Maybe i had been a little bit to euphemistic regarding the working of this little test case (yes, this is a drawback of small test cases), because here all necessary things are within one pas file resp. the main form unit. Transfering to real life resp. to constructs with encapsulated components subsequent requirements might appear.
Maybe i'll open another "how to" thread for that (as being definitiely distinct from the issue of this inital OP), because it might be interesting for other newbies like me too.