Test Driven Development: By Example

Chapter 11

The Root of All Evil

$5 + 10 CHF = $10 if rate is 2:1

$5 * 2 = $10

Make “amount” private

Dollar side effects?

Money rounding?

equals()

hashCode()

Equal null

Equal object

5 CHF * 2 = 10 CHF

Dollar/Franc duplication

Common equals

Common times

Compare Francs to Dollars

Currency?

Delete testFrancMultiplication?

The two subclasses, Dollar and Franc, have only their constructors. But because a constructor is not reason enough to have a subclass, we want to delete the subclasses.

We can replace references to the subclasses with references to the superclass without changing the meaning of the code. First Franc:

Franc

Click here to view code image

static Money franc(int amount){
   return new Money(amount, "CHF");
}

Then Dollar:

Dollar

Click ...