Add instructions for manual testing for instruction testing

docs/DeveloperGuide.md

@@ -555,6 +555,16 @@ testers are expected to do more *exploratory* testing.
     1. Other incorrect delete commands to try: `delete`, `delete x`, `...` (where x is larger than the list size)<br>
        Expected: Similar to previous.
 
+### Undoing the last operation
+1. Undoing an execution that modifies the CampusConnect data
+   1. Prerequisites: Perform any operation that modifies the state (all executions except for list and find) to ensure there is an action to undo.
+
+   1. Test case: undo 
+   Expected: The last operation is undone, restoring the previous state. The list updates accordingly, and a status message confirms the undo action.
+
+   1. Test case: undo immediately after starting the application (with no operations performed)
+   Expected: No undo operation is performed. An error message appears in the status message, indicating there is no action to undo.
+
 ### Finding a person
 
 1. Finding a person with tags