What is the test for disqualifying a trial judge?

"Code of Civil Procedure section 170.6 provides in substance that any party to an action may make a motion, supported by an affidavit of prejudice, to disqualify the trial judge, commissioner, or referee. If the motion is timely and properly filed, the judge must recuse himself without further proof and the cause must be reassigned to another judge. When an affidavit of prejudice has been timely filed, the judge's disqualification is automatic and mandatory. Once properly and timely challenged, the judge loses jurisdiction to proceed and all his subsequent orders and judgments are void." (Lawrence v. Superior Court (1988) 206 Cal.App.3d 611, 615-616, 253 Cal.Rptr. 748; internal quotation marks omitted.)