The MCP Server Testing Guide: How to Test Before You Ship

The MCP Server Testing Guide: How to Test Before You Ship Most MCP server tutorials skip testing entirely. That's fine for demos — not for anything you're going to install in production or distribute to users. Here's a practical testing approach. Unit Testing Tool Handlers Extract tool handler logic into pure functions that are easy to test: // Bad: logic buried in handler (hard to test) server.setRequestHandler(CallToolRequestSchema, async (request) => { if (request.params.name === 'get_price') { const data = await fetch(`https://api.example.com/price/${request.params.arguments.ticker}`); return { content: [{ type: 'text', text: JSON.stringify(await data.json()) }] }; } }); // Good: logic extracted (easy to test) export async function getPrice(ticker: string): Promise<{ price: number; currency: string }> { const res = await fetch(`https://api.example.com/price/${ticker}`); if (!res.ok) throw new Error(`API error: ${res.status}`); const data = await res.json(); return { price: