The best and most accurate test for Covid-19 is the well-known laboratory PCR test (nasal swab). Rapid Antigen Tests (RAT) are now a more convenient, though slightly less accurate test which can be done at home.   Given how common Covid-19 is in the community, they are accurate in diagnosing Covid-19 if you do have symptoms. In certain circumstances, you may be recommended to have a PCR test even if your RAT is negative.