MCP Conformance Test Framework

A framework for testing MCP (Model Context Protocol) client implementations against the specification.

[!WARNING] This repository is a work in progress and is unstable. Join the conversation in the #conformance-testing-wg in the MCP Contributors discord.

Quick Start

Testing Clients

npm install
npm run start -- --command "tsx examples/clients/typescript/test1.ts" --scenario initialize

Testing Servers

npm run test:server -- --server-url http://localhost:3000/mcp --all

Overview

The conformance test framework validates MCP client implementations by:

1. Starting a test server for the specified scenario
2. Running the client implementation with the test server URL
3. Capturing MCP protocol interactions
4. Running conformance checks against the specification
5. Generating detailed test results

Usage

npm run start -- --command "<client-command>" --scenario <scenario-name>

• --command - The command to run your MCP client (can include flags)
• --scenario - The test scenario to run (e.g., "initialize")

The framework appends the server URL as the final argument to your command.

Test Results

Results are saved to results/<scenario>-<timestamp>/:

• checks.json - Array of conformance check results with pass/fail status
• stdout.txt - Client stdout output
• stderr.txt - Client stderr output

Example Clients

• examples/clients/typescript/test1.ts - Valid MCP client (passes all checks)
• examples/clients/typescript/test-broken.ts - Invalid client missing required fields (fails checks)

Available Scenarios

• initialize - Tests MCP client initialization handshake
  • Validates protocol version
  • Validates clientInfo (name and version)
  • Validates server response handling

Architecture

See src/runner/DESIGN.md for detailed architecture documentation.

Key Components

• Runner (src/runner/) - Orchestrates test execution and result generation
• Scenarios (src/scenarios/) - Test scenarios with custom server implementations
• Checks (src/checks.ts) - Conformance validation functions
• Types (src/types.ts) - Shared type definitions

Adding New Scenarios

1. Create a new directory in src/scenarios/<scenario-name>/
2. Implement the Scenario interface with start(), stop(), and getChecks()
3. Register the scenario in src/scenarios/index.ts

See src/scenarios/initialize/ for a reference implementation.