test: getgroups() may contain duplicate GIDs

Some systems may have multiple group names with the same group ID, in
which case getgroups() returns duplicate values, where `id -G` will
filter the duplicates. Unique and sort the arrays so they can be
compared.
Backport-PR-URL: #12468
PR-URL: #10389
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

Author: sam-github

test/parallel/test-process-getgroups.js

@@ -1,21 +1,23 @@
 'use strict';
 constcommon=require('../common');
-constassert=require('assert');
-constexec=require('child_process').exec;
+
+// Check `id -G` and `process.getgroups()` return same groups.
 
 if(common.isOSX){
 common.skip('Output of `id -G` is unreliable on Darwin.');
 return;
 }
+constassert=require('assert');
+constexec=require('child_process').exec;
 
 if(typeofprocess.getgroups==='function'){
-constgroups=process.getgroups();
+constgroups=unique(process.getgroups());
 assert(Array.isArray(groups));
 assert(groups.length>0);
 exec('id -G',function(err,stdout){
-if(err)throwerr;
-constreal_groups=stdout.match(/\d+/g).map(Number);
-assert.strictEqual(groups.length,real_groups.length);
+assert.ifError(err);
+constreal_groups=unique(stdout.match(/\d+/g).map(Number));
+assert.deepStrictEqual(groups,real_groups);
 check(groups,real_groups);
 check(real_groups,groups);
 });
@@ -24,3 +26,7 @@ if (typeof process.getgroups === 'function') {
 functioncheck(a,b){
 for(leti=0;i<a.length;++i)assert.notStrictEqual(b.indexOf(a[i]),-1);
 }
+
+functionunique(groups){
+return[...newSet(groups)].sort();
+}