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eventEmitter.js
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285 lines (242 loc) · 7.04 KB
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import chai from 'chai';
import chaiAsPromised from 'chai-as-promised';
import { assert as assertInc } from '../counter.js';
import eventEmitter from '../../src/utils/eventEmitter.js';
chai.use(chaiAsPromised);
const expect = chai.expect;
describe('EventEmitter', () => {
let emitter = eventEmitter();
afterEach('Reset state', () => {
// TODO: Better way to clear events
emitter = eventEmitter();
});
afterEach(() => {
// Assert each function has asserted properly
assertInc(0, 'Failed to assert before finishing');
});
describe('the instance', () => {
it('is an object', () => {
expect(emitter).to.be.an.instanceOf(Object);
});
it('is immutable', () => {
expect(emitter).to.be.frozen;
});
it('has all properties', () => {
const properties = {
on: 'function',
once: 'function',
one: 'function',
until: 'function',
emit: 'function',
cancelable: 'this',
canceled: 'this',
singleton: 'this',
async: 'this',
};
Object.keys(properties).forEach((key) => {
expect(emitter).to.have.property(key);
const type = properties[key];
switch (type) {
case '': return;
case 'this':
expect(emitter[key]).to.equal(emitter);
break;
default:
expect(emitter[key]).to.be.a(type);
}
});
});
it('should be extendable', () => {
const emitter2 = {
...emitter,
};
['on', 'once', 'one', 'until'].forEach((key) => {
expect(emitter2[key]()).to.equal(emitter2);
});
});
});
describe('events', () => {
describe('on', () => {
it('should register');
it('should register different events');
it('should register multiple events');
it('should be chainable');
});
describe('emit', () => {
it('runs', () => {
emitter.on('test', () => {
expect().inc();
});
const res = emitter.emit('test');
expect(res.ran).to.be.true;
assertInc(1);
});
it('does not run', () => {
const { ran } = emitter.emit('test');
expect(ran).to.be.false;
});
it('runs multiple times', () => {
emitter.on('test', () => {
expect().inc();
});
// Not called yet
assertInc(0);
// Call twice
const { ran: emit1 } = emitter.emit('test');
const { ran: emit2 } = emitter.emit('test');
expect(emit1).to.be.true;
expect(emit2).to.be.true;
// Should now be 2
assertInc(2);
});
it('passes arguments', () => {
const args = [1, 2, 3];
emitter.on('test', (...rest) => {
expect(rest).to.deep.equal(args).and.inc();
});
emitter.emit('test', ...args);
assertInc(1);
});
it('passes an array', () => {
const args = [1, 2, 3];
emitter.on('test', (arg) => {
expect(arg).to.equal(args).and.inc();
});
emitter.emit('test', args);
assertInc(1);
});
});
describe('cancelable', () => {
it('should be canceled', () => {
emitter.on('test', function cancel() {
this.canceled = true;
expect(this.cancelable).to.be.true.and.inc();
});
const { canceled } = emitter.cancelable.emit('test');
expect(canceled).to.be.true;
assertInc(1);
});
it('should not be canceled', () => {
emitter.on('test', () => {});
const { canceled } = emitter.cancelable.emit('test');
expect(canceled).to.be.false;
});
it('should not be canceled if not cancelable', () => {
emitter.on('test', function cancel() {
expect(this.cancelable).to.be.false.and.inc();
this.canceled = true;
});
const { canceled } = emitter.emit('test');
expect(canceled).to.be.false;
assertInc(1);
});
});
describe('canceled', () => {
function test() {
expect(this.cancelable).to.be.true.and.inc();
expect(this.canceled).to.be.true.and.inc();
}
it('is canceled from the start', () => {
emitter.on('test', test);
const { canceled } = emitter.canceled.emit('test');
expect(canceled).to.be.true;
assertInc(2);
});
it('should no longer be canceled', () => {
emitter.on('test', function cancel() {
test.call(this);
this.canceled = false;
});
const { canceled } = emitter.canceled.emit('test');
expect(canceled).to.be.false;
assertInc(2);
});
it('is canceled even if not ran', () => {
const { canceled } = emitter.canceled.emit('test');
expect(canceled).to.be.true;
});
});
describe('async', () => {
it('should return a promise');
it('should run');
it('should be cancelable');
it('should be canceled');
it('should not be canceled');
it('should be delayed');
it('should retain the awaited value');
});
describe('singleton', () => {
it('should emit once', () => {
emitter.on('test', () => {
expect().inc();
});
emitter.singleton.emit('test'); // Initial call
emitter.singleton.emit('test'); // Try to call again
emitter.emit('test'); // Try to call without singleton
assertInc(1);
});
it('should emit on delay', (done) => {
emitter.singleton.emit('test');
emitter.on('test', () => {
expect().inc();
});
setTimeout(() => {
assertInc(1);
done();
}, 1);
});
it.skip('should call again if reset');
});
describe('once', () => {
it('should be called once', () => {
emitter.once('test', () => {
expect().inc();
});
emitter.emit('test');
emitter.emit('test');
assertInc(1);
});
});
describe('one', () => {
it('should be called once', () => {
emitter.one('test', () => {
expect().inc();
});
emitter.emit('test');
emitter.emit('test');
assertInc(1);
});
});
describe('until', () => {
it('should be called thrice', () => {
emitter.until('test', (count) => {
expect().inc();
return count === 3;
});
for (let i = 0; i < 5; i++) {
emitter.emit('test', i + 1);
}
// Event is called 5 times, callback is only 3
assertInc(3);
});
it('should be called thrice (async)');
});
describe('off', () => {
it('should be called until turned off', () => {
function callback() {
expect().inc();
}
emitter.on('test', callback);
emitter.emit('test');
assertInc(1);
emitter.off('test', callback);
emitter.emit('test');
assertInc(0);
});
});
});
describe('Extend', () => {
it('should override on');
it('should still process parent emit');
});
});