def METHOD_NAME(self):
    n = 13  # MAGIC NUMBER to pick one orbit
    # First, check that value of the actions are stable
    actions, angles, freqs = isochrone_xv_to_aa(
        self.w[:, n], self.potential
    )
    for i in range(3):
        assert u.allclose(actions[i, 1:], actions[i, 0], rtol=1e-5)
    for slice_ in [slice(None), 0]:
        actions, angles, freqs = isochrone_xv_to_aa(
            self.w[slice_, n], self.potential
        )
        # Compare to genfunc
        x = self.w.xyz[:, slice_, n]
        v = self.w.v_xyz[:, slice_, n]
        m = self.potential.parameters["m"].value / 1e11
        b = self.potential.parameters["b"].value
        if x.ndim > 1:
            s_w = np.vstack((
                x.to_value(u.kpc),
                v.to_value(u.km / u.s)
            ))
            aa = np.array(
                [
                    toy_potentials.angact_iso(s_w[:, i].T, params=(m, b))
                    for i in range(s_w.shape[1])
                ]
            )
            s_actions = aa[:, :3] * u.km / u.s * u.kpc
            s_angles = aa[:, 3:] * u.rad
        else:
            s_w = np.concatenate((
                x.to_value(u.kpc),
                v.to_value(u.km / u.s)
            ))
            aa = toy_potentials.angact_iso(s_w.T, params=(m, b))
            s_actions = aa[:3] * u.km / u.s * u.kpc
            s_angles = aa[3:] * u.rad
        assert u.allclose(actions, s_actions.T, rtol=1e-8)
        assert_angles_allclose(angles, s_angles.T, rtol=1e-8)
        # Test round-tripping
        if HAS_TWOBODY:
            w_rt = isochrone_aa_to_xv(actions, angles, self.potential)
            assert u.allclose(x, w_rt.xyz, atol=1E-10 * u.kpc)
            assert u.allclose(v, w_rt.v_xyz, atol=1E-10 * u.km/u.s)