If the defendant or defendants appear in a suit to enforce any lien provided by this chapter, he, she, or they shall make their answer on the merits of the complaint, and any motion or demurrer against the said complaint must be filed with the answer; and no motion shall be allowed to make complaint more definite and certain, if it appear to the court that the defendant or defendants have or should have knowledge of the facts, or that it can be made more certain and definite by facts which will appear necessarily in the testimony; but the case, unless the court sustains the demurrer to the complaint, shall be heard on the merits as speedily as possible, and amendments of the pleadings, if necessary, shall be liberally allowed.