Combinations test data

Combinations test data

I'd like to be able to test a function with a tuple from a set of fringe
cases and normal values. For example, in testing a function that returns
true when given three lengths that form a valid triangle, I'd have
specific cases, negative numbers, small numbers, large numbers, values
close-to being overflowed, etcetera. Then generating combinations of these
values, with or without repetition, to get a set of test data.
> (inf,0,-1), (5,10,1000), (10,5,5), (0,-1,5), (1000,inf,inf),
>
> ...
(I actually know the answer to this, but it might be helpful for others,
and a challenge for people here! --will post my answer(s) later on.)