Integration Testing

Test how components work together.

When to Use

• API endpoint testing
• Component interactions
• Service layer testing
• Database integration

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

Key Decisions

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