Chapter 1

Split 10 to 5 * 2 to see code duplication between data in code and data
in test
Chapter 1

Remove code duplication of 5 and 2

Step 1: Move field initialization to method
Chapter 1

Remove code duplication of 5 and 2

Step 2: Assign constructor parameter to field and replace 5 with field
Chapter 1

Remove code duplication of 5 and 2

Step 3: Replace 2 with parameter
Chapter 1

Remove code duplication of 5 and 2

Step 4: Syntactic sugar