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import createEventHub from '~/helpers/event_hub_factory';
describe('event bus factory', () => {
let eventBus;
beforeEach(() => {
eventBus = createEventHub();
});
afterEach(() => {
eventBus = null;
});
describe('underlying module', () => {
let mitt;
beforeEach(() => {
jest.resetModules();
jest.mock('mitt');
// eslint-disable-next-line global-require
mitt = require('mitt');
mitt.mockReturnValue(() => ({}));
const createEventHubActual = jest.requireActual('~/helpers/event_hub_factory').default;
eventBus = createEventHubActual();
});
it('creates an emitter', () => {
expect(mitt).toHaveBeenCalled();
});
});
describe('instance', () => {
it.each`
method
${'on'}
${'once'}
${'off'}
${'emit'}
`('binds $$method to $method ', ({ method }) => {
expect(typeof eventBus[method]).toBe('function');
expect(eventBus[method]).toBe(eventBus[`$${method}`]);
});
});
describe('once', () => {
const event = 'foobar';
let handler;
beforeEach(() => {
jest.spyOn(eventBus, 'on');
jest.spyOn(eventBus, 'off');
handler = jest.fn();
eventBus.once(event, handler);
});
it('calls on internally', () => {
expect(eventBus.on).toHaveBeenCalled();
});
it('calls handler when event is emitted', () => {
eventBus.emit(event);
expect(handler).toHaveBeenCalled();
});
it('calls off when event is emitted', () => {
eventBus.emit(event);
expect(eventBus.off).toHaveBeenCalled();
});
it('calls the handler only once when event is emitted multiple times', () => {
eventBus.emit(event);
eventBus.emit(event);
expect(handler).toHaveBeenCalledTimes(1);
});
describe('when the handler thows an error', () => {
beforeEach(() => {
handler = jest.fn().mockImplementation(() => {
throw new Error();
});
eventBus.once(event, handler);
});
it('calls off when event is emitted', () => {
expect(() => {
eventBus.emit(event);
}).toThrow();
expect(eventBus.off).toHaveBeenCalled();
});
});
});
});
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