The information in
A1's reply is correct, and the thread he's linked is really valuable in terms of information about the interview day so I'd recommend you have a read.
USyd has probably the best interview/place offer ratio of all the school-leaver pathways, with roughly 2/3 of interviewees receiving an offer. Usually, the written test / interview is held on campus for local applicants, with a nice tour of the campus, activities, and lunch interspersed throughout the day, but this year it appears (from USyd's website) that the interview day will be held entirely online. I'm not sure how that'll work -- I imagine they'll release more details to applicants later in the year.