def METHOD_NAME(variants_vec_backends_once):
    # Snell's law
    theta_i = dr.linspace(mi.Float, 0, dr.pi / 2, 20)
    F, cos_theta_t, _, _ = mi.fresnel(dr.cos(theta_i), 1.5)
    theta_t = dr.acos(cos_theta_t)
    assert dr.allclose(dr.sin(theta_i) - 1.5 * dr.sin(theta_t), dr.zeros(mi.Float, 20), atol=1e-5)