It tests for the presence of the virus with a PCR assay which is a laboratory-based process that takes 48 hrs to return the result once the laboratory receives the sample back. This will confirm the presence or absence of the Covid-19 virus in those individuals. This will inform both the individual and the community whether that person is potentially infective or not.

These tests are considered to be fit for purpose because there is an extremely low probability of a false positive. 
A positive test has great value because the individual then knows that they have had the Covid-19 infection and have developed an immune response. Negative tests should be treated with caution.   

The relative sensitivity of the 2019-nCoV IgG/IgM Rapid Test Cassette (BNCP-402 and BNCP-402S) is more than 99.9% for IgG and 85% for IgM, the relative specificity is 98% for IgG and 96% for IgM compared with PCR result.
These tests are considered to be fit for purpose because there is an extremely low probability of a false positive. 
A positive test has great value because the individual then knows that they have had the Covid-19 infection and have developed an immune response.Negative tests should be treated with caution.   
A negative antibody test result may indicate either, that the antibody titre levels are not high enough to be detected, or that the patient has not been infected by the virus.
This is why communication and informed consent are vital. 
Our recommendation is that clients should be tested for both the Antibody and the  PCR Test. This is the only way to be certain that you have developed an immune response and that the Covid-19 virus has left your body.