tddlisted

# Skill: /tdd ## Purpose Scaffold a test-driven development cycle: write a failing test first, implement the minimal code to pass it, then refactor — with an explicit gate that the test is red before any implementation is written. ## When to Use - Implementing a new function, class, or module from scratch - Fixing a bug where a regression test should prevent recurrence - The user says "tdd this", "write tests first", or "red-green-refactor" - Any feature work where correctness is more important than speed of first draft ## Steps 1. **Understand the behavior to implement.** Read any referenced plan, issue, or existing tests. Clarify the acceptance criterion in one sentence: "Given X, when Y, then Z." 2. **Write the failing test (RED).** Create the test file before writing any implementation: Example — adding a `parse_duration` function: ```python # tests/unit/test_parse_duration.py import pytest from tools.time_utils import parse_duration def test_parse_duration_minutes(): assert parse_duration("5m") == 300 def test_parse_duration_hours(): assert parse_duration("2h") == 7200 def test_parse_duration_invalid_raises(): with pytest.raises(ValueError, match="invalid duration"): parse_duration("banana") ``` 3. **Run the test and confirm it FAILS.** This is a hard gate — do not write implementation until you see a red failure: ```bash pytest tests/unit/test_parse_duration.py -v ``` Expected: `FAILED` or