How to use CATT to test functions modules?

Hi,

I am trying to use CATT to test functions modules. After reading about it on help.sap.com, here is the procedure I tried to test a simple function module WRITE_MESSAGE which searches at concatenates messages from T100 –

1. Run transaction code SCAT

2. Enter a name for the test case: ZWRITE_MESSAGE

3. Test Case -> Record function module

4. A popup window appears titled “CATT: Record function module”, enter the function module name : WRITE_MESSAGE

5. Click the button “Record” to arrive at the screen “Catt : Maintain Functions Test Case ZWRITE_MESSAGE” (which is empty), but the popup window “CATT: Record function module” still remains, and there is no other choice but to click the button “Record” again

6. At the screen “Test Function module initial screen”, enter some import parameters : MSGID = ‘EU’, MSGNO = 178, MSGTYP = I

7. Run the test and a popup info window appears “Recording ended”

8. Click enter to arrive at the “Test Function module Result screen” to see the export parameter MESSG is correctly filled

9. Click return to “Test case attribute screen”

10. Click save, choose local object to receive message “Attributes saved”

Now I am stuck, how do I choose which comparisons are to be carried out?