def METHOD_NAME(self):
    x = np.array([1])
    y = np.array([2])
    mu_r = 1.0
    mu_t = 10.0
    # positive parity
    parity = 1
    ############
    # rotation 1
    ############
    phi_G = np.pi
    f_xx, f_xy, f_yx, f_yy = self.const_mag.hessian(x, y, mu_r, mu_t, parity, phi_G)
    # rotate
    x__, y__ = util.rotate(x, y, phi_G)
    # evaluate
    f__xx, f__xy, f__yx, f__yy = self.const_mag.hessian(
        x__, y__, mu_r, mu_t, parity, 0.0
    )
    # rotate back
    kappa = 1.0 / 2 * (f__xx + f__yy)
    gamma1__ = 1.0 / 2 * (f__xx - f__yy)
    gamma2__ = f__xy
    gamma1 = np.cos(2 * phi_G) * gamma1__ - np.sin(2 * phi_G) * gamma2__
    gamma2 = +np.sin(2 * phi_G) * gamma1__ + np.cos(2 * phi_G) * gamma2__
    f_xx_rot = kappa + gamma1
    f_yy_rot = kappa - gamma1
    f_xy_rot = gamma2
    # compare
    npt.assert_almost_equal(f_xx, f_xx_rot, decimal=4)
    npt.assert_almost_equal(f_yy, f_yy_rot, decimal=4)
    npt.assert_almost_equal(f_xy, f_xy_rot, decimal=4)
    npt.assert_almost_equal(f_xy, f_yx, decimal=8)
    ############
    # rotation 2
    ############
    phi_G = np.pi / 3.0
    f_xx, f_xy, f_yx, f_yy = self.const_mag.hessian(x, y, mu_r, mu_t, parity, phi_G)
    # rotate
    x__, y__ = util.rotate(x, y, phi_G)
    # evaluate
    f__xx, f__xy, f__yx, f__yy = self.const_mag.hessian(
        x__, y__, mu_r, mu_t, parity, 0.0
    )
    # rotate back
    kappa = 1.0 / 2 * (f__xx + f__yy)
    gamma1__ = 1.0 / 2 * (f__xx - f__yy)
    gamma2__ = f__xy
    gamma1 = np.cos(2 * phi_G) * gamma1__ - np.sin(2 * phi_G) * gamma2__
    gamma2 = +np.sin(2 * phi_G) * gamma1__ + np.cos(2 * phi_G) * gamma2__
    f_xx_rot = kappa + gamma1
    f_yy_rot = kappa - gamma1
    f_xy_rot = gamma2
    # compare
    npt.assert_almost_equal(f_xx, f_xx_rot, decimal=4)
    npt.assert_almost_equal(f_yy, f_yy_rot, decimal=4)
    npt.assert_almost_equal(f_xy, f_xy_rot, decimal=4)
    npt.assert_almost_equal(f_yx, f_xy_rot, decimal=4)