What is the test for ineffective assistance of counsel?

"In order to establish a violation of the right to effective assistance of counsel, a defendant must show that counsel's performance was inadequate when measured against the standard of a reasonably competent attorney, and that counsel's performance prejudiced defendant's case in such a manner that his representation 'so undermined the proper functioning of the adversarial process that the trial cannot be relied on as having produced a just result.' [Citations.] Moreover, 'a court need not determine whether counsel's performance was deficient before examining the prejudice suffered by the defendant as a result of the alleged deficiencies.' [Citation.] Prejudice is shown when there is a 'reasonable probability that, but for counsel's unprofessional errors, the result of the proceeding would have been different. A reasonable probability is a probability sufficient to undermine confidence in the outcome.' [Citations.] If defendant fails to show that he was prejudiced by counsel's performance, we may reject his ineffective assistance claim without determining whether counsel's performance was inadequate. [Citation.]" (People v. Sanchez (1995) 12 Cal.4th 1, 40-41, disapproved on other grounds in People v. Doolin (2009) 45 Cal.4th 390.)