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