RSpec 和 Factory 用于测试 next，prev 记录

Question

我有一个用户模型，其中包含下一个和上一个用户的方法：

def next_user
  User.where("id > ?", id).order("id ASC").first
end

def prev_user
  User.where("id < ?", id).order("id DESC").first
end

我正在尝试使用 RSpec 和 Factory girl 设置一个测试来对此进行测试，但我不确定该方法 - 我才刚刚开始使用 TDD。

我正在尝试这个：

describe "previous_next" do
   let(:user) { FactoryGirl.create(:user) }
   let(:next_user) { FactoryGirl.create(:user) }

   it "should know the next user" do
     expect(user.next_user).to eq next_user
   end

   it "should know the previous user" do
     expect(next_user.prev_user).to eq user
   end
end

这是错误

1) User previous_next should know the next user
 Failure/Error: expect(user.next_user).to eq next_user

   expected: #<User id: 7624, name: "Example User", email: "sample9@email.com", created_at: "2013-01-13 04:31:19", updated_at: "2013-01-13 04:31:19", password_digest: "$2a$04$mbzI.yXYd9eSSfXbjChROewwvCHLFQI6qq5IUNzAKo9O...", remember_token: "KMSmiEeOr6f_Sgi8KJffIA", admin: false, plan_id: nil, password_reset_token: nil, password_reset_sent_at: nil, stripe_customer_token: nil>
        got: nil

   (compared using ==)
 # ./spec/models/user_spec.rb:93:in `block (3 levels) in <top (required)>'

 2) User previous_next should know the previous user
    Failure/Error: expect(next_user.prev_user).to eq user

   expected: #<User id: 7626, name: "Example User", email: "sample11@email.com", created_at: "2013-01-13 04:31:19", updated_at: "2013-01-13 04:31:19", password_digest: "$2a$04$uzrKmsXmVY7jUdRtfnfhUe89Jgy1176zE2UxdH90imJR...", remember_token: "gl10QvxjSMZYQS3JIgbREg", admin: false, plan_id: nil, password_reset_token: nil, password_reset_sent_at: nil, stripe_customer_token: nil>
        got: nil

   (compared using ==)
 # ./spec/models/user_spec.rb:97:in `block (3 levels) in <top (required)>'

如果我将 next_user 记录创建为 :user 工厂的实例，为什么它的值为 nil？

Answer 1

问题是 let 懒惰地评估，直到你要求它们才创建记录。

使用let! 而不是let。这会急切地评估它们并强制在测试之前创建记录。