You may find the National Fuel Gas Code to be helpful.  Look in Part 4, Inspection, Testing, and Purging.  You should be able very quilckly to adapt the code requirements to your needs.  For instance it gives you the duration requirements based on volume of fuel line, the test medium requirements, the pressure requirements (1.5 times the maximum working pressure), etc.  Also, if this is a municipal inspector he may have additional requirements that will need to be incorporated into a procedure.