Added tests for verifying content length presence in response headers

Author: adityapandit17

activestorage/test/controllers/blobs/proxy_controller_test.rb

@@ -137,6 +137,17 @@ class ActiveStorage::Blobs::ProxyControllerTest < ActionDispatch::IntegrationTes
     assert request.session_options[:skip],
       "Expected request.session_options[:skip] to be true"
   end
+
+  test "rails_storage_proxy include Content-Length header" do
+    Rails.application.config.active_storage.resolve_model_to_route = :rails_storage_proxy
+    blob = create_file_blob(filename: "racecar.jpg")
+
+    get rails_storage_proxy_url(blob)
+
+    assert_response :success
+    assert_not_nil response.headers["Content-Length"], "Content-Length header should be included in proxy mode"
+    assert_equal blob.byte_size.to_s, response.headers["Content-Length"], "Content-Length header should match blob size"
+  end
 end
 
 class ActiveStorage::Blobs::ExpiringProxyControllerTest < ActionDispatch::IntegrationTest