Why is `before_save` not working in Rails 4?

Question

When I try u = User.new followed by u.save, the before_save method is not being fired.

Here's my User model:

class User < ActiveRecord::Base
  attr_accessor :password
  before_save :encrypt_password

  def encrypt_password
    puts "Its getting called"
  end
end

https://railsforum.com/topic/1741-rails-4-and-before-save-method/