Antibody testing

What do you guys think about Antibody testing for COVID-19? It’s now widely available to anyone - Quest Diagnostics using Abbott test which is FDA approved with over 99% accuracy. Doctors are telling me that at this point antibodies do not mean immunity - they claim there is no evidence. But why wouldn’t there be some immunity or could it at least mean that if I have antibody and get infected again - it shouldn’t be worse than the first time?
The virus doesn’t seem to be mutating (yet)? Science on original SARS and MERS suggests antibodies do mean immunity and so is common cold strains (other coronaviruses). The test is $119, I am more than willing to test myself.