The phrase "powerful testament" means something that provides strong evidence or proof of something, usually used to describe a statement, action, or event that strongly supports or verifies a belief or claim. Full definition
It would be an incredibly powerful testament to the will of the American people, one which would show the country and the world that we respect and embrace diversity. (religion.blogs.cnn.com)
I think it's a really powerful testament to how a bit of leadership and vision at that local government level can actually have a fairly wide - ranging impact.» (nexusmedianews.com)
While the Opsis board isn't a mainstream device by any stretch, the fact that it's creator was able to build a niche device and sell it on a crowdfunding site using what is essentially a custom chip is a powerful testament to how the democratization of FPGAs could change things. (fortune.com)