tdd

把测试驱动开发落到实处：先写会失败的测试、并在你确认后才实现功能，测试就是规范，不能为实现而放宽。适用于实现新功能或修 bug 时按 TDD 流程工作，不适合纯文档、配置或已有测试覆盖的重构。流程上会和你约定每轮的反馈颗粒度（比如一条测试一轮或批量测试），保持小步快迭代。

# TDD Loop

**The test is the specification.** Once a test fails for the right reason, it must not be weakened to accommodate the
implementation.

Agree the feedback loop size with the user first — one test per cycle, or a batch prepared ahead. It depends on the
task. If unsure, prefer fewer tests per cycle.

## 1. Choose the test type

What the behavior needs decides this, not preference:

- **Unit** — pure. No network, no containers, no infrastructure. Use in-memory fakes and stubs. Must pass anywhere with
  zero setup.
- **Integration** — needs live infrastructure (a container, a database, a real service).
- **End-to-end** — full flows through the public entry point.

**Then find how this