What is the test for successfully challenging a guilty plea based on ineffective assistance of counsel?

In order to show counsel's performance fell below an objective standard of reasonableness, Defendant must identify "material, specific errors and omissions that fall outside the wide range of professionally competent assistance." United States v. Molina, 934 F.2d 1440, 1447 (9th Cir. 1991) (citation omitted). When a defendant challenges a guilty plea based on ineffective assistance of counsel, the inquiry focuses on "whether the plea represents a voluntary and intelligent choice among the alternative courses of action open to the defendant." United States v. Shah, 878 F.2d 1156, 1158 (9th Cir. 1989) (citation omitted). "A defendant who pleads guilty upon the advice of counsel may only attack the voluntary and intelligent character of the guilty plea by showing that the advice he received from counsel was not within the range of competence demanded of attorneys in criminal cases." United States v. Signori, 844 F.2d 635, 638 (9th Cir. 1988). In making this determination, the court applies a "strong presumption that counsel's conduct falls within the wide range of reasonable professional assistance . . . ." Strickland, 466 U.S. at 689. A deficient performance requires showing "counsel made errors so serious that counsel was not functioning as 'counsel' guaranteed by the Sixth Amendment." Id. at 687.