MCP Hello World Test Server

A minimal Model Context Protocol (MCP) server implementation designed specifically as a test double/mock server for testing MCP client code. This server provides predictable, simple responses that make it easy to write assertions in unit and integration tests.

Purpose

This skill is **not for production use**. It serves as a lightweight, controllable MCP server for testing scenarios where you need to:

When to Use This Skill

Use this skill when you need to:

1. **Test MCP client implementations** - Verify your client correctly handles MCP protocol messages

2. **Debug MCP integrations** - Manually inspect request/response flows

3. **Develop against MCP** - Work on MCP features without requiring a full AI service

4. **Validate protocol coverage** - Test client behavior across different transport modes

Installation

Install as a development dependency:

```bash

npm install --save-dev mcp-hello-world

or

pnpm add --save-dev mcp-hello-world

or

bun add --dev mcp-hello-world

```

Running the Server

STDIO Mode (Recommended for Testing)

Run directly via npx or equivalent:

```bash

npx mcp-hello-world

or

pnpm dlx mcp-hello-world

or

bunx mcp-hello-world

```

The server listens on stdin and writes MCP responses to stdout. Connect using MCP Inspector or your client code.

HTTP/SSE Mode (Network Testing)

For HTTP-based clients:

```bash

Build first

pnpm build # or bun run build

Start HTTP server

pnpm start:http # or bun run start:http

```

Server runs on `http://localhost:3000` with:

Available Test Capabilities

The server provides these fixed MCP capabilities for testing:

Resources

**Static Resource: `hello://world`**

**Dynamic Resource: `greeting://{name}`**

Tools

**Tool: `echo`**

**Tool: `debug`**

Prompts

**Prompt: `helpful-assistant`**

Testing Example (Node.js + Jest/Vitest)

```typescript

import { spawn } from 'child_process';

import { MCPClient } from '../src/my-mcp-client';

describe('MCP Client Tests', () => {

let serverProcess;

let client: MCPClient;

beforeAll(() => {

// Spawn mcp-hello-world server

serverProcess = spawn('npx', ['mcp-hello-world']);

// Connect your client to the spawned process

client = new MCPClient(serverProcess.stdin, serverProcess.stdout);

});

afterAll(() => {

serverProcess.kill();

});

it('echoes messages with Hello prefix', async () => {

const response = await client.sendRequest({

jsonrpc: '2.0',

id: 1,

method: 'tools/invoke',

params: { name: 'echo', parameters: { message: 'test' } }

});

expect(response.result.content[0].text).toBe('Hello test');

});

it('retrieves greeting resource', async () => {

const response = await client.sendRequest({

jsonrpc: '2.0',

id: 2,

method: 'resources/get',

params: { uri: 'greeting://Bob' }

});

expect(response.result.data).toBe('Hello Bob!');

});

});

```

Important Notes

Benefits for Testing

1. **Isolation** - Test client logic without external service dependencies

2. **Predictability** - Fixed responses simplify test assertions

3. **Speed** - Fast startup and response times for rapid test cycles

4. **Lightweight** - Minimal dependencies reduce test environment complexity

5. **Protocol Coverage** - Verify client behavior across transport mechanisms

Source

Package: `mcp-hello-world` (npm)

Repository: https://github.com/lobehub/mcp-hello-world