class MyTestClass
  include SimpleMongo::Model
  field :test
  
  validations do 
    validates_custom :test do |field|
      field == "something"      
    end
  end
  
  before_save do
    self.test = 'pablo'
  end
end

connection = SimpleMongo::Connection.new(:database => 'test')

model = MyTestClass.new(:test => 'yay')

model.save

puts model.test