- 新增 6 个测试场景 (config load pipe, handler errors, service aggregation, engine degradation, openai decoder edges, negative tests) - 更新测试工具规格 (mockgen, in-memory SQLite) - 覆盖率目标从 >80% 提升至 >85% - 新增 test-unit 和 test-integration Makefile 命令 - 新增死代码清理和 mockgen 需求 - 归档变更至 openspec/changes/archive/2026-04-22-improve-backend-testing/