Sec[Section] 1 Be it enacted by the people of the State of Illinois, represented in the General Assembly, That hereafter in all trials in the circuit Courts in all actions upon contracts, either express or implied, no plaintiffs shall be required to prove on trial any partnership set forth in the declaration, unless the defendant shall have filed an affidavit1 of himself or other credible person, stating the belief of the affiant that the names of the persons constituting the partnership are not correctly set forth in the declaration of the plaintiffs; nor shall such proof be required in trials before Justices of the Peace, unless the defendant or some credible person, shall make oath of his belief that the plaintiffs were not partners at the time the contract, on which suit was instituted, was made.