I have packaging and packaging auditing background. Asking if Micro testing is need for food packaging is a bit like asking how long is a piece of string. It depends.....
It is all about risk. It is a combination of food packaging and process. Is there a risk in packaging or food , can it be introduced through packaging. Will the risk be processed out?
If there is no risk there is not need to test. If there is a risk there is a need to test.
If you pack aseptic juice - the containter, the product and the environment in which you pack needs to be sterile. Yes.
In a can or glass where you will process up above 70 degrees. No
For milk or meat that is not further processed and prone to spoilage: Yes
For cardboard that is prone to yeast and mould: Yes
For water that is not processed but bottles are washed before filling: probably No
For containers that are not immediately blown and prone to dust with not other rinse or process: Yes
For bottles for dry herbs: Probably No as the herbs may have a higher microbial load than the bottle.
So it depends on food packaging and process.
In a nutshell there are requirements for food contact surfaces to be safe.