Javascript mocking library for websockets and socket.io

Contents

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

Installation

1npm install mock-socket

1import { WebSocket, Server } from 'mock-socket';

Usage

1import test from 'ava';
2import { Server } from 'mock-socket';
3
4class ChatApp {
5  constructor(url) {
6    this.messages = [];
7    this.connection = new WebSocket(url);
8
9    this.connection.onmessage = event => {
10      this.messages.push(event.data);
11    };
12  }
13
14  sendMessage(message) {
15    this.connection.send(message);
16  }
17}
18
19test.cb('that chat app can be mocked', t => {
20  const fakeURL = 'ws://localhost:8080';
21  const mockServer = new Server(fakeURL);
22
23  mockServer.on('connection', socket => {
24    socket.on('message', data => {
25      t.is(data, 'test message from app', 'we have intercepted the message and can assert on it');
26      socket.send('test message from mock server');
27    });
28  });
29
30  const app = new ChatApp(fakeURL);
31  app.sendMessage('test message from app'); // NOTE: this line creates a micro task
32
33  // NOTE: this timeout is for creating another micro task that will happen after the above one
34  setTimeout(() => {
35    t.is(app.messages.length, 1);
36    t.is(app.messages[0], 'test message from mock server', 'we have stubbed our websocket backend');
37    mockServer.stop(t.done);
38  }, 100);
39});

Advanced Usage

Stubbing the "global"

1import { WebSocket, Server } from 'mock-socket';
2
3/*
4 * By default the global WebSocket object is stubbed out when 
5 * a new Server instance is created and is restored when you stop
6 * the server.
7 * However, you can disable this behavior by passing `mock: false`
8 * to the options and manually mock the socket when you need it.
9 */
10const server = new Server('ws://localhost:8080', { mock: false });
11
12/*
13 * If you need to stub something else out you can like so:
14 */
15
16window.WebSocket = WebSocket; // Here we stub out the window object

Server Methods

1const mockServer = new Server('ws://localhost:8080');
2
3mockServer.on('connection', socket => {
4  socket.on('message', () => {});
5  socket.on('close', () => {});
6  socket.on('error', () => {});
7
8  socket.send('message');
9  socket.close();
10});
11
12mockServer.clients(); // array of all connected clients
13mockServer.emit('room', 'message');
14mockServer.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.

1import test from 'ava';
2import { SocketIO, Server } from 'mock-socket';
3
4class ChatApp {
5  constructor(url) {
6    this.messages = [];
7    this.connection = new io(url);
8
9    this.connection.on('chat-message', data => {
10      this.messages.push(event.data);
11    });
12  }
13
14  sendMessage(message) {
15    this.connection.emit('chat-message', message);
16  }
17}
18
19test.cb('that socket.io works', t => {
20  const fakeURL = 'ws://localhost:8080';
21  const mockServer = new Server(fakeURL);
22
23  window.io = SocketIO;
24
25  mockServer.on('connection', socket => {
26    socket.on('chat-message', data => {
27      t.is(data, 'test message from app', 'we have intercepted the message and can assert on it');
28      socket.emit('chat-message', 'test message from mock server');
29    });
30  });
31
32  const app = new ChatApp(fakeURL);
33  app.sendMessage('test message from app');
34
35  setTimeout(() => {
36    t.is(app.messages.length, 1);
37    t.is(app.messages[0], 'test message from mock server', 'we have subbed our websocket backend');
38
39    mockServer.stop(t.done);
40  }, 100);
41});

Contributing

The easiest way to work on the project is to clone the repo down via:

1git clone git@github.com:thoov/mock-socket.git
2cd mock-socket
3yarn install

Then to create a local build via:

1yarn build

Then create a local npm link via:

1yarn link

At this point you can create other projects / apps locally and reference this local build via:

1yarn 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:

1yarn test

Linting

This project uses eslint and a rules set from airbnb's javascript style guides. To run linting:

1yarn lint

Formatting

This project uses prettier. To run the formatting:

1yarn format

Code Coverage

Code coverage reports are created in /coverage after all of the tests have successfully passed. To run the coverage:

1yarn 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.