API Mock Server

API Mock Server

Instantly create a mock API server from an OpenAPI/Swagger spec.

Instructions

Step 1: Get the Spec

Accept from user:

• File path (JSON/YAML)
• URL to a spec
• Inline endpoint definitions → convert to OpenAPI 3.0

If no spec exists, help define endpoints interactively and generate one.

Step 2: Start the Mock Server

# Primary: Prism (Stoplight)
npx @stoplight/prism-cli mock <spec-file> --port ${PORT:-4010} --dynamic

# Alternative: json-server for simple REST
npx json-server --watch db.json --port ${PORT:-4010}

• --dynamic generates realistic fake data from schema constraints
• Default port: 4010

Step 3: Verify

# Test a sample endpoint
curl -s http://localhost:4010/api/resource | jq .

# List all routes (Prism logs them on startup)

Fallback: Custom Express Server

If prism is unavailable, generate a minimal Express server:

const express = require('express');
const app = express();
app.use(express.json());
// Auto-generate routes from spec...

Edge Cases

• CORS: Add --cors flag or set Access-Control-Allow-Origin: * for browser testing
• Auth mocking: Return 401 for endpoints with security schemes when no token provided
• Large specs: Prism handles them fine; json-server may need splitting
• Port conflicts: Check with lsof -i :<port> before starting

Security

• Mock servers are for development only — never expose to public internet
• Don't include real API keys or credentials in mock responses

Requirements

• Node.js 16+ (for npx)
• No API keys needed