Use expresso and socket.io-client to test server, but the testing process does not stop

I wanna use socket.io-client to test my socket.io server. And I tried to run expresso with the following file. The data is printed in console. Then the process hangs there and beforeExit is never executed until I terminate the process with Ctrl-C. I suppose after the callback is done from the server, beforeExit should be called and then the process stops. But it is not like that, Why?

var assert = require('assert');
exports.testAsync = function(beforeExit){
    var io = require('socket.io-client');
    var socket = io.connect('http://localhost:8000');
    socke开发者_JAVA百科t.on('connect', function(err) {
        assert.isUndefined(err);
        socket.emit('set nickname', 'apple', function(data) {
        assert.equal(data, 'ok');
            console.log(data);
        });
    });
    beforeExit(function(){
        console.log("exit");
        socket.disconnect();
    });
};

Strange. I'm using Expresso 0.9.2 and exactly the same code you wrote works as expected. But of course, I don't have any server running.

Is this the entire content of your test file?