test: favor assertions over console logging

Communicate about leaked globals via `AssertionError` rather than
`console.log()`.

PR-URL: #11547
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Gibson Fahnestock <[email protected]>
Reviewed-By: Timothy Gu <[email protected]>
Reviewed-By: Yuta Hiroto <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: James M Snell <[email protected]>

test/common.js

@@ -399,8 +399,7 @@ process.on('exit', function() {
   if (!exports.globalCheck) return;
   const leaked = leakedGlobals();
   if (leaked.length > 0) {
-    console.error('Unknown globals: %s', leaked);
-    fail('Unknown global found');
+    fail(`Unexpected global(s) found: ${leaked.join(', ')}`);
   }
 });