mocking-and-mcp-testing

name	Mocking and MCP Testing
description	Specialized guidelines on testing GLPI REST endpoints alongside the MCP Server protocol.

Mocking and testing the MCP Protocol

Purpose

The primary objective of testing this server is to ensure the MCP input payloads from natural language prompts are well parsed, structured, and executed without directly pinging a live GLPI REST API (which depends on tokens, passwords and strict network settings).

Methodology

1. Mock the Service logic (jest.mock)

You should avoid making realistic network HTTP requests from the glpi-client.ts. By abstracting src/services/, you test whether the src/tools/ correctly pass instructions.

import { myServiceFunction } from '../../services/glpi-client';
// Use jest to mock the imported dependency entirely
jest.mock('../../services/glpi-client');

2. Mocking Returns

You must manually specify what the mocked function should return as an asynchronous promise. E.g.:

const mockServiceFunction = myServiceFunction as jest.MockedFunction<typeof myServiceFunction>;
mockServiceFunction.mockResolvedValue({ status: 200, data: 'Mocked Ticket Object' });

3. Verify Formatting Tools

The Model Context Protocol requires tools to respond with an array of structured text. Always assert that tools return exactly:

{
    content: [
      {
        type: "text",
        text: expect.any(String) // Usually JSON serialized or formatted markdown
      }
    ]
}

4. Throw Errors to Verify Resiliency

Validate the catch {} mechanisms returning error strings instead of crashing the MCP Server.

mockServiceFunction.mockRejectedValue(new Error('GLPI API Timeout'));
// your expectations should verify that the MCP tool gracefully outputs the text: "Error: GLPI API Timeout".