testing failed promises with mocha's built-in promise support

How should I be testing, with mocha and chai, that my promise has failed?

I am confused, because I initially thought I should be using 'mocha-as-promised', but that package is now deprecated (I'm using mocha 2.1.0), with the advice to just use the promise testing that's now built into mocha. see: http://ift.tt/OZTbha

Another post recommends doing away with the 'done' argument to the it() callback - not sure I understand why, since my understanding that passing in the 'done' parameter was the way to signal that a test was being tested asynchronously. see: How to I properly test promises with mocha and chai?

Anyway, I've tried to reduce my issue to the below code - please help me modify this so that I can test that my promise indeed fails.

it.only("do something (negative test)", function (done) {

  var Q = require('q');

  function makePromise() {
    var deferred = Q.defer();
    deferred.reject(Error('fail'));
    return deferred.promise;
  };

  makePromise()
  .then(done, done);

});