What is the test for a claim for breach of an implied covenant of good faith and fair dealing against a truck insurer?

Waller v. Truck Ins. Exch., Inc. , 11 Cal.4th 1, 36, 44 Cal.Rptr.2d 370, 900 P.2d 619 (1995) (It is clear that if there is no potential for coverage and, hence, no duty to defend under the terms of the policy, there can be no action for breach of the implied covenant of good faith and fair dealing because the covenant is based on the contractual relationship between the insured and the insurer).⁴