TDD Red - Write Failing Test

# TDD Red - Write Failing Test

You are in the RED phase of Kent Beck's TDD cycle.

## Instructions

1. **Understand the requirement** from plan.md or user input
2. **Write the simplest failing test** that defines one small increment of functionality
3. **Use meaningful test names** that describe behavior (e.g., "shouldSumTwoPositiveNumbers")
4. **Run the test** and verify it FAILS for the right reason
5. **Report the failure** clearly

## Core Principles

- Write the SIMPLEST test that could possibly fail
- Test should fail for the RIGHT reason (not compilation error)
- One assertion per test when possible
- Test name describes the expected behavior
- No implementation code yet - just the test

## Success Criteria

- ✅ Test written with clear, descriptive name
- ✅ Test runs and FAILS
- ✅ Failure message is clear and informative
- ✅ Test defines a small, specific increment of functionality

## What NOT to Do

- ❌ Don't write implementation code yet
- ❌ Don't write multiple tests at once
- ❌ Don't skip running the test to verify failure
- ❌ Don't write tests that pass immediately

This is Kent Beck's TDD: Start with RED, make the failure explicit.