Refine Development Plan

Overview

Good plans eliminate ambiguity through clear requirements, break work into clear phases, and always include refactoring to capture implementation insights.

When to Use This Skill

Planning Principles

1. Plans Must Be Actionable and Unambiguous

Every step should be concrete enough that another agent could execute it without guessing.

• ❌ "Improve error handling" → ✓ "Add try-catch to API calls in user-service.ts, return 400 with error message"
• ❌ "Update tests" → ✓ "Add test case to auth.test.ts: 'should reject expired tokens with 401'"

NEVER include thinking output or other stream-of-consciousness prose mid-plan.

2. Push Back on Unclear Requirements

When requirements are ambiguous, ask questions before proceeding.

3. Tests Define Requirements

Writing test cases forces disambiguation. Use test definition as a requirements clarification tool.

4. TDD is Non-Negotiable

All plans follow: Red → Green → Refactor. The refactor phase is MANDATORY.

The TDD Workflow

Red Phase: Write Failing Tests First

Purpose: Define success criteria through concrete test cases.

What to test:

• Happy path (normal usage), edge cases (boundaries, empty/null), error conditions (invalid input, failures), integration points

Test types:

• Unit tests: Individual functions in isolation (most tests should be these - fast, focused)
• Integration tests: Component interactions (use for critical paths)
• E2E tests: Complete workflows (use sparingly)

Write descriptive test cases:

If you can't write the test, you don't understand the requirement and MUST ask for clarification.

Green Phase: Make Tests Pass

Purpose: Implement minimal working solution.

Focus on correctness first. Hardcode if needed. Add just enough logic. Resist urge to "improve" code. Run tests frequently.

Refactor Phase: Improve the Implementation

Purpose: Apply insights gained during implementation.

This phase is MANDATORY. During implementation you'll discover better structure, repeated patterns, and simplification opportunities.

When to Extract vs Keep Duplication:

This is highly subjective, so use the following rules of thumb combined with good judgement:

1. Follow the "rule of three": if the exact 10+ lines are repeated verbatim 3+ times, extract it.
2. The "wrong abstraction" is harder to fix than duplication.
3. If extraction would harm readability, prefer duplication.

Common refactorings:

• Rename for clarity
• Simplify complex conditionals
• Extract repeated code (if meets criteria above)
• Apply design patterns

Constraints:

• All tests must still pass after refactoring
• Don't add new features (that's a new Red phase)

Plan Refinement Process

Step 1: Review Current Plan for Completeness

• Clear context explaining why
• Specific, unambiguous requirements
• Test cases defined before implementation
• Step-by-step implementation approach
• Explicit refactor phase
• Verification steps

Step 2: Identify Gaps

Look for missing tests, vague steps, no refactor phase, ambiguous requirements, missing verification.

Step 3: Handle Unclear Requirements

If you can't write the plan without this information, ask the user. Otherwise, make reasonable assumptions and note them in the plan.

Step 4: Define Test Cases

For each requirement, write concrete test cases. If you struggle to write test cases, you need more clarification.

Step 5: Structure with Red-Green-Refactor

Organize the plan into three explicit phases.

Step 6: Add Verification Steps

Specify how to confirm the change works (automated tests + manual checks).

Tips for Success

1. Start with tests: If you can't write the test, you don't understand the requirement.
2. Be specific: "Update API" is not a step. "Add error handling to POST /users endpoint" is.
3. Always refactor: Even if code looks good, ask "How could this be clearer?"
4. Question everything: Ambiguity is the enemy.
5. Think in phases: Red → Green → Refactor.
6. Keep plans manageable: If plan exceeds ~10 files or >5 phases, consider splitting.

Remember: A good plan makes implementation straightforward. A vague plan leads to confusion, rework, and bugs.