@Override
        public Optional<Credentials> validate(final CallContext ctx, Credentials credentials) {
            throw new CredentialsException("fail");
        }
Test cases for {@link LocalCachingAuthenticator}.

@author Misagh Moayyed
@since 1.8
pac4j-core/src/test/java/org/pac4j/core/credentials/authenticator/LocalCachingAuthenticatorTests.java