Programming

Steps

1. Pre-test refactor for legacy code: Sprout Method, Sprout Class, Wrap Method, Wrap Class

2. Write test: Arrange, Act, Assert

3. Write code

4. Refactor code

   Smell	Refactoring
   Large class	Extract Class Apply Single Responsibility
   Long method	Extract Method Make Composed Method
   Code not self-explanatory	Rename Make Composed Method Apply Ubiquitous Language Apply Single Responsibility
   Duplication	Extract Method Extract Class

5. Refactor test

   Smell	Refactoring
   Test method name says "what", not "why"	Rename to communicate "why"
   Multiple asserts in test method	1 assert per test method
   Long data setup	Create Test Data Builders
   Complicated setup of collaborators	Use mocks
   Fragile shared fixtures	No shared fixtures between test classes

References

• Refactoring
• Test Driven Development
• Domain-Driven Design
• Working Effectively with Legacy Code
• xUnit Test Patterns

Model the Domain

Object Categories

• People: Actor, Role
• Places: Place, Outer Place
• Things: Item, Specific Item, Assembly, Part, Container, Content, Group, Member
• Events: Transaction, Composite Transaction, Line Item, Follow-up Transaction

Object Collaboration Patterns

• Generic - Specific
  • Actor - Role
  • Item - Specific Item
  • Composite Transaction - Line Item
• Whole - Part
  • Container - Content
  • Assembly - Part
  • Group - Member
  • Outer Place - Place
• Transaction - Specific
  • Transaction - Role
  • Transaction - Specific Item
  • Transaction - Place
  • Follow-up Transaction - Transaction
  • Line Item - Specific Item

References

• Modeling on the Right Side of the Brain by Nicholas Henry
• Streamlined Object Modeling

Refactoring Legacy Code

1. Write regression test
   • Feed in input, have code generate output for assertions
   • Test all conditional branches
   • Test edge cases
   • Minimize number of tests
2. Refactor code
   • Extract class, makes method extraction easier, because shared state is in member variables
   • Extract methods
   • Remove "chart junk"
   • Seek regularity in code. Make moves to make code more regular.

References

• Therapeutic Refactoring by Katrina Owen

What and How to Test

Message	Query	Command
Incoming	Assert return value	Assert public side effects
Sent to Self	Don't test	Don't test
Outgoing	Don't test	Use mock

References

• The Magic Tricks of Testing by Sandi Metz

5 Rules

• 100 lines per class
• 5 lines per method
• 4 parameters per method (each hash parameter counts as 1)
• 1 instance variable per rails view
• 2 class names per rails controller action (business, presenter)

References

• Rules by Sandi Metz