Implement front calls in a test

Implementing a custom front call in your test.

1. Write a function that takes a front call request as a parameter and returns the front call answer.
   This function has the following format:

   FUNCTION myCustomFrontCall (request ggc.FrontCallRequest INOUT) RETURNS ggc.FrontCallAnswer

   See the sample function implementation of standard.feInfo("feName") in Example: custom front call (BDL).

2. Register this function for callback before the function play is called.
   For example, in the MAIN block of your scenario:

   MAIN
       # Register custom front call handler
       CALL ggc.registerFrontCallHandler(FUNCTION myCustomFrontCall)
       # ...
       CALL play()
       EXIT PROGRAM 0
   END MAIN

3. In your test application, make sure you have a front call action that you can test.

   For example, a menu action:

   MAIN
       DEFINE answer STRING
       OPEN FORM f FROM "frontcall"
   
       DISPLAY FORM f
       MENU "FrontCall"
         ON ACTION fename
           CALL ui.Interface.frontcall("standard","feinfo", ["fename"],[answer])
           MESSAGE answer
           ON ACTION quit
           EXIT MENU
       END MENU
   END MAIN

4. In the play function of your scenario test the action ( fename in the example ).
   For example:

   FUNCTION play()   
       DEFINE msg ggc.Message
       CALL ggc.action("fename")
       CALL ggc.getMessage() RETURNING msg.*
       DISPLAY msg.message
       ...
   END FUNCTION