What is the test for assistance of counsel under the Sixth Amendment?

assistance of counsel under the Sixth Amendment entails deficient performance under an objective standard of professional reasonableness and prejudice under a similarly objective standard of a reasonable probability of a more favorable outcome in the absence of the deficient performance." (People v. Cole (2004) 33 Cal.4th 1158, 1202, fn. 11.)

"[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. . . . If it is easier to dispose of an ineffectiveness claim on the ground of lack of sufficient prejudice, which we expect will often be so, that course should be followed." (Strickland v. Washington (1984) 466 U.S. 668, 697.)