Integration Test Generator

Integration Test Generator

Generate comprehensive integration tests for Python applications that test multiple interacting components together.

When to Use Integration Tests

Integration tests verify that multiple components work correctly together:

• Service Integration: REST/GraphQL APIs communicating with each other
• Database Integration: Repositories, ORM models, transaction handling
• External Services: Payment gateways, email services, third-party APIs
• Event-Driven: Message queues, event publishers/consumers
• Full Stack: Complete workflows through multiple layers (API → business logic → database)

Test Structure

Basic Integration Test Template

import pytest
from myapp.services import ServiceA, ServiceB

class TestServiceIntegration:
    """Test integration between ServiceA and ServiceB."""

    @pytest.fixture
    def service_a(self):
        """Setup ServiceA with test configuration."""
        return ServiceA(config={"mode": "test"})

    @pytest.fixture
    def service_b(self, service_a):
        """Setup ServiceB that depends on ServiceA."""
        return ServiceB(service_a=service_a)

    def test_services_communicate_correctly(self, service_a, service_b):
        """Test that ServiceB correctly uses ServiceA."""
        # Arrange
        test_data = {"key": "value"}

        # Act
        service_a.store(test_data)
        result = service_b.process()

        # Assert
        assert result["key"] == "value"
        assert result["processed"] is True

Test Fixtures Pattern

Use fixtures to set up and tear down test dependencies:

@pytest.fixture(scope="function")
def db_session():
    """Create a fresh database for each test."""
    engine = create_engine("sqlite:///:memory:")
    Base.metadata.create_all(engine)
    Session = sessionmaker(bind=engine)
    session = Session()

    yield session  # Test runs here

    session.close()

@pytest.fixture
def test_user(db_session):
    """Create a test user and clean up after test."""
    user = User(username="testuser", email="test@example.com")
    db_session.add(user)
    db_session.commit()

    yield user

    db_session.delete(user)
    db_session.commit()

Common Integration Test Patterns

API Integration Tests

Test multiple API endpoints working together:

def test_create_user_then_create_order(test_client):
    # Create user
    user_response = test_client.post("/api/users", json={"username": "test"})
    user_id = user_response.json()["id"]

    # Create order for user
    order_response = test_client.post(
        "/api/orders",
        json={"user_id": user_id, "items": [...]}
    )

    # Verify integration
    assert order_response.status_code == 201
    assert order_response.json()["user_id"] == user_id

Database Integration Tests

Test repository interactions and transactions:

def test_user_order_relationship(db_session, user_repo, order_repo):
    # Create user
    user = user_repo.create(username="test")
    db_session.commit()

    # Create orders
    order1 = order_repo.create(user_id=user.id, total=50.00)
    order2 = order_repo.create(user_id=user.id, total=75.00)
    db_session.commit()

    # Verify relationship
    retrieved_user = user_repo.get_by_id(user.id)
    assert len(retrieved_user.orders) == 2

External Service Integration

Test integration with external APIs using mocks:

import responses

@responses.activate
def test_payment_integration():
    # Mock external payment API
    responses.add(
        responses.POST,
        "https://api.payment.com/charge",
        json={"transaction_id": "txn_123", "status": "success"},
        status=200
    )

    # Test integration
    payment_service = PaymentService()
    result = payment_service.charge(amount=99.99, card_token="tok_test")

    assert result["status"] == "success"
    assert len(responses.calls) == 1

Detailed Patterns and Examples

For comprehensive integration test patterns, see:

patterns.md - Detailed examples for:

• REST and GraphQL API integration
• Database and repository integration
• Transaction testing
• Message queue integration
• Full stack integration tests
• External service mocking

test_data.md - Test data builders and fixtures:

• Builder pattern for test data
• Database fixtures
• Factory pattern usage
• API response builders

Best Practices

1. Test Isolation

Each test should be independent:

@pytest.fixture(scope="function")  # New instance per test
def db_session():
    # Fresh database for each test
    engine = create_engine("sqlite:///:memory:")
    Base.metadata.create_all(engine)
    # ...

2. Setup and Teardown

Always clean up test data:

@pytest.fixture
def test_resource():
    # Setup
    resource = create_resource()

    yield resource

    # Teardown - always runs even if test fails
    delete_resource(resource)

3. Use Test Builders

Create reusable test data builders:

def make_user(username="test", **kwargs):
    defaults = {"email": f"{username}@example.com", "is_active": True}
    return User(**{**defaults, **kwargs, "username": username})

# Usage
admin = make_user("admin", role="admin")
inactive = make_user("inactive", is_active=False)

4. Test Real Scenarios

Test complete user workflows:

def test_complete_checkout_workflow(test_client, db_session):
    # 1. Create user
    user = create_test_user()

    # 2. Add items to cart
    add_to_cart(user.id, product_id=1, quantity=2)

    # 3. Checkout
    order = checkout(user.id, payment_method="credit_card")

    # 4. Verify all integrations
    assert order.status == "confirmed"
    assert order.user_id == user.id
    assert len(order.items) == 1
    assert get_cart(user.id).items == []  # Cart emptied

5. Mock External Dependencies

Use mocks for external services to avoid network calls:

from unittest.mock import Mock, patch

def test_with_mocked_email_service():
    with patch('myapp.services.EmailService') as mock_email:
        mock_email.send.return_value = {"message_id": "123"}

        # Test code that uses email service
        result = send_confirmation_email("user@example.com")

        # Verify mock was called correctly
        mock_email.send.assert_called_once()
        assert result["message_id"] == "123"

Quick Reference

pytest Commands

# Run all integration tests
pytest tests/integration/

# Run specific test file
pytest tests/integration/test_user_order.py

# Run tests matching pattern
pytest -k "test_integration"

# Run with verbose output
pytest -v tests/integration/

# Run with coverage
pytest --cov=myapp tests/integration/

Common Fixtures

# Database session
@pytest.fixture(scope="function")
def db_session():
    """Fresh database for each test."""

# Test client for API testing
@pytest.fixture
def test_client():
    """Test client for FastAPI/Flask app."""
    with TestClient(app) as client:
        yield client

# Mock external service
@pytest.fixture
def mock_payment_gateway():
    with patch('myapp.services.PaymentGateway') as mock:
        yield mock

Assertion Patterns

# Verify status codes
assert response.status_code == 201

# Verify data structure
assert "id" in response.json()
assert len(response.json()["items"]) == 2

# Verify relationships
assert order.user_id == user.id
assert user.orders[0].id == order.id

# Verify side effects
assert email_service.send.called
assert db_session.query(Order).count() == 1