Let me share my experience.
My flight was on 15th Oct at 3 AM From Delhi to Toronto.
reached Delhi on 13th at 11:50 PM (Teached early because next domestic flight was on 14th night and than I won’t have enough time to do COVOD test)
stayed in Hotel inside the airport for 24 hours.
during my stay on 14th Oct in morning 10AM I went for RTPCR test near metro station and than came back to room.
I was in line for more than an hour and everything was done by 11:30 AM .
on 14th afternoon at 2:48 I received my result for COVID 19 and it was negative .
left my hotel room at 11:30 PM in night and went for checkin .
big line up again and no management.
air india will ask you for COVID 19 negative report, arrive can app , and visa or PR card .
after that security and than immigration.
I am happy to reach Canada on 15th October becuase my citizenship oath is on 16th October.