You may use a vehicle with an automatic transmission to do the driving licence test. However, the licence must be endorsed to the effect that it is valid only for driving an automatic transmission vehicle. (See official wording from the Road Traffic Act, below.)
18. Application for and issue of driving licence
(4) If an examiner for driving licences has satisfied himself or herself in terms of subsection (3) that an applicant for a driving licence is competent, to drive a motor vehicle of the class to which such applicant’s application relates, the examiner shall issue, or authorise a person employed by the driving licence testing centre concerned to issue, a driving licence in the prescribed manner to such applicant in respect of that class of motor vehicle, and the examiner or the said authorised person shall—
(a) in the case where the applicant has in terms of subsection (2) provided a motor vehicle equipped with an automatic transmission or the motor vehicle is electrically powered, endorse the driving licence to the effect that authorisation is granted only for the driving of a motor vehicle equipped with an automatic transmission or which is electrically powered, as the case may be;
It is recommended therefore that the test be taken using a manual transmission vehicle so that such a restriction does not apply.
For Insurance Puposes you will need to be a licensed driver and must be able to legally drive that specific vehicle without restrictions.