Solving mock tests before facing any particular exam is very necessary and beneficial as well as you are able to judge yourself very well as where do you stand, what all things you are confident about and what all things you need to revise again.

Below is the link of the GSEB HSC boards sample papers, refer to the site below..

https://school.careers360.com/articles/gseb-hsc-question-papers

Best wishes. Thank you.