Plain Ruby class that's meant to behave like ActiveRecord model without database persistence.

plain_model.rb

class PlainModel

  include ActiveModel::Model
  include ActiveSupport::Callbacks
  include ActiveModel::Validations::Callbacks

 define_callbacks :save

 def save
   if valid?
     run_callbacks :save do
       true 
     end
   else
     false
   end
  end
end