Testing Strategies for Upgrading ModPacks

[Geoff]

So with development of all the mods fairly active and various issues I have experienced hosting MindCrack, I would like to come up with some strategies to test out upgrading various mods or modpacks without impacting the existing users.

Some of the areas I believe should be tested are:

• Test upgrading the world file
• Test creation of a new world and create a stress setup in the world

For upgrading the existing world file I have seen the world go south with massive chunk errors that would render gameplay dead-in-the-water. Sometimes it works until someone starts firing up something like automatic processing and then errors will appear or travel to some spot in the world and then find chunk errors.
On the creation of a new world it would seem this should be the safest when updating mods but if you are going beyond vanilla and doing TickThreading I would like to figure out some way to stress that out.
Love to hear from other Admin's their upgrade strategies for Modpacks to reduce user impacts if things go wrong.