ruby-on-rails - 删除 rspec 中的测试 - 更改(模型，:count) failing - Why is reload needed?

Question

TLDR:App.count 需要重新加载才能看到创建的记录。为什么？

我找到了很多关于测试 DELETE 方法的引用资料，如下所示:

expect { delete_request }.to change(App, :count).by(-1)

这是有道理的，并且适用于一些类似的场景。但是，我在测试不应该执行的删除时遇到了一个问题，例如当没有用户登录时。

我从这里开始，用两种方法来测试同一件事:

require 'rails_helper'

RSpec.describe V1::AppsController, type: :controller do
  let(:user) { create(:user) }
  let(:app) { create(:app, account: user.account) }

  describe 'DELETE destroy when you are not logged in' do
    let(:delete_request) { delete :destroy, id: app, format: :json }

    it 'does not delete the app (.count)' do
      expect { delete_request }.not_to change(App, :count)
    end

    it 'does not delete the app (.exists?)' do
      delete_request
      expect(App.exists?(app.id)).to eq(true)
    end
  end
end

这是 rspec 所说的:

V1::AppsController
  DELETE destroy when you are not logged in
    does not delete the app (.count) (FAILED - 1)
    does not delete the app (.exists?)

Failures:

  1) V1::AppsController DELETE destroy when you are not logged in does not delete the app (.count)
     Failure/Error: expect { delete_request }.not_to change(App, :count)
       expected #count not to have changed, but did change from 0 to 1
     # ./spec/controllers/v1/delete_test_1.rb:11:in `block (3 levels) in <top (required)>'

2 examples, 1 failure

请注意最令人困惑的部分:预期#count 没有改变，但确实从 0 变为 1。嗯？我试图进行非法删除，但我的记录数增长 了一个？另请注意，明确检查主题记录是否仍然存在是有效的。

所以我又尝试了一些，发现我可以通过在 expect() 之前重新加载来解决问题:

it 'does not delete the app (.count)' do
  puts "App.count is #{App.count} (after create(:app))"
  app.reload
  puts "App.count is #{App.count} (after reload)"
  expect { delete_request }.not_to change(App, :count)
  puts "App.count is #{App.count} (after request)"
end

现在 rspec 很高兴:

V1::AppsController
  DELETE destroy when you are not logged in
App.count is 0 (after create(:app))
App.count is 1 (after reload)
App.count is 1 (after request)
    does not delete the app (.count)
    does not delete the app (.exists?)

2 examples, 0 failures

基于所有这些，我决定坚持使用 exists? 方法。但另一个(可能更大)问题是，我在互联网上找到的所有测试样本都用于测试创建记录，例如 expect { create_request }.to change(App, :count).by(1)可能是误报，如果他们看到与我相同的结果，并假设记录是在实际上是缓存工件时创建的？

那么，知道为什么 App.count 需要 reload 才能看到当前值吗？

Answer 1

发生这种情况是因为当 ruby​​ 调用 delete_request 方法时，它会调用 app 方法，并创建一个 App

要对此进行测试，请在调用 expect rspec 方法之前创建应用:

it 'does not delete the app (.count)' do
  app #creates the app
  expect { delete_request }.not_to change(App, :count)
end

看看let的文档:

Use let to define a memoized helper method. The value will be cached across multiple calls in the same example but not across examples.

Note that let is lazy-evaluated: it is not evaluated until the first time the method it defines is invoked. You can use let! to force the method's invocation before each example.

https://www.relishapp.com/rspec/rspec-core/v/2-11/docs/helper-methods/let-and-let