HR procedures manual

I still don't understand why you are referring to a one-time inspection of something as a test of control - in doing this the auditor merely obtains information that is relevant to understanding risk in the payroll (in this instance). An HR manual will cover all the HR policies and procedures relevant to the function of HR. An internal audit manual will cover all the HR policies and procedures relevant to the function of internal audit. Etc It wouldn't make sense that such manuals cover policies and procedures that are not within their remit.