Hi Douglas,
If the number of failing cases is one out of 1,000,000 or more, the
probability to find one is infinitesimal.
The percentage of failure in the sqrt case was even smaller (it
requires crafting the trailing bits of integer whose highBit > 100)...
I don't believe that fuzz testing is really the effective way in this context.
Only the setup is effective (very simple and cheap - though we have to
bound our LargePositiveInteger...).
Shooting in the dark is effective only in crowded places.
White box testing is certainly much more effective in such cases.

Le mar. 18 mai 2021 à 20:15, Douglas Brebner <kirtai+st at gmail.com> a écrit :
>
> On 17/05/2021 13:14, Nicolas Cellier wrote:
> > Alternatively, we can try and test with randomly generated inputs, but
> > that's a bit like shooting in the dark.
> Isn't that the whole point of fuzz testing which seems quite effective
> in other languages?
>