What is the test for assisting and abets the commission of a crime?

A person aids and abets the commission of a crime when he or she, with knowledge of the unlawful purpose of the perpetrator, and with the intent or purpose of committing, facilitating or encouraging commission of the crime, by act or advice, aids, promotes, encourages, or instigates the commission of the crime. (People v. Prettyman (1996) 14 Cal.4th 248, 259.) The jury may consider facts such as presence at the scene of the crime, and companionship and conduct before and after the offense, including flight, in deciding whether a defendant knew of the perpetrator's intentions and intended to facilitate or encourage the crime. (People v. Mitchell (1986) 183 Cal.App.3d 325, 330.)