hould add classes when loading new items', function(done) {
        grid.cellClassNameGenerator = (column, model) => model.item.value;
        scrollToEnd(grid, () => {
          const rows = getRows(grid.$.items);
          const lastRow = rows[rows.length - 1];
          const cell = lastRow.firstElementChild;
          assertClassList(cell, ['foo199']);
          done();
        });
      });

      it('should not throw with falsy return value', () => {
        expect(() => grid.cellClassNameGenerator = 