Integration Testing

Test how components work together.

API Integration Test

import { describe, test, expect } from 'vitest'; import request from 'supertest'; import { app } from '../app';

describe('POST /api/users', () => { test('creates user and returns 201', async () => { const response = await request(app) .post('/api/users') .send({ email: 'test@example.com', name: 'Test' });

expect(response.status).toBe(201);
expect(response.body.id).toBeDefined();
expect(response.body.email).toBe('test@example.com');

});

test('returns 400 for invalid email', async () => { const response = await request(app) .post('/api/users') .send({ email: 'invalid', name: 'Test' });

expect(response.status).toBe(400);
expect(response.body.error).toContain('email');

}); });

FastAPI Integration Test

import pytest from httpx import AsyncClient from app.main import app

@pytest.fixture async def client(): async with AsyncClient(app=app, base_url="http://test") as ac: yield ac

@pytest.mark.asyncio async def test_create_user(client: AsyncClient): response = await client.post( "/api/users", json={"email": "test@example.com", "name": "Test"} )

assert response.status_code == 201
assert response.json()["email"] == "test@example.com"

@pytest.mark.asyncio async def test_get_user_not_found(client: AsyncClient): response = await client.get("/api/users/nonexistent")

assert response.status_code == 404

Test Database Setup

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

@pytest.fixture(scope="function") def db_session(): """Fresh database per test.""" engine = create_engine("sqlite:///:memory:") Base.metadata.create_all(engine) Session = sessionmaker(bind=engine) session = Session()

yield session

session.close()
Base.metadata.drop_all(engine)

React Component Integration

import { render, screen } from '@testing-library/react'; import userEvent from '@testing-library/user-event'; import { QueryClientProvider } from '@tanstack/react-query';

test('form submits and shows success', async () => { const user = userEvent.setup();

render( <QueryClientProvider client={queryClient}> <UserForm /> </QueryClientProvider> );

await user.type(screen.getByLabelText('Email'), 'test@example.com'); await user.click(screen.getByRole('button', { name: /submit/i }));

expect(await screen.findByText(/success/i)).toBeInTheDocument(); });

Coverage Targets

Area Target

API endpoints 70%+

Service layer 80%+

Component interactions 70%+

Key Decisions

Decision Recommendation

Database In-memory SQLite or test container

Execution < 1s per test

External APIs MSW (frontend), VCR.py (backend)

Cleanup Fresh state per test

Common Mistakes

• Shared test database state

• No transaction rollback

• Testing against production APIs

• Slow setup/teardown

Related Skills

• unit-testing

• Isolated tests

• msw-mocking

• Network mocking

• e2e-testing

• Full flow testing

Capability Details

api-testing

Keywords: api, endpoint, httpx, testclient Solves:

• Test FastAPI endpoints

• Integration test patterns

• API contract testing

database-testing

Keywords: database, fixture, transaction, rollback Solves:

• Test database operations

• Use transaction rollback

• Create test fixtures

test-plan-template

Keywords: plan, template, strategy, coverage Solves:

• Integration test plan template

• Coverage strategy

• Test organization