There is no confirmation by A.R. Rahman or any media outlet that he tested positive for COVID-19.
On April 1, A.R. Rahman thanked the healthcare workers who are working during the pandemic and urged the public to avoid congregating in religious places. On July 12, Rahman tweeted wishes and prayers in response to Amitabh Bachchan testing positive for COVID-19. He joined lyricist Prasoon Joshi for a musical tribute to the nation's fight against COVID-19. Apart from the above, there have been no media stories about him contracting COVID-19, and he has not made any such announcements.
The COVID-19 pandemic has given rise to a lot of potentially dangerous misinformation. For reliable advice on COVID-19 including symptoms, prevention and available treatment, please refer to the World Health Organisation or your national healthcare authority.