For anyone not aware of what a Tech test is in comparison to a Beta, hopefully I can expand on that a bit more.
Beta’s and Alpha’s are done for 1 specific reason, and that is to test the game itself. Bug hunting is practically the name of the game, and players are let loose into the game in the hopes that they find minor bugs and report them. (Major bugs hopefully got squished before this, so that’s why you hope they only find minor ones.) As well as this, for something like Battleborn a Beta would also provide a lot of raw data that Gearbox can use to check on things such as balance and popularity. It is kinda like market research if anyone is aware of the business world.
Now, a Technical Test is done for a entirely different reason. While reporting bugs is still helpful, that is not the name of the game this time. For any game that relies on a Multiplayer Server, Tech Test’s are vital as the whole point is to push the servers to and beyond their limits. In fact, I am sorry to tell you guys this, but if the Tech Test goes like they pretty much all normally do, the game servers will crash. A lot. But that is the whole point. Giving a small window for people to play the game, while reducing the control to the amount of people who can join the servers, pushes them to an extreme and beyond. Once Gearbox can find the breaking point, they can then from there try to push the breaking point further, or decide that it is at a good point, they just need to add controls into the system to stop it going past that on release. And that is the true aim of a Tech Test. It is preparing for when the game releases, getting ready for that huge inflow of people onto the servers, and making sure it does not break them. If anyone has played Diablo 3 on launch, you know how painful broken servers can be.
TL;DR Beta is about fixing the game. Tech Test is about breaking the servers, almost like breaking in a new pair of shoes. Rather get blisters a few weeks before Prom night than wear painful shoes and kill your feet on the night, right? 