FactoryGirl使い方メモ ref: http://qiita.com/blueplanet/items/b023e26e0ecd79231136

event.rb

class Event < ActiveRecord::Base
  has_many :groups
end

file3.txt

FactoryGirl.define do
  factory :seq_group, class: Group do
    sequence(:name) { |n| "group #{n}"}
    sequence(:description) {|n| "description #{n}"}
    sequence(:img_url) {|n| "http://test.com/#{n}.jpg"}
  end

  factory :group_event, class: Group , parent: :seq_group do
    events {
      [FactoryGirl.create(:seq_event)]
    }
  end
end

group.rb

class Group < ActiveRecord::Base
  has_many :events
  has_many :members
end

group_event.rb

FactoryGirl.define do
  factory :group_event, class: Group do
    members {
      FactoryGirl.create_list(:seq_user, 10)
    }
  end
end