Test to check room broadcasting

I have a test that checks if the joined event is emitted correctly when a users subscribe to a room. However, I want to write a test to make sure when chatUser2 joins room2 that the joined event is only received by her and not client1 in room1

How would I write a test to make sure client1.on('joined') is NOT called when client2 connects?

var should = require('should'), 
io = require('socket.io-client'),
path = require('path'),
express = require(path.resolve('./config/lib/express')),
mongoose = require('mongoose'),
sinon = require('sinon'),
app, agent, credentials, user, sale;

var chatUser1 = {'name':'Tom', 'room':'room1'};
var chatUser2 = {'name':'Sally', 'room':'room2'};


describe("Socket Server",function(){
    it('Should not broadcast joined event to unsubscribed rooms', function(done){

        var client1 = io.connect(socketURL, options);
        client1.on('connect', function(data){
            client1.emit('subscribe', chatUser1);

              client1.on('joined', function(data){
                data.should.equal(chatUser1.name + " has joined "+chatUser1.room);

                });

            var client2 = io.connect(socketURL, options);

            client2.on('connect', function(data){
              client2.emit('subscribe', chatUser2);
            });

            client2.on('joined', function(data){

                data.should.equal(chatUser2.name + " has joined "+chatUser2.room);
              client1.disconnect();
              client2.disconnect();
              done();
            });


        });

    });
});