在RoR教程中，
test/test_helper.rb
...
class ActiveSupport::TestCase
# Run tests in parallel with specified workers
parallelize(workers: :number_of_processors)
# Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
fixtures :all
include ApplicationHelper
# Returns true if a test user is logged in.
def is_logged_in?
!session[:user_id].nil?
end
...
清楚地表明；is_loged_in"是在类ActiveSupport:：TestCase中定义的，然而，ActionDispatch类的集成测试怎么可能找到它呢？如图所示：
test/integration/user_signup_test.rb
require 'test_helper'
class UsersSignupTest < ActionDispatch::IntegrationTest
...
test "valid signup information with account activation" do
...
log_in_as(user)
assert_not is_logged_in?
# Invalid activation token
get edit_account_activation_path("invalid token", email: user.email)
assert_not is_logged_in?
# Valid token, wrong email
get edit_account_activation_path(user.activation_token, email: 'wrong')
assert_not is_logged_in?
# Valid activation token
get edit_account_activation_path(user.activation_token, email: user.email)
assert user.reload.activated?
follow_redirect!
assert_template "users/show"
assert is_logged_in?
end
end
根据我的理解，除非；is_loged_in"在类ActionDispatch中定义，它应该抛出类似"的错误；nomethoderror，未定义的is_loged_in&"；，然而，为什么不是这样呢？
ActionDispatch::IntegrationTest从ActiveSupport::TestCase继承了许多其他内容，因此在ActiveSupport::TestCase中进行的任何修改也将在子类中可用。
请理解，在test_helper.rb中，class ActiveSupport::TestCase不会创建新类，而是重新打开现有类以添加一些更改。