is $resp, "\xf0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 'Get a non-blocking challenge response';
is length($resp), 20, 'Response is the proper length';
is $pre, 1, 'The pre-challenge callback is called';
is $resp, "\xf0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 'Get a non-blocking challenge response';
is length($resp), 20, 'Response is the proper length';
is $pre, 1, 'The pre-challenge callback is called';