python-testing

Python Testing

This skill provides comprehensive Python testing patterns using pytest as the primary testing framework.

Testing Framework

Use pytest as the testing framework for its powerful features and clean syntax.

Basic Test Structure

def test_user_creation():
    """Test that a user can be created with valid data"""
    user = User(name="Alice", email="[email protected]")

    assert user.name == "Alice"
    assert user.email == "[email protected]"
    assert user.is_active is True

Test Discovery

pytest automatically discovers tests following these conventions:

• Files: test_*.py or *_test.py
• Functions: test_*
• Classes: Test* (without __init__)
• Methods: test_*

Fixtures

Fixtures provide reusable test setup and teardown:

import pytest
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

@pytest.fixture
def db_session():
    """Provide a database session for tests"""
    engine = create_engine("sqlite:///:memory:")
    Session = sessionmaker(bind=engine)
    session = Session()

    # Setup
    Base.metadata.create_all(engine)

    yield session

    # Teardown
    session.close()

def test_user_repository(db_session):
    """Test using the db_session fixture"""
    repo = UserRepository(db_session)
    user = repo.create(name="Alice", email="[email protected]")

    assert user.id is not None

Fixture Scopes

@pytest.fixture(scope="function")  # Default: per test
def user():
    return User(name="Alice")

@pytest.fixture(scope="class")  # Per test class
def database():
    db = Database()
    db.connect()
    yield db
    db.disconnect()

@pytest.fixture(scope="module")  # Per module
def app():
    return create_app()

@pytest.fixture(scope="session")  # Once per test session
def config():
    return load_config()

Fixture Dependencies

@pytest.fixture
def database():
    db = Database()
    db.connect()
    yield db
    db.disconnect()

@pytest.fixture
def user_repository(database):
    """Fixture that depends on database fixture"""
    return UserRepository(database)

def test_create_user(user_repository):
    user = user_repository.create(name="Alice")
    assert user.id is not None