"I didn't. I thought it would be a waste to kill an animal without knowing."

And so he thought it best to test. He's glad for it too. There are plenty of hostile animals back home, but even then he doesn't normally attack them unless they attack him first.

If Hanzo hadn't been so keen on attacking, he might not have tested it at all. He doesn't take the matter of wandering into an animal's territory lightly.