Write down test cases for Notepad to "Save/Save as" a file. Write down Functional, UI, Performance, Load, Stress Test cases - scenario in "Save/Save as".
Answer :
Click File-Save (should open a window and should ask you the file name and path as well)
Check for .extension like it should be .txt only
Check for short-key like (Ctrl+S) and ask for same option as above (should open an window and should ask you the file name and path as well)
Save as (should open the same window with same file name path)
If you change that file name and path in that window then it should accept.
If you dont give any name in it then data should not be saved.