What is the legal test for using the word "mandatory" in a statute?

The word "mandatory" may be used in a statute to refer to a duty that a governmental entity is required to perform as opposed to a power that it may, but need not exercise. As a general rule, however, a " 'directory' or 'mandatory' designation does not refer to whether a particular statutory requirement is 'permissive' or 'obligatory,' but instead simply denotes whether the failure to comply with a particular procedural step will or will not have the effect of invalidating the governmental action to which the procedural requirement relates." (Morris v. County of Marin, supra, 18 Cal.3d 901, 908, 136 Cal.Rptr. 251, 559 P.2d 606.) If the action is invalidated, the requirement will be termed "mandatory." If not, it is "directory" only.