diff --git a/tests/arab_to_roman.aer b/tests/arab_to_roman.aer
index b5a8cfa..da10a16 100644
--- a/tests/arab_to_roman.aer
+++ b/tests/arab_to_roman.aer
@@ -1,6 +1,6 @@
 class Program {
 
-	private function num2Roman($num) {
+	private function num2Roman(int $num) {
 		$n = intval($num);
 		$result = '';
 		$lookup = array('M' => 1000, 'CM' => 900, 'D' => 500, 'CD' => 400,
diff --git a/tests/debug_backtrace.aer b/tests/debug_backtrace.aer
index 4c50763..1a441ce 100644
--- a/tests/debug_backtrace.aer
+++ b/tests/debug_backtrace.aer
@@ -4,7 +4,7 @@ class Program {
 		$this->b($this->a('First A'), $this->a('Second A'), $this->a('Third A'));
 	}
 
-	function a($p) {
+	function a(string $p) {
 		$backtrace = debug_backtrace();
 		if(isset($backtrace[0]['args'])) {
 			var_export($backtrace[0]['args']);
@@ -14,7 +14,7 @@ class Program {
 		return $p;
 	}
 
-	function b($p1, $p2, $p3) {
+	function b(string $p1, string $p2, string $p3) {
 		print("$p1, $p2, $p3");
 	}
 
diff --git a/tests/singleton_test.aer b/tests/singleton_test.aer
index 03d9ddf..847267d 100644
--- a/tests/singleton_test.aer
+++ b/tests/singleton_test.aer
@@ -17,7 +17,7 @@ final class Test {
 		return $this->value;
 	}
 
-	public function set($value = 0) {
+	public function set(int $value = 0) {
 		$this->value = $value;
 	}
 }
diff --git a/tests/unicode_characters.aer b/tests/unicode_characters.aer
index d164afe..9b2bd80 100644
--- a/tests/unicode_characters.aer
+++ b/tests/unicode_characters.aer
@@ -1,6 +1,6 @@
 class Unicode {
 
-	public function unicon($str, $to_uni = true) {
+	public function unicon(string $str, bool $to_uni = true) {
 		$cp = array('А' => 'А', 'а' => 'а',
 			"Б" => "Б", "б" => "б",
 			"В" => "В", "в" => "в",
diff --git a/tests/utf8_variables.aer b/tests/utf8_variables.aer
index ecdeeeb..5f6e9ca 100644
--- a/tests/utf8_variables.aer
+++ b/tests/utf8_variables.aer
@@ -12,7 +12,7 @@ class Program {
 		print($this->概要 + "\n");
 	}
 
-	private function isUTF8($str) {
+	private function isUTF8(string $str) {
 		$b = 0;
 		$c = 0;
 		$bits = 0;