An attempt to force a prediction to be added after its completion when items are queued in the obvious way. Tests whether the parser handles the situation correctly; it can handle completion items repeatedly, or it can add null predictions earlier, or it can check each newly predicted item to see if it has already been completed.

L(G) = {'', 'a', 'aa' }, 'a' is ambiguous.

      S: X, X.
      X: 'a'; .
    

aaa