Introduce and re-use turbo_stream_broadcasts helper

lib/turbo/broadcastable/test_helper.rb

@@ -60,16 +60,10 @@ module TestHelper
       def assert_turbo_stream_broadcasts(stream_name_or_object, &block)
         block&.call
 
-        stream_name = stream_name_from(stream_name_or_object)
-        payloads = broadcasts(stream_name)
-
-        assert payloads.present?, "Expected at least one broadcast on #{stream_name.inspect}, but there were none"
-
-        payloads.flat_map do |payload|
-          html = ActiveSupport::JSON.decode(payload)
-          document = Nokogiri::HTML5.parse(html)
+        turbo_stream_broadcasts(stream_name_or_object).tap do |payloads|
+          stream_name = stream_name_from(stream_name_or_object)
 
-          document.at("body").element_children
+          assert payloads.present?, "Expected at least one broadcast on #{stream_name.inspect}, but there were none"
         end
       end
 
@@ -115,6 +109,18 @@ def assert_no_turbo_stream_broadcasts(stream_name_or_object, &block)
 
         assert payloads.empty?, "Expected no broadcasts on #{stream_name.inspect}, but there were #{payloads.count}"
       end
+
+      def turbo_stream_broadcasts(stream_name_or_object)
+        stream_name = stream_name_from(stream_name_or_object)
+        payloads = broadcasts(stream_name)
+
+        payloads.flat_map do |payload|
+          html = ActiveSupport::JSON.decode(payload)
+          document = Nokogiri::HTML5.parse(html)
+
+          document.at("body").element_children
+        end
+      end
     end
   end
 end