PostMock

Instant Mock API Server Generator - Create mock servers from Postman collections or OpenAPI specs in seconds!

PostMock is a powerful interactive CLI tool that instantly generates mock API servers from your existing Postman collections or OpenAPI specifications. Perfect for frontend development, testing, and prototyping when you need a working API server without waiting for backend implementation.

✨ Features

• 🚀 Instant Setup - Generate a mock server in seconds
• 📚 Multiple Formats - Support for Postman (.json) and OpenAPI (.yaml/.yml/.json)
• 🎭 Smart Mocking - Uses existing examples or generates realistic fake data
• 🔄 Dynamic Responses - Generate different responses for each request
• ⚡ Hot Reload - Automatically restart server when files change
• 🎯 CORS Support - Built-in CORS for frontend integration
• ⏱️ Delay Simulation - Simulate network latency
• 🐳 Docker Ready - Easy containerization
• 📊 Health Checks - Built-in health monitoring endpoints
• 💬 Interactive CLI - User-friendly prompts for all configuration options

🚀 Quick Start

Installation

npm install -g postmock

Basic Usage

Simply run the command and follow the interactive prompts:

postmock

The CLI will guide you through:

• Selecting your input file (Postman collection or OpenAPI spec)
• Choosing the port number
• Setting up delay simulation
• Enabling dynamic responses
• Configuring CORS
• Setting up hot reload

Example Interactive Session

🚀 Welcome to PostMock!
Generate mock API servers from Postman collections or OpenAPI specs

? Enter the path to your Postman collection (.json) or OpenAPI spec (.yaml/.json) file: examples/postman.json
? What port would you like to run the server on? 4000
? Enter simulated delay range in milliseconds (e.g., 100-300) or press Enter for no delay: 0
? Would you like to generate random responses for every request? No
? Enable CORS for cross-origin requests? Yes
? Enable hot reload to watch for file changes and restart server? No

✅ Mock API server running on http://localhost:4000

📖 Configuration Options

The interactive CLI will prompt you for the following settings:

Setting	Description	Default
Input File	Path to your Postman collection or OpenAPI spec	Required
Port	Port to run server on	4000
Delay Simulation	Simulated delay range in ms (e.g., 100-300)	0 (no delay)
Dynamic Responses	Generate random responses every request	false
CORS	Enable CORS for cross-origin requests	true
Hot Reload	Watch for file changes and restart server	false

🔧 Examples

Simple Mock Server

postmock
# Follow prompts to select your API file
# Server starts on default port 4000

Custom Configuration

postmock
# Select your OpenAPI spec file
# Choose port 5000
# Enable dynamic responses
# Set delay to 200-500ms
# Enable hot reload

📁 Input File Formats

Postman Collection

{
  "info": {
    "name": "My API Collection"
  },
  "item": [
    {
      "name": "Get Users",
      "request": {
        "method": "GET",
        "url": {
          "raw": "{{baseUrl}}/users",
          "host": ["{{baseUrl}}"],
          "path": ["users"]
        }
      },
      "response": [
        {
          "body": "{\"users\": [{\"id\": 1, \"name\": \"John Doe\"}]}"
        }
      ]
    }
  ]
}

OpenAPI Specification

openapi: 3.0.0
info:
  title: My API
  version: 1.0.0
paths:
  /users:
    get:
      summary: Get users
      responses:
        '200':
          description: Successful response
          content:
            application/json:
              example:
                users:
                  - id: 1
                    name: John Doe

🎯 Use Cases

Frontend Development

• Start building frontend immediately without waiting for backend
• Test API integrations with realistic data
• Develop offline-first applications

Testing & QA

• Create consistent test environments
• Test error handling with controlled responses
• Performance testing with configurable delays

Prototyping

• Demo API contracts to stakeholders
• Rapid API design iteration
• Proof of concept development

CI/CD

• Automated testing against mock APIs
• Consistent test environments
• No external dependencies

🔌 API Endpoints

Health Check

GET /_health

Returns server status and endpoint count.

Mock Endpoints

All endpoints defined in your input file will be automatically created with appropriate HTTP methods and paths.

🤝 Contributing

We welcome contributions! Please feel free to submit a Pull Request.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

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Happy Mocking! 🎭

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Made with ❤️ by Win Khant Aung