tdd-workflow

Test-Driven Development Workflow

Goal

Enforce the discipline of writing tests before implementation code. Every feature starts with a failing test (RED), passes with minimal code (GREEN), then improves through refactoring while green. Never skip the test-first step.

Dependencies

Tools

• pytest — Test runner. Invoked via uv run pytest.
• Bash — Runs test commands to confirm RED/GREEN status.

Connectors

• Project test infrastructure — Existing tests/ directory with pytest configuration.

Context

The Red-Green-Refactor Cycle

RED: Write failing test
  ↓
GREEN: Write minimal code to pass
  ↓
REFACTOR: Improve code while keeping tests green
  ↓
(repeat)

TDD Rules

1. Never write production code without a failing test
2. Write only enough test to fail (compilation failures count)
3. Write only enough code to pass the failing test
4. Refactor only when tests are green

Test Organization

tests/
├── unit/                    # Fast, isolated tests
├── integration/             # Tests with real dependencies
└── e2e/                     # Full system tests

Coverage Guidance

Focus on meaningful coverage, not 100%:

• Critical business logic: 90%+
• Edge cases and error paths
• Integration points

Don't obsess over: simple getters/setters, framework boilerplate, generated code.

Process

Step 0: Load Stored Feedback

python ${CLAUDE_PLUGIN_ROOT}/scripts/feedback_manager.py autonomous-sdlc show-feedback

Apply relevant feedback: tdd_workflow, test_generation, general.

Step 1: RED — Write a Failing Test

# tests/test_user_service.py
def test_create_user_returns_user_with_id():
    """Test that creating a user returns a user with an assigned ID."""
    service = UserService()
    user = service.create_user(name="Alice", email="[email protected]")

    assert user.id is not None
    assert user.name == "Alice"
    assert user.email == "[email protected]"

Run to confirm failure:

uv run pytest tests/test_user_service.py::test_create_user_returns_user_with_id -x
# Expected: FAILED (UserService doesn't exist)

Step 2: GREEN — Minimal Implementation

Write just enough code to make the test pass:

# src/user_service.py
from dataclasses import dataclass
import uuid

@dataclass
class User:
    id: str
    name: str
    email: str

class UserService:
    def create_user(self, name: str, email: str) -> User:
        return User(id=str(uuid.uuid4()), name=name, email=email)

Run to confirm pass:

uv run pytest tests/test_user_service.py::test_create_user_returns_user_with_id -x
# Expected: PASSED

Step 3: REFACTOR — Improve Structure While Green

Refactoring means improving code structure without changing behavior. Do not add new features here.

# src/user_service.py — structural improvement only
from dataclasses import dataclass, field
import uuid

@dataclass
class User:
    name: str
    email: str
    id: str = field(default_factory=lambda: str(uuid.uuid4()))

class UserService:
    def create_user(self, name: str, email: str) -> User:
        return User(name=name, email=email)

uv run pytest tests/test_user_service.py -x
# Should still pass — behavior unchanged, structure improved

Step 4: Next RED Cycle — Add Validation

New behavior requires a new failing test first:

# RED: Write failing test for validation
def test_create_user_validates_empty_name():
    service = UserService()
    with pytest.raises(ValueError, match="Name cannot be empty"):
        service.create_user(name="", email="[email protected]")

uv run pytest tests/test_user_service.py -x
# Expected: FAILED (no validation exists yet)

# GREEN: Add just enough code to pass
class UserService:
    def create_user(self, name: str, email: str) -> User:
        if not name.strip():
            raise ValueError("Name cannot be empty")
        return User(name=name, email=email)

Then repeat for email validation, normalization, etc. — always RED first.

Test-First Checklist

Before implementing any feature:

• Write test for happy path
• Write test for error cases
• Write test for edge cases
• Run tests (confirm RED)
• Implement minimal code
• Run tests (confirm GREEN)
• Refactor if needed
• Run full suite

Output

Working tests and implementation code produced through the red-green-refactor cycle. The test suite serves as living documentation of the system's behavior.