      firstCell = getContainerCell(grid.$.items, 0, 0);

        // Polyfills may add some extra classes to cells
        initialCellClasses = Array.from(firstCell.classList);
      });

      const assertClassList = (cell, expectedClasses) =>
        expect(Array.from(cell.classList)).to.deep.equal(initialCellClasses.concat(expectedClasses));

      it('should add classes for cells', () => {
        grid.cellClassNameGenerator = (column, model) => 'foo';
        assertClassList(firstCell, ['foo']);
       