Randox worked fine for us on our embarkation in Rome on 8th May.
We received the tests by post, performed the tests, scanned the test and uploaded to Randox before departure to Civitavechia.
Within a few hours, 2maybe 3hours, we received our certificate by email which was accepted by the embarkation team in Rome
We also used Randox earlier in the year for a PCR test that wasn't`t required as the rules changed when we were on our trip. Using the dropbox facility was very efficient with a result returned within14 hours.
Overall, I have complete confidence in Randox
I would also recommend testing prior to doing the Randox test, just for peace of mind.