Integration & Contract Testing

Focused patterns for testing API boundaries, cross-service contracts, component integration, database layers, property-based verification, and schema validation.

Quick Reference

References

Checklists

Scripts & Templates

Examples

Stateful API Testing (emulate — FIRST CHOICE)

For GitHub, Vercel, and Google API integration tests, emulate is the first choice. It provides full state machines that model real API behavior — not static mocks.

See rules/emulate-stateful-testing.md for the full decision matrix, seed-start-test-assert pattern, and incorrect/correct examples.

Quick Start: API Integration Test

TypeScript (Supertest)

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');
  });
});

Python (FastAPI + httpx)

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"

Coverage Targets

Key Principles

1. Test at boundaries -- API inputs, database queries, service calls, external integrations
2. Fresh state per test -- In-memory databases, transaction rollback, no shared mutable state
3. Use matchers in contracts -- Like(), EachLike(), Term() instead of exact values
4. Property-based for invariants -- Roundtrip, idempotence, commutativity properties
5. Validate schemas at edges -- Zod .safeParse() at every API boundary
6. Evidence-backed completion -- Exit code 0, coverage reports, timestamps

When to Use This Skill

• Writing API endpoint tests (Supertest, httpx)
• Setting up React component integration tests with providers
• Creating database integration tests with isolation
• Implementing Pact consumer/provider contract tests
• Adding property-based tests with Hypothesis
• Validating Zod schemas at API boundaries
• Planning a testing strategy for a new feature or service

Related Skills

• ork:testing-unit — Unit testing patterns, fixtures, mocking
• ork:testing-e2e — End-to-end Playwright tests
• ork:emulate-seed — Seed configuration authoring for emulate providers
• ork:database-patterns — Database schema and migration patterns
• ork:api-design — API design patterns for endpoint testing