TDD GREEN Phase

Version: v0.18.0

Guide through GREEN phase: implementing minimum code to make failing test pass.

When to Use

• RED phase test verified as failing
• User responds "Done-Next-Step" after RED phase
• Moving from RED to GREEN in TDD cycle

Objective

Write the minimum code to make the test pass.

Correct: Implements exactly what test requires, simplest solution Incorrect: Over-engineers, adds untested features, premature optimization

Workflow

Step 1: Understand Test Requirements

• What behavior is expected?
• What inputs/outputs?
• What edge cases covered?

Step 2: Plan Minimal Implementation Avoid: Features not in test, abstractions not needed, premature optimization

Step 3: Implement (Single Code Block)

TASK: [Description]
STEP 1: Open implementation file
STEP 2: Navigate to location
STEP 3: Add/modify implementation code
STEP 4: Context about choices
STEP 5: Save file
STEP 6: Run test command
STEP 7: Verify test PASSES
STEP 8: Report: Did test pass?

Step 4: Verify Success

• Test executed without errors
• Test passed (green)
• No other tests broke
• Implementation is minimal

Step 5: Analyze

• Passes → "Done-Next-Step" → REFACTOR phase
• Still fails → Revise implementation
• Other tests fail → Fix regressions first

Principles

1. YAGNI: Implement only what test requires
2. Simplest Thing: Hard-coded values acceptable if test passes
3. Let Tests Drive Design: Test tells you the interface
4. Hard-Code First: Generalize when more tests require it

Implementation Strategies

• Fake It: Return expected value (temporary)
• Obvious Implementation: Straightforward solution
• Triangulation: Multiple tests force generalization

Anti-Patterns

• Feature creep (adding untested features)
• Optimization before profiling
• Copy-paste without understanding

Checklist

• Target test now PASSES
• Implementation is minimal
• No regressions (full suite green)
• User reported via "Done-Next-Step"

End of TDD GREEN Phase Skill