factory_girl_rails：创建关联的子级时，不会填充工厂构建的模型实例的has_many关联

class User < ActiveRecord::Base
  has_many :tasks
  belongs_to :project
end

class Task < ActiveRecord::Base
  belongs_to :user
  belongs_to :project
end

class Project < ActiveRecord::Base
  has_many :users
  has_many :tasks
end

Factory.define :task do |t|
  t.association :user
  t.association :project
  t.after_create {|t| t.user.tasks << t}
  t.after_create {|t| t.project.tasks << t}
end

scenario \"user with tasks from one project is assigned another task from the same project\" do
  user = Factory.create :user
  (1..5).each { Factory.create(:task, :user => user, :project => user.project)}
  visit_project_path user.project
  correctly_fill_in_new_task_fields
  click_button \"Create task\" #creates a new task for the above user
  assert user.tasks.size == 6 #currently fails
end

user.tasks.size == 5

Task.where(:user_id => user.id).size == 6