What is the test for determining whether an insurance policy's terms are ambiguous or uncertain?

"On the other hand, '[i]f the terms of a promise are in any respect ambiguous or uncertain, it must be interpreted in the sense in which the promisor believed, at the time of making it, that the promisee understood it.' [Citations.] This rule, as applied to a promise of coverage in an insurance policy, protects not the subjective beliefs of the insurer but, rather, 'the objectively reasonable expectations of the insured.' [Citation.] Only if this rule does not resolve the ambiguity do we then resolve it against the insurer. [Citation.]" (Bank of the West v. Superior Court, supra, 2 Cal.4th at pp. 1264-1265.) "In determining whether an ambiguity exists, the words of the policy must be interpreted according to the plain meaning that a layperson would ordinarily attach to them.

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