At the time and place appointed for the hearing, or at such other time to which the same may be postponed, upon satisfactory proof, by affidavit or otherwise, of proper mailing and publication of notice, as required by the preceding sections, the court shall conduct said hearing, and the heirs at law, devisees and legatees of the decedent and all persons interested in the estate, may appear and contest such application, and the court may examine, under oath, the applicant and all other persons who come before the court for that purpose.