Unit testing Node.js and WebSockets (Socket.io)
Could anyone provide a rock-solid, dead-simple unit test for Node.js using WebSockets (Socket.io)?
I'm using socket.io for Node.js, and have looked at socket.io-client for establishing the client connection to a server in the test. However, I seem to be missing something.
In the example below, "worked..." never gets printed out.
var io = require('socket.io-client')
, assert = require('assert')
, expect = require('expect.js');
describe('Suite of unit tests', function() {
describe('First (hopefully useful) test', function() {
var socket = io.connect('http://localhost:3001');
socket.on('connect', function(done) {
console.log('worked...');
done();
});
it('Doing some things with indexOf()', function() {
expect([1, 2, 3].indexOf(5)).to.be.equal(-1);
expect([1, 2, 3].indexOf(0)).to.be.equal(-1);
});
});
});
Instead, I simply get:
Suite of unit tests
First (hopefully useful) test
✓ Doing some things with indexOf()
1 test complete (26 ms)
Any suggestions?
Solution 1:
After further poking and prodding, I found some incredibly useful information. In the author's example, he points out the critical step of establishing socket listeners in the before hooks.
This example works:
Assuming a server is listening for socket connections at
localhost:3001, of course
var io = require('socket.io-client')
, assert = require('assert')
, expect = require('expect.js');
describe('Suite of unit tests', function() {
var socket;
beforeEach(function(done) {
// Setup
socket = io.connect('http://localhost:3001', {
'reconnection delay' : 0
, 'reopen delay' : 0
, 'force new connection' : true
});
socket.on('connect', function() {
console.log('worked...');
done();
});
socket.on('disconnect', function() {
console.log('disconnected...');
})
});
afterEach(function(done) {
// Cleanup
if(socket.connected) {
console.log('disconnecting...');
socket.disconnect();
} else {
// There will not be a connection unless you have done() in beforeEach, socket.on('connect'...)
console.log('no connection to break...');
}
done();
});
describe('First (hopefully useful) test', function() {
it('Doing some things with indexOf()', function(done) {
expect([1, 2, 3].indexOf(5)).to.be.equal(-1);
expect([1, 2, 3].indexOf(0)).to.be.equal(-1);
done();
});
it('Doing something else with indexOf()', function(done) {
expect([1, 2, 3].indexOf(5)).to.be.equal(-1);
expect([1, 2, 3].indexOf(0)).to.be.equal(-1);
done();
});
});
});
I found that the placement of done() in the beforeEach, socket.on('connect'...) listener was crucial to having the connection get established. For example, if you comment out done() in the listener, then add it one scope out (just before exiting the beforeEach), you'll see the "no connection to break..." message instead of the "disconnecting..." message. Like so:
beforeEach(function(done) {
// Setup
socket = io.connect('http://localhost:3001', {
'reconnection delay' : 0
, 'reopen delay' : 0
, 'force new connection' : true
});
socket.on('connect', function() {
console.log('worked...');
//done();
});
socket.on('disconnect', function() {
console.log('disconnected...');
});
done();
});
I'm new to Mocha, so there's probably a very obvious reason to the initiated for placing done() within the socket scope itself. Hopefully that little detail will save others in my shoes from hair pulling.
For me, the above test (with correct scoping of done()) outputs:
Suite of unit tests
First (hopefully useful) test
◦ Doing some things with indexOf(): worked...
✓ Doing some things with indexOf()
disconnecting...
disconnected...
◦ Doing something else with indexOf(): worked...
✓ Doing something else with indexOf()
disconnecting...
disconnected...
2 tests complete (93 ms)
Solution 2:
Offering an extension of the accepted answer here. Has basic client to server communication useful as boilerplate for other future tests. Using mocha, chai, and expect.
var io = require('socket.io-client')
, io_server = require('socket.io').listen(3001);
describe('basic socket.io example', function() {
var socket;
beforeEach(function(done) {
// Setup
socket = io.connect('http://localhost:3001', {
'reconnection delay' : 0
, 'reopen delay' : 0
, 'force new connection' : true
, transports: ['websocket']
});
socket.on('connect', () => {
done();
});
socket.on('disconnect', () => {
// console.log('disconnected...');
});
});
afterEach((done) => {
// Cleanup
if(socket.connected) {
socket.disconnect();
}
io_server.close();
done();
});
it('should communicate', (done) => {
// once connected, emit Hello World
io_server.emit('echo', 'Hello World');
socket.once('echo', (message) => {
// Check that the message matches
expect(message).to.equal('Hello World');
done();
});
io_server.on('connection', (socket) => {
expect(socket).to.not.be.null;
});
});
});
Solution 3:
Dealing with callbacks and promises yourself can be difficult and non trivial examples quickly become very complex and hard to read.
