Confirms

This report confirms his betrayal.

An exception which confirms the rule.

The evidence confirms it.

Your story only confirms my suspicions about your bad behavior.

Then first with eager joy / "O Goddess-born," the bold Achates cries, / "how now? What purpose doth thy mind devise? / Lo! all are safe – ships, comrades brought again; / one only fails us, who before our eyes / sank in the midst of the engulfing main. / All else confirms the tale thy mother told thee plain."

Are you more likely to believe a story if it confirms your pre-existing beliefs? That is called confirmation bias.

Her current attitude confirms what we had guessed.

His current attitude confirms what we had guessed.

Call the doctor so that he confirms the appointment.

I wonder if I'm expecting too much from myself. When I succeed, I've already been expecting to succeed, so I don't feel really proud. When I don't succeed, it confirms the idea that I'm useless, and I accept the loss and shut down.