Test Driven Development: By Example

Chapter 1. Multi-Currency Money

We'll start with the object that Ward created at WyCash, multi-currency money (refer to the Introduction). Suppose we have a report like this:

Instrument	Shares	Price	Total
IBM	1000	25	25000
GE	400	100	40000
		Total	65000

To make a multi-currency report, we need to add currencies:

Instrument	Shares	Price	Total
IBM	1000	25 USD	25000 USD
Novartis	400	150 CHF	60000 CHF
		Total	65000 USD

We also need to specify exchange rates:

From	To	Rate
CHF	USD	1.5

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

What behavior will we need to produce the revised report? Put another way, what set of tests, when passed, will demonstrate the presence of code we are confident will compute the report correctly?

• We need ...