Add some comments, to see if they are working.

tests/hello_world.aer

@@ -1,7 +1,12 @@
+#!/usr/local/bin/aer
 class Program {
 
+	/*
+	 * Program entry point.
+	 * It does not take any arguments.
+	 */
 	public void main() {
-		print('Hello world!');
+		print('Hello world!'); // single line comment
 	}
 
 }