@fetchproxy/test-helpers

Vitest mock utilities for @fetchproxy/server. Drop-in FetchproxyServer replacement that captures constructor options and exposes spy-able lifecycle + data methods — so you can assert what your FetchproxyTransport adapter is passing to the underlying server without spinning up a real WebSocket.

Why

Every downstream *-mcp repo that wraps @fetchproxy/server ends up re-implementing the same module-scoped ctorCalls array and ad-hoc MockFetchproxyServer class to verify it's threading options (keepAliveIntervalMs, bridgeReviveDelayMs, fetchTimeoutMs, …) through to the constructor. The keep-alive cohort of 0.8.1 PRs (zillow#87, redfin#77, compass#72, homes#49, onehome#46, opentable#57, resy#38) all carried near-identical copies of the same ~25 lines. This package hoists it once.

Install

npm install --save-dev @fetchproxy/test-helpers

vitest (>=1.0) and @fetchproxy/server are peer dependencies.

Usage

import { describe, it, expect, beforeEach, vi } from 'vitest';
import { createMockFetchproxyServer } from '@fetchproxy/test-helpers';

// Module-scoped so vi.mock's hoisted factory can close over it.
const helpers = createMockFetchproxyServer();

vi.mock('@fetchproxy/server', async () => {
  return { FetchproxyServer: helpers.MockServer };
});

beforeEach(() => helpers.reset());

it('passes keepAliveIntervalMs through to FetchproxyServer', async () => {
  const { FetchproxyTransport } = await import('../src/transport-fetchproxy.js');
  new FetchproxyTransport({ version: '0.0.0-test' });

  expect(helpers.getLastCtorOpts()?.keepAliveIntervalMs).toBe(25_000);
});

it('captures the Authorization header on the right URL', async () => {
  const { FetchproxyTransport } = await import('../src/transport-fetchproxy.js');
  const t = new FetchproxyTransport({ version: '0.0.0-test' });

  // Override the default empty-string stub on a specific test.
  const opts = helpers.getLastCtorOpts();
  // ...assert captureHeaders, then exercise:
  // (the MockServer instance's captureRequestHeader spy is on the
  // instance the transport just created; reach it via your transport's
  // public seams or override the spy before the call.)
});

API

createMockFetchproxyServer()

Returns { MockServer, ctorCalls, getLastCtorOpts, reset }:

| Field | Type | What it does | | ------------------- | ----------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------- | | MockServer | class | Drop into the vi.mock('@fetchproxy/server', ...) factory as FetchproxyServer. Constructed with new MockServer(opts). | | ctorCalls | FetchproxyServerOpts[] | Live, append-only list of every new MockServer(...) call's opts. Referentially stable across reset() (mutated in place). | | getLastCtorOpts() | () => FetchproxyServerOpts \| undefined | The most recent ctor opts; undefined when none. | | reset() | () => void | Clears ctorCalls in place and .mockClear()s every previously-created instance's spy methods. Call from beforeEach. |

MockFetchproxyServerInstance

Each new MockServer(opts) instance has these vi.fn()-backed spies (default stubs return undefined / empty string; tests override per case via mockResolvedValue / mockImplementation):

• listen() / close() — lifecycle no-ops.
• request() / fetch() — data verbs.
• captureRequestHeader() — header-capture verb.
• bridgeHealth() — health snapshot.

License

MIT.