Add specs to ensure rendering does not conflict with Rails send_data calls

Author: Nitemaeric

spec/system/dummy/controllers/api/v1/health_controller.rb

@@ -6,6 +6,10 @@ class HealthController < Api::ApplicationController
       def index
         render(json: { ok: true })
       end
+
+      def download
+        send_data("binary data content", filename: "report.txt", type: "text/plain")
+      end
     end
   end
 end

spec/system/dummy/controllers/base_controller.rb

@@ -1,7 +1,20 @@
 # frozen_string_literal: true
 
 class BaseController
-  def render(json:)
+  def render(json: nil, body: nil, **options)
+    return body if body
+
     JSON.parse(JSON.generate(json))
   end
+
+  # Simulates Rails' send_data method which internally calls render
+  # See: https://api.rubyonrails.org/classes/ActionController/DataStreaming.html
+  #
+  # Note: Rails calls render with a Hash (not keyword arguments):
+  #   render options.slice(:status, :content_type).merge(body: data)
+  #
+  # We simulate this exactly to catch any issues with Hash vs kwargs handling
+  def send_data(data, options = {})
+    render(**options.slice(:status, :content_type).merge(body: data))
+  end
 end

spec/system/rendering_spec.rb

@@ -116,5 +116,21 @@
         expect(controller.index).to eq(expected_json)
       end
     end
+
+    describe "#download" do
+      it "returns binary data without serialization" do
+        expect(controller.download).to eq("binary data content")
+      end
+
+      it "does not call serialize" do
+        expect(controller).not_to receive(:serialize)
+        controller.download
+      end
+
+      it "does not call lookup_serializer" do
+        expect(controller).not_to receive(:lookup_serializer)
+        controller.download
+      end
+    end
   end
 end