TDD GREEN Phase

Version: {{VERSION}}

When to Use

• RED phase test has been verified as failing
• Proceeding autonomously from RED phase
• Implementing feature to pass test

GREEN Phase Objective

Write the minimum code to make the test pass.

Workflow

Step 1: Understand Test Requirements

• What behavior is expected?
• What inputs does test provide?
• What output/result does test expect?

Step 2: Plan Minimal Implementation

Include:

• Minimum logic needed
• Required data structures
• Expected return values

Avoid:

• Features not in test
• Abstractions not yet needed
• Premature optimization

Step 3: Implement to Pass Test

Provide single code block:

TASK: [Brief description]

STEP 1: [Open implementation file]
STEP 2: [Navigate to location]
STEP 3: [Add implementation code]
STEP 4: [Explanation]
STEP 5: [Save file]
STEP 6: [Run test command]
STEP 7: [Verify test PASSES]
STEP 8: [Report back: Did test pass?]

Step 4: Verify and Proceed

If test passes: Proceed to REFACTOR phase If test fails: Revise implementation, repeat If other tests fail: Fix regressions first

Best Practices

YAGNI (You Aren't Gonna Need It)

Good: Implements exactly what test requires Poor: Implements untested features "just in case"

Simplest Thing That Works

Test: Function should return sum of two numbers

WRONG: Generic calculation engine with plugins
RIGHT: Function returns a + b

Hard-Code First, Generalize Later

Test expects result: 5
Implementation: return 5

Next test expects different result
-> Now implement real logic

Common Mistakes

1. Over-Implementation - Adding features not required
2. Premature Abstraction - Creating abstractions before needed
3. Ignoring Test Failure Details - Not reading expectations
4. Breaking Existing Tests - Run full suite

Implementation Strategies

Strategy	When	Example
Fake It	Simple test	return 5
Obvious	Clear solution	return a + b
Triangulation	Unsure how to generalize	Multiple tests force generalization

Checklist Before REFACTOR Phase

• Target test PASSES
• Implementation is minimal
• No existing tests broke
• Code is understandable
• No untested features added

Resources

• resources/green-phase-checklist.md
• resources/minimal-implementation-guide.md
• resources/triangulation-examples.md

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End of TDD GREEN Phase Skill