formally declare, especially in writing or on a printed document
… give a certificate to sb
"His high fever attested to his illness"
"The buildings in Rome manifest a high level of architectural sophistication"
"This decision demonstrates his sense of fairness"
"I am licensed to practice law in this state"
"certified grade AAA meat"
Can you certify for his ability as a teacher?
I believe it to be true, but I am not able to certify to that effect.