What is the test for informed consent in medical malpractice cases?

The "doctrine of informed consent recognized in Cobbs v. Grant, supra, 8 Cal.3d 229, 104 Cal.Rptr. 505, 502 P.2d 1, was imposed 'so that patients might meaningfully exercise their right to make decisions about their own bodies.' [Citation.]" (Arato v. Avedon (1993) 5 Cal.4th 1172, 1183, 23 Cal.Rptr.2d 131, 858 P.2d 598.)