Question

TLDR：App.count需要重新加载才能看到创建的记录。为什么？

我发现很多引用测试DELETE方法，如下所示：

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

这是有道理的，适用于某些类似的场景。但是，在测试不应该工作的删除时，我发现了一个问题，例如没有用户登录时。

这是我开始的地方，有两种方法可以测试同样的事情：

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

这就是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：expected #count not to have changed, but did change from 0 to 1。咦？我试图进行非法删除，我的记录数增长一个？另请注意，明确检查主题记录的检查仍然有效。

所以我玩了一些，发现我可以在expect（）之前重新加载来修复问题：

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

从这一切开始，我决定坚持使用exists?方法。但另一个（可能更大）的问题是，我在互联网上发现的所有测试样本，如果他们看到与我相同的结果，并且假设记录，那么测试创建像expect { create_request }.to change(App, :count).by(1)这样的记录的所有测试样本都可能是误报。实际上它是一个缓存工件吗？

那么，知道为什么App.count需要reload才能看到当前值？

Answer 1

这是因为当ruby调用delete_request方法时，它会调用app方法，并创建一个App

要测试此功能，请在调用expect rspec方法之前创建应用程序：

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

查看let的文档：

使用let来定义memoized帮助器方法。该值将被缓存   在同一个示例中跨多个调用但不跨越示例。

请注意，let是懒惰评估的：直到第一个才会评估它   调用它定义的方法的时间。你可以用let！迫使   每个例子之前的方法调用。

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

在rspec中删除测试 - 更改（模型，：计数）失败 - 为什么需要重新加载？

1 个答案: