When a person answers questions in court as a witness.
Merriam-Webster Online Dictionary
testify (verb)intransitive verb
1.
a) to make a statement based on personal knowledge or belief bear witness
b) to serve as evidence or proof
2.
to express a personal conviction
3.
transitive verb
to make a solemn declaration under oath for the purpose of establishing a fact (as in a court)
1.
a) to bear witness to - attest
b) to serve as evidence of - prove
2.
archaic
a) to make known (a personal conviction)
b) to give evidence of - show
3.
to declare under oath before a tribunal or officially constituted public body
Merriam-Webster Online Thesaurus
testify (verb)to make a solemn declaration under oath for the purpose of establishing a fact
SYNONYMS:
attest, depose, swear, witnessRELATED WORDS:
verify; vouch; promise, vowto declare (something) to be true or genuine
SYNONYMS:
attest, authenticate, avouch, testify (to), vouch (for), witnessRELATED WORDS:
guarantee, warrant; affirm, assert, aver, avow, profess, vow