People tested for Covid19 despite showing no symptoms

https://www.bbc.co.uk/sport/football/52260490

Article is from the BBC where some unknown author wrote how Sir Kenny Dalglish, a prominent figure in and outside of football, went to hospital for an infection and was checked for Covid19 despite showing no symptoms.

Despite not suffering any ailments Kenny then locked himself away in isolation.
Has anybody who has tested positive been tested again before coming out of isolation.