private static YubiKeyAuthenticationHandler getHandler(final YubicoClient client) {
        return new YubiKeyAuthenticationHandler(client,
            new DirectObjectProvider<>(mock(MultifactorAuthenticationProvider.class)));
    }
Test cases for {@link YubiKeyAuthenticationHandler}.

@author Misagh Moayyed
@since 4.1
support/cas-server-support-yubikey/src/test/java/org/apereo/cas/adaptors/yubikey/YubiKeyAuthenticationHandlerTests.java