[Pkg-javascript-devel] Bug#926720: node-miller-rabin: FTBFS randomly (uses a non-prime to test the test)

[Jakub Wilk]

* Santiago Vila <sanvila at debian.org>, 2019-04-09, 15:32:
>AFAIK, this being a primality test, I assume the outcome is either "not 
>prime" or "maybe prime", so the only way to test the test is by giving 
>a known prime and expect "maybe prime" as output.
>
>So: Why is the test calling mr.test with 221, which is not prime? (221 
>= 13 x 17)

Correctly implemented Miller-Rabin test should have false positives only 
with negligible probability.

>And why this fails randomly? Does the test perform random calculations 
>internally and it's therefore not deterministic?

Yes.

>Even in such case I don't see how a non-prime like 221 may help to 
>catch obvious errors in a test suite for a primality test.

It's just proven to be useful.

Please restore the test and fix the code instead.

NB, it's been already reported upstream that the number of iterations 
this implementation chooses in not adequate:
https://github.com/indutny/miller-rabin/issues/9

-- 
Jakub Wilk