Rails assert_select没有找到HAML元素

Question

在尝试创建无效对象时，尝试断言我的错误面板正在显示。

我有这个测试::

test 'invalid category submission results in failure' do
  get new_category_path
  assert_template 'categories/new'
  assert_no_difference 'Category.count' do
    post_via_redirect categories_path, category: {name: ''}
  end
  assert_template 'categories/new'
  assert_select 'h2.panel-title'    #<---Problem here
  assert_select 'div.panel-body'
  # assert_match 'prohibited', response.body  #<---This works
end

UI显示::

执行test ::

时出现此错误

1) Failure:
CreateCategoriesTest#test_invalid_category_submission_results_in_failure [/Users/jeffrey/Documents/workspace/Ruby/Udemy_Rails_Course/rails_projects/alpha-blog/test/integration/create_categories_test.rb:23]:
Expected at least 1 element matching "h2.panel-title", found 0..
Expected 0 to be >= 1.

如果我注释掉2＆＃34; assert_select＆＃34;声明并取消注释＆＃34; assert_match＆＃34;声明，然后我的测试通过，因为它检测到＆＃34;禁止＆＃34;在response.body。

所以关于为什么＆＃34;断言_选择＆＃34;找不到我的元素，即使它们显然在那里？