If you need to automate a GUI app, like you would script a CLI app with expect, use xdotool. It should be in your repo. What you can do for example:

( gedit & ) ; sleep 1; for key in H  e l l o Return W o r l d ; do xdotool key $key; done

Find the key codes by running xev from your terminal and looking at stdout of xev:

KeyRelease event, serial 47, synthetic NO, window 0x3600001,
    root 0xe3, subw 0x0, time 569860511, (65,758), root:(1385,779),
    state 0x10, keycode 23 (keysym 0xff09, Tab), same_screen YES,
    XLookupString gives 1 bytes: (09) " "
    XFilterEvent returns: False

For Tab.