Test Driven Development: By Example

Chapter 4

Privacy

$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

Now that we have defined equality, we can use it to make our tests more “speaking.” Conceptually, the operation Dollar.times() should return a Dollar whose value is the value of the receiver times the multiplier. Our test doesn’t exactly say that:

Click here to view code image

public void testMultiplication() {
   Dollar five= new Dollar(5);
   Dollar product= five.times(2);
   assertEquals(10, product.amount);
   product= five.times(3);
   assertEquals(15, product.amount);
}

We can rewrite the first assertion to compare Dollars to Dollars:

Click here to view code image

public void testMultiplication() ...