code: public void used( final TestCaseDef testCase)
      {
      // Note: must accumulate tuples into a separate list to avoid ConcurrentModificationException when updating used/unused membership.
      List<Tuple> usedTuples =
        IteratorUtils.toList(
          IteratorUtils.filteredIterator(
            IteratorUtils.chainedIterator(
              unused_.iterator(),
              used_.iterator()),
            tuple -> testCase.usesTuple( tuple)));
  
      for( Tuple tuple : usedTuples)
        {
        used( tuple);
        }
      }
docs: Asserts use of all tuples contained in the given test case.