testify to (something)
To give sworn testimony that something is true. The doctor was asked to testify to the extent of the plaintiff's injuries in the criminal negligence lawsuit against the construction company. I was happy to testify for Daniel's whereabouts on the evening in question, as I had been with him the whole night.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
testify to something
to swear to something. I will testify to your whereabouts if you wish. I think I know what happened, but I would not testify to it.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
1. To make a statement based on personal knowledge in support of some asserted fact; bear witness to something: Many astronauts have testified to the thrill of weightlessness. The witness testified to the accuracy of the defendant's story.
2. To serve as evidence: The wreckage testifies to the strength of the storm.
The American Heritage® Dictionary of Phrasal Verbs. Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.