I'm doing a lot of QA in my startups. There are several layers: 1. One model (Opus) writes a code, another model (Sonnet, Qwen, Kimi) writes unit tests using requirements and code; 2. Full code review by me. Just to understand what is going on in the codebase; 2. Integration tests are running with PlayWright MCP. Another model validates UI per requirements; 3. Substantive runtime tests prepared by me or human QA team. All features should be included into testing, plus regression testing of existing features, plus edge cases. QA in AI era becomes more important than coding skills. So keep it in a good shape.