升级后的 Rails 和 rspec 现在测试未通过

Question

我不太明白为什么这些测试突然没有通过：

Failure/Error: @user = test_sign_in(Factory(:user))
     NoMethodError:
       undefined method `test_sign_in' for #<RSpec::Core::ExampleGroup::Nested_3::Nested_1::Nested_2:0x00000100a908e8>

有很多测试在 test_sign_in 上失败，然后另一个测试失败：

     1) SessionsController POST 'create' with valid email and password should sign the user in
     Failure/Error: controller.should be_signed_in
     NoMethodError:
       undefined method `authenticate?' for nil:NilClass
     # ./spec/controllers/sessions_controller_spec.rb:51:in `block (4 levels) in <top (required)>'

  2) SessionsController DELETE 'destroy' should sign a user out
     Failure/Error: controller.should_not be_signed_in
     NoMethodError:
       undefined method `authenticate?' for nil:NilClass
     # ./spec/controllers/sessions_controller_spec.rb:66:in `block (3 levels) in <top (required)>'

  3) UsersController POST 'create' success should sign the user in
     Failure/Error: controller.should be_signed_in
     NoMethodError:
       undefined method `authenticate?' for nil:NilClass
     # ./spec/controllers/users_controller_spec.rb:171:in `block (4 levels) in <top (required)>'

  4) Users sign in/out success should sign a user in and out
     Failure/Error: controller.should be_signed_in
       expected signed_in? to return true, got false
     # ./spec/requests/users_spec.rb:68:in `block (4 levels) in <top (required)>'