rst: 'a',
            last: 'b'
          }
        });
        expect(grid.size).to.equal(3);
        expect(getContent(0, 0)).to.equal('a');
      });

      it('should be observed for mutation', () => {
        grid.set('items.0.name.first', 'new');
        expect(getContent(0, 0)).to.equal('new');
      });

      it('should handle null', () => {
        grid.items = null;
        expect(grid.size).to.equal(0);
      });

      it('should set array data provider', () => {
        expect(grid.dataProvide