Tdd Cycle

Complete TDD Cycle

Overview

This skill orchestrates a complete Test-Driven Development cycle, guiding through all phases: RED (write failing test), GREEN (make it pass), REFACTOR (improve structure), and proper commits. Use this when you want to complete one full TDD iteration.

When to Use

Use this skill when:

• Ready to implement next test from PLAN.md
• Want to follow complete TDD workflow
• Need guidance through all TDD phases
• Want structured approach to one iteration
• Following disciplined TDD practice

Complete Workflow

Phase 1: RED - Write Failing Test

Execute tdd-red skill:

1. Find next unmarked test in PLAN.md
2. Write a failing test with Korean description
3. Run tests to confirm failure
4. Mark test as [ ] in PLAN.md

Success Criteria:

• Test fails for the right reason (missing functionality)
• Test name clearly describes behavior
• All other tests still pass
• No compilation errors

Use: /red command or tdd-red skill

Phase 2: GREEN - Make It Pass

Execute tdd-green skill:

1. Verify we have a failing test
2. Implement MINIMUM code to make test pass
3. Run ALL tests to confirm they pass
4. Mark test as [x] in PLAN.md

Success Criteria:

• New test now passes
• All existing tests still pass
• No compiler warnings
• Used simplest possible implementation

Use: /green command or tdd-green skill

Phase 3: REFACTOR - Improve Structure

Execute tdd-refactor skill (if needed):

1. Verify all tests are passing
2. Identify code smells or duplication
3. Make structural improvements one at a time
4. Run tests after each change
5. Keep tests green throughout

Success Criteria:

• All tests still passing
• Code quality improved
• Duplication reduced
• Structure is clearer

When to Skip:

• Code is already clean
• No obvious improvements needed
• Would be premature optimization

Use: /refactor command or tdd-refactor skill

Phase 4: COMMIT - Save Progress

Commit Strategy:

If Structural Changes Were Made:

1. First, commit structural changes separately:

   /commit-tidy
   

   • Use "refactor:" or "tidy:" prefix
   • Clearly indicate structural changes only

2. Then, commit behavioral changes:

   /commit-behavior
   

   • Use "feat:", "fix:", or appropriate prefix
   • Describe what functionality was added

If No Structural Changes:

• Just commit behavioral changes:

  /commit-behavior
  

Commit Prerequisites:

• ALL tests passing
• NO compiler warnings
• NO linter errors
• Clear commit message

Phase 5: REPEAT - Next Test

Prepare for Next Cycle:

1. Verify clean state (all tests pass)
2. Review PLAN.md for next test
3. Start new RED phase when ready

Execution Flow

START
  ↓
RED: Write failing test
  ↓
Confirm test fails? ──No──> Fix test
  ↓ Yes
GREEN: Implement minimum code
  ↓
All tests pass? ──No──> Debug & fix
  ↓ Yes
Need refactoring? ──Yes──> REFACTOR: Improve structure
  ↓ No                        ↓
  ←───────────────────────────┘
COMMIT: Save changes
  ↓
Next test? ──Yes──> START
  ↓ No
DONE

Key Principles

RED Phase:

• Write smallest failing test
• Test one thing only
• Fail for right reason

GREEN Phase:

• Simplest implementation
• No premature optimization
• Make it work, not perfect

REFACTOR Phase:

• Only when green
• One change at a time
• Keep tests green

COMMIT Phase:

• Separate structural from behavioral
• All tests passing
• Clear messages

Important Reminders

• NEVER skip RED - always write test first
• NEVER write more code than needed in GREEN
• NEVER refactor on red tests
• ALWAYS run tests after each phase
• ALWAYS keep commits small and focused
• ONE test at a time
• ONE refactoring at a time

Useful Commands

Within this cycle, you can use:

• /red - Execute RED phase
• /green - Execute GREEN phase
• /refactor - Execute REFACTOR phase
• /tidy - Make structural changes (Tidy First)
• /commit-tidy - Commit structural changes
• /commit-behavior - Commit behavioral changes
• /run-tests - Run all tests
• /next-test - View next test in PLAN.md

Example Complete Cycle

1. RED: Write test "should calculate total price with discount"

   • Test fails: calculateTotalWithDiscount is not defined

2. GREEN: Implement basic calculation

   function calculateTotalWithDiscount(price, discount) {
     return price - discount;
   }
   

   • All tests pass

3. REFACTOR: Extract validation logic

   • Add input validation
   • Extract discount calculation
   • All tests still pass

4. COMMIT:

   • Commit refactoring: "refactor: extract discount calculation logic"
   • Commit feature: "feat: add total price calculation with discount"

5. REPEAT: Move to next test

Next Steps

After completing one full cycle:

1. Verify clean state
2. Check PLAN.md for next test
3. Start new cycle with RED phase
4. Continue until feature complete