If you’re sick with a viral illness you don’t need a test to know you’re at risk of passing it on to other people.
Yet the consequences of spreading covid are far more serious than most viral illnesses. Fine if you isolate when any symptoms occur. I never test but I isolate when any cold like symptoms or worse are present.
If we don't change our attitude to how we behave when ill we have learned nothing and the next pandemic may well be as bad or worse.