What is the legal test for striking testimony from a witness who refuses to submit to cross-examination?

"Where a witness refuses to submit to cross-examination, or is unavailable for that purpose, the conventional remedy is to exclude the witness's testimony on direct." (Fost, supra, 80 Cal.App.4th at p. 735.) Moreover where a witness "frustrates" cross-examination by declining to answer some or all of the questions, the court may strike all or part of the testimony. (People v. Price (1991) 1 Cal.4th 324, 421.) The decision whether to strike the direct examination, or a partial strike of the testimony, of a witness who does not submit to cross-examination is left to the discretion of the trial court. (People v. Reynolds (1984) 152 Cal.App.3d 42, 47-48.)