on a technical note7a
a computer program / black box where you feed in a test ( input) and it spits out infected or not infected = ( total function ) (1)
has a radically different behaviour to one where you feed in a test ( input ) and it spits out - yes you are infected, and otherwise whirs and mutters to itself. ( = partial function) (2)
I think (1) is more suitable to covid testing altho (2) is more versatile and can do or cope with more things (Surprisingly, as Turing first found in his v first paper on the enscheidungsproblem