A proving ground, also referred to as a testing ground, was a military location where personnel, weapons and similar technologies were tested.
In the 1940s, a proving ground was located in Nevada and was the site of the detonation of a nuclear weapon in 1947. Quark, Odo, Rom, and Nog later brought Quark's Treasure to the proving ground, where they flew into the nuclear explosion. (DS9: "Little Green Men")
Another Earth proving ground for nuclear weapons in the same era was located at the Bikini Atoll. (ENT: "Stratagem")
The Xindi maintained a proving ground in the Calindra system, where they tested a prototype for their weapon in late 2153. (ENT: "Stratagem")
A region of space in the Delta Quadrant designated Subspace Munitions Range 434 was used for weapons tests by an unknown species in 2377. (VOY: "Human Error")