Tidy First

tidy-first

Instructions

Follow Kent Beck's "Tidy First" approach by strictly separating structural changes from behavioral changes in all development work.

Core Principle

Separate all changes into two distinct types:

1. STRUCTURAL CHANGES: Rearranging code without changing behavior

   • Renaming variables, functions, classes
   • Extracting methods or functions
   • Moving code to different files or modules
   • Reorganizing code structure
   • Improving code organization

2. BEHAVIORAL CHANGES: Adding or modifying actual functionality

   • Adding new features
   • Fixing bugs
   • Changing business logic
   • Modifying functionality

Golden Rules

Never Mix Change Types

• Never mix structural and behavioral changes in the same commit
• Each commit should be either purely structural OR purely behavioral
• This makes code review easier and debugging simpler

Structural Changes First

• Always make structural changes first when both are needed
• Tidy the code before adding new behavior
• Prepare the structure to receive new functionality

Validate Structural Changes

• Validate structural changes do not alter behavior
• Run all tests before making structural changes
• Run all tests after making structural changes
• Tests must pass both before and after - same results
• If behavior changes, it wasn't a pure structural change

Workflow

When Making Structural Changes

1. Ensure all tests are currently passing
2. Make one structural change at a time
3. Run tests to verify behavior unchanged
4. Commit the structural change with clear message
5. Repeat for next structural change if needed

When Making Behavioral Changes

1. Complete all structural changes first
2. Commit all structural changes separately
3. Now make behavioral changes
4. Follow TDD cycle (Red → Green → Refactor)
5. Commit behavioral changes separately

Commit Discipline

Commit Message Format

Use the commit-message skill format:

• Structural changes: ♻️ refactor or 🧹 tidy
• Behavioral changes: ✨ feat or 🐛 fix

Commit Requirements

Only commit when:

1. ALL tests are passing
2. ALL compiler/linter warnings have been resolved
3. The change represents a single logical unit of work

Commit Frequency

• Use small, frequent commits rather than large, infrequent ones
• Each structural change gets its own commit
• Each behavioral change gets its own commit

Code Quality Standards

Apply these principles during structural changes:

• Eliminate duplication ruthlessly

  • Look for repeated code patterns
  • Extract common functionality
  • Use DRY (Don't Repeat Yourself) principle

• Express intent clearly through naming and structure

  • Use descriptive names for variables, functions, classes
  • Make code self-documenting
  • Structure code to reveal intent

• Make dependencies explicit

  • Clearly show what depends on what
  • Avoid hidden dependencies
  • Use dependency injection where appropriate

• Keep methods small and focused on a single responsibility

  • Each function/method should do one thing well
  • Follow Single Responsibility Principle
  • Extract large methods into smaller, focused ones

• Minimize state and side effects

  • Prefer pure functions when possible
  • Make side effects explicit and controlled
  • Reduce mutable state

Refactoring Patterns

Use established refactoring patterns with their proper names:

• Extract Method: Pull code into a new method
• Rename: Change names to better express intent
• Move Method: Relocate method to more appropriate class
• Extract Class: Split large class into smaller ones
• Inline Method: Replace method call with method body
• Replace Temp with Query: Replace temporary variable with method
• Introduce Parameter Object: Group parameters into object

Examples

Structural Change Example

// Before Refactoring
func CalculateTotal(price float64, taxRate float64) float64 {
    tax := price * taxRate
    return price + tax
}
// After Refactoring - Extract Method
func CalculateTotal(price float64, taxRate float64) float64 {
    tax := CalculateTax(price, taxRate)
    return price + tax
}
func CalculateTax(price float64, taxRate float64) float64 {
    return price * taxRate
}

Behavioral Change Example

// Before Behavioral Change
func CalculateTotal(price float64, taxRate float64) float64 {
    tax := price * taxRate
    return price + tax
}
// After Behavioral Change - Change Tax Calculation
func CalculateTotal(price float64, taxRate float64) float64 {
    tax := price * taxRate * 1.1 // New tax logic
    return price + tax
}

Benefits

• Easier code review: Reviewers can quickly verify structural changes don't alter behavior
• Safer refactoring: Tests guarantee no behavior changed
• Better git history: Clear separation makes debugging easier
• Easier rollback: Can revert behavioral changes without losing structural improvements
• Lower risk: Small, focused changes reduce chance of introducing bugs