Leaks eventually happens though and a Reddit thread has been constantly updated with informations coming directly from the field test.
As you'd expect from a beta, everything posted below is subject to change and/or be removed so keep that in mind.
The biggest information is that battles are not unfolding in turn based fashion like you'd normally expect from a Pokémon title.
Everything's real time and works with a stamina bar require you to even dodge left or right by swiping the screen. Area of Effect attacks seem to hit Pokémon regardless of whether you dodge or not.
You'll also have to choose between three teams: Red, Blue and Yellow (as a neat way of mentioning the first generation of Pokémon games).
Gyms are buildings that you can capture. To do so, you'll have to place one of your Pokémon there. Eventually, your other Pokémon will fight against it and gain levels.
Gyms can also be captured but you'll have to fight multiple times against it until the Gym's points reach to zero.
You'll be able to find Pokémon in the wild as previously announced but you won't see where they are. The game will just tell you how far away they are located, the rest is up to you.
You'll also find a camera switch to enable the AR view.
Keep an eye on that Reddit thread as it's constantly updated with more informations.