Sometimes personality tests seem to be trying to find out incredibly obscure details about you, by asking weird or unexpected questions. Psychologists disagree about the usefulness of these questions, and in any case the most reputable firms do not usually use the more extreme formulations. But if you are confronted with very personal questions you have a choice: answer honestly, trusting that your employer has a serious purpose in asking, and is not just trying to embarrass you or dig up personal details to gossip about; or refuse to answer.
It may be reasonable and appropriate just to leave an answer blank if you do not feel happy answering it. Of course this will come up as a matter for discussion later on, but that it the right time to discuss your objections. Explain calmly why you felt unable to answer. You should not be marked down in any way for wanting to keep certain information private.