What is the test for a right to confront a witness at a preliminary hearing?

"The right to confrontation is basically a trial right. It includes both the opportunity to cross-examine and the occasion for the jury to weigh the demeanor of the witness. A preliminary hearing is ordinarily a much less searching exploration into the merits of a case than a trial, simply because its function is the more limited one of determining whether probable cause exists to hold the accused for trial." (Barber v. Page, supra, 390 U.S. at p. 725.)