Ted M. Young https://maketestable.com/ @jitterted Stop Obsessing About Primitives from the MAKE YOUR CODE MORE TESTABLE series Ted M. Young Java Trainer, Coach, & Live Coder [email protected] https://ted.dev @JitterTed (Twitch, Twitter, YouTube) Discord: https://discord.gg/9XDfBSZ 

Ted M. Young https://maketestable.com/ @jitterted Ask Questions As You Need To 

Ted M. Young https://maketestable.com/ @jitterted Primitive Obsession The Code Smell 

Ted M. Young https://maketestable.com/ @jitterted Primitives: What Are They? • int, long, char • boolean • String • List, Map, Set 

Ted M. Young https://maketestable.com/ @jitterted Primitives: Where Are They? • Instance variables (fields) • Method parameters • Return values • Not local variables 

Ted M. Young https://maketestable.com/ @jitterted Primitives: What’s Wrong? • Mixes responsibilities • Not self-documenting • Leads to dispersed logic 

Ted M. Young https://maketestable.com/ @jitterted Fixing Primitive Obsession Create New Types 

Ted M. Young https://maketestable.com/ @jitterted Enum Usage: Limited Options Known at Coding Time 

Ted M. Young https://maketestable.com/ @jitterted Enum Examples • Playing Card Suit or Rank • Hearts, Clubs; Ace, 2, 3…, Queen, King • Game Outcomes • Beat Dealer, Lost to Dealer, Went “Bust”, Won Blackjack • Option Contract Type • Put or Call • Coffee Ingredient 

Ted M. Young https://maketestable.com/ @jitterted Enum: Turn Logic into Constant 

Ted M. Young https://maketestable.com/ @jitterted Enum: Turn Logic into Constant 

Ted M. Young https://maketestable.com/ @jitterted Value Object Usage: Many Options, May Change Dynamically 

Ted M. Young https://maketestable.com/ @jitterted unconstrained number constrained type 1 100 Wager int -2,147,483,648 2,147,483,647 

Ted M. Young https://maketestable.com/ @jitterted unconstrained date constrained type 2021-01-15 ExpirationDate LocalDate -999999999-01-01 +999999999-12-31 2021-02-19 2020-11-20 2020-12-18 2021-03-19 2021-04-16 

Ted M. Young https://maketestable.com/ @jitterted Other Value Objects Money • Contains Currency and Amount Birthdate Color Identifiers • UserId, CustomerId 

Ted M. Young https://maketestable.com/ @jitterted Stateful Type Usage: Holds Mutable State 

Ted M. Young https://maketestable.com/ @jitterted Stateful Types Inventory Level Blackjack Hand Order Quantity 

Ted M. Young https://maketestable.com/ @jitterted Refactoring to New Type InventoryLevel 

Ted M. Young https://maketestable.com/ @jitterted 

Ted M. Young https://maketestable.com/ @jitterted Feature Envy Behavior implemented against data in another object 

Ted M. Young https://maketestable.com/ @jitterted Fix Scalar Primitive Obsession 1. Fix Feature Envy: gather usages via getter and setter 2. Remove getter & setter via inlining 3. Move scalar field to a new class 4. Change old scalar to instance of new type 5. Replace getter with new type’s methods 

Ted M. Young https://maketestable.com/ @jitterted Fix Collection Primitive Obsession 1. Move collection field to new class via getter 2. Look for Feature Envy (usages of new getter) 3. Extract and Move Methods to new class 4. Continue until no more accesses via getter 5. Inline & remove getter 

Ted M. Young https://maketestable.com/ @jitterted Further Constrain Data Exposure • Look for public methods that: • Can now be private • Return unconstrained types 

Ted M. Young https://maketestable.com/ @jitterted Questions? Ted M. Young Java Trainer, Coach, & Live Coder [email protected] https://ted.dev @JitterTed (Twitch, Twitter, YouTube) 

Ted M. Young https://maketestable.com/ @jitterted Thank You Ted M. Young Java Trainer, Coach, & Live Coder [email protected] https://ted.dev @JitterTed (Twitch, Twitter, YouTube) Discord: https://discord.gg/9XDfBSZ