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

[Santiago Vila]

Package: src:node-miller-rabin
Version: 4.0.1-4
Severity: serious
Tags: ftbfs patch

Dear maintainer:

I tried to build this package in buster but it failed:

--------------------------------------------------------------------------------
[...]
 debian/rules build-indep
dh build-indep --with nodejs
   dh_update_autotools_config -i
   dh_autoreconf -i
   dh_auto_test --buildsystem=nodejs -i
	/bin/sh -e debian/tests/pkg-js/test


  Miller-Rabin
    1) should test number for primality


  0 passing (93ms)
  1 failing

  1) Miller-Rabin
       should test number for primality:

      AssertionError [ERR_ASSERTION]: The expression evaluated to a falsy value:

  assert(!mr.test(new bn(221)))

      + expected - actual

      -false
      +true
      
      at Context.<anonymous> (test/api-test.js:8:5)
      at callFn (/usr/lib/nodejs/mocha/lib/runnable.js:354:21)
      at Test.Runnable.run (/usr/lib/nodejs/mocha/lib/runnable.js:346:7)
      at Runner.runTest (/usr/lib/nodejs/mocha/lib/runner.js:442:10)
      at /usr/lib/nodejs/mocha/lib/runner.js:560:12
      at next (/usr/lib/nodejs/mocha/lib/runner.js:356:14)
      at /usr/lib/nodejs/mocha/lib/runner.js:366:7
      at next (/usr/lib/nodejs/mocha/lib/runner.js:290:14)
      at Immediate._onImmediate (/usr/lib/nodejs/mocha/lib/runner.js:334:5)



dh_auto_test: /bin/sh -e debian/tests/pkg-js/test returned exit code 1
make: *** [debian/rules:8: build-indep] Error 1
dpkg-buildpackage: error: debian/rules build-indep subprocess returned exit status 2
--------------------------------------------------------------------------------

The failure happens randomly. Sometimes it happens, sometimes it does not,
so the only recipe to reproduce it is to try many times.

I've put two build logs here:

https://people.debian.org/~sanvila/build-logs/node-miller-rabin/

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)

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

Proposed patch below.

Thanks.

--- a/test/api-test.js
+++ b/test/api-test.js
@@ -5,7 +5,6 @@ var bn = require('bn.js');
 describe('Miller-Rabin', function() {
   it('should test number for primality', function() {
     this.timeout(8000);
-    assert(!mr.test(new bn(221)));
     assert(mr.test(new bn(257)));
 
     var p = new bn('dba8191813fe8f51eaae1de70213aafede8f323f95f32cff' +