test.js

var Bookshelf = require('bookshelf');

var MySql = Bookshelf.initialize({
	client: 'mysql',
	connection: {
		host     : '127.0.0.1',
		user     : 'root',
		password : '',
		database : 'testdb',
		charset  : 'utf8'
	}
});

var User = MySql.Model.extend({

	tableName: 'users',
	
	initialize: function(){
		this.on('saving', this.validate, this);
	},

	validate: function(){
		throw new Error('this is always thrown!');
	}

});

new User({ col: '12345' }).save().catch(function(e){
	console.log('Error: ', e);
});