tdd-workflow_skill

Overview

This skill enforces a strict TDD workflow and guides the Red-Green-Refactor cycle for Python projects. It ensures tests are created first, confirms intended failures, drives minimal implementation to pass tests, and mandates refactoring with full test re-runs and quality checks. Use it to make feature work, bug fixes, and refactors safe, incremental, and reviewable.

How this skill works

When enabled, the skill requires a test to be created or identified in the tests/ directory before any implementation edits. It runs the test suite to confirm failure (Red), guides a minimal implementation to make that test pass (Green), then triggers refactoring while re-running all tests and static analysis tools. The skill blocks implementation work if the test file is missing or a failing-test prerequisite is unmet, and it requests explicit user approval at key transitions.

When to use it

• Starting a new feature implementation
• Beginning a bug fix that needs a reproducible test
• Starting a refactor that requires safety guarantees
• Enforcing test-driven culture on a team
• When you need traceable, incremental progress for reviewers

Best practices

• Create tests in tests/ with names like test_<feature>_<situation>_<expected_result>
• Keep implementations minimal in Green—only enough code to pass the failing test
• Always confirm the test fails before implementing to validate the test's value
• Run static analysis and formatting (ruff, mypy) after Green and before finalizing refactor
• Re-run the entire test suite after refactor to prevent regressions

Example use cases

• Add a login endpoint: write tests in tests/test_auth.py, confirm failure, implement minimal auth code, then refactor safely
• Fix a reported bug: write a failing test that reproduces the bug, verify it fails, implement fix, run full tests and linters
• Refactor a module: add tests that assert current behavior, confirm they fail if you change API, refactor incrementally with tests green at each step
• Introduce a new service under src/services/: create corresponding tests in tests/test_<service>.py before editing implementation