pubsub.spec.js

/* eslint-env jest */
const pubsub = require("./pubsub");

describe("PubSub", () => {
  let events;
  const callback = jest.fn();

  beforeEach(() => {
    events = pubsub();
    callback.mockClear();
  });

  it("has simple API", () => {
    const keys = Object.keys(events).sort().join();
    expect(keys).toBe("pub,sub");
  });

  it("passes data to callback", () => {
    events.sub(callback);
    events.pub("foo");

    expect(callback).toHaveBeenCalledTimes(1);
    expect(callback).toHaveBeenCalledWith("foo");
  });

  it("removes callback when it is unsubscibed", () => {
    const unSub = events.sub(callback);
    unSub();
    events.pub("foo");

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

  it("does not call a callback twice", () => {
    events.sub(callback);
    events.sub(callback);
    events.pub("foo");

    expect(callback).toHaveBeenCalledTimes(1);
    expect(callback).toHaveBeenCalledWith("foo");
  });

  it("does not leak on pub", () => {
    events.sub(callback);
    const result = events.pub("foo");

    expect(result).toBeUndefined();
  });
});