What is the test for ineffective assistance in a personal injury action?

"If the record contains an explanation for the challenged aspect of counsel's representation, the reviewing court must determine 'whether the explanation demonstrates that counsel was reasonably competent and acting as a conscientious, diligent advocate.' [Citation.] On the other hand, if the record contains no explanation for the challenged behavior, an appellate court will reject the claim of ineffective assistance 'unless counsel was asked for an explanation and failed to provide one, or unless there simply could be no satisfactory explanation.'" (People v. Cudjo (1993) 6 Cal.4th 585, 623.)