Stream.of((Cell<String, String, Integer>) cell).collect(collector);
      fail("Expected NullPointerException");
    } catch (NullPointerException expected) {
    }
  }

  public void testToTableConflict() {
    Collector<Cell<String, String, Integer>, ?, Table<String, String, Integer>> collector =
        TableCollectors.toTable(
            Cell::getRowKey, Cell::getColumnKey, Cell::getValue, HashBasedTable::create);