[Mongoose] multiple validation errors on Document#save

gistfile1.js

// package.json file
////////////////////

{
  "name": "test",
  "version": "0.0.1",
  "dependencies": {
    "mongoose": "3.1.2"
  }
}

// app.js
////////////////////

mongoose = require('mongoose')
var db = mongoose.createConnection('localhost', 'multi_validation_test');

/* Schema definition */
var userSchema = new mongoose.Schema({
  email     : { type: String, unique: true, required: true, trim: true },
  password  : { type: String, required: true, trim: true },
})

/* Validations */
userSchema.path('password').validate(function(value) { return value.length >= 6 }, 'minLength')
userSchema.path('password').validate(function(value) { return value.length >= 5 }, 'minLength2')
userSchema.path('password').validate(function(value) { return /[0-9]/.test(value) }, 'noNumberFound')

/* Model declaration */
var User = db.model('User', userSchema)

var u = new User({ email: "jean-luc@godard.fr", password: "lefou" })
u.save(function(err, user) {
  console.log(err)
})