工厂女孩有很多:通过验证

class Activity < ActiveRecord::Base
  has_many  :clientships, :dependent => :destroy
  has_many  :clients, :through => :clientships
end

class Clientship < ActiveRecord::Base
  belongs_to  :client
  belongs_to  :activity

  validates_presence_of :client_id
  validates_presence_of :activity_id, :unless => :new_record?
end

class Client < ActiveRecord::Base
  has_many  :clientships
  has_many  :activities, :through => :clientships
end

我无法创建:活动工厂,因为我得到验证错误“ ".

我的工厂是这样的:

Factory.define :activity do |a|
  a.association :staff, :factory => :user
  a.clientships { |cs| [cs.association :clientship] }
end

Factory.define :clientship do |cs|
  cs.association(:client)
end

Factory.define :client do |c|
  c.first_name {Factory.next(:name)}
  c.last_name {Factory.next(:name)}
end

@activity = Factory(:activity)

请帮帮我!