dev-tools.js

export function deferredResolve(response, milliseconds = 250) {
  milliseconds = _.isInteger(milliseconds) ? milliseconds : 0;
  return new Ember.RSVP.Promise((resolve, reject) => {
    Ember.run.later(() => {
      resolve(response);
    }, milliseconds);
  });
}

export function deferredReject(response, milliseconds = 250) {
  milliseconds = _.isInteger(milliseconds) ? milliseconds : 0;
  return new Ember.RSVP.Promise((resolve, reject) => {
    Ember.run.later(() => {
      reject(response);
    }, milliseconds);
  });
}

new Ember.RSVP.Promise((resolve, reject) => {
  setTimeout(() => { 
    resolve(promise); 
  }, _.random(250, 500))
});