The popularity of diet fads is a 'testimony to' the fact that people want a quick fix for their health and weight problems.
It is 'testimony to' her courage and persistence that she worked for so long in the face of such adversity.
There were contradictions in her 'testimony'.
(..) All you had all day was that salad. Do you wanna get something to eat? I can't. I'm not a bad guy. I know that. When there's emotional testimony, I assume % of it is exaggeration. And the other ? Perjury. Creation myths need a devil. What happens now? Sy and the others are having a steak (..)2010 The Social Network
(..) Can we do that? It's been almost three hours. And frankly, you did spend an awful lot of time embarrassing Mr. Zuckerberg with the girl's testimony from the bar. I'm not embarrassed, she just made a lot of that up. She was under oath. Then I guess that would be the first time (..)2010 The Social Network