The tradition, which involves the inspection of girls' genitalia, has drawn an outcry from human rights advocates who say it is an invasion of privacy and degrading towards women.
But traditionalists see the practice as an integral part of Zulu culture, and argue that it promotes sex education while also preventing the spread of Aids in a country where one in seven people are estimated to be HIV-positive.
"It has always been there amongst the Zulus. I really do not see it stopping," said Princess Thembi Zulu-Ndlovu, organiser of the largest virginity test in the country which takes place in conjunction with the Royal Reed Dance ceremony for maidens every September.
The cultural festival attracts tens of thousands of girls from all corners of the country who carry riverbed reeds in a procession to the Royal Palace where they dance bare-breasted for Zulu King Goodwill Zwelithini at Nongoma in northern KwaZulu-Natal province.
"The main reason for the testing is to maintain the purity of a woman... (and) it really does help in the prevention of the spread of Aids," Zulu-Ndlovu, who is Zwelithini's sister, said.
Girls must be exposed to custom at early age
The National Assembly is this week to debate a Children's Bill which would ban virginity testing for girls younger than 16 years old.
Already the bill has been amended, taking into account objections from traditional leaders to restrict the ban on virginity testing to girls under 16. Consent must be given for girls older than 16.
But Zulu-Ndlovu believes girls must be exposed to the custom at an early age. "If you start at 18 they wouldn't know anything about it. She must become familiar with the practice. Sometimes we do it as early as six months, sometimes three years, because then it is very easy to detect whether a child has been raped.
"Starting late doesn't serve the purpose," said Zulu-Ndlovu.
According to custom, the elder women in the community conduct the tests, in some families as often as once a month.
During the testing which is a private event among women, the girls lie down on the ground and spread their legs for "ukuhlolwa kwezintombi" (inspection of girls).
Virgins get certificates
"We sort of look at the private parts. We look for (signs of) penetration," explained Zulu-Ndlovu, adding that the inspection also helps to identify victims of sexual abuse.
"When you buy a new sofa or a cushion that has never been sat on, you can tell the difference between a sofa that had always carried somebody and the new one.
"That's how you tell when you test."
The result of the test is proclaimed on the spot, with some virgins receiving documents certifying their status. Having passed the test, the girls are then free to take part in the reed dance before the king.
Traditional leaders see virginity testing as part of sex education.