https://www.reddit.com/r/Flights/comments/meg4j6/flight_from_canada_to_us_how_to_get_tested/
Happy to help with this!! So what I did was get the Rapid Antigen test from Shoppers Drug Mart (was $40) and I took the completed result form with me to Pearson, plus I printed and filled out this attestation form (https://www.cdc.gov/quarantine/fr-proof-negative-test.html
).
When I went to enter the Air Canada security, there was an agent there who took my rapid test form plus the attestation and there were no issues! I hope this helps, safe travels!!