Agree on severity definitions before the first bug is filed. Clear criteria prevent every bug from becoming a negotiation.
Look for: mutual respect, shared ownership of quality, clear bug reporting with reproduction steps and impact, severity definitions agreed upfront, using data to resolve disagreements, and focusing on the user impact rather than who is right. Best candidates are seen as allies, not adversaries.
Tests interpersonal skills and professional maturity. The QA-developer relationship can be adversarial or collaborative. Look for candidates who build trust and focus on shared goals rather than finding fault.