We have an excellent COVID testing laboratory situated 1.5km from the hotel.
This is a drive-through facility (the test is done whilst you sit in an Uber organised by the hotel). The test is a PCR test (suitable for all airlines and countries immigration control). The results are delivered by email normally within 4 hours of the test (allow 24 hrs before your flight just in case). The cost is ZAR850 per person. Booking is not necessary (or possible) as the facility is a drive-through. The facility is open 7 days a week.
https://nextbio.co.za/nextpath/ (Scroll down to where it says “Gauteng”)