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diff --git a/remote/test/puppeteer/packages/puppeteer-core/src/common/EventEmitter.test.ts b/remote/test/puppeteer/packages/puppeteer-core/src/common/EventEmitter.test.ts
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+/**
+ * @license
+ * Copyright 2023 Google Inc.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {describe, it, beforeEach} from 'node:test';
+
+import expect from 'expect';
+import sinon from 'sinon';
+
+import {EventEmitter} from './EventEmitter.js';
+
+describe('EventEmitter', () => {
+ let emitter: EventEmitter<Record<string, unknown>>;
+
+ beforeEach(() => {
+ emitter = new EventEmitter();
+ });
+
+ describe('on', () => {
+ const onTests = (methodName: 'on' | 'addListener'): void => {
+ it(`${methodName}: adds an event listener that is fired when the event is emitted`, () => {
+ const listener = sinon.spy();
+ emitter[methodName]('foo', listener);
+ emitter.emit('foo', undefined);
+ expect(listener.callCount).toEqual(1);
+ });
+
+ it(`${methodName} sends the event data to the handler`, () => {
+ const listener = sinon.spy();
+ const data = {};
+ emitter[methodName]('foo', listener);
+ emitter.emit('foo', data);
+ expect(listener.callCount).toEqual(1);
+ expect(listener.firstCall.args[0]).toBe(data);
+ });
+
+ it(`${methodName}: supports chaining`, () => {
+ const listener = sinon.spy();
+ const returnValue = emitter[methodName]('foo', listener);
+ expect(returnValue).toBe(emitter);
+ });
+ };
+ onTests('on');
+ // we support addListener for legacy reasons
+ onTests('addListener');
+ });
+
+ describe('off', () => {
+ const offTests = (methodName: 'off' | 'removeListener'): void => {
+ it(`${methodName}: removes the listener so it is no longer called`, () => {
+ const listener = sinon.spy();
+ emitter.on('foo', listener);
+ emitter.emit('foo', undefined);
+ expect(listener.callCount).toEqual(1);
+ emitter.off('foo', listener);
+ emitter.emit('foo', undefined);
+ expect(listener.callCount).toEqual(1);
+ });
+
+ it(`${methodName}: supports chaining`, () => {
+ const listener = sinon.spy();
+ emitter.on('foo', listener);
+ const returnValue = emitter.off('foo', listener);
+ expect(returnValue).toBe(emitter);
+ });
+ };
+ offTests('off');
+ // we support removeListener for legacy reasons
+ offTests('removeListener');
+ });
+
+ describe('once', () => {
+ it('only calls the listener once and then removes it', () => {
+ const listener = sinon.spy();
+ emitter.once('foo', listener);
+ emitter.emit('foo', undefined);
+ expect(listener.callCount).toEqual(1);
+ emitter.emit('foo', undefined);
+ expect(listener.callCount).toEqual(1);
+ });
+
+ it('supports chaining', () => {
+ const listener = sinon.spy();
+ const returnValue = emitter.once('foo', listener);
+ expect(returnValue).toBe(emitter);
+ });
+ });
+
+ describe('emit', () => {
+ it('calls all the listeners for an event', () => {
+ const listener1 = sinon.spy();
+ const listener2 = sinon.spy();
+ const listener3 = sinon.spy();
+ emitter.on('foo', listener1).on('foo', listener2).on('bar', listener3);
+
+ emitter.emit('foo', undefined);
+
+ expect(listener1.callCount).toEqual(1);
+ expect(listener2.callCount).toEqual(1);
+ expect(listener3.callCount).toEqual(0);
+ });
+
+ it('passes data through to the listener', () => {
+ const listener = sinon.spy();
+ emitter.on('foo', listener);
+ const data = {};
+
+ emitter.emit('foo', data);
+ expect(listener.callCount).toEqual(1);
+ expect(listener.firstCall.args[0]).toBe(data);
+ });
+
+ it('returns true if the event has listeners', () => {
+ const listener = sinon.spy();
+ emitter.on('foo', listener);
+ expect(emitter.emit('foo', undefined)).toBe(true);
+ });
+
+ it('returns false if the event has listeners', () => {
+ const listener = sinon.spy();
+ emitter.on('foo', listener);
+ expect(emitter.emit('notFoo', undefined)).toBe(false);
+ });
+ });
+
+ describe('listenerCount', () => {
+ it('returns the number of listeners for the given event', () => {
+ emitter.on('foo', () => {});
+ emitter.on('foo', () => {});
+ emitter.on('bar', () => {});
+ expect(emitter.listenerCount('foo')).toEqual(2);
+ expect(emitter.listenerCount('bar')).toEqual(1);
+ expect(emitter.listenerCount('noListeners')).toEqual(0);
+ });
+ });
+
+ describe('removeAllListeners', () => {
+ it('removes every listener from all events by default', () => {
+ emitter.on('foo', () => {}).on('bar', () => {});
+
+ emitter.removeAllListeners();
+ expect(emitter.emit('foo', undefined)).toBe(false);
+ expect(emitter.emit('bar', undefined)).toBe(false);
+ });
+
+ it('returns the emitter for chaining', () => {
+ expect(emitter.removeAllListeners()).toBe(emitter);
+ });
+
+ it('can filter to remove only listeners for a given event name', () => {
+ emitter
+ .on('foo', () => {})
+ .on('bar', () => {})
+ .on('bar', () => {});
+
+ emitter.removeAllListeners('bar');
+ expect(emitter.emit('foo', undefined)).toBe(true);
+ expect(emitter.emit('bar', undefined)).toBe(false);
+ });
+ });
+
+ describe('dispose', () => {
+ it('should dispose higher order emitters properly', () => {
+ let values = '';
+ emitter.on('foo', () => {
+ values += '1';
+ });
+ const higherOrderEmitter = new EventEmitter(emitter);
+
+ higherOrderEmitter.on('foo', () => {
+ values += '2';
+ });
+ higherOrderEmitter.emit('foo', undefined);
+
+ expect(values).toMatch('12');
+
+ higherOrderEmitter.off('foo');
+ higherOrderEmitter.emit('foo', undefined);
+
+ expect(values).toMatch('121');
+ });
+ });
+});