diff --git a/test/parallel/test-process-getgroups.js b/test/parallel/test-process-getgroups.js
index 2d7a93c9a32c75..390f188cf5bf4d 100644
--- a/test/parallel/test-process-getgroups.js
+++ b/test/parallel/test-process-getgroups.js
@@ -1,21 +1,23 @@
 'use strict';
 const common = require('../common');
-const assert = require('assert');
-const exec = 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;
 }
+const assert = require('assert');
+const exec = require('child_process').exec;
 
 if (typeof process.getgroups === 'function') {
-  const groups = process.getgroups();
+  const groups = unique(process.getgroups());
   assert(Array.isArray(groups));
   assert(groups.length > 0);
   exec('id -G', function(err, stdout) {
     assert.ifError(err);
-    const real_groups = stdout.match(/\d+/g).map(Number);
-    assert.strictEqual(groups.length, real_groups.length);
+    const real_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') {
 function check(a, b) {
   for (let i = 0; i < a.length; ++i) assert.notStrictEqual(b.indexOf(a[i]), -1);
 }
+
+function unique(groups) {
+  return [...new Set(groups)].sort();
+}