Rails做單元測試時，我們自己手動去創建所有的fixtures會是個噩夢，有沒有什么好的方案呢?
我們可以利用數據庫里已有的數據，寫一個rake tast來把數據庫的數據復制出來到YAML文件里:
CreateFixturesFromLiveData/lib/tasks/extract_fixtures.rake

desc 'Create YAML test fixtures from data in an existing database.
Defaults to development database. Set RAILS_ENV to override.'

task :extract_fixtures => :environment do
  sql = "SELECT * FROM %s"
  skip_tables = ["schema_info"]
  ActiveRecord::Base.establish_connection
  (ActiveRecord::Base.connection.tables - skip_table).each do |table_name|
    i = "000"
    File.open("#{RAILS_ROOT}/test/fixtures/#{table_name}.yml", 'w') do |file|
      data = ActiveRecord::Base.connection.select_all(sql % table_name)
      file.write data.inject({}) {|hash, record|
        hash["#{table_name}_#{i.succ!}"] = record
        hash
      }.to_yaml
    end
  end
end

好了，現在我們運行rake extract_fixtures，則test/fixtures/目錄下將生成每個表的數據的yml文件