Depends on what you've heard.
Does it do much for test? Not really. It'll normalize low levels.
However, it's been shown to significantly increase DHEA, DHT, and decrease elevated prolactin (a big deal).
Effect of oral administration of Tribulus terrestris extract on semen quality and body fat index of infertile men. - PubMed - NCBI
Run it through sci-hub to get full text. Wish they tested total testosterone.
It seemingly acts as a non-aromatizing DHEA analog.
I've been taking TT for awhile and the effects are undeniable. Blood work coming. Others across internet have had their DHT test above range along with an increase of DHEA. Fertility and pregnancy forums have long reported Tribulus' effectiveness in that realm.
Make sure the Tribulus product has protodioscin when buying.