Collocations for testify - verb

be prepared to, be willing to | be unwilling to, refuse to | call sb to, force sb to
The president''s former aides were called to testify at his trial.

against
She refused to testify against her brother.

before
She was unwilling to testify before Congress.

for
a Mafia member who was prepared to testify for the authorities

to
A senior officer testified to the existence of police hit squads. | A large number of witnesses testified to the tribunal.

testify in court