<?php

$arrayFirst = [1,2,3,4,5];
$arraySecond = [2,5,4];

foreach ($arrayFirst as $key => $valueFirst){
	foreach ($arraySecond as $valueSecond) {
		if ($valueFirst == $valueSecond){
			unset($arrayFirst[$key]);
			echo  "ID выполненного теста: $valueFirst\n";
		} 
	}
}

foreach ($arrayFirst as $value){
	echo "ID невыполненного теста: $value\n";
}