Learnings

`FactoryBot::DuplicateDefinitionError` on dev server startup

Context: My development server (./bin/dev) failed to boot, reporting FactoryBot::DuplicateDefinitionError: Factory already registered: learning.
Cause: The factory_bot_rails gem was included in the group :development, :test do block in the Gemfile. This caused FactoryBot's Railtie to load factory definitions (spec/factories/*.rb) during development environment initialization (e.g., via Spring or initial boot), potentially conflicting with other initializers or running twice.
Resolution: I moved gem "factory_bot_rails" exclusively to the group :test do block in the Gemfile and ran rbenv exec bundle install.
Learning: I learned that gems intended solely for testing (like factory_bot_rails, shoulda-matchers, capybara) should typically only be included in the :test group in the Gemfile. Including them in :development can lead to unexpected behavior, errors during server startup, or unnecessary loading as their initializers might run inappropriately or cause conflicts.