testify
verb [ I or T ]
uk/ˈtestɪfaɪ/ us LAW
to make a formal statement about something, especially in a court of law:
testify that He testified that the store owner had lied when he applied for the state license.
The senator testified to the House Committee on Financial Services.
to say that something is true:
Managing people is not easy, as many new managers can testify.
Phrasal verb
testify to sth