integration-testing

Integration Testing Standards

Quick Navigation: Level 1: Quick Start (5 min) → Level 2: Implementation (30 min) → Level 3: Mastery (Extended)

Level 1: Quick Start (<2,000 tokens, 5 minutes)

Core Principles

1. Test Real Interactions: Verify actual communication between components
2. Isolated Environments: Use Docker containers for reproducible tests
3. Fast Feedback: Keep integration tests under 30 seconds when possible
4. Contract Testing: Verify API contracts between services
5. Database Testing: Test with real databases, not mocks

Essential Checklist

• Testcontainers: Docker-based test dependencies (database, cache, message queue)
• API testing: REST/GraphQL endpoints tested with real HTTP
• Database migrations: Test schema migrations and rollbacks
• Contract tests: Provider-consumer contract verification
• Test data management: Fixtures and cleanup strategies
• Service mocking: External services mocked with WireMock/MockServer
• Docker Compose: Test environment orchestration
• CI integration: Tests run in isolated containers

Quick Example

# pytest integration test with Testcontainers
import pytest
from testcontainers.postgres import PostgresContainer
from sqlalchemy import create_engine
import requests

@pytest.fixture(scope="module")
def postgres_container():
    """Start PostgreSQL container for testing."""
    with PostgresContainer("postgres:16") as postgres:
        yield postgres

@pytest.fixture
def db_engine(postgres_container):
    """Create database engine with test container."""
    connection_url = postgres_container.get_connection_url()
    engine = create_engine(connection_url)
    # Run migrations
    run_migrations(engine)
    yield engine
    engine.dispose()

def test_create_user_integration(db_engine):
    """Test user creation with real database."""
    # Arrange
    user_data = {'email': '[email protected]', 'name': 'Test User'}

    # Act
    response = requests.post('http://localhost:8000/api/users', json=user_data)

    # Assert
    assert response.status_code == 201
    user_id = response.json()['id']

    # Verify in database
    with db_engine.connect() as conn:
        result = conn.execute("SELECT * FROM users WHERE id = %s", (user_id,))
        user = result.fetchone()
        assert user['email'] == '[email protected]'