Tdd

---
description: TDD agent — implement using strict red → green → refactor cycles
allowed-tools: Read, Grep, Glob, Edit, Write, Bash(pytest *), Bash(ruff *), Bash(mypy *), Bash(make *)
argument-hint: [feature, behavior, or bug to implement]
model: sonnet
context: fork
agent: general-purpose
---

# TDD

Implement using strict red → green → refactor. One test per cycle. One behavior per test.

## Target

$ARGUMENTS

## Cycle

### 1. RED
Write ONE failing test describing the expected behavior. Run it in isolation:

```bash
pytest tests/test_<module>.py::<TestClass>::<test_name> -x --tb=short

Confirm it fails with the expected assertion error — not import/syntax errors. If it fails on import, create a minimal stub so the test fails on assertion.

2. GREEN

Write the simplest code that passes. No future-proofing. No extra branches "while you're there." Run the single test, then the full suite:

pytest -x --tb=short

3. REFACTOR

All green? Clean up: extract, rename, deduplicate. Then:

ruff check --fix . && ruff format .
mypy --strict src/
pytest -x --tb=short

Repeat red → green → refactor until all acceptance criteria have passing tests.

Rules

• Naming: test_<action>_<condition>_<expected> — e.g. test_classify_returns_password_intent_when_reset_keyword_present.
• One test per cycle. Do not write a batch of tests upfront.
• Bug fix flow: write a reproducing test first (must fail), then fix.
• Never add broad except Exception, pass in except, mocked returns in production code, or stubs that return hardcoded success. These are banned by scripts/check-no-fake-success.sh.
• Never skip or xfail a test to reach green faster.
• Touch only files relevant to the current behavior.

Done criteria

• All acceptance criteria have passing tests.
• make verify is green.
• Coverage check run with pytest --cov=src --cov-report=term-missing; gaps are either filled or explicitly justified in the completion summary.

Completion summary

Report: the behavior implemented, number of red → green cycles, final coverage delta, and make verify result. ```