def test_expandingbox_like(self, opt):
        """
        Make sure SubDimensions aren't an obstacle to expanding boxes.
        """
        grid = Grid(shape=(8, 8))
        x, y = grid.dimensions

        u = TimeFunction(name='u', grid=grid)
        xi = SubDimension.middle(name='xi', parent=x, thickness_left=2, thickness_right=2)
        yi = SubDimension.middle(name='yi', parent=y, thickness_left=2, thickness_right=2)

        eqn = Eq(u.forward, u + 1)
        eqn = eqn.subs({x: xi, y: yi})

        op = Operator(eqn, opt=opt)

        op.apply(time=3, x_m=2, x_M=5, y_m=2, y_M=5,
                 xi_ltkn=0, xi_rtkn=0, yi_ltkn=0, yi_rtkn=0)

        assert np.all(u.data[0, 2:-2, 2:-2] == 4.)
        assert np.all(u.data[1, 2:-2, 2:-2] == 3.)
        assert np.all(u.data[:, :2] == 0.)
        assert np.all(u.data[:, -2:] == 0.)
        assert np.all(u.data[:, :, :2] == 0.)
        assert np.all(u.data[:, :, -2:] == 0.)