Why am I getting two different encrypted hashes from node.bcrypt even though password and salt are the same?
vows.describe('User').addBatch
  'User':
    topic: ->
      user = new User
        name: 'test.user'

    '#authenticate':
      topic: (user) ->
        promise = new events.EventEmitter
        password = User.generatePassword()
        user.set 'password', password
        user.save (err) ->
          User.authenticate user.name, password, (err, user) ->
            if (err) promise.emit 'error', err
            else promise.emit 'success', user
        promise

      'should return a user': (err, user) ->
        assert.isNotNull user

bcrypt = require 'bcrypt'
mongoose = require 'mongoose'

User = new mongoose.Schema
  name: { type: String, unique: true }
  password_salt: String
  password_hash: String

User.virtual('password')
  .set (pass) ->
    salt = bcrypt.gen_salt_sync(10)
    @set 'password_salt', salt
    @set 'password_hash', bcrypt.encrypt_sync pass, salt

User.static
  generatePassword: ->
    # just generates 8 characters of alphanumerics

  authenticate: (name, password, next) ->
    @findOne { name: name }, (err, user) ->
      if user
        bcrypt.compare password, user.password_hash, (err, res) ->
          if res is true then next(err, user) else next(err, null)
      else
        next(err, user)

# spec/models/user_spec.coffee

# Rest of the test snippet above...
user.save (err) ->
  console.log "1 Pass: #{password}n
               1 Salt: #{user.password_salt}n
               1 Hash: #{user.password_hash}"
# Rest of the test snippet above...

# models/user.coffee

# Rest of user model snippet above...
bcrypt.compare password, user.password_hash, (err, res) ->
  console.log "2 Pass: #{password}n
               2 Salt: #{user.password_salt}n
               2 Hash: #{user.password_hash}nn

               2 Encrypt Again: #{bcrypt.encrypt_sync password, user.password_salt}"
# Rest of user model snippet above...

# console.log output

1 Pass: Q8ZE0Yj1
1 Salt: $2a$10$o0sRXPchaW2R841MWRCT3u
1 Hash: $2a$10$o0sRXPchaW2R841MWRCT3uj80ecPs1QX4kTfC/hzG.2kMa8RaCsZu

2 Pass: Q8ZE0Yj1
2 Salt: $2a$10$o0sRXPchaW2R841MWRCT3u
2 Hash: $2a$10$o0sRXPchaW2R841MWRCT3uj80ecPs1QX4kTfC/hzG.2kMa8RaCsZu
2 Encrypt Again: $2a$10$o0sRXPchaW2R841MWRCT3ukGkrfpJuzZFKJcdX0WiNHONuJTy