Rails：如何测试委托方法？答案

【问题标题】：Rails: How to test delegated methods?Rails：如何测试委托方法？
【发布时间】：2016-08-21 10:43:45
【问题描述】：

在我 reworked 我的 rails 应用程序之后，我在测试中遇到了一些我无法弄清楚的错误。我认为通过“委托”Rails 神奇地知道即使在测试要使用哪些测试数据、进行测试时，我也不必再次在夹具中声明那些委托数据（因为我还没有找到任何关于它的信息）。由于我使用的是脚手架测试，因此我认为它们至少应该无缝地工作——这可能是一个愚蠢的想法......

也许你有一个想法？提前致谢！

这里是模型：

class Box < ActiveRecord::Base
  belongs_to :practice
  delegate :prac_name, to: :practice

  has_many :students

  validates :practice_id, presence: true
  validates :box_name,    presence: true, length: { in: 2..20 }
end

class Practice < ActiveRecord::Base
  has_many  :boxes

  validates :prac_name, presence: true, length: { in: 5..50 }
end

控制器：

# GET /boxes
def index
  @boxes = Box.all.order(box_name: :asc)
end

观点：

<tbody>
  <% @boxes.each do |box| %>
    <tr>
      <td><%= box.box_name %></td>
      <td><%= box.prac_name %></td>
      <td><%= link_to 'Show', box %></td>
      <td><%= link_to 'Edit', edit_box_path(box) %></td>
      <td><%= link_to 'Delete', box, method: :delete, data: { confirm: 'Are you sure?' } %></td>
    </tr>
  <% end %>
</tbody>

赛程：

# box
one:
  box_name: MyString
  practice_id: 1

two:
  box_name: MyString
  practice_id: 1

# practice
one:
  prac_name: MyString

two:
  prac_name: MyString

这里是测试：

test 'should get index' do
  get :index
  assert_response :success
  assert_not_nil assigns(:boxes)
end

结果是我从警卫/minitest 收到此错误消息，用于“获取索引”和“显示框”。为什么练习为零？（ActionView::Template::Error: Box#prac_name 委托给 practice.prac_name，但是 practice 是 nil）不是通过 practice fixture 声明的吗？显然不是，但为什么呢？

