What is conftest.py in pytest?

Question

Accepted Answer

**conftest.py** provides **shared fixtures** and configuration for pytest.

```python
# conftest.py
import pytest
from fastapi.testclient import TestClient
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

# Database fixture (shared across all tests)
@pytest.fixture(scope="session")
def db_engine():
    engine = create_engine("sqlite:///test.db")
    Base.metadata.create_all(engine)
    yield engine
    Base.metadata.drop_all(engine)

@pytest.fixture(autouse=True)
def db_session(db_engine):
    Session = sessionmaker(bind=db_engine)
    session = Session()
    yield session
    session.rollback()
    session.close()

# Client fixture
@pytest.fixture
def client(app):
    return TestClient(app)

# Auth fixture
@pytest.fixture
def auth_headers():
    token = create_test_token(user_id=1)
    return {"Authorization": f"Bearer {token}"}

# Test file
# tests/test_users.py
def test_create_user(client, db_session):
    response = client.post("/users/", json={"name": "Alice"})
    assert response.status_code == 201

def test_get_users(client, auth_headers):
    response = client.get("/users/", headers=auth_headers)
    assert response.status_code == 200
```

**Features:**
- Fixtures are auto-discovered.
- Hierarchical conftest.py files.
- Hooks for customization.
- Plugin registration.

Python: What is conftest.py in pytest?