[tool.pytest.ini_options]
markers = [
    "slow: marks tests as slow (deselect with '-m \"not slow\"')",
    "integration: marks tests requiring external services",
    "smoke: critical path tests for CI/CD",
]

import pytest

@pytest.mark.slow
def test_complex_analysis():
    result = perform_complex_analysis(large_dataset)
    assert result.is_valid

# Run: pytest -m "not slow"  # Skip slow tests
# Run: pytest -m smoke       # Only smoke tests

[tool.pytest.ini_options]
addopts = ["-n", "auto", "--dist", "loadscope"]

@pytest.fixture(scope="session")
def db_engine(worker_id):
    """Isolate database per worker."""
    db_name = "test_db" if worker_id == "master" else f"test_db_{worker_id}"
    engine = create_engine(f"postgresql://localhost/{db_name}")
    yield engine

@pytest.fixture
def user_factory(db_session) -> Callable[..., User]:
    """Factory fixture for creating users."""
    created = []

    def _create(**kwargs) -> User:
        user = User(**{"email": f"u{len(created)}@test.com", **kwargs})
        db_session.add(user)
        created.append(user)
        return user

    yield _create
    for u in created:
        db_session.delete(u)

# NEVER use expensive fixtures without session scope
@pytest.fixture  # WRONG - loads every test
def model():
    return load_ml_model()  # 5s each time!

# NEVER mutate global state
@pytest.fixture
def counter():
    global _counter
    _counter += 1  # WRONG - leaks between tests

# NEVER skip cleanup
@pytest.fixture
def temp_db():
    db = create_db()
    yield db
    # WRONG - missing db.drop()!

# NEVER use time.sleep (use mocking)
def test_timeout():
    time.sleep(5)  # WRONG - slows tests