What is the test for a judicial declaration of rights?

"The purpose of a judicial declaration of rights in advance of an actual tortious incident is to enable the parties to shape their conduct so as to avoid a breach. '[Declaratory] procedure operates prospectively, and not merely for the redress of past wrongs. It serves to set controversies at rest before they lead to repudiation of obligations, invasion of rights or commission of wrongs; in short, the remedy is to be used in the interests of preventive justice, to declare rights rather than execute them.' [Citations.]" (Babb v. Superior Court (1971) 3 Cal.3d 841, 848.)