### Question:
AuthenticatorTransportConverter { @SuppressWarnings("squid:S1168") public Set<String> convertSetToStringSet(Set<AuthenticatorTransport> values) { if (values == null) { return null; } return values.stream().map(this::convertToString).collect(Collectors.toSet()); }  AuthenticatorTransport convert(String value); @SuppressWarnings("squid:S1168") Set<AuthenticatorTransport> convertSet(Set<String> values); String convertToString(AuthenticatorTransport value); @SuppressWarnings("squid:S1168") Set<String> convertSetToStringSet(Set<AuthenticatorTransport> values);  }### Answer:
@Test void convertSetToStringSet_test() { assertThat(converter.convertSetToStringSet(Collections.singleton(AuthenticatorTransport.USB))).containsExactly("usb"); }
@Test void convertSetToStringSet_null_test() { assertThat(converter.convertSetToStringSet(null)).isNull(); }