api-testing

API Testing

Expert knowledge for testing HTTP APIs with Supertest (TypeScript/JavaScript) and httpx/pytest (Python).

When to Use This Skill

Use this skill when...	Use configure-plugin:configure-api-tests instead when...
Writing Supertest endpoint tests against an Express/Fastify app	Setting up Pact consumer/provider contract testing infrastructure
Writing httpx + pytest tests for a Python REST/GraphQL API	Validating an OpenAPI specification or wiring schema (Zod/AJV) checks into CI
Validating request/response shapes, status codes, and auth flows in test code	Auditing or scaffolding API contract testing tooling for a project
Asserting error handling (4xx/5xx) and integration state in functional tests	Adding breaking-change detection workflows to CI

Core Expertise

API Testing Capabilities

• Request testing: Headers, query params, request bodies
• Response validation: Status codes, headers, JSON schemas
• Authentication: Bearer tokens, cookies, OAuth flows
• Error handling: 4xx/5xx responses, validation errors
• Integration: Database state, external services
• Performance: Response times, load testing basics

TypeScript/JavaScript (Supertest)

Installation

# Using Bun
bun add -d supertest @types/supertest

# Using npm
npm install -D supertest @types/supertest

Basic Setup with Express

// app.ts
import express from 'express'

export const app = express()
app.use(express.json())

app.get('/api/health', (req, res) => {
  res.json({ status: 'ok' })
})

app.post('/api/users', (req, res) => {
  const { name, email } = req.body
  if (!name || !email) {
    return res.status(400).json({ error: 'Missing required fields' })
  }
  res.status(201).json({ id: 1, name, email })
})

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

describe('API Tests', () => {
  it('returns health status', async () => {
    const response = await request(app)
      .get('/api/health')
      .expect(200)

    expect(response.body).toEqual({ status: 'ok' })
  })

  it('creates a user', async () => {
    const response = await request(app)
      .post('/api/users')
      .send({ name: 'John Doe', email: '[email protected]' })
      .expect(201)

    expect(response.body).toMatchObject({
      id: expect.any(Number),
      name: 'John Doe',
      email: '[email protected]',
    })
  })

  it('validates required fields', async () => {
    const response = await request(app)
      .post('/api/users')
      .send({ name: 'John Doe' })
      .expect(400)

    expect(response.body.error).toBeDefined()
  })
})