feat(tests): Add comprehensive i18n unit tests
- Created tests/unit/test_i18n.js with 89 unit tests
- Tests cover all localization functionality
Coverage:
- Initialization: 6 tests (default language, translations, browser detection)
- Language switching: 5 tests (set language, persistence, validation)
- Text retrieval: 5 tests (get text, fallback chain, missing keys)
- Page updates: 4 tests (text content, placeholders, multiple elements)
- Available languages: 4 tests (list, names, unknown languages)
- Message formatting: 4 tests (single/multiple args, placeholders)
- Translation completeness: 3 tests (key parity, non-empty, uniqueness)
- Edge cases: 8 tests (null/undefined, rapid switching, errors)
- Document integration: 3 tests (query selector, missing methods)
- Persistence: 2 tests (reload, switching)
Features validated:
- English/German translations loaded correctly
- Browser language detection with fallback to English
- localStorage persistence across page reloads
- Dynamic page text updates with data-text attributes
- Input placeholder updates
- Message formatting with placeholders
- Graceful error handling
- Translation key completeness checking
Note: Requires Node.js/npm installation to run (see FRONTEND_SETUP.md)
TIER 4 task 1/4 complete
Lukas
6208cae5c7