Add failing test case for #9654

railties/test/application/rendering_test.rb

@@ -0,0 +1,45 @@
+require 'isolation/abstract_unit'
+require 'rack/test'
+
+module ApplicationTests
+  class RoutingTest < ActiveSupport::TestCase
+    include ActiveSupport::Testing::Isolation
+    include Rack::Test::Methods
+
+    def setup
+      build_app
+      boot_rails
+    end
+
+    def teardown
+      teardown_app
+    end
+
+    test "Unknown format falls back to HTML template" do
+      app_file 'config/routes.rb', <<-RUBY
+        AppTemplate::Application.routes.draw do
+          get 'pages/:id', to: 'pages#show'
+        end
+      RUBY
+
+      app_file 'app/controllers/pages_controller.rb', <<-RUBY
+        class PagesController < ApplicationController
+          layout false
+
+          def show
+          end
+        end
+      RUBY
+
+      app_file 'app/views/pages/show.html.erb', <<-RUBY
+        <%= params[:id] %>
+      RUBY
+
+      get '/pages/foo'
+      assert_equal 200, last_response.status
+
+      get '/pages/foo.bar'
+      assert_equal 200, last_response.status
+    end
+  end
+end