Sequelize promises vs. event emitter

gistfile1.js

it('supports transactions', function() {
  return Support.prepareTransactionTest(this.sequelize).bind({}}).then(function(sequelize) {
    this.sequelize = sequelize;
    this.Article = sequelize.define('Article', { 'title': DataTypes.STRING });
    this.Label   = sequelize.define('Label', { 'text': DataTypes.STRING });

    this.Article.hasMany(this.Label);

    return sequelize.sync({ force: true });
  }).then(function() {
    return Promise.all([
      this.Article.create({ title: 'foo' }),
      this.Label.create({ text: 'bar' })
    ]);
  }).spread(function (article, label) {
    this.article = article;
    this.label = label;
    return this.sequelize.transaction();
  }).then(function(t) {
    this.t = t;
    return this.article.setLabels([ this.label ], { transaction: this.t });
  }).then(function() {
    return this.Article.all({ transaction: this.t });
  }).then(function(articles) {
    return articles[0].hasLabel(this.label).then(function(hasLabel) {
      expect(hasLabel).to.be.false;
    });
  }).then(function () {
    return this.Article.all({ transaction: this.t });
  }).then(function(articles) {
    return articles[0].hasLabel(label, { transaction: this.t }).then(function(hasLabel) {
      expect(hasLabel).to.be.true;
      return this.t.rollback();
    });
  });
});

it('supports transactions', function(done) {
  Support.prepareTransactionTest(this.sequelize, function(sequelize) {
    var Article = sequelize.define('Article', { 'title': DataTypes.STRING })
      , Label   = sequelize.define('Label', { 'text': DataTypes.STRING })

    Article.hasMany(Label)

    sequelize.sync({ force: true }).success(function() {
      Article.create({ title: 'foo' }).success(function(article) {
        Label.create({ text: 'bar' }).success(function(label) {
          sequelize.transaction(function(t) {
            article.setLabels([ label ], { transaction: t }).success(function() {
              Article.all({ transaction: t }).success(function(articles) {
                articles[0].hasLabel(label).success(function(hasLabel) {
                  expect(hasLabel).to.be.false
                  Article.all({ transaction: t }).success(function(articles) {
                    articles[0].hasLabel(label, { transaction: t }).success(function(hasLabel) {
                      expect(hasLabel).to.be.true
                      t.rollback().success(function() { done() })
                    })
                  })
                })
              })
            })
          })
        })
      })
    })
  })
})