and latest working draft, to authenticatorClientPIN:
"newPin" be the UTF-8 representation of "newPinUnicode".
"curPin" be the UTF-8 representation of "curPinUnicode"
So authenticator should check newPin and curPin against UTF-8 encoding, then test tool should test this with wrong/correct UTF-8 encoding input parameters.
According to CTAP 2.0 Proposed Standard: https://fidoalliance.org/specs/fido-v2.0-ps-20190130/fido-client-to-authenticator-protocol-v2.0-ps-20190130.html
and
CTAP 2.1 Review Draft: https://fidoalliance.org/specs/fido2/fido-client-to-authenticator-protocol-v2.1-rd-20191217.html
and latest working draft, to authenticatorClientPIN:
"newPin" be the UTF-8 representation of "newPinUnicode". "curPin" be the UTF-8 representation of "curPinUnicode"
So authenticator should check newPin and curPin against UTF-8 encoding, then test tool should test this with wrong/correct UTF-8 encoding input parameters.