What is the test for a "aider and abettor" to be found guilty of assisting in the commission of a crime?

An aider and abettor must "act with knowledge of the criminal purpose of the perpetrator and with an intent or purpose either of committing, or of encouraging or facilitating commission of, the offense. [Citations.] [] When the definition of the offense includes the intent to do some act or achieve some consequence beyond the actus reus of the crime [citation], the aider and abettor must share the specific intent of the perpetrator. . . . [A]n aider and abettor will 'share' the perpetrator's specific intent when he or she knows the full extent of the perpetrator's criminal purpose and gives aid or encouragement with the intent or purpose of facilitating the perpetrator's commission of the crime. [Citations.] The liability of an aider and abettor extends also to the natural and reasonable consequences of the acts he [or she] knowingly and intentionally aids and encourages." (People v. Beeman (1984) 35 Cal.3d 547, 560.)