test-proxy-recorder

VCR for Playwright — record real API responses once, replay them deterministically on CI. Covers Next.js & TanStack Start SSR, browser, and WebSocket traffic. No backend, no hand-written mocks.

                Record mode                          Replay mode

  App ──> Proxy ──> Real API            App ──> Proxy ──> Disk
            │                                         │
            └──> saves to disk                        └──> serves saved responses
                 (.mock.json)                              (.mock.json)

Why

Every flaky e2e run has the same root cause: the network. This records real traffic once, then replays it byte-for-byte on CI — so tests pass with the backend off.

• No backend on CI — replay from disk, no network.
• No manual mocks — capture real interactions, never hand-write fixtures.
• SSR + browser + WebSocket — record wherever requests originate.

Comparison

test-proxy-recorder is the one that records real traffic across SSR, browser, and WebSockets without hand-written mocks — that combination is the gap the others leave open.

Feature	test-proxy-recorder	routeFromHAR	MSW	Polly.js	playwright-network-cache	Mocky Balboa
Record real traffic	✅	✅	❌	✅	✅	❌
Server-side (SSR)	✅	❌	✅	⚠️	❌	✅
Browser-side	✅	✅	✅	✅	✅	✅
WebSocket	✅	❌	✅	❌	❌	❌
Playwright-native	✅	✅	❌	❌	✅	✅
Maintained	✅	✅	✅	❌	✅	✅

⚠️ Polly.js intercepts Node HTTP, so SSR mocking is possible inside the app process, but not as part of a Playwright run. MSW and Mocky Balboa replay real responses too — but you hand-write the mocks rather than recording them.

See the full comparison in the docs — including when to reach for something else.

Quick start

Fastest path — hand it to your AI coding agent. Copy this, swap in your backend URL, and paste it into Claude Code / Cursor / etc. (it runs init and finishes the wiring):

# Set up test-proxy-recorder for end-to-end tests in this project, then follow the instructions that `init` prints. Run these commands:
  npm install --save-dev test-proxy-recorder
  npx @tanstack/intent@latest install
  npx test-proxy-recorder init http://localhost:3002 --port 8100 --dir ./e2e/recordings
# Then complete the steps init prints: point the app's API base URL at the proxy in dev/test only, tag server-side fetches (Next.js), add a smoke test, and verify record → replay.

Prefer to wire it by hand:

npm install --save-dev test-proxy-recorder
npx test-proxy-recorder init http://localhost:3002 --port 8100 --dir ./e2e/recordings

init scaffolds everything non-destructively: proxy config, a Playwright fixture, a global teardown, package.json scripts, and (on Next.js) wires SSR fetch tagging into your root layout via registerProxyFetch(). It finishes by printing a tailored AI-agent prompt for the app-specific steps it can't guess.

The one thing init can't guess is which env var holds your API base URL. Point it at the proxy when the recorder is enabled, at the real backend otherwise — the proxy never runs in production:

const API_BASE =
  process.env.NODE_ENV === 'production' && !process.env.TEST_PROXY_RECORDER_ENABLED
    ? 'https://api.example.com'
    : 'http://localhost:8100'; // proxy address from `init`

Then set MODE = 'record', run once against the real API, flip to 'replay', and commit e2e/recordings/. CI now runs with the backend off.

Full walkthrough: quick start · manual setup.

Did that just save you an afternoon of hand-writing mocks? A ⭐ on GitHub takes one second and is how the next person fighting flaky e2e tests finds this. I'm a solo maintainer and read every star as a signal to keep going.

Examples

Full working apps in apps/, each with its own README:

• Next.js 16 — SSR + browser + WebSocket chat
• Next.js Edge runtime — registerProxyFetch for concurrent replay
• TanStack Start — SSR + browser, TanStack Query, ISR, WebSocket, and a real Cognito login
• Chrome extension — browser-only, replayed offline
• Crypto ticker — third-party WebSocket feed
• Authenticated app — real Cognito login, protected API replayed

Docs

Everything else lives at test-proxy-recorder.dev/docs: how it works, CLI, config, secret redaction, Next.js integration, TanStack Start integration, API reference, FAQ.

Using an AI coding agent? npx @tanstack/intent@latest install adds skills so it generates correct setup code. See the AI agent skills guide.

Requirements

• Node.js >= 20.0.0
• @playwright/test >= 1.0.0 (peer dependency)

Feedback & contributing

This is built and maintained in the open by one person, and every bit of feedback steers what gets built next:

• ⭐ Star the repo — the fastest way to support it, and it genuinely helps others discover it.
• Hit a rough edge or have an idea? Open an issue or say hi in Discord — even a one-line "this confused me" is gold.
• Want to contribute? PRs welcome.

AI skill

Using an AI coding agent (Claude Code, Cursor, Copilot, …)? The library ships @tanstack/intent skills so the agent generates correct setup code. Install the package, then write the agent guidance:

npm install --save-dev test-proxy-recorder
npx @tanstack/intent@latest install

install adds skill-discovery guidance to your agent config (CLAUDE.md, .cursorrules, …); the agent loads the proxy-setup, nextjs-ssr, and tanstack-start skills on demand. List or load them directly with npx @tanstack/intent@latest list and npx @tanstack/intent@latest load test-proxy-recorder#proxy-setup. Full guide: AI agent skills.

The skill sources live in packages/test-proxy-recorder/skills/.

License

MIT