During a daily stand up, the tester engages the developer in a discussion about what...

Ask the tester and developer to discuss it after the meeting, since it is not a part of the daily stand up.

Encourage the discussion to resolve impediments.

After the meeting, escalate this issue to the tester's supervisor to ensure that this does not reoccur.

Ask more questions about the testing techniques to obtain clarification on team efforts for quality improvements.