How do you get those beta test?
It started off by chance actually.
A particular company/developer had released a piece of software that worked in conjunction with its MIDI hardware. The problem was that it was full of bugs...some obvious, some not so much. I started off just sending them the bugs I found–specifically, I would video capture, take detailed notes to demonstrate how I would make the bugs occur. I would also analyze/submit crash reports and even provide them with some ideas. In turn, they would send me a new build, I would put it through its paces again and respond back with a report, etc. So basically, I started trying to assist the developer/company pro bono and was able to get my foot in the door, albeit a little bit.
They eventually provided me with some perks if I kept assisting them so I did. Once things got quiet, I would find another company/developer with some new software and repeated the process over–searched out for bugs and provided concrete evidence/instructions so that they could reenact the action the caused the error. At this point, I would inform them of my previous experience (after getting permission from the previous company so that I didn't violate NDA) and would see if they wanted me on board to lend a hand.
I've done this with several companies/developers. Sometimes (a lot of times) they won't be interested, but then there are the times where they are interested in having an outside source review their material.
Keep in mind, this is very low-level beta testing. I'm never on-site with the companies (most of them are in other countries or the other side of U.S.) nor am I given access to alpha/prototypes and I'm certainly not employed by them and therefore won't be credited for shit (which I give 0 fucks about). I've been lent some gear to test on 3 occasions, but was required to return it. The early beta-software is great, but more often than not it's quite time consuming because your goal is to try and "break" it. Once you've found a means to "break," you have to do so several times to ensure you've nailed down how to recreate it for the big guys.
TBH, I don't do it for the glory or for the perks (though they can be nice from time to time), moreso, I do it for companies/developers who's products I think have awesome potential and don't mind putting a little time into. Admittedly, it's been about 6 months or so since I've done any testing because my time has been stretched incredibly thin due to dealing with baby girl's health issues and essentially working two jobs while trying to squeeze in some studio time during the very late hours of the night.
Cheers.