Tests fail for Node.js >= 12

Sharing the logs:
```
✗ same error for bad prime
---
operator: equal
expected: 1
actual: 9
at: Test. (/home/nilesh/ups/diffie-hellman/test.js:127:5)
...
✗ same error for bad prime non testable generator
---
operator: equal
expected: 1
actual: 5
at: Test. (/home/nilesh/ups/diffie-hellman/test.js:130:5)
...
✓ same error for good prime wrong generator
✗ same error for good prime non testable generator
---
operator: equal
expected: 0
actual: 4
at: Test. (/home/nilesh/ups/diffie-hellman/test.js:136:5)
...

tests 233
pass 230
fail 3

Failed Tests: There were 3 failures

✗ check errors same error for bad prime
✗ check errors same error for bad prime non testable generator
✗ check errors same error for good prime non testable generator

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! diffie-hellman@5.0.3 test: `node test.js | tspec`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the diffie-hellman@5.0.3 test script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! /home/nilesh/.npm/_logs/2020-01-31T15_53_55_954Z-debug.log

```

Commencez par les assertions en échec dans test.js aux lignes 127, 130 et 136, puis exécutez la commande npm test indiquée dans le rapport avec Node.js 12 ou version ultérieure. C’est terminé lorsque les trois vérifications d’erreur passent et que la suite complète indique 233 tests réussis sans échec.

Rédigé par le modèle d'indexation à partir du texte de l'issue.