There is a tool called socket.io-await-test available via NPM that allows you to suspend/wait in a test until events have been triggered using the await keyword.
describe("wait for tests", () => {
it("resolves when a number of events are received", async () => {
const tester = new SocketTester(client);
const pongs = tester.on('pong');
client.emit('ping', 1);
client.emit('ping', 2);
await pongs.waitForEvents(2) // Blocks until the server emits "pong" twice.
assert.equal(pongs.get(0), 2)
assert.equal(pongs.get(1), 3)
})
})
Solution 4:
Check out this boilerplate solution that's based on promises and good practice. You can test your servers entire io events with it, no sweat. You just need to copy a boilerplate test and add your own code as needed.
Checkout the repo on GitHub for full source code.
https://github.com/PatMan10/testing_socketIO_server
const io = require("socket.io-client");
const ev = require("../utils/events");
const logger = require("../utils/logger");
// initSocket returns a promise
// success: resolve a new socket object
// fail: reject a error
const initSocket = () => {
return new Promise((resolve, reject) => {
// create socket for communication
const socket = io("localhost:5000", {
"reconnection delay": 0,
"reopen delay": 0,
"force new connection": true
});
// define event handler for sucessfull connection
socket.on(ev.CONNECT, () => {
logger.info("connected");
resolve(socket);
});
// if connection takes longer than 5 seconds throw error
setTimeout(() => {
reject(new Error("Failed to connect wihtin 5 seconds."));
}, 5000);
}
);
};
// destroySocket returns a promise
// success: resolve true
// fail: resolve false
const destroySocket = socket => {
return new Promise((resolve, reject) => {
// check if socket connected
if (socket.connected) {
// disconnect socket
logger.info("disconnecting...");
socket.disconnect();
resolve(true);
} else {
// not connected
logger.info("no connection to break...");
resolve(false);
}
});
};
describe("test suit: Echo & Bello", () => {
test("test: ECHO", async () => {
// create socket for communication
const socketClient = await initSocket();
// create new promise for server response
const serverResponse = new Promise((resolve, reject) => {
// define a handler for the test event
socketClient.on(ev.res_ECHO, data4Client => {
//process data received from server
const { message } = data4Client;
logger.info("Server says: " + message);
// destroy socket after server responds
destroySocket(socketClient);
// return data for testing
resolve(data4Client);
});
// if response takes longer than 5 seconds throw error
setTimeout(() => {
reject(new Error("Failed to get reponse, connection timed out..."));
}, 5000);
});
// define data 4 server
const data4Server = { message: "CLIENT ECHO" };
// emit event with data to server
logger.info("Emitting ECHO event");
socketClient.emit(ev.com_ECHO, data4Server);
// wait for server to respond
const { status, message } = await serverResponse;
// check the response data
expect(status).toBe(200);
expect(message).toBe("SERVER ECHO");
});
test("test BELLO", async () => {
const socketClient = await initSocket();
const serverResponse = new Promise((resolve, reject) => {
socketClient.on(ev.res_BELLO, data4Client => {
const { message } = data4Client;
logger.info("Server says: " + message);
destroySocket(socketClient);
resolve(data4Client);
});
setTimeout(() => {
reject(new Error("Failed to get reponse, connection timed out..."));
}, 5000);
});
const data4Server = { message: "CLIENT BELLO" };
logger.info("Emitting BELLO event");
socketClient.emit(ev.com_BELLO, data4Server);
const { status, message } = await serverResponse;
expect(status).toBe(200);
expect(message).toBe("SERVER BELLO");
});
});
---- Foot Note ----
Depending on how you setup your server environment, you may experience environmental conflict between socket.io and socket.io-client running from the same project simultaneously. In which case it would be better to separate the project into a "test client" and a server. Checkout below repo if you get this issue.
https://github.com/PatMan10/testing_socketIO_server_v2