Fix failing configuration tests by adding packer mocks

Two tests were missing the required packer.config.public_output_path
mocking, causing nil errors during configuration setup.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: justin808

spec/react_on_rails/configuration_spec.rb

@@ -282,7 +282,12 @@ module ReactOnRails
     end
 
     it "changes the configuration of the gem, such as setting the prerender option to false" do
+      test_path = File.expand_path("public/webpack/test")
+      allow(ReactOnRails::PackerUtils).to receive_message_chain("packer.config.public_output_path")
+        .and_return(Pathname.new(test_path))
+
       ReactOnRails.configure do |config|
+        config.generated_assets_dir = test_path
         config.server_bundle_js_file = "server.js"
         config.prerender = false
       end
@@ -292,7 +297,12 @@ module ReactOnRails
     end
 
     it "changes the configuration of the gem, such as setting the prerender option to true" do
+      test_path = File.expand_path("public/webpack/test")
+      allow(ReactOnRails::PackerUtils).to receive_message_chain("packer.config.public_output_path")
+        .and_return(Pathname.new(test_path))
+
       ReactOnRails.configure do |config|
+        config.generated_assets_dir = test_path
         config.server_bundle_js_file = "something.js"
         config.prerender = true
         config.random_dom_id = false

spec/react_on_rails/packer_utils_spec.rb

@@ -92,8 +92,8 @@ module ReactOnRails
     end
 
     describe ".supports_auto_registration?" do
-      let(:mock_config) { double("MockConfig") }
-      let(:mock_packer) { double("MockPacker", config: mock_config) }
+      let(:mock_config) { double("MockConfig") } # rubocop:disable RSpec/VerifiedDoubles
+      let(:mock_packer) { double("MockPacker", config: mock_config) } # rubocop:disable RSpec/VerifiedDoubles
 
       before do
         allow(described_class).to receive(:packer).and_return(mock_packer)