Javascript mocking library for websockets and socket.io

Contents

• Installation
• Basic Usage
• Advanced Usage
• Typescript Support
• Socket.IO
• Contributing
• Feedback

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 stubbed 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 when 
 * a new Server instance is created and is restored when you stop
 * the server.
 * However, you can disable this behavior by passing `mock: false`
 * to the options and manually mock the socket when you need it.
 */
const server = new Server('ws://localhost:8080', { mock: false });

/*
 * 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.on('error', () => {});

  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.