Just vomit out some squiggles. There's no legal requirement in any situation for your signature to correspond to anything.
Alternatively, you could use your knowledge that you were just tested on to construct an argument for why deeming a test fraudulent based on some asinine squiggle vomit system is kind of complete bullshit. I mean, for fork's sake, you are training to be a lawyer after all, so do some got dang lawyering in such an instance.