### Question:
LanguageServiceImpl implements LanguageService { @Override public List<String> findAllLanguageCodes() { return languageRepo.findAllLanguageCodes(); } @Autowired  LanguageServiceImpl(
        LanguageRepo languageRepo,
        @Lazy ModelMapper modelMapper, HttpServletRequest request); @Override List<LanguageDTO> getAllLanguages(); @Override String extractLanguageCodeFromRequest(); @Override Language findByCode(String code); @Override List<String> findAllLanguageCodes();  }### Answer:
@Test public void findAllLanguageCodes() { List<String> code = Collections.singletonList(language.getCode()); when(languageRepo.findAllLanguageCodes()).thenReturn(code); assertEquals(code, languageService.findAllLanguageCodes()); }