private CellScanner doCreateCellScanner(final int listsCount, final int itemsPerList) {
    List<CellScannable> cells = new ArrayList<>(listsCount);
    for (int i = 0; i < listsCount; i++) {
      CellScannable cs = new CellScannable() {
        @Override
        public CellScanner cellScanner() {
          return new TestCellScanner(itemsPerList);
        }
      };
      cells.add(cs);
    }
    return CellUtil.createCellScanner(cells);
  }
Was overflowing if 100k or so lists of cellscanners to return.
hbase-common/src/test/java/org/apache/hadoop/hbase/TestCellUtil.java