isfull() - lists

Just wondering how you can check the isfull() function when implementing a linked list. what test can be run to check if it has been written correctly?

most lists are open ended in terms of length, so the isfull() method seems inappropriate, at first blush anyway.

was some function (coreleft with borland..mabye?) and one that worked for microsoft (getglobalmemor mabye?) that returned how much memory was left to deligate from the freestore. I'd just assume check each addition as I allocated it with exception handling though...if I even worried about it at all.