@arcote.tech/arc-testing

In-process test harness for Arc. Write use-case-shaped tests on bun:test using the same scope API the client uses — no port, no mocks of the framework, full type inference from your context.

import { createHarness } from "@arcote.tech/arc-testing";

const h = await createHarness(myContext);

// declare current state
await h.seed.rows("plan", [{ _id: "plan_pro", price: 4900 }]);

// an authenticated actor — the SAME scope API as the app
const creator = h.scope(userToken, { projectId });

await creator.mutation().startCheckout({ projectId, planId: "plan_pro" });
const order = await creator.query().paymentOrder.findOne({ _id: orderId });

// a webhook / route, in-process (real route boundary, no port)
await h.route("payuWebhook", { orderId, status: "COMPLETED" });

// drain the async listener cascade deterministically (no setTimeout)
await h.settle();

// assert events + state with native bun:test expect
expect(h.events.ofType("subscriptionActivated")).toHaveLength(1);
expect(await creator.query().subscription.findOne({ _id: projectId }))
  .toMatchObject({ status: "active" });

API

| | | |---|---| | createHarness(context) | builds the harness (in-memory SQLite, declarative seeds run, listeners active) | | h.scope(token, params) | an authenticated scope — .mutation() (= client useMutation), .query() (= client useQuery, awaited rows) | | h.anonymous() | a scope with no identity (public caller) | | h.seed.rows(store, rows) | raw insert into a view/aggregate store (like withSeed); rows need _id | | h.seed.event(type, payload, { as }) | publish through real projection handlers (and listeners) | | h.route(name, body, { headers, token }) | invoke a route/webhook in-process (real verification + protection gate) | | h.settle() | resolve once the async listener cascade has fully drained | | h.events | typed log: .ofType(name), .last(name), .count(name), .all() |

mutation() / query() are the exact client ScopeAPI accessors (core's MutationExecutor / QueryAccessor) — element names, params, payloads and rows are all inferred from your context. No new naming layer, no any.

Recipe: testing the real billing buy-subscription-card (platform)

Prerequisites (one-time, user-gated):

1. Publish @arcote.tech/arc, @arcote.tech/arc-host, @arcote.tech/arc-testing to npm.
2. Add @arcote.tech/arc-testing to packages/billing devDependencies (npm, not link: — link: breaks the Docker build).

PayU-free reaction test (avoids the external gateway by injecting the domain event, then asserting the real billing listener cascade — grant → activation):

import { describe, it, expect, beforeEach } from "bun:test";
import { createHarness, type Harness } from "@arcote.tech/arc-testing";
import { getBillingContext } from "@ndt/billing";
import { userToken } from "@ndt/auth";

describe("buy-subscription-card (billing reaction)", () => {
  let h: Harness<ReturnType<typeof getBillingContext>>;
  const accountId = "acc_test";

  beforeEach(async () => { h = await createHarness(getBillingContext()); });

  it("paid order → grant → subscription activated", async () => {
    const user = h.scope(userToken, { accountId, role: "user" });

    // inject the 'payment completed' domain event with the caller's identity,
    // then let the real billingPaymentGrant → billingSubscriptionActivation chain run
    await h.seed.event(
      "paymentOrderCompleted",
      { _id: "order_1", userId: accountId, amountPLNGrosz: 4900, kind: "subscription" },
      { as: { tokenName: "user", params: { accountId, role: "user" } } },
    );
    await h.settle();

    expect(h.events.ofType("subscriptionActivated")).toHaveLength(1);
    const sub = await user.query().subscription.findOne({ _id: accountId });
    expect(sub).toMatchObject({ /* active subscription shape */ });
  });
});

For the full checkout-through-webhook flow (startCheckoutCardAsUser → payuWebhook), stub the PayU client the checkout/route modules call, then drive it with creator.mutation().startCheckoutCardAsUser(...) and h.route("payuWebhook", payuBody) exactly as the self-proof does (tests/buy-subscription-like.test.ts).