post.rb

# sudo gem install faker

require 'faker'

Factory.define :post do |post|
  post.title { Faker::Lorem.sentence }
  post.body  { Faker::Lorem.paragraphs.join(' ') }
end

training.rake

desc "Load db with test data"
task :populate => ['db:reset', :environment] do
  require 'factory_girl'
  load File.join(Rails.root, 'test', 'factories', 'post.rb')

  10.times { Factory(:post) }
end