Re: microcontroller ic test
If you dont use it in some critical device no problem, but if you use it for some medilac measurement, heating/cooling control, alarm systems,... and similar things, replace it with new. Better dont mix used with new, use some separation technique, boxes or similar thing.
You can always put some testing firmware inside that uC to test his pins. That firmware should gives some well known signals on pins whics you expecting and monitoring with some analyzer or scope.
When I ususally use some uC or other IC on protoboard that uC is not used in final device or back in my private stock of semiconductors, thise parts stay just for testing in separated box.