Add more tests.

tests/reference_test.aer

@@ -0,0 +1,13 @@
+class Program {
+
+	function add_by_ref(int &$val) {
+		$val += 7;
+	}
+
+	function main() {
+		int $num = 7;
+		$this->add_by_ref($num);
+		var_dump($num);
+	}
+
+}