@use-everywhere/test-utils

Test seams for use-everywhere: run several simulated tabs in one process, with no browser and no globals.

pnpm add -D @use-everywhere/test-utils

import { createScenario } from "@use-everywhere/test-utils";

it("two tabs converge", async () => {
  const browser = createScenario();
  const cartA = browser.tab().store("cart", { items: 0 });
  const cartB = browser.tab().store("cart", { items: 0 });

  cartA.set("items", 3);
  await browser.settle();

  expect(cartB.getSnapshot().items).toBe(3);
  browser.dispose();
});

Close is not crash

The reason multi-tab code is hard is that a tab can leave in two ways, and only one of them says goodbye. Both are one call here:

const browser = createScenario();
const a = browser.tab();
const b = browser.tab();
const first = a.leader("app");
const second = b.leader("app");

a.crash(); // the wire is cut mid-sentence: no goodbye, no resignation
await browser.settle();

expect(second.getSnapshot().isLeader).toBe(true); // the platform reclaimed the seat

close() closes the primitives and then the wire, so peers are told. crash() closes the wire first and reclaims the tab's Web Locks, so peers have to notice — which is the path that finds the bugs.

What's in the box

| Export | What it is | | ------------------------------ | -------------------------------------------------------------------------------- | | createScenario(options?) | One simulated browser: a shared hub, shared Web Locks, and tabs | | FakeLockManager | navigator.locks with FIFO queueing and reclamation on crash | | FakeWindow, fakeWindowPair | Enough Window for openWindow / connectToOpener, including hostile messages | | tick, snapshotWindow | The two waits that matter: delivery, and the late-joiner snapshot window | | MemoryHub, MemoryTransport | Re-exported from @use-everywhere/core/testing — same classes, one import |

createScenario({ election: 'heartbeat' }) runs the election that plain-http origins get, where Web Locks does not exist. Test both if you ship to one.

One primitive per name per tab

A Tab is a lifecycle group. Each primitive created through it gets its own connection to the hub — the same shape a real tab has when it uses several bus names — so a presence and a store created on one name in one tab announce themselves as two clients. Keep one primitive per name per tab and the simulation matches a browser exactly.

Docs

Testing guide

License

MIT © Jonatan Kruszewski