Update tests to use more strict data types instead of mixed.

tests/arab_to_roman.aer

@@ -3,7 +3,7 @@ class Program {
 	private function num2Roman(int $num) {
 		int $n = intval($num);
 		string $result = '';
-		mixed $lookup = array('M' => 1000, 'CM' => 900, 'D' => 500, 'CD' => 400,
+		int[] $lookup = array('M' => 1000, 'CM' => 900, 'D' => 500, 'CD' => 400,
 			'C' => 100, 'XC' => 90, 'L' => 50, 'XL' => 40,
 			'X' => 10, 'IX' => 9, 'V' => 5, 'IV' => 4, 'I' => 1);
 

tests/unicode_characters.aer

@@ -1,8 +1,8 @@
 class Unicode {
 
 	public function unicon(string $str, bool $to_uni = true) {
-		mixed $cpp;
-		mixed $cp = array('А' => 'А', 'а' => 'а',
+		string $cpp;
+		string[] $cp = array('А' => 'А', 'а' => 'а',
 			"Б" => "Б", "б" => "б",
 			"В" => "В", "в" => "в",
 			"Г" => "Г", "г" => "г",