Integration testing a node.js socket.io server - node.js

Question

I'm trying to set up a server to respond to socket.io clients using nodejs, express and socket.io. I want to write tests to probe the server and make sure it's handling the events correctly and sending appropriate responses to the client.
I tried writing some automated tests using jest but I couldn't figure out how to actually emit events to the server and have it respond.
Unit testing Node.js and WebSockets (Socket.io)
I checked out the above post but it didn't work for me...

Answer 1

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: reject 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 () => {
try {
// 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;
expect(status).toBe(200);
expect(message).toBe("SERVER ECHO");
} catch (error) {
logger.error(error);
}
});
test("test BELLO", async () => {
try {
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");
} catch (error) {
logger.error(error);
}
});
});