What is the test for a person to be found guilty of aiding and abetting a crime?

"All persons concerned in the commission of a crime . . . whether they directly commit the act constituting the offense, or aid and abet in its commission . . . are principals in any crime so committed." ( 31.) "If the defendant himself [or herself] commits the offense, he [or she] is guilty as a direct perpetrator. If he [or she] assists another, he [or she] is guilty as an aider and abettor." (People v. Perez (2005) 35 Cal.4th 1219, 1225.) "[A]ider and abettor liability requires proof in three distinct areas: (a) the direct perpetrator's actus reusa crime committed by the direct perpetrator, (b) the aider and abettor's mens reaknowledge of the direct perpetrator's unlawful intent and an intent to assist in achieving those unlawful ends, and (c) the aider and abettor's actus reusconduct by the aider and abettor that in fact assists the achievement of the crime." (Ibid.) The latter aiding and abetting requirement is satisfied where the aider and abettor "by act or advice aids, promotes, encourages or instigates, the commission of the crime." (People v. Beeman (1984) 35 Cal.3d 547, 561.)