What is the test for ineffective assistance of counsel?

To demonstrate ineffective assistance of counsel, defendant must show both that counsel's representation fell below an objective standard of reasonableness under prevailing professional norms, and that there is a reasonable probability that, but for counsel's unprofessional errors, the result would have been different. (Strickland v. Washington (1984) 466 U.S. 668, 687.) A reviewing court must afford great deference to trial counsel's actions and must presume that the challenged actions constituted sound trial strategy. (Id. at p. 689.)