What is the test for awarding expert witness fees under section 998 of the California Code of Civil Procedure?

In contrast, the award of expert witness fees under Code of Civil Procedure section 998 was proper absent an abuse of discretion. "'"The reasonableness of a defendant's section 998 settlement offer is evaluated in light of 'what the offeree knows or does not know at the time the offer is made.'" 'Where the defendant obtains a judgment more favorable than its offer, "'the judgment constitutes prima facie evidence showing the offer was reasonable. . . .'"' '"Whether a section 998 offer was reasonable and made in good faith is left to 'the sound discretion of the trial court."' '"In reviewing an award of costs and fees under Code of Civil Procedure section 998, the appellate court will examine the circumstances of the case to determine if the trial court abused its discretion in evaluating the reasonableness of the offer or its refusal." "'["]The burden is on the party complaining to establish an abuse of discretion, and unless a clear case of abuse is shown and unless there has been a miscarriage of justice a reviewing court will not substitute its opinion and thereby divest the trial court of its discretionary power."'"'" (Najah, supra, 230 Cal.App.4th at pp. 143-144, citations omitted; see Adams v. Ford Motor Co. (2011) 199 Cal.App.4th 1475, 1484 (Adams).)