refactor-process

Refactor Process

Apply the execution contract before this procedure.

Quick Reference

Aspect	Rule
Pre-requisite	Characterization tests must exist and be Green before any edits
Step Size	One atomic transformation at a time (rename variable, extract method, etc.)
Verification	Run tests after every single step
No Behavior Changes	No new features, bug fixes, or changed return values during refactoring
Rollback	If tests turn Red, undo immediately — do not debug in a broken state

Process Steps

Step 1: Establish the Baseline

• Run the existing tests for the class or module.
• If coverage is missing or weak, write characterization tests (tests that capture the current behavior, including edge cases and errors).
• Verify all tests are Green before proceeding.

Step 2: Plan the Steps

• Identify the goal (e.g., extract a complex method into its own class, simplify a conditional block).
• Break the goal into a sequence of atomic refactoring operations (rename, extract, inline, move, replace conditional, etc.).

Step 3: Execute and Verify Loop

For each planned step:

1. Make the singular, atomic code modification.
2. Run the tests.
3. If Green, save/commit the step and proceed.
4. If Red, discard the change (e.g., via git checkout or undo), analyze the root cause, and try a smaller step.

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Checkpoint Pattern

Pause and align with the user:

1. Baseline Checkpoint: Show the characterization tests and current implementation before making any edits.
2. Refactoring Proposal: Outline the planned steps of transformations.
3. Completion Checkpoint: Present the final refactored code and the test suite validation report.

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Example Refactoring Loop (Extract Method)

Baseline (Green):

class ReportGenerator
  def generate(data)
    # Formats raw data to report
    formatted = data.map { |row| "#{row[:id]}: #{row[:name].strip.capitalize}" }
    
    # Renders report
    "=== Report ===\n" + formatted.join("\n") + "\n=============="
  end
end

Step 1: Extract Formatter Logic (Atomic Edit):

class ReportGenerator
  def generate(data)
    formatted = format_rows(data)
    "=== Report ===\n" + formatted.join("\n") + "\n=============="
  end

  private

  def format_rows(data)
    data.map { |row| "#{row[:id]}: #{row[:name].strip.capitalize}" }
  end
end

Action: Run tests immediately. Confirm Green.

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Anti-Patterns

• Behavior Creep: Keep refactoring and behavior changes (bug fixes, optimizations) in completely separate commits.
• The "Giant Leap" Refactor: Multiple non-trivial changes at once make failures hard to diagnose; always take the smallest possible atomic step.

Integration

Context	Next Skill
Establishing baseline coverage	test-planning-process → tdd-process
Documenting newly extracted APIs	write-yard-docs
Post-refactoring review	review-process