Agent skill

api-testing

HTTP API testing for TypeScript (Supertest) and Python (httpx, pytest). Test REST APIs, GraphQL, request/response validation, authentication, and error handling.

View SKILL.md on GitHub Repository

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Forks 14

Install this agent skill to your Project

npx add-skill https://github.com/secondsky/claude-skills/tree/main/plugins/api-testing/skills/api-testing

SKILL.md

API Testing

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

TypeScript/JavaScript (Supertest)

Installation

bash

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

# or: npm install -D supertest @types/supertest

Basic Setup

typescript

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: 'john@example.com' })
      .expect(201)

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

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

Request Methods

typescript

// GET
await request(app).get('/api/users').expect(200)

// POST with body
await request(app)
  .post('/api/users')
  .send({ name: 'John' })
  .expect(201)

// PUT
await request(app)
  .put('/api/users/1')
  .send({ name: 'Jane' })
  .expect(200)

// DELETE
await request(app).delete('/api/users/1').expect(204)

Headers and Query Parameters

typescript

// Set headers
await request(app)
  .get('/api/protected')
  .set('Authorization', 'Bearer token123')
  .expect(200)

// Query parameters
await request(app)
  .get('/api/users')
  .query({ page: 1, limit: 10 })
  .expect(200)

Authentication Testing

typescript

describe('Authentication', () => {
  let authToken: string

  beforeAll(async () => {
    const response = await request(app)
      .post('/api/auth/login')
      .send({ email: 'user@example.com', password: 'password123' })
      .expect(200)

    authToken = response.body.token
  })

  it('accesses protected endpoint', async () => {
    await request(app)
      .get('/api/protected')
      .set('Authorization', `Bearer ${authToken}`)
      .expect(200)
  })

  it('rejects without token', async () => {
    await request(app).get('/api/protected').expect(401)
  })
})

Error Handling

typescript

it('handles validation errors', async () => {
  const response = await request(app)
    .post('/api/users')
    .send({ email: 'invalid-email' })
    .expect(400)

  expect(response.body).toMatchObject({
    error: 'Validation failed',
    details: expect.any(Array),
  })
})

it('handles not found', async () => {
  await request(app).get('/api/users/999999').expect(404)
})

Python (httpx + pytest)

Installation

bash

uv add --dev httpx pytest-asyncio

Basic Setup

python

import pytest
from fastapi.testclient import TestClient
from main import app

client = TestClient(app)

def test_health_check():
    response = client.get("/api/health")
    assert response.status_code == 200
    assert response.json() == {"status": "ok"}

def test_create_user():
    response = client.post(
        "/api/users",
        json={"name": "John Doe", "email": "john@example.com"}
    )
    assert response.status_code == 201
    data = response.json()
    assert data["name"] == "John Doe"
    assert "id" in data

def test_not_found():
    response = client.get("/api/users/999")
    assert response.status_code == 404

Fixtures

python

@pytest.fixture
def auth_token(client):
    response = client.post(
        "/api/auth/login",
        json={"email": "user@example.com", "password": "password123"}
    )
    return response.json()["token"]

def test_protected_endpoint(client, auth_token):
    response = client.get(
        "/api/protected",
        headers={"Authorization": f"Bearer {auth_token}"}
    )
    assert response.status_code == 200

File Upload

python

def test_file_upload(client, tmp_path):
    test_file = tmp_path / "test.txt"
    test_file.write_text("test content")

    with open(test_file, "rb") as f:
        response = client.post(
            "/api/upload",
            files={"file": ("test.txt", f, "text/plain")}
        )

    assert response.status_code == 200

GraphQL Testing

typescript

it('queries GraphQL endpoint', async () => {
  const query = `
    query GetUser($id: ID!) {
      user(id: $id) { id name email }
    }
  `

  const response = await request(app)
    .post('/graphql')
    .send({ query, variables: { id: '1' } })
    .expect(200)

  expect(response.body.data.user).toMatchObject({
    id: '1',
    name: expect.any(String),
  })
})

Performance Testing

typescript

it('responds within acceptable time', async () => {
  const start = Date.now()
  await request(app).get('/api/users').expect(200)
  const duration = Date.now() - start
  expect(duration).toBeLessThan(100) // 100ms threshold
})

Best Practices

Group related endpoints in describe blocks
Reset database between tests
Validate status codes first
Check response structure
Test error message format
Mock external services
Test both happy path and error cases

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