IllegalStateException.class,
        () ->
            Stream.of(immutableCell("one", "uno", 1), immutableCell("one", "uno", 2))
                .collect(collector));
  }

  public void testToTableMerging() {
    Collector<Cell<String, String, Integer>, ?, Table<String, String, Integer>> collector =
        TableCollectors.toTable(
            Cell::getRowKey,
            Cell::getColumnKey,