transactionのテスト
Instant rails をアップデータした後
rails test create database test_development; mysql test_development < db/create; create table accounts ( id int not null auto_increment, number varchar(10) not null, balance decimal(10,2) default 0.0, primary key (id) ) type=InnoDB; class Account < ActiveRecord::Base def withdraw(amount) adjust_balance_and_save(-amount) end def deposit(amount) adjust__balance_and_save(amount) end private def adjust_balance_and_save(amount) self.balance += amount save! end def validate errors.add(:balance,"is negative") if balance < 0 end