If the plaintiff believe that the answer of the garnishee is untrue, or that it is not a full discovery as to the debt due by the garnishee, or as to the property in his possession belonging to the defendant, he shall, at the term when the answer is filed, unless the court grant further time, contest the same, in writing, specifying in what particular he believes the answer to be incorrect. Thereupon, the court shall try the issue at once, unless cause be shown for a continuance, as to the truth of the answer, and shall render judgment upon the facts found, when in plaintiff's favor, as if they had been admitted by the answer, but if the answer be found correct, the garnishee shall have judgment for costs against the plaintiff.