model.js

/*
 * barnstormer
 * https://github.com/condenast/barnstormer
 *
 * Copyright (c) 2013 Condé Nast. All rights reserved.
 */

var sync;

if (typeof define !== 'function') {
  var define = require('amdefine')(module);
  sync = require('../../lib/mongo_sync');
}

define(function (require) {
  'use strict';

  var Backbone = require('backbone');

  if(typeof sync !== 'undefined'){
    Backbone.sync = sync;
  }

  var NewsletterStory = Backbone.Model.extend({
    url: '/parse',
    idAttribute: '_id',
    defaults: {
      hed: '',
      dek: '',
      trunc_hed: '',
      img: '',
      url: '',
      section: '',
      expand: false,
      name: ''
    }
  });

  return NewsletterStory;
});

rconf.js

/* global requirejs */

requirejs.config({
  baseUrl: '../',
  hbs: {
    disableI18n: true,
    helperPathCallback: function (name) {
      'use strict';
      return 'views/helpers/' + name;
    }
  },
  paths: {
    'jquery': 'components/jquery/jquery',
    'underscore': 'components/underscore/underscore',
    'backbone': 'components/backbone/backbone',
    'handlebars': 'components/handlebars/handlebars',
    'hbs': 'components/require-handlebars-plugin/hbs',
    'i18nprecompile': 'components/require-handlebars-plugin/hbs/i18nprecompile',
    'json2': 'components/require-handlebars-plugin/hbs/json2',
    'moment': 'components/moment/moment',
    'bootstrap': 'components/bootstrap/js/bootstrap'
  },
  shim: {
    'backbone': {
      deps: ['underscore', 'jquery'],
      exports: 'Backbone'
    },
    'handlebars': {
      exports: 'Handlebars'
    },
    'underscore': {
      exports: '_'
    },
    'bootstrap': {
      deps: ['jquery'],
      exports: 'jQuery.fn.modal'
    }
  }
});

requirejs.config({
  baseUrl: window.PHANTOMJS ? '../' : '/../',
});

So grunt mocha provides a window object, so if you block code from running on the front end with typeof window === 'undefined' that doesn't work in your test suite. For some reason wrapping your code in:

if(typeof window === 'undefined'){ 
    Backbone.sync = require('../../lib/mongo_sync'); 
}

Would cause a script error with require when trying to import it. (Seriously.)

This is the only pattern I've gotten working yet to make code run only in a particular environment and still have the test suite work...