Contemporary accounts attest to his courage and determination.

当时的报道证实了他的勇气和决心。

I can attest to the absolute truth of his statement.

我可以证实他的话是千真万确的。

But some users attest to quantifiable benefits.

但有些用户却也证实了可量化的收益。

Several witnesses can attest to her good character.

好几个证人可以证明他为人正派。

Again, something I can attest to first-hand.

又一次，我本人也能亲自作证。