Testing Stop Lamp

I just bought a Craftsman Mini Coil Cord Circuit Tester in order to check the fuse on the stop lamps for my 1988 Corolla because they are no longer illuminating. Of course fuse blown, so I replaced the fuse and step on the brake pedal, Pop Fuse is blown again. So I stuck the probe around the fuses and the test light doesn't illuminate and the stop light is once again blown. SO i check what i think is the tail light control relay were the stop lamp wire is conected to it. Not only does it illuminate the test light buzzes, its never before buzzed, does anyone know what this is? Or how i can fix it?


Thank you.