def METHOD_NAME(self):
    x, y = util.make_grid(numPix=10, deltapix=0.1)
    delta = 0.00001
    d_phi_dx = calc_util.d_phi_dx(x, y)
    d_phi_dx_delta = calc_util.d_phi_dx(x + delta, y)
    d_phi_dy = calc_util.d_phi_dy(x, y)
    d_phi_dxx = calc_util.d_phi_dxx(x, y)
    d_phi_dxx_num = (d_phi_dx_delta - d_phi_dx) / delta
    npt.assert_almost_equal(d_phi_dxx_num, d_phi_dxx, decimal=1)
    d_phi_dy_delta = calc_util.d_phi_dy(x, y + delta)
    d_phi_dyy = calc_util.d_phi_dyy(x, y)
    d_phi_dyy_num = (d_phi_dy_delta - d_phi_dy) / delta
    npt.assert_almost_equal(d_phi_dyy_num, d_phi_dyy, decimal=1)
    d_phi_dx_delta_y = calc_util.d_phi_dx(x, y + delta)
    d_phi_dxy = calc_util.d_phi_dxy(x, y)
    d_phi_dxy_num = (d_phi_dx_delta_y - d_phi_dx) / delta
    npt.assert_almost_equal(d_phi_dxy_num, d_phi_dxy, decimal=1)