Need to have a heartworm test done on my 3 year old pit bull. How much are the tests

I don't have a regular vet. I get his rabies n all done at the mobile clinics at tractor supply

Im not exactly sure however i can tell you please just know you have got to be firm with them. Myself along with my mother and my father have been talked into getting tests and treatment our dogs didnt need in the 1st place. They are genuinely concerned with your animals well being bit some of the tests n vaccines they reccomend arent nessary. I stick to my regular vet, Dr.Inscoe unless my dogs need extensive treatment. Hope you pit is ok!