When a dev sends the provision file and app file, you put the mp in the app folder and select them both. Drag or send them to applications under itunes, then test your little heart out
Just have to wait and find a thread where devs are asking for some beta testers and apply. Or you can sign-up at ibetatest.com and wait for games to show up there. It's mostly about timing and being in the right place to become a beta tester.
Once you get a copy running, in my opinion a good beta tester will go through and play the crap out of it, and if you notice a bug, try to remember exactly what you were doing when the bug occurred. It helps to remember the specifics of where the bug happened, that helps the dev out a lot.
I also like to take screenshots if there is an issue that can be seen versus just being performance related. Pic makes it much easier to explain.
Yes, reproducibility is key, if you aren't able to give clear instructions on how to make the problem happen fairly reliably the bug report will be pretty much useless to the developer.
If you want to show that you can be a good asset as a beta tester, pick a game that you are playing and find a bug in it. Then create a report on that bug which would show that you know what you are doing. For example, I found a bug in Fallout 3 a while back that was kind of neat. I'll have to make up the location info because I don't remember it all offhand. Here's a format example: Bug: When discarding large numbers of inventory items, objects may be teleported to the entrance portal of the zone. Occurence: When exploring the Police Headquarters, I entered office in southwest corner and climbed wooden ramp over filing cabinets. Due to irregularity in terrain I became stuck as I was overburdened and could not jump above small lip in terrain. I discarded 70 lbs of weapons en masse, and returned to play. I was no longer burdened and was able to jump down. The weapons were not present. Upon returning to the zone entrance I found all the weapons I had discarded present at the zone portal. Reproduction: Occurs in version 0.99a1 This bug requires the attached save game to reproduce. (You would put the steps to reproduce here in numerical order) 1. Access inventory. 2. Discard 10 assault rifles without exiting inventory screen. 3. Close pipboy. 4. Weapons will not be present. 5. Return to zone portal. Weapons will be at those coordinates. etc. etc. It's likely not going to be as tedious as that for us iphone devs, but that's what you could expect a typical bug report to look like for a developer using Bugzilla or Jira in their studio.
