livebook/assets/test/lib/pubsub.test.js

import PubSub from "../../js/lib/pubsub";

test("subscribed callback is called on the specified topic", () => {
  const pubsub = new PubSub();
  const callback1 = jest.fn();
  const callback2 = jest.fn();

  pubsub.subscribe("topic1", callback1);
  pubsub.subscribe("topic2", callback2);
  pubsub.broadcast("topic1", { data: 1 });

  expect(callback1).toHaveBeenCalledWith({ data: 1 });
  expect(callback2).not.toHaveBeenCalled();
});

test("subscribe returns a subscription object that can be destroyed", () => {
  const pubsub = new PubSub();
  const callback1 = jest.fn();

  const subscription = pubsub.subscribe("topic1", callback1);
  subscription.destroy();
  pubsub.broadcast("topic1", {});

  expect(callback1).not.toHaveBeenCalled();
});