diff --git a/src/main/java/com/mycompany/app/App.java b/src/main/java/com/mycompany/app/App.java
index f3a5e51..55a2c53 100644
--- a/src/main/java/com/mycompany/app/App.java
+++ b/src/main/java/com/mycompany/app/App.java
@@ -191,6 +191,7 @@ public static void main(String[] args) {
        
         Callee cee = new Callee();
         Caller  cer = new Caller(cee);
+        System.out.println("test call back");
         cer.go();