Signing Stream interview questions

Applied through my university's job search platform. I was given a somewhat normal interview by the CEO, and at the end of the interview I was given this question (paraphrased): "We like you, but we're not sure if you'd be the right fit. How would you like to work without pay for a few weeks so we can evaluate your performance?" I replied by asking if this is legal (it is not), and the interviewer incorrectly responded that it is. I declined the offer over email soon afterwards. It was clear that this company's CEO was attempting to unlawfully use recent college grads as a source of cheap labor.