Tdd Rigor

Skill: TDD Rigor (Superpowers Port)

When to Use

Use when implementing any feature or bugfix, before writing implementation code. Enforces the Iron Law of TDD.

Prerequisites

• Requirements or bug reproduction steps.
• Working test environment (pytest, vitest).

Process

The TDD process follows a strict red-green-refactor cycle for every functional change.

1. RED - Write Failing Test

Write a minimal test demonstrating the target behavior.

• Use pytest for Python.
• Use vitest for TypeScript/React.
• Ensure the test name is descriptive (e.g., test_rejects_empty_input).

2. Verify RED - Watch It Fail

CRITICAL GATE: You must run the test and capture the failure.

• Confirm failure is due to missing logic.
• Confirm failure message is expected.

3. GREEN - Minimal Code

Write just enough code to make the test pass.

• No "while I'm here" improvements.
• No extra features (YAGNI).

4. Verify GREEN - Watch It Pass

CRITICAL GATE: You must run all tests.

• Confirm the new test passes.
• Confirm no regressions in existing tests.

5. REFACTOR - Clean Up

Clean up the implementation while keeping tests green.

Best Practices

Maintain high TDD standards by following these essential practices.

The Iron Law

NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST. If you wrote code before the test: Delete it. Start over.

Anti-Patterns (Avoid)

• Testing Mocks: Don't test that a mock was called; test that the behavior occurred.
• Test After implementation: Proves nothing. You never saw it catch the bug.
• Immediate Pass: If a new test passes immediately, it's not testing new behavior. Fix the test.

Verification Checklist

• Every new function has a test.
• Watched each test fail before implementing.
• Each test failed for expected reason.
• Wrote minimal code to pass.
• Output is pristine (no warnings/errors).