Honestly, I don't think I'm really qualified to answer that. I haven't gone for the interview yet.
@Stef., would you please guide us here ? Thanks!
I remember reading that the following
original documents are a MUST:
Passports (all, including expired ones that fall within your eligibility period)
Driver's license, Health Card (All original ID proofs that you submitted with your app)
COPR
PR card
English language proof (original IELTS/transcript/degree/dimploma)
Also, found the following quote from someone who went for the test. Hope it helps.