What is the test for using section 654 of the California Criminal Code to determine whether an act or omission is punishable by the same section of the law?

Subdivision (a) of section 654 provides that "[a]n act or omission that is punishable in different ways by different provisions of law shall be punished under the provision that provides for the longest potential term of imprisonment, but in no case shall the act or omission be punished under more than one provision. . . ." The purpose of the statute is to ensure that the punishment is commensurate with the defendant's culpability. (People v. Perez (1979) 23 Cal.3d 545, 550-551 (Perez).)