Chai-spy should have been called fail

I'd like to test that a socket got opened. For this I tried to supply a chai spy, to see that the connection callback got called. Everything looks fine, I got the code sample from chai-spi docs. But the test fails. The strange this is that I can see in the output log, that the function got called.

The only thing I can think of is, that the assertion got called before the callback. Anyway I'm new to node, any help appreciated.

var chai = require('chai');
var spies = require('chai-spies');
var should = chai.should();
var expect = chai.expect;
var io = require('socket.io-client');

chai.use(spies);

function onConnect(socket) {
    console.log('monkey');
}

describe('Socket', function(done) {
    it('Opens the socket', function(done) {
        var spy = chai.spy(onConnect);
        var socket = io.connect('http://localhost:3000');
        socket.on('connect', spy);
        //expect(spy).to.have.been.called();
        spy.should.have.been.called();
        done();
    });
});

Test output:

  2) Socket Opens the socket:
     AssertionError: expected { Spy } to have been called
      at Context.<anonymous> (test/test.socket.js:19:30)



monkey