Problema com closures!

gistfile1.txt

var assert = require("assert")
var mongo = require('./mongo.js')

var databaseUrl = "leitordecarga"; 
var collections = ["tables"]
var db = require("mongojs").connect(databaseUrl, collections);

callback = [];
db.open(function(err, db) {
    if (!err) {
        console.log("db opened!");
    }else {
        console.log(err);
    }
    db.collection('tables', function(err, collection) {
        collection.find({}, function(err, cursor) {
            cursor.each(function(err, item){
                callback.push(item);
            });
        });
    });
});



describe('array_to_tree', function(){
  describe('transform array to tree structure', function(){
    it('array com um elemento', function(){
      assert.equal(mongo.array_to_tree(1),1);<------como ter acesso ao array callback aqui???
    })
  })
})