We used to have playable camping section where you can setup tents and dig trenches.
Through iteration, however, we found it more tedious than fun after the initial experience so it was removed and camping simplified.
So in short, what's in the trailer isn't in the game anymore. Some elements of the old camping may return in combat. Like how you can place landmines during combat (which was originally designed for camping defense).
As for the testing grounds, it'd disabled temporarily and will return with more features to test in it.