Extend singleton test.

tests/singleton_test.aer

@@ -2,6 +2,11 @@ final class Test {
 	private int $value;
 
 	private void __construct() {
+		print('Constructor called.' + "\n");
+	}
+
+	private void __destruct() {
+		print('Destructor called.' + "\n");
 	}
 
 	/* This is singleton */