test-driven-development

# Test-Driven Development (TDD)

## Overview

Write the test first using REAL systems. Watch it fail. Write minimal code to pass.

**Core principle**: If you didn't watch the test fail against a real system, you don't know if it tests the right thing.

**Violating the letter of the rules is violating the spirit of the rules.**

## Shannon Enhancement: NO MOCKS

**This is NOT optional**. Shannon TDD combines:
1. Superpowers TDD discipline (RED-GREEN-REFACTOR)
2. Shannon NO MOCKS philosophy (real systems only)

**Result**: Tests that actually prove software works in production.

## When to Use

**Always**:
- New features
- Bug fixes
- Refactoring
- Behavior changes

**Exceptions (ask your human partner)**:
- Throwaway prototypes
- Generated code
- Configuration files

Thinking "skip TDD just this once"? Stop. That's rationalization.

## The Iron Law

```
NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST
NO MOCKS IN TESTS (Shannon requirement)
```

Write code before the test? Delete it. Start over.

Use mocks in tests? Delete them. Use real systems.

**No exceptions**:
- Don't keep it as "reference"
- Don't "adapt" it while writing tests
- Don't look at it
- Delete means delete

Implement fresh from tests. Period.

## Red-Green-Refactor

```dot
digraph tdd_cycle {
    rankdir=LR;
    red [label="RED\nWrite failing test\n(REAL systems)", shape=box, style=filled, fillcolor="#ffcccc"];
    verify_red [label="Verify fails\ncorrectly", shape=diamond];
    green [label="GREEN\nMinimal code", shape=box, style=filled, fillcolor="#ccffcc"];
    verify_green [label="Verify passes\nAll green", shape=diamond];
    refactor [label="REFACTOR\nClean up", shape=box, style=filled, fillcolor="#ccccff"];
    verify_mocks [label="NO MOCKS\ncheck", shape=diamond, style=filled, fillcolor="#ffffcc"];
    next [label="Next", shape=ellipse];

    red -> verify_mocks;
    verify_mocks -> verify_red [label="no mocks"];
    verify_mocks -> red [label="MOCKS\nFOUND"];
    verify_red -> green [label=