Define url_options as system test case does

See:
rails/rails@ea77dbf#diff-ff5f366a442b8761d35f94807700fa77R162

Author: JonRowe

lib/rspec/rails/example/system_example_group.rb

@@ -100,6 +100,10 @@ def driven_by(driver, **driver_options, &blk)
           @driver = ::ActionDispatch::SystemTestCase.driven_by(driver, **driver_options, &blk).tap(&:use)
         end
 
+        def url_options
+          default_url_options.merge(host: Capybara.app_host)
+        end
+
         before do
           @routes = ::Rails.application.routes
         end

spec/rspec/rails/example/system_example_group_spec.rb

@@ -18,6 +18,22 @@ module RSpec::Rails
         end
       end
 
+      describe '#url_options' do
+        it 'has the rails system test default host' do
+          rails_url_options = {}
+          group = RSpec::Core::ExampleGroup.describe do
+            include SystemExampleGroup
+
+            specify { rails_url_options.merge!(url_options) }
+          end
+          expect(group.run).to be true
+
+          expect(
+            rails_url_options
+          ).to match hash_including(host: ActionDispatch::SystemTesting::TestHelpers::SetupAndTeardown::DEFAULT_HOST)
+        end
+      end
+
       describe '#driver' do
         it 'uses :selenium driver by default' do
           group = RSpec::Core::ExampleGroup.describe do