Asynchronous Unit Tests in Ruby

Question

I'm testing some javascript libraries I've built by using ruby's harmony. Everything is working perfectly except AJAX calls — does anyone have any ideas how to achieve this?

My code looks something like this (I'm using RightJS):

my.js

function makerequest(argument) {
    new Xhr('http://mysite.com/some/jsonp'),{
        jsonp: true,
        params: {something: argument},
        onSuccess: function() {
            // Calls a function defined outside my library
            parse_response(this.json)
        }
    }).send()
}

test_makerequest.rb

require 'rubygems'
require 'harmony'
require 'test/unit'
require 'shoulda'

class RequestTest < Test::Unit::TestCase
    context "The requesty thing" do
        setup do
            @page = Harmony::Page.new
            @page.load(File.expand_path('js/my.js'))
        end

        should "get stuff from mysite.com" do
            # Here I need to define a 'parse_response' which this
            # should section will wait for and then do an 'assert'
            # on the results.
            results = callback_to_get_results_from__make_request
            @page.execute('make_request("an argument")')
            assert results == {'foo' => 'bar'}
        end
    end
end

So yeah, my question is, how should I assign results above such that I can get the results of the async callback?