### Question:
TppController implements TppRestApi { @Override public ResponseEntity<Map<CountryCode, String>> getSupportedCountryCodes() { return ResponseEntity.ok(ibanGenerationService.getCountryCodes()); }  @Override void login(String login, String pin); @Override ResponseEntity<Set<Currency>> getCurrencies(); @Override ResponseEntity<Map<CountryCode, String>> getSupportedCountryCodes(); @Override ResponseEntity<BankCodeStructure> getBankCodeStructure(String countryCode); @Override ResponseEntity<String> getRandomTppId(String countryCode); @Override ResponseEntity<Void> register(User user); @Override ResponseEntity<Void> remove(); @Override ResponseEntity<Void> transactions(String accountId); @Override ResponseEntity<Void> account(String accountId); @Override ResponseEntity<Void> user(String userId); @Override ResponseEntity<Void> revert(RevertRequestTO revertRequest);  }### Answer:
@Test void getSupportedCountryCodes() { when(ibanGenerationService.getCountryCodes()).thenReturn(getSuppCountryCodes()); ResponseEntity<Map<CountryCode, String>> response = tppController.getSupportedCountryCodes(); assertTrue(response.getStatusCode().is2xxSuccessful()); assertEquals(Objects.requireNonNull(response.getBody()).size(), COUNTRY_CODES.size()); }