websocket-mockup

library1.3.1jsnpmunverified

websocket-mockup is a lightweight mock WebSocket server and client implementation for testing, supporting both server-side and W3C WebSocket API shims. Version 1.3.1 is the latest stable release, with infrequent updates. It allows developers to simulate WebSocket connections without a real server, ideal for unit and integration tests. Key differentiators include simple API, event-driven request handling, and support for custom host routing. Unlike heavier solutions like mock-socket, this package focuses on mimicking the Node.js ws library server interface.

testing

npm install websocket-mockup

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · WEBSOCKET-MOCKUP

websocket-mockup

testingjavascriptv1.3.1

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

WebSocketServer

✓ const { WebSocketServer } = require('websocket-mockup')

✗ import { WebSocketServer } from 'websocket-mockup'

Package does not provide ESM exports; CommonJS require only.

WebSocket

✓ const { WebSocket } = require('websocket-mockup')

✗ const WebSocket = require('websocket-mockup')

Must destructure; default export is an object containing both classes.

default import

✓ const mockup = require('websocket-mockup'); const { WebSocketServer } = mockup;

✗ import mockup from 'websocket-mockup'

No default export; TypeError will occur.

Creates a mock WebSocket server and client, demonstrates message exchange and event handling.

const { WebSocketServer, WebSocket } = require('websocket-mockup'); const server = new WebSocketServer({ host: 'test.local' }); server.on('request', (request) => { const connection = request.accept(request.requestedProtocols[0], request.origin); connection.on('message', (msg) => { if (msg.type === 'utf8') connection.sendUTF(msg.utf8Data); connection.close(); }); }); const ws = new WebSocket('wss://test.local'); ws.onopen = () => ws.send('Hello'); ws.onmessage = (event) => console.log(event.data);

Debug

Known issues

gotchaWebSocket constructor does not implement connection timeout; tests may hang if server not set up.

fix

Ensure server is listening before creating client, or use a timeout in test environment.

affects: >=1.0.0

gotchaEvent names are lowercase: 'onopen', 'onmessage', not 'open', 'message'.

fix

Use property assignment (ws.onopen = handler) or addEventListener if shimmed.

affects: >=1.0.0

gotcharequest.accept() must be called synchronously inside the 'request' event listener; async calls may fail.

fix

Move await logic outside the event handler.

affects: >=1.0.0

gotchaBinary messages use ArrayBuffer; TextEncoder/TextDecoder needed for text/binary conversion.

fix

Wrap binaryData in Buffer or decode with TextDecoder as needed.

affects: >=1.0.0

Errors

Common errors & fixes

TypeError: Class constructor WebSocketServer cannot be invoked without 'new'

Using decorator or call expression without 'new' in strict mode.

fix

Add 'new': new WebSocketServer({ ... }).

TypeError: Cannot read properties of undefined (reading 'accept')

Accessing request.accept before server starts listening or request not received.

fix

Ensure server is created and 'request' event fires; use async/await with server setup.

Error: connect ECONNREFUSED 127.0.0.1:80

Attempting to connect to a real WebSocket server instead of mock (URL not matched).

fix

Use a URL with host matching server's host option, e.g., 'wss://test.local'.

Upgrade

Version history

1.3.1latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

15 hits · last 30 days

node

Resources

githubhttps://github.com/medooze/websocket-mockup ↗

packagewebsocket-mockup ↗

homepagehttps://github.com/medooze/websocket-mockup#readme ↗