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

" 'Aider and abettor liability is premised on the combined acts of all the principals, but on the aider and abettor's own mens rea.' [Citation.] We have defined the required mental states and acts for aiding and abetting as: '(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.' " (People v. Thompson (2010) 49 Cal.4th 79, 116-117.)