Tra từ testify - Từ điển Oxford Advanced Learner 8th

test·ify [testify testifies testified testifying] BrE [ˈtestɪfaɪ] NAmE [ˈtestɪfaɪ] verb (testi·fies, testi·fy·ing, testi·fied, testi·fied)
1. intransitive, transitive to make a statement that sth happened or that sth is true, especially as a witness in court
•~ (against/for sb) She refused to testify against her husband.
•There are several witnesses who will testify for the defence.
•~ about sth He was summoned to testify before a grand jury about his role in the affair.
•~ to sth/to doing sth Evans testified to receiving $200 000 in bribes.
•~ (that)… He testified (that) he was at the theatre at the time of the murder.
•+ speech ‘I was approached by a man I did not recognize,’ she testified.
2. transitive ~ (that)… (formal)to say that you believe sth is true because you have evidence of it
•Too many young people are unable to write or spell well, as employers will testify.
3. intransitive (especially NAmE)to express your belief in God publicly
Derived: ↑testify to something
Verb forms:

Word Origin:
late Middle English: from Latin testificari, from testis ‘a witness’.

Example Bank:
•A senior officer testified to the existence of police hit squads.
•He took the stand to testify at the trial of his colleague.
•Several witnesses have come forward to testify against her.
•She refused to testify against her brother.
•She was unwilling to testify before Congress.
•The basis for the perjury conviction was he had testified falsely under oath.
•The president's former aides were called to testify at his trial.
•a Mafia member who was prepared to testify for the authorities