tdd

Tests verify behavior through public interfaces, not implementation details. Code can change entirely; tests shouldn't. A good test reads like a specification — "user can checkout with valid cart" tells you exactly what capability exists. These tests survive refactors because they don't care about internal structure.

DO NOT write all tests first, then all implementation. This is "horizontal slicing" — treating RED as "write all tests" and GREEN as "write all code."

Correct approach: Vertical slices via tracer bullets. One test → one implementation → repeat. Each test responds to what you learned from the previous cycle.

使用垂直切片示踪子弹工作流程指导测试驱动的开发。在实现功能、修复错误或编写应驱动设计的测试时使用。通过公共接口强制编码前进行规划、增量红绿重构周期以及基于行为的测试。触发器：“TDD”、“首先测试”、“编写测试”、“跟踪子弹”或通过测试实现增量功能。 来源：sadiksaifi/agents。