Stubbing email sending in tests

gistfile1.js

// This is the simplest possible approach - use a custom module to wrap a single, pre-configured 
// mail transport instance and then use sinon.js to stub out that modules sendmail()

// This approach has its limitations, but it is still better than having 'if(NODE_ENV === 'test')'
// all over the code base.

// -- app/sendmail.js --

var nodemailer = require('nodemailer');
var config = require('config').email;

var transport = nodemailer.createTransport(config.transport, config.transportOptions);
module.exports.sendmail = function(message) {
  return transport.sendMail(message);
}

// -- test/common.js --

// modules are loaded only once and then cached, so we get the same instance every time
var sendmail = require('../app/sendmail'); 
sinon.stub(sendmail, 'sendmail').yields(null, {
  message: '250 2.0.0 OK 1403606574 og3sm31277838pbc.48 - gsmtp',
  messageId: 'adefbd50fb8c11e3a3ac0800200c9a66@localhost'
});

// -- in all test files --

require('../../common'); // include the common setup for every test