autosave => false should be same as not declaring autosave

  has_many :brakes, :autosave => false

Above statement is not same as

 has_many :brakes

class Car < ActiveRecord::Base
  has_many :brakes, :autosave => false

  def self.lab
    Car.delete_all
    Brake.delete_all
    c = Car.create
    c.brakes.build(:name => nil)
    c.save
    c.reload
    puts c.brakes.size #=> 0
  end
end

class Car < ActiveRecord::Base
  has_many :brakes#, :autosave => false (notice the # earlier in the string)

  def self.lab
    Car.delete_all
    Brake.delete_all
    c = Car.create
    c.brakes.build(:name => nil)
    c.save
    c.reload
    puts c.brakes.size #=> 1
  end
end