What is Mcp Testing Kit

mcp-testing-kit is a testing library designed specifically for testing Model Context Protocol (MCP) servers, providing utilities to connect, send requests, receive notifications, and assert server behavior.

Use cases

Use cases for mcp-testing-kit include unit testing of MCP server functionalities, integration testing for end-to-end scenarios, and automated testing in CI/CD pipelines to maintain code quality.

How to use

To use mcp-testing-kit, install it via npm with the command $ npm i -D mcp-testing-kit. Then, you can write tests using your preferred testing framework, such as vitest or jest, to connect to your MCP server and validate its functionality.

Key features

Key features of mcp-testing-kit include compatibility with any testing framework, a lightweight design that provides essential utilities for testing MCP servers, and support for TypeScript.

Where to use

mcp-testing-kit is used in software development environments where MCP servers are implemented, particularly in testing scenarios to ensure server functionality and reliability.

mcp-testing-kit

The testing library you need to test your MCP servers.

Overview

mcp-testing-kit provides utilities to test Model Context Protocol (MCP) servers. It allows you to connect to an MCP server instance, send requests, receive notifications, and assert server behavior in your tests.

Features

• Works with any testing framework (vitest, jest etc)
• Lightweight, provides “just enough” utils to test an MCP server.
• Typescript

Installation

$ npm i -D mcp-testing-kit

Example

Suppose you have an MCP server defined in example/basic/src/index.ts:

// mcp-server.ts
import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { z } from "zod";

const server = new McpServer({ name: 'simple-mcp-server', version: '1.0.0' });

server.tool(
  'add',
  'Add two numbers MCP style',
  { 
    a: z.number().describe('first number'), 
    b: z.number().describe('second number') 
  },
  async ({ name }) => ({
    messages: [
      { role: 'user', content: { type: 'text', text: String(a + b) } }
    ]
  })
);

export default server;

You can write a test using mcp-testing-kit like this:

// mcp-server.test.js
import server from "../src/index.js";
// Use your favorite testing framework.
import { describe, it, expect, afterEach } from "vitest";
import { connect, close } from "../../../index.js";

describe("Basic MCP server", () => {
  afterEach(async () => {
    await close(server);
  });

  it("Should return correct sum when `sum` is called", async () => {
    // Connect to the server and create a mock client.
    const client = await connect(server);
    const result = await client.callTool("greeting-template", { a: 10, b: 2 });
    expect(result.content[0].text).toEqual("12");
  });
});

How it works

• Creates a dummy transport layer to connect to the MCP Server directly instead of relying on HTTP/SSE.
• Provides abstractions for invoking the tools/resources/prompts directly on the server.

API

connect(server: Server)

Connects to an MCP server instance and returns a client with the following methods:

close(server: Server)

Closes the MCP server instance.

More Examples

See example/basic for a full-featured MCP server and corresponding tests.

License

MIT