Trying to figure out what I'm doing wrong with this module definition. In this implementation, the history member keeps throwing as undefined when calling this.history.push in addToHistory...

bugs-tests.js

var should = require('should'),
  bugs = require('../bugs.js');

describe('bugs', function(){
	describe('when creating a new bug', function(){
		describe('with no parameters', function() {
			it('should return an error');
		});

		describe('with the default title parameter', function() {		
			it('it should return a new bug object', function(){
				var newBug = bugs.createBug('new bug');
				should.exist(newBug);
			});
			it('should have the title that was passed as an argument to the create function', function(){
				var newBug = bugs.createBug('test bug');
				newBug.title.should.equal('test bug');
			});
			it('should be in an active state', function(){
				var newBug = bugs.createBug('test bug');
				newBug.status.should.equal('Backlog');
			});
			it('should have a single item in history indicating that the bug was created', function(){
				var newBug = bugs.createBug('test bug');
				newBug.history.length.should.equal(1);
			});
			it('should have an item added to the database');
		});
	});
});

bugs.js

var mongoclient = require('mongodb').MongoClient,
  mongolocation = '';

var Bug = (function() {
	var save = function(){
		mongoclient.connect(mongolocation, function(err, db){
			if(err)	console.dir(err);
			var bugscollection = db.collection('bugs');

		});
	},
	addToHistory = function(comments, stateChanges){
		this.history.push({
			addedOn: new Date(),
			comments: comments,
			changes: stateChanges });
	},
	toBacklog = function(comments) {
		this.status = 'Backlog';
		addToHistory(comments, {'status':'Backlog'});
	};
	
	return {
		toBacklog : toBacklog,
		status : undefined,
		title : undefined,
		history : []
	};
})();

var createBug = function(title) {
	var newbug = Object.create(Bug);
	newbug.title = title;
	newbug.toBacklog('Bug created');
	return newbug;
}

var getBug = function(bugID){
	//todo
};

module.exports.createBug  = createBug;
module.exports.getBug = getBug;