What Ruby, Rails and RSpec versions are you using?

Ruby version: 3.4.5
Rails version: 8.0.2
RSpec version: 3.13

• rspec-core 3.13.5
• rspec-expectations 3.13.5
• rspec-mocks 3.13.5
• rspec-rails 8.0.1
• rspec-support 3.13.4

Observed behaviour

In rack v3.2, when running tests generated by rails generate scaffold / scaffold_controller, the following warning is displayed:

/path-to-app/vendor/bundle/ruby/3.4.0/gems/rspec-rails-8.0.1/lib/rspec/rails/matchers/have_http_status.rb:219: warning: Status code :unprocessable_entity is deprecated and will be removed in a future version of Rack. Please use :unprocessable_content instead.

For example, in the following request spec, the warning occurs at the expect(response).to have_http_status(:unprocessable_entity) line.

# spec/requests/posts_spec.rb
  describe "POST /create" do
...
    context "with invalid parameters" do
...
      it "renders a response with 422 status (i.e. to display the 'new' template)" do
        post posts_url, params: { post: invalid_attributes }
        expect(response).to have_http_status(:unprocessable_entity)
      end
    end
  end

Expected behaviour

When running tests generated by rails generate scaffold / scaffold_controller in rack v3.2, no warning should be displayed.

The reason for the warning is that starting in rack v3.2, passing obsolete values such as :unprocessable_entity to Rack::Utils.status_code will trigger a warning.
Replacing :unprocessable_entity with :unprocessable_content removes the warning, but it would be preferable if tests generated by rails generate scaffold / scaffold_controller did not produce warnings without manual changes.

Can you provide an example reproduction?

Example app

https://github.com/taketo1113/rails-sample-rspec-rails

Steps to reproduce

rails spec

The tests pass, but the following warning is displayed:

/path-to-app/vendor/bundle/ruby/3.4.0/gems/rspec-rails-8.0.1/lib/rspec/rails/matchers/have_http_status.rb:219: warning: Status code :unprocessable_entity is deprecated and will be removed in a future version of Rack. Please use :unprocessable_content instead.

Additional Information: workaround for existing code

After upgrading to rack 3.2, It can fix the warnings in existing test code by replacing :unprocessable_entity with :unprocessable_content in request specs and controller specs.

# spec/requests/posts_spec.rb
  describe "POST /create" do
...
    context "with invalid parameters" do
...
      it "renders a response with 422 status (i.e. to display the 'new' template)" do
        post posts_url, params: { post: invalid_attributes }
-        expect(response).to have_http_status(:unprocessable_entity)
+        expect(response).to have_http_status(:unprocessable_content)
      end
    end
  end