ERROR["test_should_get_index", BoxesControllerTest, 3.196711939992383]
 test_should_get_index#BoxesControllerTest (3.20s)
ActionView::Template::Error:         ActionView::Template::Error: Box#prac_name delegated to practice.prac_name, but practice is nil: #<Box id: 298486374, box_name: "MyString", created_at: "2016-04-27 07:54:37", updated_at: "2016-04-27 07:54:37", practice_id: 1>
            app/models/box.rb:3:in `rescue in prac_name'
            app/models/box.rb:3:in `prac_name'
            app/views/boxes/index.html.erb:17:in `block in _app_views_boxes_index_html_erb__3226877961716035159_70232972217220'
            activerecord (4.2.6) lib/active_record/relation/delegation.rb:46:in `each'
            activerecord (4.2.6) lib/active_record/relation/delegation.rb:46:in `each'
            app/views/boxes/index.html.erb:14:in `_app_views_boxes_index_html_erb__3226877961716035159_70232972217220'
            actionview (4.2.6) lib/action_view/template.rb:145:in `block in render'
            activesupport (4.2.6) lib/active_support/notifications.rb:164:in `block in instrument'
            activesupport (4.2.6) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
            activesupport (4.2.6) lib/active_support/notifications.rb:164:in `instrument'
            actionview (4.2.6) lib/action_view/template.rb:333:in `instrument'
            actionview (4.2.6) lib/action_view/template.rb:143:in `render'
            actionview (4.2.6) lib/action_view/renderer/template_renderer.rb:54:in `block (2 levels) in render_template'
            actionview (4.2.6) lib/action_view/renderer/abstract_renderer.rb:39:in `block in instrument'
            activesupport (4.2.6) lib/active_support/notifications.rb:164:in `block in instrument'
            activesupport (4.2.6) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
            activesupport (4.2.6) lib/active_support/notifications.rb:164:in `instrument'
            actionview (4.2.6) lib/action_view/renderer/abstract_renderer.rb:39:in `instrument'
            actionview (4.2.6) lib/action_view/renderer/template_renderer.rb:53:in `block in render_template'
            actionview (4.2.6) lib/action_view/renderer/template_renderer.rb:61:in `render_with_layout'
            actionview (4.2.6) lib/action_view/renderer/template_renderer.rb:52:in `render_template'
            actionview (4.2.6) lib/action_view/renderer/template_renderer.rb:14:in `render'
            actionview (4.2.6) lib/action_view/renderer/renderer.rb:46:in `render_template'
            actionview (4.2.6) lib/action_view/renderer/renderer.rb:27:in `render'
            actionview (4.2.6) lib/action_view/rendering.rb:100:in `_render_template'
            actionpack (4.2.6) lib/action_controller/metal/streaming.rb:217:in `_render_template'
            actionview (4.2.6) lib/action_view/rendering.rb:83:in `render_to_body'
            actionpack (4.2.6) lib/action_controller/metal/rendering.rb:32:in `render_to_body'
            actionpack (4.2.6) lib/action_controller/metal/renderers.rb:37:in `render_to_body'
            actionpack (4.2.6) lib/abstract_controller/rendering.rb:25:in `render'
            actionpack (4.2.6) lib/action_controller/metal/rendering.rb:16:in `render'
            actionpack (4.2.6) lib/action_controller/metal/instrumentation.rb:44:in `block (2 levels) in render'
            activesupport (4.2.6) lib/active_support/core_ext/benchmark.rb:12:in `block in ms'
            /Users/andy/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/benchmark.rb:303:in `realtime'
            activesupport (4.2.6) lib/active_support/core_ext/benchmark.rb:12:in `ms'
            actionpack (4.2.6) lib/action_controller/metal/instrumentation.rb:44:in `block in render'
            actionpack (4.2.6) lib/action_controller/metal/instrumentation.rb:87:in `cleanup_view_runtime'
            activerecord (4.2.6) lib/active_record/railties/controller_runtime.rb:25:in `cleanup_view_runtime'
            actionpack (4.2.6) lib/action_controller/metal/instrumentation.rb:43:in `render'
            actionpack (4.2.6) lib/action_controller/metal/implicit_render.rb:10:in `default_render'
            actionpack (4.2.6) lib/action_controller/metal/implicit_render.rb:5:in `send_action'
            actionpack (4.2.6) lib/abstract_controller/base.rb:198:in `process_action'
            actionpack (4.2.6) lib/action_controller/metal/rendering.rb:10:in `process_action'
            actionpack (4.2.6) lib/abstract_controller/callbacks.rb:20:in `block in process_action'
            activesupport (4.2.6) lib/active_support/callbacks.rb:117:in `call'
            activesupport (4.2.6) lib/active_support/callbacks.rb:117:in `call'
            activesupport (4.2.6) lib/active_support/callbacks.rb:555:in `block (2 levels) in compile'
            activesupport (4.2.6) lib/active_support/callbacks.rb:505:in `call'
            activesupport (4.2.6) lib/active_support/callbacks.rb:505:in `call'
            activesupport (4.2.6) lib/active_support/callbacks.rb:92:in `__run_callbacks__'
            activesupport (4.2.6) lib/active_support/callbacks.rb:778:in `_run_process_action_callbacks'
            activesupport (4.2.6) lib/active_support/callbacks.rb:81:in `run_callbacks'
            actionpack (4.2.6) lib/abstract_controller/callbacks.rb:19:in `process_action'
            actionpack (4.2.6) lib/action_controller/metal/rescue.rb:29:in `process_action'
            actionpack (4.2.6) lib/action_controller/metal/instrumentation.rb:32:in `block in process_action'
            activesupport (4.2.6) lib/active_support/notifications.rb:164:in `block in instrument'
            activesupport (4.2.6) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
            activesupport (4.2.6) lib/active_support/notifications.rb:164:in `instrument'
            actionpack (4.2.6) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
            actionpack (4.2.6) lib/action_controller/metal/params_wrapper.rb:250:in `process_action'
            activerecord (4.2.6) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
            actionpack (4.2.6) lib/abstract_controller/base.rb:137:in `process'
            actionview (4.2.6) lib/action_view/rendering.rb:30:in `process'
            actionpack (4.2.6) lib/action_controller/test_case.rb:639:in `process'
            actionpack (4.2.6) lib/action_controller/test_case.rb:67:in `process'
            actionpack (4.2.6) lib/action_controller/test_case.rb:514:in `get'
            test/controllers/boxes_controller_test.rb:9:in `block in <class:BoxesControllerTest>'
            minitest (5.8.4) lib/minitest/test.rb:108:in `block (3 levels) in run'
            minitest (5.8.4) lib/minitest/test.rb:205:in `capture_exceptions'
            minitest (5.8.4) lib/minitest/test.rb:105:in `block (2 levels) in run'
            minitest (5.8.4) lib/minitest/test.rb:256:in `time_it'
            minitest (5.8.4) lib/minitest/test.rb:104:in `block in run'
            minitest (5.8.4) lib/minitest.rb:331:in `on_signal'
            minitest (5.8.4) lib/minitest/test.rb:276:in `with_info_handler'
            minitest (5.8.4) lib/minitest/test.rb:103:in `run'
            minitest-reporters (1.1.8) lib/minitest/reporters.rb:48:in `run_with_hooks'
            minitest (5.8.4) lib/minitest.rb:778:in `run_one_method'
            minitest (5.8.4) lib/minitest.rb:305:in `run_one_method'
            minitest (5.8.4) lib/minitest.rb:293:in `block (2 levels) in run'
            minitest (5.8.4) lib/minitest.rb:292:in `each'
            minitest (5.8.4) lib/minitest.rb:292:in `block in run'
            minitest (5.8.4) lib/minitest.rb:331:in `on_signal'
            minitest (5.8.4) lib/minitest.rb:318:in `with_info_handler'
            minitest (5.8.4) lib/minitest.rb:291:in `run'
            minitest (5.8.4) lib/minitest.rb:152:in `block in __run'
            minitest (5.8.4) lib/minitest.rb:152:in `map'
            minitest (5.8.4) lib/minitest.rb:152:in `__run'
            minitest (5.8.4) lib/minitest.rb:129:in `run'
            minitest (5.8.4) lib/minitest.rb:56:in `block in autorun'
            /Users/andy/.rvm/rubies/ruby-2.2.1/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
            /Users/andy/.rvm/rubies/ruby-2.2.1/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
            -e:1:in `<main>'

