As someone who's built and repaired many amplifiers over many years, I wouldn't attempt to power test into a one ohm load!.
Rewire your loads to give either 8 ohms or 4 ohms, then do the tests - 8 ohms is preferred, as I very much doubt the amplifiers capability into low impedance loads.
As Audioguru says, the spec of the amp almost certainly won't handle sinewaves - which means you can't get a meaningful measurement out of it. Perhaps you may be able to with only an 8 ohm load, which is why I suggested 8 ohms rather than 4 ohms.
A poor quality amplifier has a much larger chance of failing during power tests, so keep them VERY short! - and don't be too surprised if you hear a loud bang, and see clouds of smoke :lol:
As Audioguru also said, you need to be aware of the high current requirements - they will be extremely high, requiring a big battery and very thich, very short, leads.