@applicaster/zapp-react-dom-app/Polyfills/DeviceEventEmitter/__tests__/deviceEventEmitter.test.js

Zapp App Component for Applicaster's Quick Brick React Native App

const { DeviceEventEmitter } = require("../index");

describe("DeviceEventEmitter polyfill", () => {
  const listener = jest.fn();
  const listener2 = jest.fn();
  const listener3 = jest.fn();

  const EVENT_1 = "event_1";
  const EVENT_2 = "event_2";

  beforeEach(() => {
    DeviceEventEmitter.reset();
    listener.mockClear();
    listener2.mockClear();
    listener3.mockClear();
  });

  it("is an object", () => {
    expect(DeviceEventEmitter).toHaveProperty("addListener");
    expect(DeviceEventEmitter).toHaveProperty("emitEvent");

    expect(DeviceEventEmitter.addListener).toBeFunction();
    expect(DeviceEventEmitter.emitEvent).toBeFunction();
  });

  it("adds listeners", () => {
    const initialListeners = DeviceEventEmitter.getListeners();
    expect(initialListeners).toEqual({});

    DeviceEventEmitter.addListener(EVENT_1, listener);

    expect(DeviceEventEmitter.getListeners()).toEqual({
      [EVENT_1]: [listener],
    });

    DeviceEventEmitter.addListener(EVENT_1, listener2);

    expect(DeviceEventEmitter.getListeners()).toEqual({
      [EVENT_1]: [listener2, listener],
    });

    DeviceEventEmitter.addListener(EVENT_2, listener3);

    expect(DeviceEventEmitter.getListeners()).toEqual({
      [EVENT_1]: [listener2, listener],
      [EVENT_2]: [listener3],
    });
  });

  it("invokes the listeners when an event is being triggered", () => {
    const payload = { foo: "bar" };

    DeviceEventEmitter.addListener(EVENT_1, listener);
    DeviceEventEmitter.addListener(EVENT_1, listener2);
    DeviceEventEmitter.addListener(EVENT_2, listener3);

    DeviceEventEmitter.emitEvent(EVENT_1, payload);

    expect(listener).toHaveBeenCalledWith(payload);
    expect(listener2).toHaveBeenCalledWith(payload);
    expect(listener3).not.toHaveBeenCalled();
  });

  it("removes the listener", () => {
    const removeListener = DeviceEventEmitter.addListener(EVENT_1, listener);
    const removeListener2 = DeviceEventEmitter.addListener(EVENT_1, listener2);
    const removeListener3 = DeviceEventEmitter.addListener(EVENT_2, listener3);

    expect(removeListener).toHaveProperty("remove");
    expect(removeListener.remove).toBeFunction();
    expect(removeListener2).toHaveProperty("remove");
    expect(removeListener2.remove).toBeFunction();
    expect(removeListener3).toHaveProperty("remove");
    expect(removeListener3.remove).toBeFunction();

    expect(DeviceEventEmitter.getListeners()).toEqual({
      [EVENT_1]: [listener2, listener],
      [EVENT_2]: [listener3],
    });

    removeListener.remove();

    expect(DeviceEventEmitter.getListeners()).toEqual({
      [EVENT_1]: [listener2],
      [EVENT_2]: [listener3],
    });

    removeListener3.remove();

    expect(DeviceEventEmitter.getListeners()).toEqual({
      [EVENT_1]: [listener2],
      [EVENT_2]: [],
    });

    removeListener2.remove();

    expect(DeviceEventEmitter.getListeners()).toEqual({
      [EVENT_1]: [],
      [EVENT_2]: [],
    });
  });
});