Quickstart - ProdBreak

By the end of this page you’ll have a real test that points the Stripe SDK at a ProdBreak sandbox, forces a 402 card_declined, and asserts your code handles it — running locally and in CI.

We use Stripe here because everyone knows its 402. The flow is identical for every pack — swap stripe for twilio, github, deck, or your own pack and the control surface doesn’t change.

Install the CLI and your test plugin

The CLI spins up sandboxes; the plugin wires the sandbox into your test framework’s lifecycle.

Jest
Vitest
pytest

npm install --save-dev @prod-break/cli @prod-break/jest

npm install --save-dev @prod-break/cli @prod-break/vitest

pip install prod-break          # CLI + SDK
pip install prod-break-pytest   # the pytest fixture plugin

Start a sandbox

Run one Stripe sandbox locally. It prints a URL and an instance-minted key — the key authenticates you to this one isolated world.

npx prod-break run stripe
# ▸ sandbox ready   url=http://localhost:8801   key=pbw_3f9a…   pack=stripe@0.1.0

Your test plugin reads PRODBREAK_URL / PRODBREAK_KEY from the environment, so export what the CLI prints (or let the plugin spawn the instance for you — see Parallel workers).

Write your first test

The fixture hands you two things: client() — the real Stripe SDK, already pointed at this world — and a control handle (seed, faults, world, clock, webhooks, exogenous).

Jest
Vitest
pytest

sample.test.ts

import { useSandbox } from "@prod-break/jest";

const sandbox = useSandbox(); // installs reset() between tests

test("a declined card surfaces the vendor error to my code", async () => {
  const sb = sandbox();

  // arm the outcome your code must survive — out-of-band, fires on the next charge
  await sb.faults.arm("charges", "create", {
    status: 402,
    code: "card_declined",
    count: 1,
  });

  const stripe = sb.client(); // real Stripe SDK, base URL already repointed
  await expect(
    stripe.charges.create({ amount: 2000, currency: "usd", source: "tok_visa" }),
  ).rejects.toMatchObject({ code: "card_declined", statusCode: 402 });
});

sample.test.ts

import { test } from "@prod-break/vitest"; // injects a per-test `sandbox`

test("a declined card surfaces the vendor error to my code", async ({ sandbox }) => {
  // arm the outcome your code must survive — out-of-band, fires on the next charge
  await sandbox.faults.arm("charges", "create", {
    status: 402,
    code: "card_declined",
    count: 1,
  });

  const stripe = sandbox.client(); // real Stripe SDK, base URL already repointed
  await expect(
    stripe.charges.create({ amount: 2000, currency: "usd", source: "tok_visa" }),
  ).rejects.toMatchObject({ code: "card_declined", statusCode: 402 });
});

test_sample.py

import pytest

def test_declined_card_surfaces_vendor_error(stripe_sandbox):
    # arm the outcome your code must survive — out-of-band, fires on the next charge
    stripe_sandbox.faults.arm("charges", "create",
                              status=402, code="card_declined", count=1)

    stripe = stripe_sandbox.client()  # real Stripe SDK, base URL already repointed
    with pytest.raises(stripe.error.CardError):
        stripe.Charge.create(amount=2000, currency="usd", source="tok_visa")
    # stripe_sandbox resets the world automatically at test teardown

You armed the fault out of band rather than passing a magic input. That’s deliberate: it’s the one control that works even when unmodified app code — not your test — makes the call. See Connect your app.

Run it

Jest
Vitest
pytest

npx jest

npx vitest run

pytest

Green. You just tested an error path that’s a nuisance to trigger against the real Stripe — with no mocks to maintain and your app’s real SDK exercising the real wire format.

What just happened

One instance = one world. The CLI booted an isolated sandbox and minted its own key. Your test got that whole world to itself; the plugin reset()s it between tests so they stay independent. (Worlds →)
You forced a cause, the sandbox produced the effect. You armed a fault; ProdBreak returned Stripe’s real error envelope. You never hand-wrote a response body. (Forced outcomes →)
Your app didn’t change. Only the base URL moved. The Stripe SDK serialized, signed, and sent the exact request it always does. (Connect your app →)

Next steps

Seed history

Start a test from the exact state you need.

Test a webhook

Receive a real signed webhook and assert on it.

Force a failed branch

Drive a workflow down its failure arm on demand.

Make CI deterministic

Collapse durations so cascades fire inline, no flake.

​What just happened

​Next steps

Seed history

Test a webhook

Force a failed branch

Make CI deterministic

What just happened

Next steps