I travelled 2 weeks back. They do it for free there but please have a layover of more than 6 hours to be sure. Results are available online and via SMS to your mobile phone. You can get a free printout at one of the counters. Also, the directions for the testing counters are clearly visible at the arrival terminals. Don't miss them (in my case, I had to go opposite to the direction of the arriving crowd at the terminal). Also, check for Dubai Connect program. They gave a hotel for free for me. I had a layover of 11 hours but man, I spent only 2 hours at hotel because visa on arrival for Dubai Connect took 5 hours and waiting for hotel shuttle took roughly an hour. I submitted documents in advance over email but the program is so mismanaged. Seems visa on arrival will take time. You also get free 24 hour SIM card with 1 GB data at immigration counter (you can use it if you have SIM ejection tool)
Also, if it helps, in my case I didn't receive results on my mobile or online. I panicked a bit and when checked with other travelers at the hotel, they also confirmed what my other friends told me, that their results were available within 2 hours from testing. I went to the testing counter at airport just few hour prior to my check in flight to Canada and the lady there was super helpful. She said there is no way results are not in the system (either invalid or positive should also be a result in the system), so she tried all permutations and combinations with my passport number. Apparently,the testing lady entered D for 0 in the passport number. Sigh!
