Test-Driven Development (TDD)

Priority: P1 (OPERATIONAL)

The Iron Law

NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST. If you wrote code before the test: Delete it. Start over. No "adapting" or keeping as reference.

The TDD Cycle

1. •RED: Write a minimal failing test. Verify failure (Expected error, not typo).
2. •GREEN: Write the simplest code to pass. Verify pass (Pristine output).
3. •REFACTOR: Clean up code while staying green.

Core Principles

• •Watch it Fail: If you didn't see it fail, you didn't prove the test works.
• •Minimalism: Don't add features/options beyond the current test (YAGNI).
• •Real Over Mock: Prefer real dependencies unless they are slow/flaky. Avoid Anti-Patterns.

Verification Checklist

• • Every new function/method has a failing test first?
• • Failure message was expected (feature missing, not setup error)?
• • Minimal code implemented (no over-engineering)?
• • Common Pitfalls avoided?

Expert References

• •TDD Patterns & Discovery Protocols
• •Testing Anti-Patterns (Safety First)