谢谢！

【问题讨论】：

2 个问题：1. 夹具中的 yml 是否相同？ 2. 你确定存在 id 1 的练习吗？注意：fixtures 不是很有用的做法，请尝试使用 factory_girl 来创建模型实例
嗨。感谢您的快速回复！ @1：是的，这就是 box.yml 和 practice.yml 的内容。 @2：我认为fixtures是在测试期间填充在test.db中的数据。在那个逻辑中，我认为通过宣布“练习一”练习不能为零。或者哪个是测试数据？在我的seeds.rb实践中也充满了。
那么答案是什么？
抱歉，按回车换行“太混乱了”...
你在测试环境中使用过 seeds.db 吗？它主要用于developpemt，尝试使用factory_girl，您也可以使用pry gem 在异常之前为代码设置断点。确保 practice.id=1 是否存在

标签： ruby-on-rails testing

【解决方案1】：

在考虑了 cmets 之后，我再次查看了 test.sqlite 并发现了我在固定装置中的错误：我没有明确声明另一个表的 id，而是将其更改为另一个表的名称并引用像这样：

one:
  box_name: MyString
  practice: one

two:
  box_name: MyString
  practice: two

现在我的测试通过了。因此，正如我最初假设的那样，“代表”不是问题。不过，我会看看 factory_girl。

#wrong
practice_id: 1

#right
practice: one

【讨论】：