JarCasting 
Javascript mocking library for websockets and socket.io
Contents
Installation
npm install mock-socket
import { WebSocket, Server } from 'mock-socket';
Usage
import test from 'ava';
import { Server } from 'mock-socket';
class ChatApp {
constructor(url) {
this.messages = [];
this.connection = new WebSocket(url);
this.connection.onmessage = event => {
this.messages.push(event.data);
};
}
sendMessage(message) {
this.connection.send(message);
}
}
test.cb('that chat app can be mocked', t => {
const fakeURL = 'ws://localhost:8080';
const mockServer = new Server(fakeURL);
mockServer.on('connection', socket => {
socket.on('message', data => {
t.is(data, 'test message from app', 'we have intercepted the message and can assert on it');
socket.send('test message from mock server');
});
});
const app = new ChatApp(fakeURL);
app.sendMessage('test message from app'); // NOTE: this line creates a micro task
// NOTE: this timeout is for creating another micro task that will happen after the above one
setTimeout(() => {
t.is(app.messages.length, 1);
t.is(app.messages[0], 'test message from mock server', 'we have subbed our websocket backend');
mockServer.stop(t.done);
}, 100);
});
Advanced Usage
Stubbing the "global"
import { WebSocket, Server } from 'mock-socket';
/*
* By default the global WebSocket object is stubbed out. However,
* if you need to stub something else out you can like so:
*/
window.WebSocket = WebSocket; // Here we stub out the window object
Server Methods
const mockServer = new Server('ws://localhost:8080');
mockServer.on('connection', socket => {
socket.on('message', () => {});
socket.on('close', () => {});
socket.send('message');
socket.close();
});
mockServer.clients(); // array of all connected clients
mockServer.emit('room', 'message');
mockServer.stop(optionalCallback);
Typescript Support
A declaration file is included by default. If you notice any issues with the types please create an issue or a PR!
Socket IO
Socket.IO has limited support. Below is a similar example to the one above but modified to show off socket.io support.
import test from 'ava';
import { SocketIO, Server } from 'mock-socket';
class ChatApp {
constructor(url) {
this.messages = [];
this.connection = new io(url);
this.connection.on('chat-message', data => {
this.messages.push(event.data);
});
}
sendMessage(message) {
this.connection.emit('chat-message', message);
}
}
test.cb('that socket.io works', t => {
const fakeURL = 'ws://localhost:8080';
const mockServer = new Server(fakeURL);
window.io = SocketIO;
mockServer.on('connection', socket => {
socket.on('chat-message', data => {
t.is(data, 'test message from app', 'we have intercepted the message and can assert on it');
socket.emit('chat-message', 'test message from mock server');
});
});
const app = new ChatApp(fakeURL);
app.sendMessage('test message from app');
setTimeout(() => {
t.is(app.messages.length, 1);
t.is(app.messages[0], 'test message from mock server', 'we have subbed our websocket backend');
mockServer.stop(t.done);
}, 100);
});
Contributing
The easiest way to work on the project is to clone the repo down via:
git clone git@github.com:thoov/mock-socket.git
cd mock-socket
yarn install
Then to create a local build via:
yarn build
Then create a local npm link via:
yarn link
At this point you can create other projects / apps locally and reference this local build via:
yarn link mock-socket
from within your other projects folder. Make sure that after any changes you run yarn build!
Tests
This project uses ava.js as its test framework. Tests are located in /tests. To run tests:
yarn test
Linting
This project uses eslint and a rules set from airbnb's javascript style guides. To run linting:
yarn lint
Formatting
This project uses prettier. To run the formatting:
yarn format
Code Coverage
Code coverage reports are created in /coverage after all of the tests have successfully passed. To run the coverage:
yarn test:coverage
Feedback
If you have any feedback, encounter any bugs, or just have a question, please feel free to create a github issue or send me a tweet at @thoov.